Progressive Stepwise Fracture

Progressive stepwise fracture is being differentiated from fatigue fracture in that the stress cycles in progressive stepwise fracture are not periodic, as is usually the case in metal fatigue. In stepwise fracture, the crack will progress whenever a stress of sufficient magnitude is periodically experienced. If during that use the application of the applied stress exceeds the threshold stress level necessary to make the crack grow (or jump forward in the metal structure) the crack will extend. The spacing between steps will present a fracture surface very similar to metal fatigue. Progressive stepwise fracture will often present a dimple rupture fracture topography.