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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
Journal Basic Information
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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Controller Design and Validation of Radial Active Magnetic Bearing Systems Considering Dynamical Changes Due To Rotational Speeds
Jeong, Jin Hong ; Yoo, Seong Yeol ; Noh, Myounggyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 925~932
DOI : 10.3795/KSME-A.2014.38.9.925
If a rotor possesses a high gyroscopic coupling or the running speed is high, the dynamical changes in the rotor become prominent. When active magnetic bearings are used to support such rotors, it is necessary for the bearing controller to take these dynamical changes into consideration. Independent-axis controllers, which are the most commonly used, modulate the bearing force solely based on the sensor output of the same axis. However, this type of controller has difficulties in overcoming the dynamical changes. On the other hand, mixed-axis controllers transform the sensor output into components corresponding to the vibrational modes. A separate controller can then be designed for each vibrational mode. In this way, the controller can be designed based on the dynamics of the rotor. In this paper, we describe a design process for a mixed-axis controller that uses a detailed mathematical model of the system. The performance of the controller is evaluated based on the ISO sensitivity requirements and unbalance response, while considering the change in the system dynamics due to the running speed.
Comparison of Projection-Based Model Order Reduction for Frequency Responses
Won, Bo Reum ; Han, Jeong Sam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 933~941
DOI : 10.3795/KSME-A.2014.38.9.933
This paper provides a comparison between the Krylov subspace method (KSM) and modal truncation method (MTM), which are typical projection-based model order reduction methods. The frequency responses are compared to determine the numerical accuracies and efficiencies. In order to compare the numerical accuracies of the KSM and MTM, the frequency responses and relative errors according to the order of the reduced model and frequency of interest are studied. Subsequently, a numerical examination shows whether a reduced order can be determined automatically with the help of an error convergence indicator. As for the numerical efficiency, the computation time needed to generate the projection matrix and the solution time to perform a frequency response analysis are compared according to the reduced order. A finite element model for a car suspension is considered as an application example of the numerical comparison.
Influence of Indenter Tip Geometry and Poisson's Ratio on Load-Displacement Curve in Instrumented Indentation Test
Lee, Jin Haeng ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 943~951
DOI : 10.3795/KSME-A.2014.38.9.943
The tip geometries of the pyramidal and conical indenters used for micro/nano-indentation tests are not sharp. They are inevitably rounded because of their manufacturability and wear. In many indentation studies, the tip geometries of the pyramidal indenters are simply assumed to be spherical, and the theoretical solution for spherical indentation is simply applied to the geometry at a shallow indentation depth. This assumption, however, has two problems. First, the accuracy of the theoretical solution depends on the material properties and indenter shape. Second, the actual shapes of pyramidal indenter tips are not perfectly spherical. Hence, we consider the effects of these two problems on indentation tests via finite element analysis. We first show the relationship between the Poisson's ratio and load-displacement curve for spherical indentation, and suggest improved solutions. Then, using a possible geometry for a Berkovich indenter tip, we analyze the characteristics of the load-displacement curve with respect to the indentation depth.
Property Estimation of Functionally Graded Materials Between M2 Tool Steel and Cu Fabricated by Powder Metallurgy
Jeong, Jong-Seol ; Shin, Ki-Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 953~958
DOI : 10.3795/KSME-A.2014.38.9.953
The use of functionally graded materials (FGMs) may enhance thermal conductivity without reducing the desired strength in many applications such as injection molds embedding conformal cooling channels and cutting tools with heat sinks (or cooling devices). As a fundamental study for cutting tools having FGM heat sinks between M2 tool steel and Cu, six FGM specimens (M2 and Cu powders were premixed such that the relative compositions of M2 and Cu were 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 wt%) were fabricated by powder metallurgy in this study. The cross sections of these specimens were observed by optical microscopy, and then the material properties (such as thermal conductivity, specific heat, and coefficient of thermal expansion) related to heat transfer were measured and analyzed.
Axial Collapse Characteristics of Aluminum/Carbon Fiber Reinforced Plastic Composite Thin-Walled Members with Different Section Shapes
Hwang, Woo Chae ; Lee, Kil Sung ; Cha, Cheon Seok ; Kim, Ji Hoon ; Ra, Seung Woo ; Yang, In Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 959~965
DOI : 10.3795/KSME-A.2014.38.9.959
In the present study, we aimed to obtain design data that can be used for the side members of lightweight cars by experimentally examining the types of effects that the changes in the section shape and outermost layer of an aluminum (Al)/carbon fiber reinforced plastic (CFRP) composite structural member have on its collapse characteristics. We have drawn the following conclusions based on the test results: The circular Al/CFRP composite impact-absorbing member in which the outermost layer angle was laminated at
was observed to be 52.9 and 49.93 higher than that of the square and hat-shaped members, respectively. In addition, the energy absorption characteristic of the circular Al/CFRP composite impact-absorbing member in which the outermost layer angle was laminated at
was observed to be 50.49 and 49.2 higher than that of the square and hat-shaped members, respectively.
Fabrication of Glass Microstructure Using Laser-Induced Backside Wet Etching
Kim, Bo Sung ; Park, Min Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 967~972
DOI : 10.3795/KSME-A.2014.38.9.967
The good light permeability and hardness of glass allow it to be used in various fields. Non-conventional machining methods have been used for glass machining because of its brittle properties. As one non-contact machining method, a laser has advantages that include a high machining speed and the fact that no tool making is required. However, glass has light permeability. Thus, the use of a laser to machine glass has limitations. A nanosecond pulse laser can be used at low power for laser-induced backside wet etching, which is an indirect method. In previous studies, a short-wave laser that had good light absorption but a high price was used. In this study, a near-infrared laser was used to test the possibility of glass micro-machining. In particular, when deeper machining was conducted on a glass structure, more problems could result. To solve these problems, microstructure manufacturing was conducted using ultrasonic vibration.
Design of Light Trapping System of Thin Film Solar Cell Using Phase Field Method
Heo, Namjoon ; Yoo, Jeonghoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 973~978
DOI : 10.3795/KSME-A.2014.38.9.973
This study focused on the design of the reflecting layer of a light trapping system fora thin film solar cell using topology optimization based on the phase field method. Therefore, incident light was caused to propagate in the desired direction by reflecting it from this layer, which is the design domain. The same method was applied to the conceptual design of an infrared stealth structure in near infrared range. The results using the phase field method were compared with those using the density method. The design objective was to maximize the Poynting vector value representing the energy flux, which was measured in a measuring domain to control the reflected wave direction. A finite element analysis and optimization process were performed using the commercial package COMSOL combined with the MATLAB programming.
A Numerical Study of Automotive Indoor Thermal Comfort Model According to Boarding Conditions and Parameters Related to HVAC
Yoon, Seong Hyun ; Park, Jun Yong ; Son, Deok Young ; Choi, Yunho ; Park, Kyungseok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 979~988
DOI : 10.3795/KSME-A.2014.38.9.979
Recently, the interest in the thermal comfort is ever increasing as the time people stay in the automobile is gradually increasing. So far, however, the cooling performance of the HVAC(heating and ventilation air conditioning) system is evaluated by thermal environment criteria such as indoor air velocity and temperature, not by a thermal comfort index. Furthermore, the precise criteria has not been established yet when the thermal comfort for the automobile is evaluated using numerical analysis. In this study, the numerical analysis of automobile indoor thermal comfort according to various parameters such as HVAC operating mode, airflow, passenger boarding conditions is performed during the HVAC system's initial operating time(20 minutes). The solar ray tracing model and S2S radiation model are used and validated to simulate an external heat source. Based on this study, an evaluation model which can predict the thermal comfort index for the combination of the above parameters is presented.
Design of Static Gait Algorithm for Hexapod Subsea Walking Robot: Crabster
Yoo, Seong Yeol ; Jun, Bong Huan ; Shim, Hyungwon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 989~997
DOI : 10.3795/KSME-A.2014.38.9.989
In this paper, we describe a design method for the static walking algorithm of a subsea hexapod robot called Crabster (CR200). To design the gait algorithms of a hexapod robot, we propose a design method that uses a gait schedule vector and leg pair vector to secure convenience and expandability. Several walking algorithms are designed that are capable of being applied to CR200 according to the underwater environment and explorative conditions. In addition, gait transition is freely performed between algorithms by applying common control parameters to them. The gait algorithms designed using the proposed method are simulated using MATLAB and validated against the results of experiments.
Effect of Initial Crack Location on Spatial Randomness of Fatigue Crack Growth Resistance in Friction Stir Welded AA7075-T651 Plates
Kim, Seon Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 999~1004
DOI : 10.3795/KSME-A.2014.38.9.999
In the present paper, the effects of initial crack location on spatial randomness of fatigue crack growth resistance (FCGR) in friction stir welded (FSWed) AA7075-T651 plates were studied. The objective of this study is to characterize the statistical properties of FCGR for three different types of initial crack location (ICL) specimens. In this work, the FCGR coefficients were treated as a spatial random process. It was found that the FCGR coefficients for all initial crack location specimens closely followed a two parameter Weibull distribution. The shape parameter of the Weibull distribution for BM-ICL specimens showed the largest value of 7.50, and that for the WM-ICL specimens showed the smallest value of 2.61. In addition, the autocorrelation functions for all the ICL specimens followed the exponential function.
Experimental Investigation to Establish Correlation Between Specific Film Thickness and Vibration Signals in Spur Gear System
Kim, Jong Sik ; Amarnath, M. ; Lee, Sang Kwon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 1005~1012
DOI : 10.3795/KSME-A.2014.38.9.1005
Gears are critical elements in automobiles, and their use as power transmitting machine elements in engineering applications is quite extensive. In the areas of contact between gear teeth, the condition of a gear is likely to deteriorate due to contact fatigue, wear, material defects, lubrication failure, etc. Thus, it is necessary to monitor its condition to ensure smooth power transmission. Gear teeth deterioration causes failures such as abrasive wear, scuffing, pitting, and spalling. These failures lead to a higher level of vibration signals in the gear system. This paper presents the results of an experiment on the surface fatigue wear of a spur gear system. The correlation between the estimated specific film thickness, statistical parameter of the vibration signals, and Stribeck curve was considered in this study.
Study on Effect of Particle Size of Ferrous Iron and Polishing Abrasive on Surface Quality Improvement
Lee, Sung-Ho ; Son, Byung-Hun ; Kwak, Jae-Seob ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 1013~1018
DOI : 10.3795/KSME-A.2014.38.9.1013
Magnetic Abrasive Polishing (MAP) process is a nontraditional method for polishing the surface of workpiece by using the flexibility of tool. At present, a mixture of polishing abrasives and ferrous particles is used as the tool in the MAP process. Previously, an experiment was conducted with different sizes of polishing abrasives with an aim to improve the polishing accuracy. However, the sizes of ferrous particles are also expected to have a dominant effect on the process, warranting a study on the effect of the size of ferrous iron particles. In this study, an experiment was conducted using three different sizes of ferrous particles. Iron powder of average diameters 8, 78 and
was used as ferrous particles. The effect of each ferrous particle size was evaluated by comparing the improvements in surface roughness. The particle size of a ferrous iron was found to play a significant role in MAP and particles of
facilitated the best improvement in surface roughness.
An Optimal Design of a Pedestrian Safety System Using a Design Scenario
Yun, Yong Won ; Park, Gyung Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 1019~1027
DOI : 10.3795/KSME-A.2014.38.9.1019
Vehicle-into-pedestrian traffic accidents show a very high mortality rate compared to their frequency of occurrence. Throughout the world, governments and insurance companies tend to establish and implement new safety standards for pedestrian protection. In order to improve the performance of pedestrian protection, the Korean government has evaluated the pedestrian safety of vehicles under the Korea New Car Assessment Program (K-NCAP) since 2007. The pedestrian protection performance has improved gradually, but it remains insufficient. A pedestrian protection system consisting of a hood lift system and a pedestrian airbag can be a solution to pedestrian safety. A pedestrian airbag design procedure based on a newly defined design scenario is introduced to reduce the head injury criterion of pedestrians. The proposed design scenario is discussed from a practical viewpoint and applied to manufacture pedestrian protection systems.
Spherical-Coordinate-Based Guiding System for Automatic 3D Shape Scanning
Park, Sang Wook ; Maeng, Hee-Young ; Lee, Myoung Sang ; Kwon, Kil Sun ; Na, Mi-Sun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 1029~1036
DOI : 10.3795/KSME-A.2014.38.9.1029
Several types of automatic 3D scanners are available for use in the 3D scanning industry, e.g., an automatic 3D scanner that uses a robot arm and one that uses an automatic rotary table. Specifically, these scanners are used to obtain a 3D shape using automatic assisting devices. Most of these scanners are required to perform numerous operations, such as merging, aligning, trimming, and filling holes. We are interested in developing an automatic 3D shape collection device using a spherical-coordinate-based guiding system. Then, the aim of the present study is to design an automatic guiding system that can automatically collect 3D shape data. We develop a 3D model of this system and measuring data which are collected by a personal computer. An optimal design of this system and the geometrical accuracy of the measured data are both evaluated using 3D modeling software. The developed system is then applied to an object having a highly complex shape and manifold sections. Our simulation results demonstrate that the developed system collects higher-quality 3D data than the conventional method.
A Study on CMP Characteristics According to Shape of Colloidal Silica Particles
Kim, Moonsung ; Jeong, Haedo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 1037~1041
DOI : 10.3795/KSME-A.2014.38.9.1037
Slurry used for polishing semiconductors processed by exchange, pressurization, and multi-step feeding has been studied to investigate the effect of the size and shape of slurry particles on the oxide CMP removal rate. First, spherical silica sol was prepared by the ion exchange method. The spherical silica particle was used as a seed to grow non-spherical silica sol in accordance with the multi-step feeding of silicic acid by the ion exchange and pressurization methods. The oxide removal rate of both non-spherical silica sol and commercially available slurry were compared with increasing average particle size in the oxide CMP. The more alkaline the pH level of the non-spherical silica sol, the higher was the removal rate and non-uniformity.
Study of Production and Material Properties of Micro Screw Using SWCH18A and SUS XM7 Materials
Ra, Seung-Woo ; Kim, In-Rak ; Hwang, Sung Tack ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 9, 2014, Pages 1043~1048
DOI : 10.3795/KSME-A.2014.38.9.1043
As micro screws feature reduced screw lengths and pitches, the resulting clamping force diminishes because of the reduced length of the actual joints. The elements of the clamping force are material, geometry, and friction. We studied the shrinking size of the screw and the methods to improve the clamping force by changing the material. We developed a micro screw using SWCH18A and SUS XM7 materials, and obtained the precision and thickness of the pitch through three-dimensional measurement. We also measured the external resistance of the micro screw by applying the Vicker's hardness test and conducted a break surface analysis using a break torque test and SEM for obtaining the break characteristics.