bluuebunny/crossref_metadata_2025 huggingface dataset:
A Modified Classical Nucleation Theory for Plastic Foam Processing
Authors: Wong Anson , Park Chul B.
Published: March 2016

This paper elucidates a modified Classical Nucleation Theory (CNT) that considers the effects of stress variations and existence of microvoids in plastic foaming processes. The stress effect has been incorporated into the CNT by a local pressure variation term that describes the dynamic conditions of industrial plastic foaming processes (e.g., extrusion foaming, injection foam molding). Also, the free energy barrier equation has been modified to include nucleation events from existing gas clusters. Both phenomena have been observed experimentally via in-situ plastic foaming visualization to confirm the modified theory. Combining the stress and preexisting gas clusters considerations, the modified CNT described in this paper improves the traditional CNT in describing cell nucleation phenomena in plastic foaming processes.
A Modular Low-Speed Wind Tunnel With Two Test Sections and Variable Inflow Angle
Authors: Wagner Robert , Dönnebrink Kai , Reinker Felix , Hasselmann Karsten , Rejek Jonas , aus der Wiesche Stefan
Published: March 2016

A modular low-speed wind tunnel system was designed and developed. Due to the modular concept, the wind tunnel permitted open-jet operation, cascade testing or closed-circuit operation. The closed-circuit wind tunnel had two test sections, and it had a high quality test-section with variable flow angle that is particular valuable for airfoil or blade testing. Physical calibration of the wind tunnel facility validated the design rules and CFD methods used and demonstrated that these techniques can be employed successfully for future wind tunnel designs. A detailed study of the thermal behavior of the closed-circuit wind tunnel was conducted. A feedback control method based on a PI control law was developed and tested for the wind tunnel speed.
Transient Model for Particle Dispersion Generated by High Momentum Respiratory Activities in Spaces Ventilated by Displacement Ventilation System
Authors: Habchi Carine Hanna , Ghali Kamel , Ghaddar Nesreen
Published: March 2016

A transient zonal model wit is developed to study particle distribution resulting from transient respiratory activities in spaces ventilated by displacement ventilation system (DV). Two transient sub-models are coupled: a transport model of exhaled particles computing the percentage of generated particles penetrating the infected thermal plume and tracking the exhaled jet propagation, and a transport model predicting particle exchange between the different affected layers and regions. A parametric study was performed to determine the effect of different factors on the risk of cross-infection between the occupants: exhalation velocity, DV flow rate, distance separating the occupants and particle diameter. It was observed that with the increase of the DV flow rate, the ventilation effectiveness increases reducing particle accumulation in the breathing zone. The risk of cross-contamination becomes higher for reduced separating distance between the occupants, and for increased cough velocity, as the momentum of released droplets and their quantity increase. Therefore, it was found that to reduce cross-infection, measures can be considered as avoiding getting close to an infected occupant and covering the mouth during a cough. In addition, assisting DV system by chair fans is expected to reduce cross-contamination by increasing the strength of the rising thermal plumes.
Examining Adaptive Expertise: A Novel Comparison of Student and Practicing Engineer CAD Modeling Performance
Authors: Johnson Michael D. , Ozturk Elif , Yalvac Bugrahan , Valverde Lauralee , Peng Xiaobo , Liu Ke
Published: March 2016

Computer-aided design (CAD) tools are critical in the current fast-paced digital product commercialization environment. As firms move towards a model based enterprise, it becomes more important for engineers to develop the skills necessary to efficiently and effectively model components in CAD. The status of CAD education and training has often been decried as focusing too much on declarative knowledge, namely how to do specific procedures in a specific software program. This is opposed to the strategic knowledge or expertise that is adaptable to other CAD programs. To better inform CAD education and modeling procedures, an understanding of how experts model and model in novel situations is presented. Specifically, and novel to this work, the adaptive nature of these practicing professional’s CAD expertise is examined and compared to that of relatively novice students. The methods comprise a combination of screen capture data, model attributes, and the results of interviews to assess adaptive expertise.

Practicing engineers are found to spend a smaller percentage of their modeling time engaged in actual modeling procedures (doing time). Significant differences related to model attributes include: practicing engineers being less likely to use pattern features, more likely to have incorrect feature terminations, and more likely to use more complex features (as measured by feature density). Results show practicing engineers as less likely to highlight strategies related to adaptive expertise prior to the modeling activity. Post interview results show practicing engineers with more manifestations of adaptive expertise. These results are in agreement with previous literature examining both general and CAD modeling expertise.
Thermal Analysis of a Laser Peeling Technique for Removing Micro Edge Cracks of Ultrathin Glass Substrates for Web Processing
Authors: Yang Tian-Shiang , Chen Guang-Di , Chen Kuo-Shen , Hong Rong-Can , Chiu Tz-Cheng , Wen Chang-Da , Li Chun-Han , Huang Chien-Jung , Chen Kun-Tso , Lin Mao-Chi
Published: March 2016

Ultrathin glass is a promising substrate material for web processing (also called roll-to-roll processing) of flexible electronics, but is highly susceptible to breaking and cracking due to the almost inevitable presence of substrate-edge defects. Recently, a novel technique for removing the micro cracks on the edges of ultrathin glass substrates was devised at ITRI. It amounts to shining a CO2 laser on one edge of a substrate, which induces spontaneous peeling of a thin layer containing preexisting cracks on the edge from the substrate, resulting in an essentially crack-free new substrate edge. Exploiting the thinness of ultrathin glass substrates, here we propose a simplified two-dimensional thermal model for the laser peeling process, and obtain an analytic expression for the transient temperature variation in a substrate being peeled. This enables us to locate the “thermally affected zone” in the substrate, which turns out to be impressively similar in size and shape to the substrate-edge peels observed in experiments. Moreover, a quantitative criterion for the minimum cooling rate required for the progression of the peeling process is obtained. The results here thus provide useful insights into the laser peeling mechanism, and can be used to expedite the optimization of process parameters. Some preliminary purely numerical results using a finite element method (FEM) based software also are briefly discussed here.
A Numerical Model to Analyze the Thermal Behavior of a Propellant Increment
Authors: Blecker K. , Hadim H.
Published: March 2016

The purpose of this study is to develop a numerical model of the thermal behavior of a propellant increment exposed to a variety of thermal environments and packaging conditions and predict the temperature distribution throughout the increment. The temperature distribution and bulk temperature of the propellant within the increment directly influence the burn rate and resulting pressure profile. The burn rate and pressure profile directly impact the range and stability of the munition which can result in a safety hazard if not properly accounted for.

This study has two parts; first a numerical model is developed and second an experiment is designed and carried out to validate the numerical model. The experiment involves instrumenting a propellant increment with a series of thermocouples and heating it in a controlled laboratory environment. Temperature data is collected with a dedicated data collector and retained for analysis and validation of the numerical model. The numerical model accounts for variable thermal solar loading, various packaging configurations, and orientation.

Initial results indicate that while there are points in the interior of the increment that come within 10 percent of the actual bulk temperature of the entire increment, the surface of the increment is not a good basis for prediction of the bulk temperature or temperature distribution within the increment. Additional analysis must be conducted to provide a viable estimate of the temperature distribution and bulk temperature of the increment based on the surface temperature in conjunction with knowledge of the exposure conditions.
Development of a Novel Hybrid Unified Viscoplastic Constitutive Model
Authors: Varela J. Luis A. , Stewart Calvin M.
Published: March 2016

Hastelloy X and stainless steel 304 are alloys widely used in industrial gas turbines components, petrochemical industry and energy generation applications; In the Pressure Vessel and Piping (PVP) industries they are used in nuclear and chemical reactors, pipes and valves applications. Hastelloy X and stainless steel 304 are favored for these types of applications where elevated temperatures are preferred for better systems’ efficiencies; they are favored due to its high strength and corrosion resistance at high temperature levels. A common characteristic of these alloys, is its rate-dependent mechanical behavior which difficult the prediction of the material response for design and simulation purposes. Therefore, a precise unified viscoplastic model capable to describe Hastelloy X and stainless steel 304 behaviors under a variety of loading conditions at high temperatures is needed to allow a better and less conservative design of components. Numerous classical unified viscoplastic models have been proposed in literature, to predict the inelastic behavior of metals under extreme environments. Based on Miller and Walker classical unified constitutive models a novel hybrid unified viscoplastic constitutive model is introduced in the present work, to describe the inelastic behavior caused by creep and fatigue effects at high temperature. The presented hybrid model consists of the combination of the best aspects of Miller and Walker model constitutive equations, with the addition of a damage rate equation which provides a description of the damage evolution and rupture prediction capabilities for Hastelloy X and stainless steel 304. A detailed explanation on the meaning of each material constant is provided, along with its impact on the hybrid model behavior. Material constants were calculated using the recently developed Material Constant Heuristic Optimizer (MACHO) software, to ensure the use of the optimal material constants values. This software uses the simulated annealing algorithm to determine the optimal material constants in a global surface, by comparing numerical simulations to an extensive database of experimental data. To validate the capabilities of the proposed hybrid model, numerical simulation results are compared to a broad range of experimental data at different stress levels and strain amplitudes; besides the consideration of two alloys in the present work, would demonstrate the model’s capabilities and flexibility to model multiple alloys behavior. Finally a quantitative analysis is provided to determine the percentage error and coefficient of determination between the experimental data and numerical simulation results to estimate the efficiency of the proposed hybrid model.
Experimental Characterization of the Flow Instabilities of a Mixed-Flow Multiphase Pump Operating Air and Water Through Local Visualization and Analysis of Dynamic Measurements
Authors: Serena Alberto , Bakken Lars E.
Published: March 2016

Part load operation of pumps generates flow and machine instabilities, which are not desirable and should be avoided as they result in premature wear and mechanical problems. Two-phase flow introduces additional challenges, both at the design and operational stages, due to the different phase behavior and mutual interaction. The phenomena involved present an intermittent character and are strongly dependent on the specific geometry and operating conditions. Despite the recent promising development of numerical simulations capabilities, an accurate characterization of the flow mechanisms still relies on real tests, which are needed to validate the numerical models too. An advanced laboratory test facility built at the Norwegian University of Science and Technology provides the required optical access to the pump channels, and high-speed recordings, along with local measurements of the pressure pulsations, allow to describe the flow structures in terms of location, length and time scales, and relate them to overall machine measurements, such as flow, pressure and torque. This provides a wide collection of test data of great value for a further understanding of the surging phenomenon, the development of a surging onset prediction model and a control strategy.

Tests are performed covering the whole range of flow rates; a characteristic surging condition is identified and described in the article.
Analysis of Tool Wear and Hole Quality During Ultrasonic Assisted Drilling (UAD) of Carbon Fibre Composite (CFC) / Titanium Alloy (Ti6Al4V) Stacks
Authors: Dahnel Aishah Najiah , Ascroft Helen , Barnes Stuart , Gloger Maximilian
Published: March 2016

Carbon Fibre Composite (CFC) and titanium (Ti) alloys have been widely employed in the aerospace industry due to their high strength to weight ratios. For making a military aircraft body, these materials are usually stacked together with titanium alloys serving as the airframe, while CFC is the outer skin. Drilling is often performed in one shot from the CFC outer skin through to the titanium alloy airframe for the purpose of assembling them by mechanical means using rivets, screws, nuts and bolts. Conventional drilling of these CFC/Ti stacks, however, often results in two major issues; rapid tool failure and poor hole quality. This paper considers the potential of employing Ultrasonic Assisted Drilling (UAD) on stack materials in order to improve tool life and hole quality. Experiments comparing conventional drilling and UAD on CFC/Ti6Al4V stack using reground 6.121 mm-diameter TiAlN coated tungsten carbide twist drills are presented. Reground drills were used by way of replicating typical current practice in industry. A constant cutting speed and feed rate of 50 m/min and 0.05 mm/rev, respectively was used in both experiments. During UAD experiments, ultrasonic amplitude and frequency was fixed at 2.6 μm and 42.7 kHz, respectively. A total of 100 holes were drilled in the stacks during each drilling processes (conventional drilling and UAD). Machinability was assessed in terms of thrust forces, tool wear, hole diameter, CFC delamination and titanium burr. Thrust forces were measured using a dynamometer; tool wear was examined using an optical microscope and a Scanning Electron Microscope (SEM); and holes diameter were measured using a bore micrometer. Hole defects; CFC entry delamination was examined and quantified using an optical microscope, while titanium exit burr were investigated using both an optical microscope and a depth gauge. The dominant types of tool wear during drilling of CFC/Ti6Al4V stacks were caused by titanium adhesion/fusion on the cutting edges. In addition, abrasive wear caused by abrading carbon fibres against cutting edges were also observed. Poor hole quality of the stacks included inconsistent diameter of CFC and titanium holes; CFC delamination at the hole entrance and burr formation as the drill exited the titanium. The difference in thrust forces produced by conventional drilling and UAD were minor. It was observed that UAD resulted in less tool wear rate and a reduction of adhered titanium alloy on the cutting edges, more consistent hole diameters and less titanium burr compared to conventional drilling. However, larger CFC delamination was observed during UAD than conventional drilling.
An Extended Finite Element Model of Crevice and Pitting Corrosion
Authors: Duddu Ravindra , Kota Nithyanand , Qidwai Siddiq
Published: March 2016

A sharp interface model formulation is developed for simulating the electrochemical environment in crevices/pits due to galvanic corrosion in aqueous media. The concentration of ionic species and the electrical potential in the crevice is established using the non-dimensionalized Nernst-Planck equations along with the assumption of local electro-neutrality. The crevice/pit interface fluxes are defined in terms of the cathodic and anodic current densities using Butler-Volmer kinetics. The extended finite element method is used to discretize the governing equations and the level set function to describe the interface morphology independent of the underlying finite element mesh. The advantage of this formulation is that it eliminates the need for cumbersome mesh generation and remeshing when the interface morphology changes. Numerical investigations of steady-state intergranular crevice corrosion in idealized Al-Mg alloy microstructures in two-dimensions are conducted to establish the viability of the formulation. Simulation results predict large pH and chloride concentration within the crevice environment, which leads us to the conclusion that chemical reactions and precipitation play a prominent role during crevice corrosion.
Effect of Vortex Street on Mixing Enhancement in a Mixing Layer
Authors: Zhang DongMing
Published: March 2016

In this paper, the effect of vortex street on increasing mixing in a mixing layer is investigated numerically. The end of the splitter plate is made into square cylinder shape in order to set a square cylinder in the mixing layer for generating the vortex street. The vortex street is formed behind the cylinder in the initial stage of the mixing layer when the top and bottom streams flow over the square cylinder. The large scale vortices in the vortex street are utilized to enhance mixing of two different-speed streams in the mixing layer. The reason of the asymmetry of the vortex street is explained. The case of a mixing layer between two walls is also studied numerically. The results of numerical simulation show that small velocity difference between two streams is good for mixing enhancement in the confined mixing layer. The vortex street has a good effect on mixing enhancement in a mixing layer.
CFD Analysis of a Gas Turbine Engine Test Cell to Understand and Alleviate Infrasound
Authors: Pearson John T. , Sheoran Yogi , Schuster Bill
Published: March 2016

Gas turbine engines often pass through tests in enclosed test facilities. One problem that arises during these tests is the infrasound phenomenon. Infrasound can be a problem for many reasons, ranging from rattling windows to structural damage to the test cell. The aim of this paper is to understand the cause of severe infrasound experienced at Honeywell Aerospace and to evaluate and select a solution using advanced Computational Fluid Dynamics (CFD) techniques. These CFD simulations modeled an entire test cell with an engine in place, which is a more complete approach than what is reported in the literature. The DES turbulence model was applied in a transient, compressible, turbulent simulation in order to capture small pressure fluctuations. Test data taken using an engine/test cell configuration that does not cause problems was used to successfully validate the CFD approach. It was found that the narrow, high-velocity exhaust plume examined in this study impacted the convex blast plate in the aft portion of the test cell having diffused only slightly. The exhaust then rebounded and buffeted the plume, causing extreme dynamic loading. Through a modification to the blast basket, it was shown that the problem would be alleviated and sound pressure levels in the test cell would be reduced by 5 to 32 dB, depending on location in the test cell.
Effect of Heating Atmosphere on the Spectral Emissivity of the Usibor® 1500P Steel During Austenitization
Authors: Shi C. J. , Daun K. J. , Wells M. A.
Published: March 2016

Variations in spectral emissivity of Usibor® 1500P steel during a two-step austenitization and in two different heating atmospheres, argon and air, are measured in-situ using a near infrared spectrometer and ex-situ with a Fourier transform infrared reflectometer. Phase transformations of the Al-Si coating and surface oxidation lead to the changes in surface phase composition and surface roughness, which in turn influences the spectral emissivity. In the first step heating at 610°C, the abrupt increase of spectral emissivity in argon and air is due to the transformation of the Al-Si metallic surface into the Al7Fe2Si intermetallic surface and an increase in surface roughness. Through the second step heating at 900°C, the progressive decrease of spectral emissivity with soak time in argon is caused by the surface phase transformation from Al5Fe2 into AlFe with a decrease in surface roughness. In contrast, surface oxidization with an increase in surface roughness significantly increases the spectral emissivity after two minutes soaking in air.
Transient Thermofluids Analysis of a Ground-Level Integrated Diverse Energy Storage (GLIDES) System
Authors: Odukomaiya Adewale , Momen Ayyoub M. , Abu-Heiba Ahmad , Gluesenkamp Kyle , Abdelaziz Omar , Graham Samuel
Published: March 2016

In this work, a novel Ground-Level Integrated Diverse Energy Storage (GLIDES) system which can store energy via input of electricity or heat and deliver dispatchable electricity is presented [1]. The proposed system is low-cost and hybridizes compressed air and pumped-storage approaches that will allow for the off-peak storage of intermittent renewable energy for use during peak times. A detailed control-volume energy analysis of the system is carried out, yielding a set of coupled differential equations which are discretized using a finite difference scheme and used to model the transient response during charging and discharging. The energy analysis includes coupled heat transfer and pressure drop analysis used to predict system losses for more accurate round trip efficiency (RTE) calculations and specific energy density (ED) predictions. Preliminary analysis of the current prototype indicates an electric-to-electric RTEE of 66% (corresponding to shaft-to-shaft mechanical RTEM of 78%) and ED of 2.5 MJ/m3 of air, given initial air volume and pressure of 2 m3 and 70 bar. The electric power output ranges from a max of 2.5 kW to a min of 1.2 kW and the output current ranges from a max of approximately 21 amps to approximately 10 amps at 120 V, 60 Hz dispatchable electricity, over a period of approximately 50 minutes. Additionally, it is shown that heat transfer enhancement to the point of a 5-fold increase in air heat transfer rates results in a near 5% improvement in RTEE (70% considering all component losses). Additional component efficiency improvements and efficiency gains due to system scale-up could see higher achievable RTEs.
Energy Absorption Characteristics of a Carbon Fiber Composite Automobile Lower Rail: A Comparative Study
Authors: Ali Muhammad , Alam Khairul , Ohioma Eboreime
Published: March 2016

Composite materials have emerged as promising materials in applications where low weight and high strengths are desired. Aerospace industry has been using composite materials for past several decades exploiting their characteristics of high strength to weight ratio over conventional homogenous materials. To provide a wider selection of materials for design optimization, and to develop lighter and stronger vehicles, automobile industries have been exploring the use of composites for a variety of components, assemblies, and structures. Composite materials offer an attractive alternate to traditional metals as designers have greater flexibility to optimize material and structural shapes according to functional requirements. However, any automotive structure or part constructed from composite materials must meet or exceed crashworthiness standards such as Federal Motor Vehicle Safety Standard (FMVSS) 208. Therefore, for a composite structure designed to support the integrity of the automotive structure and provide impact protection, it is imperative to understand the energy absorption characteristics of the candidate composite structures. In the present study, a detailed finite element analysis is presented to evaluate the energy absorbing characteristics of a carbon fiber reinforced polymer composite lower rail, a critical impact mitigation component in automotive chassis. For purposes of comparison, the analysis is repeated with equivalent aluminum and steel lower rails. The study was conducted using ABAQUS CZone module, finite element analysis software. The rail had a cross-sectional dimension of 62 mm (for each side), length of 457.2 mm, and a wall thickness of 3.016 mm. These values were extracted from automobile chassis manufacturer’s catalog. The rail was impacted by a rigid plate of mass 1 tonne (to mimic a vehicle of 1000 Kg gross weight) with an impact velocity of 35 mph (15646.4 mm/s), which is 5 mph over the FMVSS 208 standard, along its axis. The simulation results show that the composite rail crushes in a continuous manner under impact load (in contrast to a folding collapse deformation mode in aluminum and steel rails) which generates force-displacement curve with invariable crushing reactive force for the most part of the crushing stroke. The energy curves obtained from reactive force-displacement graphs show that the composite rail absorbs 240% and 231% more energy per unit mass as compared to aluminum and steel rails. This shows a significant performance enhancement over equivalent traditional metal (aluminum and steel) structures and suggests that composite materials in conjunction with cellular materials/configurations have a tremendous potential to improve crashworthiness of automobiles while offering opportunities of substantial weight reductions.
Assessing the Design Innovation Potential of Timber Prefabricated Housing Through Axiomatic Design
Authors: Marchesi Marianna , Kim Sang-Gook , Matt Dominik T.
Published: March 2016

Despite the current building sector slowdown in Italy, timber housing industry market is growing. But its growth has been limited mainly by the high costs of ad-hoc full-customized buildings and the lack of customer appreciation for mass-produced buildings. In order to satisfy the current demand for affordable customized housing, building industry should focus on solutions based on the combination of personalized and mass-produced parts. In this way, clients would have the chance to personalize crucial parts, and building industry can limit costs by the mass-production of the others. This combination between mass production and customization involves artefact flexibility and robustness with regard to the designer’s viewpoint. These requirements are set in the conceptual design phase, but in this stage architect’s decision making is not adequately supported. Since Axiomatic Design (AD) is able to support the analysis of designs with respect to the specified requirements, AD is applied to the review of prefabricated housing archetypes and current timber construction systems. This study shows the effectiveness of applying AD to prefabricated building design: crucial design decisions that affect the specified requirements are identified; inputs limiting their fulfilment in the timber building prefabrication are highlighted, and recommendations for developing adequate systems are provided.
Thermodynamic Modelling of an Adsorption Chiller Based on a Zeolite
Authors: Badami Marco , Portoraro Armando , Simonetti Marco , Tebaldi Paolo
Published: March 2016

Low power adsorption chillers with low desorption temperatures deserve particular attention, because of the possibility of driving them with a solar thermal system integrated with buildings. The monitoring of a recent solar cooling installation in Turin, Italy, has pointed out the opportunity of developing a dynamic mathematical model, in order to simulate the transient performances of this plant. Focusing on the aforementioned low power-low temperature adsorption chiller category, this work proposes a numerical model of the systems, that include a novel zeolite as the adsorbent and water as the refrigerant fluid. The simulation results have been verified by means of the nominal values of one of the very few commercial chillers of this typology available on the market, and have compared with experimental data found in the literature for similar plants.
Advanced Exergy Analysis Based on the Parametric Study of the Regasification of LNG Integrated Into an Air Separation Process
Authors: Tesch S. , Morosuk T. , Tsatsaronis G.
Published: March 2016

The growing demand for natural gas leads to an increasing LNG market. The amount of traded LNG has more than doubled during the last decade. This trend is intensified by the rising number of liquefaction plants (export terminals) and regasification plants (import terminals). At the end of the year 2013 there were 86 liquefaction plants in 17 exporting countries and 104 import terminals in 29 importing countries. Also the number of floating regasification plants is growing. It is expected that the LNG market will grow with 7 % per year until 2020. In comparison, the market for gaseous natural gas only will increase with approxematly 1.8 % per year. The difference could be led back to the several advantages, when using LNG. Thus LNG enables the extraction of natural gas in offsite areas and leads to a flexible gas market. Especially with improving the efficiency of each part of the LNG chain — liquefaction, transportation, storage and regasification — and its fallen prices the LNG market will continue to grow. For the regasification of LNG different processes have been used, while mainly the vaporization via direct or indirect heating is applied. Due to their location at the coast of the importing country, seawater, air or the combustion gases coming from natural gas are used as thermal energy. A further possibility is the combination of regasification of LNG with generating electricity. Additionally, the regasification of LNG could be integrated into chemical processes (oil refinery and petrochemical plants), where low temperature refrigeration is required. The authors have already reported a concept for the integration of the regasification of LNG into an air separation and liquefactions process, i.e. into a cryogenic processes. In previous publications, an evaluation of the conventional air separation unit in combination with the LNG regasification has been reported. It was emphasized that the integration of LNG leads to a lower power consumption for the entire system. This paper deals with an improved concept for integrating the regasification of LNG into an air separation process. Due to structural changes, comparing the first design and the new design, the system can be further improved from the thermodynamic point of view. The aim of this paper is to discover the potential for improvement by the parametric study. The results obtained from the sensitivity analysis (energetic and exergetic) are reported as well as the results obtained from the advanced exergetic analysis. Some options for new designs of this system are be developed.
Lateral Motion Control of a Vehicle Using the Rear Steer: Simulation Study
Authors: Lee Jin-Woo , Litkouhi Bakhtiar B.
Published: March 2016

The lateral motion control is a key element for automated driving vehicle technology. Typically, the front steering system has been used as the primary actuator for vehicle lateral motion control. Alternatively, this paper presents a new method of the lateral motion control using a rear steer. When combined with the front steer actuator, the rear steer can generate more dynamically responsive turning of the vehicle. In addition, the rear steer can be used as a secondary back up actuator when the front steer actuator fails to operate during automated driving mode. Similar to the prior research that has used the front steer actuator for the lateral control, the control methodology presented in this paper maintains the same hierarchical framework, i.e., sensor fusion, path prediction, path planning, and motion control. Since the rear steer is in play for the vehicle lateral motion control, the equations for the path prediction and vehicle dynamics are re-derived with non-zero front steer and rear steer angles. Combined with the rear steering dynamics, the model predictive control (MPC) technique is applied for motion error minimization. This paper describes the theoretical part of the algorithm, and provides simulation results to show effectiveness of the algorithm. Future work will include vehicle implementation, testing, and evaluation.
In-Mine Experimental Investigation of Temperature Rise and Development of a Validated Thermal Simulation Model of a Mobile Refuge Alternative
Authors: Yan Lincan , Yantek David , Bissert Pete , Klein Mark
Published: March 2016

Mine Safety and Health Administration (MSHA) regulations require underground coal mines to use refuge alternatives (RAs) to provide a breathable air environment for 96 hrs. One of the main concerns with the use of mobile RAs is the heat and humidity buildup inside the RA. The accumulation of heat and humidity can result in miners suffering heat stress or even death. To investigate this issue, the National Institute for Occupational Safety and Health (NIOSH) conducted testing on a training ten-person, tent-type, RA in its Safety Research Coal Mine (SRCM) in a test area that was isolated from the mine ventilation system. The test results using sensible and latent heat showed that the average measured air temperature within the RA increased by 20.6°F (11.4°C) and the relative humidity approached 90 %RH. The test results were used to benchmark a thermal simulation model of the tested RA. The validated thermal simulation model predicted the average air temperature inside the RA, at the end of 96 hours, to within 1°F (0.6°C) of the measured average air temperature.
Improved Mechanical Preload Measurement of Bolted Joints for Light Weight Design With CFRP Components
Authors: Jenne M. , Hubbertz H. , Friedrich C. , Bär C.
Published: March 2016

Bolted joints are widely used in the automotive industry. New requirements in terms of lightweight design and the use of fiber reinforced plastics need revised design guidelines. The preload of a bolted joint is crucial for monitoring its performance and condition. This paper gives an overview of common methods for preload measurement and focuses on techniques which deal with the specific need in R&D. Two systems, based on a mechanical length measurement of the bolt are described in detail. One system uses a conventional micrometer spindle and the other system a precise length gauge. Sources of errors are discussed and the most significant factors to achieve a precise measurement are given. In summary, the preload measurement by a mechanical length measurement, either with a micrometer spindle or with a length gauge, is easy to handle and enables to receive accurate results in R&D.
Heat Transfer Modeling in a Double Wall Helical Coil Heat Exchanger
Authors: Bentley Jonathan , Cui Jie
Published: March 2016

Double wall helical coil heat exchangers are widely used in a variety of applications. These heat exchangers are used anywhere that requires an added layer of protection from cross-fluid contamination such as in indirect water heaters. Here, the coil is heating a potable water tank with coil water which is often infused with a glycol mixture. Since contamination of the potable water would be detrimental to human health, the added protection of a double wall coil is necessary. Unfortunately, the double wall coil is inherently difficult to design due to unknown intertubular contact. This intertubular contact is hidden in nature and difficult to evaluate by nondestructive means.

This paper uses STAR-CCM+ to create a computational fluid dynamic model of the double wall helical coil in respect to GAMA indirect water heater continuous draw test conditions. Using CFD, the model is validated with single wall helical coil Nusselt number correlations determined from experimentation. Then, a parametric study is performed to determine what parameters of the coil can be changed to effectively overcome the intertubular thermal loss.

From this study, it is found that tube length has a linear positive relationship with coil output density and can be used to calculate necessary lengths for a desired output. Also, it was found that the experimental Nusselt number correlations identify with the results calculated by the double wall CFD model when intertubular contact percentage is used as a correction factor.
Independence Measure (IM) Using Independence Priority Number (IPN) in Axiomatic Design Framework
Authors: Do Sung-Hee
Published: March 2016

Axiomatic Design is becoming a preferred system design process tool for insuring the quality and efficiency of design processes for products and services. One aspect of Axiomatic Design is modeling and analyzing the functional independence of proposed solutions. Axiomatic Design provides for comparing and ranking solutions by three categories of functional coupling: Uncoupled, Decoupled and Coupled (1). However, given two potential solutions within the same functional coupling category, Axiomatic Design technology cannot further rank these solutions without additional information. This paper proposes that the degree of functional coupling can be assessed to provide further discrimination between solutions within the same coupling category. Using complexity concepts, this paper proposes two additional metrics, the Independence Priority Number (IPN) and the Independence Measure (IM) to further rank the potential robustness of alternative solutions using the Independence Axiom of the Axiomatic Design process. With IPN and IM metrics, design professionals can better assess the functional robustness of their proposal at the earliest phase of design, conceptual design synthesis.
Stiffness Boundary Conditions for Critical Damping in Balance Recovery
Authors: Piovesan Davide , Kennett C. J. , Chavez-Romero Raúl , Panza Michael J. , Cárdenas Antonio
Published: March 2016

This paper presents the analysis of a third-order linear differential equation representing the control of a muscle-tendon system, during quiet standing. The conditions of absolute stability and critical damping are analyzed. This study demonstrates that, for small oscillations, when the gravitational effect is modeled as a destabilizing negative stiffness and muscle-tendon stiffness is positive, the energy required to reach a critically damped state is very high. The high energy consumption is a consequence of a specific high threshold of muscle-tendon stiffness needed to achieve critical damping.

An approximated graphical method confirms that during a hold and release paradigm intended to perturb quiet standing, the ankle response to fall recovery is proper of a third-order system. Furthermore, a direct estimation of the muscle and tendon parameters was obtained.
Evolutionary Electromechanical Stability in Stressed Viscoelastic Dielectrics
Authors: Li Bo , Liu Xuejing , Chen Hualing
Published: March 2016

Constant mechanical load offers stabilization in the electromechanical actuation of dielectric elastomer. Due to the viscoelasticity, the electromechanical coupling performance of dielectric elastomer varies with time as its stability evolves. The parameters of viscoelasticity are calibrated experimentally. By establishing a thermodynamics model, the evolutionary paths of electromechanical deformation are classified and investigated, where a transition, from unstable to stable, is identified. The critical time and critical load on the transition is determined, providing a path forward for improving performance of dielectric elastomer.
Numerical Analysis of Peristaltic Flow Through the Pharyngeal Duct
Authors: Preciado-Méndez M. , Salinas-Vázquez M. , Vicente W. , Brito-de La Fuente E. , Ascanio G.
Published: March 2016

This work was aimed to study numerically the food bolus flow through the pharynx. Using a 2D geometry obtained elsewhere, a three-dimensional code has been developed for the study exclusively of the fluid inside the pharynx considering a non-Newtonian fluid. Three-dimensional geometries of the pharynx at ten different instants using high-order polynomials were generated. For any time range investigated, the shape of the pharynx was introduced into a Cartesian grid by using the technique of immersed boundaries and three-dimensional interpolations. The geometry evolved within this grid and the equations of fluid mechanics were numerically solved. The effect of the pharyngeal walls on the fluid was modeled from the theory of elastic membranes. Flow fields in terms of the axial velocity, pressure, shear rate and viscosity were obtained.
Innovative Volumetric Solar Receiver Micro-Design Based on Numerical Predictions
Authors: Capuano Raffaele , Fend Thomas , Hoffschmidt Bernhard , Pitz-Paal Robert
Published: March 2016

Due to the continuous global increase in energy demand, Concentrated Solar Power (CSP) represents an excellent alternative, or add-on to existing systems for the production of energy on a large scale.

In some of these systems, the Solar Power Tower plants (SPT), the conversion of solar radiation into heat occurs in certain components defined as solar receivers, placed in correspondence of the focus of the reflected sunlight.

In a particular type of solar receivers, defined as volumetric, the use of porous materials is foreseen. These receivers are characterized by a porous structure called absorber. The latter, hit by the reflected solar radiation, transfers the heat to the evolving fluid, generally air subject to natural convection.

The proper design of these elements is essential in order to achieve high efficiencies, making such structures extremely beneficial for the overall performances of the energy production process.

In the following study, a parametric analysis and an optimized characterization of the structure have been performed with the use of self-developed numerical models.

The knowledge and results gained through this study have been used to define an optimization path in order to improve the absorber microstructure, starting from the current in-house state-of-the-art technology until obtaining a new advanced geometry.
Modeling the Radiative Heat Transfer in Selective Laser Sintering of Polymers: Scattering Effect
Authors: Liu Xin , Boutaous Mhamed , Xin Shihe
Published: March 2016

A numerical model, coupling radiative and conductive heat transfer in a polymer powder bed and providing a local temperature field, is proposed. To simulate the polymer sintering by laser heating as in additive manufacturing, a double-lines scanning of a laser beam over a thin layer of polymer powder is studied. An effective volumetric heat source, using a modified Monte Carlo method, is estimated from laser radiation scattering and absorption in a semi-transparent polymer powder bed. In order to quantify the laser-polymer interaction, the heating and cooling of the material is modeled and simulated with different types heat sources by both finite element method (FEM) and discrete element method (DEM). To highlight the importance of introducing the semi-transparent behavior of such materials and in order to validate our model, the results are compared with works of other researchers taken from literatures.
Analysis of Autoregressive Energy Models of a Research House
Authors: Fumo Nelson , Lackey Daniel C. , McCaslin Sara
Published: March 2016

Energy consumption from buildings is a major component of the overall energy consumption by end-use sectors in industrialized countries. In the United States of America (USA), the residential sector alone accounts for half of the combined residential and commercial energy consumption. Therefore, efforts toward energy consumption modeling based on statistical and engineering models are in continuous development. Statistical approaches need measured data but not buildings characteristics; engineering approaches need building characteristics but not data, at least when a calibrated model is the goal. Among the statistical models, the linear regression analysis has shown promising results because of its reasonable accuracy and relatively simple implementation when compared to other methods. In addition, when observed or measured data is available, statistical models are a good option to avoid the burden associated with engineering approaches. However, the dynamic behavior of buildings suggests that models accounting for dynamic effects may lead to more effective regression models, which is not possible with standard linear regression analysis. Utilizing lag variables is one method of autoregression that can model the dynamic behavior of energy consumption. The purpose of using lag variables is to account for the thermal energy stored/release from the mass of the building, which affects the response of HVAC equipment to changes in outdoor or weather parameters. In this study, energy consumption and outdoor temperature data from a research house are used to develop autoregressive models of energy consumption during the cooling season with lag variables to account for the dynamics of the house. Models with no lag variable, one lag variable, and two lag variables are compared. To investigate the effect of the time interval on the quality of the models, data intervals of 5 minutes, 15 minutes, and one hour are used to generate the models. The 5 minutes time interval is used because that is the resolution of the acquired data; the 15 minutes time interval is used because it is a common time interval in electric smart meters; and one hour time interval is used because it is the common time interval for energy simulation in buildings. The primary results shows that the use of lag variables greatly improves the accuracy of the models, but a time interval of 5 minutes is too small to avoid the dependence of the energy consumption on operating parameters. All mathematical models and their quality parameters are presented, along with supporting graphical representation as a visual aid to comparing models.