EFFECT OF PARTIAL DEPTH CRACKS ON THE NATURAL FREQUENCY OF TWISTED BLADES: A 3-D FINITE ELEMENT ANALYSIS

It is possible that fatigue cracks may appear in turbomachine blades which are subjected to extreme conditions during operation. Such cracks may become the cause of failure. The feasibility of considering the natural frequency as a parameter for detecting full depth cracks has been considered earlier. The present paper not only compares the result for full depth cracks with the previous work but also presents results for partial depth cracks. It concludes with the suggestion that the natural frequency is too poor a parameter for the diagnosis of partial depth cracks. However, experimental verification is suggested and a cautionary note about extrapolation of conclusions to rotating structures is also provided.