Ultrasound transmission and reflection tomography for nondestructive testing using experimental data.

Area of Science:

• Materials Science
• Physics
• Engineering

Background:

• Nondestructive testing (NDT) is crucial for evaluating material integrity without causing damage.
• Ultrasonic tomography offers a non-invasive method for internal structure analysis.
• Accurate reconstruction of material properties like velocity is essential for effective NDT.

Purpose of the Study:

• To demonstrate the feasibility of reconstructing the velocity structure of objects with high spatial resolution and sensitivity using ultrasonic tomography.
• To propose and validate a tomographic experimental scheme with object rotation for multi-angle ultrasonic sounding.
• To develop and apply efficient computational methods for solving the nonlinear inverse problem in ultrasound tomography.

Main Methods:

• Implementation of a tomographic experiment using linear antenna transducer arrays operating at approximately 5 MHz.
• Conducting experiments on samples with embedded inserts featuring different sound propagation velocities.
• Formulating the velocity structure reconstruction as a nonlinear inverse problem for a scalar wave equation.
• Developing and utilizing efficient iterative methods, including a two-stage approach, for solving the inverse problem on a supercomputer.

Main Results:

• Successful reconstruction of the velocity structure and insert boundaries in both transmission and reflection schemes.
• Achieved a spatial resolution of approximately 1 mm with a velocity contrast sensitivity of 2% in the transmission scheme.
• Demonstrated the capability to reconstruct detailed velocity variations within inspected objects.

Conclusions:

• The study confirms the effectiveness of ultrasonic tomography for high-resolution velocity structure reconstruction.
• The proposed multi-angle sounding scheme and iterative methods provide a robust solution for nonlinear inverse problems in ultrasound.
• This technique holds significant potential for advanced nondestructive testing applications requiring precise material characterization.