Fracture energy approach for the identification of changes in the wood caused by the drying processes

Pleschberger, Hermann; Hansmann, Christian; Müller, Ulrich; Teischinger, Alfred

doi:10.1007/s00226-013-0578-z

Cited by 7 publications

(4 citation statements)

References 20 publications

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“…To identify changes caused by the drying of solid wood, Pleschberger et al (2013) measured the specific FrE. They found that drying teakwood following a kiln schedule resulted in a small but significant decrease in the specific FrE in the RL as well as the TL crack propagation systems.…”

Section: Effects Of Tm On Toughnessmentioning

confidence: 99%

The toughness of hygrothermally modified wood

Hughes

Hill²,

Pfriem

2015

Holzforschung

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The mechanical properties of thermally modified wood are discussed with regard to toughness. The molecular origins of the mechanical properties and, in particular, the role of the hemicelluloses are considered. The important role of water and its interaction with the cell wall components is also examined. The properties are discussed from the point of view of composite theory, with the three main macromolecular components acting as reinforcement, matrix and interfacial coupling agent. The important role that hemicelluloses play as a coupling agent between the cellulosic microfibril reinforcement and the lignin-rich matrix is highlighted. Destruction of the hemicelluloses during the thermal modification process has a profound effect upon the mechanical behaviour.

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Section: Effects Of Tm On Toughnessmentioning

confidence: 99%

The toughness of hygrothermally modified wood

Hughes

Hill²,

Pfriem

2015

Holzforschung

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“…As a result, the surface layers of the material become wet, moisture content in different layers of the wood becomes equal and drying stresses relaxation happens. [15]. Because no energy is consumed during the cooling period of the wood, this leads to a significant reduction of its spending [7,10] and reducing the cost of drying process for 24% [7].…”

Section: Analysis Of Publicationsmentioning

confidence: 99%

“…The frequency of cycles "heating -cooling" during drying should be carried out only in the period when the wood contains free water. Subsequent application of such cycles does not affect the rate of bound moisture removal [10,15]. After the wood reaches moisture content Wcur = 20 % the temperature of the drying agent should be maintained at a constant level without oscillation until the end of the process [3,23].…”

Section: Analysis Of Publicationsmentioning

confidence: 99%

Influence of Temperature Fields on the Quality of Dried Wood Products

Pinchevska

Spirochkin

Zavialov

et al. 2021

MSF

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The reasons of white spots appearance in the middle of oak timber are determined. These white spots reduce the cost of the lamina made of oak timbers - the front covering of floorboards. It is proposed to intensify the drying process by using oscillating drying schedules to avoid this defect. A method for calculating the duration of such drying is proposed. This method includes the peculiarities of heating and cooling periods kinetics of oak timbers with 25 mm and 30 mm thickness. The inexpediency of using the oscillation of the drying agent parameters in the range of wood moisture content below 20% has been established. An adequate model for calculating wood temperature and air humidity during wood heating and cooling periods has been developed using heat and mass transfer criteria and experimentally determined oak wood moisture conductivity coefficient. Based on the results of theoretical and experimental studies oscillating drying schedules of different thickness oak timbers are offered. Tests of the proposed schedules in industrial conditions showed no discoloration of the central layers of European oak (Quercus robur) timbers. The drying process duration was reduced by 1.5–2.4 times and energy consumption were reduced by 1.53 times.

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“…In addition, in the crack in the longitudinal direction of the test piece cracks, the crack growth basically belongs to the unsteady state, and the bearing capacity of the test piece decreases rapidly. According to Pleschberger's research [51], the highest point of each curve represents the critical point of rapid crack growth, because the critical value Fcrit = Fmax can be determined. The slope of the straight line segment of each displacement load curve is inversely proportional to the crack length, and the inverse of the slope is the compliance 𝐶 𝑖 of the specimen corresponding to the different crack length.…”

Section: Determine the Energy Release Rate (G Ic )mentioning

confidence: 99%

Thermodynamic Approach for the Identification of Instability in the Wood Using Acoustic Emission Technology

Zhao

2020

Forests

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In order to monitor the crack growth of the wood material better and reduce failure risks, this paper studied the attenuation characteristics of acoustic emission signals in wood through pencil lead breaking (PLB) tests, in the aim of estimating the true amplitude value of the acoustic emission source signal. The tensile test of the double cantilever beam (DCB) specimens was used to simulate the crack tip growth within wood material, monitoring acoustic activity and location of crack tips within wood material using acoustic emission technology and digital image correlation (DIC). Results showed that the attenuation degree of acoustic emission signals increased exponentially as the propagation distance increased, and the relationship between relative amplitude attenuation rate and the propagation distance of the acoustic emission signal was established by the regression method, which provides the input parameters for the establishment of the crack instability prediction model in the next step. Based on a thermodynamic approach, a theoretical model for predicting crack instability was established, and the model was verified by DCB tests. The model uses acoustic emission parameters as the basis for judging whether the crack is instable. It provides theoretical support for the application of acoustic emission technology in wood health monitoring.

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Fracture energy approach for the identification of changes in the wood caused by the drying processes

Cited by 7 publications

References 20 publications

The toughness of hygrothermally modified wood

The toughness of hygrothermally modified wood

Influence of Temperature Fields on the Quality of Dried Wood Products

Thermodynamic Approach for the Identification of Instability in the Wood Using Acoustic Emission Technology

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