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  • 1
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    A review of fracture mechanics life technology (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Current lifetime prediction technology for structural components subjected to cyclic loads was reviewed. The central objectives of the project were to report the current state of and recommend future development of fracture mechanics-based analytical tools for modeling and forecasting subcritical fatigue crack growth in structures. Of special interest to NASA was the ability to apply these tools to practical engineering problems and the developmental steps necessary to bring vital technologies to this stage. A survey of published literature and numerous discussions with experts in the field of fracture mechanics life technology were conducted. One of the key points made is that fracture mechanics analyses of crack growth often involve consideration of fatigue and fracture under extreme conditions. Therefore, inaccuracies in predicting component lifetime will be dominated by inaccuracies in environment and fatigue crack growth relations, stress intensity factor solutions, and methods used to model given loads and stresses. Suggestions made for reducing these inaccuracies include: development of improved models of subcritical crack growth, research efforts aimed at better characterizing residual and assembly stresses that can be introduced during fabrication, and more widespread and uniform use of the best existing methods.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Marshall Space Flight Center Advan. High Pressure O2(H2 Technol.; p 5-19
    Format: application/pdf
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  • 2
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    A review of fracture mechanics life technology (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Lifetime prediction technology for structural components subjected to cyclic loads is examined. The central objectives of the project are: (1) to report the current state of the art, and (2) recommend future development of fracture mechanics-based analytical tools for modeling subcritical fatigue crack growth in structures. Of special interest is the ability to apply these tools to practical engineering problems and the developmental steps necessary to bring vital technologies to this stage. The authors conducted a survey of published literature and numerous discussions with experts in the field of fracture mechanics life technology. One of the key points made is that fracture mechanics analyses of crack growth often involve consideration of fatigue and fracture under extreme conditions. Therefore, inaccuracies in predicting component lifetime will be dominated by inaccuracies in environment and fatigue crack growth relations, stress intensity factor solutions, and methods used to model given loads and stresses. Suggestions made for reducing these inaccuracies include development of improved models of subcritical crack growth, research efforts aimed at better characterizing residual and assembly stresses that can be introduced during fabrication, and more widespread and uniform use of the best existing methods.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-3957 , NAS 1.26:3957
    Format: application/pdf
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  • 3
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    Predicting the Fatigue life of Structures (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Report reviews fracture-mechanics technology for predicting life expectancy of structural components subjected to cyclic loads. Report covers analytical tools for modeling and forecasting subcritical fatigue-crack growth in structures. It emphasizes use of tools in practical, day-to-day problems of engineering design, development, and decisionmaking.
    Keywords: MATERIALS
    Type: MFS-27049 , NASA Tech Briefs (ISSN 0145-319X); 9; 2; P. 102
    Format: text
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  • 4
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    NASCRAC - A computer code for fracture mechanics analysis of crack growth (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: NASCRAC - a computer code for fracture mechanics analysis of crack growth - is described in this paper. The need for such a code is increasing as requirements grow for high reliability and low weight in aerospace components. The code is comprehensive and versatile, as well as user friendly. The major purpose of the code is calculation of fatigue, corrosion fatigue, or stress corrosion crack growth, and a variety of crack growth relations can be selected by the user. Additionally, crack retardation models are included. A very wide variety of stress intensity factor solutions are contained in the code, and extensive use is made of influence functions. This allows complex stress gradients in three-dimensional crack problems to be treated easily and economically. In cases where previous stress intensity factor solutions are not adequate, new influence functions can be calculated by the code. Additional features include incorporation of J-integral solutions from the literature and a capability for estimating elastic-plastic stress redistribution from the results of a corresponding elastic analysis. An example problem is presented which shows typical outputs from the code.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: AIAA PAPER 87-0847
    Format: text
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  • 5
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    Automated Shell Theory for Rotating Structures (ASTROS) (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Computer program can be used to analyze any disk or shell of revolution of arbitrary cross section under inertial loads caused by rotation about shell axis and under various static loads, including thermal gradients. Geometric shapes incorporated in program are ellipsoidal, spherical, ogival, toroidal, conical, circular plate, cylindrical, and parabolic.
    Keywords: MATHEMATICS AND INFORMATION SCIENCES
    Type: MFS-21970
    Format: application/pdf
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  • 6
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    Automated shell theory for rotating structures (ASTROS) (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A computer program for analyzing axisymmetric shells with inertial forces caused by rotation about the shell axis is developed by revising the STARS II shell program. The basic capabilities of the STARS II shell program, such as the treatment of the branched shells, stiffened wall construction, and thermal gradients, are retained.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-6485 , M-367
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  • 7
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    A finite element approach to the structural instability of beam columns, frames, and arches (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Stiffness matrix for structural stability analyses on beam columns, frames, and arches
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-5782 , M-351
    Format: application/pdf
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  • 8
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    Decision theory in structural reliability (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Some fundamentals of reliability analysis as applicable to aerospace structures are reviewed, and the concept of a test option is introduced. A decision methodology, based on statistical decision theory, is developed for determining the most cost-effective design factor and method of testing for a given structural assembly. The method is applied to several Saturn V and Space Shuttle structural assemblies as examples. It is observed that the cost and weight features of the design have a significant effect on the optimum decision.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Annual Reliability and Maintainability Symposium; Jan 28, 1975 - Jan 30, 1975; Washington, DC
    Format: text
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  • 9
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    The use of subjective expert opinions in cost optimum design of aerospace structures (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The results of two questionnaires sent to engineering experts are statistically analyzed and compared with objective data from Saturn V design and testing. Engineers were asked how likely it was for structural failure to occur at load increments above and below analysts' stress limit predictions. They were requested to estimate the relative probabilities of different failure causes, and of failure at each load increment given a specific cause. Three mathematical models are constructed based on the experts' assessment of causes. The experts' overall assessment of prediction strength fits the Saturn V data better than the models do, but a model test option (T-3) based on the overall assessment gives more design change likelihood to overstrength structures than does an older standard test option. T-3 compares unfavorably with the standard option in a cost optimum structural design problem. The report reflects a need for subjective data when objective data are unavailable.
    Keywords: STATISTICS AND PROBABILITY
    Type: AIAA PAPER 75-139 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 20, 1975 - Jan 22, 1975; Pasadena, CA
    Format: text
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  • 10
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    Reliability-based econometrics of aerospace structural systems: Design criteria and test options (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The design criteria and test options for aerospace structural reliability were investigated. A decision methodology was developed for selecting a combination of structural tests and structural design factors. The decision method involves the use of Bayesian statistics and statistical decision theory. Procedures are discussed for obtaining and updating data-based probabilistic strength distributions for aerospace structures when test information is available and for obtaining subjective distributions when data are not available. The techniques used in developing the distributions are explained.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TN-D-7646
    Format: application/pdf
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