Dear Simulation experts:

I am modeling two pieces screwed together using "bolt". At the edge of the bolt head, I got high stress and the stress increases when I refine the elements in that area. Is this due to numerical singularity and can be ignored? If this is real, how can it be designed out? Thanks!

Pei

I am modeling two pieces screwed together using "bolt". At the edge of the bolt head, I got high stress and the stress increases when I refine the elements in that area. Is this due to numerical singularity and can be ignored? If this is real, how can it be designed out? Thanks!

Pei

Thanks for the reply!

I am using "bolt" BC to model the screws. So, the screws are not physically in the model. Plus, the screw heads act on a flat surface, so, I cannot add any fillet.

I just ran the same model using ANSYS. In ANSYS, it can model bolts with pre-load and the screws are physically in the model. I did not get the same high stress in the same areas. However, in ANSYS, I got high stress (but, not as high as predicted in SolidWorks) at 4 spots on the inside edges of the screw holes.

So, ANSYS and SolidWorks gave two different results near the screws areas. I am not sure which one to trust. I probably need to try a third FEA package?!

Pei

If you find it is not possible to refine your mesh to the point where results converge (stop increasing w/ finer mesh), you need to reevaluate the construction of your model.

Thanks for the answers.

SolidWorks support engineer sent me an article indicated that bolt connector is not accurate near the bolt region. After physically modeled the bolts in SolidWorks (and ANSYS), I found that this is true (the high stress near the bolt head is gone). Unfortunately, it is critical in my case that the stress is accurate, so, I have to physically include the bolts in my model.

I am also refining my element size to make sure I get converged solution.

Pei

Another thing to consider is the plastic deformation that occurs when a bolt exerts stress beyond yield.