Investigation on the influence of friction effect on tube deformation in 3D free bending process

DOI:	10.11809/bqzbgcxb2023.02.031
Keywords:	free bending; friction effect; U R relationship; wall thickness distribution; cross sectional distortion
Abstract:	In the process of three dimensional free bending in which a tube is in a less constrained state, the friction effect between the bending die and the tube has a significant effect on the plastic deformation of tube free bending. To improve tube forming quality during the free bending process, it is necessary to study the evolution of bending radius, wall thickness distribution and cross sectional distortion of the tube under different friction conditions. In this paper, a free bending mechanical model considering the friction force of the bending die to the tube is established. Through the finite element simulation and free bending tests, stress and strain distribution, cross sectional distortion rate and wall thickness distribution in the free bending process of the tube with different friction coefficients are studied. The results show that, under the condition of the same bending die offset (U), the bending radius (R) of the formed pipe decreases with a decrease of the friction coefficient. In addition, the inner wall thickness of the curved arc increases significantly, while the outer wall thickness of the curved arc attenuates at a decreasing speed. With the increase of the friction coefficient, the cross section distortion rate first increases and then gradually flattens. Therefore, when tubes of different materials and bending dies are used, it is necessary to consider the friction effect on tube free bending deformation to obtain the bending tube that meets the quality requirements.
Published:	2023-02-28
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