An investigation on crack growth rate of fatigue and induction heating thermo-mechanical fatigue (TMF) in Hastelloy X superalloy via LEFM, EPFM and integration models

摘要

In this research, fatigue and induction heating thermo-mechanical fatigue (TMF) were performed on Hastelloy X superalloy in the small and large scale yielding in plane stresses mode. The crack growth rates were measured and formulated by fracture mechanics parameters. Furthermore, the fatigue life was predicted by employing resistance curves technique. The TMF behavior of this superalloy was investigated. The results demonstrated that in-phase loading TMF conditions lead to short fatigue life (more crack growth rate) at high strain amplitudes and temperatures up to 600 °C. For higher temperatures, the predominant damage was due to creep. A model based on damage contributions due to pure fatigue and cyclic creep has been presented for predicting TMF crack growth rates. Fracture mechanic method was used to suggest a model for fatigue part of TMF crack growth rate, while the temperature effects during TMF crack growth rate was considered to be due to cyclic creep. In addition the TMF crack healing or crack closure occur during application of induced eddy currents were investigated explicitly, as environmental effects of induction heating. The results show the higher current density in the crack tip area produced more heat and resulted in a significant rise in temperature. So it was concluded that the compressive thermal stress due to change of thermal expansion causes crack healing.