Home About us Contact
|
Home About us Contact | ||
|
|
||
Deformation Process (deformation + process)
Selected AbstractsDeformation by examples: a density flow approachCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 2 2007Hoi-Chau Leung Abstract In this article, a shape transformation technique is introduced for deforming objects based on a given deformation example. The example consists of two reference shapes representing two different states of an object. The reference shapes are assumed to morph from one state to the other. The evolution between the two reference shapes determines the shape transformation function. Any given objects can then be deformed by the same transformation. A continuous 4D Radial Basis Function is used to construct a density flow field (an extension of the optical flow in computer vision) representing the shape transformation of the example in 3-space. Objects embedded in the density flow field are deformed by moving vertices of the objects along the density flow vectors. Additional parameters are introduced to control the process of the deformation. This provides explicit control on the shape of the object obtained in the deformation process. Copyright © 2007 John Wiley & Sons, Ltd. [source] Formability of Accumulative Roll Bonded Aluminum AA1050 and AA6016 Investigated Using Bulge Tests,ADVANCED ENGINEERING MATERIALS, Issue 12 2008I. Topic The paper reports one of the very first attempts to investigate the formability of ultrafine-grained aluminum sheets produced by a severe plastic deformation process known as accumulative roll bonding. During hydraulic bulge testing the samples showed a tendency to higher achievable burst pressures and/or von Mises equivalent strains with increasing number of accumulative roll bonding cycles, indicating promising deformation behaviour and good formability. [source] Microstructures and adiabatic shear bands formed by ballistic impact in steels and tungsten alloyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2003Z. Q. DUAN ABSTRACT Projectiles of sintered tungsten alloy were fired directly at two kinds of steel target plates. The microstructures near the perforation of a medium, 0.45% carbon steel target plate can be identified along the radial direction as: melted and rapidly solidified layer, recrystallized fine-grained layer, deformed fine-grained layer, deformed layer and normal matrix. The adiabatic shear bands cannot be found in this intermediate strength steel. The microstructures along the radial direction of perforation of 30CrMnMo steel target plate are different from that of the medium carbon steel. There was a melted and rapidly solidified layer on the surface of the perforation, underneath there was a diffusing layer, and then fine-grained layer appeared as streamlines. Several kinds of adiabatic shear bands were found in this higher strength steel; they had different directions and widths, which were relative to the shock waves, as well as the complex deformation process of penetration. The deformation of the projectiles was rather different when they impacted on target plates of medium carbon steel and 30CrMnMo steel. The projectile that impacted on the medium carbon steel target plate was tamped and its energy dissipated slowly, while that which impacted on the 30CrMnMo steel target plate was sheared and the energy dissipated quickly. [source] A simplified analysis of interface failure under compressive normal stress and monotonic or cyclic shear loadingINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2005Zenon Mróz Abstract Interface damage and delamination is usually accompanied by frictional slip at contacting interfaces under compressive normal stress. The present work is concerned with an analysis of progressive interface failure using the cohesive crack model with the critical stress softening and frictional traction present at the contact. Both monotonic and cyclic loadings are considered for anti-plane shear of an elastic plate bonded to a rigid substrate by means of cohesive interface. An analytical solution can be obtained by neglecting the effect of minor shear stress component. The analysis of progressive delamination process revealed three solution types, namely: short, medium and long plate solutions. The long plate solution was obtained under an assumption of quasistatic progressive growth of the delamination zone. In view of snap back response, the quasistatic deformation process cannot be executed by either traction or displacement control. The states of frictional slip accompanied by shake down or incremental failure are distinguished in the case of cyclic loading, related to load amplitude and structural dimensions. The analysis provides a reference solution for numerical treatment of more complex cases. Copyright © 2005 John Wiley & Sons, Ltd. [source] Fabric evolution during hydromechanical loading of a compacted siltINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2004Olivier Cuisinier Abstract A study was undertaken on a compacted silt to determine fabric modifications induced by suction and/or stress variations. The link between fabric and hydromechanical behaviour was also investigated. A suction-controlled oedometer, using air overpressure, was developed for this purpose and mercury intrusion porosimetry was employed to determine sample fabric. The initial samples fabric was made of macro and micropores. It was shown that suction increase produced a strong decrease in the macroporosity associated with an increase in microporosity. However, some macropores were not significantly affected by the suction increase; this phenomenon might be related to the initial fabric of the samples. Second, it appears that loading under saturated conditions also produces strong fabric modification: the higher the applied stress, the lower the macroporosity. Soil fabric depends on the maximum stress experienced by the soil. Finally, some tests have shown the influence of suction, as well as the role of the degree of saturation, on the deformation process and the mechanical behaviour. The test results show that in the case of unsaturated mechanical loading, all macropores are not destroyed by the mechanical loading. Copyright © 2004 John Wiley & Sons, Ltd. [source] Reliability-based preform shape design in forgingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 11 2005Jalaja Repalle Abstract A reliability-based optimization method is developed for preform shape design in forging. Forging is a plastic deformation process that transforms a simple shape of workpiece into a predetermined complex shape through a number of intermediate shapes by the application of compressive forces. Traditionally, these intermediate shapes are designed in a deterministic manufacturing domain. In reality, there exist various uncertainties in the forging environment, such as variations in process conditions, billet/die temperatures, and material properties. Randomness in these parameters could lead to variations in product quality and often induce heavy manufacturing losses. In this research, a robust preform design methodology is developed in which various randomnesses in parameters are quantified and incorporated through reliability analysis and uncertainty quantification techniques. The stochastic response surface approach is used to reduce computation time by establishing a relationship between the process performance and shape and random parameters. Finally, reliability-based optimization is utilized for preform shape design of an engine component to improve the product quality and robustness. Copyright © 2005 John Wiley & Sons, Ltd. [source] Fracture of poly(vinylidene fluoride): a combined synchrotron and laboratory in-situ X-ray scattering studyJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Günther A. Maier Semi-crystalline polymers show a complex fracture mechanism, which is controlled by the micro-mechanisms associated with formation and breakdown of a plastic deformation region. Such regions develop at notches, cracks or other stress-raising defects. In the present paper, we use time-resolved synchrotron X-ray scattering techniques during the deformation process in poly(vinylidene fluoride) to study the plastic zone formation and fracture processes at different strain rates. This gives new insight into the micro-mechanisms of cavitation, lamellae separation and fibril formation in this particular material. [source] Physical Properties of PBMA- b -PBA- b -PBMA Triblock Copolymers Synthesized by Atom Transfer Radical PolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2003Luis Martín-Gomis Abstract The physical properties of well-defined poly(butyl methacrylate)- block -poly(butyl acrylate)- block -poly(butyl methacrylate) (PBMA- b -PBA- b -PBMA) triblock copolymers synthesized by atom transfer radical polymerization (ATRP) are reported. The glass transition and the degradation temperature of copolymers were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC measurements showed phase separation for all of the copolymers with the exception of the one with the shortest length of either inner or outer blocks. TGA demonstrated that the thermal stability of triblock copolymers increased with decreasing BMA content. Dynamic mechanical analysis was used for a preceding evaluation of adhesive properties. In these block copolymers, the deformation process under tension can take place either homogeneously or by a neck formation depending on the molecular weight of the outer BMA blocks and on the length of the inner soft BA segments. Microindentation measurements were also performed for determining the superficial mechanical response and its correlation with the bulk behavior. Stress-strain curves for the different PBMA- b -PBA- b -PBMA specimens at room temperature and at 10 mm/min. [source] Strain-Controlled Tensile Deformation Behavior and Relaxation Properties of Isotactic Poly(1-butene) and Its Ethylene CopolymersMACROMOLECULAR SYMPOSIA, Issue 1 2004Mahmoud Al-Hussein Abstract The tensile deformation behaviour of poly(1-butene) and two of its ethylene copoloymers was studied at room temperature. This was done by investigating true stress-strain curves at constant strain rates, elastic recovery and stress relaxation properties and in-situ WAXS patterns during the deformation process. As for a series of semicrystalline polymers in previous studies, a strain-controlled deformation behaviour was found. The differential compliance, the recovery properties and the stress relaxation curves changed simultaneously at well-defined points. The strains at which these points occurred along the true stress-strain remained constant for the different samples despite their different percentage crystallinities. The well-defined way in which the different samples respond to external stresses complies with the granular substructure of the crystalline lamellae in a semicrystalline polymer. [source] Increasing stable deformation by declining temperature during the processMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4-5 2008J. Ziegelheim Abstract Recently increasing amount of light metal sheets, especially based on magnesium, is being involved into various structural constructions and functional components. Such a rising trend can be observed, for instance, at automotive, aerospace and electronic industry. On the other hand there exist some processing difficulties, such as forming limits, caused by crystalline structure. To make processing of magnesium materials most reasonable with a maximum economical and material's effect, detailed investigation of the material's mechanical behavior is necessary to realize. Especially, an use of superplasticity is a point of the main interest. By optimum settings of the deformation process (especially temperature and strain rate) the superplastic conditions were determined optimally. Moreover, it was discovered that variable temperature very positively affects the superplasticity of magnesium materials. Actually by changing temperature conditions during the deformation, even higher level of superplastic deformation without rupture can be obtained. This very interesting fact was observed at the elevated temperatures that decrease almost constantly during the deformation process. Thus previously widely used constant temperature treatment opens door to the dynamic problems of searching for the optimal temperature gradient and its variation. [source] Bulk anisotropy Nd-Fe-B/,-Fe nanocomposite permanent magnets prepared by sonochemistry and spark plasma sinteringPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007Peili Niu Abstract NdFeB/,-Fe nanocomposite magnetic powders were prepared by sonochemical process. The powders were then submitted to a hot press and subsequent hot deformation process by spark plasma sintering (SPS) technique. Effect of ,-Fe content on structure and magnetic properties of both isotropic and anisotropic magnets was investigated. For hot pressed magnets, the remanence increases with the content of ,-Fe, while the coercive force drops simultaneously. After hot deformation, the magnets with no more than 2 vol% ,-Fe exhibit obvious anisotropic characteristic. For the magnets with more ,-Fe, however, the magnetic anisotropy disappears due to the absence of (00l) crystal texture after deformation. It is, therefore, expected that ,-Fe content plays an important role in the formation of C-axis crystal texture during hot deformation process. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microstructure and magnetic properties of backward extruded NdFeB ring magnets by the CAPA processPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004Hyoung-Tae Kim Abstract The inhomogeneity in microstructure and magnetic properties of a ring magnet prepared by backward extrusion with a current-applied pressure-assisted process has been investigated. The initial part (top part) of a ring magnet prepared by back extrusion shows a high coercivity which is comparable to the raw powder. It exhibits isotropic characteristics along the three orthogonal directions probably due to small deformation. The last part (bottom part) of the ring magnet has a a low coercivity with large grains because high current flows through the pressurized punches during the whole deformation process as to increase the temperature and grain growth. The middle part is under an appropriate deformation with short time exposure at high temperature, therefore it maintains a relatively high remanent polarization with high coercivity. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of mold temperature on the long-term viscoelastic behavior of polybutylene terepthalatePOLYMER ENGINEERING & SCIENCE, Issue 5 2008K. Banik The effect of mold temperature variation during injection molding on the long-term viscoelastic behavior of polybutylene terepthalate (PBT) was studied by dynamic mechanical thermal analysis (DMTA) and flexural creep tests. The time,temperature superposition (TTS) principle was applied to the experimental data and the master curves were created to predict their long-term behavior. The WLF and Arrhenius models were verified for the shift data in the investigating temperature range and the activation energies for the deformation process were calculated based on the Arrhenius equation. Further a four-element Burger model was applied to the creep results to represent the creep behavior of the PBT processed at two different mold temperatures and to better understand the deformation mechanism. Differential scanning calorimetry (DSC) and density measurements were accomplished to characterize the process-dependent microstructures. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Discontinuous deformation in an elastic material.POLYMER ENGINEERING & SCIENCE, Issue 10 2007Part 1. The concept of energy or work dissipation from a perfectly elastic material, due to a discontinuous deformation mechanism, is developed in this study. Dissipation occurs even from a perfectly elastic material, preferably an elastomer, when subjected to a discontinuous "jump" stretch or "jump" contraction. Stretching an elastomeric member through free extension requires a large amount of work. Such a sudden jump stretch of an elastic material is difficult to accomplish and is equivalent to thermodynamic free compression of a gas. The amount of work required can greatly exceed the strain energy stored in the material if the extension were applied without the jump or "shock" process. Interestingly, only part of the stored energy is recovered on unloading the elastomer the same way (through contraction). Excess work lost in contraction dissipates as heat but is not due to the common viscoelastic/plastic losses associated with internal friction in solids. Dissipation is possible even from a perfectly elastic material. Energy values associated in this jump deformation process are independent of the stress,strain curve path, and depend only on initial and final states for the material. Heat dissipation from an elastic rubber belt is examined and some applications extended from the developed principle are enunciated. POLYM. ENG. SCI., 47:1511,1520, 2007. © 2007 Society of Plastics Engineers [source] Starch-filled ternary polymer composites.POLYMER ENGINEERING & SCIENCE, Issue 10 2004II: Room temperature tensile properties The room temperature tensile properties of granular starch-filled low-density polyethylene (PE) and starch-filled blends of PE and poly(hydroxy ester ether) (PHEE) are presented. At low filler contents (,f), the filled PE:PHEE blend has a higher yield stress and tensile strength than either the starch/PE composites or the unfilled matrix. The increase in the yield stress indicates that matrix yielding occurs before debonding. At high filler contents, the tensile strength of the filled blend is again greater than the strength of the starch/PE composites. This increase in strength is the result of higher debonding stresses in the ternary composite. In both materials there is a change in the deformation process at a critical filler content, ,cr. Below ,cr, deformation involves the growth of debonded regions; above ,cr, deformation is confined to narrow damaged zones. There is a reduction in the strain at failure when this change in the deformation process occurs. Although the PHEE surface coating affects the debonding stress and the tensile strength, it does not affect the strain at failure or the tensile modulus. For both composite materials, the increase in modulus with ,f can be adequately described using a simplified form of the Kerner equation. Polym. Eng. Sci. 44:1839,1847, 2004. © 2004 Society of Plastics Engineers. [source] Technical note: Virtual reconstruction of a fragmentary clavicleAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009Stefano Benazzi Abstract We report a procedure for the virtual reconstruction of incomplete human bones applicable to skeletal remains from archaeological excavations or to reconstructive and prosthetic surgery. To test the procedure, we reconstructed a fragmented left clavicle on the basis of the contralateral clavicle. The procedure involved 3-D laser scanner acquisition of the left clavicle (complete but broken into two parts), the same manually reconstructed bone, and the intact right clavicle, which was mirror-imaged and used as a reference for the reconstruction of the whole left clavicle. Because it was not possible to recognize homologous anatomical landmarks, on the two reference models (a mirror-image copy of the right clavicle and the main fragment of the left), we identified three grids with an increasing number of corresponding landmarks, which constituted the framework of the deformation process. The three reconstructed digital models of the clavicle closely approximated the model of the original clavicle. They also showed that an increasing number of landmarks did not significantly improve the reconstructed model. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] Gaussian curvature estimates for the convex level sets of p -harmonic functionsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 7 2010Xi-Nan Ma We give a positive lower bound for the Gaussian curvature of the convex level sets of p -harmonic functions with the Gaussian curvature of the boundary and the norm of the gradient on the boundary. Combining the deformation process, this estimate gives a new approach to studying the convexity of the level sets of the p -harmonic function. © 2010 Wiley Periodicals, Inc. [source] Seismotectonics of the Sinai subplate , the eastern Mediterranean regionGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2003Amos Salamon SUMMARY We define the Sinai subplate, from a seismotectonic perspective, as a distinct component in the plate tectonics of the eastern Mediterranean region. This is based on the tectonic characteristics of a comprehensive listing of all ML, 4 recorded seismicity in the region during the 20th century, on newly calculated and recalculated fault plane mechanisms of first P -wave arrivals and on published solutions based on waveform inversion of broad-band data. The low seismicity level and scarcity of strong events in the region required a thorough search for useful data and a careful examination of the reliability of the focal solutions. We gathered all available records of first P -wave onsets from the ISS and ISC Bulletins and the local seismic networks. Altogether, we were able to calculate 48 new focal mechanisms and 33 recalculated ones of events that occurred during the years 1940,1992. With the increasing number of teleseismic and regional broad-band stations in the later years, we added 37 solutions based on teleseismic and regional waveform inversions of events that occurred during 1977,2001. These mechanisms enabled us to examine the seismotectonic character of the Sinai subplate. The strike and rake directions of the calculated mechanisms usually reflect the geometry and the large-scale type of deformation observed along the boundaries of the Sinai subplate,the Dead Sea Transform, the Cypriot Arc convergent zone and the Suez Rift. Nevertheless, along each of these boundaries we found anomalous solutions that attest to the complexity of the deformation processes along plate margins. Earthquakes along the Dead Sea Transform exhibit mainly sinistral transtension and transpression, reflecting its leaky manner and local change in the transform geometry. The presence of other unexpected mechanisms near the transform, however, reflects the heterogeneous deformation it induces around. As expected, thrust mechanisms along the Cypriot Arc mirror its convergent nature and typical curved geometry. Transtension and transpressional solutions in the eastern segment of the arc reflect the sinistral shear motion between Anatolia and Sinai there. However, shear mechanisms found between Cyprus and the Eratosthenes Seamount pose a problem regarding its collision process. Most intriguing of all are ML, 4 thrust and shear solutions found in the Gulf of Suez. They are associated with predominantly normal mechanisms within a rift zone and therefore constitute a unique phenomenon, yet to be deciphered. [source] A constitutive model for the dynamic and high-pressure behaviour of a propellant-like material: Part I: Experimental background and general structure of the modelINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2001Hervé Trumel Abstract This paper is the first part of a work that aims at developing a mechanical model for the behaviour of propellant-like materials under high confining pressure and strain rate. The behaviour of a typical material is investigated experimentally. Several microstructural deformation processes are identified and correlated with loading conditions. The resulting behaviour is complex, non-linear, and characterized by multiple couplings. The general structure of a relevant model is sought using a thermodynamic framework. A viscoelastic-viscoplastic-compaction model structure is derived under suitable simplifying assumptions, in the framework of finite, though moderate, strains. Model development, identification and numerical applications are given in the companion paper. Copyright © 2001 John Wiley & Sons, Ltd. [source] Analysis of microstructure development in shearbands by energy relaxation of incremental stress potentials: Large-strain theory for standard dissipative solidsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2003Christian Miehe Abstract We propose a fundamentally new approach to the treatment of shearband localizations in strain softening elastic,plastic solids at finite strains based on energy minimization principles associated with microstructure developments. The point of departure is a general internal variable formulation that determines the finite inelastic response as a standard dissipative medium. Consistent with this type of inelasticity we consider an incremental variational formulation of the local constitutive response where a quasi-hyperelastic stress potential is obtained from a local constitutive minimization problem with respect to the internal variables. The existence of this variational formulation allows the definition of the material stability of an inelastic solid based on weak convexity conditions of the incremental stress potential in analogy to treatments of finite elasticity. Furthermore, localization phenomena are interpreted as microstructure developments on multiple scales associated with non-convex incremental stress potentials in analogy to elastic phase decomposition problems. These microstructures can be resolved by the relaxation of non-convex energy functionals based on a convexification of the stress potential. The relaxed problem provides a well-posed formulation for a mesh-objective analysis of localizations as close as possible to the non-convex original problem. Based on an approximated rank-one convexification of the incremental stress potential we develop a computational two-scale procedure for a mesh-objective treatment of localization problems at finite strains. It constitutes a local minimization problem for a relaxed incremental stress potential with just one scalar variable representing the intensity of the microshearing of a rank-one laminate aligned to the shear band. This problem is sufficiently robust with regard to applications to large-scale inhomogeneous deformation processes of elastic,plastic solids. The performance of the proposed energy relaxation method is demonstrated for a representative set of numerical simulations of straight and curved shear bands which report on the mesh independence of the results. Copyright © 2003 John Wiley & Sons, Ltd. [source] Numerical study of consistency of rate constitutive equations with elasticity at finite deformationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 9 2002Ruocheng Lin Abstract The present work is concerned with the numerical study of the elasticity consistency of the spatial rate equations using the conventional Oldroyd, Truesdell, Cotter,Rivlin, Jaumann and Green,Naghdi rates and the three novel co-rotational ,E - and ,ŻL -based, logarithmic rates, and of the rotated material rate equation describing the relationship between the material time derivatives of the rotated Kirchhoff stress and material logarithmic strain. To this end, three integration procedures for updating stress are presented. The stress responses of several typical deformation processes are simulated. According to the numerical results we know that among the spatial rate equations only the logarithmic rate equation is consistent with elasticity under constant material parameters. Integrating the other spatial rate equations will provide path-dependent stress response. These numerical conclusions support the arguments in H. Xiao et al. (Acta Mechanica 1999; 138:31,50). The reasons leading to elasticity inconsistency of spatial rate equations are analysed. If the material parameters are assumed to be strain-dependent, the logarithmic rate equation loses also its elasticity-consistent property. The numerical results prove also that the spatial logarithmic and rotated material rate equations are equivalent to each other. Copyright © 2002 John Wiley & Sons, Ltd. [source] Experimental Investigation of Eclogite Rheology and Its Fabrics at High Temperature and PressureJOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2007J. ZHANG Abstract Eclogite plays an important role in mantle convection and geodynamics in subduction zones. An improved understanding of processes in the deeper levels of subduction zones and collision belts requires information on eclogite rheology. However, the deformation processes and associated fabrics in eclogite are not well understood. Incompatible views of deformation mechanism have been proposed for both garnet and omphacite. We present here deformation behaviour of eclogite at temperatures of 1027,1427 °C, confining pressures of 2.5,3.5 GPa, and strain rates of 1 × 10,5 s,1 to 5 × 10,4 s,1. We obtained a power-law creep for the high temperature and pressure deformation of a ,dry' eclogite (50 vol.% garnet, 40% omphacite and 10% quartz) with A = 103.3 ± 1.0, n = 3.5 ± 0.4, ,E =403 ± 30 KJ mol,1 and ,V = 27.2 cm3 mol,1. The two principal minerals of eclogite have greatly different strengths. Progressive increase of garnet results in a smooth increase in strength. Analysis by electron back-scattered diffraction shows that: (1) garnet displays pole figures with near random distributions of misorientation angle under both dry and wet conditions; (2) omphacite shows pronounced lattice preferred orientations (LPOs), suggesting a dominant dislocation creep mechanism. Further investigation into the water effects on eclogite show: (3) water content does not influence the style of omphacite fabric but increases slightly the fabric strength; (4) grain boundary processes dominate the deformation of garnet under high water fugacity or high shear-strain conditions, yielding a random LPO similar to that of non-deforming garnet, despite the strong shape preferred orientation (SPO) observed. {110} [001] slip may dominate the deformation of rutile. Quartz displays complicated and inconsistent LPOs in eclogite. These results are remarkably similar to observations from deformed eclogites in nature. [source] Fluid dynamics and subsurface sediment mobilization processes: an overview from Southeast CaribbeanBASIN RESEARCH, Issue 4 2010Éric Deville ABSTRACT This paper discusses the origin and the dynamics of subsurface sediment mobilization processes in tectonically mobile regions and shale-rich environment. This is illustrated by the example of Trinidad and the south of the Barbados prism. In this area of the southeast Caribbean, geophysical acquisitions have spectacularly shown the widespread development of sediment mobilization features in the interference area between the southern part of the Barbados prism and the active turbidite system of the Orinoco. Numerous mud volcanoes are especially developed along ramp anticline crests through hydraulic fracture systems. The area also exhibits trends of structures that correspond to massive uplifts of well-preserved turbidite and hemipelagic sediments that cut up the surrounding sediments. Some of these structures are complicated by the development of collapse structures, calderas and superimposed mud volcanoes. The mobilized sediments expelled by the mud volcanoes are not only liquefied argillaceous but also fine sandy material from deep horizons, and various shallower formations pierced by the mud conduits. Both in the Barbados prism and in Trinidad, the expelled mud is rich in thin, angular and mechanically damaged quartz grains, which are probably cataclastic flows issued from sheared and collapsed deep sandy reservoirs. The exotic clasts and breccias result mostly from hydraulic fracturing. In Trinidad, the gas phase is mainly deep thermogenic methane associated with hydrocarbon generation at depth. Subsurface sediment mobilization notably differs from salt mobilization by the role taken by the fluid dynamics that control overpressured shale mobilization and induce sediment liquefaction. A reaction chain of several deformation processes develops around the conduits. Massive sedimentary uplift corresponds to large movements of stratified solid levels, possibly due to the tectonic inversion of pre-existing mud volcano systems. All these phenomena are controlled by the development of overpressure at depth. No evidence for piercing shale diapirs has been observed in the area studied. [source] | |||||||||||||||||||||||||||||||