タール合材の動的応答

Non-destructive methods of testing structures have a good point which we may measure object as it is. We can understand mechanical properties of materials by the method. It is known as a general measurement method in rheology, which is the method to determine these properties by analysing the dynamic response of these oscillations.
On properties of materials, there are various problems in designing, constructing and others, so it is expected that they are made clear by applying method to materials.
The excitation to a testpiece is a unit impulse by knocking with the hammer. The response is received with the transducer, observed with the sychroscope and recorded with the camera.
The dynamic response is expressed in the equation of vibratory motion
(d^2x)/(dt^2) + 2ε (dx)/(dt) + n^2x = 0
where, ε : viscous resistanse, n : property frequency.
This motion is a damping oscillation, when n>ε>0.
The interpretation is as follows.
1. The period T' and the (double) amplitude ωk are measured from the oscillogram.
2. The damping ratio υ and the logarithmic decrement ∧ are determined.
3. The coefficients of the eqaution, ε and n, are derived from these factors.
4. The damping constant h is indicated by ε and n, i, e. h = ε/n.
The coefficient n^2 depends on the dynamical elastic modulus and the index h is the factor concerning the ratio of viscosity to elasticity. The quality of the tar mixture depends on the ratio of the tar content in the mixture by weight.
To determine the mechanical properties of material, two factors are noticed. They are property frequency n and damping constant h. The relation between the constant h and percentage contents of tar in the mixture (by weight) is shown in Fig 4. This result agrees with those from other tests. The method of testing will be much useful and practical.