Analysis of shop crane arm

[szeles1996]

I am trying to analyze the stresses in a shop crane, however i have a hard time believing the results on the arm portion where the hollow-sections go into each other. The rest of the analysis is fine. My question is what type of contact should i use? As of now it is set to sliding/no-seperation (between the two hollow-sections), and the contact between the pin and the hollow-sections is set to surface. 

As i run the simulation i returns with results above 500 MPa ( 8 mm mesh size) if i reduce the mesh-size the situation becomes even worse. (i use half symetry) 

What would be the most realistic contact between two hollow-sections which go into each other? I know it can hold the load, my design is based of an existing one (the material thickness). I cannot attach any screenshots .. 😕 

I would highly appreciate any suggestions! 

[John_Holtz]

Hi @szeles1996

Based on your description (the stress continues to increase as the mesh is reduced), it sounds like a singularity. If that is the case, the high stress can be ignored. (Singularities can occur where there is a discontinuity, such as at the edge where a constraint or load ends.)

I suggest that you inspect the displacements closely to see if they are behaving correctly. In other words, is the "no separation" the correct behavior? I think it will be hard for anyone to say whether sliding/no separation is correct or not without seeing anything about what you are analyzing.

[marwan_azzam]

Hello @szeles1996,

To add to what John said, it's hard to tell without seeing what you're working with.  If the stresses are worse with a finer mesh this could very well be some kind of singularity such as a sharp edge.

Perhaps you can make a simple (2 or 3 part) model that exhibits the same high stress and share it with us.

If this simple model does not show the high stress then it will be useful to you in learning more about your model.

Marwan