Under the skin of polishing - from nano to macro

这项建议汇集了物理、化学和工程领域互补领域的专家，以探索具有潜在高实际影响的新科学。将玻璃和类似材料加工成精密、抛光的表面是我们认为理所当然的许多产品和服务背后的“隐藏宝石”-无论是在精确控制光线分布(例如防眩光大灯)方面，还是在成像中聚焦光线。从医用X射线相机到卫星光学，都需要精密、光滑的表面，表面误差很小，但只有微米的几分之一(可能是人类头发宽度的千分之一)，粗糙度小到几个原子。此外，在高功率激光应用中，高度局部化的缺陷可能会散射光线，降低对比度，或导致组件故障。抛光‘磨擦’表面，以消除先前硬磨削造成的损坏，然后控制表面轮廓以满足设计要求。从历史上看，这些步骤是由高技能的工匠执行的，随着他们退休，他们的供应越来越少。现代的数控机床现在省去了许多繁琐的工作，但即便如此，仍需要多次抛光/测量周期才能达到精致的质量水平。基本原因是，经过大约400年的光学制造，人们对其潜在的“摩擦”过程仍远未完全了解。一种实用的装置通常部署某种旋转工具，用含有细微研磨粉的液体浆料输送。该工具在玻璃表面上移动，通常具有复杂的轮廓。刀具和玻璃之间微观水平上的流体流动的细节是复杂的，并控制着个别磨粒与玻璃的局部相互作用。然后，在原子(纳米)尺度上，化学攻击、塑性流动和脆性断裂表现出一种复杂的“舞蹈”，控制着材料的去除方式。在此之前，各种机构的工作往往集中在流体流动或纳米尺度的去除上，代表着不同的学科。但是，单独模拟流体流动(计算流体动力学)忽略了化学和断裂力学。相反，纳米尺度的分子动力学忽略了重要的流体流动问题。正如我们所建议的那样，以前没有人做过的事情是将这些不同的方法结合起来，由实时过程监控数据和高性能计算支持。然后，CFD可以为分子动力学提供预测的粒子轨迹，CFD中的粒子可以被视为化学反应而不是惰性。然后，这些模型可以结合在一个统一的大规模和可预测的去除过程宏观模型中。通常，科学突破出现在学科之间的交界处--这正是本提案的重点。这个模型将通过对完整表面的抛光试验、利用实时工艺数据来预测去除，以及对哪些材料在哪里去除以及任何缺陷的后处理测量来进一步开发。这有望实时揭示表面是如何进展的，当它被泥浆窒息时，直接检查是不可见的。然后，可以‘动态’地调整过程，以保持目标上的清除，并提高结果的准确性。我们的目标是减少所需的过程周期数，并深入了解缺陷产生的原因以及如何控制缺陷。在实现上述目标的过程中，在纳米、微观和宏观尺度上开发的数学和计算机模型将描述分子和流体的基本方面。这将是普遍适用的，包括不同的材料和磨料。另一个重要的应用是这种方法可能是变革性的--机械系统(轴承、滑道、人体关节植入物等)中材料磨损的基础工艺。因此，从抛光等过程中的“故意磨损”的基础研究开始，有望对我们理解和控制日常生活中摩擦和磨损的“附带磨损”产生深远的重大影响！

This proposal brings together experts in complementary areas of physics, chemistry and engineering, to explore new science with potentially high practical impact.Processing glass and similar materials to precise, polished surfaces is the "hidden gem" behind many products and services we take for granted - both in precise control of the distribution of light (e.g. anti-glare headlamps), or to focus light in imaging. From medical X-ray cameras to satellite optics, precise, smooth surfaces are required, with surface errors but small fractions of a micron (maybe 1/1000 the width of a human hair), with roughness down to a few atoms. Also, highly localised defects can scatter light, reducing contrast, or lead to component failure in high-power laser applications. Polishing 'rubs' surfaces to remove damage from prior hard-grinding, and then controls surface-contours to meet design requirements. Historically, these steps were performed by highly-skilled craftspeople, who are in ever-shorter supply as they retire. Modern CNC machines now take much of the drudgery out, but even so, multiple polish/measure cycles are needed to reach refined levels of quality. The basic reason is that, after some 400 years of optical manufacture, the underlying 'rubbing' processes are still far from perfectly understood. A practical setup typically deploys some kind of rotating tool, fed with a liquid slurry containing a fine abrasive powder. The tool moves over a glass surface, often with complex contours. Details of fluid-flow at the microscopic level between tool and glass are complex, and control local interactions of individual abrasive particles with the glass. Then, at the atomic ('nano') scale, chemical-attack, plastic-flow and brittle-fracture perform a complex 'dance', controlling how material is removed.Prior work at various institutions has tended to focus on fluid flow OR nano-scale removal, representing distinct disciplines. But, modelling fluid-flow alone (computational fluid dynamics) omits chemistry and fracture-mechanics. Conversely, nano-scale molecular dynamics omits important fluid-flow issues. What nobody has done before, as we propose, is to combine these distinct approaches, supported by real-time process-monitoring data, and high-performance computing. Then CFD can provide molecular dynamics with predicted particle-trajectories, and particles in CFD can be treated as chemically-reactive rather than inert. The models can then by brought together in a unified large-scale and predictive macro model of removal-processes. Often, scientific breakthroughs arise at the INTERFACES between disciplines - precisely where this proposal focusses.This model will be further developed through polishing trials of complete surfaces, drawing on real-time process-data to predict removal, and post-process measurement of what material has been removed where, plus any defects. This promises to reveal how a surface progresses in real-time, when it is smothered with slurry and invisible to direct inspection. Processes can then be tuned 'on the fly' to keep removal on-target, and improve accuracy of the result. Our aim is then to reduce the number of process cycles required, and give insight into why defects arise and how to control them. In implementing the above, the mathematical and computer models developed at nano, micro and macro scales will describe fundamental aspects of molecules and fluids. This will be generally applicable, including different materials and abrasives. Another important application arises where the methods could be transformative - processes underlying materials wearing in mechanical systems (bearings, slide-ways, human joint-implants etc). So, what starts out as fundamental research into "intentional wear" in processes such as polishing, promises to have a profoundly significant impact on our understanding and control of "incidental wear" in things that rub - and wear-out - in everyday life!