• Journal of the Korean Society of Industry Convergence
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• v.25 no.2_2
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• pp.239-245
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• 2022

Using the fatigue limit (∆σ_unsm) and residual stress (σ_r) of the UNSM smooth specimen, the harmless maximum crack depth (a_hlm) according to the crack aspect ratio (As) was evaluated. In addition, the relationship between the minimum crack depth (a_NDI1, a_NDI2) detectable by non-destructive inspection(NDI), the crack depth (a₂₅, a₅₀) that reduces the fatigue limit by 25% and 50%, and a_hlm were evaluated. The harmless crack condition was determined by the deepest crack point (point A). Since a_hlm is larger than a₂₅ and a₅₀, a₂₅ and a₅₀ can secure the safety and reliability of steel via UNSM. Because a_NDI1 and a_NDI2 are larger than a₂₅ and a₅₀, cracks in a₂₅ and a₅₀ cannot be detected by non-destructive testing. Therefore it is necessary to apply more precise NDI.

• Journal of Yeungnam Medical Science
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• v.7 no.1
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• pp.81-93
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• 1990

The author fractographically analyized the cause of metal failure(the first time this procedure has been used for this metal failure)and also analyized it clinically. In this study, I selected eight cases which have been analyized fractographically. In all these cases, the analysis was done after treatment of metal failure of implants internally fixed to femur shaft fractures at the Department of Orthopedic Surgery, Yeung-Nam University Hospital during the six year period from May 1983 to September 1989. 1. Metal failure occured in five dynamic-compression plates, one Jewett nail, one screw in Rowe plate, and one interlocking nail. 2. The clinical cause of metal failure was deficiency of medial butress in five cases, incorrect position of implant in one case, and incorrect selection of implant in two cases. 3. The time interval between internal fixation and metal failure was four months in one case, between five months to twelve months in six cases, three years in one case. 4. The fractographically analytical cause of metal failure was ; first, impact failure, one case, second, fatigue failure, six cases, machining mark(stress liser), four cases type : low consistent cyclic fatigue failure irregular cyclic fatigue failure third, stress corrosion crack, one case. 5. 316L Stainless Steel has good resistance to corrosion. However, when its peculiar surface film is destroyed by fretting, it shows pitting corrosion. This is, perhaps, the main cause of metal failure. 6. It is possible that mechanical injury occured in implants during the manufacturing of implants or that making a screw hole is the main cause of metal failure.