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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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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 36, Issue 12 - Dec 2012
Volume 36, Issue 11 - Nov 2012
Volume 36, Issue 10 - Oct 2012
Volume 36, Issue 9 - Sep 2012
Volume 36, Issue 8 - Aug 2012
Volume 36, Issue 7 - Jul 2012
Volume 36, Issue 6 - Jun 2012
Volume 36, Issue 5 - May 2012
Volume 36, Issue 4 - Apr 2012
Volume 36, Issue 3 - Mar 2012
Volume 36, Issue 2 - Feb 2012
Volume 36, Issue 1 - Jan 2012
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Ductile Failure Simulation of Tensile Plates with Multiple Through-Wall Cracks Based on Damage Mechanics
Jeon, Jun-Young ; Kim, Nak-Hyun ; Oh, Chang-Sik ; Kim, Yun-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 245~252
DOI : 10.3795/KSME-A.2012.36.3.245
This paper proposes a simple numerical method, based on the stress-modified fracture strain-damage model with the stress-reduction technique, for predicting the failure behaviors of ductile plates with multiple through-wall cracks. This technique is implemented using the user-defined subroutines provided in ABAQUS. For validation, the results simulated using the proposed method are compared with published experimental data of Japanese researchers.
Numerical Method for Improving the Accuracy of Molten Metal Flow
Choi, Young-Sim ; Hong, Jun-Ho ; Hwang, Ho-Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 253~258
DOI : 10.3795/KSME-A.2012.36.3.253
The Cartesian grid system has generally been used in casting simulations, even though it does not represent sloped and curved surfaces very well. These distorted boundaries cause several problems, and special treatment is necessary to resolve them. A cut cell method on a Cartesian grid has been developed for the simulation of threedimensional mold filling. Cut cells at a cast/mold interface are generated on Cartesian grids, and the governing equations are computed using the volume and areas of the cast at the cut cells. In this paper, we propose a new method based on the partial cell treatment (PCT) that can consider the cutting cells which are cut by the cast and the mold. This method provides a better representation of the surface geometry, and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian gird system. Various test examples for several casting process are computed and validated.
Evaluations of Magnetic Abrasive Polishing and Distribution of Magnetic Flux Density on the Curvature of Non-Ferrous Material
Kim, Sang-Oh ; Kwak, Jae-Seob ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 259~264
DOI : 10.3795/KSME-A.2012.36.3.259
Automatic magnetic abrasive polishing (MAP), which can be applied after machining of a mold on a machine tool without unloading, is very effective for finishing a free-form surface such as a complicated injection mold. This study aimed to improve the efficiency of MAP of a non-ferrous mold surface. The magnetic array table and control of the electromagnet polarity were applied in the MAP of a free-form surface. In this study, first, the magnetic flux density on the mold surface was simulated to determine the optimal conditions for the polarity array. Then, the MAP efficiency for polishing a non-ferrous mold surface was estimated in terms of the change in the radius of curvature and the magnetic flux density. The most improved surface roughness was observed not only in the upward tool path but also in the working area of larger magnetic flux density.
Design of a Web-Based System for Collaborative Power-Boat Manufacturing
Lee, Philippe ; Lee, Dong-Kun ; Back, Myung-Gi ; Oh, Dae-Kyun ; Choi, Yang-Ryul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 265~273
DOI : 10.3795/KSME-A.2012.36.3.265
The business environment is changing rapidly because of the global crisis. In order to survive and enhance competitiveness in the global market, global manufacturing companies are trying to overcome the crisis through the convergence of production infrastructure and IT technology. The importance of systems to support the integration of manufacturing processes, collaboration in product development, and information integration of providers and producers is therefore increasing. In this paper, research is conducted on the design and implementation of a collaboration system to support a power-boat manufacturing company in this situation of increased demand for collaboration and information integration. The system was designed through product-structure and production-process analysis, support product data management, and enterprise contents management. The company involved in the power-boat development project is expected to show an improvement in productivity through the integrated management of information and collaboration provided by this system.
Evaluation of Notch Effect on the Dynamic Strain Aging Behavior of Carbon Steel Piping Material
Lee, Sa-Yong ; Kim, Jin-Weon ; Kim, Hong-Deok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 275~282
DOI : 10.3795/KSME-A.2012.36.3.275
In this study, tensile tests were performed using standard and notched-bar specimens under two different displacement rates and various temperatures, in order to investigate the effects of the stress and strain concentration at the notched section on the dynamic strain aging (DSA) behavior of carbon steel piping material. In addition, finite element simulations were conducted to evaluate quantitatively the stress and strain states for both types of specimen under uniaxial tensile loading. The results showed that serration and an increase in tensile strength, which are considered to be evidence of DSA in carbon steels, can be observed from tensile tests for notched-bar specimens. It was also found that the temperature region of DSA observed in the notched-bar specimens was higher than the DSA region observed in the standard tensile specimens tested under the same displacement rate. The results of finite element analysis showed that this behavior is associated with the high strain rate at the notched section, which is caused by the stress and strain concentration.
The Effects of Process Parameters of Multi-Stage Forming on Springback for a U-Channel made of Ultra-High-Strength Steel
Suh, Chang-Hee ; Jung, Yun-Chul ; Lim, Yong-Hee ; Yun, Hyo-Yun ; Lee, Kyung-Hoon ; Kim, Young-Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 283~288
DOI : 10.3795/KSME-A.2012.36.3.283
Ultra-high-strength steels (UHSSs) are widely used for lightweight automobile parts, and the control of springback is very important in sheet-metal forming. The object of this study is to verify the effects of multi-stage forming process parameters for U-channel-type automobile parts made of UHSS. Finite element analysis is carried out to predict the formability and springback. The main parameters considered for the multi-stage forming process are the die angle, die radius, and punch-forming direction. It is shown that multi-stage forming is very effective for reducing springback, and that a small punch-forming angle and die radius reduce springback, whereas the die angle does not have a large effect.
Omnidirectional Mobile Robot Capable of Variable Footprinting Based on Hub-Type Drive Module
Kim, Hyo-Joong ; Cho, Chang-Nho ; Kim, Hwi-Su ; Song, Jae-Bok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 289~295
DOI : 10.3795/KSME-A.2012.36.3.289
In recent years, an increased amount of research has been carried out on mobile robots to improve the performance of service robots. Mobile robots maximize the mobility of service robots, thus allowing them to work in different areas. However, conventional service robots have their center of mass placed high above the ground, which may cause them to fall when moving at high speed. Furthermore, hub-type actuators, which are often used for mobile robots, are large and expensive. In this study, we propose a mobile robot with a hub-type actuator unit and a variable footprint mechanism. The proposed variable footprint mechanism greatly improves the stability and mobility of the robot, allowing it to move freely in a narrow space and carry out various tasks. The performance of the proposed robot is verified experimentally.
Analysis of Wind-Turbine Blade Behavior Under Static Dual-Axis Loads
Son, Byung-Jik ; Huh, Yong-Hak ; Kim, Dong-Jin ; Kim, Jong-Il ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 297~304
DOI : 10.3795/KSME-A.2012.36.3.297
For the assessment of the performance of a wind-turbine blade, a simulated loading test may be required. In this study, the blade behavior was investigated through numerical analysis using a dual-axis loading test, closely simulating the real operation conditions. The blade structure for the 100-kW-class wind-turbine system was modeled using the finite element (FE) program ANSYS. The failure criteria and buckling analysis under dual-axis loading were examined. The failure analysis, including fiber failure and inter-fiber failure, was performed with Puck's failure criterion. As the dual-axis load ratio increases, the relatively increased stress occurs at the trailing edge and skin surface 3300-3600 mm away from the root. Furthermore, it is revealed that increasing the dual-axis load ratio makes the location that is weakest against buckling move toward the root part. Thus, it is seen that the dual-axis load test may be an essential requirement for the verification of blade performance.
A Study on the Optimization of the Natural Frequency of a Ring-Stiffened Cylindrical Shell
Chang, Jin-Geon ; Lee, Young-Shin ; Yang, Tae-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 305~311
DOI : 10.3795/KSME-A.2012.36.3.305
For the optimization of the fundamental natural frequency of stiffened cylindrical shells, simulations were performed for cylindrical shells that were stiffened with between one and five ring stiffeners. ANSYS 11.0 was used to simulate the optimization for the natural frequency. The Subproblem Approximation Method was applied as the optimization method. The design function of the optimization was the geometry of the T-shaped ring stiffener, and the constraint function was the maximum additional volume, constrained to a 10% increase. The objective function of the optimization was chosen to maximize the fundamental natural frequency. The performance index for optimal design was defined as the ratio of the natural frequency to the volume of the unstiffened and stiffened shells. The optimal performance index was obtained for the shell stiffened with three rings.
Limit Loads for Circular Wall-Thinned Feeder Pipes Considering Bend Angle
Bae, Kyung-Dong ; Je, Jin-Ho ; Kim, Jong-Sung ; Kim, Yun-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 313~318
DOI : 10.3795/KSME-A.2012.36.3.313
In CANDU, feeder pipes supply heavy water to pressure tube and steam generator. Under service conditions, Flow-Accelerated Corrosion (FAC) produces local wall-thinning in the feeder pipes. The wall-thinning in these pipes affects the integrity of the piping system, as verified in previous research. This paper provides limit loads for wallthinned feeder pipes with
bend angles, and proposes an equation that predicts the limit loads for wallthinned feeder pipes with arbitrary bend angles. On the basis of finite element limit analyses, limit loads are obtained for wall-thinned feeder pipes under in-plane bending and internal pressure. There are two cases of in-plane bending: the in-plane closing direction and the in-plane opening direction. The material is considered the effect of the large deformation, so an elastic-perfectly-plastic material is assumed in the calculations.
A Study on the Properties of Laser-Welded Boron Steel for Hot Stamping According to the Heat-Treatment Conditions
Hwang, Seok-Hwan ; Nam, Ki-Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 319~324
DOI : 10.3795/KSME-A.2012.36.3.319
The hot-stamping technique is a forming method for manufacturing high-strength parts, in which the part is cooled rapidly after press forming above the austenite transformation temperature. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to investigate the microstructure and mechanical properties according to the heat-treatment conditions. Die-quenching from various temperatures was conducted for different elapsed heat-treatment times. Laser-welded boron steel after quenching has a tensile strength of 1454 MPa and an elongation of 6 %. It has 94 % of the tensile strength of the base metal (1522 MPa). These properties can provide practical information for the use of boron steels for hot stamping.
Structure Analysis and Design Optimization of Stiffeners in LNG Tanks
Jin, Cheng-Zhu ; Jin, Kyo-Kook ; Ha, Sung-Kyu ; Seo, Heung-Seok ; Yoon, Ihn-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 325~330
DOI : 10.3795/KSME-A.2012.36.3.325
This paper describes the structural analysis and optimization of stiffeners used in inner tanks for liquid natural gas (LNG) storage, so that the costs can be minimized while the critical buckling load of the inner tank still exceeds the external pressure exerted by the perlite. The original calculation of perlite pressure applied to the inner tank was based on Zick's code, which led to the overestimation of the external pressure, and consequently, an oversized stiffener. In this study, the effects of the material properties of perlite on the external pressure distribution are scrutinized, and the optimum dimensions of a single stiffener are finally obtained through a series of parametric studies. A 15% decrease in the cost of the stiffener compared with the original design is achieved.
A Study on Crashworthiness Optimization of Front Side Members using Bead Shape Optimization
Lee, Jun-Young ; Lee, Jung-Suk ; Lee, Yong-Hoon ; Bae, Bok-Soo ; Kim, Kyu-Hak ; Yim, Hong-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 331~337
DOI : 10.3795/KSME-A.2012.36.3.331
In this study, the front side member is optimized using a topography optimization technique. Optimization of a simple beam is conducted before optimization of the front side member. The objective function is set to minimize the first buckling factor in the longitudinal direction. The design variable corresponds to the perturbation of nodes normal to the shell's mid-plane space. The crash analysis is conducted on a simple beam, which is optimized by Response Surface Method and the topography optimization technique. In order to verify the topography optimization technique, the results of the RSM and topography optimization model are compared. Consequently, we confirm the satisfactory performance of the topography optimization technique, and apply this topography optimization to the front side member. Thus, the front side member is optimized and its crashworthiness is increased.
Development and Verification of a Dynamic Analysis Model for the Current-Collection Performance of High-Speed Trains Using the Absolute Nodal Coordinate Formulation
Lee, Jin-Hee ; Park, Tae-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 339~346
DOI : 10.3795/KSME-A.2012.36.3.339
The pre-evaluation of the current-collection performance is an important issue for high-speed railway vehicles. In this paper, using flexible multibody dynamic analysis techniques, a simulation model of the dynamic interaction between the catenary and pantograph is developed. In the analysis model, the pantograph is modeled as a rigid body, and the catenary wire is developed using the absolute nodal coordinate formulation, which can analyze large deformable parts effectively. Moreover, for the representation of the dynamic interaction between these parts, their relative motions are constrained by a sliding joint. Using this analysis model, the contact force and loss of contact can be calculated for a given vehicle speed. The results are evaluated by EN 50318, which is the international standard with regard to analysis model validation. This analysis model may contribute to the evaluation of high-speed railway vehicles that are under development.
Shape Design of FPCB Connector to Improve Assembly Performance
Kim, Dae-Young ; Park, Hyung-Seo ; Kim, Woong-Kyeom ; Pyo, Chang-Ryul ; Kim, Heon-Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 36, issue 3, 2012, Pages 347~353
DOI : 10.3795/KSME-A.2012.36.3.347
Recently, multi-functionalization (as in smart phones) has been in demand, and the connectors connecting the electrical signals of each board in a cellular phone have become key components. The miniaturization of these connectors is required to achieve a finer pitch design and enhance the electrical signal transfer capacity. However, the miniaturization of connectors reduces the structural safety, and a finer pitch design may cause contact problems under external impact. In this paper, a preliminary design for miniaturized, finer-pitch connectors is suggested for a product with 50 pins and a thickness of 0.2 mm. The assembly process of the FPCB (Flexible Printed Circuit Board) and connector was simulated to ensure the holding force between the two components and avoid overstressing. The design optimization process was performed with the Taguchi method. Fatigue analysis was also conducted to predict the fatigue life of the terminal, and the theoretical and experimental results were compared.