Vibrational Fatigue and Structural Dynamics for Harmonic and Random Loads

The presented study experimentally and theoretically researches the vibrational fatigue analysis of the aluminium-alloy specimen at harmonic and random loads. The relation between vibrational fatigue for deterministic and random vibration loads is demonstrated with presented experiments and standard frequency-based counting methods. Firstly, a new fatigue testing methodology is proposed to obtain the material fatigue parameters with harmonic base-vibration excitation. With the developed methodology it is possible to monitor in real-time the principal stress amplitude at the specimen as well as to track the natural frequency shift and the increase of the structural damping of the specimen due to the accumulated fatigue damage. Secondly, with a validated numerical model of the specimen the mechanical stress transmissibility of the structure was obtained for the case of the random-vibration base excitation. Finally, by respecting the mechanical stress response along with experimentally obtained material fatigue parameters the vibration fatigue life was estimated for the case of random vibration load. The numerical fatigue life is in good accordance with the experimental one (obtained with the electro-dynamic shaker). The presented research shows new possibilities in the area of accurate high-cycle vibration fatigue life-estimation of dynamic structures.