• 한국군사과학기술학회지
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• 제2권1호
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• pp.110-120
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• 1999

본 논문은 흡습환경에서 온도변화를 겪는 무한히 긴 속빈 실린더의 시간변화에 따른 흡습열 응력 변화에 관해서 연구한 것이다. 평면변형률 가정에 기초한 흡습열탄성론의 방정식이 열과 습기 사이의 연성효과를 고려하여 수립되었다. 시간경과에 따른 흡습열 응력을 구하기 위한 완전한 형태의 해가 연성분리기법과 변수분리방법을 이용하여 구하였으며, 온도와 습도 집중치의 분포를 포함한 수치적인 적용 예에 대한 결과를 분석하였다. 시간경과에 따른 흡습열 특성이 직교이방성 속빈원통벽에서 변위와 응력의 변화 및 분포에 미치는 영향을 함께 제시하였다.

• 소성∙가공
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• 제8권5호
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• pp.498-506
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• 1999

The metal forming processes of aluminum alloy wheel forging at elevated temperature are analyzed by the finite element method. A coupled thermo-mechanical model for analysis of plastic deformation and geat transfer is adapted in the finite element formulation. In order to consider the strain-rate effects on material properties and the flow stress dependence on temperatures, rigid-viscoplasticity is introduced in this formation. In this paper, several process conditions were applied to the dimulation such as die speed, rib thickness, and depth of die cavity. Simulation results are compared, and discussed with each case. Metal flow, die pressure distributions, temperature distributions, velocity fields and forging loads are summarized as basic data for process design and selection of a proper press equipment.

• 유공압시스템학회논문집
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• 제8권3호
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• pp.21-26
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• 2011

Nonlinear seal friction in pneumatic cylinders can impede the performance of pneumatic systems designed for high precision positioning with favorable high speed actuation. The behaviour of an elastomeric piston seals in high speed pneumatic cylinders is analyzed by nonlinear finite element analysis using ABAQUS. The contact pressures, stress and strain distributions and frictional forces of the squeeze type piston seal are simulated with variation of the seal radial installed interference, the operating pressures, friction coefficients and piston rod velocities. The nonlinear finite element model of the squeeze type piston seal is used to predict deformation of a seal, friction force and contact pressure distributions.

• 유공압시스템학회:학술대회논문집
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• 유공압시스템학회 2010년도 춘계학술대회
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• pp.99-104
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• 2010

Nonlinear seal friction in pneumatic cylinders can impede the performance of pneumatic systems designed for high precision positioning with favorable high speed actuation. The behaviour of an elastomeric piston seal in high speed pneumatic cylinders is analysed by nonlinear finite element analysis using ABAQUS. The contact pressures, stress and strain distributions and frictional forces of the piston seal are simulated with variation of interference fits, supply pressures, friction coefficients and piston rod velocities. The nonlinear finite element model of the piston seal is used to predict deformation of a seal, friction force and contact pressure distributions.

• 한국구조물진단유지관리공학회 논문집
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• 제11권2호
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• pp.103-108
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• 2007

본 연구에서는 압전 특성과 표면전위계를 이용한 응력측정 방법을 제안하였다. 다시 말하면 이 응력측정방법은 압전소자에서 발생한 전위를 표면전위계로 측정하게 하는 방법으로서, 이 표면전위는 구조물 부재의 변형률에 비례한다는 특성을 이용하여, 구조물 부재의 각 위치에서의 발생하는 응력을 변형률로부터 계산할 수 있게 된다. 또한, 구조물 부재의 응력분포를 보다 간편하게 구하기 위해서 비접촉 측정법을 이용한 응력분포 측정 Tape를 제작하였다. 특히, 이 Tape는 균열이나 홈과 같이 이상응력 발생 가능한 위치에서의 ${\sigma}_x$, ${\sigma}_y$, ${\tau}_{xy}$의 응력을 측정 뿐만 아니라 국부 응력해석에 활용되었고 그 적용성을 검토하기 위해서 홈이 있는 실험편에 대해서 반복하중 시험결과와 FEM 해석의 결과와 비교 분석하였다.

• Steel and Composite Structures
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• 제32권2호
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• pp.253-264
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• 2019

This paper presents the combination resonances of FG porous (FGP) cylindrical shell under two-term excitation. The effect of structural damping on the system response is also considered. With regard to classical plate theory of shells, von-$K{\acute{a}}rm{\acute{a}}n$ equation and Hook law, the relations of stress-strain is derived for shell. According to the Galerkin method, the discretized motion equation is obtained. The combination resonances are obtained by using the method of multiple scales. Four types of FGP distributions consist of uniform porosity, non-symmetric porosity soft, non-symmetric porosity stiff and symmetric porosity distribution are considered. The influence of various porosity distributions, porosity coefficients of cylindrical shell and amplitude excitations on the combination resonances for FGP cylindrical shells is investigated.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1740-1747
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• 2000

Under repeated rolling, initial plastic deformation introduces residual stresses which render the steady cyclic state purely elastic. This is called the process of shakedown. Many studies have been done about the shakedown in semi-infinite half space using calculated Hertizian pressure. In this paper shakedown processes in a shaft are studied by finite element analyses of a two dimensional(plane strain) model with elastic-linear-kinematic-hardening-plastic material subjected to repeated, frictionless rolling contact. Symmetric and non-symmetric pressure distributions are obtained using a simplified model of the bearing-shaft assembly. The rolling contact is simulated by repeatedly translating both pressure distributions along the surface of the shaft. By the influence of the non-symmetric pressure, larger residual radial tensile stress is generated in the immediate subsurface layer, which may make a crack propagate and, the subsurface undergoes a zigzag plastic deformation during the shakedown process, which may lead to a crack initiation.

• 대한기계학회논문집A
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• 제39권11호
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• pp.1183-1189
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• 2015

본 연구는 풍력발전기용 동력 전달부품의 테이퍼 연결장치 설계에 관한 것이다. 요구되는 전달토크의 크기, 동력을 전달하는 축의 직경, 테이퍼 링의 접촉면적 그리고 압축 면압을 부과하기 위한 볼트의 체결력 등이 테이퍼 연결장치 설계의 주요 변수이다. 테이퍼 연결의 계산은 축대칭 평면 변형률 조건의 복합링 구조로 가정하여 응력과 변형량을 계산 하였다. 축에 작용하는 면압은 요구 전달동력을 이용하여 계산하였고, 보강링에 작용하는 면압은 축과 허브의 변형량 일치 조건을 이용하여 계산하는 방법을 제안하였다. 복합링의 수식으로 구한 반경방향의 변형량으로 테이퍼 각도를 고려한 축방향 습동거리를 계산하였다. 수식으로 구한 응력과 상대습동거리의 타당성을 검증하기 위하여 유한요소해석을 수행하였으며 축방향의 하중이 발생하는 테이퍼면에서 원주방향의 응력이 최대 10% 수준의 오차를 보이고 있으나 그 외 응력분포와 상대습동거리는 수식적인 방법과 해석적인 방법이 일치함을 확인하였다.

• Advances in nano research
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• 제12권6호
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• pp.617-627
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• 2022

In the current study, the nonlinear impact of the Von-Kármán theory on the vibrational response of nonhomogeneous structures of functionally graded (FG) nano-scale tubes is investigated according to the nonlocal theory of strain gradient theory as well as high-order Reddy beam theory. The inhomogeneous distributions of temperature-dependent material consist of ceramic and metal phases in the radial direction of the tube structure, in which the thermal stresses are applied due to the temperature change in the thickness of the pipe structure. The general motion equations are derived based on the Hamilton principle, and eventually, the acquired equations are solved and modeled by the Meshless approach as well as a computer simulation via intelligent mathematical methodology. The attained results are helpful to dissect the stability of the MEMS and NEMS.

• Smart Structures and Systems
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• 제30권3호
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• pp.245-253
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• 2022

A two-layer beam consisting of an elastoplastic layer and a functional layer made of shape memory alloy (SMA) TiNi is considered. Constitutive relations for SMA are set by a microstructural model capable to calculate strain increment produced by arbitrary increments of stress and temperature. This model exploits the approximation of small strains. The equations to calculate the variations of the strain and the internal variables are based on the experimentally registered temperature kinetics of the martensitic transformations with an account of the crystallographic features of the transformation and the laws of equilibrium thermodynamics. Stress and phase distributions over the beam height are calculated by steps, by solving on each step the boundary-value problem for given increments of the bending moment (or curvature) and the tensile force (or relative elongation). Simplifying Bernoulli's hypotheses are applied. The temperature is considered homogeneous. The first stage of the numerical experiment is modeling of preliminary deformation of the beam by bending or stretching at a temperature corresponding to the martensitic state of the SMA layer. The second stage simulates heating and subsequent cooling across the temperature interval of the martensitic transformation. The curvature variation depends both on the total thickness of the beam and on the ratio of the layer's thicknesses.