Abstract
Kinematic bending of profiles allows to manufacture parts with high flexibility concerning the geometry. Still, the production of profiles with asymmetric cross-sections regarding the force application axis using kinematic bending processes offers challenges regarding springback and warping. These geometric deviations can be reduced by partial, cross-sectional heating during the process as it lowers the flow stress locally. In this work, the influence of partial, cross-sectional heating during a three-roll push-bending process on the warping and springback of L-profiles is investigated. Numerical and experimental methods reveal the influence of temperature on warping and springback. A newly developed analytical model predicts the warping and bending moment in the design phase and assists to understand the effect of warping reduction through partial heating during plastic bending. With increasing temperature of the heated profile area, the warping is reduced up to 76% and the springback of the bend profiles is decreased up to 44%. The warping reduction is attributed to a shift in stress free fiber due to the temperature gradient between heated and room temperature areas. The shift of stress-free fiber leads to an adapted shear center position, resulting in an approximated “quasi-symmetric” bending case.
Highlights
The warping of profiles with an asymmetric cross-section regarding the force application axis during bending is a common issue in profile bending
Warping is reduced through partial, cross-sectional heating in kinematic bending processes of asymmetric profiles
To reduce warping and springback in ofthe of can profiles with asymmetric shown that partial heating of the cross section leads to a springback reduction of at least ometry in the force application axis, partial heating of the cross-section can be used
Summary
The warping of profiles with an asymmetric cross-section regarding the force application axis during bending is a common issue in profile bending. To use heating as a warping reduction measure, a flow stress gradient in the profile. The products used a wedge-shaped heating strategy to realize the bending of rectangular tubes The produced in this process are not subject to springback. Warping is reduced through partial, cross-sectional heating in kinematic bending processes of asymmetric profiles. Cross-sectional heating in the bending of asymmetric profiles is correlated with the stress-free fiber position. To prove the defined hypotheses, L-profiles of S500MC are tested in a three-roll push bending process with partial-cross sectional heating and consequent water-jet cooling. With the geometrically validated FEM results in the unloaded state, the model in the continuous push-bending phase is used to describe the bending moment, warping, and position of stress-free fiber during the process. TRT k kf v vf x, x, y,y,zz xx0 , , yy0 yyf yym yypl αα aaT εεel εεpl εεpl εεpl,0, θθ νν σσ σσB τ τ
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