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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 37, Issue 12 - Dec 2013
Volume 37, Issue 11 - Nov 2013
Volume 37, Issue 10 - Oct 2013
Volume 37, Issue 9 - Sep 2013
Volume 37, Issue 8 - Aug 2013
Volume 37, Issue 7 - Jul 2013
Volume 37, Issue 6 - Jun 2013
Volume 37, Issue 5 - May 2013
Volume 37, Issue 4 - Apr 2013
Volume 37, Issue 3 - Mar 2013
Volume 37, Issue 2 - Feb 2013
Volume 37, Issue 1 - Jan 2013
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Real-Time Algorithm for Relative Position Estimation Between Person and Robot Using a Monocular Camera
Lee, Jung Uk ; Sun, Ju Young ; Won, Mooncheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1445~1452
DOI : 10.3795/KSME-A.2013.37.12.1445
In this paper, we propose a real-time algorithm for estimating the relative position of a person with respect to a robot (camera) using a monocular camera. The algorithm detects the head and shoulder regions of a person using HOG (Histogram of Oriented Gradient) feature vectors and an SVM (Support Vector Machine) classifier. The size and location of the detected area are used for calculating the relative distance and angle between the person and the camera on a robot. To increase the speed of the algorithm, we use a GPU and NVIDIA's CUDA library; the resulting algorithm speed is ~ 15 Hz. The accuracy of the algorithm is compared with the output of a SICK laser scanner.
Analysis of Cracking Characteristics with Indenter Geometry Using Cohesive Zone Model
Hyun, Hong Chul ; Lee, Jin Haeng ; Lee, Hyungyil ; Kim, Dae Hyun ; Hahn, Jun Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1453~1463
DOI : 10.3795/KSME-A.2013.37.12.1453
In this study, we investigated the effect of the indenter geometry on the crack characteristics by indentation cracking test and FEA. We conducted various cohesive finite element simulations based on the findings of Lee et al. (2012), who examined the effect of cohesive model parameters on crack size and formulated conditions for crack initiation and propagation. First, we verified the FE model through comparisons with experimental results that were obtained from Berkovich and Vickers indentations. We observed whether nonsymmetrical cracks formed beneath the surface during Berkovich indentation via FEA. Finally, we examined the relation between the crack size and the number of cracks. Based on this relation and the effect of the indenter angle on the crack size, we can predict from the crack size obtained with an indenter of one shape (such as Berkovich or Vickers) the crack size for an indenter of different shape.
Electrical and Mechanical Properties of Carbon Particle Reinforced Rubber for Electro-Active Polymer Electrode
Lee, Jun Man ; Ryu, Sang Ryeoul ; Lee, Dong Joo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1465~1471
DOI : 10.3795/KSME-A.2013.37.12.1465
The electrical and mechanical properties of room temperature vulcanized (RTV) silicone rubber composites are investigated as functions of multi-walled carbon nanotube (CNT), carbon black (CB), and thinner content. The thinner is used to improve the CNT and CB dispersion in the matrix. The electrical and mechanical properties of the composite with CNT are improved when compared to the composite with CB at the same content. As the thinner content is 80 phr, the electric resistance of the composite decreases significantly with the CNT content and shows contact point saturation of CNT at 2.5 phr. As the thinner content increases, the dispersion of conductive particles improves; however, the critical CB content increases because of the reduction in the CB weight ratio. It is believed that an electrode that needs good flexibility and excellent electrical properties can be manufactured when the amount of CNT and CB are increased with the thinner content.
Design of Rotary Atomizer Using Characteristics of Thin Film Flow on Solid Surfaces
Park, Boo Seong ; Kim, Bo Hung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1473~1482
DOI : 10.3795/KSME-A.2013.37.12.1473
A disc-type rotary atomizer affords advantages such as superior paint transfer efficiency, uniformity of paint pattern and particle size, and less consumption of compressed air compared to a spray-gun-type atomizer. Furthermore, it can be applied to all types of painting materials, and it is suitable for large-scale processes such as car painting. The painting quality, which is closely related to the atomizer performance, is determined by the uniformity and droplet size in accordance with the design of the bell disc surface. This study establishes the basics of how to design a surface by modeling the operating bell disc's RPM, diameter, surface angle, and film thickness considering dye characteristics such as the viscosity, density, and surface affinity.
Analysis of Dynamic Characteristics of Water Injection Pump
Lee, Jong Myeong ; Lee, Jeong Hoon ; Ha, Jeong Min ; Ahn, Byung Hyun ; Kim, Won Cheol ; Choi, Byeong Keun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1483~1487
DOI : 10.3795/KSME-A.2013.37.12.1483
Water injection pump outputs oil with high pressure during this process, seawater is injected into the well to recover the well pressure and maintain high productivity. A water injection pump has high productivity, and therefore, it serves as a key piece of equipment in marine plants. In this light, water injection pumps are being studied widely in industry. In this study, the rotor dynamics is analyzed to determine the natural frequency according to the bearing stiffness and operation speed change. This study aims to establish the pump reliability through critical speed, stability, and unbalance response analysis.
Numerical Study of Breakup Process of Diesel Spray
Yeom, Jeong Kuk ; Jung, Woo Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1489~1495
DOI : 10.3795/KSME-A.2013.37.12.1489
High-pressure flows are ubiquitous in many industrial fields. A representative application is fuel injection using a common-rail control system in diesel engines, where the injection pressure in the injector exceeds 1000 bar. In high-speed injection, the fluid injected through the nozzle undergoes breakup owing to the interaction with the ambient gas. The breakup process influences mixture formation, which in turn influences combustion in diesel engines. Therefore, it is very important to analyze the breakup process of fuel spray. The Reitz and Diwakar model and cascade atomization and breakup (CAB) model were used in this study as sub-models for the numerical analysis of the breakup process of fuel spray. This study aims to precisely analyze the breakup process of spray and to investigate the breakup frequency of the injected fuel. Consequently, it proposes a suitable sub-model for analyzing the breakup process of a diesel spray by using CFX, a commercial CFD program.
Influence of Punch Velocity on Gas Hydrogen Embrittlement Behaviors in SA372 Steel
Bae, Kyung-Oh ; Shin, Hyung-Seop ; Baek, Un-Bong ; Nahm, Seung-Hoon ; Park, Jong-Seo ; Lee, Hae-Moo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1497~1502
DOI : 10.3795/KSME-A.2013.37.12.1497
When using hydrogen gas as an ecofriendly energy sources, it is necessary to conduct a safety assessment and ensure thereliability of the hydrogen pressure vessel against hydrogen embrittlement expected in the steel materials. In this study, by applying the in-situ SP test method, the gas hydrogen embrittlement behaviors in SA372 steel, which is commonly used as a pressurized hydrogen gas storage container, were evaluated. To investigate the hydrogen embrittlement behavior, SP tests at different punch velocities were conducted for specimens with differently fabricated surfaces at atmospheric pressure and under high-pressure hydrogen gas conditions. As a result, the SA372 steel showed significant hydrogen embrittlement under pressurized hydrogen gas conditions. The effect of punch velocity on the hydrogen embrittlement appeared clearly; the lower punch velocity case indicated significant hydrogen embrittlement resulting in lower SP energy. The fractographic morphologies observed after SP test also revealed the hydrogen embrittlement behavior corresponding to the punch velocity adopted. Under this pressurized gas hydrogen test condition, the influence of specimen surface condition on the extent of hydrogen embrittlement could not be determined clearly.
Evaluation of Indentation Fracture Toughens in Brittle Materials Based on FEA Solutions
Hyun, Hong Chul ; Lee, Jin Heang ; Felix, Rickhey ; Lee, Hyungyil ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1503~1512
DOI : 10.3795/KSME-A.2013.37.12.1503
In this study, we proposed an indentation evaluation method for fracture toughness using cohesive finite element simulations. First, we examined the effect of material properties (yield strain, Poisson's ratio, and elastic modulus) on crack size during Vickers indentation and then generated a regression formula that explains the relations among fracture toughness, indentation load, and crack size. We also proposed another indentation formula for fracture toughness evaluation using the contact size a and E/H (H: hardness). Finally, we examined the relation between the crack size and the indenter shapes. Based on this, we can generate from the formula obtained using the Vickers indenter a formula for an indenter of different shapes. Using the proposed method, fracture toughness is directly estimated from indentation data.
Nanoaperture Design in Visible Frequency Range Using Genetic Algorithm and ON/OFF Method Based Topology Optimization Scheme
Shin, Hyun Do ; Yoo, Jeonghoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1513~1519
DOI : 10.3795/KSME-A.2013.37.12.1513
A genetic algorithm (GA) is an optimization technique based on natural evolution theory to find the global optimal solution. Unlike the gradient-based method, it can design nanoscale structures in the electric field because it does not require sensitivity calculation. This research intends to design a nanoaperture with an unprecedented shape by the topology optimization scheme based on the GA and ON/OFF method in the visible frequency range. This research mainly aims to maximize the transmission rate at a measuring area located 10nm under the exit plane and to minimize the electric distribution at other locations. The finite element analysis (FEA) and optimization process are performed by using the commercial package COMSOL combined with the Matlab programming. The final results of the optimized model are analyzed by a comparison of the electric field intensity and the spot size of near field with those of the initial model.
Teleoperation of Pneumatic Artificial Muscles Based on Joint Stiffness of Master Device
Kim, Ryeong Hyeon ; Kang, Bong Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1521~1527
DOI : 10.3795/KSME-A.2013.37.12.1521
This study proposes a wearable master device that can measure the joint stiffness and the angular displacement of a human operator to enhance the adapting capability of a slave system. A lightweight inertial sensor and the exoskeleton mechanism of the master device can make an operator feel comfortable, and artificial pneumatic muscles having a working principle similar to that of human muscles improve the performance of the slave device on emulating what a human operator does. Experimental results revealed that the proposed master/slave system based on the muscle stiffness sensor yielded uniform tracking performance compared with a conventional position-feedback controller when the payload applied to the slave system changed.
Design of Rotating Moving-Magnet-Type VCM Actuator for Miniaturized Mobile Robot
Shin, Bu Hyun ; Lee, Seung-Yop ; Lee, Kyung-Min ; Oh, Dongho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1529~1534
DOI : 10.3795/KSME-A.2013.37.12.1529
A voice coil actuator with a rotating moving magnet has been developed for a miniaturized mobile robot. The actuator has simple structure comprising a magnet, a coil, and a yoke. Actuator performance is predicted using a linearized theoretical model, and dynamic performance based on the air-gap between the magnet and the coil is predicted using motor constant and restoring constant obtained through finite element simulations. The theoretical model was verified using a prototype with 60 Hz resonance and 80 Hz bandwidth. We found that an input of 1.5 V can make the actuator rotate by
statically. The driving configuration of the proposed actuator can be simplified because of its implementation of open-loop control.
Dynamic Analysis of Rotor Systems Considering Ball Bearing Contact Mechanism
Kim, YoungJin ; Lee, Jongmahn ; Oh, Dongho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1535~1540
DOI : 10.3795/KSME-A.2013.37.12.1535
We propose a finite element modeling method considering the ball bearing contact mechanism, and the developed method was verified through experimental and analytical results of inner and outer race-type rotor systems. A comparison of the proposed method with conventional method reveals that there is little difference in the results of the inner race-type rotor system, but there are considerable differences in the results of the outer race-type rotor system such that predictions of greater accuracy can be made. Therefore, the proposed method can be used for accurately predicting the dynamic characteristics of an outer race-type rotary machine.
Optimization of Design Parameters for Lock-Claws of Pneumatic Fitting Using Taguchi Method
Kwon, Tae Ha ; Suh, Chang Hee ; Lee, Rac Gyu ; Oh, Sang Kyun ; Jung, Yun-Chul ; Lim, Hwan Bin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1541~1546
DOI : 10.3795/KSME-A.2013.37.12.1541
The stress concentration of lock-claws, which are one of the important parts for pneumatic fitting for a flexible tube connection, was investigated by finite element simulation. In this study, the generation of the local plastic deformation was predicted when the tube was hooked up to a pneumatic fitting in order to disperse the stress concentration, and design optimization was carried out using the Taguchi method. For the optimization, the outer width, bending angle, and inner radius of the lock-claws are used as main variables. As a result, their respective contribution ratios are revealed as 81.3%, 10.9%, and 1.5%. The ratio of the total stress distribution was improved by 4% compared with the initial design of the lock-claws.
Forced Vibration Modeling of Rail Considering Shear Deformation and Moving Magnetic Load
Kim, Jun Soo ; Kim, Seong Jong ; Lee, Hyuk ; Ha, Sung Kyu ; Lee, Young-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1547~1557
DOI : 10.3795/KSME-A.2013.37.12.1547
A forced vibration model of a rail system was established using the Timoshenko beam theory to determine the dynamic response of a rail under time-varying load considering the damping effect and stiffness of the elastic foundation. By using a Fourier series and a numerical method, the critical velocity and dynamic response of the rail were obtained. The forced vibration model was verified by using FEM and Euler beam theory. The permanent deformation of the rail was predicted based on the forced vibration model. The permanent deformation and wear were observed through the experiment. Parametric studies were then conducted to investigate the effect of five design factors, i.e., rail cross-section shape, rail material density, rail material stiffness, containment stiffness, and damping coefficient between rail and containment, on four performance indices of the rail, i.e., critical velocity, maximum deflection, maximum longitudinal stress, and maximum shear stress.
Analysis of Dynamic Interaction Between Maglev Vehicle and Guideway
Kim, Ki-Jung ; Han, Hyung-Suk ; Yang, Seok-Jo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1559~1565
DOI : 10.3795/KSME-A.2013.37.12.1559
This study aims to investigate the dynamic interaction characteristics between Maglev vehicles and an elevated guideway. A more detailed model for the dynamic interaction of the vehicle/guideway is proposed. The proposed model incorporates a 3D full vehicle model based on prototyping, flexible guideway by a modal superposition method, and levitation electromagnets including the feedback controller into an integrated model. The proposed model was applied to an urban transit Maglev developed for a commercial application to analyze the dynamic response of the vehicle and guideway, and the effect of the surface roughness of the rail, mid-span guideway deflections, and air gap variations are then investigated from the numerical simulation.
Heat Transfer and Radiation Shielding Analysis for Optimal Design of Radioisotope Thermoelectric Generator
Son, Kwang Jae ; Hong, Jintae ; Yang, Young Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1567~1572
DOI : 10.3795/KSME-A.2013.37.12.1567
To supply electric power in certain extreme environments such as a spacecraft or in military applications, a radioisotope thermoelectric generator has been highlighted as a useful energy source owing to its high energy density, long lifetime, and high reliability. A radioisotope thermoelectric generator generates electric power by using the heat energy converted from the radioactive energy of a radioisotope. In this study, FE analyses such as radiation shield analysis, heat transfer analysis, and power recovery rate analysis have been carried out to achieve an optimal design for a radioisotope thermoelectric generator using
Development of Induction Brazing System for Sealing Instrumentation Feedthrough Part of Nuclear Fuel Test Rig
Hong, Jintae ; Kim, Ka-Hye ; Heo, Sung-Ho ; Ahn, Sung-Ho ; Joung, Chang-Young ; Son, Kwang-Jae ; Jung, Yang-Il ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 12, 2013, Pages 1573~1579
DOI : 10.3795/KSME-A.2013.37.12.1573
To test the performance of nuclear fuels, coolant needs to be circulated through the test rig installed in the test loop. Because the pressure and temperature of the coolant is 15.5 MPa and
respectively, coolant sealing is one of the most important processes in fabricating a nuclear fuel test rig. In particular, 15 instrumentation cables installed in a test rig pass through the pressure boundary, and brazing is generally applied as a sealing method. In this study, an induction brazing system has been developed using a high frequency induction heater including a vacuum chamber. For application in the nuclear field, BNi2 should be used as a paste, and optimal process variables for Ni brazing have been found by several case studies. The performance and soundness of the brazed components has been verified by a tensile test, cross section test, and sealing performance test.