• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.447-451
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• 2015

The objective of this study is to predict the structural characteristics of a heat exchanger mounted on an aircraft engine using finite element analysis. The plastic fracture and life of the heat exchanger were estimated by a thermo-mechanical analysis. Tensile tests were conducted under high temperature conditions (700, 800, 900, 1000 K) using five specimens to obtain the mechanical properties of the Inconel 625 tubes. To assess the structural characteristics of the heat exchanger, the full and partial models were applied under the operating conditions given by the thermo-mechanical and inertial load. As a result, the case, tubesheet, flange, and mounting components have a reasonable safety margin to the allowable stress assuming a fatigue strength of Inconel 625 of 10000 cycles under 1000 K.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.652-658
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• 2016

In this paper, the theoretical research and simulation using the Finite Element Method (FEM) to design and form a micro-pattern for an ultrasonic horn is described. The present method is based on an initial design estimate obtained by FEM analysis. The natural and resonant frequencies required for the ultrasonic tool horn used for forming the fine pattern were predicted by finite element analysis. FEM analysis using ANSYS S/W was used to predict the resonant frequency for the optimum technical design of the ultrasonic horn vibration mode shape. When electrical power is supplied to the ultrasonic transducer, it is converted into mechanical movement energy, leading to vibration. The RFID TAG becomes the pattern formed on the insulating sheet by using the longitudinal vibration energy of the ultrasonic tool horn. The FEM analysis result is then incorporated into the optimal design and manufacturing of the ultrasonic tool horn.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.78-84
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• 2012

Mold may experience deterioration of molding quality as the abrasion of mold occurring due to friction between mold and molded product works as allowance in the course of press process. Therefore, to improve the wear-resistance of mold, methods like nitriding, carburizing, flame and induction surface hardening treatment etc have been applied. However, as such methods are accompanied by problems like shape limitation or product deformation etc, laser surface treatment technology is under review as surface treatment method that can solve such problems. Therefore, in this study, mold material cast iron was surface-treated by using high power diode laser. In previous report 1 and report 2, the heat treatment characteristics were compared by the differences of die materials and shapes, then this paper observed microstructure by using optical microscope and scanning electronic microscope to analyze the structural difference of hardened zone, interface area and base metal after heat treatment. And the structural condition was grasped through EDS. As a result of microstructure, hardened zone showed formation of acicular martensite.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.4
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• pp.73-79
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• 2003

With the variation of Ag concentration in bath, current density, duty cycle, additive and agitation for electroplating of Sn-Ag solder, the compositions and the morphologies of solder were studied. It was possible to controll Ag content in Sn-Ag solder by varying Ag concentration in bath and current density. The microstructure size of Sn-Ag solder decreased with increasing current density. Duty cycle of pulse electroplating and quantity of additive affected on Ag content of deposit and surface roughness. In this work eutectic Sn-Ag solder bumps with fine pitch of 30 $\mu\textrm{m}$ and height of 15 $\mu\textrm{m}$ was formed successfully. The Ag content of electrodeposited solder was confirmed by EDS and WDS analyses and the surface morphologies was analyzed by SEM and 3D surface analyzer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.589-594
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• 2014

Recently, higher capacity and energy density of lithium ion batteries are increasingly demanded for enhancing their performance in view of the rise in the commercial distribution of electric and hybrid vehicles. Computational analysis of a porous structure of vanadium pentoxide cathode was performed, employing a phase field model. The incipient model was designed as a spherical structure with cylindrical-shaped pores. Modifying the diameters and lengths of the pore cylinder and the number of pores, we considered different conditions for the porous vanadium pentoxide cathodes for analyzing their effect on the amount of lithium ion intercalated to them. Subsequently, we optimized the porous structure to contain the largest amount of intercalated lithium ion during discharge.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.6 s.312
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• pp.16-26
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• 2006

In this paper, we propose a 3D shape restoration system which measures height and surface shape of transparent ITO glass and delivers errors in focal length and incident angle of laser beam to femto-second laser micromachining. The proposed system is composed of a line scan laser, a high resolution camera, a linear motion guide synchronized to image capturing, and a control station. Also, we define the sensitivity indices that represent a relation between measurement error and a position of a camera and scan laser, and utilize it for optimum design. The results of the proposed system are compared with results of SPM(Scanning Probe Microscope) and prove the usefulness of the system.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.993-998
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• 1998

In this study TiNi/A16061 shape memory composite is introduced as one of new material using a shape memory alloy. High tensile strength of composite due to compressive residual stress in matrix by the shape memory effect of TiNi fiber can be produced. This composite can remove the tensile residual stress by the difference of coefficients of thermal expansion between fiber and matrix. one of the significant weak point of metal matrix composite. In this paper, shape memory composites are made by squeeze casting. And then, microstructure and fatigue properties of the composites by shape memory effect above inverse transformation temperature A, of TiNi alloy are discussed. The results of the fatigue crack control properties of TiNi/A16061 shape memory composite by a squeeze casting are summarized as follows the effect of fatigue crack propagation control at 363K increases according to the increase of volume fraction and prestrain in composites.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.293-299
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• 2022

Recently, various stakeholder are interested in microplastic to cause pollution of the marine's ecosystem and effort to conduct study of product's life cycle to reduce pollution of marine's ecosystem. The micorplastic refer to materials of the nano- to micro- sized units and it can be classified into primary and secondary. The primary microplastic mean the manufactured for use in the specific field such as the microbead of the cosmetic or cleanser. also, secondary mean the unintentionally generated during use of the product such as the textile crumb by the doing the laundry. Tire and Road Wear Particles(TRWPs) are also defined as secondary microplastic. Typically, TRWPs are created by friction between the tread compound's rubber of the tire and the surface of the road du ring the driving cars. Most of the generated TRWPs exist on the roadside and some of them were carried to marine by the rainwater. In this study, we perform the quantitative analysis of the TRWPs existed in fine dust at the roadside. So, we collected the dust from the roadside in Chungcheongnam-do's C site with a movement of 1,300 cars per the hour. The collected samples were separated according to size and density. And shape analysis was performed using the Scanning Electron Microscope(SEM). We were possible to discover a lot of TRWPs at the fine dust of the 100 ± 20 ㎛. And we analysis it u sing the Thermo Gravimetric Analysis(TGA) and Gas Chromatography/Mass Spectrometer(GC/MS) for the quantitative components from the tire. As a result, it was confirmed that TRWPs generated from the roadside fine dust were included the 0.21 %, and the tire and road components in the generated TRWPs consisted of the 3:7 ratio.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.96-96
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• 2003

비정질 합금은 기존 결정질 합금에서는 얻을 수 없는 독특한 물리적, 화학적, 기계적, 전자기적 특성을 나타내는 것으로 알려져 있다. 비정질을 형성하기 위해서는 매우 큰 냉각속도가 필요하므로 제조 가능한 비정질 합금은 분말, ribbon, 박판 형태로 제한되어 있다. 최근 비정질 분말 제조 및 벌크 비정 질에 관한 연구는 많은 발전을 보아 왔지만, 아직도 고청정 비정질 합금 분말의 제조와 대량 생산화 관해서는 많은 연구가 요구된다. 본 연구에서는 고청정 Ni-Zr-Ti-Si-(Sn)계 벌크 비정질 분말을 가스분무법으로 제조하였다. 제조된 합금 분말은 각 입도 별로 구분하여, XRD 분석을 통하여 비정질 형성 가능 입도을 분석하였다. 분말의 외형은 SEM으로 분석하였으며, 미세구조는 TEM을 사용하였다. 열적특성은 DSC 분석으로 조사하였다. 또한 제조한 비정질 분말의 미세구조와 비교하기 위하여 Tg와 Tx 온도범위에서 열처리 한 분말의 미세구조를 분석하였다. XRD 분석 결과, 가스분무법으로 제조된 Ni-Zr-Ti-Si-(Sn) 분말 중에서 75$\mu\textrm{m}$ 이하의 분말은 비정질상을 가졌으며, 75$\mu\textrm{m}$ 이상의 분말은 결정질 또는 비정질의 혼합 상으로 구성되었다. 비정질 분말 회수율은 약 60% 이상이었다. 미세 TEM 분석에서 75$\mu\textrm{m}$ 이하 분말은 전형적인 비정질 Halo 형상을 보였으며, 결정질이 혼합된 분말은 비정질 기지상에 결정질 응고 수지상 조직이 혼합되어 있음을 확인하였다.

• 기계와재료
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• v.23 no.3
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• pp.16-29
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• 2011

결정 합금 대비 비정질 합금은 높은 경도를 갖기 때문에 마모 저항성도 좋고 내부 식성 등 환경에 대한 저항성도 월등하며, 또한 과냉된 액상 상태까지 재가열하게 되면 낮은 점성도를 갖게 되므로 복잡한 3차원적인 형상을 가지는 부품을 환경에 대한 저항성, 피로 저항성, 강도 및 경도 등을 모두 고려하여 높은 정밀도를 가지고 제조하는 것이 가능하므로 우수한 물성을 갖는 구조 및 기능성 재료로의 다양한 응용이 타진되고 있다. 이러한 비정질 합금의 변형 거동에 대한 연구는 대부분 유리 천이 온도 이하에서의 전단 및 파단에 이르는 이른바 불균일 변형(Inhomogeneous Deformation) 거동에 대한 이해를 위한 실험 및 해석적 연구에 집중되어 왔다. 반면 상업화의 기반이 되는 고상 기반 2차 정형 성형은 과냉 액상 영역에서의 구조 완화 및 결정화롤 대표되는 미세 구조 제어 균일 변형(Homogeneous Deformation)에 대한 이해 없이는 불가능하므로, 이러한 관점에서 비정질 합금 특유의 점성 유동 특성을 이용한 균일 변형 응용 예시 및 미세구조 변화 연계 해석 기술의 현황을 소개하고자 한다.