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Development of Prediction Method for Dynamic Strain on Windshield during Passenger Airbag Deployment | The objective of this study is to accurately predict the dynamic strain on the windshield caused by the deployment of the airbag in a short term without vehicle tests. The following assumption is made as to the dynamic pressure distribution on the windshield: The deployment of the airbag is fast enough to ignore spatial difference in the patterns of the pressure time histories. Given this assumption, significant parameters of the dynamic pressure distribution are as follows: 1) the distribution of the maximum pressure during contact between the airbag and the windshield, and 2) the characteristic of the force time histories applied to the windshield by the deploying airbag. In this study, the prediction method consists of a simplified airbag deployment test and an FE simulation. The simple deployment test was conducted to measure the peak pressure distribution between the airbag and a flat panel simulating the windshield. The pressure time history curves were determined by scaling the force time histories from the load cells. The scale factor was identified for each of the measuring points on the pressure measurement film. Prescribed pressure time histories were directly applied to the part of the FE mesh specifically used to load the windshield. In order to validate the developed prediction method, the strain from the FE simulation was compared with that from strain gauges in the vehicle tests. The results showed that the predicted strain on the windshield caused by the airbag deployment correlated well with the data measured in the vehicle tests, suggesting that the prediction method developed in this study can be a valuable tool for improving the efficiency of development. |
Prediction of Structureborne Noise in a Fully Trimmed Vehicle Using Poroelastic Finite Elements Method (PEM) | Since the last decade, the automotive industry has expressed the need to better understand how the different trim parts interact together in a complete car up to 400 Hz for structureborne excitations. Classical FE methods in which the acoustic trim is represented as non-structural masses (NSM) and high damping or surface absorbers on the acoustic cavity can only be used at lower frequencies and do not provide insights into the interactions of the acoustic trims with the structure and the acoustic volume. It was demonstrated in several papers that modelling the acoustic components using the poroelastic finite element method (PEM) can yield accurate vibro-acoustic response such as transmission loss of a car component [1,2,3]. The increase of performance of today's computers and the further optimization of commercial simulation codes allow computations on full vehicle level [4,5,6] with adequate accuracy and computation times, which is essential for a car OEM. This paper presents a study of a fully trimmed vehicle excited by structureborne excitations with almost all acoustic trims such as seats, dash insulator, instrument panel, headliner… which are modelled as poroelastic finite element (PEM) parts. Simulation results are compared with extensive measurement results. The interactions between structure, acoustic trims and acoustic volume are illustrated and finally the analysis of several design changes such as trim material properties or geometry modifications is demonstrated. |
A Computational Aeroacoustic Study of Windshield Wiper Influence on Passenger Vehicle Greenhouse Windnoise | This paper presents an approach to numerically simulate greenhouse windnoise. The term “greenhouse windnoise” here describes the sound transferred to the interior through the glass panels of a series vehicle. Different panels, e.g. the windshield or sideglass, are contributing to the overall noise level. Attached parts as mirrors or wipers are affecting the flow around the vehicle and thus the pressure fluctuations which are acting as loads onto the panels. Especially the wiper influence and the effect of different wiper positions onto the windshield contribution is examined and set in context with the overall noise levels and other contributors. In addition, the effect of different flow yaw angles on the windnoise level in general and the wiper contributions in particular are demonstrated. As computational aeroacoustics requires accurate, highly resolved simulation of transient and compressible flow, a Lattice-Boltzmann approach is used. The noise transmission through the interior is then modeled by statistical energy analysis (SEA), representing the vehicle cabin and the panels excited by the flow. Results are verified by comparisons to windtunnel experiments. |
Attenuation of Aeroacoustic Noise of a Typical Van Using Passive Devices through CFD Simulation | The present numerical analysis aims at studying the effect of changes in profile of van on aero-acoustic noise and aerodynamic drag. The numerical analysis is carried out using commercial CFD software, ANSYS Fluent, with k-epsilon & Large Eddy Simulation turbulence models. In present study five models of truck are analysed, including baseline model at different Reynolds numbers, namely 0.391, 0.415 and 0.457 million. In order to reduce the aero-acoustic noise, various profile modifications have been adapted on existing van model by adding a top and bottom diffuser at the rear of the truck. The comparison has been done with respect to coefficient of drag, coefficient of pressure, pressure contours for all four cases. It is observed from the simulation results among different modifications of truck, adding a top and bottom diffuser of 15 degrees at the rear end of truck gives the maximum reduction in aero-acoustic noise up to 9.4% and aerodynamic drag reduction of 3.8 % as compared to baseline model, at a speed of 81 km/h. |
Performance Analysis on 3D Printed Beak-Shaped Automotive Tail Fin Filled with Honeycomb Cellular Structure | The concept of “bionic design” has driven the developments of automotive design. In this paper, a novel beak-shaped automotive tail fin with honeycomb cellular structure is proposed based on the idea of “bionic design”. Beak-shaped appearance is utilized to meet the requirement of aerodynamics performance, inner honeycomb cellular structure is filled to achieve more lightweight space. This paper starts from the establishment of three dimensional (3D) model based on the real characteristics of sparrow’s beak. On this basis, aerodynamic performances of novel beak-shaped tail fin and conventional shark tail fin are analyzed by experiment. Finally, the stiffness and modal analyses of solid beak-shaped tail fin and honeycomb beak-shaped tail fin are carried out respectively. The results indicate that the deformation of solid beak-shaped tail fin and honeycomb beak-shaped tail fin satisfy the basic requirements. In addition, the first order modal frequencies of solid and honeycomb beak-shaped tail fins are both far away from body vibration frequency and effectively avoid resonance. Compared with solid beak-shaped tail fin, the weight of honeycomb beak-shaped tail fin decreases by about 25%. Thus, the novel honeycomb beak-shaped tail fin proposed in this work demonstrates outstanding performance in terms of aerodynamic performances, structural stiffness enhancement and weight reduction. |
Automatic Speech Recognition System Considerations for the Autonomous Vehicle | As automakers begin to design the autonomous vehicle (AV) for the first time, they must reconsider customer interaction with the Automatic Speech Recognition (ASR) system carried over from the traditional vehicle. Within an AV, the voice-to-ASR system needs to be capable of serving a customer located in any seat of the car. These shifts in focus require changes to the microphone selection and placement to serve the entire vehicle. Further complicating the scenario are new sources of noise that are specific to the AV that enable autonomous operation. Hardware mounted on the roof that are used to support cameras and LIDAR sensors, and mechanisms meant to keep that hardware clean and functioning, add even further noise contamination that can pollute the voice interaction. In this paper, we discuss the ramifications of picking up the intended customer’s voice when they are no longer bound to the traditional front left “driver’s” seat. Considerations are made to the possibilities of new microphone construction and layouts to provide coverage for all potential passengers, and cost-efficient minimal microphone packages are discussed. Additionally, if the automaker chooses to initiate the ASR interaction with a “wake up word”, instead of installing Push to Talk (PTT) buttons for every seat, we discuss how the multiple microphone’s placements can be leveraged to identify the seat issuing the command, and focus further ASR interactions with that location in the car. |
A Non-Contact Technique for Vibration Measurement of Automotive Structures | The automotive and aerospace industries are increasingly using the light-weight material to improve the vehicle performance. However, using light-weight material can increase the airborne and structure-borne noise. A special attention needs to be paid in designing the structures and measuring their dynamics. Conventionally, the structure is excited using an impulse hammer or a mechanical shaker and the response is measured using uniaxial or multi-axial accelerometers to obtain the dynamics of the structure. However, using contact-based transducers can mass load the structure and provide data at a few discrete points. Hence, obtaining the true dynamics of the structure conventionally can be challenging. In the past few years, stereo-photogrammetry and three-dimensional digital image correlation have received special attention in collecting operating data for structural analysis. These non-contact optical techniques provide a wealth of distributed data over the entire structure. However, the stereo camera system is limited by its field of view of the cameras and can only measure the response on the parts of the structure that cameras have the line of sight. Therefore, a single pair of Digital Image Correlation (DIC) cameras may not be able to provide deformation data for the entire structure. In current work, a multi-view 3D DIC approach is used to predict the vibrational characteristics of a full vehicle. A pair of DIC cameras is roved over the entire vehicle to capture the deformation data of each field of view. The measured data includes the geometry and displacement data which is mapped into the global coordinate system using 3D transformation matrices. The obtained data in the time domain for each field of view is transformed to the frequency domain using the Fast Fourier Transformation (FFT) to extract the operational deflection shapes and resonant frequencies for each field of view. The obtained deflection shapes are scaled and stitched in the frequency domain to extract the operating deflection shapes of full vehicle. |
Extensive Correlation Study of Acoustic Trim Packages in Trimmed Body Modeling of an Automotive Vehicle | In the automotive sector, the structure borne noise generated by the engine and road-tire interactions is a major source of noise inside the passenger cavity. In order to increase the global acoustic comfort, predictive simulation models must be available in the design phase. The acoustic trims have a major impact on the noise level inside the car cavity. Although several publications for this kind of simulations can be found, an extensive correlation study with measurement is needed, in order to validate the modeling approaches. In this article, a detailed correlation study for a complete car is performed. The acoustic trim package of the measured car includes all acoustic trims, such as carpet, headliner, seats and firewall covers. The simulation methodology relies on the influence of the acoustic trim package on the car structure and acoustic cavities. The challenge lies in the definition of an efficient and accurate framework for acoustic trimmed bodies. Two different approaches to achieve this objective are reviewed. In the first approach, the acoustic trim package is modeled as a set of porous and solid layers represented by finite elements in physical coordinate system. The acoustic trim models update the modal fluid / structure model of the car body and car cavity. The second approach uses impedance surfaces to apply the acoustic absorption of the trim on the car cavity side. It uses a Virtual Kundt’s tube. Both approaches are solved as state of the art modal analysis. The result of the correlation study with measurements provides acceleration and Sound Pressure Level (SPL) results for different configurations and excitations, introducing the Root Mean Squared Deviation (RMSD). The expected difference between the two approaches is obtained. The first approach results in higher correlation accuracy than the second approach, while the second approach has advantages in computational time. |
Towards a Quiet Vehicle Cabin Through Digitalization of HVAC Systems and Subsystems Aeroacoustics Testing and Design | With the rise of electric autonomous vehicles, it has become clear that the cabin of tomorrow will drastically evolve to both improve ride experience and reduce energy consumption. In addition, autonomy will change the transportation paradigm, leading to a reinvention of the cabin seating layout which will offer the opportunity to climate systems team to design quiet and even more energy efficient systems. Consequently, Heat and Ventilation Air Conditioning (HVAC) systems designers have to deliver products which perform acoustically better than before, but often with less development time. To success under such constraints, designers need access to methods providing both assessment of the system (or subsystems) acoustic performance, and identification of where the designs need to be improved to reduce noise levels. Such methods are often needed before a physical prototype is requested, and thus can only be achieved in a timely manner through digital testing. Previous studies have demonstrated the ability of a CFD/CAA approach based on the Lattice Boltzmann Method (LBM) to predict HVAC system noise including real and complex ducts, registers, mixing unit and blower geometries. This LBM low dissipative numerical approach has indeed been shown to accurately capture turbulent and convective mechanisms and to propagate acoustic waves in ducted systems and in free-field. Combined with a noise source identification strategy, these methods provide the ability to visualize the noise sources inside the system, as well as to identify and rank noise-generating design features - a unique design methodology not available with physical testing. In this paper, such an approach is presented based on two HVAC systems layout, targeting two different vehicles. To answer the need for systems and subsystems predictions, simulation results are correlated to experiment for configurations with blower alone, blower + air intake, and for full HVAC system (blower + air intake + mixing unit). Finally, an in-depth analysis of the flow noise sources contributions to a microphone location is performed, and countermeasures are discussed. |
New ‘Bottlebrush’ Electroactive Polymers Make Dielectric Elastomers Increasingly Viable for Use in Devices | A multi-institutional research team has developed a new electroactive polymer material that can change shape and size when exposed to a relatively small electric field. The advance overcomes two longstanding challenges regarding the use of electroactive polymers to develop new devices, opening the door to a suite of applications ranging from microrobotics to designer haptic, optic, microfluidic, and wearable technologies. The work was performed by researchers at North Carolina State University, the University of North Carolina at Chapel Hill, Carnegie Mellon University, and the University of Akron. |
2021 Ford Bronco aims to kick some Jeep | “There is nothing on this truck that is superfluous - no decorative chrome or extraneous styling. It's designed for function, not fashion,” explained Paul Wraith, chief designer for Ford's much-anticipated 2021 Bronco. “Super-short overhangs for aggressive approach, departure and breakover angles. Slim ‘hips’ for off-road agility. Everything is exactly where you need it. Getting that stuff right is harder than you think,” he admitted. To create the much-anticipated U725 (as the new 2- and 4-door Bronco is known internally and by suppliers), Wraith and his team decided to veer outside of Ford's traditional product-development process. It was the only way to execute the program's broad scope and unique requirements. “As we developed the truck, we invented a new human-centered methodology,” Wraith told media ahead of Bronco's July 13 unveiling. “We made low-fidelity models out of foam-core packing materials which drove our [prototype] shops crazy,” he said. “And we ended up skipping a whole bunch of typical studio processes. This stirred things up quite a bit.” |
Getting driverless trucks onto roadways | Autonomous developers at TuSimple address many technical issues, but they also must consider regulations and operating modes. The developers who are creating autonomous systems have plenty of complex technical questions that must be analyzed and solved, but their challenges don't stop there. Design teams also have to plan for the use cases of driverless vehicles, even going so far as to plan for what might happen if the vehicle has to sacrifice itself to avoid a serious accident. The challenges associated with the sea change wrought by autonomous trucking has opened the door for startups like TuSimple, a Chinese startup that's partially funded by Nvidia. The company is developing digital control systems, focusing on both the prototypes needed to prove the safety of driverless trucks as well as the many issues associated with getting them into day-to-day operations. |
Trucking Without Truckers | The challenges are myriad, but automated-trucking developer TUSimple believes the efficiencies of true depot-to-depot driverless hauling are too promising to ignore. The developers who are creating autonomous systems have plenty of complex technical questions that must be analyzed and solved, but their challenges don't stop there. Design teams also have to plan for the use cases of driverless vehicles, even going so far as to plan for what might happen if the vehicle has to sacrifice itself to avoid a serious accident. The challenges associated with the sea change wrought by autonomous trucking has opened the door for companies such as TuSimple, a Chinese startup that's partially funded by Nvidia. The company is developing digital control systems, focusing on both the prototypes needed to prove the safety of driverless trucks as well as the many issues associated with getting them into day-to-day operations. |
Steel stands TALL | Mobility's longtime incumbent material maintains its star status for vehicle structures through constant innovation-and a collaborative development model. In 2014, just before Ford shook the industry with the introduction of its aluminum-intensive F-150, Ducker Worldwide released a study for the aluminum industry. The report predicted that the light metal would dominate the North American light-truck segment in the next new-model development cycle. Some seven out of ten pickups in the next round were going to be AL-intensive, the study opined. A tidal wave appeared to be building. Five years later, not a single pickup has entered production with an AL-intensive cab and bed. While Ford changed over the body structures of its all-new 2018 large SUVs to aluminum, steel rules the midsized 2019 Ranger. In the enemy camps, the 2019 Chevrolet and GMC Silverado and Sierra 1500 and their brawnier HD cousins continue GM's mixed-materials strategy for pickups and SUVs. FCA's Ram and Jeep brands have stuck mainly with steel structures; the new JL-series Jeep Wrangler changed to aluminum doors (and hinges), hood, fenders and windshield frame, utilizing Alcoa's new C6A1 high-form alloy and its 6022 and A951 alloys. |
Thermal Technology System Acquires Heat Data to Count People | The Flowslide, developed by Royal Boon Edam Group Holding BV, is a combination of a revolving door and curved sliding panels, installed at Charles de Gaulle Airport, Paris. The Flowslide offers a complete physical separation between two crossing passenger flows on a single floor, allowing arriving and departing passengers to use a single door. The entry and exit points open and close alternatively within the curved wall of the revolving door, while keeping the passengers separate. As the two sets of passengers never come into contact with each other — despite using the same doorway — the Flowslide has enabled today's higher levels of security to be met, without the need to redevelop the terminal. |
Fabrication of Lightweight Armored Doors for HMMWVs | A document describes a concept for fabricating lightweight armored doors for the Army’s high-mobility multipurpose wheeled vehicles (HMMWVs). Essentially, the concept is to reinforce high-hard (HH) steel armored doors used on some HMMWVs with a laminated, woven, high-tensile-strength glassfiber/ polyester-matrix composite that has performed well as armor material in previous military applications. A fabrication procedure for implementing the concept, described in the document, can be summarized as follows: |
RoboSimian Software System from the DARPA Robotics Challenge Finals | A software architecture to allow semi-autonomous mobile manipulation of highly dexterous robots under degraded communications was developed to enable remote operation of a mobile manipulation robot as a first responder in a disaster-response scenario. The software architecture is structured to be adaptable at the lowest level and repeatable at the highest level. This architecture strikes the right balance between autonomy and supervision, and lets the robot excel in its capabilities (repeatability, strength, precision) and lets the operators excel at their capabilities (situational awareness, context, high-level reasoning). |
Airborne Hyperspectral Imaging System | A document discusses a hyperspectral imaging instrument package designed to be carried aboard a helicopter. It was developed to map the depths of Greenland’s supraglacial lakes. The instrument is capable of telescoping to twice its original length, allowing it to be retracted with the door closed during takeoff and landing, and manually extended in mid-flight. While extended, the instrument platform provides the attached hyperspectral imager a nadircentered and unobstructed view of the ground. |
Driving the CAR toward 54.5 mpg | Chances are good that if you're involved with automotive manufacturing strategy, you know Jay Baron. As President and CEO of the Center for Automotive Research (CAR) in Ann Arbor, Dr. Baron and his research teams are engaged with technology issues across a broad front, but even a brief conversation with him reveals his deep passion for plants, advanced processes and materials. Get him talking about lightweighting and he won't stop. The following exchange was taken from our July 2016 interview. At what point does the rising cost of vehicle compliance allow the over-the-horizon lightweighting technologies to enter production? |
Racing toward autonomous future, Cadillac and Mercedes-Benz reveal sultry, drive-it-yourself concept cars | In the autonomous-vehicle future, will the ultimate luxury become driving for yourself? That appears to be the suggestion from General Motors' Cadillac premium-car unit and Germany's Mercedes-Benz-both unveiled lusciously-proportioned concept cars at August's Monterey Car Week, where executives for both companies took pains to say the vehicles would be best enjoyed if, well, you actually drove them. |
Concurrent Development Environment Combining Mechanical and Control Systems for PBD and PSD | Due to advancements in multi-body dynamic analysis methodologies, virtual prototyping has been extended into various fields. Those methods can be applied to confirm behavior of the mechanical systems, to determine the necessary driving forces, and to predict the loads for each component of the system. Further, those methods combined with the control system have been applied to the controller tuning. Virtual evaluation environments have been developed, including the multi-body dynamic analysis, and have been applied to a power back door system (PBD) and a power sliding door system (PSD). As a result, development costs and timing have been reduced due to the utilization of these new evaluation methods. |
Simulation of Hot Stamping Process With Advanced Material Modeling | Advanced material modeling was conducted to describe the thermal-mechanical behavior of Boron Steel during hot stamping, a process in which blanks at 900 °C are formed and quenched between cold dies. Plastic deformation, thermal dilatation and phase transformation were incorporated in the constitutive model and a user-defined subroutine was developed to interface with LS-DYNA. Simulation was conducted on the hot stamping process of a door intrusion beam to gain insight into the physics of the process. Results showed significant influence of the thermal cycle on final product. It was also demonstrated that the program developed can be used as an early feasibility tool to determine baseline processing parameters and to detect potential defects in products without physical prototyping. |
Honeywell's Automotive Door Latch Design is Ideal for Corporate Latch Strategy | In response to consumer demand, automakers are adding more safety, security, and convenience features to vehicle access control systems. Also, in a continuing effort to be more profitable, automakers are reducing costs by outsourcing the design of systems/sub-systems/components, reducing their supply base, and minimizing part numbers by sharing components across several platforms. In an attempt to improve efficiency and productivity, many OEM's have adopted a “corporate latch” strategy, implementing the same latch across several manufacturing platforms and marketing divisions. Honeywell's revolutionary door latch design efficiently and cost effectively addresses vehicle OEMs' current and future requirements for performance and functionality. Utilizing this modular latch design allows OEMs to maximize design re-use, minimize tooling and development costs, hasten time to market, reduce program risk by utilizing pre-proven/validated designs and allows for upgrades in functionality through transparent design modifications that appear seamless within the application. Honeywell's Universal Latch provides all levels of functionality within the same packaging envelope and is the perfect enabler for a “corporate latch” strategy. Features and functions offered by the latch include: Central Locking Super Locking Selective Locking Electric Child Safety Power Door Releasing (Unlatching) Power Door Closing (Cinching) Most impressive is the fact that Honeywell's latch provides all of these features and functions with one small motor! Currently, competitive latch designs require the utilization of as many as three distinct motors to offer the same capabilities. This paper will present characterization data for the Universal Latch and compare its performance to competitive latches currently on vehicles. Furthermore, a feature value analysis will be provided to illustrate the benefits and savings the Honeywell design can provide to the entire access control system. After considering all of the facts presented in the paper, the reader will easily conclude that Honeywell's automotive door latch is smaller, lighter, quieter, faster, safer, and more cost effective than any automotive door latching/locking system on the market today. |
Validation of Non-linear Load-Controlled CAE Analyses of Oil-Canning Tests of Hood and Door Assemblies | Two finite element methodologies for simulating oil-canning tests on closure assemblies are presented. Reflecting the experimental conditions, the simulation methodologies assume load-controlled situations. One methodology uses an implicit finite-element code, namely ABAQUS®, and the other uses an explicit code, LS-DYNA®. It is shown that load-displacement behavior predicted by both the implicit and explicit codes agree well with experimental observations of oil-canning in a hood assembly. The small residual dent depth predictions are in line with experimental observations. The method using the implicit code, however, yields lower residual dent depth than that using the explicit code. Because the absolute values of the residual dent depths are small in the cases examined, more work is needed, using examples involving larger residual dent depth, to clearly distinguish between the two procedures. The analysis performed using the implicit code was significant more efficient (in terms of CPU hours) than the analysis done using the explicit code. The effects of forming strains are qualitatively examined. Forming induced thickness changes and plastic strains may not have a significant effect on oil-canning behavior, but may influence the residual dent depth strongly. Further reinforcement of the predictability of the methodology is demonstrated by an oil-canning simulation, using the implicit code, of a door assembly. |
Reliability Analysis of Systems with Nonlinear Limit States; Application to Automotive Door Closing Effort | In this paper, an efficient method for the reliability analysis of systems with nonlinear limit states is described. It combines optimization-based and simulation-based approaches and is particularly applicable for problems with highly nonlinear and implicit limit state functions, which are difficult to solve by conventional reliability methods. The proposed method consists of two major parts. In the first part, an optimization-based method is used to search for the most probable point (MPP) on the limit state. This is achieved by using adaptive response surface approximations. In the second part, a multi-modal adaptive importance sampling method is proposed using the MPP information from the first part as the starting point. The proposed method is applied to the reliability estimation of a vehicle body-door subsystem with respect to one of the important quality issues -- the door closing effort. The superiority of the proposed method, in terms of efficiency and accuracy, is demonstrated with a numerical example of highly nonlinear limit state problem, as well as an automotive door closing effort application. A generalized framework for reliability estimation is also proposed for problems with large numbers of random variables and complicated limit states. |
An Acoustical Imaging Processing for the Localization of Acoustic Sources inside a Vehicle: Method and Results for Tests on Road | The localization of acoustic sources inside a moving vehicle presents at least two main difficulties. The zone to be explored may be important (such as a door, a window, the toe board): the use of a sound intensity probe may take an expensive time for the context of a moving car. The other difficulty is the presence of a background noise, increasing with the car speed. These two difficulties may be overcome by the use of a robust acoustical imaging method, but the utilization of the system requires a few precautions for the implementation and for the interpretation of the acoustic images. The purpose of this paper is to present the chosen acoustical imaging processing, based on the beamforming method, and the procedure for the set-up and tests. This processing and the procedure are applied for experimental tests on the road and for different configurations: constant and decelerating speed. Acoustic images are presented for the case of sources on a passenger door. To improve the interpretation of the results, acoustic images are obtained for different tape configurations. This study shows a good robustness of the system and reliable results. In addition, the use of beamforming processing allows a reduced time for the set-up and for the measurements. |
Update on the Pininfarina “Turbulence Generation System” and its effects on the Car Aerodynamics and Aeroacoustics | The Turbulence Generation System designed and built in Pininfarina in the years 1999-2002, has been in operation since the beginning of 2003. The purpose of this device is to reproduce in the wind tunnel a flow condition more similar to that found by the cars on the road, in terms of velocity profile and turbulence intensity/length scale. The paper reports an updated description of its mechanical and aerodynamic characteristics. Then it reports examples of results measured on some cars, in the condition of turbulent flow, regarding: Aerodynamics - time averaged and time-dependent aero coefficients. Aeroacoustics - auto spectra and psycho acoustic parameters. Deformation/vibration of some car body parts (bonnet, doors). The differences between these results and those measured in standard low-turbulence conditions are presented. In addition a description of some techniques that are used for these time-dependent measurements is reported. |
Robust Design of Glass Run-Channel Seal | Glass run-channel seals are located between DIW (Door in White) and window glass. They are designed to allow window glass to move smoothly while other two major requirements are met; (1) Provide insulation to water leakage and noise, and (2) Stabilize the window glass during glass movement, door slamming and vehicle operation. For a robust glass guidance system, it is critical to minimize the variation of seal compression force. In addition, it is desired to maintain a low seal compression force, which meets the minimum requirement for insulating water leakage/noise and stabilizing the window glass, for enhancing the durability of glass guidance system. In this paper, a robust synthesis and design concepts on the glass run-channel seal is presented. The developed concept is demonstrated with test data. |
Ballistic Armoring of Passenger Cars on the Assembly Line Adds Quality and Passengers Comfort by Using Advanced and Light Weight Composite Materials | Light weight composite materials were developed to provide ballistic protection to automobiles against handgun bullets and to increase passengers comfort by the elimination of UV radiation and reduction of infra-red solar energy and interior noise, without compromising the driving performance of the car. Structural designs were incorporated to be able to armor the car on the assembly line with the added benefits of turn-over time, cost reduction and quality of the finished assembly. Weight reduction of armor materials have been achieved with CrystalGard® and YellowGard®. For windows and windshield, CrystalGard® 17mm provides better ballistic protection against NIJ Level IIIA with a 27% weight reduction than the standard 21mm glass solution by using a double layer of polycarbonate. SolarBlock® eliminates the UV radiation and reduces 95% of the infra-red solar energy for added passengers comfort. For the ceiling, doors, dashboard and trunk, YellowGard® provides more than 80% weight reduction when compared with steel and reduces interior noise. YellowGard® is a thermo-formable Kevlar® fabric coated with a thermoplastic resin developed for ease of installation during assembly, resistance to high temperature and humidity, and reduced delamination upon multiple bullet hits. Advantages of online assembly of ballistic protection include the reinforcement of the door latch and column areas for durability, the adjustment of the suspension system to the original driving performance changed due to the extra weight, and the installation of the Kevlar® panels to the frame and doors during the assembly of the car to avoid cutting and welding the frame structure. |
Swing Gate Development and Correlation Studies | This paper documents the Engineering design of the rear door system for Ford's South American New Vehicle. This Closure system represents a first for the Engineering Department of Ford branded products and it also offers many industry firsts for the customer. This paper is not a concise A-Z document on Closure design, but a detailed report listing the important factors to consider in a Swing Gate. |
A Low Cost, Lightweight Solution for Soft Seamless Airbag Systems | OEM and Tier One integrated suppliers are in constant search of cockpit system components that reduce the overall number of breaks across smooth surfaces. Traditionally, soft instrument panels with seamless airbag systems have required a separate airbag door and a tether or steel hinge mechanism to secure the door during a deployment. In addition, a scoring operation is necessary to ensure predictable, repeatable deployment characteristics. The purpose of this paper is to demonstrate the development and performance of a cost-effective soft instrument panel with a seamless airbag door that results in a reduced number of parts and a highly efficient manufacturing process. Because of the unique characteristics of this material, a cost-effective, lightweight solution to meet both styling requirements, as well as safety and performance criteria, can be attained. |
A Robust Procedure for Convergent Nonparametric Multivariate Metamodel Design | Fast-running metamodels (surrogates or response surfaces) that approximate multivariate input/output relationships of time-consuming CAE simulations facilitate effective design trade-offs and optimizations in the vehicle development process. While the cross-validated nonparametric metamodeling methods are capable of capturing the highly nonlinear input/output relationships, it is crucial to ensure the adequacy of the metamodel error estimates. Moreover, in order to circumvent the so-called curse-of-dimensionality in constructing any nonlinear multivariate metamodels from a realistic number of expensive simulations, it is necessary to reliably eliminate insignificant inputs and consequently reduce the metamodel prediction error by focusing on major contributors. This paper presents a robust data-adaptive nonparametric metamodeling procedure that combines a convergent variable screening process with a robust 2-level error assessment strategy to achieve better metamodel accuracy. A door seal gap example is presented to illustrate the effectiveness and efficiency of the procedure. |
Most Efficient Practice of Nearfield Measurements Inside a Car for Improving Acoustic Comfort | A continuously growing demand comes from the automotive industry for optimization of materials and sound insulating products implementation inside the car, so as to propose the best acoustic performance at reduced costs. The acoustical holography system dBVISION developed by 01dB Acoustics & Vibration provides part of the solution to such a demand. Its demonstrated capability of measuring the acoustic field inside a vehicle makes it an advanced tool for performing extensive studies of the acoustic transparency of car openings as well as wind tunnel measurements. The developed technique allows now for: 1- Detailed localization of noise sources or acoustic weakness points inside the vehicle, 2- Knowledge of the acoustic energy distribution on elementary surfaces (such as doors, windscreen, roof, sealing system, etc.), 3- Reconstruction of the energy radiated by elementary surfaces in order to predict the acoustic pressure at the driver's and passengers' ears, 4- Estimation of the acoustic incidence of local modifications on components of the tested car. Technical background, together with the main features of this acoustical imaging system, will be exposed and the presentation will illustrate with practical examples how this fits to the project engineer process considering new acoustically driven design methods for a complete understanding and control of all components and systems involved in the car performance. |
New-Generation PC/ABS Blends Help Meet Performance & Styling Requirements for Instrument Panel & Other Interior Components | New targets for auto-interior components seek to improve thermal aging, low-temperature impact strength, recyclability, emissions/odor, processing productivity, and costs in order to meet new requirements for a 10-year car and new standards for consumer comfort. The pace of these demands is creating opportunities for blending technologies in a range of applications, including instrument panels, glove-box doors, top covers, retainers, and trim. A new generation of high-performance polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) resins based on proprietary formulation technology has been specifically developed to meet these demands in IP and other interior applications. This paper will focus specifically on a high-impact grade for IPs (in both standard- and low-emission formulations). This new technology was benchmarked against several earlier generation products from the same family, a new high-flow version using the same technology, and several competitive offsets. The results show a new class of PC/ABS blends offering best-in-class thermal aging, hydrolytic stability, low-temperature impact strength, and - for select applications - excellent odor and emissions. This has been accomplished without sacrificing processing performance. In fact, the new grades offer a broader processing window and faster cycle times for increased productivity and lower part costs. |
Vehicular Electrical System Under Value Engineering Optic | This work shows the “Value Methodology” application looking for to identify new alternatives for vehicular electrical energy system (battery, starter, generator, coils etc.). These alternatives must be feasible to the nowadays automobiles system. The electrical system studied in this job points out to engine with its main assembled options, or accessories, as air-conditioning, hydraulic power system (HPS), electrical lifter window, a thief deterrents alarm, door lockers, etc. Heavy electrical traffic conditions, which demand more energy, representing a bigger electrical charge, are being considered in this analysis. The main focus of this job is to show the internal parts reduction, meaning a better final cost to suppliers and carmakers, and consequently a better vehicle performance. Improvements achieved through this study must be appreciated. |
Anti Pinch Protection for Power Operated Features | Due to the ever-increasing number of power operated features in today's motor vehicle – electric window openers with auto-up function, power doors and lift gates, to mention just a few – and, of course a desire for more and more luxury features, safety is becoming a more and more important topic. This discourse describes the technology and the application of tactile (pressure sensitive) anti pinch systems and a non-touch (presence sensing) system which works on the basis of ultrasound. These systems are designed to be used as an alternative or in addition to indirect, motor-controlled anti pinch systems. |
The History of Laminated Steel | This paper discusses the background and history of “laminated steel” (commonly called “noiseless steel” or MPM). It provides the early development, where it came from, and how it was introduced to North America as a new tool for engineering acoustical solutions. A progressive timeline shows laminated steel from its earliest inception in Europe to its current role in today’s global market. Case histories along with examples of successful applications detail its important contribution in advancing the technology for component damping. Many manufacturing sources as well as end users have been impacted over the decades since it was first introduced. Some of those companies will be noted. The background information for this paper is provided by many of the individuals who were involved in the very early stages of its introduction as well those who are currently working to utilize the technology of laminated steel. |
An Acoustic Target Setting and Cascading Method for Vehicle Trim Part Design | One of the major concerns in the vehicle trim part design is the acoustic targets, which are generally defined by absorption area or coefficients, and sound transmission loss (STL) or sound insertion loss (SIL). The breaking down of acoustic targets in vehicle design, which is generally referred to as cascading, is the process of determining the trim part acoustic targets so as to satisfy full vehicle acoustic performance. In many cases, these targets are determined by experience or by subjective evaluation. Simulation based transfer path analysis (TPA), which traces the energy flow from source, through a set of paths to a given receiver, provides a systematic solution of this problem. Guided by TPA, this paper proposes a component level target setting approach that is based on the statistical energy analysis (SEA), an efficient method for vehicle NVH analysis in mid and high frequencies. Using a validated SEA model of the vehicle under consideration, the contributions of common noise sources and paths, which are generally defined on parts of sheet-metal with trim parts attached, can be evaluated. This allows the prediction of interior noise level due to various possible sound packages. On the base of this, acoustic target setting of trim parts can be defined as the solution of a mathematical optimization problem. The targets such as SIL of trim parts at certain frequency range are taken as design variables, and the vehicle level performance like the sound pressure level (SPL) at driver’s ear is incorporated into constraint functions. This approach is versatile and is suitable for traditional ICE vehicles and modern EVs. It can be used on a vehicle prototype at the early stages for target cascading, or on an existing vehicle model for NVH improvement. Several cases and examples on this target setting method have been discussed in the paper. |
Inverse Vibration Problem Used for the Characterization of the Damping Added by a Trim Foam on a Plate | Many solutions exist to insure the NVH comfort of ground and air vehicles, like heavy mass (bitumen pads), viscoelastic treatments and absorbing foams. The trim foam appears as an alternative to heavy solutions. To know the potential of these foams, a study of their capacities to damp vibration is done. A system, composed of a suspended plate, with a foam on it, is characterized in different contact conditions at the foam-plate interface (glued or not) and with different foam type. An experimental test facility is developed to identify the global damping of the structure: a laser vibrometer measures the displacement field of the foam-plate structure, and then an inverse method is used to determine the structural parameters. By changing the contact at the interface, it is possible to identify the contribution of the friction forces to the global damping of the structure. Another type of damping is the viscoelastic damping due to the intrinsic characteristics of the trim foam. With the help of FEA, it is possible to understand the influence of the damping effect. The implemented inverse methods are the Force Analysis Technique (FAT) and the Corrected Force Analysis Technique (CFAT), originally used for effort identification on a system. They are based on the motion equation of the system and the displacement field. In this study, these methods allow to determine the structural parameters, such as the elastic storage modulus and the loss factor. |
Study of the Glass Contribution to the Interior Acoustics of a Car and Related Countermeasures | This paper shows that the combination of a glass and passive acoustic treatment manufacturers can bring different benefits and considerably improve the interior acoustics of a vehicle. Glazing contributes to the design of the vehicle in addition to its primary role, good visibility and safety. From an acoustic point of view, this brings a challenge for the interior comfort. Indeed, glazing has no absorption and classically has an acoustic insulation weakness around its coincident frequency. In most of the cases, these different aspects make glazing one of the main contributors to the sound pressure level in the passenger compartment, and the trend is not one of change. However, there are possible countermeasures. One of which is the use of laminated glazing with acoustic PVB. This solution allows reducing the loss of insulation performance at the coincidence frequency. The other is the usage of passive interior acoustic trims. When properly positioned and optimized, the latter can be very effective and can tackle the frequency range that poses a problem. Especially since some technologies allow, by their process, to choose between the improvements of insulation or absorption. The aim of this paper is to understand the impact of the glazing on the interior acoustic for tires excitations. For that study, a measurement campaign together with some simulations models (FE and SEA) have been carried over on a European C-segment vehicle. A ranking of the different contributions is proposed. Then, in a second part, the countermeasures to improve the interior sound pressure level by adding optimized glazing and sound packages are presented. |
Using Statistical Energy Analysis to Optimize Sound Package for Realistic Load Cases | The statistical energy analysis (SEA) is widely used to support the development of the sound package of cars. This paper will present the preparation of a model designed to investigate the sound package of the new Audi A3 and associated correlation against measurements. Special care was given during the creation of the model on the representation of the structure to enable the analysis of structure borne energy flow on top of the classical airborne analysis usually done with SEA. The sound package was also detailed in the model to allow further optimization and analysis of its performance. Two real life load cases will be presented to validate the model with measurements. First, the dominating powertrain and a second load case with dominating rolling noise. An analysis of the contribution of the different source components and a way to diagnose the weak paths of the vehicle will be presented. The focus of this investigation is the application of optimally adjusted treatment. |
Extended Solution of a Trimmed Vehicle Finite Element Model in the Mid-Frequency Range | The acoustic trim components play an essential role in Noise, Vibration and Harshness (NVH) behavior by reducing both the structure borne and airborne noise transmission while participating to the absorption inside the car and the damping of the structure. Over the past years, the interest for numerical solutions to predict the noise including trim effects in mid-frequency range has grown, leading to the development of dedicated CAE tools. Finite Element (FE) models are an established method to analyze NVH problems. FE analysis is a robust and versatile approach that can be used for a large number of applications, like noise prediction inside and outside the vehicle due to different sources or pass-by noise simulation. Typically, results feature high quality correlations. However, future challenges, such as electric motorized vehicles, with changes of the motor noise spectrum, will require an extension of the existing approaches. In this paper, the vibro-acoustic frequency response of an existing MSC Nastran FE model is extended using the Actran Statistical Energy Analysis (SEA) approach, Virtual SEA. In Virtual SEA, the necessary information required to build the SEA system is extracted from the FE models. The fluid-structure Coupling Loss Factors (CLF) are computed through the Statistical modal Energy distribution Analysis (SmEdA) method. This method is a suitable candidate to account for acoustic trim effects based on analytical approach. The case studied consists of a trimmed body car model transfer function calculation. The result of the case study is an extensive correlation study containing measured and simulated transfer functions in low and mid-frequency range. Simulation results are derived from two approaches, FE method and Virtual SEA method. |
Linking Body-In-White and Trimmed Body Dynamic Characteristics in View of Body-In-White Mode Shape Target Setting | Target setting at Body-In-White (BIW) level is typically done for natural frequencies of global modes. Target values are commonly set based on experience or from benchmark studies with competitor vehicles. A link between these targets at BIW level and the vibro-acoustic targets at Trimmed Body (TB) level is not yet well established. Therefore, it is not always guaranteed that the TB targets will be met when the targets at BIW level are reached. Also, the other way around, not reaching a frequency target for a certain BIW mode does not necessarily imply that TB targets will not be met. Hence, there is a clear need for getting more insights in the relation between BIW dynamic properties and TB vibration behavior. In this paper techniques will be presented that establish the link between BIW and TB dynamic behavior. In addition, a large DOE campaign has been carried out to further link these dynamic properties to specific areas in the body design. Key elements in this paper are the introduction of a novel modal reduction method to extract the essential information from a large set of TB modes and a subspace correlation technique to link the critical TB modes with the global BIW modes. The results obtained with this study demonstrate that it is not enough to consider only natural frequencies of the BIW modes as a target but that their shape must be taken into account as well. |
Evaluation of Laminated Side Glazing and Curtain Airbags for Occupant Containment in Rollover | By their nature as chaotic, high-energy events, rollovers pose a high risk of injury to unrestrained occupants, in particular through exposure to projected perimeter contact and ejection. While seat belts have long been accepted as a highly effective means of retaining and restraining occupants in rollover crashes, it has been suggested that technologies such as laminated safety glazing or rollover-activated side curtain airbags (RSCAs) could alternatively provide effective occupant containment. In this study, a full-scale dolly rollover crash test was performed to assess the occupant containment capability of laminated side glazing and RSCAs in a high-severity rollover event. This allowed for the analysis of unrestrained occupant kinematics during interaction with laminated side glazing and RSCAs and evaluation of failure modes and limitations of laminated glazing and RSCAs as they relate to partial and complete ejection of unrestrained occupants. The dolly rollover was performed with a 2010 Chevrolet Express at a nominal speed of 43 mph, with unbelted anthropomorphic test devices (ATDs) positioned in the driver, right front passenger, and designated third, fourth, and fifth row seating positions. Vehicle dynamics and occupant kinematics were analyzed through evaluation of vehicle instrumentation, on-board and off-board real-time and high-speed video, post-test survey of the debris field, and post-test inspection of the vehicle and ATDs. Neither laminated side glazing nor RSCAs prevented complete or partial ejection of the ATDs. Two of the ATDs were completely ejected during the dolly rollover and six other ATDs were partially ejected. Fracture and peripheral separation of laminated side glazing was observed in association with ground contact, vehicle deformation, and ATD loading. Ejection in seating positions adjacent to RSCAs was observed in association with ATD loading and out-of-position interaction with the airbags. The findings of the present study demonstrate that laminated side glazing and rollover-activated side curtain airbags are not substitutes for proper seat belt use. |
Enhanced Windshield CAE NVH Model for Interior Cabin Noise | This paper describes a reliable CAE methodology to model the linear vibratory behavior of windshields. The windshield is an important component in vehicle NVH performance. It plays an integral role in interior cabin noise. The windshield acts as a large panel typically oriented near vertical at the front of vehicle’s acoustic cavity, hence modeling it accurately is essential to have a reliable prediction of cabin interior noise. The challenge to model the windshield accurately rises from the structural composition of different types of windshields. For automotive applications, windshields come in several structural compositions today. In this paper, we will discuss two types of windshield glass used primarily by automotive manufacturers. First type is the typical laminated glass with polyvinyl butyral (PVB) layer and second type is the acoustic glass with PVB and vinyl layers. Acoustic glass improves acoustic characteristics of the glass in a frequency range of ~ 1200 Hz to ~4000 Hz. Low frequency interior cabin noise studied with Finite Element Analysis (FEA) is typically below 400 Hz. The acoustic glass doesn’t provide substantial benefits in this range and in many cases we see an adverse contribution at lower frequencies since the acoustic windshield tend to be softer. In this paper, frequency dependency of PVB layer and acoustic vinyl layers are investigated. Multiple modeling techniques for windshield are demonstrated and the results are compared to physical tests. Finally an enhanced windshield modeling technique for low frequency interior cabin noise is proposed. |
Virtual Verification of Light Reflection for Cluster and Side Mirror in Real Time Scenario | In the very automobile world trends are changing at a very fast pace, due to continuous expectation changes by user and new regulatory requirements demand from government authorities with a very stringent timeline. In the current scenario, manufacturer has to wait for mock up for concept selection and physical proto build to conclude open points of design verification. This complete process takes more than a year to enhance the design maturity for further builds. In VECV we have created Cluster design standard to meet different level of cluster illumination & reflection at virtual level. We are defining the cluster light illumination based on our rigorous study on cluster reflection impact on side glass, windscreen and mirror. Accordingly we have packaged our mirror to minimize the impact of cluster reflection on mirror visibility. With the help of virtual verification of cluster and Side mirror inter co-relation of packaging, we significantly reduced the time loss and save huge cost required for developing proto build. Different options of mirror and cluster can be verified in quick session. With the help of virtual verification of mirror and cluster we are able to meet different regulatory compliances for light illumination without building a single proto build. |
Road Noise Prediction Assessment Using CAE Instead of Costly and Time Consuming Physical Tests | Virtual Product Development (VPD) with a vision to eliminate prototype testing is the recent trend in the automotive industry. Reducing the total vehicle development period with optimized output has been the major advantage of this new trend, fueled by increasing competition and shorter product life cycle. In this regard, Computer Aided Engineering (CAE) has taken a more significant role than ever in the vehicle development programs. Prediction of road noise in passenger cars is one of the important attributes to NVH (Noise Vibration Harness) Simulations. In the present work, CAE - NVH simulation of road noise is carried out on the finite element model of the vehicle, eliminating the costly and laborious test procedures & the process of awaiting information from various departments. One of the major challenges in these simulations are generating the load inputs for the structure-borne road noise in a cost and time saving method with accuracy. An alternative to the existing MBD/Test input method is explored in the present work. Enforced displacements in the frequency domain are generated using ISO 8608 standard road profiles and are used as input to the vehicle system. Time and cost of the total procedure is reduced drastically by this procedure with more than acceptable accuracy & correlation. The results are validated with the available test data & existing MBD CAE input methods of predicting the interior noise of the passenger cars. |
Prediction of Aeroacoustical Interior Noise of a Car, Part-2 Structural and Acoustical Analyses | One-way coupled simulation method that combines CFD, structural and acoustical analyses has been developed aiming at predicting the aeroacoustical interior noise for a wide range of frequency between 100 Hz and 4 kHz. Statistical Energy Analysis (SEA) has been widely used for evaluating transmission of sound through a car body and resulting interior sound field. Instead of SEA, we directly computed vibration and sound in order to investigate and understand propagation paths of vibration in a car body and sound fields. As the first step of this approach, we predicted the pressure fluctuations on the external surfaces of a car by computing the unsteady flow around the car. Secondly, the predicted pressure fluctuations were fed to the subsequent structural vibration analysis to predict vibration accelerations on the internal surfaces of the car. Finally, an acoustical analysis was performed to predict sound fields in the cabin by using particle velocities of sound on the interior surfaces of the car, predicted by the structural analysis. To transfer predicted surface data, such as pressure fluctuations, vibration accelerations and particle velocities of sound, from one simulation to another, we adopted a parallel coupling tool. As the second part of our research, this paper presents results of the structural vibration analysis and that of the acoustical analysis, together with those measured by wind tunnel tests. In our research, a light automobile, for which all the interior components were removed and the underfloor shape was simplified, was employed for a case study. The wind tunnel tests were performed with a freestream velocity of 100 km/h. Both the predicted interior surface accelerations and interior noise level agreed well with the measured equivalents up to 2 kHz. |
Aero-Vibro-Acoustic Wind Noise-Simulation Based on the Flow around a Car | Aim of the ongoing development of passenger cars is to predict the interior acoustics early in the development process. A significant noise component results from the flow phenomena in the area of the side window. Wind noise is a physical problem that involves the three complicated aspects each governed by different physics: The complex turbulent flow field in the wake of the a-pillar and the side mirror is characterized by velocity and pressure fluctuations. The flow field generates sound which is transmitted into the passenger cabin. In addition to that, it excites the structure, resulting in a radiation of structure-borne noise into the interior of the car. Therefore, the sound generation is governed by fluid dynamics of the air flow. The sound transmission through the structure due to vibrations is determined by structural mechanics of the body structure. The sound propagation inside the cabin is influenced by interior room acoustics. In the present work, different CFD simulations of the exterior flow were conducted to investigate the sound generation due to external air turbulence. For this purpose, a simplified model of an automobile was used. Additionally vibro and aeroacoustic simulations were conducted to solve the other two parts of the problem and to gain insight into the sound transmission into the passenger cabin. |
The Application of Superelement Modeling Method in Vehicle Body Dynamics Simulation | In this paper, we propose a method of dynamics simulation and analysis based on superelement modeling to increase the efficiency of dynamics simulation for vehicle body structure. Using this method, a certain multi-purpose vehicle (MPV) body structure was divided into several subsystems, and the modal parameters and frequency response functions of which were obtained through superelement condensation, residual structure solution, and superelement data restoration. The study shows that compared to the traditional modeling method, the computational time for vehicle body modal analysis can be reduced by 6.9% without reducing accuracy; for the purpose of structural optimization, the computational time can be reduced by 87.7% for frequency response analyses of optimizations; consistency between simulation and testing can be achieved on peak frequency points and general trends for the vibration frequency responses of interior front row floors under accelerating conditions. The results indicate that the method has good engineering value, and is suitable for the study of dynamics problems of vehicle bodies. |
In-Cabin Aeroacoustics of a Full-Scale Transport Truck | The noise generated by the flow of air past a transport truck is a key design factor for the manufacturers of these vehicles as the sound levels in the cabin are a significant component of driver comfort. This paper describes a collaboration between Volvo GTT and the National Research Council Canada to measure the in-cabin aeroacoustics of a full-scale cab-over tractor in the NRC 9 m Wind Tunnel. Acoustic instrumentation was installed inside the tractor to record cabin noise levels and externally to acquire tunnel background noise data. Using a microphone mounted on the driver’s-side tunnel wall as a reference to remove variations in background noise levels between data points, differences in cabin noise levels were able to be detected when comparing the tractor with different configurations. The good repeatability of the data allowed for differences of as little as 0.5 dB to be measured. A procedure to estimate the transfer function from the wall reference microphone to the cabin microphones was implemented which, though of limited success, provided insights into the acoustic environment of the test section. The main conclusion of this project is that aeroacoustic measurements can be carried out in the NRC 9 m Wind Tunnel in conjunction with an aerodynamic entry for full-scale transport trucks. |
Vibration Test Machine and Operation Procedure | This SAE Recommended Practice provides procedures, and information to conduct vibration (impact) tests on lighting devices and their components as well as other safety equipment used on vehicles. |
Collision Deformation Classification | The purpose and scope of this SAE Recommended Practice is to provide a basis for classification of the extent of vehicle deformation caused by vehicle accidents on the highway. It is necessary to classify collision contact deformation (as opposed to induced deformation) so that the accident deformation may be segregated into rather narrow limits. Studies of collision deformation can then be performed on one or many data banks with assurance that the data under study are of essentially the same type.1 The seven-character code is also an expression useful to persons engaged in automobile safety, to describe appropriately a field-damaged vehicle with conciseness in their oral and written communications. Although this classification system was established primarily for use by professional teams investigating accidents in depth, other groups may also find it useful. The classification system consists of seven characters, three numeric, and four alphameric, arranged in a specific order. The characters describe the deformation detail concerning the direction, location, size of the area, and extent which, combined together, form a descriptive composite of the vehicle damage. The individual character positions are referred to by column number for identification and computer storage compatibility as illustrated in Figure 1. The definition of each classification is provided in subsequent sections. An Appendix is also provided to assist in application and interpretation. |
Integrated Mechatronic Design and Simulation of a Door Soft Close Automatic with Behavioral Models of Smart Power ICs | Based on the example of a door soft close automatic the potential of integrated system simulation in the automotive systems development is demonstrated. The modeling approach is covering several physical domains like mechanics, electromagnetics and semiconductor physics. With adequate simplifying methods a time efficient model is generated, which allows system optimization in the concept phase. Time consuming redesigns can thus be minimized. |
Highly Efficient Robust Optimization Design Method for Improving Automotive Acoustic Package Performance | To consider the influence of uncertainty in the design process of automotive acoustic packages, the robustness of the acoustic packaging system performance must be improved, and the low-efficiency problem of the two-layer nesting robustness optimization model must be solved. This article proposes a highly efficient robustness optimization design method for improving the performance of the automotive acoustic package. First, the full vehicle model was established based on the statistical energy analysis method, and the accuracy of the model was verified through acoustic transfer function (ATF) testing. The parameters affecting the sound absorption and insulation performance of the key acoustic packaging parts were selected as the uncertain parameters, and their sensitivity was analyzed. The possibility degree method of interval numbers was introduced to convert the two-layer nesting robustness optimization model to a single-layer optimization model, and the efficient robust design of the automotive acoustic packaging was realized. The acoustic packaging parts of a sport utility vehicle (SUV) were analyzed and optimized using the proposed efficient and robust optimization method. After optimization, the total mass of the acoustic packaging parts decreased by 10.8%, the radius of the perturbation interval of the interior noise decreased by more than 25% compared with the initial value, and the robustness of the system greatly improved. |
Strat-X | Experiments in space can be expensive and infrequent, but Earth’s upper atmosphere is accessible via large scientific balloons, and can be used to address many of the same fundamental questions. Scientific balloons are made of a thin polyethylene film inflated with helium, and can carry atmospheric sampling instruments on a gondola suspended underneath the balloon that eventually is returned to the surface on a parachute. For stratospheric flights between 30 and 40 km above sea level, balloons typically reach the float altitude 2-3 hours after launch, and travel in the direction of the prevailing winds. |
Access System Senses Finger Vibrations to Verify Users | The market for smart security access systems is expected to grow rapidly, reaching nearly $10 billion by 2022. Today's smart security access systems mainly rely on traditional techniques that use intercoms, cameras, cards, or fingerprints to authenticate users. These systems require costly equipment, complex hardware installation, and diverse maintenance needs. |
Smart Fabric Stores Information Without Electronics | Conductive thread — embroidery thread that can carry an electrical current — often is combined with other types of electronics to create fabric that lights up or communicates. This thread also has magnetic properties that can be manipulated to store either digital data, or visual information like letters or numbers. This data can be read by a magnetometer, an inexpensive instrument that measures the direction and strength of magnetic fields, and is embedded in most smartphones. |
Level Zero HERO | Wrangler Rubicon has 10.9 in of ground clearance and industry-leading approach, departure and breakaway angles to uphold its heritage for off-road dominance. Okay, maybe the 2018 Jeep Wrangler could be considered SAE autonomy Level 0.5- after all, the all-new version of Jeep's icon does offer a couple of automated driver-assist features. If you must. But apart from that concession to contemporary development trends, the new Wrangler is unabashed in its dedication to the analog driving experience: It's updated, upgraded and more refined, but it's unquestionably the most elemental new vehicle of 2018. After all, name another all-new model that pridefully comes to market at the dawn of the automated-driving epoch with solid front and rear axles, a windshield that folds down and doors that come off. |
Delayed Latching Mechanism | Uncontrolled and rapid movement of equipment and people through security gates has been a major problem for security personnel. In situations pertaining to facility security, it is desirable to delay the passage of a person through an entrance or an exit for a small interval of time, such as several seconds or up to a minute. Often, authorization to proceed is provided by an electronic signal to unlock the passageway. Such electronic signals are initiated remotely by a person in authority, such as a guard in a control room viewing a security camera, or a person who verifies the identity of the requester through a two-way audio connection. |
42V PowerNet in Door Applications | This article describes the effects of a future 42V automotive electrical system on the vehicle electronics, focusing mainly on the consequences for power semiconductors and their associated technologies. Taking the example of a door module, it then shows how existing 14V loads can be operated on the 42V PowerNet and what advantages result for operation of adjusted 42V loads. The following different problem-solving approaches are presented for typical loads such as power windows, electrically positioned and heated outside mirrors, and central locking: Power windows: A test motor specially developed for the 42V supply is continuously operated directly from the electrical system using suitable power semiconductors. Central locking: A conventional 14V motor is operated at 42V, its operating point being set using pulse width modulation (PWM). Remaining door module: Smaller 14V mirror motors and the control electronics are supplied from a second 14V system. This second supply can be taken from the current 14V system or generated locally by appropriate switching regulators, or even by a central DC/DC converter from 42V. |
Assessment of the Vehicle's Interior Wind Noise Due to Measurement of Exterior Flow Quantities | The optimal styling of the exterior surface of a vehicle and its suspension system have a direct impact on interior wind noise. Both are determined in early project phases when no hardware prototype is available. Turbulent flows produce both external pressure fluctuations at the vehicle shell, known as hydrodynamic excitation, and sound waves, known as acoustic excitation. Hydrodynamic and acoustic sound sources are evaluated separately and relative to each other in the frequency domain in order to perform evaluations of different body shapes. The technical aim of the presented work is to investigate how acoustic quantities measured at the outside of a vehicle can be used to assess the influence of styling modifications to interior sound pressure level. The methodology is required to be capable of being integrated into the serial development process and therefore be quickly applicable. MAGNA STEYR Engineering has conducted extensive research to develop a method to ensure the best option is selected in the early project stages. |
Performance Test for Windshield Defrosting Systems for Off-Road, Self-Propelled Work Machines | This SAE Standard establishes uniform test procedures for the defrosting systems of off-road, self-propelled work machines used in construction, general purpose industrial, agricultural, and forestry machinery as referenced in table one of this document. It includes tests that can be conducted with uniform test equipment in commercially available laboratory facilities, as well as in an appropriate outdoor environment. |
Windshield with Enhanced Infrared Reflectivity Enables Packaging a Driver Monitor System in a Head-Up Display | Integration of a driver monitor system (DMS) in a head-up display (HUD) gives the monitor camera a continuous view of the driver’s face, since the driver always faces the road ahead. However, with both infrared (IR) illuminator and IR camera packaged in the HUD, reflectivity of the windshield is important at IR wavelengths used by the camera. Not only is windshield IR reflectivity important for a clear camera image of the driver’s face, but increasing windshield reflectivity also decreases the effect of ambient sunlight on the camera image of the driver’s face. We describe a method to measure windshield reflectivity, both for the 940 nm band used by a DMS, and for visible light for the HUD. The measurement method uses a fiber-optic spectrometer, two collimating lenses, and a method to compensate for sample tilt. The lenses are mounted on a stage that adjusts the height above the sample. As an example, this method was used to characterize an IR reflecting windshield, prepared for a prototype automotive HUD. At 940 nm, and 45° angle of incidence, the measured reflectivity is > 85% for unpolarized incident light. For visible light at 550 nm, and 62° angle of incidence, the measured reflectivity is 13.9% for both an IR reflecting windshield and for a reference windshield, for unpolarized incident light. The prototype windshield gives a good reflected image for the DMS IR camera and a good HUD image as seen by the driver. The method used to prepare this prototype windshield is suitable for high-volume production. |
Passenger Car Side Door Latch Systems | This SAE Recommended Practice establishes minimum performance requirements and test procedures for evaluating and testing passenger car side door latch systems. It is limited to tests that can be conducted on uniform test fixtures and equipment in commercially available laboratory test facilities. The test procedures and minimum performance requirements outlined in this document are based on currently available engineering data. It is intended that all portions of the document will be periodically reviewed and revised, as additional knowledge regarding vehicle latch performance under impact conditions is developed. |
Access Systems for Off-Road Machines | Minimum criteria are provided for steps, stairways, ladders, walkways, platforms, handrails, handholds, guardrails, and entrance openings which permit ingress to and egress from operator, inspection, maintenance or service platforms on off-road work machines parked in accordance with the manufacturer's instructions. |
Sound Measurement—Off-Road Self-Propelled Work Machines Operator-Work Cycle | This SAE Standard sets forth the procedures to be used in measuring sound levels and determining the time weighted sound level at the operator's station(s) of specified off-road self-propelled work machines. This document applies to the following work machines which have operator stations as specified in SAE J1116: • Crawler Loader • Grader • Log Skidder • Wheel Loader • Crawler Tractor with Dozer • Pipelayer • Dumper • Wheel Tractor with Dozer • Trencher • Tractor Scraper • Backhoe • Sweeper • Roller/Compactor • Hydraulic Excavator • Pad Foot Wheel Compactor with Dozer • Excavator and Wheel Feller-Buncher The instrumentation requirements and specific work cycles for these machines are described. The method used to calculate the time weighted average sound level at the operator station(s) is specified for Leq(5), or optional exchange rates, during continuous operation in a work cycle representing continuous medium to heavy work. The work cycles provide a repeatable reproduceable means to uniformly measure working machines against a “yard stick. A method to relate the time weighted average sound level at the operator station(s) to estimate operator sound exposure with part load work, supervision, and rest breaks is also provided. |
Integrated CAE Methods for Perceived Quality Assurance of Vehicle Outer Panels | Oil canning and initial stiffness of the automotive roofs and panels are considered to be sensitive customer ‘perceived quality’ issues. In an effort to develop more accurate objective requirements, respective simulation methods are continuously being developed throughout automotive industries. This paper discusses a latest development on oil canning predictions using LS-DYNA® Implicit, including BNDOUT request, MORTAR contact option and with the stamping process involved, which resulted in excellent correlations especially when it comes to measurements at immediate locations to the feature lines of the vehicle outer panels. Furthermore, in pursuit of light-weighting vehicles with thinner roofs, a new CAE method was recently developed to simulate severe noise conditions exhibited on some of developmental properties while going through a car wash. This paper introduces such a method to discuss Fluid Structure Interaction (FSI) approach using an Arbitrary Lagrangian Eulerian (ALE) formulation in LS-DYNA® for vehicle roof car wash boom noise prediction. This CAE method was developed to simulate force behavior from airflow as the car wash air blowers are expelling high speed air at the vehicle roofs during car wash. LS-DYNA® was proven an appropriate tool to precisely simulate popping noises by creating instantaneous local instabilities - recoverable/non-recoverable - and continuous fluttering of the roof. This paper additionally briefs the history of oil canning CAE method developments from inaccurate hand push evaluation to approaches using MSC Nastran® to Abaqus/Standard®, and then the final evolution to LS-DYNA® Implicit to provide optimized vehicle solutions. |
New Trivial Principal Component Method: System Modeling | Principal Component Analysis (PCA) is a powerful statistical technique used for understanding variation in the observed data and decomposing variation along eigenvectors, known as Principal Components (PCs), by considering variance-covariance structure of the data. Traditionally, eigenvectors that contain most of the variation or information are selected to reduce variables in data reduction. Eigenvalues of low magnitude are considered to be noise and often, not included in the dataset to accomplish dimensional reduction. Analogously, in Principal Component Regression (PCR), PCs with large eigenvalues are selected without considering correlation between the source variables and the dependent response. This inherent deficiency may lead to inferior regression modelling. While addressing this issue, an alternative to PCR is developed and proposed in this paper. In this method, a principal component associated with zero eigenvalue is termed Trivial Principal Component (TPC). This novel method involves the formulation of the TPC by including output response in the covariance matrix and then, extracting the Eigen-pairs. The TPC contains the relationship between the dependent response and the source variables and is used for extracting linear coefficients. In other words, the TPC is formulated to determine sensitivities taking into account correlation relationship between the output response and source variables. Example problems are presented to illustrate methodology and accuracy of the TPC method. Results of this method are applied on a practical production problem to make manufacturing changes for improved quality. |
Experimental Studies on Different Actuator-Sensor Configurations of Active Control Systems for the Reduction of Noise and Vibration in Vehicles | Current developments in the automotive industry such as downsizing, the use of cylinder deactivation and consistent lightweight construction increasingly enable the application of active control systems for the further reduction of noise and vibration in vehicles. In the past few years, different configurations of actuators and sensors for the realization of an active control system have been investigated and evaluated experimentally. Active engine mounts, inertial mass actuators and structural integrated actuators can be used to reduce either structural vibrations or the interior noise level. As a result, a variety of different topology concepts for the realization of an active control system arises. These can be divided into an active vibration control scenario, the direct influence of the sound field with loudspeakers or the application of structural actuators for the reduction of the interior sound pressure. In the latter case, microphones are used as error sensors for the active control system. With regard to the selection of a suitable actuator-sensor configuration special attention is required as several transfer paths for airborne and structure borne noise are existing. Furthermore, the attainable bandwidth of the applied control systems topology depends on the selection of a suitable actuator-sensor configuration and an adequate number of actuators and sensors in order to enable global control and to avoid local effects. This paper summarizes and compares different actuator-sensor configurations for the control of noise and vibration in vehicles. Beside the control performance, it highlights the electrical power requirements for the control of engine induced interior noise as a function of the selected actuator-sensor configuration. |
Development of New Test Method for Compression Load and Permanent Deformation of Weather Strip | The automotive weather strip performs functions of isolating water, dust, noise and vibration from the outside. To achieve good sealing performance, weather strip should be designed to have the high contact force and wide contact area. The compression load of weather strip is important for closing force in initial quality, but the permanent deformation is used to predict influx of wind noise over long periods of time. To check these accurately and easily, a new test method is demanded. So this paper introduces a new test method to predict the compression load and permanent deformation of 3D full vehicle by using ABAQUS. Uniaxial tension and creep tests were conducted to obtain the material data. The lab test for the permanent deformation was accelerated at high temperature during shorter time of 300 hours. Herein Proposed test method can provide accurate prediction under the different loading conditions and section shapes, and will also save time and cost. |
Ford GT Body Engineering - Delivering the Designer's Vision in 24 Months | The objective was to engineer a world-class supercar body that faithfully reproduces the 2002 Concept and pays homage to the 1960's road racer. The car had to be designed, developed and launched in 24 months, while meeting tough requirements for function, weight, occupant package and aerodynamics. Challenging features such as the cantilevered door, “clamshell” engine decklid and a deeply contoured hood were to be included. This paper will discuss how a dedicated team of enthusiasts can have a flexible approach to the engineering process, material selections and manufacturing processes to achieve the designer's vision in 24 months (Figure 1). |
Intrusion Resistance of Safety Glazing Systems for Road Vehicles | This SAE Recommended Practice specifies an intrusion resistance test method for glazing systems installed in motor vehicles. Intrusion resistance performance is determined not solely by the glazing but also by the glazing attachment to the vehicle and by the vehicle structure. Therefore, the glazing/ attachment/vehicle structure must be tested as a single unit. This test determines intrusion resistance only. The test applies to those materials that meet the requirements for use as safety glazing materials as specified in Safety Standard ANSI/SAE Z26.1 or other applicable standards. The test applies to all installation locations. |
Noise and Vibration Prediction and Validation for Off-Highway Vehicle Cab Using Hybrid FE-SEA Methodology | Operator noise is an important aspect for noise and vibration of off-highway vehicles and a quieter cab is critical for the operator comfort. The noise level inside the cab is influenced by structural and acoustic transfer paths. In this paper, we used hybrid FE-SEA approach to consider both structural and acoustic transfer path as FEM and SEA methods individually face limitations in high and low frequencies respectively. A hybrid FE-SEA cab model was built to predict the structural and acoustic transfer functions. The analysis model was built with the systematic approach validated at each step with the laboratory test results. For the structural transfer function, structural excitations were applied at four cab mount locations and accelerations at various locations on the cab were validated. For the acoustic transfer function, the cab was excited with the volume velocity source inside the cab and sound power output of various panels were calculated and compared to the test results. Good agreement was observed between the simulation and the test results for both structural transfer path and acoustic transfer path. |
Measurement and Presentation of Truck Ride Vibrations | There are two ways to assess the characteristics of ride vibrations of a vehicle during its operation. Subjective evaluation and objective measurement. Subjective assessments of the ride vibrations experienced by drivers during ride evaluations are generally performed by a panel of drivers and/or passengers who are instructed to operate or ride a group of vehicles in a predetermined manner in order to subjectively assess the levels and characteristics of ride vibrations. Figures 6A through 6C show examples of subjective evaluation forms presently in use. The disadvantages of the subjective method include need for careful experimental design, need for statistically unbiased samples, complexity of human perceptions of vibrations, and difficulty in comparing qualitative data of vehicles evaluated at different times and/or by different groups of people. Often ride characterization is not an easy task using only qualitative or descriptive terms. Therefore, it is necessary and desirable to develop objective techniques to enable ride engineers and others to measure ride vibrations during ride assessment in a quantitative manner. This recommendation details a uniform method for the measurement of ride vibrations of all Class 7 and 8 commercial vehicles, including both combination vehicles and straight trucks. Vibrations are to be measured utilizing cab and seat-pad mounted accelerometers in vertical (z axis) and fore/aft (x axis) directions. The measurement in lateral direction (y axis) is optional as these vibrations from a ride assessment standpoint are seldom significant in commercial vehicles. Several currently utilized methods of displaying, analyzing, and combining the measured accelerations are presented. This recommendation does not make any statements concerning how well any of the objective ride measures will correlate to subjective evaluations of ride, nor does it deal with any limits or establish any desirable values for acceptable ride. It is recognized that objective ride evaluation methods have some disadvantages due to the complexities of these measures, sophistication of instrumentation and analysis techniques, etc. Therefore, it is recommended that technically trained personnel conduct the objective tests and analyze the data. |
A Strategy for Developing an Inclusive Load Case for Verification of Squeak and Rattle Noises in the Car Cabin | Squeak and rattle (S&R) are nonstationary annoying and unwanted noises in the car cabin that result in considerable warranty costs for car manufacturers. Introduction of cars with remarkably lower background noises and the recent emphasis on electrification and autonomous driving further stress the need for producing squeak- and rattle-free cars. Automotive manufacturers use several road disturbances for physical evaluation and verification of S&R. The excitation signals collected from these road profiles are also employed in subsystem shaker rigs and virtual simulations that are gradually replacing physical complete vehicle test and verification. Considering the need for a shorter lead time and the introduction of optimisation loops, it is necessary to have efficient and inclusive excitation load cases for robust S&R evaluation. In this study, a method is proposed to truncate and identify the important parts of the different road profiles that are often used for S&R physical verification and then merge them to develop one representative excitation load case. The criteria for signal truncation were based on the S&R risk and severity metrics calculated from the vibration response at the critical interfaces for S&R. the method was used in a case study involving the instrument panel of a passenger car. Results of the virtual simulation and the rig tests were compared with the complete vehicle test. The proposed synthesised signal generation strategy was validated by physical testing through measuring vibration signals. The results supported the possibility of replacing multiple S&R excitation signals with one single representative inclusive signal, while the quality of S&R risk prediction from the system response was maintained. The outcome of this work can lead to a more efficient physical and virtual S&R verification in the development process of passenger cars. |
Coupled-SEA Application to Full Vehicle with Numerical Turbulent Model Excitation for Wind Noise Improvement | Wind noise is becoming a higher priority in the automotive industry. Several past studies investigated whether Statistical Energy Analysis (SEA) can be utilized to predict wind noise. Because wind noise analysis requires both radiation and transmission modeling in a wide frequency band, turbulent-structure-acoustic-coupled-SEA is being used. Past research investigated coupled-SEA’s benefit, but the model is usually simplified to enable easier consideration on the input side. However, the vehicle is composed of multiple interior parts and possible interior countermeasure consideration is needed. To enable this, at first, a more detailed coupled-SEA model is built from the acoustic-SEA model which has a larger number of degrees of freedom for the interior side. Then, the model is modified to account for sound radiation effects induced by turbulent and acoustic pressure. Another concern about utilizing the coupled-SEA to wind noise development is the estimation of the turbulent and acoustic input. Several options are available for identifying the input, such as on-road data measurement, CFD simulation, and numerical turbulent model estimation. Because the turbulent model can be helpful to consider the countermeasure direction, the turbulent model application to coupled-SEA is considered. However, an appropriate turbulent model is still unclear whereas there are many kinds of turbulent models proposed. Due to this, as the next step, this paper performs a validation study in a wind tunnel to identify the suitable turbulent model for the wind noise simulation. Lastly, the entire method is validated with on-road measurements. A detailed coupled-SEA model under appropriate turbulent model input simulates test case conditions and its prediction accuracy is discussed along with a wind noise. |
Prediction and Validation of Cab Noise in Agricultural Equipment | To improve overall customer experience, it is imperative to minimize the noise levels inside agricultural equipment cab. Up-front prediction of acoustic performance in product development is critical to implement the noise control strategies optimally. This paper discusses the methodology used for virtual modeling of a cab on agricultural equipment for prediction of interior noise. The Statistical Energy Analysis (SEA) approach is suitable to predict high frequency interior noise and sound quality parameters such as articulation index and loudness. The cab SEA model is developed using a commercial software. The structural and acoustic excitations are measured through physical testing in various operating conditions. The interior noise levels predicted by the virtual model are compared with the operator ear noise levels measured in the test unit. The resultant SPL spectrum from SEA correlates well with the test. This model is used to optimize the noise control treatments and improve the NVH performance of the cab. |
Theoretic Analysis of Factor to Affect Door Closing Force by Positioning Error of Assembly Fixture | In order to analyze positioning errors of assembly fixture of car SANTANA 2000, a 3D CAD model of fixture is built in this paper. Six typical deviation models are defined on the basis of six points positioning principle for fixture. The assembly gap distribution between door and side frame is analyzed and the influence of different deviation patterns on assembly gap is studied, and the effect of assembly gaps on door closing force is evaluated meanwhile. The results show that positioning errors of door assembly fixture is one of the most important factors to affect the door closing force. |
The Development of Testing Device for Compression Deformation of Automotive Door Weather-strip Seals | Automotive door system weather-strip seals play a major role in determining door closing effort, isolating the passenger compartment from water and reducing the wind noise inside the vehicle. They are typically dual extrusion bulbs of sponge and dense rubber. The bulbs can be round, triangular or free form in shape with a height of approximately 15-30 mm. The special properties of dense and sponge rubber material are (1) High extensibility. (2) Low extensional and shear modulus. Dense rubbers are nearly incompressible. Sponge rubbers are, on the other hand, very compressible. (3) Nonlinear force vs. extension behavior. Because of the above-mentioned factors, the deformation of the automotive door weather-strip seal during the compression is very complicated. A testing set has been developed for obtaining compression deformation of the door weather-strip by using stereovision theory. Precision instruments of optical grating and force sensor are also integrated in this set. Force-displacement response characteristics of compression at varied speed can be controlled. This work will lay solid foundations for characteristic and structure as well as optimization design of the automotive weather-strip. |
The Effects of Unsteady On-Road Flow Conditions on Cabin Noise: Spectral and Geometric Dependence | The in-cabin sound pressure level response of a vehicle in yawed wind conditions can differ significantly between the smooth flow conditions of the aeroacoustic wind tunnel and the higher turbulence, transient flow conditions experienced on the road. Previous research has shown that under low turbulence conditions there is close agreement between the variation with yaw of in-cabin sound pressure level on the road and in the wind tunnel. However, under transient conditions, sound pressure levels on the road were found to show a smaller increase due to yaw than predicted by the wind tunnel, specifically near the leeward sideglass region. The research presented here investigates the links between transient flow and aeroacoustics. The effect of small geometry changes upon the aeroacoustic response of the vehicle has been investigated. It was found that sideglass pressures showed close agreement at all turbulence levels while surface sound pressure levels also showed similar behaviour under a wide range of on-road flow conditions. While the overall sideglass sound pressure level changed under the various yaw conditions, the change in shape of the frequency spectrum was less significant. Geometry changes made to a base vehicle reduced the sensitivity of the in-cabin noise to on-road turbulence, showing that shape-change can modify sensitivity to on-road turbulence. |
NVH Challenges for Low Cost and Light Weight Small Cars | In worldwide automotive markets, the migration of customers towards smaller cars having compact, fuel-efficient design is well established and accepted as an engineering challenge by global automotive OEMs. Tata Motors of India has established a precedent by developing an ultra low cost and light weight car (the Nano), and has thereby created a new market segment for such cars that are more affordable to most of the population. This is now becoming established as a brand of low cost, safe transport in both rural and urban market segments. Despite the market moving towards such compact, fuel-efficient designs, customers are unwilling to lose many of the vehicle attributes to which they have been accustomed in previous types of entry-level cars. Addressing this marketing requirement places some significant challenges before the designers of this type of car. This paper considers some of the fundamental technical challenges faced in delivering acceptable NVH performance in a light weight, low cost car. One of the most significant issues is the use of engines with lower cylinder counts than conventional cars, leading to strong impulsiveness and lower firing frequencies. These can become problematic when mounted in vehicle structures that have a high interior volume in proportion to their mass and are often not able to meet established norms for benchmark vibro-acoustic performance. Other matters considered include the high ratio of power train mass to total vehicle mass and the higher ratio of laden to un-laden mass. Such vehicles are also generally intended for manufacture by lower skilled workers in regions with little or no automotive assembly heritage, so they must be designed for ease of “right first time” assembly. Using the example of this product, some of the possible solutions to these challenges faced by the NVH team are examined. The paper will show that it is feasible to deliver market-acceptable NVH behavior despite the strong constraints inherent in such types of vehicle, by means of lean and innovative design. |
Experimental Method Extracting Dominant Acoustic Mode Shapes for Automotive Interior Acoustic Field Coupled with the Body Structure | For a numerical model of vibro-acoustic coupling analysis, such as a vehicle noise and vibration, both structural and acoustical dynamic characteristics are necessary to replicate the physical phenomenon. The accuracy of the analysis is not enough for substituting a prototype phase with a digital phase in the product development phases. One of the reasons is the difficulty of addressing the interior acoustical characteristics due to the complexity of the acoustical transfer paths, which are a duct and a small hole of trim parts in a vehicle. Those complex features affect on the nodal locations and the body coupling surface of acoustic mode shapes. In order to improve the accuracy of the analysis, the physical mechanisms of those features need to be extracted from experimental testing. The accuracy of the vibro-acoustic coupled system model for the low frequency range depends on how accurately modal characteristics are represented at the input, output, and the structure-acoustic coupling surface. Therefore, this study focus on extracting the detailed acoustic mode shapes on the coupling surface for the improvement of the model accuracy. The non-linear least square method as the one utilized in the previous study was applied to the new test data sets of an actual vehicle. In the previous study, it had one remaining issue, which was how to extract acoustic mode shapes in the frequency range of higher damping and higher acoustic modal densities. In order to solve this issue, the number of acoustic excitation was increased considering acoustic mode shapes. The eight loudspeakers were utilized as an acoustical excitation to excite acoustic modes evenly in the acoustic interior dimensions for higher frequency. With the results of this testing, the acoustic modes of an actual vehicle with heavy damping were accurately extracted as the complex mode shapes of no phase lag between nodes, which looks similar the un-coupled normal modes without rotation in animation up to 200Hz. The synthesized FRFs were replicated well with only the extracted several dominant acoustic mode shapes. |
Body Induced Boom Noise Control by Hybrid Integrated Approach for a Passenger Car | Vehicle incab booming perception, a low frequency response of the structure to the various excitations presents a challenging task for the NVH engineers. The excitation to the structure causing boom can either be power train induced, depending upon the number of cylinders or the road inputs, while transfer paths for the excitation is mainly through the power train mounts or the suspension attachments to the body. The body responds to those input excitations by virtue of the dynamic behavior mainly governed by its modal characteristics. This paper explains in detail an integrated approach, of both experimental and numerical techniques devised to investigate the mechanism for boom noise generation. It is therefore important, to understand the modal behavior of the structure. The modal characteristics from the structural modal test enable to locate the natural frequencies and mode shapes of the body, which are likely to get excited due to the operating excitations. The critical transfer paths for the excitation through the structure have been identified with the help of transfer path analysis, while running mode analysis indicate the dynamic behavior of the structure due to the excitation. Similarly, the acoustic modal analysis describes the fundamental acoustic modal characteristics of the cabin cavity. The introduction of the experimental running mode inputs of the structure to the acoustic finite element model makes the hybrid analysis possible. The panel contribution analysis focuses on the components that have the significant contribution in the booming noise for in-phase as well as out of phase panels. The modifications revealed from the systematic study by hybrid approach, has led to substantial reduction in the booming noise both objectively and subjectively. This paper also describes the improvements suggested to reduce the boom noise. |
High-Frequency Time Domain Source Path Contribution: From Engine Test Bench Data to Cabin Interior Sounds | This work presents an application of airborne source path contribution analysis with emphasis on prediction of wideband sounds inside a cabin from measurements made around a stand-alone engine. The heart of the method is a time domain source path receiver technique wherein the engine surface is modeled as a number of source points. Nearfield microphone measurements and transfer functions are used to quantify the source strengths at these points. This acoustic engine model is then used in combination with source-to-receiver transfer functions to calculate sound levels at other positions, such as at the driver's ear position. When combining all the data, the in-cabin engine sound can be synthesized even before the engine is physically installed into the vehicle. The method has been validated using a powertrain structure artificially excited by several shakers playing band-limited noise so as to produce a complicated vibration pattern on the surface. First the excited structure is studied alone; next a vehicle cabin was lowered onto the structure without touching. As a result we can compare the combination of using only in-vehicle operating/transfer data or using powertrain only operating data and in-vehicle transfer data for synthesizing interior sounds. Very good agreement between the two procedures was obtained and comparable to the actual sound measured inside the cabin during operation. In addition to verifying the above procedure, the same near-field microphone setup, whether powertrain alone or with cab on top, can be used to assess the radiated sound power from the vibrating structure. The procedure is outlined and the obtained sound power spectra are validated against a standardized hemisphere sound power measurement showing very good agreement in general. |
Further Development of the PNCA: New Panel Noise Contribution Reference-Related (PNCAR) | The Panel Noise Contribution Analysis (PNCA) is a well-known methodology for an airborne Transfer Path Analysis (TPA) in car interior. Pressure contribution from the individual panels at a reference point can be very accurately calculated. Acoustic Trim package treatment can therefore be optimized in terms of frequency and panel area which saves money and time. The method uses only one type of sensors so called particle velocity probes for measuring source strength as well as transfer function (with a reciprocal measurement). Traditionally the PNCA makes use of a big amount of probes at fixed points (about 50) hence non-stationary conditions can be measured as well. Typically the measurement is performed in 3 sessions resulting in 150 individual panels. Because of the low spatial resolution the method can only be used at mid-low frequency range. The new Panel Noise Contribution Analysis Referenced (PNCAR) implements a new post-processing technique which uses a reference sensor in order to extract the relative phase information for the individual panel and frequency of interest. This technique makes it possible to use a limited amount of probes for measuring a whole car interior. Typically 11 probes are used in 11 sessions. Consequently, the methodology becomes more robust and commercially more affordable than conventional PNCA. A real measurement in driving condition was done on the highway in order to validate the methodology. Two different approaches to apply the theory derivations are compared and discussed. |
The influence of A-pillar obscuration/location on driver visibility | During the early phase of vehicle development, one of the key design attributes to consider is visibility for the driver. Visibility is the ability to see one’s surrounding environment while they are driving. Therefore, it is one of the key requirements to be considered during the vehicle design. Certain vehicle characteristics such as the size of windshield and the design of the pillars influence the perception of visibility for the driver. One specific characteristic influencing satisfaction is A-pillar obscuration and location, which is the subject of this paper. The objective of this project is to analyze the relationship between the A-pillar obscuration/location with the driver satisfaction under real world driving conditions, based on research, statistical data analysis and dynamic clinics. Other influences, such as the position of the occupant in the seat was also studied and captured in this paper. |
Vehicle Passenger Door Hinge Systems | The scope of this SAE Recommended Practice is to establish recommended uniform test procedures and minimum static load requirements for vehicle passenger door hinge systems. Tests are described that can be conducted on test fixtures and equipment in laboratory test facilities. The test procedures and minimum performance requirements outlined in this document are based on currently available engineering data. It is intended that all portions of the document be periodically reviewed and revised as additional knowledge regarding vehicle hinge system performance under impact conditions is developed. |
3D Simulation Methodology to Predict Passenger Thermal Comfort Inside a Cabin | The vehicle Heating, Ventilation and Air conditioning (HVAC) system is designed to meet both the safety and thermal comfort requirements of the passengers inside the cabin. The thermal comfort requirement, however, is highly subjective and is usually met objectively by carrying out time dependent mapping of parameters like the velocity and temperature at various in-cabin locations. These target parameters are simulated for the vehicle interior for a case of hot soaking and its subsequent cool-down to test the efficacy of the AC system. Typically, AC performance is judged by air temperature at passenger locations, thermal comfort estimation along with time to reach comfortable condition for human. Simulating long transient vehicle cabin for thermal comfort evaluation is computationally expensive and involves complex cabin material modelling. Lattice-Boltzman (LBM) based PowerFLOW solver coupled with Finite element based PowerTHERM solver is employed in this study to simulate long transient soak and Cooldown along with thermal comfort. Additionally, the human thermal physiology is modeled, to account for subjective evaluation of the in-cabin thermal environment. Berkeley comfort model library is available in PowerTHERM. The model takes care of the vasodilation and vasoconstriction effects, based on the external human ambient, along with the effects of clothing and the passenger metabolic rate. Vasodilation and vasoconstriction regulate the blood flow by widening or narrowing the blood vessels depending upon the warm or cold ambient conditions. LBM based flow solver is used to predict convective heat transfer phenomenon for both the exterior and interior of the cabin. The conduction and the radiation effects including the solar loading were solved using PowerTHERM. Physical test is conducted under controlled ambient conditions of climate chamber for a car cabin. Results from the coupled approach correlates well the test results for both hot soaked and cool-down conditions with a significant reduction in simulation time. During the cabin cool-down phase, passenger thermal comfort is predicted using Predictive Mean Vote. This process is further used to study the effect of change in properties of the glazing surfaces for predicting cabin thermal environment like heat ingress and cabin surface and air temperatures. Thermal comfort is also predicted and compared with baseline design. Glazing material sensitivity is carried out for absorbing and reflective glass material and its impact on cabin surface and air temperature and thermal comfort is predicted here. This process is deployed and found useful for predicting vehicle level thermal comfort. |
Systematic CAE Approach to Minimize Squeak Issues in a Vehicle Using Stick-Slip Test Parameters | Due to recent advancements in interior noise level and the excessive use of different grade leathers and plastics in automotive interiors, squeak noise is one of the top customer complaints. Squeak is caused by friction induced vibration due to material incompatibility. To improve costumer perception, interior designs are following zero gap philosophy with little control on tolerances leading to squeak issues. Often manufacturers are left with costly passive treatments like coatings and felts. The best option is to select a compatible material with color and finish; however, this will reduce the design freedom. Material compatibility or stick-slip behavior can be analyzed with a tribology test stand. However, this test is performed on a specimen rather than actual geometry. There were instances, when a material pair was found incompatible when tested on a specimen, but never showed any issue in actual part and vice versa. Thus, interface stiffness and system sensitivity between the parts are important while analyzing the stick-slip behavior before implementing any solutions. To improve the process vehicle interiors are analyzed by CAE methods to evaluate stick-slip behavior by utilizing SSP test data. The CAE methodology considers wide range of input load cases, global and local system sensitivity, local geometries, and connection stiffness to get realistic results from squeak simulations, which otherwise not possible with stick-slip testing. In the present study, “no relative movement no squeak” philosophy is used to drive the design of interior trims to avoid squeaks. Squeak risk at interface is evaluated by comparing in-plane relative displacement with ‘1/ IRmax’ value obtained from stick-slip testing. Meaningful information has been extracted through linear static analysis to understand the influence of preloading on contact forces between the interfaces. This approach has improved the squeak prevention process in product development without changing materials or usage of passive treatments. |
Truck Front Cabin Mount Tuning for Cabin Noise Boom, Overall Interior Noise and Vibration Reduction | In today’s automobile industry refined NVH performance is a key feature and of high importance governing occupant comfort and overall quality impression of vehicle. In this paper interior noise and vibration measurement is done on one of the light truck and few dominant low frequency noise booms were observed in operation range. Modal analysis was done for the cabin at virtual as well as experimental level and few modes were found close to these noise booms. Vibrations were measured across the cabin mounts and it was found that the isolation of front mounts is not effective at lower frequencies. Taking this as an input, the mount design was modified to shift the natural frequency and hence improve the isolation behavior at the lowest dominant frequency. This was followed by static and dynamic measurement of the mounts at test rig level to characterize the dynamic performance and stiffness conclusion. Finally the interior noise and vibration measurement is carried out on truck fitted with selected mounts and substantial vibration, overall noise reduction and drastic boom noise reduction was achieved. This paper takes up a real-time noise scenario, its root cause analysis and establishment of final solution for same. It covers various activities like noise, vibration measurement and analysis, virtual and experimental modal evaluation, mount transmissibility evaluation followed by design and tuning for corrects stiffness, and finally verification at rig and vehicle level. Hence this works runs through complete flow of NVH development cycle. The cabin mount design patent registration is approved. |
Electromagnetic Analysis of Permanent Magnet Brushed DC Motor for Automotive Applications—Part 1 | Permanent magnet brushed DC (PMBDC) motors are mostly preferred in many automotive applications because of better power density and easier control. Five different automotive applications such as electric parking brake (EPB), power seat, power window, sunroof drive, and tire air pump are chosen and discussed in this paper. A step-by-step electromagnetic analysis is carried out for all the designed models. Low-cost ferrite-based magnets are used for cost reduction keeping the efficiency as high above 77% in all the models. Comparison on performance and cost are discussed in the conclusion section. |
Reinforcement of Low-Frequency Sound by Using a Panel Speaker Attached to the Roof Panel of a Passenger Car | The woofer in a car should be large to cover the low frequencies, so it is heavy and needs an ample space to be installed in a passenger car. The geometry of the woofer should conform to the limited available space and layout in general. In many cases, the passengers feel that the low-frequency contents are not satisfactory although the speaker specification covers the low frequencies. In this work, a thin panel is installed between the roof liner and the roof panel, and it is used as the woofer. The vibration field is controlled by many small actuators to create the speaker and baffle zones to avoid the sound distortion due to the modal interaction. The generation of speaker and baffle zones follows the inverse vibro-acoustic rendering technique. In the actual implementation, a thin acrylic plate of 0.53x0.2 m2 is used as the radiator panel, and the control actuator array is composed of 16 moving-coil actuators. The shape of the desired speaker zone is an ellipse, and the required amplitude of this piston source is pre-calculated to satisfy the desired sound radiation at the ear position. The gain of the actuator array to properly generate the desired vibration field is obtained by solving an inverse problem constructed by the transfer mobility between each actuator and field point on the plate. For the recruitment of the low-frequency deficiency of human auditory characteristics, the desired sound spectrum is set to follow the equal-loudness contour of 40 phons. It is confirmed that the woofer in a car can be replaced by the developed panel speaker. |
Linear Impact Procedure for Occupant Ejection Protection | The objective of this document is to enhance the test procedure that is used for ejection mitigation testing per the NHTSA guidelines as mentioned in the FMVSS226 Final Rule document (NHTSA Docket No. NHTSA-2011-0004). The countermeasure for occupant ejection testing is to be tested with an 18kg mass on a guided linear impactor using the featureless headform specifically designed for ejection mitigation testing. SAE does not endorse any particular countermeasure for ejection mitigation testing. However, the document reflects guidelines that should be followed to maintain consistency in the test results. Examples of currently used countermeasures include the Inflatable Curtain airbags and Laminated Glass. The testing procedure is as follows: 1 Determine the daylight opening 2 Identify target locations per the FMVSS226 Final Rule §5.2 a Target locations for all windows and daylight openings b Perform the target elimination process c Reconstitute the targets 3 Determine the zero-plane 4 In case of advanced glazing, determine if the glazing has to be part of the test and pre-brake it at a 75mm offset a If yes, than follow the procedure for pre-breaking the laminated glazing 5 Run the test a At 5.6m/s with a 1.5s delay b At 4.4m/s with a 6.0s delay |
Buffeting Noise Characteristics and Control of Automobile Side Window | The computational fluid dynamics (CFD) software STAR-CCM+, Large Eddy Simulation (LES) method, and the Dynamic Smagorinsky-Lilly sub-lattice Model (DSLM) are used to study the buffeting noise characteristics of automobile side windows. Buffeting noise control methods are studied, and a comparison with experimental data verified the correctness of the simulation. Results show that periodic vortexing of the window opening area causes the strong pressure pulsation in the passenger compartment, and the combined effect of two mechanisms, namely, acoustic feedback and Helmholtz resonance, generates the buffeting noise. The sound pressure level (SPL) of buffeting noise produced by opening only the front window is lower than that of the rear window; Adding a rear mirror convex structure and a rain baffle structure reduces the buffeting noise SPL of the front window by 4.5 dB and 7.8 dB, respectively; Adding a convex structure and a non-smooth structure in the B pillar reduces the buffeting noise SPL of the rear window by 3.8 dB and 2.2 dB, respectively. |
Analyzing Effects of Upperbody on Road Noise of Platform-Sharing Vehicles | Platform sharing is widely used for reducing time and cost of vehicle development. It has been believed that vehicles that employ the same platform show similar performances of noise and vibration. Recently, however, it is observed that two vehicles that share the same platform present a noticeable difference in road noise. The structural difference between the two vehicles is located only at the upperbody of a Body In White (BIW). In order to investigate the effects of the upperbody on the road noise, several analyses such as (1) input point stiffness, (2) noise transfer function (NTF), and (3) road noise are performed using finite element (FE) models of the vehicles. As a result, it is found that the upperbody affects the NTF of the trimmed body and the road noise, which explains the dissimilarity of the road noise for the two vehicles. A novel method based on equivalent radiated power (ERP) is proposed to assess the upperbody. It is shown that analysis results obtained using the method show good correlation to the NTF of the trimmed body, which determines the road noise. Thus the proposed method can be used to assess an upperbody and predict the road noise of platform-sharing vehicles in the early stage of vehicle development. |
An Aspect of Noise Vibration and Harshness Issues in Electric Vehicles | Electric vehicles (EVs) are gaining ground more recently. New powertrains like electric and hybrid come with new noise, vibration, and harshness (NVH) issues previously unknown. A new approach to acoustic engineering is required to study NVH issues in EVs. The two primary dominant sources in an internal combustion engine (ICE) are engine noise due to combustion, and exhaust noise would not be there for EVs. EVs are less noisy, but several motor or battery cooling noises are encountered during design and validation. NVH is an indispensable part of subsystem integration in the EV powertrain. This article deals with various noise issues generally observed in EVs and their possible treatment to achieve the comfort car, satisfying customer expectations. The NVH-related problems for EVs are categorized into five categories: motor, wind, road, auxiliary, and other noises like integration. A detailed study of each category/problem type and NVH-suppression methods are discussed. The selection of powertrain mount architecture and its impact on load transfer and crash performance are also presented in this article. A balancing approach is required for NVH, durability, and crash requirements. |
Acoustical Materials: Solving the Challenge of Vehicle Noise | For a limited time only, SAE is offering a 20% discount off the list price of $70. Purchase today for $56. What is acoustics? What is noise? How is sound measured? How can the vehicle noise be reduced using sound package treatments? Pranab Saha answers these and more in Acoustical Materials. Acoustics is the science of sound, including its generation, propagation, and effect. Although the propulsion sources of internal combustion engine (ICE) vehicles and electric motor-powered vehicles (EV) are different and therefore their propulsion noises are different, both types of vehicles have shared noise concerns: Tire and road noise Wind noise Vehicle noise and vibration issues have been there almost from the inception of vehicle manufacturing. The noise problem in a vehicle is very severe and is difficult to solve only by modifying the sources of noise and vibration. Sound package treatments address the noise and vibration issues along the path to reduce in-cabin noise. In Acoustical Materials, readers will grasp the science of reducing sound and vibration using sound absorbers, sound barriers, and vibration dampers. Sound provides information on the proper operation of the vehicle, but if unchecked, can detract from the consumer experience within the vehicle and create noise pollution outside the vehicle. Acoustical Materials provides essential information on the basics of sound, vehicle noise source, how these are measured, how vehicle owners perceive sound, and ultimately, how to solve noise problems in vehicles using sound package materials. |
Influence of Inner Panel Structure in Overall Liftgate Performance | Prevailing global industry has set an environment that fosters the search for new procedures, technology and/or knowledge that allows time reduction in vehicle development and, at the same time, to offer the best strength and reliability characteristics to the customers. Constant improvement mindset is applied to those systems that yield the highest interaction with the final user, among those, it is paramount to take notice of systems like the vehicle closures (such as liftgates, hood, doors, etc.). In automotive industry, the efforts to comply with high standards are often focused to incorporate new materials, which are resistant and lightweight, on the other hand, this project explores the liftgate behavior from a more fundamental standpoint, which is the geometry and how it is related to the requirements that the liftgate should comply with. In this article, a research was conducted to establish which components have a high influence in the structural integrity of the liftgate, using as a starting point the structural testing’s that are performed to sign off the closures design during the product development stage. Furthermore, a comparison analysis between different liftgate structures, stand out the geometric design patterns of the interior panel of the liftgate that is present in the hatchback and sport utility vehicles. Finally, this project includes optimization proposals that determined the inner panel geometric form that enables the liftgate to comply with the structural requirements and comparison of the liftgate assessments results between the commonly used profiles across the industry. |
The 747-400 Dreamlifter - Swing Tail Door Alignment and Latch Mechanism | One essential feature of the 787 production system is the 747-400 Large Cargo Freighter (LCF), also known as the Dreamlifter,[1] and its ability to quickly and efficiently transport large components from global manufacturing locations to the final assembly site in Everett, Washington. This unique airplane has a tail section (Swing Tail) that opens to allow cargo loading. Quickly loading and unloading cargo is largely dependent on the reliable operation of the integral swing tail door alignment and latching systems. The swing tail door is approximately 23 feet horizontally by 29 feet vertically in size. The alignment and latching systems are required to function in a wide range of environmental conditions including temperature extremes and high winds. At the same time, these systems must ensure that flight loads are safely transmitted from the tail to the airplane fuselage without inducing undue fuselage preloads and without excessive play in the latching system. These requirements presented a developmental challenge that called for an innovative solution for adjustment of the latching and alignment mechanisms. |