Effect of strain history and load cycle asymmetry on the fracture toughness characteristics of alloy VT9

1. It was shown that the unidirectional accumulation of plastic strain during low-cycle loading leads to a reduction in the critical fatigue fracture toughness of alloy VT9. 2. The process of sign-changing reversible deformation does not change the critical value of the fatigue fracture toughness of alloy VT9, regardless of the strain amplitude. 3. The load-cycle asymmetry coefficient Rσ significantly affects both the amount of unidirectionally accumulated plastic strain and the critical stress intensity factor in the low-cycle fatigue region, lowering the value of the latter in the transition from pulsating loading (Rσ = 0) to symmetrical loading (Rσ = -1).