Influence of transversal vibration on cutting performance and surface integrity during ultrasonic peening drilling of Al-Li alloys

Abstract

Advanced hole-making process is of great importance to enhance the fatigue performance of Al-Li alloy part in aviation industry. Ultrasonic peening drilling (UPD), in which an ultrasonic transversal vibration is applied to the cutting tools, is a recently proposed hole-making method that integrates precision-machining and surface strengthening by single-shot operation. In the study, kinematics, material removal mechanism and strengthening mechanism for UPD of Al-Li alloy by helical fluted reamers are analyzed. The effect of transversal vibration on the cutting performance and surface integrity is studied through comparative experiments between UPD and conventional drilling (CD) of Al-Li alloy holes. The experimental results show that UPD exhibits superior cutting performance with a maximum reduction of 52.6% in thrust force and 52.3% in torque, respectively, compared to CD. Moreover, narrower dimensional tolerance is obtained in UPD due to the reduced transversal force and improved machining stability. Additionally, deeper plastic deformation, higher surface microhardness and residual compressive stress of machined holes are obtained by UPD. The electron back-scattered diffraction (EBSD) analysis confirms that deeper machined affect area and grain refinement are realized in UPD. Therefore, the results indicate that UPD is a feasible method for achieving high-precision and strengthened holes for Al-Li alloy.