How to calculate stiffness from compliance ( *.out file of Optistruct)?

Yaseen_22346
Yaseen_22346 New Altair Community Member
edited December 2020 in Community Q&A

Hi there,

I want to validate stiffness of my dummy parts in assembly. Compliance and Epsilon is what we gets, in *.out file of Optistruct. Compliance is inverse of stiffness. So the value of compliance  i am getting is 3.384886e5  and if i inverse it (K=1/C) then I am getting   2.9543092 e-6 ( this stiffness value can't too small)!?

I would appreciate a response.

 

Regards,

Yaseen Khan

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Answers

  • Adriano Koga_20259
    Adriano Koga_20259 New Altair Community Member
    edited December 2020

    Hi @Yaseen 

     

    Compliance is a measure that can be interpreted as a indirect measure of inverse stiffness.

    If you look at the OptiStruct documentation you will find the math behind compliance, and hopefully it will make it clear.

     

    For a fixed load vector F, Compliance can be calculated as a vector product of the forces applied, multiplied by the displacement vector (U) found under this loading. So:

    C = f'*U

    So, for a certain fixed load, the higher the displacements, the higher the compliance. Which can be understood as a indirect measure of stiffnes. If for the same load, your new structure presents a lower average displacement (with smaller compliace), them, your structure is stiffer, compared to the old one that presentts larger displacements (with larger compliance).

     

    If you take a look at OS help or any Topology Optimization theory you will find a detailed explanation about compliance.

    Hope this helps.

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