• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.195-200
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• 2007

We analyzed a sequence of multi-stage automatic cold forging processes composed of four axisymmetric processes followed by a non-axisymmetric process using rigid-plastic finite element based forging simulators. The forging sequence selected for an example involves a piercing process and a heading process accompanying folding or overlapping, which all make it difficult to simulate the processes. To reduce computational time and to enhance the solution reliability, only the non-symmetric process was analyzed by the three-dimensional approach after the axisymmetric processes were analyzed by the two-dimensional approach. It has been emphsized that this capability is very helpful in simulating the multi-stage automatic forging processes which are next to axisymmetric.

• 구강회복응용과학지
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• 제22권1호
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• pp.37-53
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• 2006

Purpose: The purpose of this study was to investigate the influences of the jaw dimension on the bone stress. Materials and Methods: Root analogue implant of Frialit-2 Synchro model in the jaw bone of various thickness from 8mm to 13mm were modelled axisymmetrically for a series of finite element analyses. As load conditions, non-axisymmetric lateral load of 20N and an oblique load of 50N, as well as an axisymmetric vertical load of 50N were taken into consideration. Results: The cervical area of implant under the axisymmetric load and the base cortical bone under the non axisymmetric load condition were the areas of main concern where the higher level of stress were likely to be obtained. Conclusion: The results indicated that at the two concerned areas drastically different stress distribution could take place as a function of the load conditions. Under the vertical load, the lower level of stress was observed for the narrow jaw bone at the cervical cortical bone whereas stress at the base cortical bone remained virtually unchanged. Under the non axisymmetric load condition, however, the stress at the base cortical bone increased very rapidly as the jaw bone width increased without inducing any significant change in the stress level at the cervical area.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1992년도 춘계학술대회 논문집 92
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• pp.27-46
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• 1992

In this study a new simplified three-dimensional numerical method and the associated computer program have been developed to simulate the non-axisymmetric extrusion processes. The two-dimensional rigid-plastic finite element method under the generalized plane-strain condition, is combined with the slab method. To define the die geometry for non-axisymmetric extrusion, area mapping technique was used. Streamlined die surface was used to miniminze the total extrusion pressure. Extrusion of square, hexagonal and "T" section from round billet have been simulated and experimented with a model material. The computed results were in good agreement with the experiments in cross-sectional grid distortion. Computational results will be valuable for designing tool geometries and corresponding processes.

• International Journal of Aeronautical and Space Sciences
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• 제11권2호
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• pp.59-68
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• 2010

The aim of this work is to analyze high temperature flows around an axisymmetric blunt body taking into account chemical and vibrational non-equilibrium state for air mixture species. For this purpose, a finite volume methodology is employed to determine the supersonic flow parameters around the axisymmetric blunt body. This allows the capture of a shock wave before a blunt body placed in supersonic free stream. The numerical technique uses the flux vector splitting method of Van Leer. Here, adequate time stepping parameters, along with Courant, Friedrich, Lewis coefficient and mesh size level are selected to ensure numerical convergence, sought with an order of $10^{-8}$.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.386-390
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• 2006

Global consumption of aspheric lens will expand rapidly due to golbal transformation of the electronics based industry to optics based mechatronics. Especially, F-Theta lens is one of important parts in Laser Scanning Unit(LSU) because it affects the optical performance of LSU dominantly. Non axisymmetric machine based processing techologies are required to obtain high accuracy in utlra-precision aspheric core, the most important component in plastic injection molded F-Theta lens assembly. In this study, the core with non-axisymmetric aspheric shape which is used to emit the F-Theta lens was processed using the ultra precision processing technology and the shape accuracy of the core was measured. And the results there of were evaluated and compared with the emitted shape accuracy of F-Theta lens.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1410-1413
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• 2003

Drawing is a basic plastic deformation method and productive manufacturing process make wire. rod and variety section geometry bar. Study for the rod drawing process of rod was researched long littles. but non-axisymmetric drawing process is weak. So metal flow is very irregular in non-axisymmetric drawing process and difficult to define about material deformation generally. In this paper, to solve material deformation, use finite element method and then define suitable shape for rod to hexagonal drawing dies. And research corner filling rate and surface roughness for the high strength steel hexagonal bar produced defined dies.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 추계학술대회논문집
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• pp.143-149
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• 1995

A simple kinematically admissible velocity field is proposed to drtermine the final-stage extrusion load and the average extruded length in the square-die forward extrusion of non-axisymmetric bars from circular billets. The proposed velocity field is applied to the square-die extrusion of trochoidal gear-shaped bars and rectangular-shaped bars, the profile function of a rectangular being approximated by using a Fourier series. Experiments have been carried out with hard solder billets at room temperature. The theoretical predictions of the extrusion load are in good agreements with the experimental results and there is generally reasonable agreements in average extruded length between theory and experiment.

• 소성∙가공
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• 제4권4호
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• pp.390-397
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• 1995

A simple kinematically admissible velocity field is proposed to determine the final-stage extrusion load and the average extruded length in the square-die forward extrusion of non-axisymmetric bars from circular billets. The proposed velocity field is applied to the square-die extrusion of trochoidal gear-shaped bars and rectangular-shaped bars. The profile function of a rectangle is approximated by using a Fourier series. Experiments have been carried out with hard solder billets at room temperature. The theoretical predictions of the extrusion load are in good agreements with the experimental results and there is generally reasonable agreements in average extruded length between theory and experiment.

• 한국정밀공학회지
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• 제15권11호
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• pp.21-31
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• 1998

This study described computer aided die design system for cold forging of non-axisymmetric parts. To design the die of cold forging. an integrated approach based on a rule-base system and commercial F. E. code were adopted. This system is implemented on the personal computer and its environment is a commercial CAD package named as AutoCAD. The system includes four modules. In the initial data input module, the variables which are necessary to design of die are inputted by user and die material are selected from the database. In the analysis and redesign module, stress distrubution action on the designed die is analyzed by commercial FEM code NISA II. The designed die is modified to prevent failure in both states of stress free and pressurizing. The developed system provides powerful capabilities for die design of non-axisymmetric parts.

• 한국정밀공학회지
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• 제12권3호
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• pp.42-52
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• 1995

An UBET(Upper Bound Elemental Techniquel) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flashless non-axisymmetric forging. To analyze the process easily, it is suggested that the deforma- tion is divided into two different parts. Those are axisymmetric part in corner and plane- strain part in lateral. The total power consumption is minimized through combination of two deformation parts by building block method, form which the upper-bound forging load, the flow pattern, the grid pattern, the velocity distribution and the effective strain are deter- mined. To show the merit of flashless forging, the results of flashless and flash-forging processes are compared through theory and experiment. Experiments have been carried out with plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agrement with the experimental results.