Fe2O3-Al纳米铝热剂与超细RDX复合物的制备与性能

采用溶胶-凝胶方法,制备出了纳米铝热剂nano-Fe2O3-Al,并获得了其与超细RDX的复合含能材料nanoFe2O3-Al/SFRDX。采用BET法、SEM、XRD综合表征了nano-Fe2O3-Al的结构,采用TG/DSC联用技术测试了nano-Fe2O3-Al的热性能,结果表明气凝胶铝热剂的反应温度更低;nano-Fe2O3-Al的静电火花感度测试结果表明纳米铝热剂对静电十分敏感。对nano-Fe2O3-Al/SFRDX在无约束条件和密闭条件下的燃烧行为进行了研究,高速相机照片法发现在无约束条件下,nanoFe2O3-Al燃烧高达300 m/s,且nano-Fe2O3-Al/SFRDX具有在无约束条件下由燃烧转为爆轰的趋势。     

温度对WC-WB-CoCr涂层高温摩擦磨损性能的影响

采用超音速火焰喷涂(HVOF)制备了WC-WB-CoCr涂层,研究了温度对WC-WB-CoCr涂层高温摩擦磨损性能的影响。通过SEM、XRD和显微硬度仪对涂层的微观组织、相结构和力学性能进行表征。通过摩擦磨损试验机和拉曼光谱仪研究了WC-WB-CoCr涂层的高温摩擦学性能和氧化产物,采用台阶仪扫描磨痕形貌并计算WC-WB-CoCr涂层的磨损率。结果表明：WC-WB-Co-Cr涂层主要由WC和CoW₂B₂组成,涂层结构致密,与基体结合紧密;随着磨损试验温度升高,涂层的摩擦系数从0.66降低到0.57,涂层的磨损率随着温度的升高而升高,但是其磨损率增长程度随着温度的升高而降低。在高温磨损过程中,磨痕表面的氧化膜主要由WO₃和CoWO₄组成,且CoWO₄比WO₃表现出更好的耐高温磨损性能。涂层的主要磨损机制为氧化磨损、疲劳磨损和粘着磨损。     

Messtechnische Herausforderungen bei der Analyse von hochdynamischen Aufprallbeanspruchungen

Metrological challenges analyzing high dynamic impact on reinforced slabs The comprehension of high dynamic impact processes on reinforced concrete structures is of essential importance for the dimensioning of structures regarding exceptional loading scenarios like airplane impacts. Since, for high strain rates in comparison with quasi‐static conditions an altered material behavior appears, an adequate methodology and application of appropriate measurement is required to assess the structural behavior of building components. The present paper describes the metrological methodology and the challenges of the experimental investigations of reinforced concrete slabs under impact with loading periods of only a few μs or ms. The determination of time history curves of impact velocities, bearing forces, displacements and the determination of sound wave velocities inside the structure requires an appropriate high sampling rate with the signal recording. The results lately lead to a holistic assessment of the structural behavior and the damage phenomena of such processes.     

Vibration velocity control standard of buried pipeline under blast loading of adjacent tunnel

With the rapid development and construction of China’s transportation system, more and more projects are being conducted near existing buried pipelines, which will inevitably influence the safety of the pipelines. Among the safety issues related to buried pipelines, blasting during the construction of an adjacent tunnel is one of the most adverse factors for existing pipelines. To ensure the safety and normal operation of the pipelines, a method for determining the peak vibration velocity control standard for buried pipelines under blast loading is established in this study. The acceleration time-history function that acts on the rock mass under the blasting seismic wave is derived as external excitation acting on the pipeline. By using the acceleration time-history function as input and combining it with a dynamic and static analysis of the pipeline, the critical vibration velocity of pipelines under the action of blast loading can be determined by the von Mises yield criterion of the buried pipeline material. Using the Dashanpi No. 1 tunnel project in Shenzhen, China as a background, the critical velocity control standard for buried pipelines under tunnel blast loading can be set at 190 mm/s without considering either the initial defects or the corrosion conditions during the operation.     

新型四带小型胶联改造

针对新型结构产品设备,将设备厂家因设计缺陷造成的问题进行逐一改造,以满足产品生产的需求,也列轮胎生产行业的类似设备改善提供实例,节约新设备投资。     

塑料产品注射速度的选择

本文介绍了注射速度高低的特点及其选择的原则,通过合理选择注射速度以及对注射速度曲线的给定与修正,可以克服注塑缺陷,改善制品的质量,提高工艺的经济性。     

沥青混合料的拌和流动特性及和易性指数

为定量评价沥青混合料的拌和流动特性,深化认识混合料强度构成的演变机理,文章利用自行开发的一种变速拌和试验装置,在不同拌和速率（20~50r·min1）和拌和温度（130~180℃）下,对不同沥青种类、不同沥青用量和不同级配类型的沥青混合料进行拌和功率测试,分析拌和流动特性,建立拌和流变模型,定义拌和和易性指数。研究结果表明：拌和试验装置的功率测试误差小于5%,测试数据稳定可靠,可用来表征沥青混合料的拌和功率;拌和温度越高,拌和速率越小,所耗费的拌和功率越少,沥青混合料越容易拌和;沥青混合料的拌和流变模型服从线性的宾汉黏塑性模型,模型直线的斜率表征混合料的拌和黏度,截距反映内在塑限;拌和和易性指数可以定义为模型直线对拌和速率之面积的倒数,从理论上综合考虑黏塑性流动参数;沥青越黏稠,沥青用量越大,集料颗粒越粗,沥青混合料的拌和阻力越大,和易性越差;从强度构成的演变机理来看,集料的组成特性决定内在塑性极限,沥青砂浆的黏性决定黏性强度即牛顿黏性流强度。     

不锈钢/碳钢TIG焊熔池表面流动行为

为研究异种钢在钨极惰性气体保护焊过程中的熔池表面流动行为,以粒子示踪法为基础,通过激光熔池表面反射的方法,对304不锈钢/Q235碳钢、316L不锈钢/Q235碳钢焊接过程中熔池表面液态金属的流动行为进行了研究,分析了熔池表面示踪粒子的运动趋势,并以此为依据计算了熔池表面液态金属的流动速度.结果表明,在不锈钢/碳钢的TIG焊过程中,熔池表面的液态金属存在从不锈钢侧流向碳钢侧的流动行为.其中,示踪粒子在304不锈钢/Q235碳钢的焊接熔池表面平均流动速度约为25.3 mm/s,在316L不锈钢/Q235碳钢的焊接熔池表面平均流动速度约为21.6 mm/s.     

纵向通风下隧道长度对临界风速的影响分析

临界风速可有效控制烟气蔓延,是隧道防灾通风重要参数。为分析隧道长度对临界风速的影响,采用量纲分析法构建临界风速与隧道长度关系公式,并分别在5 MW和30 MW火源热释放速率下,对不同长度隧道的火灾进行数值模拟以量化研究隧道长度对临界风速的影响。结果表明,隧道长度对临界风速具有影响,且不同火源释放速率时影响也有所不同:无量纲火源热释放速率小于0.15时,临界风速随隧道长度增大呈现1/41次方增长关系;无量纲火源热释放速率高于0.15时,临界风速随隧道长度增大呈现1/25次方增长关系。进而建立了考虑隧道长度的无量纲临界风速计算公式。