Investigation on variation characteristics of bent tube axis and determination of bending die motion trajectory in free bending process

Abstract

In free bending process, the axis shape of bent tube is determined by the motion path of bending die. The bent tubes with different bending radii and bending directions can be integrally formed at one time by continuously adjusting the position and posture of die. To accurately form the pre-designed bent tube, the formation mechanism of bending arc of tube in free bending process was analyzed. The mathematical model between bending radius and de ection was established and the moving direction of bending die was also determined according to the plane space azimuth where the bending arc segment is located.The formation process of transition segments with variable curvature and variable bending direction is illustrated during the movement of bending die and the in uence law of transition segment on the axis shape was also explored. By comparing the axis deviation of experimental and simulate bent tubes, the length of transition segment and the moving path of bending die can be optimized. Finally, the applicability of free bending forming technology in forming bent tubes with different shape features was veri ed by conducting the free bending experiments on bent tubes with three typical shapes. Due to the high exibility of free bending forming technology, the work in this paper could promote the engineering application of this technology in the precise control of axis shape of bent tube.

Modeling and Experimental Investigation of U-R Relationship of AA6061-T6 Tubes Manufactured via Free Bending Forming Process

“…In addition, various complicated bent tubes are manufactured successfully using the FBF process [26]. Due to the technology's many remarkable advantages, it has been widely used in aerospace, nuclear power, automobiles, ships, and many other engineering fields [27]. On the other hand, compared to rotary draw bending, which relies on mold constraints [28], the FBF process offers less constraint on the tube during bending.…”

“…Currently, the FBF forming process equipment mainly includes three-axis, five-axis, six-axis, and even seven-axis components based on a parallel mechanism [27][28][29]. This technology encompasses a three-axis free-bending mechanism, which consists of five main parts: the bending die, spherical bearing, guiding, compacting, and propulsive mechanisms [27]. All FBF experiments focus on accurately controlling the bending die's trajectory in the bending process [28].…”