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Fundamentals And Applications Of Ultrasonic Waves

A comprehensive review on blade tip timing-based health monitoring: status and future

This review article is focused on the analysis of the state of the art of sensors for guided ultrasonic waves for the detection and localization of impacts for structural health monitoring (SHM). The recent developments in sensor technologies are then reported and discussed through the many references in recent scientific literature. The physical phenomena that are related to impact event and the related main physical quantities are then introduced to discuss their importance in the development of the hardware and software components for SHM systems. An important aspect of the article is the description of the different ultrasonic sensor technologies that are currently present in the literature and what advantages and disadvantages they could bring in relation to the various phenomena investigated. In this context, the analysis of the front-end electronics is deepened, the type of data transmission both in terms of wired and wireless technology and of online and offline signal processing. The integration aspects of sensors for the creation of networks with autonomous nodes with the possibility of powering through energy harvesting devices and the embedded processing capacity is also studied. Finally, the emerging sector of processing techniques using deep learning and artificial intelligence concludes the review by indicating the potential for the detection and autonomous characterization of the impacts.

Ultrasonic Guided-Waves Sensors and Integrated Structural Health Monitoring Systems for Impact Detection and Localization: A Review.

Blade tip clearance is one of the important parameters affecting the performance, safety and stability of a gas turbine engine. However, it is difficult to measure the tip clearance in real time an...

https://journals.sagepub.com/doi/pdf/10.1177/0020294019877514

A review of blade tip clearance–measuring technologies for gas turbine engines:

With Industry 4.0 becoming increasingly pervasive, the importance and usage of sensors has increased several folds. Industry 4.0 refers to a new phase in the industrial revolution that mainly focuses on interconnectivity, automation, machine learning, and real-time data. Real-time structural health monitoring (SHM) of components in the industrial process is one of the crucial and important component of Industry 4.0. SHM of components exposed to high-temperature ( $\sim 650^{\circ }\text{C}$ ) is becoming increasingly important nowadays. However, harsh and high temperature environments impose a great challenge towards their implementation. This review is an attempt to demonstrate the development, application, limitations and recent advancement of the existing sensors used for SHM. Some sensors such as eddy current (EC) sensors and fiber Bragg grating (FBG) sensors have been discussed in detail. A phenomenological study of the electromagnetic sensor for the SHM of engineering components that are exposed to high temperature has been addressed. State-of-the-art fabrication methodologies such as low temperature co-fired ceramic (LTCC) technology for such type of sensors for high temperature SHM applications have been elucidated. Future challenges and opportunities for SHM applications of high temperature sensors have been highlighted.

Recent Advancements in the Development of Sensors for the Structural Health Monitoring (SHM) at High-Temperature Environment: A Review

The need for non-destructive testing/structural health monitoring (SHM) is becoming increasingly important for gas turbine manufacturers. Incipient cracks have to be detected before catastrophic events occur. With respect to condition-based maintenance, the complex and expensive parts should be used as long as their performance or integrity is not compromised. In this study, the main failure modes of turbines are reported. In particular, we focus on the turbine blades, turbine vanes and the transition ducts of the combustion chambers. The existing monitoring techniques for these components, with their own particular advantages and disadvantages, are summarised in this review. In addition to the vibrational approach, tip timing technology is the most used technique for blade monitoring. Several sensor types are appropriate for the extreme conditions in a gas turbine, but besides tip timing, other technologies are also very promising for future NDT/SHM applications. For static parts, like turbine vanes and the transition ducts of the combustion chambers, different monitoring possibilities are identified and discussed.

A Review of NDT/Structural Health Monitoring Techniques for Hot Gas Components in Gas Turbines

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.

A nonlinear ultrasonic modulation method for crack detection in turbine blades

/pdf/ultrasonically-stimulated-thermography-for-crack-detection-1p6vdfz7.pdf

Frank Mevissen

Papers

A Review of NDT/Structural Health Monitoring Techniques for Hot Gas Components in Gas Turbines

A nonlinear ultrasonic modulation method for crack detection in turbine blades

Ultrasonically stimulated thermography for crack detection of turbine blades

Creep detection of Hastelloy X material for gas turbine components with nonlinear ultrasonic frequency modulation

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