We present a novel algorithm for adaptive triangular mesh coarsening. The algorithm has two stages. First, the input triangular mesh is refined by iteratively applying the adaptive subdivision operator that performs a...We present a novel algorithm for adaptive triangular mesh coarsening. The algorithm has two stages. First, the input triangular mesh is refined by iteratively applying the adaptive subdivision operator that performs a so-called red-green split. Second, the refined mesh is simplified by a clustering algorithm based on centroidal Voronoi tessellations (CVTs). The accuracy and good quality of the output triangular mesh are achieved by combining adaptive subdivision and the CVTs technique. Test results showed the mesh coarsening scheme to be robust and effective. Examples are shown that validate the method.展开更多
In this paper,we apply the material point method(MPM),also known as a meshfree method,to examine the crush behaviour of thin tubular columns.Unlike the finite element method,randomly-distributed-weak-particle triggers...In this paper,we apply the material point method(MPM),also known as a meshfree method,to examine the crush behaviour of thin tubular columns.Unlike the finite element method,randomly-distributed-weak-particle triggers were used to account for the deformation behaviour of collapse modes.Both symmetric and asymmetric modes of deformation and their associated mean collapse loads are determined for an elasto-plastic constitutive law describing the tubular columns.Attention was devoted to the accuracy and the convergence of the MPM simulation,which is determined by the number of the particles and the size of the background cells used in our explicit solver.Furthermore,a novel contact approach was adopted to establish the crush behaviour of the tubular columns.Two aspects of the work were accordingly examined,including three different crush velocities(5,10 and 15 m/s) and varied geometrical features of the tube(t/d and l/d) based on the deformation history.The results of our model,which were compared with existing analytical predictions and experimental findings,identify the critical geometric features of the tubular columns that would dictate the deformation mode as being either progressive collapse or following Euler's buckling mode.展开更多
An efficient Galerkin meshfree formulation for three dimensional simulation of large deformation failure evolution in soils is presented. This formulation utilizes the stabilized conforming nodal integration, where fo...An efficient Galerkin meshfree formulation for three dimensional simulation of large deformation failure evolution in soils is presented. This formulation utilizes the stabilized conforming nodal integration, where for the purpose of stability and efficiency a Lagrangian smoothing strain at nodal point is constructed and thereafter the internal energy is evaluated nodally. This formulation ensures the linear exactness, efficiency and spatial stability in a unified manner and it makes the conventional Galerkin meshfree method affordable for three dimensional simulation. The three dimensional implementation of stabilized conforming nodal integration is discussed in details. To model the failure evolution in soil medium a coupled elasto-plastic damage model is used and an objective stress integration algorithm in combination of elasto-damage predictor and plastic corrector method is employed for stress update. Two typical numerical examples are shown to demonstrate the effectiveness of the present method for modeling large deformation soil failure.展开更多
基金supported by the National Natural Science Foundation of China (No. 60773179)the National Basic Research Program (973) of China (No. 2004CB318000)
文摘We present a novel algorithm for adaptive triangular mesh coarsening. The algorithm has two stages. First, the input triangular mesh is refined by iteratively applying the adaptive subdivision operator that performs a so-called red-green split. Second, the refined mesh is simplified by a clustering algorithm based on centroidal Voronoi tessellations (CVTs). The accuracy and good quality of the output triangular mesh are achieved by combining adaptive subdivision and the CVTs technique. Test results showed the mesh coarsening scheme to be robust and effective. Examples are shown that validate the method.
基金supported by the National Basic Research Program of China (Grant No. 2010CB832701)Natural Sciences and Engineering Research Council of Canada (NSERC)
文摘In this paper,we apply the material point method(MPM),also known as a meshfree method,to examine the crush behaviour of thin tubular columns.Unlike the finite element method,randomly-distributed-weak-particle triggers were used to account for the deformation behaviour of collapse modes.Both symmetric and asymmetric modes of deformation and their associated mean collapse loads are determined for an elasto-plastic constitutive law describing the tubular columns.Attention was devoted to the accuracy and the convergence of the MPM simulation,which is determined by the number of the particles and the size of the background cells used in our explicit solver.Furthermore,a novel contact approach was adopted to establish the crush behaviour of the tubular columns.Two aspects of the work were accordingly examined,including three different crush velocities(5,10 and 15 m/s) and varied geometrical features of the tube(t/d and l/d) based on the deformation history.The results of our model,which were compared with existing analytical predictions and experimental findings,identify the critical geometric features of the tubular columns that would dictate the deformation mode as being either progressive collapse or following Euler's buckling mode.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10972188, 10602049)the Program for New Century Excellent Talents in University from China Education Ministry (Grant No. NCET-09-0678)the Fundamental Research Funds for the Central Universities of China (Grant No. 2010121073)
文摘An efficient Galerkin meshfree formulation for three dimensional simulation of large deformation failure evolution in soils is presented. This formulation utilizes the stabilized conforming nodal integration, where for the purpose of stability and efficiency a Lagrangian smoothing strain at nodal point is constructed and thereafter the internal energy is evaluated nodally. This formulation ensures the linear exactness, efficiency and spatial stability in a unified manner and it makes the conventional Galerkin meshfree method affordable for three dimensional simulation. The three dimensional implementation of stabilized conforming nodal integration is discussed in details. To model the failure evolution in soil medium a coupled elasto-plastic damage model is used and an objective stress integration algorithm in combination of elasto-damage predictor and plastic corrector method is employed for stress update. Two typical numerical examples are shown to demonstrate the effectiveness of the present method for modeling large deformation soil failure.
