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TWO TYPES of bench wear tests employed by the General Motors Research Laboratories are described, and examples are given to illustrate the application of the tests to material development problems. It is shown that correlation of a bench test with service may be achieved even when the laboratory test conditions do not appear to duplicate service conditions exactly. It is postulated that this behaviour is related to the formation of certain types of surface films during the wearing process. Some preliminary results are given of a study of the influence of lubricant type and material composition on the formation of anti-wear films.

THE PURPOSE of this experiment was to determine the role of residual stresses in fatigue strength independent of other factors usually involved when residual stresses are introduced. It consisted of an investigation of the influence of residual stresses introduced by shotpeening on the fatigue strength of steel (Rockwell C hardness 48) in unidirectional bending. Residual stresses were varied by peening under various conditions of applied strain. This process introduced substantially the same amount and kind of surface cold working with residual stresses varying over a wide range of values. It was found that shotpeening of steel of this hardness is beneficial primarily because of the nature of the macro-residual-stresses introduced by the process. There is no gain attributable to “strain-hardening” for this material. An effort was made to explain the results on the basis of three failure criteria: distortion energy, maximum shear stress, and maximum stress.*

PEARLITIC malleable iron crankshafts are being used in the new Pontiac engine as a result of recent developments. This paper discusses the physical properties of pearlitic malleable iron such as elastic modulus, fatigue endurance, and tensile strength. According to the author, definite machining economies result from using pearlitic malleable iron crankshafts.

A comprehensive test program was conducted to correlate aerodynamic drag measurements from the General Motors Aerodynamics Laboratory with coastdown results. An improved method of coastdown testing was used to minimize the sources of error in determining aerodynamic drag. Several vehicles were tested, covering a large range of aerodynamic drag values, representative of current and future production vehicles. Wind tunnel and coastdown results were determined to be in good agreement, with an average drag coefficient difference of only. 008 (2%).

Eigenvalues of a simple rotating flexible disk-shaft system are obtained using different methods. The shaft is supported radially by non-rigid bearings, while the disk is situated at one end of the shaft. Eigenvalues from a finite element and a multi-body dynamic tool are compared against an established analytical formulation. The Campbell diagram based on natural frequencies obtained from the tools differ from the analytical values because of oversimplification in the analytical model. Later, detailed whirl analysis is performed using AVL Excite multi-body tool that includes understanding forward and reverse whirls in absolute and relative coordinate systems and their relationships. Responses to periodic force and base excitations at a constant rotational speed of the shaft are obtained and a modified Campbell diagram based on this is developed. Whirl of the center of the disk is plotted as an orbital or phase plot and its rotational direction noted.

Meeting the California Medium-Duty truck emissions standards presents a significant challenge to automotive engineers due to the combination of sustained high temperature exhaust conditions, high flow rates and relatively high engine out emissions. A successful catalyst for an exhaust treatment system must be resistant to high temperature deactivation, maintain cold start performance and display high three-way conversion efficiencies under most operating conditions. This paper describes a catalyst technology and precious metal loading study targeting a California Medium-Duty truck LEV (MDV2) application. At the same time a direction is presented for optimizing toward the Federal Tier 1 standard through reduction of precious metal use. The paper identifies catalytic formulations for a twin substrate, 1.23 L medium-coupled converter. Two are used per vehicle, mounted 45 cm downstream of each manifold on a 5.7 L V8 engine.

AS a basis for the analyses of this symposium, a hypothetical car has been used to evaluate the engine power distribution in performance. Effects of fuel,-engine accessories, and certain car accessories are evaluated. The role of the transmission in making engine power useful at normal car speeds is also discussed. Variables encountered in wind and rolling resistance determinations are reevaluated by improved test techniques. Net horsepower of the car in terms of acceleration, passing ability and grade capability are also summarized.

Four multigrade engine oils, containing the same base oil plus SE additive package but VI improvers of differing shear stability, were evaluated in 80 000 km of high-speed, high-temperature vehicle service. Bearing, piston ring and valve guide wear, as well as oil consumption, oil filter plugging and engine cleanliness were all worse for the engines operated on the low-shear stability oils. The wear differences were traced to differences in high-shear-rate viscosity, while the cleanliness, filter plugging and oil consumption differences occurred because of excessive wear or polymer shear degradation. These results suggest that engine oil viscosity should be specified under high-shear-rate conditions.

Certain problems associated with conventional vehicular speed sensing, such as wheel slip, wheel lock, and variable rolling radius, can be alleviated by employing microwave speed sensing. It is expected that true speed sensing will augment a number of automotive and other ground transportation applications. An experimental, two-horn, 55 GHz continuous wave radar speedometer designed to measure true ground speed in the presence of vehicular perturbations is described; the system has an ultimate design frequency of 60 GHz. An Impatt diode, solid-state transmitter was incorporated in this design because of its inherent advantages. The RF portion of the transmitter-receiver unit, including the dipole feed, is housed on a single microstrip circuit on an alumina substrate 1/2 X 1/4 in (12.7 X 6.35 mm). Vertically polarized beams incident at angles of 35 deg with respect to the horizontal system were chosen as a design compromise.

A practical methodology is presented for the synthesis of Chassis Systems and their integration into a vehicle design to achieve a specified vehicle dynamic performance. By focusing on the fundamental performance requirements of gain, response time, and stability in midrange handling and the higher level design parameters of front and rear cornering compliance it is possible to find optimum values for these design parameters. The balancing of these higher level design parameters, in the context of overall vehicle performance, determines primary system requirements for the front suspension, rear suspension, tires, and steering system which may in turn be met by a variety of specific hardware designs.

CFD (Computational Fluid Dynamics) has been used to analyze vehicle air flow. In cross wind conditions an asymmetrical flow field around the vehicle is present. Under these circumstances, in addition to the forces present with symmetric air flow (drag and lift forces and pitching moment), side forces and moments (rolling and yawing) occur. Issues related to fuel economy, driveability, sealing effects (caused by suction exerted on the door), structural integrity (sun roof, spoiler), water management (rain deposit), and dirt deposit (shear stress) have been investigated. Due to the software developments and computer hardware improvements, results can be obtained within a reasonable time frame with excellent accuracy (both geometry and analytical solution). The flow velocity, streamlines, pressure field, and component forces can be extracted from the analysis results through visualization to identify potential improvement areas.

The strain-life approach is now commonly used for fatigue life analysis and predictions in the ground vehicle industry. This approach requires the use of material properties obtained from strain-controlled uniaxial fatigue tests. These properties include fatigue strength coefficient (σf′), fatigue strength exponent (b), fatigue ductility coefficient (εf′), fatigue ductility exponent (c), cyclic strength coefficient (K′), and cyclic strain hardening exponent (n′). To obtain the aforementioned properties for the material, raw data from stable cyclic stress-strain loops are fitted in log-log scale. These data include total, elastic and plastic strain amplitudes, stress amplitude, and fatigue life. Values of the low cycle fatigue properties (σf′, b, εf′, c) determined from the raw data depend on the method of measurement and fitting. This paper examines the merits and influence of using different measurement and fitting methods on the obtained properties.

The purpose of this paper is to illustrate the use of Taguchi experimental methods as a development tool for designing a manufacturing process for inner door panels. Through analysis of experimental results, it was possible to identify critical manufacturing variables, as well as demonstrate inherent process capability.

The Urban Vehicle Design Competition was inspired by the success of the Clean Air Car Race and the Great Electric Car Race. The academic community recognized the tremendous educational value of these events, and encouraged development of UVDC from its inception. The project was designed by engineering students to benefit students throughout North America. The rules of the competition include technical paper requirements that make the competition extremely attractive to professors who wish to build a course around this theme. The response of more than 2000 engineering students at 80 universities throughout the United States and Canada has indicated the success of the structure of the competition. The first major objective of the UVDC project has been met. Ninety-three teams throughout the country entered the UVDC design portion of the contest. The second portion of the project is the prototype contest of August 1972.

Accurate, real-world determination of tire force and moment properties is essential for computer modeling of vehicle handling. Characterizing these properties on surfaces ranging from dry pavement to snow to ice presents significant challenges. This paper reviews recent progress and results in this area for light truck tires using a test vehicle custom-designed for this purpose. It provides examples for free-rolling cornering, straight-line acceleration / braking and acceleration / braking in turns. The discussion then turns to the question of adapting the technology used to characterizing of tires for Class 8 vehicles.

A requirement for larger trucks and higher operating speed is indicated. The present report presents wind tunnel data on drag of a Chevrolet truck-trailer combination. Possible means of drag reduction are examined. Although side force and yawing moment data are presented, their effect on directional stability are not, at present analyzed.

A detailed description of the oxidative stability of GM's DEXRON®-VI Factory Fill Automatic Transmission Fluid (ATF) is provided, which can be integrated into a working algorithm to estimate the end of useful oxidative life of the fluid. As described previously, an algorithm to determine the end of useful life of an automatic transmission fluid exists and is composed of two simultaneous counters, one monitoring bulk oxidation and the other monitoring friction degradation [1]. When either the bulk oxidation model or the friction model reach the specified limit, a signal can be triggered to alert the driver that an ATF change is required. The data presented in this report can be used to develop the bulk oxidation model. The bulk oxidation model is built from a large series of bench oxidation tests. These data can also be used independent of a vehicle to show the relative oxidation resistance of this fluid, at various temperatures, compared to other common lubricants.

The National Space Biomedical Research Institute (NSBRI), established in 1997, is a twelve-university consortium dedicated to research that will impact mankind's next exploratory steps. The NSBRI's Education and Public Outreach Program (EPOP), is supporting NASA's education mission to, “Inspire the next generations…as only NASA can,” through a comprehensive Kindergarten through post-doctoral education program. The goals of the EPOP are to: communicate space exploration biology to schools; support undergraduate and graduate space-based courses and degrees; fund postdoctoral fellows to pursue space life sciences research; and engage national and international audiences to promote understanding of how space exploration benefits people on Earth. NSBRI EPOP presents its accomplishments as an educational strategy for supporting science education reform, workforce development, and public outreach.

Splash and spray conditions created by tractor-trailer combinations operating on the Federal highway system have been studied and tested for many years with mixed results. Past events are reviewed briefly in this paper. In additional testing during 1983, using new state-of- the-art splash/spray suppressant devices, some encouragement was provided that these devices could work. The 1984 Motor Vehicle Manufacturers Association (MVMA) test program was designed to develop practicable and reliable test procedures to measure effectiveness of splash and spray reduction methods applied to tractor-trailer combination vehicles. Over 40 different combinations of splash/spray suppression devices on five different tractors and three van trailer types were tested. The spray-cloud densities for some 400 test runs were measured by laser transmissometers and also recorded by still photography, motion pictures, and videotape. On-site observers made subjective ratings of spray density.

A rotating spacecraft which encloses an atmospheric pressure vessel poses unique challenges for thermal control. In any given location, the artificial gravity vector is directed from the center to the periphery of the vehicle. Its local magnitude is determined by the mathematics of centripetal acceleration and is directly proportional to the radius at which the measurement is taken. Accordingly, we have a system with cylindrical symmetry, featuring microgravity at its core and increasingly strong gravity toward the periphery. The tendency for heat to move by convection toward the center of the craft is one consequence which must be addressed. In addition, fluid flow and thermal transfer is markedly different in this unique environment. Our strategy for thermal control represents a novel approach to address these constraints. We present data to theoretically and experimentally justify design decisions behind the Mars Gravity Biosatellite's proposed payload thermal control subassembly.