Aging Detection And Experimental Study Of Polyethylene Gas Pipeline Based On Ultrasound

Due to the rapid development of polymer material science and technology,the gas pipeline field has undergone a revolutionary change of "replacing steel with plastic".Polyethylene(PE)is a semi-crystalline thermoplastic high-molecular material with stable chemical properties,easy to process and shape,and excellent mechanical properties,which has been widely used in industrial production and People's Daily life.The conduit that makes with polyethylene material,showed a lot of advantages such as light weight,wear-resisting,anticorrosion in practical application,already replaced steel pipe gradually in a lot of occasions such as water supply conduit and gas conduit.However,as a kind of polymer organic material,its aging problem is inevitable,which brings great safety risks to the engineering application of polyethylene gas pipeline.This study takes PE80 gas pipe as the object,mainly from the following aspects:(1)The aging behavior of polyethylene pipe in service environment was analyzed,and the mechanical property test and thermal stability test were carried out.The aging state of polyethylene pipe was characterized by the impact strength and oxidation induction time.(2)The short-time Fourier transform(STFT)was used for time-frequency analysis of ultrasonic pulse signals to obtain the ultrasonic sound velocity spectrum and attenuation spectrum of different aging samples,and to analyze the changes of ultrasonic sound velocity and attenuation coefficient with the detection frequency,as well as the changes of ultrasonic sound velocity and attenuation coefficient with the aging degree.(3)The frequency spectrum of ultrasonic pulse signals of different samples was analyzed,and the ultrasonic nonlinear coefficient was calculated according to the amplitude of fundamental wave and second harmonic wave,and the relationship between the ultrasonic nonlinear coefficient and the aging degree of polyethylene was analyzed.(4)Based on the above test data,the internal relationship between ultrasonic nonlinear response and material performance was analyzed,and the relationship between ultrasonic nonlinear coefficient and material macroscopic performance(impact strength,oxidation induction time)was established,which provided an important basis for evaluating the aging state of the polyethylene pipeline in service.