Investigation for parametric vibration of rolling mill

The vibration unsteady condition of rolling mill caused by flexural vibration of strip has been investigated. The parametric flexural vibration equation of rolled strip has been established. The parametric flexural vibration stability of rolled strip has been studied and the regions of stability and unstability have been determined based on Floquet theory and perturbation method. The flexural vibration of strip is unstable when the frequency of variable tension is two times as the natural frequency of flexural vibration strip. The characteristic of current in a temp driving motor’s main loop has been studied and tested, it has been proved that there are 6 harmonic component and 12 harmonic component in main loop of driving motor electricity. The vertical vibration of working roller has been tested, the test result approves that the running unsteady is caused by parametric vibration. It attaches importance to the parametric vibration of rolling mill.

Vibration energy harvesting for low frequency using auto-tuning parametric rolling pendulum under exogenous multi-frequency excitations

An electromagnetic parametrically excited rolling pendulum energy harvester with self-tuning mechanisms subject to multi-frequency excitation is proposed and investigated in this paper.The system consists of two uncoupled rolling pendulum.The resonance frequency of each the rolling pendulum can be automatically tuned by adjusting its geometric parameters to access parametric resonance.This harvester can be used to harvest the energy at low frequency.A prototype is developed and evaluated.Its mathematical model is derived.A cam with rolling follower mechanism is employed to generate multi-frequency excitation.An experimental study is conducted to validate the proposed concept.The experimental results are confirmed by the numerical results.The harvester is successfully tuned when the angular velocity of the cam is changed from 1.149 to 1.236 Hz.

Torsional self-excited vibration of rolling mill

The roller’s torsional self excited vibration caused by roller stick slip, and its influence on strip surface quality have been studied. Based on analysis of roller working surface stick slip, roller rotation dynamics equations have been established. The nonlinear sliding frictional resistance has been linearized, and dynamics equations have been solved according to the characteristics of stick and slip between roller and strip. The results show that: 1) with decreasing stick time t 1, torsional vibration wave pattern gradually transforms from serration into sinusoid, and frictional self excited vibration can cover all frequency components which are lower than that of free vibration; 2) stick time t 1 is directly proportional to torque increment Δ M R , and is inversely proportional to live shaft stiffness K and drive shaft rotational velocity ω ; 3) when slip time t 2 is basically steady, the longer the stick time, the larger the energy that system absorbs and discharges. As the slip time is a constant, it easily arouses strip surface shear impact and surface streaks.

Forced transverse vibration of rolls for four-high rolling mill

In order to investigate the forced transverse vibration of rolls under distributed draught pressure and moment of bending roll force,the forced transverse vibration model of rolls for four-high rolling mill was established. The work roll and backup roll were considered as elastic continuous bodies that were joined by a Winkler elastic layer. According to Euler-Bernoulli beam theory,the forced transverse vibration of rolls was analyzed based on modal superposition method. The forced vibration equations were established when the draught pressure and moment of bending roll force were imposed on the rolls respectively. Numerical modeling was made on 2 030 mm cold tandem rolling mill of Baoshan Iron and Steel Company. Simulation results show that when the work roll is only subjected to different forms of draught pressures,the vibration curves of work roll and backup roll are quadratic curves with amplitudes of 0.3 mm and 45 μm,respectively. When only the moments of bending roll force are imposed on the work roll and backup roll,the vibration curves of work roll and backup roll are quadratic curves,and the amplitudes are 5.0 and 1.6 μm,respectively. The influence of moment of bending roll force on the vibration of work roll is related with the bending roll force.

Study on Vertical Vibration Characteristics of the 2-DOF Strip Rolling Mill Model with a Single Weak Defect on the Work Roll Bearing Outer Raceway

Considering the influence caused by a early single pit defect on the outer raceway of the work roll bearing,a 2-DOF plate strip rolling mill vertical vibration model with a single point weak fault on the outer raceway was established.With the practical parameters of the roughing mill of the 1780 hot continuous rolling mill,the vertical vibration characteristics of the rolling mill work roll with different rotating speed and different single pit defect area on the bearing outer raceway are analyzed by numerical simulation.It is found that with the change of the rotation speed of the work roll,different nonlinear vibration behaviors occurred,such as superharmonic resonance,main resonance,com-bined resonance and sub-harmonic resonance.Especially the subharmonic resonance of the work roll is more harmful than the main resonance when the work roll speed is twice the rotation speed corresponding to the first and second natural frequency of the rolling mill.This work provides a theoretical basis for further clarifying the effect caused by a early defect of the work roll bearing on the mill vibration.

Analytical Modeling and Mechanism Analysis of Time-Varying Excitation for Surface Defects in Rolling Element Bearings

Surface defects,including dents,spalls,and cracks,for rolling element bearings are the most common faults in rotating machinery.The accurate model for the time-varying excitation is the basis for the vibration mechanism analysis and fault feature extraction.However,in conventional investigations,this issue is not well and fully addressed from the perspective of theoretical analysis and physical derivation.In this study,an improved analytical model for time-varying displacement excitations(TVDEs)caused by surface defects is theoretically formulated.First and foremost,the physical mechanism for the effect of defect sizes on the physical process of rolling element-defect interaction is revealed.According to the physical interaction mechanism between the rolling element and different types of defects,the relationship between time-varying displacement pulse and defect sizes is further analytically derived.With the obtained time-varying displacement pulse,the dynamic model for the deep groove bearings considering the internal excitation caused by the surface defect is established.The nonlinear vibration responses and fault features induced by surface defects are analyzed using the proposed TVDE model.The results suggest that the presence of surface defects may result in the occurrence of the dual-impulse phenomenon,which can serve as indexes for surface-defect fault diagnosis.

基于ADAMS/Vibration的轧辊磨床测量装置振动特性仿真

研究测量装置的振动特性和抗振性能对提高磨床测量和磨削精度有重要的意义。针对实际振动测试难度较大以及理论分析不确定因素太大等问题,提出了一种将理论与振动仿真测试相结合的方法。利用ADAMS/Vibration软件建立测量装置的振动分析虚拟样机模型,求解系统各阶固有频率和模态主振型以及频率响应,进行自由振动和受迫振动分析,为测量装置的设计与优化提供基础。

Characteristic of Torsional Vibration of Mill Main Drive Excited by Electromechanical Coupling

In the study of electromechanical coupling vibration of mill main drive system, the influence of electrical system on the mechanical transmission is considered generally, however the research for the mechanism of electromechanical interaction is lacked. In order to research the electromechanical coupling resonance of main drive system on the F3 mill in a plant, the cycloconverter and synchronous motor are modeled and simulated by the MTLAB/SIMUL1NK firstly, simulation result show that the current harmonic of the cycloconverter can lead to the pulsating torque of motor output. Then the natural characteristics of the mechanical drive system are calculated by ANSYS, the result show that the modal frequency contains the component which is close to the coupling vibration frequency of 42Hz. According to the simulation result of the mechanical and electrical system, the closed loop feedback model including the two systems are built, and the mechanism analysis of electromechanical coupling presents that there is the interaction between the current harmonic of electrical system and the speed of the mechanical drive system. At last, by building and computing the equivalent nonlinear dynamics model of the mechanical drive system, the dynamic characteristics of system changing with the stiffness, damping coefficient and the electromagnetic torque are obtained. Such electromechanical interaction process is suggested to consider in research of mill vibration, which can induce strong coupling vibration behavior in the rolling mill drive system.

Investigation for Electromechanical Coupling Unstability of Rolling Mill

The unsteady condition of rolling Mill vibration that was caused by flexural vibration of strip was investigated. The parametric flexural vibration equation of rolled strip was established. The parametric flexural vibration stability of rolled strip was studied and region of stability and unstability was determined based on Floquet theory and perturbation method. The flexural-vibration of strip was unstable if the frequency of variable tension was twice as the natural frequency of flexural-vibration strip. The characteristics of electric current in a temp driving motor’s main loop was studied and tested, and approved that there were 6 humorous current ponderance and 12 humorous current ponderance in main circuit of driving motor. Vertical vibration of working roller was tested, the test approved that there were running unsteady caused by parametric vibration. It attached importance to the parametric vibration of rolling mill.

Dynamic characteristics of cold rolling mill and strip based on flatness and thickness control in rolling process

The dynamic model of cold rolling mill based on strip flatness and thickness integrated control was proposed,containing the following sub-models:the rolling process model,the dynamic model of rolls along axial direction,and the compensation model.Based on the rule of volume flow rate,the dynamic rolling process model was built.The work roll and backup roll were taken as elastic continuous bodies,the effect of shear and moment of inertia were taken into consideration,and then the dynamic model of rolls was built.The two models were coupled together,and the dynamic model of rolling mill was built.In the dynamic model,the thermal expansion of the rolls,the wear of the rolls and other related parameters can not be considered.In order to compensate the dynamic model,the coupled static model of rolls and strip was applied.Then,according to the inner relationship of these models,the dynamic model and the compensation model were coupled,and the dynamic model of rolling mill based on the strip flatness and thickness integrated control was built.The dynamic simulation of the rolling process was made,and the dynamic thickness and the dynamic flatness information were obtained.This model not only provides a theory basis for the virtual rolling,but also provides a platform for the application of advanced control theory.

Study on Rolling Mill Gear Box and Design of Multichannel Fault Diagnosis

Gear box places an important role rolling mill.Its reliability decides the machine operation.Due to the important role,if the key machine is broken because of gear box′s malfunction,the whole production devices will be influeued.Therefore,it′s very important to monitor the gear box online.Good monitoring system can help companies to better process fault diagnosis.The design sets up a monitoring system with Enwatch polled mode on-line acquisition module and Odyssey software.By calculating the data,the problem of the monitoring system is find,the plans to collect signal is made,the problems of monitoring gear box′s multichannel vibration are solved and the malfunctions initially are estimated according to the signal,which has theoretical basis and practical meanings.

ROLLING MILL SYSTEM DYNAMIC DESIGN

It is studied how the aluminum foil chatter mark is produced and controlled The stableness of hydraulic AGC system,fluid vibration of capsule system,and electromechanical coupling of AC/AC VVVF system and de coupling are also studied It is shown that rolling mill design should go to system dynamic design from traditional design The framed drawing of system dynamic design program is presented.

Application of dynamic vibration absorber for vertical vibration control of corrugated rolling mill

A variable mass tuned particle absorber is designed for the nonlinear vertical vibration control of the corrugated rolling mill in the composite plate rolling process.Considering the nonlinear damping and nonlinear stiffness between the corrugated interface,a three-degree-of-freedom nonlinear vertical vibration mathematical model of corrugated rolling mill based on dynamic vibration absorber control is established.The multi-scale method is used to solve the amplitude–frequency characteristic curve equation of the installed dynamic vibration absorber(DVA)system.The effects of stiffness coefficient and damping coefficient on the amplitude–frequency characteristic curve are analyzed.The expressions of the dynamic developed factor of the corrugated roll are derived,and the influence laws of mass ratio,frequency ratio and damping ratio on the dynamic amplification factor are analyzed.The optimal parameters of the DVA are obtained by adaptive genetic algorithm.The control effect of the DVA on the nonlinear vertical vibration is studied by numerical simulation.The feasibility of the designed dynamic absorber is verified through experiments.The results show that the designed dynamic absorber can effectively suppress the vertical vibration of the corrugated roller.

Remaining Useful Life Prediction of Rolling Bearings Based on Recurrent Neural Network

In order to acquire the degradation state of rolling bearings and achieve predictive maintenance,this paper proposed a novel Remaining Useful Life(RUL)prediction of rolling bearings based on Long Short Term Memory(LSTM)neural network.The method is divided into two parts:feature extraction and RUL prediction.Firstly,a large number of features are extracted from the original vibration signal.After correlation analysis,the features that can better reflect the degradation trend of rolling bearings are selected as input of prediction model.In the part of RUL prediction,LSTM that making full use of the network’s memory in time is used to improve the accuracy of RUL prediction.The proposed method is validated by life cycle experimental data of bearings,and the RUL prediction results of LSTM model are compared with Support Vector Regression(SVR)and Light Gradient Boosting Machine(LightGBM)models respectively.The results show that the proposed method is more suitable for RUL prediction of rolling bearings.

Vibrations of tandem cold rolling mill: coupled excitation of rolling force and variable stiffness of fault-free back-up roll bearing

Vibration issues of a five-stand tandem cold rolling mill were found in the steel production practice,and the experimental observation and numerical analysis indicated that the vibrations were related to the back-up roll bearing.The results were validated by replacing the back-up roll bearing with the new bearing resulting in 30%decline in vibration amplitude.Models describing the four-row cylindrical roller bearing and the vertical system of the cold rolling mill including the bearing were established.Moreover,the mechanisms of periodic excitation and amplified vibrations of fault-free bearing were explained theoretically,along with the analysis of bifurcation behaviors of the motion states of the roller bearing and rolling mill system.It is found that the energy transmitted between vibrations with different frequencies if multiple excitation frequencies in the rolling mill system were close.

Extended-state-observer-based robust torsional vibration suppression for rolling mill main drive system with input saturation

A robust torsional vibration suppression strategy is proposed for the main drive system of the rolling mill subject to uncertainties,disturbances and input saturation.With given model information incorporated into observer design,an extended state observer that relies only on roller speed measurements is developed to estimate the system states and lumped uncertainties of the rolling mill main drive system.To handle the motor torque saturation,an auxiliary signal system with the same order as the plant is constructed.The error between the control input and plant input is taken as the input of the constructed auxiliary system,and a number of signals are generated to compensate for the effect of the motor torque saturation.Furthermore,a robust output feedback controller is introduced to obtain better transient and steady-state performance of the rolling mill main drive system and the stability of the closed-loop system is strictly proved via Lyapunov theory.Finally,comparative simulations are performed to verify the effectiveness and superiority of the proposed control strategy.

A New Differential Operator Method to Study the Mechanical Vibration

In this paper, we propose a unified differential operator method to study mechanical vibrations, solving inhomogeneous linear ordinary differential equations with constant coefficients. The main advantage of this new method is that the differential operator D in the numerator of the fraction has no effect on input functions (i.e., the derivative operation is removed) because we take the fraction as a whole part in the partial fraction expansion. The method in various variants is widely implemented in related fields in mechanics and engineering. We also point out that the same mistakes in the differential operator method are found in the related references [1-4].

滚子与内圈打滑行为诱导的振动特性

针对滚子打滑试验研究困难的问题,通过分析滚子-内圈运动副的相对运动关系得出运动副振动特征频率的计算公式,在此基础上开展打滑试验,提取滚子纯滚动、打滑状态下的振动信号并采用短时傅里叶变换进行时频域分析,结果表明:滚子打滑会诱发一定的振动响应,其频率与滚子、内圈的转动频率相关,理论计算结果与试验结果较为吻合,可用于测算滚子打滑程度;滚子由纯滚动状态转变为打滑状态或由打滑状态转变为纯滚动状态时,纵向、切向振动的幅值均会发生突变,切向振动信号占主要成分且幅值更大。

建筑结构钢板热轧轧机DBN-PSO振动预报及应用

利用实时监测数据(Real-Time Monitoring Data,RMD)参数分析轧机振动状态,综合运用深度置信网络(Deep Belief Networks,DBN)与粒子群(Particle Swarm Optimization,PSO)算法构建轧机振动仿真模型,实现RMD参数的深度挖掘,并达到轧机振动的预报效果。通过融合处理能够获得非常接近实际振动过程的预测数据,具备优异预测能力。结合现场测试的初始数据预测误差在3.5%范围内,跟轧机振动情况相符。当轧制速率变慢后,振动加速度出现了降低结果;入口张力对轧机的振动加速度具有反向作用;轧机振动加速度相对出口张力表现为正相关特点;以不同宽度的轧件进行测试发现轧机振动加速度保持基本恒定的状态。该研究对提高热轧轧机运行稳定性,对保证建筑结构钢板成形精度具有很好的指导意义,可以拓宽到其它的成形设备优化领域。

非充气轮胎的滚动越障振动仿真分析

采用仿真分析方法探究非充气轮胎的滚动越障振动特性。建立非充气轮胎的有限元模型,对辐条式原始非充气轮胎(简称原始轮胎)和轮辐仿生优化非充气轮胎(简称优化轮胎)的滚动越障振动进行仿真分析,研究滚动速度和障碍物高度对原始轮胎和优化轮胎的径向和纵向振动的影响,以及两种轮胎的振动特性与其滚动越障时接地压力峰值标准差之间的关系。结果表明:越障时滚动速度和障碍物高度的增大会加剧非充气轮胎的径向和纵向振动;与原始轮胎相比,优化轮胎的减振效果主要体现在滚动速度和障碍物高度变化时其振动特性较为平稳;接地压力峰值标准差能够在一定程度上表征非充气轮胎的振动强度。非充气轮胎的滚动越障振动仿真分析为其动态特性研究奠定了一定的理论基础,对提高车辆的稳定性具有重要的意义。