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I was performing a simple static structural analysis using Ansys to check the stress value for different materials. I have kept the below parameters constant:

  1. Geometry
  2. Force (in N)
  3. Area on which the force is applied

I changed the materials from copper through PVC. However, the value of stress didn't changed. From what I have inferred about stress is: The stress remains constant in elastic regime, and once the material enters plastic regime, the value of stress changes. However, in Ansys (or any other Multiphysics software employing FEA, like Pro Mechanica of PTC Creo) the stress value is fairly constant, irrespective of materials. I am confused, for why this happens. Please see below stress values for Structural Steel, Aluminum & PVC respectively.
Any help is greatly appreciated.

P.S. I have checked this question (Stress analysis for the same configuration but different material) as well, but this doesn't answers my questions Structural Steel Aluminum PVC

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  • $\begingroup$ perhaps the units of stress would be a clue. These things make more sense when you aren't looking at software to give you answers. $\endgroup$
    – Tiger Guy
    Commented Aug 8, 2023 at 16:31
  • $\begingroup$ In the elastic range, did you check the max/min stresses output against hand cal? $\endgroup$
    – r13
    Commented Aug 8, 2023 at 16:45
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    $\begingroup$ The stress is applied TO the material, not because OF it. $\endgroup$
    – Solar Mike
    Commented Aug 8, 2023 at 18:49
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    $\begingroup$ Stress is the force or pressure applied to the material. Strain is how it deforms. So if you apply a constant force to a constant area for different materials, why would the force be dependent on the material? Recheck your definition of stress and what you think it is. $\endgroup$
    – DKNguyen
    Commented Aug 8, 2023 at 20:16

2 Answers 2

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In linear elasticity with small deformations (which is default for many FEA software), the stress might not depend on material, if you use only one material in the analysis and stresses come from forces, moments or pressures. This is often the case with very simple cases like the one you have shown.

If you want to investigate what happens in plastic regime, you have to set up appropriate plastic material model, e.g. kinematic hardening and use nonlinear analysis.

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Oh for goodness sake, this is statics 101. The stress in a beam in bending in the linear range is M/I=sigma/y

There are no material properties in that equation.

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  • $\begingroup$ Said that in my comment. $\endgroup$
    – Solar Mike
    Commented Aug 10, 2023 at 20:57

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