Nondestructive Evaluation, Geosciences, and Electronics

SwRI provides industry and government clients with the latest advances in nondestructive evaluation technologies, an important focus at the Institute. Techniques such as SwRI-pioneered magnetostrictive sensor technology detect corrosion and cracking, thus preventing failure of a variety of structures, including pipelines and suspension bridges. SwRI's expertise also has led to advances in ultrasonic evaluation of nuclear reactor vessels, aquifer and hydrocarbon reservoir characterization, optics, and specialized electronics applications.

Institute-developed magnetostrictive sensor (MsS™) technology was used to inspect the entire length of the 100-meter-long suspender ropes on New York City's George Washington Bridge, the largest suspension bridge in the United States. From one probe location, the low-cost MsS technique detects geometric features and defects in the suspender ropes without requiring paint removal.

Sponsored by the Federal Highway Administration (FHWA), Institute engineers tested the applicability of magnetostrictive sensor (MsS) technology, a long-range guided wave inspection technology invented and patented by SwRI, to inspect suspender ropes on the George Washington Bridge in New York City. The low-cost MsS technique allowed detection of geometric features and defects in the suspender without requiring any paint removal. The test results showed that, from a single test location and without scanning the sensor along the rope, the MsS technique could examine the entire 330 feet (100 meters) of suspender rope, including remote, difficult-to-access areas.

SwRI recently extended the capability of the MsS technique for piping inspection from longitudinal (L) wave mode operation to include torsional (T) wave mode operation. The T-mode is a shear wave and therefore does not interact with liquid in the pipe. As a result, the T-mode method (patent pending) provides better inspection data in liquid-filled pipes such as water pipelines or product pipelines in refineries or chemical plants. It also provides superior inspection data in bitumen-coated and buried pipelines. To operate MsS in the T-mode, a magnetized thin nickel strip is bonded to the circumference of a pipe. The T-mode is generated in the nickel strip by using an MsS coil installed over the strip. The generated wave is coupled to the pipe and subsequently propagates along the length of the pipe. Detection is achieved in the reverse manner.

A microelectromechanical systems (MEMS) locking latch and mirror hinge structure is shown in its fabricated state. SwRI engineers designed the device to secure a raiseable plate, such as a mirror, to a moveable base. The latching mechanism requires only one assembly step and securely locks the mirror into a permanent vertical position.

Engineers at SwRI are developing a new generation of data acquisition equipment to enable more efficient ultrasonic (UT) examination of nuclear reactor vessels. Since these examinations can only be performed when the plant is off-line, conducting them in the shortest possible time with the highest reliability is critical to reducing maintenance cost and ensuring safe operation. Commercial data acquisition equipment relies exclusively on computer post-processing, significantly extending the time required to complete an examination. The SwRI specialized acquisition hardware offers real-time preprocessing functionality including integrated UT receivers, time-controlled gain, waveform averaging, data compaction, peak amplitude/location detection, and dual memory buffering for high-speed data uploads. The first commercial use of this new hardware is expected to occur in Japan in 2002.

The Institute has developed a method to extend the applicability of SwRI-patented MsS technology to a wide range of materials for the purpose of long-range guided wave inspection and monitoring of structural integrity. The new method (patent pending) makes use of a magnetized ferromagnetic strip bonded to the structure being inspected. An MsS probe generates guided waves in the strip, which propagates the waves into the material. The ferromagnetic strip is inexpensive and can be attached permanently to the structure. Data collected as a function of time can be compared to a reference data set, and changes caused by corrosion, erosion, or cracking can be detected. Preliminary investigations of this technology on piping and plate detected changes as small as 0.5 percent of the cross-sectional area. Preliminary studies also were conducted to detect changes in bond quality of adhesively bonded structures and defect (cracking and corrosion) growth around fasteners in aluminum. In each case, the technology improved detection of defects by an order of 10.

A new pipe inspection method developed at SwRI makes use of an MsS probe (white band) and a magnetized ferromagnetic strip (silver band). The probe generates guided waves in the strip, which then propagates the waves into the pipe wall. The strip is permanently attached to the pipe, allowing data to be collected at various times and compared to existing data. The result is early detection of erosion, corrosion, or cracking. This inspection method can be used on pipe ranging from 2 to 24 inches in diameter, as well as plate.

SwRI surveyed existing technologies for a major snack food manufacturer to aid in the selection of an appropriate method of process monitoring. To assess the placement of items on a conveyor belt, SwRI investigated various optical techniques, including laser contrast scanning and machine vision. SwRI recommended the most suitable optical sensor available for the task and described an alternative method of process monitoring for those situations in which more accurate data were needed.

The Institute has provided more than 2,000 test specimens and calibration blocks to the nuclear, petrochemical, and oil and gas industries. These specimens are used as the basis for inspecting critical components in nuclear power plants, oil and gas pipelines, and other materials where nondestructive evaluation is necessary. Mockups of actual components are fabricated, and cracks of known size and shape are implanted to simulate the actual cracks and nonconformities that might be found in the field. Institute engineers have developed techniques to create typical fabrication-induced and simulated service-induced flaws in both austenitic and ferritic materials. These flaw manufacturing techniques allow flaws to be placed almost anywhere in a specimen, at any orientation, with very little weld metal surrounding the flaw.

SwRI engineers have developed microelectromechanical systems (MEMS) for a variety of applications including optical switching, electrical relays, and on-chip material analysis. Engineers demonstrated successfully the use of an optical switch that is capable of switching between channels in a few milliseconds. Each actuator is operated electrostatically and has a small mirror on the end to reflect a light beam from one optical fiber to another. The device occupies less than 25 square millimeters and can be scaled to larger numbers of ports. Such a device could be used as a cross-connect switch in an all-optical telecommunications network. Engineers also developed actuators that can produce high forces to interact with macro-scale components, as well as several novel thermally based actuators. They are studying the mechanical and fatigue properties of MEMS devices using these actuators to load and deform a variety of on-chip test structures.

Under sponsorship of the U.S. Department of Transportation, SwRI engineers developed new methods to assess mechanical damage in transmission pipelines during in-line inspections. Evaluation of the methods on full-scale test specimens was implemented with a precision scanner designed to operate inside a pressurized chamber consisting of a damaged pipe, a hemispherical end closure, and a bolted flange, which provided electrical and mechanical control connections to the outside. With the chamber filled with water under controlled pressures, gimbal-mounted sensors were scanned over rectangular areas that included defects. Magnitude and phase data were collected for axial and hoop components of the nonlinear harmonic response. These data were correlated with elastic-plastic finite element analyses of the defects to produce assessment criteria relating nondestructive measurement to defect severity.

The Institute has developed a technique that accurately measures the thickness of aerospace materials to make them safer and lighter and to improve their performance. The thickness of these high-strength single-crystal materials must be determined to achieve maximum safety and performance. Because the velocity of sound varies with direction in single-crystal materials, the use of the wrong velocity could generate inaccuracies in the thickness measurements. The technique developed by SwRI uses ultrasound to compute accurate sound velocity.

The Institute generates models to understand the physics of wave propagation and attenuation in randomly variable media, such as those occurring in aquifers and hydrocarbon reservoirs. These images show z-displacement caused by simulated waves propagating through two three-dimensional model rock cores. The left image is from a homogeneous rock core and shows a regular wave structure. The right image is from a heterogeneous rock core with many small cavities.

SwRI has entered the second phase of work with the Central Research Institute of the Electric Power Industry of Japan for predicting and characterizing degradation in protective MCrAlY coatings used on gas turbine engine blades. Inspection techniques using eddy current testing, previously developed in the laboratory, are being extended for application in the field to turbines. The work also includes the development of specimens and test methods for blades with thermal barrier coatings used in advanced turbines operating at high temperatures.

Since the Defense Advanced Research Projects Agency TENT (Test and Experimentation NeTted) facility became operational in 2000, an aggressive test and experimentation program with biological and biomimetic systems has been conducted in the one-acre, 40-foot-tall enclosure. Experiments have included honeybees seeking explosives, honeybees collecting aerosols, honeybee mating (to exclude Africanized bees), moths seeking pheromones, motion control in rats, and bioantenna sensor testing. In addition to acting as an independent third-party tester, the Institute has supplied scientific and engineering support for the various university researchers who have developed the insect/animal biological systems.

In support of U.S. Marine Corps requirements for non-lethal means to deny entry to certain areas, the Institute identified an anti-traction gel formulation consisting of commercially available materials. When diluted with water, the semisolid gel forms a near-zero coefficient of friction between the coated surface and a foot or tire. The mixture also adheres to vertical surfaces, such as walls and windows, and is effective on a variety of materials, including concrete, wood, grass, glass, and metal. Institute engineers also developed man-portable and vehicle-transportable systems for dispensing the anti-traction formula.

A team of SwRI volunteers has participated in investigations of speech intelligibility by attempting to identify words in computerized self-administered tests. Through this testing, researchers can learn which features of speech are most important to understanding. One significant finding of this ongoing project is that the differences between monaural, stereo, and binaural hearing have a dramatic effect on speech intelligibility. Understanding these differences will help clients design audio equipment that more closely matches how people hear.

Institute scientists developed an integrated approach based on nuclear magnetic resonance (NMR) and acoustic techniques to characterize pore structures in vuggy carbonate aquifers in south Florida. The analysis provided information with which to evaluate NMR core signatures for well log calibration. Pore size distribution, based on digital images, provides the range of relaxation times for micro-, macro-, and vuggy porosity which helps scientists evaluate NMR signatures from core plugs. The information is extrapolated to studies of hydrocarbon reservoirs for purposes of characterizing permeability and porosity.

2001 Annual Report SwRI Home