Application Cases

Pipes are widely used in industry as the primary means of transporting fluids such as oil, gas, and water, making the assurance of pipeline safety critically important. Ultrasonic guided wave testing is highly efficient and convenient, making it well-suited for pipeline inspection. Currently, pipeline guided wave testing primarily employs axisymmetric mode guided waves, with flexural modes rarely utilized due to their complex motion patterns and the difficulty of generating them in a pure form, resulting in overly complex and uninterpretable signals. However, the unique characteristics of flexural modes, such as circumferential focusing, offer the potential to address challenging pipeline inspection scenarios. This experiment focuses on a key issue hindering the detection of flexural modes in pipelines: the pure excitation of flexural modes in pipes. A helical excitation method is used to generate flexural mode guided waves in pipes, laying the foundation for pipeline flexural mode detection.

Experimental Name: Study on Excitation Method for Flexural Mode Guided Waves in Pipes Under Helical Loads

Experimental Principle:
Based on the magnetostrictive effect and guided wave mode matching theory, iron-cobalt alloy strips are used under orthogonal magnetic fields (a permanent magnet bias field and a coil alternating field) to generate shear stress waves propagating along a helical path (12.8° inclination angle, determined by Ray-Plate theory). This precisely excites the F(1,2) flexural mode, which is dominated by circumferential displacement. The quasi-non-dispersive properties at a 50 kHz excitation frequency suppress multi-mode interference. A quarter-circumference magnetostrictive sensor at the receiving end captures the circumferential displacement component. Combined with a mode decomposition algorithm, the helical wavefront characteristics are verified as the interference effect of axial phase differences between orthogonal components of the same mode. Additionally, a 22% energy conversion to the F(1,3) mode is observed during end-face reflection. With an 87% electromagnetic-to-acoustic energy conversion efficiency (achieved by optimizing the alloy thickness to 0.15 mm) and a modal purity of 82%–86%, the feasibility of exciting flexural guided waves under helical loads is confirmed. This provides a new method for circumferential defect localization in pipelines.

Experimental Block Diagram:

Experimental Setup Photo:

Experimental Procedure:
First, a helical excitation device was designed based on the magnetostrictive effect. Iron-cobalt alloy strips were helically attached to the outer wall of a stainless steel pipe with an outer diameter of 89 mm and a wall thickness of 5.5 mm, with a helical angle of 12.8°. A 30-turn excitation coil and permanent magnets were used to generate an alternating magnetic field. An arbitrary waveform generator produced a 5-cycle tone-burst signal at 50 kHz, which was amplified by the power amplifier ATA-3080 to drive the sensor and generate helical tangential loads. At the other end of the pipe, a quarter-circumference magnetostrictive receiving sensor array was arranged. The guided wave signals were acquired through a signal conditioning module and a data acquisition system.

Application Fields:
Monitoring of chip packaging polishing processes, surface integrity assessment of aerospace components, quality control in medical device processing, high-precision optical component manufacturing (e.g., mirror polishing), etc.

Application Scenarios:
Pipelines, flexural modes, normal mode expansion, ultrasonic guided waves, non-destructive testing, magnetostrictive effect

Product Recommendation:ATA-300/3000 Series Power Amplifier

Figure: ATA-300/3000 Series Power Amplifier Specifications and Parameters