Hi,
As I understand from the VUMAT documentation, the coordinates of tensorial quantities in a VUMAT are expressed in a corotational coordinate system. The later is either the global coordinate system, or a user-defined orientation, rotated by R, where R is obtained from the polar decomposition of the transformation gradient F.
Am I right in assuming that R is the rigid body rotation at the end of the increment? If yes, what about the -Old quantities (stressOld, stretchOld)? Are those also expressed in the corotated system at the end of the increment? Or are they expressed in the corotated system at the beginning of the increment?
As I understand from the VUMAT documentation, the coordinates of tensorial quantities in a VUMAT are expressed in a corotational coordinate system. The later is either the global coordinate system, or a user-defined orientation, rotated by R, where R is obtained from the polar decomposition of the transformation gradient F.
Am I right in assuming that R is the rigid body rotation at the end of the increment? If yes, what about the -Old quantities (stressOld, stretchOld)? Are those also expressed in the corotated system at the end of the increment? Or are they expressed in the corotated system at the beginning of the increment?