A modified friction model and its application in finite-element analysis of friction stir welding process

Abstract

The application of the Eulerian based computational solid mechanic (CSM) models in numerical modeling of friction stir welding (FSW) is not deeply studied, because implementing a complicated friction model in an Eulerian based CSM model is challenging. To overcome this, the literature used Eulerian based computational fluid dynamics (CFD) models. On the other hand, due to the usage of finite element methods (FEMs) instead of finite volume methods (FVMs), the accuracy of CSM is higher than CFD. In this paper, for the first time, a modified friction model is implemented in an Eulerian based CSM model. To investigate the influence of the friction model on the stress, material flow, equivalent plastic strain and temperature, a comparison between the modified friction model and the Coulomb friction model is done. Developing the modified friction model results in achieving four phases for the relationship between the relative velocity and ratio between the shear stress and pressure. The comparisons of FE models show that, the modified friction model has been successful in simulating the partial sliding/sticking condition, because of achieving a uniform pattern for the stress with the maximum values of 150 MPa. Moreover, a successful prediction the material flow, heat flux, equivalent plastic strain and temperature is also obtained. Maximum values of the equivalent plastic strain is found to be 14. A “M” shape form, shifted to the advancing side with the peak temperature of 413 °C (5 mm far from the welding center) is also found. Finally, the results of the model in which the modified friction model is employed are found to be in correlation with experiments and the literature.