Papers by Author: Mohammed Nouari

Abstract: From a series of experiments carried out in this study, the machining characteristic of aeronautical material, titanium alloy Ti6Al4V, under dry orthogonal cutting is determined by the relations among material removal rate (MRR), tool rake angle (), and the other nine parameters in orthogonal cutting concept. Continuous and serrated chip forms are observed and chip form is determined by the flow localization parameter (). It is found that the critical values of  in which serrated chip formed are ranging from  = 4.71 to  = 5.37 or at the chip load from 0.0045 to 0.006 mm2/min. The number of tooth (frequency) on serrated chip increases with cutting speed (V). The tool failure modes found in this study are normal flank wear, notch wear, chipping and catastrophic failure. Tool chip adhesion caused by adhesive wear mechanism and high rake angle weakened the tool cutting edge play important roles on the failure mode of the straight tungsten carbide cutting tool used in this study.

Abstract: In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. Surface roughness, lay, defects, microhardness and microstructure alterations are studied. The result of surface roughness judges that the CVD-coated carbide fails to produce better Ra value than the uncoated. Lay is characterized by cutting speed and feed speed directions. Feed mark, tearing surface, chip layer formation as built up layer (BUL), and deposited microchip are the defects. Microhardness is altered down to 350 microns beneath the machined surface. The first 50 microns is the soft sub-surface caused by thermal softening in ageing process. Microstructure alteration is observed in this sub-surface. Down to 200 microns is the hard sub-surface caused by the cyclic internal work hardening and then it is gradually decreasing to the bulk material hardness. It is concluded that dry machining titanium alloy is possible using uncoated carbide with cutting condition limited to finish or semi-finish for minimizing surface integrity alteration.