Mehrab Madhoushi; Hamid Hatefnia
Abstract
In this study, ground penetration radar (GPR) was used to assess the internal defects and decay of structural old timber in buildings and compare it with the sound wood. For this purpose, twelve samples of three wood species of beech, oak and yew with dimensions of 120 × 60 × 400 mm, and ...
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In this study, ground penetration radar (GPR) was used to assess the internal defects and decay of structural old timber in buildings and compare it with the sound wood. For this purpose, twelve samples of three wood species of beech, oak and yew with dimensions of 120 × 60 × 400 mm, and as flat sawn were selected. Two samples from beech species with severe decay and two samples from oak species with mild decay were selected from old buildings. Sound and completely dry samples of these species (two samples from each species) were also obtained from forest trees as an indicator. Four yew samples without decay were selected only from the old buildings. Holes with a diameter of 2 and 8 mm were drilled in decayed and also two yew samples. The samples were scanned perpendicular to the fibers direction using a HF antenna of 2.3 GHz. The condition of data collection and processing were the same for all samples. After the initial data collection, in order to increase the resolution and better interpretation of the image, different filtration process was applied using image processing software Reflexw. The results showed that the relative dielectric coefficient was higher in decayed wood, and due to the difference in reflection coefficient between sound and decayed wood, they can be distinguished from each other. It was also possible to detect holes of 8 mm in oak and yew species.
Physics and Mechanical Wood
Parastoo Majdabadifarahani; Mehran Roohnia; amir lashgari
Abstract
DOR:98.1000/1735-0913.1398.34.87.66.1.1585.1588 This study deals with the possibility of evaluation and estimating the wood density in Quercus castaneifolia and Fagus orientalis. Wood samples were prepared and cut firstly in 4×20×30 cm (thickness×width×length). Then their density ...
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DOR:98.1000/1735-0913.1398.34.87.66.1.1585.1588 This study deals with the possibility of evaluation and estimating the wood density in Quercus castaneifolia and Fagus orientalis. Wood samples were prepared and cut firstly in 4×20×30 cm (thickness×width×length). Then their density was calculated after 72 hours of conditioning in an oven at 60°C temperature. In thermography process, the temporal temperature was monitored in 1st, 5th, 10, 20, 30, 45 and 60th minutes of cooling (monitoring steps). Investigating the effects of shape factor and dimension on thermographic density evaluation errors, the specimens were cut down in two more steps to 3×20×30 cm and 2×15×20 cm and the course of thermography experiments was repeated. The relationships of shape factor, density and the ratio of density to the shape factor with the logarithmic cooling rate were evaluated separately. Results showed that density without considering the shape factor variations was not sufficiently correlated to the cooling rate. But the ratios of the density to their proper shape factors were promising for the density evaluations from the cooling rates. However, it is suggested to revise this non-destructive method using a larger variety of the wood specimens and species.
Management and Economics wood
Mehrab Madhoushi; Vajihe Mojerian Galogahi; Mohammadreza Masteri Farahani
Abstract
Radiography is a method of non-destructive for evaluating the quality of wood construction machinery in order to detect the defects due to natural degradation. The objective of this study was to investigate the assessment of Poplar (Populus deltoides) and beech (Fagus orientalis) wood defects arising ...
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Radiography is a method of non-destructive for evaluating the quality of wood construction machinery in order to detect the defects due to natural degradation. The objective of this study was to investigate the assessment of Poplar (Populus deltoides) and beech (Fagus orientalis) wood defects arising from the decaying by using x-ray non-destructive method. In this study, for each of species, uncolored (no coating) and colored samples by acid catalyzed lacquers and nitrocellulose lacquers were used. Decay resistance test based on modified ASTM D1413 standard was performed. The decay process was done in the periods of 1, 2 and 3 months with use of Coriolus versicolor fungus at laboratory condition. After each of these periods, for the decay of the samples, x-ray imaging by using an imaging at the lateral, tangential and radial direction was done. Results of weight loss confirmed the presence of decay in the radiographic images. The results showed that after 1, 2 and 3 months of exposure to fungus, fungal degradation leads to weight loss in the painted and unpainted samples. So that, the weight loss caused by decay in beech was less than poplar samples. As well, the weight loss of unpainted was less than painted samples, which was also statistically significant. The x-ray results of unpainted and painted samples at the cross, tangential and radial directions indicate that decay has a more impact on beech in comparison to poplar wood structure. The study as well showed that the protective layer has partly a barrier for decay destruction in these samples.
