The energy‐based multistage fatigue crack growth life prediction model for DRMMCs

Abstract

A complex closed form expression for the multistage fatigue crack growth life has been developed to predict the fatigue life of discontinuous reinforced metal matrix composites. The multistage fatigue crack growth model includes the microstructural features of composite such as aspect ratio, volume fraction of reinforcement, constraint of fibre in the matrix, and interfacial bonding strength. It characterizes the fatigue damage evolution in various stages of crack nucleation/initiation and the growth of crack culminating in failure. A fatigue crack initiation model is presented, using energy balance equation, considering the nucleation process of phase transformation. The short crack growth life is estimated using the dependency of cyclic crack‐tip opening displacement that is directly correlated with the fatigue crack growth rate whereas the long crack growth life is evaluated using Li and Ellyin model. The sensitivity analysis of crack initiation model is performed to provide in‐depth knowledge on the mechanistic aspect. The sensitivity analysis shows that the little variation in the parameters “cyclic strain hardening exponent” (n′), “cyclic strength coefficient” (K′), and short crack length (asc) significantly affects the total fatigue crack growth life. It is observed that reinforcement increases the cyclic plastic deformation level and cyclic plastic zone size near the crack tip, under the total strain‐controlled conditions. The effect of total fatigue crack growth life is found to be significant in low cycle fatigue applications.