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Problems in Contact Dynamics Between Solids
Published in Nikolay Goloshchapov, Contact Dynamics, 2019
Also, we have to understand that the time of relaxation is the time of transition of a system of particles or elements of some volume of substance from the one equilibrium state into another. The physical relaxation is not the relaxation, which is taken in the mechanical oscillation. It is obvious that some molecular, submolecular or subatomic structures have their own times of relaxations, but the total relaxation time or the effective relaxation time is the time of relaxation, which matches the time when all relaxation processes inside of a substance are completely finished. Therefore, this total time of relaxation has to be taken into account in both the cases, when a volume of contact is isotropic or anisotropic medium. In contact dynamics, it is very important to know the time of relaxation process in the phase of viscoelastic compression between two surfaces, because at the point of maximum compression the velocity of mutual approach between surfaces equals zero, and all kinetic energy transforms into potential energy of deformations, and part of kinetic energy dissipates in result of an internal friction. This is similar to the new equilibrium state. Thus, the time of the phase of compression (or time the maximum mutual approach) and the effective time of relaxation in this phase have a common physical nature; and they are dependent on each other.
Fluctuations in granular materials
Published in Y. Kishino, Powders and Grains 2001, 2020
R. P. Behringer, Junfei Geng, D. Howell, E. Longhi, G. Reydellet, L. Vanel, E. Clément, S. Luding
A different approach, contact dynamics (Radjai et al. 1996), resolves the indeterminacy of static Coulomb friction. This model also predicts P(F) ∝ exp(−F/Fo) for large forces, and a distribution at small F that appears to be consistent with experiment.
Influence of the friction modelling decisions on the acceptance of the running behaviour of a friction-damped locomotive
Published in Vehicle System Dynamics, 2023
Pedro Millan, João Pagaimo, Hugo Magalhães, Pedro Antunes, Jorge Ambrósio
Tangential contact force models replicate the friction forces of two contacting bodies sliding relative to each other. These are generally classified into static and dynamic models, depending on the details of the phenomena considered. The static tangential contact models describe friction as a function of the normal force and tangential velocity, while the dynamic friction models additionally consider the local deformation at contact dynamics and, consequently, the time lag between the kinematic conditions and the force development. This work discusses, alternatively, two static models, that are often available in commercial software, and one dynamic model that provides a more detailed description of the friction phenomena but that is more complex to implement, and has a greater number of parameters to select. Thus, a broad range of friction contact models available for friction damped freight vehicle suspensions modelling is discussed here.
Guest Associate Technical Editor Letter
Published in Research in Nondestructive Evaluation, 2022
The topic of closed crack defects is continued by Kevin Truyaert, Vladislav Aleshin, and Koen Van Den Abeele (KU Leuven, Belgium, and University of Lille, France) in “Qualitative Analysis of a 3D Multiphysics Model for Nonlinear Ultrasonics and Vibration Induced Heating at Closed Defects.” The study considers a three-dimensional (3D) finite element method (FEM) model of contact nonlinearity and calculates the heat generated by nonlinear interface vibrations. The first contact dynamics task addresses conventional clapping/friction nonlinear mechanisms and results in the higher harmonic vibration spectra used for recognition and imaging of defects in NNDT. The nonlinear vibration spectrum combined with energy dissipation due to interface friction causes the temperature rise, which is a background of nonlinear vibrothermography. The model developed enables fine mapping of the nonlinear spectrum and the temperature distributions around the defect and along the crack line.
Trends in vehicle motion control for automated driving on public roads
Published in Vehicle System Dynamics, 2019
Matthijs Klomp, Mats Jonasson, Leo Laine, Leon Henderson, Enrico Regolin, Stefan Schumi
As can be seen from Figure 12, state-estimation of feedback variables are important for VMC and a comprehensive review of state estimation can be found in [9]. Tyre/road friction estimation has attracted particular attention and an extensive review on this model-based friction and estimation without tyre model is available in [103]. One particular challenge in vehicle state and friction estimation is given by small friction utilisation: this topic is extensively discussed in [104,105] for side-slip angle and forces estimation, and in [106] for the road friction. In addition to this, the estimation and compensation of the brake linings coefficient of friction in modern brake-by-wire systems represent another challenging task owing to the stochastic characteristic of the frictional contact dynamics [107]. Recent publications on real-time robust identification of tyre and brake linings friction can be found in [108–110], respectively.