USING LASER REFLECTIVE HOLOGRAPHY AND SPECKLE INTERFEROMETRY TO INVESTIGATE THE THREE-DIMENSIONAL DISPLACEMENT FIELD AROUND A CRACK TIP FOR A CENTRALLY-CRACKED STRIP.

The strips are made of aluminum alloy LY12-CZ, and are subjected to uniaxial tension and large-scale yield conditions. The following results are described: (1) the change in the size and contour of the plastic zone when the load is increased by steps; (2) the curve of load P versus deformation DELTA within a fixed gauge length; (3) the curve of the crack-opening displacement (COD) versus the axial load; (4) the critical crack-opening displacement (COD*) when the propagation becomes imminent; (5) the in-plane displacement distribution around a crack tip; and (6) the strain distribution and singularity in the near-tip region.