What does "multi-frequency testing" refer to in ultrasonic NDT?

Multi-frequency testing in ultrasonic non-destructive testing (NDT) involves employing multiple ultrasonic frequencies during the inspection process. This approach is advantageous because different frequencies can interact with various material types or thicknesses in unique ways. Higher frequencies provide better resolution and are beneficial for detecting smaller defects, while lower frequencies can penetrate denser materials more effectively and are ideal for assessing thicker sections.

By utilizing multiple frequencies, inspectors can optimize defect detection and characterization, increasing the likelihood of identifying flaws that might be missed if only a single frequency were employed. This technique enhances the overall effectiveness of the ultrasonic testing process, leading to more reliable and accurate results across differing materials and applications.