ИСТИНА

The creep rupture of tensile long rods in the aggressive medium is investigated. The influence of the aggressive medium is determined by the diffusion penetration of its elements in the material of rod. The diffusion process is gradually slowing down with the accumulation of environmental elements in the material of the rod. This process is modelled using the diffusion equation, where the diffusion coefficient is a monotone decreasing function of the concentration . As an example, consider two types of such dependencies: , , - diffusion coefficient at the initial time , and - constant coefficients. On the border of the material of rod and external environment, the condition is mass transfer. The approximate method for solving the diffusion equation based on introduction of the diffusion front. This approach allows us to divide all the material of the rod on the perturbed (where the environment has already penetrated into the material) and undisturbed area (where there is no penetration of the medium), and then determine the motion on the boundary between these regions over time. At the same boundary and initial condition are satisfied exactly and the diffusion equation satisfied by the integral over the entire volume of the rod. We consider two stages of the diffusion process, such as, the penetration of the front stage and the stage of the saturation. The comparison of solutions of the diffusion equation for the two proposed dependencies is indicated. The influence of dependencies on the creep rupture of the tension rod examines by using the Rabotnov’s kinetic theory of creep and creep rupture. The paper presents the relevant calculations, graphs of dependencies and conclusions. This investigation was supported by the grant of Russian Foundation of Basic Research № 14-08-00528 REFERENCES 1. Rabotnov Yu.N. “Creep Problems in Structural Members.” Amsterdam. North Holland. 1969. 2. Lokoshchenko A.M. ”Simulation of Creep and Creep Rupture of Metals”. Moscow. Moscow State Industrial University. 2007. 3. Lokoshchenko A.M. “Creep and Creep Rupture Strength of Metals in Aggressive Medium.” Moscow. Lomonosov Moscow State University Press. 2000. 4. Fomin L.V. “Description of Creep Rupture Strength of Tensile Rod with Rectangular and Circular Cross-Section at High Temperature Air Media”. Bulletin of the Samara State Technical University. Series of Phis.-Math. Sciences. No. 3(32). pp. 87-97. 2013.