The method of kinematic excitation reconstruction based on measured suspension dynamic responses – experimental verification

The paper presents the method of kinematic road excitation reconstruction based on measured suspension dynamic responses and its reconstruction with use of estimated displacements of unsprung mass as a preliminary approximation of kinematic excitation and tracking control system with a PID controller that allows for faithful reconstruction of unsprung mass accelerations and, in turn, kinematic excitations. The authors performed an experimental verification of the method with use of one axle car trailer and measurements of road profile and acquiring signals of suspension dynamics responses. The signal processing methodology and obtained results are presented for random and determined excitations. The necessary requirements to use the method effectively were defined and its limitations were listed.

Evaluation of Stress and Fatigue of a Rail Vehicle Suspension Component

The article discusses the use of pivot bearing friction liners, made of selected materials, in railway freight wagons’ spherical centre bowls. Comparative studies on the effect of suspension dynamics on the equivalent stresses in the liner material were carried out using the finite element method and multibody simulation. The results show the magnitude and location of the highest stresses in the liner with varying input loads, friction coefficients and interacting materials. The analysis is a basis for a simulation method for predicting the fatigue life of the suspension friction liner placed in the centre bowl between the bogie frame and the vehicle body.

Generation of acoustic-Brownian noise in nuclear magnetic resonance under non-equilibrium thermal fluctuations

We present an analytical study on generation of acoustic-Brownian noise in nuclear magnetic resonance (NMR) induced as a result of thermal fluctuations of the magnetic moments under non-equilibrium thermal interactions which has not been explored independent of Nyquist–Johnson noise until now. The mechanism of physical coupling between non-equilibrium thermal fluctuations and magnetic moments is illustrated using Lighthill’s formulation on suspension dynamics. We discover that unlike Nyquist–Johnson noise which has a uniform spectral density across a range of frequencies, the spectral dependence of acoustic-Brownian noise decreases with an increase in frequency and resembles Brownian noise associated with a particle in a potential well. The results have applications in the field of image enhancement algorithm as well as noise reduction instrumentation in NMR systems.

Performance Evaluation of Train Suspension Energy Harvesting Shock Absorber on Railway Vehicle Dynamics

Railway transportation has been increasingly significant for modern society in recent decades. To enable smart technology, such as health monitoring and electromagnetic braking for railway vehicles, a mechanical motion rectifier (MMR) based energy harvesting shock absorber (EHSA) has been proposed and proved to be capable of scavenging energy from the train suspension vibration. When installed on the train, MMR-EHSA works as a tunable damper in parallel with an inerter. This new suspension form brings great potential for further optimization of suspension dynamics but is rarely researched before. In this paper, the influence of the energy harvesting shock absorber (EHSA) on the railway vehicle dynamics performance is studied. A ten-degree of freedom vehicle model is established, with MMR shock absorber’s nonlinearity taken into account, with the purpose to analyze the influence of the EHSA on the ride comfort and wheel-rail vertical forces. Simulations are conducted by replacing the traditional shock absorber from train secondary suspension with the EHSA. Results show that EHSA could respectively harvest 180 W and 40 W average power at AAR 6th and 5th rail irregularity. In addition, compared with the traditional shock absorber, the MMR-EHSA can provide a higher ride comfort for passengers and slightly reduce the wheel-rail contact force.