Elastic Slip Research Articles

Study On Power Transmitting Efficiency Of CVT Using A Dry Hybrid V-belt

This paper presents the net power transmitting efficiency of CVT using a newly developed dry hybrid V-belt. The efficiency was measured by using a devised testing machine, which eliminates other power losses due to periphemls such as shafl flanges. Torques on both pulkys were measured with high accuracy by using strain gauges which were glued on the cantilever shafts. The CVT efficiency is divided into three regions with respeet to applied torque. At a low range of applied torque: region I, the efficien~ of CVT increases shmply with respeet to the applied torque, beeause the bending loss is almost constant for applied torque but the torque increases the total transmitting power. At region II (a middle range of applied torque), the efficiency is also constant with respect to transmitting torque since the relative energy loss due to belt bending decreases while the energy loss due to elastic slip increases with increasing the transmitting torque. They are equivalent with each other at this region, The efficiency sharply decreases at region III due to the remarkably increasing of the slip. The tmnsmitting efficiency increases with the low contraction force. The CVT shows the high transmitig ellkieney at the speed ratio 1.0. The transmitting efficiency decreases when the CVT system has the misalignrnenq because the sharing deformation of the belt strand influences the transmitting efficiency as well as the bending deformation. The appropriate initial setting misalignment exists to reduce the influence of the misalignment. It is found that the relationship between the traction coefficient and the transmitting efficiency is independent on the contraction force, speed ratio and the misalignment. The tmction coefficient could be a nondimensional applied torque for characterizing the efficiency of the dry hybrid V-belt type CVT.

Three-Dimensional Dislocation Density Analysis of Bulk Semiconductor Single Crystal During CZ Growth Process.

A three-dimensional finite element computer program is developed for calculating dislocation density in bulk single crystal during Czochralski (CZ) growth process. In this program, crystal anisotropy in elastic constants and slip systems is taken into account. The Hassen-Sumino model is used as a uni-axial creep constitutive equation, which is extended to multi-axial stress state by using the theory of crystal plasticity. Dislocation density analyses of a silicon bulk single crystal are performed in the cases of both and pulling directions by use of this program. It is found that the dislocation density increases very rapidly from initial state to steady state. Significant differences are found between both pulling directions in distribution pattern of stress and dislocation density.

Dislocation density analyses of GaAs bulk single crystal during growth process (effects of crystal anisotropy)

A computer code was developed for simulation of dislocation density in a bulk single crystal during the Czochralski growth process. In this computer code, the effects of crystal anisotropy such as the elastic constants and slip directions were approximately taken into account by averaging the Young's modulus, the Poisson's ratio and the resolved shear stress along the azimuthal direction. Axisymmetric finite element analysis can be applied to quantitative estimation of dislocation density during single crystal growth process by using such averaging technique together with the Haasen–Alexander–Sumino model as a creep constitutive equation of a single crystal at elevated temperatures. Dislocation density analyses were performed for both the [0 0 1] and [1 1 1] growth directions of a GaAs bulk single crystal. As a result, although the [1 1 1] growth direction has the larger average Young's modulus than the [0 0 1] growth direction, the former gives lower dislocation density than the latter.

Slip Modulus of FRP Sheets Bonded to Concrete

An analytical tension-stiffening model was developed for fiber-reinforced polymer (FRP) sheets bonded to reinforced concrete based on equilibrium equations and the assumption of linear behavior between bond stress and slip. Experimental measurements were made on small- and large-scale specimens. For the small-scale specimens, the primer coat thickness (adhesive thickness between concrete and FRP sheet) was varied for each specimen. By comparisons of the experimental data to the analytical results, the slip modulus at the concrete/FRP sheet and concrete/steel interface was established at the service load level. From this study, it was found that primer coat thickness has a modest influence on the slip modulus of the repaired member, and stiffening of this interface slightly enhances the stiffness of the specimen. After the formation of secondary and diagonal tension cracks, the stiffness of the specimen dropped rapidly and the linearly elastic slip modulus assumption could not be applied. The slip modulus at the concrete/steel rebar interface is less than at the concrete/FRP sheet interface and the slip modulus is independent of the type of FRP sheet.

Stress state of laminar systems formed from shells of revolution with nonrigid layer contact

An approach is developed for determination of the strain state of elastic systems of layered orthotropic shells of revolution with elastic slip layers when the difference in the tangential displacements of the contact-surface layers is proportional to the tangential stress with a coefficient dependent on the arc length of the generatrix. A resolving system of differential equations and the conditions of the mating sections are obtained for the systems. Results are presented for the solution of specific problems.

Dislocation Density Analyses of Bulk Semiconductor Single Crystal during CZ Growth Process. Effects of Crystal Anisotropy.

A computer code was developed for simulation of dislocation density in a bulk single crystal during the Czochralski(CZ) growth process. In this computer code, the effects of crystal anisotropy such as the elastic constants and slip directions were approximately taken into account by averaging the Young's modulus, the Poisson's ratio and the resolved shear stress along the azimuthal direction. Axisymmetric finite element analysis can be applied to quantitative estimation of dislocation density during single crystal growth process by using such averaging technique together with the Hassen-Sumino model as a creep constitutive equation of a single crystal at elevated temperatures. Dislocation density analyses were performed for both the[001]and [111]growth directions of an InP single crystal. As a result, although the[111]growth direction has the larger average Young's modulus than the[001]growth direction, the former gives lower dislocation density than the latter.

A general FE algorithm for 3D incremental analysis of frictional contact problems of elastoplasticity

A theoretical basis of the original incremental description of the frictional contact problem of two thermo-elastic or thermo-elastoplastic (with or without isotropic hardening) bodies moving together is presented. The contact models allows the contact area to change. The friction models account for either Coulomb or elasto-Coulombian slips and assume either constant or varying friction coefficient. The general FE algorithm takes advantage of the proper variational formulation based on the incremental form of the potential energy functional. A general flow diagram for the problem solution is presented. Generation of element stiffnesses and forces, global stiffness matrix and global nodal force vector formation are mentioned in order to provide a background for a thorough presentation of the procedures due to contact aspects such as an algorithm for division of the potential contact area into component parts of gap, adhesion, and slip (or gap, elastic slip, and elasto-Coulombian slip), an algorithm for imposing unilateral normal contact and adhesion constraints, an algorithm for calculation of frictional terms (friction force increments and surface stiffnesses), and special iterative scheme within an incremental step. The algorithm is coded in program PLAST described in a companion paper.

A Microscopic Theory for Predicting Loads in Storage Bins for Granular Materials

A two-dimensional model for predicting loads in granular material storage bins was developed from the micromechanics approach, in which force equilibrium is considered at the particle (microscopic) level. The significance of this approach is to allow some particle property parameters to be used in calculations of stresses in storage bins for granular materials. Three key assumptions are made in the model: (1) the granular medium has a hexagonal structure consisting of elastic spheres, (2) rotation and slip of particles are negligible, and (3) stresses are uniform across the bin cross-section. Predictions by the proposed model are in close agreement with the experimental data reported by three different groups of researchers for maize and wheat storage bins. Janssen's equation, recommended by most design standards and codes, has been shown to be a special case of the present theory. The traditional assumption of constant lateral to vertical stress ratio was found to be valid only for frictionless walls or rigid particles.

On Micromechanical Evolutionary Damage Models for Polycrystalline Ceramics

Evolutionary micromechanical constitutive models for polycrystalline MgO ceramics with distributed dislocations and integranular microcracks are presented. Based on the description of dominant modes of microstructural changes in polycrystals, the kinetics of microcrack evolution in a typical grain is studied. Four basic deformation modes are considered within the micromechanics framework—the elastic deformation, slip band, microcrack nucleation, and microcrack kinking mechanisms. In particular, a slip band is assumed to be caused by the Frank-Read dislocation source, and a microcrack is assumed to be nucleated by the Zener-Stroh mechanism. At the onset, the stress-strain relation of the polycrystalline MgO ceramics is taken as linearly elastic. As the loading stress increases, slips will occur first in those crystals having the "easiest" slip planes at an angle of 45 degree. At some point, the stress in front of a dislocation pileup will exceed the cohesive strength of an intergranular plane. Therefore, a microcrack will nucleate on the grain boundary ("Cleavage 2" process). By computing the strain and compliance contributions due to many probabilistically distributed and evolutionary dislocations, microcracks and kinked microcracks, effective moduli and stress-strain relations can be derived based on micromechanics and approximate effective medium methods. Effects of different grain size distributions are investigated in detail by considering five cases (the fixed grain size, uniform distribution, normal distribution, square-root normal distribution, and linear decreasing distribution functions). The proposed models are subsequently applied to uniaxial tensile loadings, biaxial loadings, and residual stresses. Several interesting evolutionary examples are also presented to illustrate the capability and behavior of the proposed micromechanical damage models.

Influence of interfacial slits with elastic slip on the propagation of SH waves

This work examines the influence of various parameters, especially the effect of elastic slip at a single slit or a periodic array of slits situated at the interface between two isotropic elastic media on the propagation of waves. The analysis consists of transforming the formulation of the problem into an integral equation for the jump of the diffracted elastic displacement, at the interface, and solving this numerically after decomposition into Chebyshev polynomials and truncation of the resulting infinite series by use of an energy conservation criterion. The effects are illustrated on two characteristic features, the polar diagram of the amplitude of the far‐field diffracted displacement, and the transmission and reflection coefficients. The features revealed provide an indication of the usefulness of the results in assessing the quality of bonding at interfaces via a wave‐analysis technique.

Kinematics of finite elastoplastic deformation

A model in which plastic deformation occurs as a result of crystallographic slip is used to derive a formula for decomposing a deformation gradient into parts attributable to elastic and plastic deformation processes. The dislocation kinematics are those in long use, for example by Rice (1971, J. Mech. Phys. Solids 19, 433) and by Hill and Havner (1982, J. Mech. Phys. Solids 30, 5). The analysis presented here differs from that given by these authors in that it concerns total deformation (and its elastic and plastic parts) rather than incremental deformation. The decomposition obtained is inherent in the physics of the deformation process, arising naturally when the spatial discreteness of the active slip planes is taken into account. Expressions for the decomposition components are obtained by means of volumetric averaging of contributions of elastic deformation and slip to the total deformation. The decomposition captures the effects of isoclinic orientation central to Mandel's (1973, Int. J. Solids Struct. 9, 725) theory, but without introduction of the intermediate configuration that arises when the deformation is assumed to be expressible as though the plastic and elastic deformations occurred sequentially. Because no intermediate configuration arises, the established objectivity principle applies without modification and the concept of elastic embedding that is essential to proper selection of temporal rates is implemented quite naturally. Although the new decomposition is motivated by dislocation-mechanical considerations, the result is a continuum-mechanical expression that can be used in other contexts in which the sites of inelastic deformation are spatially separated in the material.

Forearc Deformation and Great Subduction Earthquakes: Implications for Cascadia Offshore Earthquake Potential

The maximum size of thrust earthquakes at the world's subduction zones appears to be limited by anelastic deformation of the overriding plate. Anelastic strain in weak forearcs and roughness of the plate interface produced by faults cutting the forearc may limit the size of thrust earthquakes by inhibiting the buildup of elastic strain energy or slip propagation or both. Recently discovered active strike-slip faults in the submarine forearc of the Cascadia subduction zone show that the upper plate there deforms rapidly in response to arc-parallel shear. Thus, Cascadia, as a result of its weak, deforming upper plate, may be the type of subduction zone at which great (moment magnitude approximately 9) thrust earthquakes do not occur.

Interfacial waves in the presence of areas of slip

Interfacial waves are considered propagating along, or incident upon, an interface between two orthotropic elastic materials which presents special mechanical matching conditions, involving elastic slip along the whole of the interface or in localized areas (one isolated interfacial crack or a periodic array of such cracks). The study is made with a view to applications in geophysics and dynamical non-destructive evaluation techniques. The work highlights those results (Stoneley waves, existence of an additional SH mode with a cut-off, diffraction pattern of the far field) which will be useful in a qualitative and quantitative characterization of the interface, especially concerning the presence of cracks and the quality of the bond.

A two-stage micromechanics model for short fatigue cracks: Hussain, K., De Los Rios, E.R. and Navarro, A. Eng. Fract. Mech. (Feb. 1993) 44 (3), 425–436

The effect of slip amplitude on the fretting fatigue behaviour of several alloy steels was investigated. Fretting fatigue experiments were conducted on flat fretting junctions under axial tension at a stress ratio of 0.1, with fretting surfaces of the same material. At a normal pressure of 24.5 MPa, the fretting fatigue lives of 2Cr13 and 35CrMo (quenched, tempered for 2 h and air cooled) show a minimum value at a slip amplitude of about 20 μm. At a normal pressure of 49 MPa, the fretting fatigue lives of 35CrMo (quenched, tempered for 2 h and air cooled) steel decrease with increasing slip amplitude. In the range of elastic slip, the variations of tangential stress and alternating stress are in phase, i.e. the fretted area experiences proportional loading. In the range of macro-slip, the variations of tangential stress and alternating stress are out of phase owing to the occurrence of stick-slip movement, so the fretted area experiences non-proportional loading. When the normal pressure is 49 MPa, the fretted areas show ripple features at slip amplitudes of 10 μm. With increasing slip amplitude, the depth of wear scars increases and wear damage becomes more severe. At slip amplitudes of above 45 μm, adhesive transfer occurs between the fretting-damaged surfaces of 2Cr13 specimens, while abrasive ploughing takes place between the fretting-damaged surfaces of 35CrMo and 60Si2Mn specimens.

Elastic stresses and slip intersections with f.c.c. twins

When slip takes place in f.c.c. metals containing annealing twins, slip may be reflected from a twin boundary, or it may be parallel to the twin boundary in the matrix and the twin, or it may pass continuously from matrix to twin to matrix. Finite element method (FEM) calculations permitted a determination of the matrix-twin orientation where each type of behavior would take place. Experiments were carried out on 70–30 α-brass bicrystals, tri-crystals and multi-crystals to check the calculations. Experiments were found to agree with calculations. When reflecting slip occured adjacent to a pile-up in a twin, it was possible to determine the identity of the reflecting slip system from FEM calculations and from a determination of the stresses resulting from the pile-up on the ( 11 1 ) [101] T slip system. It was also possible to identify the slip systems in the matrix, slip systems which operated as a result of the pile-up. For orientations in which slip would be reflected from a twin boundary calculations revealed that stress distributions were not the same for thick and thin twin cases, a situation which would produce transmission of slip across the thin twin but not the thick twin.

Geodetic evidence for conjugate faulting during the 1988 Tennant Creek, Australia earthquake sequence

SUMMARY Repeat levelling measurements and detailed topographic profiles from the epicentral area of the 1988 January 22 Tennant Creek, Australia earthquakes are used to constrain the geometry of faulting associated with three M 6+ earthquakes. The observed elevation changes are modelled assuming elastic deformation and uniform slip on several faults. The vertical deformation data are poorly fit by a single-fault model, and require at least three distinct faults. In the preferred model, two faults on either end of the zone of surface rupture have similar orientations, but the central fault has an orientation conjugate to the flanking faults. This interpretation is consistent with the identification of the fault planes with well-defined, dipping zones of aftershock hypocentres determined with data from portable seismograph arrays. It is also consistent with the sense of surficial deformation documented by 75 topographic profiles across the scarps. However, a fourth fault associated with possible conjugate faulting in the central fault segment at the time of the second main shock is not required by the levelling data.

Effect of slip amplitude on fretting fatigue

The effect of slip amplitude on the fretting fatigue behaviour of several alloy steels was investigated. Fretting fatigue experiments were conducted on flat fretting junctions under axial tension at a stress ratio of 0.1, with fretting surfaces of the same material. At a normal pressure of 24.5 MPa, the fretting fatigue lives of 2Cr13 and 35CrMo (quenched, tempered for 2 h and air cooled) show a minimum value at a slip amplitude of about 20 μm. At a normal pressure of 49 MPa, the fretting fatigue lives of 35CrMo (quenched, tempered for 2 h and air cooled) steel decrease with increasing slip amplitude. In the range of elastic slip, the variations of tangential stress and alternating stress are in phase, i.e. the fretted area experiences proportional loading. In the range of macro-slip, the variations of tangential stress and alternating stress are out of phase owing to the occurrence of stick-slip movement, so the fretted area experiences non-proportional loading. When the normal pressure is 49 MPa, the fretted areas show ripple features at slip amplitudes of 10 μm. With increasing slip amplitude, the depth of wear scars increases and wear damage becomes more severe. At slip amplitudes of above 45 μm, adhesive transfer occurs between the fretting-damaged surfaces of 2Cr13 specimens, while abrasive ploughing takes place between the fretting-damaged surfaces of 35CrMo and 60Si2Mn specimens.

Elastic anisotropy and slip systems in diamond structure elements

Elastic anisotropy and slip systems in diamond structure elements

Experimental investigation of elastic turbulence and boundary slip of elastomers over a broad temperature interval

Ethylene-propylene copolymer, a typical stereo rubber, has been investigated by capillary viscometry. Ethylene-propylene copolymer possesses high thermooxidative stability, which has made it possible to study its viscosity properties, determine the onset of elastic turbulence and boundary slip, and measure the slip rate over a very broad temperature interval, from room temperature to 260° C. The flow of elastomers differs from that of thermoplastics in that at relatively low strain rates flow is complicated by the boundary slip effect. The mean boundary slip velocities of the copolymer at shear stresses above 106 dynes/cm2 are measured in tens of centimeters per second. As the temperature rises, they rapidly increase.

Discussions to T. Yokobori: Brittle fracture with interaction between elastic crack and near-by slip band

Discussions to T. Yokobori: Brittle fracture with interaction between elastic crack and near-by slip band