Investigation Of Residual Stress Redistribution During Elastic Shakedown In Welded Plates

  • Jazeel Rahman Chukkan

    Student thesis: Doctoral ThesisDoctor of Philosophy

    Abstract

    This research investigated the effect of the elastic shakedown on the redistribution of as welded residual stresses under a limited number of load cycles in butt and fillet welded specimens. Elastic shakedown is said to have occurred in a component under external cyclic load when the material responds plastically in the first few cycles followed by an
    elastic response.
    Four separate specimens manufactured from DH36 (shipbuilding steel) and Gas Metal Arc Welding were studied in which two were butt-welded plates, and two were fillet welded plates. Residual stress redistribution in the transverse and the longitudinal direction was investigated separately under cyclic load. Ten and three load cycles were applied on the butt, and fillet welded plates respectively. The variation of longitudinal and transverse residual stresses through-the-thickness of the plates were also investigated.
    Neutron diffraction was carried out to determine residual stresses. The measurement was conducted in the as-welded condition and, after one, three and ten load cycles. The measured as-welded residual stress in both butt and fillet welded plate indicated that the magnitude recommended by structural integrity codes are conservative. Also, an applied load in any direction induced redistribution of residual stresses in both transverse and longitudinal component. Residual stress state in each specimen were predicted using 3D
    welding process simulations. Subsequently, numerical simulation of residual stress redistribution under cyclic loads were performed on weld plates. Shakedown limit analysis was implemented to define the shakedown limit of each weld plate using plastic work done as shakedown criterion. Based on the determined shakedown limit, a shakedown region was defined. A methodology of assessment using the defined shakedown region is used to investigate residual stress redistribution.
    The study indicates that, under the considered load levels, the butt-welded plates were achieving shakedown state whereas the fillet welded plates did not achieve shakedown state. The numerical methods and experimental data presented in this work can offer guidance to structural integrity assessment of welded components undergoing shakedown and help produce more accurate and less conservative residual stress predictions. The proposed shakedown region can be upscaled to bigger structures for subsequent development of a procedure for allowance of elastic shakedown in design calculations.
    Date of Award2020
    Original languageEnglish
    Awarding Institution
    • Coventry University
    SponsorsLloyd’s Register Foundation
    SupervisorMichael Fitzpatrick (Supervisor) & Xiang Zhang (Supervisor)

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