Amir Homan Hemmasi; mostafa kohantorabi
Abstract
In this study the relationship between dynamic modulus of elasticity from longitudinal vibration method with static modulus of elasticity and bending strength in two directions: the Parallel machine direction and machine direction have been investigated. For this purpose 4 plates ...
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In this study the relationship between dynamic modulus of elasticity from longitudinal vibration method with static modulus of elasticity and bending strength in two directions: the Parallel machine direction and machine direction have been investigated. For this purpose 4 plates of particleboard with dimensions 124× 90 ×1.6 cm (length× width× thickness) were selected and free longitudinal vibration test in PMD and MD were performed on each plates. After that the primary plates were cut to four plates with dimensions 62× 44 ×1.6 cm (length× width× thickness) and longitudinal vibration test in PMD and MD were performed on each plates again. Finally each plates were cut to the beams with dimensions 36× 1.6 ×1.6 cm and longitudinal vibration test and and static bending test were performed on them. The results show that good correlation between dynamic modulus of elasticity from longitudinal vibration test and static modulus of elasticity and bending strength (result of beams extracted from each plates) in both size of plates in two size (124× 90 ×1.6 and 62× 44 ×1.6 cm) and beams extracted from each plates in two directions (PMD and MD). In addition there was good correlation between dynamic modulus of elasticity of longitudinal vibration from two size plates (124× 90 ×1.6 and 62× 44 ×1.6 cm). When the samples smaller than primary plates, the dynamic modulus of elasticity values were increased, that it due to the diffusion of waves in samples with larger dimensions. In general, according to results of this research it can be concluded that by applying the appropriate correction factors, longitudinal vibration method an efficiency method for calculation of dynamic and static modulus of elasticity and estimate of the modulus of rupture in plates in full sized.
Physics and Mechanical Wood
mostafa kohantorabi; Mehran Roohnia; Shadabeh Fathi
Abstract
In this study, 10 samples of beech wood, without apparent defect, with dimensions of 360 × 16 × 16 cm (length × radial × tangential) were selected, and after being exposed to variable temperature (60, 80, 100, 120, 140, 160, and 180°C) and moisture ...
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In this study, 10 samples of beech wood, without apparent defect, with dimensions of 360 × 16 × 16 cm (length × radial × tangential) were selected, and after being exposed to variable temperature (60, 80, 100, 120, 140, 160, and 180°C) and moisture content conditions (moisture content in conditions of: saturated with water (EMC=35±5%), equilibrium moisture content exposed to air (EMC=19±5%), and conditioning moisture content in a climatic chamber (EMC=12±2%), they underwent free flexural vibration test in two longitudinal-tangential and longitudinal-radial planes, and some of the physical, mechanical, and acoustical properties in both planes were investigated. The results showed that the correlation coefficient of the first three modes of flexural vibration in both planes under climatic chamber had a similar situation, but when the samples were in the water-saturated condition, they showed an adverse behavior in each plane. The effect of increasing the temperature above 100°C caused stresses resulting from shrinkage leading to the development of micro-cracks and reduction in the modulus of elasticity of cell walls and ultimately reduction in wave propagation ability of wood, thus increase in the damping vibration values in both longitudinal-tangential and longitudinal-radial planes of the samples. Also, the concurrent changes in modulus of elasticity and damping vibration in both vibration planes are a desirable indicator for monitoring the process from the primary logging process stages to processes such as wood drying and heat treatment.
Mohammad reza Ghaznavi; Mehran Rohnia; Abdolsaber Yaghmaeipour
Abstract
The possibility of estimating some acoustical properties of particleboard panels such as "Acoustical coefficient" and "Acoustical Converting efficiency" using vibrational non-destructive techniques was investigated. Particleboard plates with the dimensions of 50×50, 100×50 and 150×50 ...
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The possibility of estimating some acoustical properties of particleboard panels such as "Acoustical coefficient" and "Acoustical Converting efficiency" using vibrational non-destructive techniques was investigated. Particleboard plates with the dimensions of 50×50, 100×50 and 150×50 were used. For each plate, three replicated samples were prepared and after conditioning and the measurement of weight and dimensions, the flexural vibration test was performed on plate free-free test. In order to be ensured of the accuracy of the test, panels were converted to beams with the dimensions of 500×50×16 mm and then the same test was repeated on these samples. The results obtained from flexural vibration test of plates and beams were compared. The results indicated that it is possible to evaluate the Acoustic Coefficient and Acoustical Converting Efficiency factors with adequate accuracy using the testing method used in this study.
