A method of monitoring fatigue of a stressed component part such as in nuclear power plants or aircraft, with sensors attached to the outside of the component part to be monitored, includes feeding values measured by the sensors at the component parts to be monitored at a given timing cycle to a process computer. The process computer contains a first arithmetic unit (LCID) which determines weighting factors for addressing mechanical unit load cases and/or directly comparing stresses specific to a load case, from the measured values with the aid of a stress file (LCL) of specified unit load cases, and storing them in a working memory. They are assigned in a second arithmetic unit (HSP VSP), in accordance with the comparison stresses determined by the first arithmetic unit (LCID) and/or on the basis of measured data stored in the working memory (FIFO II), after they are resolved in accordingly weighted unit values, utilizing a first memory including two unit load case libraries (TLL, MLL). They are stored in a weighted manner and in a timing cycle in a second memory (STACK VSP). The second memory is controlled with a third arithmetic unit (RFL). A partial usage factor obtained during an evaluation cycle of the component part is calculated from a comparison stress curve, utilizing fatigue curves stored in a memory (FAT). The partial usage value is added to a previous usage factor stored in a further working memory (RAM USE I), whereby an actual overall usage factor (Uges) is obtained.
