Title Promoter Affiliations Abstract "On-site detection of degradation in reinforced concrete structures in operational conditions using the acoustic emission technique" "Els Verstrynge" "Materials and Constructions" "Worldwide, deterioration of reinforced concrete structures (RC) calls for effective methods to detect damage and evaluate the efficiency of repair interventions. In the viewpoint of efficient inspection, the acoustic emission (AE) technique is an ideal choice as it allows nondestructive and continuous monitoring of the structure. However, the potential to detect deterioration of RC structures under operational conditions has not been fully exploited yet. On the one hand, due to the passive nature of the AE technique, elastic waves are only captured when the damage occurs. Moreover, natural degradation processes such as reinforcement corrosion and alkali-silica reaction are typically slow and emit low energy signals making it challenging to detect the elastic waves in operational conditions. On the other hand, due to economical restraints and time considerations, continuous monitoring is not always possible. The aim of this project is to develop a framework for AE detection of degradation processes in operational conditions, with focus on the on-site application of this technique for existing RC structures. The project focuses on developing valuable alternatives for continuous monitoring for existing RC structures in operational conditions. Both periodic measurements and activation protocols for ongoing natural degradation processes will be investigated. The methodology will be validated on three case studies. " "Active control of concrete curing by acoustic emission (ACCCAE)" "Dimitrios Angelis" "Mechanics of Materials and Constructions" "Acoustic monitoring has recently significantly contributed to the understanding of processes in fresh cementitious media. The ambition of this project is, for the first time, to use the real time acoustic emission (AE) behavior to control the curing of the material, aiming at better mechanical properties and at the same time use the recorded data to make projections towards the final quality of the hardened medium. Processes like hydration and shrinkage cracking, which are crucial for mechanical properties gain, also produce high amounts of detectable AE during the fresh state. Therefore, acoustic techniques due to their non-invasive and sensitive nature in combination with optical techniques for displacement measurements form an excellent platform to study the material but most importantly to steer the curing during the very delicate phase of hydration taking advantage of the real time information. This obtains even higher importance when considering modern admixtures like super absorbent polymers and the effort to control their behavior, an aspect that is also treated herein in order to improve the material performance. Optimizing the mechanical properties of a given mix ensures long standing materials, contributing to sustainability of the built environment which is the driving force behind the research. VUB and UGent have strong tradition of cooperation in the field, while contribution from Kyoto University guarantees feedback from a technologically advanced partner." "Reconstruction of Wave Forms for Parameter Correction and Pattern Recognition for Acoustic Emission Testing on Pressure Vessels" "Martine Wevers" "Structural Composites and Alloys, Integrity and Nondestructive Testing (SCALINT)" "The aim of this project is to improve the analysis of acoustic emission testing on cylindrical pressure vessels. The analysis of acoustic emission tests on pressure vessels is currently based on signal parameters. Those signal parameters are extracted from the wave form as it is measured by the sensor which is the closest to the source. This approach comes with the drawback that changes to the wave form occurring prior to arrival of the wave at the sensor, potentially can influence the analysis.  In this project, a new analysis technique is elaborated which makes use of all available information to determine the waveform at the source. The new technique should show improved resistance against influences by extraneous noise or irregularities on the propagation path in order to be industrially applicable. Since the result of the new analysis technique is a corrected waveform, corrected signal parameters can be extracted. This will make the analysis technique compatible with currently used evaluation criteria. After the new technique had been developed, this project will investigate how frequently encountered irregularities on the path between source and sensor can be recognized. Furthermore, the project involves a validation study of the new analysis technique on pressure vessels in industrial environment. Finally, the analysis technique provides an improved basis for pattern recognition, which can be a basis for new applications of acoustic emission." "Active control of concrete curing by acoustic emission (ACCCAE)" "Acoustic monitoring has recently significantly contributed to the understanding of processes in fresh cementitious media. The ambition of this project is, for the first time, to use the real time acoustic emission (AE) behavior to control the curing of the material, aiming at better mechanical properties and at the same time use the recorded data to make projections towards the final quality of the hardened medium. Processes like hydration and shrinkage cracking, which are crucial for mechanical properties gain, also produce high amounts of detectable AE during the fresh state. Therefore, acoustic techniques due to their non-invasive and sensitive nature in combination with optical techniques for displacement measurements form an excellent platform to study the material but most importantly to steer the curing during the very delicate phase of hydration taking advantage of the real time information. This obtains even higher importance when considering modern admixtures like super absorbent polymers and the effort to control their behavior, an aspect that is also treated herein in order to improve the material performance. Optimizing the mechanical properties of a given mix ensures long standing materials, contributing to sustainability of the built environment which is the driving force behind the research. VUB and UGent have strong tradition of cooperation in the field, while contribution from Kyoto University guarantees feedback from a technologically advanced partner." "AE-FracMasS: advanced Acoustic Emission analysis for Fracture mode identification in Masonry Structures" "Martine Wevers" "Structural Composites and Alloys, Integrity and Nondestructive Testing (SCALINT), Materials and Constructions" "Detecting the initiation and growth of damage and the identification of the dominant damage mechanism within a structural component is of paramount engineering importance as it allows to effectively (re-) design or reinforce the structure to withstand the observed failure mode. The behavior of masonry under compression is particularly complex as its structural response is related to the relative mechanical properties of the bricks/blocks, the mortar and their interface. Up to now, experimental characterization of the fracture modes has been based on deformation monitoring of the masonry’s outer surface. In this project, Acoustic Emission (AE) technique will be applied and combined with advanced full-field deformation detection techniques for fracture mode characterization in masonry. AE is a non-destructive technique that allows the detection, location and characterization of a crack propagating within a material by detecting and analyzing the highfrequency elastic waves being produced by the fracture process. The combination of numerical simulation and experimental work at small and large scale as studied in this project provides a damage mode characterization scheme needed for the detailed understanding of the fracture modes in masonry, based on the properties of its constituents. This fundamental knowledge can be applied for the optimization of masonry-components design and for in-situ structural health monitoring of masonry structures." "Fracture Characterization of Masonry in Compression with Acoustic Emission Analysis and Numerical Modeling" "Els Verstrynge" "Building Materials and Building Technology Section, Materials and Constructions, Structural Composites and Alloys, Integrity and Nondestructive Testing (SCALINT)" "Masonry under compression exhibits complex structural interactions among brick units and mortar joints which remains a true challenge to understand.Its structural response is related to the relative mechanical properties of the bricks/blocks, the mortar and their interface. In this research, experimental and numerical analysis will be applied to deduce information on the fracture progress in masonry under compression. An extensive experimental research program includes series of compression tests on masonry samples categorized into three different scales, such as (a) small-scale couplets, (b) full-scale couplets and (c) masonry walls. Different non-destructive testing (NDT) methods such as micro-CT, digital image correlation, acoustic emission and numerical methods are applied to obtain adequate information on the triaxial behavior and fracture modes in masonry under compression. Micro-CT is applied on small-scale masonry couplets to evidence the crack initiation at a micro-scale level. Digital image correlation is applied on full-scale masonry couplets to validate if there is a strong size and shape effect on the crack initiation and propagation. An AE-based test procedure for the damage quantification in masonry under cyclic compressive loads is developed. AE critical damage limits from concrete are applied and validated in masonry. It is the first time that these AE indices are investigated in masonry. Finite element micro models are developed to predict the fracture modes in masonryunder compression. The results of the numerical model are compared with experimental results and the influence of material properties on the fracture modes is also performed. Finally, masonry fracture characterization scheme from coupled NDT and numerical methods provides the detailed understanding of the fracture modes in masonry under compression. Lastly, based on numerical results, new AE-based critical damage limits is proposed." "Treatment of wastewater from the Cuban petrochemical industry based on activated carbon adsoption technology: improved acoustic emission method for textural analysis and adsorption performance of used carbons." "Materials Chemistry, University of Santiago de Cuba" "PW is part of a large volume of waste produced by the oil industry. It contains dissolved organic components and heavy metals, and both difficult the break down into the environment. In many cases PW is poured into the sea and water resources without any previous treatment. Therefore, a proper management and reuse strategy of the PW are crucial for a sustainable eco-friendly process. In this research, a treatment plant will be proposed for this residual base in sedimentation as first step. The use of AC for the treatment of the liquid phase obtained by sedimentation of the PW constitutes a proposal with significant environmental benefit, achieving a reduction of the pollutant load of the wastewater due to the adsorption of compounds present in it. Technological limitations of Cuban industries make the porous characterization of these materials almost impossible in the country. Therefore, the study and neither optimization of industrial processes dealing with adsorption are not possible. This research will investigate AC as a potential remediation tool for this wastewater based on a technique of characterization using acoustic emission analysis to optimize the use of this adsorbent material." "Acoustic monitoring as an in-process quality assurance method for pressure welding processes" "Koenraad Faes" "Belgian Welding Institute npo" "SOUNDWELD will investigate a new promising real-time non-destructive examination technique for welding processes, based on acoustic emission during the weld cycle. The acoustic emission technique is based on the detection and conversion of high-frequency elastic waves into electrical signals. Acoustic emission monitoring (AEM) is currently being used for the surveillance of industrial processes or structures. In this project, the application of this technology will be expanded towards welding processes: refill friction stir spot welding, arc welding, resistance spot welding, and magnetic pulse welding. " "Innovative NDT Techniques for Aircraft Maintenance: Acoustic Fuel Tank Monitoring and Thermal Fuselage Inspections" "Martine Wevers" "Structural Composites and Alloys, Integrity and Nondestructive Testing (SCALINT)" "In this work, non-invasive measurement methods are used to solve problems in daily aircraft maintenance. The measurement methods used are based on the Acoustic Emission Technique, Infrared Thermography and Laser Doppler Vibrometry. The procedures and analysis methods are not entirely new, but they can, however, be considered new in the context of the described aircraft maintenance work. Therefore, it is possible to speak of innovative non-invasive measurement methods in aircraft maintenance. Two explicit questions that arise directly from aircraft maintenance in daily operations are addressed.A well-known problem in civil aviation is water accumulation in fuel tanks, which aircraft operators face daily. This water accumulation and the resulting ice that forms during flight can lead to costly and sometimes very dangerous situations. Therefore, efforts are underway to develop a reliable detection system to determine the remaining amount of accumulated ice after flight and during recovery operations. By using such a technology, it would be possible to increase the safety and efficiency of aircraft operations in this highly competitive market. This PhD manuscript discusses the use of the Acoustic Emission Technique to reliably and non-invasively monitor the melting of ice in fuel tanks. This technique is based in principle on the fact that a phase transition is often accompanied by stress relaxation, which can be used to monitor the process. Therefore, the melting of ice can essentially be monitored with AE without directly accessing the ice. The findings presented in this work can potentially lead to new technologies for ice detection, especially in remote areas that are not easily accessible with other techniques.The second application of novel inspection methods based on non-invasive measurement methods concerns the inspection of fasteners in aluminum joints. In the aerospace industry, such inspections are time-consuming and costly, but mandatory. Until today, manual methods use mainly the naked eye and do not allow the tracking of damaging behavior over time or objective comparison between different inspections. A digital inspection procedure addresses both shortcomings while leading to a significant reduction in inspection time. The aim is to compare three inspection methods based on measurements on a serviceable aircraft component. An essential part of this is the development of a new digital and automated inspection method based on in-plane heatwave thermography, which is based on the analysis of thermal disturbances caused by irregularities in the plate-like structure. Simultaneously, measurements are made using ultrasonic lock-in thermography and a scanning laser Doppler vibrometer. Benchmarking of all three methods is performed on an operational aircraft fuselage panel. The data presented confirm the feasibility of detecting damage and qualifying countersunk rivets and screws in aluminum fuselage panels using the methods discussed." "Acoustic Emission-based Assessment of Reinforcement Corrosion: Damage Monitoring and Bond Modelling of Corrosion Effects in Reinforced Concrete" "Els Verstrynge" "Structural Composites and Alloys, Integrity and Nondestructive Testing (SCALINT), Materials and Constructions" "Reinforcement corrosion is believed to be the major deterioration phenomenon in reinforced concrete (RC) structures, causing large direct and indirect financial costs. While tools for modelling and design of new RC structures are mature, methods for modelling and assessment of the remaining structural capacity of existing RC structures are much less developed. A prerequisite for the assessment of these structures is the development of reliable techniques for experimental and in-situ damage level rating, as well as the development of accurate models that can describe the complex structural effects of reinforcement corrosion.This thesis covers both monitoring and modelling of corrosion-induced damage in RC. Three objectives are set. The first objective is the development and upscaling of passive and active acoustic emission (AE) monitoring protocols for the detection, localisation, quantification, and characterisation of corrosion-induced damage. The second objective is to obtain reliable data sets to investigate the effect of corrosion and to develop reliable models. The third and final objective is the development of a finite element (FE) model to determine bond-slip relations that describe the reinforcement-concrete interface behaviour.A first part of the thesis focusses on the upscaling of the AE technique. Therefore, an extensive experimental program has been set up to develop AE protocols for corrosion-induced damage in RC. The protocols were applied on three sample sizes: small mortar cylinders (scale 1), RC prisms (scale 2), and RC beams (scale 3). It is found that the AE technique is able to detect corrosion in RC. However, dedicated filtering is necessary in order to reliably localise and characterise AE events. Therefore, a post-processing protocol is developed which significantly improves the localisation results. It is also found that concrete cracking can be identified from cumulative AE energy curves and the peak and centre frequency of the AE signals. Moreover, the AE technique is able to determine the onset of concrete cracking earlier than a visual inspection. Unfortunately, the AE technique does not allow to accurately quantify the amount of mass loss of the rebar due to corrosion. A clustering algorithm is developed to characterise AE sources. The results are compared with micro-CT images (scale 1) and dummy samples (scale 2 and scale 3) to assign possible AE damage sources to the different clusters such as corrosion and concrete cracking.In a second part, mechanical tests are performed which consist of pull-out tests on RC prisms, and three-point bending tests on RC beams. Pull-out tests are performed to investigate the difference in rebar type and corrosion level, as well as the effect of confinement on the pull-out behaviour. A major contribution is the establishment of corrosion level-bond relations and crack width-bond relations, almost non-existent in the literature for smooth rebars. It is found that AE curves enable distinguishing between the type of rebar and the corrosion level. Although the localisation result is significantly improved by application of the developed post-processing protocol, accurate localisation of the crack growth during the pull-out test is shown to be more difficult to localise correctly when the sample is heavily damaged. Three-point bending tests are performed on concrete beams reinforced with a ribbed rebar. For high corrosion levels, the failure load decreases and the failure mode shifts from bending to debonding. In this case, no clear correlation is observed between the difference in corrosion level and cumulative AE events and cumulative AE energy. The application of the clustering algorithm, however, allows to distinguish between the corrosion levels.In a third part, an FE bond model is developed which is calibrated and validated on the previously described pull-out tests. The aim of the model is to obtain bond-slip relations that can be implemented in FE models to describe the structural capacity of corroded RC beams. It is found that incorporating the corrosion accomodation region and the flow of corrosion products into corrosion-induced cracks is important to determine the pressure build-up of corrosion products. A two-phased approach is developed, containing a crack model to step-wise calculate the crack volume, and a bond model to simulate the pull-out behaviour. Every modelling step is considered carefully without overcomplicating the modelling approach. The results of the model are in good agreement with the experimental data for all corrosion levels under investigation."