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Deep-hole drilling is among the most critical precision machining processes for production of high-performance discrete components. The effects of drilling with superimposed, controlled low-frequency modulation - Modulation-Assisted Machining (MAM) - on the surface textures created in deep-hole drilling (ie, gun-drilling) are discussed. In MAM, the oscillation of the drill tool creates unique surface textures by altering the burnishing action typical in conventional drilling. The effects of modulation frequency and amplitude are investigated using a modulation device for single-flute gun-drilling on a computer-controlled lathe. The experimental results for the gun-drilling of titanium alloy with modulation are compared and contrasted with conventional gun-drilling. The chip morphology and surface textures are characterized over a range of modulation conditions, and a model for predicting the surface texture is presented. Implications for production gun-drilling are discussed.

The creation of nanostructured materials with enhanced mechanical properties by controlled chip formation has been demonstrated. The present study examines the microstructure and mechanical properties of chips from various alloys -Waspaloy AMS 5704, Inconel 718, Al 6061-T6, and titanium - produced in aerospace machining operations. While the deformation conditions with respect to chip formation may be ‘less than controlled’ in these cases, it is nevertheless seen that the chips created are composed entirely of nanocrystalline structures of high hardness and strength. The microstructural characteristics and properties of these chips are compared and contrasted with those produced under controlled conditions of strain and temperature. The results suggest that aerospace machining chips can be up-scaled as high-performance structural materials with substantial cost benefits.