Mechanical Characteristics of Repair Welds in a Thick Plate (Report II) : Validity of Two-dimensional Plane-deformation Analysis(Mechanics, Strength & Structural Design)

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As repair welding is performed in a limited range, the mechanical behavior is three-dimensional problem. Then, a huge amount of computing time and expense are required for carrying out three-dimensional thermo-elasto-plastic analysis. So, it is important to study possibility of replacing three-dimensional problem with one-or two-dimensional one by keeping the mechanical condition of three-dimensional problem. In the region which undergoes the temperature history of a quasi-stationary state, the magnitude and the distribution of residual stress and plastic strain are same at each cross section along weld line if the rigidity to thermal expansion and shrinkage is uniform. The shorter repair weld length is and the slower travel speed is, the more the stress component δ_y (perpendicular to weld line) increases. In addition, the slower travel speed is, the more the plastic strain component ε^ρ_χ (along weld line) decreases. Only when weld length is long and there is no temperature gradient along weld line, three-dimensional problems can, in the strict sense of the production mechanism, be replaced by two-dimensional (plane-deformation) problems. Besides, as magnitude of residual stress is limited by the yield strength of material, it can be accurately estimated by plane-deformation analysis. If travel speed is slower, it needs to be noted to underestimate the stress component δ_y in plane-deformation analysis. Whereas, since the magnitude and distribution of plastic strain are largely affected by the mechancial boundary conditions, estimation of plastic strain is less accurate than that of residual stress in plane-deformation analysis. In this study, if the region cooled down up to 400℃ experiences the temperature history of a quasi-stationary state (the weld length; e*0.2m, at least the middle parts of model undergoes a quasi-stationary state of temperature), under the condition of travel speed υ*0.0055m/s, the magnitude and the distribution of welding residual stress and plastic strain can be estimated by plane-deformation analysis. Only the distribution and the magnitude of residual stress can be estimated under the condition of travel speed υ*0.0017m/s.
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Mechanical Characteristics of Repair Welds in a Thick Plate (Report II) : Validity of Two-dimensional Plane-deformation Analysis(Mechanics, Strength & Structural Design)

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