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Numerical simulation of fatigue crack growth (FCG) is presented, based on the application of the extended finite element method (XFEM). Couple of case studies are presented, as a review of recent experience of the Belgrade school of XFEM simulations, established at the Faculty of Mechanical Engineering. Case studies comprised Charpy specimen with initial crack at the notch tip, oil rig pipe with an axial surface crack, pressure vessels with a crack at the welded joint with connecting pipe, turbine shaft with a crack at the transition radius, optimization of a wing spar in respect to FCG, the effect of mesh size on fatigue life estimation of a stringer panel, fatigue life estimation of wing‐to‐fuselage connecting lug, geometry effect on fatigue life of orthopedic plates and fatigue life of hip implant. Based on these case studies, XFEM is discussed in respect to its accuracy and efficiency. It is concluded that XFEM is a versatile tool for simulation of FCG, providing an excellent option for precise and reliable fatigue life of a cracked component. [ABSTRACT FROM AUTHOR]

The experimental determination of aerodynamic characteristics of lift and drag of B787 aircraft using the „Force Balance" method was carried out in the subsonic wind tunnel „Miroslav Nenadović" of the Faculty of Mechanical Engineering, University of Belgrade. This experimental testing most faithfully represents a real case, and the simulated conditions correspond to the geographic location of Nikola Tesla Airport in Belgrade. This method of testing is considered to be the most reliable. Aerodynamic characteristics were obtained by testing the aircraft model. The reconstruction of the wind field for the intended location was, as with most current assessments, carried out using a numerical model which enables the precise determination of wind zones with adequate characteristics. The accuracy of determining the roughness of the terrain and the influence of obstables were taken into account during the assessment. All the assessments were carried out with the average annual wind speed, as well as on the basis of data on the maximum wind gust in the past hundred years. A numerical threedimensional meso model was used which was confirmed in our conditions as well. Following that the methodology of testing was determined, the setup in the wind tunnel was made and the experiment was performed. The experiment was carried out for eight directions for the value of the wind strength which was obtained using the numerical model. The measurement was performed using the „Force balance" method for measuring lift and drag. The load actuators with sensors were used for measuring the forces of lift and drag during the testing. The actuators were connected to the computer via sensors and the data were recorded in real time. The obtain results of aerodynamic characteristics, lift and drag, fall within the range od expected value. On the diagrams shown, it can be observed that the trend of the curves is of a satisfactory character. This methodology of experimental aerodynamics presented in the paper proved to be very reliable for future experimental analyses. [ABSTRACT FROM AUTHOR]

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