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Title: Measurement and mapping of residual stresses in welded nuclear components
Author: Serasli, Karim H. A.
ISNI:       0000 0004 5923 678X
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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The presence of high magnitude residual stresses (i.e. locked-in stresses) in welded nuclear components causes material degradation, local yielding and plastic deformation. Their presence provides the potential for premature failure, and compromise the integrity of the structure. The purpose of this research is to explore the application and development of mechanical strain relaxation methods for residual stress measurement. These techniques are applied in this thesis to welded samples that replicate welds in nuclear power components. The standard, incremental and overcore deep-hole drilling (DHD) methods are mechanical strain relaxation techniques that use material deformation created by material removal to measure residual stresses. These techniques are investigated to gain an improved understanding of their application and limitations to measure residual stresses near to or in excess of the yield strength within components. Calibrations of the incremental DHD method are carried out using finite element analysis of models with known stress distributions (e.g. uni-axial, bi-axial, uniform, non-uniform stresses). The calibration analyses are used later by introducing correction factors to determine the overall uncertainty due to material removal during the measurement process. Residual stress measurements are undertaken on different welded components that vary in geometry and material composition. The welded samples are used to test the accuracy and reliability of the various DHD methods. The measurements are compared with alternative measurement methods and FE welding simulations. Finally, mapping techniques for the reconstruction of residual stress field are applied. Localised and incomplete residual stress distributions obtained from measurements are introduced into elastic FE models replicating the dimensions of practical components to reconstruct the residual stresses. Reconstructed residual stresses are compared with additional measurements and FE welding simulations. Residual stresses exist due to incompatible mismatch strains that are contained in the region of inelastic strain. This work shows that obtaining accurate residual stresses in this region of inelastic strain is sufficient to reconstruct a complete residual stress field in close agreement with the original.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available