Ultrasonic Flaw Sizing and Inherent Errors

Nondestructive test methods are used to detect specific types of anomalies within a material, but detection is only half the battle. For an anomaly to be characterized as a Defect it must be quantified by size, shape, and location within the material, and gaged against applicable acceptance criteria. Ultrasound is used extensively across industry to determine the quality level of various types of welds, laminates, bonded components, wrought product, and forged materials as it is considered a quantifiable method. If an anomaly is detected during inspection the reflected ultrasonic energy is optimized and compared against some form of representative standard. Though this process has been common practice for many decades it is important to understand the inherent error associated with measuring reflected energy. Calibration standards are relied on heavily for this practice as they are reproducible to a high level of accuracy and repeatability, but direct comparison to actual flaws can be misleading.