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Transactions of the Korean Society of Mechanical Engineers A
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The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 27, Issue 12 - Dec 2003
Volume 27, Issue 11 - Nov 2003
Volume 27, Issue 10 - Oct 2003
Volume 27, Issue 9 - Sep 2003
Volume 27, Issue 8 - Aug 2003
Volume 27, Issue 7 - Jul 2003
Volume 27, Issue 6 - Jun 2003
Volume 27, Issue 5 - May 2003
Volume 27, Issue 4 - Apr 2003
Volume 27, Issue 3 - Mar 2003
Volume 27, Issue 2 - Feb 2003
Volume 27, Issue 1 - Jan 2003
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Flow Phenomena in Micro-channel Filling Process (II) - Numerical Analysis -
Kim, Dong-Sung ; Lee, Kwang-Cheol ; Kwon, Tai-Hun ; Lee, Seung-S. ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 657~665
DOI : 10.3795/KSME-A.2003.27.5.657
Several interesting results were obtained from the flow visualization experiment in the accompanying paper, Part I. in the present study, Part II, a numerical study has been carried out to explain the detailed flow phenomena in micro-channel filling process. Hele-Shaw flow approximation was applied to the micro-channel geometry based on the small characteristic length. And surface tension effect has been introduced on the flow front as the boundary condition with the help of a dynamic contact angle concept between the melt front and the wall. A dimensional analysis for numerical results was carried out and a strong relationship between dimensionless pressure and Capillary number is obtained. The numerical analysis results are compared with the flow visualization experimental observations. And the numerical system developed in the present study seems to be able to predict the interesting micro-channel filling flow characteristics observed from experiments.
Control of Vehicle Yaw Moment using Sliding Mode with Time-Varying Switching Surface
Lee, Chang-Ro ; Yang, Hyun-Seok ; Park, Young-Pil ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 666~672
DOI : 10.3795/KSME-A.2003.27.5.666
This paper presents a design of the controller for vehicle lateral dynamics using active yaw moment. Vehicle lateral motion is incorporated with directional controllability and stability. These are conflicting each other from the view of vehicle handling performance. To compromise the trade-off between these two aspects, we suggest a new control algorithm based on the sliding mode with time-varying switching surface according to the body side slip angle. The controller can deal with the nonlinear region in vehicle driving condition and be robust to the parameter uncertainties in the plant model. Control performance is evaluated from the simulation for the vehicle of real parameters on the road with various tire-road frictions.
A Study on Prediction of Stress Intensity Factor and Fatigue Crack Growth Behavior Using the X-ray Diffraction Technique
Lim, Man-Bae ; Boo, Myung-Hawn ; Kong, Yu-Sik ; Yoon, Han-Ki ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 673~680
DOI : 10.3795/KSME-A.2003.27.5.673
This study verified the relationship between fracture mechanics parameters(ΔK, ΔK
max/) and X-ray parameters (
r/, B) for SG365 steel at elevated temperature up to 300
. The fatigue crack propagation test were carried out and X-ray diffraction technique according to crack length direction was applied to fatigue fractured surface. The residual stress on the fracture surface was found to increase low ΔK region, reach to a maximum value at a certain value of K
max/ or ΔK and then decrease. Residual stress were independent on stress ratio by arrangement of ΔK and half value breadth were independent by the arrangement of K
max/. The equation of
r/ - ΔK was established by the experimental data. Therefore, tincture mechanics parameters could be estimated by the measurement of X-ray parameters.
Integration of T-Search and Dynamic-Window Concept for Accelerated Searching Speed in Delaunay Triangulation
Kang, Hyun-Joo ; Yoon, Sug-Joon ; Kong, Ji-Young ; Kim, Kang-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 681~687
DOI : 10.3795/KSME-A.2003.27.5.681
Terrain surfaces have to be modeled in very detail and wheel-surface contacting geometry must be well defined in order to obtain proper ground-reaction and friction forces fur realistic simulation of off-road vehicles. Delaunay triangulation is one of the most widely used methods in modeling 3-dimensional terrain surfaces, and the T-search is a relevant algorithm for searching resulting triangular polygons. The T-search method searches polygons in a successive order and may not allow real-time computation of off-road vehicle dynamics if the terrain is modeled with many polygons, depending on the computer performance used in the simulation. The dynamic T-search, which is proposed in this paper, combines conventional T-search and the concept of the dynmaic-window search which uses reduced searching windows or sets of triangular surface polygons at each frame by taking advantage of the information regarding dynamic charactereistics of a simulated vehicle. Numerical tests show improvement of searching speeds by about 5% for randomly distributed triangles. For continuous search following a vehicle path, which occurs in actual vehicle simulation, the searching speed becomes 4 times faster.
A Study on the Real Time Auto-Balancing of a Casing Oscillator Using Posture Feedback Control
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 688~696
DOI : 10.3795/KSME-A.2003.27.5.688
The casing oscillator used for basic construction of buildings, factories and bridges is a construction machine, which rotates and rolls the casing to insert it into the ground. It is very important that the casing is positioned perpendicular to the sea level regardless of the slope of the ground. In this paper, we present a new casing oscillator that doesn`t need additional work to level the ground for the casing insertion. The kinematic analysis fur work space of a casing oscillator is presented and carried out with auto-balancing of the casing oscillator using posture feedback control.
Moving Object Tracking Using Active Contour Model
Han, Kyu-Bum ; Baek, Yoon-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 697~704
DOI : 10.3795/KSME-A.2003.27.5.697
In this paper, the visual tracking system for arbitrary shaped moving object is proposed. The established tracking system can be divided into model based method that needs previous model for target object and image based method that uses image feature. In the model based method, the reliable tracking is possible, but simplification of the shape is necessary and the application is restricted to definite target mod el. On the other hand, in the image based method, the process speed can be increased, but the shape information is lost and the tracking system is sensitive to image noise. The proposed tracking system is composed of the extraction process that recognizes the existence of moving object and tracking process that extracts dynamic characteristics and shape information of the target objects. Specially, active contour model is used to effectively track the object that is undergoing shape change. In initializatio n process of the contour model, the semi-automatic operation can be avoided and the convergence speed of the contour can be increased by the proposed effective initialization method. Also, for the efficient solution of the correspondence problem in multiple objects tracking, the variation function that uses the variation of position structure in image frame and snake energy level is proposed. In order to verify the validity and effectiveness of the proposed tracking system, real time tracking experiment for multiple moving objects is implemented.
Thermal Stress Due to a Hot - Spot on the Laminated Plate in High Temperature Superconducting Fault Current Limiter
Yang, Kyeong-Jin ; Kang, Ki-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 705~712
DOI : 10.3795/KSME-A.2003.27.5.705
Analysis for the thermal stress distribution in the laminated plates containing a hot-spot(local heating region) is performed. It is assumed that the local heating region induces only mechanical stress by the thermal expansion but effect of the thermal conduction is neglected. The region is regarded equivalent to a homogeneous inclusion expanding in a laminated medium. As an example, Au/YBCO/Al
laminate which is often employed for High Temperature Superconducting Fault Current Limiter(HTS FCL) has been analyzed. Effects of heat input, thickness of each layer and the got spot size upon the stress distribution in the hot-spot have been investigated. For a constant heat generation into the hot-spot, as the thickness of the Al
substrate increases, the stress in the YBCO layer is peculiarly oscillated, and the curvature of laminate has a maximum at a certain thickness of the Al
Development of Residual Stress Analysis Procedure for Fitness-For-Service Assessment of Welded Structure
Kim, Jong-Sung ; Jin, Tae-Eun ; P. Dong ; M. Prager ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 713~723
DOI : 10.3795/KSME-A.2003.27.5.713
In this study, a state of art review of existing residual stress analysis techniques and representative solutions is presented in order to develope the residual stress analysis procedure for fitness-for-service (FFS) assessment of welded structure. Critical issues associated with existing residual stress solutions and their treatments in performing FFS are discussed. It should be recognized that detailed residual stress evolution is an extremely complicated phenomenon that typically involves material-specific ther-momechanical/metallurgical response, welding process physics, and structural interactions within a component being welded. As a result, computational procedures can vary significantly from highly complicated numerical techniques intended only to elucidate a small part of the process physics to cost-effective procedures that are deemed adequate for capturing some of the important features in a final residual stress distribution. Residual stress analysis procedure for FFS purposes belongs to the latter category. With this in mind, both residual stress analysis techniques and their adequacy for FFS are assessed based on both literature data and analyses performed in this investigation.
Finite Element Analysis and Development of Interim Consolidated 5-N Curve for Fatigue Design of Welded Structure
Kim, Jong-Sung ; Jin, Tae-Eun ; Hong, Jeong-Kyun ; P. Dong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 724~733
DOI : 10.3795/KSME-A.2003.27.5.724
Fatigue design rules for welds in the ASME Boiler and Pressure Vessels Code are based on the use of Fatigue Strength Reduction Factors(FSRF) against a code specified fatigue design curve generated from smooth base metal specimens without the presence of welds. Similarly, stress intensification factors that are used in the ASME B3l.1 Piping Code are based on component S-N curves with a reference fatigue strength based on straight pipe girth welds. But the determination of either the FSRF or stress intensification factor requires extensive fatigue testing to take into account the stress concentration effects associated with various types of component geometry, weld configuration and loading conditions. As the fatigue behavior of welded joints is being better understood, it has been generally accepted that the difference in fatigue lives from one type of weld to another is dominated by the difference in stress concentration. However, general finite element procedures are currently not available for effective determination of such stress concentration effects. In this paper, a mesh-insensitive structural stress method is used to re-evaluate the S-N test data, and then more effective method is proposed for pressure vessel and piping fatigue design.
A Continuous Scanning Laser Doppler Vibrometer for Mode Shape Analysis
Park, Kyi-Hwan ; Choi, Ji-Eun ; La, Jong-Pil ; Wang, Sem-Yung ; Kyoung, Yong-Soo ; Kim, Koung-Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 734~741
DOI : 10.3795/KSME-A.2003.27.5.734
This paper addresses the vibration mode shape Measurement technique utilizing a Continuous Scanning Laser Doppler Vibrometer (CSLDV). The continuous scanning capability is added to the conventional discrete Laser Doppler Vibrometer by reflecting the laser beams on the surface of the object using two oscillating mirrors. The bow scanning resulted from the proposed scanning method is eliminated by feedback control. The velocity output signal from the CSLDV is modulated to give the spatial velocity distribution in terms of coefficients which are obtained from the Fast Fourier Transformation of the time dependent velocity signal. Using the Chebyshev series from, the analysis of the vibration mode shape techniques for straight line scanning and 2 dimensional scanning are presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a cantilever and plate
Effect of Wall Thinned Shape and Pressure on Failure of Wall Thinned Nuclear Piping Under Combined Pressure and Bending Moment
Shim, Do-Jun ; Lim, Hwan ; Choi, Jae-Boong ; Kim, Young-Jin ; Kim, Jin-Won ; Park, Chi-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 742~749
DOI : 10.3795/KSME-A.2003.27.5.742
Failure of a pipeline due to local wall thinning is getting more attention in the nuclear power plant industry. Although guidelines such as ANSI/ASME B31G and ASME Code Case N597 are still useful fer assessing the integrity of a wall thinned pipeline, there are some limitations in these guidelines. For instance, these guidelines consider only pressure loading and thus neglect bending loading. However, most Pipelines in nuclear power plants are subjected to internal pressure and bending moment due to dead-weight loads and seismic loads. Therefore, an assessment procedure for locally wall thinned pipeline subjected to combined loading is needed. In this paper, three-dimensional finite element(FE) analyses were performed to simulate full-scale pipe tests conducted for various shapes of wall thinned area under internal pressure and bending moment. Maximum moments based on true ultimate stress(
u,t/) were obtained from FE results to predict the failure of the pipe. These results were compared with test results, which showed good agreement. Additional finite element analyses were performed to investigate the effect of key parameters, such as wall thinned depth, wall thinned angle and wall thinned length, on maximum moment. Also, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect on the maximum moment.
Usefulness of Creep Work-Time ]Relation for Determining Stress Intensity Limit of High-Temperature Components
Kim, Woo-Gon ; Lee, Kyung-Yong ; Ryu, Woo-Seog ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 750~757
DOI : 10.3795/KSME-A.2003.27.5.750
In order to determine creep stress intensity limit of high-temperature components, the usefulness of the creep work and time equation, defined as W
Profile Shift Coefficient of Gear System Considering Teeth Deflection
Park, Su-Jin ; Yoo, Wan-Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 758~763
DOI : 10.3795/KSME-A.2003.27.5.758
A profile shifted gear system was analyzed to select the optimum profile shift coefficient, which minimizes gear teeth deflection. Contact force and deformation overlap were calculated by means of FEM and contact theory. The deformation overlap is suggested for an effective indicator to represent the whole deformation of gear system. The optimum value of profile shift coefficients was presented with respect to the deformation of gear system.
Compliant Mechanism Design with Geometrical Advantage
Kim, Young-Gi ; Min, Seung-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 764~771
DOI : 10.3795/KSME-A.2003.27.5.764
To control the motion generated by a compliant mechanism the design method using specified geometrical advantage is proposed. The optimization problem is formulated to minimize the difference between the specified and the current geometrical advantage of a mechanism and topology optimization is applied to determine the layout of a mechanism. The results of several test problems including a displacement converter design and a gripper design are compared with a multi-criteria model and show that the design of an accurate compliant mechanism with specified geometrical advantage can be obtained.
Laser Processing Characteristic of Polystyrene Foam Pattern
Kim, Jae-Do ; Kang, Kyoung-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 772~778
DOI : 10.3795/KSME-A.2003.27.5.772
Polystyrene foam is easily melted and vapoured by heat, has a proper quality in the pattern manufacturing and has a low price. The objective of this study is to develop a rapid prototyping method fur polystyrene foam pattern manufacuring to use the eliminative pattern casting (EPC). Applying fur the rapid prototyping concept reversely, the unnecessary part of section is vapored away by heat source of laser beam. In order to examine the applicability between laser beam process and polystyrene foam material, the basic experiments such as hole, line, plane and contour process are carried out. With these results, various three-dimensional shape patterns are made and this rapid prototyping tool for polystyrene foam manufacturing.
Error Evaluation of Linearized Equation for a Servovalve in Hydraulic Control Systems
Kim, Tae-Hyung ; Lee, Ill-Yeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 779~788
DOI : 10.3795/KSME-A.2003.27.5.779
This study evaluates the approximation errors of the existing linearized equation for a servovalve nonlinear flowrate characteristic. At first, the errors are evaluated on flowrate/pressure characteristics diagrams. Subsequently, they are investigated with time response simulation results for several hydraulic control systems. To enable systematic evaluation of computational error, the authors propose three kinds of equations with restructured forms of the existing linearized equation. As results of the evaluations, it is ascertained that comparatively good computational accuracy can be achieved with the existing linearized equation when both an operating point for the linearized equation and operating range of the hydraulic system stay near the flowrate axis of the flowrate/pressure characteristics diagram. In addition, the results show that comparatively big computational error may occur when operating range of a hydraulic system stay apart from the flowrate axis of the flowrate/pressure characteristics diagram.
A New Linearized Equation for Modelling a Servovalve in Hydraulic Control Systems
Kim, Tae-Hyung ; Lee, Ill-Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 789~797
DOI : 10.3795/KSME-A.2003.27.5.789
In the procedure of the hydraulic control system design, a linearized approximate equation described by the first order terms of Taylor series has been widely used. Such a linearized equation is effective just near the operating point, However, pressure and flowrate in actual hydraulic systems are usually not confined near an operating point. This study suggests a new linearized flow equation for a servovalve as a modified form of the conventional linearized flow equation. Subsequently, a procedure to determine effective operating point for the new linearized equation is proposed. From the evaluations of time responses and frequency responses obtained from simulations for a hydraulic control system, the effectiveness of the new linearized equation and the procedure to determine effective operating point is confirmed.
Structural Optimization Using Tabu Search in Discrete Design Space
Lee, Kwon-Hee ; Joo, Won-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 798~806
DOI : 10.3795/KSME-A.2003.27.5.798
Structural optimization has been carried out in continuous or discrete design space. Methods for continuous design have been well developed though they are finding the local optima. On the contrary, the existing methods for discrete design are extremely expensive in computational cost or not robust. In this research, an algorithm using tabu search is developed fur the discrete structural designs. The tabu list and the neighbor function of the Tabu concepts are introduced to the algorithm. It defines the number of steps, the maximum number for random searches and the stop criteria. A tabu search is known as the heuristic approach while genetic algorithm and simulated annealing algorithm are attributed to the stochastic approach. It is shown that an algorithm using the tabu search with random moves has an advantage of discrete design. Furthermore, the suggested method finds the reliable optimum for the discrete design problems. The existing tabu search methods are reviewed. Subsequently, the suggested method is explained. The mathematical problems and structural design problems are investigated to show the validity of the proposed method. The results of the structural designs are compared with those from a genetic algorithm and an orthogonal array design.
Reduction of Surface Roughness and Build Time with Model Splitting Method for Multi-Jet Modeling 3D Printer Parts
Kim, Ho-Chan ; Lee, In-Tak ; Lee, Kyung-Chang ; Lee, Suk ; Lee, Seok-Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 807~814
DOI : 10.3795/KSME-A.2003.27.5.807
3D printers are widely used to verify the designs in the early stage of product development, and are required to have short build time. However, the build time is still too long for a quick design review for engineers. This research focuses on how to split the prototype in order to reduce the build time and improve surface roughness. In order to verify the feasibility of prototype splitting, the build time and the roughness have been experimentally measured for various parts and build orientations. Based on the experimental results an expert system was developed for splitting the original CAD mod el by using an efficient splitting method. It can recommend a splitting plane based on build time, surface roughness and the number of divided parts. It is shown that the model splitting reduces the build time significantly and improves surface quality wit bout rough surfaces where the support was removed.
Analysis of Aluminium Ring Rolling Process Using Thermo-Rigid-Plastic Finite Element Method
Koo, Sang-Wan ; Lee, Jong-Chan ; Yun, Su-Jin ; Kim, Nak-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 815~822
DOI : 10.3795/KSME-A.2003.27.5.815
The ring rolling process involves not only three-dimensional non-steady material flow and continuous change of radius and thickness of the ring workpiece but also heat transfer among workpiece, rolls and environment. In this study, deformation and heat transfer analyses were conducted by using the three-dimensional thermo-rigid-plastic finite element method. Three cases of plain ring rolling process were, respectively, simulated for the predictions of roll forces and the highest temperature zone during the aluminum process that ductile fracture often occurs. In addition, to prevent fishtail phenomena of the ring workpiece, axial rolls were used for this study.
New Fracture Toughness Test Method of Zircaloy-4 Nuclear Fuel Cladding
Oh, Dong-Joon ; Ahn, Sang-Bok ; Hong, Kwon-Pyo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 823~832
DOI : 10.3795/KSME-A.2003.27.5.823
To define the causes of cladding degradation which can take place during the operation of nuclear power plants, it is required to develop the new fracture toughness test of spent fuel cladding. The fracture toughness of Zircaloy-4 cladding was estimated using the recently developed KAERI embedded Charpy (KEC) specimen. Axially notched KEC specimens cut directly from unirradiated fuel claddings, were tested in a way similar to the standard toughness test method of a Single Edge Bending (SEB) specimen. The results of KEC fracture toughness test at room temperatures were discussed and compared with those of the previous other studies. In conclusions, even though the KEC fracture toughness test of nuclear fuel claddings was easier and more reliable than those developed earlier, the results from the cladding fracture tests were not the material characteristics but the specific fracture parameters which were deeply related to the specification of claddings. In addition, the phenomenon of a thickness yielding was not observed from the fracture surface. It was closely related to the fact that the plane strain condition of the KEC specimen was changed to the plane stress condition during crack advancing. It was also supported by the fractographic evidence that the formation of ductile dimples at the crack initiation became the similar appearance such as a quasi-cleavage after the sufficient crack advancing.
Stiffener Modeling for Rectangular Plates Employing the Dirac`s Delta Function and Modal Analysis
Hur, Sung-Chul ; Yoo, Hong-Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 833~839
DOI : 10.3795/KSME-A.2003.27.5.833
The effects of stiffeners on the modal characteristics of rectangular plates are investigated. A modeling method for the modal analysis of rectangular plates with stiffeners is presented. A mass density Dirac`s delta function is used to idealize the stiffeners mathematically. The equations of motion for the plates are derived and transformed into a dimensionless form. To confirm the accuracy of the method presented in this study, numerical result are obtained and compared to those of a commercial program. The mode shape variations due to some parameter variations are also exhibited.
Effect of Surface Treatment on Adhesive Strength Properties of Al/PC Adhesive Joints
Seo, Do-Won ; Yoon, Ho-Cheol ; Yoo, Sung-Chol ; Lim, Jae-Kyoo ; Lutz Dorn ;
Transactions of the Korean Society of Mechanical Engineers A, volume 27, issue 5, 2003, Pages 840~847
DOI : 10.3795/KSME-A.2003.27.5.840
The bonding of adhesive joints of adhesive joints is influenced by the surface roughness of the joining Parts. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, it is shown that surface treatment affects adhesive strength and durability of alumina/polycarbonate single-lap .joints, and leading speed affects tensile-shea strength of adhesive Joints. To evaluate effect of surface treatments on the adhesive strength, several surface treatment methods are used, that is, cleaning, grinding, SiC polishing and sand blasting. It is shown that an optimum value of the surface roughness exists with respect to the tensile-shea strength of adhesive joints. The adhesive strength shows linear relationship with the surface roughness and loading speed. And the mechanical removal of disturbing films of lubricants, impurities and oxides make adhesive strength increase significantly.