Browse Publications Technical Papers 2001-01-0501
2001-03-05

Determination of b1 Coefficients From Lower and Higher Speed Impacts Using Peak Force 2001-01-0501

There is considerable published vehicular crash data, with much of the testing being associated with higher impact severities. Crash coefficients derived from these impact tests have been utilized by accident reconstructionists to simulate the behavior of vehicles in other situations. However, the suitability of these coefficients for the analysis of lower severity collisions has not been determined. The use of rigid, massive barrier impact testing can provide a measure of the b1 coefficient and stiffness for that particular vehicle. In addition, if the effective b1 coefficient for a vehicle is known, the effective b1 coefficient of a second vehicle can be determined from vehicle to vehicle impact testing.
Measurement of peak force at a given closing velocity during a collision yields the system natural frequency. If the vehicle is impacted into a rigid, massive barrier, the measured peak force will directly yield the natural frequency and the effective b1 coefficient for that particular vehicle.
Crash test data, extracted from the published technical literature as well as the National Highway Traffic Safety Administration (NHTSA) database, is examined for a limited set of vehicles in both the lower and higher severity impact regimes. Comparisons between the b1 coefficients derived in the lower and higher severity impact regimes are made for a given vehicle. A striking phenomenon is noted from this limited set of vehicles. Namely, the effective b1 coefficient determined from peak force measurements at lower impact severities is very similar in magnitude to the b1 coefficients derived from higher speed impact severity testing using both a Campbell model approximation and peak forces, for a given vehicle. The use of b1 coefficients derived from higher severity impacts could be instrumental in the determination of collision forces and changes in vehicle speed in lower and moderate severity impacts, where minimal, if any, permanent crush is developed.

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