Three-Dimensional Thermomechanical Simulation and Experimental Validation on Failure of Dissimilar Material Welds
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TRODUCTION
DISSIMILAR material weld (DMW) joints between low-alloy steel and 304 austenitic SS are used as the primary heat-transport piping system in typical boiling water reactors in nuclear power plants.[1] The nozzle piping material is ASTM A508 Grade 3 Class I low-alloy ferritic steel (LAS), and the pipelines connecting the material are SA312 Type 304LN austenitic SS (304LN SS). The transition joint exhibits good strength and corrosion resistance under operating conditions.[2] Due to the complex microstructure and chemical changes across the fusion boundary, these DMW experiences crack during service. Probable reasons for component failure were discussed in detail elsewhere.[3] During the fabrication of joints, one of the most preferable welding consumables is Ni-base alloys, as they have great potential over conventional austenitic
R. SANTOSH, Master Tech Student, and J. KORODY, Professor, are with the Department of Mechanical and Manufacturing Engineering, Manipal Institute of Technology, Manipal 576104, India. S. K. DAS, Principal Scientist, G. DAS, Senior Principal Scientist, and M. GHOSH, Senior Scientist, are with the Materials Science & Technology Division, CSIR_National Metallurgical Laboratory, Jamshedpur 831007, India. Contact e-mail: [email protected] S. KUMAR, Scientific Officer D, and P. K. SINGH, Scientific Officer G, are with the Reactor Safety Division, Bhaba Atomic Research Centre, Mumbai 400085, India. Manuscript submitted November 9, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
steel.[4–8] These alloys have a coefficient of thermal expansion between ferrite and austenite. They play a major role in restricting the carbon diffusion through the fusion boundary from the low-alloy steel side. Simulation of these dissimilar material joints subjected to operating conditions may provide knowledge about the condition of the materials during service with respect to stress field, temperature distribution, heat generation, and deformation. In this respect, ANSYSbased simulations were attempted earlier in an effort to understand the phenomena. Basic finite-element models for structural and heat-transfer processes were given by Ramamurthy[9] and Chandraptla and Belegundu.[10] Welding simulation using the finite-element method (FEM) was developed for figuring heat flux in ellipsoid and double ellipsoid models. In a different endeavour, computations were used with a nonlinear transient finite-element heat flow program for stress analysis of welds.[11] In this respect, Gaussian distribution models were developed for application in laser, electron, and plasma welding.[12] Akella et al. investigated laser beam joining of similar materials and used constant heat flux with a Gaussian beam source.[12] A contour method for measuring residual stresses in 319L SS plate was also proposed by a different group.[13] Sachin et al. carried out a two-dimensional (2-D) analysis for copper to steel dissimilar metal joint with FORTAN (IBM).[14] They investigated the residual stress distribution in the transverse direction of the weld. It
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