The Traffic Accident Reconstruction Origin -ARnews-

Re: Occupant G Forces

Ed Phillips (edphill@aol.com)
Sun, 15 Dec 1996 00:29:52 -0500 (EST)

Joe - The first question is HOW are you going to measure the forces? Accelerometers? If so at what Hz? Or are you going to do it empiracally, or from film analysis? I should think a more responsive analysis would be F = m dv/dt, where (ideally) you would know the mass of the occupant, and from accelerometers or film, the change in speeds over tiny increments of time. If the occupant is modeled as a point-mass you could consider the head and chest as one - but they are really separate as the angular acceleration experienced by the head is a function of height, belt location, head mass, etc. And injuries may be caused inertially or from direct force application. The unrestrained occupant and restrained occupant both have the same initial velocity as the vehicle - but their change of velocity over time relates to how they are restrained and what they impact (belt vs. dash vs. windshield vs. steering wheel - etc). Good luck on your research, let me know if I can help in any way.
Ed Phillips
edphill@aol.com

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