Application Cases

Experimental Name: Single Defect Guided Wave Testing Experiment

Research Focus: Pipeline transportation plays an indispensable role in today's national economy and industrial transportation sectors, offering economic, efficient, and safe advantages. However, pipelines are not maintenance-free during service. Over time or due to manufacturing defects, pipelines can develop flaws, ultimately leading to safety incidents. Therefore, improving existing pipeline defect detection techniques and researching new methods are of great significance for ensuring the reliable operation of pipeline transportation systems.

Ultrasonic guided waves have been extensively studied for both short and long-distance pipeline inspection due to their unique advantages and have become an important defect detection method. This paper investigates the focusing effect of time-reversed guided wave detection through theoretical analysis, numerical simulation, and experimental validation based on the influence of different parameters. The specific research content is divided into the following three parts:

Firstly, for time-reversal signals containing different modal information of defects, the focusing effects under different time window widths were explored, laying the foundation for subsequent research. Direct guided wave testing and time-reversal guided wave testing were conducted on pipelines with crack defects at different circumferential angles, radial depths, and axial lengths. The results were compared to investigate the influence of parameter changes on guided wave detection and time-reversal focusing. Based on the single-defect model, a pipeline containing dual defects was established to study the focusing effects at Defect 1 and Defect 2, and the influence of different axial spacings and circumferential angles between the dual defects on the waveform, mode, and amplitude after time reversal.

Secondly, addressing situations where the pipeline is partially exposed or ensuring complete coupling between the transducer and the pipeline is difficult during actual inspection, a partial loading time-reversal guided wave detection method was proposed. This method selects appropriate channel positions and numbers for time-reversal loading during secondary excitation based on the displacement data received from each channel in direct guided wave detection. The interaction between guided waves and single defects was analyzed, the circumferential distribution of defect energy was studied, and based on this, using energy, defect reflection rate, etc., as indicators, schemes were designed to explore how changes in the number and position of channels affect the focusing effect.

Finally, an experimental system was set up to perform defect detection on an actual pipeline, determine the axial position of the defect, and compare it with the actual position and simulation results. The focusing effect under changing window widths was verified using a combination of experiment and numerical simulation, and the feasibility for defects at different circumferential angles, different radial depths, and partial loading was validated.

Experimental Objective: To improve the detection accuracy for small defects in pipelines, and to lay a foundation for the faster application of ultrasonic guided wave time-reversal testing in practical inspection engineering, adapting to the issue of incomplete transducer coupling during actual detection processes.

Test Equipment: Arbitrary waveform generator, ATA-8202 RF power amplifier, transceiver switch, ATA-5320 preamplifier, digital oscilloscope.

Experimental Process: The ATA-8202 RF power amplifier features an LCD panel display, operates in Class A mode, and offers advantages such as high linearity, low distortion, long service life, and stable performance. It has a saturated output power of 200W, a power gain of 47dB, and gain adjustment in 0.5dB steps. During the experiment, the selected excitation signal remained consistent with the finite element simulation. Sixteen length-expansion piezoelectric transducers uniformly arranged around the pipe end, combined with a transceiver switch, achieved the signal transmission and reception functions. The modulated pulse signal generated by the waveform generator, after enhancement by the power amplifier, achieved axial loading on the transducers, thereby exciting the generation of longitudinal mode guided waves. These guided wave signals propagated along the pipe axis, interacted with defects in the pipeline, and generated reflected and transmitted waves. Subsequently, the reflected echo signals were recaptured by the transducers and converted into weak electrical signals. This signal was further amplified by the preamplifier and transmitted to the oscilloscope for recording. Finally, this detection process was displayed in real-time on the host computer.

Figure 1-1: Experimental platform and setup

Experimental Results: This experiment established an ultrasonic guided wave pipeline defect detection system. Direct guided wave detection and time-reversal guided wave detection were performed on a pipeline with corrosion defects, and partial loading guided wave detection was experimentally validated. The following conclusions were drawn:
(1) The axial positioning of corrosion defects in the pipeline using guided wave detection is relatively accurate with small errors. Ultrasonic guided waves can effectively detect corrosion defects in pipelines.
(2) The defect reflection rate in time-reversal guided wave detection increases with the widening of the time-reversal window, consistent with the simulation conclusions.
(3) As the pit density increases, the defect reflection rates for both direct guided wave detection and time-reversal guided wave detection increase, with a more significant improvement observed for smaller corrosion defects.
(4) When the circumferential loading angle is small, more non-axisymmetric guided wave modes are excited. After interaction with the defect, the modal composition becomes more complex, making the defect wave packet difficult to identify.

Figure: Experimental signals for different loading positions

Figure: Experimental detection results for defects with different pit densities

Product Recommendation: ATA-8000 Series RF Power Amplifier

Figure: ATA-8000 Series RF Power Amplifier Specifications and Parameters

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