Wall thickness distribution of Cu-Al bimetallic tube based on free bending process

In this study, we focused on bimetallic tube comprising copper and aluminum (Cu-Al) and proposed a theoretical model of its wall thickness distribution by the free bending technology. Compared to the single metal tube, the minimum thickness of the copper tube is smaller than the minimum thickness of the copper layer in the Cu-Al bimetallic tube, whereas the minimum thickness of the aluminum tube is greater than that of the Cu-Al bimetallic tube under different bending radii; the maximum wall thickness of the copper tube is larger than that of the copper layer in the Cu-Al bimetallic tube, whereas the maximum wall thickness of the aluminum tube is smaller than that of the aluminum layer in the Cu-Al bimetallic tube. Further, the reliability of the proposed theoretical model was verified by finite element simulation and experiments. Both of these results showed that the wall thickness distribution of the bimetallic layer of the metal tube tends to be more uniform. The offset rule of the strain neutral layer of Cu-Al bimetallic tube in the free bending process was also revealed. Moreover, the difference between the U-R curve of the Cu-Al bimetallic tube and the single metal tube was also investigated, and the results indicated that the U-R curve of the Cu-Al bimetallic tube is roughly located between the U-R curves of copper and aluminum.