터보차져의 파손현상과 열응력 해석

최복록 한국기계기술학회 2013 한국기계기술학회지 Vol.15 No.6

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.

샤시 프레임의 용접부 피로평가를 고려한 구조해석

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.

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.

엔진 배기매니폴드의 배기가스 누설 해석

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.

샤시 프레임의 용접부 내구성을 고려한 구조해석

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.

전달함수와 진동응답 측정에 의한 원심펌프에서의 유체력 특성에 관한 연구

최복록,박진무,김광은,Choi, Bok-Lok,Park, Jin-Moo,Kim, Kwang-Eun 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.8

Operating excitation forces of the linear vibratory system are normally determined by direct measurement techniques using load cells, strain gauges, etc. But, hydraulic forces of the rotating turbomachinery such as centrifugal pumps are exerted on an impeller due to asymmety of the flow by the interaction between pump impeller and volute. So, investigations of wide range of hydraulic designs and geometric deviations are difficult by direct method. This paper presents a hybrid approach for fourier transformed operational excitation forces, which uses pseudo-inverse matrix of the transfer matrix for the system and the measured vibrational data with standard installed pump. The determination of the transfer function matrix is based on a linear rotor/stationary system and steady state harmonic response in finite element analysis. And, vibrational data is collected in both vertical and horizontal directions at inboard and outboard bearing housings. The results of the process may be enhanced by making acceleration measurements at many more locations than there are forces to be determined.

열사이클 하중으로 인한 실린더헤드의 균열 메카니즘에 관한 열피로 해석

최복록 한국기계기술학회 2020 한국기계기술학회지 Vol.22 No.1

Engine components subjected to cyclic thermal and mechanical loads may experience low-cycle or high-cycle fatigue failures. In particular, both of these failures can easily occur in aluminum cylinder heads, which are exposed to high temperatures and combustion pressures. Predicting the fatigue characteristics of the cylinder head are very important in the design stage of engine development. In this study, a finite element analysis was performed to predict the low-cycle thermal fatigue around exhaust ports of the cylinder head. Temperature distributions are obtained through the heat transfer analysis considering thermal cyclic test. The analysis result involves large plastic deformations, indicating compressive stresses at high temperatures and subsequently turn into tensile stresses at cold conditions. And the results showed that the critical regions such as exhaust port with large plastic strains coincided well with crack locations from thermal cyclic test. Next, design changes were made to the critical areas of the exhaust ports, and the results showed that the durability was improved by about 60% over the initial model and there were no problems in the thermal fatigue test.

Prediction of Sealing Performance of V-Coupling of Turbocharger Housing Using Analytical and Finite Element Analysis

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.

지지구조물의 동특성을 고려한 회전축 모델의 진동해석

최복록,박진무,Choe, Bok-Rok,Park, Jin-Mu 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.4

Support dynamics are often important in rotordynamic analyses. It may well happen in real situation of machines such as centrifugal pumps or turbines operating on flexible structure. This paper presents the applications of the impedance coupling method and the improved rotor model for including the support effects on the interaction with the rotor. The impedance coupling techniques are based on the FRFs of each substructure. Its dynamic stiffness matrix can be assembled to generate the system matrix, which satisfy the constraint conditions in the connection coordinates. And, the improved rotor uses the simplified spring-mass models as support properties. The equivalent support models are directly incorporated into the finite element rotor model. To verify the suggested analytical procedures, the results are compared to those of the pump system.