Fatigue damage evaluation of notched specimens through resonance and anti-resonance data

The evaluation concerning the fatigue strength of mechanical components normally requires the execution of expensive tests. The fact that such relevant tests are also destructive and, therefore, can be carried out over a limited amount of specimens should also be taken into consideration. Finally, they require an a-priori knowledge of the possible damage site. It would be interesting to develop a technique, which is able to follow the fatigue failure process through the life of the mechanical components in order to forewarn a final failure. This paper deals with the development of a promising technique based on the analysis of a particular set of modal data to which fatigue strength of elementary mechanical components can be correlated. The modal data which the paper is dealing with are resonance and anti-resonance data associated to a certain set of specimens. Some recent experimental researches have also been conducted in the mentioned respect. However, these studies have been limited to natural frequency changes only for spot-welded joints and for composite materials. The literature clearly lacks relevant investigation aimed at considering a larger set of modal data (resonance and anti-resonance frequencies) as well as lacking the influence of the load level on the detection capability of the technique. The specimens have been submitted to a large number of fatigue tests and valuable correlations have been extracted between modal data changes and the evolution due to the relevant fatigue loads in the high-cycle regime. The high number of statistics involved in the experimental tests clearly shows how the previously mentioned modal data can forewarn a final failure. (c) 2005 Elsevier Ltd. All rights reserved.