Numerical Simulation on Nugget Formation and Evolution in Spot Welding of Aluminum Alloy |
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Authors: | CHENG Fangjie ZHANG Jianyou HU Shengsun SHAN Ping |
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Institution: | 1. School of Material Science and Engineering, Tianjin University, Tianjin 300072, China;Tianjin Key Lab of Advanced Welding and Joining, Tianjin 300072, China 2. School of Material Science and Engineering, Tianjin University, Tianjin 300072, China |
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Abstract: | With the squeeze of electrode tips, the oxide film on aluminum (Al) alloy surface is broken and numbers of micro-gaps are
formed randomly. The micro-gaps act as conducting spots at the beginning of welding, so the contact resistance is extremely
high and unstable in spot welding of Al alloy. In this paper, a new contact resistance model is adopted to simulate the nugget
forming process. This model describes the random distribution characteristic of conducting spots. The simulation results indicate
that, within the first 5 ms of welding current (AC, 50 Hz), the temperature distribution at the workpieces interface is seriously
irregular. In addition, the nugget does not nucleate from the weld center and grow continuously, however, it nucleates randomly
from several points almost instantaneously and then merges into an entity quickly. Experimental results agreed with the numerical
simulation. |
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Keywords: | aluminum alloy spot welding nugget oxide film contact resistance |
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