• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.465-468
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• 2000

The procedure of semi-solid forming is composed of heating a billet, forming, compression holding and ejecting step. There are several methods to heat a billet during semi-solid forming process such as electric heating and induction heating. Usually in semi-solid forming process, induction heating has been adopted to achieve more uniform temperature of semi-solid material. Although induction heating is better method than any others, however, there is still difference of temperature between internal part and surface part of semi-solid material. Worse yet, in case of high liquid fraction of semi-solid material, liquid of the billet will flow down though solid of the billet still remains, which is very difficult to handle. In the present study, induction heating of semi-solid material with compulsive surface cooling has been performed to obtain uniform distribution of temperature. Distribution of temperature of the billets was measured and compared with that of conventional distribution of temperature. By this new induction heating method, not only temperature over the whole billet become uniform, but also control of temperature is possible.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.658-661
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• 2003

The transmission loss coefficient is very important acoustic property in parallel with absorption and acoustic impedance categorizing the acoustical materials, which can control the acoustical problems. At the same time, the transmission loss coefficient is a key parameter to choose the optimum material for the analysis of acoustical characteristics of material using SEA(Statistical Energy Analysis). In this paper, the transmission loss coefficient measurement system using 4-microphone impedance tube is proposed, based on the idea calculating the full transfer matrix of the acoustical sample to test. The theoretical background and measurement system are introduced, and finally the measurement results are verified.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.25 no.1
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• pp.78-84
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• 2002

This paper is a study for the computerization program of incoming and outgoing processes of a number of parts and a great amount of material for producing products in flood industry, which was required by a medium-sized company located at Cheon-An. The program consists of four databases, one main form, seventeen subforms, and eight report forms. Concretely speaking, the four databases are prepared for products, semi-products, material, and reports, and the seventeen subforms are those for current inventory, used quantity, safty stock, product specification, etc. With the program, users can be helped and save manpower, time and cost in incoming and outgoing processes of parts and material for producing products and in their real time operation and decision-making.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.75-78
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• 2002

SFFS(Solid Freeform Fabrication System) is commercializing to rapid prototyping concept in world-wide some corporations including the States, have much technological problems yet and need new mode for agile solid freeform fabrication as well as prototyping. In this paper, we design an automatic control algorithm that the cutting path of laser beam, on the SFFS, is controlled with constant speed. The designed algorithm for constant-speed path control is implemented and experimented in the $CAFL^{VM}$ (Computer Aided Fabrication of Lamination for Various Material) system, the new SFFS which is developed in this paper. Its process is an automated fabrication method in which a 3D object is constructed from STL(SToreoLithography) 2D data, derived from CAD 3D image, by sequentially laminating the part cross-sections. The constant-speed path control is started from the STL data. After STL file is modified in data format to be available for control. The fabrication of the 2D part is, with constant speed, conducted from the 23 position data by laser beam. we confirm its high-performance through experiment results from the application into $CAFL^{VM}$ system.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.171-176
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• 2005

This paper presents a novel Intelligent-Welding-Carriage (IWC) for automation of curved block in shipbuilding. The curved block is usually used in both front and back side of the ship. In curved block root gap is big, 1-7 (mm) and inclination, 0-30 (deg). Since available conventional carriage type is limited to use below root gap of 3 (mm), only manual welding is employed in curved block. To adopt an IWC in curved block, it requires control of the welding conditions, i.e., voltage. current, weaving speed, dwell time and travel speed, with respect to root gap and inclination to achieve good welding qualify. In this paper, an IWC is developed for automization of welding operation to accommodate gap and inclination. Kinematics model and dynamics using Lagrangian formulation of the manipulator is introduced. IWC utilizes a database to perform accurate welding. The database is programmed based on numerous experimental test results with respect to gap, inclination, material, travel speed, weaving condition, voltage, and current. Finally, experimental result using PID control is addressed for verifying the trajectory tracking accuracy of end-effector.

• The Journal of Korea Robotics Society
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• v.12 no.3
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• pp.263-269
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• 2017

Recently, soft robots using soft materials are presented. Thanks to soft materials, soft robots have flexible, highly-stretchable or adaptable features. However, due to the flexibility of soft material, it is hard for soft robots to control accurately or perform high force. To deal with these limitations, variable stiffness technology, which enables the stiffness control of structure, has been developed. In this research, a dual-stiffness structure that is actuated by the assembly of two flexible structures are presented. Each flexible structure consists of flexible film part and rigid parts placed at regular intervals. The flexibility of film between rigid parts allows each structure to move softly. On the other hand, by combining two structures rigid part of each part constrain the degrees of freedom of the other side part. And this causes the stiffness of whole structure to be increased. This paper will cover concepts, design, analysis and experiments of this structure.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.230-236
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• 2007

The quality control of composite structure includes inspection, testing and monitoring in all processes from receiving inspection to part fabrication. The purpose of these activities is to ensure that the design objectives are consistently achieved. The quality factors include material, receiving inspection, storage and shelf-life control, environmental control, testing, inspection and record control. This paper presents the process verification method using destructive test and quality control method in composite structure of aircraft. And it is believed that the destructive test will be basis to obtain a reliability of non-destructive test in complex composite structure and to ensure the design requirements in composite part.

• Journal of the Korea Furniture Society
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• v.17 no.4
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• pp.15-26
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• 2006

This article is composed of three parts in this article. The first part reviews, in the general, condition on Chinese forest resource history and analyzes the change in different historical times. The present condition and existing problems are discussed in the second part, where analyzes the existing problems in different distribution areas. In the third part, the solutions are raised to solve the problems mentioned in the second part. Finally the objective and strategy for sustainable development of Chinese forest resources are put forward.

• Journal of Drive and Control
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• v.11 no.3
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• pp.47-54
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• 2014

Clutches are an integral part of the automatic transmission for changing gears. Modern automatic transmissions make extensive use of wet multiple-disc clutches employing hydraulic actuation mechanism with electronic control. Although nowadays, highly advanced shifting algorithm implements the superior shift quality and transmission efficiency, its performance should be based on smooth, reliable engagement with a reasonably durable friction material as well as stable clutch piston dynamics. Particularly, clutch filling control is the crucial part of shifting process because only the open-loop control is available due to the lack of measurement. In this paper, the effect of clutch-fill control parameters on clutch piston dynamics is experimentally investigated by using clutch piston test equipment which enables the clutch piston to actuate similar to real shifting conditions. The experimental analysis results can be expected to be utilized for the calibration of proportional solenoid valve as reference current profile data in vehicle test.

• Tribology and Lubricants
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• v.31 no.4
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• pp.170-176
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• 2015

As a continuation of Part I, which developed a design formula of the minimum corner radius (R_min) for restraining tribological failures, Part II investigates design parameters such as material properties and contact force. As design examples, Al 7075-T651, SST 304 and HT-9 are chosen for the materials and 1, 10 and 100 kN are used for the forces. The results show that the difference in R_min decreases as either the elastic modulus increases or the contact force decreases. Given the same material and force, the permissible R_min decreases as the flat region increases and vice versa. Because the R_min values obtained from the examples are very small, the dimensions of the corner radius normally designed in engineering structures are regarded acceptable. The von Mises stress evaluated for a typical example, which is far below the yield strength, confirms this interpretation. Nevertheless, the present work can provide a design criterion as well as a guideline for quality control in the manufacturing of, in particular, contact corners, which has not been attempted before to the best of the author’s knowledge. In addition, this paper considers the problem of a step that may be formed in the contact contour by using a similar approach. The result shows that no size of the step is permissible.