Evolution of Residual Stress Based on Curvature Coupling in Multi-Roll Levelling

Abstract

Residual stress is the main cause of flatness defects in sheet metal and the basic method to improve the shape quality of the sheet is to reduce and eliminate the residual stress by multi-roll levelling. The curvature coupling between repeated sheet bendings in multi-roll levelling greatly affects the accuracy of the analysis of the residual stress evolution, which is rarely considered in current research. Aiming to address this problem, a method for eliminating residual stress by multi-roll levelling based on curvature coupling is discussed in this article. An evaluation criterion and an analysis model are proposed to investigate the evolution of the residual stress in multi-roll levelling considering the curvature coupling between bendings. The effects of the intermesh of the work rolls and the plastic deformation of the sheet on the residual stress are also discussed. The results show that multi-roll levelling will cause rolling residual stress while reducing the initial residual stress of the sheet and the larger plastic deformation caused by the intermesh of the work rolls at the entry is beneficial for the complete elimination of the initial residual stress, but the rolling residual stress will increase at the same time. Therefore, the total residual stress of the sheet after levelling depends on the appropriate levelling parameters.

Study on Symmetry and Asymmetry Rolling of AA2519-T62 Alloy at Room-Temperature and Cryogenic Conditions

“…Nevertheless, a possible explanation is the non-uniform deformation of the rolled samples. Plastic deformation in a whole volume of the material at room temperature is easier to achieve, resulting in strain hardening affecting the entire cross-section [ 42 , 43 ], as reflected in the microhardness distribution in the C1.2 sample ( Figure 4 ). The situation where each layer of AA2519-T62 during cryorolling achieves different strain hardening may be considered a potential technological problem and requires further development of this technology.…”

Elastic-plastic analysis with pre-integrated beam finite element based on state diagrams: Elastic-perfectly plastic flow

“…The inelastic response deeply affects the artefact's final shape after the loading and releasing process [1][2][3]. Metal forming technique, recurrent in stretchbending [4][5][6][7], press-brake bending [8,9] and cold rolling [10,11] processes, is widely applied in ground vehicles and aerospace engineering. As a matter of fact, one of the most difficult challenges is the reliable prediction of spring-back.…”

“…As a matter of fact, one of the most difficult challenges is the reliable prediction of spring-back. An accurate evaluation of it is the focal point of many theoretical and applied research [7,9,[11][12][13]; these brought out that several factors govern the results, such as geometrical constraints, material response and loading history.…”

The Selection of Leveler Parameters Using FEM Simulation

“…As a result of numerical modeling, the leveler setups were selected to match typical industrially available equipment. Also, in [ 26 ], a numerical method for eliminating residual stress by multi-roll leveling based on curvature coupling was discussed. The obtained results show that multi-roller leveling technology will cause rolling residual stress while reducing the initial residual stress of the sheet, and the larger plastic deformation caused by the intermesh of the work rollers at the entry is beneficial for the complete elimination of the initial residual stress, but the rolling residual stress will increase at the same time.…”