Crack detection in beams in noisy conditions using scale fractal dimension analysis of mode shapes

Journal of Intelligent Material Systems and Structures

et al. 2014

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Delamination is a typical form of damage in composite plates. Identification of delamination in plates has been a focus of increasing research interest in relatively recent years. This study develops a new approach, termed a scale waveform dimension analysis of two-dimensional mode shapes, to identify delamination in composite plates. The scale waveform dimension analysis comprises two components: decomposition of a mode shape into scale mode shapes and waveform dimension analysis of scale mode shapes. The first component acts as a splitter that broadly splits a noisy mode shape into three sets of trend-, noise-, and damage-scale mode shapes, from which the damage scale mode shapes can be selected for use in damage characterization; the second component functions as a detector to detect abnormalities of damage scale mode shapes, to indicate the presence and location of delamination. The efficacy of the method is numerically studied and experimentally examined using composite plates containing small delamination. The results show that the proposed method can identify delamination with great accuracy in noisy conditions, needing no intact baseline mode shapes nor any prior knowledge of either the material properties or boundary conditions of the plate being inspected.

Section: Smss For Isolating Damage Componentmentioning

confidence: 99%

Non-baseline identification of delamination in plates using wavelet-aided fractal analysis of two-dimensional mode shapes

Bai

Radzieński

Journal of Intelligent Material Systems and Structures

et al. 2014

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“…The spectral element method (SEM) has been widely applied in structural dynamic analyses, including studies of wave propagation in solids (Lonkar and Chang, 2014; Nanda et al., 2014; Nanda and Kapuria, 2015) and structural modal analysis (Lee et al., 2013; Bai et al., 2014; Chen et al., 2014; Fakhar-Izadi and Dehghan, 2015). By constructing spectral element matrices based on exact dynamic displacement functions, the SEM with a few spectral elements can efficiently obtain accurate solutions of structural dynamic behaviors (Lee et al., 2002).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of high-order modes and damage effects of multi-crack beams using enhanced spectral element method

Journal of Vibration and Control

Bai

et al. 2018

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Exact evaluation of high-order modes of a multi-crack Euler–Bernoulli beam using the conventional spectral element method (SEM) suffers from the deficiency of numerical ill-conditioning, mainly due to round-off errors in floating-point computations involved in evaluating the spectral element stiffness matrix, therefore, the modeling of the multiple cracks intensively increases the complexity of the matrix. To address this limitation, an enhanced SEM with the spectral element stiffness matrix constructed in a set of local coordinate systems is developed. With the method, two sets of local coordinate systems are created to derive two types of spectral element stiffness matrices for a multi-crack beam. The proposed spectral element stiffness matrices are of improved capacities to characterize the high-order modes of a multi-crack beam by largely eliminating the round-off errors involved in the conventional SEM. Moreover, the function of evaluating high-order modes endows the enhanced SEM with distinctive capability to reveal the effect of multiple cracks on the modal property of a multi-crack beam. The effectiveness of the proposed method in evaluating high-order modes and revealing the effects of multiple cracks on the modal property of a beam is investigated on various damage cases.

“…The modal strain energy method is another method developed from mode shapes. Cracks can cause changes in modal strain energy, and in turn they can be identified by such changes [ 32 , 35 , 36 , 37 , 38 , 39 ]; recently, modern signal processing methods such as wavelet transform (WT) [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ] and fractal dimension (FD) [ 50 , 51 , 52 , 53 , 54 ] have been applied to mode shapes for crack identification by characterizing the crack-caused singularities therein. Recent attention to crack identification methods relying on mode shape has focused on the robustness of the methods to environmental noise interference [ 30 , 33 ].…”

Section: Introductionmentioning

confidence: 99%

Crack Identification in CFRP Laminated Beams Using Multi-Resolution Modal Teager–Kaiser Energy under Noisy Environments

Ding

et al. 2017

Materials

Carbon fiber reinforced polymer laminates are increasingly used in the aerospace and civil engineering fields. Identifying cracks in carbon fiber reinforced polymer laminated beam components is of considerable significance for ensuring the integrity and safety of the whole structures. With the development of high-resolution measurement technologies, mode-shape-based crack identification in such laminated beam components has become an active research focus. Despite its sensitivity to cracks, however, this method is susceptible to noise. To address this deficiency, this study proposes a new concept of multi-resolution modal Teager–Kaiser energy, which is the Teager–Kaiser energy of a mode shape represented in multi-resolution, for identifying cracks in carbon fiber reinforced polymer laminated beams. The efficacy of this concept is analytically demonstrated by identifying cracks in Timoshenko beams with general boundary conditions; and its applicability is validated by diagnosing cracks in a carbon fiber reinforced polymer laminated beam, whose mode shapes are precisely acquired via non-contact measurement using a scanning laser vibrometer. The analytical and experimental results show that multi-resolution modal Teager–Kaiser energy is capable of designating the presence and location of cracks in these beams under noisy environments. This proposed method holds promise for developing crack identification systems for carbon fiber reinforced polymer laminates.