Query_modeling soft contact in Abaqus

[Tinni1]

Hello,

I am simulating a compression test of a cold-formed steel column connected to a small length of U sections at both ends with self-tapping screws. In the post-buckling analysis, I have defined contact conditions between the U section web and the top nodes of the column sections. Initially, I defined normal behavior as hard contact. Now, I want to model a soft contact condition (contact between the column and the U section) to check if that is in better agreement with the test results.
I am initially trying a linear pressure overclosure relationship, where we need to define the contact stiffness, k.
I have been initially trying the k value as some fraction of the material's modulus of elasticity.

My questions are:
1. Is there any better way to predict the k value? If yes, could you please advise?
2. If I want to try the exponential relationship, how do I predict the C_0 (distance at zero pressure) and P_0 (pressure at zero distance value?

 

[FEA way]

There are some general tips regarding k (basically, a multiple of Young’s modulus of the underlying material, as you said) but it’s really case dependent and you should test different values and see how the results change. Especially take a closer look at penetrations - those will let you determine whether the solution is acceptable or not.

 

[Tinni1]

Thanks, I am doing a sensitivity study with k values, as you have advised.
Could you have some idea of the k value from contact pressure?
It would be great if you could provide some direction around this.

 

[FEA way]

Changes in contact stiffness may influence contact pressure distribution so you should check if its more uniform. Apart from that, it’s mostly about penetrations and convergence.

 

[Tinni1]

Thank you so much!