| Project/Area Number |
14350519
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
船舶工学
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| Research Institution | National University Corporation Yokohama National University |
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Principal Investigator |
SUMI Yoichi Yokohama National University, Graduate School of Engineering, Professor, 大学院・工学研究院, 教授 (80107367)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAMURA Yasumi Yokohama National University, Graduate School of Engineering, Associate Professor, 大学院・工学研究院, 助教授 (50262407)
WADA Taishi Yokohama National University, Graduate School of Engineering, Associate Professor, 大学院・工学研究院, 助教授 (60359700)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥14,600,000 (Direct Cost: ¥14,600,000)
Fiscal Year 2004: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2003: ¥10,100,000 (Direct Cost: ¥10,100,000)
Fiscal Year 2002: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Keywords | corroded plate / surface geometry / elongation / ultimate strength / similarity law / size effect / stress analysis / structural integrity / 強度試験 / 変形能試験 / 表面形状計測 / 任意表面形状加工 / CAD・CAM / 寸法効果 / 腐食形状再現加工 / ランダムプロセス / 不規則表面形状 / パワースペクトル / 形状数値生成 / 表面形状加工 / 摂動法 |
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| Research Abstract |
Although the fracture energy absorbed by a corroded plate may be considerably reduced due to its localization of plastic deformation during the fracture process, experimental and numerical investigations have not clarified the behavior in details yet. In the present study, experimental investigations are made by reproducing steel plates having surfaces similar to those due to actual corrosion, where the surface geometries are generated by a CAD system and steel plates are machined by a CAM system to simulate corroded surfaces. This approach is possible because the reductions of ultimate strength and elongation are mainly caused by the effects of the undulated surface geometry, and not because of the chemical process of corrosion. Having completed the CAD/CAM system, simulated fracture tests of corroded plates can be carried out very efficiently without the corrosion process to prepare the test specimens.
Three kinds of series tests have been carried out with regard to the ultimate strength and the deformability of corroded plates ;
1.tests of similarity for pitting corrosion,
2.tests to examine the effects of pitting patterns,
3.tests to examine the sample-size effects of test plates with general corrosion.
The main conclusions are as follows ;
1.Considerable reduction of deformability is observed for plates with pitting and general corrosion.
2.Different size coupons with the same geometries give almost the same results so that similarity law exists for a certain range of the size of test specimens.
3.Isolatedpits show considerable reduction of elongation in comparison with those due to densely existing pits.
4.With regard to the size effect of test specimen, smaller coupons exhibit higher ultimate strength and elongation. This clear tendency may suggest the needs of further research to find out the proper test procedure in order to estimate the mechanical properties of corroded plates of an actual ship.
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