The adaptive remeshing technique for quadrilateral elements consists of modules thetrigger of remeshing, the new mesh generation, adaptive refinement and interpolationof field variables. The new adaptive mesh genemtio...The adaptive remeshing technique for quadrilateral elements consists of modules thetrigger of remeshing, the new mesh generation, adaptive refinement and interpolationof field variables. The new adaptive mesh genemtion is the key problem. First, acoarse mesh is created by using 'loop algorithm'. Subsequent local mesh adaptiverefinement is performed based on effective strain. Finally, a typical example of upset-ting is given to test efficient of techniques, from which it is verified that the remeshingalgorithm developed here exhibits good performance and has high accuracy.展开更多
Surface subsidence induced by underground mining is a typical serious geohazard.Numerical approaches such as the discrete element method(DEM)and finite difference method(FDM)have been widely used to model and analyze ...Surface subsidence induced by underground mining is a typical serious geohazard.Numerical approaches such as the discrete element method(DEM)and finite difference method(FDM)have been widely used to model and analyze mining-induced surface subsidence.However,the DEM is typically computationally expensive,and is not capable of analyzing large-scale problems,while the mesh distortion may occur in the FDM modeling of largely deformed surface subsidence.To address the above problems,this paper presents a geometrically and locally adaptive remeshing method for the FDM modeling of largely deformed surface subsidence induced by underground mining.The essential ideas behind the proposed method are as follows:(i)Geometrical features of elements(i.e.the mesh quality),rather than the calculation errors,are employed as the indicator for determining whether to conduct the remeshing;and(ii)Distorted meshes with multiple attributes,rather than those with only a single attribute,are locally regenerated.In the proposed method,the distorted meshes are first adaptively determined based on the mesh quality,and then removed from the original mesh model.The tetrahedral mesh in the distorted area is first regenerated,and then the physical field variables of old mesh are transferred to the new mesh.The numerical calculation process recovers when finishing the regeneration and transformation.To verify the effectiveness of the proposed method,the surface deformation of the Yanqianshan iron mine,Liaoning Province,China,is numerically investigated by utilizing the proposed method,and compared with the numerical results of the DEM modeling.Moreover,the proposed method is applied to predicting the surface subsidence in Anjialing No.1 Underground Mine,Shanxi Province,China.展开更多
Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic...Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.展开更多
A new method of three-dimensional remeshing is proposed for rigid-plastic finiteelement analysis of a complicated forging process.The forging process of a cylindricalhousing has been simulated to show the effectivenes...A new method of three-dimensional remeshing is proposed for rigid-plastic finiteelement analysis of a complicated forging process.The forging process of a cylindricalhousing has been simulated to show the effectiveness of the scheme.The result ofsimulation shows that the computation can be effectively carried out by using the des-cribed remeshing scheme.展开更多
A new method for estimating the posterior error of linear triangular element is presented. According to the specified accuracy, the element size and node spacing function of adaptive h-version mesh refinement are pred...A new method for estimating the posterior error of linear triangular element is presented. According to the specified accuracy, the element size and node spacing function of adaptive h-version mesh refinement are predicted. The main domain is divided by the isolines of node spacing into subregions in which mesh regeneration is realized. This remeshing refinement process implements mesh subdivision and mesh de-refinement in onecycle.展开更多
Mode tracking is required in the structural optimization when the frequencies of certain specified modes must be maintained within a suitable range.A simple tracking method employing the mode number is invalid or misl...Mode tracking is required in the structural optimization when the frequencies of certain specified modes must be maintained within a suitable range.A simple tracking method employing the mode number is invalid or misleading when local modes appear or disappear during mesh updating.In this work,a mode tracking scheme combining the nearest neighbor method(NNM)with the modal assurance criterion(MAC)is proposed.Several NNM algorithms are compared,and the k-dimensional tree(kd-tree)NNM is used to transform eigenvectors(mode shapes)from different scales to identical one.A threshold determination method is implemented for the MAC to assess the similarities in all the calculated modes.On the basis of the mode tracking scheme,specified modes can be tracked between different finite element method(FEM)models which have different meshes and optimized shapes.The effectiveness is verified through an example of shape optimization using an electric motor structure.展开更多
This paper proposes a self-adaptive approach to converting irregular genus-O meshes into those with subdivision connectivity. To assure a maximal utilization of the multiresolution techniques on the remesh, we map the...This paper proposes a self-adaptive approach to converting irregular genus-O meshes into those with subdivision connectivity. To assure a maximal utilization of the multiresolution techniques on the remesh, we map the original mesh onto the unit sphere and construct a base mesh with only four vertices. We also introduce a self-adaptive relocation operation, which is used to adapt the vertex distribution of the spherical subdivision mesh to that of the parameterized mesh, to improve the visual appearance of the remesh. The experimental results show that our method can not only make the number of irregular vertices in the remesh as small as possible, but also preserve the details of the original mesh well.展开更多
Surface remeshing is widely required in modeling, animation, simulation, and many other computer graphics applications. Improving the elements' quality is a challenging task in surface remeshing. Existing methods ...Surface remeshing is widely required in modeling, animation, simulation, and many other computer graphics applications. Improving the elements' quality is a challenging task in surface remeshing. Existing methods often fail to efficiently remove poor-quality elements especially in regions with sharp features. In this paper, we propose and use a robust segmentation method followed by remeshing the segmented mesh. Mesh segmentation is initiated using an existing Live-wire interaction approach and is further refined using local mesh operations. The refined segmented mesh is finally sent to the remeshing pipeline, in which each mesh segment is remeshed independently. An experimental study compares our mesh segmentation method as well as remeshing results with representative existing methods. We demonstrate that the proposed segmentation method is robust and suitable for remeshing.展开更多
Sheet metal spinning is an incremental forming process for producing axisymmetric thinwalled parts through continuous local deformation under the action of rollers.While studying the spinning process by finite element...Sheet metal spinning is an incremental forming process for producing axisymmetric thinwalled parts through continuous local deformation under the action of rollers.While studying the spinning process by finite element(FE)method,a critical bottleneck is the enormous simulation time.For beating off this challenge,a novel multi-mesh method is developed.The method can dynamically track the movement of rollers and adaptively refine the mesh.Thus,a locally refined quadrilateral computation mesh can be generated in the locally-deforming zone and reduce the unnecessary fine elements outside the locally-deforming zone.In the multi-mesh system,the fine elements and coarse elements are extracted from a storage mesh and a background mesh,respectively.Meanwhile,the hanging nodes in the locally refined mesh are removed by designing 4-refinement templates.Between computation mesh and storage mesh,a bi-cubic parametric surface fitting algorithm and accurate remapping methods are conducted to transmit geometric information and physical fields.The proposed method has been verified by two spinning processes.The results suggest that the method can save time by up to about 67%with satisfactory accuracy,especially for distributions of thickness and strain compared with the fully refined mesh.展开更多
文摘The adaptive remeshing technique for quadrilateral elements consists of modules thetrigger of remeshing, the new mesh generation, adaptive refinement and interpolationof field variables. The new adaptive mesh genemtion is the key problem. First, acoarse mesh is created by using 'loop algorithm'. Subsequent local mesh adaptiverefinement is performed based on effective strain. Finally, a typical example of upset-ting is given to test efficient of techniques, from which it is verified that the remeshingalgorithm developed here exhibits good performance and has high accuracy.
基金supported by the National Natural Science Foundation of China(Grant Nos.11602235 and 41772326)the Fundamental Research Funds for the Central Universities of China(Grant No.2652018091)。
文摘Surface subsidence induced by underground mining is a typical serious geohazard.Numerical approaches such as the discrete element method(DEM)and finite difference method(FDM)have been widely used to model and analyze mining-induced surface subsidence.However,the DEM is typically computationally expensive,and is not capable of analyzing large-scale problems,while the mesh distortion may occur in the FDM modeling of largely deformed surface subsidence.To address the above problems,this paper presents a geometrically and locally adaptive remeshing method for the FDM modeling of largely deformed surface subsidence induced by underground mining.The essential ideas behind the proposed method are as follows:(i)Geometrical features of elements(i.e.the mesh quality),rather than the calculation errors,are employed as the indicator for determining whether to conduct the remeshing;and(ii)Distorted meshes with multiple attributes,rather than those with only a single attribute,are locally regenerated.In the proposed method,the distorted meshes are first adaptively determined based on the mesh quality,and then removed from the original mesh model.The tetrahedral mesh in the distorted area is first regenerated,and then the physical field variables of old mesh are transferred to the new mesh.The numerical calculation process recovers when finishing the regeneration and transformation.To verify the effectiveness of the proposed method,the surface deformation of the Yanqianshan iron mine,Liaoning Province,China,is numerically investigated by utilizing the proposed method,and compared with the numerical results of the DEM modeling.Moreover,the proposed method is applied to predicting the surface subsidence in Anjialing No.1 Underground Mine,Shanxi Province,China.
基金This work was supported by the Brain Korea 2lProject and the Grallt of Post-Doc Program, KyungpookNational University (1999).
文摘Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.
文摘A new method of three-dimensional remeshing is proposed for rigid-plastic finiteelement analysis of a complicated forging process.The forging process of a cylindricalhousing has been simulated to show the effectiveness of the scheme.The result ofsimulation shows that the computation can be effectively carried out by using the des-cribed remeshing scheme.
文摘A new method for estimating the posterior error of linear triangular element is presented. According to the specified accuracy, the element size and node spacing function of adaptive h-version mesh refinement are predicted. The main domain is divided by the isolines of node spacing into subregions in which mesh regeneration is realized. This remeshing refinement process implements mesh subdivision and mesh de-refinement in onecycle.
基金the National Natural Science Foundation of China(No.51775336)the Shanghai Pujiang Program(No.17PJD019)
文摘Mode tracking is required in the structural optimization when the frequencies of certain specified modes must be maintained within a suitable range.A simple tracking method employing the mode number is invalid or misleading when local modes appear or disappear during mesh updating.In this work,a mode tracking scheme combining the nearest neighbor method(NNM)with the modal assurance criterion(MAC)is proposed.Several NNM algorithms are compared,and the k-dimensional tree(kd-tree)NNM is used to transform eigenvectors(mode shapes)from different scales to identical one.A threshold determination method is implemented for the MAC to assess the similarities in all the calculated modes.On the basis of the mode tracking scheme,specified modes can be tracked between different finite element method(FEM)models which have different meshes and optimized shapes.The effectiveness is verified through an example of shape optimization using an electric motor structure.
文摘This paper proposes a self-adaptive approach to converting irregular genus-O meshes into those with subdivision connectivity. To assure a maximal utilization of the multiresolution techniques on the remesh, we map the original mesh onto the unit sphere and construct a base mesh with only four vertices. We also introduce a self-adaptive relocation operation, which is used to adapt the vertex distribution of the spherical subdivision mesh to that of the parameterized mesh, to improve the visual appearance of the remesh. The experimental results show that our method can not only make the number of irregular vertices in the remesh as small as possible, but also preserve the details of the original mesh well.
基金the National Natural Science Foundation of China(Nos.61772523,61372168,61620106003,and 61331018)supported by a Chinese Government Scholarship
文摘Surface remeshing is widely required in modeling, animation, simulation, and many other computer graphics applications. Improving the elements' quality is a challenging task in surface remeshing. Existing methods often fail to efficiently remove poor-quality elements especially in regions with sharp features. In this paper, we propose and use a robust segmentation method followed by remeshing the segmented mesh. Mesh segmentation is initiated using an existing Live-wire interaction approach and is further refined using local mesh operations. The refined segmented mesh is finally sent to the remeshing pipeline, in which each mesh segment is remeshed independently. An experimental study compares our mesh segmentation method as well as remeshing results with representative existing methods. We demonstrate that the proposed segmentation method is robust and suitable for remeshing.
基金co-supported by the supports of Guangdong Basic and Applied Basic Research Foundation(No.2019B1515120047)the National Natural Science Foundation of China(No.52130507)。
文摘Sheet metal spinning is an incremental forming process for producing axisymmetric thinwalled parts through continuous local deformation under the action of rollers.While studying the spinning process by finite element(FE)method,a critical bottleneck is the enormous simulation time.For beating off this challenge,a novel multi-mesh method is developed.The method can dynamically track the movement of rollers and adaptively refine the mesh.Thus,a locally refined quadrilateral computation mesh can be generated in the locally-deforming zone and reduce the unnecessary fine elements outside the locally-deforming zone.In the multi-mesh system,the fine elements and coarse elements are extracted from a storage mesh and a background mesh,respectively.Meanwhile,the hanging nodes in the locally refined mesh are removed by designing 4-refinement templates.Between computation mesh and storage mesh,a bi-cubic parametric surface fitting algorithm and accurate remapping methods are conducted to transmit geometric information and physical fields.The proposed method has been verified by two spinning processes.The results suggest that the method can save time by up to about 67%with satisfactory accuracy,especially for distributions of thickness and strain compared with the fully refined mesh.
