A novel method of processing sheet metals: Electric-pulse triggered energetic materials forming

Abstract

• A novel high-velocity sheet metal forming method is proposed: ETEF. The energetic materials (EMs) were introduced into the EHF system, and the electrical explosion of metal wire ignited EMs and released energy. • The EMs under the 10 wt.%Al/90 wt.%AP conditions exhibited the highest energy release efficiency, the energy grade of EMs was determined to be 3.04 kJ/g in this work. Under discharge voltage of 3 kV, the bulging height of DP600 specimen from ETEF was increased by 162 % relative to that from EHF. • Compared with that of EHF/7 kV, the strain concentration area of the sheet under the ETEF was wider (about 60 mm). The maximum major strain and maximum thinning rate of the specimen under the 2 g/3 kV/10 wt.% Al/90 wt.% AP conditions were reduced by 10.6 % and 13.1 %, respectively. • The dynamic deformation of the DP600 specimens during ETEF were presented for the first time by LS-DYNA. The EMs were ignited by electric explosion of metal wire to realize the coupling of two kinds of energy. To improve the formability of sheet metals at room temperature and overcome the limitation of the upper limit of energy storage in electrohydraulic forming (EHF), a novel sheet metal forming is proposed: electric-pulse triggered energetic materials forming (ETEF). The power to deform a metal sheet originates from the electrical explosion of a metal wire in a liquid chamber and that releasing chemical energy from the energetic materials (EMs) being triggered. Equi-biaxial stretching tests of DP600 were carried out through ETEF with different weight ratios and changing grams under a low discharge voltage. The final profiles, strain and thickness distribution of the sheet were analyzed. The energetic materials with 10 wt.%Al/90 wt.%AP had an energy level of 3.04 kJ/g, and the bulging height of the deformed specimen was 34 mm, which was higher than the energy levels obtained under other testing conditions. Compared with that of the 7 kV specimen of the same bulging height (34 mm) obtained by EHF, the strain concentration region of the specimen processed under the 2 g/3 kV/10 wt.% Al/90 wt.%AP conditions widened by 52.5 %, and the maximum major strain and maximum thinning rates were lower by 10.6 % and 13.1 %, respectively. The dynamic deformation characteristics of the DP600 specimens during ETEF were presented for the first time by LS-DYNA. The values obtained for the DP600 sheet were as follows: maximum bulging height, 32 mm; maximum effective strain rate, 1521/s; and maximum speed, 258 m/s.