Analytical, numerical and experimental study of cutting force during thermally enhanced ultrasonic assisted milling of hardened AISI 4140

• Developing a hybrid milling process with the name of Thermally Enhanced Ultrasonic Assisted Milling (TEUAM).
• Application of finite element method to predict temperature field and vibration characteristics of the workpiece.
• Experimental investigation and statistical analysis of the cutting force in CM, UAM, TEM, and TEUAM of hardened AISI 4140.
• Development of finite element model to predict cutting force numerically during CM, UAM, TEM and TEUAM.
• Development of analytical model based on chip thickness to evaluate cutting force during CM, UAM, TEM and TEUAM.

Two advanced machining methods as thermally enhanced machining and ultrasonic assisted machining has been considered in many studies, recently. In this paper, a new hybrid milling process is presented by gathering the characteristics of these two methods. A special experimental setup is applied and numerical and analytical models are developed to predict cutting force during the hybrid process. 3D thermal finite element analysis is applied to determine the axial depth of cut and engagement (the radial depth of cut) by measuring the dimensions of softened material. Full factorial experimental design is applied to investigate the effect of hybrid machining parameters on the mean cutting force. 2D finite element model is developed to predict the mean cutting force of the hybrid milling process. The analytical model is developed based on chip thickness as well as consideration of thermal softening of the material caused by the concentrated heat source. Major events in numerical and analytical models are external concentrated heat source and ultrasonic vibrations that are implemented successfully. According to the results, the application of thermally enhanced ultrasonic assisted milling on hardened AISI 4140 with the amplitude of 10 µm and temperature of 900 °C could reduce cutting force about 27% in comparison to conventional milling with feed of 0.063 mm/tooth. Experimental results presented a good agreement with numerical and analytical methods which can show the ability of developed methods to predict mean cutting force.