Research On Vector Form Intrinsic Finite Element Crack Propagation Algorithms And Applications

During the use of municipal water supply pipelines,cracks will occur under the influence of external loads,chemical corrosion and biological effects.Under the continuous internal pressure,crack propagation is easy to be initiated,which leads to tube burst,which is inconvenient to urban production and life.In this paper,a three-dimensional model of municipal buried water supply pipeline is established,and the crack propagation process of municipal water supply pipeline under load is simulated by using the theory of vector finite element shell element.The main research work includes:(1)Based on the theory of vector finite element shell element,the matlab program is compiled,and the correctness of the self-programming program in simulating small and large deformation of components is verified by an example.(2)Based on the basic assumptions and concepts of the vector finite element method,a more efficient method,the edge-rotation method,is established to calculate the in-plane reverse rigid body rotation angle of the element in the path element.Four examples of rigid body motion,small deformation,large deformation and practical engineering are used to verify the method.On the basis of ensuring the accuracy of calculation,the process is simple and the efficiency of the original algorithm is improved.(3)The strain energy density factor method is introduced into the vector finite element method as the fracture criterion.Combining with the calculation characteristics of the vector finite element method,the solution to the special problems in dealing with the fracture problem by using this method is given.Finally,the feasibility and accuracy of this method in simulating fracture problems are verified by the experimental examples of unilateral crack propagation and three-point bending of concrete beams.(4)A three-dimensional model of municipal water supply pipeline is established according to the actual engineering situation.Considering several factors affecting pipeline cracking under actual working conditions,the effects of pipeline material,length of soil void zone,thickness of pipe wall and diameter ratio of pipeline on longitudinal crack propagation were studied.This paper makes full use of the advantage of the process analysis of the vector finite element method in dealing with discontinuous problems,and makes further research on the crack propagation of municipal buried pipes.At the same time,a more efficient method is proposed to improve the computational efficiency of two-dimensional and three-dimensional elements of vector finite element method..