Application of Modal Analysis to Damage Detection in Composite Laminates

Volume 2 ◽  
2004 ◽  
Author(s):  
Huiwen Hu ◽  
Bor-Tsuen Wang ◽  
Jing-Shiang Su
Keyword(s):  
Modal Analysis ◽  
Composite Laminates ◽  
Strain Energy ◽  
Promising Result ◽  
Differential Quadrature Method ◽  
Damage Index ◽  
Laminate Plate ◽  
Modal Testing ◽  
Dynamic Responses ◽  
Mode Shapes

A nondestructive detection of damage in composite laminates by using modal analysis is investigated in this paper. Continued fiber-reinforced composite AS4/PEEK was used to fabricate a symmetrical laminate plate and a surface crack was created in one side of the laminate plate. The results of modal testing are presented for the application of modal analysis to the laminate plate before and after damage. Changes in mode shapes, mode shape slopes and strain energies were used to calculate the damage index for indicating the damage location. Differential quadrature method (DQM) was introduced to solve the problem of partial derivatives function in strain energy formula. A 3-D finite element model was created for comparison with the experimental results. The model accurately predicted the dynamic responses. It was found that damage index using strain energy method provides a more promising result than other methods in locating the damage.

Damage Detection of Surface Crack in Composite Quasi-Isotropic Laminate Using Modal Analysis and Strain Energy Method

2006 ◽  
Vol 306-308 ◽  
pp. 757-762 ◽  
Author(s):  
Hui Wen Hu ◽  
Bor Tsuen Wang ◽  
Cheng Hsin Lee
Keyword(s):  
Damage Detection ◽  
Modal Analysis ◽  
Surface Crack ◽  
Strain Energy ◽  
Differential Quadrature Method ◽  
Damage Index ◽  
Mode Shapes ◽  
Cutting Machine ◽  
Before And After ◽  
Energy Formula

This paper presents a damage detection of surface crack in composite laminate. Carbon/epoxy composite AS4/PEEK was used to fabricate a quasi-isotropic laminate [0/90/±45]2s. Surface crack was created by using laser cutting machine. Modal analysis was performed to obtain the mode shapes of the laminate before and after damage. The mode shapes were then adopted to compute the strain energy, which was used to define a damage index. Consequently, the damage index successfully predicted the location of surface crack in the laminate. Differential quadrature method (DQM) was introduced to calculate the partial differential terms in strain energy formula.

scholarly journals Looseness localization for bolted joints using Bayesian operational modal analysis and modal strain energy

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401880869 ◽  
Author(s):  
Yu-Jia Hu ◽  
Wei-Gong Guo ◽  
Cheng Jiang ◽  
Yun-Lai Zhou ◽  
Weidong Zhu
Keyword(s):  
Modal Analysis ◽  
Strain Energy ◽  
Damage Index ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Bolted Joints ◽  
Mode Shapes ◽  
Bolted Connections ◽  
Modal Strain Energy ◽  
Beam Structures

Bayesian operational modal analysis and modal strain energy are employed for determining the damage and looseness of bolted joints in beam structures under ambient excitation. With this ambient modal identification technique, mode shapes of a damaged beam structure with loosened bolted connections are obtained based on Bayesian theory. Then, the corresponding modal strain energy can be calculated based on the mode shapes. The modal strain energy of the structure with loosened bolted connections is compared with the theoretical one without bolted joints to define a damage index. This approach uses vibration-based nondestructive testing of locations and looseness of bolted joints in beam structures with different boundary conditions by first obtaining modal parameters from ambient vibration data. The damage index is then used to identify locations and looseness of bolted joints in beam structures with single or multiple bolted joints. Furthermore, the comparison between damage indexes due to different looseness levels of bolted connections demonstrates a qualitatively proportional relationship.

Damage Modes Detection of Composite Laminates Using Improved Modal Strain Energy Method

2011 ◽  
Vol 338 ◽  
pp. 375-379
Author(s):  
Jia Hui ◽  
Xiao Peng Wan ◽  
Mei Ying Zhao
Keyword(s):  
Composite Laminates ◽  
Strain Energy ◽  
Composite Laminate ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Damage Index ◽  
Qualitative Description ◽  
Mode Shapes ◽  
Modal Strain Energy ◽  
Damage Level

Damage causes changes in structural parameters, which in turn, modify dynamic properties, such as natural frequencies and mode shapes. Based on this assumption, this paper presents a new approach to detect different damage modes of composite laminates. Finite element modal analysis is performed on the composite laminate to obtain the modal mode shapes used to compute the modal strain energy. Consequently, an improved damage index is defined by using the ratio of modal strain energies of composite laminates before and after damage. The proposed method is validated using a numerical simulation of a composite laminate with damages in some elements, which are simulated by reducing elements’ material stiffness properties under a combined material properties degradation rule. The result shows that six kinds of damage modes of composite laminates can be detected by this method preferably and give a qualitative description for the damage level.

Experimental Modal Analysis of a Half-Scale Model Twin-Engine Aircraft Rear Fuselage Engine Mount Support Frame

2017 ◽  
Author(s):  
Diego A. Chamberlain ◽  
Chris K. Mechefske
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Testing Procedure ◽  
Modal Testing ◽  
Scale Model ◽  
Mode Shapes ◽  
Component Testing ◽  
Fitting Procedures ◽  
Engine Mount ◽  
Set Up

Experimental modal testing using an impact hammer is a commonly used method for obtaining the modal parameters of any structure for which the vibrational behavior is of interest. Natural frequencies and associated mode shapes of the structure can be extracted directly from measured FRFs (Frequency Response Functions) through various curve fitting procedures. This paper provides an overview of the modal testing conducted on an aerospace component. Testing set-up, experimental equipment and the methodology employed are all described in detail. Further validation of the testing procedure was done by ensuring that the experimental results satisfy the requirements of repeatability, reciprocity and linearity. The relevant ISO standard has been referenced and important concepts to modal analysis are expanded upon. Recorded natural frequencies, coherence and a description of the observed mode shapes are presented along with notable trends.

Study on the Method of Crack Detection of Steel Rods Based on Modal Analysis

2012 ◽  
Vol 249-250 ◽  
pp. 3-8
Author(s):  
Hong Chun Sun ◽  
Yue Cheng Deng ◽  
Yuan Cheng You
Keyword(s):  
Modal Analysis ◽  
Crack Detection ◽  
Damage Index ◽  
Least Square ◽  
Mode Shapes ◽  
Destructive Testing ◽  
Damage Location ◽  
Damage Degree ◽  
Method Of Least Square ◽  
Petroleum Chemical

Steel rods are widely used in the areas of petroleum, chemical, architecture and transportation, steel rods with cracks will cause terrible accident and great losses when working in production practice. In view of traditional Non-destructive Testing (NDT) method can only realize static detection, this paper provide the method based on modal calculate analysis, including the choice of damage index and the judgment of damage degree and damage location for cracks of steel rods. The damage location is judged by the strain mode shape difference curve and the function expression of damage degrees and mutation degrees of curvature mode shapes is acquired by the method of least square fitting, which can achieve quantitative analysis of single crack of steel rods, this provide theoretical support and technical reference for experimental modal analysis and dynamic NDT.

Finite Element Model Verification for the Use of Piezoelectric Sensor in Structural Modal Analysis

2006 ◽  
Vol 22 (2) ◽  
pp. 107-114 ◽  
Author(s):  
B.-T. Wang ◽  
P.-H. Chen ◽  
R.-L. Chen
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Piezoelectric Materials ◽  
Piezoelectric Sensor ◽  
Model Verification ◽  
Modal Testing ◽  
Mode Shapes ◽  
Response Analysis ◽  
Pvdf Film ◽  
Element Analysis

AbstractThis paper presents the theoretical modal analysis for the use of PVDF sensor in structural modal testing via finite element analysis (FEA). A series of rectangular PVDF films are adhered on the surface of cantilever beam as sensors, while the point impact force is applied as the actuator for experimental modal analysis (EMA). Natural frequencies and mode shapes determined from both FEA and EMA are validated. In FEA, the beam structure is modeled by 3D solid elements, and the PVDF films are modeled by 3D coupled field piezoelectric elements. Both modal analysis and harmonic response analysis are performed to obtain the structural modal parameters and frequency response functions, respectively. Results show that both FEA and EMA results agree well. In particular, the PVDF sensor mode shapes, proportional to the slope difference between the two edges of PVDF film, are numerically and experimentally validated by FEA and EMA, respectively. Therefore, the simulation of PVDF films for vibration analysis in FEA can be verified and easily extended to other complex structures that may contain piezoelectric materials.

Modal Analysis and Dynamic Responses of a Hysteretically Damped Axle Shaft With a Transverse Crack

2019 ◽  
Author(s):  
C. Shravankumar ◽  
Yash K. Sarda ◽  
V. Thamarai Selvan
Keyword(s):  
Modal Analysis ◽  
Condition Monitoring ◽  
Crack Detection ◽  
Natural Frequencies ◽  
Fatigue Cracks ◽  
Dynamic Responses ◽  
Mode Shapes ◽  
Fast Fourier Transformation ◽  
Transverse Loads ◽  
Eigen Value

Abstract An axle shaft supports rotating elements, and is fitted to the housing by means of bearings. It mostly does not transmit torque, with exceptions such as in train axles. Non-rotating axles are subjected to bending moments due to dynamic transverse loads. Axles such as in automobiles are marked with occasional failures due to fatigue cracks, which can prove serious, if the cracks are not detected early. Vibration based condition monitoring is the field concerned with crack detection based on the dynamic responses of the system. In this light, the present paper discusses the vibration analysis of a cracked axle. The cracked shaft is modelled using finite element method, for transverse vibration conditions. The shaft is modelled based on Euler-Bernoulli theory for bending, while the crack is modelled based on fracture mechanics approach. After modelling, modal analysis of the system is carried out, with the consideration of proportional hysteretic damping. The Eigen value problem provides the natural frequencies and mode shapes. The Frequency Response Functions (FRF’s) magnitude and phase plots are obtained, from which the natural frequencies and structural damping loss factors can be calculated. Further, the free vibration and forced vibration system time responses are obtained, using numerical integration methods. The corresponding responses in frequency domain are obtained using Fast Fourier Transformation (FFT). The FRF’s and dynamic responses of the shaft without and with crack are comparatively studied. The study provides the platform for condition monitoring of shaft cracks.

Investigation of Nonlinear Vibro-Acoustic Wave Modulation Mechanisms in Composite Laminates

2013 ◽  
Vol 569-570 ◽  
pp. 96-102 ◽  
Author(s):  
Łukasz Pieczonka ◽  
Wieslaw Jerzy Staszewski ◽  
Tadeusz Uhl
Keyword(s):  
Acoustic Wave ◽  
Composite Laminates ◽  
Low Frequency ◽  
Laminate Plate ◽  
Mode Shapes ◽  
Vibration Modes ◽  
Low Frequency Vibration ◽  
Composite Laminate Plate ◽  
Thermographic Camera ◽  
Frequency Excitation

This paper investigates the effect of low-frequency vibration and the related temperature field on nonlinear vibro-acoustic wave modulations. Experimental modal analysis was used to find natural frequencies and mode shapes of a composite laminate plate with seeded delamination. Temperature distribution was analyzed with a thermographic camera in the vicinity of damage for the identified vibration modes. These frequencies of these vibration modes were then used for low-frequency excitation in nonlinear acoustic tests. The correlation between the thermal field and the observed wave modulations was analyzed.

Modal Analysis of Systems Using a Neuro-Fuzzy Approach

2010 ◽  
Author(s):  
Farbod Khoshnoud ◽  
Clarence W. de Silva
Keyword(s):  
Neural Networks ◽  
Modal Analysis ◽  
Mode Shape ◽  
Iterative Process ◽  
Analysis Data ◽  
Modal Testing ◽  
Mode Shapes ◽  
Vibration Sensors ◽  
Fuzzy Neural ◽  
Vibration Modeling

A novel method of modal analysis for vibration modeling of systems is presented in this paper. In the developed method, first, mode shapes of the structure that is being analyzed are approximated. The approximate mode shapes are expressed by fuzzy sets where approximate deflections or displacement magnitudes of the mode shapes are described by fuzzy linguistic terms such as Zero, Medium, and Large. Fuzzy membership functions provide a means of dealing with the imprecisely defined system and it gives access to a large repertoire of tools available in the field of fuzzy reasoning. Second, fuzzy representations of the approximate mode shapes, called Fuzzy Mode Shapes in this paper, are updated using modal analysis data as obtained through experimentation. Finally, artificial neural networks are used as a tool to obtain an accurate version of the mode shape data by learning the target set of the data. An appropriate analogy of the application of Fuzzy Mode Shapes in the first step is the Starting Mode Shape Vectors in numerical eigenvector problem where the starting vector is updated through an iterative process. In this paper iterative updating process of mode shapes is carried out for the application of experimental modal testing. In this approach the differences between the fuzzy mode shapes and the corresponding measured modal testing data are minimized through an iterative process. In validating the developed technique for vibration modeling of one-dimensional and two-dimensional elastic bodies and structures, modeling of elastic beams, a clamped-free-clamped-free plate and a frame are used as illustrative examples. The solutions of the corresponding simulations are compared with the results from finite element computations and analytical model solutions. The good agreement of the results obtained for these models justifies the application of the developed method in experimental vibration modeling of systems. Use of the fuzzy-neural approach as developed in the paper expands the coverage of experimentally measured data, which is normally limited to a small number of measurement sets due to the limited number of available vibration sensors in the analyzed system. Neural networks provide a satisfactory interpolation of two sets of data including a) modal test data, which is accurate but is normally available only for a few measured points, and b) Fuzzy Mode Shapes, which are available for large number of points but are approximate.

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