The Application of Modal Analysis in Hole-Defect in Lumber

Song, Shi Quan; Xu, Hua; Wang, Li Hai

doi:10.4028/www.scientific.net/kem.467-469.1776

Cited by 3 publications

(4 citation statements)

References 3 publications

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“…Despite the extensive studies of vibration nondestructive analysis on damaged wood-based composites, only a few effective and practical techniques were found for position and degree identification of wood-based composites damage (Choi et al 2007;Roohnia et al 2014;Reinprecht and Hibký 2011). Modal analyses has proven to be an effective method for defects detection (Khademieslam et al 2011;Ma et al 2008;Song et al 2011). Therefore, this paper focuses on the study of a practical method for effective detection of bubble defects in poplar LVL by combining wavelet packet energy curvature method with 3-scale wavelet packet decomposition of nondestructive vibration signals.…”

Section: Introductionmentioning

confidence: 99%

Detection and Location of Defects in Laminated Veneer Lumber by Wavelet Package Analysis

Zhu¹,

Liu²

2014

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Large numbers of vibration signals of wood-based panels are unsteady and complicated, which means that detection can be difficult. The wavelet transform is an effective method to detect these signals, which are otherwise difficult to detect using the Fast Fourier Transform (FFT). This paper presents a study on nondestructive detection of bubble defects seen in poplar laminated veneer lumber (LVL) using a combination of modal analysis and wavelet transform. The energy spectrum of wavelet packet decomposition due to a vibration signal is investigated. The vibration nondestructive test is used to study the relationship between bubble and changes of LVL physical properties. Results show that a bubble defect leads to a variation of energy dissipation in LVL vibration, and it is mode-dependent. For relatively small bubbles, the bubble-induced changes in natural frequencies are too small to be detected by the nondestructive method. However, by analyzing the energy spectrum of wavelet packet decomposition, smaller bubbles can be detected using the nondestructive vibration signals. The position and degree of defects can be ascertained by the wavelet packet energy curvature method at the same time.

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Section: Introductionmentioning

confidence: 99%

Detection and Location of Defects in Laminated Veneer Lumber by Wavelet Package Analysis

Zhu¹,

Liu²

2014

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“…Previous authors (CAM et al, 2004;DIVOS et al, 2001;SOBUE et al, 2010;SONG et al, 2011) studied the influence of defect on the dynamic behavior of wood in order to detect and positioned the local heterogeneities. Divos et al (2001), by the means of a time analysis technique, showed that the amplitude of the received signal was more sensitive to the presence of defect than the measurement of the propagation velocity.…”

Section: Introductionmentioning

confidence: 99%

“…The defect position was well identified, but the procedure was limited to the identification of two dominant defects. Song et al (2011) used a modal analysis technique allowing the determination of the mode shapes and resonance frequencies. They were not able to determine the position of the defect by the change rate of frequency.…”

Section: Introductionmentioning

confidence: 99%

Orientation and Position Effects of a Local Heterogeneity on Flexural Vibration Frequencies in Wooden Beams

Roohnia

Brancheriau²

2015

CERNE

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Studying the influence of defect on the dynamic behavior of wood in order to detect the local heterogeneities is of great importance in non-destructive testing of wood. The natural heterogeneities in wood are oriented in a volume. However, onedimensional models are still used in dynamic characterization of wooden beams. The aim of this study was to experimentally investigate the effects of the orientation and position of an artificial defect on the flexural vibration frequencies. Different batches of Fagus orientalis specimens were drilled in the radial direction at five positions along the specimen. Dynamic tests in free flexural vibration were performed on the specimens before and after drilling both in the longitudinal-radial (LR) and longitudinal-tangential (LT) bending plan. The behavior in free flexural vibration was found to be different depending on the position and orientation of heterogeneity. When the drilling axis lies in the bending plane (LR), the weakening of frequency was maximal at the location of an antinode of vibration. On the contrary, the frequency offset was maximal in the place of a vibration node when the drilling axis was orthogonal to the bending plane (LT). EFEITOS DA ORIENTAÇÃO E DA POSIÇÃO DE UMA HETEROGENEIDADE LOCAL SOBRE AS FREQUENCIAS DE VIBRAÇÃO DE FLEXÃO DE VIGAS DE MADEIRARESUMO: Estudar a influência de um defeito sobre o comportamento dinâmico da madeira, a fim de detectar as heterogeneidades locais, é de grande importância em ensaios não destrutivos. As heterogeneidades naturais da madeira são orientadas em um volume. Entretanto, modelos unidimensionais ainda são utilizados para a caracterização dinâmica de vigas de madeira. Objetivou-se, neste estudo, investigar experimentalmente os efeitos da orientação e da posição de um defeito artificial nas frequências de vibração de flexão. Diferentes lotes de amostras de Fagus orientalis foram perfurados na direção radial, em cinco posições, ao longo do comprimento da amostra. Os ensaios dinâmicos em vibração de flexão livre foram realizados nas amostras antes e depois da perfuração nos planos de flexão longitudinal-radial (LR) e longitudinal-tangencial (LT). O comportamento em vibração de flexão livre foi diferente em função da posição e da orientação da heterogeneidade. Quando o eixo de perfuração estava no plano de flexão (LR), o enfraquecimento das frequências foi máximo, no local de um antinode de vibração. O deslocamento de frequência, apresentou comportamento contrário, ou seja, foi máximo na zona de um nó de vibração, quando o eixo de perfuração era ortogonal em relação ao plano de flexão (LT).

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“…Sobue et al (2010) exploited an inverse solution procedure enabling the identification of the defect position within a beam, which was made possible by the resonance frequency of longitudinal vibrations. Song et al (2011) tested larch lumber pieces using a modal analysis technique, while frequency response functions (FRF) were derived. In their approach, modal parameters, including the first four natural frequencies and the first three modal shapes, were distinguished by the single modal method.…”

Section: Introductionmentioning

confidence: 99%

Identification of the Severity and Position of a Single Defect in a Wooden Beam

Roohnia¹,

Tajdini²

2014

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In the present paper changes of validity in Euler-Bernoulli's elementary theory of flexural vibration for homogeneous materials were tested with respect to changing severity and position of a single defect in wood. As an orthotropic material, wood has different material properties or strengths in different orthogonal directions. A set of absolutely clear specimens of oriental beech was chosen and hand drilled in different diameters (severities) at different relative distances from an end oriented in the R direction. A clear specimen showed a steady decrease in evaluated moduli of elasticity related to increasing mode numbers. After creating the defects, this steady decrease line showed some breakages. The slope breakages of modally evaluated elastic moduli in LT and LR vibrations are suggested as potential finger-prints of single hole defects in the specimen by considering the shape and rate of breakages in the decreasing lines. The recognition scenarios of slope breakages for defect severity and position are summarized.

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The Application of Modal Analysis in Hole-Defect in Lumber

Cited by 3 publications

References 3 publications

Detection and Location of Defects in Laminated Veneer Lumber by Wavelet Package Analysis

Detection and Location of Defects in Laminated Veneer Lumber by Wavelet Package Analysis

Orientation and Position Effects of a Local Heterogeneity on Flexural Vibration Frequencies in Wooden Beams

Identification of the Severity and Position of a Single Defect in a Wooden Beam

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