The Reorientation of the Kangâmiut Dike Swarm, West Greenland

1975 ◽  
Vol 12 (2) ◽  
pp. 158-173 ◽  
Author(s):  
A. Escher ◽  
J. C. Escher ◽  
J. Watterson
Keyword(s):  
Simple Shear ◽  
Shear Plane ◽  
Boundary Region ◽  
Ductile Deformation ◽  
Shear Direction ◽  
Average Amount ◽  
Southern Boundary ◽  
Crustal Shortening ◽  
West Greenland ◽  
Simple Shear Deformation

The Nagssugtoqidian belt in West Greenland is formed mainly of Archaean rocks which were strongly reworked during the early Proterozoic. Investigation of the southern boundary region has resulted in a model for the tectonic reworking based on the geometry of homogeneous simple shear deformation. Two differently oriented swarms of mainly pre-kinematic dikes are used as strain indicators at the deformation boundary. Gneiss tectonite fabrics have been used to determine that the shear plane dips northwest at 20–40° and that the shear direction along this plane is towards the southeast. The average amount of simple shear strain (S = 6) has been determined from the degree of dike reorientation. This mechanism has resulted in a ductile overthrusting of the reworked rocks over the Archaean foreland, giving a crustal shortening of ca. 66%. The area investigated represents a deep tectonic level. At higher levels ductile deformation would be expected to give way to thrust and fold nappe development. The displacements demonstrated are those which might be expected in the deformed margins of colliding continental plates.

TEXTURES OF EQUAL CHANNEL ANGULAR PRESSED 1050 ALUMINUM ALLOY STRIPS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5977-5984
Author(s):  
JAE YEOL PARK ◽  
SEUNG-HYUN HONG ◽  
DONG NYUNG LEE
Keyword(s):  
Aluminum Alloy ◽  
Simple Shear ◽  
Deformation Texture ◽  
Shear Direction ◽  
Process Variables ◽  
Oblique Angle ◽  
Angular Pressing ◽  
Simple Shear Deformation ◽  
Fcc Alloy ◽  
1050 Aluminum Alloy

In order to improve the deep drawability of aluminum and aluminum alloy sheets, it is desirable to increase the ND//<111> component in their textures. The ND//<111> component is known to develop in shear-deformed fcc alloy sheets. The equal-channel angular pressing (ECAP) is a process in which materials undergo approximately simple shear deformation. The deformation texture of ECAPed strips can change depending on process variables such as the texture of starting strips, the oblique angle, the number of pressing passes, and the shear direction. The deformation and deformation texture have been analyzed.

Influence of a Slip Plane Orientation with Respect to the Shear Plane of ECAP on Microstructure of Copper Single Crystal Subject to One Pressing at Room Temperature

2008 ◽  
Vol 584-586 ◽  
pp. 387-392 ◽  
Author(s):  
Soichi Katayama ◽  
Hiroyuki Miyamoto ◽  
Alexei Vinogradov ◽  
Satoshi Hashimoto
Keyword(s):  
Simple Shear ◽  
Crystallographic Orientation ◽  
Room Temperature ◽  
Electron Backscatter Diffraction ◽  
Pure Copper ◽  
Shear Bands ◽  
Large Angle ◽  
Shear Plane ◽  
Deformation Twinning ◽  
Shear Direction

This paper describes the influence of initial crystallographic orientation on the formation of dense shear bands in pure copper single crystals subjected to equal-channel angular pressing (ECAP) for one pass at room temperature. Local orientation change during simple shear by ECAP traced by electron backscatter diffraction (EBSD) indicated that the shear bands were formed when twinning plane and direction become parallel to the macroscopic shear plane and shear direction of simple shear strain, respectively. Orientation splitting associated with shear bands have a twinning relation. The shear bands were delineated by large-angle grain boundaries, having close relation to twinning relation with matrix, suggesting the role of deformation twinning as their nucleation sites. The activation of deformation twinning is suggested and can be rationalized by favorable crystallographic orientation and critical dislocation density as indicated elsewhere by the present authors.

Texture Evolution in Pure Copper Processed by Equal Channel Angular Extrusion with Extended Processing Routes

2010 ◽  
Vol 667-669 ◽  
pp. 271-276 ◽  
Author(s):  
Sai Yi Li ◽  
Hao Li
Keyword(s):  
Simple Shear ◽  
Equal Channel Angular Extrusion ◽  
Texture Evolution ◽  
Pure Copper ◽  
Shear Plane ◽  
Processing Route ◽  
Shear Direction ◽  
Face Centered Cubic ◽  
Wide Range ◽  
Angular Extrusion

An experimental characterization of texture evolution during equal channel angular extrusion (ECAE) of pure copper was conducted up to 8 passes considering an extended range of processing routes. These routes are featured by 0°, 45°, 90°, 135°, and 180° rotation about the billet longitudinal axis after each pass, and were designated as R0, R45, R90, R135, and R180, respectively. They were implemented using new die designs with the cross-section of the die channels as a 24-sided regular convex polygon and with die angle (Φ) of 90° and 120°, respectively. X-ray diffraction measurements show that for both die sets, the textures developed via the different routes all show orientation concentrations along fibers with the {111} planes parallel to the macroscopic simple shear plane and <110> directions parallel to the macroscopic simple shear direction, yet the locations and orientation densities of the main texture components vary significantly with the pass number and the processing route. After 4 to 8 passes, the texture is found to be the weakest via route R180 for both die sets, and strongest via R0 or R45. For a given route and pass number, the texture developed with Φ = 120° is generally weaker than its counterpart with Φ = 90°. These results thus confirm the general tendencies of texture development in face-centered cubic metals with {111}<110> slip as the dominant deformation mechanisms, albeit in a wide range of processing route or deformation history.

scholarly journals New sights in crenulation geometry developed in anisotropic materials undergoing simple shear deformation

2021 ◽  
Author(s):  
Yuanbang Hu ◽  
Tamara de Riese ◽  
Paul Bons ◽  
Shugen Liu ◽  
Albert Griera ◽  
...  
Keyword(s):  
Structural Geology ◽  
Numerical Simulations ◽  
Shear Deformation ◽  
Simple Shear ◽  
Shear Bands ◽  
Shear Plane ◽  
Initial Orientation ◽  
Mechanical Anisotropy ◽  
Simple Shear Deformation ◽  
Shear Localisation

&lt;p&gt;Deformation of foliated rocks commonly leads to crenulation or micro-folding, with the development of cleavage domains and microlithons. We here consider the effect of mechanical anisotropy due to a crystallographic preferred orientation (CPO) that defines the foliation, for example by of alignment of micas. Mechanical anisotropy enhances shear localisation (Ran, et al., 2018; de Riese et al., 2019), resulting in low-strain domains (microlithons) and high-strain shear bands or cleavage domains. We investigate the crenulation patterns that result from moderate strain simple shear deformation, varying the initial orientation of the mechanical anisotropy relative to the shear plane. &amp;#160;&lt;/p&gt;&lt;p&gt;We use the Viscoplastic Full-Field Transform (VPFFT) crystal plasticity code coupled with the modelling platform ELLE (http://www.elle.ws; Llorens et al., 2017) to simulate the deformation of anisotropic single-phase material with an initial given CPO in dextral simple shear in low to medium strain. Deformation is assumed to be accommodated by glide along the basal, prismatic and pyramidal slip systems of a hexagonal model mineral. An approximately transverse anisotropy is achieved by assigning a small critical resolved shear stress to the basal plane. An initially point-maximum CPO at variable angles to the shear plane defines the initial straight foliation at different angles to the shear plane, limiting ourselves to orientations in which the foliation is in the stretching field. The resulting crenulation geometries strongly depend on the orientation of the foliation and we observe four types of localisation behaviour: (1) synthetic shear bands, (2) antithetic shear bands, (3) initial formation of antithetic shear bands and subsequent development of synthetic shear bands, and (4) distributed, approximately shear-margin parallel strain localisation, but no distinct shear bands.&lt;/p&gt;&lt;p&gt;The numerical simulations not only show the evolving strain-rate field, but also the predicted finite strain pattern of existing visible foliations. We show the results for layers parallel to the foliation, but also cases where the visible layering is at an angle to the mechanical anisotropy (e.g. in case of distinct sedimentary layers and a cleavage that controls the mechanical anisotropy). A wide range of crenulation types form as a function of the initial orientation of the visible layering and mechanical anisotropy (comparable to C, C' and C'' shear bands and compressional crenulation cleavage). Most importantly, some of may be highly misleading and may easily be interpreted as indicating the opposite sense of shear.&lt;/p&gt;&lt;p&gt;Reference&lt;/p&gt;&lt;p&gt;de Riese, T., et al. (2019). Shear localisation in anisotropic, non-linear viscous materials that develop a CPO: A numerical study. Journal of Structural Geology, 124, 81-90. DOI: 10.1016/j.jsg.2019.03.006&lt;/p&gt;&lt;p&gt;Llorens, M.-G., et al. (2017). Dynamic recrystallisation during deformation of polycrystalline ice: insights from numerical simulations. Philosophical Transactions of the Royal Society A, Special Issue on Microdynamics of Ice, 375: 20150346. DOI: 10.1098/rsta.2015.0346.&lt;/p&gt;&lt;p&gt;Ran, H., et al. (2018). Time for anisotropy: The significance of mechanical anisotropy for the development of deformation structures. Journal of Structural Geology, 125, 41-47. DOI: 10.1016/j.jsg.2018.04.019&lt;/p&gt;

scholarly journals The Nordre Strømfjord shear zone and the Arfersiorfik quartz diorite in Arfersiorfik, the Nagssugtoqidian orogen, West Greenland

2006 ◽  
Vol 11 ◽  
pp. 145-162 ◽  
Author(s):  
Kai Sørensen ◽  
John A. Korstgård ◽  
William E. Glassley ◽  
Bo Møller Stensgaard
Keyword(s):  
Shear Zone ◽  
Volcanic Rocks ◽  
Quartz Diorite ◽  
Ductile Deformation ◽  
Chemical Compositions ◽  
West Greenland ◽  
South West ◽  
Wide Range ◽  
Inland Ice ◽  
Zone Deformation

The Nordre Strømfjord shear zone in the fjord Arfersiorfik, central West Greenland, consists of alternating panels of supracrustal rocks and orthogneisses which together form a vertical zone up to 7 km wide with sinistral transcurrent, ductile deformation, which occurred under middle amphibolite facies conditions. The pelitic and metavolcanic schists and paragneisses are all highly deformed, while the orthogneisses appear more variably deformed, with increasing deformation evident towards the supracrustal units. The c. 1.92 Ga Arfersiorfik quartz diorite is traceable for a distance of at least 35 km from the Inland Ice towards the west-south-west. Towards its northern contact with an intensely deformed schist unit it shows a similar pattern of increasing strain, which is accompanied by chemical and mineralogical changes. The metasomatic changes associated with the shear zone deformation are superimposed on a wide range of original chemical compositions, which reflect magmatic olivine and/ or pyroxene as well as hornblende fractionation trends. The chemistry of the Arfersiorfik quartz diorite suite as a whole is comparable to that of Phanerozoic plutonic and volcanic rocks of calc-alkaline affinity.

Stable equilibrium configurations of an oblate capsule in simple shear flow

2016 ◽  
Vol 791 ◽  
pp. 738-757 ◽  
Author(s):  
C. Dupont ◽  
F. Delahaye ◽  
D. Barthès-Biesel ◽  
A.-V. Salsac
Keyword(s):  
Aspect Ratio ◽  
Shear Flow ◽  
Simple Shear ◽  
Capillary Number ◽  
Stable Equilibrium ◽  
Viscosity Ratio ◽  
Shear Plane ◽  
Initial Orientation ◽  
Simple Shear Flow ◽  
Mechanical Equilibrium

The objective of the paper is to determine the stable mechanical equilibrium states of an oblate capsule subjected to a simple shear flow, by positioning its revolution axis initially off the shear plane. We consider an oblate capsule with a strain-hardening membrane and investigate the influence of the initial orientation, capsule aspect ratio$a/b$, viscosity ratio${\it\lambda}$between the internal and external fluids and the capillary number$Ca$which compares the viscous to the elastic forces. A numerical model coupling the finite element and boundary integral methods is used to solve the three-dimensional fluid–structure interaction problem. For any initial orientation, the capsule converges towards the same mechanical equilibrium state, which is only a function of the capillary number and viscosity ratio. For$a/b=0.5$, only four regimes are stable when${\it\lambda}=1$: tumbling and swinging in the low and medium$Ca$range ($Ca\lesssim 1$), regimes for which the capsule revolution axis is contained within the shear plane; then wobbling during which the capsule experiences precession around the vorticity axis; and finally rolling along the vorticity axis at high capillary numbers. When${\it\lambda}$is increased, the tumbling-to-swinging transition occurs for higher$Ca$; the wobbling regime takes place at lower$Ca$values and within a narrower$Ca$range. For${\it\lambda}\gtrsim 3$, the swinging regime completely disappears, which indicates that the stable equilibrium states are mainly the tumbling and rolling regimes at higher viscosity ratios. We finally show that the$Ca$–${\it\lambda}$phase diagram is qualitatively similar for higher aspect ratio. Only the$Ca$-range over which wobbling is stable increases with$a/b$, restricting the stability ranges of in- and out-of-plane motions, although this phenomenon is mainly visible for viscosity ratios larger than 1.

Shear properties of passive ventricular myocardium

2002 ◽  
Vol 283 (6) ◽  
pp. H2650-H2659 ◽  
Author(s):  
Socrates Dokos ◽  
Bruce H. Smaill ◽  
Alistair A. Young ◽  
Ian J. LeGrice
Keyword(s):  
Shear Deformation ◽  
Simple Shear ◽  
Ventricular Myocardium ◽  
Left Ventricular ◽  
Shear Deformations ◽  
Shear Properties ◽  
Nonlinear Viscoelastic ◽  
Myocardial Layers ◽  
Shear Modes ◽  
Simple Shear Deformation

We examined the shear properties of passive ventricular myocardium in six pig hearts. Samples (3 × 3 × 3 mm) were cut from adjacent regions of the lateral left ventricular midwall, with sides aligned with the principal material axes. Four cycles of sinusoidal simple shear (maximum shear displacements of 0.1–0.5) were applied separately to each specimen in two orthogonal directions. Resulting forces along the three axes were measured. Three specimens from each heart were tested in different orientations to cover all six modes of simple shear deformation. Passive myocardium has nonlinear viscoelastic shear properties with reproducible, directionally dependent softening as strain is increased. Shear properties were clearly anisotropic with respect to the three principal material directions: passive ventricular myocardium is least resistant to simple shear displacements imposed in the plane of the myocardial layers and most resistant to shear deformations that produce extension of the myocyte axis. Comparison of results for the six different shear modes suggests that simple shear deformation is resisted by elastic elements aligned with the microstructural axes of the tissue.

scholarly journals Recrystallization processes, microstructure and crystallographic preferred orientation evolution in polycrystalline ice during high-temperature simple shear

2019 ◽  
Vol 13 (5) ◽  
pp. 1495-1511 ◽  
Author(s):  
Baptiste Journaux ◽  
Thomas Chauve ◽  
Maurine Montagnat ◽  
Andrea Tommasi ◽  
Fabrice Barou ◽  
...  
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Simple Shear ◽  
Shear Plane ◽  
Preferred Orientation ◽  
Dislocation Slip ◽  
Crystallographic Preferred Orientation ◽  
Polycrystalline Ice

Abstract. Torsion experiments were performed in polycrystalline ice at high temperature (0.97 Tm) to reproduce the simple shear kinematics that are believed to dominate in ice streams and at the base of fast-flowing glaciers. As clearly documented more than 30 years ago, under simple shear ice develops a two-maxima c axis crystallographic preferred orientation (CPO), which evolves rapidly into a single cluster CPO with a c axis perpendicular to the shear plane. Dynamic recrystallization mechanisms that occur in both laboratory conditions and naturally deformed ice are likely candidates to explain the observed CPO evolution. In this study, we use electron backscatter diffraction (EBSD) and automatic ice texture analyzer (AITA) to characterize the mechanisms accommodating deformation, the stress and strain heterogeneities that form under torsion of an initially isotropic polycrystalline ice sample at high temperature, and the role of dynamic recrystallization in accommodating these heterogeneities. These analyses highlight an interlocking microstructure, which results from heterogeneity-driven serrated grain boundary migration, and sub-grain boundaries composed of dislocations with a [c]-component Burgers vector, indicating that strong local stress heterogeneity develops, in particular, close to grain boundaries, even at high temperature and high finite shear strain. Based on these observations, we propose that nucleation by bulging, assisted by sub-grain boundary formation and followed by grain growth, is a very likely candidate to explain the progressive disappearance of the c axis CPO cluster at low angle to the shear plane and the stability of the one normal to it. We therefore strongly support the development of new polycrystal plasticity models limiting dislocation slip on non-basal slip systems and allowing for efficient accommodation of strain incompatibilities by an association of bulging and formation of sub-grain boundaries with a significant [c] component.

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