• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.264-267
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• 2001

by three-dimensional finite element method. The guide roll is an intermediately supported trans-axle miler, so called I-STAR roll, which was designed by VAI. The guide roll has been used in POSCO since 1998. Though the number of stowage in casting has been apparently decreased since thef it has occasionally been failed during operation. The simulations were carried out to find out the status of stress and deformation as well as improvement of the guide roll. The thermal effect is much more dominant than ferro-static pressure or others in stress and deformation of the guide roll. The material of the guide roll is SCM440.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.70-73
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• 2006

In the present study, the flow-softening behavior occurring during high temperature deformation of AZ31 Mg alloy was investigated. Flow softening of AZ31 Mg alloy was attributed to (1) thermal softening by deformation heating and (2) microstructural softening by dynamic recrystallization. Artificial neural networks method was used to derive the accurate amounts of thermal softening by deformation heating. A series of mechanical tests (High temperature compression and load relaxation tests) was conducted at various temperatures ($250^{\circ}C{\sim}500^{\circ}C$) and strain rates ($10^{-4}/s{\sim}100/s$) to formulate the recrystallization kinetics and grain size relation. The effect of DRX kinetics on microstructure evolution (fraction of recrystallization) was evaluated by the unified SRX/DRX (static recrystallization/dynamic recrystallization) approaches

• 대한기계학회논문집A
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• 제29권5호
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• pp.762-769
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• 2005

This paper presents a method to investigate the characteristics of a hydrodynamic bearing of a HDD spindle motor due to elevated temperature considering the variation of the clearance as well as the lubricant viscosity. Iterative finite element analysis of the heat conduction and the thermal deformation is performed to determine the viscosity and clearance of a hydrodynamic bearing due to elevated temperature until the temperature of the bearing area converges. Proposed method is verified by comparing the calculated temperature with the measured one in elevated surrounding temperature as well as in room temperature. This research shows that elevated temperature changes the clearance as well as the lubricant viscosity of the hydrodynamic bearing of a HDD spindle motor. Once the viscosity and the clearance of a hydrodynamic bearing of a HDD spindle motor are determined, finite element analysis of the Reynolds equation is performed to investigate the static and dynamic characteristics of a hydrodynamic bearing of a HDB spindle motor due to elevated temperature. It also shows that the variation of clearance due to elevated temperature is another important design consideration to affect the static and dynamic characteristics of a hydrodynamic bearing of a HDD spindle motor

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.556-563
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• 2003

This paper presents a method to investigate the characteristics of a hydrodynamic bearing of a HDD spindle motor due to elevated temperature considering the variation of the clearance as well as the lubricant viscosity. Iterative finite element analysis of the heat conduction and the thermal deformation is performed to determine the viscosity and clearance of a hydrodynamic bearing due to elevated temperature until the temperature of the bearing area converges. Proposed method is verified by comparing the calculated temperature with the measured one in elevated surrounding temperature as well as in room temperature. This research shows that elevated temperature changes the clearance as well as the lubricant viscosity of the hydrodynamic bearing of a HDD spindle motor. Once the viscosity and clearance of a hydrodynamic bearing of a HDD spindle motor are determined, finite element analysis of the Reynolds equation is performed to investigate the static and dynamic characteristics of a hydrodynamic bearing of a HDD spindle motor due to elevated temperature. It also shows that the variation of clearance due to elevated temperature is another important design consideration to affect the static and dynamic characteristics of a hydrodynamic bearing of a HDD spindle motor.

• 한국생산제조학회지
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• 제9권4호
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• pp.99-107
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• 2000

In this study, a static and dynamic characteristics analysis system for machine tool spindle systems with 3 lobe sliding bearing is developed based on Timoshenko theory, finite element method and windows programming techniques. And the characteristics value of 3 lobe sliding bearing such as eccentricity ratio, attitude angle, friction coefficient , stiffness coefficients, damping coefficients and so on, are determined by using the thermal equilibrium conditions of spindle systems. Since the developed system has various analysis modules related to static deformation analysis, modal analysis, frequency responses analysis and so on, it can be utilized to perform systematically the design an devaluation process of spindle systems with 3 lobe sliding bearing under windows GUI environment.

• Steel and Composite Structures
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• 제27권6호
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• pp.761-775
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• 2018

In the present work, the recently developed non-polynomial shear deformation theories are assessed for thermo-mechanical response characteristics of laminated composite plates. The applicability and accuracy of these theories for static, buckling and free vibration responses were ascertained in the recent past by several authors. However, the assessment of these theories for thermo-mechanical analysis of the laminated composite structures is still to be ascertained. The response characteristics are investigated in linear and non-linear thermal gradient and also in the presence and absence of mechanical transverse loads. The laminated composite plates are modelled using recently developed six shear deformation theories involving different shear strain functions. The principle of virtual work is used to develop the governing system of equations. The Navier type closed form solution is adopted to yield the exact solution of the developed equation for simply supported cross ply laminated plates. The thermo-mechanical response characteristics due to these six different theories are obtained and compared with the existing results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.629-634
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• 1996

Heat generation in machine operating condition makes thermal deformation and thermalstress in the structure, which results in the change the contact characteristics of machine joint such s change of shrinkage fit, contact heat conductance and contact pressure. As the change of contact pressure is related to variation of static, dynamic and thermalcharacteristics, the prediction of transient contact perssure is strongly required. This paper presents some analytical results which will be effective to predict static and dynamic characteristics of the compound cylindrical structure.

• 한국세라믹학회지
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• 제52권2호
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• pp.108-113
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• 2015

In an effort to evaluate the practicability of an imprinting technique for amorphous chalcogenide film in Ge-based compositions, we investigate the deformation behavior of the surface of amorphous $GeSe_2$ film deposited via a thermal evaporation route according to varying static loads applied at elevated temperatures. We observe that, under these static loading conditions, crystallization tends to occur on its surface relatively more easily than in As-based $As_2Se_3$ films. As for the present $GeSe_2$ film, higher processing temperatures are required in order to make its surface reflect the given stamp patterns well; however, in this case, its surface becomes partially crystallized in the monoclinic $GeSe_2$ phase. The increased vulnerability of this amorphous $GeSe_2$ film toward surface crystallization under static loading, when compared with the $As_2Se_3$ counterpart, is explained in terms of the topological aspects of its amorphous structure.

• 한국정밀공학회지
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• 제31권8호
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• pp.653-658
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• 2014

Roll-to-Roll printing process has become a great issue as a breakthrough for low cost and mass production of electronic devices such as organic thin film transistor, and etc. To print the electronic devices, multi-layer printing is essential, and high precision register control is required for this process. Unlike stop-and-repeat printing process, it is impossible to control the register in a static state since the roll-to-roll process is a continuous system. Therefore, the behavior of web such as polyethylene terephthalate (PET) and polyimide (PI) by the tensile and thermal stress generated in the roll-to-roll process as well as motor control of driven rolls has to be considered for a high precision register control. In this study, the correlation between curing temperature and thermal deformation of PET web is analyzed. Finally, it is verified experimentally that the temperature disturbance generates the more serious register error under the higher curing temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.9-15
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• 2001

In the case of a crack propagation, a portion of the work of inelastic deformation near the crack tip is dissipated as heat. In order to understand the thermal effect on fracture toughness, tensile test was carried out using thermocouples to monitor the variation of temperature with SA516 Gr70. The experimental results show that the temperature of specimen was increased $3.6^{\circ}C$ at static load condition. And the thermal effect was investigated connected with the steady-state stress in the vicinity of a crack propagation in the elastic-plastic C-T specimen theoretically. And fracture toughness, the energy to make crack surfaces, presented correctively. The fracture toughness with considering heat at the blunting of the crack tip ws lower about 19.3% than that of ignoring heat. So, it is resonable to apply the fracture toughness with considering thermal energy and it would be good explanation for constraint effect depending on the configuration in the presence of excessive plasticity.