hermit.failure
==============

.. py:module:: hermit.failure

.. autoapi-nested-parse::

   ``failure_index`` / ``failure_field`` -- Tsai-Wu failure, wired to ``Orientation``.

   ``hermit._laminate.failure.tsai_wu_field`` documents its input as **laminate**-frame
   strains, but the DG0 strain-measure output is in the **element** in-plane frame. So
   the *same* ``Tε(θ)`` (engineering-Voigt strain rotation, element -> laminate axes)
   the constitutive path already applies (``hermit.fenics.kinematics.strain_rotation`` /
   ``hermit.csdl_helpers.rotate_abd``) is applied to the strains first, before calling
   ``tsai_wu_field`` (unmodified -- it already uses the correct ``(xz, yz)``
   transverse-shear ordering, see that module's docstring). This is covered by
   ``tests/test_material_api.py::test_failure_index_respects_orientation`` ("two
   spellings of one physical laminate must agree").

   This module's entry points take mid-surface strain / curvature / shear directly,
   in the **element frame, FE cell order** -- the raw DG0 strain-measure convention
   ``hermit.fenics.ops.strain_fields`` produces. ``hm.failure_index(state, ...)`` /
   ``hm.failure_field(state, ...)`` (``hermit.outputs``) are the public entry points;
   they assemble those measures off a solved ``ShellState`` and call in here.

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Functions
---------

.. autoapisummary::

   hermit.failure.failure_field
   hermit.failure.failure_index


Module Contents
---------------

.. py:function:: failure_field(mid_strain, curvature, shear_strain, material, orientation_cs=None, *, faces=(-0.5, 0.5))

   
   ``(n_cells, 3)`` / ``(n_cells, 3)`` / ``(n_cells, 2)`` **element**-frame
   engineering-Voigt strain / curvature / shear (FE cell order -- e.g.
   ``model.strain_measure_op()``'s raw output) + a composite ``Material`` ->
   ``(n_cells, n_plies * len(faces))`` Tsai-Wu failure indices, rotated into the
   laminate frame by ``material.orientation`` first (``None`` => no rotation).
















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.. py:function:: failure_index(mid_strain, curvature, shear_strain, material, orientation_cs=None, *, rho=100.0, faces=(-0.5, 0.5))

   
   KS-aggregated scalar (``< 1`` safe) -- see ``failure_field``.
















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