umat.C File Reference

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Functions
void	FOR_NAME (umat, UMAT)

Function Documentation

FOR_NAME()

void FOR_NAME	(	umat	,
		UMAT
	)

Definition at line 15 of file umat.C.

{
  if (*nprops != 2)
    throw std::invalid_argument("This UMAT requires exactly two properties.");

  double E = props[0];
  double nu = props[1];
  double G = E / 2.0 / (1.0 + nu);
  double lambda = 2.0 * G * nu / (1.0 - 2.0 * nu);
  double eps[6];

  // Build stress as in
  // https://github.com/michael-schw/Abaqus-UMAT-Cpp-Subroutine/blob/main/umat.cpp
  for (int i = 0; i < 6; i++)
    eps[i] = stran[i] + dstran[i];

  auto eps_trace = eps[0] + eps[1] + eps[2];

  for (int i = 0; i < 3; i++)
  {
    stress[i] = lambda * eps_trace + 2.0 * G * eps[i];
    stress[i + 3] = G * eps[i + 3];
  }

  Eigen::Matrix<double, 6, 6> C;
  buildStiffnessMatrix(C, G, lambda);

  for (int i = 0; i < 6; i++)
    for (int j = 0; j < 6; j++)
      ddsdde[6 * i + j] = 0.0;

  for (int i = 0; i < 3; i++)
  {
    ddsdde[6 * i + 0] = C(0, i);
    ddsdde[6 * i + 1] = C(1, i);
    ddsdde[6 * i + 2] = C(2, i);
    ddsdde[6 * (i + 3) + (i + 3)] = C(i + 3, i + 3);
  }
}