Optimisation of the bore reaming process in hybrid stacks made of carbon fibre and metal alloys

The present work aims to improve the existing technology of reaming bores in hybrid stacks containing a composite material interlayered with titanium and aluminium alloys. The study was conducted using statistical approaches at the stages of experimental design and data processing in the Statistica 6 and Microsoft Excel 2010 software. The bore roughness was measured using a Taylor Hobson Form Talysurf i200 contact profilometer. The height of the tool build-up edge was investigated using a Bruker ContourGT-K1 optical profilometer. Bore diameters were determined using a Carl Zeiss Contura G2 coordinate measuring machine. An experimental study was carried out using an Atlas Copco PFD-1500 automatic feed drilling unit and a 14 mm MAPAL reamer with a replaceable head. A methodology for a comprehensive experimental study of boring and reaming processes in the “OT4 titanium alloy - VT6 titanium alloy - polymeric composite materials - VT6 titanium alloy - 1933 aluminium alloy” hybrid stack was developed and implemented. It was found that the most significant factors affecting the parameters of bore accuracy, in particular, the deviation from the true bore longitudinal section profile, include the cutting speed in the first and the second degree, as well as the feed. The optimum cutting modes are a cutting speed of 7.24 m/min, a feed of 0.27 mm/rev and a machining allowance of 0.5 mm. As a result, the time of reaming one bore is reduced by 4.6 times. The optimum cooling method, ensuring the increased accuracy and reduced roughness of the bore in the aluminium alloy layer, is cooling by carbon dioxide at a temperature of -56.5°C. As a result of experimental works, basic laws governing the boring and reaming processes in multicomponent hybrid stacks composed by carbon-fibre-reinforced plastics with titanium and aluminium alloys were investigated.

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