향판용 관행수종(慣行樹種)과 대체가능수종(代替可能樹種)의 자유진동적 성질에 관한 연구 = Studies on The Free Vibrational Properties of Traditional and Replaceable Species for Sounding Board

다국어 초록 (Multilingual Abstract)

This study was carried out to investigate the free vibrational properties of traditional and replaceable species for sounding board, using piezoelectrical accelerometer and signal analyzer.
In the study, the frequency equations of free-free beam carrying a concentrated mass in the transverse vibration and of free-mass beam in the longitudinal vibration were used.
The results obtained were as follows.
1. Average values of dynamic modules of rigidity of Korean commercial species measured were as follows.
Paulownia tomatosa (Thunb.) Steudel : 5.590×10^9 dyne/㎠
Tilia amurensis Rupr.: 5.414×10^9 dyne/㎠
Macckia amurensis Rupr. : 10.044×10^9 dyne/㎠
Fraxirtus mandshurica Rupr.: 8.876×10^9 dyne/㎠
Ulmus davidiana var. japonica Nakai : 8.677×10^9 dyne/㎠
Pious rigida Miller : 6.33×10^9 dyne/㎠
Fiaxinus rhynchaphylla Hance : 4.666×10^9 dyne/㎠
2. The ratio of dynamic transverse Young's modules to dynamic modules of rigidity, E_T/G_(LT), was 24.922 for Fraxinus rhynchophylla Hance, which was the highest, 7.317 for Paulownia tomentasa (Thunb.) Steudel, which was the lowest among Korean commercial species measured.
3. The value of longitudinal dynamic Young's modules was about 3.7% and 19.8%, respectively, higher than those of transverse dynamic and static Young's modules.
The value of transverse dynamic Young's modules was about 15.5% higher than that of static Young's modules.
4. Predicted value of MOR in terms of correlation coefficient by transverse dynamic Young's modulus was slightly higher than that of static Young's modules, but no significance was found out.
5. Transverse dynamic Youne's modulus was (2.002 ± 0.288)×10^(11) dyne/㎠ for Fraxinus mandshurica Rupr., which was the highest, (0.601 ± 0.100)×10^(11) dyne/㎠ for Paulownia tomentosa (Thunb.) Steudel, which was the lowest among Korean commercial species measured.
The sound velocity of sitka spruce was 5,685 m/sec, which was the highest.
6. Internal friction of Paulownia tomentosa (Thunb.) Steudel was shown the lowest value among Korean commercial species, (8.795 ± 1.795)×10^(3), but was higher than that of sitka spruce, (7.331 ± 0.991)×10^(3).
Internal friction was shown negative correlation with density and dynamic Young's modules, respectively,
7. K value was affected largely by internal friction and was the highest, 2.225×10^8 for Paulvwnia tomentosa (Thunb.) Steudel and was the lowest, 0.550×10^8 for Fraxinus rhynchophylla Hance.
K value of Paulownfa tomentosa (Tunb.) Steudel was higher than that of sitka spruce and K values of melapi and cottonwood, which have been considered to be replaceable species with sitka spruce in the piano industry, were lower than those of Pautawnia tomentosa (Thunb.) Steudel and Tilia amurensis Rupr..