double HomogeneousMooneyRivlinIsotropicMaterial::ComputeEnergy(int elementIndex, double * invariants)
{
double Ic = invariants[0];
double IIc = invariants[1];
double IIIc = invariants[2];
double energy = 0.5 * (-6.0 + (Ic * Ic - IIc) / pow(IIIc, 2.0 / 3.0)) * mu01 +
(-3.0 + Ic / pow(IIIc, 1.0 / 3.0)) * mu10 +
pow(-1.0 + sqrt(IIIc), 2.0) * v1;
AddCompressionResistanceEnergy(elementIndex, invariants, &energy);
return energy;
}
double HomogeneousNeoHookeanIsotropicMaterial::ComputeEnergy(int elementIndex, double * invariants)
{
double IC = invariants[0];
double IIIC = invariants[2];
double J = sqrt(IIIC);
double logJ = log(J);
// Note: computation of J and logJ will fail for an inverted element.
// The IsotropicHyperelasticFEM class will prevent inversions (assuming proper
// threshold was set), so normally this is not an issue.
double energy = 0.5 * muLame * (IC - 3.0) - muLame * logJ + 0.5 * lambdaLame * logJ * logJ;
AddCompressionResistanceEnergy(elementIndex, invariants, &energy);
return energy;
}
