Prediction on Remaining Life of a V-Notched Beam by Measured Modal Frequency

Abstract

A prediction method for the remaining life of a V-notched beam using measured modal frequencies is proposed in this article. The main purpose is to provide a new monitoring method of crack growth for a cantilever beam. At first, the fatigue crack growth characteristic and the change law of modal frequencies of a V-notched cantilever beam under cyclic loading were studied by experiments. Subsequently, the relation of modal frequencies and crack growth were analyzed. Thereafter, the decrease ratio of the first modal frequency was employed to reflect the crack damage so as to set up the relation of the modal frequency and the crack damage, and the evolution model between the crack damage and the cyclic loading numbers were set up. A prediction method for crack growth life was proposed for a cantilever beam based on the decrease ratio of the first modal frequency in the end. The remaining life of a V-notched cantilever beam can be obtained using the proposed method with a given endured loading cycles and the corresponding measured modal frequency. Results indicate that the remaining fatigue life of the V-notched cantilever beam is related to the decrease ratio of the modal frequency, and the predicted remaining life is in good agreement with the measured remaining life as the crack depth extends to a certain value.