Experimental and numerical investigation of friction coefficient effects on defects in horizontal tube bending process

Abstract

The aim of this paper is to investigate defects in a thin-walled tube bending process (without using mandrel and booster) and effects of friction between the dies and tube on wrinkles. In the tube bending process, there are several effective parameters such as wall thickness, outer diameter-to-wall thickness ratio, centerline bending radius-to-outer diameter ratio and friction coefficient. Any mismatch in the selection of the process parameters would cause defects inducing undesirable variations in wall thickness and cross-section distortion. In this work, firstly, tubes with several wall thickness values are bent, and the final depths of wrinkling and wall thickness change are reviewed. Then, to study the process numerically, numerical simulations are carried out. Then, a series of experimental tests are carried out to verify the simulation results. A comparison between numerical and experimental results shows a reasonable agreement. Finally, in order to obtain a suitable friction condition, the effects of friction coefficients on defects are studied. For this purpose, a series of simulations has been carried out. It shows that at a certain friction coefficient, a minimum wrinkling depth can be observed and variations in the friction coefficient between the dies and tube has no effective influence on wall thinning and thickening.

Inhibiting thinning in tube bending by a superposition effect under a boosting movement

“…In particular, the friction between the die and the tube has an essential influence on the boosting effect of the die. Therefore, it is necessary to introduce suitable friction coefficients in the simulation [10,29,30]. According to the bending characteristics of the tube, the classical coulomb friction is used to describe the friction properties between the tube and each forming die.…”