4/19/2023 0 Comments Wings 3d snap![]() This has theoretically a tremendous impact on design of Joined Wings: under certain conditions an apparently safe and quasi-linear steady-state condition may actually be unsafe if the post-critical analysis is ignored. More important, the concept of bi-stability was discussed and shown to cause branch-jumping phenomena at load levels far below the nominal critical condition (identified through the nonlinear static analysis as the snap-buckling). (2014c) discussed the effects of the non-conservative loads of the follower type on the SBR. One of the most important physical aspects was the bending moment transferring through the joint: a reduction of the amount of transferred bending moment, obtained by changing the boundary conditions at the joint, significantly reduced the risk of snap-buckling instability, although at expense of the overall stiffness of the structure.Ĭavallaro et al. Stiffening the compressed upper wing actually decreased the critical load in addition, the lower-to-upper-wing bending stiffness ratio was shown to be one of the major parameters ruling the snap-buckling phenomenon. Load repartition between the wings, joint size, and sweep angle had an important impact on the stability properties.Ĭavallaro et al., 2012, Cavallaro et al., 2014a presented several counter-intuitive aspects. The so-called Snap-Buckling Region (SBR) for Joined Wings was then introduced. Moreover, the wing system might be sensitive to snap-buckling type of instability for some combinations of structural parameters. (2013b) demonstrated via nonlinear investigations that the linear buckling analysis is not very reliable as far as the static critical condition is concerned. Only recently (see Demasi et al., 2013b, Cavallaro et al., 2012, Cavallaro et al., 2014c, Cavallaro et al., 2014a), the research moved on the fundamental understanding of the peculiar nonlinear response of Joined Wings, with focus on the so-called PrandtlPlane configurations (e.g., Frediani, 1999, Frediani, 2002, Frediani, 2003, Frediani, 2005, Frediani et al., 2012). Different works discussed theoretical aspects related to the structural nonlinearities (Sotoudeh and Hodges, 2011) and also involved aeroelastic investigations (Patil, 2003, Demasi and Livne, 2005, Demasi and Livne, 2009b, Cavallaro et al., 2014). Besides numerical approach, also experimental work (Kim et al., 2011, Boston et al., 2010) was carried out to explore the joined-wing Sensocraft (Reichenbach et al., 2011, Scott et al., 2011, Heeg and Morelli, 2011) response when subjected to follower static loads. Several efforts considered mechanical loading and showed a highly complex nonlinear behavior of Joined Wings. This suggests taking one step back and focusing on the nature of the involved nonlinearities, with the final goal of capturing the essential underlying physics for a more accurate and efficient design of reduced order models. ![]() ![]() Unfortunately, even advanced reduced order modeling techniques proved not to be very effective (see Demasi and Livne, 2007, Demasi and Palacios, 2010, Phlipot et al., 2014, Teunisse et al., 2014) when Joined Wings were considered. In this scenario, reduced order models specifically tailored to retain the important nonlinearities of Joined Wings can be an ideal solution. On the other hand, neglecting structural nonlinearities in the early design stages may lead to a posteriori-verified unacceptable solutions and can determine a significant increase of design costs. What has proven to be very effective in the past for classical cantilevered configurations, then, cannot (Kim et al., 2008) be directly translated into procedures that have the same degree of computational efficiency and accuracy, when Joined Wings are considered (Weisshaar and Lee, 2002). Employment of these lower fidelity tools is actually a practical requirement since a Multi-Disciplinary Optimization (MDO) generally involves a large amount of analyses. As a consequence, preliminary design complexity is increased (Blair et al., 2005): existing procedures successfully adopted by the aerospace industry rely mainly on linear tools not able to correctly reproduce these effects. Typical joined-wing configurations (Wolkovitch, 1986, Chambers, 2005) are characterized by significant structural geometric nonlinearities (Blair et al., 2005, Kim et al., 2008, Liu et al., 2010).
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