TRANSPORTATION VEHICLES

This project examined the utility of scale model experiments for automobile crashworthiness research. The accuracy of small-scale testing was demonstrated by direct comparison between a scale model experiment and the test of a full-scale automobile in high speed impact. The applicability of modeling to a wide variety of structural elements was also demonstrated by scale-model experiments with five hydraulic and plastic-deformation energy absorbers. We concluded that scale models can replace full-scale experiments with good accuracy for many applications. The cost effectiveness of scale modeling was assessed by comparing the costs of full scale experiments with 1/3- to 1/8-scale experiments that meet the same objectives. These comparisons showed that a scale-model test program can reduce costs by up to a factor of 4 and reduce the time to complete the program by up to a factor of 3.

The interaction of the bumper and energy-absorbing frame of an Experimental Safety Vehicle (ESV) during impact against a rigid pole at 50 mph was investigated with 1/8-scale models of the ESV. The models duplicated the mass and energy-absorbing characteristics of the ESV and the materials and important construction details of full-scale bumpers. Aluminum alloy and high-strength steel bumpers with equivalent full-scale weights from 48-146 lb were tested. The accuracy of the modeling technique was demonstrated by favorable comparison with full-scale experiments conducted by Ford Motor Co. The more extensive tests possible with the scale models showed that successful bumpers could be made of 7075-T6 aluminum and would weigh less than 64 lb in full scale.

Scale model experiments were used extensively in the development of a crashworthy structure for the Minicars Research Safety Vehicle (RSV). For low weight and improved crashworthiness, the RSV structure combined urethane foam with a thin steel shell to replace conventional all-steel construction. One-fifth scale model experiments were used to incorporate this new technology in the design of a vehicle within strict time and cost limits. The particular problems addressed in the experiments included tailoring the force-deflection properties of the front-end structure, identifying weak points in the design by testing complete vehicle structures, and determining the effects of redesigning key structural members. An example of a 90 degree car-to-car impact for scale model RSVs is shown in Movie 1.

One-fifth scale model experiments were performed to investigate the structural characteristics that make large and small vehicles compatible in in-line and asymmetric frontal impacts. Designs for a subcompact and full size car with increased compatibility were developed and tested in scale model experiments. The experiments were interpreted in terms of occupant response with a one-degree-of-freedom analytical model of an occupant and airbag restraint system. We found that subcompact to full-size cars can be made to provide survivable accelerations in both 50-mph barrier impacts and 75-mph frontal car-to-car impacts. However, asymmetry generally decreases performance to such an extent that designs cannot be based on in-line impact performance alone. The utility of scale models in the study of automobile sheet metal response was also investigated. A 1/5-scale model of the front-end sheet metal of a full-size car was built and tested in a barrier impact. Comparison of the scale-model test with a corresponding full-scale test showed that scale modeling is also a useful tool in investigating the crash response of this type of structure.

A 1/5-scale experiment was performed to simulate the impact of a railroad locomotive into an automobile at 50 mph. Comparison with two full-scale experiments was made on the basis of those response features needed to assess occupant safety: vehicle trajectory, deformation, and acceleration. The scale-model experiment reproduced these response features within the repeatability of the two full-scale tests.