• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.195-198
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• 2000

It can be acquired the high effective productivity through of high speed, precision of machine tools, and then, machine tools will be got a competitive power. Industrially advanced countries already developed that the high speed feed is 60m/min using the high speed ball screw. Also, a lot of problems have happened the feed drive system. It is necessary to study about the characteristics of thermal deformation played a more critical role than static stiffness and dynamic rigidity in controlling the level of machining accuracy. In spite of the improving the thermal deformation characteristics of machine tools at the design stage, there are always some residual errors that have to be compensated for during machining. In this study, thermal deformation error automated compensation device with multiple linear regression is proposed that thermal deformation error can be eliminated at the machining stage. The developed device has been practically applied to the feed drive unit.

• Journal of the Korean Society of Clothing and Textiles
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• v.22 no.7
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• pp.816-825
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• 1998

This study surveys the thermal property and air permeability to the weight reduction rate of PET fabrics. For this purpose, 12 kinds of satin and 18 kinds of plain weave fabrics are prepared with change of the physical properties such as weft yarn count, t.p.m. and density. The weight reduction rate was 0%, 12%, 25% and 30%. The warm/cool feeling(Qmax), thermal insulating value(T.I.V.) and thermal conductivity(K) were measured by KES-F7 System and discussed in relation with the weight reduction rate, weft yarn linear density, t.p.m., weft density of fabric and weave structure.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.345-350
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• 1999

The effectiveness of software error compensation for thermally induced machine tool errors relies on the prediction accuracy of the pre-established thermal error models. The selection of optimal sensor locations is the most important in establishing these empirical models. In this paper, a methodology for the selection of optimal sensor locations is proposed to establish a robust linear model which is not subjected to collinearity. Correlation coefficient and time delay are used as thermal parameters for optimal sensor location. Firstly, thermal deformation and temperatures are measured with machine tools being excited by sinusoidal heat input. And then, after correlation coefficient and time delays are calculated from the measured data, the optimal sensor location is selected through hard c-means clustering and sequential selection method. The validity of the proposed methodology is verified through the estimation of thermal expansion along Z-axis by spindle rotation.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.215-221
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• 1999

The object of the thermal error compensation system in machine tools is improving the accuracy of a machine tool through real time error compensation. The accuracy of the machine tool totally depends on the accuracy of thermal error model. A thermal error model can be obtained by appropriate combination of temperature variables. The proposed method for optimal variable selection in the thermal error model is based on correlation grouping and successive regression analysis. Collinearity matter is improved with the correlation grouping and the judgment function which minimizes residual mean square is used. The linear model is more robust against measurement noises than an engineering judgement model that includes the higher order terms of variables. The proposed method is more effective for the applications in real time error compensation because of the reduction in computational time, sufficient model accuracy, and the robustness.

• Advances in nano research
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• v.7 no.3
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• pp.181-190
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• 2019

The thermal buckling temperature values of the graded carbon nanotube reinforced composite shell structure is explored using higher-order mid-plane kinematics and multiscale constituent modeling under two different thermal fields. The critical values of buckling temperature including the effect of in-plane thermal loading are computed numerically by minimizing the final energy expression through a linear isoparametric finite element technique. The governing equation of the multiscale nanocomposite is derived via the variational principle including the geometrical distortion through Green-Lagrange strain. Additionally, the model includes different grading patterns of nanotube through the panel thickness to improve the structural strength. The reliability and accuracy of the developed finite element model are varified by comparison and convergence studies. Finally, the applicability of present developed model was highlight by enlighten several numerical examples for various type shell geometries and design parameters.

• Structural Engineering and Mechanics
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• v.87 no.1
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• pp.29-46
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• 2023

Critical thermal buckling of functionally graded porous (FGP) sandwich plates under various types of thermal loading is considered. It is assumed that the mechanical and thermal nonhomogeneous properties of FGP sandwich plate vary smoothly by distribution of power law across the thickness of sandwich plate. In this paper, porosity defects are modeled as stiffness reduction criteria and included in the rule of mixture. The thermal environments are considered as uniform, linear and nonlinear temperature rises. The critical buckling temperature response of FGM sandwich plates has been analyzed under various boundary conditions. By comparing several numerical examples with the reference solutions, the results indicate that the present analysis has good accuracy and rapid convergence. Further, the effects of various parameters like distribution shape of porosity, sandwich combinations, aspect ratio, thickness ratio, boundary conditions on critical buckling temperature of FGP sandwich plate have been studied in this paper.

• Steel and Composite Structures
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• v.51 no.2
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• pp.139-151
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• 2024

In this research, a semi-analytical solution is presented for computing mechanical displacements and thermal stresses in rotating thick cylindrical pressure vessels made of functionally graded material (FGM). The modulus of elasticity, linear thermal expansion coefficient, and density of the cylinder are assumed to change along the axial direction as a power-law function. It is also assumed that Poisson's ratio and thermal conductivity are constant. This cylinder was subjected to non-uniform internal pressure and thermal loading. Thermal loading varies in two directions. The governing equations are derived by the first-order shear deformation theory (FSDT). Using the multilayer method, a functionally graded (FG) cylinder with variable thickness is divided into n homogenous disks, and n sets of differential equations are obtained. Applying the boundary conditions and continuity conditions between the layers, the solution of this set of equations is obtained. To the best of the researchers' knowledge, in the literature, there is no study carried out bi-directional thermoelastic analysis of clamped-clamped rotating FGM thick-walled cylindrical pressure vessels under variable pressure in the longitudinal direction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.82-85
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• 2002

Due to various advantages over the conventional linear motion device such as ball-screw, linear motors have been used in wide variety of industrial applications for years. Driven by increased demand for precision machine tools, the importance of high positioning accuracy, high stiffness and high thrust are greatly increasing. In this paper, thrust ripple, detent force and thermal behavior are considered for the development of high performance linear motor whose thrust is up to 4, 000N. This paper presents a comprehensive study for an iron core type linear motor characteristics that include the influence of PM position on thrust thrust ripple by detent farce and motor dynamics as well.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.98-101
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• 2001

Linear motor feature a direct connection to the machine tool, therefore a direct route for heat transfer. The heat dissipation of linear motor machine is affected by the maximum temperature rise of the primary part, coil and the cooling method. To minimize temperature induced dimension changes and decrements of performance, linear motor machine require effective cooling mechanism. To evaluate cooling performance of existing linear motor machine, some experiments about temperature profile are performed using thermocouple recorder. Due to the lack of information about internal structure, only some finite element modeling is prepared and analyzed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.33-36
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• 1997

The merits of linear motor are high speed, high acceleration and goad positioning accuracy. In addition, Linear motor for high quality machme tool call for high thrust, high stiffness. In using linear motor we also consider thrust ripple, detent force and thermal behavior. In this research, Iron core type single sided linear DC motor(LDM) is designed which thrust is 6,000 N. To accomplish this design, Various research is hlfilled l~ke the relation of thrust and permanent magnet position angle, the variation of detent force and thrust ripple, dynamic characteristics, and so on.