An analytical model of hot rolling force for a thick plate by combining globally optimal approximation yield criterion and egg-circular velocity field

For the sake of solving the problem that it is difficult to be integrated for the Mises specific plastic power due to its nonlinearity,a new linear criterion,named the globally optimal approximation criterion,is constructed by the polygonal approximation to the Mises circle.The new criterion is proved to be the linear function of the principal stress componentsσ1,σ2 andσ3 and the trajectory of it on theπ-plane is a non-equiangular but equilateral dodecagon intersecting the Mises circle.The theoretical results of the current criterion described by the Lode stress parameters are in excellent accordance with the experimental results.Meanwhile,according to the trend that the metallic flow velocity between rollers aggrandizes gradually from the inlet to the outlet during the hot rolling of a thick plate,a biomimetic velocity field is proposed in which the horizontal velocity component fits the egg-circular curve distribution.The velocity field and its simulated results agree quite well.Subsequently,using the determined linear criterion,energy analysis of the constructed velocity field is utilized to obtain the interior deformation power,while the vector decomposition approach is utilized to obtain the frictional power and shear power.On this basis,the overall power is obtained and the analytical solutions are generated for the rolling torque,rolling force and the coefficient of the stress state under different egg curves by minimizing the neutral angle.Furthermore,the parameter optimization of the characteristic parameterρwhich affects the slope of the egg-circular curve is carried out and the best egg-circular curve which can minimize the energy consumption is determined.The best agreement between the theoretical and observed values of rolling force and rolling torque is under this curve,and the mean relative errors of the rolling torque and rolling force are no more than 2.93%,while the maximum error is no more than 8.35%.

Analysis of Hot Tandem Rolling Force with Logarithmic Velocity Field and EA Yield Criterion

In order to analyze the hot tandem roiling force, a new logarithmic velocity field is proposed. Using the field and linear EA （equal area） yield criterion, the plastic deformation power for plate rolling is analyzed, and the friction power is obtained based on the co-line vector inner product method. Then analytical solution of plate rolling power functional is obtained. Finally, by minimizing the power functional, the rolling torce and torque are received. Compared with those measured ones in hot tandem rolling on-line, the calculated rolling forces are in good agreement with the actual measured ones since the maximum error is less than 12~. Moreover, the effects of various rolling conditions such as thickness reduction, friction factor and shape factor, upon separating force, location of neutral an- gle, and stress state coefficient are discussed systematically.

Simplified Weighted Velocity Field for Prediction of Hot Strip Rolling Force by Taking into Account Flattening of Rolls

The weighted velocity field was simplified for analysis of hot strip rolling. Using the field and GM （geometric midline） yield criterion, the deformation power, friction power and shear power were obtained respectively. Summing the partial power contributions, the total deformation power for strip rolling was presented. Then, by minimizing the power function, the rolling force was obtained; meanwhile, considering the effect of roll elastic flattening, iterative calculation of the roll radius was carried out until the radius was convergent. On line data were corn pared with the calculated results to verify the model accuracy. It was indicated that the calculated rolling forces were basically in agreement with the measured ones since the maximum error was less than 10.0%. Moreover, the effects of various rolling conditions such as thickness reduction, friction factor and shape factor, upon separating force, location of neutral angle, and stress state coefficient were discussed systematically.

Rolling Force and Rolling Moment in Spline Cold Rolling Using Slip-line Field Method

Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.

Simulation of faceted dendrite growth of non-isothermal alloy in forced flow by phase field method

Numerical simulation based on a new regularized phase field model was presented to simulate the dendritic shape of a non-isothermal alloy with strong anisotropy in a forced flow. The simulation results show that a crystal nucleus grows into a symmetric dendrite in a free flow and into an asymmetry dendrite in a forced flow. As the forced flow velocity is increased, both of the promoting effect on the upstream arm and the inhibiting effects on the downstream and perpendicular arms are intensified, and the perpendicular arm tilts to the upstream direction. With increasing the anisotropy value to 0.14, all of the dendrite arms tip velocities are gradually stabilized and finally reach their relative saturation values. In addition, the effects of an undercooling parameter and a forced compound flow on the faceted dendrite growth were also investigated.

Prediction and Analysis of the Force and Shape Parameters in Variable Gauge Rolling

Variable gauge rolling is a new process to obtain a plate for which the thickness changes continuously by continuously and dynamically adjusting the roll gap upward and downward in the rolling process.This technology is an efective method for producing lightweight,low-cost,and economical plates.However,variable gauge rolling is an unsteady process,and the changes in the force and deformation parameters are complex.In this research,based on the minimum energy theory of the variational principle and considering the characteristics of the roll movement and workpiece deformation comprehensively,the internal plastic deformation,friction,shear and tension powers,and the minimum result of the total power functional in upward and downward rolling are obtained with the frst integral and then with a variation of adopting the specifc plastic power and strain rate vector inner product.The analytical results of the deformation and force parameters are also established using the variational method.Then the precision of this model is certifed using the measured values in a medium plate hot rolling plant and the experimental data for Tailor Rolled Blank rolling.Good agreement is found.Additionally,the variation rule of bite angle,neutral angle,and location neutral points are shown,and the change mechanism of the friction parameter on the stress state efect coefcient is given in variable gauge rolling.This research proposes a new mathematical model for rolling process control that provides a scientifc basis and technical support for obtaining an accurate section shape in variable gauge rolling production.

Energy Method in Stretch Reducing Process of Steel Tube

According to the theories for stretch reducing process and steel tube plastic deformation, the energy method was used to mesh the rolled deformation zone of the steel tube into the upper limit elements, and an admissible velocity field was constructed to deduce a series of formulas of the inner virtual power consumption of deformed bodies. The roiling force during the stretch reducing process could be obtained by optimizing the upper limit power, which could provide guidelines for a proper choice of the stretch reducing process and devices for steel tube companies, as well as new products and devices.

A Semi-Analytical Method for the PDFs of A Ship Rolling in Random Oblique Waves

The PDFs(probability density functions) and probability of a ship rolling under the random parametric and forced excitations were studied by a semi-analytical method. The rolling motion equation of the ship in random oblique waves was established. The righting arm obtained by the numerical simulation was approximately fitted by an analytical function. The irregular waves were decomposed into two Gauss stationary random processes, and the CARMA(2, 1) model was used to fit the spectral density function of parametric and forced excitations. The stochastic energy envelope averaging method was used to solve the PDFs and the probability. The validity of the semi-analytical method was verified by the Monte Carlo method. The C11 ship was taken as an example, and the influences of the system parameters on the PDFs and probability were analyzed. The results show that the probability of ship rolling is affected by the characteristic wave height, wave length, and the heading angle. In order to provide proper advice for the ship’s manoeuvring, the parametric excitations should be considered appropriately when the ship navigates in the oblique seas.

基于改进人工势场-PSO算法的农业机器人全区域覆盖研究

为解决智慧无人农业中农业机器人对复杂农田的全区域覆盖作业问题,对农业机器人全区域作业覆盖进行研究,提出了一种基于人工势场改进的粒子群路径优化算法,并将其与回溯法相结合实现对农田的全区域路径覆盖。改进算法将人工势场中的势能场构建以及合力值动态调节方法引入粒子群算法,设置合力值调节因子来更新粒子群的速度更新函数,同时根据每个粒子的搜寻情况实时更新引力源参数值。与传统粒子群算法相比,改进粒子群算法寻找的最短路径减少10.6%,算法收敛速率提升12.8%;与传统算法与回溯法结合相比,改进粒子群算法与回溯法的结合使得全区域覆盖路径重复率减少了12.7%。

NUMERICAL SIMULATION OF SUCCINONITRITE DENDRITIC GROWTH IN A FORCED FLOW

Numerical simulation based on phase field method is performed to describe solidification process of pure material in a free or forced flow. The evolution of the interface is showed, and the effects of mesh grid and flow velocity on succinonitrite shape are studied. These results indicate that crystal grows into an equiaxial dendrite in a free flow and into an asymmetrical dendritic in a forced flow. With increasing flow velocity, the upstream dendritic arm tip grows faster and the downstream arm grows slower. However, the evolution of the perpendicular tip has no significant change. In addition, mesh grid has no influence on dendritic growth shape when mesh grid is above 300×300.

Prediction of Velocity and Deformation Fields During Multipass Plate Hot Rolling by Novel Mixed Analytical-Numerical Method

An integrated mathematical model is proposed to predict the velocity field and strain distribution during multi-pass plate hot rolling. This model is a part of the mixed analytical-numerical method （ANM） aiming at predic- tion of deformation variables, temperature and microstructure evolution for plate hot rolling. First a velocity field with undetermined coefficients is developed according to the principle of volume constancy and characteristics of metal flow during rolling, and then it is solved by minimizing the total energy consumption rate. Meanwhile a thermal model coupling with the plastic deformation is exploited through series function solution to determine temperature distribution and calculate the flow stress. After that, strain rate field is calculated through geometric equations and strain field is derived by means of difference method. This model is employed in simulation of an industrial seven pass plate hot rolling process. The velocity field result and strain field result are in good agreement with that from FEM simulation. Furthermore, the rolling force and temperature agree well with the measured ones. The compari- sons verify the validity of the presented method. The calculation of temperature, strain and strain rate are helpful in predicting microstructure. Above all, the greatest advantage of the presented method is the high efficiency, it only takes 12 s to simulate a seven-pass schedule, so it is more efficient than other numerical methods such as FEM.

粘性等效船舶横摇运动降阶预报方法

针对船舶耐波性中的经典横摇问题,本文提出一种针对横摇运动预报的粘性等效降阶方法。在该方法计算框架中,首先采用粘流模型和无粘模型分别模拟船体的强迫放大运动,预报不同运动幅度下的水动力力矩。其次,应用能量等效法获取船舶横摇阻尼随KC数变化的修正函数。最后,在横摇运动响应预报中,基于欧拉方程求解无粘流体,应用获取的阻尼修正函数,对横摇阻尼进行实时修正,以提高预报精度。为验证该方法的有效性,分别采用VEROM模型和RANS粘性模型对典型二维船体中段的横摇响应进行预报,对比结果表明:VEROM模型与RANS模型预报精度相当,但前者的计算时间可缩减到RANS模型的5%。

三维速度场建立方法

三维速度场在油气勘探中具有广泛的应用前景,但由于多种技术限制一直未能成功实现。在对比分析现有各种平均速度(场)建立方法原理及优缺点的基础上,优选模型层析法,通过技术攻关,解决了数据体层位自动追踪法和层位解释法相结合的空间倾角场建立技术、速度谱排列影响消除技术、射线追踪层速度求取技术、最小张力法离散数据空间网格化平滑技术等多项长期以来阻碍三维速度场建立的技术难题,建立了胜利油区首个三维速度场——东营凹陷三维速度场,实现了模型层析法建立三维速度场由理论到应用的跨越。模型层析法建立的三维速度场精度高、适用范围广、效果好,具有广阔的应用前景。

筒仓装卸料时力场及流场的离散单元法模拟

利用离散单元法研究了筒仓装卸料过程中的力场和速度场 ,以期揭示宏观力学行为的内在机理。首先介绍了离散单元法的基本原理 ,然后用物理模型实验测试和模拟了筒仓壁法向压力及物料流动过程 ,最后用离散单元法研究了筒仓内部压力和物料颗粒速度场 ,并探讨了颗粒密度和物料密实度的影响。与物理实验结果对比表明 。

纵凸筋钢板轧制力的计算

利用能量法可以推导出纵凸筋钢板轧制力的计算式，并对纵凸筋钢板轧制力进行了计算．结果表明，计算值与实测值两者相当吻合，这对局部不均匀变形问题的理论分析有重要意义．

单辊搅拌技术制备2A11半固态材料过程的数值模拟

简述了单辊搅拌技术制备 2A11半固态材料基本原理·利用ANSYS有限元分析软件包中CFD14 1单元 ,对制备 2A11半固态材料过程中耦合场进行了数值模拟 ,得出了温度场与速度场的分布规律·在轧辊作用下 ,靠轧辊越近 ,合金液体层运动速度越大 ,离轧辊越远 ,液体层运动速度越小·在近轧辊处出现速度最大值 ,在近靴处出现明显的速度递减·由于轧辊的转动 ,使合金等温线发生偏移 ,近轧辊侧温度偏高·

Sr^(2+)和Ba^(2+)水分子体系结构和结合能的从头算和ABEEM/MM研究

应用从头算方法和ABEEM/MM浮动电荷分子力场,研究了水合碱土离子团簇Sr2+/Ba2+(H2O)n(n=1-6),构建了离子-水相互作用的ABEEM/MM势能函数,获得了水合离子团簇的稳定结构,计算了结合能.计算结果表明,ABEEM/MM方法的结果和从头算方法的结果有很好的一致性.进一步应用ABEEM/MM对Sr2+和Ba2+水溶液进行了分子动力学模拟.对Sr2+水溶液,得到的Sr2+-水中氧原子的径向分布函数的第一和第二最高峰分别位于0.257和0.464nm处,第一和第二水合层的配位水分子数分别为9.2和11.4;对Ba2+水溶液,得到的Ba2+与水中氧原子的径向分布函数的第一和第二最高峰分别位于0.269和0.467nm处,第一和第二水合层的配位水分子数分别为9.9和12.4.这与实验值或其它理论模拟结果有较好的一致性.对比外层的水分子,金属离子的极化作用使得溶液中第一水合层中水分子的O―H键长增长,HOH键角减小.

角平分屈服准则解析热轧厚板展宽轧制力

根据厚板轧制变形特点,提出了适用于展宽轧制阶段的二维流函数速度场。利用角平分屈服准则对提出的速度场进行解析求得了内部变形功率表达式。采用共线矢量内积法与积分中值定理分别求得了摩擦功率与剪切功率表达式。经总功率泛函最小化获得了轧制力矩与轧制力的解析解。与国内某厂320 mm板坯的实际轧制数据比较表明,该解析解具有较高的预测精度,最大误差不超过10.45%。轧制工艺参数分析表明,随着压下率的增加或几何因子的减小,轧制力矩与轧制力增加;摩擦系数对轧制力矩和轧制力的影响较小。

开式冷挤压成形功率及挤压力的研究

给出了开式冷挤压动可容连续速度场及上限挤压力计算公式，讨论了主要参数对挤压力的影响，理论分析结果得到了实验验证。

高密点地震资料面波压制的自适应波束方法

在单点采集的地震记录上,面波能量非常强,有效信号淹没于其中,地震资料的信噪比较低。在常规地震资料处理中,通常采用相位匹配法和高通滤波法对面波进行压制,但存在面波去除不干净或损害有效低频反射波等问题,即使是F-K滤波和小波变换面波压制等改进方法也或多或少地存在同样的问题。为解决这一问题,提出了自适应波束面波压制方法。该方法利用有效反射波和面波在视速度上的差异,通过设计合理的代价函数,不断优化滤波器的权系数,可以在面波区有效衰减面波能量,保全有效反射波。对新疆亚肯北地区某测线高密度单点采集资料,利用自适应波束方法进行面波压制,取得了很好的效果,在去除面波的同时有效信号得到了保护,资料的信噪比得到了提高。