HOLOGRAPHIC STUDY OF DISPLACEMENT-FIELDS AND CRACK-PROPAGATION IN NOTCHED WOOD SPECIMENS SUBJECTED TO WEDGE-SPLITTING TESTS

Holographic interferometry is used to observe the components of displa cement fields and detect crack initiation and its subsequent growth in a number of notched specimens of wood subjected to wedge-splitting te sts. The technique allows for a continuous real-time observation of th e evolution of the deformation behavior of wood specimens with the inc rease in the notch opening. The displacement maps show the highly anis otropic and non-homogeneous nature of wood. It is found that in the pi ne wood specimen the force at which the crack begins is about two-thir ds of the peak load. The iso values of the in-plane displacement on th e same specimen type are computed numerically by applying finite eleme nt analysis based on the concept of linear fracture mechanics, to each step of crack opening. The numerically generated displacement maps ar e compared with those obtained by holographic interferometry on real s pecimens. The presence of monotonic and non-monotonic displacement beh avior of crack surfaces during crack growth in wood specimens is ident ified from the interferometrically obtained results. A discussion of t he phenomena is given based on numerical simulator.