ABSTRACT
The previous chapters have considered diagnostics based on gas path measurements. In this chapter, we look at a problem where vibration characteristics are used for gas turbine diagnostics. The present chapter focuses on turbine blade damage. Turbine blades undergo cyclic loading causing structural deterioration, which can lead to failure. It is important to know how much damage has taken place at any particular time to monitor the condition or health of the blade and to avoid any catastrophic failure of the blades. Several studies look at damage at a given time during the operational history of the structure. This is typically called diagnostics and involves detection, location, and isolation of damage from a set of measured variables. The detection function is most fundamental, as it points out if the damage is present or not. However, some level of damage due to microcracks and other defects is always present in a structure. The important issue of indicating when to detect damage depends on how much life is left in the structure. It is not advantageous to detect small levels of damage in a structure. It would be useful if damage detection were triggered some time before final failure.
