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

Xiaodong Zhu, Yu Liu

Abstract


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.

Keywords


LVL; Defect detection; Non-destructive technique; Natural frequency; Wavelet transform; Energy curvature

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Welcome to BioResources! This online, peer-reviewed journal is devoted to the science and engineering of biomaterials and chemicals from lignocellulosic sources for new end uses and new capabilities. The editors of BioResources would be very happy to assist you during the process of submitting or reviewing articles. Please note that logging in is required in order to submit or review articles. Martin A. Hubbe, (919) 513-3022, hubbe@ncsu.edu; Lucian A. Lucia, (919) 515-7707, lucian.lucia@gmail.com URLs: bioresourcesjournal.com; http://ncsu.edu/bioresources ISSN: 1930-2126