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Development of an Ultrasonic Inspection Technique for Sizing of Cracks in Complex Geometry Plant Components

This paper discusses the development of an ultrasonic time of flight diffraction-based inspection technique for sizing surface-breaking vertical cracks in complex geometry plant components like a solid steam turbine rotor with integral discs. A simple geometric model was developed. Specimens containing vertical notches simulating cracks in real-life rotors and holding devices for affixing the transmitter and receiver probes in plane and on opposite sides of the disc-like portion of the specimens were designed and fabricated. Experiments were conducted, and the results show that the inspection technique developed here can size such cracks with reasonable accuracy. The technique can be useful for in-situ condition assessment and remaining life assessment of aged, in-service complex geometry plant components.

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