Post-processing of the full matrix of ultrasonic transmit-receive array data for non-destructive evaluation
TL;DR: This paper describes an alternative approach in which the full matrix of time domain signals from every transmitter–receiver pair is captured and post-processed and shown to offer significant performance advantages for NDE.
Abstract: Processing of ultrasonic array data is traditionally based on having parallel transmission circuits that enable staggered firing of transmitter elements to produce the desired wavefront. This paper describes an alternative approach in which the full matrix of time domain signals from every transmitter–receiver pair is captured and post-processed. Various post-processing approaches are modelled and assessed in terms of their ability to image a point-like reflector. Experimental results are then presented which show good quantitative agreement with the modelled results. An advanced processing algorithm is also implemented which allows the array to be focused at every point in the target region in both transmission and reception. This approach is shown to offer significant performance advantages for NDE.
Citations
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TL;DR: The use of ultrasonic arrays for non-destructive evaluation has been extensively studied in the literature as mentioned in this paper, where the main advantages of arrays are their increased flexibility over traditional single element transducers, and their ability to produce immediate images of the test structure.
Abstract: An ultrasonic array is a single transducer that contains a number of individually connected elements. Recent years have seen a dramatic increase in the use of ultrasonic arrays for non-destructive evaluation. Arrays offer great potential to increase inspection quality and reduce inspection time. Their main advantages are their increased flexibility over traditional single element transducer methods, meaning that one array can be used to perform a number of different inspections, and their ability to produce immediate images of the test structure. These advantages have led to the rapid uptake of arrays by the engineering industry. These industrial applications are underpinned by a wide range of published research which describes new piezoelectric materials, array geometries, modelling methods and inspection modalities. The aim of this paper is to bring together the most relevant published work on arrays for non-destructive evaluation applications, comment on the state-of the art and discuss future directions. There is also a significant body of published literature referring to use of arrays in the medical and sonar fields and the most relevant papers from these related areas are also reviewed. However, although there is much common ground, the use of arrays in non-destructive evaluation offers some distinctly different challenges to these other disciplines.
818 citations
TL;DR: In this article, a general imaging methodology, termed multi-mode total focusing method, is proposed in which any combination of modes and reflections can be used to produce an image of the test structure.
Abstract: Ultrasonic arrays allow a given scatterer to be illuminated from a wide range of angles and hence are capable of extracting significant information about the scatterer. In this paper a general imaging methodology, termed multi-mode total focusing method, is proposed in which any combination of modes and reflections can be used to produce an image of the test structure. Like the total focusing method, this approach is implemented by post-processing the full matrix of array data to achieve a synthetic focus at every pixel in the image. A hybrid model is used to predict the array data and demonstrate the performance of the multi-mode imaging concept. This hybrid model combines far field scattering coefficient matrices with a ray-based wave propagation model. This allows the inclusion of longitudinal waves, shear waves and wave mode conversions. It is shown that, with prior knowledge of likely scatterer location and orientation, the mode combination and array location can be optimised to maximise the performance of array inspections. A practically relevant weld inspection application is then described and its optimisation is discussed.
208 citations
Cites methods from "Post-processing of the full matrix ..."
...Total focusing method (TFM) is based on identical principles to SAFT except that data from every transmitter–receiver combination is used in the imaging process [10,11]....
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TL;DR: A Fourier-domain approach to full-matrix imaging based on the wavenumber algorithm used in synthetic aperture radar and sonar, which has an improved point-spread function and provides better imagery and is several orders of magnitude faster than the TFM.
Abstract: Ultrasonic imaging using full-matrix capture, e.g., via the total focusing method (TFM), has been shown to increase angular inspection coverage and improve sensitivity to small defects in nondestructive evaluation. In this paper, we develop a Fourier-domain approach to full-matrix imaging based on the wavenumber algorithm used in synthetic aperture radar and sonar. The extension to the wavenumber algorithm for full-matrix data is described and the performance of the new algorithm compared with the TFM, which we use as a representative benchmark for the time-domain algorithms. The wavenumber algorithm provides a mathematically rigorous solution to the inverse problem for the assumed forward wave propagation model, whereas the TFM employs heuristic delay-and-sum beamforming. Consequently, the wavenumber algorithm has an improved point-spread function and provides better imagery. However, the major advantage of the wavenumber algorithm is its superior computational performance. For large arrays and images, the wavenumber algorithm is several orders of magnitude faster than the TFM. On the other hand, the key advantage of the TFM is its flexibility. The wavenumber algorithm requires a regularly sampled linear array, while the TFM can handle arbitrary imaging geometries. The TFM and the wavenumber algorithm are compared using simulated and experimental data.
197 citations
Cites background or methods from "Post-processing of the full matrix ..."
...note that the locations of the transducer elements are discrete and therefore, in practice, the tfM is implemented using a summation [2]....
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..., the tfM [2], is its superior computational performance....
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..., the total focusing method, focus the array at every point in the image, giving better defect resolving capabilities [2]....
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...full matrix data acquisition is commonplace in the field of seismic imaging [15], and it has been shown to provide improved detection and characterization accuracy and noise performance for nde [2], [3]....
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...the array performance indicator [2] is a useful metric for quantifying the image resolution....
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TL;DR: In this article, a review of advances reported in the NDE of thick-section composites (structures of thickness above 15 mm are considered for the purposes of this review), and identifies future research opportunities to overcome the limitations of existing technologies.
Abstract: Nondestructive evaluation (NDE) research on composite materials has been ongoing for several decades, during which time their use has expanded significantly in the aerospace, marine, petrochemical, energy, construction and transport sectors. Initially, many composites were employed as fairings or reinforcements, but they are being increasingly used in primary and secondary load-bearing structures, where a mechanical failure has significantly greater safety implications. This increased scope has resulted in composite structures of significant thickness and complexity. Despite this, there has not been a corresponding increase in research pertinent to the detection and characterisation of defects in thick structures, apart from a brief period of interest by the NDE community in the early 1990s. This review critically assesses advances reported in the NDE of thick-section composites (structures of thickness above 15 mm are considered for the purposes of this review), and identifies future research opportunities to overcome the limitations of existing technologies.
158 citations
TL;DR: The present manuscript intends to review the ultrasonic testing techniques applied to additive manufacturing products; either in-situ or offline; and the codes and standards which are currently being developed for ultrasonic tested products are introduced.
139 citations
References
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01 Jan 1982
TL;DR: The Review of Progress in Quantitative NDE (ROPQN) as mentioned in this paper is the world's leading conference in reporting annually new research and development results in quantitative NDE and promotes communication between the research and engineering communities and emphasize current reporting of work in progress.
Abstract: The Review of Progress in Quantitative NDE is the world's leading conference in reporting annually new research and development results in quantitative NDE. The conference reports on both fundamental and applied advances in NDE and promotes communication between the research and engineering communities and emphasize current reporting of work in progress. Attendees include representatives of academia (including students), industry, and government with approximately one-half coming from the United States and the other half from overseas. This volume represents the best report of ongoing work that is available anywhere. Connections and overlap with the medical diagnostic community are highlighted.
1,989 citations
Book•
01 Jan 1987
1,194 citations
"Post-processing of the full matrix ..." refers methods in this paper
...An inverse Fourier transform can then applied to transform the signal back to the time domain, but in practice it is more useful for subsequent post-processing to obtain the complex Hilbert transform [11] of the resulting time domain...
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TL;DR: The first pulse-echo phased array B-scan sector images using a 128-element, one-dimensional (1-D) linear CMUT array is presented and preliminary investigations on the effects of crosstalk among array elements on the image quality are performed.
Abstract: Piezoelectric materials have dominated the ultrasonic transducer technology. Recently, capacitive micromachined ultrasonic transducers (CMUTs) have emerged as an alternative technology offering advantages such as wide bandwidth, ease of fabricating large arrays, and potential for integration with electronics. The aim of this paper is to demonstrate the viability of CMUTs for ultrasound imaging. We present the first pulse-echo phased array B-scan sector images using a 128-element, one-dimensional (1-D) linear CMUT array. We fabricated 64- and 128-element 1-D CMUT arrays with 100% yield and uniform element response across the arrays. These arrays have been operated in immersion with no failure or degradation in performance over the time. For imaging experiments, we built a resolution test phantom roughly mimicking the attenuation properties of soft tissue. We used a PC-based experimental system, including custom-designed electronic circuits to acquire the complete set of 128/spl times/128 RF A-scans from all transmit-receive element combinations. We obtained the pulse-echo frequency response by analyzing the echo signals from wire targets. These echo signals presented an 80% fractional bandwidth around 3 MHz, including the effect of attenuation in the propagating medium. We reconstructed the B-scan images with a sector angle of 90 degrees and an image depth of 210 mm through offline processing by using RF beamforming and synthetic phased array approaches. The measured 6-dB lateral and axial resolutions at 135 mm depth were 0.0144 radians and 0.3 mm, respectively. The electronic noise floor of the image was more than 50 dB below the maximum mainlobe magnitude. We also performed preliminary investigations on the effects of crosstalk among array elements on the image quality. In the near field, some artifacts were observable extending out from the array to a depth of 2 cm. A tail also was observed in the point spread function (PSF) in the axial direction, indicating the existence of crosstalk. The relative amplitude of this tail with respect to the mainlobe was less than -20 dB.
508 citations
05 Oct 2003
TL;DR: This paper compares chirp and Golay code performance with respect to image quality and system requirements, then shows clinical images that illustrate the current applications of coded excitation in B-mode, harmonic, and flow imaging.
Abstract: Resolution and penetration are primary criteria for clinical image quality. Conventionally, high bandwidth for resolution was achieved with a short pulse, which results in a tradeoff between resolution and penetration. Coded excitation extends the bounds of this tradeoff by increasing signal-to-noise ratio (SNR) through appropriate coding on transmit and decoding on receive. Although used for about 50 years in radar, coded excitation was successfully introduced into commercial ultrasound scanners only within the last 5 years. This delay is at least partly due to practical implementation issues particular to diagnostic ultrasound, which are the focus of this paper. After reviewing the basics of biphase and chirp coding, we present simulation results to quantify tradeoffs between penetration and resolution under frequency-dependent attenuation, dynamic focusing, and nonlinear propagation. Next, we compare chirp and Golay code performance with respect to image quality and system requirements, then we show clinical images that illustrate the current applications of coded excitation in B-mode, harmonic, and flow imaging.
326 citations
"Post-processing of the full matrix ..." refers methods in this paper
...If the signal to random noise ratio is an issue this can be improved by averaging or use of encoded signals such as Golay sequences [17]....
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Book•
01 Jan 1981
TL;DR: In this article, the authors present a comprehensive exam glossary with answers to Exercises, including a list of symbols and a compilation of abstracts for exam preparation, as well as a discussion of the main components of the exam.
Abstract: PART 1 SONOGRAPHIC PRINCIPLES CHAPTER 1 Introduction Sonography Doppler Ultrasound Review Exercises CHAPTER 2 Ultrasound Sound Pulsed Ultrasound Attenuation Echoes Review Exercises CHAPTER 3 Transducers Construction and Operation Beams and Focusing Automatic Scanning Detail Resolution Review Exercises CHAPTER 4 Imaging Instruments Beam Former Signal Processor Image Processor Display Review Exercises PART 2 DOPPLER PRINCIPLES CHAPTER 5 Doppler Effect Flow Stenoses Doppler Equation Doppler Angle Review Exercises CHAPTER 6 Color-Doppler Instruments Color-Doppler Principle Instruments Doppler-Shift Displays Doppler-Power Displays Review Exercises CHAPTER 7 Spectral-Doppler Instruments Continuous-Wave Instruments Pulsed-Wave Instruments Spectral Analysis Spectral Displays Review Exercises PART 3 MISCELLANEOUS TOPICS CHAPTER 8 Artifacts Propagation Attenuation Spectral Doppler Color Doppler Review Exercises CHAPTER 9 Performance and Safety Performance Measurements Output Measurements Bioeffects Safety Review Exercises CHAPTER 10 Review Comprehensive Exam Glossary Answers to Exercises Appendix A: Compilation of Key Points Appendix B: List of Symbols Appendix C: Compilation of Equations Appendix D: Compilation of Boxes and Tables Appendix E: Mathematics Review Appendix F: Physics Review Appendix G: Additional Material for Exam Preparation Appendix H: Compilation of Advanced Topics Appendix I: Doppler Principles (condensed) References Index
294 citations
"Post-processing of the full matrix ..." refers background in this paper
...Hence commercial dynamic depth focusing systems favour a small number of broad focal zones in transmission with finer focal control on reception [15]....
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