Relationship between Deformation Behaviour and Metal Properties in Sheet Metal Forming : Study of Factors Influencing Drawability and Stretchability of Circular Blanks

Abstract

Factors influencing formability in pure stretch-forming, combined-forming and deep-drawing are discussed from a new standpoint, that is, the formability assessment based on the components of the forming depth and the fracture mode. In pure stretch-forming, it is confirmed experimentally and by numerical analysis that the forming depth is markedly correlated to n-value, but little to r-value, although this depth attains a maximum at r=1.0∼1.5. In case a punch profile fracture occurs in combined-forming, the relative load-carrying capacity T_cr/(A_o*S_T) has a proportional relation with both the stretched-out and -in components, which are newly defined in the present investigation, and thus with the forming depth which equals the sum of the components. From considerations of this parameter T_cr/(A_o*S_T), a simple method to predict the limiting drawing ratio and the forming depth at the ratio is proposed.