Numerical and experimental investigation of the effect of local heating on the reduction of the spring back defect in the flexible roll forming process

One of the limitations of traditional roll forming is the production of parts with fixed cross-sections, so the flexible roll forming process was created to produce parts with variable cross-sections. The most important defects of this process, include warping, spring back, deviation from the desired position of the edge, wrinkling of the edge, and fracture in the corners. In this paper, the numerical and experimental investigation of the effect of heating the sheet during the flexible roll-forming process on the spring back defect was discussed. For this purpose, the simulation of the thermomechanical finite elements of the process was carried out in Abaqus software. Experimental tests were conducted using a flexible roller forming machine made in Shahid Rajaee University of Tehran along with additional local heating mechanisms in five temperatures 25, 100, 200, 300, and 400 to validate the simulation results. A laser thermometer was used to measure the sheet temperature. To prevent laser light reflection and error in temperature calculation, the sheet was matted by carbon coating. Results showed that with the increase in temperature, the spring back compared to forming at ambient temperature decreased in both types of aluminum, and with the increase of yield strength, the spring back increased. By increasing the temperature up to 400°C compared to the ambient temperature, the spring back in thickness 1mm and 1.5mm, decreased by 33.5 and 41.2%, respectively; also, the comparison of simulation and experimental results showed a good agreement.