Mechanical strain sensing by broadband time reversal in plates

Area of Science:

• Materials Science
• Mechanical Engineering
• Signal Processing

Background:

• Ultrasonic measurement of longitudinal strain using Time Reversal (TR) technique shows low signal sensitivity.
• Inverse filter signal processing improves sensitivity but reduces signal energy and signal-to-noise ratio (SNR).

Purpose of the Study:

• To present a physical solution to enhance the sensitivity of ultrasonic strain sensing systems.
• To introduce one-bit time reversal (TR) for simplified hardware and evaluate its feasibility.
• To investigate the influence of the transfer function on strain sensitivity using a novel figure of merit.

Main Methods:

• Utilized a strain sensing system with piezocomposite transducers for generating and sensing guided ultrasonic waves in a plate.
• Employed Time Reversal (TR) for phase compensation of dispersion and edge reflections, enabling wave time-recompression.
• Introduced and compared one-bit TR with conventional twelve-bit TR signal processing.
• Developed a figure of merit relating focused energy to total signal energy to assess TR performance.

Main Results:

• System sensitivity was improved using 2-2 piezocomposite transducers operating between 0.2-3.0 MHz.
• Experiments up to 150 μm/m strain showed a linear response in focus amplitude.
• The proposed figure of merit correlates with strain sensitivity.
• One-bit TR maintained focus quality and proved feasible for the measurement technique.

Conclusions:

• The study successfully enhanced ultrasonic strain sensing sensitivity through physical solutions and one-bit TR.
• One-bit TR offers a feasible and hardware-simplifying alternative to conventional TR for strain measurement.
• The developed figure of merit provides a valuable tool for evaluating TR system performance and sensitivity.