Learning Forum

[ty.wu]

Hi, I tried to simulate the contact problem in a dovetail joint as illustrated below:

I have a problem in mesh convergence test where the contact stress keeps increasing as the mesh gets finer. The global mesh size is 1 mm and mesh size along the contact edges is decreased from 0.32 mm to 0.02 mm, the stress results are summarized in the following table:

Example of mesh:

Convergence history:

 The maximum von Mises stress is always at the upper contact point where the fillet starts; for example, when the edge element size is 0.01mm, the stress distribution looks like:

I also tried adaptive meshing by inserting a convergence in the stress output with 1% allowable change, but the results did not make sense:

Please point out where I am doing wrong and how I can get converged results.

Information about this project: 2D plane stress analysis. Linear elastic material properties assumed (no plasticity). Frictional contact defined between two surfaces with a coefficient of 0.3. I also tried different element order, contact modes, contact methods and stiffness; activated large deflections; changedfillet radii, but the results were not satisfactory.

[Ashish Khemka]

Hello,

What is the nature of the stress - tensile or compressive? I think it should be compressive in nature (check principal stress at the location) and can be ignored. How far is the spread of the stress? Is it limited to 1 or 2 elements? Also, see if the points raised in the following post look relevant to you: Singularity at sharp corner How to deal?

Regards,

Ashish Khemka

 

[ty.wu]

Hi Ashish,

Thank you very much for your reply!

It is compressive but I don't think it can be ignored. It is limited to 2 elements. I have also tried methods suggested in that question but I was still having the problem. 

I plotted the von Mises stresses along the contact edge using different element sizes. Except for two points where the stress keeps increasing, the stress results in other areas converge very quickly. How can I avoid this problem and how to determine which mesh to use? Thank you very much for your help!