变厚度轧制非稳态过程中力能和变形参数的变化机理研究

Variable gauge rolling is an effective method for producing light weight, low cost and economical plate. However, variable gauge rolling is an unsteady process. The changes of force and deformation parameters, such as rolling force, rolling torque, forward slip etc., are complex and the mechanism is not clear yet. All these factors lead to poor dimensional accuracy in the transition zone, which affects further processing and using of products. Based on the minimum energy theory of the variational principle and considering the characteristics of roll movement and workpiece deformation comprehensively, the total power functional and its minimum value in upward and downward rolling are gained respectively by first integral and then variation adopting specific plastic power of linear yield criterion and strain rate vector inner product. The analytical models of force and deformation parameters are also established using variational method. Then the accuracy of these models is verified by the experimental data in variable gauge rolling. The computing approach of deformation parameters is studied in transition region of different shapes. The change mechanism of the rolling, geometric and friction parameters on force and deformation parameters is given in variable gauge rolling. The optimization methods of force and deformation parameters in unsteady state are researched based on small sample learning by combining finite element simulation and experimental data. The force and deformation parameters with high precision are obtained in upward and downward rolling. The high precision rolling in the thickness, length and position is achieved in transition region. Scientific basis and technical support for obtaining accurate section shape in variable gauge rolling production will be provided in this project.

变厚度轧制是生产轻量化、低成本、节约型板材的有效方法，但变厚轧制为非稳态过程，轧制力和力矩、前滑等力能与变形参数变化复杂且机理尚未明确，致使变厚过渡区形状尺寸精度差，影响产品后续加工和使用。本项目考虑轧辊移动和轧件变形特点，基于变分原理的最小能原理，采用线性屈服准则比塑性功率和矢量内积等方法，先积分再变分，分别获得趋厚与趋薄轧制总功率泛函及其最小值，建立基于变分解法的变厚度轧制力能和变形参数解析模型，然后利用变厚轧制实验数据验证模型准确性，并研究过渡区不同形状类型下变形参数计算方法。基于以上研究阐明变厚轧制中轧制参数、几何参数、摩擦参数对力能和变形参数的变化机理，同时结合有限元模拟和实验数据研究基于小样本学习的非稳态下力能和变形参数的优化方法，获得趋厚与趋薄轧制中高精度力能和变形参数，实现过渡区厚度、长度和位置的高精度轧制。本项目为变厚轧制生产中获得精确断面形状提供科学依据和技术支撑。

变厚度轧制是在轧制过程中连续动态地上下调节轧辊辊缝，获得厚度连续变化板带的技术，变厚度板具有减轻结构重量、减少焊缝、生产效率和成材率高等优点。但变厚轧制为非稳态过程，轧制力能与变形参数变化复杂且机理尚未明确。本项目利用变分解法研究了变厚度轧制过程。.考虑轧辊上移或下移的影响，针对变厚度冷轧和热轧的变形特点，分别建立满足趋厚轧制与趋薄轧制变形区运动许可条件的速度场及应变速率场。采用线性屈服准则、共线矢量内积和中值定理的方法得到变形区的内部塑性变形功率泛函、摩擦功率泛函、剪切功率泛函和张力功率泛函，进而得到塑性区的总功率泛函、轧制力矩、轧制力、中性角的解析模型。采用了广义胡克定律，考虑前后张力对弹性区影响，分析趋厚轧制与趋薄轧制过程中入口弹性变形区和出口弹性恢复区形状，突破传统将接触弧简化为弦或者二次曲线的方式，轧制力积分时将对轧制方向长度方向的积分其转化为对接触角变化的积分，得到弹性区轧制力的精确解。针对轧制力与压扁半径耦合的问题，采用考虑张力影响的Hitchcock压扁半径模型迭代求解轧制力。选取TRB实验数据和MAS轧制现场的实测轧制力和过渡区尺寸数据，验证本项目建立模型计算结果的准确性。.基于模型研究了力能和变形参数的变化机理，咬入角和中性角在趋厚轧制时逐渐减小，在趋薄轧制时逐渐增大。趋厚轧制时中性点趋向变形区入口，趋薄轧制时中性点趋向变形区出口。前张力增加或后张力减小时中性角增加。这些变形参数是微跟踪策略的基本参数，用于控制变厚度板过渡区的长度。应力状态影响系数在趋厚轧制时逐渐增大，在趋薄轧制时逐渐减小。前后张力与轧制力成反比，摩擦因子越大轧制力越大。基于力能参数和轧机弹跳方程确定变厚板过渡区辊缝的设定值，用于控制变厚度板过渡区的厚度。提出变厚度轧制过程工艺参数的优化方法，提高模型预测精度。.发表学术论文15篇，其中SCI收录10篇；申请发明专利9项，其中授权3项，获得山西省科技进步一等奖1项。

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