Effects Of Thermal And Ultrasound Pre-treatments On Vibrated Properties Of Metasequoia

In this paper, metasequoia (Metasequoia glyptostroboides Hu & Cheng) with the dimension of 230mm×50mm×3mm was taken as the experimental material. The thermal treatment, ultrasound pre-treatment and ultrasound-thermal union experiment were carried out at the temperature of 120℃-220℃, the ultrasound power of 160-340W, and treated time of 3-12min, respectively to improve the acoustic properties of metasequoia. The main conclusions are as follows.1. The thermal treatment, ultrasound pre-treatment and ultrasound-thermal union treatment had improved specific module of metasequoia by 44.39%-82.87%、34.93%-65.33%、 82.19%-122.22% respectively, and had decreased the logarithmic decremen by 4.06%-9.45%, 8.98%-16.41%、20.56-24.32% severally. However, when the thermal treated temperature was too high and the ultrasound treated time was too long, the specific module would decrease and the logarithmic decremen would increase on the contrary, and the acoustic properties of wood decreased simultaneously. The ultrasound-thermal union treatment has the optimal result by superimposing the advantages of two treated measures. The process optimization of the union treatment is the ultrasound power of 340W, treated time of 9min, then dried with solar energy intermittently, finally treated with temperature of 200 ℃ and keep for 30min.2. The content of benzene-ethanol extractives of the specimens decreased 9.12%,66.68%, 80.62% averagely after thermal, ultrasonic, and union treatment respectively, for 1%NaOH the decrese were 11.35%、19.35%、26.31%, for hot water the decrese were 26.19%,31.43%,52.66%. Different kinds of extracts decreased with the increase of thermal temperature, the power and treated time of ultrasound. These three kinds of extracts had significant influence on logarithmic decremen of metasequoia, and the logarithmic decremen decreased as the extracts becaming less.3. The crystallinity of metasequoia increased 3.87%,4.20%,7.45% averagely after thermal, ultrasonic, and union treatment respectively. The crystallinity increased with the advance of thermal temperature, the power and treated time of ultrasound. However, when the thermal treated temperature was too high and the ultrasound treated time was too long, the crystallinity would decrease. The crystallinity of metasequoia had significant influence on its specific module, and the specific module increased as the crystallinity becaming larger.