The paper provides a state of the art review of guided wave based structural health monitoring (SHM). First, the fundamental concepts of guided wave propagation and its implementation for SHM is explained. Following sections present the different modeling schemes adopted, developments in the area of transducers for generation, and sensing of wave, signal processing and imaging technique, statistical and machine learning schemes for feature extraction. Next, a section is presented on the recent advancements in nonlinear guided wave for SHM. This is followed by section on Rayleigh and SH waves. Next is a section on real-life implementation of guided wave for industrial problems. The paper, though briefly talks about the early development for completeness,. is primarily focussed on the recent progress made in the last decade. The paper ends by discussing and highlighting the future directions and open areas of research in guided wave based SHM.

https://iopscience.iop.org/article/10.1088/0964-1726/25/5/053001/pdf

Guided wave based structural health monitoring: A review

The renewable energy industry is undergoing continuous improvement and development worldwide, wind energy being one of the most relevant renewable energies. This industry requires high levels of reliability, availability, maintainability and safety (RAMS) for wind turbines. The blades are critical components in wind turbines. The objective of this research work is focused on the fault detection and diagnosis (FDD) of the wind turbine blades. The FDD approach is composed of a robust condition monitoring system (CMS) and a novel signal processing method. CMS collects and analyses the data from different non-destructive tests based on acoustic emission. The acoustic emission signals are collected applying macro-fiber composite (MFC) sensors to detect and locate cracks on the surface of the blades. Three MFC sensors are set in a section of a wind turbine blade. The acoustic emission signals are generated by breaking a pencil lead in the blade surface. This method is used to simulate the acoustic emission due to a breakdown of the composite fibers. The breakdown generates a set of mechanical waves that are collected by the MFC sensors. A graphical method is employed to obtain a system of non-linear equations that will be used for locating the emission source. This work demonstrates that a fiber breakage in the wind turbine blade can be detected and located by using only three low cost sensors. It allows the detection of potential failures at an early stages, and it can also reduce corrective maintenance tasks and downtimes and increase the RAMS of the wind turbine.

/pdf/a-new-fault-location-approach-for-acoustic-emission-4sbyppm6w4.pdf

A New Fault Location Approach for Acoustic Emission Techniques in Wind Turbines

Recently, there has been a growing interest in deploying smart materials as sensing components of structural health monitoring systems In this arena, piezoelectric materials offer great promise for researchers to rapidly expand their many potential applications The main goal of this study is to review the state-of-the-art piezoelectric-based sensing techniques that are currently used in the structural health monitoring area These techniques range from piezoelectric electromechanical impedance and ultrasonic Lamb wave methods to a class of cutting-edge self-powered sensing systems We present the principle of the piezoelectric effect and the underlying mechanisms used by the piezoelectric sensing methods to detect the structural response Furthermore, the pros and cons of the current methodologies are discussed In the end, we envision a role of the piezoelectric-based techniques in developing the next-generation self-monitoring and self-powering health monitoring systems

https://www.mdpi.com/1424-8220/20/13/3730/pdf

Piezoelectric Sensing Techniques in Structural Health Monitoring: A State-of-the-Art Review

/pdf/new-pipe-notch-detection-and-location-method-for-short-3ut1lhbdrz.pdf

New Pipe Notch Detection and Location Method for Short Distances employing Ultrasonic Guided Waves

In this study, a two-level scanning strategy for a noncontact laser ultrasonic measurement system is proposed to expedite the inspection of a wind turbine blade. First, coarse scanning of the entire blade is performed with a low spatial resolution for initial delamination localisation. Then, dense scanning with a high spatial resolution is performed only within the identified delaminated region for delamination visualization. This study especially focuses on the initial delamination localisation using adaptive coarse scanning. Laser ultrasonic responses from two pitch-catch paths, names inspection pairs, are obtained within a specified coarse scanning grid. Then, potential delamination locations within the given grid are estimated through time-of-flight analysis of delamination reflected waves. Once potential delamination locations are estimated, new inspection pairs are placed near the potential locations for precise localisation. These steps are repeated for every coarse scanning grids on the ta...

Delamination localization in wind turbine blades based on adaptive time-of-flight analysis of noncontact laser ultrasonic signals

This paper presents a variety of structural health monitoring (SHM) techniques, based on the use of piezoelectric active-sensors, used to determine the structural integrity of wind turbine blades. Lamb wave propagation, frequency response functions, and a time series based method are utilized to analyze the wind turbine blade. For these experiments, a 1m section of a 9m CX100 blade is used. Different types of simulated damage are introduced into this structure and a performance matrix is created to compare the validity and functionality of each technique. Overall, these three methods yielded sufficient damage detection to warrant further investigation into field deployment. Time series analysis shows the most effective and reliable to detect damage while lamb wave testing could locate, as well as detect the onset of damage. This paper summarizes considerations needed to design such SHM systems, experimental procedures and results, and additional issues that can be used as guidelines for future investigations.

Structural Damage Identification in Wind Turbine Blades Using Piezoelectric Active Sensing

This paper presents the experimental results of active-sensing structural health monitoring (SHM) techniques, which utilize piezoelectric transducers as sensors and actuators, for determining the structural integrity of wind turbine blades. Specifically, Lamb wave propagations and frequency response functions at high frequency ranges are used to estimate the condition of wind turbine blades. For experiments, a 1 m section of a CX-100 blade is used. The goal of this study is to assess and compare the performance of each method in identifying incipient damage with a consideration given to field deployability. Overall, these methods yielded a sufficient damage detection capability to warrant further investigation. This paper also summarizes the SHM results of a full-scale fatigue test of a 9 m CX-100 blade using piezoelectric active sensors. This paper outlines considerations needed to design such SHM systems, experimental procedures and results, and additional issues that can be used as guidelines for future investigations.

/pdf/damage-identification-of-wind-turbine-blades-using-13nm8sgpv4.pdf

Damage Identification of Wind Turbine Blades Using Piezoelectric Transducers

The paper presents a discussion of the design, development, and assembly of Structural Health Monitoring (SHM)
experiments launched in space on a sub-orbital flight. Onboard experiments were focused on investigating the utility of
piezoelectric wafer active sensors (PWAS) as active elements of spacecraft SHM systems and the electro-mechanical
impedance method as a promising SHM methodology for space systems. A Magneto-elastic active sensor (MEAS) was
used to record in-flight dynamics of the payload. The list of PWAS experiments included a bolted-joint experiment, an
adhesive endurance experiment, and an experiment to monitor PWAS condition during spaceflight. Electromechanical
impedances of piezoelectric sensors were recorded in-flight at varying input frequencies using onboard microcontroller
units. PWAS and MEAS data were recovered from the payload after landing. Details of the sub-orbital flight
experiments are considered and conclusions pertaining to flight results are presented. The paper discusses issues
encountered during design, development, and assembly of the payload and aspects central to successful demonstration of
the SHM during sub-orbital space flight.

Abraham Light-Marquez

Papers

Structural Damage Identification in Wind Turbine Blades Using Piezoelectric Active Sensing

Damage Identification of Wind Turbine Blades Using Piezoelectric Transducers

Design, development, and assembly of sub-orbital space flight structural health monitoring experiment