Materials Research and Structural Mechanics

The Institute enhances catalyst performance and formulates new catalysts to improve production processes for the chemical and petrochemical industries. Shown here is a computer simulation of the molecular structure of faujasite, a zeolyte used in commercial catalysis applications.

Materials research, development, and testing activities at the Institute encompass the formulation and synthesis of new materials, evaluation of their performance under service conditions, and assessment of the remaining useful life of critical components and structures. Composites, metals, polymers, ceramics, cements, and adhesives are some of the materials being evaluated. An integrated approach to structural mechanics embraces the analysis, design, and testing of a variety of aerospace, land, and sea-based structures.

The second phase of development of the Institute's Ion Beam Surface Modification Facility is nearing completion with the installation of a high-energy plasma bucket ion source that allows the modification of materials by direct ion implantation, thereby strengthening their surface structures. This versatile facility also offers the capability for sequential coating processes, such as combining ion beam-assisted deposition with diamond-like carbon (DLC) coatings. Tests of these coatings have shown exceptionally low friction and wear at temperatures up to 500°F, and DLC coatings up to four square feet in area have been applied to industrial steel tools such as polishing disks and injection and press molds.

The surface structures of tools, dies, and other components are strengthened by bombarding the material's surface with a high-intensity ion beam. The Institute maintains the largest and most versatile commercial facility in North America for the surface modification of materials either through ion implantation or ion-beam assisted coating processes.

Ion beam DLC coating technology is also being used to solve biomaterials problems such as wear of orthopedic components, biocompatibility of pacemaker wire leads, and bacterial infections associated with implanted medical devices. Coating biomaterials with DLC promises to make them more resistant to rejection or associated problems.

Specialty materials processing facilities, such as this furnace used to process glass and glass ceramics, allow SwRI engineers to develop and improve bioceramics and other biomaterials.

A major problem with mechanical heart valves is the thrombosis, or blood clotting, that can be induced by interactions between the surface of the valve and red blood cells. Institute researchers are developing proprietary surface coatings based on ion beam technology that offer excellent resistance to clotting.

A separate technology based on acoustic emission detection of flaws in heart valves was recently implemented in an assembly-line production facility as a quality assurance tool to help eliminate the small percentage of flawed heart valve components. Unlike existing optical detection devices, the acoustic emission technique can detect subsurface and very small surface imperfections.

To improve materials for biomedical implant applications, Institute scientists are developing stronger and more bioactive glass ceramic materials using ion beam surface modification technology. Bioactive glass ceramics are the only materials known to form a strong chemical and physical bond with bone.

Stereoimaging strain analysis, previously developed at SwRI under U.S. Air Force and Navy sponsorship, is being applied to help solve the problem of bone mineral loss during long-term space flight and to understand bone response to cyclic stresses and overloads. The technique has proved ideal for relating load-induced microdeformation to bone microstructure and architecture. A unique model was developed in conjunction with this effort that successfully creates microgravitational-induced minimal bone loss in laboratory rats.

Improved performance of aerospace systems such as engines and airframe components depends on the development and application of novel materials. A new intermetallic alloy containing fine-grained titanium aluminide is being examined by SwRI and McDonnell-Douglas Aerospace for the U.S. Air Force. The material shows potential for high-temperature aerospace applications where ductility, toughness, and fatigue resistance are essential. Researchers are investigating the influence of alloy microstructure on fatigue and fracture properties using Institute-developed micromechanics theories and experimental techniques.

Institute engineers examine a helical gear used for power transmission. SwRI performs root cause failure analyses on a wide variety of equipment used in many industries.

Ceramic coatings provide thermal protection for advanced materials in a variety of applications, from the space shuttle to gas-fired turbine engines. Coating damage must be repaired quickly to prevent catastrophic failure. With funding from NASA-Johnson Space Center, SwRI is developing a preceramic polymer-based repair method for coated space shuttle components that does not require removing the damaged part. In a related effort funded by the Electric Power Research Institute (EPRI), SwRI is developing chemical methods to repair damaged thermal barrier coatings on gas turbine hot section components -- those in high-temperature operating areas.

For the Gas Research Institute (GRI), SwRI is evaluating three classes of commercial pipe lining techniques -- swage-lining, U-liner, and Ultrapipe^TM -- for rehabilitating damaged natural gas distribution pipes. Results of materials testing and analyses, full-scale testing of lined pipes, and fracture mechanics modeling of service histories have led to the development of installation and operating guidelines for the use of these lining techniques.

The Institute has developed a major program in combustion turbine materials technology. Projects include the critical assessment of a new turbine blade alloy and associated coatings for a consortium of oil and gas companies. For EPRI, Institute engineers are operating the Materials Center for Combustion Turbines and developing advanced coating technology, including repair methods and studies of ways to slow coating degradation. A project for the U.S. Department of Energy entails life modeling of thermal barrier coatings and methodologies for life prediction of turbine disks subjected to high temperatures and cyclic loads. Extensive evaluations of hot section components are being conducted for a number of domestic and international clients.

SwRI maintains a major program in materials technology for the study of combustion turbines. Components from land-based gas turbines, such as the buckets being examined here, are studied by Institute engineers to help prevent failures, reduce maintenance costs, and increase component life.

A project is under way for the Federal Aviation Administration to develop a probabilistically based damage tolerance design code to help ensure the safe operating life of commercial aircraft gas turbine rotors and disks. Four aircraft gas turbine manufacturers are collaborating with SwRI and will incorporate the code into their design systems. Issues addressed will include characterization and detection of anomalies in titanium alloys, the movement of these anomalies during forging, and the initiation and growth of flaws due to the presence of anomalies.

A major industrial consortium effort sponsored by the National Center for Manufacturing Sciences is in progress to integrate advanced fiber optic sensors, invented at the Institute, with intelligent computer control algorithms and state-of-the-art computer models for polymer processing. The integrated materials processing system, called the Mechanoclave', will soon be installed in a Texas Instruments manufacturing facility, where it will be used to produce radomes for a new missile system. This is the only materials processing system to combine advanced sensors and computer models with artificial intelligent control.

Many nuclear power plants use borated water as a primary coolant to control reactor temperature. Coolant leaks can cause significant corrosion of steel reactor components as a result of evaporation and the formation of concentrated boric acid on heated surfaces. SwRI is performing a multi-year research program for EPRI to develop boric acid corrosion rate data under realistic, simulated operating conditions at temperatures between 200 and 600°F. Results will enable utility engineers to estimate corrosion rates and define measures to ensure that boric acid corrosion does not compromise the integrity of reactor components.

Institute engineers are developing technology to assess the structural integrity of damaged high-pressure natural gas pipes. A method to predict when a crack or similar defect in a pipe wall will result in a leak rather than a long axially propagating crack or rupture has been developed for natural gas transmission pipelines. This approach is being extended to study transient dynamic crack propagation, both to determine conditions when crack arrest is ensured and to design mechanical crack arrestors should pipe material toughness be insufficient to arrest a rapidly propagating crack under normal operating conditions.

To better understand pipeline behavior, the Institute is conducting a series of full-scale tests of a 48-inch diameter pipe for the Alyeska Pipeline Service Company. Tests included pressure, axial, and lateral loading to mimic conditions such as those experienced in arctic regions. (Photo courtesy of J.A. Maple and Associates.)

Since 1961, the T-38 aircraft has served as an advanced fighter trainer for the Air Force, a role that might extend well into the next century. The Institute recently completed a full-scale fatigue test of the T-38 wing for the San Antonio Air Logistics Center. Based on the laboratory test results and flight service data, analyses were performed using fracture mechanics and probabilistic methods to predict the replacement life of the wing. Expected wing replacement rate schedules were computed to the year 2040. These schedules will be used to support future wing maintenance and replacement decisions for the T-38.

Air force officers and engineers from the Republic of Korea and Turkey are being trained at SwRI to conduct aircraft durability and damage tolerance testing and analysis. The six-month program provides classroom instruction on aircraft loads, stresses, and fracture mechanics, as well as hands-on training in materials testing and laboratory practices. This technology transfer program assists allied countries in developing the capability to monitor and extend the service life of the aging T-37 jets used by their military forces.

For the U.S. Air Force Wright Laboratory, SwRI is devising engineering concepts that would allow strategic variations in the structural stiffness of high-performance, or aeroelastic, fighter wings. The goal is to couple stiffness variations with fundamental aeroelastic responses of the wing, so a single outboard aileron can provide effective controls throughout the aircraft's operating range. This ability would eliminate the need for a control function on the horizontal tail of fighter aircraft, directly contributing to the new generation of tailless fighters desired by the Air Force.

An exact 1/2-scale structural model of the top front section of the sail (conning tower) for an SSN 688 Los Angeles class attack submarine was built and tested to failure at SwRI. The purpose of the project was to provide an experimental test and associated data for the validation of a computer analysis model being used by the client for structural response analyses. Researchers instrumented the interior of the sail model at various locations and developed software to continuously monitor load plane displacements and adjust hydraulic cylinder pressure, to apply the desired load magnitude while maintaining the correct loading angle. The sail model was loaded to a maximum of 1.4 million pounds at failure.

In a program for the U.S. Navy, Institute engineers constructed an exact 1/2-scale structural model of the top front section of the sail of an SSN 688 Los Angeles class attack submarine. The model was then placed in a load frame and loaded to failure.

In a project for the Naval Biodynamics Laboratory, development continued this year on a model of the human cervical spine that will help assess the probability of injuries from rapid deceleration or aircraft seat ejection. The cervical spine model is based on integration of the SwRI-developed NESSUS^TM probabilistic analysis program with ABAQUS^TM, a commercial finite element program, and incorporates laboratory and sled test data for animals and humans.

SwRI has developed a probabilistic analysis parallel processing capability that allows structural analyses to be performed in parallel on multiple workstations. This new capability significantly reduces the amount of computer time necessary to obtain accurate probabilistic results and allows SwRI researchers to develop new algorithms and solution methods for a broad range of industrial and government applications. The technique was recently used to complete a probabilistic fatigue analysis of multiple site damage in an aircraft fuselage in two days. Without parallel processing, the same analysis would have taken three weeks.

The Institute has conducted specialty testing of large bore marine hoses for more than 20 years. During the past year, a major foreign marine hose manufacturer contracted with SwRI to conduct performance and specialized tests of a prototype liquified petroleum gas (LPG) floating hose, which transfers refrigerated LPG at -49 degrees C from a storage vessel to a moored export tanker. During the program, SwRI designed and built two unique systems for hose testing. One cycled the hose in bending fatigue while maintaining a temperature of -49 degrees C, and the other safely monitored and controlled the temperature of a full-size hose while holding the rated pressure for 30 days with LPG. These hoses are to be part of an LPG transfer system being designed by Chevron Nigeria Limited for the Nigerian National Petroleum Corporation.

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