Effect of frequency and low temperatures on the failure characteristics of steel 15G2AFDps in the low-cycle region

Abstract

1. In the quasistatic region of low-cycle fatigue, the character of microfailure of steel 15G2AFDps does not change with a change in temperature from +20°C to −140°C and a change in frequency from 0.3 to 15 Hz, and may be classified as a ductile transcrystalline fracture with signs of intergranular fracture. 2. In fatigue failure in the low-cycle region, a crack is initiated on the surface of the specimen and is propagated into the metal layer through grain bodies. 3. Specimen fractures at temperatures below −100°C occur in a quasibrittle manner, but occur in a ductile manner at higher temperatures. Consequently, there is a correlation between the temperature dependence of the value of crack opening Δp and the change in the microrelief of the surface in the fracture zone. 4. The sharp drop in the value of Δp for steel 15G2AFDps in the temperature range −80 to −100°C is related not to a brittle, but to a quasi-brittle transition, and the brittle transition temperature for steel 15G2AFDps is below −140°C.