Next Article in Journal
Sequential Low-Thrust Orbit-Raising of All-Electric Satellites
Previous Article in Journal
Pareto Optimal PID Tuning for Px4-Based Unmanned Aerial Vehicles by Using a Multi-Objective Particle Swarm Optimization Algorithm
Previous Article in Special Issue
The Industry Internet of Things (IIoT) as a Methodology for Autonomous Diagnostics in Aerospace Structural Health Monitoring
Open AccessArticle

A Nonlinear Ultrasonic Modulation Method for Crack Detection in Turbine Blades

Materials Research Centre, Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK
Author to whom correspondence should be addressed.
Aerospace 2020, 7(6), 72;
Received: 17 April 2020 / Revised: 27 May 2020 / Accepted: 1 June 2020 / Published: 4 June 2020
(This article belongs to the Special Issue Selected Papers from IWSHM 2019)
In modern gas turbines, efforts are being made to improve efficiency even further. This is achieved primarily by increasing the generated pressure ratio in the compressor and by increasing the turbine inlet temperature. This leads to enormous loads on the components in the hot gas region in the turbine. As a result, non-destructive testing and structural health monitoring (SHM) processes are becoming increasingly important to gas turbine manufacturers. Initial cracks in the turbine blades must be identified before catastrophic events occur. A proven method is the linear ultrasound method. By monitoring the amplitude and phase fluctuations of the input signal, structural integrity of the components can be detected. However, closed cracks or small cracks cannot be easily detected due to a low impedance mismatch with the surrounding materials. By contrast, nonlinear ultrasound methods have shown that damages can be identified at an early stage by monitoring new signal components such as sub- and higher harmonics of the fundamental frequency in the frequency spectrum. These are generated by distortion of the elastic waveform due to damage/nonlinearity of the material. In this paper, new global nonlinear parameters were derived that result from the dual excitation of two different ultrasound frequencies. These nonlinear features were used to assess the presence of cracks as well as their qualitative sizes. The proposed approach was tested on several samples and turbine blades with artificial and real defects. The results were compared to samples without failure. Numerical simulations were conducted to investigate nonlinear elastic interaction of the stress waves with the damage regions. The results show a clear trend of nonlinear parameters changing as a function of the crack size, demonstrating the capability of the proposed approach to detect in-service cracks. View Full-Text
Keywords: nonlinear ultrasound; crack detection; gas turbines nonlinear ultrasound; crack detection; gas turbines
Show Figures

Figure 1

MDPI and ACS Style

Mevissen, F.; Meo, M. A Nonlinear Ultrasonic Modulation Method for Crack Detection in Turbine Blades. Aerospace 2020, 7, 72.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

Search more from Scilit
Back to TopTop