Slip Processes Research Articles

Experimental Study on Acoustic Emission Features and Energy Dissipation Properties during Rock Shear-Slip Process.

The features of rock shear-slip fracturing are closely related to the stability of rock mass engineering. Granite, white sandstone, red sandstone, and yellow sandstone specimens were selected in this study. The loading phase of "shear failure > slow slip > fast slip" was set up to explore the correlation between fracture type, acoustic emission (AE) features, and energy dissipation during the rock fracturing process. The results show that there is a strong correlation between fracture type, energy dissipation, and AE features. The energy dissipation ratio of tension-shear (T-S) composite, shear, and tensile types is 10:100:1. The fracture types in the shear failure phase are mainly tensile and TS composite types. The differential mechanism of energy dissipation of different rocks during the shear-slip process is revealed from the physical property perspectives of mineral composition, particle size, and diagenetic mode. These results provide a necessary research basis for energy dissipation research in rock failure and offer an important scientific foundation for analyzing the fracture propagation problem in the shear-slip process. They also provide a research basis for further understanding the acoustic emission characteristics and crack type evolution during rock shear and slip processes, which helps to better understand the shear failure mechanism of natural joints and provides a reference for the identification of precursors of shear disasters in geotechnical engineering.

Permeability Evolution of Bituminous Coal Fractures during the Shear Slip Process

Permeability Evolution of Bituminous Coal Fractures during the Shear Slip Process

Object slip detection sensor based on triboelectric nanogenerator

Existing gripping devices limit the way of gripping the object, and the object may slide due to insufficient friction, when the manipulator grips the object, the object may slip phenomenon, which leads to the manipulator can not complete the gripping work normally. In order to solve this problem, this paper proposes a robotic slipping sensor to detect the slipping state of the object and its slipping distance, the sensor through the friction of two different materials and electrostatic induction phenomenon of triboelectricity and the peak voltage signal to determine whether the contact object produces the phenomenon of slipping and its slipping distance. This design integrates two rectangular copper foils and two polytetrafluoroethylene (PTFE) films together to form a triboelectricity nanogenerator in independent layer mode, which judges the slip distance of an object by the peak voltage signal generated by the object’s slip, which is flexible and can be combined with a robot to make the robot more flexible and convenient in its work. In order to verify the performance of this sensor, horizontal slip test and vertical slip test were conducted. In the horizontal slip test and vertical slip test, the peak voltage signal output from the TENG sensor has a linear relationship with the slip distance of the object. The sensor and the object contact slip process ends after 100 ms, the oscilloscope will output the peak voltage signal, so that according to the size of the peak voltage signal to determine the object in the range of 0–10 cm slip distance, for judging whether the object appears to slip phenomenon and the occurrence of the phenomenon of the slip distance it produces provides a flexible program.

Unique stick–slip crack dynamics of double-network hydrogels under pure-shear loading

In this work, we have found that a prenotched double-network (DN) hydrogel, when subjected to tensile loading in a pure-shear geometry, exhibits intriguing stick-slip crack dynamics. These dynamics synchronize with the oscillation of the damage (yielding) zone at the crack tip. Through manipulation of the loading rate and the predamage level of the brittle network in DN gels, we have clarified that this phenomenon stems from the significant amount of energy dissipation required to form the damage zone at the crack tip, as well as a kinetic contrast between the rapid crack extension through the yielding zone (slip process) and the slow formation of a new yielding zone controlled by the external loading rate (stick process).

Frictional process, AE characteristics, and permeability evolution of rough fractures on Longmaxi shale with specific roughness under water injection

Studying the frictional process, acoustic emission (AE) characteristics and permeability evolution of fractures under water injection is fundamental for proposing theories and methods to control the stability of geological structures. In this work, the shear-flow test was conducted on Longmaxi shale fractures with different specific roughness to analyze the frictional deformation and mechanical properties of shale fractures during the frictional slip process, and the influence of effective normal stress and surface morphology was investigated. AE monitoring technology was also utilized to reveal the AE evolution during the frictional slip process. Based on the AF/RA values, AE signals were subjected to cluster analysis using the Gaussian Mixture Model (GMM) to distinguish and quantify the crack types and proportions during frictional slip. Combining the development of cracks and considering the ratio of worn area, a theoretical analytical expression was established to reasonably describe the friction-damage evolution, classifying the friction-damage during the frictional slip process into tensile and shear damage, respectively. Meanwhile, the permeability evolution of Longmaxi shale fractures was also studied in detail. A theoretical model capable of describing and predicting the permeability evolution was proposed under the condition that the permeability evolution and damage process of Longmaxi shale fractures correspond to each other. Finally, the interaction between asperities on shale fractures with different surface morphologies during the frictional slip process was discussed, and the influence mechanism of surface morphology on permeability evolution was revealed.

Investigation on dynamic mechanism of fault slip and casing deformation during multi-fracturing in shale gas wells

Fracturing horizontal well casing deformation has become very prominent, particularly in tectonic stress-concentrated shale gas fields, limiting the efficient development progress of shale gas. The main failure mode of casing shearing deformation had been attributed to fault slip caused by multi-fracturing. The current research did not provide a clear picture of the dynamic evolution relationship between hydraulic fracturing, fault slip, and casing deformation. In this paper, the dynamic model of fault slip induced by formation pressure change is established, incorporating the effects of stress drop, physical change of friction, and casing and cement-sheath resistance loads. The discontinuous displacement approach and explicit/implicit coupling iteration methods are used to reveal the relationships between the effective normal stress, shear stress, friction coefficient, and sliding velocity during the fault slip process. Furthermore, the microscopic process of casing deformation sheared by fault slip is investigated using static equilibrium theory, and a characterization method for determining the amount casing deformation caused by real-scale fault slip is proposed. The results show that three stages exist in the process of casing deformation sheared by fault slip, including trigger activation stage, accelerated slip stage, and deceleration slip stage. Fault slip is clearly influenced by fault strike. To reduce the amount of fault slip, the fault direction with the maximum in-situ stress should be avoided as much as possible. Serious casing deformation still occurs for large-scale activated faults even though the optimization measure of wellbore structure has been well taken. To fundamentally reduce the possibility of casing shear deformation, it is necessary to prevent fault slip through optimizing the design of hydraulic fracturing. This study lays the theoretical groundwork for the casing deformation control method in shale gas wells.

Impact of fault slip induced by water injection on casing deformation: a numerical study

Fluid injection can cause fault reactivation and slip due to weakened cementation strength. The resulting fault slippage poses significant challenges to wellbore and casing integrity. To address this, we developed a multi-scale 3D finite element model, integrating reservoir, and near-wellbore components and applied to an offshore well in China’s ZD Reservoir, an area that has experienced fault reactivations (and casing deformations of wells intersecting reactivated faults) due to routinely water injection in nearby wells. Based on the actual formation’s wellbore-fault angle, a full-size fault is inserted into the model. The traction–separation law (TSL) describes progressive fault damage induced by waterflooding. The model also simulates the impact of fault slippage on cement failure and casing deformation. Research findings indicate that fluid injection reduces friction and shear cementation strength between faults, leading to reactivated fault slippage. The slip process involves three stages: low-level, sharply rising, and high-level stages, each exhibiting reduced fault friction and shear cementation strength. These outcomes provide insights to prevent casing damage during water flooding, optimizing injection points, or using better cement recipes at minimal cost.

Evolutionary patterns of shear behavior and crack distribution during fault slip

Near-fault mineral resource excavation activities have the potential to induce fault slip, leading to the occurrence of earthquakes. This study explores the effects of dip angle and confining stress on the fault slip process caused by mining stress adjustment indoor tests and numerical simulations. It reveals the evolutionary patterns of shear behavior and crack distribution during the fault slip process. The results indicate that similar to shear stress, the acoustic emission activity associated with fault slip under mining stress exhibits distinct phase characteristics: A few cracks are randomly distributed in the linear steady stage → Isolated crack points cluster gather near the fault in the nonlinear steady stage → Cracks, mainly shear cracks, propagate along the fault in the meta-instability stage → Tension cracks connect shear cracks to propagate perpendicular to the fault in the instability stage. Generally, the fault slip process is governed by shear failure, accounting for over 75 %. Dip angle and confining stress significantly affect the shear behavior and crack distribution during fault slip. The constraint effect of confining stress causes intermittent slip of faults. An inverse relationship exists between peak stress intensity, the number of cracks, and the area impacted by shear slip and the dip angle. Accordingly, this research proposes support measures for areas at potential slip risk on faults, considering slip mechanical conditions and crack distribution characteristics. These results offer a method for identifying different stages of fault slip based on crack propagation, providing theoretical support for the monitoring and early warning of mining-induced fault slip.

Analysis of dynamic characteristics of whipping effect on l-shaped main steam pipe considering fluid-structure interaction effect

To investigate the whipping effect on the L-shaped main steam pipe utilized in the marine steam systems, the fluid-structure interaction (FSI) method is utilized to numerically analyze its dynamic characteristics. The numerical results illustrate that the dynamic response of whipping effect with rupture position B on the oblique pipe section is more severe with the significantly larger displacement of L-shaped pipe and anti-whip restraints and more complex frequency characteristics than that of whipping effect with rupture position A on the right-angled elbow. The mode transition phenomenon is also observed in the case with rupture position B. The maximum deformation concentrates on different parts when burst of pipes occurs at different positions and the deformation with rupture position B is several times larger than that with rupture position A. The increase of gap between anti-whip restraints intensifies the whipping effect, but it also reduces the maximum restraint force. The friction acts as the resistance in the slip process and thus contributes to the protection against whipping effect. The anti-whip restraints E closed to rupture position B on the oblique pipe section has better performance than anti-whip restraints D in the protection against horizontal whipping effect.

Mechanical response of monolayer graphene via a multi-probe approach

Push-to-pull (PTP) testing is employed to probe the uniaxial tensile response of freestanding monolayer graphene. Various analytical approaches are employed to estimate the elastic modulus of end-clamped graphene samples, combining in-situ Raman spectroscopy and scanning electronic microscope (SEM) measurements. The utilization of spatially resolved Raman-derived strains for assessing the elastic properties of monolayer graphene leads to results consistent with previous experimental and theoretical values of the elastic modulus (approximately 1 TPa). Molecular dynamics (MD) simulations of (pristine and defective) freestanding graphene sheets uniaxially loaded under varying clamping conditions are performed to support the experimental observations. The computational results indicate that the mechanical responses of the sheets are affected by the type, the spatial profile, and the heterogeneity of the clamping. When uniaxial pulling of end-clamped graphene is applied by a substrate adhering to the graphene sheet through van der Waals forces (as in PTP testing), the elastic modulus may be highly underestimated due to often inhomogeneous stress distribution and slippage processes. The MD simulations predict that the elastic modulus of pristine monolayer graphene is approximately 1 TPa, whereas its fracture strength can reach values of up to 110 GPa. Overall, this study underscores the limitations of traditional analyses of PTP experiments (utilizing indentation readouts and SEM imaging) and proposes new potential avenues (involving Raman measurements) for future research on the elastic properties of 2D materials.

Study on the bond-slip performance of glass fiber reinforced polymer bars and marine concrete under repeated loading

The bond property between glass fiber reinforced polymer (GFRP) bars and concrete under repeated loading is critical in determining the suitability of GFRP bars for marine engineering. This study investigates the bond strength and slip between GFRP bars and marine concrete under repeated loads using a beam-type test. The 16 groups of beam specimens are fabricated, and 50 repeated loads are applied to them. The influences of loading level and loading times on bond strength, slip process, slippage, and residual slippage are analyzed. The loss rate of bond strength exceeds 50%, and irrecoverable cracks in the steel hinge of beam specimens are observed when the repeated load level is 65% of the ultimate load. The slippages rise as the loading level increases. When the number of repeated loadings reaches about 8, the slippage is 50% of the entire slippage, and then the slip difference gradually decreases, and slippages no longer increase. Residual slippages increase with the loading level, but they increase initially and then stabilize with the loading times. The fitting curves agree well with the experimental results, indicating that they could be employed to describe the bond property of GFRP bars in marine concrete under repeated loading.

Analysis of Influencing Factors of Slippage and the Dynamic Process of Fault Slip Caused by Multi-Stage Fracturing

Casing deformation is evident during the development of shale oil and gas wells in the Sichuan and Junggar Basins in China. Their casing deformation characteristics, distribution law of deformation points, and main controlling factors were analyzed. According to the analysis results, shear is the main cause of casing deformation of shale oil and gas wells in the Sichuan and Junggar Basins in China and has the characteristics of “a dense heel end and a sparse toe end”. Faults account for 75% of casing deformation points, and fault slip caused by multi-stage fracturing is the primary factor responsible. The calculation model for fault slip that takes into account fracturing fluid invasion was established, and the dynamic variation law of fault slip was clarified: the fracturing fluid intruded into the fault, the relative dislocation of the damaged fault was caused by gravity, and the fault slippage was caused by the increase in fault activation length. This resulted in a linear increase in fault slippage, and the slippage reached its maximum when the fracturing fluid completely penetrated the fault and reached the fault boundary. The slip amount has a positive correlation with the fault length and the in situ stress difference; it increases first and then decreases with the increase in the fault dip angle. The slip amount reaches its maximum when the fault dip angle reaches 45°.

Numerical simulations of fault stick–slip characteristics in different temperature fields at laboratory scale

With the increasing demand for deep engineering development, there is an urgent need to study the evolution and formation mechanisms of the stick–slip process in faults at high temperatures. Although research on fault stick–slip behaviors at room temperature and laboratory scales has yielded some findings, exploring them at high temperatures is challenging, especially when acoustic emission (AE) monitoring is involved. To address this, the research conducted numerical simulations of fault stick–slip characteristics under thermo-mechanical coupling using the discrete element method to solve the problem. This approach aimed to provide insights into fault stick–slip behaviors and AE characteristics across different temperature fields. Subsequently, the evolution of the stress–strain characteristics (the number of stick–slip cycles, slip-initiation stress, slip-initiation stress drop, and maximum stress drop), energy dissipation, and AE characteristics (energy, magnitude, failure mechanism, and b-value) in the stick–slip process were systematically analyzed. The findings of this study aim to address existing shortcomings in AE tests and simulation methods related to fault stick–slip behaviors at high temperatures.

Confined Layer Slip Process in Nanolaminated Ag and Two Ag/Cu Nanolaminates.

The exceptional strength of nanolaminates is attributed to the influence of their fine stratification on the movement of dislocations. Through atomistic simulations, the impact of interfacial structure on the dynamics of an edge dislocation, which is compelled to move within a nanoscale layer of a nanolaminate, is examined for three different nanolaminates. In this study, we model confined layer slip in three structures: nanolaminated Ag and two types of Ag/Cu nanolaminates. We find that the glide motion is jerky in the presence of incoherent interfaces characterized by distinct arrays of misfit dislocations. In addition, the glide planes exhibit varying levels of resistance to dislocation motion, where planes with intersection lines that coincide with misfit dislocation lines experience greater resistance than planes without such intersection lines.

Micro-Mechanism Relations Between Deformation and Damage Behavior of Materials at Elevated Temperature

Deformation of metallic materials at elevated temperatures occurs by the movement of atoms either individually or in a group by diffusion, grain boundary sliding, and the slip processes as facilitated by vacancy, dislocations, and grain boundaries. The constitutive relationship for deformation is developed based on the contributions of external test conditions like temperature and strain rate or stress applied and the internal conditions like chemical composition, phases present, and the length scale of microstructures. Deformation can occur coherently by synergisms of all participating mechanisms, failing to which becomes a source for initiating the damage in the material. The same mechanisms that were initially responsible for deformation to occur then become the facilitators for void nucleation and its growth, which then go through cavity coalescence, and crack formation on the way to cause ultimate fracture of materials. The constitutive relationships for damage mechanisms then take the form that promotes the removal of atoms from the damaged part to a farther site, which further enhances the act of material damage. In the present work, the micro-mechanisms responsible for deformation and failure will be examined to evolve a relationship towards establishing connectivity between these two processes by integrating the effects of internal and external variables for a range of materials.

3D microscopy at the nanoscale reveals unexpected lattice rotations in deformed nickel.

In polycrystalline metals, plastic deformation is accompanied by lattice rotations resulting from dislocation glide. Following these rotations in three dimensions requires nondestructive methods that so far have been limited to grain sizes at the micrometer scale. We tracked the rotations of individual grains in nanograined nickel by using three-dimensional orientation mapping in a transmission electron microscope before and after in situ nanomechanical testing. Many of the larger-size grains underwent unexpected lattice rotations, which we attributed to a reversal of rotation during unloading. This inherent reversible rotation originated from a back stress-driven dislocation slip process that was more active for larger grains. These results provide insights into the fundamental deformation mechanisms of nanograined metals and will help to guide strategies for material design and engineering applications.

Three-dimensional finite-element modeling of Coulomb stress changes on normal and thrust faults caused by pore fluid pressure changes and postseismic viscoelastic relaxation

Abstract The analysis of Coulomb stress changes has become an important tool for seismic hazard evaluation because such stress changes may trigger or delay subsequent earthquakes. Processes that can cause significant Coulomb stress changes include coseismic slip and transient postseismic processes such as poroelastic effects and viscoelastic relaxation. However, the combined influence of poroelastic effects and viscoelastic relaxation on co- and postseismic Coulomb stress changes has not been systematically studied so far. Here, we use three-dimensional finite-element models with arrays of normal and thrust faults to investigate how pore fluid pressure changes and viscoelastic relaxation overlap during the postseismic phase. In different experiments, we vary the permeability of the upper crust and the viscosity of the lower crust or lithospheric mantle while keeping the other parameters constant. In addition, we perform experiments in which we combine a high (low) permeability of the upper crust with a low (high) viscosity of the lower crust. Our results show that the coseismic (i.e., static) Coulomb stress changes are altered by the signal from poroelastic effects and viscoelastic relaxation during the first month after the earthquake. For sufficiently low viscosities, the Coulomb stress change patterns show a combined signal from poroelastic and viscoelastic effects already during the first postseismic year. For sufficiently low permeabilities, Coulomb stress changes induced by poroelastic effects overlap with the signals from viscoelastic relaxation and interseismic stress accumulation for decades. Our results imply that poroelastic and viscoelastic effects have a strong impact on postseismic Coulomb stress changes and should therefore be considered together when analyzing Coulomb stress transfer between faults.

Viscoelastic third-order nanofluid MHD flow for wire coating purpose inside canonical coating die with variable viscosity effect: numerical and analytical solutions

The polyethene coating is frequently functionalized to cables or pipes for corrosion prevention, voltage differential, mechanical characteristics, and environmental legislation. The metal coating technique, in particular, is important in a variety of commercial applications. Coaxial extrusion, immersion, and electromagnetic application are examples of wire surface treatments. The wire coating procedure necessitates an increase in thermal performance. As a result, this research aims to determine how floating nanoparticles affect the mass and heat transport mechanisms of non-Newtonian fluid in the posttreatment for cable coating processes. For nanofluids, the Buongiorno model is used, including variable viscosity. The original mathematical formulation in terms of nonlinear ODEs for bvph2 is altered to first-order ODEs using similarity transformation. The data collection for the projected bvph2 is developed for variables related to the proposed model manipulating the velocity consuming the explicit bvph2 technique. The exercise, confirmation, and analysis processes of the ND-solve method are utilized to appraise the attained results of bvhp2 for numerous cases, and an assessment of the achieved consequences is executed with available statistics set to pattern the correctness and efficiency of the suggested algorithm for the scrutiny of non-Newtonian fluid problem connected bvph2. The prevailing uniformity of recommended conclusions with published findings designates the legitimacy of the structure, and the accurateness of 10−6 is also accomplished. The analytical findings of this investigation revealed that within the Reynolds modeling, the stress on the whole wire surface combined with shear forces at the surface predominates Vogel’s model. The contribution of nanomaterials upon force on the entire surface of wire and shear forces at the surface appears positive. A non-Newtonian feature can increase the capping substance’s velocity. This research could aid in the advancement of wire coating technologies. For the first instance, the significance of nanotechnology during wire coating evaluation is explored by utilizing Brownian motion with generation/absorption slip processes. For time-dependent viscosity, two alternative models are useful.

Identification of Stribeck Model Parameters to Accurately Reveal Stick–Slip Characteristics of a Disc–Block Friction System

Stick–slip vibration is simultaneously influenced by several factors that share complicated coupling relationships. In this research, an experimental investigation was performed to analyze the evolution law of stick–slip characteristics at different working conditions using a tribometer. The results showed that the disc rotational speed and normal force had noticeable impact on both stick–slip vibration and coefficient of friction (COF). Then the Stribeck model, which can characterize COF characteristics in the stick–slip process, was employed and the parameters were identified to construct a dynamic relationship between working conditions and COF. Further, numerical simulations respectively considering and neglecting the dynamic relationship between working conditions and Stribeck model parameters were conducted via an established tribometer analytical model. It was found that the simulation results considering the influence of working conditions on Stribeck model parameters were in better agreement with the experimental results, as the stick–slip vibration depends on the combined effect of working conditions and Stribeck model parameters. Therefore, the dynamic relationship between working conditions and Stribeck model parameters is crucial to accurately reveal stick–slip characteristics.

A DFT analysis on the superlubricity performance of structural superlubricity micro/nano-component on silicon-based surface

Friction and wear are important factors which limit the development of Micro-electromechanical Systems (MEMS). Therefore, the research and preparation of wear-resistant micro and nano-functional structures in the field of MEMS has profound importance. Structural superlubricity micro/nano-components (the atomic layers are in incommensurate contact, which means that the friction and wear rate is nearly zero when the layers slide) are expected to be the basic micro and nano functional structures for fabricating ultra wear-resistant MEMS. At present, there is a lack of research on the properties of structural superlubricity micro/nano-components on the surface of silicon, which is known to be the most mainstream base material for MEMS. In this paper, the electronic properties and the atomic-scale friction of the silicon-based surface structural superlubricity micro/nano-components are simulated using first-principles calculations based on the Density functional theory (DFT). By analyzing the silicon-based surface structural superlubricity micro/nano-component with adhesion performances and superlubricity characteristics. The calculation shows that the binding energy value of its lower graphene layer is larger than that of the upper layer during the slip process, and it is found that the friction force of the silicon-based structure can reach the range of 10−3 nN and the average friction coefficient can reach the range of 10−3 in the incommensurate state. Throughout the sliding process, electrostatic repulsion plays an important role in the tribological properties. The larger the electrostatic repulsion, the smoother the potential energy fluctuation, indicating less friction, while the analysis of the charge mechanism further justifies the conclusion.