Deformation, rolling and sliding of particles and particle aggregates

颗粒系统在外力作用下，如机械载荷，在不同的长度和时间尺度上表现出重组过程。这个项目的目的是将宏观过程与单个粒子的运动联系起来。共焦显微镜和高分辨率机械测试(如纳米压痕和扫描力显微镜)的结合，为在实际系统中以高空间和时间分辨率研究已知外力作用下细颗粒(直径大于1微米)的三维运动提供了可能。我们已经开发了测量和图像分析技术，可以自动跟踪粒子在机械载荷(例如剪切)下的平移和旋转。通过对大颗粒系统的测量，我们的目标是识别和了解相关过程。因此，我们打算涵盖剪切速率、颗粒形状和颗粒相互作用的广泛范围。结果应与真实(宏观)系统上的接触力学模拟和实验进行比较。同时，我们计划测量光滑颗粒和粗糙颗粒之间的毛细作用力。特别是，我们的目标是了解毛细管力对毛细管桥的大小和形状的依赖性。在这种情况下，液膜的厚度和粘度以及颗粒运动的速度也应改变。我们计划将结果与基于能量的表面演化和分子动力学模拟进行比较。

Particulate systems under external forces, like mechanical load, exhibit reorganization processes on various length and times scales. This project aims at relating macroscopic processes to the motion of single particles. A combination of confocal microscopy and high resolution mechanical testing (like nano indentation and scanning force microscopy) opens the possibility to study the three-dimensional motion of fine particles (diameter larger than 1 µm) under know applied forces with a high spatial and temporal resolution in real systems. We have developed measurement and image analysis techniques to a level that allows an automatic tracking of the translation and rotation of the particles under mechanical load (e.g. shear). With measurements on large particulate systems we aim at identifying and understanding the relevant processes. Thereby we intend to cover a broad range of shear rate, particle shapes, and particle interactions. The results shall be compared to contact mechanics simulations and experiments on real (macroscopic) systems. In parallel we plan to measure the capillary forces between smooth and rough particles. In particular we aim at understanding the dependency of the capillary force on the size and shape of the capillary bridge. In this case also the thickness and viscosity of the liquid film, as well as the velocity of the particle motion shall be varied. We plan to compare the results with energy based Surface-Evolver and molecular dynamics simulations.