• 대한기계학회논문집A
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• 제20권1호
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• pp.189-205
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• 1996

The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.

• 드라이브 ㆍ 컨트롤
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• 제15권3호
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• pp.43-48
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• 2018

The hydraulic control valve, used in the CPB (cold-pad-Batch) cold dyeing system, passes through a pressurized material that absorbs the dye. The hydraulic control of the hydraulic control panel shall be driven in a uniform and precisely controlled manner, as it interferes directly with the dyschromatism. In this study, an acceleration test model was employed to verify the durability of the hydraulic control of the hydraulic control panel, which was manufactured by the scenic model, and the pre-roll angle was analyzed before the performance of acceleration test. Based on the change in the amount of deformation of the padder roll the durability of the padder roll was analyzed along with verification of the durability of the skin and the rubber coating in contact with the fabric. Furthermore, the accelerated test method used for hydraulic controlled multi-cell padder rolls was verified.

• Tribology and Lubricants
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• 제28권5호
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• pp.203-211
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• 2012

Atomic force microscopy (AFM) has been used as a tool, not only for imaging surfaces, but also for measuring surface forces and mechanical properties at the nano-scale. Force calibration is crucial for quantitatively measuring the forces that act between the AFM probe of a force sensing cantilever and a sample. In this work, the lateral force calibrations of a V-shaped cantilever were performed using the finite element method, multiple pivot loading, and thermal noise methods. As a result, it was shown that the multiple pivot loading method was appropriate for the lateral force calibration of a V-shaped cantilever. Further, through crosschecking of the abovementioned methods, it was concluded that the thermal noise method could be used for determining the lateral spring constants as long as the lateral deflection sensitivity was accurately determined. To obtain the lateral deflection sensitivity from the sticking portion of the friction loop, the contact stiffness should be taken into account.

• Advances in nano research
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• 제5권2호
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• pp.69-97
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• 2017

In this study, nonlinear response of laminated functionally graded carbon nanotube reinforced composite (FG-CNTRC) plate under low-velocity impact based on the Eshelby-Mori-Tanaka approach in thermal conditions is studied. The governing equations are derived based on higher-order shear deformation plate theory (HSDT) under von $K\acute{a}rm\acute{a}n$ geometrical nonlinearity assumptions. The finite element method with 15 DOF at each node and Newmark's numerical integration method is applied to solve the governing equations. Four types of distributions of the uniaxially aligned reinforcement material through the thickness of the plates are considered. Material properties of the CNT and matrix are assumed to be temperature dependent. Contact force between the impactor and the laminated plate is obtained with the aid of the modified nonlinear Hertzian contact law models. In the numerical example, the effect of layup (stacking sequence) and lamination angle as well as the effect of temperature variations, distribution of CNTs, volume fraction of the CNTs, the mass and the velocity of the impactor in a constant energy level and boundary conditions on the impact response of the CNTRC laminated plates are investigated in details.

• 한국자기학회지
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• 제21권5호
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• pp.180-184
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• 2011

자기장 자극시스템을 통하여 순간펄스 고자기장을 손바닥과 발바닥 그리고 무릎에 인가한 후 체열진단시스템을 통하여 모세혈관을 포함한 인체의 혈관 자극에 의한 혈류개선 효과를 연구하였다. 연령별, 성별 구분을 통하여 자극 후 체열진단을 통해 공통적으로 자극부위에 온도가 상승하는 결과를 얻었으며, 자기장 자극기 코일에서 발생하는 자체 발열량을 제거하기 위해 플라스틱 재질의 성형물로 신체와의 직접적인 접촉을 차단시켰으며 일정거리를 유지하여 실험하였다. 그 결과 비접촉을 통하여 순수하게 자기장의 펄스파형이 피부에 가까운 혈관을 자극하여 내부 전자기 에너지가 피부에 온도상승을 가져온 것으로 고찰된다.

• Journal of information and communication convergence engineering
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• 제20권4호
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• pp.303-308
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• 2022

Simulating the heat transfer in a composite material is an important topic in material science. Difficulties arise from the fact that adjacent materials cannot match perfectly, resulting in discontinuity in the temperature variables. Although there have been several numerical methods for solving the heat-transfer problem in imperfect contact conditions, the methods known so far are complicated to implement, and the computational times are non-negligible. In this study, we developed a ResNet-type deep neural network for simulating a heat transfer model in a composite material. To train the neural network, we generated datasets by numerically solving the heat-transfer equations with Kapitza thermal resistance conditions. Because datasets involve various configurations of composite materials, our neural networks are robust to the shapes of material-material interfaces. Our algorithm can predict the thermal behavior in real time once the networks are trained. The performance of the proposed neural networks is documented, where the root mean square error (RMSE) and mean absolute error (MAE) are below 2.47E-6, and 7.00E-4, respectively.

• 한국정밀공학회지
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• 제12권9호
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• pp.148-155
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• 1995

The object of this study is to achieve a gteater understanding of meterial removal process and its mechanism. In this study, some applications of finite element techniques are applied to analyze the chip formation and cutting heat generation mechanism of metal cutting. To know the effect of cutting parameters, simulations employed some independent cutting variables change, such as constitutive deformation laws of workpiece and tool material, frictional coefficients and tool-chip contact interfaces, cutting speed, tool rake angles, depth of cut and this simulations also include large elastic-plastic defor- mation, adiabetic thermal analysis. Under a usual plane strain assumption, quasi-static, thermal-mechanical coupling analysis generate detailed informations about chip formation process and cutting heat generation mechanism Some cutting parameters are affected to cutting force, plastic deformation of chip, shear plane angle, chip thickness and tool-chip contact length and reaction force on tool, cutting temperature and thermal behavior. Several aspects of the metal cutting process predicted by the finite element analysis provide information about tool shape design and optimal cutting conditions.

• Structural Engineering and Mechanics
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• 제90권4호
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• pp.357-370
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• 2024

Due to the fact that the mechanism of the effects of temperature and initial geometric imperfection on low-velocity impact problem of axially moving plates is not yet clear, the present paper is to fill the gap. In the present paper, the nonlinear dynamic behavior of axially moving imperfect graphene platelet reinforced metal foams (GPLRMF) plates subjected to lowvelocity impact in thermal environment is analyzed. The equivalent physical parameters of GPLRMF plates are estimated based on the Halpin-Tsai equation and the mixing rule. Combining Kirchhoff plate theory and the modified nonlinear Hertz contact theory, the nonlinear governing equations of GPLRMF plates are derived. Under the condition of simply supported boundary, the nonlinear control equation is discretized with the help of Gallekin method. The correctness of the proposed model is verified by comparison with the existing results. Finally, the time history curves of contact force and transverse center displacement are obtained by using the fourth order Runge-Kutta method. Through detailed parameter research, the effects of graphene platelet (GPL) distribution mode, foam distribution mode, GPL weight fraction, foam coefficient, axial moving speed, prestressing force, temperature changes, damping coefficient, initial geometric defect, radius and initial velocity of the impactor on the nonlinear impact problem are explored. The results indicate that temperature changes and initial geometric imperfections have significant impacts.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2002년도 춘계학술대회 논문집
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• pp.127-132
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• 2002

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.783-786
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• 1996

In the temperature analysis, the heat transfer between the workpiece and the die has an important influence upon the temperature distribution. The accuracy of thermal analysis depends on the proper description of boundafy conditions. A t the contact surface of two materials with different temperature, this requires the knowledge of overall heat transfer coefficients. In order to evaluate the overall heat transfer coefficients, a technique is developed. This technique involves temperature measurement at the contact surface during hot upsetting operations and finite element computation to calcualte the overall heat transfer coefficient.