11 documents found, page 1 of 2
Wheel-rail contact models in the presence of switches and crossings
Magalhães, H.; Marques, Filipe; Antunes, P.; Flores, Paulo; Pombo, J.; Ambrósio, J.; Qazi, A.; Sebes, M.; Yin, H.; Bezin, Y.The development and implementation of wheel-rail contact models in multibody codes are two active research topics, aiming at improving the accuracy of numerical results and computational efficiency of the dynamics analysis. However, the realism of numerical results is challenged when considering switches and crossings (S&C), where the most adverse wheel-rail contact conditions occur. This paper presents a bench...
Wheel-rail contact models in the presence of switches and crossings
Magalhães, H.; Marques, F.; Antunes, P.; Flores, P.; Pombo, João; Ambrósio, J.; Qazi, A.; Sebes, M.; Yin, H.; Bezin, Y.The development and implementation of wheel-rail contact models in multibody codes are two active research topics, aiming at improving the accuracy of numerical results and computational efficiency of the dynamics analysis. However, the realism of numerical results is challenged when considering switches and crossings (S&C), where the most adverse wheel-rail contact conditions occur. This paper presents a bench...
A finite element methodology to model flexible tracks with arbitrary geometry f...
Costa, J. N.; Antunes, Pedro; Magalhães, Hugo; Pombo, João; Ambrósio, J.The dynamic analysis of railway vehicles requires an accurate representation of the vehicle, the track geometry and structure, and their interaction. Generally, flexible track models with curved geometries represent the rails with straight beam elements, which results in a piecewise linear representation of the rails. Consequently, the wheel-rail contact mechanics are not properly captured, and the wheel-rail c...
Contact detection approach between wheel and rail surfaces
Marques, Filipe; Magalhães, H.; Pombo, J.; Ambrósio, J.; Flores, PauloThis work presents a general formulation to identify the contact points for the interaction between wheels and rails in the context of railway dynamics simulations. This formulation treats the wheel and rail as parametric surfaces and searches the contact between each wheel strip and the rail independently to avoid the numerical difficulties due to the wheel concave zone. This methodology assumes the rail as lo...
An optimization approach to generate accurate and efficient lookup tables for e...
Magalhães, H.; Marques, F.; Liu, B.; Pombo, João; Flores, P.; Ambrósio, J.; Bruni, S.In a wide number of engineering applications, the interpolation of a lookup table (LUT) can substitute expensive calculations. The generation of a LUT consists of pre-calculating a set of quantities from a collection of points that covers the study domain where the interpolation is possible. Nevertheless, the selection of points where the exact calculation is performed is of utmost importance for the LUT size a...
A co-simulation approach to the wheel–rail contact with flexible railway track
Antunes, P.; Magalhães, H.; Ambrósio, J.; Pombo, João; Costa, J.The standard approach to railway vehicle dynamic analysis includes running the vehicle multibody models in rigid railway tracks. The wheel–rail contact, independently of the rolling contact model used, is either handled online or via lookup tables. This traditional approach disregards the coupling effects between the railway vehicle dynamics and the railway track flexibility. In this work the assumption of rigi...
Extracting clusters from aggregate panel data: a market segmentation study
Trindade, G.; Dias, J. G.; Ambrósio, J.This paper introduces a new application of the Sequential Quadratic Programing (SQP) algorithm to the context of clustering aggregate panel data. The optimization applies the SQP method in parameter estimation. The method is illustrated on synthetic and empirical data sets. Distinct models are estimated and compared with varying numbers of clusters, explanatory variables, and data aggregation. Results show a go...
Railway vehicle performance optimization using virtual homologation
Magalhães, H.; Madeira, JFA; Ambrósio, J.; Pombo, J.Unlike regular automotive vehicles, which are designed to travel in different types of roads, railway vehicles travel mostly in the same route during their life cycle. To accept the operation of a railway vehicle in a particular network, a homologation process is required according to local standard regulations. In Europe, the standards EN 14363 and UIC 518, which are used for railway vehicle acceptance, requir...
Mathematical techniques for geometrical detection of contact within multibody s...
Machado, M.; Flores, Paulo; Ambrósio, J.Within a multibody dynamics algorithm, the occurrence of contact events is checked at each time integration step, being the contact forces computed, together with other existing forces, and then introduced into the Newton-Euler equations of motion as external generalized forces. In general, the evaluation of these contact forces relies on constitutive laws, which have to be selected according to the material’s ...
Development of a biomechanical multibody knee model
Machado, M.; Flores, P.; Ambrósio, J.; Completo, A.The purpose of this work is to develop a mathematical model for the knee joint under the framework of multibody system dynamics. The model is composed by two bodies: the femur, which is stationary, and the tibia, which is considered to move relative to the femur. Due to their higher stiffness compared to that of the articular cartilages, the femur and tibia are modeled as rigid bodies. The articular cartilages ...