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학술연구/단체지원/교육 등 연구자 활동을 지속하도록 DBpia가 지원하고 있어요.
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논문 기본 정보
- 자료유형
- 학위논문
- 저자정보
- 발행연도
- 2013
- 저작권
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Recently, the high surface quality of oil tempered spring steel wire for valve springs with high fatigue strength is essential since surface defect can occur initiate the crack propagation. The aim of this study is to investigate the fatigue life of super high strength steel(SHSS) springs according to surface flaws of oil tempered spring steel wire.
V-shape surface defects were introduced in the initial workpiece and the evolution of deformation behavior and stress distribution such defects was simulated during the manufacturing spring. The FE-simulations were performed to check the local stress distributions around surface flaws using an SHSS spring, which are determined by analysis results of cold coiling and measured residual stresses. The residual stress of valve spring after hot setting process was measured by X-ray diffraction (XRD). Since the size of the defect is significantly smaller than the whole model, a submodeling technique was used to study a local part of a model. A local stress concentration is observed at the surface flaw and stress on other areas was at the same level as the no-defect model. S-N curves have been determined by rotary bending fatigue test machine with specimens which have same residual stress level of valve spring. The fatigue lives were predicted in comparison with S-N curves and calculated alternating stress. The calculated alternating stress increases as as surface depth increase because of stress concentration and decrease in compressive residual stress from shotpeening.
The performed investigation can help with quality control for oil tempered wire.
V-shape surface defects were introduced in the initial workpiece and the evolution of deformation behavior and stress distribution such defects was simulated during the manufacturing spring. The FE-simulations were performed to check the local stress distributions around surface flaws using an SHSS spring, which are determined by analysis results of cold coiling and measured residual stresses. The residual stress of valve spring after hot setting process was measured by X-ray diffraction (XRD). Since the size of the defect is significantly smaller than the whole model, a submodeling technique was used to study a local part of a model. A local stress concentration is observed at the surface flaw and stress on other areas was at the same level as the no-defect model. S-N curves have been determined by rotary bending fatigue test machine with specimens which have same residual stress level of valve spring. The fatigue lives were predicted in comparison with S-N curves and calculated alternating stress. The calculated alternating stress increases as as surface depth increase because of stress concentration and decrease in compressive residual stress from shotpeening.
The performed investigation can help with quality control for oil tempered wire.
목차
1. 서 론 11.1 연구 배경 11.2 연구 목적 및 내용 22. 밸브스프링 제조 공정 별 표면 흠의 형상 변화 52.1 Oil Tempered Wire의 표면 흠 표준화 52.1.1 표면 흠 형상 분류 52.1.2 표면 흠 방향 분류 72.1.3 표준화 된 표면 흠 72.2 공정 별 흠 형상변화 82.2.1 개요 82.2.2 스프링 성형(Cold coiling) 공정 92.2.3 쇼트피닝(Shot peening) 공정 112.2.4 핫세팅(Hot setting) 공정 123. 밸브스프링제조 공정 별 잔류응력 분포 143.1 이론적 배경 143.2 쇼트피닝(Shot peening) 공정 153.2.1 잔류응력 측정 153.2.2 유한요소해석 163.3 핫세팅(Hot setting) 공정 163.3.1 잔류응력 측정 164. 밸브스프링의 피로수명 예측 184.1 스프링 강도해석 184.2 피로시험 204.3 S-N 선도 적용 및 수명예측 225. 결 론 25참고 문헌 27Table 29Figure 34Abstract 62
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