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Thomas Powers

Bio: Thomas Powers is an academic researcher from Babcock & Wilcox. The author has contributed to research in topics: Signal & Ultrasonic sensor. The author has an hindex of 7, co-authored 7 publications receiving 1133 citations.

Papers
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Patent
01 Aug 1986
TL;DR: An ultrasonic apparatus for testing a material comprises an oscillator (10) which generates a selected frequency in the ultrasonic range, and a transducer (1) is connected to the oscillator for applying an ultrasonic signal to the material and for receiving an echo signal back from the material.
Abstract: An ultrasonic apparatus for testing a material comprises an oscillator (10) which generates a selected frequency in the ultrasonic range. A transducer (1) is connected to the oscillator (10) for applying an ultrasonic signal to the material and for receiving an echo signal back from the material. A phase detector (5) receives the echo signal and an in-phase oscillator signal to generate a first display signal, and a phase detector (6) receives a quadrature signal (90° out of phase from the oscillator signal) and the echo signal to generate a second display signal. The first and second display signals are utilised in a visual display, such as a cathode ray tube (8), to generate an image. The image changes according to the phase shift between the ultrasonic signal transmitted into the material and the echo signal, which, in turn, can be utilised to determine the presence and depth of a flaw or boundary in the material.

1,017 citations

Patent
03 Sep 1991
TL;DR: An ultrasonic method and apparatus for measuring liquid level in a vessel employing an acoustic waveguide (16) connected to an ultrasonic transducer (14) and the vessel (18) is described in this article.
Abstract: An ultrasonic method and apparatus for measuring liquid level in a vessel employing an acoustic waveguide (16) connected to an ultrasonic transducer (14) and the vessel (18). Guiding means (24) situated inside a vessel (18) directs the acoustic energy pulse to a surface (22) of the liquid. The acoustic energy pulse is reflected from the surface (22) and returned along the guiding means (24) to the acoustic waveguide (16). A pulser/receiver (10) connected thereto measures the reflected acoustic energy pulse for determining liquid level from the transit time.

61 citations

PatentDOI
TL;DR: In this paper, an electromagnetic acoustic transducer comprising a magnet and a coil is located in the interior space of a bolt near the bolt, where the coil provides a current while the magnet provides a magnetic field such that the magnet and the coil generate an ultrasonic signal with the bolt.
Abstract: A device for measuring a load on a part such as a bolt (2), comprises a socket (15) have walls defining an interior space (17) wherein the socket engages the bolt for transmitting a load to the bolt. An electromagnetic acoustic transducer (20) comprising a magnet (28) and a coil (26) is located in the interior space of the socket near the bolt. The coil provides a current while the magnet provides a magnetic field such that the magnet and the coil generate an ultrasonic signal with the bolt. A detector is used to detect and measure a change in the ultrasonic signal at the bolt.

21 citations

Patent
28 Dec 1987
TL;DR: In this article, a method for inspecting the surface of a workpiece for the presence of flaws using a ferrofluid as a penetrant which is applied to surface of the workpiece and then scanning the surface with electrical detection means placed adjacent to the surface for providing responses indicative of the existence of flaws.
Abstract: A method for inspecting the surface of a workpiece for the presence of flaws using a ferrofluid as a penetrant which is applied to the surface of the workpiece and then scanning the surface of the workpiece with electrical detection means placed adjacent to the surface for providing responses indicative of the presence of flaws in the surface of the workpiece. If desired, a magnetic field can be used to induce the flow of the ferrofluid into any flaws prior to inspection, and for post-inspection cleanup as well. By the use of a ferrofluid, the sensitivity of the electrical detection means, advantageously of the eddy current type, is enhanced in typical applications, and also allows the use of an eddy current probe to inspect workpieces made of nonconductive and/or nonferromagnetic materials.

10 citations

Patent
15 Jan 1985
TL;DR: In this paper, the authors present a linear scan UL detector that stores the reflected ultrasonic signals from each of a plurality of locations along a scan path over a piece of material to be tested.
Abstract: ENHANCEMENT OF LINEAR SCAN ULTRASONICS ABSTRACT OF THE DISCLOSURE An ultrasonic testing method and apparatus stores the reflected ultrasonic signals from each of a plurality of locations along a scan path over a piece of material to be tested. For each individual location, the reflected signal at that location is added to contributing signals from each other location to produce a composite signal which has a good signal-to-noise ratio. The contributing signals from each other location is formed by multiplying the signal of those other locations by a corrective phase shift factor which is a characteristic of a time delay for a reflected signal from the other locations to the individual location of interest. The contributing signal from each other location thus represents a rotated reflected signal from the other locations.

10 citations


Cited by
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Book
11 Aug 2014
TL;DR: The semi-analytical finite element method (SAFE) has been used for guided wave modeling as discussed by the authors, which has been shown to be useful in the analysis and display of non-destructive testing.
Abstract: Preface Acknowledgments 1. Introduction 2. Dispersion principles 3. Unbounded isotropic and anisotropic media 4. Reflection and refraction 5. Oblique incidence 6. Waves in plates 7. Surface and subsurface waves 8. Finite element method for guided wave mechanics 9. The semi-analytical finite element method (SAFE) 10. Guided waves in hollow cylinders 11. Circumferential guided waves 12. Guided waves in layered structures 13. Source influence on guided wave excitation 14. Horizontal shear 15. Guided waves in anisotropic media 16. Guided wave phased arrays in piping 17. Guided waves in viscoelastic media 18. Ultrasonic vibrations 19. Guided wave array transducers 20. Introduction to guided wave nonlinear methods 21. Guided wave imaging methods Appendix A: ultrasonic nondestructive testing principles, analysis and display technology Appendix B: basic formulas and concepts in the theory of elasticity Appendix C: physically based signal processing concepts for guided waves Appendix D: guided wave mode and frequency selection tips.

823 citations

Journal ArticleDOI
TL;DR: In this article, the authors provide a vision of ultrasonic guided wave inspection potential as we move forward into the new millennium and provide a brief description of the sensor and software technology that will make ultrasonic guidance wave inspection commonplace in the next century.
Abstract: Ultrasonic guided wave inspection is expanding rapidly to many different areas of manufacturing and in-service inspection. The purpose of this paper is to provide a vision of ultrasonic guided wave inspection potential aswe move forward into the new millennium. An increased understanding of the basic physics and wave mechanics associated with guided wave inspection has led to an increase in practical nondestructive evaluation and inspection problems. Some fundamental concepts and a number of different applications that are currently being considered will be presented in the paper along with a brief description of the sensor and software technology that will make ultrasonic guided wave inspection commonplace in the next century.

623 citations

Journal ArticleDOI
TL;DR: In this paper, the state-of-the-art in piezoelectric-wafer active sensors structural health monitoring and damage detection is reviewed, and two main detection strategies are considered: the E/M impedance method for near field damage detection, and wave propagation methods for far-field damage detection.
Abstract: Piezoelectric wafer active sensors may be applied on aging aircraft structures to monitor the onset and progress of structural damage such as fatigue cracks and corrosion. The state of the art in piezoelectric-wafer active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) the Electro–Mechanical (E/M) impedance technique are cited and briefly discussed. For health monitoring of aging aircraft structures, two main detection strategies are considered: the E/M impedance method for near field damage detection, and wave propagation methods for far-field damage detection. These methods are developed and verified on simple-geometry specimens and on realistic aging aircraft panels with seeded cracks and corrosion. The experimental methods, signal processing, and damage detection algorithms are tuned to the specific method used for structural interrogation. In the E/M impedance method approach, the high-frequency spectrum, representative of the structural resonances, is recorded. Then, overallstatistics damage metrics can be used to compare the impedance signatures and correlate the change in these signatures with the damage progression and intensity. In our experiments, the (1 � R 2 ) 3 damage metric was found to best fit the results in the 300–450 kHz band. In the wave propagation approach, the pulse-echo and acousto-ultrasonic methods can be utilized to identify the additional reflections generated from crack damage and the changes in transmission phase and velocity associated with corrosion damage. The paper ends with a conceptual design of a structural health monitoring system and suggestions for aging aircraft installation utilizing active-sensor arrays, data concentrators, wireless transmission, and a health monitoring and processing unit.

587 citations

Journal Article
TL;DR: In this article, a review of electrochemical and non-decreasing techniques from the point of view of corrosion assessment and their applications to bridges, buildings and other civil engineering structures is presented.

460 citations

Journal ArticleDOI
TL;DR: In this paper, two modifications of this technique have been developed: Vibro-Modulation (VM) and Impact-Induced Vibrations (IM), employing CW and impact-induced vibrations, respectively.
Abstract: Recent theoretical and experimental studies demonstrated that a weakly or incompletely bonded interfaces exhibit highly nonlinear behavior. One of acoustic manifestations of such nonlinearity is the modulation of a probing high-frequency ultrasonic wave by low-frequency vibration. The vibration varies the contact area modulating the phase and amplitude of higher frequency probing wave passing through the interface. In the frequency domain, the result of this modulation manifests itself as side-band spectral components with respect to the frequency of the probing wave. This modulation effect has been observed experimentally for various materials (metals, composites, concrete, sandstone, glass) with various types of contact-type defects (interfaces): cracks, debondings, delaminations, and microstructural material damages. Study of this phenomenon revealed correlation between the developed modulation criterion and the quantitative characteristics of the interfaces, such as its size, loading condition, and bonding strength. These findings have been used for the development of an innovative nondestructive evaluation technique, namely Vibro-Acoustic Modulation Technique. Two modifications of this technique have been developed: Vibro-Modulation (VM) and Impact-Modulation (IM), employing CW and impact-induced vibrations, respectively. The examples of applications of these methods include crack detection in steel pipes, aircraft and auto parts, bonded composite plates etc. These methods also proved their effectiveness in the detection of cracks in concrete.

390 citations