Stress Concentrations/Singularities?

[shaw600]

Hi

I have modeled a beam in solidworks and the maximum stress is different to my hand calculations.

The stress is on an edge of the beam not a face. I have read somewhere that this can cause stress concentrations/singularities...

Could someone please explain this to me?

 

[MartinShane]

shaw - I'm assuming that you got your stress results from the SW Simulation package, in that case it is possible for stress results in a sharp re-entrant corner to be divergent (infinite).

I believe elasticity theory indicates that the stress in such an area is infinite under load, but in reality, there is never a perfectly sharp internal edge, so we do not see automatic failure of every non filleted corner. However your CAD model is based on a mathematical model that may truly have "sharp" edges. As a result, your FEA result will try to approximate the stress in each element, and your computed results will be completely dependent on the mesh size.

One way to test for this would be to re-run your simulation with progressively finer meshing. If you have a singularity causing divergent stress results you will see the stress results increase with each progressively finer mesh.

If you can post a picture of your results and a description of the loading you used for the calculations I assume someone would be able to help find the issue, or give a better explanation than mine.

 

[shaw600]

your explanation is great and will do for what i need it for

thank you i will try the finer mesh this evening!