Hysteresis Friction Research Articles

Investigation of dynamic heat generation and transfer behavior and energy dissipation for nonlinear synchronous belt transmission

Study on energy dissipation and temperature distribution of synchronous belt transmission is of great importance in industrial engineering field, which is highly related to transmission efficiency estimation, thermal fatigue life prediction, and product design. However, the complex behaviors of viscoelastic hysteresis and meshing friction make it much more difficult to investigate heat generation and transfer mechanism of synchronous belt than other products. To accurately predict temperature and energy dissipation, a thermo-mechanical coupling model was developed through combining experiment and finite element analysis method, in which material nonlinearity of rubber hyper-viscoelasticity, and contact nonlinearity of meshing interference were comprehensively considered. Meanwhile, the friction heat flux partition coefficient and convective heat transfer coefficient were theoretically computed and corrected. As a result, the temperature distribution, hysteresis and friction energy dissipation of synchronous belt could be computed accurately, the transmission efficiency was estimated as well. The simulation temperatures of various operating conditions were confirmed by testing results. The presented methodology can completely predict energy dissipation and temperature distribution of synchronous belt transmission, which has far-reaching consequences in the engineering application filed.

Numerical analysis of the dependence of rubber hysteresis loss and heat generation on temperature and frequency

The hysteresis loss and the heat generation of rubber compounds under different ambient temperatures and frequencies were predicted in terms of the viscoelastic theory. The cross-linking densities and the dynamic compressive properties were measured in order to partially reveal the microstructures and the viscoelastic response of rubber specimens. Based on the experimental data of storage and loss moduli, a piecewise fitting method was established to determine the viscoelastic constitutive model parameters. Then the dynamic compressive process of natural rubber specimen was analyzed by the finite element method. The obtained hysteresis loss and the energy dissipation were used to predict the transient and steady-state temperature field. The results reveal that the dependence of rubber hysteresis loss on the frequency at a lower ambient temperature plays a more important role in predicting the heat generation of rubber compounds; the dependence becomes weaker as the ambient temperature increases.

Hysteresis friction and nonlinear viscoelasticity of rubber composites

Abstract Evaluation of tire friction is essential from the perspective of enhancing vehicle performance and improving its safety. Earlier investigations have identified rubber adhesion and hysteresis as two fundamental mechanisms underlying tire friction. This contribution aims at analyzing the effect of nonlinear viscoelastic behavior of tire treads on their hysteresis friction coefficient. Tire tread is a composite material made of synthetic or natural rubber reinforced with particles such as carbon black or silica. Hysteresis that refers to energy dissipation during a cyclic deformation is an essential feature of mechanical behavior of rubber composites. The effect of nonlinear viscoelasticity of filled rubbers on the hysteresis friction of tire treads is not well understood. In this contribution, we use an analytical model to predict the hysteresis friction of filled rubbers sliding on a rough surface. The model accounts for the nonlinear viscoelasticity of the slider subjected to finite strains. It will be shown that the kinetic coefficient of friction directly correlates with the magnitude of strain. Comparison of model results against the experimental measurements for tire tread materials reveals that the predicted friction coefficients become comparable with experimental data at large strains (8–10%). This study suggests that the nonlinear viscoelasticity of tire treads needs to be taken into account in order to have a more realistic assessment of frictional performance of tires.

Thixotropic Mechanics in Soft Hydrated Sliding Interfaces

Soft hydrated permeable surfaces exhibit unique lubrication behaviors, including recently discovered frictional hysteresis. This duration-dependent frictional effect can be analogous to the thixotropic fluid response under shear-driven Couette flow. We illustrate torque-speed hysteresis loops using tribo-rheometry measurements between an aluminum annulus and polyacrylamide surface. Frictional torque response was measured under stepwise sliding speed increments at five different step durations. The torque-sliding speed curves exhibit hysteresis loops and the shape of the hysteresis loops depends on step durations. Longer duration shows greater hysteresis with higher average friction. Torque curves at highest speeds converge to one line with a power law exponent of α = 0.7. Based on the experimental data, a hydrogel lubrication model was developed using a thixotropic fluid model, where viscosity change is described as a competition between structural buildup and breakdown. Simulation using the model correlates well with the experimental results, indicating the existence of effective structural change on the hydrogel surface.

Modeling of Microslip Friction and Its Application in the Analysis of Underplatform Damper

This paper presents a theoretical model for analyzing the damping effect of underplatform dampers for turbine blades. At first, tangential and normal contact stiffness of the friction damper were studied based on a flat-to-flat contact model. The analytic expressions of contact stiffness were presented. Then, a microslip model was developed, and the frictional hysteresis loops were obtained by the Masing hypothesis. The so-called “B–B” (Blade to Blade) model was studied in this paper, and both cylindrical and wedge-shaped dampers were calculated in the case studied. The inertia and rotating effect of the damper were ignored for simplicity. Thus, the damper’s motion between blade platform locations could be determined by iteration of force balance equations of the damper once the blades’ motions as inputs of the system were determined. The effect of normal load on the contact stiffness was ignored for simplicity. The friction force was linearized by harmonic balanced method, considering only the first-order harmonic terms. Finally, the relationship between damping ratio and the maximum vibration stress of the blades was calculated to assess the damping effect of the damper.

Numerical determination of hysteresis friction on different length scales and comparison to experiments

The interaction between tread materials of tires and rough pavement structures mainly depends on the characteristics of the road surface, the slip velocity, the contact pressure, temperature conditions and the elastomeric material itself. The subsequent description introduces two different numerical approaches, a three-dimensional multiscale homogenization methodology, which considers the asperities at different length scales of the surface texture and a microscale approach, which reduces the surface texture to a two-dimensional microscopic characterization. The results of the numerical approaches, which base on the same input information, are compared to experimental data in order to validate the outcome. Since local stress concentrations are the origin of wear, a realistic modeling of rubber friction on rough surfaces concerning different length scales of surface texture provides an important input to a subsequent modeling of wear of the tire tread as well as of the pavement asperities.

Q-factor of the oscillatory system of the tuning fork resonator taking into account the elastic hysteresis friction

The article is devoted to the solution of the problem of calculating the Q-factor of an oscillating circuit of a vibration-frequency sensor with a tuning fork. Obtaining mathematical models and dependencies for calculating the metrological characteristics of sensing elements of sensors is an actual metrological task today.Currently, most of the applied designs of vibration-frequency sensors use an oscillatory system with a tuning fork. A common disadvantage of the tuning fork resonators is the low Q-factor of the oscillation systems, which does not allow to provide high accuracy of measurement, which significantly limits the scope of the measuring instrument. One of the promising directions for eliminating these drawbacks in instrumentation is the use of new materials, forms of sensitive elements, manufacturing technologies for vibration frequency sensors. At the same time, modern approaches to the design of measuring instruments, first of all, require developers to improve mathematical models used in the design of sensing elements for specific conditions.Most mathematical models for calculating the quality factor of oscillating systems use the oscillation equation for resonators with linear viscous friction, when the generalized friction force depends linearly on the generalized velocity. In this case, the linear model does not always correctly reflect energy losses in the sensor oscillation system.

Real-Time Dynamic Observation of Micro-Friction on the Contact Interface of Friction Lining.

This paper aims to investigate the microscopic friction mechanism based on in situ microscopic observation in order to record the deformation and contact situation of friction lining during the frictional process. The results show that friction coefficient increased with the shear deformation and energy loss of the surfacee, respectively. Furthermore, the friction mechanism mainly included adhesive friction in the high-pressure and high-speed conditions, whereas hysteresis friction was in the low-pressure and low-speed conditions. The mixed-friction mechanism was in the period when the working conditions varied from high pressure and speed to low pressure and speed.

Evaluation of wetting transparency and surface energy of pristine and aged graphene through nanoscale friction

Friction on few-layer graphene supported by Si/SiOx and mica substrates was investigated using atomic force microscopy (AFM) and coordinated molecular dynamics (MD) simulations to examine friction hysteresis and wetting transparency. Experiments showed that graphene exhibited higher overall friction, as well as hysteresis, in high humidity conditions, while the hysteresis was not observed under dry conditions. Additionally, as samples were aged under ambient environmental conditions, the work of adhesion increased by an approximate factor of two, likely from oxidation of the surface or adsorption of oxygen containing species from the lab environment. When graphene was supported by mica substrates no significant friction hysteresis was observed. MD simulations showed similar influences to the friction forces with surface energy. Both experiments and simulations suggest that wetting transparency, or a small variation in surface energy resulting from varying the number of graphene layers, contributes to the layer dependent friction forces measured on graphene.

Biomechanically Inspired Machines, Driven by Muscle Like Acting NiTi Alloys

The Shape of the Memory Alloy (SMA) is a very promising class of metallic materials with interesting non-linear properties such as Pseudo-Elasticity (PE), memory (MEM) and damping capacity due to high mechanical hysteresis and internal friction. Research shows a bioinventory approach to Shape Memory Alloy (SMA) design, a class of intelligent materials capable of reacting to a pulse (thermal for SMA) with shrinkage. Martensitic transformations in shape-effect crystals under the effect of external forces lead to large deformations of an inelastic nature. In some materials, these reversible deformations are in the range from one digit to at least two digits. The recovery of accumulated inelastic deformation and, as a consequence, the return to the original shape of the body can occur both in the process of unloading at a constant temperature (superelastic effect) and in heating (a form memory effect). Both effects are exciting with regard to their application in compact servomotors when heating the effect of shape memory generates stresses in most materials. If the shape memory alloy faces any shape recovery resistance, it can generate reactive force. The importance of this effect in technical applications is that the reactive force significantly exceeds the force that caused the initial change of shape. This can be used to produce a useful mechanical work. The biomechanically inspired machine that is discussed in the paper refers to pairs of muscle antagonists that are part of the skeletal muscles and are usually arranged in opposition so that a group of muscles contractors another group that relaxes or prolongs. The study proposes a model, a solution not only to design a specific application but also to provide an approach to be used for a wide range of adaptive applications (switching windows, intelligent shadows, parking and urban shelters, etc.). The shape changes in response to various external stimuli. The use of pairs of antagonists provides a solution for SMA-optimized systems where the main and proven advantages are: Easier and quicker shape change, the energy requirement for system operation, lower costs for SMA training and lack of overheating problems.

Mechanical properties of PVA brushes and its relation with hysteresis friction

Mechanical properties of PVA brushes and its relation with hysteresis friction

Improved formulation for running torque in angular contact ball bearings

This paper presents an improved computational model for the angular contact ball bearing (ACBB) running torque. Considering the general loading condition, the friction torque formula of individual bearing balls was derived. Five friction components were considered: elastohydrodynamic lubrication (EHL) rolling resistance, elastic hysteresis friction, differential sliding loss, spinning friction, and lubricant viscous drag effect. The formulas for elastohydrodynamic lubrication rolling resistance and spinning friction, which contribute significantly to the ACBB running torque, were improved by investigating and re-formulating the contact related formulas. The friction coefficient between the ball and races was investigated in order to choose a suitable and reliable formula for the proposed model. The proposed model was verified through a comparison with formulas provided by a bearing manufacturer and with a set of experimental data.

Frictional Hysteresis Model for Stick–Slip Behavior of Magnetorheological Elastomer Under Various Magnetic Field Strengths

In recent studies, many mathematical models have been introduced to describe the shear deformation characteristics of a magnetorheological elastomer (MRE). Owing to its beneficial elastomeric characteristics, an MRE can be adopted in novel controllable devices such as friction dampers and brakes. In this study, mathematical models are introduced to identify the frictional behavior of an MRE under different magnetic field conditions. Specifically, the improved LuGre (I-LuGre) model and the strain-stiffening model are compared using a system identification method. To identify the model that best describes the stick/slip behavior of an MRE, a harmonic frictional force was exerted on its surface with magnetic fields of varying strength. The I-LuGre model showed a precise correlation with the experimental results, and the strain-stiffening model was shown to have a simple structure for describing the frictional phenomenon. The system output error of the I-LuGre model remained within smaller errors than that of the strain-stiffening model. The parameter variations of each model that can be utilized to construct a control strategy are provided herein.

Evaluation of Adhesion and Hysteresis Friction of Rubber–Pavement System

Tire-pavement friction is a key component in road safety. Adhesion and hysteresis are the two main mechanisms that affect the friction between rubber tires and pavements. This study experimentally examined the relationship between rubber–pavement adhesion and friction. The adhesive bond energy between rubber and pavement surfaces was calculated by measuring the surface energy components of rubber and aggregates. The friction was measured in the laboratory using a dynamic friction tester. The results revealed that there is a fair correlation between the adhesive bond energy and measured coefficient of friction. A rubber–pavement system with higher adhesion provided higher friction at low speed. In addition, the results demonstrated that there is a strong correlation between rubber–pavement friction and rubber properties. Softer rubber provided higher friction and vice versa. The results of this study provide an experimental verification of the relationship between adhesion and pavement surface friction. The adhesive bond energy and rubber rheological properties could be incorporated in computational models to study tire-pavement friction in different conditions (e.g., speed and temperature).

Inchworm Inspired Pneumatic Soft Robot Based on Friction Hysteresis

In this paper, we present an inchworm-inspired pneumatic soft robot that requires only one degree-of-freedom control to generate continuous linear locomotion on various surfaces. The locomotion is realized by the friction hysteresis resulting from the deformability of one robot leg, which is passively enabled by the robot design. The inchworm robot is made of a single material, has a single degree of freedom, and only requires the air pressure as a single-channel control signal to realize continuous locomotion.

Analysis of selected friction properties with the Froude pendulum as an example

The paper presents the method of friction parameters identification of the shaft-sleeve kinematic pair with the Froude pendulum as an example. Experimental and numerical tests covered the range of a small relative displacement of frictional pairs at which the hysteresis friction effects appear as well as the range of significant sliding velocities when the frictional force value results from the static relation to the friction coefficient characteristics. The pendulum motion description has involved a modified LuGre model, in which the Stribeck curve was replaced by cubic b-spline curve to enable the complex course approximation of friction coefficient characteristics. The specific behaviours of the pendulum motion observed during the experimental tests have been reproduced by simulating the modified LuGre model. Moreover, the numerical tests have demonstrated that the radial pendulum clearance up to 0.1 mm causes high-frequency oscillation, not substantially affecting the pendulum trajectory and sliding velocity.

Tough Nano‐Architectured Conductive Textile Made by Capillary Splicing of Carbon Nanotubes

Flexible electronics require electrically conductive and mechanically reliable nanoscale thin films. However, thin metal films have low fracture energy, which limits the performance of flexible devices. We demonstrate the design and synthesis of highly conductive, strong and tough nano‐architectured textile by capillary splicing of aligned carbon nanotubes (CNT). Owing to the strong van der Waals forces among CNTs, the pristine CNT network has average strength of 170 MPa. The average fracture energy of the textile is 16 kJ/m2, 50 folds higher than metal nanofilms. The high toughness results from crack bifurcations and friction hysteresis in a dissipation zone propagating several millimeters ahead of the crack tip. This material is suitable for applications ranging from smart skin and flexible sensors.

Mixed control scheme for accurate control of robotic flexible endoscope

Tendon-driven endoscopes are mainly used in the current practice. Their flexible bodies may change frequently during the processes of biopsy, endoscopic mucosal resection or endoscopic submucosal dissection. These changes lead to backlash hysteresis and nonlinear friction effects, which make it difficult to achieve accurate control. To address this problem, a mixed control scheme based on the combination of discrete and continuous models was proposed and quantitatively compared with a conventional feedback control scheme, a feedforward control scheme and an adaptive control scheme. These experiments were conducted using a robotic gastroscope. The results showed that our control scheme can achieve more accurate tracking performance when the configuration changes frequently, with mean square error of tracking performance decreased by 50–75%.

Modelling friction characteristics in turbine blade vibrations using a fourier series expansion of a real friction hysteresis

A new contact model is proposed to simulate the forced response of a two degree of freedom mechanical model which resembles the simplest form of a friction damped turbine blade. The model scales a measured friction hysteresis to the current state of the mechanical model to obtain the contact force. The equations of motion are solved iteratively with a Newton-Raphson method using an analytical Jacobian. Furthermore the nonlinear system is linearised by using the Monoharmonic Balance Method. Based on experiments functions are found that scale a single hysteresis in such a way that a wide range of contact states can be predicted sufficiently well. The forced response of the mechanical model using the proposed contact model shows good agreement with the forced response using an Elastic Coulomb Friction Model.

Influence of fluid viscosity and wetting on multiscale viscoelastic lubrication in soft tribological contacts.

Friction (and lubrication) between soft contacts is prevalent in many natural and engineered systems and plays a crucial role in determining their functionality. The contribution of viscoelastic hysteresis losses to friction in these systems has been well-established and defined for dry contacts; however, the influence of fluid viscosity and wetting on these components of friction has largely been overlooked. We provide systematic experimental evidence of the influence of lubricant viscosity and wetting on lubrication across multiple regimes within a viscoelastic contact. These effects are investigated for comparatively smooth and rough elastomeric contacts (PTFE-PDMS and PDMS-PDMS) lubricated by a series of Newtonian fluids with systematically controlled viscosity and static wetting properties, using a ball-on-disc tribometer. The distinct tribological behaviour, characterised generally by a decrease in the friction coefficient with increasing fluid viscosity and wettability, is explained in terms of lubricant dewetting and squeeze-out dynamics and their impact on multi-scale viscoelastic dissipation mechanisms at the bulk-, asperity-, sub-asperity- and molecular-scale. It is proposed that lubrication within the (non-molecularly) smooth contact is governed by localised fluid entrapment and molecular-scale (interfacial) viscoelastic effects, while additional rubber hysteresis stimulated by fluid-asperity interactions, combined with rapid fluid drainage at low speeds within the rough contact, alter the general shape of the Stribeck curve. This fluid viscosity effect is in some agreement with theoretical predictions. Conventional methods for analysing and interpreting tribological data, which typically involve scaling sliding velocity with lubricant viscosity, need to be revised for viscoelastic contacts with consideration of these indirect viscosity effects.