Bolt preload
Bolt preload
(OP)
I thought by preloading a bolt then loading the joint with a smaller load, the bolt should not see any increase in stress.
When checking the bolt loads in Cosmos it always seems to adds a bit. I've tried all sorts of setups and even very low direct pull loads to try & eliminate any bending etc. but it always adds this little bit to the preload.
Why?
Thanks
When checking the bolt loads in Cosmos it always seems to adds a bit. I've tried all sorts of setups and even very low direct pull loads to try & eliminate any bending etc. but it always adds this little bit to the preload.
Why?
Thanks






RE: Bolt preload
For most applications (say bolting 2 metal plates together) the joint stiffness is much higher than the bolt stiffness, so the bolt only sees a very small additional load amount. Here is a link that I've found helpful:
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RE: Bolt preload
The bolt preload is only a means to preset a compressive load on the bolted parts (at the expense, of course, of a strong traction stress in the bolt). Due to the different compliances of bolt, on one side, and flanged parts, on the other side, the effect of a high-prestress joint is that the working load is "split" on a part which acts to make the traction load on the bolt HIGHER, and a much bigger part which acts to "decompress" the flanged parts. BUT IN NO CASE THE PRELOAD CAN CANCEL OUT THE EXTERNAL WORKING LOAD !!!!! This is not physical !!!
See UNI-10011 or, better, VDI-2230.
Regards