Parametric Formulae for Elastic Stress Concentration Factor at the Weld Toe of Distorted Butt-Welded Joints

Abstract

The evaluation of the stress concentration factor (SCF) at the notches of welds is of importance, especially for butt-welded joints that are widespread in the industry. Some empirical formulae can be found in the literature to estimate the SCF at the weld toes of butt-welded joints, while few solutions are available for the distorted joints under tensile fatigue test conditions. In the present study, the existing SCF formulae for butt-welded joints loaded in tension are examined and discussed. The influence of the weld width on SCF, which is commonly ignored or misestimated by existing solutions, is investigated comprehensively based on a large set of two-dimensional (2D) finite element analyses. Consequently, a new precise parametric formula for the elastic SCF at the weld toe of geometrically symmetric butt-welded joints under tension is proposed, together with a wide application range. Moreover, the analysis is also extended to consider joints with angular distortion. A two-step finite element analysis is employed to simulate the clamping and loading procedures in the fatigue test. Similarly, the parametric formulae for the assessment of clamping-induced stress and SCF caused by angular distortion are carried out as well based on the results from finite element analyses. The formulae proposed by this paper are finally tested and proved to be valid and precise.

Parametric Formula for Stress Concentration Factor of Fillet Weld Joints with Spline Bead Profile

“…A spline model which considered the shape of butt weld joints was suggested by Luo [ 19 ], while the proposed parametric formula could not be used to calculate the SCF of fillet weld. Hence, the spline model considering the profile of fillet weld is proposed as schematically reported in Figure 1 b.…”

“…The precision of the SCF parametric formulae should be evaluated within the corresponding application ranges. According to former researches [ 19 ], the SCF at the weld toe is independent of the absolute values of the parameters; however, it is influenced by their relative ratios. Hence, the normalized parameter ranges were determined for the subsequent parametric formula as listed below: Stiffener thickness T/t : 0.3–2.0; Bottom weld toe radius r 1 / t : 0.003–0.36; Top weld toe radius r 2 / t : 0.003–0.36; Bottom flank angle θ 1 : 20°–90° Top flank angle θ 2 : 20°–90° Bottom weld leg length L 1 / t : 0.3–2.0; Top weld leg length L 2 / t : 0.3–2.0; Salient point position 1/n : 0.2–0.9; and Hump height H/t : 0.0–0.3.…”

“…The neural network method [ 15 ], developed in recent years, is also available to ensure a high accuracy in the estimation of the SCF. A variety of formulae considering key geometric parameters have been proposed based on the numerical methods considering different types of welded joints, including the cruciform joints [ 16 ], T-shape joints [ 17 ], lap joints [ 18 ], and butt joints [ 19 ]. Modifications of the aforementioned formulae have also been carried out in order to address particular cases such as loading types (bending load and tensile load) [ 20 ], weld shape after grinding [ 21 ], additional weld [ 22 ], and penetration ratio [ 23 ].…”

Generalized SCF Formula of Out-Of-Plane Gusset Welded Joints and Assessment of Fatigue Life Extension by Additional Weld

“…The spline model, which was recently proposed, provides a favorable convex shape resembling the real weld geometry. For instance, Luo [ 23 ] uses the spline model to simulate the butt weld and proposes the parametric formulae of SCF with a precision of 95%. The current parametric formulae of SCF are usually proposed for the butt weld or the cruciform fillet weld, which can be simulated by simple 2D FE models considering the plane strain state.…”

Stress Concentration Factors for Welded Plate T-Joints Subjected to Tensile, Bending and Shearing Loads

“…Various types of the weld face geometry—plane, convex, or concave—may be obtained during manufacturing, which generally depend on the welding method, position, and parameters of the process, e.g., welding speed, current, etc. Some examples of real weld shapes and profiles influencing SCF values in cases of as-welded and intentionally improved weld toe zones are also given in References [ 25 , 26 , 27 , 28 , 29 ]. Many techniques have also been developed to improve the endurance limit and reliability of the structure (grinding, milling, re-melting techniques, etc.)…”