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Re: pin shear stress
Anthony Botting Aug 12, 2011 10:17 AM (in response to Adam Fain)Hi Adam:
The hand calculation looks correct but I recall that it represents the average shear stress over the entire pin cross section. You might try plotting the TXY or TXZ (or whichever shear component is appropriate). Nevertheless the stress exactly at the boundary between the fixture and the load would be very high because of the singularity (the super-rigidity of the fixture right at the boundary). You might try a contact analysis with a bearing holding the pin (as opposed to fixing the pin ends), which would help mitigate the stresses due to the elasticity of the bearing. Still, I believe the stress at the contact junction would be very high, but perhaps not that high. Hope this helps a little. -Tony -
Re: pin shear stress
Loren Sackett Aug 12, 2011 12:35 PM (in response to Adam Fain)In pin.jpg, you applied the load on the portion of the pin that would be in contact with the jaw, but the restraints on the pin go all the they around the pin. You will get better results if you only apply the restraints on the portions of the pin that will be in contact (in other words the restraints should be only on the side of the pin opposite to the applied force).
Doing an FEA with contact elements (as Anthody suggested) will give even better results.
On another note, FEA results are usually not very accurate in the immediate vicinity of boundary conditions (especially fixed restraints). I usually validate pins using hand calculations only in order to avoid the problems you are seeing.
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Re: pin shear stress
Adam Fain Aug 12, 2011 5:14 PM (in response to Adam Fain)Thank you both for the responses. I plotted the stress as TXY and it gave me very close results to what I had calculated, which makes sense. I ended up modeling the Jawhead and inserting the pin into that then running the simulation.
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Jawhead.jpg 119.4 KB
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