UMAT results are different with and without *orientation

 I have tried to validate my code by comparing the results with the in-built ABAQUS fung model results for uniaxial, biaxial and simple shear test on a single cube element. Uniaxial and biaxial both tests are correct and agreed excellently with ABAQUS predicted results. But the simple shear test results are not similar with the ABAQUS results. All the tests were performed with *orientation.

Observation for simple shear test results:

1.       Simple shear test results are not same with ABAQUS predicted results when the UMAT is used with *orientation.

2.       When I didn’t use any *orientation with the UMAT and used global base, the simple shear test results were same with ABAQUS results.

3.       But when I used *orientation same as global coordinate (1,0,0, 0,1,0), the simple shear test results of that UMAT got changed and didn’t match with ABAQUS.

I have tried several things but still unable to identify the reasons behind that. I wonder if you could have the explanations for the same.

Thanks and Regards,