中性子回折法による高張力鋼突合せ溶接材の残留応力評価(<特集>X線材料強度)

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Welding technique is utilized for many structures as a technique jointing some components. The residual stress, however, induced by welding affects the mechanical properties or failure mechanism. Therefore, it is important to know the residual stress states near the weld zone accurately for improving the reliability of structures. In this study, the residual stress distributions of a double-V butt weld plate were measured using neutron diffraction technique, and the generating mechanism of residual stresses was also discussed. The double-V butt weld plate was fabricated by using Ni-Cr steel (SNC631) which is one of the high tensile strength steel, and its residual stress distributions were measured using diffractometer for residual stress analysis (RESA) located in JRR-3 at Japan Atomic Energy Research Institute. At first, some coupon samples were cut from weld plate in order to measure the lattice constant in stress-free condition. As a result of measuring the lattice constant using coupon samples, the lattice constant was increasing near the weld zone because of some phase transformations such as martensitic transformation due to weld process. Secondly, the residual stress distributions of weld plate were measured with αFe110, αFe200, and αFe211. The residual stress distributions evaluated by each diffraction were almost the same profile throughout the welded plate since no plastic strain was observed near the weld zone. The residual stress near the weld zone was tensile stress of almost half value of yield strength of Ni-Cr steel. It might be reasons why we obtained these results that the tensile residual stresses did not reach yield strength since the transformation expansion of high tensile strength steel is larger than that of mild steel and the tensile residual stress starts to generate at low temperature. It was, therefore, confirmed that the neutron stress measurement can determine the residual stress distribution of welded sample of high tensile strength steel without consideration of the plastic deformation.
社団法人日本材料学会の論文
2005-07-15

中性子回折法による高張力鋼突合せ溶接材の残留応力評価(<特集>X線材料強度)

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