钢缆断丝NDT信号实时处理的一种有效方法

本文在分析钢丝绳断丝无损检测信号特点的基础上，经过试验，对比闻几种常用的信号处理方法，提出一种有效的能用于实时处理的方法，可以准确地识别钢丝绳断丝信号．     

高噪下的钢丝绳断丝定量检测

研究高噪情况下的钢丝绳断丝定量检测信号处理。利用时域与频域相结合的处理算法实现断丝的特征提取，采用这些方法对高噪下的钢丝绳磁检测信号进行处理，能够清楚地区分噪声和损伤信号。该方法运算量小，适合于实时在线的钢丝绳检测。     

三峡升船机钢丝绳断丝与磨损检测原理与实现

根据三峡升船机钢丝绳的使用特点，提出了三峡升船机钢丝绳检测的原理与方法，采用周向多回路对钢丝绳轴向励磁，利用漏磁场原理检测钢丝绳断丝，磁桥回路检测钢丝绳磨损量，并实现在一个传感器中对断丝和磨损两种缺陷信息的综合检测。在信号处理方面设计了相应的电路和软件，实现了缺陷的定量分析。     

基于主成分分析和BP神经网络的钢丝绳断丝定量检测方法

针对目前钢丝绳断丝定量检测中存在的问题,充分利用主成分分析与BP神经网络的优点,提出了基于主成分分析与BP神经网络相结合的钢丝绳断丝定量检测方法。采用主成分分析法对钢丝绳断丝信号的原始特征属性进行预处理,得到钢丝绳断丝信号主成分特征属性,并以此作为BP神经网络的输入,建立钢丝绳断丝信号主成分特征属性与断丝数目之间的关系,并对钢丝绳断丝数目进行预测;主成分分析方法减少了原始特征属性的维数,消除了属性之间的相关性;同时,主成分特征属性作为BP神经网络的输入,也简化了网络的结构。实例测试结果表明,基于主成分分析的神经网络钢丝绳断丝检测方法与常规BP神经网络方法相比,具有更高的检测精度和更少的计算量。     

三峡升船机钢丝绳断丝与磨损检测原理及实现

根据三峡升船机钢丝绳的使用特点，提出了三峡升船机钢丝绳检测的原理与方法，采用周向多回路对钢丝绳轴向励磁，利用漏磁场原理检测钢丝绳断丝，磁桥回路检测钢丝绳磨损量，并实现在一个传感器中对断丝和磨损两种缺陷信息的综合检测。在信号处理方面设计了相应的电路和软件，实现了缺陷的定量分析。     

钢丝绳断丝检测仪器评估中标样制作方法研究

标准试样制作是钢丝绳无损检测仪器性能评估中的关键环节,其优劣决定了评估的效率和有效性。通过分析断丝检测流程、揭示影响仪器断丝检测能力的因素后,提出断丝配置的等相对差法和等绝对差法,比较了两者的适用性,等绝对差法对高精度仪器有效,等相对差法对低精度仪器有效。最后提出了评估中优选钢丝绳试样的方法。     

一种钢丝绳自动检测装置的设计

为了克服钢丝绳人为检测法误差大、判断不可靠的缺点,根据漏磁法和磁桥路检测原理,并在集成霍尔元件和LCD矩阵式键盘的基础上,开发了一种既可在线进行钢丝绳断丝位置、断丝根数判别,又可与PC机联机工作实现智能化检测诊断的高精度钢丝绳缺陷检测装置。     

自激过程与非齐次Poisson过程用于钢丝绳断丝计数过程的建模与…

对于钢丝绳集中断丝过程，提出了断丝自激点过程的建模方法，对于钢丝绳均匀断丝过程，提出了断丝非齐次Ｐｏｉｓｓｏｎ过程的建模方法，依据极大似然估计原理，给出了钢丝绳寿命预测方法和钢丝绳最佳更换期。     

预应力混凝土梁腐蚀断丝水下监测试验研究

采用人工通电加速腐蚀的方法模拟混凝土梁内预应力钢筋的自然断裂过程从而获得真实的断丝声发射信号,应用高频声发射传感器和分布式光纤监测系统从水下采集预应力钢筋断裂时产生的声信号,分析信号的时频域特征和时域统计特征参数,结果表明：断丝信号的超声波段在水中传播时发生频散,应采用20 kHz以下的时域统计特征识别断丝信号;铠装光缆可以接收到在水中传播的断丝信号,其在时频图上表现为一条竖直的条带,并且能量主要集中分布于100～200 Hz。采用时域统计特征参数分析光纤监测信号时,需要设定较小的门槛值截取信号进行分析;对于光纤水声监测工况来说,峰值指标的信噪比较低,裕度和峭度指标更适合于用来识别断丝信号。该研究为开发预应力混凝土结构断丝水下声光纤监测系统奠定了基础。     

基于迁移学习的钢丝绳断丝定量检测方法EI北大核心CSCD

针对目前钢丝绳断丝定量检测的问题,利用深度卷积神经网络强大的特征提取能力,提出一种基于迁移学习的钢丝绳断丝定量识别方法。通过连续小波变换将原始断丝漏磁信号转换成时频图。将预训练网络GoogLeNet的低层参数直接迁移,使用标记好的时频图对网络高层进行参数调整,得到最终的目标模型。通过内外部断丝试验验证了所提出的定量识别模型的效果,将传统的BP(back propagation)神经网络与所提出的方法进行对比。结果表明:基于迁移学习的断丝定量识别方法能准确区分钢丝绳的内外部断丝故障,分类准确率达到了97.2%;与传统BP神经网络相比,所提出的方法对各种断丝具有更好的识别性能。     

Nondestructive Evaluation of a Haulage Rope in a Monocable Continuously Moving Passenger Ropeway

The theoretical basis of detecting wire rope anomalies using permanent magnetic field has been fully established. The local faults (LF) such as broken wires and loss of metal area (LMA) signals are provided by nondestructive evaluation instruments. These signals represent the electronic equivalent of the mechanical anomalies present in the wire rope. The saturating magnetic field of the instrument makes the anomalies visible to the magnetic sensors placed around the rope. The condition of a haulage rope (construction 6X19) in a monocable continuously moving passenger ropeway has been studied using this nondestructive method, and the results are presented in this paper.     

悬索桥缆索钢丝损伤超声导波检测数值模拟

为了实现对大跨悬索桥缆索钢丝损伤的有效检测,采用理论分析和数值模拟相结合的方法,对超声导波无损检测技术进行研究。通过理论求解钢丝中导波的频散曲线,分析频散特性和波结构,选取中心频率为200 kHz的L(0,1)模态进行钢丝断丝损伤检测;利用有限元软件,研究了钢丝中导波的频散特性和波结构,通过二维傅里叶变换技术对钢丝中的低阶导波模态进行识别,进一步分析了缺陷尺寸和角度对L(0,1)模态缺陷反射系数的影响;最后,对L(0,1)模态在两根钢丝和七根钢丝的断丝处的缺陷回波进行了数值模拟。数值模拟与理论分析结果相吻合,说明低频L(0,1)模态可以有效地对缆索钢丝断丝损伤进行远距离检测。     

Failure Analysis of Failed Wire Rope

Failure of an old rope from a stringing lattice transmission towers occurred in winter while the rope was being removed to make way for a new rope. Fracture took place around mid-span. At that time, ambient temperature was −22 °C. Wire rope was in service for nearly 50 years. We were given the mandate to determine the reasons for the fracture of the wire rope and also to suggest measures to prevent such failures from occurring. The study involved laboratory testing (mechanical and metallographic) of representative wire rope samples. The effect of low temperature (from room temperature to −40 °C) on the tensile behavior of wires and wire rope samples was evaluated. In addition, we designed an instrumented impact test to assess the effect of notches, low temperatures and dynamic loading on the fracture behavior; however, no standards were available for direct comparison. Optical metallography was used to judge the extent of corrosion and the nature of microstructure and the cleanliness of the steel. The fracture morphology of broken tensile and impact specimens was carried out using scanning electron microscopy to establish relations between test parameters and fracture modes. Results indicate that considerations have to be given to the occurrence of corrosion, notches, low temperatures, and dynamic loading conditions when replacing wire ropes and this may necessitate the replacement of wire rope earlier than the time dictated by the criterion of 10% loss in breaking strength. Results also indicate that impact testing is a better evaluator of the susceptibility of wire ropes to brittle fracture than tensile tests.     

Estimation of subsample time delay differences in narrowbandultrasonic echoes using the Hilbert transform correlation

In many areas the time delay of arrival (TDOA) is desired. In the case of narrowband signals we propose a fast and simple method to estimate small time delays. This method is shown to have the same or better accuracy as the cross correlation methods for small delays in the order of fractions of the sample interval. It is based on using the Hilbert transform in correlation between two signals and consists of only one scalar product, which makes it fast. It may also be used in applications with narrowband signals where the measurements are repeatable, such as ultrasonic imaging and nondestructive testing. In ultrasonic applications, due to fluctuations in the insonified media, a small random time shift may be present causing the signals to be misaligned in time. Averaging signals under these conditions will result in a distortion of the signal shape. We propose an averaging method to avoid this and to accomplish a higher SNR without the distortion. Simulations and experiments from ultrasonic applications are presented     

Bending fatigue behaviour of bearing ropes working around pulleys of different materials

Nondestructive quantitative detection and artificial detection were carried out to study bending fatigue behaviour and failure mechanisms of wire ropes. When working around nylon pulleys, wire ropes exhibit a slowly increasing of fracture rate and total damage in one lay length. The bending fatigue life of wire ropes is twice longer than that of ropes working around steel pulleys. The primary failure mode of wire ropes working around nylon pulleys is fatigue fracture and the fracture surfaces of wires exhibit a wide crack propagation zone and narrow tear zone.     

Electromagnetic testing,a reliable method for the inspection of wire ropes in service

The art of wire rope inspection has progressed rapidly over the past few years. Presently available electromagnetic instruments are now much easier to operate and provide an important (in some cases indispensable) element of wire rope inspection. Test data obtained from these instruments can provide accurate quantitative estimates of safety-related wire rope parameters such as loss of metallic cross-sectional area (LMA) and provide a more reliable basis for estimating the condition and remaining service life of a rope. This paper illustrates the use of modern nondestructive test methods to assess the safety of wire ropes in service.     

基于小波变换的裂谱分析法

 为了提高超声无损检测（UNDT）和无损评价（UNDE）中基础数据的信噪比（SNR）,提出了一种基于小波变换多分辨率分析的裂谱分析新方法．该方法在分析传统裂谱分析（SSP）方法原理及其局限性的基础上,通过采用小波变换多分辨率分析能力将原始超声回波信号进行等Q子带分解,然后按照一定的信噪分离规则来消除噪声,达到提高信噪比的目的．实验结果表明,与传统裂谱分析方法相比,该方法提高了消噪性能的稳定性,增强了湮没晶粒(或其他散射体)散射中的缺陷回波信号能力．