Shigehiro Hayashi

Study on The Optimization Method of Vibration Level for The New Standard of ISO6954

For the standard valuation of the vibration in the superstructure, ISO6954 is generally used, and the vibration levels must be designed to satisfy the valuation curve sufficiently which is set by this standard. We used the Optimization Method in this vibration control design. However, ISO6954 was substantially revised in December 2000. At the previous ISO6954, the vibration strength was found for every single number of the cycles and only of those maximum values was evaluated, based on the guideline. But after the revision, it introduces the weight function, based on ISO/CD2631-2 and then, we must evaluate an overall value with the amplitude set in the weight. So we must use multiple numbers of cycle components. With the revision of ISO6954, we have to correct the previous optimization system to correspond to the new standard. In this case, we pay attention to the engine force which has multiple numbers of cycle components and adopt the inertia power of the engine piston and connecting rod. In this study, we calculated the relationship between engine revolution and weighted root mean square value, and applied the sensitivity analysis to this relationship. Thus, we verified the validity of this sensitivity analysis. And more, we reconstructed the optimization method for the new standard. In this method, we adopted the previous standard as objective function for the purpose of lowering a specific response, and the new standard as constraint function. As a result of this study, we verified the validity of the new optimization method.

A Study on a Method to Obtain the Modulus of Velocity Distribution which is the Coefficient of the Damping Matrix based on the Theory of Periodic Boundary Layer

The outstanding obstacle to estimate vibration level is that the precise damping of fluid and structure can not be estimated because the mechanism of the damping has not been explicated. Recently, the damping matrix based on dissipation energy caused by fluid viscosity is obtained, but it has a weak point that virtual kinematic viscosity coefficient νw must be used in the shallow water to express the phenomena.In this paper, to express the phenomena in the shallow water, modulus of velocity distribution βw is introduced as a new parameter, and the damping matrix is redefined by using βw. We can regard βw as the parameter to estimate the influence of the water depth upon the damping matrix, because it is proportional constant on the damping matrix. If βw is given according to the water depth, not only the frequency response curve in the shallow water can be reproduced but also the frequency response curve in the deep water can be estimated by using the transfer function in the shallow water. Therefore it is necessary to develop a method to experimentally obtain βw. Hence the authors developed the method by using the partial differential iteration method which is one of the curve fit algorithm. The formulation and the results are described.

A STUDY ON THE EFFECT OF MEASUREMENT POINTS UPON REDUCED ADDED MASS MATRIX

A new method of combination analysis using experimental modal analysis and BEM was developed by the authors. To use this new method, the effect of arrangement of the measurement points upon the solution of the modal-BEM combinational analysis must be explained. In this paper, the effect is explained by some concrete parametric calculations on an ellipsoid of revolution. As the result of analysis on the calculations, 21 points distribution at regular intervals is enough for the number of the observation points to apply the method to the vertical bending vibration mode even below 4 node. Then the effect of rotation vector is analyzed, it is explained that the accuracy of the solution without considering the rotation vector cannot be better than on higher vibration mode, if many observation points are set. This is verified by comparison with experiments in deep water and shallow water.