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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
Selecting the target year
Optimal Electron Beam Characteristics by Lenses Analysis Using Scanning Electron Microscopy
Bae, Jinho ; Kim, Dong Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 1~9
DOI : 10.3795/KSME-A.2015.39.1.001
This paper presents a design method for optimizing the focused beam characteristics, which are mainly determined by the condenser lenses in a scanning electron microscopy (SEM) design. Sharply reducing the probe diameter of electron beams by focusing the condenser lens (i.e., the rate of condensation) is important because a small probe diameter results in high-performance demagnification. This study explored design parameters that contribute to increasing the SEM resolution efficiently using lens analysis and the ray tracing method. A sensitivity analysis was conducted based on those results to compare the effects of these parameters on beam focusing. The results of this analysis on the design parameters for the beam characteristics can be employed as basic key information for designing a column in SEM.
Study on Tensile Fatigue Behavior of Thermal Butt Fusion in Safety Class III High-Density Polyethylene Buried Piping in Nuclear Power Plants
Kim, Jong Sung ; Lee, Young Ju ; Oh, Young Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 11~17
DOI : 10.3795/KSME-A.2015.39.1.011
High-density polyethylene (HDPE) piping, which has recently been applied to safety class III piping in nuclear power plants, can be butt-joined through the thermal fusion process, which heats two fused surfaces and then subject to axial pressure. The thermal fusion process generates bead shapes on the butt fusion. The stress concentrations caused by the bead shapes may reduce the fatigue lifetime. Thus, investigating the effect of the thermal butt fusion beads on fatigue behavior is necessary. This study examined the fatigue behavior of thermal butt fusion via a tensile fatigue test under stress-controlled conditions using finite element elastic stress analysis. Based on the results, the presence of thermal butt fusion beads was confirmed to reduce the fatigue lifetime in the low-cycle fatigue region while having a negligible effect in the medium- and high-cycle fatigue regions.
Meta-model-based Design Method for Frequency-domain Performance Reliability Improvement
Son, Young Kap ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 19~26
DOI : 10.3795/KSME-A.2015.39.1.019
This paper proposes a design method for improving the frequency-domain performance reliability of dynamic systems with uncertain and degrading components. Discrete frequencies are used in this method as surrogates for the frequency band of interest, and the conformance of the frequency responses to the specification at these frequencies is utilized to model the frequency-domain performance reliability. A meta-model for the frequency responses, an extreme-value event, and the set-theory are integrated to improve the computational efficiency of the reliability estimation. In addition, a sample-based approach is presented to evaluate and optimize the estimated performance reliability. A case study of a vibration absorber system showed that the proposed design method has engineering applications.
Comparison of Crack Growth Test Results at Elevated Temperature and Design Code Material Properties for Grade 91 Steel
Lee, Hyeong-Yeon ; Kim, Woo-Gon ; Kim, Nak-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 27~35
DOI : 10.3795/KSME-A.2015.39.1.027
The material properties of crack growth models at an elevated temperature were derived from the results of numerous crack growth tests for Mod.9Cr-1Mo (ASME Grade 91) steel specimens under fatigue loading and creep loading at an elevated temperature. These crack growth models were needed for defect assessment under creep-fatigue loading. The mathematical crack growth rate models for fatigue crack growth (FCG) and creep crack growth (CCG) were determined based on the test results, and the models were compared with those of the French design code RCC-MRx to investigate the conservatism of the code. The French design code RCC-MRx provides an FCG model and a CCG model for Grade 91 steel in Section III Tome 6. It was shown that the FCG model of RCC-MRx is conservative, while the CCG model is non-conservative compared with the present test data. Thus, it was shown that further validation of the property was required. Mechanical strength tests and creep tests were also conducted, and the test results were compared with those of RCC-MRx.
Experimental Investigation on Admittance-Based Piezoelectric Sensor Diagnostic Process
Jo, HyeJin ; Park, Tong-Il ; Park, Gyuhae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 37~43
DOI : 10.3795/KSME-A.2015.39.1.037
Structural health monitoring (SHM) techniques based on the use of active-sensing piezoelectric (PZT) materials have received considerable attention. The validation of the PZT functionality during SHM operation is critical to successfully implementing a reliable SHM system. In this study, we investigated several parameters that affect the admittance-based sensor diagnostic process. We experimentally identified the temperature dependency of the active-sensor diagnostic process. We found that the admittance-based sensor diagnostic process can differentiate the adhesion conditions of bonding materials that are used to install a PZT on a structure, which is important when designing a sensor diagnostic process for an SHM system.
Non-linear Characteristic Modeling of Frictional Suspension Using Measured Data
Yoon, Chang Gyu ; Jang, Jin Seok ; Jin, Jae Hoon ; Yoo, Wan Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 45~53
DOI : 10.3795/KSME-A.2015.39.1.045
Large-capacity of household washing machine can become unbalanced during the dehydration process. To solve this problem, several types of suspensions have been installed in a washing machine. In this study, physical tests were carried out on a frictional suspension, and the nonlinear characteristics were modeled by combining several simple physical models. The parameters were estimated based on the least squares solution. The simulation and test results were compared to verify the validity of the friction damper model.
Numerical Analysis of Intense Electric Current Pulse to Disperse Shaped Charge Metal Jet
Park, Hyeong Gyu ; Kim, Dong Kyu ; Kim, Si Woo ; Joo, Jae Hyun ; Song, Woo Jin ; Kim, Jeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 55~62
DOI : 10.3795/KSME-A.2015.39.1.055
The electromagnetic force induced by an intense electric current pulse, which generates an electromagnetic field around the metal jet originating from a shaped charge, can disperse and scatter the high-speed metal jet. An electric device consisting of an RLC circuit applies an intense electric current pulse that flows in the circuit while the metal jet passes between two electrodes. In this study, the metal jet formation was simulated using the ALE technique in 2-D, and a 3-D finite element model was mapped using 2-D simulation results to induce the electric current directly. The deformed shapes of the metal jet and the electromagnetic force were calculated using a finite element analysis by inducing the electric current directly, and the major parameters of the intense electric current pulse for breaking up the metal jet were examined.
Evaluation of Probabilistic Fatigue Crack Propagation Models in Mg-Al-Zn Alloys Under Maximum Load Conditions Using Residual of Random Variable
Choi, Seon Soon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 63~69
DOI : 10.3795/KSME-A.2015.39.1.063
The primary aim of this paper is to evaluate the probabilistic fatigue crack propagation models using the residual of a random variable and to present the probabilistic model fit for the probabilistic fatigue crack growth behavior in Mg-Al-Zn alloys under maximum load conditions. The models used in this study were prepared by applying a random variable to empirical fatigue crack propagation models such as the Paris-Erdogan model, Walker model, Forman model, and modified Forman model. It was verified that the good models for describing the stochastic variation of the fatigue crack propagation behavior in Mg-Al-Zn alloys under maximum load conditions were the `probabilistic Paris-Erdogan model` and `probabilistic Walker model`. The influence of the maximum load conditions on the stochastic variation of fatigue crack growth is also considered.
Replication of Hybrid Micropatterns Using Selective Ultrasonic Imprinting
Lee, Hyun Joong ; Jung, Woosin ; Park, Keun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 71~77
DOI : 10.3795/KSME-A.2015.39.1.071
Ultrasonic imprinting is a micropattern replication technology for a thermoplastic polymer surface that uses ultrasonic vibration energy; it has the advantages of a short cycle time and low energy consumption. Recently, ultrasonic imprinting has been further developed to extend its functionality: (i) selective ultrasonic imprinting using mask films and (ii) repetitive ultrasonic imprinting for composite pattern development. In this study, selective ultrasonic imprinting was combined with repetitive imprinting in order to replicate versatile micropatterns. For this purpose, a repetitive imprinting technology was further extended to utilize mask films, which enabled versatile micropatterns to be replicated using a single mold with micro-prism patterns. The replicated hybrid micropatterns were optically evaluated through laser light images, which showed that versatile optical diffusion characteristics can be obtained from the hybrid micropatterns.
Electro-Mechanical Modeling and Performance Analysis of Floating Wave Energy Converters Utilizing Yo-Yo Vibrating System
Sim, Kyuho ; Park, Jisu ; Jang, Seon-Jun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 79~87
DOI : 10.3795/KSME-A.2015.39.1.079
This paper proposes a floating-type wave energy conversion system that consists of a mechanical part (yo-yo vibrating system, motion rectifying system, and power transmission system) and electrical part (power generation system). The yo-yo vibrating system, which converts translational input to rotational motion, is modeled as a single degree-of-freedom system. It can amplify the wave input via the resonance phenomenon and enhance the energy conversion efficiency. The electromechanical model is established from impedance matching of the mechanical part to the electrical system. The performance was analyzed at various wave frequencies and damping ratios for a wave input acceleration of 0.14 g. The maximum output occurred at the resonance frequency and optimal load resistance, where the power conversion efficiency and electrical output power reached 48% and 290 W, respectively. Utilizing the resonance phenomenon was found to greatly enhance the performance of the wave energy converter, and there exists a maximum power point at the optimum load resistance.
The Study on Weldability of Boron Steel and Hot-Stamped Steel by Using Laser Heat Source (III) - Comparison on Laser Weldability of Boron Steel and Hot-Stamped Steel -
Choi, So Young ; Kim, Jong Do ; Kim, Jong Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 89~94
DOI : 10.3795/KSME-A.2015.39.1.089
This study was conducted to compare the laser weldability of boron steel and hot-stamped steel. In general, boron steel is used in the hot-stamping process. Hot-stamping is a method for simultaneously forming and cooling boron steel in a press die after heating it to the austenitizing temperature. Hot-stamped steel has a strength of 1500 MPa or more. Thus, in this study, the laser weldability of boron steel and thet of hot-stamped steel were investigated and compared. A continuous wave disk laser was used to produce butt and lap joints. In the butt welding, the critical cooling speed at which full penetration was obtained in the hot-stamped steel was lower than that of boron steel. In the lap welding, the joint widths were similar regardless of the welding speed when full penetration was obtained.
Relationship Between Flat End-mill Shape and Geometrical Characteristics in Side Walls Generated by End-milling Process
Kim, Kang ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 95~103
DOI : 10.3795/KSME-A.2015.39.1.095
This paper presents the effects of the tool shape on the geometrical characteristics of flat end-milled side walls. A tool shape is characterized by such parameters as helix angle, number of cutting edges, and diameter. The geometrical characteristics of the side walls are represented by the surface profiles in the feed and axial directions, which are orthogonal to each other. The geometrical defects in each direction are estimated based on the instantaneous apparent cutting areas, which are represented by the interference area between the tool and workpiece and that between the cutting edge and workpiece. It is confirmed that a geometrical defect in the feed direction is formed when the tool leaves the workpiece and the curvature of the tool path changes. Defects in the axial direction are also found in the side walls, except for the defect zone in the feed direction. An up-cut using an end-mill with a steeper helix angle, a greater number of cutting edges, and a smaller diameter are thus found to improve the geometrical accuracy of end-milled side walls.
High-Power Continuous-Wave Laser-Induced Damage to Complementary Metal-Oxide Semiconductor Image Sensor
Kim, Jin-Gyum ; Choi, Sungho ; Yoon, Sunghee ; Jhang, Kyung-Young ; Shin, Wan-Soon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 105~109
DOI : 10.3795/KSME-A.2015.39.1.105
This paper presents the results of an experimental analysis of the high-power laser (HPL)-induced damage to a complementary metal-oxide semiconductor (CMOS) image sensor. Although the laser-induced damages to metallic materials have been sufficiently investigated, the damages to electric-optic imaging systems, which are very sensitive to HPLs, have not been studied in detail. In this study, we experimentally analyzed the HPL-induced damages to a CMOS image sensor. A near-infrared continuous-wave (CW) fiber laser was used as the laser source. The influences of the irradiance and irradiation time on the permanent damages to a CMOS image sensor, such as the color error and breakdown, were investigated. The experimental results showed that the color error occurred first, and then the breakdown occurred with an increase in the irradiance and irradiation time. In particular, these damages were more affected by the irradiance than the irradiation time.
Characterization of Color Change in Injection Molding Process Using Hot Runner
Hong, Ji Sun ; Shim, Hee Soo ; Lee, Ji-Hyun ; Kwon, Min-Kyung ; Chung, Dong-Il ; Kim, Sun Kyoung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 111~115
DOI : 10.3795/KSME-A.2015.39.1.111
In injection molding process using hot runners, color change is a critical issue. This work proposes a method of assessing the color change characteristics of thermoplastics polymers. A method that utilizes a capillary die to measure degree of color change has been devised and implemented. The extrudate from the capillary die has been imaged and quantized to a gray scale value. Based on the gray scale value, the degree of color change has been determined. Under given temperatures and extrusion velocity, its trend along with the number of extrusion has been obtained and analyzed.
Development of Coolant Flow Simulation System for Nuclear Fuel Test Rigs
Hong, Jintae ; Joung, Chang-Young ; Heo, Sung-Ho ; Kim, Ka-Hye ;
Transactions of the Korean Society of Mechanical Engineers A, volume 39, issue 1, 2015, Pages 117~123
DOI : 10.3795/KSME-A.2015.39.1.117
To remove heat generated during a burn-up test of nuclear fuels, the heat generation rate of nuclear fuels should be calculated accurately, and a coolant should be circulated in the test loop at an adequate flow rate. HANARO is an open pool-type reactor with an independent test loop for the burn-up test of nuclear fuels. A test rig is installed in the test loop, and a coolant is circulated through the test loop to maintain the temperature of the nuclear fuel rods within a desired temperature during an irradiation test. The components and sensors in the test rig can be broken or malfunction owing to the flow-induced vibration. In this study, a coolant flow simulation system was developed to verify and confirm the soundness of components and sensors assembled in the test rig with a high flow rate of the coolant.