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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 38, Issue 12 - Dec 2014
Volume 38, Issue 11 - Nov 2014
Volume 38, Issue 10 - Oct 2014
Volume 38, Issue 9 - Sep 2014
Volume 38, Issue 8 - Aug 2014
Volume 38, Issue 7 - Jul 2014
Volume 38, Issue 6 - Jun 2014
Volume 38, Issue 5 - May 2014
Volume 38, Issue 4 - Apr 2014
Volume 38, Issue 3 - Mar 2014
Volume 38, Issue 2 - Feb 2014
Volume 38, Issue 1 - Jan 2014
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Mode II and Mixed Mode Fracture of Single Layer Graphene Sheet
Nguyen, Minh-Ky ; Yum, Young-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 105~113
DOI : 10.3795/KSME-A.2014.38.2.105
The mode II fracture behavior of a single-layer graphene sheet (SLGS) containing a center crack was characterized with the results of an atomistic simulation and an analytical model. The fracture of zigzag graphene models was analyzed with molecular dynamics and the mode II fracture toughness was found to be
. The in-plane shear fracture of a cellular material was analyzed theoretically for deriving the
of SLGS, and FEM results were obtained. Mixed-mode fracture of SLGS was studied for various mode I and mode II ratios. The mixed-mode fracture criterion was determined, and the obtained fracture envelope was in good agreement with that of another study.
Development of RecurDyn Module for Wind Turbine Analysis Applying BEM Theory
Lim, Dae Guen ; Yoo, Wan Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 115~120
DOI : 10.3795/KSME-A.2014.38.2.115
In this study, a module is developed for modeling and analyzing dynamic behavior of a wind turbine using RecurDyn, which is a commercial multi-body dynamics software developed by FunctionBay, Inc. The wind turbine consists of tower, nacelle, hub and blades. Tower and blades are regarded as flexible bodies for considering elastic effect using beam theory and spring force. In this paper, a constant speed wind was assumed and aerodynamic force is modeled using BEM theory. Dynamic analysis applying this aerodynamic force is carried out. To verify the validity of analysis results, these results are compared to those of GH-Bladed which is a commercial software for analyzing wind turbine system distributed by Garrad Hassan.
Mode III Fracture Toughness of Single Layer Graphene Sheet Using Molecular Mechanics
Nguyen, Minh-Ky ; Yum, Young-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 121~127
DOI : 10.3795/KSME-A.2014.38.2.121
An atomistic-based finite bond element model for predicting the tearing mode (mode III) fracture of a single-layer graphene sheet (SLGS) is developed. The model uses the modified Morse potential for predicting the maximum strain relationship of graphene sheets. The mode III fracture of graphene under out-of-plane shear loading is investigated with extensive molecular mechanics simulations. Molecular mechanics is used for describing the displacements of atoms in the area near a crack tip, and linear elastic fracture mechanics is used outside this area. This work shows that the molecular mechanics method can provide a reliable and yet simple method for determining not only the shear properties of SLGS but also its mode III fracture toughness in the armchair and the zigzag directions; the determined mode III fracture toughness values of SLGS are
Target-Tracking System for Mobile Surveillance Robot Using CAMShift Image Processing Technique
Seo, Bong-Cheol ; Kim, Sung-Soo ; Lee, Dong-Youm ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 129~136
DOI : 10.3795/KSME-A.2014.38.2.129
Target-tracking systems are important for carrying out effective surveillance missions using mobile surveillance robots. In this paper, we propose a target-tracking algorithm using camera image data for a three-axis mobile surveillance robot and carry out an actual hardware test for verifying the proposed algorithm. The heading direction vector of a camera system is deduced from the position error between the viewfinder center and the object center in a camera image. The position error is obtained using the CAMShift(Continuously Adaptive Mean Shift) algorithm, an image processing technique. The performance test of an actual three-axis mobile surveillance robot was carried out for verifying the proposed target-tracking algorithm in a real environment.
Dynamic Modeling and Control Techniques for Multi-Rotor Flying Robots
Kim, Hyeon ; Jeong, Heon Sul ; Chong, Kil To ; Lee, Deok Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 137~148
DOI : 10.3795/KSME-A.2014.38.2.137
A multi-rotor is an autonomous flying robot with multiple rotors. Depending on the number of the rotors, multi-rotors are categorized as tri-, quad-, hexa-, and octo-rotor. Given their rapid maneuverability and vertical take-off and landing capabilities, multi-rotors can be used in various applications such as surveillance and reconnaissance in hostile urban areas surrounded by high-rise buildings. In this paper, the unified dynamic model of each tri-, quad-, hexa-, and octo-rotor are presented. Then, based on derived mathematical equations, the operation and control techniques of each multi-rotor are derived and analyzed. For verifying and validating the proposed models, operation and control technique simulations are carried out.
Wi-Fi-Based Low-Complexity Floor Number Determination Method Based for Multistory Buildings
Shi, Jian ; Li, Xiang ; Jung, Honggyu ; Kim, Jinoh ; Shin, Yoan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 149~156
DOI : 10.3795/KSME-A.2014.38.2.149
Floor number determination has attracted considerable attention because many applications require accurate floor number information for providing better localization services in multistory buildings. This paper describes a Wi-Fi-based, low-complexity floor number determination method for multistory buildings. In our scheme, with the exception of floor ID and received signal strength of each WAP, detailed information on the wireless access point (WAP) coordinates is not needed. The multi-wall-floor model is used for the simulation and analysis. The simulation results show that the floor determination accuracy is nearly 100 given an adequate deployment density of WAPs on each floor. The results also show that the proposed method provides a good estimate of floor number even when only a few WAPs are implemented on each floor. Specifically, the proposed method can work under extreme conditions, i.e., where there are no WAPs on a floor.
Development of Multidimensional Gap Conductance Model for Thermo-Mechanical Simulation of Light Water Reactor Fuel
Kim, Hyo Chan ; Yang, Yong Sik ; Koo, Yang Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 157~166
DOI : 10.3795/KSME-A.2014.38.2.157
A light water reactor (LWR) fuel rod consists of zirconium alloy cladding tube and uranium dioxide pellets with a slight gap between them. The modeling of heat transfer across the gap between fuel pellets and the protective cladding is essential to understanding fuel behavior under irradiated conditions. Many researchers have been developing fuel performance codes based on finite element method (FE) to calculate temperature, stress and strain for multidimensional analysis. The gap conductance model for multi-dimension is difficult issue in terms of convergence and nonlinearity because gap conductance is function of gap thickness which depends on mechanical analysis at each iteration step. In this paper, virtual link gap element (VLG) has been proposed to resolve convergence issue and nonlinear characteristic of multidimensional gap conductance. In terms of calculation accuracy and convergence efficiency, the proposed VLG model has been evaluated for variable cases.
Derivation of Elastic Stress Concentration Factor Equations for Debris Fretting Flaws in Pressure Tubes of Pressurized Heavy Water Reactors
Kim, Jong Sung ; Oh, Young Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 167~175
DOI : 10.3795/KSME-A.2014.38.2.167
If volumetric flaws such as bearing pad fretting flaws and debris fretting flaws are detected in the pressure tubes of pressurized heavy water reactors during in-service inspection, the initiation of fatigue cracks and delayed hydrogen cracking from the detected volumetric flaws shall be assessed by using elastic stress concentration factors in accordance with CSA N285.8-05. The CSA N285.8-05 presents only an approximate formula based on linear elastic fracture mechanics for the debris fretting flaw. In this study, an engineering formula considering the geometric characteristics of the debris fretting flaw in detail was derived using two-dimensional finite element analysis and Kinectrics, Inc.`s engineering procedure with slight modifications. Comparing the application results obtained using the derived formula with the three-dimensional finite element analysis results, it is found that the results obtained using the derived formula agree well with the results of the finite element analysis.
Investigation into Variations of Welding Residual Stresses and Redistribution Behaviors for Different Repair Welding Widths
Park, Chi-Yong ; Lee, Hwee-Sueng ; Huh, Nam-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 177~184
DOI : 10.3795/KSME-A.2014.38.2.177
In this study, we investigated the variations in welding residual stresses in dissimilar metal butt weld due to width of repair welding and re-distribution behaviors resulting from similar metal welding (SMW) and mechanical loading. To this end, detailed two-dimensional axi-symmetric finite element (FE) analyses were performed considering five different repair welding widths. Based on the FE results, we first evaluated the welding residual stress distributions in repair welding. We then investigated the re-distribution behaviors of the residual stresses due to SMW and mechanical loads. It is revealed that large tensile welding residual stresses take place in the inner surface and that its distribution is affected, provided repair welding width is larger than certain value. The welding residual stresses resulting from repair welding are remarkably reduced due to SMW and mechanical loading, regardless of the width of the repair welding.
Optimum Design of Pitch Reducer for Wind Turbine Using Genetic Algorithm
Kim, Jeong Gil ; Park, Young Jun ; Lee, Geun Ho ; Nam, Yong Yun ; Yang, Woo Yeoul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 185~192
DOI : 10.3795/KSME-A.2014.38.2.185
Planetary gear design is complex because it involves a combination of discrete variables such as module, integer variables such as the number of teeth, and continuous variables such as face width and aspect ratio. Thus, an optimum design technique is needed. In this study, we applied a genetic algorithm to the design optimization of a planetary gear. In this algorithm, tooth root strength and surface durability are assessed with fundamental variables such as the number of teeth, module, pressure angle, and face width. With the help of this technique, gear designers could reduce trial and error in the initial design stages, thus cutting the time required for planetary gear design.
Temperature-Dependent Stress Analysis of Rotating Functionally Graded Material Gas Turbine Blade Considering Operating Temperature and Ceramic Particle Size
Lee, Ki Bok ; Yoo, Hong Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 193~203
DOI : 10.3795/KSME-A.2014.38.2.193
Temperature-dependent stress analysis and heat transfer analysis of a rotating gas turbine blade made of functionally graded materials (FGMs) are presented considering turbine operating temperature and ceramic particle size. The material properties of functionally graded materials are assumed to vary continuously and smoothly across the thickness of the thin-walled blade. For obtaining system stiffness reflecting these characteristics, the one-dimensional heat transfer equation is applied along the thickness of the thin-walled blade for determining the temperature distribution. Using the results of the temperature analysis, the equations of motion of a rotating blade are derived with hybrid deformation variable modeling method along with the Rayleigh-Ritz assumed mode methods. The validity of the derived rotating blade model is evaluated by comparing its transient responses and temperature distribution with the results obtained using a commercial finite element code. The maximum tensile stress with operating speed and gradient index are obtained. Furthermore, the gradient index that minimizes blade temperature was investigated.
Application of Excitation Moment for Enhancing Fault Diagnosis Probability of Rotating Blade
Kim, Jong Su ; Choi, Chan Kyu ; Yoo, Hong Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 205~210
DOI : 10.3795/KSME-A.2014.38.2.205
Recently, pattern recognition methods have been widely used by researchers for fault diagnoses of mechanical systems. A pattern recognition method determines the soundness of a mechanical system by detecting variations in the system`s vibration characteristics. Hidden Markov models (HMMs) and artificial neural networks (ANNs) have recently been used as pattern recognition methods in various fields. In this study, a HMM-ANN hybrid method for the fault diagnosis of a mechanical system is introduced, and a rotating wind turbine blade with a crack is selected for fault diagnosis. The existence, location, and depth of said crack are identified in this research. For improving the diagnostic accuracy of the method in spite of the presence of noise, a moment with a few specific frequencies is applied to the structure.
Implementation and Validation of EtherCAT Support in Integrated Development Environment for Synchronized Motion Control Application
Lee, Jongbo ; Kim, Chaerin ; Kim, Ikhwan ; Kim, Youngdong ; Kim, Taehyoun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 211~218
DOI : 10.3795/KSME-A.2014.38.2.211
Recently, software-based programmable logic controller (PLC) systems, which are implemented in standard PLC languages on general hardware, are gaining popularity because they overcome the limitations of classical hardware PLC systems. Another noticeable trend is that the use of integrated development environment (IDE) is becoming important. IDEs can help developers to easily manage the growing complexity of modern control systems. Furthermore, industrial Ethernet, e.g. EtherCAT, is becoming widely accepted as a replacement for conventional fieldbuses in the distributed control domain because it offers favorable features such as short transmission delay, high bandwidth, and low cost. In this paper, we implemented the extension of open source IDE, called Beremiz, for developing EtherCAT-based real-time, synchronized motion control applications. We validated the EtherCAT system management features and the real-time responsiveness of the control function by using commercial EtherCAT drives and evaluation boards.
Automatic Combination & Assembly System for Phone Camera Lens Module
Song, Jun Yeob ; Ha, Tae Ho ; Lee, Chang Woo ; Kim, Dong Hoon ; Jeon, Jong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 219~225
DOI : 10.3795/KSME-A.2014.38.2.219
An automatic combination and assembly system for phone-camera lens modules was developed. The system enables the assembly of the relative orientation of the individual lenses making up the lens module. Conventional assembly systems assemble a lens module from eight assembly units. The developed system reduces this number to half by combining each lens and a spacer into a single assembly unit. Also, the number of transfer stages for sequential assembly is minimized without increasing the assembly time. Therefore, high productivity and a footprint that is only about 25 % of that of a conventional assembly system can be realized. The system features a modular design to allow it to cope with rapid changes in the market. Only a few components, such as the picker and guide, need to be replaced for changing to a new assembly model.
Vibration Characteristics of a Wire-Bonding Ultrasonic Horn
Kim, Young Woo ; Yim, Vit ; Han, Daewoong ; Lee, Seung-Yop ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 2, 2014, Pages 227~233
DOI : 10.3795/KSME-A.2014.38.2.227
This study investigates the vibration characteristics of a wire-bonding piezoelectric transducer and ultrasonic horn for high-speed and precise welding. A ring-type piezoelectric stack actuator is excited at 136 kHz to vibrate a conical-type horn and capillary system. The nodal lines and amplification ratio of the ultrasonic horn are obtained using a theoretical analysis and FEM simulation. The vibration modes and frequencies close to the driving frequency are identified to evaluate the bonding performance of the current wire-bonder system. The FEM and experimental results show that the current wire-bonder system uses the bending mode of 136 kHz as the principal motion for bonding and that the transverse vibration of the capillary causes the bonding failure. Because the major longitudinal mode exists at 119 kHz, it is recommended that the design of the current wire-bonding system be modified to use the major longitudinal mode at the excitation frequency and to minimize the transverse vibration of capillary in order to improve the bonding performance.