Numerical and Experimental Study on Nugget Formation Process in Resistance Spot Welding of Aluminum Alloy

The weld nugget formation in the resistance spot welding(RSW) of aluminum alloy was investigated in the present study. The nugget formation process was directly observed by using a digital high-speed camera. Numerical simulation was also employed to investigate the nugget formation process. The results showed that for the RSW of two aluminum alloy sheets, a nugget was first formed in the workpiece/workpiece(W/W) interface and grew along the radial direction and axial direction of the sheets, and then it became a large elliptical nugget. For the RSW of three aluminum alloy sheets, two small nuggets were firstly formed in two W/W interfaces and grew along the axial direction and radial direction; finally they fused into one nugget. Besides, there existed a critical welding time, after which the nugget size remained nearly unchanged. This indicates that a long welding time is unnecessary for the RSW of aluminum alloy. In addition, the calculated nugget radius was compared with the experimental results, which showed that the simulation results agreed well with the experimental results.     

居高临下 纵横捭阖——例谈初中历史教材使用的理性思考与实践探索

<正>一本教材,不一样的教师,不一样的诠释,呈现不一样的教学精彩和教育效能,如同一样的食材在不同的厨师手中变幻出香味不同的菜肴。毋庸置疑,教材使用体现着教师的“学养”和“教养”,亦是把教材的“营养”转化为学生的“学科素养”的起点,值得理性思考与实践探索。