Damage Detection in Laminated Composite Plates and Shells Using Second Derivatives of Mode Shape Data Through Dynamic Analysis of These Structures

2015 ◽  
Author(s):  
Mahendran Govindasamy ◽  
Chandrasekaran Kesavan ◽  
Malhotra Santkumar
Keyword(s):  
Damage Detection ◽  
Mode Shape ◽  
Laminated Composite ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Experimental Investigations ◽  
Structural Elements ◽  
Plate And Shell ◽  
Second Derivatives ◽  
Derivatives Of

The main objective of this study is to evaluate the dynamics-based techniques for damage detection in laminated composite cantilevered rectangular plates and cylindrical shells with damages in the form of surface macro-level cracks using finite element analysis (FEA). However, the quantitative change in global vibration characteristics is not sufficiently sensitive to local structural damages especially to small size damages. Hence certain parameters called damage indicators based on mode shape curvature, which are the second derivatives of the vibration characteristics (mode shapes), are used in this study to detect the location and size of even small damages accurately in laminated composite structures. The commercial FEA package ANSYS is used for the theoretical modal analysis to generate the natural frequencies and normalized mode shapes of the intact and damaged structures. Experimental investigations are carried out on the laminated plate and shell structural elements to provide a validation of the analysis. Experimental investigations are carried out on the laminated composite (E-glass unidirectional fibers reinforced epoxy resin) cantilevered plate and shell structural elements to provide a validation of the analysis. The effectiveness of these methods is clearly demonstrated by the results obtained.

FiniteElement Vibration Characteristics of Composite Hypar Shallow Shells with Various Edge Supports

2005 ◽  
Vol 11 (10) ◽  
pp. 1291-1309 ◽  
Author(s):  
S. Sahoo ◽  
D. Chakravorty
Keyword(s):  
Boundary Conditions ◽  
Numerical Experiments ◽  
Laminated Composite ◽  
Shell Element ◽  
Vibration Characteristics ◽  
The Other ◽  
Mode Shapes ◽  
Review Of The Literature ◽  
Shallow Shells ◽  
Fundamental Frequencies

A review of the literature reveals that information regarding fundamental frequencies and mode shapes of shallow laminated composite hypar shells with practical civil engineering boundary conditions is not available. The present investigation aims to fill this gap by applying an eight-noded isoparametric shell element as the tool. Numerical experiments are carried out for different parametric variations including boundary conditions and stacking orders to obtain the fundamental frequencies and mode shapes. Some of the results are used for validating the correctness of the present approach by comparing with the existing benchmark, while the other results are studied meticulously to extract a set of meaningful conclusions regarding the free vibration characteristics of composite shallow hypar shells.

scholarly journals Vibration-Based Damage Detection in Beams by Cooperative Coevolutionary Genetic Algorithm

2014 ◽  
Vol 6 ◽  
pp. 624949 ◽  
Author(s):  
Kittipong Boonlong
Keyword(s):  
Genetic Algorithm ◽  
Damage Detection ◽  
Cantilever Beam ◽  
Cross Section ◽  
Random Noise ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Test Problems ◽  
Uniform Cross Section ◽  
Coevolutionary Genetic Algorithm

Vibration-based damage detection, a nondestructive method, is based on the fact that vibration characteristics such as natural frequencies and mode shapes of structures are changed when the damage happens. This paper presents cooperative coevolutionary genetic algorithm (CCGA), which is capable for an optimization problem with a large number of decision variables, as the optimizer for the vibration-based damage detection in beams. In the CCGA, a minimized objective function is a numerical indicator of differences between vibration characteristics of the actual damage and those of the anticipated damage. The damage detection in a uniform cross-section cantilever beam, a uniform strength cantilever beam, and a uniform cross-section simply supported beam is used as the test problems. Random noise in the vibration characteristics is also considered in the damage detection. In the simulation analysis, the CCGA provides the superior solutions to those that use standard genetic algorithms presented in previous works, although it uses less numbers of the generated solutions in solution search. The simulation results reveal that the CCGA can efficiently identify the occurred damage in beams for all test problems including the damage detection in a beam with a large number of divided elements such as 300 elements.

scholarly journals Measuring Strain Response Mode Shapes with a Continuous-Scan LDV

2002 ◽  
Vol 9 (1-2) ◽  
pp. 19-27 ◽  
Author(s):  
Anthony B. Stanbridge ◽  
Milena Martarelli ◽  
David J. Ewins
Keyword(s):  
Mode Shape ◽  
Response Mode ◽  
Mode Shapes ◽  
Stress And Strain ◽  
Governing Equations ◽  
Convenient Means ◽  
Straight Line ◽  
Polynomial Series ◽  
Spatial Derivatives ◽  
Derivatives Of

A continuous-scan LDV is a convenient means for measuring the response mode shape (ODS) of a vibrating surface, particularly in view of the fact that the ODS is automatically derived as a spatial polynomial series. Second spatial derivatives of the deflection equations are therefore easily derived, and these should, in principle, give curvature equations from which, for a beam or plate of known cross-section, stresses and strains can be obtained directly. Unfortunately, the stress and strain distributions depend critically on higher terms in the original ODS series, which are not accurately measured. This problem can be avoided by a method described here, which enables accurate stress and strain distributions to be derived, from a straight-line LDV scan along a uniform beam, using only five terms in the mode-shape polynomial series. A similar technique could be applied to uniform plates but the analysis and the governing equations are rather more complicated.

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.

Prediction of Unmeasured Mode Shape Using Artificial Neural Network for Damage Detection

2013 ◽  
Vol 61 (1) ◽  
Author(s):  
L. D. Goh ◽  
N. Bakhary ◽  
A. A. Rahman ◽  
B. H. Ahmad
Keyword(s):  
Neural Network ◽  
Damage Detection ◽  
Mode Shape ◽  
Health Monitoring ◽  
Spline Interpolation ◽  
Measured Data ◽  
Mode Shapes ◽  
Modal Data ◽  
Artificial Neural ◽  
Shape Data

Artificial neural networks (ANNs) have received much attention in the field of vibration–based damage detection since the 1990s, due to their capability to predict damage from modal data. However, the accuracy of this method is highly dependent on the number of measurement points, especially when the mode shape is used as an indicator for damage detection. With a high number of measurement points, more information can be fed to the ANN to detect damage; therefore, more reliable results can be obtained. Nevertheless, in practice, it is uneconomical to install sensors on every part of a structure; thus the capability of ANNs to detect damage is quite limited. In this study, an ANN is applied to predict the unmeasured mode shape data based on a limited number of measured data. To demonstrate the accuracy of the proposed method, the results are compared with the Cubic Spline interpolation (CS) method. A parametric study is also conducted to investigate the sensitivity of the number of measurement points to the proposed method. The results show that the ANN provides more reliable results compared to the CS method as it is able to predict the magnitude of mode shapes at the unmeasured points with a limited number of measurement points. The application of a two–stage ANN showed results with a high potential for overcoming the issue of using a limited number of sensors in structural health monitoring.

Modal analysis of cylindrical panels at elevated temperatures under nonuniform heating conditions: Experimental investigation

2020 ◽  
pp. 095440622093673
Author(s):  
CM Twinkle ◽  
C Nithun ◽  
Jeyaraj Pitchaimani ◽  
Vasudevan Rajamohan
Keyword(s):  
Free Vibration ◽  
Elevated Temperatures ◽  
Laminated Composite ◽  
Free Vibration Analysis ◽  
Cylindrical Panel ◽  
Experimental Results ◽  
Mode Shapes ◽  
Experimental Investigations ◽  
Nonuniform Heating ◽  
Cylindrical Panels

In this study, experimental investigations carried out to analyze the influences of different in-plane temperature variations on buckling and free vibration responses of metal and fiber-reinforced laminated composite cylindrical panels are presented. Initially, critical buckling temperature is calculated then free vibration analysis is performed as a function of the buckling temperature to analyze the changes in the natural frequencies and mode shapes. Experimental results revealed that the thermal buckling strength of the panel is significantly influenced by the nature of the heating condition. Similarly, significant changes in free vibration mode shapes are observed with the rise in temperature and also according to the heating conditions. It is also observed that, with the increase in temperature, nodal and anti-nodal lines of free vibration modes shifting towards the heating source. The experimental results are compared with the numerical simulation for the studies on the isotropic cylindrical panel and both the results are in good agreement.

Detection and Localisation of Structural Damage Based on the Polynomial Annihilation Edge Detection: An Experimental Verification

2013 ◽  
Vol 569-570 ◽  
pp. 1273-1280 ◽  
Author(s):  
Cecilia Surace ◽  
Massimiliano Mattone ◽  
Marco Gherlone
Keyword(s):  
Edge Detection ◽  
Damage Detection ◽  
Structural Damage ◽  
High Spatial Resolution ◽  
Mode Shapes ◽  
Laser Vibrometer ◽  
Numerical Assessment ◽  
Polynomial Annihilation ◽  
Vibration Tests ◽  
Derivatives Of

The present paper describes an experimental validation of a new structural damage detection method based on the Polynomial Annihilation Edge Detection (PAED) technique. It is well known that concentrated damage such as a crack, causes a discontinuity in the rotations and consequently in the first derivatives of the mode shapes. On this basis, the PAED, a numerical method for detecting discontinuities in smooth piecewise functions and their derivatives, can be applied to the problem of damage detection and localisation in beam-like structures for which only post-damage mode shapes are available. As described in this paper, in order to verify this approach experimentally (a numerical assessment having already been documented in previous papers), vibration tests on a cantilever steel beam with a saw-cut have been performed and the Operational Deflection Shapes (ODS) determined. As the approach requires a reasonably high spatial resolution of the ODS, a scanning laser vibrometer, capable of acquiring data rapidly at a very large number of observation points, was used.

scholarly journals Cooperative Coevolution with Dynamic Species-Size Strategy for Vibration-Based Damage Detection in Plates

2017 ◽  
Vol 3 (3) ◽  
pp. 12
Author(s):  
Jitti Pattavanitch ◽  
Puttha Jeenkour ◽  
Kittipong Boonlong
Keyword(s):  
Genetic Algorithm ◽  
Damage Detection ◽  
Element Model ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Cooperative Coevolution ◽  
First Case ◽  
The Difference ◽  
Actual Damage ◽  
Coevolutionary Genetic Algorithm

Vibration-based damage detection is based on the fact that vibration characteristics such as natural frequencies and mode shapes of structures are changed when the damage occurs. This paper proposes dynamic species-size strategy in cooperative coevolution concept. The resulting algorithm, cooperative coevolutionary genetic algorithm with dynamics species-size (CCGADSS), is used as the optimization algorithm in the vibration-based damage detection in plates. The objective function is numerically calculated from the difference between experimentally vibration characteristics and numerically evaluated vibration characteristics of the predicted damage. In finite element model for objective calculation, the plates are equally divided into 64 elements. There are 2 different cases with dissimilar occurred damage in plates are considered. In first case, the plate hase only one region consisting of 4 elements which are together connected and have same damage. In second case, there are 5 separated elements which are damaged differently. In order to demonstrate the performance of the dynamic species-size strategy, 3 optimization algorithms, which are genetic algorithm (GA), cooperative coevolutionary genetic algorithm (CCGA), and CCGADSS. The results indicate that CCGADSS is superior to GA and CCGA. Moreover solutions obtained using CCGADSS are quite close the actual damage. These results show that the dynamic species-size strategy can enhance performance of cooperative coevolution concept.

scholarly journals Effect of Moment of Inertia of Attached Mass on Natural Frequencies of Cantilevered Symmetrically Laminated Plates

2018 ◽  
Vol 1 (2) ◽  
pp. 35-39
Author(s):  
Kenji Hosokawa
Keyword(s):  
Free Vibration ◽  
Natural Frequencies ◽  
Laminated Composite ◽  
Composite Plates ◽  
Vibration Characteristics ◽  
Laminated Plates ◽  
Moment Of Inertia ◽  
Mode Shapes ◽  
Attached Mass ◽  
Structural Applications

Since composite materials such as laminated composite plates have high specific strength and high structural efficiency, they have been usedin many structural applications. It is therefore very important to make clear the vibration characteristics of the laminated plates for the designand the structural analysis. Especially, the vibration characteristics of the laminated plates with attached mass are essential. However, wecannot find the theoretical or experimental approaches for the free vibration of laminated plates with attached mass. In the present study, theexperimental and numerical approaches are applied to the free vibration of cantilevered symmetrically laminated plates with attached mass.First, by applying the experimental modal analysis technique to the cantilevered symmetrically laminated plates with attached mass, thenatural frequencies and mode shapes of the plates are obtained. Next, the natural frequencies and mode shapes of the cantileveredsymmetrically laminated plates with attached mass are calculated by Finite Element Method (FEM). Finally, from the experimental andnumerical results, the effect of the moment of inertia of the attached mass to the natural frequencies and mode shapes of the cantileveredsymmetrically laminated plates are clarified.

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