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 studi...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.展开更多
The problem of the laser-generated guided elastic waves in hollow cylinders is inves-tigated numerically by using the method of eigen-function expansion. The explicit expression of the transient waveform is given for ...The problem of the laser-generated guided elastic waves in hollow cylinders is inves-tigated numerically by using the method of eigen-function expansion. The explicit expression of the transient waveform is given for the case of the outer surface of the hollow cylinder beat axi-symmetrically by four laser pulses with same energy. The characteristics of the transient waveform are explained based on the dispersive relations.展开更多
基金Project(51265044)supported by the National Natural Science Foundation of ChinaProject(2013TT2028)supported by the Science and Technology Project of Hunan Province of ChinaProject(2012QK162)supported by the Science and Technology Project of General Administration of Quality Supervision,Inspection and Quarantine of China
文摘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.
基金the Doctoral Foundation of Education Ministry of China(GrantNo.1999028432) and the Natural Science Foundation of Jiangsu Province(Grant No.BK97031).
文摘The problem of the laser-generated guided elastic waves in hollow cylinders is inves-tigated numerically by using the method of eigen-function expansion. The explicit expression of the transient waveform is given for the case of the outer surface of the hollow cylinder beat axi-symmetrically by four laser pulses with same energy. The characteristics of the transient waveform are explained based on the dispersive relations.