Nondestructive Evaluation of Effects of Moisture Content and ‎Temperature ‎on the ‎Elastic Properties of Beech Wood ‎Using Flexural Vibration Test

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 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.‎

Keywords

• Moisture
• Temperature
• Vibration
• Online control
• Timoshenko beam theory
• Acoustic