Origins of defects in ferromagnetic materials

Abstract

Any discussion of defects in any material must define what is meant by the term. In absolute terms it must be accepted that there is no such thing as a perfect material or a perfect component or structure in the practical world. Taking this as the basis for a definition of a defect is not very helpful as it includes imperfections in the material at an atomic level which cannot be seen even with optical microscopy at one end of the scale through to defects which can be seen with the naked eye. The definition of a defect which is the most useful in the context of non-destructive testing is an imperfection or flaw which, by its presence, makes a material, structure or component unfit for its intended use. This definition has the great merit of forcing everyone from the design engineer through to the inspector to consider the state of fitness for purpose and the significance of the test results.