Skrypnyk I. The development of the methods for estimation of structural materials degradation and durability in aggressive enviroment under sustained static loading

New mathematical models for description of damage initiation in the intergranular regions of structural materials due to their degradation are developed. The mathematical model for grain boundary void growth is developed and numerical formulae is proposed for estimation of void growth kinetic. The new relations for estimation of internal pressure of hydrogen and methane (in the case of hydrogen attack) in metal cavities are proposed. Using obtained relations the methodology for calculation of Nelson curves for carbon and low alloyed steels is developed. The percolation theory is developed to enable the description of intergranular damage evolution in the structural materials. Based on this developement a method for estimation of critical level of damage is proposed. A non-linear visco-elasticity model of relaxation type is developed. This model is implemented into commerical finite element package MARC.