DEVELOPMENT OF 600m/s SUPER HIGH-SPEED AND NANOMETER ORDER ULTRA PRECISION MACHINE TOOL

本研究旨在将超高速加工技术应用于塑性材料的静态塑性波传播速度之上，以最大限度地减少加工影响层的深度，全面提高塑性材料加工的表面精度。在断裂强度的大部分范围内，延性材料都表现为塑性。然而，当加工速度超过其静态塑料波传播速度时，它们会变得“脆化”。这一行为显著减少了加工过程中的塑性流动/变形和加工硬化，从而可能改善整个表面的完整性，即使它伴随着产生裂纹的可能性。在这样的动机下，一种安装了超细进给系统的超高速机床被开发出来，以防止裂纹的产生。在该机床中，采用300m/S空气静压轴承的砂轮轴和工件轴分别旋转，可达到600m/S的相对磨削速度。对纯铝和铝合金进行了多次磨削试验。结果表明，在低于静态扩展速率的加工速度下，塑性流动较大，而在高于静态扩展速率的加工速度下，塑性流动几乎不存在，说明静态塑性扩展速率是去除机理不同的断裂点。为了在理论上支持实验结果的有效性，还对实验中使用的相似材料进行了几个分子动力学模拟。结果表明，当磨削速度超过静态塑性波传播速率时，磨削机理与普通磨削完全不同。因此，本研究证实了超高速超精密加工延性材料的有效性。

This study aims to minimize the depth of the work-affected layer and totally improve the surface accuracy in the ductile material machining by applying the super high-speed machining over the speed of the materials' static plastic wave propagation rate. The ductile materials behave plastically throughout most of its fracture strength range. However, they become "brittle" as machining speed exceeds its static plastic wave propagation rate. This behavior leads to a significant reduction in plastic flow/deformation and work hardening during the machining process, so as possibly to improve the total surface integrity, even though it is accompanied with the possibility of crack generation. Under such motivations, a super high-speed machine tool mounted an ultra fine infeed system to prevent crack generation was developed. In the machine tool, by the rotation of grinding wheel shaft and workpiece shaft which adopted the air static pressure bearing at 300m/s, respectively, the 600m/s relative grinding speed can be achieved. Several grinding experiments were conducted on pure aluminum and aluminum alloy. As a result, a big amount of plastic flow is developed at the machining speed below the static propagation rate, whereas plastic flow hardly resides at the machining speed beyond the static propagation rate, and it is clarified that the static plastic propagation rate is a breaking point from where the removal mechanism is different. In order to theoretically support the validity of the experimental results, several molecular dynamics simulations were also conducted on similar materials used in the experiments. As a result, it is also verified that the grinding mechanism at the speed which exceeds the static plastic wave propagation rate is completely different from that of the ordinary grinding process. Consequentially, this study confirmed the effectiveness of super high-speed and ultra precision machining of ductile materials.