Search NASA⌕ Search

SEARCH · Search NASA

Results for “strains effect”

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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Orientation dependence of the stress rupture properties of Nickel-base superalloy single crystals

The influence of orientation of the stress rupture behavior of Mar-M247 single crystals was studied. Stress rupture tests were performed at 724 MPa and 774 C where the effect of anisotropy is prominent. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factors for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The stress rupture lives were found to be greatly influenced by the lattice rotations required to produce intersecting slip, because steady-state creep does not begin until after the onset of intersecting slip. Crystals which required large rotations to become oriented for intersecting slip exhibited a large primary creep strain, a large effective stress level at the onset of steady-state creep, and consequently a short stress rupture life. A unified analysis was attained for the stress rupture behavior of the Mar-M247 single crystals tested in this study at 774 C and that of the Mar-M200 single crystals tested in a prior study at 760 C. In this analysis, the standard 001-011-111 stereographic triangle was divided into several regions of crystallographic orientation which were rank ordered according to stress rupture life for this temperature regime. This plot indicates that those crystals having orientations within about 25 deg of the 001 exhibited significantly longer lives when their orientations were closer to the 001-011 boundary of the stereographic triangle than to the 001-111 boundary.

Mackay, R. A.↗
NASA NTRS1986

High temperature monotonic and cyclic deformation in a directionally solidified nickel-base superalloy

Directionally solidified (DS) MAR-M246+Hf was tested in tension and fatigue, at temperatures from 20 C to 1093 C. Tests were performed on (001) oriented specimens at strain rates of 50 % and 0.5 % per minute. In tension, the yield strength was constant up to 704 C, above which the strength dropped off rapidly. A strong dependence of strength on strain rate was seen at the higher temperatures. The deformation mode was observed to change from heterogeneous to homogeneous with increasing temperature. Low Cycle Fatigue tests were done using a fully reversed waveform and total strain control. For a given plastic strain range, lives increased with increasing temperature. For a given temperature strain rate had a strong effect on life. At 704 C, decreasing strain rates decreased life, while at the higher temperatures, decreasing strain rates increased life, for a given plastic strain range. These results could be explained through considerations of the deformation modes and stress levels. At the higher temperatures, marked coarsening caused beneficial stress reductions, but oxidation limited the life. The longitudinal grain boundaries were found to influence slip behavior. The degree of secondary slip adjacent to the boundaries was found to be related to the degree of misorientation between the grains.

Huron, Eric S.↗
NASA NTRS2004

Strain-Gage Loads Calibration Parametric Study

This paper documents a parametric study of various aircraft wing-load test features that affect the quality of the resultant derived shear, bending-moment, and torque strain-gage load equations. The effect of the following on derived strain-gage equation accuracy are compared: single-point loading compared with distributed loading, variation in applied test load magnitude, number of applied load cases, and wing-box-only compared with control-surface loading. The subject of this study is an extensive wing-load calibration test of the Active Aeroelastic Wing F/A-18 airplane. Selected subsets of the available test data were used to derive load equations using the linear regression method. Results show the benefit of distributed loading and the diminishing-return benefits of test load magnitudes and number of load cases. The use of independent check cases as a quality metric for the derived load equations is shown to overcome blind extrapolating beyond the load data used to derive the load equations.

Lokos, William A.↗
NASA NTRS2013

Design and Development of Functionally Effective Human-Machine Interfaces for Firing Room Displays

This project involves creating software for support equipment used on the Space l aunch System (SLS). The goal is to create applications and displays that will be used to remotely operate equipment from the firing room and will continue to support the SLS launch vehicle to the extent of its program. These displays include design practices that help to convey information effectively, such as minimizing distractions at normal operating state and displaying intentional distractions during a warning or alarm state. The general practice for creating an operator display is to reduce the detail of unimportant aspects of the display and promote focus on data and dynamic information. These practices include using minimalist design, using muted tones for background colors, using a standard font at a readable text size, displaying alarms visible for Immediate attention, grouping data logically, and displaying data appropriately varying on the type of data. Users of these displays are more likely to stay focused on operating for longer periods by using design practices that reduce eye strain and fatigue. Effective operator displays will improve safety by reducing human errors during operation, which will help prevent catastrophic accidents. This report entails the details of my work on developing remote displays for the Hypergolics ground system. Before developing a prototype display, the design and requirements of the system are outlined and compiled into a document. Then each subsystem has schematic representations drawn tha.t meet the specifications detailed in the document. The schematics are then used as the outline to create display representations of each subsystem. Each display is first tested individually. Then the displays are integrated with a prototype of the master system, and they are tested in a simulated environment then retested in the real environment. Extensive testing is important to ensure the displays function reliably as intended.

Cho, Henry↗
NASA NTRS2013

Design and Development of Functionally Effective Human-Machine Interfaces for Firing Room Displays

This project involves creating software for support equipment used on the Space Launch System (SLS). The goal is to create applications and displays that will be used to remotely operate equipment from the firing room and will continue to support the SLS launch vehicle to the extent of its program. These displays include design practices that help to convey information effectively, such as minimizing distractions at normal operating state and displaying intentional distractions during a warning or alarm state. The general practice for creating an operator display is to reduce the detail of unimportant aspects of the display and promote focus on data and dynamic information. These practices include using minimalist design, using muted tones for background colors, using a standard font at a readable text size, displaying alarms visible for immediate attention, grouping data logically, and displaying data appropriately varying on the type of data. Users of these displays are more likely to stay focused on operating for longer periods by using design practices that reduce eye strain and fatigue. Effective operator displays will improve safety by reducing human errors during operation, which will help prevent catastrophic accidents. This report entails the details of my work on developing remote displays for the Hypergolic fuel servicing system. Before developing a prototype display, the design and requirements of the system are outlined and compiled into a document. Then each subsystem has schematic representations drawn that meet the specifications detailed in the document. The schematics are then used as the outline to create display representations of each subsystem. Each display is first tested individually. Then the displays are integrated with a prototype of the master system, and they are tested in a simulated environment then retested in the real environment. Extensive testing is important to ensure the displays function reliably as intended.

displays↗
NASA NTRS1972

Aspect of cumulative fatigue damage under multiaxial strain cycling.

The concept of order of loading and its effect on cumulative fatigue damage under multiaxial strain cyclings was investigated. The effect is illustrated through nonlinear relationships between biaxial fatigue damage and cycle-ratio diagrams. Uniaxial theories such as Miner's method, the convergence method, and the double linear damage rule in its special and generalized form, were examined and extended to the biaxial case through the octahedral shear strain theory. The generalized double linear damage rule was found more applicable to biaxial cumulative fatigue damage.

Zamrik, S. Y.↗
NASA NTRS2013

Aligned Carbon Nanotube Tape for Sensor Applications

For this effort, will concentrate on three applications: Vibration Gyroscope utilizes piezoelectric properties of the tape and Coriolis effect Accelerometer utilizes the piezoresistive property Strain Gauge utilizes piezoresistive property Accelerometer and Strain Gauge can also utilize piezoelectric effect Test piezoelectric properties using facilities at the Microfabrication Laboratory (AMRDEC) . Enhance piezoelectric effect using polyvinylidine fluoride and P(VDF ]TrFE) which is readily polarizable .Spray matrix solution while winding fiber; Sandwich of CNT tape and PVDF film (DOE .Two Level) . Construct and test prototype vibration gyroscope . Construct and test prototype accelerometer using cantilever design . Test strain sensitivity of CNT tape against industrial strain gauge . Embed CNT tape in composite samples as well as on surface and test to failure (4 ]point bend) A piezoelectric device exhibits an electrical response from a mechanical applied stress. . A piezoelectric device has both capacitance and resistance properties in which by applying an electric field from a waveform will exert a mechanical stress that can be monitored for a response. . The typical waveform applied is a sinusoidal waveform of a defined voltage for a defined period. The defined voltage is driven from 0 volts to the positive defined volts then back to 0 and driven to negative defined volts then back to 0. . Example. Vmax set to 10V and period set to 10 ms. . Voltage will start at zero, go to 10 volts, return to zero, go to ]10 volts and return to zero during 10 ms. . Applying this electrical field to a DUT, the capacitance response and resistance response can be observed. CNT tape is easier to manufacture and cheaper than micromachining silicon or other ceramic piezoelectric used in gyroscopes and accelerometers CNT tape properties can be modified during manufacture for specific application CNT tape has enhanced mechanical and thermal properties in addition to unique electrical properties CNT tape as a strain gauge in Structural Health Monitoring will provide an excellent material to embed within composite structures

Tucker, Dennis S.↗
NASA NTRS1976

A description of the mechanical behavior of composite solid propellants based on molecular theory

Both the investigation and the representation of the stress-strain response (including rupture) of gum and filled elastomers can be based on a simple functional statement. Internally consistent experiments are used to sort out the effects of time, temperature, strain and crosslink density on gum rubbers. All effects are readily correlated and shown to be essentially independent of the elastomer when considered in terms of non-dimensionalized stress, strain and time. A semiquantitative molecular theory is developed to explain this result. The introduction of fillers modifies the response, but, guided by the framework thus provided, their effects can be readily accounted for.

Landel, R. F.↗
NASA NTRS1965

Dynamic response of biological materials.

Effect of varying strain rate on physical properties of bone and muscle tissue, measuring load and time displacement with constant-velocity compression test machine

STRAIN RATE↗
NASA NTRS1972

Optical polarimetric properties of the Echo 2 and PAGEOS 1 engineering surfaces

Experimental investigations of the percent polarization of sunlight reflected from the surfaces of each of the Echo 2 Satellite and PAGEOS (Passive Geodetic Earth Orbiting Satellite) were performed to determine the stability of their surfaces in the space environment. The Echo 2 surface material was amorphous phosphate chemically bonded to a rolled aluminum substrate while the PAGEOS 1 surface material is vapor deposited aluminum on a poly (ethylene terephthalate) film. The stability of the satellites' surfaces was analyzed by comparing the light polarizing properties of the satellites, to those of test surfaces representative of the satellites' surfaces. The properties of flat test surfaces were measured experimentally in the laboratory, and the effects of surface strain, surface geometry, and vacuum upon these properties were examined. The laboratory analyses revealed that the polarization properties of the Echo 2 surface were significantly affected by surface geometry and vacuum, and that the properties of the PAGEOS 1 surface were not significantly altered by any of the above mechanisms.

Lee, R. B., III↗
NASA NTRS1981

Mechanical characterization of PMR-15 graphite/polyimide bolted joints

Data are presented for the static and viscoelastic performance of Celion 6000/PMR-15 graphite/polyimide composite belted joints over the 21 to 315 C temperature range. Two laminate configurations were obtained by sectioning a panel into subpanels oriented parallel and perpendicular to the laminate principal direction. Three replicates of each specimen geometry were tested at each of the test temperatures for the two laminate configurations, and failure load was defined as the maximum load attained as indicated by the load/deflection curve. Effects of strain-rate on strength and failure mode behavior were assessed at room temperature for strain rates of 0.002, 0.01, 0.10, and 1.00/s, and creep behavior was examined for the case of bearing deformations at temperatures of 21 and 177 C. Results are presented, including: (1) two distinct mechanisms were responsible for bearing failure and related to laminate configuration, (2) the + or - 45 deg plies carried the shearing load in composite bolted joints, and (3) the material exhibited strain-rate sensitivity which varied with laminate configuration.

Wilson, D. W.↗
NASA NTRS1984

Muon spin rotation studies

The bulk of the muon spin rotation research work centered around the development of the muon spin rotation facility at the Alternating Gradient Synchrotron (AGS) of Brookhaven National Laboratory (BNL). The collimation system was both designed and fabricated at Virginia State University. This improved collimation system, plus improvements in detectors and electronics enabled the acquisition of spectra free of background out to 15 microseconds. There were two runs at Brookhaven in 1984, one run was devoted primarily to beam development and the other run allowed several successful experiments to be performed. The effect of uniaxial strain on an Fe(Si) crystal at elevated temperature (360K) was measured and the results are incorporated herein. A complete analysis of Fe pulling data taken earlier is included.

Source record↗
NASA NTRS1986

Distribution of nitrogen and defects in SiO(x)N(y)/Si structures formed by the thermal nitridation of SiO2/Si

Previously reported nitrogen distributions in SiO2 films on Si which have been thermally nitrided at 1000 C have been explained by a kinetic model of the nitridation process which rests upon the effects of interfacial strain. A critical test of this kinetic model is the validity of the predictions regarding nitrogen distributions obtained at other nitridation temperatures. In this work, nitrogen distributions determined via X-ray photoelectron spectroscopy are reported for samples nitrided at 800 and 1150 C, and are shown to be consistent with the kinetic model. In addition, the intensity of a fluorine marker is found to correlate with the nitrogen distribution, and is postulated to be related to kinetically generated defects in the dielectric film, consistent with the strain-dependent energy of formation of defects proposed recently to explain electrical data.

Vasquez, R. P.↗
NASA NTRS1986

An X-ray photoelectron spectroscopy study of the thermal nitridation of SiO2/Si

The dependence of the nitrogen distribution in thermally nitrided SiO2 films on the nitridation time and temperature has been studied by means of X-ray photoelectron spectroscopy (XPS). The photoelectron peak intensities were measured by fitting Voigt profiles to the XPS spectra and were used to calculate the film composition as a function of film depth, applying an analytical method described in detail. The times of appearance of the maxima in interfacial nitrogen concentration are shown for 800, 1000, and 1150 C, and the data are related to a kinetic model of Vasquez and Madhukar (1985), which considers the effect of interfacial strain on the nitridation kinetics. In addition, the intensity of a fluorine marker (from the HF used in the etching step) was found to correlate with the nitrogen concentration. It is postulated that the F bonds preferentially to defects. This hypothesis and the measured F intensities are consistent with the proposed strain-dependent energy of defect formation.

Vasquez, R. P.↗
NASA NTRS1986

A kinetic model for the thermal nitridation of SiO2/Si

To explain the observed nitrogen distributions in thermally nitridated SiO2 films, a kinetic model is proposed in which the nitridation process is simulated, using the first-order chemical kinetics and Arrhenius dependence of the diffusion and reaction rates on temperature. The calculations show that initially, as the substrate reacts with diffusing nitrogen, a nitrogen-rich oxynitride forms at the SiO2-Si interface, while at nitridation temperatures above 1000 C, an oxygen-rich oxynitride subsequently forms at the interface, due to reaction of the substrate with an increasingly concentrated oxygen displaced by the slower nitridation of the SiO2. This sequence of events results in a nitrogen distribution in which the peak of the interfacial nitrogen concentration occurs away from the interface. The results are compared with the observed nitrogen distribution. The calculated results have correctly predicted the positions of the interfacial nitrogen peaks at the temperatures of 800, 1000, and 1150 C. To account for the observed width of the interfacial nitrogen distribution, it was found necessary to include in the simulations the effect of interfacial strain.

Vasquez, R. P.↗
NASA NTRS1987

Solution methods for one-dimensional viscoelastic problems

A recently developed differential methodology for solution of one-dimensional nonlinear viscoelastic problems is presented. Using the example of an eccentrically loaded cantilever beam-column, the results from the differential formulation are compared to results generated using a previously published integral solution technique. It is shown that the results obtained from these distinct methodologies exhibit a surprisingly high degree of correlation with one another. A discussion of the various factors affecting the numerical accuracy and rate of convergence of these two procedures is also included. Finally, the influences of some 'higher order' effects, such as straining along the centroidal axis are discussed.

Stubstad, John M.↗