Modal nudging and elastic tailoring for blade-stiffened wing structures

叶片加固机翼结构的模态微移和弹性剪裁

• 批准号: 2747472
• 金额: --
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2747472
• 关键词: Modal; nudging; elastic; tailoring; blade

Aerospace requirements put an emphasis on developing lightweight structures to help reduce fuel consumption and related costs. Typically, designers in aerospace engineering use thin-walled structures which are periodically stiffened with ribs, frames and longerons, i.e. semi-monocoque structures, as an efficient solution. However, slender and thin-walled structures often exhibit undesirable elastic nonlinearities and instabilities that need to be remedied at the cost of mass efficiency. However, it has been demonstrated that incorporating well-behaved elastic nonlinearities offers the means to recuperate the baseline's efficiency or even improve upon it. Modal nudging is a recently introduced tailoring technique, whereby mode shapes from the post buckling regime are seeded as initial perturbations to the geometry of the perfect structure. The small alterations to the geometry of a structure can be used to connect stable pre-buckling responses to stable post-bucking ones. This characteristic increases the load carrying capability of the structure by removing critical bifurcations and stabilising the post-buckling response removing any of the undesirable instabilities which may typically be encountered post-bucking. As an additional benefit, in stabilising the post-buckling response, modal nudging also ameliorates imperfection sensitivity. Ultimately, the stabilisation of post-buckling responses, the increase in load-carrying capacity, and the reduction in imperfection sensitivity, are conducive to further lightweighting of aerospace, semi-monocoque structures. Preliminary work has shown that modal nudging via geometric alterations can successfully be used to increase the load carrying capacity and the compliance of blade-stiffened wing structures. With a judicious selection of the post-buckling modes seeded onto the original geometry, the nonlinear load-displacement trajectory of a structure can be closely controlled and optimised for compliance, load-carrying capacity, or additional functionality. The drawback of the geometric approach is that small perturbations to the initial geometry are difficult and costly to manufacture. Moreover, certain applications do not permit geometric changes. That is the case, for instance, in aerodynamic structures where any geometric alteration would disrupt flow and performance. A more suitable approach to nudging could then be controlling the nonlinear behaviour by elastic tailoring. This can, for example, be achieved by localised shifting of the neutral axis, by laminate design, or by smoothly varying the material properties using composite tow-steering. This project will investigate the efficacy of elastic tailoring through composite materials to replace geometric imperfection seeding for the modal nudging technique. The first objective is to demonstrate, by design and analysis of numerical prototypes, that semi-monocoque structures can be nudged through stiffness tailoring. The second objective of the project is to verify the numerical findings in experimental tests, by designing, building, and testing a prototype blade-stiffened aircraft panel. The challenge is to design and build a physical prototype that exhibits the desired structural behaviour, and which is robust to manufacturing imperfections. To achieve this objective, an understanding of the effect of manufacturing imperfections on the mechanical behaviour of the nonlinear structure is necessary. Accurate experimentation on the nudged prototype structures will enable the validation of the numerical analyses and will enable practical applications of well-behaved nonlinear structural responses.

航空航天要求强调开发轻型结构，以帮助减少燃料消耗和相关成本。通常，航空航天工程中的设计者使用周期性地用肋、框架和纵梁加强的薄壁结构，即半硬壳式结构，作为有效的解决方案。然而，细长和薄壁结构通常表现出不希望的弹性非线性和不稳定性，需要以质量效率为代价进行补救。然而，它已被证明，将表现良好的弹性非线性提供的手段来恢复基线的效率，甚至提高后it. Modal轻推是最近推出的剪裁技术，从而从后屈曲制度的模式形状种子作为初始扰动的几何形状的完美结构。结构几何形状的微小变化可用于连接稳定的屈曲前响应和稳定的屈曲后响应。该特性通过消除临界分叉和稳定后屈曲响应来增加结构的承载能力，从而消除通常可能在后屈曲中遇到的任何不期望的不稳定性。作为一个额外的好处，在稳定后屈曲响应，模态轻推也改善了缺陷的敏感性。最终，稳定后屈曲响应，增加承载能力，并在缺陷的敏感性降低，有利于进一步轻量化的航空航天，半硬壳式结构。 初步工作表明，通过几何改变的模态轻推可以成功地用于增加叶片加强翼结构的承载能力和柔度。通过对初始几何形状的后屈曲模式进行明智的选择，可以密切控制结构的非线性载荷-位移轨迹，并优化其柔度、承载能力或附加功能。几何方法的缺点是对初始几何形状的小扰动是困难的并且制造成本高。此外，某些应用不允许几何变化。例如，在空气动力学结构中，任何几何变化都会破坏流动和性能。一个更合适的方法轻推然后可以控制的非线性行为的弹性剪裁。例如，这可以通过中性轴的局部移位、层压设计或使用复合牵引转向平滑地改变材料特性来实现。本计画将探讨借由复合材料弹性剪裁以取代模态轻推技术的几何缺陷播种的功效。 第一个目标是证明，通过设计和分析的数字原型，半硬壳式结构可以通过刚度微调。 该项目的第二个目标是通过设计、制造和测试原型叶片加强飞机壁板来验证实验测试中的数值结果。面临的挑战是设计和建立一个物理原型，表现出所需的结构行为，这是强大的制造缺陷。为了实现这一目标，制造缺陷的非线性结构的力学行为的影响的理解是必要的。精确的实验上轻推原型结构将使数值分析的验证，并将使实际应用的良好的非线性结构响应。