Theoretical analysis of air bending at high temperature

Abstract

This paper is focused on the theoretical analysis of air bending at high temperature. A thermo-mechanical model able to predict temperature distribution and main bending parameters is developed. Thermal model assumes local heating of the sheet along bend length and is based in previous numerical model. The influence of temperature in mechanical properties of the sheet is taken into account with temperature dependent parameters of constitutive equation. Mechanical model is formulated in order to satisfy industrial requirements. Desired geometry of the piece fixes final bending angle after unloading, so this parameter is the input of the model. An iterative calculation process is used to solve presented equations obtaining curvature, sheet shape, contact force and springback. These parameters are very important in industrial processes, allowing establishment of punch displacement and maximum force to make the desired workpiece. Other results may be obtained from this model: moment distribution, maximum stress and strain. These results are related to important features of the actual process, like tools design and formability limits of the sheet.