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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.

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.

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.

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.

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.

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.

Various proposals for emissions cleanup systems have shown the desirability of regulating engine air-fuel ratio within precise limits. For this purpose a prototype exhaust sensor has been investigated. The sensor is a ceramic device, made of stabilized zirconia, which operates via electrochemical principles. It is placed directly in the exhaust stream and generates a voltage signal which is an approximate indication of engine air-fuel ratio. Several sensors have been installed in situ on engines operated under controlled dynamometer conditions. Fundamental response characteristics of the sensors have been determined. The results of this investigation, together with descriptions of the construction and installation configuration of the prototype sensor, are discussed.

A radiometric method has been developed for the determination of camshaft wear during engine operation. After a radioactive tracer is induced at the tips of one or more cam lobes by the technique of surface layer activation, calibration procedure are performed to determine the amount of radioactive material remaining versus the depth worn. The decrease in γ-ray intensity measured external to the engine is then directly related to cam lobe wear. By incorporating a high-resolution detector and an internal radioactive standard,measurement accuracy better than ±0.2 μm at 95% confidence has been achieved. Without the requirement of engine disassembly, this method has provided unique measurements of break-in wear and wear as a function of operating conditions. Because this approach requires only low levels of radiation, it has significant potential applications in wear control.

Future low emissions engines will burn unleaded gasoline. Compared with engines of 1970, future engines will have lower concentrations of NOx in the blowby gases, and lower blowby flow-rates; however, oil temperatures will probably be unchanged. The consequences of these conditions for engines using high quality (SE) oils at current drain intervals are: virtual elimination of rust, reduction of sludge, no effect on wear and oil thickening, and possible worsening of varnish. Therefore, extension of the drain interval with SE engine oils in the future may be possible, but final decisions will depend on the findings of research in the areas of engine wear and varnish, and oil thickening.

Utilization of numerically controlled milling has been found particularly attractive in producing, in limited quantities, the three-dimensional curved surfaces characteristic of turbomachinery. In experimental and developmental programs its use can result in decreased fabrication cost, reduced lead time, and improved dimensional accuracy. Following a review of the general classifications of numerically controlled milling machines available for manufacture of such parts, illustrations are given of some of the procedures and techniques employed in their use. A variety of parts made using numerical control serve as examples.

This study explores the application of viscoelastic modeling for characterization of the response of the brain to impulsive loading with the objective of learning whether such models could exhibit the same time dependency of strain or likelihood of injury, as exhibited by the Severity Index, HIC Index, Wayne Tolerance Curve, and other similar representations of tolerance. The mathematical relationships between viscoelastic properties and the corresponding time dependency of tolerance are shown for Newtonian, Bingham plastic, and Pseudo-Bingham, as well as more general behavior. Preliminary static and dynamic tests upon small mammalian material are described with particular attention given to strain in the vicinity of the brainstem as a function of loading profile. Both the theoretical and experimental results show that the falling time dependency of the above indexes can be interpreted in terms of nonlinear viscoelastic response.

To lower emissions from a multicylinder engine, the air-fuel ratio must be optimized in all cylinders. If uniform fuel distribution is achieved, then the cylinder-to-cylinder air distribution is of particular interest. A probe system has been developed to measure mass flow rates to individual cylinders during operation of a complete engine. Fast response measurements of pressure, temperature, and flow velocity are made in the intake port near the valve during the intake portion of the cycle. High-speed collection of the large volume of data was accomplished through on-line use of an IBM 1800 computer. A V8 455 CID (7457 cm3) engine with stock intake and single exhaust system was used in the initial application of the mass flow probe. Measurements of 30-40 individual cycles were combined to calculate the mean volumetric efficiency for each cylinder.

Noise produced by automotive ignition systems can deteriorate the performance of nearby communication systems. An important step toward alleviating this difficulty is to characterize the ignition noise. Measurements have been made of the noise peak amplitude distribution of a number of identically equipped vehicles over a fixed period of time. Both vertical and horizontal polarizations were used, and measurements were made at two frequencies, 145 and 230 MHz. These statistics were then compared to various probability distributions to attempt to characterize the amplitude distribution of the noise. The distributions studied were: the log-normal, the exponential, the Rayleigh, and the Weibull distributions. It was concluded that the best fit was provided by the Weibull distribution. The parameters of the best fitting distribution are primarily a function of the antenna's polarization, with frequency having only a minor effect.

Forces necessary for fracture under localized loading have been obtained experimentally for a number of regions of the head. Three of these, the frontal, temporoparietal, and zygomatic, have been studied in sufficient detail to establish that the tolerances are relatively independent of impulse duration, in contrast with the tolerance of the brain to closed-skull injury. Significantly lower average strength has been found for the female bone structure. Other regions reported upon more briefly are mandible, maxilla, and the laryngotracheal cartilages of the neck. Pressure distribution has been measured over the impact area, which has been 1 sq in. in these tests, and the relationship between applied force as measured and as predicted from a head accelerometer is examined.

At the 1970 SAE International Automobile Safety Conference, the first experimental chest impact results from a new, continuing biomechanics research program were presented and compared with earlier studies performed elsewhere by one of the authors using a different technique. In this paper, additional work from the current program is documented. The general objective remains unchanged: To provide improved quantification of injury tolerance and thoracic mechanical response (force-time, deflection-time, and force-deflection relationships) for blunt sternal impact to the human cadaver. Fourteen additional unembalmed specimens of both sexes (ranging in age from 19-81 years, in weight from 117-180 lb, and in stature from 5 ft 1-1/2 in to 6 ft) have been exposed to midsternal, blunt impacts using a horizontal, elastic-cord propelled striker mass. Impact velocities were higher than those of the previous work, ranging from 14-32 mph.

Conventional radial lip oil seals can be made more effective by utilizing helical grooving beneath the contact lip surface. Miniature hydrodynamic pumps so formed aid the radial lip seal in containing the oil by generating fluid forces opposite in direction to the leakage flow forces. This seal-shaft combination has been termed the Hydroseal. Four factorial experiments were conducted to evaluate the effect of helix angle, groove depth, groove width, and number of grooves on sealing performance. The criterion used as a basis for selecting the optimum design were leakage, wear, hardening of the sealing surface, and pumping capacity. These data indicated that the best hydroseal design was one with three grooves, 0.0003 in. deep, 0.014 in. wide, having a helix angle of 45 deg.

To promote improved automotive safety, present Federal specifications require the reduction of glare by sunlight reflection from a trim surface by restricting its intensity. The specifications imply that matte surfaces must be used. The alternative described herein reduces glare of reflected sunlight from reflective surfaces by decreasing the apparent size of the image. The necessary demagnification is obtained by utilization of surface curvature. The maximum radius of curvature is calculated by geometric optics.

THIS PAPER discusses the Stirling thermal enging from four points of view: 1. The ideal, thermodynamic point of view, showing the inherent potentialities of the ideal Stirling cycle in comparison to the basic cycles of other engines. 2. The physical engine and its method of operation with respect to the ideal cycle and the limitations of practical mechanics. 3. Performance data from the first modern Stirling engines ever operated in the United States, evaluating the relationship between the new engine and other more familiar engines of similar sizes. This comparative discussion serves to demonstrate the advantages and disadvantages of the Stirling engine and to indicate its proper place in the 1960 family of prime movers. 4. A look backward into the century of history behind the modern engine pointing out significant milestones in the engine's development.

Engine oil test Sequences IIA and IIIA have been developed to replace Sequences I, II, and III. These new sequences are designed to evaluate lubricants for use in current passenger car engines under severe (MS) service conditions. Lubricant performance is evaluated with respect to scuffing wear, rust, corrosion, deposits, and rumble. The Sequence IIA and IIIA test procedure involves major changes which affect the evaluation of engine rusting and provides improved correlation between test results and short-trip service. Average engine rust ratings correlate with service data within ±0.5 numbers. The new test also provides better repeatability and reproducibility in a significantly shorter schedule. The rust repeatability and reproducibility is less than ±0.2 and ±0.6 numbers, respectively. Test time has been reduced 52%.

This paper describes a computer study made by the General Motors Corp. Research Laboratories to determine what percentage of the energy supplied to the axle of a passenger car is available for recovery through regeneration. Several weight classes of passenger cars were studied using three driving schedules-city, suburban, and highway. For each vehicle run in accordance with the prescribed driving schedules, two ratio percentages were obtained: (1) the ratio of energy available for recovery to the total energy supplied to the axle, and (2) the above ratio modified by assumed efficiencies in the propulsion and regeneration systems.