Fatigue crack growth characterization and simulation of a porous steel

The cyclic mechanical behaviour of a high strength sintered steel was investigated. During the fatigue tests on notched specimens, the details of the crack propagation were surveyed by light or scanning electron microscopy. Those observations and the fractographic analysis showed that the network of pores and the nature of the sintering bridges appear to be critical parameters. Furthermore, two crack growth steps were identified: one step in mode I and an another step in which the crack forks off. The fatigue crack growth was simulated by a method based on linear elastic mechanics taking into account the microstructural features of the material. This simulation was used to analyse the possibilities of crack bifurcation. Sintered neck microcracks in front of the main crack were introduced. The influence of pores characteristics on crack growth rate was also investigated.