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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 39, Issue 12 - Dec 2015
Volume 39, Issue 11 - Nov 2015
Volume 39, Issue 10 - Oct 2015
Volume 39, Issue 9 - Sep 2015
Volume 39, Issue 8 - Aug 2015
Volume 39, Issue 7 - Jul 2015
Volume 39, Issue 6 - Jun 2015
Volume 39, Issue 5 - May 2015
Volume 39, Issue 4 - Apr 2015
Volume 39, Issue 3 - Mar 2015
Volume 39, Issue 2 - Feb 2015
Volume 39, Issue 1 - Jan 2015
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Property Evaluation Method Using Spherical Indentation for High-Yield Strength Materials
Choi, Youngsick ; Marimuthu, Karuppasamy Pandian ; Lee, Jin Haeng ; Lee, Hyungyil ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1079~1089
DOI : 10.3795/KSME-A.2015.39.11.1079
In this paper, we propose a method to evaluate the material properties of high-yield strength materials exceeding 10GPa from spherical indentation. Using a regression equation considering four indentation variables, we map the load displacement relation into a stress-strain relation. To calculate the properties of high-strength materials, we then write a program that produces material properties using the loading / unloading data from the indentation test. The errors in material properties computed by the program are within 0.3, 0.8, and 6.4 for the elastic modulus, yield strength, and hardening coefficient, respectively.
Fracture Behavior of Graphite Material at Elevated Temperatures Considering Oxidation Condition
Choi, Hoon Seok ; Kim, Jae Hoon ; Oh, Kawng Keun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1091~1097
DOI : 10.3795/KSME-A.2015.39.11.1091
Graphite material has been widely used for making the rocket nozzle throat because of its excellent thermal properties. However, when compared with typical structural materials, graphite is relatively weak with respect to both strength and toughness, owing to its quasi-brittle behavior, and gets oxidized at
. Therefore, it is important to evaluate the thermal and mechanical properties of this material for using it in structural applications. This study presents an experimental method to investigate the fracture behavior of ATJ graphite at elevated temperatures. In particular, the effects of major parameters such as temperature, loading, and oxidation conditions on strength and fracture characteristics were investigated. Uniaxial compression and tension tests were conducted in accordance with the ASTM standard at room temperature,
. Fractography analysis of the fractured specimens was carried out using an SEM.
Effects of Metal Coatings on Adhesive Characteristics of Gecko-like Micro Structures
Kim, Gyu Hye ; An, Tea Chang ; Hwang, Hui Yun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1099~1103
DOI : 10.3795/KSME-A.2015.39.11.1099
Recently, there have been several studies on the inspiration and application of optimized natural structures. One study introduced a new adhesion method that was inspired by the feet of geckos because of their superior features such as high adhesion strength, ease-of-removal, and they are environmentally friendly. Various micro- or nano-structures were fabricated and tested for gecko-like dry adhesives, but gecko-like dry adhesives that were developed became easily worn from frequent use. In this study, we propose a metal-coating method to improve the durability of gecko-like dry adhesives. We evaluate the initial adhesion strength and durability by performing repeated adhesion tests on a glass plate. The initial adhesive strength of gold-coated micro-structures was 60% of that for non-coated ones. However, the adhesive strength of gold-coated micro-structures was kept as 58% of their initial adhesion strength, while that of non-coated ones was only 40%.
Prediction of Dynamics of Bellows in Exhaust System of Vehicle Using Equivalent Beam Modeling
Hong, Jin Ho ; Kim, Yong Dae ; Lee, Nam Young ; Lee, Sang Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1105~1111
DOI : 10.3795/KSME-A.2015.39.11.1105
The exhaust system is one of the major sources of vibrations, along with the suspension system and engine. When the exhaust system is connected directly to the engine, it transfers vibrations to the vehicle body through the body mounts. Therefore, in order to reduce the vibrations transmitted from the exhaust system, the vibration characteristics of the exhaust system should be predicted. Thus, the dynamic characteristics of the bellows, which form a key component of the exhaust system, must be modeled accurately. However, it is difficult to model the bellows because of the complicated geometry. Though the equivalent beam modeling technique has been applied in the design stage, it is not sufficiently accurate in the case of the bellows which have complicated geometries. In this paper, we present an improved technique for modeling the bellows in a vehicle. The accuracy of the modeling method is verified by comparison with the experimental results.
FRF based Position Controller Design through System Identification for A Hydraulic Cylinder
Seo, Hyoung Kyu ; Kim, Dong Hwan ; Park, Jong Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1113~1121
DOI : 10.3795/KSME-A.2015.39.11.1113
In this study, we have focused on the design of a controller and an operating program for the operation of the hydraulic actuators used in a shaker. To control the motion of the shaker accurately, the position of each hydraulic cylinder should be controlled precisely even under an uncertain environment. For this purpose, we have suggested a control algorithm using an FRF (frequency response function) based control which senses the behavior of the actuator in advance, calculates a transfer function through the system identification method, and provides the final control input. The experimental results on the performance of this system were compared with that of a simple PID control algorithm.
Shape Optimization of Three-Way Reversing Valve for Cavitation Reduction
Lee, Myeong Gon ; Lim, Cha Suk ; Han, Seung Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1123~1129
DOI : 10.3795/KSME-A.2015.39.11.1123
A pair of two-way valves typically is used in automotive washing machines, where the water flow direction is frequently reversed and highly pressurized clean water is sprayed to remove the oil and dirt remaining on machined engine and transmission blocks. Although this valve system has been widely used because of its competitive price, its application is sometimes restricted by surging effects, such as pressure ripples occurring in rapid changes in water flow caused by inaccurate valve control. As an alternative, one three-way reversing valve can replace the valve system because it provides rapid and accurate changes to the water flow direction without any precise control device. However, a cavitation effect occurs because of the complicated bottom plug shape of the valve. In this study, the cavitation index and percent of cavitation (POC) were introduced to numerically evaluate fluid flows via computational fluid dynamics (CFD) analysis. To reduce the cavitation effect generated by the bottom plug, the optimal shape design was carried out through a parametric study, in which a simple computer-aided engineering (CAE) model was applied to avoid time-consuming CFD analysis and difficulties in achieving convergence. The optimal shape design process using full factorial design of experiments (DOEs) and an artificial neural network meta-model yielded the optimal waist and tail length of the bottom plug with a POC value of less than 30%, which meets the requirement of no cavitation occurrence. The optimal waist length, tail length and POC value were found to 6.42 mm, 6.96 mm and 27%, respectively.
Wear Characteristics of Cylinder-Liner Materials for Diesel Engine at Elevated Temperature
Kim, Jin-Yeol ; Kim, Jae-Hoon ; Oh, Kwang-Keun ; Lee, Seung-Hak ; Chang, Joon-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1131~1136
DOI : 10.3795/KSME-A.2015.39.11.1131
In a diesel engine, the wear of the cylinder liner occurs because of the continuous reciprocating motion of the piston ring. This wear reduces the performance of the diesel engine and shortens its service life. This study evaluated the wear characteristics of GT metal and a conventional metal used for cylinder liners using a ship's diesel engine. Wear tests were performed at temperatures of
, and under loads of 10 N, 30 N, and 50 N. The amount of wear, specific wear rate, and friction coefficient were evaluated for each condition. To analyze the wear mechanism, observations were made on an SEM. In the case of both metals, abrasive and adhesion wear occurred on the wear surfaces at room temperature, and corrosion wear was observed at high temperatures. The amount of wear and the specific wear rate of the GT metal were lower than those of the conventional metal at all temperatures, and hence it can be concluded that the wear characteristics of the GT metal are much better.
Finite Element Analysis of Stage II Crack Growth and Branching in Fretting Fatigue
Jung, Hyun Su ; Cho, Sung-San ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1137~1143
DOI : 10.3795/KSME-A.2015.39.11.1137
The stage II fretting fatigue crack growth and branching, i.e., the process of fretting fatigue crack growth starting in an inclined direction and then changing to the normal direction, is analyzed using the finite element method. The fretting fatigue experiment data of A7075-T6 are used in the analysis. The applicability of maximum tangential stress intensity factor, maximum tangential stress intensity factor range, and maximum crack growth rate as the crack growth direction criteria is examined. It is revealed that the stage II crack growth before and after the branching cannot be simulated with a single criterion, but can be done when different criteria are applied to the two stages of crack growth. Moreover, a method to determine the crack length at which the branching occurs is proposed.
A Study on Variations of the Low Cycle Fatigue Life of a High Pressure Turbine Nozzle Caused by Inlet Temperature Profiles and Installation Conditions
Huh, Jae Sung ; Kang, Young Seok ; Rhee, Dong Ho ; Seo, Do Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1145~1151
DOI : 10.3795/KSME-A.2015.39.11.1145
High pressure components of a gas turbine engine must operate for a long life under severe conditions in order to maximize the performance and minimize the maintenance cost. Enhanced cooling design, thermal barrier coating techniques, and nickel-base superalloys have been applied for overcoming them and furthermore, material modeling, finite element analysis, statistical techniques, and etc. in design stage have been utilized widely. This article aims to evaluate the effects on the low cycle fatigue life of the high pressure turbine nozzle caused by different turbine inlet temperature profiles and installation conditions and to investigate the most favorable operating condition to the turbine nozzle. To achieve it, the structural analysis, which utilized the results of conjugate heat transfer analysis as loading boundary conditions, was performed and its results were the input for the assessment of low cycle fatigue life at several critical zones.
Experimental Research of ZrO
/BCP/PCL Scaffold with Complex Pore Pattern for Bone Tissue Regeneration
Sa, Min-Woo ; Shim, Hae-Ri ; Kim, Jong Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1153~1159
DOI : 10.3795/KSME-A.2015.39.11.1153
Recently, synthetic biopolymers and bioceramics such as poly (
-caprolactone)(PCL), hydroxyapatite, tricalcium phosphate, biphasic calcium phosphate(BCP), and zirconia have been used as substrates to generate various tissues or organs in tissue engineering. Thus, the purpose of this study was the characterization of
/BCP/PCL(ZBP) scaffold for bone tissue regeneration. Based on the result of single-line test, blended 3D ZBP scaffolds with fully interconnected pores and new complex pore pattern of
-type and staggered-type were successfully fabricated using a polymer deposition system. Furthermore, the effect of ZBP scaffold on mechanical property was analyzed. In addition, in vitro cell interaction of ZBP scaffold on MG63 cells was evaluated using a cell counting kit-8(CCK-8) assay.
Effect of Lateral Deformations of Guideway on Guidance Characteristics of Maglev Train
Kim, Ki-Jung ; Lee, Jae-Kyoung ; Han, Hyung-Suk ; Yang, Seok-Jo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1161~1167
DOI : 10.3795/KSME-A.2015.39.11.1161
A slender guideway is essential in improving aesthetically and reducing its construction cost which accounts for about 70% of overall investment for maglev system. As the slender guideway, however, may increase its deformation, its effect on levitation stability and guidance performance needs to be analyzed. The purpose of this study is to analyze the effect on guidance characteristics of maglev due to the lateral deformation of the guideway girder and lateral irregularity of guiderail. For doing this, 3D model considering lateral deformation of girder and irregularity of rail of the guideway is developed. Using the dynamic interaction model integrated with the proposed guideway and maglev vehicle including electromagnetics and its controller, guidance characteristics of maglev are analyzed. It is analyzed that the effect on lateral deformation of girder is relatively small compared to deformation on the lateral irregularities of guiderail.
Development of Stand-Alone Risk Assessment Software for Optimized Maintenance Planning of Power Plant Facilities
Choi, Woo Sung ; Song, Gee Wook ; Kim, Bum Shin ; Chang, Sung Ho ; Lee, Sang Min ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1169~1174
DOI : 10.3795/KSME-A.2015.39.11.1169
Risk-Risk-based inspection (RBI) has been developed in order to identify risky equipments that can cause major accidents or damages in large-scale plants. This assessment evaluates the equipment's risk, categorizes their priorities based on risk level, and then determines the urgency of their maintenance or allocates maintenance resources. An earlier version of the risk-based assessment software is already installed within the equipment management system; however, the assessment is based on examination by an inspector, and the results can be influenced by his subjective judgment, rather than assessment being based on failure probability. Moreover, the system is housed within a server, which limits the inspector's work space and time, and such a system can be used only on site. In this paper, the development of independent risk-based assessment software is introduced; this software calculates the failure probability by an analytical method, and analyzes the field inspection results, as well as inspection effectiveness. It can also operate on site, since it can be installed on an independent platform, and has the ability to generate an I/O function for the field inspection results regarding the period for an optimum maintenance cycle. This program will provide useful information not only to the field users who are participating in maintenance, but also to the engineers who need to decide whether to extend the lifecycle of the power machinery or replace only specific components.
Analysis of Heat Transfer Characteristics Based on Design Factors for Determining the Internal Geometry of Metal Insulation in Nuclear Power Plant
Song, Ki O ; Yu, Jeong Ho ; Lee, Tae Ho ; Jeon, Hyun Ik ; Ha, Seung Woo ; Cho, Sun Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1175~1181
DOI : 10.3795/KSME-A.2015.39.11.1175
A heat insulating material used in the industrial site normally derives its heat insulating performance by using a low thermal conductivity material such as glass fiber. In case of the metal insulation for nuclear power plant, in contrast, only TP 304 stainless steel foil having high thermal conductivity is the only acceptable material. So, it is required to approach in structural aspect to ensure the insulation performance. In this study, the design factors related to the metal insulation internal structure were determined considering the three modes of heat transfer, i.e., conduction, convection, and radiation. The analysis of heat flow was used to understand the ratio of the heat transfer from each factor to the overall heat transfer from all the factors. Based on this study, in order to minimize the convection phenomenon caused by the internal insulation, a multiple foil was inserted in the insulation. The increase in the conduction heat transfer rate was compared, and the insulation performance under the three modes of heat transfer was analyzed in order to determine the internal geometry.
Tapered Joint Design for Power Transmission of MW-grade Wind Turbine
Kang, JongHun ; Bae, JunWoo ; On, Hanyong ; Kwon, Yongchul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1183~1189
DOI : 10.3795/KSME-A.2015.39.11.1183
This study focuses on the design of the tapered joints of a wind power turbine. The main variables of the tapered joint are the transmitted torque, shaft diameter, contact area of the tapered ring, and tightening torque of the bolts, which applies a compressive pressure from the hub to the shaft. The stress distribution of the taper fit was calculated under axisymmetric plane strain conditions because of the small taper angle. The axial displacement of the clamp can be calculated from the radial elastic deformation and the taper angle. The stress field of each ring is obtained from the cylinder stress equation. To verify the accuracy of the calculation, finite element (FE) analysis was performed, and the results of the calculation and FE analysis were compared. The hoop stress of the tapered surface showed a discrepancy of approximately 10, but the trends of the stress distributions of each component and the relative movement obtained by FE analysis were in good agreement with the analytical calculation results.
Development of Simplified Finite Element Models for Welded Joints
Song, Seong-Il ; Ahn, Sung Wook ; Kim, Young Geul ; Kim, Hyun-Gyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 11, 2015, Pages 1191~1198
DOI : 10.3795/KSME-A.2015.39.11.1191
In this paper, we develop simplified finite element (FE) models for butt-, lap- and T-welded joints by performing numerical and experimental experiments. Three-point bending tests of butt- and lap-welded specimens are performed to obtain the stiffness of the specimens and the strains at points near the welding beads. Similarly the stiffness and strains of T-welded specimen are measured by applying a point load at the end of the specimen. To develop simplified FE models, we consider the shape parameters of width, thickness and the angle of weld elements in the numerical simulations. The shape parameters of the simplified FE models are determined by building linear regression models for the experimental data sets.