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The performance of aeronautic critical components is strongly dependent on its fatigue behavior, which is directly linked to their surface integrity condition. Broaching operation is a machining operation extensively used for the manufacturing of some features due to the good dimensional quality and surface integrity condition obtained. Thus, the characteristics of surface integrity obtained in broaching is a key aspect to be considered for the improvement of the fatigue life. This work proposes a Finite Element Method (FEM) model for the prediction of the surface integrity (material damage and residual stresses) of the workpiece obtained after the broaching process using the commercial finite element software DEFORM 2D. The model includes a self-characterized Johnson-Cook flow stress constitutive law for the titanium alloy Ti64. Experimental tests were carried out in an EKIN RAS 10x160x320 hydraulic broaching machine at different cutting conditions for the validation of the predictive model. Apart from the fundamental output variables, such as, forces and chip morphology, a comprehensive study of the surface integrity of the machined piece was done. The residual stresses generated by the cutting process were measured by the hole-drilling technique. Microstructural alterations (material damage) of the workpiece was analyzed by optical microscopy and Scanning Electron Microscope. Finally, the surface topography was examined by contact and optical profilometers. The results of the predictions showed significant good agreement with the experimental tests.

The guarantee of surface integrity has become a primary objective for researchers when analysing the reliability of machined aircraft aluminium alloy structural parts in high-speed machining. This work studies the effect of cutting speed on the surface integrity of face milled 7050-T7451 aluminium workpieces. First, 7050-T7451 aluminium workpieces were face milled under dry conditions using three cutting speeds (200, 800, 1400 m/min) at constant feed (0.20 mm/tooth) and depth of cut (1 mm). An indexable face milling cutter with a diameter of 50 mm with five uncoated inserts was used in the face milling tests. During the machining process, cutting forces were acquired employing a Kistler dynamometer in order to understand the influence of the mechanical load on the final surface quality. The surface roughness p roduced by the milling process was measured using a portable rugosimeter. The residual stresses generated by the cutting process were measured by the holedrilling technique. In addition, small specimens were cut out from the workpieces and microstructural alterations of the surface layer were analysed employing optical microscopy techniques. The results demonstrate that the magnitude of residual stresses and the thickness of the affected layer is sensitive to the cutting speed, while surface roughness and microstructural defects do not show significant variations for the tested conditions.