1995 Fiscal Year Final Research Report Summary
Study on Fatigue Strength Design of Welded-joint under random loading
| Project/Area Number |
05452312
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
海洋工学
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| Research Institution | University of Tokyo |
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Principal Investigator |
MACHIDA Susumu Univ.of Tokyo, Faculty of Engineering, Professor, 大学院・工学系研究科, 教授 (70010692)
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| Co-Investigator(Kenkyū-buntansha) |
KANEDA Shigehiro Univ.of Tokyo, Faculty of Engineering, Associate, 大学院・工学系研究科, 助手 (90010892)
YOSHINARI Hitoshi Univ.of Tokyo, Faculty of Engineering, A.Professor, 大学院・工学系研究科, 助教授 (20167737)
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| Project Period (FY) |
1993 – 1995
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| Keywords | Structual model specimen / "Storm Model" block loading / Fatigue assessment / The foatigue crack opening / closere phenomenon / "High-precision Compliance Mesurement System" / The effect of past loading history / Compliance / Change rate of compliance / RPG load |
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| Research Abstract |
The fatigue crack propagation tests using structural model specimens are carried out under constant loading and the "Storm Model" block loading. Also study on the reliability of the current fatigue assessment methods and the application of fracture mechanics to fatigue assesment are made.
Moreover, for the purpose of proper understanding of the fatigue crack opening/closure phenomenon, detailed observations of change in the strain near fatigue crack tip using "High-precision Compliance Measurement System" and CCT specimens are carried out.
As a result, the following four main points are obtained.
1) The fatigue assessment based on S-N diagram obtained from constant loading fatigue tests can not take into account the effect of past loading history. So the accuracy of this assessment turn out to be extremely lowered under some loading patterns. (for example, the loading pattern in which retardation is remarkable)
2) The fatigue assessment based on S-N diagram obtained form block loading fati
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gue tests can take into account the effect of the loading pattern within one block. So the accuracy of this assessment is higher than the above mentioned method 1) but it even can not take into account the effect of interaction of different block, then further high accuracy of this assessment depend on how quantitatively the block loading model reflects the actually loading pattern.
3) The fatigue assessment based on fracture mechanics can take into account the effect of past loading history, so the accuracy of this assessment could be higher than above mentioned method 2) if proper fatigue crack propagation model was established. Also further high accuracy of this assessment depend on proper understanding of the fatigue crack propagation behavior especially of the fatigue crack opening/closure phenomenon.
4) Successful measurement of the hysteresis curve of load vs.strain with high accuracy was made and, introducing the curve of compliance and the change rate of compliance during one cycle we succeeded in the automatically measurement of the Closing load and RPG load. Less
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Research Products
(24 results)
