Secondary Development Of Interface Element Constitutive Model And Parameter Uncertainty Research

The research on the basic mechanical properties of cement matrix composites at the macro-scale has been very mature,and some scholars have turned to study the effects of material components and meso-structure to the macro-mechanical properties from the meso-scale.In the study of meso-model of cement-based materials,the cohesive zone model(CZM)is widely used to study the meso-mechanical properties of cement-based materials because it can well represent the fracture process zone.The study of composites shows that the constitutive model of interface element has an important influence on the mechanical behavior of materials,and the material parameters of interface element can not be obtained by experimental means.Therefore,in this paper,based on the secondary development of material subroutine,three kinds of interface element constitutive models are developed and applied to study the basic mechanical properties of rubber concrete under uniaxial tension and compression.In the case of the Bayesian framework,the sensitivity of mode I and II fracture parameters based on cohesive zone model and the sensitivity and uncertainty of mesoscopic model parameters of cement-based materials are studied.The main work of this paper is as follows:1)Random aggregate modeling is an important link in the establishment of mesoscopic model.This paper summarizes the relevant literature from a mathematical view and gives the mathematical method of judging the interference of plane ellipse and polygon random aggregate.In view of the fact that the literature method is not suitable for the possible collinearity of two straight lines and three vertices,this paper improves the literature method,and the improved method is not only suitable for the case of three points collinear,but also has higher execution efficiency.2)On the basis of elaborating the embedding principle and main points of interface element in detail,the article uses the Abaqus script and GUI secondary development to write a GUI plug-in for batch embedding of interface element in Python language,and shows the efficiency of this plug-in through an example.3)In view of the imperfection of the expression of the equivalent peak stress of the cohesive element in some literatures,this paper gives a complete expression of the equivalent peak traction force,and proves that the expression given in the literature is a special case of this expression.4)Three constitutive models of interface elements are compiled through the material subroutine interface VUMAT reserved by Abaqus,and the detailed mathematical expressions of the three constitutive models are given.Finally,the constitutive model is applied to study the basic mechanical properties of three kinds of rubber concrete materials under uniaxial tension and compression.5)The Bayesian probabilistic sensitivity analysis method is used to complete the sensitivity analysis of the material parameters of type I and II based on cohesive element and the mesoscopic model of cement-based materials.The highly sensitive parameters of cement-based materials are updated by modular Bayesian approach combined with parameter prior distribution and experimental data.