Investigation of liquid medium concentration and pressure on formability in laser-activated high-speed hydraulic microforming

Laser-activated high-speed hydraulic microforming is a typical high-speed hydroforming technology with a closed liquid chamber that uses laser shock wave pressure as driving source and suitable for microforming of magnesium–lithium alloy foil. Free-bulging experiments of laser-activated high-speed hydraulic microforming and corresponding numerical simulations using LS-DYNA finite element analysis software were conducted. Homogenisation mechanism of liquid shock wave pressure was revealed using numerical simulations, and whipping effect during dynamic deformation of the workpiece caused by the homogenous liquid shock wave pressure was found which could improve plastic formability of the workpiece. Increasing the concentration of the liquid medium NaCl solution was effective in increasing strain rate during dynamic plastic deformation of the workpiece, which in turn increased the pulsed laser energy threshold and resulted in increased free-bulging height. Meanwhile, the maximum thinning rate tolerated by the micro free-bulging feature at the threshold pulsed laser energy also increased with the concentration of the liquid medium.