Dependences of the characteristics of creep and long-term strength on the cross-sectional dimensions of specimens

We analyze the available experimental data according to which a decrease in the cross-sectional dimensions of specimens leads to a significant increase in the creep rate and a decrease in the service life. This sclae effect is explained by the corrosion fracture of the surface layers of a metal. We propose a procedure for the phenomenological description of these data based on the concept of Rabotnov. According to this procedure, we consider two time-dependent kinetic parameters, namely, the thickness of a destroyed surface layer and the degree of damage to the material distributed over the remaining part of the cross section. It is shown that the application of proposed equations to the analysis of the experimental data significantly (by a factor of 3–12) decreases the overall discrepancy between the experimental and theoretical characteristics of creep and long-term strength as compared with the use of the standard equations in which the scale effect is neglected.