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DOE OSTI2024

Achieving high-ZT in Te/Se-based thermoelectric materials via volume-constrained shear-induced plastic deformation

This study investigated the correlation between severe plastic deformation and microstructural evolution, along with the corresponding response in the thermoelectric performance. Specifically, severe plastic deformation introduced into intrinsically brittle thermoelectric materials like Bi 2 Te 3 - x Se x leads to microstructural changes ranging from nano- to micro- scales, including phase transformation, phase segregation, and stacking faults. The resultant residual strain and lattice defects in the Bi 2 Te 3-x Se x materials led to engineering of electronic bands, which increases the effective mass of electrons while controlling their concentration, thereby enhancing the power factor.

36 MATERIALS SCIENCE↗

NASA NTRS1987

Gear tooth stress measurements on the UH-60A helicopter transmission

The U.S. Army UH-60A (Black Hawk) 2200-kW (3000-hp) class twin-engine helicopter transmission was tested at the NASA Lewis Research Center. Results from these experimental (strain-gage) stress tests will enhance the data base for gear stress levels in transmissions of a similar power level. Strain-gage measurements were performed on the transmission's spiral-bevel combining pinions, the planetary Sun gear, and ring gear. Tests were performed at rated speed and at torque levels 25 to 100 percent that of rated. One measurement series was also taken at a 90 percent speed level. The largest stress found was 760 MPa (110 ksi) on the combining pinion fillet. This is 230 percent greater than the AGMA index stress. Corresponding mean and alternating stresses were 300 and 430 MPa (48 and 62 ksi). These values are within the range of successful test experience reported for other transmissions. On the fillet of the ring gear, the largest stress found was 410 MPa (59 ksi). The ring-gear peak stress was found to be 11 percent less than an analytical (computer simulation) value and it is 24 percent greater than the AGMA index stress. A peak compressive stress of 650 MPa (94 ksi) was found at the center of the Sun gear tooth root.

Oswald, Fred B.↗

NASA NTRS1988

Development of a unified constitutive model for an isotropic nickel base superalloy Rene 80

Accurate analysis of stress-strain behavior is of critical importance in the evaluation of life capabilities of hot section turbine engine components such as turbine blades and vanes. The constitutive equations used in the finite element analysis of such components must be capable of modeling a variety of complex behavior exhibited at high temperatures by cast superalloys. The classical separation of plasticity and creep employed in most of the finite element codes in use today is known to be deficient in modeling elevated temperature time dependent phenomena. Rate dependent, unified constitutive theories can overcome many of these difficulties. A new unified constitutive theory was developed to model the high temperature, time dependent behavior of Rene' 80 which is a cast turbine blade and vane nickel base superalloy. Considerations in model development included the cyclic softening behavior of Rene' 80, rate independence at lower temperatures and the development of a new model for static recovery.

Ramaswamy, V. G.↗

NASA NTRS1996

Temperature-Dependent Effects on the Mechanical Behavior and Deformation Substructure of Haynes 188 Under Low-Cycle Fatigue

The mechanical behavior of a cobalt-nickel-chromium-tungsten superalloy, Haynes 188, is being critically examined at the NASA Lewis Research Center. This dynamic, strain-aging (DSA) alloy is used for combustor liners in many military and commercial aircraft turbine engines and for the liquid oxygen posts in the main injectors of the space shuttle main engine. Its attractive features include a good combination of high monotonic yield and tensile strength, and excellent fabricability, weldability, and resistance to high-temperature oxidation for prolonged exposures.

Source record↗

NASA NTRS1979

Weight Saving Technology

The airplane shown below is the Beech Super King Air, an executive transport built by Beech Aircraft corporation, Wichita, Kansas. Its development was aided by the NASA computer program known as NASTRAN(Registered TradeMark) (NASA Structural Analysis), which electronically analyzes a computerized design and predicts how it will react to many different conditions of stress and strain. In this instance the program was employed in analysis of the airplane's structure and engine mounts. NASTRAN was similarly used in development of other Beech planes, such as the T-34C military trainer and the new single-engine Skipper light-plane, which is making its debut this year. At its Boulder, Colorado facility, Beech has used NASTRAN in analysis of fuel tanks for space vehicles. The company reports it has achieved cost savings and improved its design/analysis capabilities through use of the NASA program. NASTRAN and other government-generated computer programs are made available to industry through NASA's Computer Software Management and Information Center (COSMIC)(Registered TradeMark) at the University of Georgia.

Source record↗

NASA NTRS2012

NASA Tech Briefs, May 2012

Topics covered include: An "Inefficient Fin" Non-Dimensional Parameter to Measure Gas Temperatures Efficiently; On-Wafer Measurement of a Multi-Stage MMIC Amplifier with 10 dB of Gain at 475 GHz; Software to Control and Monitor Gas Streams; Miniaturized Laser Heterodyne Radiometer (LHR) for Measurements of Greenhouse Gases in the Atmospheric Column; Anomaly Detection in Test Equipment via Sliding Mode Observers; Absolute Position of Targets Measured Through a Chamber Window Using Lidar Metrology Systems; Goldstone Solar System Radar Waveform Generator; Fast and Adaptive Lossless Onboard Hyperspectral Data Compression System; Iridium Interfacial Stack - IrIS; Downsampling Photodetector Array with Windowing; Optical Phase Recovery and Locking in a PPM Laser Communication Link; High-Speed Edge-Detecting Line Scan Smart Camera; Optical Communications Channel Combiner; Development of Thermal Infrared Sensor to Supplement Operational Land Imager; Amplitude-Stabilized Oscillator for a Capacitance-Probe Electrometer; Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data; Histogrammatic Method for Determining Relative Abundance of Input Gas Pulse; Predictive Sea State Estimation for Automated Ride Control and Handling - PSSEARCH; LEGION: Lightweight Expandable Group of Independently Operating Nodes; Real-Time Projection to Verify Plan Success During Execution; Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data; Web-Based Customizable Viewer for Mars Network Overflight Opportunities; Fabrication of a Cryogenic Terahertz Emitter for Bolometer Focal Plane Calibrations; Fabrication of an Absorber-Coupled MKID Detector; Graphene Transparent Conductive Electrodes for Next- Generation Microshutter Arrays; Method of Bonding Optical Elements with Near-Zero Displacement; Free-Mass and Interface Configurations of Hammering Mechanisms; Wavefront Compensation Segmented Mirror Sensing and Control; Long-Life, Lightweight, Multi-Roller Traction Drives for Planetary Vehicle Surface Exploration; Reliable Optical Pump Architecture for Highly Coherent Lasers Used in Space Metrology Applications; Electrochemical Ultracapacitors Using Graphitic Nanostacks; Improved Whole-Blood-Staining Device; Monitoring Location and Angular Orientation of a Pill; Molecular Technique to Reduce PCR Bias for Deeper Understanding of Microbial Diversity; Laser Ablation Electrodynamic Ion Funnel for In Situ Mass Spectrometry on Mars; High-Altitude MMIC Sounding Radiometer for the Global Hawk Unmanned Aerial Vehicle; PRTs and Their Bonding for Long-Duration, Extreme-Temperature Environments; Mid- and Long-IR Broadband Quantum Well Photodetector; 3D Display Using Conjugated Multiband Bandpass Filters; Real-Time, Non-Intrusive Detection of Liquid Nitrogen in Liquid Oxygen at High Pressure and High Flow; Method to Enhance the Operation of an Optical Inspection Instrument Using Spatial Light Modulators; Dual-Compartment Inflatable Suitlock; Large-Strain Transparent Magnetoactive Polymer Nanocomposites; Thermodynamic Vent System for an On-Orbit Cryogenic Reaction Control Engine; Time Distribution Using SpaceWire in the SCaN Testbed on ISS; and Techniques for Solution- Assisted Optical Contacting.

Source record↗

NASA NTRS2003

Advanced Packaging Technology Used in Fabricating a High-Temperature Silicon Carbide Pressure Sensor

The development of new aircraft engines requires the measurement of pressures in hot areas such as the combustor and the final stages of the compressor. The needs of the aircraft engine industry are not fully met by commercially available high-temperature pressure sensors, which are fabricated using silicon. Kulite Semiconductor Products and the NASA Glenn Research Center have been working together to develop silicon carbide (SiC) pressure sensors for use at high temperatures. At temperatures above 850 F, silicon begins to lose its nearly ideal elastic properties, so the output of a silicon pressure sensor will drift. SiC, however, maintains its nearly ideal mechanical properties to extremely high temperatures. Given a suitable sensor material, a key to the development of a practical high-temperature pressure sensor is the package. A SiC pressure sensor capable of operating at 930 F was fabricated using a newly developed package. The durability of this sensor was demonstrated in an on-engine test. The SiC pressure sensor uses a SiC diaphragm, which is fabricated using deep reactive ion etching. SiC strain gauges on the surface of the diaphragm sense the pressure difference across the diaphragm. Conventionally, the SiC chip is mounted to the package with the strain gauges outward, which exposes the sensitive metal contacts on the chip to the hostile measurement environment. In the new Kulite leadless package, the SiC chip is flipped over so that the metal contacts are protected from oxidation by a hermetic seal around the perimeter of the chip. In the leadless package, a conductive glass provides the electrical connection between the pins of the package and the chip, which eliminates the fragile gold wires used previously. The durability of the leadless SiC pressure sensor was demonstrated when two 930 F sensors were tested in the combustor of a Pratt & Whitney PW4000 series engine. Since the gas temperatures in these locations reach 1200 to 1300 F, the sensors were installed in water-cooled jackets, as shown. This was a severe test because the pressure-sensing chips were exposed to the hot combustion gases. Prior to the installation of the SiC pressure sensors, two high-temperature silicon sensors, installed in the same locations, did not survive a single engine run. The durability of the leadless SiC pressure sensor was demonstrated when both SiC sensors operated properly throughout the two runs that were conducted.

Beheim, Glenn M.↗

NASA NTRS2008

Fiber Optic Sensing Monitors Strain and Reduces Costs

In applications where stress on a structure may vary widely and have an unknown impact on integrity, a common engineering strategy has been overbuilding to ensure a sufficiently robust design. While this may be appropriate in applications where weight concerns are not paramount, space applications demand a bare minimum of mass, given astronomical per-pound launch costs. For decades, the preferred solution was the tactic of disassembly and investigation between flights. Knowing there must be a better way, Dr. Mark Froggatt, of Langley Research Center, explored alternate means of monitoring stresses and damage to the space shuttle. While a tear-it-apart-and-have-a-look strategy was effective, it was also a costly and time consuming process that risked further stresses through the very act of disassembly and reassembly. An alternate way of monitoring the condition of parts under the enormous stresses of space flight was needed. Froggatt and his colleagues at Langley built an early-warning device to provide detailed information about even minuscule cracks and deformations by etching a group of tiny lines, or grating, on a fiber optic cable five-thousandths of an inch thick with ultraviolet light. By then gluing the fiber to the side of a part, such as a fuel tank, and shining a laser beam down its length, reflected light indicated which gratings were under stress. Inferring this data from measurements in light rather than in bonded gauges saved additional weight. Various shuttle components now employ the ultrasonic dynamic vector stress sensor (UDVSS), allowing stress detection by measuring light beamed from a built-in mini-laser. By measuring changes in dynamic directional stress occurring in a material or structure, and including phase-locked loop, synchronous amplifier, and contact probe, the UDVSS proved especially useful among manufacturers of aerospace and automotive structures for stress testing and design evaluation. Engineers could ensure safety in airplanes and spaceships with a narrower, not overbuilt, margin of safety. For this development, in 1997, Discover Magazine named Froggatt a winner in the "Eighth Annual Awards for Technological Innovation" from more than 4,000 entries.

Source record↗

DOE OSTI2026

Altermagnetic polar metallic phase in ultrathin epitaxially strained RuO 2 films

Altermagnetism refers to a wide class of magnetic orders featuring magnetic sublattices with opposite spins related by rotational symmetries, resulting in nontrivial spin splitting and magnetic multipoles. However, the direct observation of the altermagnetic transition remains elusive. Here, by combining theoretical analysis, electrical transport, X-ray, and optical spectroscopies, we establish a phase diagram in hybrid molecular beam epitaxy-grown RuO 2 /TiO 2 (110) films, mapping symmetries along with altermagnetic/electronic/structural phase transitions as functions of film thickness and temperature. This features an altermagnetic metallic polar phase in epitaxially strained 2 nm films, suggesting a potential link between polar metals and altermagnetic materials. Such a clear signature of a magnetic phase transition at ~500 K is observed exclusively in ultrathin strained films, unlike in bulk RuO 2 single crystals. These results highlight the power of epitaxial heterostructure engineering to induce altermagnetism in systems initially nonmagnetic, opening avenues for realizing emergent quantum phases with multifunctional properties.

RuO2 thin film↗

NASA NTRS2003

Sintering and Interface Strain Tolerance of Plasma-Sprayed Thermal and Environmental Barrier Coatings

Ceramic thermal and environmental barrier coatings will be more aggressively designed to protect gas turbine engine hot section SiC/SiC Ceramic Matrix Composite (CMC) components in order to meet future engine higher fuel efficiency and lower emission goals. A coating system consisting of a zirconia-based oxide topcoat (thermal barrier) and a mullite/BSAS silicate inner coat (environmental barrier) is often considered a model system for the CMC applications. However, the coating sintering, and thermal expansion mismatch between the zirconia oxide layer and the silicate environmental barrier/CMC substrate will be of major concern at high temperature and under thermal cycling conditions. In this study, the sintering behavior of plasma-sprayed freestanding zirconia-yttria-based thermal barrier coatings and mullite (and/or barium-strontium-aluminosilicate, i.e., BSAS) environmental barrier coatings was determined using a dilatometer in the temperature range of 1200-1500 C. The effects of test temperature on the coating sintering kinetics were systematically investigated. The plasma-sprayed zirconia-8wt.%yttria and mullite (BSAS) two-layer composite coating systems were also prepared to quantitatively evaluate the interface strain tolerance of the coating system under thermal cycling conditions based on the dilatomentry. The cyclic response of the coating strain tolerance behavior and interface degradation as a function of cycle number will also be discussed.

Zhu, Dongming↗

NASA NTRS1980

Comparison of elastic and elastic-plastic structural analyses for cooled turbine blade airfoils

Elastic plastic stress strain states in cooled turbine blade airfoils were calculated by three methods for the initial takeoff transient of an advanced technology aircraft engine. The three analytical methods compared were a three dimensional elastic plastic, finite element analysis, a three dimensional, elastic, finite element analysis, and a one dimensional, elastic plastic, beam theory analysis. Structural analyses were performed for eight cases involving different combinations of mechanical and thermal loading on impingement cooled airfoils with and without leading edge film cooling holes. The von Mises effective total strains at maximum takeoff computed from the elastic and elastic plastic finite element analyses agreed with 9 percent for rotating airfoils and 28 percent for stationary airfoils with the elastic results on the conservative side.

Kaufman, A.↗

DOE OSTI2025

Structural analysis of the NifL-NifA complex reveals the molecular basis of anti-activation of nitrogen fixation gene expression in Azotobacter vinelandii

Understanding the molecular basis of regulated nitrogen (N 2 ) fixation is essential for engineering N 2 -fixing bacteria that fulfill the demand of crop plants for fixed nitrogen, reducing our reliance on synthetic nitrogen fertilizers. In Azotobacter vinelandii and many other members of Proteobacteria, the two-component system comprising the anti-activator protein (NifL) and the Nif-specific transcriptional activator (NifA)controls the expression of nif genes, encoding the nitrogen fixation machinery. The NifL-NifA system evolved the ability to integrate several environmental cues, such as oxygen, nitrogen, and carbon availability. The nitrogen fixation machinery is thereby only activated under strictly favorable conditions, enabling diazotrophs to thrive in competitive environments. While genetic and biochemical studies have enlightened our understanding of how NifL represses NifA, the molecular basis of NifA sequestration by NifL depends on structural information on their interaction. Here, we present mechanistic insights into how nitrogen fixation is regulated by combining biochemical and genetic approaches with a low-resolution cryo-electron microscopy (cryo-EM) map of the oxidized NifL-NifA complex. Our findings define the interaction surface between NifL and NifA and reveal how this interaction can be manipulated to generate bacterial strains with increased nitrogen fixation rates able to secrete surplus nitrogen outside the cell, a crucial step in engineering improved nitrogen delivery to crop plants.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2024

Simultaneous measurement of temperature and strain by cascaded fiber Bragg grating-silicon Fabry-Perot interferometer sensor

We report a fiber-optic sensor configuration with a cascaded fiber Bragg grating (FBG) and a silicon Fabry-Perot interferometer (FPI) for simultaneous measurement of temperature and strain. The sensor is composed of a 5 mm FBG on a single mode fiber and a 100μm thick silicon FPI attached to the tip of the optical fiber. The FBG is surface mounted on the host structure, and the FPI tip is suspended. Due to the stress-free, cantilever configuration, the silicon FPI is insensitive to strain, but sensitive to temperature with a sensitivity much higher than the FBG due to the large thermo-optic coefficient of silicon. The sensor is tested from room temperature to 100°C with varying strain up to ∼150με. The silicon FPI provides high temperature sensitivity of 89 pm/°C unaffected by strain. Since the FBG is attached to the host structure, it is affected by both thermal and mechanical strain; the sensitivity of these was experimentally obtained 32 pm/°C and 1.09 pm / με, respectively. Interrogated with a broadband light source and a high-speed spectrometer, the sensor shows temperature and strain resolutions of 1.9 × 10 −3 °C and 0.042 με, respectively. Here, due to the small size, enhanced sensitivity, and high resolution, this cascaded FBG-FPI sensor can be used in applications where accurate measurement of temperature and strain is required.

42 ENGINEERING↗

DOE OSTI2024

Predicting non-linear stress–strain response of mesostructured cellular materials using supervised autoencoder

Recent breakthroughs in advanced manufacturing capabilities have made it possible to design and print sophisticated topologies of cellular structures using diverse engineering materials such as metals, polymers, and ceramics. In these architectured materials, it is often desirable to tailor the mechanical properties by altering the unit cell topology. This necessitates an in-depth understanding of how the topology of the unit cell structure affects the macroscopic behavior of the material in both the linear and the non-linear regimes encountered under large compression. Here, we have developed a machine learning (ML) approach capable of accelerating the prediction of the stress–strain response of a polymer-based cellular structure under uniaxial confined compression. As part of generating the training data for ML, 60,000 mesostructures were generated using a relatively novel approach based on cellular automata, and their corresponding stress–strain responses were obtained from the finite element simulations. Principal component analysis (PCA) was used to reduce the dimensionality of the stress–strain curves. With only 20 principal components, PCA captured 99.89% of the variance in the stress–strain curves while reducing the dimensionality by 5X. ML using supervised autoencoder was able to successfully speed up the prediction of the non-linear stress–strain response of a unit cell by up to 4600X. The proposed method can serve as an efficient data generation tool and a rapid means for predicting the structure–property relationship through accelerated forward modeling of cellular materials under compaction, in cases where the macroscopic stress–strain response is governed by the unit-cell topology.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Interleaved bond frustration in a triangular lattice antiferromagnet

Frustration of long-range order via lattice geometry amplifies fluctuations and generates ground states that are highly sensitive to perturbations. Traditionally, geometric frustration is used to engineer unconventional magnetic states; however, the charge degree of freedom and bond order can be similarly frustrated. Finding materials that host both frustrated magnetic and bond networks holds promise for engineering structural and magnetic states with the potential of coupling to one another via either magnetic or strain fields. Here we identify an unusual instance of this coexistence in the triangular lattice antiferromagnets LnCd 3 P 3 (Ln = lanthanides). These compounds feature two-dimensional planes of unique trigonal planar CdP 3 units with an underlying bond instability that is frustrated via emergent kagome ice correlations. This bond instability is interleaved in between layers of frustrated magnetic moments. Furthermore, our results establish LnCd 3 P 3 as a rare materials class in which frustrated magnetism is embedded within a dopable semiconductor with a frustrated bond order instability.

Gomez Alvarado, S. J. [University of California, S↗

NASA NTRS1978

Thermal-structural mission analyses of air-cooled gas turbine blades

Cyclic temperature and stress-strain states in cooled turbine blades were calculated for a simulated mission of an advanced technology aircraft engine. TACT1 (three dimensional heat transfer) and MARC (nonlinear structural analysis) computer programs were used to analyze impingement cooled airfoils, with and without leading-edge film cooling. Creep was the predominant damage mode, particularly around film cooling holes. Radially angled holes exhibited less creep than holes normal to surface. Beam-type analyses of all-impingement cooled airfoils gave fair agreement with MARC results for initial creep.

Kaufman, A.↗

NASA NTRS1979

Thermal-structural mission analyses of air-cooled gas turbine blades

Cyclic temperature and stress-strain states in cooled turbine blades were calculated for a simulated mission of an advanced technology aircraft engine. TACTl (three dimensional heat transfer) and MARC (nonlinear structural analysis) computer programs were used to analyze impingement cooled airfoils, with and without leading-edge film cooling. Creep was the predominant damage mode, particularly around film cooling holes. Radially angled holes exhibited less creep than holes normal to surface. Beam-type analyses of all-impingement cooled airfoils gave fair agreement with MARC results for initial creep.

Kaufman, A.↗

NASA NTRS1988

Evaluation of structural analysis methods for life prediction

The utility of advanced constitutive models and structural analysis methods are evaluated for predicting the cyclic life of an air-cooled turbine blade for a gas turbine aircraft engine. Structural analysis methods of various levels of sophistication were exercised to obtain the cyclic stress-strain response at the critical airfoil location. Calculated strain ranges and mean stresses from the stress-strain cycles were used to predict crack initiation lives by using the total strain version of the strain range partitioning life prediction method. The major results are given and discussed.

Kaufman, A.↗