• Transactions of Materials Processing
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• v.14 no.1 s.73
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• pp.21-28
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• 2005

This paper is concerned with the quantitative effect of design parameters on a stamped part of the auto-body. The considered parameters in this paper are the blank holding force, the draw-bead force, the blank size which greatly affect the metal flow during stamping. The indicators of formability selected in this paper are failures such as tearing, wrinkling and the amount of springback. The stamping process of the front side inner member is simulated using the finite element analysis changing the design parameters. The numerical results demonstrate that the blank holding force cannot control the local metal flow during forming although it controls the overall metal flow. The modification of the initial blank size considering the punch opening line ensures the local wrinkling and reduces the amount of springback after forming. The restraining force of draw-bead controls the metal flow in the local area and reduces the amount of excess metal. It is noted that the parametric study of design parameters such as blank holding force, the blank size and the draw-bead are very important in the process design of the complicated member.

• Korea-Australia Rheology Journal
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• v.19 no.1
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• pp.27-33
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• 2007

The co-extrusion of multi-layer films has been studied with the focus on its process stability. As in the single-layer film casting process, the productivity of the industrially important multi-layer film casting and the quality of thus produced films have often been hampered by various instabilities occurring in the process including draw resonance, a supercritical Hopfbifurcation instability, frequently encountered when the draw ratio is raised beyond a certain critical value. In this study, this draw resonance instability along with the neck-in of the film width has been investigated for a three-layer film casting using a varying width non-isothermal 1-D model of the system with Phan-Thien and Tanner (PTT) constitutive equation known for its robustness in portraying extensional deformation processes. The effects of various process conditions, e.g., the aspect ratio, the thickness ratio of the individual film layers, and cooling of the process, on the stability have been examined through the nonlinear stability analysis.

• Membrane and Water Treatment
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• v.13 no.2
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• pp.63-72
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• 2022

Choline chloride-glycerol (1:2 mol), a natural deep eutectic solvent (NADES) is examined as a draw solution in forward osmosis (FO) for dewatering application. The NADES is easy to prepare, low in toxicity and environmentally benign. A polyamide thin film composite membrane was used. Characterization of the membrane confirmed porous membrane structure with good hydrophilicity and a low structural parameter (722 ㎛) suitable for FO application. A dilute solution of 20% (v/v) NADES was enough to generate moderate water flux (14.98 L m^-2h^-1) with relatively low reverse solute flux (0.125 g m^-2h^-1) with deionized water feed. Application in dewatering industrial wastewater feed showed reasonably good water flux (11.9 L m^-2h^-1) which could be maintained by controlling the external concentration polarization and fouling/scaling mitigation via simple periodic deionized water wash. In another application, clarified sugarcane juice could be successfully concentrated. Recovery of the draw solute was accomplished easily by chilling utilizing thermo responsive phase transition property of NADES. This study established that low concentration NADES can be a viable alternative as a draw solute for dewatering of wastewater and other heat sensitive applications along with a simple recovery process.

• Journal of the Korean Society of Clothing and Textiles
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• v.13 no.4
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• pp.427-436
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• 1989

Poly (vinyl alcohol) films, which .were annealed at various different annealing conditions, were carried out by uniaxial stretching them with free width in water and were investigated drawing behaviours and rupture phenomena. l) After dipping the specimen into the water, it took about 15 min. for the specimen's swelling to approach to equilibrium. 2) When the film annealed at $180^{\circ}C$ for 10 min. was drawn at $20^{\circ}C$. it was shown very toughness. 3) By means of birefringence measurements, the total molecular orientation of the annealed films increased until the draw ratio of 4, but drawing them above the draw ratio of 5, that of untreated films increased. 4) In the case of the mechanical properties of the drawn films. the annealed films tended to good trend for the draw ratios between 1 and 4. but drawing them above the draw ratio of 5. the untreated films tended to good trend for them.

• Transactions of Materials Processing
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• v.32 no.5
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• pp.276-286
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• 2023

The field of sheet metal forming using press technology has become essential in modern mass production systems. Draw bead is often used to enhance formability. However, optimal draw bead design often requires excessive time and cost due to iterative experimentation and sometimes results in some defects. Given these challenges, there is a need to enhance formability by introducing segmented blank holders without draw beads. In this paper, the feasibility of a localized holding strategy using segmented blank holders is evaluated without the use of draw beads. The possibility for improving the formability was evaluated by utilizing a combination of the forming limit diagram and the wrinkle pattern-based defect indicators. Artificial neural networks were used for predicting defect indicators corresponding to arbitrary input holding forces and the NSGA-II optimization algorithm is used to find optimum blank holder forces yielding better defect indicators than the original process with drawbeads. Using optimum holding forces obtained from the proposed procedure, the stamping process with the segmented blank holders can yield better formability than the conventional process with drawbeads.

• Journal of The Korean Association For Science Education
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• v.34 no.8
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• pp.719-730
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• 2014

The purpose of this study was to investigate elementary school students' perceptions about science, engineering and technology and their images of scientists, engineers, and technicians. In order to investigate students' images of scientists, engineers, technicians and student's perception of science, engineering, and technology, we used the tools "Draw a scientist at work, Draw an engineer at work, and Draw a technician at work". We have revised the tool DAST (Draw a scientist test), which was used in Fralick et al.'s study (2009). Subjects were 209 6th grade students sampled from an elementary school in G-city in Korea. According to the results of this study, the students' representative image of a scientist was similar to stereotypical scientist image in previous studies, but the students perceived science as a field of research with various professionals. The students' representative image of an engineer was a man with short hair, no beard or mustache, wearing ordinary clothes but no glasses. The engineer was designing or constructing a ship, a robot, a computer, and an airplane. The students' representative image of a technician was a man with short hair, wearing protective goggles and a mask for welding. The technician was fixing a car, a robot, a rocket, etc. and working with wrenches, hammers, screw drivers, welding machines, etc. Many students didn't perceive engineering and technology as fields of research. Also, many students didn't variously perceive engineering and technology as fields and ways of study.

• Proceedings of the Korean Fiber Society Conference
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• 1993.06a
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• pp.78-79
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• 1993

• Proceedings of the Korean Fiber Society Conference
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• 1994.10a
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• pp.99-99
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• 1994

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.152-155
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• 2003

In order to examine the springback of aluminum alloy sheets, AL1050 and AL5052, in the warm forming which forms the sheet above room temperature, the stretch bending and draw bending tests in various working temperatures were carried out. While the springbacks of AL5052 and AL1050 are tremendously reduced over 150$^{\circ}C$ in the stretch bending test, the springbacks in the draw bending test are rapidly reduced in 150$^{\circ}C$-200$^{\circ}C$ for AL5052 and 200$^{\circ}C$-250$^{\circ}C$ for AL1050. Using the FEM program, the forming and springback processes are analyzed. Though springback amounts of analysis result are slightly bigger than those of experiment, they showed the same trend in the decreasing springback as the forming temperature increases.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.5
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• pp.31-46
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• 1999

A drying paper strives to shrink due to the shrinkage of the individual paper fibres. Laboratory results show that a reduction of the shrinkage or an imposed stretch leads to a large increase in tensile stiffness and a large decrease in strain at break. In c cylinder drying section the water in the web is repeatedly heated on the drying cylinder and evaporated in the free draw. To evaluate the drying process regarding influence on paper properties these sub-processes, or drying phases, have to be studied separately. The effect of the conditions on the drying cylinder and on the VacRoll is investigated in pilot trails. Both the fabric tension on the drying cylinder and on the VacRoll reduces the shrinkage of the paper. The laboratory results are used as input to a numerical simulation of the conditions in the free draw. If the web width is increased or the length of the free draw is reduced the mean shrinkage of the paper web is reduced . However, the difference in shrinkage between the middle and the edge of the web is increased.