Air-coupled ultrasound inspection of glued laminated timber
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Sergio J. Sanabria
,
Roman Furrer
Abstract
A novel air-coupled ultrasound (ACU) 120 kHz normal transmission system enabled successful imaging of bonding and saw cut defects in multilayered glulam beams up to 280 mm in height with a signal-to-noise ratio (SNR) of 40 dB. The main wave propagation paths were modeled; quasi-longitudinal and quasi-transverse modes were coupled in each lamella and the sound field was found to be shifted from the insonification axis as a function of the ring angle, leading to interference of wave paths in the receiver and to 15 dB amplitude variability in defect-free glulam. The assessment was improved with spatial processing algorithms that profited from the arbitrary scanning resolution and high reproducibility of ACU. Overlapped averaging reduced in-band noise by 15 dB, amplitude tracking captured only the first incoming oscillation, thus minimizing diffraction around defect regions, and image normalization compensated 6 dB of systematic amplitude variability across the fiber direction. The application of ACU to in situ defect monitoring was demonstrated by using multiparameter difference imaging of measurements of the same sample with and without saw cut defects. The segmentation of the defect geometry was improved significantly and the amplitude variability was reduced by 10 dB. Further work is planned to model additional insonification setups and grain and density heterogeneities.
©2011 by Walter de Gruyter Berlin New York
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- Composition of the heartwood essential oil of incense cedar (Calocedrus decurrens Torr.)
- Meetings
- Meetings
Articles in the same Issue
- Publisher’s Note
- Publisher’s Note
- ORIGINAL ARTICLES
- Brightness reversion of eucalyptus kraft pulp: Effect of carbonyl groups generated by hypochlorous acid oxidation
- MgSO4 vs. Mg(OH)2 as a cellulose protector in oxygen delignification
- Hydrogen peroxide and supercritical carbon dioxide: a new bleaching stage for Eucalyptus kraft-O2 pulps
- Preparation and physical characterization of strongly swellable oligo(oxyethylene) lignin hydrogels
- Activation of pine kraft lignin by Fenton-type oxidation for cross-linking with oligo(oxyethylene) diglycidyl ether
- Determination of pectin content of eucalyptus wood
- Theory of transport processes in wood below the fiber saturation point. Physical background on the microscale and its macroscopic description
- The effect of galactan content on the mechano-sorptive strain in loblolly pine
- Genetic and environmental variation in heartwood colour of Australian blackwood (Acacia melanoxylon R.Br.)
- Aging of wood: Analysis of color changes during natural aging and heat treatment
- Thermal behaviour of Norway spruce and European beech in and between the principal anatomical directions
- Air-coupled ultrasound inspection of glued laminated timber
- Optical characteristics of wood investigated by time-of-flight near infrared spectroscopy
- Comparison of NDE techniques for assessing mechanical properties of unjointed and finger-jointed lumber
- Potential of pulp and paper sludge as a formaldehyde scavenger agent in MDF resins
- FT-IR imaging microscopy to localise and characterise simultaneous and selective white-rot decay within spruce wood cells
- Effects of ionic strength, monoethanolamine, copper, and pH on adsorption of alkyl dimethyl benzyl ammonium chloride in wood
- Long-term performance of fused borate rods for limiting internal decay in Douglas-fir utility poles
- SHORT NOTE
- Composition of the heartwood essential oil of incense cedar (Calocedrus decurrens Torr.)
- Meetings
- Meetings
