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![Acoustic resonance spectroscopy Additionally the exciting force of the hammer is recorded and provides extra information of the internal structure. A similar technique is for example used at the Transrapid test track [4], where the train is inspected every evening using a standardized tool to tap on the surface. The measurements are then compared to previous results measured at the same points. Changes in the signals point to internal damages as delaminations. An advantage of this technique is the contact free and therefore fast measurement. The technique also works outdoor and is not affected by a wet or dirty surface.](profile/Anne-Juengert/publication/228576960/figure/fig5/AS:668618299809796@1536422433307/Acoustic-resonance-spectroscopy-Additionally-the-exciting-force-of-the-hammer-is-recorded.png)
Acoustic resonance spectroscopy Additionally the exciting force of the hammer is recorded and provides extra information of the internal structure. A similar technique is for example used at the Transrapid test track [4], where the train is inspected every evening using a standardized tool to tap on the surface. The measurements are then compared to previous results measured at the same points. Changes in the signals point to internal damages as delaminations. An advantage of this technique is the contact free and therefore fast measurement. The technique also works outdoor and is not affected by a wet or dirty surface.
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Facing the climate change the use of renewable energies gains in importance. Especially the wind energy branch grows very fast. Bigger and more powerful wind mills will be built in the next decades and the safety of the mills will play a major role. Wind turbines are treated as buildings and therefore have to be inspected at regular intervals. Espe...
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A portable thermosonic inspection system has been developed incorporating a miniature microbolometer array camera. The vibrations excited during a test are monitored using a high frequency microphone and assessed automatically to validate the test. An investigation of the correlation between thermosonic heating and vibration excitation energy in co...
Citations
... The use of computer vision (CV) technologies, particularly deep learning (DL), can considerably increase the accuracy of damage detection on images of CH structures and detect damages that are not visible by traditional visual inspections, allowing them to mark them as visible defects. In this regard, artificial-intelligence (AI)-assisted visual [2] and Ciampa et al. [3] ) and high-risk locations (modified from Pham and La [4] ), d-f) drone-based inspections with an interface to watch the footage in real-time (Figures adapted from Otero and Gagliardo [ 5 ] and Li and Liu [6] ). ...
Applying computer science techniques such as artificial intelligence (AI), deep learning (DL), and computer vision (CV) on digital image data can help monitor and preserve cultural heritage (CH) sites. Defects such as weathering, removal of mortar, joint damage, discoloration, erosion, surface cracks, vegetation , seepage, and vandalism and their propagation with time adversely affect the structural health of CH sites. Several studies have reported damage detection in concrete and bridge structures using AI techniques. However, few studies have quantified defects in CH structures using the AI paradigm, and limited case studies exist for their applications. Hence, the application of AI-assisted visual inspections for CH sites needs to be explored. AI-assisted digital inspections assist inspection professionals and increase confidence levels in the damage assessment of CH buildings. This review summarizes the damage assessment techniques using image processing techniques, focusing mainly on DL techniques applied for CH conservation. Several case study applications of CH buildings are presented where AI can assist in traditional visual inspections.
... Experimental results indicate that both techniques effectively locate and monitor high-damage regions and flaws within the blade structure. Jungert [67] investigated two distinct acoustic techniques for the detection of damage in WTBs. The impulse-echo method is employed to detect regions of the blade that are either missing or in contact with each other, from the outer surface of the blade. ...
The increasing demand for wind power requires more frequent inspections to identify defects in the Wind Turbine Blades (WTBs). These defects, if not detected, can compromise the structural integrity and safety of wind turbines. As WTBs are crucial and costly components, they may suffer material degradation and fatigue failure, which affects their performance and safety. Thus, the urgency for efficient and regular monitoring to maintain their structural integrity is greater than ever. This review paper explores innovative methods in fatigue testing, damage detection, and structural reliability in WTBs, focusing on the use of recent inspection methods, including those that take advantage of drones. Drones are used to identify defects such as cracks, erosion, and coating irregularities using high-resolution imagery with the onboard cameras. Various investigators have developed novel data-driven approaches, incorporating machine learning and deep learning, to accurately identify these defects. Although deep learning-based image processing has been successful in other public infrastructure contexts, its application to wind turbine inspection from aerial images presents unique challenges. This paper also highlights the critical role of failure inspection in enhancing the operational integrity of WTBs, showcasing state-of-the-art deep learning techniques that are pivotal for identifying and analyzing failures in WTBs from images captured by drones. The paper provides insights into the latest developments in using drone imagery for blade defect detection, contrasting this method with traditional non-destructive techniques. This approach could significantly transform the wind energy industry by offering a more efficient, automated, and precise way of ensuring the structural health of wind turbines. Unlike previous studies that predominantly focus on isolated aspects such as inspection or fatigue, this review paper not only integrates the three major aspects of WTBs integrity in terms of aerial inspection, image processing using machine learning, and structural integrity of the blade but also undertakes an extensive examination of the prevailing methodologies in the field, pinpointing crucial gaps and challenges. It provides a detailed review of existing research, covering various areas including automated inspection, image processing techniques, fatigue analysis, and the reliability of wind turbines. This approach enriches the discourse by offering a multifaceted perspective on WTB maintenance, thereby advancing the understanding of operational integrity within the field of wind energy.
... They found that the blade surface shedding sound pressure level was the highest. To determine whether the material had been damaged, Jüngert [131] used microphones to record the sound of repeated excitation of the blade by a hammer and compared it before and after. Subsequently, to avoid errors due to technical changes in the tapping operation by technicians, a new method was proposed using instrumented percussion equipment to generate a fixed, controllable signal combined with a local acoustic resonance spectrum [132]. ...
Monitoring and maintaining the health of wind turbine blades has long been one of the challenges facing the global wind energy industry. Detecting damage to a wind turbine blade is important for planning blade repair, avoiding aggravated blade damage, and extending the sustainability of blade operation. This paper firstly introduces the existing wind turbine blade detection methods and reviews the research progress and trends of monitoring of wind turbine composite blades based on acoustic signals. Compared with other blade damage detection technologies, acoustic emission (AE) signal detection technology has the advantage of time lead. It presents the potential to detect leaf damage by detecting the presence of cracks and growth failures and can also be used to determine the location of leaf damage sources. The detection technology based on the blade aerodynamic noise signal has the potential of blade damage detection, as well as the advantages of convenient sensor installation and real-time and remote signal acquisition. Therefore, this paper focuses on the review and analysis of wind power blade structural integrity detection and damage source location technology based on acoustic signals, as well as the automatic detection and classification method of wind power blade failure mechanisms combined with machine learning algorithm. In addition to providing a reference for understanding wind power health detection methods based on AE signals and aerodynamic noise signals, this paper also points out the development trend and prospects of blade damage detection technology. It has important reference value for the practical application of non-destructive, remote, and real-time monitoring of wind power blades.
... Jüngert et al. [7] used two different acoustic techniques for wind turbine blade inspection; local resonance spectroscopy and audible sound. Both methods were found to give information about the internal structure of the area being inspected. ...
Wind turbines vibration signals carry useful information about their conditions. However, such signals are usually very complex and comprise high number of vibratory signatures. Moreover, the cost of setting up vibration measurement systems using conventional accelerometers is very high especially in the case of multi-location measuring points are required. This paper contributes towards developing an inexpensive and accurate condition monitoring method based on remotely measured air-born acoustic signals. Fault detection capabilities are assessed by determining its coherence with the well-understood vibration induced signals. A new generation of recently improved condenser microphone used as input for the proposed coherence analysis algorithm. Special arrangement to eliminate reverberation problems associated with air-borne acoustic signals was designed. Consequently, coherence analysis is carried out to compare the information supplied by the accelerometer and the microphone of a three bladed horizontal wind turbine under different operating conditions. The air-borne acoustic signal exhibits good coherence with the vibration ones at rotating speed, gear meshing frequencies and fan passing frequency bands. More important, air-borne acoustic data was found to contain more pronounced information within wider spectrum compared with the vibration measurements. The presented results open doors for deeper investigations on the diagnostic capabilities of such technique and probably lead to fully adoption by the wind turbine industry.
... High-resolution (up to microscale), easy to use and costeffective monitoring Sensitivity of these methods to the background noise limits their applicability in offshore environments; limited distance between measurement point and damage location. (Jüngert, 2008, Tziavos et al., 2020, DeCew et al., 2013 Strain monitoring Reliable and easy to implement for nonoperating (offshore) and onshore platforms large amount of uncertainty induced by the involved external parameters such as wind and wave loading and scouring effect. Also, in offshore environment it is difficult to measure the wave and wind loads. ...
Committee Mandate
Concern for advances in structural model testing and full-scale experimentation and in-service monitoring and their role in the design, construction, inspection and maintenance of ship and offshore structures. This shall include new developments in: best practice and uncertainty analysis; experimental techniques; full field imaging and sensor systems; big data applications for ship and offshore structures; and correlation between model, full-scale and numerical datasets.
Introduction
Design methods and rule requirements have to be benchmarked with experimental or service history data. The Goal Based Standards (GBS) approach by IMO, see e.g., IMO Res. 296(87), 454(100) or MSC.1/Circ.1394, require benchmarking of standards by measuring the performance of methodologies, assessments, criteria and requirements by using indicators that can be compared with an accepted standard or with experimental and/or service history data, performance levels or outcomes known to be reliable. This approach calls for a systemic use of experimental results and monitoring of data from ships during construction, in-service and possibly from the end of the life cycle. Thus, the elaboration of experimental outcomes and the handover of information into engineering and management practice need to be further addressed and standardized to fully exploit their potential.
Further, the continues growth of complexity in ship and offshore structures potentially designed outside the range of empirical references calls for reliable means of validation. While computer simulations are continuously improving at the same time, their improvement to a large extent depends on a physical understanding of the underlying phenomena to be captured. Therefore, experimental investigations are essential in driving further developments and innovations through their accurate feedback when performed correctly and meaningful. The latter is however challenging, especially with increased complexity of the phenomena to be investigated. Therefore, this report summarizes the expertise of the contributing authors with respect to their corresponding research fields. The report seeks to give a general overview of the specific experiments dealt with therein, presents the latest publications, possible obstacles to be addressed and closes with future recommendations for further developments and integration of the experiments into engineering practice and scientific developments.
The report at first covers a section on scaling laws relevant to any experiment followed by specific testing concerning: digital image correlation (DIC), hydrodynamics of flexible structures, wave-in-deck, hybrid models, friction, vibrations, fatigue at low temperatures, corrosion, large scale impact, large scale wind turbine blades, full-scale ice loads, health monitoring and digital twin models. Further, a benchmark study on free vibrations of a cantilever beam is carried out to demonstrate the vast possibilities to carry out such seemingly simple experiment followed by a discussion of the results achieved. The report is concluded with a summary and an outline of further research and development recommendations.
... To date, the periodic structural health inspection of wind turbine blades is made by professional climbers while the wind turbine is shut down. The inspection is mainly limited to visual inspection and simple manual tapping tests with a hammer [54,55]. It allows detecting surface damages in defined critical areas. ...
... The different failures in the structure can be detected depending on different characteristics of the emitted signal, i.e., counts, rise time, peak amplitude, arrival time, duration, and signal energy content [57]. This technique is commonly used in the industry for the control of composites [55,58,59], and allows steady-state wind turbine blade control [13]. This method is already protected with several patents [60][61][62][63]. ...
The growing demands for electrical energy, especially renewable, is boosting the development of wind turbines equipped with longer composite blades. To reduce the maintenance cost of such huge composite parts, the structural health monitoring (SHM) is an approach to anticipate and/or follow the structural behaviour along time. Apart from the development of traditional non-destructive testing methods, in order to reduce the use of intrusive instrumentation there is a growing interest for the development of “self-sensing materials”. An interesting route to achieve this, can be to introduce carbon nanofillers such as nanotubes (CNT) in the composite structures, which enables to create systems that are sensitive to both strain and damage. This review aims at updating the state of the art of this topic so far. A first overview of the existing SHM techniques for thermoset based wind turbine blades composites is presented. Then, the use of self-sensing materials for strain and damage sensing is presented. Different strategies are overviewed and discussed, from the design of conductive composites such as carbon fibres reinforced polymers, to the elaboration of conductive
nano-reinforced polymer composites. The origins of sensing mechanisms along with the percolation theory applied to nanofillers dispersed in polymer matrices are also detailed.
... In the design process of wind turbine rotor blades, fatigue is one of the most important issues [4]. Therefore, excessive experimental characterisation of wind turbine composite materials [5,6] and rotor blade damage behaviour [5,[7][8][9][10][11] has been conducted over the last decades in addition to improving design and fatigue life prediction methods [1,4,12]. An improvement of the fatigue characteristics of the glass fibre-reinforced plastics (GFRP) not only increases the reliability of the rotor blades but also enables their size to be enlarged through a mass-reduced design. ...
... With angle-ply configurations used in rotor blades, for example for the skin and the shear webs of the main spar [4,10], results are relevant for technical application. Typical damages such as parallel cracking of the skin [10], stress-whitening due to microcracks and interlaminar delamination [9] result from mechanisms that can be effectively delayed and slowed down by means of boehmite particles. Overall, matrix modification with lowcost taurine-modified boehmite particles is a promising approach for enhancing the fatigue resistance of wind turbine rotor blade materials. ...
Advanced nanoparticle-reinforced glass fibre composites represent a promising approach to improving the service life of fatigue-loaded structures such as wind turbine rotor blades. However, processing particle-reinforced resins using advanced infusion techniques is problematic due to, for example, higher viscosity as well as filtering effects. In this work, the effects of boehmite nanoparticles on viscosity, static properties and fatigue life are investigated experimentally. Whereas rheological analysis reveals a significant increase of viscosity in the case of pristine boehmite particles, an additional taurine surface modification of the particles can effectively reduce viscosity increase. As regards mechanical properties, significant improvements of both static as well as fatigue properties are found. The addition of 15 wt.% of boehmite particles increases fatigue life by a maximum of 270% compared to the unmodified fibre-reinforced epoxy. Transmitted light-based investigation of the damage mechanisms shows delayed initiation and smaller growth rates for laminates containing boehmite particles. At the same time, the observed mechanisms and their accumulation along the relative cycle number do not change significantly. In addition, by characterising autonomous heating, the so-called Risitano fatigue limit is determined. The results reveal that with increasing particle content there is an increase in the fatigue limit.
... The main concern with the overall operation of the wind tower is that it is too expensive to inspect and to maintain. Moreover, it is dangerous or hazardous for people to carry out inspection on the tower [1]. ...
Mmaintenance of wind turbine farms is a huge task, with associated significant risks and potential hazard to the safety and wellbeing of people who are responsible for carrying the tower inspection tasks. Periodic inspections are required for wind turbine tower to ensure that the wind turbines are in full working order, with no signs of potential failure. Therefore, the development of an automated wind tower inspection system has been very crucial for the overall performance of the renewable wind power generation industry. In order to determine the life span of the tower, an investigation of robot design is discussed in this paper. It presents how a mechanical spring-loaded climbing robot can be designed and constructed to climb and rotate 360° around the tower. An adjustable circular shape robot is designed that allows the device to fit in different diameters of the wind generator tower. The rotational module is designed to allow the wheels to rotate and be able to go in a circular motion. The design further incorporates a suspension that allows the robot to go through any obstacle. This paper also presents afiniteelement spring stress analysis and Simulink control system model to find the optimal parameters that are required for the wind tower climbing robot.
... Minor external damages tends to lead to a loss in AEP. Damage inspection and detection can be accomplished by acoustic emission sensors [184], visual cameras [185], tomography [186], and vibration-based estimation using accelerometers [187]. ...
Operations and maintenance of offshore wind turbines (OWTs) play an important role in the development of offshore wind farms. Compared with operations, maintenance is a critical element in the levelized cost of energy, given the practical constraints imposed by offshore operations and the relatively high costs. The effects of maintenance on the life cycle of an offshore wind farm are highly complex and uncertain. The selection of maintenance strategies influences the overall efficiency, profit margin, safety, and sustainability of offshore wind farms. For an offshore wind project, after a maintenance strategy is selected, schedule planning will be considered, which is an optimization problem. Onsite maintenance will involve complex marine operations whose efficiency and safety depend on practical factors. Moreover, negative environmental impacts due to offshore maintenance deserve attention. To address these issues, this paper reviews the state-of-the-art research on OWT maintenance, covering strategy selection, schedule optimization, onsite operations, repair, assessment criteria, recycling, and environmental concerns. Many methods are summarized and compared. Limitations in the research and shortcomings in industrial development of OWT operations and maintenance are described. Finally, promising areas are identified with regard to future studies of maintenance strategies.
... Turbine blades are subjected to high stress during operation and failure can cause significant economic losses [2]. They consist of a fiber-reinforced polymer composite (PRF) and balsa wood [3]. ...
The wind energy sources promote the generation of electricity, being environmentally safe, clean and its use has been growing in Brazil, especially in the northeastern states with the implementation of new wind farms. Wind turbines, however, are subject to weather, risk of animal shocks, materials carried by the wind, and the vibrations of the system itself. The blade is the most important component of a wind turbine and is the one with the greatest risk of failure. They are usually made of a composite fiber-reinforced polymer matrix and balsa wood as structural reinforcement. As the material composing this blade has heterogeneous and anisotropic characteristics, conventional inspection techniques are not considered effective. The non-destructive Tap Test technique can be a safe option in composite materials because it does not suffer from these limitations. The objective of this work is to inspect composite plates of polymeric resin used in wind turbines with discontinuities using the non-destructive Tap Test technique, where regions with and without defect were analyzed. The collected signals from an accelerometer and a microphone were processed, to allow the extraction of features and the recognition of discontinuities with the aid of a neural network.
