【新文速递】2023年9月23日固体力学SCI期刊最新文章_ACT_UM_GID

【新文速递】2023年9月23日固体力学SCI期刊最新文章

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Journal of the Mechanics and Physics of Solids

Adhesion in soft contacts is minimum beyond a critical shear displacement

Oliver C., Dalmas D., Scheibert J.

doi:10.1016/j.jmps.2023.105445

超过临界剪切位移时，软接触的粘附力最小

The most direct measurement of adhesion is the pull-off force, i.e. the tensile force necessary to separate two solids in contact. For a given interface, it depends on various experimental parameters, including separation speed, contact age and maximum loading force. Here, using smooth contacts between elastomer spheres and rigid plates, we show that the pull-off force also varies if the contact is sheared prior to separation. For shear displacements below a critical value about 10% of that necessary to yield gross sliding, the pull-off force steadily decreases as shear increases. For larger shear, the pull-off force remains constant, at a residual value 10%–15% of its initial value. Combining force measurements and in situ imaging, we show how the unloading path leading to contact separation is modified by the initial shear. In particular, we find that the residual pull-off force prevails if the contact reaches full sliding during unloading. Based on those observations, a first modelling attempt of the critical shear displacement is proposed, involving a competition between jump instability and transition to sliding. Overall, those results offer new insights into the interplay between adhesion and friction, provide new constraints on adhesion measurements and challenge existing adhesive models. They will be useful wherever soft contacts undergo both normal and shear stresses, including tire grip, soft robotics, haptics and animal locomotion.

粘附力最直接的测量方法是拉力，即分离接触的两个固体所需的拉力。对于给定的界面，它取决于各种实验参数，包括分离速度、接触时间和最大加载力。在此，我们利用弹性体球和刚性板之间的光滑接触，证明如果接触在分离前发生剪切，拉脱力也会发生变化。当剪切位移低于产生大滑动所需的 10% 临界值时，拉脱力会随着剪切力的增加而逐渐减小。对于较大的剪切力，拉脱力保持恒定，残值为初始值的 10%-15%。结合力测量和原位成像，我们展示了导致接触分离的卸载路径是如何被初始剪切力改变的。特别是，我们发现如果接触在卸载过程中达到完全滑动，则残余拉脱力会占主导地位。基于这些观察结果，我们提出了临界剪切位移的首次建模尝试，其中涉及跳跃不稳定性和向滑动过渡之间的竞争。总之，这些结果为了解粘附和摩擦之间的相互作用提供了新的视角，为粘附测量提供了新的约束条件，并对现有的粘附模型提出了挑战。它们将在软接触同时承受法向应力和剪切应力的任何情况下发挥作用，包括轮胎抓地力、软机器人、触觉和动物运动。

来源：复合材料力学仿真Composites FEM

【新文速递】2023年9月25日复合材料SCI期刊最新文章

今日更新：Composites Part B: Engineering 1 篇Composites Part B: EngineeringA functional coating with mechanoluminescent properties for sensing cavitation erosion and early warning of protection failureWu Yuli, Hou Guoliang, Cui Haixia, Zhang Yue, Chen Lei, An Yulong, Zhou Huidi, Chen Jianmindoi:10.1016/j.compositesb.2023.111021具有机械发光特性的功能涂层，用于感知空化侵蚀和预警保护失效Protective materials coated on the surface of fluid machinery are often used to slow down the damage caused by cavitation. Once the protective material fails, there is no real-time monitoring to predict, which will directly threaten the safe operation of the equipment. In this work, we designed a functional SrAl2O4: Eu2+, Dy3+ coating by atmospheric plasma spraying (APS), which can sense the impact of bubble implosion and realize the early warning of the failure of anti-cavitation erosion polyurethane (PU) coating. It is found that the luminescent properties of the functional coatings are easily affected by lattice defects, amorphous phase and valence state of europium ions. The functional coating is more sensitive to the perception of micro-jets and shock waves after vacuum thermal reduction treatment, and can distinguish the difference in stress by the brightness of the light. More importantly, when the surface polyurethane coating is removed by cavitation erosion (CE) down to 0.1 mm, this functional coating emits light to warn the polyurethane coating of impending failure. Therefore, this work provided a solution for sensing CE and predicting when the protection would fail.涂覆在流体机械表面的保护材料通常用于减缓气蚀造成的损坏。一旦保护材料失效，无法实时监测预测，将直接威胁设备的安全运行。在这项工作中，我们利用大气等离子喷涂（APS）技术设计了一种功能性 SrAl2O4: Eu2+, Dy3+ 涂层，它能感知气泡内爆的冲击力，实现对防气蚀侵蚀聚氨酯（PU）涂层失效的预警。研究发现，功能涂层的发光特性容易受到晶格缺陷、非晶相和铕离子价态的影响。真空热还原处理后的功能涂层对微喷射和冲击波的感知更加敏感，并能通过光的亮度区分应力的不同。更重要的是，当表面聚氨酯涂层被空化侵蚀（CE）去除至 0.1 毫米时，这种功能涂层会发光，警告聚氨酯涂层即将失效。因此，这项工作为感知 CE 和预测保护何时失效提供了一种解决方案。来源：复合材料力学仿真Composites FEM