Papers by Keyword: Damage Detection

Abstract: The distinctive paper is devoted to approbation of new defect identification methodology based on the dynamic characteristics of real construction. Mathematically formalized procedure of the methodology is implemented at the test bench. The proposed algorithm identifies a defect. The features of results obtained from the procedure are described.

Abstract: The distinctive paper is devoted to new defect identification methodology based on dynamic characteristics of real construction. The methodology is founded on mathematically formalized procedure of FE-model adaptation by measured and calculated eigen pairs of dynamic system. Main steps of the methodology are described. Application of the methodology together with standing wave method might allow to identify deviations of stiffness parameters of a real construction facility.

Abstract: This work presents a practical solution intended for dynamic diagnosis of the technical systems based on a set of computational methods for processing and analyzing of the acquired signals. This ensemble of methods leads to the joint time-frequency evaluations and assures a multiple way to estimate the potential damages of certain parts of the tested system. Short-Time-Fourier-Transformation, Cepstrum analysis, power spectral density estimate, together with a group of stochastic estimators composes the structured procedure for dynamic diagnosis. The proposed approach of dynamic diagnosis combines the advantages of the time domain analysis, such as the simplicity and the possibility of parameters investigation during their time evolution, with the power of spectral complex evaluations, sustained by the distribution and shifting trend of spectrum. Hereby it has provided a suitable tool for characterization of spectral composition changes in time during the entire experimental tests. This information is able to reveal the dynamic behaviour changes of supervised parts, components or entire system.

Abstract: This paper presents a novel non-destructive method to locate and size damages in frame structures, performed by examining and interpreting changes in measured vibration response. The method bases on a relation, prior contrived by the authors, between the strain energy distribution in the structure for the transversal vibration modes and the modal changes (in terms of natural frequencies) due to damage. Using this relation a damage location indicator DLI was derived, which permits to locate cracks in spatial structures. In this paper an L-frame is considered for proving the applicability of this method. First the mathematical expressions for the modes shapes and their derivatives were determined and simulation result compared with that obtained by finite element analysis. Afterwards patterns characterizing damage locations were derived and compared with measurement results on the real structure; the DLI permitted accurate localization of any crack placed in the two structural elements.

Abstract: In civil engineering field, huge amount of structural health monitoring work is required throughout the service life of the structures. In pursuing an autonomous, real-time and online non-destructive evaluation (NDE) method, piezo-impedance transducer (PZT) has attracted more and more attention from researchers in recent years. Although up to now, the real application of Electro-Mechanical Impedance (EMI) method with PZT on structure health monitoring is not utilized, experiments results shows its impressive potential.

Abstract: Industrial structures deteriorate generally in an uncontrollable rate. To assess the short-term impact due to hazards and the long-term deterioration process due to physical aging and routine operation, structural health monitoring (SHM) is proposed. In this paper as a model of vessel a simply supported beam under constant distributed force is investigated. The objective is to estimate the severity of damage in a known location with sensing devices. As no actuation is consider the problem is solved statically. Finite element method by using MATLAB software to calculate the global stiffness matrix of the smart beam has been applied. It is expected the results show that higher severity of damage causes higher deflection and higher sensor of voltage.

Abstract: Several techniques have been researched for detecting damage in plates. Each of these techniques offers their own unique advantages in detecting certain types of damage with various levels of analytical complexity. Lamb waves are guided waves that exist in thin walled structures. Because this type of wave can travel long distance with little attenuation, they have been studied intensively for structural health monitoring, especially in the past few decades. This paper presents an overview of using the Lamb waves in damage detection including the theory of lamb waves and the lamb-wave-based damage identification.

Abstract: Gear is one of the most important and commonly used components in machine system. Early detection of gear damage is crucial to prevent the machine system from malfunction. This paper proposes a method for detection of damaged tooth based on support vector machines. Statistical parameters of standard deviation, root mean square value, maximum value and mean value are extracted from the vibration signal as representative features of tooth conditions to be input to the support vector machine classifier. The validity of the presented method is confirmed by the application of detecting early damaged tooth during the cyclic fatigue test. The vibration acceleration on gear box is acquired as original data. Furthermore, the signal of each gear tooth is separately extracted from the signal for a further analysis.The experimental results demonstrate the effectiveness of the proposed method.

Abstract: Optical self-sensing employs the reinforcing fibres as self-sensing elements thus eliminating the need for additional sensing elements in smart materials. At present optical self-sensing systems employ expensive optical adhesives to lower the refractive index of the matrix as the refractive index of the cladding material must be lower than the light-guiding glass fibres. In this study the refractive index of an aerospace certified, commercial laminating resin (Araldite LY5052/Aradur HY5052) was reduced with propylene carbonate, (a commercial reactive diluent). This modified resin with lower refractive index facilitated light transmission through impregnated E-glass reinforcing fibres used as optical self-sensing elements in composites. The effects of propylene carbonate addition on the mechanical properties of the epoxy were also analysed and presented here.

Abstract: Operational modal identification techniques, also known as Ambient modal or Output Only modal, have been in recent years object of growing interest within several applications typical of civil, mechanical and aerospace engineering. In this paper, two of them, known as EFDD and SSI, are fully implemented by means of in-house codes and applied on a finite element beam model dynamic response time data, in order to evaluate their accuracy, focusing on the lowest system’s natural frequencies. Assessments of the techniques’ robustness to a disturbance in the random excitation, reliability when implementing on a small number of measurement channels and in localization and quantification of a given damage in multiple sites are also performed and presented.