【作者】 乔良；

【导师】 何勇； 张先锋；

【作者基本信息】 南京理工大学 ， 火炮、自动武器与弹药工程， 2013， 博士

【摘要】 多功能含能结构材料(Multifunctional Energetic Structural Materials, MESMs)是一类通常由铝热剂、金属间化合物、金属高分子化合物、以及一些亚稳态的金属化合物组成的混合物。因其同时具有结构强度和冲击反应释能特性,在高效毁伤与防护方面有着重要的应用前景。冲击载荷作用下含孔隙的MESMs颗粒间的碰撞形成热点进而发生化学反应,该过程受控于颗粒形状、尺寸、分布等细观特性。本文对这一涉及材料冲击空间宏细观尺度下热-力-化学多场响应的复杂问题,针对以Al/W/PTFE为代表的MESMs,通过数值模拟、理论计算及实验验证方法研究材料细观特性对其冲击反应的影响,建立了两者之间的关联机制。主要研究内容如下：(1)针对MESMs含孔隙多组分混合物特点,开展了MESMs冲击物态方程以及冲击温升控制的冲击反应热化学模型研究从现有密实态单质材料物态方程入手,基于零温混合物冷能叠加原理、Wu-Jing模型结合热力学关系建立了含孔隙多组分混合物的冲击物态方程。之后从等压路径出发,考虑自由电子项的贡献得到了MESMs的冲击温升计算方法。最后,将Arrhenius反应速率模型与反应动力学模型相结合,建立了基于冲击温升控制的MESMs冲击反应热化学模型。并利用该模型对典型的MESMs进行了冲击反应计算。(2)以MESMs类颗粒材料细观分布特性为基础,进行了可真实反映材料细观特性的细观模型生成方法研究首先,从材料细观结构入手,分别从颗粒形状、尺寸和分布三方面进行分析并引入相关参数。之后,利用随机生成方法从颗粒形状、尺寸两方面计算得到初步的材料细观模型。最后,采用智能优化算法,从颗粒位置分布角度对模型中颗粒位置进行更新,直至获得满足真实统计规律的模型。基于此方法,得到了Al/W/PTFE细观模型。(3)基于多物质欧拉算法,开展典型MESMs冲击压缩细观行为数值模拟研究利用动力学有限元软件AUTODYN,通过合适的算法、材料模型及初始、边界条件的选择和加载,在不考虑冲击反应的情况下实现MESMs冲击压缩过程的细观模拟。并以Al/W/PTFE为例,计算得到了不同材料组分及颗粒粒径尺寸下的冲击压缩Hugoniot参数及热力学响应情况。结果表明,Al/W/PTFE中材料组分配比、颗粒粒径尺寸在很大程度上影响着其冲击压缩Hugoniot参数以及热力学响应。经分析得到了材料组分、颗粒粒径尺寸对冲击压缩响应的影响规律。(4)以细观模拟动力学响应为输入参数,开展细观冲击响应与宏观反应行为关联机制研究采用宏细观方法将细观尺度上MESMs冲击压缩模拟结果与宏观冲击反应热化学模型相结合,将冲击压缩热-力学响应扩展至热-力-化学响应,实现了对冲击反应的模拟计算。并对不同冲击速度、组分配比及颗粒粒径尺寸下的Al/W/PTFE的进行冲击反应计算,得到相应的反应结果,进而分析得到冲击反应与细观特性的关联机制。(5)开展不同配方与颗粒级配关系MESMs冲击压缩动力学响应特性验证实验研究采用模压成型和真空烧结工艺方法制备了不同材料组分、颗粒级配关系的Al/W/PTFE试件,开展了准静态及低速动态冲击压缩实验。准静态压缩实验中,由材料应力-应变曲线,分析了材料组分和颗粒级配关系对材料宏观强度的影响规律。并用SEM拍摄实验前后的试件细观照片,直观获取了材料准静态压缩前后颗粒情况。低速动态冲击压缩实验中,利用PVDF压电传感器测量得到不同方案试件对应的冲击波参数。实验结果表明,Al/W/PTFE材料组分配比、颗粒粒径尺寸对材料宏观强度以及冲击压缩Hugoniot参数影响明显,验证了之前细观模拟所得结论。更多还原

【Abstract】 Mulitifunctional Energetic Structural Materials (MESMs) are evolving as a new class of mixture which usually including thermites, intermetallics, metal-polymer mixture, metastable intermolecular composites. As the MESMs could provide dual functions of structural strength and energy release characteristics under intensive shock loading, there is a promising application in both efficient damage and protection field. The shock-induced chemical reaction (SICR) behavior of MESMs is significantly influnced by their mesostructure. During the shock compression process, particles of MESMs collide with each other, followed by temperature rising in the surface interface, hot spot formed and reaction initiation. Therefore, chemical reaction is controlled by the mesoscale characteristics, such as the mean particle size, the variation in particle size, shape and distribution of the particles. In this work, such a complex shock compression problem that refers the spatial from mesoscale to macroscale and couple thermal-mechanical-chemical response is investigated. Al/W/PTFE which is typical MESMs is seleted and mesoscale numerical simulation, theoretical analysis and experimental research are used to conducted on such the problem. The main contents could be summaried as follows:(1) Based on the multi-components with porosities mixtures characteristics of MESMs, the shock equation of state for MESMs and temperature controlled shock-induced chemical model were been investigated.In order to analyze the dynamic behaviour and temperature rise of MESMs, an equation of state for multi-components with porosities was developed by combining the equation of state for solid, cold energy mixture theory and Wu-Jing model. Then, the temperature rise under shock compression is calculated from isobaric path incorporate with thermodynamic relations, in which the contribution of free electrons was considered. Finally, the Arrhenius reaction rate and Avrami-Erofeev kinetic models that are controlled by shock temperature are used to calculate the extent of reaction of MESMs. A thermochemical model for shock-induced reactions, which includes the reaction efficiency, is given by combining shock temperature rise with chemical reaction kineties. Theoretical calculations are compared with experimental results for several typical MESMs.(2) According to the mesoscale distribution characterstics of MESMs, a method which could generate the mesoscale model of MESMs following the real mesoscale distribution was developed.Based on the mesoscale structural characteristics of the particles metal materials, several control parameters including particle shape, particle size and particle position were introduced to describe its meso-scale characteristics. Methods as random number generation method, intelligent optimization algorithm and relevant constraint were adopted, for the purpose of making the simulation model gradually approaching to the real particle distribution in meso-scale. It shows that the randomly generated simulation model which meets the statistical laws could reproduce the distribution of real particles. With the method, mesoscale model of Al/W/PTFE with different schemes were generated.(3) Based on the multi-materials Euler algorithm, the shock compression response of typical MESM were been investigated in mesoscale.By exploiting AUTODYN FEM software, after appropriate algorithm, material model, boundary and loading conditions were selected and loading, the shock compression of MESMs in mesoscale were simulated without considering the chemical reaction. Typical MESMs (Al/W/PTFE) was selected to investigate the effect of material component and particle size on the Hugoniot parameters and thermodynamic response under shock compression. The results show that the Al/W/PTFE material component ratio, particle size size to a large extent influence the impact of compression the Hugoniot parameters as well as the thermodynamic response.(4) The shock compression response of MESMs in mesoscale was associated with the shock reactions model in macroscale by consider the thermodynamic response from simulation as an input parameters.The shock compression responses of MESMs in mesoscale were incorporated with the shock-induced chemical reaction model in macroscale by multiscale method. Therefore, the shock compression responses were extent to themo-mechanic-chemical response. And the shock reaction results under different shock velocity, material component ratio, particle size were obtained.(5) The shock compression response of MESMs under different material component ratio, and particle size were investigated by experimental verification.Molding and sintering process were used to manufacture the Al/W/PTFE speciments with different material component ratio and particle size. Then, quasi-static and low-speed dynamich shock compression experiments were conducted on the speciments, the effect on the strength was acquired from strain-stress curve. Post-shock microstructural analysis of recovered material with SEM and comparison of calculated and measured product states is used to establish the criterion for reaction occurring in different granular or mesostructure characteristics At the same time the hypervelocity flyer plate impact experiment was carried out to investigate the reaction response of typical MESMs and time resolved stress measurement (using PVDF gauges) which is to be used to determine the shock state.更多还原