McHenry Forum - Crash Reconstruction & Simulation

Q: What range of values should be used in SMAC for inter-vehicle friction? A: From our SAE paper 970947 SMAC-97 : "The Inter-vehicle friction coefficient of the SMAC collision model ( AMU, SMAC input card 13, field 7 ) is based on coulomb friction. Coulomb friction is independent of the sliding...

Q: According to Gillespie, the center of the turn must lie on a projection of the rear axle, with the radius of the curve through the center of gravity of the vehicle. The perpendicular of both front wheels also must also pass through the center of the turn. A: In real cars, at low speed the rear wh...

The INCR referred to in the link is the International Network of Collision Reconstructionists. I am a member and contributor to INCR. INCR is a newsgroup Dec 2019: NOW ON Groups.IO https://groups.io/g/INCR (Was on Yahoo. Yahoo dumped groups! #NOT groups.yahoo.com/neo/groups/INCR/info) From the site:...

I have posted pages from CRASH3 manual for those interested in what is the 'effective mass'. Please see EFFECTIVE MASS in Momentum Also see pg 54-57 of 1976 report User's Manual for the CRASH program Here are the pages of interest: Effective Mass Concept Related page from 1976 Crash Manual May 2024:...

The friction decrement with speed is normally associated with wet pavement. From a discussion from our m-smac user's manual on friction loss with speed: In general, on wet surfaces, the effective tire-surface friction coefficient decreases with speed and c (card 12:field 7) can be used to simulate t...

2 words of wisdom on CRASH type damage analysis (whatever flavor: EDCRASH, WinCRASH, etc): Be Careful! In 1988, Tumbus and Smith wrote SAE paper 880072: Measurement protocol for quantifying vehicle damage from an energy basis point of view ]. In the paper they presented some ideas for a standardized...

New: Use this link to go to the latest post on this thread Some Simplified Momentum Misconceptions: And please note this is not to dismiss simplified momentum analysis, it is to help all who use it to understand the assumptions, to encourage that they test a range of assumed input numbers to reveal...

Some comments on Momentum analysis: (1) The collision between two vehicles is not the same as a collision between two pool balls. More like two crushable rectangular boxes on wheels. And vehicles are not 'balls' or 'points', they are finite dimensioned crushable objects which may behave quite differ...

CASR Speed Study In 1994 & 1998 McHenry Software participated in a study of crashes with the Road Accident Research Unit (RARU) of the University of Adelaide, Australia. They now go by the name Centre for Automotive Safety research (CASR) Summary The Road Accident Research Unit at Adelaide Univ...

For historical information, check out " Roadside Design for Safety " by Stonex (1960). It may be in other Stonex papers (some published through SAE since they include a lot of history on crash safety research). In the 1960 paper he towed vehicles sideways through wet and dry sod. In the St...