Thermo-mechanical fatigue damage behavior for Ni-based superalloy under axial-torsional loading

Fatigue–oxidation–creep damage model under axial-torsional thermo-mechanical loading

“…Thus, for oxidation damage calculation, von Mises criterion can be used to calculate the equivalent stress under proportional and non-proportional multiaxial loadings during the calculation process. In addition, the use of von Mises equivalent stress also means that the action of compressive stress on the oxidation damage is the same as that of tensile stress, which is consistent with the research on oxidation damage behavior in Li et al (2018).…”

“…For example, the failure life under MIPTOP 90 loading (1063 cycles) is more than two times of that under MIPTOP 180 loading (457cycles). Under MIPTOP 180 loading, the compressive stress corresponding high temperature cannot induce creep damage (Kraemer et al, 2017;Li et al, 2018;Miller et al, 1992), thus the creep damage can be negligible on this loading condition, which can also be proved by the transgranular fracture under MIPTOP 180 loading, as shown in Figure 6. The situation is the same under MIPTOP 90 loading, that is, the creep damage can also be ignored under MIPTOP 90 loading.…”

“…In this investigation, uniaxial TMF tests, AT-TMF tests, and isothermal axial-torsional low-cycle fatigue (AT-LCF) tests were carried out on the Ni-based superalloy GH4169, and the experimental details are described in Li et al (2018Li et al ( , 2019 and Shang et al (2007). For the uniaxial TMF tests, the thermal phase angle (between the axial mechanical strain and the temperature) needs to be controlled.…”

“…Moreover, the oxide layer is formed on the crack growth surface with the growth of fatigue microcrack, thus oxidation damage can also lead to transgranular fracture. However, the creep damage can induce the intergranular fracture, which can drastically decrease the fatigue life (Guth et al, 2015;Li et al, 2018). Therefore, in order to accumulate different types of damages correctly, this article proposes that the intergranular damage should be equivalent to the transgranular damage, that is, the intergranular creep damage needs to be equivalent to the transgranular damage before accumulating with the fatigue and oxidation damages.…”

“…Moreover, the damage behavior is more complex under axialtorsional thermo-mechanical fatigue (AT-TMF) loading. The creep damage can be induced by the tensile stress at high temperature, and be increased by the shear stress at the same time (Li et al, 2018). The compressive stress corresponding high temperature cannot contribute to the creep damage under TMF loading (Kraemer et al, 2017;Miller et al, 1992).…”