Fracture of Kirchhoff plates is analyzed by the theory of complex variables and boundary collocation method. The deflections, moments and shearing forces of the plates are assumed to be the functions of complex variab...Fracture of Kirchhoff plates is analyzed by the theory of complex variables and boundary collocation method. The deflections, moments and shearing forces of the plates are assumed to be the functions of complex variables. The functions can satisfy a series of basic equations and governing conditions, such as the equilibrium equations in the domain, the boundary conditions on the crack surfaces and stress singularity at the crack tips. Thus, it is only necessary to consider the boundary conditions on the external boundaries of the plate, which can be approximately satisfied by the collocation method and least square technique. Different boundary conditions and loading cases of the cracked plates are analyzed and calculated. Compared to other methods, the numerical examples show that the present method has many advantages such as good accuracy and less computer time. This is an effective semi_analytical and semi_numerical method.展开更多
Boundary Collocation Method (BCM) based on Eigenfunction Expansion Method (EEM), a new numerical method for solving two-dimensional wave problems, is developed. To verify the method, wave problems on a series of b...Boundary Collocation Method (BCM) based on Eigenfunction Expansion Method (EEM), a new numerical method for solving two-dimensional wave problems, is developed. To verify the method, wave problems on a series of beaches with different geometries are solved, and the errors of the method are analyzed. The calculation firmly confirms that the results will be more precise if we choose more rational points on the beach. The application of BCM, available for the problems with irregular domains and arbitrary boundary conditions, can effectively avoid complex calculation and programming. It can be widely used in ocean engineering.展开更多
In this paper a group of stress functions has been proposed for the calculation of a crack emanating from a hole with different shape (including circular, elliptical, rectangular, or rhombic hole) by boundary collocat...In this paper a group of stress functions has been proposed for the calculation of a crack emanating from a hole with different shape (including circular, elliptical, rectangular, or rhombic hole) by boundary collocation method. The calculation results show that they coincide very well with the existing solutions by other methods for a circular or elliptical hole with a crack in an infinite plate. At the smae time, a series of results for different holes in a finite plate has also been obtained in this paper. The proposed functions and calculation procedure can be used for a plate of a crack emanating from an arbitrary hole.展开更多
In this paper, we combine the Muskhelishvili's complex variable method and boundary collocation method, and choose a set of new stress function based on the stress boundary condition of crack surface, the higher prec...In this paper, we combine the Muskhelishvili's complex variable method and boundary collocation method, and choose a set of new stress function based on the stress boundary condition of crack surface, the higher precision and less computation are reached. This method is applied to calculating the stress intensity factor for a finite plate with an inclined crack. The influence of θ (the obliquity of crack) on the stress intensity factors, as well as the number of summation terms on the stress intensity factor are studied and graphically represented.展开更多
A, novel collocation method for a coupled system of singularly perturbed linear equations is presented. This method is based on rational spectral collocation method in barycentric form with sinh transform. By sinh tra...A, novel collocation method for a coupled system of singularly perturbed linear equations is presented. This method is based on rational spectral collocation method in barycentric form with sinh transform. By sinh transform, the original Chebyshev points are mapped into the transformed ones clustered near the singular points of the solution. The results from asymptotic analysis about the singularity solution are employed to determine the parameters in this sinh transform. Numerical experiments are carried out to demonstrate the high accuracy and efficiency of our method.展开更多
Evaluation of the electric field at the surface of a conductor,which is well described by the Poisson equation,is of great importance on many occasions in power systems.This paper proposes a collocation boundary eleme...Evaluation of the electric field at the surface of a conductor,which is well described by the Poisson equation,is of great importance on many occasions in power systems.This paper proposes a collocation boundary element method where the unknown surface charge density function is assumed to be either azimuth independent or dependent.Detailed formulas,including the quadrature rules and how to accelerate the computation when the target point lies far away from the integral element,are proposed.Numerical examples are shown to confirm the convergence of the method,and manifest the great advantage for the evaluation of the electric field around slender conductors.展开更多
A new calculation formula of THM coupling stress intensity factor was derived by the boundary collocation method, in which an additional constant stress function was successfully introduced for the cracked specimen wi...A new calculation formula of THM coupling stress intensity factor was derived by the boundary collocation method, in which an additional constant stress function was successfully introduced for the cracked specimen with hydraulic pressure applied on its crack surface. Based on the newly derived formula, THM coupling fracture modes (including tensile, shear and mixed fracture mode) can be predicted by a new fracture criterion of stress intensity factor ratio, where the maximum axial load was measured by self-designed THM coupling fracture test. SEM analyses of THM coupling fractured surface indicate that the higher the temperature and hydraulic pressure are and the lower the confining pressure is, the more easily the intergranular (tension) fracture occurs. The transgranular (shear) fracture occurs in the opposite case while the mixed-mode fracture occurs in the middle case. The tested THM coupling fracture mechanisms are in good agreement with the predicted THM coupling fracture modes, which can verify correction of the newly-derived THM coupling stress intensity factor formula.展开更多
The singular boundary method (SBM) is a recent meshless boundary collocation method that remedies the perplexing drawback of fictitious boundary in the method of fundamental solutions (MFS). The basic idea is to u...The singular boundary method (SBM) is a recent meshless boundary collocation method that remedies the perplexing drawback of fictitious boundary in the method of fundamental solutions (MFS). The basic idea is to use the origin intensity factor to eliminate singularity of the fundamental solution at source. The method has so far been applied successfully to the potential and elasticity problems. However, the SBM solution for large-scale problems has been hindered by the operation count of O(N^3) with direct solvers or O(N^2) with iterative solvers, as well as the memory requirement of O(N^2). In this study, the first attempt was made to combine the fast multipole method (FMM) and the SBM to significantly reduce CPU time and memory requirement by one degree of magnitude, namely, O(N). Based on the complex variable represen- tation of fundamental solutions, the FMM-SBM formulations for both displacement and traction were presented. Numerical examples with up to hundreds of thousands of unknowns have successfully been tested on a desktop computer. These results clearly illustrated that the proposed FMM-SBM was very efficient and promising in solving large-scale plane elasticity problems.展开更多
文摘Fracture of Kirchhoff plates is analyzed by the theory of complex variables and boundary collocation method. The deflections, moments and shearing forces of the plates are assumed to be the functions of complex variables. The functions can satisfy a series of basic equations and governing conditions, such as the equilibrium equations in the domain, the boundary conditions on the crack surfaces and stress singularity at the crack tips. Thus, it is only necessary to consider the boundary conditions on the external boundaries of the plate, which can be approximately satisfied by the collocation method and least square technique. Different boundary conditions and loading cases of the cracked plates are analyzed and calculated. Compared to other methods, the numerical examples show that the present method has many advantages such as good accuracy and less computer time. This is an effective semi_analytical and semi_numerical method.
基金financially supported by the Special Fund for Marine Renewable Energy Projects(Grant Nos.GHME2010GC01 and GHME2013ZB01)the National Natural Science Foundation of China(Grant Nos.51109201 and 41106031)
文摘Boundary Collocation Method (BCM) based on Eigenfunction Expansion Method (EEM), a new numerical method for solving two-dimensional wave problems, is developed. To verify the method, wave problems on a series of beaches with different geometries are solved, and the errors of the method are analyzed. The calculation firmly confirms that the results will be more precise if we choose more rational points on the beach. The application of BCM, available for the problems with irregular domains and arbitrary boundary conditions, can effectively avoid complex calculation and programming. It can be widely used in ocean engineering.
文摘In this paper a group of stress functions has been proposed for the calculation of a crack emanating from a hole with different shape (including circular, elliptical, rectangular, or rhombic hole) by boundary collocation method. The calculation results show that they coincide very well with the existing solutions by other methods for a circular or elliptical hole with a crack in an infinite plate. At the smae time, a series of results for different holes in a finite plate has also been obtained in this paper. The proposed functions and calculation procedure can be used for a plate of a crack emanating from an arbitrary hole.
基金Supported by the Teaching and Research Award Fund for Outstanding Young Teachers in Higher Education Institutions of MOE, and NNSF(10161009) of P. R. of China.
文摘In this paper, we combine the Muskhelishvili's complex variable method and boundary collocation method, and choose a set of new stress function based on the stress boundary condition of crack surface, the higher precision and less computation are reached. This method is applied to calculating the stress intensity factor for a finite plate with an inclined crack. The influence of θ (the obliquity of crack) on the stress intensity factors, as well as the number of summation terms on the stress intensity factor are studied and graphically represented.
基金Acknowledgments. The support from the National Natural Science Foundation of China under Grants No.10671146 and No.50678122 is acknowledged. The authors are grateful to the referee and the editor for helpful comments and suggestions.
文摘A, novel collocation method for a coupled system of singularly perturbed linear equations is presented. This method is based on rational spectral collocation method in barycentric form with sinh transform. By sinh transform, the original Chebyshev points are mapped into the transformed ones clustered near the singular points of the solution. The results from asymptotic analysis about the singularity solution are employed to determine the parameters in this sinh transform. Numerical experiments are carried out to demonstrate the high accuracy and efficiency of our method.
基金This work was supported by the National Natural Science Foundation of China under grant 51577098the National Key Research and Development Program of China under grant 2016YFB0901005.
文摘Evaluation of the electric field at the surface of a conductor,which is well described by the Poisson equation,is of great importance on many occasions in power systems.This paper proposes a collocation boundary element method where the unknown surface charge density function is assumed to be either azimuth independent or dependent.Detailed formulas,including the quadrature rules and how to accelerate the computation when the target point lies far away from the integral element,are proposed.Numerical examples are shown to confirm the convergence of the method,and manifest the great advantage for the evaluation of the electric field around slender conductors.
基金Project(11072269)supported by the National Natural Science Foundation of ChinaProject(20090162110066)supported by the Research Fund for the Doctoral Program of Higher Education of China
文摘A new calculation formula of THM coupling stress intensity factor was derived by the boundary collocation method, in which an additional constant stress function was successfully introduced for the cracked specimen with hydraulic pressure applied on its crack surface. Based on the newly derived formula, THM coupling fracture modes (including tensile, shear and mixed fracture mode) can be predicted by a new fracture criterion of stress intensity factor ratio, where the maximum axial load was measured by self-designed THM coupling fracture test. SEM analyses of THM coupling fractured surface indicate that the higher the temperature and hydraulic pressure are and the lower the confining pressure is, the more easily the intergranular (tension) fracture occurs. The transgranular (shear) fracture occurs in the opposite case while the mixed-mode fracture occurs in the middle case. The tested THM coupling fracture mechanisms are in good agreement with the predicted THM coupling fracture modes, which can verify correction of the newly-derived THM coupling stress intensity factor formula.
基金Project supported by the National Basic Research Program of China(973 ProjectNo.2010CB832702)+4 种基金the National Science Funds for Distinguished Young Scholars of China(No.11125208)the National Natural Science Foundation of China(Nos.11125208 and 11302069)the 111 project under Grant B12032Jiangsu Province Graduate Students Research and Innovation Plan(No.KYZZ 0138)the scholarship from the China Scholarship Council(CSC)(No.201306710026)
文摘The singular boundary method (SBM) is a recent meshless boundary collocation method that remedies the perplexing drawback of fictitious boundary in the method of fundamental solutions (MFS). The basic idea is to use the origin intensity factor to eliminate singularity of the fundamental solution at source. The method has so far been applied successfully to the potential and elasticity problems. However, the SBM solution for large-scale problems has been hindered by the operation count of O(N^3) with direct solvers or O(N^2) with iterative solvers, as well as the memory requirement of O(N^2). In this study, the first attempt was made to combine the fast multipole method (FMM) and the SBM to significantly reduce CPU time and memory requirement by one degree of magnitude, namely, O(N). Based on the complex variable represen- tation of fundamental solutions, the FMM-SBM formulations for both displacement and traction were presented. Numerical examples with up to hundreds of thousands of unknowns have successfully been tested on a desktop computer. These results clearly illustrated that the proposed FMM-SBM was very efficient and promising in solving large-scale plane elasticity problems.