A Study of the Process Zone at the Crack Tip (Behaviour of the Voids at the Crack Tip of an Aluminum Alloy Specimen) : Solid-Mechanics, Strength of Materials

概要

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The plastic zone created at a crack tip is observed microscopically by using scanning electron microscope. CT specimens of 2017-T 4 and 7075-T 6 aluminum alloy are loaded onto or into the J_<IC> level and the crack tip regions are observed, so that the size of the process zone (PZ) and the fracture mechanism in it are estimated. The results are as follows: (1) In the process zone, the number of nucleated voids and their diameters decreased along the propagation direction of the crack. The size of PZ is about 100-130μm for 2017-T 4 and 50-150μm for 7075-T 6. (2) The diameter of the void which is nucleated at the inclusion in the process zone, increased with the increase in J value and became saturated just before separation; that is, at the nucleation of the dimple. (3) The coalescence of voids seems to occur in two ways. (4) For ductile fracture, as in 2017-T 4 and 7075-T 6, the crack tip is always blunted both on the blunting line and the R-curve.
一般社団法人日本機械学会の論文
1987-08-15