Abstract: The rupture instability and its critical blank-holder force of cylindrical deep drawing in sheet forming process are theoretically and experimentally investigated. The wall of cup drawing is the common tangent region due to the punch, die profile and the clearance of them. The stress distribution of flange, die profile and wall segment are established by Mises- Hill yield function and Tresca criterion. The stress function of the crucial surface occurring rupture instability is constructed. Furthermore, the critical blank-holder force occurs rupture ins- tability is obtained. The effects of various parameters including draw ratio, strain hardening, normal anisotropy, friction coe- fficient and radial pushing force on rupture instability are showed, analyzed and discussed. During the experiment using 08Al steel sheet as workpieces hydraulic pressure is applied on the blank as blank-holder force and the periphery of the cup flange as radial pushing force. Good agreement is found between the theoretical calculations and the experimental results.

Key words: Critical blank-holder force, Deep drawing, Instability, Rupture, Sheet forming