Curling of thin tubes: Analytical and experimental study

The curling of thin tubes under compressive loads produces double walled tubes for many engineering applications. Experiments have been performed on annealed copper, low carbon steel, stainless steel, and aluminum tubes to determine the relationship between the curling process parameters and the tube geometry, as well as tube material properties. Effects of friction and work hardening during forming are included in the analysis. The analytical and experimental results are compared with published results to determine the validity of the proposed analytical model. The model can be used to determine the curling load and the correct die radius for successful curling. For simple and quick determination of the die radius, the present work introduces design curves, which correlate the tube geometry with the radius of the forming die.