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57543 KiB

Open AccessFeature PaperArticle

Inspection of Piezoceramic Transducers Used for Structural Health Monitoring

by Inka Mueller and Claus-Peter Fritzen

Materials 2017, 10(1), 71; https://doi.org/10.3390/ma10010071 - 16 Jan 2017

Cited by 39 | Viewed by 5890

The use of piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM) purposes is state of the art for acousto-ultrasonic-based methods. For system reliability, detailed information about the PWAS itself is necessary. This paper gives an overview on frequent PWAS faults and [...] Read more.

The use of piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM) purposes is state of the art for acousto-ultrasonic-based methods. For system reliability, detailed information about the PWAS itself is necessary. This paper gives an overview on frequent PWAS faults and presents the effects of these faults on the wave propagation, used for active acousto-ultrasonics-based SHM. The analysis of the wave field is based on velocity measurements using a laser Doppler vibrometer (LDV). New and established methods of PWAS inspection are explained in detail, listing advantages and disadvantages. The electro-mechanical impedance spectrum as basis for these methods is discussed for different sensor faults. This way this contribution focuses on a detailed analysis of PWAS and the need of their inspection for an increased reliability of SHM systems. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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2036 KiB

Open AccessArticle

Monitoring the Damage State of Fiber Reinforced Composites Using an FBG Network for Failure Prediction

by Esat Selim Kocaman, Erdem Akay, Cagatay Yilmaz, Halit Suleyman Turkmen, Ibrahim Burc Misirlioglu, Afzal Suleman and Mehmet Yildiz

Materials 2017, 10(1), 32; https://doi.org/10.3390/ma10010032 - 3 Jan 2017

Cited by 23 | Viewed by 6241

Abstract

A structural health monitoring (SHM) study of biaxial glass fibre-reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading is performed using fibre Bragg grating (FBG) optical sensors embedded in composites at various locations to monitor the evolution of local strains, [...] Read more.

A structural health monitoring (SHM) study of biaxial glass fibre-reinforced epoxy matrix composites under a constant, high strain uniaxial fatigue loading is performed using fibre Bragg grating (FBG) optical sensors embedded in composites at various locations to monitor the evolution of local strains, thereby understanding the damage mechanisms. Concurrently, the temperature changes of the samples during the fatigue test have also been monitored at the same locations. Close to fracture, significant variations in local temperatures and strains are observed, and it is shown that the variations in temperature and strain can be used to predict imminent fracture. It is noted that the latter information cannot be obtained using external strain gages, which underlines the importance of the tracking of local strains internally. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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1213 KiB

Open AccessArticle

A Bayesian Approach for Sensor Optimisation in Impact Identification

by Vincenzo Mallardo, Zahra Sharif Khodaei and Ferri M. H. Aliabadi

Materials 2016, 9(11), 946; https://doi.org/10.3390/ma9110946 - 22 Nov 2016

Cited by 30 | Viewed by 4658

Abstract

This paper presents a Bayesian approach for optimizing the position of sensors aimed at impact identification in composite structures under operational conditions. The uncertainty in the sensor data has been represented by statistical distributions of the recorded signals. An optimisation strategy based on [...] Read more.

This paper presents a Bayesian approach for optimizing the position of sensors aimed at impact identification in composite structures under operational conditions. The uncertainty in the sensor data has been represented by statistical distributions of the recorded signals. An optimisation strategy based on the genetic algorithm is proposed to find the best sensor combination aimed at locating impacts on composite structures. A Bayesian-based objective function is adopted in the optimisation procedure as an indicator of the performance of meta-models developed for different sensor combinations to locate various impact events. To represent a real structure under operational load and to increase the reliability of the Structural Health Monitoring (SHM) system, the probability of malfunctioning sensors is included in the optimisation. The reliability and the robustness of the procedure is tested with experimental and numerical examples. Finally, the proposed optimisation algorithm is applied to a composite stiffened panel for both the uniform and non-uniform probability of impact occurrence. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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4823 KiB

Open AccessArticle

Linear and Nonlinear Guided Wave Imaging of Impact Damage in CFRP Using a Probabilistic Approach

by Jan Hettler, Morteza Tabatabaeipour, Steven Delrue and Koen Van Den Abeele

Materials 2016, 9(11), 901; https://doi.org/10.3390/ma9110901 - 7 Nov 2016

Cited by 56 | Viewed by 5353

Abstract

The amount and variety of composite structures that need to be inspected for the presence of impact damage has grown significantly in the last few decades. In this paper, an application of a probabilistic ultrasonic guided wave imaging technique for impact damage detection [...] Read more.

The amount and variety of composite structures that need to be inspected for the presence of impact damage has grown significantly in the last few decades. In this paper, an application of a probabilistic ultrasonic guided wave imaging technique for impact damage detection in carbon fiber-reinforced polymers (CFRP) is presented. On the one hand, a linear, baseline-dependent, technique utilizing the well-known correlation-based RAPID method and an array of piezoelectric transducers is applied to detect impact-induced damage in plate-like composite structures. Furthermore, a baseline-independent nonlinear extension of the standard RAPID method is proposed, and its performance is demonstrated both numerically and experimentally. Compared to the conventional RAPID, the baseline-free version suffers from a somewhat lower imaging quality. However, this drawback is compensated by the fact that no damage-free (intact) baseline is necessary for successful imaging of damage. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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4394 KiB

Open AccessArticle

An Integrated Health Monitoring Method for Structural Fatigue Life Evaluation Using Limited Sensor Data

by Jingjing He, Yibin Zhou, Xuefei Guan, Wei Zhang, Yanrong Wang and Weifang Zhang

Materials 2016, 9(11), 894; https://doi.org/10.3390/ma9110894 - 4 Nov 2016

Cited by 17 | Viewed by 4583

Abstract

A general framework for structural fatigue life evaluation under fatigue cyclic loading using limited sensor data is proposed in this paper. First, limited sensor data are measured from various sensors which are preset on the complex structure. Then the strain data at remote [...] Read more.

A general framework for structural fatigue life evaluation under fatigue cyclic loading using limited sensor data is proposed in this paper. First, limited sensor data are measured from various sensors which are preset on the complex structure. Then the strain data at remote spots are used to obtain the strain responses at critical spots by the strain/stress reconstruction method based on empirical mode decomposition (REMD method). All the computations in this paper are directly performed in the time domain. After the local stress responses at critical spots are determined, fatigue life evaluation can be performed for structural health management and risk assessment. Fatigue life evaluation using the reconstructed stresses from remote strain gauge measurement data is also demonstrated with detailed error analysis. Following this, the proposed methodology is demonstrated using a three-dimensional frame structure and a simplified airfoil structure. Finally, several conclusions and future work are drawn based on the proposed study. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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5656 KiB

Open AccessArticle

A Multi-Level Decision Fusion Strategy for Condition Based Maintenance of Composite Structures

by Zahra Sharif Khodaei and M.H. Aliabadi

Materials 2016, 9(9), 790; https://doi.org/10.3390/ma9090790 - 21 Sep 2016

Cited by 51 | Viewed by 5585

Abstract

In this work, a multi-level decision fusion strategy is proposed which weighs the Value of Information (VoI) against the intended functions of a Structural Health Monitoring (SHM) system. This paper presents a multi-level approach for three different maintenance strategies in which the performance [...] Read more.

In this work, a multi-level decision fusion strategy is proposed which weighs the Value of Information (VoI) against the intended functions of a Structural Health Monitoring (SHM) system. This paper presents a multi-level approach for three different maintenance strategies in which the performance of the SHM systems is evaluated against its intended functions. Level 1 diagnosis results in damage existence with minimum sensors covering a large area by finding the maximum energy difference for the guided waves propagating in pristine structure and the post-impact state; Level 2 diagnosis provides damage detection and approximate localization using an approach based on Electro-Mechanical Impedance (EMI) measures, while Level 3 characterizes damage (exact location and size) in addition to its detection by utilising a Weighted Energy Arrival Method (WEAM). The proposed multi-level strategy is verified and validated experimentally by detection of Barely Visible Impact Damage (BVID) on a curved composite fuselage panel. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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3865 KiB

Open AccessArticle

Monitoring Poisson’s Ratio Degradation of FRP Composites under Fatigue Loading Using Biaxially Embedded FBG Sensors

by Erdem Akay, Cagatay Yilmaz, Esat S. Kocaman, Halit S. Turkmen and Mehmet Yildiz

Materials 2016, 9(9), 781; https://doi.org/10.3390/ma9090781 - 19 Sep 2016

Cited by 12 | Viewed by 5922

Abstract

The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to [...] Read more.

The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to obtain strain data. Fiber Bragg Grating (FBG) sensors have many advantages for strain measurement over conventional ones. Thus, the present paper suggests a novel method for biaxial strain measurement using embedded FBG sensors during the fatigue testing of FRP composites. Poisson’s ratio and its reduction were monitored for each cyclic loading by using embedded FBG sensors for a given specimen and correlated with the fatigue stages determined based on the variations of the applied fatigue loading and temperature due to the autogenous heating to predict an oncoming failure of the continuous fiber-reinforced epoxy matrix composite specimens under fatigue loading. The results show that FBG sensor technology has a remarkable potential for monitoring the evolution of Poisson’s ratio on a cycle-by-cycle basis, which can reliably be used towards tracking the fatigue stages of composite for structural health monitoring purposes. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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6489 KiB

Open AccessArticle

Guided Wave Based Crack Detection in the Rivet Hole Using Global Analytical with Local FEM Approach

by Md Yeasin Bhuiyan, Yanfeng Shen and Victor Giurgiutiu

Materials 2016, 9(7), 602; https://doi.org/10.3390/ma9070602 - 21 Jul 2016

Cited by 56 | Viewed by 6930

Abstract

In this article, ultrasonic guided wave propagation and interaction with the rivet hole cracks has been formulated using closed-form analytical solution while the local damage interaction, scattering, and mode conversion have been obtained from finite element analysis. The rivet hole cracks (damage) in [...] Read more.

In this article, ultrasonic guided wave propagation and interaction with the rivet hole cracks has been formulated using closed-form analytical solution while the local damage interaction, scattering, and mode conversion have been obtained from finite element analysis. The rivet hole cracks (damage) in the plate structure gives rise to the non-axisymmetric scattering of Lamb wave, as well as shear horizontal (SH) wave, although the incident Lamb wave source (primary source) is axisymmetric. The damage in the plate acts as a non-axisymmetric secondary source of Lamb wave and SH wave. The scattering of Lamb and SH waves are captured using wave damage interaction coefficient (WDIC). The scatter cubes of complex-valued WDIC are formed that can describe the 3D interaction (frequency, incident direction, and azimuth direction) of Lamb waves with the damage. The scatter cubes are fed into the exact analytical framework to produce the time domain signal. This analysis enables us to obtain the optimum design parameters for better detection of the cracks in a multiple-rivet-hole problem. The optimum parameters provide the guideline of the design of the sensor installation to obtain the most noticeable signals that represent the presence of cracks in the rivet hole. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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5323 KiB

Open AccessArticle

Fatigue Damage Monitoring of a Composite Step Lap Joint Using Distributed Optical Fibre Sensors

by Leslie Wong, Nabil Chowdhury, John Wang, Wing Kong Chiu and Jayantha Kodikara

Materials 2016, 9(5), 374; https://doi.org/10.3390/ma9050374 - 14 May 2016

Cited by 31 | Viewed by 6442

Abstract

Over the past few decades, there has been a considerable interest in the use of distributed optical fibre sensors (DOFS) for structural health monitoring of composite structures. In aerospace-related work, health monitoring of the adhesive joints of composites has become more significant, as [...] Read more.

Over the past few decades, there has been a considerable interest in the use of distributed optical fibre sensors (DOFS) for structural health monitoring of composite structures. In aerospace-related work, health monitoring of the adhesive joints of composites has become more significant, as they can suffer from cracking and delamination, which can have a significant impact on the integrity of the joint. In this paper, a swept-wavelength interferometry (SWI) based DOFS technique is used to monitor the fatigue in a flush step lap joint composite structure. The presented results will show the potential application of distributed optical fibre sensor for damage detection, as well as monitoring the fatigue crack growth along the bondline of a step lap joint composite structure. The results confirmed that a distributed optical fibre sensor is able to enhance the detection of localised damage in a structure. Full article

(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)

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