Influence of anisotropy and lubrication on wrinkling of circular plates using bifurcation theory

In this research, wrinkling in cylindrical deep drawing of a circular plate in the flange area is studied and the critical blank holder force in the deep-drawing operations has been achieved. Analytical model based on the Hill’s bifurcation method is used with regard to the inner edge of an annular plate that is subjected to tensile stress. The analysis is formulated in the form of large deformation assumption. The friction between the plate and the die, and the strain-hardening parameters are also investigated. The result of this analysis is the critical blank holder force, which is related to the critical wrinkling condition in the flange area. The Abaqus/Explicit is also used for the finite element simulations. Experimental study in order to validate the results of the analytical and finite element simulations has been performed. Analytical method, experimental tests and finite element method have been investigated to obtain critical blank holder force for four materials: ST12, ST14, copper and brass. These results showed that ST12 and copper plates have the highest and lowest compressive instability, respectively. To study the effect of plastic anisotropy of sheet on the wrinkling, some cold work operations and then heat treatment operations was carried out on three different types of plate parts. The results show that by increasing the plastic anisotropy of plate, wrinkling is partially delayed. The effect of lubricant used in the experimental tests, has been also studied. The effect of three various yield functions on the critical blank holder force, has been studied.