No abstract

No abstract

No abstract

Being very strong and of limited ductility, Ti alloys require special techniques to manufacture the parts with complex shapes. Many of these technologies are based on superplastic and near-to-superplastic deforming. In these processes the transformation of the microstructure of the material can be very significant and can lead to changes in the mechanical properties of the material during deformation. Because of this an appropriate description of the correlation between mechanical loading, changes in microstructure and mechanical behavior of material is required. A phenomenological scalar model with an internal variable based on a statistical description of microstructure is proposed and used for simulation of the high temperature deformation of Ti-6Al-4V alloy. The problems of obtaining the parameters of the model and sensitivity of the model to the accuracy of this process are discussed.

Rotary forming is an exciting route for forming flanges of different angles from seamless tubes of high-strength materials. True to its incremental nature, the process offers great flexibility, but the issues encountered are atypical and complex. One such issue observed in experimental trials is the internal buckling of tubes during specific instances of flange formation. The origin of this instability is non-trivial, and ordinarily, finite-element (FE) models fail to capture this instability. To analyse and understand the problem, systematic experimental trials were carried out using different tube thicknesses, tube materials and tool kinematics. This paper summarises the results from a critical analysis to establish (1) a criteria for quantifying the instability and identifying the instances of its occurrence, (2) a validation methodology to fine-tune FE models for the process, and (3) use of FE models to understand the influence of tool path in the flange forming stage.