Ultrasonic-assisted machining is an advanced method which allows significant improvements in processing of materials. In this study, a finite element model is developed to study the effect of ultrasonic vibration on machinability of AISI 304 stainless steel in which the results are compared with conventional cutting process. A pneumatic quick-stop device and an optical microscope are applied to validate the simulation results by measuring shear angle and sticky region experimentally. As a result, the analysis of heat generation in primary and secondary deformation zones shows that temperature increases in the primary zone when ultrasonic vibration is used, while a significant reduction in temperature is seen in the tool–chip contact zone. This area is considerably effective on the length of sticky region. Moreover, the influence of cutting speed and feed rate on tool–chip engagement time is investigated by the analysis of cutting force profile.