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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Mechanism of Influence of Nanocrystal Sizes on the Parameters of the Curves of the Pseudoelastic and Thermoelastic Deformations of Alloys with the Shape Memory Effect

The data available in the literature on the influence of the nanocrystal sizes of alloys with the shape memory effect on the parameters of the curves of their pseudoelastic and thermoelastic deformation are analyzed in the framework of the theory of diffuse martensitic transitions (DMT). The peculiarity of the DMT theory is that it is based on both thermodynamic and kinetic relationships that make it sensitive to the alloy structure on the mesoscopic scale. This enables one to state the functional dependence of the parameter of the martensitic deformation of the nanocrystals on the size of their cross section D. As a result of the analysis, it is found that the coefficient of the strain (martensitic) hardening and the hysteresis of the pseudoelastic strain curves of submicrocrystals of the Ni{sub 54}Fe{sub 19}Ga{sub 27} are changed with D by law 1/D{sup 2}. The temperature range (M{sub s} – M{sub f}) of the martensitic transition in TiNi alloy nanocrystals is changed by analogy law. These dependences are results of the constrained displacement of dislocations of the phase transformation by transverse sizes of the crystal. A kinetic mechanism of the appearance of the critical nanocrystal size D{sub k} is established; the transition of austenite to martensite does not occur at transverse crystal sizes smaller than the critical size.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Compact Thermoelastic Cooling System

Maryland Energy & Sensor Technologies, LLC (MEST) demonstrated novel compression-based compact thermoelastic coolers which can be operated in a continuous (non-reciprocating) manner. Roller-based systems were developed which use NiTi (Nickel titanium alloy or Nitinol) wire coils as the refrigerants continuously fed into the rollers for rejecting heat and delivering cooling. Additive manufacturing was used to print heat-exchange subsystems of different shapes and dimensions. Direct cooling of water as the medium was clearly demonstrated, and a clear path toward achieving delivered cooling of up to 400 W per a roller was demonstrated. Some of the innovations developed here included affixing wound coils of NiTi wires around rollers, engineering the shape of the heat-exchanger to enhance the heat exchange coefficient, and introducing a heat rejection mechanism.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1966

Coupled thermoelasticity of bars.

Boundary value problems for semiinfinite bars made of coupled thermoelastic material solved by new functions that are corrections to classic tabulated functions

ERROR FUNCTION↗
DOE OSTI2018

Exponential and Polynomial Decay in a Thermoelastic-Bresse System with Second Sound

In this paper we study the well-posedness and the asymptotic stability of a one-dimensional thermoelastic Bresse system, where the heat conduction is given by Cattaneo’s law effective in the shear angle displacements. We establish the well-posedness of the system and prove that the system is exponentially stable depending on the parameters of the system. Furthermore, we show that in general, the system is not exponential stable. In this regards, we prove that the solution decays polynomially.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Thermoelastic-plastic flow equations in general coordinates

The equations governing the thermoelastic-plastic flow of isotropic solids in the Prandtl- Reuss and small anisotropy approximations in Cartesian coordinates are generalized to arbitrary coordinate systems. In applications the choice of coordinates is dictated by the symmetry of the solid flow. Here, the generally invariant equations are evaluated in spherical, cylindrical (including uniaxial), and both prolate and oblate spheroidal coordinates.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

High pressure thermoelasticity and sound velocities of Fe-Ni-Si alloys

The Earth's iron-dominant core is known to contain nickel from cosmochemical analysis and some amount of light elements from geophysical constraints on density and seismic wave velocities. Although there have been several studies to constrain thermoelastic properties of iron-alloys, there has been no systematic study on the effects of nickel and light elements on properties of iron using the same experimental methods and data analysis approach. We conducted nuclear resonant inelastic X-ray scattering and X-ray diffraction experiments on body-centered cubic and hexagonal close-packed (hcp) Fe 0.91 Ni 0.09 and Fe 0.8 Ni 0.1 Si 0.1 up to 104 GPa and 86 GPa, respectively, and compare to similar measurements conducted on hcp-Fe up to 171 GPa. Specifically, we determine the Debye sound velocity from the low-energy transfer region of the (partial) phonon density of states (DOS) using the equation of state determined for each material and a new approach which utilizes information criteria and probability distributions. Nickel decreases the shear velocity of iron, while 10 at% Si has little to no effect on the shear velocity of Fe 0.91 Ni 0.09 . We observe that the shape of the phonon DOS of these alloys remains similar with increasing pressure. In the measured compression range, we therefore apply a generalized scaling law to describe the volume dependence of the phonon DOS and find that the vibrational Grüneisen parameters of hcp-Fe 0.91 Ni 0.09 are nearly indistinguishable from those hcp-Fe and those for Fe 0.8 Ni 0.1 Si 0.1 trend lower. From the vibrational free energy, we constrain the harmonic vibrational component of thermal pressure, which shows a significant positive deviation from theoretical calculations of hcp-Fe at pressures and temperatures of Earth's core. Collectively, our results demonstrate that the effects of nickel should be considered when modeling iron-rich planetary cores.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Thermoelastic Properties of Eclogitic Garnets and Omphacites: Implications for Deep Subduction of Oceanic Crust and Density Anomalies in the Upper Mantle

In this work, synchrotron-based high-pressure/high-temperature single-crystal X-ray diffraction experiments to ~24 GPa and 700 K were conducted on eclogitic garnets (low-Fe: Prp 28 Alm 38 Grs 33 Sps 1 and high-Fe: Prp 14 Alm 62 Grs 19 Adr 3 Sps 2 ) and omphacites (low-Fe: Quad 57 Jd 42 Ae 1 and high-Fe: Quad 53 Jd 27 Ae 20 ), using an externally heated diamond anvil cell. Fitting the pressure-volume-temperature data to a third-order Birch-Murnaghan equation of state yields the thermoelastic parameters including bulk modulus ($K_{T0}$), its pressure derivative ($K'_{T0}$), temperature derivative (($∂K_T/∂T)_P$), and thermal expansion coefficient ($α_T$). The densities of the high-Fe and low-Fe eclogites were then modeled along typical geotherms of the normal mantle and the subducted oceanic crust to the transition zone depth (550 km). The metastable low-Fe eclogite could be a reason for the stagnant slabs within the upper range of the transition zone. Eclogite would be responsible for density anomalies within 100–200 km in the upper mantle of Asia.

58 GEOSCIENCES↗
DOE OSTI2024

Thermoelastic Anomaly of Iron Carbonitride Across the Spin Transition and Implications for Planetary Cores

Carbon and nitrogen are considered as candidate light elements present in planetary cores. However, there is limited understanding regarding the structure and physical properties of Fe-C-N alloys under extreme conditions. Here diamond anvil cell experiments were conducted, revealing the stability of hexagonal-structured Fe 7 (N 0.75 C 0.25 ) 3 up to 120 GPa and 2100 K, without undergoing any structural transformation or dissociation. Notably, the thermal expansion coefficient and Grüneisen parameter of the alloy exhibit a collapse at 55–70 GPa. First-principles calculations suggest that such anomaly is associated with the spin transition of iron within Fe 7 (N 0.75 C 0.25 ) 3 . Our modeling indicates that the presence of ∼1.0 wt% carbon and nitrogen in liquid iron contributes to 9–12% of the density deficit of the Earth's outer core. The thermoelastic anomaly of the Fe-C-N alloy across the spin transition is likely to affect the density and seismic velocity profiles of (C,N)-rich planetary cores, thereby influencing the dynamics of such cores.

Geology↗
DOE OSTI2013

Thermoelastic investigation of a quartz tuning fork used in infrared spectroscopy

The performances of quartz tuning forks (QTF) used in infrared spectroscopy for pollutant detection are investigated. The transduction between light and QTF vibration is elucidated, thanks to QTF encapsulation under vacuum. From the sensitivity enhancement which is obtained, we conclude that their interaction is photo-thermoelastic rather than photo-thermoacoustic. A mapping of the local sensitivity of the QTF is obtained by scanning its faces with the excitation probe beam. The comparison between the signal mapping and the theoretical strain mapping indicates that the most efficient areas of the QTF correspond to the areas where the strain or stress is the highest.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Laser thermoelastic generation in metals above the melt threshold

An approach is presented for calculating thermoelastic generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation. Detailed consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the appearance and subsequent growth and then contraction of the melt pool, and the time dependent thermal conduction in the melt and surrounding solid throughout. The excitation of the ultrasound takes place during and shortly after the laser pulse and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. It is shown how, because of this, the output of the thermal simulations can be expressed as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response to these force distributions is obtained by two methods, the one based on the elastodynamic Green's functions for plate geometry determined by the Cagniard generalized ray method and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported on the epicentral displacement response of a 3.12 mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Thermoelastic study of nanolayered structures using time-resolved X-ray diffraction at high repetition rate

We investigate the thermoelastic response of a nanolayered sample composed of a metallic SrRuO{sub 3} electrode sandwiched between a ferroelectric Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} film with negative thermal expansion and a SrTiO{sub 3} substrate. SrRuO{sub 3} is rapidly heated by fs-laser pulses with 208 kHz repetition rate. Diffraction of X-ray pulses derived from a synchrotron measures the transient out-of-plane lattice constant c of all three materials simultaneously from 120 ps to 5 μs with a relative accuracy up to Δc/c = 10{sup −6}. The in-plane propagation of sound is essential for understanding the delayed out-of-plane compression of Pb(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Ab initio studies on phase transition, thermoelastic, superconducting and thermodynamic properties of the compressed cubic phase of AlH{sub 3}

The phase transition, thermoelastic, lattice dynamic, and thermodynamic properties of the cubic metallic phase AlH{sub 3} were obtained within the density-function perturbation theory. The calculated elastic modulus and phonon dispersion curves under various pressures at 0 K indicate the cubic phase is both mechanically and dynamically stable above 73 GPa. The superconducting transition temperature T{sub c} was calculated using the Allen-Dynes modification of the McMillan formula based on BCS theory. The calculations show that T{sub c} for the cubic phase AlH{sub 3} is 8.5 K (μ{sup *}=0.1) at the onset of this phase (73 GPa), while decreases to 5.7 K at 80 GPa and almost disappears at 110 GPa, consisting with experimental phenomenon that there was no superconducting transition observed down to 4 K over a wide pressure range 110–164 GPa. It is found that the soft phonon mode for branch 1, namely, the lowest acoustic mode, plays a crucial role in elevating the total EPC parameter λ of cubic AlH{sub 3}. And the evolution of T{sub c} with pressure follows the corresponding change of this soft mode, i.e. this mode is responsible for the disappearance of T{sub c} in experiments. Meanwhile, the softening of this lowest acoustic mode originates from the electronic momentum transfer from M to R point. This phenomenon provides an important insight into why drastic changes in the diffraction pattern were observed in the pressure range of 63–73 GPa in Goncharenko's experiments. Specifically, once finite electronic temperature effects are included, we find that dynamical instabilities can be removed in the phonon dispersion for P≥63 GPa, rendering the metastability of this phase in the range of 63–73 GPa, and T{sub c} (15.4 K) becomes remarkably high under the lowest possible pressure (63 GPa) compared with that of under 73 GPa (8.5 K). Our calculations open the possibility that finite temperature may allow cubic AlH{sub 3} to be dynamically stabilized even for pressures below 73 GPa. It is reasonable to deduced that if special techniques, such as rapid decompression, quenching, and annealing, are implemented in experiments, higher T{sub c} can be observed in hydrides or hydrogen-rich compounds under much lower pressure than ever before.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗