Computational and Experimental Studies of Flexible Fiber Flows in a Normal-Stress-Fixed Shear Cell

AIChE Journal ◽  
2018 ◽  
Vol 65 (1) ◽  
pp. 64-74 ◽  
Author(s):  
Y. Guo ◽  
K. Buettner ◽  
V. Lane ◽  
C. Wassgren ◽  
W. Ketterhagen ◽  
...  
Keyword(s):  
Normal Stress ◽  
Experimental Studies ◽  
Shear Cell ◽  
Flexible Fiber

An Experimental Study of the Rapid Flow of Dry Cohesionless Metal Powders

1986 ◽  
Vol 53 (4) ◽  
pp. 935-942 ◽  
Author(s):  
K. Craig ◽  
R. H. Buckholz ◽  
G. Domoto
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Normal Stress ◽  
Experimental Studies ◽  
Metal Powders ◽  
Shear Surface ◽  
Shear Cell ◽  
Rapid Flow ◽  
Cell Test ◽  
Solids Content

This paper studies the rapid shearing flow of dry metal powders. To perform this study, we built and used an annular shear cell test apparatus. In this apparatus the dry metal powders are rapidly sheared by rotating one of the shear surfaces while the other shear surface remains fixed. The shear stress and normal stress on the stationary surface were measured as a function of three parameters: the shear-cell gap thickness, the shear-rate and the fractional solids content. Stresses are measured while holding both the fractional-solids content and the gap thickness at prescribed values. The results show the dependence of the normal stress and the shear stress on the shear-rate. Likewise, a significant stress dependence on both the fractional solids content and the shear-cell gap thickness was observed. Our experimental results are compared with the results of other reported experimental studies.

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.

Experimental Studies on Mechanical Properties of Rock Joints under Dynamic Loading

2006 ◽  
Vol 326-328 ◽  
pp. 1709-1712 ◽  
Author(s):  
Hai Bo Li ◽  
Hai Peng Feng ◽  
Bo Liu ◽  
Jun Ru Li
Keyword(s):  
Mechanical Properties ◽  
Normal Stress ◽  
Rock Joint ◽  
Experimental Studies ◽  
Shear Stiffness ◽  
Shear Velocity ◽  
Rock Joints ◽  
Normal Stresses ◽  
Deformation Properties ◽  
Strength And Deformation

In order to study the strength and deformation properties of rock joint under different shear velocities, normal stresses and undulation angles, series testes are conducted by a RMT-150C testing machines with artificial concrete rock joint samples in the present paper. Base on the experimental results, it can be found that the peak shear strengths decrease with the increment of shear velocity, and the decreasing rates tend to decrease with the increasing shear velocity. The shear strength of rock joints increase with the increasing undulation angles, and linearly increase with the increment of normal stress. It is also indicated that the shear stiffness increase with the increasing normal stress, undulation angle as well as the shear velocity with a decreasing tendency.

Laboratory Observations of Fault Strength in Response to Changes in Normal Stress

2012 ◽  
Vol 79 (3) ◽  
Author(s):  
Brian Kilgore ◽  
Julian Lozos ◽  
Nick Beeler ◽  
David Oglesby
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Shock Loading ◽  
Experimental Studies ◽  
Earthquake Hazard ◽  
Direct Shear ◽  
Earthquake Simulation ◽  
Sliding Surfaces ◽  
Simulation Techniques ◽  
Fault Strength

Changes in fault normal stress can either inhibit or promote rupture propagation, depending on the fault geometry and on how fault shear strength varies in response to the normal stress change. A better understanding of this dependence will lead to improved earthquake simulation techniques, and ultimately, improved earthquake hazard mitigation efforts. We present the results of new laboratory experiments investigating the effects of step changes in fault normal stress on the fault shear strength during sliding, using bare Westerly granite samples, with roughened sliding surfaces, in a double direct shear apparatus. Previous experimental studies examining the shear strength following a step change in the normal stress produce contradictory results: a set of double direct shear experiments indicates that the shear strength of a fault responds immediately, and then is followed by a prolonged slip-dependent response, while a set of shock loading experiments indicates that there is no immediate component, and the response is purely gradual and slip-dependent. In our new, high-resolution experiments, we observe that the acoustic transmissivity and dilatancy of simulated faults in our tests respond immediately to changes in the normal stress, consistent with the interpretations of previous investigations, and verify an immediate increase in the area of contact between the roughened sliding surfaces as normal stress increases. However, the shear strength of the fault does not immediately increase, indicating that the new area of contact between the rough fault surfaces does not appear preloaded with any shear resistance or strength. Additional slip is required for the fault to achieve a new shear strength appropriate for its new loading conditions, consistent with previous observations made during shock loading.

Particle Flow Behavior in a Shear Cell Device

2011 ◽  
Author(s):  
Adam Rosenkrantz ◽  
John Tichy
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Film Thickness ◽  
Normal Stress ◽  
Small Scale ◽  
Ongoing Research ◽  
Shear Cell ◽  
Discrete Particle ◽  
Frictional Shear Stress ◽  
Load Carrying

This presentation describes ongoing research performed on a simple shear cell apparatus, previously described [1]. As a complement, discrete particle simulations and continuum models have been used to predict normal and shear forces in the ongoing experiments. The trends and orders-of-magnitude of the models and experiment are in basic agreement. Theoretical models used are constructed with basic principles, rather than curve fitting, to obtain effective properties of the mixture such as viscosity or conductivity. The experiment itself serves to determine the effects of shear rate, packing fraction, particle size and film thickness on the load carrying normal stress. Additionally, the frictional shear stress can be investigated. The working particulate medium within the apparatus consists of glass of aluminum spheres, poly-dispersed over four size increments, all less than 1.00 mm diameter. The upper annular disk is held stationary in a rotational sense by a force transducer, and applies predetermined normal stress values which vary according to a system of interchangeable counterweights. The lower transfer surface and the sidewalls of the annular ring are rotated by applied mechanical torque. Experimental trials consist of shear initiation, after which the trough velocity, film thickness, supporting load, and frictional torque are measured. From these measurements one can calculate the average shear rate, the average load-carrying normal stress, the average frictional shear stress, and the solids volume fraction. Such third body granular flow may apply to some solid lubrication mechanisms, and to applications such as smart clutches and dampers. The continuum theory presented is unique in that it addresses solid-like behavior and its transition to fluidized behavior. The discrete particle dynamics rely on the conceptual models of Iordanoff and colleagues [2]. Our findings are that the two theoretical predictions agree reasonably with the experimental results, suggesting validity of the approach. These results are promising, and may be used to further develop high level predictive models. Furthermore, similar methods of small scale experimental particle simulation can be used to develop simpler more usable continuum approaches.

Discussions of Tire Ground Pressure Distribution Model

2011 ◽  
Vol 243-249 ◽  
pp. 4356-4359 ◽  
Author(s):  
Yan Ru Li
Keyword(s):  
Pressure Distribution ◽  
Normal Stress ◽  
Experimental Studies ◽  
Distribution Model ◽  
Mathematics Model ◽  
Tire Pressure ◽  
Distribution Models ◽  
Ground Pressure ◽  
The Law

Though there have been some experimental studies to discuss laws of grounding shape and grounding pressure, the acknowledged mathematics model has not established. In order to discuss the law of tire ground pressure distribution, pressure distribution models of round rectangles grounding shape and ellipse grounding shape are advanced differently. Parameters setting method and 3-D graph of different ground pressure distribution are presented, and expressions of ground area, mean ground pressure, most ground pressure and the normal stress on the ground are deduced. Results show that the grounding shape of tire is close to ellipse or rectangle as load varying, and the distribution of grounding pressure express convex or concave under different tire pressure and loading.

3-D reconstruction and analysis of mammalian mitotic spindle structure

1992 ◽  
Vol 50 (1) ◽  
pp. 578-579
Author(s):  
Kent McDonald ◽  
David Mastronarde ◽  
Rubai Ding ◽  
Eileen O'Toole ◽  
J. Richard McIntosh
Keyword(s):  
Cross Sections ◽  
Mitotic Spindle ◽  
Experimental Studies ◽  
Video Camera ◽  
Three Dimensions ◽  
Mitotic Spindles ◽  
Black And White ◽  
Reconstruction Methods ◽  
Spindle Structure ◽  
Tissue Culture Line

Mammalian spindles are generally large and may contain over a thousand microtubules (MTs). For this reason they are difficult to reconstruct in three dimensions and many researchers have chosen to study the smaller and simpler spindles of lower eukaryotes. Nevertheless, the mammalian spindle is used for many experimental studies and it would be useful to know its detailed structure.We have been using serial cross sections and computer reconstruction methods to analyze MT distributions in mitotic spindles of PtK cells, a mammalian tissue culture line. Images from EM negatives are digtized on a light box by a Dage MTI video camera containing a black and white Saticon tube. The signal is digitized by a Parallax 1280 graphics device in a MicroVax III computer. Microtubules are digitized at a magnification such that each is 10-12 pixels in diameter.

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