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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

A novel method for the intermittent supercharging of an internal combustion engine in a vehicle is described. During full throttle operation, high pressure motivating air entrains ambient air and compresses it to an intermediate pressure in the diffuser of an air ejector. Flowing through the carburetor and into the engine, the supplemental air augments engine power, reducing vehicle acceleration time by as much as one-third. By allowing engine size to be reduced, better economy without loss of performance is possible. Typical vehicle installations are described and problem areas discussed.

This paper summarizes an analysis, design, and test project in which a dummy chest structure was developed. The chest consisted of mechanical elements that had been characterized by computer simulations as giving responses to blunt frontal impacts necessary for biofidelity. An analysis of mechanical rib structures indicated that materials having a high ratio of yield stress to modulus of elasticity were required. Only metals having unusually high yield strengths, such as spring steels, qualified. A mechanical system was developed with steel ribs pivoted at each end as a primary spring. A secondary spring was a pair of commercially available die springs acting in parallel with the ribs after 25.4 mm (1.00 in) deflection. A fluid damper was developed to provide the damping. The chest structure was tested under conditions modified from those used by Kroell. The modifications were holding the spine rigidly and reducing the impact masses.

A viscoelastic neck structure that responds to impact environments in a manner similar to the human neck is described. The neck structure consists of four ball-jointed segments and one pin-connected “nodding” segment with viscoelastic resistive elements inserted between segments that provide bending resistance as well as the required energy dissipation. Primary emphasis was placed on developing appropriate flexion and extension responses with secondary emphasis placed on axial, lateral, and rotational characteristics. The methods used to design the resistance elements for the neck structure are discussed. Three variations of the resistive elements have been developed that meet the response characteristics based on the data of Mertz and Patrick. However, no single resistive element has satisfied the flexion and extension characteristics simultaneously, but such an element appears to be feasible.

Various laboratory methods for measuring chip resistance were compared and found to rate different finishes in different orders. A field survey showed that a gravelometer using gravel rather than other media correlated well with actual service results. The necessity of preparing chip resistance test panels which very closely duplicate the actual finish obtained on cars was shown. The nature of chipping has been studied and improved rating systems developed. Detailed drawings, test procedures, and rating systems for the SAE gravelometer have been proposed for publication.

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.