jiwang yan

Ultra-precision machining is an advanced method for production of materials with nanoscale surface roughness. It is widely used in the manufacturing of precision components for defense, aerospace, optics, and electronics industries. For this feature, only a few industrial countries have access to this technology. Due to the high precision of this technology, many factors can affect the final surface quality. Machine components, machining conditions, tool geometry and material, environmental condition, workpiece material as well as vibration, are among the factors that are reviewed in this article. Afterwards, the effect of cutting depth on machining mechanism and surface quality is investigated using molecular dynamics investigation. The results revealed that when the ratio of cutting depth to tool edge radius becomes lower than 0.5, the effective rake angle would be bigger than the nominal rake angle. Furthermore, under this condition, the dominant machining mechanism is extrusion, which is different from the micro cutting mechanism. Finally, a series of experiments was conducted to study the impact of the undeformed chip thickness on the chip morphology and surface topography. For this purpose, Field Emission Scanning Electron Microscopy, 2D ultra-precision point autofocus probe as well as white light interferometer were exploited. The results indicated that at the lower relative tool sharpness, chip tearing occurs. Besides, by increasing this parameter to 100nm, silicon nano-ribbons is created.

Porous materials are a special class of engineering materials which have received increasing interest for technical and medicinal applications within the last decade. However, one of the main challenges in the cutting of porous structure is the microfractures occurred around pores having a profound impact on the final surface quality. In this study, the effect of tool geometry on the magnitude of microfractures around pores of porous silicon has been investigated. The results reveal that as rake angle decreases, microfractures around pore edges increase influencing the cutting pressure. The calculated pressure in the contact area shows a decrease as the rake angle decreases. Increase in microfractures can be explained based on a large tensile stress area formed beneath the tool cutting edge as tool tip feeds toward pore. The simulation results agree well with the experimental results. The findings also reveal that by choosing the optimal tool rake angle in the cutting process, a nanometric surface flatness (25 nanometer) can be achieved on porous silicon.n.