2009 Fiscal Year Final Research Report
Evaluation for the Effect of Surface Qualities on Fatigue Strength Based on the Measurement of Crack Initiation Life
| Project/Area Number |
19560146
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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 |
Design engineering/Machine functional elements/Tribology
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| Research Institution | University of Miyazaki |
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Principal Investigator |
DENG Gang University of Miyazaki, 工学部, 教授 (90237040)
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| Co-Investigator(Kenkyū-buntansha) |
NAKANISHI Tsutomu 宮崎大学, 工学部, 教授 (40038055)
MAEDA Kohji 宮崎大学, 工学部, 准教授 (50219268)
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| Project Period (FY) |
2007 – 2009
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| Keywords | 疲労き裂 / 疲労き裂発生検出 / イオンスパッタ膜 / 疲労き裂発生寿命 / 浸炭焼入異常層 / 表面粗さ / 電解研磨 |
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| Research Abstract |
The crack initiation detection method using an ion-sputtered film was used as a practical method to investigate the effects of the surface roughness and non-martensite layer on the crack initiation life in the three-point bending tests. Three types of the test pieces finished with different grinding processes and case carburized test piece were used in the fatigue tests. As the results obtained in this research, it is confirmed that the crack initiation life predominantly determines the fatigue life, and the effect of surface roughness on the fatigue life is restricted only to the crack initiation stage ; the crack initiation life decreases with the increase of the surface roughness. Increasing the surface quality from 1.27μmRa to 0.03μmRa can get 2～3 times of crack initiation life. Non-martensite layer formed during case carburization process decreases surface hardness as well as the fatigue life, removal the non-martensite layer by electrolytic polishing will lead to a higher fatigue life and fatigue strength.
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