Fatigue Damage Assessment of Tensile Specimen considering Bilinear Damage Process

Abstract Fatigue damage assessment in design phase is an important component of structural health monitoring and is conventionally assessed using Linear Damage Rule. The effect of sequence of loading and bifurcation of the fatigue damage process has not been considered in Miner’s Linear Damage Rule. This method has been improved considering damage curve in crack initiation and crack propagation stage. The transition point from crack initiation to crack propagation known as ‘knee-point’ plays an important role in the analysis. This method is further modified by considering opening stress in crack propagation stage. The effect of sequence of loading has also been considered in the proposed methodologies. The method is illustrated with an example of dynamically induced stress in a slender bar under uniform axial time varying force. Various parameters which affect the fatigue damage of the bar like stress range, excitation frequency and damping coefficient are also studied. It is found that conventional Miner’s Linear Damage Rule estimates higher damage index compared to the present method incorporating bilinear stages of fatigue damage process.