Numerical and experimental investigation of nonlinear properties of rubber absorber in rail fastening

International audienceA nonlinear dynamic model of a rubber absorber in railway fastening systems is proposed, based on the superposition principle to simulate its nonlinear vibrational behavior. A dynamic experiment was carried out to obtain all model parameters. The accuracy of the model was supported by good agreement between measured and simulated results, and it should therefore be an effective mechanical tool for simulating and characterizing the nonlinear behavior of rubber absorbers in rail fastening systems at particular vibrational modes. Excitation frequency dependency and amplitude dependency of the nonlinear dynamic stiffness were also selected for further study. The results indicate that characteristics of the nonlinear dynamic stiffness are closely associated with both displacement amplitude and frequency, although frequency dependency is not as great as amplitude dependency

Bruit de contact pneumatique chaussée

International audienceBruit de contact pneumatique chaussé

A fast method for computing convolutions with structural Green's functions: application to tyre dynamic contact problems

International audienceTyre/road contact is the main source of car noise at speeds greater than 50 km/h. In this context, we have developed a new approach for modelling tyre vibrations and contact with rigid road surfaces during rolling. For tyres, a periodic model is used to compute Green's functions. The response of tyres can, thus, be modelled over a large frequency range. Then, a fast convolution and a new contact model are developed and examples of computations of contact stress are given for real road textures. Spectra of stress for different tyre velocities are also compute

A fast algorithm for computing dynamic tyre road contact forces

International audienceTire/road contact is the principal source of car noise at speeds greater than 50 km/h. In this context, we have developed a new approach for modelling the tire vibrations and the contact with the rigid road surfaces during rolling. For the tire, a periodic model is used to compute Green's functions. The response of the tire can thus be modelled over a large frequency range. Then a fast convolution and contact model is developed and examples of computations of contact forces are given for real road textures. Spectra of forces for different tire velocities are also computed

Une méthode rapide pour calculer un produit de convolution avec une fonction de Green : application au problème de contact dynamique

International audienceDans ce travail, nous proposons une nouvelle démarche pour calculer le produit de convolution de façon rapide et efficace. L'idée est de simplifier la fonction de Green dans le domaine fréquentiel en la décomposant dans une base modale. Les paramètres modaux identifiés sont ensuite utilisés pour construire une convolution rapide. Cette démarche a été adaptée au problème de contact dynamique. Pour illustrer l'efficacité de la méthode, deux exemples sont présentés. Les déplacements et les forces de contact obtenus par cette méthode sont comparés à ceux obtenus à l'aide de la convolution classique

Numerical evaluation of tyre/road contact pressures using a multi-asperity approach

International audienceThe interaction between the tyre and the road surface is responsible for many physical problems such as skid resistance, rolling resistance or noise generation. This paper deals with the numerical study of tyre/road contact. A two-scale iterative method is used for solving the contact problem between a multi-asperity road surface and an elastic half-space. This method has been used successfully for idealized rough surfaces. However, for efficient applications to real surfaces, an appropriate partition of the surfaces is required. A partitioning method is proposed to describe road surfaces using classical image processing and a new load/penetration relation for a single road asperity is introduced. In order to evaluate the efficiency of the method, numerical results for a small sample of road are compared to a classical matrix inversion method, which show at macro-scale a rather good accuracy to predict tyre/road noise. At micro-scale both methods give the same results, but the multi-asperity method is much less time-consuming. Then numerical evaluation of tyre/road static contact pressures for different road textures at full contact area is presented. This approach with new preconditioning can be a reliable and efficient method to simulate contact problems with large surfaces

4-Tosyl-1-oxa-4-aza­spiro­[4.5]deca-6,9-dien-8-one

In the mol­ecule of the title compound, C15H15NO4S, the two six-membered rings are almost parallel to each other [dihedral angle = 1.87 (9)°] and perpendicular to the mean plane through the five-membered ring [dihedral angles of 89.98 (10) and 89.04 (10)°]. The crystal structure is stabilized by inter­molecular C—H⋯O hydrogen-bonding inter­actions