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.

Analysis of Modal Parameters of Adhesively Bonded Double-Strap Joints by the Modal Strain Energy Method

1993 ◽  
Author(s):  
Mohan D. Rao ◽  
Krishna M. Gorrepati
Keyword(s):  
Strain Energy ◽  
Natural Frequencies ◽  
Structural Parameters ◽  
Flexural Vibration ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Adhesively Bonded ◽  
Modal Strain Energy ◽  
Joint System ◽  
Damping Material

Abstract This paper presents the analysis of modal parameters (natural frequencies, damping ratios and mode shapes) of a simply supported beam with adhesively bonded double-strap joint by the finite-element based Modal Strain Energy (MSE) method using ANSYS 4.4A software. The results obtained by the MSE method are compared with closed form analytical solutions previously obtained by the first author for flexural vibration of the same system. Good agreement has been obtained between the two methods for both the natural frequencies and system loss factors. The effects of structural parameters and material properties of the adhesive on the modal properties of the joint system are also studied which are useful in the design of the joint system for passive vibration and noise control. In order to evaluate the MSE and analytical results, some experiments were conducted using aluminum double-strap joint with 3M ISD112 damping material. The experimental results agreed well with both analytical and MSE results indicating the validity of both analytical and MSE methods. Finally, a comparative study has been conducted using various commercially available damping materials to evaluate their relative merits for use in the design of these joints.

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.

Analysis of Modal Parameters of Adhesively Bonded Double-Strap Joints by the Modal Strain Energy Method

1996 ◽  
Vol 118 (1) ◽  
pp. 28-35 ◽  
Author(s):  
K. M. Gorrepati ◽  
M. D. Rao
Keyword(s):  
Strain Energy ◽  
Natural Frequencies ◽  
Structural Parameters ◽  
Flexural Vibration ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Adhesively Bonded ◽  
Modal Strain Energy ◽  
Joint System ◽  
Damping Material

This paper presents the analysis of modal parameters (natural frequencies, damping and mode shapes) of a simply supported beam with adhesively bonded double-strap joint by the finite-element based Modal Strain Energy (MSE) method using ANSYS 4.4A software. The results obtained by the MSE method are compared with closed form analytical solutions previously obtained by the author for flexural vibration of the same system. Good agreement has been obtained between the two methods for both the natural frequencies and system loss factors. The effects of structural parameters and material properties of the adhesive on the modal properties of the joint system are also studied which are useful in the design of the joint system for passive vibration and noise control. In order to evaluate the MSE and analytical results, some experiments were conducted using aluminum double-strap joints with 3M ISD112 damping material. The experimental results agreed well with both analytical and MSE results indicating the validity of both analytical and MSE methods. Finally, a comparative study has been conducted using various commercially available damping materials to evaluate their relative merits for use in the design of these joints.

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.

Nondestructive Damage Detection of Two Dimensional Plate Structures Using Modal Strain Energy Method

2008 ◽  
Vol 24 (4) ◽  
pp. 319-332 ◽  
Author(s):  
H.-W. Hu ◽  
C.-B. Wu
Keyword(s):  
Energy Method ◽  
Strain Energy ◽  
Damage Index ◽  
Mode Shapes ◽  
Two Dimensional ◽  
Plate Structures ◽  
Modal Strain Energy ◽  
Modal Strain Energy Method ◽  
Before And After ◽  
Strain Energy Method

AbstractA nondestructive detection method of surface cracks in two dimensional plate structures using modal strain energy method is investigated in this paper. Experimental modal analysis (EMA) is conducted on an aluminum alloy 6061 thin plate to obtain the mode shapes before and after damage under a completely free boundary condition. The measured mode shapes are used to compute the strain energy of the plate. Limited by the measured points, a differential quadrature method is employed to compute the partial differential terms in strain energy formula. A damage index is then defined based on strain energy ratio of the plate before and after damage. This damage index is employed to identify the location of surface crack in plate structure. A finite element analysis (FEA) is also performed to access this approach and demonstrate a feasible process for the experimental work. Good correlation between FEA and EMA results is obtained. The damage index obtained from both FEA and EMA successfully identify the location of surface crack in the aluminum plate. Only few measured mode shapes of the plate are required in this method, which provides a quick, flexible, inexpensive and nondestructive technique to identify the damagein local and global 2D plate structures.

scholarly journals Identification of Mistuning Characteristics of Bladed Disks From Free Response Data

1998 ◽  
Author(s):  
Marc P. Mignolet ◽  
Alejandro Rivas-Guerra
Keyword(s):  
Dynamic Models ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Identification Problem ◽  
Forced Response ◽  
Mode Shapes ◽  
Likelihood Principle ◽  
Bladed Disks ◽  
Block Test

The focus of the present investigation is on the estimation of the dynamic properties, i.e. masses, stiffnesses, natural frequencies, mode shapes and their statistical distributions, of turbomachine blades to be used in the accurate prediction of the forced response of mistuned bladed disks. As input to this process, it is assumed that the lowest natural frequencies of the blades alone have been experimentally measured, for example in a broach block test. Since the number of measurements is always less than the number of unknowns, this problem is indeterminate in nature. Two distinct approaches will be investigated to resolve the shortfall of data. The first one relies on the imposition of as many constraints as needed to insure a unique solution to this identification problem. Specifically, the mode shapes and modal masses of the blades are set to their design/tuned counterparts while the modal stiffnesses are varied from blade-to-blade to match the measured natural frequencies. The second approach, based on the maximum likelihood principle, yields estimates of all the structural parameters of the blades through the minimization of a specified “cost function”. The accuracy of these two techniques in predicting the forced response of mistuned bladed disks will be assessed on simple dynamic models of the blades.

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