Numerical Solution of Thin-walled Tube Bending Springback with Exponential Hardening Law

The process of manufacturing thin-walled tubes which show exponential hardening is investigated. The analysis is based on the feedback analysis of bending springback tests. The springback angle is calculated using a formula which is derived from numerical methods. The experiments and finite element calculations prove that the formula agrees well with the test results. However, for tubes with strong hardening characteristics, certain discrepancies exist. The springback angle increases linearly with the ratio of plastic and elastic modulus, and decreases nonlinearly with increasing hardening index. The larger the ratio of plastic and elastic modulus, the greater the amount of reduction as the hardening index increases. The amount of increment in the springback angle incurred by the increase of the normalized bending radius is greater for smaller hardening index values. For thin-walled tubes, after unloading, the elastic component takes a higher percentage in the total deformation as the relative wall thickness increases, causing the springback angle to increase slightly. However, when the growth rate of the cross section inertia moment is greater than that of the proportion of elastic deformation, the springback angle tends to decrease slightly as the normalized wall thickness increases. The formula will be applied to promote the technical development in springback prediction, control and compensation.