Local Ratcheting Response in Dissimilar Metal Weld Joint: Characterization Through Digital Image Correlation Technique
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JMEPEG DOI: 10.1007/s11665-017-2919-9
Local Ratcheting Response in Dissimilar Metal Weld Joint: Characterization Through Digital Image Correlation Technique Surajit Kumar Paul, Satish Roy, S. Sivaprasad, H.N. Bar, and S. Tarafder (Submitted April 3, 2017; in revised form August 5, 2017) Ratcheting fatigue behavior of different alloys and their weld joints has been a topic of interest in the past few decades. However, little information is available about the ratcheting response in different zones, when a composite weld section is subjected to asymmetric loading cycle. This work aims at understanding the local ratcheting response in various zones of a dissimilar metal weld (DMW) joint. Digital image correlation technique has been used to measure local ratcheting strain components of a DMW joint. Accumulation of ratcheting strain in various zones of a DMW joint was found to be different, harder region accumulating negligible and softer region accumulating larger local ratcheting strain. Fatigue crack initiation or neck formation occurred in soft region owing to high ratcheting strain accumulation. Keywords
digital image correlation, dissimilar metal weld joint, local strains, progressive strain accumulation, ratcheting
1. Introduction Dissimilar metal welds (DMW) are commonly used in pressurized water and boiling water nuclear reactors in connections between the ferritic components and austenitic piping systems. These welds are typically fabricated by using either austenitic stainless steels or nickel base alloys as weld consumables. The joining of two entirely different materials can lead to a more complex microstructural region in the weld interface, thereby leading to regimes of significantly different mechanical properties. Depending upon the welding procedure and the consumables employed, the variations in the local microstructural conditions and the mechanical properties thereof can be more complicated. As the structural safety is governed by the weakest link, it is important to ensure that unwarranted failure does not take place. This requires a careful evaluation of the mechanical behavior in all the regions of the welded component. The in-service load fluctuations can lead to accumulation of fatigue damage. The large difference in the plastic deformation behavior between ferritic and austenitic steels in DMW joint may also lead to a significant strain concentration in the interface and liable to act as a source of localized damage, leading to an early crack initiation. Understanding the cyclic deformation behavior of different regions of DMW joint is thus imperative. Depending upon the type of loading condition, low Surajit Kumar Paul, Fatigue and Fracture Group, CSIR-National Metallurgical Laboratory, Jamshedpur 831007, India; and Department of Mechanical Engineering, Indian Institute of Technology Patna, Bihar 801103, India; and Satish Roy, S. Sivaprasad, H.N. Bar, and S. Tarafder, Fatigue and Fracture Group, CSIR-National Metallurgical Laboratory, Jamshedpur 831007, India. Contact e-mail: paulsurajit@ yah
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