Stick-slip Research Articles

Influence of operating conditions in nonlinear vibration of a drill-string

In this work, the vibrational analysis of an oil drill-string is carried out concerning nonlinear and nonsmooth dynamical model with coupled axial-torsional modes. This study aims to investigate the influence of operating conditions to avoid bit-bounce and stick-slip phenomena. A discrete lumped dynamic model with two degrees of freedom is considered. Dry friction and the possibility of loss of contact between the bit and the formation introduce two nonsmooth conditions into the system. Numerical simulations are performed to obtain the dynamic responses and to evaluate critical operating conditions. A parametric analysis is carried out to determine the influence of the weight on the drill bit and the angular velocity of the rotary table on the severity of critical vibrations for different drilling depths. A map is obtained, where normal operation, stick-slip, and bit-bounce responses are defined, allowing a choice of suitable parameters so that the drill-string does not experience critical vibration issues. The results indicate that the safety region, where normal operation is realized, depends on the drilling depth. However, when the angular velocity of the rotary table is equal to 10 rad/s and the weight on the drill bit is greater than 55 kN ensures normal operation for any drilling depth.

Stick–Slip Suppression in Drill String Systems Using a Novel Adaptive Sliding Mode Control Approach

A novel control technique is presented in this paper, which is based on a first-order adaptive sliding mode that ensures convergence in a finite time without any prior information on the upper limits of the parametric uncertainties and/or external disturbances. Based on an exponent reaching law, this controller uses two dynamically adaptive control gains. Once the sliding mode is reached, the dynamic gains decrease in order to loosen the system’s constraints, which guarantees minimal control effort. The proof of convergence was demonstrated according to Lyapunov’s criterion. The proposed algorithm was applied to a drill string system to evaluate its performance because such systems present variable operating conditions caused by, for example, the type of rock. The effectiveness of the proposed controller was evaluated by conducting a comparative study that involved comparing it against a commonly used sliding mode controller, as well as other recent adaptive sliding mode control techniques. The different mathematical performance measures included energy consumption. The proposed algorithm had the best performance measures with the lowest energy consumption and it was able to significantly improve the functioning of the drill string system. The results indicated that the proposed controller had 20% less chattering than the classic SM controller. Finally, the proposed controller was the most robust to uncertainties in system parameters and external disturbances, thus demonstrating the auto-adjustable features of the controller.

Optimizing Machining Efficiency in High-Speed Milling of Super Duplex Stainless Steel with SiAlON Ceramic Inserts

Super duplex stainless steels (SDSSs) are widely utilized across industries owing to their remarkable mechanical properties and corrosion resistance. However, machining SDSS presents considerable challenges, particularly at high speeds. This study investigates the machinability of SDSS grade SAF 2507 (UNS S32750) under high-speed milling conditions using SiAlON insert tools. Comprehensive analysis of key machinability indicators, including chip compression ratio, chip analysis, shear angle, tool wear, and friction conditions, reveals that lower cutting speeds optimize machining performance, reducing cutting forces and improving chip formation. Finite element analysis (FEA) corroborates the efficacy of lower speeds and moderate feed rates. Furthermore, insights into friction dynamics at the tool–chip interface are offered, alongside strategies for enhancing SDSS machining. This study revealed the critical impact of cutting speed on cutting forces, with a significant reduction in forces at cutting speeds of 950 and 1350 m/min, but a substantial increase at 1750 m/min, particularly when tool wear is severe. Furthermore, the combination of 950 and 1350 m/min cutting speeds with a 0.2 mm/tooth feed rate led to smoother chip surfaces and decreased friction coefficients, thus enhancing machining efficiency. The presence of stick–slip phenomena at 1750 m/min indicated thermoplastic instability. Optimizing machining parameters for super duplex stainless steel necessitates balancing material removal rate and surface integrity, as the latter plays an important role in ensuring long-term performance and reliability in critical applications.

Frictional Behavior of Chestnut (Castanea sativa Mill.) Sawn Timber for Carpentry and Mechanical Joints in Service Class 2

Wood is poised to become a material of choice for future construction. When appropriately managed, it is a renewable material with unique mechanical properties. Thus, there has been a growing demand for hardwoods, including Castanea sativa Mill., the focal point of this investigation, for structural applications. Albeit in a limited capacity, Eurocode 5-2 offers friction coefficients for softwoods, but it falls short for hardwoods. These coefficients play a critical role in numerical simulations involving friction, enabling the optimization of joints and, by extension, the overall structural integrity. Test samples were evaluated at 15% and 18% moisture content (Service Class 2) for various orientations of timber-to-timber and timber-to-steel friction. The results provide an experimental database for numerical simulations and highlight the influence of moisture on the stick–slip phenomenon, which was absent for the timber-to-timber tests, as well as on the rising friction values. At 18%, the static and kinetic coefficients were 0.70 and 0.48 for timber-to-timber and 0.5 and 0.50 for timber-to-steel. The increase was around 50% for timber-to-timber friction and over 170% for timber-to-steel pairs. Moreover, the findings proved a relationship between both coefficients and the validity of the linear estimation approach within the 12–18% moisture commonly applied to softwoods.

Contact-angle hysteresis on rough surfaces: mechanical energy balance framework

Using as a starting point conservation of momentum, a multiphase mechanical energy balance equation is derived that accounts for multiple material phases and interfaces present within a moving control volume. This balance is applied to a control volume that is anchored to a three-phase contact line as it advances continuously over the surface of a rough and chemically homogeneous and inert solid. Using semi-quantitative models for the material behaviour occurring within the control volume, an order of magnitude analysis is performed to neglect insignificant terms, producing an equation for predicting contact-angle hysteresis from a knowledge of the interface dynamics occurring around the three-phase contact line. It is shown that the viscous energy dissipation that occurs during the ‘stick–slip’ motion of the three-phase contact line, being the cause of contact-angle hysteresis on rough surfaces, can be calculated from changes in intermediate equilibrium interface states. The balance is applied to the Wenzel, Cassie–Baxter and Fakir (super-hydrophobic) wetting states, showing for the Fakir case that significant dissipation occurs during both interface advance and recede, and relating these dissipations to interfacial area changes that occur around the ‘stick–slip’ events.

Non-Linear Dynamics of Simple Elastic Systems Undergoing Friction-Ruled Stick–Slip Motions

The stick–slip phenomenon is a jerking motion that can occur while two objects slide over each other with friction. There are several situations in which this phenomenon can be observed: between the slabs of the friction dampers used to mitigate vibrations in buildings, as well as between the components of the base isolation systems used for seismic protection. The systems of this kind are usually designed to work in a smooth and flawless manner, but under particular conditions undesired jerking motions may develop, yielding complex dynamic behavior even when only a few degrees of freedom are involved. A simplified approach to the problems of this kind leads to the mechanical model of a rigid block connected elastically to a rigid support and at the same time with friction to a second rigid support, both the supports having a prescribed motion. Despite the apparent simplicity of this model, it is very useful for studying important features of the non-linear dynamics of many physical systems. In this work, after a suitable formulation of the problem, the equations of motion are solved analytically in the sticking and sliding phases, and the influence of the main parameters of the system on its dynamics and limit cycles is investigated and discussed.

On heat transfer in Carreau fluid flow with thermal slip: An artificial intelligence (AI) based decisions integrated with Lie symmetry

It is well accepted that non-Newtonian fluid flow narrating differential systems with thermal slip conditions at the surface plays an important role in instabilities subject to polymer extrusion like stick–slip and gross-melt-fracture instabilities. Therefore, the present article contains the artificial neural networking evaluation of the friction at magnetized porous surface having thermal and velocity slip boundary conditions. The Carrea fluid flow is mathematically formulated at a porous surface. The novelty is enhanced by considering velocity slip boundary condition, thermal slip boundary condition, chemical reaction, magnetic field, and heat generation effects. The flow differential equations are reduced by using Lie symmetry analysis. The reduced equations are solved by using the shooting method. The neural networking model is constructed by engaging 132 values of SFC. 92 (70%) is marked for training, and 20 (15%) each is marked for validation and testing. 10 number of neurons are chosen in the hidden layer. Levenberg-Marquardt algorithm is carried out to train the network. The performance of the constructed neural networking model is evaluated by MSE and R. The developed ANN is the best to predict the friction values at the magnetized porous plate. Owning to predicted values of ANN, SFC shows inciting values towards the magnetic field parameter.

The impact of hydroxyapatite crystal structures and protein interactions on bone's mechanical properties

Hydroxyapatite (HAP) constitutes the primary mineral component of bones, and its crystal structure, along with the surface interaction with proteins, significantly influences the outstanding mechanical properties of bone. This study focuses on natural hydroxyapatite, constructing a surface model with calcium vacancy defects. Employing a representative model of aspartic acid residues, we delve into the adsorption mechanism on the crystal surface and scrutinize the adsorption forms of amino acid residues on HAP and calcium-deficient hydroxyapatite (CDHA) surfaces. The research also explores the impact of different environments on adsorption energy. Furthermore, a simplified sandwich structure of crystal-polypeptide-crystal is presented, analyzing the distribution of amino acid residue adsorption sites on the crystal surface of the polypeptide fragment. This investigation aims to elucidate how the stick–slip mechanism of polypeptide molecules on the crystal surface influences the mechanical properties of the system. By uncovering the interface mechanical behavior between HAP and osteopontin peptides, this article offers valuable theoretical insights for the construction and biomimetic design of biocomposites.

Evaluation of Frictional Influence and Thermal Analysis of Flexible Paper‐Based Materials Used in the Vertical Form–Fill–Seal Process: An Experimental Study

ABSTRACTThis study evaluated the frictional behaviour of flexible polymer‐coated and dispersion‐coated materials used in vertical form–fill–seal (VFFS) machines. A laboratory‐scale friction measurement device was developed to investigate the relationship between different surface topographies, roughness and frictional properties. Furthermore, surface roughness, contact angle and surface energy of the material were analysed and a microscopic analysis was performed to further understand the effect of material properties on friction. Thermal camera analysis was performed to measure the temperature changes within the material during the film‐transport stage of the VFFS machine. The friction measurement results indicated that the sliding direction did not affect the static and kinetic coefficients of friction. The significant influence of friction on the surface topography of the plate (forming shoulder and tube) was particularly evident. Some materials experienced the stick–slip phenomenon during sliding, depending on the surface type. Teflon tape, which is commonly used in the forming tubes of VFFS machines, exhibited the lowest coefficient of friction. Thermal camera analysis revealed that polymer‐coated paper materials generated more heat than dispersion‐coated papers during VFFS trials and thermoplastic films generated the least heat. No clear relationship between the surface roughness of the paper, fibre orientation, surface energy and friction coefficient was noted. Furthermore, paper‐based materials exhibited a higher coefficient of friction, which is possibly related to the dispersion components of surface energy. The findings of this study provide additional knowledge for designing the forming tube, shoulder geometry and surface plate to minimize the occurrence of defects, such as wrinkles, in paper‐based packages.

Deformation and Frictional Failure of Granular Media in 3D Analog and Numerical Experiments

Frictional sliding along grain boundaries in brittle shear zones can result in the fragmentation of individual grains, which ultimately can impact slip dynamics. During deformation at small scales, stick–slip motion can occur between grains when existing force chains break due to grain rearrangement or failure, resulting in frictional sliding of granular material. The rearrangement of the grains leads to dilation of the granular package, reducing the shear stress and subsequently leading to slip. Here, we conduct physical experiments employing HydroOrbs, an elasto-plastic material, to investigate grain comminution in granular media under simple shear conditions. Our findings demonstrate that the degree of grain comminution is dependent on both the normal force and the size of the grains. Using the experimental setup, we benchmark Discrete Element Method (DEM) numerical models, which are capable of simulating the movement, rotation, and fracturing of elasto-plastic grains subjected to simple shear. The DEM models successfully replicate both grain comminution patterns and horizontal force fluctuations observed in our physical experiments. They show that increasing normal forces correlate with higher horizontal forces and more fractured grains. The ability of our DEM models to accurately reproduce experimental results opens up new avenues for investigating various parameter spaces that may not be accessible through traditional laboratory experiments, for example, in assessing how internal friction or cohesion affect deformation in granular systems.

Nonlinear vibrations of bolted flange joint plate system considering the stick–slip–separation state: theory and experiment

Nonlinear vibrations of bolted flange joint plate system considering the stick–slip–separation state: theory and experiment

Compact stick–slip piezoelectric rotary motor with reduced undesired backward motion

Compact stick–slip piezoelectric rotary motor with reduced undesired backward motion

Fast to Slow Slip Transition in Stick-Slip Friction of Polymer Gels with Artificial Roughness

Fast to Slow Slip Transition in Stick-Slip Friction of Polymer Gels with Artificial Roughness

Mechanical testing and engineering applicability analysis of SAP concrete used in buffer layer design for tunnels in active fault zones

Abstract To tackle the challenge of dislocation damage when tunnels traverse active fault zones, this study introduces the concept of using brittle buffer materials for anti-dislocation. Building on this concept, we propose a novel concrete buffer material utilizing large-sized spherical super absorbent polymers (SAP) as a porogen, aimed at ensuring the safety of tunnel structures during active fault dislocations. To investigate the feasibility and superiority of SAP concrete as a buffer material compared to other similar materials, we prepared samples with three different SAP concrete proportions and conducted a series of physical and mechanical tests. The results show that SAP pre-hydrated with 0.2 mol·L−1 sodium carbonate solution exhibits a slower rate of moisture loss in the cement slurry, aiding the hydration reaction of concrete. The permeability coefficient of SAP concrete is approximately 10−7 cm·s−1, slightly lower than foam concrete of the same density level. SAP concrete buffer material demonstrates significant brittleness, in contrast to the mostly ductile nature of other buffers such as foam concrete and rubberized concrete. Utilizing the brittle nature of SAP concrete materials, when applied to tunnels affected by stick–slip active fault dislocations, its instantaneous loss of compressive capacity provides excellent yield performance, thus protecting the tunnel lining from damage. However, under certain circumferential pressure conditions, both the peak and residual strength of SAP concrete significantly increase. High peak and residual strengths do not favor the effective buffering effect of SAP concrete; therefore, an approach involving the intermittent arrangement of precast buffer blocks has been proposed for application.

Anchoring-mediated stick-slip winding of cholesteric liquid crystals.

The stick-slip phenomenon widely exists in contact mechanics, from the macroscale to the nanoscale. During cholesteric-nematic unwinding by external fields, there is controversy regarding the role of planar surface anchoring, which may induce discontinuous stick-slip behaviors despite the well-known continuous transitions observed in past experiments. Here we observe three regimes, namely, constrained, stick-slip, and sliding-slip, under mechanical winding with different anchoring conditions, and measure the corresponding forces by the surface force balance. These behaviors result from a balance of cholesteric elastic torque and surface torque, reminiscent of the slip morphology on frictional substrates [T. G. Sano et al., Phys. Rev. Lett. 118, 178001 (2017)10.1103/PhysRevLett.118.178001], and provide evidence of dynamics in static rotational friction.

Experimental Study on the Slip–Stick Vibration of Plane Gate

The slip–stick vibration intensity of a plane gate is usually large, which often brings serious safety risks to itself and the auxiliary structure. The slip–stick vibration of a plane gate is investigated using an experimental model test. The test conditions mainly focus on the gate-closing and gate-opening processes in transient flow. Based on the results, comparison diagrams of the slip–stick vibration response versus the external fluid excitation are constructed. The intensity and period of the slip–stick vibration both gradually increase with the opening degree of the plane gate decreasing. The frequency of slip–stick vibration is consistent with the natural frequency of the equivalent system, indicating that the slip–stick vibration is a nonlinear self-excited vibration. The slip–stick vibration and fluid excitation acting on the plane gate have a significant difference in response intensity and dominant frequency. In addition, a difference in gate support material can have a significant effect on the slip–stick vibration intensity. Therefore, the friction factor between gate support and track, rather than the fluid excitation, is the direct cause of slip–stick vibration, which can further prove that the slip–stick vibration is a friction-induced vibration caused by the gate’s active motion, enriching the theory of the gate’s vibration.

Experiments and simulations for dynamic yarn pull-out response of Kevlar® fabrics

This work presents a novel experimental method for performing dynamic yarn pull-out using a modified tensile split Hopkinson pressure bar. The pull yarn is fixed to a piezoelectric load cell, while the woven fabric specimen is displaced at pull-out velocities ranging from 22 to 32 m/s. Pull-out force, displacement, and energy absorption over time are quantified for commercially available Kevlar® KM2+ woven fabric with pull lengths L = 5 mm and 27 mm in both quasi-static (QS) and dynamic loading. Dynamic peak pull-out force increases over QS by as much as 290–460% and 170–220% for L = 5 mm and L = 27 mm, respectively, and overall energy absorption increases by 140–420% and 40–140% for L = 5 mm and L = 27 mm, respectively. In QS loading, stick–slip interactions result in forces dropping by approximately 70–80% between oscillating peaks for L = 5 mm and 30–40% between peaks for L = 27 mm, and displacements between peaks are typically 1.5 mm, corresponding to two yarn crossings or two spans. However, at dynamic rates, stick–slip stage force drops by 100% after the first and all subsequent peaks due to the dynamic release of the pull yarn from the fabric, resulting in the pull yarn passing through multiple yarn crossings. To better understand the underlying mechanisms for these observations, finite element simulations of the experiments are performed. Strain rate dependent longitudinal shear stiffness of the yarn is found to significantly affect the dynamic yarn pull-out response and explain the enhanced dynamic yarn pull-out peak force and energy absorption. While the shorter yarn of L = 5 mm experiences a more uniform loading along the entire length, non-uniform loading via progressive uncrimping is observed in the longer yarn of L = 27 mm along the length.

Modeling for Hysteresis Contact Behavior of Bolted Joint Interfaces with Memory Effect Penalty Constitution

A novel penalty contact constitution was developed to replicate the hysteresis memory effect observed in contact interfaces. On this basis, a refined finite element analysis (FEA) was performed to study the stick–slip friction contact behavior of bolted joint interfaces. The analysis was validated by comparing it with the experimental hysteresis loops in the literature. The simulated hysteresis loops were subsequently used to identify four parameters of the Iwan model. Additionally, the effects of bolt clamping, friction coefficient, and excitation amplitude were individually examined. It was found that the deterioration in bolt clamping performance resulted in a decrease in both the equivalent joint stiffness and energy dissipation. Similarly, the reduction in the friction coefficient yielded a comparable impact. Furthermore, the identified model parameters of critical stick–slip force and displacement exhibited a quasi-linear relationship to the bolt preload and friction coefficient.

Effect of fretting regimes on the fretting corrosion behavior of stainless steel in artificial crevices

Fretting crevice corrosion at the fastening interfaces of stainless-steel products is an unavoidable issue in the medical, marine, and nuclear industries. In this study, the effects of the fretting regimes on the fretting corrosion in artificial crevices were investigated, and the results showed that fretting initiated severe corrosion inside the crevice under the stick regime. Under the stick–slip and slip regimes, the volume loss was dominated by fretting corrosion, without initiating crevice corrosion.

Characterization of seismicity from different glacial bed types: machine learning classification of laboratory stick-slip acoustic emissions

Abstract Subglacial seismicity presents the opportunity to monitor inaccessible glacial beds at the epicentral location and time. Glaciers can be underlain by rock or till, a first order control on bed mechanics. Velocity-weakening, necessary for unstable slip, has been shown for each bed type, but is much stronger and evolves over more than an order of magnitude longer distances for till beds. Utilizing a de-stiffened double direct shear apparatus, we found conditions for instability at freezing temperatures and high slip rates for both bed types. During stick–slip stress-drops, we recorded acoustic emissions with piezoelectric transducers frozen into the ice. The two populations of event waveforms appear visually similar and overlap in their statistical features. We implemented a suite of supervised machine learning algorithms to classify the bed type of recorded waveforms and spectra, with prediction accuracy between 65–80%. The Random Forest Classifier is interpretable, showing the importance of initial oscillation peaks and higher frequency energy. Till beds have generally higher friction and resulting stress-drops, with more impulsive first arrivals and more high frequency content compared to rock emissions, but rock beds can produce many till-like events. Seismic signatures could enhance interpretation of bed conditions and mechanics from subglacial seismicity.