Effect of carbody flexibility on the dynamic performance of an empty freight wagon

The structural flexibility of passenger car bodies is paid most attention in research due to the effect it has on the passenger ride comfort. But as we are moving towards high speed and lightweight freight Railway stock, the issue of structural flexibility becomes essential in the case of freight wagons also. This paper investigates the effect of including the structural flexibility of the carbody of Indian Railway open freight car BOXNHL in the dynamic analysis. A mid surface meshed model of the subject carbody is developed using Hyperworks. Then, modal analysis is done using MSC FEA to identify the dominant flexible body modes. A simulation study has been conducted using NUCARS (New and Untried Car Analytic Regime Simulation) for an empty freight car on straight track and curve. Four types of carbodies have been considered for comparison- rigid carbody, flexible carbody having modal damping factor 0.04, 0.03, and 0.02. Vertical and lateral accelerations are chosen as the representative dynamic response parameters. The novelty of the present work lies in analyzing the effect of modal damping factors on the different response parameters (vertical and lateral accelerations) of empty BOXNHL freight wagon at different speeds. The field test results have been compared with the simulation results for identifying the modal damping factor with a minimum standard deviation.