scholarly journals Structural identification of the mathematical model of the functioning of tribosystems under conditions of boundary lubrication

2021 ◽  
Vol 100 (2) ◽  
pp. 26-33
Author(s):  
A. Voitov
Keyword(s):  
Differential Equation ◽  
Quality Factor ◽  
Boundary Lubrication ◽  
Input Signal ◽  
Methodological Approach ◽  
Structural Identification ◽  
Material Structure ◽  
Sliding Speed ◽  
Time Constants ◽  
Operating Modes

In the work, a methodological approach to obtaining mathematical models was further developed, which describe the functioning of tribosystems in stationary and transient modes under boundary lubrication conditions.The structural identification of the tribosystem as an object of modeling the functioning of tribosystems in the conditions of boundary lubrication is performed. It is established that the operation of tribosystems is described by a third-order differential equation and, in contrast to the known ones, takes into account the function of changing the quality factor of the tribosystem during running-in. It is shown that the nature of the functioning of tribosystems under conditions of ultimate lubrication depends on the gain and time constants included in the differential equation. It is shown that the coefficient К1 takes into account the degree of influence of the input signal (load, sliding speed, tribological characteristics of the lubricating medium), on the value of the output signal (quality factor of the tribosystem). Coefficient К2 takes into account the magnitude of the change of the output parameters (volumetric wear rate and friction coefficient) when changing the values of the input parameters (load, sliding speed, quality factor of the tribosystem. Coefficient К3 takes into account the degree of influence of the input signal on the restructuring of the material structure in the surface layers of the triboelements.The time constants of the tribosystem characterize the inertia of the processes occurring in the tribosystem, during running-in, or during changes in operating modes. Increasing the time constants makes the process less susceptible to changes in the input signal, the running-in process increases over time, and the tribosystem becomes insensitive to small changes in load and slip speed. Conversely, the reduction of time constants makes the tribosystem sensitive to any external changes.

scholarly journals Parametric identification of the mathematical model of the functioning of tribosystems in the conditions of boundary lubrication

2021 ◽  
Vol 101 (3) ◽  
pp. 6-14
Author(s):  
A. Voitov ◽  
Keyword(s):  
Quality Factor ◽  
Time Constant ◽  
Boundary Lubrication ◽  
Rapid Change ◽  
Parametric Identification ◽  
Surface Layers ◽  
Sliding Speed ◽  
External Conditions ◽  
Time Required ◽  
Friction Surfaces

The parametric identification of the tribosystem as an object of modeling the functioning of tribosystems in the conditions of boundary lubrication is performed in the work. Using the analysis of the dimensions of significant factors, expressions are obtained to calculate the gain and time constants. It is established that the coefficient takes into account the degree of influence of the load, sliding speed, tribological characteristics of the lubricating medium on the quality factor of the tribosystem. It is shown that the increase in the coefficient will have a positive effect on the processes inherent in tribosystems during operation. Coefficient – characterizes the magnitude of the change in volumetric wear rate and friction coefficient when changing the magnitude of the load, sliding speed, quality factor of the tribosystem. Coefficient – characterizes the ability of the tribosystem to self-organize when changing the values of the input parameters by rearranging the surface layers of materials from which the triboelements are made during secondary running-in. It is shown that the value of the coefficient is large will contribute to the rapid change in the roughness of the friction surfaces, the restructuring of the structure of the surface layers, the appearance of oxidizing films on the friction surfaces (secondary structures). It is proved that the time constant – this is the time required to change the roughness of the friction surfaces and rearrange the structure of the materials of the surface layers when changing external conditions. Time constant characterizes the time during which there is a stabilization of the temperature gradient by volume of triboelements, taking into account the thermal conductivity of materials when changing external conditions. Time constant characterizes the time during which the tribosystem returns to a steady state of operation after the cessation of the outrageous force, or the time to stabilize the parameters in the new mode of operation. It is proved that the value will be optimal for the process of self-organization. It is shown that one of the factors that can control the value , this is the sliding speed

Experimental and Modeling Studies for Understanding Shoe-Floor-Contaminant Friction and Designing for Slip-Resistance

2012 ◽  
Author(s):  
Kurt Beschorner
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Boundary Lubrication ◽  
Viscous Fluids ◽  
Finite Element Models ◽  
Sliding Speed ◽  
Friction Coefficients ◽  
Real Area Of Contact ◽  
Lubrication Regime ◽  
Real Area

Insufficient friction at the shoe-floor interface causes a large number of slip and falling accidents each year. Developing solutions for enhancing shoe-floor-contaminant friction requires understanding the mechanisms that contribute to slippery surfaces. Over the past several years, our research group has conducted several experimental and modeling studies to reveal the critical tribological mechanisms contributing to shoe-floor-contaminant friction. This extended abstract will discuss the findings of these studies to: 1) determine the lubrication regime(s) that is/are most relevant to under-shoe conditions during slipping; 2) quantify how under-shoe conditions, shoes and flooring affect the two main contributions to boundary lubrication: adhesion and hysteresis; and 3) describe how this information can be used to design slip-resistant shoes and flooring. To identify the lubrication regime, interfacial pressures at the shoe-floor-contaminant interface were measured and coefficient of friction was monitored. Low viscous fluids and shoes with at least 2mm of tread were found to have negligible interfacial pressures and moderate friction coefficients (0.07–0.40). Untreaded shoes combined with high viscous fluids led to high interfacial pressures that supported up to 40% of the normal load and low friction coefficients (<0.01). These results suggest that mixed/elasto-hydrodynamic lubrication is relevant in some untreaded conditions but that boundary lubrication is relevant for most other conditions. In boundary lubrication, the primary factors contributing to friction are adhesion and hysteresis. Experimental data and finite element models demonstrate that hysteresis friction increases with floor roughness and the ratio of shoe to floor hardness. Adhesion friction is dependent on real area of contact and the shear stress required to break junctions. Experimental data suggests that adhesion is dependent on the fluid lubricant, sliding speed, floor roughness and shoe material. Finite element models confirm that a reduction in the real area of contact occurs with increasing floor roughness and sliding speed, consistent with the experimental adhesion effects. Ensuring that the shoe-floor-fluid interface is operating in the boundary lubrication regime requires establishing minimum tread threshold for fluid lubricants that are likely to be found in a given environment. Designing a high hysteresis shoe-floor combination is preferred because it is relatively unaffected by fluid contaminants or under-shoe conditions (i.e. sliding speed). Therefore, ensuring a minimum tread depth is used along with increasing floor roughness and shoe to floor hardness may be effective in addition to minimum tread thresholds.

scholarly journals Robust Switching Control Strategy for a Transmission System with Unknown Backlash

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Qiang Ling ◽  
Zhe Yan ◽  
Honghai Shen ◽  
Jiquan Li ◽  
Yongyang Wang
Keyword(s):  
Input Signal ◽  
Control Strategy ◽  
Current Mode ◽  
Operating Mode ◽  
Switching Control ◽  
Transmission System ◽  
Operating Modes ◽  
Supervisory Controller ◽  
Switching Control Strategy ◽  
Backlash Nonlinearity

This paper proposes a robust switching control strategy for a transmission system with unknown backlash. Firstly, the adverse effects of backlash nonlinearity in the transmission system are analyzed. Then the backlash model and different operating modes of the transmission system with backlash are investigated. For each operating mode, an individual controller is designed to make the system robust against the unknown backlash and various frequencies of the input signal. Moreover, a supervisory controller is proposed to estimate the current mode of the transmission system and coordinate the controller switching between different modes. Simulations are done to verify that our switching control strategy can efficiently reduce the oscillation caused by backlash and is quite robust against the variation of the frequency of the input signal.

On Material Constitutional Thought

2020 ◽  
pp. 102-122
Author(s):  
Camila Vergara
Keyword(s):  
Political Power ◽  
Methodological Approach ◽  
Niccolo Machiavelli ◽  
Legal Positivism ◽  
Material Structure ◽  
Power Structures ◽  
Written Text ◽  
Niccolò Machiavelli ◽  
Constitutional Thought

This chapter proposes a methodological approach to the study of constitutions that goes beyond the written text and jurisprudence in order to incorporate the material structure of society. It interprets the factual organization and exercise of power that is allowed and enabled by foundational institutions, rules, and procedures. It also discusses the premise of material constitutionalism on the idea that the organization of political power cannot be analyzed without taking into account political and socioeconomic power structures. The chapter establishes a constitutional ideology that stands opposed to legal positivism, formalism, and proceduralism. It traces the material approach back to Niccolò Machiavelli and distinguishes between institutionalist and critical strands.

An Approximate Analytical Solution of the Problem of Fluid Filtration in the Multilayer Porous Medium

2016 ◽  
Vol 13 (06) ◽  
pp. 1650042 ◽  
Author(s):  
Normakhmad Ravshanov ◽  
Nozim Kurbonov ◽  
Abduvali Mukhamadiev
Keyword(s):  
Differential Equation ◽  
Porous Media ◽  
Oil And Gas ◽  
Mathematical Problem ◽  
Heterogeneous Porous Media ◽  
Fluid Filtration ◽  
Operating Modes ◽  
Hydrogeological Parameters ◽  
Hydrogeological Characteristics ◽  
Production Wells

This paper deals with a mathematical problem statement of unsteady fluid flow in heterogeneous porous media with various hydrogeological characteristics. In order to solve the problem the authors developed an approximate analytical method. The method allows multidimensional differential equation in partial derivatives describing the process of fluid filtration in layered porous media to become one-dimensional differential equation. There was obtained a calculation formula for determining the process of mass transfer between the layers, depending on the operating modes of production wells and hydrogeological parameters of filtration layers. The model and the algorithm can be used as a mathematical support for the processes of development of oil and gas fields.

Using a 3-Dimensional Viscoelastic Finite Element Model to Analyze the Effects of Floor Roughness, Sliding Speed and Material Properties on Shoe-Floor Friction

2012 ◽  
Author(s):  
Gurjeet Singh ◽  
Vikas Hasija ◽  
Pradeep L. Menezes ◽  
Kurt Beschorner
Keyword(s):  
Numerical Simulations ◽  
Material Property ◽  
Boundary Lubrication ◽  
Material Properties ◽  
Experimental Studies ◽  
Health Concern ◽  
Contributing Factors ◽  
Sliding Speed ◽  
Hysteresis Friction ◽  
Adhesion Friction

Slip and fall accidents are a major occupational health concern. Important factors affecting shoe-floor friction is critical to identifying and resolving unsafe surfaces and designing. Experimental studies have indicated that several factors including floor roughness, sliding speed and shoe materials affect shoe-floor friction although the precise nature of the mechanism behind this phenomenon is not well understood. In addition, recent studies have suggested that boundary lubrication is highly relevant to slipping and that adhesion and hysteresis are the main contributing factors to boundary lubrication. The purpose of this study is to perform the numerical simulations to analyze the effects of floor roughness (asperity height), sliding speed and material properties on ratio of real area of contact and normal force (relevant to adhesion friction) and hysteresis friction for a viscoelastic shoe material interacting with a hard floor surface. A 3D shoe model and 3D vinyl floor model was simulated with speed 0.01 m/s, 0.5 m/s, 0.75 m/s and 1 m/s in three different floor surfaces. The material property was also varied in the numerical simulations. The study showed that roughness affects both the hysteresis and adhesion friction whereas sliding speed and material property affects the adhesion friction only. The dependence of adhesion and hysteresis friction on roughness, sliding speed and material property is useful in understanding the shoe-floor friction phenomenon and development of slip resistant sports and work shoes.

scholarly journals Influence of Sliding Speed on Boundary Lubrication

1963 ◽  
Vol 6 (24) ◽  
pp. 833-839
Author(s):  
Yukio MIYAKAWA
Keyword(s):  
Boundary Lubrication ◽  
Sliding Speed

New Bench Test to Study Mild Lubricated Wear

2005 ◽  
Author(s):  
J. Y. Fan ◽  
Hugh A. Spikes
Keyword(s):  
Boundary Lubrication ◽  
Bench Test ◽  
Sliding Speed ◽  
Mild Wear ◽  
Lubrication Conditions

This extended abstract describes a new bench test for measuring and studying mild, lubricated wear. The method combines MTM, which is able to produce contra-rotation so as to obtain high sliding speed while retaining low entrainment speed and thus boundary lubrication conditions, with ICP which is employed to analyze trace levels of iron in lubricants so as to monitor mild wear throughout a test.

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