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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 34, Issue 12 - Dec 2010
Volume 34, Issue 11 - Nov 2010
Volume 34, Issue 10 - Oct 2010
Volume 34, Issue 9 - Sep 2010
Volume 34, Issue 8 - Aug 2010
Volume 34, Issue 7 - Jul 2010
Volume 34, Issue 6 - Jun 2010
Volume 34, Issue 5 - May 2010
Volume 34, Issue 4 - Apr 2010
Volume 34, Issue 3 - Mar 2010
Volume 34, Issue 2 - Feb 2010
Volume 34, Issue 1 - Jan 2010
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Numerical Investigation of Frictional Effects and Compensation of Frictional Effects in Split Hopkinson Pressure Bar (SHPB) Test
Cha, Sung-Hoon ; Shin, Hyun-Ho ; Kim, Jong-Bong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 511~518
DOI : 10.3795/KSME-A.2010.34.5.511
The split Hopkinson pressure bar (SHPB) has been widely used to determine the mechanical properties of materials at high loading rates. However, to ensure test reliability, the source of measurement error must be identified and eliminated. During the experiment, specimens were placed between the incident and the transmit bar. Contact friction between the test bars and specimen may cause errors. In this study, numerical experiments were carried out to investigate the effect of friction on the test results. In the SHPB test, the stress measured by the transmitted bar is assumed to be the flow stress of the test specimen. However, performing numerical experiments, it was shown that the stress measured by the transmit bar is axial stress components. When the contact surface is frictionless, the flow stress and axial stress of the specimen are approximately equal. On the other hand, when the contact surface is not frictionless, the flow stress and axial stress are no longer equal. The effect of friction on the difference between the flow stress and axial stress was investigated.
Analysis of Vibration Characteristics of a Full Vehicle Model Using Substructure Synthesis Method
Kim, Bum-Suk ; Kim, Bong-Soo ; Yoo, Hong-Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 519~525
DOI : 10.3795/KSME-A.2010.34.5.519
The finite element (FE) method is generally used to model and simulate the physical behavior of large structures, such as passenger vehicles or aircraft. However, FE analysis involves a very large computation time and cost for developing the analysis model. Therefore, the vibration characteristics of large structural systems are often analyzed using the component mode synthesis (CMS) method, which is one of the substructure synthesis methods. In this study, the vibration characteristics of passenger vehicles are analyzed by using the substructure synthesis method. A passenger vehicle model, which includes a vehicle body, suspension systems, and a sub-frame, is presented. The physical components of the vehicle system are modeled as equivalent substructures using the Craig-Bampton method of CMS. The vibration characteristics, such as the natural frequencies and mode shapes and frequency response, of the vehicle system are determined. The effects of variations in some design parameters on the vibration characteristics of the full vehicle model are also investigated.
Design of Backrest and Seat Pan of Chairs on the Basis of Haptics-Aided Design Method
Jin, Yong-Jie ; Lee, Sang-Duck ; Song, Jae-Bok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 527~533
DOI : 10.3795/KSME-A.2010.34.5.527
The feeling that is evoked when products are handled has become increasingly important in the design of products primarily used by humans. In the traditional product design process, prototypes are built several times in order to evaluate the feeling evoked during use. However, these design processes can be optimized by adopting a haptic simulator that can serve as a prototype. The design method based on the use of the haptic simulator is called haptics-aided design (HAD), which is the main subject of this paper. Here, a new HAD method that can be effectively used to design a custom-made chair is proposed. A haptic simulator, which is composed of a haptic chair and an intuitive graphical user interface, was developed. The simulator can adjust the impedance of the backrest and seat pan of a chair in real time. The haptic chair was used instead of real prototypes in order to evaluate the comfort of the initially designed seat pan and backrest on the basis of their stiffness and damping values. It was shown that the HAD method can be effectively used to design a custom-made chair and can be extended to other product design processes.
Digital Dilution Chip Based on Use of Selective Inter-well Valve Control
Lee, Dong-Woo ; Cho, Young-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 535~539
DOI : 10.3795/KSME-A.2010.34.5.535
We present a digital dilution chip comprising a
array of wells; the chip can be employed to change the dilution ratio as well as to initiate reactions among diluted samples by using the inter-well valve around the well. In previous dilution devices, streams comprising sample and dilution solutions were merged and separated by a branched microchannel. Therefore, the dilution ratio could not be changed until the structure of the branched microchannel was changed. The present device merges and splits the wells filled with sample or dilution solution by controlling inter-well valves around the wells. Thus, it is possible to change the dilution ratio by changing the sequence in which merging and splitting sequence of each well filled with sample or dilution solution. In experiments, we found that the chip could be used to change linear or exponential dilution ratios within an error of 16.7% and to initiate reactions among the samples within a reaction error of 17.7%.
Mean-Variance-Validation Technique for Sequential Kriging Metamodels
Lee, Tae-Hee ; Kim, Ho-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 541~547
DOI : 10.3795/KSME-A.2010.34.5.541
The rigorous validation of the accuracy of metamodels is an important topic in research on metamodel techniques. Although a leave-k-out cross-validation technique involves a considerably high computational cost, it cannot be used to measure the fidelity of metamodels. Recently, the mean
validation technique has been proposed to quantitatively determine the accuracy of metamodels. However, the use of mean
validation criterion may lead to premature termination of a sampling process even if the kriging model is inaccurate. In this study, we propose a new validation technique based on the mean and variance of the response evaluated when sequential sampling method, such as maximum entropy sampling, is used. The proposed validation technique is more efficient and accurate than the leave-k-out cross-validation technique, because instead of performing numerical integration, the kriging model is explicitly integrated to accurately evaluate the mean and variance of the response evaluated. The error in the proposed validation technique resembles a root mean squared error, thus it can be used to determine a stop criterion for sequential sampling of metamodels.
Numerical Study on Effect of Using Elastic Pads in Flexible Forming Process
Heo, Seong-Chan ; Seo, Young-Ho ; Noh, Hak-Gon ; Ku, Tae-Wan ; Kang, Beom-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 549~556
DOI : 10.3795/KSME-A.2010.34.5.549
In general, materials that can be used to form elastic pads, such as urethane and rubber, are often used in flexible forming processes by inserting the pads between a blank and flexible die for smoothing the forming surface that is formed by a reconfigurable die. In this study, the effects of the elastic pad on formability in the flexible forming process for sheet metals are investigated by performing numerical simulations. In the simulation, the hyperelastic material model is used, where the urethane elastic pads serve as elastic cushions. Case studies are carried out for elastic materials with different hardness values and thicknesses. The results are used to evaluate formability by comparing the configuration of the deformed blank and its major cross-sectional profiles. It is verified that the elastic pad used in the flexible forming process for sheet materials should be hard and that its thickness should be chosen appropriately.
Digital Variable Focal Liquid Lens
Lee, Dong-Woo ; Cho, Young-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 557~560
DOI : 10.3795/KSME-A.2010.34.5.557
We have designed a digital variable-focal-length liquid lens by using 4-bit actuators. Each bit actuator consists of 1, 2, 4, and 8 unit actuators, squeezes discrete fluidic volume of
different levels into the lens The 4-bit digital actuation mode (
different lens curvatures and focal lengths. The on/off control of the bit actuators helps in solving the main problem associated with analog liquid lenses, i.e., precise control of the pressure or volume of the fluid for changing the lens curvature and focal length. Experimentally, it has been found that the 4-bit actuators allow 0.074 nl (
) of the given fluid per bit to enter the lens and help in increasing the focal length from 3.63 mm to 38.6 mm in
different levels; no high-cost controllers are required for precise control of the pressure or volume in this case. Therefore, the present digital liquid lens is more suitable to integrated optical systems by reducing additional component for pressure and volume control.
A Study on Fatigue Design of STS301L Fillet Welded Joint
Baek, Seung-Yeb ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 561~565
DOI : 10.3795/KSME-A.2010.34.5.561
Stainless steel sheets are widely used as structural materials for the manufacture of railroad cars and commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. For the fatigue design of gas welded joints such as fillet joints and plug joints, it is necessary to obtain information on the stress distribution at the weldment and the fatigue strength of the gas welded joints. Moreover the influence of the geometrical parameters corresponding to the gas welded joints on the stress distribution and fatigue strength must be evaluated.
curves were obtained from the data recorded in fatigue tests. Using these results, the
curves were rearranged according the relation between
and the maximum stress at the edge of the fillet welded joint.
A Study on Size Optimization for Rocket Motor with a Torispherical Dome
Choi, Young-Gwi ; Shin, Kwang-Bok ; Kim, Won-Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 567~573
DOI : 10.3795/KSME-A.2010.34.5.567
In this study, we evaluated the structural integrity and weight of a rocket motor with a torispherical dome by size optimization. Size optimization was achieved by first-order and sub-problem methods, using the Ansys Parametric Design Language (APDL). For rapid design verification, a modified 2D axisymmetric finite-element model was used, and the bolt pre-tension load was expressed as function of the ratio of the cross-sectional area. The thickness of the dome and the cylindrical part of the rocket motor were selected as the design parameters. Our results showed that the weight and structural integrity of the rocket motor at the initial design stage could be determined more rapidly and accurately with the modified 2D axisymmetric finite-element model than with the 3D finite-element model; further, the weight of the rocket motor could be saved to maximum of 17.6% within safety limit.
Integrated Numerical Analysis of Induction-Heating-Aided Injection Molding Under Interactive Temperature Boundary Conditions
Eom, Hye-Ju ; Park, Keun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 575~582
DOI : 10.3795/KSME-A.2010.34.5.575
In recent years, several rapid-mold-heating techniques that can be used for the injection molding of thin-walled parts or micro/nano structures have been developed. High-frequency induction heating, which involves heating by electromagnetic induction, is an efficient method for the rapid heating of mold surfaces. The present study proposes an integrated numerical model of the high-frequency induction heating process and the resulting injection molding process. To take into account the effects of thermal boundary conditions in induction heating, we carry out a fully integrated numerical analysis that combines electromagnetic field calculation, heat transfer analysis, and injection molding simulation. The proposed integrated simulation is extended to the injection molding of a thin-wall part, and the simulation results are compared with the experimental findings. The validity of the proposed simulation is discussed according to the ways of the boundary condition imposition.
Effect of Interface on the Properties of Cord-Rubber Composites
Lim, Hyun-Woo ; Kim, Jong-Kuk ; Yum, Young-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 583~588
DOI : 10.3795/KSME-A.2010.34.5.583
The nonlinearity and high deformability of rubber make accurate analysis of the behavior of cord-rubber composites a challenging task. Some researchers have adopted the third phase between cord and rubber and have carried out three-phase modeling. However, it is difficult to determine the thickness and properties of the interface in cord-rubber composites. In this study, a two-dimensional finite-element method (2D FEM) is used to investigate the effective and normalized moduli of cord-rubber composites having interfaces of various thicknesses; this model takes into account the 2D generalized plane strain and a plane strain element. The neo-Hookean model is used for the properties of rubber, several interface properties are assumed and three loading directions are selected. It is found that the properties and thickness of the interface can affect the nonlinearity and the effective modulus of cord-rubber composites.
Welding Residual Stress Determination and Crack Analysis in Butt-Welded Thin-Walled Plate by Finite-Element Method
Shim, Kwang-Bo ; Bae, Hong-Yeol ; Jeon, Jun-Young ; Song, Tae-Kwang ; Kim, Yun-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 589~596
DOI : 10.3795/KSME-A.2010.34.5.589
In this study, we calculate the welding residual stresses for a butt-welded thin-walled plate by carrying out three-dimensional finite-element analyses. To study the effect of mechanical boundary conditions on the welding residual stresses, various boundary conditions are considered. The welding residual stresses obtained in the measurements and finite-element analyses are validated by comparing them with the welding residual stress profiles in the R6 code. The results of this study are used to analyze the influence of residual stress on the crack formation in thin-section weldments.
Design of a Mechanical Joint for Zero Moment Crane By Kriging
Kim, Jae-Wook ; Jangn, In-Gwun ; Kwak, Byung-Man ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 597~604
DOI : 10.3795/KSME-A.2010.34.5.597
This study focuses on the design of a mechanical joint for a zero moment crane (ZMC), which is a specialized loading/unloading system used in a mobile harbor (MH). The mechanical joint is based on the concept of zero moment point (ZMP), and it plays an important role in stabilizing a ZMC. For effective stabilization, it is necessary to ensure that the mechanical joint is robust to a wide variety of loads; further, the joint must allow the structures connected to it to perform rotational motion with two degrees of freedom By adopting a traditional design process, we designed a new mechanical joint; in this design, a universal joint is coupled with a spherical joint, and then, deformable rolling elements are incorporated. The rolling elements facilitate load distribution and help in decreasing power loss during loading/unloading. Because of the complexity of the proposed system, Kriging-based approximate optimization method is used for enhancing the optimization efficiency. In order to validate the design of the proposed mechanical joint, a structural analysis is performed, and a small-scale prototype is built.
Isolating Vibration in Miniature Linear Cryogenic Cooler with Tuned Vibration Absorber
Kim, Young-Keun ; Kim, Hong-Bae ; Kim, Eung-Hyun ; Kim, Kyung-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 605~609
DOI : 10.3795/KSME-A.2010.34.5.605
In modern surveillance equipment, infrared (IR) sensors are essential for detection and observation. The IR sensor is connected to a miniature cryogenic cooler to maintain the temperature at very low levels, i.e., temperatures as low as 77 K. However, the quality of the image captured by the sensor is degraded by the transmission of vibration disturbances from the cooler. Therefore, to maintain high image quality, the compressor vibration and the force transmitted to the sensor have to be mitigated. For the compressor vibration isolating system, a tuned dynamic vibration absorber, combined with a passive isolator, is proposed. A cryogenic compressor bracket and springs are designed to allow the absorber mass to mitigate the vibration jitter in the axial direction. The system design is analyzed and evaluated in terms of the dynamic suppression of the harmonic force at the operating frequency of the cooler.
Development of Computational Orthogonal Array based Fatigue Life Prediction Model for Shape Optimization of Turbine Blade
Lee, Kwang-Ki ; Han, Seung-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 611~617
DOI : 10.3795/KSME-A.2010.34.5.611
A complex system involves a large number of design variables, and its operation is non-linear. To explore the characteristics in its design space, a Kriging meta-model can be utilized; this model has replaced expensive computational analysis that was performed in traditional parametric design optimization. In this study, a Kriging meta-model with a computational orthogonal array for the design of experiments was developed to optimize the fatigue life of a turbine blade whose behavior under cyclic rotational loads is significantly non-linear. The results not only show that the maximum fatigue life is improved but also indicate that the accuracy of computational analysis is achieved. In addition, the robustness of the results obtained by six-sigma optimization can be verified by comparison with the results obtained by performing Monte Carlo simulations.
Influence of Heat Treatment Conditions on Temperature Control Parameter ((t
) for Shape Memory Alloy (SMA) Actuator in Nucleoplasty
Oh, Dong-Joon ; Kim, Cheol-Woong ; Yang, Young-Gyu ; Kim, Tae-Young ; Kim, Jay-Jung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 619~628
DOI : 10.3795/KSME-A.2010.34.5.619
Shape Memory Alloy (SMA) has recently received attention in developing implantable surgical equipments and it is expected to lead the future medical device market by adequately imitating surgeons' flexible and delicate hand movement. However, SMA actuators have not been used widely because of their nonlinear behavior called hysteresis, which makes their control difficult. Hence, we propose a parameter,
, which is necessary for temperature control, by analyzing the open-loop step response between current and temperature and by comparing it with the values of linear differential equations.
is a pole of the transfer function in the invariant linear model in which the input and output are current and temperature, respectively; hence,
is found to be related to the state variable used for temperature control. When considering the parameter under heat treatment conditions,
was found to assume the lowest value, and
was irrelevant to the heat treatment.
Examination and Improvement of Accuracy of Three-Dimensional Elastic Crack Solutions Obtained Using Finite Element Alternating Method
Park, Jai-Hak ; Nikishkov, G.P. ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 629~635
DOI : 10.3795/KSME-A.2010.34.5.629
An SGBEM (symmetric Galerkin boundary element method)-FEM alternating method has been proposed by Nikishkov, Park and Atluri. This method can be used to obtain mixed-mode stress intensity factors for planar and nonplanar three-dimensional cracks having an arbitrary shape. For field applications, however, it is necessary to verify the accuracy and consistency of this method. Therefore, in this study, we investigate the effects of several factors on the accuracy of the stress intensity factors obtained using the abovementioned alternating method. The obtained stress intensity factors are compared with the known values provided in handbooks, especially in the case of internal and external circumferential semi-elliptical surface cracks. The results show that the SGBEM-FEM alternating method yields accurate stress intensity factors for three-dimensional cracks, including internal and external circumferential surface cracks and that the method can be used as a robust crack analysis tool for solving field problems.
Design of a Vibration-Powered Piezoelectric Energy-Harvesting Module by Considering Variations in Excitation Frequency
Kim, Jae-Eun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 637~644
DOI : 10.3795/KSME-A.2010.34.5.637
A vibration-powered piezoelectric energy harvester yields the maximum power output when its resonant frequency is made equal to the excitation frequency; however, the power output is dramatically decreased when the energy harvester is operated at off-resonance frequency. It has been observed that the resonant frequency of a piezoelectric energy harvester may change with time and that the excitation frequency often varies when the energy harvester is used in real applications. Hence, in this study, we propose a piezoelectric energy-harvesting module that is suitable for excitations in a certain frequency range. The frequency characteristics of the electrical output of the module are studied through analysis and experiment. A simple frequency tuning method is also suggested for the proposed energy-harvesting module; in this method, frequency tuning is achieved by changing the electrical connections between the constituent energy-harvesting units of the module.
Study on Torsional Strength of Induction-Hardened Axle Shaft
Kang, Dae-Hyun ; Lee, Bum-Jae ; Yun, Chang-Bae ; Kim, Kang-Wuk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 645~649
DOI : 10.3795/KSME-A.2010.34.5.645
Induction hardening has been used to improve the torsional strength and characteristics of wear for axle shaft that is used to transmit driving torque from the differential to the wheel in automobiles. After the rapid heating and cooling processes of induction hardening are carried out, the shaft has residual stress and material properties change; this affects the allowable transmitted torque. The objective of this study is to predict the distribution of residual stress and estimate the torsional strength of induction-hardened axle shafts with residual stress. In this study, the finite element method is used to study the thermomechanical behavior of the material, and the results are compared with experimental results. The results indicate that the torsional strength of the axle shaft depends on the surface hardening depth and distribution of residual stress.
Durability Design of Composite Piston in Marine Diesel Engines
Son, Jung-Ho ; Ha, Man-Yeong ; Ahn, Sung-Chan ; Choi, Seong-Wook ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 5, 2010, Pages 651~657
DOI : 10.3795/KSME-A.2010.34.5.651
A composite piston with a crown made of steel and a skirt made of NCI is used in a marine diesel engine, which has a maximum firing pressure of over 180 bar and a high thermal load. In the fatigue design of the composite piston, the fatigue is influenced by factors such as the load type, surface roughness, and temperature; further, the distribution ratio of the firing force from the crown to the skirt is important for optimizing the design of the crown and skirt. In this study, the stress gradient method was used to consider the effect of the load type. The temperature field on the piston was predicted by cocktail-shaking cooling analysis, and influence of high temperature on fatigue strength was investigated. The load transfer ratio and contact pressure were optimized by design of the surface shape and accurate tolerance analysis. Finally, the cooling performance and durability design of the composite piston were verified by performing a long-term prototype test.