Statistical identification of geometric parameters for high speed train catenary

Pantograph/catenary interaction is known to be strongly dependent on the static geometry of the catenary, this research thus seeks to build a statistical model of this geometry. Sensitivity analyses provide a selection of relevant parameters affecting the geometry. After correction for the dynamic nature of the measurement, provide a database of measurements. One then seeks to solve the statistical inverse problem using the maximum entropy principle and the maximum likelihood method. Two methods of multivariate density estimations are presented, the Gaussian kernel density estimation method and the Gaussian parametric method. The results provide statistical information on the significant parameters and show that the messenger wire tension of the catenary hides sources of variability that are not yet taken into account in the model

Benchmarking Signorini and exponential contact laws for an industrial train brake squeal application

Contact representation of structure interactions for finite element models is nowadays of great interest in the industry. Two contact modellig strategies exist in the literature, either based on a perfect contact with no interpenetration of structures at contact points, or based on functional laws releasing the contact constraint through pressure-penetration relationships. Both strategies require very different and rarely documented numerical implementations, making difficult any objective comparison. This paper presents a benchmark between ideal contact and a functional law of the exponential type applied to squeal simulations by complex mode analysis of an industrial railway brake

Introduction of variability in pantograph-catenary dynamic simulations

Currently, pantograph-catenary dynamic simulations codes are mainly based on deterministic approaches. However, the contact force between catenary and pantograph depends on many key parameters that are not always quantified precisely. To get a better chance of addressing extreme or combinations of critical conditions, methodologies to consider variability are thus necessary. Aerodynamic forces and geometrical irregularities of catenaries are thought to be significant sources of variability in measurement and this paper proposes methods to take them into account. Results are compared with measurements to see the importance of the considered parameters with respect to global variability observed in measurements

Damping characterization of a high speed train catenary

Catenary damping has long been a tuning parameter in pantograph-catenary dynamic interaction models. As the computed contact force is highly sensitive to the choice of damping model or coefficients, it became critical to measure it independently of the pantograph. Original tests have been conducted on a real catenary and damping identification shows a very low level of damping for a large frequency range. A fitted Rayleigh model and a combined modal and Rayleigh model are proposed and compared with a reference damping model found in literature as well as with the tests. Finally, the consequences on a typical contact force simulation are analysed and the most relevant model is chosen

Damping characterization of a high speed train catenary

Catenary damping has long been a tuning parameter in pantograph-catenary dynamic interaction models. As the computed contact force is highly sensitive to the choice of damping model or coefficients, it became critical to measure it independently of the pantograph. Original tests have been conducted on a real catenary and damping identification shows a very low level of damping for a large frequency range. A fitted Rayleigh model and a combined modal and Rayleigh model are proposed and compared with a reference damping model found in literature as well as with the tests. Finally, the consequences on a typical contact force simulation are analysed and the most relevant model is chosen

Waves, modes and properties with a major impact on dynamic pantograph-catenary interaction

Understanding the dynamic behavior of the pantograph-catenary system is crucial for design improvement, but many factors inuence the contact force, which is the main design objective. To give a proper un-derstanding of dynamic characteristics, the paper uses a combination of mass drop tests on a catenary, analytic models and parametric _nite element model simulations allowing a ne analysis of the inuence of train speed. The _rst contributor to contact force variations is the geometry of the catenary under gravity loading. This parameter is however shown to be insu_cient to explain higher frequency e_ects. The second contributor is the propagation of waves in the contact and messenger wires. The inuence of wave dis-persion is _rst demonstrated, which emphasizes the importance of considering the bending sti_ness. Wave compensation by droppers and reections at the mast are then shown to be important. Characteristic times associated with wave group velocities are _nally used to explain the series of harmonic contributions visible in spectra in the catenary and pantograph frames. Finally, modes are shown to play a role particularly when their frequencies coincide with other contributions. The notion of mode groups, associated wave velocities and relevant design variables are discussed. Several observations pave the way for future work on catenary design

Simulation des vibrations d’organes moteur complexes à amortissement non-standard par méthodes modales étendues

Généralisation des méthodes de synthèse modale avec prise en compte appropriée de viscoélastiques (variations en fréquence et température), issue d'itérations sur résidus considérant les efforts viscoélastiques comme perturbation non-linéaire d'un modèle élastique. Des comparaisons sont réalisées avec des solutions de référence sur plusieurs cas dont une structure moteur à géométrie complexe et viscoélastiques localisés, sur des implémentations MATLAB/SDT et NASTRAN/DMAP

Sensitivity analysis of catenary geometry on current collection quality

A global sensitivity analysis is led on catenary parameters such as dropper lengths, height of the messenger wire at masts and mechanical tensions in the wires thanks to the Sobol indices. All parameters are defined using experimental measurements. A set of geometric and dynamic criteria is selected as output and the contribution of theinput parameters to the output variability is quantified. It is shown that the dynamicinteraction is mainly sensitive to the mechanical tensions in contact and messenger wires whereas existing geometric criteria are mainly dependent on height of messenger wire at masts. Moreover, selected geometric criteria available using geometry measurements are hardly correlated with dynamic criteria

Squeal complex eigenvalue analysis, advanced damping models and error control

Estimation of brake systems stability related to noise emission is part of the industry state-of-the-art for brake design. Improved assessment of stability would allow better NVH performance from early design stages thus reducing costs related to late redesign and testing. The prediction capability however remains challenged due to the complexity of brake noise phenomena. In particular, integration and resolution of complex systems with damping is a difficult task that is commonly overlooked. This paper proposes two ideas to improve stability estimation. From the solver side, a convergence indicator is proposed to quantify the convergence of the complex eigenvalues for subspace based methods. The error obtained can be directly used to enhance the computation subspace and a priori enhancement is suggested. From the modelling side, a damping strategy based on sub-assembly modal damping ratios is proposed allowing direct exploitation of test measurements or refined sub-assembly simulations for damping estimation. Sub-assembly damping can thus be accounted for at the system level including all possible effects like joint dissipation or composite materials

Introduction of variability into pantograph–catenary dynamic simulations

Currently, pantograph-catenary dynamic simulations are mainly based on deterministic approaches. However, the contact force between catenary and pantograph depends on many key parameters that are not always quantified precisely and can vary in time and space. To get a better chance of addressing extreme or combined critical conditions, methodologies to consider variability are thus necessary. Aerodynamic forces and geometrical irregularities of catenaries are thought to be significant sources of variability in measurement and this paper proposes methods to take them into account. Results are compared with measurements to correlate the effect of the considered parameters with experimentally observed variability. Finally, a virtual certification example is shown, with a study of the influence of speed on the impact of variability.SNC