On Wavelets-Based Holder Exponents for Clamped-Clamped Beams Crack Identification

2011 ◽  
Vol 94-96 ◽  
pp. 381-387 ◽  
Author(s):  
Run Bo Bai ◽  
Hai Hong Xu ◽  
Xin Xin Zhang
Keyword(s):  
Structural Damage ◽  
Comprehensive Analysis ◽  
Mode Shapes ◽  
Crack Identification ◽  
Structural Damage Detection ◽  
Hölder Exponent ◽  
Beam Type ◽  
Clamped Beams ◽  
Hölder Exponents ◽  
Different Order

Structural damage detection by the Holder exponent receives much attention recently. Many investigations have been successfully applied to the crack identification, especially for the beam-type structures. However, a comprehensive analysis of the Holder exponent has been absent. Result in some conclusions had been drawn are unilateral. In this paper, the mode shapes of the clamped-clamped beams are analytical studied and a program calculating the Holder exponents of the mode shape signals with different damages is compiled with MATLAB. By comprehensively studying the Holder exponents of the clamped-clamped beams with cracks of different sizes, locations, and different order modes, a new phenomenon that the values of the Holder exponent vary with different locations of the crack is detected. The results also show that the Holder exponent decreases with the increase of the mode number. However, there are not obvious relations between the Holder exponent and the order of the mode for the whole beam locations.

scholarly journals Crack Identification and Localization In Structural Beams Using Numerical and Experimental Modal Analysis- A Review

2020 ◽  
pp. 62-68
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Structural Damage ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Crack Identification ◽  
Engineering Structures ◽  
Aircraft Wings ◽  
Crack Location ◽  
Damaged Beams

This article presents a critical review of recent research done on crack identification and localization in structural beams using numerical and experimental modal analysis. Crack identification and localization in beams are very crucial in various engineering applications such as ship propeller shafts, aircraft wings, gantry cranes, and Turbo machinery blades. It is necessary to identify the damage in time; otherwise, there may be serious consequences like a catastrophic failure of the engineering structures. Experimental modal analysis is used to study the vibration characteristics of structures like natural frequency, damping and mode shapes. The modal parameters like natural frequency and mode shapes of undamaged and damaged beams are different. Based on this reason, structural damage can be detected, especially in beams. From the review of various research papers, it is identified that a lot of the research done on beams with open transverse crack. Crack location is identified by tracking variation in natural frequencies of a healthy and cracked beam

Effects of Noise on Measured Ritz Vectors

1997 ◽  
Author(s):  
David C. Zimmerman ◽  
Timothy T. Cao
Keyword(s):  
Structural Damage ◽  
Element Model ◽  
Mode Shapes ◽  
Structural Damage Detection ◽  
Structural Dynamic ◽  
Response Data ◽  
Statistical Variation ◽  
Ritz Vectors ◽  
Traditional Mode ◽  
Model Correlation

Abstract Ritz vectors offer many advantages over the traditional mode shapes in the areas of model reduction and structural dynamic simulation. Building upon the recent development of an experimental method to extract Ritz vectors from measured dynamic response data, these vectors were also demonstrated to offer great potential in the areas of finite element model correlation and structural damage detection. In this paper, a Monte Carlo simulation is performed to study the accuracy and stability of Ritz vectors extracted from this new procedure using noise corrupted response data. The statistical variation of Ritz parameters and modal parameters extracted from the same data is made to assess the sensitivity of Ritz vector extraction to measured noise.

scholarly journals Structural Damage Detection Using Slopes of Longitudinal Vibration Shapes

2015 ◽  
Author(s):  
W. Xu ◽  
W. D. Zhu ◽  
S. A. Smith
Keyword(s):  
Steady State ◽  
Damage Detection ◽  
Structural Damage ◽  
Longitudinal Vibration ◽  
Harmonic Excitation ◽  
Mode Shapes ◽  
Noise Robustness ◽  
Steady State Response ◽  
Structural Damage Detection ◽  
State Response

While structural damage detection based on flexural vibration shapes, such as mode shapes and steady-state response shapes under harmonic excitation, has been well developed, little attention is paid to that based on longitudinal vibration shapes that also contain damage information. This study originally formulates a slope vibration shape for damage detection in bars using longitudinal vibration shapes. To enhance noise robustness of the method, a slope vibration shape is transformed to a multiscale slope vibration shape in a multiscale domain using wavelet transform, which has explicit physical implication, high damage sensitivity, and noise robustness. These advantages are demonstrated in numerical cases of damaged bars, and results show that multiscale slope vibration shapes can be used for identifying and locating damage in a noisy environment. A three-dimensional (3D) scanning laser vibrometer is used to measure the longitudinal steady-state response shape of an aluminum bar with damage due to reduced cross-sectional dimensions under harmonic excitation, and results show that the method can successfully identify and locate the damage. Slopes of longitudinal vibration shapes are shown to be suitable for damage detection in bars and have potential for applications in noisy environments.

scholarly journals Structural damage detection based on improved frequency change ratio

2019 ◽  
Vol 272 ◽  
pp. 01010
Author(s):  
Jian WANG ◽  
Huan JIN ◽  
Xiao MA ◽  
Bin ZHAO ◽  
Zhi YANG ◽  
...  
Keyword(s):  
Damage Detection ◽  
Health Monitoring ◽  
Structural Damage ◽  
Detection Method ◽  
Mode Shapes ◽  
Frequency Change ◽  
Damage Localization ◽  
Structural Damage Detection ◽  
Practical Application ◽  
Slight Damage

Frequency Change Ratio (FCR) based damage detection methodology for structural health monitoring (SHM) is analyzed in detail. The effectiveness of damage localization using FCR for some slight damage cases and worse ones are studied on an asymmetric planar truss numerically. Disadvantages of damage detection using FCR in practical application are found and the reasons for the cases are discussed. To conquer the disadvantages of FCR, an Improved Frequency Change Ratio (IFCR) based damage detection method which takes the changes of mode shapes into account is proposed. Verification is done in some damage cases and the results reveal that IFCR can identify the damage more efficiently. Noisy cases are considered to assess the robustness of IFCR and results indicate that the proposed method can work well when the noise is not severe.

scholarly journals Frequency Contour-Strip Method for Characterization of Damage in Structures under Noisy Conditions

2021 ◽  
Vol 11 (23) ◽  
pp. 11479
Author(s):  
Jiayi Peng ◽  
Hao Xu ◽  
Hailei Jia ◽  
Dragoslav Sumarac ◽  
Tongfa Deng ◽  
...  
Keyword(s):  
Structural Damage ◽  
Damage Identification ◽  
Contour Line ◽  
Crack Identification ◽  
Dynamic Feature ◽  
Strip Method ◽  
Line Method ◽  
Beam Type ◽  
Noisy Conditions ◽  
Eigen Frequency

Eigen-frequency, compared with mode shape and damping, is a more practical and reliable dynamic feature to portray structural damage. The frequency contour-line method relying on this feature is a representative method to identify damage in beam-type structures. Although this method has been increasingly applied in the area of damage identification, it has two significant deficiencies: inefficiency in establishing the eigen-frequency panorama; and incompetence to identify cracks in noisy conditions, considerably impairing the effectiveness in identifying structural damage. To overcome these deficiencies, a novel method, termed the frequency contour-strip method, is developed for the first time. This method is derived by extending the frequency contour line of 1D to frequency contour strip of 2D. The advantages of the frequency contour-strip method are twofold: (i) it uses the isosurface function to instantly produce the eigen-frequency panorama with a computational efficiency several orders of magnitude higher than that of the frequency contour-line method; and (ii) it can accommodate the effect of random noise on damage identification, thereby thoroughly overcoming the deficiencies of the frequency contour-line method. With these merits, the frequency contour-strip method can characterize damage in beam-type structures with more efficiency, greater accuracy, and stronger robustness against noise. The proof of concept of the proposed method is performed on an analytical model of a Timoshenko beam bearing a crack and the effectiveness of the method is experimentally validated via crack identification in a steel beam.

scholarly journals Structural Damage Detection Using Slopes of Longitudinal Vibration Shapes

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
W. Xu ◽  
W. D. Zhu ◽  
S. A. Smith ◽  
M. S. Cao
Keyword(s):  
Steady State ◽  
Damage Detection ◽  
Structural Damage ◽  
Longitudinal Vibration ◽  
Harmonic Excitation ◽  
Mode Shapes ◽  
Noise Robustness ◽  
Steady State Response ◽  
Structural Damage Detection ◽  
State Response

While structural damage detection based on flexural vibration shapes, such as mode shapes and steady-state response shapes under harmonic excitation, has been well developed, little attention is paid to that based on longitudinal vibration shapes that also contain damage information. This study originally formulates a slope vibration shape (SVS) for damage detection in bars using longitudinal vibration shapes. To enhance noise robustness of the method, an SVS is transformed to a multiscale slope vibration shape (MSVS) in a multiscale domain using wavelet transform, which has explicit physical implication, high damage sensitivity, and noise robustness. These advantages are demonstrated in numerical cases of damaged bars, and results show that MSVSs can be used for identifying and locating damage in a noisy environment. A three-dimensional (3D) scanning laser vibrometer (SLV) is used to measure the longitudinal steady-state response shape of an aluminum bar with damage due to reduced cross-sectional dimensions under harmonic excitation, and results show that the method can successfully identify and locate the damage. Slopes of longitudinal vibration shapes are shown to be suitable for damage detection in bars and have potential for applications in noisy environments.

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