Effect of Welding Residual Stresses on Fracture Toughness Testing : Part 1 : FEM Analysis of CTOD Specimens in Multipass Weldments of Thick Plates(Mechanics, Strength & Structure Design)

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This paper examines the prediction and incorporation of residual stresses in fracture test data evaluations. In the present situation, there is several methods of allowing for residual stresses in elastic-plastic fracture mechanics, but all of the approaches imply such simplifying assumptions that could contribute to the observed scattering, and eventually produce over conservative results. Part 1 deals with the Finite Element Method analysis of Crack Tip Opening Displacement specimens of thick plates, paying special attention to the peculiarities in behavior of cracks with different lengths. Calculations of stress and strain fields, together with the shape and size of the plastic zones in front of crack tips, are presented for several load levels and crack depths. Opening displacement in the crack tip, values of the rotation factor under bending and J integrals are obtained in order to characterize the different behavior of deep and shallow cracks, when residual stresses are absent from the model. In Part 2, residual stresses will be introduced using thermal elasto-plastic FEM analysis and fracture parameters recalculated to assess their actual effect as compared with the unstressed specimen.
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