Real Time Fatigue Monitoring Using OMA

The fatigue phenomenon can produce premature failure in structural and mechanical components when they are subjected to dynamic cyclic loadings. One of the most commonly used methodologies in fatigue design consists of determining the stresses time histories from variable amplitude load models, calculating the stress spectrum using the rainflow technique and evaluating the total fatigue damage using Miner’s rule. To simplify the calculations, the standards often consider simplified constant amplitude loading histories. In order to reduce the uncertainty associated with the stresses at each point of the structure, this paper presents a methodology to estimate stresses at different points of a structure, using experimental measurements (accelerations, velocities or displacements) at a limited number of points, and modal parameters (numerical or experimental). If stresses are estimated in real time, it is possible to perform fatigue monitoring of the structure, i.e. to calculate the accumulated damage over time, providing valuable information for estimating the remaining life of structures in service. This methodology also has the advantage of being combinable with other damage detection techniques based on operational modal analysis (OMA).