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The geometric filtering phenomenon is first analyzed with a simplified vertical vehicle model. Analytical solutions obtained with this model show that geometric filtering phenomenon consists of ‘wheelbase filtering’ and ‘bogie spacing filtering’ effects. The wheelbase filtering effect occurs when there is neither car body bounce nor pitch response at certain track wavelengths, whereas the bogie spacing filtering effect occurs when there is a null in either the car body bounce or pitch response at particular track wavelengths. Then, the correlated frequency response function for railway vehicles is defined to assess the effect of geometric filtering upon the resonant frequencies of a flexible car body. It is found that if the car body’s first bending frequency coincides with the peak values of bounce acceleration transmissibility, that is, it is near the null pitch response frequencies, resonant vibration of the flexible car body will happen. Finally, to suppress the resonant vibration of the flexible car body, it is proposed to use a dynamic vibration absorber (DVA) suspended under the car body underframe. The DVA parameters are optimized according to car body bending frequency and the null pitch frequency. The optimal DVAs show very good performance and robustness in suppression of the car body resonant vibration.

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High structural modal frequencies of car body are beneficial as they ensure better vibration control and enhance ride quality of railway vehicles. Modal sensitivity optimization and elastic suspension parameters used in the design of equipment beneath the chassis of the car body are proposed in order to improve the modal frequencies of car bodies under service conditions. Modal sensitivity optimization is based on sensitivity analysis theory which considers the thickness of the body frame at various positions as variables in order to achieve optimization. Equipment suspension design analyzes the influence of suspension parameters on the modal frequencies of the car body through the use of an equipment-car body coupled model. Results indicate that both methods can effectively improve the modal parameters of the car body. Modal sensitivity optimization increases vertical bending frequency from 9.70 to 10.60 Hz, while optimization of elastic suspension parameters increases the vertical bending frequency to 10.51 Hz. The suspension design can be used without alteration to the structure of the car body while ensuring better ride quality.

In the present manuscript fracture propagation in a saturated porous medium is modeled based on the classical Biot theory, where solid skeleton and fluid flow are represented by separate two layers. The non‐ordinary state‐based peridynamics (NOSBPD) layer is employed to capture deformation including fracturing of the solid skeleton, while the fluid flow is controlled by the finite element method (FEM) layer. The interaction between the layers is realized by considering the effects of pore pressure from the FEM layer on the NOSBPD layer and, vice versa, the effect of the volumetric strain, porosity, and permeability variations from the NOSBPD layer on the FEM layer. The coupling terms retain their parent characteristics, that is, the interaction term in the momentum balance equation is approximated by the local FEM formulation whereas the interaction term in the mass balance equation is approximated by the nonlocal NOSBPD formulation. By doing so, the model retains the flexibility of coupling two independent discretizations. The coupled system is solved by a fully implicit solution scheme. The accuracy of the proposed method has been verified against available closed‐form solutions and published numerical approaches for the pressure‐ and fluid‐driven facture propagation problems.

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The influence of vehicle-track dynamic coupling on the fatigue failure of coil springs within the primary suspension of metro vehicles Steel coil springs are commonly used in the primary suspension of rail vehicles, usually in the form of two concentric springs. They exhibit strong internal resonances, which can lead to high vibration amplitudes within the spring itself. In some metro vehicles, large numbers of spring failures have occurred due to fatigue fracture in working conditions. The cause of these failures is investigated by studying the vehicle/track interaction, the modal response of the coil springs and the stresses occurring within them in working conditions. A finite element model is used to determine the modal parameters of the primary suspension. The resulting dynamic stiffness matrix is then included in a multi-body vehicle model and coupled to a model of the track. This coupled model is used to investigate the effect of the dynamic properties of both the springs and the track on the stresses in the springs. The springs exhibit strong internal resonances at around 50-60 Hz, at which very large stresses occur in both springs. This frequency range coincides with the P2 resonance frequency (wheelset mass bouncing on the track stiffness) for the standard slab track system used on this metro system. For other track systems, the P2 resonance occurs at a different frequency and the stresses are lower. These results are confirmed with field test data. From the stresses the weakest position in the inner spring is identified, which is found to correspond to the position of common breakages found in field observations. Some guidelines are proposed for reducing the vibration and stress, so that the fatigue fracture incidents can be reduced.