Estimation of ship lightweight reduction by means of application of sandwich plate system

Sendvič panel sistem predstavlja alternativu konvencionalnom orebrenom panelu i sastoji se od dva metalna lima razdvojena ispunom od elastomera. Uzimajući u obzir visok odnos čvrstoće i težine, jednostavnost konstrukcije, otpornost na udare i eksploziju, SPS je široko rasprostranjen u mnogim industrijama, a najviše u remontu brodova. Mada se često navode veoma optimističke prognoze u vezi potencijalnih ušteda u ukupnoj težini konstrukcije, činjenica je da još nijedan kompletan trup broda od SPS-a nije zaista napravljen. Ideja ovog rada je da se analiziraju mogućnosti SPS-a u ovoj nameni. Kao primer trupa broda je uzeta tipična rečna barža. Kombinujući različite koncepte gradnje i tipove brodova, ukupno 21 model konvencionalne konstrukcije broda je definisan i njihove težine su detaljno sračunate. Isto je urađeno pod pretpostavkom da je barža napravljena od SPS-a, koristeći 'Lloyd's Provisional Rules'. Svi rezultati su sistematski poređeni i analizirani.Sandwich plate system is an alternative to conventional stiffened plate composition that consists of two metal plates separated by an elastomer core. Considering high strength to weight ratio, simplicity, blast and ballistic properties of the material, SPS has been widely used in a range of industries but its most dominant application has become ship repair. Regarding new buildings some very brave estimations of possible weight savings can be found, but still no complete hull made of SPS has been actually produced. The idea of this paper is to analyze possibilities of SPS for such application. A typical river barge is used as the basic hull shape. Combining different framing concepts and cargo types 21 different model of conventional hull structure is defined and their weights calculated. Subsequently the same is done presuming that barge hull is built of SPS, and using related Lloyd's Provisional Rules. All results are systematically compared and analyzed

Hot spot along corner curvature of rectangular plate opening

Koncentracija napona u uglu kvadratnog otvora u ploči je poznata činjenica. Najčešće se uzima da je najveća koncentracija napona u samom temenu ugla (na ugaonoj koordinati od 45 stepeni u slučaju kvadratnog otvora). Rigoroznije analize, ipak, prikazuju da ovo baš nije najtačnije. Iako maksimalni napon nikada "ne napušta" ugao, u nekim proračunima koncentracije napona, ozbiljnije analize ovog fenomena dobijaju na značaju. U ovom radu prikazani su i poređeni rezultati analitičke, numeričke i eksperimentalne analize tačne pozicije koncentracije napona u uglu otvora, u slučaju ploče pri istezanju.Development of stress concentration in the corner zone of rectangular plate opening is a well-known fact. It is usually literally taken that the largest stress concentration factor (SCF) occurs exactly in the corner (at angle coordinate of 45 degrees in case of square opening). More rigorous analyses, however, reveal that this is not perfectly true. Although maximum stress never really "leaves the corner", for some hot-spot analyses, more scrupulous investigation of this phenomenon has significance. In this paper, results of some analytical, numerical and experimental investigations of this topic, for plate in tension, are presented and compared

Hot spot along corner curvature of rectangular plate opening

Koncentracija napona u uglu kvadratnog otvora u ploči je poznata činjenica. Najčešće se uzima da je najveća koncentracija napona u samom temenu ugla (na ugaonoj koordinati od 45 stepeni u slučaju kvadratnog otvora). Rigoroznije analize, ipak, prikazuju da ovo baš nije najtačnije. Iako maksimalni napon nikada "ne napušta" ugao, u nekim proračunima koncentracije napona, ozbiljnije analize ovog fenomena dobijaju na značaju. U ovom radu prikazani su i poređeni rezultati analitičke, numeričke i eksperimentalne analize tačne pozicije koncentracije napona u uglu otvora, u slučaju ploče pri istezanju.Development of stress concentration in the corner zone of rectangular plate opening is a well-known fact. It is usually literally taken that the largest stress concentration factor (SCF) occurs exactly in the corner (at angle coordinate of 45 degrees in case of square opening). More rigorous analyses, however, reveal that this is not perfectly true. Although maximum stress never really "leaves the corner", for some hot-spot analyses, more scrupulous investigation of this phenomenon has significance. In this paper, results of some analytical, numerical and experimental investigations of this topic, for plate in tension, are presented and compared

Stress concentration on the contour of a plate opening of an arbitrary corner radius of curvature

Nowadays the title problem is usually dealt with using the finite element method (FEM). However, due to a high stress gradient an extremely fine mesh is needed in the vicinity of the contour, and even then the results obtained are of a questionable accuracy in the zones with a small radius of curvature (corners of rectangular openings). In this paper, a different - analytical -approach to the problem was applied by using Muskhelishvilli's solutions based on conformal mapping. Involving functions of a complex variable - and so being very complicated - these solutions were practically applicable for a narrow corner-radius-of-curvature spectrum only. However, after an adequate transformation and reduction to a programmable algorithm, they allowed systematic analyses for an arbitrary small corner radius of the contour and thus a more accurate formulation of its influence on the stress concentration factor (SCF) in a convenient manner

Optimization of stiffened pannels based on quasi-analytical strength response functions

Stiffened panels are basic constituents of wide scope of structures, their optimization being the focal point of optimization of any such structure as a whole. The main obstacle in application of sophisticated optimization software tools of today for that task is the lack of general formulation of relations between load and response parameters of such models. They are necessary to define programmable failure calculation as a built-in strength assessment module in any closed, repetitive optimization algorithm. Basic authors' idea is to overcome that problem using Bubnov's quasi-analytical formulae developed for analysis of ship hull plating grillages more than a century ago. In the first phase of this research, Bubnov's formulae were incorporated in Monte Carlo optimization algorithm, forming BiM - Bubnov in Monte Carlo procedure for optimization of laterally loaded stiffened panels. Results of this research are published in [1]. In this paper, attempt is made to further simplify the procedure by means of using extremely user friendly Excel Solver for optimization tasks. As a result, BiES - Bubnov in Excel Solver, a closed, programmable algorithm for optimization of laterally loaded stiffened panels is developed. The performance of the algorithm is tested on series of examples alternatively analyzed using FEM

A case of unconventional use of finite element method in ship hydrostatic calculation

The pontoon bridge, or so called The Bridge on the Barges, consisting of longitudinally connected standard inland barges, was to be built on the river Danube. The first step of the structural design was to evaluate vertical displacements and forces at the points of hinge connection of the barges, for various cases of traffic load distribution along the bridge. Instead of performing standard hydrostatic calculations of immersion and trim of the vessels, whole structure was modeled as a chain of rigid beams elastically supported by buoyancy - and analyzed using the finite element method

A case of unconventional use of finite element method in ship hydrostatic calculation

The pontoon bridge, or so called The Bridge on the Barges, consisting of longitudinally connected standard inland barges, was to be built on the river Danube. The first step of the structural design was to evaluate vertical displacements and forces at the points of hinge connection of the barges, for various cases of traffic load distribution along the bridge. Instead of performing standard hydrostatic calculations of immersion and trim of the vessels, whole structure was modeled as a chain of rigid beams elastically supported by buoyancy - and analyzed using the finite element method

Optimization of stiffened pannels based on quasi-analytical strength response functions

Stiffened panels are basic constituents of wide scope of structures, their optimization being the focal point of optimization of any such structure as a whole. The main obstacle in application of sophisticated optimization software tools of today for that task is the lack of general formulation of relations between load and response parameters of such models. They are necessary to define programmable failure calculation as a built-in strength assessment module in any closed, repetitive optimization algorithm. Basic authors' idea is to overcome that problem using Bubnov's quasi-analytical formulae developed for analysis of ship hull plating grillages more than a century ago. In the first phase of this research, Bubnov's formulae were incorporated in Monte Carlo optimization algorithm, forming BiM - Bubnov in Monte Carlo procedure for optimization of laterally loaded stiffened panels. Results of this research are published in [1]. In this paper, attempt is made to further simplify the procedure by means of using extremely user friendly Excel Solver for optimization tasks. As a result, BiES - Bubnov in Excel Solver, a closed, programmable algorithm for optimization of laterally loaded stiffened panels is developed. The performance of the algorithm is tested on series of examples alternatively analyzed using FEM

Simplified numerical analyses of stiffened panels

Stiffened panels are basic constituents of wide scope of structures and thus one of the most important study topics in the field of strength analysis. Although they are successfully dealt using FEM these days, related models are complex and time consuming. In this paper, a simplified strength calculation procedure is proposed. FEM models are reduced to unstiffened thin plates only, while influence of stiffeners is directly incorporated in plates` stiffness matrixes. Elastic parameters of unstiffened panels are obtained for the case of both membrane and bending response of the structure, and derived from the assumption that maximum displacement and Von Mises stress are equal in stiffened and unstiffened panels. Orthotropic plate theory is widely used for modeling the bending behavior of unstiffened panels. Proposed method is thoroughly explained and tested in few examples by comparison with results obtained for conventional models of same structures

Stress concentration on the contour of a plate opening: analytical, numerical and experimental approach

The objective of the paper is to analyze the stress concentration factor (SCF) in the corner of a rectangular plate opening with small radii of curvature and various methods for its derivation. Besides the finite element method, as the most used approach today, there are some analytical and experimental procedures that can obtain stress concentration results in such spots. An analytical approach can deliver prediction of the SCF around the corner but cannot illustrate the stress field opposite to the finite element method. On the other hand, finite element analysis needs much computation time to deal with very sensitive and fine mesh generation around concentration zones. Experimental devices, such as strain gauges are not able to perform measurements on areas where high gradient of stress occurs due to their lack of sensitiveness and larger dimensions compared to the measured part of a structure. The paper presents Digital Image Correlation (DIC) technique that obtains not only stress concentration, where other devices fail, but also provides full displacement, strain and stress field's even where a high gradient of stress exists. These three methods are discussed, compared and illustrated on the model of a plate with rectangular opening subjected to tension