Application Cases

Experiment Name: Application of Power Amplifiers in Measurement Experiments of Helical Guided Wave Signals in Pipes

Experimental Content:
Measuring quasi-Lamb guided waves propagating helically along the pipe wall to investigate their propagation characteristics.

Research Direction: Guided wave nondestructive testing in pipes

Testing Equipment: Signal generator, ATA-2022B high-voltage amplifier, longitudinal wave straight probe, PZT, oscilloscope, computer, etc.

Experimental Procedure:
When the ratio of wall thickness to radius is less than 10%, the propagation behavior of Lamb waves in a pipe can be approximately considered similar to that in a plate. However, due to the circumferential continuity of the pipe, guided waves propagate omnidirectionally in a helical manner. In the experiment, an excitation function was designed and generated by a signal generator, then amplified by a power amplifier to excite Lamb waves on the pipe surface. A receiving array was arranged at the opposite end, and signals from each receiving probe in the array were sequentially measured to identify propagation patterns and compare them with theoretical results.

The power amplifier model selected for this experiment was the ATA-2022B high-voltage amplifier, which amplifies signals within 1 MHz. During the experiment, the signal generator produced a 5-cycle cosine signal modulated by a Hanning window, with a center frequency of 200 kHz. Although the maximum output voltage of the signal generator alone could drive the piezoelectric transducer, the signal was too weak for effective reception. Therefore, the power amplifier was essential. Based on the experiment, a signal separation algorithm using dictionary reconstruction was designed to separate overlapping helical guided wave signals, enabling quantitative analysis of the separated signals.

Schematic diagram of helical guided wave propagation along the pipe wall. Experimental platform for measuring helical guided waves in pipes

Experimental Results:
Sixteen sets of helical guided wave signals were measured from the receiving array. Their propagation patterns could be predicted by planning paths on a flat plate. Based on the acquired signals, overlapping signals from intact pipes and pipes with defects were successfully separated. Quantitative analysis of the error validated the effectiveness of this separation algorithm.

(a) Original received signal of helical guided waves; (b) Reconstructed signal based on dictionary reconstruction; (c)–(h) Separated single-component guided wave signals.

(a) A₀ mode signal separated from the original signal (including both intact and defect signals); (b) S₀ mode signal separated from the original signal (including both intact and defect signals).

Figure: ATA-2022B High-Voltage Amplifier Specifications and Parameters