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Correcting lamé parameters for plane stress model#1209

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kinnala merged 2 commits into
kinnala:masterfrom
luedkej:master
May 24, 2026
Merged

Correcting lamé parameters for plane stress model#1209
kinnala merged 2 commits into
kinnala:masterfrom
luedkej:master

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@luedkej

@luedkej luedkej commented May 22, 2026

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The former calculation of the lamé parameters lambda and mu is to the best of my understanding wrong. The updated fromulae correspond to the derivation of the lamé parameters derived from the generalized Hooks Law for sigma_zz = 0.

Copilot AI review requested due to automatic review settings May 22, 2026 23:02

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Pull request overview

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Copilot was unable to run its full agentic suite in this review.

Updates plane_stress to return plane-stress Lamé parameters and expands the docstring to a full NumPyDoc-style description.

Changes:

  • Changes plane_stress(E, nu) to return (lambda, mu) for plane stress using standard formulas.
  • Replaces the one-line docstring with a detailed Parameters/Returns docstring.

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Comment thread skfem/models/elasticity.py Outdated
Comment on lines +47 to +48
return (E * nu / (1. - nu**2),
E / (2. * (1. + nu)))
Comment thread skfem/models/elasticity.py Outdated
Comment on lines +30 to +31
"""Map Young's modulus and Poisson ratio to plane stress lame parameters.

Comment on lines +39 to +44
Returns
-------
float
The first Lamé parameter for plane stress scenario (lambda)
float
The second Lamé parameter for plane stress scenario (mu)
@kinnala

kinnala commented May 23, 2026

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Thanks a lot, I wonder what kind of brainrot lead to this. I don’t remember ever using this function. I’ll just once again verify this formula from some source before merging.

@kinnala kinnala merged commit eb101a9 into kinnala:master May 24, 2026
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3 participants