Experimental Investigation of Thermal-buckling Characteristics of Flanged, Thin-shell Leading Edges


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The leading edges of winged hypersonic aircraft are known to be subjected to intense aerodynamic heating (ref. 1) in flight. Detailed research investigations into specific types of leading edges suitable for hypersonic use have been limited. The heat-sink concept, although excessive in weight and limited to short durations of heating (ref. 2), has been the most widely used type of leading edge for hypersonic application. Limited experimental and analytical work on shell types of leading edges (refs. 3 and 4) has been conducted; however, the thermal-buckling behavior of leading edges has been defined only in analytical studies, such as references 5 and 6. These theories include simplifying assumptions, which impose limitations on their applicability to design problems. A series of experimental investigations into the thermal-buckling behavior of flanged, thin-shell leading edges has been conducted at the NASA Flight Research Center, Edwards, Calif.







NASA Technical Note


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A Comparison of Experimental and Calculated Thin-Shell Leading-Edge Buckling Due to Thermal Stresses


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High-temperature thin-shell leading-edge buckling test data are analyzed using NASA structural analysis (NASTRAN) as a finite element tool for predicting thermal buckling characteristics. Buckling points are predicted for several combinations of edge boundary conditions. The problem of relating the appropriate plate area to the edge stress distribution and the stress gradient is addressed in terms of analysis assumptions. Local plasticity was found to occur on the specimen analyzed, and this tended to simplify the basic problem since it effectively equalized the stress gradient from loaded edge to loaded edge. The initial loading was found to be difficult to select for the buckling analysis because of the transient nature of thermal stress. Multiple initial model loadings are likely required for complicated thermal stress time histories before a pertinent finite element buckling analysis can be achieved. The basic mode shapes determined from experimentation were correctly identified from computation. Jenkins, Jerald M. Armstrong Flight Research Center NASA-TM-100416, H-1440, NAS 1.15:100416 RTOP 506-43-81...







NASA Scientific and Technical Reports


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