• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.835-837
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• 2017

본 연구에서는 필라멘트 와인딩을 이용한 원통형 복합재 격자구조체의 제작 공정을 서술하였다. 원통형 복합재 격자구조체는 크게 네 단계의 제작 공정을 통해 제작된다. 격자 형상을 갖는 실리콘 금형을 맨드릴에 설치하고 연속 섬유를 실리콘 금형 위에 와인딩 한다. 섬유의 와인딩 후 모든 영역에서 동일한 두께를 갖도록 섬유 교차부의 압착 공정을 수행한다. 마지막으로 복합재 격자구조체를 오븐에서 경화하고 금형을 탈형한다. 제작된 제품의 치수는 설계 사양과 비교하여 2.4%의 오차가 발생하는 것을 확인하였다.

• Design & Manufacturing
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• 제15권3호
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• pp.13-18
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• 2021

In plate forming technology, cylindrical drawing process is widely used in industry due to technological development. In this study, we used stainless steel 3042B and stainless steel 304J1, which are the most commonly used materials in the production of cold and hot water tanks for water purifiers, among cylindrical drawing products. Under the same conditions, the thickness of the sidewall of the product formed by drawn experiment was studied. As a result of the experiment, the bottom thickness of stainless steel 304J1 was considered to be thick. It is judged that the defect rate can be reduced by changing the breaking phenomenon of the floor surface of the cold and hot water bottles to the material of stainless steel 304j1. Stainless steel 304 2B material shows a sharp change in thickness from punch corner R to sidewall position, while stainless steel 304J1 material showed a uniform change from punch corner R to sidewall position. Stainless steel 304J1 material is considered to improve the clamping of the product in the process of extracting the product after hand drawing. The appearance of stainless steel 3042B products is considered to produce more wrinkles in the flange, which exerts greater tensile force on the sidewall during molding, resulting in uneven sidewall thickness.

• Design & Manufacturing
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• 제16권2호
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• pp.39-45
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• 2022

Sheet Metal Forming by Press Forming Process takes a lot of time and cost from mold design to manufacturing. Therefore, all of die-makers are continuously conducting research to reduce the number of mold processes or the size of blanks to reduce costs. In the case of Forming complex shapes such as automobile component, wrinkles and cracks occur, so draw beads are used. Draw beads play an important role in suppressing the inflow of materials and minimizing the size of blanks. Factors that affect material flow include draw bead, blank holding pressure, lubricant, and surface roughness of punch and die. Most of the factors affect friction. In this study, after classifying circular beads and rectangular beads in cylindrical drawing molds using the AutoForm analysis program, the factors affecting the material inflow were considered.

• 대한기계학회논문집
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• 제16권2호
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• pp.348-355
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• 1992

Casting structures and properties are determined by the solidification speed in the metal mold. The heat transfer characteristics of the interface between the mold and the casting is one of the major factors that control the solidification speed. According to Sully's research, the thermal resistance exists due to the air-gap formation at the mold-casting interface during the freezing process and the interface heat transfer coefficient is used to describe the degree of it. In this study, one-dimensional Stefan problem with air-gap resistance in the cylindrical geometry is considered and heat transfer characteristics is numerically examined. The temperature distribution and solidification speed are obtained by using the modified variable time step method. And the effects of the major parameters such as mold geometry, thermal conductivity, heat transfer coefficient and initial temperature of casting on the thermal characteristics are investigated.

• Design & Manufacturing
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• 제2권2호
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• pp.33-37
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• 2008

This paper describes the optimization of injection molding conditions to minimize sink marks. Sink marks, which refer to a small depression on the surface opposite a thick wall thickness, are often encounted in injection molded plastic parts. Part geometry, material properties and processing conditions during injection molding can affect the sink mark depth. We designed the runner system which is possible balanced filling to cavities using CAE program and then obtained optimal processing conditions by Taguchi's Robust Design technique. By actual injection molding using optimized mold and molding conditions, it confirmed that sink mark depth decreased zero compared to 1mm level in the conventional mold and process.

• 소성∙가공
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• 제4권1호
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• pp.39-47
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• 1995

The compression molding of SMC (sheet molding compund) at room temperature was analyzed based on rigid-viscoplastic approach by three dimensional finite element program. The developed program was tested by solving the three dimensional compression of wedge type specimens of aluminum alloys at various processing conditions. The simulation results were compared well to the experimental results available in the literature. based on this comparison the program was proved to be valid and was further applied in solving compression molding of SMC, which is a thermosetting material reinforced with chopped fiber glass. To investigate the effects of friction conditions and mold closing speeds for compression molding of SMC charge at room temperature, compressions of the cylindrical and rectangular shaped SMC were analyzed for various friction conditions and mold closing speeds. The calculated load values were compared to the experimental results for the compression molding of cylindrical specimen.

• Design & Manufacturing
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• 제17권1호
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• pp.33-39
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• 2023

The ball end mill is a type of cutting tool that is widely used to process complex mold shapes including aspheric surfaces. Unlike the flat end mill in which the cutting edge is formed on the cylindrical handle, the cutting edge is formed from the cylindrical handle to the hemispherical shape, which is advantageous for processing curved shapes. However, since the cutting speed continuously changes during machining due to the helix angle of the cutting edge or the machining inclination angle, it is difficult to obtain a precise machined surface. Therefore, in this paper, machining was performed while changing the helix angle of the ball end mill and the angle of the machining slope under the same cutting conditions for STD 11 material, which is widely used as a mold material. Through this, the effect of the two variables on the roughness of the machined surface was analyzed. As a result, if the helix angle was 0 degrees, it showed the best surface roughness of Ra. 0.16 ㎛. When the helix angle was 20 degrees, the best surface roughness of Ra. 0.18 ㎛ was occurred.

• 한국구조물진단유지관리공학회지
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• 제18권4호
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• pp.13-22
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• 2014

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.187-188
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• 2013

• Structural Engineering and Mechanics
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• 제16권3호
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• pp.361-369
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• 2003

In this paper, the structural behavior of R/C cylindrical panel is analyzed by experimental results. To avoid the geometric imperfection, R/C shell specimens are made by use of a stiff steel mold. From experimental results, the load carrying behavior of R/C cylindrical panel is presented under an external lateral pressure. Even if R/C shell does not posses geometric imperfections, the inaccuracy of the reinforcement position strongly affects to the ultimate strength and the failure patterns of such shells. To explain these effects, FEM nonlinear analyses are done under the same conditions as those of experiments. The behavior of R/C cylindrical shells are well simulated under the consideration of both the geometric imperfection and several inaccuracies.