en سیستم های مکاترونیک Mechatronic systems پژوهشي Research Nonlinear hunting speeds of railway vehicles running on a tangent track are analytically obtained using Hopf bifurcation theory in this paper. The railway vehicle model consists of nonlinear primary yaw dampers, nonlinear flange contact stiffness as well as the clearance between the wheel flange and rail tread. Linear and nonlinear critical speeds are obtained using Bogoliubov method. A comprehensive parametric study is then carried out and effects of different parameters like the magnitudes of lateral clearance, damping values, wheel radius, bogie mass, lateral stiffness and the track gauge on linear and nonlinear hunting speeds are investigated. Bifurcation, Critical speed, Nonlinear, Hunting, Bogoliubov method 186 196 http://ase.iust.ac.ir/browse.php?a_code=A-10-49-1&slc_lang=en&sid=1 D. Younesian younesian@iust.ac.ir 18003194753284600351 18003194753284600351 Yes A.A. Jafari 18003194753284600352 18003194753284600352 No R. Serajian 18003194753284600353 18003194753284600353 No