Which ultrasonic testing method is effective for sizing flaws that are open to the ID surface in the mid-wall region, 30% to 60% through wall depth?

The bimodal ultrasonic testing method is particularly effective for sizing flaws that are open to the inside diameter (ID) surface, especially in the mid-wall region where the flaw depth is between 30% to 60% through the wall thickness. This method employs two different ultrasonic wave modes to gather detailed information about the flaw's characteristics.

Bimodal testing utilizes both longitudinal and shear waves, allowing for a more comprehensive analysis of the reflector's shape and orientation. When a flaw is open to the ID surface, the combination of these waves helps in accurately interpreting the extent and size of the flaw. By employing different modes, the testing can differentiate the responses completely, thus providing improved resolution and reliability in identifying the flaw's dimensions, which is critical for ensuring the structural integrity of the material being tested.

Furthermore, this technique is advantageous in applications where a deeper understanding of the flaw's position and size is imperative for safety and compliance with industry standards. Therefore, the application of bimodal ultrasonic testing leads to better decision-making regarding repairs, mitigations, or continued service of the component being inspected.