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

Abstract

The existing parametric formulae to calculate the notch stress concentration factor of fillet welds often result in reduced accuracy due to an oversimplification of the real weld geometry. The present work proposes a parametric formula for the evaluation of the notch SCF based on the spline weld model that offers a better approximation of the real shape of the fillet weld. The spline model was adopted in FE analyses on T-shape joints and cruciform joints models, under different loading conditions, to propose a parametric formula for the calculation of the SCF by regression analysis. In addition, the precision of parametric formulae based on the line model was examined. The magnitude of the stress concentration was also analyzed by means of its probability distribution. The results show that the line model is not accurate enough to calculate the SCF of fillet weld if the weld profile is considered. The error of the SCF by the proposed parametric formulae is proven to be smaller than 5% according to the testing data system. The stress concentration of cruciform joints under tensile stress represents the worst case scenario if assessed by the confidence interval of 95% survival probability.

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

“…One of the welded joints was scanned and shown in Figure 1 b. The weld model in this research was built based on the spline model proposed for the fillet welded joints of cruciforms [ 22 ]. As seen in Figure 1 b, the weld toes on the main plate and attachment were simulated by arcs, which were connected by a spline curve with a convex shape.…”

“…The 8-node solid element C3D8 was used for tensile load and the reduced integration element C3D8R was used for bending load in order to control the shear locking. As it is known that the SCF at the weld toe is independent of the absolute values of the parameters but influenced by their relative ratios [ 22 ], the following discussion is conducted based on the same main plate thickness ( t ), and the ratios of all parameters to the t are variable. An example of double-attachment gusset model under tensile stress with t = 6 mm, T/t = 1.0, r 1 /t = 0.043, r 2 /t = 0.043, θ 1 = 60°, θ 2 = 60°, L 1 /t = 1.0, L 2 /t = 1.0, n = 3, H/t = 1, L_main/t = 60, W/t = 8, L_attach/t = 18, and H_attach/t = 8 is shown in Figure 3 a.…”

“…The line model, which is widely used in the SCF assessment, simplifies the convex shape of weld to a straight line [ 20 , 21 ]. However, it has been verified that the weld shape is usually arc-shaped and its approximation with a straight line can result in reduced accuracy of the SCF [ 22 ]. The spline model, which was recently proposed, provides a favorable convex shape resembling the real weld geometry.…”

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

“…In such cases, appropriate statistic data obtained directly from real structures and regarding changed values and shapes of weldments are necessary. Examples of such data in the form of histograms can be found in the literature [ 21 , 22 , 23 , 24 , 25 ]. 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.…”

“…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.)…”