Abstract
Analytical model of temporary and residual stresses for butt welding with thorough penetration was described assuming planar section hypothesis and using integral equations of stress equilibrium of the bar and simple Hooke’s law. In solution the effect of phase transformations (structure changes and structural strains) has been taken into account. Phase transformations during heating are limited by temperature values at the beginning and at the end of austenitic transformation, depending on chemical composition of steel while the progress of phase transformations during cooling is determined on the basis of TTT-welding diagram. Temperature values at the beginning and at the end of transformation are conditioned by the speed of heating. Kinetics of diffusional transformation is described basing on Johnson-Mehl-Avrami-Kolmogorov equation, while martensitic transformation, basing on Koistinen-Marburger equation. Stresses in elasto-plastic state are determined by iteration, using elastic solutions method with changeable longitudinal modulus of elasticity, conditioned by stress-strain curve. Computations of stress field have been conducted for one-side butt welded of two steel flats made from S235 steel. It has enabled a clear interpretation of influence of temperature field and phase transformation on stresses caused by welding using Submerged Arc Welding (SAW) method.
Highlights
Modeling of thermomechanical states during welding requires the determination of temperature field
Calculated state of residual normal stresses after welding is characterised by high values of tensile stresses in weld, fusion and full transformation zones as well as by a sudden decrease of their values in partial transformation zone
Whereas in parent material areas outside heat affected zone compressive stresses occur. Correctness of such residual stress distribution was proved by experimental results presented in literature
Summary
Modeling of thermomechanical states during welding requires the determination of temperature field. Modeling the temperature field in many technological processes requires the movement heat source taking into account. Such an approach is found in descriptions of temperature fields in welding processes [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15], as well as in the machining processes [16,17,18,19]. The effect of phase transformation in the solid state has been taken into consideration among others in [20,21,22,23,24]
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