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超声振动红外热像法(VT)是红外热像无损检测的重要方法之一,在裂纹等紧贴型缺陷检测中有特殊的应用优势。为了寻找适宜的振动激励条件,用解析法分析了材料热特性(热导率和热扩散系数)和缺陷深度对温升的影响,分析了试件支撑条件和几何尺寸对共振频率的影响。结果表明,复合材料较金属材料容易实现VT检测。对金属件宜用短时超声激励,而对复合材料件宜用较长时间的超声激励。从共振角度看,采用简支方式和超声激励相组合是比较好的选择。 相似文献
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利用有限元方法模拟微裂纹在强超声作用下的摩擦发热现象 总被引:1,自引:0,他引:1
采用有限元方法,对强超声作用下金属板中裂纹面的动接触行为以及摩擦发热现象进行了三维热力耦合模拟。在有限元模型中,利用压电-热弹类比方法模拟功率超声换能器激励,而采用基于罚函数方法的接触-碰撞算法模拟裂纹面之间的动接触相互作用。通过有限元模拟,定量计算了裂纹面上的摩擦发热现象,对功率超声换能器激励下裂纹板的振动特性、裂纹面的动态接触过程以及裂纹处的温度分布进行了分析。有限元仿真结果可以合理解释在超声红外热像技术中观察到的现象。 相似文献
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超声图像的小波去噪及多尺度边缘提取 总被引:2,自引:0,他引:2
提出与超声成像图像适应的小波统计域去噪和多尺度边缘提取结合的缺陷识别方法。在目前存在的多种分析模型基础上,根据统一的尺度一空间分析广泛图像小波分解系数的模型框架,结合概率模型,利用软门限和经典维纳估计方法压制噪声。通过不同信号在多尺度分析中的不同动态特性,提取表示缺陷特征的图像信号。 相似文献
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Application of ultrasonic method in asphalt concrete testing for fatigue life estimation 总被引:3,自引:0,他引:3
Mesut Tigdemir S. Figen Kalyoncuoglu U. Yalcin Kalyoncuoglu 《NDT & E International》2004,37(8):597-602
This paper presents the possibilities of applying ultrasonic methods in asphalt concrete specimen testing in order to estimate fatigue life using ultrasonic characteristics of specimens. The procedures and results of testing cylinder shaped samples of both ultrasonic analysis and fatigue life testing are described. The ultrasonic method was first used in order to obtain the seismic characteristics of specimens. Then, the specimens were tested for fatigue lives using the repeated-loading indirect tensile test equipment (SDU-Asphalt Tester). To be able to model the fatigue lives, in addition to conventional fatigue model parameters new parameters from this ultrasonic analysis were taken into consideration. These additional parameters are acquired from the seismic measurements. Hence, only by examining the ultrasonic method, it will be possible to predict the fatigue lives of the specimens non-destructively. 相似文献
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超声检测图像分辨率的维纳滤波去卷积研究 总被引:2,自引:0,他引:2
为了研究改善超声检测横向分别率以及缺陷检测精度的方法,对聚焦换能器和非聚焦换能器的超声检测成像结果进行了比较,结果表明聚焦换能器在焦点位置具有较高的横向分辨率。为了提高平面非聚焦换能器的成像分辨率,根据平面换能器的平底孔散射模型,计算出换能器的点扩展函数,并利用维纳(Wiener)滤波进行去卷积研究。结果表明,只要选取适当的滤波参数,去卷积处理能有效改善成像检测的横向分辨率。 相似文献
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超声B扫描伪象剔除技术研究 总被引:3,自引:0,他引:3
超声B扫描成象检测中,由于超声多次反射的影响经常出现伪象,导致检测结果不准确。在分析多次回波形成机理的基础上,阐述了B超伪象剔除原理,研制了实施装置。实验结果表明,该方法不仅伪象剔除效果好,而且成象效率高.还具有较强的去噪作用。 相似文献
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Inspecting damaged structures repaired with composite patches is one of the most challenging issues of different industries, especially in aeronautical vehicles. Various inspection methods such as ultrasonic (UT) and thermographic methods are commonly applied to the patches and bondings. Although, both ultrasonic and thermographic inspections have their own capabilities, they are also associated with some limitations especially in the inspection of complicated structures such as multilayers. Different data fusion techniques can be used to overcome these limitations, by exploiting the advantages of each inspection technique to achieve the goal to have a more precise and reliable defects assessment. In this paper, different image fusion algorithms are used to fuse the UT C-scan and thermal images obtained from thermographic inspection of carbon/epoxy patches bonded to an aluminum plate. The inspected specimen contained several delaminations of various sizes and locations along with some disbond defects which were artificially embedded in five samples of composite patches. The resulting images of 28 fusion algorithms and the input images have been quantitatively compared using Average Differences (AD) to clarify the efficiency of the fusion algorithm. Comparing results revealed that contrast pyramid was selected as the best image fusion algorithms which can be used for NDE fusion of carbon/epoxy patches bonded to an aluminum plate. 相似文献
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This paper presents a novel approach to the problem of nondestructive pipeline testing using ultrasonic imaging. The identification of the flaw type and its dimensions are the most important problems in the pipeline inspection. Unlike typical methods, a decision based neural network is used for the detection of flaws. We train a generalized regression neural network to determine the dimensions of the corrosions and generate the whole image of both the internal and external walls of the oil pipeline. As an improvement to the detection algorithm, we introduce fuzzy decision-based neural network algorithms for the detection and classification of the corrosions. The simulation and experimental systems results show that these new methods outperform the existing methods. 相似文献
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采用解析几何理论与方法,对TKY管节点焊缝进行了数学模型的构建.在获得管节点焊缝截面图形基础上,按照规定尺寸绘制焊缝接头,并依据实物尺寸绘制相控阵探头轮廓和超声波的声束线.运用计算机辅助技术实现了焊接接头声束覆盖范围可视化效果,较好地指导了相控阵检测工艺设计,能够对TKY管节点焊缝超声检测盲区进行评估,从而克服了相控阵超声检测参数设置的盲目性.对人工设计的Y形管节点焊缝试样检测表明,利用超声相控阵成像技术和计算机辅助技术相结合手段有助于管节点焊缝作快速检测和评价. 相似文献