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Zero Stresses/Reaction Forces using UMAT

rajan_prithivi's picture


While I tried to simulate a simple uniaxial loading and a simple cube geometry ( single crystal)- I obtaine d zero reaction forces at the constraint nodes.. while in Animation the displacements are fine. I could see the stretching of the specimen but i am getting absolute zero values of stresses and reaction forces.

I have used UMAT many time and I am facing this particular problem in recent times. Is there anything to do with the .inp file ?

If any of you have encountered a similar problem, kindly help !!




Other than simple solutions such as reload the ODB file and check if you've asked for displacements in the output database (which you have since you can see them in the animations) and all that good stuff, try just writing the values of stresses, strains and dispalcements directly onto the MSG file using WRITE (7,*) in the UMAT sourcecode. I use this to brute force debug my codes. You could also do this to particular elements by doing something like IF (NOEL .EQ. 111) THEN WRITE(7,*) 'RF IS SO AND SO'

This should probably tell you what's happening in the code while it's running. Good luck with the debugging process! Also, hope Dr. Sangid is doing fine! I miss armstrong hall!

rajan_prithivi's picture

Many thanks Aswin...I shall try that.

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