Friction penalty formulation doubts in Radioss 2022

Silvio G.
Silvio G. Altair Community Member
edited March 27 in Community Q&A

Hello all,

I am modeling the pre-tensioning of a bolt in Radioss. To check for slipping, I compare the FT output from the contact interface with FN*static_friction. However, I notice that FT is always lower than FN*static_friction, even though the animations clearly show that the contact is in the slipping phase. I also noticed that slipping occurs when the external load crosses FN*static_friction, which is correct, but I would also expect that FT >= FN*static_friction during this phase. I tried to modify the stiffness of the contact, and FT/FN also vary, which is correct, since they are dependent from it.

Can someone explain how this is possible?

Forces.png model.jpg
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Answers

  • Marina_Lima
    Marina_Lima
    Altair Employee

    Hi Silvio,

    It is possible that the tangential force exceeding the normal force multiplied by static friction is influenced by the length of the pretensioned part. Depending on how the force is applied relative to the part's length, it can create a moment at the contact interface, potentially reducing the tangential force. Additionally, I have observed in some bolt pretensioned models that interference between the bolt elements and the parts can increase the normal force at the contact interface.

    Best regards,

    Marina Lima

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