Life-time Prediction of a FKM O-ring using Intermittent Compression Stress Relaxation (CSR) and Time-temperature Superposition (TTS) Principle

간헐 압축응력 완화와 시간-온도 중첩 원리를 이용한 FKM 오링의 수명 예측 연구

  • Lee, Jin-Hyok (Department of Polymer Engineering, Pusan National University) ;
  • Bae, Jong-Woo (Rubber Material Research Division, Korea Institute of Footwear & Leather Technology) ;
  • Kim, Jung-Su (Rubber Material Research Division, Korea Institute of Footwear & Leather Technology) ;
  • Hwang, Tae-Jun (Rubber Material Research Division, Korea Institute of Footwear & Leather Technology) ;
  • Park, Sung-Doo (Sam Jung Ind. Co.) ;
  • Park, Sung-Han (Agency for Defense Development) ;
  • Min, Yeo-Tae (Samsung Techwin Co.) ;
  • Kim, Won-Ho (Department of Chemical Engineering, Pusan National University) ;
  • Jo, Nam-Ju (Department of Polymer Engineering, Pusan National University)
  • 이진혁 (부산대학교 고분자공학과) ;
  • 배종우 (한국신발피혁연구소 산업소재융합기술센터 고무연구팀) ;
  • 김정수 (한국신발피혁연구소 산업소재융합기술센터 고무연구팀) ;
  • 황태준 (한국신발피혁연구소 산업소재융합기술센터 고무연구팀) ;
  • 박성두 (삼정산업) ;
  • 박성한 (국방과학연구) ;
  • 여태민 (삼성테크윈) ;
  • 김원호 (부산대학교 화학공학과) ;
  • 조남주 (부산대학교 고분자공학과)
  • Received : 2010.08.30
  • Accepted : 2010.10.05
  • Published : 2010.12.31

Abstract

Intermittent CSR testing was used to investigate the degradation of an FKM O-ring, also the prediction of its life-time. An intermittent CSR jig was designed taking into consideration the O-ring's environment under use. The testing allowed observation of the effects of friction, heat loss, and stress relaxation by the Mullins effect. Degradation of O-rings by thermal aging was observed between 60 and $160^{\circ}C$. In the high temperature of range ($100-160^{\circ}C$) O-rings showed linear degradation behavior and satisfied the Arrhenius relationship. The activation energy was about 60.2 kJ/mol. From Arrhenius plots, predicted life-times were 43.3 years and 69.9 years for 50% and 40% failure conditions, respectively. Based on TTS (time-temperature superposition) principle, degradation was observed at $60^{\circ}C$, and could save testing time. Between 60 and $100^{\circ}C$ the activation energy decreased to 48.3 kJ/mol. WLF(William-Landel-Ferry) plot confirmed that O-rings show non-linear degradation behavior under $80^{\circ}C$. The life-time of O-rings predicted by TTS principle was 19.1 years and 25.2 years for each failure condition. The life-time predicted by TTS principle is more conservative than that from the Arrhenius relationship.

간헐 CSR 측정법을 이용하여 FKM 오링의 노화 거동과 수명 예측에 관하여 연구하였다. Intermittent CSR 지그는 오링의 실제 사용환경을 고려하여 설계 제작하였다. 각 측정 조건에 따른 마찰 영향, 열 손실 영향 및 Mullins 효과에 의한 간헐 CSR의 응력 거동 변화를 관찰하였다. 오링의 노화 거동은 $60{\sim}160^{\circ}C$에서의 가속 노화 연구를 통하여 관찰하였다. 고온 영역($100{\sim}160^{\circ}C$)에서 오링은 선형 노화 거동을 나타내었으며, 아레니우스 관계를 만족시켰다. 이때의 활성화 에너지는 60.2 kJ/mol로 나타났다. 아레니우스 도식으로 부터, 오링의 예측 수명은 고장 조건 50%와 40%에 대하여 각각 43.3 년과 69.6 년으로 나타났다. 시간-온도 중첩 원리를 이용하여 $60^{\circ}C$에서의 노화 거동을 관찰하였으며, 실험 시간을 절약 할 수 있었다. $60{\sim}100^{\circ}C$의 저온 영역에서의 활성화 에너지는 48.3 kJ/mol로 감소하였다. WLF(William-Landel-Ferry) 도식을 통하여 FKM 오링은 $100^{\circ}C$ 이하에서 비선형 노화 거동을 나타내는 것을 확인하였다. 시간-온도 중첩 원리로부터, FKM 오링의 수명은 고장 조건 50%와 40%에 대하여 각각 19.1년과 25.2년으로 나타났다. 시간-온도 중첩 원리를 이용하여 예측한 오링의 수명이 아레니우스 관계에 의한 수명 보다 보수적인 것으로 나타났다.

Keywords

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