A torsional fatigue model based on M-integral in DD6 nickel based alloy

not-yet-known not-yet-known not-yet-known unknown In this paper, an innovative torsional fatigue model is investigated based on the concept of M-integral in DD6 nickel based alloy. It is demonstrated that the Δ M/ AP as the driving force of fatigue damage can well describe the kinetics of fatigue damage evolution of the DD6 nickel based alloy under torsional fatigue loading. The new form of fatigue damage evolution rate ( dVD/dN) and fatigue driving force (Δ M/AP) are introduced. For the experimental study, the change of the total potential energy ( CTPE) is introduced to measure the value of M-integral. The fatigue tests show that the torsional fatigue damage evolution can be divided into three stages from the initiation and aggregation of microcracks to the growth of macrocracks. During stage I, the relationship between VD and fatigue number N satisfies a quadratic function, and the relationship between dVD/dN and ∆M/ AP is logarithmically linear independent of the load size. During stage II, VD and fatigue number N satisfy a linear relationship. During stage III, macroscopic cracks/pores appear, and the damage evolution rate begins to increase until fracture. It is concluded that the proposed fatigue model based on M-integral can accurately predict the torsional fatigue lifetime of the DD6 nickel based alloy.