Experimental study of the constant-probability crack growth curves under constant amplitude loading

This paper is concerned with the application of a mathematical model that describes the fatigue crack growth evolution and associated scatter in polycrystalline solids. The model has been built on the basis that an analogy exists between a particular discontinuous Markovian stochastic process, namely the general pure birth process, and the crack propagation process. The, crack evolution and scatter were then defined in terms of material, stress and crack-length dependent properties and crack tip incubation time. The application of the model is carried out by comparing the constant-probability crack growth curves generated for three different load levels with those obtained from testing sixty A1 7075-T6 specimens for each load level. A photographic method was utilized to measure the cracklength in this test program, by recording the residual deformation that accompanies the flanks of the crack during propagation. © 1987