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Acoustic emission related to instantaneous strain in Tasmanian eucalypt timber during seasoning

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Summary

Acoustic Emission (AE) was measured in 30 mm-thick backsawn and quartersawn Tasmanian Oak (Eucalyptus regnans F. muell) boards drying at temperatures in the vicinity of 20 °C. By varying the diffusion coefficient used in a non-linear drying simulation program, calculated half-thickness moisture profiles were matched to measured profiles in a sample board. Once the measured and calculated drying behaviour was satisfactorily matched, the AE measured in an endmatched board closely followed the surface instantaneous strain calculated with the program. The AE activity increased once the surface instantaneous strain attained the proportional limit. The AE is not simply related to drying temperature or humidity but rather to a complex interaction between the two parameters.

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Abbreviations

ca :

Moisture concentration in air (kg/m3)

cs :

Moisture concentration at the board surface (kg/m3)

D:

Diffusion coefficient (m2/hr)

DBT:

Dry bulb temperature (°C)

ei :

Instantaneous strain

RH:

Relative humidity (%)

WBT:

Wet bulb temperature (°C)

ρ:

Basic density (kg/m3)

References

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Additional information

The author is pleased to acknowledge the assistance of Emeritus Professor A. R. Oliver, Associate Professor P. E. Doe, University of Tasmania, the Australian Furniture Research and Development Institute and the Tasmanian Timber Promotion Board

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Booker, J.D. Acoustic emission related to instantaneous strain in Tasmanian eucalypt timber during seasoning. Wood Sci.Technol. 28, 249–259 (1994). https://doi.org/10.1007/BF00204211

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Keywords

  • Diffusion Coefficient
  • Timber
  • Acoustic Emission
  • Complex Interaction
  • Material Processing