Cross-section deformation behaviors of a thin-walled rectangular tube of continuous varying radii in the free bending technology

Thin-walled rectangular tube bent parts of continuous varying radii are widely used in aircraft, aerospace, aviation, radar, and several high-tech industries to save space and satisfy the internal structure compact of the specific products. In the previous years, the applications of thin-walled rectangular tubes were hindered because of the distortion in the cross-section area, which occurred during deformation. Nevertheless, due to its unique characteristic, free bending technology is highly suitable to form tubular components with a variable bending radii and bends in several planes. Thus, in this study, the deformation behavior of a thin-walled tube (with a rectangular cross-section area) of continuous varying radii during free bending technology was investigated. Besides, a stress analysis model was proposed to predict the equivalent stress and strain distribution. The proposed model was verified using simulations and experimentation. Furthermore, the influence of two key parameters (feeding speed and fillet radius) on the formability of a thin-walled rectangular tube was discussed. The remarkable results obtained from this study verify that free bending technology is a significant forming technology to manufacture rectangular thin-walled tubes with continuous varying radii.