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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Effect of space exposure of some epoxy matrix composites on their thermal expansion and mechanical properties (AO 138-8)

The experiment objectives are: to detect a variation of the coefficient of thermal expansion (CTE) of composite samples; to detect an evolution of mechanical properties; to compare the behavior of two epoxy resins. The CTE is measured by interferometric method in a vacuum chamber. The following mechanical tests are achieved on the samples: interlaminar shear strength; flexural strength; flatwise tensile strength. The results are reported.

Jabs, Heinrich↗
NASA NTRS2005

Thermal and Mechanical Property Characterization of the Advanced Disk Alloy LSHR

A low solvus, high refractory (LSHR) powder metallurgy disk alloy was recently designed using experimental screening and statistical modeling of composition and processing variables on sub-scale disks to have versatile processing-property capabilities for advanced disk applications. The objective of the present study was to produce a scaled-up disk and apply varied heat treat processes to enable full-scale demonstration of LSHR properties. Scaled-up disks were produced, heat treated, sectioned, and then machined into specimens for mechanical testing. Results indicate the LSHR alloy can be processed to produce fine and coarse grain microstructures with differing combinations of strength and time-dependent mechanical properties, for application at temperatures exceeding 1300 F.

Gabb, Timothy P.↗
NASA NTRS2000

Mechanical properties and fiber type composition of chronically inactive muscles

A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

Non-NASA Center↗
NASA NTRS1972

Thermal and mechanical treatments for nickel and some nickel-base alloys: Effects on mechanical properties

This report deals with heat treating and working nickel and nickel-base alloys, and with the effects of these operations on the mechanical properties of the materials. The subjects covered are annealing, solution treating, stress relieving, stress equalizing, age hardening, hot working, cold working, combinations of working and heat treating (often referred to as thermomechanical treating), and properties of the materials at various temperatures. The equipment and procedures used in working the materials are discussed, along with the common problems that may be encountered and the precautions and corrective measures that are available.

Hall, A. M.↗
NASA NTRS1972

The effect of hot salt on the mechanical properties of several superalloys

The effect of sodium chloride on unstressed, transverse, tensile, metal specimens at elevated temperatures was determined. Results indicate that the mechanical properties of Inconel 718, Rene 41, titanium base alloy 13V-11Cr-3Al, Hastelloy X, HS25 (L605), HS188, and TDNiCr suffer degradation in tensile strength and ductility due to hot salt exposure.

Nelson, E. E.↗
NASA NTRS1979

The improvement of cryogenic mechanical properties of Fe-12 Mn and Fe-8 Mn alloy steels through thermal/mechanical treatments

An investigation has been made to improve the low temperature mechanical properties of Fe-8Mn and Fe-12Mn-0.2 Ti alloy steels. A reversion annealing heat treatment in the two-phase (alpha + gamma) region following cold working has been identified as an effective treatment. In an Fe-12Mn-0.2Ti alloy a promising combination of low temperature (-196 C) fracture toughness and yield strength was obtained by this method. The improvement of properties was attributed to the refinement of grain size and to the introduction of a uniform distribution of retained austenite (gamma). It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated alpha-prime martensitic structure and absence of epsilon martensite. As a result, a significant reduction of ductile to brittle transition temperature was obtained.

Hwang, S. K.↗
NASA NTRS1987

Effect of LID (Registered) processing on the microstructure and mechanical properties of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo titanium foil-gauge materials

A study was undertaken to determine the mechanical properties and microstructures resulting from Liquid Interface Diffusion (LID -Registered) processing of foil-gauge specimens of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo coated with varying amounts of LID material. In addition, the effects of various elevated temperature exposures on the concentration profiles of the LID alloying elements were investigated, using specimens with a narrow strip of LID material applied to the surface. Room and elevated temperature tensile properties were determined for both coated and uncoated specimens. Optical microscopy was used to examine alloy microstructures, and scanning electron microscopy to examine fracture surface morphologies. The chemical concentration profiles of the strip-coated specimens were determined with an electron microprobe.

Balckburn, Linda B.↗
NASA NTRS1984

Experimental and Theoretical Studies of Moisture and Temperature Effects on the Mechanical Properties of Graphite/Epoxy Laminates and Neat Resins

The properties of high performnce composites which are strongly dependent on the physical properties of the matrix resin were studied. Moisture adversely affect the properties of both neat epoxy resin and epoxy matrix composites. Inhomogeneous swelling as to the moisture degradation of mechanical properties, both in the neat resin and the composite. It is postulated that the postcuring process can change structure/moisture interactions and partially alleviate its adverse effects. The study is directed toward are understanding of the physical/mechanical/thermodynamic aspects of this problem.

Sternstein, S. S.↗
NASA NTRS1998

Structures and Mechanical Properties of Natural and Synthetic Diamonds

A revolution in diamond technology is in progress as the low-pressure process becomes an industrial reality. It will soon be possible to take advantage of the demanding properties of diamond to develop a myriad of new applications, particularly for self-lubricating, wear, and superhard coatings. The production of large diamond films or sheets at low cost, a distinct possibility in the not-too-distant future, may drastically change tribology technology, particularly solid lubricants and lubricating materials and systems. This chapter reviews the structures and properties of natural and synthetic diamond to gain a better understanding of the tribological properties of diamond and related materials to be described in the following chapters. Atomic and crystal structure, impurities, mechanical properties, and indentation hardness of diamond are described.

Miyoshi, Kazuhisa↗
NASA NTRS1985

Ultrasonic evaluation of mechanical properties of thick, multilayered, filament wound composites

A preliminary investigation is conducted to define capabilities and limitations of ultrasonic and acousto-ultrasonic measurements related to mechanical properties of filament wound graphite/epoxy composite structures. The structures studied are segments of filament wound cylinders formed of multiple layers of hoop and helical windings. The segments consist of 24 to 35 layers and range from 3.02 to 3.34 cm in wall thickness. The resultant structures are anisotropic, heterogeneous, porous, and highly attenuating to ultrasonic frequencies greater than 1 MHz. The segments represent structures to be used for space shuttle booster cases. Ultrasonic velocity and acousto-ultrasonic stress wave factor measurement approaches are discussed. Correlations among velocity, density, and porosity, and between the acousto-ultrasonic stress wave factor and interlaminar shear strength are presented.

Kautz, H. E.↗
NASA NTRS2003

Microstructure and Mechanical Properties of Extruded Gamma Met PX

A gamma TiAl alloy with a high Nb content is being assessed as a compressor blade material. The microstructure and mechanical properties of extruded Ti-45Al-X(Nb,B,C) (at %) were evaluated in both an as-extruded condition and after a lamellar heat treatment. Tensile behavior of both as-extruded and lamellar heat treated specimens was studied in the temperature range of RT to 926 C. In general, the yield stress and ultimate tensile strength reached relatively high values at room temperature and decreased with increasing deformation temperature. The fatigue strength of both microstructures was characterized at 650 C and compared to a baseline TiAl alloy and to a Ni-base superalloy. Tensile and fatigue specimens were also exposed to 800 C for 200 h in air to evaluate the alloy's environmental resistance. A decrease in ductility was observed at room temperature due to the 800 C exposure but the 650 C fatigue properties were unaffected. Compressive and tensile creep testing between 727 and 1027 C revealed that the creep deformation was reproducible and predictable. Creep strengths reached superalloy-like levels at fast strain rates and lower temperatures but deformation at slower strain rates and/or higher temperature indicated significant weakening for the as-extruded condition. At high temperatures and low stresses, the lamellar microstructure had improved creep properties when compared to the as-extruded material. Microstructural evolution during heat treatment, identification of various phases, and the effect of microstructure on the tensile, fatigue, and creep behaviors is discussed.

Draper, S. L.↗
NASA NTRS1991

The effect of copper, chromium, and zirconium on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloys

The present study evaluates the effect of the systematic variation of copper, chromium, and zirconium contents on the microstructure and mechanical properties of a 7000-type aluminum alloy. Fracture toughness and tensile properties are evaluated for each alloy in both the peak aging, T8, and the overaging, T73, conditions. Results show that dimpled rupture essentially characterize the fracture process in these alloys. In the T8 condition, a significant loss of toughness is observed for alloys containing 2.5 pct Cu due to the increase in the quantity of Al-Cu-Mg-rich S-phase particles. An examination of T8 alloys at constant Cu levels shows that Zr-bearing alloys exhibit higher strength and toughness than the Cr-bearing alloys. In the T73 condition, Cr-bearing alloys are inherently tougher than Zr-bearing alloys. A void nucleation and growth mechanism accounts for the loss of toughness in these alloys with increasing copper content.

Wagner, John A.↗
NASA NTRS1983

Dynamic Mechanical Properties of N-Phenylnadimide Modified PMR Polyimide Composites

The rheological behavior of newly developd Celion 6000/N-phenylnadimide modified PMR polyimide and PMR-15 composites was investigated. The dynamic mechanical properties were correlated with the structure of N-phenylnadimide modified PMR polyimides. The storage modulus (G'), loss modulus (G''), and loss tangent (tan delta) of four composite systems were measured over a temperature range from -150 to 400 C. Three well defined peaks were seen in the regions of 360, 100, and -120 C, corresponding to the alpha, beta, and gamma relaxations, respectively, of the matrix resins. The activation energies of the alpha, beta, and gamma relaxations were estimated to be 232, 60, and 14 kcal/mole, respectively, for PMR-15. Addition of N-phenylnadimide to the PMR-15 composition lowered the glass transition temperature and the activation energies of PMR-15 polyimide. The dynamic mechanical data appear to be consistent with the formation of a copolymer from N-phenylnadimide and a PMR-15 prepolymer.

Pater, R. H.↗
NASA NTRS1988

Static mechanical properties of 30 x 11.5 - 14.5, type 8 aircraft tires of bias-ply and radial-belted design

An investigation was conducted to determine the static mechanical properties of a 30 x 11.5 to 14.5, Type 8, bias-ply and radial-belted aircraft tire. The properties measured were the spring rate and damping characteristics of each tire from vertical- and lateral-loading hysteresis loops. Mass moment of inertia tests were also conducted. The results of the study are presented along with a discussion of the advantages and disadvantages of each type of tire.

Davis, Pamela A.↗
NASA NTRS1987

Ultrasonic evaluation of mechanical properties of thick, multilayered, filament-wound composites

A preliminary investigation is conducted to define capabilities and limitations of ultrasonic and acousto-ultrasonic measurements related to mechanical properties of filament wound graphite/epoxy composite structures. The structures studied are segments of filament wound cylinders formed of multiple layers of hoop and helical windings. The segments consist of 24 to 35 layers and range from 3.02 to 3.34 cm in wall thickness. The resultant structures are anisotropic, heterogeneous, porous, and highly attenuating to ultrasonic frequencies greater than 1 MHz. The segments represent structures to be used for Space Shuttle booster cases.Ultrasonic velocity and acousto-ultrasonic stress wave factor measurement approaches are discussed. Correlations among velocity, density, and porosity, and between the acousto-ultrasonic stress wave factor and interlaminar shear strength are presented.

Kautz, H. E.↗
NASA NTRS1990

Influence of interfacial shear strength on the mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composites

An evaluation is made of the influence of interfacial microstructure and shear strength on the mechanical properties of a 30 vol pct uniaxially-aligned SiC fiber-reinforced reaction-bonded Si3N4-matrix composite whose interface microstructure was varied through control of fabrication conditions and by heat-treatment in an oxidizing environment. The carbon-rich coating of the as-produced SiC fibers was stable in composites fabricated at 1200 C in an N or N + 4-percent H mixture for 40 hrs. This coating was degraded in composites fabricated at 1350 C in N + 4 percent H for 40 and 72 hrs, as well as after heat-treatment in an oxidizing environment at 600 C for 100 hrs even after fabrication at 1200 C in N. This degradation occurred via carbon removal.

Bhatt, Ramakrishna T.↗
NASA NTRS1994

Mechanical properties of crosslinked polymer coatings

The objectives of this experiment are to: fabricate and test thin films to explore relations between a polymer's structure and its mechanical properties; expose students to testing methods for hardness and impact energy that are simple to perform and which have results that are easy to comprehend; show importance of polymer properties in materials that students frequently encounter; illustrate a system which displays a tradeoff between strength and impact resistance, the combination of which would need to be optimized for a particular application; and to expose students to coatings technology and testing.

Csernica, Jeffrey↗