立辊轧机主传动系统扭振的数值分析

由于轧制工艺的改进,某厂立辊轧机主传动系统需要承受更大的轧制力矩.因此该传动系统的强度如何是问题的关键,文中对轧机的传动系统的动态性能进行了分析,为轧机承受重负荷下的安全运行提供了可靠的依据.     

中厚板轧机的同步轴振动模型研究

通过理论和实测相结合的方法,对4200立辊轧机主传动系统进行分支闭合系统的扭振分析.发现了两辊轧制时出现负力矩的原因,结果表明:理论计算与现场测试是一致的.     

含间隙多自由度轧机传动系统非线性扭振动力特性

建立含间隙多自由度轧机传动系统非线性扭振动力学模型,通过坐标变换将非线性方程组解耦成独立方程,采用改进的林滋泰德—庞加莱法(Modified Lindstedt-Poincare,MLP)法求解轧制负载摩擦和外扰激励下非线性系统的解析近似解,并运用MLP法与多尺度法相结合的方法得到该系统的分岔响应方程.采用奇异性理论研究系统在非自治情形下的分岔特性,得到不同参数下系统的分岔形态以及保持轧机稳定振动的参数区域.以某厂1780轧机传动系统为实际算例,将其简化成4自由度非线性扭振模型,通过实际参数分析非线性刚度、间隙量、扰动力矩以及轧制力变化对传动系统扭振幅频响应的影响.其中,扰动力矩与间隙量是影响轧机传动系统扭振的主要因素,通过控制扰动力矩及间隙量可以降低扭振的幅值.研究结果为含间隙的轧机传动系统扭振特性提供一定的理论指导和参考.     

轧机主传动机电耦合扭振系统机理分析及影响因素研究

轧机主传动系统作为传递运动和力矩的主要装置,是一个复杂的机电系统,其机电耦合因素是导致轧机扭振异常变化的重要原因之一。此主要研究轧机主传动系统扭转振动的动力学分析,对比分析不考虑电机与考虑电机反馈的主传动系统扭振,从机理分析机电系统的固有属性;然后建立直流电机驱动下的轧机主传动扭振系统力学模型和数学模型;再采用Matlab/Simulink仿真,对主传动扭振系统失稳状态进行研究,进而分析不确定性参数对轧机主传动系统扭振的影响。研究结果可为进一步揭示轧机扭振系统的振荡规律以及控制策略的制定奠定理论基础。     

轧机主传动位移延时反馈系统自激振动机理研究

在考虑连轧机前后张力差造成的阻力矩基础上,建立了轧机主传动系统位移延时反馈自激振动模型.分析了由稳定过渡到不稳定的一种中间极限状态,即产生等幅振动的可能性,可知位移延时反馈等价于位移与速度同时反馈,它同时改变了系统的阻尼与刚度,并分析了轧制参数对轧机主传动位移延时反馈系统稳定性的影响.进行了变速轧制防止轧机主传动系统位移延时反馈自激振动的理论分析,仿真结果表明了变速防振方法的有效性.     

轧机主传动系统强非线性扭振研究

建立含非线性刚度的两自由度轧机主传动系统扭振模型,通过参数代换得到该系统的强非线性动力学方程。应用能量迭代法得出系统存在主振动和亚谐振动周期解的必要条件,并求解此二阶强非线性非自治系统的频响函数及解析近似解。以某厂3800轧机主传动系统为例,利用数值仿真研究了非线性刚度、线性阻尼、扰动力矩对系统主振动和1/3次亚谐振动幅频特性的影响规律。研究结果为分析此类含非线性刚度的轧机主传动系统扭振特性提供一定的理论指导和参考。     

轧机主传动位移延时反馈系统的Hopf分岔研究

在考虑轧机前后张力差造成的阻力矩基础上,针对传统轧机主传动系统模型忽略位移延时的缺点,建立了轧机主传动位移延时反馈系统的数学模型。分析了系统的局部稳定性和Hopf分岔的存在性,从理论上得到了延时临界值,并通过实验仿真得出的时间历程图、相图以及分岔图验证了当延时等于临界值时,轧机主传动位移延时反馈系统确实产生了Hopf分岔,从而得出了从生产工艺的角度加大轧制速度可以避免延时产生的不良影响,为进一步研究、控制轧机主传动系统提供了新思路。     

未知扰动下冷轧机扭振自适应预定性能控制

轧机振动一直是板带材轧制生产中普遍存在并难于解决的问题.针对冷轧机主传动系统由于外界不确定性扰动导致的扭振问题,提出一种自适应预定性能控制策略,有效抑制了轧机主传动系统的扭转振动.基于拉格朗日动力学方程,考虑刚度、摩擦及电动机死区等非线性特性和外界不确定性扰动对轧机主传动系统的影响,建立具有下三角结构的轧机主传动系统模型.针对该不确定性非线性模型设计一种自适应预定性能控制器(Adaptive prescribed performance controller,APPC),并利用Lyapunov稳定性理论对所设计的控制器进行严格的理论证明,得出系统的有界稳定性.针对某厂2 030 mm冷连轧机主传动系统进行Matlab数值仿真分析,试验结果表明轧辊转速跟踪误差被严格地限制在预定域内,有效避免了扭振现象的产生.通过性能函数的引入,为轧机的扭转振动问题提供了一种有效的控制策略.     

轧钢机主传动系统扭振故障分析

在测量和计算了产生轧钢机主传动系统扭振故障的轧制力矩基础上，分析了引起轧钢机主传动系统扭振的原因；设计了扭振监测、诊断和控制系统，这个系统在钢铁企业的应用取得了令人满意的效果。     

基于动态轧制力的轧机垂扭耦合系统非线性振动机理研究

针对轧机垂扭耦合系统非线性振动机理研究还不完善的问题,考虑轧辊与轧件间动态轧制力因素影响,建立了垂直振动系统和主传动系统的动态轧制力模型。在此基础上,考虑轧辊摩擦力的动态分量,建立了基于动态轧制力的轧机二自由度垂扭耦合振动系统模型。利用相平面法和Poincare映射方法分析了垂直振动系统发生主共振的情况下,垂直振动系统的线性阻尼、外扰力和主传动系统的线性阻尼变化对轧机垂扭耦合振动的影响。研究结果表明当参数变化时系统呈现周期运动、准周期运动和混沌运动等多种运动状态,可通过调整参数值避免系统产生混沌现象,提高系统的稳定性。分析结果为工程中解决轧机垂扭耦合系统的振动问题提供了一种参考。     

芯辊进给速度对环件冷轧工艺的影响规律

环件冷轧是一种先进的塑性加工工艺,而其中芯辊的进给速度对环件冷轧工艺有重要影响。本文针对环件冷轧工艺的特点,以数值仿真法为主要研究方法,以有限元分析软件ABAQUS为平台,利用弹塑性动态显式有限元法对环件冷轧变形过程进行了三维数值模拟,研究揭示了矩形截面环件开式冷轧工艺中总压下量不变时芯辊进给速度对轧制力、轧制力矩和环件轴向宽展的影响规律,并分析了进给速度与环件咬入之间的关系。结果表明:进给速度相对较小时,环件的宽展以及鱼尾形状系数随进给速度的增大而急剧减小,端面变得平整;当进给速度进一步增大时,环件宽展以及鱼尾形状系数变化不大;进给速度对鱼尾形状系数的影响主要取决于进给速度对环件外层附近金属的轴向流动的影响;随着芯辊进给速度的增大,轧制力和轧制力矩也相应增大,因此对轧环机力能参数的要求也提高;芯辊进给速度的增大不利于环件的咬入。     

An upper bound method for analysis of three-dimensional deformation in the flat rolling of bars

A new upper bound method for the analysis of three-dimensional deformation in the flat rolling of bars is proposed. In the conventional upper bound method, stress distribution is not calculated. Hence, a new method of calculating stress distribution is proposed in which the hydrostatic stress in each element and the contact stress on the contact surface between material and roll in each element are calculated. In the conventional upper bound method, the structure of the computer program also depends highly on the kinematically admissible velocity fields assumed. Hence, a new method of analysis in which the structure of the computer program depends minimally on the kinematically admissible velocity fields assumed is proposed. In the analysis of strip rolling, the calculated roll force and roll torque agree with the roll force and roll torque calculated from Sims’ slab method. In the analysis of the flat rolling of bars, the calculated width spread agrees with the width spread obtained by experiments reported in the literature. The effects of a reduction in thickness, roll radius, material width-to-height ratio, front tension, back tension, and front and back tensions on the width spread, forward slip, roll force and roll torque are demonstrated. Hence, the validity of the new upper bound method is confirmed.     

An application of fuzzy inference for studying the dependency of roll force and roll torque on process variables in cold flat rolling

In this work, the roll force and roll torque in a cold flat rolling process are modelled using first order Takagi–Sugeno fuzzy models. The fuzzy models predict the most likely lower and upper estimates of the roll force and roll torque. Although the fuzzy models can be based on the experimental data, in the present work, the required data is generated by radial basis function neural networks. The neural networks, in turn, are trained by a finite element method-based code. It is demonstrated that the coefficients of the linear crisp function used to represent the output variables in the fuzzy inference system can be used for assessing the sensitivity of these variables with respect to the process variables. An algorithm to detect and suppress the outliers in the data is proposed. The effectiveness of the proposed algorithm is demonstrated through an example.     

Flow and stresses in round–oval–round roll pass sequence

Analysis of flow and stresses in isothermal steady-state round–oval–round pass sequence for the production of round bars has been obtained from a flowline field solution. The velocity, strain-rate and stress components are derived from kinematic and static considerations together with the material constitutive law and friction boundary conditions. The results obtained show that the roll pressure and friction shear traction at the roll interface are fairly uniform and the normalized average roll pressure and friction shear factor have lower values than those for flat bar rolling at the same rolling conditions. Small variations in the rolls clearance gap have no appreciable effect on the roll load and torque. Increasing friction causes a significant increase in the roll load and torque. The analysis predicts pass grooves’ dimensions, roll load and torque for different values of height reductions.     

A comparison of methods to estimate the roll torque in thin strip rolling

An energy balance method is used to calculate the roll torque associated with non-circular thin strip rolling and the results for the torque are compared with the moments of the forces exerted on the roll by the strip. An example is given in which the results of the two methods are quite different. This probably indicates that the axis of the roll is not at the point about which the moment is taken. The energy balance method is also used to estimate the torque associated with circular arc rolling. The results are compared with those calculated with Hill's formula in one example and, in another example, the comparison is made between the results from the energy method formulated in this paper and a commercial package which also uses both an energy method and Hill's formula.     

基于能量法的分布式驱动电动汽车防侧翻控制

分布式驱动电动汽车具有优越的侧倾稳定性控制功能,但基于横向载荷转移率评价进行控制并不能充分发挥其技术优势。为提升该类车型恶劣工况下的防侧翻控制能力,针对当前侧翻评价指标的不足,开展基于能量转化评价的稳定性控制研究。针对该类车型的结构特点,建立车辆系统坐标系,借助欧拉旋转角法推导了整车在侧翻运动过程中动能、势能和耗散能的表达方程;通过计算车辆失稳能量阈值与车辆实时失稳能量,提出综合多因素的车辆稳定性评价指标;基于侧翻动力学模型设计出防侧翻滑模控制器;通过在分布式驱动系统力矩阈值范围内开展基于驱动轮力矩分配的差动驱动,实现了整车的防侧翻控制。研究表明,基于能量法制定的空间失稳评价指标相较于横向载荷转移率而言,更能准确、灵敏地反映整车侧倾运动状态的变化趋势,基于其设计的防侧翻控制方法通过主动分配两侧驱动力矩,削弱了相关能量转化,有效抑制了整车侧倾运动,显著提高了侧倾稳定性。     

An approximate method for a three-dimensional analysis of rolling

A theory, based on the extremum principle for rigid perfectly plastic materials, is given for the analysis of three-dimensional deformation in rolling. Theoretical solutions are obtained for single-pass rolling in terms of sideways spread, roll torque and the location of neutral points. The results on spread and roll torque showed excellent agreement with those found by experiments in the literature.     

汽车独立悬架后桥悬置系统设计方法研究

基于汽车独立悬架后桥(ISRA)悬置系统6自由度振动分析模型,分别给出了其固有频率和能量分布的设计要求及其在零转动、静态转动和动态转动工况下的设计要求,并提出了ISRA悬置系统的优化设计方法。在绕扭矩轴的扭矩激励下,优化得到各悬置静刚度的设计值,分别计算了ISRA悬置系统的固有频率和能量分布,零转动工况下后桥质心、质心坐标系Ya轴上一点的位移及各悬置的垂向位移和垂向动反力,静态转动工况下后桥质心和扭矩轴上一点的位移。研究结果表明：利用所提方法设计的ISRA悬置系统可以满足设计要求,对后桥悬置系统设计具有参考作用。     

基于AT89S52的车轮瞬时功率测量方法研究

研究测量工程机械车轮瞬时功率的一种新方法,对滚筒转速、扭矩以及转角加速度进行测量,降低了力矩不平衡对测量精度的影响;采用AT89S52单片机对JC传感器采集的转速与扭矩脉冲信号进行测量与分析,并通过RS-232送至工控机,减小了力矩不平衡给功率测量带来的误差,对车辆动力性能和柴油车加载减速工况检测有参考价值.     

Analyses for roll force and torque in ring rolling, with some supporting experiments

Analyses are developed for predicting roll force and torque during ring rolling between plain cylindrical rolls. A nomograph is given to allow easy application of the theory. Conventional analyses for flat rolling are not generally appropriate to ring rolling, whereas the present theory considers the particular roll geometry and rolling conditions encountered in the process.Measurements of roll force and torque, taken during ring rolling experiments, are shown to be in good agreement with the theoretical predictions. The experiments are carried out on a new experimental mill having a mandrel which retracts axially for loading and unloading the ring, and is symmetrically supported between roller bearings within a four-column frame during rolling. This arrangement is believed to offer certain advantages over most commercial machines.