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Fracture & Fatigue Cracks

SAGA is used on fracture mechanics projects where a standard S-N curve approach is not considered appropriate. The fracture mechanics program is based on the Paris’ Law approach described in SSC-409, which evaluates the growth of external and internal crack types typically found in ship structures.

The loading that drives fatigue stress ranges is defined by a Weibull distribution of a stress range. This is calculated by loading and solving an FEA model. The model program allows us to investigate the effect of:

Crack Curve Graph
  • Initial Crack Length
  • Residual Stress in the Structure
  • Compressive Stress
  • Wheeler Retardation Model
  • Shape Geometry Effects in Case of a Damaged Area

Finite Element Model stress ranges are used in SAGA to calculate a fracture damage ratio. The amount of cycles in a design event is presented as a ratio of the amount of cycles to failure.

Crack Model