A New Technique for Clutter Reduction in Ultrasonic Imaging

Newhouse, V.L.; Karpur, Prasanna; Rose, Joseph L.; Amir, I.

doi:10.1109/ultsym.1985.198664

Cited by 7 publications

(4 citation statements)

References 3 publications

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“…Time-averaged mean and mean-squared values were effective when the back surface response was relatively strong but were relatively ineffective for low amplitude signals (Hargreaves 1988). However, split-spectrum based polarity thresholding (Shankar et al 1989), either alone or in combination with other processing techniques such as minimization (Newhouse et al 1985) appears to significantly improve detectability in CASS specimens. A maximum entropy model of spectral analysis also had limited success (Hargreaves 1988).…”

Section: Ultrasonic Classification Of Centrifugally Cast Stainless mentioning

confidence: 98%

Ultrasonic Characterization of Cast Austenitic Stainless Steel Microstructure: Discrimination between Equiaxed- and Columnar-Grain Material ? An Interim Study

Ramuhalli¹,

Good²,

Diaz³

et al. 2009

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Executive SummaryUltrasonic nondestructive evaluation (NDE) and inspection of cast austenitic stainless steel (CASS) components used in the nuclear power industry is neither as effective nor reliable as is needed. With current ultrasonic methods these limitations are in large part due to the detrimental effects of wavemicrostructure interactions on the interrogating ultrasonic beam and interference that results from ultrasonic backscatter. The root cause of these phenomena is the coarse-grain microstructure inherent to this class of materials. Some ultrasonic techniques are found to perform better for particular microstructural classifications and this has led to the hypothesis that an ultrasonic inspection can potentially be optimized for a particular microstructural class. For optimized ultrasonic technique selection, methods will be needed to reliably classify the microstructure in-situ, which is then used to guide the selection and optimization of the inspection. This document summarizes scoping experiments that investigate potential in-situ ultrasonic methods for classification and/or characterization of the material microstructures in CASS components, when making measurements from the outside surface of a pipe.The focus of this preliminary study was to evaluate ultrasonic measurement methods to determine if responses from different known microstructures can be differentiated and hence if in-service characterization of cast austenitic stainless steel (CASS) is potentially feasible. On the basis of an initial literature evaluation, two ultrasonic parameters, (i) the time-of-flight ratio between shear and longitudinal waves and (ii) the attenuation for normal incidence longitudinal waves, were selected for investigation. Scoping experiments were performed to determine the ability of these measured parameters to discriminate between different microstructures in CASS components. The objective was to determine if a more thorough and staged exploration would be justified in progressing toward the real-time characterization of CASS for use as feedback to optimize current or new ultrasonic in-service inspection methodologies. With this objective in mind, measurements were restricted to techniques that potentially should be robust if carried forward to an eventual field implementation.The first parameter investigated was a time-of-flight ratio of a normal incidence shear wave to that of a normal incidence longitudinal wave (TOFRSL). The ratio removes dependency on component thickness which may not be accurately known or reported in the field. The second parameter was the attenuation of a normal incidence longitudinal wave. The selected CASS specimens used for the experimental study were five equiaxed-grain material samples and five columnar-grain material samples, and these were used for a two-class discrimination problem.TOFRSL estimates and a threshold algorithm classified all 10 material samples correctly and indicated a potentially reliable and robust technique. Qualitative longitudinal wave attenuation estimate...

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Section: Ultrasonic Classification Of Centrifugally Cast Stainless mentioning

confidence: 98%

Ultrasonic Characterization of Cast Austenitic Stainless Steel Microstructure: Discrimination between Equiaxed- and Columnar-Grain Material ? An Interim Study

Ramuhalli¹,

Good²,

Diaz³

et al. 2009

View full text Add to dashboard Cite

show abstract

“…Time-averaged mean and mean-squared values were effective when the back surface response was relatively strong but were relatively ineffective for low amplitude signals (Hargreaves 1988). However, split-spectrum based polarity thresholding (Shankar et al 1989), either alone or in combination with other processing techniques such as minimization (Newhouse et al 1985) appears to significantly improve detectability in challenging materials, such as CASS specimens. A maximum entropy model of spectral analysis also had limited success (Hargreaves 1988).…”

Section: Figure 43 Nominal and Faulted Gaussian Distributionsmentioning

confidence: 99%

Prognostics and Health Management in Nuclear Power Plants: A Review of Technologies and Applications

Coble¹,

Ramuhalli²,

Bond³

et al. 2012

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Recent years have seen a resurgence of nuclear power worldwide, with interest in extending the operating life of the approximately 436 reactors currently in service (as of March, 2012), 61 new reactors being constructed, and as many as 162 under consideration. Renewed worldwide interest in nuclear power has been somewhat tempered by the March 2011 incident at Fukushima Dai-ichi in Japan. However, nuclear power is still considered a key element in meeting future worldwide sustainable energy, energy security, and emissions goals. Currently, three separate thrusts to safe and economical nuclear power development for energy security are being pursued in the United States: (i) longer term operation for the legacy fleet, from 40-60 and possibly 60-80 years; (ii) near-term new nuclear plants with a 60-year design life; and (iii) small modular reactors, which are expected to employ light water reactor technology at least in the medium term. Within these activities, attention is turning to enhanced methods for plant component and structural health management.The operating U.S. fleet includes 104 light water reactors. In addition, there are now (as of May 2012) four new nuclear power plants (AP-1000 plants) under construction in the United States, and two delayed plants are being completed by the Tennessee Valley Authority. There is also interest in the United States in small modular reactors (SMRs), which could be easier to match to existing grid infrastructure and which could replace aging coal fired plants. The current low price for natural gas presents a challenge to the economics of nuclear power, at least in the short term; however, some recent studies have demonstrated that nuclear generation will be competitive in the longer term (at least in some markets) when anticipated escalation in gas prices and the cost of building, operating, and maintaining gas-fired plants are considered over those same time periods.This report reviews the current state of the art of prognostics and health management (PHM) for nuclear power systems and related technology currently applied in field or under development in other technological application areas, as well as key research needs and technical gaps for increased use of PHM in nuclear power systems. The historical approach to monitoring and maintenance in nuclear power plants (NPPs), including the Maintenance Rule for active components and Aging Management Plans for passive components, are reviewed. An outline is given for the technical and economic challenges that make PHM attractive for both legacy plants through Light Water Reactor Sustainability (LWRS) and new plant designs. There is a general introduction to PHM systems for monitoring, fault detection and diagnostics, and prognostics in other, non-nuclear fields. The state of the art for health monitoring in nuclear power systems is reviewed. A discussion of related technologies that support the application of PHM systems in NPPs, including digital instrumentation and control systems, wired and wireless sensor techno...

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“…Time-averaged mean and mean-squared values were effective when the back surface response was relatively strong but were relatively ineffective for low amplitude signals. 24 However, split-spectrum based polarity thresholding, 33 either alone or in combination with other processing techniques such as minimization 35 appears to significantly improve detectability in CASS specimens. A maximum entropy model of spectral analysis also had limited success.…”

Section: Algorithms For Cassmentioning

confidence: 99%

Evaluation of signal processing tools for improving phased array ultrasonic weld inspection

et al. 2011

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Cast austenitic stainless steel (CASS) that was commonly used in U.S. nuclear power plants is a coarse-grained, elastically anisotropic material. In recent years, low-frequency phased-array ultrasound has emerged as a leading candidate for the inspection of welds in CASS piping, due to the relatively lower interference in the measured signal from ultrasonic backscatter. However, adverse phenomena (such as scattering from the coarse-grained microstructure, and beam redirection and partitioning due to the elastically anisotropic nature of the material) result in measurements with a low signal-to-noise ratio (SNR), and increased difficulty in discriminating between signals from flaws and signals from benign geometric factors. There is therefore a need for advanced signal processing tools to improve the SNR and enable rapid analysis and classification of measurements. This paper discusses recent efforts at PNNL towards the development and evaluation of a number of signal processing algorithms for this purpose. Among the algorithms being evaluated for improving the SNR (and, consequently, the ability to discriminate between flaw signals and non-flaw signals) are wavelets and other time-frequency distributions, empirical mode decompositions, and split-spectrum processing techniques. A range of pattern-recognition algorithms, including neural networks, are also being evaluated for their ability to successfully classify measurements into two or more classes. Experimental data obtained from the inspection of a number of welds in CASS components are being used in this evaluation.

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A New Technique for Clutter Reduction in Ultrasonic Imaging

Cited by 7 publications

References 3 publications

Ultrasonic Characterization of Cast Austenitic Stainless Steel Microstructure: Discrimination between Equiaxed- and Columnar-Grain Material ? An Interim Study

Ultrasonic Characterization of Cast Austenitic Stainless Steel Microstructure: Discrimination between Equiaxed- and Columnar-Grain Material ? An Interim Study

Prognostics and Health Management in Nuclear Power Plants: A Review of Technologies and Applications

Evaluation of signal processing tools for improving phased array ultrasonic weld inspection

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