유압 브레이커 관통볼트의 FMECA 기반의 신뢰성 평가와 제조 공정 최적화
FMECA-based Reliability Assessment and Manufacturing Process Optimization for Hydraulic Breaker Through-bolts
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This study aimed to solve the field fatigue failure rate (10%) of SCM440 through-bolts in hydraulic breakers by optimizing the manufacturing process. FMECA results indicated that the root cause was not material limitations but defects in thread machining and heat treatment processes. Consequently, a process improvement was implemented by adopting a 'post-heat-treatment thread rolling' method to induce compressive residual stress at the thread root. To statistically verify the reliability of the improved components, an accelerated life test (ALT) was designed for 300,000 cycles, targeting a B10 life of 165 hours at 80% confidence. Test results showed that all four specimens passed without failure, statistically validating the life target. This proves that manufacturing process optimization is a valid engineering solution to reduce field failure rates.
Abstract
This study aimed to solve the field fatigue failure rate (10%) of SCM440 through-bolts in hydraulic breakers by optimizing the manufacturing process. FMECA results indicated that the root cause was not material limitations but defects in thread machining and heat treatment processes. Consequently, a process improvement was implemented by adopting a 'post-heat-treatment thread rolling' method to induce compressive residual stress at the thread root. To statistically verify the reliability of the improved components, an accelerated life test (ALT) was designed for 300,000 cycles, targeting a B10 life of 165 hours at 80% confidence. Test results showed that all four specimens passed without failure, statistically validating the life target. This proves that manufacturing process optimization is a valid engineering solution to reduce field failure rates.