In order to increase the corrosion resistance of magnesium alloy AZ91 in corrosion environments containing chlorides, the alloy surface has been modified by plasma electrolytic oxidation (PEO). The chemical composition of electrolyte in the PEO process consisted of 12 g/L Na₃PO₄·12 H₂O and 1 g/L KOH, and a direct current was applied to the sample. The corrosion resistance of PEO coating and as-cast AZ91 (sample without PEO coating) was assessed using two different electrochemical methods: electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (PDP) in 0.1 M NaCl at laboratory temperature. In addition to the electrochemical methods, the morphology of the oxidic coating was observed in the cross-sectional and top surface view by using the SEM technique. For better determination of the microstructure and PEO coating, chemical composition EDX analysis was used. The results of the experiments show that the formation of the PEO coating on AZ91 alloy has a more positive effect on the corrosion resistance in 0.1 M NaCl based on electrochemical methods than in the case of the formed coating on AZ31 alloy from the previous study. Based on electrochemical measurements in the selected environment, the formation of PEO coating on AZ91 was accompanied by a significant increase in polarisation resistance after short-term exposure compared to the as-cast surface. The EIS results showed a 73 times higher R_p value for PEO coated AZ91 when compared to the as-cast AZ91. Correspondingly, a 27 times lower i_corr value was observed for PEO coated AZ91 than in the case of substrate AZ91 in 0.1 M NaCl. At the same time, the typically porous and inhomogeneous structure of the formed PEO coating on the magnesium alloy AZ91 was demonstrated.

A surface treatment process, composed of plasma electrolytic oxidation (PEO) and sealing by temporary oil preservation system containing corrosion inhibitors, was performed on AZ31 magnesium alloy in order to improve its corrosion resistance i...

The principles of the friction welding (FW) process of the two different non-ferrous metals, aluminum and copper, are presented in this paper. Considering that the bimetallic Al-Cu joints find applications in electrical engineering, as well as in other industrial fields, the basic characteristics and compatibility of these metals are discussed, along with the influence of various parameters on the properties of their friction welded joints. The experimental study involved rotation friction welding (RFW), which was used to weld aluminum and copper samples. The samples were monitored for shortening due to the applied deformation, as well as the size of the formed mushroom. Then, the central part of the welded joint was cut from the welded samples to determine the hardness and microstructure of the joint. At the end of the research, the possibility of applying software for the design of a numerical model for analysis of the possibility of joining aluminum and copper, with the same input parameters as those used in the experiment, was considered. The numerical simulation exhibited a high agreement with the experimental results.

Roller blinds are devices that are retracted and wrapped in a box above the window opening and are used to protect against the solar radiation. Those are the wellknown devices with distinct advantages over the fixed external dimming elements. The influence of external blinds on the internal thermal environment in climatic conditions in the Republic of Serbia, the city of Kragujevac, was considered in this research. An external blind was installed in the test room and its influence on the internal temperature was compared with the internal temperature of the room without the blind. Real-time monitoring was carried out in February and August 2023. The results presented in this paper show that the blind reduces the temperature in summer by 3.57ºC and increases it in winter by 1.76ºC. The cooling load can be reduced by about 20%, and the heat load by about 15%.

This study delves into the analysis of interface crack propagation originating from a right-angle corner along the bonding plane between the two plates composed of dissimilar materials. The research explores three distinct crack front shapes: concave, triangular, and convex (quarter-circle). The obtained results, meticulously presented in this paper, offer valuable insights into the nature of the crack propagation along these geometries. The findings elucidate that in the case of a convex crack front, the edges demonstrate a significantly accelerated propagation compared to the rest of the crack front. Conversely, for the triangular and concave crack fronts, the central region experiences faster propagation compared to the edges. These revelations lead to a generalized conclusion regarding the stability of different crack front shapes, highlighting the triangular crack front as the most stable configuration in this context. The implications of these observations provide essential knowledge for understanding and managing crack propagation in composite structures, offering potential applications in various engineering domains.

The rotary excavator is a complex machine system, the main part of the ECS (excavator-conveyer-spreader) system, used in open-pit mining. Such a machine’s service life can last for decades, it generally operates in the harsh exploitation conditions, which requires that its vital structures must be continuously controlled and well maintained. Damage or fracture of parts or assemblies of a rotary excavator can be caused by influence of various manufacturing, construction, exploitation conditions or environmental factors. Analysis of those eventual failures can be performed by various methods, out of which the most suitable are the failure analysis methods, for example the fault-tree analysis (FTA), the Ishikawa fishbone (cause-and-effect) diagrams or the failure modes and effects analysis (FMEA). In this article are presented results of the fault tree analysis of possible causes of rotary excavator’s parts, as well as measures to prevent their damages and/or fractures and to extend the service life of an excavator as a whole. The model of the organizational system for the rotary excavator’s maintenance is given, as well.