基于真实细观形貌的固体推进剂力学性能虚单元预示方法

Virtual element method for mechanical properties prediction of solid propellants based on real mesomorphology

真实的细观形貌是进行固体推进剂细观力学性能预示的基础。通过CT扫描图片处理获得了固体推进剂真实的细观几何形貌及各组分参数,并生成了固体推进剂颗粒填充模型;采用多边形网格剖分方案,减少使用常规单元时各组分颗粒尺度差异带来的低质量网格影响;通过对单元和节点的后处理,设计了应对真实细观形貌的周期边界条件处理方案;引入虚单元法(VEM)开展固体推进剂细观力学性能预示,设计含夹杂算例,验证了VEM以及周期边界条件处理方案的可行性和准确性;利用内聚力单元模拟基体与颗粒间的“脱湿”效应,对真实细观模型以及颗粒填充模型开展了等效松弛模量测试。仿真结果表明,真实细观模型中不规则的颗粒几何形状会抑制“脱湿”现象的发生,其表现出的等效松弛模量较颗粒填充模型大。此外,两类模型预示的松弛模量最大相对误差为13.1%,这表明在固体推进剂配方设计中颗粒填充模型可以替代真实的几何模型进行固体推进剂等效力学性能的预示。结合VEM在应对固体推进剂各组分几何尺度差异以及周期性边界条件设计方面的优势,可进一步利用VEM开展三维固体推进剂力学性能的预示。

The real mesomorphology is the basis for predicting the mesomechanical properties of solid propellants.The real me⁃so⁃geometry morphology and component parameters of the solid propellant were obtained by processing the CT scan images,and the solid propellant particle filling model was generated.The polygonal mesh division scheme was adopted to reduce the effect of low⁃quality mesh caused by the difference of particle size of each component when using conventional elements.Through the post⁃pro⁃cessing of the elements and nodes,the periodic boundary condition processing scheme was designed to deal with the real mircomor⁃phology.The virtual element method(VEM)was introduced to predict the mesomechanical properties of solid propellants.The fea⁃sibility and accuracy of VEM and periodic boundary condition treatment schemes were verified by designing examples with inclu⁃sions.The effect of“dewetting”between matrix and particles was simulated by cohesive element,and the equivalent relaxation modulus was tested for the real mesoscopic model and the particle⁃filled model.The simulation results show that the irregular parti⁃cle geometry in the real mesoscopic model can inhibit the phenomenon of“dewetting”,and the equivalent relaxation modulus of the model is larger than that of the particle⁃filled model.In addition,the maximum relative error of the relaxation modulus predicted by the two types of models is 13.1%,which indicates that the particle filling model can replace the real geometric model to predict the equivalent mechanical properties of solid propellants in the design of propellant formulation.Combined with the advantages of VEM in dealing with the geometric scale difference of solid propellant components and the design of periodic boundary conditions,VEM can be further used to predict the mechanical properties of three⁃dimensional solid propellants.