Coupled dynamic modeling of rolls model and metal model for four high mill based on strip crown control

The crown is a key quality index of strip and plate,the rolling mill system is a complex nonlinear system,the strip qualities are directly affected by the dynamic characteristics of the rolling mil.At present,the studies about the dynamic modeling of the rolling mill system mainly focus on the dynamic simulation for the strip thickness control system,the dynamic characteristics of the strip along the width direction and that of the rolls along axial direction are not considered.In order to study the dynamic changes of strip crown in the rolling process,the dynamic simulation model based on strip crown control is established.The work roll and backup roll are considered as elastic continuous bodies and the work roll and backup roll are joined by a Winkler elastic layer.The rolls are considered as double freely supported beams.The change rate of roll gap is taken into consideration in the metal deformation,based on the principle of dynamic conservation of material flow,the two dimensional dynamic model of metal is established.The model of metal deformation provides exciting force for the rolls dynamic model,and the rolls dynamic model and metal deformation model couple together.Then,based on the two models,the dynamic model of rolling mill system based on strip crown control is established.The Newmark-β method is used to solve the problem,and the dynamic changes of these parameters are obtained as follows:(1) The bending of work roll and backup roll changes with time;(2) The strip crown changes with time;(3) The distribution of rolling force changes with time.Take some cold tandem rolling mill as subject investigated,simulation results and the comparisons with experimental results show that the dynamic model built is rational and correct.The proposed research provides effective theory for optimization of device and technological parameters and development of new technology,plays an important role to improve the strip control precision and strip shape quality.     

PROFILE AND FLATNESS CONTROL SYSTEM IN 1 700 mm HOT STRIP MILLS OF ANSTEEL

Varying contact-length backup roll and linearly variable crown work roll are provided for improving the mill performance of profile and flatness control. Integrated with theses technologies, relevant profile and flatness control models are developed for hot strip mills on the basis of large amount of finite element calculation. These models include shape setup control model in process control system, bending force feedforward control model, crown feedback control model and flatness feedback control model in basis automation system. Such a profile and flatness control system with full functions is applied in 1 700 mm industrial hot strip mills of Ansteel. Large amount of production data shows that the crown precision with the tolerance of±18 μm is over 90%, the strip percentage which the actual flatness is within ±25 I-unit surpasses 96%, and general roll consume is reduced by 28% by using the profile and fiatness control system. In addition, schedule-free rolling is realized.     

Modeling,Simulation and Experiment of Electro-hydraulic Screw Down Servo System of Seamless Tube Rolling Mill

Electro-hydraulic screw down servo system(HSDS) is widely used in seamless tube rolling mill in western companies.But in Chinese companies,mechanical screw down system(MSDS) is popularly equipped and has a serious disadvantage that the roller would often be locked when it is overloaded.For the purpose of designing the first set of domestic twin-roller,four-cylinder and six-framework electro-hydraulic HSDS of seamless tube rolling mill,an experiment system that can simulate the process of seamless tube rolling is constructed.A digital simulation model of the experiment system is built with AMESim software and validated by comparing the simulation results with experiment results.The sudden load response of the screw piston position is studied with the built model and the experiment system.To improve the HSDS’s positioning accuracy with large load,a hybrid control scheme of combining load disturbance feedforward compensation(LDFC) method based on servo valve’s pressure-stroke feature and anti-saturation integral control(ASIC) is proposed.Both results of simulation and experiment indicate that the transient response time of the single-roller HSDS with the proposed scheme decreases from 0.65 s to less than 0.2 s without static error.To improve the system dynamic stiffness and production qualified rate,a flow rate feedforward compensation(FFC) control strategy based on oil compressibility to dynamic position error is proposed.This FFC strategy is validated with experiments in which the transient error caused by sudden load is reduced to less than 25% of that without FFC.By extending the simulation model to HSDS of a twin-roller,four-cylinder rolling mill,analyzing the mill deformation,and applying the LDFC,ASIC and FFC to the HSDS,the dynamic performance and positioning accuracy of compensated multi-roller HSDS at biting moment are predicted.The research results provide a theoretical and experimental basis for the design of HSDS of seamless steel tube rolling mill.     

SENSITIVITY ANALYSIS FOR ROLLING PROCESS BASED ON SUPPORT VECTOR MACHINE

A method for the calculation of the sensitivity factors of the rolling process has been obtained by differentiating the roll force model based on support vector machine. It can eliminate the algebraic loop of the analytical model of the rolling process. The simulations in the first stand of five stand cold tandem rolling mill indicate that the calculation for sensitivities by this proposed method can obtain a good accuracy, and an appropriate adjustment on the control variables determined directly by the sensitivity has an excellent compensation accuracy. Moreover, the roll gap has larger effect on the exit thickness than both front tension and back tension, and it is more efficient to select the roll gap as the control variable of the thickness control system in the first stand.     

Research and application of non-symmetrical roll bending control of cold rolling mill

The existing research of the flatness control for strip cold rolling mainly focuses on the calculation of the optimum adjustment of individual flatness actuator in accordance with the flatness deviation,which can be used for general flatness control.However,it does not work for some special rolling processes,such as the elimination of ultra single side edge-waves and the prevention of strip break due to tilting roll control overshooting.For the purpose of solving these problems,the influences of non-symmetrical work roll bending and intermediate roll bending on flatness control were analyzed by studying efficiencies of them.Moreover,impacts of two kinds of non-symmetrical roll bending control on the pressure distribution between rolls were studied theoretically.A non-symmetrical work roll bending model was developed by theoretical analysis in accordance with practical conditions.The model was applied to the revamp of a 1250 6-H reversible universal crown mill (UCM) cold mill.Theoretical study and practical applications show that the coordination utilization of the non-symmetrical work roll bending control and tilting roll control was effective in flatness control when there appeared bad strip single side edge waves,especially when the incoming strip was with a wedge shape.In addition,the risk of strip break due to tilting control overshooting could be reduced.Furthermore,the non-symmetrical roll bending control can reduce the extent of uneven distribution of pressure between rolls caused by intermediate roll shifting in flatness control and slow down roll wear.The non-symmetrical roll bending control technology has important theoretical and practical significance to better flatness control.     

CAD/CAE OF THE WORKING CHARACTERISTICS OF A NEW TYPE OF FLUID COUPLING SHOCK ABSORBER

For purpose of simulation of the working characteristics of a new type of fluid coupling shock absorber for vibration protection of sensitive equipment, a physical model is presented by analyzing the internal fluid dynamic phenomenon with respect to the coupling shock absorber and implemented in MATLAB software package. Using the model it is possible to evaluate the importance of different factors for design of the shock absorber. In the meantime, the key-model machine is designed for coupling dynamic test. Comparisons with experimental results confirm the validity of the model. So the CAD/CAE software has been developed in MATLAB for design and experimental test of the new coupling shock absorber.     

Thermodynamic Behavior Research Analysis of Twin-roll Casting Lead Alloy Strip Process

The thermodynamic behavior of twin-roll casting(TRC) lead alloy strip process directly affects the forming of the lead strip, the quality of the lead strip and the production efficiency. However, there is little research on the thermodynamics of lead alloy strip at home and abroad. The TRC lead process is studied in four parameters: the pouring temperature of molten lead,the depth of molten pool, the roll casting speed, and the rolling thickness of continuous casting. Firstly, the thermodynamic model for TRC lead process is built.Secondly, the thermodynamic behavior of the TRC process is simulated with the use of Fluent. Through the thermodynamics research and analysis, the process parameters of cast rolling lead strip can be obtained: the pouring temperature of molten lead: 360–400 °C, the depth of molten pool: 250–300 mm, the roll casting speed: 2.5–3 m/min, the rolling thickness: 8–9 mm.Based on the above process parameters, the optimal parameters(the pouring temperature of molten lead:375–390 °C, the depth of molten pool: 285–300 mm, the roll casting speed: 2.75–3 m/min, the rolling thickness:8.5–9 mm) can be gained with the use of the orthogonal experiment. Finally, the engineering test of TRC lead alloy strip is carried out and the test proves the thermodynamic model is scientific, necessary and correct. In this paper, a detailed study on the thermodynamic behavior of lead alloy strip is carried out and the process parameters of lead strip forming are obtained through the research, which provide an effective theoretical guide for TRC lead alloy strip process.     

Nonlinear Dynamic Modeling for a Diesel Engine Propeller Shafting Used in Large Marines

Longitudinal vibration,torsional vibration and their coupled vibration are the main vibration modes of the crankshaft-sliding bearing system.However,these vibrations of the propeller-crankshaft-sliding bearing system generated by the fluid exciting force on the propeller are much more complex.Currently,the torsional and longitudinal vibrations have been studied separately while the research on their coupled vibration is few,and the influence of the propeller structure to dynamic characteristics of a crankshaft has not been studied yet.In order to describe the dynamic properties of a crankshaft accurately,a nonlinear dynamic model is proposed taking the effect of torsional-longitudinal coupling and the variable inertia of propeller,connecting rod and piston into account.Numerical simulation cases are carried out to calculate the response data of the system in time and frequency domains under the working speed and over-speed,respectively.Results of vibration analysis of the propeller and crankshaft system coupled in torsional and longitudinal direction indicate that the system dynamic behaviors are relatively complicated especially in the components of the frequency response.For example,the 4 times of an exciting frequency acting on the propeller by fluid appears at 130 r/min,while not yield at 105 r/min.While the possible abnormal vibration at over-speed just needs to be vigilant.So when designing the propeller shafting used in marine diesel engines,strength calculation and vibration analysis based only on linear model may cause great errors and the proposed research provides some references to design diesel engine propeller shafting used in large marines.     

Three-dimensional modeling for predicting the vibration modes of twin ball screw driving table

As a redundant drive mechanism, twin ball screw feed system has the advantage of high stiffness and little yaw vibration in the feeding process, while leads to increased difficulty with vibration characteristics analysis and structure optimization. Only low-dimensional structure and dynamics parameters are considered in the existing research, the complete and effective model for predicting the table＇s vibrations is lacked. A three-dimensional（3D） mechanical model of twin ball screw driving table is proposed. In order to predict the vibration modes of the table quantitatively, an analytical formulation following a comprehensive approach is developed, where the drive system is modeled as a lumped mass-spring system, and the Lagrangian method is used to obtain the table＇s independent and coupled axial, yaw, and pitch vibration modes. The frequency variation of each mode is studied for different heights of the center of gravity, nut positions and table masses by numerical simulations. Modal experiment is carried out on the Z-axis feed table of the horizontal machining center MCH63. The results show that for each mode, the error between the estimated and the measured frequencies is less than 13%. The independent and coupled vibration modes are in accordance with the experimental results, respectively The proposed work can serve a better understanding of the table＇s dynamics and be beneficial for optimizing the structure parameters of twin ball screw drive system in the design stage.     

ANALYSIS OF ROLL SYSTEM STABILITY ABOUT ALUMINUM FOIL MILLS

To improve roll system stability of aluminum foil mills, roll system stability of 2200 highspeed aluminum foil mill is analyzed with energy stable method. Two different restrictive conditions which gaps between chock of work roll and window of stand whether exist or not, are studied respectively. A new concept of roll system with open /closed compound pair conies up with as well for re-newably synthesizing restrictive mechanism of aluminum foil mills' chock. Through these studies, the conflict, whether reserving the gap for the roller replacement or eliminating the gap for roller's normal work, is successfully settled. This concept and analyzed result give the actual mechanism with open/closed compound restriction and the method of realizing high-speed rolling and prolonging longevity of end thrust bearing on work roll. It has important theoretical meaning and engineering value for modern technical reform of aluminum foil mills and plate strip mills.     

ENGINEERING CHARACTERISTICS AND ITS MECHANISM EXPLANATION OF VIBRATORY SYNCHRONIZATION TRANSMISSION

Vibratory synchronization transmission (VST) is a kind of special physical phenomenon ininertia vibration mechanical systems. For an inertia vibration mechancal system driven by one pair ofmotors runs in step, even the power supply of one motor is cut off, the motor can continue to keeprotating state under the vibration exciting of the machine body driven by only one other motor. And itsrotating frequency will be the same as that of the other one. The transient process of this wonderfulphysical phenomenon has not been described quantitatively according to current-existing mechanicalmodels. On the basis of investigation of the engineering characteristics of VST, a mechanical and elec-trical coupling mathematical model of a two-shaft inertia vibration machine is established. With thismodel, the transient process of VST is recurred quantitatively and successfully, and a reasonable ex-planation is given.     

VIBRATION MEASUREMENT OF DOUBLE-ENDED TUNING FORKS RESONATOR

To enhance the coherence and reliability of the double-ended tuning fork (DETF) resonator, a measurement system of resonator vibration is presented to check its dynamic characteristics. Laser Doppler techniques are utilized and the relation between DETF vibration velocity and output current of photodetector is obtained. Resonator vibration equation is also analyzed and its driving power only depends on the direct current bias voltage and the amplitude of alternative voltage. Furthermore, a special resonator driving control circuit based on measurement is designed. The amplitude and frequency of circuit is controlled by a computer so that highly stable and strong driving signal can be output. Experiments on driving and measuring double-ended tuning fork have been done. The frequency of driving signal is 8 kHz and the peak-to-peak value of driving voltage is 140 V. Experimental results indicate resonator can be drived stably by driving control circuit and dynamic characteristics of DETF may be measured in real time.     

RESEARCH ON MODELING AND CHARACTERISTICS OF THE SPINDLE DYNAMIC COUPLING ABSORBERING SYSTEM OF A SUPER－PRECISION SURFACE GRINDING MACHINE

The bearing is described by constrain matrix, and the spindle system of a NC surface grinding machine is simplified as elastic-coupling beam, then modal synthesis method is used to establish the dynamic model of beam. Moreover, the response of the end of rotor is analyzed, and the natural frequency, principle mode and other dynamic characteristics of the coupling system are studied, the law of bearing stiffness to coupling frequency and amplitude of rotor is also found. Finally, according to the actual condition, a dynamic absorber is designed. The simulation and experimental results show that the amplitude of spindle can be declined effectively when the dynamic absorber is attached.     

Influence of vehicle parameters on critical hunting speed based on Ruzicka model

While introducing foreign advanced technology and cooperating with Chinese famous research institutes,the high-speed vehicles are designed and take the major task of passenger transport in China.In high-speed vehicle,the characteristic of shock absorber is an important parameter which determines overall behavior of the vehicle.The most existing researches neglect the influence of the series stiffness of the shock absorber on the vehicle dynamic behavior and have one-sided views on the equivalent conicity of wheel tread.In this paper,a high speed passenger vehicle in China is modeled to investigate the effect of the parameters taking series hydraulic shock absorber stiffness into consideration on Ruzicka model.Using the vehicle dynamic model,the effect of main suspension parameters on critical speed is studied.In order to verify the reasonableness of shock absorber parameter settings,vibration isolation characteristics are calculated and the relationship between suspension parameters and the vehicle critical hunting speed is studied.To study the influence of equivalent conicity on vehicle dynamic behavior,a series of wheel treads with different conicities are set and the vehicle critical hunting speeds with different wheel treads are calculated.The discipline between the equivalent conicity of wheel tread and critical speed are obtained in vehicle nonlinear system.The research results show that the critical speed of vehicle much depends on wheelset positioning stiffness and anti-hunting motion damper,and the series stiffness produces notable effect on the vehicle dynamic behavior.The critical speed has a peak value with the equivalent conicity increasing,which is different from the traditional opinion in which the critical speed will decrease with the conicity increasing.The relationship between critical speed and conicity of wheel tread is effected by the suspension parameters of the vehicle.The study results obtained offer a method and useful data to designing the parameters of the high speed vehicle and simulation study.     

Dynamic Feedforward Control of a Novel 3-PSP 3-DOF Parallel Manipulator

Parallel manipulators with less than six degrees of freedom (DOF) have been increasingly used in high-speed hybrid machine tools. The structural features of parallel manipulators are dynamic, a characteristic that is particularly significant when these manipulators are used in high-speed machine tools. However, normal kinematic control method cannot satisfy the requirements of the control system. Many researchers use model-based dynamic control methods, such as the dynamic feedforward control method. However, these methods are rarely used in hybrid machine tools because of the complex dynamic model of the parallel manipulator. In order to study the dynamic control method of parallel manipulators, the dynamic feedforward control method is used in the dynamic control system of a 3-PSP (prismatic-spherical-prismatic) 3-DOF spatial parallel manipulator used as a spindle head in a high-speed hybrid machine tool. Using kinematic analysis as basis and the Newton-Euler method, we derive the dynamic model of the parallel manipulator. Furthermore, a model-based dynamic feedforward control system consisting of both kinematic control and dynamic control subsystems is established. The dynamic control subsystem consists of two modules. One is used to eliminate the influence of the dynamic characteristics of high-speed movement, and the other is used to eliminate the dynamic disturbances in the milling process. Finally, the simulation model of the dynamic feedforward control system of the 3-PSP parallel manipulator is constructed in Matlab/Simulink. The simulations of the control system eliminating the influence of the dynamic characteristics and dynamic disturbances are conducted. A comparative study between the simulations and the normal kinematic control method is also presented.The simulations prove that the dynamic feedforward control method effectively eliminates the influence of the dynamic disturbances and dynamic characteristics of the parallel manipulator on high-speed machine tools, and significantly improves the trajectory accuracy. This is the first attempt to introduce the dynamic feedfordward control method into the 3-PSP spatial parallel manipulator whose dynamic model is complex and provides a study basis for the real-time dynamic control of the high-speed hybrid machine tools.     

VISUAL SIMULATION OF COLD ROLL-FORMING BASED ON OBJECT ORIENTED PROGRAMMING

To simulate the process of cold roll-forming process, a new method is adopted. The theoretical foundation of this method is an elastic-plastic large deformation spline finite strip method based on object-oriented programming. Combined with the computer graphics technology, the visual simulation of cold roll-forming is completed and the system is established. By analyzing common channel steel, the process is shown and explained including theory method, model and result display. So the simulation system is already a kind of mature and effective tool to analyze the process of cold roll forming.     

RECYTRACK Project： Elastomeric Eco-friendly Material Based on End-of-Life Tires Blended with Organic Bind Resin for Railway Applications

RECYTRACK is a 3.5 year project granted by the European Commission through LIFE＋ 2010 program. The overall objective of the project is to demonstrate the environmental benefits and technical feasibility of the implementation of an elastomeric eco-friendly material made of end-of-life tires with resin for railway applications. Within the project, AV Ingenieros jointly with LEAM, carries out the study of the vibration behavior of the eco-friendly material, which will be applied as a mat for ballasted tracks as well as an isolated block system for slab tracks. Firstly, an analytical model capable to predict the efficiency of the eco-friendly material as a vibration mitigation measure has been developed. Subsequently, and after the implementation of the eco-friendly solutions in real railway infrastructures, its vibration behavior will be measured and validated through in situ measurements during regular service. In this paper the analytical model is defined, the elastomeric material dynamic experimental characterization is described and the under ballast mat Insertion Loss is calculated for two different soil stiffness.     

ROLLING MILL SYSTEM DYNAMIC DESIGN

0 INTRODUCTIONRolling mill system is comped of the maindriving system, screw dOwns system, tension andvelocity system, lubrication and cold system, elasticityand plasticity deformation system for rolls andblank. It is a mechanic, electric fluid and complicatedmultiunit by system.The problem of producedquality,equipment broken and low efficiency can notbe solved by traditional design, the rolling mill designshOuld go to system dynamic design from traditionaIdedgn in order to produce more …     

Technology and experiments of 42CrMo bearing ring forming based on casting ring blank

Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named ＂casting-rolling compound forming technology＂ is researched by taking the typical 42CrMo slew bearing as object. Through theoretical analysis, the design criteria of the main casting-rolling forming parameters are put forward at first. Then the constitutive relationship model of as-cast 42CrMo steel and its mathematical model of dynamic recrystallization are obtained according to the results of the hot compression experiment. By a coupled thermal-mechanical finite element model for radial-axial rolling of bearing ring, the fraction of dynamic recrystallization is calculated and recrystallized grains size are predicated. Meanwhile, the effects of the initial rolling temperature and feed rate of idle roll on material microstructure evolution are analyzed. Finally, the industrial rolling experiment is designed and performed, based on the simulation results. In addition, mechanical and metallographic tests are conducted on rolled bearing ring to get the mechanical parameters and metallographic structure. The experimental data and results show that the mechanical properties of bearing ring produced by casting-rolling compound forming technology are up to industrial standard, and a qualified bearing ring can be successfully formed by employing this new technology. Through the study, a process of forming large bearing ring directly by using casting ring blank is obtained, which could provide an effective theoretical guidance for manufacturing large ring parts. It also has an edge in saving material, lowering energy and improving efficiency.