Numerical Simulation Of Cosserat Finite Element For Contact And Large Deformation Problems

The problem of the interaction between the geotechnical body and the structure is a typical geotechnical engineering problem.In geotechnical engineering,large deformation problems and contact problems are very common and often exist at the same time.Among them,the occurrence of strain softening and strain localization problems bring a lot of difficulties to the numerical simulation of the problem of contact and progressive failure between the geotechnical body and the structure.In response to this problem,,this thesis has done the following work:1.Utilizing the secondary development function of ABAQUS finite element software,with the help of ABAQUS’s pre-processing environment,using Python language to realize the automation of Cosserat-RITSS large deformation method.An executable,freely customizable script that can automatically model,import models,divide meshes,modify INP files,map state variables,submit calculations and organize calculation results is completed.The tedious operation process that needs to be repeated many times can be automatically run with one key,which effectively improves the operation efficiency of the method and reflects its application significance.2.Aiming at the problem of poor accuracy of the mapping result in the original Cosserat-RITSS method,the MUEM mapping method was introduced into the Cosserat-RITSS method,and a relatively good effect was obtained.The finite element simulation of the penetration of the rough strip foundation proves that the method can effectively improve the mapping accuracy,solve the problems of convergence and mapping accuracy caused by extrapolation of state variables,and make the simulation results more reliable.At the same time,the model was used for several numerical experiments to discuss the characteristics and practicability of the method.3.Use the improved Cosserat-RITSS method for large deformation finite element simulation of passive earth pressure problems.The results prove that in the large deformation calculation,the introduction of Cosserat continuum theory can effectively solve the problem of strain localization caused by strain softening,that is,the grid dependence problem in the calculation of the classic continuum model.4.Under the framework of Cosserat continuum theory,the finite element format of the 2D quadrilateral four-node Cosserat interface element with thickness is derived,considering the nonlinear behavior and displacement mode of the contact problem.And in the ABAQUS finite element software,the UEL subroutine of Cosserat interface element is programmed and developed,and the numerical simulation calculation is realized.Through the comparison of calculation examples,the correctness and effectiveness are proved.5.In order to facilitate the numerical simulation calculation of the contact problem between the geotechnical body and the structure,and at the same time overcome the problems of excessive rigidity and volume self-locking of the quadrilateral four-node element,Combine the developed two-dimensional Cosserat interface element and the quadrilateral four-node Cosserat element based on the generalized variational principle.Simultaneous application of two user-defined element is realized through the UEL subroutine in the ABAQUS finite element software.