共查询到19条相似文献,搜索用时 459 毫秒
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轻质金属点阵夹层板热屈曲临界温度分析 总被引:3,自引:0,他引:3
本文针对均匀温度场下四边简支和四边固支金属点阵夹层板的临界热屈曲温度进行了求解和参数影响分析。将点阵夹芯等效为均匀连续体,并且将夹层板的剪切刚度近似为点阵夹芯的抗剪切刚度,忽略夹芯的抗弯刚度且认为夹层板主要由面板来提供抗弯刚度。对于无法获得解析解的四边固支条件,通过对未知变量进行双傅里叶展开的方法求解了Ressiner夹层板模型的临界屈曲温度,理论分析结果与有限元计算结果吻合良好。进一步分析了不同边界条件、点阵胞元构型、点阵材料相对密度、面板厚度等对临界屈曲温度的影响规律。 相似文献
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正六角形蜂窝夹芯层弯曲刚度理论分析 总被引:1,自引:0,他引:1
论文研究了由正六角形胞元构成的正六角形蜂窝夹芯层弯曲刚度.由于正六角形蜂窝夹芯层受面内载荷作用时在胞元斜壁上引起的弯矩与受面外载荷作用时在胞元斜壁上产生的弯矩有所不同,因此,基于面内变形的正六角形蜂窝夹芯层面内等效弹性参数不能用于计算正六角形蜂窝夹芯层弯曲变形.论文基于正六角形蜂窝夹芯层产生弯曲变形时三胞元壁板连接处转角为零的条件会导致正六角形胞元斜壁产生扭曲变形的事实,提出了一种新的正六角形蜂窝夹芯层理论分析方法.用论文方法计算得到的数值结果与有限元商用软件MSC.Marc计算得到的数值解进行对比,表明论文方法不但有效而且可行. 相似文献
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类桁架夹层板的等效弹性常数研究 总被引:1,自引:1,他引:0
从应变能等效出发,将具有周期性分布的夹层板的类桁架夹芯与各向异性连续材料等效,给出了相应的宏观等效弹性常数,进而用有限元方法计算了实际夹层板和等效夹层板的结构响应,用一个算例证明了该文方法的有效性.通过对类桁架夹芯的等效弹性常数的计算,结果表明该文方法可以得到较为准确的等效弹性常数,且较其它类型的均匀化方法大大降低了计算量. 相似文献
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本文研究了面板约束效应对蜂窝芯弹性性能的影响并基于六边形蜂窝芯夹层板的代表性体单元建立了考虑面板约束效应的蜂窝芯位移模式.根据真实蜂窝芯代表性单元与其等效材料的代表性单元在宏观均匀应变作用下的总弹性应变能相等,导出了蜂窝芯材料等效弹性常数的公式,进一步探讨了蜂窝几何参数对其弹性常数的影响规律.通过与现有理论结果、有限元结果和实验数据进行对比证实本文导出的弹性常数公式具有较好的预报精度.结果表明面板约束对蜂窝芯等效弹性常数有显著影响. 相似文献
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四边简支硬夹芯夹层板的弯曲问题研究 总被引:1,自引:0,他引:1
现有的夹层结构理论都是将夹芯视为软夹芯,忽略了其面内应力分量和弯曲刚度.该理论不能满足近年来出现的硬夹芯夹层结构.对此,考虑了以上被忽略的因素,修正了Reissner理论的软夹芯假设,提出了考虑夹芯面内应力分量和弯曲刚度的硬夹芯夹层板基本假设.根据最小势能原理得到了硬夹芯夹层板弯曲的基本方程和边界条件,给出了四边简支硬夹芯夹层板在横向载荷下弯曲的解析解.另外本文还研究了硬夹芯夹层板弯曲问题的有限元法,推导了四节点四边形等参单元的有限元列式,并用MATLAB编程求解了具体算例. 相似文献
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比例边界有限元是一种只需在边界上划分网格且无需基本解的半解析方法,能有效处理应力奇异性和无边界问题.论文提出了一种比例边界有限元的二阶灵敏度分析方法,可以准确而高效地求解响应关于参数的二阶梯度.首先通过建立仅需右特征向量的哈密顿矩阵特征灵敏度分析方程,发展了一种改进的比例边界有限元一阶灵敏度分析方法;其次,进一步通过构建二阶哈密顿矩阵特征灵敏度分析方程,并对比例边界有限元系统方程进行一系列二次直接微分,提出了一种半解析形式的比例边界有限元二阶灵敏度分析方法.该方法被应用于线弹性裂纹结构的形状灵敏度分析和不确定性传播分析.最后,给出了两个数值算例验证论文方法的有效性. 相似文献
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The main aim of this paper is to evaluate the effect of micro-structure variations on elastic constants of NCF (non-crimp fabric) composites. To reach this aim, a three-dimensional unit cell model is developed by the finite element code ABAQUS and mean value of elastic constants in NCF composites are determined by analytical and unit cell based methods with various boundary conditions. In addition, first- and second-order stochastic finite element formulations are derived and variances of elastic constants are computed with respect to the dispersion in length and width of the voids. Results show up to 9.1% scattering in the elastic constants. 相似文献
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采用三维模型预测了传统六角形蜂窝材料和带圆环结点六角形蜂窝材料的有效弹性性能.利用有限元法并结合周期边界条件计算了材料代表性体积单元的平均应力,进而由平均场理论获得了两种蜂窝材料全部的有效弹性常数.将传统蜂窝材料的计算结果与已有梁模型的计算结果和试验数据进行了对比,结果表明三维模型比梁模型具有更高的精度,分析了梁模型误... 相似文献
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Cellular space-charge polymer film,also called cellular piezoelectret,has very large piezoelectric effect due to their unique microvoid structure.In this article,the cellular piezoelectret film is considered to be a periodic composite material with closed-cell microvoids aligned periodically.Three dimensional finite element modeling is carried out to obtain the effective elastic modulus and piezoelectric coefficients.Sensitivity analysis was presented by modeling the effective electromechanical properties with different individual variable,including material constants and void shape parameters.By assuming a relation between void shape and void volume fraction,the finite element model can simulate quite well the inflation experiments of the voided charged Polypropylene film published in literature.Finally,the finite element model is used to explore the voided charge polymer film with non-uniform distribution of the trapped charges on the internal surface of voids.It was found that the resultant overall piezoelectric coefficients will be more significant if charges are closely gathered in the central area,and sparse in the around area of the internal surface of voids. 相似文献
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Effective elastic properties of flexible chiral honeycomb cores including geometrically nonlinear effects 总被引:1,自引:0,他引:1
Flexible chiral honeycomb cores generally exhibit nonlinear elastic properties in response to large geometric deformation, which are suited for the design of morphing aerospace structures. However, owing to their complex structure, it is standard to replace the actual core structure with a homogenized core material presenting reasonably equivalent elastic properties in an effort to increase the speed and efficiency of analyzing the mechanical properties of chiral honeycomb sandwich structures. As such, a convenient and efficient method is required to evaluate the effective elastic properties of flexible chiral honeycomb cores under conditions of large deformation. The present work develops an analytical expression for the effective elastic modulus based on a deformable cantilever beam under large deformation. Firstly, Euler–Bernoulli beam theory and micropolar theory are used to analyze the deformation characteristics of chiral honeycombs, and to calculate the effective elastic modulus under small deformation. On that basis, the expression for the effective elastic modulus is improved by including the stretching deformation of the chiral honeycomb structure for a unit cell under conditions of large deformation. The effective elastic moduli calculated by the respective analytical expressions are compared with the results of finite element analysis. The results indicate that the analytical expression obtained under consideration of the geometric nonlinearity is more suitable than the linear expressions for flexible chiral honeycomb cores under conditions of high strain and low elastic modulus. 相似文献
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Using Kelsey et al. (1958) unit load method, upper and lower bounds for the effective transverse shear moduli of a chevron folded core used in sandwich construction are analytically derived and compared to finite element computations. We found that these bounds are generally loose and that in some cases chevron folded cores are 40% stiffer than honeycomb-like cores. 相似文献
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M积分在材料构型力学中表征着缺陷自相似扩展的能量释放率,而有效弹性模量下降量在传统损伤力学中是一个具有内变量属性的损伤参数. 探讨了两者之间的特定关系,以此为材料构型力学与损伤力学搭建桥梁.借助穆斯海里什维利(Muskhelishvili)复势函数方法获取无限大弹性平面含圆形夹杂的弹性场解,根据M 积分的复势函数解析表达式得到M 积分与夹杂弹性模量的显式表达式. 随后通过有限元分析,对含复杂缺陷群的弹塑性材料进行数值模拟,结果表明内部缺陷区域的有效弹性模量下降与M 积分存在着特定关系. 基于此,提出利用材料构型力学中的外变量参数(M 积分)来替代损伤力学中的内变量参数(弹性模量下降量)描述材料的缺陷演化. 相似文献