2005 Fiscal Year Final Research Report Summary
A Study on the Micro-mechanisms for the Crack Initiation and Growth Ductile Fracture.
| Project/Area Number |
15360458
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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 |
Naval and maritime engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KANEDA Shigehiro The University of Tokyo, Graduate School of Engineering, Research Associate, 大学院・工学系研究科, 助手 (90010892)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAHASHI Jun The University of Tokyo, Graduate School of Engineering, Associate Professor, 大学院・工学系研究科, 助教授 (10222085)
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| Project Period (FY) |
2003 – 2005
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| Keywords | ductile fracture / stress triaxiality / SM490B / prestrain / AE / dimple / cleavage |
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| Research Abstract |
Relations between equivalent plastic strain and stress triaxiality were studied by fracture tests of round notched bar tensile specimens. The critical ductility curves represented by above-described relationship were constructed by fracture test results and FEM analyses.
Base material used in the tests is as received SM490B steel. The yield and ultimate strength at room temperature were 353 and 543 MPa respectively. Compressive prestrain up to 30% plastic strain was given in some specimens. The effects of prestrain and notch radius on ductile fracture initiation behavior were investigated and observed the fractured surface by scanning electron microscope (SEM).
Damage initiation behavior during the tests was detected by use of AE sensors attached to the specimens. It is shown that prestrain leads to cleavage micro-cracking and reduces ductility. From SEM-fractographs, it is found that fractured surface is 100% dimple in as-received material, in the meantime, tiny amounts of cleavage in 10% prestrain material, up to 100% cleavage in 30% prestrain material, respectively.
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