In this research, the elliptical ultrasonic vibration assisted turning was investigated analytically and experimentally. In this process, the observations about the force reduction are the results of some phenomena including the friction direction reversal during the vibration cycle, softening phenomenon and change in the machining kinematics. During one vibration cycle, the friction direction is reversed in this process, which is why the static friction models such as Coulomb model; by which the dynamic friction phenomena such as the stick-slip phenomenon cannot be reflected; are unable to model this process appropriately. To slove this problem in the present research, a dynamic friction model was employed for analytical modeling of this process and the results were verified with the experiment. To identify the model coefficients, a series of orthogonal cutting experiments along with the genetic algorithm optimization method were used. To excel the results achieved from the modeling, a new modified friction model was proposed. The results showed that the new model results had better agreement with the experimental results. The effect of the cutting speed and feed rate on the machining forces and surface roughness was also investigated experimentally. to study the effect of the ultrasonic vibration on the material properties, micro-hardness tests were performed on the chips, which showed that the softening phenomenon was occurred in Al 6061, Al 7075 T6 and copper. The experiments were performed on Al 6061, Al 7075 T6, copper and Inconel 718. Keywords: Vibration Assisted Machining, Dynamic Friction Model, Genetic Algorithm, Model Identification, Ultrasonic Vibration Tool.