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An Investigation of Vehicle HVAC Cabin Noise | Noise and vibration have an important influence on a customer's perception of vehicle quality and cabin interior noise levels are a key criteria. The interior sound levels of automobiles have been significantly reduced over the years, with reductions in power train, tire and external wind noise. One of the highest in-cabin noise levels now arises from heating, ventilating and air conditioning systems, generated by the air-rush noise at various HVAC settings. Thus quieter climate control systems are desired by car manufacturers. A systematic benchmarking study was performed to investigate the in-cabin noise of vehicles. 21 passenger cars including compact, mid-size, full-size, and a truck were selected. Tests were conducted on relatively new production vehicles in various conditions. A binaural head system was used in front passenger seat to measure noise levels. The methodology used and the experimental results were presented in this paper. It was found that the design of the HVAC system has a major influence on the vehicle in-cabin acoustic performance. The size/price of the vehicle may not correlate to the cabin quietness due to the complexity of acoustic effects in the HVAC system. |
Class A Application/Definition | This SAE Information Report will explain the differences between Class A, B, and C networks and clarify through examples, the differences in applications. Special attention will be given to a listing of functions that could be attached to a Class A communications network. |
Investigation on Wiping Noises and NVH Design Consideration in a Wiper System | As automobiles become increasingly quieter, the wiper operation noise becomes more noticeable by the customer. This paper deals with the experimental approach and the methodology to investigate the Friction induced wiping noise. Role of design in a wiper system plays a very imperative task in meeting the performance of wipers but at the same time it does not cater to the NVH issues. Some of the important design parameters which affect the NVH properties of the wiper system are highlighted in this paper. For better understanding of the system some of the best in class vehicles for SUV category were tested and compared with our test vehicle. In this study more importance given to analytical part which is more important to investigate and in depth study of the friction induced noise. For analytical study some techniques such as time frequency domain i.e. Wavelet transforms, frequency domain and time domain where extensively used. Finally ranking of the NVH design factors based on the criticality are stated in this document. These factors may be helpful during design of wiper system for better NVH, without deteriorating the functional performance. |
Sound Absorbers in Small Cavities | The automotive industry is often interested in controlling noise radiated from trim pieces in the passenger cabin. In general, there is a small air gap that separates these trim pieces from the sheet metal that is the actual source of the noise. It is common practice to place an acoustically absorbent material in this space to reduce radiated noise. In this paper the in situ noise control performance of a variety of materials is examined by placing them in a test fixture that simulates the sound field in the vicinity of vehicle pillar trim. In this fixture a noise source is positioned behind a piece of sheet metal. A flat plastic sheet that is similar in composition to pillar trim is placed a small distance away from the sheet metal. The sides and rear of the fixture are sealed so that the plastic sheet is the only significant radiator of the sound radiated from the sheet metal. The random incidence and normal incidence performance of a variety of absorbers are compared to their performance in this test fixture. In addition, the theory that relates the acoustic absorption of a material to its ability to decrease noise levels will be considered. |
Application of an Elastomeric Tuned Mass Damper for Booming Noise on an Off-highway Machine | NVH is gaining importance in the quality perception of off-highway machine performance and operator comfort. Booming noise, a low frequency NVH phenomenon, can be a significant sound issue in an off-highway machine. In order to increase operator comfort by decreasing the noise levels and noise annoyance, a tuned mass damper (TMD) was added to the resonating panel to suppress the booming. Operational deflection shapes (ODS) and experimental modal analysis (EMA) were performed to identify the resonating panels, a damper was tuned in the lab and on the machine to the specific frequency, machine operational tests were carried out to verify the effectiveness of the damper to deal with booming noise. |
A New Modeling Technique of Large Trim Part Air Passages for An Accurate Acoustic Model | Finite element models based on the design drawing information are widely applied in the early development stage in the automotive industry. During this stage, the performances of noise and vibration of a vehicle are evaluated by the calculation using FE models. Therefore, it is extremely important to secure the accuracy of the calculation by FE models. Otherwise the problem does not solved with the countermeasures implemented in FE models. To predict sound pressure levels in the passenger compartment, an acoustic model for the compartment must be precisely created. Experimental analysis have shown in the past that narrow air gaps between interior trim parts or between a trim part and a body structure have a high impact on the acoustic transfer functions even in the low frequency range where the issues on booming noise and road noise are often addressed. However, the narrow gaps are usually not modeled in FE models because a lot of small finite elements are needed to express the narrow gaps and much resource is required for the calculation. In this study an acoustic leakage element is proposed to model the narrow air gaps. This element consists of one hexahedral element representing air gaps and several rigid elements connecting adjacent acoustic fields. Specifications for the hexahedral element are experimentally identified by using Helmholtz resonator. The proposed method is verified by the comparisons between the measured and calculated acoustic transfer functions of a vehicle. |
Brake Grind Noise Reduction Potential on Vehicle Level - A TPA Study | Rust accumulated on disc rotor surfaces causes brake judder and excessive grind noise. This low frequency noise phenomenon is audible especially at low vehicle speed without masking from other noise sources like wind and road noise or power train sound. This often leads to customer complaints resulting in significant warranty costs. Alternative drive systems like hybrid or full electric power trains will emphasize this problem. Most studies concentrate on optimization of the brake system to reduce low frequency brake noise. In this work, the potential for optimization on vehicle level was investigated. The most effective NVH optimization can be achieved by improving and matching the acoustic properties of the vehicle and the brake system. In a first step, the main structure borne noise transfer paths have been identified by means of Transfer Path Analysis. A detailed analysis of the relevant transfer paths shows critical sound transmission of the suspension system and its attachments to the vehicle body. The potential of this approach for brake noise optimization is demonstrated by an example. As a second step, the radiating body surfaces contributing to the perceived brake noise have been identified using panel contribution analysis. This helps to optimize the vehicle body structure and trim package. The potential for improvements has been predicted using a modified interior noise synthesis model. The results have been verified experimentally by principal modifications to the vehicle. |
Operational Modal Analysis Techniques used for Global Modes Identification of Vehicle Body Excited from a Vehicle in Idle Engine | With the purpose to identify the root cause of increased levels of vibration felt at idle speed in a popular vehicle prototype a study was conducted using techniques for analysis of vibration transmission between components of a vehicle, using Mechanical Vibrations Analysis and Operational Modal Analysis, for the analysis of the operational modes was used ODS - Operational Deflection Shape technique which is possible only see the shapes related to probable modes. The experimental results were compared with results for the modal analysis by Finite Element Method (FEM). The vehicles used are identical prototypes, but with different levels of vibration. Therefore, to study there is a vehicle with satisfactory levels and a second with unsatisfactory levels. This study demonstrates the methodology used to identify the cause of the different behaviors between cars and also discuss the improvements made in the body according to the results of the numerical experimental confrontation. |
CHARACTERISATION OF PASSENGER VEHICLE IN-CABIN NOISE USING OMA AND SOUND QUALITY TECHNIQUES - AN INTEGRATED APPROACH | In the recent past, interior noise quality has developed into a decisive aspect for the evaluation of overall vehicle quality. The paper discusses the effect of structural modes of vibration caused in a passenger car during its operational conditions and its effect of noise inside the cabin. In order to characterize the body modes under road operation, OMA is used and the Interior noise quality of car cabin is judged by the Sound quality tools. Based on the jury evaluation, the problem is identified and problem area is identified with operational modal analysis techniques to take the countermeasure and verification of the study is done. The relation of body modes is established to overall cabin noise performance and improvements are checked with use of Modification Prediction tool after identifying the critical areas. This study is helpful in developing the new vehicle modal faster and also to analyze and to take countermeasure at earlier stages of developments. |
Acoustic-Structural Sensitivity Analysis and Optimism of Car Body Multilayer Panels | Acoustic-structural sensitivity analysis for coupled acoustic-structural systems can be conveniently and quickly used in dynamic modifications of car body panels to reduce interior sound pressure level. In practice, car body panels are multilayered structure which consists of the outside skin, the interior trim, and the air gap or absorbent layer between them. The vibration characteristics and the capability of sound insulation of multilayer panels are very important factors which dominate acoustic response in car cavity. A simplified car body model is made to investigate the effects of multilayer panels on interior sound levels. With the model, the relation between the acoustic response of the cavity and the property of multilayer panels are achieved. The validity of theoretical analysis is verified through a comparison between the experiment and the numerical simulation results. Finally, acoustic-structural sensitivity analysis of car body multilayer panels is evaluated synthetically. The panels’ structure is optimized, and car interior sound level is improved. |
Modeling Airborne Noise Transmission in a Truck using Statistical Energy Analysis | Statistical Energy Analysis (SEA) was used during the design of a new heavy duty truck. This paper provides an overview of the building and validation process of an airborne SEA model of a typical commercial vehicle. Predictions of interior noise levels are compared against tests. A noise path contribution analysis is presented, demonstrating how the impact of potential design changes on the interior sound levels can be evaluated with an SEA model. |
Vehicle Airborne Noise Analysis Using Boundary Element and Finite Element Energy Based Methods | The Energy Finite Element Analysis (EFEA) has been developed for computing the structural vibration and the interior noise level of complex structural-acoustic systems by solving governing differential equations with energy densities as primary variables. A finite element approach is employed for the numerical solution of the governing differential equations. Results from EFEA simulations have been compared successfully with test results for Naval, automotive, and aircraft structures. The Energy Boundary Element Analysis (EBEA) has been developed for conducting exterior acoustic simulations using the acoustic energy density as primary variable in the formulation. EBEA results have been compared successfully to the test results in the past for predicting the exterior acoustic field around a vehicle structure due to external noise sources. In this paper, the EBEA and EFEA methods are combined for predicting the interior noise levels in a vehicle due to exterior acoustic sources. The EBEA is employed for computing the acoustic field around a vehicle structure due to exterior acoustic noise sources (i.e. tire source, engine source, etc.). The computed exterior acoustic field comprises the excitation for the EFEA analysis. The vehicle structure, the acoustic treatment, and the interior acoustic volumes are represented in the EFEA model. The interior noise level in the vehicle is computed by the EFEA. Predictions for the interior noise level (expressed in a noise reduction format) are compared favorably with test results for two separate types of excitation. A generic case study is presented for computing the interior noise due to exterior acoustic excitation from a transmission and a driveline. |
Acoustics Inside the Space Shuttle Orbiter and the International Space Station | The acoustics environment in enclosed habitable space vehicles and modules is important to mission safety, crew health, and efficient operations. Noise is unwanted sound that can interfere with crew communications and sleep, creating habitability concerns, hearing loss, or other health issues. This paper discusses the acoustic environment and the noise control efforts in the Space Shuttle Orbiter and the International Space Station, and the lessons learned from these efforts. Included is the need to apply the design discipline of acoustics early in the design process, to establish reasonable acoustic limits and “design them into” vehicles/modules, and to apply noise control to ensure that limits are met. Program management needs to be supportive of these efforts. |
Optimization of Sound Packages for Commercial Vehicles Using Panel Contribution Analysis | Microphone array-based Panel Contribution Analysis (PCA) is a new technique used for Sound Package design optimization for commercial vehicles. The technique allows for noise control performance and cost optimization. This technique ranks the contribution of fully trimmed structural panels (e.g. floor, roof, etc.) and leaks in a vehicle cabin to the noise levels experienced by a driver while the vehicle is in cruising operation. Often the noise and vibration sources (engine, transmission, exhaust, aerodynamic noise, tires, etc) cannot be easily modified, thus the only practical action to solve noise problems is to design the noise control treatments applied to the vehicle panels. Panels that have a large contribution to the noise levels at the driver's ear are heavily treated with noise control materials, whereas panels with low contribution get little to no treatment. This paper describes a microphone array-based PCA technique, and the results of a successful application of it to optimize the interior noise level performance of a new commercial vehicle. The application results clearly indicated the dominant contributing panels to the sound pressure levels at the driver's ear. |
A PU Probe Array Based Panel Noise Contribution Analysis Whilst Driving | This paper presents new developments on hot wire anemometer based panel noise contribution analysis. The used sensor allows the direct measurement of particle velocity. Some historical remarks are given and the latest developments of the technique are reported. Four steps are required to determine the panel noise contribution of the interior of a vehicle and to visualize the results in 3D. In a first step the probes are positioned on the interior surfaces and their x, y, z coordinates are measured. Based on these data a 3D geometry model is created. The geometry data are acquired using a specially designed 3D digitizer. The second step is a measurement in a certain mode of operation. This step can be done in a laboratory but it is also possible to perform the measurement whilst driving the vehicle on the road. Stationary as well as non stationary running conditions like e.g. run ups are accessible and do not limit the applicability of the method. The third step is the determination of the transfer paths from the panels to a certain listening position. This measurement is done reciprocally. In a fourth and last step the transfer paths are linked with the operational data gathered in step two. The results are then visualized using the 3D geometry model. This paper describes the measurement of a conventional car with a resolution of 180 panels. Since an array of 45 probes was used step 2 and step 3 had to be repeated 4 times. The complete measurement typically takes approximately 3 days. |
Mapping 3D Sound Intensity Streamlines in a Car Interior | Sound source localization techniques in a car interior are hampered by the fact that the cavity usually is governed by a high number of (in)coherent sources and reflections. In the acoustic near field, particle velocity based intensity probes have been demonstrated to be not susceptible to these reflections allowing the individual panel contributions of these (in)coherent sources to be accurately determined. In the acoustic far field (spherical) beam forming techniques have been used outdoors in the free field, which analyze the directional resolution of a sound field incident on the array. Recently these techniques have also been applied inside cars, assuming that sound travels in a straight path from the source to the receivers. However, there is quite some evidence that sound waves do not travel in a straight line. The Maritime Institute of Stetting in Poland made numerous 3 D sound intensity measurements demonstrating an erratic pattern of sound intensity streamlines [1], [2] His approach was transferred from a lab to an actual car cabin upon request of a larger European car manufacturer. At 900 positions inside the car the 3D intensity is measured with a 3 D sound intensity probes using three particle velocity sensors. Such a probe is not susceptible to the pressure-intensity index. Several speakers that are driven in sequence are used as controlled sound sources. The results demonstrate that even with a single sound source, the 3D intensity streamlines are strongly bending, suggesting that far field techniques do not point towards the sound source. |
A Balanced Approach for Wind Noise Control | A balanced approach for wind noise control is presented in this paper. This approach is focused on improved sound insulation and low mass. Initially, the Sound Transmission Loss (STL) of tempered, standard laminated and acoustic laminated glasses for different thicknesses was measured in a STL suite. The critical frequency range was identified from in-vehicle noise measurements. These STL data and in-vehicle results provided the relevant information for a proposal with better acoustic performance and lower mass. The efficiency of this proposal was confirmed with new in-vehicle measurements. |
Ultrasound Techniques for Leak Detection | Leak detection of vehicle cabin interiors is an important quality inspection phase that typically has been handled with various time consuming, or potentially product damaging techniques. Leak detection in tank or pressure vessel applications is almost always a concern for gas or fluid containment in vehicles and in many other industries. Numerous techniques exist for the detection of leaks in these and other types of structures. When testing is required in a production environment, often the speed of leak detection is very important if all samples must be tested. The use of several ultrasound based methods for leak detection in vehicle cabins and pressure vessel applications is presented here. Ultrasound waves are typically classified as having spectral content greater than 20 kHz. In the case of leak detection in a production environment, frequently the ultrasonic spectrum is largely free from background noise content that dominates the audible spectrum. The method for the response measurement of ultrasonic signals presented here is with the implementation of high frequency microphones. The excitation methods presented here are an active method utilizing an ultrasonic emitter, a passive method relying on the passing of air through leak locations, and a vibro-acoustic method utilizing a small electro-dynamic shaker. The methods presented here have been tested for the existence of leaks in some structures, but have not been tested in this paper for the existence flaws and defects that may potentially lead to leaks in some structures after prolonged use. |
Shearplate – A New Innovative Approach to Reduce Powertrain Noise | This Paper is evaluating the development and effectiveness of using a Shearplate, a new and innovative approach to reduce powertrain noise and vibrations. The results show that the approach is offering monumental improvements in terms of reduced noise and vibrations. Sound quality evaluations also show very clearly that the approach is an effective countermeasure to the targeted problems. With the knowledge gathered during the development and with what is partly presented in this paper we now have an additional tool that car manufacturers can deploy in their efforts to design more fuel efficient and cleaner burning engines without sacrificing NVH performance. |
How Advances in On-Road NVH Simulator Technology Have Enabled Firm Targets for Delivery at the Concept Phase | One of the great challenges of the NVH development process is to ensure that customers and stakeholders in the vehicle team are involved in sound quality decision making throughout a new vehicle programme. Recent developments of interactive NVH simulators have enabled a cost-effective customer-focused method for capturing the opinions and decision making processes of people who are not NVH experts. This paper describes the latest enhancement to the NVH Simulator approach which allows the sounds of virtual vehicles to be evaluated whilst driving on-road. The sounds are created and presented to the driver in such a way that they appear totally natural and the assessor is not aware that they are synthesized. Since the subjective evaluations are performed on normal roads, key decision makers can understand, sign up with confidence to, and appreciate the value of the proposed sounds. The main emphasis of this paper is a recent case study in which the “On-Road” and “Desktop” simulators were used at the concept stage to deliver an exciting sound to enhance and compliment a new B-segment vehicle. The paper explains how the tools were used to: Set vehicle level sound quality targets to enhance the appeal of the vehicle, including customer surveys and the use of the On-Road Simulator for final sign off at target confirmation drive events. Understand the path and source contributions of a donor vehicle and key competitor. Create and demonstrate a strategy for practical realisation of the vehicle level target. The paper concludes with a discussion of the benefits of the approach and summarizes the next steps in the development of the technology and process. |
Use of SEA to Support Sound Package Design Studies and Vehicle Target Setting | Statistical Energy Analysis (SEA) vehicle models are well-accepted tools for predicting the high-frequency interior acoustic effects of a design change to the structure or sound package of the vehicle. [1] SEA models do not strongly depend on geometric details, which allows SEA to be uniquely used as an analysis tool very early in the vehicle design phase to identify potential Noise, Vibration, and Harshness (NVH) issues caused by proposed changes to acoustic or vibration source levels, component materials, construction details, or sound package details of the vehicle. SEA models can also be used to suggest alternatives while the vehicle is still in the development stages to compensate for a predicted or known degradation to NVH in a vehicle due to a design or source level change. This paper presents a case study in which validation testing and an SEA model were combined to obtain recommendations for the most effective sound package changes to meet NVH targets. The motivation behind this study and the role and benefits of the SEA model are presented. An overview of standard uses of SEA for vehicle design for component-level and full-vehicle level is given. SEA model validation methodology and results are discussed. A description of the measurement test plan and methodology is provided. The use of the SEA model to predict combinations of sound package changes to compensate for changes and to reach NVH targets for a new vehicle and the corresponding results are presented. Conclusions from the work are summarized. |
In Situ PU Surface Impedance Measurements for Quality Control at the End of an Assembly Line | With PU probes the sound pressure and acoustic particle velocity can be measured directly. Over recent years, the in situ surface impedance method, making use of such a probe, has proven to be an alternative to Kundt's tube measurements for product development type of work. The in situ method can also be used for the purpose of quality control on the acoustic material, be it during manufacturing or assembly, ensuring the best possible way to monitor the practical effectiveness of the acoustic package designed earlier on. In order to assess the variance of the acoustic package material leaving the assembly line, a relevant number of samples were taken over time. The quality of both the headliners, and the passenger seats were measured, of 25 cars of the same type. The robustness of the measurement method will be discussed, and the results will be presented. |
Squeak and Rattle Prevention in the Design Phase Using a Pragmatic Approach | Squeaks and Rattles (S&R) today are one of the main issues leading to a down ranking in quality perception of interiors in vehicles. Being annoyed by these types of noises, customers are driving up warranty and goodwill cost to many billion per vehicle model on lifetime. Still most of the problems are solved by automotive manufacturers and suppliers after they appear in hardware testing. Usually expensive solutions like felts and oil/grease are selected to solve the problem. However prevention is the key to eliminate unwanted Squeaks and Rattles early in the design phase based on CAD data and material information. This paper shows a pragmatic approach to support the design engineer to create a virtually S&R free CAD-model. |
Modeling of In-Cabin Climate and Fogging of Windshield | Passenger safety is considered as the central issue in vehicle design. One of the important factors that strongly affect driving safety is visibility through the windshield. Present model is mainly focused on the problem of fogging of windshields including the effects of latent heat and humidity. Model was studied for different climatic conditions like hot humid climate and cold climate. The effect of surface parameters like static contact angle, on defogging was also studied. Further, the effect of AC on in-cabin climate was also studied. Experimental results for condensation on a glass plate very well resembled with the glass-model results. The model helps in predicting fogging and understanding the actual thermal parameters leading to it and hence can be useful in optimizing these parameters so as to reduce fogging. It serves as a useful tool in optimizing the performance of an air conditioner. |
A Review and Analysis of the Performance of Laminated Side Glazing in Rollover Accidents | Advanced glazing has been investigated as a means by which to reduce occupant ejection in rollover accidents. However, most testing on these advanced glazing materials has not effectively captured the occupant kinematics typically seen in actual rollover accidents, and as a result, passing these tests does not ensure occupant retention. While current work has attempted to characterize the dynamic (impact) and static (push-out) material properties necessary for understanding the containment performance of advanced glazing, most testing has consisted of single impacts. Rollover accidents typically include multiple impacts and potentially long duration centrifugal forces on the side glazing. As such, there is little test and/or simulation data to support the theory that advanced glazing would substantially reduce the risk of occupant ejection in rollover accidents. The risk of head injury due to occupant impacts may not be significantly different between tempered and laminated glazing, but higher neck forces have generally been reported for laminated glazing. The laceration potential of laminated glazing may also be significant. This paper reviews the existing literature and testing in the area of automotive glazing materials, with specific emphasis on the containment potential of advanced glazing. We also present an analysis of the centrifugal forces on side window glazing due to occupant contact during rollover accidents. These forces most likely exceed the containment potential of laminated glazing. |
Reducing a Sports Activity Vehicle's Aeroacoustic Noise using a Validated CAA Process | Developing a low interior noise level of vehicles is a big challenge - even a greater one if one thinks about aeroacoustics. Aeroacoustic noise and its origins are usually identified with the help of prototypes when exterior design changes or the replacement of exterior parts like side mirrors are very limited. However, computational aeroacoustic (CAA) methods in virtual project phases offer more design options for the vehicle's geometric shape. The early consideration of aeroacoustic relevant design changes helps to keep project costs low by avoiding tool changes. This paper describes MAGNA STEYR's virtual aeroacoustic process starting from standardized model generation and simulation of wind noise, including the validation of computational results via comparison with measurement data gathered in an acoustic wind tunnel. The simulations are carried out using the commercial CAA code “PowerFLOW” (Exa) based on the Lattice-Boltzmann method. CAA post-processing results with the aim to detect hot spots and to derive effective measures are presented. As a typical application, a design modification example is highlighted: Pressure fluctuations on a vehicle's side window are influenced strongly by the design of the a-pillar. Improvement potential was identified by analyzing simulations results and a-pillar modifications were developed which led to a validated interior noise reduction of 1 dB(A). |
Vibro-Acoustic Simulation of Side Windows and Windshield Excited by Realistic CFD Turbulent Flows Including Car Cavity | Nowadays, the interior vehicle noise due to the exterior aerodynamic field is an emerging topic in the acoustic design of a car. In particular, the turbulent aerodynamic pressure generated by the air flow encountering the windshield and the side windows represents an important interior noise source. As a consequence PSA Peugeot Citroën is interested in the numerical prediction of this aerodynamic noise generated by the car windows with the final objective of improving the products design and reducing this noise. In the past, several joint studies have been led by PSA and Free Field Technologies on this topic. In those studies an efficient methodology to predict the noise transmission through the side window has been set up. It relies on a two steps approach: the first step involves the computation of the exterior turbulent field using an unsteady CFD solver (in this case EXA PowerFlow). The second step consists in the computation of the vibro-acoustic transmission through the side window using the finite element vibroacoustic solver Actran. The present paper extends this methodology for the handling of multiple windows, i.e., the two front side windows and the windshield. The complete car cavity is modeled as well. First, a complete description of the method and the finite element model is provided, from the boundary conditions to the different components involved, like the windows, the seals and the car cavity. The total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements for a real car model. The influence of the flow yaw angle (0° versus 10° orientation) is also assessed. |
Studies on Neutral Gear Rattle in Early Stage Design | In today's competitive automobile market, customers have become more sensitive towards NVH behavior of the vehicle than ever. The noise generated by gear rattle is one of the main contributors towards customer's overall NVH perception. This paper adopts a model based design approach towards gear rattle phenomenon to predict the tendency of gear rattle at a very early stage of design. This up-front understanding of gear rattle will potentially reduce the expensive design changes and iterations at later stages. A single unloaded gear pair is modeled in AMESim software, which is then extended to the complete gearbox in neutral condition. The sensitivity of rattle index for different input parameters is studied. Analysis on uncertainty propagation is carried out to find the rattle index distribution for Gaussian variation of input parameters. A novel rattle index based on Jerk is proposed and compared with the existing index. Both the indices are later predicted for the complete gearbox and the contribution of each pair towards rattle is analyzed. |
Design Optimization of Acoustic Enclosure for Noise Reduction of Diesel Generator Set | Diesel engine generator (DG) sets used in industrial plants and residential/official buildings cause serious noise problems if not (canopised) properly. Generally, DG set engines used are with rotational speed of 1500 rpm. In present study automotive diesel engine with 3000 rpm speed was converted for Genset application. Due to higher speed, engine noise levels and its cooling requirements were quite high. Objective of the study was to optimize the design of an enclosure for the said DG set to meet requirements of low noise and proper ventilation to comply MoEF legislative limits. A detailed Noise Source Identification (NSI) was carried out to identify and rank different noise sources. A Hybrid approach which consists of experimental DOE and simulation based on Boundary Element Method (BEM) was used for enclosure design. Design variables like enclosure dimensions, sound absorbing materials and louvers were used in optimization study. Final validation was done on modified enclosure prototype for noise level and internal temperature. Substantial noise level reduction of 8 dB was achieved with appropriate ventilation. |
Road Test Measurement and SEA Model Correlation of Dominant Vehicle Wind Noise Transfer Paths | In order to effectively use CAE to meet wind noise NVH targets, it is important to understand the main wind noise transfer paths. Testing confirmation of these paths by means of acoustic wind tunnel test is expensive and not always available. An on-road test procedure including a “windowing” method (using barriers) was developed to measure wind noise contribution at important higher frequencies through the main transfer paths, which were shown by test to be the glasses at a typical operating condition in which wind noise was dominant. The test data was used to correlate a full-vehicle SEA (Statistical Energy Analysis) model that placed emphasis on the glass properties, main noise transfer paths, and interior acoustic spaces while simplifying all other transmission paths. A method for generating wind noise loads was developed using measured glass vibration data, exterior pressure data, and interior acoustic data. The individual glass paths were correlated and a baseline model was developed including the noise contribution of all glass paths and a lumped non-glass flanking path. Design studies of the glass properties were performed, especially to explore the overall acoustic performance potential of laminated glasses, individually and in combination, which have potential to reduce vehicle weight. These results and recommendations of how this technique and baseline model can be extended to other vehicle body styles and conditions are presented. |
Can You Hear It Now? Time-Domain Source-Path-Contribution Applied To a Diesel Engine | Source-Path-Contribution (also known as transfer path analysis or noise path analysis) comprise a well-known set of techniques that have traditionally been performed in the frequency domain. With advancements and modern techniques, these same principles can be applied accurately in the time-domain. Foremost among the benefits of this are an ability to analyze transient events, and the ability to listen to the contributions from various sources instead of merely viewing them. This paper demonstrates the analysis of a diesel engine vehicle utilizing time-domain source-path-contribution techniques. |
Influence of the Gyroscopic Effects on Friction Induced Vibration in Aircraft Braking in System | Aeronautical brakes are subject to non-linear unstable vibrations. In particular, two modes appear and present a risk for the structure. Firstly, the whirl modes consist of a rotating bending motion of the axle out-of-phase with the brake torque tube. It is due to a coupling of two bending modes of the axle in orthogonal directions. Secondly, the brake squeal mode resulting from stick-slip or sprag-slip phenomena consists of a rotational motion of the brake around the axle. Those vibrations are not resulting from an external excitation but are friction-induced self-excited. Hence, they are dependent on tribological phenomena specific to carbon disks and are in particular controlled by the friction coefficient μ. In order to take into account the dynamical aspect in brake design, Messier-Bugatti-Dowty wants to simulate modes and acceleration g's levels. This article deals with the improvement of such a model. A finite element of the brake exists. It is able to reproduce whirl modes and squeal mode. In order to improve it, physical phenomena must be introduced. Here, the impact of gyroscopic effects is evaluated. For this, an analytical model is built to determine the consequences on frequencies and stability. |
A Study of Experimental Acoustic Modal Analysis of Automotive Interior Acoustic Field Coupled with the Body Structure | 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. This study focus on extracting the detailed acoustic mode shapes on the coupling surface for the improvement of the model accuracy. In order to extract the acoustic mode shapes on the coupling surface from an experimental test, the applied method is initially evaluated by FE model results. As the next step, the same procedure in the previous step is applied to the test data of an actual vehicle for the purpose of extracting the detailed acoustic mode shapes at the coupling surface of the body structure and cabin interior acoustic field. |
Vehicle Mid-Frequency Response Using the Superelement Component Dynamic Synthesis Technique | This paper presents the Component Dynamic Synthesis (CDS) superelement creation, which contains the loading frequency information and is much faster than the Component Mode Synthesis (CMS) method in the residual run. The Frequency Response Functions (FRFs) are computed using the direct frequency response method and the inversion of dynamic stiffness matrix is done using the singular value decomposition (SVD) method for every discrete frequency in the frequency range of interest. The CDS will be very efficient and economical for design of experiments and robust optimization, where hundreds of runs are required. The CDS super element can be used when there is a large number of residual runs on a very large vehicle model at higher end of the frequency range of study. For the residual analysis to run as fast as possible, all components, except very small ones, need to be converted into CDS superelements. Numerical results demonstrate the efficacy of the CDS method for the prediction of mid-frequency responses for vehicle vibration and noise. |
Method for Detecting Planar Surfaces in Outdoor Urban Environments | The ability to detect and recognize buildings is important to a variety of vision applications operating in outdoor urban environments. These include landmark recognition, assisted and autonomous navigation, image-based rendering, and 3D scene modeling. The problem of detecting multiple planar surfaces from a single image has been solved with this technology. |
Practical Loop-Shaping Design of Feedback Control Systems | An improved methodology for designing feedback control systems has been developed based on systematically shaping the loop gain of the system to meet performance requirements such as stability margins, disturbance attenuation, and transient response, while taking into account the actuation system limitations such as actuation rates and range. Loop-shaping for controls design is not new, but past techniques do not directly address how to systematically design the controller to maximize its performance. As a result, classical feedback control systems are designed predominantly using ad hoc control design approaches such as proportional integral derivative (PID), normally satisfied when a workable solution is achieved, without a good understanding of how to maximize the effectiveness of the control design in terms of competing performance requirements, in relation to the limitations of the plant design. |
Safely Stopping Motion Using Discrete Wiring | Functional machine safety using discrete wiring is an established way to protect workers from injury, and protect companies from the expense associated with accidents and downtime. |
SOFIA Closed- and Open-Door Aerodynamic Analyses | Work to evaluate the aerodynamic characteristics and the cavity acoustic environment of the SOFIA (Stratospheric Observatory for Infrared Astronomy) airplane has been completed. The airplane has been evaluated in its closed-door configuration, as well as several open-door configurations (see figure). Work performed included: acoustic analysis tool development, cavity acoustic evaluation, stability and control parameter estimation, air data calibration, and external flow evaluation. |
EDITORIAL: The unforgettable pyramid on the hood | If you're old enough to remember 1990, you may recall the best television ad of the year. It showed the front end of the all-new Lexus LS400 sedan against a black background. A multi-level pyramid of champagne glasses glistened in the center of the car's hood. It was demonstration time, and the demo was all about Noise, Vibration and Harshness-and the lack of it. |
How a Tier 2 tackles NVH | Saint-Gobain invested in anechoic testing so small components can make a big NVH difference. Saint-Gobain is a company that understands how vital NVH R&D is for perceived quality. Unwelcome noise is a major challenge in premium cars, but it is the minor components that matter. For Saint-Gobain that means particularly its bearings and tolerance rings. The French company, founded in the 17th century, has become so determined these components can assist with reducing vehicle NVH that it has built its own semi-anechoic chamber, hardly a routine investment for a Tier 2 supplier. Until recently, Saint-Gobain used facilities at European universities and a specialist test site in Germany for NVH development, but its own chamber in the U.K. will help the company to better understand OEMs' systems and improve performance. The ISO 3745- and 3744-compliant facility in Bristol was established with support from Southampton University's Institute of Sound and Vibration Research (ISVR Consulting) and by Brüel & Kjaer, with headquarters near Copenhagen, Denmark. |
Compact, Lightweight, CMC-Based Acoustic Liner | In the wake of recent developments that have reduced fan and jet noise contributions to overall jet-engine noise, aircraft designers are turning their attention toward reducing engine core noise. Innovators at NASA’s Glenn and Langley Research Centers are developing a compact, lightweight acoustic liner based on oxide/oxide ceramic matrix composite (CMC) materials. |
2017 Pacifica is first hybrid minivan, rides on all-new FCA platform | Despite the popularity of SUVs and CUVs, nothing beats a minivan for its combination of interior flexibility, ingress/egress, passenger comfort, cargo hauling and, in some cases, fuel efficiency. While the segment isn't as large as it was in 2000, when sales peaked at 1.37 million deliveries in North America, about 500,000 minivans are still sold annually-ample profit-spinning volume that analysts expect will be sustained through at least 2020. As millions of customers would likely attest, the minivan is “still the best transportation ‘tool’ for families,” observed Tim Kuniskis, head of FCA's passenger car brands, when he pulled the cover off Chrysler's 2017 Pacifica-the company's sixth generation minivan. It was shown to Automotive Engineering and other media on embargo prior to the car's official debut at the 2016 North American International Auto Show. |
Enhancing Image Clarity in the SWIR | A chromatic or color-corrected lenses for use in the visible portion of the electromagnetic spectrum have been addressed in literature, textbooks, and industry journals as early as the 18th Century. Many of these accounts by scientists and optical designers detail a method of selecting two dissimilar materials to form an achromatic pair or doublet with the ability to greatly counter image blurring resulting from the dispersive nature of refractive optical elements. Whether these tried and true optical formulae produce equally successful results in wavelengths beyond the visible range warrants further examination. |
Using Fan-poled Crystals to Tune Ti:S Lasers | Titanium:Sapphire (Ti:S)-based laser systems have revolutionized ultrafast research from biological imaging to high energy physics. Ti:S has a very broad gain bandwidth (680-1080 nm) but many applications require even broader tuning ranges covering UV, visible, and longer IR wavelengths. Frequency doubling, tripling, and quadrupling extend access to the 190-540 nm range. Ultrafast optical parametric oscillators (OPOs) pumped by Ti:S lasers reach beyond 1080 nm and fill in the “Ti:S gap” (540 to 680 nm). |
Experimental Sensitivity Studies on Glass Bonding Urethanes | This paper investigates the sensitivities of glass bonding adhesives to the dynamic characteristics of automotive body structures. Experimental modal analysis was conducted to study the damping, response amplitude, and stiffness of different adhesives to a door assembly and a vehicle body. Three different glass bonding adhesives were used in this study. Performance advantages of using these adhesives are given. |
Design and Construction of a Small Reverberation Chamber | As a manufacturer of a complete line of acoustical materials American Acoustical Products needed to construct a laboratory that would allow the characterization of the acoustical properties of its materials. Reference panels of materials were available that had been previously measured for absorption in a full scale reverberation chamber. A design for a small reverberation chamber was developed based on the Toyota Specification TSL 0600G-4 which includes a small transmission window for STL measurements. This design has the advantage of being constructed with no parallel surfaces, is tall enough to walk into and is optimized for measuring samples between 9 and 30 square feet in surface area. In order to allow the facility to function effectively several innovative techniques have been employed. To maximize the reverberation time the walls were constructed using constrained layer damped and mass loaded sheetrock on a timber frame. The walls and roof were constructed without cavities to avoid resonances and all the internal surfaces including the door and transmission window sealing panel were tiled with ceramic tiles for maximum reflectivity. The room's external surfaces were lined with sound absorbing foam to improve the sound transmission loss measurements. To generate a diffuse sound field, the chamber was excited by a NXT® Distributed Mode Loudspeaker which has virtually no directivity. To measure the room response, pressure zone microphones were placed in the corners of the room where all the resonant modes have pressure maxima. Finally the analysis of the RT60 sound decay was measured by a two channel real time analyzer using a studio mixing desk to switch between microphones. Results from the small reverberation room will show how closely the measurements agree with the full scale tests carried out to ASTM C423 at the Hudson Valley Acoustics Laboratory12 |
N-Hance: Software for Identification of Critical BSR Locations in Automotive Assemblies using Finite Element Models | Today's highly competitive automotive industry is constantly looking for ways to improve the perceived quality of its vehicles. Perceived quality defined as the sense of touch, feel and sound that the customer perceives in a vehicle is seen as one of the areas with maximum potential for increasing customer satisfaction. Buzz, Squeak and Rattle (BSR) is one of the major contributors towards the perceived quality in a vehicle. Almost all of the annoying noises that the customer hears can be classified into a buzz, squeak or rattle. Traditionally BSR in subsystems and components of a vehicle have been identified and rectified through extensive hardware testing. With the auto companies and suppliers being challenged to cut structural costs, eliminate costly hardware builds, and bring products to market faster by reducing development cycles, increasing math analysis of subsystems and components for such perceived quality issues is desirable. In line with the needs of the industry to perform math-based analysis and to improve the perceived quality of vehicles, Lohitsa and GM partnered to validate N-hance. BSR. N-hance.BSR is a software tool developed exclusively to identify BSR critical-locations, for the finite element model that is subjected to a vibration profile of interest. The software has been fully automated to rank order the issues based on their severity and thus enables analysis and interpretation of the results, with minimum user input. N-hance.BSR is a fully contained software including pre and post processors, user friendly GUI and report generating capabilities. The tool was used to predict critical-locations on two different subsystems and the results from the analysis were then correlated to BSR issues identified through hardware testing. In both cases the correlation was greater than 75%, taking into account only those issues from hardware components that were adequately represented in the finite element model. An overview of the method is presented followed by results from the BSR evaluation of an instrument panel and a door. |
Solution for Direct Solar Impingement Problem on Landsat-7 ETM+ Cooler Door During Cooler Outgas in Flight | There was a thermal anomaly of the landsat-7 Enhanced Thematic Mapper Plus (ETM+) radiative cooler cold stage during the cooler outgas phase in flight. With the cooler door in the outgas position and the outgas heaters enabled, the cold stage temperature increased to a maximum of 323 K when the spacecraft was in the sunlight, which was warmer than the 316.3 K upper set point of the outgas heater controller on the cold stage. Also, the outgas heater cycled off when the cold stage was warming up to 323 K. A corrective action was taken before the attitude of the spacecraft was changed during the first week in flight. One orbit before the attitude was changed, the outgas heaters were disabled to cool off the cold stage. The cold stage temperature increase was strongly dependent on the spacecraft roll and yaw. It provided evidence that direct solar radiation entered the gap between the cooler door and cooler shroud. There was a concern that the direct solar radiation could cause polymerization of hydrocarbons, which could contaminate the cooler and lead to a thermal short. After outgas with the cooler door in the outgas position for seven days, the cooler door was changed to the fully open position. With the cooler door fully open, the maximum cold stage temperature was 316.3 K when the spacecraft was in the sunlight, and the duty cycle of the outgas heater in the eclipse was the same as that in the sunlight. It provided more evidence that direct solar radiation had entered the gap between the cooler door and cooler shroud. Cooler outgas continued for seven more days, with the cooler door fully open. The corrective actions had prevented overheating of the cold stage and cold focal plane array (CFPA), which could damage these two components. They also minimized the risk of contamination on the cold stage, which could lead to a thermal short. |
MAGDOOR - Magnesium in Structural Application | The objectives of the project is to contribute to reduced emissions by weight reduction, which in this study is made by replacing the inner door steel structure with cast magnesium. Weight target is 55 % relative steel, implying vehicle lightening by more than 25 kg, hence saving 200 litre fuel during the life of the vehicle. A magnesium door concept is expensive in high volumes, and the risks include incomplete die filling, multimetal incompatibility and low strength. Cost efficiency implies to design for integration and commonality. Ductile alloys, correct ingate shape and optimized wall thickness is necessary to meet the impact and quality requirements of the door structure. Joining Al to Mg is mainly limited to adhesives and promising Mg surface treatment alternatives to chromateing have been evaluated. |
Localized Nonlinear Model of Plastic Air Induction Systems for Virtual Design Validation Tests | Plastic air induction system (AIS) has been widely used in vehicle powertrain applications for reduced weight, cost, and improved engine performance. Physical design validation (DV) tests of an AIS, as to meet durability and reliability requirements, are usually conducted by employing the frequency domain vibration tests, either sine sweep or random vibration excitations, with a temperature cycling range typically from -40°C to 120°C. It is well known that under high vibration loading and large temperature range, the plastic components of the AIS demonstrate much higher nonlinear response behaviors as compared with metal products. In order to implement a virtual test for plastic AIS products, a practical procedure to model a nonlinear system and to simulate the frequency response of the system, is crucial. The challenge is to model the plastic AIS assembly as a function of loads and temperatures, and to evaluate the dynamic response and fatigue life in frequency domain as well. This paper presents a modeling procedure for nonlinear plastic products, such as AIS assemblies, by using an array of locally linearized systems, for virtual design validation tests. The measurement results of physical DV tests are first presented to quantify the basic nonlinear response behaviors of the plastic AIS products. The proposed finite element modeling method is then evaluated based on correlation with the measured test results. The localized nonlinear model is thus employed to simulate the frequency response of the plastic AIS products and to identify weak spots of the design. Durability evaluation of the AIS product is then conducted in terms of estimated life, based on the simulated dynamic stresses and material fatigue properties. The presented procedure has helped the engineering team to identify potential durability design problems without a prototype, and to guide the design changes and modifications. |
Standard Metrology for Vehicular Displays | The scope of this SAE Standard is to provide methods to determine display optical performance in all typical automotive ambient light illumination - with focus on High Ambient Contrast Ratio, which is critical for display legibility in a sunshine environment. It covers indoor measurements and simulated outdoor lighting. It is not the scope of this document to set threshold values for automotive compliance, however some recommended values are presented for reference. |
Effects of Brake Pad Boundary Contact Surfaces on Brake Squeal | The disc brake corner assembly is comprised of several subsystems (brake pad, caliper, rotor etc.) which have interfaces between two or more of these structures. The brake pad assembly as the subsystem connecting the rotor to the caliper has specific areas of contact which influence the onset and potential to control brake squeal. The primary excitation interface occurs between the friction pad and rotor surface. The contact is initiated by the piston apply force on the brake pad insulator. Contact interface reaction forces, displacements and deformations are generated and form the natural and geometric boundary conditions of the overall system. Brake squeal characteristics are strongly affected by these conditions. The study focuses on brake system dynamic response to interface contact conditions. The brake insulator and pad assembly interacting with the brake piston as well as caliper are evaluated. Modifications that change the system dynamics through these interfaces are also assessed by dynamometer testing. Properties including compliance, interface friction and traction, damping, decoupling and isolation are discussed with respect to their potential impact on mechanisms leading to brake squeal. Three practical solutions that have been proven to decrease brake squeal via interface modifications are demonstrated at two interface areas 1) Piston to insulator modifications via changes in friction level as well as decoupling and damping 2) Caliper assembly interface with the backing plate incorporating friction level changes with decoupling and damping at the attachment point. Comparative test results indicating the effect of these modifications are presented. |
Improvement in Noise Transmission Across Firewall of a Passenger Car | Firewall of a car separates the engine compartment from the cabin and acts as a barrier for engine noise entering the passenger compartment. Hence noise transmission through the firewall plays an important role in determining the interior noise of a car. Noise Reduction measurement technique is useful to evaluate existing and potential acoustic treatments of the firewall of a car. This paper presents two systematic measurement approaches for quantifying the acoustic performance of firewall insulation materials across the firewall of a car. First a Volume Velocity Source was placed in the passenger compartment and noise reduction was measured across the firewall with different configurations of firewall acoustic treatments. Similar exercise was repeated by installing an actual vehicle firewall in a sound transmission loss suite and measuring the noise reduction across the firewall. Measurement techniques such as leakage detection and sound intensity mapping were used to enhance the understanding of the noise transmission paths through the firewall and to rank the dominant leakage areas. Based on the above, appropriate modifications to the car have been carried out and evaluated for reducing the noise transmitted through the firewall of the car. To assess the influence of improvement in noise reduction across the firewall on the interior noise of the car, in cab noise measurements were carried out with the engine running on the test track. |
Brake NVH: Testing and Measurements | As other vehicle systems have become more refined, more attention must be placed on brake NVH issues because they can cause a negative customer experience. From the laboratory to the road, the use of technology as well as further study by engineers is helping to lessen noise, judder, and vibration in cars. This book provides readers with a fundamental understanding of current practices for measuring and testing brake NVH. From coverage of basic definitions and concepts to in-depth analysis of on-road testing procedures, it will serve as a comprehensive reference guide for brake test technicians, test engineers, lab managers, and others who work on making brakes quieter, smoother, more refined, and more reliable. Readers will learn how to test for brake noise, what tools to use, and which recent standards and practices have led to the successful measurement of brake noise and vibration. Topics covered include: • Common brake noise and vibration issues • Instrumentation, transducers, and other technical details • Measurement practice for laboratory and on-road testing • Brake pad damping and natural frequencies • Current trends in brake noise and vibration measurements |
Principles of Vibration Analysis with Applications in Automotive Engineering | This book, written for practicing engineers, designers, researchers, and students, summarizes basic vibration theory and established methods for analyzing vibrations. Principles of Vibration Analysis goes beyond most other texts on this subject, as it integrates the advances of modern modal analysis, experimental testing, and numerical analysis with fundamental theory. No other book brings all of these topics together under one cover. The authors have compiled these topics, compared them, and provided experience with practical application. This must-have book is a comprehensive resource that the practitioner will reference time and again. |
Dispersion of Test-Based NVH Characteristics at Various Trim Levels | A broad measurement campaign was run at Volvo aiming at the evaluation of dispersion in test-based NVH characteristics of a car body and at the derivation of reference data for judging the accuracy of CAE predictions. Within this work 6, nominally identical, vehicles were tested. Tests included operational noise on Complete Vehicle (CV) level (road noise, engine noise and idling noise), NTF, VTF & Acoustic FRF measurements in CV, Trimmed Body (TB) & TB-Stripped (TBS) configurations. Additionally, modal analysis and NTF, VTF, AFRF tests were carried out on 4 BIPs of the same vehicle type. Further, limited tests were carried out on 28 vehicles of the same type. The aim of the work was to study the development of dispersion with increasing complexity of the test object, from the BIP to TB and CV. In this respect this study is unique - there has been several studies regarding the dispersion in test results but the studies that trace the dispersion between different levels of complexity of the test object are scarce if not non-existent. In parallel with this, CAE activities were carried out in order to create CAE models corresponding exactly to the test objects, for all trim levels. Even the boundary conditions were modeled with great detail. In this way, it was possible to study the development of CAE prediction accuracy with increasing complexity of the test object. Further on, several classes of measurement points' locations were studied. In the paper the dispersion results will be presented and some comments regarding prediction accuracy and its assessment will be given. |
Influence of Tire Air-borne Noise on Vehicle Loudness Predicted during Design Phase Based on Hybrid Internal Noise Contribution Model | The development of new technologies that reduce engine size and improve performance, combined with the introduction of hybrid and electric vehicles, make tire noise critically important for the new generation of automobiles. Tire noise transmission into the passenger compartment can be classified as either air-borne or structure-borne sound. Both of these mechanisms are very complex to predict because tires are highly non-linear, subject to large static, dynamic and centrifugal loads; they suffer from impact, stick and slip forces; and the pumping of air in the tire grooves is complicated. Customers today demand more sophistication of products in terms of interior noise; thus, sound quality metrics have earned an important role during the design phase allowing human perception of noise to be predicted and improved with reduced cost in a way that addresses consumer preferences. Of the various metrics, loudness has been shown to be the most important metric due to consideration of masking effects on human hearing. This paper discusses global loudness assessment of a vehicle during its design phase for two different types of tires through a hybrid internal noise contribution model with the following inputs: i - powertrain forces (surrogate data); ii - tire radiated noise (measured from a carryover vehicle through of a chassis roll dynamometer within a hemi-anechoic chamber), iii - noise transfer functions (simulated using FEM), iv - acoustic noise reduction functions (simulated using SEA). |
Automotive Electronics Testing for Conductive Coated Heat Reflective Windows | The electromagnetic interference between the conductive coating in heat reflecting automotive glass and vehicle electronics can limit the application of such technology. A number of methods are available to maintain electromagnetic compatibility and the function of RF electronics in the passenger compartment, while accruing the heat load reduction benefits of the coating. This paper provides detailed test data showing the antenna performance differences resulting from the conductive windshield transmission of RF signals. |
Engineering Moveable Glass Window Seals of Automotive Door Using Upfront CAE | The traditional moveable glass window seal development process has relied heavily on physical prototypes for design verification. Due to frequent styling changes and an overall reduction in design time, physical prototypes for the glass window seals have proven to be inadequate. Utilization of computer aided engineering (CAE) tools is necessary in order to shorten lead time. CAE tools will help to decrease expensive prototyping, free up valuable manufacturing line time, and improve overall quality. A cross functional approach has been applied to expand the scope beyond traditional methods of moveable glass window seal design, such as wedged boarding, into new computerized modeling methods. The CAE was used to address major requirements of the glass window seals including glass velocity, glass stall force, sealing-ability, seal durability, seal assembly, seal appearance, and regulator motor current. A systematic process is used for the glass window system design development using CAE to insure that production parts will meet all functional and assembly process objectives. |
Dimensional Management Process Applied to Automotive Door Systems | The processes utilized in building-up and installing automotive door assemblies to a body are required to address a complex interaction of dimensional requirements. The Dimensional Management Process is employed to arrive at the optimum design and process to achieve the many functional and appearance related requirements of the door system. This paper will demonstrate the application of the Dimensional Management Process to the typical automotive door system and the use of integrated three-dimensional tolerance analysis to compare different door assembly and installation methods for the purpose of achieving an optimum appearance and functionality of the door system. |
Testing of New Composite Side Door Concepts | Car side doors are one of the most complex parts of the body, because this component has to meet a lot of requirements. Independent of the material - steel, aluminum, magnesium, or fiber-reinforced plastics (FRP) - there are multiple important requirements. In this paper, testing methodologies for self-supporting car side doors made from FRP are presented based on different conceptual design studies using these innovative materials. These doors and related testing methodologies have been developed in joint research and pre/advanced-development projects with different partners, car manufacturers as well as suppliers. The importance and benefit of benchmarks, advanced experimental material analysis, substructure and full-size component testing in the product development process is discussed. Furthermore important links to the CAE-process are referred and the significant value on the whole development process is demonstrated. Test data for new composites car side doors based on different conceptual design are presented and methodologies for further improvement of the development process suggested. |
Analytical Robust Door Hinge System Design Taguchi Approach | The automotive industry faces many competitive challenges including weight and cost reduction to meet CAFE standards. In particular, a non robust door hinge optimized for weight reduction may cause high warranty and durability problems in the field. Many analytical techniques such as optimization and sensitivity analysis have been widely used in a hinging system design. However, none of the techniques include robustness and the design variation in the analysis. This paper presents an application of finite element method coupled with the parameter design using Taguchi's design of experiment. This approach identified the hinge design variables in the pillar-hinge-door system and improved the robustness of vertical rigidity performance. |
Slam Life Assessment Method for Closures Durability | The Slam Life Assessment Method (SLAM) is a CAE solution that predicts the durability of automotive closures subject to a repetitive slamming load. Moreover, SLAM is a fully automated program that integrates several software and CAE analyses into a single turnkey solution. SLAM employs the physics of the slam event to succeed where prior analysis methods fail. Standard CAE analyses such as inertia relief, normal modes, and forced loading response cannot capture the physics of the dynamic stress states that occur during a durability slam event. Furthermore, SLAM produces insight into the behavior of the door system that cannot be gained through testing. We have shown that it is possible to predict the performance of a door subject to a slam-closed event with 80-90% reliability. This method has been realized via motivation to solve numerous door panel cracking issues associated with preliminary door designs. Correlation of SLAM methods with physical tests led to the ability to “virtually” slam and redesign doors before prototypes were made. To date, SLAM is used mainly on door systems, however, it is easily extended to hood, decklid, and liftgate systems. SLAM simulations have proven their usefulness on aluminum hood “tea cup” designs. SLAM saves product development time and money by reducing the number of prototypes needed to evaluate a design proposal. It allows evaluation of more design alternatives, reduces weight, and results in fewer production level failures. As the automotive industry moves towards a 10-year durability life, the testing times and number of samples continues to increase in order to meet these tougher requirements. Door slam testing can take several months to schedule and complete, whereas, SLAM can reduce this process to a few hours. The net result is a benefit to the customer in the form of a structurally optimized closure assembly that has no durability problems. |
Ultralight Intercostal Automatic Fastening System | A high level directive is in place at the St. Louis facility to increase the use of automation in our assembly processes. Likewise, the C-17 program has implemented a series of cost reduction initiatives. In line with these initiatives we have been implementing automatic fastening equipment into a variety of non-traditional applications. The C-17 Cargo Door Intercostals can easily be described as “non-traditional” and represent unique challenges for automatic fastening. The concept for The Intercostal Riveter uses proven drill and riveting techniques. However, it has miniaturized components and will be utilized like a portable power tool. Manipulated by a single operator, it will be maneuvered around and throughout the C-17 Cargo Door Assembly Jig. It is ultra-lightweight and will have a C-Frame constructed from carbon-epoxy composite material. |
A New Component Test Methodology Concept for Side Impact Simulation | This paper describes the development of a new component test methodology concept for simulating NHTSA side impact, to evaluate the performance of door subsystems, trim panels and possible safety countermeasures (foam padding, side airbags, etc.). The concept was developed using MADYMO software and the model was validated with a DOT-SID dummy. Moreover, this method is not restricted to NHTSA side impact, but can be also be used for simulating the European procedure, with some modifications. This method uses a combination of HYGE and VIA decelerator to achieve the desired door velocity profile from onset of crash event until door-dummy separation, and also takes into account the various other factors such as the door/B pillar-dummy contact velocity, door compliance, shape of intruding side structure, seat-to-door interaction and initial door-dummy distance. This method is capable of reproducing the characteristic “double-peak” of the door velocity profile and, can be used for side airbag evaluation, by simulating the close-in velocity and distance between the side structure and dummy. In this approach, the door velocity profile is simulated in four phases: In the first phase, a pre-crushed door mounted on a ‘Door sled’ (at approximately the same distance from the dummy as in a car), is accelerated by the HYGE until it impacts the stationary dummy, to generate the first peak. In the second phase, from the onset of dummy contact, the door sled is decelerated by a honeycomb block (mounted on another ‘Base sled’), simulating the first ride-down of the velocity profile. During this phase, the HYGE is dormant. In the third phase, the HYGE accelerates both the Door and Base sleds together to simulate the second peak. In the fourth phase, the Door and Base sleds are decelerated until door-dummy separation by means of a VIA decelerator system, thus simulating the entire door velocity profile from start of crash event until the door and dummy separate. In conclusion, the MADYMO model demonstrates the feasibility of the concept, pending experimental prove-out on the sled. |
Thermal Qualification of the Sciamachy Passive Cryogenic Cooler | This paper describes the design and qualification of this SCIAMACHY Radiant Cooler and focuses on the methods and results of the thermal balance and thermal verification test of the Radiator Reflector Unit flight model, performed late summer 1998. A new type of temperature control has been used that proved to increase speed, simplicity and accuracy of the test itself as well as the evaluation afterwards. The RRU TB/TV test was successful in gathering all significant thermal parameters. After refurbishment of the cooler door and a requalification test of its transient performance all cooler parameters are acceptable and its thermal performance is within specification. |
Accuracy Determination of Sheet Metal Forming Simulation Using One-Step Code | The use of numerical simulation in the design of stamped components has become common industrial practice. Inverse one-step codes are among the fastest to provide answers but, unlike incremental codes, they need an additional verification phase. Given this context, IVECO has conducted experimental testing work on the plastic deformations measured on two industrial components obtained by means of sheet steel stamping. The two components, one with structural functions (sliding door upper reinforcement) and the other one with esthetic functions (rear left door skin), have been selected as representative of the various feasibility and process issues connected with sheet metal drawing. |
Experimental and Computational Study of Vehicle Surface Contamination on a Generic Bluff Body | This paper focuses on methods used to model vehicle surface contamination arising as a result of rear wake aerodynamics. Besides being unsightly, contamination, such as self-soiling from rear tyre spray, can degrade the performance of lighting, rear view cameras and obstruct visibility through windows. In order to accurately predict likely contamination patterns, it is necessary to consider the aerodynamics and multiphase spray processes together. This paper presents an experimental and numerical (CFD) investigation of the phenomenon. The experimental study investigates contamination with controlled conditions in a wind tunnel using a generic bluff body (the Windsor model.) Contamination is represented by a water spray located beneath the rear of the vehicle. The aim is to investigate the fundamentals of contamination in a case where both flow field and contamination patterns can be measured, and also to provide validation of modelling techniques in a case where flow and spray conditions are known. CFD results were obtained using both steady RANS and unsteady URANS solvers, combined with particle tracking methods. Steady RANS does not capture the wake structures accurately and this affects the contamination prediction. URANS is able to recover the large-scale wake unsteadiness seen in the experimental data, but the difference between the experimental and computational contamination distributions is still notable. The CFD is also able to provide further insight by showing the behaviour of particles of different sizes. Large particles are found to take on a ballistic trajectory and penetrate the wake. In contrast, small particles are shown to be less likely to become entrained into the wake. |
PSV Emergency Exits: Passenger Behaviour and Exit Design | This study tested the speed and ease with which individual passengers could open and use the emergency exits currently provided on buses and coaches. The survey found that passengers believed that certain emergency exits, such as doors and hinged windows, would be easy to use in an emergency, that they knew how to use them and that instructions would help if they were uncertain. Twenty exit types were then tested with passengers, including emergency doors, ‘continental’ doors, roof hatches, hinged windows, breakglass windows and the emergency operation of service doors. It was found that passengers' expectations were generally not being met. Inappropriate handle design, location, feedback, anti-tamper cover guards and unclear instructions were found to result in significant delays in evacuation. The study recommends design improvements in these areas together with a consistent approach to the design and provision of emergency exit signage, conspicuity and instructions. It also recommends that high level doors are equipped with steps and that if window exits are to be retained these should be hinged rather than break-glass as the latter have severe disadvantages. |
Safety and Security Considerations of New Closure Systems | A closure system for automotive security and driver comfort has been developed. The system combines a passive entry system and an electronic door latch system. The passive entry system utilises a single chip transponder for vehicle immobilisation, passive entry and remote control functionality. The form factor free transponder enables the integration into a key fob or a smart card. The system can be activated by either pulling the door handle or by using a push button transponder. Due to the inductive coupling between the transponder and the vehicle mounted antennas, the vehicle door or trunk opens on successful verification as if there were no locks. Additionally, inside the vehicle, the transponder can be used as a far range immobiliser. The electronic door latch system utilises electronically controlled latches. Symmetrical housing of the electronic latch (E-latch) and the absence of a mechanical connection to the actuators enable the latch to be used not only for the left and right side doors but also for trunk applications. The locking pawl of the E-latch is controlled by an electric motor and the functionality is entirely software dependent. |
Design and Development of a Generic Door Hardware Module Concept | This paper documents the design methodology, part performance, and economic considerations for a generic hardware module applied to a front passenger-car door. Engineering thermoplastics (ETPs), widely used in automotive applications for their excellent mechanical performance, design flexibility, and parts integration, can also help advance the development of modular door-hardware systems. Implementation of these hardware carriers is being driven by pressures to increase manufacturing efficiencies, reduce mass, lower part-count numbers, decrease warranty issues, and cut overall systems costs. In this case, a joint team from GE Plastics, Magna-Atoma International/Dortec, and Excel Automotive Systems assessed the opportunity for using a thermoplastic door hardware module in a current mid-size production vehicle. Finite-element analysis showed that the thermoplastic module under study withstood the inertial load of the door being slammed shut at low, room, and elevated temperatures. |
Sound Quality of Impulsive Noises: An Applied Study of Automotive Door Closing Sounds | This paper discusses four general attributes which quantify the character of an impulsive sound event. These attributes include the time duration, amplitude and frequency content of the impulsive noise. A three dimensional plot relating time, frequency and amplitude have been developed for the presentation of the measured data. This format allows graphic illustration of the noise event, providing fast interpretation and communication of the measured sound. Application of this methodology to the sound of an automotive door closing event is presented here. Representative door closing sound events are analyzed, with correlation presented between the attributes above to dynamic events of the physical hardware within the door and vehicle systems. Modifications of the door-in-white, internal door hardware, seal systems and additional content are investigated for their effect on the sound quality of the door closing event. Finally, recommended values for these attributes are presented. In general, a pleasing door closing sound event will be developed if the stated values are obtained. Furthermore, general insight is also provided that would indicate how directional changes to these attributes may allow customization of the door closing sound event to achieve a desired sound quality. |
Sound Transmission Analysis of Vehicle Door Sealing System | A finite element-based acoustic-structure interaction analysis tool has been developed to determine the noise transmission loss characteristics of door seal systems. This tool has been applied to determine the effects of the individual parameters, such as seal material density, seal constitutive model, separation distance between seal layers, external cavity shape, and seal prestress field, on noise transmission characteristics. Our findings indicate that the external and internal cavity shapes, seal material density, and deformed seal geometry are the key factors affecting the noise transmission through seal system. Increasing seal material density decreases the resonance frequencies and increases the overall sound transmission loss. Changing the separation distance between seal layers changes the sound transmission characteristics without changing the compression load deflection behavior of the seal system. Moving the resonant frequencies to desired frequency regions, we can reduce seal system contribution to the vehicle interior noise level. The nature of the resonance frequencies of this coupled system have also been determined. This analysis tool was applied to determine the noise transmission characteristics of a vehicle door seal system, and the seal system contribution to the vehicle interior noise level. |
A Field Evaluation of the S-1 Pedestrian Guard: Transit and Shuttle Bus Applications | The need to reduce the injury to pedestrians that are run over or pinned beneath a bus is an ongoing concern for transit authorities and other operators. Occasionally, a pedestrian will be run over by the right rear wheel while exiting the rear door. This accident occurs in various scenarios such as when people exit the bus and become entangled in the door grab bars, or when they fall between the curb and the bus while it approaches or departs. With all scenarios, the S-1 Gard acts similar to a cow catcher, pushing the fallen pedestrian out and away from the rear tire. This paper will: outline various incident scenarios, evaluate the S-1 Gard's performance in a city environment, review installation of the guard as well as its maintenance requirements. The purpose of this paper is to bring to the attention of transit authorities and shuttle operators the overall value of this device. |
Performance Improvement in Leak Noise Reduction | One of the most important quality required for luxury vehicle is quieter cabin. Up to the present, for its improvement, various countermeasures have been carried out. For example, additional weather-strips were added around door for noise reduction and quieter engines were developed. But, with all these performance improvements, local leak noise becomes major remaining. In order to achieve quieter vehicles, the noise has to be stopped by every possible means. In this report, performance improvement in noise reduction is studied by connecting both ends of inner belt weather-strip and glass run. And the influence of connecting portion for glass sliding durability is evaluated. |
Development and Application of Laser Scanning Method to Automotive Component Manufacturing | The majority of current measurement methods in the manufacturing arena use coordinate measurement machines (CMM) and special gages with fixtures. The use of CMM's for offline metrology is prevalent throughout the manufacturing community, however the time required to inspect a part is sometimes prohibitive. The special low cost gages open the door to operator error and in most cases it cannot capture more than few measurements at once. Automated laser scanning equipment was selected to evaluate the possibility of reduced inspection as well as for global quality feedback. Although many laser scanning methods and applications are available in the market today, very little is understood with regards to its capabilities and its use in the automotive manufacturing arena particularly for the inspection of large parts. This paper explores the methodology one can use to apply such devices to improve upon current quality methods for both large and small automotive parts. |
Surface Finishing Compression Molding (SFC): A Comparative Cost Study for Paint vs. Paint Film Finishing | New technologies are required to sustain an industrial society. Their fragile early life must be nurtured by the risk takers in the beginning stages of development for new technologies to survive. In the automotive industry, new technologies that focus on reduced cost, reduced pollution and/or reduced energy consumption are being carefully evaluated. The Valyi Surface Finishing Compression Molding (SFC Molding®) process addresses all three issues1,2. This process is in the early stage of development. Large, thermoplastic, exterior panels (door/hood size) have been made on commercial equipment to demonstrate general feasibility but there are no “show me” production parts for the risk averse. In the absence of production case studies, an investor (licensee candidate) must examine the potential benefits of the process relative to the state-of-the-art technology. This paper examines an approximation of the cost to produce a major exterior panel (roof) by SFC molding versus conventional steel and paint. |
A Study of Occupant Ejection Mitigation During Rollovers for Front Row Occupants | As a part of its ejection mitigation research, the National Highway Traffic Safety Administration (NHTSA) has proposed a linear impact test that uses a featureless head-form to impact a vehicle's side windows' daylight opening at various positions. The test measures the excursion of the head-form beyond the plane of the window glazing. The intention is to evaluate the ability of a vehicle's ejection mitigation countermeasures, such as the curtain airbag or other vehicle features, to manage the impactor energy and limit excursion. However, at this time NHTSA has not yet established the performance criteria for the excursion. Additionally, there is no clear agreement on the energy level to be used for ejection mitigation testing. The agency has considered three energy levels for the head-form impact: 178, 280, and 400 Joules [ 9 ]. This paper discusses the results from computer modeling used to study an ejection representative energy level that can be employed for evaluating ejection mitigation systems. Additionally, the authors will present a parameter study in which the stiffness of a curtain airbag has been optimized considering both the NHTSA's ejection mitigation research test method as well as side impact performance. |
A FE Based Procedure for Optimal Design of Damping Package, with Presence of the Insulation Trim | Typically, in the automotive industry, the design of the body damping treatment package with respect to NVH targets is carried out in such a way to achieve panel mobility targets, within given weight and cost constraints. Vibration mobility reduction can be efficiently achieved thanks to dedicated CAE FE tools, which can take into account the properties of damping composites, and also, which can provide their optimal location on the body structure, for a minimal added mass and a maximized efficiency. This need has led to the development of different numerical design and optimization strategies, all based on the modeling of the damping composites by mean of equivalent shell representations, which is a versatile solution for the full vehicle simulation with various damping layouts. However, these approaches, which can estimate correctly the beneficial vibration effect of damping pads application on the vehicle body, address the body NVH target with no consideration of the impact that the presence of the insulation on body panels can have on the final vibration result. On the other hand, the efforts carried out in the last years for FE implementations of Biot's system of equations have led to simulation methods at vehicle level, which can take into consideration the dynamical behaviour of porous materials and which allow including in an efficient and flexible way sound package parts into vehicle FE models used for NVH analyses. This paper presents a FE-based procedure, thanks to which it is possible to design the optimal damping lay-out with respect of panel mobility targets, while taking into account the presence of the insulation part on body panels. In a first section a design methodology for damping layout is presented. This method, that is completely integrated in Nastran, is able to provides the ranking and vibration pattern of the vehicle panels with highest mobility for a given frequency range and set of loads in order to maximize the effect of the damping treatment. Then the problem of the influence of the acoustic treatment on the panel vibrations has been addressed. The proposed solution is represented by an implementation in MSC/Nastran of the Biot-Allard theory for porous media. This procedure allows a smart coupling of structural FE model with a FE boundary representation of the acoustic part. In the last section, the benefits of the joined use of the two techniques are highlighted by mean of their application on a simple test case as well as on a full-vehicle. |
Electromagnetic Compatibility of Conductive Heat Reflecting Automotive Windows | One of the challenges of automotive designs which utilize heat reflecting glazing is the conductivity of the reflective coating. Significant attenuation of electromagnetic energy occurs when devices which send or receive signal through the glazing are mounted on or very near heat reflecting windows. A number of methods are available to maintain electromagnetic compatibility and the function of these and other devices in the passenger compartment which communicate with devices outside of the vehicle. |
Helmholtz Resonators Acting as Sound Source in Automotive Aeroacoustics | Helmholtz-resonators are discussed in technical acoustics normally in conjunction with attenuation of sound, not with amplification or even production of sound. On the other hand everybody knows the sound produced by a bottle, when someone blows over the orifice. During the investigation of the sound produced in body gaps it was found that the underlying flow physics are closely related to the Helmholtz-resonator. But different from the typical Helmholtz-resonator generated noise – as for example the blown bottle or, from the automotive world, the sun roof buffeting – there is no fluid resonance involved in the process. For body gaps the random pressure fluctuation of the turbulent boundary layer is sufficient to excite the acoustic resonance in the cavity. The sound generation is characterized by a continuous rise in sound pressure level with increasing velocity, the rise is proportional to U with varying exponents. It will be shown that the fluid resonance is shifted to much higher velocities than one would expect from Rossiters feedback model. This is the reason that it can not be found in body gaps. Nevertheless even without fluid resonance the body gaps represent the most important noise source for modern automobiles. A vehicle is much more silent in the interior if all gaps are closed as if, for example, the wing mirrors are removed and the A-Pillar-radius is doubled. The shift of the fluid resonance to higher velocities mentioned above is associated with a reduced transport velocity for vortices over small orifices. Experimental evidence will be shown that this transport velocity is dramatically reduced for orifices buried under a thick turbulent boundary layer. |
Scaling Laws in Automotive Aeroacoustics | Scaling laws - for example the variation of sound pressure with wind speed - are a key to the physical understanding of aeroacoustic phenomena. Aeroacoustics in Automotive applications differs from other fields of aeroacoustics: It is limited to low Mach numbers, the flow field is dominated by separated flows and the radiation into the far field is typically not of primary interest. On the other hand there are of course many common problems and findings shared with other fields in aeroacoustics. Therefore it is important to identify common areas with other, probably more advanced directions in aeroacoustics. But this has to be done without forgetting the practical demands of automotive application. Main sources for interior wind noise in vehicles are leakage noise, cavity noise and the noise generated by separated flows at the outer surface. All three of these noise sources will be investigated in this paper. Of special interest will be the dependence on the wind velocity. It will be shown that three different exponents (U4, U6 and U8), corresponding in aeroacoustics to monopole, dipole and quadrupole noise, can be present in a single source. |
Time - Frequency Analysis Techniques Applied to Automotive Noise and Vibration Signals | Automotive stationary noise and vibration signals are normally analyzed using Fourier methods. However, many noise and vibration signals are non-stationary (transient or time-varying). In those situations, the time characteristics of the signals can be lost using standard Fourier methods. Lately, time-frequency (TF) analysis methods have become more popular and are applied in many different areas of NVH (Noise, Vibration, and Harshness) in order to preserve the time-frequency information. The objective of this paper is to present some of the different time-frequency analysis tools, such as the Short Time Fourier transform (spectrogram), the Gabor Transform, the Wavelet transforms (scalograms), and the Wigner-Ville Distribution. Examples of application of these techniques to automotive non-stationary noise and vibration signals are presented. |
Noise Source Localization on Washing Machines by Conformal Array Technique and Near Field Acoustic Holography | The acoustic emission of a washing machine has been deeply studied by comparing three different techniques, which are: - conventional acoustic intensity, - planar near-field acoustic holography and - conformal array technique based on the Helmotz Equations Least Squares method. These techniques have been used to measure the front of a washing machine, i.e. the more critical side from the acoustic comfort point of view in the working environment. The acoustic intensity measurement has been taken as reference for the comparison of the two other techniques. The sound intensity probe has been scanned over a grid of several discrete positions and the acoustic intensity and pressure on the measurement plane have been determined. For both the conformal and planar near-field acoustic holography techniques an antenna of 30 microphones has been employed scanning over several positions in order to cover the entire washing machine front with a spatial resolution of 2.5 cm (maximum frequency 13720 Hz). Advantages and limitations of the noise source location techniques have been examined thoroughly. |
Experimental Investigation into Friction Induced Noise of Automotive Wiper System | The test is carried out to examine the vehicle interior noise, windscreen vibration and wiper blade vibration induced by wiper friction, under the combination conditions with various wiping speed and windscreen wetness. The noise's time-frequency characteristics, influence factors and noise source were approached by means of time domain, frequency domain and time-frequency domain analysis. The results indicated that wiper noise can be classified into reversal noise and wiping noise. The reversal noise is characterized by impulsive noise, and wiping noise is featured by wide-band noise with harmonic components. The nature of both types of noises is strongly affected by the windshield wetness; however, it is far less affected by the wiping speed. The wiping noise is mainly resulted from lateral and vertical vibration of wiper blades. Nevertheless, the wiping noises under wet and half-dry conditions are respectively caused by the wiper blade vibration of driver side and that of co-driver side. |
Aeroacoustics Predictions of Automotive HVAC Systems | Acoustics comfort is a key point for the ground transportation market and in particular in the automotive area. A significant contributor to the noise levels in the cabin in the range 200Hz to 3000Hz is the HVAC (Heating, Ventilating, and Air Conditioning) system, consisting of sub-systems such as the air intake duct, thermal mixing unit, blower, ducts, and outlet vents. The noise produced by an HVAC system is mainly due to aeroacoustics mechanisms related to the flow fluctuations induced by the blower rotation. The structure borne noise related to the surface induced vibrations and to the noise transmission through the dash or plastic panels may also contribute but is not considered in this study. This study presents a digital approach for HVAC aeroacoustics noise predictions related to the ducts and outlet vents. In order to validate the numerical method flow and acoustics measurements are performed on production HVAC systems placed in an anechoic room. The flow is generated using a fan located outside the room and a muffler is used to create a silent incoming flow. The dependency between the volume flow rate and the noise levels is investigated together with the effect of the outlet vents on the aeroacoustics mechanisms. The aeroacoustics simulations are performed using a time explicit, unsteady and compressible method in which flow and acoustics are calculated at the same time. The numerical results are compared to the experimental ones and certain analyses, not easily accessible through measurements, are provided. In particular, duct mode behavior and the influence of the outlet vents on the acoustic radiation are highlighted. The numerical predictions are shown to correlate reasonably well to the test measurements, and the developed method can be used during the vehicle development process to evaluate and optimize the aeroacoustics performance of the HVAC system. |
Attenuation of Vehicle Noise using Different Trunk Insulation Systems | Attenuation of noise from the rear of a vehicle was evaluated for different trunk insulation systems using a combination of poro-elastic material modeling and a full vehicle SEA model. The model considered the interaction between the trunk and the passenger cabin. The sound absorption coefficients and acoustic impedance for each of the material systems used in the trunk were measured and the poro-elastic Biot properties were calculated to define the acoustic treatments in the SEA model. Several levels of acoustical treatment for the trunk were studied ranging from a trunk with no decorative liner to a trunk with a liner and maximum acoustical treatment. The results show the contribution of the trunk material in reducing cabin noise for different levels of noise originating at the rear of the vehicle. These results demonstrate the value of combining poro-elastic material modeling and SEA models for selecting efficient material systems early in a vehicle design. They also highlight vehicle designs that require acoustically tuned trunk material to prevent compromises in the overall NVH performance. |
Vehicle Noise, Vibration, and Sound Quality | This book gives readers a working knowledge of vehicle vibration, noise, and sound quality. The knowledge it imparts can be applied to analyze real-world problems and devise solutions that reduce vibration, control noise, and improve sound quality in all vehicles—ground, aerospace, rail, and marine. Also described and illustrated are fundamental principles, analytical formulations, design approaches, and testing techniques. Whole vehicle systems are discussed, as are individual components. The latest measurement and computation tools are presented to help readers with vehicle noise, vibration, and sound quality issues. The book opens with a presentation of the fundamentals of vibrations and basic acoustic concepts, as well as how to analyze, test, and control noise and vibrations. The next 2 chapters delve into noise and vibrations that emanate from powertrains, bodies, and chassis. The book finishes with an in-depth discussion on evaluating noise, vibration, and sound quality, giving readers a solid grounding in the fundamentals of the subject, as well as information they can apply to situations in their day-to-day work. This book is intended for: •Upper-level undergraduate and graduate students of vehicle engineering •Practicing engineers •Designers •Researchers •Educators |
International Space Station United States Operational Segment Crew Quarters On-orbit vs. Design Performance Comparison | The International Space Station (ISS) United States Operational Segment (USOS) received the first two permanent ISS Crew Quarters (CQ) on Utility Logistics Flight Two (ULF2) in November 2008. As many as four CQs can be installed in the Node 2 element to increase the ISS crew member size to six. The CQs provide crew members with private space that has enhanced acoustic noise mitigation, integrated radiation-reduction material, communication equipment, redundant electrical systems, and redundant caution and warning systems. The rack-sized CQ system has multiple crew member restraints, adjustable lighting, controllable ventilation, and interfaces that allow each crew member to personalize his or her CQ workspace. The deployment and initial operational checkout during integration of the ISS CQ to Node 2 is described in this paper. On-orbit to original design performance is also compared for the following key operational parameters: interior acoustic performance, airflow rate, temperature rise, and crew member feedback on provisioning and re-straint layout. |
International Space Station USOS Crew Quarters Development | The International Space Station (ISS) United States Operational Segment (USOS) currently provides a Temporary Sleep Station (TeSS) as crew quarters for one crewmember in the Laboratory Module. The Russian Segment provides permanent crew quarters (Kayutas) for two crewmembers in the Service Module. The TeSS provides limited electrical, communication, and ventilation functionality. A new permanent rack sized USOS ISS Crew Quarters (CQ) is being developed. Up to four CQs can be installed into the Node 2 element to increase the ISS crewmember size to six. The new CQs will provide private crewmember space with enhanced acoustic noise mitigation, integrated radiation reduction material, controllable airflow, communication equipment, redundant electrical systems, and redundant caution and warning systems. The rack sized CQ is a system with multiple crewmember restraints, adjustable lighting, controllable ventilation, and interfaces that allow each crewmember to personalize their CQ workspace. Providing an acoustically quiet and visually isolated environment, while ensuring crewmember safety, is critical for crewmember rest and comfort to enable long term crewmember performance. The numerous human factor, engineering, and program considerations during the concept, design, and prototyping are outlined in the paper. |
Development of an Automatic Windshield Defogging System | The development of an automatic defogging system using an accurate windshield humidity sensor and the existing HVAC hardware is described herein. Improved cabin temperature control and forward visibility for the driver was achieved using a sophisticated automatic defogging strategy integrated into the Automatic Temperature Control microprocessor. Laboratory tests were conducted under various weather conditions and test modes using a climate wind tunnel and field tests were conducted in North America The automatic defogging system worked well in all cases |
Modelling of the Combustion Influence on Diesel Engines Noise Level for MAR-I Applications | Since January 2015, Brazil put into effect the PROCONVE/MAR-I (Programa de Controle da Poluição do Ar por Veículos Automotores para Máquinas Agrícolas e Rodoviárias), which drives the country to the same stringent emissions standards used by the American (EPA Tier III) and European (Euro Stage IIIA) markets. As a result, new pollutants and noise emissions levels were established and although very important for the society health, this issue (noise) has been left behind in this kind of vehicle. Therefore, an extremely challenging target has to be pursued, regarding the current political and economical situation and also the resources availability to achieve those targets. The present work investigates the influence of the noise generated during the combustion process in MAR-I engines by modeling the calibration parameters, which allows to identify the contribution of the combustion in the global engine noise and possibly reducing it and hence the product reckoned costs. |
Vibroacoustic Transfer Function Study in the Design of Vehicle Suspensions | Noise, vibration and Harshness in the automotive industry became important mainly because the development of modern automobiles and the increased of customer demands for quieter vehicles and with comfortable vibration levels. The sources of vibration and noise inside the vehicle are caused by the engine, tires, transmission systems, suspension, air conditioning, among others. In this work, vibroacoustic transfer function is obtained to analyze the internal noise in two sport utility vehicle with distinctive silhouette. Furthermore, it was analyzed the influence of elastomeric bushings rigidity of the damper in reducing internal noise and vibration and the effect of adding mass in some framework positions for attenuation of vibration peaks due to structural resonance. In the physical tests, it was used accelerometers installed on top of the fixing bracket of the damper and in specific positions in the vehicle body, a microphone installed on the right ear position of the passenger of the right rear seat and an impact hammer used to excite the system to obtain the vibroacoustic transfer function. Temporal measurements are carried out with vehicles on irregular track to a constant speed. The data are processed and analyzed in the frequency domain. The results show that the use of vibroacoustic transfer function is important for understanding and analysis of the noise within the vehicle cabin and that changes in the stiffness of the dampers bushings can reduce noise within the vehicle. Furthermore, the adding of mass to the structure was efficient to attenuate the vibration due to structural resonance. |
Practical Approaches for Detecting DoS Attacks on CAN Network | Some of the recent studies reveal that it is possible to access the in-vehicle networks and inject malicious messages to alter the behavior of the vehicle. Researchers have shown that, it is possible to hack a car’s communication network and remotely take control of brake, steering, power window systems, etc. Hence, it becomes inevitable to implement schemes that detect anomalies and prevent attacks on Controller Area Network (CAN). Our work explores the complete anomaly detection process for CAN. We cover the techniques followed, available tools and challenges at every stage. Beginning with what makes CAN protocol vulnerable, we discuss case studies about attacks on CAN with major focus on Denial of Service (DoS) attack. We analyze the pattern of normal CAN messages obtained from real vehicle, along with patterns of simulated attack data using different methods/tools. The work in this paper presents a statistical data analysis based machine learning algorithm with two approaches “time-based” and “message-based” to detect DoS attack on CAN bus. Comparative analysis of observations and accuracy results are highlighted. The average accuracy obtained for “time-based” approach is 81% while that for “message-based” is 80%. |
CFD/CAE Combinations in Open Cavity Noise Predictions for Real Vehicle Sunroof Buffeting | Though some practitioners consider the simulation process for sunroof and side window buffeting to be mature, there remain considerable uncertainties and inefficiencies as how in predictive methodologies to account for interior panel flexibility, vehicle structural stiffness, seals leakages and interior materials surface finish. Automotive OEMs and component suppliers rightly target flow simulation of open sunroofs and passenger windows with a view to reducing the severely uncomfortable low-frequency booming disturbance. The phenomenon is closely related to open cavity noise experienced also in other transportation sectors; for example in Aerospace, landing gear and store release cavities, and in Rail Transportation, cavities for HVAC intakes and the bogie environment. Recent studies published by the author demonstrate that the uncertainties can be correctly quantified by modeling. This publication defines a hierarchy of CFD/CAE based methods which overcome many of the a-posteriori tuning of simulations based on experiment, and considerably improve the predictive nature and efficiency of the simulation process. The methods range from fully deterministic simulations to phenomenological models requiring standard experimental pre-qualifications of the acoustical response of the system. The former involves CAE-coupling of CFD (Computational Fluid Dynamics) to CAA (Computational Aeroacoustics) and to CSM (Computational Structural Mechanics). The latter incorporates new correlation models published here for the first time. |
Dynamic Alert Generation Technology for Health & Usage Monitoring Systems | Current alert setting methodologies based on setting defect detection alert thresholds for vibration and other Health & Usage Monitoring Systems (HUMS) indicators have many limitations, principally there is necessarily a compromise to be achieved between the true negative and false positive diagnostic metrics. This is true for all alert detection techniques from fixed thresholds through to Support Vector Machines. In this paper we describe techniques, validated using helicopter HUMS data, which do not invoke this compromise and independently minimise both the true negative and false positive rates. This paper will also demonstrate how the alert processing can be made more robust and overcome the problems introduced by HUMS data being both non-stationary, non-ergodic i.e. characteristics that change both with time and from platform to platform. Two techniques utilised in the CFAR-Autotrend proprietary alert detection technology are described; a) The Constant False Alarm Rate technique for setting thresholds based on signal amplitude and detecting level changes b) The Box- Car technique for the automatic detection of local trends. These techniques produce alerts that are based on a significant change in local, not global, conditions in the data stream and are not based on an a priori model of the statistics of the signal. The performance of these techniques on real world HUMS generated vibration data and the engineering of the processes to automatically produce reliable and robust alerts are reviewed. False positives have been verified to be reduced to be less than 10% of true positives; a level where the diagnostics process becomes robust. The sensitivity to defects is improved to a level where the true negative rate has been reduced to a level where the diagnostic processes can be relied on and the prognostic interval becomes reliable. The consequential impact of this level of performance on HUMS dynamic alert processing is assessed. The automation of alert processing breaks the link between the number of aircraft fitted with HUMS and the manpower required to process the data. More importantly it will permit the scarce resource of HUMS specialists trained to diagnose defects to be concentrated on that task, not dissipated processing false alerts. For the future the Remaining Useful Life (RUL) realised from the increased sensitivity of the technique is at a magnitude where the benefits promised by Condition Based Maintenance can become a reality. |
Direct Aeroacoustics Predictions of Automotive HVAC Systems based on Lattice Boltzmann Method | The demand for low noise level in vehicle cabin continues to rise lately. In particular, noise generated by eco-friendly cars such as hybrid and electric ones tends to become lower and lower. In this market environment, the noise contributions caused by HVAC systems are also increasing. Therefore, it becomes increasingly important to accurately predict noise generated by HVAC systems and analyze the noise sources and resolve the noise issue. In this study, direct acoustics prediction approach based on Lattice Boltzmann Method is applied to predict the flow-induced noise from HVAC systems including blower and ducts and find noise sources. In order to validate the simulation result, acoustics measurements are performed on HVAC systems in an anechoic room and the results are compared to each other. A new technique is applied to finding a noise source for a specific frequency and shows improved noise level through modifying the geometry related to noise sources detected by the simulation. |
Comprehensive Hybrid Stiff Insulators Family: The Chips Urethane Contribution | The lightweighting research on noise treatments since years tends to prove the efficiency of the combination of good insulation with steep insulation slopes with broadband absorption, even in the context of bad passthroughs management implying strong leakages. The real issue lies more in the industrial capacity to adapt the barrier mass per unit area to the acoustic target from low to high segment or from low petrol to high diesel sources, while remaining easy to manipulate. The hybrid stiff insulator family can realize this easily with hard felts barriers backfoamed weighting from 800 g/m2 to 2000 g/m2 typically with compressions below 10 mm. Above these equivalent barrier weights and traditional compressions of 7 mm for example, the high density of the felts begins to destroy the open porosity and thus the absorption properties (insulation works anyway here, whenever vibration modes do not appear due to too high stiffness…). The felt costs begin to be critical for these intermediate weights above 2000 g/m2 as well. From 2000 g/m2 up to 3000 g/m2 or 3500 g/m2 equivalent barriers, the use of a traditional intermediate heavy layer is still not relevant from a process and cost point of view (ABA - Absorber/Barrier/Absorber systems). An original way to circumvent the issue consists in using a double porosity material like compressed chips urethane bound with bicomponent thin fibers. Airflow resistivities and porosities remain high while reasonable even at high compressions and thus deliver very good absorption, while being stiff enough to allow mass-spring like insulation slopes, as well as not too stiff in order to avoid bad modal resonances. The acoustic performance of this unconventional hybrid stiff insulator solution will be discussed with poro-elastic finite element modeling compared to measurements and to other hybrid stiff or ABA existing solutions of the same mass per unit area. |
A Subjective Evaluation Method for Sound Insulation of Vehicle Body in Reverberation Room and an Objective Prediction Model | A subjective evaluation method for the air-borne sound insulation of vehicle body in reverberation room is developed and the correlation between the subjective preference and objective noise reduction level (NRL) is investigated in this paper. The stationary vehicle's interior noise is recorded by using a digital artificial head under a given white noise excitation in the reverberation room, which demonstrates more credible than those in traditional road test methods. The recorded noises of six different vehicles are replayed and evaluated subjectively by 22 appraisers in a sound quality room. The paired comparison scoring method is employed and the check and statistic methods for the subjective scores are introduced. The subjective preference is introduced and calculated by the statistics and normalization of the effective scores, which can indicate an overall preference ranking of all the six vehicles numerically. Furthermore, an objective prediction model is established based on the correlation analyses and linear regressions. The subjective preference is proved to be attributed to the average NRL in 2k-5kHz frequency range only. The subjective evaluation method and the prediction model provide the guidance for the evaluation, prediction, target setting and optimization of the vehicle sound insulation. |
Improved Full Vehicle Finite Element Tire Road Noise Prediction | This paper presents the application to full vehicle finite element simulation of a steady state rolling tire/wheel/cavity finite element model developed in previous work and validated at the subsystem level. Its originality consists in presenting validation results not only for a wheel on a test bench, but for a full vehicle on the road. The excitation is based on measured road data. Two methods are considered: enforced displacement on the patch centerline and enforced displacement on a 2D patch mesh. Finally the importance of taking the rotation of the tire into account is highlighted. Numerical results and test track measurements are compared in the 20-300 Hz frequency range showing good agreement for wheel hub vibration as well as for acoustic pressure at the occupant’s ears. |