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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Monitoring deformation at the Geysers Geothermal Field, California using C-band and X-band interferometric synthetic aperture radar

In this study, we resolve deformation at The Geysers Geothermal Field using two distinct sets of interferometric synthetic aperture radar (InSAR) data. The first set of observations utilize archived European Space Agency C-band synthetic aperture radar data from 1992 through 1999 to image the long-term and large-scale subsidence at The Geysers. The peak range velocity of approximately 50 mm/year agrees with previous estimates from leveling and global positioning system observations. Data from a second set of measurements, acquired by TerraSAR-X satellites, extend from May 2011 until April 2012 and overlap the C-band data spatially but not temporally. These X-band data, analyzed using a combined permanent and distributed scatterer algorithm, provide a higher density of scatterers (1122 per square kilometer) than do the C-band data (12 per square kilometer). The TerraSAR-X observations resolve 1 to 2 cm of deformation due to water injection into a Northwest Geysers enhanced geothermal system well, initiated on October 2011. Lastly, the temporal variation of the deformation is compatible with estimates from coupled numerical modeling.

58 GEOSCIENCES↗
DOE OSTI2016

N = 1 Deformations and RG flows of N = 2 SCFTs, part II: non-principal deformations

We continue to investigate the N = 1 deformations of four-dimensional N = 2 superconformal field theories (SCFTs) labeled by a nilpotent element of the flavor symmetry [1]. This triggers a renormalization group (RG) flow to an N = 1 SCFT. We systematically analyze all possible deformations of this type for certain classes of N = 2 SCFTs: conformal SQCDs, generalized Argyres-Douglas theories and the E 6 SCFT. We find a number of examples where the amount of supersymmetry gets enhanced to N = 2 at the end point of the RG flow. Most notably, we find that the SU(N) and Sp(N) conformal SQCDs can be deformed to flow to the Argyres-Douglas (AD) theories of type (A 1 ,D 2 N-1 ) and (A 1 ,D 2 N ) respectively. This RG flow therefore allows us to compute the full superconformal index of the (A 1 ,D N ) class of AD theories. Moreover, we find an infrared duality between N = 1 theories where the fixed point is described by an N = 2 AD theory. We observe that the classes of examples that exhibit supersymmetry enhancement saturate certain bounds for the central charges implied by the associated two-dimensional chiral algebra.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Single Crystal Plasticity Model with Deformation Twinning for the High Rate Deformation of β-HMX

Deformation twinning is an active deformation mechanism during loading along certain crystallographic directions of β-cyclotetramethylene tetranitramine (β-HMX). In this work, a finite strain thermomechanical model is extended to include twinning as a deformation mechanism in addition to plastic slip. The stress is derived from the free energy expression including a term representing the equation of state. The crystal plasticity framework is used to divide the total strain into inelastic and elastic component, where the elastic part is used in the expression for the free energy. The twin systems are treated as pseudo slip systems and the shear rate on the twin systems is evaluated in terms of the twin resistance and the projection of the stress tensor. The model parameters were calibrated against a set of plate impact experiments performed on β-HMX by Dick et al. The remaining plate impact experiments are used to evaluate the predictive capability of the model. The quality of the model fits and predictions is discussed from a physical and modeling perspective. Particularly, the role of twin modeling on results is highlighted. Finally, the model is used to explore the relationship between the propensity for twinning and crystal orientation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Bright x-rays reveal shifting deformation states and effects of the microstructure on the plastic deformation of crystalline materials

The plastic deformation of crystalline materials is usually modeled as smoothly progressing in space and time, yet modern studies show intermittency in the deformation dynamics of single-crystals arising from avalanche behavior of dislocation ensembles under uniform applied loads. However, once the prism of the microstructure in polycrystalline materials disperses and redistributes the load on a grain-by-grain basis, additional length and time scales are involved. Thus, the question is open as to how deformation intermittency manifests for the nonuniform grain-scale internal driving forces interacting with the finer-scale dislocation ensemble behavior. In this work we track the evolution of elastic strain within individual grains of a creep-loaded titanium alloy, revealing widely varying internal strains that fluctuate over time. Here, the findings provide direct evidence of how flow intermittency proceeds for an aggregate of ~700 grains while showing the influences of multiscale ensemble interactions and opening new avenues for advancing plasticity modeling.

36 MATERIALS SCIENCE↗
DOE OSTI2015

37 97Rb60: The Cornerstone of the Region of Deformation around A ~ 100

Excited states of the neutron-rich nuclei 97,99 Rb were populated for the first time using the multistep Coulomb excitation of radioactive beams. Comparisons of the results with particle-rotor model calculations provide clear identification for the ground-state rotational band of 97 Rb as being built on the πg 9/2 [431] 3/2+ Nilsson-model configuration. The ground-state excitation spectra of the Rb isotopes show a marked distinction between single-particle-like structures below N=60 and rotational bands above. The present study defines the limits of the deformed region around A~100 and indicates that the deformation of 97 Rb is essentially the same as that observed well inside the deformed region. It further highlights the power of the Coulomb-excitation technique for obtaining spectroscopic information far from stability. The 99 Rb case demonstrates the challenges of studies with very short-lived postaccelerated radioactive beams.

Sotty, C.↗
NASA NTRS1989

Dynamic grid deformation using Navier-displacement equation for deforming wings

For dynamic and aeroelastic applications of maneuvering wings, the solid boundaries undergo rigid-body motion and aeroelastic deformation. For rigid-body motion, the conservative fluid dynamics equation, in terms of the Eulerian description, is written in terms of a moving frame of reference, and the problem is solved on a time-independent body-conformed grid. For both rigid-body motion and aeroelastic deformation, the Navier-displacement equation, in terms of the Lagrangian coordinates, is modified for fluid-flow problems. It is used along with the Eulerian description of the conservative fluid dynamics equations to account for the grid deformation.

Kandil, Osama A.↗
NASA NTRS1992

Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transformation temperature

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is considered a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems. More importantly though, probing the deformation mechanisms operating in fatigue will lead to a better understanding of NiAl's unique characteristics. Low cycle fatigue properties have been reported on binary NiAl in the past year, yet those studies were limited to two temperature ranges: room temperature and near 1000 K. Eventually, fatigue property data will be needed for a wide range of temperatures and compositions. The intermediate temperature range near the brittle-to-ductile transition was chosen for this study to ascertain whether the sharp change occurring in monotonic behavior also occurs under cyclic conditions. An effort was made to characterize the dislocation structures which evolved during fatigue testing and comment on their role in the deformation process.

Antolovich, Stephen D.↗
NASA NTRS2003

A Variational Principle for Reconstruction of Elastic Deformations in Shear Deformable Plates and Shells

A variational principle is formulated for the inverse problem of full-field reconstruction of three-dimensional plate/shell deformations from experimentally measured surface strains. The formulation is based upon the minimization of a least squares functional that uses the complete set of strain measures consistent with linear, first-order shear-deformation theory. The formulation, which accommodates for transverse shear deformation, is applicable for the analysis of thin and moderately thick plate and shell structures. The main benefit of the variational principle is that it is well suited for C(sup 0)-continuous displacement finite element discretizations, thus enabling the development of robust algorithms for application to complex civil and aeronautical structures. The methodology is especially aimed at the next generation of aerospace vehicles for use in real-time structural health monitoring systems.

Tessler, Alexander↗
DOE OSTI2020

Topology optimization of multiple deformable bodies in contact with large deformations

Previous works in topology optimization of structures with contact boundary conditions have concentrated on the two-dimensional rigid obstacle problem. This is because the contact analysis of multiple three-dimensional deformable bodies with meshes that are non-matching across the contact interface requires computationally complex contact algorithms beyond the scope of previous optimization investigations. Here, our research is devoted to addressing topology design problems with multiple deformable three-dimensional components in contact using state-of-the-art contact algorithms.

42 ENGINEERING↗
DOE OSTI2015

Phase transformation as the single-mode mechanical deformation of silicon

The mixture of the metastable body-centered cubic (bc8) and rhombohedral (r8) phases of silicon that is formed via nanoindentation of diamond cubic (dc) silicon exhibits properties that are of scientifc and technological interest. This letter demonstrates that large regions of this mixed phase can be formed in crystalline Si via nanoindentation without signifcant damage to the surrounding crystal. Cross-sectional transmission electron microscopy is used to show that volumes 6 μm wide and up to 650 nm deep can be generated in this way using a spherical tip of ~21.5 μm diameter. The phase transformed region is characterised using both Raman microspectroscopy and transmission electron microscopy. It is found that uniform loading using large spherical indenters can favor phase transformation as the sole deformation mechanism as long as the maximum load is below a critical level. We suggest that the sluggish nature of the transformation from the dc-Si phase to the metallic (b-Sn) phase normally results in competing deformation mechanisms such as slip and cracking but these can be suppressed by controlled loading conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Deformation mechanisms, defects, heat treatment, and thermal conductivity in large grain niobium

The physical and mechanical metallurgy underlying fabrication of large grain cavities for superconducting radio frequency accelerators is summarized, based on research of 1) grain orientations in ingots, 2) a metallurgical assessment of processing a large grain single cell cavity and a tube, 3) assessment of slip behavior of single crystal tensile samples extracted from a high purity ingot slice before and after annealing at 800 °C / 2 h, 4) development of crystal plasticity models based upon the single crystal experiments, and 5) assessment of how thermal conductivity is affected by strain, heat treatment, and exposure to hydrogen. Because of the large grains, the plastic anisotropy of deformation is exaggerated, and heterogeneous strains and localized defects are present to a much greater degree than expected in polycrystalline material, making it highly desirable to computationally anticipate potential forming problems before manufacturing cavities.

36 MATERIALS SCIENCE↗
DOE OSTI2016

X-ray metrology and performance of a 45-cm long x-ray deformable mirror

We describe experiments with a 45-cm long x-ray deformable mirror (XDM) that have been conducted in End Station 2, Beamline 5.3.1 at the Advanced Light Source. A detailed description of the hardware implementation is provided. We explain our one-dimensional Fresnel propagation code that correctly handles grazing incidence and includes a model of the XDM. This code is used to simulate and verify experimental results. Initial long trace profiler metrology of the XDM at 7.5 keV is presented. The ability to measure a large (150-nm amplitude) height change on the XDM is demonstrated. The results agree well with the simulated experiment at an error level of 1 μrad RMS. Lastly, direct imaging of the x-ray beam also shows the expected change in intensity profile at the detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Deformation of a super-elastic NiTiNb alloy with controllable stress hysteresis

Room temperature deformation of a Ni{sub 46.7}Ti{sub 42.8}Nb{sub 10.5} alloy was studied by in-situ synchrotron X-ray diffraction. Compared to binary NiTi alloy, the Nb dissolved in the matrix significantly increased the onset stress for Stress-Induced Martensite Transformation (SIMT). The secondary phase, effectively a Nb-nanowire dispersion in a NiTi-Nb matrix, increased the elastic stiffness of the bulk material, reduced the strain anisotropy in austenite families by load sharing during SIMT, and increased the stress hysteresis by resisting reverse phase transformation during unloading. The stress hysteresis can be controlled over a wide range by heat treatment through its influences on the residual stress of the Nb-nanowire dispersion and the stability of the austenite.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Deformation Behavior and Microstructural Evolution of Reeled Pipeline Steels during Cyclic Plastic Deformation

API X60 steel used for reeled pipeline was subjected to different amounts of cyclic plastic deformation (CPD) by multiple tension–compression tests in order to study the deformation behavior and microstructural evolution during each stage of reel-lay installation process. It was found that the yield strength was significantly reduced by about 110 MPa during the first CPD cycle due to the Bauschinger effect. However, the yield strength was little affected by the subsequent CPD cycles, and the yield strength difference between tension and compression tended to reach a steady-state value of 23 MPa after multiple CPD cycles. With the increase in CPD cycles, the proportion of low-angle grain boundaries declined from 50.9 to 35.7%, and the CPD contributed to the formation of immovable dislocation walls and cells due to the dislocation rearrangement, causing the stable yield strength. The CPD process with strain level of 3% had no prominent effect on the tensile strength and elongation, because the change in microstructures was not enough to alter the work hardening completely after multiple CPD cycles.

36 MATERIALS SCIENCE↗