复合材料厚壁圆筒的疲劳损伤研究

基于能量耗散法,推导出了复合材料厚壁圆筒的疲劳损伤和疲劳寿命函数;在此基础上,采用有限元软件 ABAQUS 建立复合材料圆筒模型,进行了模拟周期内压载荷作用下的疲劳仿真计算,得到了随着循环数的增加,疲劳损伤变量不断增大和材料性能不断退化的损伤规律。以同样的方法和载荷边界条件计算了全金属圆筒疲劳损伤的起始和演化。对比结果表明：相同循环次数作用下,后者的裂纹扩展长度和张开位移更大;随着循环次数的增加,后者的疲劳破坏比前者更剧烈,更难预测。     

基于双目视觉的火炮身管指向全自动测量方法

火炮装备前或服役过程中需要进行身管指向测量以校正火控系统偏差。目前普遍使用双经纬仪进行身管指向测量,该方法的测量效率低,难以满足未来战场环境下火控系统的快速标校。提出了基于双目视觉的身管指向高精度、自动化测量方法,利用合作标志点分析身管转动,将身管转动分解为先后两次绕轴运动,结合铅垂线测量实现身管指向解算,利用LM(Levenberg-Marquardt)算法进行指向优化,得到身管指向最终结果。于实验室开展了半实物仿真,并在某火炮厂进行了实测验证。结果表明,火炮身管的高低角测量精度优于0.15°,其方向角测量精度优于0.12°,两姿态角的重复性偏差均优于0.0035°。所提方法具备高精度、高鲁棒性、全自动的优势,可实现未来战场环境下火炮身管指向的全自动测量。     

Electromagnetic control of the instability in the liquid metal flow over a backward-facing step

The tile-type electromagnetic actuator (TEA) and stripe-type electromagnetic actuator (SEA) are applied to the active control of the perturbation energy in the liquid metal flow over a backward-facing step (BFS). Three control strategies consisting of base flow control (BFC), linear model control (LMC) and combined model control (CMC) are considered to change the amplification rate of the perturbation energy. CMC is the combination of BFC and LMC. SEA is utilized in BFC to produce the streamwise Lorentz force thus adjusting the amplification rate via modifying the flow structures, and the magnitude of the maximum amplification rate could reach to 6 orders. TEA is used in LMC to reduce the magnitude of the amplification rate via the wall-normalwise Lorentz force, and the magnitude could be decreased by 2 orders. Both TEA and SEA are employed in CMC where the magnitude of the amplification rate could be diminished by 3 orders. In other words, the control strategy of CMC could capably alter the flow instability of the liquid metal flow.