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

The Korean Society of Mechanical Engineers (대한기계학회)
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Fatigue Assessment of High Strength Steel Welded Joints Under Bending Loading

굽힘 하중하의 고장력강 용접 연결부의 피로 평가

  • Received : 2014.02.20
  • Accepted : 2014.08.18
  • Published : 2014.10.01
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Abstract

In this study, a fatigue assessment method for vehicle suspension systems having welded geometries was established under a bending loading condition. For the fatigue life estimation of the actual product's welded joints made of different steels, bending fatigue tests were performed on welded specimens with a simplified shape for obtaining the moment-fatigue-life plot. Further, geometry modeling of the simplified welded specimens was conducted. Results of finite element analysis were used to obtain the stress-fatigue-life plot. The analysis results were also used to calculate the stress concentration factors for notch-factor-based fatigue life estimation. The test results were compared with results of the general notch-factor-based fatigue life estimation for improving fatigue assessment. As a result, it was concluded that both the welded fatigue tests and the notch-factor-based fatigue life estimation are necessary for accurate fatigue assessment.

본 연구에서는 자동차 서스펜션 구조에 일반적으로 사용되는 용접부 형상에 대하여 굽힘 하중에 의한 피로수명을 예측할 수 있는 절차를 개발하였다. 이종 재료로 이루어진 실제 제품 용접 연결부의 피로수명 예측을 위해, 복잡한 형상의 제품을 단순화한 용접 시편을 설계하고 이에 대한 굽힘 피로 시험을 진행한 후 모멘트-피로수명(M-N) 선도를 제시하였다. 응력 집중에 의한 영향을 분석하기 위해 시편의 형상을 모델링 한 후 정적 하중에 대한 유한요소해석을 수행하여 균열 발생부의 응력을 구하고 응력-피로수명(S-N) 선도를 제시하였다. 유한요소해석을 통해 구한 응력과 이론 계산을 통해 구해준 응력을 이용하여 응력집중계수를 계산하였고, 응력집중부의 피로평가 방법 개선을 위해 보편적으로 사용되는 피로노치계수 평가법과 굽힘 피로 시험 결과를 비교 검토하였다. 그 결과, 이종 재질 용접 연결부의 정확한 피로 수명평가를 위해서는 기하형상을 고려한 피로노치계수 평가 분석뿐만 아니라 두 소재의 맞대기 용접 시편에 대한 피로 시험을 수행해 주어야 할 것으로 판단된다.

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References

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