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Silva Fennica 1926-1997
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Articles by G. Don Kulasiri

Category: Research article

article id 460, category Research article
Hong Ling, Sandhya Samarasinghe, G. Don Kulasiri. (2009). Modelling variability in full-field displacement profiles and Poisson ratio of wood in compression using stochastic neural networks. Silva Fennica vol. 43 no. 5 article id 460. https://doi.org/10.14214/sf.460
Vertical and horizontal displacement profiles in compression parallel-to-grain in a 20 x 20 mm area (30 x 21 or 630 points) in the Tangential–Longitudinal (T–L) and Radial Longitudinal (R–L) sections of small wood columns were obtained from digital image correlation applied to simultaneously captured images of the two surfaces. These consisted of 21 displacement realisations of 30 points along the length of the specimen. They revealed considerable local variations. Stochastic neural networks were successfully developed to simulate trends and noise across and along a specimen in both displacements as well as Poisson ratios in T–L and R–L sections for two selected load levels of 20kN and 40kN. These networks specifically embed noise characteristics extracted from data to generate realistic displacement and Poisson ratio realisations with inherent variability. Models were successfully validated using independent data extracted based on bootstrapping method with high accuracy with R2 ranging from 0.79 to 0.91. The models were further validated successfully using a second approach involving Confidence Intervals generated from the data extracted from the models. Models and experimental results revealed that for 20kN load, both vertical and horizontal displacements in T–L section were less heterogeneous across the specimen (smaller vertical shearing and horizontal strain, respectively) than those in the R–L section. For the 40kN load, both displacement profiles in the T–L section were less noisy and more compact than those for the 20kN load indicating less heterogeneity due to compaction of structure. In the R–L section, larger vertical shearing and horizontal strains persisted at 40 kN load. Poisson ratio decreased with load and it was nonlinear in both sections but T–L section showed much less noise across the specimen than the R–L section.
  • Ling, Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Canterbury, New Zealand ORCID ID:E-mail:
  • Samarasinghe, Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Canterbury, New Zealand ORCID ID:E-mail: sandhya.samarasinghe@lincoln.ac.nz (email)
  • Kulasiri, Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Canterbury, New Zealand ORCID ID:E-mail:
article id 630, category Research article
S. Samarasinghe, G. D. Kulasiri. (2000). Displacement fields of wood in tension based on image processing: Part 2. Crack-tip displacements in mode-I and mixed-mode fracture. Silva Fennica vol. 34 no. 3 article id 630. https://doi.org/10.14214/sf.630
Near tip displacement fields for tensile loaded cracked rubber and wood with a crack parallel-, perpendicular-to-grain, and a parallel-to-grain crack inclined 30°, 45°, and 60° to the load axis were obtained from digital image correlation (DIC). Theoretical displacements were also obtained for rubber and wood using isotropic and orthotropic fracture theory, respectively. The results showed that DIC can reveal fine details of the nature of displacements and the influences of crack tip in both rubber and wood. Experimental crack tip displacements for wood compare well with theory; particularly, when load is perpendicular-to-grain. Some anomalies were found in the tip displacements in the direction of the tracheids due to the unique nature of their behaviour not accounted for by theory. Mixed-mode crack tip displacement fields for wood clearly showed the increasing influence of crack angle on the displacements, and the displacements perpendicular to crack compared very well with theory. The displacements parallel to crack showed some variations owing to the involvement of tracheids.
  • Samarasinghe, Lincoln University, Appl. Computing, Mathematics and Statistics Group, P.O. Box 84, Canterbury, New Zealand ORCID ID:E-mail:
  • Kulasiri, Lincoln University, Appl. Computing, Mathematics and Statistics Group, P.O. Box 84, Canterbury, New Zealand ORCID ID:E-mail: kulasird@tui.lincoln.ac.nz (email)
article id 629, category Research article
S. Samarasinghe, G. D. Kulasiri. (2000). Displacement fields of wood in tension based on image processing: Part 1. Tension parallel- and perpendicular- to grain and comparisons with isotropic behaviour. Silva Fennica vol. 34 no. 3 article id 629. https://doi.org/10.14214/sf.629
Displacement fields for tensile loaded rubber and wood in parallel- and perpendicular-to-grain were obtained from digital image correlation. The results showed that the digital image correlation can reveal fine details of the nature of displacements in both rubber and wood. It was found that when load is perpendicular-to-grain, the lignin matrix produces uniform displacement fields similar to that of isotropic rubber. Uniform displacement fields also observed when lignin is involved in contraction due to Poisson effect in parallel-to-grain tension. However, when tracheids carry the load in parallel-to-grain loading, or are compressed in perpendicular-to-grain loading, a complex displacement pattern distorted by internal shear stress and slippage is produced.
  • Samarasinghe, Lincoln University, Appl. Computing, Mathematics and Statistics Group, P.O. Box 84, Canterbury, New Zealand ORCID ID:E-mail:
  • Kulasiri, Lincoln University, Appl. Computing, Mathematics and Statistics Group, P.O. Box 84, Canterbury, New Zealand ORCID ID:E-mail: kulasird@tui.lincoln.ac.nz (email)
article id 652, category Research article
M. J. Youngman, G. D. Kulasiri, I. M. Woodhead, G. D. Buchan. (1999). Use of combined constant rate and diffusion model to simulate kiln-drying of Pinus radiata timber. Silva Fennica vol. 33 no. 4 article id 652. https://doi.org/10.14214/sf.652
This paper presents the use of a combined constant drying-rate and diffusion model to simulate the drying of Pinus radiata timber under kiln-drying conditions. The constant drying-rate and diffusion coefficients of the model, which control the drying rate of individual pieces of timber, were determined from calibrating the model against the experimental drying curves obtained under the kiln-drying conditions. The experimental drying curves were obtained from the gravimetric measurements of the moisture content of timber during kiln drying. Statistical relationships were developed for the constant drying-rate and the diffusion coefficients of the model as functions of kiln temperature and the dry basis density of timber. To determine the effects of variability of timber, a simulation scheme was developed based on the model, the probability distribution of the density of timber, the equations for the constant drying-rate coefficient and the diffusion coefficient. The model and the associated simulation method provides a simple way to estimate the drying time of a stack of timber using parameters determined from experimental results for the specific timber kiln.
  • Youngman, Lincoln University, Appl. Management and Computing Division, P.O. Box 84, Canterbury, New Zealand ORCID ID:E-mail:
  • Kulasiri, Lincoln University, Appl. Management and Computing Division, P.O. Box 84, Canterbury, New Zealand ORCID ID:E-mail: kulasird@tui.lincoln.ac.nz (email)
  • Woodhead, Lincoln University, Appl. Management and Computing Division, P.O. Box 84, Canterbury, New Zealand ORCID ID:E-mail:
  • Buchan, Lincoln University, Appl. Management and Computing Division, P.O. Box 84, Canterbury, New Zealand ORCID ID:E-mail:

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