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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 21, Issue 12 - Dec 1997
Volume 21, Issue 11 - Nov 1997
Volume 21, Issue 10 - Oct 1997
Volume 21, Issue 9 - Sep 1997
Volume 21, Issue 8 - Aug 1997
Volume 21, Issue 7 - Jul 1997
Volume 21, Issue 6 - Jun 1997
Volume 21, Issue 4 - Apr 1997
Volume 21, Issue 5 - Jan 1997
Volume 21, Issue 3 - Jan 1997
Volume 21, Issue 2 - Jan 1997
Volume 21, Issue 1 - Jan 1997
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Algebraic Method for Computation of Natural Frequency and Mode Shape Sensitivities
Jung, Gil-Ho ; Kim, Dong-Ok ; Lee, Chong-Won ; Lee, In-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 707~718
DOI : 10.22634/KSME-A.19126.96.36.1997
This paper presents an efficient numerical method for the computation of eigenpair derivatives for a real symmetric eigenvalue problem with distinct and multiple eigenvalues. The method has a very simple algorithm and gives an exact solution. Furthermore, it saves computer sotrage and CPU time. The algorithm preserves not only the symmetricity but also the band width of the matrices, allowing efficient computer storage and solution techniques. Results from the proposed method for calculating the eigenpair derivatives are compared with those from Rudisill and Chu's method and Nelson's method which is known efficient one in the case of distinct natural frequencies. As an example to demonstrate the efficiency of the proposed method in the case of distinct eigenvalues, a cantilever plate is considered. The design parameter of the cantilever plate is its thickness. For the eigenvalue problem with multiple natural frequencies, the adjacent eigenvectors are used in the algebraic equation as side conditions, lying adjacent to the multiplicity of multiple natural frequency distinct eigenvalues, which appear when design parameter varies. A cantilever beam is used to demonstrate the efficiency of the proposed method in the case of multiple natural frequencies. Results form the proposed method for calculating the eigenpair derivatives are compared with those from Dailey's method(an amendation of Ojalvo's work) which finds the exact eigenvector derivatives. The design parameter of the cantilever beam is its height. Data is presented showing the amount of CPU time used to compute the first ten eigenpair derivatives by each method. It is important to note that the numerical stability of the proposed method is proved.
A Study on the Improvement of the Load Pressure Feedback Mechanism of the Proportional Pressure Control Valve
Oh, In-Ho ; Jang, Ji-Seongng ; Lee, Ill-Yeong ; Chung, Dai-Jong ; Cho, Sung-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 719~726
DOI : 10.22634/KSME-A.19188.8.131.529
The proportional pressure control valve having versatile functions and higher performance is an essential conponent in the open loop controlled rear wheel steering gear of the four wheel steering system in a passenger car. In this study, the authors suggest a new type of load pressure feedback mechanism which can make it easy to change the range of controlled pressure without changing the capacity of solenoid. The concept of suggested mechanism, composed of the pressure chamber with throttles in series, was described. The mathematical model was derived from the rear wheel steering gear consisting of a valve and a cylinder for the purpose of analyzing the valve characteristics. And the programme for computing the characteristic of the valve was developed. Experiments were performed to confirm the performance of the valve and computations were carried out to ascertain the usefulness of the developed programme. The results from computations fairly coincide with those from experiments. And the results from experiments and computations show that the performance of new valve was as good as that of the already developed one and the new valve has advantages such as the easiness of changing the range of controlled pressure and the decrease of power loss at neutral position without the decline of performance.
Die Shape Design for Cold Forged Products Using the Artificial Neural Network
Kim, D.J ; Kim, T.H ; Kim, B.M ; Choi, J.C ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 727~734
DOI : 10.22634/KSME-A.19184.108.40.2067
In practice, the design of forging processes is performed based on an experience-oriented technology, that is designer's experience and expensive trial and errors. Using the finite element simulation and the artificial neural network, we propose an optimal die geometry satisfying the design conditions of final product. A three-layer neural network is used and the back propagation algorithm is employed to train the network. An optimal die geometry that satisfied the same between inner extruded rib and outer extruded one is determined by applying the ability of function approximation of neural network. The neural networks may reduce the number of finite element simulation for determine the optimal die geometry of forging products and further they are usefully applied to physical modelling for the forging design.
Analysis of Filling in Injection Molding with Compressibility
Han, Kyeong-Hee ; Im, Yong-Taek ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 735~745
DOI : 10.22634/KSME-A.19220.127.116.115
In this study, the compressibility of resin was considered in filling analysis to account for the possible packing type flow. A numerical simulation program employing a hybrid finite element/finite difference scheme was developed to solve Hele-Shaw flow of the compressible viscous fluid at non-isothermal conditions. To advance the melt front, a control volume approach was adopted. Thin complex 3-D shapes of cavities, runners, and sprues were discretized by employing triangular, cylindrical and/or rectangular strip elements. Mass conservation was applied to each control volume to solve for the pressure distribution. Directly applying a constant mass flow rate at the inlet removes calculation of the apparent pressure boundary conditions, resulting in better simulation condition. The Cross model was used to model viscosity and the Tait equation was employed to represent density as a function of temperature and pressure. The validity of the developed program was verified through comparisons with available data in the literature and the effect of compressibility on the pressure distribution was discussed. To reduce computation time, 1-D and 2-D elements were used instead of applying triangular elements and the numerical results were compared to each other.
Analysis of Temperature Distribution in a Rolling Tire due to Strain Energy Dissipation
Park, Hyun-Cheol ; Youn, Sung-Kie ; Song, Tae-Sok ; Kim, Nam-Jeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 746~755
DOI : 10.22634/KSME-A.1918.104.22.1686
This paper addresses the systematic procedure using sequential approach for the analysis of the coupled thermo-mechanical behavior of a steady rolling tire. Not only the knowledge of mechanical stresses but also of the temperature loading in a rolling tire are very important because material damage and material properties are significantly affected by the temperature. In general, the thermo-mechanical behavior of a pneumatic tire is highly complex transient phenomenon that requires the solution of a dynamic nonlinear coupled themoviscoelasticity problem with heat source resulting from internal dissipation and friction. In this paper, a sequential approach, with effective calculation schemes, to modeling this system is presented in order to predict the temperature distribution with reasonable sccuracies in a steady state rolling tire. This approach has the three major analysis modules-deformation, dissipation, and thermal modules. In the dissipation module, an analytic method for the calculation of the heat source in a rolling tire is established using viscoelastic theory. For the verification of the calculated temperature profiles and rolling resistance at different velocities, they were compared with the measured ones.
A Dynamic Modeling and Analysis for High-speed Walking of a Quadrupedal Robot
Kang, Sung-Chul ; Yoo, Hong-Hee ; Kim, Mun-Sang ; Lee, Kyo-Il ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 756~768
DOI : 10.22634/KSME-A.1922.214.171.1246
In order to control a dynamic gait of quadrupedal walking robot, the equations of motion of the whole mechanism are required. In this research, the equations of motion are formulated analytically using Kane's dynamic approach. As a dynamic gait model, a trot gait has been adopted. The degree of freedom of whole mechanism could be reduced to 7 by idealizing the kinematic feature of the trot gait. Using the equations of motion formulated, the results of the redundant-joint torque analysis and the simulation of dynamic walking motion are presented.
Multiple Objective Scheduling of Flexible Manufacturing Systems Using Petri Nets
Yim, Seong-Jin ; Lee, Doo-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 769~779
DOI : 10.22634/KSME-A.19126.96.36.1999
This paper presents an approach to multiple objective scheduling of flexible manufacturing systems(FMS). The approach is an extension of the scheduling method that formulates scheduling problems using Petrinets, and applies heuristic search to find optimal or near-optimal schedules with a single objective. New evaluation functions are developed to optimize simultaneously the makespan and the total operating cost. A scheduling example is used to demonstrate the effectiveness of the proposed approach.
Finite Element Analysis of Carbon Steel according to Shape and Distribution of Phase
Seo, Dae-Cheol ; Lee, Duck-Hee ; Lee, Jung-Ju ; Nam, Soo-Woo ; Choo, Wung-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 780~790
DOI : 10.22634/KSME-A.19188.8.131.520
In this study, the stress-strain relations of steels have been calculated as a function of microstructural morphologies of each phase by use of FEM program(i.e. ABAQUS). The mechanical behavior of low carbon steels is affected by the microstructural factors such as yield ratio, volume fraction, shape and distribution of each phase and so on. The effects of shape, volume fraction and yield ratio of each phase on the mechanical behavior were analyzed by using unit cell and whole specimen size models. Results obtained are summarized as follows. As the yield ratio of hard phase to that of soft phase and volume fraction of hard phase were increased, stress level of flow curves were increased. It was found that in whole specimen size model, as the particle size was decreased, higher stress level was shown. Lastly the relationship between microstructure and tensile properties was examined by using the steels with various microstructural morphologies.
Friction and Wear Characteristics of Plasma Coated Surface of Casting Aluminum Alloy
Chae, Young-Hun ; Ren, Jing-Ri ; Park, Jun-Mock ; Kim, Seock-Sam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 791~799
DOI : 10.22634/KSME-A.19184.108.40.2061
The wear characteristics and wear mechanisms of plasma sprayed Al/sub 2/ O/sub 3/-40%TiO/sub 2/ and Cr/sub 2/O/sub 3/ deposited on casting aluminum alloy(AC4C) were investigated. Specimens were processed for various coating thicknesses. Ball on disk type wear tester was used for wear test. The scratch test on plasma sprayed coating surface showed that critical load to break the coating layer was greater than 40 N. The critical load increase with the increase of coating thickness of specimens. The friction coefficient of Cr/sub 2/O/sub 3/ coating layer was less than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. The wear resistance of Cr/sub 2/O/sub 3/ coating layer was greater than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. Microscopic observation of worn surfaces was made by SEM. SEM observation showed that the main mechanism of wear for Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer was abrasive wear under 50 N. For the case of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer, as the surface cracks perpendicular to sliding direction propagated, the wear debris was generated in wear track. However, the main mechanism of wear for Cr/sub 2/O/sub 3/ coating layer was brittle fracture under 150 N.
A Study on the Decision Process of the Length Dimension of a Mechanical System
Cheon, G.J ; Lee, J.H ; Han, D.C ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 800~808
DOI : 10.22634/KSME-A.19220.127.116.110
Decision process for length dimension in the mechanical system design process has been studied with a washing machine transmission as a model. The results are, (i) the length dimensions of the non-shaft elements are independent of other elements, (ii) the length dimensions of the shaft elements are dependent on the dimensions of the non-shaft elements located inside and outside of that elements, (iii) the length dimensions of the inner shaft elements are dependent on those of the outer shaft elements located parallel, (iv) the length dimensions of the shaft elements located serial are independent of each other.
A Non-recursive Formulation of Dynamic Force Analysis in Recursive Multibody Dynamics
Kim, Seong-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 809~818
DOI : 10.22634/KSME-A.1918.104.22.1689
An efficient non-recursive formulation of dynamic force analysis has been developed for serially connected multibody systems. Although derivation of equations of motion is based on a recursive dynamic formulation with joint relative coordinates, in the proposed formulation, dynamic forces such as joint reaction forces and driving force are computed non-recursively for specified joints. The efficiency of the proposed formulation has been proved by the operational count and the CPU time measure, comparing with that of the conventional recursive Newton-Euler formulation. A simulation of 7-DOF RRC robot arm has been carried out to validate solutions of reaction forces by comparing with those from a commercial dynamic analysis program DADS.
Optimal Design of a Fine Actuator for Optical Pick-up
Lee, Moon-G ; Gweon, Dae-Gab ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 819~827
DOI : 10.22634/KSME-A.1922.214.171.1249
In this paper, a new modeling of a fine actuator for an optical pick-up has been proposed and multiobjective optimization of the actuator has been performed. The fine actuator is constituted of the bobbin which is supported by wire suspension, the coils which wind around the bobbin, and the magnets which cause the magnetic flux. If current flows in the coils, magnetic force is so produced as to be balanced with spring force of wire, so the bobbin is pisitioned. In this model the transfer function from input voltage to output displacementof bobbin has been obtained so that we can describe this integrated system with electromagnetic and mechanical parts. Wire suspension is regarded as a continuous Euler beam, damper as distributed viscous damping, and bobbin as a rigid body which can move up- and down- ward motion only. According to the model, the high frequency dynamic characteristics of the fine actuator can be known and the effect of damping can be investigated while the conventional second order model cannot. In multiobjective optimization, two objective functions have been chosen to maximize the fundamental frequency and the sensitivity with respect to the input voltage of the actuator so that Pareto's optimal solutions have been obtained using .epsilon.-constraint method. These objective functions will satisfy the trends which will enhance the access speed and reduce the tracking error in the optical pick-up technology of next generation. In the result of optimization, we obtain the designs of the optical pick-up fine actuator which has high speed, high sensitivity and low resonant peak. Furthermore, we offer the relation between two object functions so that the designer can make easy choice.
A Comparative Study of Material Flow Stress Modeling by Artificial Neural Networks and Statistical Methods
Chun, Myung-Sik ; Yi, Joon-Jeong ; Jalal, B. ; Lenard, J.G. ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 828~834
DOI : 10.22634/KSME-A.19126.96.36.1998
The knowledge of material stress-strain behavior is an essential requirement for design and analysis of deformation processes. Empirical stress-strain relationship and constitutive equations describing material behavior during deformation are being widely used, despite suffering some drawbacks in terms of ease of development, accuracy and speed. In the present study, back-propagation neural networks are used to model and predict the flow stresses of a HSLA steel under conditions of constant strain, strain rate and temperature. The performance of the network model is comparedto those of statistical models on rate equations. Well-trained network model provides fast and accurate results, making it superior to statistical models.
Analysis of Wear Debris for Machine Condition Diagnosis of the Lubricated Moving Surface
Seo, Yeong-Baek ; Park, Heung-Sik ; Jeon, Tae-Ok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 835~841
DOI : 10.22634/KSME-A.19188.8.131.525
Microscopic examination of the morphology of wear debris is an accepted method for machine condition and fault diagnosis. However wear particle analysis has not been widely accepted in industry because it is dependent on expert interpretation of particle morphology and subjective assessment criteria. This paper was undertaken to analyze the morphology of wear debris for machine condition diagnosis of the lubricated moving surfaces by image processing and analysis. The lubricating wear test was performed under different sliding conditions using a wear test device made in our laboratory and wear testing specimen of the pin-on-disk-type was rubbed in paraffine series base oil. In order to describe characteristics of debris of various shape and size, four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) have been developed and outlined in the paper. A system using such techniques promises to obviate the need for subjective, human interpretation of particle morphology in machine condition monitoring, thus to overcome many of the difficulties in current methods and to facilitate wider use of wear particle analysis in machine condition monitoring.
Fatigue Crack Initiation and Propagation From Two Micro Hole Defects
Song, Sam-Hong ; Bae, Joon-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 842~849
DOI : 10.22634/KSME-A.19184.108.40.2062
The aim of this study is an investigation of the interaction of two micro hole defects affecting fatigue crack initation life and propagation behavior. The locatio of two micro hole defects was considered as an angle of alignment and the distance between the centers of two micro hole defects. The fatigue cracking behavior is experimented under bending. When micro defects are located close to each other, the fatigue crack initiation lives are varied with their relative locations. In the experiments, the area of local plastic strain strongly played a role in the fatigue crack initiation lives. Therefore we introduce a parameter which contains the plastic deformation area at stress concentrations and propose a fatigue crack initiation life prediction curve. In addition, the directions and propagation rates of fatigue cracks initiated at two micro hole defects are studied experimentally.
Finite Element Analysis and Local a Posteriori Error Estimates for Problems of Flow through Porous Media
Lee, Choon-Yeol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 850~858
DOI : 10.22634/KSME-A.19220.127.116.110
A new a posteriori error estimator is introduced and applied to variational inequalities occurring in problems of flow through porous media. In order to construct element-wise a posteriori error estimates the global error is localized by a special mixed formulation in which continuity conditions at interfaces are treated as constraints. This approach leads to error indicators which provide rigorous upper bounds of the element errors. A discussion of a compatibility condition for the well-posedness of the local error analysis problem is given. Two numerical examples are solved to check the compatibility of the local problems and convergence of the effectivity index both in a local and a global sense with respect to local refinements.
Robust Design and Tolerancing for the Performance Improvement of Stabilized Mirror System under Vehicle Vibration
Lee, Chong-Won ; Jeong, Ho-Seop ; Sohn, Seok-Man ;
Transactions of the Korean Society of Mechanical Engineers A, volume 21, issue 5, 1997, Pages 859~869
DOI : 10.22634/KSME-A.1918.104.22.1689
In this paper, the robust design and tolerancing of the stabilized mirror is performed to increase its stabilization performance under vehicle vibration. Based on the sensitivity analysis, the seven important control factors are first identified, and then the optimal as well as robust values in the sense of Taguchi method are obtained. Finally, the tolerances associated with each design variables are determined based on a successive sensitivity analysis of the simulated system response so that the deviation in the response from the target value meets the specification requirements. The proposed tolerancing method features that it is a robust but conservative design method and that the computational effort is much less than the Monte Carlo simulation method.