ねじり試験による木材のせん断弾性係数の測定(II) : 幅変動法の検討

In this paper，the measurement method of shear moduli uslng the plural specimens with different aspect ratios，namely width-variation method，was examined by comparing the moduli obtained from the torsional moment-shear strains relations of single specimens.
Sitka spruce（Picea sitchensis Carr.）and konara（Japanese oak，Quenrcus serrata Murray）were used
for the specimens. Specimens were cut with various angles between the grain direction and an axis of geometrical symmetry，which was deined as‘grain angleφ”Specimens on which strain gauges were bonded were twisted around the radial direction. Shear moduli on the side planes were obtamed by the torsional moment shear strain relations and the torsional moment-torsional angle relations of plural specimens. These shear moduli obtained by the different procedures were compared with each other，and following results were obtained
（l）When the grain angle φ was in the range near around 45 degrees，the shear moduli were obtained properly by the both methods because the speicmen was nearly isotropic.
（2）When the grain angle φ approached to O degrees，the shear modulus of spruce was obtained properly. Nevertheless，the shear modulus of konara was not given by the width-variation method properly because the shear modulus on the plane with large stiffness varied by the variance of shear modulus on the plane with small stiffness.