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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 29, Issue 12 - Dec 2005
Volume 29, Issue 11 - Nov 2005
Volume 29, Issue 10 - Oct 2005
Volume 29, Issue 9 - Sep 2005
Volume 29, Issue 8 - Aug 2005
Volume 29, Issue 7 - Jul 2005
Volume 29, Issue 6 - Jun 2005
Volume 29, Issue 5 - May 2005
Volume 29, Issue 4 - Apr 2005
Volume 29, Issue 3 - Mar 2005
Volume 29, Issue 2 - Feb 2005
Volume 29, Issue 1 - Jan 2005
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Design of Combined Radial and Axial 4-pole Electromagnetic Bearing (I) - with Uncoupled Bias Flux -
Kim Ha-Yong ; Kim Seung-Jong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1561~1566
DOI : 10.3795/KSME-A.2005.29.12.1561
In this paper, a new compact active magnetic bearing(AMB) is proposed in which radial and axial bearings are integrated in one bearing unit. It consists of four U-shaped cores circumferentially connected by yokes and two-layer coils for radial and axial controls. For the radial control action, it has the same principle as conventional homopolar AMBs, while for the axial control, it uses the Lorentz force generated by the interaction of the bias flux for radial control and the axial control flux. The proposed structure makes it easy to design a compact AMB because it has no disk for axial control. This paper introduces the proposed structure, principle, and design process based on the magnetic flux analysis. By using a control algorithm with feedforward action to compensate the coupled flux effect, the feasibility of the proposed AMB is experimentally verified.
Design of Combined Radial and Axial 4-pole Electromagnetic Bearing (II) - with Coupled Bias Flux -
Kim Ha-Yong ; Kim Seung-Jong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1567~1573
DOI : 10.3795/KSME-A.2005.29.12.1567
This paper introduces a new active magnetic bearing(AMB) that can provide both radial and axial control functions in one bearing unit without axial disk. It has a structure of double four-pole AMB or a four-pole AMB where each core is split into two axially. The cores have two kinds of coil winding; they independently generate fluxes on the planes perpendicular or parallel to the shaft. For the radial control action, it works just like a conventional four-pole AMB. Meanwhile, for the axial control, it uses the Lorentz force generated by the interaction of the bias flux for radial control and the axial control flux. In this paper, the proposed structure, principle, and design process based on magnetic flux analysis are introduced, and its feasibility is experimentally verified by using a simple PD control algorithm with a feedforward loop to compensate the coupled flux effect.
Spectral Element Analysis of the Pipeline Conveying Internal Unsteady Fluid
Park, Jong-Hwan ; Lee, U-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1574~1585
DOI : 10.3795/KSME-A.2005.29.12.1574
In this paper, a spectral element model is developed for the uniform straight pipelines conveying internal unsteady fluid. Four coupled pipe-dynamics equations are derived first by using the Hamilton`s principle and the principles of fluid mechanics. The transverse displacement, the axial displacement, the fluid pressure and the fluid velocity are all considered as the dependent variables. The coupled pipe-dynamics equations are then linearized about the steady state values of the fluid pressure and velocity. As the final step, the spectral element model represented by the exact dynamic stiffness matrix, which is often called spectral element matrix, is formulated by using the frequency-domain solutions of the linearized pipe-dynamics equations. The FFT-based spectral dynamic analyses are conducted to evaluate the accuracy of the present spectral element model and also to investigate the structural dynamic characteristics and the internal fluid transients of an example pipeline system.
Identification of the Structural Damages in a Cylindrical Shell
Kim, Sung-Hwan ; Lee, U-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1586~1596
DOI : 10.3795/KSME-A.2005.29.12.1586
In this paper, a structural damage identification method (SDIM) is developed to identify the line crack-like directional damages generated within a cylindrical shell. First, the equations of motion for a damaged cylindrical shell are derived. Based on a theory of continuum damage mechanics, a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness, which is dependent of the size and the orientation of the damage with respect to the global coordinates. The present SDIM is then derived from the frequency response function (FRF) directly solved from the equations of motion of a damaged shell. In contrast with most existing SDIMs which require the modal parameters measured in both intact and damaged states, the present SDIM may require only the FRF-data measured at damaged state. By virtue of utilizing FRF-data, one may choose as many sets of excitation frequency and FRF measurement point as needed to acquire a sufficient number of equations for damage identification analysis. The numerically simulated damage identification tests are conducted to study the feasibility of the present SDIM.
Spectral Estimation of the Pass-by Noise of an Acoustic Source
Lim Byoung-Duk ; Kim Deok-Ki ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1597~1604
DOI : 10.3795/KSME-A.2005.29.12.1597
The identification of a moving noise source is important in reducing the source power of the transport systems such as airplanes or high speed trains. However, the direct measurement using a microphone running with noise source is usually difficult due to wind noise, white the source motion distorts the frequency characteristics of the pass-by sound measured at a fixed point. In this study the relationship between the spectra of the source and the pass-by sound signal is analyzed for an acoustic source moving at a constant velocity. Spectrum of the sound signal measured at a fixed point has an integral relationship with the source spectrum. Nevertheless direct conversion of the measured spectrum to the source spectrum is ill-posed due to the singularity of the integral kernel. Alternatively a differential equation approach is proposed, where the source characteristics can be recovered by solving a differential equation relating the source signal to the distorted measurement in time domain. The parameters such as the source speed and the time origin, required beforehand, are also determined only from the frequency-phase relationship using an auxiliary measurement. With the help of the regularization method, the source signal is successfully recovered. The effects of the parameter errors to the estimated frequency characteristics of the source are investigated through numerical simulations.
Limit Load and Fully Plastic Stress Analysis for Circular Notched Plates and Bars Using Fully Plastic Analysis
Oh Chang-Kyun ; Myung Man-Sik ; Kim Yun-Jae ; Park Jin-Moo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1605~1614
DOI : 10.3795/KSME-A.2005.29.12.1605
For the last four decades, tension test of notched bars has been performed to investigate the effect of stress triaxiality on ductile fracture. To quantify the effect of the notch radius on stress triaxiality, the Bridgman equation is typically used. However, recent works based on detailed finite element analysis have shown that the Bridgman equation is not correct, possibly due to his assumption that strain is constant in the necked ligament. Up to present, no systematic work has been performed on fully plastic stress fields for notched bars in tension. This paper presents fully plastic results for tension of notched bars and plates in plane strain, via finite element limit analysis. The notch radius is systematically varied, covering both un-cracked and cracked cases. Comparison of plastic limit loads with existing solutions shows that existing solutions are accurate for notched plates, but not for notched bars. Accordingly new limit load solutions are given for notched bars. Variations of stress triaxiality with the notch radius and depth are also given, which again indicates that the Bridgman solution for notched bars is not correct and inaccuracy depends on the notch radius and depth.
Micro Cell Counter Using a Fixed Control Volume Between Double Electrical Sensing Zones
Lee Dong Woo ; Yi Soyeon ; Cho Young-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1615~1620
DOI : 10.3795/KSME-A.2005.29.12.1615
We present a novel flow-rate independent cell counter using a fixed control volume between double electrical sensing zones. The previous device based on the single electrical cell sensing in a given flow-rate requires an accurate fluid volume measurement or precision flow rate control. The present cell counter, however, offers the flow-rate independent method for the cell concentration measurement with counting cells in a fixed control volume of
. In the experimental study, using the RBC (Red Blood Cell), we have compared the measured RBC concentrations from the fabricated devices with those from Hemacytometer. The previous and present devices show the maximum errors of
, which are in the measurement error range of Hemacytometer (about
). The present device also shows the flow-rate independent performance at the constant flow-rates (
) and the varying flow-rate (4, 2, and
). Therefore, we demonstrate that the present cell counter is a simple and automated method for the cell concentration measurement without requiring an accurate fluid measurement and precision flow-rate control.
Development of Stress-Modified Fracture Strain Criterion for Ductile Fracture of API X65 Steel
Oh Chang-Kyun ; Kim Yun-Jae ; Park Jin-Moo ; Baek Jong-Hyun ; Kim Woo-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1621~1628
DOI : 10.3795/KSME-A.2005.29.12.1621
This paper presents a stress-modified fracture strain for API X65 steel used for gas pipeline, as a function of stress triaxiality. To determine the stress-modified fracture strain, tension test of bars with four different notch radii, made of API X65 steel, is firstly performed, from which true fracture strains are determined as a function of notch radius. Then detailed elastic-plastic, large strain finite element (FE) analyses are performed to estimate variations of stress triaxiality in the notched bars with load. Combining experimental with FE results provides the true fracture strain as a function of stress triaxiality, which is regarded as a criterion of ductile fracture. Application of the developed stress-modified fracture strain to failure prediction of gas pipes made of API X65 steel with various types of defects is discussed.
Optimum Sensitivity of Objective Function Using Equality Constraint
Shin Jung-Kyu ; Lee Sang-Il ; Park Gyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1629~1637
DOI : 10.3795/KSME-A.2005.29.12.1629
Optimum sensitivity analysis (OSA) is the process to find the sensitivity of optimum solution with respect to the parameter in the optimization problem. The prevalent OSA methods calculate the optimum sensitivity as a post-processing. In this research, a simple technique is proposed to obtain optimum sensitivity as a result of the original optimization problem, provided that the optimum sensitivity of objective function is required. The parameters are considered as additional design variables in the original optimization problem. And then, it is endowed with equality constraints to penalize the additional variables. When the optimization problem is solved, the optimum sensitivity of objective function is simultaneously obtained as Lagrange multiplier. Several mathematical and engineering examples are solved to show the applicability and efficiency of the method compared to other OSA ones.
A Study on the Wet Type Ultrasonic Flow-meter System Development
Lee Eung-Suk ; Kwon Oh-Hoon ; Rho Myung-Hwan ; Lee Hyung-Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1638~1644
DOI : 10.3795/KSME-A.2005.29.12.1638
This paper suggests fur the study on a fluid velocity measuring system using ultrasonic transducer. In general, the time difference method to measure the distance between transducers has been known. In this paper, the practical technology for manufacturing ultrasonic flow meter system is studied using the time difference method. The ultrasonic transducer was designed and manufactured. The transmission and receiving algorithm for ultrasonic signal was studied. The ultrasonic flow measuring system was experimented in laboratory using a water reservoir for verifying the distance measuring accuracy. Finally, it was tested in flow calibration laboratory for the velocity measuring performance. The system, designed in this study, showed 0.3 mm resolution in distance measurement. For precise flow measurement, a high speed triggering algorithm is required for ultrasonic signal receiving.
New Suction Mechanism Using Permanent Magnet
Seo Sungkeun ; Lee Seunghee ; Park Jong Hyeon ; Jang Taesa ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1645~1652
DOI : 10.3795/KSME-A.2005.29.12.1645
Pick-and-place systems using suction cups have been being widely used and continuously developed in production automation. There are, however, some drawbacks in constructing such systems. One of them is that it generates high level noise due to air compressors. And the system must have complex constitutions of mechanical component such as air compressors, air tubes, air valves, etc. Moreover, it needs continuous air supply to maintain vacuum in suction cups. If there is a failure in any suction cup, the total suction system may fail owing to air leakage. To overcome these drawbacks, we propose PMS (Permanent Magnet Suction) mechanism which has permanent magnets for vacuuming suction cups with no air compressor. The basic concept of PMS mechanism is to rotate permanent magnets with fixed angle. Simple rotation of permanent magnets changes the direction of the magnetic force applied at the suction cups. Since each suction cup has no direct connection with any of the others, the air leakage at one suction cup is not critical. The proposed suction mechanism was designed and fabricated. With some experiments, the feasibility and performance of the PMS mechanism was shown. The strong points of the PMS mechanism are in its simple structure, generating low noise, high energy efficiency, and no need of continuous energy supply.
A Measure for Improvement in Accuracy by Performance Evaluation of a DPRMs
Choi Youngsam ; Chung Jintai ; Lee Kyeyoung ; Han Changsoo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 29, issue 12, 2005, Pages 1653~1659
DOI : 10.3795/KSME-A.2005.29.12.1653
In this study, the performance of a DPRMs is evaluated and the measurement precision for the pile driving is presented. The DPRMs is a visual-measurement system for the pile rebound and the penetration movement using a high speed line-scan camera. The DPRMs generates the measurement deviation. It is caused by the strong impact for the pile driving. To reduce it, the vibration signal analysis about the pile driving is performed. As a result, it is confirmed that the tilting frequency of a camera-tripod structure corresponding to excitation frequency range of the ground is under 40Hz. Through the structure modification, the camera-tripod structure is redesigned to the model being free itself from the excitation frequency range of the ground. By the verification testing about the improvement effects, it is inspected that the tilting and measurement deviation of the redesigned DPRMs are reduced.