Glenn M. Light

Magnetostrictive sensor for active health monitoring in structures

A flat magnetostrictive sensor for active health monitoring of a large area of a structure has been developed. The sensor consists of a thin nickel foil and a coil placed over the nickel and, much like a strain gauge, is permanently bonded to the surface of a structure under monitoring. When activated, the sensor generates guided waves in the structure for interrogation and detects signals that are reflected back from the structural geometries and defects in the structure. Since guided waves can travel a long distance in the structure, a large area of the structure can be interrogated and monitored by using the sensor. By periodically acquiring the data and comparing it with the baseline data established at the time of sensor installation, structural changes occurred over that time can be quickly determined for suitable structural management decision. In addition to the ability to actively inspect and monitor a large area of the structure, the sensor is also rugged and inexpensive and therefore has high potential for practical use. As an example of its applicability to aircraft structure, data showing the monitoring of defect growth in fastener holes in a wing structure are presented.

Cylindrically Guided Waves in a Transversely Isotropic Shaft

The propagation of a longitudinal wave in an isotropic cylinder has been used in the inspections of pumps and shafts of a nuclear power plant [1]. An ultrasonic technique called the “cylindrically guided wave technique” (CGWT) has been developed that can detect simulated circumferential defects through long metal paths in metallic materials being used for bolts and studs [1]. In the recent development of the sizing process for the cylindrically guided wave technique, the wave scattering at the circumferential crack can be formulated in terms of the guided cylindrical waves which mathematically result from the cylinder frequency equation. Therefore, a detailed investigation of the cylinder frequency equation is in order in the sizing process for bolt and pump-shaft inspections.

Ultrasonic transducer for extreme temperature environments

An ultrasonic piezoelectric transducer that is operable in very high and very low temperatures. The transducer has a dual housing structure that isolates the expansion and contraction of the piezoelectric element from the expansion and contraction of the housing. Also, the internal components are made from materials having similar coefficients of expansion so that they do not interfere with the motion of the piezoelectric element.

Review of magnetostrictive transducers (MsT) utilizing reversed Wiedemann effect

Magnetostrictive transduction has been widely utilized in NDE applications, specifically for generation and reception of guided waves for 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 typical choice for long-range inspection applications because the wave motion is in the plane of the structure. Magnetostrictive-based sensors have been available for several years for these wave modes based on the Wiedemann effect. For these sensors, a permanent magnetic bias is applied that is perpendicular to the direction of the propagated guided wave. This bias field strains the material that the guided wave is generated in preferentially in the desired particle motion direction. A time-varying magnetic field oriented parallel to the direction of guided wave propagation is also induced in the material. This time-varying field is induced using an electric coil located near the material surface. The intera...

Application of the cylindrically guided wave technique for bolt and pump shaft inspections

Abstract Elastic wave propagation in a bounded medium significantly differs from that in an unbounded medium. The bounded medium in the form of a cylinder acts like a solid waveguide directing the wave with its geometry. A continuous or a pulsed wave interacts with cylindrical boundaries producing mode-converted signals in addition to the backwall echo. The signals are received at constant time intervals directly proportional to the diameter of a solid cylindrical object such as a bolt or an anchor stud. The Cylindrically Guided Wave Technique (CGWT) makes intelligent use of the mode-converted signals, or trailing pulses, to detect corrosion wastages and cracks in cylindrical objects.

Transmission line model for simulation of guided-wave defect signals in piping

A simple transmission line model for analytically simulating the guided-wave signal reflected from a volumetric defect of arbitrary shape in piping is described. In the model, the guided-wave interaction with a defect is treated as the one-dimensional problem of plane wave reflection from a boundary of multilayered media of different acoustic impedances in a transmission line. Results of simulation show good qualitative agreement with experimentally measured signals.

Magnetostrictive Sensor Long-Range Guided-Wave Technology for Long-Term Monitoring of Piping and Vessels

Long-range guided-wave technology is a recently developed inspection method for surveying large areas of structures and is widely used as a screening tool for corrosion defects in piping. Because of its ability to examine a structure over a long distance, this technology with permanently installed probes is ideal for on-line long-term structural health monitoring of pressure vessels or piping for improved safety, operation, and maintenance. The magnetostrictive sensor (MsS) technology is a guided-wave technology developed at authors’ institution. It uses a probe that consists of thin ferromagnetic strip and coil for guided-wave generation and detection. The MsS probe is inexpensive and can be used on components up to 300°C. Applications of the MsS for long-term monitoring of pressure vessels and piping are presented, including the configuration of MsS probes, types of guided-wave mode used, defect types detectable with guided waves, and example data.Copyright

Embedded Thin-Film Sensor for Crack Detection and Monitoring in Fracture Critical Turbine Engine Components

The development and implementation of an integrated health management system has the potential to significantly enhance the reliability and readiness of high-value assets, while concurrently decreasing sustainment costs. A key aspect of this approach is on-board sensing to provide continual feedback on the evolving damage state at the material and component level. This paper summarizes the development and status of an embedded, thin-film, wireless, sensor for detecting and monitoring material damage state (i.e., cracking) in critical turbine engine components at elevated temperature. The potential benefits of on-board detection and monitoring of defects, as compared to periodic depot inspections, were previously assessed using probabilistic simulations. These results provided target sensitivities for the development of the thin-film sensor. The status of the sensor system is summarized including its ability to generate elastic waves and detect/monitor fatigue cracks in engineering materials at temperatures to 500°F (260°C). Crack detection sensitivities with and without load application are compared, as well as those for wired versus wireless signal transmission.© 2006 ASME

ULTRASONIC WAVEGUIDE TECHNIQUE FOR DETECTION OF SIMULATED CORROSION WASTAGES

Abstract Elastic wave propagation in a bounded medium significantly differs from that in an unbounded medium. The bounded medium in the form of a cylinder acts like a solid waveguide directing the wave with its geometry. A continuous or a pulsed wave interacts with cylindrical boundaries producing mode-converted signals in addition to the backwall echo. The signals are received at constant time Intervals directly proportional to the diameter of a solid cylindrical object such as a bolt or an anchor stud. The Cylindrically Guided Wave Technique (CGWT) makes intelligent use of the mode-converted signals, or trailing pulses, to detect corrosion wastages in cylindrical objects.

Radiographic image processing for industrial applications

One advantage of working with digital images is the opportunity for enhancement. While it is important to preserve the original image, variations can be generated that yield greater understanding of object properties. It is often possible to effectively increase dynamic range, improve contrast in regions of interest, emphasize subtle features, reduce background noise, and provide more robust detection of faults. This paper describes and illustrates some of these processes using real world examples.