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Technical Paper

A Calibration Study of CFD for Automotive Shapes and CD

An extensive calibration study has been initiated to assess the predictive ability of CFD (Computational Fluid Dynamics) for the aerodynamic design of automotive shapes. Several codes are being checked against a set of detailed wind tunnel measurements on ten car-like shapes. The objective is to assess the ability of numerical analysis to predict the CD (drag coefficient) influence of the rear end configuration. The study also provides a significant base of information for investigating discrepancies between predicted and measured flow fields and for assessing new numerical techniques. This technical report compares STAR-CD predictions to the wind tunnel measurements. The initial results are quite encouraging. Calculated centerline pressure distributions on the front end, underbody and floor compare well for all ten shapes. Wake flow structures are in reasonable agreement for many of the configurations. Drag, lift, and pitching moment trends follow the experimental measurements.
Technical Paper

A Comparison of Time Domain and Frequency Domain Test Methods for Automotive Components

Frequency domain testing has had limited use in the past for durability evaluations of automotive components. Recent advances and new perspectives now make it a viable option. Using frequency domain testing for components, test times can be greatly reduced, resulting in considerable savings of time, money, and resources. Quality can be built into the component, thus making real-time subsystem and full vehicle testing and development more meaningful. Time domain testing historically started with block cycle histogram tests. Improved capabilities of computers, controllers, math procedures, and algorithms have led to real time simulation in the laboratory. Real time simulation is a time domain technique for duplicating real world environments using computer controlled multi-axial load inputs. It contains all phase information as in the recorded proving ground data. However, normal equipment limitations prevent the operation at higher frequencies.
Technical Paper

A Discussion of Aerodynamic Interference Effects Between a Race Car and a Race Track Retaining Wall (A Wind Tunnel NASCAR Case Study)

This report should not be looked upon as an end in itself, but rather as a thought provoker. It raises the question that there may be an additional dimension to race car aerodynamics other than just open roadway drag reduction, stability and handling performance. Some situations are seldom considered, nor even addressed, in public forums. Based upon wind tunnel test data, the authors show, at least for this one test setup, that significantly large changes in aerodynamic forces can be generated on a NASCAR stock car racer by its close proximity to the stationary retaining wall around a race track.
Technical Paper

A Dynamometer Study of Off-Cycle Exhaust Emissions - The Auto/Oil Air Quality Improvement Research Program

Four vehicle fleets, consisting of 3 to 4 vehicles each, were emission tested on a 48″ roll chassis dynamometer using both the FTP urban dynamometer driving cycle and the REP05 driving cycle. The REP05 cycle was developed to test vehicles under high speed and high load conditions not included in the FTP. The vehicle fleets consisted of 1989 light-duty gasoline vehicles, 1992-93 limited production FFV/VFV methanol vehicles, 1992-93 compressed natural gas (CNG) vehicles and their gasoline counterparts, and a 1992 production and two prototype ethanol FFV/VFV vehicles. All vehicles (except the dedicated CNG vehicles) were tested using Auto/Oil AQIRP fuels A and C2. Other fuels used were M85 blended from A and C2, E85 blended from C1, which is similar to C2 but without MTBE, and four CNG fuels representing the range of in-use CNG fuels. In addition to bag measurements, tailpipe exhaust concentration and A/F data were collected once per second throughout every test.
Technical Paper

A Feedgas HC Emission Model for SI Engines Including Partial Burn Effects

A model is presented which incorporates the key mechanisms in the formation and reduction of unburned HC emissions from spark ignited engines. The model includes the effects of piston crevice volume, oil layer absorption / desorption, partial burns, and in-cylinder and exhaust port oxidation. The mechanism for the filling and emptying of the piston crevice takes into account the location of the flame front so that the flow of both burned gas and unburned gas is recognized. Oxidation of unburned fuel is calculated with a global, Arrhenius-type equation. A newly developed submodel is included which calculates the amount of unburned fuel to be added to the cylinder as a result of partial burns. At each crankangle, the submodel compares the rate of change of the burned gas volume to the rate of change of the cylinder volume.
Technical Paper

A Gasoline Engine Cycle that Permits High Expansion Operation with Reduced Part Load Throttling Losses by Modulating Charge Mass and Temperature

A four-stroke, spark-ignition engine is described that seeks to achieve high expansion ratio and low throttling losses at light load, whilst retaining good knock resistance at full load operation and without the need for expensive mechanical changes to the engine. The engine does, however, incorporate a second inlet (transfer) valve and associated transfer port linked to the intake port. The timing of the transfer valve is different from that of the main inlet valve. Load modulation is achieved by control of the gas outflow from the transfer port. A computer model of the engine is first validated against measured data from a conventional engine. Comparisons are made of incylinder pressure at part load conditions, total air flowrate through the engine and intake port air velocities as a function of crank angle position.
Technical Paper

A Method to Measure Air Conditioning Refrigerant Contributions to Vehicle Evaporative Emissions (SHED Test)

Although the intent of the SHED test (Sealed Housing for Evaporative Determination) is to measure evaporative fuel losses, the SHED sampling methodology in fact measures hydrocarbons from all vehicle and test equipment sources. Leakage of air conditioning (AC) refrigerant is one possible non-fuel source contributing to the SHED hydrocarbon measurement. This report describes a quick and relatively simple method to identify the contribution of AC refrigerant to the SHED analyzer reading. R134A (CH2FCF3), the hydrofluorocarbon refrigerant used in all current automotive AC systems, as well as its predecessor, the chlorofluorocarbon R12, can be detected using the gas chromatography methods currently in place at many emissions labs for the speciation of exhaust and evaporative hydrocarbon emissions.
Technical Paper

A Novel Capability for Crush Testing Crash Energy Management Structures at Intermediate Rates

The crush performance of lightweight composite automotive structures varies significantly between static and dynamic test conditions. This paper discusses the development of a new dynamic testing facility that can be used to characterize crash performance at high loads and constant speed. Previous research results from the Energy Management Working Group (EMWG) of the Automotive Composites Consortium (ACC) showed that the static crush resistance of composite tubes can be significantly greater than dynamic crush results at speeds greater than 2 m/s. The new testing facility will provide the unique capability to crush structures at high loads in the intermediate velocity range. A novel machine control system was designed and projections of the machine performance indicate its compliance with the desired test tolerances. The test machine will be part of a national user facility at the Oak Ridge National Laboratory (ORNL) and will be available for use in the summer of 2002.
Technical Paper

A Time-Domain Fatigue Life Prediction Method for Vehicle Body Structures

Fatigue analysis using finite element models of a full vehicle body structure subjected to proving ground durability loads is a very complex task. The current paper presents an analytical procedure for fatigue life predictions of full body structures based on a time-domain approach. The paper addresses those situations where this kind of analysis is necessary. It also discusses the major factors (e.g., stress equivalencing procedure, cycle counting method, event lumping and load interactions) which affect fatigue life predictions in the procedure. A comparison study is conducted which explores the combination of these factors favorable for realistic fatigue life prediction. The concepts are demonstrated using a body system model of production size.
Technical Paper

A Vehicle Micro Corrosion Environmental Study of Field and Proving Ground Tests

This paper presents the progress of an ongoing vehicle micro corrosion environment study. The goal of the study is to develop an improved method for estimating vehicle corrosion based on the Total Vehicle Accelerated Corrosion Test at the Arizona Proving Ground (APG). Although the APG test greatly accelerates vehicle corrosion compared to the field, the “acceleration factor” varies considerably from site-to-site around the vehicle. This method accounts for the difference in corrosivity of various local corrosion environments from site-to-site at APG and in the field. Correlations of vehicle microenvironments with the macroenvironment (weather) and the occurrence of various environmental conditions at microenvironments are essential to the study. A comparison of results from APG versus field measurements generated using a cold rolled steel based corrosion sensor is presented.
Technical Paper

ACT - Ford's Automatically Controlled Transportation System

This paper contains a technical description of the Ford Motor Co.'s ACT system which has been designed to meet transportation needs in a wide variety of urban applications. The discussion covers the systems design features and operation of the driverless rubber-tired vehicles, the guideway, and the system's ability to meet expanding needs by a modular approach to the command and control design. Descriptions of Ford's new Cherry Hill Test Track and the first installations at the Fairlane Town Center in Dearborn, Mich., and the Bradley International Airport, Hartford, Conn., are also presented.
Technical Paper

Agile Metrology: The Next Generation of Measuring Machines

All dimensional measurement systems, including Coordinate Measuring Machines (CMMs), share certain common characteristic elements. These systems include one or more of the following items: a sensor, a mechanism for supporting the sensor, a device for moving the support mechanism, a technique for planning how the support mechanism will be moved, and a device for analyzing sensor data. By recognizing these common features and capitalizing on the benefits of modularity and interchangeability of these features, the next generation of measuring machines will be able to easily accommodate new sensor technology and to meet the changing demands placed on dimensional inspection processes quickly and cost effectively.
Technical Paper

An Angular Sensor for Transmission Error Inspection

To serve the need of in-line rear axle diagnostics as well as other types of transmission inspection, an angular sensor development has been undertaken. It has resulted in a new device, incorporated into a system which performs angular error sensing at three levels. High precision of better than 0.003% in velocity variations is achieved. A continuous check of the null-error status of the devices is maintained in order to ensure maximum reliability of the readings. An easy on-site calibration check is available which eliminates the need for any precision calibrating fixture. The device is configured to accommodate a pass-through drive shaft for in-line mounting. A rugged design and immunity to rotor imperfections are advantageous in a plant environment.
Technical Paper

Analysis of Vehicle Pillar Cavity Foam Block Effect on Interior Noise Using SEA

Closed cell foam has been used for filling vehicle pillar cavities at select locations to block road noise transmitted through pillars. In the past, most pillar foam implementations in vehicle programs were driven by subjective improvements in interior sound. In this study road test results are used to correlate a detailed CAE (Computer-Aided Engineering) model based on the statistical energy analysis method. Noise reduction characteristics of pillar with a number of foam block fillings were then studied using the CAE model. The CAE models provided means to model and understand the mechanism of noise energy flow through pillar cavities. A number of insightful conclusions were obtained as result of the study.
Technical Paper

Application of Random Vibration Test Methods for Automotive Subsystems Using Power Spectral Density (PSD)

The object of this paper is to develop a random vibration laboratory test specification for automotive subsystems using the Power Spectral Density (PSD) method. This development is based on the 150k mile field data collected from vehicle proving grounds. The simulated vibration bench test will be used to simulate the energy of the 150k mile field data. The developed specification will include 3 axis random vibration profiles of appropriate duration. The Power Spectral Density method converts the time-domain field data into the frequency-domain data. The Enveloped Energy method groups the similar road PSD profiles to produce a generic PSD profile. The Inverse Law allocates an adjusted duration to the desired PSD energy level. The Road Test Specification provides the duration time for the developed bench test. The n-Soft tool [1] is utilized for data reduction analysis. The Bench Test Specification of the Fuel subsystem is a pilot for this development.
Technical Paper

Automatic Datalogging Techniques for Automotive Applications

New instrumentation designs require extensive proveout in the vehicle environment. The sheer magnitude of information required to evaluate today’s microprocessor-based systems precludes manual data collection and analysis. A method of automating the data collection process through direct communication with the instrumentation module is discussed. A design for an automatic data collector, or datalogger, is presented.
Technical Paper

Automatic Transmission Gear Whine Simulation and Test Correlation

In order to effectively evaluate automatic transmission gear noise and vibration performance using a hemi-anechoic test facility, it is essential to understand the coupling mechanism between the transmission internals and the dynamometers and associated shafting. Once this coupling mechanism is well understood, each major frequency response of the resulting torsional vibration operating data can be properly categorized according to the source: transmission-internal, facility, or driveshaft. This knowledge helps noise and vibration engineers properly manage vibration peaks in transmission operating data by ensuring that the issue of concern is not inadvertently influenced by the facility system. Analytical simulations and tests were performed on a transmission operated in a hemi-anechoic facility to evaluate gear vibration using various driveshafts, followed by a program of vehicle testing.
Technical Paper

Axial Collapse of Thin Wall Cylindrical Column

In order to understand the crush behavior of complex structural system such as a vehicle, one must first acquire the knowledge of crush characteristics of structural components that constitute the system and control its crush performance. In this paper, the crush strength characteristics and modes of collapse of thin walled circular columns are mathematically formulated. The formulation is based on the stability of shell structure subjected to axial crush, where various stages of collapse are identified and crush characteristics pertinent to column design are quantified. The effect of column size and the material properties on the collapse stability and crush strength characteristics of thin walled shell components are discussed. The size and number of folds for the axisymmetric “ring” mode and the nonsymmetric “diamond” mode are determined.
Technical Paper

Bench Level Automotive Electrical and Electromagnetic Compatibility Validation Test Process Improvements (Analysis of Survey Results from Test Laboratories)

In an effort to reduce the cost and time associated with bench level automotive electrical and electromagnetic compatibility (EMC) validation tests, a survey was created to request advice from the test labs that perform this testing. The survey focuses particularly on the development of the test plan document and the preparation of the test setup. The survey was sent to a targeted group of individuals with experience in performing this type of testing. The invitees work at laboratories that represent the majority of labs in the world that are authorized to perform component electrical / EMC validation testing for automotive original equipment manufacturers (OEMs). There were a significant number of responses; it is possible that representatives from all of the invited laboratories responded. The survey results provide demographic information about the test labs and their participants.
Technical Paper

Bending Fatigue Behavior of Carburized Gear Steels: Four-Point Bend Test Development and Evaluation

The ability to evaluate the bending fatigue behavior of carburized low alloy steels in a laboratory and relate these measurements to performance of high contact ratio helical gears is important to the design and development of transmissions. Typical methods of evaluating bending fatigue performance of carburized gear steels do not directly represent helical planetary gears because they lack the geometric and loading conditions of planetary pinions. The purpose of this study is twofold; 1) development of a lab fatigue test to represent the fatigue performance of planetary pinion gears tested in a dynamometer and 2) evaluation of the influence of alloy content on bending fatigue performance of two steel alloys. The steels under evaluation were modified 8620M and 4615M alloys machined into bend bars with a notch representing a gear root and carburized to a case depth of approximately 0.35 mm (using the same carburizing cycle as the planetary pinion gears).