The non-isothermal gravimetric method for study the thermal decomposition kinetic of HNBB and HNS explosives

The hexanitrostilben (HNS) is a thermally stable explosive that can be prepared from hexanitrobibenzyl (HNBB). Therefore, the investigation of thermal stability of HNBB can be important in the yield of preparation of HNS. The decomposition kinetic of HNBB and HNS are studied by non-isothermal gravimetric method. The TG/DTG curves in non-isothermal method are obtained in range of 25°C–400 °C at heating rates of 3 °C/min, 5 °C/min, 8 °C/min, 10 °C/min and 12 °C/min. The data of weight-temperature are used for calculation of activation energy (E_a) of thermal decomposition reactions by methods of Ozawa, Kissinger, Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) as model-free methods and Strink's equation as model-fitting method. The compensation effect is used for prediction of mechanism and determination of pre-exponential factor (lnA) of the decomposition reaction. A reduction 60 kj/mol for the average of activation energy of thermal decomposition reaction of HNBB is obtained versus HNS. This result shows the lower thermal stability of HNBB in comparison to HNS. The Avrami equation (A_3/2) with function f(α) = 3/2(1-α)[-ln(1-α)]^1/3 indicates the predicted mechanism for thermal decomposition reaction both explosives.     

餐厨垃圾热风干燥过程特性及模拟

为了考察不同温度(60～100℃)对2种餐厨垃圾在热风干燥过程中的水分变化规律及动理学特性的影响,利用7个数学模型对餐厨垃圾干燥过程的水分变化规律进行了拟合对比。结果表明:温度是影响干燥的重要因素。干燥温度越高,餐厨垃圾达到平衡含水率所需时间越短;烹饪过程可以改变餐厨垃圾的热阻,增加其活化能;用Page模型和Modified Page模型描述餐厨垃圾热风干燥过程拟合精度最佳;2种餐厨垃圾有效湿分扩散系数分别为1.37×10-9～2.47×10-9,5.14×10-10～2.05×10-9m2/s,活化能分别为13.86,34.05 kJ/mol。     

聚溴化苯乙烯阻燃聚乙烯热解动力学研究

用聚溴化苯乙烯作为阻燃剂，制备了阻燃聚乙烯（PE），利用TG方法研究了PE和阻燃PE在氮气气氛下的热解动力学行为，并用改进的非等温动力学方法研究了其热解动力学。结果表明，加入阻燃剂后材料的初始分解温度提前，阻燃材料的热解区间变宽，阻燃体系的平均失重速率下降，最大失重速率下降，主要分解阶段的残炭率高于未阻燃PE，聚溴化苯乙烯阻燃效果明显，可用于聚乙烯阻燃，说明大分子溴系阻燃剂具有较好的发展潜力。氮气气氛下未阻燃聚乙烯的热解过程只存在一个失重阶段，而阻燃材料在相同温度范围内呈现不同的失重阶段，且在各失重阶段其反应机理函数也发生变化；活化能、指前因子都有所不同，阻燃材料的活化能大于未阻燃材料，且活化能在整个失重阶段是随着温度和转化率的变化而变化的，说明阻燃剂的加入改变了材料的热解行为。     

Damage modeling of ballistic penetration and impact behavior of concrete panel under low and high velocities

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete panels. This paper is divided into two parts. The first part consists of numerical modeling of reinforced concrete panel penetrated with a spherical projectile using concrete damage plasticity (CDP) model, while the second part focuses on the comparison of CDP model and Johnson-Holmquist-2 (JH-2) damage model and their ability to describe the behavior of concrete panel under impact loads. The first and second concrete panels have dimensions of 1500 mm × 1500 mm × 150 mm and 675 mm × 675 mm × 200 mm, respectively, and are meshed using 8-node hexahedron solid elements. The impact object used in the first part is a spherical projectile of 150 mm diameter, while in the second part steel projectile of a length of 152 mm is modeled as rigid element. Failure and scabbing characteristics are studied in the first part. In the second part, the com-parison results are presented as damage contours, kinetic energy of projectile and internal energy of the concrete. The results revealed a severe fracture of the panel and high kinetic energy of the projectile using CDP model comparing to the JH-2 model. In addition, the internal energy of concrete using CDP model was found to be less comparing to the JH-2 model.     

受油类污染棉纤维的热分解动力学研究

利用热分析技术对受油类污染的棉纤维的热分解特性和热分解动力学进行了研究。经过不同机制热分解模型的拟合，提出了受实验用油污染棉纤维的热分解动力学机理，并建立了其热分解动力学方程。结果表明：受油类污染的样品比未受污染的热分解起始温度明显降低，其热分解过程主要分为两个阶段，第一个阶段的热分解动力学机理为一维扩散控制，第二个阶段的热分解动力学机制相对复杂，可能为相边界反应，圆柱形或是球形对称机理。     

激光熔覆搭接过程残余应力应变的有限元计算

激光熔覆过程中产生的残余应力与应变对熔覆层的裂纹开裂倾向有重要影响。利用有限元法对激光多道搭接过程熔覆层的残余应力和应变进行计算,计算过程中主要考虑瞬时温度变化引起的热应力、σ-ε曲线、有限元网格、力学边界条件4个方面。热应力主要在温度场计算结果的基础上求得;σ-ε曲线采用的是线性强化材料的弹塑性曲线;有限元网格主要采用分区划分的形式进行。通过计算,得到了搭接后的熔覆层上关键点的残余应力和应变分别为1 400 MPa和2.2×10^-2。结果表明：搭接熔覆层交界处的点产生焊趾裂纹的倾向最大,第1道熔覆顶点处产生横向裂纹的倾向次之。     

A reusable planar triggered spark-gap switch batched-fabricated with PCB technology for medium-and low-voltage pulse power systems

Triggered spark-gap switch is a popular discharge switch for pulse power systems. Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in the systems. Such switches are one-shot due to electrodes being too thin to sufficiently resist spark-erosion. Additionally, these switches did not employ any structures in securing internal gas composition, resulting in inconsistent performance under harsh atmospheres. In this work, a novel planar triggered spark-gap switch (PTS) with a hermetically sealed cavity was batched-prepared with printed circuit board (PCB) technology, to achieve reusability with low cost. The proposed PTS was inspected by micro-computed tomography to ensure PCB techniques meet the requirements of machining precision. The results from electrical experiments demonstrated that PCB PTS were consistent and reusable with lifespan over 20 times. The calculated switch voltage and circuit current were consistent with those derived from real-world measurements. Finally, PCB PTS was used to introduce hexanitrostilbene (HNS) pellets in a pulse power system to verify its performance.     

钢质管道挤压变形过程数值模拟

基于对钢质输油管道挤压变形原理的分析,建立上下刀具加载作用下钢质输油管道挤压变形模型,采用扩展拉格朗日方法求解三维接触挤压问题,完成20号无缝钢挤压变形过程的数值模拟。将模拟试验数据与前人实际试验数据进行对比与验证,模拟结果与实际试验结果吻合。该模型可以用于模拟不同规格管道挤压变形情况,得到管道挤压变形的位移、载荷和应力分布规律,为管道应急抢修提供理论和实践依据。     

Sandwich structure for enhancing the interface reaction of hexanitrohexaazaisowurtzitane and nanoporous carbon scaffolds film to improve the thermal decomposition performance

Improving the thermal decomposition performance of hexanitrohexaazaisowurtzitane (CL-20) by appropriate methods is helpful to promote the combustion performance of CL-20-based solid propellants. In this study, we synthesized a sandwich structure of CL-20 and nanoporous carbon scaffolds film (NCS) and emphatically studied the thermal decomposition performance of the composite structure. Thermogravimetric analysis and differential scanning calorimetry were used to measure the thermal decomposition process of the composite structure. The kinetic parameters of thermal decomposition were calculated by the thermal dynamic analysis software AKTS. These results showed that the thermal decomposition performance of the sandwich structure of CL-20 and NCS was better than CL-20. Among the tested samples, NCS with a pore size of 15 nm had the best catalytic activity for the thermal decomposition of CL-20. Moreover, the thermal decomposition curve of the composite structure at the heating rate of 1 K/min was deconvoluted by mathematical method to study the thermal decomposition process. And a possible catalytic mechanism was proposed. The excellent thermal decomposition performance is due to the sandwich structure enhances the interface reaction of CL-20 and NCS. This work may promote the extensive use of CL-20 in the field of solid rocket propellant.     

Design and analysis of a scheme for the naval gun test shell entering the bore

The test shell without projectile belt is widely used in the teaching, inspection and maintenance of modern automatic naval guns. In order to ensure the normal work of each mechanism, it is very important to design the buffer and limit of the test shell during the process of entering the bore. Taking a certain type of medium caliber naval gun as the research object, the design of colloidal fluid damper and cartridge lock was proposed to ensure the reliability of entering the bore and closing the breechblock. By combining the simulation methods of computational fluid dynamics (CFD) and multibody system dy-namic (MBD), it was analyzed whether the structural design can meet the engineering requirements. The research results show that the colloidal fluid damper can dissipate a large amount of kinetic energy of the shell, and the cartridge lock can limit the rebound movement. The combination of the two ensures the smooth process of closing the breechblock. The research provides a design method for the process of the test shell entering the bore, and provides theoretical support for the feasibility of the method.     

Effect of friction stir processing on mechanical properties and heat transfer of TIG welded joint of AA6061 and AA7075

Tungsten inert gas (TIG) welding is the most commonly used joining process for aluminum alloy for AA6061 and AA7075 which are highly demanded in the aerospace engineering and the automobile sector, but there are some defects occur during TIG welding like micro-crack, coarse grain structure, and porosity. To improve these defects, the TIG welded joint is processed using friction stir processing (FSP). This paper presents the effect of friction stir processing on TIG welding with filler ER4043 and ER 5356 for dissimilar aluminum alloy AA6061 and AA7075. The mechanical characterization, finite element formulation and mathematical equations of heat transfer of TIG + FSP welded joints are investigated using ANSYS Fluent software by adjusting process parameters of FSP. The results show that the maximum compressive residual stress 73 MPa was obtained at the fusion zone (FZ) of the TIG weldment with filler ER4043, whereas minimum compressive residual stress 37 MPa was obtained at stir zone (SZ) of the TIG+FSP with filler 5356. The maximum heat flux 5.33 × 106 W/m2 and temperature 515 ℃ have observed at tool rotation 1600 rpm with a feed rate of 63 mm/min. These results give a satisfactory measure of confidence in the fidelity of the simulation     

基于LabVIEW的地下震源定位系统设计

针对小区域浅层地下震源定位中,由于震动信号受传输介质复杂、传感器不稳定等因素影响,出现初至波提取困难、震源定位低精度等问题,设计了基于LabVIEW的地下震源定位系统,实现三轴信号合成、基于小波变换的阈值去噪、基于改进的长短时窗(STA/LTA)的初至提取、基于时差技术(TDOA)的联合定位算法等功能模块。结果表明,该软件在10 m×10 m×3 m的区域内,初至特征提取精确到10-4s,定位精度精确到0.1 m,可以广泛应用于爆破定位、信息侦查等领域。     

Chain damage effects of multi-spaced plates by reactive jet impact

Chain damage is a new phenomenon that occurs when a reactive jet impacts and penetrates multi-spaced plates.The reactive jet produces mechanical perforations on the spaced plates by its kinetic energy(KE),and then results in unusual chain rupturing effects and excessive structural damage on the spaced plates by its deflagration reaction.In the present study,the chain damage behavior is initially demonstrated by experiments.The reactive liners,composed of 26 wt％Al and 74 wt％PTFE,are fabricated through a pressing and sintering process.Three reactive liner thicknesses of 0.08 CD,0.10 CD and 0.12 CD(charge diameter)are chosen to carry out the chain damage experiments.The results show a chain rupturing phenomenon caused by reactive jet.The constant reaction delay time and the different penetration velocities of reactive jets from liners with different thicknesses result in the variation of the deflagration position,which consequently determines the number of ruptured plates behind the armor.Then,the finite-element code AUTODYN-3D has been used to simulate the kinetic energy only-induced rupturing effects on plates,based on the mechanism of behind armor debris(BAD).The significant discrepancies between simulations and experiments indicate that one enhanced damage mechanism,the behind armor blast(BAB),has acted on the ruptured plates.Finally,a theoretical model is used to consider the BAB-induced enhancement,and the analysis shows that the rupturing area on aluminum plates depends strongly upon the KE only-induced pre-perforations,the mass of reactive materials,and the thickness of plates.     

陕西蒲城Q_2黄土物质组成试验研究

利用激光散射粒度分布分析仪、X射线衍射仪等先进的测试手段和化学成分分析,得到了陕西蒲城Q2黄土的物质组成特点,包括颗粒组成、矿物成分、化学成分、易溶盐含量、酸碱特性等,并指出与Q3黄土的差异。为深入研究Q2黄土的湿陷机理和工程地质特性以及解释与Q3黄土工程性质的差异提供科学依据。     

面内阶跃载荷下薄板弹性动力屈曲差分解

根据薄板微元的动力平衡分析导出薄板动力屈曲控制方程,由屈曲瞬间能量转换率守恒条件得出一个压缩波前屈曲变形的附加约束方程,由此得到求解薄板动力屈曲问题的完备定解条件.以受载边夹支的薄板为倒,利用有限差分法得出了薄板前三阶动力屈曲模态和相应的两个特征参数值,并对比分析了薄板静、动力屈曲的差别.分析表明,薄板动力屈曲过程中产生屈曲动能,比静力屈曲要吸收更多的外部能量.     

A quasi-isentropic model of a cylinder driven by aluminized explosives based on characteristic line analysis

A quasi-isentropic study on the process of driving a cylinder with aluminized explosives was carried out to examine the influence of the aluminum (Al) reaction rate on cylinder expansion and the physical parameters of the detonation products. Based on the proposed quasi-isentropic hypothesis and relevant isentropic theories, the characteristic lines of aluminized explosives driving a cylinder were analyzed, and a quasi-isentropic model was established. This model includes the variation of the cylinder wall velocity and the physical parameters of the detonation products with the Al reaction degree. Using previously reported experimental results, the quasi-isentropic model was verified to be applicative and accurate. This model was used to calculate the physical parameters for cylinder experiments with aluminized cyclotrimethylenetrinitramine explosives with 15.0 % and 30.0 % Al content. The results show that this quasi-isentropic model can be used not only to calculate the cylinder expansion rule or Al reaction degree, but also to calculate the physical parameters of the detonation products in the process of cylinder expansion. For explosives with 15.0 % and 30.0 % Al, 24.3 % and 18.5 % of the Al was found to have reacted at 33.9 μs and 34.0 μs, respectively. The difference in Al content results in different reaction intensity, occurrence time, and duration of two forms of reaction (diffusion and kinetic) between the Al powder and the detonation products; the post-detonation burning reaction between the Al powder and the detonation products prolongs the positive pressure action time, resulting in a continuous rise in temperature after detonation.     

La掺杂纳米TiO2光催化降解TNT的动力学

以掺杂La的纳米TiO2作光催化剂，研究了光催化降解TNT的动力学规律，考察了TNT初始质量浓度、催化剂用量、初始pH、通氧速率及光照强度等因素对TNT光催化降解的影响。试验结果表明：在不同初始质量浓度、初始pH、通氧速率、光照强度及催化剂用量为0．3～2．0g／L的条件下，TNT光催化降解反应遵循拟一级动力学规律，且可用Langmuir-Hinshelwood动力学模型描述；当催化剂用量为0．1g／L时，该反应可认为是震缀反应．     

浓缩富集＋基因芯片快速检测水体中致病菌

为了实现对水体致病菌的快速检测和监控，研究开发了一套预浓缩富集配合基因芯片检测的方法，对模拟和实际水样进行了检测，并与传统检测方法进行了比较。结果表明，通过对水样的浓缩集菌，基因芯片对致病菌的检出率（以肠炎沙门氏菌为单一检测对象）达到1．0×10^3cfu／mL，较原来提高了100倍；可以在8h内同步完成13种对人类有重大危害的致病菌的快速检测。     

新型背腔式对数周期缝隙天线阵列设计

介绍了一种新型背腔式对数周期缝隙天线单元,对其各参数特性进行了分析,并采用这种新型天线单元设计了9×7天线阵列。通过HFSS13进行天线阵列的设计。仿真结果表明,该天线阵列在1.5 GHz~6 GHz的工作带宽内,驻波比小于3,回波损耗小于-10 d B,天线阵列最大增益为29.6 d Bi,在整个工作带宽内,增益均大于20 d Bi。具有良好的定向辐射能力,可用于UWB雷达、探测等领域。     

小水线面双体船单点硬搁浅数值仿真分析

利用非线性有限元数值仿真技术,对某 SWATH 典型实船单点硬搁浅过程进行研究,得出小水线面船搁浅过程中的搁浅戢荷、能量吸收、结构损伤特性和运动情况.结果表明,小水线面搁浅过程中 X 方向的搁浅载荷是主要载荷,结构的损伤变形只波及触底区域附近结构,搁浅部位支柱的应力不高,没有明显的塑性变形,搁浅损伤路径略向船体内侧倾斜,SWATH 的潜体壳板和潜体纵骨发挥了重要的吸能作用,经历搁浅第一阶段后小水线面船的刺余动能大部分转换为 X 向平动动能,少部分转化为 Z 向平动动能及绕 X 轴和 Z轴的旋转动能.