抄録
The effect of the outflow volume of the pressure medium on the fluid-lubrication effect during the sheet hydroforming was investigated experimentally. The hydraulic pressures in the flange area obtained for the sheet hydroforming during which the hydraulic pressure was pressurized using pump were higher than those of the sheet hydroforming during which the pump was not utilized. This might be owing to the difference in the outflow volume of the pressure medium. On the other hand, the drawability of the sheet was almost independent of with or without using pump. Examining the so-called effective punch force, we found that the effect of the difference in the outflow volume of the pressure medium on the fluid-lubrication effect was negligible. We concluded from these results that the fluid-lubrication effect was affected significantly by the existence or non-existence of the outflow of the pressure medium, i.e. the lubricant oil, but it was almost independent of the outflow volume of the pressure medium. Furthermore we also found that the hydraulic pressure distribution in the flange area would not affect the fluid-lubrication effect.
