The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Xuanmin Song - One of the best experts on this subject based on the ideXlab platform.
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Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method
Energies, 2021Co-Authors: Yuming Huo, Zhu Defu, Wang Zhonglun, Xuanmin SongAbstract:In longwall top coal caving (LTCC), the resource recovery ratio of the working face is directly determined by the top coal recovery ratio. An investigation of the evolution of top coal Drawing characteristics and revealing the evolution of top coal Drawing parameters is necessary when providing guidance for caving parameter selection and improving the top coal recovery ratio. Based on in-situ measurements of the size distribution of caved top coal blocks in Wangjialing coal mine, a finite difference method (FDM)–discrete element method (DEM) coupled method was applied to establish a “continuous–discontinuous” numerical model and the process from the first coal Drawing to the common coal Drawing was simulated with 17 separate working face advances. The evolution of the Drawing body (DB), loose body (LB), and top coal boundary (TCB) was obtained. The results show that, the evolution of parameters of DB such as shape and size, Drawing amount, length and deflection angle of the long axis of the profile ellipsoid tended to decrease first, then increase, decrease again, and finally stabilise; the increment of the LB advance coal wall distance and the coal pillar distance was close to 0 m in the common coal Drawing Stage, while width increment of the LB was close to the Drawing interval (0.865 m). The TCB formed after each coal Drawing round was fitted based on the improved “Hook” function. The evolution of height and radius of curvature of TCB’s stagnation point was analysed. This was divided into three Stages: the first (first to third Drawing rounds) was the initial mining influence Stage, the second (fourth to ninth Drawing rounds) was the transitional caving Stage, and the third (after tenth Drawing round) was the common coal Drawing Stage.
Yuming Huo - One of the best experts on this subject based on the ideXlab platform.
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Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method
Energies, 2021Co-Authors: Yuming Huo, Zhu Defu, Wang Zhonglun, Xuanmin SongAbstract:In longwall top coal caving (LTCC), the resource recovery ratio of the working face is directly determined by the top coal recovery ratio. An investigation of the evolution of top coal Drawing characteristics and revealing the evolution of top coal Drawing parameters is necessary when providing guidance for caving parameter selection and improving the top coal recovery ratio. Based on in-situ measurements of the size distribution of caved top coal blocks in Wangjialing coal mine, a finite difference method (FDM)–discrete element method (DEM) coupled method was applied to establish a “continuous–discontinuous” numerical model and the process from the first coal Drawing to the common coal Drawing was simulated with 17 separate working face advances. The evolution of the Drawing body (DB), loose body (LB), and top coal boundary (TCB) was obtained. The results show that, the evolution of parameters of DB such as shape and size, Drawing amount, length and deflection angle of the long axis of the profile ellipsoid tended to decrease first, then increase, decrease again, and finally stabilise; the increment of the LB advance coal wall distance and the coal pillar distance was close to 0 m in the common coal Drawing Stage, while width increment of the LB was close to the Drawing interval (0.865 m). The TCB formed after each coal Drawing round was fitted based on the improved “Hook” function. The evolution of height and radius of curvature of TCB’s stagnation point was analysed. This was divided into three Stages: the first (first to third Drawing rounds) was the initial mining influence Stage, the second (fourth to ninth Drawing rounds) was the transitional caving Stage, and the third (after tenth Drawing round) was the common coal Drawing Stage.
Jinwang Zhang - One of the best experts on this subject based on the ideXlab platform.
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Theoretical description of Drawing body shape in an inclined seam with longwall top coal caving mining
International Journal of Coal Science & Technology, 2019Co-Authors: Jiachen Wang, Weijie Wei, Jinwang ZhangAbstract:Understanding the characteristics of Drawing body shape is essential for optimization of Drawing parameters in longwall top coal caving mining. In this study, both physical experiments and theoretical analysis are employed to investigate these characteristics and derive a theoretical equation for the Drawing body shape along the working face in an inclined seam. By analyzing the initial positions of drawn marked particles, the characteristics of the Drawing body shape for different seam dip angles are obtained. It is shown that the Drawing body of the top coal exhibits a shape-difference and volume-symmetry characteristic, on taking a vertical line through the center of support opening as the axis of symmetry, the shapes of the Drawing body on the two sides of this axis are clearly different, but their volumes are equal. By establishing theoretical models of the Drawing body in the initial Drawing Stage and the normal Drawing Stage, a theoretical equation for the Drawing body in an inclined seam is proposed, which can accurately describe the characteristics of the Drawing body shape. The shape characteristics and volume symmetry of the Drawing body are further analyzed by comparing the results of theoretical calculations and numerical simulations. It is shown that one side of the Drawing body is divided into two parts by an inflection point, with the lower part being a variation development area. This variation development area increases gradually with increasing seam dip angle, resulting in an asymmetry of the Drawing body shape. However, the volume symmetry coefficient fluctuates around 1 for all values of the seam dip angle variation, and the volumes of the Drawing body on the two sides are more or less equal as the variation development volume is more or less equal to the cut volume. Both theoretical calculations and numerical simulations confirm that the Drawing body of the top coal exhibits the shape-difference and volume-symmetry characteristic.
Hervé Laurent - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of springback using the split-ring test for an AA5754 aluminum alloy
Finite Elements in Analysis and Design, 2010Co-Authors: Hervé Laurent, Renaud Grèze, Marta Oliveira, Luís Menezes, Pierre-yves Manach, José Luís AlvesAbstract:The split-ring test provides a simple benchmark for correlating springback obtained by finite element analysis (FEA) with experimental measurements. This test consists in cutting a ring specimen from a full drawn cup and then to split the ring longitudinally along a radial plane. The difference between the ring diameters, before and after splitting, gives a direct measure of the springback phenomenon, and indirectly, of the amount of residual stresses in the drawn cup. In this paper, the numerical simulation of the deep Drawing process and splitting of an aluminum alloy AA5754-O ring is performed using both the finite element code ABAQUS and the in-house code DD3IMP. The trimming of the ring is carried out with a devoted program, DD3TRIM, which allows the geometrical and material state remapping treatment of solid hexahedral element meshes. The punch-force evolution during deep Drawing and thickness distribution obtained numerically are compared with experimental ones provided in [1] (Laurent et al., 2009). The influence of finite element formulation, mesh size and yield criteria on the numerical results for the ring opening is evaluated. The stress distributions in the cup, at the end of the Drawing Stage are analyzed and some explanations concerning their influence on springback mechanisms are given.
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Influence of constitutive model in springback prediction using the split-ring test
International Journal of Mechanical Sciences, 2009Co-Authors: Hervé Laurent, Renaud Grèze, Pierre-yves Manach, Sandrine ThuillierAbstract:Abstract The aim of this paper is to compare several plastic yield criteria to show their relevance on the prediction of springback behavior for a AA5754-0 aluminum alloy. An experimental test similar to the Demeri Benchmark Test [Demeri MY, Lou M, Saran MJ. A benchmark test for springback simulation in sheet metal forming. In: Society of Automotive Engineers, Inc., vol. 01-2657, 2000] has been developed. This test consists in cutting a ring specimen from a full drawn cup, the ring being then split longitudinally along a radial plan. The difference between the ring diameters, before and after splitting, gives a direct measure of the springback phenomenon, and indirectly, of the amount of residual stresses in the cup. The whole deep Drawing process of a semi-blank and numerical splitting of the ring are performed using the finite element code Abaqus. Several material models are analyzed, all considering isotropic and kinematic hardening combined with one of the following plasticity criteria: von Mises, Hill’48 and Barlat’91. This last yield criterion has been implemented in Abaqus. Main observed data are force–displacement curves during forming, cup thickness according to material orientations and ring gap after splitting. The stress distributions in the cup, at the end of the Drawing Stage, and in the ring, after springback, are analyzed and some explanations concerning their influence on springback mechanisms are given.
Sang Wook Lee - One of the best experts on this subject based on the ideXlab platform.
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A study on the bi-directional springback of sheet metal stamping
Journal of Materials Processing Technology, 2005Co-Authors: Sang Wook LeeAbstract:Abstract The U-draw bending process is traditionally adopted to evaluate the springback of drawn sheet metals because of its large amount and uni-directional characteristic of springback. The results of springback of the U-draw bending process are, however, more or less limited to apply to general stamping processes. In this work, the bi-directional springback of drawn sheet metal parts is studied using the modified U-draw bending process. In the process, a strip with the fixed width is drawn by the elliptical tool and laid freely. Therefore, the primary springback along the longitudinal direction and the secondary springback along the transverse direction of the strip occur at the same time. In the numerical analysis, the explicit time integration method is used in the simulation of Drawing Stage, whereas the implicit time integration method is applied to the springback Stage in order to get readily the static solution. To verify the results of numerical analysis, the experiment is also carried out. Both results are shown to be generally coincident with each other. The study is considered to be helpful to understand multi-directional springback phenomena which take place generally in industrial sheet metal stamping processes.
