Papers by Keyword: Damage Location

Abstract: Composite material brings many challenges in structural health monitoring (SHM), especially in internal damage detecting. CFRP-OFBG, using Optical Fiber Bragg Grating (OFBG) sensors embedded in Carbon Fiber Reinforced Polymer (CFRP) composite structures, has been widely used in the field of structural reinforcement with smart sensing features. This work developed a real-time monitor system to detect internal damage by using dense arrayed fiber-optic sensor embedded in CFRP-OFBG. A classical triangulation procedure is selected and improved in damage location detection algorithm. Experimental results showed this design is an efficient and lightweight system in detecting internal damage for CFRP-OFBG materials.

Abstract: According to the regular pattern of the grid structure truss, learning from the methods applied to composite damage detection, for grid structure, the paper proposed the concept of the amplitude matrix which comes from cross-correlation function of response signals. A corresponding amplitude distribution map can be obtained. The injuries in different position bring different amplitude distribution maps. The damage area would be determined by comparing these maps with the map derived from intact structure.

Abstract: This paper researches a robust damage identification system considering the effects of the environmental and operational conditions based on distributed fiber Bragg grating system. Initially a well-verified method is used to identify damage, but the failure result is obtained. The environmental and operational variations causing the false-positive indication are analyzed, such as the temperature, the change of the excitation and the relaxation phenomenon of the sensors. The Hilbert-Huang Transform method is used to decompose the dynamic strain signal into several intrinsic mode function components, the physical meanings of which are discussed. Then the second level component is used as the damage-induced signal component. Lastly the damage index based on the autoregressive model and Mahalanobis distance is constructed to detect and locate damage.

Abstract: This paper discusses the main issues of Uncertainty Analysis (UA) in general and also argues and illustrates its particular relevance to structural dynamics. Brief descriptions are given of the most prevalent of the many frameworks for uncertainty representation. The three main uncertainty-related problems of relevance to structural dynamics are then discussed, namely quantification, fusion and propagation. In order to illustrate the application of ideas of UA in a realistic scenario, there then follows a case study conducted on an aerospace structure, namely the wing of a Gnat trainer aircraft. The case study considers evidence-based classifiers as an alternative to probabilistic classifiers for the problem of damage location within the context of Structural Health Monitoring. Dempster-Shafer theory is employed to construct neural network classifiers with the potential to admit ignorance, rather than misclassify.

Abstract: The research to identify and locate the damage to the engineering structure mainly aimed at some simple structure forms before, such as beam and framework. Damage shows changes of local characteristics of the signal, while wavelet analysis can reflect local damage traits of the signal in time domain and frequency domain. For confirming the validity and applicability of structural damage identification methods, wavelet analysis is used to spatial structural damage detection. The wavelet analysis technique provides new ideas and methods of spatial steel structural damage detection. Based on the theory of wavelet singularity detection，with the injury signal of modal strain energy as structural damage index，the mixing of the modal strain energy and wavelet method to identify and locate the damage to the spatial structure is considered. The multiplicity of the bars and nodes can be taken into account, and take the destructive and nondestructive modal strain energy of Kiewitt-type reticulated shell with 40m span as an example of numerical simulation，the original damage signal and the damage signal after wavelet transformation is compared. The location of the declining stiffness identified by the maximum of wavelet coefficients，analyzed as signal by db1 wavelet，and calculate the graph relation between coefficients of the wavelets and the damage to the structure by discrete or continuous wavelet transform, and also check the accuracy degree of this method with every damage case. Finally，the conclusion is drawn that the modal strain energy and wavelet method to identify and locate the damage to the long span reticulated shell is practical, effective and accurate, that the present method as a reliable and practical way can be adopted to detect the single and several locations of damage in structures.

Abstract: Wavelet transform can characterize the local features of the signal in the time domain and frequency domain, enlarges and identifies the mutation signal of the structural response at different scales as a new signal analysis tools. In this paper, based on the structural deflection curve, propose a wavelet-based method to identify the beam structural damage. Use wavelet function to decompose the deflection curve of the structure after injury. Determine the existence of damage by the change and distribution of wavelet transform coefficients, determine the damage location, and simulate a cantilever bridge to verify this method.

Abstract: Damage detection and location in aerospace composites is currently of great interest in the research community and is being driven by the need to reduce weight of commercial aircrafts and hence make substantial environmental improvements. The increased use of composites as safety critical components has led to the need for development of structural health monitoring (SHM) systems. Acoustic Emission (AE) offers an excellent potential for delivering the necessary information of damage detection to maintenance engineers in terms of location however there are currently no methodologies that can use AE signals to characterise damage sources. This paper explores a methodology for damage characterisation based on measuring the amplitude ratio (MAR) of the two primary plate wave modes, to allow identification of in-plane (matrix cracking) and out-of-plane sources (delamination). Results from a large-scale buckling test show good correlation between signal characterization and observed damage mechanisms.

Abstract: To understand more about Lamb waves on composite laminates damage detection features, the Lamb wave group velocity dispersion curves are calculated and plotted by using dichotomy method in MATLAB. The signal parameters are chosen according to Group velocity dispersion curves. The dynamic response signals of the composite plate are obtained by finite element method. Damage location is calculated by the actual group velocity of Lamb wave and time of flight of the difference signal before and after damage.

Abstract: The fiber reinforced composite materials were widely used for aerospace aircrafts and missile weapons, and the delamination was a major problem which reduced the structural integrity and reliability of the solid rocket motor (SRM) composite shell seriously. In order to locate the delamination damage, the fiber Bragg grating (FBG) strain sensors network was embedded in SRM shell, and a multi-step approach of delamination damage location based on strain energy was performed: the strain field was measured in a scatter grid by the FBG strain sensors network in hydraulic testing; then the continuous displacement and strain field was reconstructed with relative sensors data using a moving least square (MLS) mesh-free fitting method; the strain energy of each subregions was calculated from the reconstructed data; finally the damaged subregions was identified successfully by singularity value of strain energy. The results of simulation and experiment indicated that the damage identification and location only required the measure of strain field of the SRM shell, and the presented approach achieved higher accuracy.

Abstract: Detection and identification of structural damage at the earliest possible stage is a vital part of the monitoring and servicing of structural during their lifetime. In this paper, damage monitoring is studied on some kinds of structures use wavelet analysis, such as plate, and framework. The research shows this damage detection technique is made to determine the damage occurring time, positions and degrees and to realize an early discovery and diagnosis on the damage, which offers a basis for realizing lifespan prediction of the structure and ensuring safety of engineering structure.