Theory Manual Version 3.4
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Subsubsection 5.6.5.1: Strain Energy Density Up Subsection 5.6.5: Constitutive Models Subsubsection 5.6.5.3: Specific Strain Energy

#### 5.6.5.2 Simo Damage Criterion

Simo [70, 71] proposed a damage criterion related to the strain energy density, This damage measure is valid for isotropic or anisotropic materials, since the strain energy density must satisfy the frame-invariance of Eq.1↓ by construction. Its resulting damage surface normal is where we have used the result of Eq.(5.6.5.1-2). The normal reduces to the null tensor in the limit when and tend to zero.
Subsubsection 5.6.5.1: Strain Energy Density Up Subsection 5.6.5: Constitutive Models Subsubsection 5.6.5.3: Specific Strain Energy