| Co-Investigator(Kenkyū-buntansha) |
NAKAJIMA Akira Saga University, Associate Professor, 理工学部, 助教授 (60039295)
KANEDA Motohiro Kyushu Institute of Technology, Professor, 工学部, 教授 (90039123)
URA Akira Nagasaki University, Professor, 工学部, 教授 (40037825)
MURAKAMI Teruo Kyushu University, Associate Professor, 工学部, 助教授 (90091347)
YAMAMOTO Yuji Kyushu University, Professor, 工学部, 教授 (10037997)
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| Budget Amount *help |
¥5,300,000 (Direct Cost: ¥5,300,000)
Fiscal Year 1986: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1985: ¥4,600,000 (Direct Cost: ¥4,600,000)
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| Research Abstract |
In order to clarify the mechanism of surface fatigue in contact, two-roller test, three dimensional rolling contact test (simulated the contact condition of rail and wheel), fretting test and repetitive compression test were conducted. By two roller tests, following conclusions were obtained: (1) Asperity interaction of surface roughness is most important factor for occurrence of rolling fatigue, i. e., pitting, micro pitting and spalling. (2) In especial, the running-in condition is controlled by the asperity contact frequency Naf, defined by the number of contact positions of higher hardness roller with different microgeometries which are brought into contact with any one position of mating lower hardness roller, and Naf controls the severity of asperity contact and the occurrence of rolling fatigue. (3) The rolling fatigue limits under severe asperity contacts are determined by the limiting Hertzian pressure where running-in occurs or not. (4) Micro-Pitting of carburized steel are c
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ontrolled by the value of roughness which is limit of occurrence of running-in. By fretting tests, it was clarified that the tangential traction have an influence on the contact fatigue by promoting the occurrence of tensile stresses which always appear in three dimensional contacts, owing to macro geometrical condition or micro asperity contacts. The occurrences of fatigue cracks in the macro geometrical three dimensional contact (i. e. the simulated rail-and-wheel contact) and the repetitive compression tests certify above conclusion. The gear tests and the repetitive compression tests also showed that particles of solid, e. g. the particles of solid lubricants contained in gear oil, are possible to be the sources of stress concentrations, and therefore it should be small enough. By the analysis of cracking from the failure mechanics, the propagations of cracks were predicted. Furthermore, it was shown that the running-in condition or the severity of asperity contacts can be estimated from the cross-corelation function of roughness profile measured three-dimensionally. Less
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