ON THE NATURE OF THE INCUBATION PERIOD OF DELAYED RUPTURE OF QUENCHED STEEL.

The influence of the level of applied stress is investigated with regard to the delayed rupture of quenched steel. Loading above a certain level of stress causes delayed rupture. This is defined as the threshold stress sigma //t//h of delayed rupture. It is shown that sigma //t//h is near the elasticity limit of the steel. If quenched steel is held during the incubation period at a stress above the threshold, the recovery process is not so intensive and the steel exhibits an increased tendency to delayed rupture. Soaking in the incubation period presumably causes relaxation of residual intrinsic microstresses by the formation of defects of the microcrack type.