Document Type : Physics and Mechanical Wood
Author
Ph.D.student in wood science and Instructor, Department of Wood and Paper Industry Sciences, National University of Skills
Abstract
Background and Objective: Wood is a unique renewable natural resource that plays a vital role in the socio-economic development of countries. Walnut (Juglans regia) is a durable and mature-trunked tree species found in temperate and subtropical forests of Asia, Europe, and America. In Iran, it is one of the most important wood species, widely used in industries such as furniture, veneer, and construction panels. Therefore, obtaining detailed physical and mechanical characteristics of this species is essential.
Materials and Methods: In this study, sampling was carried out from walnut trees in the forests of Barkala village, Kordkuy County (Golestan Province), at an altitude of 1434 meters above sea level. Three healthy trees were randomly selected and harvested. The average diameter at breast height was 51.3 cm, and the average age of the trees was approximately 51 years. Tests were conducted according to ISO 3129 and ASTM D-143 standards for physical and mechanical properties, respectively. Approximately 319 samples were tested for physical properties and 246 for mechanical properties. Physical characteristics examined included oven-dry density, basic density, green density, maximum moisture content, shrinkage, and swelling. Mechanical properties included bending strength, modulus of elasticity, compression parallel to grain, tensile strength (parallel and perpendicular), shear strength parallel to grain, hardness, and cleavage resistance. The samples prepared for mechanical tests were placed in a climate chamber for four weeks at a temperature of 20 degrees Celsius and a relative humidity of 65 percent so that the humidity of all samples during mechanical tests was 12. To perform mechanical tests, a SANTOM 150 testing machine with appropriate load cells for each test located at Imam Mohammad Baqer National University of Skills and Knowledge, Sari, was used.
Results: The green, oven-dry, and basic densities were found to be 1.16, 0.63, and 0.54 g/cm³, respectively. Longitudinal, radial, tangential, and volumetric shrinkage were 0.4%, 5.65%, 8.30%, and 14.35%, respectively. Corresponding swelling values were 0.51%, 5.71%, 8.88%, and 15.1%, and the maximum moisture content reached 105.14%. Mechanical properties measured included: bending strength (102.46 N/mm²), modulus of elasticity (10246.02 N/mm²), compression parallel to grain (34.11 N/mm²), tensile strength parallel and perpendicular to grain (146.17 and 9.66 N/mm²), shear strength parallel to grain (11.54 N/mm²), hardness (6622.70 N), and cleavage resistance (1.69 N/mm²). The results obtained show the positive effect of age on the mechanical properties of wood. Of course, factors such as geographical factors and altitude above sea level also have an effect on the physical properties of wood, such as swelling and elongation of wood. Of course, in this study, it was found that the effect of tree age on the mechanical properties of wood has a completely positive effect.
Conclusion: The walnut trees from the Barkala village of Kordkuy in Golestan Province showed favorable density and generally superior mechanical properties compared to walnut wood from four other provinces previously studied. This may be due to the higher average age of the trees in this region. Given the strong mechanical properties, this wood is well-suited for use in parquet flooring, furniture, veneer, and construction panels
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