Fig 7 - uploaded by Dénes Kollár
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Operating points and working conditions for solid wire and flux cored electrodes. The current-voltage equations of the solid lines for the solid wire and flux cored electrodes are í µí± í µí± í µí±í µí±í µí±í µí± (í µí°¼) = 0.103í µí°¼ − 0.45 (1) í µí± í µí±í µí±í µí±¢í µí±¥ (í µí°¼) = 0.02318í µí°¼ + 17 (2)
Source publication
The most sufficient welding parameters and settings of manufacturing technologies are currently mainly determined by experiments for standardised production in the practice. It is a time-consuming method, while there is a large amount of waste during the 'trial and error' process of distinct welding technologies. Virtual fabrication and virtual tes...
Context in source publication
Context 1
... of electrodes is 1.2 mm, while shielding gas is EN ISO 14175 -M21 -ArC -18. Eighty-two weld passes are laid using solid wire electrodes and eighty-one weld passes are carried out applying flux cored electrodes, hence, the number of data points is equal to the number of weld passes in Figure 7. A linear regression analysis is carried out using the least squares method to determine the welding current-voltage relationship for globular and spray arc metal transfer modes, marked with continuous solid lines, for both electrodes. ...
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Local and highly nonuniform heating during welding and subsequent cooling cause complex thermal cycles inducing residual stresses and deformations in the weldment. There are numerous in-process control methods and post-weld corrective methods that can be used to mitigate welding-induced residual stresses and distortions. However, these can be expensive and time-consuming techniques. Validated numerical models can reduce the number of regular experiments during optimization and be applied for advanced manufacturing and design purposes; thus, manufacturing-induced imperfections and realistic structural behaviour can be determined. The dissertation focuses on three different research topics in the field of steel structures using numerical simulations consisting of virtual manufacturing and virtual testing. First, a numerical modelling framework is developed and validated for simulating arc welding processes in order to predict temperature, stress and deformation fields during welding and to consider welding-induced imperfections based on welding simulations in geometrically and materially nonlinear analyses with imperfections for resistance calculations. Secondly, a weld process model, focusing on modelling the physics of heat generation, is developed and validated using a three-dimensional heat transfer model and Goldak's double ellipsoidal heat source model for a metal active gas welding power source. The weld pool size is predicted in fillet and groove welds with fair precision in structural steel weldments and two different electrode types. Manufacturing and testing of steel corrugated web girders are in the focus of the third research topic. A finite element model is developed and validated for welding simulation of corrugated web girders; an automated Frenet-Serret frame is also developed in order to simplify modelling the movement of the heat source along the two-dimensional welding trajectory. The physical background of typical deformations during welding of this girder type is explained based on experimental and numerical results. Typical welding-induced longitudinal residual stress distributions of corrugated web girders are determined and compared with conventional flat web I-girders. Results demonstrate that the residual stress distribution for corrugated web girders and conventional I-girders are significantly different due to 'accordion effect' and different welding trajectories. Mainly membrane residual stresses are typical for girders with flat web, while bending residual stresses dominate for corrugated web girders. Shear buckling resistance of corrugated web girders are determined using equivalent geometric imperfections based on EN 1993-1-5 and models considering virtual manufacturing-based residual stresses and geometric imperfections. It is demonstrated that the application of virtual manufacturing and virtual testing may ensure increased shear buckling resistance in advanced design.
