بررسی اثر درز جوش طولی لوله در هنگام بازرسی فراصوتی لوله با امواج هدایت شده متقارن

Low-pressure fluid transmission lines are largely manufactured by cold rolling of a plate followed by resistance welding of the two edges of the plate. Consequently, these pipes have a straight weld seam along their length. In this paper, a finite element method is used for simulating the propagation of symmetric guided wave modes L(0,2), L(0,1) and T(0,1) in straight seam welded pipes. A comparison is made between the propagation of these wave modes in seamless and seam welded pipes. Results indicate that the angular amplitude profiles of the L(0,2) and T(0,1) modes do not change much in the presence of the seam weld. However, the presence of the straight seam weld significantly affects the propagation of the L(0,1) mode along the pipe. While the angular displacement profile for the L(0,2) and T(0,1) modes are almost symmetric, for the L(0,1) mode, the angular displacement profile shows high asymmetry. This asymmetric behavior impairs the sensitivity of this mode to the detection of defects in the proximity of the weld line. As a result, the guided wave modes L(0,2) and T(0,1) are considered to be suitable for inspection of straight seam welded pipes but L(0,1) is not recommended for this purpose.