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Two widely used computer programs developed for the analysis of vehicle collisions are CRASH and SMAC. This paper reviews stiffness parameters which are used in the application of these programs, and methods to select these parameters. The paper also introduces a rational method to select stiffness parameter KV for the SMAC program. The CRASH program expresses the vehicle force-crush relationship as FC = A + B*CR, where FC is the force per unit width, and CR is the vehicle residual crush. The “stiffness parameters,” A and B, define a linear relation with a zero-crush intercept. For collinear impacts, these parameters are used in determining crush energy, which in turn is used in determining changes in velocities of the impacting vehicles. Over the years, considerable effort has been expended by numerous researchers to determine A and B for a variety of vehicles, and a substantial body of vehicle crash test data has been developed and analyzed to this end.

For automotive crash tests resulting in significant test vehicle yaw rate, direct integration of accelerometer data does not yield the correct velocity or Delta-V components (even for accelerations sensed at the vehicle center-of-gravity). This paper discusses the effects of yaw rate on the integration of accelerometer data and develops a methodology to properly calculate the velocity and Delta-V at any location on the test vehicle. This methodology is applied to crash test data and compared to results observed from high-speed film. A discussion regarding Delta-V in a yawing vehicle, and its significance to occupant kinematics and injury potential, is also presented.

Engineering Dynamics Corporation (EDC) recently updated the Human, Vehicle, Environment (HVE) software program to enable modeling of passenger cars and light trucks towing trailers. This paper reports on a comparison between the HVE EDSMAC4 collision module of the 3-dimensional computer simulation program and instrumented crash tests, in which one vehicle in each test was a pickup truck pulling a trailer. Use of the EDSMAC4 trailer model was found to provide better correlation between the simulation and test damage profiles, rest positions, vehicle trajectories, velocities, and Delta-V. It was also determined that the NHTSA-derived stiffness coefficients are sensitive to the impact configuration and depending on the impact configuration, it may be necessary to refine the coefficients according to the configuration.

This report presents two test methods and results of a study involving unrestrained dummies in dynamic rollover tests. Data are presented showing dummy head kinematics in relation to the interior of the vehicle as the vehicle experiences deceleration prior to the trip.

Considerable research has been dedicated to establishing the amount of energy absorbed during different types of collisions. In the early 1960’s, motor vehicle manufacturers began conducting barrier crash tests consistent with SAE suggested procedures. This allowed investigators to establish the amount of energy that went into metal deformation in the tested vehicle. Over the years, there have been many advances in establishing the amount of crush energy in a particular accident, including the development of several computer programs. Four two-vehicle, single-moving rear-impact crash tests were conducted to compare the effect of override and offset. Override comparisons were made using a moving, rigid barrier or a heavy truck as the impactor, and each pair of tests having either offset or full rear engagement. All four tests were conducted using a like make and model four-door sedan as the target vehicle. Each test had the same available crush energy for the car.

Pitch-over events are common in motorcycle accidents, and can be caused by impact to the front wheel and occasionally by hard brake application. In either case, the rider of the motorcycle can be propelled over the handlebars as the motorcycle pitches rear-end up. In accidents caused by pitch-over braking, the accident investigator may be faced with limited evidence and then must rely on analyzing the throw distance of the rider in attempting to reconstruct the pre-accident speed of the motorcycle. This analysis can be complicated by the presence of a second rider (the passenger) on the motorcycle. Pitch over caused by front wheel impact can be similarly complex. Although motorcycle deformation as a result of front wheel impact has been studied [1], circumstances surrounding the nature of the deformation, or the impact itself, may require that the trajectory of the rider be analyzed in order to determine the pre-impact motorcycle speed.