Journal of Materials Processing Technology 213 (2013) 1433–1439 Contents lists available at SciVerse ScienceDirect Journal of Materials Processing Technology jou rnal h om epa g e: www.elsevier.com/locate/jmatprotec Coupled Eulerian Lagrangian finite element modeling of friction stir welding processes Fadi Al-Badour ∗ , Nesar Merah, Abdelrahman Shuaib, Abdelaziz Bazoune Mechanical Engineering Department, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran 31261, Saudi Arabia a r t i c l e i n f o Article history: Received 30 November 2012 Received in revised form 8 February 2013 Accepted 25 February 2013 Available online 4 March 2013 Keywords: Friction stir welding Finite element modeling Coupled Eulerian Lagrangian Void formation a b s t r a c t A 3-dimensional localized finite element model (FEM) is developed to predict likely conditions that result in defect generation during friction stir welding (FSW). The workpiece is modeled using Eulerian formulation, while the tool is modeled using Lagrangian. Coulomb’s frictional contact model is adopted to define the tool workpiece interaction, while the welding speed is defined by material inflow and outflow velocities. The numerical results show that the coefficient of friction has a major effect on void formation; the lower the friction coefficient is applied, the larger the void is formed. Furthermore, welding using force control (FC) at lower welding speed results in smaller void size and wider plastic zone, leading to higher quality weld. © 2013 Elsevier B.V. All rights reserved. 1. Introduction FSW problem is a multi-physics problem that includes excessive material deformation and heat flow. Different modeling tech- niques such as computational fluid dynamics (CFD) and arbitrary Lagrangian Eulerian formulation (ALE) have been used to simu- late FSW process. Ulysse (2002) was the first to model FSW using commercial CFD software FIDAP. He studied the effects of weld- ing and tool rotational speeds on temperature, loads on the tool pin, and flow of particles near the rotating pin. Ignoring heat gen- erated by friction contact and heat loss to the backing plate, he found that the forces on the pin increase with increasing welding speed, and decrease with increasing rotational speed. Tempera- tures predictions were overestimated compared to experimentally measured ones. Colegrove and Shercliff Hugh (2005) used FLU- ENT (commercial CFD package) to study FSW process, considering rigid visco-plastic material behavior as in Ulysse (2002). But unlike Ulysse, they considered tool pin threads with full sticking condi- tion, and included heat dissipation to backing plate. The authors addressed a number of drawbacks in the model, such as the pre- dicted size of the deformation zone which was found to be much larger than observed experimentally, overestimation of the weld temperature, and underestimation of tool traversing force. Kim et al. (2010) showed that the implementation of a proper thermal boundary condition at the interface between the workpiece and the backing plate is important for prediction of accurate results. ∗ Corresponding author. Tel.: +966 569163321; fax: +966 3 860 2949. E-mail addresses: fbadour@kfupm.edu.sa, fbodour@hotmail.com (F. Al-Badour). With the advancement in computational power, researchers also used ALE re-meshing methodology with explicit solver to sim- ulate steady state FSW. Deng and Xu (2004) modeled FSW and simulated the metal flow pattern around the FSW tool assum- ing plane strain conditions. The model considered experimentally measured temperatures which were applied as body loads. The authors used Abaqus Dynamic Explicit, to compare two tool pin-workpiece contact interaction models: modified Coulomb’s frictional model and constant rate slip model. The comparison of the two models, based on tangential velocity, showed no large difference between the two models. Schmidt and Hattel (2005) developed a localized thermo-mechanical model to study the steady state FSW of 2xxx Aluminum alloy. Their model was gen- erated using commercial FEM package Abaqus, and solved using coupled temperature–displacement dynamic explicit where the material behavior was assumed to obey Johnson–Cook rule (1983). The results of their investigation shows that the cooling rate plays a significant role in defect formation with higher cooling rate lead- ing to faulty deposition of material behind the tool pin. Zhang et al. (2007), employed a model similar to that of Deng and Xu (2004), but considering 3D geometry. They found that the nugget zone was much affected by the axial force than thermo-mechanical and heat affected zones. Zhang (2008) used both classical and modified Coulomb’s frictional model conditions. He found that both models predicted similar results at low tool rotational speeds. The classical Coulomb’s model failed to work for higher tool rotational speeds due to the increase in the dynamic effect of the welding tool. Later, Zhang and Zhang (2009) used an approach similar to that of Schmidt and Hattel (2005) to study the effect of welding parameters on material flow and residual stresses in friction stir butt welded Al 0924-0136/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jmatprotec.2013.02.014