Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “COMPRESSION TESTING”

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.

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

At least 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Elucidating the impact of stress states on grain boundary passivation in Ni-5Cr using the Rhines pack method

The oxidation behavior of a Ni–5Cr (at.%) alloy was evaluated at 420 ° C using the Rhines pack method and simultaneous tensile and compressive stress states via a miniature four-point bending fixture. At this moderate temperature, grain boundaries dominate mass transport and the resulting oxidation response. Oxidation produced approximately 1μ⁢m-wide protective Cr 2 O 3 films capping some grain boundaries and penetrative, intergranular Cr-rich oxides at other grain boundaries. Externally applied tensile and compressive stress during oxidation increased the prevalence of Cr 2 O 3 cap formation compared to no applied stress, with tensile stress resulting in more Cr 2 O 3 caps than compressive stress. The observed oxide cap morphology was similar across all test conditions. Regions under compressive stress showed an order of magnitude greater Cr depletion depth along the grain boundary. Chromium nitrides (CrN), likely from N contamination of the Rhines pack cell, were observed both at the oxide–metal interface and intergranularly within the alloy. Collectively these results demonstrate that applied stress promotes localized protective oxide cap formation over grain boundaries, with compressive stress additionally promoting deeper Cr depletion. Furthermore the experimental approach helped separate out the effects of stress on local oxide formation and grain boundary passivation.

4 point bend↗
NASA NTRS1957

Investigation of the Compressive Strength and Creep Lifetime of 2024-T3 Aluminum-Alloy Plates at Elevated Temperatures

The results of elevated-temperature compressive strength and creep tests of 2024-t3 (formerly 24s-t3) aluminum alloy plates supported in v-grooves are presented. The strength-test results indicate that a relation previously developed for predicting plate compressive strength for plates of all materials at room temperature is also satisfactory for determining elevated-temperature strength. Creep-lifetime results are presented for plates in the form of master creep-lifetime curves by using a time-temperature parameter that is convenient for summarizing tensile creep-rupture data. A comparison is made between tensile and compressive creep lifetime for the plates and a method that made use of isochronous stress-strain curves for predicting plate-creep failure stresses is investigated.

Mathauser, Eldon E↗
NASA NTRS1980

Study of the influence of hole quality on composite materials

The influence of hole quality on the structural behavior of composite materials was investigated. From an industry survey it was determined that the most frequent imperfections encountered during hole fabrication are chipout, delamination, and oversize conditions. These hole flaw types were generated in critical areas of static, compression, and fatigue specimens fabricated from T300/5208 graphite/epoxy system. The specimens were tested in static and cyclic pin bearing modes in addition to compression loading. Results of these tests are presented and discussed. The hole chipout defect reduced the static and cyclic endurance characteristics. Oversize holes also lowered the cyclic pin bearing endurance, but had no influence of the static pin bearing characteristics. Delamination had no insignificant influence on the static tension and cyclic pin bearing characteristics. Compression tests demonstrated a deleterious effect for chipout of delamination defects. Hole quality requirements proposed are discussed.

Pengra, J. J.↗
NASA NTRS1978

Testing composite sheets at high temperatures

Candidate materials for skins of flexural sandwich beams can be compressive- or tensile-tested at high temperature by using corrosion resistant steel (CRES) for core material. Tests with CRES core have been made at temperatures as high as 260 C. Future tests at temperatures above 371 C may be permissible.

Jones, J. S.↗
DOE OSTI2014

Micromechanical and in situ shear testing of Al–SiC nanolaminate composites in a transmission electron microscope (TEM)

Nanolaminate composites show promise as high strength and toughness materials. Still, due to the limited volume of these materials, micron scale mechanical testing methods must be used to determine the properties of these films. To this end, a novel approach combining a double notch shear testing geometry and compression with a flat punch in a nanoindenter was developed to determine the mechanical properties of these films under shear loading. To further elucidate the failure mechanisms under shear loading, in situ TEM experiments were performed using a double notch geometry cut into the TEM foil. Aluminum layer thicknesses of 50nm and 100nm were used to show the effect of constraint on the deformation. Higher shear strength was observed in the 50 nm sample (690±54 MPa) compared to the 100 nm sample (423±28.7 MPa). Additionally, failure occurred along the Al-SiC interface in the 50 nm sample as opposed to failure within the Al layer in the 100 nm sample.

36 MATERIALS SCIENCE↗
NASA NTRS1937

The Quiescent-Chamber Type Compression-Ignition Engine

Report presents the results of performance tests of a single-cylinder 4-stroke-cycle compression-ignition engine having a vertical disk form of combustion chamber without air flow. The number, size, and direction of the orifices of the fuel-injection nozzles used were independently varied. A table and graphs are presented showing the performance of the engine with different nozzles; results of tests at different compression ratios, boost pressures, and coolant temperatures are also included.

Foster, H H↗
DOE OSTI2015

Resistance of fly ash-Portland cement blends to thermal shock

Thermal-shock resistance of high-content fly ash-Portland cement blends was tested in the following ways. Activated and non-activated blends with 80-90 % fly ash F (FAF) were left to set at room temperature, then hydrated for 24 hours at 85°C and 24-more hours at 300°C and tested in five thermal-shock cycles (600°C heat - 25°C water quenching). XRD, and thermal gravimetric analyses, along with calorimetric measurements and SEM-EDX tests demonstrated that the activated blends form more hydrates after 24 hours at 300°C, and achieve a higher short-term compressive strength than do non-activated ones. Sodium meta-silicate and sodaash engendered the concomitant hydration of OPC and FAF, with the formation of mixed crystalline FAF-OPC hydrates and FAF hydrates, such as garranite, analcime, and wairakite, along with the amorphous FAF hydration products. In SS-activated and non-activated blends separate OPC (tobermorite) and FAF (amorphous gel) hydrates with no mixed crystalline products formed. The compressive strength of all tested blends decreased by nearly 50% after 5 thermal-shock test cycles. These changes in the compressive strength were accompanied by a marked decrease in the intensities of XRD patterns of the crystalline hydrates after the thermalshock. As a result, there was no significant difference in the performance of the blends with different activators

15 GEOTHERMAL ENERGY↗
DOE OSTI2018

Assessment of bearing capacity of axially loaded monopiles based on centrifuge tests

The monopile has been widely used to support offshore and coastal structures. A series of centrifuge tests has been performed to investigate the bearing capacity of large diameter monopiles in sandy soil. Both static tests and cyclic tests have been conducted for open-ended and close-ended model piles, and the effects of influence factors, such as loading rates, embedment depths, and loading histories are considered. The piles are then loaded by a sequence of compressive-tensile loadings to estimate the tension capacity, from which the shaft friction is derived. The cyclic load tests are performed with five varying load intensities, and the accumulated settlement is assessed. The centrifuge tests indicate that the pile bearing capacity tends to increase with the initial penetration depth, and the stress state of soil greatly influences the pile behavior. The tensile shaft friction is smaller compared to the compression test. The capacities of the piles reduce significantly under the axial cyclic load, and the maximum cyclic load intensity should be limited to 75% of the ultimate bearing capacity. The API design method is used to calibrate with the centrifuge test results. The method overestimates the bearing capacity at larger depths, and a conservative reduction factor is required.

17 WIND ENERGY↗
NASA NTRS1980

Graphite-epoxy panel compression strength reduction due to local impact

A review of results from on-going research to investigate the effects of low-velocity impact on the compressive strength of graphite-epoxy structures is presented. Extensive tests have been conducted on sandwich beams, laminated plates and stiffened panels. Conditions for failures were investigated by impact tests on statically loaded test specimens. The effects of compression load intensity were such that lightly loaded graphite structures (such as aircraft secondary structure) were insensitive to impact damage. In more heavily loaded structures, (such as wing panels), however, appreciable reductions in compressive strength occurred. The implications of the tests for structural design are discussed by comparing panel masses for designs where ultimate strains have been reduced due to impact considerations with the masses of designs with higher ultimate strains. Finally, preliminary test data is presented to show the possibility of improvements in damage tolerance achievable by using an alternate matrix material.

Card, M. P.↗
NASA NTRS1950

Determination of Plate Compressive Strengths at Elevated Temperatures

The results of local-instability tests of h-section plate assemblies and compressive stress-strain tests of extruded 75s-t6 aluminum alloy, obtained to determine flat-plate compressive strength under stabilized elevated temperature conditions, are given for temperatures up to 600 degrees F. The results show that methods available for calculating the critical compressive stress at room temperature can also be used at elevated temperatures if the applicable compressive stress-strain curve for the material is given.

Heimerl, George J↗
DOE OSTI2021

Fracturing process of micro-concrete under uniaxial and triaxial compression: Insights from in-situ X-ray mechanical tests

This paper presents an experimental study of concrete at meso-scale (aggregates, macro-pores and mortar matrix) in order to get a better understanding of the local failure mechanisms known to drive the macroscopic mechanical behaviour of the material. The main originality comes from conducting in-situ X-ray mechanical tests on micro-concrete samples of realistic composition (including cement, sand, aggregates and water), under uniaxial compression and, for the first time, under triaxial compression at 5 MPa, 10 MPa and 15 MPa confining pressures. A timeseries analysis of the set of 3D images coming from each test allows for the measurement of the 3D kinematic fields (displacement and strain fields) throughout the experiments. The different failure patterns observed for each loading path are discussed, along with a quantification of the 3D fracturing processes at the scale of the largest heterogeneities (aggregates and macro-pores). With an increasing level of confinement, the transition from brittle to ductile response is observed, as well as an increase of the strength of the material. The pronounced impact of the meso-scale heterogeneities of concrete on their local failure mechanisms is highlighted. It is shown that strain localisation mainly originates between aggregates and mortar matrix, with the shape and location of the largest aggregates and macro-pores essentially driving the propagation of the cracking network.

36 MATERIALS SCIENCE↗
NASA NTRS2006

Atomic Oxygen Exposure of Polyimide Foam for International Space Station Solar Array Wing Blanket Box

Onorbit photos of the International Space Station (ISS) solar array blanket box foam pad assembly indicate degradation of the Kapton film covering the foam, leading to atomic oxygen (AO) exposure of the foam. The purpose of this test was to determine the magnitude of particulate generation caused by low-Earth orbital environment exposure of the foam and also by compression of the foam during solar array wing retraction. The polyimide foam used in the ISS solar array wing blanket box assembly is susceptible to significant AO erosion. The foam sample in this test lost one-third of its mass after exposure to the equivalent of 22 mo onorbit. Some particulate was generated by exposure to simulated orbital conditions and the simulated solar array retraction (compression test). However, onorbit, these particles would also be eroded by AO. The captured particles were generally <1 mm, and the particles shaken free of the sample had a maximum size of 4 mm. The foam sample maintained integrity after a compression load of 2.5 psi.

Finckenor, M. M.↗
DOE OSTI2016

Ppb-level mid-infrared ethane detection based on three measurement schemes using a 3.34-μm continuous-wave interband cascade laser

A ppb-level mid-infrared ethane (C 2 H 6 ) sensor was developed using a continuous-wave, thermoelectrically cooled, distributed feedback interband cascade laser emitting at 3.34 μm and a miniature dense patterned multipass gas cell with a 54.6-m optical path length. The performance of the sensor was investigated using two different techniques based on the tunable interband cascade laser: direct absorption spectroscopy (DAS) and second-harmonic wavelength modulation spectroscopy (2f-WMS). Three measurement schemes, DAS, WMS and quasi-simultaneous DAS and WMS, were realized based on the same optical sensor core. A detection limit of ~7.92 ppbv with a precision of ±30 ppbv for the separate DAS scheme with an averaging time of 1 s and a detection limit of ~1.19 ppbv with a precision of about ±4 ppbv for the separate WMS scheme with a 4-s averaging time were achieved. An Allan–Werle variance analysis indicated that the precisions can be further improved to 777 pptv @ 166 s for the separate DAS scheme and 269 pptv @ 108 s for the WMS scheme, respectively. For the quasi-simultaneous DAS and WMS scheme, both the 2f signal and the direct absorption signal were simultaneously extracted using a LabVIEW platform, and four C 2 H 6 samples (0, 30, 60 and 90 ppbv with nitrogen as the balance gas) were used as the target gases to assess the sensor performance. A detailed comparison of the three measurement schemes is reported. Here, atmospheric C 2 H 6 measurements on the Rice University campus and a field test at a compressed natural gas station in Houston, TX, were conducted to evaluate the performance of the sensor system as a robust and reliable field-deployable sensor system.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Fabrication and Testing of Soy-Based Polyurethane Foam for Insulation and Structural Applications

This study is focused on the fabrication and evaluation of polyurethane (PU) foam fabricated using soy-based polyol that can potentially replace conventional petroleum-based PU foam for thermal applications. Rigid soy-based PU foam samples investigated in this study were produced by copolymerization of diisocyanate with soy-based polyol in presence of Xiameter X0193 surfactant, dibutyltin dilaurate (DBTL) as a catalyst, and water as a blowing agent. Different formulations with varying amounts of blowing agent and catalyst were investigated to optimize the mechanical and thermal properties of soy-based PU foam when compared to commercial petroleum-based foam as a control sample. The prepared samples were tested for density, compressive strength, thermal conductivity, tensile strength, dimensional stability, and thermal stability using the ASTM standards. The cellular structure of the fabricated foam samples was investigated using scanning electron microscopy. It was observed that an increase in density leads to a decrease in insulation. Overall, soy-based foams exhibited similar thermal conductivity as compared to petroleum-based foams.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Temperature effects on deformation and serration behavior of high-entropy alloys (HEAs)

Many materials are known to deform under shear in an intermittent way with slip avalanches detected as acoustic emission and serrations in the stress–strain curves. Similar serrations have recently been observed in a new class of materials, called high-entropy alloys (HEAs). Here, we discuss the serration behaviors of several HEAs from cryogenic to elevated temperatures. The experimental results of slow compression and tension tests are compared with the predictions of a slip-avalanche model for the deformation of a broad range of solids. The results shed light on the deformation processes in HEAs. Temperature effects on the distributions of stress drops and the decrease of the cutoff (i.e., of the largest observed slip size) for increasing temperature qualitatively agree with the model predictions. As a result, the model is used to quantify the serration characteristics of HEAs, and pertinent implications are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Combining 3D printing of copper current collectors and electrophoretic deposition of electrode materials for structural lithium-ion batteries

Serving as a proof of concept, additive manufacturing and electrophoretic deposition are leveraged in this work to enable structural lithium-ion batteries with load-bearing and energy storage dual functionality. The preparation steps of a complex 3D printed copper current collector, involving the formulation of a photocurable resin formulation, as well as the vat photopolymerization process followed by a precursors-based solution soaking step and thermal post-processing are presented. Compression and microhardness testing onto the resulting 3D printed copper current collector are shown to demonstrate adequate mechanical performance. Electrophoretic deposition of graphite as a negative electrode active material and other additives was then performed onto the 3D printed copper collector, with the intention to demonstrate energy storage functionality. Half-cell electrochemical cycling of the 3D multi-material current collector/negative electrode versus lithium metal finally demonstrates that structural battery components can be successfully obtained through this approach.

25 ENERGY STORAGE↗