Unique Characteristics of Pulse-Echo Sensing Systems for Ultrasonic Immersion Testing in Harsh Environments

Area of Science:

• Materials Science
• Non-destructive Testing
• Acoustics

Background:

• Ultrasonic testing is valuable for inspecting systems in harsh environments (high temperature, radiation, chemicals).
• Existing research heavily focuses on harsh environment effects on piezoelectric materials, with less on other transducer aspects.
• Pulse-echo immersion testing presents unique challenges in discerning target echoes from reverberations.

Purpose of the Study:

• To demonstrate unique characteristics of pulse-echo immersion testing for harsh environments.
• To investigate the influence of electrode thickness, couplant, backing material, and acoustic matching layer.
• To evaluate signal processing methods for improving target echo detection.

Main Methods:

• Utilized finite element simulations and laboratory experiments.
• Employed an aluminum nitride piezoelectric element mounted on a vessel wall.
• Investigated wave propagation through a vessel wall into a fluid with a target.

Main Results:

• Identified challenges in distinguishing target echoes from vessel wall reverberations, especially with short fluid travel distances.
• Demonstrated that a simple subtractive signal-processing method effectively minimizes reverberations when acoustic matching is insufficient.
• Confirmed successful detection of sufficient target echoes for time-of-flight determination and identification of surface anomalies.

Conclusions:

• Optimized pulse-echo immersion testing parameters and signal processing enhance inspection capabilities in challenging conditions.
• The developed methods allow for reliable detection of targets and surface features, even with signal interference.
• This approach advances non-destructive evaluation in harsh industrial settings.