Under Deformation Type, the theory which is used for the structural mechanics is selected:

• Without Geometric Nonlinearity: This approach is faster and more reliable than the geometric nonlinear case. More material models are available in GeoDict for this case (e.g., Plasticity and Damage models). The boundary conditions for this experiment type are given as mean strains or mean stresses in the analyzed volume.
  • Here, the infinitesimal strain theory applies (see more information on Wikipedia). This is the linearized form of the finite strain theory (which applies to With Geometric Nonlinearity).
  • It is assumed that only small deformations occur, for example it is assumed that no rotations occur.
  • This is the simpler theory, but it is much more robust and easier to solve and is therefore preferable in most use cases. We recommend to always try Without Geometric Nonlinearity first.
  • For applications with larger deformations use Without Geometric Nonlinearity together with Calculate on Deformed Geometry.
  • The internal calculations are based on the engineering strain and stress.
• With Geometric Nonlinearity: Should be used when the theory of small deformations does not hold anymore. A nonlinear problem must be solved; therefore, the computation might be considerably slower than for the geometric linear case. The boundary conditions for this experiment type are given as mean displacement gradient or mean nominal stresses in the analyzed volume.
  • Here, the finite strain theory applies (see more information on Wikipedia)
  • Here, large deformations are considered, this means that also the effect of rotations is considered correctly.
  • This theory is more complete, but also much more complicated to solve (Finite Strain Theory).
  • The internal calculations are based on the true strain and stress. Nevertheless, if the deformations are small, the strains in the nonlinear definitions do not deviate largely from the strains in the linear definition (e.g., for small strains, the Green Lagrange Strain is close to the Strain for Without Geometric Nonlinearity).