Parallel Shear Research Articles

Physical and mechanical wood properties of two varieties of Pinus caribaea

This study aimed to characterize the properties of wood from Pinus caribaea var. hondurensis and Pinus caribaea var bahamensis, in 7-year-old individuals, in the municipality of Batatais, State of São Paulo, Brazil. For this, twelve trees of each species/variety were felled, and a 1 m long log was removed from the base of each tree. Samples were taken from the obtained logs to evaluate the physical-mechanical properties of the wood. It was verified that the woods of Pinus caribaea var. hondurensis and Pinus caribaea var. bahamensis do not differ significantly from each other for: Apparent density, basic density, compression parallel to the grain, shear parallel to grain, modulus of elasticity, volumetric shrinkage, anisotropy coefficient, radial shrinkage, and tangential shrinkage. The wood of the species/variety Pinus caribaea var. bahamensis showed a significantly higher modulus of rupture than the variety Pinus caribaea var. hondurensis. Regarding the use of wood from these species/variety, at a younger age, both showed potential use for different purposes. Since this initial assessment can be used as an indication of pre-selection of wood for the various segments of the timber industry, mainly for uses that do not have many restrictions in structural applications and dimensional variation.

Dynamic behavior of grain boundaries with misorientations in the vicinity of Σ3 coherent and incoherent twin boundaries in Al bicrystals

The migration behaviour of different grain boundaries with misorientations close to the Σ3 CSL orientation relationship in high purity Al bicrystals under the capillary driving force and applied mechanical stress was investigated. The experiments were performed by an in-situ technique to observe and measure the boundary migration with a scanning electron microscope. The ability of the nearly Σ3 60°〈111〉 incoherent {110} and {112} boundaries to move under capillary driving force was found to depend critically on the initial boundary inclination. While boundaries with inclinations near {112} can easily assume a curved shape and migrate, boundaries with an initial {110} plane remain stationary or form non-mobile facets. This is attributed to the essential anisotropy of the inclination dependence of the energy γ(ψ) of 60°〈111〉 tilt boundaries with differently high torque dγ/dψ around {112} and {110} inclinations, as revealed by atomistic simulations of the respective boundaries. The Σ3 70.5°〈110〉 tilt boundary with the geometry corresponding to the coherent {111} twin boundary, was found to be immobile under both driving forces applied. The 59.2° 〈111〉 tilt grain boundary with geometry near the Σ3 {110} incoherent twin boundary was found to be quite mobile under applied shear stress. The measured migration activation enthalpy H = 0.45 eV for this boundary is the lowest among the values obtained in previous experiments for any other stress driven grain boundary in Al bicrystals of the same purity. Moreover, this boundary migrated with a zero coupling factor, i.e. without producing any measurable shear parallel to the boundary plane.

Re-Analysis of Historical Data and Model Calibration of Duration of Load Effect on Structural Timber

The duration of load (DOL) effect in structure timber refers to the degradation of strength and stiffness that occurs under long-term continuous loading. This paper investigated the DOL effect in structure timber using DOL tests and DOL damage models. Based on the empirical-fitted formulae, the DOL coefficients were derived for three long-term sustained loads in bending, tension perpendicular to grain, and shear parallel to grain, and the results were compared and analyzed with the Madison equation, Gerhards model, Nielsen model, and Foschi and Yao model derivations to verify the applicability of the DOL empirical model and the three DOL damage models. The results show that based on the historical data of the DOL tests, the Madison empirical formula was found to be better applied to the derivation of DOL coefficients under the bending and tension perpendicular to grain long-term sustained loading, and the derivation of DOL coefficients under shear loading is not satisfactory. Among the three DOL damage models, the Foschi and Yao model was better than the Gerhards and Nielsen models for fitting the DOL test results under bending, tension perpendicular to grain, and shear parallel to grain. The DOL coefficients derived based on the Foschi and Yao model are more comparable to test results and resemble those derived from the Madison formula.

Global Stability of a Conduction-Diffusion System with Superimposed Plane Parallel Shear Flows

Global Stability of a Conduction-Diffusion System with Superimposed Plane Parallel Shear Flows

Restratification in Late Winter Lakes Induced by Cabbeling

AbstractThe under‐ice fluid dynamics during late winter in many freshwater settings remain poorly understood. One example is how cabbeling, the generation of dense water by mixing water masses on different sides of the temperature of maximum density (Tmd), affects the vertical transport. Using high resolution numerical simulations of the development of a stratified parallel shear flow, we show that when the temperature stratification passes through Tmd, cabbeling modifies the three‐dimensional aspects of the instability with the net effect of forming an emergent, stable stratification after a brief period of strong mixing. This stratification effectively separates the quiescent upper layer from the turbulent one below, thereby limiting transport and mixing between them. We propose a simple model for the vertical fluid flux during the mixing regime, and discuss a potential mechanism responsible for the emergent stratification as well as its sensitivity to the bulk Richardson number.

Enhanced dissipation and Taylor dispersion in higher‐dimensional parallel shear flows

AbstractWe consider the evolution of a passive scalar advected by a parallel shear flow in an infinite cylinder with bounded cross section, in arbitrary space dimension. The essential parameters of the problem are the molecular diffusivity , which is assumed to be small, and the wave number in the streamwise direction, which can take arbitrary values. Under generic assumptions on the shear velocity , we obtain optimal decay estimates for large times, both in the enhanced dissipation regime and in the Taylor dispersion regime . Our results can be deduced from resolvent estimates using a quantitative version of the Gearhart–Prüss theorem, or can be established more directly via the hypocoercivity method. Both approaches are explored in the present example, and their relative efficiency is compared.

The interplay of bedrock fractures and glacial erosion in defining the present‐day land surface topography in mesoscopically isotropic crystalline rocks

AbstractThis paper addresses the effect of fractures within crystalline bedrock on glacial erosion processes in fast flowing hard bed glacier environments. In particular, we examine (i) whether the fracture type is critical for the capability of a glacier to erode the bedrock through quarrying/plucking processes and (ii) whether we can recognize specific fracture‐controlled erosion signatures from bedrock surface morphologies. We conducted an investigation within the northern part of the Åland Islands, southern Finland, where the ice‐flow direction (N–S) has remained constant through Late Pleistocene glaciations and where the bedrock is characterized by a lack of any mesoscopic anisotropies (such as foliation) and hence provides an optimal target to recognize the relationships between fractures and erosional morphologies. We characterized the fracture systems within the bedrock using both UAV‐acquired orthophotographs and standard field approaches and extrapolated the results to larger scales using LiDAR‐based digital elevation models. Our findings indicate that individual joints or shear fractures are associated with the development of minor vertical breaks along the bedrock surface. However, they do not provide sufficient mechanical weakness zones in the bedrock to allow effective glacial quarrying, even though their lengths can be relatively large (>50 m). By contrast, the linkage of several parallel shear fractures or the presence of larger faults with gouge‐bearing cores and well‐developed damage zones leads to localized disintegration of the rock material and the subsequent development of distinct topographic depressions along the bedrock surface. Consequently, the results allow predictions to be made about the bedrock features underlying the observed topographic signatures along the bedrock surface. Applied to the area of this investigation, abrasion associated with N–S‐directed glacial flows is responsible for the N–S‐oriented elongate but smooth fjord‐like megagrooves, whereas the more abrupt topographic breaks were generated by quarrying controlled by sub‐vertical, E–W‐trending zones of localized brittle deformation.

Physical and mechanical properties of glued laminated bamboo

Certain bamboo species have mechanical properties that are compatible with construction material. Despite this, their low shear strength, the presence of nodes in their culms, and their circular geometry inhibit the expansion of the use of this material as construction material. One technique that can solve these problems is glued laminated bamboo (GLB). Based on such findings, this paper aims to evaluate the physical and mechanical properties of glued laminated bamboo of the Dendrocalamus giganteus species. Two glues were used: resorcinol-formaldehyde (PRF) and polyvinyl acetate (PVAc). The following physical and mechanical characterization tests were performed on glued laminated bamboo: water absorption, density, compression parallel to fiber direction, tension parallel to fiber direction, shear parallel to the glue layer, shear parallel to fiber direction, and bending. The results, analyzed using statistical models, showed that the GLB has physical and mechanical properties comparable to those of hardwoods.

Океаническая кора, трансрегиональные зоны сдвига и Амеразийская микроплита в мел-кайнозойской геодинамике формирования океана в Арктике

The author has reconstructed the structural-tectonic setting of the Late Cretaceous-Early Cenozoic stage of the geodynamic evolution of the Arctic Ocean. It is shown that the oceanic crust in the Eurasian and Canadian basins occupies a much smaller area than previously thought and was formed in both on blocks of the continental basement strongly stretched by Cretaceous rifting. Due to the processes, large and extended transregional shear zones were set in motion: the Chukchi-Canadian during the opening of the Canadian basin in the Early Cretaceous, and the continental marginal ones — Khatanga-Lomonosov and Northern Greenland-Canadian, the activation of shear movements in which is associated with the Late Cretaceous-Paleocene time, when the consistent formation of the Makarov and Eurasian basins took place. As a result new composite Amerasian microplate was detached and set in motion, which combined the blocks of Arctic Alaska, the Canadian Basin, the Chukchi Rise, the Alpha–Mendeleev Rise, the Podvodnikov and Makarov Basins, and the Lomonosov Ridge. The movement of the microplate along approximately parallel large shear zones at the edges of the Canadian Arctic and Siberian-Chukotka shelves was directed towards the Pacific subduction zone. The movement of the Amerasian microplate was accompanied by rifting and detachment of the Lomonosov Ridge from the Barents-Kara margin, opening of the Eurasian Basin in the rear of the ridge, and transform displacements — right-sided along the Khatanga-Lomonosov zone and left-sided along the North Greenland-Canadian fault zone. At the same time, as a result of the movement of the Amerasian microplate, the previously unified area of Cretaceous plateau basalts (HALIP) was broken, and the Central Arctic province of magmatism was separated and moved away from the Barents Sea province.

Testing Velocity-field Lensing on IllustrisTNG Galaxies

Weak gravitational lensing shear could be measured far more precisely if information about unlensed attributes of source galaxies were available. Disk galaxy velocity fields supply such information, at least in principle, with idealized models predicting orders of magnitude more Fisher information when velocity-field observations are used to complement images. To test the level at which realistic features of disk galaxies (warps, bars, spiral arms, and other substructure) inject noise or bias into such shear measurements, we fit an idealized disk model, including shear, to unsheared galaxies in the Illustris TNG100 simulation. The inferred shear thus indicates the extent to which unmodeled galaxy features inject noise and bias. We find that γ +, the component of shear parallel to the galaxy’s first principal axis, is highly biased and noisy because disks violate the assumption of face-on circularity, displaying a range of intrinsic axis ratios (0.85 ± 0.11). The other shear component, γ ×, shows little bias and is well-described by a double Gaussian distribution with central core scatter σ core ≈ 0.03, with low-amplitude, broad wings. This is the first measurement of the natural noise floor in the proposed velocity-field lensing technique. We conclude that the technique will achieve impressive precision gains for measurements of γ ×, but little gain for measurements of γ +.

Seismic Azimuthal Anisotropy Beneath a Fast Moving Ancient Continent: Constraints From Shear Wave Splitting Analysis in Australia

AbstractSeismic azimuthal anisotropy beneath Australia is investigated using splitting of the teleseismic PKS, SKKS, and SKS phases to delineate asthenospheric flow and lithospheric deformation beneath one of the oldest and fast‐moving continents on Earth. In total 511 pairs of high‐quality splitting parameters were observed at 116 seismic stations. Unlike other stable continental areas in Africa, East Asia, and North America, where spatially consistent splitting parameters dominate, the fast orientations and splitting times observed in Australia show a complex pattern, with a slightly smaller than normal average splitting time of 0.85 ± 0.33 s. On the North Australian Craton, the fast orientations are mostly N‐S, which is parallel to the absolute plate motion (APM) direction in the hotspot frame. Those observed in the South Australian Craton are mostly NE‐SW and E‐W, which are perpendicular to the maximum lithospheric horizontal shortening direction. In east Australia, the observed azimuthal anisotropy can be attributed to either APM induced simple shear or lithospheric fabric parallel to the strike of the orogenic belts. The observed spatial variations of the seismic azimuthal anisotropy, when combined with results from depth estimation utilizing the spatial coherency of the splitting parameters and seismic tomography studies, suggest that the azimuthal anisotropy in Australia can mostly be related to simple shear in the rheologically transition layer between the lithosphere and asthenosphere. Non‐APM parallel anisotropy is attributable to modulations of the mantle flow system by undulations of the bottom of the lithosphere, with a spatially variable degree of contribution from lithospheric fabric.

Double Plane Direct Shear Apparatus for Determination of Adhesion Factor in Clays

Abstract A modified direct shear assembly with two parallel shear planes was designed to enable the simultaneous and independent measurement of cohesive and adhesive resistance; it is named the “double-plane direct shear device.” The three-block specimen box of the device has top and middle blocks filled with soil specimen and the bottom block is made of solid steel. The middle box is laterally displaced while restraining the top and bottom box, leading to concurrent shearing along two parallel shear planes. Results from quick undrained testing of kaolinite at five different consistency indexes (Ic) and three different vertical stresses (σv) are presented. The stress–deformation curves show greater mobilization of adhesive stress than cohesive stress at low deformations at all Ic and σv. The deformation required for the complete mobilization of cohesive and adhesive stresses and their variation with Ic and σv is discussed. A parameter crossover deformation (dco) is defined to identify the region where adhesive stress is greater than cohesive stress, which would be useful in applications where soil stickiness is of concern. The results show that the presence of partial drainage increases the dco, which results in an increased deformation range over which adhesive stress is greater than cohesive stress, thereby increasing the stickiness susceptibility. Furthermore, results show that the adhesion factor (α, defined as the ratio of adhesion to undrained cohesion) always stayed below unity under undrained conditions, whereas under partial drainage conditions, values of α greater than unity were obtained. The study concludes that for the application where soil stickiness is of concern, the determination of α and its usage to analyze stickiness susceptibility should be performed under simulation of appropriate drainage boundary conditions.

Convective momentum transport and multiscale organization in simulated shear parallel mesoscale convective systems

The way in which moist convection interacts with large scale flows is a major contemporary research issue. Organized mesoscale systems are, in particular, important for the interactions between convection and the ambient shear. Here we present numerical simulations of mesoscale systems evolving in a background shear using the Research and Weather Forecasting model. We are particularly interested in the long time integration, allowing the systems to repeatedly develop and die and effectively interact with the background shear. Starting with a typical African and equatorial jet-shear, the simulated solution goes through various phases or stages. First, a transient state, consisting of scattered squall-like systems that are aligned perpendicular to the background shear, develops and then evolves into a regime of multiscale mesoscale systems with large stratiform anvils. During the latter period the background wind changes substantially through the effect of both up scale and down scale convective momentum transport. At this stage, the systems become aligned parallel to the wind shear, with elongated stratiform anvils in which meso-beta scale convective cells evolve and propagate in the shear direction, relative to the stratiform anvils. These results are reminiscent of the development of shear parallel mesoscale convective systems observed for instance in the Eastern Pacific ITCZ and corroborate recent theoretical results obtained with a simple multi-cloud model. As such they have important implications for the parameterization of CMT in climate models.

Physical and Mechanical Properties Performance between Untreated and Treated with CCA Treatment at Different Age Groups of Fast-Growing Acacia Hybrid of Sarawak

An effort was carried out to fully utilise fast-growing Acacia hybrid usage in the timber engineering field; however, the research data are still lacking. This paper aims to evaluate the physical and mechanical properties performance between untreated (control) and treated with 10% copper chrome arsenic of Acacia hybrid collected from Daikin Plantation Sdn. Bhd. Bintulu, Sarawak at air-dry condition at different age groups using the small clear method. Mechanical properties test refers to shear parallel to grain (tangential and radial directions), cleavage (tangential and radial directions), and tension parallel to grain test. Meanwhile, the physical properties test refers to moisture content (MC) and density test. After treatment, mechanical properties increase with an average of 13.67%; meanwhile, moisture content decreased with an average of 0.58% or 0.09% MC, and density slightly increased with an average of 0.44% or 0.002 g/cm3. Results indicate that 10-year-old Acacia hybrid exhibits the highest strength values in shear parallel to the grain, tension parallel to the grain, and cleavage, followed by 13-year-old and 7-year-old. Treated samples in the tangential direction performed better with consistent mean results than that of the untreated samples, while radial direction gave a high average strength increment when treated.

Нижнепалеолитическая стоянка-мастерская Кусимово-8 (Южное Зауралье)

Introduction. Comprehensive and efficient investigations of the earliest peopling of the Southern Urals became possible after the discovery of Mysovaya site in Abzelilovsky District of Bashkortostan (Russia). The Paleolithic materials from this site were considered mixed — Acheulean/Mousterian — or Mousterian proper. In recent years, the Lower and Middle Paleolithic site of Kusimovo-8 has been discovered nearby. This is a scattered workshop site on pebble flint outcrops within the terrace surface of the Bannoe-Sabakty paleolake. Goals. The study attempts an insight into the earliest peopling of the Southern Urals, describes and analyzes the Lower Paleolithic collection. Results. The finds were identified on the basis of technical and typological characteristics and preservation parameters. The collection comprises a total of 121 items, most of the objects made of flint pebbles and only two bifaces made of diabase. Nucleuses with patinated surfaces (19 items) are diverse enough: mainly flat cores of parallel and sub-parallel shearing are available to be quantitatively followed by radial, fan-shaped, and orthogonal cores. The tools are represented by oval and almond-shaped hand axes, cleavers, piked tools, a chopper, biface blanks, and various side-scrapers. The stratigraphy of test pits shows the presence of two cultural horizons: flint chips were found under the Middle Paleolithic cultural layer (grayish-brown loam with dolomite gravel) — 0.5 m lower in yellowish-brown loam. Paleoecological analyses of the pits attest to that yellowish-brown loam deposits can be dated to the Middle Pleistocene. Similar conditions were identified for Lower Paleolithic finds discovered at Mysovaya site. Similarity of both the sites makes it possible to conclude as to comparable ages of these collections and that they may cluster together within one Karyshkino-type industry which unites a majority of Lower Paleolithic sites across the Southern Transurals, all of them to form a specific variant of the Tayacian.

Нижнепалеолитическая стоянка-мастерская Кусимово-8 (Южное Зауралье)

Introduction. Comprehensive and efficient investigations of the earliest peopling of the Southern Urals became possible after the discovery of Mysovaya site in Abzelilovsky District of Bashkortostan (Russia). The Paleolithic materials from this site were considered mixed — Acheulean/Mousterian — or Mousterian proper. In recent years, the Lower and Middle Paleolithic site of Kusimovo-8 has been discovered nearby. This is a scattered workshop site on pebble flint outcrops within the terrace surface of the Bannoe-Sabakty paleolake. Goals. The study attempts an insight into the earliest peopling of the Southern Urals, describes and analyzes the Lower Paleolithic collection. Results. The finds were identified on the basis of technical and typological characteristics and preservation parameters. The collection comprises a total of 121 items, most of the objects made of flint pebbles and only two bifaces made of diabase. Nucleuses with patinated surfaces (19 items) are diverse enough: mainly flat cores of parallel and sub-parallel shearing are available to be quantitatively followed by radial, fan-shaped, and orthogonal cores. The tools are represented by oval and almond-shaped hand axes, cleavers, piked tools, a chopper, biface blanks, and various side-scrapers. The stratigraphy of test pits shows the presence of two cultural horizons: flint chips were found under the Middle Paleolithic cultural layer (grayish-brown loam with dolomite gravel) — 0.5 m lower in yellowish-brown loam. Paleoecological analyses of the pits attest to that yellowish-brown loam deposits can be dated to the Middle Pleistocene. Similar conditions were identified for Lower Paleolithic finds discovered at Mysovaya site. Similarity of both the sites makes it possible to conclude as to comparable ages of these collections and that they may cluster together within one Karyshkino-type industry which unites a majority of Lower Paleolithic sites across the Southern Transurals, all of them to form a specific variant of the Tayacian.

Characterizing the Tensile Behavior of Double Wire-Feed Electron Beam Additive Manufactured “Copper–Steel” Using Digital Image Correlation

The paper presents the results of the evaluation of the mechanical characteristics of samples of multi-metal “copper-steel” structures fabricated by additive double wire electron beam method. The global and local mechanical characteristics were evaluated using uniaxial tensile tests and full-field two-dimensional digital image correlation (DIC) method. DIC revealed the peculiarities of the fracture stages: at the first stage (0.02<ε≤0.08) the formation of V-shaped shear lines occurs; at the second stage (0.08<ε≤0.15) transverse shear lines lead to the formation of a block structure; at the third stage (0.15<ε≤0.21) the plasticity resource ends in the central part of the two necks cracks are formed, and the main crack is the cause of the fracture of the joint. It is found that shear lines are formed first in copper and then propagate to steel. Electron microscopy proves that uniformly distributed iron particles could always be found in the “Fe-Cu” and “Cu-Fe” interfaces. Additionally, the evolution of average strain rates and standard deviations were measured (calculated) in the regions of necks in copper and steel regions. New shear approach shows that the most of angles for parallel shears components are ±45°, rupture angles are about 0°, and combined account of these two types of shears provides us additional discrete angles.

Estimation of mechanical properties in Eucalyptus woods towards physical and anatomical parameters

• Regression models are accurate to estimate mechanical properties of eucalypts for construction. • Optical microscopy may predict MOE, compression strength and shear stress parallel to the grain. • Bulk density and height of rays are essential parameters to predict mechanical properties of eucalypts. There is a perceptible opportunity to utilize eucalypts in value-added wooden products with structural features for construction. But, tests to determine the wood properties require specific equipment and technical training. As alternative, the study utilized optical microscopy to measure some anatomical elements of 10 eucalypt varieties to estimate their mechanical properties in line with anatomical parameters and bulk densities using regression models. Eight anatomical properties about constituent sizes and six mechanical properties about compression behaviors were evaluated. Regression models were positively conclusive, as R 2 values were 94.15, 92.95 and 77.77 for the modulus of elasticity in compression parallel, compression parallel strength and shear stress parallel to the grain, respectively.

Structural geology of the Cadillac Group along the Malartic segment of the Larder Lake Cadillac deformation zone, Quebec, and implications for gold mineralization

The gold-endowed Larder Lake Cadillac deformation zone (LLCDZ) in the Abitibi greenstone belt of the Archean Superior Province generally trends east but swings to the southeast along the Malartic segment in Quebec. Immediately north of the LLCDZ along this segment, deformation of the less than ca. 2687 Ma metasedimentary Cadillac Group began with the formation of isoclinal F1 folds, which are overprinted by post-2676 ± 2.0 Ma regional F2 folds with an axial planar S2 cleavage oriented parallel to the trend of the Malartic segment. Auriferous quartz veins strike east–west (085°) anticlockwise to bedding and S2. They are folded into sigmoidal S-shaped folds due to sinistral shear parallel to bedding. Later dextral shearing segmented the veins and folded the F2 folds into Z-shaped F3 folds. The veins are similar in structural chronology, fluid isotopic composition (calculated [Formula: see text] value between –9.5‰ and –3.4‰ and [Formula: see text] values of 12‰), and isotopic re-equilibration temperatures (469 and 498 °C, quartz–biotite oxygen thermometer) to the veins at the nearby Canadian Malartic deposit to the east. They possess comparable Au–As–Sb association and sericite-arsenopyrite alteration halo, as other Cadillac-Group-hosted veins at the Lapa mine to the west. Collectively, they constitute a vein field that extends across the entire length of the Malartic segment. Contrary to recent interpretations of the Malartic segment as an early accretionary structure that controlled the emplacement of gold deposits, its southeast trend is interpreted as the short limb of a broad Z-shaped flexure that formed during later F3 folding of the LLCDZ.

Punching Shear Behavior of Flat Slab Strengthen with Y-Type Perfobond Shear

This study demonstrates the behavior of a flat slab experimentally and numerically with two different types of shear reinforcements. Ten slabs were cast and tested in the experimental part. The samples were divided into two groups; the first consists of steel fiber, and the second has no steel fiber. Two control samples were considered with only flexural reinforcement, while the other eight samples had two types of shear reinforcement; the first was rebar to form a Y-shape, while the other was a steel plate formed as a Y-type perfobond. Shear reinforcement is provided by employing radial and parallel shear reinforcement. The tested samples in the experimental part have been simulated numerically using the Abaqus/CAE program. As a result of the laboratory examination, it was determined that the addition of steel fibers increased the ultimate load by (7.4% to 20.58%) for models with steel fibers compared to models without steel fibers. It was determined that the presence of steel plates in the models increased their capacity by 2.4% for ultimate load and by (6% to 50%) for deflection compared to ultimate load and deflection in models with steel bars. In Abaqus, the models with steel fibers were found to be 12.7%-26.6% stronger than those without them.