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In this article, the issue of the Goldak heat source model modification was analysed for the Metal-Cored Arc Welding (MCAW) process utilizing gas mixtures based on different argon, carbon dioxide and oxygen ratios. In order to define the specific dimensions of the Goldak heat source model, bead on plate welding was performed at three heat level inputs. Consequently, a 3D scanning of samples was performed as well as a macrograph analysis for each experiment condition. The acquired results show that both the heat input and shielding gas compositions influence the weld geometry and shape of fusion.

Aquaculture is expanding sector on the global level resulting in higher concerns for its sustainability. Generally, sustainability can be defined as a process of meeting the needs of the present without compromising the ability of future generations to meet their needs, and it is considered to be constituted of three pillars: the economy, society and environment. This work considers environmental pillar of sustainability of mariculture systems, with a goal to investigate effect of alternative powering options in mariculture on its lifetime environmental footprint. In this sense the alternative mariculture system from Koričan at al. (2022) has been considered. This work, as a result of INTEL- MARIC project, conducted at UNIZAG FSB considers set of alternative fuels (LNG, Methanol, Biodiesel) and associated emissions (CO2, NOx, SO, and PM) of the mariculture system. The life-cycle assessment (LCA) indicates that significant environmental benefits are possible in case of alternative mariculture system layouts and by use of alternative fuels like for instance methanol or biodiesel.

The offshore multi-use setting represents a model that minimizes spatial competition and advocates its’ multipurpose. Aquavoltaics represent a system of floating solar panels and aquaculture farms working in synergy, ensuring sustainable and efficient food and renewable energy production. In an offshore multi-use setting in the Adriatic Sea, aquavoltaics could be applied in different ways. An extended literature overview is conducted on the topic to accentuate already existing examples of aquavoltaics in use and propose a conceptual model that would be operable in the Adriatic Sea....

In this paper the authors conducted a numerical investigation of residual stress distribution on two butt-welded plates. Subsequently, they incorporated the obtained residual stresses into a welded model that included a hypothetical semielliptic crack. The stress intensity factors (SIFs) were calculated using the eXtended Finite Element Method (X-FEM). The obtained SIFs results match very well with the analytical results of the API 579-1 standard with the biggest difference being 6.73%. Similar differences can be noticed in the comparison between X-FEM and the results obtained by the conventional Finite Element Method (FEM), where the biggest difference between these two results is 6.75%.

Aquaculture has been the fastest-growing food production sector for decades. Nowadays, it is directed towards economically, socially, and environmentally acceptable production. Mariculture production begins at the sea, in cages, where fish is being kept until the appropriate market weight and size is achieved. There are different ways how it can affect the marine environment. Fish products, feces, medicine, food, and other factors have an impact on the sea quality parameters. Marine pollution considers the presence of undesirable materials in the ocean environment that affect mariculture, affecting the seawater's physical, chemical, and biological conditions. To help prevent and to monitor marine pollution, sensors connected with artificial intelligence, Internet-of- Things, applications, and other software are used. The use of multiparameter probes with different sensors in the sea enables the detection of changes in real-time and instantaneous warning. A mobile application connected to the probe provides information about parameters like salinity, sea temperature, oxygen, depth, pH etc. The goal of the developed mobile application is to prevent more serious marine pollution and impact on the production and environment by monitoring sea conditions, reacting on time in the case of anomalies, recognizing unusual patterns in the parameter value distribution from the existing data, as well as expanding the circle of people who can notice and report possible pollution. An early warning algorithm is being developed based on normal, abnormal, and reference values. This work introduces the development of a mobile app, with the emphasis on the basic requirements of the end-user.

The paper proposes a novel staggered phase-field framework for modelling brittle and ductile fractures in monotonic and cyclic loading regimes. The algorithm consists of two mesh layers (displacement and phase field) and a single special-purpose, user-defined finite element, which controls global convergence of the coupled problem and passing of the solution variables between mesh layers. The proposed algorithm is implemented into FE software ABAQUS. For the problem of high cyclic fatigue, a cycle-skipping scheme is also introduced. The proposed methodology is verified on the usual benchmark examples. Small-strain theory is applied, but it has been demonstrated that extension to large strains is straightforward using only the ABAQUS built-in option. The efficiency and stability of the proposed framework was proven by comparison of computational time and the number of iterations per increment in the RCTRL scheme.

In order to continue the development of mariculture in a sustainable manner, fish farms tend to be relocated to further offshore sea areas. A great number of offshore cage farms has been designed, built and put into use over the last few decades, which implicates only further development in that direction. An overview of existing structures for mariculture installations has been conducted in order to analyse technical characteristics of different cage designs and their applicability to potential off-shore farm locations in the Adriatic sea. An extended SWOT analysis was carried out in order to single out systems with greater application potential taking into account conditions in the Adriatic sea and present fish farming practices. Different options are ranked and a preliminary solution of the regionally applicable fish farming cage is proposed to allow further refinement of conceptual designs taking into account not only the technical features but also other factors. This study discusses technical parameters that must be considered for effective offshore mariculture, which have to be additionally combined with other parameters in order to fully support production.

For centuries, constitutive material behaviour is described by long-established analytical expressions. Such constitutive material models, as well as material constants, have been obtained using many experimental trials conducted over many years throughout history. Traditionally, these expressions have been sufficient to describe classical engineering problems. However, due to increasing exploitation of known materials and usage of new materials with heterogeneous microstructure, there is need for more accurate and better description of the material constitutive behaviour. Several different approaches have been proposed to describe the constitutive behaviour of heterogeneous materials over past few decades, among which the most popular is the multiscale method. Although the results of multiscale numerical simulations are satisfactory accurate, the two-scale calculation is time-consuming and computationally expensive process. For this reason, many homogenization methods (reduced homogenization methods) have been developed that seek to find the optimum between the accuracy of the results and the complexity of the calculation. A robust and efficient method of homogenization with a reduced number of degrees of freedom, based on machine learning, has led to significant acceleration of multiscale modelling. The use of reduced order homogenization to solve multiscale problems has proven to be extremely useful for obtaining a large database that will be used to create neural network-based material models. The present work shows the use of the mentioned methods for numerical modelling of nodular cast iron. Calculations are performed on a nodular cast iron RVE using the clustering, and a large database is obtained for different cases of monotonic loading. This database is used to train the neural networks. The entire analysis is performed assuming small strains and plane strain. Deformations are used as input data for neural networks, while the goal is to accurately predict homogenized stress. Neural networks are made using open-source software TensorFlow and Keras API based on the Python programming language.

Welding is used as primary joining technology in various industries like civil engineering, ship- building and heavy-duty machinery building, etc., where machine components of significant thickness need to be welded together. In recent times, many researchers and companies are trying to improve the efficiency of existing welding processes, which is mostly measured in higher deposition rate of molten metal per unit of time. After improving the efficiency of existing welding processes, is to achieve lower values of tensile residual stresses in the welded joint, or in other words to achieve the highest possible values of mechanical properties of the welded joint. Since lower values of residual stresses are hard to achieve without implementing welding in multiple passes, other procedures should be applied after the welding. The most common technology for reduction of residual stresses is post-weld heat treatment. In order to reduce the costs of the testing, the numerical models of heat treatment will be developed on the basis of obtained experimental data in order to examine each PWHT parameter in detail.

Separated phase field algorithm is derived, for the problems of brittle fracture in monotonic and cyclic loading regime.

Kao i u mnogim drugim područjima, u posljednje vrijeme numeričke simulacije sve više nadopunjuju skupe i vremenski zahtjevne eksperimente. Pritom metoda konačnih elemenata, kao jedna od najčešće korištenih numeričkih metoda, ima nezaobilaznu ulogu u projektiranju i procjeni radnog vijeka inženjerskih konstrukcija. Posebno je to slučaj u analizi konstrukcija složenije geometrije i materijala pri složenijim opterećenjima, gdje rješenja dobivena primjenom inženjerskih normi mogu biti dosta konzervativna. Stoga je preporuka da se za dobivanje optimalne konstrukcije, izrazi iz normi kombiniraju s rezultatima numeričke analize. Težište predavanja je na primjeni naprednih numeričkih metoda temeljenih na metodi konačnih elemenata u projektiranju i procjeni radnog vijeka opreme pod tlakom. U prvom dijelu predavanja prikazat će se primjeri projektiranja opreme pod tlakom primjenom novih normi i numeričke analize. Za posude pod tlakom koje uključuju nerazornim metodama otkrivene pukotine, u drugom dijelu predavanja prikazat će se postupak procjene integriteta, odnosno stupnja opasnosti od loma, što može uvelike doprinijeti pouzdanosti, sigurnosti i procjeni vijeka trajanja.