In this paper, we give a short overview of the basic concept of stress integration for inelastic material models. This methodology was introduced by the author, initially for thermo-elasticplastic and creep deformation of metals, termed as ‘effective-stress-function’ (ESF), and then generalized to the ‘governing parameter method&r...

By MILOŠ KOJIĆ

Dynamic analysis of engineering structures is essential in the design process, providing insights into their behavior under various loading conditions. This paper focuses on the comparative study of implicit and explicit dynamic analysis methods using the PAK software and FEMAP with the Nastran software. Both methods have distinct advantages and di...

By VLADIMIR DUNIĆ, MILOŠ PEŠIĆ, MIROSLAV ŽIVKOVIĆ, RADOVAN SLAVKOVIĆ

The paper presents the procedure of implicit stress integration for constitutive models for soil and rock. The theoretical basis of Mohr-Coulomb, Matsuoka-Nakai, Hoek-Brown and Hyperbolic soil constitutive models are presented. Stress integration was performed using the theory of incremental plasticity. The general procedure of implicit stress inte...

By DRAGAN RAKIĆ, MIROSLAV ŽIVKOVIĆ

The concrete damaged plasticity (CDP) model is one of the most popular constitutive models implemented into various Finite Element Method software. The application to the real structures is documented in the literature, but still there are some doubts about the response in combination with the various finite elements. Simple benchmark examples simu...

By VLADIMIR DUNIĆ, NENAD GRUJOVIĆ, ALEKSANDAR BODIĆ, DRAGAN RAKIĆ, MIROSLAV ŽIVKOVIĆ

The paper presents various examples of the application of the PAK software and its modules for thermal, filtration, and stress–strain analysis of different complex engineering structures such as gravity dams, arch dams, embankment dams, tunnels, and mines. Examples of research, studies, and projects in which PAK has been applied to assess the...

By DEJAN DIVAC, SLOBODAN RADOVANOVIĆ, MAJA PAVIĆ, NIKOLA MILIVOJEVIĆ, VLADIMIR MILIVOJEVIĆ, MIROSLAV ŽIVKOVIĆ, DRAGAN RAKIĆ, SNEŽANA VULOVIĆ

A water supply system with radial wells (RWs) extends usually over tens of kilometers horizontally and tens of meters deep within the soil. Water flows through the soil and then through several lateral screens to the vertical shaft. Lateral screens represent perforated pipes with lengths in meters and diameters measured in centimeters. A common app...

By VLADIMIR RANKOVIĆ, NENAD FILIPOVIĆ, BOBAN STOJANOVIĆ, VELIBOR ISAILOVIĆ, MILOŠ KOJIĆ

This paper presents a method for improving the numerical analysis of contact problems using a penalty formulation. Since contact phenomena are inherently nonlinear, particularly in the case of large deformations, an incremental solution strategy is required. Conventional Newton-Raphson algorithms often face convergence problems when many nodes make...

By SNEŽANA VULOVIĆ, MIROSLAV ŽIVKOVIĆ, NENAD GRUJOVIĆ, MARKO TOPALOVIĆ

The interaction between the Finite Element Method (FEM) and Smoothed Particle Hydrodynamics (SPH) is crucial in multiphysics simulations of granular–structure systems, impacts, and material behavior. This paper presents a penalty-based contact algorithm with Coulomb friction for FEM–SPH coupling. The method accounts for static and dynam...

By MARKO TOPALOVIĆ, MILOŠ IVANOVIĆ, SNEŽANA VULOVIĆ, ALEKSANDAR NIKOLIĆ, MIROSLAV ŽIVKOVIĆ

Degradation of structural integrity and fatigue life estimation remain critical challenges in engineering, including biomedical applications. Fracture mechanics and crack propagation prediction are highly sensitive to material parameters, with the Stress Intensity Factor being the most significant physical parameter for the estimation of crack stre...

By GORDANA JOVIČIĆ, VLADIMIR MILOVANOVIĆ, ALEKSANDRA VULOVIĆ, MIROSLAV ŽIVKOVIĆ, NENAD ĐORĐEVIČ, NENAD FILIPOVIĆ

Two-equation turbulent models are widely used in finite element analysis of fluid flow. The PAK program package was upgraded from the classical laminar flow to the turbulent k-omega model. The turbulence model was validated using the case of fluid flow in a backward-facing step channel. The analysis results show good agreement with experimental dat...

By ALEKSANDAR NIKOLIĆ, MIROSLAV ŽIVKOVIĆ, NENAD FILIPOVIĆ, MARKO TOPALOVIĆ

This paper introduces the CAD user interface software developed to support example-driven simulations using the PAK finite element code. Built upon years of research and development by the authors, CAD represents a custom-built platform for three-dimensional model setup and result visualization, tightly integrated with the PAK solver. It facilitate...

By MILJAN MILOŠEVIĆ, VLADIMIR SIMIĆ, BOGDAN MILIĆEVIĆ, VELIBOR ISAILOVIĆ, VLADIMIR RANKOVIĆ, MILOŠ IVANOVIĆ, ŽARKO MILOŠEVIĆ, DALIBOR NIKOLIĆ, DANKO MILAŠINOVIĆ, ARSO VUKIĆEVIĆ, LAZAR OTAŠEVIĆ, MILETA STOJANOVIĆ, NENAD FILIPOVIĆ, MILOŠ KOJIĆ, BOBAN STOJANOVIĆ

This paper contains two parts – the first is related to the mechanics of lung microstructure, and the second is a formulation of a multiscale-multiphysics model of the lung. The second part considers the entire lung that relies on the mechanics of the microstructure and recently developed a multiscale composite finite element of the lung tiss...

By MILOŠ KOJIĆ, IVO VLASTELICA, BOBAN STOJANOVIĆ, VLADIMIR RANKOVIĆ, AKIRA TSUDA

Solvent removal by diffusion from a polymer solution occurs in various technological processes, such dry spinning of synthetic silk-like fibers. There, it is important to determine the diffusion coefficient which is dependent on the solvent concentration, assuming the validity of Fick’s law. In order to prove the internal diffusion within the...

By NIKOLA KOJIĆ, ALEKSANDAR KOJIĆ, MILOŠ KOJIĆ

This paper presents the integration of muscle fatigue modeling into the finite element solver PAK, based on an extended version of Hill’s phenomenological model. While traditional muscle models focus primarily on force generation, this study incorporates fatigue dynamics to provide a more realistic representation of muscle performance over ti...

By BOBAN STOJANOVIĆ, MILOŠ KOJIĆ, SRBOLJUB MIJAILOVICH

Finite element (FE) modeling the motion of deformable bodies within a fluid, as well as the interaction between the bodies, has been a continuous challenge over the years. There are in principle two approaches – loose and strong coupling between the FE models of the two domains, with their advantages and drawbacks. We here present our concept...

By VELIBOR ISAILOVIĆ, MILJAN MILOŠEVIĆ, NIKOLA KOJIĆ, MILOŠ KOJIĆ

This review summarizes scientific findings from three European Commission FP7 projects. The first, ARTREAT (2008-2013), focused on a multi-level, patient-specific model of artery and atherogenesis for outcome prediction, treatment decision support, and virtual hands-on training. An original method for plaque formation and development was created an...

By NENAD FILIPOVIĆ, MILOŠ RADOVIĆ, TIJANA ĐUKIĆ, IGOR SAVELJIĆ, BOGDAN MILIĆEVIĆ, EXARCHOS THEMIS, OBERDAN PARODI, DIMITRIS FOTIADIS

In silico clinical trials are set to transform medicine by enabling virtual testing and simulation, which streamline the development of medical devices and pharmaceuticals while reducing costs and duration. The SILICOFCM platform offers a innovative, multi-modular approach designed to optimize overall heart function and monitor the effectiveness of...

By NENAD FILIPOVIĆ, IGOR SAVELJIĆ, TIJANA GEROSKI, SMILJANA TOMAŠEVIĆ, MILJAN MILOŠEVIĆ, BOGDAN MILIĆEVIĆ, MOMČILO PRODANOVIĆ, SRBOLJUB MIJAILOVIĆ, MILOŠ KOJIĆ

Cardiovascular diseases are among the leading causes of mortality worldwide, necessitating advanced computational modeling to study their underlying mechanisms and explore potential treatments. In this paper, we present a multiphysics computational model that integrates cardiac mechanics, electrophysiology, and mass transport, implemented within th...

By MILJAN MILOŠEVIĆ, BOGDAN MILIĆEVIĆ, VLADIMIR SIMIĆ, NENAD FILIPOVIĆ, MILOŠ KOJIĆ

This study presents the use of computational modeling to improve understanding of hypertrophic cardiomyopathy (HCM) and its progression to heart failure. A review of related work highlights advances and challenges in computational modeling and integration of clinical data for model development and validation. Using parametric model of the left hear...

By SMILJANA TOMAŠEVIĆ, BOGDAN MILIĆEVIĆ, MILJAN MILOŠEVIĆ, NENAD FILIPOVIĆ

Huxley-type muscle models offer a physiologically grounded description of cardiac contraction but remain computationally prohibitive for large-scale, multi-scale simulations. This article reviews surrogate modeling strategies that alleviate these costs for ventricular biomechanics, with emphasis on data-driven (RNN/TCN/GRU) and physics-informed (PI...

By BOGDAN MILIĆEVIĆ, MILOŠ IVANOVIĆ, BOBAN STOJANOVIĆ, MILJAN MILOŠEVIĆ, MILOŠ KOJIĆ, NENAD FILIPOVIĆ

Aortic dissection is a severe clinical condition that demands a thorough understanding of the interactions between the true and false lumens. In this study, numerical simulations were performed for two patients, generating two preoperative and two postoperative models. The analyses were carried out using the PAKSF solver, a specialized tool for flu...

By IGOR SAVELJIĆ, TIJANA ĐUKIĆ, SMILJANA TOMAŠEVIĆ, NENAD FILIPOVIĆ

X-ray angiography is one of the diagnostic procedures applied in clinical practice to analyze the state of patient-specific coronary arteries. During this examination a parameter called fractional flow reserve (FFR) is invasively measured to quantitatively assess the existence of potential stenosis and its significance. The software proposed in thi...

By TIJANA ĐUKIĆ, OGNJEN PAVIĆ, LAZAR DAŠIĆ, TIJANA GEROSKI, NENAD FILIPOVIĆ

This paper describes software developed based on numerical implementation of algorithms for coupled acoustic – structure interaction. This class of problems implies coupling of the fluid domain, with sound wave propagation, and the domain of solid, which vibrates under the pressure caused by sound waves from the fluid domain. The physical beh...

By VELIBOR ISAILOVIĆ, NENAD FILIPOVIĆ, MILICA NIKOLIĆ, MILOŠ KOJIĆ

Wave acoustic equation is implemented and solved using finite element method in PAK solver to simulate propagation of sound waves, that cause oscillations of ear’s components, such as cochlea (part of inner ear). To simulate mechanical behaviour of cochlea, behaviour of fluid in chambers and behaviour of basilar membrane which separates them ...

By MILICA NIKOLIĆ, VELIBOR ISAILOVIĆ, NENAD FILIPOVIĆ

Understanding the biomechanical response of a femoral bone under physiological loads is critical for assessing bone health and fracture risk, particularly in aging populations affected by osteopenia and osteoporosis. This study investigates the mechanical behavior of the femoral bone under standing loading conditions across three bone states: healt...

By ALEKSANDRA VULOVIĆ, GORDANA JOVIČIĆ, NENAD FILIPOVIĆ

Material transport by diffusion is present in nature, as well as in living organisms as a vital process. The basic and generally used is a phenomenologically established law, named Fick’s law, It states that the material flux is proportional to the concentration gradient and that the material flows from the higher to lower concentration. Howe...

By MILOŠ KOJIĆ, MILJAN MILOŠEVIĆ, ALESSANDRO GRATTONI, MAURO FERRARI

The extremely complex biological and biochemical processes are mainly treated by laboratory and clinical investigations. In recent decades, the application of computational modeling has become more important in research and applications in the medical sciences. Despite enormous efforts and achievements in this modeling, there is still a need for ne...

By MILOŠ KOJIĆ, MILJAN MILOŠEVIĆ, VLADIMIR SIMIĆ, BOGDAN MILIĆEVIĆ

Metastasis involves the dissemination of circulating tumor cells (CTCs) from the primary tumor, their survival in the bloodstream, and eventual colonization of distant organs. Adhesive interactions with platelets, leukocytes, and endothelial cells are critical to CTC survival and extravasation. Platelet adhesion enhances CTC viability and promotes ...

By VLADIMIR SIMIĆ, MILJAN MILOŠEVIĆ, ALEKSANDAR NIKOLIĆ, SHAO NING, XUEWU LIU, FRANSISCA LEONARD, MILOŠ KOJIĆ

Mass transport is a fundamental process in living organisms, responsible for the delivery of oxygen, nutrients, and drugs from blood vessels to tissues, as well as the removal of waste products back to the vascular and lymphatic systems. This exchange occurs across various biological barriers, including blood vessel walls and cellular membranes, an...

By VLADIMIR SIMIĆ, MILJAN MILOŠEVIĆ, BODAN MILIĆEVIĆ, E.J. KOAY, XUEWU LIU, ANTONIO MARTINO, ROSSANA TERRACCIANO, CARLY FILGUEIRA, MILOŠ KOJIĆ

This study investigates the drug release performance of electrospun composite nanofiber mats, which hold significant promise as drug carriers for site-specific delivery in therapeutic applications such as cancer therapy. Predicting drug release rates from poly(D,L-lactic-co-glycolic acid) (PLGA) nanofibers produced via emulsion electrospinning is c...

By MILJAN MILOŠEVIĆ, VLADIMIR SIMIĆ, BODAN MILIĆEVIĆ, DUŠICA STOJANOVIĆ, MIRJANA GRKOVIĆ, MILOŠ BJELOVIĆ, PETAR USKOKOVIĆ, MILOŠ KOJIĆ