Right-lateral shear and rotation as the explanation for strike-slip faulting in eastern Tibet
England, Philip; Molnar, Peter
1990-01-01
Bounds are placed here on the rate of rotation proposed by Cobbold and Davy (1988) for the major strike-slip faults in the eastern Tibetan Plateau. It is also concluded here that the image of lateral transport on such faults, known also as continental escape, extrusion, or expulsion, is an illusion, and that instead the left-lateral slip on east-striking plates in eastern Tibet is a manifestation of north-striking right-lateral simple shear. If this conclusion is correct, the east-striking left-lateral faults and the crustal blocks between them are rotating clockwise at 1-2 deg/Myr, the east-west dimension of eastern Tibet is shortening at 10-20 mm/yr, and little material is moving eastward out of India's path into Eursasia by left-lateral simple shear.
Falling balls and simple shearing strain
International Nuclear Information System (INIS)
Brun, J L; Pacheco, A F
2006-01-01
The problem of particles falling under gravity allows us to relate Hamiltonian mechanics to such different subjects as elasticity and fluid mechanics. It is with this in mind that mechanics gives us the opportunity of introducing, in a rather simple and unusual form, some concepts such as vorticity, the incompressibility condition or simple shear strain to physics students at the undergraduate level
Study on shear properties of coral sand under cyclic simple shear condition
Ji, Wendong; Zhang, Yuting; Jin, Yafei
2018-05-01
In recent years, the ocean development in our country urgently needs to be accelerated. The construction of artificial coral reefs has become an important development direction. In this paper, experimental studies of simple shear and cyclic simple shear of coral sand are carried out, and the shear properties and particle breakage of coral sand are analyzed. The results show that the coral sand samples show an overall shear failure in the simple shear test, which is more accurate and effective for studying the particle breakage. The shear displacement corresponding to the peak shear stress of the simple shear test is significantly larger than that corresponding to the peak shear stress of the direct shear test. The degree of particle breakage caused by the simple shear test is significantly related to the normal stress level. The particle breakage of coral sand after the cyclic simple shear test obviously increases compared with that of the simple shear test, and universal particle breakage occurs within the whole particle size range. The increasing of the cycle-index under cyclic simple shear test results in continuous compacting of the sample, so that the envelope curve of peak shearing force increases with the accumulated shear displacement.
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Choi, Se Bin; Lee, Joon Sang [Dept. of Mechanical Engineering, Yonsei Unversity, Seoul (Korea, Republic of)
2015-08-15
We simulate an emulsion system under simple shear rates to analyze its rheological characteristics using the lattice Boltzmann method (LBM). We calculate the relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, and surfactant concentration. The relative viscosity of emulsions decreased with an increase in temperature. We observed the shear-thinning phenomena, which is responsible for the inverse proportion between the shear rate and viscosity. An increase in the interfacial tension caused a decrease in the relative viscosity of the decane-in-water emulsion because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.
Comparison of direct shear and simple shear responses of municipal solid waste in USA
Fei, Xunchang; Zekkos, Dimitrios
2017-01-01
Although large-size simple shear (SS) testing of municipal solid waste (MSW) may arguably provide a more realistic estimate of the shear strength (τ ) of MSW than the most commonly used direct shear (DS) testing, a systematic comparison between
Langenheim, Victoria; Jachens, Robert C.; Clynne, Michael A.; Muffler, L. J. Patrick
2016-01-01
Interpretation of magnetic and new gravity data provides constraints on the geometry of the Hat Creek Fault, the amount of right-lateral offset in the area between Mt. Shasta and Lassen Peak, and confirmation of the influence of pre-existing structure on Quaternary faulting. Neogene volcanic rocks coincide with short-wavelength magnetic anomalies of both normal and reversed polarity, whereas a markedly smoother magnetic field occurs over the Klamath Mountains and its Paleogene cover. Although the magnetic field over the Neogene volcanic rocks is complex, the Hat Creek Fault, which is one of the most prominent normal faults in the region and forms the eastern margin of the Hat Creek Valley, is marked by the eastern edge of a north-trending magnetic and gravity high 20-30 km long. Modeling of these anomalies indicates that the fault is a steeply dipping (~75-85°) structure. The spatial relationship of the fault as modeled by the potential-field data, the youngest strand of the fault, and relocated seismicity suggests that deformation continues to step westward across the valley, consistent with a component of right-lateral slip in an extensional environment. Filtered aeromagnetic data highlight a concealed magnetic body of Mesozoic or older age north of Hat Creek Valley. The body’s northwest margin strikes northeast and is linear over a distance of ~40 km. Within the resolution of the aeromagnetic data (1-2 km), we discern no right-lateral offset of this body. Furthermore, Quaternary faults change strike or appear to end, as if to avoid this concealed magnetic body and to pass along its southeast edge, suggesting that pre-existing crustal structure influenced younger faulting, as previously proposed based on gravity data.
Micromechanics of soil responses in cyclic simple shear tests
Directory of Open Access Journals (Sweden)
Cui Liang
2017-01-01
Full Text Available Offshore wind turbine (OWT foundations are subjected to a combination of cyclic and dynamic loading arising from wind, wave, rotor and blade shadowing. Under cyclic loading, most soils change their characteristics including stiffness, which may cause the system natural frequency to approach the loading frequency and lead to unplanned resonance and system damage or even collapse. To investigate such changes and the underlying micromechanics, a series of cyclic simple shear tests were performed on the RedHill 110 sand with different shear strain amplitudes, vertical stresses and initial relative densities of soil. The test results showed that: (a Vertical accumulated strain is proportional to the shear strain amplitude but inversely proportional to relative density of soil; (b Shear modulus increases rapidly in the initial loading cycles and then the rate of increase diminishes and the shear modulus remains below an asymptote; (c Shear modulus increases with increasing vertical stress and relative density, but decreasing with increasing strain amplitude. Coupled DEM simulations were performed using PFC2D to analyse the micromechanics underlying the cyclic behaviour of soils. Micromechanical parameters (e.g. fabric tensor, coordination number were examined to explore the reasons for the various cyclic responses to different shear strain amplitudes or vertical stresses. Both coordination number and magnitude of fabric anisotropy contribute to the increasing shear modulus.
Comparison of direct shear and simple shear responses of municipal solid waste in USA
Fei, Xunchang
2017-10-25
Although large-size simple shear (SS) testing of municipal solid waste (MSW) may arguably provide a more realistic estimate of the shear strength (τ ) of MSW than the most commonly used direct shear (DS) testing, a systematic comparison between the shear responses of MSW obtained from the two testing methods is lacking. In this study, a large-size shear device was used to test identical MSW specimens sampled in USA in DS and SS. Eight DS tests and 11 SS tests were conducted at vertical effective stresses of 50–500 kPa. The stress–displacement response of MSW in SS testing was hyperbolic and a maximum shear stress was reached, whereas a maximum shear stress was not reached in most DS tests. The τ, effective friction angle (ϕ ′) and cohesion (c ′) of MSW were obtained from DS and SS tests by using a displacement failure criterion of 40 mm. τ in SS testing was found to be equal to or lower than τ in DS testing with ratios of τ between 73 and 101%. SS testing resulted in higher ϕ ′ but lower c ′ than DS testing. The shear strength parameters were lower than those obtained in previous studies from DS tests at 55 mm displacement.
A simple shear limited, single size, time dependent flocculation model
Kuprenas, R.; Tran, D. A.; Strom, K.
2017-12-01
This research focuses on the modeling of flocculation of cohesive sediment due to turbulent shear, specifically, investigating the dependency of flocculation on the concentration of cohesive sediment. Flocculation is important in larger sediment transport models as cohesive particles can create aggregates which are orders of magnitude larger than their unflocculated state. As the settling velocity of each particle is determined by the sediment size, density, and shape, accounting for this aggregation is important in determining where the sediment is deposited. This study provides a new formulation for flocculation of cohesive sediment by modifying the Winterwerp (1998) flocculation model (W98) so that it limits floc size to that of the Kolmogorov micro length scale. The W98 model is a simple approach that calculates the average floc size as a function of time. Because of its simplicity, the W98 model is ideal for implementing into larger sediment transport models; however, the model tends to over predict the dependency of the floc size on concentration. It was found that the modification of the coefficients within the original model did not allow for the model to capture the dependency on concentration. Therefore, a new term within the breakup kernel of the W98 formulation was added. The new formulation results is a single size, shear limited, and time dependent flocculation model that is able to effectively capture the dependency of the equilibrium size of flocs on both suspended sediment concentration and the time to equilibrium. The overall behavior of the new model is explored and showed align well with other studies on flocculation. Winterwerp, J. C. (1998). A simple model for turbulence induced flocculation of cohesive sediment. .Journal of Hydraulic Research, 36(3):309-326.
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Bagherpour, E., E-mail: e.bagherpour@semnan.ac.ir [Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Department of Mechanical Engineering, Doshisha University, Kyotanabe, Kyoto 610–0394 (Japan); Qods, F., E-mail: qods@semnan.ac.ir [Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Ebrahimi, R., E-mail: ebrahimy@shirazu.ac.ir [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Miyamoto, H., E-mail: hmiyamot@mail.doshisha.ac.jp [Department of Mechanical Engineering, Doshisha University, Kyotanabe, Kyoto 610–0394 (Japan)
2016-06-01
In the present paper the role of shear reversal on microstructure, texture and mechanical properties of pure copper during a single pass of the simple shear extrusion (SSE) process was investigated. For SSE processing an appropriate die with a linear die profile was designed and constructed, which imposes forward shear in the first half and reverse shear in the second half channels. Electron back-scattering diffraction (EBSD), transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) were used to evaluate the microstructure of the deformed samples. The geometrical nature of this process imposes a distribution of strain results in the inhomogeneous microstructure and the hardness throughout the plane perpendicular to the extrusion direction. Strain reversal during the process results in a slight reduction in dislocation density, the hardness and mean disorientation angle of the samples, and an increase in the grain size. After a complete pass of SSE, dislocation density decreased by ~14% if compared to the middle of the process. This suggests that the dislocation annihilation occurred by the reversal of the shear strain. The simple shear textures were formed gradually and the strongest simple shear textures were observed on the middle of the SSE channel. The degree of the simple shear textures decreases with the distance from the middle plane where the shear is reversed, but the simple shear textures are still the major components after exit of the channel. Hardness variation was modeled by contributions from dislocation strengthening and grain boundary strengthening, where dislocation density is approximated by the misorientation angle of LAGBs which are regarded as dislocation cell boundaries. As a result, the hardness can be predicted successfully by the microstructural features, i.e. the low-angle boundaries, the mean misorientation angle and the fraction of high-angle grain boundaries.
A new method to study simple shear processing of wheat gluten-starch mixtures
Peighambardoust, S.H.; Goot, A.J. van der; Hamer, R.J.; Boom, R.M.
2004-01-01
This article introduces a new method that uses a shearing device to study the effect of simple shear on the overall properties of pasta-like products made from commercial wheat gluten-starch (GS) blends. The shear-processed GS samples had a lower cooking loss (CL) and a higher swelling index (SI)
International Nuclear Information System (INIS)
Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo
2013-01-01
In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments
Energy Technology Data Exchange (ETDEWEB)
Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo [Sogang Univ., Seoul (Korea, Republic of)
2013-10-15
In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.
Effect of Asymmetric Rolling on Plastic Anisotropy of Low Carbon Steels during Simple Shear Tests
International Nuclear Information System (INIS)
Gracio, J. J.; Vincze, G.; Panigrahi, B. B.; Kim, H. J.; Barlat, F.; Rauch, E. F.; Yoon, J. W.
2010-01-01
Simple shear tests are performed on low carbon steel pre-deformed in conventional, asymmetric and orthogonal-asymmetric rolling. The simple-shear tests were carried out at 0 deg. , 45 deg. and 135 deg. with respect to the previous rolling direction. For a reduction ratio of 15%, a transient stagnation in the hardening rate is observed at reloading for all changes in strain path. The shear stress level, the hardening rate and extent of the plateau appear to be insensitive to the preliminary applied rolling conditions. After a reduction ratio of 50%, plastic instability was detected at reloading for all the changes of strain path and rolling conditions studied. A specific heat treatment was then designed allowing the material to become ductile after rolling while retaining the fine microstructure and therefore the high strength. Promising results were obtained essentially for 45 deg. shear tests.
Angular velocity of a spheroid log rolling in a simple shear at small Reynolds number
Meibohm, Jan; Candelier, Fabien; Rosen, Tomas; Einarsson, Jonas; Lundell, Fredrik; Mehlig, Bernhard
2016-11-01
We analyse the angular velocity of a small neutrally buoyant spheroid log rolling in a simple shear. When the effect of fluid inertia is negligible the angular velocity ω -> equals half the fluid vorticity. We compute by singular perturbation theory how weak fluid inertia reduces the angular velocity in an unbounded shear, and how this reduction depends upon the shape of the spheroid (on its aspect ratio). In addition we determine the angular velocity by direct numerical simulations. The results are in excellent agreement with the theory at small but not too small values of the shear Reynolds number, for all aspect ratios considered. For the special case of a sphere we find ω / s = - 1 / 2 + 0 . 0540Re 3 / 2 where s is the shear rate and Re is the shear Reynolds number. This result differs from that derived by Lin et al. who obtained a numerical coefficient roughly three times larger.
Direct test of a nonlinear constitutive equation for simple turbulent shear flows using DNS data
Schmitt, François G.
2007-10-01
Several nonlinear constitutive equations have been proposed to overcome the limitations of the linear eddy-viscosity models to describe complex turbulent flows. These nonlinear equations have often been compared to experimental data through the outputs of numerical models. Here we perform a priori analysis of nonlinear eddy-viscosity models using direct numerical simulation (DNS) of simple shear flows. In this paper, the constitutive equation is directly checked using a tensor projection which involves several invariants of the flow. This provides a 3 terms development which is exact for 2D flows, and a best approximation for 3D flows. We provide the quadratic nonlinear constitutive equation for the near-wall region of simple shear flows using DNS data, and estimate their coefficients. We show that these coefficients have several common properties for the different simple shear flow databases considered. We also show that in the central region of pipe flows, where the shear rate is very small, the coefficients of the constitutive equation diverge, indicating the failure of this representation for vanishing shears.
The interaction of two spheres in a simple-shear flow of complex fluids
Firouznia, Mohammadhossein; Metzger, Bloen; Ovarlez, Guillaume; Hormozi, Sarah
2017-11-01
We study the interaction of two small freely-moving spheres in a linear flow field of Newtonian, shear thinning and yield stress fluids. We perform a series of experiments over a range of shear rates as well as different shear histories using an original apparatus and with the aid of conventional rheometry, Particle Image Velocimetry and Particle Tracking Velocimetry. Showing that the non-Newtonian nature of the suspending fluid strongly affects the shape of particle trajectories and the irreversibility. An important point is that non-Newtonian effects can be varied and unusual. Depending on the shear rate, nonideal shear thinning and yield stress suspending fluids might show elasticity that needs to be taken into account. The flow field around one particle is studied in different fluids when subjected to shear. Then using these results to explain the two particle interactions in a simple-shear flow we show how particle-particle contact and non-Newtonian behaviors result in relative trajectories with fore-aft asymmetry. Well-resolved velocity and stress fields around the particles are presented here. Finally, we discuss how the relative particle trajectories may affect the microstructure of complex suspensions and consequently the bulk rheology. NSF (Grant No. CBET-1554044-CAREER).
Light-scattering properties of undiluted human blood subjected to simple shear
Steenbergen, Wiendelt; Kolkman, R.G.M.; de Mul, F.F.M.
1999-01-01
An experimental investigation was performed into the effect of simple shear on the light-scattering properties of undiluted human blood. Undiluted human blood was enclosed between two glass plates with an adjustable separation between 30 and 120 mm and with one plate moving parallel to the other.
Experimental study and FEM simulation of the simple shear test of cylindrical rods
Wirti, Pedro H. B.; Costa, André L. M.; Misiolek, Wojciech Z.; Valberg, Henry S.
2018-05-01
In the presented work an experimental simple shear device for cutting cylindrical rods was used to obtain force-displacement data for a low-carbon steel. In addition, and FEM 3D-simulation was applied to obtain internal shear stress and strain maps for this material. The experimental longitudinal grid patterns and force-displacement curve were compared with numerical simulation results. Many aspects of the elastic and plastic deformations were described. It was found that bending reduces the shear yield stress of the rod material. Shearing starts on top and bottom die-workpiece contact lines evolving in an arc-shaped area. Due to this geometry, stress concentrates on the surface of the rod until the level of damage reaches the critical value and the fracture starts here. The volume of material in the plastic zone subjected to shearing stress has a very complex shape and is function of a dimensionless geometrical parameter. Expressions to calculate the true shear stress τ and strain γ from the experimental force-displacement data were proposed. The equations' constants are determined by fitting the experimental curve with the stress τ and strain γ simulation point tracked data.
Assembly of vorticity-aligned hard-sphere colloidal strings in a simple shear flow
Cheng, X.
2011-12-23
Colloidal suspensions self-assemble into equilibrium structures ranging from face- and body-centered cubic crystals to binary ionic crystals, and even kagome lattices. When driven out of equilibrium by hydrodynamic interactions, even more diverse structures can be accessed. However, mechanisms underlying out-of-equilibrium assembly are much less understood, though such processes are clearly relevant in many natural and industrial systems. Even in the simple case of hard-sphere colloidal particles under shear, there are conflicting predictions about whether particles link up into string-like structures along the shear flow direction. Here, using confocal microscopy, we measure the shear-induced suspension structure. Surprisingly, rather than flow-aligned strings, we observe log-rolling strings of particles normal to the plane of shear. By employing Stokesian dynamics simulations, we address the mechanism leading to this out-of-equilibrium structure and show that it emerges from a delicate balance between hydrodynamic and interparticle interactions. These results demonstrate a method for assembling large-scale particle structures using shear flows.
Nested separatrices in simple shear flows: the effect of localized disturbances on stagnation lines
Wilson, M.C.T.; Gaskell, P.H.; Savage, M.D.
2005-01-01
The effects of localized two-dimensional disturbances on the structure of shear flows featuring a stagnation line are investigated. A simple superposition of a planar Couette flow and Moffatt's [J. Fluid Mech. 18, 1--18 (1964)] streamfunction for the decay of a disturbance between infinite stationary parallel plates shows that in general the stagnation line is replaced by a chain of alternating elliptic and hyperbolic stagnation points with a separation equal to 2.78 times the half-gap betwee...
Levels of conflict in reasoning modulate right lateral prefrontal cortex.
Stollstorff, Melanie; Vartanian, Oshin; Goel, Vinod
2012-01-05
Right lateral prefrontal cortex (rlPFC) has previously been implicated in logical reasoning under conditions of conflict. A functional magnetic resonance imaging (fMRI) study was conducted to explore its role in conflict more precisely. Specifically, we distinguished between belief-logic conflict and belief-content conflict, and examined the role of rlPFC under each condition. The results demonstrated that a specific region of rlPFC is consistently activated under both types of conflict. Moreover, the results of a parametric analysis demonstrated that the same region was modulated by the level of conflict contained in reasoning arguments. This supports the idea that this specific region is engaged to resolve conflict, including during deductive reasoning. This article is part of a Special Issue entitled "The Cognitive Neuroscience of Thought". Copyright © 2011 Elsevier B.V. All rights reserved.
Angular velocity of a sphere in a simple shear at small Reynolds number
Meibohm, J.; Candelier, F.; Rosén, T.; Einarsson, J.; Lundell, F.; Mehlig, B.
2016-12-01
We analyze the angular velocity of a small neutrally buoyant spheroid log rolling in a simple shear. When the effect of fluid inertia is negligible the angular velocity ω equals half the fluid vorticity. We compute by singular perturbation theory how weak fluid inertia reduces the angular velocity in an unbounded shear, and how this reduction depends upon the shape of the spheroid (on its aspect ratio). In addition we determine the angular velocity by direct numerical simulations. The results are in excellent agreement with the theory at small but not too small values of the shear Reynolds number Res, for all aspect ratios considered. For the special case of a sphere we find ω /s =-1 /2 +0.0540 Res3 /2 where s is the shear rate. The O (Res3 /2) correction differs from that derived by Lin et al. [J. Fluid Mech. 44, 1 (1970), 10.1017/S0022112070001659], who obtained a numerical coefficient roughly three times larger.
International Nuclear Information System (INIS)
Dirras, G.; Bouvier, S.; Gubicza, J.; Hasni, B.; Szilagyi, T.
2009-01-01
The present work focuses on understanding the mechanical behavior of bulk ultrafine-grained nickel specimens processed by spark plasma sintering of high purity nickel nanopowder and subsequently deformed under large amplitude monotonic simple shear tests and strain-controlled cyclic simple shear tests at room temperature. During cyclic tests, the samples were deformed up to an accumulated von Mises strain of about ε VM = 0.75 (the flow stress was in the 650-700 MPa range), which is extremely high in comparison with the low tensile/compression ductility of this class of materials at quasi-static conditions. The underlying physical mechanisms were investigated by electron microscopy and X-ray diffraction profile analysis. Lattice dislocation-based plasticity leading to cell formation and dislocation interactions with twin boundaries contributed to the work-hardening of these materials. The large amount of plastic strain that has been reached during the shear tests highlights intrinsic mechanical characteristics of the ultrafine-grained nickel studied here.
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Dirras, G., E-mail: dirras@univ-paris13.fr [LPMTM - CNRS, Institut Galilee, Universite Paris 13, 99 Avenue J.B. Clement, 93430 Villetaneuse (France); Bouvier, S. [LPMTM - CNRS, Institut Galilee, Universite Paris 13, 99 Avenue J.B. Clement, 93430 Villetaneuse (France); Gubicza, J. [Department of Materials Physics, Eoetvoes Lorand University, P.O.B. 32, Budapest H-1518 (Hungary); Hasni, B. [LPMTM - CNRS, Institut Galilee, Universite Paris 13, 99 Avenue J.B. Clement, 93430 Villetaneuse (France); Szilagyi, T. [Department of Materials Physics, Eoetvoes Lorand University, P.O.B. 32, Budapest H-1518 (Hungary)
2009-11-25
The present work focuses on understanding the mechanical behavior of bulk ultrafine-grained nickel specimens processed by spark plasma sintering of high purity nickel nanopowder and subsequently deformed under large amplitude monotonic simple shear tests and strain-controlled cyclic simple shear tests at room temperature. During cyclic tests, the samples were deformed up to an accumulated von Mises strain of about {epsilon}{sub VM} = 0.75 (the flow stress was in the 650-700 MPa range), which is extremely high in comparison with the low tensile/compression ductility of this class of materials at quasi-static conditions. The underlying physical mechanisms were investigated by electron microscopy and X-ray diffraction profile analysis. Lattice dislocation-based plasticity leading to cell formation and dislocation interactions with twin boundaries contributed to the work-hardening of these materials. The large amount of plastic strain that has been reached during the shear tests highlights intrinsic mechanical characteristics of the ultrafine-grained nickel studied here.
Bias of shear wave elasticity measurements in thin layer samples and a simple correction strategy.
Mo, Jianqiang; Xu, Hao; Qiang, Bo; Giambini, Hugo; Kinnick, Randall; An, Kai-Nan; Chen, Shigao; Luo, Zongping
2016-01-01
Shear wave elastography (SWE) is an emerging technique for measuring biological tissue stiffness. However, the application of SWE in thin layer tissues is limited by bias due to the influence of geometry on measured shear wave speed. In this study, we investigated the bias of Young's modulus measured by SWE in thin layer gelatin-agar phantoms, and compared the result with finite element method and Lamb wave model simulation. The result indicated that the Young's modulus measured by SWE decreased continuously when the sample thickness decreased, and this effect was more significant for smaller thickness. We proposed a new empirical formula which can conveniently correct the bias without the need of using complicated mathematical modeling. In summary, we confirmed the nonlinear relation between thickness and Young's modulus measured by SWE in thin layer samples, and offered a simple and practical correction strategy which is convenient for clinicians to use.
International Nuclear Information System (INIS)
Aouafi, A.; Bouvier, S.; Gasperini, M.; Lemoine, X.; Bouaziz, O.
2007-01-01
Reverse simple shear tests are used to analyse the Bauschinger effect and the evolution of the kinematic hardening for a wide range of equivalent von Mises strain [0.025 - 0.3]. This work is carried out on two high strength low-alloyed steels. In order to investigate the effect of the precipitates on the macroscopic behaviour, a ferritic mild steel is used as a reference. Different phenomenological descriptions of the back-stress tensor are examined in order to analyse their ability to describe the experimental behaviour
Doubly self-consistent field theory of grafted polymers under simple shear in steady state
International Nuclear Information System (INIS)
Suo, Tongchuan; Whitmore, Mark D.
2014-01-01
We present a generalization of the numerical self-consistent mean-field theory of polymers to the case of grafted polymers under simple shear. The general theoretical framework is presented, and then applied to three different chain models: rods, Gaussian chains, and finitely extensible nonlinear elastic (FENE) chains. The approach is self-consistent at two levels. First, for any flow field, the polymer density profile and effective potential are calculated self-consistently in a manner similar to the usual self-consistent field theory of polymers, except that the calculation is inherently two-dimensional even for a laterally homogeneous system. Second, through the use of a modified Brinkman equation, the flow field and the polymer profile are made self-consistent with respect to each other. For all chain models, we find that reasonable levels of shear cause the chains to tilt, but it has very little effect on the overall thickness of the polymer layer, causing a small decrease for rods, and an increase of no more than a few percent for the Gaussian and FENE chains. Using the FENE model, we also probe the individual bond lengths, bond correlations, and bond angles along the chains, the effects of the shear on them, and the solvent and bonded stress profiles. We find that the approximations needed within the theory for the Brinkman equation affect the bonded stress, but none of the other quantities
Orientational dynamics of a triaxial ellipsoid in simple shear flow: Influence of inertia.
Rosén, Tomas; Kotsubo, Yusuke; Aidun, Cyrus K; Do-Quang, Minh; Lundell, Fredrik
2017-07-01
The motion of a single ellipsoidal particle in simple shear flow can provide valuable insights toward understanding suspension flows with nonspherical particles. Previously, extensive studies have been performed on the ellipsoidal particle with rotational symmetry, a so-called spheroid. The nearly prolate ellipsoid (one major and two minor axes of almost equal size) is known to perform quasiperiodic or even chaotic orbits in the absence of inertia. With small particle inertia, the particle is also known to drift toward this irregular motion. However, it is not previously understood what effects from fluid inertia could be, which is of highest importance for particles close to neutral buoyancy. Here, we find that fluid inertia is acting strongly to suppress the chaotic motion and only very weak fluid inertia is sufficient to stabilize a rotation around the middle axis. The mechanism responsible for this transition is believed to be centrifugal forces acting on fluid, which is dragged along with the rotational motion of the particle. With moderate fluid inertia, it is found that nearly prolate triaxial particles behave similarly to the perfectly spheroidal particles. Finally, we also are able to provide predictions about the stable rotational states for the general triaxial ellipsoid in simple shear with weak inertia.
Assembly of vorticity-aligned hard-sphere colloidal strings in a simple shear flow
Cheng, X.; Xu, X.; Rice, S. A.; Dinner, A. R.; Cohen, I.
2011-01-01
under shear, there are conflicting predictions about whether particles link up into string-like structures along the shear flow direction. Here, using confocal microscopy, we measure the shear-induced suspension structure. Surprisingly, rather than flow
International Nuclear Information System (INIS)
Bagherpour, E.; Qods, F.; Ebrahimi, R.; Miyamoto, H.
2016-01-01
In the present paper commercially pure copper was processed by simple shear extrusion (SSE) technique up to 12 passes using the so-called route C. For SSE processing an appropriate die with a linear die profile was designed and constructed. Effect of SSE passes on isotropy and uniformity of microstructures are focused. Electron back-scattering diffraction (EBSD) was used to evaluate the microstructure of the deformed samples in three orthogonal planes. To investigate the microstructural uniformity EBSD maps were taken from center to periphery of the extrusion direction plane (ED-plane) samples. Significant evolution in grain refinement was achieved down to sub-micron grain size in all planes. Hardness measurements show a considerable increase in hardness of the material after the processing, which confirms the microstructural evolutions. EBSD scans revealed a homogeneous ultrafine grained microstructure after 12 passes. Micro-shear bands were found as potential sites for accelerating the formation of new grains by fragmentation of the initial grains. The total frequency of coincidence site lattice (CSL) boundaries including Σ3 boundaries increased by the increasing of SSE passes. The higher fraction of low to high angle grain boundaries of SSE compared to equal channel angular pressing is an evidence for the cyclic behavior of SSE technique.
Energy Technology Data Exchange (ETDEWEB)
Bagherpour, E., E-mail: e.bagherpour@semnan.ac.ir [Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Department of Mechanical Engineering, Doshisha University, Kyotanabe, Kyoto 610-0394 (Japan); Qods, F., E-mail: qods@semnan.ac.ir [Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Ebrahimi, R., E-mail: ebrahimy@shirazu.ac.ir [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Miyamoto, H., E-mail: hmiyamot@mail.doshisha.ac.jp [Department of Mechanical Engineering, Doshisha University, Kyotanabe, Kyoto 610-0394 (Japan)
2016-09-30
In the present paper commercially pure copper was processed by simple shear extrusion (SSE) technique up to 12 passes using the so-called route C. For SSE processing an appropriate die with a linear die profile was designed and constructed. Effect of SSE passes on isotropy and uniformity of microstructures are focused. Electron back-scattering diffraction (EBSD) was used to evaluate the microstructure of the deformed samples in three orthogonal planes. To investigate the microstructural uniformity EBSD maps were taken from center to periphery of the extrusion direction plane (ED-plane) samples. Significant evolution in grain refinement was achieved down to sub-micron grain size in all planes. Hardness measurements show a considerable increase in hardness of the material after the processing, which confirms the microstructural evolutions. EBSD scans revealed a homogeneous ultrafine grained microstructure after 12 passes. Micro-shear bands were found as potential sites for accelerating the formation of new grains by fragmentation of the initial grains. The total frequency of coincidence site lattice (CSL) boundaries including Σ3 boundaries increased by the increasing of SSE passes. The higher fraction of low to high angle grain boundaries of SSE compared to equal channel angular pressing is an evidence for the cyclic behavior of SSE technique.
Study of Axes Rotation during Simple Shear Tests on Aluminum Sheets
International Nuclear Information System (INIS)
Duchene, L.; Diouf, B.; Lelotte, T.; Flores, P.; Habraken, A. M.; Bouvier, S.
2007-01-01
In order to model accurately the anisotropic material behavior during finite element simulations, a precise description of the material yield locus is required. Beside the shape (linked to the material model used), the size (related to the isotropic hardening) and the position (kinematic hardening) of the yield locus, its orientation is of particular interest when large rotations of the material are encountered during the simulations. This paper proposes three distinct methods for the determination of the material yield locus rotation: a method based on the Constant Symmetric Local Velocity Gradient (CSLVG), a corotational method and a method based on the Mandel spin. These methods are compared during simple shear tests of an aluminum sheet
Direct Simple Shear Test Data Analysis using Jupyter Notebooks on DesignSafe-CI
Eslami, M.; Esteva, M.; Brandenberg, S. J.
2017-12-01
Due to the large number of files and their complex structure, managing data generated during natural hazards experiments requires scalable and specialized tools. DesignSafe-CI (https://www.designsafe-ci.org/) is a web-based research platform that provides computational tools to analyze, curate, and publish critical data for natural hazards research making it understandable and reusable. We present a use case from a series of Direct Simple Shear (DSS) experiments in which we used DS-CI to post-process, visualize, publish, and enable further analysis of the data. Current practice in geotechnical design against earthquakes relies on the soil's plasticity index (PI) to assess liquefaction susceptibility, and cyclic softening triggering procedures, although, quite divergent recommendations on recommended levels of plasticity can be found in the literature for these purposes. A series of cyclic and monotonic direct simple shear experiments was conducted on three low-plasticity fine-grained mixtures at the same plasticity index to examine the effectiveness of the PI in characterization of these types of materials. Results revealed that plasticity index is an insufficient indicator of the cyclic behavior of low-plasticity fine-grained soils, and corrections for pore fluid chemistry and clay minerology may be necessary for future liquefaction susceptibility and cyclic softening assessment procedures. Each monotonic, or cyclic experiment contains two stages; consolidation and shear, which include time series of load, displacement, and corresponding stresses and strains, as well as equivalent excess pore-water pressure. Using the DS-CI curation pipeline we categorized the data to display and describe the experiment's structure and files corresponding to each stage of the experiments. Two separate notebooks in Python 3 were created using the Jupyter application available in DS-CI. A data plotter aids visualizing the experimental data in relation to the sensor from which it was
Ren, Zhiqiang; Harshe, Yogesh M; Lattuada, Marco
2015-06-02
In this work we build on our previous paper (Harshe, Y. M.; Lattuada, M. Langmuir 2012, 28, 283-292) and compute the breakage rate of colloidal aggregates under the effect of shear forces by means of Stokesian dynamics simulations. A library of clusters made of identical spherical particles covering a broad range of masses and fractal dimension values (from 1.8 to 3.0) was generated by means of a combination of several Monte Carlo methods. DLVO theory has been used to describe the interparticle interactions, and contact forces have been introduced by means of the discrete element method. The aggregate breakage process was investigated by exposing them to well-defined shear forces, generated under both simple shear and uniaxial extensional flow conditions, and by recording the time required to reach the first breakage event. It has been found that the breakage rate of clusters was controlled by the potential well between particles as described by DLVO theory. A semiempirical Arrhenius-type exponential equation that relates the potential well to the breakage rate has been used to fit the simulation results. The dependence of the breakage process on the radius of gyration, on the external shear strength, and on the fractal dimension has been obtained, providing a very general relationship for the breakage rate of clusters. It was also found that the fragment mass distribution is insensitive to the presence of electrostatic repulsive interactions. We also clarify the physical reason for the large difference in the breakage rate of clusters between simple shear and the uniaxial extensional flow using a criterion based on the energy dissipation rate. Finally, in order to answer the question of the minimum cluster size that can break under simple shear conditions, a critical rotation number has been introduced, expressing the maximum number of rotations that a cluster exposed to simple shear could sustain before breakage.
Production of structured soy-based meat analogues using simple shear and heat in a Couette Cell
Krintiras, G.A.; Gobel, T.W.; Goot, van der A.J.; Stefanidis, G.D.
2015-01-01
A Couette Cell device was employed to provide proof of concept for the production of structured meat analogues by application of simple shear flow and heat to a 31 wt% Soy Protein Isolate (SPI)–Wheat Gluten (WG) dispersion. Three relevant process parameters (temperature, time and rotation rate) were
Energy Technology Data Exchange (ETDEWEB)
Bagherpour, E., E-mail: e.bagherpour@semnan.ac.ir [Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Department of Mechanical Engineering, Doshisha University, Kyotanabe, Kyoto 610-0394 (Japan); Qods, F., E-mail: qods@semnan.ac.ir [Faculty of Metallurgical and Materials Engineering, Semnan University, Semnan (Iran, Islamic Republic of); Ebrahimi, R., E-mail: ebrahimy@shirazu.ac.ir [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Miyamoto, H., E-mail: hmiyamot@mail.doshisha.ac.jp [Department of Mechanical Engineering, Doshisha University, Kyotanabe, Kyoto 610-0394 (Japan)
2017-01-02
In the present paper the variation of microstructural parameters and tensile properties of ultrafine-grained copper processed by simple shear extrusion (SSE) via namely route C in 1, 2, 4, 6, 8 and 12 passes is described. TEM analysis showed that the microstructure evolves from lamellar boundaries and elongated cells towards a more equiaxed homogeneous microstructure. After 12 passes, the grain fragmentation occurred in all the directions without any significant elongation in the grains. The minimum cell size is achieved after eight passes. Evaluation of dislocation density using scanning transmission electron microscopy observations shows a gradual increase of dislocation from one to eight passes following a reduction afterward. Yield stress and ultimate tensile stress reach a maximum after eight passes. The uniform elongation attains its minimum after eight passes. Reduction in dislocation density, grain growth, formation of Moiré fringes and twinning after twelve passes of SSE are some of the evidences for the softening. The critical grain size for the formation of nano twins (the onset of grain growth) is predicted. Prosperous prediction of yield stress using a strength–structure relationship helps in the understanding of the effect of dislocation density and microstructural observations.
A New Accurate yet Simple Shear Flexible Triangular Plate Element with Linear Bending Strains
DEFF Research Database (Denmark)
Damkilde, Lars; Pedersen, Ronnie
2010-01-01
The paper describes a new shear flexible triangular element. The formulation is based on displacement interpolation of the transverse displacement of the midsurface and the rotations of the cross-sections, and the element is fully compatible. The basic principle is to use a so-called balanced...... interpolation so that the part of the shear strains that relates to the transverse displacement has the same polynomial variation as the part of the shear strains that relates to the rotations of the cross-section. This balanced interpolation in combination with complete polynomial interpolations prevents shear...... are virtually the same. The slightly incompatible formulation can be implemented directly into commercial codes....
Simple shearing flow of dry soap foams with tetrahedrally close-packed structure
Energy Technology Data Exchange (ETDEWEB)
Reinelt, Douglas A. [Department of Mathematics, Southern Methodist University, Dallas, Texas 75275-0156 (United States); Kraynik, Andrew M. [Engineering Sciences Center, Sandia National Laboratories, Albuquerque, New Mexico 87185-0834 (United States)
2000-05-01
The microrheology of dry soap foams subjected to quasistatic, simple shearing flow is analyzed. Two different monodisperse foams with tetrahedrally close-packed (TCP) structure are examined: Weaire-Phelan (A15) and Friauf-Laves (C15). The elastic-plastic response is evaluated by using the Surface Evolver to calculate foam structures that minimize total surface area at each value of strain. The foam geometry and macroscopic stress are piecewise continuous functions of strain. The stress scales as T/V{sup 1/3}, where T is surface tension and V is cell volume. Each discontinuity corresponds to large changes in foam geometry and topology that restore equilibrium to unstable configurations that violate Plateau's laws. The instabilities occur when the length of an edge on a polyhedral foam cell vanishes. The length can tend to zero smoothly or abruptly with strain. The abrupt case occurs when a small increase in strain changes the energy profile in the neighborhood of a foam structure from a local minimum to a saddle point, which can lead to symmetry-breaking bifurcations. In general, the new structure associated with each stable solution branch results from an avalanche of local topology changes called T1 transitions. Each T1 cascade produces different cell neighbors, reduces surface energy, and provides an irreversible, film-level mechanism for plastic yield behavior. Stress-strain curves and average stresses are evaluated by examining foam orientations that admit strain-periodic behavior. For some orientations, the deformation cycle includes Kelvin cells instead of the original TCP structure; but the foam does not remain perfectly ordered. Bifurcations during subsequent T1 cascades lead to disorder and can even cause strain localization. (c) 2000 Society of Rheology.
A calcified epidermoid cyst within right lateral ventricle: A report of a rare case
Ranjan Kumar Sahoo; Debahuti Mohapatra; Pradipta Tripathy
2016-01-01
A young patient reported to neurosurgery outdoor department with symptoms of increased intracranial pressure. Noncontrast computed tomography examination showed a single calcified mass within right lateral ventricle with mild hydrocephalus. Contrast-enhanced magnetic resonance imaging revealed nonenhancing single mass within right lateral ventricle with mild hydrocephalus. Intraventricular calcified choroid papilloma/calcified epidermoid were radiological differentials. The mass was excised, ...
Structural predictor for nonlinear sheared dynamics in simple glass-forming liquids.
Ingebrigtsen, Trond S; Tanaka, Hajime
2018-01-02
Glass-forming liquids subjected to sufficiently strong shear universally exhibit striking nonlinear behavior; for example, a power-law decrease of the viscosity with increasing shear rate. This phenomenon has attracted considerable attention over the years from both fundamental and applicational viewpoints. However, the out-of-equilibrium and nonlinear nature of sheared fluids have made theoretical understanding of this phenomenon very challenging and thus slower to progress. We find here that the structural relaxation time as a function of the two-body excess entropy, calculated for the extensional axis of the shear flow, collapses onto the corresponding equilibrium curve for a wide range of pair potentials ranging from harsh repulsive to soft and finite. This two-body excess entropy collapse provides a powerful approach to predicting the dynamics of nonequilibrium liquids from their equilibrium counterparts. Furthermore, the two-body excess entropy scaling suggests that sheared dynamics is controlled purely by the liquid structure captured in the form of the two-body excess entropy along the extensional direction, shedding light on the perplexing mechanism behind shear thinning.
Structural predictor for nonlinear sheared dynamics in simple glass-forming liquids
Ingebrigtsen, Trond S.; Tanaka, Hajime
2018-01-01
Glass-forming liquids subjected to sufficiently strong shear universally exhibit striking nonlinear behavior; for example, a power-law decrease of the viscosity with increasing shear rate. This phenomenon has attracted considerable attention over the years from both fundamental and applicational viewpoints. However, the out-of-equilibrium and nonlinear nature of sheared fluids have made theoretical understanding of this phenomenon very challenging and thus slower to progress. We find here that the structural relaxation time as a function of the two-body excess entropy, calculated for the extensional axis of the shear flow, collapses onto the corresponding equilibrium curve for a wide range of pair potentials ranging from harsh repulsive to soft and finite. This two-body excess entropy collapse provides a powerful approach to predicting the dynamics of nonequilibrium liquids from their equilibrium counterparts. Furthermore, the two-body excess entropy scaling suggests that sheared dynamics is controlled purely by the liquid structure captured in the form of the two-body excess entropy along the extensional direction, shedding light on the perplexing mechanism behind shear thinning.
Destrade, Michel; Goriely, Alain; Saccomandi, Giuseppe
2011-01-01
We study the propagation of two-dimensional finite-amplitude shear waves in a nonlinear pre-strained incompressible solid, and derive several asymptotic amplitude equations in a simple, consistent, and rigorous manner. The scalar Zabolotskaya (Z) equation is shown to be the asymptotic limit of the equations of motion for all elastic generalized neo-Hookean solids (with strain energy depending only on the first principal invariant of Cauchy-Green strain). However, we show that the Z equation c...
Snijkers, F.; Kirkwood, K. M.; Vlassopoulos, D.; Leal, L. G.; Nikopoulou, A.; Hadjichristidis, Nikolaos; Coppola, S.
2016-01-01
We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.
Snijkers, F.
2016-03-31
We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.
Klein, D. Harley; Leal, L. Gary; García-Cervera, Carlos J.; Ceniceros, Hector D.
2007-02-01
We consider the behavior of the Doi-Marrucci-Greco (DMG) model for nematic liquid crystalline polymers in planar shear flow. We found the DMG model to exhibit dynamics in both qualitative and quantitative agreement with experimental observations reported by Larson and Mead [Liq. Cryst. 15, 151 (1993)] for the Ericksen number and Deborah number cascades. For increasing shear rates within the Ericksen number cascade, the DMG model displays three distinct regimes: stable simple shear, stable roll cells, and irregular structure accompanied by disclination formation. In accordance with experimental observations, the model predicts both ±1 and ±1/2 disclinations. Although ±1 defects form via the ridge-splitting mechanism first identified by Feng, Tao, and Leal [J. Fluid Mech. 449, 179 (2001)], a new mechanism is identified for the formation of ±1/2 defects. Within the Deborah number cascade, with increasing Deborah number, the DMG model exhibits a streamwise banded texture, in the absence of disclinations and roll cells, followed by a monodomain wherein the mean orientation lies within the shear plane throughout the domain.
A calcified epidermoid cyst within right lateral ventricle: A report of a rare case
Directory of Open Access Journals (Sweden)
Ranjan Kumar Sahoo
2016-01-01
Full Text Available A young patient reported to neurosurgery outdoor department with symptoms of increased intracranial pressure. Noncontrast computed tomography examination showed a single calcified mass within right lateral ventricle with mild hydrocephalus. Contrast-enhanced magnetic resonance imaging revealed nonenhancing single mass within right lateral ventricle with mild hydrocephalus. Intraventricular calcified choroid papilloma/calcified epidermoid were radiological differentials. The mass was excised, removed from the lateral ventricles and found to be calcified epidermoid on gross and microscopic examination, which is rare.
Destrade, M.
2010-12-08
We study the propagation of two-dimensional finite-amplitude shear waves in a nonlinear pre-strained incompressible solid, and derive several asymptotic amplitude equations in a simple, consistent and rigorous manner. The scalar Zabolotskaya (Z) equation is shown to be the asymptotic limit of the equations of motion for all elastic generalized neo-Hookean solids (with strain energy depending only on the first principal invariant of Cauchy-Green strain). However, we show that the Z equation cannot be a scalar equation for the propagation of two-dimensional shear waves in general elastic materials (with strain energy depending on the first and second principal invariants of strain). Then, we introduce dispersive and dissipative terms to deduce the scalar Kadomtsev-Petviashvili (KP), Zabolotskaya-Khokhlov (ZK) and Khokhlov- Zabolotskaya-Kuznetsov (KZK) equations of incompressible solid mechanics. © 2010 The Royal Society.
Destrade, M.; Goriely, A.; Saccomandi, G.
2010-01-01
We study the propagation of two-dimensional finite-amplitude shear waves in a nonlinear pre-strained incompressible solid, and derive several asymptotic amplitude equations in a simple, consistent and rigorous manner. The scalar Zabolotskaya (Z) equation is shown to be the asymptotic limit of the equations of motion for all elastic generalized neo-Hookean solids (with strain energy depending only on the first principal invariant of Cauchy-Green strain). However, we show that the Z equation cannot be a scalar equation for the propagation of two-dimensional shear waves in general elastic materials (with strain energy depending on the first and second principal invariants of strain). Then, we introduce dispersive and dissipative terms to deduce the scalar Kadomtsev-Petviashvili (KP), Zabolotskaya-Khokhlov (ZK) and Khokhlov- Zabolotskaya-Kuznetsov (KZK) equations of incompressible solid mechanics. © 2010 The Royal Society.
Kovaleva, Elizaveta; Klötzli, Urs; Wheeler, John; Habler, Gerlinde
2018-02-01
This study documents the strain accommodation mechanisms in zircon under amphibolite-facies metamorphic conditions in simple shear. Microstructural data from undeformed, fractured and crystal-plastically deformed zircon crystals are described in the context of the host shear zone, and evaluated in the light of zircon elastic anisotropy. Our work challenges the existing model of zircon evolution and shows previously undescribed rheological characteristics for this important accessory mineral. Crystal-plastically deformed zircon grains have axis oriented parallel to the foliation plane, with the majority of deformed grains having axis parallel to the lineation. Zircon accommodates strain by a network of stepped low-angle boundaries, formed by switching between tilt dislocations with the slip systems {010} and {110} and rotation axis [001], twist dislocations with the rotation axis [001], and tilt dislocations with the slip system {001} and rotation axis [010]. The slip system {110} is newly described for zircon. Most misorientation axes in plastically-deformed zircon grains are parallel to the XY plane of the sample and have [001] crystallographic direction. Such behaviour of strained zircon lattice is caused by elastic anisotropy that has a direct geometric control on the rheology, deformation mechanisms and dominant slip systems in zircon. Young's modulus and P wave velocity have highest values parallel to zircon [001] axis, indicating that zircon is elastically strong along this direction. Poisson ratio and Shear modulus demonstrate that zircon is also most resistant to shearing along [001]. Thus, [001] axis is the most common rotation axis in zircon. The described zircon behaviour is important to take into account during structural and geochronological investigations of (poly)metamorphic terrains. Geometry of dislocations in zircon may help reconstructing the geometry of the host shear zone(s), large-scale stresses in the crust, and, possibly, the timing of
International Nuclear Information System (INIS)
Krommes, J.A.
1999-01-01
Highly simplified models of random flows interacting with background microturbulence are analyzed. In the limit of very rapid velocity fluctuations, it is shown rigorously that the fluctuation level of a passively advected scalar is not controlled by the rms shear. In a model with random velocities dependent only on time, the level of cross-correlations between the flows and the background turbulence regulates the saturation level. This effect is illustrated by considering a simple stochastic-oscillator model, both exactly and with analysis and numerical solutions of the direct-interaction approximation. Implications for the understanding of self-consistent turbulence are discussed briefly
Non-constant link tension coefficient in the tumbling-snake model subjected to simple shear
Stephanou, Pavlos S.; Kröger, Martin
2017-11-01
The authors of the present study have recently presented evidence that the tumbling-snake model for polymeric systems has the necessary capacity to predict the appearance of pronounced undershoots in the time-dependent shear viscosity as well as an absence of equally pronounced undershoots in the transient two normal stress coefficients. The undershoots were found to appear due to the tumbling behavior of the director u when a rotational Brownian diffusion term is considered within the equation of motion of polymer segments, and a theoretical basis concerning the use of a link tension coefficient given through the nematic order parameter had been provided. The current work elaborates on the quantitative predictions of the tumbling-snake model to demonstrate its capacity to predict undershoots in the time-dependent shear viscosity. These predictions are shown to compare favorably with experimental rheological data for both polymer melts and solutions, help us to clarify the microscopic origin of the observed phenomena, and demonstrate in detail why a constant link tension coefficient has to be abandoned.
Adhesion behavior of endothelial progenitor cells to endothelial cells in simple shear flow
Gong, Xiao-Bo; Li, Yu-Qing; Gao, Quan-Chao; Cheng, Bin-Bin; Shen, Bao-Rong; Yan, Zhi-Qiang; Jiang, Zong-Lai
2011-12-01
The adhesion of endothelial progenitor cells (EPCs) on endothelial cells (ECs) is one of the critical physiological processes for the regenesis of vascular vessels and the prevention of serious cardiovascular diseases. Here, the rolling and adhesion behavior of EPCs on ECs was studied numerically. A two-dimensional numerical model was developed based on the immersed boundary method for simulating the rolling and adhesion of cells in a channel flow. The binding force arising from the catch bond of a receptor and ligand pair was modeled with stochastic Monte Carlo method and Hookean spring model. The effect of tumor necrosis factor alpha (TNF- α) on the expression of the number of adhesion molecules in ECs was analyzed experimentally. A flow chamber system with CCD camera was set up to observe the top view of the rolling of EPCs on the substrate cultivated with ECs. Numerical results prove that the adhesion of EPC on ECs is closely related to membrane stiffness of the cell and shear rate of the flow. It also suggests that the adhesion force between EPC and EC by P-selectin glycoprotein ligand-1 only is not strong enough to bond the cell onto vessel walls unless contributions of other catch bond are considered. Experimental results demonstrate that TNF- α enhanced the expressions of VCAM, ICAM, P-selectin and E-selectin in ECs, which supports the numerical results that the rolling velocity of EPC on TNF- α treated EC substrate decreases obviously compared with its velocity on the untreated one. It is found that because the adhesion is affected by both the rolling velocity and the deformability of the cell, an optimal stiffness of EPC may exist at a given shear rate of flow for achieving maximum adhesion rates.
New method for evaluation of perigastric invasion of gastric cancer by right lateral position CT
International Nuclear Information System (INIS)
Shirakawa, T.; Fukuda, K.; Tada, S.
1996-01-01
The purpose of this study was to evaluate usefulness of right lateral position CT in determining invasion of gastric cancer into adjacent organs. We assessed whether position shift, a change in the relative location of a gastric tumor and adjacent organs between the supine position and right lateral position CT, was a useful sign for absence of invasion into perigastric organs. In 37 patients with advanced gastric cancer with doubtful invasion into adjacent organs by conventional CT after 500 ml water oral intake, additive right lateral CT was performed. Of 24 cases of lesions in the gastric body, 16 had a position shift and no invasion into adjacent organs at surgery (T3), and 8 had no position shift and invasion (T4). The accuracy was 100%. Six gastric cardial and 7 pyloric tumors showed no position shift, and 3 cardial and 2 pyloric tumors were proved to be nonivasive (T3). The accuracy of cardial and pyloric tumor was 50 and 71%. We concluded that position shift may be useful in the diagnosis of invasion of adjacent organs by gastric cancer, limited to in cases with gastric body cancer. (orig.)
Viallat, Annie; Abkarian, Manouk; Dupire, Jules
2015-11-01
The analytical model presented by Keller and Skalak on the dynamics of red blood cells in shear flow described the cell as a fluid ellipsoid of fixed shape. It was extended to introduce shear elasticity of the cell membrane. We further extend the model when the cell discoid physiological shape is not a stress-free shape. We show that spheroid stress-free shapes enables fitting experimental data with values of shear elasticity typical to that found with micropipettes and optical tweezers. For moderate shear rates (when RBCs keep their discoid shape) this model enables to quantitatively determine an effective cell viscosity, that combines membrane and hemoglobin viscosities and an effective shear modulus of the membrane that combines shear modulus and stress-free shape. This model allows determining RBC mechanical parameters both in the tanktreading regime for cells suspended in a high viscosity medium, and in the tumbling regime for cells suspended in a low viscosity medium. In this regime,a transition is predicted between a rigid-like tumbling motion and a fluid-like tumbling motion above a critical shear rate, which is directly related to the mechanical parameters of the cell. A*MIDEX (n ANR-11-IDEX-0001-02) funded by the ''Investissements d'Avenir'', Region Languedoc-Roussillon, Labex NUMEV (ANR-10-LABX-20), BPI France project DataDiag.
Nonequilibrium Langevin dynamics: A demonstration study of shear flow fluctuations in a simple fluid
Belousov, Roman; Cohen, E. G. D.; Rondoni, Lamberto
2017-08-01
The present paper is based on a recent success of the second-order stochastic fluctuation theory in describing time autocorrelations of equilibrium and nonequilibrium physical systems. In particular, it was shown to yield values of the related deterministic parameters of the Langevin equation for a Couette flow in a microscopic molecular dynamics model of a simple fluid. In this paper we find all the remaining constants of the stochastic dynamics, which then is simulated numerically and compared directly with the original physical system. By using these data, we study in detail the accuracy and precision of a second-order Langevin model for nonequilibrium physical systems theoretically and computationally. We find an intriguing relation between an applied external force and cumulants of the resulting flow fluctuations. This is characterized by a linear dependence of an athermal cumulant ratio, an apposite quantity introduced here. In addition, we discuss how the order of a given Langevin dynamics can be raised systematically by introducing colored noise.
International Nuclear Information System (INIS)
Satoh, Akira; Hayasaka, Ryo; Majima, Tamotsu
2008-01-01
We have treated a dilute dispersion composed of ferromagnetic rodlike particles with a magnetic moment normal to the particle axis, such as hematites, to investigate the influences of the magnetic field strength, shear rate, and random forces on the orientational distribution of rodlike particles and also on transport coefficients, such as viscosity and diffusion coefficient. In the present analysis, these rodlike particles are assumed to conduct the rotational Brownian motion in a simple shear flow as well as an external magnetic field. The results obtained here are summarized as follows. In the case of a strong magnetic field and a smaller shear rate, the rodlike particle can freely rotate in the xy-plane with the magnetic moment continuing to point the magnetic field direction. On the other hand, for a strong shear flow, the particle has a tendency to incline in the flow direction with the magnetic moment pointing to the magnetic field direction. In the case of the magnetic field applied normal to the direction of the sedimentation, the diffusion coefficient gives rise to smaller values than expected, since the rodlike particle sediments with the particle axis inclining toward directions normal to the movement direction and, of course, toward the direction along that direction
Mori, Hirohito; Rafiq, Kazi; Kobara, Hideki; Nishiyama, Noriko; Fujihara, Shintaro; Yachida, Tatsuo; Ayagi, Maki; Tani, Joji; Miyoshi, Hisaaki; Masaki, Tsutomu
2014-01-01
Previously, we reported the efficacy of a newly developed inverted overtube in shortening the hemostatic time and obtaining a clear endoscopic view in emergency endoscopic hemostasis. This device also helped us to perform gastric endoscopic submucosal dissection (ESD) more safely by changing the direction of gravity in the right lateral position. To perform a safe ESD, it is important to make an appropriate angle and distance between the electric knife and the gastric mucosa. In this position...
Smirni, Daniela; Turriziani, Patrizia; Mangano, Giuseppa Renata; Bracco, Martina; Oliveri, Massimiliano; Cipolotti, Lisa
2017-07-28
A growing body of evidence have suggested that non-invasive brain stimulation techniques, such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), can improve the performance of aphasic patients in language tasks. For example, application of inhibitory rTMS or tDCs over the right frontal lobe of dysphasic patients resulted in improved naming abilities. Several studies have also reported that in healthy controls (HC) tDCS application over the left prefrontal cortex (PFC) improve performance in naming and semantic fluency tasks. The aim of this study was to investigate in HC, for the first time, the effects of inhibitory repetitive TMS (rTMS) over left and right lateral frontal cortex (BA 47) on two phonemic fluency tasks (FAS or FPL). 44 right-handed HCs were administered rTMS or sham over the left or right lateral frontal cortex in two separate testing sessions, with a 24h interval, followed by the two phonemic fluency tasks. To account for possible practice effects, an additional 22 HCs were tested on only the phonemic fluency task across two sessions with no stimulation. We found that rTMS-inhibition over the left lateral frontal cortex significantly worsened phonemic fluency performance when compared to sham. In contrast, rTMS-inhibition over the right lateral frontal cortex significantly improved phonemic fluency performance when compared to sham. These results were not accounted for practice effects. We speculated that rTMS over the right lateral frontal cortex may induce plastic neural changes to the left lateral frontal cortex by suppressing interhemispheric inhibitory interactions. This resulted in an increased excitability (disinhibition) of the contralateral unstimulated left lateral frontal cortex, consequently enhancing phonemic fluency performance. Conversely, application of rTMS over the left lateral frontal cortex may induce a temporary, virtual lesion, with effects similar to those reported in left frontal
Schurman, Lesley D; Smith, Terry L; Morales, Anthony J; Lee, Nancy N; Reeves, Thomas M; Phillips, Linda L; Lichtman, Aron H
2017-07-13
Although rodent models of traumatic brain injury (TBI) reliably produce cognitive and motor disturbances, behavioral characterization resulting from left and right hemisphere injuries remains unexplored. Here we examined the functional consequences of targeting the left versus right parietal cortex in lateral fluid percussion injury, on Morris water maze (MWM) spatial memory tasks (fixed platform and reversal) and neurological motor deficits (neurological severity score and rotarod). In the MWM fixed platform task, right lateral injury produced a small delay in acquisition rate compared to left. However, injury to either hemisphere resulted in probe trial deficits. In the MWM reversal task, left-right performance deficits were not evident, though left lateral injury produced mild acquisition and probe trial deficits compared to sham controls. Additionally, left and right injury produced similar neurological motor task deficits, impaired righting times, and lesion volumes. Injury to either hemisphere also produced robust ipsilateral, and modest contralateral, morphological changes in reactive microglia and astrocytes. In conclusion, left and right lateral TBI impaired MWM performance, with mild fixed platform acquisition rate differences, despite similar motor deficits, histological damage, and glial cell reactivity. Thus, while both left and right lateral TBI produce cognitive deficits, laterality in mouse MWM learning and memory merits consideration in the investigation of TBI-induced cognitive consequences. Copyright © 2017. Published by Elsevier B.V.
Mori, Hirohito; Rafiq, Kazi; Kobara, Hideki; Nishiyama, Noriko; Fujihara, Shintaro; Yachida, Tatsuo; Ayagi, Maki; Tani, Joji; Miyoshi, Hisaaki; Masaki, Tsutomu
2014-02-14
Previously, we reported the efficacy of a newly developed inverted overtube in shortening the hemostatic time and obtaining a clear endoscopic view in emergency endoscopic hemostasis. This device also helped us to perform gastric endoscopic submucosal dissection (ESD) more safely by changing the direction of gravity in the right lateral position. To perform a safe ESD, it is important to make an appropriate angle and distance between the electric knife and the gastric mucosa. In this position, the distance to gastric mucosa is reduced, and the angle of the electric knife changes from vertical to somewhat oblique, facilitating safer cutting.
Constable, Merryn D; Becker, Stefanie I
2017-10-01
According to the Sapir-Whorf hypothesis, learned semantic categories can influence early perceptual processes. A central finding in support of this view is the lateralized category effect-namely, the finding that categorically different colors (e.g., blue and green hues) can be discriminated faster than colors within the same color category (e.g., different hues of green), especially when they are presented in the right visual field. Because the right visual field projects to the left hemisphere, this finding has been popularly couched in terms of the left-lateralization of language. However, other studies have reported bilateral category effects, which has led some researchers to question the linguistic origins of the effect. Here we examined the time course of lateralized and bilateral category effects in the classical visual search paradigm by means of eyetracking and RT distribution analyses. Our results show a bilateral category effect in the manual responses, which is combined of an early, left-lateralized category effect and a later, right-lateralized category effect. The newly discovered late, right-lateralized category effect occurred only when observers had difficulty locating the target, indicating a specialization of the right hemisphere to find categorically different targets after an initial error. The finding that early and late stages of visual search show different lateralized category effects can explain a wide range of previously discrepant findings.
Bartel, Esther Maria; Neubauer, Franz; Heberer, Bianca; Genser, Johann
2014-12-01
Based on structural and fabric analyses at variable scales we investigate the evaporitic gypsum-dominated Comeglians-Paularo shear zone in the Southern Alps (Friuli). It represents the lateral western termination of the brittle Fella-Sava Fault. Missing dehydration products of gypsum and the lack of annealing indicate temperatures below 100 °C during development of the shear zone. Despite of such low temperatures the shear zone clearly exhibits mylonitic flow, thus evidencing laterally coeval activity of brittle and viscous deformation. The dominant structures within the gypsum rocks of the Lower Bellerophon Formation are a steeply to gently S-dipping foliation, a subhorizontal stretching lineation and pure shear-dominated porphyroclast systems. A subordinate simple shear component with dextral displacement is indicated by scattered σ-clasts. Both meso- and microscale structures are characteristic of a subsimple shear type of deformation with components of both coaxial and non-coaxial strain. Shortening in a transpressive regime was accommodated by right-lateral displacement and internal pure shear deformation within the Comeglians-Paularo shear zone. The shear zone shows evidence for a combination of two stretching faults, where stretching occurred in the rheologically weaker gypsum member and brittle behavior in enveloping lithologies.
International Nuclear Information System (INIS)
Astill, M.; Sunderland, A.; Waine, M.G.
1980-01-01
A shear machine for irradiated nuclear fuel elements has a replaceable shear assembly comprising a fuel element support block, a shear blade support and a clamp assembly which hold the fuel element to be sheared in contact with the support block. A first clamp member contacts the fuel element remote from the shear blade and a second clamp member contacts the fuel element adjacent the shear blade and is advanced towards the support block during shearing to compensate for any compression of the fuel element caused by the shear blade (U.K.)
International Nuclear Information System (INIS)
Zhongchun, Li; Xiaoming, Song; Shengyao, Jiang; Jiyang, Yu
2014-01-01
Highlights: • A VOF simulation of bubble in low viscosity fluid was conducted. • Lift force in different viscosity fluid had different lateral migration characteristics. • Bubble with different size migrated to different direction. • Shear stress triggered the bubble deformation process and the bubble deformation came along with the oscillation behaviors. - Abstract: Two phase flow systems have been widely used in industrial engineering. Phase distribution characteristics are vital to the safety operation and optimization design of two phase flow systems. Lift force has been known as perpendicular to the bubbles’ moving direction, which is one of the mechanisms of interfacial momentum transfer. While most widely used lift force correlations, such as the correlation of Tomiyama et al. (2002), were obtained by experimentally tracking single bubble trajectories in high viscosity glycerol–water mixture, the applicability of these models into low viscosity fluid, such as water in nuclear engineering system, needs to be further evaluated. In the present paper, bubble in low viscosity fluid in shear flow was investigated in a full 3D numerical simulation and the volume of fluid (VOF) method was applied to capture the interface. The fluid parameter: fluid viscosity, bubble parameter: diameter and external flow parameters: shear stress magnitude and liquid velocity were examined. Comparing with bubble in high viscosity shear flow and bubble in low viscosity still flow, relative large bubble in low viscosity shear flow keep an oscillation way towards the moving wall and experienced a shape deformation process. The oscillation amplitude increased as the viscosity of fluid decreased. Small bubble migrated to the static wall in a line with larger migration velocity than that in high viscosity fluid and no deformation occurred. The shear stress triggered the oscillation behaviors while it had no direct influence with the behavior. The liquid velocity had no effect on
International Nuclear Information System (INIS)
Huang Kemin; Feng Yanlin; Wen Guanghua; Liang Weitang; Yu Fengwen; Liu Dejun
2013-01-01
Objective: To explore the value of right lateral decubitus position MPI for differentiating myocardial perfusion defect from cardiac anterior wall attenuation artificial defect, caused by breast of woman. Methods: Forty-nine patients(average age (61.5±8.4) years) who had low likelihood of coronary artery disease and had perfusion defect in the anterior wall after exercise stress 99 Tc m -MIBI MPI were included. All underwent supine and right lateral decubitus position during resting SPECT images. The myocardial perfusion SPECT images at left ventricle were reconstructed and were measured by Bull's-eye, based on the counts. Results from both supine position imaging and right lateral decubitus position imaging were compared. Paired t test was used to statistically analyse the data by SPSS 13.0. Results: Compared with supine position, the counts of the anterior, inferior, apex and lateral wall in right lateral decubitus position were significantly higher: (71.30±3.53)% vs (66.50±3.85)%, (70.06±4.45)% vs (65.44±4.16)%, (77.90±3.00)% vs (75.81±4.08)%,(79.30±2.26)% vs (72.60±3.87)% (t=6.731, 5.286, 3.555, 10.885, all P<0.01). The counts of septal wall were significantly lower ((66.60±3.98)% vs (70.06±4.51)%, t=-4.625, P<0.01) in right lateral decubitus position than that in supine position. Among the different regions of anterior wall, the counts of the anterior-middle ((76.40 ± 3.80)% vs (68.60 ± 4.76)%) and anterior-apex region ((77.10±3.24)% vs (69.00±3.54)%) were significantly higher (t=9.916, 8.870, both P<0.01) in right lateral decubitus position than those in supine position, but there was insignificance ((56.94±6.06)% vs (58.50±4.98)%, t=-1.493, P>0.05) at anterior-basal region. The artificial defect of different degrees in anterior wall was observed in all patients in supine position, 23 cases (46.9%, 23/49) showed artificial defect in the anterior-middle region and 16 cases (32.7%, 16/49) in the anterior-apex region. All artificial defect
International Nuclear Information System (INIS)
Shn, Dong Rock; Ryu, Dae Shick; Park, Man Soo; Jung, Seung Mun; Ahn, Jae Hong; Lee, Jong Hyeog; Choi, Soo Jung
2012-01-01
We observed patients in whom the fluid collection in the right lateral portion of the superior aortic recess on computed tomography (CT) scans mimicked a right anterior mediastinal mass on chest PA radiographs. The purpose of this study was to assess chest PA and CT features of these patients. All chest PA radiographs and CT scans in 9 patients were reviewed by two radiologists on a consensus basis; for the presence of pleural effusion, pulmonary edema and heart size on chest PA radiographs. For the portion of the fluid collection in the superior aortic recess (SAR), a connection between the right lateral portion of the SAR (rSAR) and posterior portion of the SAR (pSAR) on CT scans, and the distance between the right lateral margin of the rSAR and the right lateral margin of the superior vena cava. Fluid collection in the rSAR on CT scans caused a right anterior mediastinal mass or a bulging contour on chest PA radiographs in all women patients. All patients showed cardiomegaly, five patients had pleural effusion, and two patients had mild pulmonary edema. Further, eight patients showed a connection between the rSAR and the pSAR. The characteristic features of these patients are the right anterior mediastinal mass-like opacity due to fluid collection in the rSAR, are bulging contour with a smooth margin and cardiomegaly regardless of pulmonary edema on the chest PA radiographs, and fluid connection between the rSAR and the pSAR on CT scans
Energy Technology Data Exchange (ETDEWEB)
Shn, Dong Rock; Ryu, Dae Shick; Park, Man Soo; Jung, Seung Mun; Ahn, Jae Hong; Lee, Jong Hyeog; Choi, Soo Jung [Dept. of Radiology, Gangneung Asan Hospital, College of Medicine, University of Ulsan, Gangneung (Korea, Republic of)
2012-09-15
We observed patients in whom the fluid collection in the right lateral portion of the superior aortic recess on computed tomography (CT) scans mimicked a right anterior mediastinal mass on chest PA radiographs. The purpose of this study was to assess chest PA and CT features of these patients. All chest PA radiographs and CT scans in 9 patients were reviewed by two radiologists on a consensus basis; for the presence of pleural effusion, pulmonary edema and heart size on chest PA radiographs. For the portion of the fluid collection in the superior aortic recess (SAR), a connection between the right lateral portion of the SAR (rSAR) and posterior portion of the SAR (pSAR) on CT scans, and the distance between the right lateral margin of the rSAR and the right lateral margin of the superior vena cava. Fluid collection in the rSAR on CT scans caused a right anterior mediastinal mass or a bulging contour on chest PA radiographs in all women patients. All patients showed cardiomegaly, five patients had pleural effusion, and two patients had mild pulmonary edema. Further, eight patients showed a connection between the rSAR and the pSAR. The characteristic features of these patients are the right anterior mediastinal mass-like opacity due to fluid collection in the rSAR, are bulging contour with a smooth margin and cardiomegaly regardless of pulmonary edema on the chest PA radiographs, and fluid connection between the rSAR and the pSAR on CT scans.
Directory of Open Access Journals (Sweden)
Korhan ESAT
2016-12-01
Full Text Available The Eskişehir Fault Zone is one of the prominent neotectonic structures of Turkey. It separates the west Anatolian extensional province and the strike-slip induced northwest central Anatolian contractional area in the Anatolian Block. Its southeastern part is generally divided into three branches, namely the Ilıca, Yeniceoba, and Cihanbeyli from north to south, respectively. The right lateral strike-slip Ilıca branch (IB is an approximately 100-km-long fault and it is composed of several segments in a northwest-southeast direction. The slickensides, subsidiary fractures, cataclastic zone, fracture-controlled drainage pattern, right lateral stream deflections, deformation in the Quaternary unit observing in the seismic reflection sections, and seismicity of the region all indicate that the IB is an active right lateral strike-slip fault. The IB has also a regional tectonic importance as a boundary fault between the contractional and the extensional regions in central Anatolia considering that it is the southern limit of the contraction-related structures in the west-southwest of Ankara.
Stanley, Richard G.; Barron, John A.; Powell, Charles L.
2017-12-22
We used geological field studies and diatom biostratigraphy to test a published hypothesis that Neogene marine siliceous strata in the Maricopa and Parkfield areas, located on opposite sides of the San Andreas Fault, were formerly contiguous and then were displaced by about 80–130 kilometers (km) of right-lateral slip along the fault. In the Maricopa area on the northeast side of the San Andreas Fault, the upper Miocene Bitterwater Creek Shale consists of hard, siliceous shale with dolomitic concretions and turbidite sandstone interbeds. Diatom assemblages indicate that the Bitterwater Creek Shale was deposited about 8.0–6.7 million years before present (Ma) at the same time as the uppermost part of the Monterey Formation in parts of coastal California. In the Parkfield area on the southwest side of the San Andreas Fault, the upper Miocene Pancho Rico Formation consists of soft to indurated mudstone and siltstone and fossiliferous, bioturbated sandstone. Diatom assemblages from the Pancho Rico indicate deposition about 6.7–5.7 Ma (latest Miocene), younger than the Bitterwater Creek Shale and at about the same time as parts of the Sisquoc Formation and Purisima Formation in coastal California. Our results show that the Bitterwater Creek Shale and Pancho Rico Formation are lithologically unlike and of different ages and therefore do not constitute a cross-fault tie that can be used to estimate rightlateral displacement along the San Andreas Fault.In the Maricopa area northeast of the San Andreas Fault, the Bitterwater Creek Shale overlies conglomeratic fan-delta deposits of the upper Miocene Santa Margarita Formation, which in turn overlie siliceous shale of the Miocene Monterey Formation from which we obtained a diatom assemblage dated at about 10.0–9.3 Ma. Previous investigations noted that the Santa Margarita Formation in the Maricopa area contains granitic and metamorphic clasts derived from sources in the northern Gabilan Range, on the opposite side of
Directory of Open Access Journals (Sweden)
Renato de Lima Santos
2007-04-01
Full Text Available A 22 year-old horse developed cholelithiasis with marked atrophy of the right lateral hepatic lobe. The horse had a history of intermittent colic since three years of age, and one of the first episodes of colic was associated with icterus. The size of the right lateral hepatic lobe was extremely reduced. There was a large choledocholith in the common hepatic duct, and several hepatoliths and choleliths in the intra- and extra-hepatic billiary ducts. Microscopically, there was severe atrophy of the right lobe with diffuse proliferation of connective tissue and billiary ducts. The left lateral lobe had peri-portal fibrosis with proliferation of billiary ducts, and billiary stasis. Chemical analysis of the calculi detected amorphous and triple phosphate, bilirubin, calcium, and iron.Um cavalo de 22 anos de idade desenvolveu quadro de colelitíase severa com atrofia do lobo lateral direito. O animal tinha histórico de cólica recorrente, desde os três anos de idade, sendo que um dos primeiros episódios de cólica foi acompanhado de icterícia. O lobo hepático lateral direito estava extremamente diminuído de volume. Havia um grande coledocólito localizado no ducto hepático comum e inúmeros hepatólitos e colélitos nos ductos biliares intra e extra-hepáticos. Microscopicamente, foi observada atrofia acentuada do lobo direito, com proliferação difusa de tecido conjuntivo fibroso e de ductos biliares. O lobo lateral esquerdo apresentava fibrose periportal difusa associada à proliferação acentuada de ductos biliares e estase biliar. Análise química das concreções detectou fosfato triplo e amorfo, bilirrubina, cálcio e ferro.
Graham, Rodney
2017-04-01
We are here, of course, because 1967 saw the publication of John Ramsay's famous book. Two years later a memorable field trip from Imperial College to the Outer Hebrides saw John on a bleak headland on the coast of North Uist where a relatively undeformed metadolerite within Lewisian (Precambrian) gneisses contained ductile shear zones with metamorphic fabrics in amphibolite facies. One particular outcrop was very special - a shear zone cutting otherwise completely isotropic, undeformed metadolerite, with an incremental foliation starting to develop at 45° to the deformation zone, and increasing in intensity as it approached the shear direction. Here was proof of the process of simple shear under ductile metamorphic conditions - the principles of simple shear outlined in John Ramsay's 1967 book clearly visible in nature, and verified by Ramsay's mathematical proofs in the eventual paper (Ramsay and Graham, 1970). Later work on the Lewisian on the mainland of Scotland, in South Harris, in Africa, and elsewhere applied Ramsay's simple shear principles more liberally, more imprecisely and on larger scale than at Caisteal Odair, but in retrospect it documented what seems now to be the generality of mid and lower crustal deformation. Deep seismic reflection data show us that on passive margins hyper-stretched continental crust (whether or not cloaked by Seaward Dipping Reflectors) seems to have collapsed onto the mantle. Crustal faults mostly sole out at or above the mantle - so the Moho is a detachment- an 'outer marginal detachment', if you like, and, of course, it must be a ductile shear. On non-volcanic margins this shear zone forms the first formed ocean floor before true sea floor spreading gets going to create real oceanic crust. Gianreto Manatschal, Marcel Lemoine and others realised that the serpentinites described in parts of the Alps are exposed remnants of this ductile shear zone. Associated ophicalcite breccias tell of sea floor exposure, while high
Evaluation of size effect on shear strength of reinforced concrete ...
Indian Academy of Sciences (India)
of the longitudinal and the web reinforcement, shear span-to-depth ratio and the ... A simple equation for predicting the shear strength of reinforced concrete deep ..... AASHTO 2007 LRFD Bridge Design Specifications, American Association of ...
Umakanthan, Ramanan; Petracek, Michael R; Leacche, Marzia; Solenkova, Nataliya V; Eagle, Susan S; Thompson, Annemarie; Ahmad, Rashid M; Greelish, James P; Ball, Stephen K; Hoff, Steven J; Absi, Tarek S; Balaguer, Jorge M; Byrne, John G
2010-03-01
The study aim was to determine the safety and benefits of minimally invasive mitral valve surgery without aortic cross-clamping for mitral valve surgery after previous cardiac surgery. Between January 2006 and August 2008, a total of 90 consecutive patients (38 females, 52 males; mean age 66 +/- 9 years) underwent minimally invasive mitral valve surgery after having undergone previous cardiac surgery. Of these patients, 80 (89%) underwent mitral valve replacement and 10 (11%) mitral valve repair utilizing a small (5 cm) right lateral thoracotomy along the 4th or 5th intercostal space under fibrillatory arrest (mean temperature 28 +/- 2 degrees C). The predicted mortality, calculated using the Society of Thoracic Surgeons (STS) algorithm, was compared to the observed mortality. The mean ejection fraction was 45 +/- 13%, mean NYHA class 3 +/- 1, while 66 patients (73%) had previous coronary artery bypass grafting and 37 (41%) had previous valve surgery. Twenty-six patients (29%) underwent non-elective surgery. Cardiopulmonary bypass was instituted through axillary (n = 19), femoral (n = 70) or direct use aortic (n = 1) cannulation. Operative mortality was 2% (2/90), lower than the STS-predicted mortality of 7%. Three patients (3%) developed acute renal failure postoperatively, one patient (1%) required new-onset hemodialysis, and one (1%) developed postoperative stroke. No patients developed postoperative myocardial infarction. The mean postoperative packed red blood cell transfusion requirement at 48 h was 2 +/- 3 units. Minimally invasive right thoracotomy without aortic cross-clamping is an excellent alternative to conventional redo-sternotomy for reoperative mitral valve surgery. The present study confirmed that this technique is safe and effective in reducing operative mortality in high-risk patients undergoing reoperative cardiac surgery.
The brittle-viscous-plastic evolution of shear bands in the South Armorican Shear Zone
Bukovská, Zita; Jeřábek, Petr; Morales, Luiz F. G.; Lexa, Ondrej; Milke, Ralf
2014-05-01
Shear bands are microscale shear zones that obliquely crosscut an existing anisotropy such as a foliation. The resulting S-C fabrics are characterized by angles lower than 45° and the C plane parallel to shear zone boundaries. The S-C fabrics typically occur in granitoids deformed at greenschist facies conditions in the vicinity of major shear zones. Despite their long recognition, mechanical reasons for localization of deformation into shear bands and their evolution is still poorly understood. In this work we focus on microscale characterization of the shear bands in the South Armorican Shear Zone, where the S-C fabrics were first recognized by Berthé et al. (1979). The initiation of shear bands in the right-lateral South Armorican Shear Zone is associated with the occurrence of microcracks crosscutting the recrystallized quartz aggregates that define the S fabric. In more advanced stages of shear band evolution, newly formed dominant K-feldspar, together with plagioclase, muscovite and chlorite occur in the microcracks, and the shear bands start to widen. K-feldspar replaces quartz by progressively bulging into the grain boundaries of recrystallized quartz grains, leading to disintegration of quartz aggregates and formation of fine-grained multiphase matrix mixture. The late stages of shear band development are marked by interconnection of fine-grained white mica into a band that crosscuts the original shear band matrix. In its extremity, the shear band widening may lead to the formation of ultramylonites. With the increasing proportion of shear band matrix from ~1% to ~12%, the angular relationship between S and C fabrics increases from ~30° to ~40°. The matrix phases within shear bands show differences in chemical composition related to distinct evolutionary stages of shear band formation. The chemical evolution is well documented in K-feldspar, where the albite component is highest in porphyroclasts within S fabric, lower in the newly formed grains within
Degree of coupling in high-rise mixed shear walls structures
Indian Academy of Sciences (India)
A simple method of analysis is presented to determine the inﬂuence of single shear walls (SSW) on the degree of coupling DoC and on the peak shear demand PSD for beams of coupled shear walls (CSW) in mixed shear wall structures (MSW). Non-coupled lateral load resisting structures such as singular planar walls and ...
Semiconductor laser shearing interferometer
International Nuclear Information System (INIS)
Ming Hai; Li Ming; Chen Nong; Xie Jiaping
1988-03-01
The application of semiconductor laser on grating shearing interferometry is studied experimentally in the present paper. The method measuring the coherence of semiconductor laser beam by ion etching double frequency grating is proposed. The experimental result of lens aberration with semiconductor laser shearing interferometer is given. Talbot shearing interferometry of semiconductor laser is also described. (author). 2 refs, 9 figs
Vâgberg, Daniel; Olsson, Peter; Teitel, S.
2017-05-01
We report on numerical simulations of simple models of athermal, bidisperse, soft-core, massive disks in two dimensions, as a function of packing fraction ϕ , inelasticity of collisions as measured by a parameter Q , and applied uniform shear strain rate γ ˙. Our particles have contact interactions consisting of normally directed elastic repulsion and viscous dissipation, as well as tangentially directed viscous dissipation, but no interparticle Coulombic friction. Mapping the phase diagram in the (ϕ ,Q ) plane for small γ ˙, we find a sharp first-order rheological phase transition from a region with Bagnoldian rheology to a region with Newtonian rheology, and show that the system is always Newtonian at jamming. We consider the rotational motion of particles and demonstrate the crucial importance that the coupling between rotational and translational degrees of freedom has on the phase structure at small Q (strongly inelastic collisions). At small Q , we show that, upon increasing γ ˙, the sharp Bagnoldian-to-Newtonian transition becomes a coexistence region of finite width in the (ϕ ,γ ˙) plane, with coexisting Bagnoldian and Newtonian shear bands. Crossing this coexistence region by increasing γ ˙ at fixed ϕ , we find that discontinuous shear thickening can result if γ ˙ is varied too rapidly for the system to relax to the shear-banded steady state corresponding to the instantaneous value of γ ˙.
Vesicle dynamics in shear and capillary flows
International Nuclear Information System (INIS)
Noguchi, Hiroshi; Gompper, Gerhard
2005-01-01
The deformation of vesicles in flow is studied by a mesoscopic simulation technique, which combines multi-particle collision dynamics for the solvent with a dynamically triangulated surface model for the membrane. Shape transitions are investigated both in simple shear flows and in cylindrical capillary flows. We focus on reduced volumes, where the discocyte shape of fluid vesicles is stable, and the prolate shape is metastable. In simple shear flow at low membrane viscosity, the shear induces a transformation from discocyte to prolate with increasing shear rate, while at high membrane viscosity, the shear induces a transformation from prolate to discocyte, or tumbling motion accompanied by oscillations between these two morphologies. In capillary flow, at small flow velocities the symmetry axis of the discocyte is found not to be oriented perpendicular to the cylinder axis. With increasing flow velocity, a transition to a prolate shape occurs for fluid vesicles, while vesicles with shear-elastic membranes (like red blood cells) transform into a coaxial parachute-like shape
Experimental study of shear rate dependence in perpetually sheared granular matter
Liu, Sophie Yang; Guillard, François; Marks, Benjy; Rognon, Pierre; Einav, Itai
2017-06-01
We study the shear behaviour of various granular materials by conducting novel perpetual simple shear experiments over four orders of magnitude of relatively low shear rates. The newly developed experimental apparatus employed is called "3D Stadium Shear Device" which is an extended version of the 2D Stadium Shear Device [1]. This device is able to provide a non-radial dependent perpetual shear flow and a nearly linear velocity profile between two oppositely moving shear walls. Using this device, we are able to test a large variety of granular materials. Here, we demonstrate the applicability of the device on glass beads (diameter 1 mm, 3 mm, and 14 mm) and rice. We particularly focus on studying these materials at very low inertial number I ranging from 10-6 to 10-2. We find that, within this range of I, the friction coefficient μ of glass beads has no shear rate dependence. A particularly appealing observation comes from testing rice, where the attainment of critical state develops under much longer duration than in other materials. Initially during shear we find a value of μ similar to that found for glass beads, but with time this value decreases gradually towards the asymptotic critical state value. The reason, we believe, lies in the fact that rice grains are strongly elongated; hence the time to achieve the stable μ is primarily controlled by the time for particles to align themselves with respect to the shear walls. Furthermore, the initial packing conditions of samples also plays a role in the evolution of μ when the shear strain is small, but that impact will eventually be erased after sufficient shear strain.
Experimental study of shear rate dependence in perpetually sheared granular matter
Directory of Open Access Journals (Sweden)
Liu Sophie Yang
2017-01-01
Full Text Available We study the shear behaviour of various granular materials by conducting novel perpetual simple shear experiments over four orders of magnitude of relatively low shear rates. The newly developed experimental apparatus employed is called “3D Stadium Shear Device” which is an extended version of the 2D Stadium Shear Device [1]. This device is able to provide a non-radial dependent perpetual shear flow and a nearly linear velocity profile between two oppositely moving shear walls. Using this device, we are able to test a large variety of granular materials. Here, we demonstrate the applicability of the device on glass beads (diameter 1 mm, 3 mm, and 14 mm and rice. We particularly focus on studying these materials at very low inertial number I ranging from 10−6 to 10−2. We find that, within this range of I, the friction coefficient μ of glass beads has no shear rate dependence. A particularly appealing observation comes from testing rice, where the attainment of critical state develops under much longer duration than in other materials. Initially during shear we find a value of μ similar to that found for glass beads, but with time this value decreases gradually towards the asymptotic critical state value. The reason, we believe, lies in the fact that rice grains are strongly elongated; hence the time to achieve the stable μ is primarily controlled by the time for particles to align themselves with respect to the shear walls. Furthermore, the initial packing conditions of samples also plays a role in the evolution of μ when the shear strain is small, but that impact will eventually be erased after sufficient shear strain.
Right Lateral Cerebellum Represents Linguistic Predictability.
Lesage, Elise; Hansen, Peter C; Miall, R Chris
2017-06-28
Mounting evidence indicates that posterolateral portions of the cerebellum (right Crus I/II) contribute to language processing, but the nature of this role remains unclear. Based on a well-supported theory of cerebellar motor function, which ascribes to the cerebellum a role in short-term prediction through internal modeling, we hypothesize that right cerebellar Crus I/II supports prediction of upcoming sentence content. We tested this hypothesis using event-related fMRI in male and female human subjects by manipulating the predictability of written sentences. Our design controlled for motor planning and execution, as well as for linguistic features and working memory load; it also allowed separation of the prediction interval from the presentation of the final sentence item. In addition, three further fMRI tasks captured semantic, phonological, and orthographic processing to shed light on the nature of the information processed. As hypothesized, activity in right posterolateral cerebellum correlated with the predictability of the upcoming target word. This cerebellar region also responded to prediction error during the outcome of the trial. Further, this region was engaged in phonological, but not semantic or orthographic, processing. This is the first imaging study to demonstrate a right cerebellar contribution in language comprehension independently from motor, cognitive, and linguistic confounds. These results complement our work using other methodologies showing cerebellar engagement in linguistic prediction and suggest that internal modeling of phonological representations aids language production and comprehension. SIGNIFICANCE STATEMENT The cerebellum is traditionally seen as a motor structure that allows for smooth movement by predicting upcoming signals. However, the cerebellum is also consistently implicated in nonmotor functions such as language and working memory. Using fMRI, we identify a cerebellar area that is active when words are predicted and when these predictions are violated. This area is active in a separate task that requires phonological processing, but not in tasks that require semantic or visuospatial processing. Our results support the idea of prediction as a unifying cerebellar function in motor and nonmotor domains. We provide new insights by linking the cerebellar role in prediction to its role in verbal working memory, suggesting that these predictions involve phonological processing. Copyright © 2017 Lesage et al.
Relations Between Shear and Normal Stresses in a Step-Shear Experiment
DEFF Research Database (Denmark)
Hassager, Ole; Pedersen, Sven
1978-01-01
The Lodge-Meissner step-shear relation for simple fluids is examined. It is demonstrated that the relation depends critically on two assumptions for the integral expansion of the simple fluid: First, the use of the Cauchy strain tensor as strain measure, and second, that the memory functions...... are bounded. It is pointed out that many simple differential and integral models do not satisfy these criteria and hence predict deviations from the Lodge-Meissner relation....
Starch-zein beldns formed by shear flow
Habeych Narvaez, E.A.; Dekkers, B.; Goot, van der A.J.; Boom, R.M.
2008-01-01
A newly in-house developed shearing device was used to explore the formation of new types of microstructures in concentrated starch¿zein blends. The device allowed processing of the biopolymer blends under homogeneous, simple shear flow conditions. Water and glycerol were added as plasticizers.
A single variable shear deformable nonlocal theory for transversely ...
Indian Academy of Sciences (India)
Rameshchandra P Shimpi
2018-05-11
May 11, 2018 ... Abstract. In this paper, a simple single variable shear deformable nonlocal theory for bending of micro- and ... the models based upon continuum mechanics are widely .... of the body. ...... Elsevier Science Ltd, Oxford, UK. pp.
Graybill, George
2007-01-01
Just how simple are simple machines? With our ready-to-use resource, they are simple to teach and easy to learn! Chocked full of information and activities, we begin with a look at force, motion and work, and examples of simple machines in daily life are given. With this background, we move on to different kinds of simple machines including: Levers, Inclined Planes, Wedges, Screws, Pulleys, and Wheels and Axles. An exploration of some compound machines follows, such as the can opener. Our resource is a real time-saver as all the reading passages, student activities are provided. Presented in s
Shear flow stabilization of the hydromagnetic Rayleigh-Taylor instability
International Nuclear Information System (INIS)
Roderick, N.F.; Shumlak, U.; Douglas, M.; Peterkin, R.E. Jr.; Ruden, E.
1997-01-01
Numerical simulations have indicated that shear flow may help stabilize the hydromagnetic Rayleigh-Taylor instability in imploding plasma z-pinches. A simple extension to a model presented in Chandrasekhar has been developed to study the linear stability of incompressible plasma subjected to both a shear flow and acceleration. The model has been used to investigate the stability plasma implosion schemes using externally imposed velocity shear which develops from the plasma flow itself. Specific parameters were chosen to represent plasma implosions driven by the Saturn and PBFA-Z, pulsed power generators at Sandia National Laboratories. Results indicate a high shear is necessary to stabilize the z-pinch implosions studied
Accurate shear measurement with faint sources
International Nuclear Information System (INIS)
Zhang, Jun; Foucaud, Sebastien; Luo, Wentao
2015-01-01
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys
... Han M, Partin AW. Simple prostatectomy: open and robot-assisted laparoscopic approaches. In: Wein AJ, Kavoussi LR, ... M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health ...
International Nuclear Information System (INIS)
Ponce, W.A.; Zepeda, A.
1987-08-01
We present the results obtained from our systematic search of a simple Lie group that unifies weak and electromagnetic interactions in a single truly unified theory. We work with fractionally charged quarks, and allow for particles and antiparticles to belong to the same irreducible representation. We found that models based on SU(6), SU(7), SU(8) and SU(10) are viable candidates for simple unification. (author). 23 refs
Shear Elasticity and Shear Viscosity Imaging in Soft Tissue
Yang, Yiqun
In this thesis, a new approach is introduced that provides estimates of shear elasticity and shear viscosity using time-domain measurements of shear waves in viscoelastic media. Simulations of shear wave particle displacements induced by an acoustic radiation force are accelerated significantly by a GPU. The acoustic radiation force is first calculated using the fast near field method (FNM) and the angular spectrum approach (ASA). The shear waves induced by the acoustic radiation force are then simulated in elastic and viscoelastic media using Green's functions. A parallel algorithm is developed to perform these calculations on a GPU, where the shear wave particle displacements at different observation points are calculated in parallel. The resulting speed increase enables rapid evaluation of shear waves at discrete points, in 2D planes, and for push beams with different spatial samplings and for different values of the f-number (f/#). The results of these simulations show that push beams with smaller f/# require a higher spatial sampling rate. The significant amount of acceleration achieved by this approach suggests that shear wave simulations with the Green's function approach are ideally suited for high-performance GPUs. Shear wave elasticity imaging determines the mechanical parameters of soft tissue by analyzing measured shear waves induced by an acoustic radiation force. To estimate the shear elasticity value, the widely used time-of-flight method calculates the correlation between shear wave particle velocities at adjacent lateral observation points. Although this method provides accurate estimates of the shear elasticity in purely elastic media, our experience suggests that the time-of-flight (TOF) method consistently overestimates the shear elasticity values in viscoelastic media because the combined effects of diffraction, attenuation, and dispersion are not considered. To address this problem, we have developed an approach that directly accounts for all
Eruptive shearing of tube pumice: pure and simple
Dingwell, Donald B.; Lavallée, Yan; Hess, Kai-Uwe; Flaws, Asher; Marti, Joan; Nichols, Alexander R. L.; Gilg, H. Albert; Schillinger, Burkhard
2016-01-01
Understanding the physicochemical conditions extant and mechanisms operative during explosive volcanism is essential for reliable forecasting and mitigation of volcanic events. Rhyolitic pumices reflect highly vesiculated magma whose bubbles can serve as a strain indicator for inferring the state of stress operative immediately prior to eruptive fragmentation. Obtaining the full kinematic picture reflected in bubble population geometry has been extremely difficult, involving dissection of a s...
Adiabatic Shear Bands in Simple and Dipolar Viscoplastic Materials
1991-08-01
d Engineering Mechanics. University of Missouri-Holla. Holla. MO 65401-0249. C S.A Mace -r. Germam .Maxirr. Cork. - DrucK GmbH Carl-i -0&sset7«v...iaxirn Gorki - Druck GmoH Car:- -Ossietzk^ -Str 30 11 7400 Auenöurs I _LL 1+ Xf . . M „ .,Mqon ACTA MECHANICA Acta Mechamca 86, .31—.1...points 13, 14, 15 and 17 becomes clear from the results plotted in Fig. 3d . The plots of the temperature rise at other points con- sidered are not
Evolution of thermal ion transport barriers in reversed shear/ optimised shear plasmas
International Nuclear Information System (INIS)
Voitsekhovitch, I.; Garbet, X.; Moreau, D.; Bush, C.E.; Budny, R.V.; Gohil, P.; Kinsey, J.E.; Talyor, T.S.; Litaudon, X.
2001-01-01
The effects of the magnetic and ExB rotation shears on the thermal ion transport in advanced tokamak scenarios are analyzed through the predictive modelling of the evolution of internal transport barriers. Such a modelling is performed with an experimentally validated L-mode thermal diffusivity completed with a semi-empirical shear correction which is based on simple theoretical arguments from turbulence studies. A multi-machine test of the model on relevant discharges from the ITER Data Base (TFTR, DIII-D and JET) is presented. (author)
Shear-induced inflation of coronal magnetic fields
International Nuclear Information System (INIS)
Klimchuk, J.A.
1990-01-01
Using numerical models of force-free magnetic fields, the shearing of footprints in arcade geometries leading to an inflation of the coronal magnetic field was examined. For each of the shear profiles considered, all of the field lines become elevated compared with the potential field. This includes cases where the shear is concentrated well away from the arcade axis, such that B(sub z), the component of field parallel to the axis, increases outward to produce an inward B(sub z) squared/8 pi magnetic pressure gradient force. These results contrast with an earlier claim, shown to be incorrect, that field lines can sometimes become depressed as a result of shear. It is conjectured that an inflation of the entire field will always result from the shearing of simple arcade configurations. These results have implications for prominence formation, the interplanetary magnetic flux, and possibly also coronal holes. 38 refs
Shear Strength of Concrete I-Beams - Contributions of Flanges
DEFF Research Database (Denmark)
Teoh, B. K.; Hoang, Cao Linh; Nielsen, Mogens Peter
1999-01-01
The contribution of flanges to the shear strength of reinforced concrete beams has up to now either been neglected or evaluated by very simple empirical formulas. However, the contribution may sometimes be large, up to 20-30%. In this paper the flange contribution for shear reinforced I-beams has...... range of geometrical parameters. The comparisons show that the method suggested does indeed lead to very accurate results....
Kelemen, P. B.; Hirth, G.
2004-12-01
Localized ductile shear zones with widths of cm to m are observed in exposures of Earth's shallow mantle (e.g., Kelemen & Dick JGR 95; Vissers et al. Tectonophys 95) and dredged from oceanic fracture zones (e.g., Jaroslow et al. Tectonophys 96). These are mylonitic (grain size 10 to 100 microns) and record mineral cooling temperatures from 1100 to 600 C. Pseudotachylites in a mantle shear zone show that shear heating temperatures can exceed the mantle solidus (e.g., Obata & Karato Tectonophys 95). Simple shear, recrystallization, and grain boundary sliding all decrease the spacing between pyroxenes, so olivine grain growth at lower stress is inhibited; thus, once formed, these shear zones do not "heal" on geological time scales. Reasoning that grain-size sensitive creep will be localized within these shear zones, rather than host rocks (grain size 1 to 10 mm), and inspired by the work of Whitehead & Gans (GJRAS 74), we thought these might undergo repeated shear heating instabilities. In this view, as elastic stress increases, the shear zone weakens via shear heating; rapid deformation of the weak shear zone releases most stored elastic stress; lower stress and strain rate coupled with diffusion of heat into host rocks leads to cooling and strengthening, after which the cycle repeats. We constructed a simple numerical model incorporating olivine flow laws for dislocation creep, diffusion creep, grain boundary sliding, and low T plasticity. We assumed that viscous deformation remains localized in shear zones, surrounded by host rocks undergoing elastic deformation. We fixed the velocity along one side of an elastic half space, and calculated stress due to elastic strain. This stress drives viscous deformation in a shear zone of specified width. Shear heating and thermal diffusion control temperature evolution in the shear zone and host rocks. A maximum of 1400 C (where substantial melting of peridotite would occur) is imposed. Grain size evolves during dislocation
DEFF Research Database (Denmark)
Hansen, Klaus
This report gives a summary of the present information on the behaviour of vertical keyed shear joints in large panel structures. An attemp is made to outline the implications which this information might have on the analysis and design of a complete wall. The publications also gives a short...
Sheared Electroconvective Instability
Kwak, Rhokyun; Pham, Van Sang; Lim, Kiang Meng; Han, Jongyoon
2012-11-01
Recently, ion concentration polarization (ICP) and related phenomena draw attention from physicists, due to its importance in understanding electrochemical systems. Researchers have been actively studying, but the complexity of this multiscale, multiphysics phenomenon has been limitation for gaining a detailed picture. Here, we consider electroconvective(EC) instability initiated by ICP under pressure-driven flow, a scenario often found in electrochemical desalinations. Combining scaling analysis, experiment, and numerical modeling, we reveal unique behaviors of sheared EC: unidirectional vortex structures, its size selection and vortex propagation. Selected by balancing the external pressure gradient and the electric body force, which generates Hagen-Poiseuille(HP) flow and vortical EC, the dimensionless EC thickness scales as (φ2 /UHP)1/3. The pressure-driven flow(or shear) suppresses unfavorably-directed vortices, and simultaneously pushes favorably-directed vortices with constant speed, which is linearly proportional to the total shear of HP flow. This is the first systematic characterization of sheared EC, which has significant implications on the optimization of electrodialysis and other electrochemical systems.
International Nuclear Information System (INIS)
Biver, E.; Sims, J.
1997-01-01
This paper, originally presented at the WM'96 Conference in Tucson Arizona, describes a concept of a specialised decommissioning tool designed to operate underwater and to reduce the volume of radioactive components by shearing and compacting. The shear compactor was originally conceived to manage the size reduction of a variety of decommissioned stainless steel tubes stored within a reactor fuel cooling pond and which were consuming a substantial volume of the pond. The main objective of this tool was to cut the long tubes into shorter lengths and to compact them into a flat rectangular form which could be stacked on the pond floor, thus saving valuable space. The development programme, undertaken on this project, investigated a wide range of factors which could contribute to an extended cutting blade performance, ie: materials of construction, cutting blade shape and cutting loads required, shock effects, etc. The second phase was to review other aspects of the design, such as radiological protection, cutting blade replacement, maintenance, pond installation and resultant wall loads, water hydraulics, collection of products of shearing/compacting operations, corrosion of the equipment, control system, operational safety and the ability of the equipment to operate in dry environments. The paper summarises the extended work programme involved with this shear compactor tool. (author)
Wall shear stress hot film sensor for use in gases
International Nuclear Information System (INIS)
Osorio, O D; Silin, N
2011-01-01
The purpose of this work is to present the construction and characterization of a wall shear stress hot film sensor for use in gases made with MEMS technology. For this purpose, several associated devices were used, including a constant temperature feedback bridge and a shear stress calibration device that allows the sensor performance evaluation. The sensor design adopted here is simple, economical and is manufactured on a flexible substrate allowing its application to curved surfaces. Stationary and transient wall shear stress tests were carried on by means of the calibration device, determining its performance for different conditions.
Triglyceride glucose index and common carotid wall shear stress.
Tripolino, Cesare; Irace, Concetta; Scavelli, Faustina B; de Franceschi, Maria S; Esposito, Teresa; Carallo, Claudio; Gnasso, Agostino
2014-02-01
Alterations in wall shear stress contribute to both clinical and subclinical atherosclerosis. Several conditions such as hypertension, diabetes, and obesity can impair shear stress, but the role of insulin resistance has never been investigated. The present study was designed to investigate whether insulin resistance assessed by TyG Index associates with wall shear stress in the common carotid artery. One hundred six individuals were enrolled. Blood pressure, lipids, glucose, and cigarette smoking were evaluated. TyG Index was calculated as log[fasting triglycerides × fasting glucose / 2]. Subjects underwent blood viscosity measurement and echo-Doppler evaluation of carotid arteries to calculate wall shear stress. The association between TyG Index and carotid wall shear stress was assessed by simple and multiple regression analyses. TyG Index was significantly and inversely associated with carotid wall shear stress both in simple (r = -0.44, P glucose greater than 100 mg/dL, and triglycerides greater than 150 mg/dL. The present findings suggest that increasing insulin resistance, as assessed by TyG Index, associates with atherosclerosis-prone shear stress reduction in the common carotid artery.
Shear strength of non-shear reinforced concrete elements
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange...
Interfacial shear behavior of composite flanged concrete beams
Directory of Open Access Journals (Sweden)
Moataz Awry Mahmoud
2014-08-01
Full Text Available Composite concrete decks are commonly used in the construction of highway bridges due to their rapid constructability. The interfacial shear transfer between the top slab and the supporting beams is of great significance to the overall deck load carrying capacity and performance. Interfacial shear capacity is directly influenced by the distribution and the percentage of shear connectors. Research and design guidelines suggest the use of two different approaches to quantify the required interfacial shear strength, namely based on the maximum compressive forces in the flange at mid span or the maximum shear flow at the supports. This paper investigates the performance of flanged reinforced concrete composite beams with different shear connector’s distribution and reinforcing ratios. The study incorporated both experimental and analytical programs for beams. Key experimental findings suggest that concentrating the connectors at the vicinity of the supports enhances the ductility of the beam. The paper proposes a simple and straight forward approach to estimate the interfacial shear capacity that was proven to give good correlation with the experimental results and selected code provisions. The paper presents a method to predict the horizontal shear force between precast beams and cast in-situ slabs.
Relations between a micro-mechanical model and a damage model for ductile failure in shear
DEFF Research Database (Denmark)
Tvergaard, Viggo; Nielsen, Kim Lau
2010-01-01
Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro-cracks, w......Gurson type constitutive models that account for void growth to coalescence are not able to describe ductile fracture in simple shear, where there is no hydrostatic tension in the material. But recent micro-mechanical studies have shown that in shear the voids are flattened out to micro...
Experiments on sheet metal shearing
Gustafsson, Emil
2013-01-01
Within the sheet metal industry, different shear cutting technologies are commonly used in several processing steps, e.g. in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material.Numerical models to predict forces and sheared edge geometry for different sheet metal grades and different shear parameter set-ups a...
Goff, R. W.
1978-01-01
The studies considered the major meteorological factors producing wind shear, methods to define and classify wind shear in terms significant from an aircraft perturbation standpoint, the significance of sensor location and scan geometry on the detection and measurement of wind shear, and the tradeoffs involved in sensor performance such as range/velocity resolution, update frequency and data averaging interval.
A simple model of bedform migration
DEFF Research Database (Denmark)
Bartholdy, Jesper; Ernstsen, Verner Brandbyge; Flemming, Burg W
2010-01-01
and width) of naturally-packed bed material on the bedform lee side, qb(crest). The model is simple, built on a rational description of simplified sediment mechanics, and its calibration constant can be explained in accordance with estimated values of the physical constants on which it is based. Predicted......A model linking subaqueous dune migration to the effective (grain related) shear stress is calibrated by means of flume data for bedform dimensions and migration rates. The effective shear stress is calculated on the basis of a new method assuming a near-bed layer above the mean bed level in which...... the current velocity accelerates towards the bedform crest. As a consequence, the effective bed shear stress corresponds to the shear stress acting directly on top of the bedform. The model operates with the critical Shields stress as a function of grain size, and predicts the deposition (volume per unit time...
Onset of shear thinning in glassy liquids: Shear-induced small reduction of effective density.
Furukawa, Akira
2017-01-01
We propose a simple mechanism for describing the onset of shear thinning in a high-density glassy liquid. In a shear flow, along the compression axis, the overlap between neighboring particles is more enhanced than that at equilibrium, meaning that the "effective" size is reduced along this axis. On the other hand, along the extension axis perpendicular to the compression axis, the average structural configurations are stretched, but it does not indicate the expansion of the "effective" size itself. This asymmetric shear flow effect for particles results in a small reduction of the "effective" density. Because, in glass-forming liquids, the structural relaxation time τ_{α} strongly depends on the density ρ, even a very small reduction of the effective density should lead to a significant decrease of the relaxation time under shear flow. We predict that the crossover shear rate from Newtonian to non-Newtonian flow behaviors is given by γ[over ̇]_{c}=[ρ(∂τ_{α}/∂ρ)]^{-1}, which can be much smaller than 1/τ_{α} near the glass transition point. It is shown that this prediction is consistent with the results of molecular dynamics simulations.
Energy Technology Data Exchange (ETDEWEB)
Butler, B.D.; Hanley, H.J.M.; Straty, G.C. [National Institute of Standards and Technology, Boulder, CO (United States); Muzny, C.D. [Univ. of Colorado, Boulder, CO (United States)
1995-12-31
An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.
Forflytning: shear og friktion
DEFF Research Database (Denmark)
2005-01-01
friktion). Formålet med filmprojektet er: At give personalet i Apopleksiafsnittet viden om shear og friktion, så det motiveres til forebyggelse. Mål At udarbejde et enkelt undervisningsmateriale til bed-side-brug Projektbeskrivelse (resume) Patienter med apopleksi er særligt udsatte for tryksår, fordi de...... ofte er immobile, har svært ved at opretholde en god siddestilling eller ligger tungt i sengen som følger efter apopleksien Hvis personalet bruger forkert lejrings-og forflytningsteknik, udsættes patienterne for shear og friktion. Målgruppen i projektet er de personer, der omgås patienterne, dvs...
2012-09-13
pneumatically operated paste dumper and belt conveyor system, the loss in weight feeder system, the hydraulically operated shear roll mill, the pellet...out feed belt conveyor , and the pack out system comprised of the metal detector, scale, and pack out empty and full drum roller conveyors . Page | 4...feed hopper and conveyor supplying the loss in weight feeder were turned on, and it was verified that these items functioned as designed . The
Turbulent shear layers in confining channels
Benham, Graham P.; Castrejon-Pita, Alfonso A.; Hewitt, Ian J.; Please, Colin P.; Style, Rob W.; Bird, Paul A. D.
2018-06-01
We present a simple model for the development of shear layers between parallel flows in confining channels. Such flows are important across a wide range of topics from diffusers, nozzles and ducts to urban air flow and geophysical fluid dynamics. The model approximates the flow in the shear layer as a linear profile separating uniform-velocity streams. Both the channel geometry and wall drag affect the development of the flow. The model shows good agreement with both particle image velocimetry experiments and computational turbulence modelling. The simplicity and low computational cost of the model allows it to be used for benchmark predictions and design purposes, which we demonstrate by investigating optimal pressure recovery in diffusers with non-uniform inflow.
Plasticity Approach to Shear Design
DEFF Research Database (Denmark)
Hoang, Cao Linh; Nielsen, Mogens Peter
1998-01-01
The paper presents some plastic models for shear design of reinforced concrete beams. Distinction is made between two shear failure modes, namely web crushing and crack sliding. The first mentioned mode is met in beams with large shear reinforcement degrees. The mode of crack sliding is met in non......-shear reinforced beams as well as in lightly shear reinforced beams. For such beams the shear strength is determined by the recently developed crack sliding model. This model is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed...... in uncracked concrete. Good agree between theory and tests has been found.Keywords: dsign, plasticity, reinforced concrete, reinforcement, shear, web crushing....
Shear viscosity of phase-separating polymer blends with viscous asymmetry
International Nuclear Information System (INIS)
Jeon, H. S.; Hobbie, E. K.
2001-01-01
Rheo-optical measurements of phase separating polymer mixtures under simple shear flow have been used to investigate the influence of domain morphology on the viscosity of emulsionlike polymer blends, in which the morphology under weak shear is droplets of one coexisting phase dispersed in a matrix of the second. The structure and viscosity of low-molecular-weight polybutadiene and polyisoprene mixtures, phase separated by quenching to a temperature inside the coexistence region of the phase diagram, were measured as a function of shear rate and composition. In the weak shear regime, the data are in qualitative agreement with an effective medium model for non-dilute suspensions of slightly deformed interacting droplets. In the strong shear regime, where a stringlike pattern appears en route to a shear-homogenized state, the data are in qualitative agreement with a simple model that accounts for viscous asymmetry in the components
Hu, Wei; Xu, Qiang; Wang, Gonghui; Scaringi, Gianvito; Mcsaveney, Mauri; Hicher, Pierre-Yves
2017-11-01
We present results of ring shear frictional resistance for mudstone granules of different size obtained from a landslide shear zone. Little rate dependency of shear resistance was observed in sand-sized granules in any wet or dry test, while saturated gravel-sized granules exhibited significant and abrupt reversible rate-weakening (from μ = 0.6 to 0.05) at about 2 mm/s. Repeating resistance variations occurred also under constant shear displacement rate. Mudstone granules generate mud as they are crushed and softened. Shear-thinning and thixotropic behavior of the mud can explain the observed behavior: with the viscosity decreasing, the mud can flow through the coarser soil pores and migrate out from the shear zone. This brings new granules into contact which produces new mud. Thus, the process can start over. Similarities between experimental shear zones and those of some landslides in mudstone suggest that the observed behavior may play a role in some landslide kinematics.
Practical Weak-lensing Shear Measurement with Metacalibration
Energy Technology Data Exchange (ETDEWEB)
Sheldon, Erin S. [Brookhaven National Laboratory, Bldg. 510, Upton, NY 11973 (United States); Huff, Eric M. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States)
2017-05-20
Metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observe that for images with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measured galaxy properties to induce significant selection effects. Using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.
Estimated strength of shear keys in concrete dams
Energy Technology Data Exchange (ETDEWEB)
Curtis, D.D. [Hatch Energy, Niagara Falls, ON (Canada); Lum, K.K.Y. [BC Hydro, Burnaby, BC (Canada)
2008-07-01
BC Hydro requested that Hatch Energy review the seismic stability of Ruskin Dam which was constructed in 1930 at Hayward Lake in British Columbia. The concrete gravity dam is founded nearly entirely on rock in a narrow valley. The vertical joints between blocks are keyed and grouted. The strength of the shear keys was assessed when a non-linear finite element model found that significant forces were being transferred laterally to the abutments during an earthquake. The lateral transfer of loads to the abutment relies on the strength of the shear keys. The dynamic finite element analysis was used to determine the stability of the dam. A review of the shear strength measurements reported in literature showed that the measurements compared well to those obtained by BC Hydro from cores taken from Ruskin Dam. The cohesive strength obtained using the Griffith failure criteria was also in good agreement with both sets of measurements. A simple ultimate shear strength equation was developed using the Mohr-Coulomb failure criteria to determine combined cohesive and frictional strength of shear keys. Safety factors of 2.0 for static loads and 1.5 for seismic loads were proposed to reduce the ultimate strength to allowable values. It was concluded that given the relatively high shear strength established for the shear keys, the abutment rock or dam/abutment contact will control the amount of load which can arch to the abutments. 8 refs., 4 tabs., 5 figs.
Interaction of equal-size bubbles in shear flow.
Prakash, Jai; Lavrenteva, Olga M; Byk, Leonid; Nir, Avinoam
2013-04-01
The inertia-induced forces on two identical spherical bubbles in a simple shear flow at small but finite Reynolds number, for the case when the bubbles are within each other's inner viscous region, are calculated making use of the reciprocal theorem. This interaction force is further employed to model the dynamics of air bubbles injected to a viscous fluid sheared in a Couette device at the first shear flow instability where the bubbles are trapped inside the stable Taylor vortex. It was shown that, during a long time scale, the inertial interaction between the bubbles in the primary shear flow drives them away from each other and, as a result, equal-size bubbles eventually assume an ordered string with equal separation distances between all neighbors. We report on experiments showing the dynamic evolution of various numbers of bubbles. The results of the theory are in good agreement with the experimental observations.
International Nuclear Information System (INIS)
Lin, Kevin K; Young, Lai-Sang
2008-01-01
Guided by a geometric understanding developed in earlier works of Wang and Young, we carry out numerical studies of shear-induced chaos in several parallel but different situations. The settings considered include periodic kicking of limit cycles, random kicks at Poisson times and continuous-time driving by white noise. The forcing of a quasi-periodic model describing two coupled oscillators is also investigated. In all cases, positive Lyapunov exponents are found in suitable parameter ranges when the forcing is suitably directed
Lin, Kevin K.; Young, Lai-Sang
2008-05-01
Guided by a geometric understanding developed in earlier works of Wang and Young, we carry out numerical studies of shear-induced chaos in several parallel but different situations. The settings considered include periodic kicking of limit cycles, random kicks at Poisson times and continuous-time driving by white noise. The forcing of a quasi-periodic model describing two coupled oscillators is also investigated. In all cases, positive Lyapunov exponents are found in suitable parameter ranges when the forcing is suitably directed.
2015-03-12
0030] FIG. 7 is an isometric view of a deformable ring of the bolt shear force sensor of the present invention with an optical Attorney Docket No...102587 9 of 19 fiber having Bragg gratings wound around the ring; [0031] FIG. 8 is an isometric view of the deformable ring with wire strain... strength . [0047] Once the joint is subjected to an external load (see force arrows “F” and “F/2”); any frictional resistance to slip is overcome and
Veríssimo, G. S.; Paes, J. L. R.; Valente, Isabel; Cruz, Paulo J. S.; Fakury, R. H.
2006-01-01
This work presents the design of a new shear connector and the corresponding results obtained on push-out tests. This new shear connector consists on a steel rib with indented cut shape that provides resistance to longitudinal shear and prevents transversal separation between the concrete slab and the steel profile (uplift). Adding to this, the connector openings cut makes easier the arrangement of transversal reinforcement bars. The installation of the connectors is simple and requires only ...
Pinney, Rhiannon; Liverpool, Tanniemola B; Royall, C Patrick
2016-12-21
We consider a binary Lennard-Jones glassformer whose super-Arrhenius dynamics are correlated with the formation of particles organized into icosahedra under simple steady state shear. We recast this glassformer as an effective system of icosahedra [Pinney et al., J. Chem. Phys. 143, 244507 (2015)]. From the observed population of icosahedra in each steady state, we obtain an effective temperature which is linearly dependent on the shear rate in the range considered. Upon shear banding, the system separates into a region of high shear rate and a region of low shear rate. The effective temperatures obtained in each case show that the low shear regions correspond to a significantly lower temperature than the high shear regions. Taking a weighted average of the effective temperature of these regions (weight determined by region size) yields an estimate of the effective temperature which compares well with an effective temperature based on the global mesocluster population of the whole system.
Ab initio study of Ni2MnGa under shear deformation
Directory of Open Access Journals (Sweden)
Zelený Martin
2015-01-01
Full Text Available The effect of shear deformation on Ni2MnGa magnetic shape memory alloy has been investigated using ab initio electronic structure calculations. We used the projector-augmented wave method for the calculations of total energies and stresses as functions of applied affine shear deformation. The studied nonmodulated martensite (NM phase exhibits a tetragonally distorted L21 structure with c/a > 1. A large strain corresponding to simple shears in {001}, {100} and {100} systems was applied to describe a full path between two equivalent NM lattices. We also studied {101} shear which is related to twining of NM phase. Twin reorientation in this system is possible, because applied positive shear results in path with significantly smaller energetic barrier than for negative shear and for shears in other studied systems. When the full relaxation of lattice parameters is allowed, the barriers further strongly decrease and the structures along the twinning path can be considered as orthorhombic.
Texture evolution by shear on two planes during ECAP of a high-strength aluminum alloy
International Nuclear Information System (INIS)
Wang Shuncai; Starink, Marco J.; Gao Nong; Qiao Xiaoguang; Xu Cheng; Langdon, Terence G.
2008-01-01
The evolution of texture was examined during equal-channel angular pressing (ECAP) of an Al-Zn-Mg-Cu alloy having a strong initial texture. An analysis of the local texture using electron backscatter diffraction demonstrates that shear occurs on two shear planes: the main shear plane (MSP) equivalent to the simple shear plane, and a secondary shear plane which is perpendicular to the MSP. Throughout most regions of the ECAP billet, the MSP is close to the intersection plane of the two channels but with a small (5 deg.) deviation. Only the {1 1 1} and {0 0 1} shear systems were activated and there was no experimental evidence for the existence of other shear systems. In a small region at the bottom edge of the billet that passed through the zone of intersection of the channels, the observed textures were fully consistent with the rolling textures of Copper and Goss
Bechert, D. W.
1982-01-01
The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.
Nelson, Arif Z.; Ewoldt, Randy H.
2017-11-01
Design in fluid mechanics often focuses on optimizing geometry (airfoils, surface textures, microfluid channels), but here we focus on designing fluids themselves. The dramatically shear-thinning ``yield-stress fluid'' is currently the most utilized non-Newtonian fluid phenomenon. These rheologically complex materials, which undergo a reversible transition from solid-like to liquid-like fluid flow, are utilized in pedestrian products such as paint and toothpaste, but also in emerging applications like direct-write 3D printing. We present a paradigm for yield-stress fluid design that considers constitutive model representation, material property databases, available predictive scaling laws, and the many ways to achieve a yield stress fluid, flipping the typical structure-to-rheology analysis to become the inverse: rheology-to-structure with multiple possible materials as solutions. We describe case studies of 3D printing inks and other flow scenarios where designed shear-thinning enables performance remarkably beyond that of Newtonian fluids. This work was supported by Wm. Wrigley Jr. Company and the National Science Foundation under Grant No. CMMI-1463203.
Inductive shearing of drilling pipe
Ludtka, Gerard M.; Wilgen, John; Kisner, Roger; Mcintyre, Timothy
2016-04-19
Induction shearing may be used to cut a drillpipe at an undersea well. Electromagnetic rings may be built into a blow-out preventer (BOP) at the seafloor. The electromagnetic rings create a magnetic field through the drillpipe and may transfer sufficient energy to change the state of the metal drillpipe to shear the drillpipe. After shearing the drillpipe, the drillpipe may be sealed to prevent further leakage of well contents.
Shear structuring as a new method to make anisotropic structures from soy-gluten blends
Grabowska, K.J.; Tekidou, S.; Boom, R.M.; Goot, van der A.J.
2014-01-01
The concept of shear-induced structuring was applied to concentrated blends of soy protein isolate (SPI) and wheat gluten (WG) to create novel semi-solid food textures. Concurrent simple shear deformation and heating (95 °C) of the protein blends generated original structures consisting of fibers or
Sandeep S. Nair; Sudhir Sharma; Yunqiao Pu; Qining Sun; Shaobo Pan; J.Y. Zhu; Yulin Deng; Art J. Ragauskas
2014-01-01
A new method to prepare nanolignin using a simple high shear homogenizer is presented. The kraft lignin particles with a broad distribution ranging from large micron- to nano-sized particles were completely homogenized to nanolignin particles with sizes less than 100 nm after 4 h of mechanical shearing. The 13C nuclear magnetic resonance (NMR)...
Influence of steady shear flow on dynamic viscoelastic properties of ...
Indian Academy of Sciences (India)
Unknown
temporary network formed by the fibres, their entangle- ment etc. The structural density is also a function of vol- ume fraction of reinforcing fibres (Amari et al 1992). The complex flow pattern encountered during moulding/ stamping are generally far from simple steady or oscilla- tory shear flow. Therefore, it is important to ...
Shear in high strength concrete bridge girders : technical report.
2013-04-01
Prestressed Concrete (PC) I-girders are used extensively as the primary superstructure components in Texas highway bridges. : A simple semi-empirical equation was developed at the University of Houston (UH) to predict the shear strength of PC I-girde...
Magnetorheological dampers in shear mode
International Nuclear Information System (INIS)
Wereley, N M; Cho, J U; Choi, Y T; Choi, S B
2008-01-01
In this study, three types of shear mode damper using magnetorheological (MR) fluids are theoretically analyzed: linear, rotary drum, and rotary disk dampers. The damping performance of these shear mode MR dampers is characterized in terms of the damping coefficient, which is the ratio of the equivalent viscous damping at field-on status to the damping at field-off status. For these three types of shear mode MR damper, the damping coefficient or dynamic range is derived using three different constitutive models: the Bingham–plastic, biviscous, and Herschel–Bulkley models. The impact of constitutive behavior on shear mode MR dampers is theoretically presented and compared
A Novel Geometry for Shear Test Using Axial Tensile Setup
Directory of Open Access Journals (Sweden)
Sibo Yuan
2018-05-01
Full Text Available This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile tests, large tensile tests and shear tests. For the whole campaign, a common equipment should be employed to minimize the impact of the testing device. As a consequence, for the shear tests, the geometry of the specimen must be carefully designed in order to adapt the force value and make it comparable to the one obtained for the tensile tests. Like most of the existing shear-included tensile test specimens, the axial loading is converted to shear loading at a particular region through the effect of geometry. A symmetric shape is generally preferred, since it can restrict the in-plane rotation of the shear section, keep shear increasing in a more monotonic path and double the force level thanks to the two shear zones. Due to the specific experimental conditions, such as dimensions of the furnace and the clamping system, the position of the extensometer or the restriction of sheet thickness (related to the further studies of size effect at mesoscale and hot temperature, several geometries were brought up and evaluated in an iterative procedure via finite element simulations. Both the numerical and experimental results reveal that the final geometry ensures some advantages. For instance, a relatively low triaxiality in the shear zone, limited in-plane rotation and no necking are observed. Moreover, it also prevents any out-of-plane displacement of the specimen which seems to be highly sensitive to the geometry, and presents a very limited influence of the material and the thickness.
HIERARCHICAL PROBABILISTIC INFERENCE OF COSMIC SHEAR
International Nuclear Information System (INIS)
Schneider, Michael D.; Dawson, William A.; Hogg, David W.; Marshall, Philip J.; Bard, Deborah J.; Meyers, Joshua; Lang, Dustin
2015-01-01
Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the global shear inference, thereby rendering our algorithm computationally tractable for large surveys. With simple numerical examples we demonstrate the improvements in accuracy from our importance sampling approach, as well as the significance of the conditional distribution specification for the intrinsic galaxy properties when the data are generated from an unknown number of distinct galaxy populations with different morphological characteristics
Shear flow in smectic A liquid crystals
International Nuclear Information System (INIS)
Stewart, I W; Stewart, F
2009-01-01
This paper considers the onset of a shear-induced instability in a sample of smectic A liquid crystal. Unlike many previous models, the usual director n need not necessarily coincide with the local smectic layer normal a; the traditional Oseen constraint (∇xa=0) is not imposed when flow is present. A recent dynamic theory for smectic A (Stewart 2007 Contin. Mech. Thermodyn. 18 343-60) will be used to examine a stationary instability in a simple model when the director reorientation and smectic layer distortions are, firstly, assumed not to be coupled to the velocity and, secondly, are supposed coupled to the velocity. A critical shear rate at which the onset of the instability occurs will be identified, together with an accompanying critical director tilt angle and critical wavenumber for the associated smectic layer undulations. Despite some critical phenomena being largely unaffected by any coupling to the flow, it will be shown that the influence of some material parameters, especially the smectic layer compression constant B 0 and the coupling constant B 1 , upon the critical shear rate and critical tilt angle can be greatly affected by flow.
Shear strength of non-shear reinforced concrete elements
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
The paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions.In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding...
Topics in the Analysis of Shear-Wave Propagation in Oblique-Plate Impact Tests
National Research Council Canada - National Science Library
Scheidler, Mike
2007-01-01
This report addresses several topics in the theoretical analysis of shock waves, acceleration waves, and centered simple waves, with emphasis on the propagation of shear waves generated in oblique-plate impact tests...
Flexible Micropost Arrays for Shear Stress Measurement
Wohl, Christopher J.; Palmieri, Frank L.; Hopkins, John W.; Jackson, Allen M.; Connell, John W.; Lin, Yi; Cisotto, Alexxandra A.
2015-01-01
of delicate micro-electromechanical devices impede the use of most direct shear sensors. Similarly, the cavity required for sensing element displacement is sensitive to particulate obstruction. This work was focused on developing a shear stress sensor for use in subsonic wind tunnel test facilities applicable to an array of test configurations. The non-displacement shear sensors described here have minimal packaging requirements resulting in minimal or no disturbance of boundary layer flow. Compared to previous concepts, device installation could be simple with reduced cost and down-time. The novelty lies in the creation of low profile (nanoscale to 100 µm) micropost arrays that stay within the viscous sub-layer of the airflow. Aerodynamic forces, which are related to the surface shear stress, cause post deflection and optical property changes. Ultimately, a reliable, accurate shear stress sensor that does not disrupt the airflow has the potential to provide high value data for flow physics researchers, aerodynamicists, and aircraft manufacturers leading to greater flight efficiency arising from more in-depth knowledge on how aircraft design impacts near surface properties.
Temperature dependence of transport coefficients of 'simple liquid ...
African Journals Online (AJOL)
... has been investigated. The study carried out at two densities, r* = 0.60 and r* = 0.95. Result shows erratic variations of the shear viscosity in the two lattices structures. KeyWords: Temperature effect, face centred, simple cubic, transport properties, simple liquid. [Global Jnl Pure & Appl. Sci. Vol.9(3) 2003: 403-406] ...
A Piezoelectric Shear Stress Sensor
Kim, Taeyang; Saini, Aditya; Kim, Jinwook; Gopalarathnam, Ashok; Zhu, Yong; Palmieri, Frank L.; Wohl, Christopher J.; Jiang, Xiaoning
2016-01-01
In this paper, a piezoelectric sensor with a floating element was developed for shear stress measurement. The piezoelectric sensor was designed to detect the pure shear stress suppressing effects of normal stress generated from the vortex lift-up by applying opposite poling vectors to the: piezoelectric elements. The sensor was first calibrated in the lab by applying shear forces and it showed high sensitivity to shear stress (=91.3 +/- 2.1 pC/Pa) due to the high piezoelectric coefficients of PMN-33%PT (d31=-1330 pC/N). The sensor also showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the device. The usable frequency range of the sensor is 0-800 Hz. Keywords: Piezoelectric sensor, shear stress, floating element, electromechanical symmetry
Shear Stress-Relative Slip Relationship at Concrete Interfaces
Directory of Open Access Journals (Sweden)
Keun-Hyeok Yang
2016-01-01
Full Text Available This study develops a simple and rational shear stress-relative slip model of concrete interfaces with monolithic castings or smooth construction joints. In developing the model, the initial shear cracking stress and relative slip amount at peak stress were formulated from a nonlinear regression analysis using test data for push-off specimens. The shear friction strength was determined from the generalized equations on the basis of the upper-bound theorem of concrete plasticity. Then, a parametric fitting analysis was performed to derive equations for the key parameters determining the shapes of the ascending and descending branches of the shear stress-relative slip curve. The comparisons of predictions and measurements obtained from push-off tests confirmed that the proposed model provides superior accuracy in predicting the shear stress-relative slip relationship of interfacial shear planes. This was evidenced by the lower normalized root mean square error than those in Xu et al.’s model and the CEB-FIB model, which have many limitations in terms of the roughness of the substrate surface along an interface and the magnitude of equivalent normal stress.
Shear transfer capacity of reinforced concrete exposed to fire
Ahmad, Subhan; Bhargava, Pradeep; Chourasia, Ajay
2018-04-01
Shear transfer capacity of reinforced concrete elements is a function of concrete compressive strength and reinforcement yield strength. Exposure of concrete and steel to elevated temperature reduces their mechanical properties resulting in reduced shear transfer capacity of RC elements. The objective of present study is to find the effect of elevated temperature on shear transfer capacity of reinforced concrete. For this purpose pushoff specimens were casted using normal strength concrete. After curing, specimens were heated to 250°C and 500°C in an electric furnace. Cooled specimens were tested for shear transfer capacity in a universal testing machine. It was found that shear transfer capacity and stiffness (slope of load-slip curve) were reduced when the specimens were heated to 250°C and 500°C. Load level for the initiation of crack slip was found to be decreased as the temperature was increased. A simple analytical approach is also proposed to predict the shear transfer capacity of reinforced concrete after elevated temperature.
Hamimi, Z.; El-Sawy, E. K.; El-Fakharan, A. S.; Shujoon, A.; Matsah, M.; El-Shafei, M.
2012-04-01
Ad-Damm Shear Zone (ASZ) is a NE-trending fault zone separating Jeddah and Asir tectonostratigraphic terranes in the Neoproterozoic juvenile Arabian Shield. ASZ extends ~380 km, with an average width ~2-3 km, from the eye-catching Ruwah Fault Zone in the eastern shield to the Red Sea Coastal plain. It was believed to be one of the conjugate shears of the NW- to NNW- trending sinistral Najd Shear System based on noteworthy dextral shear criteria recorded within the 620 Ma sheared granites of Numan Complex, as well as right-lateral offsets within quartz veins and dikes transected by the shear zone. The present study is an integrated field-based structural analysis and remote sensing. We utilized the ASTER data for lithologic discrimination and automatic structural lineament extraction and analysis of the Neoproterozoic basement lithologies encountered along and within the vicinity of ASZ. Various false color composite images were generated and evaluated for lithological mapping and structural lineaments. The obtained map was analyzed using GIS techniques to interpret the behavior of the existing lineaments and their spatial distribution. Based on the results of the ASTER data, two significant areas; around Bir Ad-Damm and to the south of Wadi Numan, are selected for detailed field investigation. Shear-sense indicators and overprinting relations clearly show a complicated Neoproterozoic history of ASZ, involving at least three deformations: (1) an early attenuated NE-SW sinistral shearing; followed by (2) a SE-directed thrusting phase resulted in the formation SE-verging thrusts and associated thrust-related folds; and (3) late NE-SW intensive dextral transcurrent shearing played a significant role in the creation of mesoscopic shear-zone related folds, particularly in the area near Bir Ad-Damm. Such deformation history demonstrates the same episode of Neoproterozoic deformation exhibited in the NE-trending shear zones in the Arabian-Nubian Shield (ANS).
SEDflume - High Shear Stress Flume
Federal Laboratory Consortium — The U.S. Army Corps of Engineers High Shear Stress flume (SEDflume) is designed for estimating erosion rates of fine-grained and mixed fine/coarse grained sediments...
Seismic behavior of semi-supported steel shear walls
DEFF Research Database (Denmark)
Jahanpour, A.; Jönsson, J.; Moharrami, H.
2012-01-01
During the recent past decade semi-supported steel shear walls (SSSW) have been introduced as an alternative to the traditional type of steel plate shear walls. In this system the shear wall does not connect directly to the main columns of the building frame; instead it is connected to a pair...... of secondary columns that do not carry vertical gravity loads. In this paper, the interaction between the wall plate and the surrounding frame is investigated experimentally for typical SSSW systems in which the wall-frame has a bending-dominant behavior. Based on the possible storey failure mechanisms...... a simple method is proposed for design of the floor beams. A quasi static cyclic experimental study has been performed in order to investigate the collapse behavior of the wall-plate and surrounding frame. Furthermore the test setup has been developed in order to facilitate standardized cyclic tests...
Size effects in shear interfaces
GARNIER, J
2001-01-01
In physical modelling (centrifuge tests, calibration chambers, laboratory tests), the size of the soil particles may not be negligible when compared to the dimensions of the models. Size effects may so disturb the response of the models and the experimental data obtained on these cannot be extended to true scale conditions. Different tests have been performed to study and quantify the size effects that may happen in shear interfaces between soils and structures : modified shear box tests, pul...
Multifractal spectra in shear flows
Keefe, L. R.; Deane, Anil E.
1989-01-01
Numerical simulations of three-dimensional homogeneous shear flow and fully developed channel flow, are used to calculate the associated multifractal spectra of the energy dissipation field. Only weak parameterization of the results with the nondimensional shear is found, and this only if the flow has reached its asymptotic development state. Multifractal spectra of these flows coincide with those from experiments only at the range alpha less than 1.
Shear Alfven waves in tokamaks
International Nuclear Information System (INIS)
Kieras, C.E.
1982-12-01
Shear Alfven waves in an axisymmetric tokamak are examined within the framework of the linearized ideal MHD equations. Properties of the shear Alfven continuous spectrum are studied both analytically and numerically. Implications of these results in regards to low frequency rf heating of toroidally confined plasmas are discussed. The structure of the spatial singularities associated with these waves is determined. A reduced set of ideal MHD equations is derived to describe these waves in a very low beta plasma
Experimental observation of shear thickening oscillation
DEFF Research Database (Denmark)
Nagahiro, Shin-ichiro; Nakanishi, Hiizu; Mitarai, Namiko
2013-01-01
We report experimental observations of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed...
Shear layer flame stabilization sensitivities in a swirling flow
Directory of Open Access Journals (Sweden)
Christopher Foley
2017-03-01
Full Text Available A variety of different flame configurations and heat release distributions exist in high swirl, annular flows, due to the existence of inner and outer shear layers as well a vortex breakdown bubble. Each of these different configurations, in turn, has different thermoacoustic sensitivities and influences on combustor emissions, nozzle durability, and liner heating. This paper presents findings on the sensitivities of the outer shear layer- stabilized flames to a range of parameters, including equivalence ratio, bulkhead temperature, flow velocity, and preheat temperature. There is significant hysteresis for flame attachment/detachment from the outer shear layer and this hysteresis is also described. Results are also correlated with extinction stretch rate calculations based on detailed kinetic simulations. In addition, we show that the bulkhead temperature near the flame attachment point has significant impact on outer shear layer detachment. This indicates that understanding the heat transfer between the edge flame stabilized in the shear layer and the nozzle hardware is needed in order to predict shear layer flame stabilization limits. Moreover, it shows that simulations cannot simply assume adiabatic boundary conditions if they are to capture these transitions. We also show that the reference temperature for correlating these transitions is quite different for attachment and local blow off. Finally, these results highlight the deficiencies in current understanding of the influence of fluid mechanic parameters (e.g. velocity, swirl number on shear layer flame attachment. For example, they show that the seemingly simple matter of scaling flame transition points with changes in flow velocities is not understood.
Shear bands as growing instabilities in viscoanelastic media with memory
Directory of Open Access Journals (Sweden)
Marina Dolfin
2013-09-01
Full Text Available In this paper we investigate the critical conditions under which a small perturbation in an homogeneous continuum can possibly grows into a shear band instability. In particular, we analyze from a thermodynamical viewpoint the phenomenon of shear bands in viscoanelastic media with memory. It is emphasized, in the scientific literature, that the specific adopted rheology strongly affects the results so that a special attention has to be paid, also for engineering purposes, to the accuracy of the rheological model. Several well-known rheological model (for instance the so called Maxwell or Jeffreys media are particular cases of the general model we adopt in the paper to analyze shear bands. Instability conditions, giving rise to shear bands formation, are obtained by introducing small perturbations around an homogeneous deformation into the system of differential equations governing the problem of homogeneous deformations in the considered continuous medium; as a result a non-homogeneous linear dynamical system is obtained whose stability is analyzed. A research perspective in view of a possible comparison with experimental results is proposed; in particular the simple methodology proposed in the paper should be applied in view of using the phenomenon of the initiation of shear bands to calculate the thermomechanical coefficients of real materials.
Vescovi, Dalila; Berzi, Diego; Richard, Patrick; Brodu, Nicolas
2014-01-01
International audience; We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed av...
... Solitary Kidney Your Kidneys & How They Work Simple Kidney Cysts What are simple kidney cysts? Simple kidney cysts are abnormal, fluid-filled ... that form in the kidneys. What are the kidneys and what do they do? The kidneys are ...
International Nuclear Information System (INIS)
Punjabi, Alkesh; Ali, Halima; Farhat, Hamidullah
2009-01-01
Extra terms are added to the generating function of the simple map (Punjabi et al 1992 Phys. Rev. Lett. 69 3322) to adjust shear of magnetic field lines in divertor tokamaks. From this new generating function, a higher shear map is derived from a canonical transformation. A continuous analog of the higher shear map is also derived. The method of maps (Punjabi et al 1994 J. Plasma Phys. 52 91) is used to calculate the average shear, stochastic broadening of the ideal separatrix near the X-point in the principal plane of the tokamak, loss of poloidal magnetic flux from inside the ideal separatrix, magnetic footprint on the collector plate, and its area, and the radial diffusion coefficient of magnetic field lines near the X-point. It is found that the width of the stochastic layer near the X-point and the loss of poloidal flux from inside the ideal separatrix scale linearly with average shear. The area of magnetic footprints scales roughly linearly with average shear. Linear scaling of the area is quite good when the average shear is greater than or equal to 1.25. When the average shear is in the range 1.1-1.25, the area of the footprint fluctuates (as a function of average shear) and scales faster than linear scaling. Radial diffusion of field lines near the X-point increases very rapidly by about four orders of magnitude as average shear increases from about 1.15 to 1.5. For higher values of average shear, diffusion increases linearly, and comparatively very slowly. The very slow scaling of the radial diffusion of the field can flatten the plasma pressure gradient near the separatrix, and lead to the elimination of type-I edge localized modes.
Shear strength of non-shear reinforced concrete elements
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed in uncracked concrete.Proposals have been made on how the derived standard solutions may be applied to more complicated cases, such as continuous beams, beams......The report deals with the shear strength of statically indeterminate reinforced concrete beams without shear reinforcement. Solutions for a number of beams with different load and support conditions have been derived by means of the crack sliding model developed by Jin- Ping Zhang.This model...
Giammarinaro, Bruno; Espíndola, David; Coulouvrat, François; Pinton, Gianmarco
2018-01-01
Focusing is a ubiquitous way to transform waves. Recently, a new type of shock wave has been observed experimentally with high-frame-rate ultrasound: shear shock waves in soft solids. These strongly nonlinear waves are characterized by a high Mach number, because the shear wave velocity is much slower, by 3 orders of magnitude, than the longitudinal wave velocity. Furthermore, these waves have a unique cubic nonlinearity which generates only odd harmonics. Unlike longitudinal waves for which only compressional shocks are possible, shear waves exhibit cubic nonlinearities which can generate positive and negative shocks. Here we present the experimental observation of shear shock wave focusing, generated by the vertical motion of a solid cylinder section embedded in a soft gelatin-graphite phantom to induce linearly vertically polarized motion. Raw ultrasound data from high-frame-rate (7692 images per second) acquisitions in combination with algorithms that are tuned to detect small displacements (approximately 1 μ m ) are used to generate quantitative movies of gel motion. The features of shear shock wave focusing are analyzed by comparing experimental observations with numerical simulations of a retarded-time elastodynamic equation with cubic nonlinearities and empirical attenuation laws for soft solids.
Modeling of shear wall buildings
Energy Technology Data Exchange (ETDEWEB)
Gupta, A K [North Carolina State Univ., Raleigh (USA). Dept. of Civil Engineering
1984-05-01
Many nuclear power plant buildings, for example, the auxiliary building, have reinforced concrete shear walls as the primary lateral load resisting system. Typically, these walls have low height to length ratio, often less than unity. Such walls exhibit marked shear lag phenomenon which would affect their bending stiffness and the overall stress distribution in the building. The deformation and the stress distribution in walls have been studied which is applicable to both the short and the tall buildings. The behavior of the wall is divided into two parts: the symmetric flange action and the antisymmetry web action. The latter has two parts: the web shear and the web bending. Appropriate stiffness equations have been derived for all the three actions. These actions can be synthesized to solve any nonlinear cross-section. Two specific problems, that of lateral and torsional loadings of a rectangular box, have been studied. It is found that in short buildings shear lag plays a very important role. Any beam type formulation which either ignores shear lag or includes it in an idealized form is likely to lead to erroneous results. On the other hand a rigidity type approach with some modifications to the standard procedures would yield nearly accurate answers.
Universal behaviour of silica suspensions gelled under shear
International Nuclear Information System (INIS)
Hanley, H J M; Muzny, C D; Bartlett, J; Drabarek, E
2007-01-01
The shear-influenced gelation of three aqueous suspensions consisting of silica particles of nominal diameter 7, 12 and 24 nm, respectively, is reported. It is shown that the viscosity/stress of a gelling system increases with time after gel initiation, reaches a maximum, then falls to a plateau value. A very simple relation between this maximum stress and the precursor volume fraction is verified experimentally
A Hammer-Impact, Aluminum, Shear-Wave Seismic Source
Haines, Seth
2007-01-01
Near-surface seismic surveys often employ hammer impacts to create seismic energy. Shear-wave surveys using horizontally polarized waves require horizontal hammer impacts against a rigid object (the source) that is coupled to the ground surface. I have designed, built, and tested a source made out of aluminum and equipped with spikes to improve coupling. The source is effective in a variety of settings, and it is relatively simple and inexpensive to build.
Schellart, W. P.
2000-01-01
Laboratory tests have been carried out on dry granular materials such as quartz sand, glass microspheres and sugar with different grain size, rounding and sphericity. The measurements have been made with a simple shear test machine for different values of normal stress (~ 50-900 Pa). Shear stress
FEM Simulation of Incremental Shear
International Nuclear Information System (INIS)
Rosochowski, Andrzej; Olejnik, Lech
2007-01-01
A popular way of producing ultrafine grained metals on a laboratory scale is severe plastic deformation. This paper introduces a new severe plastic deformation process of incremental shear. A finite element method simulation is carried out for various tool geometries and process kinematics. It has been established that for the successful realisation of the process the inner radius of the channel as well as the feeding increment should be approximately 30% of the billet thickness. The angle at which the reciprocating die works the material can be 30 deg. . When compared to equal channel angular pressing, incremental shear shows basic similarities in the mode of material flow and a few technological advantages which make it an attractive alternative to the known severe plastic deformation processes. The most promising characteristic of incremental shear is the possibility of processing very long billets in a continuous way which makes the process more industrially relevant
SHEAR ACCELERATION IN EXPANDING FLOWS
Energy Technology Data Exchange (ETDEWEB)
Rieger, F. M. [ZAH, Institut für Theoretische Astrophysik, Universität Heidelberg, Philosophenweg 12, D-69120 Heidelberg (Germany); Duffy, P., E-mail: frank.rieger@mpi-hd.mpg.de, E-mail: peter.duffy@ucd.ie [University College Dublin, Belfield, Dublin 4 (Ireland)
2016-12-10
Shear flows are naturally expected to occur in astrophysical environments and potential sites of continuous non-thermal Fermi-type particle acceleration. Here we investigate the efficiency of expanding relativistic outflows to facilitate the acceleration of energetic charged particles to higher energies. To this end, the gradual shear acceleration coefficient is derived based on an analytical treatment. The results are applied to the context of the relativistic jets from active galactic nuclei. The inferred acceleration timescale is investigated for a variety of conical flow profiles (i.e., power law, Gaussian, Fermi–Dirac) and compared to the relevant radiative and non-radiative loss timescales. The results exemplify that relativistic shear flows are capable of boosting cosmic-rays to extreme energies. Efficient electron acceleration, on the other hand, requires weak magnetic fields and may thus be accompanied by a delayed onset of particle energization and affect the overall jet appearance (e.g., core, ridge line, and limb-brightening).
Computerized lateral-shear interferometer
Hasegan, Sorin A.; Jianu, Angela; Vlad, Valentin I.
1998-07-01
A lateral-shear interferometer, coupled with a computer for laser wavefront analysis, is described. A CCD camera is used to transfer the fringe images through a frame-grabber into a PC. 3D phase maps are obtained by fringe pattern processing using a new algorithm for direct spatial reconstruction of the optical phase. The program describes phase maps by Zernike polynomials yielding an analytical description of the wavefront aberration. A compact lateral-shear interferometer has been built using a laser diode as light source, a CCD camera and a rechargeable battery supply, which allows measurements in-situ, if necessary.
Spinning and tumbling of micron-sized triangles in a micro-channel shear flow
Fries, J.; Kumar, M. Vijay; Mihiretie, B. Mekonnen; Hanstorp, D.; Mehlig, B.
2018-03-01
We report on measurements of the angular dynamics of micron-sized equilaterally triangular platelets suspended in a micro-channel shear flow. Our measurements confirm that such particles spin and tumble like a spheroid in a simple shear. Since the triangle has corners, we can observe the spinning directly. In general, the spinning frequency is different from the tumbling frequency and the spinning is affected by tumbling. This gives rise to doubly periodic angular dynamics.
The non-monotonic shear-thinning flow of two strongly cohesive concentrated suspensions
Buscall, Richard; Kusuma, Tiara E.; Stickland, Anthony D.; Rubasingha, Sayuri; Scales, Peter J.; Teo, Hui-En; Worrall, Graham L.
2014-01-01
The behaviour in simple shear of two concentrated and strongly cohesive mineral suspensions showing highly non-monotonic flow curves is described. Two rheometric test modes were employed, controlled stress and controlled shear-rate. In controlled stress mode the materials showed runaway flow above a yield stress, which, for one of the suspensions, varied substantially in value and seemingly at random from one run to the next, such that the up flow-curve appeared to be quite irreproducible. Th...
Shear design and assessment of reinforced and prestressed concrete beams based on a mechanical model
Marí Bernat, Antonio Ricardo; Bairán García, Jesús Miguel; Cladera Bohigas, Antoni; Oller Ibars, Eva
2016-01-01
Safe and economical design and assessment of reinforced (RC) and prestressed concrete (PC) beams requires the availability of accurate but simple formulations which adequately capture the structural response. In this paper, a mechanical model for the prediction of the shear-flexural strength of PC and RC members with rectangular, I, or T sections, with and without shear reinforcement, is presented. The model is based on the principles of concrete mechanics and on assumptions supported by the ...
Shear-induced partial translational ordering of a colloidal solid
Ackerson, B. J.; Clark, N. A.
1984-08-01
Highly charged submicrometer plastic spheres suspended in water at low ionic strength will order spontaneously into bcc crystals or polycrystals. A simple linear shear orients and disorders these crystals by forcing (110) planes to stack normal to the shear gradient and to slide relative to each other with a direction parallel to the solvent flow. In this paper we analyze in detail the disordering and flow processes occurring beyond the intrinsic elastic limit of the bcc crystal. We are led to a model in which the flow of a colloidal crystal is interpreted as a fundamentally different process from that found in atomic crystals. In the colloidal crystal the coupling of particle motion to the background fluid forces a homogeneous flow, where every layer is in motion relative to its neighboring layers. In contrast, the plastic flow in an atomic solid is defect mediated flow. At the lowest applied stress, the local bcc order in the colloidal crystal exhibits shear strains both parallel and perpendicular to the direction of the applied stress. The magnitude of these deformations is estimated using the configurational energy for bcc and distorted bcc crystals, assuming a screened Coulomb pair interaction between colloidal particles. As the applied stress is increased, the intrinsic elastic limit of the crystal is exceeded and the crystal begins to flow with adjacent layers executing an oscillatory path governed by the balance of viscous and screened Coulomb forces. The path takes the structure from the bcc1 and bcc2 twins observed at zero shear to a distorted two-dimensional hcp structure at moderate shear rates, with a loss of interlayer registration as the shear is increased. This theoretical model is consistent with other experimental observations, as well.
Grouted Connections with Shear Keys
DEFF Research Database (Denmark)
Pedersen, Ronnie; Jørgensen, M. B.; Damkilde, Lars
2012-01-01
This paper presents a finite element model in the software package ABAQUS in which a reliable analysis of grouted pile-to-sleeve connections with shear keys is the particular purpose. The model is calibrated to experimental results and a consistent set of input parameters is estimated so that dif...... that different structural problems can be reproduced successfully....
Meniscal shear stress for punching.
Tuijthof, Gabrielle J M; Meulman, Hubert N; Herder, Just L; van Dijk, C Niek
2009-01-01
Experimental determination of the shear stress for punching meniscal tissue. Meniscectomy (surgical treatment of a lesion of one of the menisci) is the most frequently performed arthroscopic procedure. The performance of a meniscectomy is not optimal with the currently available instruments. To design new instruments, the punching force of meniscal tissue is an important parameter. Quantitative data are unavailable. The meniscal punching process was simulated by pushing a rod through meniscal tissue at constant speed. Three punching rods were tested: a solid rod of Oslash; 3.00 mm, and two hollow tubes (Oslash; 3.00-2.60 mm) with sharpened cutting edges of 0.15 mm and 0.125 mm thick, respectively. Nineteen menisci acquired from 10 human cadaveric knee joints were punched (30 tests). The force and displacement were recorded from which the maximum shear stress was determined (average added with three times the standard deviation). The maximum shear stress for the solid rod was determined at 10.2 N/mm2. This rod required a significantly lower punch force in comparison with the hollow tube having a 0.15 mm cutting edge (plt;0.01). The maximum shear stress for punching can be applied to design instruments, and virtual reality training environments. This type of experiment is suitable to form a database with material properties of human tissue similar to databases for the manufacturing industry.
Centrifuges and inertial shear forces
Loon, van J.J.W.A.; Folgering, H.T.E.; Bouten, C.V.C.; Smit, T.H.
2004-01-01
Centrifuges are often used in biological studies for 1xg control samples in space flight microgravity experiments as well as in ground based research. Using centrifugation as a tool to generate an Earth like acceleration introduces unwanted inertial shear forces to the sample. Depending on the
Morrison, Gerald L.; Winslow, Robert B.; Thames, H. Davis, III
1996-01-01
The mean and phase averaged pressure and wall shear stress distributions were measured on the stator wall of a 50% eccentric annular seal which was whirling in a circular orbit at the same speed as the shaft rotation. The shear stresses were measured using flush mounted hot-film probes. Four different operating conditions were considered consisting of Reynolds numbers of 12,000 and 24,000 and Taylor numbers of 3,300 and 6,600. At each of the operating conditions the axial distribution (from Z/L = -0.2 to 1.2) of the mean pressure, shear stress magnitude, and shear stress direction on the stator wall were measured. Also measured were the phase averaged pressure and shear stress. These data were combined to calculate the force distributions along the seal length. Integration of the force distributions result in the net forces and moments generated by the pressure and shear stresses. The flow field inside the seal operating at a Reynolds number of 24,000 and a Taylor number of 6,600 has been measured using a 3-D laser Doppler anemometer system. Phase averaged wall pressure and wall shear stress are presented along with phase averaged mean velocity and turbulence kinetic energy distributions located 0.16c from the stator wall where c is the seal clearance. The relationships between the velocity, turbulence, wall pressure and wall shear stress are very complex and do not follow simple bulk flow predictions.
Comparison of Shear Strength Properties for Undisturbed and Reconstituted Parit Nipah Peat, Johor
Azhar, A. T. S.; Norhaliza, W.; Ismail, B.; Abdullah, M. E.; Zakaria, M. N.
2016-11-01
Shear strength of soil is required to determine the soil stability and design the foundations. Peat is known as a soil with complex natural formations which also contributes problems to the researchers, developers, engineers and contractors in constructions and infrastructures. Most researchers conducted experiment and investigation of shear strength on peat using shear box test and simple shear test, but only a few had discovered the behavior of peat using triaxial consolidated undrained test. The aim of this paper is to determine the undrained shear strength properties of reconstituted peat and undisturbed peat of Parit Nipah, Johor for comparison purposes. All the reconstituted peat samples were formed with the size that passed opening sieve 3.35 mm and preconsolidation pressure at 100 kPa. The result of undrained shear strength of reconstituted peat was 21kPa for cohesion with the angle of friction, 41° compare to the undisturbed peat with cohesion 10 kPa and angle of friction, 16°. The undrained shear strength properties result obtained shows that the reconstituted peat has higher strength than undisturbed peat. For relationship deviator stress-strain, σd max and excess pore pressure, Δu, it shows that both of undisturbed and reconstituted gradually increased when σ’ increased, but at the end of the test, the values are slightly dropped. The physical properties of undisturbed and reconstituted peat were also investigated to correlate with the undrained shear strength results.
Shear behaviour of reinforced phyllite concrete beams
International Nuclear Information System (INIS)
Adom-Asamoah, Mark; Owusu Afrifa, Russell
2013-01-01
Highlights: ► Phyllite concrete beams often exhibited shear with anchorage bond failure. ► Different shear design provisions for reinforced phyllite beams are compared. ► Predicted shear capacity of phyllite beams must be modified by a reduction factor. -- Abstract: The shear behaviour of concrete beams made from phyllite aggregates subjected to monotonic and cyclic loading is reported. First diagonal shear crack load of beams with and without shear reinforcement was between 42–58% and 42–92% of the failure loads respectively. The phyllite concrete beams without shear links had lower post-diagonal cracking shear resistance compared to corresponding phyllite beams with shear links. As a result of hysteretic energy dissipation, limited cyclic loading affected the stiffness, strength and deformation of the phyllite beams with shear reinforcement. Generally, beams with and without shear reinforcement showed anchorage bond failure in addition to the shear failure due to high stress concentration near the supports. The ACI, BS and EC codes are conservative for the prediction of phyllite concrete beams without shear reinforcement but they all overestimate the shear strength of phyllite concrete beams with shear reinforcement. It is recommended that the predicted shear capacity of phyllite beams reinforced with steel stirrups be modified by a reduction factor of 0.7 in order to specify a high enough safety factor on their ultimate strength. It is also recommended that susceptibility of phyllite concrete beams to undergo anchorage bond failure is averted in design by the provision of greater anchorage lengths than usually permitted.
International Nuclear Information System (INIS)
Collins, T.
1985-08-01
A simple criterion governs the beam distortion and/or loss of protons on a fast resonance crossing. Results from numerical integrations are illustrated for simple sextupole, octupole, and 10-pole resonances
Energy Technology Data Exchange (ETDEWEB)
Collins, T.
1985-08-01
A simple criterion governs the beam distortion and/or loss of protons on a fast resonance crossing. Results from numerical integrations are illustrated for simple sextupole, octupole, and 10-pole resonances.
Shear instability of a gyroid diblock copolymer
DEFF Research Database (Denmark)
Eskimergen, Rüya; Mortensen, Kell; Vigild, Martin Etchells
2005-01-01
-induced destabilization is discussed in relation to analogous observations on shear-induced order-to-order and disorder-to-order transitions observed in related block copolymer systems and in microemulsions. It is discussed whether these phenomena originate in shear-reduced fluctuations or shear-induced dislocations....
Statistical Model of Extreme Shear
DEFF Research Database (Denmark)
Larsen, Gunner Chr.; Hansen, Kurt Schaldemose
2004-01-01
In order to continue cost-optimisation of modern large wind turbines, it is important to continously increase the knowledge on wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... by a model that, on a statistically consistent basis, describe the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of high-sampled full-scale time series measurements...... are consistent, given the inevitabel uncertainties associated with model as well as with the extreme value data analysis. Keywords: Statistical model, extreme wind conditions, statistical analysis, turbulence, wind loading, statistical analysis, turbulence, wind loading, wind shear, wind turbines....
Shear failure of granular materials
Degiuli, Eric; Balmforth, Neil; McElwaine, Jim; Schoof, Christian; Hewitt, Ian
2012-02-01
Connecting the macroscopic behavior of granular materials with the microstructure remains a great challenge. Recent work connects these scales with a discrete calculus [1]. In this work we generalize this formalism from monodisperse packings of disks to 2D assemblies of arbitrarily shaped grains. In particular, we derive Airy's expression for a symmetric, divergence-free stress tensor. Using these tools, we derive, from first-principles and in a mean-field approximation, the entropy of frictional force configurations in the Force Network Ensemble. As a macroscopic consequence of the Coulomb friction condition at contacts, we predict shear failure at a critical shear stress, in accordance with the Mohr-Coulomb failure condition well known in engineering. Results are compared with numerical simulations, and the dependence on the microscopic geometric configuration is discussed. [4pt] [1] E. DeGiuli & J. McElwaine, PRE 2011. doi: 10.1103/PhysRevE.84.041310
Development of a structural model for the nonlinear shear deformation behavior of a seismic isolator
International Nuclear Information System (INIS)
Lee, Jae Han; Koo, Gyeong Hoi; Yoo, Bong
2002-02-01
The seismic excitation test results of an isolated test structure for artificial time history excitation are summarized for structure models of the isolated structure and isolation bearing. To simulate the response characteristic of isolated structure, shear hysteresis curves of isolators are analyzed. A simple analysis model is developed representing the actual dynamic behaviors of the test model, and the seismic responses using the simple model of the isolated structure and structure models, which are developed such as linear and bilinear models for isolators, are performed and compared with those of the seismic tests. The developed bilinear model is well applicable only to large shear strain area of LLRB
Haptic Edge Detection Through Shear
Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent
2016-03-01
Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals.
CFD simulation of estimating critical shear stress for cleaning flat ...
Indian Academy of Sciences (India)
Sumit Kawale
2017-11-22
Nov 22, 2017 ... Jet impingement; wall shear stress; cleaning of flat plate; turbulence model; critical shear stress; ... On comparing the theoretical predictions with wall shear ... distance and Reynolds number on peak value of local shear stress ...
Continuous shear - a method for studying material elements passing a stationary shear plane
DEFF Research Database (Denmark)
Lindegren, Maria; Wiwe, Birgitte; Wanheim, Tarras
2003-01-01
circumferential groove. Normally shear in metal forming processes is of another nature, namely where the material elements move through a stationary shear zone, often of small width. In this paper a method enabling the simulation of this situation is presented. A tool for continuous shear has beeen manufactured...... and tested with AlMgSil and copper. The sheared material has thereafter been tested n plane strain compression with different orientation concerning the angle between the shear plane and the compression direction....
Conductivity of an inverse lyotropic lamellar phase under shear flow
Panizza, P.; Soubiran, L.; Coulon, C.; Roux, D.
2001-08-01
We report conductivity measurements on solutions of closed compact monodisperse multilamellar vesicles (the so-called ``onion texture'') formed by shearing an inverse lyotropic lamellar Lα phase. The conductivity measured in different directions as a function of the applied shear rate reveals a small anisotropy of the onion structure due to the existence of free oriented membranes. The results are analyzed in terms of a simple model that allows one to deduce the conductivity tensor of the Lα phase itself and the proportion of free oriented membranes. The variation of these two parameters is measured along a dilution line and discussed. The high value of the conductivity perpendicular to the layers with respect to that of solvent suggests the existence of a mechanism of ionic transport through the insulating solvent.
Simulations of Granular Particles Under Cyclic Shear
Royer, John; Chaikin, Paul
2012-02-01
We perform molecular dynamics (MD) simulations of spherical grains subjected to cyclic, quasi-static shear in a 3D parallelepiped shear cell. This virtual shear cell is constructed out of rough, bumpy walls in order to minimize wall-induced ordering and has an open top surface to allow the packing to readily dilate or compact. Using a standard routine for MD simulations of frictional grains, we simulate over 1000 shear cycles, measuring grain displacements, the local packing density and changes in the contact network. Varying the shear amplitude and the friction coefficient between grains, we map out a phase diagram for the different types of behavior exhibited by these sheared grains. With low friction and high enough shear, the grains can spontaneously order into densely packed crystals. With low shear and increasing friction the packing remains disordered, yet the grains arrange themselves into configurations which exhibit limit cycles where all grains return to the same position after each full shear cycle. At higher shear and friction there is a transition to a diffusive state, where grains continue rearrange and move throughout the shear cell.
Experimental investigation of single small bubble motion in linear shear flow in water
International Nuclear Information System (INIS)
Li, Zhongchun; Zhao, Yang; Song, Xiaoming; Yu, Hongxing; Jiang, Shengyao; Ishii, Mamoru
2016-01-01
Highlights: • The bubble motion in simple linear shear flow was experimentally investigated. • The bubble trajectories, bubble velocity and drag and lift force were obtained using image process routine. • The bubble trajectory was coupled with a zigzag motion and incline path. • The lift force was kept negative and it decreased when bubble diameter and shear flow magnitude increased. - Abstract: The motion of small bubble in a simple shear flow in water was experimental studied. Stable shear flow with low turbulence level was achieved with curved screen and measured using LDV. The bubbles were captured by high speed camera and the captured images were processed with digital image routine. The bubble was released from a capillary tube. The instantaneous bubble position, bubble velocity and forces were obtained based on the captured parameters. The quasi-steady lift coefficient was determined by the linear fitting of the bubble trajectory of several cycles. The results indicated that the lateral migration was coupled with the zigzag motion of bubble in the present experiment. The bubble migrated to the left side and its quasi-steady lift coefficient was negative. Good repeatable results were observed by measurements of 18 bubbles. The bubble motion in shear flow in water was first experimental studied and negative lift force was observed in the present study condition. The lift coefficient decreased when shear stress magnitude or bubble diameter increased in the present experiment condition.
The importance of strain localisation in shear zones
Bons, Paul D.; Finch, Melanie; Gomez-Rivas, Enrique; Griera, Albert; Llorens, Maria-Gema; Steinbach, Florian; Weikusat, Ilka
2016-04-01
The occurrence of various types of shear bands (C, C', C'') in shear zones indicate that heterogeneity of strain is common in strongly deformed rocks. However, the importance of strain localisation is difficult to ascertain if suitable strain markers are lacking, which is usually the case. Numerical modelling with the finite-element method has so far not given much insight in the development of shear bands. We suggest that this is not only because the modelled strains are often not high enough, but also because this technique (that usually assumes isotropic material properties within elements) does not properly incorporate mineral deformation behaviour. We simulated high-strain, simple-shear deformation in single- and polyphase materials with a full-field theory (FFT) model coupled to the Elle modelling platform (www.elle.ws; Lebensohn 2001; Bons et al. 2008). The FFT-approach simulates visco-plastic deformation by dislocation glide, taking into account the different available slip systems and their critical resolved shear stresses in relations to the applied stresses. Griera et al. (2011; 2013) have shown that this approach is particularly well suited for strongly anisotropic minerals, such as mica and ice Ih (Llorens 2015). We modelled single- and polyphase composites of minerals with different anisotropies and strengths, roughly equivalent to minerals such as ice Ih, mica, quartz and feldspar. Single-phase polycrystalline aggregates show distinct heterogeneity of strain rate, especially in case of ice Ih, which is mechanically close to mica (see also Griera et al. 2015). Finite strain distributions are heterogeneous as well, but the patterns may differ from that of the strain rate distribution. Dynamic recrystallisation, however, usually masks any strain and strain rate localisation (Llorens 2015). In case of polyphase aggregates, equivalent to e.g. a granite, we observe extensive localisation in both syn- and antithetic shear bands. The antithetic shear bands
Bormann, Jayne M.; Hammond, William C.; Kreemer, Corné; Blewitt, Geoffrey
2016-04-01
We present 264 new interseismic GPS velocities from the Mobile Array of GPS for Nevada Transtension (MAGNET) and continuous GPS networks that measure Pacific-North American plate boundary deformation in the Central Walker Lane. Relative to a North America-fixed reference frame, northwestward velocities increase smoothly from ∼4 mm/yr in the Basin and Range province to 12.2 mm/yr in the central Sierra Nevada resulting in a Central Walker Lane deformation budget of ∼8 mm/yr. We use an elastic block model to estimate fault slip and block rotation rates and patterns of deformation from the GPS velocities. Right-lateral shear is distributed throughout the Central Walker Lane with strike-slip rates generally Bodie Hills, Carson Domain, and Mina Deflection are between 1-4°/Myr, lower than published paleomagnetic rotation rates, suggesting that block rotation rates have decreased since the Late to Middle Miocene.
Giarola, Diana; Capuani, Domenico; Bigoni, Davide
2018-03-01
A shear band of finite length, formed inside a ductile material at a certain stage of a continued homogeneous strain, provides a dynamic perturbation to an incident wave field, which strongly influences the dynamics of the material and affects its path to failure. The investigation of this perturbation is presented for a ductile metal, with reference to the incremental mechanics of a material obeying the J2-deformation theory of plasticity (a special form of prestressed, elastic, anisotropic, and incompressible solid). The treatment originates from the derivation of integral representations relating the incremental mechanical fields at every point of the medium to the incremental displacement jump across the shear band faces, generated by an impinging wave. The boundary integral equations (under the plane strain assumption) are numerically approached through a collocation technique, which keeps into account the singularity at the shear band tips and permits the analysis of an incident wave impinging a shear band. It is shown that the presence of the shear band induces a resonance, visible in the incremental displacement field and in the stress intensity factor at the shear band tips, which promotes shear band growth. Moreover, the waves scattered by the shear band are shown to generate a fine texture of vibrations, parallel to the shear band line and propagating at a long distance from it, but leaving a sort of conical shadow zone, which emanates from the tips of the shear band.
Shear strength in corner region of reinforced concrete duct type structures to be embedded in soil
International Nuclear Information System (INIS)
Aoyagi, Y.; Endo, T.
1993-01-01
Reinforced concrete ducts for accommodating emergency cooling water pipes are generally embedded in soil. The structures is classified as one of the most important structures in terms of earthquake resistant design. During a strong earthquake it is subjected to shear deformations in concerted movement with surrounding soil. The comer regions of the duct should be designed against shear with moment combined. However, the complicated stress conditions in the region render the design more intricate in comparison with the case of simple determinate RC beam type structures. With the above situation in mind an experimental study was conducted, in which prototype as well as one half scale models representing the stress conditions in the region of interest were loaded and brought to failure in shear. The cross section of the prototype test model without shear reinforcements was 60 (height) x 30cm (width), and the tensile reinforcement ratio was 2.58%. The following results were obtained within the limit of the experimental study. (1) The shear capacity predicted by Japanese Design Code for linear RC members over-estimated the experimental ones with a considerably large safety margin of 4.4-5.0. (2) An improved design procedure to be applied to the specific structure was proposed, which gave a reasonable safety factor against shear failure of 1.7-2.0. (3) Combined smeared and discrete cracking model was utilized to simulate the shear failure mechanism, which could realistically pursue experimental behaviors. (author)
Flexural Strengthening of RC Slabs Using a Hybrid FRP-UHPC System Including Shear Connector
Directory of Open Access Journals (Sweden)
Jiho Moon
2017-01-01
Full Text Available A polymeric hybrid composite system made of UHPC and CFRP was proposed as a retrofit system to enhance flexural strength and ductility of RC slabs. While the effectiveness of the proposed system was confirmed previously through testing three full-scale one-way slabs having two continuous spans, the slabs retrofitted with the hybrid system failed in shear. This sudden shear failure would stem from the excessive enhancement of the flexural strength over the shear strength. In this study, shear connectors were installed between the hybrid system and a RC slab. Using simple beam, only positive moment section was examined. Two full-scale RC slabs were cast and tested to failure: the first as a control and the second using this new strengthening technique. The proposed strengthening system increased the ultimate load carrying capacity of the slab by 70%, the stiffness by 60%, and toughness by 128%. The efficiency of shear connectors on ductile behavior of the retrofitted slab was also confirmed. After the UHPC top is separated from the slab, the shear connector transfer shear load and the slab system were in force equilibrium by compression in UHPC and tension in CFRP.
Domino structures evolution in strike-slip shear zones; the importance of the cataclastic flow
Moreira, N.; Dias, R.
2018-05-01
The Porto-Tomar-Ferreira do Alentejo dextral Shear Zone is one of the most important structures of the Iberian Variscides. In its vicinity, close to Abrantes (Central Portugal), a localized heterogeneous strain pattern developed in a decimetric metamorphic siliceous multilayer. This complex pattern was induced by the D2 dextral shearing of the early S0//S1 foliation in brittle-ductile conditions, giving rise to three main shear zone families. One of these families, with antithetic kinematics, delimits blocks with rigid clockwise rotation surrounded by coeval cataclasites, generating a local domino structure. The proposed geometrical and kinematic analysis, coupled with statistical studies, highlights the relation between subsidiary shear zones and the main shear zone. Despite the heterogeneous strain pattern, a quantitative approach of finite strain was applied based on the restoration of the initial fracture pattern. This approach shows the importance of the cataclastic flow coupled with the translational displacement of the domino domain in solving space problems related to the rigid block rotation. Such processes are key in allowing the rigid block rotation inside shear zones whenever the simple shear component is a fundamental mechanism.
Shear Alfven wave excitation by direct antenna coupling and fast wave resonant mode conversion
International Nuclear Information System (INIS)
Borg, G.G.
1994-01-01
Antenna coupling to the shear Alfven wave by both direct excitation and fast wave resonant mode conversion is modelled analytically for a plasma with a one dimensional linear density gradient. We demonstrate the existence of a shear Alfven mode excited directly by the antenna. For localised antennas, this mode propagates as a guided beam along the steady magnetic field lines intersecting the antenna. Shear Alfven wave excitation by resonant mode conversion of a fast wave near the Alfven resonance layer is also demonstrated and we prove that energy is conserved in this process. We compare the efficiency of these two mechanisms of shear Alfven wave excitation and present a simple analytical formula giving the ratio of the coupled powers. Finally, we discuss the interpretation of some experimental results. 45 refs., 7 figs
Krüger, Timm
2012-01-01
The rheology of dense red blood cell suspensions is investigated via computer simulations based on the lattice Boltzmann, the immersed boundary, and the finite element methods. The red blood cells are treated as extended and deformable particles immersed in the ambient fluid. In the first part of the work, the numerical model and strategies for stress evaluation are discussed. In the second part, the behavior of the suspensions in simple shear flow is studied for different volume fractions, particle deformabilities, and shear rates. Shear thinning behavior is recovered. The existence of a shear-induced transition from a tumbling to a tank-treading motion is demonstrated. The transition can be parameterized by a single quantity, namely the effective capillary number. It is the ratio of the suspension stress and the characteristic particle membrane stress. At the transition point, a strong increase in the orientational order of the red blood cells and a significant decrease of the particle diffusivity are obser...
Accounting for the speed shear in wind turbine power performance measurement
DEFF Research Database (Denmark)
Wagner, Rozenn
the vertical wind shear and the turbulence intensity. The work presented in this thesis consists of the description and the investigation of a simple method to account for the wind speed shear in the power performance measurement. Ignoring this effect was shown to result in a power curve dependant on the shear...... for turbulence intensity suggested by Albers. The second method was found to be more suitable for normalising the power curve for the turbulence intensity. Using the equivalent wind speed accounting for the wind shear in the power performance measurement was shown to result in a more repeatable power curve than......The power curve of a wind turbine is the primary characteristic of the machine as it is the basis of the warranty for it power production. The current IEC standard for power performance measurement only requires the measurement of the wind speed at hub height and the air density to characterise...
Statistical Model of Extreme Shear
DEFF Research Database (Denmark)
Hansen, Kurt Schaldemose; Larsen, Gunner Chr.
2005-01-01
In order to continue cost-optimisation of modern large wind turbines, it is important to continuously increase the knowledge of wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... by a model that, on a statistically consistent basis, describes the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of full-scale measurements recorded with a high sampling rate...
Hassan, Mahmoud; Abu-Alam, Tamer; Stüwe, Kurt; Klötzli, Urs
2013-04-01
The metamorphic complexes of the Arabian-Nubian Shield were exhumed by different exhumation mechanisms (i.e. in extension or oblique transpression regime) during the Pan African activity of Najd Fault System - the largest pre-Mesozoic shear zone on Earth. The different exhumation mechanisms could be the consequence of (i) orientation of the complexes at slightly different angles with respect to the overall orientation of the principal stresses of the Najd Fault System, (ii) exhumation from different depths, or (iii) change of the stress regime through time. In order to test the third hypothesis, geochronological work will be applied on a representative suite of complexes across the Najd Fault System. In particular we focus on three complexes in the Arabian part of the shield named Qazaz, Hamadat and Wajh. In general, the metamorphic complexes of the Arabian part of the shield exhibit left-lateral transcurrent tectonism along the NW-SE Najd faults and right-lateral movement along conjugate NE-SW striking structures. The whole unit forms an anastomosing network of planar structures that demarcate large fish-shaped bodies of high grade metamorphics. The Hamadat complex is surrounded by a left-lateral greenshist facies WNW-ESE Ajaj shear zone. The complex consists of folds that are strongly pinched to the north and more open to the south marked by a well-developed parallel stretching sub-horizontal lineation. Granite intrusions along and across the Ajaj shear zone may allow testing the timing of the deformation. Deformed and non-deformed samples of these granites will be examined by age dating to determine the absolute timing of the metamorphism and the deformation for the complex. Some 20 samples are currently being prepared for zircon dating. Whilst no results are available at the time of writing of this abstract, they will be presented at EGU 2013.
Numerical rigid plastic modelling of shear capacity of keyed joints
DEFF Research Database (Denmark)
Herfelt, Morten Andersen; Poulsen, Peter Noe; Hoang, Linh Cao
2015-01-01
Keyed shear joints are currently designed using simple and conservative design formulas, yet these formulas do not take the local mechanisms in the concrete core of the joint into account. To investigate this phenomenon a rigid, perfectly plastic finite element model of keyed joints is used....... The model is formulated for second-order conic optimisation as a lower bound problem, which yields a statically admissible stress field that satisfies the yield condition in every point. The dual solution to the problem can be interpreted as the collapse mode and will be used to analyse the properties...
Predicting Shear Transformation Events in Metallic Glasses
Xu, Bin; Falk, Michael L.; Li, J. F.; Kong, L. T.
2018-03-01
Shear transformation is the elementary process for plastic deformation of metallic glasses, the prediction of the occurrence of the shear transformation events is therefore of vital importance to understand the mechanical behavior of metallic glasses. In this Letter, from the view of the potential energy landscape, we find that the protocol-dependent behavior of shear transformation is governed by the stress gradient along its minimum energy path and we propose a framework as well as an atomistic approach to predict the triggering strains, locations, and structural transformations of the shear transformation events under different shear protocols in metallic glasses. Verification with a model Cu64 Zr36 metallic glass reveals that the prediction agrees well with athermal quasistatic shear simulations. The proposed framework is believed to provide an important tool for developing a quantitative understanding of the deformation processes that control mechanical behavior of metallic glasses.
Shear wall ultimate drift limits
International Nuclear Information System (INIS)
Duffey, T.A.; Goldman, A.; Farrar, C.R.
1994-04-01
Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated
Testing and modeling dowel and catenary action in rebars crossing shear joints in RC
DEFF Research Database (Denmark)
Sørensen, Jesper Harrild; Hoang, Linh Cao; Olesen, John Forbes
2017-01-01
presents a simple, second order plasticity model to describe the non-linear regime of the load-displacement relationship. In the model, kinematic relations and the normality condition of plastic theory are utilized to establish a unique link between the imposed shear displacement and combinations of moment...
Origins of Shear Jamming for Frictional Grains
Wang, Dong; Zheng, Hu; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert
2016-11-01
Granular systems have been shown to be able to behave like solids, under shear, even when their densities are below the critical packing fraction for frictionless isotropic jamming. To understand such a phenomena, called shear jamming, the question we address here is: how does shear bring a system from a unjammed state to a jammed state, where the coordination number, Z, is no less than 3, the isotropic jamming point for frictional grains? Since Z can be used to distinguish jammed states from unjammed ones, it is vital to understand how shear increases Z. We here propose a set of three particles in contact, denoted as a trimer, as the basic unit to characterize the deformation of the system. Trimers, stabilized by inter-grain friction, fail under a certain amount of shear and bend to make extra contacts to regain stability. By defining a projection operator of the opening angle of the trimer to the compression direction in the shear, O, we see a systematically linear decrease of this quantity with respect to shear strain, demonstrating the bending of trimers as expected. In addition, the average change of O from one shear step to the next shows a good collapse when plotted against Z, indicating a universal behavior in the process of shear jamming. We acknowledge support from NSF DMR1206351, NASA NNX15AD38G, the William M. Keck Foundation and a RT-MRSEC Fellowship.
Low-rise shear wall failure modes
International Nuclear Information System (INIS)
Farrar, C.R.; Hashimoto, P.S.; Reed, J.W.
1991-01-01
A summary of the data that are available concerning the structural response of low-rise shear walls is presented. This data will be used to address two failure modes associated with the shear wall structures. First, data concerning the seismic capacity of the shear walls with emphasis on excessive deformations that can cause equipment failure are examined. Second, data concerning the dynamic properties of shear walls (stiffness and damping) that are necessary to compute the seismic inputs to attached equipment are summarized. This case addresses the failure of equipment when the structure remains functional. 23 refs
Saboo, Nikhil; Singh, Bhupendra; Kumar, Praveen; Vikram, Durgesh
2018-02-01
This study focuses on evaluating the flow behavior of conventional and polymer modified asphalt binders in steady- and dynamic-shear domain, for a temperature range of 20-70 °C, using a Dynamic Shear Rheometer (DSR). Steady-shear viscosity and frequency sweep tests were carried out on two conventional (VG 10 and VG 30) and two polymer (SBS and EVA) modified asphalt binders. Applicability of the Cox-Merz principle was evaluated and complex viscosity master curves were analyzed at five different reference temperatures. Cross model was used to simulate the complex viscosity master curves at different temperatures. It was found that asphalt binders exhibited shear-thinning behavior at all the test temperatures. The critical shear rate increased with increase in temperature and was found to be lowest for plastomeric modified asphalt binder. The Cox-Merz principle was found to be valid in the zero-shear viscosity (ZSV) domain and deviated at higher frequency/shear rate for all the binders. Results from the study indicated that the ratio of ZSV can be successfully used as shift factors for construction of master curves at different reference temperatures. Cross model was found to be suitable in simulating the complex viscosity master curves at all the test temperatures. Analysis of model parameters indicated that a strong relationship exists between ZSV and the critical shear rate. ZSV and critical shear rate varied exponentially with temperature. This relationship was used to propose a simple equation for assessing the shift factors for construction of master curves.
Laboratory observation of magnetic field growth driven by shear flow
Energy Technology Data Exchange (ETDEWEB)
Intrator, T. P., E-mail: intrator@lanl.gov; Feng, Y.; Sears, J.; Weber, T. [Los Alamos National Laboratory, M.S. E526, Los Alamos, New Mexico 87545 (United States); Dorf, L. [Applied Materials, Inc., Santa Clara, CA 95054 (United States); Sun, X. [University of Science and Technology, Hefei (China)
2014-04-15
Two magnetic flux ropes that collide and bounce have been characterized in the laboratory. We find screw pinch profiles that include ion flow v{sub i}, magnetic field B, current density J, and plasma pressure. The electron flow v{sub e} can be inferred, allowing the evaluation of the Hall J×B term in a two fluid magnetohydrodynamic Ohm's Law. Flux ropes that are initially cylindrical are mutually attracted and compress each other, which distorts the cylindrical symmetry. Magnetic field is created via the ∇×v{sub e}×B induction term in Ohm's Law where in-plane (perpendicular) shear of parallel flow (along the flux rope) is the dominant feature, along with some dissipation and magnetic reconnection. We predict and measure the growth of a quadrupole out-of-plane magnetic field δB{sub z}. This is a simple and coherent example of a shear flow driven dynamo. There is some similarity with two dimensional reconnection scenarios, which induce a current sheet and thus out-of-plane flow in the third dimension, despite the customary picture that considers flows only in the reconnection plane. These data illustrate a general and deterministic mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence.
Contractile recovery of microtissues after giant shear events
Morley, Cameron; Bhattacharjee, Tapomoy; Ellison, Sarah; Sawyer, W.; Angelini, Thomas
Cells are often dispersed in extracellular matrix (ECM) gels like collagen and Matrigel as minimal tissue models. Generally, large-scale contraction of these constructs is observed, in which the degree of contraction of the entire system correlates with cell density and ECM concentration. The freedom to perform diverse mechanical experiments on these contracting constructs is limited by the challenges of handling and supporting these delicate samples. Here, we present a method to create simple cell-ECM constructs that can be manipulated with significantly reduced experimental limitations. We 3D print mixtures of MCF10A cells and ECM (collagen-I and Matrigel) into a 3D growth medium made from jammed microgels. With this approach, we are able to apply shear stresses to the cell constructs times after printing and observe the collective response. Preliminary results reveal that, following shear deformations that exceed 300% and dramatically smear cells and matrix in space, the cells actively re-contract the construct toward the un-sheared construct. These results suggest that new principles of collective recovery can be employed for tissue engineering applications using jammed microgels as a re-configurable support medium.
Shear thinning behaviors in magmas
Vetere, F. P.; Cassetta, M.; Perugini, D.
2017-12-01
Studies on magma rheology are of fundamental importance to understanding magmatic processes from depth to surface. Since viscosity is one of the most important parameter controlling eruption mechanisms, as well as lava flow emplacement, a comprehensive knowledge on the evolution of magma viscosities during crystallization is required. We present new viscosity data on partly crystalized basalt, andesite and analogue lavas comparable to those erupted on Mercury's northern volcanic plains. High-temperature viscosity measurements were performed using a rotational Anton Paar RheolabQC viscometer head at the PVRG labs, in Perugia (Italy) (http://pvrg.unipg.it). The relative proportion of phases in each experimental run were determined by image analysis on BS-SEM images at different magnifications; phases are glasses, clinopyroxene, spinel, plagioclase for the basalt, plagioclase and spinel for the andesite and pure enstatite and clinopyroxenes, for the analogue Mercury's composition. Glass and crystalline fractions determined by image analysis well correlate with compositions of residual melts. In order to constrain the viscosity (η) variations as a function of crystallinity, shear rate (γ) was varied from 0.1 to 5 s-1. Viscosity vs. time at constant temperature shows a typical S-shape curve. In particular, for basaltic composition η vary from 3.1-3.8 Pa s [log η] at 1493 K and crystallinity of 19 area % as γ vary from 1.0 to 0.1 s-1; the andesite viscosity evolution is 3.2 and 3.7 Pa s [log η] as γ varies from 1 to 0.1 at 1493 K and crystal content of 17 area %; finally, Mercury's analogue composition was investigated at different temperature ranging from 1533 to 1502 K (Vetere et al., 2017). Results, for γ = 0.1, 1.0 and 5.0 s-1, show viscosity variation between 2.7-4.0, 2.5-3.4 and 2.0-3.0 [log η inPa s] respectively while crystallinity vary from 9 to 27 (area %). As viscosity decreases as shear rate increases, these data points to a shear thinning behaviour
Turbulence suppression by E x B shear in JET optimized shear pulses
International Nuclear Information System (INIS)
Beer, M.A.; Budny, R.V.; Challis, C.D.; Conway, G.
2000-01-01
The authors calculate microinstability growth rates in JET optimized shear plasmas with a comprehensive gyrofluid model, including sheared E x B flows, trapped electrons, and all dominant ion species in realistic magnetic geometry. They find good correlation between E x B shear suppression of microinstabilities and both the formation and collapse of the internal transport barrier
International Nuclear Information System (INIS)
Fuchs, J.
1990-08-01
A complete classification of simple currents of WZW theory is obtained. The proof is based on an analysis of the quantum dimensions of the primary fields. Simple currents are precisely the primaries with unit quantum dimension; for WZW theories explicit formulae for the quantum dimensions can be derived so that an identification of the fields with unit quantum dimension is possible. (author). 19 refs.; 2 tabs
Self-diffusion in dense granular shear flows.
Utter, Brian; Behringer, R P
2004-03-01
Diffusivity is a key quantity in describing velocity fluctuations in granular materials. These fluctuations are the basis of many thermodynamic and hydrodynamic models which aim to provide a statistical description of granular systems. We present experimental results on diffusivity in dense, granular shear flows in a two-dimensional Couette geometry. We find that self-diffusivities D are proportional to the local shear rate gamma; with diffusivities along the direction of the mean flow approximately twice as large as those in the perpendicular direction. The magnitude of the diffusivity is D approximately gamma;a(2), where a is the particle radius. However, the gradient in shear rate, coupling to the mean flow, and strong drag at the moving boundary lead to particle displacements that can appear subdiffusive or superdiffusive. In particular, diffusion appears to be superdiffusive along the mean flow direction due to Taylor dispersion effects and subdiffusive along the perpendicular direction due to the gradient in shear rate. The anisotropic force network leads to an additional anisotropy in the diffusivity that is a property of dense systems and has no obvious analog in rapid flows. Specifically, the diffusivity is suppressed along the direction of the strong force network. A simple random walk simulation reproduces the key features of the data, such as the apparent superdiffusive and subdiffusive behavior arising from the mean velocity field, confirming the underlying diffusive motion. The additional anisotropy is not observed in the simulation since the strong force network is not included. Examples of correlated motion, such as transient vortices, and Lévy flights are also observed. Although correlated motion creates velocity fields which are qualitatively different from collisional Brownian motion and can introduce nondiffusive effects, on average the system appears simply diffusive.
Tensile and shear strength of adhesives
Stibolt, Kenneth A.
1990-01-01
This experiment is conducted in a freshman-level course: Introduction to Engineering Materials. There are no prerequisites for the course although students should have some knowledge of basic algebra. The objectives are to tension and shear test adhesives and to determine the tensile and shear properties of adhesives. Details of equipment of procedure are given.
Crosswind Shear Gradient Affect on Wake Vortices
Proctor, Fred H.; Ahmad, Nashat N.
2011-01-01
Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.
Shear stresses around circular cylindrical openings
Hoogenboom, P.C.J.; Van Weelden, C.; Blom, C.M.B.
2010-01-01
In this paper stress concentrations are studied around circular cylindrical openings or voids in a linear elastic continuum. The loading is such that a uniform shear stress occurs in the continuum, which is disturbed by the opening. The shear stress is in the direction of the centre axis of the
Simulations of biopolymer networks under shear
Huisman, Elisabeth Margaretha
2011-01-01
In this thesis we present a new method to simulate realistic three-dimensional networks of biopolymers under shear. These biopolymer networks are important for the structural functions of cells and tissues. We use the method to analyze these networks under shear, and consider the elastic modulus,
Rating precast prestressed concrete bridges for shear
2008-12-01
Shear capacity of real-world prestressed concrete girders designed in the 1960s and 1970s is a concern because : AASHTO Standard Specifications (AASHTO-STD) employed the quarter-point rule for shear design, which is less : conservative for shea...
Shear Driven Synthesis of Polymeric Micro- and Nanomaterials
Tian, Tian
Polymeric micro- and nanomaterials play a significant role in various current and emerging technologies. A liquid shear based method was developed to fabricate a wide range of polymeric materials, which include fibers, sheets, ribbons, rods and spheres in a scalable, cost-effective and simple way. During the process, droplet shearing, droplet deformation, droplet breaking up and polymer precipitation occur simultaneously. The size and morphology of the resultant structures are determined by the dominating process which is further controlled by the experimental parameters including polymer concentration, polymer molecular weight and antisolvent concentration. Among all of these structures, nanofibers have attracted the latest research interest due to the unique properties. Current leading fiber production approaches in the market possess certain drawbacks. For example, the throughput of electrospinning is limited to around 2.5 kg/hr and the diameter of fiber produced by wet spinning cannot be below micrometer while melt spinning is only applicable to melt-processable polymers. The breakthrough of our liquid shear driven technique for fiber synthesis is that it produces fibers with diameter from 200 nm to several micrometers from a wide range of liquid- processable polymers with high commercial yield (up to 12 kg/hr). Thus in Chapter 2, the optimum parameters range for fiber formation is established and the effects of those parameters on fiber size are investigated. In the original liquid shear method, medium with high viscosity is needed to exert strong shear stress on the droplet and to stretch the droplets to long strand. However, the viscous medium complicates the post sample washing procedure and introduces the potential slippery danger in the working area. Thus a non-viscous medium shearing method is developed in Chapter 3 and it is the first time proposed that the synthesis of PLA or PS nanofibers can be completed in the aqueous ethanol medium. Colloid science
The effect of shear flow on the rotational diffusivity of a single axisymmetric particle
Leahy, Brian; Koch, Donald; Cohen, Itai
2014-11-01
Colloidal suspensions of nonspherical particles abound in the world around us, from red blood cells in arteries to kaolinite discs in clay. Understanding the orientation dynamics of these particles is important for suspension rheology and particle self-assembly. However, even for the simplest case of dilute suspensions in simple shear flow, the orientation dynamics of Brownian nonspherical particles are poorly understood at large shear rates. Here, we analytically calculate the time-dependent orientation distributions of particles confined to the flow-gradient plane when the rotary diffusion is small but nonzero. For both startup and oscillatory shear flows, we find a coordinate change that maps the convection-diffusion equation to a simple diffusion equation with an enhanced diffusion constant, simplifying the orientation dynamics. For oscillatory shear, this enhanced diffusion drastically alters the quasi-steady orientation distributions. Our theory of the unsteady orientation dynamics provides an understanding of a nonspherical particle suspension's rheology for a large class of unsteady flows. For particles with aspect ratio 10 under oscillatory shear, the rotary diffusion and intrinsic viscosity vary with amplitude by a factor of ~ 40 and ~ 2 , respectively.
Friction of Shear-Fracture Zones
Riikilä, T. I.; Pylväinen, J. I.; Åström, J.
2017-12-01
A shear fracture of brittle solids under compression undergoes a substantial evolution from the initial microcracking to a fully formed powder-filled shear zone. Experiments covering the entire process are relatively easy to conduct, but they are very difficult to investigate in detail. Numerically, the large strain limit has remained a challenge. An efficient simulation model and a custom-made experimental device are employed to test to what extent a shear fracture alone is sufficient to drive material to spontaneous self-lubrication. A "weak shear zone" is an important concept in geology, and a large number of explanations, specific for tectonic conditions, have been proposed. We demonstrate here that weak shear zones are far more general, and that their emergence only demands that a microscopic, i.e., fragment-scale, stress relaxation mechanism develops during the fracture process.
Imaging Shear Strength Along Subduction Faults
Bletery, Quentin; Thomas, Amanda M.; Rempel, Alan W.; Hardebeck, Jeanne L.
2017-11-01
Subduction faults accumulate stress during long periods of time and release this stress suddenly, during earthquakes, when it reaches a threshold. This threshold, the shear strength, controls the occurrence and magnitude of earthquakes. We consider a 3-D model to derive an analytical expression for how the shear strength depends on the fault geometry, the convergence obliquity, frictional properties, and the stress field orientation. We then use estimates of these different parameters in Japan to infer the distribution of shear strength along a subduction fault. We show that the 2011 Mw9.0 Tohoku earthquake ruptured a fault portion characterized by unusually small variations in static shear strength. This observation is consistent with the hypothesis that large earthquakes preferentially rupture regions with relatively homogeneous shear strength. With increasing constraints on the different parameters at play, our approach could, in the future, help identify favorable locations for large earthquakes.
Thrombus Formation at High Shear Rates.
Casa, Lauren D C; Ku, David N
2017-06-21
The final common pathway in myocardial infarction and ischemic stroke is occlusion of blood flow from a thrombus forming under high shear rates in arteries. A high-shear thrombus forms rapidly and is distinct from the slow formation of coagulation that occurs in stagnant blood. Thrombosis at high shear rates depends primarily on the long protein von Willebrand factor (vWF) and platelets, with hemodynamics playing an important role in each stage of thrombus formation, including vWF binding, platelet adhesion, platelet activation, and rapid thrombus growth. The prediction of high-shear thrombosis is a major area of biofluid mechanics in which point-of-care testing and computational modeling are promising future directions for clinically relevant research. Further research in this area will enable identification of patients at high risk for arterial thrombosis, improve prevention and treatment based on shear-dependent biological mechanisms, and improve blood-contacting device design to reduce thrombosis risk.
Experimental study on the adiabatic shear bands
International Nuclear Information System (INIS)
Affouard, J.
1984-07-01
Four martensitic steels (Z50CDV5 steel, 28CND8 steel, 35NCDV16 steel and 4340 steel) with different hardness between 190 and 600 Hsub(B) (Brinell hardness), have been studied by means of dynamic compressive tests on split Hopkinson pressure bar. Microscopic observations show that the fracture are associated to the development of adiabatic shear bands (except 4340 steel with 190 Hsub(B) hardness). By means of tests for which the deformation is stopped at predetermined levels, the measurement of shear and hardness inside the band and the matrix indicates the chronology of this phenomenon: first the localization of shear, followed by the formation of adiabatic shear band and ultimatly crack initiation and propagation. These results correlated with few simulations by finite elements have permitted to suggest two mecanisms of deformation leading to the formation of adiabatic shear bands in this specific test [fr
Imaging shear strength along subduction faults
Bletery, Quentin; Thomas, Amanda M.; Rempel, Alan W.; Hardebeck, Jeanne L.
2017-01-01
Subduction faults accumulate stress during long periods of time and release this stress suddenly, during earthquakes, when it reaches a threshold. This threshold, the shear strength, controls the occurrence and magnitude of earthquakes. We consider a 3-D model to derive an analytical expression for how the shear strength depends on the fault geometry, the convergence obliquity, frictional properties, and the stress field orientation. We then use estimates of these different parameters in Japan to infer the distribution of shear strength along a subduction fault. We show that the 2011 Mw9.0 Tohoku earthquake ruptured a fault portion characterized by unusually small variations in static shear strength. This observation is consistent with the hypothesis that large earthquakes preferentially rupture regions with relatively homogeneous shear strength. With increasing constraints on the different parameters at play, our approach could, in the future, help identify favorable locations for large earthquakes.
Eisenhardt, K M; Sull, D N
2001-01-01
The success of Yahoo!, eBay, Enron, and other companies that have become adept at morphing to meet the demands of changing markets can't be explained using traditional thinking about competitive strategy. These companies have succeeded by pursuing constantly evolving strategies in market spaces that were considered unattractive according to traditional measures. In this article--the third in an HBR series by Kathleen Eisenhardt and Donald Sull on strategy in the new economy--the authors ask, what are the sources of competitive advantage in high-velocity markets? The secret, they say, is strategy as simple rules. The companies know that the greatest opportunities for competitive advantage lie in market confusion, but they recognize the need for a few crucial strategic processes and a few simple rules. In traditional strategy, advantage comes from exploiting resources or stable market positions. In strategy as simple rules, advantage comes from successfully seizing fleeting opportunities. Key strategic processes, such as product innovation, partnering, or spinout creation, place the company where the flow of opportunities is greatest. Simple rules then provide the guidelines within which managers can pursue such opportunities. Simple rules, which grow out of experience, fall into five broad categories: how- to rules, boundary conditions, priority rules, timing rules, and exit rules. Companies with simple-rules strategies must follow the rules religiously and avoid the temptation to change them too frequently. A consistent strategy helps managers sort through opportunities and gain short-term advantage by exploiting the attractive ones. In stable markets, managers rely on complicated strategies built on detailed predictions of the future. But when business is complicated, strategy should be simple.
The theoretical tensile strength of fcc crystals predicted from shear strength calculations
International Nuclear Information System (INIS)
Cerny, M; Pokluda, J
2009-01-01
This work presents a simple way of estimating uniaxial tensile strength on the basis of theoretical shear strength calculations, taking into account its dependence on a superimposed normal stress. The presented procedure enables us to avoid complicated and time-consuming analyses of elastic stability of crystals under tensile loading. The atomistic simulations of coupled shear and tensile deformations in cubic crystals are performed using first principles computational code based on pseudo-potentials and the plane wave basis set. Six fcc crystals are subjected to shear deformations in convenient slip systems and a special relaxation procedure controls the stress tensor. The obtained dependence of the ideal shear strength on the normal tensile stress seems to be almost linearly decreasing for all investigated crystals. Taking these results into account, the uniaxial tensile strength values in three crystallographic directions were evaluated by assuming a collapse of the weakest shear system. Calculated strengths for and loading were found to be mostly lower than previously calculated stresses related to tensile instability but rather close to those obtained by means of the shear instability analysis. On the other hand, the strengths for loading almost match the stresses related to tensile instability.
Minimization of complementary energy to predict shear modulus of laminates with intralaminar cracks
International Nuclear Information System (INIS)
Giannadakis, K; Varna, J
2012-01-01
The most common damage mode and the one examined in this work is the formation of intralaminar cracks in layers of laminates. These cracks can occur when the composite structure is subjected to mechanical and/or thermal loading and eventually lead to degradation of thermo-elastic properties. In the present work, the shear modulus reduction due to cracking is studied. Mathematical models exist in literature for the simple case of cross-ply laminates. The in-plane shear modulus of a damaged laminate is only considered in a few studies. In the current work, the shear modulus reduction in cross-plies will be analysed based on the principle of minimization of complementary energy. Hashin investigated the in-plane shear modulus reduction of cross-ply laminates with cracks in inside 90-layer using this variational approach and assuming that the in-plane shear stress in layers does not depend on the thickness coordinate. In the present study, a more detailed and accurate approach for stress estimation is followed using shape functions for this dependence with parameters obtained by minimization. The results for complementary energy are then compared with the respective from literature and finally an expression for shear modulus degradation is derived.
Cetin, S.; Konca, A. O.; Dogan, U.; Floyd, M.; Karabulut, H.; Ergintav, S.; Ganas, A.; Paradisis, D.; King, R. W.; Reilinger, R. E.
2017-12-01
The 2014 Mw6.9 Gokceada (strike-slip) and 2017 Mw6.3 Lesvos (normal) earthquakes represent two of the set of faults that accommodate the transition from right-lateral strike-slip faulting on the North Anatolian Fault (NAF) to normal faulting along the Gulf of Corinth. The Gokceada earthquake was a purely strike-slip event on the western extension of the NAF where it enters the northern Aegean Sea. The Lesvos earthquake, located roughly 200 km south of Gokceada, occurred on a WNW-ESE-striking normal fault. Both earthquakes respond to the same regional stress field, as indicated by their sub-parallel seismic tension axis and far-field coseismic GPS displacements. Interpretation of GPS-derived velocities, active faults, crustal seismicity, and earthquake focal mechanisms in the northern Aegean indicates that this pattern of complementary faulting, involving WNW-ESE-striking normal faults (e.g. Lesvos earthquake) and SW-NE-striking strike-slip faults (e.g. Gokceada earthquake), persists across the full extent of the northern Aegean Sea. The combination of these two "families" of faults, combined with some systems of conjugate left-lateral strike-slip faults, complement one another and culminate in the purely extensional rift structures that form the large Gulfs of Evvia and Corinth. In addition to being consistent with seismic and geodetic observations, these fault geometries explain the increasing velocity of the southern Aegean and Peloponnese regions towards the Hellenic subduction zone. Alignment of geodetic extension and seismic tension axes with motion of the southern Aegean towards the Hellenic subduction zone suggests a direct association of Aegean extension with subduction, possibly by trench retreat, as has been suggested by prior investigators.
Alabdulmohsin, Ibrahim M.
2018-03-07
We will begin our treatment of summability calculus by analyzing what will be referred to, throughout this book, as simple finite sums. Even though the results of this chapter are particular cases of the more general results presented in later chapters, they are important to start with for a few reasons. First, this chapter serves as an excellent introduction to what summability calculus can markedly accomplish. Second, simple finite sums are encountered more often and, hence, they deserve special treatment. Third, the results presented in this chapter for simple finite sums will, themselves, be used as building blocks for deriving the most general results in subsequent chapters. Among others, we establish that fractional finite sums are well-defined mathematical objects and show how various identities related to the Euler constant as well as the Riemann zeta function can actually be derived in an elementary manner using fractional finite sums.
Alabdulmohsin, Ibrahim M.
2018-01-01
We will begin our treatment of summability calculus by analyzing what will be referred to, throughout this book, as simple finite sums. Even though the results of this chapter are particular cases of the more general results presented in later chapters, they are important to start with for a few reasons. First, this chapter serves as an excellent introduction to what summability calculus can markedly accomplish. Second, simple finite sums are encountered more often and, hence, they deserve special treatment. Third, the results presented in this chapter for simple finite sums will, themselves, be used as building blocks for deriving the most general results in subsequent chapters. Among others, we establish that fractional finite sums are well-defined mathematical objects and show how various identities related to the Euler constant as well as the Riemann zeta function can actually be derived in an elementary manner using fractional finite sums.
Katz, Abbott
2011-01-01
Get the most out of Excel 2010 with Excel 2010 Made Simple - learn the key features, understand what's new, and utilize dozens of time-saving tips and tricks to get your job done. Over 500 screen visuals and clear-cut instructions guide you through the features of Excel 2010, from formulas and charts to navigating around a worksheet and understanding Visual Basic for Applications (VBA) and macros. Excel 2010 Made Simple takes a practical and highly effective approach to using Excel 2010, showing you the best way to complete your most common spreadsheet tasks. You'll learn how to input, format,
Mazo, Gary
2011-01-01
If you have a Droid series smartphone - Droid, Droid X, Droid 2, or Droid 2 Global - and are eager to get the most out of your device, Droids Made Simple is perfect for you. Authors Martin Trautschold, Gary Mazo and Marziah Karch guide you through all of the features, tips, and tricks using their proven combination of clear instructions and detailed visuals. With hundreds of annotated screenshots and step-by-step directions, Droids Made Simple will transform you into a Droid expert, improving your productivity, and most importantly, helping you take advantage of all of the cool features that c
International Nuclear Information System (INIS)
Sator, N.
2003-01-01
This article concerns the correspondence between thermodynamics and the morphology of simple fluids in terms of clusters. Definitions of clusters providing a geometric interpretation of the liquid-gas phase transition are reviewed with an eye to establishing their physical relevance. The author emphasizes their main features and basic hypotheses, and shows how these definitions lead to a recent approach based on self-bound clusters. Although theoretical, this tutorial review is also addressed to readers interested in experimental aspects of clustering in simple fluids
Thouzery, Michel
2014-01-01
Fondée par les producteurs du Syndicat Inter-Massifs pour la Production et l’Économie des Simples (S.I.M.P.L.E.S), l’association base son action sur la recherche et le maintien d’une production de qualité (herboristerie et préparations à base de plantes) qui prend en compte le respect de l’environnement et la pérennité des petits producteurs en zone de montagne. Actions de formation Stages de découverte de la flore médicinale sauvage, Stages de culture et transformation des plantes médicinale...
International Nuclear Information System (INIS)
Dobrzynski, L; Akjouj, A; Djafari-Rouhani, B; Al-Wahsh, H; Zielinski, P
2003-01-01
We present a simple multiplexing device made of two atomic chains coupled by two other transition metal atoms. We show that this simple atomic device can transfer electrons at a given energy from one wire to the other, leaving all other electron states unaffected. Closed-form relations between the transmission coefficients and the inter-atomic distances are given to optimize the desired directional electron ejection. Such devices can be adsorbed on insulating substrates and characterized by current surface technologies. (letter to the editor)
Morales, L. F. G.; Rybacki, E.; Dresen, G. H.; Kilian, R.
2015-12-01
In the Earth's middle to lower crust, strain is frequently localized along ductile shear zones, which commonly nucleate at structural and material heterogeneities. To investigate shear zone nucleation and development due to heterogeneities, we performed constant strain-rate (CSR) and constant stress (CS) simple shear (torsion) deformation experiments on Carrara marble samples containing weak (limestone) inclusions. The experiments were conducted in a Paterson-type gas deformation apparatus at 900 °C temperature and 400 MPa confining pressure and maximum bulk shear strains of 3. Peak shear stress was about 20 MPa for all the samples, followed by smooth weakening and steady state behavior. The strain is predominantly localized in the host marble within the process zone in front of the inclusion, defined by a zone of intense grain size reduction due to dynamic recrystallization. In CS tests a narrow shear zone developed in front of the inclusion, whereas in CSR experiments the deformation is more heterogeneously distributed, up to g=3.. In the later, secondary foliations oblique to the process zone and alternating thin, high-strain layers are common. In samples deformed at the same shear strain (g=1), the average recrystallized grain size in the process zone is similar for CS and CSR conditions. Crystallographic preferred orientation (CPO) measurements shows that different grain sizes have slightly different CPO patterns. CPO strength varies for different grain sizes, with a CPO strength peak between 40-50 μm, decreasing progressively within smaller grain size, but with secondary peaks for different coarse-grained sizes. Our observations suggest that the initial formation and transient deformation of shear zones is strongly affected by loading conditions.
IMAGE ANALYSIS FOR MODELLING SHEAR BEHAVIOUR
Directory of Open Access Journals (Sweden)
Philippe Lopez
2011-05-01
Full Text Available Through laboratory research performed over the past ten years, many of the critical links between fracture characteristics and hydromechanical and mechanical behaviour have been made for individual fractures. One of the remaining challenges at the laboratory scale is to directly link fracture morphology of shear behaviour with changes in stress and shear direction. A series of laboratory experiments were performed on cement mortar replicas of a granite sample with a natural fracture perpendicular to the axis of the core. Results show that there is a strong relationship between the fracture's geometry and its mechanical behaviour under shear stress and the resulting damage. Image analysis, geostatistical, stereological and directional data techniques are applied in combination to experimental data. The results highlight the role of geometric characteristics of the fracture surfaces (surface roughness, size, shape, locations and orientations of asperities to be damaged in shear behaviour. A notable improvement in shear understanding is that shear behaviour is controlled by the apparent dip in the shear direction of elementary facets forming the fracture.
DEFF Research Database (Denmark)
Rosendahl, Mads
2002-01-01
-like language. Our aim is to extract a simple notion of driving and show that even in this tamed form it has much of the power of more general notions of driving. Our driving technique may be used to simplify functional programs which use function composition and will often be able to remove intermediate data...
Dix, M. G.; Harrison, D. R.; Edwards, T. M.
1982-01-01
Bubble vial with external aluminum-foil electrodes is sensing element for simple indicating tiltmeter. To measure bubble displacement, bridge circuit detects difference in capacitance between two sensing electrodes and reference electrode. Tiltmeter was developed for experiment on forecasting seismic events by changes in Earth's magnetic field.
Eggen, Per-Odd
2009-01-01
This article describes the construction of an inexpensive, robust, and simple hydrogen electrode, as well as the use of this electrode to measure "standard" potentials. In the experiment described here the students can measure the reduction potentials of metal-metal ion pairs directly, without using a secondary reference electrode. Measurements…
International Nuclear Information System (INIS)
Blain, J.F.
1969-01-01
The results obtained by application to argon and sodium of the two important methods of studying the structure of liquids: scattering of X-rays and neutrons, are presented on one hand. On the other hand the principal models employed for reconstituting the structure of simple liquids are exposed: mathematical models, lattice models and their derived models, experimental models. (author) [fr
International Nuclear Information System (INIS)
De Luca, R; Faella, O
2014-01-01
Mathematical fireworks are reproduced in two dimensions by means of simple notions in kinematics and Newtonian mechanics. Extension of the analysis in three dimensions is proposed and the geometric figures the falling tiny particles make on the ground after explosion are determined. (paper)
African Journals Online (AJOL)
In the present study, 78 mapped simple sequence repeat (SSR) markers representing 11 linkage groups of adzuki bean were evaluated for transferability to mungbean and related Vigna spp. 41 markers amplified characteristic bands in at least one Vigna species. The transferability percentage across the genotypes ranged ...
Temiz, Burak Kagan; Yavuz, Ahmet
2015-01-01
This study was done to develop a simple and inexpensive wave driver that can be used in experiments on string waves. The wave driver was made using a battery-operated toy car, and the apparatus can be used to produce string waves at a fixed frequency. The working principle of the apparatus is as follows: shortly after the car is turned on, the…
Problems pilots face involving wind shear
Melvin, W. W.
1977-01-01
Educating pilots and the aviation industry about wind shears presents a major problem associated with this meteorological phenomenon. The pilot's second most pressing problem is the need for a language to discuss wind shear encounters with other pilots so that the reaction of the aircraft to the wind shear encounter can be accurately described. Another problem is the flight director which gives a centered pitch command for a given angular displacement from the glide slope. It was suggested that they should instead be called flight path command and should not center unless the aircraft is actually correcting to the flight path.
Shear viscosity of liquid mixtures: Mass dependence
International Nuclear Information System (INIS)
Kaushal, Rohan; Tankeshwar, K.
2002-06-01
Expressions for zeroth, second, and fourth sum rules of transverse stress autocorrelation function of two component fluid have been derived. These sum rules and Mori's memory function formalism have been used to study shear viscosity of Ar-Kr and isotopic mixtures. It has been found that theoretical result is in good agreement with the computer simulation result for the Ar-Kr mixture. The mass dependence of shear viscosity for different mole fraction shows that deviation from ideal linear model comes even from mass difference in two species of fluid mixture. At higher mass ratio shear viscosity of mixture is not explained by any of the emperical model. (author)
Shear Melting of a Colloidal Glass
Eisenmann, Christoph; Kim, Chanjoong; Mattsson, Johan; Weitz, David A.
2010-01-01
We use confocal microscopy to explore shear melting of colloidal glasses, which occurs at strains of ˜0.08, coinciding with a strongly non-Gaussian step size distribution. For larger strains, the particle mean square displacement increases linearly with strain and the step size distribution becomes Gaussian. The effective diffusion coefficient varies approximately linearly with shear rate, consistent with a modified Stokes-Einstein relationship in which thermal energy is replaced by shear energy and the length scale is set by the size of cooperatively moving regions consisting of ˜3 particles.
Shear viscosity of liquid mixtures Mass dependence
Kaushal, R
2002-01-01
Expressions for zeroth, second, and fourth sum rules of transverse stress autocorrelation function of two component fluid have been derived. These sum rules and Mori's memory function formalism have been used to study shear viscosity of Ar-Kr and isotopic mixtures. It has been found that theoretical result is in good agreement with the computer simulation result for the Ar-Kr mixture. The mass dependence of shear viscosity for different mole fraction shows that deviation from ideal linear model comes even from mass difference in two species of fluid mixture. At higher mass ratio shear viscosity of mixture is not explained by any of the emperical model.
The biomechanics of simple steatosis and steatohepatitis
Parker, K. J.; Ormachea, J.; Drage, M. G.; Kim, H.; Hah, Z.
2018-05-01
Magnetic resonance and ultrasound elastography techniques are now important tools for staging high-grade fibrosis in patients with chronic liver disease. However, uncertainty remains about the effects of simple accumulation of fat (steatosis) and inflammation (steatohepatitis) on the parameters that can be measured using different elastographic techniques. To address this, we examine the rheological models that are capable of capturing the dominant viscoelastic behaviors associated with fat and inflammation in the liver, and quantify the resulting changes in shear wave speed and viscoelastic parameters. Theoretical results are shown to match measurements in phantoms and animal studies reported in the literature. These results are useful for better design of elastographic studies of fatty liver disease and steatohepatitis, potentially leading to improved diagnosis of these conditions.
Shear strength of clay and silt embankments.
2009-09-01
Highway embankment is one of the most common large-scale geotechnical facilities constructed in Ohio. In the past, the design of these embankments was largely based on soil shear strength properties that had been estimated from previously published e...
Localization in inelastic rate dependent shearing deformations
Katsaounis, Theodoros
2016-09-18
Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, indicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing structure and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions. © 2016 Elsevier Ltd
Recent progress in shear punch testing
International Nuclear Information System (INIS)
Hamilton, M.L.; Toloczko, M.B.; Lucas, G.E.
1994-09-01
The shear punch test was developed in response to the needs of the materials development community for small-scale mechanical properties tests. Such tests will be of great importance when a fusion neutron simulation device is built, since such a device is expected to have a limited irradiation volume. The shear punch test blanks a circular disk from a fixed sheet metal specimen, specifically a TEM disk. Load-displacement data generated during the test can be related to uniaxial tensile properties such as yield and ultimate strength. Shear punch and tensile tests were performed at room temperature on a number of unirradiated aluminum, copper, vanadium, and stainless steel alloys and on several irradiated aluminum alloys. Recent results discussed here suggest that the relationship between shear punch strength and tensile strength varies with alloy class, although the relationship determined for the unirradiated condition remains valid for the irradiated aluminum alloys
Enhancing Rotational Diffusion Using Oscillatory Shear
Leahy, Brian D.; Cheng, Xiang; Ong, Desmond C.; Liddell-Watson, Chekesha; Cohen, Itai
2013-01-01
Taylor dispersion - shear-induced enhancement of translational diffusion - is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced
Remote Sensing Wind and Wind Shear System.
Contents: Remote sensing of wind shear and the theory and development of acoustic doppler; Wind studies; A comparison of methods for the remote detection of winds in the airport environment; Acoustic doppler system development; System calibration; Airport operational tests.
Shear-induced phase changes in mixtures
International Nuclear Information System (INIS)
Romig, K.D.; Hanley, H.J.M.
1986-01-01
A thermodynamic theory to account for the behavior of liquid mixtures exposed to a shear is developed. One consequence of the theory is that shear-induced phase changes are predicted. The theory is based on a thermodynamics that includes specifically the shear rate in the formalism and is applied to mixtures by a straightforward modification of the corresponding states, conformalsolution approach. The approach is general but is used here for a mixture of Lennard-Jones particles with a Lennard-Jones equation of state as a reference fluid. The results are discussed in the context of the Scott and Van Konynenberg phase classification. It is shown that the influence of a shear does affect substantially the type of the phase behavior. Results from the model mixture are equated loosely with those from real polymeric liquids
Evaluating interfacial shear stresses in composite hollo
Directory of Open Access Journals (Sweden)
Aiham Adawi
2016-09-01
Full Text Available Analytical evaluation of the interfacial shear stresses for composite hollowcore slabs with concrete topping is rare in the literature. Adawi et al. (2014 estimated the interfacial shear stiffness coefficient (ks that governs the behavior of the interface between hollowcore slabs and the concrete topping using push-off tests. This parameter is utilized in this paper to provide closed form solutions for the differential equations governing the behavior of simply supported composite hollowcore slabs. An analytical solution based on the deformation compatibility of the composite section and elastic beam theory, is developed to evaluate the shear stresses along the interface. Linear finite element modeling of the full-scale tests presented in Adawi et al. (2015 is also conducted to validate the developed analytical solution. The proposed analytical solution was found to be adequate in estimating the magnitude of horizontal shear stress in the studied composite hollowcore slabs.
Localization in inelastic rate dependent shearing deformations
Katsaounis, Theodoros; Lee, Min-Gi; Tzavaras, Athanasios
2016-01-01
Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, indicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing structure and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions. © 2016 Elsevier Ltd
Acoustic waves in unbounded shear flows
International Nuclear Information System (INIS)
Chagelishvili, G.D.; Khujadze, G.R.; Lominadze, J.G.; Rogava, A.D.
1996-05-01
The linear evolution of acoustic waves in fluid flow with constant density and uniform shear of velocity is investigated. The process of the mean flow energy extraction by the three-dimensional acoustic waves which is due to the non-normality of linear dynamics in shear flows is analyzed. The thorough examination of the dynamics of different physical quantities, specifying the wave evolution, is outlined. The revealing of the behaviour becomes possible owing to the nonmodal approach that has been extensively used in the study of the perturbations evolution in shear flows since the beginning of the nineties. In addition, a detailed analyses of the physics of shear energy gain by vortex and acoustic perturbations is presented. (author). 28 refs, 7 figs
Stress analysis of shear/compression test
International Nuclear Information System (INIS)
Nishijima, S.; Okada, T.; Ueno, S.
1997-01-01
Stress analysis has been made on the glass fiber reinforced plastics (GFRP) subjected to the combined shear and compression stresses by means of finite element method. The two types of experimental set up were analyzed, that is parallel and series method where the specimen were compressed by tilted jigs which enable to apply the combined stresses, to the specimen. Modified Tsai-Hill criterion was employed to judge the failure under the combined stresses that is the shear strength under the compressive stress. The different failure envelopes were obtained between the two set ups. In the parallel system the shear strength once increased with compressive stress then decreased. On the contrary in the series system the shear strength decreased monotonicly with compressive stress. The difference is caused by the different stress distribution due to the different constraint conditions. The basic parameters which control the failure under the combined stresses will be discussed
Possible accuracy of the Cotton-Mouton polarimetry in a sheared toroidal plasma conversion
International Nuclear Information System (INIS)
Kravtsov, Y.A.; Chrzanowski, J.
2011-01-01
The Cotton-Mouton effect in the sheared plasma with helical magnetic lines is studied, using the equation for the complex amplitude ratio (CAR). A simple model for helical magnetic lines in plasma of toroidal configuration is suggested. Equation for CAR is solved perturbatively, treating the shear angle variations as a small perturbation, caused by the spiral form of the magnetic lines. It is shown that the uncertainty of the polarization measurements in the toroidal plasma with a spiral form of the magnetic lines does not exceed 1.0-2.0%, which determines the limiting accuracy of the Cotton-Mouton polarimetry. It is furthermore pointed out that the method of a priori subtraction of the '' sheared '' term may significantly improve the accuracy of the Cotton-Mouton polarimetry. (authors)
Tailoring the gradient ultrafine-grained structure in low-carbon steel during drawing with shear
Directory of Open Access Journals (Sweden)
G. I. Raab
2016-04-01
Full Text Available Conventional drawing and drawing with shear were conducted on the rods of low-carbon steel. Deformation by simple drawing forms basically a homogenous structure and leads to a uniform change in microhardness along the billet volume. A comparative analysis of the models of these processes showed that shear drawing of steel at room temperature reduces energy characteristics in half, normal forces on the die – by 1,8, and enhances the strain intensity from 0,5 to 1,6. During drawing with shear, strain-induced cementite dissolution occurs and a gradient structure is formed, which increases the microhardness of the surface layer up to values close to 7 000 MPa.
A Shear Strain Route Dependency of Martensite Formation in 316L Stainless Steel.
Kang, Suk Hoon; Kim, Tae Kyu; Jang, Jinsung; Oh, Kyu Hwan
2015-06-01
In this study, the effect of simple shearing on microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. Two different shear strain routes were obtained by twisting cylindrical specimens in the forward and backward directions. The strain-induced martensite phase was effectively obtained by alteration of the routes. Formation of the martensite phase clearly resulted in significant hardening of the steel. Grain-size reduction and strain-induced martensitic transformation within the deformed structures of the strained specimens were characterized by scanning electron microscopy - electron back-scattered diffraction, X-ray diffraction, and the TEM-ASTAR (transmission electron microscopy - analytical scanning transmission atomic resolution, automatic crystal orientation/phase mapping for TEM) system. Significant numbers of twin networks were formed by alteration of the shear strain routes, and the martensite phases were nucleated at the twin interfaces.
Cottrell, William; Montero, Miguel
2018-02-01
In this note we investigate the role of Lloyd's computational bound in holographic complexity. Our goal is to translate the assumptions behind Lloyd's proof into the bulk language. In particular, we discuss the distinction between orthogonalizing and `simple' gates and argue that these notions are useful for diagnosing holographic complexity. We show that large black holes constructed from series circuits necessarily employ simple gates, and thus do not satisfy Lloyd's assumptions. We also estimate the degree of parallel processing required in this case for elementary gates to orthogonalize. Finally, we show that for small black holes at fixed chemical potential, the orthogonalization condition is satisfied near the phase transition, supporting a possible argument for the Weak Gravity Conjecture first advocated in [1].
Unicameral (simple) bone cysts.
Baig, Rafath; Eady, John L
2006-09-01
Since their original description by Virchow, simple bone cysts have been studied repeatedly. Although these defects are not true neoplasms, simple bone cysts may create major structural defects of the humerus, femur, and os calcis. They are commonly discovered incidentally when x-rays are taken for other reasons or on presentation due to a pathologic fracture. Various treatment strategies have been employed, but the only reliable predictor of success of any treatment strategy is the age of the patient; those being older than 10 years of age heal their cysts at a higher rate than those under age 10. The goal of management is the formation of a bone that can withstand the stresses of use by the patient without evidence of continued bone destruction as determined by serial radiographic follow-up. The goal is not a normal-appearing x-ray, but a functionally stable bone.
Modeling and implementation of wind shear data
Frost, Walter
1987-01-01
The problems of implementing the JAWS wind shear data are discussed. The data sets are described from the view of utilizing them in an aircraft performance computer program. Then, some of the problems of nonstandard procedures are described in terms of programming the equations of aircraft motion when the effects of temporal and spatially variable winds are included. Finally, some of the computed effects of the various wind shear terms are shown.
Hydrodynamical fluctuations in smooth shear flows
International Nuclear Information System (INIS)
Chagelishvili, G.D.; Khujadze, G.R.; Lominadze, J.G.
1999-11-01
Background of hydrodynamical fluctuations in a intrinsically/stochastically forced, laminar, uniform shear flow is studied. The employment of so-called nonmodal mathematical analysis makes it possible to represent the background of fluctuations in a new light and to get more insight into the physics of its formation. The basic physical processes responsible for the formation of vortex and acoustic wave fluctuation backgrounds are analyzed. Interplay of the processes at low and moderate shear rates is described. Three-dimensional vortex fluctuations around a given macroscopic state are numerically calculated. The correlation functions of the fluctuations of physical quantities are analyzed. It is shown that there exists subspace D k in the wave-number space (k-space) that is limited externally by spherical surface with radius k ν ≡ A/ν (where A is the velocity shear parameter, ν - the kinematic viscosity) in the nonequilibrium open system under study. The spatial Fourier harmonics of vortex as well as acoustic wave fluctuations are strongly subjected by flow shear (by the open character of the system) at wave-numbers satisfying the condition k ν . Specifically it is shown that in D k : The fluctuations are non-Markovian; the spatial spectral density of energy of the vortex fluctuations by far exceeds the white-noise; the term of a new type associated to the hydrodynamical fluctuation of velocity appears in the correlation function of pressure; the fluctuation background of the acoustic waves is completely different at low and moderate shear rates (at low shear rates it is reduced in D k in comparison to the uniform (non-shear) flow; at moderate shear rates it it comparable to the background of the vortex fluctuations). The fluctuation background of both the vortex and the acoustic wave modes is anisotropic. The possible significance of the fluctuation background of vortices for the subcritical transition to turbulence and Brownian motion of small macroscopic
Line Crack Subject to Antiplane Shear.
1978-07-01
shear is obtained for the initiation of fracture. If the concept of the surface tension is usedone is able to calculate the cohesive stress for brittle ...Expression of the Griffith -racture criterion for brittle fracture. We have arrived at this result via the maximum shear-stress hypothesis, rather than...Crescent Beach Road, Glen Cove Prof. G.S. Heller Long Island, New York 11542 Division of Engineering Brown University Prof. Daniel
Shear Strains, Strain Rates and Temperature Changes in Adiabatic Shear Bands
1980-05-01
X14A. It has been found that when bainitic and martensitic steels are sheared adiabatically, a layer of material within ths shear zone is altezed and...Sooiety for Metals, Metals Park, Ohio, 1978, pp. 148-0. 21 TABLE II SOLID-STATE TRANSFORMATIONS IN BAINITIC STEEL TRANSFORMATION TRANSFORMATION...shear, thermoplastic, plasticity, plastic deformation, armor, steel IL AnSRACT ( -=nba asoa.tm a naeoesM iN faity by bleak n bet/2972 Experiments
Shear flow effect on ion temperature gradient vortices in plasmas with sheared magnetic field
DEFF Research Database (Denmark)
Chakrabarti, N.; Juul Rasmussen, J.
1999-01-01
The effect of velocity shear on ion temperature gradient (ITG) driven vortices in a nonuniform plasma in a curved, sheared magnetic field is investigated. In absence of parallel ion dynamics, vortex solutions for the ITG mode are studied analytically. It is shown that under certain conditions...... and ultimately lead to a dominating monopolar form. The effects of magnetic shear indicate it may destroy these structures. (C) 1999 American Institute of Physics....
Information technology made simple
Carter, Roger
1991-01-01
Information Technology: Made Simple covers the full range of information technology topics, including more traditional subjects such as programming languages, data processing, and systems analysis. The book discusses information revolution, including topics about microchips, information processing operations, analog and digital systems, information processing system, and systems analysis. The text also describes computers, computer hardware, microprocessors, and microcomputers. The peripheral devices connected to the central processing unit; the main types of system software; application soft
Modern mathematics made simple
Murphy, Patrick
1982-01-01
Modern Mathematics: Made Simple presents topics in modern mathematics, from elementary mathematical logic and switching circuits to multibase arithmetic and finite systems. Sets and relations, vectors and matrices, tesselations, and linear programming are also discussed.Comprised of 12 chapters, this book begins with an introduction to sets and basic operations on sets, as well as solving problems with Venn diagrams. The discussion then turns to elementary mathematical logic, with emphasis on inductive and deductive reasoning; conjunctions and disjunctions; compound statements and conditional
Resolution of axial shear strain elastography
International Nuclear Information System (INIS)
Thitaikumar, Arun; Righetti, Raffaella; Krouskop, Thomas A; Ophir, Jonathan
2006-01-01
The technique of mapping the local axial component of the shear strain due to quasi-static axial compression is defined as axial shear strain elastography. In this paper, the spatial resolution of axial shear strain elastography is investigated through simulations, using an elastically stiff cylindrical lesion embedded in a homogeneously softer background. Resolution was defined as the smallest size of the inclusion for which the strain value at the inclusion/background interface was greater than the average of the axial shear strain values at the interface and inside the inclusion. The resolution was measured from the axial shear strain profile oriented at 45 0 to the axis of beam propagation, due to the absence of axial shear strain along the normal directions. The effects of the ultrasound system parameters such as bandwidth, beamwidth and transducer element pitch along with signal processing parameters such as correlation window length (W) and axial shift (ΔW) on the estimated resolution were investigated. The results show that the resolution (at 45 0 orientation) is determined by the bandwidth and the beamwidth. However, the upper bound on the resolution is limited by the larger of the beamwidth and the window length, which is scaled inversely to the bandwidth. The results also show that the resolution is proportional to the pitch and not significantly affected by the axial window shift
Behavior of Tilted Angle Shear Connectors
Khorramian, Koosha; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.
2015-01-01
According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type. PMID:26642193
Behavior of Tilted Angle Shear Connectors.
Directory of Open Access Journals (Sweden)
Koosha Khorramian
Full Text Available According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type.
Cosmology with cosmic shear observations: a review.
Kilbinger, Martin
2015-07-01
Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations.
Edge Sheared Flows and Blob Dynamics
Energy Technology Data Exchange (ETDEWEB)
Myra, J.; D' Ippolito, D.; Russell, D., E-mail: jrmyra@lodestar.com [Lodestar Research Corporation, Boulder (United States); Davis, W. M.; Zweben, S. [Princeton Plasma Physics Laboratory, Princeton (United States); Terry, J.; LaBombard, B. [Massachusetts Institute of Technology, Cambridge (United States)
2012-09-15
Full text: A study of sheared flows in the edge and scrape-off layer (SOL) and their interaction with blob-filaments is presented. Edge sheared flows are believed to be important for the L-H, and H-L transitions. Blob generation and dynamics impacts both the (near-separatrix) scrape-off-layer (SOL) width critical for power handling in the divertor, and the interaction of plasma in the far SOL with plasma-facing components. These topics are critical for ITER and future devices. A fluid-based 2D curvature-interchange model embedded in the SOLT code is employed to study these issues. Sheared binormal flows both regulate the power flux crossing the separatrix and control the character of emitted turbulence structures such as blob-filaments. At a critical power level (depending on parameters) the laminar flows containing intermittent, but bound, structures give way to full-blown blob emissions signifying a transition from quasi-diffusive to convective transport. In order to diagnose sheared flows in experiments and assess their interaction with blobs, a blob-tracking algorithm has been developed and applied to both NSTX and Alcator C-Mod data. Blob motion and ellipticity can be affected by sheared flows, and are diagnosed and compared with seeded blob simulations. A picture of the interaction of blobs and sheared flows is emerging from advances in the theory and simulation of edge turbulence, combined with ever-improving capabilities for edge diagnostics and their analysis. (author)
Shear induced structures in crystallizing cocoa butter
Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.
2004-03-01
Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.
A viscoplastic shear-zone model for episodic slow slip events in oceanic subduction zones
Yin, A.; Meng, L.
2016-12-01
Episodic slow slip events occur widely along oceanic subduction zones at the brittle-ductile transition depths ( 20-50 km). Although efforts have been devoted to unravel their mechanical origins, it remains unclear about the physical controls on the wide range of their recurrence intervals and slip durations. In this study we present a simple mechanical model that attempts to account for the observed temporal evolution of slow slip events. In our model we assume that slow slip events occur in a viscoplastic shear zone (i.e., Bingham material), which has an upper static and a lower dynamic plastic yield strength. We further assume that the hanging wall deformation is approximated as an elastic spring. We envision the shear zone to be initially locked during forward/landward motion but is subsequently unlocked when the elastic and gravity-induced stress exceeds the static yield strength of the shear zone. This leads to backward/trenchward motion damped by viscous shear-zone deformation. As the elastic spring progressively loosens, the hanging wall velocity evolves with time and the viscous shear stress eventually reaches the dynamic yield strength. This is followed by the termination of the trenchward motion when the elastic stress is balanced by the dynamic yield strength of the shear zone and the gravity. In order to account for the zig-saw slip-history pattern of typical repeated slow slip events, we assume that the shear zone progressively strengthens after each slow slip cycle, possibly caused by dilatancy as commonly assumed or by progressive fault healing through solution-transport mechanisms. We quantify our conceptual model by obtaining simple analytical solutions. Our model results suggest that the duration of the landward motion increases with the down-dip length and the static yield strength of the shear zone, but decreases with the ambient loading velocity and the elastic modulus of the hanging wall. The duration of the backward/trenchward motion depends
Shape oscillations of elastic particles in shear flow.
Subramaniam, Dhananjay Radhakrishnan; Gee, David J
2016-09-01
Particle suspensions are common to biological fluid flows; for example, flow of red- and white-blood cells, and platelets. In medical technology, current and proposed methods for drug delivery use membrane-bounded liquid capsules for transport via the microcirculation. In this paper, we consider a 3D linear elastic particle inserted into a Newtonian fluid and investigate the time-dependent deformation using a numerical simulation. Specifically, a boundary element technique is used to investigate the motion and deformation of initially spherical or spheroidal particles in bounded linear shear flow. The resulting deformed shapes reveal a steady-state profile that exhibits a 'tank-treading' motion for initially spherical particles. Wall effects on particle trajectory are seen to include a modified Jeffrey׳s orbit for spheroidal inclusions with a period that varies inversely with the strength of the shear flow. Alternately, spheroidal inclusions may exhibit either a 'tumbling' or 'trembling' motion depending on the initial particle aspect ratio and the capillary number (i.e., ratio of fluid shear to elastic restoring force). We find for a capillary number of 0.1, a tumbling mode transitions to a trembling mode at an aspect ratio of 0.87 (approx.), while for a capillary number of 0.2, this transition takes place at a lower aspect ratio. These oscillatory modes are consistent with experimental observations involving similarly shaped vesicles and thus serves to validate the use of a simple elastic constitutive model to perform relevant physiological flow calculations. Copyright © 2016 Elsevier Ltd. All rights reserved.
Evolution of allowable stresses in shear for lumber
Robert L. Ethington; William L. Galligan; Henry M. Montrey; Alan D. Freas
1979-01-01
This paper surveys research leading to allowable shear stress parallel to grain for lumber. In early flexure tests of lumber, some pieces failed in shear. The estimated shear stress at time of failure was generally lower than shear strength measured on small, clear, straight-grained specimens. This and other engineering observations gave rise to adjustments that...
A New Hyperbolic Shear Deformation Theory for Bending Analysis of Functionally Graded Plates
Directory of Open Access Journals (Sweden)
Tahar Hassaine Daouadji
2012-01-01
Full Text Available Theoretical formulation, Navier’s solutions of rectangular plates based on a new higher order shear deformation model are presented for the static response of functionally graded plates. This theory enforces traction-free boundary conditions at plate surfaces. Shear correction factors are not required because a correct representation of transverse shearing strain is given. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Numerical illustrations concern flexural behavior of FG plates with metal-ceramic composition. Parametric studies are performed for varying ceramic volume fraction, volume fractions profiles, aspect ratios, and length to thickness ratios. Results are verified with available results in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static bending behavior of functionally graded plates.
International Nuclear Information System (INIS)
Gaur, Gurudatt; Das, Amita
2012-01-01
The study of electron velocity shear driven instability in electron magnetohydrodynamics (EMHD) regime in three dimensions has been carried out. It is well known that the instability is non-local in the plane defined by the flow direction and that of the shear, which is the usual Kelvin-Helmholtz mode, often termed as the sausage mode in the context of EMHD. On the other hand, a local instability with perturbations in the plane defined by the shear and the magnetic field direction exists which is termed as kink mode. The interplay of these two modes for simple sheared flow case as well as that when an external magnetic field exists has been studied extensively in the present manuscript in both linear and nonlinear regimes. Finally, these instability processes have been investigated for the exact 2D dipole solutions of EMHD equations [M. B. Isichenko and A. N. Marnachev, Sov. Phys. JETP 66, 702 (1987)] for which the electron flow velocity is sheared. It has been shown that dipoles are very robust and stable against the sausage mode as the unstable wavelengths are typically longer than the dipole size. However, we observe that they do get destabilized by the local kink mode.
a Predictive Model of Permeability for Fractal-Based Rough Rock Fractures during Shear
Huang, Na; Jiang, Yujing; Liu, Richeng; Li, Bo; Zhang, Zhenyu
This study investigates the roles of fracture roughness, normal stress and shear displacement on the fluid flow characteristics through three-dimensional (3D) self-affine fractal rock fractures, whose surfaces are generated using the modified successive random additions (SRA) algorithm. A series of numerical shear-flow tests under different normal stresses were conducted on rough rock fractures to calculate the evolutions of fracture aperture and permeability. The results show that the rough surfaces of fractal-based fractures can be described using the scaling parameter Hurst exponent (H), in which H = 3 - Df, where Df is the fractal dimension of 3D single fractures. The joint roughness coefficient (JRC) distribution of fracture profiles follows a Gauss function with a negative linear relationship between H and average JRC. The frequency curves of aperture distributions change from sharp to flat with increasing shear displacement, indicating a more anisotropic and heterogeneous flow pattern. Both the mean aperture and permeability of fracture increase with the increment of surface roughness and decrement of normal stress. At the beginning of shear, the permeability increases remarkably and then gradually becomes steady. A predictive model of permeability using the mean mechanical aperture is proposed and the validity is verified by comparisons with the experimental results reported in literature. The proposed model provides a simple method to approximate permeability of fractal-based rough rock fractures during shear using fracture aperture distribution that can be easily obtained from digitized fracture surface information.
Effect of Shear History on Rheology of Time-Dependent Colloidal Silica Gels
Directory of Open Access Journals (Sweden)
Paulo H. S. Santos
2017-11-01
Full Text Available This paper presents a rheological study describing the effects of shear on the flow curves of colloidal gels prepared with different concentrations of fumed silica (4%, 5%, 6%, and 7% and a hydrophobic solvent (Hydrocarbon fuel, JP-8. Viscosity measurements as a function of time were carried out at different shear rates (10, 50, 100, 500, and 1000 s−1, and based on this data, a new structural kinetics model was used to describe the system. Previous work has based the analysis of time dependent fluids on the viscosity of the intact material, i.e., before it is sheared, which is a condition very difficult to achieve when weak gels are tested. The simple action of loading the gel in the rheometer affects its structure and rheology, and the reproducibility of the measurements is thus seriously compromised. Changes in viscosity and viscoelastic properties of the sheared material are indicative of microstructural changes in the gel that need to be accounted for. Therefore, a more realistic method is presented in this work. In addition, microscopical images (Cryo-SEM were obtained to show how the structure of the gel is affected upon application of shear.
Applying a Stiffened Stitched Concept to Shear-Loaded Structure
Jegley, Dawn C.
2014-01-01
NASA and The Boeing Company have worked to develop new low-cost, lightweight composite structures for aircraft. A stitched carbon-epoxy material system was developed to reduce the weight and cost of transport aircraft structure, first in the NASA Advanced Composites Technology (ACT) Program in the 1990's and now in the Environmentally Responsible Aviation (ERA) Project. By stitching through the thickness of a dry carbon fiber material prior to cure, the need for mechanical fasteners is almost eliminated. Stitching also provides the benefit of reducing or eliminating delaminations, including those between stiffener flanges and skin. The stitched panel concept used in the ACT program used simple blade-stiffeners as stringers, caps, and clips. Today, the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept is being developed for application to advanced vehicle configurations. PRSEUS provides additional weight savings through the use of a stiffener with a thin web and a unidirectional carbon rod at the top of the web which provides structurally efficient stiffening. Comparisons between stitched and unstitched structure and between blade-stiffened and rod-stiffened structure are presented focusing on a panel loaded in shear. Shear loading is representative of spar loading in wing structures.
Shear-induced changes of electrical conductivity in suspensions
Energy Technology Data Exchange (ETDEWEB)
Crawshaw, John; Meeten, Gerald [Schlumberger Cambridge Research, Cambridge (United Kingdom)
2006-12-15
The effect of shear on electrical conductivity (rheo-conduction) is studied to give information about particle behaviour in suspensions. Past work is reviewed, and expressions are derived for the rheo-conduction of a suspension of nonconducting spheroids in a conducting matrix for current flow, parallel and normal to the suspension flow direction. A simple apparatus to study rheo-conduction in pipe flow is described, and measurements of steady and time-dependent effects are reported for various suspensions of colloidal particles. Suspensions of anisometric rod- and platelike particles at low concentrations showed rheo-conductive changes of sign, magnitude and relaxation that were consistent with the particle shape, concentration and interactions. The rheo-conductive response decreased with increasing volume fraction for platelike kaolinite particles, attributed to orientational jamming. Spherical latex particles gave unexpected rheo-conductive changes consistent with shear disruption of a conductive network of particles. It is concluded that rheo-conduction measurements are a useful adjunct to conventional rheometry. (orig.)
Energy spectrum of tearing mode turbulence in sheared background field
Hu, Di; Bhattacharjee, Amitava; Huang, Yi-Min
2018-06-01
The energy spectrum of tearing mode turbulence in a sheared background magnetic field is studied in this work. We consider the scenario where the nonlinear interaction of overlapping large-scale modes excites a broad spectrum of small-scale modes, generating tearing mode turbulence. The spectrum of such turbulence is of interest since it is relevant to the small-scale back-reaction on the large-scale field. The turbulence we discuss here differs from traditional MHD turbulence mainly in two aspects. One is the existence of many linearly stable small-scale modes which cause an effective damping during the energy cascade. The other is the scale-independent anisotropy induced by the large-scale modes tilting the sheared background field, as opposed to the scale-dependent anisotropy frequently encountered in traditional critically balanced turbulence theories. Due to these two differences, the energy spectrum deviates from a simple power law and takes the form of a power law multiplied by an exponential falloff. Numerical simulations are carried out using visco-resistive MHD equations to verify our theoretical predictions, and a reasonable agreement is found between the numerical results and our model.
Exponential Shear Flow of Linear, Entangled Polymeric Liquids
DEFF Research Database (Denmark)
Neergaard, Jesper; Park, Kyungho; Venerus, David C.
2000-01-01
A previously proposed reptation model is used to interpret exponential shear flow data taken on an entangled polystyrenesolution. Both shear and normal stress measurements are made during exponential shear using mechanical means. The model iscapable of explaining all trends seen in the data......, and suggests a novel analysis of the data. This analysis demonstrates thatexponential shearing flow is no more capable of stretching polymer chains than is inception of steady shear at comparableinstantaneous shear rates. In fact, all exponential shear flow stresses measured are bounded quantitatively...
Dimensional analysis made simple
International Nuclear Information System (INIS)
Lira, Ignacio
2013-01-01
An inductive strategy is proposed for teaching dimensional analysis to second- or third-year students of physics, chemistry, or engineering. In this strategy, Buckingham's theorem is seen as a consequence and not as the starting point. In order to concentrate on the basics, the mathematics is kept as elementary as possible. Simple examples are suggested for classroom demonstrations of the power of the technique and others are put forward for homework or experimentation, but instructors are encouraged to produce examples of their own. (paper)
Applied mathematics made simple
Murphy, Patrick
1982-01-01
Applied Mathematics: Made Simple provides an elementary study of the three main branches of classical applied mathematics: statics, hydrostatics, and dynamics. The book begins with discussion of the concepts of mechanics, parallel forces and rigid bodies, kinematics, motion with uniform acceleration in a straight line, and Newton's law of motion. Separate chapters cover vector algebra and coplanar motion, relative motion, projectiles, friction, and rigid bodies in equilibrium under the action of coplanar forces. The final chapters deal with machines and hydrostatics. The standard and conte
Wooldridge, Susan
2013-01-01
Data Processing: Made Simple, Second Edition presents discussions of a number of trends and developments in the world of commercial data processing. The book covers the rapid growth of micro- and mini-computers for both home and office use; word processing and the 'automated office'; the advent of distributed data processing; and the continued growth of database-oriented systems. The text also discusses modern digital computers; fundamental computer concepts; information and data processing requirements of commercial organizations; and the historical perspective of the computer industry. The
Deane, Sharon
2003-01-01
ASP Made Simple provides a brief introduction to ASP for the person who favours self teaching and/or does not have expensive computing facilities to learn on. The book will demonstrate how the principles of ASP can be learned with an ordinary PC running Personal Web Server, MS Access and a general text editor like Notepad.After working through the material readers should be able to:* Write ASP scripts that can display changing information on a web browser* Request records from a remote database or add records to it* Check user names & passwords and take this knowledge forward, either for their
Hansen, Jean-Pierre
1986-01-01
This book gives a comprehensive and up-to-date treatment of the theory of ""simple"" liquids. The new second edition has been rearranged and considerably expanded to give a balanced account both of basic theory and of the advances of the past decade. It presents the main ideas of modern liquid state theory in a way that is both pedagogical and self-contained. The book should be accessible to graduate students and research workers, both experimentalists and theorists, who have a good background in elementary mechanics.Key Features* Compares theoretical deductions with experimental r
Study of shear thickening behavior in colloidal suspensions
Directory of Open Access Journals (Sweden)
N Maleki Jirsaraee
2015-01-01
Full Text Available We studied the shear thickening behavior of the nano silica suspension (silica nanoparticles 12 nm in size suspended in ethylene glycol under steady shear. The critical shear rate for transition into shear thickening phase was determined at different concentrations and temperatures. The effect of temperature and concentration was studied on the shear thickening behavior. In silica suspension, it was observed that all the samples had a transition into shear thickening phase and also by increasing the temperature, critical shear rate increased and viscosity decreased. Our observations showed that movement in silica suspension was Brownian and temperature could cause a delay in transition into shear thickening phase. Yet, we observed that increasing the concentration would decrease critical shear rate and increase viscosity. Increasing temperature increased Brownian forces and increasing concentration increased hydrodynamic forces, confirming the contrast between these two forces for transition into shear thickening phase for the suspensions containing nano particles
Probabilistic simple sticker systems
Selvarajoo, Mathuri; Heng, Fong Wan; Sarmin, Nor Haniza; Turaev, Sherzod
2017-04-01
A model for DNA computing using the recombination behavior of DNA molecules, known as a sticker system, was introduced by by L. Kari, G. Paun, G. Rozenberg, A. Salomaa, and S. Yu in the paper entitled DNA computing, sticker systems and universality from the journal of Acta Informatica vol. 35, pp. 401-420 in the year 1998. A sticker system uses the Watson-Crick complementary feature of DNA molecules: starting from the incomplete double stranded sequences, and iteratively using sticking operations until a complete double stranded sequence is obtained. It is known that sticker systems with finite sets of axioms and sticker rules generate only regular languages. Hence, different types of restrictions have been considered to increase the computational power of sticker systems. Recently, a variant of restricted sticker systems, called probabilistic sticker systems, has been introduced [4]. In this variant, the probabilities are initially associated with the axioms, and the probability of a generated string is computed by multiplying the probabilities of all occurrences of the initial strings in the computation of the string. Strings for the language are selected according to some probabilistic requirements. In this paper, we study fundamental properties of probabilistic simple sticker systems. We prove that the probabilistic enhancement increases the computational power of simple sticker systems.
Schilstra, Maria J; Martin, Stephen R
2009-01-01
Stochastic simulations may be used to describe changes with time of a reaction system in a way that explicitly accounts for the fact that molecules show a significant degree of randomness in their dynamic behavior. The stochastic approach is almost invariably used when small numbers of molecules or molecular assemblies are involved because this randomness leads to significant deviations from the predictions of the conventional deterministic (or continuous) approach to the simulation of biochemical kinetics. Advances in computational methods over the three decades that have elapsed since the publication of Daniel Gillespie's seminal paper in 1977 (J. Phys. Chem. 81, 2340-2361) have allowed researchers to produce highly sophisticated models of complex biological systems. However, these models are frequently highly specific for the particular application and their description often involves mathematical treatments inaccessible to the nonspecialist. For anyone completely new to the field to apply such techniques in their own work might seem at first sight to be a rather intimidating prospect. However, the fundamental principles underlying the approach are in essence rather simple, and the aim of this article is to provide an entry point to the field for a newcomer. It focuses mainly on these general principles, both kinetic and computational, which tend to be not particularly well covered in specialist literature, and shows that interesting information may even be obtained using very simple operations in a conventional spreadsheet.
Piezoelectric energy harvesting through shear mode operation
International Nuclear Information System (INIS)
Malakooti, Mohammad H; Sodano, Henry A
2015-01-01
Piezoelectric materials are excellent candidates for use in energy harvesting applications due to their high electromechanical coupling properties that enable them to convert input mechanical energy into useful electric power. The electromechanical coupling coefficient of the piezoelectric material is one of the most significant parameters affecting energy conversion and is dependent on the piezoelectric mode of operation. In most piezoceramics, the d 15 piezoelectric shear coefficient is the highest coefficient compared to the commonly used axial and transverse modes that utilize the d 33 and the d 31 piezoelectric strain coefficients. However, complicated electroding methods and challenges in evaluating the performance of energy harvesting devices operating in the shear mode have slowed research in this area. The shear deformation of a piezoelectric layer can be induced in a vibrating sandwich beam with a piezoelectric core. Here, a model based on Timoshenko beam theory is developed to predict the electric power output from a cantilever piezoelectric sandwich beam under base excitations. It is shown that the energy harvester operating in the shear mode is able to generate ∼50% more power compared to the transverse mode for a numerical case study. Reduced models of both shear and transverse energy harvesters are obtained to determine the optimal load resistance in the system and perform an efficiency comparison between two models with fixed and adaptive resistances. (paper)
Evaluation of shear mounted elastomeric damper
Zorzi, E.; Walton, J.
1982-01-01
Viton-70 elastomeric shear mounted damper was built and tested on a T-55 power turbine spool in the rotor's high speed balancing rig. This application of a shear mounted elastomeric damper demonstrated for the first time, the feasibility of using elastomers as the primary rotor damping source in production turbine engine hardware. The shear damper design was selected because it was compatible with actual gas turbine engine radial space constraints, could accommodate both the radial and axial thrust loads present in gas turbine engines, and was capable of controlled axial preload. The shear damper was interchangeable with the production T-55 power turbine roller bearing support so that a direct comparison between the shear damper and the production support structure could be made. Test results show that the Viton-70 elastomer damper operated successfully and provided excellent control of both synchronous and nonsynchronous vibrations through all phases of testing up to the maximum rotor speed of 16,000 rpm. Excellent correlation between the predicted and experienced critical speeds, mode shapes and log decrements for the power turbine rotor and elastomer damper assembly was also achieved.
Ballooning mode stabilization by moderate sheared rotation
International Nuclear Information System (INIS)
Hameiri, E.
1996-01-01
Sheared toroidal plasma rotation has been known for some time to have a stabilizing effect on the ballooning modes. A recent calculation showed that a large flow shear, with dΩ/dq of the order of the Alfven toroidal frequency, can stabilize the ballooning modes. This latest result is, in fact, not so optimistic. For observed flows with Mach number of order unity one gets dΩ/dq smaller by a factor O(√β) from the required level (if the flow shear length is of the same order as the magnetic shear length). Moreover, the calculation does not take into account a possibly large transient growth of the mode amplitude due to its Floquet structures We show here that, in fact, there is a general tendency of the ballooning mode to stabilize as soon as the flow shear dΩ/dq exceeds the (O√β smaller) open-quotes slowclose quotes magnetosonic wave frequency. Our analysis is perturbative, where the small parameter is related to the small coupling between the slow and Alfven waves-as is the case in a high aspect-ratio tokamak. (In the perturbation it is important to take the Hamiltonian nature of the governing equations into account.) Moreover, our results apply to the relevant transient growth of the mode amplitude
Delayed shear enhancement in mesoscale atmospheric dispersion
Energy Technology Data Exchange (ETDEWEB)
Moran, M.D. [Atmospheric Environment Service, Ontario (Canada); Pielke, R.A. [Colorado State Univ., Fort Collins, CO (United States)
1994-12-31
Mesoscale atmospheric dispersion (MAD) is more complicated than smaller-scale dispersion because the mean wind field can no longer be considered steady or horizontally homogeneous over mesoscale time and space scales. Wind shear also plays a much more important role on the mesoscale: horizontal dispersion can be enhanced and often dominated by vertical wind shear on these scales through the interaction of horizontal differential advection and vertical mixing. Just over 30 years ago, Pasquill suggested that this interaction need not be simultaneous and that the combination of differential horizontal advection with delayed or subsequent vertical mixing could maintain effective horizontal diffusion in spite of temporal or spatial reductions in boundary-layer turbulence intensity. This two-step mechanism has not received much attention since then, but a recent analysis of observations from and numerical simulations of two mesoscale tracer experiments suggests that delayed shear enhancement can play an important role in MAD. This paper presents an overview of this analysis, with particular emphasis on the influence of resolvable vertical shear on MAD in these two case studies and the contributions made by delayed shear enhancement.
Examining shear processes during magma ascent
Kendrick, J. E.; Wallace, P. A.; Coats, R.; Lamur, A.; Lavallée, Y.
2017-12-01
Lava dome eruptions are prone to rapid shifts from effusive to explosive behaviour which reflects the rheology of magma. Magma rheology is governed by composition, porosity and crystal content, which during ascent evolves to yield a rock-like, viscous suspension in the upper conduit. Geophysical monitoring, laboratory experiments and detailed field studies offer the opportunity to explore the complexities associated with the ascent and eruption of such magmas, which rest at a pivotal position with regard to the glass transition, allowing them to either flow or fracture. Crystal interaction during flow results in strain-partitioning and shear-thinning behaviour of the suspension. In a conduit, such characteristics favour the formation of localised shear zones as strain is concentrated along conduit margins, where magma can rupture and heal in repetitive cycles. Sheared magmas often record a history of deformation in the form of: grain size reduction; anisotropic permeable fluid pathways; mineral reactions; injection features; recrystallisation; and magnetic anomalies, providing a signature of the repetitive earthquakes often observed during lava dome eruptions. The repetitive fracture of magma at ( fixed) depth in the conduit and the fault-like products exhumed at spine surfaces indicate that the last hundreds of meters of ascent may be controlled by frictional slip. Experiments on a low-to-high velocity rotary shear apparatus indicate that shear stress on a slip plane is highly velocity dependent, and here we examine how this influences magma ascent and its characteristic geophysical signals.
Shear modulation experiments with ECCD on TCV
International Nuclear Information System (INIS)
Cirant, S.; Alberti, S.; Gandini, F.; Behn, R.; Goodman, T.P.; Nikkola, P.
2006-01-01
Anomalous electron transport is determined by turbulence, which in turn is affected by magnetic shear. A novel application of electron cyclotron current drive (ECCD), aiming at localized shear modulation, has been applied on the TCV tokamak for experiments on shear-dependent electron transport. Pairs of EC beams, absorbed at the same radius, with one oriented for co- and the other for counter-injection, are modulated out of phase in order to force a local modulation of current-density at constant input power. Off-axis deposition (ρ dep = 0.24) is performed to avoid the central region, where the low heat flux would make transport analysis difficult. In addition some sawteeth control is achieved in this way. A significant impact on local shear is achieved with I ECCD ∼ 0.1I OH , even when the modulation period is much shorter than the current diffusion time across the whole plasma radius. The main result is that although source (heat and particle) terms are constant, both electron density and temperature are modulated during alternated ECCD. Once equilibrium effects are taken into account for appropriate mapping of Thomson scattering measurements onto flux coordinates, modulation of T e and electron pressure, peaked on-axis, is confirmed at all radii internal to EC deposition. The best confinement occurs for co-injection, in which case a local decrease (∼55%) in the magnetic shear causes a decrease in the electron thermal diffusivity of a similar amount (∼65%)
Charge-density-shear-moduli relationships in aluminum-lithium alloys.
Eberhart, M
2001-11-12
Using the first principles full-potential linear-augmented-Slater-type orbital technique, the energies and charge densities of aluminum and aluminum-lithium supercells have been computed. The experimentally observed increase in aluminum's shear moduli upon alloying with lithium is argued to be the result of predictable changes to aluminum's total charge density, suggesting that simple rules may allow the alloy designer to predict the effects of dilute substitutional elements on alloy elastic response.
Structural mechanisms of formation of adiabatic shear bands
Directory of Open Access Journals (Sweden)
Mikhail Sokovikov
2016-10-01
Full Text Available The paper focuses on the experimental and theoretical study of plastic deformation instability and localization in materials subjected to dynamic loading and high-velocity perforation. We investigate the behavior of samples dynamically loaded during Hopkinson-Kolsky pressure bar tests in a regime close to simple shear conditions. Experiments were carried out using samples of a special shape and appropriate test rigging, which allowed us to realize a plane strain state. Also, the shear-compression specimens proposed in were investigated. The lateral surface of the samples was investigated in a real-time mode with the aid of a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time made it possible to trace the evolution of plastic strain localization. Use of a transmission electron microscope for studying the surface of samples showed that in the regions of strain localization there are parts taking the shape of bands and honeycomb structure in the deformed layer. The process of target perforation involving plug formation and ejection was investigated using a high-speed infra-red camera. A specially designed ballistic set-up for studying perforation was used to test samples in different impulse loading regimes followed by plastic flow instability and plug ejection. Changes in the velocity of the rear surface at different time of plug ejection were analyzed by Doppler interferometry techniques. The microstructure of tested samples was analyzed using an optical interferometer-profilometer and a scanning electron microscope. The subsequent processing of 3D deformation relief data enabled estimation of the distribution of plastic strain gradients at different time of plug formation and ejection. It has been found that in strain localization areas the subgrains are elongated taking the shape of bands and undergo fragmentation leading to the formation of super-microcrystalline structure, in which the
Beyond Simple Headquarters Configurations
DEFF Research Database (Denmark)
Dellestrand, Henrik; Kappen, Philip; Nell, Phillip Christopher
We investigate “dual headquarters involvement”, i.e. corporate and divisional headquarters’ simultaneous involvement in subsidiaries’ innovation development projects. Analyses draw on 85 innovation projects in 23 multibusiness firms and reveal that cross-divisional innovation importance, i.......e., an innovation that is important for the firm beyond the divisional boundaries, drives dual headquarters involvement in innovation development. Contrary to expectations, on average, a non-significant effect of cross-divisional embeddedness on dual headquarters involvement is found. Yet, both cross......-divisional importance and embeddedness effects are contingent on the overall complexity of the innovation project as signified by the size of the development network. The results lend support for the notion that parenting in complex structures entails complex headquarters structures and that we need to go beyond simple...
Givant, Steven
2017-01-01
This monograph details several different methods for constructing simple relation algebras, many of which are new with this book. By drawing these seemingly different methods together, all are shown to be aspects of one general approach, for which several applications are given. These tools for constructing and analyzing relation algebras are of particular interest to mathematicians working in logic, algebraic logic, or universal algebra, but will also appeal to philosophers and theoretical computer scientists working in fields that use mathematics. The book is written with a broad audience in mind and features a careful, pedagogical approach; an appendix contains the requisite background material in relation algebras. Over 400 exercises provide ample opportunities to engage with the material, making this a monograph equally appropriate for use in a special topics course or for independent study. Readers interested in pursuing an extended background study of relation algebras will find a comprehensive treatme...
Energy Technology Data Exchange (ETDEWEB)
Graham, Peter W.; /Stanford U., ITP; Horn, Bart; Kachru, Shamit; /Stanford U., ITP /SLAC; Rajendran, Surjeet; /Johns Hopkins U. /Stanford U., ITP; Torroba, Gonzalo; /Stanford U., ITP /SLAC
2011-12-14
We explore simple but novel bouncing solutions of general relativity that avoid singularities. These solutions require curvature k = +1, and are supported by a negative cosmological term and matter with -1 < w < -1 = 3. In the case of moderate bounces (where the ratio of the maximal scale factor a{sub +} to the minimal scale factor a{sub -} is {Omicron}(1)), the solutions are shown to be classically stable and cycle through an infinite set of bounces. For more extreme cases with large a{sub +} = a{sub -}, the solutions can still oscillate many times before classical instabilities take them out of the regime of validity of our approximations. In this regime, quantum particle production also leads eventually to a departure from the realm of validity of semiclassical general relativity, likely yielding a singular crunch. We briefly discuss possible applications of these models to realistic cosmology.
SIMPLE for industrial radiography
International Nuclear Information System (INIS)
Azhar Azmi; Abd Nassir Ibrahim; Siti Madiha Muhammad Amir; Glam Hadzir Patai Mohamad; Saidi Rajab
2004-01-01
The first thing industrial radiographers have to do before commencing radiography works is to determine manually the amount of correct exposure that the film need to be exposed in order to obtain the right density. The amount of exposure depends on many variables such as type of radioisotope, type of film, nature of test-object and its orientation, and specific arrangement related to object location and configuration. In many cases radiography works are rejected because of radiographs fail to meet certain reference criteria as defined in the applicable standard. One of the main reasons of radiograph rejection is due to inadequate exposure received by the films. SIMPLE is a software specially developed to facilitate the calculation of gamma-radiography exposure. By using this software and knowing radiographic parameters to be encountered during the work, it is expected that human error will be minimized, thus enhancing the quality and productivity of NDT jobs. (Author)
Molecular genetics made simple
Directory of Open Access Journals (Sweden)
Heba Sh. Kassem
2012-07-01
Full Text Available Genetics have undoubtedly become an integral part of biomedical science and clinical practice, with important implications in deciphering disease pathogenesis and progression, identifying diagnostic and prognostic markers, as well as designing better targeted treatments. The exponential growth of our understanding of different genetic concepts is paralleled by a growing list of genetic terminology that can easily intimidate the unfamiliar reader. Rendering genetics incomprehensible to the clinician however, defeats the very essence of genetic research: its utilization for combating disease and improving quality of life. Herein we attempt to correct this notion by presenting the basic genetic concepts along with their usefulness in the cardiology clinic. Bringing genetics closer to the clinician will enable its harmonious incorporation into clinical care, thus not only restoring our perception of its simple and elegant nature, but importantly ensuring the maximal benefit for our patients.
Molecular genetics made simple
Kassem, Heba Sh.; Girolami, Francesca; Sanoudou, Despina
2012-01-01
Abstract Genetics have undoubtedly become an integral part of biomedical science and clinical practice, with important implications in deciphering disease pathogenesis and progression, identifying diagnostic and prognostic markers, as well as designing better targeted treatments. The exponential growth of our understanding of different genetic concepts is paralleled by a growing list of genetic terminology that can easily intimidate the unfamiliar reader. Rendering genetics incomprehensible to the clinician however, defeats the very essence of genetic research: its utilization for combating disease and improving quality of life. Herein we attempt to correct this notion by presenting the basic genetic concepts along with their usefulness in the cardiology clinic. Bringing genetics closer to the clinician will enable its harmonious incorporation into clinical care, thus not only restoring our perception of its simple and elegant nature, but importantly ensuring the maximal benefit for our patients. PMID:25610837
Directory of Open Access Journals (Sweden)
Ahmet YILDIRIM
2014-07-01
Full Text Available Individuals in terms of the economy in which we live is one of the most important phenomenon of the century. This phenomenon present itself as the only determinant of people's lives by entering almost makes itself felt. The mo st obvious objective needs of the economy by triggering motive is to induce people to consume . Consumer culture pervades all aspects of the situation are people . Therefore, these people have the blessing of culture , beauty and value all in the name of w hatever is consumed. This is way out of the siege of moral and religious values we have is to go back again . Referred by local cultural and religious values, based on today increasingly come to the fore and the Muslim way of life appears to be close to th e plain / lean preferred by many people life has been a way of life. Even the simple life , a way of life in the Western world , a conception of life , a philosophy, a movement as it has become widely accepted. Here in determining the Muslim way of life Pr ophet. Prophet (sa lived the kind of life a very important model, sample, and determining which direction is known. Religious values, which is the carrier of the prophets, sent to the society they have always been examples and models. Because every aspect of human life, his life style and the surrounding area has a feature. We also value his life that he has unknowingly and without learning and skills and to understand it is not possible to live our religion . We also our presentation, we mainly of Islam o utlook on life and predicted life - style, including the Prophet of Islam 's (sa simple life to scrutinize and lifestyle issues related to reveal , in short Islam's how life has embraced and the Prophet. Prophet's will try to find answers to questions reg arding how to live.
The effects of buoyancy on shear-induced melt bands in a compacting porous medium
Butler, S. L.
2009-03-01
It has recently been shown [Holtzman, B., Groebner, N., Zimmerman, M., Ginsberg, S., Kohlstedt, D., 2003. Stress-driven melt segregation in partially molten rocks. Geochem. Geophys. Geosyst. 4, Art. No. 8607; Holtzman, B.K., Kohlstedt, D.L., 2007. Stress-driven melt segregation and strain partitioning in partially molten rocks: effects of stress and strain. J. Petrol. 48, 2379-2406] that when partially molten rock is subjected to simple shear, bands of high and low porosity are formed at a particular angle to the direction of instantaneous maximum extension. These have been modeled numerically and it has been speculated that high porosity bands may form an interconnected network with a bulk, effective permeability that is enhanced in a direction parallel to the bands. As a result, the bands may act to focus mantle melt towards the axis of mid-ocean ridges [Katz, R.F., Spiegelman, M., Holtzman, B., 2006. The dynamics of melt and shear localization in partially molten aggregates. Nature 442, 676-679]. In this contribution, we examine the combined effects of buoyancy and matrix shear on a deforming porous layer. The linear theory of Spiegelman [Spiegelman, M., 1993. Flow in deformable porous media. Part 1. Simple analysis. J. Fluid Mech. 247, 17-38; Spiegelman, M., 2003. Linear analysis of melt band formation by simple shear. Geochem. Geophys. Geosyst. 4, doi:10.1029/2002GC000499, Article 8615] and Katz et al. [Katz, R.F., Spiegelman, M., Holtzman, B., 2006. The dynamics of melt and shear localization in partially molten aggregates. Nature 442, 676-679] is generalized to include both the effects of buoyancy and matrix shear on a deformable porous layer with strain-rate dependent rheology. The predictions of linear theory are compared with the early time evolution of our 2D numerical model and they are found to be in excellent agreement. For conditions similar to the upper mantle, buoyancy forces can be similar to or much greater than matrix shear-induced forces. The
Shear and extensional properties of kefiran.
Piermaría, Judith; Bengoechea, Carlos; Abraham, Analía Graciela; Guerrero, Antonio
2016-11-05
Kefiran is a neutral polysaccharide constituted by glucose and galactose produced by Lactobacillus kefiranofaciens. It is included into kefir grains and has several health promoting properties. In the present work, shear and extensional properties of different kefiran aqueous dispersions (0.5, 1 and 2% wt.) were assessed and compared to other neutral gums commonly used in food, cosmetic and pharmaceutics industries (methylcellulose, locust bean gum and guar gum). Kefiran showed shear flow characteristics similar to that displayed by other representative neutral gums, although it always yielded lower viscosities at a given concentration. For each gum system it was possible to find a correlation between dynamic and steady shear properties by a master curve including both the apparent and complex viscosities. When studying extensional properties of selected gums at 2% wt. by means of a capillary break-up rheometer, kefiran solutions did not show important extensional properties, displaying a behaviour close the Newtonian. Copyright © 2016 Elsevier Ltd. All rights reserved.
On transformation shear of precipitated zirconia particles
International Nuclear Information System (INIS)
Zhang, J.M.; Lam, K.Y.
1993-01-01
A model is proposed to investigate the transformation shear of the precipitated zirconia particles which undergo a stress-induced lattice transformation from tetragonal to monoclinic symmetry. Kinematically admissible twinning planes and the corresponding twinning elements are determined according to the continuum theory of dispacive phase transformation. It is postulated that only one twinning mode prevails in each transformed particle and that the minimization of elastic strain energy change dictates the morphology of the transformed variants. The transformation shear is determined by the twinning mode and the volume fraction of the corresponding variant. Numerical calculations show that each of the six kinematically admissible twinning modes may be kinematically favorable and therefore operate in constrained particle. The actual transformation shear in a transformed particle is shown to be dependent on the transformation stress, on the particle shape as well as on the lattice orientation relative to the principal axes of the ellipsoidal particle
On shear rheology of gel propellants
Energy Technology Data Exchange (ETDEWEB)
Rahimi, Shai; Peretz, Arie [RAFAEL, MANOR Propulsion and Explosive Systems Division, Haifa (Israel); Natan, Benveniste [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)
2007-04-15
Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel-Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine-based fuels, gelled with polysaccharides, were characterized as shear-thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red-fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers-Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed. (Abstract Copyright [2007], Wiley Periodicals, Inc.)
Combined shearing interferometer and hartmann wavefront sensor
International Nuclear Information System (INIS)
Hutchin, R. A.
1985-01-01
A sensitive wavefront sensor combining attributes of both a Hartmann type of wavefront sensor and an AC shearing interferometer type of wavefront sensor. An incident wavefront, the slope of which is to be detected, is focussed to first and second focal points at which first and second diffraction gratings are positioned to shear and modulate the wavefront, which then diverges therefrom. The diffraction patterns of the first and second gratings are positioned substantially orthogonal to each other to shear the wavefront in two directions to produce two dimensional wavefront slope data for the AC shearing interferometer portion of the wavefront sensor. First and second dividing optical systems are positioned in the two diverging wavefronts to divide the sheared wavefront into an array of subapertures and also to focus the wavefront in each subaperture to a focal point. A quadrant detector is provided for each subaperture to detect the position of the focal point therein, which provides a first indication, in the manner of a Hartmann wavefront sensor, of the local wavefront slope in each subaperture. The total radiation in each subaperture, as modulated by the diffraction grating, is also detected by the quadrant detector which produces a modulated output signal representative thereof, the phase of which relative to modulation by the diffraction grating provides a second indication of the local wavefront slope in each subaperture, in the manner of an AC shearing interferometer wavefront sensor. The data from both types of sensors is then combined by long term averaging thereof to provide an extremely sensitive wavefront sensor
Enhancing Rotational Diffusion Using Oscillatory Shear
Leahy, Brian D.
2013-05-29
Taylor dispersion - shear-induced enhancement of translational diffusion - is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle\\'s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids. © 2013 American Physical Society.
Seismic behavior of reinforced concrete shear walls
International Nuclear Information System (INIS)
Wang, F.; Gantenbein, F.
1989-01-01
Reinforced concrete shear walls have an important contribution to building stiffness. So, it is necessary to know their behavior under seismic loads. The ultimate behavior study of shear walls subjected to dynamic loadings includes: - a description of the nonlinear global model based on cyclic static tests, - nonlinear time history calculations for various forcing functions. The comparison of linear and nonlinear results shows important margins related to the ductility when the bandwidth of the forcing function is narrow and centred on the wall natural frequency
Shear reinforced beams in autoclaved aerated concrete
DEFF Research Database (Denmark)
Cornelius, Thomas
2010-01-01
Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different combinat....... Codes for designing prefabricated reinforced components of aircrete structures have adopted these recently developed approaches.......Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different...
Shear zones between rock units with no relative movement
DEFF Research Database (Denmark)
Koyi, Hemin; Schmeling, Harro; Burchardt, Steffi
2013-01-01
Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two "blocks" that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other. Such ...... given credit for and may be responsible for some reverse kinematics reported in shear zones....... or wakes, elongated bodies (vertical plates or horizontal rod-like bodies) produce tabular shear zones or wakes. Unlike conventional shear zones across which shear indicators usually display consistent symmetries, shear indicators on either side of the shear zone or wake reported here show reverse...... kinematics. Thus profiles exhibit shear zones with opposed senses of movement across their center-lines or -planes.We have used field observations and results from analytical and numerical models to suggest that examples of wakes are the transit paths that develop where denser blocks sink within salt...
Shear thinning and shear thickening of a confined suspension of vesicles
Nait Ouhra, A.; Farutin, A.; Aouane, O.; Ez-Zahraouy, H.; Benyoussef, A.; Misbah, C.
2018-01-01
Widely regarded as an interesting model system for studying flow properties of blood, vesicles are closed membranes of phospholipids that mimic the cytoplasmic membranes of red blood cells. In this study we analyze the rheology of a suspension of vesicles in a confined geometry: the suspension, bound by two planar rigid walls on each side, is subject to a shear flow. Flow properties are then analyzed as a function of shear rate γ ˙, the concentration of the suspension ϕ , and the viscosity contrast λ =ηin/ηout , where ηin and ηout are the fluid viscosities of the inner and outer fluids, respectively. We find that the apparent (or effective viscosity) of the suspension exhibits both shear thinning (decreasing viscosity with shear rate) or shear thickening (increasing viscosity with shear rate) in the same concentration range. The shear thinning or thickening behaviors appear as subtle phenomena, dependant on viscosity contrast λ . We provide physical arguments on the origins of these behaviors.
Effect of Boundary Condition on the Shear Behaviour of Rock Joints in the Direct Shear Test
Bahaaddini, M.
2017-05-01
The common method for determination of the mechanical properties of the rock joints is the direct shear test. This paper aims to study the effect of boundary condition on the results of direct shear tests. Experimental studies undertaken in this research showed that the peak shear strength is mostly overestimated. This problem is more pronounced for steep asperities and under high normal stresses. Investigation of the failure mode of these samples showed that tensile cracks are generated at the boundary of sample close to the specimen holders and propagated inside the intact materials. In order to discover the reason of observed failure mechanism in experiments, the direct shear test was simulated using PFC2D. Results of numerical models showed that the gap zone size between the upper and lower specimen holders has a significant effect on the shear mechanism. For the high gap size, stresses concentrate at the vicinity of the tips of specimen holders and result in generation and propagation of tensile cracks inside the intact material. However, by reducing the gap size, stresses are concentrated on asperities, and damage of specimen at its boundary is not observed. Results of this paper show that understanding the shear mechanism of rock joints is an essential step prior to interpreting the results of direct shear tests.
Moore, Johnathan; Crandall, Dustin; Gill, Magdalena; Brown, Sarah; Tennant, Bryan
2018-04-01
Fluid flow in the subsurface is not well understood in the context of "impermeable" geologic media. This is especially true of formations that have undergone significant stress fluctuations due to injection or withdrawal of fluids that alters the localized pressure regime. When the pressure regime is altered, these formations, which are often already fractured, move via shear to reduce the imbalance in the stress state. While this process is known to happen, the evolution of these fractures and their effects on fluid transport are still relatively unknown. Numerous simulation and several experimental studies have been performed that characterize the relationship between shearing and permeability in fractures; while many of these studies utilize measurements of fluid flow or the starting and ending geometries of the fracture to characterize shear, they do not characterize the intermediate stages during shear. We present an experimental apparatus based on slight modifications to a commonly available Hassler core holder that allows for shearing of rocks, while measuring the hydraulic and mechanical changes to geomaterials during intermediate steps. The core holder modification employs the use of semi-circular end caps and structural supports for the confining membrane that allow for free movement of the sheared material while preventing membrane collapse. By integrating this modified core holder with a computed tomography scanner, we show a new methodology for understanding the interdependent behavior between fracture structure and flow properties during intermediate steps in shearing. We include a case study of this device function which is shown here through shearing of a fractured shale core and simultaneous observation of the mechanical changes and evolution of the hydraulic properties during shearing.
Directory of Open Access Journals (Sweden)
2005-11-01
Full Text Available Quasispecies are clouds of genotypes that appear in a population at mutation-selection balance. This concept has recently attracted the attention of virologists, because many RNA viruses appear to generate high levels of genetic variation that may enhance the evolution of drug resistance and immune escape. The literature on these important evolutionary processes is, however, quite challenging. Here we use simple models to link mutation-selection balance theory to the most novel property of quasispecies: the error threshold-a mutation rate below which populations equilibrate in a traditional mutation-selection balance and above which the population experiences an error catastrophe, that is, the loss of the favored genotype through frequent deleterious mutations. These models show that a single fitness landscape may contain multiple, hierarchically organized error thresholds and that an error threshold is affected by the extent of back mutation and redundancy in the genotype-to-phenotype map. Importantly, an error threshold is distinct from an extinction threshold, which is the complete loss of the population through lethal mutations. Based on this framework, we argue that the lethal mutagenesis of a viral infection by mutation-inducing drugs is not a true error catastophe, but is an extinction catastrophe.
International Nuclear Information System (INIS)
Narayanan, R.; Kalavathy, K.R.
1989-01-01
In any nuclear reactor, the start-up channels monitor the neutron flux during the start-up operation and give the alarm signals for safety purposes. Normally, a fission chamber is used as a detector to detect the low level neutron fluxes. The output of the detector after amplification and discrimination is shaped in a pulse shaper to provide constant width, constant height pulses for further processing in rate meters. The shaped pulses also go to a scaler timer, where they are counted for fixed time intervals and the accumulated counts displayed. The scaler timer described in this paper uses LSIs to get at a simple, compact and reliable unit. The design is centered around two LSIs. MOS Counter Timebase LSI type MK 5009P (U1) is used to generate the gating pulses. A 1 MHz crystal is used to generate the system clock. A 4 bit address selects the desired gating intervals of 1 or 10 or 100 seconds. In fact, MK 5009 is a very versatile LSI in a 16 pin DIP package, consisting of a MOS oscillator and divider chain. It is binary encoded for frequency division selection ranging from 1 to 36 x 10. With an input frequency of 1 MHz, MK 5009 provides the time periods of 1 μs to 100 seconds, one minute, ten minute and one hour periods. (author)
A Simple Accelerometer Calibrator
International Nuclear Information System (INIS)
Salam, R A; Islamy, M R F; Khairurrijal; Munir, M M; Latief, H; Irsyam, M
2016-01-01
High possibility of earthquake could lead to the high number of victims caused by it. It also can cause other hazards such as tsunami, landslide, etc. In that case it requires a system that can examine the earthquake occurrence. Some possible system to detect earthquake is by creating a vibration sensor system using accelerometer. However, the output of the system is usually put in the form of acceleration data. Therefore, a calibrator system for accelerometer to sense the vibration is needed. In this study, a simple accelerometer calibrator has been developed using 12 V DC motor, optocoupler, Liquid Crystal Display (LCD) and AVR 328 microcontroller as controller system. The system uses the Pulse Wave Modulation (PWM) form microcontroller to control the motor rotational speed as response to vibration frequency. The frequency of vibration was read by optocoupler and then those data was used as feedback to the system. The results show that the systems could control the rotational speed and the vibration frequencies in accordance with the defined PWM. (paper)
Chirality-specific lift forces of helix under shear flows: Helix perpendicular to shear plane.
Zhang, Qi-Yi
2017-02-01
Chiral objects in shear flow experience a chirality-specific lift force. Shear flows past helices in a low Reynolds number regime were studied using slender-body theory. The chirality-specific lift forces in the vorticity direction experienced by helices are dominated by a set of helix geometry parameters: helix radius, pitch length, number of turns, and helix phase angle. Its analytical formula is given. The chirality-specific forces are the physical reasons for the chiral separation of helices in shear flow. Our results are well supported by the latest experimental observations. © 2016 Wiley Periodicals, Inc.
Shear zones between rock units with no relative movement
DEFF Research Database (Denmark)
Koyi, H.; Schmeling, H.; Burchardt, S.
2012-01-01
, elongated bodies (vertical plates or horizontal rod-like bodies) produce tabular shear zones. Unlike conventional shear zones across which shear indicators ideally display consistent symmetries, shear indicators on either sides of the shear zone reported here show reverse kinematics. Thus profiles exhibit...... by progressive extension and (perhaps) where slabs of subducted oceanic lithosphere delaminate from the continental crust and sink into the asthenosphere. We also argue that such shear zones may be more common than they have been given the credit for and may be responsible for some of the kinematic reversals...
Kim, Sang-Hyo; Kim, Kun-Soo; Lee, Do-Hoon; Park, Jun-Seung; Han, Oneil
2017-11-22
Shear connectors are used in steel beam-concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13.
Modeling of the blood rheology in steady-state shear flows
International Nuclear Information System (INIS)
Apostolidis, Alex J.; Beris, Antony N.
2014-01-01
We undertake here a systematic study of the rheology of blood in steady-state shear flows. As blood is a complex fluid, the first question that we try to answer is whether, even in steady-state shear flows, we can model it as a rheologically simple fluid, i.e., we can describe its behavior through a constitutive model that involves only local kinematic quantities. Having answered that question positively, we then probe as to which non-Newtonian model best fits available shear stress vs shear-rate literature data. We show that under physiological conditions blood is typically viscoplastic, i.e., it exhibits a yield stress that acts as a minimum threshold for flow. We further show that the Casson model emerges naturally as the best approximation, at least for low and moderate shear-rates. We then develop systematically a parametric dependence of the rheological parameters entering the Casson model on key physiological quantities, such as the red blood cell volume fraction (hematocrit). For the yield stress, we base our description on its critical, percolation-originated nature. Thus, we first determine onset conditions, i.e., the critical threshold value that the hematocrit has to have in order for yield stress to appear. It is shown that this is a function of the concentration of a key red blood cell binding protein, fibrinogen. Then, we establish a parametric dependence as a function of the fibrinogen and the square of the difference of the hematocrit from its critical onset value. Similarly, we provide an expression for the Casson viscosity, in terms of the hematocrit and the temperature. A successful validation of the proposed formula is performed against additional experimental literature data. The proposed expression is anticipated to be useful not only for steady-state blood flow modeling but also as providing the starting point for transient shear, or more general flow modeling
Finite Strain Analysis of the Wadi Fatima Shear Zone in Western Arabia, Saudi Arabia
Kassem, O. M. K.; Hamimi, Z.
2018-03-01
Neoproterozoic rocks, Oligocene to Neogene sediments and Tertiary Red Sea rift-related volcanics (Harrat) are three dominant major groups exposed in the Jeddah tectonic terrane in Western Arabia. The basement complex comprises amphibolites, schists, and older and younger granites unconformably overlain by a post-amalgamation volcanosedimentary sequence (Fatima Group) exhibiting post-accretionary thrusting and thrust-related structures. The older granites and/or the amphibolites and schists display mylonitization and shearing in some outcrops, and the observed kinematic indicators indicate dextral monoclinic symmetry along the impressive Wadi Fatima Shear Zone. Finite strain analysis of the mylonitized lithologies is used to interpret the deformation history of the Wadi Fatima Shear Zone. The measured finite strain data demonstrate that the amphibolites, schists, and older granites are mildly to moderately deformed, where XZ (axial ratios in XZ direction) vary from 2.76 to 4.22 and from 2.04 to 3.90 for the Rf/φ and Fry method respectively. The shortening axes ( Z) have subvertical attitude and are associated with subhorizontal foliation. The data show oblate strain ellipsoids in the different rocks in the studied area and indication bulk flattening strain. We assume that the different rock types have similar deformation behavior. In the deformed granite, the strain data are identical in magnitude with those obtained in the Fatima Group volcanosedimentary sequence. Finite strain accumulated without any significant volume change contemporaneously with syn-accretionary transpressive structures. It is concluded that a simple-shear deformation with constant-volume plane strain exists, where displacement is strictly parallel to the shear plane. Furthermore, the contacts between various lithological units in the Wadi Fatima Shear Zone were formed under brittle to semi-ductile deformation conditions.
Lightweight concrete modification factor for shear friction.
2013-10-01
This report describes the results of a study initiated to examine the influence of concrete unit weight on the direct shear transfer across an interface of concretes cast at different times. This type of interface is common with structural precast co...
Shear of ordinary and elongated granular mixtures
Hensley, Alexander; Kern, Matthew; Marschall, Theodore; Teitel, Stephen; Franklin, Scott
2015-03-01
We present an experimental and computational study of a mixture of discs and moderate aspect-ratio ellipses under two-dimensional annular planar Couette shear. Experimental particles are cut from acrylic sheet, are essentially incompressible, and constrained in the thin gap between two concentric cylinders. The annular radius of curvature is much larger than the particles, and so the experiment is quasi-2d and allows for arbitrarily large pure-shear strains. Synchronized video cameras and software identify all particles and track them as they move from the field of view of one camera to another. We are particularly interested in the global and local properties as the mixture ratio of discs to ellipses varies. Global quantities include average shear rate and distribution of particle species as functions of height, while locally we investigate the orientation of the ellipses and non-affine events that can be characterized as shear transformational zones or possess a quadrupole signature observed previously in systems of purely circular particles. Discrete Element Method simulations on mixtures of circles and spherocylinders extend the study to the dynamics of the force network and energy dissipated as the system evolves. Supported by NSF CBET #1243571 and PRF #51438-UR10.
Shear Adhesion of Tapered Nanopillar Arrays.
Cho, Younghyun; Minsky, Helen K; Jiang, Yijie; Yin, Kaiyang; Turner, Kevin T; Yang, Shu
2018-04-04
Tapered nanopillars with various cross sections, including cone-shaped, stepwise, and pencil-like structures (300 nm in diameter at the base of the pillars and 1.1 μm in height), are prepared from epoxy resin templated by nanoporous anodic aluminum oxide (AAO) membranes. The effect of pillar geometry on the shear adhesion behavior of these nanopillar arrays is investigated via sliding experiments in a nanoindentation system. In a previous study of arrays with the same geometry, it was shown that cone-shaped nanopillars exhibit the highest adhesion under normal loading while stepwise and pencil-like nanopillars exhibit lower normal adhesion strength due to significant deformation of the pillars that occurs with increasing indentation depth. Contrary to the previous studies, here, we show that pencil-like nanopillars exhibit the highest shear adhesion strength at all indentation depths among three types of nanopillar arrays and that the shear adhesion increases with greater indentation depth due to the higher bending stiffness and closer packing of the pencil-like nanopillar array. Finite element simulations are used to elucidate the deformation of the pillars during the sliding experiments and agree with the nanoindentation-based sliding measurements. The experiments and finite element simulations together demonstrate that the shape of the nanopillars plays a key role in shear adhesion and that the mechanism is quite different from that of adhesion under normal loading.
A Shear Banding Model for Penetration Calculations
2000-04-01
mechanism of strength reduction to zero within a shear band in three different steels, includ- ing AISI 4340 with RHC 44, which is reasonably similar to RHA...TECH LIB CHINA LAKE CA 93555-6001 CDR NAVAL SUR WAR CTR C S COFFEY PPARK FZERILLI CODE 4140 R K GARRET JR JMCKIRGAN TECH LIB 101 STRAUSS AVE
Prediction of turbulent shear layers in turbomachines
Bradshaw, P.
1974-01-01
The characteristics of turbulent shear layers in turbomachines are compared with the turbulent boundary layers on airfoils. Seven different aspects are examined. The limits of boundary layer theory are investigated. Boundary layer prediction methods are applied to analysis of the flow in turbomachines.
Structural relaxation monitored by instantaneous shear modulus
DEFF Research Database (Denmark)
Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil
1998-01-01
time definition based on a recently proposed expression for the relaxation time, where G [infinity] reflects the fictive temperature. All parameters entering the reduced time were determined from independent measurements of the frequency-dependent shear modulus of the equilibrium liquid....
Comparison of turbulent particle dispersion models in turbulent shear flows
Directory of Open Access Journals (Sweden)
S. Laín
2007-09-01
Full Text Available This work compares the performance of two Lagrangian turbulent particle dispersion models: the standard model (e.g., that presented in Sommerfeld et al. (1993, in which the fluctuating fluid velocity experienced by the particle is composed of two components, one correlated with the previous time step and a second one randomly sampled from a Wiener process, and the model proposed by Minier and Peirano (2001, which is based on the PDF approach and performs closure at the level of acceleration of the fluid experienced by the particle. Formulation of a Langevin equation model for the increments of fluid velocity seen by the particle allows capturing some underlying physics of particle dispersion in general turbulent flows while keeping the mathematical manipulation of the stochastic model simple, thereby avoiding some pitfalls and simplifying the derivation of macroscopic relations. The performance of both dispersion models is tested in the configurations of grid-generated turbulence (Wells and Stock (1983 experiments, simple shear flow (Hyland et al., 1999 and confined axisymmetric jet flow laden with solids (Hishida and Maeda (1987 experiments.
Directory of Open Access Journals (Sweden)
Lizeth Torres
2018-05-01
Full Text Available The principal aim of a spectral observer is twofold: the reconstruction of a signal of time via state estimation and the decomposition of such a signal into the frequencies that make it up. A spectral observer can be catalogued as an online algorithm for time-frequency analysis because is a method that can compute on the fly the Fourier transform (FT of a signal, without having the entire signal available from the start. In this regard, this paper presents a novel spectral observer with an adjustable constant gain for reconstructing a given signal by means of the recursive identification of the coefficients of a Fourier series. The reconstruction or estimation of a signal in the context of this work means to find the coefficients of a linear combination of sines a cosines that fits a signal such that it can be reproduced. The design procedure of the spectral observer is presented along with the following applications: (1 the reconstruction of a simple periodical signal, (2 the approximation of both a square and a triangular signal, (3 the edge detection in signals by using the Fourier coefficients, (4 the fitting of the historical Bitcoin market data from 1 December 2014 to 8 January 2018 and (5 the estimation of a input force acting upon a Duffing oscillator. To round out this paper, we present a detailed discussion about the results of the applications as well as a comparative analysis of the proposed spectral observer vis-à-vis the Short Time Fourier Transform (STFT, which is a well-known method for time-frequency analysis.
Shear localization and microstructure in coarse grained beta titanium alloy
Energy Technology Data Exchange (ETDEWEB)
Wang, Bingfeng, E-mail: biw009@ucsd.edu [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha, Hunan (China); Wang, Xiaoyan [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Li, Zezhou [Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Ma, Rui [School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Zhao, Shiteng [Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Xie, Fangyu [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Zhang, Xiaoyong [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China)
2016-01-15
Adiabatic shear localization plays an important role in the deformation and failure of the coarse grained beta titanium alloy Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe with grain size about 1 mm at high strain rate deformation. Hat shaped specimens with different nominal shear strains are used to induce the formation of shear bands under the controlled shock-loading experiments. The true stress in the specimens can reach about 1040 MPa where the strain is about 1.83. The whole shear localization process lasts about 35 μs. The microstructures within the shear band are investigated by optical microscopy, scanning electron microscopy / electron backscatter diffraction, and transmission electron microscopy. The results show that the width of the shear bands decreases with increasing nominal shear strain, and the grains in the transition region near the shear band are elongated along the shear band, and the core of the shear band consists of the ultrafine deformed grains with width of 0.1 μm and heavy dislocations. With the aims of accommodating the imposed shear strain and maintaining neighboring grain compatibility, the grain subdivision continues to take place within the band. A fiber texture is formed in the core of the shear band. The calculated temperature rise in the shear band can reach about 722 K. Dynamic recovery is responsible for the formation of the microstructure in coarse grained beta titanium alloy.
Cargo Release from Polymeric Vesicles under Shear
Directory of Open Access Journals (Sweden)
Yingying Guo
2018-03-01
Full Text Available In this paper we study the release of cargo from polymeric nano-carriers under shear. Vesicles formed by two star block polymers— A 12 B 6 C 2 ( A B C and A 12 B 6 A 2 ( A B A —and one linear block copolymer— A 14 B 6 ( A B , are investigated using dissipative particle dynamics (DPD simulations. A - and C -blocks are solvophobic and B -block is solvophilic. The three polymers form vesicles of different structures. The vesicles are subjected to shear both in bulk and between solvophobic walls. In bulk shear, the mechanisms of cargo release are similar for all vesicles, with cargo travelling through vesicle membrane with no preferential release location. When sheared between walls, high cargo release rate is only observed with A B C vesicle after it touches the wall. For A B C vesicle, the critical condition for high cargo release rate is the formation of wall-polymersome interface after which the effect of shear rate in promoting cargo release is secondary. High release rate is achieved by the formation of solvophilic pathway allowing cargo to travel from the vesicle cavity to the vesicle exterior. The results in this paper show that well controlled target cargo release using polymersomes can be achieved with polymers of suitable design and can potentially be very useful for engineering applications. As an example, polymersomes can be used as carriers for surface active friction reducing additives which are only released at rubbing surfaces where the additives are needed most.
Spurious Shear in Weak Lensing with LSST
Energy Technology Data Exchange (ETDEWEB)
Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.
2012-09-19
The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.
High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates
Becnel, Andrew C.
This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter
Naesliden Project: direct shear tests of filled and unfilled joints
Energy Technology Data Exchange (ETDEWEB)
Ludvig, B.
1980-05-15
Joints from the Naesliden mine have been tested in a small field shear box and in a large shear rig. The large shear rig is described in detail, and its ability to test joints with an area of 600 mc/sup 2/ at a maximum normal stress of up to 20 MPa is emphasized. The stiffness and shear strength of the discontinuities in the Naesliden mine is presented. The values estimated at direct shear tests are compared with results from in situ measurements and tests on drillcores. The results show that the in situ measurements give lower values for the shear resistance than the direct shear tests. Estimation of the normal stiffness for joints in drill cores gave much higher stiffness than the estimations in the shear rig.
Shear stress and interleukin-8 (IL-8) on the proliferation ...
African Journals Online (AJOL)
Endothelial progenitor cells (EPCs) derived from bone marrow, are also found ... into tissues and neovascularization, the cells are exposed to fluid shear stress. ... Both shear stress and IL-8 can influence the process of EPCs repair in wound.
Shear Wave Generation by Decoupled and Partially Coupled Explosions
National Research Council Canada - National Science Library
Stevens, Jeffry L; Xu, Heming; Baker, G. E
2008-01-01
The objective of this project is to investigate the sources of shear wave generation by decoupled and partially coupled explosions, and the differences in shear wave generation between tamped and decoupled explosions...
Stress relaxation of shear in metals during shock loading
International Nuclear Information System (INIS)
Glazyrin, V.P.; Platova, T.M.
1988-01-01
Constructed determining equation, taking into account stress relaxation of shear, was used to calculate the evolution of plane shock waves of primary and secondary compression in metals. Values of shear stress and viscosity coefficient were
Heat Treatment of Al 7075 for Ejection Seat Shear Wire
National Research Council Canada - National Science Library
Wong, Catherine
1999-01-01
.... Current lots of Al 6061 could not duplicate the double shear breaking load values and so it was attempted to achieve the required double shear breaking load in the Al 7075 alloy with a stable microstructure...
To determine the slow shearing rate for consolidation drained shear box tests
Jamalludin, Damanhuri; Ahmad, Azura; Nordin, Mohd Mustaqim Mohd; Hashim, Mohamad Zain; Ibrahim, Anas; Ahmad, Fauziah
2017-08-01
Slope failures always occur in Malaysia especially during the rainy seasons. They cause damage to properties and fatalities. In this study, a total of 24 one dimensional consolidation tests were carried out on soil samples taken from 16 slope failures in Penang Island and in Baling, Kedah. The slope failures in Penang Island are within the granitic residual soil while in Baling, Kedah they are situated within the sedimentary residual soil. Most of the disturbed soil samples were taken at 100mm depth from the existing soil surface while some soil samples were also taken at 400, 700 and 1000mm depths from the existing soil surface. They were immediately placed in 2 layers of plastic bag to prevent moisture loss. Field bulk density tests were also carried out at all the locations where soil samples were taken. The field bulk density results were later used to re-compact the soil samples for the consolidation tests. The objective of the research is to determine the slow shearing rate to be used in consolidated drained shear box for residual soils taken from slope failures so that the effective shear strength parameters can be determined. One dimensional consolidation tests were used to determine the slow shearing rate. The slow shearing rate found in this study to be used in the consolidated drained shear box tests especially for Northern Malaysian residual soils was 0.286mm/minute.
López-Barrón, Carlos R; Gurnon, A Kate; Eberle, Aaron P R; Porcar, Lionel; Wagner, Norman J
2014-04-01
We present direct measurements of the evolution of the segmental-level microstructure of a stable shear-banding polymerlike micelle solution during flow startup and cessation in the plane of flow. These measurements provide a definitive, quantitative microstructural understanding of the stages observed during flow startup: an initial elastic response with limited alignment that yields with a large stress overshoot to a homogeneous flow with associated micellar alignment that persists for approximately three relaxation times. This transient is followed by a shear (kink) band formation with a flow-aligned low-viscosity band that exhibits shear-induced concentration fluctuations and coexists with a nearly isotropic band of homogenous, highly viscoelastic micellar solution. Stable, steady banding flow is achieved only after approximately two reptation times. Flow cessation from this shear-banded state is also found to be nontrivial, exhibiting an initial fast relaxation with only minor structural relaxation, followed by a slower relaxation of the aligned micellar fluid with the equilibrium fluid's characteristic relaxation time. These measurements resolve a controversy in the literature surrounding the mechanism of shear banding in entangled wormlike micelles and, by means of comparison to existing literature, provide further insights into the mechanisms driving shear-banding instabilities in related systems. The methods and instrumentation described should find broad use in exploring complex fluid rheology and testing microstructure-based constitutive equations.
The mechanical stability of retained austenite in low-alloyed TRIP steel under shear loading
Energy Technology Data Exchange (ETDEWEB)
Blondé, R., E-mail: r.j.p.blonde@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Materials Innovation Institute, Mekelweg 2, 2628 CD Delft (Netherlands); Jimenez-Melero, E., E-mail: enrique.jimenez-melero@manchester.ac.uk [Dalton Cumbrian Facility, The University of Manchester, Westlakes Science and Technology Park, Moor Row, Cumbria CA24 3HA (United Kingdom); Zhao, L., E-mail: lie.zhao@tudelft.nl [Materials Innovation Institute, Mekelweg 2, 2628 CD Delft (Netherlands); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Schell, N., E-mail: norbert.schell@hzg.de [Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max Planck Strasse 1, 21502 Geesthacht (Germany); Brück, E., E-mail: e.h.bruck@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Zwaag, S. van der, E-mail: s.vanderzwaag@tudelft.nl [Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands); Dijk, N.H. van, E-mail: n.h.vandijk@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)
2014-01-31
The microstructure evolution during shear loading of a low-alloyed TRIP steel with different amounts of the metastable austenite phase and its equivalent DP grade has been studied by in-situ high-energy X-ray diffraction. A detailed powder diffraction analysis has been performed to probe the austenite-to-martensite transformation by characterizing simultaneously the evolution of the austenite phase fraction and its carbon concentration, the load partitioning between the austenite and the ferritic matrix and the texture evolution of the constituent phases. Our results show that for shear deformation the TRIP effect extends over a significantly wider deformation range than for simple uniaxial loading. A clear increase in average carbon content during the mechanically-induced transformation indicates that austenite grains with a low carbon concentration are least stable during shear loading. The observed texture evolution indicates that under shear loading the orientation dependence of the austenite stability is relatively weak, while it has previously been found that under tensile load the {110}〈001〉 component transforms preferentially. The mechanical stability of retained austenite in TRIP steel is found to be a complex interplay between the interstitial carbon concentration in the austenite, the grain orientation and the load partitioning.
Droplet breakup driven by shear thinning solutions in a microfluidic T-junction
Chiarello, Enrico; Gupta, Anupam; Mistura, Giampaolo; Sbragaglia, Mauro; Pierno, Matteo
2017-12-01
Droplet-based microfluidics turned out to be an efficient and adjustable platform for digital analysis, encapsulation of cells, drug formulation, and polymerase chain reaction. Typically, for most biomedical applications, the handling of complex, non-Newtonian fluids is involved, e.g., synovial and salivary fluids, collagen, and gel scaffolds. In this study, we investigate the problem of droplet formation occurring in a microfluidic T-shaped junction, when the continuous phase is made of shear thinning liquids. At first, we review in detail the breakup process, providing extensive, side-by-side comparisons between Newtonian and non-Newtonian liquids over unexplored ranges of flow conditions and viscous responses. The non-Newtonian liquid carrying the droplets is made of Xanthan solutions, a stiff, rodlike polysaccharide displaying a marked shear thinning rheology. By defining an effective Capillary number, a simple yet effective methodology is used to account for the shear-dependent viscous response occurring at the breakup. The droplet size can be predicted over a wide range of flow conditions simply by knowing the rheology of the bulk continuous phase. Experimental results are complemented with numerical simulations of purely shear thinning fluids using lattice Boltzmann models. The good agreement between the experimental and numerical data confirm the validity of the proposed rescaling with the effective Capillary number.
Effect of shear strain on the deflection of a clamped magnetostrictive film-substrate system
International Nuclear Information System (INIS)
Ming Zhenghui; Ming Li; Bo Zou; Xia Luo
2011-01-01
The effect of in-plane shear strain of a clamped bimorph on the deflection produced by magnetization of the film is investigated. The deflection is found by minimizing the Gibbs free energy with respect to four parameters, strains and curvatures along x and y directions at the interface, by assuming that the curvature in the y direction varies as a function of aspect ratio w/l along x. A set of standard linear equations of four parameters are obtained and the deflection is expressed in terms of the four parameters by solving the equations using Cramer rules. The inconsistencies pointed out by previous authors are also reviewed. For actuators made of thick and short clamped film-substrate system, the in-plane shear deformation should not be omitted. The present calculation model can give a relatively simple and accurate prediction of deflection for thick and short specimens of aspect ratio w/l<10, which supports the results obtained by finite element modeling. - Highlights: → We model the deflection of a thick magnetostrictive film-substrate cantilever plate. → Total stress along z from magnetic field is not zero without external force. → Effect of in-plane shear strain in calculating deflection examined. → Analytical solution of deflection obtained by assuming a curvature function. → Shear strain for short cantilever film-substrate plate considered.
Research Status on Bonding Behavior of Prefabricated Concrete Shear Wall
Wang, Donghui; Liu, Xudong; Wang, Sheng; Li, Shanshan
2018-03-01
Prefabricated shear wall structure adapts to the development and requirements of China’s residential industrialization. The key to the prefabricated concrete shear wall structure is the connection between the prefabricated members, where the reliability of the connection of the concrete joint is related to the overall performance and seismic effect of the structure. In this paper, the microstructures of the joint surface and shear properties are analysed, and the formula for calculating the shear strength of the joint is obtained.
Experimental Investigation of Adiabatic Shear Banding at Different Impact Velocities
1993-01-01
plasticity and ASB’s is the Double-notch Shear specimen, it has been decided to use this concept in shear testing at medium and high strain rates...is the Double-notch Shear specimen. it has been decided to use this concept in shear testing at medium and high strain rates. Originally, Campbell...7] C. Fressengeas, Analyse dynamique 61asto-viscoplastique de l’h6tdrogdndit6 de la ddforma- tion plastique de cisalllement, Proc. Int. Conf. on
International Nuclear Information System (INIS)
Jiquan Li; Kishimoto, Y.; Tuda, T.
2000-01-01
The separate structure of two branches of the sheared slab η i mode near the minimum-q magnetic surface is analysed and the effects of plasma rotation shears are considered in the weak magnetic shear region. Results show that the separation condition depends on the non-monotonous q profile and the deviation of rational surface from the minimum-q surface. Furthermore, it is found that the diamagnetic rotation shear may suppress the perturbation of the sheared slab η i mode at one side of the minimum-q surface, the poloidal rotation shear from the sheared E-vector x B-vector flow has a similar role to the slab mode structure when it possesses a direction same as the diamagnetic shear. A plausible interrelation between the separate structures of the two branches of the sheared slab mode and the discontinuity or gap of the radially global structure of the drift wave near the minimum-q surface observed in the toroidal particle simulation (Kishimoto Y et al 1998 Plasma Phys. Control. Fusion 40 A663) is discussed. It seems to support such a viewpoint: the double or/and global branches of the sheared slab η i mode near the minimum-q surface may become a bridge to connect the radially global structures of the drift wave at two sides of the minimum-q surface and the discontinuity may originate from the separate structures of these slab modes for a flatter q profile. (author)
Evaluation of size dependent design shear strength of reinforced ...
Indian Academy of Sciences (India)
to the development of the size dependent models on the shear strength in ... predict the diagonal cracking strength and the ultimate shear strength of RC ... ing strength of normal beams was by Zsutty (1968) based on the data base available without .... The comparison of the calculated shear strength of the beams is shown.
Modified bond model for shear in slabs under concentrated loads
Lantsoght, E.O.L.; Van der Veen, C.; De Boer, A.
2015-01-01
Slabs subjected to concentrated loads close to supports, as occurring for truck loads on slab bridges, are less studied than beams in shear or slab-column connections in punching. To predict the shear capacity for this case, the Bond Model for concentric punching shear was studied initially.
Fluid Effects on Shear Waves in Finely Layered Porous Media
International Nuclear Information System (INIS)
Berryman, J G
2004-01-01
Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored by this modulus by a term that ranges from the smallest to the largest shear moduli of the VTI system. But, since there are five shear moduli in play, the increase in shear energy overall is reduced by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of shear modulus, being about 20% of the permitted range, when gas is fully replaced by liquid. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% partially offsets the effect of this shear modulus increase. Thus, an increase of shear wave speed on the order of 5 to 10% is shown to be possible when circumstances are favorable - i.e., when the shear modulus fluctuations are large (resulting in strong anisotropy), and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity
Non-homogeneous flow profiles in sheared bacterial suspensions
Samanta, Devranjan; Cheng, Xiang
Bacterial suspensions under shear exhibit interesting rheological behaviors including the remarkable ``superfluidic'' state with vanishing viscosity at low shear rates. Theoretical studies have shown that such ``superfluidic'' state is linked with non-homogeneous shear flows, which are induced by coupling between nematic order of active fluids and hydrodynamics of shear flows. However, although bulk rheology of bacterial suspensions has been experimentally studied, shear profiles within bacterial suspensions have not been explored so far. Here, we experimentally investigate the flow behaviors of E. coli suspensions under planar oscillatory shear. Using confocal microscopy and PIV, we measure velocity profiles across gap between two shear plates. We find that with increasing shear rates, high-concentration bacterial suspensions exhibit an array of non-homogeneous flow behaviors like yield-stress flows and shear banding. We show that these non-homogeneous flows are due to collective motion of bacterial suspensions. The phase diagram of sheared bacterial suspensions is systematically mapped as functions of shear rates an bacterial concentrations. Our experiments provide new insights into rheology of bacterial suspensions and shed light on shear induced dynamics of active fluids. Chemical Engineering and Material Science department.
Nongeometrically converted shear waves in marine streamer data
Drijkoningen, G.G.; El Allouche, N.; Thorbecke, J.W.; Bada, G.
2012-01-01
Under certain circumstances, marine streamer data contain nongeometrical shear body wave arrivals that can be used for imaging. These shear waves are generated via an evanescent compressional wave in the water and convert to propagating shear waves at the water bottom. They are called
Diagonal Cracking and Shear Strength of Reinforced Concrete Beams
DEFF Research Database (Denmark)
Zhang, Jin-Ping
1997-01-01
The shear failure of non-shear-reinforced concrete beams with normal shear span ratios is observed to be governed in general by the formation of a critical diagonal crack. Under the hypothesis that the cracking of concrete introduces potential yield lines which may be more dangerous than the ones...
Material model for shear of the buffer - evaluation of laboratory test results
International Nuclear Information System (INIS)
Boergesson, Lennart; Dueck, Ann; Johannesson, Lars-Erik
2010-12-01
The report describes the material model of bentonite used for analysing a rock shear through a deposition hole. The old model used in SR-Can has been considerably changed. The new reference model that has been developed for SR-Site is described and motivated. The relevant properties of the buffer that affect the response to a rock shear are (in addition to the bentonite type) the density (which yields a swelling pressure), the shear strength, the stiffness before the maximum shear stress is reached and the shear rate, which also affects the shear strength. Since the shear caused by an earthquake is very fast and the hydraulic conductivity of the bentonite is very low there is no possibility for the pore water in the water saturated bentonite to be redistributed. Since the compressibility of water and particles are negligible, the bentonite can be modelled as a solid material that cannot change volume but only exhibit shear deformations. A proper and simple model that behaves accordingly is a model with von Mises' stress modelled as a function of the strain (stress-strain model). The model is elastic-plastic with an E-modulus that determines the behaviour until the material starts yielding whereupon the plastic strain is modelled as a function of von Mises' stress and added to the elastic strain. Included in the model is also a strain rate dependency of the stress-strain relation, which ranges between the strain rates 10 -6 1/s 3 1/s. The reference material model is derived from a large number of laboratory tests made on different bentonites at different strain rates, densities and with different techniques. Since it cannot be excluded that the exchangeable cat-ions in the Na-bentonite MX-80 is exchanged to calcium-ions the Ca-bentonite Deponit CaN is proposed to be used as reference material. The overall conclusion is that a relevant and probably also slightly conservative material model of Ca-converted MX-80 is derived, presented and well motivated
Friction of polymer hydrogels studied by resonance shear measurements.
Ren, Huai-Yin; Mizukami, Masashi; Tanabe, Tadao; Furukawa, Hidemitsu; Kurihara, Kazue
2015-08-21
The friction between an elastomer and a hard surface typically has two contributors, i.e., the interfacial and deformation components. The friction of viscoelastic hydrogel materials has been extensively studied between planar gel and planar substrate surfaces from the viewpoint of an interfacial interaction. However, the geometry of the contact in practical applications is much more complex. The contribution of geometric and elastic deformation terms of a gel to friction could not be neglected. In this study, we used resonance shear measurements (RSMs) for characterizing the shear response of a glass sphere on a flat polymer hydrogel, a double network (DN) gel of 2-acrylamide-2-methylpropanesulfonic acid and N,N-dimethylacrylamide. The contact mechanics conformed to the Johnson-Kendall-Roberts theory. The observed resonance curves exhibited rather sharp peaks when the DN gel and the silica sphere were brought into contact, and their intensity and frequency increased with the increase in the normal load. We proposed a simple physical model of the shearing system, and the elastic (k2) and viscous (b2) parameters of the interface between a silica sphere and a flat DN gel were obtained. The friction force from elastic deformation and viscous dissipation terms was then estimated using the obtained parameters. It was revealed that the elastic parameter (k2) increased up to 1780 N m(-1) at a normal load of 524 mN, while the viscous parameter (b2) was zero or quite low (friction force between a flat DN gel and a silica sphere in air was dominated by the elastic term due to the local deformation by contact with the silica sphere. By adding water, the elastic parameter (k2) remained the same, while the viscous parameter (b2) slightly increased. However, the viscous term fviscous was still much smaller than felastic. To the best of our knowledge, this study was the first quantitative estimation of the contribution of the elastic deformation term to the friction in the case
Characterization of commercial magnetorheological fluids at high shear rate: influence of the gap
Golinelli, Nicola; Spaggiari, Andrea
2018-07-01
This paper reports the experimental tests on the behaviour of a commercial MR fluid at high shear rates and the effect of the gap. Three gaps were considered at multiple magnetic fields and shear rates. From an extended set of almost two hundred experimental flow curves, a set of parameters for the apparent viscosity are retrieved by using the Ostwald de Waele model for non-Newtonian fluids. It is possible to simplify the parameter correlation by making the following considerations: the consistency of the model depends only on the magnetic field, the flow index depends on the fluid type and the gap shows an important effect only at null or very low magnetic fields. This lead to a simple and useful model, especially in the design phase of a MR based product. During the off state, with no applied field, it is possible to use a standard viscous model. During the active state, with high magnetic field, a strong non-Newtonian nature becomes prevalent over the viscous one even at very high shear rate; the magnetic field dominates the apparent viscosity change, while the gap does not play any relevant role on the system behaviour. This simple assumption allows the designer to dimension the gap only considering the non-active state, as in standard viscous systems, and taking into account only the magnetic effect in the active state, where the gap does not change the proposed fluid model.
a simple a simple excitation control excitation control excitation
African Journals Online (AJOL)
eobe
field voltages determined follow a simple quadratic relationship that offer a very simple control scheme, dependent on only the stator current. Keywords: saturated reactances, no-load field voltage, excitation control, synchronous generators. 1. Introduction. Introduction. Introduction. The commonest generator in use today is ...
Shear viscosity, cavitation and hydrodynamics at LHC
International Nuclear Information System (INIS)
Bhatt, Jitesh R.; Mishra, Hiranmaya; Sreekanth, V.
2011-01-01
We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.
Design Against Propagating Shear Failure in Pipelines
Leis, B. N.; Gray, J. Malcolm
Propagating shear failure can occur in gas and certain hazardous liquid transmission pipelines, potentially leading to a large long-burning fire and/or widespread pollution, depending on the transported product. Such consequences require that the design of the pipeline and specification of the steel effectively preclude the chance of propagating shear failure. Because the phenomenology of such failures is complex, design against such occurrences historically has relied on full-scale demonstration experiments coupled with empirically calibrated analytical models. However, as economic drivers have pushed toward larger diameter higher pressure pipelines made of tough higher-strength grades, the design basis to ensure arrest has been severely compromised. Accordingly, for applications where the design basis becomes less certain, as has occurred increasing as steel grade and toughness has increased, it has become necessary to place greater reliance on the use and role of full-scale testing.
Internal shear cracking in bulk metal forming
DEFF Research Database (Denmark)
Christiansen, Peter; Nielsen, Chris Valentin; Bay, Niels Oluf
2017-01-01
This paper presents an uncoupled ductile damage criterion for modelling the opening and propagation of internal shear cracks in bulk metal forming. The criterion is built upon the original work on the motion of a hole subjected to shear with superimposed tensile stress triaxiality and its overall...... performance is evaluated by means of side-pressing formability tests in Aluminium AA2007-T6 subjected to different levels of pre-strain. Results show that the new proposed criterionis able to combine simplicity with efficiency for predicting the onset of fracture and the crack propagation path for the entire...... cracking to internal cracks formed undert hree-dimensional states of stress that are typical of bulk metal forming....
Structures and shear response of lipid monolayers
International Nuclear Information System (INIS)
Dutta, P.; Ketterson, J.B.
1993-02-01
This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases
Motional Effect on Wall Shear Stresses
DEFF Research Database (Denmark)
Kock, Samuel Alberg; Torben Fründ, Ernst; Yong Kim, Won
Atherosclerosis is the leading cause of death and severe disability. Wall Shear Stress (WSS), the stress exerted on vessel walls by the flowing blood is a key factor in the development of atherosclerosis. Computational Fluid Dynamics (CFD) is widely used for WSS estimations. Most CFD simulations...... are based on static models to ease computational burden leading to inaccurate estimations. The aim of this work was to estimate the effect of vessel wall deformations (expansion and bending) on WSS levels....
Self-organization in circular shear layers
DEFF Research Database (Denmark)
Bergeron, K.; Coutsias, E.A.; Lynov, Jens-Peter
1996-01-01
Experiments on forced circular shear layers performed in both magnetized plasmas and in rotating fluids reveal qualitatively similar self-organization processes leading to the formation of patterns of coherent vortical structures with varying complexity. In this paper results are presented from...... both weakly nonlinear analysis and full numerical simulations that closely reproduce the experimental observations. Varying the Reynolds number leads to bifurcation sequences accompanied by topological changes in the distribution of the coherent structures as well as clear transitions in the total...
Stent implantation influence wall shear stress evolution
Bernad, S. I.; Totorean, A. F.; Bosioc, A. I.; Petre, I.; Bernad, E. S.
2016-06-01
Local hemodynamic factors are known affect the natural history of the restenosis critically after coronary stenting of atherosclerosis. Stent-induced flows disturbance magnitude dependent directly on the strut design. The impact of flow alterations around struts vary as the strut geometrical parameters change. Our results provide data regarding the hemodynamic parameters for the blood flow in both stenosed and stented coronary artery under physiological conditions, namely wall shear stress and pressure drop.
Magnetic field reconnexion in a sheared field
International Nuclear Information System (INIS)
Ugai, M.
1981-01-01
A nonlinear development of the Petschek mode in a sheared magnetic field where there is a field component Bsub(z) along an X line is numerically studied. It is found that finite-amplitude intermediate waves, adjacent to the slow shock, may eventually stand in the quasi-steady configuration; on the other hand, the fundamental characteristics of the Petschek-mode development are scarcely influenced, either qualitatively or quantitatively, by the Bsub(z) field. (author)
Is simple nephrectomy truly simple? Comparison with the radical alternative.
Connolly, S S; O'Brien, M Frank; Kunni, I M; Phelan, E; Conroy, R; Thornhill, J A; Grainger, R
2011-03-01
The Oxford English dictionary defines the term "simple" as "easily done" and "uncomplicated". We tested the validity of this terminology in relation to open nephrectomy surgery. Retrospective review of 215 patients undergoing open, simple (n = 89) or radical (n = 126) nephrectomy in a single university-affiliated institution between 1998 and 2002. Operative time (OT), estimated blood loss (EBL), operative complications (OC) and length of stay in hospital (LOS) were analysed. Statistical analysis employed Fisher's exact test and Stata Release 8.2. Simple nephrectomy was associated with shorter OT (mean 126 vs. 144 min; p = 0.002), reduced EBL (mean 729 vs. 859 cc; p = 0.472), lower OC (9 vs. 17%; 0.087), and more brief LOS (mean 6 vs. 8 days; p < 0.001). All parameters suggest favourable outcome for the simple nephrectomy group, supporting the use of this terminology. This implies "simple" nephrectomies are truly easier to perform with less complication than their radical counterpart.
Alfven eigenmodes in shear reversed plasmas
International Nuclear Information System (INIS)
Breizman, B.N.; Berk, H.L.; Pekker, M.S.; Sharapov, S.E.; Hawkes, N.C.; Borba, D.N.; Pinches, S.D.
2003-01-01
Experiments on JT-60U and JET have shown that plasma configurations with shear reversal are prone to the excitation of unusual Alfven Eigenmodes by energetic particles. These modes emerge outside the TAE frequency gap, where one might expect them to be strongly damped. The modes often appear in bunches and they exhibit a quasi-periodic pattern of predominantly upward frequency sweeping (Alfven Cascades) as the safety factor q changes in time. This work presents a theory that explains the key features of the observed unusual modes including their connection to TAE's as well as the modifications of TAE's themselves near the shear reversal point. The developed theory has been incorporated into a reduced numerical model and verified with full geometry codes. JET experimental data on Alfven spectroscopy have been simulated to infer the mode numbers and the evolution of q min in the discharge. This analysis confirms the values of q that characterize the internal transport barrier triggering in reversed shear plasmas. (author)
Cosmic Shear With ACS Pure Parallels
Rhodes, Jason
2002-07-01
Small distortions in the shapes of background galaxies by foreground mass provide a powerful method of directly measuring the amount and distribution of dark matter. Several groups have recently detected this weak lensing by large-scale structure, also called cosmic shear. The high resolution and sensitivity of HST/ACS provide a unique opportunity to measure cosmic shear accurately on small scales. Using 260 parallel orbits in Sloan textiti {F775W} we will measure for the first time: beginlistosetlength sep0cm setlengthemsep0cm setlengthopsep0cm em the cosmic shear variance on scales Omega_m^0.5, with signal-to-noise {s/n} 20, and the mass density Omega_m with s/n=4. They will be done at small angular scales where non-linear effects dominate the power spectrum, providing a test of the gravitational instability paradigm for structure formation. Measurements on these scales are not possible from the ground, because of the systematic effects induced by PSF smearing from seeing. Having many independent lines of sight reduces the uncertainty due to cosmic variance, making parallel observations ideal.
Shear viscosity and out of equilibrium dynamics
El, Andrej; Xu, Zhe; Greiner, Carsten
2009-01-01
Using Grad’s method, we calculate the entropy production and derive a formula for the second-order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance, the shear tensor and the shear viscosity to entropy density ratio η/s are numerically calculated by an iterative and self-consistent prescription within the second-order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with η/s obtained using the Navier-Stokes approximation, the present result is about 20% larger at a QCD coupling αs ∼ 0.3 (with η/s ≈ 0.18) and is a factor of 2–3 larger at a small coupling αs ∼ 0.01. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on η/s, except when employing a small αs . On the other hand, we demonstrate that for such small αs , the gluon syst...
Shear viscosity and out of equilibrium dynamics
El, Andrej; Xu, Zhe; Greiner, Carsten
2009-01-01
Using the Grad's method we calculate the entropy production and derive a formula for the second order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance the shear tensor and the shear viscosity to entropy density ratio $\\eta/s$ are numerically calculated by an iterative and self-consistent prescription within the second order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with $\\eta/s$ obtained using the Navier-Stokes approximation, the present result is about 20% larger at a QCD coupling $\\alpha_s \\sim 0.3$(with $\\eta/s\\approx 0.18$) and is a factor of 2-3 larger at a small coupling $\\alpha_s \\sim 0.01$. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on $\\eta/s$, except when employing a small $\\alpha_s$. On the other hand, we demonstrate th...
Turbulent shear control with oscillatory bubble injection
International Nuclear Information System (INIS)
Park, Hyun Jin; Oishi, Yoshihiko; Tasaka, Yuji; Murai, Yuichi; Takeda, Yasushi
2009-01-01
It is known that injecting bubbles into shear flow can reduce the frictional drag. This method has advantages in comparison to others in simplicity of installation and also in environment. The amount of drag reduction by bubbles depends on the void fraction provided in the boundary layer. It means, however, that certain power must be consumed to generate bubbles in water, worsening the total power-saving performance. We propose oscillatory bubble injection technique to improve the performance in this study. In order to prove this idea of new type of drag reduction, velocity vector field and shear stress profile in a horizontal channel flow are measured by ultrasonic velocity profiler (UVP) and shear stress transducer, respectively. We measure the gas-liquid interface from the UVP signal, as well. This compound measurement with different principles leads to deeper understanding of bubble-originated drag reduction phenomena, in particular for unsteady process of boundary layer alternation. At these experiments, the results have demonstrated that the intermittency promotes the drag reduction more than normal continuous injection for the same void fraction supplied.
Shear viscosity and out of equilibrium dynamics
International Nuclear Information System (INIS)
El, Andrej; Xu Zhe; Greiner, Carsten; Muronga, Azwinndini
2009-01-01
Using Grad's method, we calculate the entropy production and derive a formula for the second-order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance, the shear tensor and the shear viscosity to entropy density ratio η/s are numerically calculated by an iterative and self-consistent prescription within the second-order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with η/s obtained using the Navier-Stokes approximation, the present result is about 20% larger at a QCD coupling α s ∼0.3 (with η/s≅0.18) and is a factor of 2-3 larger at a small coupling α s ∼0.01. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on η/s, except when employing a small α s . On the other hand, we demonstrate that for such small α s , the gluon system is far from kinetic and chemical equilibrium, which indicates the break down of second-order hydrodynamics because of the strong nonequilibrium evolution. In addition, for large α s (0.3-0.6), the Israel-Stewart hydrodynamics formally breaks down at large momentum p T > or approx. 3 GeV but is still a reasonably good approximation.
Wave anisotropy of shear viscosity and elasticity
Rudenko, O. V.; Sarvazyan, A. P.
2014-11-01
The paper presents the theory of shear wave propagation in a "soft solid" material possessing anisotropy of elastic and dissipative properties. The theory is developed mainly for understanding the nature of the low-frequency acoustic characteristics of skeletal muscles, which carry important diagnostic information on the functional state of muscles and their pathologies. It is shown that the shear elasticity of muscles is determined by two independent moduli. The dissipative properties are determined by the fourth-rank viscosity tensor, which also has two independent components. The propagation velocity and attenuation of shear waves in muscle depend on the relative orientation of three vectors: the wave vector, the polarization vector, and the direction of muscle fiber. For one of the many experiments where attention was distinctly focused on the vector character of the wave process, it was possible to make a comparison with the theory, estimate the elasticity moduli, and obtain agreement with the angular dependence of the wave propagation velocity predicted by the theory.
International Nuclear Information System (INIS)
Pichardo, Samuel; Hynynen, Kullervo
2007-01-01
Shear mode transmission through the skull has been previously proposed as a new trans-skull propagation technique for noninvasive therapeutic ultrasound (Clement 2004 J. Acoust. Soc. Am. 115 1356-64). The main advantage of choosing shear over longitudinal mode resides on the fact that there is less wavefront distortion with the former. In the present study, the regions of the brain suitable for shear-mode transmission were established for a simple focused ultrasound device. The device consists of a spherically curved transducer that has a focal length of 10 cm, an aperture between 30 0 and 60 0 and operates at 0.74 MHz. The regions suitable for shear-mode transmission were determined by the shear wave acoustic windows that matched the shape of the device acoustic field. The acoustic windows were calculated using segmentation and triangulation of outer and inner faces of skull from 3D-MRI head datasets. Nine heads of healthy adults were analyzed. The surface considered for the calculations was the head region found above the supra-orbital margin. For every inspected point in the brain volume, the axis of the device was determined by the vector between this inspection point and a point located in the center of the brain. Numerical predictions of the acoustic field, where shear-mode conversion through the skull was considered, were obtained and compared to the case of water-only conditions. The brain tissue that is close to the skull showed suitable acoustic windows for shear waves. The central region of the brain seems to be unreachable using shear-mode. Analysis of the acoustic fields showed a proportional relation between the acoustic window for shear mode and the effective degree of focusing. However, this relation showed significant differences among specimens. In general, highly focused fields were obtained when the acoustic window for shear waves (A SW ) intersected more than 67% of the entering acoustic window (A TX ) of the device. The average depth from the
Shear induced orientation of edible fat and chocolate crystals
Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.
2003-03-01
Shear-induced orientation of fat crystallites was observed during crystallization of cocoa butter, milk fat, stripped milk fat and palm oil. This universal effect was observed in systems crystallized under high shear. The minor polar components naturally present in milk fat were found to decrease the shear-induced orientation effect in this system. The competition between Brownian and shear forces, described by the Peclet number, determines the crystallite orientation. The critical radius size, from the Gibbs-Thomson equation, provides a tool to understand the effect of shear at the onset stages of crystallization.
Analytical solution for shear bands in cold-rolled 1018 steel
Voyiadjis, George Z.; Almasri, Amin H.; Faghihi, Danial; Palazotto, Anthony N.
2012-06-01
Cold-rolled 1018 (CR-1018) carbon steel has been well known for its susceptibility to adiabatic shear banding under dynamic loadings. Analysis of these localizations highly depends on the selection of the constitutive model. To deal with this issue, a constitutive model that takes temperature and strain rate effect into account is proposed. The model is motivated by two physical-based models: the Zerilli and Armstrong and the Voyiadjis and Abed models. This material model, however, incorporates a simple softening term that is capable of simulating the softening behavior of CR-1018 steel. Instability, localization, and evolution of adiabatic shear bands are discussed and presented graphically. In addition, the effect of hydrostatic pressure is illustrated.
Experimental and numerical study of plastic shear instability under high-speed loading conditions
International Nuclear Information System (INIS)
Sokovikov, Mikhail; Chudinov, Vasiliy; Bilalov, Dmitry; Oborin, Vladimir; Uvarov, Sergey; Plekhov, Oleg; Terekhina, Alena; Naimark, Oleg
2014-01-01
The behavior of specimens dynamically loaded during the split Hopkinson (Kolsky) bar tests in a regime close to simple shear conditions was studied. The lateral surface of the specimens was investigated in a real-time mode with the aid of a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time made it possible to trace the evolution of plastic strain localization. The process of target perforation involving plug formation and ejection was examined using a high-speed infra-red camera and a VISAR velocity measurement system. The microstructure of tested specimens was analyzed using an optical interferometer-profilometer and a scanning electron microscope. The development of plastic shear instability regions has been simulated numerically
Dilatancy of Shear Transformations in a Colloidal Glass
Lu, Y. Z.; Jiang, M. Q.; Lu, X.; Qin, Z. X.; Huang, Y. J.; Shen, J.
2018-01-01
Shear transformations, as fundamental rearrangement events operating in local regions, hold the key of plastic flow of amorphous solids. Despite their importance, the dynamic features of shear transformations are far from clear, which is the focus of the present study. Here, we use a colloidal glass under shear as the prototype to directly observe the shear-transformation events in real space. By tracing the colloidal-particle rearrangements, we quantitatively determine two basic properties of shear transformations: local shear strain and dilatation (or free volume). It is revealed that the local free volume undergoes a significantly temporary increase prior to shear transformations, eventually leading to a jump of local shear strain. We clearly demonstrate that shear transformations have no memory of the initial free volume of local regions. Instead, their emergence strongly depends on the dilatancy ability of these local regions, i.e., the dynamic creation of free volume. More specifically, the particles processing the high dilatancy ability directly participate in subsequent shear transformations. These results experimentally enrich Argon's statement about the dilatancy nature of shear transformations and also shed insight into the structural origin of amorphous plasticity.
Adiabatic shear localization in ultrafine grained 6061 aluminum alloy
Energy Technology Data Exchange (ETDEWEB)
Wang, Bingfeng, E-mail: biw009@ucsd.edu [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083 (China); Ma, Rui; Zhou, Jindian [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Li, Zezhou; Zhao, Shiteng [Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); Huang, Xiaoxia [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)
2016-10-15
Localized shear is an important mode of deformation; it leads to catastrophic failure with low ductility, and occurs frequently during high strain-rate deformation. The hat-shaped specimen has been successfully used to generate shear bands under controlled shock-loading tests. The microstructure in the forced shear band was characterized by optical microscopy, microhardness, and transmission electron microscopy. The true flow stress in the shear region can reach 800 MPa where the strain is about 2.2. The whole shear localization process lasts for about 100 μs. The shear band is a long and straight band distinguished from the matrix by boundaries. It can be seen that the grains in the boundary of the shear band are highly elongated along the shear direction and form the elongated cell structures (0.2 µm in width), and the core of the shear band consists of a number of recrystallized equiaxed grains with 0.2−0.3 µm in diameters, and the second phase particles distribute in the boundary of the ultrafine equiaxed new grains. The calculated temperature in the shear band can reach about 667 K. Finally, the formation of the shear band in the ultrafine grained 6061 aluminum alloy and its microstructural evolution are proposed.
Shear Capacity of C-Shaped and L-Shaped Angle Shear Connectors
Tahmasbi, Farzad; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.; Tahir, M. M.
2016-01-01
This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress in L-shaped angle connectors takes place in the weld attachment to the beam, whereas in the C-shaped angle connectors, it is in the attached leg. The location of maximum concrete compressive damage is rendered in each case. Finally, a new equation for prediction of the shear capacity of C-shaped angle connectors is proposed. PMID:27478894
Shear Capacity of C-Shaped and L-Shaped Angle Shear Connectors.
Directory of Open Access Journals (Sweden)
Farzad Tahmasbi
Full Text Available This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress in L-shaped angle connectors takes place in the weld attachment to the beam, whereas in the C-shaped angle connectors, it is in the attached leg. The location of maximum concrete compressive damage is rendered in each case. Finally, a new equation for prediction of the shear capacity of C-shaped angle connectors is proposed.
Experimental study of a shear wall with numerous small openings
International Nuclear Information System (INIS)
Sotomura, K.; Murazumi, Y.; Yoshizaki, S.; Ezaki, T.
1981-01-01
Many small openings for piping and ducts are usually required in the shear walls for PWR nuclear power plant. It is generally believed that such openings oadversely affect the strength and stiffness of shear walls. However, little information is available concerning the behavior of walls with numerous small openings. Therefore, tests using wall specimens and an analysis using an FEM program were carried out to investigate this behavior. Main findings are as follows: 1) The ultimate strength of a shear wall with numerous small openings may be obtained by using the effective area at the critical cross section of the shear wall. 2) Shear walls with openings can be restored to the same shear strength and stiffness as shear walls without openings by diagonal reinforcement. (orig./HP)
Directory of Open Access Journals (Sweden)
Zebbiche Toufik
2014-09-01
Full Text Available The presented work is to develop a numerical computation program to determine the distribution of the shear stress to shear in closed tubes with asymmetric single thin wall section with a constant thickness and applications to airfoils and therefore determining the position and value of the maximum stress. In the literature, there are exact analytical solutions only for some sections of simple geometries such as circular section. Hence our interest is focused on the search of approximate numerical solutions for more complex sections used in aeronautics. In the second stage the position of the shear center is determined so that the section does not undergo torsion. The analytic function of the boundary of the airfoil is obtained by using the cubic spline interpolation since it is given in the form of tabulated points.
Directory of Open Access Journals (Sweden)
John D. Clayton
2014-07-01
Full Text Available A nonlinear continuum phase field theory is developed to describe amorphization of crystalline elastic solids under shear and/or pressure loading. An order parameter describes the local degree of crystallinity. Elastic coefficients can depend on the order parameter, inelastic volume change may accompany the transition from crystal to amorphous phase, and transitional regions parallel to bands of amorphous material are penalized by interfacial surface energy. Analytical and simple numerical solutions are obtained for an idealized isotropic version of the general theory, for an element of material subjected to compressive and/or shear loading. Solutions compare favorably with experimental evidence and atomic simulations of amorphization in boron carbide, demonstrating the tendency for structural collapse and strength loss with increasing shear deformation and superposed pressure.
Ultrasound viscoelasticity assessment using an adaptive torsional shear wave propagation method
Energy Technology Data Exchange (ETDEWEB)
Ouared, Abderrahmane [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9, Canada and Institute of Biomedical Engineering, University of Montréal, Montréal, Québec H3T 1J4 (Canada); Kazemirad, Siavash; Montagnon, Emmanuel [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9 (Canada); Cloutier, Guy, E-mail: guy.cloutier@umontreal.ca [Laboratory of Biorheology and Medical Ultrasonics, University of Montréal Hospital Research Center (CRCHUM), Montréal, Québec H2X 0A9 (Canada); Department of Radiology, Radio-Oncology and Nuclear Medicine, University of Montréal, Montréal, Québec H3T 1J4 (Canada); Institute of Biomedical Engineering, University of Montréal, Montréal, Québec H3T 1J4 (Canada)
2016-04-15
Purpose: Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite element method (FEM) models. In this study, a new method is proposed for the quantification of both shear storage and loss moduli of confined lesions, in the context of breast imaging, using adaptive torsional shear waves (ATSWs) generated remotely with radiation pressure. Methods: A FEM model was developed to solve the inverse wave propagation problem and obtain viscoelastic properties of interrogated media. The inverse problem was formulated and solved in the frequency domain and its robustness to noise and geometric constraints was evaluated. The proposed model was validated in vitro with two independent rheology methods on several homogeneous and heterogeneous breast tissue-mimicking phantoms over a broad range of frequencies (up to 400 Hz). Results: Viscoelastic properties matched benchmark rheology methods with discrepancies of 8%–38% for the shear modulus G′ and 9%–67% for the loss modulus G″. The robustness study indicated good estimations of storage and loss moduli (maximum mean errors of 19% on G′ and 32% on G″) for signal-to-noise ratios between 19.5 and 8.5 dB. Larger errors were noticed in the case of biases in lesion dimension and position. Conclusions: The ATSW method revealed that it is possible to estimate the viscoelasticity of biological tissues with torsional shear waves when small biases in lesion geometry exist.
GREAT3 results - I. Systematic errors in shear estimation and the impact of real galaxy morphology
Energy Technology Data Exchange (ETDEWEB)
Mandelbaum, R.; Rowe, B.; Armstrong, R.; Bard, D.; Bertin, E.; Bosch, J.; Boutigny, D.; Courbin, F.; Dawson, W. A.; Donnarumma, A.; Fenech Conti, I.; Gavazzi, R.; Gentile, M.; Gill, M. S. S.; Hogg, D. W.; Huff, E. M.; Jee, M. J.; Kacprzak, T.; Kilbinger, M.; Kuntzer, T.; Lang, D.; Luo, W.; March, M. C.; Marshall, P. J.; Meyers, J. E.; Miller, L.; Miyatake, H.; Nakajima, R.; Ngole Mboula, F. M.; Nurbaeva, G.; Okura, Y.; Paulin-Henriksson, S.; Rhodes, J.; Schneider, M. D.; Shan, H.; Sheldon, E. S.; Simet, M.; Starck, J. -L.; Sureau, F.; Tewes, M.; Zarb Adami, K.; Zhang, J.; Zuntz, J.
2015-05-01
We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, the third in a sequence of challenges for testing methods of inferring weak gravitational lensing shear distortions from simulated galaxy images. GREAT3 was divided into experiments to test three specific questions, and included simulated space- and ground-based data with constant or cosmologically varying shear fields. The simplest (control) experiment included parametric galaxies with a realistic distribution of signal-to-noise, size, and ellipticity, and a complex point spread function (PSF). The other experiments tested the additional impact of realistic galaxy morphology, multiple exposure imaging, and the uncertainty about a spatially varying PSF; the last two questions will be explored in Paper II. The 24 participating teams competed to estimate lensing shears to within systematic error tolerances for upcoming Stage-IV dark energy surveys, making 1525 submissions overall. GREAT3 saw considerable variety and innovation in the types of methods applied. Several teams now meet or exceed the targets in many of the tests conducted (to within the statistical errors). We conclude that the presence of realistic galaxy morphology in simulations changes shear calibration biases by ~1 per cent for a wide range of methods. Other effects such as truncation biases due to finite galaxy postage stamps, and the impact of galaxy type as measured by the Sérsic index, are quantified for the first time. Our results generalize previous studies regarding sensitivities to galaxy size and signal-to-noise, and to PSF properties such as seeing and defocus. Almost all methods’ results support the simple model in which additive shear biases depend linearly on PSF ellipticity.
Cosmic shear measurement with maximum likelihood and maximum a posteriori inference
Hall, Alex; Taylor, Andy
2017-06-01
We investigate the problem of noise bias in maximum likelihood and maximum a posteriori estimators for cosmic shear. We derive the leading and next-to-leading order biases and compute them in the context of galaxy ellipticity measurements, extending previous work on maximum likelihood inference for weak lensing. We show that a large part of the bias on these point estimators can be removed using information already contained in the likelihood when a galaxy model is specified, without the need for external calibration. We test these bias-corrected estimators on simulated galaxy images similar to those expected from planned space-based weak lensing surveys, with promising results. We find that the introduction of an intrinsic shape prior can help with mitigation of noise bias, such that the maximum a posteriori estimate can be made less biased than the maximum likelihood estimate. Second-order terms offer a check on the convergence of the estimators, but are largely subdominant. We show how biases propagate to shear estimates, demonstrating in our simple set-up that shear biases can be reduced by orders of magnitude and potentially to within the requirements of planned space-based surveys at mild signal-to-noise ratio. We find that second-order terms can exhibit significant cancellations at low signal-to-noise ratio when Gaussian noise is assumed, which has implications for inferring the performance of shear-measurement algorithms from simplified simulations. We discuss the viability of our point estimators as tools for lensing inference, arguing that they allow for the robust measurement of ellipticity and shear.
Aspiration of human neutrophils: effects of shear thinning and cortical dissipation.
Drury, J L; Dembo, M
2001-12-01
It is generally accepted that the human neutrophil can be mechanically represented as a droplet of polymeric fluid enclosed by some sort of thin slippery viscoelastic cortex. Many questions remain however about the detailed rheology and chemistry of the interior fluid and the cortex. To address these quantitative issues, we have used a finite element method to simulate the dynamics of neutrophils during micropipet aspiration using various plausible assumptions. The results were then systematically compared with aspiration experiments conducted at eight different combinations of pipet size and pressure. Models in which the cytoplasm was represented by a simple Newtonian fluid (i.e., models without shear thinning) were grossly incapable of accounting for the effects of pressure on the general time scale of neutrophil aspiration. Likewise, models in which the cortex was purely elastic (i.e., models without surface viscosity) were unable to explain the effects of pipet size on the general aspiration rate. Such models also failed to explain the rapid acceleration of the aspiration rate during the final phase of aspiration nor could they account for the geometry of the neutrophil during various phases of aspiration. Thus, our results indicate that a minimal mechanical model of the neutrophil needs to incorporate both shear thinning and surface viscosity to remain valid over a reasonable range of conditions. At low shear rates, the surface dilatation viscosity of the neutrophil was found to be on the order of 100 poise-cm, whereas the viscosity of the interior cytoplasm was on the order of 1000 poise. Both the surface viscosity and the interior viscosity seem to decrease in a similar fashion when the shear rate exceeds approximately 0.05 s(-1). Unfortunately, even models with both surface viscosity and shear thinning studied are still not sufficient to fully explain all the features of neutrophil aspiration. In particular, the very high rate of aspiration during the
Viscoelasticity, nonlinear shear start-up, and relaxation of entangled star polymers
Snijkers, Frank
2013-07-23
We report on a detailed rheological investigation of well-defined symmetric entangled polymer stars of low functionality with varying number of arms, molar mass of the arms, and solvent content. Emphasis is placed on the response of the stars in simple shear, during start-up, and for relaxation upon flow cessation. To reduce experimental artifacts associated with edge fracture (primarily) and wall slip, we employ a homemade cone-partitioned plate fixture which was successfully implemented in recent studies. Reliable data for these highly entangled stars could be obtained for Weissenberg numbers below 300. The appearance of a stress overshoot during start-up with a corresponding strain approaching a value of 2 suggests that in the investigated shear regime the stars orient but do not stretch. This is corroborated by the fact that the empirical Cox-Merx rule appears to be validated, within experimental error. On the other hand, the (shear) rate dependent steady shear viscosity data exhibit a slope smaller than the convective constraint release slope of -1 (for linear polymers) for the investigated range of rates. The broadness of the stress overshoot reflects the broad linear relaxation spectrum of the stars. The initial stress relaxation rate, reflecting the initial loss of entanglements due to the action of convective constraint release in steady shear flow, increases with Weissenberg number. More importantly, when compared against the relevant rates for comb polymers with relatively short arms, the latter are slower at larger Weissenberg numbers. At long times, the relaxation data are consistent with the linear viscoelastic data on these systems. © 2013 American Chemical Society.
Steady shear rate rheology of suspensions, as described by the gaint floc model
Stein, H.N.; Laven, J.
2001-01-01
The break-down of a particle network by shear is described as the development of shear planes: a region able to withstand low shear stresses may break down under a larger stress; thus with increasing shear stress and shear rate, the mutual distance (A) between successive shear planes decreases
Estimation of basal shear stresses from now ice-free LIA glacier forefields in the Swiss Alps
Fischer, Mauro; Haeberli, Wilfried; Huss, Matthias; Paul, Frank; Linsbauer, Andreas; Hoelzle, Martin
2013-04-01
In most cases, assessing the impacts of climatic changes on glaciers requires knowledge about the ice thickness distribution. Miscellaneous methodological approaches with different degrees of sophistication have been applied to model glacier thickness so far. However, all of them include significant uncertainty. By applying a parameterization scheme for ice thickness determination relying on assumptions about basal shear stress by Haeberli and Hoelzle (1995) to now ice-free glacier forefields in the Swiss Alps, basal shear stress values can be calculated based on a fast and robust experimental approach. In a GIS, the combination of recent (1973) and Little Ice Age (LIA) maximum (around 1850) glacier outlines, central flowlines, a recent Digital Elevation Model (DEM) and a DEM of glacier surface topography for the LIA maximum allows extracting local ice thickness over the forefield of individual glaciers. Subsequently, basal shear stress is calculated via the rheological assumption of perfect-plasticity relating ice thickness and surface slope to shear stress. The need of only very few input data commonly stored in glacier inventories permits an application to a large number of glaciers. Basal shear stresses are first calculated for subsamples of glaciers belonging to two test sites where the LIA maximum glacier surface is modeled with DEMs derived from accurate topographic maps for the mid 19th century. Neglecting outliers, the average resulting mean basal shear stress is around 80 kPa for the Bernina region (range 25-100 kPa) and 120 kPa (range 50-150 kPa) for the Aletsch region. For the entire Swiss Alps it is 100 kPa (range 40-175 kPa). Because complete LIA glacier surface elevation information is lacking there, a DEM is first created from reconstructed height of LIA lateral moraines and trimlines by using a simple GIS-based tool. A sensitivity analysis of the input parameters reveals that the performance of the developed approach primarily depends on the
Torsional shear flow of granular materials: shear localization and minimum energy principle
Artoni, Riccardo; Richard, Patrick
2018-01-01
The rheological properties of granular matter submitted to torsional shear are investigated numerically by means of discrete element method. The shear cell is made of a cylinder filled by grains which are sheared by a bumpy bottom and submitted to a vertical pressure which is applied at the top. Regimes differing by their strain localization features are observed. They originate from the competition between dissipation at the sidewalls and dissipation in the bulk of the system. The effects of the (i) the applied pressure, (ii) sidewall friction, and (iii) angular velocity are investigated. A model, based on the purely local μ (I)-rheology and a minimum energy principle is able to capture the effect of the two former quantities but unable to account the effect of the latter. Although, an ad hoc modification of the model allows to reproduce all the numerical results, our results point out the need for an alternative rheology.
Shear and loading in channels: Oscillatory shearing and edge currents of superconducting vortices
Wambaugh, J. F.; Marchesoni, F.; Nori, Franco
2003-04-01
Via computer simulations we study the motion of quantized magnetic flux-lines, or vortices, confined to a straight pin-free channel in a strong-pinning superconducting sample. We find that, when a constant current is applied across this system, a very unusual oscillatory shearing appears, in which the vortices moving at the edges of the channel periodically trail behind and then suddenly leapfrog past the vortices moving in the inner rows. For small enough driving forces, this oscillatory shearing dynamic phase is replaced by a continuous shearing phase in which the distance between initially-nearby vortices grows in time, quickly destroying the order of the lattice. An animation of this novel “oscillatory leapfrogging shear” effect of the vortex edge currents appears in http://www-personal.engin.umich.edu/˜nori/channel/
Angela Mihai, L.
2013-03-01
Finite element simulations of different shear deformations in non-linear elasticity are presented. We pay particular attention to the Poynting effects in hyperelastic materials, complementing recent theoretical findings by showing these effects manifested by specific models. As the finite element method computes uniform deformations exactly, for simple shear deformation and pure shear stress, the Poynting effect is represented exactly, while for the generalised shear and simple torsion, where the deformation is non-uniform, the solution is approximated efficiently and guaranteed computational bounds on the magnitude of the Poynting effect are obtained. The numerical results further indicate that, for a given elastic material, the same sign effect occurs under different shearing mechanisms, showing the genericity of the Poynting effect under a variety of shearing loads. In order to derive numerical models that exhibit either the positive or the negative Poynting effect, the so-called generalised empirical inequalities, which are less restrictive than the usual empirical inequalities involving material parameters, are assumed. © 2012 Elsevier Ltd.
Oshino, Satoru; Kishima, Haruhiko; Ohnishi, Yu-ichiro; Iwatsuki, Koichi; Saitoh, Youichi
2016-03-01
Catheter shearing is one of the most common complications of various neurosurgical modalities that use an intrathecal lumbar catheter. The sheared catheter fragment often can spontaneously migrate into the spinal canal; however, in some cases, the end of the fragment will remain outside the spinal canal. In this situation, the consulting neurosurgeons may try to retrieve the catheter fragment by approaching it directly through the catheter tract. This simple maneuver, however, can cause the fragment to slip into the spinal canal before it is secured, as we experienced recently in 2 cases. Because the fragment of the sheared catheter slipped while manipulating it within the catheter tract, we suggest that surgeons not approach the fragment along the tract to prevent it from migrating downward. Using the operative findings of an illustrative case, we describe how to avoid downward migration of the catheter fragment when retrieving a sheared lumbar catheter. We found that the sheared catheter of a lumbar-peritoneal shunt was slowly slipping along with the pulsatile movement of cerebrospinal fluid within the catheter tract. We successfully retrieved the fragment by approaching it from outside the catheter tract. We propose that surgeons approach the fragment from outside of the catheter tract. One should keep in mind a simple phrase, 'Do not follow the tail', when retrieving the sheared lumbar catheter fragment. Copyright © 2016 Elsevier Inc. All rights reserved.
Caenen, Annette; Pernot, Mathieu; Peirlinck, Mathias; Mertens, Luc; Swillens, Abigail; Segers, Patrick
2018-04-01
Shear wave elastography (SWE) is a potential tool to non-invasively assess cardiac muscle stiffness. This study focused on the effect of the orthotropic material properties and mechanical loading on the performance of cardiac SWE, as it is known that these factors contribute to complex 3D anisotropic shear wave propagation. To investigate the specific impact of these complexities, we constructed a finite element model with an orthotropic material law subjected to different uniaxial stretches to simulate SWE in the stressed cardiac wall. Group and phase speed were analyzed in function of tissue thickness and virtual probe rotation angle. Tissue stretching increased the group and phase speed of the simulated shear wave, especially in the direction of the muscle fiber. As the model provided access to the true fiber orientation and material properties, we assessed the accuracy of two fiber orientation extraction methods based on SWE. We found a higher accuracy (but lower robustness) when extracting fiber orientations based on the location of maximal shear wave speed instead of the angle of the major axis of the ellipsoidal group speed surface. Both methods had a comparable performance for the center region of the cardiac wall, and performed less well towards the edges. Lastly, we also assessed the (theoretical) impact of pathology on shear wave physics and characterization in the model. It was found that SWE was able to detect changes in fiber orientation and material characteristics, potentially associated with cardiac pathologies such as myocardial fibrosis. Furthermore, the model showed clearly altered shear wave patterns for the fibrotic myocardium compared to the healthy myocardium, which forms an initial but promising outcome of this modeling study.
Shear thickening in suspensions: the lubricated-to-frictional contact scenario
Morris, Jeffrey
2017-11-01
Suspensions of solid particles in viscous liquids can vary from low-viscosity liquids to wet granular materials or soft solids depending on the solids loading and the forces acting between particles. When the particles are very concentrated, these mixtures are ''dense suspensions.'' Dense suspensions often exhibit shear thickening, an increase in apparent viscosity as the shear rate is increased. In its most extreme form, order of magnitude increases in viscosity over such a narrow range in shear rate occur that the term discontinuous shear thickening (DST) is applied. DST is particularly striking as it occurs in the relatively simple case of nearly hard spheres in a Newtonian liquid, and is found to take place for submicron particles in colloidal dispersions to much larger particle corn starch dispersions. We focus on simulations of a recently developed ``lubricated-to-frictional'' rheology in which the interplay of viscous lubrication, repulsive surface forces, and contact friction between particle surfaces provides a scenario to explain DST. Our simulation method brings together elements of the discrete-element method from granular flow with a simplified Stokesian Dynamics, and can rationalize not only the abrupt change in properties with imposed shear rate (or shear stress), but also the magnitude of the change. The large change in properties is associated with the breakdown of lubricating films between particles, with activation of Coulomb friction between particles. The rate dependence is caused by the shearing forces driving particles to contact, overwhelming conservative repulsive forces between surfaces; the repulsive forces are representative of colloidal stabilization by surface charge or steric effects, e.g. due to adsorbed polymer. The results of simulation are compared to developments by other groups, including a number of experimental studies and a theory incorporating the same basic elements as the simulation. The comparison to experiments of the
Compression and shear properties of elastomeric bearing using finite element analysis
Directory of Open Access Journals (Sweden)
2Faculty of Science and Technology, Chiang Mai Rajabhat University, Muang, Chiang Mai, 50300 Thailand.
2006-09-01
Full Text Available Standard size samples of four natural rubber compounds, varying the amount of carbon black from 10 to 70 phr, were characterised under uniaxial compression and simple shear tests in order to obtain the strain energy function constants. These constants were then used as hyperelastic material constants for the Windows-based finite element package (COSMOS/M version 1.75. The investigated bearings, made with those NR compounds, had the approximate area and thickness of 50x106 mm2 and 50 mm respectively. Each compound of bearing consisted of four different values of shape factor ranging from about 0.33 to 1.70, according to the number of reinforcing plates in the bearing. Three deformation modes of compression, shear and compression-shear were predicted. Good agreement was found between twelve compression model predictions and the corresponding experimental values of bearings, containing 10, 20 and 40 phr of carbon black and each of which consisted of four different layers of reinforcing metal plates (0, 1, 2 and 3 layers. On the other hand, deviation from the predicted valve was clearly seen in the 70 phr black bearing case. The percentage difference increased with respect to the increasing number of reinforcing plates or the rising shape factor. Therefore, the improved FEA model was supplemented with an imaginary elastic glue layer between the rubber block and metal plate as glue failure compensation. The optimum value of the elastic layers modulus is 8 MPa while the thickness of the layer depends on the total thickness or total volume of rubber block. This model can predict the 70 phr carbon black bearings, having shape factor ranging from 0.5 to 2.35 for 11 cases. The FEA prediction of shear behaviour agrees well with the experimental data for all four bearing compounds and there is no effect of shape factor on shear stress. Moreover, shear stress does not depend on the compressive force applied to like bearing before shear and the FEA results
Yada, Norihisa; Tamaki, Nobuhura; Koizumi, Yohei; Hirooka, Masashi; Nakashima, Osamu; Hiasa, Yoichi; Izumi, Namiki; Kudo, Masatoshi
2017-01-01
Performing shear wave imaging is simple, but can be difficult when inflammation, jaundice, and congestion are present. Therefore, the correct diagnosis of liver fibrosis using shear wave imaging alone might be difficult in mild-to-moderate fibrosis cases. Strain imaging can diagnose liver fibrosis without the influence of inflammation. Therefore, the combined use of strain and shear wave imaging (combinational elastography) for cases without jaundice and congestion might be useful for evaluating fibrosis and inflammation. We enrolled consecutive patients with liver disease, without jaundice or liver congestion. Strain and shear wave imaging, blood tests, and liver biopsy were performed on the same day. The liver fibrosis index (LF index) was calculated by strain imaging; real-time tissue elastography, and the shear wave velocity (Vs) was calculated by shear wave imaging. Fibrosis index (F index) and activity index (A index) were calculated as a multiple regression equation for determining hepatic fibrosis and inflammation using histopathological diagnosis as the gold standard. The diagnostic ability of F index for fibrosis and A index for inflammation were compared using LF index and Vs. The total number of enrolled cases was 388. The area under the receiver operating characteristic (AUROC) was 0.87, 0.80, 0.83, and 0.80, at diagnosis of fibrosis stage with an F index of F1 or higher, F2 or higher, F3 or higher, and F4, respectively. The AUROC was 0.94, 0.74, and 0.76 at diagnosis of activity grade with an A index of A1 or higher, A2 or higher, and A3, respectively. The diagnostic ability of F index for liver fibrosis and A index for inflammation was higher than for other conventional diagnostic values. The combined use of strain and shear wave imaging (combinational elastography) might increase the positive diagnosis of liver fibrosis and inflammation. © 2017 S. Karger AG, Basel.
Experimental Research on Boundary Shear Stress in Typical Meandering Channel
Chen, Kai-hua; Xia, Yun-feng; Zhang, Shi-zhao; Wen, Yun-cheng; Xu, Hua
2018-06-01
A novel instrument named Micro-Electro-Mechanical System (MEMS) flexible hot-film shear stress sensor was used to study the boundary shear stress distribution in the generalized natural meandering open channel, and the mean sidewall shear stress distribution along the meandering channel, and the lateral boundary shear stress distribution in the typical cross-section of the meandering channel was analysed. Based on the measurement of the boundary shear stress, a semi-empirical semi-theoretical computing approach of the boundary shear stress was derived including the effects of the secondary flow, sidewall roughness factor, eddy viscosity and the additional Reynolds stress, and more importantly, for the first time, it combined the effects of the cross-section central angle and the Reynolds number into the expressions. Afterwards, a comparison between the previous research and this study was developed. Following the result, we found that the semi-empirical semi-theoretical boundary shear stress distribution algorithm can predict the boundary shear stress distribution precisely. Finally, a single factor analysis was conducted on the relationship between the average sidewall shear stress on the convex and concave bank and the flow rate, water depth, slope ratio, or the cross-section central angle of the open channel bend. The functional relationship with each of the above factors was established, and then the distance from the location of the extreme sidewall shear stress to the bottom of the open channel was deduced based on the statistical theory.
Modeling combined tension-shear failure of ductile materials
International Nuclear Information System (INIS)
Partom, Y
2014-01-01
Failure of ductile materials is usually expressed in terms of effective plastic strain. Ductile materials can fail by two different failure modes, shear failure and tensile failure. Under dynamic loading shear failure has to do with shear localization and formation of adiabatic shear bands. In these bands plastic strain rate is very high, dissipative heating is extensive, and shear strength is lost. Shear localization starts at a certain value of effective plastic strain, when thermal softening overcomes strain hardening. Shear failure is therefore represented in terms of effective plastic strain. On the other hand, tensile failure comes about by void growth under tension. For voids in a tension field there is a threshold state of the remote field for which voids grow spontaneously (cavitation), and the material there fails. Cavitation depends on the remote field stress components and on the flow stress. In this way failure in tension is related to shear strength and to failure in shear. Here we first evaluate the cavitation threshold for different remote field situations, using 2D numerical simulations with a hydro code. We then use the results to compute examples of rate dependent tension-shear failure of a ductile material.
Evaluation of composite shear walls behavior (parametric study
Directory of Open Access Journals (Sweden)
Ali Nikkhoo
2017-11-01
Full Text Available Composite shear walls which are made of a layer of steel plate with a concrete cover in one or both sides of the steel plate, are counted as the third generation of the shear walls. Nowadays, composite shear walls are widely utilized in building new resisting structures as well as rehabilitating of the existing structures in earthquake-prone countries. Despite of its advantages, use of the composite shear walls is not yet prevalent as it demands more detailed appropriate investigation. Serving higher strength, flexibility and better energy absorption, while being more economical are the main advantages of this system which has paved its path to be used in high-rise buildings, structural retrofit and reservoir tanks. In this research, channel shear connectors are utilized to connect the concrete cover to the steel plate. As a key parameter, variation in the distance of shear connectors and their arrangement on the behavior of composite shear walls has been scrutinized. In addition, the shear stiffness, flexibility, out of plane displacement and the energy absorption of the structural system has been explored. For this purpose, several structural models with different shear distances and arrangements have been investigated. The obtained results reveal that with increase in shear connectors’ distance, the wall stiffness would reduce while its lateral displacement increases up to eighty percent While the out of plane displacement of the steel plate will reduce up to three times.
Vescovi, D.; Berzi, D.; Richard, P.; Brodu, N.
2014-05-01
We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed average volume fraction and distance between the walls. The results of the numerical simulations are used to derive boundary conditions appropriated in the cases of large and small bumpiness. Those boundary conditions are, then, employed to numerically integrate the differential equations of Extended Kinetic Theory, where the breaking of the molecular chaos assumption at volume fraction larger than 0.49 is taken into account in the expression of the dissipation rate. We show that the Extended Kinetic Theory is in very good agreement with the numerical simulations, even for coefficients of restitution as low as 0.50. When the bumpiness is increased, we observe that some of the flowing particles are stuck in the gaps between the wall spheres. As a consequence, the walls are more dissipative than expected, and the flows resemble simple shear flows, i.e., flows of rather constant volume fraction and granular temperature.
International Nuclear Information System (INIS)
Vescovi, D.; Berzi, D.; Richard, P.; Brodu, N.
2014-01-01
We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed average volume fraction and distance between the walls. The results of the numerical simulations are used to derive boundary conditions appropriated in the cases of large and small bumpiness. Those boundary conditions are, then, employed to numerically integrate the differential equations of Extended Kinetic Theory, where the breaking of the molecular chaos assumption at volume fraction larger than 0.49 is taken into account in the expression of the dissipation rate. We show that the Extended Kinetic Theory is in very good agreement with the numerical simulations, even for coefficients of restitution as low as 0.50. When the bumpiness is increased, we observe that some of the flowing particles are stuck in the gaps between the wall spheres. As a consequence, the walls are more dissipative than expected, and the flows resemble simple shear flows, i.e., flows of rather constant volume fraction and granular temperature
Wall shear stress fixed points in cardiovascular fluid mechanics.
Arzani, Amirhossein; Shadden, Shawn C
2018-05-17
Complex blood flow in large arteries creates rich wall shear stress (WSS) vectorial features. WSS acts as a link between blood flow dynamics and the biology of various cardiovascular diseases. WSS has been of great interest in a wide range of studies and has been the most popular measure to correlate blood flow to cardiovascular disease. Recent studies have emphasized different vectorial features of WSS. However, fixed points in the WSS vector field have not received much attention. A WSS fixed point is a point on the vessel wall where the WSS vector vanishes. In this article, WSS fixed points are classified and the aspects by which they could influence cardiovascular disease are reviewed. First, the connection between WSS fixed points and the flow topology away from the vessel wall is discussed. Second, the potential role of time-averaged WSS fixed points in biochemical mass transport is demonstrated using the recent concept of Lagrangian WSS structures. Finally, simple measures are proposed to quantify the exposure of the endothelial cells to WSS fixed points. Examples from various arterial flow applications are demonstrated. Copyright © 2018 Elsevier Ltd. All rights reserved.
Extrusion Bioprinting of Shear-Thinning Gelatin Methacryloyl Bioinks.
Liu, Wanjun; Heinrich, Marcel A; Zhou, Yixiao; Akpek, Ali; Hu, Ning; Liu, Xiao; Guan, Xiaofei; Zhong, Zhe; Jin, Xiangyu; Khademhosseini, Ali; Zhang, Yu Shrike
2017-06-01
Bioprinting is an emerging technique for the fabrication of 3D cell-laden constructs. However, the progress for generating a 3D complex physiological microenvironment has been hampered by a lack of advanced cell-responsive bioinks that enable bioprinting with high structural fidelity, particularly in the case of extrusion-based bioprinting. Herein, this paper reports a novel strategy to directly bioprint cell-laden gelatin methacryloyl (GelMA) constructs using bioinks of GelMA physical gels (GPGs) achieved through a simple cooling process. Attributed to their shear-thinning and self-healing properties, the GPG bioinks can retain the shape and form integral structures after deposition, allowing for subsequent UV crosslinking for permanent stabilization. This paper shows the structural fidelity by bioprinting various 3D structures that are typically challenging to fabricate using conventional bioinks under extrusion modes. Moreover, the use of the GPG bioinks enables direct bioprinting of highly porous and soft constructs at relatively low concentrations (down to 3%) of GelMA. It is also demonstrated that the bioprinted constructs not only permit cell survival but also enhance cell proliferation as well as spreading at lower concentrations of the GPG bioinks. It is believed that such a strategy of bioprinting will provide many opportunities in convenient fabrication of 3D cell-laden constructs for applications in tissue engineering, regenerative medicine, and pharmaceutical screening. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Propagation of waves in shear flows
Fabrikant, A L
1998-01-01
The state of the art in a theory of oscillatory and wave phenomena in hydrodynamical flows is presented in this book. A unified approach is used for waves of different physical origins. A characteristic feature of this approach is that hydrodynamical phenomena are considered in terms of physics; that is, the complement of the conventionally employed formal mathematical approach. Some physical concepts such as wave energy and momentum in a moving fluid are analysed, taking into account induced mean flow. The physical mechanisms responsible for hydrodynamic instability of shear flows are conside
Multifractal spectra in homogeneous shear flow
Deane, A. E.; Keefe, L. R.
1988-01-01
Employing numerical simulations of 3-D homogeneous shear flow, the associated multifractal spectra of the energy dissipation, scalar dissipation and vorticity fields were calculated. The results for (128) cubed simulations of this flow, and those obtained in recent experiments that analyzed 1- and 2-D intersections of atmospheric and laboratory flows, are in some agreement. A two-scale Cantor set model of the energy cascade process which describes the experimental results from 1-D intersections quite well, describes the 3-D results only marginally.
A New Annular Shear Piezoelectric Accelerometer
DEFF Research Database (Denmark)
Liu, Bin; Kriegbaum, B.
2000-01-01
This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass...... prototype. Reasonable agreement between the experimental results of the physical prototype and the simulation results is achieved. The design becomes more efficient. In addition, Type 4511 has a built in DeltaTronâ charge amplifier with ID and complies with IEEE-P1451.4 standard, which is a smart transducer...
Patient Education Sheet Simple Solutions for Dry Eye The SSF thanks J. Daniel Nelson, MD, Associate Medical Director, Specialty Care HealthPartners Medical Group & Clinics, and Professor of Ophthalmology, University of ...
Simple Tidal Prism Models Revisited
Luketina, D.
1998-01-01
Simple tidal prism models for well-mixed estuaries have been in use for some time and are discussed in most text books on estuaries. The appeal of this model is its simplicity. However, there are several flaws in the logic behind the model. These flaws are pointed out and a more theoretically correct simple tidal prism model is derived. In doing so, it is made clear which effects can, in theory, be neglected and which can not.
Lin, Neil Y. C.
2013-12-01
Using high-speed confocal microscopy, we measure the particle positions in a colloidal suspension under large-amplitude oscillatory shear. Using the particle positions, we quantify the in situ anisotropy of the pair-correlation function, a measure of the Brownian stress. From these data we find two distinct types of responses as the system crosses over from equilibrium to far-from-equilibrium states. The first is a nonlinear amplitude saturation that arises from shear-induced advection, while the second is a linear frequency saturation due to competition between suspension relaxation and shear rate. In spite of their different underlying mechanisms, we show that all the data can be scaled onto a master curve that spans the equilibrium and far-from-equilibrium regimes, linking small-amplitude oscillatory to continuous shear. This observation illustrates a colloidal analog of the Cox-Merz rule and its microscopic underpinning. Brownian dynamics simulations show that interparticle interactions are sufficient for generating both experimentally observed saturations. © 2013 American Physical Society.
Determination of wall shear stress from mean velocity and Reynolds shear stress profiles
Volino, Ralph J.; Schultz, Michael P.
2018-03-01
An analytical method is presented for determining the Reynolds shear stress profile in steady, two-dimensional wall-bounded flows using the mean streamwise velocity. The method is then utilized with experimental data to determine the local wall shear stress. The procedure is applicable to flows on smooth and rough surfaces with arbitrary pressure gradients. It is based on the streamwise component of the boundary layer momentum equation, which is transformed into inner coordinates. The method requires velocity profiles from at least two streamwise locations, but the formulation of the momentum equation reduces the dependence on streamwise gradients. The method is verified through application to laminar flow solutions and turbulent DNS results from both zero and nonzero pressure gradient boundary layers. With strong favorable pressure gradients, the method is shown to be accurate for finding the wall shear stress in cases where the Clauser fit technique loses accuracy. The method is then applied to experimental data from the literature from zero pressure gradient studies on smooth and rough walls, and favorable and adverse pressure gradient cases on smooth walls. Data from very near the wall are not required for determination of the wall shear stress. Wall friction velocities obtained using the present method agree with those determined in the original studies, typically to within 2%.
Miao, Hongchen; Huan, Qiang; Wang, Qiangzhong; Li, Faxin
2017-02-01
The non-dispersive fundamental shear horizontal (SH 0 ) wave in plate-like structures is of practical importance in non-destructive testing (NDT) and structural health monitoring (SHM). Theoretically, an omnidirectional SH 0 transducer phased array system can be used to inspect defects in a large plate in the similar manner to the phased array transducers used in medical B-scan ultrasonics. However, very few omnidirectional SH 0 transducers have been proposed so far. In this work, an omnidirectional SH 0 wave piezoelectric transducer (OSH-PT) was proposed, which consists of a ring array of twelve face-shear (d 24 ) trapezoidal PZT elements. Each PZT element can produce face-shear deformation under applied voltage, resulting in circumferential shear deformation in the OSH-PT and omnidirectional SH 0 waves in the hosting plate. Both finite element simulations and experiments were conducted to examine the performance of the proposed OSH-PT. Experimental testing shows that the OSH-PT exhibits good omnidirectional properties, no matter it is used as a SH 0 wave transmitter or a SH 0 wave receiver. This work may greatly promote the applications of SH 0 waves in NDT and SHM. Copyright Â© 2016 Elsevier B.V. All rights reserved.
Lin, Neil Y. C.; Goyal, Sushmit; Cheng, Xiang; Zia, Roseanna N.; Escobedo, Fernando A.; Cohen, Itai
2013-01-01
Using high-speed confocal microscopy, we measure the particle positions in a colloidal suspension under large-amplitude oscillatory shear. Using the particle positions, we quantify the in situ anisotropy of the pair-correlation function, a measure of the Brownian stress. From these data we find two distinct types of responses as the system crosses over from equilibrium to far-from-equilibrium states. The first is a nonlinear amplitude saturation that arises from shear-induced advection, while the second is a linear frequency saturation due to competition between suspension relaxation and shear rate. In spite of their different underlying mechanisms, we show that all the data can be scaled onto a master curve that spans the equilibrium and far-from-equilibrium regimes, linking small-amplitude oscillatory to continuous shear. This observation illustrates a colloidal analog of the Cox-Merz rule and its microscopic underpinning. Brownian dynamics simulations show that interparticle interactions are sufficient for generating both experimentally observed saturations. © 2013 American Physical Society.
Test and lower bound modeling of keyed shear connections in RC shear walls
DEFF Research Database (Denmark)
Sørensen, Jesper Harrild; Herfelt, Morten Andersen; Hoang, Linh Cao
2018-01-01
This paper presents an investigation into the ultimate behavior of a recently developed design for keyed shear connections. The influence of the key depth on the failure mode and ductility of the connection has been studied by push-off tests. The tests showed that connections with larger key...
Test and Analysis of a New Ductile Shear Connection Design for RC Shear Walls
DEFF Research Database (Denmark)
Sørensen, Jesper Harrild; Hoang, Linh Cao; Olesen, John Forbes
2017-01-01
-bar loops. Contrary to the classical shear connections, the planes of the U-bar loops are here parallel to the plane of the wall elements. This feature enables a construction-friendly installation of the elements without the risk of rebars clashing. The core of mortar inside each U-bar loop is reinforced...
Zhou, Bang-Guo; Wang, Dan; Ren, Wei-Wei; Li, Xiao-Long; He, Ya-Ping; Liu, Bo-Ji; Wang, Qiao; Chen, Shi-Gao; Alizad, Azra; Xu, Hui-Xiong
2017-08-01
To evaluate the diagnostic performance of shear wave arrival time contour (SWATC) display for the diagnosis of breast lesions and to identify factors associated with the quality of shear wave propagation (QSWP) in breast lesions. This study included 277 pathologically confirmed breast lesions. Conventional B-mode ultrasound characteristics and shear wave elastography parameters were computed. Using the SWATC display, the QSWP of each lesion was assigned to a two-point scale: score 1 (low quality) and score 2 (high quality). Binary logistic regression analysis was performed to identify factors associated with QSWP. The area under the receiver operating characteristic curve (AUROC) for QSWP to differentiate benign from malignant lesions was 0.913, with a sensitivity of 91.9%, a specificity of 90.7%, a positive predictive value (PPV) of 74.0%, and a negative predictive value (NPV) of 97.5%. Compared with using the standard deviation of shear wave speed (SWS SD ) alone, SWS SD combined with QSWP increased the sensitivity from 75.8% to 93.5%, but decreased the specificity from 95.8% to 89.3% (P breast lesions.
Development of local shear bands and orientation gradients in fcc polycrystals
International Nuclear Information System (INIS)
Beaudoin, A.J. Jr.; Mecking, H.; Kocks, U.F.
1995-01-01
A finite element formulation which derives constitutive response from crystal plasticity theory is used to examine localized deformation in fcc polycrystals. The polycrystals are simple, idealized arrangements of grains. Localized deformations within individual grains lead to the development of domains that are separated by boundaries of high misorientation. Shear banding is seen to occur on a microscopic scale of grain dimensions. The important consequences of these simulations are that the predicted local inhomogeneities are meeting various requirements which make them possible nucleation sites for recrystallization
Effect of stress-state and spacing on voids in a shear-field
DEFF Research Database (Denmark)
Tvergaard, Viggo
2012-01-01
in the overall average stress state can be prescribed. This also allows for studies of the effect of different initial void spacing in the two in-plane coordinate directions. The stress states considered are essentially simple shear, with various levels of tensile stresses or compressive stresses superposed, i.......e. low positive stress triaxiality or even negative stress triaxiality. For high aspect ratio unit cells a clear localization band is found inside the cell, which actually represents several parallel bands, due to periodicity. In the materials represented by a low aspect ratio unit cell localization...
Turbulence-assisted shear exfoliation of graphene using household detergent and a kitchen blender
Varrla, Eswaraiah; Paton, Keith R.; Backes, Claudia; Harvey, Andrew; Smith, Ronan J.; McCauley, Joe; Coleman, Jonathan N.
2014-09-01
To facilitate progression from the lab to commercial applications, it will be necessary to develop simple, scalable methods to produce high quality graphene. Here we demonstrate the production of large quantities of defect-free graphene using a kitchen blender and household detergent. We have characterised the scaling of both graphene concentration and production rate with the mixing parameters: mixing time, initial graphite concentration, rotor speed and liquid volume. We find the production rate to be invariant with mixing time and to increase strongly with mixing volume, results which are important for scale-up. Even in this simple system, concentrations of up to 1 mg ml-1 and graphene masses of >500 mg can be achieved after a few hours mixing. The maximum production rate was ~0.15 g h-1, much higher than for standard sonication-based exfoliation methods. We demonstrate that graphene production occurs because the mean turbulent shear rate in the blender exceeds the critical shear rate for exfoliation.To facilitate progression from the lab to commercial applications, it will be necessary to develop simple, scalable methods to produce high quality graphene. Here we demonstrate the production of large quantities of defect-free graphene using a kitchen blender and household detergent. We have characterised the scaling of both graphene concentration and production rate with the mixing parameters: mixing time, initial graphite concentration, rotor speed and liquid volume. We find the production rate to be invariant with mixing time and to increase strongly with mixing volume, results which are important for scale-up. Even in this simple system, concentrations of up to 1 mg ml-1 and graphene masses of >500 mg can be achieved after a few hours mixing. The maximum production rate was ~0.15 g h-1, much higher than for standard sonication-based exfoliation methods. We demonstrate that graphene production occurs because the mean turbulent shear rate in the blender exceeds
Microalga propels along vorticity direction in a shear flow
Chengala, Anwar; Hondzo, Miki; Sheng, Jian
2013-05-01
Using high-speed digital holographic microscopy and microfluidics, we discover that, when encountering fluid flow shear above a threshold, unicellular green alga Dunaliella primolecta migrates unambiguously in the cross-stream direction that is normal to the plane of shear and coincides with the local fluid flow vorticity. The flow shear drives motile microalgae to collectively migrate in a thin two-dimensional horizontal plane and consequently alters the spatial distribution of microalgal cells within a given suspension. This shear-induced algal migration differs substantially from periodic rotational motion of passive ellipsoids, known as Jeffery orbits, as well as gyrotaxis by bottom-heavy swimming microalgae in a shear flow due to the subtle interplay between torques generated by gravity and viscous shear. Our findings could facilitate mechanistic solutions for modeling planktonic thin layers and sustainable cultivation of microalgae for human nutrition and bioenergy feedstock.
Transport reduction via shear flow modification of the cross phase
International Nuclear Information System (INIS)
Ware, A.S.; Terry, P.W.; Diamond, P.H.; Carreras, B.A.
1996-01-01
As a model example of the effect of E x B shear flow on the cross phase between electrostatic potential and pressure fluctuations, a nonlinear theory of resistive pressure gradient driven turbulence (RPGDT) in a shear flow is presented. This work builds on numerical studies of RPGDT, which have shown that both flow shear and curvature can affect the cross phase as well as the fluctuation levels. In this work, we show that the effect of shear flow on transport can be expressed through the temporal response of pressure to potential. It is shown heuristically that even in the case where the fluctuation levels are not modified, the flow shear still acts to reduce the phase angle between potential and pressure fluctuations, thereby suppressing transport. The scaling of the cross phase with flow shear and flow curvature is presented. (author)
Critical wall shear stress for the EHEDG test method
DEFF Research Database (Denmark)
Jensen, Bo Boye Busk; Friis, Alan
2004-01-01
In order to simulate the results of practical cleaning tests on closed processing equipment, based on wall shear stress predicted by computational fluid dynamics, a critical wall shear stress is required for that particular cleaning method. This work presents investigations that provide a critical...... wall shear stress of 3 Pa for the standardised EHEDG cleaning test method. The cleaning tests were performed on a test disc placed in a radial flowcell assay. Turbulent flow conditions were generated and the corresponding wall shear stresses were predicted from CFD simulations. Combining wall shear...... stress predictions from a simulation using the low Re k-epsilon and one using the two-layer model of Norris and Reynolds were found to produce reliable predictions compared to empirical solutions for the ideal flow case. The comparison of wall shear stress curves predicted for the real RFC...
Yielding and flow of sheared colloidal glasses
International Nuclear Information System (INIS)
Petekidis, G; Vlassopoulos, D; Pusey, P N
2004-01-01
We have studied some of the rheological properties of suspensions of hard-sphere colloids with particular reference to behaviour near the concentration of the glass transition. First we monitored the strain on the samples during and after a transient step stress. We find that, at all values of applied step stress, colloidal glasses show a rapid, apparently elastic, recovery of strain after the stress is removed. This recovery is found even in samples which have flowed significantly during stressing. We attribute this behaviour to 'cage elasticity', the recovery of the stress-induced distorted environment of any particle to a more isotropic state when the stress is removed. Second, we monitored the stress as the strain rate dot γ of flowing samples was slowly decreased. Suspensions which are glassy at rest show a stress which becomes independent of dot γ as dot γ →0. This limiting stress can be interpreted as the yield stress of the glass and agrees well both with the yield stress deduced from the step stress and recovery measurements and that predicted by a recent mode coupling theory of sheared suspensions. Thus, the behaviours under steady shearing and transient step stress both support the idea that colloidal glasses have a finite yield stress. We note however that the samples do exhibit a slow accumulation of strain due to creep at stresses below the yield stress
Shear viscosity coefficient from microscopic models
International Nuclear Information System (INIS)
Muronga, Azwinndini
2004-01-01
The transport coefficient of shear viscosity is studied for a hadron matter through microscopic transport model, the ultrarelativistic quantum molecular dynamics (UrQMD), using the Green-Kubo formulas. Molecular-dynamical simulations are performed for a system of light mesons in a box with periodic boundary conditions. Starting from an initial state composed of π,η,ω,ρ,φ with a uniform phase-space distribution, the evolution takes place through elastic collisions, production, and annihilation. The system approaches a stationary state of mesons and their resonances, which is characterized by common temperature. After equilibration, thermodynamic quantities such as the energy density, particle density, and pressure are calculated. From such an equilibrated state the shear viscosity coefficient is calculated from the fluctuations of stress tensor around equilibrium using Green-Kubo relations. We do our simulations here at zero net baryon density so that the equilibration times depend on the energy density. We do not include hadron strings as degrees of freedom so as to maintain detailed balance. Hence we do not get the saturation of temperature but this leads to longer equilibration times
Inplane shear capacity of reinforced composite masonry block walls
International Nuclear Information System (INIS)
White, W.H.; Tseng, W.S.
1981-01-01
The objective of this paper is to describe a test program performed to determine the inplane shear capacity, stiffness and ductility of composite masonry walls subjected to earthquake type loadings. Specimens were simultaneously subjected to a range of compressive loads to simulate dead load; and inplane shear loads with full load reversal to simulate the earthquake cycling load. The influence of horizontal and vertical reinforcing steel percentages on the inplane shear capacity, stiffness and ductility was also investigated. (orig./HP)
Effects of magnetic shear on current penetration in a tokamak
International Nuclear Information System (INIS)
Zhang Pengyun; Wang Long
2001-01-01
The penetrations of the parallel and perpendicular components of plasma currents are interrelated to each other due to the existence of magnetic shear in a tokamak configuration. Effects of the shear on the penetration of Fourier components of toroidal plasma current are analysed in a cylindrical column model. The current penetration is obviously strengthened by the shear for a bell-bike conductivity profile and low safety factor and low aspect ratio
Sheared-root inocula of vesicular-arbuscular mycorrhizal fungi.
Sylvia, D M; Jarstfer, A G
1992-01-01
For efficient handling, vesicular-arbuscular mycorrhizal fungi should be processed into small and uniform inocula; however, processing can reduce the inoculum density. In this article we describe the preparation and use of sheared-root inocula of Glomus spp. in which inoculum densities were increased during processing. Our objectives were to determine inoculum viability and density after shearing and to ascertain if the sheared inocula could be pelletized or used with a gel carrier. Root samples were harvested from aeroponic cultures, blotted dry, cut into 1-cm lengths, and sheared in a food processor for up to 80 s. After shearing, the inoculum was washed over sieves, and the propagule density in each fraction was determined. Sheared inocula were also encapsulated in carrageenan or used in a gel carrier. Shearing aeroponically produced root inocula reduced particle size. Propagule density increased with decreasing size fraction down to a size of 63 mum, after which propagule density decreased. The weighted-average propagule density of the inoculum was 135,380 propagules g (dry weight) of sheared root material. Sheared roots were encapsulated successfully in carrageenan, and the gel served as an effective carrier. Aeroponic root inoculum was stored dry at 4 degrees C for 23 months without significant reduction in propagule density; however, this material was not appropriate for shearing. Moist roots, useful for shearing, began to lose propagule density after 1 month of storage. Shearing proved to be an excellent method to prepare viable root inocula of small and uniform size, allowing for more efficient and effective use of limited inoculum supplies.
Low-n shear Alfven spectra in axisymmetric toroidal plasmas
International Nuclear Information System (INIS)
Cheng, C.Z.; Chance, M.S.
1985-11-01
In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfven continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed. 17 refs., 4 figs
Numerical modeling of shear stimulation in naturally fractured geothermal reservoirs
Ucar, Eren
2018-01-01
Shear-dilation-based hydraulic stimulations are conducted to create enhanced geothermal systems (EGS) from low permeable geothermal reservoirs, which are initially not amenable to energy production. Reservoir stimulations are done by injecting low-pressurized fluid into the naturally fractured formations. The injection aims to activate critically stressed fractures by decreasing frictional strength and ultimately cause a shear failure. The shear failure leads to a permanent ...
Shear wave elastography with a new reliability indicator
Directory of Open Access Journals (Sweden)
Christoph F. Dietrich
2016-09-01
Full Text Available Non-invasive methods for liver stiffness assessment have been introduced over recent years. Of these, two main methods for estimating liver fibrosis using ultrasound elastography have become established in clinical practice: shear wave elastography and quasi-static or strain elastography. Shear waves are waves with a motion perpendicular (lateral to the direction of the generating force. Shear waves travel relatively slowly (between 1 and 10 m/s. The stiffness of the liver tissue can be assessed based on shear wave velocity (the stiffness increases with the speed. The European Federation of Societies for Ultrasound in Medicine and Biology has published Guidelines and Recommendations that describe these technologies and provide recommendations for their clinical use. Most of the data available to date has been published using the Fibroscan (Echosens, France, point shear wave speed measurement using an acoustic radiation force impulse (Siemens, Germany and 2D shear wave elastography using the Aixplorer (SuperSonic Imagine, France. More recently, also other manufacturers have introduced shear wave elastography technology into the market. A comparison of data obtained using different techniques for shear wave propagation and velocity measurement is of key interest for future studies, recommendations and guidelines. Here, we present a recently introduced shear wave elastography technology from Hitachi and discuss its reproducibility and comparability to the already established technologies.
Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2010-01-01
This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear...... capacity of beams loaded primarily in shear and if ECC can partially or fully replace the conventional transverse steel reinforcement in beams. However, there is a lack of understanding of how the fibers affect the shear carrying capacity and deformation behavior of structural members if used either...
Simulation of shear and turbulence impact on wind turbine performance
DEFF Research Database (Denmark)
Wagner, Rozenn; Courtney, Michael; Larsen, Torben J.
Aerodynamic simulations (HAWC2Aero) were used to investigate the influence of the speed shear, the direction shear and the turbulence intensity on the power output of a multi-megawatt turbine. First simulation cases with laminar flow and power law wind speed profiles were compared to the case...... of a uniform inflow. Secondly, a similar analysis was done for cases with direction shear. In each case, we derived a standard power curve (function of the wind speed at hub height) and power curves obtained with various definitions of equivalent wind speed in order to reduce the scatter due to shear. Thirdly...
Development of Shear Connections in Steelconcrete Composite Structures
Biegus, Antoni; Lorenc, Wojciech
2015-03-01
Different types of shear connectors and modelling techniques are presented. Basic research conducted or presented after year 2000 is taken into consideration, following the idea of concrete dowel implemented in the form of perfobond strip at the beginning of the 1980s by F. Leonhardt. The latest research in the field of continuous shear connectors applied in bridges is highlited with special focus at the composite dowel shear connection, as it seems to be the most modern solution being strongly introduced to the industry. Final shape of composite dowel shear connection is presented.
Results of shear studies with 241-AY-101 sludge
International Nuclear Information System (INIS)
WARRANT, R.W.
2001-01-01
The Department of Energy's Tanks Focus Area (TFA) authorized a project to study the effect of shear on the settling properties of high-level waste sludge to support retrieval programs. A series of settling studies was conducted on a composite sample of tank 241-AY-101 (AY-101) material. Comparisons were made with duplicate samples that were sheared with a tissue homogenizer and allowed to settle. Aliquots of sheared and unsheared settled solids were submitted for chemical and radiological analyses. There are five major conclusions from the study that apply to AY-101 sludge: (1) Sludge settling rates are detectably decreased after shearing of particles by means of a tissue homogenizer. A significant decrease in the settling rates was measured after 2 minutes of shearing. A smaller additional decrease in the settling rates was observed after an additional 10 minutes of shearing. (2) Sodium and Cesium appear to be present in both the liquid and solid phases of the composite sample. (3) The shearing of the solids does not appear to significantly change the distribution of the radionuclides, ( 241 Am, 90 Sr, Total Alpha, or other radionuclides), within the solids. (4) The mean particle diameter decreases after shearing with the tissue homogenizer and affects the settling rate in proportion to the square of the particle diameter. (5) The sonication of the unsheared particles produces a similar particle size reduction to that of shearing with a tissue homogenizer. It is difficult to quantitatively compare the shear produced by a mixer pump installed in a double-shell tank with that produced by the tissue homogenizer in the laboratory. On a qualitative basis, the mixing pump would be expected to have less mechanical and more hydraulic shearing effect than the tissue homogenizer. Since the particle size distribution studies indicate that (for the AY-101 solids) the breaking up of particle aggregates is the main means of particle size reduction, then the hydraulic shearing
Improvement of shearing machine in the Tokai Reprocessing Plant
International Nuclear Information System (INIS)
Takae, Akiyoshi; Otani, Yoshikuni
1994-01-01
The shearing machine in the Tokai Reprocessing Plant has been improved and refurbished through its operational experience for about 20 years. Every component except the shear housing and magazine is changed for improved things by PNC, while the shearing machine had been designed and fabricated originally by a French Company. The improvement of the shearing machine was carried out for the purpose of settling the problems which were experienced in the past operation, and improving durability, remote maintainability, and operability. The details of their improvement work are described. (author)
Shear wave elastography with a new reliability indicator.
Dietrich, Christoph F; Dong, Yi
2016-09-01
Non-invasive methods for liver stiffness assessment have been introduced over recent years. Of these, two main methods for estimating liver fibrosis using ultrasound elastography have become established in clinical practice: shear wave elastography and quasi-static or strain elastography. Shear waves are waves with a motion perpendicular (lateral) to the direction of the generating force. Shear waves travel relatively slowly (between 1 and 10 m/s). The stiffness of the liver tissue can be assessed based on shear wave velocity (the stiffness increases with the speed). The European Federation of Societies for Ultrasound in Medicine and Biology has published Guidelines and Recommendations that describe these technologies and provide recommendations for their clinical use. Most of the data available to date has been published using the Fibroscan (Echosens, France), point shear wave speed measurement using an acoustic radiation force impulse (Siemens, Germany) and 2D shear wave elastography using the Aixplorer (SuperSonic Imagine, France). More recently, also other manufacturers have introduced shear wave elastography technology into the market. A comparison of data obtained using different techniques for shear wave propagation and velocity measurement is of key interest for future studies, recommendations and guidelines. Here, we present a recently introduced shear wave elastography technology from Hitachi and discuss its reproducibility and comparability to the already established technologies.
Failure modes of low-rise shear walls
International Nuclear Information System (INIS)
Farrar, C.R.; Reed, J.W.; Salmon, M.W.
1993-01-01
A summary of available data concerning the structural response of low-rise shear walls is presented. These data will be used to address two failure modes associated with shear wall structures. First, the data concerning the seismic capacity of the shear walls are examined, with emphasis on excessive deformations that can cause equipment failure. Second, the data concerning the dynamic properties of shear walls (stiffness and damping) that are necessary for computing the seismic inputs to attached equipment are summarized. This case addresses the failure of equipment when the structure remains functional
Direct Shear Behavior of Fiber Reinforced Concrete Elements
Directory of Open Access Journals (Sweden)
Hussein Al-Quraishi
2018-01-01
Full Text Available Improving the accuracy of load-deformation behavior, failure mode, and ultimate load capacity for reinforced concrete members subjected to in-plane loadings such as corbels, wall to foundation connections and panels need shear strength behavior to be included. Shear design in reinforced concrete structures depends on crack width, crack slippage and roughness of the surface of cracks. This paper illustrates results of an experimental investigation conducted to investigate the direct shear strength of fiber normal strength concrete (NSC and reactive powder concrete (RPC. The tests were performed along a pre-selected shear plane in concrete members named push-off specimens. The effectiveness of concrete compressive strength, volume fraction of steel fiber, and shear reinforcement ratio on shear transfer capacity were considered in this study. Furthermore, failure modes, shear stress-slip behavior, and shear stress-crack width behavior were also presented in this study. Tests’ results showed that volume fraction of steel fiber and compressive strength of concrete in NSC and RPC play a major role in improving the shear strength of concrete. As expectedly, due to dowel action, the shear reinforcement is the predominant factor in resisting the shear stress. The shear failure of NSC and RPC has the sudden mode of failure (brittle failure with the approximately linear behavior of shear stress-slip relationship till failure. Using RPC instead of NSC with the same amount of steel fibers in constructing the push-off specimen result in high shear strength. In NSC, shear strength influenced by the three major factors; crack surface friction, aggregate interlock and steel fiber content if present. Whereas, RPC has only steel fiber and cracks surface friction influencing the shear strength. Due to cementitious nature of RPC in comparisons with NSC, the RPC specimen shows greater cracks width. It is observed that the Mattock model gives very satisfactory
Shear crack formation and propagation in reinforced Engineered Cementitious Composites
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2011-01-01
capacity of beams loaded primarily in shear. The experimental program consists of ECC with short randomly distributed polyvinyl alcohol (PVA) fiber beams with different stirrup arrangements and conventional reinforced concrete (R/C) counterparts for comparison. The shear crack formation mechanism of ECC......This paper describes an experimental investigation of the shear behaviour of beams consisting of steel reinforced Engineered Cementitious Composites (R/ECC). Based on the strain hardening and multiple cracking behaviour of ECC, this study investigates the extent to which ECC influences the shear...
Shear weakening for different lithologies observed at different saturation stages
Diethart-Jauk, Elisabeth; Gegenhuber, Nina
2018-01-01
For this study, samples from different lithologies ("Leitha"-limestone, "Dachstein"-limestone, "Haupt"-dolomite, "Bunt"-sandstone, Grey Berea sandstone, granite, quartzite and basalt) were selected. Samples were dried at 70 °C, respectively 105 °C and were saturated with brine. Mass, porosity, permeability, compressional and shear wave velocity were determined from dry and brine saturated samples at laboratory conditions, based on an individual measurement program. Shear modulus was calculated to find out, if shear weakening exists for the dataset. Shear weakening means that shear modulus of dry samples is higher than of saturated samples, but it is assumed that shear modulus is unaffected by saturation. "Dachstein"-limestone and basalt show shear weakening, quartzite samples show both weakening and hardening. Granite samples are affected by temperature, after drying with 105 °C no change can be observed anymore. "Bunt"-sandstone samples show a change in the shear modulus in a small extent, although they may contain clay minerals. The other lithologies show no effect. Explanations for carbonate samples can be the complicated pore structure, for basalt it could be that weathering creates clay minerals which are known as causes for a change of the shear modulus. Fluid viscosity can also be an important factor.
Strain gradient drives shear banding in metallic glasses
Tian, Zhi-Li; Wang, Yun-Jiang; Chen, Yan; Dai, Lan-Hong
2017-09-01
Shear banding is a nucleation-controlled process in metallic glasses (MGs) involving multiple temporal-spatial scales, which hinders a concrete understanding of its structural origin down to the atomic scale. Here, inspired by the morphology of composite materials, we propose a different perspective of MGs as a hard particle-reinforced material based on atomic-scale structural heterogeneity. The local stable structures indicated by a high level of local fivefold symmetry (L5FS) act as hard "particles" which are embedded in the relatively soft matrix. We demonstrate this concept by performing atomistic simulations of shear banding in CuZr MG. A shear band is prone to form in a sample with a high degree of L5FS which is slowly quenched from the liquid. An atomic-scale analysis on strain and the structural evolution reveals that it is the strain gradient effect that has originated from structural heterogeneity that facilitates shear transformation zones (STZs) to mature shear bands. An artificial composite model with a high degree of strain gradient, generated by inserting hard MG strips into a soft MG matrix, demonstrates a great propensity for shear banding. It therefore confirms the critical role strain gradient plays in shear banding. The strain gradient effect on shear banding is further quantified with a continuum model and a mechanical instability analysis. These physical insights might highlight the strain gradient as the hidden driving force in transforming STZs into shear bands in MGs.
Ruppel, Antonia; Läufer, Andreas; Lisker, Frank; Jacobs, Joachim; Elburg, Marlina; Damaske, Detlef; Lucka, Nicole
2013-04-01
Structural investigations were carried out along the Main Shear Zone (MSZ) of western Sør Rondane (22°-25°E, 71.5°-72.5°S) to gain new information about the position of the East-/West-Gondwana suture and the ancient plate tectonic configuration during Gondwana amalgamation. The WSW-ENE striking MSZ divides south-western Sør Rondane in a northern amphibolite-facies terrane and a southern tonalite-trondhjemite-granodiorite (TTG) terrane. The structure can be traced over a distance of ca. 100 km and reaches several hundred meters in width. It is characterized by a right-lateral sense of movement and marked by a transpressional and also transtensional regime. Ductilely deformed granitoids (ca. 560 Ma: SHRIMP U-Pb of zircon) and ductile - brittle structures, which evolved in a transitional ductile to brittle regime in an undeformed syenite (ca. 499-459 Ma, Ar-Ar mica), provide a late Proterozoic/ early Paleozoic time limit for the activity of the shear zone (Shiraishi et al., 2008; Shiraishi et al., 1997). Documentation of ductile and brittle deformation allows reconstructing up to eight deformation stages. Cross-cutting relationships of structural features mapped in the field complemented by published kinematic data reveal the following relative age succession: [i] Dn+1 - formation of the main foliation during peak metamorphism, [ii] Dn+2 - isoclinal, intrafolial folding of the main foliation, mostly foliation-parallel mylonitic shear zones (1-2 meter thick), [iii] Dn+3 - formation of tight to closed folds, [iv] Dn+4 - formation of relatively upright, large-scale open folds, [v] Dn+5 - granitoid intrusion (e.g. Vengen granite), [vi] Dn+6 - dextral shearing between amphibolite and TTG terranes, formation of the MSZ, [vii] Dn+7 - intrusion of late- to post-tectonic granitoids, first stage of brittle deformation (late shearing along MSZ), intrusion of post-kinematic mafic dykes, [viii] Dn+8 - second stage of brittle deformation including formation of conjugate fault
Haxhimali, Tomorr; Rudd, Robert E.; Cabot, William H.; Graziani, Frank R.
2015-11-01
We present molecular dynamics (MD) calculations of shear viscosity for asymmetric mixed plasma for thermodynamic conditions relevant to astrophysical and inertial confinement fusion plasmas. Specifically, we consider mixtures of deuterium and argon at temperatures of 100-500 eV and a number density of 1025 ions/cc. The motion of 30 000-120 000 ions is simulated in which the ions interact via the Yukawa (screened Coulomb) potential. The electric field of the electrons is included in this effective interaction; the electrons are not simulated explicitly. Shear viscosity is calculated using the Green-Kubo approach with an integral of the shear stress autocorrelation function, a quantity calculated in the equilibrium MD simulations. We systematically study different mixtures through a series of simulations with increasing fraction of the minority high-Z element (Ar) in the D-Ar plasma mixture. In the more weakly coupled plasmas, at 500 eV and low Ar fractions, results from MD compare very well with Chapman-Enskog kinetic results. In the more strongly coupled plasmas, the kinetic theory does not agree well with the MD results. We develop a simple model that interpolates between classical kinetic theories at weak coupling and the Murillo Yukawa viscosity model at higher coupling. This hybrid kinetics-MD viscosity model agrees well with the MD results over the conditions simulated, ranging from moderately weakly coupled to moderately strongly coupled asymmetric plasma mixtures.
Xu, Chet C; Chan, Roger W; Sun, Han; Zhan, Xiaowei
2017-11-01
A mixed-effects model approach was introduced in this study for the statistical analysis of rheological data of vocal fold tissues, in order to account for the data correlation caused by multiple measurements of each tissue sample across the test frequency range. Such data correlation had often been overlooked in previous studies in the past decades. The viscoelastic shear properties of the vocal fold lamina propria of two commonly used laryngeal research animal species (i.e. rabbit, porcine) were measured by a linear, controlled-strain simple-shear rheometer. Along with published canine and human rheological data, the vocal fold viscoelastic shear moduli of these animal species were compared to those of human over a frequency range of 1-250Hz using the mixed-effects models. Our results indicated that tissues of the rabbit, canine and porcine vocal fold lamina propria were significantly stiffer and more viscous than those of human. Mixed-effects models were shown to be able to more accurately analyze rheological data generated from repeated measurements. Copyright © 2017 Elsevier Ltd. All rights reserved.
Zhang, Ye; Zhang, Yi; Burke, Jeffrey M; Gleitsman, Kristin; Friedrich, Sarah M; Liu, Kelvin J; Wang, Tza-Huei
2016-12-01
An inexpensive, magnetic thermoplastic nanomaterial is developed utilizing a hierarchical layering of micro- and nanoscale silica lamellae to create a high-surface-area and low-shear substrate capable of capturing vast amounts of ultrahigh-molecular-weight DNA. Extraction is performed via a simple 45 min process and is capable of achieving binding capacities up to 1 000 000 times greater than silica microparticles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Simple arithmetic: not so simple for highly math anxious individuals.
Chang, Hyesang; Sprute, Lisa; Maloney, Erin A; Beilock, Sian L; Berman, Marc G
2017-12-01
Fluency with simple arithmetic, typically achieved in early elementary school, is thought to be one of the building blocks of mathematical competence. Behavioral studies with adults indicate that math anxiety (feelings of tension or apprehension about math) is associated with poor performance on cognitively demanding math problems. However, it remains unclear whether there are fundamental differences in how high and low math anxious individuals approach overlearned simple arithmetic problems that are less reliant on cognitive control. The current study used functional magnetic resonance imaging to examine the neural correlates of simple arithmetic performance across high and low math anxious individuals. We implemented a partial least squares analysis, a data-driven, multivariate analysis method to measure distributed patterns of whole-brain activity associated with performance. Despite overall high simple arithmetic performance across high and low math anxious individuals, performance was differentially dependent on the fronto-parietal attentional network as a function of math anxiety. Specifically, low-compared to high-math anxious individuals perform better when they activate this network less-a potential indication of more automatic problem-solving. These findings suggest that low and high math anxious individuals approach even the most fundamental math problems differently. © The Author (2017). Published by Oxford University Press.
Generalized Gradient Approximation Made Simple
International Nuclear Information System (INIS)
Perdew, J.P.; Burke, K.; Ernzerhof, M.
1996-01-01
Generalized gradient approximations (GGA close-quote s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. copyright 1996 The American Physical Society
Rheometry-PIV of shear-thickening wormlike micelles.
Marín-Santibañez, Benjamín M; Pérez-Gonzalez, José; de Vargas, Lourdes; Rodríguez-Gonzalez, Francisco; Huelsz, Guadalupe
2006-04-25
The shear-thickening behavior of an equimolar semidilute aqueous solution of 40 mM/L cetylpyridinium chloride and sodium salicylate was studied in this work by using a combined method of rheometry and particle image velocimetry (PIV). Experiments were conducted at 27.5 degrees C with Couette, vane-bob, and capillary rheometers in order to explore a wide shear stress range as well as the effect of boundary conditions and time of flow on the creation and destruction of shear-induced structures (SIS). The use of the combined method of capillary rheometry with PIV allowed the detection of fast spatial and temporal variations in the flow kinematics, which are related to the shear-thickening behavior and the dynamics of the SIS but are not distinguished by pure rheometrical measurements. A rich-in-details flow curve was found for this solution, which includes five different regimes. Namely, at very low shear rates a Newtonian behavior was found, followed by a shear thinning one in the second regime. In the third, shear banding was observed, which served as a precursor of the SIS and shear-thickening. The fourth and fifth regimes in the flow curve were separated by a spurtlike behavior, and they clearly evidenced the existence of shear-thickening accompanied by stick-slip oscillations at the wall of the rheometer, which subsequently produced variations in the shear rate under shear stress controlled flow. Such a stick-slip phenomenon prevailed up to the highest shear stresses used in this work and was reflected in asymmetric velocity profiles with spatial and temporal variations linked to the dynamics of creation and breakage of the SIS. The presence of apparent slip at the wall of the rheometer provides an energy release mechanism which leads to breakage of the SIS, followed by their further reformation during the stick part of the cycles. In addition, PIV measurements allowed the detection of apparent slip at the wall, as well as mechanical failures in the bulk of the
Simulation of shear thickening in attractive colloidal suspensions.
Pednekar, Sidhant; Chun, Jaehun; Morris, Jeffrey F
2017-03-01
The influence of attractive forces between particles under conditions of large particle volume fraction, ϕ, is addressed using numerical simulations which account for hydrodynamic, Brownian, conservative and frictional contact forces. The focus is on conditions for which a significant increase in the apparent viscosity at small shear rates, and possibly the development of a yield stress, is observed. The high shear rate behavior for Brownian suspensions has been shown in recent work [R. Mari, R. Seto, J. F. Morris and M. M. Denn PNAS, 2015, 112, 15326-15330] to be captured by the inclusion of pairwise forces of two forms, one a contact frictional interaction and the second a repulsive force often found in stabilized colloidal dispersions. Under such conditions, shear thickening is observed when shear stress is comparable to the sum of the Brownian stress, kT/a 3 , and a characteristic stress based on the combination of interparticle force, i.e. σ ∼ F 0 /a 2 with kT the thermal energy, F 0 the repulsive force scale and a the particle radius. At sufficiently large ϕ, this shear thickening can be very abrupt. Here it is shown that when attractive interactions are present with the noted forces, the shear thickening is obscured, as the viscosity shear thins with increasing shear rate, eventually descending from an infinite value (yield stress conditions) to a plateau at large stress; this plateau is at the same level as the large-shear rate viscosity found in the shear thickened state without attractive forces. It is shown that this behavior is consistent with prior observations in shear thickening suspensions modified to be attractive through depletion flocculation [V. Gopalakrishnan and C. F. Zukoski J. Rheol., 2004, 48, 1321-1344]. The contributions of the contact, attractive, and hydrodynamics forces to the bulk stress are presented, as are the contact networks found at different attractive strengths.
Research Advances on Fabricated Shear Wall System
Liu, Xudong; Wang, Donghui; Wang, Sheng; Zhai, Yu
2018-03-01
With the rapid development of the construction industry, building energy consumption has been increasing, has become a problem that can not be ignored. It is imperative to develop energy-saving buildings. A new type of prefabricated shear wall is assembled and partially assembled by prefabricated parts, and some concrete is spliced together. The new structure has good integrity, seismic resistance and excellent energy saving and environmental protection performance. It reduces building energy consumption to a great extent. Therefore, the design method, manufacturing process, site assembly process and key technical problems of the system are discussed. For the construction industry gradually entered the energy conservation, environmental protection, safety and durability of sustainable development laid the foundation.
Friction welding; Magnesium; Finite element; Shear test.
Directory of Open Access Journals (Sweden)
Leonardo Contri Campanelli
2013-06-01
Full Text Available Friction spot welding (FSpW is one of the most recently developed solid state joining technologies. In this work, based on former publications, a computer aided draft and engineering resource is used to model a FSpW joint on AZ31 magnesium alloy sheets and subsequently submit the assembly to a typical shear test loading, using a linear elastic model, in order to conceive mechanical tests results. Finite element analysis shows that the plastic flow is concentrated on the welded zone periphery where yield strength is reached. It is supposed that “through the weld” and “circumferential pull-out” variants should be the main failure behaviors, although mechanical testing may provide other types of fracture due to metallurgical features.
The phase mixing of shear Alfven waves
International Nuclear Information System (INIS)
Uberoi, C.
1993-04-01
The phase mixing of shear Alfven waves is discussed as a current sheets crossover phenomena by using the well-behaved time dependent solution of the Alfven wave equation. This method is a more direct approach than the initial value problem technique to find the collisionless damping time of the surface waves, which as it represents the coherency loss is argued to be the phase mixing time. The phase mixing time obtained by both the methods compares well. The direct method however, has an advantage that no particular profile for the magnetic field variation need to be chosen and secondly the phase mixing time and the time scale for which the resistivity effects become important can be expressed conveniently in terms of Alfven transit times before crossover. (author). 11 refs
Seismic shear waves as Foucault pendulum
Snieder, Roel; Sens-Schönfelder, Christoph; Ruigrok, Elmer; Shiomi, Katsuhiko
2016-03-01
Earth's rotation causes splitting of normal modes. Wave fronts and rays are, however, not affected by Earth's rotation, as we show theoretically and with observations made with USArray. We derive that the Coriolis force causes a small transverse component for P waves and a small longitudinal component for S waves. More importantly, Earth's rotation leads to a slow rotation of the transverse polarization of S waves; during the propagation of S waves the particle motion behaves just like a Foucault pendulum. The polarization plane of shear waves counteracts Earth's rotation and rotates clockwise in the Northern Hemisphere. The rotation rate is independent of the wave frequency and is purely geometric, like the Berry phase. Using the polarization of ScS and ScS2 waves, we show that the Foucault-like rotation of the S wave polarization can be observed. This can affect the determination of source mechanisms and the interpretation of observed SKS splitting.
Shear buckling of cylindrical vessels benchmark exercise
International Nuclear Information System (INIS)
Dostal, M; Austin, N.; Combescure, A.; Peano, A.; Angeloni, P.
1987-01-01
In Liquid Metal Fast Breeder Reactors (LMFBR) potential shear buckling failures of the primary vessel, induced through seismic excitations, have to be considered. The problem is particularly severe in pool type reactors due to their large size, radius of approximately 10 m, coupled with small wall thicknesses of 50 mm and less. The object of this paper is to provide a comparison of three different computer codes capable of performing buckling analyses and to demonstrate on practical problems the level of accuracy that may be expected in design analyses. Three computer codes were examined ABAQUS, CASTEM (INCA/BILBO) and NOVNL and the computer results were compared directly with experimental data and other commonly used empirical formula. The joint effort was co-ordinated through the CEC Working Group on Codes and Standards AG2. (orig./GL)
Lattice shear distortions in fluorite structure oxides
International Nuclear Information System (INIS)
Faber, J. Jr.; Mueller, M.H.; Hitterman, R.L.
1979-01-01
Crystallographic shear distortions have been observed in fluorite structure, single crystals of UO 2 and Zr(Ca)O 2 /sub-x/ by neutron-diffraction techniques. These distortions localize on the oxygen sublattice and do not require the presence of an external strain. The internal rearrangement mode in UO 2 is a transverse, zone boundary q vector = 2π/a (0.5, 0.0) deformation with amplitude 0.014 A. In Zr(Ca)O/sub 2-x/, the mode is a longitudinal, q vector = 2-/a (0,0,0.5) deformation with amplitude 0.23 A. Cation-anion elastic interactions dominate in selecting the nature of the internal distortion
Illuminating magma shearing processes via synchrotron imaging
Lavallée, Yan; Cai, Biao; Coats, Rebecca; Kendrick, Jackie E.; von Aulock, Felix W.; Wallace, Paul A.; Le Gall, Nolwenn; Godinho, Jose; Dobson, Katherine; Atwood, Robert; Holness, Marian; Lee, Peter D.
2017-04-01
Our understanding of geomaterial behaviour and processes has long fallen short due to inaccessibility into material as "something" happens. In volcanology, research strategies have increasingly sought to illuminate the subsurface of materials at all scales, from the use of muon tomography to image the inside of volcanoes to the use of seismic tomography to image magmatic bodies in the crust, and most recently, we have added synchrotron-based x-ray tomography to image the inside of material as we test it under controlled conditions. Here, we will explore some of the novel findings made on the evolution of magma during shearing. These will include observations and discussions of magma flow and failure as well as petrological reaction kinetics.
Reynolds stress and shear flow generation
DEFF Research Database (Denmark)
Korsholm, Søren Bang; Michelsen, Poul; Naulin, V.
2001-01-01
The so-called Reynolds stress may give a measure of the self-consistent flow generation in turbulent fluids and plasmas by the small-scale turbulent fluctuations. A measurement of the Reynolds stress can thus help to predict flows, e.g. shear flows in plasmas. This may assist the understanding...... of improved confinement scenarios such as H-mode confinement regimes. However, the determination of the Reynolds stress requires measurements of the plasma potential, a task that is difficult in general and nearly impossible in hot plasmas in large devices. In this work we investigate an alternative method......, based on density measurements, to estimate the Reynolds stress, and demonstrate the validity range of this quantity, which we term the pseudo-Reynolds stress. The advantage of such a quantity is that accurate measurements of density fluctuations are much easier to obtain experimentally. Prior...
3D imaging of vesicles in hyaloclastic fragments - clues to syn-eruptive shear conditions
Helo, C.; Flaws, A.; Hess, K.; Franz, A.; Clague, D. A.; Dingwell, D. B.
2011-12-01
3D imaging of stretched vesicles in hyaloclastic fragments has been used to investigate the shear environment of mild pyroclastic eruptions at mid-ocean ridges. X-ray computed tomography offers an attractive non-invasive method to investigate geomaterials at a high resolution for the geometry of the different phases. In this study, we have imaged vesicles within two types of basaltic glass fragments. Stretched, ellipsoid-shaped vesicles in thin limu o Pele and tubular vesicles in a pumiceous fragment. Both types originate from pyroclastic activity on Axial Seamount, Juan de Fuca ridge. Rapid quenching of the glass has prevented extensive bubble relaxation and information about syn-eruptive shear and differential stress conditions is stored, as the dimensions of a stretched bubble directly relates to the extent and mode of shearing. The X-ray tomography data was processed using a set of codes based on edge detection and ellipsoid fitting to acquire quantitative information on the shape of the stretched vesicles. Preliminary results demonstrate, that the geometry of the stretched vesicles, e.g., the elongation of the vesicle with respect to the calculated undeformed radius, is in accordance with simple shear scenarios. Stored differential stress ranges from 5 kPa to 90 kPa with shear rates between 3.2x102 s-1 and 5.7x3 s-1 within a single limu o Pele fragment. This range may be explained by either variable time available for relaxation as the cooling front proceeds through the fragment, complex interplay in space and time between fragmentation and quenching, bubble clusters mutually inhibiting each others extend of deformation, or any combination of these. Bubble relaxation time scales are less then 0.005 s providing constraints on the timeframe for cooling to the glass transition. Qualitative analyses of the tube pumice indicates that the tubular structures grow in length by coalescence of vertically aligned ellipsoid-shaped vesicles, and in width by coalescence of
International Nuclear Information System (INIS)
Choedkiatsakul, I.; Ngaosuwan, K.; Assabumrungrat, S.; Tabasso, S.; Cravotto, G.
2015-01-01
A new simple flow system which is made up of a multi-rotor high-shear mixer connected to a multimode microwave reactor has been assembled. This simple loop reactor has been successfully used in the NaOH-catalyzed transesterification of refined palm oil in methanol. Thanks to optimal mass/heat transfer, full conversion was achieved within 5 min (biodiesel yield of 99.80%). High-quality biodiesel was obtained that is in accordance with international specifications and analytical ASTM standards. The procedure's high efficiency and low energy consumption should pave the way for process scale up. - Highlights: • The combination of HSM-MW flow system for biodiesel production has been proposed. • Highly efficient mass and heat transfer in transesterification reaction. • The hybrid reactor enables a complete conversion in 5 min reaction time. • The new system halved the energy consumption of conventional processes
A wall shear stress sensor using a pair of sidewall doped cantilevers
Nguyen, Thanh-Vinh; Kazama, Ryohei; Takahashi, Hidetoshi; Takahata, Tomoyuki; Matsumoto, Kiyoshi; Shimoyama, Isao
2017-07-01
In this paper, we report on a micro-electro mechanical system (MEMS)-based piezoresistive sensor for measuring shear stress induced by an airflow. The advantages of the proposed sensor include a simple sensing method and a high resonance frequency due to the small size of the sensing elements. Our sensor consists of a pair of 3 µm thick cantilevers with piezoresistors formed on the sidewall of their hinges to detect lateral deformation in the cantilevers induced by an airflow. Each cantilever has a 200 µm × 400 µm plate supported by two 150 µm long, 4 µm wide beams. The piezoresistors on the two cantilevers are designed to deform in opposite manners when a shear stress is applied and in the same manner when a pressure is applied. Therefore, the applied shear stress can be detected from the difference in the responses of the two cantilevers without becoming conflated with pressure. In this paper, the design, fabrication and evaluation of the proposed sensor are reported and compared to numerical simulation results. From the experimental results, the resolution of the sensor and its first resonance frequency are 1.3 Pa and 3.9 kHz, respectively. Moreover, we show that the effect of temperature on the readout of the sensor can be eliminated using a temperature-compensating piezoresistor fabricated on the same sensor chip. Finally, using the fabricated sensor, the measurement of the shear stress induced by an airflow with velocity between -10 and 10 m s-1 is demonstrated.
A wall shear stress sensor using a pair of sidewall doped cantilevers
International Nuclear Information System (INIS)
Nguyen, Thanh-Vinh; Shimoyama, Isao; Kazama, Ryohei; Takahashi, Hidetoshi; Takahata, Tomoyuki; Matsumoto, Kiyoshi
2017-01-01
In this paper, we report on a micro-electro mechanical system (MEMS)-based piezoresistive sensor for measuring shear stress induced by an airflow. The advantages of the proposed sensor include a simple sensing method and a high resonance frequency due to the small size of the sensing elements. Our sensor consists of a pair of 3 µ m thick cantilevers with piezoresistors formed on the sidewall of their hinges to detect lateral deformation in the cantilevers induced by an airflow. Each cantilever has a 200 µ m × 400 µ m plate supported by two 150 µ m long, 4 µ m wide beams. The piezoresistors on the two cantilevers are designed to deform in opposite manners when a shear stress is applied and in the same manner when a pressure is applied. Therefore, the applied shear stress can be detected from the difference in the responses of the two cantilevers without becoming conflated with pressure. In this paper, the design, fabrication and evaluation of the proposed sensor are reported and compared to numerical simulation results. From the experimental results, the resolution of the sensor and its first resonance frequency are 1.3 Pa and 3.9 kHz, respectively. Moreover, we show that the effect of temperature on the readout of the sensor can be eliminated using a temperature-compensating piezoresistor fabricated on the same sensor chip. Finally, using the fabricated sensor, the measurement of the shear stress induced by an airflow with velocity between −10 and 10 m s −1 is demonstrated. (paper)
Spectral and evolutionary analysis of advection-diffusion equations and the shear flow paradigm
International Nuclear Information System (INIS)
Thyagaraja, A.; Loureiro, N.; Knight, P.J.
2002-01-01
Advection-diffusion equations occur in a wide variety of fields in many contexts of active and passive transport in fluids and plasmas. The effects of sheared advective flows in the presence of irreversible processes such as diffusion and viscosity are of considerable current interest in tokamak and astrophysical contexts, where they are thought to play a key role in both transport and the dynamical structures characteristic of electromagnetic plasma turbulence. In this paper we investigate the spectral and evolutionary properties of relatively simple, linear, advection-diffusion equations. We apply analytical approaches based on standard Green's function methods to obtain insight into the nature of the spectra when the advective and diffusive effects occur separately and in combination. In particular, the physically interesting limit of small (but finite) diffusion is studied in detail. The analytical work is extended and supplemented by numerical techniques involving a direct solution of the eigenvalue problem as well as evolutionary studies of the initial value problem using a parallel code, CADENCE. The three approaches are complementary and entirely consistent with each other when appropriate comparison is made. They reveal different aspects of the properties of the advection-diffusion equation, such as the ability of sheared flows to generate a direct cascade to high wave numbers transverse to the advection and the consequent enhancement of even small amounts of diffusivity. The invariance properties of the spectra in the low diffusivity limit and the ability of highly sheared, jet-like flows to 'confine' transport to low shear regions are demonstrated. The implications of these properties in a wider context are discussed and set in perspective. (author)
Contact force structure and force chains in 3D sheared granular systems
Mair, Karen; Jettestuen, Espen; Abe, Steffen
2010-05-01
Faults often exhibit accumulations of granular debris, ground up to create a layer of rock flour or fault gouge separating the rigid fault walls. Numerical simulations and laboratory experiments of sheared granular materials, suggest that applied loads are preferentially transmitted across such systems by transient force networks that carry enhanced forces. The characterisation of such features is important since their nature and persistence almost certainly influence the macroscopic mechanical stability of these systems and potentially that of natural faults. 3D numerical simulations of granular shear are a valuable investigation tool since they allow us to track individual particle motions, contact forces and their evolution during applied shear, that are difficult to view directly in laboratory experiments or natural fault zones. In characterising contact force distributions, it is important to use global structure measures that allow meaningful comparisons of granular systems having e.g. different grain size distributions, as may be expected at different stages of a fault's evolution. We therefore use a series of simple measures to characterise the structure, such as distributions and correlations of contact forces that can be mapped onto a force network percolation problem as recently proposed by Ostojic and coworkers for 2D granular systems. This allows the use of measures from percolation theory to both define and characterise the force networks. We demonstrate the application of this method to 3D simulations of a sheared granular material. Importantly, we then compare our measure of the contact force structure with macroscopic frictional behaviour measured at the boundaries of our model to determine the influence of the force networks on macroscopic mechanical stability.
Sheared flow layer formation in tokamak plasmas with reversed magnetic shear
International Nuclear Information System (INIS)
Dong, J.Q.; Long, Y.X.; Mou, Z.Z.; Zhang, J.H.; Li, J.Q.
2005-01-01
Sheared flow layer (SFL) formation due to magnetic energy release through tearing-reconnections in tokamak plasmas is investigated. The characteristics of the SFLs created in the development of double tearing mode, mediated by electron viscosity in configurations with non-monotonic safety factor q profiles and, therefore, two rational flux surfaces of same q value, are analyzed in detail as an example. Quasi-linear simulations demonstrate that the sheared flows induced by the mode have desirable characteristics (lying at the boundaries of the magnetic islands), and sufficient levels required for internal transport barrier (ITB) formation. A possible correlation of the SFLs with experimental observations, that double transport barrier structures are preferentially formed in proximity of the two rational surfaces, is also proffered. (author)
Motion of dislocation kinks in a simple model crystal
International Nuclear Information System (INIS)
Koizumi, H.; Suzuki, T.
2005-01-01
To investigate the effects of lattice periodicity on kink motion, a molecular-dynamic simulation for a kink in a screw dislocation has been performed in a simple model lattice of diamond type. The Stillinger-Weber potential is assumed to act between atoms. Under applied stresses larger than 0.0027G, a long distance motion of a kink is possible, where G is the shear modulus. A moving kink emits lattice waves and loses its kinetic energy, which is compensated by the applied stress. The kink attains a terminal velocity after moving a few atomic distances. The kink velocity is not proportional to the applied stress, and exceeds the shear wave velocity when the applied stress is larger than 0.026G. The energy loss of the moving kink is one order of magnitude smaller than that of a moving straight dislocation and is about the same order of magnitude as the theoretical value of phonon-scattering mechanisms at room temperature
Emergence Issues - not so simple
African Journals Online (AJOL)
Anaesthetics Supplement: Emergence Issues - not so simple. S Afr Fam Pract 2014. Vol 56 No 2 Supplement 1. Introduction. Emergence from anaesthesia is by definition the process of return to baseline physiological function of all organ systems after cessation of administration of general anaesthesia and is the stage from ...
MINAMI, Haruo
2016-01-01
For a compact simple Lie group $G$, we show that the element $[G, \\mathcal{L}] \\in \\pi^S_*(S^0)$ represented by the pair $(G, \\mathcal{L})$ is zero, where $\\mathcal{L}$ denotes the left invariant framing of $G$. The proof relies on the method of E. Ossa [Topology, 21 (1982), 315–323].
International Nuclear Information System (INIS)
Kimsanov, B.Kh.; Karimov, M.B.
1998-01-01
From glycerin derivatives the considerable interest is present simple ethers because many of them are biological active and found wide practical using as an effect drugs, inters for thin organic synthesis, vehicle for injections, regulators of plants growth, reagents, components for perfumery-cosmetic goods and etc
Solving Simple Kinetics without Integrals
de la Pen~a, Lisandro Herna´ndez
2016-01-01
The solution of simple kinetic equations is analyzed without referencing any topic from differential equations or integral calculus. Guided by the physical meaning of the rate equation, a systematic procedure is used to generate an approximate solution that converges uniformly to the exact solution in the case of zero, first, and second order…
Grief: Difficult Times, Simple Steps.
Waszak, Emily Lane
This guide presents techniques to assist others in coping with the loss of a loved one. Using the language of 9 layperson, the book contains more than 100 tips for caregivers or loved ones. A simple step is presented on each page, followed by reasons and instructions for each step. Chapters include: "What to Say"; "Helpful Things to Do"; "Dealing…
DEFF Research Database (Denmark)
Ellum, J.C.
Anvisningen gennemgår dimensioneringen og bringer detaljerede konstruktionstegninger til simple stålrammebygninger, dvs. lukkede, fritliggende bygninger i én etage, hvor tagkonstruktionen ud over egenlast kun er påvirket af naturlaster, dvs. sne og vind. Dimensioneringen sker ved at udfylde et di...
Simple models with ALICE fluxes
Striet, J
2000-01-01
We introduce two simple models which feature an Alice electrodynamics phase. In a well defined sense the Alice flux solutions we obtain in these models obey first order equations similar to those of the Nielsen-Olesen fluxtube in the abelian higgs model in the Bogomol'nyi limit. Some numerical solutions are presented as well.
Shear strength properties of naturally occurring bituminous sands
CSIR Research Space (South Africa)
Anochie-Boateng, Joseph
2009-06-01
Full Text Available because of the cohesive nature of bitumen contents. However, results from the direct shear tests were comparable to properties of oil sands reported earlier from various other laboratory tests. Based on the direct shear test results, Mohr-Coulomb failure...
Structural behavior of human lumbar intervertebral disc under direct shear.
Schmidt, Hendrik; Häussler, Kim; Wilke, Hans-Joachim; Wolfram, Uwe
2015-03-18
The intervertebral disc (IVD) is a complex, flexible joint between adjacent vertebral bodies that provides load transmission while permitting movements of the spinal column. Finite element models can be used to help clarify why and how IVDs fail or degenerate. To do so, it is of importance to validate those models against controllable experiments. Due to missing experimental data, shear properties are not used thus far in validating finite element models. This study aimed to investigate the structural shear properties of human lumbar IVDs in posteroanterior (PA) and laterolateral (LL) loading directions. Fourteen lumbar IVDs (median age: 49 years) underwent direct shear in PA and LL loading directions. A custom-build shear device was used in combination with a materials testing machine to load the specimens until failure. Shear stiffness, ultimate shear force and displacement, and work to failure were determined. Each specimen was tested until complete or partial disruption. Median stiffness in PA direction was 490 N/mm and in LL direction 568 N/mm. Median ultimate shear force in the PA direction was 2,877 N and in the LL direction 3,199 N. Work to failure was 12 Nm in the PA and 9 Nm in the LL direction. This study was an experiment to subject IVDs to direct shear. The results could help us to understand the structure and function of IVDs with regard to mechanical spinal stability, and they can be used to validate finite element models of the IVD.
Ordering fluctuations in a shear-banding wormlike micellar system
DEFF Research Database (Denmark)
Angelico, R.; Rossi, C. Oliviero; Ambrosone, L.
2010-01-01
We present a first investigation about the non-linear flow properties and transient orientational-order fluctuations observed in the shear-thinning lecithin–water–cyclohexane wormlike micellar system at a concentration near to the zero-shear isotropic–nematic phase transition. From rheological...
Shear behavior of concrete beams externally prestressed with Parafil ropes
Directory of Open Access Journals (Sweden)
A.H. Ghallab
2013-03-01
Full Text Available Although extensive work has been carried out investigating the use of external prestressing system for flexural strengthening, a few studies regarding the shear behavior of externally prestressed beams can be found. Five beams, four of them were externally strengthened using Parafil rope, were loaded up to failure to investigate the effect of shear span/depth ratio, external prestressing force and concrete strength on their shear behavior. Test results showed that the shear span to depth ratio has a significant effect on both the shear strength and failure mode of the strengthened beams and the presence of external prestressing force increased the ultimate load of the tested beams by about 75%. Equations proposed by different codes for both the conventional reinforced concrete beams and for ordinary prestressed beams were used to evaluate the obtained experimental results. In general, codes equations showed a high level of conservatism in predicting the shear strength of the beams. Also, using the full strength rather than half of the concrete shear strength in the Egyptian code PC-method improves the accuracy of the calculated ultimate shear strength.
Wind Shear Characteristics at Central Plains Tall Towers (presentation)
Energy Technology Data Exchange (ETDEWEB)
Schwartz, M.; Elliott, D.
2006-06-05
The objectives of this report are: (1) Analyze wind shear characteristics at tall tower sites for diverse areas in the central plains (Texas to North Dakota)--Turbines hub heights are now 70-100 m above ground and Wind measurements at 70-100+ m have been rare. (2) Present conclusions about wind shear characteristics for prime wind energy development regions.
Flow behavior at different shear rates for dry powders
Singh, A.; Singh, A.; Luding, Stefan; Nürnberg Messe GmbH,
2010-01-01
Using Discrete Element Simulations (DEM), an effort is made to study the so called “Split bottom ring shear cell” where a slow, quasi-static deformation leads to wide shear bands. Density, velocity and deformation gradients as well as structure and stress tensors, can be computed by a single
Midbroken Reinforced Concrete Shear Frames Due to Earthquakes
DEFF Research Database (Denmark)
Köylüoglu, H. U.; Cakmak, A. S.; Nielsen, Søren R. K.
A non-linear hysteretic model for the response and local damage analyses of reinforced concrete shear frames subject to earthquake excitation is proposed, and, the model is applied to analyse midbroken reinforced concrete (RC) structures due to earthquake loads. Each storey of the shear frame...
Shear rheological properties of fresh human faeces with different ...
African Journals Online (AJOL)
Samples were further tested for moisture content, total solids, volatile content, and ash content. Faecal samples were found to have a yield stress; there was a decrease in apparent viscosity with increasing shear rate. For any given shear rate, higher apparent viscosities are associated with lower moisture contents. Across a ...
Parametric excitation of drift waves in a sheared slab geometry
International Nuclear Information System (INIS)
Vranjes, J.; Weiland, J.
1992-01-01
The threshold for parametric excitation of drift waves in a sheared slab geometry is calculated for a pump wave that is a standing wave along the magnetic field, using the Hasegawa-Mima nonlinearity. The shear damping is counteracted by the parametric coupling and the eigenvalue problem is solved analytically using Taylor's strong coupling approximation. (au)
Solitary drift waves in the presence of magnetic shear
International Nuclear Information System (INIS)
Meiss, J.D.; Horton, W.
1982-07-01
The two-component fluid equations describing electron drift and ion acoustic waves in a nonuniform magnetized plasma are shown to possess nonlinear two-dimensional solitary wave solutions. In the presence of magnetic shear, radiative shear damping is exponentially small in L/sub s//L/sub n/ for solitary drift waves, in contrast to linear waves
Interfacial stresses in strengthened beam with shear cohesive zone ...
Indian Academy of Sciences (India)
The results of parametric study are compared with those of Smith and Teng. They confirm the accuracy of the proposed approach in predicting both interfacial shear and normal stresses. Keywords. Strengthened beam; interfacial stresses; cohesive zone; shear deformation. 1. Introduction. The FRP plates can be either ...
Opportunities for shear energy scaling in bulk acoustic wave resonators
Jose, Sumy; Hueting, Raymond Josephus Engelbart
2014-01-01
An important energy loss contribution in bulk acoustic wave resonators is formed by so-called shear waves, which are transversal waves that propagate vertically through the devices with a horizontal motion. In this work, we report for the first time scaling of the shear-confined spots, i.e., spots
Shear-Induced Membrane Fusion in Viscous Solutions
Kogan, Maxim; Feng, Bobo; Nordé n, Bengt; Rocha, Sandra; Beke-Somfai, Tamá s
2014-01-01
Large unilamellar lipid vesicles do not normally fuse under fluid shear stress. They might deform and open pores to relax the tension to which they are exposed, but membrane fusion occurring solely due to shear stress has not yet been reported. We
Deformation of footwall rock of Phulad Shear Zone, Rajasthan ...
Indian Academy of Sciences (India)
Phulad Shear Zone (PSZ) of Delhi Fold Belt in Rajasthan is a northeasterly striking ductile shear zone with a well developed mylonitic foliation (035/70E) and a downdip stretching lineation. The deformation in the PSZ has developed in a transpressional regime with thrusting sense of movement. The northeastern unit, i.e. ...
Shear design of wood beams : state of the art
Lawrence A. Soltis; Terry D. Gerhardt
1988-01-01
Current shear design technology in the United States for lumber or glued- laminated beams is confusing. This report summarizes shear stress and strength research including both analytical and experimental approaches. Both checked and unchecked beams are included. The analytical work has been experimentally verified for only limited load conditions and span-to- depth...
Wind Shear Systems Implementation Plan, Benefit/Cost Study.
1980-08-01
not. Accordingly, the three self contained Wind Shear Systems currently being marketed by avionics manufacturers are considered to have lower relative... RESEARC { AND I’iVEIOPMEN1 The FAA research ni d development ffort has taken a threefold appro,,ch to the vind sh#ear problem. Ore. approach was to
E x B shearing rate in quasi-symmetric plasmas
International Nuclear Information System (INIS)
Hahm, T.S.
1997-01-01
The suppression of turbulence by the E x B shear is studied in systems with quasi-symmetry using the nonlinear analysis of eddy decorrelation previously utilized in finite aspect ratio tokamak plasmas. The analytically derived E x B shearing rate which contains the relevant geometric dependence can be used for quantitative assessment of the fluctuation suppression in stellarators with quasi-symmetry
Seismic cycle feedbacks in a mid-crustal shear zone
Melosh, Benjamin L.; Rowe, Christie D.; Gerbi, Christopher; Smit, Louis; Macey, Paul
2018-07-01
Mid-crustal fault rheology is controlled by alternating brittle and plastic deformation mechanisms, which cause feedback cycles that influence earthquake behavior. Detailed mapping and microstructural observations in the Pofadder Shear Zone (Namibia and South Africa) reveal a lithologically heterogeneous shear zone core with quartz-rich mylonites and ultramylonites, plastically overprinted pseudotachylyte and active shear folds. We present evidence for a positive feedback cycle in which coseismic grain size reduction facilitates active shear folding by enhancing competency contrasts and promoting crystal plastic flow. Shear folding strengthens a portion of a shear zone by limb rotation, focusing deformation and promoting plastic flow or brittle slip in resulting areas of localized high stress. Using quartz paleopiezometry, we estimate strain and slip rates consistent with other studies of exhumed shear zones and modern plate boundary faults, helping establish the Pofadder Shear Zone as an ancient analogue to modern, continental-scale, strike-slip faults. This feedback cycle influences seismicity patterns at the scale of study (10s of meters) and possibly larger scales as well, and contributes to bulk strengthening of the brittle-plastic transition on modern plate boundary faults.