Abstract

Due to their high strength and good wear resistance, nitro-carburizing materials have been used for many machine components. However, the nitro-carburizing materials are found to have one disadvantage ; that is, their strength and fatigue life show larger scatter than those of non-heated metals. In this paper, therfore, the statistical chracteristics of non-heated and nitro-carburized specimens for SCM415 are investi- gated under two different of stress levels 1.15 .sigma. /sub .omega. / .leq. / .sigma. / sub .alpha. / .leq. / 1.25 .sigma. /sub .omega. /. Seven specimens at each stress level are tested by using rotating bending fatigue tester. The relation between a crack length and fatigue cycles can be arranged for Weibull distribution, and S-N curve using 95% reliability function is obtalined for nitro-carburized specimen.

Keywords

• Nirto-carburized treatment;
• Fatigue life;
• Weibull distribution;
• Statistical paremeter;
• Coefficient of variation;
• Crack propagation;
• Reliability function

• 침탄질화 처리;
• 피로수명;
• 와이블분포;
• 통계변수;
• 변동계수;
• 균열전파;
• 신뢰도 함수;