Abstract
Friction stir welding of aluminium alloys widely used in automotive and aerospace application due to its advanced and lightweight properties. The behaviour of FSW joints plays a significant role in the dynamic characteristic of the structure due to its complexities and uncertainties therefore the representation of an accurate finite element model of these joints become a research issue. In this paper, various finite elements (FE) modelling technique for prediction of dynamic properties of sheet metal jointed by friction stir welding will be presented. Firstly, nine set of flat plate with different series of aluminium alloy; AA7075 and AA6061 joined by FSW are used. Nine set of specimen was fabricated using various types of welding parameters. In order to find the most optimum set of FSW plate, the finite element model using equivalence technique was developed and the model validated using experimental modal analysis (EMA) on nine set of specimen and finite element analysis (FEA). Three types of modelling were engaged in this study; rigid body element Type 2 (RBE2), bar element (CBAR) and spot weld element connector (CWELD). CBAR element was chosen to represent weld model for FSW joints due to its accurate prediction of mode shapes and contains an updating parameter for weld modelling compare to other weld modelling. Model updating was performed to improve correlation between EMA and FEA and before proceeds to updating, sensitivity analysis was done to select the most sensitive updating parameter. After perform model updating, total error of the natural frequencies for CBAR model is improved significantly. Therefore, CBAR element was selected as the most reliable element in FE to represent FSW weld joint.
Highlights
Friction stir welding (FSW) is rapidly used to join thin sheet metal with similar and dissimilar materials in the application of shipbuilding, aerospace, railway and automotive [1,2,3]
The primary goal of this study is to present an appropriate way on how to model FSW welded joints between dissimilar materials using finite element method
Three types of modelling using rigid body element Type 2 (RBE2), CBAR and CWELD were developed and the suitability of these three modelling was compared using correlation between natural frequency and mode shapes extracted from experimental modal analysis (EMA) and finite element analysis (FEA) for set E
Summary
Friction stir welding (FSW) is rapidly used to join thin sheet metal with similar and dissimilar materials in the application of shipbuilding, aerospace, railway and automotive [1,2,3]. Even though prediction task through computational methods are widely used in predicting the behaviour of welds on a complete structure, developing a numerical model of the weld itself is a complex issue This is mainly because of the existence of many local effects that are not taken into account by FE modelling when predicting frequencies and modes. There have been several studies in the literature reporting on modelling of FSW [7,8,9,10,11] concentrated in simulation of the process and limit capacity analysis Modelling for these types of analysis required detailed mesh in order to work out a smooth stress field within and around FSW weld joint. Model updating will be carried out for selected to improve correlation between experiment and numerical counterparts
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