MECHANICAL BEHAVIOUR CHARACTERISATION OF DISSIMILAR WELDS

Abstract

Dissimilar metal joints between plates of mild steel and austenitic steel are widely used in various fields like nuclear power plant. It is seen from literature available that a significant number of operation failures in power plants have occurred due to occurrence of fracture in the dissimilar welded joints. Extensive fracture mechanics based studies are required for mechanical characterization of these dissimilar welds, So as to prevent any possible failures. Nowadays various methodologies are being used to evaluate the fracture behaviour, one such area of study is damage mechanics. Micromechanical Analysis is an extensively used tool in damage mechanics based studies to evaluate the fracture resistance as it conquers the problem of geometric dependency observed, while carrying out fracture tests on different types of specimens. Micromechanical Analysis is done considering nucleation, growth and coalescence of voids in a material following large scale plasticity, which is usually exhibited by materials before final fracture. Various types of models form the core of micromechanical analysis, one such model is GTN model. The present work deals with the experimental evaluation of GTN model parameters of weld zone and base materials of a dissimilar metal joint. These assessed parameters form the basis of the study of mechanical fracture behaviour of different zones ie. Weld zone and Base Materials. SEM Micrographs were taken for the various specimens and various loading conditions using the Scanning electron microscope and image analysis of these SEM micrographs has been carried out evaluate the various GTN parameters experimentally. The mechanical strength characteristics of the dissimilar welds have also been assessed by performing the tensile testing of weld zone and base materials of the dissimilar Joint.