• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.85-90
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• 2010

Friction welding is a common practice to join axially symmetrical parts for automobile industry applications. The shaft for automobile reverse idle gear is generally produced by forging steel, SF 45. This method is not so good because of high cost of material and production. In this study, in order to investigate the possibility of application of SM 45C to SF 45 dissimilar friction welding, the dissimilar friction welded joints were performed using 20 mm diameter solid bar in forging steel(SF 45) to carbon steel(SM 45C). The optimal friction welding parameters were selected to ensure reliable quality welds on the basis of visual examination, tensile test, micro-Virkers hardness surveys of the bond of area and optical microstructure investigations for welded joint parts. Finally, post weld heat treatment(PWHT) of the high-frequency induction hardening was performed for the friction welded specimens under the optimal welding conditions. And then, the mechanical properties were compared for as-welded and PWHT in SM 45C to SF 45.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.970-976
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• 1996

An ester-carbonate copolymer was synthesized, in which carbonate was inserted into a biodegradable aliphatic polyester, poly(butylene succinate) (PBS), to modify its mechanical properties. The synthesis was carried out by condensation reactions in two steps. In the first step, oligo(butylene succinate) was prepared by the reaction of succinic acid with 1,4-butanediol (BD). In the second step, it was reacted with oligohexamethylenecarbonate diol (OHMCG) to prepare the ester-carbonate copolymer. Titanium(IV) isopropoxide (TIP) was used as a catalyst for the reaction. The structure of the copolymer was confirmed by FT-IR and $^1H$-NMR and the thermal behavior and mechanical properties were investigated by differential scanning calorimetry (DSC) and universal testing machine (UTM), respectively. It was found that optimum amount of the catalyst for the formation of high molecular weight copolymer was 1wt% for succinic acid. When the BD:OHMCG is in the range 149:1~249:1, the copolymer with high viscosity was obtained. As the OHMCG content was increased, melting temperature ($T_m$) of the copolymer was decreased. When BD:OHMCG is 149:1, the copolymer showed a increase in ultimate strain by two times and the slight decrease in modulus compared to those of PBS.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.47-54
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• 2013

This study investigates the crack growth behavior due to primary water stress corrosion cracking (PWSCC) in the dissimilar metal butt weld of a reactor piping using Alloy 82/182. First, detailed finite element stress analyses were performed to predict the stress distribution of the dissimilar metal butt weld in which the hydrostatic and the normal operating loads as well as the weld residual stresses were considered to evaluate the stress redistribution due to mechanical loadings. Based on the stress distributions along the wall thickness of the dissimilar metal butt weld, the crack growth behavior of the postulated axial and circumferential cracks were predicted, from which the crack growth diagram due to PWSCC was proposed. The present results can be applied to predict the crack growth rate in the dissimilar metal butt weld of reactor piping due to PWSCC.

• The Journal of the Acoustical Society of Korea
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• v.10 no.2
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• pp.13-22
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• 1991

The presence of an unbalanced mass is originated the common source of vibration in machines with rotating rotor. In this study, the unbalanced rigid rotor mounted on an overhang shaft is balanced using the static balancing procedure, and the compensation mass is estimated by the phase angle method and four run method. Also, the reduction of vibration level before and after balancing is examined. In the experimental results, it is shown that the vibration due to the unbalanced mass is decreased by eliminating the effect of the unbalance. Above all, the four run method is proved more effective on the ability of vibration reduction, in small unbalanced mass, the phase angle method.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.163-173
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• 2014

In this study, a modeling method is based on representing a road generation system with several rigid bodies, i.e, pad, shaft, torsional damper, oneway-clutch, gear system, and electricity generator. The simulation software is developed to evaluate the performance of a road generation system. It is used to determine parametric dimension for optimal design with the theoretically calculated results from the simulation software. The parametric dimensions are included as capacity, length, and angle of equipment. The transient responses at the conditions of low and high vehicle speed are compared with the calculated results as torque, power, out energy etc. Consequently, before manufacturing system, the analysis of simulation results shows that the proposed concept and system has efficiency and confidence.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.378-381
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• 2009

A rotating stall, an instable phenomenon of compressor, brings about reducing the pressure rise, the efficiency of compressor and a mechanical demage. In order to improve instability and extend operating range, it was performed that a stability enhancement experiment applying air injection method at the 4-stage low-speed axial compressor. The coanda nozzle was used to inject air in axial direction at rotor tip and 8 injectors were set up at regular interval at the upstream of 1st stage rotor. At 80% speed, injectors were worked before rotating stall happened. As injecting the 5.4% air of mode inception flow rate, the stability of compressor operation enhanced about 4%.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.102-109
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• 2006

In this Paper, Support Vector Machine(SVM) and Artificial Neural Network(ANN) are used for developing the defect diagnostic algorithm of the aircraft turbo-shaft engine. The system that uses the ANN falls in a local minima when it learns many nonlinear data, and its classification accuracy ratio becomes low. To make up for this risk, the Separate Learning Algorithm(SLA) of ANN has been proposed by using SVM. This is the method that ANN learns selectively after discriminating the defect position by SVM, then more improved performance estimation can be obtained than using ANN only. The proposed SLA can make the higher classification accuracy by decreasing the nonlinearity of the massive data during the training procedure.

• Journal of Korea Technology Innovation Society
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• v.7 no.2
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• pp.223-255
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• 2004

이 논문은 Carlsson and Stanklewicz(1991)가 창안한 기술시스템(technological systems)의 개념을 한국과 스웨덴의 산업용로봇에 적용하여, 양자를 비교 분석하고자 하였다. 먼저 기술시스템의 개념을 재구축하고, 동태적인 측면에서 시스템의 진화과정을 보강한 다음, 한국과 스웨덴의 산업용로봇에 대한 기존 연구를 활용하여 양 기술시스템의 중요한 특징들을 비교하고 그 성과를 측정하였다. 한국과 스웨덴에 있어서 산업용로봇 기술시스템의 진화과정은 공히 미국, 일본 등 기술선도국을 모방하는 입장에 있었음에도 불구하고 '학습기간'이 20여 년 이상 소요됨을 보여주었다. 뿐만 아니라 양 시스템의 진화과정. 특히 태동기(embryo stage)에 있어서 정부의 역할이 매우 컸던 것으로 분석되었다. 그러나 기술시스템의 구성요소인 산업네트워크, 기술하부구조, 그리고 제도적하부구조 면에서 강약점 및 특징의 차이가 있음을 발견하였다. 기술시스템의 동태적 성과면에서는 한국의 경우가 스웨덴의 경우보다 상대적으로 더 우월한 것으로 평가되었다. 이는 스웨덴 시스템에서는 초기에 우위를 누렸던 기계, 전기, 그리고 메카트로닉스 기술의 우위와 사용자 능력이 점차 약화되어온 반면에 한국의 시스템은 기술하부구조 등이 취약하였지만 해외시스템과의 연계, 재벌 내에서의 기업간 연계, 산학연 협동, 그리고 지역내 연계 등 시스템내의 연계성이 기술적으로 취약한 부분을 보전해 주었기 때문인 것으로 분석되었다. 따라서 어느 한 기술시스템이 자생적으로 생명력을 이어가기 위해서는 시스템 구성요소의 개별적 형성 및 발전보다는 구성요소간 그리고 시스템내의 다양한 활동주체들의 상호작용과 연계성이 중요함을 강조하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.397-404
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• 2012

In this research, a numerical study was carried out on the mixing and flow characteristics of a vane-type static mixer for the reduction of $NO_x$ in the SCR systems from the diesel exhaust environments. The mixer was located at a distance of 57 times the pipe diameter away from the inlet. The analyses were performed by changing various parameters such as vane angles, blockage ratio, and location of the vane. Flow characteristics through the mixer were characterized by the uniformity index, swirl number, and pressure drop. The results show that uniformity index, pressure coefficient and swirl number are substantially influenced by the vane angle, blockage ratio and position of the vane of the mixer. In particular, the swirl number was increased when the vane was located near the pipe wall, or the vane angle was increased or scale was extended.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.125-125
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• 2017

본 연구에서 원추형 태양열 집광기의 흡수관 표면의 흑색 도색 여부에 따른 효율분석을 수행하였다. 원추형 집광기 시스템은 열 손실 최소화 및 집광비가 우수한 $45^{\circ}$의 원추각을 갖는 원추형 집광기를 설계 및 제작하였다. 원추형 태양열 집광시스템은 열매체 축열을 위한 온도센서가 내장된 축열조와 태양에너지를 집열시키는 원추형 집광기, 유량측정을 위한 유량계, 열매체의 강제순환을 위한 펌프로 구성되어있다. 또한 지속적인 태양추적을 위해 2축 태양 추적 장치를 설치하였다. 흡수관은 원추형 집광기의 중심부에 설비되었으며, 열매체의 순환을 위해 이중 열교환기 구조로 제작되었다. 흡수관의 길이는 열 손실을 최소화하기 위하여 집광기의 높이와 동일하게 설계하였다. 원추형 집광시스템의 작동유체인 물은 펌프에 의해 흡수관과 축열조를 강제순환 하게되고, 용량이 70L인 축열조에 흡수관으로부터 흡수된 태양 복사열이 저장된다. 원추형 집광시스템의 성능실험은 청명한 날 유량 2L/min, 4L/min, 6L/min에 대해 수행되었으며, 집열효율을 계산하여 비교 및 분석하였다. 흑색으로 도색된 흡수기를 부착한 원추형 집광시스템의 집열효율은 82.25%로 나타났으며, 무 도색 흡수관을 갖는 원추형 집광시스템은 73.26%의 집열효율을 나타내었다. 따라서 본 연구를 통해 흡수관 표면의 흑색 도색이 원추형 집광시스템의 집열효율에 큰 영향을 미친다는 것을 알 수 있었다.