Effects of Thermal Gradients in High-Temperature Ultrasonic Non-Destructive Tests.

Area of Science:

• Materials Science
• Non-Destructive Testing
• Acoustics

Background:

• Ultrasonic inspection is crucial for industrial equipment integrity, particularly in high-temperature environments like the oil and gas sectors.
• Standard ultrasonic testing methods face challenges at elevated temperatures, leading to inaccuracies in flaw detection and sizing.
• Temperature gradients cause acoustic anisotropy, distorting ultrasonic beams and potentially compromising safety and quality assessments.

Purpose of the Study:

• To develop a mathematical tool for correcting focal laws in ultrasonic inspections conducted at high temperatures.
• To mitigate positioning and sizing errors of flaws caused by thermal distortions in ultrasonic signals.
• To improve the reliability of non-destructive testing in demanding industrial applications.

Main Methods:

• Utilized ray tracing concepts and a heat propagation model for solids.
• Incorporated an experimentally determined linear approximation of sound speed dependence on temperature.
• Developed a focal law correction tool to adjust ultrasonic beam paths considering temperature gradients.

Main Results:

• The developed tool successfully calculated relative firing delays for active elements, accounting for thermal gradients.
• Demonstrated a significant reduction of over 68% in flaw positioning errors.
• Validated the effectiveness of focal law correction in high-temperature ultrasonic inspections.

Conclusions:

• The mathematical tool effectively corrects focal laws, significantly enhancing the accuracy of ultrasonic flaw positioning at high temperatures.
• This advancement is vital for maintaining product quality and equipment integrity in industries with elevated operating conditions.
• The study provides a practical solution to a critical challenge in non-destructive evaluation under thermal stress.