Validity of bolt‐removal and gap‐insertion techniques to experimentally simulate the vibration of a cracked rotor

Abstract

Experimental studies of the vibration of a cracked rotor are essential in the development of vibration monitoring techniques. The greatest difficulty in conducting experimental parameter studies is the extensive amount of work required when placing a fatigue crack (FC) of known size and location in the structure. Two alternative techniques, the bolt-removal method (BRM) and the gap-insertion method (GIM), have been suggested to provide an easy mechanism to experimentally simulate the behaviour of a breathing crack. This study aims to qualitatively and quantitatively evaluate these methods and compare them with the results from a grown FC in a slow rotating drum specimen. Deflection results show good agreement, particularly in the vertical direction. For the horizontal direction the two simulation techniques overestimate the deflection from the FC for large crack sizes. However, overall GIM and BRM provide close enough results to support the usage in experimental parameter studies at significantly lower cost.