伴随多面体粒子破碎的散粒体系统离散元数值研究

The problem that the partial particles in propellant bed are fracture under the load is the mechanical problem of granular system with partial polyhedral particles' brittle fracture. Dense accumulated structure of granular system which is made up of many polyhedral particles only need the position and angle of the particles. The code of discrete element method which describes granular system made up of the polyhedral particles is optimized. The optimized ways are to use the fast contact detection algorithm and reasonable contact model. Especially, the fast contact detection algorithm is the key technique. And then, the dense accumulated structure of propellant bed is obtained through using the code. In order to study the brittle fracture level of single particle, the spring-sphere random fracture model based on discrete element method is reasonably chosen. The anther key technique, associating the complex variable differentiation and experiment, is used to solve the problem of computational parameters. And then, propellant particles are numerical simulated under the different conditions. Combined application between the brittle fracture model and the code of discrete element method which describes granular system made up of the polyhedral particles, and partially solving the problem that the contact parameters are wholly trial, and on the basis of the integration and development of discrete element method, the code of granular system with partial polyhedral particles' brittle fracture is obtained. Propellant bed is numerical simulated using the code under the different conditions. This project is to solve the mechanical problem of granular system, propellant bed, with partial polyhedral particles' brittle fracture, and is the basis of designing the high function canon.

发射药床在外载荷作用下的部分药粒发生破碎问题，其实质是伴随部分粒子脆性破碎的多面体粒子组成的散粒体系统力学问题。针对发射药床初始堆积结构仅需药粒位置和方位特点，解决空间接触识别算法难题，合理选择接触模型，优化多面体粒子组成的散粒体系统离散元程序，生成密实的发射药床初始堆积结构；针对发射药粒破碎定量研究特点，合理选择脆性材料的破碎模型，结合复变量求导法及试验解决破碎模型中计算参数选取难题，采用基于离散元的弹簧-球单元随机破碎模型数值研究发射药粒不同工况下的破碎问题；有机结合破碎模型和多面体单元散粒体系统离散元程序，部分解决接触参数完全试算问题，通过整合和进一步发展现有的离散单元法，研发能够解决伴随部分粒子破碎的多面体粒子组成的散粒体系统受力分析的数值方法和程序，数值研究发射药床的力学性能。为解决发射药床伴随脆性药粒破碎的散粒体系统力学问题提供技术保障，为高性能火炮研制提供科学依据。

高初速已成为现代高性能火炮的主要特点之一。提高弹丸初速，通常采用的方法是提高装填密度和采用高能发射药，这使得膛内燃烧与力学环境越来越恶劣。发射药床在发射过程中发生膛炸等安全性事故，根本的原因是发射前期发射药粒发生大量的破碎。发射药床在外载荷作用下的部分药粒发生破碎问题，其实质是伴随部分粒子脆性破碎的多面体粒子组成的散粒体系统力学问题。本研究针对伴随部分粒子脆性破碎的多面体粒子组成的散粒体系统力学问题，完成了如下研究内容：从空间快速接触识别算法和接触模型简化两个方面入手，优化多面体粒子组成的散粒体系统离散元程序，生成了单基发射药床初始堆积结构；在已有破碎模型基础上，发展了弹簧－球单元的随机破碎模型及程序，定量模拟研究了单基发射药粒的破碎；将单个脆性粒子的弹簧－球单元的随机破碎模型应用到优化后的多面体粒子组成的散粒体系统离散元程序中，实现了散粒体系统多面体粒子破碎的数值方法及程序，数值研究了单基发射药床的力学性能；结合复变量求导法及试验部分解决了计算模型中计算参数选取难题。本项目的完成为解决发射药床伴随脆性药粒破碎的散粒体系统力学问题提供技术保障，为高性能火炮研制提供了科学依据。