Experimental and Numerical Analysis of Springback Behavior Under Elevated Temperatures in Micro Bending Assisted by Resistance Heating

Abstract

In the micro bending process, thinner foils may indicate larger springback due to the size effect of strain gradient. Heat-assisted micro bending is an effective process to reduce the springback and improve the accuracy of the products. In order to investigate the mechanism of springback behavior of pure titanium foils under elevated temperature, experimental and numerical analysis were carried out for different thickness foils (0.02, 0.05, and 0.1mm) with the same hardness. The results show that the springback angle decreases with increasing temperature. In the experiments, it is observed that the springback angle increases with decreasing foil thickness at room temperature, while the springback angle decreases with decreasing foil thickness at temperatures of 300oC or higher. This tendency cannot be found in the results from numerical analysis, which is explained by the surface layer model and strain gradient theory. It is suggested that the influence of surface grains on the properties of the material is the dominating factor for the less springback of thinner foils at elevated temperatures. This indicates better accuracy of the parts made by thin foils at elevated temperatures.