Abstract. The application of the finite elements method to the study of the stress-strain state of the platform of the existing shiplift is being discussed. The aim of this study is to determine the total stress of the platform and its deflection in the middle part. To obtain the necessary data the theoretical finite elements method is used for two calculation models; the platform is represented as a three-dimensional model and a rod model with the loads along two lines across the platform. According to the first calculation model the reduced stresses and the deflections in the middle of the platform are determined, as well as the stress in the nodes of the platform bearing on the launching and elevating mechanism is studied. According to the second calculation model only the total stress-strain states and the deflections in the middle of the platform are studied. The results of the calculations of the total stress-strain state and the deflections in the middle of the platform proved to be close in their values. However, considerably less time appeared to be spent to obtain the necessary results according to the second calculation model. The results of the study can be used to elevate and launch ships weighing up to 2000 tones in the case of the final assembly of the shafting line at the construction place. The results also confirm the possibility of the reliable elevating and launch of such ships. Keywords: strength; shiplift platform; reduced stress; deflection; ANSYS software package; finite element method.Аннотация. Методом конечных элементов исследовано напряженно-деформированное состояние платформы реального судоподъемника для спуска судна весом 1830 т. Применены две расчетные схемы -объемная и стержневая. Результаты расчетов приведенных напряжений и прогибов платформы по обеим расчетным схемам близки между собой. Однако стержневая схема требует на выполнение исследований значительно меньше времени. Ключевые слова: прочность; платформа судоподъемника; приведенное напряжение; прогиб; программный комплекс ANSYS; метод конечных элементов.Анотація. Методом скінченних елементів досліджено напружено-деформований стан платформи реального суднопідйомника для спуску судна вагою 1830 т. Застосовано дві розрахункові схеми -об'ємну та стержневу. Результати розрахунків приведених напруг та прогинів платформи по обох розрахункових схемах близькі між собою, проте стержнева схема потребує на виконання досліджень значно менше часу. Ключові слова: міцність; платформа суднопідйомника; приведена напруга; прогин; програмний комплекс ANSYS; метод скінченних елементів.
This paper reports the dependences that have been derived to determine the effective width of a free flange in a dangerous cross-section of the wide-flange hull girder with the breaking of the wall/edges/axis at elastic-plastic deformation depending on the applied load for a perfectly plastic material without strengthening. Currently, there are no systematic dependences to determine the effective width of the free flange of girders of this type, except for certain cases. The technique is suitable for use for both purely elastic and elastic-plastic deformation. To calculate the stressed-strained state (SSS), a finite-element method (FEM) was used to solve the three-dimensional problem from the elasticity and plasticity theory. It has been shown that the node is exposed to simple loading. The reported results were derived within the framework of the deformation theory of plasticity. The largest ratio of external load to the boundary of fluidity is 0.9. The estimation scheme takes into consideration the most unfavorable working conditions of the examined node when the safest data are acquired. The dependences were built for the theoretical coefficient of concentration in a dangerous cross-section, which is used in the proposed procedure to determine the moment of transition from the elastic stage of deformation to elastic-plastic. When determining the effective width, the complex work of the flange and its deplanation was taken into consideration by defining the SSS components in the median plane. The feasibility of the idea of designing the SSS components on the inclined plane of a free flange has been proven. In this case, there is practically a (quasi) flat stressed state, suitable for the application of classical methods to determine the effective width. The proposed technique simplifies the calculations of the strength of the examined girder.
The values of weld toe angles and weld toe radii in the butt and fillet welds produced by different welding procedures have been analyzed. The aim of the study is to determine the generalized mean values, standard deviations and lognormal distributions parameters of weld toe angles and radii for butt and fillet welds produced by SAW, MMA, and CO 2 welding. Based on the results of weld toe radii and angles measurements published in the literature for sheet thickness and steels with mechanical properties typical to ship structures generalized samples were compiled and statistically processed. Each generalized sample corresponded to a specific type of weld and welding procedure. The influence of welding position as well as some other factors, which can influence on investigated values in generalized samples, was neglected due to the small number of the measurement results. The influence of the mentioned factors on the investigated values and their magnitudes in the expected points of the fatigue crack initiation were studied separately. The largest weld toe radii were in butt welds produced by MMA welding. The obtained generalized mean values, standard deviations and lognormal distributions parameters of weld toe angles and weld toe radii allow us to approximately describe microgeometry of butt or fillet welds and may be used for estimation of the stress concentration in the ship structure welded assemblies and for the fatigue strength analysis of these assemblies.
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