Numerical Approach To Fracture Of Glass Under Biaxial Stress And The Prove Of Failure Criterion

Glass is the typical brittle material, and has been widely used in aviation, mechanics and architecture. The fracture in brittle material always initiates from the existed defects. Therefore, the investigation of the evolution and instability condition of a crack in brittle is of great importance to the reliability analysis of structures composed of brittle materials. In fact, most glass components in practice work in biaxial or multiaxial stress states, whether biaxial stresses have any influence on fracture behavior of solid is an argumental question, and this question has not been satisfactorily answered so far. On the other hand, according to LEFM theory, four fracture parameters, the stress intensity factor K , the energy release rate G, the J-integral and the crack opening displacement are equivalent, when one of the four parameters attains its critical value, other three should also attain their critical value. These four fracture controlling parameters are irrelevant to the biaxial stresses. If the biaxial stresses having influence on fracture behavior of solid has been proved, does the equivalent relationship among the stress intensity factor, the energy release rate , the crack' opening displacement and J-integral in uniaxial stress state still exist when they in biaxial stress state? If not existing any more, then what is the parameter of crack extending when glass in biaxial stress state? At the same time, how to establish the failure criterion of brittle materials in biaxial stress state is one of people's goal. These questions have not been satisfactorily answered so far. Further more, the glass tests of uniaxial tension, especially biaxial tension and the crack prefabrication have been a big problem in experiments.This study uses the methods of fracture mechanics and numerical simulation, establishes the numerical models on the bases of experimental results, and the fracture behavior of brittle materials such as glass with crack under uniaxial and biaxial plane stress has been investigated by means of numerical simulation method. The study of this side is limit in inside and outside country.The aim of this study is to clear that whether the fracture and crack extending of brittle materials are influenced by the stress parallel to the crack surface. If they are influenced by the stress parallel to the crack surface, does the equivalent relationship among the stress intensity factor, the energy release rate , the crack opening displacement and J-integral in uniaxial stress state still exist when they in biaxial stress state? If not existing any more, then what is theparameter of crack extending when glass in biaxial stress state? What is the difference of fracture parameter between uniaxial stress state and biaxial stress state? What is the failure criterion of brittle materials in biaxial stress state. This study wants to investigate the failure process of brittle materials under biaxial stress, and provides the evidence to analyze the failure of structure.In this study, the fracture behavior of brittle materials under biaxial plane stress has been investigated by means of numerical simulation method with software MFPA2D (Material Failure Process Analysis). The aims of this study are to clarify the fracture dependence of brittle material on biaxial plane stress state. The observation of crack initiation and fracture behavior reveals that the biaxial stresses have strong influence on the fracture properties of glass. Thus, the fracture criterion by the stress intensity factor was questioned for the biaxial plane stress issues. It is confirmed that the tensile stress parallel to the crack plane is an important factor affecting crack arrest, while the compressive stress parallel to the crack plane contributes to crack opening.Difference in the stress distribution and failure initiation for brittle materials between uniaxial and biaxial loads was confirmed by FEM simulation. To explain the influence of biaxial stress on fracture, the relationship among the stress intensity factor K, the energy release rate...