A Study on the Crack Detection Using the Wavelet Transformation of Mode Shape for Hull Girder

2002 ◽  
Vol 39 (2) ◽  
pp. 19-27 ◽  
Author(s):  
Dae-Sung Lee ◽  
Dae-Seung Cho
Keyword(s):  
Mode Shape ◽  
Wavelet Transformation ◽  
Crack Detection ◽  
Hull Girder

scholarly journals Mode shape curvature of multiple cracked beam and its use for crack identification in beam-like structures

2020 ◽  
Author(s):  
Nguyen Tien Khiem
Keyword(s):  
Finite Difference ◽  
Mode Shape ◽  
Crack Detection ◽  
Exact Expression ◽  
Finite Difference Approximation ◽  
Theoretical Development ◽  
Difference Approximation ◽  
Crack Identification ◽  
Cracked Beam ◽  
Modal Curvature

The problem of using the modal curvature for crack detection is discussed in this paper based on an exact expression of mode shape and its curvature. Using the obtained herein exact expression for the mode shape and its curvature, it is demonstrated that the mode shape curvature is really more sensitive to crack than mode shape itself. Nevertheless, crack-induced change in the approximate curvature calculated from the exact mode shape by the central finite difference technique (Laplacian) is much greater in comparison with both the mode shape and curvature. It is produced by the fact, shown in this study, that miscalculation of the approximate curvature is straightforwardly dependent upon crack magnitude and resolution step of the finite difference approximation. Therefore, it can be confidently recommended to use the approximate curvature for multiple crack detection in beam by properly choosing the approximation mesh. The theoretical development has been illustrated by numerical results.

Damage Detection of Cantilever Beams Based on Derivatives of Mode Shapes

2014 ◽  
Vol 488-489 ◽  
pp. 817-820
Author(s):  
Jin Quan Guo ◽  
Fen Lan Ou ◽  
Jian Feng Zhong ◽  
Shun Cong Zhong ◽  
Xiao Xiang Yang ◽  
...  
Keyword(s):  
Mode Shape ◽  
Crack Detection ◽  
Shape Change ◽  
Approximation Error ◽  
Mode Shapes ◽  
Difference Approximation ◽  
Cantilever Beams ◽  
Crack Location ◽  
Displacement Mode ◽  
Derivatives Of

For the small crack detection (crack ration less than 5%), the derivatives of mode shapes of cantilever beams were used for crack detection in the beams. These derivatives consist of the slope, curvature and rate of curvature, which are the first, second and third derivatives of the displacement mode shape respectively. The presence of a crack results in a slight change in the mode shape of a structure which is manifested as a small discontinuity in the response at the crack location. It is hard to detect small cracks in beams using the direct data of mode shape change. But when the first, second and third derivatives of the displacement mode shape, that is the slope, curvature and rate of curvature, respectively, of the cracked cantilever beam provide a progressively better indication of the presence of a crack. However, `noise' effects due to the difference approximation error also begin to be magnified at higher derivatives so that it is not advantageous to go beyond the third derivatives of mode shapes. For the intact beam, these derivatives are smooth curves. So the local peaks or discontinuity on the slope, curvature and rate of curvature modal curves can be used to indicate abnormal mode shape changes at those positions. In this way, these local peak positions can be used to detect and locate cracks in the structure. The modal responses of the damaged and intact cantilever beams used were computed using the finite element method.

scholarly journals Change in mode shape nodes of multiple cracked bar: I. The theoretical study

2013 ◽  
Vol 35 (3) ◽  
Author(s):  
Nguyen Tien Khiem ◽  
Le Khanh Toan ◽  
Nguyen Thi Linh Khue
Keyword(s):  
Explicit Expression ◽  
Mode Shape ◽  
Crack Detection ◽  
Theoretical Study ◽  
Multiple Cracks ◽  
Axial Vibration ◽  
Multiple Crack ◽  
Important Indicator ◽  
Natural Modes ◽  
Exact Positions

In present paper change in position of mode shape nodes induced by multiple cracks in bar is studied with purpose to use for the multiple crack detection from measured mode shape nodes. First, there is derived an explicit expression for natural modes in axial vibration of multiple cracked bar that allows obtaining exact positions of the node in the case of single and double crack. The change in mode shape nodes induced by multiple cracks provides an important indicator for crack localization in bar. Finally, a procedure for multiple crack detection by using mode shape nodes has been proposed and examined in an example of application.

Benchmark of Damage Localisation Algorithms Using Mode Shape Data

2005 ◽  
Vol 293-294 ◽  
pp. 305-312 ◽  
Author(s):  
Joseph Morlier ◽  
F. Bos ◽  
P. Castera
Keyword(s):  
Signal Processing ◽  
Fractal Dimension ◽  
Wavelet Transform ◽  
Mode Shape ◽  
Crack Detection ◽  
Singularity Detection ◽  
Local Complexity ◽  
Noise Measurements ◽  
Signal Processing Methods ◽  
Shape Data

This paper presents a comparative study of three enhanced signal processing methods to locate damage on mode shape data. The first method called curvature mode shape is used as a reference. The second tool uses wavelet transform and singularity detection theory to locate damage. Finally we introduce the windowed fractal dimension of a signal as a tool to easily measure the local complexity of a signal. Our benchmark aims at comparing the crack detection using optimal spatial sampling under different severity, beam boundary conditions (BCs) and added noise measurements.

scholarly journals Mode shape curvature squares method for crack detection in railway prestressed concrete sleepers

2019 ◽  
Vol 105 ◽  
pp. 386-401 ◽  
Author(s):  
Rims Janeliukstis ◽  
Sandris Ručevskis ◽  
Sakdirat Kaewunruen
Keyword(s):  
Mode Shape ◽  
Prestressed Concrete ◽  
Crack Detection

Vibration Based Damage Detection in Plate-Like Structure Using Square of Mode Shape Curvature

2019 ◽  
Author(s):  
Ramesh Lanka ◽  
Putti Srinivasa Rao
Keyword(s):  
Mode Shape ◽  
Surface Crack ◽  
Crack Detection ◽  
Numerical Study ◽  
Numerical Data ◽  
Mode Shapes ◽  
Laser Vibrometer ◽  
Study Results ◽  
Before And After ◽  
The Impact

In this current work, a new methodology based on the square of mode shape curvature (SMSC) is presented that relates the mode shapes and its curvature changes before and after the damage for localization and sizing of the surface crack in plate-type structures. The significance of this method is it has the capability to portray accurate shape and exact location of the surface crack in a plate-like structure which are related to low and high elastic modes on dense and coarse measurement grids. The efficiency of the proposed SMSC is examined using experimental and numerical data acquired from modal analysis on the aluminum plate containing single and multi-surface cracks with a fixed-free condition using non-contact measurement a scanning laser vibrometer and on simple finite element plate model. As evidence of experimental and numerical study results, highly accurate crack characterization has been attained through the proposed method. In implementing this method, only a few modes of the structure are required. Further, the impact of the mode order on the effectiveness of crack detection, boundary distortion treatment, and grid density analysis was also performed by the proposed method.

Crack Detection in Rotating Cantilever Beam by Continuous Wavelet Transform

2014 ◽  
Vol 592-594 ◽  
pp. 2021-2025
Author(s):  
Amit Banerjee ◽  
G. Pohit
Keyword(s):  
Mode Shape ◽  
Crack Detection ◽  
Crack Size ◽  
Mode Shapes ◽  
The Finite Element Method ◽  
Response Data ◽  
Structure Changes ◽  
Determining Factors ◽  
Damaged Beams ◽  
Open Edge

This paper presents an investigation methodology for detection of size and location of open edge transverse crack on a rotating beams using continuous wavelength transform. Generally, vibration characteristic of abeam like structure changes significantly due to the presence of crack. However when the crack is relatively small, it is difficult to identify the presence of the crack from the vibration response data only. In the present case, vibration parameter, such as, mode shapes of damaged beams are obtained using the finite element method. The CWT is implemented with different scales on mode shape of the rotating beam to evaluate crack size and its location. It is also shown that this method can produce satisfactory results with some limitation based on mode shape profile. In addition to the the profile quality, other determining factors are scale and resolution of the detection signal

Three-Dimensional Ultrasonic Crack Detection in Anisotropic Materials

1997 ◽  
Vol 9 (2) ◽  
pp. 59-79 ◽  
Author(s):  
J. Mattsson ◽  
A. J. Niklasson ◽  
A. Eriksson
Keyword(s):  
Crack Detection ◽  
Three Dimensional ◽  
Anisotropic Materials
Sign in / Sign up

Export Citation Format

Share Document