• 소성∙가공
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• 제27권2호
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• pp.87-92
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• 2018

Auto industries have tried to employ lightweight alloys to improve the fuel efficiency of manufactured vehicles, as the environmental concern becomes an important issue. Even though the aluminum alloy is one of the most appropriate lightweight alloys for auto parts, the low formability of an aluminum alloy has been an obstacle to its application. In order to resolve the low formability problem, a recent study (Lee et al., 2017 [1]) showed that the infrared (IR) local heat treatment can improve the formability with a reduction of heating energy. However, the aforementioned study was limited to only a linear line heating. Since many of the available auto parts as applicable to vehicle manufacturing have a curved line shape, the heating experiments for a curved line should be studied. The possibility of building IR lamps having complex shapes is an advantage of the IR lamp, since it can control the heating shape. This work conducted the IR local heat treatment for the curved line. The experimental results show that the IR local heat treatment can improve the formability of the aluminum alloy for curved line. Additionally, it is shown that the IR local heat treatment also reduces the heating energy when it is compared with the furnace heating which heats a blank as a whole. A numerical simulation with a stress-based forming limit diagram also supports the experimental results.

• 대한조선학회논문집
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• 제36권3호
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• pp.134-143
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• 1999

선박의 선미부와 선수부는 복잡한 곡을 가진 블록들의 조립으로 만들어진다. 이러한 복잡한 곡률 분포를 가진 이중 곡면을 성형하기 위해서 조선소에서는 롤러 굽힘 가공과 선상 가열을 이용하고 있다. 일차적으로는 롤러 굽힘에 의한 가공으로 실린더 형상이나 원추 형상의 곡면을 만들고 난 후, 선상 가열을 수행하여 목적 형상으로 이차 가공을 한다. 본 논문은 곡면 가공에서 선행되는 일차 가공의 정보로서 가공 방향과 가공 후 형상을 결정하는데 목적이 있다. 목적 형상의 가우스 변환(Gauss mapping)으로부터 가공 방향에 관한 정보를 결정하고 목적 형상과 롤러 굽힘 가공에 의해 변형된 판 사이의 기하학적 관계를 이용하여 롤러 굽힘 가공의 모양을 결정하는 알고리즘을 제시하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.400-403
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• 2008

For the effective manufacture of doubly curved metal plates, a line array roll set (LARS) process is proposed. The suggested process utilizes a pair of upper and lower symmetric roll assemblies. In the process, the initial plate is progressed into the final shape in a stepwise or pathwise manner according to the basic principle of the incremental forming process. The deformation proceeds simultaneously in the longitudinal and transverse directions. Moreover, there is a close correlation between the deformation in the longitudinal direction and that in the transverse direction of the plates. Therefore, the finally formed shape in the incremental forming process is strongly dependent upon process conditions, such as the forming path and the forming increment. The manufacturing of arbitrary doubly curved plates with various curvatures is not an easy task because of such complicated behaviors of the plate; thus, the forming schedules for the desired shape should be carefully and accurately designed. In this study, several experiments with the LARS system were carried out for the fundamental investigation on process design for manufacturing of doubly curved plates.

• 한국CDE학회논문집
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• 제14권2호
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• pp.129-136
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• 2009

Generally, curved surfaces of ship hull are deformed by flame bending (line heating), multi-press forming, and die-less forming method. The forming methods generate the required in-plane/bending strain or displacement on the flat plate to make the curved surface. Multi-press forming imposes the forced displacements on the flat plate by controlling the position of each pressing points based upon the shape difference between the unfolded flat plate and the curved object shape. The flat plate has been obtained from the unfolding system that is independent of the ship CAD. Apparently, the curved surface and the unfolded-flat surface are expressed by different coordinate systems. Therefore, one of the issues is to find a registration of the unfolded surface and the curved shape for the purpose of minimum amount of forming works by comparing the two surfaces. This paper presents an efficient algorithm to get an optimized registration of two different surfaces in the multi-press forming of ship hull plate forming. The algorithm is based upon the ICP (Iterative Closest Point) algorithm. The algorithm consists of two iterative procedures including a transformation matrix and the closest points to minimize the distance between the unfolded surface and curved surfaces. Thereby the algorithm allows the minimized forming works in ship-hull forming.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.66-71
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• 2006

A geometric contact conditions of wheel/rail affect the dynamic behavior of rolling stock. Mechanical force acted on the wheel/rail causes excessive wear and increase the maintenance cost. In this study, we have studied the dynamic behavior of the urban railway vehicle with new and worn wheel by VAMPIRE program. And we have tested the accelerations of wheelset on the conventional line. The results of simulation are compared with the measuring data of field test. It shows that the acceleration of worn wheel is greater than the acceleration of new wheel in the straight track line but on the contrary, the acceleration of new wheel is greater than the acceleration of worn wheel in curved track. That results explain that the new wheel is worn out greater than the worn wheel in curved track line and need to be maintained more seriously when running in curved track line.

• 대한조선학회논문집
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• 제46권6호
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• pp.675-687
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• 2009

In general, the forming process of the curved hull plates consists of sub tasks, such as roll bending, line heating, and triangle heating. In order to complement the automated curved hull forming system, it is necessary to develop an algorithm to classify the curved hull plates of a ship into standard shapes with respect to the techniques of forming task, such as the roll bending, the line heating, and the triangle heating. In this paper, the curved hull plates are classified by four standard shapes and the combination of them, or saddle, convex, flat, cylindrical shape, and the combination of them, that are related to the forming tasks necessary to form the shapes. In preprocessing, the Gaussian curvature and the mean curvature at the mid-point of a mesh of modeling surface by Coon's patch are calculated. Then the nearest neighbor method to classify the input plate type is applied. Tests to verify the developed algorithm with sample plates of a real ship data have been performed.

• Steel and Composite Structures
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• 제25권3호
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• pp.347-360
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• 2017

The goal of this study is to fill this apparent gap in the area about vibration analysis of multiwalled carbon nanotubes (MWCNTs) curved panels by providing 3-D vibration analysis results for functionally graded multiwalled carbon nanotubes (FG-MWCNTs) sandwich structure with power-law distribution of nanotube. The effective material properties of the FG-MWCNT structures are estimated using a modified Halpin-Tsai equation. Modified Halpin-Tsai equation was used to evaluate the Young's modulus of MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. Also, the mass density and Poisson's ratio of the MWCNT/phenolic composite are considered based on the rule of mixtures. Parametric studies are carried out to highlight the influence of MWCNT volume fraction in the thickness, different types of CNT distribution, boundary conditions and geometrical parameters on vibrational behavior of FG-MWCNT thick curved panels. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary conditions including Free, Simply supported and Clamped at the curved edges. For an overall comprehension on 3-D vibration analysis of sandwich panel, some mode shape contour plots are reported in this research work.

• 복식
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• 제59권10호
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• pp.10-21
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• 2009

The shape of floral pattern in the period of Rococo are a pots, a flower and ribbon style, a flower and a stripe style, a lace style and a scene style etc, and also in that time an apperance of softness of curved line, delicacy and smoth line, irregular and unrestraint line, motive of tiny and extra ordinarily, little bunch of flowers, and stripe style was a feature. The style of presentation were a presentation of fixed style such effect as lace, and a presentation of realistically style emphasized a massiveness and a cubic effect, and also used a natural color, and the presentation of abstract expressed like imagined anything and fancied. Weaving expressed delicate, brilliant, fantastic, and an atmosphere with elegant. embroidery was expressed in creation with emphasized in reality. Printing was fantastic with exotic in development of chintz due to effection of orient. The based on a salon civilization, the refind beauty of taste of royalty gave a refinded feeling with over affectionate in preference with a softness of curved line, and a motive of tiny and extra ordinarily. The classical beauty of elegant was realistic in being concentrated on building up blance and homony. The natural beauty of romantic was in being devoted the theme with soft and fantastic.

• 소성∙가공
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• 제9권5호
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• pp.504-511
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• 2000

Hydroforming is a forming process enabling circular metal tubes to be produced in complex cross sections along curved axial paths. This forming process is widely used to manufacture parts in automotive industry. This paper presents bending and forming results to following angle of weld line positions. These compare to good bending, bad bending and without weld line model case. And then this result of after forming compare to each forming cases. The purpose of this paper is found that adaptive weld line position for bended final shape.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.215-219
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• 2009

For the effective manufacture of doubly curved metal plates, a line array roll set (LARS) process is proposed. The suggested process utilizes a pair of upper and lower symmetric roll assemblies. In the process, the initial plate is progressed into the final shape in a stepwise or pathwise manner according to the basic principle of the incremental forming process. In this work, the intermediate shape which is closest to a final shape is proposed to fabricate the desired shape effectively in design of forming schedule. The intermediate shape has homogeneous curvature in a longitudinal and transverse direction so that it can be fabricated easily without complicated controls of rolls in the roll set. The method of approximation using genetic algorithm is proposed and applied to some actual ship hulls to evaluate the efficiency of the algorithm.