Effect of the stressed-state form on the failure kinetics and crack resistance of martensitic-aging steel. 2. Evaluation of the crack resistance of steel

Abstract

We have examined the effect of the stressed-state from on the energy transformations in a deformed material as related to the merger of defects and crack development. We have demonstrated that with an increase in the rigidity of the stressed stale, which is achieved by altering the configuration of the narrow throat section through the action of the original concentrator, the slope of the initial linear segment of the descending branch of the diagram (corresponding to the formation and growth of a separation crack within the material) increases, while the failure energy consequently declines. Particular attention is merited by the experimentally established relationship between the characteristics of crack resistance in the steel being studied, determined from the parameters of the descending segments of the complete strain diagrams, and the rigidity of the stressed state at the instant of crack initiation. At the limit, with the maximum possible constriction within the zone of crack initiation $$(K_0 = \sigma _m /\bar \sigma = 3.25)$$ the values of the determined characteristics tend toward the critical coeffcient KIc of stress intensity in the steel.