Research On Partial Bending Technology And It's Mechanism

Bending is one of the most prevalent forming methods, which possesses a great proportion in sheet metal forming. Springback is the inevitable phenomenon caused by elastic recovery and residual stress after sheet metal bending forming. For the U-bending of sheet metals, springback represents the most important failure mode. So it is necessary to do further research to control the springback. The study on bending springback of U-shaped part can not only solve the springback problem like U-shaped parts, but also provide analyzing and solving methods to springback of complicated parts.The accuracy of springback prediction is affected by many parameters, and there is no precise theory to express them by now. The finite element method (FEM) has been popularly used to predict the springback in sheet metal forming since the 1990's. This paper uses the finite element method and elastic-plastic constitutive relationship to analyze the metal sheet forming and springback.This paper reviews the history of springback prediction, introduces the analytic method, experimentation, FEM method and achievements in this field, expatiates on the research status of springback control.This paper depicts continuous medium mechanics and metal forming theory, introduces several key techniques of sheet metal forming and springback simulation, such as large deformation increment finite element method, solved Algorithm, which supply theory reference for selecting right analytical parameters.Taking the sheet metal bending as an example, the springback mechanics theory is analyzed. According to the analysis, partial bending technology is brought forward, which divides overall bending to several parts and finishes the bending of these parts in turn. And taking the bending of U-shaped part for example, three ways of shaping including overall bending, stretch bending, partial bending are simulated separately. Compared the springback of three ways, we can get the conclusion that partial bending can reduce the springback of U-shaped part effectively.Aimed at the springback of U-shaped part, overall bending and partial bending are compared, we carry out a series of bending and springback numerical simulation experiments, and research the effect of several parameters (parts radius, pun-die clearance, sheet thickness, material hardening exponent) to springback. When partial bending is researched, U-shaped part is marked several parts, we analyse the effect of length proportion of marked parts and the bending sequence to springback.At last, focused on complex U-shaped part, three ways of shaping as bending, stretch bending and partial bending are simulated separately, the result indicates that in the processing of special shaped parts, partial bending can change stress-strain distribution effectively in the shaping, so the process can reduce the springback.