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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers A
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The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 30, Issue 12 - Dec 2006
Volume 30, Issue 11 - Nov 2006
Volume 30, Issue 10 - Oct 2006
Volume 30, Issue 9 - Sep 2006
Volume 30, Issue 8 - Aug 2006
Volume 30, Issue 7 - Jul 2006
Volume 30, Issue 6 - Jun 2006
Volume 30, Issue 5 - May 2006
Volume 30, Issue 4 - Apr 2006
Volume 30, Issue 3 - Mar 2006
Volume 30, Issue 2 - Feb 2006
Volume 30, Issue 1 - Jan 2006
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Reference Stress Based Stress Analysis for Local Creep Rupture of a T-pipe
Shin Kyu-In ; Yoon Kee-Bong ; Kim Yun-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 873~879
DOI : 10.3795/KSME-A.2006.30.8.873
To investigate applicability of the reference stress approach as simplified inelastic stress analysis to estimate local creep rupture, detailed finite element stress analyses of a T-piece pipe with different inner pressure and system loading levels are performed. The reference stresses are obtained from the finite element (FE) limit analysis based on elastic-perfectly-plastic materials, from which the local reference stress for creep rupture is determined from R5. The resulting inelastic stresses are compared with elastic stresses resulting from linear elastic FE calculations. Furthermore they are also compared with the stresses from full elastic-creep FE analyses. It shows that the stresses estimated from the reference stress approach compare well with those from full elastic-creep FE analysis, which are significantly lower than the elastic stress results. Considering time and efforts for full inelastic creep analysis of structures, the reference stress approach is shown to be a powerful tool for creep rupture estimates and also to reduce conservatism of elastic stress analysis significantly.
Sliding Mode Control with RLSN Predictor-Based Perturbation Estimation
Nam Yun-Joo ; Lee Yuk-Hyung ; Park Myeong-Kwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 880~888
DOI : 10.3795/KSME-A.2006.30.8.880
This paper presents the sliding mode control with the perturbation estimator for a nonlinear control system in the presence of perturbations including external disturbances, unpredictable parameter variations, ana unstructured dynamics. The proposed perturbation estimator is based on the Recursive Linear Smoothed Newton predictive algorithm so that it is effective to attenuate an undesired noise in high frequency band and to predict the present perturbation signal from the previous ones. Compared to conventional sliding mode control (SMC) and sliding mode control with perturbation estimation (SMCPE) introduced by Elmali and Olgac, the control algorithm proposed in this study can offer better tracking control performances and more feasible estimation characteristics. The effectiveness and superiority of the proposed control strategy are demonstrated by a series of simulations on the position tracking control of a simple two-link robot manipulator subject to velocity feedback signals including white noises.
Reliability-Based Topology Optimization Using Single-Loop Single-Vector Approach
Bang Seung-Hyun ; Min Seung-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 889~896
DOI : 10.3795/KSME-A.2006.30.8.889
The concept of reliability has been applied to the topology optimization based on a reliability index approach or a performance measure approach. Since these approaches, called double-loop single vector approach, require the nested optimization problem to obtain the most probable point in the probabilistic design domain, the time for the entire process makes the practical use infeasible. In this work, new reliability-based topology optimization method is proposed by utilizing single-loop single-vector approach, which approximates searching the most probable point analytically, to reduce the time cost. The results of design examples show that the proposed method provides efficiency curtailing the time for the optimization process and accuracy satisfying the specified reliability.
Experimental Design of Disturbance Compensation Control to Improve Stabilization Performance of Target Aiming System
Lim Jae-Keun ; Kang Min-Sig ; Lyou Joon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 897~905
DOI : 10.3795/KSME-A.2006.30.8.897
This study considers an experimental design of disturbance compensation control to improve stabilization performance of main battle tanks. An adaptive non-parametric design technique based on the Filtered-x Least Mean Square(FXLMS) algorithm is applied in the consideration of model uncertainties. The optimal compensator is designed by two-step design procedures: determination of frequency response function of the disturbance compensator which can cancel the disturbance of series of single harmonics by using the FXLMS algorithm and determination of the compensator polynomial which can fit the frequency response function obtained in the first step optimally by using a curve fitting technique. The disturbance compensator is applied to a simple experimental gun-torsion bar-motor system which simulates gun driving servo-system. Along with experimental results, the feasibility of the proposed technique is illustrated. Experimental results demonstrate that the proposed control reduces the standard deviation of stabilization error to 47.6% that by feedback control alone. The directional properties of the FXLMS Algorithm such as the direction of convergence and its convergence speed are also verified experimentally.
Complete 3D Surface Reconstruction from an Unstructured Point Cloud of Arbitrary Shape by Using a Bounding Voxel Model
Li Rixie ; Kim Seok-Il ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 906~915
DOI : 10.3795/KSME-A.2006.30.8.906
This study concerns an advanced 3D surface reconstruction method that the vertices of surface model can be completely matched to the unstructured point cloud measured from arbitrary complex shapes. The concept of bounding voxel model is introduced to generate the mesh model well-representing the geometrical and topological characteristics of point cloud. In the reconstruction processes, the application of various methodologies such as shrink-wrapping, mesh simplification, local subdivision surface fitting, insertion of is isolated points, mesh optimization and so on, are required. Especially, the effectiveness, rapidity and reliability of the proposed surface reconstruction method are demonstrated by the simulation results for the geometrically and topologically complex shapes like dragon and human mouth.
Bending Strength of Natural Woven Bamboo Fiber-reinforced Polymer Composites with Manufacturing Factors
Song Jun-Hee ; Lim Jae-Kyoo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 916~922
DOI : 10.3795/KSME-A.2006.30.8.916
In recent years there has been a growing interest for the use of natural fibers in composite applications due to their low cost, environmental friendliness, and good mechanical properties. The purpose of this study is to determine the characteristic of bending strength on bamboo fiber reinforced polymer composites. The parameters of RTM process depend on the weight ratio of bamboo fiber and resin, the number of bamboo ply and amount of hardening agent. Mechanical properties was investigated for each process factor of polymer composites. Test result shows that bending strength was a maximum(approximately 85MPa) value when composite thickness was 6mm and weight ratio of resin was 13%.
An Error Assessment of the Kriging Based Approximation Model Using a Mean Square Error
Ju Byeong-Hyeon ; Cho Tae-Min ; Jung Do-Hyun ; Lee Byung-Chai ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 923~930
DOI : 10.3795/KSME-A.2006.30.8.923
A Kriging model is a sort of approximation model and used as a deterministic model of a computationally expensive analysis or simulation. Although it has various advantages, it is difficult to assess the accuracy of the approximated model. It is generally known that a mean square error (MSE) obtained from the kriging model can't calculate statistically exact error bounds contrary to a response surface method, and a cross validation is mainly used. But the cross validation also has many uncertainties. Moreover, the cross validation can't be used when a maximum error is required in the given region. For solving this problem, we first proposed a modified mean square error which can consider relative errors. Using the modified mean square error, we developed the strategy of adding a new sample to the place that the MSE has the maximum when the MSE is used for the assessment of the kriging model. Finally, we offer guidelines for the use of the MSE which is obtained from the kriging model. Four test problems show that the proposed strategy is a proper method which can assess the accuracy of the kriging model. Based on the results of four test problems, a convergence coefficient of 0.01 is recommended for an exact function approximation.
Effect of Structural Geometry and Crack Location on Crack Driving Forces for Cracks in Welds
Oh Chang-Kyun ; Kim Jong-Sung ; Jin Tae-Eun ; Kim Yun-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 931~940
DOI : 10.3795/KSME-A.2006.30.8.931
Defect assessment of a weld zone is important in fitness-for-service evaluation of plant components. Typically a J and
estimation method for a defective homogeneous component is extended to a mismatched component, by incorporating the effect due to the strength mismatch between the weld metal and the base material. The key element is a mismatch limit load. For instance, the R6/R5 procedure employs an equivalent material concept, defined by a mismatch limit load. A premise is that if a proper mismatch limit load solution is available, the same concept can be used for any defect location (either a weld centre defect or a heat affected zone (HAZ) defect) and for any material combination (either two-material or multi-material combinations; either similar or dissimilar joints). However, validation is still limited, and thus a more systematic investigation is needed to generalise the suggestion to any geometry, any defect location and any material combination. This paper describes the effect of structural geometry on the
integral for defective similar welds, based on systematic elastic-creep 2-D and 3-D finite element (FE) analyses, to attempt to elucidate the questions given above. It is found that the existing 'equivalent material' concept is valid only for limited cases, although it provides conservative estimates of
for most of cases. A modification to the existing equivalent material concept is suggested to improve accuracy.
Reliability Estimation Using Kriging Metamodel
Cho Tae-Min ; Ju Byeong-Hyeon ; Jung Do-Hyun ; Lee Byung-Chai ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 941~948
DOI : 10.3795/KSME-A.2006.30.8.941
In this study, the new method for reliability estimation is proposed using kriging metamodel. Kriging metamodel can be determined by appropriate sampling range and sampling numbers because there are no random errors in the Design and Analysis of Computer Experiments(DACE) model. The first kriging metamodel is made based on widely ranged sampling points. The Advanced First Order Reliability Method(AFORM) is applied to the first kriging metamodel to estimate the reliability approximately. Then, the second kriging metamodel is constructed using additional sampling points with updated sampling range. The Monte-Carlo Simulation(MCS) is applied to the second kriging metamodel to evaluate the reliability. The proposed method is applied to numerical examples and the results are almost equal to the reference reliability.
Electrothermal Crack Analysis in a Finite Conductive Layer with Temperature-dependent Material Properties
Jang Yong-Hoon ; Lee Sang-Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 949~956
DOI : 10.3795/KSME-A.2006.30.8.949
The method of Greenwood and Williamson is extended to obtain a solution to the coupled non-linear problem of steady-state electrical and thermal conduction across a crack in a conductive layer, for which the electrical resistivity and thermal conductivity are functions of temperature. The problem can be decomposed into the solution of a pair of non-linear algebraic equations involving boundary values and material properties. The new mixed-boundary value problem given from the thermal and electrical boundary conditions for the crack in the conductive layer is reduced in order to solve a singular integral equation of the first kind, the solution of which can be expressed in terms of the product of a series of the Chebyshev polynomials and their weight function. The non-existence of the solution for an infinite conductor in electrical and thermal conduction is shown. Numerical results are given showing the temperature field around the crack.
Analysis of Tool and Workpiece Setup in v-Groove Micromachining
Cho Jung-Woo ; Yang Min-Yang ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 957~964
DOI : 10.3795/KSME-A.2006.30.8.957
As the requirement of LCD products which are large screen and have high brightness increases, the role of light guide panel (LGP) of which micro-features diffuse the light uniformly on surface is getting important. In general, there are many errors in machining like machine tool errors process error, setup error and etc. The amount of setup error in general machining is not so big in comparison with the others, so it is mostly neglected. But, especially in v-groove micromachining, setup error has a significant effect on micro-features. Low quality product and high cost are resulted from setup error. In v-groove micromachining, to confirm the effect of setup error, it is identified and then setup error synthesis model is derived from analysis of tool and workpiece setup. In addition, to predict the micro-features affected by setup error and enhance the production efficiency, the setup condition satisfying the tolerance of micro-features is geometrically analyzed and presented.
Evaluation of High Temperature Material Degradation for 12Cr Steel by Electrochemical Polarization Method
Seo Hyon-Uk ; Park Kee-Sung ; Yoon Kee-Bong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 965~975
DOI : 10.3795/KSME-A.2006.30.8.965
High pressure turbine blades are one of the key components in fossil power plants operated at high temperature. The blade is usually made of 12Cr steel and its operating temperature is above
. Long term service at this temperature causes material degradation accompanied by changes in microstructures and mechanical properties such as strength and toughness. Quantitative assessment of reduction of strength and toughness due to high temperature material degradation is required for residual life assessment of the blade components. Nondestructive technique is preferred. So far most of the research of this kind was conducted with low alloy steels such as carbon steel, 1.25Cr0.5Mo steel or 2.25Cr1Mo steel. High alloy steel was not investigated. In this study one of the high Cr steel, 12Cr steel, was selected for high temperature material degradation. Electrochemical polarization method was employed to measure degradation. Strength reduction of the 12Cr steel was represented by hardness and toughness reduction was represented by change of transition temperature, FATT. Empirical relationships between the electrochemical polarization parameter and significance of material degradation were established. These relationship can be used for assessing the strength and toughness on the aged high pressure blade components indirectly by using the electrochemical method.
Time-Temperature Superposition Behavior for Accelerated Fatigue Lifetime Testing of Polycarbonate(PC)
Kim Gyu-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 976~984
DOI : 10.3795/KSME-A.2006.30.8.976
Time-temperature superposition has been studied to determine the long-term fatigue life over millions of cycles for glassy polymers. π le superposition is supposed to make an accelerated lifetime testing (ALT) technique possible. Dog-bone shaped specimens made of carbon filled Polycarbonate (PC) were tested under fatigue, based on the stress-lifetime approach (S-N curve). Fatigue-induced localized yield-like deformation is considered as the defect leading to fatigue and its evolution behavior is characterized by a modified energy activation model in which temperature is considered as fatigue acceleration factor. This model allows the reduced time concept to account for effects of different temperature in short-term fatigue data to determine long-term fatigue life through the use of time-temperature superposition that is applicable under a low frequency and isothermal conditions. The experimental results validated that the proposed technique could be a possible method for accelerated lifetime testing (ALT) of time-dependent polymeric materials.
Performance Improvement of a Moment Method for Reliability Analysis Using Kriging Metamodels
Ju Byeong-Hyeon ; Cho Tae-Min ; Jung Do-Hyun ; Lee Byung-Chai ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 985~992
DOI : 10.3795/KSME-A.2006.30.8.985
Many methods for reliability analysis have been studied and one of them, a moment method, has the advantage that it doesn't require sensitivities of performance functions. The moment method for reliability analysis requires the first four moments of a performance function and then Pearson system is used for the probability of failure where the accuracy of the probability of failure greatly depends on that of the first four moments. But it is generally impossible to assess them analytically for multidimensional functions, and numerical integration is mainly used to estimate the moment. However, numerical integration requires many function evaluations and in case of involving finite element analyses, the calculation of the first fo 따 moments is very time-consuming. To solve the problem, this research proposes a new method of approximating the first four moments based on kriging metamodel. The proposed method substitutes the kriging metamodel for the performance function and can also evaluate the accuracy of the calculated moments adjusting the approximation range. Numerical examples show the proposed method can approximate the moments accurately with the less function evaluations and evaluate the accuracy of the calculated moments.
Evaluation of Limit Loads for Surface Cracks in the Steam Generator Tube
Kim Hyun-Su ; Kim Jong-Sung ; Jin Tae-Eun ; Kim Hong-Deok ; Chung Han-Sup ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 993~1000
DOI : 10.3795/KSME-A.2006.30.8.993
Operating experience of steam generators has shown that cracks of various morphology frequently occur in the steam generator tubes. These cracked tubes can stay in service if it is proved that the tubes have sufficient safety margin to preclude the risk of burst and leak. Therefore, integrity assessment using exact limit load solutions is very important for safe operation of the steam generators. This paper provides global and local limit load solutions for surface cracks in the steam generator tubes. Such solutions are developed based on three-dimensional (3-D) finite element analyses assuming elastic-perfectly plastic material behavior. For the crack location, both axial and circumferential surface cracks, and for each case, both external and internal cracks are considered. The resulting global and local limit load solutions are given in polynomial forms, and thus can be simply used in practical integrity assessment of the steam generator tubes.
A Study on the Robust Optimal Supporting Positions of TFT-LCD Glass Panel
Huh Jae-Sung ; Jung Byung-Chang ; Lee Tae-Yoon ; Kwak Byung-Man ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 1001~1007
DOI : 10.3795/KSME-A.2006.30.8.1001
In this paper we present robust optimal supporting positions for large glass panels used for TFT-LCD monitors when they are stored in a cassette during manufacturing process. The criterion taken is to minimize their maximum deflection. Since they are supported by some supports and have large deformations, contact analysis with a geometrically nonlinear effect is necessary. In addition, the center of a panel can not be positioned exactly as intended and should be considered as uncertainties. To take into account of these effects, the mean and the standard deviation of system response functions, particularly the deflection of the panels, need be calculated. A function approximation moment method (FAMM) is utilized to estimate them. It is a special type of response surface methodology for structural reliability analysis and can be efficiently used to estimate the two stochastic properties, that is, the system performance and the perturbations caused by uncertainties. For a design purpose, they are to be minimized simultaneously by some optimization algorithm to obtain robust optimal supporting positions.
Closed-Form Plastic Collapse Loads of Pipe Bends Under Combined Pressure and In-Plane Bending
Oh Chang-Sik ; Kim Yun-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 1008~1015
DOI : 10.3795/KSME-A.2006.30.8.1008
Based on three-dimensional (3-D) FE limit analyses, this paper provides plastic limit, collapse and instability load solutions for pipe bends under combined pressure and in-plane bending. The plastic limit loads are determined from FE limit analyses based on elastic-perfectly plastic materials using the small geometry change option, and the FE limit analyses using the large geometry change option provide plastic collapse loads (using the twice-elastic-slope method) and instability loads. For the bending mode, both closing bending and opening bending are considered, and a wide range of parameters related to the bend geometry is considered. Based on the FE results, closed-form approximations of plastic limit and collapse load solutions for pipe bends under combined pressure and bending are proposed.
Shape Optimal Design of the Door Frame of a Microwave Oven to Minimize Its Twisting Deformation
Lee Boo-Youn ; Koo Jin-Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 30, issue 8, 2006, Pages 1016~1023
DOI : 10.3795/KSME-A.2006.30.8.1016
When one opens the door of a microwave oven during its operation, twisting deformation of the door occurs, which may cause leakage of microwave through the gap between the door and the front plate. A numerical optimization is implemented to minimize the gap by maximizing twisting stiffness of the door of the oven. Design variables are deformed, which describe the shape of the bead in the horizontal and vertical flanges of the door frame. To minimize the twisting deformation, Two optimal design problems to find shapes of the bead in the flange are established. The problems are solved by a numerical optimization technique, their results being evaluated.