Experimental and Discrete Dislocation Dynamics Approach to Initiation of Cleavage Fracture under Short Pulse Loads

Abstract

Mode I crack initiation properties under stress intensity pulses with durations of 25, 50 and 100 µs are investigated by experiment and discrete dislocation dynamics. The cleavage fracture initiation is examined under the consideration of the pile-up of dislocations against an obstacle ahead of the crack tip and the coalescence of piled-up dislocations. In the experiment, under very short pulse loads with the duration of less than 50 µs, the dynamic fracture toughness, K Id remarkably increases and the crack tip opening displacement is closely correlated with K Id . The numerical results are compared with the experimental ones in reasonable agreement.

Numerical approach to dimple fracture under very short pulse loading

“…Following the current specimen configuration, the main crack length 2a is 40 mm in x-direction. In the model, a slip system is considered at only one crack tip, because effects of dislocations on a slip system at the other crack tip could be negligibly small from estimation from simple calculation of stresses at a position 40 mm distant from a dislocation in an infinite plane as mentioned in the previous work [7]. Therefore, the main crack tip plasticity is represented by only two arrays of discrete edge dislocations.…”

“…The effect of impulsive loading duration on the plasticity ahead of crack tip has been successfully investigated by discrete dislocation dynamics (DDD) [6]. This DDD model has been also extended to cleavage fracture under short pulse loading [7]. This work aims to obtain the insight into time effect on the initiation of dimple fracture subjected to short pulse loading.…”