• Transactions of Materials Processing
• /
• v.20 no.8
• /
• pp.611-618
• /
• 2011

Flow forming is an incremental forming process in which rollers are used to form cylindrical parts with repeated turning of both roller and starting material. Both sheet and tube can be used as the starting material. The process is highly useful for producing hollow shaped parts from a tube, with the benefit of the average strain in the final shape being significantly lower than that from a sheet material. In the present study, the flow forming process was studied and optimized for producing a hollow shaped part from seamless steel tube by both experiment and numerical analysis. Upon considering the difficulty of forming seamless steel sheet, the thickness reduction was distributed over several tool paths. In the end, an optimum process condition was attained, and the experiment verified the simulation results.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.10
• /
• pp.701-707
• /
• 2000

This paper proposes a tension control to compensate friction loss using on-line friction torque observer for a continuous strip processing line. Friction loss of roller results in significant deviation of strip tension, accordingly it has an influence on the operation of other adjacent rolls. To avoid tension variation of the strip, a friction torque observer is designed in adjacent roll, which operates in speed control mode. The observed torque is added to the torque limit reference of the pay-off reel for on-line compensation of both friction loss and acceleration/deceleration torque at the same time. The simulation and experimental results show improvement of tension control performance by the proposed friction compensation method.

• Proceedings of the KIEE Conference
• /
• 2000.07b
• /
• pp.1096-1098
• /
• 2000

This paper proposes a tension control to compensate friction loss using on-line friction torque observer for a continuous strip processing line. Friction loss of roller results in significant deviation of strip tension. accordingly it has an influence on the operation of other adjacent rolls. To avoid tension variation of the strip, a friction torque observer is designed in adjacent roll, which operates in speed control mode. The experimental results show improvement of tension control performance by the proposed friction compensation method.

• Journal of the Microelectronics and Packaging Society
• /
• v.27 no.2
• /
• pp.19-26
• /
• 2020

Flexible displays have been evolved into curved, foldable, and rollable as the degree of bending increases. Due to the presence of brittle electrodes (e.g. indium-tin oxide (ITO)) that easily cracked and delaminated under severe bending deformation, lowering mechanical stress of the electrodes has been critical issue. Because of this, mechanical stress of brittle electrode in flexible displays has been analyzed mostly in terms of bending radius. On the other hand, in order to make rollable display, various mechanical components such as roller and spring are needed to roll-up or extend the screen for the rollable display apparatus. By these mechanical components, brittle electrode in the rollable display is subjected to the excessive tensile stress due to the retracting force as well as the bending stress by the roller. In this study, mechanical deformation of rollable OLED display was modeled considering boundary conditions of the apparatus. An analytical modeling based on the classical beam theory was introduced in order to investigate the mechanical behavior of the rollable display. In addition, finite element analysis (FEA) was used to analyze the effect of mechanical components in the apparatus on the brittle electrode. Furthermore, a strategy for improving the mechanical reliability of the rollable display was suggested through controlling the stiffness of adhesives in the display panel.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.10
• /
• pp.1255-1260
• /
• 2012

The densification behavior of titanium powder in the direct powder rolling process was investigated. An analytical model for the roll-backlash phenomenon during this process was proposed to conduct a realistic finite element analysis. Furthermore, the roll-backlash was quantitatively analyzed, and the relative densities of the greenstrip along the rolling direction were precisely estimated. Finally, the slip and nip phenomena were identified by calculating the contact pressure and shear stress between the titanium powder and the roller in order to understand the densification behavior of the powder during the rolling process.

• Asian Journal of Turfgrass Science
• /
• v.18 no.1
• /
• pp.37-46
• /
• 2004

The purpose of this study is to find the suitable putting green maintenance equipment for improving the quality of putting green. This study was carried out to investigate the green speed(i.e., ball roll distance) by different the types of greens mower(between work-behind greens mower and riding greens mower), the types of reel blades(between 9 blades and II blades) and the types of roller(between riding soil sprayer and lightweight roller). Green speed of golf course putting greens is assessed by use of Stimpmeter. The west course of Lakeside Country Club was selected for the case study. The results are summarized as follows; 1. The green speed was faster in 3.8 mm moving height treatment plot using work-behind greens mower than in 3.8 mm moving height treatment plot using riding greens mower right after the moving and even after eight hours had passed, and it was statistically significant at a 95% confidence level. Therefore, work-behind greens mower was judged to be a proper equipment type for the fast green management practice than riding greens mower. 2. The green speed was faster in 3.2 mm mowing height treatment plot using work-behind greens mower equipped with II blades than in 3.2 mm mowing height treatment plot using work-behind greens mower equipped with 9 blades, and this result was statistically significant at a 95% confidence level. Therefore, II-blade was judged to be a proper blade type for the fast green management practice than 9-blade. 3. The difference in green speed (green speed increased after rolling) between a treatment plot mowed at 3.0 mm mowing height with the work-behind greens mower and then rolled a single time with riding soil sprayer and a treatment plot mowed at 3.0 mm mowing height with the work-behind greens mower and then rolled once with lightweight roller was not statistically significant at a 95% confidence level. However, the difference in green speed (green speed decreased after rolling) between two treatment plots measured after eight hours had passed was statistically significant at a 95% confidence level. Therefore, the lightweight roller was judged to be a proper roller type for the fast green management practice than the riding soil sprayer.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.7 no.2
• /
• pp.186-193
• /
• 2002

A new integrated torque and speed control algorithm has been proposed for the load balancing of rollers in continuous strip processing line(CSPL). Using the proposed method, the output torque and speed can be controlled to follow the reference in spite of nonideal effects such as the speed reference error and/or the controller gain difference between rolls. This new algorithm can be easily implemented in a motor drive system of each roll as it does not require the torque feedback of the others. Through the simulation and experiments for a simple CSPL consists of four driven rolls, the load balancing performance of the proposed scheme is presented and compared with that of conventional method.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.3 no.2
• /
• pp.92-99
• /
• 1991

A moored body in the sea is subjected to second-order wave forces as well as to linear oscillatory ones. The second-order farces contain slowly-varying components, of which the characteristic frequency can be as low as the natural frequency of horizontal motions of the moored body. As a consequence, the slowly-varying force can excite unexpectedly large horizontal excursion of the body, which may cause a serious damage on the mooring system. In design analysis of Turret-type mooring system which is one of the interesting mooring systems for a floating body. the slowly-varying drift forces and the transient motion of the system during weathervaning are very important. In this paper the slowly-varying drift forces were calculated by using the Quadratic Transfer Function with considering the second order free-wave contributions. Additionaly the transient surge motion of the moored body was simulated with including the roll of the time-memory effect. In this simulation the spring constant of the spread Turret mooring system is updated at every time step for considering the nonlinear effect.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.5
• /
• pp.29-34
• /
• 2017

In this paper, we report a method of improving the productivity of lead wire fabricated through the rolling process by increasing its linear velocity. The most important point to consider when raising the linear velocity is that the original specifications must still be adhered to. In other words, the dimensional tolerance must be satisfied when increasing the linear velocity of the wire without causing cracks. However, if the linear velocity of the wire is increased, the degree of reduction must also be increased, which causes more damage to the wire and increases the load on its surface. Therefore, we studied a three step rolling process which can satisfy the specifications of the wire produced through the two step rolling process and improve the productivity. In this study, only the roll gap of the three-stage rolling roller is assumed to be a variable, while the other conditions are the same as the field conditions. In addition, through the PIANO (Process Integration, Design and Optimization) tool, the (optimum?) surface roughness and maximum stress are maintained.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.1476-1479
• /
• 1996

The ring rolling process is one of the best known ring production method. The present model based control system was designed for rings with rectangle cross-section yet. An Adaptive Fuzzy Control for Closed-Die Ring-Rolling was developed in order to enhance the flexibility of the radial-axial ring rolling machine and to produce the rings with highly complex cross-section profile, roller bearing rings. A fuzzy method was implemented because of its simple application and to utilize the known process knowledge. The quality of the control system was estimated by die filling grad, which is strong dependent on the rising time of the controller. The rolling process parameters were also varied to determine their influence on filling of the ring profile. Die filling met the requirement of the industry.