Shen Wang

Background: Shakedown occurs in elastoplastic bodies subject to cyclic loading when limited plastic deformation in the early stages of cycling gives rise to residual stresses that arrest the plastic response. As a result, purely elastic behavior is recovered upon further load cycling. Objective: This paper outlines a new procedure for identifying macroscopic shakedown responses using minimal kinematic measurements from digital image correlation and a purely elastic finite element model. Method: In contrast to traditional shakedown detection methods that track the evolution of total or equivalent plastic strains upon cycling, the proposed approach obviates assumptions about the inelastic nature of the constituent material of interest altogether. The proposed approach is inspired by Melan’s static lower bound shakedown theorem and it offers advantages in terms of computational and experimental effort, providing robustness against material uncertainties, and flexibility for a variety of applications. Results: The approach is demonstrated on aluminum metamaterial sheets that are auxetic due to their arrangement of periodic perforations. In the demonstration, a set of uniaxial experiments at room temperature are analyzed where a range of cyclic stress amplitudes are imposed at non-zero mean stresses. Conclusions: The proposed shakedown determination protocol was verified by comparing with traditional methods that track the incremental evolution of equivalent plastic strain. The new procedure provides a rapid and robust approach that is suitable for high-throughput experimentation. Graphical On Detecting Elastoplastic Shakedown Using Minimal Digital Image Correlation Results and an Elastic Model: Demonstration for AA6061 Auxetic Sheets

Vibration in hot tandem rolling mills has been a problem in the iron and steel industry mainly due to its unpredictability. In this work, vibration data of the second finishing mill (F2) stand of a hot tandem rolling mill are collected and analyzed, and a mathematical model based on the coupling of a non-uniform deformation process, mill structure and hydraulic control system is constructed. The influence of different inlet thickness fluctuation forms, structural parameters and control parameters on the vibration behavior is analyzed. It is concluded that the low-frequency thickness fluctuation with additional skewness can cause the resonance of each subsystem of the rolling mill. The deviation angle of the roll system influences the vibration harmonic output of the rolling mill under a single low-frequency thickness fluctuation excitation. The compensation parameter in the thickness control system affects the natural frequency of the vertical system.

The operation of the world’s first multimode continuous casting and rolling F3 (3rd finishing mill stand) finishing mill was hampered by frequent vibrations. Mill vibrations were found to be caused by the transmission and coupling of vibration energy flow. In this study, an overall finite element model of the F3 stand is established based on the structural sound intensity method and harmonic response analysis method, and then, the intrinsic energy flow modes and energy flow harmonic response of the F3 stand are obtained. Further, the effects of the steady-state rolling force variation, preload torque variation, rolling force fluctuation, torque fluctuation, and its phase angle difference on the vibration energy flow of the mill are analyzed. Finally, the effects of the mill damping ratio, strip width, and strip modulus on the vibration energy flow under double dynamic load are discussed to reveal the inherent characteristics of the mill vibration energy flow. The results show that the vibration energy flow of the mill increases with the increase of strip modulus, rolling force, and moment fluctuation; the phase angle difference of rolling moment shows a “V” trend change on the vibration energy flow; the change of strip width has a greater effect on the vibration energy flow of the vertical system; and for the damping ratio of 0.01–0.1, the reduction of the vibration energy flow at all excitation frequencies is obvious.

The vibration of the vertical system of a cold rolling mill is a major concern for factory production. In factory production, it is found that the thickness control system with dynamic stiffness compensation of the rolling mill has a significant impact on the rolling mill vibration. In this work, a mechanical hydraulic coupling vibration model of a cold rolling mill with a thickness control system with dynamic stiffness compensation was established. MATLAB/Simulink was used to simulate and analyze the vibration response characteristics of the mechanical structure of the rolling mill and mechanical hydraulic coupling system considering the dynamic stiffness compensation control mode and position control mode of the upper cylinder. We found that the control system changed the vibration response of the mechanical structure, and different control modes have different effects on the vibration response curve. When the rolling mill works in the vibration area, the thickness difference at the strip steel outlet would be larger. Considering the rolling mill vibration and strip surface quality, the excitation of the strip inlet thickness can be achieved by adjusting the dynamic stiffness compensation system and changing the rolling speed reasonably to achieve good vibration suppression and control effects.