Bearing Factor - Contact Stress

This might help...

http://en.wikipedia.org/wiki/Bearing_capacity

You will need to be more specific in your discription of your question. As this could mean the Bearing Capcity of soil loading as well, as another has pointed out. I think your looking to for load capcitiy, but I do not want to put words in your mouth.

Hi,

Yes you are right there sorry for not being clear enough...

i am designing a no-go tool in a cylindrical tube to support other equipment when it lands on the shoulder of the no-go: looks something similar to the sketch below.

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Now from standard calulations to find the max allowabel force that the shoulder can allow befre it starts deforming etc is given by Force = Area x Bearing factor x yield strenght - and this is without any saftey factor...

i still cannot understand the reason behind the Bearing factor for the material because apparently there is a relationship between the material and angle... which is abit confusing!

Appreciate any ideas...

Bearing factor came about as a way to compare the bearing capacity of parts with cylindrical contact compared to the capacity based on purely on contact area. It is dangerous to act like it is a constant, as it is geometry dependent! I have seen it misused like it is a material property.

FEA analysis will confirm that a tapered cylindrical shoulder does indeed have more bearing capacity than a square one, but the stress is NOT the same for every geometry.

The higher capacity comes about because one part is generally compressed in all directions (axially, radially, and tangentially), which lowers the resultant stress, as the principle stresses tend to cancel each other out, i.e. equal principle stresses result in zero resultant stress. Also, the other part, which usually has axial compression, radial compression and tangential tension (trying to expand) has surrounding material that is not subject to the bearing force. This acts as a constraint and lowers the stress.

If a cylinder were pushed into a flat surface, that would be pure bearing, and it will fail at its yield stress. A "bearing factor" does not apply.

The bottom line is you should really confirm with FEA than trust a published Bearing Factor, which is probably based on a specific situation and assumed to be general!

I encountered this and a little investigation found it was based on an experiment done by students in the early 80s for my company. They simply compared the actual yield loads to the calculated area. This was before FEA was generally available.