Multiscale Modeling of Fracture in Polycrystalline Materials.

Plastic Deformation;Texture;Finite Element Analysis;Simulation;Peridynamics;Microstructure;Crack Initiation;Crack Propagation;Grain Boundaries;Naval Architecture and Marine Engineering;Engineering;Naval Architecture and Marine Engineering

Sun, ShangVlahopoulos, Nickolas ;

University of Michigan

关键词: Plastic Deformation;    Texture;    Finite Element Analysis;    Simulation;    Peridynamics;    Microstructure;    Crack Initiation;    Crack Propagation;    Grain Boundaries;    Naval Architecture and Marine Engineering;    Engineering;    Naval Architecture and Marine Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/108936/shangsun_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In this context, a new statistical theory is proposed that takes into account thecoupling between grain size, shape and crystallographic texture using probability functions. The probability function developed in this work, termed ;;grain size orientationdistribution function;; (GSODF).The prediction of texture and strains achieved by the statistical approach is verified by comparing against the CPFE approach. The approach is found to be two orders of magnitude faster than CPFE, which allows larger metallic components simulation. Then, a concurrent multiscaling model is pursued with fine meshes are employed toresolve the individual crystals crystals in micro-scale regions where critical featuressuch as stress concentrations dominate. At larger size meshes other than the criticalregion, statistical theories are employed to approximate the microstructure interms of probability functions (Orientation density function (ODF)). The concurrentapproach is significantly faster than current algorithms for multiscale analysis of localization and failure. The prediction of the concurrent multiscale model is verifiedwith analytical elastic solutions for a wedge-opening load (WOL) specimen. Themodel is then enriched using the variational multiscale cohesive method for modelingaspects of crack propagation in polycrystalline alloys. Numerical results includingmesh convergence, and crack paths for tensile and three point bending experimentsare shown. Intergranular and transgranular cracks are successfully simulated withexceptional convergence and efficiency.The final section of this thesis explores the application of an emerging simulationtechnique, peridynamics, for modeling discontinuities in polycrystalline microstructures.A quasi{static implementation of the theory is developed. Results are compared with crystal plasticity finite element (CPFE) analysis for the problem of plane strain compression of a planar polycrystal. The stress, strain field distribution and the texture formation predicted by CPFE and peridynamis are found to compare well. One promising feature of peristatics is its ability to model fine shear bands that occur naturally in deforming polycrystalline aggregates. Simulations are used to study the origin and evolution of these shear bands as a function of strain and slip geometry. In the future, combination of peridynamics with statistical descriptors is anticipated for efficient modeling of failure at the macroscale.