薄壁管材高速滚珠旋压工艺拟动力学特性及其可控机理研究

The technology of ball spinning is used in the tube-shaped part smanufacturing because of characteristics of high precision and material performance improvement.The requirement of improving production efficiency and reducing consumption impels the research to develop towards high speed.This research project takes the quasi dynamics features as the breakthrough point,and takes the high-speed strain performance as the constraint condition,and then stydies the laws influenced by the across scales micro change by high speed features and inhomogeneous loads of the balls.At the same time,this research project would study the relationship between the feartures of spinning,rolling and slipping under the condition of high speed and the changes for the organizational performance of the workpiece,and would study the relationship between the complex friction behavior of balls and local heating rules.Then,study the controllable mechanism and control methods for the quasi dynamics parameters in the process of ball spinning.The thoretical analysis software according to the research contents would be developed,and the test-bed would be reformed and the experimental work would be carried out for a elected alloy,and the parameters of geometric accuracy,heating,ball spinning force would be tested to verify the theoretical model.At last,the neural network would be established according to the relationship between the quasi dynamic feartures and thegeometric accuracy and organizational performance,and the process parameters could be optimized and reconsituted based on the controllability of quasi dynamic parameters.This project will enhance the ball spinning theory to the precise level,and supply a basis for the design of the process and tools.

滚珠旋压由于可提高材料性能、精度高等优点而被用于生产高质量、薄壁管筒类零件。生产效率的提高和节能降耗的要求使其向着高速方向发展。本项目以高速滚珠旋压过程中表现出的拟动力学特性为切入点，以旋件的高速应变性能为约束，研究高速特性所导致的滚珠与旋件接触状态的跨尺度微变迁与滚珠受力非均匀分布对壁厚精度、旋压力能参数的影响；同时研究滚珠高速情况下旋、滚、滑等拟动力学参数引起的旋件组织性能的变化，以及滚珠与旋件的复杂摩擦行为与局部发热规律；继而研究高速滚珠在旋压过程中拟动力学参数可控机理与方法。针对研究内容开发理论分析软件，改造实验装置，对典型合金进行实验，实施几何精度、发热升温、旋压力等工艺参数的测试，验证理论模型；开发滚珠拟动力学特性对旋件几何精度与组织性能影响的神经网络模型，根据拟动力学参数的可控性对旋压工艺参数进行优化与重构。本项目将使滚珠旋压分析更接近精确化水平，为工艺和模具设计提供依据。

本项目对薄壁管高速滚珠旋压拟动力学特性进行了系统研究。. 1.根据空间解析几何理论得到了滚珠与管坯的接触边界方程，通过对曲线积分得到了各接触区投影面积，假设钢球压入管件时平均压力近似相等计算各旋压分力。. 2.为了得到更加精确的旋压力计算结果，通过假设入口断面角速度，进行了滚珠旋压功率的计算，由虚功率原理和变分极值原理求出最优化的总功率，进而求得旋压力。. 3.在实验观测的基础上提出滚珠的运动假设，并考虑滚珠所受离心力与陀螺力矩，综合了滚珠的“旋、滚、滑”特性建立了滚珠的拟动力学模型；解析计算滚珠的各点受力及滚珠三维公转、自转角速度。. 4.通过非线性动力学有限元计算，分析了滚珠离心力、陀螺力矩随着转速与模环锥角的变化规律；结果表明：滚珠与工件和锥环的接触力偶和滚珠离心力以及陀螺力矩是造成滚珠甩脱的主要原因。. 5.为了更加精确的对AZ31镁合金滚珠旋压过程进行模拟，建立了基于BP 神经网络的不同温度和应变速率下的应力预测模型。结果表明，该 BP 网络模型预测精度高，且操作高效简洁，可代替传统的计算过程繁杂的应力本构计算模型。. 6.以AZ31镁合金薄壁管为例，基于仿真实验结果，探讨了主要工艺参数及其相互之间的耦合作用对变形影响区内相对应力三轴度平均值的影响；并对这四者之间的关系进行了多元非线性函数关系拟合；实验结果表明：最小应力三轴度下镁合金管坯的塑性成型性能得到了提高。. 7.通过有限元模拟得出了滚珠旋压变形影响区的温度随着摩擦系数，模具转速，减薄量和进给比的变化规律，发现在6000rpm转速和0.4mm减薄量时变形影响区的温度可以达到220℃以上，可以满足镁合金的温热成形的温度要求。. 8.改造并建立了卧式和立式高速滚珠旋压试验台，针对AZ31镁合薄壁管，在不同工艺参数下的金相组织变化进行了实验和分析；对上述的滚珠旋压力、变形区温升、基于应力三轴度的镁合金管塑性性能提升、高速滚珠旋压的临界转速进行了实验研究。