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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 26, Issue 12 - Dec 2002
Volume 26, Issue 11 - Nov 2002
Volume 26, Issue 10 - Oct 2002
Volume 26, Issue 9 - Sep 2002
Volume 26, Issue 8 - Aug 2002
Volume 26, Issue 7 - Jul 2002
Volume 26, Issue 6 - Jun 2002
Volume 26, Issue 5 - May 2002
Volume 26, Issue 4 - Apr 2002
Volume 26, Issue 3 - Mar 2002
Volume 26, Issue 2 - Feb 2002
Volume 26, Issue 1 - Jan 2002
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Deterministic Fracture Mechanics Analysis of Nuclear Reactor Pressure Vessel Under Rot Leg Leak Accident
Lee, Sang-Min ; Choi, Jae-Boong ; Kim, Young-Jin ; Park, Youn-Won ; Jhung, Myung-Jo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2219~2227
DOI : 10.3795/KSME-A.2002.26.11.2219
In a nuclear power plant, reactor pressure vessel (RPV) is the primary pressure boundary component that must be protected against failure. The neutron irradiation on RPV in the beltline region, however, tends to cause localized damage accumulation, leading to crack initiation and propagation which raises RPV integrity issues. The objective of this paper is to estimate the integrity of RPV under hot leg leaking accident by applying the finite element analysis. In this paper, a parametric study was performed for various crack configurations based on 3-dimensional finite element models. The crack configuration, the crack orientation, the crack aspect ratio and the clad thickness were considered in the parametric study. The effect of these parameters on the maximum allowable nil-ductility transition reference temperature (
) was investigated on the basis of finite element analyses.
Design and Performance Test of the Shoe Holder Spring of the Axial Piston Pump
Chun, Young-Jun ; Choi, Jin-Ho ; Chung, Hee-Taeg ; Lee, Sang-Chan ; Kim, Tae-Il ; Kim, Dong-Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2228~2236
DOI : 10.3795/KSME-A.2002.26.11.2228
The axial piston pump by which the mechanical energy is converted into hydraulic energy has been widely used in a press, a injection molding machine and construction equipments due to the high specific power compared to the electric power system. In this paper, the one-piece shoe holder spring of the axial piston pump to simplify its structure and reduce this manufacturing cost was designed and tested. The finite element analyses using the 3-D shell element and contact element were performed to determine the thickness, width and initial angle of the shoe holder spring. Also, the compressive tests of the shoe holder spring were performed and their results were compared with those of the finite element analysis. Also, the performance and endurance limit of axial piston pump with the shoe holder spring were tested and evaluated.
Study on Kinematic Calibration of a Parallel-typed Machining Center Tool
Lee, Min-Ki ; Kim, Tae-Sung ; Park, Kun-Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2237~2244
DOI : 10.3795/KSME-A.2002.26.11.2237
This research develops a low-cost and high accuracy kinematic calibration method based on the following principles: 1) the platform locations are accurately measured by a constrained movement to inspect a calibration target; 2) the constrained movement is chosen to guarantee the parameter observability; 3) the mechanical fixture to constrain the movement and the sensor to check the constrained movement are implemented by low-cost and high-accuracy devices; 4) the calibration is easily done at an industrial environment. The kinematic parameters calibrated with respect to a single plane aren`t influenced due to the misalignment of the plane. A parameter observability is successfully obtained even through one planar constraint, which guarantees that all kinematic parameters are estimated by minimizing the cost function.
Optimum Design of the Process Parameter in Sheet Metal Forming with Design Sensitivity Analysis using the Direct Differentiation Approach (I) -Design Sensitivity Analysis-
Kim, Se-Ho ; Huh, Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2245~2252
DOI : 10.3795/KSME-A.2002.26.11.2245
Design sensitivity analysis scheme is proposed in an elasto -plastic finite element method with explicit time integration using a direct differentiation method. The direct differentiation is concerned with large deformation, the elasto-plastic constitutive relation, shell elements with reduced integration and the contact scheme. The design sensitivities with respect to the process parameter are calculated with the direct analytical differentiation of the governing equation. The sensitivity results obtained from the present theory are compared with that obtained by the finite difference method in a class of sheet metal forming problems such as hemi-spherical stretching and cylindrical cup deep-drawing. The result shows good agreement with the finite difference method and demonstrates that the preposed sensitivity calculation scheme is a pplicable in the complicated sheet metal forming analysis and design.Ā
Analysis of Tube Expansion by Hydroforming
Lee, Jae-Won ; Park, Jong-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2253~2261
DOI : 10.3795/KSME-A.2002.26.11.2253
Recently the hydroforming technology has drawn a lot of attention because of its capability to produce high quality and light weight parts. In the present study, the tube expansion - one of the simplest hydroforming processes, has been investigated in order to understand fundamental phenomena such as deformation characteristics and effect of process parameters. As a result, the most important process parameters, which determine the state of stress at the expanded zone, were found to be pressure and die displacement. If the stress becomes equi-axial tension at the zone, necking occurs at some distance from the weld line and develops into a crack along the axial direction. Some aspects of mechanical property measurements as well as distributions of hardness and microstructure are also discussed in this paper.Ā
Optimum Design of the Process Parameter in Sheet Metal Forming with Design Sensitivity Analysis using the Direct Differentiation Approach (II) -Optimum Process Design-
Kim, Se-Ho ; Huh, Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2262~2269
DOI : 10.3795/KSME-A.2002.26.11.2262
Process optimization is carried out to determine process parameters which satisfy the given design requirement and constraint conditions in sheet metal forming processes. Sensitivity -based-approach is utilized for the optimum searching of process parameters in sheet metal forming precesses. The scheme incorporates an elasto-plastic finite element method with shell elements . Sensitivities of state variables are calculated from the direct differentiation of the governing equation for the finite element analysis. The algorithm developed is applied to design of the variablc blank holding force in deep drawing processes. Results show that determination of process parameters is well performed to control the major strain for preventing fracture by tearing or to decrease the amount of springback for improving the shape accuracy. Results demonstrate that design of process parameters with the present approach is applicable to real sheet metal forming processes
Dynamic Analysis of a Cantilever Beam with the Payametric Excitation in Rotation
Im, Hyung-Bin ; Chung, Jin-Tai ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2270~2276
DOI : 10.3795/KSME-A.2002.26.11.2270
Dynamic stability of a rotary oscillating cantilever beam is presented in this study. Using the stretch deformation instead of the conventional axial deformation, three linear partial differential equations are derived from Hamilton`s principle and transformed into dimensionless forms. Stability diagrams of the first order approximate solutions are obtained by using the multiple scale perturbation method. The stability diagrams show that relatively large unstable regions exist near the combination of the first chordwise bending natural frequency and the first stretch natural frequency. This result is verified by using the generalized -
Evaluation Method of Interface Strength in Bonded Dissimilar Materials of AU/Epxy
Chung, Nam-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2277~2286
DOI : 10.3795/KSME-A.2002.26.11.2277
The application of bonded dissimilar materials to industries as automobiles, aircraft, rolling stocks, electronic devices and engineering structures is increasing gradually because these materials, compared to the homogeneous materials, have many advantages for material properties. In spite of such wide applications of bonded dissimilar materials, the evaluation method of quantitative strength considering the stress singularities for its bonded interface has not been established clearly. In this paper, the stress singularity for Bctors and the stress intensity factors were analyzed by boundary element method(BEM) for the scarf joints of Al/Epoxy with and without a crack, respectively. From static fracture experiments of the bonded scarf joints, a fracture criterion and a evaluation method of interface strength in bonded dissimilar materials were proposed and discussed.
The Mixed Mode fatigue Crack Propagation Behavior with the Variation of Stress Ratio
Song, Sam-Hong ; Choi, Ji-Hoon ; Lee, Jeong-Moo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2287~2296
DOI : 10.3795/KSME-A.2002.26.11.2287
Most cracks in the structure occur under mixed mode loading and those fatigue crack propagation behavior heavily depends on the stress ratio. So, it is necessary to study the fatigue behavior under mixed mode loading as the stress ratio changes. In this paper, the fatigue crack propagation behavior was respectively investigated at stress ratio 0.1, 0.3, 0.5, 0.7 and we changed the loading application angle into 0
to apply various loading mode. The mode I and II stress intensity factor of CTS specimen used in this study was calculated by the displacement extrapolation method using FEM (ABAQUS). Using both the experiment and FEM analysis, we have concluded the relationship between crack propagation rate and stress intensity factor range at each loading mode due to the variation of stress ratio. Also, when the crack propagated under given stress ratio and loading mode condition, we have concluded the dominant factors of the crack propagation rate at each case.
Thermal Deformation Analysis of Shadow Mask in a Flat TV and Prediction of Electron Beam Landing Shift by FEM
Kim, Jeong ; Park, Soo-Kil ; Kang, Beom-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2297~2304
DOI : 10.3795/KSME-A.2002.26.11.2297
Two-dimensional and three-dimensional finite element methods have been used to analyze the deformation behavior of a shadow mask due to thermal and tension load. The shadow mask inside the Braun tube of a TV set has numerous slits through which the electron beams are guided to land on the designed phosphor of red, green or blue. Its thermal deformation therefore causes landing shift of the electron beam and results in decolorization of a screen. For the realistic finite element analysis, the effective thermal conductivity and the effective elastic modulus arc calculated, and then the shadow mask is modeled as shell without slits. Next a transient thermal analysis of the shadow mask is performed, wherein thermal radiation is a major heat transfer mechanism. Analysis of the resulting thermal deformation is followed, from which the landing shift of the electron beam is obtained. The present finite element scheme may be efficiently used to reduce thermal deformation of a shadow mask and in developing prototypes of a large screen flat TV.
Failure Probability Estimation of Flaw in CANDU Pressure Tube Considering the Dimensional Change
Kwak, Sang-Log ; Lee, Joon-Seong ; Kim, Young-Jin ; Park, Youn-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2305~2311
DOI : 10.3795/KSME-A.2002.26.11.2305
The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and heavy water coolant. Pressure tubes are installed horizontally inside the reactor and only selected samples are periodically examined during in-service inspection. In this respect, a probabilistic safety assessment method is more appropriate fur the assessment of overall pressure tube safety. The failure behavior of CANDU pressure tubes, however, is governed by delayed hydride cracking which is the major difference from pipings and reactor pressure vessels. Since the delayed hydride cracking has more widely distributed governing parameters, it is impossible to apply a general PFM methodology directly. In this paper, a PFM methodology for the safety assessment of CANDU pressure tubes is introduced by applying Monte Carlo simulation in determining failure probability Initial hydrogen concentration, flaw shape and depth, axial and radial crack growth rate and fracture toughness were considered as probabilistic variables. Parametric study has been done under the base of pressure tube dimension and hydride precipitation temperature in calculating failure probability. Unstable fracture and plastic collapse are used for the failure assessment. The estimated failure probability showed about three-order difference with changing dimensions of pressure tube.
The Least-Squares Meshfree Method for Linear Elasticity
Kwon, Kie-Chan ; Park, Sang-Hoon ; Youn, Sung-Kie ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2312~2321
DOI : 10.3795/KSME-A.2002.26.11.2312
The first-order least-squares meshfree method for linear elasticity is presented. The conventional and the compatibility-imposed least-squares formulations are studied on the convergence behavior of the solution and the robustness to integration error. Since the least-squares formulation is a type of mixed formulation and induces positive-definite system matrix, by using shape functions of same order for both primal and dual variables, higher rate of convergence is obtained for dual variables than Galerkin formulation. Numerical examples also show that the presented formulations do not exhibit any volumetric locking for the incompressible materials.
Evaluation of Corrosion Degradation Characteristics of Turbine Blade Material Using Backward Radiated Ultrasound
Song, Sung-Jin ; Kim, Young-H. ; Bae, Dong-Ho ; Jung, Min-Ho ; Kwon, Sung-Duk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2322~2327
DOI : 10.3795/KSME-A.2002.26.11.2322
The corrosion degradation characteristics of the 12Cr alloy steel, which is widely used in fossil power plants as a turbine blade material, are evaluated nondestructively by use of the backward radiated Rayleigh surface wave. In order to evaluate corrosion degradation characteristics, we constructed automated system for the backward radiation, and the frequency dependency of the Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in the specimens. The velocity of the surface wave decrease as the increase of the aging time in the backward radiation profile, which seems to result from the increase of the effective degrading layer thickness. And, amplitude of the surface wave increase as the aging time, which seems to result from the increase of the intergranular corrosion. The result observed in this study demonstrates high potential of the backward radiated ultrasound as a tool for the nondestructive evaluation of the corrosion degradation characteristics of the aged materials.
Nondestructive Evaluation on Strength Characteristic and Damage Behavior of Al 7075/CFRP Sandwich Composite
Lee, Jin-Kyung ; Yoon, Han-Ki ; Lee, Joon-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2328~2335
DOI : 10.3795/KSME-A.2002.26.11.2328
A hybrid composite material has many potential usage due to the high specific strength and the resistance to fatigue, when compared to other composite materials such as fiber reinforced plastic(FRP) and metal matrix composite(MMC). However, the fracture mechanism of hybrid composite material is extremely complicated because of the bonding structure of metals and FRP. In this study, Al 7075 sheets and carbon epoxy preprags were used to fabricate the hybrid composite. Recently, nondestructive technique has been used to evaluate the fracture mechanism of these composite materials. AE technique was used to clarify the microscopic damage behavior and failure mechanism of A17075/CFRP hybrid composite. It was found that AE paralneters such as AE event, energy and amplitude were effective to evaluate the failure process of Al 7075/CFRP composite. In addition, the relationship between the AE signal and the characteristics of fracture surface using optical microscope was discussed.
Effect of Composition on Cutting Characteristics and Reliability Analysis of Ti(C,N) Cermet Tool
Park, June-Seuk ; Kim, Seong-Won ; Kwon, Won-Tae ; Kang, Shin-Hoo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2336~2341
DOI : 10.3795/KSME-A.2002.26.11.2336
When WC and group IV elements are added to Ti(C,N)-Ni cermet, microstructures of the cermet is changed. The change effects directly on the property of the material. In this study, the amount of WC and group IV elements of Ti(C,N) cermet tool was investigated. The composition of WC was changed from 5 to 20wt% to determine the effect of WC on the cutting performance of cermet tool. The more WC was added, the longer the tool life of the cermet tool was. The cermet with lwt% ZrC and l4wt% WC showed the best cutting performance among the investigated cermet tools. The cutting performance of cermet cutting tools suggests the possibility in interrupted cutting for reliability test experimentation was performed repeatedly with
cermet tool machining SCM440. The flank wear of cermet cutting tool at given time condition is suitable for Normal distribution and Log normal distribution by Chi squared test.
Numerical Analysis of ]Residual Stresses and Birefringence in Injection/Compression Molded Center-gated Disks (I) - Modeling and Basic Results -
Lee, Young-Bok ; Kwon, Tai-Hun ; Yoon, Kyung-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2342~2354
DOI : 10.3795/KSME-A.2002.26.11.2342
The present study has numerically predicted both the flow -induced and thermally-induced residual stresses and birefringence in injection o. injection/compression molded center -gated disks. Analysis system for entire molding process was developed based on an ap propriate physical modeling including a nonlinear viscoelastic fluid model, stress-optical law, a linear viscoelastic solid model, free volume theory for density relaxation phenomena and a photoviscoelasticity and so on. Part I presents physical modeling a nd typical numerical analysis results of residual stresses and birefringence in the injection molded center-gated disk. Thermal residual stress was found to be extensional near the center, compressive near the surface and tend to become toward tensional at the surface. A double-hump profile was obtained across the thickness in birefringence distribution: nonzero birefringence is found to be thermally induced, the outer peak is due to the shear flow and subsequent stress relaxation during the filling stage a nd the inner peak is due to the additional shear flow and stress relaxation during the packing stage. Predicted birefringence including both the flow -induced and thermally-induced one becomes quite similar to the experimental one.
Numerical Analysis of Residual Stresses and Birefringence in Injection/Compression Molded Center-gated Disks (II) - Effects of Processing Conditions -
Lee, Young-Bok ; Kwon, Tai-Hun ; Yoon, Kyung-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2355~2363
DOI : 10.3795/KSME-A.2002.26.11.2355
The accompanying paper, Part 1, has presented the physical modeling and basic numerical analysis results of both the flow-induced and thermally-induced residual stress and birefringence in injection molded center gated disks. The present paper, Part II, has attempted to investigate the effects of various processing conditions of injection/compression molding process on the residual stress and birefringence. The birefringence is significantly affected by injection melt temperature, packing pressure and packing time. Birefringence in the shell layer increases as melt temperature gets lower. The inner peak of birefringence increases with packing time and packing pressure. On the other hand, packing pressure, packing time and mold wall temperature affect the thermally-induced residual stress rather significantly in the shell layer, but insignificantly in the core region. Injection/compression molding has been found to reduce the birefringence in comparison with the conventional injection molding process. In particular, mold closing velocity and initial opening thickness in the compression stage of injection/compression molding process have significant effect on the flow-induced birefringence, but not on tile thermal residual stress and the thermally induced birefringence.
Numerical Analysis of Dynamic Stress Concentrations in Axisymmetric Problems
Sim, Woo-Jin ; Lee, Sung-Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2364~2373
DOI : 10.3795/KSME-A.2002.26.11.2364
In this paper, the finite element equations for the time-domain numerical analysis of transient dynamic axisymmetric problems are newly presented. which are based on the equations of motion in convolution integral as in the previous paper. A hollow cylinder subjected to a sudden internal pressure is solved first as a benchmark problem and then the dynamic stress concentrations are analyzed in detail far hollow cylinders having inner and outer circumferential grooves subjected to sudden internal or axial loadings, all the computed results are compared with the existing or the computed ones obtained by using the commercial finite element packages Nastran and Ansys to show the validity and capability of the presented method.
The Effect of Resin Mixture Ratio on Characteristics of Tensile and T-peel Strength in Al/AFRP Laminates
Song, Sam-Hong ; Kim, Cheol-Woong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2374~2382
DOI : 10.3795/KSME-A.2002.26.11.2374
Aluminum alloy/aramid fiber reinforced plastic(Al/AFRP) laminates consists of high strength metal(A15052) and laminated aramid fiber with structural adhesive bond. The mixture ratio effect of epoxy resin curing agent accelerator on the tensile strength and T-peel strength characteristic in Al AFRP laminates were investigated in this study. The epoxy. diglycidylether of bisphenol A(DCEBA), It`as cured by methylene dianiline(MDA) with or without an accelerator(K-54). Eight different kinds of resin mixture ratios were selected for the test , five kinds of Al/AFRP laminates were named as Al/AFRP(1) and three others of Al/AFRP laminates were named as Al/AFRP(2). The comparison of tensile strength and T-peel strength with variation of resin mixture ratio were studied. Respectively. Al/AFRP(1) and Al/AFRP(2) indicated approximately 6.0 times and 7.0 times more improved maximum tensile strength in comparison with those of monolithic A15052. Al/AFRP(2) indicated approximately 1.5 times more impoved maximum T-peel strengths in comparison with those of Al/AFRP(1). As results. Al/AFRP(2) turned out to have more effective characteristics on the tensile strength and T-peel strength than those of Al/AFRP(1).
A Study on fatigue Properties with Different Edge Margin for Hole Expansion Plate
Lee, Joon-Hyun ; Lee, Dong-Suk ; Lee, Hwan-Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2383~2389
DOI : 10.3795/KSME-A.2002.26.11.2383
This paper describes an experimental study on fatigue life extension by using cold working process in fastener hole of aircraft structure. Cold working process was applied for A12024-7351 specimens by considering the effect of edge margin on fatigue life. It is generally recognized that cold working process offers a protective zone around fastener hole of aluminum aircraft structure due to the residual compressive stresses which lead to retardation of crack growth. Thus this process provides the beneficial effect of increasing the fatigue life of the component. there by decreasing maintenance costs. It has also been successfully incorporated into damage tolerance and structural integrity programs. Cold working specimens were tested at constant amplitude peak cyclic stresses. Fatigue life of cold working specimen compared with that of specimen fabricated with base material. The increase of fatigue life for cold working specimen is discussed by both considering the effect of residual compressive stresses measured by X-ray diffraction technique and quantitative effect of edge margin.
Stress Intensity factor Calculation for the Axial Semi-Elliptical Surface Flaws on the Thin-Wall Cylinder Using Influence Coefficients
Jang, Chang-Heui ; Moon, Ho-Rim ; Jeong, Ill-Seok ; Kim, Tae-Ryong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2390~2398
DOI : 10.3795/KSME-A.2002.26.11.2390
For integrity analysis of nuclear reactor pressure vessel, including the Pressurized thermal shock analysis, the fast and accurate calculation of the stress intensity factor at the crack tip is needed. For this, a simple approximation scheme is developed and the resulting stress intensity factors for axial semi-elliptical cracks in cylindrical vessel under various loading conditions are compared with those of the finite element method and other approximation methods, such as Raju-Newman`s equation and ASME Sec. Xl approach. For these, three-dimensional finite-element analyses are performed to obtain the stress intensity factors for various surface cracks with t/R
Development and Evaluation of Predictive Model for Microstructures and Mechanical Material Properties in Heat Affected Zone of Pressure Vessel Steel Weld
Kim, Jong-Sung ; Lee, Seung-Gun ; Jin, Tae-Eun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2399~2408
DOI : 10.3795/KSME-A.2002.26.11.2399
A prediction procedure has been developed to evaluate the microtructures and material properties of heat affected zone (HAZ) in pressure vessel steel weld, based on temperature analysis, thermodynamics calculation and reaction kinetics model. Temperature distributions in HAE are calculated by finite element method. The microstructures in HAZ are predicted by combining the temperature analysis results with the reaction kinetics model for austenite grain growth and austenite decomposition. Substituting the microstructure prediction results into the previous experimental relations, the mechanical material properties such as hardness, yielding strength and tensile strength are calculated. The prediction procedure is modified and verified by the comparison between the present results and the previous study results for the simulated HAZ in reactor pressure vessel (RPV) circurnferential weld. Finally, the microstructures and mechanical material properties are determined by applying the final procedure to real RPV circumferential weld and the local weak zone in HAZ is evaluated based on the application results.
Minimization of Post-processing area for Stereolithography Parts by Selection of Part Orientation
Kim, Ho-Chan ; Lee, Seok-Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2409~2414
DOI : 10.3795/KSME-A.2002.26.11.2409
The surfaces of prototypes become rough due to the stair-stepping which is the inevitable phenomenon in the Rapid Prototypes are not used only for the verification of feature. The grinding, coating, or the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. The solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. the solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the regions for post-processing. the factors to cause the surface roughness and their effects are analyzed through the experiments. Software modules are developed to predict the surface roughness of each face in the prototyping with the result. An experimental compensation method is developed to apply the modules to various RP equipments, materials and build styles. The build direction is searched with use of genetic algorithm to maximize the total areas of the surface of which roughness is better than the user-defined value.
Minimization of Initial Deflection of Multi-Layered Micro-Actuator with Step-Up Structure
Lee, Hee-Joong ; Kang, Shin-Ill ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2415~2420
DOI : 10.3795/KSME-A.2002.26.11.2415
In the present study, a new anchor design was proposed to minimize the initial deflection of micro multi-layer cantilever beam with step-up structure, which is a key component of thin film micro-mirror array. It is important to minimize the initial deflection, caused by residual stress, because it reduces the performance of the actuation. Theoretical and experimental studies were conducted to examine the cause of the initial bending deflection. It was found that the bending deflection at the anchor of the cantilever beam was the primary source of initial deflection. Various anchor designs were proposed and the initial deflections for each design were calculated by finite element analysis. The analysis results were compared with experiments. To reduce the initial deflection a secondary support was added to the conventional structure. The optimal shapes were obtained by simulation and experiment. It was found from the analysis that the ratio or horizontal and vertical dimensions of secondary support was the governing factor, which affected the initial deflection.
A Stochastic Analysis in Steam Turbine Blade Steel Using Monte Carlo Simulation
Kim, Chul-Su ; Jung, Hwa-Young ; Kang, Myung-Su ; Kim, Jung-Kyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2421~2428
DOI : 10.3795/KSME-A.2002.26.11.2421
In this study, the failure probability of the degraded LP turbine blade steel was performed using the Monte Carlo simulation to apply variation of applied stress and strength. For this purpose, applied stress under the service condition of steady state was obtained by theoretical stress analysis and the maximum Von-Mises stress was 219MPa. The fatigue strength under rotating-bending load was evaluated by the staircase method. Furthermore, 3-parameter Weibull distribution was found to be most appropriate among assumed distributions when the probabilistic distributions of tensile and fatigue strength were determined by the proposed analysis. The failure probability with various loading conditions was derived from the strength-stress interference model and the characteristic factor of safety was also estimated.
The Problem of Engine Friction Test by Strip Down Method
Cho, Myung-Rae ; Oh, Dae-Yoon ; Han, Dong-Chul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2429~2435
DOI : 10.3795/KSME-A.2002.26.11.2429
The aim of this paper is to investigate the problem of strip down method, which is usually used to evaluate the engine friction level. The validity of strip down method was investigated by theoretical analysis of friction in crank and piston assembly. The friction of cylinder and piston assembly was analyzed under the various test conditions. The measured cylinder pressure was used as boundary conditions of friction torque and loss calculation. The friction loss of crank and piston assembly was influenced by test conditions that resulted from the variation of load condition. From the results, we have known that the strip down method could be possible to distort the friction loss of engine moving components.
finite Element Modeling of a Hemispherical Asperity Adhesively Contacting the Plane Surface of Semi-Infinite Rigid Body
Cho, Sung-San ; Park, Seung-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2436~2441
DOI : 10.3795/KSME-A.2002.26.11.2436
Finite element technique considering adhesive forces is proposed and applied to analyze the behavior of elastic hemispherical asperity adhesively contacting the plane surface of semi -infinite rigid body. It is demonstrated that the finite element model simulates interfacial phenomena such as jump -to-contact and adhesion hysteresis that cannot be simulated with the currently available adhesive contact continuum models. This simulation aiso provides valuable information on contact pressure, contact region and stress distributions. This technique is anticipated to be utilized in designing a low-adhesion surface profile for MEMS/NEMS applications since various contact geometries can be analyzed with this technique.
Engineering J-Integral Estimation for Internal Axial Surface Cracks in Cylinders (II) -Optimised Reference Stress Based Estimation-
Kim, Jin-Su ; Kim, Yun-Jae ; Kim, Young-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2442~2449
DOI : 10.3795/KSME-A.2002.26.11.2442
This paper provides an reference stress based J estimation equation fur cylinders with finite internal axial surface cracks under internal pressure. In part 1, the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-0) materials is proposed. In this paper, the developed CE/EPRI -type solutions ale then re-formulated based on the reference stress concept. Such a re-formulation provides a simpler equation for J. estimation are then further extended to combined internal pressure and bending. The proposed reference stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress-strain data for a Type 304 stainless steel. Good agreement between the FE results and the proposed reference stress based J estimations provides confidence in the use of the proposed method to elastic -plastic fracture mechanics of pressurised piping.
Microlens Fabrication Method by the Modified LICA Process
Lee, Sung-Keun ; Lee, Kwang-Cheol ; Lee, Seung-S. ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2450~2456
DOI : 10.3795/KSME-A.2002.26.11.2450
Microlenses and microlens arrays are fabricated using a novel fabrication technology based on the exposure of a resist (usually PMMA) to deep X-rays and subsequent thermal treatment. The fabrication technology is very simple and produces microlenses and microlens arrays with good surface roughness (less than 1 nm). The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses is produced through the effects of volume change, surface tension, and reflow during thermal treatment of irradiated PMMA. The geometry of the microlens is determined by parameters such as the X-ray dose applied to the PMMA, the diameter of the microlens, along with the heating temperature, heating time, and cooling rate in the thermal treatment. Microlenses are produced with diameters ranging from 30 to 1500
. The modified LIGA process is used not only to construct hemispherical microlenses but also structures that are rectangular-shaped, star-shaped, etc.
Application of a Boundary element Method to the Analysis of ultrasonic Scattering by Flaws
Jeong, Hyun-Jo ; Kim, Jin-Ho ; Park, Moon-Cheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2457~2465
DOI : 10.3795/KSME-A.2002.26.11.2457
Numerical modeling of a nondestructive testing system plays an important role in many aspects of quantitative nondestructive evaluation (QNDE). The ultimate goal of a model is to predict test results for a specific flaw in a material. Thus, in ultrasonic testing, a system model should include the transducer, its radiation pattern, the beam reflection and propagation, and scattering from defects. In this paper attention is focused on the scattering model and the scattered fields by defects are observed by an elastodynamic boundary element method. Flaw types addressed are void-like and crack-like flaws. When transverse ultrasonic waves are obliquely incident on the flaw, the angular distribution of far-field scattered displacements are calculated and presented in the form of A-scan mode. The component signals obtained from each scattering problem are identified and their differences are addressed. The numerical results are also compared with those obtained by high frequency approximate solutions.
Optimal Design of Strip Casting Roll
Park, Cheol-Min ; Kang, Tae-Wook ; Park, Gyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 11, 2002, Pages 2466~2473
DOI : 10.3795/KSME-A.2002.26.11.2466
In twin roll strip casting process, the design of casting roll is the most important equipment for producing strip. Analyses of heat transfer and deformation for the casting roll are carried out by using the finite element program, ANSYS. Both the elastic deformation and the elasto-plastic deformation under a thermal load are considered in the analysis. Optimization to minimize the volume of roll is performed under the various thermal loads such as the heat flux and the roll speed. Design variables are defined by diameters and positions of the cooling hole in the roll , Although the thermal load remarkably varies, the design variables and objective function are found to be consistent.