scholarly journals Evolution of Friction and Permeability in a Propped Fracture under Shear

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Fengshou Zhang ◽  
Yi Fang ◽  
Derek Elsworth ◽  
Chaoyi Wang ◽  
Xiaofeng Yang
Keyword(s):  
Normal Stress ◽  
Shear Loading ◽  
Particle Crushing ◽  
Normal Loading ◽  
Fracture Surfaces ◽  
Frictional Strength ◽  
Transport Response ◽  
Shear Slip ◽  
High Normal Stress ◽  
Proppant Embedment

We explore the evolution of friction and permeability of a propped fracture under shear. We examine the effects of normal stress, proppant thickness, proppant size, and fracture wall texture on the frictional and transport response of proppant packs confined between planar fracture surfaces. The proppant-absent and proppant-filled fractures show different frictional strength. For fractures with proppants, the frictional response is mainly controlled by the normal stress and proppant thickness. The depth of shearing-concurrent striations on fracture surfaces suggests that the magnitude of proppant embedment is controlled by the applied normal stress. Under high normal stress, the reduced friction implies that shear slip is more likely to occur on propped fractures in deeper reservoirs. The increase in the number of proppant layers, from monolayer to triple layers, significantly increases the friction of the propped fracture due to the interlocking of the particles and jamming. Permeability of the propped fracture is mainly controlled by the magnitude of the normal stress, the proppant thickness, and the proppant grain size. Permeability of the propped fracture decreases during shearing due to proppant particle crushing and related clogging. Proppants are prone to crushing if the shear loading evolves concurrently with the normal loading.

A Truly Generalized Plane Strain Meshless Model for Combined Normal and Shear Loading of Fiber Reinforced Materials

2010 ◽  
Author(s):  
Eisa Ahmadi ◽  
M. M. Aghdam
Keyword(s):  
Direct Method ◽  
Micromechanical Model ◽  
Computation Time ◽  
Integral Form ◽  
Shear Loading ◽  
Interface Condition ◽  
Fiber Reinforced ◽  
Equilibrium Equations ◽  
Normal Loading ◽  
Fiber Reinforced Materials

A truly meshless method based on the integral form of equilibrium equations is formulated. A micromechanical model is developed to study micro-stresses in normal and shear loading of unidirectional fiber reinforced composites. A small repeating area of composite including a fiber surrounded by matrix called representative volume element (RVE) is considered as solution domain. A direct method is proposed for enforcement of the appropriate periodic boundary conditions for shear and normal loading. Especially transverse shear loading is considered in this analysis. Fully bonded interface condition is investigated and the continuity of displacements and traction is imposed to the fiber-matrix interface. Comparison of the predicted results shows excellent agreement with results in available literature. Results of this study also revealed that the presented model can provide highly accurate predictions with respectively small number of nodes and small computation time without the complexity of mesh generation.

scholarly journals Effect of Twin Boundary Motion and Dislocation-Twin Interaction on Mechanical Behavior in Fcc Metals

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2238
Author(s):  
Jaber Rezaei Mianroodi ◽  
Bob Svendsen
Keyword(s):  
Twin Boundary ◽  
Partial Dislocation ◽  
Shear Loading ◽  
Dislocation Nucleation ◽  
The Other ◽  
Boundary Motion ◽  
Normal Loading ◽  
Fcc Metals ◽  
Boundary Orientation ◽  
Normal Twin

The interplay of interface and bulk dislocation nucleation and glide in determining the motion of twin boundaries, slip-twin interaction, and the mechanical (i.e., stress-strain) behavior of fcc metals is investigated in the current work with the help of molecular dynamics simulations. To this end, simulation cells containing twin boundaries are subject to loading in different directions relative to the twin boundary orientation. In particular, shear loading of the twin boundary results in significantly different behavior than in the other loading cases, and in particular to jerky stress flow. For example, twin boundary shear loading along ⟨ 112 ⟩ results in translational normal twin boundary motion, twinning or detwinning, and net hardening. On the other hand, such loading along ⟨ 110 ⟩ results in oscillatory normal twin boundary motion and no hardening. As shown here, this difference results from the different effect each type of loading has on lattice stacking order perpendicular to the twin boundary, and so on interface partial dislocation nucleation. In both cases, however, the observed stress fluctuation and “jerky flow” is due to fast partial dislocation nucleation and glide on the twin boundary. This is supported by the determination of the velocity and energy barriers to glide for twin boundary partials. In particular, twin boundary partial edge dislocations are significantly faster than corresponding screws as well as their bulk counterparts. In the last part of the work, the effect of variable twin boundary orientation in relation to the loading direction is investigated. In particular, a change away from pure normal loading to the twin plane toward mixed shear-normal loading results in a transition of dominant deformation mechanism from bulk dislocation nucleation/slip, to twin boundary motion.

Plasticity in the Thickness Direction of Paperboard Under Combined Shear and Normal Loading

2001 ◽  
Vol 123 (2) ◽  
pp. 184-190 ◽  
Author(s):  
N. Stenberg ◽  
C. Fellers ◽  
S. O¨stlund
Keyword(s):  
Mechanical Behavior ◽  
Test Piece ◽  
Yield Function ◽  
Shear Loading ◽  
Plastic Behavior ◽  
Thickness Direction ◽  
Initial State ◽  
Normal Loading ◽  
Elastic Plastic ◽  
Out Of Plane

Creasing and offset printing are both examples of paperboard converting operations where the stress state is multiaxial, and where elastic-plastic deformation occurs in the thickness direction. Optimization of paperboard for such operations requires both advanced modeling and a better understanding of the mechanical behavior of the material. Today, our understanding and modeling of the out-of-plane properties are not as well established as our knowledge of the in-plane behavior. In order to bridge this gap, a modification of the Arcan device, which is well known in other fields, was developed for the experimental characterization of the out-of-plane mechanical behavior of paperboard. A fixture attached to the Arcan device was used to control the deformation in the test piece during loading. The test piece was glued to the device with a high viscosity adhesive and left stress-free during curing to achieve an initial state free of stresses. The apparatus proved to work well and to produce reliable results. Measurements of the mechanical behavior in combined normal and shear loading generated data points for the determination of the yield surface in the stress space. The elastic-plastic behavior in the thickness direction of paperboard was modeled assuming small-strain orthotropic linear elasticity and a quadratic yield function. Simulations using this yield function and an associative flow law showed good agreement with the test results.

A new ring-shear device for testing rocks under high normal stress and dynamic conditions

2011 ◽  
Vol 122 (1-2) ◽  
pp. 93-105 ◽  
Author(s):  
Cheng-Jie Liao ◽  
Der-Her Lee ◽  
Jian-Hong Wu ◽  
Chia-Ze Lai
Keyword(s):  
Normal Stress ◽  
Dynamic Conditions ◽  
Ring Shear ◽  
High Normal Stress

scholarly journals An analysis of the factors that control fault zone architecture and the importance of fault orientation relative to regional stress

2020 ◽  
Vol 132 (9-10) ◽  
pp. 2084-2104 ◽  
Author(s):  
John M. Fletcher ◽  
Orlando J. Teran ◽  
Thomas K. Rockwell ◽  
Michael E. Oskin ◽  
Kenneth W. Hudnut ◽  
...  
Keyword(s):  
Normal Stress ◽  
Fault Zone ◽  
High Strain ◽  
Tectonic Setting ◽  
Fault Zones ◽  
Coseismic Slip ◽  
Full Spectrum ◽  
Architectural Styles ◽  
Fault Zone Architecture ◽  
High Normal Stress

Abstract The moment magnitude 7.2 El Mayor–Cucapah (EMC) earthquake of 2010 in northern Baja California, Mexico produced a cascading rupture that propagated through a geometrically diverse network of intersecting faults. These faults have been exhumed from depths of 6–10 km since the late Miocene based on low-temperature thermochronology, synkinematic alteration, and deformational fabrics. Coseismic slip of 1–6 m of the EMC event was accommodated by fault zones that displayed the full spectrum of architectural styles, from simple narrow fault zones (< 100 m in width) that have a single high-strain core, to complex wide fault zones (> 100 m in width) that have multiple anastomosing high-strain cores. As fault zone complexity and width increase the full spectrum of observed widths (20–200 m), coseismic slip becomes more broadly distributed on a greater number of scarps that form wider arrays. Thus, the infinitesimal slip of the surface rupture of a single earthquake strongly replicates many of the fabric elements that were developed during the long-term history of slip on the faults at deeper levels of the seismogenic crust. We find that factors such as protolith, normal stress, and displacement, which control gouge production in laboratory experiments, also affect the architectural complexity of natural faults. Fault zones developed in phyllosilicate-rich metasedimentary gneiss are generally wider and more complex than those developed in quartzo-feldspathic granitoid rocks. We hypothesize that the overall weakness and low strength contrast of faults developed in phyllosilicate rich host rocks leads to strain hardening and formation of broad, multi-stranded fault zones. Fault orientation also strongly affects fault zone complexity, which we find to increase with decreasing fault dip. We attribute this to the higher resolved normal stresses on gently dipping faults assuming a uniform stress field compatible with this extensional tectonic setting. The conditions that permit slip on misoriented surfaces with high normal stress should also produce failure of more optimally oriented slip systems in the fault zone, promoting complex branching and development of multiple high-strain cores. Overall, we find that fault zone architecture need not be strongly affected by differences in the amount of cumulative slip and instead is more strongly controlled by protolith and relative normal stress.

Pullout Test Research on Interfacial Interaction of Reinforced Band and Gravelly Soil

2014 ◽  
Vol 580-583 ◽  
pp. 684-688
Author(s):  
Yan Li Wang ◽  
Zhan Lin Cheng ◽  
Wei Zhang ◽  
Yong Zhen Zuo ◽  
Zhen Lin Yu ◽  
...  
Keyword(s):  
Water Content ◽  
Normal Stress ◽  
Displacement Curve ◽  
Interface Friction ◽  
Plastic Composite ◽  
Frictional Strength ◽  
Gradual Process ◽  
Gravelly Soil ◽  
Pulling Force ◽  
Force Displacement

Taking steel-plastic composite reinforced band (CAT) and gravelly soil as the test materials, the pullout tests of reinforced band in gravelly soil with different water contents have been carried out by the laminated shear test instrument. The interface friction characteristics between reinforced band and gravelly soil are studied, and the influences of water content on the interaction characteristics are also discussed. Results show that (1) the extraction of reinforced band is a gradual process. The anchor end began to move firstly because of the extensibility of reinforced belt itself. As interface friction gradually transfer backward by, the free end start to move onward, then displacement schedule curves of the anchor end and the free end are gradually parallel, the whole movement of reinforced belt happens immediately. (2) Pulling force and displacement curve of the pullout friction test displays obviously nonlinear characteristics. Pulling force of the reinforced band increases greatly with increasing displacement at the beginning of the test, then decrease with the increasing displacement after the peak value is reached, the force-displacement curves generally exhibit strain soften characteristics. But it present strain hardening trend under greater normal stress, and pullout frictional strength increases with the increasing normal stress. (3) The pullout friction coefficient of the interface is sensitive to water content. It decreases linearly with the increasing water content.

Direct Measurement of the Contact Normal Stress Distribution between Two Smooth Joint Surfaces

2014 ◽  
Vol 638-640 ◽  
pp. 427-432
Author(s):  
Zon Yee Yang ◽  
Wei Chieh Chiu
Keyword(s):  
Shear Strength ◽  
Stress Distribution ◽  
Normal Stress ◽  
Contact Stress ◽  
Rock Joints ◽  
Wall Material ◽  
Normal Stress Distribution ◽  
Joint Surfaces ◽  
High Normal Stress ◽  
Distribution Behavior

The shear strength of rock joints is highly depended upon the failure mode of joint asperity. At lower normal stress slide-up of one asperity up over another mode, however at high normal stress the joint asperities are sheared off at the base. This research uses pressure measurement film to directly measure the contact normal stress between smooth joint surfaces. It demonstrates that the density of color impression is capable of capturing the normal stress distribution behavior. The contact normal stress distribution during shearing is changed. After shearing, the contact stress becomes large. This increase in contact normal stress is to fracture the joint wall material.

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