Slip Theory Research Articles

SLIPS OF THE TONGUE IN INDONESIAN DAILY CONVERSATION: A PSYCHOLINGUISTIC VIEW

Abstract: This research aims at analyzing speech errors, also known as slips of the tongue madeby adult Indonesians as native speakers. Those errors were analyzed regarding types andbackground of the occurence with Meringer’s theory of slips of the tongue as the framework ofthe research. This research is mainly qualitative with a descriptive approach within thepsycholinguistics view. The results show that slips of the tongue occurred by adult Indonesian asnative speakers were: 1. Exchange, 2. Anticipation, 3. Postposition, 4. Contamination, and 5.Substitution. Researchs about slips of the tongue can provide input to the language process whichis very important for language teaching. Language teachers can interact better with students if theproblems as the sources of the students' errors are identified. Above all, by comprehending varioustypes of speech errors we can increase our understanding of the acquisition, production, andperception of our language thoroughly.Key Words: speech error; slips of the tongue; psycholinguistics

Study on failure law of rock mass and slope stability by open-pit combined mining

With the continuous downward mining, more and more attention has been paid to the problem of slope stability under open-pit combined mining. Taking Zijinshan gold and copper mining as an example, the failure properties of overlying rock mass and slope stability under open-pit combined mining under different mining methods are studied by numerical simulation method, and the failure law of overlying rock mass is proposed. Combined with the geological structure distribution of 5-5 section and the influence of different mining stages, the slope stability is evaluated by slip field theory. Relevant reinforcement measures are proposed.

Study on the propagation characteristics of the casing waves in cased wells by viscoelastic slip theory

The amplitude or attenuation of casing waves is used to evaluate cement bonding quality in cased wells.At the 70~500 kHz frequency range,the casing waves generated by the acoustic tools are similar to the fundamental symmetric Lamb waves or anti-symmetric Lamb waves in acoustic terminology.The fundamental symmetric Lamb waves are called extensional waves and the fundamental anti-symmetric Lamb waves are called flexural Lamb waves.The two kinds of quasi-Lamb models show different propagation characteristics.The viscoelastic slip theory is applied to reveal the motion characteristics of extensional waves and flexural Lamb waves.The extensional wave propagating in the casing couples with the medium behind casing by shear stiffness.The existence of 0.01 mm micro annulus can cause sharp decrease of the extensional wave attenuation.By contrary,flexural Lamb-wave attenuation is not sensitive to micro annulus with lightweight cement behind the casing.The response characteristic of the flexural Lamb-wave attenuation with heavy cement behind casing is different from that with lightweight cement behind casing.The attenuation of the flexural waves shows evident increase with micro annulus existence.So the flexural Lamb-waves couple with the medium behind casing mainly by normal stiffness.With fluid micro annulus between casing and cement,the equivalent impedance of the media behind casing is less than that of heavy cement.The lower impedance can be prone to normal deformation and acoustic coupling between casing and the medium behind casing.The different response characteristics of extensional waves and flexural Lamb waves in cased wells provide possibility to determine the cementing situation in the comprehensive evaluation of cement bonding quality.

An enhancement in transportation of heat energy in yield stress dusty fluid via mono and hybrid nanoparticles

The purpose of this article is to explore simultaneous impact of dust and nano particles on thermal performance of yield stress exhibiting fluid (Casson fluid) through numerical simulations. Therefore, for mathematical formulation, conservation laws for dust and fluid phases with yield stress constitutive equation for Casson fluid are used. No slip theory is applied for the development of boundary conditions. Eventually, complex system of PDEs with suitable conditions is obtained. This complex system is formulated in a suitable finite element computational environment. Simulations are executed to investigate heat transfer enhancement mechanism in both mono and hybrid nanofluids suspended with (hybrid nanoparticles) in the presence of dust impurities. Furthermore, it is observed that the diffusion of momentum depends on the yielding stress. However, this yield stress phenomenon in hybrid nanofluid is less significant than in the mono-nanofluid. It is also noticed that a rise in magnetic field can force the motion of dusty fluid to slow down. However, this slowing down mechanism in mono-nanofluid is more significant than in hybrid nanofluid. The temperature of dust particles for both mono and hybrid nanofluids has an increasing tendency when fluid interaction parameter is increased. However, the temperature of the hybrid nano dusty fluid is greater than the temperature of the mono nano dusty fluid.

Modeling of crack bridging and failure in heterogeneous composite materials: A damage-plastic multiphase model

Bridging effects in heterogeneous composite materials are traditionally treated as tractions lumped at the crack surface. This conventional equivalence, however, may fail to reveal the fundamental mechanisms of composite toughening. Hereby, a damage-plastic multiphase model is proposed and developed which is capable of capturing the engaging bridging mechanisms of fiber reinforced cementitious composites without the need for explicit representation of fibers. The key idea is to idealize the composites as the mixture of an activated fiber phase integrating all bridging fibers and an effective Cauchy continuum phase representative of the matrix and bonded fibers which interact through a nonlinear interface. The kinematics of matrix and fiber phases are independently described through the introduction of additional slip fields. This proposed modeling framework has the following novelties: (1) a new nonlocal slip theory is proposed which allows to depict the micro-slippage of arbitrarily distributed activated fibers with a minimum number of auxiliary kinematic descriptors, (2) a unified damage-plastic framework for the fiber–matrix interface is developed, enabling the method to characterize simultaneously the slip-dependent interface, fiber pull-out and fiber rupture, and (3) it is demonstrated that the composite toughening effect originates not only from interfacial friction but also from elasto-plastic stretching of fibers and pulley force actions, among which interfacial friction is the dominating energy absorbing mechanism. The proposed damage-plastic multiphase model is validated against experimental data from the single-fiber level and the structural level.

Fluid pressure diffusion effects on the excess compliance matrix of porous rocks containing aligned fractures

SUMMARYThe presence of sets of open fractures is common in most reservoirs, and they exert important controls on the reservoir permeability as fractures act as preferential pathways for fluid flow. Therefore, the correct characterization of fracture sets in fluid-saturated rocks is of great practical importance. In this context, the inversion of fracture characteristics from seismic data is promising since their signatures are sensitive to a wide range of pertinent fracture parameters, such as density, orientation and fluid infill. The most commonly used inversion schemes are based on the classical linear slip theory (LST), in which the effects of the fractures are represented by a real-valued diagonal excess compliance matrix. To account for the effects of wave-induced fluid pressure diffusion (FPD) between fractures and their embedding background, several authors have shown that this matrix should be complex-valued and frequency-dependent. However, these approaches neglect the effects of FPD on the coupling between orthogonal deformations of the rock. With this motivation, we considered a fracture model based on a sequence of alternating poroelastic layers of finite thickness representing the background and the fractures, and derived analytical expressions for the corresponding excess compliance matrix. We evaluated this matrix for a wide range of background parameters to quantify the magnitude of its coefficients not accounted for by the classical LST and to determine how they are affected by FPD. We estimated the relative errors in the computation of anisotropic seismic velocity and attenuation associated with the LST approach. Our analysis showed that, in some cases, considering the simplified excess compliance matrix may lead to an incorrect representation of the anisotropic response of the probed fractured rock.

Friction modeling of tool-chip interface based on shear-slip theory for vibration assisted swing cutting

The vibration assisted swing cutting is a promising machining technology with characters of pseudo intermittent cutting and reverse friction. It can greatly extend tool life, reduce cutting forces and improve the surface accuracy of workpiece. In the cutting process, the tool-chip friction characteristics have a significant impact on the surface quality and machining accuracy of the work-piece. However, in the process of vibration-assisted swing cutting, the friction characteristics of tool-chip interface is not clear yet. In this paper, a new tool-chip friction model is proposed which takes into account the chip conversion layer is proposed based on shear slip theory. Moreover, the shear strain rate and chip particle velocity of the three friction regions of the tool-chip contact interface are described. the results show that the cutting speed increases from 75 m/min to 600 m/min, the cutting force decreases by 20 %, the thrust force decreases by 41 %, and the normal stress and shear stress decrease from 5.9 pa and 1.8 pa to 0, respectively. The increase of cutting speed leads to the increase of the temperature at the tip and the sticking at the tip. Comparing with the experimental results in existing references, the simulation results have good consistency and great prediction ability.

Research on Curved Path Tracking Control for Four-Wheel Steering Vehicle considering Road Adhesion Coefficient

Curved path tracking control is one of the most important functions of autonomous vehicles. First, small turning radius circular bends considering bend quadrant and travel direction restrictions are planned by polar coordinate equations. Second, an estimator of a vehicle state parameter and road adhesion coefficient based on an extended Kalman filter is designed. To improve the convenience and accuracy of the estimator, the combined slip theory, trigonometric function group fitting, and cubic spline interpolation are used to estimate the longitudinal and lateral forces of the tire model (215/55 R17). Third, to minimize the lateral displacement and yaw angle tracking errors of a four-wheel steering (4WS) vehicle, the front-wheel steering angle of the 4WS vehicle is corrected by a model predictive control (MPC) feed-back controller. Finally, CarSim® simulation results show that the 4WS autonomous vehicle based on the MPC feed-back controller can not only significantly improve the curved path tracking performance but also effectively reduce the probability of drifting or rushing out of the runway at high speeds and on low-adhesion roads.

Geomechanical constitutive modelling of gas hydrate-bearing sediments by a state-dependent multishear bounding surface model

Natural gas hydrate in marine sediments and permafrost areas is considered as an important potential energy source. Since hydrate dissociation will reduce the stability of gas hydrate-bearing sediments (GHBS) and may cause wellbore failures and geological disasters during gas production, it is necessary to reveal the mechanical behavior of GHBS for the safe exploitation of natural gas hydrate. This paper proposes a geomechanical constitutive model of GHBS within the multishear bounding surface framework. Following the slip theory of plasticity, a constitutive formulation is obtained by splitting the macro constitutive response of sediments into a macro volume response and a series of micro shear responses in spatial distributions related to virtual microshear structures. Each microshear structure describes micro shear and dilatancy responses in three orthogonal orientations. A micro stress–strain relationship and a micro stress–dilatancy relationship are established for each orientation of the microshear structure. The model comprehensively describes the consolidation, hardening, softening, dilatation, collapse, and non-coaxial characteristics of gas hydrate-bearing sediments by introducing the multishear concept, state parameter, evolution law of hydrate bonding and debonding, and collapse strain caused by hydrate dissociation. The effectiveness of the model is confirmed by simulating the available published laboratory tests on the samples of synthetic and natural GHBS under different pore pressures, temperatures, initial void ratios, hydrate saturations, and initial effective confining stresses.

Low-frequency layer-induced kinematic parameters in transversely isotropic media and orthorhombic media

SUMMARY We develop a method to compute frequency-dependent kinematic parameters for an effective orthorhombic (ORT) medium. In order to investigate the influence of fracture weaknesses on the kinematic parameters, the effective ORT medium is composed based on the linear slip theory and derived by applying the limited Baker–Campbell–Hausdorff series. The frequency-dependent kinematic parameters including vertical velocity, two normal moveout velocities defined in vertical symmetry planes, and three anelliptic parameters (two of them are defined in vertical symmetry plane and one parameter is the cross-term one). We also investigate the influence of volume fraction, frequency, velocity ratio and fracture weaknesses on the effective kinematic parameters.

Fatigue failure analysis of steel wire rope sling based on share-splitting slip theory

At present, Section integrity hypothesis is mostly used to analyze the mechanical properties and identify the damage of the cable. Based on the actual situation and considering the slip effect between the wires of the cable, two simplified calculation models of the cable are proposed based on the theory of share-splitting slip, and the model parameters are obtained through experiments. Finally, on the background of Lijiang Railway Suspension Bridge in Yunnan Province, the fatigue test of the suspension cable is carried out by using the self-developed testing device which can consider both tension and bending fatigue, and the broken steel wire is further analyzed by means of electron microscopy. The results show that two simplified calculation models of wire rope sling are proposed based on the theory of share-splitting slip, which are close to the results of the original model, but greatly improve the calculation efficiency. Comparing the results of three models, it is found that the three models can reflect the development of the slip and fatigue damage of the wire rope sling, but they have some errors with the test. The fracture morphology of the steel wire is shown by electron microscopy photographs.

Anisotropic azimuthal surface‐wave inversion for a vertically fractured and transverse isotropy medium: Theory and examples from a controlled field experiment

ABSTRACTFractures in elastic media add compliance to a rock in the direction normal to the fracture strike. Therefore, elastic wave velocities in a fractured rock will vary as a function of the energy propagation direction relative to the orientation of the aligned fracture set. Anisotropic Thomson–Haskell matrix Rayleigh‐wave equations for a vertically transverse isotropic media can be used to model surface‐wave dispersion along the principal axes of a vertically fractured and transversely isotropic medium. Furthermore, a workflow combining first‐break analysis and azimuthal anisotropic Rayleigh‐wave inversion can be used to estimate P‐wave and S‐wave velocities, Thomsen's ε, and Thomsen's δ along the principal axes of the orthorhombic symmetry. In this work, linear slip theory is used to map our inversion results to the equivalent vertically fractured and transversely isotropic medium coefficients. We carried out this inversion on a synthetic example and a field example. The synthetic data example results show that joint estimation of S‐wave velocities with Thomsen's parameters ε and δ along normal and parallel to the vertical fracture set is reliable and, when mapped to the corresponding vertically fractured and transversely isotropic medium, provides insight into the fracture compliances. When the inversion was carried out on the field data, results indicated that the fractured rock is more compliant in the azimuth normal to the visible fracture set orientation and that the in situ normal fracture compliance to tangential fracture compliance ratio is less than half, which implies some cementation may have occurred along the fractures. Such an observation has significant implications when modelling the transport properties of the rock and its strength. Both synthetic and field examples show the potential of azimuthal anisotropic Rayleigh‐wave inversion as the method can be further expanded to a more general case where the vertical fracture set orientation is not known a priori.

Fault slip envelope: a new parametric investigation tool for fault slip based on geomechanics and 3-D fault geometry

Abstract. By combining a 3-D boundary element model, frictional slip theory, and fast computation method, we propose a new tool to improve fault slip analysis that allows the user to analyze a very large number of scenarios of stress and fault mechanical property variations through space and time. Using both synthetic and real fault system geometries, we analyze a very large number of numerical simulations (125 000) using a fast iterative method to define for the first time macroscopic rupture envelopes for fault systems, referred to as “fault slip envelopes”. Fault slip envelopes are defined using variable friction, cohesion, and stress state, and their shape is directly related to the fault system 3-D geometry and the friction coefficient on fault surfaces. The obtained fault slip envelopes show that very complex fault geometry implies low and isotropic strength of the fault system compared to geometry having limited fault orientations relative to the remote stresses, providing strong strength anisotropy. This technique is applied to the realistic geological conditions of the Olkiluoto high-level nuclear waste repository (Finland). The model results suggest that the Olkiluoto fault system has a better ability to slip under the present-day Andersonian thrust stress regime than for the strike-slip and normal stress regimes expected in the future due to the probable presence of an ice sheet. This new tool allows the user to quantify the anisotropy of strength of 3-D real fault networks as a function of a wide range of possible geological conditions and mechanical properties. This can be useful to define the most conservative fault slip hazard case or to account for potential uncertainties in the input data for slip. This technique therefore applies to earthquake hazard studies, geological storage, geothermal resources along faults, and fault leaks or seals in geological reservoirs.

Applicability Analysis of Klinkenberg Slip Theory in the Measurement of Tight Core Permeability

The Klinkenberg slippage theory has widely been used to obtain gas permeability in low-permeability porous media. However, recent research shows that there is a deviation from the Klinkenberg slippage theory for tight reservoir cores under low-pressure conditions. In this research, a new experimental device was designed to carry out the steady-state gas permeability test with high pressure and low flowrate. The results show that, unlike regular low-permeability cores, the permeability of tight cores is not a constant value, but a variate related to a fluid-dynamic parameter (flowrate). Under high-pressure conditions, the relationship between flowrate and apparent permeability of cores with low permeability is consistent with Klinkenberg slippage theory, while the relationship between flowrate and apparent permeability of tight cores is contrary to Klinkenberg slip theory. The apparent permeability of tight core increases with increasing flowrate under high-pressure conditions, and it is significantly lower than the Klinkenberg permeability predicted by Klinkenberg slippage theory. The difference gets larger when the flowrate becomes lower (back pressure increases and pressure difference decreases). Therefore, the Klinkenberg permeability which is obtained by the Klinkenberg slippage theory by using low-pressure experimental data will cause significant overestimation of the actual gas seepage capacity in the tight reservoir. In order to evaluate the gas seepage capacity in a tight reservoir precisely, it is necessary to test the permeability of the tight cores directly at high pressure and low flowrate.

Deformation and Failure Mechanics of Boron Carbide–Titanium Diboride Composites at Multiple Scales

A coupled modeling and experimental investigation of the mechanical response of a dual-phase composite ceramic is reported. The material consists of boron carbide crystals interspersed with a second phase of titanium diboride, where grains of each phase are of comparable average size. Experiments show a moderate increase in flexure strength and a significant increase in fracture toughness with increasing titanium diboride content. Density functional theory provides elastic properties, surface energy on potential cleavage planes, and stacking fault energy on potential slip systems of the second phase. Energies are found lowest on the basal plane. Findings inform mesoscale simulations of the tensile response of polycrystalline aggregates. These simulations, which invoke a phase-field theory for elasticity, limited slip, and fracture, demonstrate improvement in tensile strength with increasing fraction of titanium diboride grains, in qualitative agreement with experimental trends. Refinements are suggested that would presumably provide more accurate toughness predictions.

Scaling theory of giant frictional slips in decompressed granular media

When compressed frictional granular media are decompressed, generically a fragile configuration is created at low pressures. Typically this is accompanied by a giant frictional slippage as the fragile state collapses. We show that this instability is understood in terms of a scaling theory with theoretically computable amplitudes and exponents. The amplitude diverges in the thermodynamic limit hinting to the possibility of huge frictional slip events in decompressed granular media. The physics of this slippage is discussed in terms of the probability distribution functions of the tangential and normal forces on the grains which are highly correlated due to the Coulomb condition.

Estimation of Fracture Compliance From Attenuation and Velocity Analysis of Full‐Waveform Sonic Log Data

AbstractIn fractured rocks, the amplitudes of propagating seismic waves decay due to various mechanisms, such as geometrical spreading, solid friction, displacement of pore fluid relative to the solid frame, and transmission losses due to energy conversion to reflected and transmitted waves at the fracture interfaces. In this work, we characterize the mechanical properties of individual fractures from P wave velocity changes and transmission losses inferred from static full‐waveform sonic log data. The methodology is validated using synthetic full‐waveform sonic logs and applied to data acquired in a borehole penetrating multiple fractures embedded in a granodioritic rock. To extract the transmission losses from attenuation estimates, we remove the contributions associated with other loss mechanisms. The geometrical spreading correction is inferred from a joint analysis of numerical simulations that emulate the borehole environment and the redundancy of attenuation contributions other than geometrical spreading in multiple acquisitions with different source‐receiver spacing configurations. The intrinsic background attenuation is estimated from measurements acquired in the intact zones. In the fractured zones, the variations with respect to the background attenuation are attributed to transmission losses. Once we have estimated the transmission losses associated with a given fracture, we compute the transmission coefficient, which, on the basis of the linear slip theory, can then be related to the mechanical normal compliance of the fracture. Our results indicate that the estimated mechanical normal compliance ranges from 1 × 10−13 to 1 × 10−12 m/Pa, which, for the size of the considered fractures, is consistent with the experimental evidence available.

Seismic anisotropy of a fractured rock during CO2 injection: a feasibility study

Fluid substitution plays the key role in reservoir characterization, leading to enhance understanding of the influence of fluids on seismic parameters. In general, fluid substitution tool assumes that the Earth is as an isotropic medium, which may not represent the practical field situation. Nevertheless, anisotropic fluid substitution provides important insights into the processes that control the anisotropic seismic response of a fractured rock when subjected to CO2 injection for enhanced oil recovery and its geological sequestration. Here, we examine the influence of fluid substitution in a porous yet fractured reservoir for quantitative interpretation of seismic data. This investigation involves anisotropic Gassmann’s equation and linear slip theory for fluid substitution in a transversely isotropic media with a horizontal axis of symmetry (HTI). We present a synthetic case by conceptualizing a double-layered half-space model with upper layer as shale and bottom layer as HTI sandstone, representing an Indian mature reservoir. The effects of variation in background porosity and fracture weaknesses on anisotropic (Thomsen’s) parameters, acoustic parameters including amplitude variation with angle have also been discussed. We observe that brine and oil sands to be associated with the highest elastic moduli, while CO2 sands exhibit contrasting trend. It is noteworthy that CO2 is more sensitive to fracture weakness when compared to the other reservoir fluids such as hydrocarbons and brines, as P-wave moduli (as much as 37.1%) and velocity (as high as 12.2%) reduces significantly with the increase in fracture weakness. Further, Gassmann’s assumption is validated as we noticed unchanged values in shear-wave moduli and shear-wave splitting parameter (γ) for various fluid types.

Slip theory-based numerical investigation of the fluid transport behavior on a surface with a biomimetic microstructure

This paper presented a numerical simulation of drag reduction on a superhydrophobic surface with a groove structure. The computational fluid dynamics (CFD) method was used to analyze the effect of the groove microstructure when droplets impacted a superhydrophobic surface. The simulation results revealed three main characteristics: (1) The distance the droplet spread was larger along the direction parallel to the groove and smaller perpendicular to the groove; (2) Two protruding small spheres were formed at the edge of the droplet along the groove direction; (3) During retraction, the droplets presented a narrow, cross-shaped morphology. The effect of the groove structure in the two-dimensional microchannel on drag reduction near the wall was analyzed based on slip theory by the coupled level set/volume of fluid (CLSVOF) method. The air in the superhydrophobic pit formed a low-velocity vortex, which made the fluid roll on the air surface. The rolling on the surface produced a velocity slip at the gas–liquid interface. In addition, the superhydrophobic surface had an obvious drag reduction effect in the laminar flow state, but the drag reduction effect in the turbulent state was not ideal and even increased the flow resistance at the wall.

Experimental Investigation into the Bedding Plane Slip Effect on the Overlying Strata Behavior in Longwall Top Coal Caving of Soft Coal Seam

Bedding plane shear slip becomes more obvious in rock strata with quite different mechanical properties. A composite beam model considering the behaviors of the main roof and the immediate roof in the “three‐soft” coal seam is established based on physical similarity simulation experiments and the slip theory in this paper. The movement and failure of the overlying strata and the mechanism of the bedding plane slip at the 2211 working face are studied by experimental and theoretical analysis. The results suggest that the front abutment stress distribution occurs 50 m ahead of the working face, the initial caving interval of the main roof is 55 m, and the peak stress appears at a distance 20 to 32 m ahead of the working face. The bedding plane slip areas can be divided into the obvious slip area and the slight slip area along the mining direction. The range of the obvious slip area becomes wider and the range of the slight slip area grows to be narrower as the working face advances. The bedding plane slip becomes steady after gradual increase and leads to the subsidence of the overlying strata in the “three‐soft” coal seam. The observed initial caving interval of the main roof by field measurement is 51 m, which is consistent with the results of physical similarity simulation experiments and theoretical analysis. The results demonstrate that the beam slip model proposed in this paper is reasonable and able to describe the behaviors of overlying strata and bedding plane slip.