1991 Fiscal Year Final Research Report Summary
Study on damage-free processing of brittle materials (ceramics)
| Project/Area Number |
02452104
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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 |
機械工作
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| Research Institution | Chiba University |
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Principal Investigator |
YOSHIDA Yoshitaro Chiba Univ. Fac. Eng. g. Prof., 工学部, 教授 (80174960)
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| Co-Investigator(Kenkyū-buntansha) |
WTANABE Takehiro Chiba Univ. Fac. Eng. g. Ass. Prof., 工学部, 助教授 (30009691)
SAITOH Yoshio Chiba Univ. Fac. Eng. g. Prof., 工学部, 教授 (00108218)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Damage-Free Processing / Diamond Grinding / YAG Laser Prosessing / Bending Strength / Residual Stress / Brittle Materials / Ceramics |
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| Research Abstract |
This study deals with the feasibility of damage-free processing method for brittle materials (ceramics) using processes of grinding and YAG laser machining.
The experimental results of grinding tests of ceramics indicate that there are three different kinds of surface textures in ground ceramics. The first one is generated by transgranular fractures. The bending strength of this kind of ceramics is not affected by surface texture. The second one is generated by combinations of intergranular fracture and transgranular fracture. The bending strength of this kind of ceramics is low. The last one is composed of slight quasi-plastic flow surface. The bending strength of this kind of ceramics is slightly low. The bending strength of ground ceramics is affected by damages under ground surfaces. The grinding conditions for damage-free grinding are (1) low table feed rate, (2) high peripheral speed of grinding wheel and (3) using grinding machine with high damping ratio.
The next experiment is carried out for eliminating recast layer and cracks in laser-machining ceramics. The Q-Switch YAG laser pulses controlled at below 500 ns in duration and 10 kHz in repetition rare are effective, for the purpose of crack-free machining of ceramics. It is the reason that thermal stress is most likely localized only in the laser-heated shallowo region. The integrity of crack-free surface is evaluated by the fracture strength and residual stress. The strength of ceramics laser-procussed is reduced by 10 to 20% compared with diamond ground ones because high residual compression stress layer generated by grinding is removed.
For the purpose of damage-free machining of brittle materials, it is necessary to be carried out machining under the gentle processing conditions.
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