Originally Posted by
Sean Gordon
One big rule of engineering, though, is to never point load a dome or tube. Its the reason the clamp of a bike stand uses curved jaws or v-blocks. This distributes the compressive force over a larger surface area. Because your head is round, it is almost guaranteed that it will contact other bodies at exactly one point on its surface. This is stress concentration. Think of it as a tire contact patch. Your skull is much less likely to be damaged when the load is distributed over a larger area. This is what a bicycle helmet does.
I forgot to mention before, but you should tell any bearing engineer about your "one big rule of engineering." Seems like they either forgot and got lucky, or realized that when something is designed properly, point loading isn't a problem. On a microscopic level, it isn't point loading though, just like when your head hits a flat surface it isn't point loading.
You are also mis-using the term "stress concentration" which is an entirely different concept than point loading. Read up:
http://www.efunda.com/formulae/solid...scon_intro.cfm