Computational Theory And Software Development For Structural Contact And Fracture Behaviors Using The Finite Particle Method

Numerical simulations of structural complex behaviors such as contact-impact and fracturefailure behaviors are widely used in many engineering fields.This kind of problems usually involve nonlinear and discontinuous behaviors,which are difficult to solve using traditional numerical methods,and the calculation is very time-consuming.Finite particle method is a novel numerical method for analysis of structural complex behaviors.It is suitable for solving nonlinear and discontinuous problems of structures and is easy to achieve parallel acceleration.In this paper,several structural elements and constitutive models of the finite particle method are developed,and parallel algorithms for structural contact behaviors and fracture behaviors are studied,and implemented in the software using the finite particle method.The effectiveness and computational efficiency of these methods have been verified.In addition,the parallel computing software using the finite particle method is applied to the failure behaviors of structures subjected to high-velocity impact.The main research work of this paper is as follows.On the basis of the earlier version of the parallel computing software,the functional modules of pre-processing,numerical calculation and post-processing have been improved and optimized.Specifically,the parallel computing framework of the finite particle method using GPU is extended,and two parallel solvers,i.e.,parallel contact solver and parallel fracture solver,are included in the computing framework.A general data structure suitable for parallel and serial solvers is developed,and a serial and a parallel version of the software are formed.The computational theory of quadrilateral planar element,hexahedral element,and quadrilateral thin-shell element is studied and implemented in the parallel computing software.The quadrilateral planar element includes two integration schemes,i.e.,selective reduced integration and reduced integration,the integration scheme of the hexahedral element is reduced integration,and the integration scheme of the quadrilateral thin-shell element is complete integration.The hourglass control technique is used to reduce the hourglass effect of quadrilateral planar element and hexahedral solid element.The validity of these structural elements is verified via several numerical examples.In addition,the efficiency of the serial and parallel solvers of the software,and the Abaqus element solvers are compared,and the efficiency of the developed elements using parallel acceleration is proved.The exponential isotropic hardening constitutive models for planar elements,three-dimensional solid elements,and thin shell elements are developed and implemented in the software.Firstly,the radial return algorithm and Newton-Raphson iteration are used to realize the exponential hardening constitutive calculation of three-dimensional solid element.On the basis of that,the constitutive calculation of plane strain element is converted to the constitutive calculation of three-dimensional solid element.The constitutive calculation of plane stress element and thin-shell element requires iterative calculation to obtain the strain increment satisfying the plane stress state.The validity of the exponential isotropic hardening constitutive models of the above structural elements is verified by numerical examples.Contact algorithms for planar structure and three-dimensional structure are proposed and implemented in the software.The planar contact algorithm is suitable for triangular and quadrilateral planar elements,while the three-dimensional contact algorithm is suitable for three-dimensional solid elements and thin-shell elements.The contact algorithms include two main computational procedures,namely contact search and contact force calculation.The three-dimensional space containing contact surfaces is decomposed into cubic cells,and the contact search is performed between adjacent cells to improve search efficiency.The calculations of normal and tangential contact forces are based on the penalty method and the smoothed friction model,respectively.The effectiveness of the contact algorithm for planar and three-dimensional structures is verified by the elastic and elastoplastic contact examples.In addition,the computational performance of the serial and the parallel contact solvers of the software,and Abaqus contact solver is compared.The parallel contact algorithm of the finite particle method has higher computational efficiency than serial contact algorithms.A general method for structural fracture simulations is developed and implemented in the software.The method is suitable for the fracture simulation of planar structural elements,threedimensional solid elements and thin-shell elements.The extrinsic cohesive zone model is adopted for modeling cohesive effect between fracture elements.After the fracture of structural elements,the cohesive elements become active and cohesive forces are applied to the particles of the cohesive elements.The calculation of cohesive forces is based on the monotone linearly decreasing tractionseparation law of cohesive elements.The topological updating procedures suitable for all kinds of fracture elements are studied.The validity of fracture calculation for planar,three-dimensional solid,and thin-shell elements is verified by numerical examples.In the aspect of computational efficiency,the parallel fracture algorithm of finite particle method has higher computational efficiency than serial fracture algorithms.The software using the finite particle method is applied to simulate the structural fracture behaviors due to impact.Firstly,the failure and penetration behaviors of a brittle glass structure and a ductile metal structure after high-speed impact are simulated.Secondly,the failure behavior of an H-shaped column after impact is simulated by fine modeling,and the influence of the impact height and the impact velocity on the simulation results is studied.Finally,the whole process of failure and collapse behaviors of a five-story steel frame structure subjected to high-speed impact are simulated by fine modeling.The above application research preliminarily explores the feasibility of the software using the finite particle method in simulating the impact failure behaviors of structures in practical engineering fields.