Flaw detection is a very broad subject. When writing about this in the June 2022 Quality article, Flaw Detection 101, I focused on defining what a flaw is and then discussed many of the common nondestructive testing (NDT) methods used to detect flaws. The definition I previously used was, “an indication which is determined to be a discontinuity, but one that does not exceed rejection limits.” This definition can be easily interpreted within the bounds of an NDT program that has defined tolerances and acceptance limits. But, it could also be interpreted differently when the inspections used are not trying to detect common flaw types like cracks, shrinkage, porosity, and others.
Flaws can come in many different shapes, orientations, and sizes. They can be minor material differences, surface imperfections, or anything that is not supposed to be on or in a component. The origin of a flaw can also come from many different sources, and they can be anywhere within a part. Because of this, many different inspections have been developed to find flaws. Since detection of flaws may be very difficult, it can often require either a combination of several inspections or very specific inspections to provide full part coverage.