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81.
Based on molecular dynamics simulations, the plastic deformation of silver nanowires under uniaxial tension has been studied systematically. In this paper, the mechanical properties of [111]-oriented twin nanowires with different hole sizes have been studied. The existence of holes has no effect on the elastic deformation stage. The hole on the twin boundary has two main roles in the plastic deformation stage. During the initial stages of plastic deformation, the main function of the hole is to produce new dislocations as dislocation sources at small hole sizes.Upon increasing the hole size, the main effect changes to stop dislocation slip. During the late stages of plastic deformation, the two functions of the hole complement each other, upon increasing the hole size, the function of the hole as dislocation sources becomes obvious, leading to weakening of the plasticity of the nanowires. 相似文献
82.
Thin Film Flow of a Second Grade Fluid over a Stretching/Shrinking Sheet with Variable Temperature-Dependent Viscosity
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Effects of variable viscosity on the flow and heat transfer in a thin film on a horizontal porous stretching sheet are analyzed. The steady boundary layer equations for momentum and thermal energy are simplified by using similarity transformations. The resulted and coupled nonlinear differential equations are solved by Homotopy analysis method. The results are presented graphically to interpret various physical parameters appearing in the problem. 相似文献
83.
采用分子动力学方法,模拟了不同加载速度、不同温度下单晶ZnO、TiO_2纳米线的拉伸破坏过程.通过模拟结果,对比、分析了两种单晶金属氧化物纳米线拉伸力学特性的差异.研究表明,1)ZnO纳米线的断裂机制为:表面微裂纹-微孔-微裂纹与微孔贯穿-断裂,而TiO_2纳米线的断裂机制为:局部屈服-颈缩-断裂;2)TiO_2纳米线的承载能力优于ZnO纳米线,而承受变形的能力劣于ZnO纳米线;3)温度较低的情况下,纳米线的抗拉性能较好;加载速度越高,纳米线的抗载性能越好,而抗变形能力越差. 相似文献
84.
本文通过实验研究了国产聚碳酸脂材料的拉伸力学行为,得到了这种材料在不同应变速率下的真实应力—应变曲线。实验结果表明:聚碳酸脂为应变率敏感材料,在达到峰值应力之前,泊松比接近0.5,出现颈缩之后,其泊松比远超过极限值0.5,作为光塑性模型材料,应将应变控制在5.8%以内。 相似文献
85.
简述了绝热剪切现象及其涉及的领域,指出了绝热剪切研究的意义和它重要的工程应用价值,对绝热剪切研究物现状作了扼要的总结。 相似文献
86.
87.
Measurement and Analysis of Spall Characteristics of High-Pure Aluminium at One-Dimensional Strain Loading
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With an impact velocity varying from 196.9m/s to 317.9m/s and ratios of flyer/sample thickness of 2:4 and 3:6, the free-surface velocity profiles of the shock compressed high purity aluminium (HPA 99.999%) samples are measured with a velocity interferometer system for any reflector. Based on the vibrating features of the velocity profiles, the damage behaviour of HPA is analysed. The results indicate that the vibrating amplitude increases with increasing shock stress, and the subsequent reverberations describing the spall become more obvious. When the shock stress in the material is below a critical or smaller than the threshold level, the free-surface velocity profile replicates virtually the form of the compression pulse inside the sample. When the impact stress exceeds a critical value (1.4 GPa), the micro damage would appear, and the free-surface velocity profile changes significantly, showing a series of short-duration reverberations in the profile. When the impact stress exceeds the threshold of damage, a compressive disturbance called the "spall pulse" appears in the free-surface velocity profile, and the subsequent reverberation becomes regular again. The measured spall strength of HPA is much higher than those of commercially pure aluminium reported in many references. In addition, the strength of HPA is similar to that of single-crystal aluminium. 相似文献
88.
在平面问题中,如果已知边界某点处的应力函数值和偏导数值为零,吊边界上的外载荷来构造出Airy应力函数。章利用虚拟荷和坐标变换的办法,避免了在构造Airy应力函数时可能出现的问题。 相似文献
89.
The stress-strain behavior and copper are studied by the molecular dynamics incipient yield surface of nanoporous single crystal (MD) method. The problem is modeled by a periodic unit cell subject to multi-axial loading. The loading induced defect evolution is explored. The incipient yield surfaces are found to be tension-compression asymmetric. For a given void volume fraction, apparent size effects in the yield surface are predicted: the smaller behaves stronger. The evolution pattern of defects (i.e., dislocation and stacking faults) is insensitive to the model size and void volume fraction. However, it is loading path dependent. Squared prismatic dislocation loops dominate the incipient yielding under hydrostatic tension while stacking-faults are the primary defects for hydrostatic compression and uniaxial tension/compression. 相似文献
90.
强脉冲载荷作用下弹-塑性薄圆板的大挠度动力响应 总被引:3,自引:1,他引:2
利用有限变形弹塑性连续体的最小加速度原理 ,建立了分析圆板动力响应问题的数值方法 ,并通过对均匀分布的脉冲载荷作用下铰支圆板位移响应的细致分析 ,探讨了响应过程中的饱和冲量现象 ,指出对于高载范围内的脉冲载荷 ,相应于最大变形的饱和冲量确实是存在的。结果还表明 ,虽然圆板的弹塑性动力分析非常复杂 ,但基于最小加速度原理的数值计算方法却具有简单、直接的优点。 相似文献