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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Some useful concepts for the designer in treating cumulative fatigue damage at elevated temperatures

The paper concentrates on three subjects: (1) further development of the double-linear damage rule for cumulative fatigue damage summation in the sub-creep temperature range; (2) a new consideration of the effect of strain reversals in the creep range of materials, whereby reversals that occur later in the histogram can influence the degree of damage caused by earlier loading events; and (3) the application of the minimum-commitment time-temperature parameter to the treatment of creep rupture of multiheats wherein considerable differences in properties of individual heats may occur. Numerical examples and plots are given.

Manson, S. S.↗
NASA NTRS1981

Aeronautical Engineering: A cumulative index to the 1980 issue

This bibliography is a cumulative index to reports, articles, and other documents introduced into the NASA scientific and technical information system. Abstracts for the entries cited appeared in issues 119 through 130 of Aeronautical Engineering: A Continuing Bibliography (NASA SP-7037). Subject, personal author, corporate author, contract number, and report/accession number indexes are provided.

Source record↗
NASA NTRS1981

Functions of cumulative distribution of attenuation due to rain on an interval from 9.5 Km A to 17.8 GHz

Measurement results of attenuation due to rain are reported. Cumulative distribution functions of the attenuation found in three connections are described. Differences between the distribution functions and different polarization frequencies are demonstrated. The possibilty of establishing a bond between the statistics of annual attenuation and worst month attenuation is explored.

Fedi, F.↗
NASA NTRS1981

Cumulative hardware distortion effects on coded and uncoded performance via a satellite repeater

An analytical investigation is presented of the cumulative impact of numerous hardware-induced distortions on BPSK bit-error-rate performance. Attention is given to 16 user and eight transponder constraints, as well as to the effect of filter bandlimiting. Uncoded and coded performance is evaluated with respect to both NRZ and Manchester signaling formats, and tight upper bounds to coded and uncoded SNR degradation are determined. Computed results based on TDRSS (Tracking and Data Relay Satellite System) specifications are presented as an example.

Benjamin, T.↗
NASA NTRS1984

Aerospace Medicine and Biology: 1983 cumulative index

This publication is a cumulative index to the abstracts contained in the Supplements 242 through 253 of Aerospace Medicine and Biology: A Continuing Bibliography. It includes six indexes--subject, personal author, corporate source, contract number, report number, and accession number.

Source record↗
NASA NTRS1985

Reexamination of Cumulative Fatigue Damage Laws

Treatment of accumulated fatigue damage in materials and structures subjected to a history of nonsimple repetitive loadings has received a large amount of attention in recent years. A method used for the treatment of complex loading is known as linear damage rule. It was recognized that, this method could result in unconservative predictions of material and structural behavior. An intense flurry of activity followed in the pursuit of alternative methods of analysis that would predict behavior more accurately. So many methods were introduced that it became necessary periodically to prepare review papers placing all the new methods into perspective. The current integrated view regarding the state of the art as it applies to this effort is discussed. The more recently proposed cumulative damage life prediction methods are reviewed. The double linear damage rule (DLDR), which has evolved over the past 20 years, is reexamined with the intent of improving its accuracy and applicability to engineering problems. Modifications are introduced to the analytical formulation to achieve greater compatibility between the DLDR and the so-called damage curve approach, which is an alternative continuous representation of the DLDR.

Halford, G. R.↗
NASA NTRS1986

Aerospace Medicine and Biology: A Cumulative Index to the 1985 Issues

This publication is a cumulative index to the abstracts contained in the Supplements 268 through 279 of Aerospace Medicine and Biology: A Continuing Bibliography. It includes seven indexes - subject, personal author, corporate source, foreign technology, contract number, report number, and accession number.

Source record↗
NASA NTRS1986

Re-examination of cumulative fatigue damage analysis: An engineering perspective

A method which has evolved in our laboratories for the past 20 yr is re-examined with the intent of improving its accuracy and simplicity of application to engineering problems. Several modifications are introduced both to the analytical formulation of the Damage Curve Approach, and to the procedure for modifying this approach to achieve a Double Linear Damage Rule formulation which immensely simplifies the calculation. Improvements are also introduced in the treatment of mean stress for determining fatigue life of the individual events that enter into a complex loading history. While the procedure is completely consistent with the results of numerous two level tests that have been conducted on many materials, it is still necessary to verify applicability to complex loading histories. Caution is expressed that certain phenomena can also influence the applicability - for example, unusual deformation and fracture modes inherent in complex loading - especially if stresses are multiaxial. Residual stresses at crack tips, and metallurgical factors are also important in creating departures from the cumulative damage theories; examples of departures are provided.

Manson, S. S.↗
NASA NTRS1985

Cumulative creep damage for polycarbonate and polysulfone

Creep to failure tests performed on polycarbonate and polysulfone under single and two step loadings are discussed. A cumulative damage law or modified time fraction rule is developed using a power law for transient creep response as the starting point. Experimental results are approximated well by the new rule. Damage and failure mechanisms associated with the two materials are suggested.

Zhang, M. J.↗
NASA NTRS1986

Re-examination of cumulative fatigue damage analysis - An engineering perspective

A method which has evolved in the laboratories for the past 20 yr is re-examined with the intent of improving its accuracy and simplicity of application to engineering problems. Several modifications are introduced both to the analytical formulation of the Damage Curve Approach, and to the procedure for modifying this approach to achieve a Double Linear Damage Rule formulation which immensely simplifies the calculation. Improvements are also introduced in the treatment of mean stress for determining fatigue life of the individual events that enter into a complex loading history. While the procedure is completely consistent with the results of numerous two level tests that have been conducted on many materials, it is still necessary to verify applicability to complex loading histories. Caution is expressed that certain phenomenon can also influence the applicability - for example, unusual deformation and fracture modes inherent in complex loading especially if stresses are multiaxial. Residual stresses at crack tips, and metallurgical factors are also important in creating departures from the cumulative damage theories; examples of departures are provided.

Manson, S. S.↗
NASA NTRS1988

Fine-scale traverses in cumulate rocks, Stillwater Complex: A lunar analogue study

The objective was to document finite-scale compositional variations in cumulate rocks from the Stillwater Complex in Montana and to interpret these data in the context of planetary magma fractionation processes such as those operative during the formation of the Earth's Moon. This research problem involved collecting samples in the Stillwater Complex and analyzing them by electron microprobe, X-ray fluorescence (XRF), and instrumental neutron activation analysis (INAA). The electron microprobe is used to determine the compositions of cumulus and intercumulus phases in the rocks, the XRF is used to determine the bulk-rock major element and trace element (Y, Sr, Rb, Zr, Ni, and Cr) abundances, and the INAA lab. is used to determine the trace element (Sc, Co, Cr, Ni, Ta, Hf, U, Th, and the REE) abundances of mineral separates and bulk rocks.

Elthon, Donald↗