Stick-slip Characteristics Research Articles

Study on Axial-lateral-torsion Coupling Vibration Model and Stick-slip Characteristics of Drilling String in Ultra-HPHT Curved Wells

Study on Axial-lateral-torsion Coupling Vibration Model and Stick-slip Characteristics of Drilling String in Ultra-HPHT Curved Wells

Stick slip characteristics analysis of drill string system with longitudinal and torsional coupling tool

Due to the complexity and uncertainty of downhole conditions during drilling, the torsional vibration generated at the drill bit may cause the bottom hole assembly (BHA) to excite high frequency longitudinal vibration, which may lead to the longitudinal bounce of the drill string in severe cases. The excessive vibration will seriously affects the service life of the drill bit or other downhole tools. To avoid these problems and reduce the stick-slip phenomenon, this paper proposed an innovative longitudinal-torsional coupling tool, which can generate appropriate coupling vibration. With analysis of working mechanism, theoretical research includes establishment of dynamic model of BHA connected with the tool. The cases study is carried out based on Lagrangian theory. The results show the tool can effectively suppress stick-slip vibration. By adjusting the internal design parameter, the innovative design can achieve appropriate vibration, which can enable the drilling smoother, increase the mechanical efficiency, and reduce the wear of drill bit. The innovative design can provide reference for avoiding downhole accidents and improving of drilling safety. The theoretical research results can present new ideas for the development of drill string dynamics under new situations.

Local Wear of Catechol-Containing Diblock Copolymer Layers: Wear Volume, Stick–Slip, and Nanomechanical Changes

Polymers containing catechol groups have gained a large interest, as they mimic an essential feature of mussel adhesive proteins that allow strong binding to a large variety of surfaces under water. This feature has made this class of polymers interesting for surface modification purposes, as layer functionalities can be introduced by a simple adsorption process, where the catechol groups should provide a strong anchoring to the surface. In this work, we utilize an AFM-based method to evaluate the wear resistance of such polymer layers in water and compare it with that offered by electrostatically driven adsorption. We pay particular attention to two block copolymer systems where the anchoring group in one case is an uncharged catechol-containing block and in the other case a positively charged and catechol-containing block. The wear resistance is evaluated in terms of wear volume, and here, we compare with data for similar copolymers with statistical distribution of the catechol groups. Monitoring of nanomechanical properties provides an alternative way of illustrating the effect of wear, and we use modeling to show that the stiffness, as probed by an AFM tip, of the soft layer residing on a hard substrate increases as the thickness of the layer decreases. The stick–slip characteristics are also evaluated.

Formation Mechanism of Metro Rail Corrugation Based on Wheel–Rail Stick–Slip Behaviors

Field investigation shows that most corrugations occur on the inner rail surface of curved tracks with a radius of less than 700 m. In order to explore the formation mechanism of metro corrugation, the relationship between wheel–rail stick–slip characteristics and rail corrugation is studied by combining single wheelset curving and a rigid–flexible coupling model. The numerical results illustrate that the lateral torsional stick–slip vibration of inner rail–inner wheel of the guiding wheelset on the small radius curve eventually leads to the generation of inner rail corrugation, and the lateral torsional stick–slip vibration of outer rail–outer wheel of the driven wheelset may also occur, but the intensity is weak and the probability is low. The lateral torsional stick–slip vibration of inner rail–inner wheel of the guiding wheelset on the large radius curve is also easy to cause inner rail corrugation, but the degree of inner rail corrugation is lower than that on the small radius curve; the outer rail on the large radius curve is still not easy to produce corrugation. The formation mechanism of rail corrugation on the straight track is different from that on the curve track, which is mainly related to the wheel–rail longitudinal torsional stick–slip vibration.

The effect of the mechanical property and size of the surface contacts of the brake lining on friction instability

The correlation between the size and mechanical property of the surface contacts of the brake lining and the stick-slip characteristics is studied using a Krauss tester and a scaled dynamometer. Sintered pellets produced using the ground powder of four commercial brake linings are used to estimate the mechanical property of the contacts. The results show that the stick-slip intensity is governed by the size distribution and shear strength of the contacts, suggesting that the low noise propensity of the brake lining can be achieved by avoiding the formation of large and high strength contacts through formulation optimization.

Experimental analysis of the stick-slip characteristics of faults at different loading rates.

In deep underground engineering, in a large spatial, high-stress environment, rapid excavation is likely to affect the loading rate of the fault structure and to cause stick-slip. In this study, an experiment was conducted to explore the stick-slip characteristics at different loading rates. A double-sided shear experiment and the digital speckle correlation method were used to analyze the evolution of the displacement field, the slip displacement, and the slip rate of the fault's stick-slip activity at different loading rates as well as their correlation with the loading rate. The loading rate, moment magnitude, and stress drop of the fault's stick-slip and their corresponding relationships were studied. The results show that the occurrence of stick-slip is inversely proportional to the loading rate. The evolution of the fault-slip displacement field at different loading rates is similar. At a given loading rate, the magnitude is positively correlated with the stress drop. The magnitude and stress drop are inversely related to the loading rate.

Stick–slip behaviour of mortar–rock interface under high loading rate

A modified push-out method was used to explore the bond characteristics of the mortar–rock interface in an anchor system at different loading rates. Under a high loading rate (≥ 1·12 × 10−4 s−1), stick–slip behaviour, which is usually used to describe the mechanism of earthquakes, was observed at the mortar–rock interface for the first time in this experimental research. The test results showed that the load–displacement curve under a high loading rate included four stages: elastic deformation, interface softening, residual friction and stick–slip oscillation. A micro-mechanical model of bond–slip at the mortar–rock interface was also developed. A series derivation revealed the relationships among the dilatancy stress of the mortar–rock interface, the loading rate and the stress drop of stick–slip. The mechanism of stick–slip behaviour at the mortar–rock interface was theoretically established. The modified visco-elastoplastic constitutive model established to describe the stick–slip characteristics of a mortar–rock interface was verified with experimental results using Abaqus software.

Identifying Stick-Slip Characteristics of a Smart Device on a Seismically Excited Surface Using On-Board Sensors

ABSTRACT Accelerometers in smart devices have been used to successfully detect the occurrence of seismic activity. Taking the next step of using the measured acceleration response to compute floor displacements for the purpose of assessing building seismic damage is a more challenging application. In particular, sliding of smart devices or their underlying support hinders their use for this purpose because that means that the floor drifts cannot be directly measured using the onboard sensors. This paper discusses the dynamic behavior of a free-standing smart device and presents a method for estimating the kinetic coefficient of friction between the smart device and the underlying surface based on wavelet transforms. A methodology is then presented by which a smart device can decide if its motion is representative of the motion of the floor underneath or whether it is tainted by excessive sliding action. The noise associated with a smart device’s measurement of acceleration is established and noise reduction methods to overcome them are compared. Computational simulation results and experimental data are used to demonstrate the concepts discussed in this paper.

Stick-slip vibration analysis and vibration frequency extraction of coke pushing system

Coke pushing equipment in the coke oven plant is a device used to push the red coke out of the coke chamber. The main section of the equipment is pushing rod and its major role is to push the ripe coke out of the furnace chamber. During the operation of pushing coke, we observe that there is an obvious vibration phenomenon. For the sake of more deeply investigating the mechanism of friction-induced vibration of the coke pushing device, we propose a mass-spring-damper model in this article. Then this model was used to research on the stability and stick-slip characteristic of the coke pushing system, and its speeds at the state of critical instability and critical stick-slip are obtained by theoretical calculation. Considering that the temperature of working environment may reach 1000 °C, numerical simulation of the coke pushing system has been carried out by finite element method, and the vibration frequencies in different directions are obtained. The simulation results show that the stick-slip vibration of 51 Hz occurs when the coke pushing device is working. Finally, the numerical simulation results are verified by the field test. The results of this paper have a certain guiding significance for improving the design of coke pushing device and reducing the vibration of the system.

Modeling and analysis of friction clutch at a driveline for suppressing car starting judder

Car judder is a kind of back-forth vibration during vehicle starting which caused by the torsional oscillation of the driveline. This paper presents a systematic study on the dynamic response characteristics of the clutch driven disc for suppression of the judder during vehicle starting. Self-excited vibration behavior of the clutch driven disc is analyzed based on the developed 4DOF non-linear multi-body dynamic model of the clutch driving process considering stick-slip characteristics and using Karnopp friction models. Physical parameters of a clutch determining the generations of the judder behaviors are discussed and the revised designs of the driven disc of a clutch for suppression of the judder are consequently investigated and validated with experiments for two real cars.

Experimental study on the tribological properties of CuO-based biodegradable nanolubricants for machine tool slideways

Bio-lubricants are biodegradable and non-toxic. Bio-based lubricants are an attractive alternative to conventional mineral oil-based lubricants. This study deals with the tribological investigation of biodegradable nanolubricants which could be applied in machine tool slideways. The nanoparticle used was copper oxide (CuO) and the biodegradable oils used were coconut oil, sesame oil, olive oil, sunflower oil and soybean oil. The nanolubricants were prepared by adding 0.1% wt. of CuO nanoparticles in each biodegradable base oil. Experiments were conducted on a pin on block type reciprocating friction monitor and four ball tester. Friction, stick-slip and wear characteristics were analysed. The test results showed that the addition of CuO nanoparticles in biodegradable oils improve friction reduction and antiwear properties. The mechanism of friction reduction is found to be the formation of tribofilm through deposition of CuO nanoparticles on the wear surfaces. Field testing was conducted for the best nanolubricants.

Experiments on vibration-driven stick-slip locomotion: A sliding bifurcation perspective

Abstract Dry friction appears at the contact interface between two surfaces and is the source of stick-slip vibrations. Instead of being a negative factor, dry friction is essential for vibration-driven locomotion system to take effect. However, the dry-friction-induced stick-slip locomotion has not been fully understood in previous research, especially in terms of experiments. In this paper, we experimentally study the stick-slip dynamics of a vibration-driven locomotion system from a sliding bifurcation perspective. To this end, we first design and build a vibration-driven locomotion prototype based on an internal piezoelectric cantilever. By utilizing the mechanical resonance, the small piezoelectric deformation is significantly amplified to drive the prototype to achieve effective locomotion. Through identifying the stick-slip characteristics in velocity histories, we could categorize the system’s locomotion into four types and obtain a stick-slip categorization diagram. In each zone of the diagram the locomotion exhibits qualitatively different stick-slip dynamics. Such categorization diagram is actually a sliding bifurcation diagram; crossing from one stick-slip zone to another corresponds to the triggering of a sliding bifurcation. In addition, a simplified single degree-of-freedom model is established, with the rationality of simplification been explained theoretically and numerically. Based on the equivalent model, a numerical stick-slip categorization is also obtained, which shows good agreement with the experiments both qualitatively and quantitatively. To the best of our knowledge, this is the first work that experimentally generates a sliding bifurcation diagram. The obtained stick-slip categorizations deepen our understanding of stick-slip dynamics in vibration-driven systems and could serve as a base for system design and optimization.

Effect of stick-slip on magneto-rheological elastomer with a magnetic field

This study investigated the stick-slip characteristics of a magneto-rheological elastomer (MRE) against an aluminum plate. Herein, the MRE was manufactured, and a stick-slip tester was employed to evaluate the stick-slip performance of the MRE under different velocities and load conditions with and without a magnetic field. The fast Fourier transform (FFT) of the friction force of the stick-slip and the roughness of the aluminum plate surface were calculated to confirm the stick-slip phenomenon. After the tests, the wear surfaces were observed to evaluate the wear properties of the MRE regarding the stick-slip. Results showed that the stick-slip was smaller at lower velocity. At higher velocity, the reduction of the stick-slip under a magnetic field was more clearly observed. Moreover, the wear reduced with reduced stick-slip under a magnetic field.

Influence of nonuniform network on mechanical properties of nano-silica reinforced silicone rubber

Nonuniform networks were introduced into the nano-silica reinforced silicone rubbers, by co-cross-linking of silicone gum containing 0.05 mol% vinyl ( GL) and gum containing 3 mol% vinyl ( GH), so as to improve the mechanical properties. Their network characteristics were investigated by nuclear magnetic resonance measurement, swelling experiment, dynamic mechanical analysis, and rubber process analysis. Nonuniform networks displayed high tear strengths up to 41 kN m−1 and improved tensile strengths and elongations at break. Nonuniform networks with 7–10 phr of GH had optimal mechanical properties, since densely cross-linked domains scattered in base network and imparted maximum heterogeneity. In this structure, dense domains favored high modulus, while dominated long chains contributed to large extensibility. Hence, such structure could display large elongation before fracture while showing twice modulus upturns and stick-slip tearing characteristics, which were demonstrated by Mooney–Rivlin curves, tearing curves, and scanning electron microscopic images.

Stick-slip behavior of magnetorheological fluids in simple linear shearing mode

The stick-slip motion of magnetorheological (MR) fluids under a simple linear shear mode has been experimentally reported. The critical shear strain for the onset of the stick-slip motion decreases logarithmically with the magnetic flux intensity applied. The rate of energy accumulation and releasing during stick-slip motion changed in a power law of the viscosity of the continuous phase in a range of 0.01~1000 mPa S. Different carrier fluids led to different stick-slip characteristics. The stick-slip motion can be fully suppressed with certain carrier fluids. When the MR fluids are in a shear-thickening state, the critical shear strain of the onset of the stick-slip motion is larger than a normal state. But, the relative spike amplitude of the stick-slip remains similar.

자기장에 따른 자기유변탄성체의 스틱 슬립 현상 연구

This paper investigates the stick-slip characteristic of magnetorheological elastomer (MRE) between an aluminum plate and the surface of the MRE. MRE is a smart material and it can change its mechanical behav- ior with the interior iron particles under the influence of an applied magnetic field. Stick-slip is a movement of two surfaces relative to each other that proceeds as a series of jerks caused by alternate sticking from friction and sliding when the friction is overcome by an applied force. This special tribology phenomenon can lead to unnecessary wear, vibration, noise, and reduced service life of work piece. The stick-slip phenomenon is avoided as far as possible in the field of mechanical engineering. As this phenomenon is a function of material property, applied load, and velocity, it can be controlled using the characteristics of MRE. MRE as a soft smart material, whose mechanical properties such as modulus and stiffness can be changed via the strength of an external mag- netic field, has been widely studied as a prospective replacement for general rubber in the mechanical domain. In this study, friction force is measured under different loads, speed, and magnetic field strength. From the test results, it is confirmed that the stick-slip phenomenon can be minimized under optimum conditions and can be applied in various mechanical components. Keywordsstick-slip(스틱 슬립), magneto-rheological elastomer(자기유변탄성체), friction force(마찰력), smart material(지능재료)

Analysis of Measured Friction of Rolling Balls in Raceway Grooves

Friction in linear guideways has an influence on the motion accuracy of machine tool drives. As feedback control has a lag to the friction change in reverse motion, a feedforward compensation is generally used in friction models. However, it is difficult to estimate the friction of rolling balls in raceway grooves because it involves both stick and differential slip characteristics. In this paper, a measurement method is presented using an analytical procedure to clarify micro stick and slip factors in rolling friction. In the measurement test, four balls and two raceway grooves are used to measure the friction force under dry and lubricated conditions. The locomotive bristle model is then applied to identify the stick and slip parameters, which are then compared between the various conditions of lubrication.

Tribological investigations on MoS2-based nanolubricant for machine tool slideways

The present study evaluates the tribological characteristics of molybdenum disulphide (MoS2)-based nanolubricant for its use in machine tool slideways. MoS2 nanoparticles were synthesized and physical characterization was carried out using scanning electron microscope and transmission electron microscope. The nanolubricants were prepared by adding various proportions of MoS2 nanoparticles in polyalphaolefin base oil with lecithin as dispersant. Friction, wear, and stick-slip characteristics of the nanolubricants were assessed using a pin-on-block reciprocating friction monitor simulating the actual loading conditions prevailing in machine tool slideways. Extreme pressure properties of the lubricants were determined using a four ball tester. The wear surfaces were analyzed using scanning electron microscopy and energy-dispersive spectroscopy. The results of the studies were compared with ISO VG 32, a conventional lubricant used in machine tool slideways, and it was found that the addition of MoS2 nanoparticles in polyalphaolefin base oil results in approximately 24% reduction in coefficient of friction and an increase in load-carrying capacity. The mechanism behind the improvement in tribological behavior of MoS2-based nanolubricant is most likely the formation of a thin, MoS2 tribofilm at the wear surface.

촉감 감성 해석을 위한 미끄럼 마찰 시험과 신호 분석

Abstract The friction behavior of human skin is determined by the complex interplay of the material and sur-face properties of the skin, as well as the contacting material, and strongly depends on the contact parameters(e.g., pressure and sliding velocity) and the presence of substances such as water, sweat, or skin surface lipidsat the interface. Including a study on the effect of a surface's physical roughness for skin sliding over the surface,various studies have been conducted to understand human tactile sensibility. However, to investigate products inrelation to human tactile sensibility, more objective research is needed. This study performed sliding experimentsbetween the skin and the surfaces of phone cases to understand how the texture, friction, and stick-slip char-acteristics are related. Eight phone case surfaces with different topologies and chemical (or mechanical) com-patibilities with skin were prepared and tested multiple times. Keywords finger(손가락), friction(마찰), skin tribology(피부 트라이볼로지), biotribology(바이오 트라이볼로지), haptics(햅틱스), tactile(촉감), phone case(휴대폰 케이스), touch(터치)

Stick-slip in sliding systems with tangential contact compliance

Sliding systems with a flexible body (i.e., a soft material) in the contact zone were modeled as a general two-degrees-of-freedom system that includes tangential contact compliance, and a series of dimensionless governing equations was derived. Based on the equations, a numerical simulation was conducted to study the stick-slip characteristics of the modeled system. By using six dimensionless parameters included in the equations, we obtained criteria for preventing stick-slip that can be applied to the design of sliding systems, such as the selection of soft materials for contact surfaces. In addition, some unusual phenomena caused by tangential contact compliance were observed. Even if the supporting section is overdamped, stick-slip motion can be promoted by the inertia of the mass of the contact zone; moreover, tangential contact compliance can cause serious errors in the measurement of the static and kinetic friction coefficients that uses the elongation of the supporting spring.