Mixed-mode fatigue crack growth thresholds: A personal historical review of work at the National Engineering Laboratory, 1975–1989

Mixed mode fatigue crack growth thresholds in metals were investigated at the National Engineering Laboratory from 1975 to 1989. Re-assessment confirmed that thresholds are determined by the formation and growth of mode I branch cracks at the tip of the initial crack. Lower and upper bounds can be defined, and used for design purposes. For mixed mode I and II loading, the presence of corner points and hence corner point singularities, encourages...