• Current Optics and Photonics
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• v.7 no.2
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• pp.213-221
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• 2023

The optical window, as a part of the collimator system, is the connector between the outside light source and the optical system inside a vacuum tank. The temperature and pressure difference between the two sides of the optical window cause not only thermoelastic deformation, but also refractive-index irregularities. To suppress the influence of these two changes on the performance of the collimator system, thermo-optical analysis is employed. Coefficients that characterize the deformations and refractive-index distributions are derived through finite-element analysis, and then imported into the collimator system using a user-defined surface in ZEMAX. The temperature and pressure difference imposed on the window seriously degrade the system performance of the collimator. A decentered and tilted lens group is designed to correct both field aberrations and the thermal effects of the window. Through lens-interval adjustment of the lens group, the diffraction-limited performance of the collimator can be maintained with a vacuum level of 10^-5 Pa and inside temperature ranging from -100 ℃ to 20 ℃.

• Tribology and Lubricants
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• v.7 no.1
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• pp.61-67
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• 1991

기계평면시일의 접촉 운동면에서 유체가 비압축성이고, 점성의 영향을 받는 경우에 대한 체적누설 유동량과 마찰 토오크를 멱급수의 방법을 이용하여 추정하였다. 본 연구에서 고려되고 있는 설계인자로 시일의 경사도, 접촉 운동면에서의 사인파형, 코우닝, 열탄성 변화량, 마모량, 시일의 스프링 강성도에 따른 축방햐의 변화량을 종합적으로 고려하여 해석하였다. 계산된 결과에 의하면 특히 회전속도가 증가되면 열탄성 변화량에 의한 시일의 누설 마찰 토오크가 커다란 영향을 받고 있는 것으로 나타나고 있다.

• Tribology and Lubricants
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• v.6 no.2
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• pp.34-42
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• 1990

기계명면시일의 접촉 운동면에서 유체가 비압축성이고, 점서의 영향을 받는 경우에 대한 체적 누설 유동량과 마찰 토오크를 멱급수의 방법을 이용하여 추정하였다. 본 연구에서 고려되고 있는 설계인자로 시일의 경사도, 접촉 운동면에서의 사인파형, 코우닝, 열탄성 변화량, 마모량, 시일의 스프링 강성도에 따른 축방향의 변화량을 종합적으로 고려하여 해석하였다. 계산된 결과에 의하면 특히 회전속도가 증가되면 열탄성 변화량에 의한 시일의 누설 유동량과 마찰 토오크는 커다란 영향을 받고 있는 것으로 나타나고 있다.

• Coupled systems mechanics
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• v.8 no.1
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• pp.55-70
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• 2019

This investigation is focused on the variations in transversely isotropic thick circular plate due to time harmonic thermomechanical sources. The homogeneous thick circular plate in presence and absence of energy dissipation and two temperatures has been considered. Hankel transform is used for solving field equations. The analytical expressions of conductive temperature, displacement components, and stress components are computed in the transformed domain. The effects of frequency at different values are represented graphically. Some specific cases are also figured out from the current research.

• Tribology and Lubricants
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• v.15 no.2
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• pp.199-205
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• 1999

Using a coupled thermal-mechanical analysis, the thermal distortion of the ventilated disk brakes has been investigated based on the air cooling effects during 15 braking operations. The FEM results show that the bendings and distortions of the disk toward the left side are decreased, but the sinusoidal distortion of the disk rubbing surface along the arc length of the vent hole is highly increased by increasing the convective air cooling effects, which is heavily related to the squeal, wear and micro-thermal crackings at the rubbing surfaces due to uneven dissipation rates of friction heatings.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.119-123
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• 2009

In this paper, effects of major design parameters of cold forging dies on die mechanics are quantitatively investigated with emphasis on shrink fit using a thermoelastic finite element method. A ball-stud cold forging process found in a cold forging company is selected as a test process and the effects of die insert material, shrink fit, dimension of ring, partition of die inert and clamping force on effective stress and circumferential stress are analyzed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.332-338
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• 1999

A coupled thermal-mechanical analysis has been presented for the thermal distortions of the ventilated disk brakes during IS braking operations. The FEM results show that the bendings and distortions of the disk toward the left side are decreased, but the sinusoidal distortion of the disk rubbing surface along the arc length of the vent hole is highly increased by increasing the convective air cooling effects, which is heavily related to the squeal, wear and micro-thermal crackings at the rubbing surfaces due to uneven dissipation rates of friction heatings.

• Honam Mathematical Journal
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• v.38 no.3
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• pp.435-454
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• 2016

This paper investigates the effect of dual-phase-lags on a thermoviscoelastic orthotropic solid with a cylindrical cavity. The cylindrical cavity is subjected to a thermal shock varying heat and its material is taken to be of Kelvin-Voigt type. The phase-lag thermoelastic model, Lord and Shulman's model and the coupled thermoelasticity model are employed to study the thermomechanical coupling, thermal and mechanical relaxation (viscous) effects. Numerical solutions for temperature, displacement and thermal stresses are obtained by using the method of Laplace transforms. Numerical results are plotted to illustrate the effect phase-lags, viscoelasticity, and the variability thermal conductivity parameter on the studied fields. The variations of all field quantities in the context of dual-phase-lags and coupled thermoelasticity models follow similar trends while the Lord and Shulman's model may be different. The influence of viscosity parameter and variability of thermal conductivity is very pronounced on temperature and thermal stresses of the thermoviscoelastic solids.

• Steel and Composite Structures
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• v.11 no.4
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• pp.341-358
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• 2011

This paper presents the effects of thermal environment and temperature-dependence of the material properties on axisymmetric bending of functionally graded (FG) circular and annular plates. The material properties are assumed to be temperature-dependent and graded in the thickness direction. In order to accurately evaluate the effect of thermal environment, the initial thermal stresses are obtained by solving the thermoelastic equilibrium equations. Governing equations and the related boundary conditions, which include the effects of initial thermal stresses, are derived using the virtual work principle based on the elasticity theory. The differential quadrature method (DQM) as an efficient and robust numerical tool is used to obtain the initial thermal stresses and response of the plate. Comparison studies with some available results for FG plates are performed. The influences of temperature rise, temperature-dependence of material properties, material graded index and different geometrical parameters are carried out.

• Steel and Composite Structures
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• v.26 no.1
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• pp.17-29
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• 2018

The thermal effects on the buckling, postbuckling and nonlinear vibration behaviors of composite laminated trapezoidal plates are studied. Aiming at the complex plate structure and to simulate the temperature distribution of the plate, a finite element method (FEM) is applied in this paper. In the temperature model, based on the thermal diffusion equation, the Galerkin's method is employed to establish the temperature equation of the composite laminated trapezoidal plate. The geometrical nonlinearity of the plate is considered by using the von Karman large deformation theory, and combining the thermal model and aeroelastic model, Hamilton's principle is employed to establish the thermoelastic equation of motion of the composite laminated trapezoidal plate. The thermal buckling and postbuckling of the composite laminated rectangular plate are analyzed to verify the validity and correctness of the present methodology by comparing with the results reported in the literature. Moreover, the effects of the temperature with the ply-angle on the thermal buckling and postbuckling of the composite laminated trapezoidal plates are studied, the thermal effects on the nonlinear vibration behaviors of the composite laminated trapezoidal plates are discussed, and the frequency-response curves are also presented for the different temperatures and ply angles.