In this paper, the elastic behaviour in bending of three-layer plywood cantilever beams is analysed. Deflections of straight and half-circle cantilevers, loaded with a force at free end is determined experimentally and calculated using analytical and finite element method approach. The analytical calculation of deflection for the strait cantilever is obtained using a transformed cross section. The deflection of half-circle cantilever is determined by the classical laminated plate theory and Castigliano’s theorem. Loads and cantilever dimensions are varied in the study using the design of experiment. The deflection regression models for straight and semicircular plywood cantilevers are obtained from the experimental results. Analytically and numerically determined deflections of strait and half-circle cantilevers show very good agreement. Experimentally recorded deflections are approximately 30 % higher than analytical values. Stiffness properties and deflection values are influenced by direction of fibres in the outer layers of a three-layer plywood beam.

Aluminum alloys are widely used in military and aviation industry due to their properties such as low density and high strength. During the aircraft operation there are mechanical failures of various structural components caused by numerous mechanisms such as corrosion, material defects, high cycle fatigue and the like. One of the frequent mechanical failures on air-cooled piston engines is the cylinder head cracking. This paper is the continuation a comprehensive research of the Lycoming IO-360-B1F aircraft cylinder head failure. The failure of this type has already occurred during flight and about 50 failures like this have been registered from around the world, some of them with a fatal outcome and therefore require detailed research. The paper consists of machining of the tested specimens and their testing at many different locations and in many different laboratories throughout Bosnia and Herzegovina, Serbia and Slovenia. This paper is based on a research that includes the experimental analysis of mechanical properties of Aluminum alloy 242.0 which is a constituent material of the cylinder head of the Lycoming IO-360-B1F aircraft engine on which a crack appeared. Based on chemical, metallographic, static and dynamic experimental tests of the material properties, Aluminum alloy 242.0 static and fatigue properties were obtained, S-N curve was formed and endurance limit was determined. Results of numerical simulations of experiments, confirmed by experimental results, were performed to make numerical procedures reliable due to further research. The results of the research are planned to be implemented in numerical modeling of the cylinder assembly stress-strain state under workload and in further numerical research of Lycoming IO-360-B1F cylinder assembly integrity assessment.

3D printing technology is leading to great advancements and expanding the limits in many engineering fields and education. Geometrical accuracy of the parts produced by 3D printing could be a very important characteristic for some purposes. In this paper the geometrical accuracy of parts produced by FDM (Fused Deposition Modelling) 3D printing technology is investigated. For this purpose a benchmark part is designed and size, form, orientation and location accuracy of different features on it are evaluated using coordinate measuring machine. Two different FDM desktop 3D printers are used for the benchmark part printing.

Pokusi delaminacije s grednim uzorcima se cesto koriste kod ispitivanja razlicitih suvremenih materijala sa slojevitom strukturom, i kod razlicitih vrsta ovih pokusa javljaju se i razliciti nacini loma (otvaranja pukotine). Kod pokusa s mjesovitim nacinom loma znacajno je s aspekta dizajna napraviti podjelu energije loma na udjele od razlicitih nacina loma, tj. odrediti mjesovitost nacina loma. Problematika podjele energije loma u pokusima delaminacije s grednim uzorcima je predmet velikog broja istraživanja u posljednjih tridesetak godina i kao rezultat toga predložena su razlicita rjesenja zasnovana na analitickim i numerickim metodama. Rezultati dobiveni primjenom ovih rjesenja pokazuju dobro slaganje kod primjene na pokuse sa simetricnom geometrijom uzoraka, međutim, kod primjene na pokuse s asimetricnom geometrijom uzorka pokazuju znacajno neslaganje. U ovom radu je dat osvrt na odabrana analiticka i numericka rjesenja koja se mogu primijeniti za podjelu energije loma. Razmatrane su dvije pionirske, suprotstavljene teorije, prema Williamsu i prema Hutchinsonu i Suou, te nedavno predložena, poluanaliticka, SACA metoda, koja je s novim pristupom problemu objedinila ove dvije teorije. Rezultati primjene spomenutih metoda su na primjeru pokusa delaminacije s dvostrukim grednim uzorkom, kome je jedan krak opterecen momentom savijanja, uspoređene s rezultatima odabranih numerickih istraživanja zasnovanih na primjeni modela kohezivne zone.

Delamination (fracture) tests have been numerically investigated using various cohesive zone properties. The test utilises asymmetric and symmetric double cantilever beam specimens loaded with bending moment. Energy release rate contributions from mode I and mode II fracture are calculated using a global and local approach. Mode-mixities results are presented and analysed. The numerical partitioning results for different configurations are compared to two analytical partitioning theories, namely, after Williams and after Hutchinson and Suo. Opposite to these theories, partitioning is observed to be dependent on cohesive zone properties.

In this paper the stress concentration factor for the case of set-on nozzle in a cylindrical vessel under internal pressure is researched. Two different nozzle geometries are investigated using numerical and experimental methods, FEM analysis performed in ABAQUS and strain gauges measurements. Based on numerical and experimental results, stress concentration factors defined by maximum principal and maximum von Mises equivalent stresses are calculated and compared. The comparison shows good agreement between the stress concentrations factors determined with the two different methods.

This paper deals with the determination of stress concentration factors using numerical methods. The cases of the bar with circular cross section and U-shaped groove subjected to tension and bending are considered. Determination of model parameters is achieved by combining the design-of-experiment, implemented in MATLAB, and Finite Element analysis, as an alternative to standard mechanical tests. The design-of experiment is used in order to set-up a variety of combinations of geometrical parameters, whereas the Finite Element analysis, performed in ABAQUS, is applied using obtained geometry variations in order to calculate corresponding stress concentration factors. MATLAB is also used for subsequent mathematical modeling in order to obtain appropriate expressions for stress concentration factors. Obtained mathematical models agree well with existing data from literature.

Paper received: 18.06.2020. Paper accepted: 29.06.2020. Stručni rad REZIME Pojam reverzibilnog inženjerstva u mašinstvu podrazumijeva proces kopiranja postojećeg dijela ili sklopa, za koji nije dostupna tehnička dokumentacija ili digitalni model. Reverzibilno inženjerstvo je proces otkrivanja tehnoloških principa nekog proizvoda kroz analizu njegove strukture, funkcije i rada. Ovaj proces uključuje mjerenje dimenzija i oblika proizvoda, te rekonstruiranje njegovog 3D modela. Korištenjem CAD softvera, reverzibilno inženjerstvo je prihvatljiva metoda za izradu 3D modela već postojećih fizičkih objekata. Takvi 3D modeli mogu se dalje koristiti u CAD/CAM/CAE programskim paketima. Cilj ovog rada jeste demonstracija praktične primjene reverzibilnog inženjerstva na osnovu kontaktnog mjerenja pomoću CMM-a. Rezultat ovog rada je uspješno kreiran parametarski CAD model, korištenjem IGES datoteke dobivene mjerenjem dimenzija realnog modela pomoću CMM-a.