Longitudinal bending deformation analysis of sheet metal in continuous roll forming process

Development of flexible forming is crucial for manufacturing three-dimensional sheet metal parts. In this paper, continuous roll forming (CRF) is investigated to improve the forming results, especially for doubly curved parts. The CRF process employs an upper flexible roll and a lower flexible roll as a forming tool, and the different forming shapes are achieved by controlling and adjusting the distribution of the roll gap between two rolls. This paper is focused on analysis of the longitudinal bending deformation in CRF process, the plane assumption for longitudinal bending analysis is discussed, and the formulation to calculate the longitudinal strain distributed over the cross-section is derived. Through a series of numerical simulation on CRF processes, the validity of the plane assumption and the other theoretical models to analyze the deformation in CRF are confirmed; the relationship between longitudinal elongation distribution and longitudinal bending deformation is discussed and the strain distribution in transverse, longitudinal, and thickness directions is presented. In addition, the CRF experiments on saddle-shaped and torus-shaped parts were carried out, and the theoretical analysis and simulation results are verified by experiments.