Effect of bending radius on deformation behavior of H62 brass tubes in a less constrained free bending process

Finite element method and bending experiments were carried out to survey the influence of bending radius on forming quality of H62 brass tubes in free bending process，which are widely used as key components of pipeline system in aerospace, aviation and automotive fields. Different bending radiuses ranged from 45 mm to 100 mm with an interval of 5 mm were employed to survey the forming defects. The results illustrated that both cross-section distortion and wall thickness variations at sections with angles in range of 10–20° and 160–170° were larger than other regions. The severe deformation behaviors usually occurred at the end of the tubes. Moreover, similar to the variation tendency of cross-section distortion, the changing of wall thickness decreases gradually with the increase of bending radius. Furthermore, the positions with the severer forming defects gradually moved towards to two terminals of the tubes with increasing bending radius. The variations of these deformation behaviors were mainly caused by the tangential stress and axial stress which were decomposed by an extra thrust introduced by the bending die. Based on the above force analysis and experimental results, the credible analytical equations were derived to quantify the effect of bending radius on forming precision during the practical bending process.