Localization of Fatigue Cracks Using Low-Frequency Nonlinear Lamb Waves in Numerical Perspective

2018 ◽  
Author(s):  
Jichao Xu ◽  
Nuoke Wei ◽  
Wujun Zhu ◽  
Yanxun Xiang ◽  
Fuzhen Xuan ◽  
...  
Keyword(s):  
Lamb Waves ◽  
Fatigue Cracks ◽  
Low Frequency

scholarly journals Detection of Micro-Cracks in Metals Using Modulation of PZT-Induced Lamb Waves

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3823
Author(s):  
Sang Eon Lee ◽  
Jung-Wuk Hong
Keyword(s):  
Quantitative Analysis ◽  
Crack Length ◽  
Crack Detection ◽  
Lamb Waves ◽  
Early Stage ◽  
Fatigue Cracks ◽  
Excitation Frequency ◽  
High Sensitivity ◽  
Detection Algorithm ◽  
Modulated Waves

The ultrasonic modulation technique, developed by inspecting the nonlinearity from the interactions of crack surfaces, has been considered very effective in detecting fatigue cracks in the early stage of the crack development due to its high sensitivity. The wave modulation is the frequency shift of a wave passing through a crack and does not occur in intact specimens. Various parameters affect the modulation of the wave, but quantitative analysis for each variable has not been comprehensively conducted due to the complicated interaction of irregular crack surfaces. In this study, specimens with a constant crack width are manufactured, and the effects of various excitation parameters on modulated wave generation are analyzed. Based on the analysis, an effective crack detection algorithm is proposed and verified by applying the algorithm to fatigue cracks. For the quantitative analysis, tests are repeatedly conducted by varying parameters. As a result, the excitation intensity shows a strong linear relationship with the amount of modulated waves, and the increase of modulated wave is expected as crack length increases. However, the change in the dynamic characteristics of the specimen with the crack length is more dominant in the results. The excitation frequency is the most dominant variable to generate the modulated waves, but a direct correlation is not observed as it is difficult to measure the interaction of crack surfaces. A numerical analysis technique is developed to accurately simulate the movement and interaction of the crack surface. The crack detection algorithm, improved by using the observations from the quantitative analyses, can distinguish the occurrence of modulated waves from the ambient noises, and the state of the specimens is determined by using two nonlinear indexes.

Buried Crack Detection in Aircraft Multi-Layer Structure Based on Pulsed Eddy Current

2013 ◽  
Vol 330 ◽  
pp. 536-541
Author(s):  
Sheng Lai ◽  
Hu Chen ◽  
Yue Wen Fu
Keyword(s):  
Crack Detection ◽  
Layer Structure ◽  
Fatigue Cracks ◽  
Low Frequency ◽  
Time Domain Analysis ◽  
Dynamic Imaging ◽  
Pulsed Eddy Current ◽  
Electromagnetic Detection ◽  
Electromagnetic Testing ◽  
Dual Polarity

The fatigue cracks of key parts, as one of the main damages of multilayer structure in aircraft, are important objects for aircraft structural health monitoring. Conventional electromagnetic testing which uses sinusoidal signal is high sensitive to surface cracks, but it is typically difficult to measure or predict embedding cracks. A novel electromagnetic detection technique is proposed in this paper, and dual polarity low-frequency pulse is used to excite the coil. A time-domain analysis method called time-slice is utilized to obtain the transient amplitude matrix from array signal. Good results have been presented by such dynamic imaging of simulating buried cracks in multi-layer riveted structure. Experimental results show that the new electromagnetic testing has the advantages of hidden defects detection and rapid detection, and it can effectively detect buried defects in multilayer structures of aircraft, and determine damage position.

Non-Destructive Evaluation of a Delamination in Laminates by Lamb Wave Propagation

2007 ◽  
Vol 353-358 ◽  
pp. 2345-2348
Author(s):  
Zheng Hua Qian ◽  
Feng Jin ◽  
Zi Kun Wang ◽  
Kikuo Kishimoto
Keyword(s):  
Lamb Waves ◽  
Low Frequency ◽  
Relative Location ◽  
Laminated Plate ◽  
Non Destructive Evaluation ◽  
Symmetric Plane ◽  
Expansion Coefficients ◽  
Relative Errors ◽  
Lamb Wave Propagation ◽  
Non Destructive

The diffraction of Lamb waves by a finite delamination situated on a random plane parallel to the symmetric plane of a laminated plate is taken into account. Two imaginary planes are introduced to solve the problem by adopting the method of mode matching. By taking an appropriate finite number of terms of the infinite expansion series and some selected points on the two imaginary planes through convergence and precision tests, a matrix equation is obtained to evaluate the expansion coefficients numerically. Reflection coefficients versus the normalized length a/h and the relative location h1/h of the delamination are calculated in the low-frequency domain, the relative errors are found to be less than 1%. Results obtained indicate that the theory developed in this paper is meaningful for the detection of both the size and the location of a delamination in a laminated plate by cooperating with experimental techniques for the non-destructive evaluation (NDE) technology.

Low Frequency Phased Array Application for Crack Detection in Cast Austenitic Piping

2006 ◽  
Author(s):  
Michael T. Anderson ◽  
Stephen E. Cumblidge ◽  
Steven R. Doctor
Keyword(s):  
Stainless Steel ◽  
Crack Detection ◽  
Phased Array ◽  
Fatigue Cracks ◽  
Low Frequency ◽  
Pacific Northwest National Laboratory ◽  
The United States ◽  
Coarse Grained ◽  
Inspection Method ◽  
Centrifugally Cast

As part of a multi-year program funded by the United States Nuclear Regulatory Commission (US NRC) to address nondestructive examination (NDE) reliability of inservice inspection (ISI) programs, studies conducted at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington, have focused on assessing novel NDE approaches for the inspection of coarse-grained, cast austenitic stainless steel reactor components. The primary objective of this work is to provide information to the US NRC on the utility, effectiveness and reliability of ultrasonic testing (UT) as related to the ISI of primary piping components in US commercial nuclear power plants. This paper describes progress, recent developments and results from an assessment of a portion of the work relating to the ultrasonic low frequency phased array inspection technique. Westinghouse Owner’s Group (WOG) cast stainless steel pipe segments with thermal and mechanical fatigue cracks, PNNL samples containing thermal fatigue cracks and several blank vintage specimens having very coarse grains that are representative of early centrifugally cast piping installed in PWRs, were used for assessing the inspection method. The phased array approach was implemented using an R/D Tech Tomoscan III system operating at 1.0 MHz and 500 kHz, providing composite volumetric images of the samples. Several dual, transmit-receive, custom designed low-frequency arrays were employed in laboratory trials. Results from laboratory studies for assessing detection and localization are discussed.

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