Stick-slip Effect Research Articles

Characterization of the Frictional Behavior of Steel-Polymer Interfaces with Pronounced Stick-Slip Effect for Use in Seismic Isolation

Characterization of the Frictional Behavior of Steel-Polymer Interfaces with Pronounced Stick-Slip Effect for Use in Seismic Isolation

Design and research on tuning fork piezoelectric actuator based on stick-slip effect.

Aiming at the problems of low output speed, large size, and difficult miniaturization of stacked and sandwich piezoelectric actuators, a patch-type tuning fork piezoelectric actuator model based on the stick-slip effect was designed, in which the dynamic theoretical analysis, the simulation optimization to determine the stator structure parameters, and the experimental research were carried out to obtain the stator structure parameters. The externally applied conditions (the influence model of excitation voltage, excitation frequency, and pre-pressure) on the performance output of piezoelectric actuators will promote the miniaturization and industrialization of tuning fork piezoelectric actuators in the next step. The simulation results show that the integrated output performance of the piezoelectric actuator is best when the angle of the tuning fork is 15°. After optimizing the stator chamfer to 2.5 and 4.5mm, the tangential amplitude difference of the 15° tuning fork angle actuator is the smallest. The experimental results show that the output speed of the actuator is positively linearly related to the excitation voltage, the maximum output thrust is 8 N when the excitation voltage is 100V, the excitation frequency is 20.1kHz, the pre-pressure is 7.5 N, the phase difference of the excitation signal is π/2, and the output speed of the actuator can reach 116 mm/s.

‘Big data’ in physics education: discovering the stick-slip effect through a high sample rate

With the availability of educational digital data acquisition systems, it has also become possible in physics education to generate ‘big’ data sets by (a) measuring multiple variables simultaneously, (b) increasing the sample rate, (c) extending the measurement duration, or (d) choosing a combination among these three options. In the context of this paper, we will use a simple acceleration experiment to show that a higher sample rate, resulting in a larger data set, quantitatively reveals the stick-slip effect. For this purpose, two variables are measured simultaneously, first with a low and then with a high sample rate. The purpose of this paper is to illustrate that dealing with ‘big’ data sets can add value to experimentation in physics labs by dealing with data sets that more accurately describe observations.

Analyse von Einflussparametern auf den Stick-Slip-Effekt mittels Tribometerversuchen und FE-Simulation

Brake fluids lubricate dynamic seals in automotive brake systems. Depending on the fluid, such seals tend to show a stick-slip effect, which may cause disturbing squeal noises. In order to avoid such stick-slip-noise in future systems, it is required to characterize and rate the frictional behavior of different brake fluids in an appropriate way. This paper presents a tribometer test that enables to investigate the stick-slip-effect depending on the brake fluid. For an objective evaluation, an indicator value is introduced. Furthermore, this paper presents a dynamic friction model on basis of the Stribeck-curve that allows visualization and detailed investigation of the stick-slip-effect within finite element computation.

Statistical evaluation of experimental and numerical data of stick–slip effects in harmonically excited systems

The trend towards lightweight in the automotive industry give rise to new challenges when assessing the influence of material replacements on stick–slip effects. These effects may lead to new acoustic phenomena when aluminium is applied, e.g. coming from the interfaces of the wheel assembly between the rim, brake disk hat and the wheel carrier. Detecting the key influencing parameters is an important task to avoid undesired noises or wear. Whereas self-excited oscillators were intensively discussed in the last decades, much fewer studies about harmonically excited systems were published. The goal of this study is to investigate the effect of different parameters on the stick–slip behaviour of a harmonically excited oscillator exposed to friction. Based on a statistical evaluation of huge experimental data sets with stick–slip effects, a two-degree-of-freedom model for the frictional testing machine is proposed and implemented with several friction models. These models are compared with respect to their ability to fit the measurement data and their computational effort. Numerical parameter studies including a huge amount of different parameter sets are performed to determine the effect of several parameters on the limit cycle of the dynamic system, quantified by the number of stops per cycle. The influence of more complex friction laws on the parameter maps are discussed in relation to the published results by Hong and Liu as well as Papangelo and Ciavarella.

Identification of different manifestations of nonlinear stick–slip phenomena during creep groan braking noise by using the unsupervised learning algorithms k-means and self-organizing map

Creep groan is a friction-induced, low-frequency vibration and noise phenomenon of a vehicle’s brake system which is excited by a repeating stick–slip effect. Together with high influences of design and operational parameters, the non-linear stick–slip leads to an interesting bifurcation behaviour of creep groan. For objective rating procedures, detection and classification methods considering this bifurcation behaviour are necessary. Within this study, an approach based on acoustic emission is presented. The approach harnesses high-frequency acceleration contents that accompany creep groan’s characteristic stick–slip transitions. Whereas low-frequency vibration contents below 500 Hz are mainly defined by the characteristics of the brake system and the suspension of the vehicle, vibrations in the high-frequency range above 10 kHz exhibit patterns of waveforms similar to the patterns of acoustic emission bursts. By applying non-overlapping high- and low-pass filters, a novel signal, enveloping these bursts, was created. This envelope bursts signal enables a precise detection and quantification of stick–slip transitions directly in time domain, and led to the development of a whole new set of vibration signal features. These nine signal features were used to feed the unsupervised classification algorithms k-means and Kohonen’s self-organizing map, which delivered robust and meaningful results. Four different creep groan classes were detected, where each has shown to be linked to a specific creep groan manifestation: Low-frequency groan, high-frequency groan and two transition phenomena with two/three stick–slip events per cycle were found. Classification results and their linked mechanical behaviour suggest an interaction between two significant vibration patterns during creep groan, probably a longitudinal and a torsional displacement of the axle. Aside of deeper insights in creep groan’s bifurcation behaviour, the presented study enables not only the identification of creep groan, but also the automatic classification of its manifestations in real-time, and therefore provides further possibilities for creep groan control methods.

A model for the dynamic friction behaviour of rubber-like materials

Rubber friction has received much attention because of its practical importance for modelling, for example, tyre-road friction. Many experiments were carried out and a number of theories were proposed to investigate and explain its behaviour and dependency on external conditions such as temperature and velocity. However, only a few published articles describe the observed dynamic friction behaviour using compact analytical models. Models for dry friction, such as the Dahl and LuGre models and their several variations, have been proposed to describe rubber friction. Unfortunately, they cannot reproduce many important and specific phenomena observed in experiments focused on rubber friction. In this paper, we propose a simple analytical friction model suitable to simulate the dynamic friction behaviour of rubber-like materials on rigid surface. Phenomena such as pre-sliding, sticking/sliding transitions, relaxation of the friction force at standstill and stick-slip effects can be accurately modelled. We validated the model with several experiments, obtaining a good agreement between simulation and measurements. In addition, we propose a two-dimensions (2D) extension of the model, to broaden the field of cases, in which it can be used. The capability of the model to simulate 2D anisotropic friction behaviour was validated with measurements of a vehicle tyre.

“Evaluation of a method to measure the friction coefficient between vital mandibular bone and biomedical materials”

PurposeThe aim of this study is to evaluate a developed experimental set-up to measure the coefficient of friction between fresh mandibular bone and biomaterials used in oral and maxillofacial surgery including a standardized routine for specimen preparation. Material and methodsFor this purpose, we developed a specialized routine for harvesting and preparation of cortical bone specimen from cadaveric porcine mandibles and modified a ball-plate tribometer. These harvested bone specimen were kept moist all the time. A total of 24 bone cylinders with 8 repetitions per material were examined for their coefficient of friction against stainless steel (1.4404), a titanium alloy (Ti6Al4V) and a cobalt‑chromium‑molybdenum alloy (Biosil F®) and subsequently analyzed by laser-scanning and scanning electron microscopy. ResultsThe lowest coefficients of friction between vital cortical bone and the investigated implant materials were found for Biosil F®, while the highest coefficients of friction were found for the titanium alloy Ti6Al4V. Significant differences for the initial coefficient of friction with p < 0.05 have been proven. Stick-slip effects occurred during the measurement and a layer of debris formed on the metallic samples. EDX analysis of the abrasion marks revealed that this layer consisted of elements contained in hydroxyapatites and carbon. ConclusionThe experimental set-up is suitable to perform reproducible comparative measurements of the coefficient of friction of different material combinations. A significant advantage of the methodology is the flexibility and scalability of harvesting and preparation of the bone specimen, which allows the simulation of realistic situations while measuring the coefficient of friction.

Stick–slips and jerks in an SDOF system with dry friction and clearance

Presence of dry friction and clearance discontinuities in various dynamic systems, such as friction wedge dampers in a three-piece railway freight-vehicle bogie, centre buffer coupler connecting two coaches, originate significant jerks. While nonlinear dynamics of systems, with these individual and combined discontinuities has received some attention, behavior of jerks remains unexplored. This study investigates the stick–slip effects and sources of jerks in such systems, using a representative single degree of freedom system, featuring simultaneous presence of dry friction and clearance, subjected to harmonic excitation. Den Hartog’s analytical formulations Hartog (1930) of friction mode transitions are extended numerically, to include the combined effect of dry friction and clearance, for investigation of stick–slip and jerk characteristics. It is shown that jerks can be distinguished between those arising from stick–slip effects due to dry friction and those from soft spring impacts. Limiting values of the ratio of friction force to excitation force for stick–slip motion are obtained. These frequency dependent ratios are larger than those in systems with friction alone. Multiple-stick–slip events, within a cycle, are observed at lower excitation frequencies. At higher frequencies, instances of high amplitude jerks are more than at lower excitation frequencies. A parametric study is carried out with a view to obtain the optimum range of design parameters for jerk minimization. Effects of wear and tear on jerks have also been considered through modeling of deteriorated system parameters.

Identification of the Effect of Ultrasonic Friction Reduction in Metal-Elastomer Contacts Using a Two-Control-Loop Tribometer

Pneumatic cylinders are widely used in highly dynamic processes, such as handling and conveying tasks. They must work both reliably and accurately. The positioning accuracy suffers from the stick-slip effect due to strong adhesive forces during the seal contact and the associated high breakaway forces. To achieve smooth motion of the piston rod and increased position accuracy despite highly variable position dynamics, sliding friction and breakaway force must be reduced. This contribution presents a specially designed linear tribometer that has two types of control. Velocity control allows the investigation of sliding friction mechanisms. Friction force control allows investigation of the breakaway force. Due to its bearing type, the nearly disturbance-free detection of stick-slip transients and the dynamic contact behavior of the sliding friction force was possible. The reduction of the friction force was achieved by a superposition of the piston rod’s movement by longitudinal ultrasonic vibrations. This led to significant reductions in friction forces at the rubber/metal interface. In addition, the effects of ultrasonic frequency and vibration amplitude on the friction reduction were investigated. With regard to the breakaway force, significant success was achieved by the excitation. The force control made it possible to identify the characteristic movement of the sealing ring during a breakaway process.

Effects of Stick-Slip in Behavior of Structures with Friction Damper under Near-Field Earthquakes

The present study is an attempt to investigate structures equipped with friction dampers under the influence of near-field earthquakes based on Stribeck friction behavior of velocity function. At present, the cyclic behavior of friction dampers in structural design engineering software is simple and based on the Coulomb friction force that is independent of velocity, which should be estimated and considered in terms of Stribeck velocity-dependent friction. Their sliding and vibration methods, including displacement, velocity, and acceleration, are calculated using numerical analysis and differential equation. For this purpose, the representative of the near-field records affects the structure with Stribeck frictional behavior of velocity function as a pulse of Ricker wavelet stimulation. The response of the structure is evaluated in the transition phase from impending motion with a friction coefficient of μs to kinetic motion with μk and vice versa, which makes the poor results of previous simplifications more accurate. Due to the nonlinear behavior of the damping force, programming has been used to perform nonlinear analytical dynamics. Also, behavioral models in OpenSees software are used to investigate the behavior of Stribeck friction for friction damper and to compare its results with the results obtained from accurate analysis.

Investigation on the Influence of Moisture Content and Wood Section on the Frictional Properties of Beech Wood Surface

To closely examine the mechanical properties of mortise and tenon woodworking joinery in outdoor environments, it is essential to obtain fundamental data regarding the influence of moisture content and wood section on the frictional properties of wood surfaces. In this study, the static and dynamic friction coefficients under varying moisture contents (5, 8.50, 11.25, 20, 30, 40, 50, and 60%) and wood sections (tangential, diagonal, and radial) were measured. Moreover, the equation for the relationship between moisture content and friction coefficient was obtained and variations in friction coefficients caused by the effects of moisture content and wood section on roughness and hardness were analyzed. The results showed that moisture content and wood section had significant effects on the friction coefficient of beech wood. With increasing moisture content, the static and dynamic friction coefficients both increased, and the tangential section exhibited a higher friction coefficient than the diagonal and radial sections. Furthermore, with increasing moisture content, the ratio of the dynamic friction coefficient to the static friction coefficient showed an initial increasing trend and then gradually flattened due to the stick–slip effect, and the friction coefficient showed a segmented and positive growth trend in the moisture content range of 5–60%. Ultimately, it was found that higher moisture contents had a negative effect on frictional properties, leading to rougher wood surfaces and lower hardness, and roughness was linearly correlated with the friction coefficient. These findings can assist in making accurate calculations and optimizing the structural design of wood products.

Simulacija i odstranjivanje stick-slip efekta servosistema sprovodnog aparata hidraulične turbine

Friction is a repeatable and undesirable problem in hydraulic systems where always has to be a tendency for its removal. In this paper, the friction model is presented through which the most accurate results are achieved and the way of friction compensation, approached trough technique presented with the mathematical model of a hydraulic cylinder of a hydro turbine wicket gate controlled by a servomechanism. Mathematical modelling of a servo mechanism and hydraulic actuator, and also the simulation of hydraulic cylinder as a part of a hydro turbine wicket gate hydraulic system where the stick-slip phenomenon is present between the system components that are in contact is presented. Applied results in this paper and the theory behind them precisely demonstrate under what circumstances the stick-slip phenomenon appears in such a system. The stick-slip effect is simulated using Simulink and Hopsan software and the analysis of the results are given in this paper. Removal of the stick-slip effect is presented with the design of a cascade control implemented to control the behaviour of the system and remove the appearance of a jerking motion.

Rock Breaking Mechanism and Drilling Performance of Harmonic Vibro-Impact Drilling

An improved model of displacement response of rock considering damping is proposed and the energy response model is further presented. Then, the rock breaking mechanism under harmonic vibro-impact is investigated based on the displacement response and energy response. Furthermore, the numerical simulations are conducted to analyze the principal stress of rock and drilling characteristics in axial and torsional directions under harmonic vibro-impact. Finally, the performance of the harmonic vibro-impact drilling technology is verified by the field application. Based on the analysis undertaken, it can be concluded that the periodic harmonic impact force makes the rock subjected to more tensile stress and continuous damage accumulation, which causes the efficient rock breakage. What’s more, the harmonic vibro-impact can also alleviate the stick-slip effect and bounce phenomenon of drill bit to a certain extent. Our investigations confirm that the harmonic vibro-impact can achieve the purpose of rate of penetration (ROP) improvement.

Investigation of the Helmholtz Motion of a Violin String: A Finite Element Approach

Abstract In the context of this work, a violin string motion is examined using a finite element approach. The string is formulated via ideal string elements and is bowed at one point on the string; hence, there is a nodal contact between the bow and the string. The bow movement induces the stick-slip effect, which is the cause for the violin string sound. The present paper aims at the investigation of the stick-slip phenomenon of bowed strings, considering well-known bowed string effects like the Helmholtz corner modulation, the Schelleng ripples, and the flattening effect. One key element that is used in this work is the Schelleng diagram, which indicates the “perfect” bow force depending on the bowing position. Within these parameters, the Helmholtz motion is carried out. Additionally, different friction characteristic curves are applied in order to study the impact of the rosin on the string motion.

Improved tribological and noise suppression performance of graphene/nitrile butadiene rubber composites via the exfoliation effect of ionic liquid on graphene

AbstractMinimization and suppression of friction and noise in underwater bearings remains a key aspect in modern marine vehicle industry owing to the growing need for reliability, and passenger comfort. In this study, graphene nano‐flake (Gr) was introduced into the nitrile butadiene rubber (NBR) with assistance of ionic liquid (IL). Owing to the positive charge generated by the secondary ordering layer on the Gr surface, Gr were effectively exfoliate into few layers and uniformly dispersed in the NBR matrix. Accordingly, the friction coefficient and volume wear rate decreased to 0.3124 and 6.44 × 10−6 mm3·N−1·m−1 in the nanocomposite, depicting a 31.52% and 51.9% reduction than pure NBR. It was demonstrated that the reinforced hardness and the formation of tribological layer of Gr played a vital role in the lubricating mechanism where both deformation and the continuation of the stick–slip effect were prevented. As a proof of concept, the total vibration acceleration level of the NBR/GR‐IL composite decreased from 111.37 ± 5.57 dB to 79.68 ± 3.98 dB, exhibiting good noise and vibration suppression effect. This work not only broadens the application of GR‐based materials, but also shed some light on the designing philosophy to improve the efficiency, service life and safety of the future marine vehicles.

Inclusion of the dwell time effect in the LuGre friction model

The Dahl friction model is a simple dynamic model for friction obtained by adding dynamics to the stress strain curve. The model captures many aspects of friction and has been used for simulation for a long time. A drawback with the model is that it does not display the stick-slip effect. The LuGre friction model extends the Dahl model to capture the stick-slip motion but is does not capture the fact that friction increases between two surfaces in contact. In this paper we extend the LuGre model to include the effects of dwell time. The model is verified with experiments.

Controlling material flow in incremental sheet-bulk metal Forming by thermal grading

The requirements towards lightweight components and cost-efficient processes call for innovative developments. In the case of load-adapted components with functional elements, incremental Sheet-Bulk Metal Forming (iSBMF) presents a suitable approach. Nevertheless, secondary issues such as an inhomogeneous thickness increase at the sheet-edge are unsolved so far. This inhomogeneous thickness increase leads to geometrical deviations during the subsequent forming of functional elements such as gears. To solve this problem a new process design is proposed which enables a targeted control of the material flow by thermal grading. Numerical modelling of this new process design verifies that a well-designed temperature distribution enables locally controlled yielding. Thus, the conflict of aims among high heating rates and a small heated area is investigated. The required electrical current and contact surface leads to thermal welding of the electrodes. As a result, a stick slip effect between electrodes and workpiece causes an inhomogeneous temperature distribution and impedes reaching the required temperature increase.

Comparative study between dry friction and electrorheological fluid switches for Tuned Vibration Absorbers

Tuned Vibration Absorbers are a widely used tool for suppressing the amplitude of a systems vibrations, one of the advantages being offered is that the absorber can be an add-on solution which is able to be adjusted offline. Many improvements have been made to the base system including the use of dry friction elements, and magneto- or electrorheological fluid (M-/ERF) elements. In this work the ability of both a dry friction based system and an electrorheological fluid (ERF) damper based system to reduce the amplitude response of a system over a wide range of frequencies through the use of the stick-slip effect is investigated through simulation. The unique advantage of using an ERF damper over a dry friction element are then investigated. Those are the ability of an ERF damper based system to adjust the breakaway force online and the ability of the damper to switch between the slip- and stick-states to further reduce the amplitudes over certain frequencies given that the excitation force is kept to a single frequency at a time. These investigations were first carried out through simulations and then through an experimental setup for both systems to prove the concepts in practice. The results of the experiment conclusively proved the ability of both systems to behave as predicted, especially the ability of the ERF damper to switch between stick- and slip-states to reduce vibration amplitudes in some frequencies.

Impact and stick-slip dynamics in the soft-landing on minor celestial bodies

The soft-landing on the surface of minor celestial bodies has been investigated with considering the impact and stick-slip effect. The polyhedron model is used to analyze the irregular shape and topography and geomorphology of minor celestial bodies. The soft-sphere discrete element method is used to fill the irregular minor celestial body’s polyhedron model and cover the surface of the body; and then the irregular shape, the gravitational environment, as well as the impact and hopping with the surface can be calculated precisely. The dynamical parameters of failed soft-landing and successful soft-landing are calculated and analyzed. In the cases of successful soft-landing, there are two obviously different kinds: firstly, the final position of the lander is near the target position; secondly, the final position of the lander is far from the target position. The difference of these two kinds of results is discussed. This research shows the major dynamical behavior of soft-landing on minor celestial bodies includes impact, hopping, as well as stick-slip effect. If the initial positions of soft-landing are improper chosen, the lander may become orbital motion around minor celestial body after one or more impact and hopping, or turn to quasi-periodic motion around equilibrium points without impact, or perhaps be static far from the initial position after several times of impact and hopping and leads to the failure of the deep space mission. For the successful soft-landing process, after several times of landings on the surface during the soft-landing process, the lander will finally settle on the surface of the minor celestial body. The results show that the soft-landing region should be selected as a flat area or concave region, which is far from the equatorial plane of the minor celestial bodies.