BOLTED CONSTRAINT

[ahad29]

What is the best way to simulate a bolted constraint. Say it is loaded with 3 forces and 3 moments along each axis. The two ways I can think of are

1. If there are 6 bolts on a bolt-circle of dia 6". Then I would constrain a "ring" with outer dia 6.5" and inner dia 5.5" (Depending on the bolt-head dia)

2. Constrain the inner surfaces of the clearance or tapped holes. But this way sometimes I have seen high stresses at the edge of the holes.

Please comment on the above techniques. Thanks

Ahad

 

[rob768]

Try using rigid elements, connected to a central node in the bolt hole on one end, and the nodes along the periphery of the bolt hole on the other. Thanm restrain the central nodes. You can also replace the rigid elements by (stiff) springs (one DOF). Thus you can simulate the effect of directional load (a single DOF spring takes no force when loaded out of plane)

 

[johnhors]

Ahad

1 = over-constraint and unrealistic.

2 = better - and yes you do get high stresses which are not unexpected !

 

[ahad29]

Thanks rob768 & johnhors.
johnhors, is case 1 usable if the surface is sandwiched between two plates using bolts. Thanks

Ahad