TAGGED: creep-simulation, implicit, upf
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January 2, 2024 at 10:55 amSasi Kumar TippabhotlaSubscriber
I am trying to understand how the usercreep.F subroutine, given in the Ansys customize folder (........\ANSYS Inc\
\ansys\customize\user), shown in the attached screenshot. I am unclear of the following aspects and need help to understand - Is this explicit or implicit formulation?
- If explicit, is the logic written for "delcr" corresponding to the first and second if-constructs correct? The double exponential on the RHS seems to be wrong to me. Or do I miss anything here?
- If, implicit, I not able to comprehend at all. Please help me to understand the logic and if possible direct me to the theory help in Ansys documents. I searched the ansys theory manuals and did not find anything related to the implicit formulation of the primary creep equation.
Thanks & regards,
Sasi Kumar
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January 8, 2024 at 6:44 pmJohn DoyleAnsys Employee
The usercreep.F routine, given in the Ansys customized folder, is written in FORTRAN for implicit strain hardening primary creep (TBOPT=1). See Table 4.2 of Section 4.5.5.1 of the MAPDL Material Reference Guide.
I would refer you to the MAPDLÂ Programmer's Reference (ansys.com) for more details.
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January 9, 2024 at 2:33 amSasi Kumar TippabhotlaSubscriber
Hi John, thank you for your response. My question is not about how the usercreep subroutine works. I understabd that it is based on strain hardening model of primary creep. May be my question in the original post is unclear. Let me elaborate.
I am trying to understand the implicit formulation of the creep function here. To be specific, I am trying to understand the calculation logic used for "delcr". If it is an implicit formulation (I guess it is),
delcr = e_cr(n+1) - e_cr(n) = C1*(sigma(n+1)^C2)*(e_cr(n+1)^C3)*exp(-C4/T(n+1))*delta_t
where n indicates the current time step and delta_t = t(n+1)-t(n). I expect the formulation integrates the creep function to eliminate the (n+1) terms and solve for the delcr. That is why there is a long "if-else" logic to address different scenarios. I am not able to understand how the eauations used for "delcr" calculations are arrived at. Explanation of the same is not available in the theory manual or user programmer's guide
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