2004 Fiscal Year Final Research Report Summary
Study on the Detection of Very Small Fatigue Crack and the Evaluatum of Fracture in the Welded Structures
| Project/Area Number |
15560695
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Naval and maritime engineering
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| Research Institution | NAGASAKI University |
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Principal Investigator |
KATSUTA Junichi NAGASAKI University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (20161078)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Monitoring / Welded Structures / Fatigue Damage / Fatigue Crack / Propagation of Fatigue Crack / Piezoelectric Ceramics / Paint for Crack Detection |
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| Research Abstract |
Integrity of welding parts is conventionally inspected by worker's eyes. It is very difficult to detect small fatigue crack less than several hundred millimeters by visual inspection. Existence of fatigue crack induces local corrosion, abnormal vibration, water leakage, etc. and finally fatigue crack propagation leads to catastrophic failure in welded structures. To secure the structural integrity, fatigue crack must be identified in early stage of crack propagation and must be repaired in maintenance.
The present report investigates a method to detection of the infinitesimal fatigue damage and evaluation using monitoring results in wrap-around welded joint and toe along weld bead.
And this report researches on the generation of the tensile and compressive plastic zones near the crack tip during fatigue crack propagation. And the role of each zone of the hysteresis loop denoting the relationship between loads and strains near the crack tip on fatigue propagation are studied by the fatigue crack propagation tests in the cases of constant amplitude loading, block amplitude loading and spike amplitude loading and the K& test.
As a result of this study, I verified the validity of the proposed monitoring method and clarified the effects of hysteresis loop near crack tip to fatigue crack propagation.
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