I have a fairly involved assembly that is set up as a "simple shaft" per
the PTC suggested technique. The shaft is made of two components that
are pinned together with two shoulder bolts as shown below with fits all
line-to-line (they will be a light press in the actual parts...):
Initially, I let everything be default "bonded" and it solved in about
an hour with pretty good correlation to a more elaborate model that was
run in Abaqus. (I develop concept models, run component or subassembly
Mecahnica simulations to get some level of confidence on the design,
then we pass this on to our "FEA Group" who run full assembly models
with all the bells and whistles. Then I take those results, identify
the issues, and design "fixes" to resolve the issues, verifying the
"fixes" with "A" to "B" comparisons using Mechanica... ).
NOW we have issues that require work on this joint, so I need to set up
the analysis to capture more of the true behavior. The loading is
causing the mating surface to be pulled apart which results in to much
shaft distortion at the supports. Basically, I need to revise this
joint to be stiffer. You can see that running it all bonded won't give
me any clue to whether the redesign is helping.
I set up contacts at the mating face of the two components, and at the
shoulder bolt "pin diameter" to the mating diameter in the component the
bolt passes thru (purple). I let the threads and the section of the
shoulder on the bolt be default "bonded" into the component they thread
into (deep blue) and also the head of the shoulder bolt to the face of
the component it mates to (purple). This seemed like a reasonable
compromise to keep the solution short but meaningful. Trouble is it
wouldn't solve after almost 6 hours, and was pretty much "stuck",
stationary for the last 4.
Any suggestions on a way to simplify this joint, specifically how to set
up the shoulder bolts? Would be great to get the pretension load in
there, but I'm afraid that would make the solution even more
problematic. (The full Abacus model showed reaction loads within the
capability of the thread specification of the bolt, so I'm not worried
about that.)
thanks in advance....
Paul Korenkiewicz
FEV , Inc.
4554 Glenmeade
Auburn Hills, MI, 48326-1766
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