Vehicle dynamics simulation considering multipoint contact between wheel and rail during earthquakes

Large earthquakes occurred repeatedly in Japan, and, in some cases, railway vehicles derailed and overturned during earthquakes. Safety measures are being implemented in various railway sectors, and it is important to continue investigating ways to improve safety. The vehicle dynamics simulator (VDS) developed by Railway Technical Research Institute (RTRI) has been used to analyze the behavior of railway vehicles in the event of earthquakes; however, this simulation program has some limitations in terms of the wheel-rail contact problem, which is essential for the vehicle dynamics of rolling stocks due to the performance limitations of the computers at that time. This study developed a new simulation program, i.e., the VDS-X, which includes a multipoint-contact-capable online contact calculation algorithm, thereby enabling analyses that consider the changes in contact conditions that were not fully considered by conventional methods. Using the VDS-X, the results of safety limits for sinusoidal excitations are compared with those obtained by the conventional VDS, and the differences in wheelset behavior between stopped and running conditions are investigated. The results confirm that the trends in safety limits were reproduced in a manner consistent with the conventional method. Furthermore, a detailed analysis of the contact state revealed fundamental differences in the wheel-rail contact behavior during the stopped and running conditions. The behavior under the stopped condition involves repeated two-point contact. In contrast, under the running condition, the influence of the wheel flange attempting to climb onto the rail becomes more pronounced. This indicates a correlation with a reduction in the safety limit. These results provide a new interpretation of reduced safety margins under running conditions, which has previously been observed at a macroscopic level through simulations, from the perspective of wheel-rail contact issues. The findings of this study demonstrate the importance of wheel-rail contact models of rolling stock during earthquakes.