Image Analysis Method to Quantify Fibre Separation in Wood Subjected to Fatigue Loading, 1999 International Mechanical Pulping Conference Proceedings

R. Thiruvengadaswamy

Dept. of Mechanical Engineering

D. Ouellet

Pulp and Paper Research Institute of Canada

Dept. of Mechanical Engineering

University of British Columbia

Pulp and Paper Centre

Fundamental aspects of mechanical pulping have often been studied by subjecting wood samples to cyclic loads under controlled laboratory conditions. Several methods have been developed to quantify fatigue damage in these samples, but none of them provides a direct measure of the degree of fibre separation resulting from the formation of cracks. This makes it difficult to understand the early stages of wood breakdown. To address this problem, we have developed an image analysis method to quantify the degree of fibre separation observed in transverse cross-sections of wood samples. The method was used to assess the effect of strain, strain rate, temperature and number of cycles on fibre separation in samples subjected to radial compression. By plotting the fraction of separated fibres against specific energy consumption, we were able to assess the efficiency of various loading conditions. The results indicate that strain rate strongly affects the efficiency of fibre separation. In general, a higher temperature (96 o C vs 25 o C) resulted in a lower proportion of separated fibres, but at a much lower energy requirement, thus leading to more efficient fibre separation. The image analysis method offers a reliable way to characterize fibre separation. The method also has the unique advantage of being applicable to samples loaded under any combination of compression and shear, which opens the door for a comparison of these modes of loading in future work.