• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.702-707
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• 2000

Under the rapid change of a new vehicle model, it is necessary to develop a durability analysis technique using computer simulation. In order to do this. reliable dynamic stress-time history for the vehicle components must be calculated on various road conditions. In this paper, a full vehicle simulation model which is composed of flexible frame and chassis components is proposed and verified its reliability from the comparison with field test data. Finally, dynamic stress-time history on the rear chassis components is predicted with hybrid and modal superposition method.

• 한국정밀공학회지
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• 제22권1호
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• pp.73-81
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• 2005

A multi-purpose polariscope is developed by applying an electro-mechanical control system to a diffused transmission-type circular polariscope. A conventional polariscope is only good for manual control of optical elements. The new polariscope system is devised to be controlled through two stepping motors and two magnetic clutches. The developed system has both functions of a conventional linear- and circular-polariscope. The new polariscope can be used not only for the point-wise measurement using Tardy compensation technique but also for the full-field fringe analysis using conventional and/or phase measuring techniques, if applicable.

• 한국전산구조공학회논문집
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• 제29권4호
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• pp.309-315
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• 2016

최근 치의학 분야에서도 인체에 대한 구조적이고 역학적인 이해를 위하여 유한요소해석 기법이 널리 사용되고 있다. 따라서 본 연구에서는 CT 이미지를 기반으로 하는 유한요소모델링 기법을 제안하고, 실험결과와 비교하여 검증하였다. 또한 제안된 해석기법을 통해 교합 시뮬레이션을 구현하여 정상 I급 교합과 Full-CUSP II급 교합상태의 두개골 모델에 대하여 기하비선형구조해석을 수행하였다. 그 결과, 하악골이 같은 거리만큼 이동할 때 사람의 실제 교합력 범위에서는 두 모델의 교합력에 큰 차이가 없는 것으로 나타났다. 그러나 응력분포를 비교했을 때 정상 I급 교합모델은 치아 및 치조골 전반에 응력이 균등하게 발생하는 반면, Full-CUSP II급 교합모델의 경우 일부 구역에 응력집중 현상이 나타났다. 이는 치아의 부재 및 재배열로 인하여 교합면이 달라지면서 생긴 결과라고 분석된다.

• International Journal of Korean Welding Society
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• 제5권1호
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• pp.60-65
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• 2005

In the field of welding the mechanical behavior of a welded structure under consideration may be predicted via heat transfer and welding residual stress analysis. Usually such numerical analyses are limited to small regular mesh models or test specimens. Nevertheless, there is very few strength assessment of the whole structure that includes the effect of welded residual stress. The present work is based on the specialized finite element codes for the calculation of nonlinear heat transfer details and residual stress including the external load on the welded RHS (Rectangular Hollow Section) T-joint connections of the whole structure. First the thermal history of the combined fillet and butt-welded T-joint equal width cold-formed RHS are calculated using nonlinear finite element analysis (FEA) considering the quarter model of the joint. Then using this thermal history the residual stress around the joints has been evaluated. To validity the FEA result, the calculated residual stresses were compared with the available experimental results. The residual stress obtained from the quarter model is mapped to the full model and then to the whole structure model using FEM codes. The results from the FEM codes were exported to the commercial package for visualization and further analysis applying loads and boundary conditions on the whole structure. The residual stress redistribution along with the external applied load is examined computationally.

• 한국해양공학회지
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• 제10권2호
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• pp.106-119
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• 1996

The ceramic has various high mechanical properties such as heat, abrasion, corrosion resistance and high temperature strength compared with metal. It also has low speciffic weight, low thermal expansibillity, low thermal conductivity. However, it could not be used as structural material since it is brittle and difficult for the machining. Therefore, there have been many researches to attempt to join ceramic with metal which is full of ductillity in order to compensate the weakness of ceramic.The problem is that residual stress develops around the joint area while the ceramic/metal joint material is cooled from high joining temperature to room temperature due to remarkable difference of thermal expansion coefficients between ceramic and metal. Especially, the residual stress at both edges of the specimen reduces the strngth of joint to a large amount by forming a singular stress field. In this study, two dimensional finite element method is attempted for the thermal elastic analysis. The joint residual stress of ceramic/metal developed in the cooling process is investigated and the change of joint residual stress resulted from the repetitive heat cycle is also examined. In addition, it is attempted to clarify the joint stress distribution of the case of tensile load and of the case of superposition of residual stress and actual loading stress.

• Structural Engineering and Mechanics
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• 제17권6호
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• pp.829-862
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• 2004

This paper presents a method for the nonlinear analysis of beam elements subjected to the cyclical combined actions of torsion, biaxial flexure and axial forces based on an extension of the disturbed compression field (DSFM). The theoretical model is based on a hybrid formulation between the full rotation of the cracks model and the fixed direction of the cracking model. The described formulation, which treats cracked concrete as an orthotropic material, includes a new approach for the evaluation of the re-orientation of both the compression field and the deformation field by removing the restriction of their coincidence. A new equation of congruence permits evaluating the deformation of the middle line. The problem consists in the solution of coupled nonlinear simultaneous equations expressing equilibrium, congruence and the constitutive laws. The proposed method makes it possible to determine the deformations of the beam element according to the external stresses applied.

• 한국항공우주학회지
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• 제49권8호
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• pp.617-626
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• 2021

비행체의 초음속 비행 중 고온 환경에서의 열 거동은 비행체의 열 구조 설계에 중요하다. 본 연구에서는 전역-국부 다중 디지털 이미지 상관기법을 사용하여 노치 구조물의 전 영역의 열변형 및 응력집중 현상에 대해 관찰/분석하였다. 다중 DIC 시스템은 2D DIC 시스템과 3D DIC 시스템으로 구성되었다. 가열 챔버를 이용하여 노치 시편을 가열하였으며 여러 온도에서 다중 DIC 시스템을 사용하여 구조물의 변형 이미지를 촬영하고 분석하였다. 다중 DIC 기법을 사용하여 노치 시편의 전 영역 변형률과 노치 부위의 응력집중 현상을 계측/분석하였으며 ABAQUS^TM 프로그램을 이용하여 노치 시편에 대해 유한요소해석을 진행하고 실험결과와 비교 분석하였다. 본 연구를 통해 다중 DIC 시스템의 열변형 계측과 응력 집중 현상의 연구 분석에서의 활용 가능성을 보여주었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.102-107
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• 2001

Interfacial cracks between an isotropic and orthotropic material, subjected to static far field tensile loading are analyzed using the technique of photoelasticity. The fracture parameters are extracted from the full-field isochromatic data and the same are compared with that obtained using boundary collocation method. Dynamic Photoelasticity combined with high-speed digital photography is employed for capturing the isochromatics in the case of propagating interfacial cracks. The normalized stress intensity factors for static crack is greater when $\alpha=90^{\circ}C$ (fibers perpendicular to the interface) than when $\alpha=0^{\circ}C$ (fiber parallel to the interface) and those when $\alpha=90^{\circ}C$ are similar to ones of isotropic material. The dynamic stress intensity factors for interfacial propagating crack are greater when $\alpha=0^{\circ}C$ than $\alpha=90^{\circ}C$. The relationship between complex dynamic stress intensity factor $|K_D|$ and crack speed C is similar to that for isotropic homogeneous materials, the rate of increase of energy release rate G or $|K_D|$ with crack speed is not as drastic as that reported for homogeneous materials.

• 대한기계학회논문집A
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• 제24권1호
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• pp.144-155
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• 2000

초록 The validity, of a single parameter such as stress intensity, factor K or J-integral in traditional fracture mechanics depends strongly on the geometry, and loading condition. Therefore the second parameter like T-stress measuring the stress constraint is additionally needed to characterize the general crack-tip fields. While many, research works have been done to verify, the J-T description of elastic-plastic crack-tip stress fields in plane strain specimens, limited works (especially. for bimaterials) have been performed to describe the structural surface crack-front stress fields with the two parameters. On this background, via detailed three dimensional finite element analyses for surface-cracked plates and straight pipes of homogeneous materials and bimaterials under various loadings, we investigate the extended validity or limitation of the two parameter approach. We here first develop a full 3D mesh generating program for semi-elliptical surface cracks, and calculate elastic T-stress from the obtained finite element stress field. Comparing the J-T predictions to the elastic-plastic stresses from 3D finite element analyses. we then confirm the extended validity of fracture mechanics methodology based on the J-T two parameters in characterizing the surface crack-front fields of welded plates and pipes under various loadings.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.709-713
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• 1996

The ceramic has such high qualities as light weight, abrasion resistance, heat resistance compared with metal, but since it is breakable, it can't be used as structural material and it is desirable to joining metal which is full of toughness, but, according as the ceramic/metal joint is executed at high temperature, the joint residual stress develops near the joint sides in the process of cooling the high temperature down to the suitable temperature due to difference of the thermal expansion coefficient between ceramic and metal, and the joint residualstress lowers the fracture strength. In this study, to ensure security and improvement of bending strength, 1 studies on see distribution shape of residual stress according to high thermal cycle, and the influnence of theraml cycle and distribution shape of residual stess on joint-strength.