Damage Localization by Isolating the Part of the Response Due to the Damage Only

2012 ◽  
Vol 80 (1) ◽  
Author(s):  
Akash Dixit ◽  
Sathya Hanagud
Keyword(s):  
Finite Element ◽  
Linear System ◽  
Damage Detection ◽  
Physical Parameter ◽  
Health Monitoring ◽  
Natural Frequencies ◽  
Finite Element Models ◽  
Damage Localization ◽  
Partial Mode ◽  
Baseline State

A new physical parameter is presented and it is applied to damage detection to address the two main challenges in the field of vibration-based structural health monitoring: the sensitivity of detection and the requirement of data of the baseline state. The parameter is also shown to be not affected by noise in the detection ambience. Assuming the damaged structure to be a linear system, its response can be expressed as the summation of the responses due to the undamaged and the damaged part. If the part of the response due to the damage is isolated, it forms what can be regarded as the damage signature. In this paper, the occurrence of damage signature is investigated when the damaged structure is excited at one of its natural frequencies, and it is called partial-mode contribution. The existence of damage signature as partial-mode contribution is first verified using an analytical derivation. Thereupon, its existence is ascertained using finite element models and by doing experiments. The limits of size of the damage that can be determined using the method are also investigated.

scholarly journals High-Fidelity Sensitivity Analysis of Modal Properties of Mistuned Bladed Disks Regarding Material Anisotropy

2018 ◽  
Author(s):  
Adam Koscso ◽  
Guido Dhondt ◽  
E. P. Petrov
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Coordinate Systems ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Material Orientation

A new method has been developed for sensitivity calculations of modal characteristics of bladed disks made of anisotropic materials. The method allows the determination of the sensitivity of the natural frequencies and mode shapes of mistuned bladed disks with respect to anisotropy angles that define the crystal orientation of the monocrystalline blades using full-scale finite element models. An enhanced method is proposed to provide high accuracy for the sensitivity analysis of mode shapes. An approach has also been developed for transforming the modal sensitivities to coordinate systems used in industry for description of the blade anisotropy orientations. The capabilities of the developed methods are demonstrated on examples of a single blade and a mistuned realistic bladed disk finite element models. The modal sensitivity of mistuned bladed disks to anisotropic material orientation is thoroughly studied.

scholarly journals The method of direct finite perturbation of numerical models for studying of the dynamic, stiffness and strength properties for thin-walled elements of engineering constructions.

2014 ◽  
Vol 2014 (4) ◽  
pp. 114-124
Author(s):  
Юрий Костенко ◽  
Yuriy Kostenko ◽  
Анатолий Чепурной ◽  
Anatoliy Chepurnoy ◽  
Александр Литвиненко ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Natural Frequencies ◽  
Numerical Models ◽  
Dynamic Stiffness ◽  
Strength Properties ◽  
Test Problems ◽  
Finite Element Models ◽  
Direct Perturbation ◽  
Thin Walled

The methods of direct perturbation for finite element models of thin-walled engineering constructions for sensitivity analysis of their strength, stiffness and dynamic characteristics to the change in their thickness are proposed. The approach for prediction of distribution for natural frequencies migration as result of change in their thickness are presented. The applicability of the linearized models to determine displacements, stresses and natural frequencies slightly thinned design compared to the nominal (original) are shown. The examples of test problems are given.

Structural Health Monitoring Using Synchrosqueezed Wavelet Transform on IASC-ASCE Benchmark Phase I

2020 ◽  
Vol 20 (12) ◽  
pp. 2050138
Author(s):  
Wilson D. Sanchez ◽  
Jose V. de Brito ◽  
Suzana M. Avila
Keyword(s):  
Wavelet Transform ◽  
Dynamic Response ◽  
Phase I ◽  
Damage Detection ◽  
Health Monitoring ◽  
Natural Frequencies ◽  
Detection Methods ◽  
State Of Health ◽  
Civil Structures ◽  
Synchrosqueezed Wavelet Transform

Civil structures suffer deterioration either for years of service, deficiency due to environmental factors or damages caused by factors such as earthquakes, winds, impact loads, and cyclical loads. When a structure ages, it is necessary to know its state of health and make a decision of maintenance or replacement. When a structure such as a bridge or building is subjected to destructive environmental forces, determining its state of health becomes a priority since its recovery is urgently required to function normally. Structural Health Monitoring (SHM) is a technology that aims to prevent the collapse of structures and loss of human life through early diagnosis of the health status of a structure. There are a large number of damage detection methods that can be classified into (1) non-destructive testing methods, (2) dynamic characteristics-based damage detection methods, (3) dynamic response-based, (4) multi-scale damage detection method and (5) damage detection methods with consideration of uncertainties. In this work, it is implemented synchrosqueezed wavelet transform (SWT), which can be classified as a methods based on the dynamic response. To validate the robustness of the method it is identified first, the natural frequencies of the Benchmark Phase I without damage, which consists of a steel structure of 4-story [Formula: see text] bay 3D steel frame structure subjected to ambient vibrations. Subsequently, some damage patterns are validated according to IASC-ASCE SHM Task Group. The results obtained in the identification of natural frequencies are compared with those reported in literature. SWT was efficient, presenting a minimum error of 0.12[Formula: see text] and a maximum of 3.06[Formula: see text] in the identification of natural frequencies about the AISCE-ASCE group model. SWT overcomes some other damage detection methods, which are deficient in the identification of closely spaced frequencies, commonly present in many civil structures due to symmetric geometry or similar physical properties in different directions.

scholarly journals Dynamic Response Of Tower Structures

2015 ◽  
Vol 2 ◽  
pp. 85
Author(s):  
Liga Gaile ◽  
Ivars Radinsh
Keyword(s):  
Finite Element ◽  
Structural Changes ◽  
Natural Frequencies ◽  
Resonance Effect ◽  
Dynamic Loads ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Dynamic Parameters ◽  
Vibration Level ◽  
Tower Structure

The present study focuses on the tower type structures response to the dynamic loads. The study analyzes the possible mode shapes regarding to tower structure. The estimation of mode shapes and their dependence from structural changes was made for an existing tower structure. To get an acceptable tower’s vibration level and avoid possibility of resonance effect from usual serviceability loads it was evaluated options to change natural frequencies of the structure. It is performed existing 36m high sightseeing tower dynamic analysis and proposed potential solutions to increase critical natural frequencies of the structure. In this study to obtain dynamic parameters of the sightseeing tower structure have been used finite element models and calculation techniques.

scholarly journals Damage Detection in Glass/Epoxy Laminated Composite Plates Using Modal Curvature for Structural Health Monitoring Applications

2020 ◽  
Vol 4 (4) ◽  
pp. 185
Author(s):  
Mahendran Govindasamy ◽  
Gopalakrishnan Kamalakannan ◽  
Chandrasekaran Kesavan ◽  
Ganesh Kumar Meenashisundaram
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Damage Detection ◽  
Health Monitoring ◽  
Strain Energy ◽  
Laminated Composite ◽  
Composite Plates ◽  
Laminated Composite Plates ◽  
Element Analysis ◽  
Modal Curvature

This paper deals with detection of macro-level crack type damage in rectangular E-Glass fiber/Epoxy resin (LY556) laminated composite plates using modal analysis. Composite plate-like structures are widely found in aerospace and automotive structural applications which are susceptible to damages. The formation of cracks in a structure that undergoes vibration may lead to catastrophic events such as structural failure, thus detection of such occurrences is considered necessary. In this research, a novel technique called as node-releasing technique in Finite Element Analysis (FEA), which was not attempted by the earlier researchers, is used to model the perpendicular cracks (the type of damage mostly considered in all the pioneering research works) and also slant cracks (a new type of damage considered in the present work) of various depths and lengths for Unidirectional Laminate (UDL) ([0]S and [45]S) composite layered configurations using commercial FE code Ansys, thus simulating the actual damage scenario. Another novelty of the present work is that the crack is modeled with partial depth along the thickness of the plate, instead of the through the thickness crack which has been of major focus in the literature so far, in order to include the possibility of existence of the crack up to certain layers in the laminated composite structures. The experimental modal analysis is carried out to validate the numerical model. Using central difference approximation method, the modal curvature is determined from the displacement mode shapes which are obtained via finite element analysis. The damage indicators investigated in this paper are Normalized Curvature Damage Factor (NCDF) and modal strain energy-based methods such as Strain Energy Difference (SED) and Damage Index (DI). It is concluded that, all the three damage detection algorithms detect the transverse crack clearly. In addition, the damage indicator NCDF seems to be more effective than the other two, particularly when the detection is for damage inclined to the longitudinal axis of the plate. The proposed method will provide the base data for implementing online structural health monitoring of structures using technologies such as Machine Learning, Artificial Intelligence, etc.

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.

Improving Spot Weld Models in Structural Dynamics

2003 ◽  
Author(s):  
Matteo Palmonella ◽  
Michael I. Friswell ◽  
Cristinel Mares ◽  
John E. Mottershead
Keyword(s):  
Finite Element ◽  
Structural Dynamics ◽  
Degrees Of Freedom ◽  
Dynamic Behaviour ◽  
Natural Frequencies ◽  
Spot Weld ◽  
Physical Parameters ◽  
Finite Element Models ◽  
Spot Welds ◽  
Coarse Meshes

This paper gives an overview of the finite element modelling of spot welds for the analysis of the dynamic response of structures. In particular models for dynamic analysis that use coarse meshes and equivalent parameters are considered. A major requirement for these models is their accuracy in predicting the dynamic behaviour of spot welded structures despite the low number of degrees of freedom. Three different models of spot welds are investigated [1–3] and for each model physical parameters have to be assigned based on engineering insight. The aim of the present paper is to improve the accuracy of these three models by searching for the optimum values of the parameters characterising the spot weld models using experimental data. For this purpose a benchmark structure has been analysed, consisting of a thin walled hat section beam made of two plates welded together by twenty spot welds. The predicted natural frequencies and modes of the benchmark structure have been compared to the experimental modes. Updating of the finite element models has been performed and the accuracy of the three models has been significantly improved.

Analytical and Finite Element Modal Analysis of a Hyperelastic Membrane for Micro Air Vehicle Wings

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Uttam Kumar Chakravarty
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Wind Tunnel Test ◽  
Element Model ◽  
Micro Air Vehicle ◽  
Finite Element Models ◽  
Freestream Velocity ◽  
Modal Characteristics ◽  
Aerodynamic Pressure ◽  
Air Vehicle

Analytical and finite element models are developed for investigating the modal characteristics of a hyperelastic rubber latex membrane for micro air vehicle wings applications. A radially prestretched membrane specimen is attached to a thin, rigid circular ring and vibrated in vacuum and in air at atmospheric pressure. The natural frequencies of the membrane computed by analytical and finite element models are correlated well. The natural frequencies increase with mode and prestretch level of the membrane but decrease in air from those in vacuum due to the effect of added mass of air. The damping is low and has a very minimal effect on the frequencies but helps to reduce the amplitude of vibration. Aerodynamic pressure at different angles of attack and a freestream velocity is computed from the wind tunnel test data, and a finite element model is developed for investigating the effect of the aerodynamic pressure on the modal characteristics of the membrane. It is found that the effect of aerodynamic pressure on the natural frequencies of the membrane is not significant.

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