Mechanical properties of steel 20 at small deformations

Abstract

The elastic hysteresis and residual deflections of samples made of steel 20, which correspond to the model of a thin rigid round plate pinched over the contour, have been investigated. It has been shown that annealing of the samples at 470 and 670 K weakly affects these characteristics, while after complete annealing (1170 K), the aging of steel 20 for three days is accompanied by a decrease in amplitude ωh of the elastic hysteresis by ∼20%. A postulate that there is no elasticity limit of metals, below which residual deformation would be absent, has been confirmed experimentally. It has been shown that, based on the values of ωh, the ultimate strength of metals can be estimated acting on the samples by stresses smaller than the yield stress by an order of magnitude. A giant increase (by a factor of ∼2.5) in ωh has been found after a prolonged (for 2 months) aging of steel 20 after the diffusion of hydrogen from it, which indicates the corresponding decrease in its cyclic longevity.