Collaborative Research: Investigation of Material Removal in Impact Machining by Loose Abrasives

现有的纳米加工工艺依赖于光刻和基于能量束的方法，通常需要洁净室环境和巨大的资本投资。它们的缺点包括工作材料的选择有限，化学危害，以及加工表面上的热致缺陷。该奖项支持通过纳米金刚石颗粒的影响在脆性材料中进行材料去除的研究。研究结果可以导致在室温下纳米加工的低成本替代方案，而没有现有纳米加工工艺的缺点。新工艺可以改善各种导电和非导电材料的纳米加工性，并可能在生物医学，电子，汽车，能源和金属加工行业中应用。在这些行业中的潜在应用包括用于人工组织工程的纳米结构支架、纳米结构开关和无线发射器、用于热障涂层的超低摩擦层以及用于燃料电池的纳米结构质子交换膜。 新工艺的实验平台是原子力显微镜，工件以20-160 kHz的频率振动。切削是通过松散的纳米金刚石颗粒在液体介质中的冲击来实现的。研究目的是了解动能对材料去除机制（塑性变形或脆性断裂）的影响。动能的水平取决于加工条件（主要是金刚石粒度和振动频率）。研究计划包括计算机模拟和实验研究。扩展的有限元方法将被用来模拟加工过程。在这些模型中，为了模拟金刚石颗粒在不同动能水平下对工件的冲击，工件被固定，金刚石颗粒被视为振动刚体（频率为20-160 kHz）。采用Drucker-Prager本构关系描述脆性材料的力学行为。将通过比较模型预测与实验结果来验证有限元模型。使用石墨烯、硅和玻璃样品的加工实验将通过改变金刚石颗粒的平均尺寸（5、10、15 nm）并以20-160 kHz范围内的不同频率振动工件来在不同水平的动能下进行。将使用电子显微镜和光学显微镜检查机加工表面，以确定材料去除是通过塑性变形还是脆性断裂完成的。

Existing nanomachining processes that rely on lithographic and energy beam based methods often need cleanroom environments and huge capital investments. Their shortcomings include limited choice of work materials, chemical hazards, and thermally induced defects on machined surfaces. This award supports a study of material removal in brittle materials by the impact of nano diamond particles. Research results can lead to a low cost alternative for nanomachining at room temperature without the shortcomings of existing nanomachining processes. The new process can improve the nanomachinability of a wide variety of both conductive and nonconductive materials, and may have applications in biomedical, electronic, automotive, energy, and metal working industries. Potential applications in these industries include nanostructured scaffolds for artificial tissue engineering, nanostructured switches and wireless transmitters, ultra-low friction layers for thermal barrier coatings, and nanostructured proton exchange membranes for fuel cells. The experimental platform for the new process is an atomic force microscope where workpiece is vibrated at the frequency of 20-160 kHz. Machining is achieved by the impact of loose nano diamond particles in liquid medium. The research objective is to understand effects of kinetic energy on material removal mechanism (plastic deformation or brittle fracture). The level of kinetic energy is determined by machining conditions (primarily diamond particle size and vibration frequency). The research plan consists of computer simulations and experimental studies. Extended finite element methods will be used to simulate the machining process. In these models, to mimic the impact given by the diamond particle on the workpiece at different kinetic energy levels, the workpiece is fixed and the diamond particle is treated as a vibrating rigid body (at the frequency of 20-160 kHz). Drucker-Prager constitutive law will be employed to describe the behavior of brittle materials. Finite element models will be validated by comparing model predictions with experimental results. Machining experiments using graphene, silicon, and glass samples will be performed at different levels of kinetic energy by varying the mean size of diamond particles (5, 10, 15 nm) and vibrating the workpiece at different frequencies in the range of 20-160 kHz. Machined surfaces will be examined using electron microscopy, and optical microscope to determine if the material removal is done by plastic deformation or brittle fracture.