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김헌영,김호,김중재,Kim, Heon-Young,Kim, Ho,Kim, Joong-Jae 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.12
A rubber-like material model is generally characterized by hyperelasticity and formulated by a total stress-total strain relationship because the material shows nonlinear elastic behaviour under large deformation. In this study, a pressure potential obtained by a separately interpolated pressure is introduced to the non-linear finite element formulation incorporating with incompressible or almost incompressible condition of the material. The present formulation is somewhat different from the general formulation using the pressure computed in the displacement field. A non-linear finite element analysis program is developed for the plane strain and the axisymmetric contact problems of a rubber-like material. Various examples with rubber material are analyzed for its verification. The results about deformed shapes and stress distributions thought to be meaningful in comparison with a commercial program, MARC.
단일 모드 광섬유의 굽힘손실을 이용한 다점 측정 센서 시스템
김헌영,김대현,Kim, Heon-Young,Kim, Dae-Hyun 한국비파괴검사학회 2015 한국비파괴검사학회지 Vol.15 No.1
지능형 센서 기반의 구조 건전성 감시를 통해 안전성을 확보하기 위한 연구는 우주항공을 비롯하여 기계/토목 구조물, 수송 기계 분야로 확대되었다. 특히, 실시간으로 운용되는 구조물은 사고로 인한 재산 및 인명 피해를 예방하기 위해 여러 스마트 센서 기반의 구조 건전성 감시 기술이 요구되는 결과로 이어졌다. 한편, 상용화되어 있는 대부분의 센서는 전자기 기반의 센서로써 전자기 간섭 및 부식과 같은 적용성의 제한과 환경적 요인에 취약할 수 있다. 따라서, 전자기 기반 센서의 단점을 보완하기 위한 신개념 센서로 광섬유 센서가 최근 각광을 받고 있다. 하지만, 광섬유 센서를 이용한 실제 구조물의 감시를 위해서는 고가 장비와 시스템이 요구되어 어려움이 존재한다. 따라서, 본 연구에서는 한 가닥의 광섬유를 이용하여 여러 지점에서 발생할 수 있는 충격을 검출하는 센서 시스템을 제안하였다. 이를 위해, 광섬유 굽힘 손실 현상을 이용하여 같은 충격에 대해 위치별 광 강도의 변화량 차이가 존재하도록 센서부의 모듈을 제작하였다. 그리고, 광 강도 변화에 영향을 미치는 변수들을 이용하여 실험 설계를 하였으며, 충격 위치 검출이 가능함을 실험적으로 검증하였다. Applications of smart sensors have been extended to safety systems in the aerospace, transportation and civil engineering fields. In particular, structural health monitoring techniques using smart sensors have gradually become necessary and have been developed to prevent dangers to human life and damage to assets. Generally, smart sensors are based on electro-magnets and have several weaknesses, including electro-magnetic interference and distortion. Therefore, fiber optic sensors are an outstanding alternative to overcome the weaknesses of electro-magnetic sensors. However, they require expensive devices and complex systems. This paper proposes a new, affordable and simple sensor system that uses a single fiber to monitor pressures at multiple-points. Moreover, a prototype of the sensor system was manufactured and tested for a feasibility study. Based on the results of this experimental test, a relationship was carefully observed between the bend loss conditions and light-intensity. As a result, it was shown that impacts at multiple-points could be monitored.
김헌영,최종길,김정민,이강욱,여태정,Kim, Heon-Young,Choi, Jong-Gil,Kim, Jung-Min,Lee, Kang-Wook,Yeo, Tae-Jung 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.3
Numerical analyses are carried out to evaluate the cumulative impact damage of an automotive front end bumper under the low speed crash events(CMVSS215) by using explicit code. Results of first impact simulation, which are deformed shape, thickness, stress tensors and strain tensors, are used as the initial conditions for a next impact simulation. Between the events, the residual vibration is damped out by using nodal damping, and then recovery after each event is evaluated by several methods, one of which is a springback analysis with implicite finite element analysis code. The coupled analysis scheme for the evaluation of cumulative impact damage is verified through the comparison with test results.
[구조강도부문] 도어시일 설계를 위한 고무 품 전용비선형 해석 프로그램 개발
김헌영(Heon-Young Kim),정기종(Ki-Jong Jong),김호(Jung Ho Kim) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_2
Door-Seal is a mechanical element which has the function of isolating dust, rain, noise and vibration from outside of a car. The basic requirements of door-seal are a good sealing and minimizing door closing effort these two requirements conflicting with each other has increase the difficulty in design process with highly nonlinear material, rubber and foam Using computer simulation in design process, a conventional analysis tools are hard to reflect all design parameter of door-seal. A new design tool is needed to promote the overall efficiency of design and save cost & time. In this paper, we introduce an exclusive design program for door-seal only. Non-linear finite element formulation has been developed using rubber and foam material description and a solution procedure for conflict problems are installed into formulation. Private pre-processor and post-processor are designed to have effectiveness in considering all design parameters and concept of managing all work-process including minimum door-closing velocity analysis has involved. To verify practical use, a automotive door part and door-seal component were analyzed and compared with the result commericial analysis tool and test
김헌영(Heon Young Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
Although the use of lightweight alloy sheets has rapidly increased, their applications are still limited due to low formability issues of the materials. Moreover, it is difficult to express the mechanical behavior and to predict the failure of the lightweight alloy sheets using existing elastic-plastic material models. Therefore, development of an appropriate constitutive law and a reliable failure model for the lightweight alloy sheets is needed. In this paper, the design of a cyclic tension-compression loading tester for evaluating the hardening characteristics of lightweight alloy sheets at different temperature is presented. With experimental data obtained employing this kind of specifically designed apparatus, a constitutive law of magnesium alloy sheet is suggested. Moreover, a method for formability evaluation through a finite element analysis using cross shaped cup is introduced in this study. Finally, several failure models are applied in a typical LDH (limit dome height) analysis to evaluate formability of material and in a strength analysis of welding specimens to assess the performance of welding joints considering failure effects.