Hello.
I want to model expansion in abaqus and i use uexpan subroutine to model it. In subroutine i want to calculate expansions in three principal directions (EXPAN(1),EXPAN(2),EXPAN(3)), but i don't know what is the variable key for max principal stress. In abaqus analysis user's guide i found that the variable key for minimum, intermediate, and maximum principal stress components are SP1,SP2 ,SP3. My expansion formula for three principal direction is:
EXPAN(1)=(1-(SP1/5))*ef
EXPAN(2)=(1-(SP2/5))*ef
EXPAN(3)=(1-(SP3/5))*ef
but the manual said that SP1 and SP2 are minimum and intermediate components not max principal stress.
have you checked abaqus users subroutine manual->utility subroutines?
The UEXPAN subroutine is designed for thermal expansion, not for stress induced expansion. For your problem, you should use either a UMAT (Abaqus/Standard) or a VUMAT (Abaqus/Explicit) subroutine. For these subroutines, the initial stress state is provided as an input variable. You can then use the utility subroutines (SPRINC, SPRIND, or VSPRINC, VSPRIND) to obtain the principal values of the stress tensor.
You have to define the stress using a UMAT or UMATHT. UEXPAN should be called before in order to update state variables. For Stresses you should call SPRINC (calculate principal values) or SPRIND (calculate principal values and directions) in UMAT.
I forgot to notice that i used USDFLD subroutine before UEXPAN and i don't know what is the variable key for max principal stresses in 3 directions in USDFLD subroutine that i want to use in UEXPAN.
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