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3 pages, 173 KiB

Open AccessEditorial

Interfacial Dissipative Phenomena in Tribomechanical Systems

by Antonio Papangelo

Lubricants 2021, 9(10), 104; https://doi.org/10.3390/lubricants9100104 - 15 Oct 2021

Viewed by 2033

Abstract

The last decade has experienced a tremendous development of several technologies that are likely to shape our future [...] Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

Research

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12 pages, 1264 KiB

Open AccessArticle

Roughness-Induced Adhesive Hysteresis in Self-Affine Fractal Surfaces

by Guido Violano and Luciano Afferrante

Lubricants 2021, 9(1), 7; https://doi.org/10.3390/lubricants9010007 - 7 Jan 2021

Cited by 9 | Viewed by 2475

Abstract

It is known that in the presence of surface roughness, adhesion can lead to distinct paths of loading and unloading for the area–load and penetration–load relationships, thus causing hysteretic loss. Here, we investigate the effects that the surface roughness parameters have on such [...] Read more.

It is known that in the presence of surface roughness, adhesion can lead to distinct paths of loading and unloading for the area–load and penetration–load relationships, thus causing hysteretic loss. Here, we investigate the effects that the surface roughness parameters have on such adhesive hysteresis loss. We focus on the frictionless normal contact between soft elastic bodies and, for this reason, we model adhesion according to Johnson, Kendall, and Roberts (JKR) theory. Hysteretic energy loss is found to increase linearly with the true area of contact, while the detachment force is negligibly influenced by the maximum applied load reached at the end of the loading phase. Moreover, for the micrometric roughness amplitude

h_{rms}

considered in the present work, adhesion hysteresis is found to be affected by the shorter wavelengths of roughness. Specifically, hysteresis losses decrease with increasing fractal dimension and cut-off frequency of the roughness spectrum. However, we stress that a different behavior could occur in other ranges of roughness amplitude. Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

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15 pages, 1151 KiB

Open AccessArticle

Viscoelastic Effects during Tangential Contact Analyzed by a Novel Finite Element Approach with Embedded Interface Profiles

by Jacopo Bonari and Marco Paggi

Lubricants 2020, 8(12), 107; https://doi.org/10.3390/lubricants8120107 - 19 Dec 2020

Cited by 8 | Viewed by 2781

Abstract

A computational approach that is based on interface finite elements with eMbedded Profiles for Joint Roughness (MPJR) is exploited in order to study the viscoelastic contact problems with any complex shape of the indenting profiles. The MPJR finite elements, previously developed for partial [...] Read more.

A computational approach that is based on interface finite elements with eMbedded Profiles for Joint Roughness (MPJR) is exploited in order to study the viscoelastic contact problems with any complex shape of the indenting profiles. The MPJR finite elements, previously developed for partial slip contact problems, are herein further generalized in order to deal with finite sliding displacements. The approach is applied to a case study concerning a periodic contact problem between a sinusoidal profile and a viscoelastic layer of finite thickness. In particular, the effect of using three different rheological models that are based on Prony series (with one, two, or three arms) to approximate the viscoelastic behaviour of a real polymer is investigated. The method allows for predicting the whole transient regime during the normal contact problem and the subsequent sliding scenario from full stick to full slip, and then up to gross sliding. The effects of the viscoelastic model approximation and of the sliding velocities are carefully investigated. The proposed approach aims at tackling a class of problems that are difficult to address with other methods, which include the possibility of analysing indenters of generic profile, the capability of simulating partial slip and gross slip due to finite slidings, and, finally, the possibility of simultaneously investigating dissipative phenomena, like viscoelastic dissipation and energy losses due to interface friction. Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

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12 pages, 3086 KiB

Open AccessArticle

The Basin Stability of Bi-Stable Friction-Excited Oscillators

by Merten Stender, Norbert Hoffmann and Antonio Papangelo

Lubricants 2020, 8(12), 105; https://doi.org/10.3390/lubricants8120105 - 8 Dec 2020

Cited by 5 | Viewed by 2985

Abstract

Stability considerations play a central role in structural dynamics to determine states that are robust against perturbations during the operation. Linear stability concepts, such as the complex eigenvalue analysis, constitute the core of analysis approaches in engineering reality. However, most stability concepts are [...] Read more.

Stability considerations play a central role in structural dynamics to determine states that are robust against perturbations during the operation. Linear stability concepts, such as the complex eigenvalue analysis, constitute the core of analysis approaches in engineering reality. However, most stability concepts are limited to local perturbations, i.e., they can only measure a state’s stability against small perturbations. Recently, the concept of basin stability was proposed as a global stability concept for multi-stable systems. As multi-stability is a well-known property of a range of nonlinear dynamical systems, this work studies the basin stability of bi-stable mechanical oscillators that are affected and self-excited by dry friction. The results indicate how the basin stability complements the classical binary stability concepts for quantifying how stable a state is given a set of permissible perturbations. Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

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16 pages, 642 KiB

Open AccessArticle

Friction-Induced Vibration Suppression via the Tuned Mass Damper: Optimal Tuning Strategy

by Jia Lin Hu and Giuseppe Habib

Lubricants 2020, 8(11), 100; https://doi.org/10.3390/lubricants8110100 - 20 Nov 2020

Cited by 7 | Viewed by 3534

Abstract

Friction-induced vibrations are a significant problem in various engineering applications, while dynamic vibration absorbers are an economical and effective tool for suppressing various kinds of vibrations. In this study, the archetypal mass-on-moving-belt model with an attached dynamic vibration absorber was considered. By adopting [...] Read more.

Friction-induced vibrations are a significant problem in various engineering applications, while dynamic vibration absorbers are an economical and effective tool for suppressing various kinds of vibrations. In this study, the archetypal mass-on-moving-belt model with an attached dynamic vibration absorber was considered. By adopting an analytical procedure, the optimal tuning of the absorber’s parameters was defined. Furthermore, the bifurcations occurring at the loss of stability were analytically investigated; this analysis illustrated that a properly chosen nonlinearity in the absorber’s stiffness permits controlling the supercritical or subcritical character of the bifurcation. However, a numerical analysis of the system’s dynamics, despite confirming the analytical results, also illustrated that the system’s global behavior is only slightly affected by the bifurcation character. Indeed, a dynamic vibration absorber possessing a perfectly linear restoring force function seems to provide the optimal performance; namely, it minimizes the velocity range for which stick–slip oscillations exists. Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

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19 pages, 5158 KiB

Open AccessArticle

Simulation Analysis of Erosion–Corrosion Behaviors of Elbow under Gas-Solid Two-Phase Flow Conditions

by Qunfeng Zeng and Wenchuang Qi

Lubricants 2020, 8(9), 92; https://doi.org/10.3390/lubricants8090092 - 22 Sep 2020

Cited by 4 | Viewed by 3253

Abstract

In the production and gathering process of coal gas, the complex composition of the coal gas, harsh environments, the complex medium, and high content of solid particles in slurry cause the equipment malfunctions and even failure because of erosion and corrosion. In the [...] Read more.

In the production and gathering process of coal gas, the complex composition of the coal gas, harsh environments, the complex medium, and high content of solid particles in slurry cause the equipment malfunctions and even failure because of erosion and corrosion. In the present study, COMSOL multi-physics finite element simulation software is used to simulate the erosion–corrosion behaviors of elbow in key chemical equipments. The electrochemical corrosion, solid particle erosion, chemical reaction, and turbulent flow are coupled together. The particle count method is proposed to clarify the erosion phenomenon. The simulation results show that particles with high turbulent intensity hit the wall of elbow directly, which forms a slanted elliptical erosion zone on the extrados surface at 40°–50°. The chemical reaction in turbulence has a difference in the concentration distribution of substances, and this phenomenon leads to different magnitudes of the corrosion current densities in the tube. Moreover, 1/6 released particles hit the extrados surface of the elbow. These findings are beneficial to understand the erosion–corrosion phenomena and design the elbow in key chemical equipment. Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

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19 pages, 1148 KiB

Open AccessFeature PaperArticle

A Numerical Study on Roughness-Induced Adhesion Enhancement in a Sphere with an Axisymmetric Sinusoidal Waviness Using Lennard–Jones Interaction Law

by Antonio Papangelo and Michele Ciavarella

Lubricants 2020, 8(9), 90; https://doi.org/10.3390/lubricants8090090 - 4 Sep 2020

Cited by 16 | Viewed by 3447

Abstract

Usually, roughness destroys adhesion and this is one of the reasons why the “adhesion paradox”, i.e., a “sticky Universe”, is not real. However, at least with some special type of roughness, there is even the case of adhesion enhancement, as it was shown [...] Read more.

Usually, roughness destroys adhesion and this is one of the reasons why the “adhesion paradox”, i.e., a “sticky Universe”, is not real. However, at least with some special type of roughness, there is even the case of adhesion enhancement, as it was shown clearly by Guduru, who considered the contact between a sphere and a wavy axisymmetric single scale roughness, in the limit of short-range adhesion (JKR limit). Here, the Guduru’s problem is numerically solved by using the Boundary Element Method (BEM) with Lennard–Jones interaction law, which allowed us to explore the contact solution from the rigid to the JKR limit. It is shown that adhesion enhancement stops either for low Tabor parameter, or by large waviness amplitudes, due to the appearance of internal cracks within the contact patch. We do not seem to find a clear threshold for “stickiness” (complete elimination of adhesion), contrary to other recent theories on random roughness. The enhancement effect is well captured by an equation in terms of the Johnson parameter derived by Ciavarella–Kesari–Lew, and is much larger than the Persson–Tosatti enhancement in terms of increase of real contact area due to roughness. The Persson–Tosatti energetic argument for adhesion reduction seems to give a lower bound to the effective work of adhesion. Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

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17 pages, 4793 KiB

Open AccessArticle

Numerical and Experimental Analysis of Nonlinear Vibrational Response due to Pressure-Dependent Interface Stiffness

by Dorra Nouira, Davide Tonazzi, Anissa Meziane, Laurent Baillet and Francesco Massi

Lubricants 2020, 8(7), 73; https://doi.org/10.3390/lubricants8070073 - 10 Jul 2020

Cited by 7 | Viewed by 2897

Abstract

Modelling interface interaction with wave propagation in a medium is a fundamental requirement for several types of application, such as structural diagnostic and quality control. In order to study the influence of a pressure-dependent interface stiffness on the nonlinear response of contact interfaces, [...] Read more.

Modelling interface interaction with wave propagation in a medium is a fundamental requirement for several types of application, such as structural diagnostic and quality control. In order to study the influence of a pressure-dependent interface stiffness on the nonlinear response of contact interfaces, two nonlinear contact laws are investigated. The study consists of a complementary numerical and experimental analysis of nonlinear vibrational responses due to the contact interface. The laws investigated here are based on an interface stiffness model, where the stiffness property is described as a nonlinear function of the nominal contact pressure. The results obtained by the proposed laws are compared with experimental results. The nonlinearity introduced by the interface is highlighted by analysing the second harmonic contribution and the vibrational time response. The analysis emphasizes the dependence of the system response, i.e., fundamental and second harmonic amplitudes and frequencies, on the contact parameters and in particular on contact stiffness. The study shows that the stiffness–pressure trend at lower pressures has a major effect on the nonlinear response of systems with contact interfaces. Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

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Review

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27 pages, 8248 KiB

Open AccessReview

Review on Friction and Wear Test Rigs: An Overview on the State of the Art in Tyre Tread Friction Evaluation

by Andrea Genovese, Gennaro Antonio D’Angelo, Aleksandr Sakhnevych and Flavio Farroni

Lubricants 2020, 8(9), 91; https://doi.org/10.3390/lubricants8090091 - 16 Sep 2020

Cited by 22 | Viewed by 7596

Abstract

The future evolution of autonomous mobility and road transportation will require substantial improvements in tyre adherence optimization. As new technologies being deployed in tyre manufacturing reduce total vehicle energy consumption, the contribution of tyre friction for safety and performance enhancement continues to increase. [...] Read more.

The future evolution of autonomous mobility and road transportation will require substantial improvements in tyre adherence optimization. As new technologies being deployed in tyre manufacturing reduce total vehicle energy consumption, the contribution of tyre friction for safety and performance enhancement continues to increase. For this reason, the tyre’s grip is starting to drive the focus of many tyre developments nowadays. This is because the tread compound attitude to maximize the interaction forces with the ground is the result of a mix of effects, involving polymer viscoelastic characteristics, road roughness profiles and the conditions under which each tyre works during its lifespan. In such a context, mainly concerning the automotive market, the testing, analysis and objectivation of the friction arising at the tread interface is performed by means of specific test benches called friction testers. This paper reviews the state of the art in such devices’ development and use, with a global overview of the measurement methodologies and with a classification based on the working and specimen motion principle. Most tyre friction testers allow one to manage the relative sliding speed and the contact pressure between the specimen and the counter-surface, while just some of them are able to let the user vary the testing temperature. Few devices can really take into account the road real roughness, carrying out outdoor measurements, useful because they involve actual contact phenomena, but very complex to control outside the laboratory environment. Full article

(This article belongs to the Special Issue Interfacial Dissipative Phenomena in Tribomechanical Systems)

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