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UVODRazvoj industrije kovanja značajno je uslovljen razvojem auto industrije, koja ugrađuje velike količi-ne delova dobijenih ovom tehnologijom. Proizvodnja otkivaka najveća je u Evropi, Japanu i Severnoj Americi, a uposlednje vreme velike količine otkivaka se proizvode u Kini, Koreji i Indiji. Kovanjem se takođe, dobijaju delovikoji nalaze primenu u mnogim drugim granama industrije. Prema podacima Japan Forging Association industrija otkivaka u Japanu i dalje će biti jedna od vodećih industrijskih grana koja će biti orijentisana na proizvodnju kompleksnih, preciznih i visokokvalitetnih delova [1]. Sa razvojem nauke i tehnologije i povećanjem žestoke konkurencije na tržištu, performanse kalupa postaju sve zahtevnije a pitanje veka trajanja postaje sve izraženije [2]. Kalup je jedan od značaj-nijih delova opreme u masovnoj proizvodnji čiji je kvalitet ključni faktor koji utiče na kvalitet proizvoda i na ekonomske koristi za kompanije. Jedan od glavnih problema su loša svojstva površine kalupa kao posledica destrukcije habanjem. Pitanje veka trajanja kalupa je složeno usled velikog broja faktora koji mogu uticati na vek trajanja kalupa. Habanje kalupa je kompleksna, vremenski zavisna pojava koja pre svega zavisi od četiri komponente sistema: kalupa, međusklopa, predmeta obrade i uslova obrade. Učinak ove četiri komponente može se kategorizovati u više procesa -vezanih razmatranja, uključujući dizajn kalupa, materijal kalupa, termičku obradu, podmazivanje, po-vršinsku obradu i uslove obrade. Adrese autora:1 Partizanska 34/e, 23208 Elemir, 2 Visoka tehnička škola strukovnih studija, Zrenjanin, 3 Tehnički fakultet "M. Pupin", Zrenjanin, 4 Fakultet tehničkih nauka, Novi Sad Primljeno za publikovanje: 11. 08. 2014. Dorađeno za publikovanje: 02. 10. 2014. Prihvaćeno za publikovanje: 19. 11. 2014.Kalup nameće geometriju deformisanom materijalu. Dizajn kalupnih šupljina (gravura) upravlja kliznim brzinama, temperaturom i pritiscima među sklopa. Posebno važna razmatranja sa stanovišta habanja i destrukcije su radijusi uglova (ćoškova) i zaobljenja u šupljinama kalupa. Još jedno važno razmatranje za habanje su mikro i makrostrukturne osobine materijala kalupa, njegov sastav, mikrostruktura (jednakost, unutrašnji nedostaci i sekundarni karbidi) i mehaničke i fizičke osobine. Mehanička i hemijska interakcija materijala kalupa sa radnim predmetom i kontaminirajućim materijama (podmazivanje, krhotine i ljuske) zavisi od sastava i mikrostrukture [3].Mehanička svojstva i vek trajanja kalupa može se u velikoj meri poboljšati odgovarajućom tehnikom površinskog ojačavanja. S toga tehnika površinskog ojačavanja igra veoma važnu ulogu u industriji kalupa i privlači široku pažnju. Neophodno je pronaći naprednu tehnologiju površinske modifikacije kako bi se poboljšao vek kalupa i smanjio trošak ili povećala produktivnost [4]. Nedavno uvođenje slojeva vanadijum karbida koji su metalurški vezani za površinu alata za kovanje obezbedilo je proizvođačima sredstvo za sticanje značajnih ušte-da usled poboljšanja performansi alata [5].Pošt...

The paper analyzes the constructive and usable characteristics of resilient wheels with rubber blocks and rubber "V" ring used on light railway vehicles in urban traffic conditions in order to reduce vibration and noise. These vibrations and noise have an impact on passenger comfort and create serious problems for buildings and residents near city transit lines. The sources of noise generated by train wheels due to their vibrations and possible ways of transmitting noise caused by wheel/rail interaction are stated. The paper examines and analyzes the results of previous research that have give contribution to a better understanding and adoption of the resilient wheel structure and rubber parameters in order to achieve the best noise and vibration reduction effects. Through the paper, it was found that resilient wheels can effectively reduce the rolling noise of wheel on the track by a value of 3[dB] and significantly reduce ground vibrations in a certain frequency range.

The paper gives a systematic overview of literature sources who consider impacts critical damage of mechanical, corrosive and thermal nature which may occur on railway axles during operation and which may be the causes of their fracture. The results of the research of the mechanisms that cause cracks, crack propagation and final fracture of the railway vehicle axle, such as material fatigue and the appearance of localized notches caused by paint (coating) separation, damage from ballast impact and pitting corrosion are presented. The influence of high temperatures and overheating on the axles was analyzed and an excerpt from the research published in one research report was given. Some significant suggestions for optimizing the design of the axles are highlighted which would take into account the analysis of time-varying axle stresses, stress spectrum in operation, axle tolerance to damage and the existence of residual surface stresses. The reliefs of the fracture surfaces of the axle after the railway incidents and the derailment of the rail vehicle from the rails are presented and explained.

This paper presents a discussion of the results of previous research of the effects of surface modification of structural materials and tool steels using plasma nitriding (PN) in order to improve their mechanical, tribological and corrosion behavior. The paper discusses the current status and future directions in the application of PN on various wearing components that are exposed to high loads, stresses and frequent temperature changes. The paper provides an overview of the relevant literature whose results show the most favorable or optimal parameters of the PN process aimed at achieving the best performance in terms of wear and corrosion resistance and hardness increase for the various materials considered. Systematization of literature data about research of the impact of low-temperature PN on stainless steels has placed emphasis on those process mechanisms that achieve benefits for surface layers without creating negative side effects in the form of loss of corrosion resistance. The strengthening of hot forging dies is considered through the reasons and problems that cause the need for the application of PN, and then paper focuses on the role of PN in achieving the tribological properties required to extend the service life of the die. Publications in which the nitriding of titanium alloys is investigated through the reduction of wear, increase of bearing capacity and microhardness depending on the input parameters of the process, ie the optimal parameters applied in order to obtain the best performance characteristics are cited. The application of PN to aluminum and its alloys is discussed, as well as the conditions of testing and the achieved improvements.