Modal analysis of a hydrogen-damaged pipe as shell inhomogeneous on thickness

Hydrogen corrosion of main gas and oil pipelines often leads to accidents. It is necessary assess the life hydrogen-weakened pipes. An inner layer with deteriorated mechanical characteristics formed in them under pressure hydrogen-containing medium. In paper calculation free vibrations such a tube taking into account degradation its material performed. The modeled as bilayer cylindrical shell according classical theory. Influence hydrogen-impacted taken when calculating stiffnesses displacement neutral line shell. Three variants averaging parameters determining stiffness are considered, numerical experiments carried out natural frequencies found. Comparison calculations using method finite elements ANSYS software made it possible estimate degree applicability each version averaging. Young's modulus over thickness does not "feel" asymmetry layers relative line. adding correction for radius works satisfactorily axisymmetric beam modes. next more accurate approximation average reduced radius. This allows us obtain satisfactory results wide enough frequency range modes related deformation cross section. A principle reconstruction characterizing three experimentally obtained fixed has been proposed. On basis these studies formulas proposed which allow reconstruct weakening pipe material, result hydrogen corrosion, both time from pipe.