TY JOUR TI Problems and Prospects of Improving the Design and Testing Methods of Three-Axle Trolleys for Freight Cars with Increased Axial Loads (Based on Industrial Transport) KW three-axle trolleys KW freight car KW spring suspension KW axle load KW industrial transport KW dynamics KW strength KW endurance testing KW dump car JO Bulletin of scientific research results AU Petrov, D.Y. AU Boronenko, Y.P. PY 2026 IS 2026 PB FSBEI HE "Emperor Alexander I St. Petersburg State Transport University"