Study of Sensitivity of Damage Parameters c₁, c₂, c₃ and c₄ on FB2 Material Under Low Cycle Fatigue Test

Many engineering components in power generation plants, gas turbines and petro-chemical industries operating at high temperatures undergo creep-fatigue loading conditions and they are almost invariably submitted to static, combined cycle loading or even both simultaneously. The failure can, therefore, be due to net section rupture, crack growth or a combination of both. To assess the life of such components, fracture mechanics assessment models are required throughout the entire life of the components in order to avoid potential catastrophic failures in the future. Some materials are designed with high thermal gradients to operate at high temperature environments and they are subject to cyclic strains that are produced thermally and mechanically and under these cyclic temperatures and strains, thermo-mechanical fatigue (TMF) damage occurs which will lead to the initiation of cracking and subsequent crack growth. In this paper a novel sensitivity analysis of the damage parameters c₁, c₂, c₃ and c₄ on hysteresis loops has been used based on Taguchi method in conjunction with the numerical and experimental investigation of low cycle fatigue life of 9Cr steel to predict the damage under low cycle fatigue.