The Experts below are selected from a list of 27210 Experts worldwide ranked by ideXlab platform
Dongyol Yang - One of the best experts on this subject based on the ideXlab platform.
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springback prediction for sheet Metal Forming Process using a 3d hybrid membrane shell method
International Journal of Mechanical Sciences, 2002Co-Authors: Farhang Pourboghrat, Jeong Whan Yoon, Dongyol YangAbstract:To reduce the computational time of finite element analyses for sheet Forming, a 3D hybrid membrane/shell method has been developed and applied to study the springback of anisotropic sheet Metals. In the hybrid method, the bending strains and stresses were calculated as post-Processing, considering the incremental change of the sheet geometry obtained from the membrane finite element analysis beforehand. To calculate the springback, a shell finite element model was used to unload the sheet. For verification purposes, the hybrid method was applied for a 2036-T4 aluminum alloy square blank formed into a cylindrical cup, in which stretching is dominant. Also, as a bending-dominant problem, unconstraint cylindrical bending of a 6111-T4 aluminum alloy sheet was considered. The predicted springback showed good agreement with experiments for both cases.
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improvement of formability for the incremental sheet Metal Forming Process
International Journal of Mechanical Sciences, 2000Co-Authors: T. J. Kim, Dongyol YangAbstract:In order to obtain competitiveness in the field of industrial manufacture, a reduction in the development period for the small batch manufacture of products is required. In order to meet these requirements, an incremental sheet Metal Forming Process has been developed. In this Process, a small local region of a sheet blank deforms incrementally by moving a hemispherical head tool over an arbitrary surface. In this work, an incremental sheet Metal Forming Process controlled three dimensionally by a computer has been accomplished. It has been shown by the experiments that a sheet blank is mainly subject to shear-dominant deformation. Therefore, the final thickness strain can be predicted. The uniformity of thickness throughout the deformed region is one of the key factors to improve the formability in the sheet Metal Forming Processes. Using the predicted thickness strain distribution, the intermediate geometry is decided in the manner that a shear deformation is restrained in the highly shear-deformed region and vice versa. This double-pass Forming method is found to be very effective so that the thickness strain distribution of a final shape can be made more uniform.
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optimum blank design in sheet Metal Forming by the deformation path iteration method
International Journal of Mechanical Sciences, 1999Co-Authors: S H Park, Dongyol Yang, Jeong Whan Yoon, Y H KimAbstract:Abstract Optimum blank design methods have been introduced by many researchers to reduce development cost and time in the sheet Metal-Forming Process. Direct inverse design method such as Ideal Forming (Chang and Richmond, Int J Mech Sci 1992; 34(7) and (8): 575–91 and 617–33) [7, 8] for optimum blank shape could play an important role to give a basic idea to designer at the initial die design stage of the sheet Metal-Forming Process. However, it is difficult to predict an exact optimum blank without fracture and wrinkling using only the design code because of the insufficient accuracy. Therefore, the combination of a design code and an analysis code enables the accurate blank design. In this paper, a new blank design method has been suggested as an effective tool combining the ideal Forming theory with a deformation path iteration method based on FE analysis. The method consists of two stages: the initial blank design stage and the optimization stage of blank design. The first stage generated a trial blank from the ideal Forming theory. Then, an optimum blank of the target shape is obtained with the aid of the deformation path iteration method which has been newly proposed to minimize the shape errors at the optimization stage. In order to verify the proposed method, a square cup example was investigated.
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an assessment of numerical parameters influencing springback in explicit finite element analysis of sheet Metal Forming Process
Journal of Materials Processing Technology, 1998Co-Authors: Dongyol YangAbstract:Abstract Springback is one of the key factors influencing the quality of stamped sheet Metal parts in sheet Metal manufacture. There have been diverse efforts to evaluate and/or decrease springback for a long time. Analytical methods have been mainly developed, at first, for analyzing parts of two-dimensional or simple three-dimensional geometry. Since it is almost impossible to apply analytical methods to fully three-dimensional parts in general, numerical methods including the finite element method (FEM) have recently been developed and applied to sheet Metal parts of general shape as a result of rapid progress of computing environments. However, the results of springback simulated by FEM may vary greatly according to how numerical factors are set, for example element size, punch velocity, contact penalty constant, damping ratio, etc. Therefore, a comprehensive assessment of numerical factors influencing springback is required. In this work, numerical factors influencing springback have been evaluated quantitatively using the Taguchi method. To clarify the effect of each factor, the U-draw bending Process is chosen as an evaluation problem because of its large springback. In the analysis, the explicit time integration method is used in the simulation of Forming stage, whereas the implicit time integration method is applied to the springback stage in order to get the static solution readily. Numerical experimentation has been carried out under various combinations of numerical factors. From comparison of the numerical results with the experimental results, factors important for springback have been assessed.
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an assessment of numerical parameters influencing springback in explicit finite element analysis of sheet Metal Forming Process
Journal of Materials Processing Technology, 1998Co-Authors: S W Lee, Dongyol YangAbstract:Abstract Springback is one of the key factors influencing the quality of stamped sheet Metal parts in sheet Metal manufacture. There have been diverse efforts to evaluate and/or decrease springback for a long time. Analytical methods have been mainly developed, at first, for analyzing parts of two-dimensional or simple three-dimensional geometry. Since it is almost impossible to apply analytical methods to fully three-dimensional parts in general, numerical methods including the finite element method (FEM) have recently been developed and applied to sheet Metal parts of general shape as a result of rapid progress of computing environments. However, the results of springback simulated by FEM may vary greatly according to how numerical factors are set, for example element size, punch velocity, contact penalty constant, damping ratio, etc. Therefore, a comprehensive assessment of numerical factors influencing springback is required. In this work, numerical factors influencing springback have been evaluated quantitatively using the Taguchi method. To clarify the effect of each factor, the U-draw bending Process is chosen as an evaluation problem because of its large springback. In the analysis, the explicit time integration method is used in the simulation of Forming stage, whereas the implicit time integration method is applied to the springback stage in order to get the static solution readily. Numerical experimentation has been carried out under various combinations of numerical factors. From comparison of the numerical results with the experimental results, factors important for springback have been assessed.
Jung Han Song - One of the best experts on this subject based on the ideXlab platform.
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multi stage deep drawing Process of thin sheets for the sleeve housing component of a spindle motor in hdd
Applied Mechanics and Materials, 2013Co-Authors: S M Yeon, Seo Gou Choi, Geun An Lee, Sung Jun Park, Ji Hwan Kim, Jung Han SongAbstract:High-precision micro-fluid dynamic bearing is the key part in a hard disk drive, as it offers low noise levels, high speeds and high rates of accuracy with low amount of vibration. To enhance the performance, a thin sheet component called sleeve housing are newly adopted in FDB. In this paper, multi-stage sheet Metal Forming Process is utilized to fabricate the sleeve housing component. Multi-stage drawing simulations are conducted to investigate the adequate Process parameters preventing wrinkling and tearing. From the simulation result, multi-stage drawing Processes are conducted with progressive die sets in order to evaluate the Forming accuracy. The results reveal that it is successful to fabricate the sleeve housing component with multi-stage drawing Process.
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friction behavior modeling and analysis in micro meso scale Metal Forming Process
Materials & Design, 2010Co-Authors: Linfa Peng, Jung Han Song, Jun NiAbstract:Abstract Currently, a lot of know-how in conventional Metal Forming Process cannot be directly applied to micro/meso Forming Processes due to so-called size effects. As a very important phenomenon in Metal Forming Process, friction size effects are observed with an increasing degree of miniaturization. For microForming application, the input data of friction behaviors becomes critical to obtain accurate results for Process simulation and traditional friction models are not reliable. In this paper, the evolution of friction behaviors from micro size to macro size is studied and a new uniform friction model is proposed based on the assumption of open-close lubricant pockets. A function of real contact area (RAC) α RC and normal press p / σ 0 is established by introducing size/scale factor λ to describe the influence of size effects. Therefore, the development of the friction behavior from micro/meso scale to macro scale could be depicted by this new uniform friction model. It indicates that the friction curves of micro/meso size are between those of the dry friction (upper boundary) and conventional lubricant friction (lower boundary). Moreover, finite element (FE) simulations are performed, based on the new friction model, to analyze the friction size effects in ring compression Process. It is found that the radial friction forces with the change of inner and outer diameters are totally different and their tendencies are in good accordance with the experimental results. The new uniform friction model enables more flexible modeling of friction behaviors.
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friction behavior modeling and analysis in micro meso scale Metal Forming Process
Materials & Design, 2010Co-Authors: Linfa Peng, Xinmin Lai, Hyejin Lee, Jung Han SongAbstract:Abstract Currently, a lot of know-how in conventional Metal Forming Process cannot be directly applied to micro/meso Forming Processes due to so-called size effects. As a very important phenomenon in Metal Forming Process, friction size effects are observed with an increasing degree of miniaturization. For microForming application, the input data of friction behaviors becomes critical to obtain accurate results for Process simulation and traditional friction models are not reliable. In this paper, the evolution of friction behaviors from micro size to macro size is studied and a new uniform friction model is proposed based on the assumption of open-close lubricant pockets. A function of real contact area (RAC) α RC and normal press p / σ 0 is established by introducing size/scale factor λ to describe the influence of size effects. Therefore, the development of the friction behavior from micro/meso scale to macro scale could be depicted by this new uniform friction model. It indicates that the friction curves of micro/meso size are between those of the dry friction (upper boundary) and conventional lubricant friction (lower boundary). Moreover, finite element (FE) simulations are performed, based on the new friction model, to analyze the friction size effects in ring compression Process. It is found that the radial friction forces with the change of inner and outer diameters are totally different and their tendencies are in good accordance with the experimental results. The new uniform friction model enables more flexible modeling of friction behaviors.
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simulation based prediction model of the draw bead restraining force and its application to sheet Metal Forming Process
Journal of Materials Processing Technology, 2007Co-Authors: Jung Han Song, Sung Ho ParkAbstract:Abstract Draw-bead is applied to control the material flow in a stamping Process and improve the product quality by controlling the draw-bead restraining force (DBRF). Actual die design depends mostly on the trial-and-error method without calculating the optimum DBRF. Die design with the predicted value of DBRF can be utilized at the tryout stage effectively reducing the cost of the product development. For the prediction of DBRF, a simulation-based prediction model of the circular draw-bead is developed using the Box-Behnken design with selected shape parameters such as the bead height, the shoulder radius and the sheet thickness. The value of DBRF obtained from each design case by analysis is approximated by a second order regression equation. This equation can be utilized to the calculation of the restraining force and the determination of the draw-bead shape as a prediction model. For the evaluation of the prediction model, the optimum design of DBRF in sheet Metal Forming is carried out using response surface methodology. The suitable type of the draw-bead is suggested based on the optimum values of DBRF. The prediction model of the circular draw-bead proposes the design method of the draw-bead shape. The present procedure provides a guideline in the tool design stage for sheet Metal Forming to reduce the cost of the product development.
A Langella - One of the best experts on this subject based on the ideXlab platform.
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observations on the influence of tool sheet contact conditions on an incremental Forming Process
Journal of Materials Engineering and Performance, 2011Co-Authors: M Durante, A Formisano, A LangellaAbstract:The influence of tool-sheet contact conditions on features such as surface roughness, Forming force, and formability was evaluated for components produced by incremental Forming, a highly flexible innovative sheet Metal-Forming Process. Experimental tests were carried out on sheets of AA7075T0 to create two types of component: pyramid frusta (for the evaluation of roughness and force) and cone frusta (for the evaluation of formability). Four different types of tool-sheet contact were analyzed, using two types of tool. From the experimental tests, the influence on the surface finishing and on the trend of the Forming forces depending on contact type was revealed. Contact types do not, however, influence sheet formability.
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observations on the influence of tool sheet contact conditions on an incremental Forming Process
Journal of Materials Engineering and Performance, 2011Co-Authors: M Durante, A Formisano, A LangellaAbstract:The influence of tool-sheet contact conditions on features such as surface roughness, Forming force, and formability was evaluated for components produced by incremental Forming, a highly flexible innovative sheet Metal-Forming Process. Experimental tests were carried out on sheets of AA7075T0 to create two types of component: pyramid frusta (for the evaluation of roughness and force) and cone frusta (for the evaluation of formability). Four different types of tool-sheet contact were analyzed, using two types of tool. From the experimental tests, the influence on the surface finishing and on the trend of the Forming forces depending on contact type was revealed. Contact types do not, however, influence sheet formability.
Linfa Peng - One of the best experts on this subject based on the ideXlab platform.
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friction behavior modeling and analysis in micro meso scale Metal Forming Process
Materials & Design, 2010Co-Authors: Linfa Peng, Jung Han Song, Jun NiAbstract:Abstract Currently, a lot of know-how in conventional Metal Forming Process cannot be directly applied to micro/meso Forming Processes due to so-called size effects. As a very important phenomenon in Metal Forming Process, friction size effects are observed with an increasing degree of miniaturization. For microForming application, the input data of friction behaviors becomes critical to obtain accurate results for Process simulation and traditional friction models are not reliable. In this paper, the evolution of friction behaviors from micro size to macro size is studied and a new uniform friction model is proposed based on the assumption of open-close lubricant pockets. A function of real contact area (RAC) α RC and normal press p / σ 0 is established by introducing size/scale factor λ to describe the influence of size effects. Therefore, the development of the friction behavior from micro/meso scale to macro scale could be depicted by this new uniform friction model. It indicates that the friction curves of micro/meso size are between those of the dry friction (upper boundary) and conventional lubricant friction (lower boundary). Moreover, finite element (FE) simulations are performed, based on the new friction model, to analyze the friction size effects in ring compression Process. It is found that the radial friction forces with the change of inner and outer diameters are totally different and their tendencies are in good accordance with the experimental results. The new uniform friction model enables more flexible modeling of friction behaviors.
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friction behavior modeling and analysis in micro meso scale Metal Forming Process
Materials & Design, 2010Co-Authors: Linfa Peng, Xinmin Lai, Hyejin Lee, Jung Han SongAbstract:Abstract Currently, a lot of know-how in conventional Metal Forming Process cannot be directly applied to micro/meso Forming Processes due to so-called size effects. As a very important phenomenon in Metal Forming Process, friction size effects are observed with an increasing degree of miniaturization. For microForming application, the input data of friction behaviors becomes critical to obtain accurate results for Process simulation and traditional friction models are not reliable. In this paper, the evolution of friction behaviors from micro size to macro size is studied and a new uniform friction model is proposed based on the assumption of open-close lubricant pockets. A function of real contact area (RAC) α RC and normal press p / σ 0 is established by introducing size/scale factor λ to describe the influence of size effects. Therefore, the development of the friction behavior from micro/meso scale to macro scale could be depicted by this new uniform friction model. It indicates that the friction curves of micro/meso size are between those of the dry friction (upper boundary) and conventional lubricant friction (lower boundary). Moreover, finite element (FE) simulations are performed, based on the new friction model, to analyze the friction size effects in ring compression Process. It is found that the radial friction forces with the change of inner and outer diameters are totally different and their tendencies are in good accordance with the experimental results. The new uniform friction model enables more flexible modeling of friction behaviors.
M Durante - One of the best experts on this subject based on the ideXlab platform.
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observations on the influence of tool sheet contact conditions on an incremental Forming Process
Journal of Materials Engineering and Performance, 2011Co-Authors: M Durante, A Formisano, A LangellaAbstract:The influence of tool-sheet contact conditions on features such as surface roughness, Forming force, and formability was evaluated for components produced by incremental Forming, a highly flexible innovative sheet Metal-Forming Process. Experimental tests were carried out on sheets of AA7075T0 to create two types of component: pyramid frusta (for the evaluation of roughness and force) and cone frusta (for the evaluation of formability). Four different types of tool-sheet contact were analyzed, using two types of tool. From the experimental tests, the influence on the surface finishing and on the trend of the Forming forces depending on contact type was revealed. Contact types do not, however, influence sheet formability.
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observations on the influence of tool sheet contact conditions on an incremental Forming Process
Journal of Materials Engineering and Performance, 2011Co-Authors: M Durante, A Formisano, A LangellaAbstract:The influence of tool-sheet contact conditions on features such as surface roughness, Forming force, and formability was evaluated for components produced by incremental Forming, a highly flexible innovative sheet Metal-Forming Process. Experimental tests were carried out on sheets of AA7075T0 to create two types of component: pyramid frusta (for the evaluation of roughness and force) and cone frusta (for the evaluation of formability). Four different types of tool-sheet contact were analyzed, using two types of tool. From the experimental tests, the influence on the surface finishing and on the trend of the Forming forces depending on contact type was revealed. Contact types do not, however, influence sheet formability.
