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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korean Society for Precision Engineering
Journal Basic Information
Journal DOI :
Korean Society of Precision Engineering
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Volume & Issues
Volume 7, Issue 4 - Dec 1990
Volume 7, Issue 3 - Sep 1990
Volume 7, Issue 2 - Jun 1990
Volume 7, Issue 1 - Mar 1990
Selecting the target year
A numerical study on the flow characteristics in cylinder
Kim, Chong-Eok ; Kim, Yang-Sul ; Park, Sang-Kyoo ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 1, 1990, Pages 28~36
In this paper, the flow field with steady, axisymmetric flow characteristics in cylinder has been numerically investigated. The prediction of flow in cylinder was compared to experimental result. The turbulence closure being applied was K-
model and numerical scheme was Hybrid and Power-law scheme. The results of numerical computation showed some deviation from exper- imental data in the in cial region of cylinder, where streamline curvature is significant. However, the computational results agree qualitatively well with Mores's experimental results and the difference between Hybrid and Power-law schows similar results
The Study on Automation and Development of Strip Continuous Casting by Twin Roller Type
Lee, Sang-Mae ; Kim, Young-Do ; Baek, Nam-Ju ; Gang, Chung-Gil ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 1, 1990, Pages 37~52
In this study, the characteristics of cooling and rolling during strip casting process is obtained in comparison with the experimental and analytical results. The prupose of this study is to effectively analyze the thermal and mechanical deformation of roller applying the results of the heat transfer and the pressure distribution to boundary conditions. And then the relation between strip thickness and roll deformation is shown. The second purpose is to obtain the proper condition of the continuous casting for stainless steel. The summary and conclusions can be made on the basis of the results obtained by the theories and experiments. a) The strip casting condition for the fine surface quality of tin-alloy as-cast material was obtained in accordance with the velocity of roll rotation and initial roll gap. b) The experimental condition that the dimension of the cast strip thickness coincide with that of the initial roll gap was according to the experimental result of continuous casting by twin-roll type. c) The thermoelastic finite element model to calculate the roll deformation is represented. Thermoelastic model prediction for the roll deformation are in good agreement with the experimental results considering the thermal expansion of the roll. d) The higher cooling rates were obtained by a twin-roller quenching technique. Also quenched microstructure of the rapidly solidified shell was verified. e) The magnitude of roll deformation due to the thermal expansion and roll separating force is quantit- atively represented in the analysis of continuous casting for stainless steel.
Improvement of the Lathe Tool-post for the Suppression of Chatter.
Jeong, Jun-Gi ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 1, 1990, Pages 53~62
High speed and heavy cutting performed for improving the surface quality and productivity, are often prevented due to chatter phenomena. Chatter is a violent relative vibration between workpiece and tool in machining of metals, and is an important limiting factor of production rate and surface quality, and reduces the tool life and the dynamic performance of machine tool itself. In this study, in order to suppress the chatter, a modified tool-post combined with the spring and damper was designed and used in the actual cutting test. The results of this study are summerized as follows; The spring and damper adopted in the modified tool-post have the suppressing effects of chatter, and there exists an optimum combination between spring constant and damping ratio.
Development of Automatic Welding Machine and Weld-Quality Improvement for Automobile Parts
Kim, Kyo-Hyoung ; Lee, Ki-Sul ; Lee, Taik-Soon ; Joo, Hae-Ho ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 1, 1990, Pages 63~73
Low cost automatic welding machine is developed for the purpose of welding process automation of automobile parts with two dimensional welding joints. Developed gantry type machine is equipped with X, Y and roll axis stepping motors, and dirive units units are designed by two phase on drive scheme using shift registers. Control system is constructed by single board microcomputer of Z80A CPU, and also it is equipped with parallel input output ports and counter-timer chips. Linear and circular interpolation of welding head movement is accomplished by employing software digital differential analyzers. It has been shown that contour error of develped system is withi
, meaning that the machine is suitable for CO2 arc welding process of automoble parts and is expected it's application to industry.
Control of a Helicopter in Hover Using the LQG and LQG/LTR Methods
Kim, Jong-Shik ; Ma, Sam-Sun ; Song, Myong-Hun ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 1, 1990, Pages 74~85
The LQG and LQG/LTR compensators have the same structrues in dynamics. The only difference is the values of the design parameters in the two compensators. The design parameters of the LQG and LQG/LTR compensators are selected in the sense of the least-squares error minimi- zation and loop shaping, respectively. In this paper, the LQG and LQG/ LTR design methods are applied to the helicopter in hover which is modeled as a SISO fourth order system. The dynamic characteristics and the perfor- mance of the two control systems are analyzed by the computer simulation. It is found that the LQG/LTR design method is systematic and has good performance in comparision with the LQG design method.