Computational Modeling for Bridging Size Scales in the Failure of SolidsPablo D. Zavattieri, Ph.D., Purdue University, 2000.
Major Professor: Dr. Horacio D. Espinosa.
In this work, tools and means to understand the macroscopic inelastic response of ceramics when subjected to dynamic multiaxial loading are presented for bridging scales. A micromechanical model is introduced for the dynamic finite element analysis of ceramic microstructures subjected to multiaxial dynamic loading. The model solves an initial boundary value problem using a multibody contact model integrated with interface elements. Plate impact experiments are analyzed with this model to assess intergranular microcrack initiation and evolution. A representative volume element (RVE) of a ceramic microstructure, is considered for the analysis. A large deformation elasticanisotropic viscoplasticity model for the grains is included. Cohesive interface elements are embedded along grain boundaries to simulate microcrack initiation and evolution. Their interaction and coalescence are a natural outcome of the calculated material response. Experiments are not only used to calibrate and validate the model, but also to explain the different failure mechanisms of ceramics by means of the micromechanical model. The micromechanical analysis of the experiment suggested that the damage kinetics at the grain level does not only depends on the Weibull distribution of the interfacial strength at the grain boundaries, but also depends on the grain size and shape distribution of the microstructure. Bridging between micro and macroscales is achieved by using the qualitative and quantitative results given by the micromechanical model in the continuum/discrete model, also presented in this work and which can be used to study the overall macroscopic response of ceramic including crack propagation and fragmentation.