Estimating Young's moduli based on ultrasound and full-waveform inversion.

Area of Science:

• Materials Science
• Geophysics
• Civil Engineering
• Ultrasonic Testing

Background:

• Traditional ultrasound methods for determining material properties like dynamic Young's moduli face challenges.
• Accurate determination of wave mode onset and system latency calibration are critical in conventional ultrasonic testing.
• Existing methods often require multiple measurements and complex setups for material characterization.

Purpose of the Study:

• To develop and validate a novel ultrasound-based method for estimating compression (p-wave) and shear (s-wave) velocities.
• To overcome the limitations of traditional through-transmission ultrasonic techniques.
• To enable precise material parameter determination using a single measurement and advanced inversion methods.

Main Methods:

• Utilized wavefield simulation and full-waveform inversion (FWI) for velocity estimation.
• Employed a single p-wave transducer and considered mode conversions for s-wave velocity.
• Characterized ultrasound transducer directivity using laser Doppler vibrometer measurements.
• Applied the graph-optimal-transport misfit function to solve the inverse problem.

Main Results:

• Successfully estimated p-wave and s-wave velocities in six different metal specimens.
• Achieved good agreement between simulated and measured waveforms.
• Demonstrated the precision of FWI-estimated velocities compared to manual picking.
• Validated the effectiveness of the graph-optimal-transport misfit for wave velocity inversion.

Conclusions:

• The novel FWI method provides a more efficient and accurate approach to determine material velocities.
• This study serves as a foundation for applying FWI to more complex geometries and heterogeneous materials.
• The technique simplifies ultrasonic testing by requiring only one measurement and a single transducer type.