High-resolution 3D weld toe stress analysis and ACPD method for weld toe fatigue crack initiation

Abstract

Weld toe fatigue crack initiation is highly dependent on the local weld toe stress-concentrating geometry including any inherent flaws. These flaws are responsible for premature fatigue crack initiation (FCI) and must be minimised to maximise the fatigue life of a welded joint. In this work, a data-rich methodology has been developed to capture the true weld toe geometry and resulting local weld toe stress-field and relate this to the FCI life of a steel arc-welded joint. To obtain FCI lives, interrupted fatigue test was performed on the welded joint monitored by a novel multi-probe array of alternating-current potential drop (ACPD) probes across the weld toe. This set-up enabled the FCI sites to be located, the FCI life to be determined and gave an indication of early fatigue crack propagation rates. To understand fully the local weld toe stress-field, high-resolution (5 μm) 3D linear-elastic finite-element (FE) models were generated from X-ray Micro-Computed Tomography (μ-CT) of each weld toe after fatigue testing. From these models, approximately 202 stress concentration factors (SCFs) were computed for every 1 mm of weld toe. These two novel methodologies successfully link to provide an assessment of the weld quality and this is correlated with the fatigue performance.

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Identifiers

ORCID for Somsubhro Chaudhuri: orcid.org/0000-0001-9849-5766

ORCID for Philippa Reed: orcid.org/0000-0002-2258-0347

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