【新文速递】2023年9月30日复合材料SCI期刊最新文章

International Journal of Solids and StructuresGraphic statics and symmetrySchulze Bernd, Millar Camerondoi:10.1016/j.ijsolstr.2023.112492图形静力学和对称性Reciprocal diagrams are a geometric construction dating back to Maxwell and Cremona in which a self-stressed plane framework with a planar graph is paired with another self-stressed reciprocal framework on the dual graph. Either one of the reciprocal frameworks is the form diagram of a self-stressable structure and the other is the force diagram of the corresponding axial forces. This geometric technique offers insights into the self-stresses and infinitesimal motions (mechanisms) of both frameworks in the reciprocal pair. For a symmetric framework with a fully-symmetric self-stress, we obtain an equi-symmetric reciprocal pair of plane frameworks, as well as the associated symmetric discrete dual Airy stress function polyhedra. In this paper we exploit symmetry to refine the Maxwell-Cremona correspondence by considering the decomposition of the self-stress and motion spaces into invariant subspaces corresponding to the irreducible representations of the symmetry group. As such, the familiar s = m∗ + 1 relationship for the number of self-stresses of a framework, s, and the number of mechanisms of the reciprocal,m*, is reworked into a symmetry adapted version which provides greater insights into the properties of the reciprocal framework pair. We also show how the quotient graph of a symmetric framework and its reciprocal can be used to efficiently detect infinitesimal motions, self-stresses and polyhedral liftings of different symmetry types. This allows for symmetry-adapted simplified structural analyses of symmetric structures.互易图是一种几何结构，可追溯到麦克斯韦和克雷莫纳，其中平面图上的自应力平面框架与对偶图上的另一个自应力互易框架配对。其中任何一个互易框架都是自应力结构的形式图，而另一个互易框架则是相应轴向力的力图。通过这种几何技术，可以深入了解互对框架中两个框架的自应力和无限小运动（机制）。对于具有完全对称自应力的对称框架，我们可以得到等对称互对平面框架，以及相关的对称离散双 Airy 应力函数多面体。在本文中，我们考虑将自应力和运动空间分解为对应于对称群不可还原表示的不变子空间，从而利用对称性来完善麦克斯韦-克雷莫纳对应关系。因此，我们所熟悉的s = m∗ + 1框架自应力的数量关系、s与倒数的机制数之间的 + 1 关系、m*的商图被重新制作成一个对称性适应版本，该版本能让我们更深入地了解互易框架对的特性。我们还展示了如何利用对称框架及其倒数的商图来有效检测不同对称类型的无限小运动、自应力和多面体提升。这样就可以对对称结构进行对称适配的简化结构分析。International Journal of PlasticityThe Mechanism for Li-addition Induced Homogeneous Deformation in Mg-4.5 wt. % Li AlloyXu Jing, Guan Bo, Xin Yunchang, Li Xiao, Wu Peidong, Huang Xiaoxu, Liu Qingdoi:10.1016/j.ijplas.2023.103763镁-4.5 wt%锂合金中锂离子添加诱导均匀变形的机理The mechanism by which Li additions induce a more homogeneous deformation was systematically investigated in this study by comparing the deformation behavior of pure Mg and Mg-4.5 wt. % Li using experiments, crystal plasticity simulations, and theoretical calculations. The results of the digital image correlation measurements showed that under tension along the transverse direction (TD), strong localized deformation bands with an angle of approximately 20° with respect to the TD were observed in pure Mg, but were absent in Mg-4.5 wt. % Li. Slip trace analyses indicated that basal slip was the predominant deformation mode for pure Mg, whereas that for Mg-4.5 wt. % Li was prismatic slip. A high relative activity of pyramidal slip, approximately 17%, was observed in Mg-4.5 wt. % Li at a high strain of 10%. Contraction or double twins were hardly detected during the entire tension process. Crystal plasticity simulations revealed that the 4.5 wt. % Li addition dramatically reduced the critical resolved shear stress (CRSS) ratio of pyramidal slip: prismatic slip: basal slip, which was 31.5:21:1 for pure Mg and 4.3:1.3:1 for Mg-4.5 wt. % Li. Theoretical calculations using the CRSS ratios determined by simulations revealed that easy and uniform deformation propagation induced by a dramatically reduced CRSS ratio of prismatic slip to basal slip played a more important role in improving the deformation homogeneity, in addition to the enhanced activity of pyramidal slip. The mechanisms for how Li additions improve the ductility of Mg are also revisited in this paper.本研究通过实验、晶体塑性模拟和理论计算，比较了纯镁和 Mg-4.5 wt. % Li 的变形行为，系统地研究了锂添加物诱导更均匀变形的机制。数字图像相关测量的结果表明，在沿横向（TD）拉伸的情况下，在纯镁中观察到与 TD 成约 20° 角的强局部变形带，但在 Mg-4.5 wt.滑移痕量分析表明，基底滑移是纯镁的主要变形模式，而镁-4.5 wt.在 10%的高应变下，Mg-4.5 wt. % Li 中的金字塔滑移相对活跃度较高，约为 17%。在整个拉伸过程中几乎检测不到收缩或双孪晶。晶体塑性模拟显示，4.5 wt. % Li 的添加大大降低了金字塔滑移：棱柱滑移：基底滑移的临界解析剪切应力（CRSS）比，纯 Mg 为 31.5:21:1，而 Mg-4.5 wt. % Li 为 4.3:1.3:1。利用模拟确定的 CRSS 比进行的理论计算显示，棱柱滑移与基底滑移的 CRSS 比急剧下降所引起的易于均匀变形传播，除了增强金字塔 滑移的活性外，在改善变形均匀性方面发挥了更重要的作用。本文还重新探讨了添加锂如何改善镁的延展性的机制。来源：复合材料力学仿真Composites FEM