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Traditional methods for the optimization design of the air spring are based on the deterministic assumption that the parameters are fixed. However, uncertainties widely exist during the manufacturing stage of the air spring. To model the uncertainties in air springs, evidence theory is introduced. For the response analysis of the air spring system under evidence theory, an evidence theory-based polynomial chaos method, called the sparse grid quadrature-based arbitrary orthogonal polynomial (SGQ-AOP) method, is proposed. In the SGQ-AOP method, the response of the air spring is approximated by AOP expansion, and the sparse grid quadrature is introduced to calculate the expansion coefficient. For optimization of the air spring, a reliability-based optimization model is established under evidence theory. To improve the efficiency of optimization, the SGQ-AOP method is used to establish the surrogate model for the response of the air spring. The proposed response analysis and the optimization method were employed to optimize an air spring with epistemic uncertainties, and its effectiveness has been demonstrated by comparing it with the traditional evidence theory-based AOP method.

The cell array type significantly affects the global stresses in curved honeycomb sandwich panels. In this study, the curved sandwich panels with the out-plane honeycomb core (COP) and the in-plane honeycomb core (CIP) are proposed. Their local impact resistance is numerically investigated using finite element simulation calibrated with air cannon test results. Various impact scenarios including different projectile diameters, different impacting velocities, angles, as well as locations are considered. The performances of the COP and CIP panels with similar overall mass and relative density are compared by evaluating their impact histories and energy absorption properties. It is demonstrated that the CIP panel shows improved impact mitigation and energy absorption property under local impact. However, its overall displacement is significantly larger than that of the COP panel. Based on the impact behavior of COP and CIP panels, the hybrid two-layer structures (HOI and HIO) are designed. It is found that the HIO panel shows an increase in energy absorption of approximately 3% over the COP and CIP panels and a reduction in the overall displacement of at least 28% over the CIP panel. Moreover, HIO configuration with the thinner cell wall thickness of the upper core demonstrates improved impact mitigation. [ABSTRACT FROM AUTHOR]

Based on the application of the honeycomb in the square guide rail,analyzed the tandem honeycomb deformation stability by experiments. Found tandem honeycomb is prone to instability in the impact process for the effect of uneven strength of simple honeycomb and impact load deflection. Analysis shows that the plate, with low intensity or its sectional dimension is smaller than guide rail section, is difficult to prevent honeycomb instability. To improve the effect of connection on keep tandem honeycomb deformation stability, studied the relationship among plate sectional dimension, guide rail sectional dimension and plate deflection degree from the theoretical level: when the guide rail sectional dimension unchanged, the longer the length of connection plate is, the smaller the deflection angle of plate is, the smaller the friction between plate and guide rail is, the better the guiding function of connection plate is. Based on the conclusion, designed a new guiding plate, it is not only improves tandem honeycomb deformation stability, but also solves the honeycomb peeling.

Corrosion caused by supercritical CO2 can cause serious damage to equipment. This study investigates the corrosion behaviors of iron in supercritical CO2 by molecular dynamics simulations via considering the effect of different factors including temperatures (T), the density of CO2 (ρCO2) and surface roughness of iron (λp). It is found that the corrosion process includes three stages. The first stage is dominated by CO2 diffusion. Rapid corrosion happens in the second stage, with a high reaction rate and plenty of corrosion products generated. In the third stage, these products prevent the reaction from proceeding and the system becomes stable. Moreover, it is demonstrated that the corrosion reaction is highly activated with T > 700 K. The ρCO2 has little effect on the corrosion rate, leading to the maximum reaction rates with different ρCO2 almost identical. The λp hardly affects the degree of corrosion but can accelerate the corrosion progress. [ABSTRACT FROM AUTHOR]

Monitoring the vibration offset of a car-body has been of great significance to ensure the operation safety of high-speed trains and reasonably determine the railway gauges. However, there has been scarce research on this topic. To address this limitation, this study proposes an offset measurement method based on the magnetoresistance effect that can be used for offset detection of railway car-body vibration. The magnetic field distribution of the method is simulated by the finite element method, and the feasibility is verified. In addition, the nonlinear relationship between the magnetic induction and the vibration offset is obtained by a neural network model. Finally, a magnetoresistive sensor-permanent magnet coupling monitoring system is developed, and its accuracy is verified by a series of static and dynamic tests. The test results reveal that the proposed monitoring method can effectively monitor the car-body offset relative to the track. [ABSTRACT FROM AUTHOR]

New engineering phenomena in China have renewed interest in research on the dynamic risk boundaries and characteristics of train overturning, derailment, and the interaction mechanism with aerodynamic loads in windy conditions. This study focuses on this challenge, the train aerodynamic loads characteristics, dynamic response and safety risk characteristics, and the contribution rate of different aerodynamic loads to train safety risks in different wind scenarios were investigated by computational fluid dynamics and multi-body dynamics simulation. The results reveal that when a train is completely exposed to strong winds with or without a windbreak, the safety risk assessment should focus on the overturning coefficient of the first wheelset of the first bogie of the head car. When the train is gradually exposed to strong winds, the probability of the train derailing risk is greatly increased. The train safety risk assessment should not only focus on the overturning coefficient, and more attention should be paid to the derailment coefficient of the first wheelset of the first bogie of the head car. In addition, there may be a risk of misjudgment in assessing the crosswind safety of trains from the aerodynamic point of view only by lateral force, lift force, and roll moment. [ABSTRACT FROM AUTHOR]