جستجوی مقالات مرتبط با کلیدواژه « میرایی ارتعاش » در نشریات گروه « صنایع چوب و کاغذ »

In this research, the effect of preheating in nitrogen medium on acoustic properties of walnut and white mulberry’s boards was studied. Sapwood boards of 300×20×20 mm with the green moisture content were prepared. Heat treatments were applied at 140 and 160 oC under pressure of 2 pascal for 30 and 60 minutes. Following the heat treatment, the samples were dried in a convectional laboratory kiln of 8% at 50 oC, relative humidity of 50%, and air velocity of 1 m/s to the average final moisture content of 8%. Using the free vibration method on free- free bar, the dynamic modulus of elasticity and damping factor were evaluated. Results revealed that the heat-treatment at 140 oC for 30 minutes did not have a significant effect on vibration properties of the wood samples. On the other hand, the heat-treatment at 160 oC caused a significant increase in dynamic modulus of elasticity and also a reduction in the damping factor of walnut and white mulberry samples. The FTIR spectroscopy and X-ray studies showed that the degradation of cell-wall polymers and increase in the crystallinity of the walnut wood specimens occurred due to heat treatment at 160 0C.