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Technical Paper

Weibull Renewal Analysis

1964-01-01
640624
Renewal theory concerns itself with the replacement of randomly failing parts. In the simplest case we have a one component system which is kept running continuously by replacing a failed component at the instant of failure with an identical “new” component. The random variable N(t) = the number of failures (or replacements) to time t is then of interest in many types of reliability analysis. In this paper the distribution of N(t) is considered when the underlying failure law is a Weibull distribution. Tables of the mean and standard deviation of N(t) for various values of the Weibull slope parameter are presented. Applications to warranty and spare parts analyses are also noted.
Technical Paper

Vehicle Handling Response to Aerodynamic Inputs

1964-01-01
640001
The equations of lateral motion response for four wheeled vehicles are developed for external disturbance inputs. Experimental data is obtained through use of a laterally directed hydrogen peroxide rocket motor mounted on a station wagon. The use of a rocket motor provides accurate and flexible control of location and magnitude of the input disturbance. Response data taken from these tests are compared with the responses from a computer model utilizing the disturbance equations. These results are applied to illustrate the effects of wind disturbance on vehicle handling.
Technical Paper

Vehicle Evaluation of Synthetic and Conventional Engine Oils

1975-02-01
750827
A five-vehicle, 64 000-km test with 7.45 litre V-8 engines was conducted to determine if synthetic engine oils provided performance sufficiently superior to that of conventional engine oils to permit longer oil change intervals. The results show better performance in two areas of deposit control; inferior performance with respect to wear protection; and essentially equivalent performance in the areas of fuel and oil economies. Based on these data, it was concluded that synthetic engine oils do not provide the necessary performance required to safely recommend their use for extended oil change intervals. In addition, a cost analysis shows that the use of synthetic engine oils, even at a change interval of 32 000 km, will essentially double the customers' cost compared with conventional engine oils at GM's current 12 000-km change interval.
Technical Paper

Vehicle Crush and Occupant Behavior

1967-02-01
670034
An analytical study of right angle barrier crashes has been conducted to evaluate the influence of vehicle crush distance, occupant spacing, and interior crush stiffness on the severity of occupant-interior impact. Particular attention was directed to the influence of the vehicle deceleration-time history wave shape. The study includes an analysis of a simple-point occupant and a more complicated articulated dummy. The results of these analyses are in substantial agreement and indicate that the most important factors in reducing unrestrained occupant impact severity in conventional vehicles are occupant spacing, vehicle crush distance, and interior crush stiffness. Because of practical considerations and the multiplicity of crash conditions, it is concluded that the most direct way to reduce injury and death is through improved vehicle interior crush behavior.
Technical Paper

V. I. Improvers and Engine Performance

1968-02-01
680071
The use of multigrade (V.I. improved) oils in automotive engines has increased significantly in recent years. However, the performance of these oils in terms of factors such as oil economy, wear, and noise, is not always equal to that of single grade oils. Although the initial viscosity of multigrade oils is related to both the base oil and the V.I. improver, the viscosity decreases with use, with the primary factors determining the magnitude of the change being the degree of shear and the characteristics and concentration of the V.I. improver used. This decrease in viscosity has been assumed to be the cause of the decreases in oil economy that may occur with oil use. However, viscosity changes are not believed to be the primary factor responsible since similar oil economy changes have also been observed for single grade oils. Nevertheless, the characteristics and concentration of the V.I. improver used can be a significant factor influencing oil economy.
Technical Paper

Using Interactive Graphics for the Preparation and Management of Finite Element Data

1974-02-01
740344
Interactive graphics is an aid which eliminates the data management problems that arise when manually preparing finite element models. Line and surface data representations of sheet metal automotive stampings are displayed on a cathode ray tube (CRT), and these data are then used for building finite element models. Elements are built by creating node points with the light pen or by using automatic mesh generating techniques. By using the interactive capability, the user immediately sees the results of his modeling decisions and can make changes in his model as a result of viewing his work. The interactive graphics system allows the user to define his elements, load cases, boundary conditions, and freedom sets without worrying about the grid point or element numbers. All information is communicated through the use of either the light pen or the keyboard. As information is supplied about the model, it is stored in a data base for review and possible change.
Technical Paper

Use of a Weighted-Impulse Criterion for Estimating Injury Hazard

1966-02-01
660793
This paper describes the usage of an exponential weighting factor for appraising deceleration or force impulses registered on dummies or impacting hammers in safety testing. The proposed impulse-integration procedure, it is shown, takes into account in a more rational way, and in better conformity with published injury tolerance data, the relative importance of time and intensity of the pulse than do the “peak g” or impulse-area criteria. Use of the new Severity Index for assessment of head impact pulses is illustrated. It is shown to be of special value in comparing the relative severity of pulses which differ markedly in shape (because of structural differences in the component being struck) and it is pointed out that without a weighting factor of this nature, laboratory impact tests can yield incorrect ranking of the relative safety merit of alternative designs. Automated methods for quick calculation of the Severity Index are possible.
Technical Paper

Transmission Air Breathing Suppressor (TABS) Valve - A Device for Improving Automatic Transmission Fluid Life

1974-02-01
740055
Automatic transmission fluids can oxidize with use, causing marginal transmission performance and eventual transmission malfunction. Periodic fluid changes are presently recommended to alleviate this problem. Fluid oxidation is promoted in current transmissions because they breathe air freely through a vent tube. To reduce fluid oxidation, and thereby improve fluid and transmission durability, a one-way check valve, called the Transmission Air Breathing Suppressor (TABS), was designed to restrict the intake of air into the transmission and to replace the conventional vent tube. The effectiveness of the TABS valve in reducing fluid oxidation was determined in high temperature transmission cycling tests and in taxicab tests. Fluid oxidation results with the TABS valve-equipped transmissions were compared to those with normally-vented transmissions. By reducing the amount of oxygen in the transmission gas, the TABS valve nearly eliminated fluid oxidation.
Technical Paper

Tolerance and Properties of Superficial Soft Tissues In Situ

1970-02-01
700910
Utilizing unembalmed cadaver test subjects, a series of tests was carried out to characterize quantitatively the resistance of the skin, the soft underlying tissue of the scalp, and certain other typical areas of the body to impact loading. The impacts were delivered by the use of an instrumented free-fall device similar to that previously employed for facial bone fracture experiments. In one group of tests, metal and glass edges were affixed to the impacting device to produce localized trauma under conditions which were standardized with respect to variables affecting the degree of the injury. In the second group of experiments, specimens of skin, together with underlying tissue of uniform thickness, were subjected to compressive impact between the parallel surfaces of the impacting weight and a heavy metal platen. From these latter experiments the force-time histories, coefficient of restitution, and hysteresis loops of load versus deflection were obtained for the specimens.
Technical Paper

Thoracic Tolerance to Whole-Body Deceleration

1971-02-01
710852
A professional high diver, instrumented with accelerometers, performed sixteen dives from heights between 27-57 ft. For each dive, he executed a 3/4 turn and landed supine on a 3-ft deep mattress which consisted of pieces of low-density urethane foam encased in a nylon cover. Using FM telemetry, sagittal plane decelerations were recorded for a point either on the sternum or the forehead. Impact velocities and corresponding stopping distances for the thorax and the head were calculated from high-speed movies of the dives. For a 57-ft dive, the impact velocity of the thorax was 41 mph with a corresponding stopping distance of 34.6 in. The peak resultant deceleration of the thorax was 49.2 g with a pulse duration of 100 ms. The maximum rate of change of the deceleration of the thorax was 5900 g/s. No discomfort was experienced as a result of this impact. The maximum forehead deceleration occurred during a 47.0-ft drop and exceeded 56 g with a Gadd Severity Index greater than 465.
Technical Paper

Thoracic Impact: New Experimental Approaches Leading to Model Synthesis

1973-02-01
730981
The following work was done in support of a continuing program to better characterize the behavior of the human chest during blunt sternal impact. Previous work on this problem has focused on determining the force-time, deflection-time, and force-deflection response of embalmed and fresh cadavers to impact by a 15 cm (6 in) diameter striker of variable mass traveling at velocities of 22.5-51 km/h (14-32 mph) and striking the sternum at the level of the fourth intercostal space. Additional questions persist concerning whether the anterior and posterior regions of the chest behave as highly damped masses or oscillate after impact, the relationship between force delivered to the surface of the body and the acceleration of the underlying regions, and the influence of air compressed in the lung on thoracic mechanics.
Technical Paper

The Use of a Variable-Stability Vehicle in Handling Research

1965-02-01
650659
This paper describes the use of the GMR variable stability passenger car in a brief study of driver performance in a maneuvering task. The study was part of a pilot program for evaluation of test methods and equipment for future and more extensive human factors evaluations. Three distinct types of passenger car directional control characteristics were simulated, and each configuration was driven by each of six different drivers through a complex course. The results of the investigation are presented in terms of the average driver performance with each vehicle configuration.
Technical Paper

The Turbine Interstage Diffuser

1971-02-01
710553
The incentive for use of an interstage diffuser in a free-shaft gas turbine engine is briefly examined and some pertinent published background data reviewed. Tests of two annular diffusers behind an upstream turbine show the deleterious effects of turbine exit flow nonuniformity on diffuser behavior. The flow acceleration provided by the area contraction of a power turbine nozzle located at the diffuser exit substantially improves the nature of the flow previously found to exist at the diffuser exit in the absence of the nozzle.
Technical Paper

The Relationship of Low-Temperature Rheology to Engine Oil Pumpability

1973-02-01
730478
An analysis of oil pumpability reveals that engine oil pumping failures may occur because either the oil cannot flow under its own head to the oil screen inlet, or the oil is too viscous to flow through the screen and inlet tube fast enough to satisfy pump demands. To determine which factor is controlling, the behavior of commercial, multigraded oils was observed visually at temperatures from -40 to 0°F (-40 to - 17.8°C) in a laboratory oil pumpability test apparatus. Test results revealed that pumping failures occur by the first alternative: a hole is formed in the oil, and the surrounding oil is unable to flow into the hole fast enough to satisfy the pump. Of 14 oils tested, 7 failed to be pumped because of air binding or cavitation which developed in this manner. A model, which explains these failures in terms of yield point considerations and the low shear apparent viscosity of the oils, is proposed.
Technical Paper

The Highway Safety Research Institute Dummy Compared with General Motors Biofidelity Recommendations and the Hybrid II Dummy

1974-02-01
740588
Two Highway Safety Research Institute (HSRI) dummies were tested and evaluated. Based on the analysis given, the HSI dummy should not be used for vehicle qualification testing. However, many of its components offer viable alternatives for future dummy development. The dummy was found to have inadequate biomechanical fidelity in the head, neck, and chest, although its characteristics were very promising and, as a whole, biomechanically superior to the Hybrid II. Its repeatability and reproducibility in dynamic component tests were better than the Hybrid II dummy. In particular, the HSRI friction joints were outstanding in repeatability and had a significant advantage in usability in that they do not require resetting between tests. In three-point harness and ACRS systems tests, the values of injury criteria produced by the HSRI dummy were generally lower than those obtained with the Hybrid II, especially the femur loads in the ACRS tests.
Technical Paper

The General Motors Research GT-309 Gas Turbine Engine

1965-02-01
650714
The GT-309 regenerative gas turbine engine is the latest in the series of heavy duty vehicular gas turbine engines developed by the General Motors Research Laboratories. This new engine incorporates a major engineering advance, which not only improves part-load fuel economy to the point that rivals the diesel installed economy, but also provides engine braking equal to the rated output of the engine. These improvements result from a novel system called Power Transfer, which connects the gasifier and power turbine shafts through a controlled torque coupling. This paper describes the system, its several applications, and development and evaluation studies.
Technical Paper

The GMR Sealometer A New Machine for Oil Seal Evaluation

1966-02-01
660381
The Sealometer is used for evaluating the performance of lip type oil seals and provides a dimensionless number derived from measuring the increase in temperature of a test shaft operating in a lip seal for a given time interval. With the Sealometer it is possible to study parameters that affect seal performance. As a quality control instrument, the machine provides accurate data for design. Sealometer evaluation offers a quick method of determining the life expectancy of a particular design for a particular application and eliminates the need for long life test programs.
Technical Paper

The Computation of Tearing Energy of Nicked Rubber Strips in Extension

1974-02-01
740325
To compute the tearing energy of nicked rubber strips in extension, one has to solve first the associated stress-deformation involving finite elasticity. In the past, this was a formidable task so that the tearing energy had been determined solely by experiments and only for a few testpieces. With the aid of the finite element method (FEM), it is shown that this may now be done simply through the use of the Rice's J integral. Tearing energy for two testpieces are computed and results compared with existing experimental data. The agreement is good. Because of FEM's ability to treat general geometric and loading conditions, the use of the J integral in combination with FEM to cmpute the tearing energy now allows a wider application of the tearing energy concept to more complex units than hitherto known.
Technical Paper

Some Factors Affecting Gas Turbine Passenger Car Emissions

1972-02-01
720237
The intent of this paper is to put into proper perspective the relationships among the vehicle, the thermodynamic cycle, and the combustion process as they relate to exhaust emissions from a gas turbine-powered passenger car. The influence of such factors as car size, installed power, regeneration, and other cycle variables on level road load fuel economy, and on the production of oxides of nitrogen and carbon monoxide, are examined. In limited checks against experimental data, the mathematical model of the combustor used in this study has proved to be a reliable indicator of emission trends. The calculated emission levels are not final, however, with deficiencies subject to improvement as new combustor concepts are developed.
Technical Paper

Smog Chemistry Points the Way to Rational Vehicle Emission Control

1965-02-01
650641
The results of studies of atmospheric chemistry of smog formation serve as guidelines for determining a rational basis for control of vehicle emissions. These guidelines indicate the desirability of reactive hydrocarbon reduction and the futility of nitric oxide reduction from vehicles. A system of classifying hydrocarbons as to their reactivity in smog formation is presented. Its application, in combination with, gas chromatographic analyses, to both exhaust hydrocarbon and evaporative hydrocarbon vehicle emissions is illustrated. Utilization of this approach for determining the importance of exhaust versus evaporative hydrocarbon emissions, and for measuring efficacy of control by changes in both vehicles and fuel composition is recommended.
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