Nondestructive Evaluation, Geosciences, and Electronics

The development of nondestructive evaluation technologies remains an important focus at the Institute. SwRI provides clients in industry and government with the latest advances in inspection techniques, including cylindrically guided wave, eddy current, and SwRI-pioneered magnetostrictive sensor technologies, to detect corrosion and cracking, thus preventing failure of a variety of structures. SwRI's expertise has also led to advances in electronic and microelectronic devices and systems, as well as geophysical modeling and data processing techniques.

High-axial stress in buried pipelines is induced by soil movement, subsidence, or earthquakes. These stresses can damage pipe, producing hazards for service crews and others. The magnetically induced velocity change (MIVC) method can measure throughwall average stress under biaxial stress conditions. In addition, normal variations in the material do not significantly affect measurements. Based on these properties, the technique has been chosen for further development by the Pipeline Research Council International. To make the technique practical for field use, SwRI is designing and building a small, lightweight magnetic circuit that can be handled by a single technician, reducing the number and size of the instruments needed to perform MIVC measurements. The Institute is also investigating MIVC calibration curve variability observed in different pipe grades.

SwRI engineers developed magnetostrictive sensor probes for the long-range guided-wave inspections of plate-like structures, such as large storage tanks and metallic pressure boundaries of containment in nuclear power plants. Here, the probe is tested on a 4 by 20-foot steel plate measuring 0.25-inch thick. The data obtained (right) show a notch found in the plate.

SwRI recently demonstrated the feasibility of using magnetostrictive sensor (MsS™) induced guided wave technology for detecting transverse defects under shelling in railroad rails. With support from the Transportation Technology Center, Inc.(tm), a guided wave mode was identified to detect the transverse defects. The ability to detect these flaws is important because it is difficult for conventional inspection techniques to detect damage in areas under shells, which are separations running parallel to the rail axis. The probes developed can be positioned up to 0.25 inch above the rail and still accurately detect the presence of transverse defects. Non-contacting inspection technology is attractive for rail inspection because contact probes undergo extreme wear conditions against the rail surface. In the future, SwRI will study complex guided wave physics in rails to detect additional defect types. Ultimately, this technology may be used on existing inspection cars as a supplementary inspection method.

SwRI worked with EDM International, Inc. to evaluate the ability of MsS technology to detect corrosion defects in steel utility poles. Preliminary evaluations on poles ranging from 12 to 48 inches in diameter have been promising. Corrosion defects with circumferential cross sections equivalent to 0.05-inch in diameter and up to 15 feet below the ground were found. Tests also indicated that soil does not affect the ability of the technique to detect defects, and there was no indication that the ground sleeve affected the MsS signal. Additional work to transfer technology is planned for next year.

GRI, now operating as the Gas Technology Institute, is sponsoring development of ultrasonic technology (UT) for coupling ultrasound through the high-pressure gas in a pipeline directly into the steel pipe wall, without an intervening liquid couplant. If successful, the gas-coupled technique will make it possible to augment or replace the conventional in-line magnetic inspection process with the more direct and accurate UT method. Prior work at SwRI has shown the basic concept to be feasible. Current efforts are directed toward solving practical problems of transducer design and fabrication.

This pore-scale computer tomography image shows a low-permeability region of unconnected vugs, or cavities, in rock core from a Florida aquifer. Institute scientists use such three-dimensional maps as a starting point to simulate ultrasonic wave propagation for the Department of Energy. The resulting predictions of attenuation and dispersion of seismic waves will help lead to in situ characterization methods of high permeability reservoir pathways and will result in more efficient drilling and pumping practices.

In an investigation of the effects of viscous fluid saturation on seismic wave propagation, Institute scientists compared the attenuation of seismic energy in a rock formation saturated with oil and with water. A model of the rock formation was produced using actual data from a California oil field. The core scale (resolution of mm to cm) model results show that attenuation in the oil-saturated formation is dominated by viscous fluid effects, while attenuation in the water-saturated formation is dominated by elastic scattering effects. This work, along with other projects such as a pore scale (resolution of mm to mm) investigation of core samples from a Florida aquifer for the Department of Energy, will help researchers better delineate reservoir boundaries.

With funding from the Southern Nuclear Operating Company of Alabama, SwRI engineers have developed an inverse cylindrically guided wave technique to detect and characterize borated water corrosion in the thread bolts used in heat exchanger flanges of nuclear power plants. Most corrosion destroys the mode conversion signals that allow the technique to evaluate the bolt. In borated water corrosion, however, the water produces a smooth surface as the bolt corrodes. The smooth surface allows mode-converted signals to form, producing the information needed to find the corrosion. This technology can detect and characterize borated water corrosion levels on the order of 10 percent of the bolt diameter, in bolts approximately 20 inches long and 1.5 inches in diameter.

Engineers at SwRI are developing and evaluating a set of metrics and experiments that can be used to measure the performance, capabilities, and limitations of various biologically based systems within a semi-controlled environment. These systems are being developed by teams of researchers from national laboratories, universities, nonprofit organizations, and industry. The first test is evaluating the effectiveness of trained honeybees in the detection of buried explosives. A one-acre, 40-foot-tall, net-covered structure constructed at SwRI will support these experiments and evaluations for the Defense Advanced Research Projects Agency.

Using internal research funds, SwRI scientists developed the capability for designing and testing microelectromechanical system (MEMS) actuators. This vertical thermal actuator uses resistive heating to deflect the arm toward the substrate. An electrostatic version with integrated flip-up mirrors is being used to produce an optical switch.

Using internal research funds, SwRI has developed the capability to design and test micro-electromechanical system (MEMS) actuators. These actuators use wafer fabrication technology to achieve miniature moving parts - as small as 200 by 50 by 5 µm³ - that respond to electrical and physical stimuli. The MEMS actuators were used to develop an optical cross-connect switch and a miniature, mechanical timed relay switch. The optical cross-connect switch can provide a less expensive and smaller optical switch with an increased port count for high-speed optical networks. The timed relay switch is the first MEMS device to exert force over a significant distance on an object external to the MEMS actuator.

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