China
Africa
Explore chapters and articles related to this topic
Geometric analysis of wheel-switch for new and old turnout
Published in Maksym Spiryagin, Timothy Gordon, Colin Cole, Tim McSweeney, The Dynamics of Vehicles on Roads and Tracks, 2018
Xu Zhang, Gang Shen, Dilai Chen
This paper is mainly based on a freight derailment accident in turnout. The freight can operate normally on old switch rail. When the old switch blade wore to limit, it was replaced with new switch blade. There were a few truck derailment accidents on the new switch rail. The data for the wheel profiles and rail sections comes from vehicles of 37–train, a total of 148 LM type wheel worn tread profile, as well as some switches for old and new district. The research on the relationship between wheel and rail mainly includes two aspects, one is the wheel rail contact geometry, by analysis of relationship between the static and dynamic wheel-rail contact point distribution, contact point transfer positions are basically the same [2]. This paper assumes that the wheel and rail is rigid. On the basis of the static contact, several analyses of wheel-rail contact state are conducted. Another is the interaction between wheel and rail and wheel-rail force includes normal force and tangential force, the former is studied in this paper. This paper will use the non-Hertzian theory to calculate wheel-rail contact stress.
Contact forces and noise generation during hastily separation of tyre tread blocks from road surfaces
Published in Per-Erik Austrell, Leif Kari, Constitutive Models for Rubber IV, 2017
ABSTRACT: Adhesive bonds in the passenger car tyre/road surface contact have a large influence on the contact dynamics for certain tyre/road combinations. The effect is most pronounced for road surfaces with low roughness, so-called smooth surfaces. An experimental setup was designed to study time records of contact forces and sound pressures as tyre tread samples are hastily separated from road surfaces samples. The general character of the separation process on a macroscopic length scale is described, interpreted, and related to theories on smaller scales. A single value (dynamic) adherence force is determined out of the records and it is related to the initial conditions; magnitude of preload, preload duration, and unloading rate. It was found that the exact contact geometry, on larger scales, yields the details in the contact force record and distribution of sound pressure levels in 1/3-octave bands. A model aiming at describing the observed behaviour must consider a wide range of length scales; a dynamic contact model is proposed that considers the exact contact geometry on larger scales via discretisation and uses statistical properties of the surfaces at lower scales to determine contact criteria at contact points.
Reliability Issues in Electrical Contacts
Published in Milenko Braunovic, Valery V. Konchits, Nikolai K. Myshkin, Electrical Contacts, 2017
Milenko Braunovic, Valery V. Konchits, Nikolai K. Myshkin
Figure 6.2 shows schematically the influence of the design-technological factors on the reliability and quality of electrical contacts. The selected kind of contact materials, the contact geometry, the intermediate layers separating the contacting surfaces, the quality of the deposited coatings, and the contact surface microrelief determine the apparent contact area, size, number, and distribution of contact spots. This, in its turn, influences the real and electrical contact areas, the constriction and surface film resistances, and, finally, the electrical contact reliability.
Analysis of contact behaviour on patterned tire-asphalt pavement with 3-D FEM contact model
Published in International Journal of Pavement Engineering, 2022
Binshuang Zheng, Jiaying Chen, Runmin Zhao, Junyao Tang, Rongyan Tian, Shengze Zhu, Xiaoming Huang
From the above literature review, it can be seen that although there have been many experimental and theoretical investigations to study the tire-pavement contact characteristic simply and simplified pavement model, yet, limited research studies were focused on the tire-pavement contact behaviour based on textured pavement simulation. Due to the increasingly prominent traffic accidents caused by vehicle slippage, the tire-pavement contact characteristics have gradually attracted much attention. In order to reveal the mechanism of tire pavement contact under the antilock braking system (ABS) state of the automobile, the field tests and the finite element method become the main research method. However, the field test is usually expensive and external influence factors can lead to some errors. Meanwhile, the existing tire-road contact finite element model study lacks comprehensive considerations for axle load, inflation pressure and ABS control. At the same time, regarding tire contact pressure distribution, there is almost no quantitative research on contact geometry. Therefore, it is necessary to build an accurate model of the tire-road contact process, analyse the tire-road contact behaviour of the tire during the ABS process, and explore the attenuation of the tire-road surface under the condition of dry road, which can be used for the anti-sliding asphalt road surface layer design. This work can provide a theoretical reference for vehicle turning or braking behaviour.
A wheel–rail normal contact model using the combination of virtual penetration method and strip-like Boussinesq’s integral
Published in Vehicle System Dynamics, 2023
In this section, it investigates the effectiveness of the new model via three typical examples. The first two cases use theoretical contact geometry to estimate our proposed virtual penetration method on the contact patch, and it further explores wheel–rail contact with focus on contact pressure distribution in the last case. To compare it with the existing simplified non-Hertz contact models, the famous KP method and STRIPES are employed. In the simulation, the two contacting bodies are assumed to share the same material properties with v = 0.28 and E = 206 GPa.
Exergetic port-Hamiltonian systems: modelling basics
Published in Mathematical and Computer Modelling of Dynamical Systems, 2021
Markus Lohmayer, Paul Kotyczka, Sigrid Leyendecker
Later attempts to properly unify port-Hamiltonian systems with thermodynamics diverged into three distinct frameworks: Firstly, just like exergetic port-Hamiltonian systems, Irreversible Port-Hamiltonian Systems [25] use the extensive thermodynamic variables as state variables but their structure is significantly different. The modification is necessary to encode not only the first but also the second law of thermodynamics while sticking with the total energy as the Hamiltonian function. Secondly, contact geometry is a natural setting for thinking about Legendre transformations which has been used in equilibrium thermodynamics since [26]. The contact-geometric approach has been extended to nonequilibrium thermodynamics and open systems, see e.g [27]. The core idea is to enlarge the state space such that it also includes the intensive variables. The dynamics are then restricted to a Lagrangian submanifold which is generated by a thermodynamic potential and thus expresses material properties. For one and the same thermodynamic system, there are two contact-geometric descriptions, namely one where energy (or a Legendre transformation of it) and one were entropy (or a Legendre transformation of it) is used as the generating function of the Legendre submanifold. Thirdly, Port-Thermodynamic Systems [28] are based on a symplectization of the contact-geometric description. By adding one more dimension to the state space, energetic and entropic representations can be expressed simultaneously as projectivizations. A comparison of the advantages and (current) limitations of the different frameworks is missing in the literature and is also beyond the scope of the present article. Yet, the order in which we listed the three frameworks reflects a trend of adding more geometric structure and in the two latter cases also more redundant state variables. While this may be advantageous for certain purposes, it has drawbacks as well. Successful application of a modelling framework critically depends on how easily it can be picked up by practitioners. Exergetic port-Hamiltonian systems shine because of their relative simplicity and their readily available diagrammatic language. This fits one of our main research goals, namely to develop a framework which can form an adequate basis for various near-term engineering efforts to tackle the sustainability crisis.