International Shipbuilding Progress - Volume 57, issue 3-4

Authors: Tian, Yu | Ji, Zhuo-Shang

Article Type: Research Article

Abstract: The aim of this study is to present a simple method to assess the effects of locally low-cycle fatigue (LCF) damages on the reduced ultimate strength of unstiffened ship plate structures. A LCF damage model is formulated and then it is applied to the finite element analysis (FEA) in order to identify the continuum damage mechanics (CDM) theory to be introduced in the ship structure designs. A series of non-linear FEA of simply supported plates with various locations and sizes of damages have been carried out. The large deformation theory is utilized during plastic material conditions. Based on the FEA …results, an analytical formula is derived for estimating the reduced ultimate strength of ship plates with localized damages under uniaxial compression. In the assessment method, the reduced elastic modulus E˜ is defined to calculate the material damage and the effective width b˜ is defined to calculate the plate cross sectional area damage. A comparison between the predicting formula results and the FEA results is made for a bulk carrier's bottom plate. The presented approach is applicable for a uniaxial stress state and it is used throughout this study. Show more

Keywords: Ship engineering, low-cycle fatigue (LCF), damage, reduced ultimate strength, continuum damage mechanics (CDM), plastic mechanics

DOI: 10.3233/ISP-2010-0064

Citation: International Shipbuilding Progress, vol. 57, no. 3-4, pp. 87-99, 2010

Authors: Bettle, Mark | Toxopeus, Serge L. | Gerber, Andrew

Article Type: Research Article

Abstract: Due to changes in operations, the Royal Netherlands Navy (RNLN) is operating its submarines increasingly in brown water regions (i.e., waters with restriction in width and/or depth, such as littoral areas). To improve predictions for manoeuvring in restricted waterways, the RNLN has ordered the Maritime Research Institute Netherlands (MARIN) to conduct studies regarding the influence of the seabed on the behaviour of the submarine. In this work, viscous-flow calculations are used to predict the influence of bottom clearance on the hydrodynamic forces on the Walrus class submarines. The simulations representing unrestricted-water conditions have been validated with available model test …results and good agreement was found. The details of the methodology and results of the viscous-flow calculations are presented in this article. The bottom clearance effects on hydrodynamic forces and moments are summarised. A strong non-linear influence of the bottom clearance on the vertical force and pitch moment was found. With a trim by the bow, the vertical down force can increase up to the same order of magnitude as the vertical up force that can be generated by the sail planes. Show more

Keywords: Walrus class submarine, CFD, RANS, manoeuvring, bottom effects, shallow water

DOI: 10.3233/ISP-2010-0065

Citation: International Shipbuilding Progress, vol. 57, no. 3-4, pp. 101-125, 2010

Authors: Pruyn, Jeroen F.J. | Hekkenberg, Robert G. | van Hooren, Chris M.

Article Type: Research Article

Abstract: In order to provide the basis for a fair comparison, an indicator was developed to measure the amount of work that goes into the construction of a vessel. The foundation for this Compensated Gross Tonnage was laid in the 1970s by the OECD to compensate for the differences in work involved in producing a gross ton (GT) of ship in different sizes and types. Since 2007, the CGT of a vessel of a certain type as a function of its size (measured in GT) has been expressed as CGT=A×GTB . However, no internationally accepted A and B values exist to …convert superyachts from GT to CGT. The superyacht building industry believes that this omission results in an under appreciation of the importance of the sector. This paper describes the research carried out into this subject and confirms that the current assignments for superyachts greatly under appreciate the value of the sector. Based on the current data, the most appropriate values for superyachts are 278 for A and 0.58 for B. The spread is quite large and more data would help confirm this finding. Show more

Keywords: CGT, superyachts, shipbuilding

DOI: 10.3233/ISP-2010-0066

Citation: International Shipbuilding Progress, vol. 57, no. 3-4, pp. 127-146, 2010

Authors: Masiuk, Sergii | Gorban, Volodymyr

Article Type: Research Article

Abstract: The numerical model of the hydrodynamic interaction of bodies (ships in particular), that move in ideal incompressible fluid, has been built. The model is based on the three-dimensional boundary element method, in accordance with which the surface of a body and impenetrable areas of the boundary are approximated by the system of triangular elements. The interaction of the ship with a rectangular (vertical) bulge near a vertical wall in shallow water in the conditions of current is considered. It is shown, that the forces of hydrodynamic interaction substantially differ depending on the size of a bulge and the shape of …a ship. Even small current, both in opposing and in the same direction can cause considerable change of the hydrodynamic forces. Show more

Keywords: Boundary elements method, ship interaction, hydraulic engineering structures, sway force, yaw moment, shallow water

DOI: 10.3233/ISP-2011-0067

Citation: International Shipbuilding Progress, vol. 57, no. 3-4, pp. 147-161, 2010

Article Type: Other

Citation: International Shipbuilding Progress, vol. 57, no. 3-4, pp. 163-164, 2010