Disk crack detection in spin testing using tip timing data

This paper presents a technique of detecting turbine disk cracks under spin testing by analyzing the blade tip timing data. The technique is based on the principle that the crack opening displacement of a radial edge crack in rotating disks is a function of the crack length and the square of the rotational speed. The crack opening displacement is related to the inter-blade spacing which is extracted from the tip timing data. Using the proposed method, the inter-blade spacing is plotted against both the rotor speed and the spin test cycle number for crack detection and the tracking of crack progression. The paper also presents some results obtained from analyzing a tip timing data set. The results show that, in spin testing conditions, multiple disk cracks in the test article can be detected and crack propagations can be sensitively tracked using the blade tip timing measurement.