Analysis Location

Entity type selection for Fatigue Evaluation.


HyperLife uses element centroidal stresses/strains for Fatigue Evaluation.


HyperLife supports nodal damage using Grid Point Stress or Averaged Corner Data Stress at a node. For solid elements, HyperLife evaluates only at the surface nodes. The grid point stress or the averaged corner stress is projected onto an imaginary plane to obtain plane stress. The plane stress is used in the damage calculation. Normal direction of the imaginary plane is an averaged normal direction of free faces that are attached to the grid. The normal direction is local z-axis of the imaginary plane. Local x-axis is a cross product of z-axis in basic coord. system and the local z-axis. If the z-axis in basic coord. system is parallel to the local z-axis, the local x-axis will be the x-axis in basic coord. system. Local y-axis is a cross product of the local z-axis and the local x-axis.

If a grid is shared by more than one material, HyperLife uses a tiebreaker in the following order to choose an SN curve, EN curve, or Tfl/HSS to use:
  1. Material with the least UTS.
  2. Material with the least SRI1 (SN) or S'f (EN) before SN / EN curve adjustment.
Grid-point Stress (GP) is only supported for OptiStruct result files (h3d). If the h3d result file for solid elements contains GP, Gauss Stress and Corner Stress, then preference in selection is of the following order:
  1. GP Stress
  2. Gauss Stress (averaged)
  3. Corner Stress (averaged)

Similarly, .h3d result for shell elements containing gauss stress and corner stress, preference is given to Gauss Stress (averaged). For the other result formats Corner Stress (averaged) is considered.

Nodal Evaluation is supported for SN, EN, and FOS only and not supported for nodes associated with second order elements.