So, the pliable covering would ostensibly be in quasi-static contact with the ground, and the covering would then have it's low-friction surface with the helmet shell. It doesn't say how it's constructed, but imagine Kevlar fabric on a shell with perhaps a dry lubricant between. If the covering were torn away, then subsequent friction probably wouldn't be any worse than from a conventional helmet. Besides, if the helmet lining did "snag" - on a railroad spike, or whatever - then the danger to the downed rider is probably much greater from the snagging object itself.Now the graphic he has shows some sort of covering ripping off...it could be with this helmet that there is a large spike in the torsional force at
a) the moment the covering starts to rip off,
b) when the covering has mostly been peeled off and its getting pulled of the helmet entirely when it snags on something on the pavement
c) after the covering is gone and I have the not as smooth underlying part of the helmet that was glued on to the covering which is now rubbing along the asphalt.
The chart is from a real mechanical test - of something, a helmet, I guess, from an independent lab. The spikes in tangential load do seem to be dulled with the new helmet. I'm not a bioengineer, so I don't know if it's the total impulse or the peak forces that are important. I too, have the feeling (doctorate Mat Sci, spec in mechanical behavior) that FEM can be worse than useless for systems this complex, even when performed absolutely properly. I imagine Philips might feel the same way too, but FEM "validation" is something that managers/funders seem to like, for reasons that I don't understand.As far as the fancy graphic is concerned if you read the script above it is says:
"The next stage was finite element analysis, utilising a model produced by Strasbourg University. The concepts tested showed that with zero friction and ideal materials there were theoretical improvements of up to 85% in protection against rotation and up to 40% against linear forces"
Translation: "This data is from a computer model not from an actual test with an actual helmet with actual moving asphalt
I actually did some finite element analysis in college...there are all sorts of ways to get it wrong, or to leave out of the modeling important nonlinear effects that invalidates your results.
Yep. In fact, it says "Projecting this improvement [60% reduction in torsional force] on to the current motorcycle injuries, if all riders were to wear a Phillips Helmet the potential savings could be..." A completely made-up estimate, but he's gotta have some estimate.the 6,900 lives part is amost certainly a bogus number using all sorts of assumptions.