Evaluation of drawability of tailor-welded blanks made of titanium alloys Grade 2 || Grade 5

Abstract

Titanium materials are becoming increasingly popular in modern applications. They are used whenever parts with low weight and high strength properties are required. Titanium and its alloys have been successfully used in many industrial branches especially in the automotive and aerospace industries. Titanium blanks are used to produce various parts of aircraft such as engine parts, wings or fuselages.In the paper, the numerical modeling and experimental results of the forming process for tailor-welded blanks were presented. This technology consists in joining elements that are made of different materials or have different thicknesses using welding. The blank analyzed in the work was a combination of two different titanium sheets – commercially pure titanium Grade 2 and titanium alloy Grade 5. In the paper, different properties of fusion and heat affected zone were taken into account.The sheets were joined using electron beam welding (EBW) technology. EBW is a high power density method and consequently produces a small fusion and heat affected zone (HAZ). The properties of the welded material change to a smaller extent compared to arc welding technologies. EBW is performed in vacuum which prevents the titanium from absorbing gases.The mechanical properties of the materials, the weld and HAZ were determined based on experiments. The limit curves for the analyzed titanium sheets, necessary for crack formation analysis, were determined experimentally.The titanium blanks joined using EBW technology underwent the stamping process using a hemispherical punch in order to observe the phenomena occurring during the formation of welded sheets with different mechanical properties. For comparative purposes, numerical analysis was performed using PAM-STAMP 2G, based on the finite element method. The numerical simulations included selection of the friction coefficient and blank holder force to ensure the best forming results.The aim of the experiment and numerical simulations was to determine the plastic deformation occurring in the material during the stamping process. Based on the obtained results, drawability analysis of the used titanium sheets was done. The studies have shown that proper selection of the process parameters enables forming of titanium TWB sheets made of titanium and its alloys.