Multilevel wave model in fracture mesomechanics


Relying on the analysis of the author and his co-worker’s data, this overview substantiates the basic propositions of the multilevel wave model in fracture mesomechanics. Any solid under loading is considered as a self-organized multilevel system where plastic flow and fracture are two subsequent stages of shear-stability loss at the micro-, meso- and macroscale levels. Fracture is global shear-stability loss in a loaded specimen. Two parallel (in the shape of a dipole) or conjugate (in the shape of a cross) macrobands of plastic flow localization propagate throughout the specimen cross section. They evolve self-consistently by the “phase wave ” mechanism. The macrobands are characterized by strongly localized material rotation, which is accompanied by mesofragmentation of the surrounding material as the accommodation mechanism of rotation. For macrobands conjugated in the shape of a cross there are two kinds of their self-consistency. At the first stage, the self-consistency between two half-macrobands at each side of the specimen takes place. The rotation modes of the two coupled half-macrobands are accommodated by mesofragmentation of the surrounding material. It is accompanied by the formation of a ductile neck. At the definite extent of mesofragmentation the accommodation ability of the deformed material within the area of coupled macrobands is exhausted. Then the self-consistency between the coupled half-macrobands at each side of the specimen breaks down and the neck formation is stopped. At the second stage of loading, there arises the self-consistency between half-macrobands from the opposite sides of the specimen. It is accompanied by crack propagation throughout the cross section and causes fracture of the loaded specimen. For the dipole configuration of the two opposite macrobands their self-consistency across the entire cross section arises from the very beginning. It results in quasi-brittle fracture of the specimen. The prefracture criterion of a solid under loading based on a multilevel wave model is discussed. 1

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