1993-03-01

Post-Impact Spin, 1968-1993 930653

In the reconstruction of initial speeds from the evidence available in the aftermath of an impact, if there was appreciable post-impact spin, the effect of that spin on the deceleration of the vehicle should be taken into account. This task was first studied in Germany in 1968, when Marquard published values of two useful correction factors from forward calculations of 3 spins to rest.
This landmark German study was extended in the United States in 1975, when McHenry fitted polynomials to the values of five correction factors computed for 18 spins simulated with the just-completed SMAC program. These polynomials were used within the computerized reconstruction program CRASH. However, the individual data points were never published; and since 1975, no further quantitative treatment of post-spin reconstruction has been published.
Further studies now have been performed using a verified proprietary version of SMAC, for the same family of 18 spins. The interim results suggest corrections which may be made in the polynomials of CRASH-based programs, or, if that is not possible, correction by means of the value of the tire-road friction coefficient.

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