开口曲筋板壳的承载机理及其优化研究

Various types of cutouts are inevitable for thin-walled segments in aeronautic and astronautic constructions, which may result in varying degrees of reductions in axial load-carrying capacities. Accompanied with the developments of Chinese heavy lift launch vehicle and large aircraft, the design requirements of thin wall, large diameter, super lightweight become more crucial, thus it is very essential to carry out the study on more efficient design theory and methodology of cutout reinforcements. This proposal starts with the improvement of skin-stiffener load-carrying mechanism, combining with the design requirement of cutout reinforcements, and aims to develop a novel type of curvilinear stiffened panel configuration with local negative Poisson's ratio for thin-walled structures with cutouts, then increases the load-carrying capacity by exciting advantageous tension field and loading path. Based on numerical and experimental methods, the load-carrying mechanism of such structures will be revealed, and the influence rules of geometrical imperfections on load-carrying capacities will be studied. On this basis, with regard to the discontinuous feasible region of curvilinear stiffened panels with cutouts, a corresponding design space continuation method will be established. Then this proposal will further develop an efficient multi-variable optimization algorithm based on multilevel decomposition, aiming to deal with the optimization difficulties caused by the high nonlinearity of post-buckling behavior and largely increased number of variables, and finally achieve the integrated design of near field around the cutout and far field away from the cutout for curvilinear stiffened panels with cutouts. We expect to establish an optimization method of curvilinear stiffened panels with cutouts for typical segments of future vehicles, and promote more widespread utilization of curvilinear stiffened panels.

航空航天结构中的薄壁部段不可避免地需要各类开口，常造成结构轴压承载能力不同程度的折减。我国重型运载火箭和大飞机的薄壁、大直径和超轻等设计需求变得越发苛刻，十分有必要开展更为高效的开口补强设计理论与方法研究。本申请拟从改善局部蒙皮-筋条承载模式的角度出发，提出一种适合开口薄壁结构的具备局部负泊松比效应的曲筋板壳设计，通过激发有利张力场和传力路径来提高承载力。本申请拟采用数值和实验手段，揭示这类开口曲筋板壳的承载机理，分析几何缺陷对其承载性能的影响。在此基础上，面向开口曲筋板壳优化设计中的可行域不连通问题，建立相应的设计空间连续化方法。针对开口曲筋板壳后屈曲行为的高度非线性和控制变量激增所造成的优化困难，进一步开展多变量层次化高效优化算法研究，最终实现开口曲筋板壳结构的近口区-远口区一体化设计。我们希望通过本研究建立一套可用于未来飞行器典型部段的开口曲筋板壳优化方法，推动曲筋板壳的更广泛应用。

面向航空航天领域中常见的开口薄壁结构，建立了曲筋加强型开口薄壁结构优化设计体系，突破了设计空间不连续、单次分析耗时过长等瓶颈问题，建立了基于渐进均匀等效的曲筋板壳快速后屈曲模型，阐明了局部负泊松比效应对开口结构承载性能的影响规律。主要的学术贡献包括：.1）从改善蒙皮-筋条承载模式的角度出发，自主提出了一种具备局部负泊松比效应的曲筋板壳结构设计，可在轴压载荷作用下激发出局部张力场以有效增强结构屈曲抗力。.2）针对后屈曲分析耗时过长的瓶颈问题，提出了近口-远口区自适应分区准则，基于渐进均匀化理论发展了快速后屈曲混合分析模型，分析效率大幅提高。.3）针对设计空间不连续、收敛性差等瓶颈问题，提出了简洁的曲筋族布局描述函数，建立了多变量层次化的连续分步类优化算法，计算效率和全局寻优能力大幅提升。.4）开发完成了NURBS曲筋加筋型开口薄壁结构分析软件，可实现复杂曲筋结构的一键建模与强度分析。.项目研究成果已成功应用于我国某武器型号承力舱段的开口补强设计中，实现承载效率较初样设计提高33%。伴随未来航天结构超轻、载荷极端等越发苛刻的设计需求，以及多功能性开口融合的趋势，本研究成果将有望直接应用于航天开口薄壁结构的设计中，可跨越式提高结构的承载效率。.发表SCI论文25篇（20篇JCR 1区，16篇IF>2.0），EI论文3篇，主要发表在AIAA J.、Comput. Method Appl. M.、Compos. Struct.、Struct. Multidiscip. O.、Int. J. Solids Struct.等权威期刊。相关SCI论文在发表后的短期内得到可靠度优化领域权威K.K. Choi教授、北理工方岱宁院士、西工大张卫红教授、德国宇航中心资深科学家R. Degenhardt教授、美国密歇根大学M. Collette教授等诸多著名学者的正面引用。授权国际发明专利3项（美国1项、日本2项）、中国发明专利5项。在项目执行期间，项目组成员的业务能力得到极大的历练与提升，形成了基础研究密切服务航天型号研制的研究特色。项目负责人郝鹏在项目执行期间破格晋升副教授，入选中国科协青年人才托举工程，获教育部技术发明一等奖。