Experimental Analyzes of the Forming Process of Triangular Cross-Section Tube by Circular Metal Tubes

This paper investigates forming process of circular cross-section tubes into triangular cross-section columns by the experimental method. Also, effects of Teflon-filler are studied on the plastic deformation modes. Specimens were prepared in different geometrical sizes. Effects of wall-thickness, length and diameter of tube and Teflon-filler are studied on the tube formability. A V-shape die with the angle of 90 degree was prepared from the hardened steel. For each specimen, diagrams of lateral load, absorbed energy, and specific absorbed energy versus the displacement are sketched. The results show that the tubes with the smaller diameter have the higher load capacity and energy absorption capability in the both conditions of empty and Teflon-filled. The experiments show that Teflon wallthickness and tube inner diameter are the most important parameters during the forming process of triangular columns. Also, experimental measurements indicate that lateral load and absorbed energy by the tubes are proportional to the tube initial length; but, deformation mode is independent of the tube length. Triangular tubes should form with the straight base and the apex angle of 90 degrees. Investigation of the deformation modes demonstrates that there is an optimum value for the wallthickness of cylindrical Teflon-filler and the filled tubes with the optimum Teflon has the best deformation mode. The experiments indicate that the best deformation mode occurs in the tubes with the Teflon wall-thickness of between 10-15% of tube inner diameter.