Kinetic adhesion test to determine particle surface energy.

A new hardware is described to quantify the particle surface energy by assuming that the Johnson Kendall and Roberts theory of elastic-adhesive contacts is applicable. The setup is used in the active section of the measurement, where newly designed elements provide the sharp impact needed to detach the particles under the action of their own kinetic energy. It employs a selection of sensors to provide the necessary measurements in a streamlined procedure, which lets the user complete one test in less than one minute. The temporal resolution is 1µs for the contact time measurement and the velocity has a repeatability of 1%. The surface energy is a significant parameter for the characterisation of particulate materials and is widely used in Discrete Element simulations of the bulk behaviour.

Characterisation of physical and mechanical properties of seven particulate materials proposed as traction enhancers.

Particulate materials are utilised in many applications to manipulate the friction between surfaces. This dataset provides the characteristics of particulates used as rail sand in the train's wheel/rail interface (via an on-board system) to facilitate the train's acceleration and deceleration. Seven materials are studied including Austrian rail sand, standard Great British rail sand, waste glass beads, recycled crushed glass, non-coated alumina, coated alumina, and dolomite. The main objective of this research is to provide a physical and mechanical characterisation of these granular materials in terms of their density, bulk behaviour, particle size, particle shape, hardness, reduced modulus, and mineralogical properties. In particular, three-dimensional raw and post-processed micro-computed tomography images of more than 1200 particles are shared. The results provide a detailed dataset which can be used in ongoing and future experimental and numerical investigations studying the role of particulates in the wheel/rail interface.

Node formation mechanisms in acoustofluidic capillary bridges.

Using acoustofluidic channels formed by capillary bridges two models are developed to describe nodes formed by leaky and by evanescent waves. The liquid channel held between a microscope slide (waveguide) and a strip of polystyrene film (fluid guide) avoids solid-sidewall interactions. With this simplification, our experimental and numerical study showed that waves emitted from a single plane surface, interfere and form the nodes without any resonance in the fluid. Both models pay particular attention to tensor elements normal to the solid-liquid interfaces they find that; initially nodes form in the solid and the node pattern is replicated by waves emitted into the fluid from antinodes in the stress. At fluids depths near half an acoustic wavelength, most nodes are formed by leaky waves. In the glass, water-loading reduces node-node separation and forms an overlay type waveguide which aligns the nodes predominantly along the channel. One new practical insight is that node separation can be controlled by water depth. At 0.2 mm water depths (which are smaller than a » wavelength) nodes form from evanescent waves. Here a suspension of yeast cells formed a pattern of small dot-like clumps of cells on the surface of the polystyrene film. We found the same pattern in sound intensity normal, and close, to the water-polystyrene interface. The capillary bridge channel developed for this study is simple, low-cost, and could be developed for filtration, separation, or patterning of biological species in rapid immuno-sensing applications.