多层复合膜的成型技术

阐述了用AutoLisp程序模拟塑料熔体在2层复合膜机头内的流动情况，并介绍了复合膜机头的内部结构。     

基于机器视觉与无人机的结构动位移测量方法EI北大核心CSCD

针对基于视觉的结构位移测量方法中相机分辨率不足或测量基站位置选取困难等局限,提出一种结合机器视觉与无人机的结构动位移测量方法。以静止激光灯投射在结构表面的激光光斑为参考,设计算法自动检测目标测点和激光光斑位置,逐帧计算并更新比例因子,估计并消除无人机自身的运动,从而计算目标测点的绝对位移;为验证该方法的准确性,设计一个小型框架模型试验,随后又将此方法应用于大型地震模拟振动台试验。结果表明,利用无人机进行视觉测量得到的位移响应与激光位移计和加速度计测得的参考数据具有良好的一致性,在结构动位移测量和模态参数识别上均能较好地应用。     

Monitoring damage evolution of steel strand using acoustic emission technique and rate process theory

Utilizing the acoustic emission（AE） technique, an experimental investigation into the damage evolution for steel strand under axial tension was described. The damage evolution model for steel stand relating the damage evolution to acoustic emission parameters was proposed by incorporating the AE rate process theory. The AE monitoring results indicate that damages occur in both elastic and plastic phases of steel strand. In elastic phase, AE signals are mainly sent out from the micro damage due to the surface friction among the wires of steel strand, while in plastic phase, AE signals emitted from the plastic deformation of wires. In addition, the AE cumulative parameters curves closely resemble the loading curve. The AE cumulative parameters curves can well describe the damage evolution process including the damage occurrence and damage development for steel strands. It is concluded that the AE technique is an effective and useful nondestructive technique for evaluating the damage characteristics of steel strand.     

考虑变量相关性的正交异性板细节疲劳可靠性评估

传统的疲劳可靠性评估方法忽略了功能函数中变量的相关性,致使计算得到疲劳可靠度指标精度降低。针对这一问题,基于既有悬索桥主梁细节应变和环境温度大样本监测数据,讨论疲劳功能函数变量之间的相关性关系。提出基于Copula函数的相关性变量的联合分布模型,解决联合概率分布建模中多重积分求解困难的问题。研究表明,受环境温度的影响,靠近顶板焊接细节的日等效应力幅和应力循环次数存在较强的相关性,Gaussian Copula函数可作为相关性变量的最优连接函数,对于U肋-顶板细节,桥梁结构服役100年时,考虑与不考虑变量相关性的可靠度指标值分别5.3和6.9,两者之间相差约1.3倍。当年交通增长率分别等于3%和5%时,可靠度指标在服役年限为94.6年和67.1年时间到达目标可靠度指标。对于U肋-U肋对接细节,考虑和不考虑变量的相关性对可靠性指标影响相对顶板细节较小。