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How to access the value of previous time step in General Form PDE (COMSOL 6.3)?
Posted 20.08.2025, 18:10 GMT-4 General Version 6.3 1 Reply
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Hi everyone,
I am trying to reproduce the Phase-Field Damage + Solid Mechanics coupling using only Solid Mechanics together with a General Form PDE in COMSOL 6.3. In the built-in Phase-Field Damage model, the Equation View shows in the picture.
i.e., the history variable Hd is the maximum between the current driving force Dd and its previous-time value Hd,old. When I implement my own PDE, I introduce a scalar dependent variable Hd and I would like to enforce the same update:Hd = max(Dd, Hd,old)
My question is: how do I access Hd,old in a Time Dependent study in COMSOL 6.3?
I find that someone may recommend to use pred() operator and time discrete solver. But I noticed that the solution of Phase-Field Damage + Solid Mechanics coupling can be solved by a time dependent solver, so I think PDE + Solid Mechanics can also be solved by a time dependent solver instead of a time discrete solver.
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Haiwei,
have a look into this blog contribution by Walter Frei: https://www.comsol.com/blogs/using-the-previous-solution-operator-in-transient-modeling
Cheers Edgar
-------------------Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
