Shinichi Ohno

Evaluation of SEA Loss Factors Using Structural Intensity Measurement.

This paper presents an estimation method for loss factors in Statistical Energy Analysis (SEA). SEA technique is applied to estimate the structure borne sound transmission in the middle and high frequency range, and the accuracy of SEA depends on the evaluation of factors required in SEA. Some evaluation methods for the factors have been proposed, but they require the complex analysis or the large amount of time for measurement and much knowbows. In this presented method, the power flow among subsystems in SEA is directly measured by the structural illtensity measurement, it needs no knowhows and a small scale of measurement. It is applied to make SEA models of some structures numerically and experimentally. As a result, it is confirmed that this proposed method gives the factors with high presicion for analysis.

Estimation of the Vibrational Power Supplied by a Machine that Generates Exciting Force to its Supporting Structure. The Case in which the Machine is not Separable from the Supporting Structure.

This paper proposes a method for estimating the vibrational power supplied by a machine that generates exciting force to its supporting structure through the coupling points. The basis of the method is that the vibrational power can be calculated using the mechanical impedance and the velocity at the coupling points. First, an equation for estimating the mobility at the coupling points when the machine cannot be separated from the supporting structure is derived. Then using a theoretical model of the machine and the supporting structure, estimated and theoretical values of the mobility and the vibrational power are calculated and compared, the result of which shows the validity of the method.

Contact Force Fluctuation Generated by Coupled Vibration System of Two Wheels and Railway Track.

Corrugation is a phenomenon in which periodical undulation is formed on a railway track by wheels running on it. One of the principal causes is the contact force fluctuation at the contact point between the wheel and railway track, which is generated by coupled vibration. In this study, contact forces between wheels and railway track are calculated using a model in which two masses move on an elastically supported beam and Hertzs contact elasticity between wheels and railway track is taken into account. As a result, it is shown that the ratio of the contact force of the trailing wheel to that of the leading wheel can be smaller or larger than unity and is uniquely determined by the relative contact position index introduced by us.

Estimation of the pressure of structure-borne sound radiated by an enclosure. Theory and basic examination by experiments.

A method of estimating the pressure of structure-borne sound included in noise radiated by an enclosure containing a machine that produces both noise and vibration is proposed. In this method, estimation is carried out using accelerations measured when the machine is in operation and transfer functions determined when the machine stops its operation. Specifically, the accelerations are ones measured at the points on the enclosure where the machine is connected to the enclosure, and the transfer functions are ones determined as complex ratios of the accelerations at the connecting forces to the connecting points from outside the enclosure. First, the theory of the method is derived and then its validity is the method is derived and then its validity is ascertained by experiments.

A Method to Correct the Boundary Condition in the Calculation of Natural Frequencies of the Bending Vibration of an Axially Compressed Bar

A method is proposed to correct the boundary condition in the calculation of natural frequencies of the bending vibration of an axially compressed bar that is compressed by a fiat anvil of the testing machine at its rounded end. In this method it is assumed that when the axial load is small, the boundary condition can be approximated by the simple support since the contact area is small and that when the load is increased the boundary condition approaches the fixed support since the contact area increases due to elastic deformation. The result of the calculation for a bar that is fixed at one end and is in contact with the anvil at the other rounded end shows a good agreement with that of the experiment. It is suggested that this method can be used to explain the change in the first-mode natural frequency of a bar lightly compressed at its flat end with increases in the load.