| Abstract: | A theoretical model is presented to calculate the lubricant film thickness in an unsteady hydrodynamic lubrication of cup-shaped products to be formed by the ironing process. The model covers the development of hydrodynamic lubrication in various phases of the ironing process. The model provides equations for estimating the lubricant film thickness for each phase. Experiments were conducted to study the effect of lubricant viscosity on die expansion and punch force in making cup-shaped products by the ironing process. It was found that the die expansion varied between unlubricated and lubricated cups and depended on the lubricant viscosity. The film thickness was estimated from the difference between the increased die/punch clearance, which was calculated from the expansion, and the lubricated cup wall thickness. The theoretical film thickness was compared with the estimated film thickness based on the die expansion measurement. |
