1995 Fiscal Year Final Research Report Summary
Study on Mechanism of Bending Ftigue Breakage and Strengthening Method of Gear Teeth
| Project/Area Number |
06650176
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
設計工学・機械要素・トライボロジー
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| Research Institution | Tottori University |
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Principal Investigator |
ODA Satoshi Faculty of Eng., Tottori Univ., Professor, 工学部, 教授 (50032016)
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| Co-Investigator(Kenkyū-buntansha) |
MIYACHIKA Kouitsu Faculty of Eng., Tottori Univ., Assoc.Prof., 工学部, 助教授 (30157664)
KOIDE Takao Faculty of Eng., Tottori Univ., Assoc.Prof., 工学部, 助教授 (60127446)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Gear / Fatigue Strength / Sintered Metal / Shot-Peening / Ion-Nitriding / Tufftriding / Load Variation / Miner's Hypothesis |
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| Research Abstract |
Bending fatigue tests (pulsator tests) for shot-peened sintered metal gears were carried out, and the effect of shot-peening on the bending fatigue strength of sintered metal gears was determined.
The tooth profile changes of gears due to ion-nitriding, tufftriding and case-hardening were examined, and the deformations of gears due to these strengthening methods were determined. The bending fatigue tests for ion-nitrided gears with different case depths under uniform cyclic loading conditions were carried out, and the bending fatigue strength of ion-nitrided gears was determined. Furthermore, the bending fatigue characteristics of the ion-nitrided gears under two-step loading conditions was discussed on the basis of Miner's hypothesis.
The main results obtained from this investigation are summarized as follows.
1. The surface hardnesses of case-hardened sintered metal gears increase by applying shot-peening, but the case depths of these gears do not change depending on shot-peening. The surface hardnesses do not change with the carbon content (in the range of C0.3-0.5%), but the core hardnesses increase with the carbon content.
2. The bending fatigue strengths of case-hardened sintered metal gears become 20-40% larger by applying shot-peening.
3. The tooth profile changes of gears due to ion-nitriding and tufftriding are almost equal and fairly small, but those due to case-hardening are fairly large.
4. The bending fatigue limits of S45C and SACM645 ion-nitrided gears become maximums for ion- nitriding time 34 and 17 hours, respectively, and are about 40 and 80% larger than the normalized gears. The bending fatigue limits of S45C gears become about 30% larger by tufftriding.
5. The bending fatigue breakage of ion-nitrided gears occurs by the propagation of some of small cracks which initiate at the compound layr.
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