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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers A
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 32, Issue 12 - Dec 2008
Volume 32, Issue 11 - Nov 2008
Volume 32, Issue 10 - Oct 2008
Volume 32, Issue 9 - Sep 2008
Volume 32, Issue 8 - Aug 2008
Volume 32, Issue 7 - Jul 2008
Volume 32, Issue 6 - Jun 2008
Volume 32, Issue 5 - May 2008
Volume 32, Issue 4 - Apr 2008
Volume 32, Issue 3 - Mar 2008
Volume 32, Issue 2 - Feb 2008
Volume 32, Issue 1 - Jan 2008
Selecting the target year
Evaluation of Material Characteristics by Micro/Nano Indentation Tests
Lee, Hyung-Yil ; Lee, Jin-Haeng ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 805~816
DOI : 10.3795/KSME-A.2008.32.10.805
The present work reviews the methods to evaluate elastic-plastic material characteristics by indentation tests. Especially the representative stress and strain values used in some papers are critically analyzed. The values should not only represent the load-depth curve, but also represent the whole of deformed material around the impression. We briefly introduce other indentation techniques to evaluate residual stresses, creep properties, and fracture toughness. We also review some technical problems that are related to the accuracy issues in indentation tests.
Wear Progress Model by Impact Fretting in Steam Generator Tube
Park, Chi-Yong ; Lee, Jeong-Kun ; Kim, Tae-Ryong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 817~822
DOI : 10.3795/KSME-A.2008.32.10.817
Fretting wear is one of the important degradation mechanisms of steam generator tubes in the nuclear power plants. Especially, impact fretting wear occurred between steam generator tubes and tube support plates or anti-vibration bar. Various tests have been carried out to investigate the wear mechanisms and to report the wear coefficients. Those are fruitful to get insight for the wear damage of steam generator tubes; however, most wear researches have concentrated on sliding wear of the steam generator tubes, which may not represent the wear loading modes in real plants. In the present work, impact fretting tests of steam generator tube were carried out. A wear progress model for impact-fretting wear has been investigated and proposed. The proposed wear progress model of impact-fretting wear is as follows; oxide film breaking step at the initial stage, and layer formation step, energy accumulation step and finally particle torn out step which is followed by layer formation in the stable impact-fretting progress. The wear coefficient according to the work-rate model has been also compared with one between tube and support.
High-Accuracy Digital-to-Analog Actuators Using Load Springs Compensating Fabrication Errors
Han, Won ; Lee, Won-Chul ; Cho, Young-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 823~830
DOI : 10.3795/KSME-A.2008.32.10.823
We present a high-accuracy digital-to-analog (DA) actuator using a load spring, specially designed to compensate the output displacement errors caused by fabrication errors. The compensated linear DA actuator is capable to change the slope of input-output modulation line in order to compensate fabrication errors. We design, fabricate, and characterize three different prototypes: one uncompensated design and two compensated designs respectively for a specific value and for a given range of fabrication error. The compensated linear DA actuators show the output displacement errors of
, respectively, reduced by 64.3% and 76.8% of the output displacement error,
, produced by the conventional uncompensated linear DA actuator. We experimentally verify the fabrication error compensation capability of the present compensated linear DA actuators, thus demonstrating high-accuracy actuation performance immune to fabrication errors.
A Continuous Electrical Cell Lysis Chip using a DC Bias Voltage for Cell Disruption and Electroosmotic Flow
Lee, Dong-Woo ; Cho, Young-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 831~835
DOI : 10.3795/KSME-A.2008.32.10.831
We present a continuous electrical cell lysis chip, using a DC bias voltage to generate the focused high electric field for cell lysis as well as the electroosmotic flow for cell transport. The previous cell lysis chips apply an AC voltage between micro-gap electrodes for cell lysis and use pumps or valves for cell transport. The present DC chip generates high electrical field by reducing the width of the channel between a DC electrode pair, while the previous AC chips reducing the gap between an AC electrode pair. The present chip performs continuous cell pumping without using additional flow source, while the previous chips need additional pumps or valves for the discontinuous cell loading and unloading in the lysis chambers. The experimental study features an orifice whose width and length is 20 times narrower and 175 times shorter than the width and length of a microchannel. With an operational voltage of 50 V, the present chip generates high electric field strength of 1.2 kV/cm at the orifice to disrupt cells with 100% lysis rate of Red Blood Cells and low electric field strength of 60 V/cm at the microchannel to generate an electroosmotic flow of
. In conclusion, the present chip is capable of continuous self-pumping cell lysis at a low voltage; thus, it is suitable for a sample pretreatment component of a micro total analysis system or lab-on-a-chip.
Efficient Finite Element Heat Transfer Analysis by Decomposing a Domain and Radiation Boundaries
Shin, Eui-Sup ; Kim, Yong-Uhn ; Kim, Sung-Jun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 836~843
DOI : 10.3795/KSME-A.2008.32.10.836
An efficient domain/boundary decomposition method is applied for heat transfer problems with non-linear thermal radiation boundaries. The whole domain of solids or structures is considered as set of subdomains, an interface, and radiation interfaces. In a variational formulation, simple penalty functions are introduced to connect an interface or radiation interfaces with neighboring subdomains that satisfy continuity conditions. As a result, non-linear finite element computations due to the thermal radiation boundaries can be localized within a few subdomains or radiation interfaces. Therefore, by setting up suitable solution algorithms for the governing finite element equations, the computational efficiency can be improved considerably. Through a set of numerical examples, these distinguishing characteristics of the present method are investigated in detail.
Bio-inspired Cell Deformability Monitoring Chips Based on Strain Dependent Digital Lysis Rates
Youn, Se-Chan ; Lee, Dong-Woo ; Cho, Young-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 844~849
DOI : 10.3795/KSME-A.2008.32.10.844
We present a novel cell deformability monitoring chip based on the digitally measured cell lysis rate which is dependent on the areal strain of the cell membrane. This method offers simple cell deformability monitoring by automated high-throughput testing system. We suggest the filter design considering the areal strain imposed on the cell membrane passing through the filter array having gradually increased orifice length. In the experiment using erythrocytes, we characterized the cell deformability in terms of average fracture areal strain which was
for normal and chemically treated erythrocytes, respectively. We also verified that the areal strain of 0.15 effectively discriminates the deformability difference of normal and chemically treated erythrocytes, which can be applied to the clinical situation. We compared the lysis rates and their difference for the samples from different donors and found that the present chips can be commonly used without any calibration process. The experimental results demonstrate the simple structure and high performance of the present cell deformability monitoring chips, applicable to simple and cost-effective cell aging process monitoring.
A PM-type Linear Motor Capable of Self Magnetic Levitation
Kim, Woo-Yeon ; Kim, Seung-Jong ; Lee, Jong-Min ; Chung, Sung-Chong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 850~855
DOI : 10.3795/KSME-A.2008.32.10.850
This paper suggests a new linear motor which is able to levitate as well as move its mover without any linear bearing or even additive windings. Its structure is very similar to a well-known both-sided linear motor which consists of two stators and a common mover. And the movement principle is the same with that of conventional linear motor. But unlike the conventional one, the amplitudes of phase currents are controlled to levitate the mover. In this paper, the structure and principle of the suggested bearingless linear motor are introduced in detail and its feasibility is experimentally investigated. Using the prototype and a very simple controller, we succeeded in the levitation and linear movement of the mover at a time.
Damage Mechanisms of a Piezoelectric Actuator under Electric Fatigue Loading
Woo, Sung-Choong ; Goo, Nam-Seo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 856~865
DOI : 10.3795/KSME-A.2008.32.10.856
Damage mechanisms in bending piezoelectric actuators under electric fatigue loading are addressed in this work with the aid of an acoustic emission (AE) technique. Electric cyclic fatigue tests have been performed up to
cycles on the fabricated bending piezoelectric actuators. An applied electric loading range is from -6 kV/cm to +6 kV/cm, which is below the coercive field strength of the PZT ceramic. To confirm the fatigue damage onset and its pathway, the source location and distributions of the AE behavior in terms of count rate and amplitude are analyzed over the fatigue range. It is concluded that electric cyclic loading leads to fatigue damages such as transgranular damages and intergranular cracking in the surface of the PZT ceramic layer, and intergranular cracking even develops into the PZ inner layer, thereby degrading the displacement performance. However, this fatigue damage and cracking do not cause the final failure of the bending piezoelectric actuator loaded up to
cycles. Investigations of the AE behavior and the linear AE source location reveal that the onset time of the fatigue damage varies considerably depending on the existence of a glass-epoxy protecting layer.
Modeling of the Mechanical Drivetrain of an Electric Vehicle for Investigation of Torsional Oscillation Characteristics
Kim, Ho-Gi ; Oh, Joong-Seok ; Kim, Sam-Kyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 866~872
DOI : 10.3795/KSME-A.2008.32.10.866
Torsional oscillations of the mechanical drivetrain in electric vehicles are generated under rapid driving conditions. These lead to an uncomfortable jerking of the vehicle and to an increased stress of the mechanical components. To analyze this phenomenon, a drivetrain model is constructed with lumped parameters. The model parameters are identified by geometrical design data and experimental tests. The proposed model is validated by simulation and experimental tests in the time and the frequency domains. As a result, the torsional oscillations are observed at 7Hz of a low damped natural frequency. Also, the analysis of the effect of the parameter variations on the oscillations shows that the oscillation characteristic is mainly dependent on the rotor inertia, and the stiffness of the mounting of the drive aggregate and the driveshaft. The results will be utilized on the basis of the design of an electric drivetrain and an active control of drivetrain oscillations.
Effect of Preemptive Weld Overlay on Residual Stress Mitigation for Dissimilar Metal Weld of Nuclear Power Plant Pressurizer
Song, Tae-Kwang ; Bae, Hong-Yeol ; Chun, Yun-Bae ; Oh, Chang-Young ; Kim, Yun-Jae ; Lee, Kyoung-Soo ; Park, Chi-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 873~881
DOI : 10.3795/KSME-A.2008.32.10.873
Weld overlay is one of the residual stress mitigation methods which arrest crack initiation and crack growth. Therefore weld overlay can be applied to the region where cracking is likely to be. An overlay weld used in this manner is termed a preemptive weld overlay(PWOL). In pressurized water reactor(PWR) dissimilar metal weld is susceptible region for primary water stress corrosion cracking(PWSCC). In order to examine the effect of PWOL on residual stress mitigation, PWOL was applied to a specific dissimilar metal weld of Kori nuclear power plant by finite element analysis method. As a result, strong compressive residual stress was made in PWSCC susceptible region and PWOL was proved effective preemptive repair method for weldment.
Structural Optimization of the Lower Parts in a Humanoid Considering Dynamic Characteristics
Hong, Eul-Pyo ; Lee, Il-Kwon ; You, Bum-Jae ; Kim, Chang-Hwan ; Park, Gyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 882~889
DOI : 10.3795/KSME-A.2008.32.10.882
A humanoid is a robot with its overall appearance based on that of the human body. When the humanoid moves or walks, dynamic forces act on the body structure. Although the humanoid keeps the balance by using a precise control, the dynamic forces generate unexpected deformation or vibration and cause difficulties on the control. Generally, the structure of the humanoid is designed by the designer's experience and intuition. Then the structure can be excessively heavy or fragile. A humanoid design scenario for a systematic design is proposed to reduce the weight of the structure while sufficient strength is kept. Lower parts of the humanoid are selected to apply the proposed design scenario. Multi-body dynamics is employed to calculate the external dynamic forces on the parts and structural optimization is carried out to design the lower parts. Because structural optimization using dynamic forces directly is fairly difficult, linear dynamic response structural optimization using equivalent static loads is utilized. Topology and shape optimizations are adopted for two steps of initial and detailed designs, respectively. Various commercial software systems are used for analysis and optimization. Improved designs are obtained and the design results are discussed.
A Study of Tool Planning for FRT-PLR-L/R Stamping Process by using Forming Analysis
Jung, Dong-Won ; Ko, Dae-Lim ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 890~896
DOI : 10.3795/KSME-A.2008.32.10.890
Sheet metal forming is one of the most useful and important method in manufacturing of the autobody panels because of the excellent production rate. The objectives of sheet metal forming processes are getting a desired geometrical shape of products with good quality, low cost and reasonable lead time. In this paper, we examined the validity of finite element method analysis on the automobile FRT-PLR-L/R stamping process by using the lancing engineering method. Lancing is a press operation in which a single-line cut or slit is made on part way across the strip stock, without removing any metal. As a result, it has shown that the proper lancing engineering method could prevent fracturing by improving sheet metal flow.
Cam Design of Packer Holder in Egg Grading Machine
Lee, Jang-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 10, 2008, Pages 897~904
DOI : 10.3795/KSME-A.2008.32.10.897
Egg grading machine is used in poultry raising industry to classify eggs by their weight and to pack up them. Packer holder mechanism is a main part of the egg grading machine, of which role is to take eggs fallen from conveyor belt, and afterward to transfer eggs vertically to mold tray. The vertical motion of packer holder is usually driven by slider-crank mechanism or cam. This paper describes development of the cam in packer holder based on kinematic analysis of packer holder mechanism and measurement of acceleration and noise of the cam to verify performance of it. Several cams that are designed and manufactured by the author of this paper according to different design specification are compared to determine the best solution for egg transfer in the packer holder mechanism.