Tesi: "Ultrasonic non-Destructive evaluation (UNDE)"

1

Kaynak, Mehmet. "Non-destructive Testing Of Columns Under Axial Compression Using Tranverse Vibration Technique, And Ultrasonic Approaches". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/1260465/index.pdf.

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The level of axial compressive load on an existing column is one of the most important parameters to be known. This thesis aims to investigate current state of the art of NDT techniques, their application, and investigate alternative ways of using current technology to estimate the axial compressive load on columns. For this purpose, transverse vibration technique, ultrasonic pulse velocity method, and waveform and frequency content evaluation of ultrasound are investigated and implemented. Analytical and experimental studies on column transverse vibration frequency and axial load relationship are conducted and presented. The measured experimental lateral vibration frequency of the first bending mode decreased under increased axial compressive load as expected from analytical studies. Relationships between axial load and vibration frequency are derived and defined for different boundary conditions. Relationship charts are prepared for complicated solution sets. Numerical calculations, laboratory and field tests revealed that natural frequencies of slender columns are more sensitive to axial load changes. The available ultrasonic methods are investigated and described. Stress wave propagation in anisotropic solids is studied. Previous works have shown that the propogation velocity of stress waves depends on the density, Poisson&rsquo
s ratio, modulus of elasticity of the medium, and the state of stress. The orientation of the loading direction to the wave propogation direction, the couplant (ultrasonic transmission gel) uniformity, variability in the pressure applied to hold the transducers, alignment of the transmitting and recieving transducers, accuracy and modelling of Poisson&rsquo
s ratio make the ultrasonic testing more complicated.

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2

Aoujdad, Khalid. "Caractérisatiοns ultrasοnοres du vieillissement de pales d’hydroliennes et d’éoliennes en milieu marin. : Cοnfrοntatiοn aux essais mécaniques". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMLH24.

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Cette thèse porte sur la caractérisation non destructive par ondes ultrasonores des échantillons représentatifs des pales d’éoliennes offshore, avec confrontation aux tests mécaniques. Les échantillons sont en matériaux composites à base de la résine polyester renforcée par des fibres de verre UD GFRP (Unidirectional Glass Fibers Reinforced Polyester). Ils sont soumis à un vieillissement accéléré dans l’eau de mer chauffée à 40 °C et à 60 °C, afin de simuler le milieu marin et réduire la durée d’étude. L’objectif est de trouver des paramètres acoustiques sensibles au vieillissement permettant d’évaluer l’effet du vieillissement ou de le quantifier. L’analyse par ondes guidées de Lamb a montré une diminution des vitesses de phase des modes et de la vitesse de Rayleigh, ainsi que l’augmentation de l’atténuation dans le matériau, ce qui indique que les propriétés mécaniques des matériaux se dégradent à cause du vieillissement. L’imagerie C-scan montre une dégradation de la résine, entraînant la réorganisation des fibres et la modification de leur alignement. Une modélisation numérique par la méthode des éléments finis de la propagation des ondes guidées dans ces matériaux a montré que les propriétés structurelles et géométriques des matériaux se dégradent à cause du vieillissement. Les paramètres les plus attaquées sont les constantes d’élasticité, ainsi que la masse volumique pour des vieillissement plus forts et plus longs. Enfin, le nombre des plis des renforts dans un échantillons joue un rôle important dans sa résistance au vieillissement
This thesis discusses the ultrasonic non-destructive characterization of representative samples of offshore wind turbine blades. The samples are made of composite materials based on Unidirectional Glass Fibers Reinforced Polyester (UD GFRP). Samples are subjected to accelerated aging in heated seawater at 40°C and 60°C, in order to simulate the marine environment and reduce study times. The aim is to find acoustic parameters sensitive to aging, enabling the effect of aging to be assessed or quantified. Lamb's guided wave analysis showed a decrease in mode phase velocities and Rayleigh velocity, as well as an increase in attenuation in the material, indicating that the mechanical properties of the material are degrading due to aging. C-scan imaging shows degradation of the resin, leading to reorganization of the fibers and changes in their alignment. Finite element numerical modelling of guided wave propagation in these materials has shown that the structural and geometric properties of the materials degrade with age. The parameters most affected are the elasticity constants, as well as the density for stronger and longer aging. Finally, the number of reinforcement plies in a sample plays an important role in its resistance to aging

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3

Lardner, Timothy. "New algorithms for ultrasonic non-destructive evaluation". Thesis, University of Strathclyde, 2016. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=26912.

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The push for more efficient operation of power generation stations has led to the development of advanced alloys designed to cope with the stresses of running at elevated temperatures. The micro-structure of these new alloys makes the inspection process difficult due to large grains that scatter ultrasonic energy. Aerospace components such as aircraft engine turbine blades are made from similar materials and pose the same difficulties for inspection. In addition, the complex geometries of many of these parts hinder the use of existing advanced imaging methodologies. The current inspection process involves using both individual transducers and phased arrays to collect pulse-echo data from structures. This process is not sufficient for such difficult materials and a new process must be devised, tested and deployed. This thesis presents an investigation of new practical techniques to process ultrasonic array data collected via a Full Matrix Capture. Two novel signal processing techniques are presented, evaluated and compared to the Total Focusing Method, which is currently considered as the gold standard in ultrasonic array processing. A study into efficient imaging has also been completed, which involved development of an algorithm to focus upon any point through an arbitrary refracting interface. This algorithm was implemented on a commercially available graphics card and is able to account for a curved interface in real time with no prior knowledge of the surface profile. Spatially Averaged Sub-Aperture Correlation Imaging splits the full matrix of data into a set of sub-apertures which are imaged independently from each other. These images are then combined into two sets and are input to a two-dimensional cross-correlation algorithm that outputs a weighting matrix that can be applied to the sum of all images. Signals that are from legitimate reectors are highly correlated while less-correlated indications are the result of noise from scattering and multi-path propagation. SASACI has been shown to perform well experimentally through inspection of defects within multiple highly scattering welds at a frequency of 5 MHz. Correlation for Adaptively Focused Imaging aims to correct for anisotropy within difficult materials. The longitudinal velocity within a difficult material can vary with position and using an average velocity does not guarantee a well-focused image. For each pixel in an image,CAFI calculates which samples will be used to calculate the amplitude of the pixel before cross-correlating the signals from adjacent array elements and shifting the delay to the point of maximum focus. This methodology is effective when a small area with a known reflector is being imaged, and for this reason the algorithm is suited to characterisation of reflectors. This technique was experimentally validated on a block of Inconel 625 with a number of side-drilled holes.

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4

Crutzen, Hugues P. S. "Non destructive evaluation of thermal barrier coatings". Thesis, Cranfield University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323825.

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5

Crosbie, Ross Andrew. "Quantitative non-destructive evaluation using laser generated ultrasonic pulses". Thesis, University of Hull, 1987. http://hydra.hull.ac.uk/resources/hull:5393.

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The work presented here utilises features of laser generated ultrasound for the detection of defects in solids. Ultrasound is generated noncontactively by this method and likewise many of the detection devices used do not require direct coupling to the test pieces, thus acoustic pulses with high frequency components are able to be produced and monitored on a range of samples. Steel samples coated with between 3 and 7mm of plasma-transferred arc depositions are examined for bond quality via measurements of attenuation caused by porosity in the coatings, found to be related to weld current. Surface breaking cracks, (of depth < 3mm), in such claddings are quantitatively detected by a method which utilises Rayleigh pulses. A two sided automated scanning system is described which examines samples for subsurface defects. Results from the examinations of a dural test piece, plasma sprayed steel bars and carbon fibre composite samples are presented. Resolution of defects is shown to be within 0.5mm for a 1mm thick section of the composite material. A second scanning technique, requiring access to only one sample face, is presented which employs an interferometer for detection and is thus a truly remote system. Laminar flaws are modelled using flat-bottomed holes, the dimensions of which are measured using the resonance of the bodies. A theoretical investigation using various boundary conditions suggests possible applications for quantitative NDE of structures with well defined natural vibration frequencies. The propagation of acoustic transients in plates is also examined. Possible future work concerning laser/ultrasonic NDE is discussed.

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6

Jaafar, Rosly. "Ultrasonic non-destructive evaluation of natural rubber latex suspensions". Thesis, Keele University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318988.

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This thesis describes the development of wide bandwidth ultrasonic pulse transmission and pulse echo comparison spectrometer methods to measure the ultrasonic phase velocity and absorption in natural rubber latex. Details of the quantitative design and construction of simple prototype test rigs include the mechanism of: variable path length pulse transmission, variable path length reflected pulse echo, and dual transducers reflected pulse echo. Special signal processing of experimental data, including transducer impulse response correction routines to calculate the acoustical parameters, are outlined. Measurements made using the constructed prototype test rigs are compared with each other and with data available in the pulished literature. A selection of methods to suit varying requirements for acoustical measurements in natural rubber latex samples is made. Calibration curves relating the measured ultrasonic absorption and phase velocity with the dry rubber content (d.r.c.) at temperatures of 20 to 30°C were constructed. Experiments to test the usefulness of these calibration curves were undertaken to determine if there was any deviation from the Standard Laboratory Method. A comparison between the experimental results obtained using the dual transducer reflected pulse method and the simulation of the Allegra and Hawley model with multiple scattering is presented. Good agreement was obtained between the experimental and the theoritical approaches up to 40% d.r.c. The feasibility of the detection of adulterant materials in natural rubber latex concentrates by using an ultrasonic method is discussed. Finally, the dual transducers reflected pulse echo technique is found be an alternative method to determine d.r.c. in natural rubber latex and could be used as a real time monitoring system for liquids and suspensions in a production environment.

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7

Van, Nevel Alan J. "Wavelet based noise removal for ultrasonic non-destructive evaluation /". free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9737876.

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8

Nowers, Oliver David. "Ultrasonic non-destructive evaluation of the austenitic steel welds". Thesis, University of Bristol, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.742983.

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9

Hajzargarbashi, Talieh. "Ultrasonic Non-Destructive Evaluation: Impact Point Prediction and Simulation of Ultrasonic Fields". Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/203430.

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This work has two parts. The first part of the work (in Chapters II, III, IV and V) presents a method for locating the point of impact using acoustic emission techniques.The second part of the work is modeling the ultrasonic fields generated by one and two spherical cavities placed in front of a point focused acoustic lens using the semi-analytical distributed point source method (DPSM).Acoustic emission (AE) refers to the generation of transient elastic waves during the rapid release of energy from localized sources within a material.In this work the acoustic emission has been used for locating the point of impact on anisotropic and homogeneous or non-homogenous flat plates and cylindrical structures. In these cases the wave speed is a function of the angle of propagation. An optimization function is introduced and minimized to get the location of the impact point.This method has been used on a flat (fiber reinforced polymer) plate. The proposed new objective function reduces the amount of time needed for solving the problem and improves the accuracy of prediction. The method is extended to cylindrical structures for which the objective function is written in cylindrical coordinates and the method is tested on a FRP shell.In Chapter IV an alternative method is introduced called the near-field acoustic emission (AE) beamforming method. It has been used to estimate the source locations by using a small array of sensors closely placed in a local region. To validate the effectiveness of the AE beamforming method a series of experiments on a FRP shell are conducted. The experimental results demonstrate that the proposed method can correctly predict the point of impact.The semi-analytical mesh-free technique DPSM is then used to model the ultrasonic field in front of a point focused acoustic lens; anomalies such as cavities are introduced in the medium in front of the acoustic lens and the effect of those cavities are studied. Solution of this problem is necessary to get an idea about when two cavities placed in close proximity can be distinguished by an acoustic lens and when it is not possible.

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10

Cooper, J. A. "Laser-generated ultrasound with applications to non-destructive evaluation". Thesis, University of Hull, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375636.

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11

Karimian, Seyed Fouad. "Evaluation of Adhesive Joints with Ultrasonic Digital Image Correlation". OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2054.

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Increasing use of composite materials in industry brings the need for newer and more practical methods to evaluate them. Widespread use of composite materials heavily depends on the manufacturer’s ability to unquestionably ensure its safety, given how much the user trusts them. Non-Destructive Evaluation (NDE) can be used to evaluate adhesive bondline health. This thesis employs Digital Image Correlation (DIC) method, one of the known methods in NDE, and combines it with an embedded speckle pattern in order to obtain valuable information from within the adhesive bondline. By recording the movement of the speckles and analyzing their behavior according to DIC algorithms, a strain map of the adhesive is drawn. An adhesive strain map helps find defects that might be out of sight using conventional NDE methods. This thesis discusses different possible materials to be used as the speckle pattern and chooses the one shows better results based on different criteria. Then employing the material, it records the speckle pattern using optical and ultrasonic methods to draw a strain map. By analyzing the obtained strain maps, defects within the bondline are revealed.

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12

Campbell, M. A. "An evaluation of monolithic phased arrays for Non destructive testing". Thesis, University of Strathclyde, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381502.

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13

Lau, Connie K. Y. "Non-destructive evaluation with ultrasonic pulse velocity (UPV) in concrete structure". access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174441a.pdf.

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Thesis (M.Sc.)--City University of Hong Kong, 2005.
At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.

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14

Mong, Seng Ming. "Non-destructive evaluation with ultrasonic pulse velocity (UPV) in concrete structure". access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21175032a.pdf.

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Thesis (M.Sc.)--City University of Hong Kong, 2005.
At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.

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15

Cunningham, Laura Jay. "Mathematical model based methods for characterising defects within ultrasonic non destructive evaluation". Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24898.

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This thesis considers the inverse problem of detecting and characterising flaws within heterogeneous materials using ultrasonic phased array transducers. Many imaging techniques include subjective measurements and the aim of this thesis is to develop objective mathematical model based methods which alleviate such subjectivity. Within the first method, the Kirchhoff model is used to derive an explicit expression which relates the maximum eigenvalue from a scattering matrix to the length of a crack in a homogeneous medium. It is shown that there exists a one to one relationship between this maximum eigenvalue and the crack length. The advantage of deriving this analytical approximation is that it can then be analysed to assess the crack sizing capabilities of the method given some scattering matrices from experimental data (the inverse problem). The procedure for using this method is then demonstrated by applying it to finite element simulated data from a homogeneous medium with a 5 mm long crack inclusion, the crack length recovered using this method is 4.4 mm. A second method is then presented which exploits another feature of the scattering matrix. An analytical expression which is an approximation to the first minimum in the pulse echo response of a scattering matrix is derived from the Kirchhoff model. This approach is also illustrated by sizing a 5 mm long crack within a homogeneous medium from finite element simulated data, the crack length recovered using this method is 5.8 mm. The method is then extended to form a multi-frequency technique which enables it to be applied to finite element simulated data from a 5mm long crack inclusion in a heterogeneous medium. The method is enhanced by using a convolution method to reduce the noise prior to the multi-frequency method being used. The recovered crack length using this method once the noise has been reduced is 4 mm. Finally, a detection technique based on the first stage of a time reversal is presented, within which a detection threshold specific to steel welds is proposed. This method is applied to both finite element simulated data and experimental data. Having detected a flaw the time reversal algorithm (DORT) is then used to create images which are then compared to those obtained using the Total Focusing Method.

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16

Li, Shanglei. "Intelligent Non-destructive Measurement and Evaluation Techniques for Aircraft Composites". OpenSIUC, 2013. https://opensiuc.lib.siu.edu/dissertations/764.

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The research work focuses on implementing intelligent measurement and diagnostic techniques for the non-destructive evaluation (NDE) of aircraft carbon composites. The outcome of this research work developed reliable and faster techniques to aid in the rapid assessment of defects in anisotropic carbon composites by applying ultrasonic and infrared thermography NDE methods. To fulfill the requirement of the intelligent non-destructive evaluation methods, this research is divided into four sub-researches: fuzzy logic based delamination detection, super-resolution image reconstruction for ultrasonic C-scan, ultrasonic 3D reconstruction, and polynomial fitting techniques for infrared thermography inspection. These researches focus on the improvement and optimization of current ultrasonic testing and infrared thermography inspection. They are independent but interrelated component, and they all serve the same goal which is to interpret data correctly and provide detailed information about the region of interests (ROI) for intelligent non-destructive measurement and evaluation. Details of these researches are presented in Chapter 2, 3, 4, and 5 respectively. For the ultrasonic testing, a fuzzy inference classifier will be used to generate the rule base and knowledge base for different kinds of defects in composites. It will automatically manage large amounts of signal data sets and extract the important information. Data features and NDE expert knowledge are seamlessly combined to provide the best possible diagnosis of the potential defects and problems. As a result, the outcome of this research work will help ensure the integrity and reliability of carbon composites. The C-scan image resolution of ultrasonic testing system was improved by applying super-resolution algorithms to overcome the inherent resolution limitations of the existing ultrasonic system. It greatly improves the image quality and allows for more detailed inspection of the ROI with high resolution, making defect evaluation easier and more accurate. The ultrasonic 3D reconstruction technique will be able to provide NDE inspectors with more detailed information on defect depth, volume, and 3D structure, as well as help them make quick, accurate, and reliable decisions. For the IR inspection, the thermography methods based on the thermal contrast are strongly affected by non-uniform heating which due to the heat source alignment and specimen thickness variation. The proposed polynomial curve fitting and surface fitting techniques were applied to eliminate the non-uniform heating effect by subtracting the estimated non-uniform heating pattern from the corrupted IR images. Mainly, aircraft composite material: carbon fiber reinforced polymer (CFRP) panels will be considered for this research work. Based on the preliminary study, delamination defects due to impact damage and foreign object inclusions artificially embedded in CFRP panels were successfully detected by immersion ultrasonic testing (UT) and IRT inspection. Therefore, the next step will be in improving the detection algorithm and developing an intelligent quality inspection technique for NDE testing. Powered with multiple image processing techniques and mathematical algorithms, the research result will provide high resolution images and detailed information about defect areas. In addition, it will also capable of identifying the type, shape, size, and the distribution of defect.

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17

Stonawski, Ondrej. "NON-DESTRUCTIVE EVALUATION OF CARBON/CARBON BRAKES USING AIR-COUPLED ULTRASONIC INSPECTION SYSTEMS". Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1674101471&sid=2&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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Thesis (M.S.)--Southern Illinois University Carbondale, 2008.
"Department of Mechanical Engineering and Energy Processes." Keywords: Air-coupled ultrasonic, Carbon/carbon brakes, Nondestructive evaluation. Includes bibliographical references (p. 114-115). Also available online.

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18

Freemantle, Richard James. "Ultrasonic compression wave evaluation of adhered metal sheets and thin sheet materials". Thesis, Keele University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282635.

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19

Todd, Charles Peter Debenham. "Non-destructive evaluation of adhesively bonded structures using ultrasonic Lamb waves and artificial neural networks". Thesis, Keele University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361828.

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20

Bork, Uwe. "Non-destructive evaluation of adhered metal joints using ultrasonic Lamb waves and artificial neural networks". Thesis, Keele University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241451.

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21

Thornicroft, Keith. "Ultrasonic guided wave testing of pipelines using a broadband excitation". Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/14001.

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Guided Wave Testing (GWT) is a relatively new development in non-destructive testing. Conventional Ultrasonic Testing (UT) methods are operated at high frequencies (MHz) and are capable of detecting very small (down to micrometre-scale) flaws within a range of millimetres from a transducer. GWT, however, is carried out at lower frequencies (kHz) and is capable of highlighting the position of volumetric structural detail and discontinuities, such as gross corrosion at a minimum of 9% of the cross-sectional area, tens of metres from a test location. Conventional ultrasonic testing relies on the transmission of bulk waves whereas GWT employs so-called ultrasonic guided waves (UGW). To simplify UGW inspections, several tests are conducted sequentially at a range of different excitation frequencies. The frequency bandwidth of each of these tests needs to be controlled to avoid complexities caused by the frequency dependent nature of the propagation of guided waves. This gives rise to the current GWT inspection procedure, where a number of different narrowband tests are conducted at several distinct frequencies. It is also found that different test circumstances (such as pipe coating or defect type) are inspected more easily with certain excitation frequencies than with others - and the optimum frequency can not always be predicted ahead of time. Thus, where time allows it is often beneficial to carry out a frequency sweep, whereby a large range of excitation frequencies are incrementally generated - for example, from 20 to 80kHz in 1kHz steps. This research proposes a novel approach to the existing pipeline inspection procedure by utilising the information contained within a broadband response. The overarching proposition given by this research is that the current collection procedure be entirely rewritten. This thesis will present ideas related to every area of the inspection procedure beginning with the tuning of excitation signals and concluding with recommendations on how tooling and excitation configuration can be modified to further optimise the technique for broadband excitation.

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22

Levine, Ross M. "Ultrasonic guided wave imaging via sparse reconstruction". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51829.

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Structural health monitoring (SHM) is concerned with the continuous, long-term assessment of structural integrity. One commonly investigated SHM technique uses guided ultrasonic waves, which travel through the structure and interact with damage. Measured signals are then analyzed in software for detection, estimation, and characterization of damage. One common configuration for such a system uses a spatially-distributed array of fixed piezoelectric transducers, which is inexpensive and can cover large areas. Typically, one or more sets of prerecorded baseline signals are measured when the structure is in a known state, with imaging methods operating on differences between follow-up measurements and these baselines. Presented here is a new class of SHM spatially-distributed array algorithms that rely on sparse reconstruction. For this problem, damage over a region of interest (ROI) is considered to be sparse. Two different techniques are demonstrated here. The first, which relies on sparse reconstruction, uses an a priori assumption of scattering behavior to generate a redundant dictionary where each column corresponds to a pixel in the ROI. The second method extends this concept by using multidimensional models for each pixel, with each pixel corresponding to a "block" in the dictionary matrix; this method does not require advance knowledge of scattering behavior. Analysis and experimental results presented demonstrate the validity of the sparsity assumption. Experiments show that images generated with sparse methods are superior to those created with delay-and-sum methods; the techniques here are shown to be tolerant of propagation model mismatch. The block-sparse method described here also allows the extraction of scattering patterns, which can be used for damage characterization.

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23

Brath, Alexander J. "Advanced techniques for ultrasonic imaging in the presence of material and geometrical complexity". University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1510053440115292.

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24

Zlatev, Zahari. "Ultrasonic guided wave propagation in pipes coated with viscoelastic materials". Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/12753.

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This work studies guided wave propagation in pipes coated with thick highly viscoelastic coating materials. The main motivation for this study is the problems associated with Long Range Ultrasonic Testing (LRUT) of coated pipelines. The results reported in the literature show that the proper determination of the optimum LRUT parameters depends strongly on the bulk acoustic properties of the coating materials. The bulk acoustic properties of coating materials reported in the literature show that they could vary significantly depending on the coating material age, temperature and bonding level. The methods for acoustic characterisation of coating materials reported by other researchers, have been studied and it was found that they do not take into account the temperature changes and bonding level variation. In this work, the bulk acoustic properties of two highly viscoelastic bitumen based coating materials are investigated. The conventional methods for acoustic characterisation are studied and a new method for independent measurement of bulk shear properties of bitumen is developed. The bulk acoustic properties of bitumen based coating materials are also studied by two new characterisation methods. The first method derives the bulk coating material properties from experimental data on guided wave reflection coefficients. The second method derives the coating material bulk properties from experimentally measured guided wave attenuation data. It is demonstrated that these new methods deliver much more accurate values for the bulk acoustic properties when compared to the data measured by conventional methods. The second method is used to study the temperature effect on the bulk acoustic properties and it is demonstrated that temperature has a significant effect. The validity of the acoustic properties for the two bitumen materials is investigated through comparison between numerical predictions and experimental data measured for guided wave reflection coefficients and attenuation of the torsional T(0,1) and longitudinal L(0,2) guided wave modes. Good agreement is achieved in the frequency range between 20 kHz and 100 kHz, which is typical for LRUT of pipes.

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25

Pan, Yicheng. "INTELLIGENT NON-DESTRUCTIVE EVALUATION EXPERT SYSTEM FOR CARBON-CARBON COMPOSITES USING THERMOGRAPHY, ULTRASONICS, AND COMPUTED TOMOGRAPHY". OpenSIUC, 2010. https://opensiuc.lib.siu.edu/dissertations/151.

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This study develops a reliable intelligent non-destructive evaluation (NDE) expert system for carbon-carbon (C/C) composites based on thermography, ultrasonic, computed tomography and post processing by means of fuzzy expert system technique. Data features and NDE expert knowledge are seamlessly combined in the intelligent system to provide the best possible diagnosis of the potential defects and problems. As a result, this research help ensure C/C composites' integrity and reliability. Four types of orthotropic aerospace composite material groups, which include 2-D pitched based commercial aircraft disc brakes and asmolds, 3-D PAN based C/C composites, and carbon fiber reinforced plastic (CFRP) panels, were tested. Based on the performance testing results of thermography, air-coupled ultrasonic, and x-ray computed tomography, the testing data pattern corresponding to feature and quantification of defects were found. This NDE knowledge databases were transformed to fuzzy logic expert system models. The models succeefully classified and indicated the defect's size and distribution and the intelligent systems perform NDE better than human operators. These fuzzy expert systems not only eliminate human errors in defect detection but also function as NDE experts. In addition, fuzzy expert systems improve the defect detection by incorporating fuzzy expert rules to remove noises and to measure defect size more accurately. In the future, the expert system model could be continuously updated and modified to quantify the size and distribution of defects. The systems developed here can be adapted and applied to build an intelligent NDE expert system for better quality control as well as automatic defect and porosity detection in C/C composite production process.

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26

Osman, Ahmad. "Automated evaluation of three dimensional ultrasonic datasets". Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00995119.

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Non-destructive testing has become necessary to ensure the quality of materials and components either in-service or at the production stage. This requires the use of a rapid, robust and reliable testing technique. As a main testing technique, the ultrasound technology has unique abilities to assess the discontinuity location, size and shape. Such information play a vital role in the acceptance criteria which are based on safety and quality requirements of manufactured components. Consequently, an extensive usage of the ultrasound technique is perceived especially in the inspection of large scale composites manufactured in the aerospace industry. Significant technical advances have contributed into optimizing the ultrasound acquisition techniques such as the sampling phased array technique. However, acquisition systems need to be complemented with an automated data analysis procedure to avoid the time consuming manual interpretation of all produced data. Such a complement would accelerate the inspection process and improve its reliability. The objective of this thesis is to propose an analysis chain dedicated to automatically process the 3D ultrasound volumes obtained using the sampling phased array technique. First, a detailed study of the speckle noise affecting the ultrasound data was conducted, as speckle reduces the quality of ultrasound data. Afterward, an analysis chain was developed, composed of a segmentation procedure followed by a classification procedure. The proposed segmentation methodology is adapted for ultrasound 3D data and has the objective to detect all potential defects inside the input volume. While the detection of defects is vital, one main difficulty is the high amount of false alarms which are detected by the segmentation procedure. The correct distinction of false alarms is necessary to reduce the rejection ratio of safe parts. This has to be done without risking missing true defects. Therefore, there is a need for a powerful classifier which can efficiently distinguish true defects from false alarms. This is achieved using a specific classification approach based on data fusion theory. The chain was tested on several ultrasound volumetric measures of Carbon Fiber Reinforced Polymers components. Experimental results of the chain revealed high accuracy, reliability in detecting, characterizing and classifying defects.

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Gex, Dominique. "Ultrasonic NDE testing of a gradient enhanced piezoelectric actuator (GEPAC) undergoing low frequency bending excitation". Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04062004-171807/unrestricted/gex%5Fdominique%5Fc%5F200405%5Fmast.pdf.

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Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2004.
Berthelot, Committee Chair; Lynch, Committee Member; Jacobs, Committee Member. Includes bibliographical references (leaves 111-113).

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28

Poudel, Anish. "AN INTELLIGENT SYSTEMS APPROACH FOR DETECTING DEFECTS IN AIRCRAFT COMPOSITES BY USING AIR-COUPLED ULTRASONIC TESTING". OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/594.

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Circular air-coupled ultrasonic testing (ACUT) setup for the inspection of commercial carbon-carbon composite aircraft brake disks was developed in Intelligent Measurement and Evaluation Laboratory (IMEL) at Southern Illinois University Carbondale (SIUC). The developed test setup utilizes Airstar single channel air-coupled equipment and has only manual A-scan and B-scan capability. The developed ACUT technique is unique compared to the commercial C-scan ultrasonic systems and is proficient, fast, economically feasible, and easy to implement method particularly for the inspection of carbon-carbon (C/C) composites aircraft brake disks. Prior to conducting air-coupled measurements, wobble analysis was carried out. This was important because significant wobbling in the test setup can lead to the interference of the reflected and the incident beam which would result to inaccurate ultrasonic measurements. The measured deviation due to wobbling, surface profile of the disk, design, and experimental error were relatively small. Therefore, these errors were neglected while performing ACUT measurements. For ACUT measurements, several through-transmitted amplitude signals were recorded within the C/C brake disks manually. The images were then reconstructed using Matlab based on the through-transmitted amplitude signals. Finally, a comparison was drawn between the reconstructed images and the C-scan images of the C/C brake disks obtained from the commercial Airstar C-scan ACUT system. Like commercial C-scan ACUT image results, reconstructed images were also able to detect all defects in the commercial C/C brake disks which served for the system verification and validation. In addition, defect, non-defect, and suspected areas within the C/C brake disks were quantified with air-coupled measurement. For this, light microscopy was conducted for every sample made from each C/C brake disks at lower magnification of 10X. It was concluded that it is very difficult to assess the crack or delamination situation based on a 2D micrograph of one depth. Also, it was concluded that an internal porosity and micro-cracks may not be only factors that can be related to defects. Finally, an intelligent systems approach, specifically, fuzzy logic and artificial neural network (ANN) methodologies were implemented for the automatic defect detection in commercial C/C aircraft brake disks by using air-coupled ultrasonic results. For this, a multi-layer perceptron (MLP) with two hidden layers and a scaled conjugate gradient back-propagation (BP) learning algorithm was used for the ANN training. The network training process was performed in an off-line mode using the ANN toolbox in Matlab. The network training was repeated until a steady state was reached, where there was no further change in the synaptic weights. The ANN provided plausible results in detecting the defect areas for different C/C brake disks. It was also demonstrated that the system was able to learn the rules without knowing any algorithm for automatic defect detection.

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MAHMOUD, TAREK IBRAHIM. "Evaluation of the degradation process of cement-based materials exposed to aggressive environment by using ultrasonic techniques and physical characterisation". Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/27550.

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El hormigón armado compuesto de cemento Portland fue inventado hace algo más de un siglo aproximadamente y se ha convertido en el material más utilizado en la construcción. La durabilidad de este hormigón es una de las consideraciones más importantes a ser tenidas en cuenta en el diseño de nuevas estructuras y en la evaluación estructural de las ya existentes. Cuando un hormigón sujeto a un ambientes o cargas que puede degradarlo, como puede ser su uso en puentes y ambientes marinos o si contiene grandes cantidades de alúmina o áridos reciclados, el conocimiento o predicción de su durabilidad es una aspecto crítico para su comportamiento en servicio. Los ensayos no destructivos se han mostrado como unos de los ensayos preceptivos con una importancia económica y social más relevante desde que se han aplicado para la auscultación de la durabilidad de las estructuras de hormigón pertenecientes a la ingeniería civil, donde estos materiales son ampliamente utilizados. En cualquier caso, el uso de las técnicas no destructivas en estos materiales no está suficientemente implementado, hecho este motivado por las características heterogéneas de su microestructura. De todos los métodos no destructivos aplicables para el hormigón, el uso de pulsos ultrasónicos es de gran interés para la caracterización de la microestructura y las propiedades de materiales heterogéneos. El objetivo del presente trabajo es obtener un procedimiento de evaluación del ciclo de vida del hormigón preparado y puesto en servicio para ambientes marinos. Además, será estudiado y analizado la incorporación de varias metodologías (destructivas y non destructivas) para caracterizar el proceso de degradación de morteros y hormigones expuestos a disolución de sulfato de sodio y a exposición en disolución de nitrato amónico. Con esta finalidad, una integración adecuada de diferentes técnicas será usada para la caracterización de propiedades y el seguimiento del proceso de degradación que afectan al hormigón. Como objetivos adicionales, destaca que fueron estudiadas las relaciones entre los parámetros destructivos y no destructivos, así como la relación entre los distintos parámetros no destructivos entre sí. Muchos de los estudios anteriores que han usado la inspección ultrasónica las cuáles fueron utilizadas para determinar la relación agua/cemento del mortero, de la pasta de cemento y del hormigón, o para monitorizar los cambios estructurales, para diferentes relaciones a/c, en el proceso de curado. En este trabajo de investigación fue analizado el efecto que tiene para diferentes relaciones a/c en los parámetros ultrasónicos durante el proceso de degradación. Para este objetivo, se utilizaron un Cemento Portland tipo II A L 42.5 (LPC), y otro sulforresistente tipo I 42.5R/SR (SRPC) que fueron usados en la fabricación de dos marcos de hormigón, los cuales fueron utilizados como hormigón en servicio (caso real). Para el estudio del efecto de la variación de a/c en los parámetros ultrasónicos durante la degradación se utilizaron muestras de mortero con deferentes relaciones agua cemento 0.525- 0.45- 0.375 and 0.30 a partir de LPC para obtener diferentes niveles de degradación. Para monitorizar el proceso de degradación se utilizó la inspección por pulso/eco (1 y 3.5 MHz) para la obtención del parámetro del área del perfil de atenuaciones (APA) el cual fue estimado por L Vergara et al., 2003 y usado por Fuente et al, 2004. Para seguir el proceso de curado de pasta de cemento y morteros, este parámetro ha demostrado una alta sensibilidad para caracterizar los cambios microestructurales de materiales derivados del cemento a lo largo de su curado. El método de transmisión se ha utilizado para la determinación de las velocidades de ondas longitudinales con la frecuencia de 1MHz y transversales con la frecuencia de 500 kHz. La velocidad ultrasónica también ha demostrado la capacidad para seguir los cambios microestructurales de un modo sencillo porque dicho parámetro está relacionado con la variación de las propiedades mecánicas, y bajo ciertas premisas, con la variación de la porosidad. El análisis con la imagen ultrasónica con 2 MHz fue también usada para la consecución de los mismos objetivos. Como métodos destructivos, los ensayos de resistencia a la compresión y flexión fueron los utilizados para determinar la pérdida de actividad resistente de morteros y hormigones, y la porosidad conectada al agua para analizar los cambios en la matriz porosa por el efecto de la difusión de elementos agresivos que penetran en el material provocando su degradación. La porosimetría de mercurio (MIP) fue usada para observar las variaciones del volumen y tamaño de poro y, por último, la microscopía electrónica de barrido (MEB) que fue utilizada para cuantificar y detectar los cambios en la microestructura por el ataque de elementos agresivos. Los resultados obtenidos muestran que, la degradación producida por exposición a sulfato de sodio, tiene dos etapas, en la primera etapa se forma la etringita que llena los poros pero que no produce microfisuración. En esta etapa se observó una variación en los parámetros obtenidos por ejemplo, incremento de la velocidad de la onda ultrasónica, de las resistencias a compresión y a la flexión o la disminución de la porosidad. Esta variación en los parámetros podría indicar una mejora en las prestaciones mecánicas del material objeto de la investigación, pero en realidad esto no es cierto porque los poros están llenos de etringita, provocando una expansión, que es la causa de la degradación en la segunda etapa. En dicha segunda etapa, se produce una microfisuración generalizada por la expansión de la etringita e incrementando su volumen dentro de los poros. Este hecho produjo un cambio en los parámetros medidos que contrastan con la evolución en la primera etapa, disminución de la velocidad de las ondas ultrasónicas, y de las resistencias mecánicas y consecuentemente un aumento de la porosidad. Por otro lado, la degradación por ataque de nitrato amonio tiene una única etapa debida al proceso de descalificación que comienza desde el principio del proceso de exposición y es lineal durante todo el periodo de exposición. Para ambos casos, la integración de las diversas técnicas se revela como satisfactoria para el seguimiento del proceso de degradación, encontrando buenas correlaciones entre los parámetros no destructivos y los parámetros destructivos de técnicas de análisis físico-químico.
Mahmoud, TI. (2013). Evaluation of the degradation process of cement-based materials exposed to aggressive environment by using ultrasonic techniques and physical characterisation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/27550
TESIS

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Deng, Xiaodong. "Nondestructive evaluation of thermal sprayed coating by acoustic microscopy and Eddy current testing". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0030/document.

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La thèse a mis en œuvre deux méthodes inverses pour l’évaluation non destructive d’un milieu multicouche anisotrope : la microscopie acoustique et les courants de Foucault. Pour la microscopie acoustique, nous avons adapté un modèle de propagation de l'onde acoustique dans un milieu multicouche, en calculant les coefficients de réflexion et de transmission d’un revêtement multicouche sur un substrat et en modélisant la réponse acoustique V(z) propre à la microscopie acoustique. Une méthode inverse utilisant l’algorithme de Levenberg-Marquardt donne accès à l’épaisseur, au module de Young et à la densité du revêtement. Pour les courants de Foucault, une méthode inverse similaire basée sur le formalisme de Tree a été mise au point, qui donne accès à l’épaisseur, à la conductivité électrique et à la perméabilité magnétique du revêtement. Après des vérifications de l’algorithme sur des matériaux massifs de référence, nous avons appliqué ces méthodes à un métal revêtu pour tuyauteries de centrale thermique : de l’acier inoxydable austénitique type 304 revêtu par pulvérisation thermique de superalliage Hastelloy C22 à base de nickel. La corrosion sèche sous l’effet des gaz chauds (air contenant du gaz SO2) amincit graduellement la paroi des tubes, ce qui peut les rendre dangereux. Il a fallu tenir compte de l’effet du grenaillage préalable à la pulvérisation, qui crée une mince couche de martensite à laquelle les courants de Foucault sont très sensibles : un modèle à trois couches substrat / martensite / revêtement a été utilisé. Nous avons caractérisé des échantillons de métal avant et après exposition à l’air avec ou sans SO2 à 650°C. Les deux méthodes d’évaluation non destructive permettent une détermination très satisfaisante de l’épaisseur de revêtement et se complètent bien. L’évaluation des caractéristiques physiques (acoustiques et électromagnétiques) met en évidence des hétérogénités du revêtement liées à son mode d’élaboration et des évolutions au cours du temps. Des pistes d’amélioration des méthodes sont proposées
In the current work, we investigate the nondestructive evaluation of a thermal sprayed coating (Hastelloy C22 Ni-based alloy) on substrate (type 304 austenitic stainless steel) using acoustic microscopy and ECT method. Two models were built for the evaluation of this kind of material: one is for acoustic V(z) measurement and the other is for swept eddy current measurement. The implementation of these two models is used for the evaluation and properties measurement of the thermal sprayed coatings, such as elastic properties, electromagnetic properties. In particular, the main achievements and results are as follows: 1. Acoustic wave propagation in an anisotropic multilayered medium was investigated. The formula for calculating the reflection and transmission coefficients of the multilayered medium on or without a substrate were derived, which is necessary for the modeling of acoustic V(z) measurement of the thermal sprayed coating on substrate. 2. A model was built for the acoustic V(z) measurement of the thermal sprayed coatings on substrate, which can deal with anisotropic multilayered media. Specifically, we used a model of multilayered coatings with graded properties on substrate to calculate the acoustic reflection coefficient of our sample. Treating the thermal sprayed coating, deposited on a 304 steel substrate, as FGMs, we evaluated the coating thickness and the Young’s modulus evolution along the depth of the coating. 3. A model was built for the swept eddy current measurement of the thermal sprayed coatings. Since before the spraying process, the surface of the substrate is usually shot-peened (SP), the coated material is considered as a three-layer medium. The coating thickness and electromagnetic properties of each of the 3 layers were determined by an effective reverse process. 4. The thermal sprayed coated material after exposure in different conditions, i.e., as-received, heat-treated in air and heat-treated in SO2 environment, and after different exposure time was evaluated by the integrity of acoustic microscopy and ECT method. The coating thickness and the electromagnetic properties of the coated material under different conditions were measured

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Chu, Wen-Pin, e 朱文賓. "Ultrasonic Non-Destructive Evaluation Technique and its Applications". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/57532279986232981325.

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碩士
元智大學
機械工程學系
91
Ultrasonics has been one of the most popular non-destructive evaluation techniques in resent gears. In this investigation, the ultrasonic C-Scan system is developed. Using the LabVIEW software, the data acquisition and signal process can be easily incorporated and integrated to form an automatically scanning system. There are three main functions included in the C-Scan system: (1) measuring the thickness of a thick specimen and showing the overall profile via the 3-D imaging display; (2) measuring the thickness of a thin film; (3) cross-section inspection examining the cracks, voids or imparities inside a specimen. In order to measure the thickness of a thin film the signals in time domain, which are overlap and unable to obtain the time difference between two echos, are transferred to the frequency domain by Fourier Fast Transform. The reciprocal of the frequency difference between two adjacent local minimum or maximum in frequency domain is equal to the time difference between the reflective waves of top and bottom surfaces. Incorporating the FFT into the C-Scan system to measure the thin film thickness is the most distinctive comparing to the conventional C-Scan. The capability of present C-Scan system is able to measure thickness of 0.5mm for expory and 1mm for aluminum.

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Bottillo, Alberto. "Advanced 3D Ultrasonic Non-destructive Evaluation Technique for CFRP aeronautical applications". Tesi di dottorato, 2017. http://www.fedoa.unina.it/12194/1/Bottillo_Alberto_30.pdf.

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Nowadays, carbon fiber reinforced plastic (CFRP) composite materials are massively used in a very large number of aeronautical applications such the construction of light weight aircrafts. In aeronautical field, the ultrasonic (UT) non-destructive evaluation NDE technique is are largely used for materials inspection and part quality control because it permits to examine aircraft structures without disassembling them. Damages can occur, at several scales, within this composite material (e.g. delamination) without an external indication. Consequently, each produced composite structure needs to be inspected in order to evaluate the presence of possible defects and to prevent a catastrophic failure of the airplane. In this thesis work an advanced UT NDE system was utilized to perform a reliable and repeatable UT Full Volume (FV) scanning based on pulse-echo immersion testing on three different CFRP aeronautical components that represent three case studies. The resulting ultrasonic data were processed by a custom made software, developed in Labview environment, in order to obtain a metrological characterization and a quality assessment of non-crimp fabric composite laminates (first case study) and by a second custom made software, developed in Matlab environment, in order to provide a 3D thickness reconstruction of the defects of a CFRP bonded joint laminates and of a CFRP drilled laminates (second and the third case respectively).

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Wronkowicz, Angelika. "Non-destructive evaluation of composite aircraft elements based on ultrasonic testing and image analysis". Rozprawa doktorska, 2018. https://repolis.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=48534.

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Wronkowicz, Angelika. "Non-destructive evaluation of composite aircraft elements based on ultrasonic testing and image analysis". Rozprawa doktorska, 2018. https://delibra.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=48534.

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35

(5929469), Hani A. Almansouri. "Model-Based Iterative Reconstruction and Direct Deep Learning for One-Sided Ultrasonic Non-Destructive Evaluation". Thesis, 2019.

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One-sided ultrasonic non-destructive evaluation (UNDE) is extensively used to characterize structures that need to be inspected and maintained from defects and flaws that could affect the performance of power plants, such as nuclear power plants. Most UNDE systems send acoustic pulses into the structure of interest, measure the received waveform and use an algorithm to reconstruct the quantity of interest. The most widely used algorithm in UNDE systems is the synthetic aperture focusing technique (SAFT) because it produces acceptable results in real time. A few regularized inversion techniques with linear models have been proposed which can improve on SAFT, but they tend to make simplifying assumptions that show artifacts and do not address how to obtain reconstructions from large real data sets. In this thesis, we present two studies. The first study covers the model-based iterative reconstruction (MBIR) technique which is used to resolve some of the issues in SAFT and the current linear regularized inversion techniques, and the second study covers the direct deep learning (DDL) technique which is used to further resolve issues related to non-linear interactions between the ultrasound signal and the specimen.

In the first study, we propose a model-based iterative reconstruction (MBIR) algorithm designed for scanning UNDE systems. MBIR reconstructs the image by optimizing a cost function that contains two terms: the forward model that models the measurements and the prior model that models the object. To further reduce some of the artifacts in the results, we enhance the forward model of MBIR to account for the direct arrival artifacts and the isotropic artifacts. The direct arrival signals are the signals received directly from the transmitter without being reflected. These signals contain no useful information about the specimen and produce high amplitude artifacts in regions close to the transducers. We resolve this issue by modeling these direct arrival signals in the forward model to reduce their artifacts while maintaining information from reflections of other objects. Next, the isotropic artifacts appear when the transmitted signal is assumed to propagate in all directions equally. Therefore, we modify our forward model to resolve this issue by modeling the anisotropic propagation. Next, because of the significant attenuation of the transmitted signal as it propagates through deeper regions, the reconstruction of deeper regions tends to be much dimmer than closer regions. Therefore, we combine the forward model with a spatially variant prior model to account for the attenuation by reducing the regularization as the pixel gets deeper. Next, for scanning large structures, multiple scans are required to cover the whole field of view. Typically, these scans are performed in raster order which makes adjacent scans share some useful correlations. Reconstructing each scan individually and performing a conventional stitching method is not an efficient way because this could produce stitching artifacts and ignore extra information from adjacent scans. We present an algorithm to jointly reconstruct measurements from large data sets that reduces the stitching artifacts and exploits useful information from adjacent scans. Next, using simulated and extensive experimental data, we show MBIR results and demonstrate how we can improve over SAFT as well as existing regularized inversion techniques. However, even with this improvement, MBIR still results in some artifacts caused by the inherent non-linearity of the interaction between the ultrasound signal and the specimen.

In the second study, we propose DDL, a non-iterative model-based reconstruction method for inverting measurements that are based on non-linear forward models for ultrasound imaging. Our approach involves obtaining an approximate estimate of the reconstruction using a simple linear back-projection and training a deep neural network to refine this to the actual reconstruction. While the technique we are proposing can show significant enhancement compared to the current techniques with simulated data, one issue appears with the performance of this technique when applied to experimental data. The issue is a modeling mismatch between the simulated training data and the real data. We propose an effective solution that can reduce the effect of this modeling mismatch by adding noise to the simulation input of the training set before simulation. This solution trains the neural network on the general features of the system rather than specific features of the simulator and can act as a regularization to the neural network. Another issue appears similar to the issue in MBIR caused by the attenuation of deeper reflections. Therefore, we propose a spatially variant amplification technique applied to the back-projection to amplify deeper regions. Next, to reconstruct from a large field of view that requires multiple scans, we propose a joint deep neural network technique to jointly reconstruct an image from these multiple scans. Finally, we apply DDL to simulated and experimental ultrasound data to demonstrate significant improvements in image quality compared to the delay-and-sum approach and the linear model-based reconstruction approach.

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