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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 24, Issue 12 - Dec 2000
Volume 24, Issue 11 - Nov 2000
Volume 24, Issue 10 - Oct 2000
Volume 24, Issue 9 - Sep 2000
Volume 24, Issue 8 - Aug 2000
Volume 24, Issue 7 - Jul 2000
Volume 24, Issue 6 - Jun 2000
Volume 24, Issue 5 - May 2000
Volume 24, Issue 4 - Apr 2000
Volume 24, Issue 3 - Mar 2000
Volume 24, Issue 2 - Feb 2000
Volume 24, Issue 1 - Jan 2000
Selecting the target year
Rapid Tooling by Using Metal Powder Reinforced Resin
Kim, Beom-Su ; Jeong, Hae-Do ; Bae, Won-Byeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 1~6
DOI : 10.22634/KSME-A.2000.24.1.1
As dies and molds have become more and more complicated in the recent years, the demand for lower cost and shorter production time is also growing stronger. Rapid prototyping and Tooling technologies are expected to be used for more rapid and lower cost tool fabrication. However the rapid tooling methods have not yet reached the level of application to the manufacturing of metallic dies and molds which require high dimensional accuracy. As the rapid tooling technology, there are the slurry casting, the powder casting, the direct laser sintering, and so on. Generally, in the slurry casting, the alumina powder and the water soluble phenol were mainly used. However, the mechanical properties of the phenol were not good enough to apply to molds directly. In this study, pure epoxy and two types of aluminium powder reinforced resin are applied to the slurry casting. The mechanical and thermal properties are better than phenol because the epoxy is the thermosetting resin. And mechanical characteristics such as shrinkage rate, hardness, surface roughness are measured for the sake of comparison. Metal powder reinforced resin molds are better than the resin tool form the viewpoint of shrinkage rate and hardness. Finally, it has been shown that the application possibility of this process is high, because the manufacturing time and cost savings are significant.
The Design of an Improved PID Controller by Using the Kalman Filter
Cha, In-Hyeok ; Gwon, Tae-Jong ; Han, Chang-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 7~15
DOI : 10.22634/KSME-A.2000.24.1.7
This paper suggests an auto-tuning I'll) control algorithm that uses the advantage of PID controller and improves the system performance. The PID gains being designed by th- conventional method are tuned through the plant parameter estimation. The Extended Kalman Filter is used for the estimation. It works as an observer and noise filter. Moreover, as the plant state and the uncertain parameter could be estimated simultaneously, the proposed algorithm is very useful in the tracking control of a system with uncertain parameter. The auto-tuning I'll) controller could maintain the system performance in the case that the plant parameters are uncertain or varying. The proposed control algorithm requires a correct estimation of the plant parameter. The controller stability and the performance is considered through the stability criteria and a servo motor model. The Kalman filter estimates the most sensitive plant parameter, which is determined by the sensitivity analysis.
Nonlinear Rotating Flows in Eccentric Cylinders
Sim, U-Geon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 16~28
DOI : 10.22634/KSME-A.2000.24.1.16
The steady rotating flows in eccentric annulus has been studied by a numerical method based on the spectral collocation method. The inner cylinder has a constant angular velocity while the outer on e is stationary. Flow between eccentric cylinders is of considerable technical importance as it occurs in journal bearings. In the present work, the governing equations for laminar flow are expressed as Navier-Stokes equations, including the non-linear convection terms. The solutions were utilized i, estimate the effects of the nonlinear terms on the load acting on the rotating cylinder. Based on the half and the full Sommerfeld methods, the load on the rotating cylinder is evaluated with eccentricity, by integrating the pressure and skin friction around the cylinder. The attitude angle and Sommerfeld reciprocal are calculated from the load. Also, the torque on the rotating inner cylinder was calculated. considering the skin friction. The attitude angle and Sommerfeld reciprocal are decreased with eccentricity. Viscous damping coefficient due to the skin friction becomes larger with decreasing the annular space. It is found the non-linear effects of the convection terms on the flow and the load are important. especially on the attitude angle, for relatively wide annular configurations however, the effects on those are minor for very narrow annular ones.
Effect of Ceramic Ball Inclusion on Densification of Metal Powder Compact
Park, Hwan ; Yu, Yo-Han ; Kim, Gi-Tae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 29~37
DOI : 10.22634/KSME-A.2000.24.1.29
The effect of a ceramic ball inclusion on densification behavior of a metal powder compact was investigated under cold isostatic pressing, pressureless sintering and hot isostatic pressing. To simulate those processes, proper constitutive models were implemented into a finite element program (ABAQUS). Measured density distributions of metal powder compacts were also compared with finite element results and showed the same trend with simulated results. Residual stress distributions were calculated by finite element analysis to study the effect of ceramic ball inclusions with different thermal expansion coefficients. The higher residual stress was observed in a metal powder compact when the difference between thermal expansion coefficients for a ceramic ball and metal powder became larger. Samples produced by Wing showed more uniform density distributions and lower residual stresses compared to those by sintering after cold isostatic pressing. For various sizes of ceramic ball inclusions, densification and deformation of powder compacts were also studied during hot isostatic pressing.
An Experimental Investigation of Limit Loads and Fatigue Properties of Spot Welded Specimens
Lee, Hyeong-Il ; Kim, Nam-Ho ; Lee, Tae-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 38~51
DOI : 10.22634/KSME-A.2000.24.1.38
The study on the mechanical behavior of a spot-welded specimen is largely divided into the quasi-static overload failure analysis and the fatigue failure prediction. The main issue in an overload analysis is to examine the critical loads, thereby providing a generalized overload failure criterion. As the welding spot forms a singular geometry of an external crack type, fatigue failure of spot-welded specimens can be evaluated by means of a fracture parameter. In this study, we first present the limit loads of 4 representative types of single spot-welded specimens in terms of the base metal yield strength and specimen geometries. Recasting the load vs. fatigue life relationships experimentally, obtained here, we then predict the fatigue life of spot-weld specimens with a single parameter denoted the equivalent stress intensity factor. This crack driving parameter is demonstrated to successfully describe the effects of specimen geometry and loading type in a comprehensive manner. The suggested fatigue life formula for a single spot weld can play a key, role in the design and assessment of spot-welded panel structures, in that the fatigue strength of multi-spots is eventually determined by the fatigue strength of each single spot.
Crack Size Determination Through Neural Network Using Back Scattered Ultrasonic Signal
Lee, Jun-Hyeon ; Choe, Sang-U ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 52~61
DOI : 10.22634/KSME-A.2000.24.1.52
The role of quantitative nondestructive evaluation of defects is becoming more important to assure the reliability and the safety of structure, which can eventually be used for residual life evaluation of structure on the basis of fracture mechanics approach. Although ultrasonic technique is one of the most widely used techniques for application of practical field test among the various nondestructive evaluation technique, there are still some problems to be solved in effective extraction and classification of ultrasonic signal from their noisy ultrasonic waveforms. Therefore, crack size determination through a neural network based on the back-propagation algorithm using back-scattered ultrasonic signals is established in this study. For this purpose, aluminum plate containing vertical or inclined surface breaking crack with different crack length was used to receive the back-scattered ultrasonic signals by pulse echo method. Some features extracted from these signals and sizes of cracks were used to train neural network and the neural network's output of the crack size are compared with the true answer.
Optimization of the Path of Inner Reinforcement for an Automobile Hood Using Design Sensitivity Analysis
Lee, Tae-Hui ; Lee, Dong-Gi ; Gu, Ja-Gyeom ; Han, Seok-Yeong ; Im, Jang-Geun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 62~68
DOI : 10.22634/KSME-A.2000.24.1.62
Optimization technique to find a path of an inner reinforcement of an automobile hood is proposed by using design sensitivity informations. The strength and modal characteristics of the automobile hood are analyzed and their design sensitivity analyses with respect to the thickness are carried out using MSC/NASTRAN. Based on the design sensitivity analysis, determination of design variables and response functions is discussed. Techniques improving design from design sensitivity informations are suggested and the double-layer method is newly proposed to optimize the path of stiffener for a shell structure, Using the suggested method, we redesign a new inner reinforcement of an automobile hood and compare the responses with the original design. It is confirmed that new design improved in the frequency responses without the weight increasement.
An Analysis of Flat-Crack in Homogeneous Anisotropic Solids Considering Non-Singular Term
Im, Won-Gyun ; Choe, Seung-Ryong ; An, Hyeon-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 69~78
DOI : 10.22634/KSME-A.2000.24.1.69
The one-parameter singular expression for stresses and displacements near a crack tip has been widely thought to be sufficiently accurate over a reasonable re ion for any geometry and loading conditions. In many cases, however subsequent terms of the series expansion are quantitatively significant, and so we now consider the evaluation of such terms and their effect on the predicted crack growth direction. For this purpose the problem of a cracked orthotropic plate subjected to a biaxial load is analysed. It is assumed that the material is ideal homogeneous anisotropic. BY considering the effect of the load applied parallel to the plane of the crack, the distribution of stresses and displacements at the crack tip is reanalyzed. In order to determine values for the angle of initial crack extension we employ the normal stress ratio criterion.
A Study on the Optimal Blank Design Using Sensitivity Analysis Method
Sim, Hyeon-Bo ; Son, Gi-Chan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 79~86
DOI : 10.22634/KSME-A.2000.24.1.79
In this study, a method of optimal blank design using the sensitivity analysis has been proposed. To get sensitivity a well-known commercial code PAM-STAMP has been used. In order to verify this method, formings of square cup, clover shaped cup and L shaped cup have been chosen as the examples. With the predicted optimal blank both computer simulation and experiment are performed. Excellent agreements are recognized between the numerical results and the target contour shapes. Through the investigation, the proposed systematic method of optimal blank design is found to be effective in the design of the deep drawing process.
Investigation of Formability of Cylindrical Cups in Warm Drawing of Stainless-Aluminum Clad Sheet Metal
Ryu, Ho-Yeon ; Kim, Yeong-Eun ; Kim, Jong-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 87~93
DOI : 10.22634/KSME-A.2000.24.1.87
Warm, forming technique which is one of the new forming technologies to improve formability of sheet metal is applied to the cylindrical cup drawing of stainless-aluminum. clad sheets. In experiments the temperature of die and blank holder is varied from room temperature to 18
, while the punch is cooled by circulation of coolant to increase the fracture strength of workpiece on the punch corner area. Test materials chosen for experiments are STS304-A1050-STS304, STS304-A1050-STS430 clad sheets and A1050-0 aluminum sheet. Teflon film as a lubricant is used on both sides of a workpiece. The limit drawing ratio as well as quality of drawn cups(distribution of thickness and hardness)are investigated and validity of warm drawing process is also discussed.
Development of a Computer Program for the Dynamic Analysis of Mount System with Flexible Bodies
Lee, Byeong-Hun ; Kim, Gyeong-U ; Jeong, U-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 94~102
DOI : 10.22634/KSME-A.2000.24.1.94
A computer program for three dimensional dynamic analysis of a mount system composed of rigid or flexible bodies and mount elements is developed. Cartesian coordinates and Euler parameters are used to specify the positions and orientations of the bodies. The equations of motion are formulated using Langrange equation and Langrange multiplier technique. The developed program includes routine, for inclined mount elements, several kinds of driving constrains, and external forces. The Static equilibrium analysis routine is also developed using iterative method.
Crack Length Estimation for Large Deformable Non-Linear Elastic Materials
Yang, Gyeong-Jin ; Gang, Gi-Ju ; Park, Sang-Seo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 103~109
DOI : 10.22634/KSME-A.2000.24.1.103
A method to measure the crack length in rubbery materials is described. Through dimensional analysis and experiments, an equation is derived to give the crack length as a function of the change of strain energy density in a region remote from the crack. The function is provided in a form of separated terms of loading and material, the validity of which is experimentally proved using separation parameters.
The Geometrical Mode Analysis of an Elastically Suspended Rigid Body with Planes of Symmetry
Dan, Byeong-Ju ; Choe, Yong-Je ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 110~117
DOI : 10.22634/KSME-A.2000.24.1.110
Vibration modes obtained from a modal analysis can be better explained from a screw theoretical standpoint. A vibration mode can be geometrically interpreted as a pure rotation about the vibration center in a plane and as the twisting motion on a screw in a three dimensional space. This paper, presents the method to diagonalize a spatial stiffness matrix by use of a parallel axis congruence transformation. It also describes that the stiffness matrix diagonalized by a congruence transformation, can have the planes of symmetry depending on the location of the center of elasticity. For a plane of symmetry, any vibration mode can be expressed by the axis of vibration. Analytical solutions for the axis of vibration has been derived.
A Steerable Quadruped Walking Robotic System with Legs of a Closed-Chain Mechanism
Im, Seung-Cheol ; Jeong, Hae-Seong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 118~123
DOI : 10.22634/KSME-A.2000.24.1.118
Most quadruped walking robots under current research are individually controlling every joint ic make them step or walk according to an integrated strategy. Such methods are characterized by at least one pair of an actuator and a sensor installed per each 'oint so that the robots weigh execssively and move inefficiently in terms of energy expenditure. In addition, the task of controlling all the joints simultaneously is quite complex and prone to destabilize the robot motion. These respects keep the existing walking robots away from realistic applications such as transportation even if they have potentially, outstanding adaptability to swamps or uneven terrains as opposed to wheeled vehicles. So, this paper presents a new conceptual quadruped robot developed to walk and steer only with a minimal number of actuators owing to a closed-chain mechanism. To prove its actual performance including the adaptability to various types of terrains. experiments are done with the mammal-type prototype. And. it is also shown that the same concept can be easily extended to carry out different gait forms. for instance, that of spiders only with minor modifications.
Analysis on Noise of Automotive Alternator Considering the Number of Stator Slots
Song, Jin-Seo ; Kim, Gwang-Jun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 126~133
DOI : 10.22634/KSME-A.2000.24.1.126
Noise of automotive alternators can be classified into mechanical noise, aerodynamic noise and electro-magnetic noise. which is the same as for electric motors. Previous studies show that the elect ro-magnetic noise takes a maw peak at the rotating frequency multiplied by the number of stator slots. It has not been proved clearly so far, however, that the major peak is wholely due to the stator slots. On the contrary it is well known that noise of motors. which has a mechanism similar to the alternator except that the number of stator slots in automotive alternators is in gene\integer multiple of that of rotor segments, is closely related to the number of rotor slots. Therefore, the statement that only the stator slots is the source of the major peak in the noise spectrum of alternators is suspicious although not easy, to show theoretically, that the statement is incorrect. In this paper. effects of the stator slots on the noise in an automotive alternator are experimentally investigated by intentionally modifying the number of stator slots in such a way that the number of the states is not an integer multiples of the rotor slots. It is shown that both the stator slots are not so much influential as the rotor slots and claimed that the major peak in the noise spectrum of conventional alternators is due to superposition of a component caused by the stator and a higher harmonic component caused by the rotor
Development of High Speed Train Performance Simulation Software
Jeong, Gyeong-Ryeol ; Kim, Sang-Heon ; Park, Su-Hong ; Lee, Jang-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 134~143
DOI : 10.22634/KSME-A.2000.24.1.134
A train performance simulation (TPS) software is a computer program that simulates the operation of a train system over a specified railway route and it is widely used in railroad operation and research applications. Numerical and graphical results from the simulation software, which is developed in this study, provide information on such performance variables as travel time. running speed, energy consumption at a specific time interval and in overall service time as the train moves along the route. Three types of input data are required for a computer simulation: track information, train information, and running conditions. The simulation of train performance starts with several simple mathematical models including train configuration. traction efforts, running resistance. and braking requirements. Based on the basic specifications of Korean High Speed Railway, System. this study, puts a focus on the estimation and assessment of train performance comparing. the specific train configurations of KEST20/11. CPLE20/10. PROP20/10, which are proposed from the previous G7 projects.
The 3D Surface Crack-Front Constraints in Welded Joins
Lee, Hyeong-Il ; Seo, Hyeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 144~155
DOI : 10.22634/KSME-A.2000.24.1.144
초록 The validity, of a single parameter such as stress intensity, factor K or J-integral in traditional fracture mechanics depends strongly on the geometry, and loading condition. Therefore the second parameter like T-stress measuring the stress constraint is additionally needed to characterize the general crack-tip fields. While many, research works have been done to verify, the J-T description of elastic-plastic crack-tip stress fields in plane strain specimens, limited works (especially. for bimaterials) have been performed to describe the structural surface crack-front stress fields with the two parameters. On this background, via detailed three dimensional finite element analyses for surface-cracked plates and straight pipes of homogeneous materials and bimaterials under various loadings, we investigate the extended validity or limitation of the two parameter approach. We here first develop a full 3D mesh generating program for semi-elliptical surface cracks, and calculate elastic T-stress from the obtained finite element stress field. Comparing the J-T predictions to the elastic-plastic stresses from 3D finite element analyses. we then confirm the extended validity of fracture mechanics methodology based on the J-T two parameters in characterizing the surface crack-front fields of welded plates and pipes under various loadings.
Stress Corrosion Crack Rate of STS 304 Stainless Steel in High Temperature Water
Kim, Jeong-Gi ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 156~162
DOI : 10.22634/KSME-A.2000.24.1.156
Sensitized STS 304 stainless steel crack growth rate(CGR) in high temperature water was investigated under trapezoidal wave loading test using fracture mechanics techniques. The CGR, due to stress corrosion cracking(SCC), were systematically measured as a function of the stress intensity factor and stress. holding time under trapezoidal wave loading. In high temperature water, CGR was enhanced by a synergistic effects in combination with an aggressive environment and mechanical damage. The CGR,
was basically described as a summation of the environmentally assisted crack growth rate
and fatigue crack growth rate in air $(da/dN)air,. The CGR,
, increased linearly with increasing stress holding time. The CGR,
decreased linearly with increasing stress holding time. Fracture surface mode varied from trans-granular cracking to inter-granular cracking with increasing stress holding time.
Numerical Analysis on the Signal Characteristics for Scattered Far-field of Ultrasonic SH-Wave by the Internal Cavity
Lee, Jun-Hyeon ; Lee, Seo-Il ; Park, Yun-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 163~172
DOI : 10.22634/KSME-A.2000.24.1.163
초록 In this study, the scattered far-field due to a cavity embedded in infinite media subjected to the incident SH-wave was calculated by the boundary element method. The effects of cavity shape and di stance between internal cavity and internal point in infinite media were considered. The scattered far-field of the frequency domain was transformed into the signal of the time domain by using the Inverse Fast Fourier Transform(IFFT). It was found that the amplitude of scattered signal in time domain decreased with the increase of the distance between the detecting points of ultrasonic scattered field and the center of internal cavity in media. In addition, the time delay was clearly found in time domain waveform as the distance between the detecting points of ultrasonic scattered field and the center of internal cavity was gradually increased
Efficient Algorithm for the Real-time Generation of Reflection Lines
Gang, Ju-Yeop ; Lee, Geon-U ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 173~181
DOI : 10.22634/KSME-A.2000.24.1.173
Depending upon the method of the surface generation and the quality of the boundary curves provided, the resulting surfaces may have global or local irregularities in many cases. Thus it would be necessary for the designer to evaluate the surface quality and to modify the surface. This capability is very important because the defect of the surface requires the rework of the dies that causes a big loss in cost and delivery time. To simulate the reflection line test in the actual production line, a faster generation algorithm is presented. Among., various surface interrogation methods using reflection lines, Blinn-Newell type of reflection mapping is applied to generate reflection lines on the trimmed NURBS surface. The generation of reflection lines is formulated as a surface-plane intersection problem, and solved by surface-contouring techniques. In addition, a modified reflection map is proposed to eliminate the discontinuity of reflection lines due to the configuration of the reflection map. A fast reflection line algorithm is developed utilizing an efficient traced contouring technique, and proved to be well suited for real-time quality-assessment task.
A Study on the Application of the Curvature Theory of Ruled Surfaces for the Development of Five-Axis NC Machine Real-Time Control Algorithm
Kim, Jae-Hui ; Yu, Beom-Sang ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 182~189
DOI : 10.22634/KSME-A.2000.24.1.182
This paper presents the real time control method of 5-axis NC machine for high precision and productivity based on the curvature theory, of a ruled surface. The trajectory, of NC machine is described by, way of a ruled surface generated by the points on part surface and tool axis direction vector. The curvature theory, of a ruled surface is then applied to deter-mine the motion parameters of the 5-axis machine for control. The controller computes position, orientation, and differential motion parameters of the tool in each sampling period. The real-time approach produces smoother surfaces and requires substantially less machining time compared to conventional off-line approaches. The propose real-time control method based of the curvature theory of a ruled surface may give new methodology of precision 5-axis machine control.
Crack Identification Using Optimization Technique
Seo, Myeong-Won ; Yu, Jun-Mo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 190~195
DOI : 10.22634/KSME-A.2000.24.1.190
It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the location and depth of the crack. To identify the location and depth of a crack in a structure. Nikolakopoulos et. al. used the intersection point of the superposed contours that correspond to the eigenfrequency caused by the crack presence. However the intersecting point of the superposed contours is not only difficult to find but also incorrect to calculate. A method is presented in this paper which uses optimization technique for the location and depth of the crack. The basic idea is to find parameters which use the structural eigenfrequencies on crack depth and location and optimization algorithm. With finite element model of the structure to calculate eigenfrequencies, it is possible to formulate the inverse problem in optimization format. Method of optimization is augmented lagrange multiplier method and search direction method is BFGS variable metric method and one dimensional search method is polynomial interpolation.
Automatic Generation of Tetrahedral Meshes from General Sections
Chae, Su-Won ; Lee, Gyu-Min ; Sin, Sang-Yeop ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 196~205
DOI : 10.22634/KSME-A.2000.24.1.196
Computed Tomography (CT), Nuclear Magnetic Resonance Imaging (MR1) and some ultrasound techniques make it possible to obtain cross sections of human body or mechanical parts. In CAD system, a series of sectional surfaces can also be obtained from solid models of 3D objects. In this paper we introduce a tetrahedral meshing algorithm from these series of general sections using basic operators. In this scheme. general sections of three-dimensional object are triangulated first and side surfaces between two sections are triangulated by the use of tiling process. Finally tetrahedral meshing process is performed on each layer of 3D objects, which is composed of two general sections and one side surface.
Development of CANDU Pressure Tube Integrity Evaluation System;Its Application to Sharp Flaw and Blunt Notch
Gwak, Sang-Rok ; Lee, Jun-Seong ; Kim, Yeong-Jin ; Park, Yun-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 206~214
DOI : 10.22634/KSME-A.2000.24.1.206
The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and it's containment vessel. If a flaw is found during the periodic inspection from the pressure tube s. the integrity evaluation must be carried out. and the safety requirements must be satisfied for continued service. In order to complete the integrity evaluation, complicated and iterative calculation procedures are required. Besides, a lot of data and knowledge for the evaluation are required for the entire: integrity evaluation process. For this reason. an integrity evaluation system, which provides efficient of evaluation with the help of attached databases, was developed. The developed system was built on the basis of ASME Sec. XI and FFSG(Fitness For Service Guidelines for zirconium alloy pressure tubes in operating CANDU reactors) issued by the AECL, and covers the delayed hydride cracking(DHC). This system does not only provide various databases including the 3-D finite element analysis results on pressure tubes, inspection data and design specifications but also is compatible with other commercial database software. In order to verify the developed system, several case studies have been performed and the results were compared with those from AECL. A good agreement was observed between those two results.
Development of an Optimization Technique for Robust Design of Mechanical Structures
Jeong, Do-Hyeon ; Lee, Byeong-Chae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 215~224
DOI : 10.22634/KSME-A.2000.24.1.215
In order to reduce the variation effects of uncertainties in the engineering environments, new robust optimization method, which considers the uncertainties in design process, is proposed. Both design variables and system parameters are considered as random variables about their nominal values. To ensure the robustness of performance function, a new objective is set to minimize the variance of that function. Constraint variations are handled by introducing probability constraints. Probability constraints are solved by the advanced first order second moment (AFOSM) method based on the reliability theory. The proposed robust optimization method has an advantage that the second derivatives of the constraints are not required. The suggested method is examined by solving three examples and the results are compared with those for deterministic case and those available in literature.
Development and Implementation of Algebraic Elimination Algorithm for the Synthesis of 5-SS Spatial Seven-bar Motion Generator
Lee, Tae-Yeong ; Sim, Jae-Gyeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 225~231
DOI : 10.22634/KSME-A.2000.24.1.225
Dimensional synthesis of planar and spatial mechanisms mostly requires solution-finding, procedure for a system of polynomial equations. In case the system is nonlinear, numerical techniques like Newton-Raphson are often used. But there are no logical ways for finding all possible solutions in such iterative methods. In this paper, algebraic elimination is used to get all solutions for the synthesis of 5-SS spatial mechanism with seven prescribed positions. The proposed algorithm is more suitable for computer implementation and takes less time than existing one. Two numerical examples are given to demonstrate the implemented algorithm.
Dynamic Stability of a Free-Free Beam with a Tip Rigid Body under a Controlled Pulsating Thrust
Ryu, Bong-Jo ; Lee, Gyu-Seop ; Seong, Yun-Gyeong ; Choe, Bong-Mun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 232~239
DOI : 10.22634/KSME-A.2000.24.1.232
The paper describes the parametric instability of free-free beams subjected to a controlled pulsating follower force. The beam has a tip rigid body not a mass point, and the direction of pulsating follower force is controlled by the direction control sensor. Equations of motion are derived by Hamilton's principle and the instability regions are obtained by finite element formulation. The effects of magnitude, rotary inertia, the distance between free end of the beam and the center of gravity of the rigid body on the instability types and regions are investigated by the change of the constant and periodic part of the follower force.
A Global Optimization Algorithm Based on the Extended Domain Elimination Method
O, Seung-Hwan ; Lee, Byeong-Chae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 240~249
DOI : 10.22634/KSME-A.2000.24.1.240
An improved global optimization algorithm is developed by extending the domain elimination method. The concept of triangular patch consists of two or more trajectories of local minimizations is introduced to widen the attraction region of the domain elimination method. Using the an-]c between each of three vertices of the patch and a design point, we measure the proximity, between the design point and the patch. With the Gram-Schimidt orthonormalization, this method can be extended to general n-dimensional problems. We code the original domain elimination algorithm and a patch-based algorithm. Then we compare the performance of two algorithms. Through the well-known example problems. the algorithm using patch is shown to be superior to the original domain elimination algorithm in view of computational efficiency.
Reinforcing Characteristics on Volume and Shape of Ductile Short-Fiber in Brittle Matrix Composites
Sin, Ik-Jae ; Lee, Dong-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 250~258
DOI : 10.22634/KSME-A.2000.24.1.250
The reinforcing effects of ductile short-fiber reinforced brittle matrix composites are studied by, measuring flexural strength, fracture toughness and impact energy as functions of fiber volume fraction and length. The parameters of fracture mechanics, K and J are applied to assess fracture toughness and bridging stress. It is found that fracture toughness is greatly, influenced by the bridging stress ill which fiber pull-out is occur. For the reinforcing effects as functions of fiber volume fraction(
= 1, 2, 3 %) and length(L = 3, 6. 10cm), the flexural strength is maximum at
= 1% and both fracture toughness.
Prediction of the Onset of Failures in Composite Laminated Plates with Uncertain Material Properties
Kim, Tae-Uk ; Sin, Hyo-Cheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 259~268
DOI : 10.22634/KSME-A.2000.24.1.259
Because of their superior mechanical properties to isotropic materials, composite laminated plates are used for many structural applications that require high stiffness-to-weight and strength-to-weight ratios. Composite materials are always subject to a certain amount of scatter in their elastic moduli, but most analyses and designs with the materials are usually conducted by assuming that the material properties are fixed and have no uncertainties. In this paper, a convex modeling approach is introduced to take account of such uncertainties in elastic moduli. It is used with the finite element method to predict the onset of failures in composite laminated plates subject to in-plane loading. Numerical results show that failures begin at the smaller load when the uncertainties of elastic moduli considered and therefore, such uncertainties should be considered at the design stage for the safety and reliability of the structures.
Characteristics of Herringbone-Grooved Hydrodynamic Bearing and Scanner Motor for Laser Beam Printer
Jeong, Seong-Hun ; Lee, Yeong-Je ; Jeong, Dae-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 1, 2000, Pages 269~274
DOI : 10.22634/KSME-A.2000.24.1.269
Frictions and electrical contact voltages of the herringbone-grooved hydrodynamic bearing(HHB) were 9, measured to use in a laser scanner motor. This bearing with varying loads, speeds, oil viscosity, and radial clearances successfully operated up to 28,000rpm and 0.5N. Experimental results under various environments confirmed that this bearing had excellent performance with low friction force, and operated without contact between shaft and sleeve.