Abstract
In the conventional analytical model used for heat generation in friction stir welding (FSW), the heat generated at the pin/workpiece interface is assumed to distribute uniformly in the pin volume, and the heat flux is applied as volume heat. Besides, the tilt angle of the tool is assumed to be zero for simplicity. These assumptions bring about simulating deviation to some extent. To better understand the physical nature of heat generation, a modified analytical model, in which the nonuniform volumetric heat flux and the tilt angle of the tool were considered, was developed. Two analytical models are then implemented in the FEM software to analyze the temperature fields in the plunge and traverse stage during FSW of AA6005A-T6 aluminum hollow extrusions. The temperature distributions including the maximum temperature and heating rate between the two models are different. The thermal cycles in different zones further revealed that the peak temperature and temperature gradient are very different in the high-temperature region. Comparison shows that the modified analytical model is accurate enough for predicting the thermal cycles and peak temperatures, and the corresponding simulating precision is higher than that of the conventional analytical model.
Highlights
During friction stir welding (FSW), the heat derived from the friction and plastic deformation is the key factor that dictates the final weld quality [1,2,3]
In many computational fluid dynamic (CFD) models, the contact conditions at the tool/workpiece interface are considered as full sticking, which usually leads to an overestimation of peak temperature [8,9,10]
(1) In the modified analytical model, the nonuniform volumetric heat flux and the tilt angle of the tool are considered. e side and tip of the pin are divided into several parts, and the volumetric heat flux of each part is calculated separately, which can reflect a more accurate heat generation than that of the conventional one
Summary
During friction stir welding (FSW), the heat derived from the friction and plastic deformation is the key factor that dictates the final weld quality [1,2,3]. In many CFD models, the contact conditions at the tool/workpiece interface are considered as full sticking, which usually leads to an overestimation of peak temperature [8,9,10]. In most models using the ALE formulations, the grids are remeshed in the simulating process, and the tool/workpiece interaction including friction and plastic deformation can be defined to reflect the welding process to some extent. Ree contact conditions at the tool/workpiece interface including sliding, sticking, and partial sliding/sticking are defined to describe the respective mechanisms of heat generation. Two analytical models are adopted in this paper to describe the specific heat generation, and the temperature fields including the temperature distribution and thermal cycle were compared to identify the simulating accuracy. In order to justify the analytical models, the AA6005A-T6 aluminum hollow extrusions were friction stir welded, and the comparisons between measured and numerical results in the CAM and MAM were analyzed in this work
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