Variable in which sense? If you have a non-linear material you have to update your Youngs modulus step wise. Your assumption is that your material behaves linear for small deformation steps.
If you want to change the material itself, you can do that by rebuilding the stiffness matrix. Because, the Youngs modulus is only a scaling factor the rebuilding is limited to a multiplication with the new modul.
K=2EI/L integral B^TB dxi
where E is the Youngs modulus, L is the length, I is the moment of inertia, xi is your integration domain [-1 1], K is the stiffness matrix and B is the strain-displacement matrix
Respected sir,
I want to know that material of bimodulus property that means to say that the material having stress dependent YOUNG'c modulus. If the maiteria having compressive stress then material sense the different youngs modulus as in tensile stress sense the other Youngs modulus.
If you work with ABAQUS you can easily implement such properties with an UMAT. You have to check the stresses in the gauss points. Dependend on the sign of the stresses you can change the Youngs modulus.
I have Abaqus 6.7 student edition. can it possible that the above problem is solved in that version.
Maybe you can implement it by utilizing an experimental data table. You have to define three points (one in negative direction) and the gradient of the two linear functions are your Youngs moduli in negative and positive direction. In hyperelastic material you can do it this way. However, you have to be careful. Check if you have realy linear elastic isotropic material in the end.
As far as I know simplest is to use an IF-THEN-ELSE clause in UMAT. but one question: how this work for a beam in bending? Does ABAQUS consider the change of stiffness based on updated stress at each section point?
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