1988 Fiscal Year Final Research Report Summary
Study on Improvement of Fatigue Strength of Welded Joints and Members
| Project/Area Number |
62420048
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
溶接工学
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| Research Institution | Nagoya University |
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Principal Investigator |
KUTSUNA Muneharu Nagoya University, Faculty of Engineering, Assistant Professor, 工学部, 講師 (20153299)
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| Co-Investigator(Kenkyū-buntansha) |
MASUMOTO Isao Nagoya University, Emeritus Professor, 名誉教授 (70022978)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Welded joint / Fatigue strength / Treatment for weld toe / Laser remelting / Below-A_1 heating treatment / Epoxy resin coating / Mild steel / High strength steel / 交差ビーム回転光学系 |
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| Research Abstract |
It is generally known that the fatigue strength of welded joint is less than that of base plate due to stress concentration at the weld toes and the geometry of the weld reinforcement. The following methods may be used for improving the fatigue strength by reducing the severity of notches at weld toe; (1) Peening and /or grinding the curvature surface at the weld toe (2) TIG are remelting of weld toe or weld reinforcement (3) Plastic coating the welds and base plate at the weld toes (4) Rapid cooling after hot galvanizing or heating below the A_1 point of steel In present work the possibility of laser remelting of weld toes for improving the fatigue strength of CO_2 arc welded joints of mild steel(SM41B) and high strength carbon steel (SM50A and SM58Q) were investigated using 2 KW CO_2 laser facility with KCl lens and Intersecting and Rotating Optical System( IROS). And I-shape steel bar was used to assess the fatigue strength of welded member after laser remelting, epoxy resin coating and below-A_1 heating of weld toes. The experimental results on the effect of laser remelting of weld toe on the fatigue strength of carbon steels are summarized as follows: 1) The fatigue strength of steel welded specimen was remarkably increased by laser remelting due to increase to toe radius and changes in microstructures. The improvement was 70% for SM41B steel 877.8% for SM50A and 86.4% for SM58Q. 2) The fatigue strength of I-shape welded member was not improved by laser remelting because of inadequate remelting condition.
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