The present work discusses the influence of friction in metal forming. Experiments were carried out to determine the coefficient of friction and wear displayed by bearing steel ball sliding against aluminum (Al) sheet. The steel ball represents the die surface asperity. Lithium grease was used as lubricant and dispersed by silica (SiO2) nano-particles and Multiwall carbon nanotubes (MWCNT). Frictional behavior between the inner tube diameter and expanding punch surfaces was influenced the exerted load. It was proven that load slightly increased with increasing the values of friction coefficient. Friction coefficient displayed by the grease dispersed by MWCNT displayed lower values than that dispersed by silica nanoparticles. Wear resistance provided by silica nano-particles was superior to that observed for MWCNT.Grease free of additives showed the roughest surface, while the test specimen lubricated by grease dispersed by MWCNT showed severely deformed one confirming that MWCNT effect was insignificant. Surface topography of test specimen lubricated by grease dispersed by 1.0 wt. % silica nano-particles showed the finest roughness and waviness due to the rolling action of silica particles.
S.Z. El-Abden (Tue,) studied this question.