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91.
双压电材料界面力电耦合场奇异性研究 总被引:3,自引:1,他引:2
针对不同压电材料中界面裂纹尖端的扇形区域推导出了包含基本方程、裂纹面D-P边界条件和不同压电材料交界面处的边界条件的弱形式。在该弱形式的基础上,利用特征方程展开方法(eigenfunction expansion technique),可以得到一个分析压电材料裂纹尖端处力电耦合场奇异性的特殊的一维有限元列式。该一维有限元列式只需对扇形区域在角度方向上离散,最后的总体方程为一个二次特征根方程。求解该特征根方程就可以得到压电材料裂纹尖端处力电耦合奇异场的特征解。通过数值算例表明该方法可以准确而高效地计算压电材料裂纹尖端处力电耦合奇异场的特征解,进而用该方法研究了双压电材料界面力电耦合场的奇异性。 相似文献
92.
93.
本文基于正交异性板壳有限元理论,分析了组合楼板对结构平面布置不规则的高层钢结构受力性能的影响。通过有限元分析,确定了发生平面内剪切变形时组合楼板的有效高度。结合两个工程实例。分别按弹性正交异性楼板、刚性楼板两种假定对整体结构进行水平地震作用分析。两种模型计算结果的对比分析表明.弹性正交异性板壳单元模型能更准确地分析结构的周期、内力、位移等参数。 相似文献
94.
B.A. Mlekusch 《Mechanics of Time-Dependent Materials》1998,2(2):129-169
Having the prediction of the warpage and shrinkage behaviour of injection-moulded short-fibre reinforced thermoplastics in mind, a model is developed to calculate the residual stresses. In accordance with the structure and the behaviour of these materials, a layerwise orthotropic, viscoelastic constitutive equation is used. As a cause for the stress development, a process determining the history of cooling under pressure is considered. The volume expansion of the matrix is described using a time-dependent viscoelastic free volume concept. From this, the viscoelastic functions for thermal expansion are derived as well as a time-dependent temperature shift factor. The material law of the composite is developed with the help of micromechanical considerations assuming viscoelastic matrix and elastic fibre behaviour. The residual stresses are calculated for a specially designed testing device which possesses regions of different fibre orientation. Measured fibre orientation tensors are used as simulation input. In the following, the calculated stress profiles were compared with measured values, which were determined using the layer removal technique. The calculated and measured profiles are in good agreement and show a strong influence of the fibre orientation state. The highest occurring stresses are in the same order of magnitude as the long-term strength of these materials. 相似文献
95.
96.
Ju‐Hyuck Lee Jae Young Park Eun Bi Cho Tae Yun Kim Sang A. Han Tae‐Ho Kim Yanan Liu Sung Kyun Kim Chang Jae Roh Hong‐Joon Yoon Hanjun Ryu Wanchul Seung Jong Seok Lee Jaichan Lee Sang‐Woo Kim 《Advanced materials (Deerfield Beach, Fla.)》2017,29(29)
Recently, piezoelectricity has been observed in 2D atomically thin materials, such as hexagonal‐boron nitride, graphene, and transition metal dichalcogenides (TMDs). Specifically, exfoliated monolayer MoS2 exhibits a high piezoelectricity that is comparable to that of traditional piezoelectric materials. However, monolayer TMD materials are not regarded as suitable for actual piezoelectric devices due to their insufficient mechanical durability for sustained operation while Bernal‐stacked bilayer TMD materials lose noncentrosymmetry and consequently piezoelectricity. Here, it is shown that WSe2 bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe2 bilayer with Bernal stacking. Turbostratic stacking refers to the transfer of each chemical vapor deposition (CVD)‐grown WSe2 monolayer to allow for an increase in degrees of freedom in the bilayer symmetry, leading to noncentrosymmetry in the bilayers. In contrast, CVD‐grown WSe2 bilayers exhibit very weak piezoelectricity because of the energetics and crystallographic orientation. The flexible piezoelectric WSe2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources, in contrast to monolayer WSe2 for which the device performance becomes degraded above a strain of 0.63%. 相似文献
97.
超声波在传播过程中,反射波的时间差与被测量物体的厚度成正比。采用超声波反射波脉冲信号的时间差,来检测工件涂层后内层表面的加工质量,并根据扫描工件表面的测量数据,在计算机上进行三维成像。因此,采用超声波反射波脉冲信号可以完成工件内层表面加工的测量与监测。 相似文献
98.
Steady state responses at viscous fluid/ orthotropic micropolar solid interfaces to moving point loads have been studied.
An eigenvalue approach using the Fourier transform has been employed to solve the problem. The displacement, microrotation
and stress components for the orthotropic micropolar solids so obtained in the physical domain are computed numerically by
applying numerical inversion technique. Viscosity and anisotropy effects on normal displacement, normal force stress and tangential
couple stress have been shown graphically for a particular model. Some special cases of interest have been presented. 相似文献
99.
梅甫良 《青岛理工大学学报》2004,25(1):23-28
抛弃了人为的应力和位移假设,直接从三维弹性动力方程出发,建立了正交异性地基板的状态方程,同时导出了双参数地基上四边简支层合板静力问题的解析式和动力问题的频率方程。 相似文献
100.
研究了正交各向异性的纸张的各个材料参数之间的关系,以减少描述纸张材料性能所需的独立参数,并在纸制结构分析中,合理匹配了材料参数。通过对材料单元在纯剪切载荷作用时与纯主应力载荷作用时的两种变形进行力学比较分析,获得了纸张的弹性模量、剪切模量和泊松系数之间的关系,并导出了简单数学公式。该公式在纸制结构设计、振动分析以及有限元计算等方面有实用的意义。 相似文献