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shell mesh and bolt connectors revisited

Question asked by Mark Scholten on Jul 15, 2014
Latest reply on Jul 15, 2014 by Jared Conway

Hi everyone,

 

i am setting up a static analysis of a sheetmetal duct, consisting of bolted plates. i am using shell mesh, no penetration contacts and bolt connectors. from a previous very similar project i have learnt that the stresses in bolt connectors are dependent on mesh density, especially when the length of the bolts is less than 5 times the radius. in this case that ratio is a lot smaller than 5 for all of the bolts. KB S-058593 and S-059588 suggest to use solids at least locally, but that is not an option for me, because there are very many components in the assembly. As is, the study does not complete.

 

given that i am refining the mesh around the bolt holes, would it make sense to:

  1. decrease the shank radius so that the bolt length over shank radius ratio is smaller than 5, so that the study is able to complete (the shank cross-sectional area is now way too small, so that reported stresses and strains become way too high)
  2. set the head and nut diameters to the real values to maintain the behaviour of the material around the bolt hole
  3. define a custom bolt material using a value of Enew=((old radius / new radius)^2)*Eold (this should make the strain of the bolt with reduced shank radius equal to the strain of the original bolt
  4. check bolt forces afterwards to make sure none of them break (necessary because the ultimate stress of the bolt material was unchanged).

 

 

 

does this sound reasonable or should i quit tinkering benaeth the hood and go with the work-around i used previously (switching to bonded contacts, extracting interface forces and then calculating bolt forces manually)?

 

thanks for your thoughts,

mark

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