Long-term fracture of a composite rod under tension in creep conditions in the presence of an active medium

The stress-strain state is considered and the time to fracture of a composite tensile rod during creep under the influence of an active environment is determined. The rod consists of three parts arranged symmetrically in thickness. An additional condition is accepted: all parts of the composite rod are rigidly interconnected without slipping. The creep of each part of the rod is described by a power model with different parameters. To determine the time to fracture, a kinetic equation is used that describes the accumulation of damage during the creep process. For each part of the rod, the same form of the kinetic equation is adopted, but the accumulation of damage occurs under the action of stresses that are different for each part of the rod. The influence of the active medium is determined by the diffusion penetration of its elements into the rod material. An approximate method for solving the diffusion equation based on the introduction of a diffusion front is used. The distribution of stresses in time is analyzed under the condition of penetration of the active medium into different parts of the rod with different diffusion coefficients. As a result of the study, it was shown that the ratio of the constants in the constitutive ratios of the creep of the parts of the rod affects the nature of the accumulation of damage and the distribution of stresses, and therefore, there is an influence on the sequence of destruction of the parts of the composite rod. With an increase in the exponents in the constitutive and kinetic relations, the time until the destruction of the composite rod increases. The dependence of the time to fracture on the ratio of the diffusion coefficients of the active medium in the part of the rod is determined.