Physical Simulation of a Duplex Stainless Steel Friction Stir Welding by the Numerical and Experimental Analysis of Hot
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FRICTION stir welding (FSW) is a solid-state joining technique, which has been object of intense research in the last few decades, not only due to the good quality of the resulting joints but also for eliminating solidification-related problems, such as voids, cracks, and segregation.[1] Industrial use of FSW is still focused in aluminum alloys, especially for the aeronautic, marine, and ground transportation fields. However, many researchers have proved the feasibility of applying FSW to joining steel,[2] stainless steel,[3] and titanium alloy,[4] for example. Despite the intense research, FSW still requires a better understanding on the thermomechanical history to which the material is subjected during welding. Some EDUARDO BERTONI DA FONSECA, formerly M.Sc. Student with the School of Mechanical Engineering, University of Campinas, Campinas, SP, Brazil, is now M.Sc. Graduate with the Brazilian Nanotechnology National Laboratory LNNano, CNPEM, Campinas, SP, Brazil. Contact e-mail: [email protected] TIAGO FELIPE ABREU SANTOS, Professor, formerly with the Brazilian Nanotechnology National Laboratory LNNano, CNPEM, and the School of Mechanical Engineering, University of Campinas, is now with the Department of Mechanical Engineering, Federal University of Pernambuco, Recife, PE, Brazil. SERGIO TONINI BUTTON, Professor, is with the School of Mechanical Engineering, University of Campinas. ANTONIO JOSE RAMIREZ, Professor, formerly with the Brazilian Nanotechnology National Laboratory LNNano, CNPEM, is now with the Department of Materials Science and Engineering, The Ohio State University, Columbus, OH. Manuscript submitted February 5, 2015. Article published online July 6, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A
researchers were able to measure the thermal history during welding, providing insightful relationships between the resulting microstructure and the temperatures and cooling rates measured.[4,5] However, true strain and strain rate of the material are not yet fully understood. Finite element method (FEM) and computational fluid dynamics (CFD) were both applied to address this issue, with incongruous results.[6] FEM simulations are limited in true strain and require remeshing after large deformation. On the other hand, CFD simulations consider the material as a high-viscosity fluid, which results in high strain rates and few data on true strain. As shown in Table I,[7–16] reported values of strain and strain rate calculated via CFD and FEM oscillate in a wide range. Physical simulation consists in observing the resulting microstructure of a material after processing and trying to reproduce it by means of controlled tests. Because different thermomechanical paths may lead to similar microstructures, knowledge on the system being studied is instrumental. Forest et al. employed hot compression tests to simulate HSLA-65 steel friction stir welding and reported limitations to the experimental technique.[17] On the other hand, researchers who employed torsion tests for physical simulation of F
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