The size effect on deformation behavior in microscale laser shock flexible drawing

A microscale laser shock flexible drawing (µLSFD) is a novel ultrahigh strain rate manufacturing technology that provides an effective means for fabricating complicated microparts shapes in foil. However, the size effect phenomenon in ultrahigh strain rate microforming is still largely unknown. In this work, the micro-mold and process parameters were designed to investigate the size effects based on the similarity theory. The parts were formed using annealed copper foils with four different grain sizes to study the grain size effect. The parts were fabricated by use of different micro-molds and copper foils with varying thicknesses but with the same annealing temperature to investigate the effect of feature size. The experimental results indicated that the depth of the formed parts increased with an increase in the grain size; the forming depth decreased significantly when the feature dimension was smaller than a critical value. The surface roughness and the thickness thinning ratio of the formed parts increased when the grain size and feature dimension increased. The maximum thinning ratio appeared at the bottom of the formed parts. The regression analysis revealed that the material deformation was more homogeneous with a decrease in the grain size and an increase in the feature dimensions when the µLSFD process was employed. This study provides a theoretical basis for the investigation of size effects in laser shock flexible forming.