A K Tieu

Finite element simulation of cold rolling of thin strip

Abstract In this work, the authors use a full 3D rigid plastic finite element method (FEM) to simulate the thin strip rolling taking into account the modelling of friction variation in the roll bite. A comparison of the computed results with measured values was conducted. The characteristics of the distribution of the velocity along the width of strip at the exit of the roll bite and the spread of strip for the different crown factors are presented in this paper. The modelling of the shape, profile and flatness for cold rolling of thin strip with friction variation is also discussed.

A 3-D finite element method analysis of cold rolling of thin strip with friction variation

In this paper, a three-dimensional rigid-plastic finite element method (FEM) model to simulate the cold rolling of thin strip with different friction models is described. The effects of rolling parameters, such as work roll diameters and reductions, are analysed in this study. The simulation and experimental values of rolling pressure and spread (the difference of strip width before and after rolling) show a good agreement when friction variation in the roll bite is considered. The roll separating force, spread and forward slip for constant friction and friction variation models are also compared. The friction variation in the roll bite has a significant effect on the simulation results.

Elastic–plastic finite element method simulation of thin strip with tension in cold rolling

Abstract Based on the ABAQUS/Explicit code, the authors, in this paper, analyse the roll bite for the thin strip rolling, and focus on the modelling of the deformation in a roll bite zone, considering cases with and without tension. An elastic–plastic finite element (FE) model to simulate the hump at elastic entry zone and the elastic recovery at exit zone is developed. The effect of tension on the humps can be quantified, which helps to improve the accuracy of the final product. The relationship between the hump value and rolling speed in the roll bite are also obtained from the simulation. The calculated rolling force and elastic strain at entry zone are close to the measured and theoretical values, respectively. This research can model the deformation features of strip in the roll bite, predict the elastic recovery value of strip and improve the accuracy of final products through a correct roll gap set up.

Simulation of the continuous casting process by a mathematical model

A computational three-dimensional (3D) heat transfer model has been developed and applied to calculate the temperature distribution and solid shell thickness profile of a continous cast slab in a steel plant. This developed model includes non-linear material properties of specific heat and thermal conductivity as well as phase changes during solidification. A general thermo-fluidmechanics computer program, PHOENICS, was employed to numerically solve the heat transfer equation with the associated source terms. The thermal profile and solid shell thickness calculated by mathematical model agree with those predicted by an industrial model and experimental measurements. The model could also be used to predict the optimum process parameters on casting speed, heat removal rates and associated water flow rates and roll force. These parameters could be monitored by suitable sensors and controlled through a feed back system that interfaced with the mathematical model and the sensors.

Computational Intelligence-Based Process Optimization for Tandem Cold Rolling

Abstract The requirements for the manufacturers of steel have been increased in many respects in recent years. Harsh competition among manufacturers demands a continuous reduction of production costs and improvement of product quality. The work presented herein describes maximizing rolling mill throughput and minimizing processing costs and crop losses by computational intelligence-based process modeling and optimization. In this article, an intelligent searching mechanism is introduced to optimize the rolling schedule by assessing rolling constraints and the combined cost function of tension, shape, and power distribution. The optimization results have been compared with current rolling practices based on empirical models. It is shown that the proposed model can significantly reduce the power distribution cost, maximize the safe level of strip tension, and obtain good strip shape. The proposed model is generic for complex engineering problem optimization, and is capable of multiple-objective problem solving.

A 3D finite element analysis of the hot rolling of strip with lubrication

Abstract In both rolling theory and practice, two important factors must be considered: friction and deformation resistance strength. A major handicap to producing accurate and reliable models for hot strip rolling is the lack of well-defined friction boundary conditions. In order to improve the accuracy of the computer on-line control model, in this paper, the authors developed a 3D rigid–visco-plastic finite element method (FEM) model to simulate the hot rolling of strip, considering dry and lubricated conditions. The simulation was based on the experimental conditions conducted on a Hille 100 experimental mill. Rolling pressure was measured by a sensor roll that includes a radial pin and an oblique pin. A comparison of the simulation results and experimental values, such as roll separating force and torque, taking into account the friction variation in the roll bite shows a good agreement. The application of lubrication in hot strip rolling can reduce the roll separating force, and the rolling speed also has a significant influence on the roll separating force.

A simulation of three-dimensional metal rolling processes by rigid–plastic finite element method

Abstract Using different frictional shear stress models, mesh division and number of elements in the deformation zone, this paper focuses on analysing the influence of friction variation on the convergence and results of simulation such as rolling pressure, forward slip and spread by 3D rigid–plastic FEM. The effects of mesh division and the number of elements on the precision, stability and convergence of the simulation are also discussed. This investigation shows that the frictional shear stress model with a variation in the deformation zone can provide satisfactory results that are in good agreement with experimental values, and are also more accurate than results from other methods. Suitable mesh division can improve the precision and effectiveness of the simulation. The results of the simulation are discussed for front and back tensions.

Fabrication of Nanostructured Aluminum Sheets Using Four-Layer Accumulative Roll Bonding

In this paper, an extended accumulative roll bonding (ARB) technique, called the ‘Four-Layer Accumulative Roll Bonding (FL-ARB)’ technique, is presented for the first time. This technique has been employed to produce ultrafine-grained commercial pure aluminum sheets with success. After three FL-ARB passes, the grain size of pure aluminum was seen to reduce to 380 nm. The bonding strength of the sheets after rolling has also been discussed. Theoretical calculations showed that the bonding strength of sheets processed by the FL-ARB technique can be 2–2.2 times greater than that by the traditional ARB technique. The main advantages of the FL-ARB technique are (a) improvement of the interface bonding, with increasing deformation in each pass, (b) applicability of the technique at room temperature to process most metals, and (c) generation of the largest equivalent strain in the workpiece with the same number of passes, compared with other severe plastic deformation techniques.

A fuzzy algorithm for flatness control in hot strip mill

Abstract Based on BP neural network, a flatness prediction model in hot strip mill was developed, in which the same location point data were adopted for training and testing to avoid the influence of time-delay. Two fuzzy flatness control algorithms in hot strip mill were developed, and the simulations were carried out by using the flatness prediction model as controlled objective. Conventional fuzzy control algorithm replacing PID linear control system entirely can reduce flatness error significantly. However, the control quality is not good in steady state. The coupled fuzzy-PID control algorithm reduces flatness error significantly as well as produces the desired flatness with small steady-state error and good stability. The coupled fuzzy-PID control algorithm is found to be suitable for rolling the desired flatness in hot strip mill.

Analytical approach to the cold-and-hot bond rolling of sandwich sheet with outer hard and inner soft layers

Abstract This study derives the stress field of the cold-and-hot bond rolling of unbounded sandwich sheet with outer hard and inner soft layers at the roll gap by using the direct formulation without a Runge Kutta numerical method. Constant shear friction between the roll and the sandwich, and constant shear friction at the interface of the unbounded region are assumed. Due to the sandwich sheet being unbounded before rolling, three-layer sheets are not bonded at the entrance of the roll gap. Therefore the stress field of the roll gap for this study is different from that for the sandwich sheet bonded firmly before rolling. The neutral point between the roll and the sandwich sheet, the rolling pressure distribution along contact interface between the roll and the sandwich sheet, the horizontal stress of whole sandwich sheet, the horizontal stresses in the component layers of sandwich, the shear stress at the interface of sandwich sheet, the rolling force, and rolling torque, etc. are easily and effectively calculated via this model. Furthermore, it is of great important to obtain the bonding point at the interface and the thickness ratio of sandwich sheet at the exit from this study. Additionally, the bonding conditions of the unbounded sandwich sheet are found to avoid the failure in bond rolling. This study proposed is suitable for the on-line bond rolling; it offers useful knowledge to conduct the experimental bonding conditions.