Q: I want to ask you a question about CRASH3 algorithm. There is a correction factor in CRASH3 ( 1+ tan^2. alpha). Is the alpha angle PDOF angle here? It is limited to 45 degrees to make the factor maximum 2. If it is PDOF angle, can we say that PDOF angle is limited to 45 degrees? Because i saw it can take higher values in planar impact mechanics applications of Brach.

A: Alpha is "the angle of crushing relative to a perpendicular to the involved end or side of the vehicle". It may be the same as PDOF, but for example, in side impacts Alpha is adjusted by 90 degrees. The limitations of 2 is for the correction factor based on Alpha and not on the angle Alpha.

From one of our recent publications on

ECF
- "On the basis of a recognition of the limitations on energy absorption that are imposed by realistic levels of tangential friction, a revised form of the ECF was proposed in 1986. Applications of the ECF since that time have generally been restricted to the angular range of ± 45 degrees so that only a limited evaluation of the effects of the revised ECF was possible"

Also see our related discussions on

With respect to

Brach do you mean Brach values for PDOF? Or some suggestion for correction factor that Brach suggests? And could you please provide an example as in what reference and on what page?

Please also see

Some Momentum Misconceptions for limitation of momentum and planar impact mechanics which include simplifying assumptions such as instantaneous exchange of momentum, etc.