改性双基推进剂断裂力学行为研究

发布时间：2018-05-17 00:01

本文选题：断裂行为 + 断裂准则　；参考：《南京理工大学》2015年硕士论文

【摘要】：随着固体火箭发动机朝大口径、远射程的方向发展,具有粘弹力学特征的改性双基推进剂表现出越来越明显的率相关性,尤其是在高点火冲击、高发射过载、跌落撞击等冲击载荷下,其力学性能完全区别于准静态条件。本文针对这种情况,使用脆性材料力学理论对改性双基推进剂断裂力学行为进行了研究。本文使用分离式霍普金森压杆(SHPB)和万能材料试验机对改性双基推进剂的I型和II型断裂行为进行了实验研究。I型断裂主要进行了10-4～101s-1应变率下的单轴拉伸断裂实验,得到了平面应力、应力集中对断裂性能的影响及断裂能在准静态条件下随应变率的变化规律。II型断裂研究使用剪切试件进行102-103s-1应变率下的高速撞击实验,得到了改性双基推进剂高应变率下的断裂行为判定准则；并补充以104～101s-1应变率下的剪切试件压缩实验作为对比。通过实验结果比较可知,改性双基推进剂在高应变下表现出脆性断裂现象,而准静态环境中只有在大变形下才会发生断裂,即应变率对材料断裂形式影响很大。高应变率下,断裂能与应变率呈线性相关；准静态下,断裂能与应变率呈指数相关。同时,本文还使用分离式霍普金森压杆对改性双基推进剂的本构进行了研究,得到了可以准确描述该材料在高应变率下力学行为的线性ZWT本构模型。为了将上述实验结果用于改性双基推进剂工程预测数值计算,采用FORTRAN语言对材料的本构模型和断裂行为判定准则进行了VUMAT程序实现。最后使用ABAQUS对圆柱形试件和II型剪切试件进行数值计算验证,以确定材料的本构与断裂行为判定准则的正确性。
[Abstract]:With the development of solid rocket motor in the direction of large caliber and long range, modified double base propellants with viscoelastic mechanical characteristics show more and more obvious rate correlation, especially in high ignition impact and high emission overload. Under the impact load such as drop impact, the mechanical properties are completely different from the quasi static condition. In this paper, the fracture mechanics behavior of modified double base propellants is studied by using the theory of brittle material mechanics. In this paper, the mode I and mode II fracture behaviors of modified double-base propellants have been experimentally studied by using split Hopkinson compression bar (SHPB) and universal material testing machine. The uniaxial tensile fracture tests of type I propellants at 10-4~101s-1 strain rate have been carried out. The effects of plane stress and stress concentration on fracture properties and the variation of fracture energy with strain rate under quasi-static conditions are obtained. The criterion of fracture behavior of modified double base propellant at high strain rate is obtained, and the compression test of shear specimen at 104~101s-1 strain rate is added as a comparison. The experimental results show that the modified double base propellants exhibit brittle fracture under high strain, but only under large deformation in quasi static environment, that is, the strain rate has a great influence on the fracture form of the material. At high strain rate, the fracture energy is linearly correlated with strain rate, and the fracture energy is exponentially correlated with strain rate under quasi-static condition. At the same time, the constitutive model of modified double base propellant was studied by using split Hopkinson pressure bar, and a linear ZWT constitutive model was obtained to describe the mechanical behavior of the material at high strain rate. In order to apply the above experimental results to the engineering prediction numerical calculation of modified double-base propellants, the constitutive model of the material and the criterion of fracture behavior were realized by VUMAT program using FORTRAN language. Finally, the numerical calculation of cylindrical and type II shear specimens is carried out with ABAQUS to determine the correctness of the constitutive and fracture behavior criteria of the material.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：V512

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