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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 32, Issue 12 - Dec 2008
Volume 32, Issue 11 - Nov 2008
Volume 32, Issue 10 - Oct 2008
Volume 32, Issue 9 - Sep 2008
Volume 32, Issue 8 - Aug 2008
Volume 32, Issue 7 - Jul 2008
Volume 32, Issue 6 - Jun 2008
Volume 32, Issue 5 - May 2008
Volume 32, Issue 4 - Apr 2008
Volume 32, Issue 3 - Mar 2008
Volume 32, Issue 2 - Feb 2008
Volume 32, Issue 1 - Jan 2008
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Improvement of Dao's Reverse Analysis and Determination of Representative Strain for Extracting Elastic-Plastic Properties of Materials in Analysis of Nanoindentation
Lee, Jung-Min ; Lee, Chan-Joo ; Kim, Byung-Min ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 105~118
DOI : 10.3795/KSME-A.2008.32.2.105
The newly developed analysis method for nanoindentation load-displacement curves are focused on not only obtaining elastic modulus and hardness values but also other mechanical properties, such as yield strength and strain hardening properties. Dao et al. developed a forward and reverse algorithm to extract the elasto-plastic properties of materials from the load-displacement curves obtained in nanoindentation test. These algorithms were only applicable for engineering metals (Poisson#s ratio 0.3) using the equivalent conical indenter of the Berkovich. However, the applicable metals are substantially limited because range of used in the finite element analysis is narrow. This study is designed to expand range of the applicable metals in the reverse algorithms established by Dao et al. and to improve the accuracy of that for extracting the elasto-plastic properties of materials. In this study, a representative strain was assumed to vary according to specific range of
and was defined as function of
. Also, an initial unloading slope in reverse algorithms improved in this study was not considered as independent parameters of the load-displacement curves. The mechanical properties of materials for finite element analysis were modeled with the elastic modulus, E, the yield strength,
, and the strain hardening exponents, n. We showed that the representative strain (0.033) suggested by Dao et al. was no longer applicable above the
of 400 and depended on values of
. From these results, we constructed the dimensionless functions, in where the initial unloading slope was not included, for engineering metals up to
of 1500. These functions allow us to determine the mechanical properties with greater accuracy than Dao#s study.
The Characteristic of the Hydraulic Control System with Bleed-off Center Type of a Compact Excavator
Kim, Jun-Sik ; Lee, Seung-Hyun ; Lee, Jae-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 119~126
DOI : 10.3795/KSME-A.2008.32.2.119
In this study, the characteristics of the hydraulic control system with bleed-off center type of a compact excavator were analyzed using developed analysis program. From the parametric analysis, the effects of each factor were revealed. Through the simulation with varying parameters, the system parameter effects on the controllable region and the pump pressure and load pressure variations were studied. The results were compared with the experimental ones. The results and discussions of the present paper could aid in the performance improvement of a hydraulic control system of a compact excavator.
Vibration Characteristics of Rotating Disks with Aerodynamic Effect (I) - Theoretical Analysis -
Lee, Seung-Yop ; Lim, Hyo-Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 127~134
DOI : 10.3795/KSME-A.2008.32.2.127
The aerodynamically excited vibration and natural frequency of rotating disks are analytically studied in this paper. The theoretical analysis uses a fluid-structure model where the aerodynamic effects are represented in terms of elastic, lift and drag forces. The explicit expressions on natural frequencies of the air coupled disk are obtained as functions of the aerodynamic coefficients. for the three cases where the disk rotates in three different cases (in vacuum, in open air without enclosure, and close to rigid wall). The theoretical results give that the natural frequencies of rotating disks in air are smaller than those in vacuum, because the effect of the added fluid mass decreases the frequencies. This paper also proposes an analytical method to predict the flutter speed of a rotating disk.
Vibration Characteristics of Rotating Disks with Aerodynamic Effect (II) - Experimental Verifications -
Lim, Hyo-Suk ; Yim, Vit ; Lee, Seung-Yop ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 135~142
DOI : 10.3795/KSME-A.2008.32.2.135
Experimental studies on the aerodynamic coupling effect on natural frequencies, critical speed and flutter instability of rotating disks are investigated in this paper. The theoretical analysis uses a fluid-structure model where the aerodynamic effects are represented in terms of elastic, lift and damping and stiffness components. The experiments performed using a vacuum chamber and ASMO/DVD disks rotating in vacuum, open and enclosure in several gaps with stationary wall give three main results. One is that the aerodynamic effect by the surrounding air reduces the natural frequencies and critical speeds of the vibration modes. The second is that natural frequency of disks rotating in open air is larger than that in enclosure. Finally, it is shown that the disk vibration is reduced as the gap between the disk and the rigid wall decreases.
Fabrication of Super Water Repellent Surfaces by Vacuum Plasma
Rha, Jong-Joo ; Jeong, Yong-Soo ; Kim, Wan-Doo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 143~147
DOI : 10.3795/KSME-A.2008.32.2.143
Super-hydrophobic surfaces showed that contact angle of water was higher than 140 degrees. That surface could be made several methods such as Carbon nano tubes grown vertically, PDMS asperities arrays, hydrophobic fractal surfaces, and self assembled monolayers coated by CVD and so on. However, we fabricated super-hydrophobic surfaces with plasma treatments which were very cost efficient processes. Their surfaces were characterized by static contact angles, advancing, receding, and stability against UV irradiation. Optimal surfaces showed static contact angles were higher than 150 degrees. Super-hydrophobic property was remained after UV irradiation for one week.
Elastic Analysis of a Half-Plane Containing Multiple Inclusions Using Volume Integral Equation Method
Lee, Jung-Ki ; Ku, Duck-Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 148~161
DOI : 10.3795/KSME-A.2008.32.2.148
A volume integral equation method (VIEM) is used to calculate the plane elastostatic field in an isotropic elastic half-plane containing multiple isotropic or anisotropic inclusions subject to remote loading. A detailed analysis of stress field at the interface between the matrix and the central inclusion in the first column of square packing is carried out for different values of the distance between the center of the central inclusion in the first column of square packing of inclusions and the traction-free surface boundary in an isotropic elastic half-plane containing multiple isotropic or anisotropic inclusions. The method is shown to be very accurate and effective for investigating the local stresses in an isotropic elastic half-plane containing multiple isotropic or anisotropic inclusions.
Compliance Effect Modeling Based on Quasi-Static Analysis for Real-Time Multibody Vehicle Dynamics
Kim, Sung-Soo ; Jeong, Wan-Hee ; Ha, Kyoung-Nam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 162~169
DOI : 10.3795/KSME-A.2008.32.2.162
Compliance effect consideration method for real-time multibody vehicle dynamics is proposed using quasi-static analysis. The multibody vehicle model without bush elements is used based on the subsystem synthesis method which provides real-time computation on the multibody vehicle model. Reaction forces are computed in the suspension subsystem. According to deformation from the quasi-static analysis using reaction forces and bush stiffness, suspension hardpoint locations and suspension linkage orientation are changed. To validate the proposed method, quarter car simulations of McPherson strut and multilink suspension subsystems are performed. Full car bump run simulations and fish hook handling test simulations are also carried out comparing with the ADAMS vehicle model with bush elements. CPU times are also measured to see the real-time capabilities of the proposed method.
Anti Roll Bar Force Computation Algorithm for Real Time Multibody Vehicle Dynamics
Kim, Sung-Soo ; Jeong, Wan-Hee ; Ha, Kyoung-Nam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 170~176
DOI : 10.3795/KSME-A.2008.32.2.170
Anti roll bar model for real time multibody vehicle dynamics model has been proposed using kinematic constraint. Anti roll bar have been modeled by kinematic relationship, and mass properties are neglected. Relative angle of torsion bar spring is computed by constraint about drop-link using Newton-Raphson iteration, and then the torque of torsion bar spring can be computed with the angle and torsion spring stiffness. Finally anti roll bar force acting on both knuckle can be calculated. To validate the proposed method, half car simulations of McPherson strut suspension and full car simulations are also carried out comparing with the ADAMS vehicle model with anti roll bar. CPU times are also measured to see the real-time capabilities of the proposed method.
Characteristics of the Cyclic Hardening in Low Cycle Environmental Fatigue Test of CF8M Stainless Steel
Jeong, Il-Seok ; Ha, Gak-Hyun ; Kim, Tae-Ryong ; Jeon, Hyun-Ik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 177~185
DOI : 10.3795/KSME-A.2008.32.2.177
Low-cycle environmental fatigue tests of cast austenitic stainless steel CF8M at the condition of fatigue strain rate 0.04%/sec were conducted at the pressure and temperature, 15MPa,
of a operating pressurized water reactor (PWR). The used test rig was limited to install an extensometer at the gauge length of the cylindrical fatigue specimen inside a small autoclave. So the magnet type LVDT#s were used to measure the fatigue displacement at the specimen shoulders inside the high temperature and high pressure water autoclave. However, the displacement and strain measured at the specimen shoulders is different from the one at the gauge length for the geometry and the cyclic strain hardening effect. Displacement of the fatigue specimen gauge length calculated by FEM (finite element method) used to modify the measured displacement and fatigue life at the shoulders. A series of low cycle fatigue life tests in air and PWR conditions simulating the cyclic strain hardening effect verified that the FEM modified fatigue life was well agreed with the simulating test results. The process and method developed in this study for the environmental fatigue test inside the small sized autoclave would be so useful to produce reliable environmental fatigue curves of CF8M stainless steel in pressurized water reactors.
Nano-level High Sensitivity Measurement Using Microscopic Moiré Interferometry
Joo, Jin-Won ; Kim, Han-Jun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 186~193
DOI : 10.3795/KSME-A.2008.32.2.186
] interferometry is an optical method, providing whole field contour maps of in-plane displacements with high resolution. The demand for enhanced sensitivity in displacement measurements leads to the technique of microscopic
interferometry. The method is an extension of the
interferometry, and employs an optical microscope for the required spatial resolution. In this paper, the sensitivity of
interferometry is enhanced by an order of magnitude using an immersion interferometry and the optical/digital fringe multiplication(O/DFM) method. In fringe patterns, the contour interval represents the displacement of 52 nm per fringe order. In order to estimate the reliability and the applicability of the optical system implemented, the measurements of rigid body displacements of grating mold and the coefficient of thermal expansion(CTE) for an aluminium block are performed. The system developed is applied to the measurement of thermal deformation in a flip chip plastic ball grid array package.
A Study of Fuel Gauge System Matching Method Using Characteristic Chart to Fuel Consumption Ratio in Vehicles
Lee, Seon-Bong ; Lee, Boo-Youn ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 194~201
DOI : 10.3795/KSME-A.2008.32.2.194
In the present study, fuel system matching was analyzed, and a characteristic chart for common use for design-related parts is presented. Based on the characteristic chart thus presented, controlled fuel system matching was tested for a 35-liter fuel system, and actual mass product movement coils were applied to validate the test. The keynote of the present research is the use of the characteristic chart to devise a preferred fuel system matching method. Through the present study, it will be possible to design standard parts for efficient fuel system matching in the near future.
Inverse and Forward Kinematics Analysis of 6 DOF Multi Axis Simulation Table and Verification
Jin, Jae-Hyun ; Jeon, Seung-Bae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 32, issue 2, 2008, Pages 202~208
DOI : 10.3795/KSME-A.2008.32.2.202
A 6 DOF Multi axis simulation table (MAST) is used to perform vibration and fatigue tests for parts or assemblies of automobiles, aircraft, or other systems. It consists of a table and 6 linear actuators. For its attitude control, we have to adjust the lengths of 6 actuators properly. The system is essentially a parallel mechanism. Three actuators are connected to the table directly and other three actuators are connected indirectly. Because of these, the MAST shows also a serial mechanism#s property: the inverse kinematics is more complicated than a pure parallel mechanism and each actuator can operate independently. The authors have performed a kinematics analysis of the 6 DOF MAST. We have presented an analytical and a numerical solution for the inverse and forward kinematics, and we have verified the solutions by a 3D CAD software.