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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Precision Engineering
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Journal DOI :
Korean Society of Precision Engineering
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Volume & Issues
Volume 27, Issue 12 - Dec 2010
Volume 27, Issue 11 - Nov 2010
Volume 27, Issue 10 - Oct 2010
Volume 27, Issue 9 - Sep 2010
Volume 27, Issue 8 - Aug 2010
Volume 27, Issue 7 - Jul 2010
Volume 27, Issue 6 - Jun 2010
Volume 27, Issue 5 - May 2010
Volume 27, Issue 4 - Apr 2010
Volume 27, Issue 3 - Mar 2010
Volume 27, Issue 2 - Feb 2010
Volume 27, Issue 1 - Jan 2010
Selecting the target year
Experimental Study on Characteristics of Dry Wire Electrical Discharge Machining (EDM) Process
Lee, Sang-Won ; Kim, Hong-Seok ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 11~17
This study investigates the non-traditional manufacturing process of dry wire electrical discharge machining (EDM) in which liquid dielectric is replaced by a gaseous medium. Wire EDM experiments of thin workpieces were conducted both in wet and dry EDM conditions to examine the effects of spark cycle (T), spark on-time (
), thickness of work pieces, and work material on machining performance. The material removal rate (MRR) in the dry wire EDM case was much lower than that in the wet wire EDM case. In addition, the thickness of workpiece and work-material were found to be critical factors influencing the MRR for dry EDM process. The relative ratios of spark, arc and short circuit were also calculated and compared to examine the effectiveness of processes of dry and wet wire EDM.
Study on the Superprecision Glass Molding of Aspherical Lens for Optical Communication Module
Jang, Kyung-Su ; Lee, Tae-Ho ; Rho, Tae-Yung ; Kim, Chang-Seok ; Jeong, Myung-Yung ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 18~24
Efforts to obtain more efficient coupling of light from a laser diode to a single mode fiber have continued for various applications such as links for optical fiber communication systems. In TO-can package, configuration of optimized aspherical lens is bi-aspheric and its diameter is 2.4mm. We designed and fabricated aspherical coupling lens by means of glass molding technique under consideration of glass shrinkage. By controlling the aspherical profile error and surface roughness which were below 90nm and 10nm, respectively, we obtained the low coupling loss, 5.40dB, which was able to use for coupling a single mode fiber to laser diode.
A Study for Preventing Folding Defect of the Common Rail Pipe in Heading Process
Song, Myung-Jun ; Woo, Ta-Kwan ; Jung, Sung-Yuen ; Hur, Kwan-Do ; Kim, Chul ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 25~32
With the latest automobile technology, though the third generation common rail system requires high injection pressures up to 1,800bar, the next generation diesel engine is expected to require more higher pressures than the third generation. The common rail pipe requires higher strength because it is one of the parts in the common rail system, which is influenced directly by fuel under high pressure. Preform design is very important for preventing head of the common rail pipe from folding in the heading process. In this study, die angle, curvature, outer diameter of die and length of trapped part are selected as main parameters to obtain best preform shape minimizing radius of folding. Therefore optimal design is carried out by finite element analysis and Taguchi method through main parameters. Results of the finite element analysis have good agreements with those of the experiments in the actual field.
Cutting Characteristics of Plasma Source Son Implanted Tungsten Carbide Tool
Kang, Seong-Ki ; Wang, Duck-Hyun ; Kim, Won-Il ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 33~40
In this research, the effects for surface Improvement of plasma ion implanted carbide endmill tools were observed by measuring cutting forces and tools wear affecting surface roughness in high speed cutting. From the 2nd ion mass analysis, the oxidation layer was found to be built up by sputtering. The residual gas contamination of oxygen was found to be contained impurities in nitrogen gas. The plasma implanted ion was found to be spreaded, especially the nitrogen was implanted up to 150nm depth as impressed voltage and ion implanting time. It is analyzed as bring surface improvement by spreading deeply forming oxidation on surface. The factors in Analysis of Variance(ANOVA) about mutuality cause reference of cutting force. The cutting force Fx is affected by the interaction of spindle rpm and federate, the cutting force Fy is influenced by spindle rpm and time injected ion, and cutting force Fz is affected by the interaction of impressed voltage and feedrate. Also, it was found that the cutting forces of implanted tools become lower and the surface roughness is improved by the effect of nitrogen according to the implantation.
Development of Laser-Based Resonant Ultrasound Spectroscopy(Laser-RUS) System for the Detection of Micro Crack in Materials
Kang, Young-June ; Kim, Jin-Soo ; Park, Seung-Kyu ; Baik, Sung-Hoon ; Choi, Nag-Jung ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 41~48
Non-contacting, laser-based resonant ultrasound spectroscopy (L-RUS) was applied to characterize the microstructure of a material. L-RUS is widely used by virtue of its many features. Firstly, L-RUS can be used to measure mechanical damping which related to the microstructural variations (grain boundary, grain size, precipitation, defects, dislocations etc). Secondly, L-RUS technology can be applied to various areas, such as the noncontact and nondestructive quality test for precision components as well as noncontact and nondestructive materials characterization. In addition, L-RUS technology can measure the whole field resonant frequency at once. In this paper, we evaluated material characteristics such as resonant frequency, nonlinear propagation characteristic through the development of Laser-Based Resonant Ultrasound spectroscopy (Laser-RUS) System for the detection of Micro Crack in Materials.
A Precision Rotational Device using Piezoelectric Elements and Impact Drive Mechanism
Ten, Aleksey-Deson ; Ryu, Bong-Gon ; Jeon, Jong-Up ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 49~57
This paper describes the design, construction, and fundamental testing of a precision rotational device that utilizes piezoelectric elements as a source of driving force and impact drive mechanism as a driving principle. A novel device structure is designed and the numerical simulations about the static displacement, stress distribution, and mode shape of the designed structure are performed. A fabricated rotational device has been rotated successfully by applying saw-shaped voltages to the piezoelectric elements. The one-step rotational angle was
rad at the applied voltages of 80V. The angular velocities of the device were revealed to be increased as the driving frequency and voltage were respectively increased and the preload was decreased. The device has a feature that it can be translated as well as rotated. An experimental result shows that the device was translated by
maximum when the 120V sinusoidal voltages with a phase difference of
were respectively supplied to two piezoelectric elements.
Contact Force Estimation for a Polishing Brush
Lee, Byoung-Soo ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 58~63
A new contact force estimation technique is proposed. Keeping the contact force at a certain level between finishing tool and the object is essential since the quality of the finished surface is very sensitive to the contact force during the finishing process. However, the contact force measurement cannot be obtained by simply installing load cells under machine table or in the middle of tool linkage. The reason is that the weight of the machine table and the tool linkage are much heavier than the force to be measured. To that end, a method for estimating disturbance is proposed for a system that is similar to the mechanism of the finishing machine, and the same method is applied to estimate the contact force of the brush-type finishing machine. To verify the effectiveness of the proposed method, a small scale test set-up has been built and the method has been tested.
A Complete Feature Map Building Method of Sonar Sensors for Mobile Robots
Lee, Se-Jin ; Lim, Jong-Hwan ; Cho, Dong-Woo ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 64~75
This study introduces a complete feature map building method of sonar sensors for mobile robots. This method enhances the reality of feature maps by extracting even circle features as well as line and point features from sonar data. Edge features are, moreover, generated by combining line features close to circle features extracted around comer sites. The uncertainties of the specular reflection phenomenon and wide beam width of sonar data can be, therefore, reduced through this map building method. The experimental results demonstrate a practical validity of the proposed method in those environments.
A Path Planning for Autonomous Excavation Based on Energy Function Minimization
Park, Hyong-Ju ; Bae, Jang-Ho ; Hong, Dae-Hie ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 76~83
There have been many studies regarding development of autonomous excavation system which is helpful in construction sites where repetitive jobs are necessary. Unfortunately, bucket trajectory planning was excluded from the previous studies. Since, the best use of excavator is to dig efficiently; purpose of this research was set to determine an optimized bucket trajectory in order to get best digging performance. Among infinite ways of digging any given path, criterion for either optimal or efficient bucket moves is required to be established. One method is to adopt work know-how from experienced excavator operator; However the work pattern varies from every worker to worker and it is hard to be analyzed. Thus, other than the work pattern taken from experienced operator, we developed an efficiency model to solve this problem. This paper presents a method to derive a bucket trajectory from optimization theory with empirical CLUB soil model. Path is greatly influenced by physical constraints such as geometry, excavator dimension and excavator workspace. By minimizing a energy function under these constraints, an optimal bucket trajectory could be obtained.
Optimal Water Lubrication Condition for an Axle Shaft Cold Forging
Park, Ji-Won ; Lee, Jong-Soo ; Choi, Young-Jun ; Kim, Jong-Ho ; Lee, Seok-Soon ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 84~90
The cold forging Process applies surface lubricant coating in order to smooth the friction during the cold forging process. Currently, most of the lubrication processes apply the zinc phosphate coating, which requires 11 steps and disposes sludge. But the water based lubrication process, which has been newly developed, takes 3 steps only and does not cause sludge. In this study, we present the optimal condition of water based lubrication for the cold forging of axle shaft by an experimental design method. Experimental results with minitab shall be able to predict the optimum water based lubricating conditions for the cold forging processes.
Characterization of a Thermal Interface Material with Heat Spreader
Kim, Jung-Kyun ; Nakayama, Wataru ; Lee, Sun-Kyu ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 91~98
The increasing of power and processing speed and miniaturization of central processor unit (CPU) used in electronics equipment requires better performing thermal management systems. A typical thermal management package consists of thermal interfaces, heat dissipaters, and external cooling systems. There have been a number of experimental techniques and procedures for estimating thermal conductivity of thin, compressible thermal interface material (TIM). The TIM performance is affected by many factors and thus TIM should be evaluated under specified application conditions. In compact packaging of electronic equipment the chip is interfaced with a thin heat spreader. As the package is made thinner, the coupling between heat flow through TIM and that in the heat spreader becomes stronger. Thus, a TIM characterization system for considering the heat spreader effect is proposed and demonstrated in detail in this paper. The TIM test apparatus developed based on ASTM D-5470 standard for thermal interface resistance measurement of high performance TIM, including the precise measurement of changes in in-situ materials thickness. Thermal impedances are measured and compared for different directions of heat dissipation. The measurement of the TIM under the practical conditions can thus be used as the thermal criteria for the TIM selection.
Study of Defect Prevention on Weld Zone of Magnesium Alloy by Pulse Control of Nd:YAG Laser
Kim, Jong-Do ; Lee, Jung-Han ; Kim, Jang-Soo ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 99~104
Magnesium and magnesium alloys, the lightest structural materials, have been received plenty of global attention recently. These alloys could be applied in various fields, especially the electronics industry, because of their excellent electromagnetic interference shielding. However, the welding technique of magnesium alloys has not been established. This study is related to the welding of AZ31B magnesium alloy by a short-pulsed a Nd:YAG laser. Two types of pulse waves, square pulse and variable pulse, were used to control weld defects. Results show that the crack and porosity, generated in the weld, had not been controlled by general square pulse. But through the application of variable pulse, the defects could be prevented and the good weld zone was obtained.
Investigation of Weldline Strength with Various Heating Conditions
Park, Keun ; Sohn, Dong-Hwi ; Seo, Young-Soo ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 105~112
Weldlines are generated during the injection molding process when two or more melt flows are brought into contact. The weldlines are unavoidable in the cases of presence of holes or inserts, multi-gated delivery systems, significant thickness change, etc. At the welded contact region, a 'V'-shaped notch is formed on the surface of the molded part. This 'V'-notch deteriorates not only surface appearance but also mechanical strength of the molded part. To eliminate or reduce weldlines so as to improve the weldline strength, the mold temperature at the corresponding weld locations should be maintained higher than the glass transition temperature of the resin material. The present study implements high-frequency induction heating in order to rapidly raise mold surface temperature without a significant increase in cycle time. This induction heating enables to local mold heating so as to eliminate or reduce weldlines in an injection-molded plastic part. The effect of induction heating conditions on the weldline strength and surface appearance of an injection-molded part is investigated.
A Study on Residual Stress Measurement Using Raman Spectroscopy
Kang, Min-Sung ; Kim, Sang-Young ; Park, Soo ; Koo, Jae-Mean ; Seok, Chang-Sung ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 113~118
A straight pipe is used after complicated bending work in a mechanical system. In this work process, the plastic deformation of the pipe produces residual stress in the pipe. This residual stress significantly affects the behavior of pipe fracture. For this reason, residual stress must be evaluated. Measuring the residual stress of a U-shaped pipe is difficult with existing destructive and nondestructive measurement methods. In this paper, the residual stress of a U-shaped aluminum pipe (99.7% pure aluminum) was evaluated from the Raman shift by Raman spectroscopy and FEM(Finite Element Method, FEM) analysis. The results of the stiffness test by FEM analysis are compared with those by experiments. The analyzed results of the Raman spectra showed a similar tendency with the results of the FEM analysis with respect to the residual stress distributions in U-shaped pipes. Also, the results of the bending tests showed resemblance to each other.
Development of Desktop Dry Electrical Discharge Machining (EDM) System and Experimental Performance Evaluations
Lee, Sang-Won ; Oh, Young-Seok ; Ahn, Soo-Hong ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 119~124
This paper addresses the design and fabrication of desktop die-sinking dry electrical discharge machining (EDM) system and its experimental performance analysis. The developed desktop dry EDM machine has the horizontal configuration with the size of
. The experimental performance analysis is conducted to investigate the effects of EDM conditions and dielectric gas temperature on the surface roughness of EDMed slots and number of EDM sparks. The experimental results demonstrate that low feed rate and large electrode displacement are good for better surface roughness and more number of EDM sparks. In addition, low temperature of dielectric gas results in better surface roughness.
A Micro-robotic Platform for Micro/nano Assembly: Development of a Compact Vision-based 3 DOF Absolute Position Sensor
Lee, Jae-Ha ; Breguet, Jean Marc ; Clavel, Reymond ; Yang, Seung-Han ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 125~133
A versatile micro-robotic platform for micro/nano scale assembly has been demanded in a variety of application areas such as micro-biology and nanotechnology. In the near future, a flexible and compact platform could be effectively used in a scanning electron microscope chamber. We are developing a platform that consists of miniature mobile robots and a compact positioning stage with multi degree-of-freedom. This paper presents the design and the implementation of a low-cost and compact multi degree of freedom position sensor that is capable of measuring absolute translational and rotational displacement. The proposed sensor is implemented by using a CMOS type image sensor and a target with specific hole patterns. Experimental design based on statistics was applied to finding optimal design of the target. Efficient algorithms for image processing and absolute position decoding are discussed. Simple calibration to eliminate the influence of inaccuracy of the fabricated target on the measuring performance also presented. The developed sensor was characterized by using a laser interferometer. It can be concluded that the sensor system has submicron resolution and accuracy of
over full travel range. The proposed vision-based sensor is cost-effective and used as a compact feedback device for implementation of a micro robotic platform.
Regional Morphological and Mechanical Characteristics in the Human Thoracic Vertebral Trabecular Bones
Lee, Tae-Woo ; Woo, Dae-Gon ; Ko, Chang-Young ; Kim, Han-Sung ;
Journal of the Korean Society for Precision Engineering, volume 27, issue 1, 2010, Pages 134~141
This study analyzed the regional morphological and mechanical characteristics of vertebrae by using micro-computed tomography (micro-CT) and micro finite element analysis (FEA). For the present study, the
human thoracic vertebral bones (an 85-years female and a 48-years male) were used. These were scanned by using micro-CT. Structural parameters were evaluated from the acquired 20 image data for fifteen
regions (five regions in respective layers of superior, middle and inferior part) in the thoracic vertebral trabecular bones.
cubic finite element models of each regions were created at
voxel resolution to investigate effective modulus (
). The present study indicated that there were significant differences in morphological and elastic mechanical characteristics of each region. There are close relationship between effective modulus and structural model index (SMI) in the bone of the 48-years male and between effective modulus and bone volume fraction (BV/TV) in the bone of the 85-years female. In addition, the effective modulus of central regions is about 80% stiffer than that of lateral regions at transverse plane. These findings may be likely to explain the previous result that a change of loading distribution of the vertebral trabecular bones is caused by spinal curvature and nucleus pulpous degeneration of the intervertebral disc.