A Rigid Punch Bonded to a Half Plane

1979 ◽  
Vol 46 (4) ◽  
pp. 844-848 ◽  
Author(s):  
G. G. Adams
Keyword(s):  
Shear Stress ◽  
Free Surface ◽  
Normal Stress ◽  
Half Plane ◽  
Square Root ◽  
Rigid Punch ◽  
Flat Punch ◽  
Logarithmic Singularities

The well-known solution for a rigid punch bonded to an elastic half plane has oscillatory singularities at the corners of the punch. It is shown here that the resulting displacement of the free surface of the half plane actually spirals in upon itself and is therefore physically inadmissible. The problem of a flat punch with sloped sides is then formulated and a solution obtained which does not have an oscillatory singularity. The limit is taken as the punch sides become perpendicular with its base. This leads to square root singularities in the shear stress and to logarithmic singularities in the normal stress along the bond.

scholarly journals A Paradox in Sliding Contact Problems With Friction

2003 ◽  
Vol 72 (3) ◽  
pp. 450-452 ◽  
Author(s):  
G. G. Adams ◽  
J. R. Barber ◽  
M. Ciavarella ◽  
J. R. Rice
Keyword(s):  
Half Plane ◽  
Slip Velocity ◽  
Finite Strain ◽  
Applied Pressure ◽  
Strain Analysis ◽  
Contact Problems ◽  
Rigid Punch ◽  
Flat Punch ◽  
Relative Slip ◽  
Velocity Changes

In problems involving the relative sliding to two bodies, the frictional force is taken to oppose the direction of the local relative slip velocity. For a rigid flat punch sliding over a half-plane at any speed, it is shown that the velocities of the half-plane particles near the edges of the punch seem to grow without limit in the same direction as the punch motion. Thus the local relative slip velocity changes sign. This phenomenon leads to a paradox in friction, in the sense that the assumed direction of sliding used for Coulomb friction is opposite that of the resulting slip velocity in the region sufficiently close to each of the edges of the punch. This paradox is not restricted to the case of a rigid punch, as it is due to the deformations in the half-plane over which the pressure is moving. It would therefore occur for any punch shape and elastic constants (including an elastic wedge) for which the applied pressure, moving along the free surface of the half-plane, is singular. The paradox is resolved by using a finite strain analysis of the kinematics for the rigid punch problem and it is expected that finite strain theory would resolve the paradox for a more general contact problem.

scholarly journals A Crack between Orthotropic Materials with a Shear Yield Zone at the Crack Tip

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
V. Loboda ◽  
I. Gergel ◽  
T. Khodanen ◽  
O. Mykhail
Keyword(s):  
Shear Stress ◽  
Analytical Solution ◽  
Normal Stress ◽  
Exact Analytical Solution ◽  
Crack Tip ◽  
Shear Loading ◽  
Square Root ◽  
Yield Zone ◽  
Shear Yield ◽  
Crack Tips

A plane problem for a crack between two anisotropic semi-infinite spaces under remote tensile-shear loading is considered. In the framework of the assumption that the crack faces are free of stresses an exact analytical solution of the problem is given on basis of the complex potentials approach. This solution possesses oscillating square root singularities in stresses and in the derivatives of the displacement jumps at the crack tips. To remove these singularities a new model founded on the introduction of the shear yield zones at the crack tips is suggested. This model is appropriate for the cases where interface adhesive layer is softer than the surrounding matrixes. Under this assumption the problem is reduced to the nonhomogeneous combined Dirichlet-Riemann boundary value problem with the conditions at infinity. An exact analytical solution of this problem is presented for the case of a single yield zone. The length of this zone is found from the finiteness of the shear stress at the end point of the zone. Due to such simulation the shear stress becomes finite at any point and the normal stress possesses only square root singularity at the crack tip. Therefore, the conventional stress intensity factor of the normal stress at the crack tip is used. The numerical illustration of the obtained solution is given.

Effect of Shear Surface Boundaries on Stress for Shearing Flow of Dry Metal Powders—An Experimental Study

1987 ◽  
Vol 109 (2) ◽  
pp. 232-237 ◽  
Author(s):  
K. Craig ◽  
R. H. Buckholz ◽  
G. Domoto
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Normal Stress ◽  
Particle Diameter ◽  
Surface Boundary ◽  
Metal Powders ◽  
Shear Surface ◽  
Shear Cell ◽  
Shearing Flow ◽  
Solids Content

This paper studies the rapid simple shearing flow of dry cohesionless metal powders contained between parallel rotating plates. In this study, an annular shear cell test apparatus was used; the dry metal powders are rapidly sheared by rotating one of the shear surfaces while the other shear surface remains fixed. Such a flow geometry is of interest to tribologists working in the area of dry or powder lubrication. The shear stress and normal stress on the stationary surface are measured as a function of the following parameters: shear surface boundary material and roughness, the shear-cell gap thickness, the shear-rate and the fractional solids content. Both the fractional solids content and the gap thickness are kept at prescribed values during stress measurements. In this experiment the metal powder tested is different from the shear transmission surface material; the effect on the measured normal and shear stress data are reported. The results show the dependence of the normal stress and the shear stress on the shear-rate, particle density and particle diameter. Likewise, a significant stress dependence on both the fractional solids content and the shear-cell gap thickness was observed.

Stress in Bonded Adherends for Single Lap Joints

1996 ◽  
Vol 12 (03) ◽  
pp. 167-171
Author(s):  
G. Bezine ◽  
A. Roy ◽  
A. Vinet
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Numerical Model ◽  
Stress Distribution ◽  
Normal Stress ◽  
Lap Joints ◽  
Axial Loads ◽  
Normal Stress Distribution ◽  
Single Lap Joints ◽  
Element Technique

A finite-element technique is used to predict the shear stress and normal stress distribution in adherends for polycarbonate/polycarbonate single lap joints subjected to axial loads. Numerical and photoelastic results are compared so that a validation of the numerical model is obtained. The influences on stresses of the overlap length and the shape of the adherends are studied.

scholarly journals Confined flow of suspensions modelled by a frictional rheology

2014 ◽  
Vol 759 ◽  
pp. 197-235 ◽  
Author(s):  
Brice Lecampion ◽  
Dmitry I. Garagash
Keyword(s):  
Shear Stress ◽  
Friction Coefficient ◽  
Normal Stress ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Numerical Predictions ◽  
Dry Granular Flow ◽  
Neutrally Buoyant ◽  
Constitutive Parameters ◽  
Axial Development

AbstractWe investigate in detail the problem of confined pressure-driven laminar flow of neutrally buoyant non-Brownian suspensions using a frictional rheology based on the recent proposal of Boyer et al. (Phys. Rev. Lett., vol. 107 (18), 2011, 188301). The friction coefficient (shear stress over particle normal stress) and solid volume fraction are taken as functions of the dimensionless viscous number $I$ defined as the ratio between the fluid shear stress and the particle normal stress. We clarify the contributions of the contact and hydrodynamic interactions on the evolution of the friction coefficient between the dilute and dense regimes reducing the phenomenological constitutive description to three physical parameters. We also propose an extension of this constitutive framework from the flowing regime (bounded by the maximum flowing solid volume fraction) to the fully jammed state (the random close packing limit). We obtain an analytical solution of the fully developed flow in channel and pipe for the frictional suspension rheology. The result can be transposed to dry granular flow upon appropriate redefinition of the dimensionless number $I$. The predictions are in excellent agreement with available experimental results for neutrally buoyant suspensions, when using the values of the constitutive parameters obtained independently from stress-controlled rheological measurements. In particular, the frictional rheology correctly predicts the transition from Poiseuille to plug flow and the associated particles migration with the increase of the entrance solid volume fraction. We also numerically solve for the axial development of the flow from the inlet of the channel/pipe toward the fully developed state. The available experimental data are in good agreement with our numerical predictions, when using an accepted phenomenological description of the relative phase slip obtained independently from batch-settlement experiments. The solution of the axial development of the flow notably provides a quantitative estimation of the entrance length effect in a pipe for suspensions when the continuum assumption is valid. Practically, the latter requires that the predicted width of the central (jammed) plug is wider than one particle diameter. A simple analytical expression for development length, inversely proportional to the gap-averaged diffusivity of a frictional suspension, is shown to encapsulate the numerical solution in the entire range of flow conditions from dilute to dense.

Polyethyene melt-flow examined with time-dependent thermodynamics

2016 ◽  
Vol 49 (3) ◽  
pp. 258-264
Author(s):  
Nobuyuki Nakajima
Keyword(s):  
Shear Stress ◽  
Steady State ◽  
Normal Stress ◽  
Energy Production ◽  
Normal Stress Difference ◽  
Stable Region ◽  
Steady State Flow ◽  
First Normal Stress Difference ◽  
Volume Increase ◽  
State Flow

Time-dependent thermodynamics was applied to steady-state melt flow of polyethylene. The steady-state viscosity behavior and first normal-stress difference were examined as a couple. The latter was a measure of the energy intensity (energy per volume); the time derivative of that was treated as the rate of energy production. In steady-state flow, viscosity decreased and the rate of the energy production increased with increasing shear stress. From the sign of the rate of production, steady flow was found to be in the stable region. The stress growth leading into steady-state flow was known from our previous work to be in the unstable region. This may be called pseudo-stable region. Under a constant rate of shear deformation, both shear stress and viscosity increased rapidly. A change into steady-state flow was interpreted to be the fracture point. The growth of the normal stress was slower than that of shear stress. The first normal-stress difference was a manifestation of deformation, which is a volume increase caused by shear stress. The volume increase led to fracture.

Some Mixed Boundary-Value Problems of the Semi-Infinite Strip

1957 ◽  
Vol 24 (2) ◽  
pp. 261-268
Author(s):  
G. Horvay ◽  
J. S. Born
Keyword(s):  
Shear Stress ◽  
Boundary Value Problems ◽  
Approximate Method ◽  
Normal Stress ◽  
Mixed Boundary ◽  
Boundary Value ◽  
Normal Displacement ◽  
Infinite Strip ◽  
Elastic Strip ◽  
Variational Solutions

Abstract Rigorous and approximate (variational) solutions are given for the semi-infinite elastic strip, traction-free along the long edges, when the short edge is subjected (a) to a quadratic shear displacement, zero normal stress, (b) to a cubic normal displacement, zero shear stress. The approximate method of self-equilibrating functions is extended.

Rotation of the principal stress directions due to earthquake faulting and its seismological implications

1995 ◽  
Vol 85 (5) ◽  
pp. 1513-1517
Author(s):  
Z.-M. Yin ◽  
G. C. Rogers
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Principal Stress ◽  
Stress Drop ◽  
Rotation Angle ◽  
Overburden Pressure ◽  
Rupture Area ◽  
Earthquake Faulting ◽  
Stress Directions ◽  
Before And After

Abstract Earthquake faulting results in stress drop over the rupture area. Because the stress drop is only in the shear stress and there is no or little stress drop in the normal stress on the fault, the principal stress directions must rotate to adapt such a change of the state of stress. Using two constraints, i.e., the normal stress on the fault and the vertical stress (the overburden pressure), which do not change before and after the earthquake, we derive simple expressions for the rotation angle in the σ1 axis. For a dip-slip earthquake, the rotation angle is only a function of the stress-drop ratio (defined as the ratio of the stress drop to the initial shear stress) and the angle between the σ1 axis and the fault plane, but for a strike-slip earthquake the rotation angle is also a function of the stress ratio. Depending on the faulting regimes, the σ1 axis can either rotate toward the direction of fault normal or rotate away from the direction of fault normal. The rotation of the stress field has several important seismological implications. It may play a significant role in the generation of heterogeneous stresses and in the occurrence and distribution of aftershocks. The rotation angle can be used to estimate the stress-drop ratio, which has been a long-lasting topic of debate in seismology.

Sign in / Sign up

Export Citation Format

Share Document