DefinePK

Abstract

Fracture behavior of aluminum alloys under mixed mode (Mode I+II) loading was studied. Fracture tests were carried out on A2024-T351 aluminum. Compact-tension-shear specimen was employed and angle between loading axis and the crack surface was varied from 90°(mode I) to 0°(mode II). The crack extension (crack initiation and propagation) behaviors observed by a video microscope. Under a load with relatively high mode II components, the shear type crack initiation preceded the opening type crack propagation. Final fracture was occurred by shearing instability in the pure mode II loading. The critical values of stress intensity factors at crack initiation under mode II dominant conditions become smaller than those predicted by the maximum hoop stress criterion. Shear type fracture instability occurs at the ligament when the shear stress is over the shear strength of the material. It was also found that the rolling direction and a small holes existing ahead of the crack-tip influence the crack extension behavior.