Frictional Sliding Research Articles

Temperature Rise in Frictional Sliding Contact of Elastic–Plastic Solids with Fractal Surface

Temperature Rise in Frictional Sliding Contact of Elastic–Plastic Solids with Fractal Surface

How Fault‐Normal and Shear‐Parallel Stiffness Influence Frictional Sliding Behavior

AbstractThe potential of faults to show earthquake‐generating slip instabilities depends not only on the intrinsic frictional properties of the fault zone, but also on the elasticity of the surrounding material. A velocity‐weakening fault is expected to show increasingly unstable frictional behavior with decreasing local elastic stiffness around the fault zone. Fault zone roughness can cause slip in the shear direction to be accompanied by fault‐normal movement, modulated by fault‐normal elastic properties, however these effects are poorly understood. Here, we systematically vary the stiffness surrounding the fault in both the shear‐parallel and fault‐normal directions, to investigate the origin of slip instabilities and changes in friction constitutive properties. We confirm the transition from stable sliding through slow slip to stick‐slip due to reduced fault‐parallel stiffness, and that the occurrence of different types of slip events can be explained by the ratio between shear and critical stiffness. In contrast, reducing the fault‐normal stiffness produces stick‐slip instabilities under conditions where the conventional critical stiffness criterion predicts stable sliding, and does not produce transitional slow slip events. Our data suggest that: (a) the stability criterion for frictional slip should be modified to incorporate fault‐normal stiffness, and (b) the unexpected slip instabilities may represent wrinkle‐like slip pulses, possibly due to a stiffness asymmetry introduced by lowering the fault normal stiffness on one side of the fault. This implies that earthquakes may occur when the fault‐normal stiffness, or bulk modulus for natural faults, is decreased and/or asymmetric across the fault zone, both of which may be common in nature.

Pore Pressure in Montmorillonite During Frictional Sliding

AbstractEarth's shallow crust is pervasively breached by fractures and faults that are often filled with saturated clays such as montmorillonite. Pore pressure in montmorillonite is difficult to measure due to its extremely low permeability, resulting in large uncertainties in its friction, which, in turn, may impact our understanding on the mechanical behaviors of the shallow crust. This difficulty motivates us to investigate pore pressure in montmorillonite during frictional sliding. Here we provide a first order understanding on the evolution of pore pressure in montmorillonite during frictional sliding by combining experimental data with an analytical consolidation model. Our result shows large variations in pore pressure in montmorillonite during frictional sliding, which need correction for the evaluation of friction of montmorillonite. We re‐visit this problem with the measured stresses at the end of our slow loading experiments where the modeled pore pressure approaches zero and obtain a new relation that shows a significant cohesive strength. The new relation may be united with our modeled pore pressure with a Biot‐Willis effective stress coefficient of α ∼ 0.5. X‐ray powder diffraction analysis of our samples shows evidence that intense deformation occurred during the frictional sliding with strain‐hardening, consistent with the occurrence of shear localization in the clay matrix following extended frictional sliding (Tembe et al., 2010, https://doi.org/10.1029/2009JB006383). These results suggest that our new relation may represent a constitutive relation for an intensely sheared, saturated montmorillonite in frictional sliding. Our result also suggests that substantial cohesion may appear on some natural clay‐rich faults.

Experimental Investigation on Effects of Water Injection on Rock Frictional Sliding and Its Implications for the Mechanism of Induced Earthquake

This study conducted water-induced fault slip experiments on saw-cut granite, sandstone, and limestone samples. Experimental results demonstrated that injecting 15 MPa pressurized water into the vicinity of a high-permeability sandstone fault could decrease the effective normal stress and induce fault slip but not significantly affect the stress of granite and limestone faults due to low permeability. When the pressurized water was injected into the fault plane, 1 MPa pressurized water could not significantly affect fault stress; however, the 15 MPa pressurized water caused a significant reduction in frictional strength and induced fault sliding. The actual pore pressure differed from the injection pressure and showed significant differences in three faults, resulting in the apparent difference in stress drop, slip duration, displacement, and sliding rate. Three faults showed velocity-strengthening properties at room temperature. The fault slip caused by 15 MPa pressurized water injection was a direct response of fault strength to the reduction in effective normal stress. The limestone fault was characterized by velocity-weakening behavior at 100 °C, and the sliding rate of the fault induced by the 15 MPa pressurized water injection was faster than that at room temperature. The experiment results suggest that high-pressure injection can dominate over velocity-dependent effects, inducing fault-unstable slips in velocity-strengthening faults, but is more likely to induce medium-strong earthquakes on the velocity-weakening fault.

Frictional Sliding Behaviour of Rough Fracture in Granite Under True Triaxial Loading with Implications for Fault Reactivation

Frictional Sliding Behaviour of Rough Fracture in Granite Under True Triaxial Loading with Implications for Fault Reactivation

The Sliding Keys on Inclined Deflecting‐cantilevers (SKID) device: Empirical and analytical sensitivity analysis with application in post‐tensioned frames

AbstractPreviously, the authors presented a new theoretical energy dissipating technology termed a Frictional Sliding on a Sprung Slope (FSSS) device. Its purpose was to provide significant energy dissipation to post‐tensioned (PT) frames structures. The FSSS device has a triangular‐shaped hysteretic curve, which has a zero‐force activation threshold. This enables activation for any earthquake magnitude and provides progressively greater energy dissipation with an increase in structural oscillations. In addition, it is designed to allow full self‐centring of the PT framed structure. In this paper, a physical prototype FSSS is designed, constructed and experimentally tested. The prototype replaces the theoretical springs, bearings and the constraints with pairs of cantilever bars. Consequently, it is renamed a Sliding Keys on Inclined Deflecting‐cantilever (SKID) device. Six scaled SKID configurations having different manufacturing parameters were built and tested. Also, five materials were used to investigate the sensitivity to the friction coefficient of the sliding pads. Both cyclic and fatigue tests were conducted to assess SKID performance empirically. A finite element model of SKID was then implemented in OpenSees and benchmarked against the experimental results. More than 700 one‐story one‐bay PT frames with different SKID devices (PT‐SKID frames) were numerically tested to investigate the dynamic characteristics of the structural system affecting the seismic response. Based on the extensive experimental and numerical analyses, design suggestions are provided, and the PT‐SKID self‐centring features are discussed.

Effect of Amplitude and Duration of Cyclic Loading on Frictional Sliding Instability in Granular Media: Implication to Earthquake Triggering of Landslides

AbstractStrong earthquakes with larger magnitude and longer durations trigger many landslides, however, how magnitude and duration affect landslides is still unclear. Many factors could contribute to this, including additional shear stress provided by strong ground motion, or “seismogenic liquefaction”; herein, we hypothesize that the dynamic weakening of sliding zone gouge is important. We explored the influence of earthquake magnitude and duration on landslide triggering by simulating the seismic response of sliding zone gouge using a dynamic ring‐shear device and glass spheres. The experiments showed that vibration with larger amplitudes and longer durations more easily trigger deformation and even instability in dry granular materials. We used a dynamic triaxial‐bender system to find that the shear modulus of these materials decreased with the increase in duration and amplitude of cyclic loading. We suggest that this universal decrease in shear modulus is an important landslide‐trigger mechanism. Our results revealed how magnitude and duration of earthquakes affect co‐seismic landslides and why earthquakes with larger magnitude and long durations can trigger more co‐seismic landslides.

Local Shearing Force Measurement during Frictional Sliding Using Fluorogenic Mechanophores.

When two macroscopic objects touch, the real contact typically consists of multiple surface asperities that are deformed under the pressure that holds the objects together. Application of a shear force makes the objects slide along each other, breaking the initial contacts. To investigate how the microscopic shear force at the asperity level evolves during the transition from static to dynamic friction, we apply a fluorogenic mechanophore to visualize and quantify the local interfacial shear force. When a contact is broken, the shear force is released and the molecules return to their dark state, allowing us to dynamically observe the evolution of the shear force at the sliding contacts. We find that the macroscopic coefficient of friction describes the microscopic friction well, and that slip propagates from the edge toward the center of the macroscopic contact area before sliding occurs. This allows for a local understanding of how surfaces start to slide.

Multiscale Assessments on the Frictional Sliding Surface and Wear Volume of Tire Rubber by Use of the Surface Roughness Power Spectrum

本研究では，3次元表面形状のパワースペクトル密度(PSD)を計測するときに生じる様々なノイズやバイアスを自然に除去できる補正手法を提案する．そして，その補正手法を用いて自己アフィンフラクタル表面の指標となるハースト指数の高精度な推定方法を開発する．上記の手法を砥石と摺動前後のタイヤゴムに適用してその有用性を実証する．特にタイヤゴム表面は全波数域で自己アフィン性が成立しないことを明らかにし，K相関モデルを用いた表面粗さPSDのパラメータ同定に応用する．最後に摩耗体積量と二乗平均平方根粗さとの関連付けを行い，本手法の妥当性を確認する．

Vertically and Horizontally Drawing Formation of Graphite Pencil Electrodes on Paper by Frictional Sliding for a Disposable and Foldable Electronic Device

The objective of this study is to fabricate an electrode by frictional sliding caused by a rough paper surface. The pressure exerted during drawing induces adsorption of the graphite particles by the rough paper and simultaneously reduces the surface roughness of the paper electrode. Repetitive drawing in one-way direction reduced the roughness of the paper surface, decreasing the grain boundaries of graphite. This increases the electron pathway at the electrode, thus reducing the resistance to less than 50 Ω. At the same time, repetitive drawing could confirm that unstable errors caused by the hand could help converge within a certain margin of error. We quantified the relationship between pressure and resistance when drawing on the electrode using a pencil hardness tester. In addition, the electrodes formed by repeated drawing generated a new surface grain and boundary, parallel to the drawing direction, and changed the electrode characteristics with respect to the drawing direction. The grain boundary difference based on the drawing direction was measured via a heating test of the foldable device, a sound pressure level, and laser scattering vibrometer measurements of a linear speaker. The fabricated graphite electrodes can be used in disposable foldable paper electronics because they are prepared using inexpensive materials.

Optically Stimulated Luminescence Signal Resetting of Quartz Gouge During Subseismic to Seismic Frictional Sliding: A Case Study Using Granite‐Derived Quartz

AbstractAttempts to determine the age of faulting recorded by fault rocks have been made using K–Ar, fission‐track, electron spin resonance, and luminescence dating methods. Here we report the unambiguous reduction (resetting) of optically stimulated luminescence (OSL) signals of quartz gouge after friction experiments and estimate the seismological and geological conditions required for OSL signal resetting in natural fault zones. In the experiments, we used quartz sand with a particle size of <150 μm and equivalent dose of 31.5 ± 16.6 Gy. Friction experiments were conducted with a rotary‐shear, high‐velocity friction apparatus at slip rates (V) of 200 μm s−1 to 1.3 m s−1, normal stress of 1.0 MPa, and displacement of 10 m. In the experiments conducted under dry conditions, the OSL signal starts to decrease from V = 0.25 m s−1 and becomes near zero at V ≥ 0.65 m s−1. OSL signal resetting is also observed in the experiment sheared at 1.3 m s−1 under water‐added conditions. At V = 0.25 and 0.40 m s−1, partial resetting occurs, which is characterized by coexistence of particles with and without an OSL signal. OSL signal intensity shows a strong correlation with applied power density and frictional heat during high‐velocity friction, and the signal exponentially decreases with increasing power density and temperature. The power density required for partial and complete OSL signal resetting is ~0.17 and 0.6 MW m−2, respectively. Assuming a co‐seismic fault slip rate of 0.6 m s−1, the depths required for partial and complete resetting are expected to be ≥11 and ≥42 m.

Control Charts for Statistical Process Control of the Tribocharging of Polymer Slabs in Frictional Sliding Contact

Besides the nature and condition of the surfaces in contact, several factors influence the triboelectric charging of polymer slabs in frictional sliding contact: pressure load and relative velocity between the two bodies, number of friction cycles, ambient temperature, and humidity. This paper is aimed at pointing out the peculiarities of the statistic control of such a process. Thirty experiments were performed for the optimal combination of factor values (i.e., normal force: 10 N; sliding speed: 55 mm/s; number of sliding cycles: 10) that maximize the absolute value of the average potential at the surface of the tribocharged materials: 1600 V. The capability index calculated from the experimental data was satisfactory and two Shewart charts were established for the statistical control of the process. Two out-of-control situations were simulated, in order to test the efficiency of the charts.

A New Contact Formulation for Large Frictional Sliding and Its Implement in the Explicit Numerical Manifold Method

Modelling discontinuous systems involving large frictional sliding is one of the key requirements for numerical methods in geotechnical engineering. The contact algorithms for most numerical methods in geotechnical engineering is based on the judgement of contact types and the satisfaction of contact conditions by the open–close iteration, in which penalty springs between contacting bodies are added or removed repeatedly. However, the simulations involving large frictional sliding contact are not always convergent, particularly in the cases that contain a large number of contacts. To avoid the judgement of contact types and the open–close iteration, a new contact algorithm, in which the contact force is calculated directly based on the overlapped area of bodies in contact and the contact states, is proposed and implemented in the explicit numerical manifold method (NMM). Stemming from the discretization of Kuhn–Tucker conditions for contact, the equations for calculating contact force are derived and the contributions of contact force to the global iteration equation of explicit NMM are obtained. The new contact algorithm can also be implemented in other numerical methods (FEM, DEM, DDA, etc.) as well. Finally, five numerical examples are investigated to verify the proposed method and illustrate its capability.

Instability of Frictional Sliding

Instability of Frictional Sliding

Negative Stiffness Produced by Rotation of Non‐Spherical Particles and Its Effect on Frictional Sliding

Previous research shows that the rotation of non‐spherical particles under compression might lead to the effect of apparent negative stiffness. The effect of a rotating non‐spherical particle is modeled and it is shown that under displacement‐controlled loading its dynamics is equivalent to the dynamics of inverted pendulum. Analytically and experimentally, the eigenfrequency and the stability of the inverted pendulum under changing mass is investigated. It is demonstrated that the increase of total mass leads to the decrease of eigenfrequency of the system beyond that of an ordinary pendulum. Furthermore, there exists a value of the mass when the eigen frequency becomes zero. At this point the system loses its stability. This corresponds to the results obtained for a pair of coupled linear oscillators with one negative stiffness spring. Thus the concept of negative stiffness allows formulation of a simple and accurate model of inverted pendulum and rotating non‐spherical particles. It is shown that a set of randomly sized rotating non‐spherical particles create fluctuations in the friction force, which can form a mechanism of experimentally observed friction force fluctuations.

Mixed-Mode Stress Intensity Factors in a Homogeneous Orthotropic Medium Loaded by a Frictional Sliding Rigid Flat Stamp

In this study, the crack problem for a homogeneous orthotropic medium loaded by a sliding rigid flat punch is considered. The homogeneous orthotropic medium is assumed to be a half-plane and is subjected to both normal and tangential forces through the sliding action of the punch. The crack on the homogeneous orthotropic medium is supposed to a depth of and is parallel to the direction of the normal force. The effect of the geometrical parameters and coefficient of friction on the mixed-mode stress intensity factors (mode I and mode II) is investigated using a computational approach using the finite element method. Augmented Lagrange method is used for the contact algorithm between the rigid flat punch and homogeneous orthotropic half-plane. This study may provide insight to the engineers in understanding the crack mechanisms in orthotropic materials in a comprehensive way and to identify early crack propagations under frictional loadings accurately.

Dynamic Frictional Sliding Modes between Two Homogenous Interfaces

Dynamic frictional sliding behaviour between two homogenous Homalite blocks is studied. The blocks are initially held together using a constant compressive stress. The sliding motion is initiated by impacting one of the blocks with an external object. The resulting sliding modes are inspected. Initiation of fretting is examined by studying the opening stresses in the interface.

Atomic-Scale Front Propagation at the Onset of Frictional Sliding.

Macroscopic frictional sliding emerges from atomic-scale interactions and processes at the contact interface, but bridging the gap between micro and macro scales still remains an unsolved challenge. Direct imaging of the contact surface and simultaneous measurement of stress fields during macroscopic frictional slip revealed the formation of crack precursors, questioning the traditional picture of frictional contacts described in terms of a single degree of freedom. Here we study the onset of frictional slip on the atomic scale by simulating the motion of an aluminum block pushed by a slider on a copper substrate. We show the formation of dynamic slip front propagation and precursory activity that resemble macroscopic observations. The analysis of stress patterns during slip, however, reveals subtle effects due to the lattice structures that hinder a direct application of linear elastic fracture mechanics. Our results illustrate that dynamic front propagation arises already on the atomic scales and shed light on the connections between atomic-scale and macroscopic friction.

Closed-Form Solution of the Frictional Sliding Contact Problem for an Orthotropic Elastic Half-Plane Indented by a Wedge-Shaped Punch

In this paper, the frictional contact problem of a homogeneous orthotropic material in contact with a wedge-shaped punch is considered. Materials can behave anisotropically depending on the nature of the processing techniques; hence it is necessary to develop an efficient method to solve the contact problems for orthotropic materials. The aim of this work is to develop a solution method for the contact mechanics problems arising from a rigid wedge-shaped punch sliding over a homogeneous orthotropic half-plane. In the formulation of the plane contact problem, it is assumed that the principal axes of orthotropy are parallel and perpendicular to the contact. Four independent engineering constants , , , are replaced by a stiffness parameter, , a stiffness ratio, a shear parameter, , and an effective Poisson’s ratio, . The corresponding mixed boundary problem is reduced to a singular integral equation using Fourier transform and solved analytically. In the parametric analysis, the effects of the material orthotropy parameters and the coefficient of friction on the contact stress distributions are investigated.

A Finite Element Solution for Frictional Sliding Contact between Hyper-Elastic and Rigid Bodies

This paper is devoted to the analysis of frictional contact problems with large deformations and displacements between hyper-elastic body and rigid body. The material nonlinearity and contact nonlinearity are separated and, the geometrically nonlinear behavior is described by the total Lagrange formulation. The Coulomb friction law is employed to simulate the friction between rigid vessel and rubber by the use of augmented Lagrange approach with node-to-segment formulation. A formulation of finite element is taken in this paper to describe the frictional contact problem, which is solved by the Newton-Raphson iterative procedure. It is shown that the augmented Lagrange technique significantly avoids locking and over-constraining and provides optimal convergence rate. Finally, the numerical results show that the accuracy and efficiency of augmented Lagrange approach in modeling large deformation frictional contact problem.