Influence of stiffness characteristics of a railway track on output parameters in a multibody model

Dižo, Ján; Blatnický, Miroslav · 2020 · Crossref

DOI: 10.1051/matecconf/202031801003

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Summary

This study investigates the impact of railway track stiffness and damping characteristics on the dynamic performance of a passenger railway vehicle. The research addresses the need to evaluate running safety and passenger ride comfort by comparing standard rigid track models against flexible track formulations. While rigid track assumptions are common in simulation, real-world tracks exhibit flexibility; however, the computational cost and accuracy implications of modeling this flexibility are not always clear. The authors aim to determine whether incorporating variable or constant stiffness-damping parameters significantly alters output parameters compared to rigid models. The methodology employs a multibody system simulation using the commercial software Simpack. The model consists of a passenger wagon with two bogies and a body, featuring primary and secondary suspension systems with coil springs and hydraulic dampers. The track model is analyzed under three formulations: a rigid track ("Rigid"), a flexible track with constant stiffness-damping parameters ("Flex_const"), and a flexible track with sinusoidal variable parameters dependent on traveled distance ("Flex_sin"). Simulations were conducted on a real track geometry including curves and irregularities, with the wagon traveling at speeds of 60, 90, and 110 km/h. Passenger ride comfort was assessed using the NMV index derived from floor accelerations processed according to EN 12299:2009, while running safety was evaluated using the derailment quotient (ratio of lateral to vertical wheel forces). The results indicate that track formulation has a minimal effect on passenger ride comfort. At 60 km/h, the "Flex_const" model showed only weak differences from the rigid model, while the "Flex_sin" model yielded slightly higher NMV indices, indicating reduced comfort. At 90 km/h, NMV values increased across all formulations, with "Flex_sin" again showing the highest indices. At 110 km/h, the wagon remained comfortable in most areas, though "Flex_const" showed negligible deviations from the rigid model. Regarding running safety, the "Flex_const" model partially damped dynamic effects compared to the rigid track. However, the "Flex_sin" model produced significantly greater derailment quotient amplitudes, which the authors attribute to the model’s inability to sufficiently reflect real track characteristics rather than actual physical instability. The study concludes that extending the multibody model with flexible track formulations does not significantly influence NMV ride comfort indices. However, it substantially increases computational time, rising by 15–20% for constant parameters and 45–50% for variable parameters. These findings suggest that while flexible track modeling adds computational burden, its impact on standard comfort metrics is limited. The significant derailment quotient variations in the variable stiffness model highlight potential modeling inaccuracies rather than true dynamic risks, implying that users must weigh the increased processing time against the marginal gains in simulation fidelity.

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• passenger motion sickness comfort