Ships and marine technology. Bulk carriers. Repair quality of hull structure

2000 ◽  
Pomorstvo ◽  
2021 ◽  
Vol 35 (2) ◽  
pp. 267-274
Author(s):  
Davor Bolf ◽  
Marko Hadjina ◽  
Albert Zamarin ◽  
Tin Matulja

Deformations of steel material in shipbuilding and marine technology applications as a result of mechanical or temperature influences are a well-known problem. However, in the modern shipbuilding industry, the application of alternative materials, especially composite materials, in the structure and for the equipment of the ship is increasingly represented. Consequently, there is a need to determine the deformation and change of characteristics of such composite materials as a result of various mechanical, and especially temperature influences that cause the so-called shrinkage. The basic composite production process involves connecting the matrix with a catalyst and accelerators that create temperature, then the material shrinks by cooling when it can change its dimensions and characteristics. Also, in order to achieve the best possible mechanical properties, composite materials are specially heated and then cooled according to strictly defined processes and curves. The ability to predict the characteristics and parameters of such deformations is important in the context of the application of composite materials. To define such deformations, different methods are used within individual numerical solvers, whose results can differ significantly from each other. Therefore, the authors in this paper present an established methodology for predicting mechanical and temperature deformations, and modelling of composite materials, based on the analysis of analytical methods and numerical solvers with the aim of defining the most accurate numerical solver. By applying the presented methodology, it is expected to raise the level of accuracy and quality of composite materials production as well as to raise the quality of design solutions and efficiency of production procedures during shipbuilding in particular, but also within different marine technology applications and during the product’s life cycle.


Safety ◽  
2020 ◽  
Vol 6 (4) ◽  
pp. 53
Author(s):  
Nermin Hasanspahić ◽  
Vlado Frančić ◽  
Srđan Vujičić ◽  
Lovro Maglić

Shipping is a high-risk industry and prone to accidents. A near-miss management system is an important aspect of the safety performance in shipping because the causes are the same for near-misses and accidents. Reporting, analyzing, and learning from near-misses can prevent the recurrence of accidents and thus improve safety on ships. This paper addresses near-miss management systems in shipping and provides insights into the quality of the implementation of these systems, with an emphasis on the importance of reporting. Research data were derived from two surveys and supported by data gained from near-miss reports and existing literature reviews. Professional seafarers of various ranks, ages, nationalities, and experiences, serving on tankers, cruise ships, bulk carriers, and container ships, voluntarily participated in these surveys. The first survey comprised 223 participants, and the second survey involved 22 participants. The research results indicate that near-miss reporting is inadequate, and several barriers limit appropriate near-miss reporting. The difficulty of seafarers in identifying near-miss events was found to be one of the major barriers to near-miss reporting at sea. Based on this research, a conceptual model of a near-miss management system was developed, and measures that can be applied to overcome barriers and increase reporting are proposed.


2017 ◽  
Vol 159 (B2) ◽  
Author(s):  
D Boote ◽  
T Pais ◽  
G M Vergassola ◽  
D Giannarelli

When the assembling of hull structure is completed, the sides of metal motor yachts are usually affected by bumps and hollows coming from welding plates to each other and plates to frames. These defects, normally tolerated on merchant ships, cannot be accepted on superyachts for which the external surface must be smooth and glossy. For this reason the surface finishing is achieved by a long and delicate process of filling, fairing and painting. The final result of this process is very important for the yacht aesthetics as the general appearance of the vessel depends on the external painting. As a matter of fact the quality of painting depends mainly on the undercoat preparation to assure an adequate grip and, most of all, a perfect smooth and faired surface. Despite accurate preparation and painting, surface conditions can undergo undesired alteration because of excessive heating due, as an example, to a long exposure to solar radiation. While stresses do not reach significant values because of the relatively low intensity of thermal loads, strains could still cause very slight surface distortions and undulations which are perceived by human eye as a surface defect. The phenomenon becomes particularly evident if the surface is painted with a dark colour. In this paper an investigation on the influence of temperature on the stress and strain distribution of aluminium light alloy plates coated by filler layers of different kind and thickness is reported. The study has been performed by FEM structural analyses calibrated by experimental measurements performed on laboratory specimens. This work represents the continuation of a research begun some time ago with the measurement of temperatures on yacht hulls exposed to solar radiation in different conditions.


2021 ◽  
Author(s):  
John C. Daidola

The effects of hull roughness on loss of speed at constant power are investigated. Vessel lifetime roughness profiles are postulated based on construction, coatings and maintenance. These are utilized to determine loss of speed and change in running attitude for planing boats. The formulations are directly applicable to any planing boat for which a lifetime roughness profile is constructed as presented. The approach to developing the speed/power predictions and the roughness profile is provided. This approach can be utilized to analyze the effects of roughness due to hull material utilized and quality of construction, roughness from paints and coatings and their method of application as well as damage to the coating during maintenance, deterioration of the hull structure material, as well as biofouling influenced by the type of antifouling paint or coating and method of application. It provides a means for investigating different magnitudes and scenarios of these causes of roughness rather than providing only example results.


Author(s):  
Jose Miguel Varela ◽  
C. Guedes Soares

This article addresses the main requirements and the process of creating the geometry of ship models that fulfil the highly demanding request for realism and performance of the virtual environments currently used in modern ship bridge simulators. It starts with a classification of the ships based on their role in the simulation and on the type of simulator used, and defines the main characteristics of the models. It also discusses the importance of a well-defined workflow and its impact on the modelling time and on the quality of the final product. The article provides contributions in the following areas: identification of the main requirements of polygonal models of ships for ship simulators; effective workflow for ship three-dimensional modelling and identification of most suitable modelling techniques for efficient creation of ship models. The study is supported by real examples of three-dimensional modelling of ships with different sizes and characteristics currently used by the ship manoeuvring simulator in the Centre for Marine Technology and Ocean Engineering of the University of Lisbon.


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