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Finite strain uniaxial stress #19

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#20
Closed
Finite strain uniaxial stress#19
#20

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@KnutAM
KnutAM
opened on Feb 19, 2026

When using UniaxialStress stress state for finite strain, we have 8 free components, but these involve rotation, and in some cases a singular matrix has been observed. Therefore, it could make sense to reduce the unknowns further, preventing rotation around the x-axis. Alternatively augment the stiffness to prevent rotation as a modified Newton.

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  1. p-antonioni commented on Feb 20, 2026

    @p-antonioni
    p-antonioni
    on Feb 20, 2026

    Singular matrix problem when solving the linear system at:

    MaterialModelsBase.jl/src/stressiterations.jl

    Line 295 in 2defce2

    dσᶜdϵᶜ = ∂σᶜ∂ϵᶜ - ∂σᶜ∂ϵᶠ * (∂σᶠ∂ϵᶠ \ ∂σᶠ∂ϵᶜ)

  2. KnutAM
    linked a pull request that will close this issueFix issue with singular matrix for finite strain uniaxial response #20on Apr 24, 2026
  3. KnutAM
    closed this as completedin #20on Apr 29, 2026
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