The Traffic Accident Reconstruction Origin -ARnews-

Crush Reliability

Ed Phillips (edphill@aol.com)
Sat, 19 Apr 1997 19:57:25 -0400 (EDT)

Tim,

I tried to send you a message but the e-m address was not recognized. As to your question: the resulting damage to a vehicle from
collision forces has been shown to have a very good correlation to impact
speed. In other words, how much energy the structure absorbs, under certain
conditions, can reasonably be used to determine the necessary speed required
to do that damage. The equations are in the calculus, but have been
"simplified" into an algebraic form.

How accurate is it? Well, originally it was thought to be a +/- 10% value.
More recent studies have indicated that the accuracy is a function of
residual damage, and as has been known all along the equation are more
accurate with more damage (primarily because that's where all the data lies).
There is now said to be a 95% confidence limit. Assuming it is used properly and all data is aquired and enetered as
it should be it works well.

The more crush, the more accurate. At 30 inches or so it tends to
underestimate at about 10% of the speed change, at 10 inches of post-impact
crush it does a poorer job, underestimating the actual speed change by about
25%. Again, smaller data base. Excellent discussions are found at
www.mchenrysoftware.com on the internet and in NUTI TAR book. There section
on speed from damage is extremely well written.

As far as your subject crash. If there is no excesive under/over ride, the
truck absorbs little energy (essentially acting like a moving barrier) and we
are using the data to predict the speed loss for the CAR, then it is
reasonable. It tells us next to nothing about the truck, however.

Write if I can be of more assistance.

Ed
Ed Phillips
edphill@aol.com

NOTE: You are reading in an archived session of ARnews. It is possible that this topic is still being discussed. To see if this topic is still active, or of there were any more recent posts on this topic, check later archives of ARnews.

If there is no current post, and you would like to add to this topic, link to the Current ARnews Discussion and begin a new thread. Be sure that if you are starting a new post that the thread title does not contain the abbreviation RE: Placing RE: at the beginning of a new post will confuse Hypermail and prevent others from answering your post in the future.

For example, to continue this discussion look for a thread titled

Crush Reliability

If this thread does not exist in the current archive, you can begin another one by using that title.