Multiple instability-constrained tube bending limits

Abstract Understanding the bending limits is critical to extract the forming potential and to achieve precision tube bending. The most challenging task is the development of the tube bending limits in the presence of unequal deformation induced multiple instabilities and multi-factor coupling effects. Using analytical and 3D-FE methods as well as experiments, a comprehensive map of the tube bending limits during rotary draw bending is provided under a wide range of tube sizes, material types and processing parameters. The major results show: (1) For each instability, the intrinsic factors (tube geometrical parameters, D and t, and mechanical properties, m) dependent bending limits are clarified, and evident interactive or even conflicting effects are observed. (2) Under mandrel bending, the significant effects of the intrinsic factors on the wrinkling limit are reduced, the neglected effects of D/t on the thinning limit are magnified; the significant influences of D/t on the flattening limit even become contrary, and the effects of m on wrinkling and thinning limit are opposite to that on the flattening limit. (3) Taking D/t as the basic design parameter, a conceptual multiple defect-constrained bending limit diagram (BLD) is constructed, and a knowledge-based stepwise method for determining and improving tube bending limits is proposed, considering coupling effects of multiple forming parameters, e.g., intrinsic factors, tooling/processing parameters and uncertainties. (4) The method is experimentally verified by several practical bending scenarios for different kinds of tubular materials with extreme size.

[1]  Mei Zhan,et al.  Friction role in bending behaviors of thin-walled tube in rotary-draw-bending under small bending radii , 2010 .

[2]  Mei Zhan,et al.  A study on plastic wrinkling in thin-walled tube bending via an energy-based wrinkling prediction model , 2009 .

[3]  S. Kyriakides,et al.  Bifurcation and localization instabilities in cylindrical shells under bending-II. Predictions , 1992 .

[4]  Jian Cao,et al.  Wrinkling Limit in Tube Bending , 2000, Manufacturing Engineering.

[5]  S. Kyriakides,et al.  Bifurcation and localization instabilities in cylindrical shells under bending—I. Experiments , 1992 .

[6]  David A. Field,et al.  Finite element bending analysis of oval tubes using rotary draw bender for hydroforming applications , 2005 .

[8]  Matteo Strano,et al.  Rotary draw bending of small diameter copper tubes: predicting the quality of the cross-section , 2012 .

[9]  Makoto Murata,et al.  Deformation analysis for the shear bending process of circular tubes , 2005 .

[10]  Y. Im,et al.  Determination of forming limit of a structural aluminum tube in rubber pad bending , 2003 .

[11]  Mei Zhan,et al.  The interactive effects of wrinkling and other defects in thin-walled tube NC bending process , 2007 .

[12]  Li Jin,et al.  Bendability of the wrought magnesium alloy AM30 tubes using a rotary draw bender , 2008 .

[13]  Yang He,et al.  Role of mandrel in NC precision bending process of thin-walled tube , 2007 .

[14]  He Yang,et al.  Wrinkling analysis for forming limit of tube bending processes , 2004 .

[15]  Michael J. Worswick,et al.  EFFECT OF LUBRICANT IN MANDREL-ROTARY DRAW TUBE BENDING OF STEEL AND ALUMINUM , 2005 .

[16]  Stelios Kyriakides,et al.  Yield anisotropy effects on buckling of circular tubes under bending , 2006 .

[17]  Yuansong Zeng,et al.  Experimental research on the tube push-bending process , 2002 .

[18]  Ghafoor Khodayari,et al.  Bending Limit Curve for Rotary Draw Bending of Tubular Components in Automotive Hydroforming Applications , 2008 .