Finite-Element Analysis of Oscillations in Damaged Pipeline Sections Reinforced With a Composite Material

Abstract

This work treats a finite-element analysis of the oscillations in damaged pipeline sections reinforced with a composite wrap performed by ANSYS software when the thickness of the composite wrap was 2.0, 3.0, and 4.0 mm, while the length of the wrap was 400, 600, and 800 mm, respectively. The outcome showed that to compensate for the stress concentration in the damaged zone of a pipeline with a thickness between 11.9 and 14.3 mm, the thickness of the composite wrap should be 2÷4 mm, that is, not lower than 17% of the original pipeline thickness at thinning and not lower than 34% of the original pipeline thickness at large cracks. An increment in the pipeline thickness from 11.9 up to 14.3 mm with a reinforced composite lining leads to an increment in the first oscillation frequency not higher than 0.1%. The lowest fundamental frequency was at a pipeline with lining located at the restrained supports, while the highest frequency was between two free-moving supports in the middle span. The difference between the first frequencies did not exceed the percentage of 4%. By applying a composite lining with a length of 20% of the pipeline length between a restrained support and a longitudinally movable one and a thickness of 33.6% of the nominal pipeline thickness, we were able to increase the frequency spectrum of the oscillations in comparison with the unreinforced pipeline. Therefore, for the fundamental frequency, this increment was equal to 13.9% for the operating pressure and almost four times for the critical one. Consequently, the developed approach can be used as an adjustment method for damaged pipeline sections characterized by low critical frequencies.