Defects detection in typical positions ofbend pipes using low-frequency ultrasonic guided wave

LUO Geng-sheng(罗更生)^1,2, TAN Jian-ping(谭建平)¹, WANG Liang(汪亮)³, XU Yan(许焰)⁴

(1. School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China;
2. Hunan Provincial Special Equipment Inspection and Research Institute, Changsha 410111, China;
3. Center of Public Courses, Zhuhai College of Jilin University, Zhuhai 519041, China;
4. Department of Mechanical and Electrical Engineering, Changsha University, Changsha 410022, China)

Abstract:In order to analyze the possibility of detecting defects in bend pipe using low-frequency ultrasonic guided wave, the propagation of T(0,1) mode and L(0,2) mode through straight-curved-straight pipe sections was studied. FE (finite element) models of bend pipe without defects and those with defects were introduced to analyze energy distribution,mode transition and defect detection of ultrasonic guided wave. FE simulation results were validated by experiments of four different bend pipes with circumferential defects in different positions. It is shown that most energy of T(0,1) mode or L(0,2) mode focuses on extrados of bend but little passes through intrados of bend, and T(0,1) mode or L(0,2) mode is converted to other possible non-axisymmetric modes when propagating through the bend and the defect after bend respectively. Furthermore, L(0,2) mode is more sensitive to circumferential notch than T(0,1) mode. The results of this work are beneficial for practical testing of pipes.

Key words:low-frequency ultrasonic guided wave; bend pipe; extrados of bend; intrados of bend; FE (finite element) simulation; experimental investigation