Reference-Free Breathing Crack Identification of Beam-Like Structures Using an Enhanced Spatial Fourier Power Spectrum with Exponential Weighting Functions

2019 ◽  
Vol 19 (02) ◽  
pp. 1950017 ◽  
Author(s):  
J. Prawin ◽  
A. Rama Mohan Rao
Keyword(s):  
Fatigue Crack ◽  
Power Spectrum ◽  
Crack Detection ◽  
Crack Problem ◽  
Experimental Studies ◽  
Crack Identification ◽  
Successful Implementation ◽  
Breathing Crack ◽  
Fourier Power Spectrum ◽  
Exponential Weighting

Detection of incipient damage of structures at the earliest possible stage is desirable for successful implementation of any health monitoring system. In this paper, we focus on breathing crack problem and present a new reference-free algorithm for fatigue crack detection, localization, and characterization for beam-like structures. We use the spatial curvature of the Fourier power spectrum as a damage sensitive feature for fatigue crack identification. An exponential weighting function that takes into account nonlinear dynamic signatures, such as sub- and superharmonics, is proposed in the Fourier power spectrum in order to enrich the damage-sensitive features of the structure. Both numerical and experimental studies have been carried out to test and verify the proposed algorithm.

Frequency Comparison Function Method for Real-Time Identification of Breathing Crack at Welding Joint

2020 ◽  
Vol 20 (13) ◽  
pp. 2041001
Author(s):  
Xin Wang ◽  
Nan Wu ◽  
Quan Wang
Keyword(s):  
Real Time ◽  
Crack Detection ◽  
Experimental Studies ◽  
High Sensitivity ◽  
Crack Identification ◽  
Comparison Function ◽  
Amplitude Curve ◽  
Breathing Crack ◽  
Welding Joint ◽  
Frequency Comparison

In this research, the frequency comparison function (FCF) method is proposed and studied to realize high-sensitive real-time crack identification at the welding joint area for a beam-type structure. This method is derived from the frequency response function (FRF). During FCF, we use the response signal collected from the designated point of the structure instead of the excitation. The standard deviation of the FCF amplitude curve is calculated to detect and evaluate the possible crack and its induced vibration perturbations afterward. Vibration responses are simulated in ANSYS by the use of the finite element analysis of a welded beam structure, and these signals are then analyzed with the FCF algorithm. It is concluded that FCF is an efficient method for breathing crack identification and can be easily applied under different excitation conditions, including harmonic and random ones. Meanwhile, FCF can be applied without any pre-processing algorithms such as filtering and smoothing. So, it can be used for real-time crack identification. By combining the FCF with the smart coating sensor composed of piezoelectric layers, the crack identification with high sensitivity is realized. The crack is detectable at its very early stage (starting from 3% of the beam thickness). Experimental studies under harmonic and random excitations are processed, and the results prove high sensitivity and feasibility of the proposed crack detection method.

A novel singular spectrum analysis–based baseline-free approach for fatigue-breathing crack identification

2018 ◽  
Vol 29 (10) ◽  
pp. 2249-2266 ◽  
Author(s):  
J Prawin ◽  
K Lakshmi ◽  
A Rama Mohan Rao
Keyword(s):  
Spectrum Analysis ◽  
Crack Detection ◽  
Singular Spectrum Analysis ◽  
Experimental Studies ◽  
Damage Index ◽  
Fatigue Loading ◽  
Crack Identification ◽  
Breathing Crack ◽  
Singular Spectrum ◽  
Nonlinear Harmonics

Breathing cracks are the most common type of damages that occur in structures subjected to fatigue loading. These breathing cracks induce nonlinearity in the dynamic signatures of the cracked structure which carry useful information about the damage. In this article, we present a new baseline-free algorithm using singular spectrum analysis for breathing crack detection, localization, and characterization. The major advantage of using singular spectrum analysis is that it has the ability to reliably extract the nonlinear harmonics and intermodulation components buried in the noisy components of the response of the structure with breathing crack. A new damage index based on singular spectrum analysis exploiting the nonlinear harmonics and intermodulations in the response is proposed. Numerical simulation studies are carried out to evaluate the proposed damage diagnostic algorithm and later complemented with experimental studies to demonstrate its practical application.

Crack Identification on a Cross-Stiffened Plate Panel

2004 ◽  
Author(s):  
Agung Budipriyanto ◽  
A. S. J. Swamidas ◽  
M. R. Haddara
Keyword(s):  
Crack Detection ◽  
Experimental Studies ◽  
Vibration Response ◽  
Mode Shapes ◽  
Crack Identification ◽  
Manual Inspection ◽  
Structure Monitoring ◽  
Prototype Structure ◽  
On Line ◽  
Shell Panel

Early identification of cracks in complex structures is desirable for the safety of operation and economy of maintenance of the structure. Monitoring of the vibration response of structures is a well-known technique for crack identification. As the complexity of the structure increases manual inspection becomes difficult and the use of on-line monitoring techniques for crack detection becomes more desirable. This paper discusses the use of a structure’s vibration response in the early detection of cracks. Analytical and experimental studies of the effect of cracks on the vibration response of an 1/20 scale aluminum model of the stiffened side shell panel of a tanker were carried out. The model was carefully designed to obtain natural frequencies and mode shapes similar to those of the prototype structure. The results of the analytical study were used to determine the best locations to place the sensors on the experimental model. Results of the experimental and analytical studies are reported.

Vibration-based breathing crack identification using non-linear intermodulation components under noisy environment

2019 ◽  
Vol 19 (1) ◽  
pp. 86-104 ◽  
Author(s):  
J Prawin ◽  
A Rama Mohan Rao
Keyword(s):  
Spectral Analysis ◽  
Crack Detection ◽  
Damage Index ◽  
Measurement Noise ◽  
Experimental Simulation ◽  
Crack Identification ◽  
Diagnostic Process ◽  
Breathing Crack ◽  
Spectral Correlation ◽  
Non Linear

Structural damages can result in non-linear dynamical signatures such as lower and higher order harmonics and signal modulation that can significantly enhance their detection. The conventional spectral analysis is used in most existing vibration-based damage diagnostic techniques to extract these damage-sensitive non-linear features. However, the major limitation of using spectral analysis is that the amplitudes of non-linear harmonics are highly sensitive to measurement noise and may mislead the damage diagnostic process. Keeping this in view, we present a new reference-free damage diagnostic technique for fatigue-breathing crack detection, localization and characterization using the cyclic spectral analysis-based technique. A new damage index based on spectral correlation exploiting the non-linear intermodulation in the response is proposed. The proposed cyclic spectral analysis-based diagnostics are highly immune to the measurement noise. Numerical and experimental simulation studies have been carried out by considering a beam with single and multiple breathing cracks, to test and verify the robustness and effectiveness of the proposed technique.

Breathing Crack Localization in Structures Based on Principal Component Analysis of Forced Vibration Responses

2020 ◽  
pp. 2150041
Author(s):  
J. Prawin
Keyword(s):  
Principal Component Analysis ◽  
Experimental Studies ◽  
Time History ◽  
Diagnostic Technique ◽  
Principal Component ◽  
Component Analysis ◽  
Harmonic Excitation ◽  
Crack Identification ◽  
Breathing Crack ◽  
Output Only

The identification of a breathing crack is a highly challenging inverse problem in structural health monitoring. A novel output-only damage diagnostic technique based on Principal Component Analysis (PCA) is proposed for breathing crack identification in structures excited by harmonic excitation. The proposed approach basically utilizes the residues obtained from PCA of the forced acceleration-time history responses of the structure for breathing crack identification. In this approach, the traditional single-tone, bitone and as well as multi-tone harmonic excitations are considered as input to the structure while exploring the residues of the responses for breathing crack identification. A new Damage Localization Index (DLI) based on the Fourier spectrum amplitudes of the nonlinear sensitive features (i.e. buried in residues), measured at varied locations spatially across the structure is proposed for breathing crack localization. The robustness and effectiveness of the proposed PCA-based breathing crack localization approach is verified through both numerical and experimental studies.

Breathing crack damage diagnostic strategy using improved MFCC features

2021 ◽  
pp. 1045389X2110014
Author(s):  
J. Prawin
Keyword(s):  
Filter Bank ◽  
Frequency Conversion ◽  
Experimental Studies ◽  
Spatial Location ◽  
Crack Identification ◽  
Diagnostic Strategy ◽  
Breathing Crack ◽  
Mel Frequency Cepstral Coefficients ◽  
Cepstral Analysis ◽  
Cepstral Coefficients

In this paper, a new two-stage damage diagnostic technique for breathing crack identification in using improved Mel frequency Cepstral Analysis is proposed for engineering structures. The improvements such as the centre frequencies of Mel-filter bank around the resonant frequencies and the automatic selection of cut-off frequency for frequency conversion (i.e. from Mel-scale to frequency-scale) based on the energy of the response is employed in the present work to customise the estimation of Mel-frequency Cepstral Coefficients (popularly being used for speech signals) for structural vibration responses. In the first stage of the proposed improved Mel-frequency Cepstral Coefficients (MFCC) approach for breathing crack identification, the measured acceleration time history responses are converted into Mel-frequency Cepstral Coefficients using improved Mel frequency Cepstral Analysis. The Mahanabolis distance-based measure between the improved Mel-frequency Cepstral coefficients of the healthy structure and the structure with localized damage is used for confirming the presence of breathing crack using ambient vibration data during online monitoring. In the second stage, the spatial location of breathing crack is established through offline monitoring, by exciting the structure with bitone harmonic excitation. The improved Mel-filter bank energy measured spatially across the structure is used to identify the spatial location(s) of breathing crack. The effectiveness of the proposed approach is verified using the synthetic datasets of the benchmark simply supported beam with a breathing crack, provided by Helsinki Metropolia University of Applied Sciences and a numerically simulated cantilever beam with varied spatial locations and different depths of breathing crack. Finally, experimental investigations have been carried out to demonstrate the practical viability of the proposed MFCC approach. Numerical and experimental studies concluded that the proposed damage diagnostic approach is capable of detecting and localising multiple and also subtle cracks even under varying environmental conditions with noise-contaminated measurements.

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