金属成形模具型面瞬态接触应力峰演变及原位测定研究

Starting with the analysis of the contact stress on the die surface in metal forming process, the coupling model will be built up with the stress field of the large plastic deformation and the potential gradient field of piezoelectric material based on plastic mechanics theory and piezoelectric effect theory utilizing the Finite Element Method (FEM). The distribution of the contact stress on the die surface will be focused and the distribution function of the transient contact stress peaks will be constructed. The evolution of the contact stress distribution from transient state to steady state will be investigated. A half-opened and semi-submerged measuring structure imbedded with the four-layer fine piezoelectric cable will be designed and the output signals will be calibrated, then the existence of the transient peaks of the contact stress will be tested and verified. In order to investigate the positive correlation between the contact stress peaks and the surface wear, the dynamic amplitude of the contact stress in the key wear controlled zone will be measured. A quantitative method for wear estimation on die surface will be proposed and the method will support the strength design of the precise plastic forming. The capability of the in-situ measuring system will be expanded and improved in order to integrate and package the physical experiment software and hardware to form a set of multi-channel testing instrument with multi-sensor for the interface contact stress measurement.

从分析金属成形模具型面接触应力着手，结合塑性力学理论和压电效应理论，利用有限元耦合建模方法，构建塑性大变形应力场与压电材料电势梯度场的耦合模型；研究接触应力在型面上的分布，构造瞬态接触应力峰值分布函数，探索接触应力分布由瞬态向稳态演化的规律；设计四层结构压电细缆半开放半潜式原位测量结构，标定压电输出信号，验证型面瞬态接触应力峰的存在性，测定关键磨损控制特征区接触应力的动态变化幅值，揭示接触应力峰值与模具型面磨损量之间的正相关性；阐明模具型面磨损估算的量化方法，为精密塑性成形模具强度设计提供科学依据；拓展压敏细缆半开放式半潜式原位测量结构的功能，集成封装物理实验中软硬件系统形成多测点多通道的界面接触应力检测仪器。

随着材料科学的进步，各种高强度材料正在汽车轻量化技术升级中被推广使用。随之而来的是模具磨损控制和磨损量估算难题直接影响各种高强度材料塑性成形的精度设计。工程师需要确定磨损量与冲压次数对塑性成形产品精度下降的量化关系，以便精确制定首次修模寿命，控制产品精度一致性。这对于大型车身高强钢覆盖件模具尤其重要。. 解决上述难题的关键是弄清金属板料与模具型面的接触磨损过程中，接触应力的分布特征，是否存在超高的接触应力峰值？若存在应力峰值，即可确定模具型面局部快速磨损的主要因素就是峰值的接触应力。需要进一步给出应力峰值的瞬态分布与演变过程，籍此改进传统的Archard方程磨损量估算方法，建立基于型面接触应力峰值瞬态分布的磨损量估算公式。. 为了探究接触应力峰值分布规律，项目利用有限元建模分析和基于压电细缆原位测定两种手段，获取金属板料塑性成形过程中，在模具型面上产生的接触应力分布及量值。. 基于金属塑性力学理论和压电效应理论，构建塑性大变形应力场与压电材料电势梯度场的耦合模型；分析接触应力在型面上的分布，构造瞬态接触应力峰值分布函数，揭示接触应力分布由瞬态向稳态演化的规律；设计压电细缆半开放半潜式原位测量与标定装置，标定压电细缆在相同自由度约束下的输出电信号；设定特定的采样频率，经过采集电路和放大电路获取连续的瞬态电压输出；对采集数据进行傅立叶变换和拟合处理，验证了型面瞬态接触应力峰的存在性，测定关键磨损控制特征区接触应力的动态变化幅值。将接触应力峰值与模具型面磨损量之间的量化关系带入磨损估算方程，改进了模具型面磨损量的估算方法，为精密塑性成形模具强度设计提供科学依据；项目研究过程中所设计的压敏细缆半开放式半潜式原位测量及标定装置可以改进传统基于电阻应变片的间接测量方法，后续经过集成封装可以构成多测点多通道的界面接触应力检测仪器。