Evaluation of dynamic fracture toughness parameters of locomotive axle steel by instrumented Charpy impact test

The analysis of the energy of fracture of specimens from steel OSL, which is widely used for the manufacture of railway axles under shock loading, is performed. The nature and quantitative parameters of the typical stages of the processes of plastic and brittle fracture, depending on the test temperature and stiffness of the stress state at the tip of the crack‐like defect, are established. It is shown that impact loading at 20 °C leads to the formation of the local zone of plasticity and ductile–brittle fracture of the material. An increased stiffness of the stress state at the tip of the defect at ?40 °C causes brittle fracture. An approach is developed, which is based on using the size of shear lips as a quantitative parameter of fracture under normal and low temperatures, similar in its physical essence to deformation approaches of nonlinear fracture mechanics. Based on this approach and the quantitative analysis of specimen fracture zones, the physical and mechanical scheme of specimen fracture is proposed in the presence of localized plasticity and in its absence near the tip of the concentrator.     

An investigation of T‐stresses in a plate with an inclined crack under biaxial loadings

For plates with an inclined crack of wide‐range aspect ratios under biaxial loadings, T‐stress values are calculated with three‐dimensional finite element method. The results show that the normalized T‐stress is crack length and orientation dependent. A linear equation for the relationship between normalized T‐stresses and biaxility factors is proposed to describe the normalized T‐stresses for different crack lengths and crack angles under different biaxial loadings, which is more convenient and involves wider biaxility ratios compared with the existing solutions. The plate thickness effect and the trend of normalized T‐stresses along the crack front thickness are also studied for mode I and I–II mixed‐mode cracks. Based on the analyses and comparisons, it is necessary to take the thickness effect into consideration when the crack length is long enough (a/W = 7/10). When the component of mode II is significant (β > 45°), and the biaxility ratios are negative, T‐stresses near the free surface are lower than those at other positions, which are the opposite of mode I crack and most of I–II mixed‐mode crack.     

缓蚀剂在埃洛石上的担载与释放规律研究

将粘土矿埃洛石经碱刻蚀改性,用SEM、FT-IR和BET手段对其进行表征,后作为载体与2-巯基苯并咪唑的乙醇和丙酮溶液担载制得复合体,用分光光度法研究了缓蚀剂与粘土矿埃洛石的担载和释放规律。结果表明碱刻蚀改性去除了埃洛石内表面的一部分氧化铝层,使埃洛石的比表面积和孔容增加8.66%、51.90%。在丙酮溶液中,缓蚀剂与埃洛石的担载量达到9%且该复合体在腐蚀介质中实现缓蚀剂的缓慢释放,2min可达到Q235钢的最高缓蚀效率所需的缓蚀剂质量浓度。该复合体可望用作防腐涂层中缓蚀剂缓释填料。     

单向拉伸条件下补片参数对复合材料胶接修复结构的影响

建立含中心半穿透圆孔的损伤金属板修补结构的三维有限元模型,以应力集中系数(Stress Concentration Factor,SCF)和挠度w作为复合材料胶接修复效果的指标,分析单向拉伸条件下,正方形补片的长度、厚度和铺层方式对修复效果的影响。结果表明:补片长度取孔直径的3.5倍、厚度取孔深度的0.6~0.8倍、铺层方式取0°/90°铺层时,复合材料单面修复含损伤裂纹板的效果较好。根据分析结果制备了实验件,进行了单向静拉伸实验,修补实验件的破坏强度比未修补实验件提高了10.1%。     

自动装填系统故障检测适配器设计

针对装甲车辆自动装填系统的电气故障检测需求,分析了装甲车辆自动装填系统的基本工作原理和电信号特点,设计了以单片机AT89C52为核心的装甲车辆自动装填系统电气故障检测适配器;该设计具有多CAN通信通道、开关量和模拟量采集、开关量输出功能,构建了适配器与控制终端PC机组成的上下位机测控系统,可应用于我多型号坦克、步兵战车自动装填系统的功能测试和电气故障检测,具有较好的通用性、可靠性和较强抗电磁干扰性能,实际应用效果良好。     

加权负载均衡技术在WebGIS中的应用

针对传统万维网地理信息系统并发访问能力不强的缺点,提出基于参数加权法的负载均衡策略。考虑服务器的处理能力、响应时间和服务负载,采用综合参数加权法解决地图服务器的选择问题。在.NET平台下实现该策略,采用Microsoft ACT工具对其进行压力负载测试,结果证明其稳定性、并发性和抗负载能力较高。     

自动机械臂定位精度分析

针对某种自动机械臂的控制进行了研究,该系统主要由控制单元、执行机构、测量单元及显示单元4部分组成。介绍了控制系统的工作原理,建立了机械吊臂数学模型,对转载过程中机械臂的定位精度进行了计算分析,在最大工作距离5 m范围内,机械臂定位标准差小于10 mm,达到了较高的精度,为自动转载系统的工程实现奠定了理论基础。     

基于多处理器的高速RapidIO

在典型的嵌入式系统中,系统内不同组件之间的通信速率成为制约嵌入式系统性能的瓶颈。针对传统共享总线遇到的困难,通过分析高速串行RapidIO(SRIO)接口协议及其应用,研究SRIO在多处理器系统互连中的应用及基于SRIO的加载技术。利用该协议实现的多DSP读写操作的速率达到每通道3.125 Gb/s,效率达到86%,DSP可通过SRIO实现加载。