Residual Strength and Reliability of Corroded Pipelines-Monte-Carlo Approach for Consideration of Spatially Nonuniform Material Properties

Assessment of the residual strength and workability of pipelines with detected corrosion defects assumes implementation of the limiting state criteria, which relate the parameters of pipe material and actual geometry of structure with the system of operating loading. Since the finite-element modeling is widely used for the expert analysis of the results of technical diagnostics and gives the opportunity to decrease the conservativeness of reliability determination, development of corresponding numerical techniques with regard to specific pipeline element are actual. This work proposes the numerical approach of statistical analysis of corroded pipelines limiting state. It consists in consideration of natural nonuniformity of the material properties within the limits of the finite-element description of the combined development of stress-strain state and ductile subcritical damage up to the limiting state using Monte-Carlo procedure. It allows taking into account of spatial stochastic distribution of such material characteristics as yield stress, microcleavage stress, initial concentration of nucleated porosity of ductile fracture, critical value of plastic strain, etc. It is shown, that this approach has lower conservativeness, than conventional ones, those presuppose the consideration of uniform material properties, but remains responsive enough for solution of typical engineering problems.