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|Title:||Improved defect detection using adaptive leaky NLMS filter in guided-wave testing of pipelines|
Nakhli Mahal, H
|Keywords:||adaptive ﬁltering;leaky normalized mean square;ultrasonic guided waves;pipeline inspection;SNR enhancement;signal processing|
|Abstract:||Ultrasonic guided wave (UGW) testing of pipelines allows long range assessments of pipe integrity from a single point of inspection. This technology uses a number of arrays of transducers, linearly placed apart from each other to generate a single axisymmetric wave mode. The general propagation routine of the device results in a single time domain signal, which is then used by the inspectors to detect the axisymmetric wave for any defect location. Nonetheless, due to inherited characteristics of the UGW and non-ideal testing conditions, non-axisymmetric (ﬂexural) waves will be transmitted and received in the tests. This adds to the complexity of results’ interpretation. In this paper, we implement an adaptive leaky normalized least mean square (NLMS) ﬁlter for reducing the eﬀect of non-axisymmetric waves and enhancement of axisymmetric waves. In this approach, no modiﬁcation in the device hardware is required. This method is validated using the synthesized signal generated by a ﬁnite element model (FEM) and real test data gathered from laboratory trials. In laboratory trials, six diﬀerent sizes of defects with cross-sectional area (CSA) material loss of 8% to 3% (steps of 1%) were tested. To ﬁnd the optimum frequency, several excitation frequencies in the region of 30–50 kHz (steps of 2 kHz) were used. Furthermore, two sets of parameters were used for the adaptive ﬁlter wherein the ﬁrst set of tests the optimum parameters were set to the FEM test case and, in the second set of tests, the data from the pipe with 4% CSA defect was used. The results demonstrated the capability of this algorithm for enhancing a defect’s signal-to-noise ratio (SNR).|
|Appears in Collections:||Dept of Electronic and Computer Engineering Research Papers|
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