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运用大型有限元软件Patran/Nastran分析了大开口复合材料加筋壁板的稳定性,并对不同加筋方式下壁板屈曲特征值和屈曲模态图进行了比较。结果表明:补强提高了大开口复合材料壁板的稳定性,但往往无法达到很好的效果,需要通过加筋改善其稳定性;加筋复合材料壁板稳定性较原有模型有较大提高;加筋大开口复合材料壁板屈曲特征值随筋条距开口中心距离的增加而减小,其屈曲分界线均位于筋条布置处;纵筋大开口复合材料加筋壁板一阶屈曲特征值为2.13,而横筋只达到1.08;纵筋布置对复合材料壁板稳定性影响明显高于横筋布置,可在实际工程应用中适当增加纵筋的布置。 相似文献
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加筋壁板轴压载荷下后屈曲稳定性试验研究 总被引:5,自引:0,他引:5
对11种构型的民用飞机机身加筋曲板在轴压载荷下后屈曲承载能力进行了试验和工程算法研究,深入探索了机身壁板的各种破坏模式,对极限法、Johnson)物线法与欧拉法三种工程算法比较,并且把试验结果与计算结果进行了对比。研究结果表明:壁板后屈曲轴压许用值与桁条剖面积和蒙皮厚度成线形关系,主要取决于桁条剖面积;蒙皮的局部屈曲应力对初始缺陷敏感,但局部屈曲应力的偏差对壁板的轴压破坏载荷影响不明显;与工程计算结果对比发现Johnson抛物线法计算的破坏轴压与试验结果吻合较好。 相似文献
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作为飞机上重要的承载部件,加筋壁板在发生初始屈曲后仍具有较强的后屈曲承载能力,因此研究其后屈曲特性对于确定破坏载荷具有重要意义。传统的特征值屈曲分析是以小位移小应变的线弹性理论为基础的,且不考虑结构在受载过程中结构构形的变化,因此误差较大。本文采用Riks弧长法,结合材料弹塑性理论对铝合金整体加筋壁板轴压加载后的屈曲破坏过程、传载机制、极限载荷进行了研究,并进行了轴压加载的试验验证,得到了加载过程中的应力、应变曲线以及极限载荷,还对后屈曲破坏形式进行了分析。数值模拟结果表明:本文研究的整体加筋板初始屈曲发生在蒙皮,后屈曲过程筋条是主要的承载部位,与试验中观察到的现象一致;试验中加筋板最终破坏部位发生在筋与蒙皮连接处,有限元模拟结果与试验中加筋板的最终破坏部位一致;数值模拟得到的极限载荷与试验的相对误差在5%以内。这表明基于弧长法的后屈曲计算能够准确跟踪整体加筋板的后屈曲平衡路径和预测极限载荷。 相似文献
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考虑不确定性因素的有限元屈曲模型验证 总被引:1,自引:0,他引:1
研究了考虑不确定性因素的有限元屈曲模型验证和确认方法,提出了不确定参数选择的相关性和敏度分析方法以及基于面积度量的模型评估方法.针对化铣整体壁板,开展了有限元屈曲模型验证研究,首先利用8件试验件,获得了壁板屈曲载荷的试验值,然后依据试验加载情况,建立了考虑试验台的壁板有限元模型,最后利用面积度量方法对有限元模型进行了验证和确认.本文的模型验证和确认方法可为其他工程结构开展类似的工作提供借鉴. 相似文献
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超音速气流中受热壁板的稳定性分析 总被引:3,自引:0,他引:3
采用Galerkin方法建立二维壁板的非线性气动弹性运动方程,用一阶活塞理论模拟壁板
受到的气动力. 基于李雅普诺夫间接法分析了平壁板的稳定性,得到了壁板失稳的边界
曲线;采用牛顿迭代法分析了壁板的屈曲变形,进而分析了后屈曲状态下壁板的稳定性;
在时域中分析了后屈曲状态下壁板的颤振边界. 分析结果表明,为了保证计算精度,
在二维壁板的静态失稳及过屈曲变形分析中,至少要取二阶谐波模态;在平壁板的超音速颤
振(动态失稳)边界分析中至少应取四阶模态. 还对壁板的温升,壁板长厚比、壁板密
度和气流马赫数作了无量纲变参分析,研究了这些参数的变化对壁板稳定性的影响规律. 研
究中发现,当气流速压较低时壁板一般会稳定在低阶谐波模态的屈曲变形位置,但是如果系
统出现多个渐近稳定的不动点,即使作用在壁板上的气流速压很低,壁板也有可能在较低速
压下发生二次失稳型颤振. 相似文献
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复合材料加筋板铺层优化设计的等效弯曲刚度法 总被引:2,自引:0,他引:2
借助于等效弯曲刚度法和遗传算法,建立了一种复合材料加筋板铺层顺序优化设计算法.等效弯曲刚度法基于层合板的弯曲刚度与其失稳载荷一一对应的关系,将任意铺层顺序的层合板等效成一个只有8层的对称铺层的辅助层合板,通过优化辅助层合板,得到层合板的最优弯曲刚度参数,最后以获得的最优弯曲刚度参数为约束应用遗传算法进行铺层顺序优化,获... 相似文献
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栅格加筋板的主要失效形式为整体屈曲和局部屈曲,据此提出了一种栅格加筋板布局的并行协同优化方法,将设计变量分为整体设计变量与局部设计变量,在两个子空间中并行优化,然后进行系统级协调,反复迭代至收敛。两个典型算例结果表明,本文方法优化流程清晰、算法稳定且结果可靠,可以获得最优解。 相似文献
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新的复合材料格栅加筋板的平铺等效刚度法 总被引:2,自引:0,他引:2
针对薄壁复合材料格栅加筋结构的受力特点,在改进原有力学假设的基础之上,推导了一种新的平铺等效刚度计算方法,它充分考虑了筋条和面板之间的相互作用.通过格栅单元结构布局形式的参数化表示,建立了通用的力学分析模型;该模型可用于分析各种结构布局形式和面板铺层方式下的结构总体屈曲问题,故对于航空航天结构设计非常有用.结合Rayleigh-Ritz方法,推导出了求解格栅加筋板屈曲载荷的通用线性特征方程;最后,分析了多种类型格栅结构的算例,并与现有的各种方法进行了比较,结果更为精确,因而对格栅加筋结构的优化设计具有很好的应用价值. 相似文献
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B. L. Agarwal 《Experimental Mechanics》1982,22(6):231-236
In this paper, a methodology is developed for the design of a weight-efficient, composite, curved-stiffened panel, loaded in compression well beyond the initial buckling load. A stiffened fuselage panel is designed to satisfy typical design load criteria for the moderately loaded sections of a typical fighter aircraft. Several stiffened panels are fabricated. Some panels are tested to determine experimentally the static strength and the remaining panels are subjected first to severe fatigue loading and then tested statically to determine the effect of fatigue loading on the postbuckling strengh. The experimentally observed behavior is compared with analytical predictions. The weight efficiencies of buckled and unbuckled construction are also compared. 相似文献
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The post-buckling behaviour of anisotropic stiffened panels with initial imperfections is investigated. Since buckling of the skin between the stiffeners often occurs first, a non-linear analysis is developed for symmetric panels under biaxial compression in order to obtain the out-of-plane panel deflection in the post-buckling range. The non-linear differential equations are expressed in terms of the out-of-plane displacement and the Airy function. They are solved with the Galerkin method for various boundary conditions by imposing an edge displacement control. The theoretical and experimental results obtained by the present analysis show that the transverse load can greatly influence the buckling loads and halfwave number. Since no experimental results have been found in the literature, several tests have been carried out on graphite/epoxy blade stiffened panels 900 mm long and 620 mm wide applying simultaneously biaxial compression loads with several combined ratios. An eccentricity results between longitudinal and transverse load, because the longitudinal compression is applied along the centroidal axes of the stiffened section while the transverse compression is applied to the skin panel. The correlation between the experimental and analytical results has been quite good; the experimental results demonstrate the influence of eccentricity of the transverse load on panel deflection in the pre- and post-buckling range. 相似文献
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Viggo Tvergaard 《International Journal of Solids and Structures》1973,9(12):1519-1533
For an eccentrically stiffened wide panel under compression the optimality of a design with simultaneous occurrence of buckling as a wide Euler column and local buckling of the plate between the stiffeners is investigated. The total amount of material per unit width of the panel is prescribed. As a function of the distribution of this material in the plate and the stiffeners the maximum carrying capacities are calculated approximately by application of Galerkin's method. The design with the highest carrying capacity and the design with the best ability to retain axial stiffness, corresponding to given imperfections, are determined. It is shown that imperfections move the optimum away from the coincident buckling mode design. 相似文献
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复合材料加筋结构可作为航空结构中的承力部件,其损伤与破坏对航空器的结构安全和服役性能至关重要.本文通过试验和数值仿真手段研究了短柱型复合材料结构压缩失效机理和极限承载力.通过短柱型单加筋板的轴向压缩破坏试验,分析梳理出界面脱粘和材料压溃两种典型失效形式;分别建立加筋板壳单元模型和实体单元模型,引入内聚力模型和Hashin 准则描述界面脱粘效应与材料破坏,结果表明壳单元模型配合内聚力模型和Hashin 准则可以有效地预测加筋板的极限承载力.分别讨论了加筋板长度、筋条高度、筋条/蒙皮刚度比等参数对加筋板的屈曲承载力的影响,为短柱型复合材料加筋壁板压缩损伤与破坏预测分析提供有益的参考. 相似文献
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《International Journal of Non》2002,37(4-5):801-831
PANDA2 is a code for the minimum-weight design of perfect and imperfect elastic stiffened panels and shells made of composite laminates and subjected to multiple sets of in-plane loads, edge moments, normal pressure, and temperature. The scope of PANDA2 is increased to include global optimization and the capability to handle isogrid stiffening. The enhanced program is used to find global optimum designs of internally T-isogrid and internally T-ring stiffened perfect and imperfect isotropic cylindrical shells under uniform external pressure. For the cases studied, it is found that for the perfect optimized shells the isogrid stiffening is important but the rings are not, whereas the opposite holds for the optimized shells with an initial general buckling modal imperfection of amplitude equal to one per cent of the shell radius 相似文献
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A Donnell type theory is developed for finite deflection of closely stiffened truncatedlaminated composite conical shells under arbitrary loads by using the variational calculusand smeared-stiffener theory.The most general bending-stretching coupling and the effectof eccentricity of stiffeners are considered.The equilibrium equations,boundary conditionsand the equation of compatibility are derived.The new equations.of the mixed-type ofstiffened laminated composite conical shells are obtained in terms of the transversedeflection and stress function.The simplified equations are also given for some commonlyencountered cases. 相似文献