• 대한기계학회논문집A
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• 제36권5호
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• pp.529-535
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• 2012

본 논문의 목적은 계장화 압입시험과 유한요소해석을 이용하여 아연도금강판의 기계적 물성을 추정하는 것이다. 먼저 인장시험을 통하여 유한요소해석에 요구되는 두께에 따른 아연도금강판의 기계적 물성을 획득하였으며, 이를 이용하여 유한요소해석을 수행하여 특정지점에서의 소성 응력 및 변형률을 획득하였다. 이러한 유한요소해석의 유효성은 계장화 압입시험의 하중-변위선도와 비교를 통하여 검토하였다. 유한요소해석을 통하여 구한 진응력-진변형률 곡선을 인장시험 결과와 비교하여 이의 정확성을 검증하였으며 또한 이를 바탕으로 대표 응력 및 변형률 산출지점을 재평가하였다.

• 전자공학회논문지SC
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• 제45권6호
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• pp.117-122
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• 2008

맥진은 한의 진단에 있어 중요한 요소이나 맥진 교육에 있어서 수련자와 교육자 간에 언어적 표현 외에는 적절한 교육 정보 소통의 도구가 없어 정량적이며 과학적 교육이 어려운 실정이다. 이에 본 논문에서는 맥진 시 한의사가 세 손가락을 통해 맥진 부위에 가하는 가압력 프로파일을 정량적으로 측정할 수 있는 하드웨어와 이를 기반으로 맥진 동작을 트레이닝할 수 있는 프로그램을 개발하였다. 가압력 프로파일 측정 하드웨어는 인조 팔 속 맥진 위치에 놓인 3개의 로드셀과 맥진 가압력 신호를 증폭하는 증폭부 및 상용 A/D 변환 모듈인 NI-USB 6009로 구성하였으며, 3채널 가압력 신호는 200Hz로 샘플링하였다. 하드웨어 출력 신호를 질량 값으로 교정할 수 있도록 $50{\sim}500g$ 범위의 8개 추를 인조 팔에 올려놓았을 때의 질량 대비 출력전압 테이블을 작성하였다 또한, 이 시스템을 통해 한방 전문의 3명의 맥진 가압 프로파일을 각 3회씩 측정해 보았으며, 이를 통해 한의사의 맥진은 크게 3개의 구간으로 나눌 수 있고 최대 가압력이 약 $500g{\cdot}f$인 것 등을 알 수 있게 되었다. 맥진 가압트레이닝 프로그램은 LabView를 통해 구현하였으며, 수련자가 미리 저장된 목표 맥진 가압 프로파일과 유사하도록 인조 팔을 맥진할 때의 가압 프로파일이 목표 가압 프로파일과 유사한 정도를 평가하여 일정 범위를 벗어나면 경고하고, 실습이 끝나면 목표 프로파일과 유사도 점수를 화면에 표시하도록 하였다. 더 나아가 유사도 점수의 추이를 통해 숙련 추이를 관찰 할 수 있도록 하였다. 이 시스템을 맥진 교육에 활용한다면 보다 정량적이며 과학적인 교육이 가능해질 뿐만 아니라 교육의 효율도 크게 향상될 것으로 기대된다.

• 대한기계학회논문집
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• 제17권2호
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• pp.285-299
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• 1993

본 연구에서는 UBET를 이용한 프로그램을 개발하여 소성가공 문제에 적용하였 으며, 형단조 가공에서 형 내부의 재료의 비정상 유동을 해석할 수 있는 알고리듬을 제시하였다. 매 변형단계에서 요소별 가공경화를 고려하여 자동적으로 요소시스템 (element system)을 재구성함으로써, UBET에 의한 소성가공 문제 해석을 효율적으로 할 수 있도록 하였다. 축대칭 형단조 문제에 있어서 리브의 높이대 폭의 비가 1.0, 2.0일때 UBET 및 탄소성 유한요소법에 의하여 형 내부의 재료 층만 과정을 시뮬레이션 하였으며, 단조 하중, 다이 충만도 및 재료의 유동 경향을 분석하여 적절한 유동 모델 과 초기 소재의 형상을 구하였다. 모델 재료를 사용한 형단조 모의실험을 수행하여 재료유동 및 변형 단계별 단조 하중분포 등을 구하였으며, 해석결과와 비교 분석하였 다. 또한 후방압출(backward extrusion) 및 평두형 펀치에 의한 평판압입(flat pu- nch indentation) 문제를 해석하였다. 후방압출시 모서리부의 라운딩(rounding) 효 과가 재료 유동에 미치는 영향을 고려하였으며, 평두형 펀치에 의한 평판압입에서는 상당 소성변형률(equivalent plastic strain)의 분포를 탄소성 유한요소법(elastic plastic finite element method)에 의한 결과와 비교하였다.

• 한국세라믹학회지
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• 제35권12호
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• pp.1316-1322
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• 1998

The amount of VC and C/N ratio in Ti(CN) was varied to investigate the effect of VC addition on the mi-crostructural change in Ti(CN)-Ni system. As the amount of VC addition increases in Ti(C0.7N0.3)-20Ni sys-tem a complete solid solution was observed in Ti(C0.7N0.3)-20Ni-25VC system. It implies that the ratio of the dissolution rates of Ti(C0.7N0.3)to that of VC is nearly 2:1 at the sintering conditions used in this study. It was found from the experiments that the system composed of the Ti(C0.7N0.3) phase exhibits a rimless structure and relatively small amount of solid solution. That is among Ti(C0.7N0.3) phase exhibits a rimless structure and relatively small amount of solid solution. This is among Ti(C1-xNx) phases the dissolution rate of Ti(C0.3N0.7) is the lowest. Also fracture toughness(KIC) of the cermet was measured by indentation method. Attentions were paid to crack propagation path to look for a dominant fracture mode and to cor-relate it with fracture toughness values. The fracture toughness was relatively high with the addition of VC content. But the addition of a large VC content reduced the overall toughness of the cermet. This result is explained with the difference in fracture mode.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.243-246
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• 2006

In this paper, Experimental results on the measurement of mechanical properties of fine patterns in the MEMS structure are described. The mechanical properties of embossing patterns on metallic thin foil is measured using the nano indentation system, that is developed by Korea Institute of Industrial Technology(KITECH). These micro embossing patterns are fabricated using CIP(Cold Isostatic Press) process on micro metallic thin foils(Al-1100) that are made by rolling process. These embossing patterned metallic thin foils(Al-1100) are used in the reflecting plate of BLU(Back Light Unit) and electrical/mechanical MEMS components. If these mechanical properties of fine patterns are utilized in a design procedure, the optimal design can be achieved in aspects of reliability as well as economy.

• Interaction and multiscale mechanics
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• 제3권3호
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• pp.267-276
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• 2010

A nonlocal finite element model is developed for solving elasto-static frictional contact problems of nanostructures and nanoscale devices. A two dimensional Eringen-type nonlocal elasticity model is adopted. The material is characterized by a stress-strain constitutive relation of a convolution integral form whose kernel is capable to take into account both the diffusion process of nonlocal elasticity and the scale ratio effects. The incremental convex programming procedure is exploited as a solver. Two examples of different nature are presented, the first one presents the behavior of a nanoscale contacting system and the second example discusses the nano-indentation problem.

• Journal of Welding and Joining
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• 제23권3호
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• pp.40-46
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• 2005

Air gun has been one of the good tools to press two sheet metals. However, it is not easy to control the acting force precisely. A Servo-gun is a good tool to control the acting force on the workpiece comparing with the air gun. Servo-gun has a higher tensile shear strength and lower indentation depth as well as smaller spatter. Dynamic resistance was obtained according to the acting force and welding current. As the acting force was changed during welding, the welding quality was increased.

• 자동차안전학회지
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• 제7권3호
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• pp.19-24
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• 2015

Brake pads are a component of disc brake system of automobile and consist of steel backing plates and friction material facing the disk brake rotor. Due to the repeated sliding forces and torque in vehicle braking, friction performance of brake pads are ensured. Futhermore, the brake pad is one of major tuning components in aftermarket, mechanical characteristics of the brake pad are necessary to evaluate for establishing the certification standards of tuning components. This study had performed the five specimen tests for friction coefficients and wear loss rates according to the SAE test specification. Using the instrumented indentation method, yield strength and tensile strength were measured. Friction coefficients, 0.386 - 0.489, and wear loss rates, 1.0% - 3.7% are obtained. The range of yield strength and tensile strength are 21.4 MPa - 105.3 MPa and 39.5 MPa - 176.4 MPa respectively.

• 한국정밀공학회지
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• 제11권3호
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• pp.105-121
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• 1994

In this paper, we proposed the two-parameter model for predicting the residual strength in CFRP laminated composites subjected to high velocity impact and developed and formulated it based upon Cparino's by using the ratio of impact and the normalized residual strength. Critical indentation was obtained by the statical indentation tests. Impact tests were carried out through air-gun type impact equipment with the velocities varied 30-100m/sec. Projectiles were steel balls with 5 and 7mm in diameter. Test material was carbon/epoxy. The specimens were composed of [ .+-. 45 .deg. /0 .deg. /90 .deg. ]$\_$2/ and [ .+-. 45 .deg. ]$\_$4/stacking sequences and had 0.75$\^$T/*0.26$\^$W/*100$\^$L/(mm) dimension. Results from the proposed model were in good agreement with the test data. And failure mechanism due to high velocity impact is given here to examine the initation and deveolpment of damage by fractography and ultrasonic image system. The effects of the 0 .deg. -direction ply position and the amount to damage area on the residual strength are considered here.

• 동력기계공학회지
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• 제8권3호
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• pp.18-22
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• 2004

Boiler is one of the most important utilities providing steam to turbine in order to supply mechanical energy in thermal power plant. It is composed of thousands of tubes for high efficient heat transfer. The material for boiler tubes is used in such high temperature and pressure condition as $540^{\circ}C$, 22MPa. The boiler tube material is required to resist creep damage, fatigue cracking, and corrosion damages. 2.25%Cr-1Mo steel is used for conventional boiler tubes, and austenitenite stainless steel is used for higher temperature boiler tubes. But the temperature and pressure of steam in power plant became higher for high plant efficiency. So, the property of boiler tube material must be upgaded to fit the plant property. Several boiler tube material was developed to fit such conditions. X20CrMoV12.1 steel is also developed in 1980's and used for superheater and reheater tubes in supercritical boilers. The material has martensite microstructures which is difficult to evaluate the degradation. In this thesis, degrade the X20CrMoV12.1 steel at high temperatures in electric furnace, and evaluate hardness with Vickers hardness tester and strengths with Indentation tester.