Surface alteration induced by machining

This paper, dealing with strain hardening in turning, is a comparison of numerical (Finite Element Method (FEM)) and experimental results. Orthogonal cutting was assumed as the reference working condition. A FEM model was set up to simulate experimental conditions and to evaluate the effects of cutting parameters on surfacial strain hardening. Experimental data were recorded by machining thin disks of C20 steel (1CD20 UNI EN 10017: 2005) with radial feed; several values of both cutting speeds and feed were tested. After machining, work hardening was evaluated by micro Vickers test as a function of the distance from the machined surface. Regression techniques were used to fit experimental data and to find out work hardening patterns (depth of the affected zone, maximum hardness of the surface). FEM simulations of the experiments were performed using a commercial code for forming processes. A plane strain model of a rigid-plastic workpiece was set up with suitable material and interface properties. Good agreement between numerical and experimental results was found, therefore FEM was used to model a wider range of process parameters.