Residual Stresses with Time-Independent Cyclic Plasticity in Finite Element Analysis of Welded Joints

Abstract

Due to the intense concentration of heat in a reduced area when Gas Metal Arc Welding (GMAW) is used to join mechanical components, the regions near the weld bead are subjected to severe thermal cycles. Firstly, the region close to the weld bead that is heated tends to be in compression and, when it cools, tends to be in tension. According to Pilipenko, the material is exposed to elastic compression and, then, reaching the yield limit, undergoes plastic deformation with the appearance of residual stresses followed by elastic-plastic unloading. This could be considered as a strain-stress cycle. This paper applies plastic-strain-range memorization based on time-independent cyclic plasticity theory for butt joints with single V-groove Finite Element (FE) models that were manufactured by GMAW. The theory combines both the isotropic hardening and the nonlinear kinematic hardening rule (Chaboche model) to reproduce the behavior of cyclic plasticity and thus to obtain the residual stresses in welded joint FE models. As a practical example, the proposed theory is validated by three welded joint specimens that were manufactured with different input parameters of speed, voltage, and current. An agreement between the residual stresses obtained by the FE model proposed and those obtained experimentally by the hole drilling method at different depths demonstrates that the proposed theory could be valid for modelling the residual stresses in welded joints when cyclic plasticity is considered over the range of speed, voltage, and current studied.

Using Genetic Algorithms with Multi-Objective Optimization to Adjust Finite Element Models of Welded Joints

“…Table 3 shows the range of values that were considered for each of the input parameters of the FE models studied to generate the 100 individuals. The range was the same for each of the three welded joints FE models studied and was based on experience that was gained in previous research work [11,19,20]. Table 4 shows the results of using the CFS technique to analyze the relationship between the output feature and "objective function J Totalj " for each of the three FE models of welded joints proposed, and the 13 inputs parameters.…”

“…In the field of welded joints, some authors (Bag et al [24]) have used GA to adjust the unknown parameters that define three-dimensional heat transfer FE models when the GTAW process is studied. More recently, other authors, including as Lostado et al [11], have used GA to adjust the parameters that define the temperature field in butt joints with single V-groove Finite Element (FE) models. In this case, the adjusted parameters were used for FE models in the study of Residual Stresses with Time-Independent Cyclic Plasticity.…”

“…One plate was attached to a refractory surface (see Sections 4 and 4.2). The other was supported on the refractory surface to deform freely from thermal shrinkage and stresses as the cord solidified and created angular distortion [11] (See Figure 5a). The three proposed FE models had the same height and width as the specimens that were welded and even modeled the web bead starting and ending zones (See Figure 5b).…”

“…The FE models assumed the radiation, conduction, convection, and the double ellipsoidal distribution that were considered to be the input heat flux. More recently, Lostado et al [11] studied the temperature field and the Residual Stresses with Time-Independent Cyclic Plasticity in ibutt joints with single V-groove Finite Element (FE) models.…”

Numerical prediction and experimental validation of temperature and residual stress distributions in buried‐arc welded thick plates

“…Kollár et al numerically and experimentally investigated the effects of different welding parameters on residual stresses and deformations in butt‐welded steel plates. Lostado et al and Lostado et al investigated the influence of the heat input parameters on the temperature and residual stress fields, caused by MAG welding, using genetic algorithms. Lee et al presented an efficient approach to predict the welding angular distortion of butt‐welded plates by using scalar input variables with no restriction on the mesh size in the weld vicinity, and the results were verified experimentally.…”