Estimation of the energy of crack propagation in different zones of a welded joint by the local technique

The fatigue damage of a material generally goes through of an incident or a heterogeneity producing a local stress concentration. The growth of crack is related to the existence of a plastic zone at the crack tip and accompanied by an energy dissipation. The objective of this study is to analyze the evolution of the energy at the crack tip during the propagation of a crack in a welded joint. In order to determine the energy nearest the end of the crack in the plastic zone, we used microhardness measurements. The estimate of the total strain in each measurement point was determined by a polynomial relation between Hv and _t/2 . After the determination of the average strain, the total energy in each zone was deducted. The higher value of this energy is in the Weld Metal, it is more lower in the Base Metal and even lower in the Heat Affected Zone.