Modelling and mesh generation of weld profile in tubular Y-joint

This paper describes a systematic method of modelling the weld thickness of a tubular Y joint. The intersection between the chord and the brace members is defined precisely. This intersection curve will then be used to evaluate the dihedral angle gamma, which is the angle between the chord and the brace surfaces along the intersecting line. As the dihedral angle gamma is an important parameter used to determine the weld thickness, its variation along the intersection curve and its relationship with the weld thickness is investigated first. It is shown that the smoothness of the weld path may not always be maintained if the minimum weld thickness, as specified in the American Welding Society (AWS) Codes D1.1-96, is to be followed strictly. Thus in some cases, modification of the intersection curve is necessary in order to model the weld path along the joint. Two scale factors FOSouter and FOSinner for the outer and inner intersection curves, and two constants m and n are introduced and proposed in this study. They are used to control the parameter k(TW), which in turn controls the minimum weld thickness T-W. Based on this model, an automatic mesh generator is developed to produce a well-graded finite element mesh. The stress concentration factors (SCFs) are shown to converge when the mesh is doubled and then tripled. Finally, some tubular welded specimens are fabricated. and the outer weld profiles are measured physically. It is shown that scale factors FOSouter = 0.3, FOSinner = 0.25 and constants m = 2.0, n = 0.4. are adequate to satisfy the required minimum outer weld profile. Therefore, the proposed method to model the weld size is both consistent and accurate for any tubular Y-joints. (C) 2001 Elsevier Science Ltd. All rights reserved.