Evolution and Stability of a Crack with a Process Zone. Experimental andTheoretical Studies. Two Parameter Crack Layer Model: Equilibrium, Evolution, Stability. Aging Phenomena and the Intrinsic Material Geometry

摘要

The report contains two parts: (1) Two parameter crack layer model and (2) Agingphenomena and the intrinsic material geometry. In the first part, the crack layer model is substantiated from the thermodynamic standpoint, the kinetic equations governing crack layer evolution are derived, and stability of the crack layer stationary state and propagation is analyzed. The proposed model is examined for the engineering thermoplastics studied in detail experimentally. In the second part, a variational approach to the derivation of constitutive equations of material aging is proposed. Elastic properties and irreversible deformations are represented by a 4D material metric tensor. Equations governing evolution of the tensor are obtained and studied. The theory is illustrated by examples.