Tribological behavior in micro-sheet hydroforming

In this paper, the tribological behavior and its size effects in micro-hydromechanical deep drawing (MHDD) are theoretically and experimentally investigated. It is found that a required fluid pressure for hydrodynamic lubrication significantly increases with scaling down micro-scale due to a high sealablity at small relative punch diameter to minimum thickness. Moreover, the opposite tribological size effect from a conventional microforming appears in MHDD in which the fluid medium can be kept in open lubricant pockets (OLPs) by applying a fluid pressure and, the friction coefficient decreases as a specimen size decreases. Thus, MHDD can induce the hydrodynamic lubrication and lubrication in OLPs and improve the tribological behavior in microforming by applying the appropriate fluid pressure.