Ultrasonically assisted deep drawing process: Two-stage finite element analysis and experimental verification

In this study, Ultrasonically Assisted Deep Drawing Process was developed in order to improve formability of sheet metals in Conventional Deep Drawing Process. Effects of ultrasonic vibrations, applied onto the blank holder in axial direction, on formability of sheet metal were investigated numerically by finite element analyses, and the results of such analyses were verified by deep drawing experiments. In the numerical study, a methodology for two-stage finite element analyses including transient structural and forming analysis was developed. In conventional and ultrasonically assisted deep drawing analyses, limiting drawing ratios and maximum drawable cup depths for DC01 and DC04 materials prone to certain process parameters were compared. With application of ultrasonic vibrations, an increase of up to 9% in limiting drawing ratio and up to 26% in cup depth were achieved. In the analyses performed on circular materials of identical diameters, it was determined that the thinning on sheet metal decreased by up to 43%. As result of the validation experiments, increase in limiting drawing ratio and cup depth was achieved as 11% and 31%, respectively. Numerical results were found to be in good agreement with experimental results since dynamic impact, stress superposition and contact separation effects of ultrasonic vibrations could be effectively modeled in finite element analyses with the proposed method. Small differences in obtained results may be due to the reason that it was not possible to involve the effects of acoustic softening and friction coefficient reduction on the material in numerical analyses.