Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

Validation of the EFEA Method through Correlation with Conventional FEA and SEA Results

2001-04-30
2001-01-1618
The Energy Finite Element Analysis(EFEA) is a recent development for high frequency vibro-acoustic analysis, and constitutes an evolution in the area of high frequency computations. The EFEA is a wave based approach, while the SEA is a modal based approach. In this paper the similarities in the theoretical development of the two methods are outlined. The main scope of this paper is to establish the validity of the EFEA by analyzing several complex structural-acoustic systems. The EFEA solutions are compared successfully to SEA results and to solutions obtained from extremely dense conventional FEA models.
Technical Paper

Development and Validation of a Computational Process for Pass-By Noise Simulation

2001-04-30
2001-01-1561
The Indirect Boundary Element Analysis is employed for developing a computational pass-by noise simulation capability. An inverse analysis algorithm is developed in order to generate the definition of the main noise sources in the numerical model. The individual source models are combined for developing a system model for pass-by noise simulation. The developed numerical techniques are validated through comparison between numerical results and test data for component level and system level analyses. Specifically, the source definition capability is validated by comparing the actual and the computationally reconstructed acoustic field for an engine intake manifold. The overall pass-by noise simulation capability is validated by computing the maximum overall sound pressure level for a vehicle under two separate driving conditions.
Technical Paper

An Elementary Simulation of Vibration Isolation Characteristics of Hydraulically Damped Rubber Mount of Car Engine

2001-04-30
2001-01-1453
Hydraulically damped rubber engine mounts (HDM) are an effective means of providing sufficient isolation from engine vibration while also providing significant damping to control the rigid body motions of the engine during normal driving conditions. This results in a system which exhibits a high degree of non-linearity in terms of both frequency and amplitude. The numerical simulation of vibration isolation characteristics of HDM is difficult due to the fluid-structure interaction between the main supporting rubber and fluid in chambers, the nonlinear material properties, the large deformation of rubber parts, structure contact problems among the inner parts, and the turbulent flow in the inertia track. In this paper an integrated numerical simulation analysis based on structural FEM and a lumped-parameter model of HDM is carried out.
Technical Paper

Bolt-Load Retention Behavior of a Die Cast Magnesium-Rare Earth Alloy

2001-03-05
2001-01-0425
The need for improved understanding of new magnesium alloys for the automotive industry continues to grow as the application for these lightweight alloys expands to more demanding environments, particularly in drivetrain components. Their use at elevated temperatures, such as in transmission cases, presents a challenge because magnesium alloys generally have lower creep resistance than aluminum alloys currently employed for such applications. In this study, a new die cast magnesium alloy, MEZ, containing rare earth (RE) elements and zinc as principal alloying constituents, was examined for its bolt-load retention (BLR) properties. Preloads varied from 14 to 28 kN and test temperatures ranged from 125 to 175°C. At all test temperatures and preloads, MEZ retained the greatest fraction of the initial imposed preload when compared to the magnesium alloys AZ91D, AE42, AM50, and the AM50+Ca series alloys.
Technical Paper

Rollover Propensity Evaluation of an SUV Equipped with a TRW VSC System

2001-03-05
2001-01-0128
In this paper, a simulation-based dynamic rollover evaluation procedure is described. This work is based on the worst-case methodology developed at the University of Michigan, and is the result of a collaborated research project between the University of Michigan and TRW Inc. The target vehicle studied in this paper is a large production volume SUV. This vehicle is equipped with a production-intent TRW Vehicle Stability Control (VSC) system. The main goals of this paper are to (i) study the rollover propensity of this SUV, as influenced by vehicle and environment parameters such as vehicle speed, road condition, etc.; and (ii) investigate whether, and by how much, does the VSC system influence the rollover propensity of this SUV. The modeling, evaluation procedure, and preliminary evaluation results are reported.
Technical Paper

Modeling Variability in Reaching Motions

2001-06-26
2001-01-2094
Motion prediction models may give the average reach for an individual of specified characteristics. The actual reach will vary from this reach in a manner that may depend on both systematic and random factors. We describe a modeling approach that incorporates the variability within the reaches of a given subject and that between subjects. This information is useful to designers in investigating phenomena that may not occur during the average reach but may occur during variants such as collision with an obstacle or injury due to over-exertion.
Technical Paper

Probabilistic Analysis for the Performance Characteristics of Engine Bearings due to Variability in Bearing Properties

2003-05-05
2003-01-1733
This paper presents the development of surrogate models (metamodels) for evaluating the bearing performance in an internal combustion engine without performing time consuming analyses. The metamodels are developed based on results from actual simulation solvers computed at a limited number of sample points, which sample the design space. A finite difference bearing solver is employed in this paper for generating information necessary to construct the metamodels. An optimal symmetric Latin hypercube algorithm is utilized for identifying the sampling points based on the number and the range of the variables that are considered to vary in the design space. The development of the metamodels is validated by comparing results from the metamodels with results from the actual bearing performance solver over a large number of evaluation points. Once the metamodels are established they are employed for performing probabilistic analyses.
Technical Paper

Structural Vibration of an Engine Block and a Rotating Crankshaft Coupled Through Elastohydrodynamic Bearings

2003-05-05
2003-01-1724
A comprehensive formulation is presented for the dynamics of a rotating flexible crankshaft coupled with the dynamics of an engine block through a finite difference elastohydrodynamic main bearing lubrication algorithm. The coupling is based on detailed equilibrium conditions at the bearings. The component mode synthesis is employed for modeling the crankshaft and block dynamic behavior. A specialized algorithm for coupling the rigid and flexible body dynamics of the crankshaft within the framework of the component mode synthesis has been developed. A finite difference lubrication algorithm is used for computing the oil film elastohydrodynamic characteristics. A computationally accurate and efficient mapping algorithm has been developed for transferring information between a high - density computational grid for the elastohydrodynamic bearing solver and a low - density structural grid utilized in computing the crankshaft and block structural dynamic response.
Technical Paper

Oil Film Dynamic Characteristics for Journal Bearing Elastohydrodynamic Analysis Based on a Finite Difference Formulation

2003-05-05
2003-01-1669
A fast and accurate journal bearing elastohydrodynamic analysis is presented based on a finite difference formulation. The governing equations for the oil film pressure, stiffness and damping are solved using a finite difference approach. The oil film domain is discretized using a rectangular two-dimensional finite difference mesh. In this new formulation, it is not necessary to generate a global fluidity matrix similar to a finite element based solution. The finite difference equations are solved using a successive over relaxation (SOR) algorithm. The concept of “Influence Zone,” for computing the dynamic characteristics is introduced. The SOR algorithm and the “Influence Zone” concept significantly improve the computational efficiency without loss of accuracy. The new algorithms are validated with numerical results from the literature and their numerical efficiency is demonstrated.
Technical Paper

Mathematical Modeling of Vehicle Fuel Cell Power System Thermal Management

2003-03-03
2003-01-1146
A mathematical model of vehicle fuel cell system thermal management has been developed to investigate the effects of various design and operating conditions on the thermal management and to understand the underlying mechanism. The fuel cell stack structure is represented by a lumped thermal mass model, which has the heat transfer and pressure loss characteristics of the fuel cell stack structure. The whole thermal management system is discretized into many volumes, where each flowspit is represented by a single volume, and every pipe is divided into one or more volumes. These volumes are connected by boundaries. The model is solved numerically to analyze thermal management system performance. The effects of coolant flow rates and air flow rates on the system thermal performance, the stack thermal capacity on the transient thermal performance have been investigated in detail.
Technical Paper

A Two-Tracer LIF Strategy for Quantitative Oxygen Imaging in Engines Applied to Study the Influence of Skip-Firing on In-Cylinder Oxygen Contents of an SIDI Engine

2003-03-03
2003-01-1114
The effect of skip-firing (which is often applied in optical engine work) on the available in-cylinder oxygen concentration was investigated with a laser-induced fluorescence imaging setup that combines the measurement of fluorescence signals from toluene and 3-pentanone to quantitatively determine the distribution of molecular oxygen. We describe in detail the image processing procedure for this measurement. The reduction of in-cylinder oxygen when switching from skip-fired to continuous-fired engine operation is measured and compared to traditional exhaust measurements.
Technical Paper

An Experimental Assessment of Turbulence Production, Reynolds Stress and Length Scale (Dissipation) Modeling in a Swirl-Supported DI Diesel Engine

2003-03-03
2003-01-1072
Simultaneous measurements of the radial and the tangential components of velocity are obtained in a high-speed, direct-injection diesel engine typical of automotive applications. Results are presented for engine operation with fuel injection, but without combustion, for three different swirl ratios and four injection pressures. With the mean and fluctuating velocities, the r-θ plane shear stress and the mean flow gradients are obtained. Longitudinal and transverse length scales are also estimated via Taylor's hypothesis. The flow is shown to be sufficiently homogeneous and stationary to obtain meaningful length scale estimates. Concurrently, the flow and injection processes are simulated with KIVA-3V employing a RNG k-ε turbulence model. The measured turbulent kinetic energy k, r-θ plane mean strain rates ( 〈Srθ〉, 〈Srr〉, and 〈Sθθ〉 ), deviatoric turbulent stresses , and the r-θ plane turbulence production terms are compared directly to the simulated results.
Technical Paper

Development of Dynamic Simulation Models of Seated Reaching Motions While Driving

1997-02-24
970589
A research effort was initiated to establish an empirical data base and to develop predictive models of normal human in-vehicle seated reaching motions while driving. A driving simulator was built, in which a variety of targets were positioned at typical locations a driver would possibly reach. Reaching motions towards these targets were performed by demographically representative subjects and measured by a state-of-the-art motion analysis system. This paper describes the experiment conducted to collect the movement data, and the new techniques that are being developed to process, analyze, and model the data. Some initial findings regarding the role of torso assistive motion, the effect of speed used in completing a motion on multi-segment dynamic postures, and illustrative results from kinematic modeling are presented.
Technical Paper

Life Cycle Assessment and Design of Instrument Panels: A Common Sense Approach

1997-02-24
970695
The U.S. EPA initiated the Common Sense Initiative (CSI) to develop “Cleaner, Cheaper, Smarter” environmental policy and management practices. This paper addresses the application of life cycle design and assessment tools to automotive instrument panels (IP) as part of the Automotive Manufacturing Sector CSI pilot project investigation. For this study, an “average IP” was modeled based on the instrument panels of three mid-sized U.S. car models: 1995 Chevrolet Lumina, 1996 Dodge Intrepid and 1996 Ford Taurus. This “average IP” consisted of seventeen different materials and weighed over 22 kg (49 lbs.). A life cycle inventory analysis was conducted to evaluate the environmental burdens associated with materials production, manufacturing, use, and retirement. A thorough evaluation of solid waste production and energy consumption was completed and partial inventories of air emission and water effluent releases were also conducted.
Technical Paper

An Experimental Heat Release Rate Analysis of a Diesel Engine Operating Under Steady State Conditions

1997-02-24
970889
An experimental heat release rate analysis was conducted on a six cylinder, 12.7 liter Detroit Diesel Series 60 turbocharged engine operating under steady state conditions. The overall chemical, or gross, rate of heat release and the net apparent rate of heat release were determined from experimental measurements. The gross, time averaged, heat release rate was determined by two separate concepts/methods using exhaust gas concentration measurements from the Nicolet Rega 7000 Real Time Exhaust Gas Analyzer and the measured exhaust gas flow rate. The net apparent rate of heat release was determined from the in-cylinder pressure measurements for each of the six cylinders, averaged over 80 cycles. These pressure measurements were obtained using a VXI based Tektronix data acquisition system and LabVIEW software. A computer algorithm then computed the net apparent rate of heat release from the averaged in-cylinder pressure measurements.
Technical Paper

Development of Second-by-Second Fuel Use and Emissions Models Based on an Early 1990s Composite Car

1997-02-24
971010
Simulation models for second-by-second fuel rate, and engine-out and tailpipe emissions of CO, HC, and NOx from a “composite” car in hot engine and catalyst conditions are presented and tested using Federal Test Procedure Revision Project (FTPRP) data from 15 1991-1994 cars. The models are constructed as a combination of simple science and curve fitting to the FTPRP data. The models are preliminary, the simplest models being presented to illustrate how much can be predicted with very few parameters. Fuel rate and engine out emissions of all three pollutants are accurately predicted. The tailpipe emissions models are only moderately successful, largely because we are only moderately successful in predicting catalyst pass fractions during low power driving. Nevertheless, the composite car shows regular emissions behavior, and these are modeled effectively.
Technical Paper

Longitudinal Vibration of Elastic Vehicle Track Systems

1997-02-24
971090
Real-time simulation of tracked vehicle dynamics demands very efficient modeling of the vehicle track. Multi-body dynamics models which model the response of each track pitch are complete, but require on the order of 100 degrees of freedom to capture lateral track dynamics and an additional 200 degrees of freedom to capture longitudinal (stretching) track dynamics. The sheer size of such models renders them difficult to use for rapid estimates of track response. This paper summarizes an efficient alternative for modeling vehicle tracks, as illustrated herein by a model for longitudinal track dynamics. The present model is a hybrid discrete/continuous model in which the track is modeled as a continuous uniform elastic rod which is kinematically coupled to discrete models for the sprocket, wheels, and rollers. Solution efficiency derives from transforming the dynamic track model to one employing modal coordinates.
Technical Paper

Permeability and Transient Thermal Response of Airbag Fabrics

1997-02-24
971063
The permeability of some airbag fabrics is determined, along with the Ergun coefficient signifying departure from purely viscous flow, from gas flow rates and pressure drop measurements. The dependency of these coefficients on the fabric temperature is also examined. Preliminary results are reported on the transient response of these fabrics to temporal changes in the gas flow rate and temperature. The temperature history is measured and compared with the predictions of some simple models. The models make various assumptions regarding the microscale of the fabrics. The preliminary results show that the very fine microscales do not control the time response of the fabric.
Technical Paper

Modal Content of Heavy-Duty Diesel Engine Block Vibration

1997-05-20
971948
High-fidelity overall vehicle simulations require efficient computational routines for the various vehicle subsystems. Typically, these simulations blend theoretical dynamic system models with empirical results to produce computer models which execute efficiently. Provided that the internal combustion engine is a dominant source of vehicle vibration, knowledge of its dynamic characteristics throughout its operating envelope is essential to effectively predict vehicle response. The present experimental study was undertaken to determine the rigid body modal content of engine block vibration of a modern, heavy-duty Diesel engine. Experiments were conducted on an in-line six-cylinder Diesel engine (nominally rated at 470 BHP) which is used in both commercial Class-VIII trucks, and on/off-road military applications. The engine was mounted on multi-axis force transducers in a dynamometer test cell in the standard three-point configuration.
Technical Paper

Linearity of Powertrain Acceleration Sound

1997-05-20
971982
The loudness of powertrain noise generally increases with increasing rpm. In the case of ‘linear’ powertrain acceleration sound, the loudness versus time relationship is well described by a linear function. Two studies were conducted on powertrain linearity. The first used tests of similarity and preference to determine whether subjects could detect changes in linearity. The second used a subjective test of preference to investigate how subjects' preference varied with differing degrees of linearity. In both studies, stimulus sets were created by artificially introducing a controlled degree of non-linearity into a nominally linear powertrain sound. The results of the first study indicate that linearity is a phenomenon that naive subjects can readily detect, and that it has an effect on overall preference. Furthermore, the second study shows that preference is related to the magnitude and position of nonlinearities in the growth of loudness versus time during an acceleration run.
X