A Method of Detecting Circumferential Defects of Hollow Cylinder Using the Principle of Ultrasonic Dispersion Compensation
A hollow cylinder and dispersion compensation technology, which is applied in the direction of processing the response signal of the detection, can solve problems such as difficult to do, loss of detection range, etc., and achieve the effect of improving accuracy
Active Publication Date: 2017-11-10
ZHEJIANG UNIV
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Problems solved by technology
But this requires a completely symmetrical excitation of the T(0,1) mode on the pipe, which is difficult to achieve in practice
In addition, increasing the resolution of detecting defects often requires a higher center frequency, which, however, results in a loss of effective detection range
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[0065] Detect a 304 stainless steel pipe with the above method. The pipe length is 1500mm, the outer diameter is 101mm, and the wall thickness is 1mm. A 0.1mm thick and 10mm wide magnetostrictive material 8 is attached to one end of the pipe. The magnetostrictive material 8 is iron Cobalt vanadium alloy, and the excitation coil 5 is surrounded by the magnetostrictive material 8. Then, between the circumferential defect 7 and the excitation coil 5, the magnetostrictive material 8 is also pasted at a distance of 322mm from the excitation coil 5; then the magnetic field excitation controller 1 is controlled to transmit voltage pulse signals to the excitation coil 5 and the receiving coil 6. Receive the reference signal s first propagated from the excitation coil 5 ref (θ, t) and the echo signal s reflected from the circumferential defect 7 obj (θ,t), along the circumference of the pipeline, collect data every 11°15', collecting 32 sets of data. The data processing process is as m...
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Abstract
The invention discloses a method for detecting the peripheral defect of a hollow cylinder by an ultrasonic frequency dispersion compensation principle. The method comprises the following steps of (1) stimulating out ultrasonic guide waves in the hollow cylinder, and using a guide wave receiver for respectively obtaining a reference signal s<ref>(theta,t) and a peripheral defect echo signal s<obj>(theta,t); (2) calculating the peripheral defect position according to the time differences and the sound speed of the two signals; (3) performing two-dimensional Fourier transform on the s<ref>(theta,t) and the s<obj>(theta,t), exerting the phase shifting, and performing the one-dimension Fourier conversion relevant to the (n-theta) transform pair to obtain the distributions shown as the accompanying drawing on a (theta, omega) domain; (4) using the first distribution shown as the accompanying drawing as the reference for performing Wiener filtering on the second distribution shown as the accompanying drawing; (5) calculating the distribution A(theta) of the amplitude value s<dec> (theta,t) along the hollow cylinder peripheral rotating angle theta and the half height width of the distribution A(theta), i.e., the peripheral dimension of the defect of the hollow cylinder. The method has the advantages that the measurement on the position and the dimension of the peripheral defect of the hollow cylinder is realized; higher precision is realized.
Description
Technical field [0001] The invention relates to the nondestructive detection of the circumferential defect of a hollow cylinder, and in particular to a method for detecting the position and size of the circumferential defect of the hollow cylinder by using a guided wave dispersion compensation algorithm. Background technique [0002] Nowadays, pipelines are used more and more in the transportation industry, and pipeline accidents have also increased, which has brought huge losses to the national economy and threatened people's lives. Therefore, it is particularly important to conduct economical, applicable, simple and effective non-destructive testing of pipelines. The use of ultrasonic guided wave technology for nondestructive testing of pipeline defects has also attracted more and more attention. [0003] In the existing research, Gazis et al. gave a calculation expression for the dynamic analysis of a hollow cylinder under the assumption of linear isotropic elasticity. Their wo...
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IPC IPC(8): G01N29/44
Inventor 居冰峰周兆忠王传勇孙泽青杜慧林孙安玉
Owner ZHEJIANG UNIV