TITLE:
Electromagnetic Expansion and Fragmentation of Hollow Aluminium 5052 Tube
AUTHORS:
Hitesh Choudhary, Chiradeep Gupta, Nirupama Tiwari, Tanmay Kolge, Rajeev Kapoor, Archana Sharma
KEYWORDS:
Electromagnetic Forming, Aluminium Alloys, High-Speed Imaging
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.8 No.6,
October
27,
2020
ABSTRACT: Electromagnetic forming is a high-speed forming
technology by which hollow profiles can be compressed or expanded. It is done
with a pulsed magnetic field to apply Lorentz’ forces at electrically conductive
material. Electromagnetic hollow tube expansion is limited by the fragmentation
tendency. This work attempts to use a combination of analytical and
computational approach to compute the net tangential stress during tube
expansion. A simplified analytical framework to estimate the temporal evolution
of plastic stresses present in aluminium alloy AA5052 at low and high applied
magnetic pressures is developed based upon dynamic imaging. The time resolved
images captured using current synchronised high speed camera record the overall
dimensional changes of the tube that is validated by multi-physics simulation
of expansion process. Imaging of hollow tube expansions at two selected peak
currents has been carried out at various current levels in the range 76 - 160
kA. The direct visualisation of the increase in the tube diameter at two
current levels provided a comparison of the developing net tangential stresses
in the hollow tube during the undamaged and fragmented expansion. Imaging of
tube expansion also facilitates the estimation of the strain rate experienced
by the tube and was in the range of ~1700 s-1 to ~1200 s-1.
The propensity of fragmentation was found to be due to the level and duration
of generated tangential stresses above the yield stress during expansion of the
aluminium tubes. Presented study provides a mean of exploiting the enhanced
formability of aluminium alloys using electromagnetic forming.