1. Institute of Mechanical Engineering and Machine Operation, University of Zielona Gora, Szafrana 4, 65-246 Zielona Gora, Poland
2. Institute of Applied Mechanics, Poznan University of Technology, Piotrowo 3, 60-965 Poznan, Poland; Institute of Rail Vehicles, Tabor, Warszawska 181, 61-055 Poznan, Poland