大型40Cr锻钢件超声检测缺陷性质及原因分析

采用宏观分析、扫描电镜及能谱分析、金相检验、化学分析等方法对23 t粗加工毛坯超声检测缺陷进行分析,判定该大型锻钢件缺陷为白点,且在白点发裂处存在夹杂物和偏析现象,并提出相应预防措施。

大型锻件超声检测缺陷逆向跟踪及分析

针对大型锻件出现的超声检测缺陷,采用Deform 3D软件对其成形全过程进行有限元分析。将无损检测结果引入锻件的自由锻过程数值模拟结果中,采用节点跟踪方法对超声检测缺陷在成形过程中的应力、应变、位移及超声检测缺陷在钢锭中的分布进行逆向跟踪,探讨超声检测缺陷产生的原因及钢锭缺陷与超声检测缺陷之间的关系。

一种用于缺陷超声检测的相位标准差分离谱新算法

在粗晶材料超声无损检测中，分离谱处理技术可用来降低材料内部的相干噪声、但分离谱处理对滤波器阵列参数较敏感、造成性能不稳，且至今对滤波信号有效利用的解释尚不明了．本文从理论上讨论了超声检测信号滤波输出的相位统计特性，据此提出了一种基于相位标准差的分离谱新算法，用计算机模拟及实验数据对该算法的世能进行了测试并与常用的极小值分离谱算法作了对比。结果证实，相位标难差的分离谱算法有好的信噪比增强能力，且对滤波器数不敏感．

基于超声波检测的BP神经网络缺陷识别方法设计

针对石油储罐底板的缺陷损伤问题,建立局部储罐底板模型,应用超声波缺陷检测技术进行分析研究。利用ABAQUS有限元软件进行超声检测的模拟仿真分析,采集并保存接收信号,通过不同位置的发射/接收器信号时间差值对比,应用椭圆定位原理计算得到缺陷类型;从仿真模拟数据中选取不同的超声波回波信号作为神经网络的输入,借助于MATLAB软件训练出可识别底板缺陷的BP神经网络,选取多组数据进行测试,经验证,设计的BP神经网络对缺陷数据识别具有一定正确性。

超声检测在混凝土缺陷和厚度检测中的应用

阐述了混凝土超声无损检测的特点以及目前在工程应用中存在的问题和影响因素,并简单介绍了目前应用较多的超声测厚和缺陷、裂纹检测技术,以使该技术得到更广泛的应用。

钢结构焊缝超声波检测对缺陷定性浅析

使用A型脉冲反射超声波对钢结构焊缝进行检测,对发现的反射体进行性质判定的分析。从焊接缺陷的成因及反射波的特点着手探讨焊接气孔、夹渣、未焊透、未熔合、裂纹的区别及判定方法。通过检测分析,促进焊接工艺改进,为提高焊接操作人员技能水平提供参考依据。

一种基于超声缺陷回波分析的小波降噪方法

超声缺陷检测回波中存在大量噪声,图像质量差.传统的降噪方法存在着同频噪声抑制效果差等问题.文中搭建了双晶斜探头的缺陷检测平台,采集了缺陷回波,通过对缺陷回波分析,研究了缺陷信号和噪声的特点.提出了小波降噪的阈值改进方法,根据信噪比进行分段阈值降噪.回波降噪处理后,将基于希尔伯特变换的全矩阵成像应用于双晶斜探头扫描成像中,成像效果良好.实验结果表明,提出的改进小波降噪方法使得回波信噪比大幅提高,缺陷辨识度提高.

小径厚壁钢管超声探伤系统设计研究

针对壁厚与外径比大于0.2的小径厚壁无缝钢管提出了一种基于超声波检测的缺陷检测系统,完成了系统的硬件和软件设计,同时为提高系统缺陷的识别效率和准确度,通过分析小径厚壁钢管超声自动探伤系统干扰来源和传播途径,利用改进小波阈值去噪方法来去除混回波信号中的噪声提高回波信号信噪比。实验证明,超声探伤系统能够实现小径厚壁钢管的缺陷检测,小波阈值降噪法可有效去除混在超声回波信号中的各种噪声,大大提高回波信号信噪比。

核电主管道锻件心部裂纹缺陷性质分析

核电主管道锻造毛坯在中心棒套料加工过程中发现中心棒的一段出现裂纹,并伴有大量碎块。对中心棒及碎块金属进行化学成分分析、低倍、高倍检验和能谱分析,并采用Jmatpro对316LN钢平衡析出相进行了计算。结果表明,裂纹区域存在的大量条状和粒状α-Cr析出相导致局部塑性降低,变形不协调,在锻造过程中形成了裂纹。

无缝钢管在线高速无损超声探伤仪的研究与开发

无缝钢管在线高速无损超声探伤系统是当前冶金自动化设备研发的热点。本文对国内外超声检测技术的发展现状和趋势进行综合分析的基础上,进行了总体设计并将之付之实现,同时详细说明了系统设计的原理和一些关键技术。

探伤工作者的知音

探伤工作人员在现场工作时最大的苦恼,莫过于一边操探头工作、一边用计算器计算缺陷定位。最近,劳动部所属中国华龙公司、北京万通公司、借鉴国外先进资料、设计研制出了"焊缝超声检测缺陷定位尺",能为探伤工作者解除这种苦恼。在现场实际操做中,这种缺陷定位尺,以其直观、精确的定位、巧妙的构思,受到了专业工作者的好评,认为这种缺陷定位尺所具有的直接测量缺陷尺寸,直观定位的功能,避免了探伤工作中繁琐的计算,能大大提高超声检测工作效率。

Laser ultrasonic technique for surface defects detection of 6061 aluminum alloy

In order to estimate and detect the surface defect depth of metals, the transmission method of laser ultrasonic surface waves is used in this work. The laser ultrasonic detection platform taking use of thermoelastic mechanism as acoustic signal excitation method and interference receiver as acoustic signal receiver method was built, by which B-scan images of detected specimens with surface defects were collected to establish the relationship between the transmission coefficient and depth of the surface defect. Experimental results show that the amplitude of transmitted acoustic signal is related to the depth of surface defect. At last, a fitted curve of transmission coefficient using measured experimental data is obtained to estimate depth of surface defect on the 6061 aluminum alloy. Furthermore, a surface defect depth of 0.3 mm is estimated by the fitting curve with an estimated error of 16%. Therefore, a experimental method using the transmission method by laser ultrasonic is presented in this paper.

A New Method for Detecting Internal Defects in Composite Materials Based on Time of Flight

Carbon-fiber reinforced polymer composites have been widely used to achieve the light-weighted design and high performance due to superior performance. Internal defects in the composite materials are the main factors that determine their performance,which makes reliable and effective detection methods of internal defects essential. Nondestructive testing(NDT)methods are the most widely-used way due to their tremendous advantages. Though the theoretical background is found,experimental results could be quite complicated and confusing,especially for composite materials with complex defects characteristics. In this paper,experimental study on internal defects in composite materials based on the time of flight(ToF)are investigated. The Gaussian echo model and the parameter estimation methods are established to build a theoretical model for measurements. Then,the distance amplitude correction(DAC)method is proposed to effectively improve the signal-to-noise ratio(SNR)and to reduce distortion of the signal during measurements. Finally,the ToF is adopted to determine depth of internal defects. Experiment study is conducted to investigate the porosity defects and the anti-impact performance of composite materials,as well as defects in objects with various thicknesses. Experimental results show that the proposed method is quite helpful for obtaining the intuition and deep understanding of internal defects,thus contributing to the determination of product performance and its improvement.

Defects detection in typical positions of bend pipes using low-frequency ultrasonic guided wave

In order to analyze the possibility of detecting defects in bend pipe using low-frequency ultrasonic guided wave, the propagation of T(0,1) mode and L(0,2) mode through straight-curved-straight pipe sections was studied. FE(finite element) models of bend pipe without defects and those with defects were introduced to analyze energy distribution, mode transition and defect detection of ultrasonic guided wave. FE simulation results were validated by experiments of four different bend pipes with circumferential defects in different positions. It is shown that most energy of T(0,1) mode or L(0,2) mode focuses on extrados of bend but little passes through intrados of bend, and T(0,1) mode or L(0,2) mode is converted to other possible non-axisymmetric modes when propagating through the bend and the defect after bend respectively. Furthermore, L(0,2) mode is more sensitive to circumferential notch than T(0,1) mode. The results of this work are beneficial for practical testing of pipes.

探伤在网壳施工中的应用

阐述了超声波无损检验技术在网壳球管焊缝检测中的技术优势,分析了焊缝中最常见的危险性缺陷及焊接施工的技术措施。