标题： 表面完整性对功能梯度纳米梁几何结构和动力学的影响 显示英文标题

标题： Influence of surface integrity on geometry and dynamics of functionally graded nanobeams

摘要： 在本研究中，研究了表面完整性对功能梯度（FG）纳米梁力学性能的影响。 本研究报告了由于表面纹理和/或表面力学性能的变化，FG纳米梁的几何形状和动力学特性发生变化。 开发了一种具有工程表面的FG纳米梁的新模型。 该工程表面被视为一种不同的材料相，具有表面纹理（波纹和粗糙度）。 由于表面残余应力，悬臂、简支和固定-固定FG纳米梁的初始曲率被确定。 此外，它们的固有频率和模态形状根据表面完整性进行推导。 FG梁的初始曲率随着表面纹理斜率的增加和/或表面粗糙度高度的减少而增加。 此外，观察到FG梁的固有频率可能因表面完整性而减少或增加，这取决于边界条件。 因此，作为第一个前景，表面粗糙度允许振动能量沿梁长度传播，从而导致其固有频率降低，产生零频率模态。 至于另一个前景，表面粗糙度抑制了振动能量沿梁长度的传播，导致模态局域化。 结果表明，模态局域化伴随着纳米梁固有频率的增加。 提出的FG纳米梁表面完整性模型与Gurtin-Murdoch表面弹性模型进行了比较。 结果表明，该表面完整性模型优于前一种模型，因为它同时考虑了表面纹理和表面力学性能的影响。 然而， Gurtin-Murdoch模型假设纳米梁的表面是光滑的，这会导致对其力学性能的低估或高估。 显示英文摘要

摘要： In this study effects of surface integrity on the mechanics of functionally graded (FG) nanobeams are investigated. This study reports the changes in the geometry and dynamics of FG nanobeams because of changes in their surface textures and/or surface mechanical properties. A new model for FG nanobeams with engineering surfaces is developed. This engineering surface is considered as a different material phase with a surface texture (waviness and roughness). The initial curvatures of cantilever, simple supported, and clamped-clamped FG nanobeams due to surface residual stresses are determined. Moreover, their natural frequencies and mode shapes are derived depending on surface integrity. The initial curvatures of FG beams are obtained increasing with an increase in the slope of the surface texture and/or a decrease in the heights of the surface roughness. Moreover, it is observed that the natural frequencies of FG beams may decrease or increase due surface integrity depending on the boundary conditions. Thus, as a first prospect, the surface roughness allows the vibration energy to propagation over the beam length and hence its natural frequency decreases resulting in a zero-frequency mode. As for the other prospect, surface roughness inhibits the propagation of the vibration energy through the beam length leading to a mode localization. It is revealed that a mode localization is accompanied with an increase in the natural frequency of the nanobeam. The proposed surface integrity model for FG nanobeams is compared with Gurtin-Murdoch surface elasticity model. The results demonstrate that the surface integrity model is preferred over the former model where it accounts for, both, surface texture and surface mechanical properties effects. However, Gurtin-Murdoch model assumes smooth surfaces of nanobeams which leads to under/overestimations of their mechanics.