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Non-linear static studies with bolted connectors and their reaction forces

Question asked by Mark Wylie on Mar 24, 2014
Latest reply on Mar 31, 2014 by Mark Wylie

Hi guys,


I am working on quasi-static loading for a bolted electronics chassis. There are mounting bolts (QTY 6) and there are the bolts which hold the chassis together.


I am performing force balance checks under 1 G but not getting the reaction forces I would expect and wondering if anyone has had similiar issues. I am using the iterative solver with 1 time step for 1 second. Mesh is very fine. I then apply gravity. My process/results are as follows:


Model 1: Reaction forces on 6 mounting bolts only

Chassis is globally bonded. 6 bolts are modelled uing the bolted connectors. Non-Penetration contact set up on bolted joint surfaces. 1 G applied in Z.

Result: Reaction forces are correct on 6 bolts. Forces  = Mass x gravity.


Model 2: Reaction forces on 6 mounting bolts. Bolts holding chassis together (QTY 60) now included.

Chassis still gloablly bonded but all joint surfaces where bolts are present have non penetration contact set up on bolted joint surfaces. 1 G applied in Z..

Results: Reaction forces on the 6 bolts has increased by a factor of two! The mass of the additional bolts is not included so dont understand why I am getting this result.


Is this a convergence error?


Anyone have any idea what might be causing this?