Method for calculating the parameters of superplasticity of titanium alloys based on the results of test forming into a rectangular matrix at constant pressure

We propose a procedure to determine the strain rate sensitivity index of a superplastic material from the results of bulge forming of a long thin rectangular membrane under constant pressure of inertia gas. In contrast to other known procedures, the method suggested takes into consideration the presence of entry radius in the matrix set used. The mathematical model of the technological process is developed based on the main assumptions of the thin shell theory. To validate the procedure suggested the finite element analysis is fulfilled using the software package ANSYS 10 ED. Experimental approbation of the method suggested is carried out on the titanium alloys Ti-6Al-4V, a good agreement is achieved. It is shown that taking into account the influence of the entry radius allows to improve considerably the accuracy for finite element modelling. We draw the conclusion that the procedure developed may be recommended for practical usage to determine the superplastic parameters of thin sheet superplastic materials.