Dislocation detection of gas turbine materials using a nonlinear ultrasound modulation technique

Industrial gas turbines are used for generating electricity or driving other turbomachinery with the continuous development goal of further increasing machine efficiency. This is primarily achieved by raising the pressure ratio generated in the compressor and by increasing the turbine inlet temperature. Consequently, the hot gas components in gas turbines are subjected to extreme loads and the need for non-destructive testing and structural health monitoring techniques is becoming increasingly important to maintain these components. An important indicator for assessing the structural integrity is the determination of the initial plastic deformation. In this paper, a new method for the detection of plasticity was developed, which is based on a nonlinear ultrasonic two-frequency excitation. The one-dimensional wave equation was solved with a two-frequency excitation and combined with the expanded dislocation theory. As a result, various nonlinearity parameters were defined, showing a clear increasing or a decreasing behaviour with increasing plastic strain. This was experimentally proven with flat tensile specimen made of stainless steel and Inconel 718 (metal plates and additively manufactured). The new indicators allow the possibility to efficiently detect the initial plastic deformation in gas turbine components.

Automated summary

Industrial gas turbines are used to generate electricity or drive other turbomachinery, aiming to increase machine efficiency by raising the compressor's pressure ratio and the turbine's inlet temperature. As a result, the hot gas components in gas turbines face extreme loads, requiring the use of non-destructive testing and structural health monitoring techniques to ensure their integrity.