A Comparative Study of Simulation and Experiment Results for Phased Array Ultrasonic Testing for the Root Area of Low-Pressure Turbine

Non-destructive testing of the root area of a low-pressure (LP) turbine's blades and disks was performed in a restrictive manner. When the turbine blades and disks were disassembled or not, the root area surface was examined by conventional ultrasonic testing (UT), that is, magnetic particle or liquid penetrant testing. Recent developments have led to the use of phased array ultrasonic testing technology for the inspection of the root area without any disassembling of the turbine blades or disks, both of which have a high probability of crack initiation. However, before phased array ultrasonic testing can be used in a field inspection, consideration should be given to the complexity of analyzing background noise signals and unexpected UT signals from the various geometric shapes in the root area. This paper describes UT simulations of a root area in a case in which the lowpressure turbine blades and disks are assembled before the developed phased array UT technology is applied to a field examination. The UT simulations produce advance predictions of the characteristics of UT signals, the exact location of the probe inspection, and the appropriateness of the frequency of a selected probe. The testing conditions are then optimized on the basis of the simulation results.