Hybrid experimental/numerical analysis and finite element modeling of fracture of aggregate composite.

摘要

This dissertation involves the fracture study of an aggregate composite. Effects of specimen size, loading rate, fracture process zone, and contact-friction at the crack surface on fracture properties are investigated. General purpose hybrid experimental numerical methods are initially developed. These methods are based on least-square mapping-collocation technique and the smoothing finite element concept and can be used with experimental data from strain gages, moire interferometry, and holography. Stress-separation techniques for photoelasticity and thermoelasticity are also developed based on these hybrid concepts. The smoothing finite element scheme is combined with the J integral concept and the stress intensity factor for fracture analyses. Following the hybrid methods, the experimental study of the fracture mechanics properties of dam concrete is presented. This involves testing large-scale wedge splitting compact tension specimens of dam concrete. The influence of specimen size and loading rate on the fracture energy is investigated. The fracture process zone (FPZ) of concrete and mortar was then studied using moire interferometry. The stress intensity factor was determined by hybridizing moire-interferometry measured displacements and the smoothing FEM method, including quarter-point crack tip elements. The effect of the FPZ on the stress intensity factor is analyzed. Finally, the effects of crack surface contact and friction on energy release rate in mixed-mode fracture are investigated. Crack surface contact and friction are realistic features during fracture of aggregate composite such as concrete. An incremental elastoplastic contact friction constitutive model is used, and a nonlinear finite element program with an unsymmetric profile equation solver was written for modeling the rough interface mixed-mode fracture.