【作者】 谭武军；

【导师】 黄辉； 李明；

【作者基本信息】 中国工程物理研究院 ， 武器系统与运用工程， 2008， 硕士

【摘要】 含能晶体的力学性能(如弹性模量、断裂强度等)和力学行为(如位错滑移、塑性屈服、断裂破坏等)对含能材料的设计、制备,以及起爆性能和安全性能都具有重要的影响。本论文从含能晶体力学性能的宏观和微观两个方面出发,分别对晶体颗粒集合体和单晶体的力学性能进行了研究。基于含能晶体颗粒集合体力学性能与晶体品质的相关性,选用不同品质的RDX和HMX晶体进行压制试验,采用Kawakita和Heckel方程对压制曲线进行拟合,从拟合常数来评价晶体颗粒的力学性能和品质,并进一步对压制过程进行了分段分析,探讨了压制实验参数对实验结果的影响,研究了压制过程产生的声发射信号的规律。结果表明:Kawakita和Heckel压制方程的以模量倒数为量纲的拟合常数具有系综统计平均意义,可以用来表征晶体颗粒的力学性能;拟合常数越小,晶体品质越好;重结晶RDX和HMX晶体所得到的拟合常数明显小于工业级晶体颗粒,判断重结晶晶体品质比工业级颗粒高,与其它评价方法的结果一致;基于压制曲线曲率变化特点并结合压制实验过程,将晶体颗粒压制过程分为重排、破碎和压实三个阶段,破碎阶段的拟合常数结果最能真实反映含能晶体的力学性能;压制实验各参数中,模具尺寸和单位面积装粉量对实验结果的影响非常明显,样品的初始高度(密度)只有在差别较大时才会产生较大的影响,而粒径分布和加载速率的影响均非常有限;压制过程产生的声发射信号的幅度、波击计数(率)和上升时间等特征参数呈现出明显的与压制行为对应的规律。用纳米压痕方法对高品质大尺寸的β-HMX单晶体进行实验,首次测得其在(010)和(001)两个晶面上的弹性模量(分别为22.88GPa和26.05GPa)和硬度(分别为1.11GPa和0.95GPa),并采用各向异性弹塑性本构模型和文献的HMX晶体弹性常数对压痕实验进行有限元数值模拟,初步探讨了模拟和实验曲线的差别并分析了其中的原因。研究结果表明:Zaug和Sewell等人的弹性模量值均比压痕实验结果要小;采用Zaug数据的模拟曲线与实验曲线存在很大差别,与Zaug的数据计算得到的剪切模量很小有关;采用Sewell数据的模拟卸载曲线与实验曲线比较接近,表明实际上Sewell的弹性模量与压痕实验值比较接近,但二者因为测量原理不同而在数值上存在较大差异,分析认为作为三维加载方式的压痕方法获得的材料弹性参量更接近工程实际应用意义的弹性参量。本研究定量表征了RDX和HMX晶体集合体的统计平均力学性能,确定了HMX单晶体的纳米压痕方法的微观力学性能,对预测含能材料的力学行为和起爆行为具有重要的应用价值。更多还原

【Abstract】 Abstract:The mechanical properties(such as elastic modulus or fracture strength) and mechanical behaviors(for instance,dislocation slipping,plastic yielding,cracking failure and so on) of energetic crystals are crucial to the designing,preparing,detonation as well as security performances of energetic materials.In this paper,the mechanical properties of energetic crystals were investigated both from the perspectives of crystalline particle aggregates and single crystals.Owing to the high correlation of mechanical properties and crystalline qualities,RDX and HMX crystalline aggregates of different qualities were selected to be compressed so as to obtain compaction curves,which then were fit by the Kawakita and Heckel equations.The fitting constants were used to evaluate the mechanical properties and qualities of the crystals. Further studies were executed on segmentation of the compaction process and influences of the test parameters.What’s more,the rules of the acoustic emission signals,which were produced in the compression,were investigated,too.The results show that the constants of the Kawakita and Heckel equations,which are of dimension of the reciprocal of modulus and bear the meanings of ensemble average,can be employed effectively to describe the mechanical properties of the crystalline aggregates.The constant is lower and the quality is better.While the recrystalline particles have lower constant values,which approves that their qualities are better than the commercial grade ones.The evaluation results are consistent with other means,which validates the effectiveness of the method by mechanical properties. Basing on the traits of the curvature of compaction curves and the process of compressing,the compression process is divided into three regimes,i.e.rearrangement,fragmentation and compaction stages.It is the best and true reflection to the mechanical properties and interactions of aggregates to fit with the mere data of fragmentation regime.The parameter settings of compression experiment were also discussed,and the conclusion is that:the size of the mould and the charge amount per unit area straightly contribute to the results;the initial height or density acts only when the charge manners vary greatly;while the particle size distribution and loading rate have little influence.The acoustic emission(AE) signals were detected when pressing the crystalline granules.The maximum amplitude,hit count(rate) and rise time present regularly in the procedure,which corresponds to the mechanical behaviors of the granules.Theβ-HMX single crystals with high quality and large dimension were loaded by instrumented nano-indenter in the(010) and(001) plane,respectively.The modulus and hardness were acquired for the first.The elastic moduli are 22.88GPa and 26.05GPa of(010) and(001) plane respectively,while the hardness values are 1.11GPa and 0.95GPa.Finite element simulations were performed for indentation experiment,in which the anisotropic elastic-plastic constitutive model and HMX constants published in papers were used.And the differences between experimental and simulation curves were discussed preliminarily.The results show that both the modulus derived by Zaug and Sewell are markedly lower to the indentation results.The simulation curves of Zaug are very different from the experimental curves,which may be caused by its very low shear modulus.While the unloading curves of Sewell are quite close to the indentation curves,indicating that the elastic modulus by Sewell approach to the real modulus in indentation experiment,yet they are different in the numerical values just because of their differences in the principles.In this paper,the pilot studies show that the elastic properties obtained by indentation,in respect that it is three-dimensional stress statue during the loading process,are much close to the properties the engineering practice.更多还原