Damping loss in wood at mid kilohertz frequencies

✍ Scribed by J. I. Dunlop

• Book ID: 104751710
• Publisher: Springer
• Year: 1978
• Tongue: English
• Weight: 633 KB
• Volume: 12
• Category: Article
• ISSN: 0043-7719
• DOI: 10.1007/bf00390010

✦ Synopsis

The dynamic moduli and logarithmic de, crement of Rimu (Dacrydtum cupre~inum) were measured along the grain and perpendicular to it in the frequency range 45-85 kHz using a Marx regenerative oscillator system. The moduli and de~ement were observed to exhibit strong dispersions between -20 ~ and -80 ~ the actual temperature being dependent on measurement frequency and moisture content of the sample. The activation enthalpy of the dispersion mechanism varied from 3.9 kcal/mole at moisture contents in excess of 7 % to 6 kcal/ mole at lower (1%) moisture content. Impregnation of the wood with solvents produced dispersion effects different from those associated with water impregnation. It is postulated that this mechanical dispersion observed in moisture-bearing wood results from the motion of the adsorbed water molecules. * The author wishes to thank lhe Head of the Princes Risborough Laboratory, Building Reseaxch Establishment, for the hospitality and facilities provided during his year's residence, and also the Council of the University of New South Wales for their generous allowance of sabbatical leave. 0043-7719178100121004911 2.80