Air-coupled ultrasound as an accurate and reproducible method for bonding assessment of glued timber

Sanabria, Sergio J.; Mueller, Christian A.; Neuenschwander, J.; Niemz, Peter; Sennhauser, U.

doi:10.1007/s00226-010-0357-z

Cited by 40 publications

(31 citation statements)

References 16 publications

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“…The reproducibility error of ACU NTM measurements of samples of type A repeated after one year was lower than 1.5% (Sanabria et al 2010b). Flaw monitoring was demonstrated by comparing two ACU NTM measurements (with a one-day interval) of samples of type C, obtained before and after introducing saw cut defects.…”

Section: Defect Monitoring With Difference Imagingmentioning

confidence: 95%

“…The samples were scanned with a 3 axes computed-controlled mechanical scanner synchronized with an arbitrary waveform generator and a data acquisition board. The system is detailed in (Sanabria et al 2010b) together with the transmission and receiver electronics for sample groups A and B. Samples C and D were assessed with a second system developed for thick glulam inspection.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

“…non et al 2008). ACU has previously been used to assess solid wood boards, particleboard, fiber composites, veneer and glued timber boards (Fagus GreCon Greten GmbH & Co. KG 1994;Blum 1997;Benedetti 2003;Stöessel 2004;Gan et al 2005;Hasenstab 2006;Hyvärinen 2007;Vun et al 2008;Blomme et al 2010;Dahmen et al 2010;Hsu et al 2010;Sanabria et al 2010b). To the best of our knowledge, there is no current ACU application for the inspection of glulam.…”

Section: Introductionmentioning

confidence: 99%

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Air-coupled ultrasound inspection of glued laminated timber

et al. 2011

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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 inband 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.

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Section: Defect Monitoring With Difference Imagingmentioning

confidence: 95%

Section: Theoretical Considerationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Air-coupled ultrasound inspection of glued laminated timber

et al. 2011

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“…Sanabria et al [8], [9] carried out air-coupled ultrasound slanted lateral method in order to assess delamination in GLT elements and demonstrated that the method was suitable to identify lack of adhesive in glued timber objects. Dill-Langer et al [10] showed the feasibility of detection of glue-line defects of GLT elements by means of ultrasonic methods.…”

Section: Introductionmentioning

confidence: 99%

Non-Destructive Assessment of Gluing in Cross-Laminated Timber Panels

Concu¹,

Fragiacomo²,

Trulli³

et al. 2017

WIT Transactions on Ecology and the Environment

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Cross Laminated Timber (CLT) panels are wooden structural products consisting of finger jointed boards glued together and arranged in orthogonal layers. The lamination process reduces the scatter of the board properties so that minor strength reducing features such as knots and other defects are dispersed in the product. CLT panels have very high axial load-carrying capacity and bending strength, due to their large resisting areas, and high shear strength. However, the structural performance of CLT panels depends on the proper application of the glue between the layers. The bond set up at the interface between longitudinal and orthogonal layers can be seriously compromised by the lack of gluing occurring during the production process. For this reason, quality control is an essential tool for verifying the correct gluing process of CLT panels. This paper illustrates the preliminary results of an experimental programme aimed to test the effectiveness of Ultrasonic Testing (UT) in detecting adhesion anomalies and defects in CLT panels. UT was carried out on several CLT panels having different configurations (length, thickness of the layers, number of layers, timber species). For each panel, the velocity of longitudinal stress wave V was measured along several paths perpendicular to the plane of the CLT panels. V data was numerically processed and then for each panel the distribution of V on a horizontal plane was graphically represented implementing the iso-velocity curves. The match between the low-velocity areas resulting from data processing and the unglued areas visually assessed was evaluated and critically discussed.

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“…The main drawbacks are poor, coupling pressure dependent reproducibility and the difficulties of performing imaging with sufficient spatial resolution. Recently an air-coupled ultrasound system has been developed that is not limited by these shortcomings (Sanabria et al 2010a).…”

Section: Introductionmentioning

confidence: 99%

Assessment of glued timber integrity by limited-angle microfocus X-ray computed tomography

et al. 2010

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Glued timber products have an extensive range of applications in construction. In this work a Microfocus X-ray Computed Tomography method was developed to inspect gluing defects in timber samples and was applied successfully on experimental data. The bonding plane was segmented into glued and non-glued regions and imaged with 5 mm resolution. Moreover, the gap topology between timber lamellas was precisely characterised. A limited-angle reconstruction with anisotropic frame binning together with a specific glue line readout method efficiently filters out undesired wood structure highlighting the information of the adhesive joint. This method imposes limitations on the size of the specimen in only one dimension. The presence and absence of glue could be detected for glue line thicknesses over 50 μm and air gaps larger than 150 μm could be characterised. Several information reduction approaches were combined in the reconstruction process to implement the assessment of a 100 × 100 mm 2 bonding plane in less than 40 s. Detektion von Fehlverklebungen in Holzbauteilen mittels Mikrofokus Röntgen-ComputertomographieZusammenfassung Holzverklebungen gewinnen zunehmend an Bedeutung. Im Rahmen dieser Arbeit wurde ein Mikrofokus Röntgen-Computertomographie Messverfahren

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Air-coupled ultrasound as an accurate and reproducible method for bonding assessment of glued timber

Cited by 40 publications

References 16 publications

Air-coupled ultrasound inspection of glued laminated timber

Air-coupled ultrasound inspection of glued laminated timber

Non-Destructive Assessment of Gluing in Cross-Laminated Timber Panels

Assessment of glued timber integrity by limited-angle microfocus X-ray computed tomography

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