Abstract
In this work, three mathematical models for the heat generation during bobbin tool friction stir welding (BT-FSW) of aluminum using three tool pin geometries have been proposed. The models have utilized and updated the available models for the heat generation during the conventional tool friction stir welding (CT-FSW). For the validation of the models, BT-FSW experiments have been carried out for aluminum alloy AA1050 using three different pin geometries (cylindrical, square, and triangular), at different welding speeds of 200, 400, 600, 800, and 1000 mm/min and a constant tool rotation speed of 600 rpm. The welding temperatures during BT-FSW have been measured to be compared with that calculated from the models at the same parameters. It has been found that the calculated welding temperatures from the models and that measured during BT-FSW are in good agreement at all the investigated welding speeds especially in case of the square and cylindrical pins, proving the validity of the developed models for the predication of the heat generation as well as the welding temperatures. This will allow proper designing of the BT-FSW parameters and avoiding the conditions that can deteriorate the joint quality and properties.
Highlights
Bobbin tool friction stir welding (BT-FSW) is one of the FSW variants based on an innovative tool design in which the FSW tool contains two shoulders
In the BT-FSW, the lower shoulder replaces the backing plate used in conventional tool friction stir welding (CT-FSW), which reduces the vertical force to extremely lower levels [1]
Essa et al [5] has developed an analytical model for the heat generation of eccentric cylindrical pin in CT-FSW where the analytical model results and the experimental results were in agreement in terms of the less heat generated by the eccentric tool
Summary
Bobbin tool friction stir welding (BT-FSW) is one of the FSW variants based on an innovative tool design in which the FSW tool contains two shoulders. [8] developed an analytical model for heat generation during CT-FSW taking into account the two basic tribological processes that appear in the contact of the tool and weld pieces: Pure sliding (adhesion) and pure sticking (deformation). They concluded that the determination of a precise amount of heat generated during friction stir welding process is complicated since there are various uncertainties, assumptions, and simplifications of mathematical models that describe welding process. Colligan and Mishra [14] developed a conceptual model for the heat generation during FSW and introduced a method for expressing friction coefficient variation with respect to the key process variables
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