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엔진 실린더블록 하부의 Fretting 피로 평가 해석기술 개발
차상우(Sangwoo Cha),장훈(Hoon Chang),조성산(Sungsan Cho) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
Periodically, engine block-bearing cap structure is subject to the mixed bearing load from combustion and inertia mass of crank. Recently, due to the trend of lightness, cast steel is replaced with aluminum in the material of gasoline engine block. And, the load acting on the main bearing cap is rapidly rising due to the increase of engine power. Therefore, in the development stage, fretting fatigue failures are frequently occurred on the block face contacted with the bearing cap. Fretting is a kind of wear which is occurred by micro relative movement. Even though various researches have been made to figure out how it is occurred with FEA approaches, they are not enough to evaluate the phenomenon. In this study, the new FEA method is developed to mimic the dynamic behavior of the block system and to investigate the main mechanism on the fretting failures. And, varying the engine run condition and design parameters, the effectiveness of fretting fatigue durability is revealed.
상용디젤엔진 실린더 라이너 동특성 동특성 및 내구성평가 해석 기술 개발
차상우(Sangwoo Cha),이경우(Kyungwoo Lee),송재원(Jaewoon Song) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
Wet cylinder liners in heavy duty diesel engines have high local vibration velocities by piston secondary motion. This leads to liner cavitation and liner flange crack problem. The gas and inertia forces lead to the piston primary movement where the piston travels up and down form top dead center to bottom dead center and the piston secondary motion where the piston strikes or impacts the cylinder liner wall. These impacts of the piston secondary motion will be translated into cylinder liner excitations. In this paper, we evaluate wet liner durability with the two developed analysis method. The first, cavitation was evaluated with the liner dynamic analysis, and the second, liner flange durability was evaluated with the liner durability analysis. The piston excitation force was applied at the two analysis method.
실린더헤드 열변형 및 동적거동을 고려한 엔진 밸브 내구해석 기술개발
차상우(Sangwoo Cha),김지호(Jiho Kim),정준욱(Jungwook Jung) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
Automotive engine valves are subject to various stresses from such loads as combustion pressure and spring load, thermal loads and valve impact closing velocity. They interact with each other and sometimes lead to valve fatigue fractures. In this paper, finite element methods were extensively used to study valve stress behavior under various loads from durability test cycles. A 3D nonlinear thermal-mechanical model was constructed and the implicit time integration method was employed in valve transient dynamics under closing event. And, Head thermal deformation was considered. These stress results obtained from FEM were in good agreement with measured data under valve train rig test and the real crack position on the valve neck was simulated.
엔진 헤드 밸브시트 압입에 관한 공정해석 개발 및 실험적 검증
차상우(Sangwoo Cha),이경우(Kyung-Woo Lee),김치언(Chiun Kim),장훈(Hoon Chang) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Valve seats are an extremely important part of a cylinder head because the seats cool and seal the valves. The ways to insert cylinder head valve seat are freezing of valve seat press fitting, heating of head press fitting and ambient temperature press fitting. Among these, the ambient temperature press fitting is the recent trend because it is better than the other two ways for reducing installation & running cost and field claim. But it is not enough reliability of a theory yet. So the present study simulates ambient temperature press fitting developing process using Finite Element Method and shows a reliability of analytical result through comparing with the measuring value of a hoop strain and reaction force, Through this study, we provide the valuable list for verifying a reliability of ambient temperature press fitting developing process.
다양한 하중조건을 고려한 엔진밸브시트의 변형 및 마모 해석 기초 연구
고재천(JaeChun Ko),방인완(InHwan Bang),차상우(SangWoo Cha),이경우(KyungWoo Lee),신성원(SungWon Shin),윤재현(Jae Hyun Yun),이종수(JongSoo Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-2
엔진은 구동시 높은 열과 다양한 하중으로 인해 변형이 생기게 된다. 특히 밸브와 밸브시트 사이에서 다양한 하중의 영향으로 마모가 발생하게 된다. 현재까지 밸브를 포함한 엔진의 내구해석은 개발이 미흡했다. 본 연구는 밸브를 포함한 엔진의 내구해석을 통해 밸브시트 마모에 영향을 주는 인자를 찾아내는 것이다. 유한 요소 해석은 Hypermesh와 ABAQUS에 의해 수행되었다. 이번 연구에서 고려된 하중조건은 볼트 체결력, 열하중, 연소압, Max Valve Closing Force 등이다. 해석 모델은 많은 하중조건과 접촉 조건을 고려하여 보다 실제 모델과 가깝게 만들려 하였다. 마모에 대한 평가는 Archards’s equation을 바탕으로 하였다. The high levels of combustion heat and applied loadings result in deformation during the engine operation. Subsequently, due to various loading conditions, the wear also occurs between valve and valve seat. The objective of the present study is to identify the major parameters that affect the valve seat wear via structural analysis of engine and valve. The finite element analysis is conducted using Hypermesh and ABAQUS. The loading conditions considered in the present study are bolt joining force, thermal loading, combustion pressure and valve closing force, etc. The numerical model includes as many as loading and contact conditions in order to accommodate the more realistic engine environment. The wear analysis is evaluated based on the well-known Archard’s equation.