Which discontinuity type is classified as a service-induced discontinuity?

The classification of a service-induced discontinuity includes defects or irregularities that typically arise due to the processes involved in service or operational conditions rather than inherent material flaws. A fatigue crack is specifically linked to cyclic stress conditions that materials endure during their operational life, leading to material deterioration and eventual failure. This type of discontinuity develops under repeated loading and unloading, making it a clear example of a service-induced discontinuity.

In contrast, corrosion refers to the chemical or electrochemical reaction of a material, usually a metal, with its environment, leading to deterioration. Welding defects often originate from problems during the welding process itself, such as lack of fusion or porosity, which are not induced by operational service. Dimensional errors occur typically from manufacturing processes and might not relate directly to the conditions experienced in service. Therefore, fatigue cracks are distinctly categorized as service-induced, arising from the stresses experienced during use.