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Transactions of the Korean Society of Mechanical Engineers A
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 35, Issue 12 - Dec 2011
Volume 35, Issue 11 - Nov 2011
Volume 35, Issue 10 - Oct 2011
Volume 35, Issue 9 - Sep 2011
Volume 35, Issue 8 - Aug 2011
Volume 35, Issue 7 - Jul 2011
Volume 35, Issue 6 - Jun 2011
Volume 35, Issue 5 - May 2011
Volume 35, Issue 4 - Apr 2011
Volume 35, Issue 3 - Mar 2011
Volume 35, Issue 2 - Feb 2011
Volume 35, Issue 1 - Jan 2011
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Relief of Residual Stress and Estimation of Heat-Treatment Characteristics for Al6061 Alloy by Cryogenic Heat Treatment
Ko, Dae-Hoon ; Park, Ki-Jung ; Cho, Young-Rae ; Lim, Hak-Jin ; Lee, Jung-Min ; Kim, Min-Byung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1145~1153
DOI : 10.3795/KSME-A.2011.35.10.1145
The purpose of this study is to relieve the residual stress of Al6061 using cryogenic heat treatment. Experimental T6 and cryogenic heat treatments were carried out to define the convective heat-transfer coefficient, which was then applied in the finite-element method (FEM) to predict the residual stress. The predicted residual stress was compared with the residual stress measured by X-ray diffraction (XRD), and the results were in good agreement. The mechanical properties were estimated by measuring the electrical conductivity and hardness. In addition, the size and formation of the precipitations were observed by TEM and XRD analysis for both T6 and cryogenic heat treatments. The effects of the cryogenic heat treatment on the residual stress, mechanical properties, and precipitation of Al6061 alloys were thus confirmed.
Mechanical Properties and Changes in Microstructure for IN738LC with Thermal Exposure
Yoon, Yong-Keun ; Kim, Jae-Hoon ; Jeong, Dong-Hee ; Yoo, Keun-Bong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1155~1160
DOI : 10.3795/KSME-A.2011.35.10.1155
High-strength nickel-based super alloys have been widely used in aircraft engines, vessel engines, and turbine blades because of their high strength and excellent fatigue and oxidation resistance. In this study, tests were carried out to determine the total strain range and temperature for high-strength nickel-based super alloys. Prepared specimens of IN738LC were exposed to temperatures of
for 1,000.10,000 h. These specimens were subjected to tests of mechanical properties and microstructure observations. The changes in mechanical properties were related to changes in
according to the thermal exposure time.
Optimization Techniques for the Inverse Analysis of Service Boundary Conditions in a Porous Catalyst Substrate with Fluid-Structure Interaction Problems
Baek, Seok-Heum ; Cho, Seok-Swoo ; Kim, Hyun-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1161~1170
DOI : 10.3795/KSME-A.2011.35.10.1161
This paper presents a solution to the inverse problem for the service boundary conditions of thermal-flow and structure analysis in a catalyst substrate. The exhaust-gas purification efficiency of a catalyst substrate is influenced by the shape parameter, catalyst ingredients and so on and is estimated by the thermal flow uniformity. The formulations of the inverse problem of obtaining the thermal-flow parameters (inlet temperature, velocity, heat of reaction, convective heat-transfer coefficient) and the direct problem of estimating from a given outlet temperature distribution are described. An experiment was designed and the response-surface optimization technique was used to solve the proposed inverse problem. The temperature distribution of the catalyst substrate was obtained by thermal-flow analysis for the predicted thermal-flow parameters. The thermal stress and durability assessments for the catalyst substrate were performed on the basis of this temperature distribution. The efficiency and accuracy of the inverse approach have been demonstrated through the achievement of good agreement between the thermal-flow response surface model and the results of experimental vehicle tests.
Robust Design of a Dynamic System Using a Probabilistic Design Method
Ryu, Jang-Hee ; Choi, In-Sang ; Kim, Joo-Sung ; Son, Young-Kap ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1171~1178
DOI : 10.3795/KSME-A.2011.35.10.1171
This paper shows the robust design results of an actuator, a kind of dynamic system. Variations in the components comprising the actuator cause uncertainties in the system's dynamic performance. Therefore, a probabilistic design method is applied to ensure robust actuator performance to component variation. A Simulink model for the actuator was built using transfer functions for the components. The dynamic responses of the actuator were evaluated using the Simulink model. Performance indexes were approximated as quadratic functions of the design parameters through the application of the response surface methodology (RSM) with the Simulink model. Then, a probabilistic design method was applied to the approximated performance indexes to obtain optimal design parameters that would provide robust actuator performance. The optimal design was compared to the present design in terms of the performance indexes and dynamic response characteristics over time.
Fracture Mechanics Approach to X-Ray Diffraction Method for Spot Welded Lap Joint Structure of Rolled Steel Considered Residual Stress
Baek, Seung-Yeb ; Bae, Dong-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1179~1185
DOI : 10.3795/KSME-A.2011.35.10.1179
Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis,
relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints.
The Development of an Adjustable Dual-Level Load Limiter
Lee, In-Beom ; Kang, Shin-You ; Kim, Seock-Hyun ; Ryoo, Won-Wha ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1187~1191
DOI : 10.3795/KSME-A.2011.35.10.1187
In this paper, the development of an adjustable load limiter is presented, which is a component of the seat belt. The adjustable load limiter is loaded at different levels for varied weights and heights of occupant. The recent regulation FMVSS 208 demands strict safety standards for different percentiles of dummy size. In this work, high- and low-level load conditions are proposed according to dummy scale and thoracic injury criteria. The suggested load conditions were verified by performing a sled test using the benchmark model. A dual-level load limiter has been developed on the basis of these tests. Experiments were conducted on the product performance, and finite element analysis was carried out; the results confirmed the points for improvement.
Study on Sealing Characteristics of Solenoid Valve for Fuel Cells
Yun, So-Nam ; Jeong, Hwang-Hun ; Kim, Young-Bok ; Kim, Dong-Gun ; Heo, Duk-Yeal ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1193~1198
DOI : 10.3795/KSME-A.2011.35.10.1193
The solenoid valve used in fuel cell system need to have good sealing performance because the work fluid can explode in the system. Moreover, the temperature of the work fluid is extremely high in order to maintain the properties of the rubber ring that seals the solenoid valve. This study deals with the rubber ring which is made from a fluoro-elastomer. The life cycle of the rubber ring was estimated by the relational expression of Arrhenius, and the solenoid valve was tested to confirm the sealing characteristics.
Characterization and Fatigue Life Evaluation of Rubber/Clay Nanocomposites
Woo, Chang-Su ; Park, Hyun-Sung ; Joe, Deug-Hwan ; Jun, Young-Sig ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1199~1203
DOI : 10.3795/KSME-A.2011.35.10.1199
Nanocomposites were prepared through the compounding of rubber and clay. Measurements of the static and dynamic mechanical properties of different compositions over a temperature range
showed that the mechanical properties of these rubber/clay nanocomposites are superior to those of existing rubber materials. In this study, by using the parameter of the maximum Green.Lagrange strain appearing at certain locations, the relationship between fatigue life and maximum Green.Lagrange strain, and the correlations between test-piece tests and bench tests of actual rubber components are proved. In order to predict the fatigue life of rubber components at the design stage, a simple procedure of life prediction is suggested. The predicted fatigue lives of the rubber engine mounts agree fairly well with the fatigue lives determined experimentally.
Influence of Ligament Deficits and Isthmic Defects on Instability in Lumbar Spine
Choi, Dae-Kyung ; Kim, Yoon-Hyuk ; Kim, Kyung-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1205~1210
DOI : 10.3795/KSME-A.2011.35.10.1205
Spinal instability known to be related to low back pain. However, the quantitative definition of spinal instability has not been established because there is a lack of consensus regarding clinical and radiological studies. In addition, the major factors affecting such instability have not been elucidated, although disc degeneration, disc injury, ligament injury, and isthmic defects are considered to result in such problems. In this study, individual and combined influences on spinal instability with a three-dimensional finite element model of a one-level lumbar spinal motion segment were investigated, under the assumption that the rotation and translation in the sagittal plane under flexion and extension represented the instability indices. The results could be helpful in understanding the causes and mechanisms of spinal instability in the lumbar spine.
Efficient Modal Analysis of Prestressed Structures via Model Order Reduction
Han, Jeong-Sam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1211~1222
DOI : 10.3795/KSME-A.2011.35.10.1211
It is necessary to use prestressed modal analysis to calculate the modal frequencies and mode shapes of a prestressed structure such as a spinning blade, a preloaded structure, or a thermally deformed pipe, because the prestress effect sometimes causes significant changes in the frequencies and mode shapes. When the finite element model under consideration has a very large number of degrees of freedom, repeated prestressed modal analyses for investigating the prestress effects might become too computationally expensive to finish within a reasonable design-process time. To alleviate these computational difficulties, a Krylov subspace-based model order reduction, which reduces the number of degrees of freedom of the original finite element model and speeds up the necessary prestressed modal analysis with the reduced order models (ROMs), is presented. The numerical process for the moment-matching model reduction is performed directly on the full order models (FOMs) (modeled in ANSYS) by the Arnoldi process. To demonstrate the advantages of this approach for performing prestressed modal analysis, the prestressed wheel and the compressor impeller under their high-speed rotation are considered as examples.
Design Optimization of Moving-Coil Type Linear Actuator Using Level Set Method and Phase-Field Model
Lim, Sung-Hoon ; Oh, Se-Ahn ; Min, Seung-Jae ; Hong, Jung-Pyo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1223~1228
DOI : 10.3795/KSME-A.2011.35.10.1223
A moving-coil type linear actuator has been widely used in the system reciprocating short stroke because of its several advantages, such as the structural simplicity, low weight and a fast control response speed. This paper presents a design approach for improving the actuating performance with a clear expression of optimal configuration represented by a level set function. The optimization problem is formulated to minimize the variation of magnetic force at every moving displacement of the mover for fast and easy control. To consider the manufacturability of actuator, the concept of phase-field model is incorporated to control the complexity of structural boundaries. To verify the usefulness of the proposed method, the core design example of cylindrical linear actuator is performed.
Comparison and Estimation of Fretting Fatigue Damage Parameters for Aluminum Alloy A7075-T6
Hwang, Dong-Hyeon ; Cho, Sung-San ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1229~1235
DOI : 10.3795/KSME-A.2011.35.10.1229
Fatigue tests were conducted on the aluminum alloy, A7075-T6 to determine the most reliable fretting fatigue damage parameter. Specimens with grooves were used, so that either fretting fatigue crack at the pad/specimen interface or plain fatigue crack at the groove could be nucleated, depending on the pad pressure. Both the crack nucleation location and initial crack orientation were examined using optical microscopy, and the results were used to assess the reliability of the various fretting fatigue damage parameters that have been most commonly used in the literature. Finite element analysis was employed to obtain the stress and strain data of the specimen, which were needed to estimate the parameter values and the orientation of the critical plane. It was revealed that both the Fatemi.Socie and McDiarmid parameters, which assume shear-mode fatigue cracking, are the most reliable.
Pressure Analysis of the Plantar Musculoskeletal Fascia Using a Fine Finite-Element Model
Jeon, Seong-Mo ; Kim, Cheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1237~1242
DOI : 10.3795/KSME-A.2011.35.10.1237
The A detailed 3D finite-element analysis model of a human foot has been developed by converting CT scan images to 3D CAD models in order to analyze the distribution of plantar pressure. The 3D foot model includes all muscles, bones, and skin. On the basis of this model and the pressure distribution results, shoes for diabetes patients, which can make the plantar pressure distribution uniform, may be designed through finite-element contact analysis.
Shape-Simplification Analysis Model for Fatigue Life Prediction of Casting Products Considering Internal Defects
Kwak, Si-Young ; Kim, Hak-Ku ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1243~1248
DOI : 10.3795/KSME-A.2011.35.10.1243
Internal defects are a major concern in the casting process because they have a significant influence on the strength and fatigue life of casting products. In general, they cause stress concentration and can be a starting point of cracks. Therefore, it is important to understand the effects of internal defects on mechanical properties such as fatigue life. In this study, fatigue experiments on tensile specimens with internal defects were performed. The internal defects in the casting product were scanned by an industrial CT scanner, and its shape was simplified by ellipsoidal primitives for the structural and fatigue analysis. The analysis results were compared with experimental results for casting products with internal defects. It was demonstrated that it is possible to consider internal defects of casting products in stress and fatigue analysis. The proposed method provides a tool for the prediction of the fatigue life of casting products and the investigation of the effects of internal defects on mechanical performance.
High-Temperature Structural Analysis of a Small-Scale Prototype of a Process Heat Exchanger (IV) - Macroscopic High-Temperature Elastic-Plastic Analysis -
Song, Kee-Nam ; Hong, Sung-Deok ; Park, Hong-Yoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1249~1255
DOI : 10.3795/KSME-A.2011.35.10.1249
A PHE (Process Heat Exchanger) is a key component required to transfer heat energy of
generated in a VHTR (Very High Temperature Reactor) to a chemical reaction that yields a large quantity of hydrogen. A small-scale PHE prototype made of Hastelloy-X was scheduled for testing in a small-scale gas loop at the Korea Atomic Energy Research Institute. In this study, as a part of the evaluation of the high-temperature structural integrity of the PHE prototype, high-temperature structural analysis modeling, and macroscopic thermal and elastic-plastic structural analysis of the PHE prototype were carried out under the gas-loop test conditions as a preliminary qwer123$study before carrying out the performance test in the gas loop. The results obtained in this study will be used to design the performance test setup for the modified PHE prototype.
Analysis of Dispersion Characteristics of Guided Waves in Rails
Kang, Bu-Byoung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1257~1264
DOI : 10.3795/KSME-A.2011.35.10.1257
Guided ultrasonic waves propagating over long distances within a short period provide a fast long-range inspection method. However, structures with arbitrary cross-sections, such as rails, have complicated dispersion characteristics that make analysis of the ultrasonic signal difficult. Therefore, an understanding of the characteristics of the propagating waves in rails is important for the creation of a reliable and practical inspection system using guided waves. In particular, it is necessary to investigate the dispersion characteristics of the guided waves. This paper introduces a method for the calculation of the dispersion curves of KS60 rails by adopting a SAFE method, and discusses the possibility of using guided waves as a technique for rail inspection.
Seismic and Structure Analysis of a Temporary Rack Construction in a Nuclear Power Plant
Kim, Heung-Tae ; Lee, Young-Shin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1265~1271
DOI : 10.3795/KSME-A.2011.35.10.1265
In this study, the safety of a rack structure was evaluated through seismic analysis considering fluid-structure interactions using a finite-element model. The rack structure was immersed under water, so it was influenced by the water. The fluid-structure interaction can be specified in terms of the hydrodynamic effect, which is defined as the added mass per unit length. Modal analysis and seismic analysis using the Floor Response Spectrum (FRS) were carried out under Operating Basis Earthquake (OBE) and Safe Shutdown Earthquake (SSE) conditions. The analytical maximum displacements of the rack structure were 0.29 and 0.36 mm under OBE and SSE conditions, respectively. The maximum stresses were 17.9 MPa under OBE conditions and 19.6 MPa under SSE conditions; these results corresponded to 23 % and 14% of the yield strength of the applied material, respectively.
Structural Optimization of Variable Swash Plate for Automotive Compressor Using Orthogonal Polynomials
Baek, Seok-Heum ; Kim, Hyun-Sung ; Han, Dong-Seop ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1273~1279
DOI : 10.3795/KSME-A.2011.35.10.1273
The variable-swash-plate compressor has recently been adopted as a vehicle compressor to improve fuel efficiency. The rotation torque in the variable-swash-plate compressor and the pressure-affected piston have a great influence on the swash-plate design and deformation. This paper suggests the optimal configuration design by using Chebyshev orthogonal polynomial and optimization techniques. The orthogonal array (OA) and analysis of variance (ANOVA) techniques and response surface optimization, are employed to determine the main effects and their optimal design variables. According to the optimal design, we confirm an effective design variable in swash plate and explain the optimal solution, the usefulness for satisfying the constraints of maximum stress and deformation.
Statistical Distribution of Fatigue Life of Composite Materials for Small Wind-Turbine Blades
Kang, Ki-Weon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1281~1289
DOI : 10.3795/KSME-A.2011.35.10.1281
This paper deals with several statistical distribution functions for the analysis of fatigue life data of composite laminates for small wind-turbine blades. A series of tensile tests was performed on triaxial glass/epoxy laminates for loading directions of
. Then, fatigue tests were carried out to determine the fatigue life at the aforementioned loading directions and the fatigue stresses at four levels. Two-parameter Weibull, three-parameter Weibull, normal, and log-normal distributions were used to fit the fatigue life data of the triaxial composite laminates. The three-parameter Weibull distribution most accurately described the fatigue life data measured experimentally for all the cases considered. Furthermore, the variation of fatigue life was simultaneously affected by the loading direction and fatigue stress level.
Development of a Storage-Reliability Estimation Method Using Quantal Response Data for One-Shot Systems with Low Reliability-Decreasing Rates
Jang, Hyun-Jeung ; Son, Young-Kap ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1291~1298
DOI : 10.3795/KSME-A.2011.35.10.1291
This paper proposes a new reliability estimation method for one-shot systems using quantal response data, which is based on a parametric estimation method. The proposed method considers the time-variant failure ratio of the quantal response data and it can overcome the problems in parametric estimation methods. Seven reliability estimation methods in the literature were compared with the proposed method in terms of the accuracy of reliability estimation in order to verify the proposed method. To compare the accuracy of reliability estimation, the SSEs (Sum of Squared Error) of the reliability estimation results for the different estimation methods were evaluated according to the various numbers of samples tested. The proposed method provided more accurate reliability estimation results than any of the other methods from the results of the accuracy comparison.
Bayesian Parameter Estimation for Prognosis of Crack Growth under Variable Amplitude Loading
Leem, Sang-Hyuck ; An, Da-Wn ; Choi, Joo-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1299~1306
DOI : 10.3795/KSME-A.2011.35.10.1299
In this study, crack-growth model parameters subjected to variable amplitude loading are estimated in the form of a probability distribution using the method of Bayesian parameter estimation. Huang's model is employed to describe the retardation and acceleration of the crack growth during the loadings. The Markov Chain Monte Carlo (MCMC) method is used to obtain samples of the parameters following the probability distribution. As the conventional MCMC method often fails to converge to the equilibrium distribution because of the increased complexity of the model under variable amplitude loading, an improved MCMC method is introduced to overcome this shortcoming, in which a marginal (PDF) is employed as a proposal density function. The model parameters are estimated on the basis of the data from several test specimens subjected to constant amplitude loading. The prediction is then made under variable amplitude loading for the same specimen, and validated by the ground-truth data using the estimated parameters.
Robust Optimization of the Solenoid Assembly in Electromagnetic Limited Slip Differential by Considering the Uncertainties in Machining Variables
Oh, Sang-Kyun ; Lee, Kwang-Ki ; Suh, Chang-Hee ; Jung, Yun-Chul ; Kim, Young-Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1307~1313
DOI : 10.3795/KSME-A.2011.35.10.1307
The mechanical limited slip differential (LSD) in vehicles is being replaced by the electromagnetic LSD because of its fast response and better active control characteristics. The coil housing made of STS 304 is one of the most important parts in the solenoid assembly of the electromagnetic LSD. High geometrical accuracy is a prerequisite for the manufacture of such coil housings, but precision machining is difficult because of the use of STS 304 thin plate and the variance in machining variables. The aim of this study is to optimize the mean and variance of the shape accuracy in the coil housing by finding a robust solution for the machining process conditions. The mean and standard deviation of the jaw contact pressure, cutting speed, and feed rate are considered to be the major parameters for minimizing the geometrical mean and variance. The response surface model based on the second-order Taylor series is combined together to minimize the mean and variance of the shape accuracy of the coil housing.
Evaluation of Fatigue Life and Structural Analysis for Dish-Type and Spoke-Type Automobile Wheels
Kang, Sung-Soo ; Lee, Jong-Hwa ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1315~1321
DOI : 10.3795/KSME-A.2011.35.10.1315
Prior to the experimental and production stages of goods, the strengths should be evaluated in the design stage. The introduction of commercial codes at the design stage gives benefits such as cost and time economies in the production and strength evaluation. In this study, structural analysis and fatigue analysis are carried out using ANSYS modeling of the 3D geometry of the wheel. In a comparison of dish-type and spoke-type wheels, it is shown that the deformation and maximum equivalent stress for the dish-type wheels are lower than those for spoke-type wheels. Nevertheless, spoke-type wheels are often used because they are light and have exhibit excellent cooling performance. Furthermore, according to the results of life analysis, aluminum wheels show improved resistance to fatigue compared to steel wheels.
Tolerance Optimization of Lower Arm Used in Automobile Parts Considering Six Sigma Constraints
Lee, Kwang-Ki ; Han, Seung-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1323~1328
DOI : 10.3795/KSME-A.2011.35.10.1323
In the current design process for the lower arm used in automobile parts, an optimal solution of its various design variables should be found through exploration of the design space approximated using the response surface model formulated with a first- or second-order polynomial equation. In this study, a multi-level computational DOE (design of experiment) was carried out to explore the design space showing nonlinear behavior, in terms of factors such as the total weight and applied stress of the lower arm, where a fractional-factorial orthogonal array based on the artificial neural network model was introduced. In addition, the tolerance robustness of the optimal solution was estimated using a tolerance optimization with six sigma constraints, taking into account the tolerances occurring in the design variables.
Plastic Limit Loads for Slanted Circumferential Through-Wall Cracked Pipes Using 3D Finite-Element Limit Analyses
Jang, Hyun-Min ; Cho, Doo-Ho ; Kim, Young-Jin ; Huh, Nam-Su ; Shim, Do-Jun ; Choi, Young-Hwan ; Park, Jung-Soon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1329~1335
DOI : 10.3795/KSME-A.2011.35.10.1329
On the basis of detailed 3D finite-element (FE) limit analyses, the plastic limit load solutions for pipes with slanted circumferential through-wall cracks (TWCs) subjected to axial tension, global bending, and internal pressure are reported. The FE model and analysis procedure employed in the present numerical study were validated by comparing the present FE results with existing solutions for plastic limit loads of pipes with idealized TWCs. For the quantification of the effect of slanted crack on plastic limit load, slant correction factors for calculating the plastic limit loads of pipes with slanted TWCs from pipes with idealized TWCs are newly proposed from extensive 3D FE calculations. These slant-correction factors are presented in tabulated form for practical ranges of geometry and for each set of loading conditions.
Effects of Geometry of Reactor Pressure Vessel Upper Head Control Rod Drive Mechanism Penetration Nozzles on J-Groove Weld Residual Stress
Kim, Ju-Hee ; Kim, Yun-Jae ; Lee, Sung-Ho ; Hur, Nam-Young ; Bae, Hong-Yeol ; Oh, Chang-Young ; Kim, Ji-Soo ; Park, Heung-Bae ; Lee, Seung-Geon ; Kim, Jong-Sung ; Huh, Nam-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1337~1345
DOI : 10.3795/KSME-A.2011.35.10.1337
In pressurized water reactors (PWRs), the reactor pressure vessel (RPV) upper head contains numerous control rod drive mechanism (CRDM) nozzles. In the last 10 years, the incidences of cracking in alloy 600 CRDM nozzles and their associated welds has increased significantly. Several axial and circumferential cracks have been found in CRDM nozzles in European PWRs and U.S. nuclear power plants. These cracks are caused by primary water stress corrosion cracking (PWSCC) and have been shown to be driven by welding residual stresses and operational stresses in the weld region. Therefore, detailed finite-element (FE) simulations for the Korea Nuclear Reactor Pressure Vessel have been conducted in order to predict the magnitudes of the weld residual stresses in the tube materials. In particular, the weld residual stress results are compared in terms for nozzle location, geometry factor
/t, geometry of fillet, and adjacent nozzle.
Friction Stir Welding of 7075-T651 Aluminum Plates and Its Fatigue Crack Growth Property
Kim, Chi-Ok ; Sohn, Hye-Jeong ; Kim, Seon-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 35, issue 10, 2011, Pages 1347~1353
DOI : 10.3795/KSME-A.2011.35.10.1347
Friction stir welding (FSW) method has extensively been used in manufacturing methods because of the several advantages over conventional welding methods, such as better mechanical properties, reduced occurrence of joining defects, high material saving, and low production time, etc. The aim of this paper is to review the optimal FSW conditions using the previous experimental results and is to investigate the fatigue crack growth rate in three different zones, WM, HAZ and BM for FSWed Al7075-T651 aluminum plates. As far as our experiments are concerned, the optimal conditions are obtained as rotation speed, 800rpm and travelling speed, 0.5mm/sec. The fatigue crack growth rate showed strong dependency on three different zones WM, HAZ and BM, and crack driving force.