Behnam Sadeghi Najafabadi - Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Iran
Mohsen Lohmousavi - Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Iran

Pipe bending is widely used in aerospace, automotive and other industries. Wrinkling of thin-walled pipes, deformation of the cross-section and changes in thickness during pipe bending are the main problems of this process. Compressive force and internal pressure can be used to better control the bending process. If the ratio of bend radius to pipe diameter (R/D) in the bending process is between ۱ and ۱.۵, bending cannot be done with usual methods. It is important to present a new method that can remove the wrinkles in the pipe and minimize the thickness changes in its wall. In this research, a new method for press bending of high strength steel sheets has been investigated. The amount of spring return is one of the main parameters that have been investigated in this research using the finite element method and the experimental method. For this purpose, a cylinder with a diameter of ۱۰۰ mm made of ALFORM material has been formed in three steps using a steel mold specially made for this process. Then the same process is simulated with ABAQUS software. In another step of this article, ST۳۷ structural steel was used and examined, and the research process was repeated and its results were compared and examined. As expected, spring rebound in high strength steel was much higher than structural steel. From the analysis of the practical and finite element results, it was concluded that the spring return rate of ALFORM in this method is about ۵% of the diameter and this number is equal to ۱% in ST۳۷ steel. In addition, it was found that the parameter of the place of placing the sheet on the mold and the distance from the edge of the sheet to the center of the matrix is one of the issues that in the results extracted in the research, including the distance between the two edges of the part from each other after the end of the first and second steps, they reached the shape Uniform circular geometry is very effective at the end of the third stage .

Experimental Test, Spring Back, Finite Element, ABAQUS, ALFORM, ST۳۷.