What technique should be used to reconstruct low speed collisions?

General Questions related to the CRASH Program and clones
Damage Analysis & Momentum Based Analysis programs
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MSI
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What technique should be used to reconstruct low speed collisions?

Post by MSI »

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 ALL new car lots have ~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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MSI
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Posts: 1522
Joined: Thu Jun 18, 2009 12:37 pm

Re: What technique should be used to reconstruct low speed collisions?

Post by MSI »

I realized i hadn't posted up links to papers...
they are already posted to The MacInnis paper is:
  • Data and Methods for Estimating the Severity of Minor Impacts SAE paper 95-0352
    • Abstract
      Front, rear, lateral and side-swipe collisions were staged to correlate passenger vehicle damage to motion. Data from the staged collisions are used to develop severity-prediction methods for the four collision types. Human volunteers were present in many of the vehicles tested. Their responses, and the responses of human volunteers to staged impacts in other studies, are discussed in terms of impact severity.
      For front and rear impacts, data are presented that correlate the post-impact condition of bumper systems to impact severity. These data build on data previously presented. A method for computing velocity change (DeltaV) for vehicle to vehicle collisions from vehicle to barrier data is presented.
      Data from staged low-speed lateral collisions correlate target and bullet vehicle damage to linear and angular velocity change (DeltaV and DeltaW), impact location, pavement friction and collision force. It is shown how momentum, energy and restitution principles can be used to predict DeltaV and DeltaW from damage.
      For staged side-swipe collisions, damage details are correlated to the target vehicle acceleration-time history. The vehicle motion is characterized as a vibration dose.
Also found another collection of low speed bumper tests by MacInnis In addition here's the list from the other thread of papers on low speed impacts, restitution, damage analysis:
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