Various laws related to the behaviour of materials, heat, friction, elastic and plastic deformations and deformation rates are applied when machining. The mechanism of the chip formation is quite complex, which leads to equally complex theories and models representing these theories. Experimental tests are time-consuming and expensive, therefore there is a need for numerical modelling of the process. In this thesis, the orthogonal cutting process of aluminium alloy EN AW 6082 T6 based on experimental data and results obtained with numerical models is analysed. Mathematical models were obtained by regression analysis of experimental data that describe the dependence of cutting forces and temperature on processing parameters. Optimal values of cutting speed and feed were obtained by applying a genetic algorithm based on set constraints and objective functions. The influence of input parameters and numerical settings on predictions of cutting forces and temperature in the cutting zone in numerical models of orthogonal cutting of EN AW 6082 T6 alloy using the coupled Euler-Lagrange formulation was considered. With the view of improving numerical models, different hardening laws and contact conditions between the tool and the workpiece were considered. Also, hardening laws have been developed. Different hardening laws were implemented in the finite element analysis program. The accuracy of the numerical models was tested for a wide range of feed and cutting speeds. The hybrid method was implemented to predict cutting forces for the turning process. In this procedure, the results obtained by numerical modelling and the geometric and kinematic transformation models were applied. In order to validate the predicted cutting force by the hybrid method, the second part of the experimental research was carried out, which includes the measurement of cutting forces in the turning process.