hossein yousefian

The roll forming of an asymmetrical channel section is associated with a twisting defect, but this defect also occurs in a symmetrical section whose holes are asymmetrical. Therefore, first, a finite element model was presented to investigate the process. By designing the full factorial method, the important factors affecting the twisting defect and the effect of each during the cold roll forming process have been investigated. In the end, it was concluded that the thickness of the sheet and the diameter of the holes are the most important factors affecting the twisting defect. It was concluded that the greater the difference in the diameter of the holes on both sides of the channel, the higher the amount of twisting defect. For the forming angle of 45 degrees, by increasing the thickness of the sheet from 2 mm to 3 mm, the twist angle of the piece increased from 1.5 degrees to 2.5 degrees. According to the behavior of the metal, a series of experimental tests were designed and the effect of the hole diameter factor on this defect was determined. Appropriate matching of experimental and numerical results indicates reliable and verifiable numerical results.

The tube spinning process is one of the forming processes to fabricate conical seamless tubes. This process is done warm or cold, with or without mandrel. In this article, the possibility of forming of an Al-6061 conical tube by hot die-less spinning process has been investigated. An estimation of tangential force and required power can be obtained by analytical methods. So, the ideal work and upper bound methods have been utilized to derive equations for calculation of tangential force and required power of forming. An identical result was acquired for the two methods. The proposed equations can be used in design stage of the process. Furthermore, final thickness and initial length of the tube have been calculated by using of geometrical relations and constant volume law. The proposed formulation has been compared by experimental results. The final thickness and initial length of the tube are in good agreement with experimental results. An error of 0.5% and 5.5% were observed for final thickness and initial length, respectively. The obtained equation for the final thickness is a cosine function of the conical angle. Hence, it predicts higher final thickness in comparison with the sheet spinning process.