The aim of this study is to clarify the physical ? properties of woods, one of the principal materials which can be satisfactory used for aircraft construction. §1. Young's moduluses of woods. Taking advantage of the well known formula in acoustics, viz. E = 4ρl^2f^2 where ρ is density, l is length, and f is natural frequency of woods, we can calculate Young's modulus E. Device for measuring natural frequencies is illustrated in Fig. 1. A is variable oscillator, B is triode valve, C is voice coil, E is test piece, F is pick up, G is amplifier, and H is volt meter. A test piece whose dimension is 1 cm2 in cross section and 1 m in length, is suspended at the center of gravity D. The vibration of the oscillator is intensified by B, and the rod resonate with this vibrations by means of the voice coil. The vibrations of the rod is converted into electric current through the action of the pick up F, and the voltages of the currents are measured by H. The results of measuring are tabulated in Table I. Each specimen contains water of 15-2O%. §2. Shearing strength of woods. The results of shearing strength measurements of woods (the same specimens as in the case of measuring Young's moduluses) is tabulated in Table II. The sketch of test piece is shown in Fig. 2. The unit of dimension is cm.
Mendeley出力
