Our previous report has theoretically shown that the wave velocity in the circumferential direction of the tyre tread is a function of its wave length, if the bending stiffness of the tread and the effect of the elastic foundation of the side-walls of the tyre are taken in consideration, and that the minimum velocity with respect to the wave length means the critical standingwave velocity. When the impact load is given at a point of the tread, the compound wave motion composed of many single wave motions is produced. From this point of view it is most important to devise to measure conveniently the minimum wave velocity, which means the critical speed. Thus, the method to measure the minimum velocity by using the time-counter device is proposed. This device is most conveniently available when lateral accelations of the tread are used as the imputs of the start-trigger and the stop-trigger of the time-counter. The statical test method to check the standingwave phenomenon was proposed in the previous paper and to prove this analytical results, the experimental results of the statical test by concentrated load at a point of the tread and the comparison with the actual data of the drum tests are explained with good agreement.
This paper presents an approximate method to calculate the response of cylindrical solid rocket motor cases to longitudinal shock or vibration. Approximate equations are derived by use of the principle of the virtual work under the assumption of zero lateral displacement. The equations are applied to the steady state forced vibration and the shock propagation of solid rocket motor models. Numerical examples considering the case of solid cylindrical core are presented and compared with the experiments studied by WAKAHARA. And also the authors' experimental results in the case of hollow cylindrical core are presented and compared with the theoretical results.
Experiments and theoretical analysis were made on the unbalance vibration of the single spool turbo-jet engine JR 200 and of its simplified model which simulated vibration characteristics of the engine. The results of theoretical analysis by the method of transfer matrix agree well with the experimental results in the case of simplified model. In the case of JR 200 engine which has rather small length/diameter ratio, agreement of theoretical values with experimental values are not so good as in the case of the model. However, this, theoretical analysis is considered to be useful for estimating and improving vibration characteristics of a new engine, in the early stage of development. By the experiments on the model with and without squeeze film damper bearing, it is proved that the damper of this type is very effective to reduce vibration severity at the critical speeds.
In the previous report (ref. 2), it was cleared that the unbalance vibration of single spool turbo-jet engines and vibration damping effect of the squeeze film damper bearing can be estimated accurately enough for design purpose, by the theoretical calculation. Following these results, calculations of unbalance vibration of typical 2 models of 2 spool fan-jet engine were made, considering different rotational speeds of rotors. The results of the calculation show that- (1) Medium to large size 2 spool fan-jet engines have many resonance frequencies in their speed ranges, and at some speeds and at some positions, amplitude of vibration will exceed critical value, in the case of no damper bearing. (2) In the most cases, amplitude of vibration at the critical speeds can be suppressed to safe value, by using one or two damper bearing (s) at the adequate position (s).
Two major assumptions adopted in the current helicopter motion analysis are examined. It is shown numerically that to neglect the laterallongitudinal coupling motion may lead to about 20% error in the control response at lower fre- quencies, and that the quasi-static rotor assumption (or HOHENEMSER's assumption) can also produce about 20% error in the pitch damping at the frequency region of the short period mode. The coupling effect is remarkable for blades with large Lock number and is sensitive to the inflow distribution, while the effect of rotor dynamics is predominant for rotors with small Lock number or small rotational speed.