Effect of Edge Conditions on the Formability of Commercially Pure Titanium Sheet (Grade 2) at Room Temperature

Abstract

Titanium and its alloys are difficult to form, particularly at room temperature, due to their crystallographic structure and limited availability of slip systems. Such limited formability could be exacerbated by virtue of the technique used to cut the sheet. Forming limit diagrams will not necessarily recognize such effects, which can lead to failures during forming trials. An example of a situation where this could be demonstrated is in sheet with pre-fabricated holes. This work used a hemispherical punch to stretch in-plane a 20mm diameter hole prepared with laser, EDM and AWJ cutting techniques in order to quantify the edge formability of the material. It was identified that, the edge surface conditions have a major impact on the edge formability of the material. The edges of the material prepared with EDM showed very high formability tendencies compared with AWJ and laser cutting. The work proposed an alternative characterization method that could be adopted for edge formability assessment.

Keywords

• hole expansion test
• edge surface defects
• hole expansion ratio
• edge formability