International Shipbuilding Progress - Volume 34, issue 394

Authors: Yang, Seung-Il

Article Type: Research Article

Abstract: This study presents the analysis of hull-propeller interaction in terms of the inviscid and viscous components of the thrust deduction and wake. The inviscid components are calculated by the method of singularities. The calculation of the inviscid thrust deduction needs the hull wake at the propeller plane as well as the wavemaking resistance of hull alone, propeller alone and hull with propeller. The viscous components are estimated by representing them as a function of the propeller thrust load after subtracting the inviscid components from total thrust deduction and wake which are obtained by propeller load variation tests. A new …method is established to predict the powering performance of a ship for a change of the propeller working condition due to the systematic modification of a parent hull form. This study also demonstrates a practical application to the hull form improvement of a container ship whose afterbody waterplane and section shapes are systematically varied. The hull form with optimum afterbody is chosen from the power point of view and the effectiveness of the method is considered to be acceptable showing good agreement with experiments. Show more

DOI: 10.3233/ISP-1987-3439401

Citation: International Shipbuilding Progress, vol. 34, no. 394, pp. 100-111, 1987

Authors: Wenschot, P.

Article Type: Research Article

Abstract: From more than one hundred Nickel-Aluminium (Ni-Al) bronze sand cast ship propellers, the effect of thickness on the properties of the material has been investigated. For this purpose the mechanical and corrosion fatigue properties have been measured on pieces of material from the thickest part of the castings with varying thicknesses from 25 mm to 450 mm. For each range of cast section thickness the average of the results is presented. It is observed that the properties of the casting material deteriorate with increasing section thickness. Linear regression analysis has been applied to establish a relation between the properties of …the casting material and section thickness. To provide a basis for the calculation of the corrosion fatigue strength of the casting material at a given section thickness, the measured corrosion fatigue life is related to the ultimate tensile strength. By comparing corrosion fatigue curves of small and large castings, corrosion fatigue strength conditions can be set up for each range of cast section thicknesses. It is shown that the deterioration of properties of Ni-Al bronze castings with increasing section thickness is associated with microstructural changes such as coarsening of grain size and phase structure attended with segregations. Relations can be given of tensile strength and corrosion fatigue properties to grain size. From these relations, conditions for the structure can be drawn up to obtain the optimum properties of the casting material, even for thick sections of large ship propellers. These conditions can only be fulfilled by extensive testing and control of the manufacturing process. Show more

DOI: 10.3233/ISP-1987-3439402

Citation: International Shipbuilding Progress, vol. 34, no. 394, pp. 112-123, 1987