SEARCH · Search NASA

Results for “Compressive Strength”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,765 records · Page 98

All sources NASA NTRS DOE OSTI

DOE OSTI2019

Microscale shear specimens for evaluating the shear deformation in single-crystal and nanocrystalline Cu and at Cu–Si interfaces

Microscale testing has enjoyed significant developments, with the majority of testing focused on tensile/compression type tests and little focus on shear testing. With the recent advances in macroscale shear testing, we developed a novel shear structure for evaluating shear properties of bulk materials and films at the microscale. The shear response in single-crystal copper oriented along the [111] direction was found to have a yield strength of ~180 MPa. Nanocrystalline copper specimens with different orientations showed sensitivity to the film texture with a shear yield strength nearly three times that of single-crystal copper. Shear specimens were fabricated with Cu film–Si substrate interface near the middle of the shear region and compressed to fracture. Here, the shear response showed a mixed behavior of the stiff Si substrate and softer nanocrystalline film and failed in a brittle manner, indicating a response unique to the interface.

36 MATERIALS SCIENCE↗

DOE OSTI2020

PAGOSA Theory Manual

PAGOSA is a computational fluid dynamics program developed at LANL for the study of high-speed compressible flow and high-rate material deformation. PAGOSA is a three-dimensional Eulerian finite-difference code, solving problems with a wide variety of EOS, material strength, and explosive modeling options. This document presents the finite difference equations that are used in the PAGOSA continuum mechanics computer code. This program is especially intended to be used for the numerical simulation of the interactions of gases, fluids, and solids.

36 MATERIALS SCIENCE↗

NASA NTRS1991

Factors controlling the structures of magma chambers in basaltic volcanoes

The depths, vertical extents, and lateral extents of magma chambers and their formation are discussed. The depth to the center of a magma chamber is most probably determined by the density structure of the lithosphere; this process is explained. It is commonly assumed that magma chambers grow until the stress on the roof, floor, and side-wall boundaries exceed the strength of the wall rocks. Attempts to grow further lead to dike propagation events which reduce the stresses below the critical values of rock failure. The tensile or compressive failure of the walls is discussed with respect to magma migration. The later growth of magma chambers is accomplished by lateral dike injection into the country rocks. The factors controlling the patterns of growth and cooling of such dikes are briefly mentioned.

Wilson, L.↗

NASA NTRS2008

Actuated atomizer

An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

Tilton, Charles↗

DOE OSTI2016

Room temperature stress relaxation in nanocrystalline Ni measured by micropillar compression and miniature tension

In this report, we report a micropillar stress relaxation technique employing a stable displacement-controlled, in-situ scanning electron microscope indenter, and unusually large micropillars to precisely measure stress relaxation in electroplated nanocrystalline Ni thin films. The observed stress relaxation is significant under constant displacement: even well below the 0.2% offset yield strength, the stresses relax by ~4% within a minute; in the work hardening regime, stress relaxes by ~9% in 1 min. A logarithmic fit of the relaxation curves is consistent with an Arrhenius thermal activation of plasticity and suggests an activation volume in the vicinity of ~10 b 3 . The apparent and effective activation volumes diverge at lower strains, particularly in the “elastic” regime. These measurements are compared to similar measurements performed on free-standing thin film tensile coupons. Both methods yield similar results, thereby validating the applicability of pillar compression to capture time-dependent plasticity. To our knowledge, these are the first micropillar stress relaxation experiments on metals ever reported.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Mechanical and degradation property improvement in a biocompatible Mg-Ca-Sr alloy by thermomechanical processing

Magnesium-based alloys have attracted interest as a potential material to comprise biomedical implants that are simultaneously high-strength and temporary, able to provide stabilization before degrading safely and able to be excreted by the human body. Many alloy systems have been evaluated, but this work reports on improved properties through hot extrusion of one promising alloy: Mg-1.0 wt% Ca-0.5 wt%Sr. This alloy has previously demonstrated promising toxicity and degradation properties in the as-cast and rolled conditions. In the current study extrusion causes a dramatic improvement in the mechanical properties in tension and compression, as well as a low in vitro degradation rate. Microstructure (texture, second phase distribution, and grain size), bulk mechanical properties, flow behavior, degradation in simulated body fluid, and effect on osteoblast cyctotoxicity are evaluated and correlated to extrusion temperature. In conclusion, maximum yield strength of 300 MPa (above that of annealed 316 stainless steel) with 10% elongation is observed, making this alloy competitive with existing implant materials.

36 MATERIALS SCIENCE↗

DOE OSTI2021

The Impala's horn applied to posterior samples of Ti-6Al-4V strength model parameters

We have generated strength model parameters for the Preston-Tonks-Wallace (PTW) model of plastic deformation based on a collection of Ti-6Al-4V alloy data and a Bayesian framework. This data collected from the literature includes different chemistries and processes. The experiments include quasistatic compression, Split Hopkinson Pressure Bar (SHPB) compression, and Taylor cylinders. Here we use posterior parameter distributions applied to a hypothetical impact referred to as the Impala's horn. The Impala's horn is like a Taylor cylinder, but modified to have a conical pro le that is truncated before coming to a point. The smaller diameter at the impact end results in higher calculated strain rates and strains than the same velocity impact with the traditional Taylor profile. The modified geometry exercises the behavior of the strength model outside the range of conditions found in the calibration data. Here we sort posterior strength models based on their flow stress at characteristic values for this hypothetical deformation. Then we compare the performance of these posterior models based on two simple observable final state properties of the Impala's horn.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Compressive deformation behavior and strain rate sensitivity of Al-cenosphere hybrid foam with mono-modal, bi-modal and tri-modal cenosphere size distribution

Highlights: • Cenospheres of different size ranges and distributions are used in hybrid aluminium foam. • Microstructure and deformation response of hybrid foam cenosphere size distribution. • Hybrid foam with bi or tri-modal cenosphere distribution exhibits higher strength and energy absorption. • The plateau stresses and energy absorption increased marginally with strain rate. • In case of bi- or tri-modal size distribution, strain rate sensitivity and strain rate sensitivity parameter is marginally lower. - Abstract: AlSi12Cu1Mg1 aluminium alloy-cenosphere closed cell hybrid foams with different kinds of cenosphere size distribution (mono-modal, bi-modal and tri-modal) are used to see the effect of cenosphere size distribution on their deformation behavior under quasi static compressive loading conditions at different strain rates. The stress strain curves are almost similar type irrespective of the cenosphere size distribution and strain rate. However, the plateau stress and energy absorption increased significantly when one used bi-modal and or tri-modal cenosphere size distribution instead of mono-modal cenosphere size distribution. These plateau stresses and energy absorption also increased marginally with strain rate. The densification strain remained almost invariant with strain rate and cenosphere size distribution. The strain rate sensitivity and strain rate sensitivity parameter is relatively lower in case of bi-modal and tri-modal cenosphere size distribution particularly at higher relative density.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Atomistic study of silicon alloying in the spallation behavior of nanocrystalline aluminum systems

Here, the effect of concentration of the alloying element silicon (Si) on the shock and spall response of aluminum (Al) is studied using classical molecular dynamics (MD) simulations. Silicon is distributed as individual grains and as grain boundaries and the dynamic response under shock is studied for an impact velocity of 1000 m/s. A general trend observed here is that the spallation is almost exclusively intergranular and limited to Al-Si interfaces. The spall strengths are observed to a) decrease with an increase in alloying of Si as grains and b) show little increase for up to 50% grain boundary segregation. An increase in grain size of the whole system showed negligible differences in spall strength, highlighting the significance of concentration of the alloying species rather than its grain size. These results provide an atomistic understanding of light-weight metallic systems under shock compression and pave the way for designing multiphase metal matrix alloys and composites for defense/armor applications.

36 MATERIALS SCIENCE↗

NASA NTRS1971

Concentric tubes cold-bonded by drawing and internal expansion

Metal tubes bonded together without heat application or brazing materials retain strength at elevated temperatures, and when subjected to constant or cyclic temperature gradients. Combination drawing and expansion process produces residual tangential tensile stress in the outer tube and tangential compressive stress in the inner tube.

Hymes, L. C.↗

NASA NTRS1974

Collapse of long cylindrical shells under combined bending and pressure loads

The nonlinear collapse behavior of long cylindrical shell structures subject to a bending load only or combined bending and uniform normal pressure loads is studied using the STAGS computer code. Two modes of nonlinear collapse are investigated to determine maximum strength. One mode of collapse is described by circumferential flattening of the cylinder cross section, while the other mode is represented by axial wrinkling in the region of maximum compression. Results compare favorably with available published data for cylinders loaded by pure bending, and results are presented for combined loads which have not been previously reported. The collapse loads obtained in this study show that current design criteria are conservative except for a narrow range of length-to-radius ratios and pressures.

Stephens, W. B.↗

NASA NTRS1988

Blends of an ethynyl terminated imidothioether with ethynyl terminated arylene ether oligomers

An evaluation has been undertaken of blends of a novel ethynyl-terminated imidothioether with Udel P1700 polysulfone and ethynyl-terminated arylene ether oligomers. Good to excellent processability was obtained with these blends using compression molding; the cured blends displayed poor-to-good resistance to chloroform and low-to-moderately high fracture toughness, depending on the blends' crosslink density. The flexural strength and modulus of unidirectional carbon graphite laminates prepared with the blended resins were good.

Connell, J. W.↗

NASA NTRS1991

Mechanical property characterization and impact resistance of selected graphite/PEEK composite materials

To use graphite/PEEK material on highly curved surfaces requires that the material be drapable and easily conformable to the surface. The mechanical property characterization and impact resistance results are presented for laminates made from two types of graphite/PEEK materials that will conform to a curved surface. These laminates were made from two different material forms. These forms are: (1) a fabric where each yarn is a co-mingled Celion G30-500 3K graphite fiber and PEEK fiber; and (2) an interleaved material of Celion G30-500 3K graphite fiber interleaved with PEEK film. The experimental results from the fabric laminates are compared with results for laminates made from AS4/PEEK unidirectional tape. The results indicate that the tension and compression moduli for quasi-isotropic and orthotropic laminates made from fabric materials are at least 98 pct. of the modulus of equivalent laminates made from tape materials. The strength of fabric material laminates is at least 80 pct. of laminates made from tape material. The evaluation of the fabric material for shear stiffness indicates that a tape material laminate could be replaced by a fabric material laminate and still maintain 89 pct. of the shear stiffness of the tape material laminate.

Baker, Donald J.↗

NASA NTRS1991

An examination of the damage tolerance enhancement of carbon/epoxy using an outer lamina of spectra (R)

Low velocity instrumented impact testing was utilized to examine the effects of an outer lamina of ultra-high molecular weight polyethylene (Spectra) on the damage tolerance of carbon epoxy composites. Four types of 16-ply quasi-isotropic panels (0, +45, 90, -45) were tested. Some panels contained no Spectra, while others had a lamina of Spectra bonded to the top (impacted side), bottom, or both sides of the composite plates. The specimens were impacted with energies up to 8.5 J. Force time plots and maximum force versus impact energy graphs were generated for comparison purposes. Specimens were also subjected to cross-sectional analysis and compression after impact tests. The results show that while the Spectra improved the maximum load that the panels could withstand before fiber breakage, the Spectra seemingly reduced the residual strength of the composites.

Lance, D. G.↗

NASA NTRS1995

A simulated RTM process for fabricating polyimide (AMB-21) carbon fiber composites

An experimental polyimide matrix, AMB-21 - supplied by NASA/LeRC, was especially formulated to be non-carcinogenic. It was also expected to be amenable to a Resin Transfer Molding Process (RTM). AMB-21 is a solid at room temperature and must be heated to a very high temperature to obtain a fluid state. However, even after heating it to a realistic high temperature, it was found to be too viscous for use in a RTM process. As a result, a promising approach was experimented leading to the introduction of the resin into a solvent solution in order to obtain a viscosity suitable for RTM. A mixture of methanol and tetrahydroferone was found to be a suitable solvent mixture. The matrix solution was introduced into carbon-fiber preform using two techniques: (1) injection of matrix into a Resin Transfer Mold after positioning the preform into the 'mold cavity', and (2) infiltration of matrix into the preform using the 'autoclave through-the-thickness transfer process'. After completing the resin transfer (infiltration) process, the 'filled' preform was heated to 300 F for one hour to reduce the solvent content. The temperature was then increased to 400 F under a vacuum to complete the solvent evaporation and to remove volatile products of the polyimide imidization. The impregnated preform was removed from the mold and press-cured at 200 psi and 600 FF for two hours. The resulting panel was found to be of reasonably good quality. This observation was based on the results obtained from short beam shear strength (700-8000 psi) tests and microscopic examination of the cross-section indicating a very low level of porosity. Further, the flash around the molded panels from the compression molding was free of porosity indicating the removal of volatiles, solvents, and other imidization products. Based on these studies, a new RTM mold containing a diaphragm capable of applying 200 psi at 600 F has been designed and constructed with the expectation that it will allow the incorporation of all of the above processing steps, including the consolidation with the preform in the mold cavity. Moreover, the new diaphragm design will enable to process larger preform panels. Processing studies with the diaphragm mold are being initiated.

Avva, V. Sarma↗

DOE OSTI2024

AGC-4 Specimen Post-Irradiation Examination Data Interim Report

This interim report documents preliminary results of the post-irradiation examination material property testing from the fourth advanced graphite creep (AGC), AGC 4, capsule specimens. This is the fourth of a series of six irradiation test trains planned as part of the AGC experiment to fully characterize the neutron irradiation effects and radiation creep behavior of current nuclear graphite grades to moderate dose levels (=7 dpa). The AGC 4 capsule was irradiated in the Idaho National Laboratory Advanced Test Reactor at a nominal temperature of 800°C and to a peak dose of 8 dpa. Half of the AGC-4 specimens were subjected to compressive stresses to induce irradiation creep. Post-irradiation testing and measurement results are reported with the exception of thermal testing, which is still in progress, and irradiation mechanical strength testing. Additionally, some specimens initially deemed too hot to be examined in the ART Graphite laboratory may still be measured. The data reported includes specimen dimensions for both stressed and unstressed specimens to establish the irradiation creep rates, mass and dimensional data necessary to derive density, elastic constants (Young?s modulus, shear modulus, and Poisson?s ratio) from ultrasonic time of flight velocity measurements, Young?s modulus from the fundamental frequency of vibration, and electrical resistivity. A more complete evaluation of trends in the material property changes, as well as irradiation-induced creep due to the irradiation environment and applied load on the specimens, will be discussed later in AGC 4 post-irradiation examination analysis reports.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2025

AGC-4 Specimen Post-Irradiation Examination Data Interim Report

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2016

Mechanical behavior and microstructure of Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} high-entropy alloy loaded under quasi-static and dynamic compression conditions

The microstructure and the mechanical behavior of equimolar Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} high-entropy alloy in a wide range of initial strain rates between ~ 10{sup −3} s{sup −1} and ~ 3.4 × 10{sup 3} s{sup −1} were studied. A significant increment in the yield strength with increasing strain rate was observed. The yield strength at ~ 3.4 × 10{sup 3} s{sup −1} was about 40% higher than that measured at ~ 10{sup −3} s{sup −1}. Analysis by electron backscatter diffraction shows that in the low strain rate regime (up to ~ 10 s{sup −1}) the deformation occurs mainly in evenly distributed bands, while in the dynamic regime the deformation is strongly localized in macroscopic shear bands accompanied by softening even after the onset of yielding. The Kernel Average Misorientation technique reveals a high level of lattice rotation within these bands that also carries intense shear. In addition, X-ray diffraction line profile analysis indicates that the sharp increase in the flow stress is mostly related to an increase of the dislocation density. - Highlights: • Strain rate effect on the plastic behavior of Ti{sub 20}Hf{sub 20}Zr{sub 20}Ta{sub 20}Nb{sub 20} HEA was studied. • Low strain rate regime was characterized by a continuous hardening. • At high strain rates softening occurred shortly after the onset of yielding. • Intense strain localization in shear bands occurred in the high strain rate regime. • High dislocation density explained the upturn of flow stress at high strain rates.

36 MATERIALS SCIENCE↗