Numerical Analysis Of Crack Propagation Of Gravity Dam Based On High Order Finite Element Method

In recent three decades,with the development of numerical simulation method and the of computer simulation technology,the finite element method(FEM)has been rapidly developed,and are widely used in various engineering computation fields,and gradually became a kind of extremely important numerical computation method,and for many actual engineering problems,FEM has important guiding significance.Compared with the experiment method,the numerical simulation method has obvious advantages such as low cost,strong repeatability,more flexible,various working conditions can be processed,and shorter time required,also because of the finite element method has solid mathematical theory basis and it's error estimation has been already obtained,therefore,the accurate error range can be obtained by finite element method.Based on the above advantages mentioned,the finite element method has made an important contribution in the scientific and engineering computation fields,and has been widely applied in various fields,such as aerospace engineering,material science,civil engineering and mechanical engineering.But as it's limitation,for some complex problems,the finite element method meet difficulties,for example,in dealing with large deformation and discontinuous problems,the traditional finite element method can not meet the requirement of the scientific research and engineering,or can't meet precision requirement,hence,on the basis of the traditional finite element method the high order finite element method and the extended finite element method have been developed,among these methods,the extended finite element method can be used to simulate the discontinuous problems;Based on the traditional finite element method,the high order finite element method is developed to improve the problem of precision of problems solved and accelerate convergence rate.The extended finite element method is mostly used to solve discontinuous problems such as fracture problems.However,when solving the stress intensity factor,it needs to divide more grids,and the convergence speed is slower,so the calculation precision cannot meet the engineering requirements.This thesis combines the high order finite element method and the contour integral method,taking two dimensional edge crack in shear loading in a rectangular plate,three dimensional single edge-crack specimen subjected to well-distributed vertical tension and a classical concrete gravity dam under basic loads combination as examples,to solve the stress intensity factor and simulate crack propagation path.The high order finite element method has faster convergence rate,higher accuracy,the less mesh requirement,and the contour integral method is superconvergence,either through the higher order finite element method to reduce the number of grids and improve the calculation accuracy of stress and strain,and at the same time,calculation accuracy of stress intensity factor are also improved by using the contour integral method.At first,the high order finite element method is used to simulate the displacement field and stress field at the crack tip,and then the contour integral method is applied to derive the stress intensity factor and the crack propagation path.This paper analyses and compares the numerical results obtained with theoretical solution and those numerical results in literatures by other numerical method,such as the extended finite element method(XFEM)and meshless method(MLM).These results show that the stress intensity factors computed by using the high order finite element method and the contour integral method have shown higher accuracy and better numerical stability,when simulating the crack propagation path of concrete gravity dam,the numerical results are in good agreement with the experimental and other numerical results obtained by other numerical methods,such as the extended finite element method.The effectiveness of methods used are verified.This paper provides a new method for numerical simulation of crack propagation path problems.This paper mainly discusses the application of the high order finite element method combined with the contour integral method in crack propagation path of gravity dam.The results show that the high order finite element method deals with fracture problems with less grid division,high computational accuracy and better numerical stability.has a good research prospect and application value.