Author(s):
1. Predrag Živković, Faculty of Mechanical Engineering in Niš, Serbia
2. Mirjana Laković, Faculty of Mechanical Engineering in Niš, Serbia
3. Dušan Petković, Faculty of Mechanical Engineering in Niš, Serbia
4. Dragana Dimitrijević, Faculty of Mechanical Engineerning, Serbia
5. Milica Jović, Faculty of Mechanical Engeneering , Serbia