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N U 4 D Air Force Research Laboratory AFRL E Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Ohio SPRING 1998 Research and Development Efforts Help Nondestructive Evaluation Pay Off for Today's and Tomorrow's Air Force by Tobey M. Cordell how we provide the R&D base that supports Commands (MAJCOMs); and to the NDE Branch Chief' those elements of the Materials and requests from the Integrated Product Teams Air Force Research Laboratory Manufacturing Directorate engaged in (IPTs) which have been formed all across solving problems for weapon systems in the the Air Force to deal with individual The Air Force has been involved with field. systems. We focus on the needs of our the development and application of The Directorate's NDE effort has an customers to help us prioritize what new nondestructive evaluation (NDE) ever since R&D focus as well as a systems support R&D efforts are needed. This focus also the Army Air Service used X-ray focus. Our NDE R&D activities cut across helps to ensure effective transition of the radiography to explore internal defects in both of these critical areas. If there are technology after completion of the various materials back in 1926. Today, our work immediate problems in the field, the phases of R&D. spans the entire spectrum of applications. Directorate already has in place a systems At the same time we work through all On one hand, the NDE Branch works support organization to provide direct field these issues very closely with the Air Force directly with engineers and scientists in the support. If that part of the Directorate needs Nondestructive Inspection Program Office research and development community as further technical assistance, the NDE R&D (NDI PO) - also part of the Directorate, they look at new materials and processes organization becomes involved. So we have currently located at the San Antonio ALC. development. We also deal with new and a role in offering R&D support to our people We coordinate our programs very closely emerging weapon systems to ensure who are helping to solve field problems. with them because they are directly involved effective NDE methods are in place for new with NDI personnel in the field and at the systems before they go into service. Finally, Our Current Focus ALCs, and therefore are instrumental in we provide vital inspection technologies to helping to set program priorities. allow safe life extension of the Air Force's We are responsible for developing and A quarterly NDI IPT meeting, chaired aging aircraft fleet. addressing the NDE R&D needs of Air Force by the NDI PO involves the entire Also, we are heavily involved with the customers in depots and in the field. A key community of engineers and scientists whole area of sustainment of the fielded and element for R&D program development is conducting NDI research, development and aging systems in the Air Force fleet. In fact, responding to the needs of Air Force Air application. These IPT meetings are the lion's share of our work is focused on Logistics Centers (ALCs) and Major attended by the Air Force NDE R&D community, Headquarters AFMC, the MAJCOMs, and all the ALCs. Another opportunity to interface with the people in the field results from actively participating in the annual worldwide Air Force NDI managers meeting. We take advantage of these opportunities to maintain a meaningful dialogue with depot and field personnel, as well as learn of new NDI needs coming through the NDI PO Air Force solicitation process. The role of NDE R&D is to develop technologies with a goal of implementation to meet customers' future needs. To meet the full spectrum of our responsibility, about 25 percent of our organization's developmental activities are focused on the near-term (0 to 3 years to application); about 50 percent are mid-term (3 to 7 years out), ,^,-,S__—nq— Tobey Cordell and Mark Blodgett examine a scan-in-progress of a titanium alloy sampitfmrijie High Precision Scanning Acoustic Microscope. t , ,. ._i,.,. .-^.Continued on page 6 ' A- Page 2 NDE Research Update Spring 1998 New Ultrasonic Technique Enables NDE for Process Sensing of Components at High Temperatures A nondestructive evaluation technique dependable operation, reliable monitoring worked under contract with scientists from which can be used during the production during the manufacturing process is the Air Force Research Laboratory's process to verify the integrity of critical required. Hot isostatic pressing (HIP) is a Materials and Manufacturing Directorate. aerospace structural components has been case in point. They developed an ultrasonic transducer developed by scientists at the University of During HIR the workpiece is heated above capable of precision operation in a high Dayton Research Institute and the Air Force 900° C (1650° F) in a sealed container temperature environment and demonstrated Research Laboratory's Materials and pressurized with argon gas up to 140 MPa the feasibility of using ultrasound to acquire Manufacturing Directorate. Their ultrasonic (20,300 psi) to densify the material and metrology data in severe operating sensor technology allows real-time process eliminate porosity in the component. Since conditions. A prototype sensor was monitoring at operating temperatures up to traditional monitoring sensors usually successfully tested to 1100°C (2012°F) and 1100°C (2012°F). Further development of cannot withstand the required high 150 MPa (22,000 psi) without sustaining this technology will allow optimized temperatures, components must be held in damage. processing for critical components of the HIP vessel for several extra hours at Several possibilities are under considera- advanced Air Force weapon systems and maximum rated pressure and high tion to develop this sensor for use in other result in shorter production cycles and processing temperature to assure full high temperature applications such as opto- increased product yield. densification, even though a part actually electronic crystal production, real-time Many components for Air Force weapon may be completely densified in only a monitoring of casting processes, or the systems such as castings for jet engines, fraction of this time. Besides unwanted monitoring of component shape changes nickel-base superalloy turbine blades, and changes in workpiece microstructure, extra during turbine engine operation. parts made of ceramic and metal matrix processing time can add as much as $10,000 The ultrasonic transducer shows promise composites must withstand high-tempera- to the cost of a single complex component. for high temperature monitoring of materials ture operating conditions and severe To meet high temperature monitoring and components at temperatures signifi- environments. To assure the precision requirements, a team of researchers from the cantly higher than current sensors will allow. component structure necessary for University of Dayton Research Institute This can help produce shorter production cycles and maximized product yield for Air Force weapon system components. For more information, contact the NDE Technology Transfer Center at (937) 255- 2818 or e-mail [email protected]. Refer to 97-671. David Stubbs and Susan Reilly of the University of Dayton Research Institute monitor a test of the high-temperature ultrasonic sensor. (Inset) Close-up view of the sensor. Spring 1998 NDE Research Update Page 3 New Creeping Wave Ultrasonic Technique Improves Inspection of Aircraft Internal Wing Fuel Tank Structure A nondestructive evaluation technique has been developed for detecting fatigue- induced cracks on internal wing fuel tank structures equipped with fuel transfer holes, (Above) Sensor in use on test panel. also called weep holes. Scientists at the Air (Right) How the sensor works. Force Research Laboratory Materials and Manufacturing Directorate have developed a split-aperture circumferential ultrasonic load capacity, limiting their mission sensor technology technique for external capability. All C-141s were inspected to inspection of the area around internal weep determine weep hole cracking severity. To holes of fuel tank baffles on aircraft. This accomplish this, the fuel tanks had to be technique promises to be quicker and safer emptied and purged so that an operator could than conventional visual inspections. crawl inside each wing section and do a around it. If no signal comes back the hole Further development of this technology will manual inspection using a special eddy is crack-free, but if some of the signal travels permit more efficient inspections to maintain current bore-hole transducer — a time- completely around the hole and a partial- the mission readiness of "wet wing" aircraft. consuming, potentially hazardous operation. travel echo comes back the presence of a Several Air Force weapon systems are Other Air Force weapon systems with wet crack is indicated. built with internal wing structures called wet wings include the A-10 Thunderbolt II, the This can make the inspection process wings, used as fuel tanks. Inside the wing, F-15 Eagle, and the F-4 Phantom II (used much more efficient by previewing all holes a series of vertical risers at right angles to today for drone duty). from outside the wing. Only those holes the wing's leading edge serve as stiffeners. Engineers in the Nondestructive with indicated cracks must be inspected from To provide balanced fuel flow and Evaluation Branch at the Air Force Research inside the wing, so overall inspection time distribution during flight, quarter-inch weep Laboratory Materials and Manufacturing can be substantially reduced. Further work holes are drilled through each of the Directorate worked with researchers from is now proceeding to achieve system stiffeners. Weep holes become sites where the University of Cincinnati, University of viability for in-field use. fatigue cracks tend to originate, primarily Dayton Research Institute of Dayton, Ohio growing upward over time to weaken the and Advanced Quality Concepts of stiffener and diminish wing integrity. While Columbus, Ohio, to find a faster, safer, more For more information, contact the NDE downward cracks also occur and are fairly effective and convenient technique to locate Technology Transfer Center at (937) 255- easy to detect, cracks on the upper part of weep hole cracking. At the outset the use of 2818 or e-mail [email protected]. the weep hole are not readily detectable. conventional ultrasonics was investigated, Refer to 97-603. Weep hole cracks in C-141 Starlifter but it was found to be very difficult to detect aircraft wings are a case in point. Excessive cracks radiating upward from weep holes. weep hole fatigue cracks caused the To overcome this problem a dual element, grounding of 45 C-141s in August 1993 split-aperture circumferential creeping while 116 more C-141s were prohibited ultrasonic transducer inspection system was from in-flight refueling. Earlier in 1993 all developed. With it, when an ultrasonic C-141s were held to 74 percent of normal signal encounters a weep hole it travels Page 4 NDE Research Update Spring 1998 X-Ray Three-Dimensional Computed Tomography Enables Nondestructive Evaluation of Large Solid Rocket Motors Engineers at the Air Force Research 3-dimensional computed tomography sources and handling equipment. In use, the Laboratory Materials and Manufacturing (HR3DCT). partial angle CT reconstruction yields a 3- Directorate, working with a research team This solution is based on the recognition D volume image of a region concentrated led by Perceptics Corporation of Sandy, that bondline anomalies in SRMs are near the periphery of the motor. This image Utah, have developed a method for highly oriented along tangential directions of the is displayed as a linear CT slice at a fixed accurate nondestructive evaluation (NDE) SRM case. Imaging the important features radius corresponding to the bondline. It of large solid rocket motors. For the first of the bondline requires good spatial effectively unwinds the periphery of the time, flaws in inaccessible motor areas such resolution in the radial direction only, which motor and results in a high resolution true as bondlines can be clearly detected and can be easily captured while the SRM is HR3DCT image that clearly identifies quantified. Their high resolution, X-ray 3D rotated in a tangential radiography fixture. features, flaws and problems along the computed tomography system has shown The large interior of the SRM, typically bondlines. improved imaging accuracy and detection inspected using CT, need not be irradiated sensitivity for finding bondline flaws. or reconstructed. To gain good radial spatial Large solid rocket motors (SRMs) used resolution in examining large rocket motors, For more information, contact the NDE for heavy-lift expendable launch vehicles are a high-energy digital area imaging detector Technology Transfer Center at (937) 255- vital for lifting heavy payloads into space such as is used for real-time radiography is 2818 or e-mail ndedata @ml. wpafb. af mil. for Air Force and U.S. national security utilized. Refer to 97-629. needs. SRMs are typically built with an The new technology is expected to outer casing, internal insulation and solid require only minimal changes to imaging propellant, all separated by bondlines with adhesives and barrier coats. These must be accurately applied to assure correct operation and prevent flaws or gas paths to bondlines which can lead rapidly to catastrophic failure of the SRM during vehicle launch. A major problem is to correctly and precisely detect and quantify bondline defects. NDE is used to inspect SRMs for component integrity, with computed tomography (CT) and radiography as the most common methods. However, these traditional technologies have serious limitations. Radiography through the entire SRM cross-section results in low resolution at the bondline, an area where it was suspected that flaws and problems could occur. CT does not have the spatial resolution to recognize bondline separations as small as 10 mils. Working under contract to the NDE Branch of the Air Force Research Laboratory Materials and Manufacturing Directorate, a 120-inch diameter solid rocket motor mounted on a rotary inspection stand for bondline team composed of Perceptics Corporation inspection. of Sandy, Utah, Skiametrics Inc. of Winchester, Mass, Alliant Techsystems, Inc. of Magna, Utah, Lockheed Martin Missile Visit us on the Web at Systems of Palo Alto, Cal., and Tufts www.afrl.af.mil University of Boston, Mass., successfully developed a novel solution: high-resolution Spring 1998 NDE Research Update Page 5 New Inspection System for Aircraft Surfaces Improves Capability to Detect Hidden Damage Engineers from Diffracto Ltd. of Windsor, Canada and the National Research Council of Ottawa, Canada, have developed a highly efficient technique for detecting material defects in large metal and composite aircraft components. This effort was sponsored and supervised by the Air Force Research Labor- atory's Materials and Manufacturing Directorate. Their new D-Sight Aircraft Inspection System (DAIS) evaluates large surface areas on composite aircraft parts to locate subsurface problems such as impact damage and delaminations, with time savings ranging from 60 percent to over 90 percent. The portable system includes a user-friendly computer interface to manage high quantities of data. Fiber reinforced composite structures have been used on Air Force weapon systems ever since fiberglass-reinforced polyester became available in the 1970s for secondary aircraft structures such as fairings, cowlings, landing gear doors, Inspection of a EC-135 aircraft radome. movable control surfaces and fixed surfaces of wing trailing edges. Advanced materials developed in the early 1980s such as be accompanied by considerable internal lens, glass mirrors, and a retroreflective graphite/epoxy extended composite usage damage. Once a surface area of concern has screen which returns light falling on its into primary aircraft structures such as been visually identified, nondestructive surface in the same direction as the incident vertical or horizontal stabilizers. Today the ultrasonic or radiographic testing can light, all contained in a single portable unit. B-2, F-117 and F-22 all have composite determine the extent of damage hidden The aircraft surface must be reflective, or primary structural elements while the F-15, beneath the surface. be made reflective with a thin film of F-16, C-17, EC-135 andE-4 have composite Engineers at the Nondestructive highlighter. When the aircraft surface is secondary structures. Evaluation Branch of the Air Force Research illuminated by the white light source, local Composite structure damage due to Laboratory's Materials and Manufacturing surface curvature variations focus or impact by hard objects, lightning strikes, Directorate, with researchers from Diffracto disperse the light onto the retroreflective fire, and other causes, as well as hidden Ltd. of Windsor, Canada, and the National screen, showing up as bright and dark gray corrosion in metal parts, can combine with Research Council of Ottawa, Canada, scale variations for later analysis. factors such as high loads, fatigue, and wind worked to develop a cost-effective technique erosion to result in major part failures. to detect non- or barely-visible damage on Visual examination is the primary method composite and metal structures. For more information, contact the NDE to inspect aircraft weapon systems surfaces, They developed a new system called D Technology Transfer Center at (937) 255- since damaged subsurface areas are often Sight Aircraft Inspection System (DAIS) for 2818 or e-mail ndedata @ ml. wpafb. af. mil. indicated by localized changes in surface fast, efficient inspection of large areas of Refer to 97-606. shape. While the U.S. Air Force Damage aircraft surfaces to highlight prob-lems such Tolerance Design Guide regards an impact as damaged, corroded, delaminated or indentation of 0.1 inch (2.5 mm) as the disbonded areas. The DAIS system uses a minimum visibility threshold, residual charge coupled device camera, a white light impact indentations of less than this may also source mounted slightly beneath the camera Page 6 NDE Research Update Spring 1998 directly monitor changes in the posite structures, etc. NDE Research and Development Efforts, continued from page 1. structure of a vehicle without • Several 6.3 advanced develop- having to come back and ment programs are being and 25 percent are long-term (7+ years out). conduct additional inspection worked to translate 6.2 pro- These activities span the entire spectrum of operations. grams into engineering proto- current NDE methods, as well as Life extension of the ICBM fleet is types. The reliability of these development of new methods, such as laser another area of investigation — the prototypes will then be validat- based ultrasound, that may offer a new Minuteman III missiles in silos as well as ed, and they will be put to work approach, or a more rapid or reliable method Peacekeeper missiles. There are vital issues operating in field or depot of inspecting parts on a large scale. here in terms of NDE. Very large, complex environments. We deal with the development of NDE computed tomography systems are currently Each of these programs, and especially methods and systems for the entire spectrum being used by the Ogden ALC at Hill AFB the 6.3 activities, are closely coordinated of Air Force weapon systems. to inspect the Minuteman III and with our ALC and SPO customers. When • Aircraft involvement includes Peacekeeper systems. We are directly R&D programs reach the 6.3 stage, the NDE for airframes such as rapid involved in terms of providing new X-ray objective is to provide in-the-field methods for reliably locating technology that can be used by the ALC assessment of engineering prototypes to corrosion on KC-135s, as well inspection system. learn just how they will perform in actual as for aeropropulsion in service, and determine whether additional enhanced automated turbine Transitioning NDE Programs development is necessary. engine disk inspection. to Customers Follow-up activities are conducted in • As low observables are applied close coordination with our Manufacturing to more and more aircraft Our NDE R&D work spans the Technology counterparts in the Directorate. systems we are developing spectrum of funding types as well as the These activities also require involvement point inspection NDE methods points at which this work might be applied. with 6.5 Engineering Development work, that can verify the electro- For example: sponsored by Aeronautical Systems Center's magnetic integrity of those • In 6.1 basic research projects we Subsystems SPO. components. work very closely with the Air A good example of program flow is the • For space systems, we are Force Office of Scientific Mobile Automated Scanner (MAUS) involved principally in space Research (AFOSR). Currently, system. Original development was done launch systems - solid as well most of those efforts are focused during a 6.2 program with McDonnell as liquid rocket propulsion on advanced methods for Douglas (now Boeing) in St. Louis. As part systems. corrosion detection. of subsequent 6.3 efforts and with the • For satellite systems, we're • A significant number of 6.2 assistance of Air Force NDI Program Office looking at novel methods of applied research programs are funding, we were able to put these units into NDE for very lightweight underway. These include every Air Force ALC for evaluation, as well materials that need inspection efforts ranging from detection as getting some units into the Navy at but can't tolerate fluids on their of corrosion and cracking to Patuxent River NAS and Cherry Point NAS. surfaces. We're also involved looking at novel optical met- Latest versions of the MAUS are now being in what is called vehicle health hods, as well as applying used in Manufacturing Technology efforts management, where we plan to shearography to inspect com- at Oklahoma City ALC, on KC-135 tankers. Extensive laboratory work on the development of novel laser-based . . . in laser ultrasonic inspection systems for complex and composite ultrasonics for advanced inspection systems pays off. . . aircraft parts, capable of reducing inspection time by over 90 percent. Spiing 1998 NDE Research Update Page 7 NDE developmental efforts are closely coordinated among a network of key people, from scientists in AFOSR and those doing 6.1 basic research to the 6.5 personnel in ASC who work to apply field-ready NDE methods and systems directly with System Program Offices. is- |a^|^apM^HS * ~ Equally important, in-house research is under way that reaches across several key JSK^KSBK M ""SIS!.*» -«. activities. An excellent example involves research in scanning acoustic microscopy which is being used to characterize advanced fiber-reinforced composite materials, and is also being assessed for application to H1 ^I^^^^HH examination of high cycle fatigue of turbine engine components. In some cases, in-house research is under way to ensure that we have people The Mobile Automated Scanner (MAUS) system, developed for NDE work on Air Force weapon who are smart buyers of advanced systems (left), has been demonstrated on commercial applications such as composite chassis technology for the Air Force. One good components for racing cars (right). example of this is our work in laser-based ultrasound (LBU). The principal scientist working on this area has in-house research communities will be applied to develop Extending NDE Capabilities under way in an advanced laser-based enhanced solid-state X-ray detectors for Air ultrasound system. He also provided Force use. We provide national leadership in new extensive technical support to Sacramento Technology transfer involves moving areas of importance to NDE. For example, ALC as they acquired the first production Air Force NDE technologies into the right now we feel it is very important to work LBU inspection system. In-house research commercial sector. This is effective when not only the area of nondestructive helped develop a smart buyer for the Air dual-use opportunities exist for technologies inspection of systems in the field, but also Force in terms of interfacing advanced originally developed for Air Force use. By to extend the capabilities of NDE into earlier technical knowledge with the NDE needs making advanced NDE technologies phases of the product development and of the field. available for commercial applications, sales manufacturing spectrum. Our objective is Our in-house research scientists are volume increases significantly and per-unit to provide NDE systems to engineers who directly involved with their counterparts in costs drop. This helps to reduce overall costs are processing either metallic or composite the field or in the ALCs. By redirecting our to the Air Force to implement these NDE material into products, to improve program to make it more clearly customer- technologies. production effectiveness. focused, we are now structured to look at The MAUS scanner system has been We're also working to develop NDE NDE in support of materials and process extensively demonstrated to the automobile methodologies that can be used even earlier development, focused on our R&D and power boat racing industries in the hope in the development process, to characterize customers; NDE for low observable and of stirring interest in these key markets. This properties of materials while they are in space systems, primarily for our SPO could lead to reducing the overall cost of development. Thus, NDE is becoming a customers; and NDE for fielded and aging acquisition of this system for the Air Force. full-spectrum activity, one intended to pay Air Force weapon systems, closely We have also worked very closely with our off for the Air Force at every stage of product coordinated with our systems support counterparts in the civil aviation industry, development and application. counterparts, and our ALC and SPO where the MAUS has been extensively customers. demonstrated on commercial airline aircraft. A significant part of our technology transfer For more information, contact the NDE Technology Transition and Transfer effort is our continuing interface with our Technology Transfer Center at (937) 255- NDE counterparts in the FAA and NASA, 2818 or e-mail [email protected]. Technology transition and technology which includes close coordination of transfer are important for NDE R&D. developmental efforts. At the same time we Refer to 97-617. Technology transition involves moving maintain close contact with the international developed NDE technologies into the hands NDE community, particularly in the areas of Air Force depot and field customers, with of corrosion detection with British, French technologies such as the MAUS. Another and German counterparts. Ongoing key example of technology transition activities with Australian and Canadian NDE involves the development of advanced experts also help to increase our effective- digital X-ray detection methods. Here, ness in NDE R&D. technology from the industrial and medical Page 8 NDE Research Update Spring 1998 Air Force Research Laboratory x 9 Other Materials & Manufacturing AFOSR Technical Directorate How nondestructive evaluation Directorates efforts fit into the Air Force Research Laboratory system. 3 Other Manufacturing Technology Metals, Ceramics & Systems Support Divisions Division NDE Division Division Nondestructive Logistics Materials Processing & Evaluation System Integrity Fabrication Branch Support Branch Branch Branch NDE Manufacturing NDE Research Air Force NDI NDI Applications Technology & Development Program Office NDE Research Update is published periodically to provide information on NDE research and development activities by the Air Force Research Laboratory, Materials and Manufacturing Directorate. For more information on topics presented in "NDE Research Update," or to be added to our mailing list, contact the NDE Technology Transfer Center at (937) 255-2818 or e-mail [email protected]. Cleared for Public Release (ASC/PA #98-1014) y AFRL/MLLP-TTC BLDG 653 ator 2230 10TH ST STE 1 Air Force arch LaborAFRL WOFRFIGICHITA-LP ABTUTSEIRNSEOSSN AFB OH 45433-7817 e es R h Base, Ohio AW2M9FAP7RTA7LE FP/RMB IS ALOTOLRHSPE -A TE4NIT5CD/4S 3BMU3LAI-TD7NEG7U 4 1F663A5 3C TURING DIRECTORATE c Force Official Business Air DEFENSE TECHNICAL INFORMATION CENTER r Patterson ADTTITCN/O:M I a Wright- 8725 JOHN J KINGMAN ROAD SUITE 0944 e Directorate, FORT BELVOIR VA 22060-6218 es Manufacturing R d n a Materials z a i Id