1999 Fiscal Year Final Research Report Summary
Study on the dislocation emission around a crack tip by using high-voltage electron microscopy
| Project/Area Number |
10650651
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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 |
Physical properties of metals
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
HIGASHIDA Kenji Kyushu Univ. Dept. Mater. Sci. Eng., Associate Professor, 工学研究科, 助教授 (70156561)
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| Co-Investigator(Kenkyū-buntansha) |
MORIKAWA Tatsuya Kyushu Univ. Dept. Mater. Sci. Eng., Associate Professor, 工学研究科, 助手 (00274506)
ARAMAKI Masatoshi Kyushu Univ. Dept. Mater. Sci. Eng., Research Associate, 工学研究科, 助手 (50175973)
ONODERA Ryuta Kyushu Univ. Dept. Mater. Sci. Eng., Professor, 工学研究科, 教授 (40038021)
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| Project Period (FY) |
1998 – 1999
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| Keywords | fracture / crack / dislocation / HVEM |
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| Research Abstract |
Dislocation emission from a crack tip is most fundamental process to understand the toughening mechanism of crystalline materials. In the present study, dislocation emission from the tip of a crack in MgO thin crystals has been investigated based on the geometry of crack tip dislocations observed using high voltage electron microscope(HVEM). In-situ experiments in the HVEM using tensile holder were also made. The effect of crack tip shielding due to the dislocations was also calculated using 3-D Buekner-Rice weight function theory for crack-dislocation interaction.
Dislocation image analyses showed that dislocations ahead of the crack tip observed in the present study were almost right-handed(R-H)screw dislocations lying on the(011)plane, while in the crack wake many of the dislocations were left-handed(L-H)on the (011)plane. Formation of such dislocation configuration can be understood by the emission of dislocation loops from sources at a crack tip, where crack jogs, crack kinks and intersections of crack planes with free surfaces may act as significant sources for dislocation emission. 3-D stress analysis exhibits that the largest component of crack tip stress intensities induced is mode I shielding type, and that mode II component is not negligible in the present case, suggesting the induction of the crack tip shielding for the mixed stress modes of I and II through the dislocation emission from the sources indicated above.
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Research Products
(4 results)
