STRESS ANALYSIS OF ROLL RING FOR HIGH SPEED WIRE ROLLING MILLS

This paper introduces a new method for fixing type of the tungsten carbide roll ring for high speed wire rolling mills, and analyses the stresses of the roll ring. The lifetime of roll pass is twice longer that of the old one.

Study of residual stresses in tailor rolled blanked Al5J32-T4 sheets

Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization. Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the disadvantages of a welding process which was used in joining panel components. TRB offers better structural design capabilities due to the seamless transitions on the panels with different thicknesses. In spite of the advantages of the process, TRB leaves internal stresses in the panel. This residual stresses lower the formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes. In this research, the residual stresses of TRBed Al5J32-T4 sheets were studied by X-ray stress analysis, and also microstructure was observed along the rolling direction. In addition, heat treatment was done after TRB process in order to compare the residual stresses to that of the TRBed sheets before the heat treatment.

3D stress simulation and parameter design during twin-roll casting of 304 stainless steel based on the Anand model

This study first investigated cracks on the surface of an actual steel strip. Formulating the Anand model in ANSYS software, we then simulated the stress field in the molten pool of type 304 stainless steel during the twin-roll casting process. Parameters affecting the stress distribution in the molten pool were analyzed in detail and optimized. After twin-roll casting, a large number of transgranular and intergranular cracks resided on the surface of the thin steel strip, and followed a tortuous path. In the molten pool, stress was enhanced at the exit and at the roller contact positions. The stress at the exit decreased with increasing casting speed and pouring temperature. To ensure high quality of the fabricated strips, the casting speed and pouring temperature should be controlled above 0.7 m/s and 1520℃, respectively.

Flow stress equation for multipass hot-rolling of aluminum alloys

A series of simple axisymmetric compression tests were carried out on the computer servo controlled Gleeble 1 500 machine when strain rates ranged between 0.05 25 s -1 and deformation temperature 300 500 ℃. The results show that flow stress is related to the Zener Hollonom parameter Z and strain, as well as the static recrystallization fraction between passes during multipass hot deformation of 5182 aluminum alloy. Hence, a modified exponential flow stress equation was presented by considering the values of ln A and β as functions of strain, and by using the uniform softening method and incorporating the static recrystallization fraction between passes to consider the effects of residual strain during multipass hot rolling of 5182 aluminum alloy. The validity of the equation was examined by a typical non isothermal multipass deformation test.

Numerical Simulation of Temperature Field and Thermal Stress Field of Work Roll During Hot Strip Rolling

Based on the thermal conduction equations, the three-dimensional （3D） temperature field of a work roll was investigated using finite element method （FEM）. The variations in the surface temperature of the work roll during hot strip rolling were described, and the thermal stress field of the work roll was also analyzed. The results showed that the highest roll surface temperature is 593 ℃, and the difference between the minimum and maximum values of thermal stress of the work roll surface is 145.7 MPa. Furthermore, the results of this analysis indicate that temperature and thermal stress are useful parameters for the investigation of roll thermal fatigue and also for improving the quality of strip during rolling.

Three-Dimensional Analysis of Rolling by Twin Shear Stress Yield Criterion

Using the twin shear stress yield criterion, the surface integral of the co-line vectors, and the integration depending on upper limit, Kobayashi＇s three-dimensional velocity field of rolling was analyzed and an analytical expression of rolling torque and single force was obtained. Through redoing the same experiment of rolling pure lead as Sims, the calculated results by the above expression were compared with those of Kobayashi and Sims formulae. The results show that the twin shear stress yield criterion is available for rolling analysis and the calculated results by the new formula are a little higher than those by Kobayashi and Sims ones if the reduction ratio is less than 30%.

Elastoplastic 3D Deformation and Stress Analysis of Strip Rolling

An elastoplastic method for analyzing the 3D deformation, stress and transverse distribution of tension stress during cold strip rolling is developed. The analysis is based on the elastoplastic variational principle in which a kinematically admissible velocity field is constructed with the lateral flow function as an unknown function. The stress distribution and volume strain distribution are obtained by solving the simultaneous equations formed by the longitudinal differential equation of equilibrium and constitutive equations. The lateral flow function is determined by minimizing the total energy dissipation rate. Experimental investigation was carried out on a reversible cold mill. The front tension stress distributions in cold rolled strips were measured by a multi roll segmented tension sensing shapemeter. The calculated results are in good agreement with the measured ones.

Rolling Deformations and Residual Stresses of Large Circular Saw Body

Rolling path squeezes and rolling residual stresses of large diameter circular saw body for wood, generated by rolling pressure from 10 up to 120 bar were examined. X-ray diffraction, Barkhausen noise (BN) and Full Width of the peak at a Half Maximum (FWHM) (o) methods for evaluation of residual stresses were used. Dependencies of a tangential rolling residual stresses inside rolling paths upon rolling pressure p (bar) and rolling area A (mm2) were evaluated. The rolling pressure, as large as 60 bar, resulting in the rolling squeeze as high as 0.04 mm2, and, tangential residual compression stresses inside a rolling path, as large as ?TI = ?822 MPa, was considered to be the largest for the practical application.

Strip Layer Method for Analysis of the Three-Dimensional Stresses and Spread of Large Cylindrical Shell Rolling

As the traditional forging process has many problems such as low efficiency, high consumption of material and energy, large cylindrical shell rolling is introduced. Large cylindrical shell rolling is a typical rotary forming technology, and the upper and lower rolls have different radii and speeds. To quickly predict the three-dimensional stresses and eliminate fishtail defect, an improved strip layer method is developed, in which the asymmetry of the upper and lower rolls, non-uniform deformation and stress, as well as the asymmetrical spread on the end surface are considered. The deformation zone is divided into a certain number of layers and strips along the thickness and width, respectively. The transverse displacement model is constructed by polynomial function, in order to increase the computation speed greatly. From the metal plastic mechanics principle, the three-dimensional stress models are established. The genetic algorithm is used for optimization calculation in an industrial experiment example. The results show that the rolling pressure, the normal stresses, the upper and lower friction stress distributions are not similar with those of a general plate rolling. There are two relative maximum values in rolling pressure distribution. The upper and lower longitudinal friction stresses change direction nearby the upper and lower neutral points, respectively. The fishtail profile of spread on the end surface is predicted satisfactorily. The reduction could be helpful to eliminate fishtail defect. The large cylindrical shell rolling example illustrates the calculation results acquired rapidly are good agreements with the finite element simulation and experimental values of previous study. A highly effective and reliable three-dimensional simulation method is proposed for large cylindrical shell rolling and other asymmetrical rolling.

Transverse Distributions of Front and Back Tension Stresses in Cold Strip Rolling

In this paper,such a new lateral displacement function is proposed that the lateral flow velocity is con- tinuous at the entry and the exit of deformation zone.A new kind of finite strip method—the third power B-spline finite strip method—is put forward to simulate strip rolling process.Front and back tension stresses are formulated.The computed results of the transverse distributions of the front and back tension stresses are close to the experimental results.The paper lays a foundation for further analysing the three-dimensional stresses and deformations of strip rolling.

STUDY ON COUPLING MODEL OF (SEEPAGE-FIELD) AND STRESS-FIELD FOR ROLLED CONTROL CONCRETE DAM

Based on the construction interfaces in rolled control concrete dam(RCCD), the methods were proposed to calculate the influence thickness of construction interfaces and the corresponding physical mechanics parameters. The principle on establishing the coupling model of seepage_field and stress_field for RCCD was presented. A 3_D Finite Element Method(FEM) program was developed. Study shows that such parameters as the thickness of construction interfaces,the elastic ratio and the (Poisson's) ratio obtained by tests and theoretical analysis are more reasonable, the coupling model of seepage_field and stress_field for RCCD may indicate the coupling effect between the two fields scientifically, and the developed 3_D FEM program can reflect the effect of the construction interfaces more adequately. According to the study, many scientific opinions are given both to analyze the influence of the construction interfaces to the (dam's) characteristic, and to reveal the interaction between the stress_field and the seepage_field.

Investigation of Stresses on Tie Band Used to Wrap and Fasten Rolled Coils

The research was motivated to establish a scientific basis for the required number of steel tie bands used in wrapping and fastening hot rolled coils produced in steel manufacture lines for safe delivery and storage. Strain gages were installed on the tie bands and stress was recorded during the banding and delivery procedure of rolls in the field. The stress developing in the bands due to fastening of the roll and that due to springback of the coil were clearly distinguishable from the strain gage signals. Twelve hot rolled coils having different yield strength, thickness, width, and weight were tested in the recoiling field. The results showed the average tensile stress developing in the bands due to the fastening of the roll to be 151.7 ± 53.8MPa, which corresponded to one fourth of the failure strength of the steel band in the buckle region. In addition to the stress caused by fastening, average tensile stress caused by springback of the rolled coils was estimated to be 33 MPa. It increased to 79 MPa when one of the tie bands was removed from the roll. Comparing the measured stress due to springback with the theoretical stress formula yielded a proportional constant value of 0.219, and a correlation coefficient of 0.914, which demonstrate the formula to be useful in predicting springback stress. The average safety factor of the tie band was found to be 3.26 and it decreased to 2.60 when one of the bands was removed from the roll. The safety factor of the band was found to decrease with increased coil thickness because the current factory standard on the number of bands does not significantly take into account of increase in the springback force with increased coil thickness.

A Way to Determine the Maximum Inducible Residual Stresses in Steel by Mechanical Surface Treatment

The issue of determining the maximum compressive residual stress that can be induced through mechanical surface treatment is of great significance.There are two possible approaches,namely stress peening and stress rolling,both to determine the limit.Steel with high hardness may be under the yield strength,while for those with lower tensile strength,the hardness is increased,and the limit is above the tensile strength.

A NEURAL NETWORK-BASED MODEL FOR PREDICTION OF HOT-ROLLED AUSTENITE GRAIN SIZE AND FLOW STRESS IN MICROALLOY STEEL

For the great significance of the prediction of control parameters selected for hot-rolling and the evaluation of hot-rolling quality for the analysis of prod uction problems and production management, the selection of hot-rolling control parameters was studied for microalloy steel by following the neural network principle. An experimental scheme was first worked out for acquisition of sample data, in which a gleeble-1500 thermal simolator was used to obtain rolling temperature, strain, stain rate, and stress-strain curves. And consequently the aust enite grain sizes was obtained through microscopic observation. The experimental data was then processed through regression. By using the training network of BP algorithm, the mapping relationship between the hotrooling control parameters (rolling temperature, stain, and strain rate) and the microstructural paramete rs (austenite grain in size and flow stress) of microalloy steel was function appro ached for the establishment of a neural network-based model of the austeuite grain size and flow stress of microalloy steel. From the results of estimation made with the neural network based model, the hot-rolling control parameters can be effectively predicted.

STUDY OF THE 3-DIMENSIONAL STRESSES OF COLD STRIP ROLLING UNDER CENTRE WAVE

On the conditions ofthe width to thickness ratio 625 and the centre wave the 3-dimensional stresses distributions of cold strip rolling are studied by using the third power spline function finite strip method. The computed results of the rolling pressure, the 2-directional friction stresses and the front and back tension stresses agree with the experimental results well. In this paper, the frictional stresses of stagnation zone are computed by using preliminary displacement principle and the computing precision is improved.

超声滚压对激光选区熔化铝锂合金残余应力的影响模拟研究

研究了铝锂合金试样激光选区熔化残余应力分布以及超声滚压对其应力场的影响。先后建立了单道扫描模型、试样模型以及超声滚压模型;分析了单道扫描模型的温度历史,并将此温度历史扩展至试样的沉积层,最终通过热力耦合与显示动力学分析获得激光选区熔化和超声滚压后的残余应力分布。结果表明,激光选区熔化试样顶部与四周出现了较大的残余拉应力;在超声滚压作用下,试样表层产生了高频振荡的应力场,并产生了较大的瞬时应力;试样表面残余拉应力转化为压应力,随着深度增加,残余压应力先增大后逐渐减小并逐渐转变为拉应力,最终恢复至激光选区熔化后的应力状态;模拟预测的结果与试验结果吻合较好,具有合理的精度。

钢包回转台三排滚子回转轴承强度分析及结构尺寸优化研究

钢包回转台是炼钢车间中低速重载工况下工作的重要设备。某企业的钢包回转台在运行过程中出现了回转支承强度不足的问题。为了探究回转支承的破坏原因,采用理论计算和数值仿真的方法开展研究。采用赫兹接触理论对两种工况下的回转支承进行相应的研究。经过仿真验证发现,在偏载工况下,回转支承中部分滚动体的应力超过了滚动体材料的屈服应力,导致了破坏。为改善受力状态,对回转支承结构的尺寸进行了优化选择,以降低应力。

钛合金材料超声滚压加工的仿真分析与实验研究

采用普通滚压加工工艺对钛合金材料进行加工时,存在因低频冲击造成的工件残余应力分布不均匀和表面硬度低等问题,为此,开展了钛合金材料超声振动滚压工艺仿真及实验研究。首先,从理论层面分析了超声滚压加工的运动学及动力学特性,找出了影响超声滚压加工性能的相关因素;然后,采用ABAQUS有限元软件建立了钛合金材料的仿真模型,分析了超声滚压对残余应力的影响及强化机理;最后,设计了钛合金工件的超声滚压实验,研究了不同参数指标对工件加工质量的影响,并根据实验结果对仿真模型和残余应力结果进行了验证。研究结果表明:随着静载荷和超声振幅的增加,工件表面残余应力分布相对均匀且趋于平稳,表面粗糙度呈现先降低后增加的趋势,表面硬度随强化层深度的增加逐渐降低;在振幅为20μm时,工件表面质量和性能相对较好,此时残余应力均值为849 MPa,表面粗糙度均值为0.1μm。该实验结果与仿真分析结果一致,验证了所建模型的可靠性,可为滚压制造工艺参数的选取提供参考。

基于机电设备点检试验台应用的小型轧钢机设计的仿真研究

设计并研发了一款机电设备点检试验机,重点模拟热轧钢机加工流程。通过该试验机能直观了解设备真实生产运作,并具备故障排除功能。通过对试验台所用小型轧钢机的轧制力计算以及应用ANSYS对工件轧制前后进行应力分析,使培训人员深入了解实验台工作状态,为提升点检人员专业素质提供了有力支持,同时该研究方法为行业培训和实践操作提供了创新的解决方案。

随动辊压型低应力精密断料教学实验平台开发

为了增强学生对先进成形装备及低应力精密断料技术的理解,开发了随动辊压型低应力精密断料教学实验平台。该实验平台综合利用机械设计、传感器技术及计算机控制技术,将应力集中效应和随动辊压技术引入管料的精密分离断料工序中,设计了管料断面质量评价方法,对带有V型槽的45#钢及304不锈钢管料进行了裂纹可控式低应力精密下料实验,验证了断料效果。该实验平台不仅使低应力断料过程更加直观,还提升了学生对低应力精密成形技术的认识,增强了学生对“机械制造工程基础”“切削原理与刀具”及“先进制造技术”等课程的学习兴趣。