Separating plasticity-induced closure and residual stress contributions to fatigue crack retardation following an overload

- Observation of crack opening reveals that high load ratio (R=0.7) inhibits crack closure during fatigue crack propagation.
- The effect of residual stress-strain field generated during overload vanishes when the crack tip advances past the overload plastic zone.
- When operative, crack closure mechanism has a longer lasting retardation effect on the crack growth rate than residual stress.