Finite Element Analysis of the Thermo-Mechanical Evolution during Welding of Thin Walled Titanium Alloy Tubes

摘要

TB5 alloy is an ideal material used to fabricate tubes of the air-conditioning system in airplanes. Due to the thin walled character of such a tube the distortion is almost unavoidable during the welding of its longitudinal seam, which will often affect its subsequent assembly. So it is necessary to investigate the welding distortion and to reveal the influencing factors by finite element (FE) analysis prior to the actual fabrication. As a first effort the finite element model for the welding of a typical tube with the dimension of φ102mm×δ1mm×240mm is established and a 3-dimensional solid FE analysis is performed. A three-part mesh division schedule is adopted in the model construction, by which the numbers of element and node are reduced largely. The fixtures are treated as contact bodies that can not only restrain the displacement of tube in the radial direction but also act as heat sinks. After welding the fixtures are removed gradually, and this process is modeled by the speed description of the contact bodies. As revealed by the numerical simulation, the release of the fixtures causes the rearrangement of stresses. The maximum tensile stress decreases from 604MPa to 455MPa, while the maximum compressive stress increases from 53.2MPa to 112MPa. The terminal longitudinal shrinkage is 0.417mm and the deflection is 1.26mm. The prediction of the distortion is qualitatively coincident with the observation from actual welding.