Ultrasonic Testing Of Deformation Damage In Pipeline Steel And Its Welds Using Non-collinear Mixed-frequency Ultrasonic Testing Technology

It is inevitable that various degrees and types of plastic damages occurs during the operation such as high pressure and large deformations during the use of oil and gas pipelines,which can lead to fracture damages and leakage accidents.In order to quantitatively assess the degree of pipeline steel damage and its operational status,it is urgently needed for detection and evaluation.Non-collinear mixed-frequency ultrasonic testing technology has the advantages of maintaining high sensitivity,high resolution,strong anti-interference ability,and ease of implementation.Therefore,this study focuses on the detection of plastic damage and macroscopic defects in X80pipeline steel and its circumferential welded joints using non-collinear mixed-frequency ultrasonic testing technology.The specific research contents are as follows:（1）Based on nonlinear ultrasonic mixing theory,the occurrence conditions of non-collinear ultrasonic mixing were calculated.A finite element model was established using COMSOL Multiphysics simulation software.Parameters,such as excitation signal,incident angle,excitation frequency,and etc.,were optimized.A non-linear ultrasonic mixing test system was built based on RITEC RAM-5000,and non-linear ultrasonic mixing tests were performed on pre-stretched specimens.With the valid comparison of experimental results and simulation model calculation results,the maximum error is 0.3×10^-3,meeting the current research requirements.（2）Regarding the ultrasonic detection of plastic damage and macroscopic defects in X80 pipeline steel,it was found that non-collinear ultrasonic mixing signals can effectively characterize the degree of material plastic damage and macroscopic defects through non-collinear ultrasonic mixing finite element analysis.The nonlinear parameterβ₁increases with the increase of the degree of material plastic damage,and the nonlinear parameterβ₂of macroscopic defects with the presence of macroscopic defects increases,with the increase of the defect length and decreases,and with the increase of the defect width.Moreover,by studying the nonlinear parameterβ₃of the combination of material plastic damage and macroscopic defects,it was found that the nonlinear parameterβ₃is approximately equal to the sum of the nonlinear parameters of material plastic damage and macroscopic defects,and there is a linear superposition relationship ofβ₃≈β₁+β₂among the three.（3）Regarding the ultrasonic detection of circumferential welded joints in X80pipeline steel,it was found through non-collinear ultrasonic mixing finite element analysis that due to the uneven material properties of the welded joints,non-collinear ultrasonic mixing signals exhibit obvious nonlinear characteristics,and the nonlinear parameter of the transmission signal is greater than that of the reflected signal.Non-collinear ultrasonic mixing signals can effectively characterize macroscopic defects in welds,and the nonlinear parameterβ₂increases with the increase of the defect length and decreases with the increase of the defect width.The nonlinear parameterβ₂also increases with the increase of the number of macroscopic defects,and when the macroscopic defects are located in the mixing zone,the nonlinear parameterβ₂increases with the decrease of the distance between the macroscopic defects and the mixing zone center.Therefore,non-collinear ultrasonic mixing signals can effectively characterize the degree of plastic damage and the size,number,and location of macroscopic defects in X80 pipeline steel and its circumferential welded joints.The research results provide a technical approach for further assessing the remaining life of oil and gas pipelines.