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Rosner, S; Konnerth, J; Plank, B; Salaberger, D; Hansmann, C.
(2010): Radial shrinkage and ultrasound acoustic emissions of fresh versus pre-dried Norway spruce sapwood
TREES-STRUCT FUNCT. 2010; 24(5): 931-940. FullText FullText_BOKU

Acoustic emission (AE) and radial shrinkage were compared between fully saturated fresh and pre-dried Norway spruce sapwood during dehydration at ambient temperature. Hydraulic conductivity measurements, anatomical investigations on bordered pits and X-ray computed tomography (CT) scans were done to search for possible AE sources other than the breakage of the water columns inside the tracheids. Both fresh and pre-dried specimens showed radial shrinkage due to drying surface layers right from the beginning of dehydration, which induced almost no AE. Whereas no dimensional changes occurred in pre-dried wood thereafter, fresh wood showed a rapid shrinkage increase starting at 25% relative water loss. This dimensional change ceased when further moisture got lost and was even partially reversed. AE of fresh wood showed much higher activity and energy, which is a waveform feature that describes the strength of the acoustic signal. Extremely high single AE energy events were detected at this critical stage of dehydration. After partial recovery from shrinkage, neither dimensional changes nor AE activity showed differences between fresh and pre-dried wood after more than 80% relative moisture loss. Our results suggested that fresh sapwood is more prone to dehydration stresses than pre-dried sapwood. Differences in AE and shrinkage behavior might be due to the weakening or distortion of the pit membranes (cavitation fatigue), pit aspiration, structural changes of the cell walls and micro-checks, which occurred during the first dehydration cycle.
Authors BOKU Wien:
Hansmann Christian
Konnerth Johannes
Rosner Sabine
BOKU Gendermonitor:

Find related publications in this database (Keywords)
Bordered pits
Cavitation fatigue
Functional wood anatomy
Hydraulic conductance
Norway spruce (Picea abies)
Acoustic emission testing
Wood shrinkage
X-ray computed tomography

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