Shrinkage Strain in Wood under Kiln Drying Conditions

Ciprian LAZARESCU
Ph.D.Student, Research Assistant – Dept. of Wood Science – University of British Columbia
Address: 2005-2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
Tel.: 001 604 8228203. E-mail: ciprilaz@interchange.ubc.ca

Hongwei WU
Ph.D., Post-Doctoral Fellow – Dept. of Wood Science – University of British Columbia
Address: 2005-2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
Tel.: 001 604 8226153. E-mail: hwu@forestry.ubc.ca

Stavros AVRAMIDIS
Ph.D., FIWSc, FIAWS Professor – Dept. of Wood Science – University of British Columbia
Address: 2005-2424 Main Mall, Vancouver, BC V6T 1Z4, Canada
Tel.: 001 604 8226153. E-mail: stavros.avramidis@ubc.ca

Abstract:
The results of a study of wood shrinkage strains during drying at different temperatures and relative humidities are presented and discussed in this paper. The tests were performed on small clear wood specimens sawn from the tree trunk in such a manner that either the tangential or the radial direction was parallel to the length of the specimen. So far the experiments have been carried out on western hemlock (Tsuga heterophylla) while drying at 40, 60 and 70˚C. It was found that the temperature and the target moisture content have a significant influence over the shrinkage strain not only in terms of final maximum shrinkage strain but also the amount of time necessary to reach these values. Based on these experiments a material model for strains-stresses relationship during drying will be developed.

Key words: drying, shrinkage, strain, stress, hemlock, timber