Image-based Cohesive Element Modelling of Low Temperature Crack Propagation on Alloy 82 Weld Metal

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    Exposure of Alloy 82 welds to hydrogen containing, de-oxygenated aqueous environments at temperatures below 150°C can result in reduction of fracture toughness by up to an order of magnitude. Associated with this reduction is a change in fracture mechanism from ductile to brittle intergranular, commonly termed Low Temperature Crack Propagation (LTCP). The work reported in this paper aims to provide a better understanding of the effect of grain boundary micro- and meso-structure on LTCP susceptibility. Grain boundary morphology of an Alloy 82 weld microstructure was characterised using an image analysis routine, and microstructurally-faithful grain boundary profiles imported into Abaqus Finite Element (FE) software. A 2D model of the grain boundary meso-structure was then generated using cohesive elements to simulate intergranular fracture whilst avoiding determination of the stress singularity at the crack tip. Model calibration was attempted via observation of in-situ Alloy 82 crack propagation exposed to 54°C hydrogenated water, using a windowed-autoclave test facility. Constant extension rate tests at a dissolved hydrogen concentration of 65cc/kg showed a propagating crack captured during testing. Digital image correlation (DIC) was then used to estimate crack growth rates and fracture pathways, combined with post-mortem fractographic assessment. Fracture surfaces showed a mixed mode failure, with regions of intergranular fracture
    Original languageEnglish
    Title of host publicationhost publication
    PublisherEuropean Federation of Corrosion
    Publication statusPublished - Sept 2014
    EventEuropean Corrosion Congress 2014 (EuroCorr2014) - Pisa, Italy
    Duration: 8 Sept 201412 Sept 2014

    Conference

    ConferenceEuropean Corrosion Congress 2014 (EuroCorr2014)
    CityPisa, Italy
    Period8/09/1412/09/14

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