Showing papers on "Shear stress published in 1973"
TL;DR: In this paper, the results of an extensive series of tests of three types of concrete under biaxial loadings are used to develop stress-strain relations for concrete subjected to bialastic stress states, by means of a decomposition of the stresses and strains into their hydrostatic and deviatoric portions.
Abstract: The results of an extensive series of tests of three types of concrete under biaxial loadings are used to develop stress-strain relations for concrete subjected to biaxial stress states. By means of a decomposition of the stresses and strains into their hydrostatic and deviatoric portions, it was possible to express the relations between octahedral normal stresses and strains, and octahedral shear stresses and strain through use of bulk and shear moduli. These moduli can be expressed as functions of the octahedral shear stress only; formulas and coefficients are given for the values of the tangent and secant, bulk and shear moduli for the three types of concrete. The deformational behavior is described as the material reaches its failure stage. The application of these nonlinear stress-strain relations to stress analysis is indicated; a material stiffness matrix for use in finite element analysis is presented, and a partial differential equation with variable coefficients for analysis of plane-stress problems is shown.
1,774 citations
TL;DR: In this article, the authors used fracture mechanics to derive conditions for the propagation of a concentrated shear band in heavily overconsolidated clays and found that the mean resolved shear stress on that surface is markedly less than the peak shear strength.
Abstract: In heavily over-consolidated clays there is a marked peak in the observed relation between shear stress and shear strain. As the strain increases, the stress falls from a peak to a much smaller residual stress. Slopes made from such a clay often fail progressively many years after construction. Sliding occurs on a concentrated slip surface, and it is found that the mean resolved shear stress on that surface is markedly less than the peak shear strength. Concepts from fracture mechanics, and in particular the J -integral, are used to derive conditions for the propagation of a concentrated shear band of this kind. The results indicate the presence of a strong size effect, which has important implications for the use of models in soil mechanics. An elastic analysis makes it possible to determine the size of the end zone in which the shear stress on the shear band falls to its residual value. An attempt is made to assess the possible sources of the time-dependence governing propagation speed of the shear band. They include pore-water diffusion to the dilating tip of the band (which governs the rate at which local strength reductions can occur), viscoelastic deformation of the clay (which allows a gradual build-up of strain concentration at the tip of the band), and the weathering break-down of diagenetic bonds.
883 citations
TL;DR: In this paper, a theory of yielding of glassy polymers by thermally activated production of local molecular kinks is described, and the authors obtain the activation free enthalpy of this process by modeling the intermolecular energy barrier as resulting from the stress fields of two equal and opposite closely spaced wedge disclination loops extending over the molecular cross section at the points of rotation of the molecular kink.
Abstract: A theory of yielding of glassy polymers by thermally-activated production of local molecular kinks is described. It is possible to obtain the activation free enthalpy of this process by modeling the intermolecular energy barrier as resulting from the stress fields of two equal and opposite closely spaced wedge disclination loops extending over the molecular cross section at the points of rotation of the molecular kinks. The theory predicts the yield stress at absolute zero to be dependent only on the shear modulus and the Poisson's ratio, and is capable of describing the temperature, pressure, and strain rate dependences of the flow stress from absolute zero to near the glass transition temperature. Comparison of the theory with the available experimental, results on polystyrene, polyethylene-terephthalate, polycarbonate of bisphenol A, and poly-methyl-methacrylate shows excellent agreement in nearly all respects.
689 citations
TL;DR: In this paper, the theoretical stress-strain behavior of a composite with a brittle matrix, in which the fiber-matrix bond remains intact after the matrix has cracked, is described.
Abstract: The theoretical stress-strain behaviour of a composite with a brittle matrix in which the fibre-matrix bond remains intact after the matrix has cracked, is described. From a consideration of the maximum shear stress at the fibre-matrix interface, the extent of fibre debonding and the crack spacing in a partially debonded composite are derived. The energetics of cracking and the conditions leading to an enhanced matrix failure strain are then discussed and, finally, the crack spacing expected in composites containing fibres isotropically arranged in two or in three dimensions is derived for the case of very thin and hence very flexible fibres.
617 citations
TL;DR: In this paper, it has been shown that suspension by fluid turbulence of mineral solids larger than those of medium sands does not become appreciable until the bed shear stress is increased to a value exceeding 12 times its threshold value for the bed material considered.
Abstract: Owing to observational difficulties the distinction between a ‘suspended’ load of solids transported by a stream and a ‘ bed-load ’ has long remained undefined. Recently, however, certain critical experiments have thrown much light on the nature of bed-load transport. In particular, it has been shown that bed-load transport, by saltation, occurs in the absence of fluid turbulence and must therefore be due to a separate dynamic process from that of transport in suspension by the internal eddy motion of a turbulent fluid. It has been further shown that the forward motion of saltating solids is opposed by a frictional force of the same order as the immersed weight of the solids, the friction coefficient approximating to that given by the angle of slip. The maintenance of steady motion therefore requires a predictable rate of energy dissipation by the transporting fluid. The fluid thrust necessary to maintain the motion is shown to be exerted by virtue of a mean slip velocity which is predictable in the same way as, and approxim ates to, the terminal fall velocity of the solid. The mean thrust, and therefore the transport rate of saltating solids, are therefore predictable in terms of the fluid velocity close to the bed, at a distance from it, within the saltation zone, of a ‘centre of fluid thrust’ analogous to the ‘centre of pressure’. This velocity, which is not directly measurable in water streams, can be got from a knowledge of stream depth and mean flow velocity. Thus a basic energy equation is obtained relating the rate of transporting work done to available fluid transporting power. This is shown to be applicable to the transport both of wind-blown sand, and of water-driven solids of all sizes and larger than that of medium sand. Though the mean flow velocity is itself unpredictable, the total stream power, which is the product of this quantity times the bed shear stress, is readily measurable. But since the mean flow velocity is an increasing function of flow depth, the transport of solids expressed in terms of total stream power must decrease with increasing flow depth/grain size ratio. This considerable variation with flow depth has not been previously recognised. It explains the gross inconsistencies found in the existing experimental data. The theoretical variation is shown to approximate very closely to that found in recent critical experiments in which transport rates were measured at different constant flow depths. The theory, which is largely confirmed by these and other earlier experiments, indicates that suspension by fluid turbulence of mineral solids larger than those of medium sands does not become appreciable until the bed shear stress is increased to a value exceeding 12 times its threshold value for the bed material considered. This range of unsuspended transport decreases rapidly, however, as the grain size is reduced till, at a certain critical size, suspension should occur at the threshold of bed movement.
470 citations
TL;DR: In this article, a yield criterion based on the von Mises criterion was proposed, which accommodates differences in tensile and compressive yield strengths and accounts for any dependence of yielding on the hydrostatic component of the applied stress state.
Abstract: A yield criterion, not previously compared with the actual macroscopic behaviour of polymers, is herein compared with the pressure-modified octahedral shear stress criterion earlier suggested by others. This new relation, which is a version of the von Mises criterion, accommodates differences in tensile and compressive yield strengths and accounts for any dependence of yielding on the hydrostatic component of the applied stress state.
434 citations
TL;DR: In this article, a coaxial cylinder viscometer was used to evaluate the viscosities of liquid and semi-solid foods by tilting the containers and also by stirring the contents with a spoon.
Abstract: Flow properties of several liquid and semi-solid foods were characterized objectively with a coaxial cylinder viscometer. At the same time, a sensory evaluation panel compared the viscosities of these samples by tilting the containers and also by stirring the contents with a spoon. Correlation of the instrumental and sensory evaluation data established the shear stress-shear rate conditions prevailing during sensory evaluation of viscosity. The stimulus responsible for viscosity evaluation by tilting the container is the shear rate (0.1–40 sec-1) developed at a shear stress (60–600 dyne cm-2) related to the flow properties of the sample, whereas in stirring tests the stimulus is the shear stress (102–104 dyne cm-2) developed at a particular rate of shear (90–100 sec-1). In the latter type of test, the shear rate varies to some degree with the flow characteristics of the sample. Since different stimuli are involved in viscosity assessment by tilting the container or by stirring, it is possible for a series of samples to be given different ranking orders by the two methods of evaluation.
359 citations
01 Sep 1973
TL;DR: In this article, the authors developed empirical relationships which relate the force of adhesion to the viscous drag experienced by the particle, which is assumed to be embedded in a steady, viscous sublayer.
Abstract: Visser [J. Colloid Interface Sci. 34, 26 (1970)] has used hydrodynamic techniques, i.e., rotating cylinders, to study the removal of submicron particles from various substrates. He developed empirical relationships which relate the force of adhesion to the viscous drag experienced by the particle, which is assumed to be embedded in a steady, viscous sublayer. Although this technique is a valuable experimental tool, the question of how a particle is moved is evaded. Detailed investigations of the turbulent boundary layer (reported in the fluid mechanics literature) have shown that the viscous sublayer is anything but steady, and is continually disrupted by turbulent “bursts.” These bursts, which are not unlike miniature tornados, may cause instantaneous lift forces sufficient to detach a particle. This model of an unsteady sublayer has been used to predict the possible lift forces acting on the particle. These can arise either from impulsive motions or from the generation of a quasi-steady updraft over a particle by a burst. From these predicted lift forces, a removal criterion is obtained which for a given fluid reduces to τωd4/3 ⩾ constant where τω is wall shear stress and d is particle diameter. This result is shown to be in general agreement with previous empirical studies. The rate of removal can be predicted by combining this analysis of lift forces with literature data on the size and frequency of bursts. Although this latter information is taken from studies in pipe-flow and flow over a flat-plate, the predicted rates are in qualitative agreement with the experimental data from rotational instruments.
333 citations
TL;DR: In this paper, a theoretical method for predicting the deformation and the conditions for breakup of a liquid droplet freely suspended in a general linear shear field is presented, which is achieved by expanding the solution to the creeping-flow equations in powers of deformation parameter epsilon and using linear stability theory to determine the onset of bursting.
Abstract: A theoretical method is presented for predicting the deformation and the conditions for breakup of a liquid droplet freely suspended in a general linear shear field. This is achieved by expanding the solution to the creeping-flow equations in powers of the deformation parameter epsilon and using linear stability theory to determine the onset of bursting. When compared with numerical solutions and with the available experimental data, the theoretical results are generally found to be of acceptable accuracy although, in some cases, the agreement is only qualitative.
275 citations
TL;DR: In this article, the authors studied the dependence of debonding stress and pull-out stress on the embedded length of a stainless steel wire embedded in an epoxy resin and found that the effect of wire contraction on the friction process was confirmed by using different initial wire tensions.
Abstract: The extraction of a stainless steel wire embedded in an epoxy resin has been studied as a function of the embedded length. The models developed to elucidate the dependence of the debonding stress and the pull-out stress on the embedded length are applied successfully to the experimental results. The nonlinear variation of the debonding stress with the embedded length is caused by the distribution of shear stress along the wire. The variation of pull-out stress with embedded length is caused by the decrease of the frictional stress due to the Poisson contraction of the wire under tensile stress. The effect of wire contraction on the friction process was confirmed by using different initial wire tensions. The residual compressive stress at the interface due to resin shrinkage and the coefficient of friction were determined from the analysis of the pull-out process.
258 citations
TL;DR: In this article, the authors determined the shear and friction coefficients of the slip zone between the descending lithosphere and the overlying mantle where partial melting of the descending oceanic crust takes place by assuming that the frictional stress on the slip-zone is either constant or proportional to depth.
Abstract: Linear chains of active volcanoes are usually associated with oceanic trenches. It is postulated that the active volcanoes lie above the point on the slip zone between the descending lithosphere and the overlying mantle where partial melting of the descending oceanic crust takes place. By assuming that the frictional stress on the slip zone is either constant or proportional to depth, the thermal structure of the descending lithosphere is determined. The alternative theories are used to determine the shear stresses and friction coefficients for various trench-volcano systems. Values for the shear stress and friction coefficient have standard deviations of 10 and 24%, respectively. We conclude that the shear stress on a slip zone is probably weakly dependent on depth with a value near 1.35kb. Our results are compared with previous calculations.
TL;DR: In this paper, it has been found that shear moduli for small shear strain level are well correlated with N-values of the standard penetration test, and that their interrelation may be expressed by a simple, approximate Eq. G = 1200N 0.8 (tons/sq meter) regardless of soil types and depths from the ground surface.
TL;DR: Recent information from experimentally deformed dunite coupled with a reanalysis of data on the Fennoscandian postglacial rebound suggest that the rheological behavior of the upper mantle is distinctly non-Newtonian, and that theShear strain rate is proportional to the shear stress raised to about the third power.
Abstract: Recent information from experimentally deformed dunite coupled with a reanalysis of data on the Fennoscandian postglacial rebound suggest that the rheological behavior of the upper mantle is distinctly non-Newtonian, and that the shear strain rate is proportional to the shear stress raised to about the third power.
01 Jun 1973
TL;DR: In this article, numerical predictions of the hydrodynamic and heat transfer characteristics of fully developed turbulent flow in square-sectioned ducts are presented, where the turbo stresses in the plane of the cross-section, whose gradients cause the well-known secondary motion, are approximated by gradients in the axial mean velocity.
Abstract: Numerical predictions are presented of the hydrodynamic and heat transfer characteristics of fully developed turbulent flow in square-sectioned ducts.The turbo stresses in the plane of the cross-section, whose gradients cause the well-known secondary motion, are approximated by gradients in the axial mean velocity.Predicted results are in close agreement with available experimental data of primary and secondary velocities as well as the shear stress and heat flux variations around the perimeter.
TL;DR: In this article, two simultaneous second-order partial-differential equations were set up to describe the normal stresses along and across an adherend and were solved both by an approximate analytical method and a finite-difference technique: the two solutions agreed closely.
Abstract: Poisson's ratio strains in the adherends of a simple adhesive lap joint induce transverse stresses both in the adhesive and in the adherends.Two simultaneous second-order partial-differential equations were set up to describe the normal stresses along and across an adherend and were solved both by an approximate analytical method and a finite-difference technique: the two solutions agreed closely. The adhesive shear stresses can then be obtained by differentiating these solutions. The transverse shear stress has a maximum value for metals of about one-third of the maximum longitudinal shear stress, and this occurs at the corners of the lap, thus making the corners the most highly stressed parts of the adhesive.Bonding adherends of dissimilar stiffness was shown to produce greater stress concentrations in the adhesive than when similar adherends are used.
TL;DR: In this paper, a simple plane two-dimensional model of an elastic plate underlain by a viscous layer was used to investigate the viscous shearing stress of the asthenosphere on the base of the solid Earth.
Abstract: ACCORDING to global tectonics, the outer relatively strong layer of the solid Earth (lithosphere) is divided into seven major and several minor discrete plates separated from each other by the Earth's mobile belts. The mechanism of global tectonics is believed to depend partly or wholly on the application and release of strain energy at mobile belts which lie along plate margins. The isostatic response of the lithosphere to application or removal of a wide surface load such as an icecap is delayed by the viscous response of the underlying asthenosphere to elastic bending of the lithosphere1. By analogy, the viscous drag of the asthenosphere should also delay the response of the lithospheric plates to relief or application of horizontal boundary stresses on a plate edge, as indicated by an earlier calculation made by Elsasser2. We have investigated this using a simple plane two-dimensional model of an elastic plate underlain by a viscous layer. We confirm that the viscous shearing stress of the asthenosphere on the base of the lithosphere is a significant factor in causing stress to diffuse through the lithosphere. We also predict the possible occurrence of a new type of strain wave in the lithosphere, with some resemblance to Voigt waves3,4.
TL;DR: In this article, the behavior of a screw dislocation core in the presence of an external shear stress on {110} planes has been studied for a variety of effective interionic potentials, each representing a stable b. c. lattice.
Abstract: The behaviour of the ½ a screw dislocation core in the presence of an external shear stress on {110} planes has been studied for a variety of effective interionic potentials, each representing a stable b. c. c. lattice. The distortion and motion of the core are described using the concept of fractional dislocations, which are imperfect dislocations bounding a ribbon of generalized (unstable) stacking fault. Three essentially distinct types of movement are found, and the relation of these to plastic flow and twinning in real b. c. c. metals is discussed. It is found that the movement of the dislocation core can be rationalized in terms of the relative stresses needed to create generalized stacking faults on {110} and {112} planes.
TL;DR: In this paper, the Neuber stress-concentration relation for notches in an elastic-plastic material subjected to shear loading was generalized for a crack in a finite plate subjected to tensile loading.
TL;DR: In this paper, a universal velocity defect law for turbulent boundary layers developing in adverse pressure gradients is proposed, which is independent of the wall shear but related instead to the local maximum in the Reynolds stress profile.
Abstract: A universal velocity defect law for turbulent boundary layers developing in adverse pressure gradients is proposed. The velocity scale for this law is independent of the wall shear but related instead to the local maximum in the Reynolds stress profile. The proposal and its implications are checked against a very large body of experimental results and a partial connection between the mean velocity field and the shear stress field is established. A comparison between the present theory and the mixing length theory is presented. The experimental data do not appear to support many of the assumptions nor the predictions of the mixing length theory. The distinction between equilibrium and nonequilibrium layers made by Clauser is shown to be unnecessary as all classes of layers appear to conform to the new universal velocity defect law proposed, provided that the maximum shear stress is sufficiently larger than the wall shear stress.
TL;DR: In this paper, the effects of interstitial solute content and grain size on the deformation kinetics and strain hardening in titanium were investigated over the temperature range of 4.2 to 650°K and compared with previous results on single and polycrystals.
TL;DR: In this article, the authors established the variation of friction factor for different flows and rainfall conditions by statistical analysis and found that the friction factor is a function of both the flow Reynolds number, R, and the rainfall intensity.
Abstract: The variation of friction factor for different flows and rainfall conditions is established by statistical analysis. Boundary shear stress was directly measured by hot-film anemometry. The friction factor is found to be a function of both the flow Reynolds number, R , and the rainfall intensity, I , for a flow Reynolds number of less than 900. For a flow Reynolds number greater than 2,000, the friction factor is only a function of Reynolds number. A numerical model and a simplified procedure to predict the water surface profiles and boundary shear stresses for sheet flow with rainfall are presented. The computations of flow depths and boundary shear stresses are not too sensitive to the effect of uncertainties in selecting friction factor.
TL;DR: In this paper, the operative slip systems in single crystals of CsCl-type intermetallic compound FeAl deformed in compression at 77°, 300° and 473°K were determined for three different crystal orientations.
TL;DR: In this paper, the authors considered the effects of buoyancy and acceleration on the shearing stress distribution in a vertical tube and proposed an approximate theory to calculate velocity and temperature profiles under the large effects of both forces.
TL;DR: In this article, the mean velocity and the turbulence properties of a plane mixing layer are investigated and a new method is proposed to calculate shear stress distribution from a measured nondimensional mean velocity profile.
Abstract: Examination of existing literature is revealing in that although many investigations have been carried out for a plane mixing layer, only a few present turbulence measurements. It is well-known that both mean velocity and turbulence structure in a plane mixing layer are self-preserving, however there appears to be some variations in these measurements. This investigation presents new data on the mean velocity and the turbulence properties of a plane mixing layer. The turbulence measurements differ by about 25% from those obtained by previous investigators and this is attributed to differences in the experimental set up (i.e., presence or absence of a solid wall in the plane x = 0) and errors associated with hot-wire probes (i.e., longitudinal cooling and thermal wake interference). To avoid difficulties experienced by previous investigators in calculating shear stress distribution from a measured nondimensional mean velocity profile a new method is suggested and this provides good agreement between the calculated and the measured shear stress distribution. ECENTLY, considerable effort has been directed towards the study of free turbulent shear flows. In this group of shear flows a plane, turbulent, incompressible mixing layer between a uniform stream and quiescent surroundings is a com- paratively simple flow to investigate both theoretically and experimentally. However, except for a few investigations (as for example Garshore1; Hackett and Cox2) dealing with mean velocity measurements not much renewed attention appears to have been given to the plane turbulent mixing layer since the appearance of the work of Liepmann and Laufer.3 It should be recalled that Liepmann and Laufer did not measure both the lateral turbulent intensity and the shear stress presumably because is expected to be of the same magnitude as and is expected to be zero. Furthermore, techniques of hot-wire anemometry have developed considerably since their investigation and therefore it is of interest to reinvestigate the plane mixing layer. Since the completion of the present investigation Wygnanski and Fiedler4 have reported extensive and sophisticated turbu- lence measurements in this type of flow. An interesting aspect of their investigation was the geometry of the experimental apparatus. They used a trip wire and a solid wall on the zero velocity side in the plane x = 0. They also used conventional DISA x-wire probes to measure the turbulence parameters and it is now known that the conventional DISA x-wire probes are contaminated by the "thermal cross talk."5 The measurements of Wygnanski and Fiedler are compared with the results of the present investigation obtained with single hot-wires in a plane mixing layer without a solid wall in the plane x = 0. It is anticipated that such a comparison would show up differences, if any, due to the geometry of the experimental apparatus and the probes. Recently Spencer and Jones6 have investigated a general problem of a mixing layer between two parallel streams and as a special case they have reported some data on a plane mixing layer. This information consists of the spreading rate and the mean velocity profile. Although not directly related to the
TL;DR: In this paper, a tensile and creep testing was performed on double shear type specimens in a normalized stress ( τ G ) range of ~5 × 10 −7 to ~5× 10 −3, and the experimental results in the employed stress range obeyed the follo′ing phenomenological effect.
TL;DR: In this paper, the authors used the cumulant-discard approach to predict the third and fourth-order moments and the probability density of turbulent Reynolds shear stress fluctuations uv, the streamwise and normal velocity fluctuations represented by u and v respectively.
Abstract: The cumulant-discard approach is used to predict the third- and fourth-order moments and the probability density of turbulent Reynolds shear stress fluctuations uv, the streamwise and normal velocity fluctuations being represented by u and v respectively. Measurements of these quantities in a turbulent boundary layer are presented, with the required statistics of uv obtained by the use of a high-speed digital data-acquisition system. Including correlations between u and u up to the fourth order, the cumulant-discard predictions are in close agreement with the measurements in the inner region of the layer but only qualitatively follow the experimental results in the outer intermittent region. In this latter region, predictions for the third- and fourth-order moments of uv are also obtained by assuming that the properties of both turbulent and irrotational fluctuations are Gaussian and by using some of the available conditional averages of u, v and uv.
TL;DR: The second-order invariant modeling technique for turbulent flows as developed by Donaldson is applied to the atmospheric surface layer as mentioned in this paper, where the steady, high-Reynolds number equations reduce to a universal set when the variables are scaled by the shear stress and vertical heat flux as suggested by Monin and Obukhov.
Abstract: The second-order, invariant modeling technique for turbulent flows as developed by Donaldson is applied to the atmospheric surface layer. The steady, high-Reynolds number equations reduce to a universal set when the variables are scaled by the shear stress and vertical heat flux as suggested by Monin and Obukhov. Numerical integration of these equations yields results for the mean velocity gradient, mean temperature gradient, Richardson number, rms vertical velocity and temperature fluctuations, and horizontal heat flux which agree favorably with experimental observations over the complete range of stability conditions.
TL;DR: In this paper, a series of flat bed, uniform flow tests was conducted in a flume using uniform sand sizes in the range 0.13 to 3.57 mm and density 2.65 to 4.70 g/cc.
Abstract: Sand-sized sediment under certain boundary shear conditions may overpass, i.e., may move as bed load, across a loose, flat boundary of unlike size and density without being deposited, and without appreciably disturbing the boundary stability. To define the boundary shear stress necessary for overpassing, and shear stress at incipient motion for bed particles, a series of flat bed, uniform flow tests was conducted in a flume using uniform sand sizes in the range 0.13 to 3.57 mm and density 2.65 to 4.70 g/cc. Flow depths were varied from 1.0 to 8.8 cm and mean flow velocities ranged from 13.1 to 50.3 cm/s producing critical boundary shear stresses between 0.8 and 16.5 dynes/cm². With a bed grain diameter smaller than 0.9 mm, and a grain density of 2.65 g/cc, the size range of overpassing particles was greatest for grains larger than the boundary. Minimum overpassing boundary shear appears to be a function of boundary roughness and of the thickness of the laminar sublayer with respect to the diameter of the overpassing grain.