Mises stress problem

[mba0188]

Hello everyone,

I have a power distribution box with many bus bars and fuses inside. I want to do a static analysis by introducing the pressure of screws on busbars (it looks simple test). There is so many contacts (surface to surface) have modeled. The problem is with correct boundary conditions and pressure of 21 MPa I find in static that mises stress is of 10e4 even 10e5 MPa and deformation and displacement are really big and it's not normal. In brief I can't find the mistake for this case so please if someone has just an idea he can answer me.

Thanks in advance

 

[StefCon]

Hi,

Check units. Newton, mm, MPa are good to use. "pressure of screws". Is that preload? If so, did you switch from displacement to an actual force preload?

A linear material model can show high peak stress.

Hard to know but those are my guesses.

Good luck!

 

[mba0188]

Hello StefCon,

Yes it's a preload, after this first step a modal analysis will be elaborated to extract the natural frequencies of the box and application of mechanical shock to see how it behave. Boundary conditions of the frequency step were used as boundary conditions in the preload and it's not the reality in fact. Preload must not have the same boundary conditions. This modification has corrected the problem and stress becomes logic.

Many Thanks for your answer
Regards