Simulation Of Friction Stir Welding Research Articles

Comparison of two contact models in the simulation of friction stir welding process

Two contact models are used to simulate the thermo-mechanical interaction process in friction stir welding. Comparison shows that the classical Coulomb friction model can be accurate enough for the simulation of friction stir welding in lower angular velocity. But in higher angular velocity, the classical Coulomb friction model fails to work due to the increase of the dynamic effect of the welding tool. Because the shear failure of material is considered in modified Coulomb friction model, the increase of the frictional stress on the tool–plate interface is limited by the shear failure. So, this model can keep valid even when the angular velocity of the welding tool is increased to a high level.

Numerical Simulation of Friction Stir Welding by Natural Element Methods

In this work we address the problem of numerically simulating the Friction Stir Welding process. Due to the special characteristics of this welding method (i.e., high speed of the rotating pin, very large deformations, etc.) finite element methods encounter several difficulties. Meshless methods somewhat alleviate this problems, allowing for an updated Lagrangian framework in the simulation. Accuracy is not affected by mesh distortion (and hence the name meshless), but the price to pay is the computational cost, higher than in the FEM. In this paper we will show some examples on the performance of the method.

3D numerical simulation of the three stages of Friction Stir Welding based on friction parameters calibration

An Arbitrary Lagrangian Eulerian (ALE) formulation was developed to simulate the different stages of the Friction Stir Welding (FSW) process with the FORGE3® F.E. software. A splitting method was utilized: a) the material velocity/pressure and temperature fields are calculated, b) the mesh velocity is derived from the domain boundary evolution and an adaptive refinement criterion provided by error estimation, c) P1 and P0 variables are remapped. The proposed ALE formulation is applied to FSW simulation. Steady state welding, but also transient phases are simulated, showing good robustness and accuracy of the developed formulation. Friction parameters are identified for an Eulerian steady state simulation by comparison with experimental results. Simulations of the transient plunge and welding phases help to better understand the deposition process that occurs at the trailing edge of the probe, and in particular possible void formation. Flexibility and robustness of the model allows investigating the influence of threads and tooling designs.

Modelling of the residual state of friction stir welded plates

This paper presents a steady-state simulation of friction stir welding based on a prior computational method developed in [Bastier, A., Maitournam, M.H., Dang Van, K., Roger, F., 2006. Steady state thermomechanical modelling of friction stir welding. Sci. Technol. Weld. Joining 11 (3), 278–288]. This simulation includes two main steps. The first one uses an Eulerian description of the thermomechanical problem: a 3D-mixed Finite Element Model based on a Computational Fluid Dynamics package is used to establish the material flow and the temperature field during the process. In the second step, a steady-state algorithm based on an elastoviscoplastic constitutive law is used to estimate the residual state induced by the process. The steady-state assumption and the original elastoviscoplastic constitutive law are two key features of the present model. This calculation takes into account the whole thermal, metallurgical and mechanical history of the material since the algorithm is based on an integration along the path lines of the particles. The material considered is a 7050 aluminium alloy. It is observed that the longitudinal residual stress field has a two peaks profile: these two peaks are situated in the zone of high gradient of dissolved precipitates fraction. Finally, a parametric study about the influence of welding and rotational speeds is carried out. This parametric study shows that the higher the welding speed and the lower the rotational speed, the lower the temperatures and the lower residual distortions.

Numerical Simulation of Friction Stir Welding of AA6111-T4 Sheets

In an effort to develop the numerical modeling method to optimize the friction stir welding process for quality products, the plastic deformation and thermal histories of friction stir welded AA6111-T4 sheets were numerically simulated. Material and heat flow during friction stir welding were calculated considering the momentum and energy balance equations under the steady state condition. The results agreed well with the temperature measurements, suggesting that the method can be applicable to optimize the friction stir welding process, if proper mechanical and thermal properties of materials are available.

A Thermo-Fluid Analysis of the Friction Stir Welding Process

The thermo-mechanical simulation of Friction Stir Welding focuses the interest of the welding scientific and technical community. However, literature reporting material flow modeling is rather poor. The present work is based on the model developed by Heurtier [2004] and aims at improving this thermo-fluid simulation developed by means of fluid mechanics numerical and analytical velocity fields combined together. These various velocity fields are investigated separately and especially according to the power dissipated during the flow. Boundary conditions are considered through a new approach based on the kinematic analysis of the thread of the pin. An equilibrium is established between the vertical motion of the bulk material dragged in the depth of the metal sheet, and its partial circulation around the pin. The analyses of the obtained velocity fields enable the understanding of the welded zone asymmetry and highlights the bulk material mixing between the welded coupons in the depth of the sheet. A regression is performed on the relative sliding velocity of the aluminium according to the surface of the tool: shoulder and pin. Two dimension flow lines in the depth of the metal sheet are then obtained and successfully compared with the results obtained by Colegrove (2004) [1].

Thermo-mechanical model with adaptive boundary conditions for friction stir welding of Al 6061

Thermo-mechanical simulation of friction stir welding can predict the transient temperature field, active stresses developed, forces in all the three dimensions and may be extended to determine the residual stress. The thermal stresses constitute a major portion of the total stress developed during the process. Boundary conditions in the thermal modeling of process play a vital role in the final temperature profile. The heating and cooling rates with the peak temperature attained by the workpiece determine the thermal stress. Also, predicting realistic peak temperature becomes important as the operating temperature at the interface of tool-workpiece is very close to the solidus temperature of the aluminum workpiece. The convection heat-transfer coefficients of the surfaces exposed to air can be theoretically determined using Newton's law of cooling. Contact conductance depends on the pressure at the interface and has a non-uniform variation. The actual pressure distribution along the interface is dependent on the thermal stress from local temperature and non-linear stress–strain state. Therefore, applying an adaptive contact conductance can make the model more robust for process parameter variations. A finite element thermo-mechanical model with mechanical tool loading was developed considering a uniform value for contact conductance and used for predicting the stress at the workpiece and backplate interface. This pressure distribution contours are used for defining the non-uniform adaptive contact conductance used in the thermal model for predicting the thermal history in the workpiece. The thermo-mechanical model was then used in predict stress development in friction stir welding.

Numerical Simulation of Friction Stir Welding

Numerical Simulation of Friction Stir Welding