Spectral damage index for estimation of breathing crack depth in an aluminum plate using nonlinear Lamb wave

2013 ◽  
pp. n/a-n/a ◽  
Author(s):  
Nitesh P. Yelve ◽  
Mira Mitra ◽  
Prasanna M. Mujumdar
Keyword(s):  
Lamb Wave ◽  
Crack Depth ◽  
Damage Index ◽  
Aluminum Plate ◽  
Breathing Crack

Nonlinear Vibration Response of a Beam With a Breathing Crack

2012 ◽  
Author(s):  
Gang Wang
Keyword(s):  
Nonlinear Vibration ◽  
Crack Depth ◽  
Damage Index ◽  
Analytical Approximation ◽  
Breathing Crack ◽  
Detection Scheme ◽  
Solution Approach ◽  
Vibration Responses ◽  
Nonlinear Forced Vibration ◽  
Forced Responses

In this paper, a single degree of freedom system was used to model a beam with a breathing crack. Then analytical approximate solution approach was employed to solve this nonlinear vibration equation based on the Homotopy Perturbation Method (HPM). Nonlinear free vibration frequencies under different crack depth to thickness ratios were calculated and compared to the results that were predicted by the bilinear oscillator model. Both predictions were validated experimental data. It has been clearly shown that the fundamental frequency of a beam with a breathing crack is lower than the case in which the crack is assumed to be open and remains open. Nonlinear forced vibration responses containing all harmonics were determined analytically. Numerical simulation results were used to validate our analytical approximation solutions. A damage detection scheme was proposed to relate the crack depth to thickness ratio with a damage index, which is derived from the nonlinear forced responses. This damage index is able to accurately assess the breathing crack condition even for a very small crack depth.

Non-model-based damage identification of plates using measured mode shapes

2016 ◽  
Vol 16 (1) ◽  
pp. 3-23 ◽  
Author(s):  
Yongfeng Xu ◽  
Weidong Zhu
Keyword(s):  
Structural Damage ◽  
Damage Identification ◽  
Damage Index ◽  
Thickness Reduction ◽  
Aluminum Plate ◽  
Mode Shapes ◽  
Identification Method ◽  
Model Based

Mode shapes (MSs) have been extensively used to detect structural damage. This paper presents a new non-model-based damage identification method that uses measured MSs to identify damage in plates. A MS damage index (MSDI) is proposed to identify damage near regions with consistently high values of MSDIs associated with MSs of different modes. A MS of a pseudo-undamaged plate can be constructed for damage identification using a polynomial of a properly determined order that fits the corresponding MS of a damaged plate, if the associated undamaged plate is geometrically smooth and made of materials that have no stiffness and mass discontinuities. It is shown that comparing a MS of a damaged plate with that of a pseudo-undamaged plate is better for damage identification than with that of an undamaged plate. Effectiveness and robustness of the proposed method for identifying damage of different positions and areas are numerically investigated using different MSs; effects of crucial factors that determine effectiveness of the proposed method are also numerically investigated. Damage in the form of a machined thickness reduction area was introduced to an aluminum plate; it was successfully identified by the proposed method using measured MSs of the damaged plate.

scholarly journals An Aircraft Pallet Damage Monitoring Method Based on Damage Subarea Identification and Probability-Based Diagnostic Imaging

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Bin Liu ◽  
Tingzhang Liu ◽  
Yue Lin ◽  
Jianfei Zhao
Keyword(s):  
Diagnostic Imaging ◽  
Lamb Wave ◽  
Damage Index ◽  
Imaging Method ◽  
Monitoring Method ◽  
Study Results ◽  
Damage Monitoring ◽  
Weighted Algorithm ◽  
Damage Simulation ◽  
Monitoring Area

To improve the safety and economy of aircraft pallet use, an aircraft pallet damage monitoring method based on damage subarea identification and probability-based diagnostic imaging is proposed. In the proposed method, first, the large aircraft pallet monitoring area is divided into rectangular subareas, and a piezoelectric transducer sensor is pasted on each vertex of the rectangular subarea that is used to excitation and sensing the Lamb wave. Second, the damage subarea is identified according to the diagonal damage indexes. Third, the damage position in the damage subarea is calculated using the probability-based diagnostic imaging method and coordinate probability weighted algorithm. Finally, the aircraft pallet damage can be localized based on the damage subarea position. Frequency selection and damage simulation study results show that the Lamb wave is sensitive to aircraft pallet damage whose centre frequency ranges from 50 kHz to 150 kHz, and the damage index of a steel ball is less than that of all real aircraft pallet damage from 95 kHz to 125 kHz. The verification results show that the proposed method can locate aircraft pallet damage with an error of less than 2 cm.

Effect of a breathing crack on the damping changes in nonlinear vibrations of a cracked beam: Experimental and theoretical investigations

2020 ◽  
pp. 107754632096031
Author(s):  
Masoud Kharazan ◽  
Saied Irani ◽  
Mohammad Ali Noorian ◽  
Mohammad Reza Salimi
Keyword(s):  
Nonlinear Vibrations ◽  
Crack Depth ◽  
Beam Theory ◽  
Experimental Tests ◽  
Damping Coefficient ◽  
Crack Identification ◽  
Breathing Crack ◽  
Cracked Beam ◽  
Identification Method ◽  
Nonlinear Crack

The attempts to identify damping changes in a cracked beam can improve the accuracy of the nonlinear crack identification method. For the purpose of this aim, a parametric nonlinear equation of motion is obtained using the Euler–Bernoulli beam theory and parametric nonlinear breathing crack assumptions. Several experiments were conducted to identify the effect of breathing cracks on changing the damping value in nonlinear vibrations of a cracked beam. Experimental tests have revealed that increasing the crack depth and the level of excitation enlarges the damping coefficient in a vibrating beam. For this reason, the effects of the excitation force and crack depth on the structural damping coefficient are investigated. The obtained results indicated that considering the nonlinear response of a cracked beam and measuring the value of the damping changes can significantly improve the accuracy of the nonlinear crack identification method.

Application of entropy in identification of breathing cracks in a beam structure: Simulations and experimental studies

2017 ◽  
Vol 17 (3) ◽  
pp. 549-564 ◽  
Author(s):  
Buddhi Wimarshana ◽  
Nan Wu ◽  
Christine Wu
Keyword(s):  
Cantilever Beam ◽  
Time Domain ◽  
Fatigue Cracks ◽  
Unit Length ◽  
Crack Depth ◽  
Experimental Studies ◽  
Sample Entropy ◽  
Breathing Crack ◽  
Engineering Structures ◽  
Vibration Signals

A cantilever beam with a breathing crack is studied to detect the crack and evaluate the crack depth using entropy measures. During the vibration in engineering structures, fatigue cracks undergo the status from close-to-open (and open-to-close) repetitively leading to a crack breathing phenomenon. Entropy is a measure, which can quantify the complexity or irregularity in system dynamics, and hence employed to quantify the bi-linearity/irregularity of the vibration response, which is induced by the breathing phenomenon of a crack. A mathematical model of harmonically excited unit length steel cantilever beam with a breathing crack located near the fixed end is established, and an iterative numerical method is applied to generate accurate time domain vibration responses. The steady-state time domain vibration signals are pre-processed with wavelet transformation, and the bi-linearity/irregularity of the vibration signals due to breathing effect is then successfully quantified using both sample entropy and quantized approximation of sample entropy to detect and estimate the crack depth. It is observed that the method is capable of identifying crack depths even at very early stages of 3% of the beam thickness with significant increment in the entropy values (more than 200%) compared to the healthy beam. In addition, experimental studies are conducted, and the simulation results are in good agreement with the experimental results. The proposed technique can also be applied to damage identification in other types of structures, such as plates and shells.

Structural Health Monitoring of Thin Aluminum Plate Using Acoustic Sensors

2012 ◽  
Vol 622-623 ◽  
pp. 1389-1395
Author(s):  
R. Nishanth ◽  
K. Lingadurai ◽  
V. Malolan ◽  
Gowrishankar Wuriti ◽  
M.R.M. Babu
Keyword(s):  
Lamb Wave ◽  
Damage Identification ◽  
Lamb Waves ◽  
Time Domain Analysis ◽  
Ultrasonic Waves ◽  
Aluminum Plate ◽  
Identification System ◽  
Time Frequency ◽  
Thin Aluminum ◽  
Aluminum Plates

SHM is defined as “an emerging technology that can be defined as continuous, autonomous, real time, in-service monitoring of the physical condition of a structure by means of embedded or attached sensors with minimum manual intervention” .SHM provides the ability of a system to detect adverse changes within a system’s structure to enhance reliability and reduce maintenance costs. There are different Non-Destructive techniques like acoustic emission, ultrasonic, acousto-ultrasonic, guided ultrasonic waves or Lamb waves which are nowadays investigated for the development of an efficient and user-friendly damage identification system. This paper deals with the latter which is based on Lamb wave propagation. It has been developed especially for distinguishing different kinds of damages. The Lamb wave-based active SHM method uses piezoelectric (PZT) sensors to transmit and receive Lamb waves in a thin Aluminum plate. The Lamb wave modes (AO &SO) travel into the structure and are reflected by the structural boundaries, discontinuities, and damage. By studying their propagation and reflection, the presence of defect in the structure is determined. Laboratory level experiments have been carried out on thin Aluminum plates with angular, horizontal and vertical defect. The obtained waveform is filtered to avoid unwanted noise & disturbances using Savitzky-Golay filtering. The filtered waveforms are compared to differentiate the defects. Short Time Fourier Transform has been carried out on the acquired waveform. This study provides significant insight into the problem of identifying localized damages in the structure using PZT and dispersion of signal after they interact with different types of damage. Those small defects like the horizontal one that may be nearly missed in time domain analysis can also be clearly identified in the STFT analysis. Moreover the occurrence of So mode is also clearly seen. Thus, Lamb waves generated by PZT sensors and time-frequency analysis techniques could be used effectively for damage detection in aluminum plate. This study has given a complete idea of the working and the basic requirements of SHM system.

Three-Dimensional Electromechanical Impedance Model for Damaged Beams with Imperfectly Bonded Piezoelectric Patches

2011 ◽  
Vol 52-54 ◽  
pp. 1285-1290
Author(s):  
Wan Chun Li ◽  
Wei Yan ◽  
Wei Wang
Keyword(s):  
Crack Depth ◽  
Damage Index ◽  
Three Dimensional ◽  
Adhesive Layer ◽  
Coupled System ◽  
Physical Parameters ◽  
Cracked Beam ◽  
Electromechanical Impedance ◽  
Lag Model ◽  
Peel Stress

Dynamic analysis is conducted for a cracked beam with imperfectly bonded piezoelectric patches using the finite element method in the paper. The property of adhesive between the PZT patches and the host beam is taken into account based on the peel stress model as well as the shear lag model and thus the three-dimensional (3D) model of piezoelectric patch-adhesive-host beam coupled system is developed. Based on the established three-dimensional EMI model, the effect of some physical parameters such as vibration mode of main structure, the mass of adhesive layer and crack depth etc. on electromechanical impedance signatures is investigated. Finally, the root-mean-square deviation (RMSD), a kind of non-parametric damage index, is also employed to identify the damage severity of the cracked beam.

The Vibration and Modal Power Flow Analysis of a Functionally Graded Material Beam With an Open Crack

2019 ◽  
Author(s):  
Xiaotian Liang ◽  
Tianyun Li ◽  
Xing Heng ◽  
Xiaofang Hu ◽  
Xiang Zhu
Keyword(s):  
Functionally Graded Material ◽  
Power Flow ◽  
Crack Depth ◽  
Flow Analysis ◽  
Damage Index ◽  
Functionally Graded ◽  
Open Crack ◽  
Modal Power ◽  
Graded Material ◽  
Fgm Beam

Abstract The free vibration and modal power flow of a functionally graded material (FGM) beam with an open crack are studied. The crack is simulated by using the massless-rotational spring model. The natural frequencies and corresponding modal shapes of the cracked beam are obtained by the wave propagation method. A modal power flow formula of the FGM beam is deduced by Bernoulli-beam theory. A detailed parametric study is conducted to show the influences of crack location, crack depth, material property gradient, and boundary condition on the modal power flow characteristics based on a modal power flow damage index. Numerical examples show that the damage index based on the modal power flow can effectively identify the crack in the FGM beam, which provides the basis for the future study on the modal power flow based damage detection of functionally graded material structures.

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