NASA Scientific and Technical Aerospace Reports
NASA Scientific and Technical Aerospace Reports
NASA Scientific and Technical Aerospace Reports
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20040071005 <strong>NASA</strong> Marshall Space Flight Center, Huntsville, AL, USA<br />
Statistical Comparison <strong>and</strong> Improvement of Methods for Combining R<strong>and</strong>om <strong>and</strong> Harmonic Loads<br />
Brown, Andrew M.; McGhee, David S.; March 1, 2004; 6 pp.; In English; 45th AIAA/ASME/ASCE/AHS/ASC Structures,<br />
Structural Dynamics <strong>and</strong> Materials Conference, 19-22 Apr. 2004, Palm Springs, CA, USA; No Copyright; Avail: CASI; A02,<br />
Hardcopy<br />
Structures in many environments experience both r<strong>and</strong>om <strong>and</strong> harmonic excitation. A variety of closed-form techniques<br />
has been used in the aerospace industry to combine the loads resulting from the two sources. The resulting combined loads<br />
are then used to design for both yield ultimate strength <strong>and</strong> high cycle fatigue capability. This paper examines the cumulative<br />
distribution function (CDF) percentiles obtained using each method by integrating the joint probability density function of the<br />
sine <strong>and</strong> r<strong>and</strong>om components. A new Microsoft Excel spreadsheet macro that links with the software program Mathematics<br />
is then used to calculate the combined value corresponding to any desired percentile along with a curve fit to this value.<br />
Another Excel macro is used to calculate the combination using a Monte Carlo simulation. Unlike the traditional techniques,<br />
these methods quantify the calculated load value with a Consistent percentile. Using either of the presented methods can be<br />
extremely valuable in probabilistic design, which requires a statistical characterization of the loading. Also, since the CDF at<br />
high probability levels is very flat, the design value is extremely sensitive to the predetermined percentile; therefore, applying<br />
the new techniques can lower the design loading substantially without losing any of the identified structural reliability.<br />
Author<br />
<strong>Aerospace</strong> Industry; Harmonic Excitation; R<strong>and</strong>om Loads; Statistical Analysis; Dynamic Structural Analysis<br />
20040071071 <strong>NASA</strong> Marshall Space Flight Center, Huntsville, AL, USA<br />
Development of a Fatigue Crack Growth Coupon for Highly Plastic Stress Conditions<br />
Allen, Phillip A.; Aggarwal, Pravin K.; Swanson, Gregory R.; November 10, 2003; 7 pp.; In English; 45th AIAA/ASME/<br />
ASCE/AHS/ASC Structures, Structural Dynamics, <strong>and</strong> Materials Conference, 19-22 Apr. 2004, Palm Springs, CA, USA; No<br />
Copyright; Avail: CASI; A02, Hardcopy<br />
The analytical approach used to develop a novel fatigue crack growth coupon for highly plastic stress field condition is<br />
presented in this paper. The flight hardware investigated is a large separation bolt that has a deep notch, which produces a large<br />
plastic zone at the notch root when highly loaded. Four test specimen configurations are analyzed in an attempt to match the<br />
elastic-plastic stress field <strong>and</strong> crack constraint conditions present in the separation bolt. Elastic-plastic finite element analysis<br />
is used to compare the stress fields <strong>and</strong> critical fracture parameters. Of the four test specimens analyzed, the modified<br />
double-edge notch tension - 3 (MDENT-3) most closely approximates the stress field, J values, <strong>and</strong> crack constraint conditions<br />
found in the flight hardware. The MDENT-3 is also most insensitive to load misalignment <strong>and</strong>/or load redistribution during<br />
crack growth.<br />
Author<br />
Crack Propagation; Fatigue (Materials); Stress Distribution; Mechanical Properties; Plastic Properties<br />
20040073435 <strong>NASA</strong> Glenn Research Center, Clevel<strong>and</strong>, OH, USA<br />
Telescoping Mechanics: A New Paradigm for Composite Behavior Simulation<br />
Chamis, C. C.; Murthy, P. L. N.; Gotsis, P. K.; Mital. S. K.; April 2004; 24 pp.; In English<br />
Contract(s)/Grant(s): WBS-22-708-48-11<br />
Report No.(s): <strong>NASA</strong>/TM-2004-209317; E-11804; No Copyright; Avail: CASI; A03, Hardcopy<br />
This report reviews the application of telescoping mechanics to composites using recursive laminate theory. The elemental<br />
scale is the fiber-matrix slice, the behavior of which propagates to laminate. The results from using applications for typical,<br />
hybrid, <strong>and</strong> smart composites <strong>and</strong> composite-enhanced reinforced concrete structures illustrate the versatility <strong>and</strong> generality<br />
of telescoping scale mechanics. Comparisons with approximate, single-cell, <strong>and</strong> two- <strong>and</strong> three-dimensional finite-element<br />
methods demonstrate the accuracy <strong>and</strong> computational effectiveness of telescoping scale mechanics for predicting complex<br />
composite behavior.<br />
Author<br />
Composite Materials; Hybrid Composites; Laminates; Fiber Composites<br />
20040073705 Imperium, Inc., Silver Spring, MD<br />
Large Area, Real Time Inspection of Rocket Motors Using a Novel H<strong>and</strong>held Ultrasound Camera<br />
Gurney, J. W.; Lasser, M. E.; , R. S; Kula, J. P.; Rich, D. C.; Aug. 3, 2004; 10 pp.; In English<br />
Contract(s)/Grant(s): F04611-03-C-0022; Proj-3005<br />
Report No.(s): AD-A422607; AFRL-PR-ED-TP-2004-064; No Copyright; Avail: CASI; A02, Hardcopy<br />
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