船体低次固有振動数の推定
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概要
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The first important means to reduce the hull vibration is to estimate the natural frequencies of the hull as accurately as possible at an early of designing in order to avoid resonance of the hull with the service revolution of the main shaft.In this paper, a method to estimate the natural frequencies of the principal vibration modes, i.e. 2 node vertical and horizontal, 3 node vertical and horizontal vibrations o ordinary cargo ships and tankers is proposed. This method is considered to enable to estimate the natural frequencies as easily and quickly as possible only by digital computation without any specially provided plan such as weight curve.The main points in the procedure are as follows : 1) For the sake of convenienve, weight and rigidity items are considered separately.2) Weight items is dealt with in the following three parts, i.e. hull weight, added weight to the hull and added virtual weight due to surrounding water.3) Weight distribution is assumed as symmetrical amidships and the correction for asymmetry is considered later.4) Effective weight factor for the vibration when supported at the nodes of a free-free uniform beam is introduced and the correction for the difference between the actural nodes and the asummed ones is cconsidered later.5) As regards rigidity, the effectiveness is determined corresponding to the vibration mode and the hull form.6) The correction for the effects of shear deflection and rotational energy are considered.7) Finally, the mean of the ratios of frequencies obtained from the above procedure to that actually measured is introduced as an empirical correction factor.
- 社団法人日本船舶海洋工学会の論文
- 1960-07-00