Simulation of the Roller Straightening Process with Respect to Residual Stresses and the Curvature Trend

Abstract

The roller straightening process is a common method for straightening long products like beams after rolling and cooling. This process often causes an adverse residual stress state. All previous investigations operate only with the roller adjustment as correcting variable. However, this cannot properly describe the consequences on the cross section of the beam during bending. The present paper presents a concept to consider the development of curvature during the straightening process. In finite element analyses using Abaqus/Standard a beam with a rectangular cross section and simplified material properties is modeled for a fundamental and clear demonstration. The theo-retically determined residual stress state depends on the development of curvature during straight-ening. Vice versa it is possible to design a trend of curvature with the goal of tailoring the final re-sidual stress distribution to the desired optimum. The necessary roller adjustment is found in a simulation using the Abaqus user subroutine UAMP, where the curvature is permanently tuned by controlling the roller adjustment. The residual stress state resulting from these 1D considerations (“the theoretical stress state”) is verified in a subsequent 2D analysis giving the “actual stress state”. A comparison of the theoretical and the actual residual stress state illustrates the influence of the roller contact. The concept presented in this work can be applied to complex cross sections in com-bination with realistic material properties. However, for this purpose a large amount of calculation resources due to an extensive 3D modeling are needed.

Investigation of blank bow defect after roller leveller by finite element analysis

“…Grüber [7] investigated leveling process with respect to the initial stress and strain distribution in the pre-levelled sheet metal but without any information about stress distribution in levelled sheets. In papers [8,9,10] authors study residual stresses induced by roller levelers. For example, Kaiser [10] made optimization algorithm and illustrated the influence of the roller adjustments on residual stress distribution for 9 rolls leveler and 8mm thickness steel.…”

“…In papers [8,9,10] authors study residual stresses induced by roller levelers. For example, Kaiser [10] made optimization algorithm and illustrated the influence of the roller adjustments on residual stress distribution for 9 rolls leveler and 8mm thickness steel.…”

“…Numerical simulations were used by [6][7][8][9][10][11] to experimental investigation energy-power parameters and final flatness of the sheet. Madej [6] researched material hardening laws under alternating low cyclic loading and unloading and made conclusion that combined hardening model should be used.…”

Eulerian Description of Rail Straightening Process

“…In the area of rail straightening this can be documented by Refs. [3][4][5][6][7]. The simplifications relate to many aspects like neglecting the rail movement through the straightening machine, contact stress between rail and rollers or accepting different levels of stress state modeling from simple 1D beam models up to full 3Dsimulation.…”

“…Another source of variability is caused by different levels of materialmodeling. Typically, several levels of such models are created and the solution of real problem is found iterating among these different levels [3,5,7].…”