• 한국항공우주학회지
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• 제39권5호
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• pp.400-407
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• 2011

전해질 막의 응력 및 변화폭의 분포는 고분자 전해질 연료전지 (PEMFC, Polymer Electrolyte Membrane Fuel Cell)의 피로수명의 중요한 인자이다. 본 논문에서는 연료전지 운전조건의 hygro-thermal 조건에 의해 전해질 막에 발생하는 기계적 응력 해석을 모델링 하였다. 기체확산층과 전해질 막 사이의 접촉해석이 여러 가지 온도, 습도 조건에 대하여 수행되었다. 구조 모델은 온도와 상대습도에 의존하는 비선형 재료물성을 적용하였다. 몇 가지 기하학적 조건들이 모델에 적용되었다. 구조해석 결과는 전해질 막의 변형이 체결조건에 크게 의존함을 보여주었다. 실험 데이터와의 비교를 통해 운전 조건에 대하여 피로수명 예측이 수행되었다.

• Steel and Composite Structures
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• 제20권3호
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• pp.571-597
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• 2016

A new unified design formula for calculating the composite compressive strength of the axially loaded circular concrete filled double steel tubular (CFDST) short and slender columns is presented in this paper. The formula is obtained from the analytic solution by using the limit equilibrium theory, the cylinder theory and the "Unified theory" under axial compression. Furthermore, the stability factor of CFDST slender columns is derived on the basis of the Perry-Robertson formula. This paper also reports the results of experiments and finite element analysis carried out on concrete filled double steel tubular columns, where the tested specimens include short and slender columns with different steel ratio and yield strength of inner tube; a new constitutive model for the concrete confined by both the outer and inner steel tube is proposed and incorporated in the finite element model developed. The comparisons among the finite element results, experimental results, and theoretical predictions show a good agreement in predicting the behavior and strength of the concrete filled steel tubular (CFST) columns with or without inner steel tubes. An important characteristic of the new formulas is that they provide a unified formulation for both the plain CFST and CFDST columns relating to the compressive strength or the stability bearing capacity and a set of design parameters.

• 대한기계학회논문집A
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• 제30권12호
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• pp.1509-1517
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• 2006

The intervertebral fusion was reported to increase the degeneration of the neighboring region. Recently, a new technique of inserting an interspinous process fixator has been introduced to minimize the degenerative change in the lumbar spine. This study analyzed biomechanical effects of the fixator in the lumbar spine, and designed a new prototype to improve flexibility of the fixator with a reduced size. The evaluation was based on the displacement, stiffness and von-Mises stress obtained from the mechanical test and finite element analysis. A finite element lumbar model of L1 to L5 was constructed. The finite element model was used to analyze intervertebral fusion, insertion of a commercial fixator and a new prototype. The range of motion of intervertebral segments and pressures at vertebral discs were calculated from FEA. The results showed that the stiffness of the prototype was reduced by 32.9% than that of the commercial one.

• 한국전기전자재료학회논문지
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• 제21권11호
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• pp.987-994
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• 2008

The optimal structure of the Tonpilz transducer was designed. First, the FE model of the transducer was constructed, that included all the details of the transducer which used practical environment. The validity of the FE model was verified through the impedance analysis of the transducer. Second, the resonance frequency, the sound pressure, the bandwidth, and the impulsive shock pressure of the transducer in relation to its structural variables were analyzed. Third, the design method of $2^n$ experiments was employed to reduce the number of analysis cases, and through statistical multiple regression analysis of the results, the functional forms of the transducer performances that could consider the cross-coupled effects of the structural variables were derived. Based on the all results, the optimal geometry of the Tonpilz transducer that had the highest sound pressure level at the desired working environment was determined through the optimization with the SQP-PD method of a target function composed of the transducer performance. Furthermore, for the convenience of a user, the automatic process program making the optimal structure of the acoustic transducer automatically at a given target and a desired working environment was made. The developed method can reflect all the cross-coupled effects of multiple structural variables, and can be extended to the design of general acoustic transducers.

• 한국전기전자재료학회논문지
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• 제24권9호
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• pp.733-738
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• 2011

A novel design of a simple square-frame USM (ultrasonic motor) was proposed. The stator of the motor consists of a square-frame shape elastic body and four rectangular plate ceramics. The four ceramics were attached to inner surfaces of the square frame elastic body. The same phase voltages were applied to the ceramics on horizontal surfaces, and 90 degree phase difference voltage were applied to the ceramics on vertical surfaces. To find a model that generates elliptical motion at outside of the stator, the finite element analysis program ATILA was used. The analyzed results were compared to the experimental results. As result, the model EL10EH3ET0.5CL4 which generates the maximum elliptical displacement was chosen by analyzing the resonance mode according to changes in frequency.

• 전기학회논문지
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• 제66권12호
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• pp.1895-1898
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• 2017

This paper discusses methods for the torque ripple and noise reduction of DC motors for automotive air-conditioning based on electromagnetic field analysis. The target of the motor is a blower motor, and to reduce cogging torque and the torque ripple, the optimum model was selected by deforming the brush or commutator shape. In addition, to reduce the cogging torque, the model design was carried out by applying the skew method and the magnetization method of a magnet to the rotor. For optimization, the shape, material, and drive system of the motor were selected using an electromagnetic field as the analysis tool, and the method of reducing the cogging torque was applied to 4-pole, 12- and 13-slot motors considering the mechanical part. Lastly, this paper confirmed thatthemethod, which proposed how much noise, cogging torque, and vibration are reduced, improves through practical analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.676-681
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• 2001

We usually divide the noise of exhaust system into pulsation noise and flow noise. Pulsation noise is the shock wave to occur when the burning gas of low pressure emits and include harmonic having basic frequency as the exhaust cycle of engine. Flow noise is the noise that is produced when gas flow emits into the atmosphere through the pipe and has the character of frequency like pink noise which has the high level of high frequency component. A muffler is divided into reflective type and absorptive type. We usually use the muffler compounding the property of them. In this study, it is the case of transfer matrix method that a muffler is compounded to analyze the elements of each section according to sound wave's proceed direction. But we use simple model. So, we use finite element method that takes short time to analyze. Acoustic analysis gives us transfer matrix to use FEA of SYSNOISE and we use STAR-CD for fluid analysis. We made database that is based on analytical results about the muffler of expansion type, extended type, offset type, reverse type, and perforated type and developed the muffler design system to perform work efficiently.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.101-101
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• 2009

The purpose of this study is to develop the control technology of the welding distortion caused by Auto NG-GTA welding process at the STS 304 multi-pass butt weldment. For it, heat input model for Auto NG-GTA welding process was established and verified by measuring temperature change and molten pool shape at the bead-on-plate weldment. With heat input model developed, the effect of the tension load on the amount of welding distortion at the STS 304 multi-pass butt weldment was evaluated using the thermo-elasto-plastic FE analysis. In accordance with FEA results, the angular distortion and transverse shrinkage sharply decreased with an increase in tension load. This result indicates that tensioning method was verified as a countermeasure against the welding distortion of STS 304 multi-pass butt weldment.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.2
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• pp.489-494
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• 2006

The strain distribution in the vicinity of a hole in a tensile strip was measured using an image correlation method. The objective of this study is to evaluate the capability of predicting the strain component response using a constitutive model that was developed for use with paper materials. The need for a special constitutive model for paper derives from the characteristics of pronounced anisotropy and the fact that the material behaves differently under compressive loading than it does under tensile loading. The results of the simulation showed that predictions of strain distribution around the hole were in agreement with the experimental result trends, however, the agreement deteriorated as the edge of the hole was reached. It was observed that there is extensive inelastic strain that takes place around the hole prior to failure of the tensile strip. The simulation results showed that any difference between tensile and compressive behavior that may exist for paper material does not have any significant effect for the problem of this study because the level of compressive stress is quite low in comparison with compressive failure values.

• 한국산업융합학회 논문집
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• 제22권3호
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• pp.273-280
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• 2019

Carbon fiber composite laminate has been widely used in the area of sports applications such as race car, golf club, fishing rods, yacht. In this study, carbon fiber composite laminate was used in the rear upright of leisure purposed small size single-seat electric race car to reduce its unsprung mass of suspension system. The focus of this research is to investigate in finding optimal stacking lay-up of rear upright laminated with carbon fiber composite in the early design phase. Forces transferred from circuit road to rear upright were estimated through MBD(Multi-Body Dynamics)model of the rear suspension geometry. To evaluate the strength of the rear upright laminated with carbon fiber composite which generally behaves in an anisotropic or orthotropic manner, FEA(Finite Element Analysis) model suitable for composite materials was built followed by its strength was evaluated depending on different stacking lay-up. The result showed that Symmetric stacking lay-up [$45^{\circ}/-45^{\circ}/90^{\circ}/0^{\circ}$]s for frontal area and symmetric stacking lay-up with 1mm aluminum core [$45^{\circ}/-45^{\circ}/90^{\circ}/Core$]s for rear area were most suitable of 16 lay-up cases from the side of both strength based on Tasi-wu failure index and weight.