A relationship between fatigue damage estimation under multi-axis and single-axis random vibration

Random vibration testing is traditionally performed by means of single -axis testing. However, real operational environment are in general characterized by multi -axis vibration. As a consequence, single -axis testing is incapable of reproducing the actual damaging process of a component in the laboratory. In this work the damage inflicted to a cantilever beam by multiaxis and sequential single -axis random excitation is compared. A fatigue testing campaign is carried out to establish the fatigue properties of the specimen under different types of vibration environment. The results of the fatigue testing campaign are used to define a relationship between the damage inflicted by multi -axis and sequential single -axis excitations. In particular, a correction factor is defined that allows to calculate the fatigue damage under multi -axis vibration environment knowing the damage inflicted by single -axis excitations. The correction factor takes into account the different activation of the vibrating modes of the specimen caused by different types of excitations. The correction factor for multi -axis vibration environments may allow to estimate the damage caused by multi -axis vibration with the use of a single -axis shaker, as well as allowing to calculate the required testing time for a multi -axis test starting from single -axis testing procedures, improving laboratory testing in terms of costs and realism.