• Transactions of Materials Processing
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• v.7 no.4
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• pp.375-381
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• 1998

This paper presents development of finite element simulation program and analysis of hot extrusion through square dies with a mandrel. The design of extrusion dies is still an art rather than science. Die design for a new extrusion process is developed from through in-plant trials. In the present paper, a three-dimensional steady-state finite element simulation program is developed. Steady-state assumption is used for both the analyses of deformation and temperature. The developed program is effectively used to simulate hollow extrusion of several sections. Distributions of temperature effective strain rate, mean strain rate and mean stress are studied for an effective design of extrusion dies.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.14-19
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• 1996

This study presents development of finite element simulation program and analysis of hot extrusion through square dies with mandrel. The design of extrusion dies is still an art rather than science. Die design for a new extrusion is developed from through in-plant trials. In the present paper, three-dimensional steady-state finite element simulation program is developed. The developed system is effectively used to simulate extrusion of clamp shaped hollow section. The objective of the present paper is to study the possibility of integrating this method into the design of dies for extrusion of complex section. To obtain sound product, the distributions and effects of temperature, effective strain rate, mean strain rate and mean stress are studied.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.161-167
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• 1983

In this study the phenomenon of cutting stress which arises on cutting tools and work pieces in cutting process is investigated by rake angle of cutting tools and feed for this measurement, P$_{s}$-1 (high modulus, photolastic Inc.) was used as a cutting tool, P$_{s}$-3 (medium modulus, photolastic Inc.) was used as work piece and reduction apparatus was attached to the head stock, and orthogonal cutting was adapted as a cutting method and transparent glass was used to block the strain in the orientation of thickness. The followings are the results of this study. (1) Photoelastic experimental equipments have made it possible to make dynamic measurement and analyze stress distribution in cutting tool and work piece surface which has hitherto been conducted only in static measurement and analyzing method. (2) The maximum stress arising at tools and work pieces in cutting process is on the tool edge tip, and the maximum stress arising on the tip of cutting tools is equal to that on the contacting area of work pieces in values. (3) The distributions of maximum shear stress on certain parts of the cutting tools and work pieces are as follows; for cutting tools, .alpha.=12.deg., .alpha.=0.deg., .alpha.=-12.deg. in order, and for work pieces, .alpha.=-12.deg., .alpha.=0.deg., .alpha.=12.deg. in opposite order.der.

• Computers and Concrete
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• v.27 no.3
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• pp.199-210
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• 2021

The aim of this paper was to examine the continuous and discontinuous contact problems between the functionally graded (FG) layer pressed with a uniformly distributed load and homogeneous half plane using an analytical method and FEM. The FG layer is made of non-homogeneous material with an isotropic stress-strain law with exponentially varying properties. It is assumed that the contact at the FG layer-half plane interface is frictionless, and only the normal tractions can be transmitted along the contacted regions. The body force of the FG layer is considered in the study. The FG layer was positioned on the homogeneous half plane without any bonds. Thus, if the external load was smaller than a certain critical value, the contact between the FG layer and half plane would be continuous. However, when the external load exceeded the critical value, there was a separation between the FG layer and half plane on the finite region, as discontinuous contact. Therefore, there have been some steps taken in this study. Firstly, an analytical solution for continuous and discontinuous contact cases of the problem has been realized using the theory of elasticity and Fourier integral transform techniques. Then, the problem modeled and two-dimensional analysis was carried out by using ANSYS package program based on FEM. Numerical results for initial separation distance and contact stress distributions between the FG layer and homogeneous half plane for continuous contact case; the start and end points of separation and contact stress distributions between the FG layer and homogeneous half plane for discontinuous contact case were provided for various dimensionless quantities including material inhomogeneity, distributed load width, the shear module ratio and load factor for both methods. The results obtained using FEM were compared with the results found using analytical formulation. It was found that the results obtained from analytical formulation were in perfect agreement with the FEM study.

• Journal of the Korean Wood Science and Technology
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• v.16 no.4
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• pp.54-60
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• 1988

Machinabilities means inherent properties of pinus densiflora at Chunyang district to be CNC machined easily or not, and processing abilities of the tool and machine together. This explanation signifies that machinabilities have two phases of signification, depended on considering and stress either materials or tools preferentially. This paper discuss machinabilities, the following items are usually employed as the indices of stress distribution at the cutting tool rake face. The stress distributions on the chip - tool contact surface at the early stage of the chip forming and under the stage of fringe pattern in wood cutting were analyzed the photoelastic method. The tool used in the present experiment was the special cutting tool H.S.S. one made in laboratory. And isochromatic fringe pattern and isolinic line of work piece by chip-behavior during the cutting operation were photographed with the feed camera continuously. The effects on the stress, distribution on the rake face of the epoxy tool and the strain distribution in the work piece of wood plate by chip behavior are cleared in pre cent experiment.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.70-77
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• 1997

Welding is one of the most important and popular joining techniques employed in structures. In spite of, weld designs depend on the rules and regulations. Moreover, the study to optimize a shape of welding joint not may be sufficient and systematic on the theoretical and experimental sides. Therefore, in this study, a computer program based on thermal elasto plastic theory is developed for optimizing(minimizing) shape of weld joints. By the results, study is made on the characteristics of the distributions of welding residual stresses and plastic strains, and their production mechanisms. Also, Various kinds of tests are carried out to find out mechanical characteristics due to shape of weld joints. As a result of this optimization(minimization) of weld joints, the productivity and the reliability will be improved.

• Journal of Mechanical Science and Technology
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• v.17 no.4
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• pp.477-483
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• 2003

An independent kinematic hardening material model in which the reverse yielding point is defined by the Bauschinger effect factor (BEF) , has been defined for stainless steel SUS 304. The material model and the BEF are obtained experimentally and represented mathematically as continuous functions of effective plastic strain. The material model has been incorporated in a non-linear stress analysis for the prediction of reverse yielding in thick-walled cylinders during the autofrettage process of these vessels. Residual stress distributions of the independent kinematic hardening material model at the onset of reverse yielding are compared with residual stresses of an isotropic hardening model showing the significant effect of the BEF on reverse yielding predictions. Critical pressures of direct and reverse yielding are obtained for the most commonly used cylinders and a range of permissible internal pressures for an efficient autofrettaged process is recommended.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2292-2301
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• 2000

We propose an accurate and efficient estimation method of transverse shear stresses for analysis and design of laminated composite structures by 4-node quadrilateral degenerated shell elements. To get proper distributions of transverse shear stresses in each layer, we use 3-dimensional equilibrium equations instead of constitutive equations with shear correction factors which vary diversely according to the shapes of shell sections. Three dimensional equilibrium equations are integrated through the thickness direction with complete polynomial membrane stress fields, which are recovered by REP (Recovery by Equilibrium in Patches) recovery method. The 4-node quadrilateral degenerated shell element used in this paper has drilling degrees of freedom and shear stresses derived from assumed strain fields that are set up at natural coordinate systems. The numerical results demonstrate that the proposed estimation method attains reasonable accuracy and efficiency compared with other methods and FE analysis using 4-node degenerated shell elements.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.05a
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• pp.9-19
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• 1999

A clad material is a different type of the typical composites which is composed of two or more materials joined at their interface surface. The advantage of clad material is that the combination of different materials can satisfy both the need of good mechanical properties and the other demand of user such as electrical properties instantaneouly. This paper is concerned with the direct and indirect extrusion process of copper-clad aluminum rod. Extrusion of copper-clad aluminum rod was simulated using a commercially available finite element package of DEFORM. The simulations were performed for copper-clad aluminum rod to predict the distributions of temperature, effective stress, effective strain rate and moan stress for some sheath thicknesses, die exit diameters and die temperatures.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.107-110
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• 1999

The purpose of this research is for the development of a new type forging equipment H.C.G(Hyundai Continuous Grain-flow) by using two virtual build-up tools rigid viscoplastic FEM and downsized plasticine experiment. This forging equipment consists of consecutive horizontal and vertical pressure while the traditional forging method consists of only vertical pressure. Using this method high quality crankshafts can be forged as it can maintain a continuous grain flow. The factors considered in the development of equipment are die geometry for flawless deformed shape die reaction forces stress/strain distributions and continuous material flow. We carried out several numerical simulations and downsized plasticine experiments for the proper design of the forging equipment. The validity of those simulation results is confirmed by checking with the actual test results. Based on these simulation results the proper design of the H.C.G for ging equipment is enabled.