纤维增强复合材料中缺陷的红外热波成像无损检测技术

介绍了红外热波成像技术在纤维增强复合材料缺陷检测方面的应用实例,并将红外热波成像技术与传统的无损检测技术进行了比较。结果表明,红外热波成像是一种能够快速、直观、有效、准确地检测出纤维增强复合材料中分层、脱粘、气孔等典型缺陷的无损检测技术。     

铝蒙皮蜂窝夹层结构的各种无损检测方法

介绍了脉冲红外热波成像检测方法、锁相调制红外热波成像检测方法、激光剪切散斑检测方法和超声C扫描检测方法针对铝蒙皮蜂窝夹层结构进行检测的过程及结果。通过对比,说明不同方法对其进行检测的适用范围和局限性。     

红外热波成像技术在复合材料无损检测中的应用

复合材料的缺陷检测至关重要,介绍了红外热波成像技术的原理特点,重点论述了脉冲红外热波成像技术和锁相红外热波成像技术,采用上述两种技术对多种复合材料进行了检测。试验结果表明:脉冲红外热波成像技术和锁相红外热波成像技术能对多种复合材料的缺陷进行检测。     

先进复合材料中的主要缺陷与无损检测技术评价

简要介绍了先进复合材料中的缺陷类型,分析了缺陷产生的原因以及对复合材料性能的影响,对目前国内外用于先进复合材料结构的各种无损检测技术进行了比较与评价,认为超声C扫描、有源红外热波成像以及射线实时成像检测是有效检测先进复合材料中常见缺陷的技术手段.     

红外热波序列图像的图像分割与三维显示

研究了针对红外热波序列图像的图像分割和三维显示方法。红外热波无损检测只能得到被测工件表面温度变化的时间序列图像,无法直观到检测缺陷,利用三维显示技术可以产生深度三维立体图,方便技术人员更直观、精确地进行无损检测。三维显示效果的好坏直接取决于图像分割的效果。为此提出了基于局部极小值的区域生长分割算法,成功地提取出红外热波图像中缺陷成分的目标图像,并进行了三维显示,取得了较好的效果。     

红外热成像无损检测在压力容器检验中的应用

介绍了红外热成像无损检测的理论基础、硬件与软件。综述了红外热成像无损检测在压力容器检验中的应用状况,包括压力容器用金属材料疲劳检测、实验室压力容器疲劳检测、在用压力容器现场检测。指出了红外热成像无损检测在压力容器检测中的发展方向。     

红外热成像无损检测在压力容器检测中的应用

介绍了红外热成像无损检测的理论基础、硬件与软件。综述了红外热成像无损检测在压力容器检验中的应用状况，包括压力容器用金属材料疲劳检测、实验室压力容器疲劳检测、在用压力容器现场检测。指出了红外热成像无损检测在压力容器检测中的发展方向。     

红外热成像技术在无损检测中的应用

本文介绍了红外热成像技术的工作原理、红外热像仪的构成以及红外热成像技术在无损检测中的应用，并给出了一个用红外热成像技术进行无损检测的例子。结果表明红外热成像技术可以有效地实现对设备的温度监测和分析，提供了一种很有发展前途的无损检测手段。     

超声红外热波技术的研究现状

超声红外热波技术是一种新型无损检测技术,对金属试件疲劳裂纹、复合材料冲击损伤等缺陷具有良好的检测效果。简述了超声红外热波检测技术的基本原理及特点,然后从试验研究、理论研究和缺陷识别等方面归纳了该技术的国内外研究现状,最后针对现有研究中存在的不足,指出了相应的对策与建议。     

空间用太阳电池胶接缺陷的无损检测

针对空间用太阳电池的胶接缺陷开展了无损检测方法的研究,分别采用红外热波检测和空气耦合超声检测的方法进行了试验,对检测结果进行了对比分析。结果表明,红外热波检测和空气耦合超声检测均能检测出空间用太阳电池胶接的主要缺陷,其中红外热波方法的检测结果不受背面基板结构的干扰,检测速度更快。     

碳纤维增强复合材料层间界面缺陷超声成像技术

针对复合材料层压结构层间界面缺陷的无损检测与评估,通过分析超声波在碳纤维增强树脂基复合材料中的传播规律,研究入射声波在复合材料中的反射特性,利用入射声波在复合材料层间界面产生的反射信息,通过超声（B,T）扫描成像方法揭示复合材料层间界面缺陷及其三维分布。试验结果表明,采用短波长脉冲超声成像检测技术,可以有效地再现碳纤维增强树脂基复合材料层压结构中层间界面缺陷三维分布特征以及层间界面、铺层方向、纤维束取向等信息,为复合材料提供了一种有效的层间界面结构表征和缺陷检测方法。     

超声红外热像技术中裂纹的识别和重构

超声红外热像技术结合了超声激励和红外热像两种手段来检测材料和结构中裂纹等缺陷,是一种新型的无损检测技术。在推导了超声激励下裂纹热量传导的一维简化模型的基础上,采用基于控制标记符的分水岭分割和骨架描述法实现了超声红外热像技术中裂纹信息的识别与重构,并采用Matlab开发了相应的算法软件。试验结果证明了方法的可行性和准确性。     

Experimental characterization of granite damage using nonlinear ultrasonic techniques

In this paper, a nondestructive evaluation (NDE) technique based on the nonlinear second harmonic wave theory is developed and used to characterize damage of granite samples subjected to compressive loadings. The nonlinear parameter defined in the new NDE technique is measured and compared with two traditional parameters including ultrasonic pulse velocity and dynamic modulus. The nonlinear parameter is found to be much more sensitive to the damage development in granites than traditional parameters. It is shown that the increase of nonlinear parameter is close to an exponential trend with respect to the increased loading level, which also indicates a faster increase rate of the nonlinear parameter corresponding to the internal damage of granite samples. A practical damage index is thus defined based on the exponential increasing trend of the nonlinear parameter. The new damage index based on nonlinear parameter is found to have a positive correlation with the loading level. This observation suggests that the new damage index may become a valuable indicator of loading level (or correspondingly material degradation) of granites in the in situ NDE tests.     

Thermographic NDE advisory and guidance system

Analytical expressions for the thermal contrasts of defects, of varying diameters, depths and openings imaged using the flash and long pulse excitation methods, are presented. Included are: in-plane delaminations; adhesion defects and wall thinning of a fluid filled pipe. The theoretical predictions are shown to be in good agreement with experimental measurements. The analytical expressions have been incorporated in expert system-like software to enable the rapid evaluation of thermographic NDE for a specified application. The system computes the thermal contrast of user defined defects, for both excitation methods, and compares results with typical IR camera performance to assess the suitability of thermographic NDE.     

Flaw impulse response estimation in ultrasonic non-destructive evaluation using bi-cepstra

Pulse-echo measurements in ultrasonic non-destructive evaluation (NDE) are masked by the characteristics of the measuring instruments, the propagation paths taken by the ultrasonic pulses, and are considered to be corrupted by additive noise. It is assumed that the measured pulse echo is obtained by linearly convolving the defect impulse response (IR) with the measurement system response. Deconvolution operation, therefore, seeks to undo the effect of this convolution and extract the IR which is essential for defect identification. Autocorrelation (or power spectrum) deconvolution techniques are limited to the identification of minimum-phase systems. In this work, we show that higher-order cepstra can be used to deconvolve the IR of the flaw from ultrasonic echo measurements (synthetic as well as real). We also demonstrate that a deconvolution based on the use of the bi-cepstrum gives lower identification error variance when compared with the results of Wiener filtering deconvolution, specially at low signal-to-noise ratios (SNR).     

Heating characterization of the thickness-through fatigue crack in metal plate using sonic IR imaging

In sonic IR imaging, a major problem is exploring the heating characteristics of crack vicinity to guide the optimization of the test conditions. In this paper, the crack's heating characteristics of the metallic plate with an artificial fatigue crack has been studied. Experimental results showed that the during ultrasonic excitation the temperature rise of crack vicinity at the plate's excitation side is higher than that at its opposite side, whereas the total heating efficiency of the crack face appears to be stable. Through the profile mapping of the crack face, the frictional heating is mainly concentrated near the excitation side. Based on this phenomenon, we built a mathematical heat transfer model to calculate the temperature distribution of the crack vicinity and investigated the heating features of crack faces. Additionally, the mathematical model gives a quantitative relation between the depth of the heat source and the ratio of the temperature distribution of the crack vicinity at opposite side to that at the front side. This study aims to provide a quantitative evaluation method for locating the frictional heating areas in sonic IR imaging.     

On the application of magneto-optic films in NDE

Some applications of magneto-optic (MO) films in the field of nondestructive evaluation (NDE) are presented. The method for imaging and measuring of magnetic fields on micrometer scale is based on the analysis of changes of the magnetic domain structure caused by the detected field. A process of MO film evaluation and calibration is described. The existence of the leakage field around a fatigue crack in nonmagnetic austenitic material is detected by a highly sensitive MO film. An experimentally determined distribution of the excitation field of an eddy current probe is compared with results obtained by the finite element method (FEM) numerical procedure.     

多频涡流裂纹重构方法及其在金属夹芯板焊部裂纹定量检测中的应用

金属栅格夹芯板是近年来出现的一种新型多功能材料,在航天航空、舰船和铁路运输等方面具有广阔应用前景。夹芯板焊接部位若出现裂纹损伤将会对材料的力学性能和结构的安全性产生极大影响。目前尚无完善的金属栅格夹芯板定量无损检测方法。利用涡流检测技术,对夹芯板焊接部位裂纹定量检测进行了理论和试验研究,提出了一种基于多频检测信号进行裂纹重构的反问题方法。通过对十字涡流检测探头所得焊部检测信号进行反演,证实了多频涡流检测裂纹重构方法对夹芯板焊部裂纹定量检测的有效性。     

Microwave NDT of cement-based materials using far-field reflection coefficients

Periodic assessment of ageing civil structures is important for structural integrity and public safety. Numerous destructive and non-destructive techniques employing different energy sources have been proposed for structural health monitoring. Amongst the non-destructive evaluation techniques proposed for monitoring material strength and contents of concrete structures, techniques employing microwaves offer distinct advantages in that they are non-radioactive and provide good penetration, excellent contrast between steel reinforcement bar and concrete, and insensitivity to ambient temperature. In this paper, the feasibility of a far-field microwave NDE technique for concrete imaging is investigated via numerical simulations and experiments on cement based samples using far-field microwave reflection coefficients.