• 대한기계학회논문집A
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• 제24권8호
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• pp.1968-1799
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• 2000

A warpage analysis program has been developed for fiber-reinforced injection molded parts. The warpage is predicted from the residual stress and anisotropic thermo-mechanical properties coupled with fiber orientation in the integrated injection molding simulation. A simple elastic model is used for the calculation of thermally and pressure-induced residual stresses which are employed as the initial conditions in the structural analysis. To improve the reliability of warpage analysis, a new triangular flat shell element superimposing well-known efficient plate bending and membrane element is presented. The numerical examples address the necessity to use anisotropic models for fiber-reinforced materials and show that predicted warpage is in good agreement with experimentally measured one.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.745-750
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• 2000

A warpage analysis program has been developed for fiber-reinforced injection molded parts. The warpage is Predicted from the residual stress and anisotropic thermo-mechanical properties coupled with fiber orientation in the integrated injection molding simulation. A simple elastic model is used for the calculation of thermally and pressure-induced residual stresses which are employed as the initial conditions in the structural analysis. To improve the reliability of warpage analysis, a new triangular flat shell element superimposing well-known efficient plate bending and membrane element is presented. The numerical examples address the neccesity to use anisotropic models for fiber-reinforced materials and show that predicted warpage is in good agreement with experimentally measured one.

• 소성∙가공
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• 제7권1호
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• pp.72-80
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• 1998

This study is concerned with the thermo-biscoplastic finite element analysis of hot tube extrusion through square dies with a mandrel. The problem is treated as a non-steady state and the ALE description is used due to abruptly turning flow at the die aperture. Since the contact heat transfer coefficient and the friction factor are required in the analysis experiments are also carried out to determine the values, In order to apply ceramics to an extrusion die the study is focussed on under-standing the characteristics of the process. The simulated results provide the useful informations such as metal flow temperature distribution stress state etc. The elastic analysis of the dies is carried out to obtain the stress state of the ceramic dies.

• 한국전산구조공학회논문집
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• 제23권5호
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• pp.535-541
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• 2010

본 연구에서는 정상상태의 비선형 열탄성 문제에 대하여 탄성 계수 및 열전도 계수에 대해서 보조변수법을 이용한 연속체 기반의 설계민감도 방정식을 유도하였고, 온도와 변위장이 연성된 보조방정식을 정의하여 효율적으로 설계민감도 해석을 수행하여 위상 최적설계에 적용하였다. 수치 예제를 통하여 열탄성 문제에서 위상 최적설계가 갖는 요소망 의존성을 살펴보았다. 또한 열 하중이 지배적인 경우와 기계적 하중이 지배적인 경우를 비교하여 다중 물리 연성문제에서 위상 최적설계가 갖는 하중에 대한 의존성을 고찰하였다.

• 터널과지하공간
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• 제1권2호
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• pp.181-203
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• 1991

The effects of geologic structures such as rock joins and bedding planes on the thermal conductivity of a discontinuous rock mass are studied. The expressions for the equivalent thermal conductivities of jointed rock masses are derived and found to be anisotropic. The degree of anisotropy depends primarily on the thermal properties contrast between the joint phase and surrounding intact rock, the joint density expressed as volume fraction and the inclination angle of the joint. Within the context of 2-dimensional finite element heat transfer scheme, the isotherms around a circular hole are analyzed for both the isotropic and anisotropic rock masses in 3 different thermal boundary conditions. i.e. temperature, heat flux and convection boundary conditions. The temperature in the stratified anisotripic rock mass is greatly influenced by the thermal properties of the rock formation in contact with the heat source. Using the excavation-temperature coupled elastic plastic finite element method, analyzed is the thermo-mechanical stability of a circular opening subjected to 10$0^{\circ}C$ at a depth of 527m. It is found that the thermal stress concentration was enough to deteriorate the stability and form a plastic yield zone around the opening, in contrast to the safety factor greater than 2 resulted form the excavation-only analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.482-487
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• 1993

A prediction method for determining the welding residual stress by artificial neural network is proposed. A three-dimensional transient thermomechanical analysis has been performed for the CO $_{2}$ Arc Welding using the finite element method. The validity of the above results is demonstrated by experimental elastic stress relief method which is called Holl Drilling Method. The first part of numarical analysis performs a three-dimensional transient heat transfer anslysis, and the second part then uses results of the first part and performs a three-dimensional transient thermo-clasto-plastic analysis to compute transient and residual stresses in the weld. Data from the finite element method were used to train a backpropagation neural network to predict residual stress. Architecturally, the finite element method were used to train a backpropagation voltage and the current, a hidden layer to accommodate failure mechanism mapping, and an output layer for residual stress. The trained network was then applied to the prediction of residual stress in the four specimens. The results of predicted residual stress have been very encouraging.

• Journal of Welding and Joining
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• 제20권2호
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• pp.59-64
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• 2002

When the vehicle travels in an actual road, resistance spot weldments of the vehicle structure are exposed to complex loading state. Since the fatigue strength in resistance spot weldment of vehicle body can be determined by effect of residual stresses and loading state of driving, estimating actual loading state and considering residual stress effect are needed. In this study, Fatigue stress-fatigue life relation concerned residual stress effect was obtained by thermo elastic plastic finite element analysis. And applied loading in resistance spot weldments of vehicle body was calculated by dynamic analysis. Presumption of fatigue life was performed using proposed method

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.55-55
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• 2010

마그네슘 판재는 경량화 소재로 주목받는 소재이다. 본 연구는 압연 마그네슘 판재의 용접시 발생하는 온도이력 및 응력에 대한 해석을 수행하였다. 해석은 2차원 해석을 수행하였으며 해석수행에 있어서 열물성값은 기존의 데이터를 이용하였으며 응력해석은 온도별 고온 인장시험을 수행한 결과를 이용하여 해석을 수행하였다. 본 연구에서 수행한 대상은 마그네슘 압연판재인 AZ31B 이며 두께 3.5 mm 판재를 GTAW용접을 수행한 경우에 대하여 검토하였으며, 해석결과 중 온도분포의 한 예를 그림 1에 나타낸다.

• 한국레이저가공학회지
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• 제5권3호
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• pp.1-8
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• 2002

Finite element analysis and experiment were peformed to estimate the fatigue strength for the lap joint of laser weld. To consider quantitatively residual stress which effects on the fatigue strength of the lap joint of laser weld, after three dimensional modeling for the longitudinal and transverse direction, residual stress fields in the weldment were calculated using thermo-elastic-plastic finite element analysis, then the equivalent fatigue stress considering the residual stress was obtained. To ensure reliability of calculated fatigue strength, fatigue tests were performed. The calculated and experimental results showed a good agreement. The fatigue strength considering a residual stress was lower than that of without considering a residual stress in the lap joint of laser welding. The fatigue strength in the transverse direction was higher than that of longitudinal direction.

• 한국기계가공학회지
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• 제10권6호
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• pp.140-145
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• 2011

An anisotropic beam model is proposed by employing an asymptotic expansion method for thermo-mechanical multiphysics environment. An asymptotic method based on virtual work is introduced first, and then the variables of mechanical displacement and temperature rise are asymptotically expanded by taking advantage of geometrical slenderness of elastic bodies. Subsequently substituting these expansions into the virtual work principle allows us to asymptotically expand the virtual work. This will yield a set of recursive virtual works from which two-dimensional microscopic and one-dimensional macroscopic equations are systematically derived at each order. In this way, homogenized stiffnesses and thermomechanical coupling coefficients are derived. To demonstrate the validity and efficiency of the proposed approach, composite beams are taken as a test-bed example. The results obtained herein are compared to those of three-dimensional finite element analysis.