Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
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Study of Improvement in Fatigue Life of Fuel Injection Pipe of Common Rail System

커먼레일 시스템 연료분사관의 피로수명 개선에 관한 연구

  • Song, Se Arm (Dept. of Creative Engineering System, Pusan Nat'l Univ.) ;
  • Bae, Jun Ho (Research Institute of Mechanical Technology, Pusan Nat'l Univ.) ;
  • Jung, Sung Yuen (Research Institute of Mechanical Technology, Pusan Nat'l Univ.) ;
  • Kim, Chul (Research Institute of Mechanical Technology, Pusan Nat'l Univ.)
  • 송세암 (부산대학교 창의공학시스템학과) ;
  • 배준호 (부산대학교 기계기술연구원) ;
  • 정성윤 (부산대학교 기계기술연구원) ;
  • 김철 (부산대학교 기계기술연구원)
  • Received : 2013.01.31
  • Accepted : 2013.05.20
  • Published : 2013.08.01
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Abstract

The fuel injection pipe of a common rail system used in a clean diesel vehicle plays a role in supplying fuel from a rail to the injector of each cylinder connecting the engine under a repeated internal pressure. The fuel injection pressure is increased to over 200 MPa for satisfying EU emission standards and improving fuel efficiency, and a heading process and an autofrettage process are required for preventing folding defects and improving fatigue life. In this study, the flow stress and SN data of the material of the pipe are obtained through a tensile test and a fatigue test. The heading process for checking the folding defects of pipe ends is performed by using FEA. Furthermore, the optimal design of the autofrettage process for improving fatigue life considering not only the compressive residual stresses of the inner surface but also the tensile residual stresses of the outer surfaces of the pipe under the repeated internal pressure is performed by using FEA. To verify the process design, fatigue analysis for the autofrettaged pipe is performed.

클린디젤 차량용 커먼레일 시스템의 연료분사관은 연료레일로부터 각각의 엔진 실린더에 연결된 인젝터로 연료를 공급하는 역할을 하며 반복 내압을 받게 된다. EURO 배기가스 배출규정 만족 및 연비향상을 위하여 요구되는 연료의 압력은 200MPa 이상으로 증가하고 있으며, 성형결함이 발생하지 않는 헤딩공정과 내압 피로수명 향상을 위한 자긴처리 기술이 요구되고 있다. 본 논문에서는 250MPa 급 반복내압을 만족할 수 있는 파이프 소재의 유동응력와 고주기 피로 데이터를 각각의 실험을 통하여 확보하였고, 연료분사관 앞 끝의 성형결함 여부를 판단하기 위하여 헤딩공정에 대한 유한요소해석을 수행하였다. 반복내압에 대한 내구수명 향상 및 신뢰성 확보를 위해 자긴공정에 대한 유한요소해석을 통하여 외경부의 인장잔류응력까지 고려한 최적 공정설계 수행 및 피로해석을 통한 설계의 타당성을 검증하였다.

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References

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