What technique should be used to reconstruct low speed collisions?

Topics related to collision & Trajectory analysis formerly on our 'Registrants only' area however which we get asked about frequently so believe shoud be in the open forum too
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MSI
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What technique should be used to reconstruct low speed collisions?

Post by MSI » Fri Aug 23, 2019 9:53 am

Q: This question emerged from an email question about CRASH and need for a low speed collision reconstruction technique. What technique should be used to reconstruct low speed collisions?

A: First point which we’ve always made is that CRASH should be only used as a first pass reconstructions and it is particularly not good for low speed collisions.
Why?
CRASH does not include consideration for restitution in low speed collisions. And restitution acts to reduce the amount of residual deformation, for a given maximum dynamic crush, while also acting to increase the total impact speed change.
These topics go into more depth: So question obviously is what technique should one use in low speed collisions?

There have been papers on examination techniques for low speed collisions (looking at the bumper components to determine the stroke (depending on bumper type) or under the bumper cover damage. There have been many tests on many different bumpers for low speed collisions which can be obtained (not sure price, etc.)
I will look these papers up and post links to them as a response to this topic in the next week.

A problem with damage analysis is in low speed collisions is that the restitution is the highest and an assumption of folks selling crush coefficients for use with damage analysis techniques is an assumption of a ‘no damage’ intercept of around 4 mph.
That means every car in the new car lot has ~4 mph impact damage!
See the problem?

Obviously if you have tire marks, trajectory information(rest positions, etc.), that can help since there are many techniques that use both trajectory and damage for low speed collisions analysis (for example msmac3D).
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