Asymmetric Shear Research Articles

Measurements of Turbulent Jet Mixing in a Turbulent Co-Flow Including the Influence of Periodic Forcing and Heating

In this work, the turbulent mixing of a confined coaxial jet in air is investigated by means of simultaneous particle image velocimetry and planar laser induced fluorescence of the acetone seeded flow injection. The jet is injected into a turbulent duct flow at atmospheric pressure through a 90 ∘ pipe bend. Measurements are conducted in a small scale windtunnel at constant mass flow rates and three modes of operation: isothermal steady jet injection at a Dean number of 20000 (Red=32000), pulsed isothermal injection at a Womersley number of 65 and steady injection at elevated jet temperatures of ΔT=50 K and ΔT=100 K. The experiment is aimed at providing statistically converged quantities of velocity, mass fraction, turbulent fluctuations and turbulent mass flux at several downstream locations. Stochastic error convergence over the number of samples is assessed within the outer turbulent shear layer. From 3000 samples the statistical error of time-averaged velocity and mass fraction is below 1 % while the error of Reynolds shear stress and turbulent mass flux components is in the of range 5-6 %. Profiles of axial velocity and turbulence intensity immediately downstream of the bend exit are in good agreement with hot-wire measurements from literature. During pulsed jet injection strong asymmetric growing of shear layer vortices lead to a skewed mass fraction profile in comparison with steady injection. Phase averaging of single shot PLIF-PIV measurements allows to track the asymmetric shear layer vortex evolvement and flow breakdown during a pulsation cycle with a resolution of 10∘. Steady injection with increased jet temperature supports mixing downstream from 6 nozzle diameters onward.

Defect formation during preforming of a bi-axial non-crimp fabric with a pillar stitch pattern

To capture the asymmetrical shear behaviour of a bi-axial NCF with a pillar stitch, a non-orthogonal constitutive model was developed and implemented in finite element forming simulations. Preforming experiments indicate that the local distribution of defects is significantly different on both sides of each bi-axial ply, with two different defect mechanisms observed. Correlation with simulation results indicates that one defect type is caused by excessive shear, inducing out-of-plane wrinkling in regions of positive shear (macro-scale wrinkling). The other defect type is caused by fibre compression, inducing in-plane wrinkling in regions of negative shear (meso-scale wrinkling). Local distributions of shear angle and wrinkling strain were used to determine the wrinkling mode and to confirm the corresponding defect mechanism. Results indicate that simulations based on the advanced constitutive model can predict local shear angles within ±5° of experimental values and that predicted wrinkling positions and defect types correlate well with the experiments.

Tailoring the textures and mechanical properties of AZ31 alloy sheets using asymmetric composite extrusion

In the present study, an effective asymmetric composite extrusion (ACE) was used to produce AZ31 magnesium alloy sheets and compared with the composite extrusion (CE). The microstructures, textures and mechanical properties of AZ31 magnesium alloy sheets processed by CE and ACE processing at room temperature were investigated. The results demonstrated that the grains of the sheet fabricated by ACE processing were refined and the anisotropy could be improved in the tensile direction of ED, 45° and TD compared with the sheet fabricated by CE processing. The yield strength of the sheet processed by ACE was lower than that of the sheet processed by CE with the decrease of about 35MPa in the TD tensile direction, and its ductility was increased from 26.1% to 31.4% in the 45° tensile direction at room temperature. The higher n-values and lower r-values were obtained for the sheet processed by ACE processing in three tensile directions. These results led to a good formability of the sheet fabricated by ACE at room temperature. The improved mechanical properties of AZ31 Mg alloy sheet were mainly attributed to texture weakening resulting from asymmetric shear strain during ACE processing.

Formation of Late Jurassic–Early Cretaceous metamorphic core complexes in Northeast China: insight from a structural study of the Yiwulüshan ductile detachment zone

ABSTRACTLate Jurassic to Early Cretaceous extensional structures are widespread in Northeast China and the eastern part of the Asian continent. The Yiwulüshan ductile detachment shear zone, the master ductile detachment zone of the Yiwulüshan metamorphic core complex (MCC), occurs in the northern North China Craton. This shear zone dips to the northwest on the western flank and to the southeast on the eastern flank of the MCC and consists of brittle faults, breccia, chloritized microbreccia, and ductile (mylonite) zones. The well-developed mylonitic foliation and stretching lineation are characterized by oriented minerals (quartz and feldspar) that exhibit ductile deformation, including undulose extinction, deformation bands, subgrain formations, and recrystallized grains. The shear indicators, such as asymmetric porphyroclasts, S-C fabrics, and shear bands, suggest consistent top-to-the-NW shear on both the western and eastern flanks of the MCC. Strain measurements using feldspar porphyroclasts show that the strain intensity (Es), Lode’s parameter (υ), and Flinn parameter (k) range from 0.46 to 1.03, −0.23 to 0.62, and 0.23 to 1.6, respectively. Kinematic vorticity (Wk) values, estimated by the Polar Mohr diagram and the C′ methods, range from 0.61 to 0.96, with an average of 0.80, for the mylonitic deformation, and from 0.24 to 0.53, with an average of 0.37, for extensional crenulation cleavage (ecc) domains. The kinematic vorticity values, together with the regional structural background, suggest the Yiwulüshan ductile detachment zone experienced simple-shear-dominated general shearing that formed the mylonitic fabric in the early stages of extension. Later in the deformation history, pure-shear-dominated general shearing dominated when ecc developed. Strain measurements and kinematic vorticity estimates indicate that the Yiwulüshan ductile detachment zone is a lengthening-thinning shear zone. It is proposed that simple-shear-dominated general shear developed during crustal extension and that pure-shear-dominated general shear is related to the upward flow of Precambrian basement and Jurassic plutons.

Thermo-magneto-elasticity analysis of variable thickness annular FGM plates with asymmetric shear and normal loads and non-uniform elastic foundations

In the present research, a semi-analytical three-dimensional solution is developed for transversely graded annular/circular plates resting on non-uniform elastic foundations and subjected to magnetic and thermal fluxes and non-uniform and asymmetric mechanical loads. Thickness of the plate may vary exponentially along the radial direction and the inner and outer edges are restrained. All the thermal, magnetic, and elastic properties are assumed to vary in the transverse direction. Transverse distribution of the temperature is determined analytically for both the specified transverse temperature gradient and specified heat flux thermal conditions. Dependencies of the solution on the radial and transverse coordinates are determined through solving the resulting governing equations by using the differential quadrature and state space approaches in the radial and transverse directions, respectively. Effects of the material heterogeneity, thermal and mechanical boundary conditions, thickness variability, coefficients of the elastic foundation, shear to normal loads ratio, and magnetic field intensity are investigated comprehensively, through a parametric study. Results reveal that complex interactions may be observed among the elastic, thermal, and magnetic responses.

Origins of the Exchange-Bias Phenomenology, Coercivity Enhancement, and Asymmetric Hysteretic Shearing in Core-Surface Smart Nanoparticles

We have used a spin-1 Ising model Hamiltonian with dipolar (bilinear,J), quadrupolar (biquadratic,K), and dipolar-quadrupolar (odd,L) interactions in pair approximation to investigate the exchange-bias (EB), coercive field, and asymmetric hysteretic shearing properties peculiar to core/surface (C/S) composite nanoparticles (NPs). Shifted hysteresis loops with an asymmetry and coercivity enhancement are observed only in the presence of the odd interaction term in the Hamiltonian expression and their magnitudes show strong dependence on the value ofL. The observed coercivity and EB inC/SNPs originated from nonzero odd coupling energies and their dependence on temperature (T) and particle size (R) are also discussed in relation to experimental findings.

Effect of Extrusion Strain Path on Microstructure and Properties of AZ31 Magnesium Alloy Sheet

The mechanical properties of AZ31 magnesium alloy sheets processed by different extrusion strain paths were examined in correlation with concurrent microstructure and texture evolution. The conventional extrusion (CE) and asymmetric extrusion (ASE) paths were performed on Mg alloy sheets. The textures at near surface and mid-layer of ASE sheets were various throughout sheet thickness direction as a result of extra asymmetric shear strain. This can stimulate the orientation of (0002) basal planes to incline approximately 12° toward the shear direction. Moreover, the basal texture of ASE sheet was weakened compared with CE one. Enhancing the ambient formability of extruded Mg alloy sheet fabricated by ASE path was accomplished by the tilted weak basal texture.

Non-Linear Analysis of Asymmetric Shear Wall with Openings

Non-Linear Analysis of Asymmetric Shear Wall with Openings

Asymmetric first order shear horizontal guided waves propagation in a tapered plate

In this paper, through numerical simulation of the first order shear horizontal guided waves propagation in a homogeneous tapered plate, we have realized sound unidirectional transmission based on the mode conversion mechanism. We also find that the contrast transmission ratio of unidirectional transmission is highly influenced by the slope angle of tapered edge. And the working frequency range of the asymmetric transmission can be easily controlled by the height of tapered surface or the thickness of slab. This asymmetric system shows potentially significant applications in various sound devices.

From symmetric necking to localized asymmetric shearing: The role of mechanical layering

We study the formation of localized shear zones during the layer-parallel extension of viscous multi-layers using two-dimensional numerical simulations based on the finite-difference method. For power-law viscous layers and a linear viscous embedding medium, the extended multi-layer develops boudins due to necking. For power-law viscous layers embedded in a power-law viscous medium, the extended multi-layer develops first distributed necks, and subsequently a localized shear zone with a vertical offset (with a size of several layer thicknesses) along the multi-layer. During the extension, the deformation style switches from distributed and symmetric necking to localized and asymmetric shearing. A localized shear zone develops in the viscous multi-layer although the rheology is everywhere strain-rate-hardening (power-law stress exponent >1) and no material softening and/or energy feedback mechanism (e.g., shear heating combined with a temperature-dependent viscosity) is applied. The shear localization is caused by structural softening because the formation of a localized shear zone decreases the bulk resistance and hence the work required to deform the multi-layer. A localized shear zone forms in the multi-layer when the distance between the stiff layers is approximately equal to or less than the layer thickness. The shear localization was observed in multi-layers with nine and with only three stiff layers.

Greater asymmetric wall shear stress in Sievers' type 1/LR compared with 0/LAT bicuspid aortic valves after valve-sparing aortic root replacement

ObjectiveTo evaluate the role of commissure orientation on downstream blood flow patterns and ascending aortic wall shear stress (WSS) in patients with bicuspid aortic valves (BAV) after valve-sparing aortic root replacement (V-SARR). MethodsNineteen BAV patients after V-SARR (9 Sievers' type 1/LR [type 1 valve with fusion of the left and right cusps] and 10 Sievers' type 0/LAT [“naturally perfect”; type 0 valve without the presence of a raphe, and with the 2 commissures oriented right-anterior-to-left-posterior]) were imaged using time-resolved 3-D phase contrast magnetic resonance imaging. A control group of 5 unoperated tricuspid aortic valve patients were used for comparison purposes. Wall shear stress and eccentricity of flow normalized to aortic diameter were measured in planes placed perpendicular to the axis of the ascending aorta at the level of the sinotubular junction (proximal ascending), main pulmonary artery (mid-ascending), and origin of the brachiocephalic (distal ascending). ResultsThe ratio of WSS along the outer curvature to that along the inner curvature was greater in Sievers' type 1/LR patients compared with Sievers' type 0/LAT patients in the proximal (3.8 ± 1.6 vs 2.1 ± 0.9, P = .009) and mid- ascending aorta (4.5 ± 2.4 vs 2.4 ± 1.3, P = .027). Relative to control normal tricuspid patients, Sievers' type 1/LR BAV patients had a higher WSS ratio in the mid-ascending aorta (4.5 ± 2.4 vs 1.2 ± 1.2, P = .007). Conversely, WSS in Sievers' type 0/LAT patients was not different than in normal tricuspid patients. ConclusionsAfter V-SARR, BAV cusp morphology has a major impact on the pattern of blood flow and WSS in the ascending aorta.

Shear Sense Analysis of the Higher Himalayan Crystalline Belt and Tectonics of the South Tibetan Detachment System, Alaknanda-Dhauli Ganga Valleys, Uttarakhand Himalaya

In the central parts of Uttarakhand Himalaya, more than 20 km thick homoclinally NE-dipping Higher Himalayan Crystalline (HHC) Belt is thrust over the Lesser Himalaya Sedimentary Belt along the Main Central Thrust (MCT), and is almost continuously exposed between Helang and Malari along the Alaknanda and Dhauli Ganga valleys. The upper contact of this belt with the Martoli Formation of the Tethyan Himalayan Sequence is demarcated by the South Tibetan Detachment System (STDS). The belt is ubiquitously marked by small-scale asymmetrical structures like S-C and S-C' foliation, porphyroclasts and porphyroblasts, mineral fishes, intrafolial folds, duplex structures, ductile-brittle shear zones, and asymmetric shear boudins. Sense of ductile to brittle- ductile shearing has been determined from these structures across the whole belt, the MCT and the STDS, and reveals two phases of shear deformation: (a) an older top-to-SW upwards phase throughout the HHC, having an overall thrust geometry (DS1), and (b) a younger superposed top-to-NE downwards phase with normal fault sense from the middle to upper parts (DS2). These shear senses provide invaluable constraints on various tectonic models currently in use for the evolution of the Himalayan metamorphics.

Tectonic amalgamation of the Gaoligong shear zone and Lancangjiang shear zone, southeast of Eastern Himalayan Syntaxis

The Gaoligong shear zone (GLGSZ) and Lancangjiang shear zone (LCJSZ) are two major large-scale shear zones southeast of Eastern Himalayan Syntaxis (EHS) and play important roles in the accommodation of the intracontinental deformation in Southeast Asia. The two shear zones, which are mainly composed of high-grade metamorphic rocks and have long been regarded as the Precambrian basement of this area, are gradually merged northward and become tectonically amalgamated from Fugong to Gongshan area. Structural and kinematic analyses reveal that the amalgamation area has experienced strongly partitioned dextral transpression. N–S trending tight to isoclinal folds, sub-vertical foliation and sub-horizontal lineation are ubiquitously developed both within the shear zones and the Carboniferous flysch sediments of Baoshan block in between. Micro- and macro-kinematic indicators such as CS structures, rotated porphyroclasts, asymmetric shear folds, sheath folds, domino and boudin structures suggest that the shear sense of the GLGSZ and LCJSZ is dextral in the amalgamation area. Comparative analyses of strata reveal that the Baoshan block is aligned with south Qiangtang block and the Lanping–Simao block was aligned with north Qiangtang block prior to the Cenozoic large scale tectonic extrusion and rotation. The amalgamation area, which has progressively switched positions from northeast of EHS to east and southeast of EHS, is just located at the neck of the large scale boudin of south Qiangtang–Baoshan block. A boudin model is proposed for the tectonic amalgamation of the GLGSZ and LCJSZ from Fugong to Gongshan area in response to the continued northward convergence between Indian plate and Eurasian plate since early Eocene, resistance of South China block, southeastward extrusion and clockwise rotation of Baoshan block around EHS.

Torsional irregularity in multi-story structures

The purpose of this study is first to determine the conditions for excessive torsional irregularity and then to discuss the validity of code provisions. A parametric investigation is performed on six groups of typical struc- tures with varying shear wall positions, story, and axis numbers. It is found that torsional irregularity coefficients increase as the story numbers decrease, i.e., maximum irregularity coefficients occur for single-story structures. They reach maximum values when the asymmetrical shear walls are placed as close as possible to the centers of mass. However, the results obtained for floor rotations are quite contradictory. A new provisional definition for torsional irregularity coefficient based on floor rotations is proposed.

3D ELASTICITY SOLUTION FOR THE STATIC ANALYSIS OF VARIABLE THICKNESS BI-DIRECTIONAL FUNCTIONALLY GRADED CIRCULAR PLATES SUBJECTED TO NON-UNIFORM ASYMMETRIC BOUNDARY CONDITIONS

This paper investigates the static behavior of non-uniform bi-directional functionally graded (FG) circular plates embedded on gradient elastic foundations (Winkler- Pasternak type) and subjected to non-uniform asymmetric transverse and in-plane shear loads. The governing state equations are derived in terms of displacements based on 3D theory of elasticity, and assuming the material properties of the plate except the Poisson’s ratio varies continuously throughout the thickness and radial directions according to an exponential function. These equations are solved by means semianalytical method using state-space based differential quadrature method. Numerical results are displayed to clarify the effects of foundation stiffnesses, material heterogeneity indices, various foundation patterns, foundation grading indices, loads ratio and geometric parameters on the displacement and stress fields. The results are reported for the first time and the new results can be used as a benchmark solution for future researches

Influence of different extrusion processes on mechanical properties of magnesium alloy

Abstract AZ31 Mg alloy sheets were processed by the conventional symmetrical extrusion (CSE) and the asymmetric extrusion (ASE). Progressive-asymmetric extrusion (PASE) and severe strain-asymmetric extrusion (SASE) were employed for ASE processes. The texture at near-surface and mid-layer zones of ASE sheets was diverse penetrating the normal direction (ND). This was attributed to an additional asymmetric shear strain deformation during the ASE process. (0002) basal planes of PASE sheets tilt to the shear deformation direction. Meanwhile, the basal texture intensity of PASE sheets has been weakened compared with one in CSE sheets. Grain refinement and tilted weak basal texture obtained by SASE process dramatically enhances the room temperature strength and plasticity of the extruded AZ31 magnesium alloy sheets. The microstructure and mechanical responses were examined and discussed.

Tailoring texture and refining grain of magnesium alloy by differential speed extrusion process

Magnesium alloy sheets were processed by conventional extrusion (CE) and differential speed extrusion (DSE). The velocity evolutions of DSE sheets at near-surface and mid-layer region are different due to the extra asymmetric shear deformation. This simple shear enforces the near-surface microstructure to exhibit more dynamically recrystallized grains having the c-axis tilted about ±12° toward the extrusion direction. Grain refinement and tilted weak basal texture obtained by DSE process dramatically enhance the room temperature strength and plasticity of the extruded Mg alloy sheets.

The East Variscan Shear Zone: Geochronological constraints from the Capo Ferro area (NE Sardinia, Italy)

The exhumation of the Variscan High Grade Metamorphic Complex of Sardinia was driven by large-scale asymmetric shear zones which reached middle crustal levels at 325±1.3 (U–Pb, monazite) Ma. Exhumation was accompanied by heating and partial melting. The migmatization process was followed by the emplacement of syntectonic granites dated with U–Pb on zircon at 318±3Ma and 317±2Ma, which produced contact metamorphism at 315±1.3Ma (U–Pb, monazite) in mylonitic Silurian orthogneisses. The NW–SE dextral shear zone of the Capo Ferro area (NE Sardinia) is affected by partial melting, by granite emplacement and shows remarkable petrotectonic analogies to, and can thus be related to the East Variscan Shear Zone, a major intra-continental shear zone which was active in the southern European Variscides from 325Ma to 315Ma and that has been precisely dated with the U–Pb monazite system. The emplacement of migmatitic gneisses along large shear zones within this time interval is not restricted to Sardinia, but has also been observed in southern Corsica, in the French Massif Central, in the Western Alps and in central Spain. This pattern of shear zones is related to a complex geodynamic scenario, linked to the oblique convergence of the Gondwana and Laurussia plates during the Middle–Upper Carboniferous.

Shear Buckling Strength and Behaviors of Steel Plate Girder with Asymmetrical Shear Resistant Web Panel by Local Corrosion

국내에서는 교량의 공용수명 증가로 노후화 교량의 수가 급격히 증가하고 있다. 강교량의 경우, 가설위치에 따른 대기부식환경에 따라 구조부재에서의 국부 부식손상이 발생 될 수 있다. 특히 강거더 교량의 경우 부식손상이 복부판과 지점부 보강재에 집중적으로 발생된다. 복부판의 국부부식이 교량에 대하여 대칭적으로 발생하는 것이 아니므로 복부판의 국부 부식손상으로 인하여 강거더에서는 전단하중에 대하여 비대칭 복부단면이 발생할 수 있다. 따라서 본 연구에서는 유한요소해석을 통하여 강거더 비대칭 부식 복부단면의 형상비와 부식손상 정도에 따른 전단 좌굴강도 및 전단거동을 거동을 평가하였다. 또한 복부판의 부식손상 부피비와 인장영역에 대한 부식손상비를 고려하여 비대칭 국부 부식손상 단면을 가진 복부판의 전단좌굴강도 감소가 비교 평가되었다. The number of the deteriorated bridge has been sharply increased due to the increase in the bridge service period in Korea. Local corrosion problem of structural member can be occurred according to atmospheric corrosion environments based on the installation location of steel bridges. Especially, in case of the plate girder bridge, corrosion damage is concentrated on the web panel and stiffener at girder end. An asymmetrical shear resistant web section in the plate girder bridge can be caused from the local corrosion of the web panel, because local corrosion is not symmetrically occurred to the bridge. In this study, therefore, the shear buckling strength and behavior of a plate girder with asymmetrically corroded web panel was numerically evaluated using FE analysis, which was considering an aspect ratio and corrosion damage level of web panel. The shear buckling strength reduction of an asymmetrical shear resistant web panel was compared and evaluated according to corroded volume ratio for a web panel and for diagonal tension field of a web panel.

Numerical study on the development of asymmetric convection and vertical wind shear during tropical cyclone landfall

Idealized simulations on an f-plane of tropical cyclone (TC) landfall under a quiescent environment in the Southern Hemisphere are performed to investigate the effects of land–sea surface contrast on precipitation. In the control simulation, with realistic roughness and moisture over land to the south of the TC, the simulated vortex moves toward land due to a land-induced steering flow. The abrupt decrease (increase) of tangential wind at the surface leads to convergence (divergence) on the onshore (offshore) flow side. Enhanced convergence at the top of the planetary boundary layer is found on both onshore and offshore sides and is caused by advection from the surface and the enhanced offshore radial wind. The boundary-layer top convergence pattern is consistent with the rainfall distribution. Vertical wind shear develops during the landfall process associated with the low- and upper-level asymmetric flows across the model domain. The wavenumber-1-like low-level asymmetric flow is introduced by an asymmetric geopotential height field that is generated by the large area of frictionally induced convergence on the onshore side and divergence on the offshore side. The upper-level asymmetric flow is attributed to asymmetric convection and associated diabatic heating after landfall. Most rainfall is found in the down-shear right quadrant, which is consistent with previous studies that focused on the effect of environmental shear. Although the existence of feedback from the vertical wind shear to rainfall remains an open question, the relation between maximum rainfall and vertical wind shear is robust, especially when the shear magnitude is large after landfall.