cratepy.material.models.stvenant_kirchhoff.first_piola_from_second_piola

first_piola_from_second_piola(def_gradient, second_piola_stress)

First Piola-Kirchhoff from second Piola-Kirchhoff stress tensor.

\[\boldsymbol{P} = \boldsymbol{F} \boldsymbol{S}\]

where \(\boldsymbol{P}\) is the first Piola-Kirchhoff stress tensor and \(\boldsymbol{S}\) is the second Piola-Kirchhoff stress tensor.

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Parameters:

• def_gradient (numpy.ndarray (2d)) – Deformation gradient.

• second_piola_stress (numpy.ndarray (2d)) – Second Piola-Kirchhoff stress tensor.

Returns:

first_piola_stress – First Piola-Kirchhoff stress tensor.

Return type:

numpy.ndarray (2d)