Abstract: On the basis of sheet metal bending theory and with the consideration of the hardening, anisotropy and elastic deformation of material under the premise of plane deformation assumption, a theoretical analysis model of cap-shape bending is built to carry out analysis of cap-shape bending of wide sheet metal. The reverse bending phenomenon in cap-shape bending is analyzed. The formula for judging whether there is reverse bending at the corner of concave die is established, and the calculation formula of bending force is obtained under the condition of considering the reverse bending, then the calculation formulas of bending moment, bending stroke and springback angle are derived. Theoretical analysis on factors that influence the springback and bending force of sheet metal is carried out, and those have relatively great influence on bending force and springback are found, i.e. blank holder force (BHF) F, friction coefficient  and the sheet thickness δ. The theoretical calculation is compared with the test result, which shows that their trends are identical, so it can be taken as the theoretical basis for the research of bending problem as well as design of input layer and output layer of neural network recognition model, thus laying certain theoretical basis for intelligent technique of cap-shape bending.

Key words: Bending force, Cap-shape bending, Reverse bending, Springback, aeroelastic coupling, Beddoes-Lesihman, dynamic stall, multi-body model, wind turbine