Variation in ratio of diametral strain to axial strain during multistep cycling and cycling with compression hold of Cr-Mo-V steel at elevated temperature

Cr–Mo–V rotor steel has been studied using multistep tests, in axial strain control using steps of increasing amplitude, with and without holds in tension, and in one constant amplitude test with holds in compression. The results of the multistep tests confirm that the variation with cycles in the ratio of diametral strain to axial strain (a ‘Poisson's ratio’ in low-cycle fatigue) is insignificant at low strain amplitudes, but considerable at higher amplitudes. The results emphasize particularly the decline of this ratio at high amplitude in the early stages of tests with or without tensile holds. The absence of this decline in the test with compression demonstrates that the decline in the ratio for other waveforms is induced by damage peculiar to tensile deformation mechanisms, which eventually lead to easily observable cavitation.