• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.641-646
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• 2000

A milling process with 45 degree chamfered inserts produces a perfect flat surface only in theory. It is due to many unwanted factors including thermal effect, dynamic effect, the problem of the controller used and the problem of accuracy of the machine tool. In this study, introduced is a method to improve the surface roughness by redesigning of the chamfer angle of the insert, which traditionally has been 45 degree. First, the relationship between the fixed machine coordinate and the relative coordinate on the insert is derived. This transfer matrix is used to determine the new insert angle to maximize the flatness of the machined surface. A newly designed insert is manufactured, and used to carry out the experiment. It is proved that the insert designed by the proposed method produced a much flatter surface than a traditional one.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.98-111
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• 1993

Two-dimensional nonlinear free-surface wave problems are analyzed with consideration of viscosity. Navier-Stokes equation and continuity equation are solved by the application of Finite Analytic Method, and MAC scheme is used far the treatment of free surface. Surface tension effect is also considered and laminar flow is assumed. The free-surface waves in shallow water, the flows around a vortex-pair with free surface and the wave ahead of a rectangular body are simulated to test the present numerical scheme. In the shallow water problem, viscous effect due to the friction on the bottom is observed. In the second problem, the approach of a vortex-pair to the free surface is simulated to examine the interaction of vortex-pair with the free surface. In the third problem, the wave ahead of a semi-infinite floating body is simulated.

• Tribology and Lubricants
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• v.36 no.3
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• pp.147-152
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• 2020

This paper is within the framework of an adhered complete contact problem wherein the contact between a half plane and sharp edged indenter, both of which are elastic in character, is constituted. The eigensolutions of the contact shear and normal stresses, σ_rq and σ_q, respectively, are evaluated via asymptotic analysis. The ratio of σ_rq/σ_qq is investigated and compared with the coefficient of friction, μ, of the contact surface to observe the propensity to slip on the contact surface. Interestingly, there exists a region of |σ_rθ/σ_θθ| ≥ |μ|. Thus, slipping can occur, although the problem is solved under the condition of an adhered contact without slipping. Given that a tribological failure potentially occurs at the slipping region, it is important to determine the size of the slipping region. This aspect is also factored in the paper. A simple example of the adhered contact between two elastically dissimilar squares is considered. Finite element analysis is used to evaluate generalized stress intensity factors. Furthermore, it is repeatedly observed that slipping occurs on the contact surface although the size of it is extremely small compared with that of the contacting squares. Therefore, as a contribution to the field of contact mechanics, this problem must be further explained logically.

• Knowledge Management Research
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• v.20 no.3
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• pp.39-47
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• 2019

Response surface methodology (RSM) is a group of statistical modeling and optimization methods to improve the quality of design systematically in the quality engineering field. Its final goal is to identify the optimal setting of input variables optimizing a response. RSM is a kind of knowledge management tool since it studies a manufacturing or service process and extracts an important knowledge about it. In a real problem of RSM, it is a quite frequent situation that considers multiple responses simultaneously. To date, many approaches are proposed for solving (i.e., optimizing) a multi-response problem: process capability function approach, desirability function approach, loss function approach, and so on. The process capability function approach first estimates the mean and standard deviation models of each response. Then, it derives an individual process capability function for each response. The overall process capability function is obtained by aggregating the individual process capability function. The optimal setting is given by maximizing the overall process capability function. The existing process capability function methods usually use the arithmetic mean or geometric mean as an aggregation operator. However, these operators do not guarantee the Pareto optimality of their solution. Moreover, they may bring out an unacceptable result in terms of individual process capability function values. In this paper, we propose a maximin-based process capability function method which uses a maximin criterion as an aggregation operator. The proposed method is illustrated through a well-known multiresponse problem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1143-1148
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• 2002

This paper analyses the transient response of a spherical elastic shell located near fee surface and impinged by spherical step-exponential acoustic shock waves. The problem is solved through extension of a method (Huang, 1969) previously formulated for the excitation in an infinite domain, which employs the classical separation of variables, series solutions, and Laplace transform technique The effect of the free surface reflection is taken into account using the image source method. The reflection of the incident wave has been treated by the same image formulation. If the reflection of the pressure field scattered and radiated by the shell is considered, the problem becomes that of multiple scattering by two spheres. However, this is in general negligible considering errors inherent from other sources and that the scattered and radiated pressure waves emanating from the shell are small. Thus, the problem is reduced to that of a structure immersed in an infinite fluid and impinged upon the origin and the image incident.

• International Journal of CAD/CAM
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• v.3 no.1_2
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• pp.85-95
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• 2003

During the design of dies and molds, the cavity of the object is obtained by subtracting it from a surrounding rectangular block. This box is subsequently split into two halves by the parting surface. Similar problems also occur in some RP processes such as LOM, SGC, SLS and 3DP where the machine produces a block inside which the prototype is buried. Determining the orientation of the object inside the box and the corresponding parting surface taking appropriate constraints into account have been addressed by several researchers. However, given the parting surface, the problem of splitting the box development of a software package called OptiLOM (now a module of an RP software Magics 8.0), the authors realized non-triviality of this problem since the loop can spread over as many as 5 faces of the box. In this paper, the authors have tried to bring out the importance of this problem and have presented their algorithm to solve it.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1102-1110
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• 2005

In this paper, we proposed a advanced approach to resolve the trade-off problem for the threshold value determining the photo-consistency in the previous algorithms. The threshold value for the surface voxel is substituted the photo-consistency value of the inside voxel. As iterating the voxel coloring process, the threshold is approached to the optimal value for the individual surface voxel. we present an energy minimization formulation of the binary labeling problem that surface voxels classify into opacity or transparency. The energy formula consists of the data term and the smoothness term. As considering neighboring voxels in the labeling problem, the unevenness of reconstructed surface is reduced. The labeling whose energy is the global minimum can be computed using a graph cut.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.210-225
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• 2004

Statement of problem: Implant screw loosening has been remained problem in restorative practices. Surface treatment of screw plays a role of preventing screw from loosening in implant screw mechanism. Purpose : The purpose of this study was to investigate surface characteristics of TiN and ZrN film ion plated screw with titanium and gold alloy screw and to evaluate wear resistance, surface roughness, and film adhesion on screw surface using various instruments. Material and methods : GoldTite screws and titanium screws provided by 3i (Implant Innovation, USA) and TorqTite screws or titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, korea) were selected. Ion plating which is much superior to other surface modification techniques was carried out for gold screws and titanium screws using Ti and Zr coating materials with nitrogen gas. Ion nitrided surface of each abutment screw was observed with field emission scanning electron microscopy (FE-SEM, micro-diamond scratch tester, vickers hardness tester, and surface roughness tester. Results : 1) The surface of gold screw and GoldTite is more smooth than ones of other kinds of non coated screw. 2) The ZrN and TiN coated surface is the more smooth than ones of other kinds of screw. 3) The hardness of TiN and ZrN coated surface showed higher than that of non coated surface. 4) The TiN coated titanium screw and ZrN coated gold screw have a good wear resistance and adhesion on the surface. 5) The surface of ZrN coated screw showed low surface roughness compared with the surface of TiN coated screw. Conclusion : It is considered that the TiN and ZrN coated screw which would prevent a screw from loosening can be applicable to implant system and confirmed that TiN and ZrN film act as lubricant on surface of screw due to decrease of friction for recycled tightening and loosening.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.9 no.2
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• pp.75-82
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• 2005

An inverse problem of transient heat conduction in a thin finite circular plate with the given temperature distribution on the interior surface of a thin circular plate being a function of both time and position has been solved with the help of integral transform technique and also determine the thermal deflection on the outer curved surface of a thin circular plate defined as $0\;{\leq}\;r\;{\leq}\;a,\;0\;{\leq}\;z\;{\leq}\;h$. The results, obtained in the series form in terms of Bessel's functions, are illustrated numerically.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.146-159
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• 2002

An efficient method to predict the convection heat transfer coefficients on the top surface of the engine piston is proposed. The method is based on the inverse method of the thermal conduction problem and uses a numerical optimization technique. In the method, the heat transfer coefficients are numerically obtained so that the difference between analyzed temperatures from the finite element method and measured temperatures is minimized. The method can be effectively used to analyze the temperature distribution of engine pistons in case when application of prescribed-temperature boundary condition is not reasonable because of insufficient number of measured temperatures. A hollow sphere problem with an analytic solution is taken as a simple example and accuracy and efficiency is demonstrated. The method is applied to a practical large liquid petroleum gas(LPG) engine piston and the heat transfer coefficients on the top surface of the piston is successfully calculated. Resulting analyzed temperature favorably coincides with measured temperature.