Conclusion

Abstract

This thesis has described the development of an ultrasonic array system for the in situ inspection of single-crystal turbine blades. The system was intended to detect and characterise defects in the turbine blades with the highest possible accuracy to mitigate the risk of in-service failure. Single-crystal turbine blades are highly anisotropic. This has been shown to deleteriously affect the inspection of these components with ultrasonic NDE methods. Therefore, the earlier chapters of this thesis developed methods to measure and compensate for the anisotropic behaviour of single-crystal components to ensure the most accurate inspection possible. The later chapters detailed the development of an array system for the inspection of a specific turbine blade to detect root cracking. The inspection performance of the developed system was evaluated using artificial and real cracks. These evaluations showed the array system to offer greatly improved crack detection over a conventional ultrasonic inspection. However, the system was shown to exhibit lower detection sensitivity than would be required for a viable in-service inspection for this particular turbine blade scenario. In this conclusion chapter, the main findings of the thesis are presented in detail. In addition, further research work is suggested that could be used to improve the detection sensitivity and lead to accurate defect sizing for future inspection systems.