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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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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
전자기 성형에서의 테이퍼진 지속집중기의 자기압력에 관한 연구
Choe, Jae-Chan ; Jo, Yong-Cheol ; Lee, Jong-Su ; Hwang, Un-Seok ; Kim, Nam-Hwan ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 14~27
Electromagnetic Pulse Forming is the one of the high velocity forming method. When the electric energy which is charged in the capacitor bank is suddenly discharged into the electromagnetic coil, the high magnetic field occurs at the airgap between the electromagnetic coil and workpiece. Thus we can obtain the high electromagnetic pressure, which is proportional to the square of magnetic flux density. This is the basic principle of the electromagnetic pulse forming. In this paper, the equivalent L-R-C circuit is derived by computing the magnetic field and its loss of the total system. Thus, the values of the magnetic flux density and pressure can be obtained from the equation of this circuit. As a result, the computed and measured values of the maximum magnetic flux density and pressure are compared and the characteristics of the tapered field shaper are further discussed as follows; 1) The strength of magnetic flux density and pressure can be controlled by the charged energy and the size of the airgap between the inner field shaper and the workpiece. 2) During the design of the tapered field shaper, the penetration of the magnetic flux through the sharp edge should be considered.
Theoretical and Experimental Study of the Axisymmetric Fluid Pressure-Driven Hydroforming Process
Yang, Dong-Yol ; Choi, Sun-Jun ; Chung, Wan-Jin ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 28~38
The study is concerned with the theoretical and experimental investigation of axisymmetric fluid pressure-driven hydroforming of sheet metal by forming over the die cavity. The rigid-plastic finite element method is employed to calculate the stress and strain distribution. The effect of blank size and die radius is also studied in the finite element analysis. Experiments are carried out for hydroforming of cold-rolled steel sheets under various process conditions. The computational results are compared with the experimental results for the forming pressure vs. pole displacement relations and strain distributions. Comparison has shown that theoretical predictions by the finite element method are in good agreement with the experiment with the experimental observations. Thus, it is shown that the rigid-plastic finite element method is effectively used in the analysis of axisymmetric fluid pressure-driven hydroforming process.
The Behavior of Fatigue Crack Propagation between Holes in Panel
Cho, Jae-Ung ; Lee, Ok-Seop ; Kim, Sang-Cheol ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 39~46
In this study, the mechanical behavious of a center crack which propagates between two holes in a panel are investigated. It is confirmed experimentally and analytically that a center crack stops and a small crack initiates from holes and propagates to fracture because of the compressive stress arising along the path of the fatigue crack propagation. Futhermore, it is noted that regardless of the configuration of the crack and the structure, Paris' law can be applied to the fatigue crack propagation.
A Study on In-Porcess Sensor for Recognizing Cutting Conditions
Chung, Eui-Sik ; Kim, Yeong-Dae ; NamGung, Suk ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 47~57
In-process recognition of the cutting states is one of the very important technologies to increase the reliability of mordern machining process. In this study, practical methods which use the dynamic component of the cutting force are proposed to recognize cutting states (i.e. chip formation, tool wear, surface roughness) in turning process. The signal processing method developed in this study is efficient to measure the maximum amplitude of the dynamic component of cutting force which is closely related to the chip breaking (cut-off frequency : 80-500 Hz) and the approximately natural frequency of cutting tool (5, 000-8, 000 Hz). It can be clarified that the monitoring of the maximum apmlitude in the dynamic component of the cutting force enables the state of chip formation which chips can be easily hancled and the inferiority state of the machined surface to be recognized. The microcomputer in-process tool wear monitor- ing system introduced in this paper can detect the determination of the time to change cutting tool.
Calculation of rated output in diaphragm type miniature load cell
Kwon, Young-Ha ; Kang, Dae-Im ; Joo, Jin-Won ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 58~64
As the miniature load cells have small inner space and sensing elements of which are thin and very sensitive to manufacturing conditions, it is very difficult to predict the rated outputs and control them by using the compensation resistor. The very useful equation has been derived for calculation of theoretical rated outputs for diaphragm type miniature load cells when commercial diaphragm strain gages are used. Four diaphragm type miniature load cells of which capacities are from 300 N to 1, 000 N and outer diameters are 20 mm and 26.5 mm are manufactured. The differences between calculating results and actural ones are less than 5%. According to numerical analysis the decrease of rated outputs caused to main error is examined in existence of loading button.
A Study of Strain measurement by continuous wave Laser speckle photography
Kim, Gyeong-Seok ; Kim, Chung-Won ; Lee, Seung-Geon ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 65~73
Speckle photography is a simple non-contacting method for analysing surface displacement. In its basic form, the object to be studied is illuminated with a beam of laser light from any convenient direction, and a double exposure photography of the surface recorded on the fine-grain film, the object is undergone the displacement to be measured between exposures. Like this, it allows the strain field to be evaluated in two dimensions. A direct experimental comparison of speckle photography with theoretical value on a notched tensile test specimen showed that serious errors could, however, occur due to local surface tilting and due to aberra- tions of the imaging lens. Methods of minimising these effects and those of the speckle de-correlation which occurs by the various conditions are discussed.
Characteristics of Epoxy-Granite Composite Material For Ultra-Precision Machine Bed Structures
Kim, Jong-Ho ; Won, Si-Tae ; Maeng, Huee-Young ; Park, Yeong-Il ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 74~84
The machine tool structures for ultra-precision machining muxt be manufactured with materials which have high static and dynamic stiffness, high damping, a long term dimensional and thermal stability. This study aims at the development of new composite material Epoxy-Granite which exhibits the satisfactory characteristics as a material of ultra-precision mchine tool bed. The Epoxy-Granite testpieces that use epoxy resins as a binder and granite particles as a aggregate have been manufactured so as to examine the material properties about mechanical, thermal and damping characteristics. Experiments were carried out to obtain the proper manufacturing conditions of Expoxy-Granite specimens by varying the several testing conditions such as types of epoxy resins, particle sizes of granite and mixture ratio of epoxy resin and aggregate. Also, when Epoxy-Granite was compared with cast iron, GRANITAN which was imported from CMS of U.K. and granite materials, it has exhibited the superior or almost the same mechanical and damping properties and thermal conductivity, except for the thermal expansion.
A Study on the Signal Process of Cutting Forces in Turning and its Application (2nd Report) -Automatic Monitor of Chip Rorms using Cutting Forces-
Kim, Do-Yeong ; Yun, Eul-Jae ; Nam, Gung-Seok ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 85~94
In automatic metal cuttings, the chip control is one of the serious problems. So the automatic detection of chip forms is essential to the chip control in automatic metal cuttings. Cutting experiments were carried out under the variety of cutting conditions (cutting speed, feed, depth of cut and tool geometry) and with workpiece made of steel (S45C), and cutting forces were measured in-processing by using a piezoelectric type Tool Dynamometer. In this report, the frequency analysis of dynamic components, the upper frequency distributions, the ratio of RMS values, the numbers of null point and the probability density were calculated from the dynamic componeents of cutting forces filtered through various band pass filters. Experimental results showed that computer chip form monitoring system based on the cutting forces was designed and simulated and that 6 type of chip forms could be detected while in-process machining.
A Study on the Computer aided Design of Multi-Stage Cold Forging Die for Rotationally Symmetric Parts.
Choi, Jae-Chan ; Kim, Seong-Weon ; Cho, Hea-Yong ; Kim, Hyung-Sub ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 95~104
This paper descirbes some research of Computer-aided Design of multi-stage cold forging die of rotationally symmetric parts produced by the press or former. An approach to the system is based on knowledge based system. Knowledges for tool design are extracted from the plasticity theory, handbooks, relevent references and empirical know-how of experts in cold forging companies. The deveoped system is composed of three main modules such as die design module, punch design module, tool elements design module which are sued independently or in all. Using this system, design parameters (types of dies, geometric shapes and dimensions of dies, types of punches, geometric shapes and dimensions of punches, geometric shapes and dimensions of tool elements) in each operation are determined and the output is generated in graphic form. The develpoed system, aids designer, provides powerful capability for designing dies, punches and tool elements.
Grinding Characteristic of Advanced Ceramics
Jung, Yoon-Gyo ; Kang, Jae-Hoon ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 105~112
Advanced ceramics have some excellent properities as the material for the mechanical component. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. In this paper, some experiments are carried out to find the basic grinding characteristic of advanced ceramics. Representative advanced ceramics, such as AL/sub 2/ O/sub 3/, ZrO/sub 2/, SiC and Si/sub 3/N/sub 4/and ground with diamond wheels. Special attention is paid to comparison between the conventional and creep feed grinding. Results obtained in this study provide some useful informations to attain the high efficiency grinding of advanced ceramics.
An Experimental Study on the Effect of Contaminated Lubricants on Wear Characteristics
Kim, Hae-Won ; Hong, Jae-Hak ;
Journal of the Korean Society for Precision Engineering, volume 7, issue 2, 1990, Pages 113~123
To study deleterious effects of contaminants contained in lubricating systems, the effects of fine alumina particle concentration and size on the critical failure load, friction and wear characteristic were examined on boundary lubrication condition using the four ball machine. The following conclusions are deduced: The abrasive is found to cause a transition from mild wear to severe wear at less severe conditions than with clean oil. In mild wear region the friction and wear increase with particle size and concentration, but in severe wear region do not exhibit any definite trend. In relation to film thinckness there is a threshold of particle size beyond which the failure load no longer decreases with particle size.