The fracture failure modelling of three-dimensional structures composed of quasi-brittle materials subjected to different loading velocities rates by the dipole-based BEM approach and Bayes updating
Nome Completo:
Luís Philipe Ribeiro Almeida
Unidade da USP:
Escola de Engenharia de São Carlos, departamento de Estruturas
Programa de Pós-Graduação:
Engenharia de Estruturas
Nível:
Doutorado
Resumo:
The main objective of this doctoral thesis is the development of an alternative Boundary Element Method (BEM) formulation to model cohesive crack propagation in three dimensional components, including loading rate effects. In addition, a new framework to quantify viscous-cohesive parameters in Nonlinear Fracture Mechanics (NFM) problems is proposed. The developed methodology couples the viscous-cohesive dipole-based BEM approach to the Bayesian Updating with Structural reliability method (BUS). The BEM formulation used is based on the introduction of an initial stress field to represent the mechanical behavior within the Fracture Process Zone (FPZ). The degeneration of this stress field along the crack boundaries results in the quantity dipole, which captures the nonlinear fracture effects. The influence of the loading rate on the material strength within the FPZ is properly handled by a viscous function, which updates the cohesive crack model. The Park–Paulino–Roesler (PPR) cohesive zone model governs the nonlinear mechanical behavior within the FPZ. Then, an update to the PPR cohesive model, to incorporate the effects of the loading rate during the cohesive crack propagation, is also proposed. The results obtained, including mixed-mode crack propagation, through this formulation are compared with reference solutions from experimental, analytical, and numerical approaches.