Capacity discharge percussion welding is nonconventional welding process where heat source is an electric arc obtained by discharging of capacitor bank. The arching time is very short, around 10 ms, and depends on a few parameters such as: capacity of capacitor bank, voltage, movement speed of welded pieces during welding. During arching a certain amount of material is melted and after that squeezed out by applied force used in welding process. Quantity of squeezed material depends upon heat input, intensity of the force pressing the wires during welding and many other parameters. Mechanical properties of welded joints depend on welding parameters. In this paper is described the influence of capacity discharge percussion welding parameters on mechanical properties of welded joints.

Vibrations are common phenomenon in the rotating machinery, which could carry important information about condition of the rotating machinery. All specific failures in rotating machinery have their own characteristics of the vibrations. By measuring and analysis of vibrations cause of increased vibrations could be determined. Since misalignment and rotating looseness have similar frequency spectrum characteristics, it is difficult to determine which one of the failures is present. When cause of increased vibrations is determined, it is possible to plan the future steps for the repairing and neutralising present cause of the possible failure. Process of vibration analysis followed by present cause of increased vibration in rotating machinery repairing is presented in this paper through example on the ventilation system for smoke drain in the thermal power plant. ARTICLE HISTORY Received 15.01.2018 Accepted 03.03.2018 Available 15.03.2018

Temperature changes in material during welding can be registered or described in different ways: analytically, numerically or experimentally. For the analytical method, it is necessary to describe a problem by partial differential equations, the solving of which is often difficult or impossible. For the experimental results, it is necessary to have a set of specified equipment and to make one or more expensive measurements. The desired results can be obtained numerically, by using some commercial software packages or by creating one’s own software for a specific problem. All the software is based on a space and time discretization, using finite elements, finite volumes, finite difference method, or their combination. In this paper a comparison of the results obtained by the finite elements method and finite volume method was made on an example of one-dimensional transient heat conduction, the simplicity of which does not distort the generality of the obtained results and derived conclusions.

Rezime U slučaju austenitnih nerđajućih čelika, azot se može smatrati legirajućim elementom. Jedan od razloga je to što azot, kao intersticijski rastvoren u kristalnoj rešeci železa, doprinosi poboljšanju zateznih karakteristika, prvenstveno napona tečenja. Dodatno, zahvaljujući svom jakom austenitotvornom delovanju doprinosi povećanju stabilnosti austenita, čime je omogućena delimična supstitucija skupog i deficitarnog nikla. Legiranjem metala šava austenitnih nerđajućih čelika azotom moguće je uticati na njegove osobine. Kod postupaka zavarivanja sa gasnom zaštitom, metal šava se može legirati i putem dodavanja azota u zaštitni gas. U ovom radu su razmotreni neki od efekata dodavanja azota u argon zaštitni gas kod TIG zavarivanja austenitnog nerđajućeg čelika X5 CrNi 18 10. Abstract In the case of austenitic stainless steels, nitrogen can be considered as alloying element. One reason is that the nitrogen, interstitially dissolved in the crystal lattice of iron contributes to improved tensile properties, primarily of the yield point. In addition, thanks to its strong austenite forming action contributes to increasing the stability of austenite, thereby enabling partial substitution of expensive and scarce nickel. Alloying of the weld metal of austenitic stainless steels with nitrogen can affect its properties. In welding processes with gas protection, weld metal can also be alloyed through the addition of nitrogen in the shielding gas. This paper discusses some of the effects of the addition of nitrogen in argon shielding gas at TIG welding of austenitic stainless steel X5 CrNi 18 10.