weakening of metal due to microscopic changes in molecular structures caused by vibration or exposure
weakness in metal that makes it likely to break, caused for example by frequent shaking over a long period. Weakened condition of metal parts of machines, vehicles, or structures caused by repeated stresses or loadings, ultimately resulting in fracture under a stress much weaker than that necessary to cause fracture in a single application. Fatigue-resistant metals have been developed and their performance improved by surface treatments, and fatigue stresses have been significantly reduced in aircraft and other applications by designing to avoid stress concentrations