Jianyi Du (杜健逸)

Electric Discharging Machining (EDM) process is a precise method of manufacturing. While it is widely applied in industry, the mechanism of discharging model is still unknown, and accurate prediction of tool shaping is in great need to optimize machining parameters.

Simulation is used in this work to validate the discharging model and predict electrode shapes. Two models based on geometry and electric field are both tested. The results show accordance with the experiments, while the electric field model performs better in reducing errors.

As a metal alloy with the properties of liquid, Gallium-Indium Alloys have shown its wide applications in making strechable devices. The key problem is: How to make things smaller, at the same time keep precision? I built up this printing system and kept characterizing the printing processes. The printing software is based on Python+Qt5, and z-stage attachment helps stabalize the height.

Extensional rheology describes the response of fluids to elongational deformations, which is crucially relevant to everyday phenomena such as jetting, drop impact and thinning of liquid filament. In this project, we aim to develop an improved device to study extensional rheology of complex fluids such as paints, lubricants and waxes in the automotive industry, of which an improved understanding may assist in optimizing key processes such as paint spray, auto-body coating, engine lubrication, and manufacturing. In order to do so, we utilize the experimental technique of capillary thinning, and introduce an improved design of the Capillary Breakup Extensional Rheometer (CaBER) with higher accuracy, better-controlled plate actuation, and a novel environmental temperature control system. In this experimental setup, a liquid sample is rapidly stretched between two coaxial discs, which leads to the formation of a liquid bridge at the middle connecting two hemispherical liquid reservoirs at the end-plates. The temporal evolution of the radius of the resulting liquid bridge, due to elasto-visco-capillary interactions, is a quantitative probe of the underlying fluid properties. In order to validate our setup and demonstrate this new rheometer's capacity and limits, we select a rheologically well-studied system of Poly(ethylene oxide) (PEO) solutions. Then, we demonstrate that the instrument is also able to readily characterize more complex materials of interest with less well-established rheological properties, including a food thickener and two commercial automotive motor oils. Finally, we conclude with an outlook for future applications of this device to a wider range of novel materials of relevance in the automotive industry that will potentially lead to a deeper understanding of their elongational properties.