• Composites Research
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• v.27 no.2
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• pp.37-41
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• 2014

Fiber reinforced composite materials have outstanding specific strength and specific stiffness. So the use of composite materials increases in various kinds of industrial fields including sports goods such as bicycles. Composite materials are used to make structural parts with various kinds of shapes. Specially, rectangular composite tubes are used to make a few of composite bicycle frames, but there has been a few of research on this issue. Rectangular composite tubes are designed to have appropriate radius of curvature and endure bending and torsional loads. In this research, nine kinds of rectangular composite tubes having aspect ratios 1:1, 1:1.5, 1:2 and radius of curvatures R5, R10, R15 were fabricated. The carbon fiber reinforced composite material was used to make tubes having same cross sectional areas. The stacking sequence of tubes is $[0/90/{\pm}45]s$. Experimental evaluation was accomplished to apply bending and torsional load to the tubes. Experimental results show that bending and torsional characteristics depend on radius of curvature and aspect ratio of rectangular composite tubes.

• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.294-299
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• 2006

Computational simulation was performed to analyze flow velocities and particle trajectories onto the surface of bag-shaped filters with a different permeability. When the permeability of a filter is lower than that of a low-efficient fabric bag-filter widely used, the distributions of flow velocities and particle trajectories on the filter surface were not different with decreasing the filter permeability. The distributions of streamlines and radial directional gas velocities were uniform on the filter surface except for the neighbors of the bottom edge and outlet of the filter. The particle trajectories onto filter surface were more densely distributed around the bottom edge of the filter, so that the particle number on the filter surface was maximized near the bottom edge and decreased in the direction of the filter outlet.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2587-2593
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• 2014

Ceramic Injection Molding (CIM) is one of wide used processes in industry field and the applications are gradually being expanded to parts of medical and electric devices. In this study, the CIM process were analyzed with FEM and process parameters were studied and analyzed the effect on product quality. The shape of simple flat plate was compared to the shapes with the hole, with the round corner portion or with the side wall portion. If there are holes then the hole around the uneven density distribution and the defects such as weld lines could be occurred. The Large radius of the corners of the product give good formability and fluidity. Not only the shape parameters of product but also the process parameters during CIM are studied. The simulation results showed that the process parameters of temperature, initial fractions and velocity are important design parameters to improve the quality of products.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.149-156
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• 2020

Permeation grouting effectively enhances soil strength and decreases permeability of soil; however, the flow of grout is heavily affected by anisotropy of hydraulic conductivity in layers. Therefore, this study investigates the effect of permeability anisotropy on the effective radius of horizontal permeation grout using computational fluid dynamics (CFD). We modeled the horizontal permeation grout flow as a two-phase viscous fluid flow in porous media, and the model incorporated the chemical diffusion and the viscosity variation due to hardening. The numerical simulation reveals that the permeability anisotropy shapes the grout bulb to be elliptic and the dissolution-driven diffusion causes a gradual change in grout pore saturation at the edge of the grout bulb. For the grout pore saturations of 10%, 50% and 90%, the horizontal and vertical radii of grout bulb are estimated when the horizontal-to-vertical permeability ratio varies from 0.01 to 100, and the predictive model equations are suggested. This result contributes to more efficient design of injection strategy in formation layers with permeability anisotropy.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.2
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• pp.60-68
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• 2009

The objective of this paper is to design stamping die of inner reinforcement panel with DL 950 advanced high strength steel as stamping materials through numerical analyses and experiments. The stamping process was designed as bending dominant process consisting of 1 step of notching and 4 steps of bending processes. In order to obtain a proper design of the stamping die, various three-dimensional elasto-plastic finite element analyses were performed using a commercial code AUTOFORM V4.2. Design parameter of stamping die was chosen as the corner radius of the stamping die for each step. From the results of the FE analysis, feasible corner radii of the stamping die, which can minimize the deviation of corner angle of the stamped part from design data, and forming load for each part were estimated. Stamping experiments were carried out using the manufactured stamping die according to the proposed die design. The results of experiments were shown that the stamping die can successfully manufacture the inner reinforcement panel with DL 950 advanced high strength steel as base stamping material.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.251-258
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• 2014

Sunroof tracks are manufactured by press-forming extruded aluminum sheets. During press forming, cracking occurs along the sharply bent edge. The final positions of the punch and die were measured on the section, and their relation to cracking was investigated. Finite element simulation of bending to the final position was done to find the critical strains. Three-point bending tests with different material orientations, hardnesses, bending edge lengths, and bending radii were carried out in the laboratory, and finite element simulation of the three-point bending tests was performed to find the critical strains.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.7-12
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• 2010

In this work, optimization analysis has been accomplished to find important process factors for realization of vertical wall around holes punched by the punchless piercing process. Taguchi method was used for optimization analysis. Lemaitre damage theory, one of the ductile fracture models, was also adopted to simulate numerically formation of vertical wall. From the results of analysis the most influencing factor that affects the vertical wall has been revealed to be 'Corner Radius of Die'.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1453-1458
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• 2009

This study is to apply the mechanical press joining method to join two kinds of sheet metals with circular holes by mechanical pressing instead of laser beam. Usage of the mechanical pressing avoids the thermal deformation of sheet metals which occurs inevitably in laser joining. A die design has been proposed to make the mechanical press joining applicable with finite element analysis. Five design factors related to the joining force have been selected and applied to the Taguchi method for optimization. Among five factors, 'Forming Depth' and 'Punch Corner Radius' have been revealed to be the most influential ones.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.153-153
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• 2017

본 연구에서는 농작업지내 모서리 점을 이용하여 자율주행 트랙터의 경로점을 생성하는 알고리즘을 개발하였다. 작업지는 직사각형의 형태에서 거리가 긴 방향으로 직선주행 경로로 하고, 직선경로의 수는 작업폭에 의해 결정되며 홀수 또는 짝수 개일 수 있다. 또한 TM좌표계에서 직선주행 경로의 기울기는 양수 또는 음수 일 수 있으며, 선회시 전체적으로 좌회전 또는 우회전하는 경우로 구분하여, 즉 총 8가지의 경우에 대하여 조건이 주어지면 경로점을 구할 수 있도록 프로그램하였다. 선회를 위한 곡선경로 생성에는 트랙터의 최소 회전반경 데이터를 사용하였으며, 이때 새로 진입할 다음 경로가 충분히 떨어져 있는 경우에는 선회 구간에서도 직선 경로 구간이 생길 수 있음을 고려하였다. 한 주기의 경로점은 직선 경로 구간의 시작점과 끝점, 선회 구간의 시작점과 끝점, 다음 직선경로로 진입을 위해 선회하기 직전까지의 직선 구간에 대한 시작점과 끝점 등 6가지의 경우로 구분할 수 있다. 이때 어떤 끝점 경로점은 다음 조작 구간의 시작점 경로점이 되므로 최종적인 경로점 데이터는 4개가 된다. 여기서, 첫 번째 경로점 생성에서는 직선구간 진입을 위한 선회구간의 시작점과 끝점은 제외하였으며, 작업지로 진입할 수 있는 입구와 출구는 동일한 것으로 가정하여, 작업이 완료되는 지점에서 선회하여 다시 출발점으로 돌아올 수 있도록 추가 구성하였다. 실제 상황에서는 직선주행 경로의 수가 정수가 되지 않을 수 있으며, 이때는 작업 구간이 약간씩 오버랩되도록 작업폭을 조정하여 경로의 수가 항상 정수가 되도록 하였다. 알고리즘 평가에 사용된 작업 패턴은 관행적인 방법으로서 작업 포장을 반으로 나누어 8자형 패턴을 이용하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.2
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• pp.303-312
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• 2009

In this paper, we design and fabricate a disk sector antenna fed by CPW fur UWB communications. Also, we insert a rectangular slit on the arc-edge of the disk sector antenna. Then, the antenna has the directivity of E-면. In order to design the antenna, the input impedance is matched with the feed line of $50{\Omega}$ as varying the physical antenna parameters, which are the radius, the flare angle of disk sector, the length of ground, and the length of ground comer near by feed tine. Dimension of the antenna designed for UWB communication is $72mm{\times}26mm$ and bandwidth through computer simulation is $3{\sim}13GHz$. From the measured results, the bandwidth is $1.98{\sim}11GHz$. Return loss and gain of the fabricated antenna are -50.38dB, 1.34dBi at 3.5GHz, -12.27dB, 3.35dBi at 5.5GHz, -23.2dB, 3.8dBi at 8GHz and -16.17dB, 5.2dBi at 10GHz, respectively.