Search results for "shear"
showing 10 items of 804 documents
Toward more realistic viscosity measurements of tyre rubber–bitumen blends
2014
AbstractThe measurement of rheological properties of the tyre rubber bitumen blends is often challenging due to presence of suspended tyre rubber’s crumbs. Furthermore, the phase separation during the course of measurements makes the viscosity of these non-homogeneous blends difficult to ascertain. In this study, a new dual helical impeller was designed and manufactured to be used with a rotational viscometer in order to have a real-time control of the viscosity while performing a laboratory mixing of the blends. Layer based manufacturing techniques showed to be a convenient method to produce complex shaped impeller prototypes before manufacturing the more expensive stainless steel assembly…
Rheological and Flocculation Analysis of Microfibrillated Cellulose Suspension Using Optical Coherence Tomography
2018
A sub-micron resolution optical coherence tomography device was used together with a pipe rheometer to analyze the rheology and flocculation dynamics of a 0.5% microfibrillated cellulose (MFC) suspension. The bulk behavior of the MFC suspension showed typical shear thinning (power-law) behavior. This was reflected in a monotonously decreasing floc size when the shear stress exceeded the yield stress of the suspension. The quantitative viscous behavior of the MFC suspension changed abruptly at the wall shear stress of 10 Pa, which was reflected in a simultaneous abrupt drop of the floc size. The flocs were strongly elongated with low shear stresses. With the highest shear stresses, the flocs…
Predicting the equilibrium bed slope in natural streams using a stochastic model for incipient sediment motion
2011
In this paper, a method to predict the equilibrium bed slope in natural streams based on the incipient motion criterion is proposed. The method is based on the criterion suggested by Gessler to simulate the grain size distribution of the armour coat using the concept of critical shear stress of a sediment mixture. In particular, a different expression of the probability for a single particle size to be part of the armour coat is firstly proposed; then, a simple two-steps criterion is suggested to estimate the safety factor required by the proposed approach. The method is applied in three different Italian regions (Calabria, Basilicata, and Tuscany) and required several field campaigns invol…
CVBEM for solving De Saint-Venant solid under shear forces
2013
Abstract Evaluation of shear stresses distribution due to external shear forces applied to De Saint-Venant beams has been solved through Complex Variable Boundary Element Method properly extended, to benefit from advantages of this method, so far widely used for twisted solids. Extending the above method, further simplifications have been introduced such as those of performing line integrals only, instead of domain integrals. Numerical applications confirm accuracy and efficiency of the proposed extended version of the method, since the good agreement with results proposed in literature.
Bank Erosion and Secondary Circulation in a Meandering Laboratory Flume
2014
Abstract This paper reports peculiar results of experimental investigation on the secondary circulation motion of flow along a meander wave. Experiments were conducted in a large amplitude meandering laboratory channel for two values of the width-to-depth ratio. Here attention is focalized on how secondary motion affects the bank shear stress distribution, influencing the stability of the outer bank. The analysis essentially highlights that, especially for small width-to-depth ratio, as the channel curvature increases, besides the classical central-region secondary circulation cell a counter-rotating circulation cell forms in the outer-bank region. Such counter-rotating circulation cell all…
Seismic properties across an amphibolite- to greenschist-facies strain gradient (Neves area, eastern Alps, Italy): New considerations for shear zone …
2021
Abstract Detecting the presence and geometry of crustal shear zones by geophysical methods relies on our understanding of the intrinsic parameters controlling the seismic properties of these deformed rocks, over the range of pressure-temperature conditions expected in the Earth's crust. To this end, we aimed to track changes in P-wave propagation velocity (VP), anisotropy (AVP) and S-wave splitting (AVS) across a natural shear zone using experimental and electron backscatter diffraction methods. Five samples were collected across a meter-scale shear zone developed under amphibolite- to greenschist-facies in the Neves metagranodiorite (Tauern Window, Eastern Alps). With increasing strain, se…
Seismic anisotropy and its impact on imaging the shallow Alpine Fault : an experimental and modeling perspective.
2020
The transpressional Alpine Fault in New Zealand has created a thick shear zone with associated highly anisotropic rocks. Low seismic velocity zones (LVZ) and high seismic reflectivity are recorded in the Alpine Fault Zone, but no study has explored the underlying physical rock parameters of the shallow crust that control these observations. Protomylonites are the volumetrically dominant lithology of the fault zone. Here we combine experimental measurements of P‐wave speeds with numerical models of elastic wave anisotropy of protomylonite samples to explore how the fault zone can be seismically imaged. Numerical models that account for the porosity‐free real samples' fabric elastic tensors f…
Mapping in Gneiss Terrains
1990
Whatever the purpose of working in gneiss terrains, a prerequisite for success is a thorough understanding of the geometry and relative age relations of rock units and the sequence of deformation and metamorphism. Because of the three-dimensional complexity of deformation and intrusion relations in gneiss terrains, it is in most cases impossible to understand relations by visiting a single outcrop, or even by means of a small number of transects through the area under consideration. If no detailed geological maps are present, or if the subject of study is insufficiently dealt with on available maps, it will be necessary to map an area in some detail.
A single-domain Ritz approach for buckling and post-buckling analysis of cracked plates
2019
Abstract A Ritz approach for the analysis of buckling and post-buckling of plates with through-the-thickness cracks is presented. The plate behavior is described by the first order shear deformation theory and von Karman’s geometric nonlinearity. The admissible functions used in the displacements approximation are series of regular orthogonal polynomial supplemented with special functions able to decribe the dicontinuity across the crack and the singularity at the crack tips; boundary functions are used to fullfill the homogeneous essential boundary conditions. Convergence studies and analysis results are presented for buckling and post-buckling of plates with a central through-the-thicknes…
Systems for evaluating the correlation between soil cone penetrometer resistance and shear strength
2008
The aim of this research is to study possible correlations between soil compaction (and related soil cone penetrometer resistance measurements) and shear strength normal to the field plane, required to cut the soil with a subsoiler. A measurement system for sensing the soil cone penetrometer resistance was built mounting, on a frame fixed to the front part of a tractor, a rod and a penetration cone with a load cell. A load cell, mounted on the tractor drawbar, pulling a subsoiler, allowed to measure the shear strength normal to the field plane, required to cut the soil. Both load cells were connected, through a display, to a portable computer, where a software was used for acquiring the dat…