薄板结构加筋布局优化设计方法研究

提出一种两步优化策略，以加筋板结构的固有频率最大化为目标函数，以结构所受外载荷作用的最大静变形为约束条件，开展薄板结构加筋构件的布局优化设计研究。为了降低加筋布局优化的难度，提高优化设计的效率，将加筋等效为一系列弹性铰（点）支撑，以便快速获得加筋横向移动的灵敏度信息。在基本不改变结构重量的情形下，通过合理布局加筋位置，能显著改善结构的刚度分布，提高结构的整体承载能力。随后，小幅调整加筋的截面尺寸，以满足对结构最大变形的设计要求。最后，用两个算例验证了所提优化方法的可行性和有效性。     

卷积神经网络用于近红外光谱古筝面板木材分级

目前,我国乐器制作行业在古筝面板用木材等级的筛选上主要依赖于技师主观评判,但此法缺少科学理论的依据,效率低,客观性及出材率的提高等方面受到限制,无法满足乐器市场的大量需求。实现古筝面板用木材快速、智能化的分级工作是一个急需解决的课题。近红外光谱非常适用于测量含氢的有机物质。古筝面板木材主要化学成分的化学键均由含氢基团组成,不同等级板材的化学成分存在差异,这些差异反映在近红外光谱中,为判断木材等级提供了可能。同时卷积神经网络对非线性数据具有较强的特征提取能力,所以提出一种应用卷积神经网络模型对光谱数据进行分析的方法,进而判别木材的等级。应用了Savitzky Golay一阶、二阶微分两种预处理方法和核主成分分析、连续投影算法两种数据压缩方法,通过所设计的卷积神经网络模型以样本识别准确率和模型构建过程中的损失值作为判定指标选出最佳预处理和数据压缩方法。为了提高模型提取分析光谱数据的能力和避免过拟合现象,应用了多通道卷积核、批量归一化和early stopping策略,将通过两层卷积层提取的特征信息送入全连接层,从而充分提取剩余信息,通过Softmax函数获得板材的最终预测等级,从而确定了最终模型。最终Savitzky Golay一阶微分和核主成分分析为最佳数据处理方法,同时得出用于区分不同等级的古筝面板用木材的主要关键谱带,分别为1 163~1 243, 1 346~1 375和1 525~1 584 nm。将该模型应用于测试集样本,古筝面板用木材的等级识别准确率为95.5%。实验结果表明所提出的方法可以高效地处理光谱数据,有效识别区分不同等级的古筝面板用木材的关键特征,从而为广阔的乐器市场提供一定的技术支持。     

Fatigue Behavior of Composite Sandwich Panels Under Three Point Bending Load

In this paper, the bending fatigue tests of honeycomb sandwich panels are carried out by using an improved three-point bending test fixture, and the S-N curves at different stress ratios are obtained. Through the records of fatigue damage in the experiment, the failure mode of the honeycomb sandwich panels and the source of fatigue damage are determined. At the same time, through the calculation of the shear stress distribution on the honeycomb wall, the reasons for the difference in the failure morphology of the L-direction and W-direction sandwich panels are clarified. Besides, a life prediction method is proposed and its effectiveness in predicting the fatigue life of sandwich panels has been verified.     

KOITER-BOUNDARY LAYER SINGULAR PERTURBATION METHOD FOR AXIAL COMPRESSED STIFFENED CYLINDRICAL SHELLS

I.IntroductionStiffenedandunstiffenedcircularcylindricalshellsfoundwideusesasprimarystructuralcomponentsinunderwatervehicles,offshoreplatformsandotherstructuralconfigurations.Theinitialinvestigationofthebucklingofstiffenedandunstiffenedcircularcylindrical…     

投影云纹法在研究加劲板后屈曲平衡路径及后屈曲模态转化过程的应用

本文应用投影云纹法研究受压加劲板的大挠度非线性问题。用投影云纹法测量加劲板后屈曲平衡路径,记录了随着载荷的增加,加劲板后屈曲模态变化的全过程。将云纹图输入微型计算机处理,获得了加劲板的全场位移和全场应力的分布情况。用投影云纹法所测得的结果同理论计算值基本吻合。     

剪切载荷下肋板的屈曲分析与优化

利用ANSYS有限元方法分析了一系列的肋板，研究了加强肋的作用，提出了 优化肋设计的限制条件. 结果表明，由横向肋板产生的栅格数目不能小于肋板的长宽比. 换 句话说，横向加强肋必须把平板的长度划分为小于等于宽度的段. 结果还显示，加强肋的优 化几何特性与板的屈曲从整体模态到局部模态转变点相应. 而且，所有具有相似长宽比和肋 数的肋板，具有一个特定的比值$EI_{s}/aD$, 此时抗剪应力最佳.     

大挠度弯曲直梁混合变量最小势能原理的应用

应用大挠度弯曲直梁混合变量最小势能原理,求解均载两端固定大挠度柱面弯曲板条的轴向挠度分布和轴向弯矩分布．实例计算表明:该方法简单实用、精度高,是一种计算大挠度柱面弯曲板条变形的有效方法．     

固支加筋方板的大挠度塑性动力响应

本文详细分析了爆炸载荷作用下固支回筋方板的大挠度塑性动力响应，给出了各种可能的运动模拟以及相应的差别条件，导出了最大残余变形的计算式，与文献［３］的试验结果比较表明，在多数情况下符合良好。     

A DONNELL TYPE THEORY FOR FINITE DEFLECTION OF STIFFENED THIN CONICAL SHELLS COMPOSED OF COMPOSITE MATERIALS

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.     

Stability of corrugated composite noncircular cylindrical shells under external pressure

Cylindrical shells consisting of cylindrical panels of smaller radius and subjected to uniform external pressure are analyzed for stability. The geometrical parameters of the shells are approximated by Fourier series on a discrete set of points. The Timoshenko theory of shells is used. The solution is represented in the form of trigonometric series. It is shown that short-and medium-length shells with cylindrical panels are advantageous over circular shells. By selecting appropriate parameters of the panels, keeping the mass of the shell constant, it is possible to achieve a significant gain in critical loads. The shells under consideration are less effective than isotropic shells. Shells with sinusoidal corrugation under external pressure are of no practical interest __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 12, pp. 91–102, December 2007.