Jay Fisher - Academia.edu (original) (raw)

Papers by Jay Fisher

1982 American Control Conference, 1982

A signal validation methodology to improve the reliability of the information displayed to the op... more A signal validation methodology to improve the reliability of the information displayed to the operator of a nuclear power plant is presented. The general design methodology is developed and then applied to the steam generator and feedwater subsystem of a typical pressurized water reactor. Using steady-state and transient simulations of this subsystem, including realistic additive sensor noise, the developed algorithm

Journal of Dynamic Systems, Measurement, and Control, 1983

Research and Review Journal of Nondestructive Testing

Guided wave testing is now a widely accepted method for detection of structural damage in many di... more Guided wave testing is now a widely accepted method for detection of structural damage in many different types of components, from pipelines to pressure vessels to tanks. Torsional wave modes (T modes) in pipes and shear horizontal (SH) mode guided waves in plates are good candidates for finding areas with generalized corrosion, due to the absence of fluid coupling effects and their lack of dispersion. However, from our field test experience, certain types of defects are difficult to detect with conventional T mode or SH mode guided wave probes. Gradual wall thinning is one such type of defect; another is crack-like defects in or close to welds or penetrations in the pipe. Recently, Southwest Research Institute (SwRI) has developed a new sensor configuration and scanning system that overcomes these limitations. We have recently developed a linear scanning magnetostrictive transducer (MsT) probe system, in which a FeCo strip wound with radio frequency (RF) coils is attached to the st...

Proceedings., International Conference on Image Processing

This paper describes a new technique for processing eddy current images as used in nondestructive... more This paper describes a new technique for processing eddy current images as used in nondestructive evaluation of materials. A simple description of the image formation physics is given followed by a description of the current state of the art in image processing. Eddy current testing in 2-D results in a sequence of complex valued images that can be linearly combined to enhance the signal-to-noise ratio (SNR) of features of interest. A new approach that selects weights for a linear combination of the images based on SNR maximization is presented. Results on experimental data show SNR improvements up to 1100 percent over traditional two-frequency techniques. The new algorithm presented is general to any number of frequencies, and results of four-frequency processing are given.

One effective way to inspect or monitor large components such as pipes or plates is to use guided... more One effective way to inspect or monitor large components such as pipes or plates is to use guided wave testing (GWT) systems. A number of commercially available GWT systems suitable for inspection of various components at ambient and elevated temperatures have been developed by different groups. Development of GWT systems for monitoring at high temperatures is very challenging, because the sensor is exposed to a harsh environment for long periods. Some experimental work and findings related to SHM of pipes operating at temperatures up to 200°C have been reported. In the nuclear and petrochemical industries, however, there is a need for monitoring of components operating at temperatures up to 650°C. Magnetostriction is promising transduction mechanism for high temperature applications because generation of elastic waves in materials does not require soldered joints, which a limiting factor in other transducer designs. The work presented here demonstrates significant progress in the g...

The use of guided waves for long-range inspection of components is a rapidly growing segment of t... more The use of guided waves for long-range inspection of components is a rapidly growing segment of the NDE service business. Magnetostrictive sensors utilizing ferromagnetic strip material for the transduction effect have proven to be very effective for guided wave testing on a variety of components. There is still a demand for enhanced sensor characterization and the development of specific sensor characteristics. A novel magnetostrictive transducer (MsT) utilizing a reversed Wiedemann effect was introduced to the market in 2010 [1] and opened a number of new possibilities in guided wave testing. The most challenging area is structural health monitoring of components operating at elevated temperature. An extremely robust transducer design was developed and tested for this application; it is capable of functioning at high temperatures as well as stresses induced by thermal cycling. Another recent development is an automated omnidirectional probe suitable for screening of large shells s...

Materials (Basel, Switzerland), Jan 8, 2018

Magnetostrictive transduction has been widely utilized in nondestructive evaluation (NDE) applica... more Magnetostrictive transduction has been widely utilized in nondestructive evaluation (NDE) applications, specifically for the generation and reception of guided waves for the long-range inspection of components such as pipes, vessels, and small tubes. Transverse-motion guided wave modes (e.g., torsional vibrations in pipes) are the most common choice for long-range inspection applications, because the wave motion is in the plane of the structure surface, and therefore does not couple well to the surrounding material. Magnetostrictive-based sensors for these wave modes using the Wiedemann effect have been available for several years. An alternative configuration of a sensor for generating and receiving these transverse-motion guided waves swaps the biasing and time-varying magnetic field directions. This alternative design is a reversed Wiedemann effect magnetostrictive transducer. These transducers exhibit a number of unique features compared with the more conventional Wiedemann sens...

Thesis Massachusetts Institute of Technology 1978 Source American Doctoral Dissertations Source Code X1978, 1978

An automated inspection system based on eddy current testing (ET) techniques has been developed t... more An automated inspection system based on eddy current testing (ET) techniques has been developed to inspect turbine wheel blades on the APU used in NASA's Space Transportation system. The APU is a hydrazine-powered gas turbine with a 15-cm diameter Rene 41 turbine wheel, which has 123 first-stage blades and 123 second-stage blades. The flaw detection capability of the ET system is verified through comparison with fluorescent penetrant test results. Results of the comparison indicate that ET is capable of inspecting surfaces with very restrictive geometries. The ET capability requires development of probes with extremely small coils to allow inspection within 0.4 mm of the blade root and the leading and trailing edges of the blade and within a height restriction of less than 1 mm. The color 2D presentation of the ET data provided crack-growth pattern and length information similar to those found with visual techniques. It also provided visual clues to minimize geometry effects such as generated from blade edges, a neighoring blade, and changes in the blade thickness.

Review of Progress in Quantitative Nondestructive Evaluation, 1997

Journal of Pressure Vessel Technology, 1996

Over the last two years, concern has been generated about the capabilities of performing nondestr... more Over the last two years, concern has been generated about the capabilities of performing nondestructive evaluation (NDE) of the closure-head penetrations in nuclear-reactor pressure vessels. These penetrations are primarily for instrumentation and control rod drive mechanisms (CRDMs) and are usually thick-walled Inconel tubes, which are shrink-fttted into the steel closure head. The penetrations are then welded between the outside surface of the penetration and the inside surface of the closure head. Stress corrosion cracks initiating at the inner surface of the penetration have been reported at several plants. Through-wall cracks in the CRDM penetration or CRDM weld could lead to loss of coolant in the reactor vessel. The CRDM penetration presents a complex inspection geometry for conventional NDE techniques. A thermal sleeve, through which pass the mechanical linkages for operating the control rods, is inserted into the penetration in such a way that only a small annulus (nominall...

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Ultrasonic interrogation of metal alloys has been demonstrated to be effective for monitoring fat... more Ultrasonic interrogation of metal alloys has been demonstrated to be effective for monitoring fatigue-induced damage in structural health monitoring (SHM) frameworks. However, traditional probability of detection (POD) approaches as used for nondestructive evaluation (NDE) are not directly applicable given the fixed nature of the ultrasonic probe(s). One difference is that there is a lack of variation in SHM sensor response due to human factors. Thus, the primary source of variability is related to the crack geometry itself. Another difference is that experimental derivations of POD curves for SHM are exceptionally burdensome. Since the probes are fixed, repeated "inspections" with the same probes and defect provide no additional information. Thus, given a particular ultrasonic SHM method, a model-driven methodology for POD may be necessary. This paper discusses the differences between SHM and NDE and the relationship to POD interpretation. Also, an SHM case study is presented for the development of POD curves using a model-assisted formulation. Variations associated with the structure state, such as the fatigue process, environmental effects and electronic noise, are approximated from experimental observations for inclusion in POD curve creation. The specific application analyzed is monitoring of fatigue cracks near fastener holes with an energy-based feature of through-transmission ultrasonic waveforms.