Design and analysis of different horn profiles using FEM for vibration assisted machining

Ultrasonic machining is one of the hybrid machining processes which is gaining importance in the manufacturing of hard to cut materials particularly aerospace alloys. The success of ultrasonic machining will depend on the applied vibration parameters, viz. amplitude and frequency. In ultrasonic machining setup, the vibrations from the transducer are amplified and concentrated at desired location by the horn. The increment in amplitude reduces the tool work contact ratio (TWCR) and vice versa. Surface roughness, cutting forces, cutting temperatures and tool wear are affected by TWCR. Higher amplitude will reduce the TWCR and enhances the machining performance. Hence, proper design of the horn will enhance the amplification and therefore the machining efficiency. In this work, the influence of horn diameter ratio, horn profile, and length variation within the horn on deformation, amplification and effective stress are studied. Titanium is chosen as horn material. Horns of single exponential, double exponential and mixed horn profiles are studied through modeling and simulation using Finite Element Analysis (FEA). The tool end diameter of the horns is varied from 10 to 20 mm in steps of 2.5 mm for all the horn profiles. Further, double exponential and mixed horns are modeled and analyzed with three length variations in each case. All these are subjected to longitudinal vibrations along the axial direction with same amplitude and frequency. The analysis revealed that horns with lower diameter ratio are yielding high amplification. In addition, horns with double exponential profile with 5050 length variation and 10-mm tool end diameter, mixed horn with 2575 length variation and 10-mm tool end diameter are proved as best designs. The high amplification of horns at lower tool end diameters is attributed to their reduced strength because of reduced cross section. The stress concentration because of abrupt change in the cross section in case of double exponential and mixed horns also contributed to increase in effective stress.