By John German
Commercial aircraft one day might be fitted with networks of sensors that check for defects continuously. Like nerve endings in a human body, in situ sensors offer levels of vigilance and sensitivity to problems that periodic checkups cannot, says Dennis Roach of Infrastructure Assurance and Nondestructive Inspection Dept. 6416.
Such full-time monitoring could supplement, reduce, or even eliminate scheduled structural inspections of aircraft, he says.
“With sensors continually checking for the first signs of wear and tear, you can restrict your maintenance efforts to when you need human intervention,” he says.
Dennis leads a Sandia team that is evaluating some of the first sensors for structural health monitoring, or SHM, for aircraft and other safety-critical equipment.
Initially the sensors are envisioned for hot spots where flaws are expected to form. Eventually the work could lead to “smart structures” with many sensors that would self-diagnose and signal an operator when repairs are needed.
Aircraft maintenance and repairs represent about a quarter of the US commercial airline fleet’s operating costs, and those costs are rising as aircraft in the fleet age, many well beyond their design lifetimes, says Dennis.
Among the defects commonly encountered are fatigue damage, hidden cracks in hard-to-reach locations, disbonded joints, erosion, impact damage, and corrosion.
Besides aircraft, SHM techniques could monitor the structural well-being of spacecraft, weapons, rail cars, bridges, oil recovery equipment, buildings, armored vehicles, ships, wind turbines, nuclear power plants, and fuel tanks in hydrogen vehicles.
“Any structure that operates in a fatigue environment with cyclical stresses or other structurally degrading environment could benefit from frequent sensor monitoring rather than relying only on scheduled inspections,” he says.
Extension of NDI
Sandia’s SHM work is an extension of its Airworthiness Assurance Program, which for years has focused on development and evaluation of nondestructive inspection (NDI) technologies that aid human inspectors as they go over an aircraft frame or fuselage skin inch by inch looking for the consequences of aging.
Boeing’s recent incorporation of an in situ, or permanently mounted, crack-detection sensor into its NDI standard practices manual for Boeing airframes is the first time a manufacturer has adopted SHM techniques — evidence that the industry is ready to consider new ways of ensuring the safety of aircraft beyond NDI-assisted human inspection, says Dennis.
Several commercial airlines are considering applications, including Delta and Northwest, which have petitioned the Federal Aviation Administration to use embedded crack detection sensors to address specific maintenance requirements.
“When we set out to do NDI, in the back of our minds we knew that eventually we wanted to create smart structures that ‘phone home’ when repairs are needed or when the remaining fatigue life drops below acceptable levels,” Dennis says. “This is a huge step in the evolution of NDI.”
The Sandia team already has developed or evaluated several types of inexpensive, reliable sensors that can be retrofitted into aircraft structures to detect cracks, corrosion, and other flaws (see “In situ monitoring with CVM sensors” at right).
In the future, members of a ground crew might plug a diagnostic system or a laptop into a port on the aircraft and download structural health data collected during flight. Ultimately an integrated network of sensors could monitor not only structural materials but also the health of electronics, hydraulics, avionics, and other systems.
Sandia is part of a group Dennis and other industry partners formed in November 2006 — the Aerospace Industry Steering Committee for Structural Health Monitoring — to address the growing demand for standardized SHM procedures and certification requirements. The international group includes manufacturers, regulators, government agencies, the military, and universities.
The Sandia team also continues to seek acceptance for SHM outside the aerospace industry. In a Laboratory Directed Research and Development (LDRD) effort, SHM principles are being applied to monitoring bridges, buildings, and other civil infrastructures. The work has produced a mountable eddy-current sensor that uses electromagnetic waves to detect deep subsurface cracks in metal structures.
Another program with Syncrude Canada Ltd. is studying the application of SHM sensors for real-time health monitoring of mining and oil-recovery equipment.
“In other words, there is recognition that SHM’s time has come, an opinion you would not have heard from many people a few years ago,” says Dennis.
Sandia has developed or evaluated several types of inexpensive, reliable sensors that can be retrofitted into aircraft structures for structural health monitoring (SHM).
One promising sensor, a Comparative Vacuum Monitoring (CVM) sensor, is a self-adhesive rubber patch, ranging from dime- to credit-card-sized. The rubber’s underside is laser-etched with rows of tiny, interconnected channels or galleries, to which air pressure is applied. Any propagating crack in the material under the sensor breaches the galleries, and the resulting change in pressure is monitored.
The system can be set up to alarm or signal a remote site. The sensors — manufactured by Structural Monitoring Systems Inc. (SMS) of Australia — are inexpensive, reliable, durable, and easy to apply, says Dennis. More important, they provide equal or better sensitivity than is achievable with conventional inspection methods, he says.
The Sandia team first conducted laboratory evaluations of CVM sensors on different materials with a variety of thicknesses and structural shapes. Field evaluations of 22 CVM sensors on three commercial aircraft — a Northwest 757 and 767 and a Delta DC-9 — beginning in April 2005 helped validate the lab tests.
As a result of the work, Boeing recently included CVM technology in the Boeing Common Methods NDI Manual, which allows airlines to work with Boeing and the FAA to seek certification of the sensors for specific applications on specific aircraft.
This recognition of in situ crack detection as an allowable inspection method is an aviation industry first, says Dennis.
The approval is the culmination of a comprehensive, two-year validation program by
Sandia in cooperation with the FAA, Boeing, SMS, a number of US airlines, and the University of Arizona. Work on specific applications for Southwest, Northwest, and Delta Airlines is underway.
Sandia also is developing or evaluating a variety of other sensor systems — or miniaturizing technologies into mountable sensors — that can detect cracks, corrosion, and other flaws in structural elements.
Technologies being considered include flexible eddy-current arrays, capacitive micro-machined ultrasonic transducers, piezoelectric transducers that can interrogate materials over long distances, acoustic emission sensors, embedded fiber optics, nickel strip magnetostrictive sensors, and conducting paint whose resistance changes when cracks form underneath.
-- John German
By Neal Singer
Sandia researchers and their collaborators have received five R&D 100 Awards, presented by R&D Magazine to recognize what its judges deem to be the 100 most technologically significant products introduced into the marketplace over the past year.
The valued awards have been referred to as the Nobel prizes of applied research or the Oscars of invention.
Including these five, Sandia has accumulated 80 R&D 100 Awards since 1976.
“Once again, DOE’s labs are at the cutting edge of innovation with new technology developments to enhance America’s economic and national security,” DOE Secretary Samuel Bodman said. “My heartiest congratulations to the DOE researchers and scientists who have won R&D Magazine’s prestigious awards this year.”
“The R&D 100 Awards are an important metric of Sandia’s success in impacting the nation through our discovery and innovation,” says Sandia Chief Technology Officer Rick Stulen. “They also serve a key role in demonstrating to industry that Sandia is an eager partner in technology maturation.”
Novint Falcon and Novint/Sandia 3D-Touch Software (joint), is a controller that makes interactive 3-D touch possible in high-fidelity for consumer computing applications.
Founded by former Sandian Tom Anderson, and jointly submitted for R&D 100 consideration by Nathan Golden (10104 ) and industrial partners, Novint’s software is largely based on technology originally developed at Sandia and exclusively licensed to Novint for commercialization.
Haptics is the science and art of providing touch sensations with computer-generated environments so that when virtual objects are touched, they seem real and tangible. While the current primary focus of the commercial technology is computer games, there are more serious uses in which the technique could make inroads. An example might be a medical training simulator in which a doctor can feel a scalpel cut through virtual skin, feel a needle push through virtual tissue, or feel a drill passing through virtual bone. All of these types of interactions would be felt almost indistinguishably from the real-life interactions the simulator emulates.
As the handgrip is moved, the computer keeps track of a 3-D cursor. When the 3-D cursor touches a virtual object, the computer registers contact with that object and updates currents to motors in the device to create an appropriate force to the device’s handle, which the user feels. The computer updates the position of the device, and updates the currents to the motors a thousand times a second (i.e., at a 1 kilohertz rate), providing a very realistic sense of touch. Three electrical motors are connected to the three arms extending out of the device, with one motor connected to each arm. The three arms are connected to the device’s handle. At any given cycle, or 1/1000th of a second, the device can create a force on the handle in any direction of any magnitude, up to the maximum force.
Haptics is applicable across nearly all areas of computing including video games, medical training, scientific visualization, CAD/CAM, computer animation, engineering design and analysis, architectural layout, virtual toys, remote vehicle and robot control, automotive design, art, medical rehabilitation, and interfaces for the blind, to name a few. The word ‘haptics’ derives from the Greek “haptikos,” meaning to grasp, touch, or perceive.
Funding sources for the work include LDRD and DOE Defense Programs.
Mode-Filtered Fiber Amplifier: The capability of coiled fibers to dramatically increase the useful power produced by fiber lasers has led to fabrication of high-power, high-beam-quality lasers that are compact, rugged, and extremely efficient. Prior to this breakthrough, fiber lasers were thought to be restricted by fundamental physical limitations of the fiber to low output powers and pulse energies. Specifically, the small, single-mode fiber core (typically less than 10 microns in diameter) was unable to generate or transmit high optical powers without being damaged or inciting parasitic nonlinear processes. Increasing the core size increased the laser power, but only at the expense of beam quality, a tradeoff that was prohibitive for most applications.
In 2000, Sandia and Naval Research Laboratory researchers demonstrated that bend loss from a coiled, large-core (multimode) fiber can act as a kind of distributed filter, suppressing all but the desired fundamental mode. Breaking the single-mode limit allowed fiber lasers to be scaled in power by a factor of more than 100, allowing these uniquely practical sources to displace conventional solid-state lasers in numerous applications and enabling entirely new applications. The discovery, which defied the conventional wisdom of the time, earned a patent in 2002 for Jeff Koplow and Dahv Kliner (both 8368), and Lew Goldberg, the inventors listed on the current R&D 100 Award. The technique has become the de facto worldwide standard for power scaling of fiber lasers. The first commercial license for the invention was granted in 2005, and the first commercial products were offered by coapplicants Nufern and Liekki in 2006. Three other companies have licensed and commercialized the invention.
The mode-filtered fiber laser has high electrical efficiency and optical gain, low waste-heat generation, broad wavelength coverage, and diffraction-limited beam quality (the theoretical limit) that is insensitive to vibrations, thermal fluctuations, and optical power level. All this, notes Dahv, “in a package an order of magnitude smaller than traditional solid-state laser sources.” Funding sources for the work include LDRD, DoD’s Air Force Research Laboratory, and the National Science Foundation.
The ElectroNeedle™ Biomedical Sensor Array is a device that, when pressed against the skin, can make rapid diagnostic measurements in a point-of-care setting.
The ElectroNeedle patch (Lab News, July 22, 2005 can detect and identify biological markers just beneath the skin’s surface. Because the electrochemical analysis is accomplished in situ, the need to withdraw body fluid is eliminated. The height of the needles, adjustable during microfabrication, allows the biological recognition layer to be placed in intimate contact with the appropriate tissue beneath the skin’s surface. For example, interstitial fluid in the epidermal layers of skin may be accessed for the measurement of small molecules such as glucose, while blood in the deeper dermal layers can be accessed for the measurement of larger molecules such as proteins.
By combining electrochemical measurement techniques with well-defined recognition chemistries and an easy-to-use sensor, a range of biologically important species can be detected. Potential biomarkers and bioagents include carbohydrates, electrolytes, lipids, enzymes, toxins, proteins, viruses, and bacteria in a patient’s blood or interstitial cellular fluid. This will provide a painless and rapid measurement of biologically
relevant molecules without having to extract fluids for later analysis.
ElectroNeedle arrays are produced using standard microfabrication techniques — photolithography, etch, and thin-film deposition — permitting low-cost, batch production of these devices when commercialized. What makes the microfabrication unique is the microneedle material, a commercially available glass wafer — Foturan® — that can be photo-patterned and etched to make hollow microscopic needle structures that are then filled with metal to form the sensing electrodes. These microneedles are sharp enough to be inserted into the skin but rugged enough not to bend or break. Because the metal microneedle passes all the way through the glass substrate, electrical connections are made to the back of the substrate and do not interfere with the sensing needle tip.
With one patent granted and three pending, the application was submitted by Steve Casalnuovo (1714) for principal developers that include David Ingersoll (2546), Chris Apblett (1815), Stanley Kravitz (ret.), Jeb Flemming (former Sandian), Colin Buckley (former student intern), and Carrie Schmidt (1723).The work has been funded by Sandia’s LDRD program.
ArcSafe© with Pulsed Arrested Spark Discharge (PASD) is a patented electrical wiring diagnostic tool effective in detecting and then locating wiring insulation defects in complex wiring systems, including commercial and military aircraft.
PASD sends a high-voltage but extremely short-duration pulse along wires to encourage a spark breakdown at the slightest break in insulation. This causes a momentary short circuit and reflection of energy back to sensors to locate the defect, serving as a warning before a short might appear under normal operating conditions. Because the spark is so brief, it has about the same energy as a spark generated by walking across synthetic carpet and causes no damage to the wiring system being tested.
Development of PASD was sponsored by the Federal Aviation Administration (FAA) and has been incorporated into a portable diagnostic system by Astronics Advanced Electronics Systems Inc., a leading developer of aircraft electronics and diagnostics.
Says project lead Larry Schneider (1650), “PASD shows tremendous promise as the world’s only effective diagnostic capable of detecting and accurately locating such hard-to-find insulation defects as breached insulation, chafing, and insulation cracks.”
Funding sources for this project include the DOE Nuclear Energy program, FAA, and DoD.
Self-Assembling Process for Fabricating Tailored Thin Films involved development of a simple soft coating process that forms optical, electrical, and magnetic thin films from self-assembled nanoparticles.
Led by Hongyou Fan (1815-1), with Bruce Burckel (1815), Jeff Brinker (1002), and Earl Stromberg of Lockheed Martin Aeronautics, the researchers developed a wet-solution-based process employing self-assembly to create engineered nanocomposite thin films with tunable properties by varying particle composition, sizes, shapes, and particle packing density and geometry.
“Our nanoparticle surface chemistry enables dispersal in readily available commercial solvents, allowing easy and rapid production of films through spin, dip, or spray coating under ambient conditions,” says Hongyou.
With the addition of secondary organic polymers or inorganic components, the nanoparticles self-assemble into ordered arrays embedded in a matrix of the secondary component that provides additional function and robustness in mechanical stability, and durability.
“The result,” says Hongyou, “is an ordered, high-density nanocomposite film where the constituent materials are controllably incorporated on the nanometer scale.”
Semiconductor, metallic, and/or magnetic nanoparticles can be added to optimize optical, electrical, and/or magnetic properties.
For example, a film can be deposited and its index of refraction tuned by changing its nanoparticle composition, concentration, or both to exactly match the required index of refraction of a surface, yielding an optimal single-layer anti-reflective coating on optical glasses as well as on high-index substrates, such as germanium windows.
Furthermore, the added flexibility and control over thin-film properties opens the door for engineered thin films with multiple functions. For example, nanoparticle optical films can be made hydrophobic to avoid fogging and icing problems that deteriorate optical performance of the devices.
“The broad reach of this rapid self-assembly process, delivering performance across multiple markets, at radically lower cost, in an environmentally friendly manner, warrants serious consideration as a top innovation in this decade,” says Walt Werner, a principal engineer for Lockheed Martin (Maritime Systems and Sensors).
This work leveraged the fundamental research of DOE’s Basic Energy Sciences program and LDRD aimed at developing multifunctional nanomaterials for microelectronics and optics as well as structure/property investigations of self-assembled nanomaterials.
The work is an extension of work on nanoparticle self-assembly published in Science in 2004 (Lab News, April 30, 2004) led by Jeff Brinker, Hongyou Fan, and students and faculty from UNM.
Funding sources for the work have included LDRD and DOE’s Basic Energy Sciences program. -- Neal Singer
By Patti Koning
The Journal of Physical Chemistry has recently published (Vol. 111, Issue 19, May 17, 2007) a Festschrift issue to honor the career of Sandian Jim Miller (8353). The entire issue is a collection of articles submitted by combustion chemists to honor Jim’s long and productive career.
“This is really thrilling,” says Jim of his tribute issue. He describes it as a highlight of his career, along with winning the Bernard Lewis Gold Medal from the Combustion Institute last year.
A Festschrift is a book honoring a respected academic, usually in honor of an anniversary, retirement, or notable achievement. The term comes from the German word for celebration publication. This Journal of Physical Chemistry Festschrift is in honor of Jim’s 60th birthday.
“Jim is an intellectual leader and a guiding force for Sandia’s energy science program and the Combustion Research Facility,” says Terry Michalske, director of Biological and Energy Sciences Center 8300. “His Festschrift is a fitting recognition of his contributions to the international scientific community.”
Difficult to overestimate Jim’s impact
The introduction to this issue begins by stating that “Jim Miller is one of the most influential combustion modelers in the world; it is difficult to overestimate the impact that Jim Miller’s work has had on the combustion community. But because of the rigor and detail of his chemistry contributions, his remarkable influence spreads beyond the sphere of combustion to the heart of fundamental gas-phase chemical reaction theory.”
The cover (see image at right) includes a montage of images representing the impact of Jim’s work on physical chemistry and combustion. A representation of the propargyl radical, whose reactions are key to soot formation in hydrocarbon flames, and images of sooting flames are superimposed on figures taken from several of Jim’s publications.
The issue also includes an essay by Jim, titled “My Life and Career (So Far) in Combustion Chemistry.” In the essay he describes his early life, noting that he was one of the first baby boomers — born nine months after his father returned home from World War II.
Jim’s father and grandfather worked as coal miners. As a child he was not particularly drawn to science and was the first on either side of his family to attend college. He earned a BS in engineering from the University of Cincinnati and a MEng and PhD from Cornell.
Jim began working at Sandia in the spring of 1974 and helped open the Combustion Research Facility in 1980. Among the many achievements in his career, the development of CHEMKIN™ is especially notable. It is the de facto standard software for modeling chemical kinetics in combustion.
Currently Jim is working with Stephen Klippenstein of Argonne National Laboratory and a former Sandian to develop and implement a theoretical apparatus for studying chemical reactions involving multiple, interconnected potential wells. Such reactions are of paramount importance in the formation of aromatic compounds, polycyclic aromatic compounds (PAH), and soot in flames of aliphatic (non-cyclic) fuels.