The effect of high-speed train meet on wheel wear at different speeds

Purpose Considering that a meet between high-speed trains can generate aerodynamic loads, this study aims to investigate the effect of high-speed train meet on wheel wear at different speeds to provide a more accurate wheel wear model and a new idea for reducing wheel wear. Design/methodology/approach The train speed was set at 250, 300, 350 and 400 km/h separately, and a vehicle system dynamics model was constructed using the parameters of an actual high-speed train on a line. The aerodynamic forces arising from constant-speed train meet were then applied as additional excitation. Semi-Hertzian theory and Kalker’s simplified theory were used to solve the wheel/rail contact problems. The wheel wear was calculated using Archard wear model. The effect of train meet on wheel wear was analyzed for the whole train, different cars and different axles. Findings According to the results, all wheels show a wear increase in the case of one train meet, compared to the case of no train meet. At 250, 300, 350 and 400 km/h, the total wheel wear increases by 4.45%, 4.91%, 7.57% and 5.71%, respectively, over the entire operational period. The change in speed has a greater impact on wheel wear increase in the head and tail cars than in the middle car. Moreover, the average wear increase in front-axle wheels is 1.04–2.09 times that in rear-axle wheels on the same bogie. Practical implications The results will help to analyze wheel wear more accurately and provide theoretical guidance for wheel repair and maintenance from the perspective of high-speed train meet. Originality/value At present, there is a lot of focus on the impact of high-speed train meet on the dynamic performance of vehicles. However, little research is available on the influence of train meet on wheel wear. In this study, a vehicle dynamics model was constructed and the aerodynamic forces generated during high-speed train meet were applied as additional excitation. The effect of train meet on wheel wear was analyzed for the whole train, different cars and different axles. The proposed method can provide a more accurate basis for wear prediction and wheel repair.

On pressure perturbations caused by a moving heat source of the frontal type (hydrostatic mode)

The problem of perturbations of the surface pressure caused by a moving nonstationary frontal heat source (localized along one horizontal coordinate) is considered. Pressure disturbances are associated with internal gravity waves (IGWs). It is shown that when a source moves in a finite-height atmospheric layer (atmospheric waveguide) when a discrete set of vertical IGW modes is excited, there are three types of temporal variation of surface pressure at a fixed observation point. These types correspond respectively to the time signal with amplitude modulation, the signal with frequency modulated Doppler type and the signal that occurs only after passing through the source. Each type is implemented for specific values of the oscillation frequency of the source and the Mach number (the ratio of the speed of the source to the phase velocity of the IGW). At Mach numbers less than one, an oscillating source always excites wave precursors disturbances observed before the source arrives. The movement of the source in a semi-infinite atmosphere leads to additional excitation of waves that transfer energy to the upper layers of the atmosphere.

Vibration damping in road bridges – two case studies of full scale experiments

The paper presents the results of a vibration damping analysis of two road viaducts. The analysis was based on displacement signals recorded during the dynamic load tests carried out before an acceptance process of the viaducts. To create an additional excitation, a 5 cm high threshold was located on the road during low-velocity passages. The Logarithmic Decrement (LD) was calculated using an exponential curve fit to free vibration amplitudes. A fundamental frequency of vibration was considered. To minimize the influence of signal imperfections, a filtration process was carried out using bandpass Infinite Impulse Response (IIR) Bessel filter. The results were correlated for various degrees of excitation resulting from different velocities of loading vehicles and the presence of the threshold. Examples of appropriate and inadequate signals for the damping analysis were shown.

Evidence of additional excitation energy transfer pathways in the phycobiliprotein antenna system of Acaryochloris marina

To improve the energy conversion efficiency of solar organic cells, the clue may lie in the development of devices inspired by an efficient light harvesting mechanism of some aquatic photosynthetic microorganisms that are adapted to low light intensity.