I am working on reproducing the Holzapfel-Gasser-Ogden form of fiber-reinforced anisotropic material model, with the UMAT in abaqus.
With a simple proof-of-concept model, I am currently using solution-dependent variables (statev in umat, or depvar in inp file keyword) to record fiber orientations. I initialize them at the 1st increment of the model, based on the coordinates.
However, I wonder where there is a standard way to do it, e.g. access the material orientation defined using *orientation keyword. This would be much scalable than my current quick-and-dirty way of doing it.
Any comments would be appreciated. Thanks!