Prediction of ductile crack growth in a narrow gap Inconel dissimilar weld

Abstract

Predicting the behavior of large ductile crack propagation in a pipe is a major concern for many industries, especially in the nuclear industry. Leaning on the STYLE project, a European experimental program, tests are predicted using the local approach model of Gurson.The mock-up presents a narrow gap INCONEL (nickel base alloy) dissimilar metal weld joining a low alloy ferritic steel pipe and a 316L type stainless austenitic steel pipe. It was performed in the frame of the STYLE project funded by the European Commission (EC) (2010–2013). During the four points bending test on the mockup, the behavior of the crack growth was highly unexpected, and could not be deeply analyzed. The initial crack, located at the interface between the weld and the ferritic Heat-Affected Zone (HAZ), grew in the weld and deviated from it to finally reach the austenitic HAZ. A local approach modeling in order to explain the crack behavior has thus been performed, using the Gurson-Tvergaard-Needlemann (GTN) model.The characterization of the materials composing the weld was made through the STYLE project. Then, GTN parameters are identified using experimental results from the laboratory tests. The behavior of Compact Tension (CT) specimens and the pipe are then numerically predicted using finite element simulations. It is shown that the GTN model is able to catch the mechanical differences between the CT specimens and the pipe, providing a good prediction of the crack propagation during the four points bending test performed for the STYLE project.