钛合金超高应变率材料模型及其切削机理研究

Titanium alloy has been widely used to aerospace industry due to its excellent material behavior. Nowadays, numerical simulation has been widely used in titanium alloy machining as a mature technique with low cost. The prediction accuracy greatly depends on the material constitutive model. However, the condition of mechanical experiment for obtaining material model parameters exists some weakness, because the conditions of mechnical experiments for material model commonly do not cover the overall cutting condition. For example, the strain rate condition of critical cutting aeras (e.g., shear band) is 100 times as high as that of mechanical experiments, which has a critical effect on the prediction precision. Therefore, the aim of this research is to improve the material model from a high strain rate condition (100-10000s-1) to an ultra-high strain rate condition (10000-1000000s-1), according to the simulated SHPB test results and cutting experimental results under various strain rate conditions, ultimately, making breakthrough at the strain rate condition of the traditional experimental conditions. Therefore, the material model parameters under the overall strain rate condition in cutting can be obtained, therefore, the difference of the mechanical experimental condition and the cutting condition can be eliminated. Furthermore, the prediction precision of critical cutting aeras in titanium alloy cutting simulation can be improved radically, promoting the industrial apllication of the machining simulation.

钛合金以其优异的综合性能被广泛应用于航空航天等领域。数值模拟作为一种经济、成熟的建模方法，在钛合金切削仿真中发挥着越来越重要的作用。目前仿真结果的精度主要依赖材料本构模型及其参数，现有本构模型参数的获取条件存在着很大的不足，获取其参数的力学试验的应变率条件没有覆盖切削加工全域，如钛合金剪切区的应变率条件超出材料本构模型参数获取条件约100倍，这种差异已成为影响其仿真结果精度的关键问题。本项目根据材料变形属性，突破现有的力学试验应变率条件的限制，通过变应变率条件下SHPB数值模拟及切削试验，采用递推的方法，将仿真模型中材料参数由高应变率（100-10000s-1）条件逐步提高到超高应变率（10000-1000000s-1）范围。获得切削加工全域条件下的材料模型参数，从根本上消除参数获取力学试验条件与切削条件之间的差异。从本质上提高钛合金切削仿真结果的精度，推动切削加工数值模拟技术的工业应用。

本项目围绕钛合金切削加工变形属性，对切削高应变率、高温条件下的塑性、失效材料模型及切削机理展开研究。通过覆盖高应变率条件下的力学压缩实验，研究了钛合金在接近切削主剪切区高应变率、高温条件下的材料变形流动应力，并对材料变形过程中的微观结构的变化进行了研究，建立了温度相关的应变强化塑性模型。针对钛合金切削过程，揭示了切削超高应变率条件下的塑性和失效变形行为，提出了完整预测切削变形过程材料流动应力的方法，并采用有限元二次开发对钛合金切削过程进行了仿真，并通过切削实验验证。结合SHPB仿真及钛合金切削加工实验，研究了应变率对钛合金切削变形属性及切削机理的影响。完成了申请书中拟定的相关研究内容。研究成果可以为钛合金以等难加工材料的切削仿真提供可靠的流动应力建模方法，对研究钛合金切削机理及切削工艺参数优化具有重要的意义。