The paper describes results obtained from plate-impact pressure-shear friction experiments to investigate the phenomena of high-speed slip at metal-on-metal interfaces. Using a CH toolsteel/Ti-6Al-4V tribo-pair the authors have studied the effects of normal pressure, slip-speed, temperature and surface roughness on the evolution of the dynamic slip-resistance. Moreover, a finite-element procedu...

Water-hammer is a transient condition which may occur in a network as a result of rapid or slow valve closures, pump failures, changes in turbine loading, etc. It creates high and low pressure waves which travel along the system and decay as a result of wall shear stress. Comparison o experimental and theoretical results revealed the failure of steady or quasi-steady models in correctly predict...

Lubricin (LUB), a major mucinous glycoprotein of mammalian synovial fluids, is believed to provide excellent lubrication to cartilage surfaces. Consequently, when joint disease or replacement leads to increased friction and surface damage in the joint, robust synthetic LUB alternatives that could be used therapeutically to improve lubrication and surface protection are needed. Here, we report t...

A recently proposed nonlocal rheology for dense granular flow, based on the concept of nonlocal granular fluidity, has demonstrated predictive capabilities in multiple geometries. This work is concerned with determining how the parameters of this continuum model arise from the properties of the grains themselves. We perform a controlled study investigating how the surface friction of the grains...

b = a length L c = the cohesion intercept M L T Ip = the plasticity index P = a force M L T u = the pore fluid pressure ML T θ = an angle Angle μ1 = shear strength reduction factor related to time effects μ2 = shear strength reduction factor related to fissuring σ = the normal stress on a plane M L T τ = the shearing stress on a plane M L T φ = the angle of internal friction Angle ψ = an angle ...

The nanotribological responses of a series of nonionic polyoxyethylene surfactants (Tween 20, Tween 40, Tween 60, and Tween 80) were investigated after they were adsorbed from aqueous solution onto atomically smooth hydrophobic substrates. The hydrophobic surfaces were composed of a condensed monolayer of octadecyltriethoxysilane (OTE; contact angle theta>110 degrees ). The nanorheological meas...

frictional shear stress is usually determined by utilizing the coefficient of friction or the constant friction factor models. the present study deals with finite element analysis of double cup extrusion process to determine the relationship between constant friction factor (m) and coefficient of friction (µ), since the metal flow in this process is very sensitive to frictional conditions. ther...

The role of friction in the functional performance of biomaterial interfaces is widely reckoned to be critical and complicated but poorly understood. To better understand friction forces, we investigated the natural adaptation of the holdfast or byssus of mussels that live in high-energy surf habitats. As the outermost covering of the byssus, the cuticle deserves particular attention for its ad...

Model physically associating gels deformed in shear over a wide range of reduced rates displayed evidence of strain localization. The nonlinear stress responses and inhomogeneous velocity profiles observed during shear rheometry coupled with particle tracking velocimetry were associated with the occurrence of rate-dependent banding and fracture-like responses in the gel. Scaling law analysis fr...

We measure the spatial and temporal behavior of the true contact area A along a rough spatially extended interface between two blocks in frictional contact. Upon the application of shear the onset of motion is preceded by a discrete sequence of cracklike precursors, which are initiated at shear levels that are well below the threshold for static friction. These precursors arrest well before tra...