Friction is created,when two bodies slide on each other. If the contact surfaces are examined at micro level, it is seen that the surfaces have asperities. In fact the asperities get in the way and cause friction. By superposing ultrasonic oscillation to one of the bodies, the friction force is reduced .This phenomenon is widely used in metal forming and metal cutting. In recent years particular attention is paid to use such kind of oscillations. This phenomenon may be used as a replacement of lubricants in such processes due to its higher efficiency and less pollution effects. In this research an elastic-plastic model for the deformation of asperities during the sliding of two surfaces is given which is capable of predicting friction force when ultrasonic vibrations are superimposed to macroscopic motion. In this model area of asperities was considered as a beam and contact parameters were related to the dimensions of the beam and the equations related of the surface area of the contact and the vertical and horizontal forces between asperities were obtained numerically. The advantage of this model over the other existing models is that the proposed model can predict the friction force based on completely theoretical consideration without any experimental results. To validate the proposed model, it was required to have reliable experimental results. An experimental set up was designed and built for this verification. This set up have many segments. The most important segments are a generator, a transducer and a horn. The horn that is used in this study is designed using the Abaqus software. The tests for validation of the model presented in this research were carried out in longitudinal and transverse modes on Aluminum and Steel samples of different surface roughness and different speed. Comparison of experimental results with results from the theoretical model was made in three different longitudinal, transverse and bidirectional modes. The experiments show that the reduction in friction force value due to superimposition of the ultrasonic oscillations in the longitudinal direction is 100% and for the vertical direction is 32% and for the bidirectional mode is 50%. The maximum error of the model for longitudinal direction, vertical direction and bidirectional case is 22%, 14% and 10% respectively. These values demonstrate the high accuracy of the model. The proposed model was compared with the Coulomb and Dong model. The comparison show that the present model is a more accurate as compared to that of the Coulomb and Dong model. Keywords: Modeling, Friction, Asperity, Ultrasonic Oscillation, Set up , Horn