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최복록 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.4
The chassis frame generally consists of side members, cross beams, and several mounting brackets. Strength and fatigue behaviors of welded joints between members and brackets in a frame are a very complex phenomena, which comes basically due to the structural geometry, non- homogeneous material, and welding residual stresses. Therefore, the prediction of fatigue life for the welded structure is very difficult compared to that for the simple geometry. This paper presents the structural and fatigue analysis results for a body frame and welded joints under system durability loads. In order to fatigue assessment of welded joints, local stress approach is used for its simplicity, which is based on the several empirical S-N curves that are associated with welded joint types and loading modes. The estimated fatigue cycles of the welded areas in a frame were satisfied the target cycles under system load conditions.
파팅라인을 고려한 배기매니폴드와 일체형 터보차저의 열적 가진에 의한 소성변형률 크기 비교
최복록 한국기계기술학회 2021 한국기계기술학회지 Vol.23 No.1
Thermal external cracks can be initiated at the parting line, which is the dividing line that splits the core and cavity halves of a molded exhaust manifold-turbine housing. The fatigue cracks are often resulted from hot-cold cycle loads called by thermal shock cycles, and are accompanied by large plastic strains. This paper investigated the effects of parting lines of the integrated exhaust manifold-turbine housing and compared the magnitude of plastic strains directly correlated to low cycle fatigue damages or cracks. The finite element results showed that the plastic strains at runner junctions including parting line was calculated by 0.68%, which is approximately 60% higher than that of the turbine housing considering no parting line. So, if the analysis target is less than 0.50 % of plastic strain amplitude, the fatigue damages or cracks could be expected by considering the parting lines in integrated exhaust manifold-turbocharger.
엔진 폭발하중을 고려한 커넥팅로드의 좌굴해석에 관한 연구
최복록 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.3
When an engine connecting rod is designed, it’s important to consider the buckling strength as well as deformation and durability of the rod. The buckling strength of a rod is mainly affected by the shape and area of shank cross-section and boundary conditions of its small and big ends. Buckling analysis by finite element method was carried out to evaluate the elastic buckling strength of a connecting rod that has non-uniform cross section areas. And the Merchant-Rankine formula was applied to predict the inelastic critical buckling load by considering the plastic buckling strength. Finally, the maximum allowable compressive load, which has 56.57kN, was predicted by considering the 1.7 buckling safety factor. It represents an approximately 40% greater than the maximum firing pressure.
회전축계의 진동해석을 위한 지지구조물의 등가모델에 관한 연구
최복록,박진무 한국소음진동공학회 2000 소음 진동 Vol.10 No.1
This paper presents a new method for including the dynamic stiffness of the stationary parts in rotordynamic analysis. As a consequence of the support dynamics, critical speeds are varied and/or additional critical speeds are introduced. Therefore, dynamic effects of the support are often significant in high speed turbomachinery, but most of analysis has considered the support as a rigid body or a simple structure. The proposed method is based on the coupled characteristics of the driving point and transfer frequency response functions of the support system to model the equivalent spring-mass series in finite element analysis. To demonstrate the applicability of the simulation procedures provided, it is applied to the rotor model of the double suction centrifugal pump. Results of the suggested equivalent-support rotor model including coupled effects agree well with the entire pump model.
최복록,홍성기,최병호 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.6
This study uses analytical and finite element methods to predict the sealing performance by calculating the contact pressures on the back plate of a turbocharger. A mathematical model is constructed to derive the contact force on the back plate by considering the force-transfer mechanisms. Finite element analyses are performed to calculate the contact pressures caused by applying the bolt preload in the coupling system. The analytical results are consistent with those of the finite element analysis; hence, the analytical model could be helpful in determining the effects of design parameters in the early design stage of the coupling. In addition, the pressure distributions on the back plate are predicted to identify the sealing performance of the coupling.
엔진 크랭크축의 필렛 롤링 효과에 따른 구조적 특성 및 내구성 평가
최복록 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.2
Crankshaft is one of the most important moving parts in internal combustion engine. In order to design more lighter and compacter crankshaft, strength and durability analysis is significant in evaluating the engine performance and lifetime as well as overall mechanical information. In this paper, structural analysis is performed to obtain the stress amplitudes and mean stresses at critical locations of crankshaft over the engine rotational speed. The load magnitudes are calculated by considering the firing pressure, inertia force, and torsional load. Next. using the stress results and the fatigue properties of the material, durability analysis is done to calculate the fatigue safety factors. As a result, the critical areas of the crankshaft were crank pin and journal’s fillet areas, and their safety factors satisfied the analytical criteria at all rotational speed by considering the fillet rolling effect.
최복록 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.4
The chassis frame generally consists of side members, cross beams, and several mounting brackets. Strength and fatigue behaviors of welded joints between members and brackets in a frame are a very complex phenomena, which comes basically due to the structural geometry, non-homogeneous material, and welding residual stresses. Therefore, the prediction of fatigue life for the welded structure is very difficult compared to that for the simple geometry. This paper presents the structural and fatigue analysis results for a body frame and welded joints under system durability loads. In order to fatigue assessment of welded joints, local stress approach is used for its simplicity, which is based on the several empirical S-N curves that are associated with welded joint types and loading modes. The estimated fatigue cycles of the welded areas in a frame were satisfied the target cycles under system load conditions.
최복록,Choi, Bok-Lok 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.3
Exhaust manifold is generally subjected to thermal cycle loadings ; at hot condition, large compressive plastic deformations are generated, and at cold condition, tensile stresses are remained in highly deformed critical zones. These phenomena originate from that thermal expansions of the runners are restricted by inlet flange connected to the cylinder head, because the former is less stiff than the latter and, the temperature of the inlet flange is lower than that of the runners. Therefore, due to the repetitions of thermal deformation, leakage problems could be occur between inlet flange and cylinder head. In this study, we obtained pressure distributions along gasket bead lines from the finite element analysis and compared to the test results. It shows a good agreement between numerical and experimental results.