非线性Lamb波疲劳损伤监测机理研究

传统的线性Lamb波损伤监测方法对微小损伤的敏感性很低,限制了Lamb波结构健康监测技术的应用和发展.分析了非线性Lamb波传播机理以及非线性Lamb波特征参数提取方法,在此基础上对非线性Lamb波结构疲劳损伤监测机理进行了实验研究.在T6061铝板上的实验验证表明:非线性Lamb波特征参数对结构疲劳等早期微损伤具有较好的敏感性,且非线性参数与损伤程度之间存在相同的变化趋势.为金属材料结构疲劳等早期损伤的预警和评估提供了可行的思路.     

高压输电区域性重覆冰线路受损监测系统设计

通过对高压输电区域性重覆冰线路受损监测,提高高压输电稳定性,提出一种基于视觉特征重构的高压输电区域性重覆冰线路受损监测方法,并结合多层嵌入式构架进行系统设计。构建高压输电区域性重覆冰线路受损监测的视觉采集模型,采用激光扫描和红外分析方法进行高压输电区域性重覆冰线路受损部位的图像重构,构建高压输电区域性边缘轮廓检测模型,结合模板特征匹配方法进行高压输电区域性重覆冰线路受损部位检测,提取高压输电区域性重覆冰线路受损部位的异常特征信息,结合机器学习方法对提取的特征信息进行自动分类和人工智能识别,实现高压输电区域性重覆冰线路受损部位监测。采用程序加载和嵌入式的模块化设计方法,进行监测系统的集成开发设计。测试结果表明,采用该方法进行高压输电区域性重覆冰线路受损监测的智能性较高,人机交互性较好。     

钛合金结构疲劳损伤监测实验研究

飞机钛合金结构损伤的监测,对于保证飞行器的安全具有重要的意义。提出了一种涡流阵列传感器,并通过搭建监测系统,进行了TC4钛合金不同宽度裂纹扩展模拟监测实验研究。研究结果表明：当钛合金出现裂纹后,传感器各通道的输出信号与无裂纹的基准信号有较大的变化,并且随着裂纹宽度的增加,输出信号幅值比增大。同时,模拟监测实验研究表明：传感器能够准确地识别和定量监测裂纹,精度达到1mm。     

Agent-based artificial immune system approach for adaptive damage detection in monitoring networks

This paper presents an agent-based artificial immune system approach for adaptive damage detection in distributed monitoring networks. The presented approach establishes a new monitoring paradigm by embodying desirable immune attributes, such as adaptation, immune pattern recognition, and self-organization, into monitoring networks. In the artificial immune system-based paradigm, a group of autonomous mobile monitoring agents mimic immune cells (such as B-cells) in the natural immune system, interact locally with monitoring environment, and respond to emerging problems through simulated immune responses. The presented immune-inspired monitoring paradigm has been applied to structural health monitoring. The “antibody” of a mobile monitoring agent is a pattern recognition algorithm tuned to a certain type of structural damage pattern. The mobile monitoring agent performs damage diagnosis based on structural dynamic response data. Mobile monitoring agents communicate with each other and collaborate with network components based on agent interaction protocols defined in agent standards, the Foundation for Intelligent Physical Agents standards. A mobile agent system embedded in sensor nodes supports the selective generation, migration, communication, and management of mobile monitoring agents automatically. The active structural health monitoring is achieved by distributing mobile monitoring agents to the sites where they are needed. The structural damage diagnosis using mobile monitoring agents and artificial immune pattern recognition method has been tested using a scaled steel bridge structure. The test result shows the feasibility of using this approach for real-time structural damage diagnosis.     

基于圆形压电阵列的主动Lamb波损伤成像监测研究

对主动Lamb波结构健康监测中的压电阵列技术进行了研究。分析了传统的矩阵式压电阵列在应用中存在的问题,基于回声式原理研究设计了圆形压电阵列方法,分析了该方法的特点和信号采集过程,结合时间反转成像技术,实现对损伤的监测,实验结果表明:该方法能克服传统矩阵式压电阵列在应用中存在的监测范围、信号监测能力差异等问题,最后分析了圆形压电阵列还存在的问题。     

Dynamic monitoring and damage evaluation of flood in north-west Jilin with remote sensing

The greatest flood in the twentieth century hit north-east China in the summer of 1998. The movement of the flood over the Nenjiang River drainage area in the north-west of Jilin province was dynamically monitored using Radarsat data; with the landcover map at the scale of 1:100 000, interpreted from Landsat TM images, the damages from the flood were also evaluated. In this paper, a technique, similar to MVC (Maximum Value Composite) used to remove cloud contamination on NOAA AVHRR images, was applied to correct the logical errors on the flood boundaries extracted at different time. In addition the flood boundaries were vectorized via automatic tracing method, therefore the dynamic monitoring of the flood spatial process was performed better and the information of the changing inundated areas was offered more rapidly. The method produced in the study proved to be an effective approach to dynamic monitoring of flood.     

基于无线疲劳监测系统的铝合金材料疲劳损伤研究

铝合金材料具有重量轻、强度高等特点,是国民经济发展的重要基础材料,在诸多领域(如飞行器设计与制造、建筑装饰等)中占有十分重要的地位。然而,其抗疲劳性能较差,在交变荷载作用下容易产生疲劳裂纹和发生疲劳破坏。提出了一种基于无线疲劳监测系统的铝合金材料疲劳损伤研究方法,实时监测了铝合金构件的疲劳应变,并实时分析了构件的疲劳损伤状况,为研究铝合金材料的疲劳性能提供了可借鉴性的方法。     

基于Cortex-M3的齿轮传动轴损伤动态监测系统的设计与实现

针对传统的齿轮传动轴监测与诊断系统的局限性,提出了在封闭小体积环境下局域强信号的采集与传输机制.详细论述了系统的工作原理、硬件及软件设计,给出了系统的测试结果.该系统已经成功用于某型汽车发动机传动轴损伤动态监测,对齿轮传动系统的损伤动态监测起到了巨大的推动作用.     

Simultaneous identification of damage and input dynamic force on the structure for structural health monitoring

In this paper, we present an approach for simultaneous identification of the system parameters and the input dynamic force time history. The inverse problem associated with the system identification is formulated as an optimization problem and is solved using a newly developed dynamic hybrid adaptive firefly algorithm (DHAFA). A modified version of Tikhonov regularization is employed while solving the inverse problem associated with the force identification in order to improve the quality of the solution. Numerical simulation studies have been carried out by solving three distinct numerical examples. Studies presented in this paper indicate that the proposed algorithm is effective in identifying the system parameters as well as the input dynamic force simultaneously and can be effectively used for structural health monitoring purposes. Convergence studies presented in this paper on the newly developed dynamic hybrid firefly algorithm indicate that the proposed algorithm has better convergence characteristics and can be effectively employed for solving complex nonlinear optimization problems associated with system identification.     

基于光纤传输的结构损伤声发射监测系统研究

摘要：声发射检测技术作为一种先进的故障诊断技术,在大型起重设备检测行业“大行其道”。由于生产现场的环境比较复杂,不可避免地要受到各种噪声的影响。当前对声发射信号大多是靠电缆进行传输,这种传输方式有传输距离有限、信号容易受到干扰等缺点。针对传统电缆传输信号的不足之处提出使用光纤作为传输信号的媒介,设计并开发了一种基于光纤的声发射监测的信号采集系统,能够实现远程监测且信号的抗干扰能力比较好。     

基于MSC Fatigue的脉动真空灭菌器疲劳分析

针对某些脉动真空灭菌器在未达到使用寿命时内壁就出现裂纹的问题,应用MSC Patran建立其有限元模型,调用MSC Nastran进行应力分析,然后应用MSC Fatigue软件进行疲劳分析．将所得寿命分析结果与实际工程使用情况比较,发现疲劳不是脉动真空灭菌器内壁产生裂纹的主要原因．     

Multi-objective probabilistic optimum monitoring planning considering fatigue damage detection,maintenance, reliability,service life and cost

Effective and efficient service life management is essential for a deteriorating structure to ensure its structural safety and extend its service life. The difficulties encountered in the service life management are due to the uncertainties associated with detecting and identifying structural damages, and assessing and predicting the structural performance. To reduce these uncertainties, continuous long-term structural health monitoring (SHM) can be employed. However, a rational and practical SHM planning is required to simultaneously maximize the accuracy, efficiency, and cost-effectiveness in service life management. This paper proposes a probabilistic optimum SHM planning based on five objectives to be simultaneously optimized: minimizing the expected damage detection delay, minimizing the expected maintenance delay, maximizing the damage detection time-based reliability index, maximizing the expected service life extension, and minimizing the expected life-cycle cost. The formulations of the five objectives are based on the probabilistic fatigue damage assessment. The monitoring plannings associated with both a single- and a multi-objective probabilistic optimization process (MOPOP) are investigated. For efficient decision making in identifying the essential objectives and selecting a well-balanced solution among the Pareto optimal solutions, the degree of conflict among objectives and objective weights are estimated. The novel approach proposed in this paper accounts for the interdependencies among the five objectives considered and demonstrates the role of the optimum SHM planning in service life management of deteriorating structures. The proposed MOPOP SHM planning is applied to the hull structure of a ship subjected to fatigue.     

疲劳驾驶状态检测系统的设计

司机疲劳驾驶容易引起严重的交通事故,疲劳状态检测系统的研究成为计算机应用研究的重要领域.为了满足疲劳状态检测系统实时性要求,选择实时性较好的Adaboost算法来识别人眼,采用单位时间内眼睛闭合时间所占的百分率来判断疲劳状态,应用该算法后进行疲劳驾驶训练和识别研究.选择DSP移植方案并将疲劳状态检测算法移植到DSP中.经过实时检测实现的系统基本能满足实时检测疲劳驾驶的要求.     

Fatigue constrained topology optimization

We present a contribution to a relatively unexplored application of topology optimization: structural topology optimization with fatigue constraints. A probability based high-cycle fatigue analysis is combined with principal stress calculations in order to find the topology with minimum mass that can withstand prescribed variable-amplitude loading conditions for a specific life time. This allows us to generate optimal conceptual designs of structural components where fatigue life is the dimensioning factor. We describe the fatigue analysis and present ideas that make it possible to separate the fatigue analysis from the topology optimization. The number of constraints is kept low as they are applied to stress clusters, which are created such that they give adequate representations of the local stresses. Optimized designs constrained by fatigue and static stresses are shown and a comparison is also made between stress constraints based on the von Mises criterion and the highest tensile principal stresses. The paper is written with focus on structural parts in the avionic industry, but the method applies to any load carrying structure, made of linear elastic isotropic material, subjected to repeated loading conditions.     

Fatigue induced by static work

Despite its low energy cost, isometric contraction can result in the onset of local muscle fatigue. The onset of fatigue occurs more rapidly when the relative force exerted is greater than 15-20% of the maximum voluntary contraction (MVC) of the muscle considered, and when the contraction time is increased. The maximum maintenance time (limit-time) and the corresponding relative force are linked by a hyperbolic relation. Ischaemia promotes accumulation of acid metabolites produced during contraction, and hinders their elimination, thus constituting the main causal factor in the onset of local muscle fatigue. The introduction of rest periods of sufficient duration to ensure restoration of normal blood flow through the muscle is an effective way of delaying, or even preventing, the onset of muscle fatigue. Other factors may also be taken into account, such as the position in which the static work is performed, and the nature and number of muscles used simultaneously, etc. Numerous laboratory and field studies have allowed the development of various models that take into account the conditions relating to isometric contractions during static work.     

Fatigue induced by static work

Abstract

Despite its low energy cost, isometric contraction can result in the onset of local muscle fatigue. The onset of fatigue occurs more rapidly when the relative force exerted is greater than 15–20% of the maximum voluntary contraction (MVC) of the muscle considered, and when the contraction time is increased. The maximum maintenance time (limit-time) and the corresponding relative force are linked by a hyperbolic relation. Ischaemia promotes accumulation of acid metabolites produced during contraction, and hinders their elimination, thus constituting the main causal factor in the onset of local muscle fatigue. The introduction of rest periods of sufficient duration to ensure restoration of normal blood flow through the muscle is an effective way of delaying, or even preventing, the onset of muscle fatigue. Other factors may also be taken into account, such as the position in which the static work is performed, and the nature and number of muscles used simultaneously, etc. Numerous laboratory and field studies have allowed the development of various models that take into account the conditions relating to isometric contractions during static work.     

兆瓦级风力发电机组主机架疲劳分析

应用有限元法对某兆瓦级风力发电机组主机架进行极限强度分析.基于GL规范分析风力发电机组主机架疲劳计算需要考虑的载荷工况,并对主机架进行疲劳寿命分析.对计算结果进行校核评价,指出主机架结构易发生疲劳破坏的部位.分析结果可为兆瓦级风力发电机组主机架的结构设计提供参考.