scholarly journals Detection of Fatigue Cracks at Weld Toes by Crack Detection Paint and Surface SH Wave

2007 ◽  
Vol 48 (6) ◽  
pp. 1190-1195
Author(s):  
Ichihiko Takahashi ◽  
Michio Ushijima
Keyword(s):  
Crack Detection ◽  
Fatigue Cracks ◽  
Weld Toes ◽  
Sh Wave

Fatigue crack detection method using analysis of vibration signal

2017 ◽  
Vol 1 (20) ◽  
pp. 63-74 ◽  
Author(s):  
Arkadiusz Rychlik ◽  
Krzysztof Ligier
Keyword(s):  
Crack Detection ◽  
Fatigue Cracks ◽  
Fatigue Cracking ◽  
Vibration Signal ◽  
Technical Condition ◽  
Visual Methods ◽  
Signal Characteristics ◽  
Fatigue Crack Detection ◽  
Sample Structure ◽  
Change Identification

This paper discusses the method used to identify the process involving fatigue cracking of samples on the basis of selected vibration signal characteristics. Acceleration of vibrations has been chosen as a diagnostic signal in the analysis of sample cross section. Signal characteristics in form of change in vibration amplitudes and corresponding changes in FFT spectrum have been indicated for the acceleration. The tests were performed on a designed setup, where destruction process was caused by the force of inertia of the sample. Based on the conducted tests, it was found that the demonstrated sample structure change identification method may be applied to identify the technical condition of the structure in the aspect of loss of its continuity and its properties (e.g.: mechanical and fatigue cracks). The vibration analysis results have been verified by penetration and visual methods, using a scanning electron microscope.

Numerical study towards the use of a SH wave ultrasonic-based strategy for crack detection in concrete structures

2013 ◽  
Vol 49 ◽  
pp. 782-791 ◽  
Author(s):  
L. Godinho ◽  
D. Dias-da-Costa ◽  
P. Areias ◽  
E. Júlio ◽  
D. Soares
Keyword(s):  
Crack Detection ◽  
Numerical Study ◽  
Concrete Structures ◽  
Sh Wave

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.

Monitoring Fatigue Cracks and Stress Intensity Factors Based on the Distributed Dislocation Technique

2012 ◽  
Vol 525-526 ◽  
pp. 189-192
Author(s):  
Ramdane Boukellif ◽  
Andreas Ricoeur
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Crack Detection ◽  
Dimensional Space ◽  
Fatigue Cracks ◽  
Particle Swarm Algorithm ◽  
Problem Solution ◽  
Intensity Factors ◽  
Unknown Parameters ◽  
Factor Measurement

We present a method for crack detection and stress intensity factor measurement in plate structures by using strain gauges and applying the dislocation method. The presented approach is based on the strain measured at different locations on the surface of the structure. This allows both the identification of crack position parameters, such as length, location and angles with respect to a reference coordinate system and the calculation of stress intensity factors (SIF). The method solving the direct problem is based on the idea of representing the crack by a line of point dislocations. The latter are formed by applying a constant displacement between adjacent points located at either side of the crack. Thus, the approach is based on the weighted superposition of elastic Greens functions representing the strain field due to the presence of a crack, where the weights are being identified by inverse problem solution. Since the strain fields are controlled by both external loads and the crack growth the unknown parameters are crack length, position and inclination as well as loading quantities. The particle swarm algorithm (PSO) came out to be most suitable for parameter identification in a high dimensional space.

NDE Performance (POD) Curves for Fatigue Cracks in Piping Based on Industry Performance Demonstration Data

2002 ◽  
Author(s):  
S. R. Gosselin ◽  
F. A. Simonen ◽  
P. G. Heasler ◽  
S. R. Doctor ◽  
F. L. Becker
Keyword(s):  
Stainless Steel ◽  
Carbon Steel ◽  
Nuclear Energy ◽  
Crack Detection ◽  
Fatigue Cracks ◽  
Probability Of Detection ◽  
Performance Factors ◽  
Best Estimate ◽  
Industry Performance ◽  
Performance Demonstration

This paper evaluates non-destructive examination (NDE) detection capabilities of fatigue cracks in piping. Industry performance demonstration initiative (PDI) data for fatigue crack detection were used to develop a matrix of statistically based probability of detection (POD) curves that consider various NDE performance factors. Seven primary performance factors were identified — Material, Crack Geometry/Type, NDE Examination Access, NDE Procedure, Examiner Qualification, Pipe Diameter, and Pipe Wall Thickness. A database of 16,181 NDE performance observations, with 18 fields associated with each observation, was created and used to develop statistically based POD curves for 42 stainless steel and 14 carbon steel performance cases. Subsequent comparisons of the POD fits for each of the cases showed that excellent NDE performance for fatigue cracks can be expected for ferritic materials. Very little difference was observed between the POD curves for the 14 carbon steel performance cases considered in this study and NDE performance could therefore be represented by a single POD curve. For stainless steel, very good performance can also be expected for circumferential cracks located on the same side of the weld from which the NDE examination is made. POD depended primarily on component thickness. Three POD curves for stainless steel were prepared. Best estimate and the associated 95% confidence bounds POD verses through-wall depth logistic regression digital data are provided. Probabilistic fracture mechanics (PFM) calculations were performed to compare best estimate leak probabilities obtained from both the new performance-based POD curves and previous PFM models. This work was performed under joint funding by EPRI and the U.S. Department of Energy (DOE), Office of Nuclear Energy Science and Technology’s Nuclear Energy Plant Optimization (NEPO) program.

Condition Monitoring of Fatigue Cracks in Machinery Blades

2005 ◽  
Vol 36 (11) ◽  
pp. 18-23
Author(s):  
L. Gelman
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Crack Detection ◽  
Traditional Approach ◽  
Fatigue Cracks ◽  
Diagnostic Features ◽  
New Approach ◽  
Numerical Examples ◽  
Power Spectral ◽  
The Fourier Transform

A novel generic approach to fatigue crack diagnostics in machinery blades is proposed and employed. The approach consists of simultaneously using two new diagnostic features: the real and imaginary parts of the Fourier transform of vibroacoustical signal generated from a blade. This approach is more generic than traditional approach based on the power spectral density; the power spectral density is a particular case of the proposed approach. Numerical examples are given based on the processing of signals generated using a nonlinear model of a blade. The signals generated are the resonant vibroacoustical oscillations of cracked and uncracked blades under narrowband vibration excitation. The numerical examples show that the crack detection is more effective when using the new approach than when using the power spectral density approach. The presented experimental results are matched with the numerical results. The proposed approach offers an effectiveness improvement over the traditional approach based on power spectral density.

Diagnostics of Fatigue Crack in the Shaft Using Spectral Kurtosis

2019 ◽  
Author(s):  
Sagi Rathna Prasad ◽  
A. S. Sekhar
Keyword(s):  
Fatigue Crack ◽  
Crack Detection ◽  
Fatigue Cracks ◽  
Processing Technique ◽  
Rotating Machinery ◽  
Operating Conditions ◽  
Laser Vibrometer ◽  
Signal Processing Technique ◽  
Spectral Kurtosis ◽  
Vibration Data

Abstract Rotating machinery components like shafts subjected to continuous fluctuating loads are prone to fatigue cracks. Fatigue cracks are severe threat to the integrity of rotating machinery. Therefore it is indispensable for early diagnostics of fatigue cracks in shaft to avoid catastrophic failures. From the literature, it is evident that the spectral kurtosis (SK) and fast kurtogram were used to detect the faults in bearings and gears. The present study illustrates the use of SK and fast kurtogram for early fatigue crack detection in the shaft using vibration data. To perform this study, experiments are conducted on a rotor test rig which is designed and developed according to the function specification proposed by ASTM E468-11 standard. Fatigue crack is developed, on three shaft specimens, each seeded with the same circumferential V-Notch configuration, by continuous application of stochastic loads on the shaft using electrodynamic shaker in addition to the unbalance forces that arise in normal operating conditions. Vibration data is acquired from various locations of the rotor, using different sensors like miniature accelerometers, laser vibrometer and wireless telemetry strain gauge, till the shaft specimen develops fatigue crack. The analysis results show that the combination of SK and fast kurtogram is an effective signal processing technique for detecting the fatigue crack in the shaft.

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