A data‐driven analysis for fatigue failure mode identification in load‐carrying fillet welded joint with mechanical data augmentation

Abstract

Weld toe and weld root failures dominate the fatigue failures of the loadcarrying cruciform fillet welded joints. Compared to weld toe failure, the weld root failure is strongly affected by its inherent weld quality and throat size, which is more unpredictable and should be eliminated. This work proposes a weld sizing criterion in terms of two weld leg sizes and weld penetration to avoid root failure. The criterion is obtained by a data-driven approach with the help of the mechanical-directed data augmentation technique. The tractionstress-based method is applied for the data augmentation to identify the fatigue failure mode, which is statistically tested against 372 experimentally obtained fatigue data.cruciform joint, data augmentation, data driven, weld root failure, weld sizing | INTRODUCTIONThe load-carrying cruciform fillet welded joint (LCFWJ) is broadly applied to connect secondary components to main members in metal structures. [1][2][3] Two failure modes dominate the fatigue fractures of LCFWJ, namely, weld toe and root failure, depending on the load conditions and the joint geometry, as illustrated in Figure 1. Fatigue crack initiating from the weld root and propagating into the fillet weld is referred to as weld root failure, which should be eliminated during the design stage of the welded structures because of two reasons. (1) Fatigue lives according to weld root failure is usually much lower than that associated with weld toe failure. As stipulated in EN-1993-1-9, 4 the S-N curve recommended for weld root failure falls into the worst possible category, namely, FAT36, which is lower than that of the weld toe failure. 5 Ziqi Zhao and Tairui Zhang contributed equally to this work and should be considered co-first authors.

Fatigue life prediction of aluminum alloy T‐welded joints root failure based on equivalent crack method

“…As one of the critical factors affecting life, the residual stress of the welded structure must be considered in the crack growth simulation 19,20 . According to the superposition principle of influential stress intensity factors, the impact of residual stress on fatigue life prediction can be quantitatively evaluated 37 .…”

“…[Colour figure can be viewed at wileyonlinelibrary.com] crack growth simulation. 19,20 According to the superposition principle of influential stress intensity factors, the impact of residual stress on fatigue life prediction can be quantitatively evaluated. 37 In this paper, the influence of residual stress on the life of the welded structure is considered based on the mean stress method, and the influence of external load and residual stress on the stress intensity factor at the crack tip is superimposed and characterized by K eff , as given by the following equation:…”

“…The crack geometry and extension were essentially three‐dimensional, and the fracture profiles of the numerical model were generally in good agreement with the corresponding experimental profiles. Zhao et al 19 and Fang et al 20 performed 3D simulations of the welding process and fatigue crack extension, considering the weld geometry and redistribution of residual stresses. The above recent literature provides an in‐depth study around crack growth simulation, where initial defects, residual stresses, and crack growth rate remain the main factors affecting crack growth life.…”

A post‐processing procedure for predicting high‐ and low‐cycle fatigue life of welded structures based on the master E–N curve

“…Unlike the regular fatigue analysis of unwelded structures, the geometric discontinuities introduced by welded joints lead to stress/strain singularities at the weld location (such as weld root or weld toe). [14][15][16] These stresses/strains, if directly calculated by finite element (FE) analysis, will not achieve mesh convergence, often known as mesh sensitivity. 17 Consequently, researchers develop different post-process procedures based on FE results to assess the fatigue behavior of weldments.…”

Fatigue & Fracture of Engineering Materials & Structures Virtual Special Issue: Data science and machine learning for fatigue and fracture assessment

“…Zhao et al 6 proposed a weld sizing criterion in terms of two weld leg sizes and weld penetration to avoid root failure in load‐carrying cruciform fillet welded joints. The mechanical‐directed data augmentation technique was used to obtain the weld sizing criterion.…”