The Treatment Of Modified Acoustic Vibration Characteristics Of Cunninghamia Lanceolata

In this paper,Cunninghamia lanceolata with the dimension of 230mm×50mm×3mm was taken as the experimental material.The specimens were respectively treated with heat treatment(160?-220?,0.5-2h),crosslinking(5%glyoxal,24h),extraction(water,dichloromethane,benzyl-alcohol),and the combined treatment in order to improve the acoustic vibration performance of Cunninghamia lanceolata.The main conclusions are as follows.(1)When the heat temperature was not higher than 200? acoustic vibration of specimens reduced over time after rising first,when the heat treatment temperature was 220?,acoustic vibration properties of specimens declined after the trend of the rise and then fell again.220?-1h treatment was the best treatment on specimens,the specific modulus of specimens increased 11.66%and logarithmic decrement reduce 8.91%after the treatment.(2)Crosslinking reaction greatly reduced the logarithmic decrement of the specimens at the same time improve the specific modulus value of lumber.But the material density increased as the concentration of glyoxal solution became higher,this will make the specific modulus declined,so 5%was the best concentration for glyoxal solution as crosslinking treatment,and the specific modulus rose by 4.56%,logarithmic decrement decreased by 12.58%after the treatment.(3)The water extractives of specimens were terpene,alcohol and acid compounds,the specific modulus of specimens appeared a downward trend after cold water extraction,the average decline rate was 1.25%,the coefficient of logarithmic decrement appeared a slight upward trend,the average rise of 4.53%.While the organic extractives were terpene,alcohol and acid compounds,specific modulus of specimens extracted by methylene chloride and benzene alcohol average rose 3.42%and 6.82%respectively,logarithmic decrement average declined 7.61%and 8.86%,respectively.(4)The best three pre-treatments were respectively:220?-1 h heat treatment,the concentration of 5%glyoxal crosslinking treatment and benzyl-alcohol extraction for 24h.It was found that heat treatment can improve the concentration of 5%glyoxal impregnation rate,extraction process can extract the redundant glyoxal inside the specimens,thus the combined treatment can greatly reduce the density of the wood,the synergy of three methods further improves the acoustic vibration properties of Cunninghamia lanceolate,and the specifie modulus increased by 17·31%,the logarithmic decrement decreased by 18.29%after the combined treatment.