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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 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Ultrafine-grained Fe-TiB 2 high-modulus nanocomposite steel with high strength and isotropic mechanical properties by laser powder bed fusion

Fe-TiB 2 metal matrix composite, also called high-modulus steels (HMSs), are of great interest for applications in fuel-efficient transportation infrastructure, aerospace, and wear industries due to their high specific stiffness and yield strength. However, conventional cast Fe-TiB 2 HMSs often contain coarse and sharp-edged TiB 2 particles which easily trigger premature cracking during loading. Here, we synthesized a Fe-TiB 2 nanocomposite HMS via laser powder bed fusion (LPBF) additive manufacturing of mixed micro-sized powders of Fe, Ti, and Fe 2 B. We investigated the microstructure formation and mechanical behavior of the Fe-TiB 2 HMS. We found that in situ chemical reaction of Ti and Fe 2 B enables the formation of TiB 2 particles at nanoscale during rapid solidification of LPBF. These nanoscale TiB 2 particles can serve as heterogeneous nucleation sites and promote the formation of ultrafine and equiaxed α-Fe grains with random crystallographic textures, which differ from many other additively manufactured (AM) metal alloys characteristic of strong crystallographic textures. As such, isotropic mechanical properties were achieved in the AM Fe-TiB 2 nanocomposite HMS with a high elastic modulus of ~ 240 GPa, an exceptional yield strength of ~ 1450 MPa, and a large plasticity of ~ 20% under compression. Quantitative analysis reveals that the high yield strength primarily originates from strengthening contributions of the ultrafine grains with an average grain size of ~450 nm, the nanoscale TiB 2 reinforcing particles of 20–180 nm, and a high density of printing-induced dislocations of the order of 10 15 m –2 . In situ synchrotron high-energy X-ray diffraction unveils the load partitioning from the softer α-Fe matrix to the stiffer and stronger TiB 2 nanoparticles, contributing to the sustained strain hardening during compression. Our work not only provides a general pathway for achieving high-performance metal matrix nanocomposites by in situ chemical reaction and precipitation of ceramic nanoparticles during additive manufacturing, but also offers mechanistic insights into the deformation mechanism of nanoparticle-reinforced HMS composites.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Paul‐Mohr‐Coulomb failure surface of rock in the brittle regime

Abstract The Paul‐Mohr‐Coulomb failure criterion includes the intermediate principal stress σ II and friction angles at the limiting stress states of σ II = σ III and σ II = σ I , where σ I and σ III are major and minor principal stresses. Conventional triaxial compression ( σ II = σ III ), extension ( σ II = σ I ), and plane strain ( σ I ≠ σ II ≠ σ III ) experiments were performed on dry rock. The failure data were plotted in principal stress space, and material parameters were determined in the context of two internal friction angles and the theoretical uniform triaxial (all‐around equal) tensile strength. Assuming isotropy, the triaxial compression and extension results were used to construct a six‐sided pyramidal failure surface, and the extension friction angle was larger than the compression friction angle, a sufficient but not necessary condition of the intermediate stress effect. To capture the behavior of the rock in multiaxial loading, the Paul‐Mohr‐Coulomb criterion was extended to form a 12‐sided pyramid with best fit planes.

Makhnenko, Roman Y.↗
DOE OSTI2015

Microstructural investigation of plastically deformed Ti{sub 20}Zr{sub 20}Hf{sub 20}Nb{sub 20}Ta{sub 20} high entropy alloy by X-ray diffraction and transmission electron microscopy

The microstructure evolution in body-centered cubic (bcc) Ti{sub 20}Zr{sub 20}Hf{sub 20}Nb{sub 20}Ta{sub 20} high entropy alloy during quasi-static compression test was studied by X-ray line profile analysis (XLPA) and transmission electron microscopy (TEM). The average lattice constant and other important parameters of the microstructure such as the mean crystallite size, the dislocation density and the edge/screw character of dislocations were determined by XLPA. The elastic anisotropy factor required for XLPA procedure was determined by nanoindentation. XLPA shows that the crystallite size decreased while the dislocation density increased with strain during compression, and their values reached about 39 nm and 15 × 10{sup 14} m{sup −2}, respectively, at a plastic strain of ~ 20%. It was revealed that with increasing strain the dislocation character became more screw. This can be explained by the reduced mobility of screw dislocations compared to edge dislocations in bcc structures. These observations are in line with TEM investigations. The development of dislocation density during compression was related to the yield strength evolution. - Highlights: • Ti{sub 20}Zr{sub 20}Hf{sub 20}Nb{sub 20}Ta{sub 20} high entropy alloy was processed by arc-melting. • The mechanical was evaluated by RT compression test. • The microstructure evolution was studied by XLPA and TEM. • With increasing strain the dislocation character became more screw. • The yield strength was related to the development of the dislocation density.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A Synthetic Hydrogel Composite with the Mechanical Behavior and Durability of Cartilage

Here, we report the first hydrogel with the strength and modulus of cartilage in both tension and compression, and the first to exhibit cartilage-equivalent tensile fatigue strength at 100 000 cycles. These properties are achieved by infiltrating a bacterial cellulose (BC) nanofiber network with a poly(vinyl alcohol) (PVA)–poly(2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt) (PAMPS) double network hydrogel. The BC provides tensile strength in a manner analogous to collagen in cartilage, while the PAMPS provides a fixed negative charge and osmotic restoring force similar to the role of aggrecan in cartilage. The hydrogel has the same aggregate modulus and permeability as cartilage, resulting in the same time-dependent deformation under confined compression. The hydrogel is not cytotoxic, has a coefficient of friction 45% lower than cartilage, and is 4.4 times more wear-resistant than a PVA hydrogel. The properties of this hydrogel make it an excellent candidate material for replacement of damaged cartilage.

36 MATERIALS SCIENCE↗
NASA NTRS2022

A Quantitative Damage Tolerance Comparison of High Strength and High Modulus Carbon Fiber Sandwich Structure

This study presents experimental results of the compression after impact (CAI) testing of sandwich structure with face sheets made either with IM7/8552 high strength fiber or HM63/8552 high modulus fiber. While the HM63/8552 face sheet sandwich specimens would not be as damage tolerant as the IM7/8552 face sheet sandwich specimens, a quantitative measure of how much more damage tolerant the IM7/8552 face sheets were than the HM63/8552 face sheets was sought. Due to the IM7/8552 face sheets being 28% thicker than the HM63/8552 face sheets, the impact energies used needed to be adjusted for a fair comparison. The results show that the modulus is 35% lower for the IM7/8552 face sheet sandwich structure while the CAI strength

High modulus carbon fiber↗
NASA NTRS1991

Solar wind dynamic pressure variations and possible ground signatures of flux transfer events

The effects of a series of solar wind dynamic pressure pulses are followed through the solar wind, across the bow shock and magnetosheath, into the magnetosphere, and down to the dayside ionosphere. Each pressure pulse had an intrinsic solar wind origin, i.e., was not generated by processes occurring at the earth's bow shock. Both upstream and downstream of the earth's bow shock, the pulses were identified by depressed magnetic field strengths and enhanced plasma densities. The pulses compressed the magnetosheath and magnetosphere, causing satellites in the magnetosphere to briefly observe enhanced magnetic field strengths, and/or enter the low-latitude boundary layer or magnetosheath. Satellites already in the magnetosheath observed a brief burst of enhanced magnetosheath flow caused by the relative inward motion of magnetosheath flow patterns. Alfven and fast mode compressional waves propagated rapidly down to the polar ionosphere, where they produced transient ionospheric flows at latitudes equatorward of the convection reversal boundary. The flow patterns moved westward around the auroral oval.

Sibeck, D. G.↗
DOE OSTI2026

Validation of 266 nm UV Raman thermometry using the alpha-to-beta quartz transition

Ultraviolet Raman scattering is a promising diagnostic for temperature measurements relevant to dynamic compression experiments, where improved signal strength and reduced background are critical. In this work, we experimentally validate Raman thermometry at 266 nm using crystalline quartz heated through the α to β phase transition in a tube furnace. Quartz provides a useful benchmark because of its well-characterized transition temperature near 846 K at ambient pressure. Temperatures inferred from the Stokes to anti-Stokes intensity ratio are compared with thermocouple measurements and with the observed phase transition. Single-shot Raman temperatures track the thermocouple closely, with an empirical single-shot scatter of approximately ±15 K under the present conditions. Temporal averaging reduces shot-to-shot scatter and improves agreement between the Raman temperatures and thermocouple readings to within approximately 8 K, while the transition is identified within 5 K of the accepted value. Measurements are performed using the fourth harmonic of a nanosecond pulsed Nd:YAG laser at 266 nm. The shorter excitation wavelength provides enhanced Raman scattering efficiency and reduced visible background relative to conventional visible excitation. Comparison with 532 nm Raman measurements acquired in the same experimental geometry demonstrates substantially improved signal-to-noise ratio for the UV configuration. These results establish 266 nm Raman thermometry as a reliable and accurate temperature diagnostic under controlled heating conditions and provide a quantitative benchmark for future application in dynamic compression and shock physics experiments.

Chemistry - Chemical explosives↗
DOE OSTI2021

Effect of particle characteristics on the evolution of particle size, particle morphology, and fabric of sands loaded under uniaxial compression

This work presents the results and analyses of uniaxial compression experiments performed on three silica sands. The sands have comparable particle-size distributions, but their particles differ in morphology and strength. Cylindrical samples of the three sands were compressed in a loading device placed inside an X-ray microscope (XRM) and scanned at multiple stress levels during uniaxial compression. 3D tomography data of the samples obtained from the XRM at different stress levels were then analyzed to obtain the distributions of particle size, particle morphology, and interparticle contact normals within the sample. Results indicate that: (1) the compressibility of the sands loaded under uniaxial compression is closely tied to particle morphology and strength and (2) the anisotropy in the orientations of interparticle contact normals generally increases with axial stress; however, this increase is limited by the occurrence of particle crushing in the sample.

3D X-ray computed tomography↗
DOE OSTI2018

Orientation dependent spall strength of tantalum single crystals

We report that it is generally recognized that single crystals exhibit orientation-dependent elastic and plastic responses. However, it is less known how the dynamic tensile, or spall, strength depends on crystalline orientation, especially for BCC materials. It has been previously shown that the dynamic tensile strength of FCC materials is highly dependent on their plastic response under compression, with a direct correlation between plastic deformation and spall strength. In BCC materials like Ta, where the primary deformation mechanism at high strain rates is a combination of slip and twinning, the quantitative dependence of spall strength on these deformation mechanisms is less understood. To fill this gap in our knowledge, a series of non-equilibrium molecular dynamics simulations are completed for six tantalum single crystal orientations: <001>, <011>, <111>, <013>, <112>, <149>, to explore the role of directional anisotropy on ductile spallation. Our results show that due to the role of non-Schmid and release effects in BCC Ta, the evolution of plasticity follows a complex trajectory through shock compression, release, and tension. Orientations that contain residual twinning deformation have a reduced spall strength proportional to the amount of twinning present. Lastly, twins and their intersections function as regions of increased stress localization within the system due to compatibility requirements and their interactions with dislocations.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Case Studies of Fatigue Life Improvement Using Low Plasticity Burnishing in Gas Turbine Engine Applications

Surface enhancement technologies such as shot peening, laser shock peening (LSP), and low plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the compressive residual stresses that increase fatigue strength must be retained in service. For successful integration into turbine design, the process must be affordable and compatible with the manufacturing environment. LPB provides thermally stable compression of comparable magnitude and even greater depth than other methods, and can be performed in conventional machine shop environments on CNC machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engines and ground-based turbines. Improving fatigue performance by introducing deep stable layers of compressive residual stress avoids the generally cost prohibitive alternative of modifying either material or design. The X-ray diffraction based background studies of thermal and mechanical stability of surface enhancement techniques are briefly reviewed, demonstrating the importance of minimizing cold work. The LPB process, tooling, and control systems are described. An overview of current research programs conducted for engine OEMs and the military to apply LPB to a variety of engine and aging aircraft components are presented. Fatigue performance and residual stress data developed to date for several case studies are presented including: * The effect of LPB on the fatigue performance of the nickel based super alloy IN718, showing fatigue benefit of thermal stability at engine temperatures. * An order of magnitude improvement in damage tolerance of LPB processed Ti-6-4 fan blade leading edges. * Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB. * Corrosion fatigue mitigation with LPB in Carpenter 450 steel. *Damage tolerance improvement in 17-4PH steel. Where appropriate, the performance of LPB is compared to conventional shot peening after exposure to engine operating temperatures.

Prevey, Paul S.↗
DOE OSTI2021

DEM analysis of the effect of interface transition zone on dynamic splitting tensile behavior of high-strength concrete based on multi-phase model

Highlights: • Crushable aggregates with the real geometry shape are generated by using clump-cluster method. • Flat-Joint Model is adopted as the constitutive law. • The tensile strength is almost not affected by ITZ strength when its strength exceeds 0.8 times that of mortar. • A modified formula that can reflect the functional relationship between the ITZ strength and the TDIF is proposed. The tensile strength is one of the main parameters in the design of concrete structures and has an important influence on the cracking performance and durability of concrete materials. As the weak region in concrete, the strength of the interface transition zone (ITZ) directly affects the dynamic mechanical response of concrete. Meanwhile, considering that the tensile performance of concrete is far weaker than its compressive performance, the study of the strength of ITZ is of great significance to the dynamic tensile fracture characteristics and mechanical properties of concrete. In this paper, a method combining 3D scanning technology and Clump-Cluster was proposed to generate a real geometry shape model of crushable aggregate. On this basis, the 3D discrete element model (DEM) of high-strength concrete was constructed using the Flat-Joint Model (FJM). The effects of the ITZ strength on the failure mode, number of microcracks, tensile strength and strain rate effect of high-strength concrete under strain rates from 0.01/s to 100/s were studied by splitting tensile test. The simulation results indicate that the number of microcracks generated decreases with the increase of ITZ strength, and the proportion of ITZ cracks decreases obviously. When the ITZ strength exceeds the critical value of 0.8 times that of mortar, the tensile strength is almost not affected by ITZ strength. In addition, based on the numerical simulation results, a modified formula that can reflect the functional relationship between the ITZ strength and the dynamic increasing factor of the concrete tensile strength (TDIF) is proposed, and the rationality of the TDIF modified formula is verified.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Pre-compression effect on microstructure evolution of extruded pure polycrystalline magnesium during reversed tension load

Highlights: • Number of twin variants under compression along ED is dependent on grain orientation. • Tension after pre-compression results in low-SF twinning and secondary twinning. • Secondary twinning is facilitated by increasing pre-compression. • Sub-grains due to twinning enhance material strength. - Abstract: The microstructure evolution of extruded pure polycrystalline magnesium under compression followed by subsequent tension in ambient air was investigated. Solid round dog-bone shaped specimens were compressed along the extrusion direction (ED) to − 7.3% and − 12.8% true strains, respectively, and then tensioned along the ED to failure. Electron backscatter diffraction (EBSD) was used to examine the microstructure evolution using companion specimens unloaded at multiple points along the deformation curves. Pre-compression along the ED resulted in {10 1-bar 2} tension twinning which increased in volume with increasing strain until exhaustion at approximately − 10.5% true strain. Tensile reloading of the pre-compressed specimens led to a combination of low Schmid factor twinning, detwinning, and secondary {10 1-bar 2} tension twinning. Detwinning was more significant than secondary twinning in the − 7.3% pre-compressed specimens, where only one secondary twin variant was observed. {10 1-bar 2} secondary twinning was more significant in the − 12.8% pre-compressed specimens, where up to three secondary twin variants were observed. After complete detwinning of primary twins, the secondary twins were retained and appeared as sub-grains. The residual sub-grains resulted from secondary twinning may provide a strengthening mechanism for wrought Mg alloys.

36 MATERIALS SCIENCE↗
NASA NTRS2008

Constitutive Soil Properties for Unwashed Sand and Kennedy Space Center

Accurate soil models are required for numerical simulations of land landings for the Orion Crew Exploration Vehicle. This report provides constitutive material models for one soil, unwashed sand, from NASA Langley's gantry drop test facility and three soils from Kennedy Space Center (KSC). The four soil models are based on mechanical and compressive behavior observed during geotechnical laboratory testing of remolded soil samples. The test specimens were reconstituted to measured in situ density and moisture content. Tests included: triaxial compression, hydrostatic compression, and uniaxial strain. A fit to the triaxial test results defines the strength envelope. Hydrostatic and uniaxial tests define the compressibility. The constitutive properties are presented in the format of LS-DYNA Material Model 5: Soil and Foam. However, the laboratory test data provided can be used to construct other material models. The four soil models are intended to be specific to the soil conditions discussed in the report. The unwashed sand model represents clayey sand at high density. The KSC models represent three distinct coastal sand conditions: low density dry sand, high density in-situ moisture sand, and high density flooded sand. It is possible to approximate other sands with these models, but the results would be unverified without geotechnical tests to confirm similar soil behavior.

Thomas, Michael A.↗
NASA NTRS2008

Constitutive Soil Properties for Cuddeback Lake, California and Carson Sink, Nevada

Accurate soil models are required for numerical simulations of land landings for the Orion Crew Exploration Vehicle. This report provides constitutive material modeling properties for four soil models from two dry lakebeds in the western United States. The four soil models are based on mechanical and compressive behavior observed during geotechnical laboratory testing of remolded soil samples from the lakebeds. The test specimens were reconstituted to measured in situ density and moisture content. Tests included: triaxial compression, hydrostatic compression, and uniaxial strain. A fit to the triaxial test results defines the strength envelope. Hydrostatic and uniaxial tests define the compressibility. The constitutive properties are presented in the format of LS-DYNA Material Model 5: Soil and Foam. However, the laboratory test data provided can be used to construct other material models. The four soil models are intended to be specific only to the two lakebeds discussed in the report. The Cuddeback A and B models represent the softest and hardest soils at Cuddeback Lake. The Carson Sink Wet and Dry models represent different seasonal conditions. It is possible to approximate other clay soils with these models, but the results would be unverified without geotechnical tests to confirm similar soil behavior.

Thomas, Michael A.↗
NASA NTRS2011

Constitutive Soil Properties for Mason Sand and Kennedy Space Center

Accurate soil models are required for numerical simulations of land landings for the Orion Crew Exploration Vehicle (CEV). This report provides constitutive material models for two soil conditions at Kennedy Space Center (KSC) and four conditions of Mason Sand. The Mason Sand is the test sand for LaRC s drop tests and swing tests of the Orion. The soil models are based on mechanical and compressive behavior observed during geotechnical laboratory testing of remolded soil samples. The test specimens were reconstituted to measured in situ density and moisture content. Tests included: triaxial compression, hydrostatic compression, and uniaxial strain. A fit to the triaxial test results defines the strength envelope. Hydrostatic and uniaxial tests define the compressibility. The constitutive properties are presented in the format of LSDYNA Material Model 5: Soil and Foam. However, the laboratory test data provided can be used to construct other material models. The soil models are intended to be specific to the soil conditions they were tested at. The two KSC models represent two conditions at KSC: low density dry sand and high density in-situ moisture sand. The Mason Sand model was tested at four conditions which encompass measured conditions at LaRC s drop test site.

Thomas, Michael A.↗
DOE OSTI2025

Microstructural, Oxidation, and Mechanical Behavior of NbTi-Based Refractory Alloys with 5 to 10 Pct Co, Cr, and Ni Additions

NbTi-based refractory alloys with additions of Co, Cr, and Ni represent an interesting medium-entropy alloy system with potential for protective oxide film formation, high strength, and ductility. This study investigates the microstructural evolution, oxidation behavior, and mechanical properties of NbTi-based alloys containing 5 to 10 at. pct Co, Cr, and Ni. CALPHAD predictions suggest that this composition range can be heat treated to obtain a predominantly body-centered cubic matrix phase. Mechanical properties, including microhardness, yield strength, maximum strength, and specific strength are evaluated through isothermal compression tests conducted between room temperature and 800 °C. The oxidation kinetics of these alloys are assessed through discontinuous oxidation tests. Parabolic oxidation kinetics were observed for NbTi–10Ni and NbTi–5Co, while linear oxidation kinetics were found for NbTi–10Cr and NbTi–10(CoCrNi). Microstructures and oxide layers are characterized using X-ray diffraction, electron backscatter diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. All alloys exhibit significant mechanical softening between room temperature and 800 °C, with elastic-perfectly plastic flow observed at 800 °C. The addition of 10 pct Cr to NbTi resulted in two BCC phases up to 1050 °C, conflicting with CALPHAD predictions of a single-phase solid solution at this temperature, and resulting in higher flow stress at 800 °C. NbTi–10(CoCrNi) exhibited the lowest flow stress at 800 °C despite having more ‘cocktail effect’ potential and insufficient molar fractions of Co, Cr, or Ni to form a desirable protective oxide film.

36 MATERIALS SCIENCE↗