• 대한기계학회논문집A
• /
• 제30권5호
• /
• pp.568-575
• /
• 2006

The present paper provides plastic limit load solutions of axial and circumferential through-wall cracked pipes based on detailed three-dimensional (3-D) finite element (FE) limit analysis using elastic-perfectly-plastic behavior. As a loading condition, axial tension, global bending moment, internal pressure, combined tension and bending and combined internal pressure and bending are considered for circumferential through-wall cracked pipes, while only internal pressure is considered for axial through-wall cracked pipes. Especially, more emphasis is given for through-wall cracked pipes subject to combined loading. Comparisons with existing solutions show a large discrepancy in short through-wall crack (both axial and circumferential) for internal pressure. In the case of combined loading, the FE limit analyses results show thickness effect on limit load solutions. Furthermore, the plastic limit load solution for circumferential through-wall cracked pipes under bending is applied to derive plastic $\eta\;and\;{\gamma}$-factor of testing circumferential through-wall cracked pipes to estimate fracture toughness. Being based on detailed 3-D FE limit analysis, the present solutions are believed to be meaningful fur structural integrity assessment of through-wall cracked pipes.

• 대한기계학회논문집B
• /
• 제28권2호
• /
• pp.207-214
• /
• 2004

The burning velocities of conventional and oxygen-enriched methane flame in various equivalence ratio were determined by experiments. The validity of existing reaction mechanisms was examined in oxygen-enriched flame on the basis of the experiment results. Modified reaction mechanism is suggested, which was able to predict burning velocity of oxygen enriched flame as well as methane-air flame. Complementary study on reaction mechanisms shows the following results : Present experiment data were found to be more reliable in comparison with existing ones in a oxygen-enrichment condition. It was found that some modification in existing reaction mechanisms is necessary, since discrepancy between measurements and predictions is increasing with oxygen enrichment ratio. The sensitivity analysis was performed to discriminate the dominantly affecting reactions on the burning velocity in various oxygen enrichment and equivalence ratio. A modified GRI 3.0 reaction mechanism based on our experiment results was suggested, in which reaction rate coefficients of (R38) H+O$_2$<=>O+OH in GRI 3.0 reaction mechanisms were corrected based on sensitivity analysis results. This mechanism showed a good agreement in predicting the burning velocity and number density of NO in oxygen-enriched flame and would provide proper reaction information of oxygen-enriched flame at this stage.

• 한국안전학회지
• /
• 제21권6호
• /
• pp.20-25
• /
• 2006

In the design of class 1 components to apply ASME code section III NB, a fatigue is considered as one of the important failure mechanisms. Fatigue analysis procedure and standard fatigue design curve(S-N curve) is suggested in ASME code, which had to be performed to meet the integrity of components at the design step. As the plant life extension for operating power plants and the long-lived plant design, however, are being progressed, the fact which the existing ASME fatigue design curve can not consider fatigue effects sufficiently comes to the fore. To find the technical solution for these problems, a number of researches and discussion are continued up to now. In this study, the detailed fatigue analyses using the 3 dimensional modeling for the fatigue-weakened components were performed to develop the optimized fatigue analysis procedure and their results are compared with other reference solutions.

• 한국자동차공학회논문집
• /
• 제12권4호
• /
• pp.173-180
• /
• 2004

The tread pattern of a tire has an important effect on tire performances such as handling, wear, noise, hydroplaning and so on. However, a finite element analysis of a patterned tire with detailed tread blocks has been limited owing to the complexity of making meshes for tread blocks and the huge computation time. The computation time has been shortened due to the advance in the computer technology. The modeling of tread blocks usually requires creating a solid model using a CAD software. Therefore it is a very complicated and time-consuming job to generate meshes of a patterned tire using a CAD model. A new efficient and convenient method for generating meshes of a patterned tire has been developed. In this method, 3-D meshes of tread pattern are created by mapping 2-D meshes of tread geometry onto 3-D tread surfaces and extruding them through tread depth. Then, the tread pattern meshes are assembled with the tire body meshes by the tie contact constraint. Residual aligning torque and frictional energy are calculated by using a patterned tire model and compared to the experimental results. It is shown that the calculated results of a patterned tire model are in a good agreement with the experimental ones.

• 한국소음진동공학회논문집
• /
• 제15권2호
• /
• pp.148-155
• /
• 2005

As functional requirement of massive digital information storage devices are on a trend for the higher data transfer rate and lower cost, many different technical efforts are being tested and implemented in the industry. FDB(fluid dynamic bearing) is one of the major breakthroughs in rotor design in terms of TMR(track misregistration) budget. Although FDB analysis based on Reynolds' equation is well established and popularly being used for FDB design especially for the estimation of bearing stiffness, there are obvious limitations in the approach due to the inherent assumptions. A generalized analysis tool employing the full Navier-Stokes equation and the energy balance is to be beneficial for detailed FDB design. In this publication, an efficient geometry modeling method is presented that provides fully integrated inputs for general FVM/FDM(finite volume method/ finite difference method) codes. By virtue of the flexibility of the presented method, many different detailed FDB design and analysis are carried over with ease.

• 한국전산구조공학회논문집
• /
• 제13권1호
• /
• pp.139-146
• /
• 2000

본 연구는 철골 건축구조물에 관한 정보의 표현과 교환을 위하여 STEP을 이용한 구조해석 및 설계용 통합 시스템의 모델을 제시한다. 이러한 통합시스템을 구축하기 위하여 철골 구조물 제품모델을 위한 AP 230을 근간으로 기하 및 위상 정보를 나타낼 수 있는 Part 42와 상세한 구조해석을 표현할 수 있는 Part 104을 추가시키고자 한다. 이렇게 함으로서 철골구조물에 관한 종합적인 엔지니어링 정보의 표현을 보다 명확하게 하고 또한 정보의 교환을 보다 쉽게 할 수 있게 된다. 이러한 통합시스템의 개발모델에 따르면 구조물에 관한 상세정보와 시공정보들도 쉽게 추가할 수 있다.

• 대한기계학회논문집A
• /
• 제27권1호
• /
• pp.26-33
• /
• 2003

Based on detailed FE limit analyses, the present paper provides tractable approximations fer plastic limit pressure solutions fur axially through-wall-cracked pipe; axially (inner) surface-cracked pipe; circumferentially through-wall-cracked pipe; and circumferentially (inner) surface-cracked pipe. In particular, for surface crack problems, the effect of the crack shape, the semi-elliptical shape or the rectangular shape, on the limit pressure is quantified. Comparisons with existing analytical and empirical solutions show a large discrepancy in circumferential short through-wall cracks and in surface cracks (both axial and circumferential). Being based on detailed 3-D FE limit analysis, the present solutions are believed to be the most accurate, and thus to be valuable information not only for plastic collapse analysis of pressurised piping but also for estimating non-linear fracture mechanics parameters based on the reference stress approach.

• Nuclear Engineering and Technology
• /
• 제48권1호
• /
• pp.218-227
• /
• 2016

Background: Steam explosions may occur in nuclear power plants by molten fuel-coolant interactions when the external reactor vessel cooling strategy fails. Since this phenomenon can threaten structural barriers as well as major components, extensive integrity assessment research is necessary to ensure their safety. Method: In this study, the influence of yield criteria was investigated to predict the failure of a reactor cavity under a typical postulated condition through detailed parametric finite element analyses. Further analyses using a geometrically simplified equivalent model with homogeneous concrete properties were also performed to examine its effectiveness as an alternative to the detailed reinforcement concrete model. Results: By comparing finite element analysis results such as cracking, crushing, stresses, and displacements, the Willam-Warnke model was derived for practical use, and failure criteria applicable to the reactor cavity under the severe accident condition were discussed. Conclusion: It was proved that the reactor cavity sustained its intended function as a barrier to avoid release of radioactive materials, irrespective of the different yield criteria that were adopted. In addition, from a conservative viewpoint, it seems possible to employ the simplified equivalent model to determine the damage extent and weakest points during the preliminary evaluation stage.

• 한국정밀공학회지
• /
• 제21권7호
• /
• pp.53-61
• /
• 2004

Condenser tube which is used for a cooling system of automobiles is mainly manufactured by conform extrusion. However, direct extrusion using porthole die in comparison with conform extrusion has many advantages such as improvement of productivity, reduction of production cost etc. In general, the porthole die extrusion process is useful for manufacturing long tubes with hollow sections and consists of three stages(dividing, welding and forming stages). Especially, Porthole die for producing condenser tube is very complex. Thus, in order to obtain the detailed mechanics, to assist in the design of proper die shapes and sizes, and to improve the quality of products, porthole die extrusion should be analyzed in as non-steady state as possible. This paper describes FE analysis of non-steady state porthole die extrusion for producing condenser tube with multi-hole through 3D simulation in the non-steady state during the entire process to evaluate detailed metal flow, temperature distribution, welding pressure and extrusion load. Also to validate FE simulation of porthole die extrusion, a comparison of simulation and experiment results was presented in this paper.

• Journal of Information Technology Applications and Management
• /
• 제28권4호
• /
• pp.79-101
• /
• 2021

The purpose of this research is to define detailed technologies of smart city based on excellent patents through patent analysis related to major technologies of smart city, and to use quantitative indicators to classify relatively high technology importance and identify related technologies. To achieve the purpose of the study, patent collection is conducted by reflecting literature research and expert opinions based on information related to the smart city Internet of Things/Internet of Things communication core technology. Also, DEA were used to determine the relatively high technology. The inputs and outputs used in the study used quantitative indicators to determine technical value and made up of impact assessment, performance assessment and value assessment. As a result of the analysis, various technology groups were classified into smart city-related platform technologies, information sharing technologies, and network-related technologies, and based on the results of this research, it is expected that it will be able to apply technology patents related to smart cities to research and development strategies through key detailed technologies by major technologies of Smart City.