Accessing Stiffness Matrices and Internal Force Vectors for Incremental Solution in COMSOL

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Hello COMSOL Community,

I'm currently working on a phase-field fracture problem and trying to implement a custom solver that follows a Newton-Raphson iteration scheme with arc-length control, similar to what is shown in the attached image (equation 17a and 17b).

I need to access the stiffness matrices (K_uu, K_φφ, etc.) and the internal force vectors (f_int,u, f_int,φ) in COMSOL in order to calculate the solution increments (Δu, Δφ, Δλ) at each iteration. I am aware that quantities like displacement (solid.uf) and damage (solid.dmg) can be accessed, but I'm unsure how to retrieve the stiffness matrices and internal force vectors.

I would like to use them in a custom script, potentially via the mph package or COMSOL's Java API.

Thank you!



1 Reply Last Post 2024年9月3日 GMT+2 09:00
Henrik Sönnerlind COMSOL Employee

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Posted: 3 days ago 2024年9月3日 GMT+2 09:00
Updated: 3 days ago 2024年9月3日 GMT+2 16:54

The path on which you plan to embark is probably quite difficult.

If possible, I suggest that you first look at something similar to the method used in this example:

https://www.comsol.com/model/postbuckling-analysis-using-an-incremental-arc-length-method-119001

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Henrik Sönnerlind
COMSOL
The path on which you plan to embark is probably quite difficult. If possible, I suggest that you first look at something similar to the method used in this example:

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