Stress intensity factor–based fatigue crack growth laws

Stress intensity factor–based fatigue crack growth laws are now available for enriched elements. Previously, fatigue crack growth laws were based only on the strain energy release rates. You can now specify a mode mix formula for computing the effective stress intensity factor based on the following:

• The Irwin mixed-mode fracture criterion.
• A tabular form to support multiple piecewise linear log-log (crack growth rate versus effective stress intensity factor range of a load cycle) segments.
• A user-defined crack growth criterion using user subroutines in a fatigue crack growth analysis.

The stress intensity factor–based laws are not available for crack propagation or debonding along initially partially bonded surfaces where the strain energy release rate–based laws are more relevant and should continue to be used.