修正时间硬化理论的PBX蠕变模型及其应用

利用基于修正时间硬化理论的蠕变模型来模拟炸药部件的短时蠕变行为.以HMX基PBX的15次单轴压缩蠕变实验数据确定了15组模型参数,抽 取3组利用ANSYS软件进行模拟实验来验证模型.根据正态分布小概率原理最终确定了通用的蠕变模型参数.应用获得的蠕变模型对真空吸附作用下的该型PBX部件进行蠕变仿真,获得其在1h内的蠕变变形.理论分析和数值模拟结果表明,该模型能很好地描述HMX基PBX的蠕变特性,可以运用于机械加工过程中炸药部件受夹持力作用的短时蠕变仿真.     

HMX基PBX的温度环境适应性

对HMX基PBX进行了-40～+75℃温度循环试验和温度冲击试验,采用超声波参量检测方法对炸药的内部损伤进行了分析和表征。并对环境试验前后炸药的力学性能和破坏方式进行了实验研究。结果表明,温度循环试验和温度冲击试验将导致HMX基PBX产生热损伤,使HMX基PBX压缩强度轻微下降,而对拉伸强度影响不大。     

核壳型HMX@TATB复合炸药造型粉制备技术研究

核壳型HMX@TATB复合炸药不仅能够显著降低HMX炸药的感度,还能有效保持HMX的高能量密度水平,在未来钝感弹药和安全型高能推进剂领域展现了较好的应用前景,而核壳型HMX@TATB复合炸药基PBX的制备研究对其相关性能测试和后期应用研究起重要作用。本研究探索了核壳型HMX@TATB复合炸药为基PBX造型粉制备过程中的转速、温度和粘结剂的滴加速度等工艺参数对造粒包覆的影响,得到了稳定的百克级核壳型HMX@TATB为基PBX造型粉的造粒工艺。     

高品质压装HMX基PBX炸药的冲击波感度

为改善HMX基PBX的安全性能,通过隔板试验研究了高品质HMX的粒度对压装PBX炸药冲击波起爆性能的影响.结果表明·对于相对密度较高(98.5％TMD)的压装HMX基PBX,与普通品质(平均粒径30μm)相比,使用高品质HMX(20 μm)后PBX的冲击波感度下降了7％,当高品质HMX的粒度增至150μm后,其冲击波起...     

一种含LLM-105的HMX基低感高能PBX炸药

研究了不同颗粒形态的LLM-105对HMX的降感作用以及HMX/LLM-105基炸药配方用的黏结体系和钝感体系.设计出一种HMX/LLM-105配方,采用机械感度和冲击波感度以及板痕试验和圆筒试验对其安全性能和爆轰性能进行了测试.结果表明,LLM-105可作为含能钝感剂用于HMX基PBX炸药,该种含LLM-105的HMX基PBX爆速约8700 m/s、爆压34 GPa以上、比动能为1.560 kJ/g,冲击波感度比JOB-9003炸药低10%,是一种新型的低感高能炸药.     

HMX颗粒特性对压装PBX苏珊感度的影响

采用苏珊试验测试了HMX基压装PBX炸药在低速撞击下的感度,研究了HMX的晶体品质、颗粒尺寸等对PBX撞击感度的影响。结果表明,HMX晶体品质的提高有利于提升PBX的反应阈值速度;在晶体品质相当的情况下,当HMX颗粒由20μm增大到105μm时,PBX的苏珊撞击响应的阈值速度由47m/s升至59m/s,而撞击响应的程度有一定下降。苏珊试验中存在一个临界撞靶速度(约100m/s),低于该速度,含高品质HMX的PBX反应程度小于含普通品质HMX的PBX;高于该速度,含高品质HMX的PBX反应程度则大于含普通品质HMX的PBX。     

压装PBX炸药DDT管实验初始反应演化过程分析

在DDT管中采用惰性模拟材料研究电点火头和黑火药产生的初始压力对惰性模拟材料点火端面的影响;采用高速摄像机记录了DDT管内HMX基压装PBX炸药的燃烧发光过程;分析了压装PBX炸药DDT管实验初始反应演化过程。结果表明,电点火头和黑火药产生的初始压力会引起邻近脆性炸药端面裂纹形成和局部破坏,炸药燃烧的火焰沿炸药基体裂纹和炸药与管壁之间的缝隙中传播,压装PBX炸药初始反应演化与缝隙对流燃烧过程密切相关。     

HMX基PBX炸药热损伤的数值计算与实验研究

基于二维平面轴对称模型,采用有限元软件ANSYS,对HMX基PBX在温度冲击载荷作用下的温度场和应力场进行数值计算,为了验证有限元模拟分析的可靠性,对HMX基PBX药柱进行了温度冲击试验,用热电偶和声发射技术测量药柱表面的温度及热损伤。数值计算结果表明,在降温阶段,药柱侧面中部受到较大轴向拉应力作用而产生热损伤。实验结果与计算结果吻合较好,说明HMX基PBX热损伤破坏方式为拉应力破坏,抗拉强度可以较好地反映材料的耐热损伤能力。     

PBX炸药细观结构冲击点火的二维数值模拟

为了研究冲击加载下非均质炸药的点火机理,对PBX炸药细观结构在冲击加载下的响应过程进行了二维数值模拟.首先对炸药颗粒的压制过程进行数值模拟,获得PBX炸药的细观结构模型.然后对炸药冲击点火进行数值模拟计算,考虑了热力耦合作用和炸药自热反应,分析了炸药颗粒尺寸、密度和黏结剂对炸药冲击点火的影响.结果表明,冲击作用下PBX...     

PBX炸药二维冲击起爆机理的数值模拟

建立了基于KIM模型的一个化学反应速率方程模型,用于分析PBX起爆和爆轰行为的损伤作用.运用遗传算法确定了反应速率方程的相关参数,通过与Forest-Fire反应速率模型数值模拟结果对比,验证了所建模型的合理性.将所建反应速率方程模型嵌入有限元程序对PBX炸药二维冲击起爆过程进行数值模拟,数值模拟结果与试验结果吻合较好,可以描述分析受冲击加载造成孔隙率、颗粒尺寸等变化的损伤炸药的冲击起爆过程.     

Degradation of a poly(ester urethane) elastomer. IV. Sorption and diffusion of water in PBX 9501 and its components

In preparation for studying the hydrolytic degradation of Estane® 5703 in the plastic‐bonded explosive PBX 9501, the sorption (solubility) and diffusion of water in PBX 9501 and each of its components are studied experimentally and modeled theoretically. Experiments are reported that measure the weight gain or loss due to a change in the relative humidity (RH). For all of the components, the equilibrium amount of water sorbed per gram of sample is linear in the RH at low relative humidities but curves upwards at higher relative humidities. This behavior is modeled with a water cluster model. Diffusion coefficients are determined by modeling the time dependence of the water concentrations assuming Fickian diffusion, and that fits the data for some of the materials. However, all the samples that contain the explosive HMX show much more complicated behavior at high relative humidities, and that is presented and discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Enhancement of Creep Properties of TATB‐Based Polymer‐Bonded Explosive Using Styrene Copolymer

In order to investigate the effects of binder component on the creep properties of polymer‐bonded explosive (PBX), three‐point bending creep behaviors of 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB)‐based PBX and its styrene copolymer modified formulation were studied by dynamic mechanical analyzer. The experimental results showed that owing to the addition of reinforcing agent (styrene copolymer) with high glass transition temperature and high mechanical strength, the creep resistance performance of the modified formulation was improved with reduced creep strain and constant creep rate and prolonged creep failure time. A six‐element mechanical model was applied to simulate the creep behaviors of TATB‐based PBX and its modified formulation. The constitutive equation of creep curves under different conditions were obtained by nonlinear fit. The predicted theoretical results coincided quite well with the experimental data.     

Delay Mechanism of β→δ Phase Transition of Cyclotetramethylene Tetranitramine in Polymer Bonded Explosive Formulations by Heat Conduction Obstacle

The β→δ phase transition (PT) of cyclotetramethylene tetranitramine (HMX) plays an important role in the safety of explosives when they are exposed to heat. In this work the effect of HMX content on the PT of HMX in Polymer Bonded Explosive (PBX) is reported. Using in situ X‐ray diffraction (XRD) test combined with quantitative analysis, the dependence of the PT temperature and dynamic behavior of HMX in PBX formulations [HMX+triaminotrinitrobenzene (TATB)+Olefin] on the content of HMX is investigated. The results show that the β→δ PT temperature gradually increases with the reduction of HMX content and with the increase of TATB content. Additives of TATB and olefin in high concentration can form compact coatings on the HMX crystals. Such coatings can delay the nucleations of δ‐HMX by inhibiting the volumetric expansion during PT. Moreever, these coatings separate the HMX crystals and build up a heat conduction obstacle. As a result the growths of δ‐HMX are also suppressed by the coatings. In contrast, fewer additives lead to larger free surface area of HMX, which accelerates the PT.     

Bioinspired Fabrication of Insensitive HMX Particles with Polydopamine Coating

The development of a facile method for large scale production of insensitive HMX particles is of great importance for energetic materials, especially for insensitive munitions. Inspired by mussels, HMX particles with a thin, robust, wettable and uniform coating based on the self‐polymerization of dopamine were prepared by one‐step solution stirring processes in the study. The as‐prepared HMX@PDA particles showed stable shape, size, and polymorphy compared with original HMX particles. With PDA (polydopamine) coating, the HMX@PDA particles exhibited better wettability, which could improve the adhesive properties between particles and other liquid components in a PBX (plastic bonded explosive). Furthermore, the mechanical sensitivities were decreased for the HMX@PDA particles because of the uniform and smooth PDA coating decreasing the hot spots on the surface of the HMX particles. HMX@PDA particles produced by a facile scalable process might provide a promising substitute for sensitive HMX particles to enhance the safety and adhesive properties when used in PBX.     

正交法分析PBX浇注炸药爆速的影响因素

研究以奥克托今(HMX)为主体、与其他各组分混合而成的PBX炸药。通过改变炸药中主炸药与其他成分的配比、粒度和抽真空时间3个影响爆速的因素,采用3因素3水平的正交实验分析各个因素的最佳水平。结果表明,粒度对爆速的影响是最主要的;其次是配比;最后是抽真空时间。得到最佳爆速的工艺条件为:HMX质量分数90%,粗细比2∶1,抽真空时间10 min。     

Creep characterization and modelling of ordinary refractory ceramics under combined compression and shear loading conditions

Creep behaviour of ordinary refractory ceramics is evidently asymmetric under uniaxial tension and compression. In service, they are often exposed to multiaxial stress states. In the present paper, the modified shear test specimens were applied for a creep study in the shear-compression zone of the p-q diagram, and the pure shear creep parameters following the Norton-Bailey strain hardening equation were inversely identified in combination with a weighting function between pure shear and uniaxial compressive conditions. The weighting function was implemented in an in-house asymmetric creep constitutive model. The experimental curves can be well predicted with identified parameters of the asymmetric creep constitutive model. It shows that the shear creep of ordinary refractory ceramics is evidently different to uniaxial compressive/tensile creep. Consideration of shear creep in the thermomechanical modelling of industrial vessels increases the accuracy of simulation results and supports the lining concept optimization investigation.     

压制过程中PBX炸药颗粒的破碎及损伤

用扫描电镜及激光粒度仪研究了PBX炸药在不同压制条件下的微观结构变化及粒度分布。结果表明,随着成型试件密度的增加,晶体的破碎、损伤情况加重;成型试件中HM X的平均粒径随着压力的增加而减小(压制前的33.05μm到250M Pa压制后的16.92μm);在相同压力条件下,热压(70℃)制品的密度更高,但晶体的破碎却更小,热压(70℃)制品中HM X的平均粒径要大于冷压(25℃)制品中HM X的平均粒径。     

A modified creep model of epoxy adhesive at ambient temperature

The paper presents the results of experimental investigations of the creep behavior of epoxy adhesive-hardened samples. The determined creep characteristics for an assumed range of tensile stresses show that the rheological effects in the examined adhesive have already occurred very distinctly at room temperature, for a relatively short time; moreover, the examined adhesive is a nonlinear viscoelastic medium and does not obey the Boltzmann's superposition principle. The obtained results of experimental investigations were subjected to detailed analysis and mathematical treatments. As a result of these actions, the so-called modified Burgers model has been finally developed for the studied adhesive with a constant modulus of elasticity for the non-relaxing part (describing the instant elastic strain) and variables, dependent on the tensile stress, the parameter values for its relaxing part (describing non-linearly viscoelastic properties of this adhesive). The creep deformations calculated for this model have demonstrated a very good consistency with the results of experimental investigations over the assumed range of stresses and the duration time of measurements.     

Development of a High-Temperature Deformation and Life Prediction Model for an Advanced Silicon Nitride Ceramic

A new deformation model inclusive of life prediction capability is introduced for describing general thermal-mechanical loading behavior of an advanced structural ceramic at high temperatures. The model is formulated using the state variable approach. Two internal state variables, namely, "hardening" and "damage" variables, are employed to characterize the current state of the material. The model consists of three rate equations: a flow rule describes the creep rate as a function of the hardening state variable, applied stress, and temperature; and two evoluton rules describe the rate changes of the two internal variables. Material history is accounted for through the evolution of the internal variables. The model was characterized and evaluated based on experimental creep and creep rupture data of an advanced silicon nitride ceramic tested under constant and stepwise-varied loading conditions. A unique strength of the model, not empowered in conventional approaches such as the Norton power-law creep and Monkman-Grant creep rupture relations, is demonstrated with the aid of the hardening variable, which enables the effcts of thermal annealing on subsequent creep and creep rupture behavior to be delineated.     

Research on the Size of Defects inside RDX/HMX Crystal and Shock Sensitivity

Intragranular defects inside RDX/HMX were studied by optical microscopy with matching refractive (OMS), sink‐float method (SFM), and micro‐focus CT (μCT) techniques. OMS results revealed the phenomenon that RDX/HMX had more defects and cracks than RS‐RDX/RS‐HMX. μCT results indicated that RDX/HMX had more defects with larger volume than RS‐RDX/RS‐HMX. The gap test showed that critical shock pressure/gap thickness was 6.4 GPa/19.4 mm for PBX based on RDX, while they were 7.5 GPa/17.5 mm and 8.6 GPa/16.2 mm for PBX based on M‐RDX and RS‐RDX, respectively. Meanwhile, an analysis of the relationship between defects inside RDX/HMX crystal and shock sensitivity was made. Finally, the shock pressure response under impact loading was investigated by discrete element method.