| Friction stir welding (FSW) is a solid-state joining process which based on the friction welding. This new welding technique with uniqueness and superiority has been paid a great amount of attention by researchers ever since it was developed, and study of the welding performance of various materials also become one of the major fundamental researches. At present, the study of friction stir welding is focus on the microstructure and mechanical property of the welding. Although friction stir welding has been successfully used to join materials that are difficult to weld, the material flow mechanics is not clearly understanding during the friction stir welding process as the lager plastic deformation during the welding process. Therefore, a scientific knowledge based predictive model and mathematics analysis is becoming significant methods for thorough understanding of friction stir welding process. In this paper, a continuum based FEM model for friction stir welding process is proposed by DEF0RM-3D software. The various welding parameters are set in the model to analyze the relationships between the material flow and the welding parameters during the FSW process. This model is calibrated by comparing with experimental results of welding microstructure.To analyze the actual material flow of friction stir welding, the following experimentations are carried out to visualize the material flow during the friction stir welding. (1) The relationship between welding parameters and the actual material flow state can be obtained by welding LY12 aluminum to LF21 aluminum; also the material flow state of the different section of the welding can be obtained.(2) A thin sheet Cu is placed into the LF21 to investigate the macro metal flow. After the friction stir welding, the material flow is observed through the distribution of the Cu in the welding section.Comparing the FEM model and welding results we can draw conclusion: The various welding parameter such as welding velocity and rotation velocity influence the heat input of the friction stir welding process and the material plastic state, the different material flow state can be influence by the various welding parameter.It was very significant to study the 3-D material flow model of friction stir welding; it can be find out the essential of welding figuration and analyzing the hole of weld by this the material flow model. It was valuable for understanding the relationship between processing parameters and quality of the joint. It also hadpractical value to ascertain welding parameter, optimize processing technology and control the microstructure and quality of the joint. |
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