Ban D, Blagojević B, Barle J. Ship Geometry Description Using Global 2D RBF Interpolation. Journal of Naval Architecture and Shipbuilding Industry (Brodogradnja: ?asopis brodogradnje i brodogra?evne industrije), (0007-215X), 61 (2010), 3; 233-242. (pdf)
The radial basis functions (RBFs) networks are the new meshless, explicit, piecewise geometry description method, recently developed. Among many useful properties they have, RBFs belong to Reproducing Kernel Hilbert Spaces and have the best approximating property, and they are therefore might be suitable for describing complex ships’ geometry. Moreover, they are the solution of scattered data interpolation problem and can achieve high accuracy. Various types of radial basis functions and their parameters will be investigated and their applicability in 2D ship geometry description studied in this paper.
Blagojević B, Kuttenkeuler J. On Project Based Learning in Traditional Engieneering Studies. 19th Symposium on Theory and Practice of Shipbuilding SORTA 2010, 07-09. October 2010, Lumbarda, Croatia.
The paper reviews experience from the implementation of a project based design-build (DB) course given during the last year of the master level education at two specializations at the Royal Institute of Technology (KTH). Key features concerning constructive alignment, efficient learning modes, the teacher’s role, assessment and general implementation aspects are discussed. Traditional learning approach in mechanical engineering and naval architecture studies at University of Split are described and compared with methodologies developed at the KTH. Possibilities for implementation of project based learning and CDIO approach at University of Split are presented.
Rad prikazuje iskustvo u implementaciji projektno orijentiranog kolegija koji se izvodi na zadnjoj godini dva smjera diplomskih studija na Royal Institute of Technology (KTH). Razmotrene su glavne zna?ajke koje se ti?u konstruktivne orijentacije, efikasnih na?ina u?enja, uloge nastavnika, ocjenenjivanja te aspekti op?e implementacije. Opisan je tradicionalni pristup u?enja na studijima strojarstva i brodogradnje na Sveu?ilištu u Splitu i prikazana je usporedba sa metodama razvijenima na KTH. Prikazane su mogu?nosti implementacije projektno orijentiranog u?enja i CDIO pristupa na Sveu?ilištu u Splitu.
Ban D, Barle J, Blagojević B. Ship Geometry Modelling Using Radial Basis Functions Interpolation. ADVANCED SHIP DESIGN FOR POLLUTION PREVENTION, ISBN: 978-0-415-58477-7, Taylor & Francis Group, 2010., Guedes Soares, Carlos ; Parunov, Joško (Eds.).
The radial basis functions (RBFs) networks are the basis of recently developed and more widely used meshless methods. Among many useful properties they have, RBFs are recognized as the best approximators and therefore possibly suitable for describing complex ships’ geometry. Moreover, they are the solution of scattered data interpolation problem and can achieve high accuracy. Various types of radial basis functions and their parameters will be investigated and their applicability in modelling ship geometry studied in this paper.
Žiha K, Blagojević B. Fatigue Yield of Ship Structures. Proceedings of the ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering OMAE2009 May 31 - June 5, 2009, Honolulu, Hawaii, USA / Daniel Valentine, Clarkson University (ed.).
he paper on the first place summarizes the fatigue yield approach as a cause-effect interaction between fatigue damage progression and fatigue endurance. Secondly it investigates the fatigue strength worsening on experimental S-N data and the load variability effects in shipbuilding. Next it applies the Classification Society's rule-based procedure for fatigue analysis of ship’ s structure that uses a simplified fatigue strength assessment method. The example elaborates fatigue yield effect on the seagoing operation of a double hull 47400 tdw tanker. At the end the paper recommends the procedure for assessment of ship lifetime shortening due to the fatigue yielding under constant and variable amplitude block loadings.
Markovina R, Blagojević B, Vlak F. Bending fatigue behavior of shot peened Al-Li 8090T3 thin plates. Kovové Materiály (Metallic Materials), 47 (2009), 2; 115-120.
In this study, the effect of shot peening on fatigue life of Al-Li 8090T3 thin plates, which are used in the production of structural components of high-speed ships, is investigated. It is shown how various manufacturing procedures influence fatigue life of shot-peened material. Surface cleaning and protecting have a low impact on fatigue life Al-Li 8090, while cold rolling considerably improves the number of cycles that thin aluminum plates can endure. NC machining and surface polishing resulted in significant increase of the fatigue life. The experiment has shown that an adequately chosen shot peening parameters in a combination with favorable manufacturing procedures, like NC machining, may result in an increase of the fatigue life of more than 50%. It can be concluded that shot peening improves fatigue life of Al-Li 8090 T3 thin plates.
Markovina R, Blagojević B, Ban D. Kontrola procesa kugličarenja pri gradnji vrlo brzih brodova (Shot-peening control procedure in production of high-speed ships). SORTA 2008, Symposium on Theory and Practice of Shipbuilding, Pula, Croatia, October 2008.
Kugli?arenje (zrn?enje) je tehnološki proces koji se uspješno primjenjuje u zrakoplovnoj industriji u cilju pove?avanja ?vrsto?e umaranja materijala, ojacavanja površinskih slojeva u kristalnoj mreži materijala, sprje?avanja i otklanjanja korozije i napetosne korozije, trenja i kovanja te sprjecavanja i otklanjanja stvaranja mikro-naprslina i naprslina uslijed naprezanja, ali i u cilju cišcenja (dekontaminacije) površine konstrukcijskog elementa i stvaranja fine hrapavosti njegove površine za prihvat temeljnog sloja boje. Ova svojstva su vrlo poželjna i u suvremenoj brodogradnji koja teži proizvodnji vrlo-brzih brodova izradenih od laganih materijala poput razlicitih aluminijevih i titanovih slitina. Sam postupak kuglicarenja zavisi o nizu parametara koji moraju biti dobro procijenjeni, u protivnom je moguce pogoršati svojstva obradivanog materijala. Kontrola postupka je, stoga, od iznimne važnosti za osiguravanje kvalitete konacnog proizvoda. Ovaj rad prikazuje kontrolni proces kugli?arenja u proizvodnji elemenata brodske konstrukcije modernih, vrlo-brzih, brodova.
Shot peening is technological process that was successfully introduced in aircraft industry for improvement of fatigue strength and corrosion resistance of various light metals. Both properties are of great importance in a modern shipbuilding industry that tends to produce super-high-speed ships made of lightweight materials such as various aluminum and titanium alloys. Shot-peening procedure depends on many parameters that have to be carefully assessed; otherwise it is possible to even deteriorate properties of treated materials. Thus, the control process of a shot-peening procedure is of a great importance for quality assurance. This paper presents the control flow process of a shot-peening procedure in production of structural elements of super-high-speed ships.
Markovina R, Blagojević B, Ban D. Investigation of influential parameters on shot-peening of aluminum alloys. TMT2008, 12th International Research/Expert Conference 'Trends in the Development of Machinery and Associated Technology', Istanbul, Turkey, 16-20 August, 2008.
Modern high-speed ships demand application of materials that are light and with a good fatigue strength and corrosion resistance. Various aluminum alloys can be technologically improved to match these demands. It is known that shot-peening method can be applied to improve fatigue properties of aluminum alloys. However, the quality of the results obtained by this method is very sensitive to various parameters. This paper presents results of the investigation of some influential parameters, like nozzle angle and peening distance, on shot-peening of aluminum alloy Al2024-T3 that can be used in production of new types of high-speed ships in Croatian shipbuilding. Presented experiment results indicate the importance of a careful selection of shot-peening parameters since adversely chosen parameters can even lead to the aggravation of material properties.
Markovina, R., Blagojević, B., Ban, D.: Exploitation of Floating Objects in Coastal Cities, CIM 2008 Conference, Lumbarda, Croatia, 17-21 June, 2008., pp. 201-209.
The Croatian, as well as European shipbuilding industry, cannot compete with Far East shipbuilding industries in a matter of low prices and short delivery time for production of conventional new ships. The way out from continuously decreasing production lies in orientation towards building more technically demanding and complex objects, and to merge, both, regionally and through production programs. The floating objects, as marine objects without self propulsion systems, equipped with own electrical energy sources, water supplies and waste water treatment systems, that provide object’s autonomy, would be one of very useful production solution, designed in cooperation with architects and curators for different purposes: restaurants, congress centers, cafe bars and disco clubs, apartments, car parking, etc. In the paper some ideas of using a floating objects in coastal cities is presented.
Blagojević, B. Žiha, K., On the assessment of redundancy of ship structural components, OMAE2008, proceedings of the ASME 27th International Conference on Offshore Mechanics and Arctic Engineering : OMAE2008 / Soares, Carlos Guedes (ur.). Estoril : American Society of Mechanical Engineers, 2008., pp 256-262.
This paper firstly sums up some of the views on structural redundancy with particular emphasis on ship and marine structures. Next, it places the engineering decision process in the event space and, consequently, applies the representation of operational modes by systems of events. Furthermore, the paper takes some of the relations from the entropy concept in information theory. The entropy concept in probability theory is employed in the paper to redefine the structural redundancy in terms of conditional entropy of operational modes. The redundancy modeling is presented by systems of operational modes in which some of the transitive events may lead to new operational states. Finally, a ship substructure example of a stiffened panel with a girder is elaborated. The conclusion supports the thesis that the efficient structural redundancy can be comprehended as the most uniform distribution of the operational modes probabilities. Moreover, the efficient structural redundancy can be maximized.
Markovina, R., Blagojević, B., Ban, D., Peen-forming: the possibility of technology transfer from aircraft industry to the production of high-speed ships, Journal of Naval Arhcitecture and Shipbuilding Industry, Brodogradnja, 59 (2008), 1, 35-43.
Shot-peening is a widespread surface treatment method used to improve fatigue and corrosion resistance of many metals. From that technology, the peen-forming method has emerged, that has replaced traditional forming methods on many aircraft types, allowing wing designs to maximize strength to weight ratios. The new generation of high-speed ships and boats use similar lightweight building materials as aircraft industry, such as different aluminum alloys, which indicates that shot-peening and peen-forming methods could be introduced in shipbuilding industry. This paper describes peen-forming technology, which is rarely present in shipbuilding, and shows why the peen-forming should be considered as an important ship production method that may replace more costly and complex forming technologies. The paper presents application techniques, process variables, limitations and applicable designs regarding peen-forming and concludes that peen forming will have a significant role in the future of shipbuilding of fast and high - speed vessels.
Markovina, R., Blagojević, B., Ban, D.: The possibility of using peen-forming process in the new generation vessels production, Shot-peening conference, International Institute for Technology Transfer (i.i.t.t.), Noisy-le-Grand, France, 27. March 2008.
Markovina, R., Blagojević, B., Ban, D., Improvement of the fatigue properties of aluminum alloys for use in modern shipbuilding, 2nd Conference on Marine Technology, 26.-27. November 2007., Rijeka, Croatia, pp
Modern high-speed ships and super-high-speed ships demand application of materials that are uncommon in today’s shipbuilding. These materials need to be light with a good strength, fatigue and corrosion resistance and with a good welding capability. Various aluminum alloys can be technologically improved to match those demands. This paper presents a method for improvement of fatigue properties of alloys Al2024, Al8090 and Al5080 that can be used in production of new types of high-speed ships in Croatian shipbuilding.
Markovina R., Blagojević B., Ban D., Technologicaly improved strength of critical structural elements of high-speed ships, 11th International Research/Expert Conference 'Trends in the Development of Machinery and Associated Technology', TMT2007, Hammamet, Tunisia, 5-9 September 2007. pp 935-938.
Design and production of a new type of high-speed ship, named Gliding Wing, is a demanding task, due to its desired capabilities, complex structure, and hard operational conditions. It is necessary to apply new materials and include appropriate production technologies in a shipbuilding process. This paper suggests some of the materials to be used for production of thinner components resulting in an overall lighter structure. Accordingly, appropriate surface treatment technology, shot-peening, is proposed to achieve a higher strength of critical structural elements. It is also shown that same technological process can improve fatigue strength of treated elements which is of great importance due to significant fatigue problem of considered structures.
Markovina R., Blagojević B., Ban, D., Druzhba Adria project - managing ballast water problems, Journal of Marine Sciencies, Naše More, Vol.54 (5-6), 2007.
Ballast water problem is increasing problem in Adriatic Sea, today. Together with global warming effects of new species found in it, realization of "Druzhba Adria" project could furthermore threaten Adriatic Sea sensitive eco-system. With five fold increase in the amount of ballast water discharged, estimated by DnV and Fridtjof Nansen Institute, "Druzhba Adria" project would significantly influence ballast water problem in Croatian part of Adriatic Sea. Ballast Water Management problem in "Druzhba Adria" project will be discussed in this paper, and new Ballast Water Methods Assessment Criteria introduced.
Žiha, K.; Blagojević, B., Uncertainty of systems of events, Proceedings of the 28th International Conference on Information Technology Interface, ITI 2006. / Lužar, Vesna ; Vesna, Hljuz Dobrić (ed.). Dubrovnik, Croatia, 19-22 June 2006.
The paper investigates uncertainties of occurrences of sequences of events employing the entropy concept. Some aspects of probabilistic engineering event oriented system analysis also are summarized. Joint and successive sequences of events are considered with particular concern with uncertainties that could be associated with them. Numerical examples attempt to demonstrate the procedure and helpfulness to engineering modeling problems for member selection optimization.
Pavazza, R., Blagojević, B., Plazibat, B., On the cross-section distortion of large tankers subjected to bending, XVII. Symposium on Theory and Practice of Shipbuilding, SORTA 2006., Dobrinić, Julijan (ed.). Rijeka, Croatia, 19.-21.10.2006., pp 603-615.
The paper deals with distortion of hull cross-sections of large modern tankers with one longitudinal bulkhead subjected to bending in the vertical plane of symmetry. The cross-section distortion is considered in the limit case. It is assumed that hull panels — bottom, deck, sides and longitudinal bulkheads — are hinged along their longitudinal edges. The additional stresses and displacements due to distortion with respect to the stresses and displacements of the ordinary hull girder bending theory are analyzed. The assumption of “hinged cross-sections” is opposite to the assumption of “rigid cross-sections”. Both are limiting cases of stresses and deformations of actual hull structures, particularly in the case of large tankers. A comparison with the results of the finite element analysis is provided.
Pavazza, R.; Blagojević, B., On the cross-section distortion of thin-walled beams with multi-cell cross-sections subjected to bending, Elsevier Science, International Journal of of Solids and Structures, 42 (2005), pp 901-925.
This paper deals with distortion of the cross-section contour of thin-walled beams with simple multi-cell closed rectangular cross-sections. The cross-section distortion is considered in the limit case. It is assumed that beam plates are hinged together along their longitudinal edges. Double symmetric three and two-cell closed cross-sections are considered. The stresses and displacements are obtained in the closed analytical form. The additional stresses and displacements due to distortion with respect to the stresses and displacements of the ordinary theory of bending are obtained. The boundary conditions are given in the general form. Some illustrative examples are given.
Markovina, R., Blagojević, B., Bodrožić, J., Hull form modelling of the super-high-speed vessel SPALATO, type Gliding Wing, XVI Symposium on Theory and Practice of Shipbuilding, SORTA 2004., Plitvice, Croatia, 21-23.10.2004.
The ‘Gliding Wing’ is a concept of a super-high-speed vessel with a maximum achieving speed over 100 knots and flying and landing possibilities on the sea surface, using the screen-plane and WIG (Wing-In-Ground) effect. In this paper is presented a preliminary model of a hull shape of the slower vessel variant called ‘Spalato’, with the speed of about 80 knots, which is intended to operate in the Adriatic Sea. The hull modeling of the ‘Spalato’ is done with a three-dimensional surface-modeling CAD system Maxsurf that allows a systematic experimentation and rapid optimization of any new design.
Pavazza, R., Blagojević, B., On the stress distribution in thin-walled beams subjected to bending with influence of shear, 4th International Congress of Croatian Society of Mechanics (ICCSM), September, 18-20, 2003, Bizovac, Croatia.
The ordinary theories of thin-walled beams assume that cross-sections remain plane during transverse bending. These theories are restricted to relatively long beams, where warping of the cross-section due to shear can be neglected. The theories can be applied in the analysis of relatively short beams, where the shear effect cannot be neglected, by taking into account deformation due to shear. Equations that consider this effect are known as Timoshenko’s equations. Considerable attention in the past is received to determine the shear factor, by which the deflection due to shear is defined. In the Timoshenko’s equations this factor is given as the ratio between the effective shear area and total area of the cross-section (or between the total area and shear area). Thus, it is dependent on the shape of the cross-section only. The recent definitions of the shear factor, includes the Poison’s effect. This effect gives for the shear factor two to ten per cent greater values (or lower values). In this paper, the shear factor will be assumed as a pure geometrical property. The analytical solution for stress distributions will be investigated. The cross-sections with the general shape will be considered. Some solutions of the problem can be found in literature, for simple rectangular cross-sections as well as for simple thin-walled cross-sections with one axis of symmetry.
Blagojević, B., Žiha, K. and Domazet, Ž., Productional, operational and theoretical sensitivities of fatigue damage assessment in shipbuilding, SNAME, Journal of Ship Production (JSP),Vol 18, No.4, November 2002, pp 185-195.
First, this paper summarizes some of the theoretical and practical aspects of fatigue assessments in shipbuilding. The basics of the spectral fatigue analysis procedure for ship structures are mentioned. The simplified procedures are presented in more detail, due to their practical merit. The article is primarily concerned with the fatigue design procedures used by Classification Societies, as well as with possible standardizations under the auspices of IACS. Secondly, an example of fatigue damage assessment for the chemical tanker recently built in Croatian shipyards is provided in order to illustrate and compare the capabilities and differences of available procedures currently used by major Classification Societies. Finally, parametric studies are performed in order to investigate the effects of productional structural elements misalignment, constructional and fabrication tolerances, of corrosion during operations at sea, shape parameters of theoretical distributions, of selections of the S-N curves and of the combinations of local and global loads. The sensitivity analysis presented in the article provides suggestions for improving design and production of the critical parts of the ship hull construction with respect to fatigue damage.
Blagojević, B., Domazet, Ž., Simplified procedures for fatigue assessment of ship structures, 10th International Congress of the International Maritime Association of the Mediterranean (IMAM 2002), 13th-17th May 2002, Rethymnon, Crete, Hellas.
Comparison of simplified procedures for fatigue assessment of ship structural details, used by classification societies, is presented. The basics of typical fatigue design approaches are described. In order to illustrate the capabilities and differences of the procedures, comparative study is performed on a bulk carrier built in Croatian shipyard in Split. Fatigue damage is calculated for a few longitudinals in connection with transverse structural elements. Longitudinals are located in the hopper tank, topside tank and double bottom of the bulk carrier. Fatigue damage of critical details is calculated applying current rules and guidelines of the classification societies Bureau Veritas, Germanischer Lloyd and Lloyd's Register of Shipping. The effect of a few input parameters on fatigue life is studied in a parameter variation including the shape parameter of the Weibull long-term stress distribution, structural misalignment and the effect of corrosion.