Lifetime evaluation of hot forged aerospace components by linking microstructural evolution and fatigue behaviour

AbstractThe present work aims at linking the local distribution of fatigue strength in a forged part to its manufacturing process. To this purpose, a predictive fatigue strength model for Inconel 718, also including the operating temperature, is derived from a reduced set of numerous microstructural parameters. The model is implemented, along with a microstructural evolution model from earlier work , into a finite element code in order to predict the local fatigue strength distribution in a component after being subjected to an arbitrary forging process

Fatigue crack growth model including load sequence effects - Model development and calibration for railway axle steels

Beside well-known influence factors like residual stresses, component and crack geometry also load sequence effects significantly impact the crack propagation rate. In this paper two major load sequence effects, namely overloads and small loads, and their particular influence on the fatigue crack growth are investigated in detail. Both effects lead to a retardation in the crack propagation rate by increasing the plasticity-induced (overload) or the oxide-induced (small loads) crack closure. To develop a holistic fatigue crack growth model including the short crack behaviour as well as load sequence effects, the NASGRO equation is modified accordingly. This improved fatigue crack growth approach is calibrated for two common material grades for railway axles, namely EA4T and EA1N, and implemented into crack growth assessment software tools