I am currently modelling GRP Pipes in abaqus. The problem is that applying or not applying the Hashin failure criterion does not affect the answers.
Can anybody advise me of any strategies that can be applied to model it, still using Hashin (without creating UMAT subroutine)?
Hi Salar,
Hashin damage is composed of four different failure modes. The effect of Hashin damage can be seen when one of these failure modes occur. You can control the Hashin damage criteria to make sure whether the damage has occurred or not.
Hi,
You may reduce the damage initiation values to a lower level to make this work. However, this may not be modelling the actual scenario. An exact material behaviour data is essential to do this.
Hi,
Since the Hashin criterion is already modeled in Abaqus, there is no need to write UMAT for it.
The result is not getting affected means the model is not getting damaged, you can check the damage initiation criteria and check in the result that whether that initiation criterion is met or not. Also, crosscheck the material input parameters used in the failure model.
Damage initiation does not actually lead to damage unless damage evaluation is specified. However, the effect in the result values will be visible with damage initiation as well but the result will not show the actual damage of the elements.
You should select the "STATUS" output variable to eliminate the failed elements automatically in the odb output.
i think you have only specified the damage initiation and missed the input values for damage propagation. This happened with me also. When i specified the damage propagation, it worked well.
Well, the answer is in 2 parts... UMAT is only required for SOlide meshes. As long as the mesh is shell (Layered composite), you do not need UMAT. Also if the applied load generates interactive stress that is more than the allowable, then only the failure criteria gets initiated. Otherwise, if you are running a linear static, the failure criteria does not make any difference.
Did your model experience any First ply failure or Damage initiation under defined loading? This article can help you.
" A novel strategy for comparative numerical analysis of the response of buried composite and steel pipes subjected to realistic loading scenarios: FEA in cooperation with Taguchi approach "
The fact that you do not see any failure mode can be one of the following reasons:
1- Loading is less than the failure limit and has not activated any mode.
2- In the Field Output, you did not select suitable options for displaying the results
3- The system of units is not consistent.
However, there are limitations to the Hashin criteria in Abaqus. For example, it is not possible to use it for solid elements. That's why we developed a VUMATsubroutine with exponential damage evolution, which you can get from the company's store if needed.
http://en.banumusagr.com/shop/3dhashin-vumat-abaqus/
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