• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.3
• /
• pp.329-334
• /
• 2011

The characteristic of sheet metal process is the few loss of material during process, the short processing time and the excellent price and strength. The static implicit finite element method is applied effectively to analyze stamping processes from using AutoForm software. The simulation analysis can be applied to the membrane elements and shell elements. Membrane elements can be applied to good efficiency, but lower than the accuracy of shell elements. Therefore, simple drawing process applies membrane element, and spring-back and analysis of stamping process are judged that it is most efficient that apply shell clement. This study, the simulated results for stamping processes are shown and discussed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.676-677
• /
• 2006

Synthesis of zinc oxide nanorods, sheets and flower like structure were done by the sol-gel method using zinc acetate dihydrate and sodium hydroxide at $80^{\circ}C$ with 12 hours refluxing time nanorods, in case of as synthesized powder, with diameter of 20-60nm. Annealing at higher temperature (300 and $500^{\circ}C$,) in air ambient changes the morphology to sheet and flower like structure. The standard peak of zinc oxide was observed in IR at $523cm^{-1}$. The UV-VIS spectroscopy of zinc oxide shows a characteristic peak at 375nm.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.34 no.5
• /
• pp.49-55
• /
• 2002

A new method is proposed for the on-line measurement of the fiber orientation of sheet materials. The measurement of fiber orientation is very important in manufacturing paper sheets, non-woven fabrics, and glass sheets, because fiber orientation strongly affects product properties represented by, for example, dimensional stability of paper. A method developed in this research utilizes anisotropy of dielectric constants of sheet materials as a key characteristic to determine the fiber orientation. The new on-line sensor, consisting of 5 microwave dielectric resonators set in different directions, was designed to detect the fiber orientation while paper is running with high speed on a paper machine. This sensor can determine the direction and the degree of fiber orientation from the measured direction of the maximal dielectric constant and its variation, respectively. The fundamental performance of this system was examined by the static measurement of printing grade paper, which gave a satisfactory result. Then, the dynamic measurements were done at a speed of 1,000 m/min by using a high-speed test-coating machine.

• Journal of Computational Design and Engineering
• /
• v.1 no.3
• /
• pp.187-193
• /
• 2014

One of the hottest challenges in automotive industry is related to weight reduction in sheet metal forming processes, in order to produce a high quality metal part with minimal material cost. Stamping is the most widely used sheet metal forming process; but its implementation comes with several fabrication flaws such as springback and failure. A global and simple approach to circumvent these unwanted process drawbacks consists in optimizing the initial blank shape with innovative methods. The aim of this paper is to introduce an efficient methodology to deal with complex, computationally expensive multicriteria optimization problems. Our approach is based on the combination of methods to capture the Pareto Front, approximate criteria (to save computational costs) and global optimizers. To illustrate the efficiency, we consider the stamping of an industrial workpiece as test-case. Our approach is applied to the springback and failure criteria. To optimize these two criteria, a global optimization algorithm was chosen. It is the Simulated Annealing algorithm hybridized with the Simultaneous Perturbation Stochastic Approximation in order to gain in time and in precision. The multicriteria problems amounts to the capture of the Pareto Front associated to the two criteria. Normal Boundary Intersection and Normalized Normal Constraint Method are considered for generating a set of Pareto-optimal solutions with the characteristic of uniform distribution of front points. The computational results are compared to those obtained with the well-known Non-dominated Sorting Genetic Algorithm II. The results show that our proposed approach is efficient to deal with the multicriteria shape optimization of highly non-linear mechanical systems.

• Journal of the Korean Magnetics Society
• /
• v.14 no.5
• /
• pp.174-179
• /
• 2004

Attenuation of conduction noise through microstrip line attached with the high lossy iron flakes-rubber composites has been investigated in GHz frequencies. Microstrip line was designed with characteristic impedance of 50 $\Omega$ and a length corresponding to the center frequency of 3 GHz. Iron flakes were fabricated by mechanical forging of spherical iron powders using an attrition mill. The fabricated microstrip line shows a ideal propagation characteristics of S$\sub$11/ < -60 dB and S$\sub$21/ = 0 dB. Attaching a noise absorbing sheet on the microstrip line, S$\sub$11/ increases to about -10 dB and S$\sub$21/ decreases to -20～-60 dB depending on the length of absorbing sheet. The calculated power loss is as high as 80% in the frequency range 2～8 GHz. It is suggested that the most critical material parameter is magnetic loss for the enhancement of noise attenuation.

• Laser Solutions
• /
• v.9 no.2
• /
• pp.1-9
• /
• 2006

In this paper, we investigated the characteristics of fatigue fracture on TB(Tailored Blank) weldment by comparing the fatigue crack propagation characteristics of base metal with those of TB welded sheet used for vehicle body panels. We also investigated the influence of center crack on the fatigue characteristic of laser weld sheet of same thickness. We conducted an experiment on fatigue crack propagation on the base metal specimen of 1.2mm thickness of cold-rolled metal sheet(SPCSD) and 2.0mm thickness of hot-rolled metal sheet(SAPH440) and 1.2+2.0mm TB specimen. We also made an experiment on fatigue crack propagation on 2.0+2.0mm and 1.2+1.2mm thickness TB specimen which had center crack. The characteristics of fatigue crack growth on the base metal were different from those on 1.2+2.0mm thickness TB specimen. The fatigue crack growth rate of the TB welded specimens is slower in low stress intensity factor range $({\Delta}K)$ region and faster in high${\Delta}K$ region than that of the base metal specimens. The slant crack angle slightly influenced the crack propagation of the TB specimen of 2.0+2.0mm thinkness.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.869-887
• /
• 2008

Coffer dam for tunnel type spillway in inflow section of Dae-am dam was originally planned as 2 lines sheet piles with Water Zet method. But, the result of pilot test was caused of some problems that vibration during installation of pile could pollute water and water leakage could the lower part. So, sheet piles was not satisfactory for faculty of coffer dam. Structural instability of sheet pile system need to reinforcement. Characteristic of Dae-am dam was small reservoir capacity but wide drainage area, of which it was judgment that security of leakage and stability was difficult during excavation of inlet part. So, we consider that water curtain method utilized with in site pouring concrete pile method was designed at weir part of spillway. We were known about basement rock that geological boring was carried out in weir part. After taking a deep consideration, PRD method was accepted as a new method. Concrete pile by PRD was installed to below country rock. CJM method was carried out with PRD. After making concrete wall using Top-down method, earth anchors were installed for supporting it. According to the result of numerical analysis, as water level rises, wall is stable.

• Korean Chemical Engineering Research
• /
• v.50 no.3
• /
• pp.588-593
• /
• 2012

Compatibility of unsaturated polyester (UP) and low profile agent (LPA) of polystyrene (PS) have been investigated under various mixing conditions such as the ratio of UP and LPA, mixing time, mixing temperature, and input amount of 2nd UP. It was possible to obtain mixture with small particle size and low phase separation in condition of 35 g of LPA, 25 g of 1st UP input, 5 min of mixing time, 1700 rpm of mixing speed, and 45 g of 2nd UP input. It was found that compatibility of UP and LPA was very sensitive to mixing conditions. In addition, molded sample using sheet molding compound prepared by stable mixing condition appeared good properties such as low water adsorption, low shrinkage, and high gloss.

• 한국전산유체공학회:학술대회논문집
• /
• 2001.10a
• /
• pp.1-9
• /
• 2001

In this paper, some numerical methods recently developed for gas-liquid two-phase flows are reviewed. And then, a preconditioning method to solve cavitating flow by the author is introduced. This method employs a finite-difference Runge-Kutta method combined with MUSCL TVD scheme, and a homogeneous equilibrium cavitation model. So that it permits to treat simply the whole gas-liquid two-phase flow field including wave propagation, large density changes and incompressible flow characteristic at low Mach number. Finally, numerical results such as detailed observations of the unsteady cavity flows, a sheet cavitation break-off phenomena and some data related to performance characteristics of hydrofoils are shown.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.5B no.1
• /
• pp.1-5
• /
• 2005

The vector magnetic property is defined as the relationship between the magnetic field strength vector H and the magnetic flux density vector B. It is very important for the development of high efficiency and the high-density electric machines. The electrical steel sheet for the machine core shows the remarkable vector behavior by the high magnetic flux density level. In this paper, the magnetic characteristic analysis using E&S2 model is introduced as the useful technology for the design and development.