Influence of small variations of initial defects upon crack paths in creeping plates--Continuum Damage Mechanics description

摘要

It has been shown in previous works by the authors that the entire process of failure of a structure can be described within the frame of Continuum Damage Mechanics (CDM). It consists of crack initiation, growth (including branching) and proliferation throughout a structure, which terminates structure's lifetime. These characteristic periods are especially well exposed when time dependent behavior of the structure's material (e.g. creep) is taken into account. The results of numerical simulation of the process depend, however, on a number of factors like assumed constitutive equations for material behavior, values of material constants, and boundary and initial conditions. Due to the nonlinear behavior typical for metals in high temperature applications, the solutions are very sensitive to these parameters. In particular, times to reach consecutive stages of failure process can vary considerably. In the present contribution the influence of initial distribution of damage variable, which can result from material original heterogeneity or can be artificially introduced, is studied. It is demonstrated that even a small variation in these conditions can influence crack paths and - consequently - the time to final failure of a structure, which can be very different from that when zero-value initial conditions are superimposed upon damage scalar parameter.