.Titanium alloys in comparison with other alloys are newer structural materials. Due to specific properties of these alloys they are increasingly used in today’s aeronautics. Titanium alloys are characterized by little formability and high levels of spring back at room temperature. That is why they are usually formed at elevated temperatures. Results of tensile tests conducted on titanium alloys show that these alloys have good formability at temperature above 900?C and their spring back reduce significantly. Superplastic materials are capable of undergoing long elongations prior to failure. Usually elongations more than 200% are expected in superplastic forming. Also there are some alloys which show elongations more than 1000%. Superplastic forming is characterized with low stresses and high level of uniform deformation. The most important advantage of this method is manufacturing of complicated geometries which cannot be formed by traditional methods. It is important to control the strain rate of the process in superplastic forming, because these materials show the best properties in a limited range of strain rate. Simulation and numerical analysis of hot deep drawing of Ti-6Al-4V alloy sheets are among the objectives of this thesis. Unlike other superplastic simulations, the grain size effects are considered in the constitutive equation of the material which causes material modeling behavior more accurate. Furthermore, the proposed constitutive equation describes and predicts excellently the observed flow response. Structural mechanisms like grain boundary sliding and dynamic grain growth, occurring during deformation, have been investigated and mechanical properties such as flow stress, strain hardening, and strain at rupture have been determined. Simulation of the process is carried out by ABAQUS software. A user subroutine VUMAT is used for implementing the constitutive equations. Nowadays these simulations have special importance because they reduce not only the time but also the cost of process. The content of the thesis is as follows: superplasticity and methods of superplastic forming are introduced first, and then Ti-6Al-4V alloy and affecting factors on its superplastic characteristics are investigated. Finally, using an appropriate constitutive equation, superplastic deep drawing of Ti-6Al-4V alloy sheet is simulated and the results of various blank sizes are compared. In order to optimize material consumption minimum required blank size was predicted. Simulation results such as thickness distributions at different strain rates and force-time curves were obtained. A tensile test is developed to validation of these simulations, and used to investigate the effects of grain-size, and strain rate on the standard specimen. Keywords: Simulation of Hot Deep Drawing, Ti-6Al-4V alloy, ABAQUS Finite Element Code, Superplastic, and Low Strain Rate.
