Study of size effects on material deformation behaviour in micro-deep drawing of copper sheet metal

The demand on micro-parts is increasing in the last decade due to product miniaturization. When the part size is scaled down to micro- scale, the deformation behaviour Is different from the one In macro-scale due to the size effect. Therefore, It Is essential to Investigate the size effect in micro-forming process. In this research, a sheet-metal forming system which combines micro-blanking and micro-deep drawing processes was developed and the interactive effects of grain and specimen sizes on the defect formation, surface roughening and deformation load in micro-deep drawing process were investigated. Through extensive experiments, it is found that inhomogeneous deformation and compressive instability take place with the decrease of part size and Increase of grain size. This leads to the occurrence of earring and wrinkling defects in the deep-drawn part. Furthermore, the surface roughening effect Increases with the decreasing number of grains over the blank thickness. It results from the strain incompatibility among grains. It Is also found that the normalized deformation load changes with the grain and part sizes. The high deformation load in forming of micro-sized part could be caused by the increase of interfacial friction. The findings from this research thus provide a basis to facilitate the design and development of micro-parts via micro-forming. KGaA. Weinheim.