| Project/Area Number |
13650095
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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 |
Materials/Mechanics of materials
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| Research Institution | Nagasaki University |
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Principal Investigator |
IMAI Yasufumi Nagasaki University, Faculty of Engineering, Professor, 工学部, 教授 (50039682)
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| Co-Investigator(Kenkyū-buntansha) |
MOTOMURA Fumitaka Nagasaki University, Faculty of Engineering, Research Associate, 工学部, 助手 (40274625)
SAIMOTO Akihide Nagasaki University, Graduate School of Science and Technology, Associate Professor, 生産科学研究科, 助教授 (00253633)
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| Project Period (FY) |
2001 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2003: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 2002: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2001: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | Unsteady thermal stress / Crack extension / Brittle material / Thermal stress cleaving / Crack bend condition / Body force method / Inclination of crack face / Compression center / き裂分岐 |
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| Research Abstract |
Experiments reveal that when a heat source moves along a gentle curve, a thermal crack can follow its locus under appropriate cleaving condition. Hence, the thermal stress cleaving along a curvilinear path is possible just the same as the straight cleaving.
An edge crack was extended in a rectangular glass plate by an exposure of CO_2 laser. When the heating path was abruptly bent, a thermal crack did not follow exactly the heating locus but extend along an inscribed circle to the locus. Moreover, an acceleration and deceleration of crack extension was observed. These behaviors of crack extension were numerically simulated. The timing and path of crack extension was confirmed to be good consistent with the experiment. In the simulation, a crack was assumed to bend so that the mode II stress singularity disappears at the extended crack tip. This condition takes an influence of T-stress into account and a smooth crack path was achieved.
A radial pre-crack was prepared at the periphery of circular glass plate and exposure of COQ laser was moved along a circular arc inside the periphery. The crack followed after the heat over a whole circle with, keeping the same distance and processing of a diameter-reduced plate was achieved. The same stress singularity may arise at the crack tip irrespective of the crack length. This was confirmed by FEM analysis. Inclination of crack faces was also observed, which was expected from FEM analysis because a crack tends to deviate toward the free edge due to mode II stress singularity and may also extend normal to the principal stress which acts tilting to the plate surface there.
If an estimation of stress singularity due to compression center is prepared beforehand, thermal stress singularities under any experimental condition can be estimated using the corresponding quasi-steady temperature field.
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