Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Transactions of the Korean Society of Mechanical Engineers A
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
Editor in Chief :
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
Accurate Assembly and Concurrent Design of Airframe Structures
Park, Mun-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 811~823
DOI : 10.22634/KSME-A.2000.24.4.811
In design and manufacturing airframe structures which are composed of a lot of sub-assemblies and large complex profile shapes it is difficult to reduce so called hardware variations. Accordingly cost increasing factors for manufacturing airframe parts are much more than other machine parts because of the variability of fabricated details and assemlies. To improve cost and quality, accurate assembly methods and DPD techniques are proposed in this paper which are based upon using CAD/CAM techniques, the concept of KC's and the coordinated datum and index throughout the design, tooling, manufacturing and inspection. The proposed methods are applied to produce fuselage frame assemblies and related engineering aspects are described regarding the design of parts and tools in the context of concurrent digital definition. First articles and consequent mass production of frame assemblies shows a great improvement of the process capability ratio from 0.7 by the past processes to 1.0 by the proposed methods in addition to the cost reduction due to the less number of tools, reduced total assembly times and the space compaction needed by massive inventory. The need to achieve better Cpk, however, and future studies to be investigated will be addressed briefly.
Change of Glass Transition Temperature of PETG Containing Gas
Cha, Seong-Un ; Yun, Jae-Dong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 824~829
DOI : 10.22634/KSME-A.2000.24.4.824
The industries use polymer materials for many purposes because they have many merits. But these materials' costs take up too much proportion in overall cost of products that use these materials as their major material. So it is very economical for polymer industries to reduce these costs. Microcellular foaming process appeared in 1980's to solve this problem and it proved to be quite successful. This process uses inert gases such as CO2, N2. As these gases are dissolved into polymer matrices. many properties are changed. Glass transition temperature is one of these properties. DSC, DMA are devices that measures this temperature, but these are not sufficient to measure the temperature of polymer containing gas. In this paper, we devised a new tester that uses magnetism. We used this device to acquire data of the change of glass transition temperature and made Cha-Yoon model that can predict the change of glass transition temperature. Using this model, the change of this temperature can be estimated as a function of weight gain of gas. Cha-Yoon model proved that Chow's model is inappropriate to predict the change of glass transition temperature of polymer matrices containing gas.
A Study on Stress Intensity Factors and Dislocation Emission via Molecular Dynamics
Choe, Deok-Gi ; Kim, Ji-Un ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 830~838
DOI : 10.22634/KSME-A.2000.24.4.830
The paper addresses an application of molecular dynamics technique for fracture mechanics. Molecular dynamics simulation is an atomistic approach, while typical numerical methods such as finite element methods are macroscopic. Using the potential functions, which express the energy of a molecular system, a virtual specimen with molecules is set up and the trajectory of every molecule can be calculated by Newton's equation of motion. Several three-dimensional models with various types of cracks are considered. The stress intensity factors, the sizes of plastic zone as well as the dislocation emission are sought to be compared with the analytical solutions, which result in good agreement.
Modal Analysis and Velocity Control of Bowl Parts Feeder Activated by Piezoactuators
Lee, Dong-Ho ; Choe, Seung-Bok ; Kim, Jae-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 839~847
DOI : 10.22634/KSME-A.2000.24.4.839
This paper presents modal analysis and mean conveying velocity (M.C.V.) control of bowl parts feeder activated by piezoactuators. Bowl parts feeders are being widely used in many industry fields for automatic assembly line. In general, the electromagnet has been and being used as exciting actuator of these vibratory bowl feeders. However, because of complexity of its mechanism and limited capability of the electromagnet actuator, there exist various impending problems such as severe noise, nonlinear motion of parts, passive characteristics and so forth. As one of solutions for these problems, piezoelectric actuators as new actuating technology have been proposed recently to excite the bowl parts feeder. In this paper, modal analysis of the proposed model has been performed to examine the modal characteristics of the model by using commercial FEM software and modeling with respects to MCV is constructed. Finally, MCV of the parts is to be controlled to track the desired one with PID controller.
Regrasp Planner Using Look-up Table
Jo, Gyeong-Rae ; Lee, Jong-Won ; Kim, Mun-Sang ; Song, Jae-Bok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 848~857
DOI : 10.22634/KSME-A.2000.24.4.848
A pick-and-place operation in 3-dimensional environment is basic operation for human and multi-purpose manipulators. However, there may be a difficult problem for such manipulators. Especially, if the object cannot be moved with a single grasp, regrasping, which can be a time-consuming process, should be carried out. Regrasping, given initial and final pose of the target object, is a construction of sequential transition of object poses that are compatible with two poses in the point of grasp configuration. This paper presents a novel approach for solving regrasp problem. The approach consists of a preprocessing and a planning stage. Preprocessing, which is done only once for a given robot, generates a look-up table which has information of kinematically feasible task space of end-effector through all the workspace. Then, using the table planning automatically determines possible intermediate location, pose and regrasp sequence leading from the pick-up to put-down grasp. Experiments show that the presented is complete in the total workspace. The regrasp planner was combined with existing path
Application of Acoustic Emission Technique for On-Line Monitoring of Quench in Racetrack Superconducting Coil at Cryogenic Environment
Lee, Min-Rae ; Gwon, Yeong-Gil ; Lee, Jun-Hyeon ; Son, Myeong-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 858~865
DOI : 10.22634/KSME-A.2000.24.4.858
It is well recently recognized that quench is one of the serious problems for the integrity of superconducting magnets, which is mainly attribute to the rapid temperature rising in the magnet due to some extrinsic factors such as conductor motion, crack initiation etc. In order to apply acoustic emission(AE)echnique effectively to monitor and diagnose superconducting magnets, it is essential to identify the sources of acoustic emission. In this paper, an acoustic emission technique has been used to monitor and diagnose quenching phenomenon in racetrack shaped superconducting magnets at cryogenic environment of 4.2K. For these purposes special attention was paid to detect AE signals associated with the quench of superconducting magnets. The characteristics of AE parameters have been analyzed by correlating with quench number, winding tension of superconducting coil and charge rate by transport current. In addition, the source location of quench in superconducting magnet was also discussed on the basis of correlation between magnet voltage and AE energy.
Design of Siding Mode Controller with Peturbation Estimation
Kim, Nak-In ; Lee, Jong-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 866~873
DOI : 10.22634/KSME-A.2000.24.4.866
Sliding mode control(SMC) incorporated with perturbation compensation is developed here to reduce the low-frequency tracking error in the presence of wide-band frequency perturbations for a nonlinear dynamic system. The control scheme is designed for estimation of low frequency perturbations with employment of the Time Delay Control and low-pass filter. It is shown that the SMC with perturbation compensation is far superior to the conventional SMC in tracking control of the dynamic systems under model uncertainties and external disturbance conditions.
A Study on Detecting Flaws Using DC Potential Drop Method
Bae, Bong-Guk ; Seok, Chang-Seong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 874~880
DOI : 10.22634/KSME-A.2000.24.4.874
In this paper, a DC potential drop measurement system was used to find the position of the flaw on a simple thin plate. Four-point probe test was evaluated and used for this study. In the four-point probe test, the more distance between current pins provides the more measurable scope, the less voltage difference, and the more voltage difference rate. In the other hand, the more distance between voltage pins provides the less voltage difference and the less voltage difference rate. An optimized four-point probe was applied to measure the relation between voltage and the relative position of flaw to the probe. The Maxwell 21) simulator was used to analyze the electromagnetic field, and it showed that the analytical result was similar to the experimental result within 11.4% maximum error.
Offset Slider-Rocker Linkage Synthesis Using Transmission Angles as Synthesis Parameters
Gwon, Seong-Gyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 881~893
DOI : 10.22634/KSME-A.2000.24.4.881
An analytical synthesis technique for offset slider-rocker 4-bar linkages is devised where transmission angles are used as essential synthesis parameters. Finding the location where both the maximum and the minimum transmission angles arise leads to establishing the algorithm for limiting transmission angles of the slider-rocker linkage which has different offsets according to the direction of the slider. Position analysis by the algorithm gives formula for the dimensional synthesis for the linkage. Application to examples shows that the algorithm and the formula yield proper slider-rocker linkages with regard to limiting transmission angles to the maximum value.
Optimization of Chassis Frame by Using D-Optimal Response Surface Model
Lee, Gwang-Gi ; Gu, Ja-Gyeom ; Lee, Tae-Hui ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 894~900
DOI : 10.22634/KSME-A.2000.24.4.894
Optimization of chassis frame is performed according to the minimization of eleven responses representing one total frame weight, three natural frequencies and seven strength limits of chassis frame that are analyzed by using each response surface model from D-optimal design of experiments. After each response surface model is constructed form D-optimal design and random orthogonal array, the main effect and sensitivity analyses are successfully carried out by using this approximated regression model and the optimal solutions are obtained by using a nonlinear programming method. The response surface models and the optimization algorithms are used together to obtain the optimal design of chassis frame. The eleven-polynomial response surface models of the thirteen frame members (design factors) are constructed by using D-optimal Design and the multi-disciplinary design optimization is also performed by applying dual response analysis
A Study on the Coated Characteristics of Ceramic Tools
Lee, Myeong-Je ; Im, Hong-Seop ; Yu, Bong-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 900~906
DOI : 10.22634/KSME-A.2000.24.4.900
Ceramic, PCD and CBN tools are available for the difficult-to-cut-materials such as hardened carbon tool steel, stainless steel, Inconel 718 and etc. Ceramic tools are likely to be chipped and abruptly broken before the appearance of normal wear in turning. Ceramic tools are suitable for continuous in turning, not for intermittent in milling. In this study, TiN/TiCN multi-layer coated ceramic tools were found to restrain the chipping, breaking and early fracture and to increase the critical cutting speed owing to TiN/TiCN multi-layer coating in Arc Ion Plating of PVD method.
Finite Element Modeling and Mechanical Analysis of Orthodontics
Heo, Gyeong-Heon ; Cha, Gyeong-Seok ; Ju, Jin-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 907~915
DOI : 10.22634/KSME-A.2000.24.4.907
The movement of teeth and initial stress associated with the treatment of orthodontics have been successfully studied using the finite element method. To reduce the effort in preprocessing of finite element analysis, we developed two types of three-dimensional finite element models based on the standard teeth model. Individual malocclusions were incorporated in the finite element The movement of teeth and initial stress associated with the treatment of orthodontics have been successfully studied using the finite element method. To reduce the effort in preprocessing of finite element analysis, we developed two types of three-dimensional finite element models based on the standard teeth model. Individual malocclusions were incorporated in the finite element models by considering the measuring factors such as angulation, crown inclination, rotation and translations. The finite element analysis for the wire activation with a T-loop arch wire was carried out. Mechanical behavior on the movement and the initial stress for the malocclusion finite element model was shown to agree with the objectives of the actual treatment. Finite element models and procedures of analysis developed in this study would be suitably utilized for the design of initial shape of the wire and determination of activation displacements.
Damage Detection in a Bean Via the Wavelet Transform of Mode Shapes
Lee, Yong-Uk ; Kim, Yun-Yeong ; Lee, Ho-Cheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 916~925
DOI : 10.22634/KSME-A.2000.24.4.916
Perhaps, this is the first attempt which applies the wavelet transform to the fundamental vibration mode for damage detection in a beam. Contrary to most existing detection methods on mode shapes, the present method directly works only with the fundamental mode of a damaged beam: no vibration mode shape of a undamaged beam is necessary. Applying the concept of vanishing moments of wavelet functions, we show that wavelet functions are effective damage detectors. Both numerical and experimental results confirm the effectiveness of the present method
Modeling of the Powertrain System and the Vehicle Body for the Analysis of the Driving Comfortability
Park, Jin-Ho ; Lee, Jang-Mu ; Jo, Han-Sang ; Gong, Jin-Hyeong ; Park, Yeong-Il ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 926~936
DOI : 10.22634/KSME-A.2000.24.4.926
Actual and strict definition of the shift quality for the powertrain system equipped an automatic transmission must be understood through the acceleration change of the vehicle body, which the driver directly feels as a shift shock. For this reason, it is necessary to concurrently analyze the characteristics of the powertrain system and the vehicle body. This paper presents the mathematical model of the vehicle body, which is based on the equivalent lumped system, to append to the developed model of the powertrain system. The concept of tire slip is also introduced for the experimental relationship between tire/road and driving force. Using the developed dynamic simulation programs, shift transients characteristics are analyzed. Theoretical results are compared with experimental ones from real car tests in equal conditions in order to prove the validity of presented model. In these tests, the system to measure the vehicle acceleration is used with various speeds and engine throttle sensors. It is expected that the presented modeling techniques can provide good predictions of the vehicle driving comfortability.
Machined Surface Inspection Based on Surface Fairing on the Machine Tool
Lee, Se-Bok ; Kim, Gyeong-Don ; Jeong, Seong-Jong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 937~945
DOI : 10.22634/KSME-A.2000.24.4.937
The assessment of machined surface is difficult because the freeform surface must be evaluated by surface fairness as well as dimensional accuracy. In this study, the machined freeform surface is modeled by interpolating the data measured on the machine tool into the mathematical continuous surface, and then the surface model is improved with the parameterization to minimize surface fairness. The accuracy reliability of the measured data is confirmed through compensation of volumetric errors of the machine tool and of probing errors. Non-uniform B-spline surface interpolation method is adopted to guarantee the continuity of surface model. Surface fairness is evaluated with the consideration of normal curvature on the interpolated surface. The validity and usefulness of the proposed method is examined through computer simulation and experiment on the machine tool.
Stress Analysis of the Hard Disk with Overcoating Layer under the Contact with Head
Lee, Gang-Yong ; Yang, Ji-Hyeok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 946~954
DOI : 10.22634/KSME-A.2000.24.4.946
The purposes of the paper are to calculate stresses and strains of the disk with overcoating layer rotating quickly under normal loading and shear loading by contacting with head and to present material properties preventing the delamination between the disk and overcoating layer. The hard disk is modeled as two-layered disk composed with overcoating layer and the rest layers and the loading onto the disk is assumed axisymmetric. Solutions to equilibrium equations and compatibility equations are derived with the form of polynimial and Bessel function and coefficients satisfying boundary conditions are obtained differently for the case of body force, normal force and shear force. The risk of delamination are investigated for us to calculate the differences of strains at the interface between the disk and overcoating layer and the material properties preventing delamination are presented by calculating the differences of strains according to Young's modulus and density of disk.
The Observation of Fatigue Striations for Aluminum Alloy by Atomic Force Microscope(AFM)
Choe, Seong-Jong ; Gwon, Jae-Do ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 955~962
DOI : 10.22634/KSME-A.2000.24.4.955
Scanning Probe Microscope (SPM) such as Scanning Tunneling Microscope (STM) and Atomic Force Microscope (AFM) was shown to be the powerful tool for nano-scale characterization of a fracture surface . AFM was used to study cross sectional profiles and dimensions of fatigue striations in 2017-T351 aluminum alloy. Their widths (SW) and heights (SH) were measured from the cross sectional profiles of three-dimension AFM images. The following results that will be helpful to understand the fatigue crack growth mechanism were obtained. (1) Coincidence of the crack growth rate with the striation width was found down to the growth rate of 10-5 mm/cycle. (2) The relation of SH=0.085(SW)1.2 was obtained. (3) The ratio of the striation height to its width SH/SW did not depend on the stress intensity factor range K and the stress ratio R. (4) Not only the SW but also the SH changed linearly with the crack tip opening displacement (CTOD) when plotted in log-log scale. From these results, the applicability of the AFM to nano-fractography is discussed
Stress Analysis of Epitrochoidal Gerotor for Hydraulic Motor
Kim, Du-In ; Choe, Dong-Hun ; An, Hyo-Seok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 963~971
DOI : 10.22634/KSME-A.2000.24.4.963
Gerotor is a planar mechanism consisting of a rotor and lobes which form a closed space, namely a chamber. As active contact points between a rotor and lobes are subjected to very high contact stresses, wear in one or both of the rotor and lobe cannot be avoided. Therefore, in the design of Gerotor used in hydraulic motors a compromise between high torque output and contact stress is of great importance and a thorough analysis of design parameters should be conducted to achieve this compromise. In this study, a contact point is modelled as a linear spring in consideration of equivalent curvature to analyze the contact stress. As the contact stress calculation in this problem is a statically indeterminate type, a numerical iterative scheme has been adopted to obtain the solution. To fully understand the influence of design parameters on the contact stress, the relationship between pressure force, equivalent curvature, contact force and contact stress are analyzed. It is shown that the equivalent curvature of the contact point is a dominant factor that affects the maximum contact stress.
Analysis of the Ultrasonic Beam Profile Due to Variation of the Inter-Element Spacing for the Phased Array Transducer
Choe, Sang-U ; Lee, Jun-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 972~981
DOI : 10.22634/KSME-A.2000.24.4.972
The phased array transducer has two distinct advantages. One is rapid scanning comparing with the conventional mechanical or manual scanning system. Therefore, output image is represented in real-time. The other is the dynamic focusing and the dynamic steering of ultrasonic beam. Only the delay times that are controlled electrically are used to focus and to steer beam without any lenses or wedges. In this study, the profile of the ultrasonic beam for the phased array transducer has been simulated in the Huygens principle with varying the inter-element spacing of the linear phased array transducer. From the result of this study, it was found that the ultrasonic beam spread wider as the inter-element spacing was decreased. However, the focusing effect was improved, even when the number of the element was not big. In addition, there was grating lobes that are constructed when the inter-element spacing is more than half wavelength. However, this grating lobe has lower amplitude than the main lobe.
Analysis of Three Dimensional Cracks Subjected to the Mode I Loading by Using FEAM
Kim, Tae-Sun ; Park, Jae-Hak ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 982~990
DOI : 10.22634/KSME-A.2000.24.4.982
The finite element alternating method is extended further for general three dimensional cracks in an isotropic body subjected to the mode I loading. The required analytical solution for a dime dimensional crack in an infinite isotropic body is obtained by solving the integral equations. In order to remove the high singularity in integration, the technique suggested by Keat et al. was used. With the proposed method several example problems are solved in order to check the accuracy and efficiency of the method.
Stereo Matching Using Robust Estimators and Line Masks
Kim, Nak-Hyeon ; Kim, Gyeong-Beom ; Jeong, Seong-Jong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 991~1000
DOI : 10.22634/KSME-A.2000.24.4.991
Previous area-based stereo matching algorithms find the disparity by first computing the sum of squared differences (SSD) between corresponding points using a rectangular window, and then searching the position of the minimum SSD within the disparity range. These algorithms generate relatively many matching errors around depth discontinuities, since the SSD function may fail to search for the minimum because of varying disparity profiles in such areas. In this paper, in order to improve the matching accuracy around the depth discontinuities, a new correlation function based on robust estimation technique is proposed for stereo matching. In addition, while previous stereo algorithms utilize a single rectangular window for computing the correlation function, the proposed matching algorithm utilizes 4-directional line masks additionally to reduce the matching errors further. It has been turned out that the proposed algorithm reduces matching errors around depth discontinuities significantly. Experimental results are presented in this paper, comparing the performance of the proposed technique with those of previous algorithms using both synthetic and real images.
A Study on Non-propagating Crack in Fatigue Behavior of Pure Titanium
Kim, Dong-Yeol ; Kim, Jin-Hak ; Kim, Min-Geon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1001~1006
DOI : 10.22634/KSME-A.2000.24.4.1001
To verify the existing theory, non-propagating crack(NPC) does not exist in Ti which fulfills the good conditions for being of NPC, NPC detection in Ti was tried out. Also, the conception of fatigue limit in Ti and a main cause for NPC being were inquired. NPC was detected in both sharp notch root (
=0.02mm) and micro pit (diameter = 0.25mm) which held fast to the end under stressing of fatigue limit. Therefore, the existing theory was identified as mistake. But, NPC can not be detected in smooth specimen. This fact would be due to the presumption that NPC is very small or crack does not initiate in smooth specimen. Anyway, the fatigue limit of Ti does not correspond to critical stress of crack initiation but correspond to critical stress of NPC growth. Measurement on the COD of NPC in Ti showed that the crack tip was closed even under the peak stress level at fatigue limit. But, after stress relieving annealing crack tip was opened. Consequently, compressive residual stress which is induced around the crack tip is considered to be the factor causing the NPC being.
ZPM Compensation and Impedance Control for Improving Walking Stability of Biped Robots
Jeong, Ho-Am ; Park, Jong-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1007~1015
DOI : 10.22634/KSME-A.2000.24.4.1007
This paper proposes an adaptive trajectory generation strategy of using on-line ZMP information and an impedance control method for biped robots. Since robots experience various disturbances during their locomotion, their walking mechanism should have the robustness against those disturbances, which requires an on-line adaptation capability. In this context, an on-line trajectory planner is proposed to compensate the required moment for recovering stability. The ZMP equation and sensed ZMP information are used in this trajectory generation strategy. In order to control a biped robot to be able to walk stably, its controller should guarantee stable footing at the moment of feet contacts with the ground as well as maintaining good trajectory tracking performance. Otherwise, the stability of robot will be significantly compromised. To reduce the magnitude of an impact and guarantee a stable footing when a foot contacts with the ground, this paper. proposes to increase the damping of the leg drastically and to modify the reference trajectory of the leg. In the proposed control scheme, the constrained leg is controlled by impedance control using the impedance model with respect to the base link. Computer simulations performed with a 3-dof environment model that consists of combination of a nonlinear and linear compliant contact model show that the proposed controller performs well and that it has robustness against unknown uneven surface. Moreover, the biped robot with the proposed trajectory generator can walk even when it is pushed with a certain amount of external force.
Design and Analysis of Hollow Section Extrusion using Mismatching Refinement with Domain Decomposition
Park, Geun ; Yang, Dong-Yeol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1016~1023
DOI : 10.22634/KSME-A.2000.24.4.1016
The present work is concerned with three-dimensional finite element analysis of the hollow section extrusion process using a porthole die. The effects of related design parameters are discussed through the finite element simulation for extrusion of a triply-connected rectangular tubular section. For economic computation, mismatching refinement, an efficient domain decomposition method with different mesh density for each subdomain, is implemented. In order to obtain the uniform flow at the outlet, design parameters such as the hole size and the hole position are investigated and compared through the numerical analysis. Comparing the velocity distribution with that of the original design, it is concluded that the design modification enables more uniform flow characteristics. The analysis results are then successfully reflected on the industrial porthole die design
Determination of the Group Velocity and Source Location of Dispersive Plate Waves using Wavelet Transform
Jang, Yeong-Su ; Jeong, Hyeon-Jo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1024~1031
DOI : 10.22634/KSME-A.2000.24.4.1024
The plate waves propagating in thin plates have dispersive nature showing the dependence of velocities on the frequency. Wavelet transform (WT) using Gabor function can be used to analyze the dispersive waves in the time-frequency domain, and then to find the arrival time of the waves propagating in the plate. Plate waves in the aluminum plate of 3 mm thickness were identified and generated by pencil lead breaks and the lowest order symmetric (
) and antisymmetric (
) modes were analyzed by the WT method. The measured group velocities agreed very well with theoretical predictions in the frequency range of 50-400 kHz. The pencil breaks were also used to simulate acoustic emission sources in the plate, and the source location algorithm using the wavelet transform of dispersive plate waves was found to give accurate results.
The Stress Field in the Body by Tangential Loading of a Rectangular Patch on a Semi-Infinite Solid
Lee, Mun-Ju ; Gu, Yeong-Pil ; Jo, Yong-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1032~1038
DOI : 10.22634/KSME-A.2000.24.4.1032
The stress field in the body by tangential loading of a rectangular patch on a semi-infinite solid has been solved analytically using potential function. The validity of result of this study was proved by Saint-Venant's principle in the remote region and in the vicinity of the surface with superposition of point loads
Development of Robot Control and Measurement for Unknown Geometric Surface Grinding
Choe, Byeong-O ; Park, Geun-U ; Lee, Min-Gi ; Lee, Jung-Hun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1039~1046
DOI : 10.22634/KSME-A.2000.24.4.1039
This paper introduces the control and measurement of a double parallel robot manipulator applied for unknown geometric surface grinding. A measurement system is developed to recognize a grinding path by a vision camera and to observe a grinding load by a current sensor. With the measured fusion information, an intelligent controller identifies the unknown geometric surface and moves the robot along the grinding path with a constant grinding load.
Design of Unequally-Spaced Blade Arrangement for Tonal Noise Reduction
Kim, Wan-Gi ; Yun, Jong-Hak ; Han, Seong-Su ; Jeon, Se-Jong ; Seong, Hyeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1047~1054
DOI : 10.22634/KSME-A.2000.24.4.1047
A numerical simulation was made to delineate the re-distribution of tonal noise generated from the equally-spaced blade passing frequency (BPF). A pressure-wave model was employed to analyze the tonal noise. An optimal solution for diversifying the tonal peak noise was obtained by rearranging the unequally-spaced blade angles. This was based on the fact that the noise energy is transferred from BPF to the neighboring frequency band. A limit condition for the minimum blade angle spacing was imposed. The unbalancing problem was also considered to avoid the weight bias.
A Preliminary Study on Fatigue Strength of High Toughness Thermoplastic Composite Material AS4/PEEK
Song, Ji-Ho ; Gang, Jae-Yun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1055~1064
DOI : 10.22634/KSME-A.2000.24.4.1055
First, various specimen geometries, namely, coupon type, waisted type and dog-bone type, were examined to determine appropriate fatigue specimen of thermoplastic composite material AS4/PEEK and the n, fatigue strength of smooth and notched specimens of AS4/PEEK [-45/0/+45/90]2s was investigated. Fatigue tests were performed under load controlled condition at a stress ratio of 0. 1 at a frequency of 5Hz. Stiffness degradation of specimens with fatigue cycling was monitored using an automated unloading compliance technique. The waisted type specimen is found appropriate for smooth fatigue specimen geometry of AS4/PEEK. As for the effect of stress concentration, it is found that fatigue strength is higher for a 2mm-diameter hole notched specimen than a 5mm-diameter one. Fatigue notch factor decreases with the increase of fatigue life. These results are far different from the trend of fatigue strength of metallic materials. The stiffness variation of smooth specimen was only 4% at maximum until final fracture. On the other hand, the stiffness of hole notched specimen was reduced by 45% at maximum. Notched fatigue strength was compared between thermoplastic composite AS4/PEEK and thermosetting composite Graphite/Epoxy. In long-life fatigue (>104), the AS4/PEEK composite shows superior fatigue strength, but in short-life fatigue, the fatigue strength of the Graphite/Epoxy composite is nearly equal or somewhat higher than that of the AS4/PEEK composite,
Control for a Parallel Inverted Pendulum
Han, Seong-Ik ; Kim, Jong-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 4, 2000, Pages 1065~1074
DOI : 10.22634/KSME-A.2000.24.4.1065
A robust nonlinear
control method for a parallel inverted pendulum with structured perturbation and dry friction is proposed. By the random input describing function techniques, the nonlinear dry friction is approximated into the quasi-linear system. Introducing the quadratic robustness theorem, the robust
control system is constructed for the quasi-linear perturbed system. But it is difficult to design a controller due to the nonlinear correction term in Riccati equation. With some transformations on the Riccati equation containing nonlinear correction term, the design of the robust nonlinear controller can be done easily. Hence when the stiffness and mass of the parallel inverted pendulum vary in certain ranges, the proposed control scheme has the robustness for both the structured perturbation and dry friction. The results of computer simulation show the effectiveness of our proposed control method.