Using the concept of stress intensity factors, we suggest a way to include adhesion into boundary elements simulation of contacts. A local criterion concerning the maximum admissible surface stresses decides whether the adhesive bonds in particular grid points fail or not. By taking into account the grid spacing, a robust methodology is found. Validation is done using the theoretically derived cases of JKR adhesion.
The Dieterich-Ruina friction law is widely used in rock friction and earthquake dynamical contexts. It has proven very powerful and versatile over the last decades, being able to reproduce stick-slip as well as fore- and aftershocks and healing of faults. This paper shows that the Dieterich-Ruina friction law can also reproduce the accelerated creep process preceding slip event in a stick-slip system, not only for steel contact, but also for rock contact. The friction law relies on three empirical parameters, which have to be identified for each application. The most common experimental set-up is the velocity step experiment. In this paper an alternative method to identify the parameters is proposed, which uses a stick-slip experiment and a numerical fitting approach.
Structural damping is discussed for the contact of two fibers in a woven material. In the presence of both normal and tangential oscillations, structural (relaxation) damping takes place even with perfect sticking in the contact, where slip-related frictional damping disappears. For the case of an infinite coefficient of friction and small amplitudes a closed-form solution for energy lost during one oscillation cycle is obtained.
The paper is devoted to an experimental investigation of the sliding friction force between a rapidly oscillating sample and a rotating steel plate. The sliding friction force is studied experimentally as a function of the oscillating amplitude, the sliding velocity and the normal force. The results have proved the hypothesis that the coefficient of friction is a function of dimensionless oscillation amplitude and dimensionless velocity.
Adhesion between an elastomer and a steel indenter was studied experimentally and described with an analytical model. Cylindrical indenters having different roughness were brought into contact with an elastomer with various normal forces. After a “holding time”, the indenter was pulled with a constant velocity, which was the same in all experiments. We have studied the regime of relatively small initial normal loadings, large holding times and relatively large pulling velocities, so that the adhesive force did not depend on the holding time but did depend on the initially applied normal force and was approximately proportional to the pulling velocity. Under these conditions, we found that the adhesive force is inversely proportional to the roughness and proportional to the normal force. For the theoretical analysis, we used a previously published MDR-based model.
In the present paper, we discuss the impact of rigid profiles on continua with non-local criteria for plastic yield. For the important case of media whose hardness is inversely proportional to the indentation radius, we suggest a rigorous treatment based on the method of dimensionality reduction (MDR) and study the example of indentation by a conical profile.
In this study, we elaborate on the friction between a one-dimensional elastomer and a one-dimensional rigid randomly rough surface. Special emphasis is laid on the energy dissipation in the elastomer. Its subsequent temperature change is under inspection. The elastomer is modeled as a spring and a damper in parallel (Kelvin model) in a one-dimensional substitute model according to the concept of the method of dimensionality reduction (MDR). The randomly rough surface is a self-affine one-dimensional fractal whose Hurst exponent H is varied in an extended range between -1 and 3. In full contact, the temperature shift is dominated by ratio between the typical power dissipated in the elastomer to the power that is led away. It is independent of the normal force and proportional to the sliding speed squared. The flash temperature behavior is discussed for different Hurst exponents.
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