An Improved Method of Capturing the Surface Boundary of a Ti-6Al-4V Fusion Weld Bead for Finite Element Modeling
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FUSION welding techniques have been utilised in the structural joining of safety-critical components across aerospace,[1] automotive,[2] and power generation[3,4] industries for many years, thanks to high productivity rates, the considerable joint-integrity that they can offer, and their relatively inexpensive experimental and production costs.[1] While older welding methods such as tungsten inert gas (TIG) welding produce large weld pools and heat-affected zones[5] due to the size of the arc formed, newer ‘‘high power-density’’ beam type processes, such as laser welding, offer a much narrower fusion zone and R.P. TURNER, Research Fellow, M. VILLA, Ph.D. Student, Y. SOVANI, Research Fellow, C. PANWISAWAS, Research Fellow, B. PERUMAL, Research Fellow, R.M. WARD, Lecturer, J.W. BROOKS, Hanson Professor, and H.C. BASOALTO, PRISM Technical Director, are with the PRISM2 Research Group, School of Metallurgy & Materials, University of Birmingham, Birmingham, B15 2TT, UK. Contact e-mail: [email protected] Manuscript submitted September 28, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
heat-affected zone,[6] as the energy from the power source is much more focused. Computer simulation of fusion welding processes has been studied for many years,[6–9] particularly as it offers a method of analysing a joint without the need for costly experimental procedures, allows for the study of parameter-effects, and permits the investigation of through-process results, which may prove difficult or even impossible experimentally with current measurement techniques to be considered. However, a critical requirement for any fusion welding computer model is to accurately understand the size, shape, and location[6] of the molten pool boundary at any given time through the process. The specialist welding FE code Sysweld (owned and developed by ESI) requires some rudimentary weld pool dimensions to be taken (often from cross-sectioning and metallurgical analysis of a representative experimental weld),[10] as well as welding process parameter information, to allow a heat source to be fitted to predict the correct molten pool size and shape. It is reasonably well understood that the size of the molten pool reaches a steady-state during the process[11] (when a constant weld parameter set of heat source power,
30mm 1mm
20mm Weld
Graded mesh: Fine to coarse
Fig. 2—The plate dimensions and prescribed mesh of the baseline modeling set-up.
Table I. Fig. 1—An example of a weld bead formed with a more intricate boundary shape, whereby the weld narrows at the ‘‘waist’’ before flaring outward toward the base.
travel speed, and joint thickness are used), hence the weld can be simulated as a steady boundary traversing along the fixed weld path, at the relevant travel speed. In order to accurately capture the boundary of this molten pool, many researchers have used mathematical functions such as the conical function,[12] or the double ellipsoid (so-called Goldak) function.[13] Usually for wide weld pool formations, or for reasonably regular-shaped wel
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