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1.
针对机械裂纹扩展以及检测的问题,对常用的裂纹无损检测方法进行了叙述,具体介绍了磁粉检测和渗透检测技术的发展现状。对近年来新兴的激光超声检测技术、电磁超声检测技术、超声红外热成像检测技术、脉冲涡流及涡流阵列检测技术的特点、作用原理进行了详细的说明,对比了相对传统检测技术的优势,对各新型无损检测技术的发展方向进行了总结分析。研究结果表明:未来新型裂纹无损检测方法的发展趋势将由人工向智能化、全自动化、图像化检测发展,复合模式检测在新技术中的应用愈加广泛,检测仪器设备的发展以降低能耗和提高信噪比为主,新型裂纹无损检测技术在特殊工程领域的应用将更加专业化。 相似文献
2.
《Measurement》2014
Pulsed magnetic flux leakage (PMFL) testing is a new emerging and effective electromagnetic non-destructive testing (NDT) technology which combines the conventional magnetic flux leakage (MFL) technology with the theory of pulsed current. Compared with single sensor, the sensor array can scan larger areas with higher speed and lower lapsus.Finite element method (FEM) is used to get the ideal signal of MFL with defects, including signal horizontal and vertical. According to the analysis of different signal of MFL with defects, the relation between magnetic signal and defect size is received. Then a full set of PMFL system based on sensor array is used to detect the standard specimens. In order to eliminate the noise and extract the feature, the detecting signal is analyzed and processed by some pre-treatments. In the process of time-domain analysis, every peak value of sensor signal is extracted as analyzing signal, then peak values are lined as output signal of the sensor array. By analyzing different characters of curve under different defect sizes, and getting corresponding characteristic quantities, the reasons of the errors are discussed. 相似文献
3.
钢轨裂纹监测是保障铁路基础部件安全的重要研究课题之一。 超声导波在钢轨中具有衰减小、传感距离远、检测效率
高等优点,可实现钢轨长距离快速检测。 传统的超声导波传感器大都采用 PZT 陶瓷制成,质地硬脆、易碎裂,不能满足钢轨长
期在线监测使用要求。 本文提出将柔性 0~ 3 型 PZT/ 环氧树脂复合材料用作钢轨超声导波传感器,实验研究该柔性压电复合
材料的力学性能及其对导波的传感特性,结合有限元仿真分析和实验测试,分析了钢轨中激励导波模态特性及其裂纹反射波的
延迟到达时间,探讨压电复合材料传感器应用钢轨裂纹导波信号检测的适用性和有效性。 研究结果表明:PZT/ 环氧树脂复合
材料传感器具有良好的柔韧性和线性灵敏度,在 5℃ ~ 75℃ 温度范围内能够有效检测到导波信号;不同传感路径得到的钢轨导
波检测信号与有限元仿真信号基本一致,裂纹反射波到达时间相近,这将为钢轨裂纹在线监测提供新型的柔性压电复合材料传
感技术。 相似文献
4.
In this paper, a crack detection approach is presented for detecting depth and location of cracks in beam-like structures. For this purpose, a new beam element with an arbitrary number of embedded transverse edge cracks, in arbitrary positions of beam element with any depth, is derived. The components of the stiffness matrix for the cracked element are computed using the conjugate beam concept and Betti’s theorem, and finally represented in closed-form expressions. The proposed beam element is efficiently employed for solving forward problem (i.e., to gain precise natural frequencies and mode shapes of the beam knowing the cracks’ characteristics). To validate the proposed element, results obtained by new element are compared with two-dimensional (2D) finite element results and available experimental measurements. Moreover, by knowing the natural frequencies and mode shapes, an inverse problem is established in which the location and depth of cracks are determined. In the inverse approach, an optimization problem based on the new finite element and genetic algorithms (GAs) is solved to search the solution. It is shown that the present algorithm is able to identify various crack configurations in a cracked beam. The proposed approach is verified through a cracked beam containing various cracks with different depths. 相似文献
5.
钢轨踏面斜裂纹超声表面波B扫成像检测研究 总被引:2,自引:1,他引:1
由滚动接触疲劳引起的钢轨踏面斜裂纹已成为目前高速铁路在役钢轨无损检测中的重要问题,现有的铁路钢轨超声探伤车(仪)难以检测此类缺陷。采用低频超声表面波方法,沿钢轨长度方向对钢轨踏面斜裂纹进行B扫成像检测。由于钢轨轨头为带圆弧边的矩形截面,在钢轨表面激发和传播的低频表面波已不再是经典的Rayleigh波,而是一类导波,导波的多模式对表面波成像检测形成了干扰。为减小干扰,将空间平均技术应用于钢轨踏面斜裂纹的表面波B扫成像。对人工缺陷试块和钢轨试样的B扫成像实验结果表明,利用空间平均技术能有效的抑制此类干扰,提高信噪比,可对钢轨踏面斜裂纹作快速检测和定位。 相似文献
6.
漏磁检测因其显著的技术优势,被广泛应用于无损检测铁磁性构件中的缺陷,尤其是在油气管道的内检测领域。 漏磁
检测信号的空间分辨率由传感器的排布密度决定,但传感器的排布密度受其尺寸限制,尤其是对单排传感器。 因此为提升检测
信号的空间分辨率,传感器的多排、错排布置是简单易行的方法。 由于多排传感器所处位置的背景磁场不同,不同背景磁场对
检测信号的影响规律尚不清晰,因此需要对以上问题进行理论分析,并提出对多排传感器检测数据进行修正的方法。 本研究基
于磁荷理论,将缺陷检测信号划分成背景磁场和缺陷漏磁场两部分的叠加,给出了两者叠加的规律。 基于此提出了对多排传感
器的检测数据进行修正的方法,并通过 COMSOL 仿真和实验结果验证了所提方法的有效性。 相似文献
7.
在建立港口起重机轮轨接触的三维实体模型的基础上,通过商业软件ANSYS建立了车轮材料不做硬化、硬化10mm、硬化25mm、全部硬化4种有限元模型;计算了这4种模型点接触和线接触2种轮轨接触模型的接触应力和接触面积,并与相应的赫兹理论值对比。通过对不同车轮硬化处理方式的接触应力和接触面积的比较,分析硬化处理对车轮接触的影响。 相似文献
8.
A model-based identification method of transverse cracks in rotating shafts suitable for industrial machines 总被引:5,自引:1,他引:4
Paolo Pennacchi Nicol Bachschmid Andrea Vania 《Mechanical Systems and Signal Processing》2006,20(8):2112-2147
This paper presents a model-based transverse crack identification method suitable for industrial machines. The method is validated by experimental results obtained on a large test rig, which was expressly designed for investigating the dynamical behaviour of cracked horizontal rotors. The identification method and the relative theory is briefly presented, while three different types of cracks are considered: the first is a slot, therefore not actually a crack since it has not the typical breathing behaviour, the second a small crack (14% of the diameter) and the third a deep crack (47% of the diameter). The excellent accuracy obtained in identifying position and depth of different cracks proves the effectiveness and reliability of the proposed method. 相似文献
9.
Based upon the method of eigenfunction expansion and Leknitskii’s complex-variable potentials for the generalized plane deformation, the singular stress field near transverse cracks is examined for cross-ply composite laminates under two types of deformation, extension and in-plane shear. The stress singularity for each deformation is obtained from the eigenvalue equation resulting from appropriate near field conditions. It is found that the stress singularity for in-plane shear deformation is much stronger than for extension. To compute the stress intensity, use is made of the asymptotic representation for the stress and displacement field in conjunction with the singular hybrid finite element method. The numerical results are confirmed through comparison to those from other numerical techniques such as the boundary collocation method. 相似文献
10.
A clamped laminated cylindrical shell is presented to investigate nonlinear structural behavior involving geometrically nonlinear deformation. In the investigation, transverse matrix cracks are considered in the stiffness of the laminated cylindrical shell. Stiffness degradation is examined for several laminated angles and transverse crack density. Micro-mechanics theory on the composite material was used to derive the degraded stiffness of the laminated cylindrical shell due to the crack density. Iterative numerical scheme was developed to calculate the degraded composite stiffness which is a complicated relation with the crack density. A nonlinear finite element program was developed using 3-D degenerated shell element and the fist order shear deformation theory to consider the large deformation of the clamped laminated cylindrical shell. The updated Lagrangian method is used for nonlinear finite element analysis. Nonlinear structural responses of the laminated cylindrical shell were examined for various stacking sequences and crack density under transversely loaded pressure. Also, the effect of crack opening/closed was considered in the examination. Through this study, it is realized that the transverse matrix crack causes moderate stiffness reduction and affects the responses of the composite shell. 相似文献
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12.
微型机器人用于检查管道内的缺陷 总被引:1,自引:0,他引:1
管径φ10~20 mm的细小管道在工业中应用十分广泛,因此迫切需要研究一种管道检测机器人进入管道内部, 对其缺陷进行检测或维修.为此目的,近年来发展了不同类型的微型机器人,例如:气囊蠕动型、螺旋摩擦型、电磁力型、SMA型、冲击型机器人,并且取得了一些可喜进展.本文报道一种采用双压电薄膜PZT驱动器的细小管道实验微机器人,它可以携带CCD摄像机进入φ20 mm的垂直、水平或弯曲管道, 检查管壁上的小孔或裂纹.论述了此种微机器人的实验系统、结构、运动机理和性能. 相似文献
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14.
Xiangyuan Xu Doo-Ho Cho Yoon-Suk Chang Jae-Boong Choi Young-Jin Kim Hyun-Kyu Jun Jung-Won Seo Dae-Sang Kim 《Journal of Mechanical Science and Technology》2011,25(5):1215-1220
Crack propagation due to rolling contact fatigue (RCF) could be a significant potential challenge to the integrity of railway
rails because it may lead to a serious disaster. Fatigue cracks subjected to cyclic rolling contact force experience a complex
non-proportional mixed loading and complicated boundary condition. In the present research, complex crack opening/closure/sliding/locked
behaviors as the cyclic contact loading movement is analyzed considering liquid lubrication action on rail surfaces as well
as crack faces. Based on a series of FE analyses, the calculations of the effective SIF ranges for RCF cracks under certain
contact loading and boundary conditions are proposed in the form of polynomial functions which will be appropriately used
to predict RCF crack growth rate. 相似文献
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16.
本文介绍了货轮左右舷侧龙门吊轨道角焊缝连接处出现大量裂纹,从U71Mn材质轨道钢的焊接性能入手,对其化学成分及机械性能进行了分析,提出了甲板轨道安装的改进方案,即采用两边加夹板的形式固定轨道的横向移动,供同行参考。 相似文献
17.
压力容器安全运行是一项十分重要的安全工作,因此,加强压力容器焊缝及其附近微裂纹的检测就显得尤为重要.无损检测技术的应用在压力容器制造过程中显得十分重要,常规无损检测技术主要有:射线检测、超声波检测、渗透检测、涡流检测、磁粉检测.本文首先阐述了常用的无损检测方法及应用.其次,对压力容器焊缝及其附近微裂纹检测特点及步骤进行了深入的探讨,得出以下结论:只采用一种无损检测方法来检测压力容器焊缝及其附近微裂纹,无论那种检测方法如何的先进,如何的高效,进检测结果必然会存在很多局限和疏漏,容易造成漏检.压力容器焊缝及其附近微裂纹的检测应该综合运用各种无损检测方法,相互取长补短,做到合理科学地结合检测的压力容器实际情况来运用各种检测手段,确保压力容器安全运行. 相似文献
18.
Withawat Withayachumnankul Pichate Kunakornvong Channarong Asavathongkul Pitikhate Sooraksa 《The International Journal of Advanced Manufacturing Technology》2013,64(9-12):1275-1283
Lead zirconate titanate, also known as PZT, is a type of piezoelectric ceramics commonly used for actuators in modern hard disk drives (HDDs). These PZT actuators are prone to hairline surface cracks, prompting detection and removal during the HDD production. Machine vision is then utilized for automatic detection of these cracks. The developed image processing approach comprises three steps: extraction of the region of interest, enhancement of crack regions, and elimination of irrelevant features. The key step, crack region enhancement, employs image filtering with a specifically designed filter kernel, capable of extracting thin crack regions from the rough surface of PZT actuators. The experiments show that the algorithm reveals cracks with high accuracy and high sensitivity, whereas the overall processing time satisfies the industrial environment. 相似文献
19.
人眼对彩色的变化远比对灰度的变化敏感,但目前的超声无损检测结果的显示大多仍采用灰度图像方式。通过将伪彩色技术应用于超声无损检测过程,实现了超声检测缺陷结果图像的伪彩色显示,提高了无损检测结果的直观性,增强了对缺陷的表达能力。 相似文献
20.
人体运动检测是计算机视觉人体运动分析的关键环节。根据Kinect深度图像的特点,引入并改进Vi Be算法处理深度图像进行人体运动检测。考虑到深度图像中地面像素值连续性造成的地面附近运动检测困难,提出了一种自适应的图像分层处理和不同邻域模式的建模方式,增加了去除"鬼影"现象的参考模型。像素分类时增加了前景点检验步骤,通过当前像素与参考模型的比较消除"鬼影"。在模型更新方面增加了基于前景点的背景模型更新策略,解决了"黑影"现象问题。采用阈值法对分类结果进行了误检点消噪处理。实验结果表明所提出的改进Vi Be算法能够比较准确地检测出人体运动。 相似文献