1. Professor, Institute of Mechanics and Machine Design Foundations, Częstochowa Univ. of Technology, Dąbrowskiego 73, 42-200 Częstochowa, Poland.
2. Professor, Institute of Mechanics and Machine Design Foundations, Częstochowa Univ. of Technology, Dąbrowskiego 73, 42-200 Częstochowa, Poland (corresponding author).