Observation on the behavior of ultrasonic micro-hammer and its effects on the deep drawing process: Numerical simulation and experimental study

Abstract

Combining ultrasonic vibration (UV) with metal forming processes is investigated as a novel technology that has been able to reduce the forming force and enhance this process. This paper attempts to elucidate the effect of Ultrasonically Assisted Deep Drawing (UADD) process on the forming force and thickness distribution of the formed sample. Therefore, a Finite Element (FE) model is developed to simulate this process and further investigate the ultrasonic micro-hammer mechanism in UADD process. Experimental tests were conducted to validate the established numerical model. Accordingly, a robust technological equipment was designed and fabricated, so that by application of ultrasonic vibration, the drawing die will be stimulated in longitudinal mode at the frequency of 20 kHz and thus, remain in the resonant condition. A reasonable congruence was observed when the forming force results and cup configurations from experimental tests and numerical solutions were compared. Therefore, the numerical model was used to evaluate the deformation behavior of the sheet at different amplitudes and frequencies. The results confirmed continuous vibration and ultrasonic micro-hammer conditions exhibit different behavior during the UADD process, and the latter occurs when the ultrasonic die separates from the workpiece surface. Although the UV application under micro-hammer condition significantly reduces the forming force, it has a destructive effect on the thickness distribution of the sheet and causes severe thinning. The current study provides a better understanding of the ultrasonic micro-hammer and its effects on the sheet metal forming process, which is the fundamental step in exploring this process.