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S. V. Shil’ko E. M. Petrokovets Yu. M. Pleskachevskii 《Mechanics of Composite Materials》2006,42(5):477-484
The adaptive mode of frictional interaction has been studied as a self-locking effect upon contact deformation of isotropic
and anisotropic auxetic materials with a negative Poisson ratio. This effect manifests itself in the fact that the bearing
capacity of the joint rises with increasing shear load. In particular, the parameters of stress state (contact load, tangential
stresses, slippage, etc.) were determined for a double-lap joint under conditions of compression with or with out shear. The
contact interaction was analyzed by the finite-element method for three profiles of symmetrically located contact elements
(plane, cylindrical, and wedge-shaped). The Poisson ratio was varied within the range theoretically admissible for isotropic
elastic media. Analogous calculations were also performed for a joint with a deformed element made of an anisotropic auxetic
composite, whose reinforcement angle was varied. The maximum loads, tangential stresses, and slippage are obtained as nonlinear
functions of Poisson ratio (in the isotropic case) and reinforcement angle of the composite material. The stress concentration
and the increased ultimate shear forces are also estimated.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 681–692, September–October, 2006. 相似文献
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基于遗传算法的复合材料细观结构拓扑优化设计 总被引:2,自引:0,他引:2
利用高精度通用单胞模型将复合材料的细观拓扑结构与宏观力学性能结合起来,采用遗传算法对复合材料的细观结构进行优化,发展了基于遗传算法的复合材料细观结构拓扑优化设计方法.以材料的宏观力学性能为优化目标,从随机的初始细观结构出发,对复合材料纤维体积百分比进行约束,经过迭代获得满足设计要求的代表性体积单元.在优化过程中,对遗传算法的交叉过程作了较大的改进,实现了复合材料细观拓扑结构的任意变化,提高了对可行域的搜索效率.分别以极限剪切模量和泊松比为优化目标,验证了所提出优化方法的正确性和有效性. 相似文献
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Cellular polymers, such as polyethylene foams, are commonly used in the packaging industry. These materials have short service life and generate a high volume of waste after use. In order to valorize this waste and produce added-value applications, it is proposed to convert these materials into highly efficient energy absorption structures. This was done by modifying the original cellular morphology of the foams (spheroidal or polygonal) into a re-entrant structure to produce auxetic materials. This work presents an optimized process combining mechanical compression and solvent vapor evaporation-condensation leading to low density foams (77–200 kg/m3) having negative Poisson's ratios (NPR). Three series of recycled low density polyethylene (LDPE) foams with an initial density of 16, 21, and 36 kg/m3 were used to optimize the processing conditions in terms of treatment temperature, time, and pressure. From all the samples prepared, a minimum Poisson's ratio of −3.5 was obtained. To further characterize the samples, the final foam structure was analyzed to relate with mechanical properties and compare with conventional foams having positive Poisson's ratios. The results are discussed using tensile properties and energy dissipation which were shown to be highly improved for auxetic foams. Overall, the resulting foams can be used in several applications such as sport and military protection equipment. 相似文献
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利用有限元模拟方法研究了内凹负泊松比蜂窝结构的面内双轴冲击响应。用节点扰动方法建立了具有不同规则度的内凹负泊松比蜂窝结构,并将其在不同冲击速度下的变形模态、应力-应变曲线和能量耗散能力与规则蜂窝进行了对比分析。结果表明,冲击速度是内凹蜂窝结构变形模态最主要的影响因素。此外,在双轴冲击下,由于不规则度的引入,延长了应力-应变曲线的平台阶段,抑制了结构的各向异性程度,从而使结构的变形特征从局部密实转向整体密实。在能量吸收能力方面,结构的不规则性导致了密实化阶段的滞后,因此在相同的压缩程度下,其塑性耗散能低于规则模型。 相似文献
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The Poisson's ratio of a material is strictly defined only for small strain linear elastic behavior. In practice, engineering
strains are often used to calculate Poisson's ratio in place of the mathematically correct true strains with only very small
differences resulting in the case of many engineering amterials. The engineering strain definition is often used even in the
inelastic region, for example, in metals during plastic yielding. However, for highly nonlinear elastic materials, such as
many biomaterials, smart materials and microstructured materials, this convenient extension may be misleading, and it becomes
advantageous to define a strainvarying Poisson's function. This is analogous to the use of a tangent modulus for stiffness.
An important recent application of such a Poisson's function is that of auxetic materials that demonstrate a negative Poisson's
ratio and are often highly strain dependent. In this paper, the importance of the use of a Poisson's function in appropriate
circumstances is demonstrated. Interpretation methods for coping with error-sensitive data or small strains are also described. 相似文献