How to access the value of previous time step in General Form PDE (COMSOL 6.3)?

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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.



1 Reply Last Post Aug 21, 2025, 2:02 p.m. EDT
Edgar J. Kaiser Certified Consultant

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Posted: 21 minutes ago Aug 21, 2025, 2:02 p.m. EDT

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
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

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