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Technical Paper

Effect of Flow on Helmholtz Resonator Acoustics: A Three-Dimensional Computational Study vs. Experiments

2011-05-17
2011-01-1521
The effectiveness of the Helmholtz resonator as a narrow band acoustic attenuator, particularly at low frequencies, makes it a highly desirable component in a wide variety of applications, including engine breathing systems. The present study investigates the influence of mean flow grazing over the neck of such a configuration on its acoustic performance both computationally and experimentally. Three-dimensional unsteady, turbulent, and compressible Navier-Stokes equations are solved by using the Pressure-Implicit-Splitting-of-Operators algorithm in STAR-CD to determine the time-dependent flow field. The introduction of mean flow in the main duct is shown to reduce the peak transmission loss and shift the fundamental resonance frequency to a higher value.
Journal Article

An Iterative Markov Chain Approach for Generating Vehicle Driving Cycles

2011-04-12
2011-01-0880
For simulation and analysis of vehicles there is a need to have a means of generating drive cycles which have properties similar to real world driving. A method is presented which uses measured vehicle speed from a number of vehicles to generate a Markov chain model. This Markov chain model is capable of generating drive cycles which match the statistics of the original data set. This Markov model is then used in an iterative fashion to generate drive cycles which match constraints imposed by the user. These constraints could include factors such number of stops, total distance, average speed, or maximum speed. In this paper, systematic analysis was done for a PHEV fleet which consists of 9 PHEVs that were instrumented using data loggers for a period of approximately two years. Statistical analysis using principal component analysis and a clustering approach was carried out for the real world velocity profiles.
Technical Paper

Micro-Texture Tailored Friction Modeling and Discrete Application in Drawability Improvement

2010-04-12
2010-01-0982
Friction plays an important role in the deep drawing process. Previous research shows friction condition can be tailored by applying micro-textures on tooling surfaces. A friction model is proposed to reveal the mechanism of altering friction condition by configuring micro-texture. A discrete friction concept is proposed to improve drawability of sheet metal and demonstrates numerically on a non-symmetric geometry drawing process.
Journal Article

Integration of a Torsional Stiffness Model into an Existing Heavy Truck Vehicle Dynamics Model

2010-04-12
2010-01-0099
Torsional stiffness properties were developed for both a 53-foot box trailer and a 28-foot flatbed control trailer based on experimental measurements. In order to study the effect of torsional stiffness on the dynamics of a heavy truck vehicle dynamics computer model, static maneuvers were conducted comparing different torsional stiffness values to the original rigid vehicle model. Stiffness properties were first developed for a truck tractor model. It was found that the incorporation of a torsional stiffness model had only a minor effect on the overall tractor response for steady-state maneuvers up to 0.4 g lateral acceleration. The effect of torsional stiffness was also studied for the trailer portion of the existing model.
Technical Paper

Validation and Enhancement of a Heavy Truck Simulation Model with an Electronic Stability Control Model

2010-04-12
2010-01-0104
Validation was performed on an existing heavy truck vehicle dynamics computer model with roll stability control (RSC). The first stage in this validation was to compare the response of the simulated tractor to that of the experimental tractor. By looking at the steady-state gains of the tractor, adjustments were made to the model to more closely match the experimental results. These adjustments included suspension and steering compliances, as well as auxiliary roll moment modifications. Once the validation of the truck tractor was completed for the current configuration, the existing 53-foot box trailer model was added to the vehicle model. The next stage in experimental validation for the current tractor-trailer model was to incorporate suspension compliances and modify the auxiliary roll stiffness to more closely model the experimental response of the vehicle. The final validation stage was to implement some minor modifications to the existing RSC model.
Technical Paper

Simulation Results from a Model of a Tractor Trailer Vehicle Equipped with Roll Stability Control

2010-04-12
2010-01-0098
In 2007, a software model of a Roll Stability Control (RSC) system was developed based on test data for a Volvo tractor at NHTSA's Vehicle Research and Test Center (VRTC). This model was designed to simulate the RSC performance of a commercially available Electronic Stability Control (ESC) system. The RSC model was developed in Simulink and integrated with the available braking model (TruckSim) for the truck. The Simulink models were run in parallel with the vehicle dynamics model of a truck in TruckSim. The complete vehicle model including the RSC system model is used to simulate the behavior of the actual truck and determine the capability of the RSC system in preventing rollovers under different conditions. Several simulations were performed to study the behavior of the model developed and to compare its performance with that of an actual test vehicle equipped with RSC.
Technical Paper

Charging Strategy Studies for PHEV Batteries based on Power Loss Model

2010-04-12
2010-01-1238
This paper describes a new method to increase the efficiency of the battery charging process, η, which is defined as the ratio of the energy accumulated in the battery over the actual energy supplied to it. Through several simulation results, it has been found that such efficiency is a function of the current profile applied to the battery during the charging process; hence, plots describing the energy loss in the battery, time taken to achieve a desired level of charge, and power needed as a function of the charging current, are shown. In order to find the optimal charging current profile, the mathematical model of the energy loss in the battery is developed and the problem of finding the optimal current profile is formulated as an Optimal Control problem. A model based on a Lithium-Ion Battery commercially available for PHEV is used as the plant to be controlled.
Technical Paper

Generator Voltage Regulation Through Current Control in a Hybrid Electric Vehicle

2010-04-12
2010-01-1255
A novel approach to control the output voltage of the generator on a hybrid electric vehicle is proposed in this paper. In addition to the voltage control, for safety reason, it is desirable to control the current of the generator when the machine is running. In order to control the current, the reference voltage is translated to reference current by an estimator. Then current convergence is ensured by controlling the excitation voltage. Thus the over-current is prevented in the system. The rate of convergence of the voltage tracking is discussed. Robustness of the control algorithm against parameter variation is also analyzed and compared with conventional approach. Simulation results show that the safety objective is achieved without sacrificing output performance of the generator.
Journal Article

Assessment of the Simulated Injury Monitor (SIMon) in Analyzing Head Injuries in Pedestrian Crashes

2012-04-16
2012-01-0569
Objectives. Examination of head injuries in the Pedestrian Crash Data Study (PCDS) indicates that many pedestrian head injuries are induced by a combination of head translation and rotation. The Simulated Injury Monitor (SIMon) is a computer algorithm that calculates both translational and rotational motion parameters relatable head injury. The objective of this study is to examine how effectively HIC and three SIMon correlates predict the presence of either their associated head injury or any serious head injury in pedestrian collisions. Methods. Ten reconstructions of actual pedestrian crashes documented by the PCDS were conducted using a combination of MADYMO simulations and experimental headform impacts. Linear accelerations of the head corresponding to a nine-accelerometer array were calculated within the MADYMO model's head simulation.
Technical Paper

The Impact of Injection Timing on In-Cylinder Fuel Distribution in a Natural Gas Powered Engine

1997-05-01
971708
One obstacle hindering the use of port fuel injection in natural gas engines is poor idle performance due to incomplete mixing of the cylinder charge prior to ignition. Fuel injection timing has a strong influence on the mixing process. The purpose of this work is to determine the impact of fuel injection timing on in-cylinder fuel distribution. Equivalence ratio maps have been acquired by Planar Laser Induced Fluorescence in an optical engine with a production cylinder head. Experimental results have been used to determine the injection timing which produces the most uniform fuel distribution for the given engine.
Technical Paper

Plasma-Enhanced Catalysis for Automotive Exhausts

1997-05-01
971719
This paper presents a concept for enhancing catalytic removal of pollutant species from an exhaust stream by placing placing the plasma adjacent to the catalyst surface. Model calculations of the behavior of the electron energy distribution function (EEDF), which influences the chemistry and ionization levels near the surface, are performed and analyzed. Preliminary experiments attempting to reduce these theoretical ideas to practice in N2/NO mixtures, are discussed. Although removal of NO is observed, this is due to gas phase effects alone. The present experimental arrangement is not able to produce the requisite conditions outlined by theory to enact plasma-enhanced catalysis.
Technical Paper

Finite Modeling of Sheet Stamping Operations

1996-04-01
91A089
A wide variety of choices confront the potential user of finite element modeling (FEM) for sheet forming analysis. In the first part of this paper, a brief summary of the basic formulations available and sample references to them are provided. Several kinds of finite element models have been developed for analyzing sheet forming operations at OSU and in the Center for Net Shape Manufacturing. These variations began with in-plane FEM and grew into 3-D versions. In the second part of this paper, some key conclusions from these developments will be summarized. More recently, a section analysis program (SHEET-S) has been prepared and transferred to industry. The capabilities and limitations of SHEET-S will be presented in greater detail, including comparisons with experiments and industrial trials.
Technical Paper

Pedestrian head impact testing and PCDS reconstructions

2001-06-04
2001-06-0184
Pedestrian research and testing at the NHTSA Vehicle Research and Test Center has recently focused on assessment of proposed ISO and EEVC head impact test procedures, and extension of these procedures to additional vehicle frontal surfaces. In addition to test parameter sensitivity evaluation, reconstruction of PCDS (Pedestrian Crash Data Study) cases with laboratory impact tests and computer simulations has been conducted. This paper presents the results of this research.
Technical Paper

Springback Prediction Using Combined Hardening Model

2000-10-03
2000-01-2659
The main objective of this paper is to simulate the springback using combined kinematic/isotropic hardening model. Material parameters in the hardening model are identified by an inverse method. Three-point bending test is conducted on 6022-T4 aluminum sheet. Punch stroke, punch load, bending strain and bending angle are measured directly during the tests. Bending moments are then computed from these measured data. Bending moments are also calculated based on a constitutive model. Material parameters are identified by minimizing the normalized error between two bending moments. Micro genetic algorithm is used in the optimization procedure. Stress-strain curves is generated with the material parameters found in this way, which can be used with other plastic models. ABAQUS/Standard 5.8, which has the combined isotropic/kinematic hardening model, is used to simulate draw-bend of 6022-T4 series aluminum sheet. Absolute springback angles are predicted very accurately.
Technical Paper

A Comprehensive Review of Pedestrian Impact Reconstruction

1987-02-01
870605
This paper presents a review on pedestrian impact reconstruction methodology and offers a comprehensive review of the literature. Several types of analyses are discussed which can be used to reconstruct the accident scenario using the facts collected from the scene. Inclusive in this review is the utilization of skid mark analysis, debris analysis, injury/damage match-up, trajectory analysis, nighttime visibility, and alcohol effects. The pedestrian impact reconstruction methodology is illustrated with a real world case example to point out different observations which can provide insight into the pedestrian/vehicle collision reconstruction approach. The literature review provides a broad foundation of information on pedestrian impact reconstruction and can be used to supplement the techniques presented in this paper in areas related to pedestrian impact. Research advances in the area of pedestrian impact reconstruction are also discussed in this paper.
Technical Paper

Self-Tuning Optimal Control of an Active Suspension

1989-11-01
892485
The objective of this paper is to develop a self-tuning optimal control of an active suspension. An active suspension composed of an identifier and a controller is proposed in this paper. Although control strategies on active (or semi-active) suspensions have been investigated during the past few decades, some problems are not well understood yet. One of them arising from the ride control of an active suspension is that when the weight and the moments of inertia of the sprung mass are varied, the feedback gains of the controller should vary with the variation of parameters accordingly. Therefore, the identifier is proposed before the controller is designed. In the real situations, the parameter variation may occur when loadings on vehicles vary - either from passengers or payloads, especially, in the case of loading on a truck. An identification structure using parallel model reference adaptive system (MRAS) is proposed to identify the true parameters.
Technical Paper

Empirical-Numerical Simulation Technique for Improving the Quality of Rolled Rods by Roll Pass Design

1992-02-01
920783
Improper roll pass designs can lead to either underfill which results in the formation of hairline cracks on the surface of the finished bars or overfill which results in roll overloading and the formation of fins. Therefore to reduce downtime, and improve yield and quality, it becomes important to design an acceptable roll pass in reasonable time. This paper presents a methodology for roll pass design which uses a three dimensional finite element technique along with an empirical procedure to arrive at an iterative scheme for reducing the number of passes and improving metal flow in the passes. This methodology is applied to improving an existing seven pass square - to - round rolling sequence, resulting in the reduction of the number of passes and improved distributions of effective strains in the rolled product.
Technical Paper

Experimental Verification of Design Charts for Acoustic Absorbers

1997-05-20
971951
Design charts which predict acoustic absorption of porous insulators were verified experimentally using the two-microphone technique to measure the normal incidence absorption coefficient of three glass fiber materials in two different arrangements - a single-layer sample and a single layer in front of an air space, each backed by a rigid termination. The specific flow resistivities of the materials ranged from 2,000 to 52,000 mks rayls/m. Experimentally determined absorption coefficients were in agreement with those predicted by the design charts. The results indicate that these charts could be a useful tool in designing sound absorbers for practical applications.
Technical Paper

Welding Residual Stresses in Splicing Heavy Section Shapes

1997-04-07
971585
Welding residual stress is one of the primary factors responsible for cracking at the access hole interface between the flange and web plate of welded heavy W-shapes. During multi-pass welding, cracks can be found in either the flange plate or the web plate, depending upon welding sequence, joint details and access hole size. In this study, an integrated numerical and experimental investigation was conducted to evaluate the effects of welding parameters and joint geometry on the magnitude and distribution of residual stresses in thick-section butt joints. The results provide guidelines for improved design for welding of heavy W-shapes.
Technical Paper

The Application of Fuzzy Logic to the Diagnosis of Automotive Systems

1997-02-24
970208
The evolution of the diagnostic equipment for automotive application is the direct effect of the implementation of sophisticated and high technology control systems in the new generation of passenger cars. One of the most challenging issues in automotive diagnostics is the ability to assess, to analyze, and to integrate all the information and data supplied by the vehicle's on-board computer. The data available might be in the form of fault codes or sensors and actuators voltages. Moreover, as environmental regulations get more stringent, knowledge of the concentration of different species emitted from the tailpipe during the inspection and maintenance programs can become of great importance for an integrated powertrain diagnostic system. A knowledge-based diagnostic tool is one of the approaches that can be adopted to carry out the challenging task of detecting and diagnosing faults related to the emissions control system in an automobile.
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