Deformation-mechanism map for nanocrystalline metals by molecular-dynamics simulation.

PubMed

Yamakov, V; Wolf, D; Phillpot, S R; Mukherjee, A K; Gleiter, H

2004-01-01

Molecular-dynamics simulations have recently been used to elucidate the transition with decreasing grain size from a dislocation-based to a grain-boundary-based deformation mechanism in nanocrystalline f.c.c. metals. This transition in the deformation mechanism results in a maximum yield strength at a grain size (the 'strongest size') that depends strongly on the stacking-fault energy, the elastic properties of the metal, and the magnitude of the applied stress. Here, by exploring the role of the stacking-fault energy in this crossover, we elucidate how the size of the extended dislocations nucleated from the grain boundaries affects the mechanical behaviour. Building on the fundamental physics of deformation as exposed by these simulations, we propose a two-dimensional stress-grain size deformation-mechanism map for the mechanical behaviour of nanocrystalline f.c.c. metals at low temperature. The map captures this transition in both the deformation mechanism and the related mechanical behaviour with decreasing grain size, as well as its dependence on the stacking-fault energy, the elastic properties of the material, and the applied stress level.

Mechanical deformation induces depolarization of neutrophils.

PubMed

Ekpenyong, Andrew E; Toepfner, Nicole; Fiddler, Christine; Herbig, Maik; Li, Wenhong; Cojoc, Gheorghe; Summers, Charlotte; Guck, Jochen; Chilvers, Edwin R

2017-06-01

The transition of neutrophils from a resting state to a primed state is an essential requirement for their function as competent immune cells. This transition can be caused not only by chemical signals but also by mechanical perturbation. After cessation of either, these cells gradually revert to a quiescent state over 40 to 120 min. We use two biophysical tools, an optical stretcher and a novel microcirculation mimetic, to effect physiologically relevant mechanical deformations of single nonadherent human neutrophils. We establish quantitative morphological analysis and mechanical phenotyping as label-free markers of neutrophil priming. We show that continued mechanical deformation of primed cells can cause active depolarization, which occurs two orders of magnitude faster than by spontaneous depriming. This work provides a cellular-level mechanism that potentially explains recent clinical studies demonstrating the potential importance, and physiological role, of neutrophil depriming in vivo and the pathophysiological implications when this deactivation is impaired, especially in disorders such as acute lung injury.

Identifying deformation mechanisms in the NEEM ice core using EBSD measurements

NASA Astrophysics Data System (ADS)

Kuiper, Ernst-Jan; Weikusat, Ilka; Drury, Martyn R.; Pennock, Gill M.; de Winter, Matthijs D. A.

2015-04-01

Deformation of ice in continental sized ice sheets determines the flow behavior of ice towards the sea. Basal dislocation glide is assumed to be the dominant deformation mechanism in the creep deformation of natural ice, but non-basal glide is active as well. Knowledge of what types of deformation mechanisms are active in polar ice is critical in predicting the response of ice sheets in future warmer climates and its contribution to sea level rise, because the activity of deformation mechanisms depends critically on deformation conditions (such as temperature) as well as on the material properties (such as grain size). One of the methods to study the deformation mechanisms in natural materials is Electron Backscattered Diffraction (EBSD). We obtained ca. 50 EBSD maps of five different depths from a Greenlandic ice core (NEEM). The step size varied between 8 and 25 micron depending on the size of the deformation features. The size of the maps varied from 2000 to 10000 grid point. Indexing rates were up to 95%, partially by saving and reanalyzing the EBSP patterns. With this method we can characterize subgrain boundaries and determine the lattice rotation configurations of each individual subgrain. Combining these observations with arrangement/geometry of subgrain boundaries the dislocation types can be determined, which form these boundaries. Three main types of subgrain boundaries have been recognized in Antarctic (EDML) ice core¹². Here, we present the first results obtained from EBSD measurements performed on the NEEM ice core samples from the last glacial period, focusing on the relevance of dislocation activity of the possible slip systems. Preliminary results show that all three subgrain types, recognized in the EDML core, occur in the NEEM samples. In addition to the classical boundaries made up of basal dislocations, subgrain boundaries made of non-basal dislocations are also common. ¹Weikusat, I.; de Winter, D. A. M.; Pennock, G. M.; Hayles, M

Mechanical Deformation Mechanisms and Properties of Prion Fibrils Probed by Atomistic Simulations

NASA Astrophysics Data System (ADS)

Choi, Bumjoon; Kim, Taehee; Ahn, Eue Soo; Lee, Sang Woo; Eom, Kilho

2017-03-01

Prion fibrils, which are a hallmark for neurodegenerative diseases, have recently been found to exhibit the structural diversity that governs disease pathology. Despite our recent finding concerning the role of the disease-specific structure of prion fibrils in determining their elastic properties, the mechanical deformation mechanisms and fracture properties of prion fibrils depending on their structures have not been fully characterized. In this work, we have studied the tensile deformation mechanisms of prion and non-prion amyloid fibrils by using steered molecular dynamics simulations. Our simulation results show that the elastic modulus of prion fibril, which is formed based on left-handed β-helical structure, is larger than that of non-prion fibril constructed based on right-handed β-helix. However, the mechanical toughness of prion fibril is found to be less than that of non-prion fibril, which indicates that infectious prion fibril is more fragile than non-infectious (non-prion) fibril. Our study sheds light on the role of the helical structure of amyloid fibrils, which is related to prion infectivity, in determining their mechanical deformation mechanisms and properties.

Late-Paleozoic-Mesozoic deformational and deformation related metamorphic structures of Kuznetsk-Altai region

NASA Astrophysics Data System (ADS)

Zinoviev, Sergei

2014-05-01

Kuznetsk-Altai region is a part of the Central Asian Orogenic Belt. The nature and formation mechanisms of the observed structure of Kuznetsk-Altai region are interpreted by the author as the consequence of convergence of Tuva-Mongolian and Junggar lithospheric block structures and energy of collision interaction between the blocks of crust in Late-Paleozoic-Mesozoic period. Tectonic zoning of Kuznetsk-Altai region is based on the principle of adequate description of geological medium (without methods of 'primary' state recovery). The initial indication of this convergence is the crust thickening in the zone of collision. On the surface the mechanisms of lateral compression form a regional elevation; with this elevation growth the 'mountain roots' start growing. With an approach of blocks an interblock elevation is divided into various fragments, and these fragments interact in the manner of collision. The physical expression of collision mechanisms are periodic pulses of seismic activity. The main tectonic consequence of the block convergence and collision of interblock units is formation of an ensemble of regional structures of the deformation type on the basis of previous 'pre-collision' geological substratum [Chikov et al., 2012]. This ensemble includes: 1) allochthonous and autochthonous blocks of weakly deformed substratum; 2) folded (folded-thrust) systems; 3) dynamic metamorphism zones of regional shears and main faults. Characteristic of the main structures includes: the position of sedimentary, magmatic and PT-metamorphic rocks, the degree of rock dynamometamorphism and variety rock body deformation, as well as the styles and concentrations of mechanic deformations. 1) block terranes have weakly elongated or isometric shape in plane, and they are the systems of block structures of pre-collision substratum separated by the younger zones of interblock deformations. They stand out among the main deformation systems, and the smallest are included into the

Mechanical stability of heat-treated nanoporous anodic alumina subjected to repetitive mechanical deformation

NASA Astrophysics Data System (ADS)

Bankova, A.; Videkov, V.; Tzaneva, B.; Mitov, M.

2018-03-01

We report studies on the mechanical response and deformation behavior of heat-treated nanoporous anodic alumina using a micro-balance test and experimental test equipment especially designed for this purpose. AAO samples were characterized mechanically by a three-point bending test using a micro-analytical balance. The deformation behavior was studied by repetitive mechanical bending of the AAO membranes using an electronically controlled system. The nanoporous AAO structures were prepared electrochemically from Al sheet substrates using a two-step anodizing technique in oxalic acid followed by heat treatment at 700 °C in air. The morphological study of the aluminum oxide layer after the mechanical tests and mechanical deformation was conducted using scanning electron and optical microscopy, respectively. The experimental results showed that the techniques proposed are simple and accurate; they could, therefore, be combined to constitute a method for mechanical stability assessment of nanostructured AAO films, which are important structural components in the design of MEMS devices and sensors.

Soft tissue deformation modelling through neural dynamics-based reaction-diffusion mechanics.

PubMed

Zhang, Jinao; Zhong, Yongmin; Gu, Chengfan

2018-05-30

Soft tissue deformation modelling forms the basis of development of surgical simulation, surgical planning and robotic-assisted minimally invasive surgery. This paper presents a new methodology for modelling of soft tissue deformation based on reaction-diffusion mechanics via neural dynamics. The potential energy stored in soft tissues due to a mechanical load to deform tissues away from their rest state is treated as the equivalent transmembrane potential energy, and it is distributed in the tissue masses in the manner of reaction-diffusion propagation of nonlinear electrical waves. The reaction-diffusion propagation of mechanical potential energy and nonrigid mechanics of motion are combined to model soft tissue deformation and its dynamics, both of which are further formulated as the dynamics of cellular neural networks to achieve real-time computational performance. The proposed methodology is implemented with a haptic device for interactive soft tissue deformation with force feedback. Experimental results demonstrate that the proposed methodology exhibits nonlinear force-displacement relationship for nonlinear soft tissue deformation. Homogeneous, anisotropic and heterogeneous soft tissue material properties can be modelled through the inherent physical properties of mass points. Graphical abstract Soft tissue deformation modelling with haptic feedback via neural dynamics-based reaction-diffusion mechanics.

Deformation Analysis of the Main Components in a Single Screw Compressor

NASA Astrophysics Data System (ADS)

Liu, Feilong; Liao, Xueli; Feng, Quanke; Van Den Broek, Martijn; De Paepe, Michel

2015-08-01

The single screw compressor is used in many fields such as air compression, chemical industry and refrigeration. During operation, different gas pressures and temperatures applied on the components can cause different degrees of deformation, which leads to a difference between the thermally induced clearance and the designed clearance. However, limited research about clearance design is reported. In this paper, a temperature measurement instrument and a convective heat transfer model were described and used to establish the temperature of a single screw air compressor's casing, screw rotor and star wheel. 3-D models of these three main components were built. The gas force deformation, thermal- structure deformation and thermal-force coupling deformation were carried out by using a finite element simulation method. Results show that the clearance between the bottom of the groove and the top of star wheel is reduced by 0.066 mm, the clearance between the side of groove and the star wheel is reduced by 0.015 mm, and the clearance between the cylinder and the rotor is reduced by 0.01 mm. It is suggested that these deformations should be taken into account during the design of these clearances.

Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

DOE PAGES

Wu, Wei; An, Ke; Liaw, Peter K.

2014-12-23

In the current study, the deformation mechanisms of a rolled magnesium alloy were investigated under cyclic loading using real-time in situ neutron diffraction under a continuous-loading condition. The relationship between the macroscopic cyclic deformation behavior and the microscopic response at the grain level was established. The neutron diffraction results indicate that more and more grains are involved in the twinning and detwinning deformation process with the increase of fatigue cycles. The residual twins appear in the early fatigue life, which is responsible for the cyclic hardening behavior. The asymmetric shape of the hysteresis loop is attributed to the early exhaustionmore » of the detwinning process during compression, which leads to the activation of dislocation slips and rapid strain-hardening. The critical resolved shear stress for the activation of tensile twinning closely depends on the residual strain developed during cyclic loading. In the cycle before the sample fractured, the dislocation slips became active in tension, although the sample was not fully twinned. The increased dislocation density leads to the rise of the stress concentration at weak spots, which is believed to be the main reason for the fatigue failure. Furthermore, the deformation history greatly influences the deformation mechanisms of hexagonal-close-packed-structured magnesium alloy during cyclic loading.« less

Superplastic Deformation Mechanisms of Superfine/Nanocrystalline Duplex PM-TiAl-Based Alloy.

PubMed

Gong, Xuebo; Duan, Zhenxin; Pei, Wen; Chen, Hua

2017-09-19

In this paper, the equiaxed superfine/nanocrystalline duplex PM-TiAl-based alloy with (γ + α₂) microstructure, Ti-45Al-5Nb (at %), has been synthesized by high-energy ball milling and vacuum hot pressing sintering. Superplastic deformation behavior has been investigated at 1000 °C and 1050 °C with strain rates from 5 × 10 -5 s -1 to 1 × 10 -3 s -1 . The effects of deformation on the microstructure and mechanical behaviors of high Nb containing TiAl alloy have been characterized and analyzed. The results showed that, the ultimate tensile strength of the alloy was 58.7 MPa at 1000 °C and 10.5 MPa at 1050 °C with a strain rate of 5 × 10 -5 s -1 , while the elongation was 121% and 233%, respectively. The alloy exhibited superplastic elongation at 1000 and 1050 °C with an exponent (m) of 0.48 and 0.45. The main softening mechanism was dynamic recrystallization of γ grains; the dislocation slip and γ/γ interface twinning were responsible for superplastic deformation. The orientation relationship of γ/γ interface twinning obeyed the classical one: (001) γ //(110) γ .

The relationships between deformation mechanisms and mechanical properties of additively manufactured porous biomaterials.

PubMed

Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Zargarian, A; Schmauder, S

2017-06-01

Modulating deformation mechanism through manipulating morphological parameters of scaffold internal pore architecture provides potential to tailor the overall mechanical properties under physiological loadings. Whereas cells sense local strains, cell differentiation is also impressed by the elastic deformations. In this paper, structure-property relations were developed for Ti6-Al-4V scaffolds designed based on triply periodic minimal surfaces. 10mm cubic scaffolds composed of 5×5×5 unit cells formed of F-RD (bending dominated) and I-WP (stretching dominated) architectures were additively manufactured at different volume fractions and subjected to compressive tests. The first stages of deformation for stretching dominated structure, was accompanied by bilateral layer-by-layer failure of unit cells owing to the buckling of micro-struts, while for bending dominated structure, namely F-RD, global shearing bands appeared since the shearing failure of struts in the internal architecture. Promoted mechanical properties were found for stretching dominated structure since the global orientation of struts were parallel to loading direction while inclination of struts diminished specific properties for bending dominated structure. Moreover, elastic-plastic deformation was computationally studied by applying Johnson-Cook damage model to the voxel-based models in FE analysis. Scaling analysis was performed for mechanical properties with respect to the relative density thereby failure mechanism was correlated to the constants of power law describing mechanical properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Microstructure, strengthening mechanisms and hot deformation behavior of an oxide-dispersion strengthened UFG Al6063 alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asgharzadeh, H.; Kim, H.S.; Simchi, A., E-mail: simchi@sharif.edu

2013-01-15

An ultrafine-grained Al6063/Al{sub 2}O{sub 3} (0.8 vol.%, 25 nm) nanocomposite was prepared via powder metallurgy route through reactive mechanical alloying and hot powder extrusion. Scanning electron microcopy, transmission electron microscopy, and back scattered electron diffraction analysis showed that the grain structure of the nanocomposite is trimodal and composed of nano-size grains (< 0.1 {mu}m), ultrafine grains (0.1-1 {mu}m), and micron-size grains (> 1 {mu}m) with random orientations. Evaluation of the mechanical properties of the nanocomposite based on the strengthening-mechanism models revealed that the yield strength of the ultrafine-grained nanocomposite is mainly controlled by the high-angle grain boundaries rather than nanometricmore » alumina particles. Hot deformation behavior of the material at different temperatures and strain rates was studied by compression test and compared to coarse-grained Al6063 alloy. The activation energy of the hot deformation process for the nanocomposite was determined to be 291 kJ mol{sup -1}, which is about 64% higher than that of the coarse-grained alloy. Detailed microstructural analysis revealed that dynamic recrystallization is responsible for the observed deformation softening in the ultrafine-grained nanocomposite. - Highlights: Black-Right-Pointing-Pointer The strengthening mechanisms of Al6063/Al{sub 2}O{sub 3} nanocomposite were evaluated. Black-Right-Pointing-Pointer Hot deformation behavior of the nanocomposite was studied. Black-Right-Pointing-Pointer The hot deformation activation energy was determined using consecutive models. Black-Right-Pointing-Pointer The restoration mechanisms and microstructural changes are presented.« less

Investigation of spin-zero bosons in q-deformed relativistic quantum mechanics

NASA Astrophysics Data System (ADS)

Sobhani, H.; Chung, W. S.; Hassanabadi, H.

2018-04-01

In this article, Scattering states of Klein-Gordon equation for three scatter potentials of single and double Dirac delta and a potential well in the q-deformed formalism of relativistic quantum mechanics have been derived. At first, we discussed how q-deformed formalism can be constructed and used. Postulates of this q-deformed quantum mechanics are noted. Then scattering problems for spin-zero bosons are studied.

Highly deformable bones: unusual deformation mechanisms of seahorse armor.

PubMed

Porter, Michael M; Novitskaya, Ekaterina; Castro-Ceseña, Ana Bertha; Meyers, Marc A; McKittrick, Joanna

2013-06-01

Multifunctional materials and devices found in nature serve as inspiration for advanced synthetic materials, structures and robotics. Here, we elucidate the architecture and unusual deformation mechanisms of seahorse tails that provide prehension as well as protection against predators. The seahorse tail is composed of subdermal bony plates arranged in articulating ring-like segments that overlap for controlled ventral bending and twisting. The bony plates are highly deformable materials designed to slide past one another and buckle when compressed. This complex plate and segment motion, along with the unique hardness distribution and structural hierarchy of each plate, provide seahorses with joint flexibility while shielding them against impact and crushing. Mimicking seahorse armor may lead to novel bio-inspired technologies, such as flexible armor, fracture-resistant structures or prehensile robotics. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Molecular deformation mechanisms of the wood cell wall material.

PubMed

Jin, Kai; Qin, Zhao; Buehler, Markus J

2015-02-01

Wood is a biological material with outstanding mechanical properties resulting from its hierarchical structure across different scales. Although earlier work has shown that the cellular structure of wood is a key factor that renders it excellent mechanical properties at light weight, the mechanical properties of the wood cell wall material itself still needs to be understood comprehensively. The wood cell wall material features a fiber reinforced composite structure, where cellulose fibrils act as stiff fibers, and hemicellulose and lignin molecules act as soft matrix. The angle between the fiber direction and the loading direction has been found to be the key factor controlling the mechanical properties. However, how the interactions between theses constitutive molecules contribute to the overall properties is still unclear, although the shearing between fibers has been proposed as a primary deformation mechanism. Here we report a molecular model of the wood cell wall material with atomistic resolution, used to assess the mechanical behavior under shear loading in order to understand the deformation mechanisms at the molecular level. The model includes an explicit description of cellulose crystals, hemicellulose, as well as lignin molecules arranged in a layered nanocomposite. The results obtained using this model show that the wood cell wall material under shear loading deforms in an elastic and then plastic manner. The plastic regime can be divided into two parts according to the different deformation mechanisms: yielding of the matrix and sliding of matrix along the cellulose surface. Our molecular dynamics study provides insights of the mechanical behavior of wood cell wall material at the molecular level, and paves a way for the multi-scale understanding of the mechanical properties of wood. Copyright © 2014 Elsevier Ltd. All rights reserved.

Friction properties and deformation mechanisms of halite(-mica) gouges from low to high sliding velocities

NASA Astrophysics Data System (ADS)

Buijze, Loes; Niemeijer, André R.; Han, Raehee; Shimamoto, Toshihiko; Spiers, Christopher J.

2017-01-01

The evolution of friction as a function of slip rate is important in understanding earthquake nucleation and propagation. Many laboratory experiments investigating friction of fault rocks are either conducted in the low velocity regime (10-8-10-4 ms-1) or in the high velocity regime (0.01-1 m s-1). Here, we report on the evolution of friction and corresponding operating deformation mechanisms in analog gouges deformed from low to high slip rates, bridging the gap between these low and high velocity regimes. We used halite and halite-muscovite gouges to simulate processes, governing friction, active in upper crustal quartzitic fault rocks, at conditions accessible in the laboratory. The gouges were deformed over a 7 orders of magnitude range of slip rate (10-7-1 m s-1) using a low-to-high velocity rotary shear apparatus, using a normal stress of 5 MPa and room-dry humidity. Microstructural analysis was conducted to study the deformation mechanisms. Four frictional regimes as a function of slip rate could be recognized from the mechanical data, showing a transitional regime and stable sliding (10-7-10-6 m s-1), unstable sliding and weakening (10-6-10-3 m s-1), hardening (10-2-10-1 m s-1) and strong weakening (10-1-1 m s-1). Each of the four regimes can be associated with a distinct microstructure, reflecting a transition from mainly brittle deformation accompanied by pressure solution healing to temperature activated deformation mechanisms. Additionally, the frictional response of a sliding gouge to a sudden acceleration of slip rate to seismic velocities was investigated. These showed an initial strengthening, the amount of which depended on the friction level at which the step was made, followed by strong slip weakening.

Superplastic Deformation Mechanisms of Superfine/Nanocrystalline Duplex PM-TiAl-Based Alloy

PubMed Central

Gong, Xuebo; Duan, Zhenxin; Pei, Wen; Chen, Hua

2017-01-01

In this paper, the equiaxed superfine/nanocrystalline duplex PM-TiAl-based alloy with (γ + α2) microstructure, Ti-45Al-5Nb (at %), has been synthesized by high-energy ball milling and vacuum hot pressing sintering. Superplastic deformation behavior has been investigated at 1000 °C and 1050 °C with strain rates from 5 × 10−5 s−1 to 1 × 10−3 s−1. The effects of deformation on the microstructure and mechanical behaviors of high Nb containing TiAl alloy have been characterized and analyzed. The results showed that, the ultimate tensile strength of the alloy was 58.7 MPa at 1000 °C and 10.5 MPa at 1050 °C with a strain rate of 5 × 10−5 s−1, while the elongation was 121% and 233%, respectively. The alloy exhibited superplastic elongation at 1000 and 1050 °C with an exponent (m) of 0.48 and 0.45. The main softening mechanism was dynamic recrystallization of γ grains; the dislocation slip and γ/γ interface twinning were responsible for superplastic deformation. The orientation relationship of γ/γ interface twinning obeyed the classical one: (001)γ//(110)γ. PMID:28925971

Mechanics of deformations in terms of scalar variables

NASA Astrophysics Data System (ADS)

Ryabov, Valeriy A.

2017-05-01

Theory of particle and continuous mechanics is developed which allows a treatment of pure deformation in terms of the set of variables "coordinate-momentum-force" instead of the standard treatment in terms of tensor-valued variables "strain-stress." This approach is quite natural for a microscopic description of atomic system, according to which only pointwise forces caused by the stress act to atoms making a body deform. The new concept starts from affine transformation of spatial to material coordinates in terms of the stretch tensor or its analogs. Thus, three principal stretches and three angles related to their orientation form a set of six scalar variables to describe deformation. Instead of volume-dependent potential used in the standard theory, which requires conditions of equilibrium for surface and body forces acting to a volume element, a potential dependent on scalar variables is introduced. A consistent introduction of generalized force associated with this potential becomes possible if a deformed body is considered to be confined on the surface of torus having six genuine dimensions. Strain, constitutive equations and other fundamental laws of the continuum and particle mechanics may be neatly rewritten in terms of scalar variables. Giving a new presentation for finite deformation new approach provides a full treatment of hyperelasticity including anisotropic case. Derived equations of motion generate a new kind of thermodynamical ensemble in terms of constant tension forces. In this ensemble, six internal deformation forces proportional to the components of Irving-Kirkwood stress are controlled by applied external forces. In thermodynamical limit, instead of the pressure and volume as state variables, this ensemble employs deformation force measured in kelvin unit and stretch ratio.

Deformation mechanisms and evolution of the microstructure of gouge in the Main Fault in Opalinus Clay in the Mont Terri rock laboratory (CH)

NASA Astrophysics Data System (ADS)

Laurich, Ben; Urai, Janos L.; Vollmer, Christian; Nussbaum, Christophe

2018-01-01

We studied gouge from an upper-crustal, low-offset reverse fault in slightly overconsolidated claystone in the Mont Terri rock laboratory (Switzerland). The laboratory is designed to evaluate the suitability of the Opalinus Clay formation (OPA) to host a repository for radioactive waste. The gouge occurs in thin bands and lenses in the fault zone; it is darker in color and less fissile than the surrounding rock. It shows a matrix-based, P-foliated microfabric bordered and truncated by micrometer-thin shear zones consisting of aligned clay grains, as shown with broad-ion-beam scanning electron microscopy (BIB-SEM) and optical microscopy. Selected area electron diffraction based on transmission electron microscopy (TEM) shows evidence for randomly oriented nanometer-sized clay particles in the gouge matrix, surrounding larger elongated phyllosilicates with a strict P foliation. For the first time for the OPA, we report the occurrence of amorphous SiO2 grains within the gouge. Gouge has lower SEM-visible porosity and almost no calcite grains compared to the undeformed OPA. We present two hypotheses to explain the origin of gouge in the Main Fault: (i) authigenic generation consisting of fluid-mediated removal of calcite from the deforming OPA during shearing and (ii) clay smear consisting of mechanical smearing of calcite-poor (yet to be identified) source layers into the fault zone. Based on our data we prefer the first or a combination of both, but more work is needed to resolve this. Microstructures indicate a range of deformation mechanisms including solution-precipitation processes and a gouge that is weaker than the OPA because of the lower fraction of hard grains. For gouge, we infer a more rate-dependent frictional rheology than suggested from laboratory experiments on the undeformed OPA.

Modeling coupled Thermo-Hydro-Mechanical processes including plastic deformation in geological porous media

NASA Astrophysics Data System (ADS)

Kelkar, S.; Karra, S.; Pawar, R. J.; Zyvoloski, G.

2012-12-01

There has been an increasing interest in the recent years in developing computational tools for analyzing coupled thermal, hydrological and mechanical (THM) processes that occur in geological porous media. This is mainly due to their importance in applications including carbon sequestration, enhanced geothermal systems, oil and gas production from unconventional sources, degradation of Arctic permafrost, and nuclear waste isolation. Large changes in pressures, temperatures and saturation can result due to injection/withdrawal of fluids or emplaced heat sources. These can potentially lead to large changes in the fluid flow and mechanical behavior of the formation, including shear and tensile failure on pre-existing or induced fractures and the associated permeability changes. Due to this, plastic deformation and large changes in material properties such as permeability and porosity can be expected to play an important role in these processes. We describe a general purpose computational code FEHM that has been developed for the purpose of modeling coupled THM processes during multi-phase fluid flow and transport in fractured porous media. The code uses a continuum mechanics approach, based on control volume - finite element method. It is designed to address spatial scales on the order of tens of centimeters to tens of kilometers. While large deformations are important in many situations, we have adapted the small strain formulation as useful insight can be obtained in many problems of practical interest with this approach while remaining computationally manageable. Nonlinearities in the equations and the material properties are handled using a full Jacobian Newton-Raphson technique. Stress-strain relationships are assumed to follow linear elastic/plastic behavior. The code incorporates several plasticity models such as von Mises, Drucker-Prager, and also a large suite of models for coupling flow and mechanical deformation via permeability and stresses/deformations

Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects

PubMed Central

Zhang, Jie; Sheng, Lei; Liu, Jing

2014-01-01

Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks. PMID:25408295

Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects.

PubMed

Zhang, Jie; Sheng, Lei; Liu, Jing

2014-11-19

Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks.

Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects

NASA Astrophysics Data System (ADS)

Zhang, Jie; Sheng, Lei; Liu, Jing

2014-11-01

Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks.

Influence of Deformation Mechanisms on the Mechanical Behavior of Metals and Alloys: Experiments, Constitutive Modeling, and Validation

NASA Astrophysics Data System (ADS)

Gray, G. T.; Cerreta, E.; Chen, Shuh Rong; Maudlin, P. J.

2004-06-01

Jim Williams has made seminal contributions to the field of structure / property relations and its controlling effects on the mechanical behavior of metals and alloys. This talk will discuss experimental results illustrating the role of interstitial content, grain size, texture, temperature, and strain rate on the operative deformation mechanisms, mechanical behavior, and substructure evolution in titanium, zirconium, hafnium, and rhenium. Increasing grain size is shown to significantly decrease the dynamic flow strength of Ti and Zr while increasing work-hardening rates due to an increased incidence of deformation twinning. Increasing oxygen interstitial content is shown to significantly alter both the constitutive response and α-ω shock-induced phase transition in Zr. The influence of crystallographic texture on the mechanical behavior in Ti, Zr, and Hf is discussed in terms of slip system and deformation twinning activity. An example of the utility of incorporation of operative deformation mechanisms into a polycrystalline plasticity constitutive model and validation using Taylor cylinder impact testing is presented.

Mechanism for Angular Deformation of L-shaped Specimens —Influence of Filling Material and Shrinkage Factor—

NASA Astrophysics Data System (ADS)

Furuhashi, Hiroshi; Aoki, Takerou; Okabe, Sayaka; Arai, Tsuyoshi; Seto, Masahiro; Yamabe, Masashi

L-shape is the important and fundamental shape for injection molded parts. Therefore to reveal the corner angular deformation mechanism of this shape is also valuable for understanding the warpage mechanism of injection molded parts. In this study, we investigated the influence of the filling materials (fiber, talc and not filled) and two kinds of anisotropic shrinkage factors, solidification shrinkage and shrinkage caused by thermal expansion coefficient during cooling, to the angular deformation of L-shaped specimens and the following conclusions were obtained 1) The anisotropic solidification shrinkage of MD/TD and the anisotropic thermal expansion coefficient of MD/TD are considered to cause the angular deformation of L-shaped specimens. But the contribution ratios of these two anisotropies depend on the filling material for plastics. 2) The angular deformation of PP and PBT filled with glass fiber is mainly caused by the anisotropic thermal expansion coefficient and on the other hand, that of PP and PBT without filling material is caused by anisotropic solidification shrinkage. However both anisotropies cause the angular deformation of PP filled with talc. 3) The plate thickness dependence of the angular deformation of PP filled with talc is the singular peculiar phenomenon. The plate thickness dependence of anisotropic solidification shrinkage of this material (it is also singular) is considered to have an important influence on this phenomenon.

Nanoparticle Addition to Enhance the Mechanical Response of Magnesium Alloys Including Nanoscale Deformation Mechanisms

NASA Astrophysics Data System (ADS)

Paramsothy, Muralidharan; Gupta, Manoj

In this study, various magnesium alloy nanocomposites derived from AZ (Aluminium-Zinc) or ZK (Zinc-Zirconium) series matrices and containing Al2O3, Si3N4, TiC or carbon nanotube (CNT) nanoparticle reinforcement (representative oxide, nitride, carbide or carbon nanoparticle reinforcement, respectively) were fabricated using solidification processing followed by hot extrusion. The main aim here was to simultaneously enhance tensile strength and ductility of each alloy using nanoparticles. The magnesium-oxygen strong affinity and magnesium-carbon weak affinity (comparison of extremes in affinity) are both well known in the context of magnesium composite processing. However, an approach to possibly quantify this affinity in magnesium nanocomposite processing is not clear. In this study accordingly, Nanoscale Electro Negative Interface Density or NENID quantifies the nanoparticle-alloy matrix interfacial area per unit volume in the magnesium alloy nanocomposite taking into consideration the electronegativity of the nanoparticle reinforcement. The beneficial (as well as comparative) effect of the nanoparticles on each alloy is discussed in this article. Regarding the mechanical performance of the nanocomposites, it is important to understand the experimentally observed nanoparticle-matrix interactions during plastic deformation (nanoscale deformation mechanisms). Little is known in this area based on direct observations for metal matrix nanocomposites. Here, relevant multiple nanoscale phenomena includes the emanation of high strain zones (HSZs) from nanoparticle surfaces.

Preferred orientation in experimentally deformed stishovite: implications for deformation mechanisms

DOE PAGES

Kaercher, Pamela M.; Zepeda-Alarcon, Eloisa; Prakapenka, Vitali B.; ...

2014-11-07

Although the crystal structure of the high pressure SiO 2 polymorph stishovite has been studied in detail, little is known about the development of crystallographic preferred orientation (CPO) during deformation in stishovite. Insight into CPO and associated deformation mechanics of stishovite would provide important information for understanding subduction of quartz-bearing crustal rocks into the mantle. To study CPO development, we converted a natural sample of flint to stishovite in a laser heated diamond anvil cell and compressed the stishovite aggregate up to 38 GPa. We collected diffraction patterns in radial geometry to examine in situ development of crystallographic preferred orientationmore » and find that (001) poles preferentially align with the compression direction. Viscoplastic self-consistent modeling suggests the most likely slip systems at high pressure and ambient temperature are pyramidal and basal slip.« less

The deformable secondary mirror of VLT: final electro-mechanical and optical acceptance test results

NASA Astrophysics Data System (ADS)

Briguglio, Runa; Biasi, Roberto; Xompero, Marco; Riccardi, Armando; Andrighettoni, Mario; Pescoller, Dietrich; Angerer, Gerald; Gallieni, Daniele; Vernet, Elise; Kolb, Johann; Arsenault, Robin; Madec, Pierre-Yves

2014-07-01

The Deformable Secondary Mirror (DSM) for the VLT ended the stand-alone electro-mechanical and optical acceptance process, entering the test phase as part of the Adaptive Optics Facility (AOF) at the ESO Headquarter (Garching). The VLT-DSM currently represents the most advanced already-built large-format deformable mirror with its 1170 voice-coil actuators and its internal metrology based on co-located capacitive sensors to control the shape of the 1.12m-diameter 2mm-thick convex shell. The present paper reports the final results of the electro-mechanical and optical characterization of the DSM executed in a collaborative effort by the DSM manufacturing companies (Microgate s.r.l. and A.D.S. International s.r.l.), INAF-Osservatorio Astrofisico di Arcetri and ESO. The electro-mechanical acceptance tests have been performed in the company premises and their main purpose was the dynamical characterization of the internal control loop response and the calibration of the system data that are needed for its optimization. The optical acceptance tests have been performed at ESO (Garching) using the ASSIST optical test facility. The main purpose of the tests are the characterization of the optical shell flattening residuals, the corresponding calibration of flattening commands, the optical calibration of the capacitive sensors and the optical calibration of the mirror influence functions.

Mechanical properties and processes of deformation in shallow sedimentary rocks from subduction zones: An experimental study

NASA Astrophysics Data System (ADS)

Gadenne, Leslie; Raimbourg, Hugues; Champallier, Rémi; Yamamoto, Yuzuru

2014-12-01

To better constrain the mechanical behavior of sediments accreted to accretionary prism, we conducted triaxial mechanical tests on natural samples from the Miura-Boso paleo-accretionary prism (Japan) in drained conditions with confining pressures up to 200 MPa as well as postexperiments P-wave velocity (Vp) measurements. During experiments, deformation is principally noncoaxial and accommodated by two successive modes of deformation, both associated with strain-hardening and velocity-strengthening behavior: (1) compaction-assisted shearing, distributed in a several mm-wide shear zone and (2) faulting, localized within a few tens of μm-wide, dilatant fault zone. Deformation is also associated with (1) a decrease in Young's modulus all over the tests, (2) anomalously low Vp in the deformed samples compared to their porosity and (3) an increase in sensitivity of Vp to effective pressure. We interpret this evolution of the poroelastic properties of the material as reflecting the progressive breakage of intergrain cement and the formation of microcracks along with macroscopic deformation. When applied to natural conditions, these results suggest that the deformation style (localized versus distributed) of shallow (z < a few km) sediments is mainly controlled by the variations in stress/strain rate during the seismic cycle and is therefore independent of the porosity of sediments. Finally, we show that the effect of strain, through cement breakage and microcracks formation, may lower Vp for effective pressure up to 40 MPa. As a consequence, the low Vp anomalies observed in Nankai accretionary prisms by seismic imaging between 2 and 4 km depth could reflect sediment deformation rather than porosity anomalies.

Inelastic Deformation of Metal Matrix Composites. Part 1; Plasticity and Damage Mechanisms

NASA Technical Reports Server (NTRS)

Majumdar, B. S.; Newaz, G. M.

1992-01-01

The deformation mechanisms of a Ti 15-3/SCS6 (SiC fiber) metal matrix composite (MMC) were investigated using a combination of mechanical measurements and microstructural analysis. The objectives were to evaluate the contributions of plasticity and damage to the overall inelastic response, and to confirm the mechanisms by rigorous microstructural evaluations. The results of room temperature experiments performed on 0 degree and 90 degree systems primarily are reported in this report. Results of experiments performed on other laminate systems and at high temperatures will be provided in a forthcoming report. Inelastic deformation of the 0 degree MMC (fibers parallel to load direction) was dominated by the plasticity of the matrix. In contrast, inelastic deformations of the 90 degree composite (fibers perpendicular to loading direction) occurred by both damage and plasticity. The predictions of a continuum elastic plastic model were compared with experimental data. The model was adequate for predicting the 0 degree response; however, it was inadequate for predicting the 90 degree response largely because it neglected damage. The importance of validating constitutive models using a combination of mechanical measurements and microstructural analysis is pointed out. The deformation mechanisms, and the likely sequence of events associated with the inelastic deformation of MMCs, are indicated in this paper.

Fluctuating Nonlinear Spring Model of Mechanical Deformation of Biological Particles

PubMed Central

Kononova, Olga; Snijder, Joost; Kholodov, Yaroslav; Marx, Kenneth A.; Wuite, Gijs J. L.; Roos, Wouter H.; Barsegov, Valeri

2016-01-01

The mechanical properties of virus capsids correlate with local conformational dynamics in the capsid structure. They also reflect the required stability needed to withstand high internal pressures generated upon genome loading and contribute to the success of important events in viral infectivity, such as capsid maturation, genome uncoating and receptor binding. The mechanical properties of biological nanoparticles are often determined from monitoring their dynamic deformations in Atomic Force Microscopy nanoindentation experiments; but a comprehensive theory describing the full range of observed deformation behaviors has not previously been described. We present a new theory for modeling dynamic deformations of biological nanoparticles, which considers the non-linear Hertzian deformation, resulting from an indenter-particle physical contact, and the bending of curved elements (beams) modeling the particle structure. The beams’ deformation beyond the critical point triggers a dynamic transition of the particle to the collapsed state. This extreme event is accompanied by a catastrophic force drop as observed in the experimental or simulated force (F)-deformation (X) spectra. The theory interprets fine features of the spectra, including the nonlinear components of the FX-curves, in terms of the Young’s moduli for Hertzian and bending deformations, and the structural damage dependent beams’ survival probability, in terms of the maximum strength and the cooperativity parameter. The theory is exemplified by successfully describing the deformation dynamics of natural nanoparticles through comparing theoretical curves with experimental force-deformation spectra for several virus particles. This approach provides a comprehensive description of the dynamic structural transitions in biological and artificial nanoparticles, which is essential for their optimal use in nanotechnology and nanomedicine applications. PMID:26821264

Deformation modes in an Icelandic basalt: From brittle failure to localized deformation bands

NASA Astrophysics Data System (ADS)

Adelinet, M.; Fortin, J.; Schubnel, A.; Guéguen, Y.

2013-04-01

According to the stress state, deformation mode observed in rocks may be very different. Even in the brittle part of the crust a differential stress can induce shear failure but also localized compacting deformation, such as compaction bands in porous sedimentary rocks. The mode of deformation controls many hydrodynamic factors, such as permeability and porosity. We investigate in this paper two different modes of deformation in an Icelandic basalt by using laboratory seismological tools (elastic waves and acoustic emissions) and microstructural observations. First of all, we show that at low effective confining pressure (Peff = 5 MPa) an axial loading induces a shear failure in the basalt with an angle of about 30° with respect to the main stress direction. On the contrary, at high effective confining pressure (Peff ≥ 75 MPa and more) an increase of the axial stress induces a localization of the deformation in the form of subhorizontal bands again with respect to the main stress direction. In this second regime, focal mechanisms of the acoustic emissions reveal an important number of compression events suggesting pore collapse mechanisms. Microstructural observations confirm this assumption. Similar compaction structures are usually obtained for porous sedimentary rocks (20-25%). However, the investigated basalt has an initial total porosity of only about 10% so that compaction structures were not expected. The pore size and the ratio of pore to grain size are likely to be key factors for the particular observed mechanical behavior.

Constitutive Law and Flow Mechanism in Diamond Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Xiaohui; Raterron, Paul; Zhang, Jianzhong

2012-11-19

Constitutive laws and crystal plasticity in diamond deformation have been the subjects of substantial interest since synthetic diamond was made in 1950's. To date, however, little is known quantitatively regarding its brittle-ductile properties and yield strength at high temperatures. In this paper, we report, for the first time, the strain-stress constitutive relations and experimental demonstration of deformation mechanisms under confined high pressure. The deformation at room temperature is essentially brittle, cataclastic, and mostly accommodated by fracturing on {111} plane with no plastic yielding at uniaxial strains up to 15%. At elevated temperatures of 1000°C and 1200°C diamond crystals exhibit significantmore » ductile flow with corresponding yield strength of 7.9 and 6.3 GPa, indicating that diamond starts to weaken when temperature is over 1000°C. Finally, at high temperature the plastic deformation and ductile flow is meditated by the <110>{111} dislocation glide and a very active {111} micro-twinning.« less

Magma emplacement mechanisms and syn-magmatic deformation - a new approach to the Knaben area in Vest Agder, Norway

NASA Astrophysics Data System (ADS)

Stormoen, Martin Austin; Slagstad, Trond; Henderson, Iain

2014-05-01

The Knaben area, known for its molybdenite mining, defines a N-S striking (~30 degrees dip towards the east) belt, consisting of porphyry granite with a varying density of amphibolite and varieties of deformed granite, lying within the Sirdal Magmatic Belt, is important for understanding the emplacement- and deformation mechanisms of the batholith. Detailed geological mapping combined with geochronology, geochemistry, and structural geology will be the focus areas. Last autumn's fieldwork indicated that several of the formerly mapped enclaves of amphibolite and deformed granite are more coherent then previously indicated, and some have been followed for a few kilometres. Several varieties of granite make up the area, mainly a dominating red porphyry granite, and a grey molybdenite-bearing finer grained granite. Structural investigations revealed consistent "top to the west" compressional kinematics on mappable shear zone networks often displaying west-directed duplex geometries. The Knaben area could possibly comprise a boundary between two individual plutons in the Sirdal Magmatic Belt, or a zone with remaining host rock. Geochronology of the eastern and western plutons will be done. Currently, largely different paleomagnetic vectors of the eastern and western porphyry granites indicate that they are separate plutons. Exploring how the emplacement- and deformation mechanisms have acted and are related, will be one of the main objectives. If the deformed granite is host rock, or syn- to post-magmatic deformed porphyry granite has been one of the major questions. A better understanding of the formation of the Knaben area, also regarding the emplacement of molybdenite, will prove useful for understanding the regional batholith, and possibly the possibility for molybdenite to occur elsewhere. The Sirdal Magmatic Belt, and also Knaben, seem to be of great value for studying magmatic processes.

Controls of Lithospheric Mechanical Strength on the Deformation Pattern of Tien Shan

NASA Astrophysics Data System (ADS)

Li, Y.; Xiong, X.; Zheng, Y.; Hu, X.; Zhang, Y.

2015-12-01

lower crust and lithospheric mantle. Combined with results of analog models, the location and style of deformation are preliminary determined and thus the related topography evolution in the Tien Shan is mainly controlled by the lateral and depth variation in lithospheric mechanical strength of surrounding areas.

Surface Spectroscopic Signatures of Mechanical Deformation in HDPE.

PubMed

Averett, Shawn C; Stanley, Steven K; Hanson, Joshua J; Smith, Stacey J; Patterson, James E

2018-01-01

High-density polyethylene (HDPE) has been extensively studied, both as a model for semi-crystalline polymers and because of its own industrial utility. During cold drawing, crystalline regions of HDPE are known to break up and align with the direction of tensile load. Structural changes due to deformation should also manifest at the surface of the polymer, but until now, a detailed molecular understanding of how the surface responds to mechanical deformation has been lacking. This work establishes a precedent for using vibrational sum-frequency generation (VSFG) spectroscopy to investigate changes in the molecular-level structure of the surface of HDPE after cold drawing. X-ray diffraction (XRD) was used to confirm that the observed surface behavior corresponds to the expected bulk response. Before tensile loading, the VSFG spectra indicate that there is significant variability in the surface structure and tilt of the methylene groups away from the surface normal. After deformation, the VSFG spectroscopic signatures are notably different. These changes suggest that hydrocarbon chains at the surface of visibly necked HDPE are aligned with the direction of loading, while the associated methylene groups are oriented with the local C 2 v symmetry axis roughly parallel to the surface normal. Small amounts of unaltered material are also found at the surface of necked HDPE, with the relative amount of unaltered material decreasing as the amount of deformation increases. Aspects of the nonresonant SFG response in the transition zone between necked and undeformed polymer provide additional insight into the deformation process and may provide the first indication of mechanical deformation. Nonlinear surface spectroscopy can thus be used as a noninvasive and nondestructive tool to probe the stress history of a HPDE sample in situations where X-ray techniques are not available or not applicable. Vibrational sum-frequency generation thus has great potential as a platform for

Inelastic deformation of metal matrix composites: Plasticity and damage mechanisms, part 2

NASA Technical Reports Server (NTRS)

Majumdar, B. S.; Newaz, G. M.

1992-01-01

The inelastic deformation mechanisms for the SiC (SCS-6)/Ti-15-3 system were studied at 538 C (1000 F) using a combination of mechanical measurements and detailed microstructural examinations. The objectives were to evaluate the contributions of plasticity and damage to the overall MMC response, and to compare the room temperature and elevated temperature deformation behaviors. Four different laminates were studied: (0)8, (90)8,(+ or -45)2s, and (0/90)2s, with the primary emphasis on the unidirectional (0)8, and (90)8 systems. The elevated temperature responses were similar to those at room temperature, involving a two-stage elastic-plastic type of response for the (0)8 system, and a characteristic three-stage deformation response for the (90)8 and (+ or -45)2s systems. The primary effects of elevated temperatures included: (1) reduction in the 'yield' and failure strengths; (2) plasticity through diffused slip rather than concentrated planar slip (which occurred at room temperature); and (3) time-dependent deformation. The inelastic deformation mechanism for the (0)8 MMC was dominated by plasticity at both temperatures. For the (90)8 and (+ or -45)2s MMCs, a combination of damage and plasticity contributed to the deformation at both temperatures.

Tuning transport properties on graphene multiterminal structures by mechanical deformations

NASA Astrophysics Data System (ADS)

Latge, Andrea; Torres, Vanessa; Faria, Daiara

The realization of mechanical strain on graphene structures is viewed as a promise route to tune electronic and transport properties such as changing energy band-gaps and promoting localization of states. Using continuum models, mechanical deformations are described by effective gauge fields, mirrored as pseudomagnetic fields that may reach quite high values. Interesting symmetry features are developed due to out of plane deformations on graphene; lift sublattice symmetry was predicted and observed in centrosymmetric bumps and strained nanobubbles. Here we discuss the effects of Gaussian-like strain on a hexagonal graphene flake connected to three leads, modeled as perfect graphene nanoribbons. The Green function formalism is used within a tight-binding approximation. For this particular deformation sharp resonant states are achieved depending on the strained structure details. We also study a fold-strained structure in which the three leads are deformed extending up to the very center of the hexagonal flake. We show that conductance suppressions can be controlled by the strain intensity and important transport features are modeled by the electronic band structure of the leads.

Mechanical design of deformation compensated flexural pivots structured for linear nanopositioning stages

DOEpatents

Shu, Deming; Kearney, Steven P.; Preissner, Curt A.

2015-02-17

A method and deformation compensated flexural pivots structured for precision linear nanopositioning stages are provided. A deformation-compensated flexural linear guiding mechanism includes a basic parallel mechanism including a U-shaped member and a pair of parallel bars linked to respective pairs of I-link bars and each of the I-bars coupled by a respective pair of flexural pivots. The basic parallel mechanism includes substantially evenly distributed flexural pivots minimizing center shift dynamic errors.

Deformation mechanisms and resealing of damage zones in experimentally deformed cemented and un-cemented clay-rich geomaterials, at low bulk strain

NASA Astrophysics Data System (ADS)

Desbois, Guillaume; Urai, Janos L.; Schuck, Bernhardt; Hoehne, Nadine; Oelker, Anne; Bésuelle, Pierre; Viggiani, Gioacchino; Schmatz, Joyce; Klaver, Jop

2017-04-01

A microphysics-based understanding of mechanical and fluid flow properties in clay-rich geomaterials is required for extrapolating better constitutive equations beyond the laboratory's time scales, so that predictions over the long term can be made less uncertain. In this contribution, we present microstructural investigations of rocks specimens sheared in triaxial compression at low bulk strain, by using the combination of broad-ion-beam (BIB) milling and scanning electron microscopy (SEM) to infer deformation mechanisms based on microstructures imaged at sub-micron resolution. Two end-member clay-rich geomaterials from European Underground Laboratories (URL) were analysed: (i) the poorly cemented Boom Clay sediment (BC from URL at Mol/Dessel, Belgium; confining pressure [CP] = 0.375 & 1.5 MPa) and (ii) the Callovo-Oxfordian claystone (COx from the URL at Bure, France; CP = 2 & 10 MPa). Although as a first approximation the inelastic bahvior of cemented and uncemented clay-rich geomaterials can be described by similar pressure-dependent hardening plasticity models, deformed samples in this contribution show very contrasting micro-scale behaviour: microstructures reveal brittle-ductile transitional behaviour in BC, whereas deformation in COx is dominantly cataclastic. In Boom Clay, at meso-scale, shear bands exhibit characteristics that are typical of uncemented small-grained clay-rich materials deformed at high shear strains, consisting of anastomosing shears interpreted as Y- and B-shears, which bound the passively deformed microlithons. At micro- down to nano-scale, the strong shape preferential orientation of clay aggregates in the anastomosing shears is interpreted to be responsible of the shear weakness. More over, the reworking of clay aggregates during deformation contributes to the collapsing of porosity in the shear band. Ductile deformation mechanisms represented by grain-rotation, grain-sliding, bending and granular flow mechanisms are strongly involved

Main Port Mechanism for PRISMA

NASA Astrophysics Data System (ADS)

Caprini, G. C.; Ceccherini, M.; Brotini, M.; Bini, A.; Corsini, R.; Gasparini, L.; Battazza, F.; Formaro, R.

2013-09-01

A high complexity Main Port Mechanism (MPM) has been designed and produced by Selex ES in co- operation with HighFTech Engineering, an Italian PMI, in the frame of PRISMA (PRecursore IperSpettrale della Missione Applicativa) instrument.The Main Port Mechanism is located at the entrance of the Optical Head having the function of opening and closing a door.The paper describes the requirements drived the conceptual design, the detailed design and the qualification tests performed on the mechanism. A description of the foreseen test flow and set-up is also given.

Competing Grain Boundary and Interior Deformation Mechanisms with Varying Sizes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wei; Gao, Yanfei; Nieh, T. G.

In typical coarse-grained alloys, the dominant plastic deformations are dislocation gliding or climbing, and material strengths can be tuned by dislocation interactions with grain boundaries, precipitates, solid solutions, and other defects. With the reduction of grain size, the increase of material strengths follows the classic Hall-Petch relationship up to nano-grained materials. Even at room temperatures, nano-grained materials exhibit strength softening, or called the inverse Hall-Petch effect, as grain boundary processes take over as the dominant deformation mechanisms. On the other hand, at elevated temperatures, grain boundary processes compete with grain interior deformation mechanisms over a wide range of the appliedmore » stress and grain sizes. This book chapter reviews and compares the rate equation model and the microstructure-based finite element simulations. The latter explicitly accounts for the grain boundary sliding, grain boundary diffusion and migration, as well as the grain interior dislocation creep. Therefore the explicit finite element method has clear advantages in problems where microstructural heterogeneities play a critical role, such as in the gradient microstructure in shot peening or weldment. Furthermore, combined with the Hall-Petch effect and its breakdown, the above competing processes help construct deformation mechanism maps by extending from the classic Frost-Ashby type to the ones with the dependence of grain size.« less

Multi-scale Investigation on Microstructure, Mechanical Properties, and Deformation Mechanisms in Mg Alloys

NASA Astrophysics Data System (ADS)

Zhang, Dalong

Mg and its alloys are promising candidates for light-weight structural applications, e.g., aircraft, automobile, electronic, etc. However, the inherent hexagonal close packed crystal structure makes the deformation of Mg anisotropic, namely deformation only occurs predominantly by dislocation slip in the close-packed (0001) plane (i.e., basal plane), or by deformation twinning in {101¯2} planes. Both basal slip and twinning cause the crystal to re-orient. Consequently, polycrystalline Mg alloys that have undergone thermomechanical processing usually contain strong texture, i.e., preferred crystallographic orientation in grains. The texture in turn leads to anisotropic deformation in wrought Mg alloys. For example, in extruded Mg alloys, the compressive yield strength is usually much lower than the tensile yield strength (so-called yield asymmetry and strength differential). It is the anisotropy that hinders the broader application of Mg alloys. Recent modeling studies on Mg predict that certain alloying elements, particularly rare-earth elements (e.g., Y, Ce, Nd, Gd, etc.), could alter the active deformation modes and enhance homogeneous deformation and overall mechanical properties in Mg. Therefore, the objective of this dissertation research is to investigate experimentally the effects of alloying element Y in reducing the intrinsic and extrinsic anisotropy, modifying texture, and enhancing the overall strength and ductility for Mg. In addition, the research also uncovered some unexpected "side effects" of Y and these phenomena were studied and explained from a fundamental perspective. The methodology used in this work is described as follows. Ultrafine grained Mg 2.5 at.% Y alloy (UFG Mg-2.5Y) was prepared by powder metallurgy method, including gas atomization for producing Mg-2.5Y powder, degassing and hot isostatic pressing (HIP), and hot extrusion. Both the as-HIPed and the as-extruded materials were characterized by electron back-scattered diffraction (EBSD

In situ three-dimensional reciprocal-space mapping during mechanical deformation.

PubMed

Cornelius, T W; Davydok, A; Jacques, V L R; Grifone, R; Schülli, T; Richard, M I; Beutier, G; Verdier, M; Metzger, T H; Pietsch, U; Thomas, O

2012-09-01

Mechanical deformation of a SiGe island epitaxically grown on Si(001) was studied by a specially adapted atomic force microscope and nanofocused X-ray diffraction. The deformation was monitored during in situ mechanical loading by recording three-dimensional reciprocal-space maps around a selected Bragg peak. Scanning the energy of the incident beam instead of rocking the sample allowed the safe and reliable measurement of the reciprocal-space maps without removal of the mechanical load. The crystal truncation rods originating from the island side facets rotate to steeper angles with increasing mechanical load. Simulations of the displacement field and the intensity distribution, based on the finite-element method, reveal that the change in orientation of the side facets of about 25° corresponds to an applied pressure of 2-3 GPa on the island top plane.

Analytical magmatic source modelling from a joint inversion of ground deformation and focal mechanisms data

NASA Astrophysics Data System (ADS)

Cannavo', Flavio; Scandura, Danila; Palano, Mimmo; Musumeci, Carla

2014-05-01

Seismicity and ground deformation represent the principal geophysical methods for volcano monitoring and provide important constraints on subsurface magma movements. The occurrence of migrating seismic swarms, as observed at several volcanoes worldwide, are commonly associated with dike intrusions. In addition, on active volcanoes, (de)pressurization and/or intrusion of magmatic bodies stress and deform the surrounding crustal rocks, often causing earthquakes randomly distributed in time within a volume extending about 5-10 km from the wall of the magmatic bodies. Despite advances in space-based, geodetic and seismic networks have significantly improved volcano monitoring in the last decades on an increasing worldwide number of volcanoes, quantitative models relating deformation and seismicity are not common. The observation of several episodes of volcanic unrest throughout the world, where the movement of magma through the shallow crust was able to produce local rotation of the ambient stress field, introduces an opportunity to improve the estimate of the parameters of a deformation source. In particular, during these episodes of volcanic unrest a radial pattern of P-axes of the focal mechanism solutions, similar to that of ground deformation, has been observed. Therefore, taking into account additional information from focal mechanisms data, we propose a novel approach to volcanic source modeling based on the joint inversion of deformation and focal plane solutions assuming that both observations are due to the same source. The methodology is first verified against a synthetic dataset of surface deformation and strain within the medium, and then applied to real data from an unrest episode occurred before the May 13th 2008 eruption at Mt. Etna (Italy). The main results clearly indicate as the joint inversion improves the accuracy of the estimated source parameters of about 70%. The statistical tests indicate that the source depth is the parameter with the highest

Diffusion mechanism of non-interacting Brownian particles through a deformed substrate

NASA Astrophysics Data System (ADS)

Arfa, Lahcen; Ouahmane, Mehdi; El Arroum, Lahcen

2018-02-01

We study the diffusion mechanism of non-interacting Brownian particles through a deformed substrate. The study is done at low temperature for different values of the friction. The deformed substrate is represented by a periodic Remoissenet-Peyrard potential with deformability parameter s. In this potential, the particles (impurity, adatoms…) can diffuse. We ignore the interactions between these mobile particles consider them merely as non-interacting Brownian particles and this system is described by a Fokker-Planck equation. We solve this equation numerically using the matrix continued fraction method to calculate the dynamic structure factor S(q , ω) . From S(q , ω) some relevant correlation functions are also calculated. In particular, we determine the half-width line λ(q) of the peak of the quasi-elastic dynamic structure factor S(q , ω) and the diffusion coefficient D. Our numerical results show that the diffusion mechanism is described, depending on the structure of the potential, either by a simple jump diffusion process with jump length close to the lattice constant a or by a combination of a jump diffusion model with jump length close to lattice constant a and a liquid-like motion inside the unit cell. It shows also that, for different friction regimes and various potential shapes, the friction attenuates the diffusion mechanism. It is found that, in the high friction regime, the diffusion process is more important through a deformed substrate than through a non-deformed one.

Deformation Mechanism Map of Cu/Nb Nanoscale Metallic Multilayers as a Function of Temperature and Layer Thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snel, J.; Monclús, M. A.; Castillo-Rodríguez, M.

The mechanical properties and deformation mechanisms of Cu/Nb nanoscale metallic multilayers (NMMs) manufactured by accumulative roll bonding are studied at 25°C and 400°C. Cu/Nb NMMs with individual layer thicknesses between 7 nm and 63 nm were tested by in situ micropillar compression inside a scanning electron microscope. Yield strength, strain-rate sensitivities and activation volumes were obtained from the pillar compression tests. The deformed micropillars were examined under scanning and transmission electron microscopy in order to examine the deformation mechanisms active for different layer thicknesses and temperatures. The paper suggests that room temperature deformation was determined by dislocation glide at largermore » layer thicknesses and interface-related mechanisms at the thinner layer thicknesses. The high-temperature compression tests, in contrast, revealed superior thermo-mechanical stability and strength retention for the NMMs with larger layer thicknesses with deformation controlled by dislocation glide. A remarkable transition in deformation mechanism occurred as the layer thickness decreased, to a deformation response controlled by diffusion processes along the interfaces, which resulted in temperature-induced softening. Finally, a deformation mechanism map, in terms of layer thickness and temperature, is proposed from the results obtained in this investigation.« less

Deformation Mechanism Map of Cu/Nb Nanoscale Metallic Multilayers as a Function of Temperature and Layer Thickness

DOE PAGES

Snel, J.; Monclús, M. A.; Castillo-Rodríguez, M.; ...

2017-08-29

The mechanical properties and deformation mechanisms of Cu/Nb nanoscale metallic multilayers (NMMs) manufactured by accumulative roll bonding are studied at 25°C and 400°C. Cu/Nb NMMs with individual layer thicknesses between 7 nm and 63 nm were tested by in situ micropillar compression inside a scanning electron microscope. Yield strength, strain-rate sensitivities and activation volumes were obtained from the pillar compression tests. The deformed micropillars were examined under scanning and transmission electron microscopy in order to examine the deformation mechanisms active for different layer thicknesses and temperatures. The paper suggests that room temperature deformation was determined by dislocation glide at largermore » layer thicknesses and interface-related mechanisms at the thinner layer thicknesses. The high-temperature compression tests, in contrast, revealed superior thermo-mechanical stability and strength retention for the NMMs with larger layer thicknesses with deformation controlled by dislocation glide. A remarkable transition in deformation mechanism occurred as the layer thickness decreased, to a deformation response controlled by diffusion processes along the interfaces, which resulted in temperature-induced softening. Finally, a deformation mechanism map, in terms of layer thickness and temperature, is proposed from the results obtained in this investigation.« less

Structure and mechanical properties of a high-carbon steel subjected to severe deformation

NASA Astrophysics Data System (ADS)

Gorkunov, E. S.; Zadvorkin, S. M.; Goruleva, L. S.; Makarov, A. V.; Pecherkina, N. L.

2017-10-01

The structure and mechanical properties of a high-carbon eutectic steel subjected to the cold plastic deformation by hydrostatic extrusion in a wide range of true strain have been studied. Using scanning and transmission electron microscopy, it has been shown that the formation of cellular, fragmented, and submicrocrystalline structures occurs in the ferritic constituent of the pearlite structure of the steel upon extrusion. This is a consequence of the occurrence of dynamic recovery and continuous dynamic and post-dynamic recrystallization, which cause a decrease in the density of free dislocations at the true strain of more than 1.62. The partial dissolution of the carbide phase is also observed. It has been found that, at a true strain of up to 0.81, the strength properties of the investigated steel are determined mainly by subgrain, dislocation, and precipitation mechanisms of the strengthening; in the deformation range of 0.81-1.62, the role of the grainboundary strengthening increases. At strains above 1.62, grain-boundary strengthening is a prevailing mechanism in the formation of the level of strength properties of the extruded U8A steel. The ultimate tensile strength and yield stress over the entire strain range only uniquely correlate with the density of highangle boundaries; the dependences of the strength characteristics on other structural parameters are not monotonic.

Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils

PubMed Central

Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J.; Buehler, Markus J.

2015-01-01

Collagen is a ubiquitous protein with remarkable mechanical properties. It is highly elastic, shows large fracture strength and enables substantial energy dissipation during deformation. Most of the connective tissue in humans consists of collagen fibrils composed of a staggered array of tropocollagen molecules, which are connected by intermolecular cross-links. In this study, we report a three-dimensional coarse-grained model of collagen and analyze the influence of enzymatic cross-links on the mechanics of collagen fibrils. Two representatives immature and mature cross-links are implemented in the mesoscale model using a bottom-up approach. By varying the number, type and mechanical properties of cross-links in the fibrils and performing tensile test on the models, we systematically investigate the deformation mechanisms of cross-linked collagen fibrils. We find that cross-linked fibrils exhibit a three phase behavior, which agrees closer with experimental results than what was obtained using previous models. The fibril mechanical response is characterized by: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime dominated by molecule sliding and (iii) the second stiffer elastic regime related to the stretching of the backbone of the tropocollagen molecules until the fibril ruptures. Our results suggest that both cross-link density and type dictate the stiffness of large deformation regime by increasing the number of interconnected molecules while cross-links mechanical properties determine the failure strain and strength of the fibril. These findings reveal that cross-links play an essential role in creating an interconnected fibrillar material of tunable toughness and strength. PMID:25153614

A Multi-Scale Simulation Approach to Deformation Mechanism Prediction in Superalloys

NASA Astrophysics Data System (ADS)

Lv, Duchao

High-temperature alloys in general and superalloys in particular are crucial for manufacturing gas turbines for aircraft and power generators. Among the superalloy family, the Ni-based superalloys are the most frequently used due to their excellent strength-to-weight ratio. Their strength results from their ordered intermetallic phases (precipitates), which are relatively stable at elevated temperatures. The major deformation processes of Ni-based and Co-based superalloys are precipitate shearing and Orowan looping. The key to developing physics-based models of creep and yield strength of aircraft engine components is to understand the two deformation mechanisms mentioned above. Recent discoveries of novel dislocation structures and stacking-fault configurations in deformed superalloys implied that the traditional anti-phase boundary (APB)-type, yield-strength model is unable to explain the shearing mechanisms of the gamma" phase in 718-type (Ni-based) superalloys. While the onset of plastic deformation is still related to the formation of highly-energetic stacking faults, the physics-based yield strength prediction requires that the novel dislocation structure and the correct intermediate stacking-fault be considered in the mathematical expressions. In order to obtain the dependence of deformation mechanisms on a materials chemical composition, the relationship between the generalized-stacking-fault (GSF) surface and its chemical composition must be understood. For some deformation scenarios in which one precipitate phase and one mechanism are dominant (e.g., Orowan looping), their use in industry requires a fast-acting model that can capture the features of the deformation (e.g., the volume fraction of the sheared matrix) and reduces lost time by not repeating fine-scale simulations. The objective of this thesis was to develop a multi-scale, physics-based simulation approach that can be used to optimize existing superalloys and to accelerate the design of new

Effects of mechanical deformation on energy conversion efficiency of piezoelectric nanogenerators.

PubMed

Yoo, Jinho; Cho, Seunghyeon; Kim, Wook; Kwon, Jang-Yeon; Kim, Hojoong; Kim, Seunghyun; Chang, Yoon-Suk; Kim, Chang-Wan; Choi, Dukhyun

2015-07-10

Piezoelectric nanogenerators (PNGs) are capable of converting energy from various mechanical sources into electric energy and have many attractive features such as continuous operation, replenishment and low cost. However, many researchers still have studied novel material synthesis and interfacial controls to improve the power production from PNGs. In this study, we report the energy conversion efficiency (ECE) of PNGs dependent on mechanical deformations such as bending and twisting. Since the output power of PNGs is caused by the mechanical strain of the piezoelectric material, the power production and their ECE is critically dependent on the types of external mechanical deformations. Thus, we examine the output power from PNGs according to bending and twisting. In order to clearly understand the ECE of PNGs in the presence of those external mechanical deformations, we determine the ECE of PNGs by the ratio of output electrical energy and input mechanical energy, where we suggest that the input energy is based only on the strain energy of the piezoelectric layer. We calculate the strain energy of the piezoelectric layer using numerical simulation of bending and twisting of the PNG. Finally, we demonstrate that the ECE of the PNG caused by twisting is much higher than that caused by bending due to the multiple effects of normal and lateral piezoelectric coefficients. Our results thus provide a design direction for PNG systems as high-performance power generators.

Mechanical deformation of carbon nanotube nano-rings on flat substrate

NASA Astrophysics Data System (ADS)

Zheng, Meng; Ke, Changhong

2011-04-01

We present a numerical analysis of the mechanical deformation of carbon nanotube (CNT) nano-rings on flat graphite substrates, which is motivated by our recent experimental findings on the elastic deformation of CNT nano-rings. Our analysis considers a perfectly circular CNT ring formed by bending a straight individual or bundled single-walled nanotube to connect its two ends. The seamless CNT ring is placed vertically on a flat graphite substrate and its respective deformation curvatures under zero external force, compressive, and tensile forces are determined using a continuum model based on nonlinear elastica theory. Our results show that the van der Waals interaction between the CNT ring and the substrate has profound effects on the deformation of the CNT ring, and that the interfacial binding interaction between the CNT ring and the substrate is strongly modulated by the ring deformation. Our results demonstrate that the CNT ring in force-free conditions has a flat ring segment in contact with the substrate if the ring radius R ≥√EI/2Wvdw , in which EI is the flexural rigidity of the nanotube and Wvdw is the per-unit-length van der Waals energy between the flat ring segment and the substrate. Our results reveal that the load-deformation profiles of the CNT ring under tensile loadings exhibit bifurcation behavior, which is ascribed to its van der Waals interaction with the substrate and is dependent on its relaxed conformation on the substrate. Our work suggests that CNT nano-rings are promising for a number of applications, such as ultrasensitive force sensors and stretchable and flexible structural components in nanoscale mechanical and electromechanical systems.

Formation mechanism of fivefold deformation twins in a face-centered cubic alloy.

PubMed

Zhang, Zhenyu; Huang, Siling; Chen, Leilei; Zhu, Zhanwei; Guo, Dongming

2017-03-28

The formation mechanism considers fivefold deformation twins originating from the grain boundaries in a nanocrystalline material, resulting in that fivefold deformation twins derived from a single crystal have not been reported by molecular dynamics simulations. In this study, fivefold deformation twins are observed in a single crystal of face-centered cubic (fcc) alloy. A new formation mechanism is proposed for fivefold deformation twins in a single crystal. A partial dislocation is emitted from the incoherent twin boundaries (ITBs) with high energy, generating a stacking fault along {111} plane, and resulting in the nucleating and growing of a twin by the successive emission of partials. A node is fixed at the intersecting center of the four different slip {111} planes. With increasing stress under the indentation, ITBs come into being close to the node, leading to the emission of a partial from the node. This generates a stacking fault along a {111} plane, nucleating and growing a twin by the continuous emission of the partials. This process repeats until the formation of fivefold deformation twins.

Formation mechanism of fivefold deformation twins in a face-centered cubic alloy

NASA Astrophysics Data System (ADS)

Zhang, Zhenyu; Huang, Siling; Chen, Leilei; Zhu, Zhanwei; Guo, Dongming

2017-03-01

The formation mechanism considers fivefold deformation twins originating from the grain boundaries in a nanocrystalline material, resulting in that fivefold deformation twins derived from a single crystal have not been reported by molecular dynamics simulations. In this study, fivefold deformation twins are observed in a single crystal of face-centered cubic (fcc) alloy. A new formation mechanism is proposed for fivefold deformation twins in a single crystal. A partial dislocation is emitted from the incoherent twin boundaries (ITBs) with high energy, generating a stacking fault along {111} plane, and resulting in the nucleating and growing of a twin by the successive emission of partials. A node is fixed at the intersecting center of the four different slip {111} planes. With increasing stress under the indentation, ITBs come into being close to the node, leading to the emission of a partial from the node. This generates a stacking fault along a {111} plane, nucleating and growing a twin by the continuous emission of the partials. This process repeats until the formation of fivefold deformation twins.

Tuning transport properties of graphene three-terminal structures by mechanical deformation

NASA Astrophysics Data System (ADS)

Torres, V.; Faria, D.; Latgé, A.

2018-04-01

Straintronic devices made of carbon-based materials have been pushed up due to the graphene high mechanical flexibility and the possibility of interesting changes in transport properties. Properly designed strained systems have been proposed to allow optimized transport responses that can be explored in experimental realizations. In multiterminal systems, comparisons between schemes with different geometries are important to characterize the modifications introduced by mechanical deformations, especially if the deformations are localized at a central part of the system or extended in a large region. Then, in the present analysis, we study the strain effects on the transport properties of triangular and hexagonal graphene flakes, with zigzag and armchair edges, connected to three electronic terminals, formed by semi-infinite graphene nanoribbons. Using the Green's function formalism with circular renormalization schemes, and a single band tight-binding approximation, we find that resonant tunneling transport becomes relevant and is more affected by localized deformations in the hexagonal graphene flakes. Moreover, triangular systems with deformation extended to the leads, like longitudinal three-folded type, are shown as an interesting scenario for building nanoscale waveguides for electronic current.

Complex surface deformation monitoring and mechanism inversion over Qingxu-Jiaocheng, China with multi-sensor SAR images

NASA Astrophysics Data System (ADS)

Liu, Yuanyuan; Zhao, Chaoying; Zhang, Qin; Yang, Chengsheng

2018-02-01

Qingxu-Jiaocheng, China has been suffering severe land subsidence along with the development of ground fissure, which are controlled by local fault and triggered by groundwater withdrawal. With multi-sensor SAR images, we study the spatiotemporal evolution of ground deformation over Qingxu-Jiaocheng with an IPTA InSAR technique and assess the role of groundwater withdrawal to the observed deformation. Discrete GPS measurements are applied to verify the InSAR results. The RMSE of the differences between InSAR and GPS, i.e. ALOS and GPS and Envisat and GPS, are 5.7 mm and 6.3 mm in the LOS direction, respectively. The east-west and vertical components of the observed deformation from 2007 to 2010 are decomposed by using descending-track Envisat and ascending-track ALOS interferograms, indicating that the east-west component cannot be neglected when the deformation is large or the ground fissure is active. Four phases of land subsidence in the study region are successfully retrieved, and its spatiotemporal evolution is quantitatively analyzed. Lastly, a flat lying sill model with distributed contractions is implemented to model the InSAR deformation over Qingxu-Jiaocheng, which manifests that the ground deformation is mainly caused by groundwater withdrawal. This research provides new insights into the land subsidence monitoring and its mechanism inversion over Qingxu-Jiaocheng region.

Atomistic simulations of deformation mechanisms in ultralight weight Mg-Li alloys

NASA Astrophysics Data System (ADS)

Karewar, Shivraj

Mg alloys have spurred a renewed academic and industrial interest because of their ultra-light-weight and high specific strength properties. Hexagonal close packed Mg has low deformability and a high plastic anisotropy between basal and non-basal slip systems at room temperature. Alloying with Li and other elements is believed to counter this deficiency by activating non-basal slip by reducing their nucleation stress. In this work I study how Li addition affects deformation mechanisms in Mg using atomistic simulations. In the first part, I create a reliable and transferable concentration dependent embedded atom method (CD-EAM) potential for my molecular dynamics study of deformation. This potential describes the Mg-Li phase diagram, which accurately describes the phase stability as a function of Li concentration and temperature. Also, it reproduces the heat of mixing, lattice parameters, and bulk moduli of the alloy as a function of Li concentration. Most importantly, our CD-EAM potential reproduces the variation of stacking fault energy for basal, prismatic, and pyramidal slip systems that in uences the deformation mechanisms as a function of Li concentration. This success of CD-EAM Mg-Li potential in reproducing different properties, as compared to literature data, shows its reliability and transferability. Next, I use this newly created potential to study the effect of Li addition on deformation mechanisms in Mg-Li nanocrystalline (NC) alloys. Mg-Li NC alloys show basal slip, pyramidal type-I slip, tension twinning, and two-compression twinning deformation modes. Li addition reduces the plastic anisotropy between basal and non-basal slip systems by modifying the energetics of Mg-Li alloys. This causes the solid solution softening. The inverse relationship between strength and ductility therefore suggests a concomitant increase in alloy ductility. A comparison of the NC results with single crystal deformation results helps to understand the qualitative and

Mechanisms of strain accommodation in plastically-deformed zircon under simple shear deformation conditions during amphibolite-facies metamorphism

NASA Astrophysics Data System (ADS)

Kovaleva, Elizaveta; Klötzli, Urs; Wheeler, John; Habler, Gerlinde

2018-02-01

This study documents the strain accommodation mechanisms in zircon under amphibolite-facies metamorphic conditions in simple shear. Microstructural data from undeformed, fractured and crystal-plastically deformed zircon crystals are described in the context of the host shear zone, and evaluated in the light of zircon elastic anisotropy. Our work challenges the existing model of zircon evolution and shows previously undescribed rheological characteristics for this important accessory mineral. Crystal-plastically deformed zircon grains have axis oriented parallel to the foliation plane, with the majority of deformed grains having axis parallel to the lineation. Zircon accommodates strain by a network of stepped low-angle boundaries, formed by switching between tilt dislocations with the slip systems <100>{010} and < 1 bar 10>{110} and rotation axis [001], twist dislocations with the rotation axis [001], and tilt dislocations with the slip system <100>{001} and rotation axis [010]. The slip system < 1 bar 10>{110} is newly described for zircon. Most misorientation axes in plastically-deformed zircon grains are parallel to the XY plane of the sample and have [001] crystallographic direction. Such behaviour of strained zircon lattice is caused by elastic anisotropy that has a direct geometric control on the rheology, deformation mechanisms and dominant slip systems in zircon. Young's modulus and P wave velocity have highest values parallel to zircon [001] axis, indicating that zircon is elastically strong along this direction. Poisson ratio and Shear modulus demonstrate that zircon is also most resistant to shearing along [001]. Thus, [001] axis is the most common rotation axis in zircon. The described zircon behaviour is important to take into account during structural and geochronological investigations of (poly)metamorphic terrains. Geometry of dislocations in zircon may help reconstructing the geometry of the host shear zone(s), large-scale stresses in the

Modelling heat and mass transfer in bread baking with mechanical deformation

NASA Astrophysics Data System (ADS)

Nicolas, V.; Salagnac, P.; Glouannec, P.; Ploteau, J.-P.; Jury, V.; Boillereaux, L.

2012-11-01

In this paper, the thermo-hydric behaviour of bread during baking is studied. A numerical model has been developed with Comsol Multiphysics© software. The model takes into account the heat and mass transfers in the bread and the phenomenon of swelling. This model predicts the evolution of temperature, moisture, gas pressure and deformation in French "baguette" during baking. Local deformation is included in equations using solid phase conservation and, global deformation is calculated using a viscous mechanic model. Boundary conditions are specified with the sole temperature model and vapour pressure estimation of the oven during baking. The model results are compared with experimental data for a classic baking. Then, the model is analysed according to physical properties of bread and solicitations for a better understanding of the interactions between different mechanisms within the porous matrix.

Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils.

PubMed

Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J; Buehler, Markus J

2015-12-01

Collagen is a ubiquitous protein with remarkable mechanical properties. It is highly elastic, shows large fracture strength and enables substantial energy dissipation during deformation. Most of the connective tissue in humans consists of collagen fibrils composed of a staggered array of tropocollagen molecules, which are connected by intermolecular cross-links. In this study, we report a three-dimensional coarse-grained model of collagen and analyze the influence of enzymatic cross-links on the mechanics of collagen fibrils. Two representatives immature and mature cross-links are implemented in the mesoscale model using a bottom-up approach. By varying the number, type and mechanical properties of cross-links in the fibrils and performing tensile test on the models, we systematically investigate the deformation mechanisms of cross-linked collagen fibrils. We find that cross-linked fibrils exhibit a three phase behavior, which agrees closer with experimental results than what was obtained using previous models. The fibril mechanical response is characterized by: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime dominated by molecule sliding and (iii) the second stiffer elastic regime related to the stretching of the backbone of the tropocollagen molecules until the fibril ruptures. Our results suggest that both cross-link density and type dictate the stiffness of large deformation regime by increasing the number of interconnected molecules while cross-links mechanical properties determine the failure strain and strength of the fibril. These findings reveal that cross-links play an essential role in creating an interconnected fibrillar material of tunable toughness and strength. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Deformation mechanisms and grain size evolution in the Bohemian granulites - a computational study

NASA Astrophysics Data System (ADS)

Maierova, Petra; Lexa, Ondrej; Jeřábek, Petr; Franěk, Jan; Schulmann, Karel

2015-04-01

elaborated and at the same time the most promising descriptions: thermodynamics-based models with and without Zener pinning. For conditions compatible with the S1 and S2 microstructures (~800 °C and strain rate ~10-13 s-1), the calculated stable grain sizes are ~30 μm and >300 μm in the models with and without Zener pinning, respectively. This is in agreement with the contrasting grain sizes associated with S1 and S2 microstructures implying that mainly chemically induced recrystallization of S1 feldspar porphyroclasts must had played a fundamental role in the transition into the diffusion creep. The model with pinning also explains only minor changes of mean grain size associated with S2 microstructure. The S2-S3 switch from the diffusion to dislocation creep is difficult to explain when assuming reasonable temperature and strain rate (or stress). However, a simple incorporation of the effect of melt solidification into the model with pinning can mimic this observed switch. Besides the above mentioned simple models with prescribed temperature and strain rate, we implemented the grain size evolution laws into in a 2D thermo-mechanical model setup, where stress, strain rate and temperature evolve in a more natural manner. This setup simulates a collisional evolution of an orogenic root with anomalous lower crust. The lower-crustal material is a source region for diapirs and it deforms via a combination of dislocation and grain-size-sensitive creeps. We tested the influence of selected parameters in the flow laws and in the grain-size evolution laws on the shape and other characteristics of the growing diapirs. The outputs of our simulations were then compared with the geological record from the Moldanubian granulite massifs.

Deformation mechanisms of bent Si nanowires governed by the sign and magnitude of strain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lihua, E-mail: wlh@bjut.edu.cn, E-mail: xdhan@bjut.edu.cn, E-mail: j.zou@uq.edu.au; Materials Engineering, The University of Queensland, Brisbane, QLD 4072; Kong, Deli

2016-04-11

In this study, the deformation mechanisms of bent Si nanowires are investigated at the atomic scale with bending strain up to 12.8%. The sign and magnitude of the applied strain are found to govern their deformation mechanisms, in which the dislocation types (full or partial dislocations) can be affected by the sign (tensile or compressive) and magnitude of the applied strain. In the early stages of bending, plastic deformation is controlled by 60° full dislocations. As the bending increases, Lomer dislocations can be frequently observed. When the strain increases to a significant level, 90° partial dislocations induced from the tensilemore » surfaces of the bent nanowires are observed. This study provides a deeper understanding of the effect of the sign and magnitude of the bending strain on the deformation mechanisms in bent Si nanowires.« less

High Resolution Transmission Electron Microscope Observation of Zero-Strain Deformation Twinning Mechanisms in Ag

NASA Astrophysics Data System (ADS)

Liu, L.; Wang, J.; Gong, S. K.; Mao, S. X.

2011-04-01

We have observed a new deformation-twinning mechanism using the high resolution transmission electron microscope in polycrystalline Ag films, zero-strain twinning via nucleation, and the migration of a Σ3{112} incoherent twin boundary (ITB). This twinning mechanism produces a near zero macroscopic strain because the net Burgers vectors either equal zero or are equivalent to a Shockley partial dislocation. This observation provides new insight into the understanding of deformation twinning and confirms a previous hypothesis: detwinning could be accomplished via the nucleation and migration of Σ3{112} ITBs. The zero-strain twinning mechanism may be unique to low staking fault energy metals with implications for their deformation behavior.

Transpression as the main deformational event in an Archaean greenstone belt, northeastern Minnesota

NASA Technical Reports Server (NTRS)

Hudleston, P. J.; Schultz-Ela, D.; Bauer, R. L.; Southwick, D. L.

1986-01-01

Deformed and metamorphosed sedimentary and volcanic rocks of the Vermilion district constitute an Archean greenstone belt trending east-west between higher grade rocks of the Vermilion Granitic Complex to the north and the Giants Range batholith to the south. Metamorphic grade is low throughout, being lowest in the center of the belt (chlorite zone of the greenschist facies). All the measured strain, a cleavage or schistosity, and a mineral lineation in this belt are attributed to the main phase of deformation D sub 2 that followed an earlier nappe-forming event D sub 1, which left little evidence of penetrative fabric. Previous work assumed that the D sub 2 deformation resulted from north-south compression across the district. It is now believed that a significant component of this deformation resulted from dextral shear across the whole region. Thus the Vermilion fault, a late-state largely strike-slip structure that bounds the Vermilion district to the north, may simply be the latest, most brittle expression of a shear regime that was much more widespread in space and time. Features that are indicative of shear include ductile shear zones with sigmoidal foliation patterns, highly schistose zones with the development of shear bands, feldspar clasts or pyrite cubes with asymmetric pressure shadows, and the fact that the asymmetry of the F sub 2 folds is predominantly Z for at least 15 km south of the Vermilion fault.

Time for anisotropy: The significance of mechanical anisotropy for the development of deformation structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ran, Hao; de Riese, Tamara; Llorens, Maria-Gema

The forty-year history of the Journal of Structural Geology has recorded an enormous increase in the description, interpretation and modelling of deformation structures. Amongst factors that control deformation and the resulting structures, mechanical anisotropy has proven difficult to tackle. Using a Fast Fourier Transform-based numerical solver for viscoplastic deformation of crystalline materials, we illustrate in this paper how mechanical anisotropy has a profound effect on developing structures, such as crenulation cleavages, porphyroclast geometry and the initiation of shear bands and shear zones.

Time for anisotropy: The significance of mechanical anisotropy for the development of deformation structures

DOE PAGES

Ran, Hao; de Riese, Tamara; Llorens, Maria-Gema; ...

2018-05-20

The forty-year history of the Journal of Structural Geology has recorded an enormous increase in the description, interpretation and modelling of deformation structures. Amongst factors that control deformation and the resulting structures, mechanical anisotropy has proven difficult to tackle. Using a Fast Fourier Transform-based numerical solver for viscoplastic deformation of crystalline materials, we illustrate in this paper how mechanical anisotropy has a profound effect on developing structures, such as crenulation cleavages, porphyroclast geometry and the initiation of shear bands and shear zones.

Scaling laws and deformation mechanisms of nanoporous copper under adiabatic uniaxial strain compression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Fuping, E-mail: fpyuan@lnm.imech.ac.cn; Wu, Xiaolei, E-mail: xlwu@imech.ac.cn

2014-12-15

A series of large-scale molecular dynamics simulations were conducted to investigate the scaling laws and the related atomistic deformation mechanisms of Cu monocrystal samples containing randomly placed nanovoids under adiabatic uniaxial strain compression. At onset of yielding, plastic deformation is accommodated by dislocations emitted from void surfaces as shear loops. The collapse of voids are observed by continuous emissions of dislocations from void surfaces and their interactions with further plastic deformation. The simulation results also suggest that the effect modulus, the yield stress and the energy aborption density of samples under uniaxial strain are linearly proportional to the relative densitymore » ρ. Moreover, the yield stress, the average flow stress and the energy aborption density of samples with the same relative density show a strong dependence on the void diameter d, expressed by exponential relations with decay coefficients much higher than -1/2. The corresponding atomistic mechanisms for scaling laws of the relative density and the void diameter were also presented. The present results should provide insights for understanding deformation mechanisms of nanoporous metals under extreme conditions.« less

Deformation mechanisms to ameliorate the mechanical properties of novel TRIP/TWIP Co-Cr-Mo-(Cu) ultrafine eutectic alloys

PubMed Central

Kim, J. T.; Hong, S. H.; Park, H. J.; Kim, Y. S.; Suh, J. Y.; Lee, J. K.; Park, J. M.; Maity, T.; Eckert, J.; Kim, K. B.

2017-01-01

In the present study, the microstructural evolution and the modulation of the mechanical properties have been investigated for a Co-Cr-Mo (CCM) ternary eutectic alloy by addition of a small amount of copper (0.5 and 1 at.%). The microstructural observations reveal a distinct dissimilarity in the eutectic structure such as a broken lamellar structure and a well-aligned lamellar structure and an increasing volume fraction of Co lamellae as increasing amount of copper addition. This microstructural evolution leads to improved plasticity from 1% to 10% without the typical tradeoff between the overall strength and compressive plasticity. Moreover, investigation of the fractured samples indicates that the CCMCu alloy exhibits higher plastic deformability and combinatorial mechanisms for improved plastic behavior. The improved plasticity of CCMCu alloys originates from several deformation mechanisms; i) slip, ii) deformation twinning, iii) strain-induced transformation and iv) shear banding. These results reveal that the mechanical properties of eutectic alloys in the Co-Cr-Mo system can be ameliorated by micro-alloying such as Cu addition. PMID:28067248

Micro-to-nano-scale deformation mechanisms of a bimodal ultrafine eutectic composite

PubMed Central

Lee, Seoung Wan; Kim, Jeong Tae; Hong, Sung Hwan; Park, Hae Jin; Park, Jun-Young; Lee, Nae Sung; Seo, Yongho; Suh, Jin Yoo; Eckert, Jürgen; Kim, Do Hyang; Park, Jin Man; Kim, Ki Buem

2014-01-01

The outstading mechanical properties of bimodal ultrafine eutectic composites (BUECs) containing length scale hierarchy in eutectic structure were demonstrated by using AFM observation of surface topography with quantitative height measurements and were interpreted in light of the details of the deformation mechanisms by three different interface modes. It is possible to develop a novel strain accommodated eutectic structure for triggering three different interface-controlled deformation modes; (I) rotational boundary mode, (II) accumulated interface mode and (III) individual interface mode. A strain accommodated microstructure characterized by the surface topology gives a hint to design a novel ultrafine eutectic alloys with excellent mechanical properties. PMID:25265897

Mechanical stability of the cell nucleus: roles played by the cytoskeleton in nuclear deformation and strain recovery.

PubMed

Wang, Xian; Liu, Haijiao; Zhu, Min; Cao, Changhong; Xu, Zhensong; Tsatskis, Yonit; Lau, Kimberly; Kuok, Chikin; Filleter, Tobin; McNeill, Helen; Simmons, Craig A; Hopyan, Sevan; Sun, Yu

2018-05-18

Extracellular forces transmitted through the cytoskeleton can deform the cell nucleus. Large nuclear deformation increases the risk of disrupting the nuclear envelope's integrity and causing DNA damage. Mechanical stability of the nucleus defines its capability of maintaining nuclear shape by minimizing nuclear deformation and recovering strain when deformed. Understanding the deformation and recovery behavior of the nucleus requires characterization of nuclear viscoelastic properties. Here, we quantified the decoupled viscoelastic parameters of the cell membrane, cytoskeleton, and the nucleus. The results indicate that the cytoskeleton enhances nuclear mechanical stability by lowering the effective deformability of the nucleus while maintaining nuclear sensitivity to mechanical stimuli. Additionally, the cytoskeleton decreases the strain energy release rate of the nucleus and might thus prevent shape change-induced structural damage to chromatin. © 2018. Published by The Company of Biologists Ltd.

Contraction and elongation: Mechanics underlying cell boundary deformations in epithelial tissue.

PubMed

Hara, Yusuke

2017-06-01

The cell-cell boundaries of epithelial cells form cellular frameworks at the apical side of tissues. Deformations in these boundaries, for example, boundary contraction and elongation, and the associated forces form the mechanical basis of epithelial tissue morphogenesis. In this review, using data from recent Drosophila studies on cell boundary contraction and elongation, I provide an overview of the mechanism underlying the bi-directional deformations in the epithelial cell boundary, that are sustained by biased accumulations of junctional and apico-medial non-muscle myosin II. Moreover, how the junctional tensions exist on cell boundaries in different boundary dynamics and morphologies are discussed. Finally, some future perspectives on how recent knowledge about single cell boundary-level mechanics will contribute to our understanding of epithelial tissue morphogenesis are discussed. © 2017 Japanese Society of Developmental Biologists.

Compaction behavior and deformation mechanism of directly compressible textured mannitol in a rotary tablet press simulator.

PubMed

Tarlier, Nicolas; Soulairol, Ian; Bataille, Bernard; Baylac, Gilles; Ravel, Patrice; Nofrerias, Isaac; Lefèvre, Philippe; Sharkawi, Tahmer

2015-11-10

Textured mannitol powder is widely used as a pharmaceutical excipient for tablet compaction. In order to choose the right tableting parameters, it is necessary to understand its mechanical behavior during deformation under industrial tableting conditions. The aim of this study was to evaluate the mechanical behavior during deformation of a textured mannitol using a rotary tablet press simulator. Mean yield pressure (Py) obtained by Heckel modeling, Walker coefficients (W) and Stress Rate Sensitivity (SRS) were compared to reference excipients, known for either their plastic (microcrystalline cellulose) or fragmentary (lactose and dibasic calcium phosphate) deformation behavior. Py, W and SRS values showed that the studied textured mannitol has a fragmentary deformation mechanism. Furthermore, this mechanical behavior was not sensitive to lubrication, which is characteristic of fragmentary excipients. Copyright © 2015 Elsevier B.V. All rights reserved.

Multiscale analysis of bamboo deformation mechanisms following NaOH treatment using X-ray and correlative microscopy.

PubMed

Salvati, E; Brandt, L R; Uzun, F; Zhang, H; Papadaki, C; Korsunsky, A M

2018-05-01

For hundreds of years, bamboo has been employed for a variety of applications ranging from load-bearing structures to textiles. Thanks to its hierarchical structure that is functionally graded and naturally optimised, bamboo displays a variation in properties across its stem that ensures exceptional flexural performance. Often, alkaline solutions are employed for the treatment of bamboo in order to alter its natural elastic behaviour and make it suitable for particular applications. In this work we study the effect of NaOH solutions of five different concentrations (up to 25%) on the elastic properties of bamboo. By exploiting the capabilities of modern experimental techniques such as in situ synchrotron X-ray scattering and Digital Image Correlation, we present detailed analysis of the deformation mechanisms taking place in the main constituents of bamboo, i.e. fibres and matrix (Parenchyma). The principal achievement of this study is the elucidation of the deformation mechanisms at the fibre scale, where the relative sliding of fibrils plays a crucial role in the property modification of the whole bamboo stem. Furthermore, we shed light on the parenchyma toughness variation as a consequence of alkali treatments. Alkaline solutions are often employed for the treatment of bamboo in order to alter its natural elastic behaviour. In this work we study the effect of alkaline solutions on the elastic properties of bamboo. Using state of the art experimental techniques allowed shedding light on the deformation mechanisms occurring in the bamboo main constituents, i.e. fibres and matrix (parenchyma cells). Enhancement of fibre stiffness was experienced when up to 20% NaOH solution was employed, while for higher concentration a decay was observed. This effect was imputed to the modification of adhesion between fibrils induced by disruption of ligand elements (e.g. lignin). Modification of the matrix toughness was also experienced, that indicated an improved resistance to

3D mechanical stratigraphy of a deformed multi-layer: Linking sedimentary architecture and strain partitioning

NASA Astrophysics Data System (ADS)

Cawood, Adam J.; Bond, Clare E.

2018-01-01

Stratigraphic influence on structural style and strain distribution in deformed sedimentary sequences is well established, in models of 2D mechanical stratigraphy. In this study we attempt to refine existing models of stratigraphic-structure interaction by examining outcrop scale 3D variations in sedimentary architecture and the effects on subsequent deformation. At Monkstone Point, Pembrokeshire, SW Wales, digital mapping and virtual scanline data from a high resolution virtual outcrop have been combined with field observations, sedimentary logs and thin section analysis. Results show that significant variation in strain partitioning is controlled by changes, at a scale of tens of metres, in sedimentary architecture within Upper Carboniferous fluvio-deltaic deposits. Coupled vs uncoupled deformation of the sequence is defined by the composition and lateral continuity of mechanical units and unit interfaces. Where the sedimentary sequence is characterized by gradational changes in composition and grain size, we find that deformation structures are best characterized by patterns of distributed strain. In contrast, distinct compositional changes vertically and in laterally equivalent deposits results in highly partitioned deformation and strain. The mechanical stratigraphy of the study area is inherently 3D in nature, due to lateral and vertical compositional variability. Consideration should be given to 3D variations in mechanical stratigraphy, such as those outlined here, when predicting subsurface deformation in multi-layers.

Studying physical properties of deformed intact and fractured rocks by micro-scale hydro-mechanical-seismicity model

NASA Astrophysics Data System (ADS)

Raziperchikolaee, Samin

The pore pressure variation in an underground formation during hydraulic stimulation of low permeability formations or CO2 sequestration into saline aquifers can induce microseismicity due to fracture generation or pre-existing fracture activation. While the analysis of microseismic data mainly focuses on mapping the location of fractures, the seismic waves generated by the microseismic events also contain information for understanding of fracture mechanisms based on microseismic source analysis. We developed a micro-scale geomechanics, fluid-flow and seismic model that can predict transport and seismic source behavior during rock failure. This model features the incorporation of microseismic source analysis in fractured and intact rock transport properties during possible rock damage and failure. The modeling method considers comprehensive grains and cements interaction through a bonded-particle-model. As a result of grain deformation and microcrack development in the rock sample, forces and displacements in the grains involved in the bond breakage are measured to determine seismic moment tensor. In addition, geometric description of the complex pore structure is regenerated to predict fluid flow behavior of fractured samples. Numerical experiments are conducted for different intact and fractured digital rock samples, representing various mechanical behaviors of rocks and fracture surface properties, to consider their roles on seismic and transport properties of rocks during deformation. Studying rock deformation in detail provides an opportunity to understand the relationship between source mechanism of microseismic events and transport properties of damaged rocks to have a better characterizing of fluid flow behavior in subsurface formations.

NMR study on mechanisms of ionic polymer-metal composites deformation with water content

NASA Astrophysics Data System (ADS)

Zhu, Zicai; Chen, Hualing; Wang, Yongquan; Luo, Bin; Chang, Longfei; Li, Bo; Chen, Luping

2011-10-01

Ionic polymer-metal composites (IPMCs) exhibit a large dynamic bending deformation under exterior electric field. The states and proportions of water within the IPMCs have great effect on the IPMCs deformation properties. This letter investigates the influence of the proportion changes of different types of water on the deformation, which may disclose the working mechanisms of the IPMCs. We give a deformation trend of IPMCs with the reduction of water content firstly. Then by the method of nuclear magnetic resonance, various water types (water bonded to sulfonates, loosely bound water and free water) of IPMCs and their proportions are investigated in the drying process which corresponds to their different deformation states. It is obtained that the deformation properties of IPMCs depend strongly on their water content and the excess free water is responsible for the relaxation deformation.

Mechanical properties of a nitrogen-bearing austenitic steel during static and cycle deformation

NASA Astrophysics Data System (ADS)

Blinov, E. V.; Terent'ev, V. F.; Prosvirnin, D. V.

2016-09-01

The mechanical properties of a nitrogen-bearing corrosion-resistant austenitic steel containing 0.311% nitrogen have been studied during static and cyclic deformation. It is found that the steel having an ultimate strength of 930 MPa exhibits a plasticity of 33%. The endurance limit under repeated tension at 106 loading cycles is 400 MPa. The propagation of a fatigue crack at low and high amplitudes of cyclic deformation follows a ductile fracture mechanism with the presence of fatigue grooves.

Deformation of supersymmetric and conformal quantum mechanics through affine transformations

NASA Technical Reports Server (NTRS)

Spiridonov, Vyacheslav

1993-01-01

Affine transformations (dilatations and translations) are used to define a deformation of one-dimensional N = 2 supersymmetric quantum mechanics. Resulting physical systems do not have conserved charges and degeneracies in the spectra. Instead, superpartner Hamiltonians are q-isospectral, i.e. the spectrum of one can be obtained from another (with possible exception of the lowest level) by q(sup 2)-factor scaling. This construction allows easily to rederive a special self-similar potential found by Shabat and to show that for the latter a q-deformed harmonic oscillator algebra of Biedenharn and Macfarlane serves as the spectrum generating algebra. A general class of potentials related to the quantum conformal algebra su(sub q)(1,1) is described. Further possibilities for q-deformation of known solvable potentials are outlined.

Unraveling Deformation Mechanisms in Gradient Structured Metals

NASA Astrophysics Data System (ADS)

Moering, Jordan Alexander

Gradient structures have demonstrated high strength and high ductility, introducing new mechanisms to challenge conventional mechanics. This work develops a method for characterizing the shear strain in gradient structured steel and presents evidence of a texture gradient that develops in Surface Mechanical Attrition Treatment (SMAT). Mechanics underlying some theories of the strengthening mechanisms in gradient structured metals are introduced, followed by the fabrication and testing of gradient structured aluminum rod. The round geometry is intrinsically different from its flat counterparts, which leads to a multiaxial stress state evolving in tension. The aluminum exhibits strengthening beyond rule of mixtures, and texture evolution in the post-mortem sample indicates that out of plane stresses operate within the gradient. Finally, another gradient structured aluminum rod is shown to exhibit higher strength and higher elongation to failure in a variety of sample diameters and processing conditions. The GND density and microstructural evolution showed no significant changes during mechanical testing, and high resolution strain mapping was successfully completed within the core of the material. These discoveries and contributions to the field should help continue unraveling the deformation mechanisms of gradient structured metals.

A mechanical model for deformable and mesh pattern wheel of lunar roving vehicle

NASA Astrophysics Data System (ADS)

Liang, Zhongchao; Wang, Yongfu; Chen, Gang (Sheng); Gao, Haibo

2015-12-01

As an indispensable tool for astronauts on lunar surface, the lunar roving vehicle (LRV) is of great significance for manned lunar exploration. An LRV moves on loose and soft lunar soil, so the mechanical property of its wheels directly affects the mobility performance. The wheels used for LRV have deformable and mesh pattern, therefore, the existing mechanical theory of vehicle wheel cannot be used directly for analyzing the property of LRV wheels. In this paper, a new mechanical model for LRV wheel is proposed. At first, a mechanical model for a rigid normal wheel is presented, which involves in multiple conventional parameters such as vertical load, tangential traction force, lateral force, and slip ratio. Secondly, six equivalent coefficients are introduced to amend the rigid normal wheel model to fit for the wheels with deformable and mesh-pattern in LRV application. Thirdly, the values of the six equivalent coefficients are identified by using experimental data obtained in an LRV's single wheel testing. Finally, the identified mechanical model for LRV's wheel with deformable and mesh pattern are further verified and validated by using additional experimental results.

Hardening mechanisms in olivine single crystal deformed at 1090 °C: an electron tomography study

NASA Astrophysics Data System (ADS)

Mussi, Alexandre; Cordier, Patrick; Demouchy, Sylvie; Hue, Benoit

2017-11-01

The dislocation microstructures in a single crystal of olivine deformed experimentally in uniaxial compression at 1090 °C and under a confining pressure of 300 MPa, have been investigated by transmission electron tomography in order to better understand deformation mechanisms at the microscale relevant for lithospheric mantle deformations. Investigation by electron tomography reveals microstructures, which are more complex than previously described, composed of ? and ? dislocations commonly exhibiting 3D configurations. Numerous mechanisms such as climb, cross-slip, double cross-slip as well as interactions like junction formations and collinear annihilations are the source of this complexity. The diversity observed advocates for microscale deformation of olivine significantly less simple than classic dislocation creep reported in metals or ice close to melting temperature. Deciphering mechanism of hardening in olivine at temperatures where ionic diffusion is slow and is then expected to play very little role is crucial to better understand and thus model deformation at larger scale and at temperatures (900-1100 °C) highly relevant for the lithospheric mantle.

Intraplate Crustal Deformation Within the Northern Sinai Microplate: Evidence from Paleomagnetic Directions and Mechanical Modeling

NASA Astrophysics Data System (ADS)

Dembo, N.; Granot, R.; Hamiel, Y.

2017-12-01

The intraplate crustal deformation found in the northern part of the Sinai Microplate, located near the northern Dead Sea Fault plate boundary, is examined. Previous studies have suggested that distributed deformation in Lebanon is accommodated by regional uniform counterclockwise rigid block rotations. However, remanent magnetization directions observed near the Lebanese restraining bend are not entirely homogeneous suggesting that an unexplained and complex internal deformation pattern exists. In order to explain the variations in the amount of vertical-axis rotations we construct a mechanical model of the major active faults in the region that simulates the rotational deformation induced by motion along these faults. The rotational pattern calculated by the mechanical modeling predicts heterogeneous distribution of rotations around the faults. The combined rotation field that considers both the fault induced rotations and the already suggested regional block rotations stands in general agreement with the observed magnetization directions. Overall, the modeling results provide a more detailed and complete picture of the deformation pattern in this region and show that rotations induced by motion along the Dead Sea Fault act in parallel to rigid block rotations. Finally, the new modeling results unravel important insights as to the fashion in which crustal deformation is distributed within the northern part of the Sinai Microplate and propose an improved deformational mechanism that might be appropriate for other plate margins as well.

A Case Study on the Strata Movement Mechanism and Surface Deformation Regulation in Chengchao Underground Iron Mine

NASA Astrophysics Data System (ADS)

Cheng, Guanwen; Chen, Congxin; Ma, Tianhui; Liu, Hongyuan; Tang, Chunan

2017-04-01

The regular pattern of surface deformation and the mechanism of underground strata movement, especially in iron mines constructed with the block caving method, have a great influence on infrastructure on the surface, so they are an important topic for research. Based on the engineering geology conditions and the surface deformation and fracture features in Chengchao Iron Mine, the mechanism of strata movement and the regular pattern of surface deformation in the footwall were studied by the geomechanical method, and the following conclusions can be drawn: I. The surface deformation process is divided into two stages over time, i.e., the chimney caving development stage and the post-chimney deformation stage. Currently, the surface deformation in Chengchao Iron Mine is at the post-chimney deformation stage. II. At the post-chimney deformation stage, the surface deformation and geological hazards in Chengchao Iron Mine are primarily controlled by the NWW-trending joints, with the phenomenon of toppling deformation and failure on the surface. Based on the surface deformation characteristics in Chengchao Iron Mine, the surface deformation area can be divided into the following four zones: the fracture extension zone, the fracture closure zone, the fracture formation zone and the deformation accumulation zone. The zones on the surface can be determined by the surface deformation characteristics. III. The cantilever beams near the chimney caving area, caused by the NWW-trending joints, have been subjected to toppling failure. This causes the different deformation and failure mechanisms in different locations of the deep rock mass. The deep rock can be divided into four zones, i.e., the fracture zone, fracture transition zone, deformation zone and undisturbed zone, according to the different deformation and failure mechanisms. The zones in the deep rock are the reason for the zones on the surface, so they can be determined by the zones on the surface. Through these

Cell Deformation by Single-beam Acoustic Trapping: A Promising Tool for Measurements of Cell Mechanics

PubMed Central

Hwang, Jae Youn; Kim, Jihun; Park, Jin Man; Lee, Changyang; Jung, Hayong; Lee, Jungwoo; Shung, K. Kirk

2016-01-01

We demonstrate a noncontact single-beam acoustic trapping method for the quantification of the mechanical properties of a single suspended cell with label-free. Experimentally results show that the single-beam acoustic trapping force results in morphological deformation of a trapped cell. While a cancer cell was trapped in an acoustic beam focus, the morphological changes of the immobilized cell were monitored using bright-field imaging. The cell deformability was then compared with that of a trapped polystyrene microbead as a function of the applied acoustic pressure for a better understanding of the relationship between the pressure and degree of cell deformation. Cell deformation was found to become more pronounced as higher pressure levels were applied. Furthermore, to determine if this acoustic trapping method can be exploited in quantifying the cell mechanics in a suspension and in a non-contact manner, the deformability levels of breast cancer cells with different degrees of invasiveness due to acoustic trapping were compared. It was found that highly-invasive breast cancer cells exhibited greater deformability than weakly-invasive breast cancer cells. These results clearly demonstrate that the single-beam acoustic trapping technique is a promising tool for non-contact quantitative assessments of the mechanical properties of single cells in suspensions with label-free. PMID:27273365

Deformation Mechanisms of Darreh Sary Metapelites, Sanandaj‒Sirjan Zone, Iran

NASA Astrophysics Data System (ADS)

Hemmati, O.; Tabatabaei Manesh, S. M.; Nadimi, A. R.

2018-03-01

The Darreh Sary metapelitic rocks are located in the northeast of Zagros orogenic belt and Sanandaj-Sirjan structural zone. The lithological composition of these rocks includes slate, phyllite, muscovitebiotite schist, garnet schist, staurolite-garnet schist and staurolite schist. The shale is the protolith of these metamorphic rocks, which was originated from the continental island arc tectonic setting and has been subjected to processes of Zagros orogeny. The deformation mechanisms in these rocks include bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) and grain boundary migration recrystallization (GBM), which are considered as the key to estimate the deformation temperature of the rocks. The estimated ranges of deformation temperature and depth in these rocks show the temperatures of 275-375, 375-500, and >500°C and the depths of 10 to 17 km. The observed structures in these rocks such as faults, fractures and folds, often with the NW-SE direction coordinate with the structural trends of Zagros orogenic belt structures. The S-C mylonite fabrics is observed in these rocks with other microstructures such as mica fish, σ fabric and garnet deformation indicate the dextral shear deformation movements of study area. Based on the obtained results of this research, the stages of tectonic evolution of Darreh Sary area were developed.

Perturbatively deformed defects in Pöschl-Teller-driven scenarios for quantum mechanics

NASA Astrophysics Data System (ADS)

Bernardini, Alex E.; da Rocha, Roldão

2016-07-01

Pöschl-Teller-driven solutions for quantum mechanical fluctuations are triggered off by single scalar field theories obtained through a systematic perturbative procedure for generating deformed defects. The analytical properties concerning the quantum fluctuations in one-dimension, zero-mode states, first- and second-excited states, and energy density profiles are all obtained from deformed topological and non-topological structures supported by real scalar fields. Results are firstly derived from an integrated λϕ4 theory, with corresponding generalizations applied to starting λχ4 and sine-Gordon theories. By focusing our calculations on structures supported by the λϕ4 theory, the outcome of our study suggests an exact quantitative correspondence to Pöschl-Teller-driven systems. Embedded into the perturbative quantum mechanics framework, such a correspondence turns into a helpful tool for computing excited states and continuous mode solutions, as well as their associated energy spectrum, for quantum fluctuations of perturbatively deformed structures. Perturbative deformations create distinct physical scenarios in the context of exactly solvable quantum systems and may also work as an analytical support for describing novel braneworld universes embedded into a 5-dimensional gravity bulk.

Plastic deformation mechanisms in polyimide resins and their semi-interpenetrating networks

NASA Technical Reports Server (NTRS)

Jang, Bor Z.

1990-01-01

High-performance thermoset resins and composites are critical to the future growth of space, aircraft, and defense industries in the USA. However, the processing-structure-property relationships in these materials remain poorly understood. In the present ASEE/NASA Summer Research Program, the plastic deformation modes and toughening mechanisms in single-phase and multiphase thermoset resins were investigated. Both thermoplastic and thermoset polyimide resins and their interpenetrating networks (IPNs and semi-IPNs) were included. The fundamental tendency to undergo strain localization (crazing and shear banding) as opposed to a more diffuse (or homogeneous) deformation in these polymers were evaluated. Other possible toughening mechanisms in multiphase thermoset resins were also examined. The topological features of network chain configuration/conformation and the multiplicity of phase morphology in INPs and semi-IPNs provide unprecedented opportunities for studying the toughening mechanisms in multiphase thermoset polymers and their fiber composites.

A deformation mechanism of hard metal surrounded by soft metal during roll forming

PubMed Central

YU, Hailiang; TIEU, A. Kiet; LU, Cheng; LIU, Xiong; GODBOLE, Ajit; LI, Huijun; KONG, Charlie; QIN, Qinghua

2014-01-01

It is interesting to imagine what would happen when a mixture of soft-boiled eggs and stones is deformed together. A foil made of pure Ti is stronger than that made of Cu. When a composite Cu/Ti foil deforms, the harder Ti will penetrate into the softer Cu in the convex shapes according to previously reported results. In this paper, we describe the fabrication of multilayer Cu/Ti foils by the roll bonding technique and report our observations. The experimental results lead us to propose a new deformation mechanism for a hard metal surrounded by a soft metal during rolling of a laminated foil, particularly when the thickness of hard metal foil (Ti, 25 μm) is much less than that of the soft metal foil (Cu, 300 μm). Transmission Electron Microscope (TEM) imaging results show that the hard metal penetrates into the soft metal in the form of concave protrusions. Finite element simulations of the rolling process of a Cu/Ti/Cu composite foil are described. Finally, we focus on an analysis of the deformation mechanism of Ti foils and its effects on grain refinement, and propose a grain refinement mechanism from the inside to the outside of the laminates during rolling. PMID:24853192

Investigation of Deformation Dynamics in a Wrought Magnesium Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wei; Qiao, Hua; An, Ke

2014-11-01

In the present research, the deformation dynamics and the effect of the deformation history on plastic deformation in a wrought magnesium alloy have been studied using real-time in-situ neutron diffraction measurements under a continuous loading condition and elastic-viscoplastic self-consistent (EVPSC) polycrystal modeling. The experimental results reveal that the pre-deformation delayed the activation of the tensile twinning during subsequent compression, mainly resulting from the residual strain. No apparent detwinning occurred during unloading and even in the elastic region during reverse loading. It is believed that the grain rotation played an important role in the elastic region during reverse loading. The EVPSCmore » model, which has been recently updated by implementing the twinning and detwinning model, was employed to characterize the deformation mechanism during the strain-path changes. The simulation result predicts well the experimental observation from the real-time in-situ neutron diffraction measurements. The present study provides a deep insight of the nature of deformation mechanisms in a hexagonal close-packed structured polycrystalline wrought magnesium alloy, which might lead to a new era of deformation-mechanism research.« less

Inference of postseismic deformation mechanisms of the 1923 Kanto earthquake

USGS Publications Warehouse

Pollitz, F.F.; Nyst, M.; Nishimura, T.; Thatcher, W.

2006-01-01

Coseismic slip associated with the M7.9, 1923 Kanto earthquake is fairly well understood, involving slip of up to 8 m along the Philippine Sea-Honshu interplate boundary under Sagami Bay and its onland extension. Postseismic deformation after the 1923 earthquake, however, is relatively poorly understood. We revisit the available deformation data in order to constrain possible mechanisms of postseismic deformation and to examine the consequences for associated stress changes in the surrounding crust. Data from two leveling lines and one tide gage station over the first 7-8 years postseismic period are of much greater amplitude than the corresponding expected interseismic deformation during the same period, making these data suitable for isolating the signal from postseismic deformation. We consider both viscoelastic models of asthenosphere relaxation and afterslip models. A distributed coseismic slip model presented by Pollitz et al. (2005), combined with prescribed parameters of a viscoelastic Earth model, yields predicted postseismic deformation that agrees with observed deformation on mainland Honshu from Tokyo to the Izu peninsula. Elsewhere (southern Miura peninsula; Boso peninsula), the considered viscoelastic models fail to predict observed deformation, and a model of ???1 in shallow afterslip in the offshore region south of the Boso peninsula, with equivalent moment magnitude Mw = 7.0, adequately accounts for the observed deformation. Using the distributed coseismic slip model, layered viscoelastic structure, and a model of interseismic strain accumulation, we evaluate the post-1923 stress evolution, including both the coseismic and accumulated postseismic stress changes and those stresses contributed by interseismic loading. We find that if account is made for the varying tectonic regime in the region, the occurrence of both immediate (first month) post-1923 crustal aftershocks as well as recent regional crustal seismicity is consistent with the predicted

Mechanics of adsorption-deformation coupling in porous media

NASA Astrophysics Data System (ADS)

Zhang, Yida

2018-05-01

This work extends Coussy's macroscale theory for porous materials interacting with adsorptive fluid mixtures. The solid-fluid interface is treated as an independent phase that obeys its own mass, momentum and energy balance laws. As a result, a surface strain energy term appears in the free energy balance equation of the solid phase, which further introduces the so-called adsorption stress in the constitutive equations of the porous skeleton. This establishes a fundamental link between the adsorption characteristics of the solid-fluid interface and the mechanical response of the porous media. The thermodynamic framework is quite general in that it recovers the coupled conduction laws, Gibbs isotherm and the Shuttleworth's equation for surface stress, and imposes no constraints on the magnitude of deformation and the functional form of the adsorption isotherms. A rich variety of coupling between adsorption and deformation is recovered as a result of combining different poroelastic models (isotropic vs. anisotropic, linear vs. nonlinear) and adsorption models (unary vs. mixture adsorption, uncoupled vs. stretch-dependent adsorption). These predictions are discussed against the backdrop of recent experimental data on coal swelling subjected to CO2 and CO2sbnd CH4 injections, showing the capability and versatility of the theory in capturing adsorption-induced deformation of porous materials.

Crustal deformation mechanism in southeastern Tibetan Plateau: Insights from numerical modeling

NASA Astrophysics Data System (ADS)

Li, Y.; Liu, S.; Chen, L.

2017-12-01

The Indo-Asian collision developed the complicated crustal deformation around the southeastern Tibetan plateau. Numerous models have proposed to explain the crustal deformation, but the mechanism remains controversial, especially the increasing multi-geophysics data, which demonstrate the existence of lower velocity, lower resistivity and high conductivity, implying that lower crustal flow is responsible for the crustal deformation, arguing for the lower crust flow model. To address the relations between the crust flow and the surface deformation, we employ a three-dimensional viscoelastic finite model to investigate the possible influence on the surface deformation, and discuss the stress field distribution under the model. Our preliminary results suggest that lower crustal flow plays an important role in crustal deformation in southeastern Tibetan plateau. The best fitting is achieved when the flow velocity of the lower crust is approximately 10-11 mm/a faster than that of the upper crust. Crustal rheological properties affect regional crustal deformation, when the viscosity of the middle and lower crust in the South China block reaches 1022 and 1023 Pa.s, respectively; the predicted match observations well, especially for the magnitude within the South China block. The maximum principal stress field exhibits clear zoning, gradually shifting from an approximately east-west orientation in the northern Bayan Har block to southeast in the South China block, southwest in the western Yunnan block, and a radially divergent distribution in the Middle Yunnan and Southern Yunnan blocks.

The mechanics of solids in the plastically-deformable state

NASA Technical Reports Server (NTRS)

Mises, R. V.

1986-01-01

The mechanics of continua, which is based on the general stress model of Cauchy, up to the present has almost exclusively been applied to liquid and solid elastic bodies. Saint-Venant has developed a theory for the plastic or remaining form changes of solids, but it does not give the required number of equations for determining motion. A complete set of equations of motion for plastic deformable bodies is derived. This is done within the framework of Cauch mechanics. And it is supported by certain experimental facts which characterize the range of applications.

The molten globule state is unusually deformable under mechanical force

PubMed Central

Elms, Phillip J.; Chodera, John D.; Bustamante, Carlos; Marqusee, Susan

2012-01-01

Recently, the role of force in cellular processes has become more evident, and now with advances in force spectroscopy, the response of proteins to force can be directly studied. Such studies have found that native proteins are brittle, and thus not very deformable. Here, we examine the mechanical properties of a class of intermediates referred to as the molten globule state. Using optical trap force spectroscopy, we investigated the response to force of the native and molten globule states of apomyoglobin along different pulling axes. Unlike natively folded proteins, the molten globule state of apomyoglobin is compliant (large distance to the transition state); this large compliance means that the molten globule is more deformable and the unfolding rate is more sensitive to force (the application of force or tension will have a more dramatic effect on the unfolding rate). Our studies suggest that these are general properties of molten globules and could have important implications for mechanical processes in the cell. PMID:22355138

Diffusive, Displacive Deformations and Local Phase Transformation Govern the Mechanics of Layered Crystals: The Case Study of Tobermorite.

PubMed

Tao, Lei; Shahsavari, Rouzbeh

2017-07-19

Understanding the deformation mechanisms underlying the mechanical behavior of materials is the key to fundamental and engineering advances in materials' performance. Herein, we focus on crystalline calcium-silicate-hydrates (C-S-H) as a model system with applications in cementitious materials, bone-tissue engineering, drug delivery and refractory materials, and use molecular dynamics simulation to investigate its loading geometry dependent mechanical properties. By comparing various conventional (e.g. shear, compression and tension) and nano-indentation loading geometries, our findings demonstrate that the former loading leads to size-independent mechanical properties while the latter results in size-dependent mechanical properties at the nanometer scales. We found three key mechanisms govern the deformation and thus mechanics of the layered C-S-H: diffusive-controlled and displacive-controlled deformation mechanisms, and strain gradient with local phase transformations. Together, these elaborately classified mechanisms provide deep fundamental understanding and new insights on the relationship between the macro-scale mechanical properties and underlying molecular deformations, providing new opportunities to control and tune the mechanics of layered crystals and other complex materials such as glassy C-S-H, natural composite structures, and manmade laminated structures.

Simulation study of the effect of strain rate on the mechanical properties and tensile deformation of gold nanowire

NASA Astrophysics Data System (ADS)

Shi, Guo-Jie; Wang, Jin-Guo; Hou, Zhao-Yang; Wang, Zhen; Liu, Rang-Su

2017-09-01

The mechanical properties and deformation mechanisms of Au nanowire during the tensile processes at different strain rates are revealed by the molecular dynamics method. It is found that the Au nanowire displays three distinct types of mechanical behaviors when tensioning at low, medium and high strain rates, respectively. At the low strain rate, the stress-strain curve displays a periodic zigzag increase-decrease feature, and the plastic deformation is resulted from the slide of dislocation. The dislocations nucleate, propagate, and finally annihilate in every decreasing stages of stress, and the nanowire always can recover to FCC-ordered structure. At the medium strain rate, the stress-strain curve gently decreases during the plastic process, and the deformation is contributed from sliding and twinning. The dislocations formed in the yield stage do not fully propagate and further escape from the nanowire. At the high strain rate, the stress-strain curve wave-like oscillates during the plastic process, and the deformation is resulted from amorphization. The FCC atoms quickly transform into disordered amorphous structure in the yield stage. The relative magnitude between the loading velocity of strain and the propagation velocity of phonons determines the different deformation mechanisms. The mechanical behavior of Au nanowire is similar to Ni, Cu and Pt nanowires, but their deformation mechanisms are not completely identical with each other.

Deformation Mechanism of the Northern Tibetan Plateau as Revealed by Magnetotelluric Data

NASA Astrophysics Data System (ADS)

Zhang, Letian; Wei, Wenbo; Jin, Sheng; Ye, Gaofeng; Xie, Chengliang

2017-04-01

As a unique geologic unit on the northern margin of the Tibetan Plateau, the Qaidam Basin plays a significant role in constraining the vertical uplift and horizontal expansion of the northern and northeastern Tibetan Plateau. However, due to its complex evolution history and difficult logistic condition, deformation mechanism of the lithosphere beneath the Qaidam Basin is still highly debated. To better understand the lithospheric electrical structure and deformation mechanism of the Qaidam Basin, A 250 km long, NE-SW directed Magnetotelluric (MT) profile was finished in the northern portion of the Basin, which is roughly perpendicular to the thrust fault systems on the western and eastern margins of the Basin, as well as anticlinorium systems within the Basin. The profile consists of 20 broad-band MT stations and 5 long-period MT stations. Original time series data is processed with regular robust routines. Dimensionality and regional strike direction are determined for the dataset through data analysis. Based on the analysis results, 2D inversions were performed to produce a preferred model of the lithospheric electrical structure beneath the northern Qaidam Basin. Uncertainty analysis of the 2D inversion model was also conducted based on a data resampling approach. The outcome 2D electrical model was further used to estimate the distribution of temperature and melt fraction in the upper mantle based on laboratory-determined relationships between the electrical conductivity and temperature of nominally anhydrous minerals and basaltic melt by using the mixing law of Hashin-Shtrikman's bounds. All these results suggest that: (1) the crust-mantle boundary is imaged as a conductive layer beneath the western Qaidam Basin, with its temperature estimated to be 1200-1300 °C and melt fraction 5-8%, indicating decoupling deformation of the crust and upper mantle. (2) A large-scale east-dipping conductor is imaged beneath the eastern Qaidam Basin. This conductor extends

Deformation and failure mechanism of secondary cell wall in Spruce late wood

NASA Astrophysics Data System (ADS)

Adusumalli, Ramesh-Babu; Raghavan, Rejin; Ghisleni, Rudy; Zimmermann, Tanja; Michler, Johann

2010-08-01

The deformation and failure of the secondary cell wall of Spruce wood was studied by in-situ SEM compression of micropillars machined by the focused ion beam technique. The cell wall exhibited yield strength values of approximately 160 MPa and large scale plasticity. High resolution SEM imaging post compression revealed bulging of the pillars followed by shear failure. With additional aid of cross-sectional analysis of the micropillars post compression, a model for deformation and failure mechanism of the cell wall has been proposed. The cell wall consists of oriented cellulose microfibrils with high aspect ratio embedded in a hemicellulose-lignin matrix. The deformation of the secondary wall occurs by asymmetric out of plane bulging because of buckling of the microfibrils. Failure of the cell wall following the deformation occurs by the formation of a shear or kink band.

High-Temperature Deformation and Strengthening Mechanisms of Titanium Boride/nickel Aluminide Composites

NASA Astrophysics Data System (ADS)

Wang, Liqin

Intermetallic matrix composites, with ceramic particle reinforcements, are among the most important candidates for high-temperature structural applications. These composites, however, are not always stronger than their matrix materials at elevated temperatures. Some of the composites have much better high-temperature strength than their matrix materials, such as NiAl and FeAl, while others are just the opposite, e.g. TiAl, Ti_3Al, and Ni_3Al. The reasons for either the strengthening or the weakening observed in the discontinuous aluminide matrix composites are not obvious. The purpose of this research is to understand the mechanisms which caused the increase of the strength achieved by adding TiB_2 particulates to NiAl, and to recognize the fundamental principles of the deformation process in TiB_2/NiAl composites. In order to accomplish this objective, the mechanical properties and thermal activation parameters of the deformation process in TiB_2/NiAl composites have been systematically evaluated. The microstructures, dislocation structures and the interface structures of TiB _2/NiAl composites have been also thoroughly characterized before and after the deformation. Emphasis is placed on the relationship between the microstructures and mechanical properties of TiB_2/NiAl composites.

Experimental deformation of a mafic rock - interplay between fracturing, reaction and viscous deformation

NASA Astrophysics Data System (ADS)

Marti, Sina; Stünitz, Holger; Heilbronner, Renée; Plümper, Oliver; Drury, Martyn

2016-04-01

Deformation experiments were performed on natural Maryland Diabase (˜ 55% Plg, 42% Px, 3% accessories, 0.18 wt.-% H2O added) in a Griggs-type deformation apparatus in order to explore the brittle-viscous transition and the interplay between deformation and mineral reactions. Shear experiments at strain rates of ˜ 2e-5 /s are performed, at T=600, 700 and 800°C and confining pressures Pc=1.0 and 1.5 GPa. Deformation localizes in all experiments. Below 700°C, the microstructure is dominated by brittle deformation with a foliation formed by cataclastic flow and high strain accommodated along 3-5 major ultracataclasite shear bands. At 700°C, the bulk of the material still exhibits abundant microfractures, however, deformation localizes into an anastomosing network of shear bands (SB) formed from a fine-grained (<< 1 μm) mixture of newly formed Plg and Amph. These reaction products occur almost exclusively along syn-kinematic structures such as fractures and SB. Experiments at 800°C show extensive mineral reactions, with the main reaction products Amph+Plg (+Zo). Deformation is localized in broad C' and C SB formed by a fine-grained (0.1 - 0.8 μm) mixture of Plg+Amph (+Zo). The onset of mineral reactions in the 700°C experiments shows that reaction kinetics and diffusional mass transport are fast enough to keep up with the short experimental timescales. While in the 700°C experiments brittle processes kinematically contribute to deformation, fracturing is largely absent at 800°C. Diffusive mass transfer dominates. The very small grain size within SB favours a grain size sensitive deformation mechanism. Due to the presence of water (and relatively high supported stresses), dissolution-precipitation creep is interpreted to be the dominant strain accommodating mechanism. From the change of Amph coronas around Px clasts with strain, we can determine that Amph is re-dissolved at high stress sites while growing in low stress sites, showing the ability of Amph to

Deformation and failure mechanisms of graphite/epoxy composites under static loading

NASA Technical Reports Server (NTRS)

Clements, L. L.

1981-01-01

The mechanisms of deformation and failure of graphite epoxy composites under static loading were clarified. The influence of moisture and temperature upon these mechanisms were also investigated. Because the longitudinal tensile properties are the most critical to the performance of the composite, these properties were investigated in detail. Both ultimate and elastic mechanical properties were investigated, but the study of mechanisms emphasized those leading to failure of the composite. The graphite epoxy composite selected for study was the system being used in several NASA sponsored flight test programs.

A Review of Texture Evolution Mechanisms During Deformation by Rolling in Aluminum Alloys

NASA Astrophysics Data System (ADS)

Li, Shasha; Zhao, Qi; Liu, Zhiyi; Li, Fudong

2018-06-01

The current understanding of texture evolution during deformation by rolling in aluminum alloys was summarized. This included understanding the evolution mechanisms and several key factors of initial texture, microstructure, alloy composition, deformation temperature, stress-strain condition, and rolling geometry. Related models on predicting texture evolution during rolling were also discussed. Finally, for this research field, the recommendations for controlling the formation of rolling textures were proposed.

The deformation and acoustic emission of aluminum-magnesium alloy under non-isothermal thermo-mechanical loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makarov, S. V.; Plotnikov, V. A., E-mail: plotnikov@phys.asu.ru; Lysikov, M. V.

2015-10-27

The following study investigates the deformation behavior and acoustic emission in aluminum-magnesium alloy under conditions of non-isothermal thermo-mechanical loading. The accumulation of deformation in the alloy, in conditions of change from room temperature to 500°C, occurs in two temperature intervals (I, II), characterized by different rates of deformation. The rate of deformation accumulation is correlated with acoustic emission. With load increasing in cycles from 40 to 200 MPa, the value of the boundary temperature (T{sub b}) between intervals I and II changes non-monotonically. In cycles with load up to 90 MPa, the T{sub b} value increases, while an increase up to 200 MPamore » makes T{sub b} shift toward lower temperatures. This suggests that the shift of boundaries in the region of low temperatures and the appearance of high-amplitude pulses of acoustic emission characterize the decrease of the magnitude of thermal fluctuations with increasing mechanical load, leading to the rupture of interatomic bonds in an elementary deformation act.« less

Deformation mechanisms of idealised cermets under multi-axial loading

NASA Astrophysics Data System (ADS)

Bele, E.; Goel, A.; Pickering, E. G.; Borstnar, G.; Katsamenis, O. L.; Pierron, F.; Danas, K.; Deshpande, V. S.

2017-05-01

The response of idealised cermets comprising approximately 60% by volume steel spheres in a Sn/Pb solder matrix is investigated under a range of axisymmetric compressive stress states. Digital volume correlation (DVC) anal`ysis of X-ray micro-computed tomography scans (μ-CT), and the measured macroscopic stress-strain curves of the specimens revealed two deformation mechanisms. At low triaxialities the deformation is granular in nature, with dilation occurring within shear bands. Under higher imposed hydrostatic pressures, the deformation mechanism transitions to a more homogeneous incompressible mode. However, DVC analyses revealed that under all triaxialities there are regions with local dilatory and compaction responses, with the magnitude of dilation and the number of zones wherein dilation occurs decreasing with increasing triaxiality. Two numerical models are presented in order to clarify these mechanisms: (i) a periodic unit cell model comprising nearly rigid spherical particles in a porous metal matrix and (ii) a discrete element model comprising a large random aggregate of spheres connected by non-linear normal and tangential "springs". The periodic unit cell model captured the measured stress-strain response with reasonable accuracy but under-predicted the observed dilation at the lower triaxialities, because the kinematic constraints imposed by the skeleton of rigid particles were not accurately accounted for in this model. By contrast, the discrete element model captured the kinematics and predicted both the overall levels of dilation and the simultaneous presence of both local compaction and dilatory regions with the specimens. However, the levels of dilation in this model are dependent on the assumed contact law between the spheres. Moreover, since the matrix is not explicitly included in the analysis, this model cannot be used to predict the stress-strain responses. These analyses have revealed that the complete constitutive response of cermets

Significance of grain sliding mechanisms for ductile deformation of rocks

NASA Astrophysics Data System (ADS)

Dimanov, A.; Bourcier, M.; Gaye, A.; Héripré, E.; Bornert, M.; Raphanel, J.; Ludwig, W.

2013-12-01

Ductile shear zones at depth present polyphase and heterogeneous rocks and multi-scale strain localization patterns. Most strain concentrates in ultramylonitic layers, which exhibit microstructural signatures of several concomitant deformation mechanisms. The latter are either active in volume (dislocation creep), or in the vicinity and along interfaces (grain sliding and solution mass transfer). Because their chronology of appearance and interactions are unclear, inference of the overall rheology seems illusory. We have therefore characterized over a decade the rheology of synthetic lower crustal materials with different compositions and fluid contents, and for various microstructures. Non-Newtonian flow clearly related to dominant dislocation creep. Conversely, Newtonian behavior involved grain sliding mechanisms, but crystal plasticity could be identified as well. In order to clarify the respective roles of these mechanisms we underwent a multi-scale investigation of the ductile deformation of rock analog synthetic halite with controlled microstructures. The mechanical tests were combined with in-situ optical microscopy, scanning electron microscopy and X ray computed tomography, allowing for digital image correlation (DIC) techniques and retrieval of full strain field. Crystal plasticity dominated, as evidenced by physical slip lines and DIC computed slip bands. Crystal orientation mapping allowed to identify strongly active easy glide {110} <110> systems. But, all other slip systems were observed as well, and especially near interfaces, where their activity is necessary to accommodate for the plastic strain incompatibilities between neighboring grains. We also evidenced grain boundary sliding (GBS), which clearly occurred as a secondary, but necessary, accommodation mechanism. The DIC technique allowed the quantification of the relative contribution of each mechanism. The amount of GBS clearly increased with decreasing grain size. Finite element (FE) modeling

Cell-wall recovery after irreversible deformation of wood

NASA Astrophysics Data System (ADS)

Keckes, Jozef; Burgert, Ingo; Frühmann, Klaus; Müller, Martin; Kölln, Klaas; Hamilton, Myles; Burghammer, Manfred; Roth, Stephan V.; Stanzl-Tschegg, Stefanie; Fratzl, Peter

2003-12-01

The remarkable mechanical properties of biological materials reside in their complex hierarchical architecture and in specific molecular mechanistic phenomena. The fundamental importance of molecular interactions and bond recovery has been suggested by studies on deformation and fracture of bone and nacre. Like these mineral-based materials, wood also represents a complex nanocomposite with excellent mechanical performance, despite the fact that it is mainly based on polymers. In wood, however, the mechanistic contribution of processes in the cell wall is not fully understood. Here we have combined tensile tests on individual wood cells and on wood foils with simultaneous synchrotron X-ray diffraction analysis in order to separate deformation mechanisms inside the cell wall from those mediated by cell-cell interactions. We show that tensile deformation beyond the yield point does not deteriorate the stiffness of either individual cells or foils. This indicates that there is a dominant recovery mechanism that re-forms the amorphous matrix between the cellulose microfibrils within the cell wall, maintaining its mechanical properties. This stick-slip mechanism, rather like Velcro operating at the nanometre level, provides a 'plastic response' similar to that effected by moving dislocations in metals. We suggest that the molecular recovery mechanism in the cell matrix is a universal phenomenon dominating the tensile deformation of different wood tissue types.

Mechanical Deformation Behavior of Sn-Ag-Cu Solders with Minor Addition of 0.05 wt.% Ni

NASA Astrophysics Data System (ADS)

Hammad, A. E.; El-Taher, A. M.

2014-11-01

The aim of the present work is to develop a comparative evaluation of the microstructural and mechanical deformation behavior of Sn-Ag-Cu (SAC) solders with the minor addition of 0.05 wt.% Ni. Test results showed that, by adding 0.05Ni element into SAC solders, generated mainly small rod-shaped (Cu,Ni)6Sn5 intermetallic compounds (IMCs) inside the β-Sn phase. Moreover, increasing the Ag content and adding Ni could result in the change of the shape and size of the IMC precipitate. Hence, a significant improvement is observed in the mechanical properties of SAC solders with increasing Ag content and Ni addition. On the other hand, the tensile results of Ni-doped SAC solders showed that both the yield stress and ultimate tensile strengths decrease with increasing temperature and with decreasing strain rate. This behavior was attributed to the competing effects of work hardening and dynamic recovery processes. The Sn-2.0Ag-0.5Cu-0.05Ni solder displayed the highest mechanical properties due to the formation of hard (Cu,Ni)6Sn5 IMCs. Based on the obtained stress exponents and activation energies, it is suggested that the dominant deformation mechanism in SAC (205)-, SAC (0505)- and SAC (0505)-0.05Ni solders is pipe diffusion, and lattice self-diffusion in SAC (205)-0.05Ni solder. In view of these results, the Sn-2.0Ag-0.5Cu-0.05Ni alloy is a more reliable solder alloy with improved properties compared with other solder alloys tested in the present work.

Mechanical instability and percolation of deformable particles through porous networks

NASA Astrophysics Data System (ADS)

Benet, Eduard; Lostec, Guillaume; Pellegrino, John; Vernerey, Franck

2018-04-01

The transport of micron-sized particles such as bacteria, cells, or synthetic lipid vesicles through porous spaces is a process relevant to drug delivery, separation systems, or sensors, to cite a few examples. Often, the motion of these particles depends on their ability to squeeze through small constrictions, making their capacity to deform an important factor for their permeation. However, it is still unclear how the mechanical behavior of these particles affects collective transport through porous networks. To address this issue, we present a method to reconcile the pore-scale mechanics of the particles with the Darcy scale to understand the motion of a deformable particle through a porous network. We first show that particle transport is governed by a mechanical instability occurring at the pore scale, which leads to a binary permeation response on each pore. Then, using the principles of directed bond percolation, we are able to link this microscopic behavior to the probability of permeating through a random porous network. We show that this instability, together with network uniformity, are key to understanding the nonlinear permeation of particles at a given pressure gradient. The results are then summarized by a phase diagram that predicts three distinct permeation regimes based on particle properties and the randomness of the pore network.

[Application of tibial mechanical axis locator in tibial extra-articular deformity in total knee arthroplasty].

PubMed

Li, Guoliang; Han, Guangpu; Zhang, Jinxiu; Ma, Shiqiang; Guo, Donghui; Yuan, Fulu; Qi, Bingbing; Shen, Runbin

2013-07-01

To explore the application value of self-made tibial mechanical axis locator in tibial extra-articular deformity in total knee arthroplasty (TKA) for improving the lower extremity force line. Between January and August 2012, 13 cases (21 knees) of osteoarthritis with tibial extra-articular deformity were treated, including 5 males (8 knees) and 8 females (13 knees) with an average age of 66.5 years (range, 58-78 years). The disease duration was 2-5 years (mean, 3.5 years). The knee society score (KSS) was 45.5 +/- 15.5. Extra-articular deformities included 1 case of knee valgus (2 knees) and 12 cases of knee varus (19 knees). Preoperative full-length X-ray films of lower extremities showed 10-21 degrees valgus or varus deformity of tibial extra joint. Self-made tibial mechanical axis locator was used to determine and mark coronal tibial mechanical axis under X-ray before TKA, and then osteotomy was performed with extramedullary positioning device according to the mechanical axis marker.' All incisions healed by first intention, without related complications of infection and joint instability. All patients were followed up 5-12 months (mean, 8.3 months). The X-ray examination showed < 2 degrees knee deviation angle in the others except 1 case of 2.9 degrees knee deviation angle at 3 days after operation, and the accurate rate was 95.2%. No loosening or instability of prosthesis occurred during follow-up. KSS score was 85.5 +/- 15.0 at last follow-up, showing significant difference when compared with preoperative score (t=12.82, P=0.00). The seft-made tibial mechanical axis locator can improve the accurate rate of the lower extremity force line in TKA for tibia extra-articular deformity.

The effect of hydrogenation on strain hardening and deformation mechanisms in <113> single crystals of Hadfield steel

NASA Astrophysics Data System (ADS)

Astafurova, Elena; Maier, Galina; Melnikov, Eugene; Koshovkina, Vera; Moskvina, Valentina; Smirnov, Alexander; Bataev, Vladimir

2015-10-01

The effect of hydrogenation on the strain-hardening behavior and the deformation mechanisms of <113>-oriented single crystals of Hadfield steel was investigated under tension at room temperature. The stages of plastic flow and deformation mechanisms for hydrogen-charged specimens are similar to one in hydrogen-free state: slip → slip + single twinning → slip + multiple twinning. Hydrogen alloying favors to mechanical twinning, micro- and macrolocalization of plastic flow.

Deformation mechanism of CrN/nitriding coated steel in wear and nano-scratch experiments under heavy loading conditions

NASA Astrophysics Data System (ADS)

Wang, Yongguang; Chen, Yao; Zhao, Dong; Lu, Xiaolong; Liu, Weiwei; Qi, Fei; Chen, Yang

2018-07-01

CrN coatings are widely used to protect metals from wear in industrial engineering. However, fundamental deformation mechanism of these coatings under heavy loading conditions remains elusive. In this paper, multilayered hard coatings with a CrN matrix and a supporting layer were developed by means of the hybrid deposition process combined with PVD and ionicnitriding. The tribological behavior of coatings with and without ionicnitriding were investigated by a pin-on-disk arrangement under heavy loading conditions. In addition, the deformation mechanism of the multilayered hard coatings was studied by nano-scratch experiment with ramp load model, which has not been discussed previously. It was found that the deformation process of coatings could be divided into three regimes based on the evolution of frictional coefficient. The insertion of nitriding films leads to the further increase in frictional resistance owing to the elastic-plastic deformation. The results and analysis reveal some insights into the coating design for multilayered hard coatings with the consideration of deformation mechanisms.

A microstructural study of fault rocks from the SAFOD: Implications for the deformation mechanisms and strength of the creeping segment of the San Andreas Fault

NASA Astrophysics Data System (ADS)

Hadizadeh, Jafar; Mittempergher, Silvia; Gratier, Jean-Pierre; Renard, Francois; Di Toro, Giulio; Richard, Julie; Babaie, Hassan A.

2012-09-01

The San Andreas Fault zone in central California accommodates tectonic strain by stable slip and microseismic activity. We study microstructural controls of strength and deformation in the fault using core samples provided by the San Andreas Fault Observatory at Depth (SAFOD) including gouge corresponding to presently active shearing intervals in the main borehole. The methods of study include high-resolution optical and electron microscopy, X-ray fluorescence mapping, X-ray powder diffraction, energy dispersive X-ray spectroscopy, white light interferometry, and image processing. The fault zone at the SAFOD site consists of a strongly deformed and foliated core zone that includes 2-3 m thick active shear zones, surrounded by less deformed rocks. Results suggest deformation and foliation of the core zone outside the active shear zones by alternating cataclasis and pressure solution mechanisms. The active shear zones, considered zones of large-scale shear localization, appear to be associated with an abundance of weak phases including smectite clays, serpentinite alteration products, and amorphous material. We suggest that deformation along the active shear zones is by a granular-type flow mechanism that involves frictional sliding of microlithons along phyllosilicate-rich Riedel shear surfaces as well as stress-driven diffusive mass transfer. The microstructural data may be interpreted to suggest that deformation in the active shear zones is strongly displacement-weakening. The fault creeps because the velocity strengthening weak gouge in the active shear zones is being sheared without strong restrengthening mechanisms such as cementation or fracture sealing. Possible mechanisms for the observed microseismicity in the creeping segment of the SAF include local high fluid pressure build-ups, hard asperity development by fracture-and-seal cycles, and stress build-up due to slip zone undulations.

Understanding deformation mechanisms during powder compaction using principal component analysis of compression data.

PubMed

Roopwani, Rahul; Buckner, Ira S

2011-10-14

Principal component analysis (PCA) was applied to pharmaceutical powder compaction. A solid fraction parameter (SF(c/d)) and a mechanical work parameter (W(c/d)) representing irreversible compression behavior were determined as functions of applied load. Multivariate analysis of the compression data was carried out using PCA. The first principal component (PC1) showed loadings for the solid fraction and work values that agreed with changes in the relative significance of plastic deformation to consolidation at different pressures. The PC1 scores showed the same rank order as the relative plasticity ranking derived from the literature for common pharmaceutical materials. The utility of PC1 in understanding deformation was extended to binary mixtures using a subset of the original materials. Combinations of brittle and plastic materials were characterized using the PCA method. The relationships between PC1 scores and the weight fractions of the mixtures were typically linear showing ideal mixing in their deformation behaviors. The mixture consisting of two plastic materials was the only combination to show a consistent positive deviation from ideality. The application of PCA to solid fraction and mechanical work data appears to be an effective means of predicting deformation behavior during compaction of simple powder mixtures. Copyright © 2011 Elsevier B.V. All rights reserved.

Implications of Microstructural Studies of the SAFOD Gouge for the Strength and Deformation Mechanisms in the Creeping Segment of the San Andreas Fault

NASA Astrophysics Data System (ADS)

Hadizadeh, J.; Gratier, J. L.; Mittempergher, S.; Renard, F.; Richard, J.; di Toro, G.; Babaie, H. A.

2010-12-01

The San Andreas Fault zone (SAF) in the vicinity of the San Andreas Fault Observatory at Depth (SAFOD)in central California is characterized by an average 21 mm/year aseismic creep and strain release through repeating M<3 earthquakes. Seismic inversion studies indicate that the ruptures occur on clusters of stationary patches making up 1% or less of the total fault surface area. The existence of these so-called asperity patches, although not critical in determining the fault strength, suggests interaction of different deformation mechanisms. What are the deformation mechanisms, and how do the mechanisms couple and factor into the current strength models for the SAF? The SAFOD provides core samples and geophysical data including cores from two shear zones where the main borehole casing is deforming. The studies so far show a weak fault zone with about 200m of low-permeability damage zone without anomalous temperature or high fluid pressure (Zoback et al. EOS 2010). To answer the above questions, we studied core samples and thin sections ranging in measured depths (MD) from 3059m to 3991m including gouge from borehole casing deformation zones. The methods of study included high resolution scanning and transmission electron microscopy, cathodoluminescence imaging, X-ray fluorescence mapping, and energy dispersive X-ray spectroscopy. The microstructural and analytical data suggest that deformation is by a coupling of cataclastic flow and pressure solution accompanied by widespread alteration of feldspar to clay minerals and other neomineralizations. The clay contents of the gouge and streaks of serpentinite are not uniformly distributed, but weakness of the creeping segment is likely to be due to intrinsically low frictional strength of the fault material. This conclusion, which is based on the overall ratio of clay/non-clay constituents and the presence of talc in the actively deforming zones, is consistent with the 0.3-0.45 coefficient of friction for the drill

Puncture mechanics of soft elastomeric membrane with large deformation by rigid cylindrical indenter

NASA Astrophysics Data System (ADS)

Liu, Junjie; Chen, Zhe; Liang, Xueya; Huang, Xiaoqiang; Mao, Guoyong; Hong, Wei; Yu, Honghui; Qu, Shaoxing

2018-03-01

Soft elastomeric membrane structures are widely used and commonly found in engineering and biological applications. Puncture is one of the primary failure modes of soft elastomeric membrane at large deformation when indented by rigid objects. In order to investigate the puncture failure mechanism of soft elastomeric membrane with large deformation, we study the deformation and puncture failure of silicone rubber membrane that results from the continuous axisymmetric indentation by cylindrical steel indenters experimentally and analytically. In the experiment, effects of indenter size and the friction between the indenter and the membrane on the deformation and puncture failure of the membrane are investigated. In the analytical study, a model within the framework of nonlinear field theory is developed to describe the large local deformation around the punctured area, as well as to predict the puncture failure of the membrane. The deformed membrane is divided into three parts and the friction contact between the membrane and indenter is modeled by Coulomb friction law. The first invariant of the right Cauchy-Green deformation tensor I1 is adopted to predict the puncture failure of the membrane. The experimental and analytical results agree well. This work provides a guideline in designing reliable soft devices featured with membrane structures, which are present in a wide variety of applications.

The effect of deformation temperature on the microstructure evolution of Inconel 625 superalloy

NASA Astrophysics Data System (ADS)

Guo, Qingmiao; Li, Defu; Guo, Shengli; Peng, Haijian; Hu, Jie

2011-07-01

Hot compression tests of Inconel 625 superalloy were conducted using a Gleeble-1500 simulator between 900 °C and 1200 °C with different true strains and a strain rate of 0.1 s -1. Scanning electron microscope (SEM) and electron backscatter diffraction technique (EBSD) were employed to investigate the effect of deformation temperature on the microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX). It is found that the relationship between the DRX grain size and the peak stress can be expressed by a power law function. Significant influence of deformation temperatures on the nucleation mechanisms of DRX are observed at different deformation stages. At lower deformation temperatures, continuous dynamic recrystallization (CDRX) characterized by progressive subgrain rotation is considered as the main mechanism of DRX at the early deformation stage. However, discontinuous dynamic recrystallization (DDRX) with bulging of the original grain boundaries becomes the operating mechanism of DRX at the later deformation stage. At higher deformation temperatures, DDRX is the primary mechanism of DRX, while CDRX can only be considered as an assistant mechanism at the early deformation stage. Nucleation of DRX can also be activated by the twinning formation. With increasing the deformation temperature, the effect of DDRX accompanied with twinning formation grows stronger, while the effect of CDRX grows weaker. Meanwhile, the position of subgrain formation shifts gradually from the interior of original grains to the vicinity of the original boundaries.

Illustrating the Molecular Origin of Mechanical Stress in Ductile Deformation of Polymer Glasses.

PubMed

Li, Xiaoxiao; Liu, Jianning; Liu, Zhuonan; Tsige, Mesfin; Wang, Shi-Qing

2018-02-16

New experiments show that tensile stress vanishes shortly after preyield deformation of polymer glasses while tensile stress after postyield deformation stays high and relaxes on much longer time scales, thus hinting at a specific molecular origin of stress in ductile cold drawing: chain tension rather than intersegmental interactions. Molecular dynamics simulation based on a coarse-grained model for polystyrene confirms the conclusion that the chain network plays an essential role, causing the glassy state to yield and to respond with a high level of intrachain retractive stress. This identification sheds light on the future development regarding an improved theoretical account for molecular mechanics of polymer glasses and the molecular design of stronger polymeric materials to enhance their mechanical performance.

Illustrating the Molecular Origin of Mechanical Stress in Ductile Deformation of Polymer Glasses

NASA Astrophysics Data System (ADS)

Li, Xiaoxiao; Liu, Jianning; Liu, Zhuonan; Tsige, Mesfin; Wang, Shi-Qing

2018-02-01

New experiments show that tensile stress vanishes shortly after preyield deformation of polymer glasses while tensile stress after postyield deformation stays high and relaxes on much longer time scales, thus hinting at a specific molecular origin of stress in ductile cold drawing: chain tension rather than intersegmental interactions. Molecular dynamics simulation based on a coarse-grained model for polystyrene confirms the conclusion that the chain network plays an essential role, causing the glassy state to yield and to respond with a high level of intrachain retractive stress. This identification sheds light on the future development regarding an improved theoretical account for molecular mechanics of polymer glasses and the molecular design of stronger polymeric materials to enhance their mechanical performance.

Fine grained 304 ASS processed by a severe plastic deformation and subsequent annealing; microstructure and mechanical properties evaluation

NASA Astrophysics Data System (ADS)

Salout, Shima Ahmadzadeh; Shirazi, Hasan; Nili-Ahmadabadi, Mahmoud

2018-01-01

The current research is an attempt to study the effect of a novel severe plastic deformation technique so called "repetitive corrugation and straightening by rolling" (RCSR) and subsequent annealing on the microstructure and mechanical properties of AISI type 304 austenitic stainless steel. In this study, RCSR process was carried out at 200 °C on the 304 austenitic stainless steel (above Md30 temperature that is about 50 °C for this stainless steel) in order to avoid the formation of martensite phase when a high density of dislocations was introduced into the austenite phase and also high density of mechanical twins was induced in the deformed 304 austenitic stainless steel. Because of relationship between deformation temperature, stacking fault energy (SFE) and mechanisms of deformation. Thereafter subsequently, annealing treatment was applied into deformed structure in order to refine the microstructure of 304 stainless s teel. The specimens were examined by means of optical microscopy (OM), scanning electron microscopy (SEM), tensile and micro-hardness tests. The results indicate that by increasing the cycles of RCSR process (increasing applied strain), further mechanical twins are induced, the hardness and in particular, the yield stress of specimens have been increased.

Production, deformation and mechanical investigation of magnetic alginate capsules

NASA Astrophysics Data System (ADS)

Zwar, Elena; Kemna, Andre; Richter, Lena; Degen, Patrick; Rehage, Heinz

2018-02-01

In this article we investigated the deformation of alginate capsules in magnetic fields. The sensitivity to magnetic forces was realised by encapsulating an oil in water emulsion, where the oil droplets contained dispersed magnetic nanoparticles. We solved calcium ions in the aqueous emulsion phase, which act as crosslinking compounds for forming thin layers of alginate membranes. This encapsulating technique allows the production of flexible capsules with an emulsion as the capsule core. It is important to mention that the magnetic nanoparticles were stable and dispersed throughout the complete process, which is an important difference to most magnetic alginate-based materials. In a series of experiments, we used spinning drop techniques, capsule squeezing experiments and interfacial shear rheology in order to determine the surface Young moduli, the surface Poisson ratios and the surface shear moduli of the magnetically sensitive alginate capsules. In additional experiments, we analysed the capsule deformation in magnetic fields. In spinning drop and capsule squeezing experiments, water droplets were pressed out of the capsules at elevated values of the mechanical load. This phenomenon might be used for the mechanically triggered release of water-soluble ingredients. After drying the emulsion-filled capsules, we produced capsules, which only contained a homogeneous oil phase with stable suspended magnetic nanoparticles (organic ferrofluid). In the dried state, the thin alginate membranes of these particles were rather rigid. These dehydrated capsules could be stored at ambient conditions for several months without changing their properties. After exposure to water, the alginate membranes rehydrated and became flexible and deformable again. During this swelling process, water diffused back in the capsule. This long-term stability and rehydration offers a great spectrum of different applications as sensors, soft actuators, artificial muscles or drug delivery systems.

Atomic simulations of deformation mechanisms of crystalline Mg/amorphous Mg-Al nanocomposites

NASA Astrophysics Data System (ADS)

Song, H. Y.; Li, Y. L.

2015-09-01

The effects of amorphous boundary (AB) spacing on the deformation behavior of crystalline/amorphous (C/A) Mg/Mgsbnd Al nanocomposites under tensile load are investigated using molecular dynamics method. The results show that the plasticity of nano-polycrystal Mg can be enhanced with the introduction of C/A interfaces. For samples 5.2 nm in AB spacing and larger, the superior tensile ductility and nearly perfect plastic flow behavior occur during plastic deformation. The studies indicate that the cooperative interactions between crystalline and amorphous are the main reason for excellent ductility enhancements in C/A Mg/Mgsbnd Al nanocomposites.

Migmatites to mylonites - Crustal deformation mechanisms in the Western Gneiss Region, Norway

NASA Astrophysics Data System (ADS)

Lee, A. L.; Torvela, T.; Lloyd, G. E.; Walker, A.

2016-12-01

Strain and fluids localise into shear zones while crustal blocks remain comparatively dry, rigid and deform less. However when H2O is present in the crustal blocks they start to melt, deformation becomes more distributed and is no longer strongly localised into the weak shear zones. Using examples from the Western Gneiss Region (WGR), Norway, we show the deformation characteristics when mylonitic shear zones and migmatites coexist. The WGR is the lowest structural level of the Caledonian Orogeny, exposing Silurian to Devonian metamorphism and deformation of the Precambrian crust. WGR is predominantly composed of amphibolite-facies quartzofeldspathic gneiss that has undergone partial melting. This study focuses on the southwestern peninsula of the island of Gurskøy. Over a 1.2 kilometre section there is a diverse deformation sequence of migmatized gneiss, mylonitic shear zones, sillimanite bearing garnet-mica schists, augen gneiss and boudinaged amphibolite dykes resulting in a large competence differences between the lithologies over the area. The strongly deformed mylonitic shear zones extend from 5 to over 100 meters in width, but deformation is also high in the migmatitic layers as shown from S-C fabrics and isoclinal folding of leucratic and restitic layers. Microstructural evidence of dynamic recrystallization, symplectite textures and magmatic flow show deformation is widespread over the peninsula. Strain localisation, melting, and their interactions are shown by a combination of outcrop and quantitative modelling that uses field data, microstructural analysis, crystallographic preferred orientations and numerical Eshelby modelling. Detailed field mapping and microstructural analysis of samples from across the peninsula allows melt quantification and thus an understanding of strain mechanisms when melt is present. This area is important as it shows the heterogeneity of deformation within the partially melted lower crust on the sub-seismic scale.

Real-time deformations of organ based on structural mechanics for surgical simulators

NASA Astrophysics Data System (ADS)

Nakaguchi, Toshiya; Tagaya, Masashi; Tamura, Nobuhiko; Tsumura, Norimichi; Miyake, Yoichi

2006-03-01

This research proposes the deformation model of organs for the development of the medical training system using Virtual Reality (VR) technology. First, the proposed model calculates the strains of coordinate axis. Secondly, the deformation is obtained by mapping the coordinate of the object to the strained coordinate. We assume the beams in the coordinate space to calculate the strain of the coordinate axis. The forces acting on the object are converted to the forces applied to the beams. The bend and the twist of the beams are calculated based on the theory of structural mechanics. The bend is derived by the finite element method. We propose two deformation methods which differ in the position of the beams in the coordinate space. One method locates the beams along the three orthogonal axes (x, y, z). Another method locates the beam in the area where the deformation is large. In addition, the strain of the coordinate axis is attenuated in proportion to the distance from the point of action to consider the attenuation of the stress which is a viscoelastic feature of the organs. The proposed model needs less computational cost compared to the conventional deformation method since our model does not need to divide the object into the elasticity element. The proposed model was implemented in the laparoscopic surgery training system, and a real-time deformation can be realized.

Mechanisms of submicron inclusion re-equilibration during host mineral deformation

NASA Astrophysics Data System (ADS)

Griffiths, Thomas; Habler, Gerlinde; Abart, Rainer; Rhede, Dieter; Wirth, Richard

2014-05-01

data, and no subgrain boundaries. Secondly, garnet lattice rotation of up to 10° around rational garnet crystal axes is observed in connection with some already coarsened inclusions. Strain concentrations are widespread in some trails, but rare in others. A TEM foil transecting a garnet domain with concentrated lattice rotation in association with inclusions reveals well developed polygonal subgrain walls with few free dislocations. Where dislocation density is greatest, almost no <100nm inclusions are observed, whereas these are more abundant in unstrained garnet domains despite the foil being located entirely within the optically visible bleaching zone. Chlorite inclusions and formation of etch pits at dislocations at the garnet-chlorite interface demonstrate the presence of fluid along subgrain boundaries during this second bleaching process. In summary, brittle deformation in these garnets led to enhanced transport and inclusion re-equilibration by coarsening, forming inclusion trails. The precise mechanism allowing enhanced transport is still to be determined and may have involved fluid supply with or without pipe diffusion along introduced dislocations. Later ductile deformation via dislocations, concentrated at already coarsened inclusions and enhanced by fluid availability, further affected the nanoinclusion population. The inclusion trail microstructure records complex small-scale interaction between deformation and reaction, shedding light on the mechanisms by which re-equilibration and strain localisation can influence each other in deforming host-inclusion systems. Bestmann et al. (2008) Journal of Structural Geology 30: 777-790

Deformation and stabilisation mechanisms of slow rock slides in crystalline bedrock

NASA Astrophysics Data System (ADS)

Zangerl, C.; Prager, C.

2009-04-01

Deep-seated rock slides are slope instabilities which are characterised by deformation along one or several shear zones where most of the measured total slope displacement localizes. Generally, a high danger potential is given when rock slides fail in a rapid manner characterised by very high sliding velocities and/or when they develop into long run-out rock avalanches. However several field surveys and deformation monitoring data show that numerous deep-seated rock slides do not fail in a high velocity regime. In fact, many slides creep downwards at rates of some centimetres per year or even less and do not show any evidence for non-reversible acceleration in the past or in the future. Furthermore some of these slope instabilities are actually inactive (dormant) or have even reached a stabilised final state. Deformation monitoring on active rock slides show that acceleration phases characterised by velocities up to meters per day can occur. The trigger for these phases can be manifold and include heavy rainfall, snow melt, water level fluctuations of reservoirs at the slope foot, changes in the slope's equilibrium state due to antecedent slow creeping processes, changes in the material behaviour within the sliding zone, erosion along the foot of the slope, etc. Whereas the role of these triggers in promoting phases of acceleration are generally understood, the same can not be said regarding the kinematics and dynamic processes/mechanisms by which rock slide masses re-stabilise once the trigger impetus has been removed. In the context of this study the term "stabilisation" is used for rock slides which decelerate from high velocities to slow base activities or even stop moving after a certain amount of displacement. Given that reliable rock slide forecasts require the fundamental understanding of possible slope stabilisation mechanisms this study focuses on field-based and numerically obtained key-properties which influence the long-term slope deformation behaviour

Dislocation creep accommodated Grain Boundary Sliding: A high strain rate/low temperature deformation mechanism in calcite ultramylonites

NASA Astrophysics Data System (ADS)

Rogowitz, Anna; Grasemann, Bernhard

2014-05-01

Grain boundary sliding (GBS) is an important grain size sensitive deformation mechanism that is often associated with extreme strain localization and superplasticity. Another mechanism has to operate simultaneously to GBS in order to prevent overlaps and voids between sliding grains. One of the most common accommodating mechanisms is diffusional creep but, recently, dislocation creep has been reported to operate simultaneous to GBS. Due to the formation of a flanking structure in nearly pure calcite marble on Syros (Cyclades, Greece) at lower greenschist facies conditions, an extremely fine grained ultramylonite developed. The microstructure of the layer is characterized by (1) calcite grains with an average grain size of 3.6 µm (developed by low temperature/high strain rate grain boundary migration recrystallization, BLG), (2) grain boundary triple junctions with nearly 120° angles and (3) small cavities preferentially located at triple junctions and at grain boundaries in extension. These features suggest that the dominant deformation mechanism was GBS. In order to get more information on the accommodation mechanism detailed microstructural and textural analyses have been performed on a FEI Quanta 3D FEG instrument equipped with an EDAX Digiview IV EBSD camera. The misorientation distribution curves for correlated and uncorrelated grains follow almost perfect the calculated theoretical curve for a random distribution, which is typical for polycrystalline material deformed by GBS. However, the crystallographic preferred orientation indicates that dislocation creep might have operated simultaneously. We also report Zener-Stroh cracks resulting from dislocation pile up, indicating that dislocation movement was active. We, therefore, conclude that the dominant deformation mechanism was dislocation creep accommodated grain boundary sliding. This is consistent with the observed grain size range that plots at the field boundary between grain size insensitive and grain

A Computational Study of Plastic Deformation in AISI 304 Induced by Surface Mechanical Attrition Treatment

NASA Astrophysics Data System (ADS)

Zhang, X. C.; Lu, J.; Shi, S. Q.

2010-05-01

As a technique of grain refinement process by plastic deformation, surface mechanical attrition treatment (SMAT) has been developed to be one of the most effective ways to optimize the mechanical properties of various materials including pure metals and alloys. SMAT can significantly reduce grain size into nanometer regime in the surface layer of bulk materials, providing tremendous opportunities for improving physical, chemical and mechanical properties of the materials. In this work, a computational modeling of the surface mechanical attrition treatment (SMAT) process is presented, in which Johnson-Cook plasticity model and the finite element method were employed to study the high strain rate, elastic-plastic dynamic process of ball impact on a metallic target. AISI 304 steel with low stacking fault energy was chosen as the target material. First, a random impact model was used to analyze the statistic characteristics of ball impact, and then the plastic deformation behavior and residual stress distribution in AISI 304 stainless steel during SMAT were studied. The simulation results show that the compressive residual stress and vertical deformation of the surface structures were directly affected by ball impact frequency, incident impact angle and ball diameter used in SMAT process.

Mechanical Deformation of a Lithium-Metal Anode Due to a Very Stiff Separator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrese, A; Newman, J

2014-05-21

This work builds on the two-dimensional model presented by Ferrese et al. [J. Electrochem. Soc., 159, A1615 (2012)1, which captures the movement of lithium metal at the negative electrode during cycling in a Li-metal/LiCoO2 cell. In this paper, the separator is modeled as a dendrite-inhibiting polymer separator with an elastic modulus of 16 GPa. The separator resists the movement of lithium through the generation of stresses in the cell. These stresses affect the negative electrode through two mechanisms altering the thermodynamics of the negative electrode and deforming the negative electrode mechanically. From this analysis, we find that the dendrite-inhibiting separatormore » causes plastic and elastic deformation of the lithium at the negative electrode which flattens the electrode considerably when compared to the liquid-electrolyte case. This flattening of the negative electrode causes only very slight differences in the local state of charge in the positive electrode. When comparing the magnitude of the effects flattening the negative electrode, we find that the plastic deformation plays a much larger role than either the pressure-modified reaction kinetics or elastic deformation. This is due to the low yield strength of the lithium metal, which limits the stresses such that they have only a small effect on the reaction kinetics. (C) 2014 The Electrochemical Society. All rights reserved.« less

Phase transformation as the single-mode mechanical deformation of silicon

DOE PAGES

Wong, Sherman; Haberl, Bianca; Williams, James S.; ...

2015-06-25

The mixture of the metastable body-centered cubic (bc8) and rhombohedral (r8) phases of silicon that is formed via nanoindentation of diamond cubic (dc) silicon exhibits properties that are of scientifc and technological interest. This letter demonstrates that large regions of this mixed phase can be formed in crystalline Si via nanoindentation without signifcant damage to the surrounding crystal. Cross-sectional transmission electron microscopy is used to show that volumes 6 μm wide and up to 650 nm deep can be generated in this way using a spherical tip of ~21.5 μm diameter. The phase transformed region is characterised using both Ramanmore » microspectroscopy and transmission electron microscopy. It is found that uniform loading using large spherical indenters can favor phase transformation as the sole deformation mechanism as long as the maximum load is below a critical level. We suggest that the sluggish nature of the transformation from the dc-Si phase to the metallic (b-Sn) phase normally results in competing deformation mechanisms such as slip and cracking but these can be suppressed by controlled loading conditions.« less

Investigating Deformation and Failure Mechanisms in Nanoscale Multilayer Metallic Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zbib, Hussein M.; Bahr, David F.

2014-10-22

Over the history of materials science there are many examples of materials discoveries that have made superlative materials; the strongest, lightest, or toughest material is almost always a goal when we invent new materials. However, often these have been a result of enormous trial and error approaches. A new methodology, one in which researchers design, from the atoms up, new ultra-strong materials for use in energy applications, is taking hold within the science and engineering community. This project focused on one particular new classification of materials; nanolaminate metallic composites. These materials, where two metallic materials are intimately bonded and layeredmore » over and over to form sheets or coatings, have been shown over the past decade to reach strengths over 10 times that of their constituents. However, they are not yet widely used in part because while extremely strong (they don’t permanently bend), they are also not particularly tough (they break relatively easily when notched). Our program took a coupled approach to investigating new materials systems within the laminate field. We used computational materials science to explore ways to institute new deformation mechanisms that occurred when a tri-layer, rather than the more common bi-layer system was created. Our predictions suggested that copper-nickel or copper-niobium composites (two very common bi-layer systems) with layer thicknesses on the order of 20 nm and then layered 100’s of times, would be less tough than a copper-nickel-niobium metallic composite of similar thicknesses. In particular, a particular mode of permanent deformation, cross-slip, could be activated only in the tri-layer system; the crystal structure of the other bi-layers would prohibit this particular mode of deformation. We then experimentally validated this predication using a wide range of tools. We utilized a DOE user facility, the Center for Integrated Nanotechnology (CINT), to fabricate, for the first

Deformed Palmprint Matching Based on Stable Regions.

PubMed

Wu, Xiangqian; Zhao, Qiushi

2015-12-01

Palmprint recognition (PR) is an effective technology for personal recognition. A main problem, which deteriorates the performance of PR, is the deformations of palmprint images. This problem becomes more severe on contactless occasions, in which images are acquired without any guiding mechanisms, and hence critically limits the applications of PR. To solve the deformation problems, in this paper, a model for non-linearly deformed palmprint matching is derived by approximating non-linear deformed palmprint images with piecewise-linear deformed stable regions. Based on this model, a novel approach for deformed palmprint matching, named key point-based block growing (KPBG), is proposed. In KPBG, an iterative M-estimator sample consensus algorithm based on scale invariant feature transform features is devised to compute piecewise-linear transformations to approximate the non-linear deformations of palmprints, and then, the stable regions complying with the linear transformations are decided using a block growing algorithm. Palmprint feature extraction and matching are performed over these stable regions to compute matching scores for decision. Experiments on several public palmprint databases show that the proposed models and the KPBG approach can effectively solve the deformation problem in palmprint verification and outperform the state-of-the-art methods.

Terrestrial Laser Scanner Two-Face Measurements for Analyzing the Elevation-Dependent Deformation of the Onsala Space Observatory 20-m Radio Telescope's Main Reflector in a Bundle Adjustment.

PubMed

Holst, Christoph; Schunck, David; Nothnagel, Axel; Haas, Rüdiger; Wennerbäck, Lars; Olofsson, Henrik; Hammargren, Roger; Kuhlmann, Heiner

2017-08-09

For accurate astronomic and geodetic observations based on radio telescopes, the elevation-dependent deformation of the radio telescopes' main reflectors should be known. Terrestrial laser scanning has been used for determining the corresponding changes of focal lengths and areal reflector deformations at several occasions before. New in this publication is the situation in which we minimize systematic measurement errors by an improved measurement and data-processing concept: Sampling the main reflector in both faces of the laser scanner and calibrating the laser scanner in situ in a bundle adjustment. This concept is applied to the Onsala Space Observatory 20-m radio telescope: The focal length of the main reflector decreases by 9.6 mm from 85 ∘ to 5 ∘ elevation angle. Further local deformations of the main reflector are not detected.

Statistical model for the mechanical behavior of the tissue engineering non-woven fibrous matrices under large deformation.

PubMed

Rizvi, Mohd Suhail; Pal, Anupam

2014-09-01

The fibrous matrices are widely used as scaffolds for the regeneration of load-bearing tissues due to their structural and mechanical similarities with the fibrous components of the extracellular matrix. These scaffolds not only provide the appropriate microenvironment for the residing cells but also act as medium for the transmission of the mechanical stimuli, essential for the tissue regeneration, from macroscopic scale of the scaffolds to the microscopic scale of cells. The requirement of the mechanical loading for the tissue regeneration requires the fibrous scaffolds to be able to sustain the complex three-dimensional mechanical loading conditions. In order to gain insight into the mechanical behavior of the fibrous matrices under large amount of elongation as well as shear, a statistical model has been formulated to study the macroscopic mechanical behavior of the electrospun fibrous matrix and the transmission of the mechanical stimuli from scaffolds to the cells via the constituting fibers. The study establishes the load-deformation relationships for the fibrous matrices for different structural parameters. It also quantifies the changes in the fiber arrangement and tension generated in the fibers with the deformation of the matrix. The model reveals that the tension generated in the fibers on matrix deformation is not homogeneous and hence the cells located in different regions of the fibrous scaffold might experience different mechanical stimuli. The mechanical response of fibrous matrices was also found to be dependent on the aspect ratio of the matrix. Therefore, the model establishes a structure-mechanics interdependence of the fibrous matrices under large deformation, which can be utilized in identifying the appropriate structure and external mechanical loading conditions for the regeneration of load-bearing tissues. Copyright © 2014 Elsevier Ltd. All rights reserved.

Deformation of Reservoir Sandstones by Elastic versus Inelastic Deformation Mechanisms

NASA Astrophysics Data System (ADS)

Pijnenburg, R.; Verberne, B. A.; Hangx, S.; Spiers, C. J.

2016-12-01

Hydrocarbon or groundwater production from sandstone reservoirs can result in surface subsidence and induced seismicity. Subsidence results from combined elastic and inelastic compaction of the reservoir due to a change in the effective stress state upon fluid extraction. The magnitude of elastic compaction can be accurately described using poroelasticity theory. However inelastic or time-dependent compaction is poorly constrained. Specifically, the underlying microphysical processes controlling sandstone compaction remain poorly understood. We use sandstones recovered by the field operator (NAM) from the Slochteren gas reservoir (Groningen, NE Netherlands) to study the importance of elastic versus inelastic deformation processes upon simulated pore pressure depletion. We conducted conventional triaxial tests under true in-situ conditions of pressure and temperature. To investigate the effect of applied differential stress (σ1 - σ3 = 0 - 50 MPa) and initial sample porosity (φi = 12 - 24%) on instantaneous and time-dependent inelastic deformation, we imposed multiple stages of axial loading and relaxation. The results show that inelastic strain develops at all stages of loading, and that its magnitude increases with increasing value of differential stress and initial porosity. The stress sensitivity of the axial creep strain rate and microstructural evidence suggest that inelastic compaction is controlled by a combination of intergranular slip and intragranular cracking. Intragranular cracking is shown to be more pervasive with increasing values of initial porosity. The results are consistent with a conceptual microphysical model, involving deformation by poro-elasticity combined with intergranular sliding and grain contact failure. This model aims to predict sandstone deformation behavior for a wide range of stress conditions.

Control of thermal deformation in dielectric mirrors using mechanical design and atomic layer deposition.

PubMed

Gabriel, Nicholas T; Kim, Sangho S; Talghader, Joseph J

2009-07-01

A mechanical design technique for optical coatings that simultaneously controls thermal deformation and optical reflectivity is reported. The method requires measurement of the refractive index and thermal stress of single films prior to the design. Atomic layer deposition was used for deposition because of the high repeatability of the film constants. An Al2O3/HfO2 distributed Bragg reflector was deposited with a predicted peak reflectivity of 87.9% at 542.4 nm and predicted edge deformation of -360 nm/K on a 10 cm silicon substrate. The measured peak reflectivity was 85.7% at 541.7 nm with an edge deformation of -346 nm/K.

Comprehensive Deformation Analysis of a Newly Designed Ni-Free Duplex Stainless Steel with Enhanced Plasticity by Optimizing Austenite Stability

NASA Astrophysics Data System (ADS)

Moallemi, Mohammad; Zarei-Hanzaki, Abbas; Eskandari, Mostafa; Burrows, Andrew; Alimadadi, Hossein

2017-08-01

A new metastable Ni-free duplex stainless steel has been designed with superior plasticity by optimizing austenite stability using thermodynamic calculations of stacking fault energy and with reference to literature findings. Several characterization methods comprising optical microscopy, magnetic phase measurements, X-ray diffraction (XRD) and electron backscattered diffraction were employed to study the plastic deformation behavior and to identify the operating plasticity mechanisms. The results obtained show that the newly designed duplex alloy exhibits some extraordinary mechanical properties, including an ultimate tensile strength of 900 MPa and elongation to fracture of 94 pct due to the synergistic effects of transformation-induced plasticity and twinning-induced plasticity. The deformation mechanism of austenite is complex and includes deformation banding, strain-induced martensite formation, and deformation-induced twinning, while the ferrite phase mainly deforms by dislocation slip. Texture analysis indicates that the Copper and Rotated Brass textures in austenite (FCC phase) and {001}<110> texture in ferrite and martensite (BCC phases) are the main active components during tensile deformation. The predominance of these components is logically related to the strain-induced martensite and/or twin formation.

Deformation behavior and mechanical analysis of vertically aligned carbon nanotube (VACNT) bundles

NASA Astrophysics Data System (ADS)

Hutchens, Shelby B.

Vertically aligned carbon nanotubes (VACNTs) serve as integral components in a variety of applications including MEMS devices, energy absorbing materials, dry adhesives, light absorbing coatings, and electron emitters, all of which require structural robustness. It is only through an understanding of VACNT's structural mechanical response and local constitutive stress-strain relationship that future advancements through rational design may take place. Even for applications in which the structural response is not central to device performance, VACNTs must be sufficiently robust and therefore knowledge of their microstructure-property relationship is essential. This thesis first describes the results of in situ uniaxial compression experiments of 50 micron diameter cylindrical bundles of these complex, hierarchical materials as they undergo unusual deformation behavior. Most notably they deform via a series of localized folding events, originating near the bundle base, which propagate laterally and collapse sequentially from bottom to top. This deformation mechanism accompanies an overall foam-like stress-strain response having elastic, plateau, and densification regimes with the addition of undulations in the stress throughout the plateau regime that correspond to the sequential folding events. Microstructural observations indicate the presence of a strength gradient, due to a gradient in both tube density and alignment along the bundle height, which is found to play a key role in both the sequential deformation process and the overall stress-strain response. Using the complicated structural response as both motivation and confirmation, a finite element model based on a viscoplastic solid is proposed. This model is characterized by a flow stress relation that contains an initial peak followed by strong softening and successive hardening. Analysis of this constitutive relation results in capture of the sequential buckling phenomenon and a strength gradient effect

Loading system mechanism for dielectric elastomer generators with equi-biaxial state of deformation

NASA Astrophysics Data System (ADS)

Fontana, M.; Moretti, G.; Lenzo, B.; Vertechy, R.

2014-03-01

Dielectric Elastomer Generators (DEGs) are devices that employ a cyclically variable membrane capacitor to produce electricity from oscillating sources of mechanical energy. Capacitance variation is obtained thanks to the use of dielectric and conductive layers that can undergo different states of deformation including: uniform or non-uniform and uni- or multi-axial stretching. Among them, uniform equi-biaxial stretching is reputed as being the most effective state of deformation that maximizes the amount of energy that can be extracted in a cycle by a unit volume of Dielectric Elastomer (DE) material. This paper presents a DEG concept, with linear input motion and tunable impedance, that is based on a mechanical loading system for inducing uniform equi-biaxial states of deformation. The presented system employs two circular DE membrane capacitors that are arranged in an agonist-antagonist configuration. An analytical model of the overall system is developed and used to find the optimal design parameters that make it possible to tune the elastic response of the generator over the range of motion of interest. An apparatus is developed for the equi-biaxial testing of DE membranes and used for the experimental verification of the employed numerical models.

Influences of periodic mechanical deformation on pinned spiral waves

NASA Astrophysics Data System (ADS)

Chen, Jiang-Xing; Peng, Liang; Zheng, Qiang; Zhao, Ye-Hua; Ying, He-Ping

2014-09-01

In a generic model of excitable media, we study the behavior of spiral waves interacting with obstacles and their dynamics under the influences of simple periodic mechanical deformation (PMD). Depending on the characteristics of the obstacles, i.e., size and excitability, the rotation of a pinned spiral wave shows different scenarios, e.g., embedding into or anchoring on an obstacle. Three different drift phenomena induced by PMD are observed: scattering on small partial-excitable obstacles, meander-induced unpinning on big partial-excitable obstacles, and drifting around small unexcitable obstacles. Their underlying mechanisms are discussed. The dependence of the threshold amplitude of PMD on the characteristics of the obstacles to successfully remove pinned spiral waves on big partial-excitable obstacles is studied.

Room temperature deformation mechanisms of alumina particles observed from in situ micro-compression and atomistic simulations.

DOE PAGES

Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; ...

2015-09-22

Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containingmore » numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.« less

Deformation twinning in a creep-deformed nanolaminate structure

NASA Astrophysics Data System (ADS)

Hsiung, Luke L.

2010-10-01

The underlying mechanism of deformation twinning occurring in a TiAl-(γ)/Ti3Al-(α2) nanolaminate creep deformed at elevated temperatures has been studied. Since the multiplication and propagation of lattice dislocations in both γ and α2 thin lamellae are very limited, the total flow of lattice dislocations becomes insufficient to accommodate the accumulated creep strains. Consequently, the movement of interfacial dislocations along the laminate interfaces, i.e., interface sliding, becomes an alternative deformation mode of the nanolaminate structure. Pile-ups of interfacial dislocations occur when interfacial ledges and impinged lattice dislocations act as obstacles to impede the movement of interfacial dislocations. Deformation twinning can accordingly take place to relieve a stress concentration resulting from the pile-up of interfacial dislocations. An interface-controlled twinning mechanism driven by the pile-up and dissociation of interfacial dislocations is accordingly proposed.

Ductile deformation mechanisms of synthetic halite: a full field measurement approach

NASA Astrophysics Data System (ADS)

Dimanov, Alexandre; Bourcier, Mathieu; Héripré, Eva; Bornert, Michel; Raphanel, Jean

2013-04-01

Halite is a commonly used analog polycristalline material. Compared to most rock forming minerals, halite exhibits extensively ductile behavior at even low temperatures and fast deformation rates. Therefore, it allows an easier study of the fundamental mechanisms of crystal plasticity, recrystallization, grain growth and texture development than any other mineral. Its high solubility also makes it an ideal candidate for investigating pressure solution creep. Most importantly, halite is very convenient to study the interactions of simultaneously occurring deformation mechanisms. We investigated uniaxial deformation of pure synthetic NaCl polycrystals with controlled grain sizes and grain size distributions at room and moderate temperatures (400°C). The mechanical tests were combined with "in-situ" optical and scanning electron microscopy, in order to perform 2D digital image correlation (2D-DIC) and to obtain the full surface strain fields at the sample scale and at the scales of the microstructure. We observed dominantly intracrystalline plasticity, as revealed by the occurrence of physical slip lines on the surface of individual grains and of deformation bands at the microstructure (aggregate) scale, as revealed by DIC. Crystal orientation mapping (performed by EBSD) allowed relating the latter to the traces of crystallographic slip planes and inferring the active slip systems considering the macroscopic stress state and computing Schmid factors. The strain heterogeneities are more pronounced at low temperature, at both the aggregate scale and within individual grains. The local activity of slip systems strongly depends on the relative crystallographic and interfacial orientations of the adjacent grains with respect to the loading direction. The easy glide {110} <110> systems are not the only active ones. We could identify the activity of all slip systems, especially near grain boundaries, which indicates local variations of the stress state. But, we also clearly

Mechanisms of Plastic Deformation in Collagen Networks Induced by Cellular Forces.

PubMed

Ban, Ehsan; Franklin, J Matthew; Nam, Sungmin; Smith, Lucas R; Wang, Hailong; Wells, Rebecca G; Chaudhuri, Ovijit; Liphardt, Jan T; Shenoy, Vivek B

2018-01-23

Contractile cells can reorganize fibrous extracellular matrices and form dense tracts of fibers between neighboring cells. These tracts guide the development of tubular tissue structures and provide paths for the invasion of cancer cells. Here, we studied the mechanisms of the mechanical plasticity of collagen tracts formed by contractile premalignant acinar cells and fibroblasts. Using fluorescence microscopy and second harmonic generation, we quantified the collagen densification, fiber alignment, and strains that remain within the tracts after cellular forces are abolished. We explained these observations using a theoretical fiber network model that accounts for the stretch-dependent formation of weak cross-links between nearby fibers. We tested the predictions of our model using shear rheology experiments. Both our model and rheological experiments demonstrated that increasing collagen concentration leads to substantial increases in plasticity. We also considered the effect of permanent elongation of fibers on network plasticity and derived a phase diagram that classifies the dominant mechanisms of plasticity based on the rate and magnitude of deformation and the mechanical properties of individual fibers. Plasticity is caused by the formation of new cross-links if moderate strains are applied at small rates or due to permanent fiber elongation if large strains are applied over short periods. Finally, we developed a coarse-grained model for plastic deformation of collagen networks that can be employed to simulate multicellular interactions in processes such as morphogenesis, cancer invasion, and fibrosis. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

In situ investigation of deformation mechanisms in magnesium-based metal matrix composites

NASA Astrophysics Data System (ADS)

Farkas, Gergely; Choe, Heeman; Máthis, Kristián; Száraz, Zoltán; Noh, Yoonsook; Trojanová, Zuzanka; Minárik, Peter

2015-07-01

We studied the effect of short fibers on the mechanical properties of a magnesium alloy. In particular, deformation mechanisms in a Mg-Al-Sr alloy reinforced with short alumina fibers were studied in situ using neutron diffraction and acoustic emission methods. The fibers' plane orientation with respect to the loading axis was found to be a key parameter, which influences the acting deformation processes, such as twinning or dislocation slip. Furthermore, the twinning activity was much more significant in samples with parallel fiber plane orientation, which was confirmed by both acoustic emission and electron backscattering diffraction results. Neutron diffraction was also used to assist in analyzing the acoustic emission and electron backscattering diffraction results. The simultaneous application of the two in situ methods, neutron diffraction and acoustic emission, was found to be beneficial for obtaining complementary datasets about the twinning and dislocation slip in the magnesium alloys and composites used in this study.

Deformation mechanism study of a hot rolled Zr-2.5Nb alloy by transmission electron microscopy. II. In situ transmission electron microscopy study of deformation mechanism change of a Zr-2.5Nb alloy upon heavy ion irradiation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Fei; Daymond, Mark R.; Yao, Zhongwen

2015-03-14

The effect of heavy-ion irradiation on deformation mechanisms of a Zr-2.5Nb alloy was investigated by using the in situ transmission electron microscopy deformation technique. The gliding behavior of prismatic < a > dislocations has been dynamically observed before and after irradiation at room temperature and 300 degrees C. Irradiation induced loops were shown to strongly pin the gliding dislocations. Unpinning occurred while loops were incorporated into or eliminated by < a > dislocations. In the irradiated sample, loop depleted areas with a boundary parallel to the basal plane trace were found by post-mortem observation after room temperature deformation, supporting themore » possibility of basal channel formation in bulk neutron irradiated samples. Strong activity of pyramidal slip was also observed at both temperatures, which might be another important mechanism to induce plastic instability in irradiated zirconium alloys. Finally, {01 (1) over bar1}< 0 (1) over bar 12 > twinning was identified in the irradiated sample deformed at 300 degrees C.« less

Terrestrial Laser Scanner Two-Face Measurements for Analyzing the Elevation-Dependent Deformation of the Onsala Space Observatory 20-m Radio Telescope’s Main Reflector in a Bundle Adjustment

PubMed Central

Schunck, David; Nothnagel, Axel; Haas, Rüdiger; Wennerbäck, Lars; Olofsson, Henrik; Hammargren, Roger; Kuhlmann, Heiner

2017-01-01

For accurate astronomic and geodetic observations based on radio telescopes, the elevation-dependent deformation of the radio telescopes’ main reflectors should be known. Terrestrial laser scanning has been used for determining the corresponding changes of focal lengths and areal reflector deformations at several occasions before. New in this publication is the situation in which we minimize systematic measurement errors by an improved measurement and data-processing concept: Sampling the main reflector in both faces of the laser scanner and calibrating the laser scanner in situ in a bundle adjustment. This concept is applied to the Onsala Space Observatory 20-m radio telescope: The focal length of the main reflector decreases by 9.6 mm from 85∘ to 5∘ elevation angle. Further local deformations of the main reflector are not detected. PMID:28792449

Influence of the Strain History on TWIP Steel Deformation Mechanisms in the Deep-Drawing Process

NASA Astrophysics Data System (ADS)

Lapovok, R.; Timokhina, I.; Mester, A.-K.; Weiss, M.; Shekhter, A.

2018-03-01

A study of preferable deformation modes on strain path and strain level in a TWIP steel sheet was performed. Different strain paths were obtained by stretch forming of specimens with various shapes and tensile tests. TEM analysis was performed on samples cut from various locations in the deformed specimens, which had different strain paths and strain levels and the preferable deformation modes were identified. Stresses caused by various strain paths were considered and an analytical analysis performed to identify the preferable deformation modes for the case of single crystal. For a single crystal, in assumption of the absence of lattice rotation, the strain path and the level of accumulated equivalent strain define the preferable deformation mode. For a polycrystalline material, such analytical analysis is not possible due to the large number of grains and, therefore, numerical simulation was employed. For the polycrystalline material, the role of strain path diminishes due to the presence of a large number of grains with random orientations and the effect of accumulated strain becomes dominant. However, at small strains the strain path still defines the level of twinning activity. TEM analysis experimentally confirmed that various deformation modes lead to different deformation strengthening mechanisms.

Influence of the Strain History on TWIP Steel Deformation Mechanisms in the Deep-Drawing Process

NASA Astrophysics Data System (ADS)

Lapovok, R.; Timokhina, I.; Mester, A.-K.; Weiss, M.; Shekhter, A.

2018-06-01

A study of preferable deformation modes on strain path and strain level in a TWIP steel sheet was performed. Different strain paths were obtained by stretch forming of specimens with various shapes and tensile tests. TEM analysis was performed on samples cut from various locations in the deformed specimens, which had different strain paths and strain levels and the preferable deformation modes were identified. Stresses caused by various strain paths were considered and an analytical analysis performed to identify the preferable deformation modes for the case of single crystal. For a single crystal, in assumption of the absence of lattice rotation, the strain path and the level of accumulated equivalent strain define the preferable deformation mode. For a polycrystalline material, such analytical analysis is not possible due to the large number of grains and, therefore, numerical simulation was employed. For the polycrystalline material, the role of strain path diminishes due to the presence of a large number of grains with random orientations and the effect of accumulated strain becomes dominant. However, at small strains the strain path still defines the level of twinning activity. TEM analysis experimentally confirmed that various deformation modes lead to different deformation strengthening mechanisms.

Material heterogeneity in cancellous bone promotes deformation recovery after mechanical failure.

PubMed

Torres, Ashley M; Matheny, Jonathan B; Keaveny, Tony M; Taylor, David; Rimnac, Clare M; Hernandez, Christopher J

2016-03-15

Many natural structures use a foam core and solid outer shell to achieve high strength and stiffness with relatively small amounts of mass. Biological foams, however, must also resist crack growth. The process of crack propagation within the struts of a foam is not well understood and is complicated by the foam microstructure. We demonstrate that in cancellous bone, the foam-like component of whole bones, damage propagation during cyclic loading is dictated not by local tissue stresses but by heterogeneity of material properties associated with increased ductility of strut surfaces. The increase in surface ductility is unexpected because it is the opposite pattern generated by surface treatments to increase fatigue life in man-made materials, which often result in reduced surface ductility. We show that the more ductile surfaces of cancellous bone are a result of reduced accumulation of advanced glycation end products compared with the strut interior. Damage is therefore likely to accumulate in strut centers making cancellous bone more tolerant of stress concentrations at strut surfaces. Hence, the structure is able to recover more deformation after failure and return to a closer approximation of its original shape. Increased recovery of deformation is a passive mechanism seen in biology for setting a broken bone that allows for a better approximation of initial shape during healing processes and is likely the most important mechanical function. Our findings suggest a previously unidentified biomimetic design strategy in which tissue level material heterogeneity in foams can be used to improve deformation recovery after failure.

Material heterogeneity in cancellous bone promotes deformation recovery after mechanical failure

PubMed Central

Torres, Ashley M.; Matheny, Jonathan B.; Keaveny, Tony M.; Taylor, David; Rimnac, Clare M.; Hernandez, Christopher J.

2016-01-01

Many natural structures use a foam core and solid outer shell to achieve high strength and stiffness with relatively small amounts of mass. Biological foams, however, must also resist crack growth. The process of crack propagation within the struts of a foam is not well understood and is complicated by the foam microstructure. We demonstrate that in cancellous bone, the foam-like component of whole bones, damage propagation during cyclic loading is dictated not by local tissue stresses but by heterogeneity of material properties associated with increased ductility of strut surfaces. The increase in surface ductility is unexpected because it is the opposite pattern generated by surface treatments to increase fatigue life in man-made materials, which often result in reduced surface ductility. We show that the more ductile surfaces of cancellous bone are a result of reduced accumulation of advanced glycation end products compared with the strut interior. Damage is therefore likely to accumulate in strut centers making cancellous bone more tolerant of stress concentrations at strut surfaces. Hence, the structure is able to recover more deformation after failure and return to a closer approximation of its original shape. Increased recovery of deformation is a passive mechanism seen in biology for setting a broken bone that allows for a better approximation of initial shape during healing processes and is likely the most important mechanical function. Our findings suggest a previously unidentified biomimetic design strategy in which tissue level material heterogeneity in foams can be used to improve deformation recovery after failure. PMID:26929343

Tensile Deformation Temperature Impact on Microstructure and Mechanical Properties of AISI 316LN Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Xiong, Yi; He, Tiantian; Lu, Yan; Ren, Fengzhang; Volinsky, Alex A.; Cao, Wei

2018-03-01

Uniaxial tensile tests were conducted on AISI 316LN austenitic stainless steel from - 40 to 300 °C at a rate of 0.5 mm/min. Microstructure and mechanical properties of the deformed steel were investigated by optical, scanning and transmission electron microscopies, x-ray diffraction, and microhardness testing. The yield strength, ultimate tensile strength, elongation, and microhardness increase with the decrease in the test temperature. The tensile fracture morphology has the dimple rupture feature after low-temperature deformations and turns to a mixture of transgranular fracture and dimple fracture after high-temperature ones. The dominating deformation microstructure evolves from dislocation tangle/slip bands to large deformation twins/slip bands with temperature decrease. The deformation-induced martensite transformation can only be realized at low temperature, and its quantity increases with the decrease in the temperature.

Deformed supersymmetric quantum mechanics with spin variables

NASA Astrophysics Data System (ADS)

Fedoruk, Sergey; Ivanov, Evgeny; Sidorov, Stepan

2018-01-01

We quantize the one-particle model of the SU(2|1) supersymmetric multiparticle mechanics with the additional semi-dynamical spin degrees of freedom. We find the relevant energy spectrum and the full set of physical states as functions of the mass-dimension deformation parameter m and SU(2) spin q\\in (Z_{>0,}1/2+Z_{≥0}) . It is found that the states at the fixed energy level form irreducible multiplets of the supergroup SU(2|1). Also, the hidden superconformal symmetry OSp(4|2) of the model is revealed in the classical and quantum cases. We calculate the OSp(4|2) Casimir operators and demonstrate that the full set of the physical states belonging to different energy levels at fixed q are unified into an irreducible OSp(4|2) multiplet.

Size effects of primary/secondary twins on the atomistic deformation mechanisms in hierarchically nanotwinned metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Fuping; Wu, Xiaolei

2013-05-28

A series of large-scale molecular dynamics simulations have been performed to investigate the tensile properties of nanotwinned (NT) copper with hierarchically twinned structures (HTS). For the same grain size d and the same spacing of primary twins {lambda}{sub 1}, the average flow stress first increases as the spacing of secondary twins {lambda}{sub 2} decreases, reaching a maximum at a critical {lambda}{sub 2}, and then decreases as {lambda}{sub 2} becomes even smaller. The smaller the spacing for {lambda}{sub 1}, the smaller the critical spacing for {lambda}{sub 2}. There exists a transition in dominating deformation mechanisms, occurring at a critical spacing ofmore » {lambda}{sub 2} for which strength is maximized. Above the critical spacing of {lambda}{sub 2}, the deformation mechanisms are dominated by the two Hall-Petch type strengthening mechanisms: (a) partial dislocations emitted from grain boundaries (GBs) travel across other GBs and twin boundaries (TBs); (b) partial dislocations emitted from TBs travel across other TBs. Below the critical spacing of {lambda}{sub 2}, the deformation mechanism is dominated by the two softening mechanisms: (a) Partial dislocations emitted from boundaries of the primary twins travel parallel to the TBs of the secondary twins, leading to detwinning of the secondary twins; (b) Boundaries of the primary twins shift entirely, leading to thickening in one part of primary twins and thinning in the other part of primary twins. The present results should provide insights to design the microstructures for reinforcing the mechanical properties in the NT metals with HTS.« less

A mechanism for tectonic deformation on Venus

NASA Technical Reports Server (NTRS)

Phillips, Roger J.

1986-01-01

In the absence of identifiable physiographic features directly associated with plate tectonics, alternate mechanisms are sought for the intense tectonic deformation observed in radar images of Venus. One possible mechanism is direct coupling into an elastic lithosphere of the stresses associated with convective flow in the interior. Spectral Green's function solutions have been obtained for stresses in an elastic lithosphere overlying a Newtonian interior with an exponential depth dependence of viscosity, and a specified surface-density distribution driving the flow. At long wavelengths and for a rigid elastic/fluid boundary condition, horizontal normal stresses in the elastic lid are controlled by the vertical shear stress gradient and are directly proportional to the depth of the density disturbance in the underlying fluid. The depth and strength of density anomalies in the Venusian interior inferred by analyses of long wavelength gravity data suggest that stresses in excess of 100 MPa would be generated in a 10 km thick elastic lid unless a low viscosity channel occurring beneath the lid or a positive viscosity gradient uncouples the flow stresses. The great apparent depth of compensation of topographic features argues against this, however, thus supporting the importance of the coupling mechanism. If there is no elastic lid, stresses will also be very high near the surface, providing also that the viscosity gradient is negative.

EBSD characterization of low temperature deformation mechanisms in modern alloys

NASA Astrophysics Data System (ADS)

Kozmel, Thomas S., II

For structural applications, grain refinement has been shown to enhance mechanical properties such as strength, fatigue resistance, and fracture toughness. Through control of the thermos-mechanical processing parameters, dynamic recrystallization mechanisms were used to produce microstructures consisting of sub-micron grains in 9310 steel, 4140 steel, and Ti-6Al-4V. In both 9310 and 4140 steel, the distribution of carbides throughout the microstructure affected the ability of the material to dynamically recrystallize and determined the size of the dynamically recrystallized grains. Processing the materials at lower temperatures and higher strain rates resulted in finer dynamically recrystallized grains. Microstructural process models that can be used to estimate the resulting microstructure based on the processing parameters were developed for both 9310 and 4140 steel. Heat treatment studies performed on 9310 steel showed that the sub-micron grain size obtained during deformation could not be retained due to the low equilibrium volume fraction of carbides. Commercially available aluminum alloys were investigated to explain their high strain rate deformation behavior. Alloys such as 2139, 2519, 5083, and 7039 exhibit strain softening after an ultimate strength is reached, followed by a rapid degradation of mechanical properties after a critical strain level has been reached. Microstructural analysis showed that the formation of shear bands typically preceded this rapid degradation in properties. Shear band boundary misorientations increased as a function of equivalent strain in all cases. Precipitation behavior was found to greatly influence the microstructural response of the alloys. Additionally, precipitation strengthened alloys were found to exhibit similar flow stress behavior, whereas solid solution strengthened alloys exhibited lower flow stresses but higher ductility during dynamic loading. Schmid factor maps demonstrated that shear band formation behavior

Overview of deformable mirror technologies for adaptive optics and astronomy

NASA Astrophysics Data System (ADS)

Madec, P.-Y.

2012-07-01

From the ardent bucklers used during the Syracuse battle to set fire to Romans’ ships to more contemporary piezoelectric deformable mirrors widely used in astronomy, from very large voice coil deformable mirrors considered in future Extremely Large Telescopes to very small and compact ones embedded in Multi Object Adaptive Optics systems, this paper aims at giving an overview of Deformable Mirror technology for Adaptive Optics and Astronomy. First the main drivers for the design of Deformable Mirrors are recalled, not only related to atmospheric aberration compensation but also to environmental conditions or mechanical constraints. Then the different technologies available today for the manufacturing of Deformable Mirrors will be described, pros and cons analyzed. A review of the Companies and Institutes with capabilities in delivering Deformable Mirrors to astronomers will be presented, as well as lessons learned from the past 25 years of technological development and operation on sky. In conclusion, perspective will be tentatively drawn for what regards the future of Deformable Mirror technology for Astronomy.

Mechanical properties of silk: interplay of deformation on macroscopic and molecular length scales.

PubMed

Krasnov, Igor; Diddens, Imke; Hauptmann, Nadine; Helms, Gesa; Ogurreck, Malte; Seydel, Tilo; Funari, Sérgio S; Müller, Martin

2008-02-01

Using an in situ combination of tensile tests and x-ray diffraction, we have determined the mechanical properties of both the crystalline and the disordered phase of the biological nanocomposite silk by adapting a model from linear viscoelastic theory to the semicrystalline morphology of silk. We observe a strong interplay between morphology and mechanical properties. Silk's high extensibility results principally from the disordered phase; however, the crystals are also elastically deformed.

Representing Matrix Cracks Through Decomposition of the Deformation Gradient Tensor in Continuum Damage Mechanics Methods

NASA Technical Reports Server (NTRS)

Leone, Frank A., Jr.

2015-01-01

A method is presented to represent the large-deformation kinematics of intraply matrix cracks and delaminations in continuum damage mechanics (CDM) constitutive material models. The method involves the additive decomposition of the deformation gradient tensor into 'crack' and 'bulk material' components. The response of the intact bulk material is represented by a reduced deformation gradient tensor, and the opening of an embedded cohesive interface is represented by a normalized cohesive displacement-jump vector. The rotation of the embedded interface is tracked as the material deforms and as the crack opens. The distribution of the total local deformation between the bulk material and the cohesive interface components is determined by minimizing the difference between the cohesive stress and the bulk material stress projected onto the cohesive interface. The improvements to the accuracy of CDM models that incorporate the presented method over existing approaches are demonstrated for a single element subjected to simple shear deformation and for a finite element model of a unidirectional open-hole tension specimen. The material model is implemented as a VUMAT user subroutine for the Abaqus/Explicit finite element software. The presented deformation gradient decomposition method reduces the artificial load transfer across matrix cracks subjected to large shearing deformations, and avoids the spurious secondary failure modes that often occur in analyses based on conventional progressive damage models.

Exploration of mechanisms underlying the strain-rate-dependent mechanical property of single chondrocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Trung Dung; Gu, YuanTong, E-mail: yuantong.gu@qut.edu.au

2014-05-05

Based on the characterization by Atomic Force Microscopy, we report that the mechanical property of single chondrocytes has dependency on the strain-rates. By comparing the mechanical deformation responses and the Young's moduli of living and fixed chondrocytes at four different strain-rates, we explore the deformation mechanisms underlying this dependency property. We found that the strain-rate-dependent mechanical property of living cells is governed by both of the cellular cytoskeleton and the intracellular fluid when the fixed chondrocytes are mainly governed by their intracellular fluid, which is called the consolidation-dependent deformation behavior. Finally, we report that the porohyperelastic constitutive material model whichmore » can capture the consolidation-dependent behavior of both living and fixed chondrocytes is a potential candidature to study living cell biomechanics.« less

Deformation mechanism study of a hot rolled Zr-2.5Nb alloy by transmission electron microscopy. II. In situ transmission electron microscopy study of deformation mechanism change of a Zr-2.5Nb alloy upon heavy ion irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Fei; Daymond, Mark R., E-mail: mark.daymond@queensu.ca; Yao, Zhongwen

2015-03-14

The effect of heavy-ion irradiation on deformation mechanisms of a Zr-2.5Nb alloy was investigated by using the in situ transmission electron microscopy deformation technique. The gliding behavior of prismatic 〈a〉 dislocations has been dynamically observed before and after irradiation at room temperature and 300 °C. Irradiation induced loops were shown to strongly pin the gliding dislocations. Unpinning occurred while loops were incorporated into or eliminated by 〈a〉 dislocations. In the irradiated sample, loop depleted areas with a boundary parallel to the basal plane trace were found by post-mortem observation after room temperature deformation, supporting the possibility of basal channel formation inmore » bulk neutron irradiated samples. Strong activity of pyramidal slip was also observed at both temperatures, which might be another important mechanism to induce plastic instability in irradiated zirconium alloys. Finally, (011{sup ¯}1)〈01{sup ¯}12〉 twinning was identified in the irradiated sample deformed at 300 °C.« less

Changes in the physical and mechanical properties of Al-Mg alloy processed by severe plastic deformation

NASA Astrophysics Data System (ADS)

Krasnoveikin, V. A.; Kozulin, A. A.; Skripnyak, V. A.; Moskvichev, E. N.; Borodulin, D. A.

2017-12-01

This paper presents the results of studies into the effect of severe plastic deformation on the microstructure, physical and mechanical properties of coarse-grained Al-Mg alloy 1560 in the as-received state with an average grain size of 50 µm. Severe plastic deformation is performed by four-pass equal channel angular pressing (ECAP), which results in the formation of an ultrafine-grained structure with an average grain size of 3 µm in the alloy. Analysis of experimental data revealed that the physical and mechanical properties change significantly after severe plastic deformation. The microhardness of the ECAPed alloy increases by 50%, tensile yield strength by 80%, and ultimate strength by 44% in comparison with these parameters in the as-received state. The constants of approximating functions have been determined for the experimental stress-strain curves of the alloy specimens in the as-received and ECAPed states.

Deformation Mechanism on the Northern Margin of the Tibetan Plateau Inferred from Magnetotelluric Data

NASA Astrophysics Data System (ADS)

Zhang, L.; Jin, S.; Wei, W.; Ye, G.; Xie, C.

2017-12-01

As a unique geologic unit on the northern margin of the Tibetan Plateau, the Qaidam Basin plays a significant role in constraining the vertical uplift and horizontal expansion of the plateau. However, deformation mechanism of the lithosphere beneath the Qaidam Basin is still highly debated. To better understand the lithospheric electrical structure and deformation mechanism of the Qaidam Basin, A 250 km long, NE-SW directed Magnetotelluric (MT) profile was finished in the northern portion of the Basin, which is roughly perpendicular to the thrust fault systems on the western and eastern margins of the Basin. The profile consists of 20 broad-band MT stations and 5 long-period MT stations. Original time series data is processed with regular robust routines. Dimensionality and regional strike direction are determined for the dataset through data analysis. 2D inversions were performed to produce a preferred model of the lithospheric electrical structure. Uncertainty analysis of the 2D inversion model was also conducted based on a data resampling approach. The outcome 2D electrical model was further used to estimate the distribution of temperature and melt fraction in the upper mantle based on laboratory-determined relationships between the electrical conductivity and temperature of nominally anhydrous minerals and basaltic melt by using the mixing law of Hashin-Shtrikman's bounds. These results suggest that: (1) the crust-mantle boundary is imaged as a conductive layer beneath the western Qaidam Basin, with its temperature estimated to be 1200-1300 ° and melt fraction 5-8%, indicating decoupling deformation of the crust and upper mantle. (2) A large-scale east-dipping conductor is imaged beneath the eastern Qaidam Basin extending from the upper crust to upper mantle, implying vertical coherent deformation of the lithosphere. Melt fraction of this conductive region is estimated to be as high as 10%, which might accommodates a major portion of the thrust deformation on

Deformation strain is the main physical driver for skeletal precursors to undergo osteogenesis in earlier stages of osteogenic cell maturation.

PubMed

Ramani-Mohan, Ram-Kumar; Schwedhelm, Ivo; Finne-Wistrand, Anna; Krug, Melanie; Schwarz, Thomas; Jakob, Franz; Walles, Heike; Hansmann, Jan

2018-03-01

Mesenchymal stem cells play a major role during bone remodelling and are thus of high interest for tissue engineering and regenerative medicine applications. Mechanical stimuli, that is, deformation strain and interstitial fluid-flow-induced shear stress, promote osteogenic lineage commitment. However, the predominant physical stimulus that drives early osteogenic cell maturation is not clearly identified. The evaluation of each stimulus is challenging, as deformation and fluid-flow-induced shear stress interdepend. In this study, we developed a bioreactor that was used to culture mesenchymal stem cells harbouring a strain-responsive AP-1 luciferase reporter construct, on porous scaffolds. In addition to the reporter, mineralization and vitality of the cells was investigated by alizarin red staining and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Quantification of the expression of genes associated to bone regeneration and bone remodelling was used to confirm alizarin red measurements. Controlled perfusion and deformation of the 3-dimensional scaffold facilitated the alteration of the expression of osteogenic markers, luciferase activity, and calcification. To isolate the specific impact of scaffold deformation, a computational model was developed to derive a perfusion flow profile that results in dynamic shear stress conditions present in periodically loaded scaffolds. In comparison to actually deformed scaffolds, a lower expression of all measured readout parameters indicated that deformation strain is the predominant stimulus for skeletal precursors to undergo osteogenesis in earlier stages of osteogenic cell maturation. Copyright © 2017 John Wiley & Sons, Ltd.

Deformation mechanisms of NiAl cyclicly deformed near the brittle-to-ductile transformation temperature

NASA Technical Reports Server (NTRS)

Antolovich, Stephen D.; Saxena, Ashok; Cullers, Cheryl

1992-01-01

One of the ongoing challenges of the aerospace industry is to develop more efficient turbine engines. Greater efficiency entails reduced specific strength and larger temperature gradients, the latter of which means higher operating temperatures and increased thermal conductivity. Continued development of nickel-based superalloys has provided steady increases in engine efficiency and the limits of superalloys have probably not been realized. However, other material systems are under intense investigation for possible use in high temperature engines. Ceramic, intermetallic, and various composite systems are being explored in an effort to exploit the much higher melting temperatures of these systems. NiAl is considered a potential alternative to conventional superalloys due to its excellent oxidation resistance, low density, and high melting temperature. The fact that NiAl is the most common coating for current superalloy turbine blades is a tribute to its oxidation resistance. Its density is one-third that of typical superalloys and in most temperature ranges its thermal conductivity is twice that of common superalloys. Despite these many advantages, NiAl requires more investigation before it is ready to be used in engines. Binary NiAl in general has poor high-temperature strength and low-temperature ductility. On-going research in alloy design continues to make improvements in the high-temperature strength of NiAl. The factors controlling low temperature ductility have been identified in the last few years. Small, but reproducible ductility can now be achieved at room temperature through careful control of chemical purity and processing. But the mechanisms controlling the transition from brittle to ductile behavior are not fully understood. Research in the area of fatigue deformation can aid the development of the NiAl system in two ways. Fatigue properties must be documented and optimized before NiAl can be applied to engineering systems. More importantly though

Comparison of deformation mechanics for two different carbonates: oolitic limestone and laminites

NASA Astrophysics Data System (ADS)

Zihms, Stephanie; Lewis, Helen; Couples, Gary; Hall, Stephen; Somerville, Jim

2016-04-01

Carbonate rocks form under a range of conditions which leads to a diverse rock group. Even though carbonates are overall mineralogically simple, the solid-space distribution ranges from simple compositions such as oolitic limestones to highly complex networks of pores and solids as seen in coquinas. Their fundamental mechanical behaviour has been identified to be like clastic rocks (Vajdova 2004, Brantut, Heap et al. 2014). However it is very likely that this observation is not true for more complex carbonates. Triaxial tests were performed on cylindrical samples of two different carbonates; a) oolitic limestone (Bicqueley quarry, France) and b) laminite (Ariripe basin, Brazil). The samples were deformed under confining pressures of 8, 12 and 20MPa, and 20, 30 and 40MPa, respectively. All tests were stopped as soon as peak load was observed to preserve as many deformation characteristics as possible. Photographs of the samples were taken before and after deformation to allow surface analysis of deformation features. Additionally, samples were analysed post-deformation with X-ray tomography (XRT) (using the Zeiss XRadia XRM 520 at the 4D Imaging Lab at Lund University). The 3D tomography images represent the post-deformation samples' density distribution, allowing detailed, non-destructive, 3D analysis of the deformation features that developed in the triaxial testing, including the complex geometries and interactions of fractures, deformation bands and sedimentary layering. They also provide an insight into the complexity of deformation features produced due to the carbonate response. Initial results show that the oolitic limestone forms single shear bands almost the length of the sample, exhibiting similar characteristics to sandstones deformed under similar conditions. These features are observed for all three applied loads. The laminate sample deformed at the lowest confining pressure exhibits compactive features. However, the laminite samples deformed at the

Mechanical strain energy shuttle for aircraft morphing via wing twist or structural deformation

NASA Astrophysics Data System (ADS)

Clingman, Dan J.; Ruggeri, Robert T.

2004-07-01

Direct structural deformation to achieve aerodynamic benefit is difficult because large actuators must supply energy for structural strain and aerodynamic loads. This ppaer presents a mechanism that allows most of the energy required to twist or deform a wing to be stored in descrete springs. When this device is used, only sufficient energy is provided to control the position of the wing. This concept allows lightweight actuators to perform wing twisting and other structural distortions, and it reduces the onboard mass of the wing-twist system. The energy shuttle can be used with any actuator and it has been adapted for used with shape memory alloy, piezoelectric, and electromagnetic actuators.

Microstructural Evolution and Dynamic Softening Mechanisms of Al-Zn-Mg-Cu Alloy during Hot Compressive Deformation

PubMed Central

Shi, Cangji; Lai, Jing; Chen, X.-Grant

2014-01-01

The hot deformation behavior and microstructural evolution of an Al-Zn-Mg-Cu (7150) alloy was studied during hot compression at various temperatures (300 to 450 °C) and strain rates (0.001 to 10 s−1). A decline ratio map of flow stresses was proposed and divided into five deformation domains, in which the flow stress behavior was correlated with different microstructures and dynamic softening mechanisms. The results reveal that the dynamic recovery is the sole softening mechanism at temperatures of 300 to 400 °C with various strain rates and at temperatures of 400 to 450 °C with strain rates between 1 and 10 s−1. The level of dynamic recovery increases with increasing temperature and with decreasing strain rate. At the high deformation temperature of 450 °C with strain rates of 0.001 to 0.1 s−1, a partially recrystallized microstructure was observed, and the dynamic recrystallization (DRX) provided an alternative softening mechanism. Two kinds of DRX might operate at the high temperature, in which discontinuous dynamic recrystallization was involved at higher strain rates and continuous dynamic recrystallization was implied at lower strain rates. PMID:28788454

Effect of Cooling Mode on Microstructure and Mechanical Properties of Pipeline Steel for Strain Based Design and Research on its Deformation Mechanism

NASA Astrophysics Data System (ADS)

Hesong, Zhang; Yonglin, Kang

With the rapid development of oil and gas industry long distance pipelines inevitably pass through regions with complex geological activities. In order to avoid large deformation the pipelines must be designed based on strain criteria. In this paper the alloy system of X80 high deformability pipeline steel was designed which was 0.25%Mo-0.05%C-1.75%Mn. The effect of controlled cooling process on microstructure and mechanical properties of X80 high deformability pipeline steel were systematically investigated. Through the two-stage controlled cooling process the microstructure of the X80 high deformability pipeline steel were ferrite, bainite and M/A island. There were two kinds of ferrite which were polygonal ferrite (PF) and quasi-polygonal ferrite (QF). The bainite was granular bainite ferrite (GF). Along with the decrease of the start cooling temperature, the volume fraction of ferrite and M/A both increased, the yield ratio (Y/T) decreased, the uniform elongation (uEl) increased firstly with the content of ferrite increased but then decreased with the content and size of M/A increased. When the finish cooling temperature decreasing, the size of M/A became finer. As the start cooling temperature was 690 °C and the finish cooling temperature was 450 °C the volume fraction of ferrite was 23%, the size of ferrite grain was 5μm, the size of M/A island was below 1μm and the structure uniformity was the best. The deformation mechanism of X80 high deformability pipeline steel was analyzed. The best way to improve the work hardening rate was reducing the size of M/A islands on the premise of a certain volume fraction. The decreasing path of instantaneous strain hardening index (n*-value) showed three stages in the deformation process. The n*-value kept stable in the second stage, the reason was that the retained austenite transformed into martensite and the phase transition improved the strain hardening ability of the microstructure. This phenomenon was called

Deformation mechanisms during nanoindentation of sodium borosilicate glasses of nuclear interest.

PubMed

Kilymis, D A; Delaye, J-M

2014-07-07

In this paper we analyze results of Molecular Dynamics simulations of Vickers nanoindentation, performed for sodium borosilicate glasses of interest in the nuclear industry. Three glasses have been studied in their pristine form, as well as a disordered one that is analogous to the real irradiated glass. We focused in the behavior of the glass during the nanoindentation in order to reveal the mechanisms of deformation and how they are affected by microstructural characteristics. Results have shown a strong dependence on the SiO2 content of the glass, which promotes densification due to the open structure of SiO4 tetrahedra and also due to the strength of Si-O bonds. Densification for the glasses is primarily expressed by the relative decrease of the Si-O-Si and Si-O-B angles, indicating rotation of the structural units and decrease of free volume. The increase of alkali content on the other hand results to higher plasticity of the matrix and increased shear flow. The most important effect on the deformation mechanism of the disordered glasses is that of the highly depolymerized network that will also induce shear flow and, in combination with the increased free volume, will result in the decreased hardness of these glasses, as has been previously observed.

Non-geometric fluxes, quasi-Hopf twist deformations, and nonassociative quantum mechanics

NASA Astrophysics Data System (ADS)

Mylonas, Dionysios; Schupp, Peter; Szabo, Richard J.

2014-12-01

We analyse the symmetries underlying nonassociative deformations of geometry in non-geometric R-flux compactifications which arise via T-duality from closed strings with constant geometric fluxes. Starting from the non-abelian Lie algebra of translations and Bopp shifts in phase space, together with a suitable cochain twist, we construct the quasi-Hopf algebra of symmetries that deforms the algebra of functions and the exterior differential calculus in the phase space description of nonassociative R-space. In this setting, nonassociativity is characterised by the associator 3-cocycle which controls non-coassociativity of the quasi-Hopf algebra. We use abelian 2-cocycle twists to construct maps between the dynamical nonassociative star product and a family of associative star products parametrized by constant momentum surfaces in phase space. We define a suitable integration on these nonassociative spaces and find that the usual cyclicity of associative noncommutative deformations is replaced by weaker notions of 2-cyclicity and 3-cyclicity. Using this star product quantization on phase space together with 3-cyclicity, we formulate a consistent version of nonassociative quantum mechanics, in which we calculate the expectation values of area and volume operators, and find coarse-graining of the string background due to the R-flux.

Influence of Hot Plastic Deformation in γ and (γ + α) Area on the Structure and Mechanical Properties of High-Strength Low-Alloy (HSLA) Steel.

PubMed

Sas, Jan; Kvačkaj, Tibor; Milkovič, Ondrej; Zemko, Michal

2016-11-30

The main goal of this study was to develop a new processing technology for a high-strength low-alloy (HSLA) steel in order to maximize the mechanical properties attainable at its low alloy levels. Samples of the steel were processed using thermal deformation schedules carried out in single-phase (γ) and dual-phase (γ + α) regions. The samples were rolled at unconventional finishing temperatures, their final mechanical properties were measured, and their strength and plasticity behavior was analyzed. The resulting microstructures were observed using optical and transmission electron microscopy (TEM). They consisted of martensite, ferrite and (NbV)CN precipitates. The study also explored the process of ferrite formation and its influence on the mechanical properties of the material.

Fabrication, microstructure, properties and deformation mechanisms of a nanocrystalline aluminum-iron-chromium-titanium alloy by mechanical alloying

NASA Astrophysics Data System (ADS)

Luo, Hong

A multi-phase nanocrystalline Al93Fe3Cr2Ti 2 alloy containing 30 vol.% intermetallic particles was prepared via mechanical alloying starting from elemental powders, followed by hot extrusion. The grain size of 6-45 nm can be achieved after 30-hours of milling. Thermal stability of nanostructured Al93Fe3Ti2Cr 2 alloys was investigated using a variety of analytical techniques including modulated differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy. The MA-processed Al93Fe 3Ti2Cr2 alloy in the as-milled condition was composed of an Al-based supersaturated solid solution with high internal strains. Release of internal strains, intermetallic precipitation and grain growth occurred upon heating of the MA-processed Al alloy. Nevertheless, grain growth in the MA-processed Al alloy was very limited and fcc-Al grains with sizes in the range of 20 nm were still present in the alloys after exposure to 450°C (0.77 Tm). Systematic compressive tests and modulus measurements were performed as a function of temperature and strain rate to investigate the deformation behavior and mechanisms of the nc Al-Fe-Cr-Ti alloys. High strengths and moduli at both ambient and elevated temperatures have been demonstrated. The ductility of the nc Al93Fe3Cr2Ti2 alloy depends strongly on whether the oxide film at the prior powder particle boundary has been broken down or not. The MA-processed Al93Fe3Cr 2Ti2 alloy is brittle when the oxide film is continuous at PPB, and is ductile when the oxide film is broken down into discontinuous particles during extrusion. It is argued that the compressive strength at ambient temperature is controlled by propagation of dislocations into nc fcc-Al grains, whereas the compressive strength at elevated temperature is determined by dislocation propagation as well as dynamic recovery. Since the stress for dislocation propagation into nc fcc-Al grains increases with decreasing the grain size, the smaller

How rheological heterogeneities control the internal deformation of salt giants.

NASA Astrophysics Data System (ADS)

Raith, Alexander; Urai, Janos L.

2017-04-01

Salt giants, like the North European Zechstein, consist of several evaporation cycles of different evaporites with highly diverse rheologies. Common Potassium and Magnesium (K-Mg) salt are typically 10 to 100 times less viscous as halite while stringers consisting of anhydrite and carbonates are about 100 times more viscous. In most parts, these mechanically layered bodies experienced complex deformation, resulting in large scale internal folding with ruptured stringers and shear zones, as observed in seismic images. Furthermore, locally varying evaporation history produced different mechanical stratigraphies across the salt basin. Although most of these extraordinary soft or strong layers are rather thin (<100 m) compared to the dominating halite, we propose they have first order control on the deformation and the resulting structures inside salt bodies. Numerical models representing different mechanical stratigraphies of hard and soft layers inside a salt body were performed to analyze their influence on the internal deformation during lateral salt flow. The results show that a continuous or fractured stringer is folded and thrusted during salt contraction while soft K-Mg salt layers act as internal décollement. Depending on the viscosity of the fractured stringers, the shortening is mostly compensated by either folding or thrusting. This folding has large control over the internal structure of the salt body imposing a dominating wavelength to the whole structure during early deformation. Beside strong stringers, K-Mg salt layers also influence the deformation and salt flow inside the salt pillow. Strain is accumulated in the soft layers leading to stronger salt flow near these layers and extensive deformation inside of them. Thus, if a soft layer is present near a stringer, it will experience more deformation. Additionally, the strong strain concentration in the soft layers could decouple parts of the salt body from the main deformation.

Structural evolution of fault zones in sandstone by multiple deformation mechanisms: Moab fault, southeast Utah

USGS Publications Warehouse

Davatzes, N.C.; Eichhubl, P.; Aydin, A.

2005-01-01

Faults in sandstone are frequently composed of two classes of structures: (1) deformation bands and (2) joints and sheared joints. Whereas the former structures are associated with cataclastic deformation, the latter ones represent brittle fracturing, fragmentation, and brecciation. We investigated the distribution of these structures, their formation, and the underlying mechanical controls for their occurrence along the Moab normal fault in southeastern Utah through the use of structural mapping and numerical elastic boundary element modeling. We found that deformation bands occur everywhere along the fault, but with increased density in contractional relays. Joints and sheared joints only occur at intersections and extensional relays. In all locations , joints consistently overprint deformation bands. Localization of joints and sheared joints in extensional relays suggests that their distribution is controlled by local variations in stress state that are due to mechanical interaction between the fault segments. This interpretation is consistent with elastic boundary element models that predict a local reduction in mean stress and least compressive principal stress at intersections and extensional relays. The transition from deformation band to joint formation along these sections of the fault system likely resulted from the combined effects of changes in remote tectonic loading, burial depth, fluid pressure, and rock properties. In the case of the Moab fault, we conclude that the structural heterogeneity in the fault zone is systematically related to the geometric evolution of the fault, the local state of stress associated with fault slip , and the remote loading history. Because the type and distribution of structures affect fault permeability and strength, our results predict systematic variations in these parameters with fault evolution. ?? 2004 Geological Society of America.

Phase diagram of tetradecyltrimethylammonium bromide (TTAB) + water + octanol system with application of mechanical deformation

NASA Astrophysics Data System (ADS)

Yavuz, Aykut Evren; Masalci, Özgür; Kazanci, Nadide

2014-11-01

Morphological properties of tetradecyltrimethylammonium bromide (TTAB) + water + octanol system in different concentrations have been studied. In the process, isotropic phase (L1) and nematic calamitic (NC), nematic discotic (ND), hexagonal E and lamellar D anizotropic mesophases have been determined by polarizing microscopy method and partial ternary phase diagram of the system set up. Textural properties of the anisotropic mesophases of the system have been discussed and their birefringence values measured. Mechanical deformation has been applied to the mesophases. The textural properties and the birefringence values have been observed to be changed by the deformation, after and before which changes have been compared.

Detection of structural changes and mechanical properties of light alloys after severe plastic deformation

NASA Astrophysics Data System (ADS)

Krasnoveikin, V. A.; Kozulin, A. A.; Skripnyak, V. A.

2017-11-01

Severe plastic deformation by equal channel angular pressing has been performed to produce light aluminum and magnesium alloy billets with ultrafine-grained structure. The physical and mechanical properties of the processed alloys are examined by studying their microstructure, measuring microhardness, yield strength, and uniaxial tensile strength. A nondestructive testing technique using three-dimensional X-ray tomography is proposed for detecting internal structural defects and monitoring damage formation in the structure of alloys subjected to severe plastic deformation. The investigation results prove the efficiency of the chosen method and selected mode of producing ultrafine-grained light alloys.

State-variable theories for nonelastic deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, C.Y.

The various concepts of mechanical equation of state for nonelastic deformation in crystalline solids, originally proposed for plastic deformation, have been recently extended to describe additional phenomena such as anelastic and microplastic deformation including the Bauschinger effect. It has been demonstrated that it is possible to predict, based on current state variables in a unified way, the mechanical response of a material under an arbitrary loading. Thus, if the evolution laws of the state variables are known, one can describe the behavior of a material for a thermal-mechanical path of interest, for example, during constant load (or stress) creep withoutmore » relying on specialized theories. Some of the existing theories of mechanical equation of state for nonelastic deformation are reviewed. The establishment of useful forms of mechanical equation of state has to depend on extensive experimentation in the same way as that involved in the development, for example, the ideal gas law. Recent experimental efforts are also reviewed. It has been possible to develop state-variable deformation models based on experimental findings and apply them to creep, cyclic deformation, and other time-dependent deformation. Attempts are being made to correlate the material parameters of the state-variable models with the microstructure of a material. 24 figures.« less

The properties of Q-deformed hyperbolic and trigonometric functions in quantum deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deta, U. A., E-mail: utamaalan@yahoo.co.id, E-mail: utamadeta@unesa.ac.id; Suparmi

2015-09-30

Quantum deformation has been studied due to its relation with applications in nuclear physics, conformal field theory, and statistical-quantum theory. The q-deformation of hyperbolic function was introduced by Arai. The application of q-deformed functions has been widely used in quantum mechanics. The properties of this two kinds of system explained in this paper including their derivative. The graph of q-deformed functions presented using Matlab. The special case is given for modified Poschl-Teller plus q-deformed Scarf II trigonometry potentials.

Large-scale deformational systems in the South Polar Layered Deposits (Promethei Lingula, Mars): "Soft-sediment" and Deep-Seated Gravitational Slope Deformations Mechanisms

NASA Astrophysics Data System (ADS)

Guallini, Luca; Brozzetti, Francesco; Marinangeli, Lucia

2012-08-01

The present study is the first attempt at a detailed structural and kinematic analysis of large-scale deformational systems observed in the South Polar Layered Deposits (SPLDs) in the Promethei Lingula (PL) margins (Mars). By systematically collecting attitude data referable to previously unknown deformational structures and defining the cross-cut relationships of the structures, we reconstructed a deformational history consisting of two superimposed, well-defined stages. The first stage is dominated by large-scale strike-slip and transtensional faults arranged into conjugate systems and delimiting shear zones that show a wide range of subsidiary structures, including normal and reverse faults, drag folds, boudins, S-C tectonites and sub-horizontal interstratal shear planes marked by sygmoidal boudins. Other typical structures referable to this event are ductile folds (locally true convolute folds) and lobes (ball-and-pillow structures) affecting certain marker beds of the succession. We suggest that the structural assemblage might be the expression of a shallow soft-sediment tectonics that possibly occurred during warm periods of the South Pole climate. The second stage seems to affect the weaker and in certain cases pre-deformed stratigraphic levels of the SPLD succession. This stage is mainly characterized by extensional deformations caused by gravity. The consequence of the deformations is the nucleation of Deep-Seated Gravitational Slope Deformations (DSGSDs) marked by typical morphostructures, such as scarps, trenches and bulging basal contractant zones. These phenomena were never observed within an ice cap. According to terrestrial modeling, these slow collapses were caused by (1) the presence of detachment levels (i.e., subhorizontal bedding planes) along which the ice-sheet margins can slide and (2) the development of listric faults within the glacial mass, which merge with sub-horizontal shear planes in the subsurface. The presence of complex

Paleocurrent analysis of a deformed Devonian foreland basin in the northern Appalachians, Maine, USA

USGS Publications Warehouse

Bradley, D.C.; Hanson, L.S.

2002-01-01

New paleocurrent data indicate that the widespread Late Silurian and Devonian flysch and molasse succession in Maine was deposited in an ancestral, migrating foreland basin adjacent to an advancing Acadian orogenic belt. The foreland-basin sequence spread across a varied Silurian paleogeography of deep basins and small islands-the vestiges of an intraoceanic arc complex that not long before had collided with the Laurentian passive margin during the Ordovician Taconic Orogeny. We report paleocurrents from 43 sites representing 12 stratigraphic units, the most robust and consistent results coming from three units: Madrid Formation (southwesterly paleoflow), Carrabassett Formation (northerly paleoflow), and Seboomook Group (westerly paleoflow). Deformation and regional metamorphism are sufficiently intense to test the limits of paleocurrent analysis requiring particular care in retrodeformation. ?? 2002 Elsevier Science B.V. All rights reserved.

The Effect of Matrix Composition on the Deformation and Failure Mechanisms in Metal Matrix Syntactic Foams during Compression.

PubMed

Kádár, Csilla; Máthis, Kristián; Knapek, Michal; Chmelík, František

2017-02-17

The influence of the matrix material on the deformation and failure mechanisms in metal matrix syntactic foams was investigated in this study. Samples with commercially pure Al (Al) and Al-12 wt % Si (AlSi12) eutectic aluminum matrix, reinforced by hollow ceramic spheres, were compressed at room temperature. Concurrently, the acoustic emission response and the strain field development on the surface were monitored in-situ. The results indicate that the plastic deformation of the cell walls is the governing mechanism in the early stage of straining for both types of foams. At large stresses, deformation bands form both in the Al and AlSi12 foam. In Al foam, cell walls collapse in a large volume. In contrast, the AlSi12 foam is more brittle; therefore, the fracture of precipitates and the crushing of the matrix take place within a distinctive deformation band, along with an occurrence of a significant stress drop. The onset stress of ceramic sphere failure was shown to be not influenced by the matrix material. The in-situ methods provided complementary data which further support these results.

Effects of Structural Deformations of the Crank-Slider Mechanism on the Estimation of the Instantaneous Engine Friction Torque

NASA Astrophysics Data System (ADS)

CHALHOUB, N. G.; NEHME, H.; HENEIN, N. A.; BRYZIK, W.

1999-07-01

The focus on the current study is to assess the effects of structural deformations of the crankshaft/connecting-rod/piston mechanism on the computation of the instantaneous engine friction torque. This study is performed in a fully controlled environment in order to isolate the effects of structural deformations from those of measurement errors or noise interference. Therefore, a detailed model, accounting for the rigid and flexible motions of the crank-slider mechanism and including engine component friction formulations, is considered in this study. The model is used as a test bed to generate the engine friction torque,Tfa, and to predict the rigid and flexible motions of the system in response to the cylinder gas pressure. The torsional vibrations and the rigid body angular velocity of the crankshaft, as predicted by the detailed model of the crank-slider mechanism, are used along with the engine load torque and the cylinder gas pressure in the (P-ω) method to estimate the engine friction torque,Tfe. This method is well suited for the purpose of this study because its formulation is based on the rigid body model of the crank-slider mechanism. The digital simulation results demonstrate that the exclusion of the structural deformations of the crank-slider mechanism from the formulation of the (P-ω) method leads to an overestimation of the engine friction torque near the top-dead-center (TDC) position of the piston under firing conditions. Moreover, for the remainder of the engine cycle, the estimated friction torque exhibits large oscillations and takes on positive numerical values as if it is inducing energy into the system. Thus, the adverse effects of structural deformations of the crank-slider mechanism on the estimation of the engine friction torque greatly differ in their nature from one phase of the engine cycle to another.

Dislocation-accommodated grain boundary sliding as the major deformation mechanism of olivine in the Earth's upper mantle.

PubMed

Ohuchi, Tomohiro; Kawazoe, Takaaki; Higo, Yuji; Funakoshi, Ken-Ichi; Suzuki, Akio; Kikegawa, Takumi; Irifune, Tetsuo

2015-10-01

Understanding the deformation mechanisms of olivine is important for addressing the dynamic processes in Earth's upper mantle. It has been thought that dislocation creep is the dominant mechanism because of extrapolated laboratory data on the plasticity of olivine at pressures below 0.5 GPa. However, we found that dislocation-accommodated grain boundary sliding (DisGBS), rather than dislocation creep, dominates the deformation of olivine under middle and deep upper mantle conditions. We used a deformation-DIA apparatus combined with synchrotron in situ x-ray observations to study the plasticity of olivine aggregates at pressures up to 6.7 GPa (that is, ~200-km depth) and at temperatures between 1273 and 1473 K, which is equivalent to the conditions in the middle region of the upper mantle. The creep strength of olivine deforming by DisGBS is apparently less sensitive to pressure because of the competing pressure-hardening effect of the activation volume and pressure-softening effect of water fugacity. The estimated viscosity of olivine controlled by DisGBS is independent of depth and ranges from 10(19.6) to 10(20.7) Pa·s throughout the asthenospheric upper mantle with a representative water content (50 to 1000 parts per million H/Si), which is consistent with geophysical viscosity profiles. Because DisGBS is a grain size-sensitive creep mechanism, the evolution of the grain size of olivine is an important process controlling the dynamics of the upper mantle.

Freezing-induced deformation of biomaterials in cryomedicine

NASA Astrophysics Data System (ADS)

Ozcelikkale, Altug

Cryomedicine utilizes low temperature treatments of biological proteins, cells and tissues for cryopreservation, materials processing and cryotherapy. Lack of proper understanding of cryodamage that occurs during these applications remains to be the primary bottleneck for development of successful tissue cryopreservation and cryosurgery procedures. An engineering approach based on a view of biological systems as functional biomaterials can help identify, predict and control the primary cryodamage mechanisms by developing an understanding of underlying freezing-induced biophysical processes. In particular, freezing constitutes the main structural/mechanical origin of cryodamage and results in significant deformation of biomaterials at multiple length scales. Understanding of these freezing-induced deformation processes and their effects on post-thaw biomaterial functionality is currently lacking but will be critical to engineer improved cryomedicine procedures. This dissertation addresses this problem by presenting three separate but related studies of freezing-induced deformation at multiple length scales including nanometer-scale protein fibrils, single cells and whole tissues. A combination of rigorous experimentation and computational modeling is used to characterize post-thaw biomaterial structure and properties, predict biomaterial behavior and assess its post-thaw biological functionality. Firstly, freezing-induced damage on hierarchical extracellular matrix structure of collagen is investigated at molecular, fibril and matrix levels. Results indicate to a specific kind of fibril damage due to freezing-induced expansion of intrafibrillar fluid. This is followed by a study of freezing-induced cell and tissue deformation coupled to osmotically driven cellular water transport. Computational and semi empirical modeling of these processes indicate that intracellular deformation of the cell during freezing is heterogeneous and can interfere with cellular water

Constitutive modeling and dynamic softening mechanism during hot deformation of an ultra-pure 17%Cr ferritic stainless steel stabilized with Nb

NASA Astrophysics Data System (ADS)

Gao, Fei; Liu, Zhenyu; Misra, R. D. K.; Liu, Haitao; Yu, Fuxiao

2014-09-01

The hot deformation behavior of an ultra-pure 17%Cr ferritic stainless steel was studied in the temperature range of 750-1000 °C and strain rates of 0.5 to 10 s-1 using isothermal hot compression tests in a thermomechanical simulator. The microstructural evolution was investigated using electron backscattered diffraction and transmission electron microscopy. A modified constitutive equation considering the effect of strain on material constant was developed, which predicted the flow stress for the deformation conditions studied, except at 950 °C in 1 s-1 and 900 °C in 10 s-1. Decreasing deformation temperature and increasing strain was beneficial in refining the microstructure. Decreasing deformation temperature, the in-grain shear bands appeared in the microstructure. It is suggested that the dynamic softening mechanism is closely related to deformation temperature. At low deformation temperature, dynamic recovery was major softening mechanism and no dynamic recrystallization occurred. At high deformation temperature, dynamic softening was explained in terms of efficient dynamic recovery and limited continuous dynamic recrystallization. A drop in the flow stress was not found due to very small fraction of new grains nucleated during dynamic recrystallization.

A 3D Analysis of Rock Block Deformation and Failure Mechanics Using Terrestrial Laser Scanning

NASA Astrophysics Data System (ADS)

Rowe, Emily; Hutchinson, D. Jean; Kromer, Ryan A.; Edwards, Tom

2017-04-01

planes on the slope that were confining the block. It is concluded that rock blocks in White Canyon may be classified as one of five main failure mechanisms based on their pre-failure deformation and structure: planar slide, topple, rotation, wedge, and overhang, with overhang failures representing a large portion of rockfalls in this area. Overhang rockfalls in the White Canyon are characterized by blocks that (a) are not supported by an underlying discontinuity plane, and (b) generally do not exhibit pre-failure deformation. Though overhanging rock blocks are a structural subset of toppling failure, their behavior suggests a different mechanism of detachment. Future work will further populate the present database of rockfalls in White Canyon and will expand the study to include other sites along this corridor. The ultimate goal of this research is to establish warning thresholds based on deformation magnitudes for rockfalls in White Canyon to assist Canadian railways in better understanding and managing these slopes.

Soft sediment deformation structures in the Maastrichtian Ajali Formation Western Flank of Anambra Basin, Southern Nigeria

NASA Astrophysics Data System (ADS)

Olabode, Solomon Ojo

2014-01-01

Soft sediment deformation structures were recognized in the Maastrichtian shallow marine wave to tide influenced regressive sediments of Ajali Formation in the western flank of Anambra basin, southern Nigerian. The soft sediment deformation structures were in association with cross bedded sands, clay and silt and show different morphological types. Two main types recognised are plastic deformations represented by different types of recumbent folds and injection structure represented by clastic dykes. Other structures in association with the plastic deformation structures include distorted convolute lamination, subsidence lobes, pillars, cusps and sand balls. These structures are interpreted to have been formed by liquefaction and fluidization mechanisms. The driving forces inferred include gravitational instabilities and hydraulic processes. Facies analysis, detailed morphologic study of the soft sediment deformation structures and previous tectonic history of the basin indicate that the main trigger agent for deformation is earthquake shock. The soft sediment deformation structures recognised in the western part of Anambra basin provide a continuous record of the tectonic processes that acted on the regressive Ajali Formation during the Maastrichtian.

High Temperature Deformation Mechanism in Hierarchical and Single Precipitate Strengthened Ferritic Alloys by In Situ Neutron Diffraction Studies.

PubMed

Song, Gian; Sun, Zhiqian; Li, Lin; Clausen, Bjørn; Zhang, Shu Yan; Gao, Yanfei; Liaw, Peter K

2017-04-07

The ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni 2 TiAl/NiAl or single-Ni 2 TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxation behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.

High Temperature Deformation Mechanism in Hierarchical and Single Precipitate Strengthened Ferritic Alloys by In Situ Neutron Diffraction Studies

PubMed Central

Song, Gian; Sun, Zhiqian; Li, Lin; Clausen, Bjørn; Zhang, Shu Yan; Gao, Yanfei; Liaw, Peter K.

2017-01-01

The ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni2TiAl/NiAl or single-Ni2TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxation behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate. PMID:28387230

The deformation mechanisms and size effects of single-crystal magnesium

NASA Astrophysics Data System (ADS)

Byer, Cynthia M.

In this work, we seek to understand the deformation mechanisms and size effects of single-crystal magnesium at the micrometer scale through both microcompression experiments and finite element simulations. Microcompression experiments are conducted to investigate the impact of initial dislocation density and orientation on size effects. Micropillars are fabricated using a focused ion beam and tested in a Nanoindenter using a diamond fiat tip as a compression platen. Two different initial dislocation densities are examined for [0001] oriented micropillars. Our results demonstrate that decreasing the initial dislocation density results in an increased size effect in terms of increased strength and stochasticity. Microcompression along the [23¯14] axis results in much lower strengths than for [0001] oriented samples. Post-mortem analysis reveals basal slip in both [0001] and [23¯14] micropillars. The application of a stochastic probability model shows good agreement between theoretical predictions and experimental results for size effects with our values of initial dislocation density and micropillar dimensions. Size effects are then incorporated into a single-crystal plasticity model (modified from Zhang and Joshi [1]) implemented in ABAQUS/STANDARD as a user-material subroutine. The model successfully captures the phenomena typically associated with size effects of increasing stochasticity and strength with decreasing specimen size and also accounts for the changing trends resulting from variations in initial dislocation density that we observe in the experiments. Finally, finite element simulations are performed with the original (traditional, without size effects) crystal plasticity model [1] to investigate the relative activities of the deformation modes of single-crystal magnesium for varying degrees of misalignment in microcompression. The simulations reveal basal activity in all micropillars, even for perfectly aligned compression along the [0001] axis

Quantum mechanics on the h-deformed quantum plane

NASA Astrophysics Data System (ADS)

Cho, Sunggoo

1999-03-01

We find the covariant deformed Heisenberg algebra and the Laplace-Beltrami operator on the extended h-deformed quantum plane and solve the Schrödinger equations explicitly for some physical systems on the quantum plane. In the commutative limit the behaviour of a quantum particle on the quantum plane becomes that of the quantum particle on the Poincaré half-plane, a surface of constant negative Gaussian curvature. We show that the bound state energy spectra for particles under specific potentials depend explicitly on the deformation parameter h. Moreover, it is shown that bound states can survive on the quantum plane in a limiting case where bound states on the Poincaré half-plane disappear.

Structure and mechanical properties of aging Al-Li-Cu-Zr-Sc-Ag alloy after severe plastic deformation by high-pressure torsion

NASA Astrophysics Data System (ADS)

Kaigorodova, L. I.; Rasposienko, D. Yu.; Pushin, V. G.; Pilyugin, V. P.; Smirnov, S. V.

2015-04-01

The structural and phase transformations have been studied in aging commercial aluminum-lithium alloy Al-1.2 Li-3.2 Cu-0.09 Zr-0.11 Sc-0.4 Ag-0.3 Mg in the as-delivered state and after severe plastic deformation by torsion for 1, 5 and 10 revolutions under a high pressure of 4 GPa. Deformation-induced nanofragmentation and dynamic recrystallization have been found to occur in the alloy. The degree of recrystallization increases with deformation. Nanofragmentation and recrystallization processes are accompanied by the deformation-induced decomposition of solid solution and changes in both the nucleation mechanism of precipitation and the phase composition of the alloy. The influence of a nanostructured nanophase state of the alloy on its mechanical properties (microhardness, plasticity, elastic modulus, and stiffness) is discussed.

The effect of aluminum alloying on strength properties and deformation mechanisms of the <123> Hadfield steel single crystals

NASA Astrophysics Data System (ADS)

Astafurova, E. G.; Tukeev, M. S.; Chumlyakov, Yu. I.

2007-10-01

The role of aluminum alloying on strength properties and deformation mechanisms (slip, twinning) of <123> single crystals of Hadfield steel under tensile loading at T = 300 K is demonstrated. It is found out that aluminum alloying suppresses twinning deformation in the <123> single crystals and, during slip, results in a dislocation structure change from a uniform dislocation distribution to a planar dislocation structure.

A monolithic deformable mirror with latchable mechanical actuation (LATCHAMAN) for space-borne telescopes

NASA Astrophysics Data System (ADS)

Enya, Keigo; Kataza, Hirokazu; Fukushima, Mitsuhiro; Mitsui, Kenji; Okada, Norio; Iwashita, Hikaru; Haze, Kanae; Takahashi, Aoi; Kotani, Takayuki; Yamamuro, Tomoyasu; Kobayashi, Hitomi

2014-09-01

We present the concept, design, fabrication, and evaluation of a new deformable mirror (DM), which is latchable, compact, and designed to be applicable for cryogenic environments. The main body of a prototype DM was fabricated from a monolithic cuboid of aluminum using wire electrical discharge machining (EDM). A flexible structure was constructed inside the block by 3-dimensionally crossed hollowing using the EDM. The prototype has 6 × 6 channels, and its volume is 27 mm × 27 mm × 30 mm. The mirror was formed on the surface of the aluminum block using a highprecision NC lathe. The surface figure of the mirror was evaluated and 34 nm rms was obtained. The evaluated surface roughness for the center and off-center areas of the mirror was 9.2 nm rms and 7.6 nm rms, respectively Screws set at the back of the block deform the mirror via springs and the internal flexible structure. We present our first demonstration of deformation of the mirror carried out at ambient temperature. The relationship between the displacement of the screws and the deformation of the mirror was evaluated. Consequently, a linear relationship was confirmed, and no significant hysteresis was found. The application of such mirrors to telescopes used for various different objectives is discussed. We conclude that a DM based on our concept can be used for wavefront correction of space-borne telescopes, especially in the infrared wavelength region.

Gravity and thermal deformation of large primary mirror in space telescope

NASA Astrophysics Data System (ADS)

Wang, Xin; Jiang, Shouwang; Wan, Jinlong; Shu, Rong

2016-10-01

The technology of integrating mechanical FEA analysis with optical estimation is essential to simulate the gravity deformation of large main mirror and the thermal deformation such as static or temperature gradient of optical structure. We present the simulation results of FEA analysis, data processing, and image performance. Three kinds of support structure for large primary mirror which have the center holding structure, the edge glue fixation and back support, are designed and compared to get the optimal gravity deformation. Variable mirror materials Zerodur/SiC are chosen and analyzed to obtain the small thermal gradient distortion. The simulation accuracy is dependent on FEA mesh quality, the load definition of structure, the fitting error from discrete data to smooth surface. A main mirror with 1m diameter is designed as an example. The appropriate structure material to match mirror, the central supporting structure, and the key aspects of FEA simulation are optimized for space application.

Biomechanical simulation of thorax deformation using finite element approach.

PubMed

Zhang, Guangzhi; Chen, Xian; Ohgi, Junji; Miura, Toshiro; Nakamoto, Akira; Matsumura, Chikanori; Sugiura, Seiryo; Hisada, Toshiaki

2016-02-06

The biomechanical simulation of the human respiratory system is expected to be a useful tool for the diagnosis and treatment of respiratory diseases. Because the deformation of the thorax significantly influences airflow in the lungs, we focused on simulating the thorax deformation by introducing contraction of the intercostal muscles and diaphragm, which are the main muscles responsible for the thorax deformation during breathing. We constructed a finite element model of the thorax, including the rib cage, intercostal muscles, and diaphragm. To reproduce the muscle contractions, we introduced the Hill-type transversely isotropic hyperelastic continuum skeletal muscle model, which allows the intercostal muscles and diaphragm to contract along the direction of the fibres with clinically measurable muscle activation and active force-length relationship. The anatomical fibre orientations of the intercostal muscles and diaphragm were introduced. Thorax deformation consists of movements of the ribs and diaphragm. By activating muscles, we were able to reproduce the pump-handle and bucket-handle motions for the ribs and the clinically observed motion for the diaphragm. In order to confirm the effectiveness of this approach, we simulated the thorax deformation during normal quiet breathing and compared the results with four-dimensional computed tomography (4D-CT) images for verification. Thorax deformation can be simulated by modelling the respiratory muscles according to continuum mechanics and by introducing muscle contractions. The reproduction of representative motions of the ribs and diaphragm and the comparison of the thorax deformations during normal quiet breathing with 4D-CT images demonstrated the effectiveness of the proposed approach. This work may provide a platform for establishing a computational mechanics model of the human respiratory system.

Electron backscatter and X-ray diffraction studies on the deformation and annealing textures of austenitic stainless steel 310S

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nezakat, Majid, E-mail: majid.nezakat@usask.ca

We studied the texture evolution of thermo-mechanically processed austenitic stainless steel 310S. This alloy was cold rolled up to 90% reduction in thickness and subsequently annealed at 1050 °C. At the early stages of deformation, strain-induced martensite was formed from deformed austenite. By increasing the deformation level, slip mechanism was found to be insufficient to accommodate higher deformation strains. Our results demonstrated that twinning is the dominant deformation mechanism at higher deformation levels. Results also showed that cold rolling in unidirectional and cross rolling modes results in Goss/Brass and Brass dominant textures in deformed samples, respectively. Similar texture components aremore » observed after annealing. Thus, the annealing texture was greatly affected by texture of the deformed parent phase and martensite did not contribute as it showed an athermal reversion during annealing. Results also showed that when the fraction of martensite exceeds a critical point, its grain boundaries impeded the movement of austenite grain boundaries during annealing. As a result, recrystallization incubation time would increase. This caused an incomplete recrystallization of highly deformed samples, which led to a rational drop in the intensity of the texture components. - Highlights: •Thermo-mechanical processing through different cold rolling modes can induce different textures. •Martensite reversion is athermal during annealing. •Higher fraction of deformation-induced martensite can increase the annealing time required for complete recrystallization. •Annealing texture is mainly influenced by the deformation texture of austenite.« less

Understanding the mechanical coupling between magma emplacement and the resulting deformation: the example of saucer-shaped sills

NASA Astrophysics Data System (ADS)

Galland, O.; Neumann, E. R.; Planke, S.

2009-12-01

The mechanical coupling between magma intrusions and the surrounding rocks plays a major role in the emplacement of volcanic plumbing systems. The deformation associated with magma emplacement has been widely studied, such as caldera inflation/deflation, volcano deformation during dike intrusion, and doming above laccoliths. However, the feedback processes, i.e. the effect of deformation resulting from intruding magma on the propagation of the intrusion itself, have rarely been studied. Saucer-shaped sills are adequate geological objects to understand such processes. Indeed, observation show that saucer-shaped sills are often associated with dome-like structures affecting the overlying sediments. In addition, there is a clear geometrical relation between the sills and the domes: the dome diameters are almost identical to those of saucers, and the tips of the inclined sheets of saucers are superimposed on the edges of the domes. In this presentation, we report on experimental investigations of the emplacement mechanisms of saucer-shaped sills and associated deformation. The model materials were (1) cohesive fine-grained silica flour, representing brittle crust, and (2) molten low-viscosity oil, representing magma. A weak layer located at the top of the injection inlet simulates strata. The main variable parameter is injection depth. During experiments, the surface of the model is digitalized through a structured light technique based on the moiré projection principle. Such a tool provides topographic maps of the surface of the model and allows a periodic (every 1.5 s) monitoring of the model topography. When the model magma starts intruding, a symmetrical dome rises above the inlet. Subsequently, the dome inflates and widens, and then evolves to a plateau-like feature, with nearly flat upper surface and steep sides. At the end of the experiments, the intruding liquid erupts at the edge of the plateau. The intrusions formed in the experiments are saucer-shaped sills

Cardiac fluid dynamics meets deformation imaging.

PubMed

Dal Ferro, Matteo; Stolfo, Davide; De Paris, Valerio; Lesizza, Pierluigi; Korcova, Renata; Collia, Dario; Tonti, Giovanni; Sinagra, Gianfranco; Pedrizzetti, Gianni

2018-02-20

Cardiac function is about creating and sustaining blood in motion. This is achieved through a proper sequence of myocardial deformation whose final goal is that of creating flow. Deformation imaging provided valuable contributions to understanding cardiac mechanics; more recently, several studies evidenced the existence of an intimate relationship between cardiac function and intra-ventricular fluid dynamics. This paper summarizes the recent advances in cardiac flow evaluations, highlighting its relationship with heart wall mechanics assessed through the newest techniques of deformation imaging and finally providing an opinion of the most promising clinical perspectives of this emerging field. It will be shown how fluid dynamics can integrate volumetric and deformation assessments to provide a further level of knowledge of cardiac mechanics.

The Effect of Matrix Composition on the Deformation and Failure Mechanisms in Metal Matrix Syntactic Foams during Compression

PubMed Central

Kádár, Csilla; Máthis, Kristián; Knapek, Michal; Chmelík, František

2017-01-01

The influence of the matrix material on the deformation and failure mechanisms in metal matrix syntactic foams was investigated in this study. Samples with commercially pure Al (Al) and Al-12 wt % Si (AlSi12) eutectic aluminum matrix, reinforced by hollow ceramic spheres, were compressed at room temperature. Concurrently, the acoustic emission response and the strain field development on the surface were monitored in-situ. The results indicate that the plastic deformation of the cell walls is the governing mechanism in the early stage of straining for both types of foams. At large stresses, deformation bands form both in the Al and AlSi12 foam. In Al foam, cell walls collapse in a large volume. In contrast, the AlSi12 foam is more brittle; therefore, the fracture of precipitates and the crushing of the matrix take place within a distinctive deformation band, along with an occurrence of a significant stress drop. The onset stress of ceramic sphere failure was shown to be not influenced by the matrix material. The in-situ methods provided complementary data which further support these results. PMID:28772556

Soft Tissue Deformations Contribute to the Mechanics of Walking in Obese Adults

PubMed Central

Fu, Xiao-Yu; Zelik, Karl E.; Board, Wayne J.; Browning, Raymond C.; Kuo, Arthur D.

2014-01-01

Obesity not only adds to the mass that must be carried during walking, but also changes body composition. Although extra mass causes roughly proportional increases in musculoskeletal loading, less well understood is the effect of relatively soft and mechanically compliant adipose tissue. Purpose To estimate the work performed by soft tissue deformations during walking. The soft tissue would be expected to experience damped oscillations, particularly from high force transients following heel strike, and could potentially change the mechanical work demands for walking. Method We analyzed treadmill walking data at 1.25 m/s for 11 obese (BMI > 30 kg/m2) and 9 non-obese (BMI < 30 kg/m2) adults. The soft tissue work was quantified with a method that compares the work performed by lower extremity joints as derived using assumptions of rigid body segments, with that estimated without rigid body assumptions. Results Relative to body mass, obese and non-obese individuals perform similar amounts of mechanical work. But negative work performed by soft tissues was significantly greater in obese individuals (p= 0.0102), equivalent to about 0.36 J/kg vs. 0.27 J/kg in non-obese individuals. The negative (dissipative) work by soft tissues occurred mainly after heel strike, and for obese individuals was comparable in magnitude to the total negative work from all of the joints combined (0.34 J/kg vs. 0.33 J/kg for obese and non-obese adults, respectively). Although the joints performed a relatively similar amount of work overall, obese individuals performed less negative work actively at the knee. Conclusion The greater proportion of soft tissues in obese individuals results in substantial changes in the amount, location, and timing of work, and may also impact metabolic energy expenditure during walking. PMID:25380475

Mechanisms of grain refinement in aluminum alloys in the process of severe plastic deformation

NASA Astrophysics Data System (ADS)

Kaibyshev, R. O.; Mazurina, I. A.; Gromov, D. A.

2006-01-01

A study of the mechanisms of grain refinement in the process of severe plastic deformation of two aluminum alloys, i.e., 2219 bearing nanometric particles of Al3Zr and low-alloy Al-3% Cu, is described. The alloys are deformed by the method of equal channel angular pressing at 250°C to a maximum strain degree of about 12. The angles of (sub)grain boundaries in alloy 2219 are determined with the help of transmission electron microscopy by the method of Kikuchi lines. The evolution of the microstructure in alloy Al-3% Cu is studied with the help of grain-boundary maps obtained by the method of electron back-scattered diffraction.

On justification of efficient Energy-Force parameters of Hydraulic-excavator main mechanisms

NASA Astrophysics Data System (ADS)

Komissarov, Anatoliy; Lagunova, Yuliya; Shestakov, Viktor; Lukashuk, Olga

2018-03-01

The article formulates requirements for energy-efficient designs of the operational equipment of a hydraulic excavator (its boom, stick and bucket) and defines, for a mechanism of that equipment, a new term “performance characteristic”. The drives of main rotation mechanisms of the equipment are realized by hydraulic actuators (hydraulic cylinders) and transmission (leverage) mechanisms, with the actuators (the cylinders themselves, their pistons and piston rods) also acting as links of the leverage. Those drives are characterized by the complexity of translating mechanical-energy parameters of the actuators into energy parameters of the driven links (a boom, a stick and a bucket). Relations between those parameters depend as much on the types of mechanical characteristics of the hydraulic actuators as on the types of structural schematics of the transmission mechanisms. To assess how energy-force parameters of the driven links change when a typical operation is performed, it was proposed to calculate performance characteristics of the main mechanisms as represented by a set of values of transfer functions, i.e. by functional dependences between driven links and driving links (actuators). Another term “ideal performance characteristic” of a mechanism was introduced. Based on operation-emulating models for the main mechanisms of hydraulic excavators, analytical expressions were derived to calculate kinematic and force transfer functions of the main mechanisms.

Kh. A. Rakhmatulin's scientific legacy in the field of mechanics of deformable rigid bodies

NASA Astrophysics Data System (ADS)

Goldstein, R. V.; Dem'yanov, Yu. A.; Nikitin, L. V.; Smirnov, N. N.; Shemyakin, E. I.

2010-02-01

Kh. A. Rakhmatulin's scientific activity was aimed at solving the most important scientific and technical problems encountered by the country. Khalil Akhmetovich was a unique combination of a theorist and an experimenter, an engineer and an inventor, a talented teacher and a scientific research manager. He fruitfully worked in mechanics of deformable solids (the corresponding results are surveyed in the present paper) as well as in fluid mechanics (as described in detail in the journal [1] dedicated to his memory).

Fault Mechanics and Post-seismic Deformation at Bam, SE Iran

NASA Astrophysics Data System (ADS)

Wimpenny, S. E.; Copley, A.

2017-12-01

The extent to which aseismic deformation relaxes co-seismic stress changes on a fault zone is fundamental to assessing the future seismic hazard following any earthquake, and in understanding the mechanical behaviour of faults. We used models of stress-driven afterslip and visco-elastic relaxation, in conjunction with a dense time series of post-seismic InSAR measurements, to show that there has been minimal release of co-seismic stress changes through post-seismic deformation following the 2003 Mw 6.6 Bam earthquake. Our modelling indicates that the faults at Bam may remain predominantly locked, and that the co- plus inter-seismically accumulated elastic strain stored down-dip of the 2003 rupture patch may be released in a future Mw 6 earthquake. Modelling also suggests parts of the fault that experienced post-seismic creep between 2003-2009 overlapped with areas that also slipped co-seismically. Our observations and models also provide an opportunity to probe how aseismic fault slip leads to the growth of topography at Bam. We find that, for our modelled afterslip distribution to be consistent with forming the sharp step in the local topography at Bam over repeated earthquake cycles, and also to be consistent with the geodetic observations, requires either (1) far-field tectonic loading equivalent to a 2-10 MPa deviatoric stress acting across the fault system, which suggests it supports stresses 60-100 times less than classical views of static fault strength, or (2) that the fault surface has some form of mechanical anisotropy, potentially related to corrugations on the fault plane, that controls the sense of slip.

Mechanotransduction Mechanisms for Intraventricular Diastolic Vortex Forces and Myocardial Deformations: Part 1

PubMed Central

Pasipoularides, Ares

2015-01-01

Epigenetic mechanisms are fundamental in cardiac adaptations, remodeling, reverse remodeling, and disease. This 2-article series proposes that variable forces associated with diastolic RV/LV rotatory intraventricular flows can exert physiologically and clinically important, albeit still unappreciated, epigenetic actions influencing functional and morphological cardiac adaptations and/or maladaptations. Taken in-toto, the 2-part survey formulates a new paradigm in which intraventricular diastolic filling vortex-associated forces play a fundamental epigenetic role, and examines how heart cells react to these forces. The objective is to provide a perspective on vortical epigenetic effects, to introduce emerging ideas and suggest directions of multidisciplinary translational research. The main goal is to make pertinent biophysics and cytomechanical dynamic systems concepts accessible to interested translational and clinical cardiologists. I recognize that the diversity of the epigenetic problems can give rise to a diversity of approaches and multifaceted specialized research undertakings. Specificity may dominate the picture. However, I take a contrasting approach. Are there concepts that are central enough that they should be developed in some detail? Broadness competes with specificity. Would however this viewpoint allow for a more encompassing view that may otherwise be lost by generation of fragmented results? Part 1 serves as a general introduction, focusing on background concepts, on intracardiac vortex imaging methods, and on diastolic filling vortex-associated forces acting epigenetically on RV/LV endocardium and myocardium. Part 2 will describe pertinent available pluridisciplinary knowledge/research relating to mechanotransduction mechanisms for intraventricular diastolic vortex forces and myocardial deformations and to their epigenetic actions on myocardial and ventricular function and adaptations. PMID:25624114

Plastic Deformation and Failure Analysis of Phase Change Random Access Memory

NASA Astrophysics Data System (ADS)

Yang; Hongxin; Shi; Luping; Lee; Koon, Hock; Zhao; Rong; Li; Jianming; Lim; Guan, Kian; Chong; Chong, Tow

2009-04-01

Although lateral phase change random access memory (PCRAM) has attracted a lot of interest due to its simpler fabrication process and lower current compared to ovonic unified memory (OUM), it faces a problem of poor lifetime. This paper studied relation between plastic deformation and the failure of PCRAM through both experiment and simulation. OUM and lateral PCRAM incorporating Ge2Sb2Te5 were fabricated and tested. The overwriting test showed that lifetime of OUM exceeded 106 while that of lateral PCRAM was only about 100. Using atomic force microscopy (AFM), it was found that the plastic deformation after 106 overwriting reached several tens of nm for lateral PCRAM while it was negligible for OUM. The thermo-mechanical simulation results confirmed the similar results on larger plastic deformation of lateral PCRAM than that of OUM during overwriting. As plastic deformation involves of atomic bonds breaking and reforming in phase change material, the plastic deformation may be one main reason for the failure of lateral PCRAM.

An electromechanical based deformable model for soft tissue simulation.

PubMed

Zhong, Yongmin; Shirinzadeh, Bijan; Smith, Julian; Gu, Chengfan

2009-11-01

Soft tissue deformation is of great importance to surgery simulation. Although a significant amount of research efforts have been dedicated to simulating the behaviours of soft tissues, modelling of soft tissue deformation is still a challenging problem. This paper presents a new deformable model for simulation of soft tissue deformation from the electromechanical viewpoint of soft tissues. Soft tissue deformation is formulated as a reaction-diffusion process coupled with a mechanical load. The mechanical load applied to a soft tissue to cause a deformation is incorporated into the reaction-diffusion system, and consequently distributed among mass points of the soft tissue. Reaction-diffusion of mechanical load and non-rigid mechanics of motion are combined to govern the simulation dynamics of soft tissue deformation. An improved reaction-diffusion model is developed to describe the distribution of the mechanical load in soft tissues. A three-layer artificial cellular neural network is constructed to solve the reaction-diffusion model for real-time simulation of soft tissue deformation. A gradient based method is established to derive internal forces from the distribution of the mechanical load. Integration with a haptic device has also been achieved to simulate soft tissue deformation with haptic feedback. The proposed methodology does not only predict the typical behaviours of living tissues, but it also accepts both local and large-range deformations. It also accommodates isotropic, anisotropic and inhomogeneous deformations by simple modification of diffusion coefficients.

Postseismic Deformation: Different mechanisms in different times and places.

NASA Astrophysics Data System (ADS)

Segall, P.

2004-12-01

Improved understanding of postseismic deformation may elucidate time dependent stress transfer and triggered seismicity following large earthquakes. Afterslip, distributed viscoelastic flow, and poroelastic relaxation alter crustal stress and pore pressure distributions and in many cases lead to distinctive surface deformation patterns. Delayed triggering, due to rate and state dependent friction, on the other hand need not lead to detectable surface deformation. Postseismic deformation recorded following the 1999 ChiChi, Taiwan, 2003 Tokachi-Oki, Japan, and 2000 south Iceland earthquakes can be used to test for the effects of these processes. Horizontal displacements of 10 cm accumulated in the first year following the Chi-Chi quake. These are best explained with continued slip on the Chelungpu fault (Hsu et al, G.R.L. 2002). Inversions indicate the afterslip was roughly localized in a ring around the locus of maximum coseismic slip. The observed displacement pattern is inconsistent with predictions from viscoelastic and poroelastic models. Viscoelastic relaxation of the lower crust produces shortening of the hanging wall instead of the observed extension. The fully drained poroelastic response predicts deformation concentrated near the fault ends, which was not observed. Fully time dependent calculations, however, are still required because poroelastic displacements need not be monotonic. Afterslip following the M 8 Tokachi Oki earthquake is also localized around the area of high mainshock slip (Miyazaki et al, GRL, 2004). Surprisingly, the slip is not located downdip of the mainshock, but along strike of the source region. This indicates that the transient deformation is not caused by deceleration of the earthquake instability, but rather by stress increases due to the mainshock. A major question is whether intermediate depth afterslip following the Tokachi Oki and ChiChi earthquakes occurs in stable (steady state velocity strengthening) areas which will never

High temperature deformation mechanism in hierarchical and single precipitate strengthened ferritic alloys by in situ neutron diffraction studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Gian; Sun, Zhiqian; Li, Lin

Here, the ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni 2TiAl/NiAl or single-Ni 2TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxationmore » behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.« less

Dislocation-accommodated grain boundary sliding as the major deformation mechanism of olivine in the Earth’s upper mantle

PubMed Central

Ohuchi, Tomohiro; Kawazoe, Takaaki; Higo, Yuji; Funakoshi, Ken-ichi; Suzuki, Akio; Kikegawa, Takumi; Irifune, Tetsuo

2015-01-01

Understanding the deformation mechanisms of olivine is important for addressing the dynamic processes in Earth’s upper mantle. It has been thought that dislocation creep is the dominant mechanism because of extrapolated laboratory data on the plasticity of olivine at pressures below 0.5 GPa. However, we found that dislocation-accommodated grain boundary sliding (DisGBS), rather than dislocation creep, dominates the deformation of olivine under middle and deep upper mantle conditions. We used a deformation-DIA apparatus combined with synchrotron in situ x-ray observations to study the plasticity of olivine aggregates at pressures up to 6.7 GPa (that is, ~200-km depth) and at temperatures between 1273 and 1473 K, which is equivalent to the conditions in the middle region of the upper mantle. The creep strength of olivine deforming by DisGBS is apparently less sensitive to pressure because of the competing pressure-hardening effect of the activation volume and pressure-softening effect of water fugacity. The estimated viscosity of olivine controlled by DisGBS is independent of depth and ranges from 1019.6 to 1020.7 Pa·s throughout the asthenospheric upper mantle with a representative water content (50 to 1000 parts per million H/Si), which is consistent with geophysical viscosity profiles. Because DisGBS is a grain size–sensitive creep mechanism, the evolution of the grain size of olivine is an important process controlling the dynamics of the upper mantle. PMID:26601281

High temperature deformation mechanism in hierarchical and single precipitate strengthened ferritic alloys by in situ neutron diffraction studies

DOE PAGES

Song, Gian; Sun, Zhiqian; Li, Lin; ...

2017-04-07

Here, the ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni 2TiAl/NiAl or single-Ni 2TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxationmore » behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.« less

Development of TRIP-Aided Lean Duplex Stainless Steel by Twin-Roll Strip Casting and Its Deformation Mechanism

NASA Astrophysics Data System (ADS)

Zhao, Yan; Zhang, Weina; Liu, Xin; Liu, Zhenyu; Wang, Guodong

2016-12-01

In the present work, twin-roll strip casting was carried out to fabricate thin strip of a Mn-N alloyed lean duplex stainless steel with the composition of Fe-19Cr-6Mn-0.4N, in which internal pore defects had been effectively avoided as compared to conventional cast ingots. The solidification structure observed by optical microscope indicated that fine Widmannstatten structure and coarse-equiaxed crystals had been formed in the surface and center, respectively, with no columnar crystal structures through the surface to center of the cast strip. By applying hot rolling and cold rolling, thin sheets with the thickness of 0.5 mm were fabricated from the cast strips, and no edge cracks were formed during the rolling processes. With an annealing treatment at 1323 K (1050 °C) for 5 minutes after cold rolling, the volume fractions of ferrite and austenite were measured to be approximately equal, and the distribution of alloying elements in the strip was further homogenized. The cold-rolled and annealed sheet exhibited an excellent combination of strength and ductility, with the ultimate tensile strength and elongation having been measured to be 1000 MPa and 65 pct, respectively. The microstructural evolution during deformation was investigated by XRD, EBSD, and TEM, indicating that ferrite and austenite had different deformation mechanisms. The deformation of ferrite phase was dominated by dislocation slipping, and the deformation of austenite phase was mainly controlled by martensitic transformation in the sequence of γ→ ɛ-martensite→ α'-martensite, leading to the improvement of strength and plasticity by the so-called transformation-induced plasticity (TRIP) effect. By contrast, lean duplex stainless steels of Fe-21Cr-6Mn-0.5N and Fe-23Cr-7Mn-0.6N fabricated by twin-roll strip casting did not show TRIP effects and exhibited lower strength and elongation as compared to Fe-19Cr-6Mn-0.4N.

The mechanism study between 3D Space-time deformation and injection or extraction of gas pressure change, the Hutubi Underground gas storage

NASA Astrophysics Data System (ADS)

Xiaoqiang, W.; Li, J.; Daiqing, L.; Li, C.

2017-12-01

The surface deformation of underground gas reservoir with the change of injection pressure is an excellent opportunity to study the load response under the action of tectonic movement and controlled load. This paper mainly focuses on the elastic deformation of underground structure caused by the change of the pressure state of reservoir rock under the condition of the irregular change of pressure in the underground gas storage of Hutubi, the largest underground gas storage in Xinjiang, at the same time, it makes a fine study on the fault activities of reservoir and induced earthquakes along with the equilibrium instability caused by the reservoir. Based on the 34 deformation integrated observation points and 3 GPS continuous observation stations constructed in the underground gas storage area of Hutubi, using modern measurement techniques such as GPS observation, precise leveling survey, flow gravity observation and so on, combined with remote sensing technology such as InSAR, the 3d space-time sequence images of the surface of reservoir area under pressure change were obtained. Combined with gas well pressure, physical parameters and regional seismic geology and geophysical data, the numerical simulation and analysis of internal changes of reservoir were carried out by using elastic and viscoelastic model, the deformation mechanical relationship of reservoir was determined and the storage layer under controlled load was basically determined. This research is financially supported by National Natural Science Foundation of China (Grant No.41474016, 41474051, 41474097)

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

NASA Astrophysics Data System (ADS)

Molli, Giancarlo; Menegon, Luca; Malasoma, Alessandro

2017-04-01

The switching in deformation mode (from distributed to localized) and mechanism (viscous versus frictional) represent a relevant issue in the frame of processes of crustal deformation in turn connected with the concept of the brittle-"ductile" transition and seismogenesis. On the other hand the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as having a fundamental role in the localization of deformation and shear zone development, thus representing a case in which switching deformation mode and mechanisms interact and relate to each other. This contribution analyses an example of a crystal plastic shear zone localized by brittle precursor formed within a host granitic-mylonite during deformation in subduction-related environment. The studied sample come from the external Corsican continental crust units involved in alpine age subduction and characterized by a low grade blueschist facies peak assemblages. The blueschist facies host rock is cut by a thin (< 1 cm thick) brittle-viscous shear zone that preserves domains with a cataclastic microstructure overprinted by mylonitic deformation. Blue amphibole is stable in the shear zone foliation, which therefore formed under HP/LT metamorphic conditions in a subduction environment. Quartz microstructure in the damage zone flanking the brittle-viscous shear zone shows evidence of both microcracking and dislocation glide, with limited recrystallization localized in intracrystalline bands. In the mylonite portion of the shear zone, quartz forms polycrystalline ribbons of dynamically recrystallized grains with a crossed-girdle c-axis CPO. Extrapolation of laboratory-derived flow laws indicates strain rate of ca. 3.5 * 10-12 s-1 during viscous flow in the shear zone. The studied structures, possibly formed by transient instability related to episodic stress/strain rate variations, may be considered as a small scale example of fault behaviour

Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

DOE PAGES

Huang, Shenyan; Gao, Yanfei; An, Ke; ...

2014-10-22

In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticitymore » theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.« less

Topological defect clustering and plastic deformation mechanisms in functionalized graphene

NASA Astrophysics Data System (ADS)

Nunes, Ricardo; Araujo, Joice; Chacham, Helio

2011-03-01

We present ab initio results suggesting that strain plays a central role in the clustering of topological defects in strained and functionalized graphene models. We apply strain onto the topological-defect graphene networks from our previous work, and obtain topological-defect clustering patterns which are in excellent agreement with recent observations in samples of reduced graphene oxide. In our models, the graphene layer, containing an initial concentration of isolated topological defects, is covered by hydrogen or hydroxyl groups. Our results also suggest a rich variety of plastic deformation mechanism in functionalized graphene systems. We acknowledge support from the Brazilian agencies: CNPq, Fapemig, and INCT-Materiais de Carbono.

Deformation and damage mechanisms of zinc coatings on hot-dip galvanized steel sheets: Part II. Damage modes

NASA Astrophysics Data System (ADS)

Parisot, Rodolphe; Forest, Samuel; Pineau, André; Grillon, François; Demonet, Xavier; Mataigne, Jean-Michel

2004-03-01

Zinc-based coatings are widely used for protection against corrosion of steel-sheet products in the automotive industry. The objective of the present article is to investigate the damage modes at work in three different microstructures of a zinc coating on an interstitial-free steel substrate under tension, planestrain tension, and expansion loading. Plastic-deformation mechanisms are addressed in the companion article. Two main fracture mechanisms, namely, intergranular cracking and transgranular cleavage fracture, were identified in an untempered cold-rolled coating, a tempered cold-rolled coating, and a recrystallized coating. No fracture at the interface between the steel and zinc coating was observed that could lead to spalling, in the studied zinc alloy. A complex network of cleavage cracks and their interaction with deformation twinning is shown to develop in the material. An extensive quantitative analysis based on systematic image analysis provides the number and cumulative length of cleavage cracks at different strain levels for the three investigated microstructures and three loading conditions. Grain refinement by recrystallization is shown to lead to an improved cracking resistance of the coating. A model for crystallographic cleavage combining the stress component normal to the basal plane and the amount of plastic slip on the basal slip systems is proposed and identified from equibiaxial tension tests and electron backscattered diffraction (EBSD) analysis of the cracked grains. This analysis requires the computation of the nonlinear stress-strain response of each grain using a crystal-plasticity constitutive model. The model is then applied successfully to other loading conditions and is shown to account for the preferred orientations of damaged grains observed in the case of plane-strain tension.

Characterization of mechanical properties of pericardium tissue using planar biaxial tension and flexural deformation.

PubMed

Murdock, Kyle; Martin, Caitlin; Sun, Wei

2018-01-01

Flexure is an important mode of deformation for native and bioprosthetic heart valves. However, mechanical characterization of bioprosthetic leaflet materials has been done primarily through planar tensile testing. In this study, an integrated experimental and computational cantilever beam bending test was performed to characterize the flexural properties of glutaraldehyde-treated bovine and porcine pericardium of different thicknesses. A strain-invariant based structural constitutive model was used to model the pericardial mechanical behavior quantified through the bending tests of this study and the planar biaxial tests previously performed. The model parameters were optimized through an inverse finite element (FE) procedure in order to describe both sets of experimental data. The optimized material properties were implemented in FE simulations of transcatheter aortic valve (TAV) deformation. It was observed that porcine pericardium TAV leaflets experienced significantly more flexure than bovine when subjected to opening pressurization, and that the flexure may be overestimated using a constitutive model derived from purely planar tensile experimental data. Thus, modeling of a combination of flexural and biaxial tensile testing data may be necessary to more accurately describe the mechanical properties of pericardium, and to computationally investigate bioprosthetic leaflet function and design. Copyright © 2017 Elsevier Ltd. All rights reserved.

Episodic behavior of Gondwanide deformation in eastern Australia: Insights from the Gympie Terrane

NASA Astrophysics Data System (ADS)

Hoy, Derek; Rosenbaum, Gideon

2017-08-01

The mechanisms that drove Permian-Triassic orogenesis in Australia and throughout the Cordilleran-type Gondwanan margin is a subject of debate. Here we present field-based results on the structural evolution of the Gympie Terrane (eastern Australia), with the aim of evaluating its possible role in triggering widespread orogenesis. We document several deformation events (D1-D3) in the Gympie Terrane and show that the earliest deformation, D1, occurred only during the final pulse of orogenesis (235-230 Ma) within the broader Gondwanide Orogeny. In addition, we found no evidence for a crustal suture, suggesting that terrane accretion was not the main mechanism behind deformation. Rather, the similar spatiotemporal evolution of Permian-Triassic orogenic belts in Australia, Antarctica, South Africa, and South America suggest that the Gondwanide Orogeny was more likely linked to large-scale tectonic processes such as plate reorganization. In the context of previous work, our results highlight a number of spatial and temporal variations in pulses of deformation in eastern Australia, suggesting that shorter cycles of deformation occurred at a regional scale within the broader episode of the Gondwanide Orogeny. Similarly to the Cenozoic evolution of the central and southern Andes, we suggest that plate coupling and orogenic cycles in the Late Paleozoic to Early Mesozoic Gondwanide Orogeny have resulted from the superposition of mechanisms acting at a range of scales, perhaps contributing to the observed variations in the intensity, timing, and duration of deformation phases within the orogenic belt.

Deformation mechanisms of antigorite and strain localization during dehydration

NASA Astrophysics Data System (ADS)

Proctor, B.; Hirth, G.

2012-12-01

Antigorite, the high temperature and pressure serpentine polytype, is thought to exist along subduction zones between the mantle wedge and the subducting oceanic crust (e.g., Wada et al., 2008). Understanding how the rheology of antigorite changes with depth along the slab may be key to understanding seismicity along the upper plate boundary (e.g., Hacker et al., 2003). To explore this phenomenon we are conducting constant strain rate general shear experiments on antigorite-rich serpentinite at shear strain rates of 5*10^-7/s to 10^-5/s, confining pressures from 1-2 GPa and temperatures from 400-700°C. We are using microstructural observations to constrain deformation mechanisms and investigate conditions where strain localization occurs. In some experiments we employ either strain rate stepping or temperature ramping to examine the stress dependence of viscosity (i.e., determine stress exponent) and syntectonic reaction during heating. The results of our general shear experiments suggest the rheologic behavior of antigorite varies significantly with changes in temperature and pressure, similar to previous work in axial compression (e.g., Chernak and Hirth, 2010). At 400°C and 1GPa confining pressure antigorite deforms initially via steady-state ductile flow with strengths as high as 1.4 GPa at a strain rate of 10^-5/s. With increasing strain we observe weakening events that correlate with the development of shear fractures within the sample. At 2GPa pressure, the flow strength of antigorite increases to ~1.8 GPa at 10^-6/s and deformation is distributed at low strain. Strain rate stepping at these conditions suggests a very weak strain rate dependence on strength with a 5-10% change in stress for an order of magnitude strain rate step. At 700C and 1 GPa, above the thermal stability of antigorite, the steady-state strength is ~120 MPa at 10^-5/s. In these samples olivine becomes the dominant phase as antigorite progressively reacts to olivine and pyroxene. At the

Brittle-viscous deformation of vein quartz under fluid-rich lower greenschist facies conditions

NASA Astrophysics Data System (ADS)

Kjøll, H. J.; Viola, G.; Menegon, L.; Sørensen, B. E.

2015-06-01

We studied by Electron BackScatter Diffraction (EBSD) and optical microscopy a coarse-grained (ca. 0.5-6 mm) quartz vein embedded in a phyllonitic matrix to gain insights into the recrystallization mechanisms and the processes of strain localization in quartz deformed under lower greenschist facies conditions, broadly coincident with the brittle-viscous transition. The vein deformed during faulting along a phyllonitic thrust of Caledonian age within the Porsa Imbricate Stack in the Paleoproterozoic Repparfjord Tectonic Window in northern Norway. The phyllonite hosting the vein formed at the expense of a metabasaltic protolith through feldspar breakdown to form interconnected layers of fine, synkinematic phyllosilicates. In the mechanically weak framework of the phyllonite, the quartz vein acted as a relatively rigid body. Viscous deformation in the vein was initially accommodated by quartz basal slip. Under the prevailing deformation conditions, however, dislocation glide- and possibly creep-accommodated deformation of quartz was inefficient, and this resulted in localized strain hardening. In response to the (1) hardening, (2) progressive and cyclic increase of the fluid pressure, and (3) increasing competence contrast between the vein and the weakly foliated host phyllonite, vein quartz crystals began to deform by brittle processes along specific, suitably oriented lattice planes, creating microgouges along microfractures. Nucleated new grains rapidly sealed these fractures as fluids penetrated the actively deforming system. The grains grew initially by solution precipitation and later by grain boundary migration. We suggest that the different initial orientation of the vein crystals led to strain accommodation by different mechanisms in the individual crystals, generating remarkably different microstructures. Crystals suitably oriented for basal slip, for example, accommodated strain mainly viscously and experienced only minor fracturing. Instead, crystals

Analyzing the Mechanical Behavior of Polymer and Composite Materials by Means of Unique Method of Deformation Calorimetry

NASA Astrophysics Data System (ADS)

Bessonova, N. P.; Chvalun, S. N.

2018-06-01

Results are presented from long-term investigations of a wide range of polymer systems, varying from elastomers and thermoplastic elastomers to plastics and fibers. The thermophysical properties of both initial and modifying additive-containing polysiloxanes, block copolymers, and poleolefins that differ in chemical nature, structure, and composition are analyzed. It is shown that deformation calorimetry allows the simultaneous registration of mechanical (from 5 × 10-3 kg) and thermal effects (at a sensitivity of 2 × 10‒7 J/s), and the determination of changes in enthalpy, internal energy, and intra- and intermolecular contributions to the formation of the tensile stress response. In other words, it provides a unique opportunity to analyze the deformation mechanism of investigated systems and its dependence on the changing parameters.

Intraplate deformation, stress in the lithosphere and the driving mechanism for plate motions

NASA Technical Reports Server (NTRS)

Hager, Bradford H.

1988-01-01

During this period work was carried out on three fronts relevant to the understanding of intraplate deformation, stress in the lithosphere, and the driving mechanisms for plate motions: (1) observational constraints, using GPS geodesy on the deformation in the region of the boundry between the Pacific and North American plates in central and southern California; (2) numerical modeling of the effects of temperature dependent lithospheric viscosity on the stress and strain history of extensional regimes; and (3) improvement of estimates of mantle viscosity variation, the long-wave-length density variations in the mantle, and the topography of the core-mantel boundary from modeling of geoid anomalies, nutation, and changes in length of day. These projects are described in more detail, followed by a discussion of meetings attended and a list of abstracts and papers submitted and/or published.

Macro-scale deformation behavior and characterization of deformation mechanisms below µm-scale in experimentally deformed Boom Clay by using the combination of triaxial compression, X-ray µ-CT imaging, DIC, BIB cross sectioning, and SEM

NASA Astrophysics Data System (ADS)

Oelker, Anne; Desbois, Guillaume; Urai, Janos L.; Bésuelle, Pierre; Viggiani, Gioacchino; Levasseur, Séverine

2017-04-01

Boom Clay is one formation being studied in Belgium as a potential host rock for deep geological disposal of radioactive waste. This poorly indurated clay presents in its natural state favorable properties against the migration of radionuclides: low permeability, low solute diffusion rates, good retention and sorption capacity for many radionuclides and good self-sealing capacity. During construction of disposal galleries, stress redistribution will lead to perturbation of the clay and the formation around galleries of the so-called "Excavation disturbed Zone" (EdZ). The study of deformation mechanisms and evolution of Boom Clay properties at macro but also micro scale allows to assess in a more mechanistic way the evolution of Boom Clay properties in this EdZ. In this work, we show microstructural investigations of Boom Clay deformed in undrained triaxial compression by linking conventional stress/strain curves with Digital Image Correlation (DIC) and scanning electron microscopy (SEM) imaging of broad-ion-beam (BIB) milled cross-sections to deduce deformation mechanisms based on microstructures at sub-micron resolution. Two specimens, collected in Mol (Belgium) at the European Underground Laboratories (URL) on HADES level, were analyzed: The major principal stress σ1 was applied parallel as well as perpendicular to the bedding direction with an initial mean normal effective stress of 4.5 MPa and an initial pore water pressure of 2.3 MPa, which are equal to the in-situ values. Linking the resulting DIC-derived maps of incremental strains with the corresponding stress/strain curve give not only information about the moment of the shear band development, but also on the way strain evolves within the specimen throughout the rest. Incremental DIC analysis of X-ray tomographic scans performed during loading tests give a time evolution of the strain field, and subsequently allow to detect strain localization which appears close to the stress peak. Regions with a

The Surface Layer Mechanical Condition and Residual Stress Forming Model in Surface Plastic Deformation Process with the Hardened Body Effect Consideration

NASA Astrophysics Data System (ADS)

Mahalov, M. S.; Blumenstein, V. Yu

2017-10-01

The mechanical condition and residual stresses (RS) research and computational algorithms creation in complex types of loading on the product lifecycle stages relevance is shown. The mechanical state and RS forming finite element model at surface plastic deformation strengthening machining, including technological inheritance effect, is presented. A model feature is the production previous stages obtained transformation properties consideration, as well as these properties evolution during metal particles displacement through the deformation space in the present loading step.

Electric Eel-Skin-Inspired Mechanically Durable and Super-Stretchable Nanogenerator for Deformable Power Source and Fully Autonomous Conformable Electronic-Skin Applications.

PubMed

Lai, Ying-Chih; Deng, Jianan; Niu, Simiao; Peng, Wenbo; Wu, Changsheng; Liu, Ruiyuan; Wen, Zhen; Wang, Zhong Lin

2016-12-01

Electric eel-skin-inspired mechanically durable and super-stretchable nanogenerator is demonstrated for the first time by using triboelectric effect. This newly designed nanogenerator can produce electricity by touch or tapping despite under various extreme mechanical deformations or even after experiencing damage. This device can be used not only as deformable and wearable power source but also as fully autonomous and self-sufficient adaptive electronic skin system. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorbate-induced lattice deformation in IRMOF-74 series

DOE PAGES

Jawahery, Sudi; Simon, Cory M.; Braun, Efrem; ...

2017-01-09

Here, IRMOF-74 analogues are among the most widely studied metal-organic frameworks (MOFs) for adsorption applications because of their one-dimensional channels and high metal density. Most studies involving the IRMOF-74 series assume that the crystal lattice is rigid. This assumption guides the interpretation of experimental data, as changes in the crystal symmetry have so far been ignored as a possibility in the literature. Here, we report a deformation pattern, induced by the adsorption of argon, for IRMOF-74-V. This work has two main implications. First, we use molecular simulations to demonstrate that the IRMOF-74 series undergoes a deformation that is similar tomore » the mechanism behind breathing MOFs, but is unique because the deformation pattern extends beyond a single unit cell of the original structure. Second, we provide an alternative interpretation of experimental small-angle X-ray scattering profiles of these systems, which changes how we view the fundamentals of adsorption in this MOF series.« less

Adsorbate-induced lattice deformation in IRMOF-74 series

PubMed Central

Jawahery, Sudi; Simon, Cory M.; Braun, Efrem; Witman, Matthew; Tiana, Davide; Vlaisavljevich, Bess; Smit, Berend

2017-01-01

IRMOF-74 analogues are among the most widely studied metal-organic frameworks (MOFs) for adsorption applications because of their one-dimensional channels and high metal density. Most studies involving the IRMOF-74 series assume that the crystal lattice is rigid. This assumption guides the interpretation of experimental data, as changes in the crystal symmetry have so far been ignored as a possibility in the literature. Here, we report a deformation pattern, induced by the adsorption of argon, for IRMOF-74-V. This work has two main implications. First, we use molecular simulations to demonstrate that the IRMOF-74 series undergoes a deformation that is similar to the mechanism behind breathing MOFs, but is unique because the deformation pattern extends beyond a single unit cell of the original structure. Second, we provide an alternative interpretation of experimental small-angle X-ray scattering profiles of these systems, which changes how we view the fundamentals of adsorption in this MOF series. PMID:28067222

Adsorbate-induced lattice deformation in IRMOF-74 series

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jawahery, Sudi; Simon, Cory M.; Braun, Efrem

Here, IRMOF-74 analogues are among the most widely studied metal-organic frameworks (MOFs) for adsorption applications because of their one-dimensional channels and high metal density. Most studies involving the IRMOF-74 series assume that the crystal lattice is rigid. This assumption guides the interpretation of experimental data, as changes in the crystal symmetry have so far been ignored as a possibility in the literature. Here, we report a deformation pattern, induced by the adsorption of argon, for IRMOF-74-V. This work has two main implications. First, we use molecular simulations to demonstrate that the IRMOF-74 series undergoes a deformation that is similar tomore » the mechanism behind breathing MOFs, but is unique because the deformation pattern extends beyond a single unit cell of the original structure. Second, we provide an alternative interpretation of experimental small-angle X-ray scattering profiles of these systems, which changes how we view the fundamentals of adsorption in this MOF series.« less

The effect of aluminium on mechanical properties and deformation mechanisms of hadfield steel single crystals

NASA Astrophysics Data System (ADS)

Zakharova, E. G.; Kireeva, I. V.; Chumlyakov, Y. I.; Shul'Mina, A. A.; Sehitoglu, H.; Karaman, I.

2004-06-01

On single crystals of Hadfield steel (Fe-13Mn-1.3C, Fe-13Mn-2.7Al-1.3C, wt.%) the systematical investigations of deformation mechanisms - slip and twinning, stages of plastic flow, strain hardening coefficient depending on orientation of tensile axis have been carried out by methods of optical and electron microscopy, x-ray analysis. Is has been shown that the combination of low stacking fault energy (γ{SF}=0.03J/m^2) with high concentration of carbon atoms in aluminium-free steel results in development of the mechanical twinning at room temperature in all crystal orientations. The new type of twinning with formation of extrinsic stacking fault has been found out in [001] single crystals. Experimentally it has been established that alloying with aluminium leads to increase of stacking fault energy of Hadfield steel and suppresses twinning in all orientations of crystals at preservation of high values of strain-hardening coefficients θ.

Mechanism of Martensitic to Equiaxed Microstructure Evolution during Hot Deformation of a Near-Alpha Ti Alloy

NASA Astrophysics Data System (ADS)

Shams, Seyed Amir Arsalan; Mirdamadi, Shamsoddin; Abbasi, Seyed Mahdi; Kim, Daehwan; Lee, Chong Soo

2017-06-01

In this study, mechanisms of microstructural evolution during hot deformation of Ti-1100 were investigated by EBSD analysis. Misorientation angle distribution of initial microstructure showed that diffusionless martensitic phase transformation in Ti-1100 obeys Burgers orientation relationship, and most of the high-angle-grain boundaries consist of angles of 60 and 63 deg. Calculated activation energy of hot deformation ( 338 kJ/mol) and EBSD grain boundary maps revealed that continuous dynamic recrystallization (CDRX) is the dominant mechanism during hot compression at 1073 K (800 °C) and strain rate of 0.005 s-1. At a temperature range of 1073 K to 1173 K (800 °C to 900 °C), not only the array of variants lying perpendicular to compression axis but also CDRX contributes to flow softening. Increasing the rolling temperature from 1123 K to 1273 K (850 °C to 1000 °C) brought about changes in spheroidization mechanism from CDRX to conventional boundary splitting and termination migration correlated with the higher volume fraction of beta phase at higher temperatures.

Efficiency of five chemical protective clothing materials against nano and submicron aerosols when submitted to mechanical deformations.

PubMed

Ben Salah, Mehdi; Hallé, Stéphane; Tuduri, Ludovic

2016-01-01

Due to their potential toxicity, the use of nanoparticles in the workplace is a growing concern. Some studies indicate that nanoparticles can penetrate the skin and lead to adverse health effects. Since chemical protective clothing is the last barrier to protect the skin, this study aims to better understand nanoparticle penetration behaviour in dermal protective clothing under mechanical deformation. For this purpose, five of the most common types of fabrics used in protective clothing, one woven and four nonwoven, were chosen and submitted to different simulated exposure conditions. They were tested against polydispersed NaCl aerosols having an electrical-mobility diameter between 14 and 400 nm. A bench-scale exposure setup and a sampling protocol was developed to measure the level of penetration of the aerosols through the material samples of disposable coveralls and lab coat, while subjecting them to mechanical deformations to simulate the conditions of usage in the workplace. Particle size distribution of the aerosol was determined upstream and downstream using a scanning mobility particle sizer (SMPS). The measured efficiencies demonstrated that the performances of nonwoven materials were similar. Three nonwovens had efficiencies above 99%, while the woven fabric was by far, the least effective. Moreover, the results established that mechanical deformations, as simulated for this study, did not have a significant effect on the fabrics' efficiencies.

Nonlinear deformations of microcapsules in elongation flow

NASA Astrophysics Data System (ADS)

Deschamps, Julien; de Loubens, Clément; Boedec, Gwenn; Georgelin, Marc; Leonetti, Marc; Soft Matter; Biophysics Group Team

2014-11-01

Soft microcapsules are drops bounded by a thin elastic shell made of cross-linked proteins. They have numerous applications for drug delivery in bioengineering, pharmaceutics and medicine, where their mechanical stability and their dynamics under flow are crucial. They can also be used as red blood cells models. Here, we investigate the mechanical behaviour of microcapsules made of albumine in strong elongational flow, up to a stretching of 180% just before breaking. The set-up allows us to visualize the deformed shape in the two perpendicular main fields of view, to manage high capillary number and to manipulate soft microcapsules. The steady-state shape of a capsule in the planar elongational flow is non-axisymmetric. In each cross section, the shape is an ellipse but with different small axis which vary in opposite sense with the stretching. Whatever the degree of cross-linking and the size of the capsules, the deformations followed the same master-curve. Comparisons between numerical predictions and experimental results permit to conclude unambiguously that the more properly strain-energy model of membrane is the generalized Hooke model.

Foldover-free shape deformation for biomedicine.

PubMed

Yu, Hongchuan; Zhang, Jian J; Lee, Tong-Yee

2014-04-01

Shape deformation as a fundamental geometric operation underpins a wide range of applications, from geometric modelling, medical imaging to biomechanics. In medical imaging, for example, to quantify the difference between two corresponding images, 2D or 3D, one needs to find the deformation between both images. However, such deformations, particularly deforming complex volume datasets, are prone to the problem of foldover, i.e. during deformation, the required property of one-to-one mapping no longer holds for some points. Despite numerous research efforts, the construction of a mathematically robust foldover-free solution subject to positional constraints remains open. In this paper, we address this challenge by developing a radial basis function-based deformation method. In particular we formulate an effective iterative mechanism which ensures the foldover-free property is satisfied all the time. The experimental results suggest that the resulting deformations meet the internal positional constraints. In addition to radial basis functions, this iterative mechanism can also be incorporated into other deformation approaches, e.g. B-spline based FFDs, to develop different deformable approaches for various applications. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

Macroscopic inhomogeneous deformation behavior arising in single crystal Ni-Mn-Ga foils under tensile loading

NASA Astrophysics Data System (ADS)

Murasawa, Go; Yeduru, Srinivasa R.; Kohl, Manfred

2016-12-01

This study investigated macroscopic inhomogeneous deformation occurring in single-crystal Ni-Mn-Ga foils under uniaxial tensile loading. Two types of single-crystal Ni-Mn-Ga foil samples were examined as-received and after thermo-mechanical training. Local strain and the strain field were measured under tensile loading using laser speckle and digital image correlation. The as-received sample showed a strongly inhomogeneous strain field with intermittence under progressive deformation, but the trained sample result showed strain field homogeneity throughout the specimen surface. The as-received sample is a mainly polycrystalline-like state composed of the domain structure. The sample contains many domain boundaries and large domain structures in the body. Its structure would cause large local strain band nucleation with intermittence. However, the trained one is an ideal single-crystalline state with a transformation preferential orientation of variants after almost all domain boundary and large domain structures vanish during thermo-mechanical training. As a result, macroscopic homogeneous deformation occurs on the trained sample surface during deformation.

Brittle-viscous deformation of vein quartz under fluid-rich low greenschist facies conditions

NASA Astrophysics Data System (ADS)

Kjøll, H. J.; Viola, G.; Menegon, L.; Sørensen, B. E.

2015-01-01

A coarse grained, statically crystallized quartz vein, embedded in a phyllonitic matrix, was studied by EBSD and optical microscopy to gain insights into the processes of strain localization in quartz deformed under low-grade conditions, broadly coincident with the frictional-viscous transition. The vein is from a high strain zone at the front of the Porsa Imbricate Stack in the Paleoproterozoic Repparfjord Tectonic Window in northern Norway. The vein was deformed under lower greenschist facies conditions during deformation along a large out-of-sequence phyllonitic thrust of Caledonian age. The host phyllonite formed at the expense of metabasalt wherein feldspar broke down to form interconnected layers of fine, synkinematic phyllosilicates. In the mechanically weak framework of the phyllonite, the studied quartz vein acted as a relatively rigid body deforming mainly by coaxial strain. Viscous deformation was initially accommodated by basal ⟨a⟩ slip of quartz during the development of a mesoscopic pervasive extensional crenulation cleavage. Under the prevailing boundary conditions, however, dislocation glide-accommodated deformation of quartz resulted inefficient and led to dislocation tangling and strain hardening of the vein. In response to hardening, to the progressive increase of fluid pressure and the increasing competence contrast between the vein and the weak foliated host phyllonite, quartz crystals began to deform frictionally along specific, optimally oriented lattice planes, creating microgouges along microfractures. These were, however, rapidly sealed by nucleation of new grains as transiently over pressured fluids penetrated the deforming system. The new nucleated grains grew initially by solution-precipitation and later by grain boundary migration. Due to the random initial orientation of the vein crystals, strain was accommodated differently in the individual crystals, leading to the development of remarkably different microstructures. Crystals

Effects of torsional deformation on the microstructures and mechanical properties of a CoCrFeNiMo0.15 high-entropy alloy

NASA Astrophysics Data System (ADS)

Wu, Wenqian; Guo, Lin; Liu, Bin; Ni, Song; Liu, Yong; Song, Min

2017-12-01

The effects of torsional deformation on the microstructures and mechanical properties of a CoCrFeNiMo0.15 high-entropy alloy have been investigated. The torsional deformation generates a gradient microstructure distribution due to the gradient torsional strain. Both dislocation activity and deformation twinning dominated the torsional deformation process. With increasing the torsional equivalent strain, the microstructural evolution can be described as follows: (1) formation of pile-up dislocations parallel to the trace of {1 1 1}-type slip planes; (2) formation of Taylor lattices; (3) formation of highly dense dislocation walls; (3) formation of microbands and deformation twins. The extremely high deformation strain (strained to fracture) results in the activation of wavy slip. The tensile strength is very sensitive to the torsional deformation, and increases significantly with increasing the torsional angle.

Slow deformation of intervertebral discs.

PubMed

Broberg, K B

1993-01-01

Intervertebral discs exhibit pronounced time-dependent deformations when subjected to load variations. These deformations are caused by fluid flow to and from the disc and by viscoelastic deformation of annulus fibres. The fluid flow is caused by differences between mechanical and osmotic pressure. A mechanical model of lumbar disc functions allows one to calculate both the extent of fluid flow and its implications for disc height as well as the role played by viscoelastic deformation of annulus fibres. From such calculations changes in body height are estimated. Experimental results already documented in the literature offer bases for the determination of the parameters involved. Body height variations are studied, both those related to normal diurnal rhythmicity and those related to somewhat exceptional circumstances. The normal diurnal fluid flow is found to be about +/- 40% of the disc fluid content late in the evening. Viscoelastic deformation of annulus fibres contributes approximately one quarter of the height change obtained after several hours normal activity, but dominates during the first hour.

Deformation mechanism of the Cryostat in the CADS Injector II

NASA Astrophysics Data System (ADS)

Yuan, Jiandong; Zhang, Bin; Wan, Yuqin; Sun, Guozhen; Bai, Feng; Zhang, Juihui; He, Yuan

2018-01-01

Thermal contraction and expansion of the Cryostat will affect its reliability and stability. To optimize and upgrade the Cryostat, we analyzed the heat transfer in a cryo-vacuum environment from the theoretical point first. The simulation of cryo-vacuum deformation based on a finite element method was implemented respectively. The completed measurement based on a Laser Tracker and a Micro Alignment Telescope was conducted to verify its correctness. The monitored deformations were consistent with the simulated ones. After the predictable deformations in vertical direction have been compensated, the superconducting solenoids and Half Wave Resonator cavities approached the ideal "zero" position under liquid helium conditions. These guaranteed the success of 25 MeV@170 uA continuous wave protons of Chinese accelerator driven subcritical system Injector II. By correlating the vacuum and cryo-deformation, we have demonstrated that the complete deformation was the superposition effect of the atmospheric pressure, gravity and thermal stress during both the process of cooling down and warming up. The results will benefit to an optimization for future Cryostat's design.

Deformation and Failure Mechanisms of Shape Memory Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daly, Samantha Hayes

2015-04-15

The goal of this research was to understand the fundamental mechanics that drive the deformation and failure of shape memory alloys (SMAs). SMAs are difficult materials to characterize because of the complex phase transformations that give rise to their unique properties, including shape memory and superelasticity. These phase transformations occur across multiple length scales (one example being the martensite-austenite twinning that underlies macroscopic strain localization) and result in a large hysteresis. In order to optimize the use of this hysteretic behavior in energy storage and damping applications, we must first have a quantitative understanding of this transformation behavior. Prior resultsmore » on shape memory alloys have been largely qualitative (i.e., mapping phase transformations through cracked oxide coatings or surface morphology). The PI developed and utilized new approaches to provide a quantitative, full-field characterization of phase transformation, conducting a comprehensive suite of experiments across multiple length scales and tying these results to theoretical and computational analysis. The research funded by this award utilized new combinations of scanning electron microscopy, diffraction, digital image correlation, and custom testing equipment and procedures to study phase transformation processes at a wide range of length scales, with a focus at small length scales with spatial resolution on the order of 1 nanometer. These experiments probe the basic connections between length scales during phase transformation. In addition to the insights gained on the fundamental mechanisms driving transformations in shape memory alloys, the unique experimental methodologies developed under this award are applicable to a wide range of solid-to-solid phase transformations and other strain localization mechanisms.« less

Soft Ionic Electroactive Polymer Actuators with Tunable Non-Linear Angular Deformation

PubMed Central

Hong, Wangyujue; Almomani, Abdallah; Chen, Yuanfen; Jamshidi, Reihaneh; Montazami, Reza

2017-01-01

The most rational approach to fabricate soft robotics is the implementation of soft actuators. Conventional soft electromechanical actuators exhibit linear or circular deformation, based on their design. This study presents the use of conjugated polymers, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) to locally vary ion permeability of the ionic electroactive polymer actuators and manipulate ion motion through means of structural design to realize intrinsic angular deformation. Such angular deformations are closer to biomimetic systems and have potential applications in bio-robotics. Electrochemical studies reveal that the mechanism of actuation is mainly associated with the charging of electric double layer (EDL) capacitors by ion accumulation and the PEDOT:PSS layer’s expansion by ion interchange and penetration. Dependence of actuator deformation on structural design is studied experimentally and conclusions are verified by analytical and finite element method modeling. The results suggest that the ion-material interactions are considerably dominated by the design of the drop-cast PEDOT:PSS on Nafion. PMID:28773036

Soft Ionic Electroactive Polymer Actuators with Tunable Non-Linear Angular Deformation.

PubMed

Hong, Wangyujue; Almomani, Abdallah; Chen, Yuanfen; Jamshidi, Reihaneh; Montazami, Reza

2017-06-21

The most rational approach to fabricate soft robotics is the implementation of soft actuators. Conventional soft electromechanical actuators exhibit linear or circular deformation, based on their design. This study presents the use of conjugated polymers, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) to locally vary ion permeability of the ionic electroactive polymer actuators and manipulate ion motion through means of structural design to realize intrinsic angular deformation. Such angular deformations are closer to biomimetic systems and have potential applications in bio-robotics. Electrochemical studies reveal that the mechanism of actuation is mainly associated with the charging of electric double layer (EDL) capacitors by ion accumulation and the PEDOT:PSS layer's expansion by ion interchange and penetration. Dependence of actuator deformation on structural design is studied experimentally and conclusions are verified by analytical and finite element method modeling. The results suggest that the ion-material interactions are considerably dominated by the design of the drop-cast PEDOT:PSS on Nafion.

The Control of Welding Deformation of the Three-Section Arm of Placing Boom of HB48B Pump Truck

NASA Astrophysics Data System (ADS)

Wang, Zhi-ling

2018-02-01

The concrete pump truck is the construction equipment of conveying concrete with self contained base plate and distributing boom. It integrates the pump transport mechanism of the concrete pump, and the hydraulic roll-folding type distributing boom used to distribute materials, and the supporting mechanism into the automobile chassis, and it is the concrete conveying equipment with high efficient and the functions of driving, pumping, and distributing materials. The placing boom of the concrete pump truck is the main force member in the pump parts with bearing great pressure, and its stress condition is complex. Taking the HB48B placing boom as an example, this paper analyzes and studies the deformation produced by placing boom of pump truck, and then obtains some main factors affecting the welding deformation. Through the riveter “joint” size, we controlled the process parameters, post-welding processing, and other aspects. These measures had some practical significance to prevent, control, and reduce the deformation of welding.

Size effects of nano-spaced basal stacking faults on the strength and deformation mechanisms of nanocrystalline pure hcp metals

NASA Astrophysics Data System (ADS)

Wang, Wen; Jiang, Ping; Yuan, Fuping; Wu, Xiaolei

2018-05-01

The size effects of nano-spaced basal stacking faults (SFs) on the tensile strength and deformation mechanisms of nanocrystalline pure cobalt and magnesium have been investigated by a series of large-scale 2D columnar and 3D molecular dynamics simulations. Unlike the strengthening effect of basal SFs on Mg alloys, the nano-spaced basal SFs are observed to have no strengthening effect on the nanocrystalline pure cobalt and magnesium from MD simulations. These observations could be attributed to the following two reasons: (i) Lots of new basal SFs are formed before (for cobalt) or simultaneously with (for magnesium) the other deformation mechanisms (i.e. the formation of twins and the < c + a > edge dislocations) during the tensile deformation; (ii) In hcp alloys, the segregation of alloy elements and impurities at typical interfaces, such as SFs, can stablilise them for enhancing the interactions with dislocation and thus elevating the strength. Without such segregation in pure hcp metals, the < c + a > edge dislocations can cut through the basal SFs although the interactions between the < c + a > dislocations and the pre-existing SFs/newly formed SFs are observed. The nano-spaced basal SFs are also found to have no restriction effect on the formation of deformation twins.

Opto-mechanical design and gravity-deformation analysis on optical telescope in laser communication system

NASA Astrophysics Data System (ADS)

Fu, Sen; Du, Jindan; Song, Yiwei; Gao, Tianyu; Zhang, Daqing; Wang, Yongzhi

2017-11-01

In space laser communication, optical antennas are one of the main components and the precision of optical antennas is very high. In this paper, it is based on the R-C telescope and it is carried out that the design and simulation of optical lens and supporting truss, according to the parameters of the systems. And a finite element method (FEM) was used to analyze the deformation of the optical lens. Finally, the Zernike polynomial was introduced to fit the primary mirror with a diameter of 250mm. The objective of this study is to determine whether the wave-front aberration of the primary mirror can meet the imaging quality. The results show that the deterioration of the imaging quality caused by the gravity deformation of primary and secondary mirrors. At the same time, the optical deviation of optical antenna increase with the diameter of the pupil.

Hot Deformation and Dynamic Recrystallization Behavior of the Cu-Cr-Zr-Y Alloy

NASA Astrophysics Data System (ADS)

Zhang, Yi; Huili, Sun; Volinsky, Alex A.; Tian, Baohong; Chai, Zhe; Liu, Ping; Liu, Yong

2016-03-01

To study the workability and to optimize the hot deformation processing parameters of the Cu-Cr-Zr-Y alloy, the strain hardening effect and dynamic softening behavior of the Cu-Cr-Zr-Y alloy were investigated. The flow stress increases with the strain rate and stress decreases with deformation temperature. The critical conditions, including the critical strain and stress for the occurrence of dynamic recrystallization, were determined based on the alloy strain hardening rate. The critical stress related to the onset of dynamic recrystallization decreases with temperature. The evolution of DRX microstructure strongly depends on the deformation temperature and the strain rate. Dynamic recrystallization appears at high temperatures and low strain rates. The addition of Y can refine the grain and effectively accelerate dynamic recrystallization. Dislocation generation and multiplication are the main hot deformation mechanisms for the alloy. The deformation temperature increase and the strain rate decrease can promote dynamic recrystallization of the alloy.

Micro-mechanisms of Surface Defects Induced on Aluminum Alloys during Plastic Deformation at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Gali, Olufisayo A.

Near-surface deformed layers developed on aluminum alloys significantly influence the corrosion and tribological behavior as well as reduce the surface quality of the rolled aluminum. The evolution of the near-surface microstructures induced on magnesium containing aluminum alloys during thermomechanical processing has been investigated with the aim generating an understanding of the influence of individual forming parameters on its evolution and examine the microstructure of the roll coating induced on the mating steel roll through material transfer during rolling. The micro-mechanisms related to the various features of near-surface microstructure developed during tribological conditions of the simulated hot rolling process were identified. Thermomechanical processing experiments were performed with the aid of hot rolling (operating temperature: 550 to 460 °C, 4, 10 and 20 rolling pass schedules) and hot forming (operating temperature: 350 to 545 °C, strain rate: 4 x 10-2 s-1) tribo-simulators. The surface, near-surface features and material transfer induced during the elevated temperature plastic deformation were examined and characterized employing optical interferometry, SEM/EDS, FIB and TEM. Near-surface features characterized on the rolled aluminum alloys included; cracks, fractured intermetallic particles, aluminum nano-particles, oxide decorated grain boundaries, rolled-in oxides, shingles and blisters. These features were related to various individual rolling parameters which included, the work roll roughness, which induced the formation of shingles, rolling marks and were responsible for the redistribution of surface oxide and the enhancements of the depth of the near-surface damage. The enhanced stresses and strains experienced during rolling were related to the formation and propagation of cracks, the nanocrystalline structure of the near-surface layers and aluminum nano-particles. The mechanism of the evolution of the near-surface microstructure were

Hardness and deformation mechanisms of highly elastic carbon nitride thin films as studied by nanoindentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hainsworth, S.V.; Page, T.F.; Sjoestroem, H.

1997-05-01

Carbon nitride (CN{sub x}) thin films (0.18 < x < 0.43), deposited by magnetron sputtering of C in a N{sub 2} discharge, have been observed to be extremely resistant to plastic deformation during surface contact (i.e., exhibit a purely elastic response over large strains). Elastic recoveries as high as 90% have been measured by nanoindentation. This paper addresses the problems of estimating Young`s modulus (E) and hardness (H) in such cases and shows how different strategies involving analysis of both loading and unloading curves and measuring the work of indentation each present their own problems. The results of some cyclicmore » contact experiments are also presented and possible deformation mechanisms in the fullerene-like CN{sub x} structures discussed.« less

A versatile lab-on-chip test platform to characterize elementary deformation mechanisms and electromechanical couplings in nanoscopic objects

NASA Astrophysics Data System (ADS)

Pardoen, Thomas; Colla, Marie-Sthéphane; Idrissi, Hosni; Amin-Ahmadi, Behnam; Wang, Binjie; Schryvers, Dominique; Bhaskar, Umesh K.; Raskin, Jean-Pierre

2016-03-01

A nanomechanical on-chip test platform has recently been developed to deform under a variety of loading conditions freestanding thin films, ribbons and nanowires involving submicron dimensions. The lab-on-chip involves thousands of elementary test structures from which the elastic modulus, strength, strain hardening, fracture, creep properties can be extracted. The technique is amenable to in situ transmission electron microscopy (TEM) investigations to unravel the fundamental underlying deformation and fracture mechanisms that often lead to size-dependent effects in small-scale samples. The method allows addressing electrical and magnetic couplings as well in order to evaluate the impact of large mechanical stress levels on different solid-state physics phenomena. We had the chance to present this technique in details to Jacques Friedel in 2012 who, unsurprisingly, made a series of critical and very relevant suggestions. In the spirit of his legacy, the paper will address both mechanics of materials related phenomena and couplings with solids state physics issues.

High- and Low-Temperature Deformation Behavior of Different Orientation Hot-Rolled Annealed Zircaloy-4

NASA Astrophysics Data System (ADS)

Zong, Yingying; Gen, Qingfeng; Jiang, Hongwei; Shan, Debin; Guo, Bin

2018-03-01

In this paper, the hot-rolled annealed Zircaloy-4 samples with different orientation were subjected to uniaxial compression with a strain rate of 0.001 s-1 to obtain the stress-strain curves of different initial orientation samples at different temperatures. Electron backscatter diffraction (EBSD) technique and transmission electron microscope (TEM) technique were used to analyze the microstructures and textures of compressed samples. The mechanical properties and microstructural evolution of rolling directions (RD), transverse directions (TD) and normal directions (ND) were investigated under the conditions of - 150 °C low temperature, room temperature and 200 °C high temperature (simulated lunar temperature environment). The results show that the strength of Zircaloy-4 decreases with the increase in deformation temperature, and the strength in three orientations is ND > TD > RD. The deformation mechanism of hot-rolled annealed Zircaloy-4 with different orientation is different. In RD, { 10\\bar{1}0} < {a} > prismatic slip has the highest Schmid factor (SF), so it is most easy to activate the slip, followed by TD orientation, and ND orientation is the most difficult to activate. The deformed grains abide slip→twinning→slip rule, and the different orientation Zircaloy-4 deformation mechanisms mainly are the twinning coordinated with the slip.

Mechanisms of Deformation and Fracture of Thin Coatings on Different Substrates in Instrumented Indentation

NASA Astrophysics Data System (ADS)

Eremina, G. M.; Smolin, A. Yu.; Psakhie, S. G.

2018-04-01

Mechanical properties of thin surface layers and coatings are commonly studied using instrumented indentation and scratch testing, where the mechanical response of the coating - substrate system essentially depends on the substrate material. It is quite difficult to distinguish this dependence and take it into account in the course of full-scale experiments due to a multivariative and nonlinear character of the influence. In this study the process of instrumented indentation of a hardening coating formed on different substrates is investigated numerically by the method of movable cellular automata. As a result of modeling, we identified the features of the substrate material influence on the derived mechanical characteristics of the coating - substrate systems and the processes of their deformation and fracture.

Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laplanche, Guillaume; Bonneville, J.; Varvenne, C.

To reveal the operating mechanisms of plastic deformation in an FCC high-entropy alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, σ y, the activation volume varies from ~60 b3 at 77 K to ~360 b 3 at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with σ - σ y (Haasenmore » plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-solution-strengthened alloy. Lastly, these results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms.« less

Thermal activation parameters of plastic flow reveal deformation mechanisms in the CrMnFeCoNi high-entropy alloy

DOE PAGES

Laplanche, Guillaume; Bonneville, J.; Varvenne, C.; ...

2017-10-06

To reveal the operating mechanisms of plastic deformation in an FCC high-entropy alloy, the activation volumes in CrMnFeCoNi have been measured as a function of plastic strain and temperature between 77 K and 423 K using repeated load relaxation experiments. At the yield stress, σ y, the activation volume varies from ~60 b3 at 77 K to ~360 b 3 at 293 K and scales inversely with yield stress. With increasing plastic strain, the activation volume decreases and the trends follow the Cottrell-Stokes law, according to which the inverse activation volume should increase linearly with σ - σ y (Haasenmore » plot). This is consistent with the notion that hardening due to an increase in the density of forest dislocations is naturally associated with a decrease in the activation volume because the spacing between dislocations decreases. The values and trends in activation volume agree with theoretical predictions that treat the HEA as a high-concentration solid-solution-strengthened alloy. Lastly, these results demonstrate that this HEA deforms by the mechanisms typical of solute strengthening in FCC alloys, and thus indicate that the high compositional/structural complexity does not introduce any new intrinsic deformation mechanisms.« less

Matrix deformation mechanisms in HP-LT tectonic mélanges — Microstructural record of jadeite blueschist from the Franciscan Complex, California

NASA Astrophysics Data System (ADS)

Wassmann, Sara; Stöckhert, Bernhard

2012-09-01

Exhumed high pressure-low temperature metamorphic mélanges of tectonic origin are believed to reflect high strain accumulated in large scale interplate shear zones during subduction. Rigid blocks of widely varying size are embedded in a weak matrix, which takes up the deformation and controls the rheology of the composite. The microfabrics of a highly deformed jadeite-blueschist from the Franciscan Complex, California, are investigated to help understand deformation mechanisms at depth. The specimen shows a transposed foliation with dismembered fold hinges and boudinage structures. Several generations of open fractures have been sealed to become veins at high-pressure metamorphic conditions. The shape of these veins, frequently restricted to specific layers, indicates distributed host rock deformation during and after sealing. Small cracks in jadeite and lawsonite are healed, with tiny quartz inclusions aligned along the former fracture surface. Large jadeite porphyroblasts show strain caps and strain shadows. Open fractures are sealed by quartz and new jadeite epitactically grown on the broken host. Monophase glaucophane aggregates consist of undeformed needles with a diameter between 0.1 and 2 μm, grown after formation of isoclinal folds. Only quartz microfabrics indicate some stage of crystal-plastic deformation, followed by annealing and grain growth. Aragonite in the latest vein generation shows retrogression to calcite along its rims. The entire deformation happened under HP-LT metamorphic conditions in the stability field of jadeite and quartz, at temperatures between 300 and 450 °C and pressures exceeding 1-1.4 GPa. The microfabrics indicate that dissolution precipitation creep was the predominant deformation mechanism, accompanied by brittle failure and vein formation at quasi-lithostatic pore fluid pressure. This indicates low flow strength and, combined with high strain rates expected for localized deformation between the plates, a very low viscosity

Developing a Virtual Rock Deformation Laboratory

NASA Astrophysics Data System (ADS)

Zhu, W.; Ougier-simonin, A.; Lisabeth, H. P.; Banker, J. S.

2012-12-01

Experimental rock physics plays an important role in advancing earthquake research. Despite its importance in geophysics, reservoir engineering, waste deposits and energy resources, most geology departments in U.S. universities don't have rock deformation facilities. A virtual deformation laboratory can serve as an efficient tool to help geology students naturally and internationally learn about rock deformation. Working with computer science engineers, we built a virtual deformation laboratory that aims at fostering user interaction to facilitate classroom and outreach teaching and learning. The virtual lab is built to center around a triaxial deformation apparatus in which laboratory measurements of mechanical and transport properties such as stress, axial and radial strains, acoustic emission activities, wave velocities, and permeability are demonstrated. A student user can create her avatar to enter the virtual lab. In the virtual lab, the avatar can browse and choose among various rock samples, determine the testing conditions (pressure, temperature, strain rate, loading paths), then operate the virtual deformation machine to observe how deformation changes physical properties of rocks. Actual experimental results on the mechanical, frictional, sonic, acoustic and transport properties of different rocks at different conditions are compiled. The data acquisition system in the virtual lab is linked to the complied experimental data. Structural and microstructural images of deformed rocks are up-loaded and linked to different deformation tests. The integration of the microstructural image and the deformation data allows the student to visualize how forces reshape the structure of the rock and change the physical properties. The virtual lab is built using the Game Engine. The geological background, outstanding questions related to the geological environment, and physical and mechanical concepts associated with the problem will be illustrated on the web portal. In

Production of ultrafine grained aluminum by cyclic severe plastic deformation at ambient temperature

NASA Astrophysics Data System (ADS)

Bereczki, P.; Szombathelyi, V.; Krallics, G.

2014-08-01

In the present study the possibilities of grain refinement was investigated by applying large-scale of cyclic plastic deformation to aluminum at ambient temperature. The specimens are processed by multiaxial forging, which is one of the severe plastic deformation techniques. The aim of the experiments with the aluminum alloy 6082M was the determination of the equivalent stress and strain by multiaxial forging and the investigation of evolution of mechanical properties in relation with the accumulated deformation in the specimen. The mechanical properties of raw material was determined by plane strain compression test as well as by hardness measurements. The forming experiments were carried out on Gleeble 3800 physical simulator with MaxStrain System. The mechanical properties of the forged specimens were investigated by micro hardness measurements and tensile tests. A mechanical model, based on the principle of virtual velocities was developed to calculate the flow curves using the measured dimensional changes of the specimen and the measured force. With respect to the evolution of these curves, the cyclic growth of the flow stress can be observed at every characteristic points of the calculated flow curves. In accordance with this tendency, the evolution of the hardness along the middle cross section of the deformed volume has also a nonmonotonous characteristic and the magnitudes of these values are much smaller than by the specimen after plane strain compression test. This difference between the flow stresses respect to the monotonic and non-monotonic deformation can be also observed. The formed microstructure, after a 10-passes multiaxial forging process, consists of mainly equiaxial grains in the submicron grain scale.

Deformation field heterogeneity in punch indentation

PubMed Central

Murthy, Tejas G.; Saldana, Christopher; Hudspeth, Matthew; M'Saoubi, Rachid

2014-01-01

Plastic heterogeneity in indentation is fundamental for understanding mechanics of hardness testing and impression-based deformation processing methods. The heterogeneous deformation underlying plane-strain indentation was investigated in plastic loading of copper by a flat punch. Deformation parameters were measured, in situ, by tracking the motion of asperities in high-speed optical imaging. These measurements were coupled with multi-scale analyses of strength, microstructure and crystallographic texture in the vicinity of the indentation. Self-consistency is demonstrated in description of the deformation field using the in situ mechanics-based measurements and post-mortem materials characterization. Salient features of the punch indentation process elucidated include, among others, the presence of a dead-metal zone underneath the indenter, regions of intense strain rate (e.g. slip lines) and extent of the plastic flow field. Perhaps more intriguing are the transitions between shear-type and compression-type deformation modes over the indentation region that were quantified by the high-resolution crystallographic texture measurements. The evolution of the field concomitant to the progress of indentation is discussed and primary differences between the mechanics of indentation for a rigid perfectly plastic material and a strain-hardening material are described. PMID:24910521

FEM modeling of postseismic deformation of poroelastic material

NASA Astrophysics Data System (ADS)

Kawamoto, S.; Ito, T.; Hirahara, K.

2004-12-01

Following a large earthquake, postseismic deformation in the focal region has been observed by GPS, leveling measurements and the other geodetic measurements. To explain the postseismic deformation, researchers have proposed and well investigated two physical mechanisms of afterslip and viscoelastic relaxation. In some cases, however, there have been observed postseismic deformation which can not be explained by these mechanisms. Therefore, another mechanism has been proposed, where the crust is treated as "poroelastic material". This concept is called "poroelasticity". In this concept, postseismic deformation is caused by pore fluid flow due to the coseismic stress redistribution. We explored, therefore, the postseismic deformation due to pore fluid flow in a poroelastic material using finite element method (FEM), which can easily handle lateral variations of hydraulic diffusivity and elastic or plastic property. We used the FEM program 'CAMBIOT3D' originally developed by Geotech. Lab. Gunma University, Japan (2003). Because this program was developed for soil mechanics, we must have modified so as to calculate deformation due to earthquake faulting. We implemented the 'split node technique' (Melosh and Refsky, 1981) to calculate the coseismic deformation. In addition to this, we modified the program to calculate the deformation taking into account the Skempton's B. This coefficient B determines what fraction of the coseismic stress due to an earthquake is allotted to pore pressure. Without Skempton's B, coseismic pore pressure becomes too large and hence postseismic deformation is calculated too large. We evaluated the postseismic deformation in a poroelastic material to show that the poroelastic deformation is quite different from that of afterslip and viscoelastic relaxation models. In this presentation, we show the postseismic deformation due to pore fluids flow in a poroelastic material and the effect of Skempton's B. Especially, we discuss what different

High Strain Rate Deformation Mechanisms of Body Centered Cubic Material Subjected to Impact Loading

NASA Astrophysics Data System (ADS)

Visser, William

Low carbon steel is the most common grade of structural steel used; it has carbon content of 0.05% to 0.25% and very low content of alloying elements. It is produced in great quantities and provides material properties that are acceptable for many engineering applications, particularly in the construction industry in which low carbon steel is widely used as the strengthening phase in civil structures. The overall goal of this dissertation was to investigate the deformation response of A572 grade 50 steel when subjected to impact loading. This steel has a 0.23% by weight carbon content and has less than 2% additional alloying elements. The deformation mechanisms of this steel under shock loading conditions include both dislocation motion and twin formation. The goal of this work was achieved by performing experimental, analytical and numerical research in three integrated tasks. The first is to determine the relationship between the evolution of deformation twins and the impact pressure. Secondly, a stress criterion for twin nucleation during high strain rate loading was developed which can account for the strain history or initial dislocation density. Lastly, a method was applied for separating the effects of dislocations and twins generated by shock loading in order to determine their role in controlling the flow stress of the material. In this regard, the contents of this work have been categorically organized. First, the active mechanisms in body centered cubic (BCC) low carbon steel during shock loading have been determined as being a composed of the competing mechanisms of dislocations and deformation twins. This has been determined through a series of shock loading tests of the as-received steel. The shock loading tests were done by plate impact experiments at several impact pressures ranging from 2GPa up to 13GPa using a single stage light gas gun. A relationship between twin volume fraction and impact pressure was determined and an analytical model was

Deformable Organic Nanowire Field-Effect Transistors.

PubMed

Lee, Yeongjun; Oh, Jin Young; Kim, Taeho Roy; Gu, Xiaodan; Kim, Yeongin; Wang, Ging-Ji Nathan; Wu, Hung-Chin; Pfattner, Raphael; To, John W F; Katsumata, Toru; Son, Donghee; Kang, Jiheong; Matthews, James R; Niu, Weijun; He, Mingqian; Sinclair, Robert; Cui, Yi; Tok, Jeffery B-H; Lee, Tae-Woo; Bao, Zhenan

2018-02-01

Deformable electronic devices that are impervious to mechanical influence when mounted on surfaces of dynamically changing soft matters have great potential for next-generation implantable bioelectronic devices. Here, deformable field-effect transistors (FETs) composed of single organic nanowires (NWs) as the semiconductor are presented. The NWs are composed of fused thiophene diketopyrrolopyrrole based polymer semiconductor and high-molecular-weight polyethylene oxide as both the molecular binder and deformability enhancer. The obtained transistors show high field-effect mobility >8 cm 2 V -1 s -1 with poly(vinylidenefluoride-co-trifluoroethylene) polymer dielectric and can easily be deformed by applied strains (both 100% tensile and compressive strains). The electrical reliability and mechanical durability of the NWs can be significantly enhanced by forming serpentine-like structures of the NWs. Remarkably, the fully deformable NW FETs withstand 3D volume changes (>1700% and reverting back to original state) of a rubber balloon with constant current output, on the surface of which it is attached. The deformable transistors can robustly operate without noticeable degradation on a mechanically dynamic soft matter surface, e.g., a pulsating balloon (pulse rate: 40 min -1 (0.67 Hz) and 40% volume expansion) that mimics a beating heart, which underscores its potential for future biomedical applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

3D modeling of unconstrained HPT process: role of strain gradient on high deformed microstructure formation

NASA Astrophysics Data System (ADS)

Ben Kaabar, A.; Aoufi, A.; Descartes, S.; Desrayaud, C.

2017-05-01

During tribological contact’s life, different deformation paths lead to the formation of high deformed microstructure, in the near-surface layers of the bodies. The mechanical conditions (high pressure, shear) occurring under contact, are reproduced through unconstrained High Pressure Torsion configuration. A 3D finite element model of this HPT test is developed to study the local deformation history leading to high deformed microstructure with nominal pressure and friction coefficient. For the present numerical study the friction coefficient at the interface sample/anvils is kept constant at 0.3; the material used is high purity iron. The strain distribution in the sample bulk, as well as the main components of the strain gradients according to the spatial coordinates are investigated, with rotation angle of the anvil.

Effects of Deformation Texture Intensities and Precipitates on the Anisotropy of Mechanical Properties of Al-Li Alloy 2099 T83 Extrusions

NASA Astrophysics Data System (ADS)

Bois-Brochu, Alexandre; Blais, Carl; Goma, Franck Armel Tchitembo; Larouche, Daniel; Boselli, Julien; Brochu, Mathieu

The use of aluminum-lithium alloys in aerospace applications requires a thorough knowledge of how processing and product geometry impact their microstructure, texture and mechanical properties. As with other aluminum alloys, anisotropy of mechanical properties has been related to the formation of deformation textures during thermo-mechanical processes.

Acoustic Emission Determination of Deformation Mechanisms Leading to Failure of Naval Alloys. Volume 1

DTIC Science & Technology

1983-05-01

DThSRT)C- STE -CP- 18-83 Contract No. No024-10-C-5317 Acoustic Emission Determination of Deformation Mechanisms Leading to Failure of Naval Alloys J...mobile dislocation motion were both found to generate AE as well [34-36]. Phase transformations have also been known to cause AE for some time (29...of alloying constituents and the heat treatment resulted in a fairly broken, complex, microstructure. All three steels were of a tempered martensitic

Intraplate deformation, stress in the lithosphere and the driving mechanism for plate motions

NASA Technical Reports Server (NTRS)

Albee, Arden L.

1993-01-01

The initial research proposed was to use the predictions of geodynamical models of mantle flow, combined with geodetic observations of intraplate strain and stress, to better constrain mantle convection and the driving mechanism for plate motions and deformation. It is only now that geodetic observations of intraplate strain are becoming sufficiently well resolved to make them useful for substantial geodynamical inference to be made. A model of flow in the mantle that explains almost 90 percent of the variance in the observed longwavelength nonhydrostatic geoid was developed.

157. ARAIII Reactor building (ARA608) Main gas loop mechanical flow ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

157. ARA-III Reactor building (ARA-608) Main gas loop mechanical flow sheet. This drawing was selected as a typical example of mechanical arrangements within reactor building. Aerojet-general 880-area/GCRE-0608-50-013-102634. - Idaho National Engineering Laboratory, Army Reactors Experimental Area, Scoville, Butte County, ID

Deformation processes and weakening mechanisms within the frictional viscous transition zone of major crustal-scale faults: insights from the Great Glen Fault Zone, Scotland

NASA Astrophysics Data System (ADS)

Stewart, M.; Holdsworth, R. E.; Strachan, R. A.

2000-05-01

The Great Glen Fault Zone (GGFZ), Scotland, is a typical example of a crustal-scale, reactivated strike-slip fault within the continental crust. Analysis of intensely strained fault rocks from the core of the GGFZ near Fort William provides a unique insight into the nature of deformation associated with the main phase of (sinistral) movements along the fault zone. In this region, an exhumed sequence of complex mid-crustal deformation textures that developed in the region of the frictional-viscous transition (ca. 8-15 km depth) is preserved. Fault rock fabrics vary from mylonitic in quartzites to cataclastic in micaceous shear zones and feldspathic psammites. Protolith mineralogy exerted a strong control on the initial textural development and distribution of the fault rocks. At lower strains, crystal-plastic deformation occurred in quartz-dominated lithologies to produce mylonites simultaneously with widespread fracturing and cataclasis in feldspar- and mica-dominated rocks. At higher strains, shearing appears to increasingly localise into interconnected networks of cataclastic shear zones, many of which are strongly foliated. Textures indicative of fluid-assisted diffusive mass transfer mechanisms are widespread in such regions and suggest that a hydrous fluid-assisted, grainsize-controlled switch in deformation behaviour followed the brittle comminution of grains. The fault zone textural evolution implies that a strain-induced, fluid-assisted shallowing and narrowing of the frictional-viscous transition occurred with increasing strain. It is proposed that this led to an overall weakening of the fault zone and that equivalent processes may occur along many other long-lived, crustal-scale dislocations.

Investigation of the deformation mechanisms of core-shell rubber-modified epoxy at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Brown, Hayley Rebecca

The industrial demand for high strength-to-weight ratio materials is increasing due to the need for high performance components. Epoxy polymers, although often used in fiber-reinforced polymeric composites, have an inherent low toughness that further decreases with decreasing temperatures. Second-phase additives have been effective in increasing the toughness of epoxies at room temperature; however, the mechanisms at low temperatures are still not understood. In this study, the deformation mechanisms of a DGEBA epoxy modified with MX960 core-shell rubber (CSR) particles were investigated under quasi-static tensile and impact loads at room temperature (RT) and liquid nitrogen (LN 2) temperature. Overall, the CSR had little effect on the tensile properties at RT and LN2 temperature. The impact strength decreased from neat to 3 wt% but increased from neat to 5 wt% at RT and LN2 temperature, with a higher impact strength at RT at all CSR loadings. The CSR particles debonded in front of the crack tip, inducing voids into the matrix. It was found that an increase in shear deformation and void growth likely accounted for the higher impact strength at 5 wt% CSR loading at RT while the thermal stress fields due to the coefficient of thermal expansion mismatch between rubber and epoxy and an increase in secondary cracking is likely responsible for the higher impact strength at 5 wt% tested at LN2 temperature. While a large toughening effect was not seen in this study, the mechanisms analyzed herein will likely be of use for further material investigations at cryogenic temperatures.

Deformation Bands in an Exhumed Oil Reservoir, Corona del Mar, California, USA

NASA Astrophysics Data System (ADS)

Sample, J.; Woods, S.; Bender, E.; Loveall, M.

2002-12-01

Deformation bands in coarse-grained sandstones are commonly narrow zones of reduced porosity that restrict migration of fluids. Deformation bands are known from core observations and outcrop studies, but we present for the first time results from an exhumed oil reservoir. The deformation bands occur in a poorly consolidated, oil-bearing sandstone of the Miocene Monterey Formation, within the active, right-slip Newport-Inglewood fault zone (NIFZ). The deformation bands crop out as resistant ribs and fins in a very coarse-grained sandstone comprising mainly quartz and feldspar detritus. Deformation bands strike 323°, similar to the NIFZ, and dip variably (N = 113). There are three clusters of dips within the main set: 88NE, 60NE, and 47SW. A fourth cluster has an orientation of 353 °, 70W. Although the kinematic history is complex, steep bands generally are youngest. Deformation bands exhibit both normal and right-slip separations, but net slip was rarely possible to determine. The deformation bands are closely spaced. They formed by porosity reduction and locally cataclasis. Most deformation bands are oil-free, indicating formation before oil migration, and that they were barriers to flow. There are at least two modes of oil-bearing bands: 1) bands with oil in pore spaces; and 2) bands containing oil in small open pockets, especially lining the edges of bands. Case 1 suggests that porosity reduction did not completely preclude oil penetration or that at least some band formation occurred after oil migration. Case 2 is consistent with reactivation of bands as tensional features, perhaps late in the evolution of the reservoir. Other evidence for late-stage tensional deformation during oil migration includes the presence of young sandstone dikes and bitumen veins up to 7 cm in width lined with euhedral quartz. The relationships observed at Corona del Mar are generally consistent with deformation bands acting as barriers to flow, but clearly deformation bands can be

Structure of Hole 1256D: The role of mechanical deformation in superfast-spread crust

NASA Astrophysics Data System (ADS)

Tartarotti, P.; Hayman, N. W.; Anma, R.; Crispini, L.; Veloso Espinosa, E. A.; Galli, L.

2006-12-01

One view of seafloor spreading is that mechanical deformation is not significant at high spreading rates. With recovery of up to 37%, and the vertical axis known for many pieces, shipboard visual core descriptions from Hole 1256D provide an opportunity to evaluate the significance of deformational structures in EPR-, superfast- (~220 mm-yr) spread crust. From top to bottom, the structural characteristics of crustal units are: (1) A relatively flat-lying, ~100-m thick "lava pond" that is largely free of deformational structures; (2) ~184 m of shallowly dipping lava flows remarkable for hyaloclastites and a cooling-related fracture system; (3) ~466 m of massive and sheet flows with flow-related fractures, hydrothermal veins, and (fault-related) cataclastic domains; (3) A ~61 m thick transition zone that contains a well-developed (fault-related) cataclastic domain; (4) A ~346 m thick sheeted dike complex, with abundant hydrothermal veins, local breccias, and magmatic flow features. Recovered chilled dike margins have a mean dip of 70° and range from 41-88°; (5) A ~100 m thick plutonic suite contains gabbroic rocks that intrude the sheeted dikes. Gabbros contain some local brittle structures and minor (largely static) recrystallized domains, but are more noteworthy for their magmatic features: dike/gabbro contacts and flow foliations are modestly dipping (e.g., ~45°) with leucocratic melt patches concentrated toward the top of the section. Brittle structures were subordinate to magmatic processes in accommodating large extensional strain. Brittle deformation was important, however, in accommodating magmatism and hydrothermal fluid flow, thereby affecting the variation of crustal physical properties and the distribution of oceanic alteration.

Experimental Study on the Coupling Mechanism of Early-strength Backfill and Rock

NASA Astrophysics Data System (ADS)

Wang, Mingxu

2017-11-01

In order to study the interaction mechanism between the ore rock and backfill at the early stage, paraffin is chosen as the cementing agent. Based on the damage mechanics and fractal theory, the interaction mechanism between the ore rock and backfill is characterized by the relevant tests on the complex of proportioned ore rock and backfill with resistance strain gauge, crack propagation, microscopic imaging and AE. The experimental results showed that: 1) Through the axial loading test, compared with the early strength of the cemented filling and paraffin mechanical deformation characteristics, the stress and strain curves of the two had a common linear deformation law, while in the early strength of the filling elastic capacity strong, with a certain degree of resilience. 2) The bearing capacity of the backfill was weak, but the deformation ability was strong. During the bearing process, the deformation of the upper load was mainly caused by the ore rock, which leaded to the damage of the rock. 3) The distribution of AE points during the co-carrying of the filling and the ore rock was monitored by the acoustic emission instrument. The damage occurred mainly in the contact zone between the backfill and the ore rock zone. The corresponding AE point distribution also validated the crack happening.

Global rotation of mechanical metamaterials induced by their internal deformation

NASA Astrophysics Data System (ADS)

Dudek, K. K.; Gatt, R.; Mizzi, L.; Dudek, M. R.; Attard, D.; Grima, J. N.

2017-09-01

In this work, we propose the concept that a device based on mechanical metamaterials can be used to induce and control its own rotational motion as a result of internal deformations due to the conversion of translational degrees of freedom into rotational ones. The application of a linear force on the structural units of the system may be fine-tuned in order to obtain a desired type of rotation. In particular, we show, how it is possible to maximise the extent of rotation of the system through the alteration of the geometry of the system. We also show how a device based on this concept can be connected to an external body in order to rotate it which result may potentially prove to be very important in the case of applications such as telescopes employed in space.

Insights from the Lattice-Strain Evolution on Deformation Mechanisms in Metallic-Glass-Matrix Composites

DOE PAGES

Jia, Haoling; Zheng, Lili; Li, Weidong; ...

2015-02-18

In this paper, in situ high-energy synchrotron X-ray diffraction experiments and micromechanics-based finite element simulations have been conducted to examine the lattice-strain evolution in metallic-glass-matrix composites (MGMCs) with dendritic crystalline phases dispersed in the metallic-glass matrix. Significant plastic deformation can be observed prior to failure from the macroscopic stress–strain curves in these MGMCs. The entire lattice-strain evolution curves can be divided into elastic–elastic (denoting deformation behavior of matrix and inclusion, respectively), elastic–plastic, and plastic–plastic stages. Characteristics of these three stages are governed by the constitutive laws of the two phases (modeled by free-volume theory and crystal plasticity) and geometric informationmore » (crystalline phase morphology and distribution). The load-partitioning mechanisms have been revealed among various crystalline orientations and between the two phases, as determined by slip strain fields in crystalline phase and by strain localizations in matrix. Finally, implications on ductility enhancement of MGMCs are also discussed.« less

Soft-sediment deformation structures in Cambrian Series 2 tidal deposits (NW Estonia): implications for identifying endogenic triggering mechanisms in ancient sedimentary record

NASA Astrophysics Data System (ADS)

Põldsaar, Kairi

2015-04-01

Soft-sediment deformation structures (SSDS) are documented in several horizons within silt- and sandstones of the Cambrian Series 2 (Dominopolian Stage) Tiskre Formation, and some in the below-deposited argillaceous deposits of the Lükati Formation (northern part of the Baltoscandian Palaeobasin, NW Estonia). The aim of this study was to map, describe, and analyze these deformation features, discuss their deformation mechanism and possible triggers. Load structures (simple load casts, pillows, flame structures, convoluted lamination) with varying shapes and sizes occur in the Tiskre Fm in sedimentary interfaces within medium-bedded peritidal rhythmites (siltstone-argillaceous material) as well as within up to 3 m thick slightly seaward inclined stacked sandstone sequences. Homogenized beds, dish-and-pillar structures, and severely deformed bedding are also found within these stacked units and within a large tidal runoff channel infill. Autoclastic breccias and water-escape channels are rare and occur only in small-scale -- always related to thin, horizontal tidal laminae. Profound sedimentary dykes, sand volcanoes, and thrust faults, which are often related to earthquake triggered soft sediment deformation, were not observed within the studied intervals. Deformation horizon or horizons with large flat-topped pillows often with elongated morphologies occur at or near the boundary between the Tiskre and Lükati formations. Deformation mechanisms identified in this study for the various deformation types are gravitationally unstable reversed density gradient (especially in case of load features that are related to profound sedimentary interfaces) and lateral shear stress due to sediment current drag (in case of deformation structures that not related to loading at any apparent sedimentary interface). Synsedimentary liquefaction was identified as the primary driving force in most of the observed deformation horizons. Clay thixotropy may have contributed in the

Current crustal deformation of the Taiwan orogen reassessed by cGPS strain-rate estimation and focal mechanism stress inversion

NASA Astrophysics Data System (ADS)

Chen, Sean Kuanhsiang; Wu, Yih-Min; Hsu, Ya-Ju; Chan, Yu-Chang

2017-07-01

We study internal deformation of the Taiwan orogen, a young arc-continental collision belt, which the spatial heterogeneity remains unclear. We aim to ascertain heterogeneity of the orogenic crust in depth when specifying general mechanisms of the Taiwan orogeny. To reach this goal, we used updated data of continuous GPS (cGPS) and earthquake focal mechanisms to reassess geodetic strain-rate and seismic stress fields of Taiwan, respectively. We updated the both data sets from 1990 to 2015 to provide large amount of constraints on surficial and internal deformation of the crust for a better understanding. We estimated strain-rate tensors by calculating gradient tensors of cGPS station velocities in horizontal 0.1°-spacing grids via Delaunay triangulation. We determined stress tensors within a given horizontal and vertical grid cell of 0.1° and 10 km, respectively, by employing the spatial and temporal stress inversion. To minimize effects of the 1999 Mw 7.6 Chi-Chi earthquake on trends of the strain and stress, we modified observational possible bias of the cGPS velocities after the earthquake and removed the first 15-month focal mechanisms within the fault rupture zone. We also calculated the Anderson fault parameter (Aϕ) based on stress ratios and rake angles to quantitatively describe tectonic regimes of Taiwan. By examining directions of seismic compressive axes and styles of faulting, our results indicate that internal deformation of the crust is presently heterogeneous in the horizontal and vertical spaces. Directions of the compressive axes are fan-shaped oriented between N10°W and N110°W in the western and mid-eastern Taiwan at the depths of 0-20 km and near parallel to orientations of geodetic compressional axes. The orientations agreed with predominantly reverse faulting in the western Taiwan at the same depth range, implying a brittle deformation regime against the Peikang Basement High. Orientations of the compressive axes most rotated counter

Detection of precursory deformation using a TLS. Application to spatial prediction of rockfalls.

NASA Astrophysics Data System (ADS)

Abellán, Antonio; Vilaplana, Joan Manuel; Calvet, Jaume; Rodriguez, Xavier

2010-05-01

Different applications on the use of Terrestrial Laser Scanner (TLS) on rock slopes are undergoing rapid development, mainly in the characterization of 3D discontinuities and the monitoring of rock slopes. The emphasis of this research is on detection of precursory deformation and its application to spatial prediction of rockfalls. The pilot study area corresponds to the main scarp of an old slide located at Puigcercós (Catalonia, Spain). 3D temporal variations of the terrain were analyzed by comparing sequential TLS datasets. Five areas characterized by centimetric precursory deformations were detected in the study area. Of these deformations, (a) growing deformation across three areas culminated in a rockfall occurrence; and (b) another growing deformation across two areas was detected, making a subsequent rockfall likely. The areas with precursory deformations detected in Puigcercós showed the following characteristics: (a) a sub-vertical fracture delimiting the moving part from the rest of the slope; (b) an increase in the horizontal displacement upwards, typical of a toppling failure mechanism (Muller 1968; Goodman and Bray, 1976). In addition, decimetric-scale rockfalls were observed in the upper part of the moving areas, which is consistent with the observations of Rosser et al., (2007). TLS ILRIS 3D technical characteristics are as follows: high accuracy (7.2 mm at a range of 50 meters), high angular resolution (e.g. 1 point every few cm), fast data acquisition: 2,500 points/second; broad coverage; high maximum range on natural slopes: ~600m. The single point distances between the surface of reference and the successive data point clouds were computed using a conventional methodology (data vs. reference comparison). The direction of comparison was defined as the normal vector of the rock face at its central part. We focused in the study of the small scale displacements towards the origin of coordinates, which reflect the pre-failure deformation on part of

Strength of the Subduction Plate Interface beneath the Seismogenic Zone: A Microstructural Investigation of Deformation Mechanisms within a Phyllosilicate- and Amphibole-rich Shear Zone

NASA Astrophysics Data System (ADS)

Seyler, C.; Kirkpatrick, J. D.; Šilerová, D.

2017-12-01

Localization of strain at plate boundaries requires rheological weakening of the lithosphere. The rheology of the subduction plate interface is dictated by the dominant grain-scale deformation mechanisms. However, little is known about the deformation mechanisms within phases commonly found in subduction zones, such as phyllosilicates and amphiboles. We investigate the Leech River Shear Zone on Vancouver Island, British Columbia to explore deformation processes downdip of the seismogenic zone and evaluate the bulk rheology of the plate interface. This shear zone juxtaposes a metamorphosed accretionary prism against a metabasaltic oceanic plateau, representing a paleo-plate interface from the ancient Cascadia subduction zone. Preliminary geothermometry results record a prograde deformation temperature of 573.6±11.2 ˚C in the overriding accretionary wedge, and the hornblende-chlorite-epidote-plagioclase mineral assemblage suggests upper greenschist to lower amphibolite facies metamorphism of the downgoing oceanic crust. Detailed mapping of the plate interface documents a 200 m wide mylonitic shear zone developed across the lithologic contact. Asymmetric shear fabrics, isoclinal folding, boudinage, and a steeply plunging, penetrative stretching lineation are consistent with sinistral-oblique subduction. Numerous discordant quartz veins are variably sheared into sigmoidal shapes as well as isoclinally folded and boudinaged, indicating cyclical synkinematic fracture and vein formation. At the grain-scale, interconnected, anastomosing layers of muscovite, chlorite, and graphite in the accretionary prism rocks likely deformed through kinking and dislocation glide. Framework minerals such as quartz and feldspar deformed by dislocation creep. In the metabasalt, hornblende and chlorite form a continuous S—C fabric in which asymmetric hornblende porphyroclasts deformed by rigid grain rotation and dissolution-precipitation creep. The strength of the subduction plate

Flow-induced fiber deformation in a confined microchannel: in situ mechanical testing of gels

NASA Astrophysics Data System (ADS)

Duprat, Camille; Berthet, Helene; Wexler, Jason; Du Roure, Olivia; Lindner, Anke

2014-11-01

Photopolymerized hydrogels are a functional template for micro-particle fabrication, microflowsensors and microbiology experiments. The control and knowledge of their mechanical properties are paramount to many applications. We have designed a novel robust method to determine these properties. We measure the deformation of a gel beam of precisely controlled shape, under a controlled flow forcing, which provides a direct measurement of the Young's modulus of the gel upon its fabrication. We then use this method to determine the mechanical properties of the commonly used poly(ethylene glycol) diacrylate (PEGDA) under various experimental conditions. The mechanical properties of the gel can be highly tuned, yielding two orders of magnitude in the Young's modulus. We provide a simple control parameter, the UV exposure time, to have a great control over the network properties, and rationalize these observations by studying the kinetics of the polymerization reaction.

Slip as the basic mechanism for formation of deformation relief structural elements

NASA Astrophysics Data System (ADS)

Lychagin, D. V.; Alfyorova, E. A.

2017-07-01

The experimental results of investigation of the nickel single crystal surface morphology after compression deformation are presented. The quasi-periodic character of the deformation profile, common for shear deformation of different types of relief structural elements, is found. It is demonstrated that the morphological manifestation of these structural elements is determined by local shear systems along octahedral planes. The regularities of the deformation structure in these regions defining the material extrusion and intrusion regions and the specific features of disorientation accumulation are established. If reorientation of local regions takes part in the relief element formation, along with octahedral slip, much stronger growth of the surface area is observed. The possibility of application of two-dimensional and three-dimensional surface roughness parameters for description of deformation relief is considered.

Geodetic deformation monitoring at Pendidikan Diponegoro Dam

NASA Astrophysics Data System (ADS)

Yuwono, Bambang Darmo; Awaluddin, Moehammad; Yusuf, M. A.; Fadillah, Rizki

2017-07-01

Deformation monitoring is one indicator to assess the feasibility of Dam. In order to get the correct result of the deformation, it is necessary to determine appropriate deformation monitoring network and the observation data should be analyse and evaluated carefully. Measurement and analysis of deformation requires relatively accurate data and the precision is high enough, one of the observation method that used is GPS (Global Positioning System). The research was conducted at Pendidikan Undip Dams is Dam which is located in Tembang. Diponegoro Dam was built in 2013 and a volume of 50.86 m3 of water, inundation normal width of up to 13,500 m2. The main purpose of these building is not only for drainage but also for education and micro hydro power plant etc. The main goal of this reasearch was to monitor and analyze the deformation at Pendidikan Undip Dam and to determaine whether GPS measurement could meet accuracy requirement for dam deformation measurements. Measurements were made 2 times over 2 years, 2015 and 2016 using dual frequency GPS receivers with static methods and processed by Scientific Software GAMIT 10.6

Interfacial diffusion aided deformation during nanoindentation

DOE PAGES

Samanta, Amit; E., Weinan

2015-07-06

Nanoindentation is commonly used to quantify the mechanical response of material surfaces. Despite its widespread use, a detailed understanding of the deformation mechanisms responsible for plasticity during these experiments has remained elusive. Nanoindentation measurements often show stress values close to a material’s ideal strength which suggests that dislocation nucleation and subsequent dislocation activity dominates the deformation. However, low strain-rate exponents and small activation volumes have also been reported which indicates high temperature sensitivity of the deformation processes. Using an order parameter aided temperature accelerated sampling technique called adiabatic free energy dynamics [J. B. Abrams and M. E. Tuckerman, J. Phys.more » Chem. B, 112, 15742 (2008)], and molecular dynamics we have probed the diffusive mode of deformation during nanoindentation. Localized processes such as surface vacancy and ad-atom pair formation, vacancy diffusion are found to play an important role during indentation. Furthermore, our analysis suggests a change in the dominant deformation mode from dislocation mediated plasticity to diffusional flow at high temperatures, slow indentation rates and small indenter tip radii.« less

Multiple deformation mechanisms operating at seismogenic depths: Tectonic pseudotachylyte and associated deformation from the central Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Prante, M. R.; Evans, J. P.

2012-12-01

Description and identification of fault-related deformation products that are diagnostic of seismic slip have implications for the energy budget of earthquakes, fault strength, and fault-rock assemblages. We describe tectonic pseduotachylyte, cataclastic rocks, crystal-plastic deformation, and hydrothermal alteration form faults exhumed from seismogenic depths in the Volcanic Lakes area, in northern Sequoia and Kings Canyon National Park, CA, USA. Fault rock protoliths include Mesozoic granite and granodiorite plutonic and limited metasedimentary and metavolcanic rocks. These plutonic and metamorphic rocks are cross-cut by the E-W striking, steeply dipping, left-lateral strike-slip Granite Pass (GPF) and Glacier Lakes faults (GLF). Cross-cutting relationships and microstructural data suggest that the GPF is the oldest fault in the area and preserves evidence for coeval brittle and plastic crystal deformation, and hydrothermal fluid-flow. Tectonic pseudotachylyte from the area has been dated using the 40Ar/39Ar method at 76.6 ± 0.3 Ma; when placed into a thermochronologic framework for the plutonic host rock it can be inferred that the pseudotachylyte formed at depths between 2.4-6.0 km with ambient temperatures between 110-160°C. Exceptionally well preserved tectonic pseudotachylyte from the GLF and GPF contain evidence for a frictional melt origin including: 1) plagioclase spherulites and microlites, 2) injection vein morphology, 3) amygdules, 4) viscous flow banding and folds, and 5) embayed and corroded clasts. Pseudotachylyte from the GPF and GLF is associated with brittle and plastic deformation in the damage zone of the faults. Evidence for plastic deformation includes undulose extinction, deformation lamellae, subgrain development, and grain boundary bulging in quartz; and limited undulose extinction in feldspar. Additionally, abundant hydrothermal alteration and mineralization has been documented in the GPF and GLF fault zones, including, chlorite

Hot Deformation Behavior and Dynamic Recrystallization of Medium Carbon LZ50 Steel

NASA Astrophysics Data System (ADS)

Du, Shiwen; Chen, Shuangmei; Song, Jianjun; Li, Yongtang

2017-03-01

Hot deformation and dynamic recrystallization behaviors of a medium carbon steel LZ50 were systematically investigated in the temperature range from 1143 K to 1443 K (870 °C to 1170 °C) at strain rates from 0.05 to 3s-1 using a Gleeble-3500 thermo-simulation machine. The flow stress constitutive equation for hot deformation of this steel was developed with the two-stage Laasraoui equation. The activation energy of the tested steel was 304.27 KJ/mol, which was in reasonable agreement with those reported previously. The flow stress of this steel in hot deformation was mainly controlled by dislocation climb during their intragranular motion. The effect of Zener-Hollomon parameter on the characteristic points of the flow curves was studied, and the dependence of critical strain on peak strain obeyed a linear equation. Dynamic recrystallization was the most important softening mechanism for the tested steel during hot deformation. Kinetic equation of this steel was also established based on the flow stress. The austenite grain size of complete dynamic recrystallization was a power law function of Zener-Hollomon parameter with an exponent of -0.2956. Moreover, the microstructures induced under different deformation conditions were analyzed.

Analysis of the Transition in Deformation Mechanisms in Superplastic 5083 Aluminum Alloys by Orientation Imaging Microscopy

DTIC Science & Technology

2001-09-01

Analysis of the Transition in Deformation Mechanisms in Superplastic 5083 Aluminum Alloys by Orientation Imaging Microscopy 6. AUTHOR( S ) Harrell...James W. 5. FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME( S ) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943-5000 8. PERFORMING...ORGANIZATION REPORT NUMBER 9. SPONSORING / MONITORING AGENCY NAME( S ) AND ADDRESS(ES) General Motors Corp., Research and Development Center

Integrated optical design for highly dynamic laser beam shaping with membrane deformable mirrors

NASA Astrophysics Data System (ADS)

Pütsch, Oliver; Stollenwerk, Jochen; Loosen, Peter

2017-02-01

The utilization of membrane deformable mirrors has raised its importance in laser materials processing since they enable the generation of highly spatial and temporal dynamic intensity distributions for a wide field of applications. To take full advantage of these devices for beam shaping, the huge amount of degrees of freedom has to be considered and optimized already within the early stage of the optical design. Since the functionality of commercial available ray-tracing software has been mainly specialized on geometric dependencies and their optimization within constraints, the complex system characteristics of deformable mirrors cannot be sufficiently taken into account yet. The main reasons are the electromechanical interdependencies of electrostatic membrane deformable mirrors, namely saturation and mechanical clamping, that result in non-linear deformation. This motivates the development of an integrative design methodology. The functionality of the ray-tracing program ZEMAX is extended with a model of an electrostatic membrane mirror. This model is based on experimentally determined influence functions. Furthermore, software routines are derived and integrated that allow for the compilation of optimization criteria for the most relevant analytically describable beam shaping problems. In this way, internal optimization routines can be applied for computing the appropriate membrane deflection of the deformable mirror as well as for the parametrization of static optical components. The experimental verification of simulated intensity distributions demonstrates that the beam shaping properties can be predicted with a high degree of reliability and precision.

Characterising Seismicity at Alutu, an Actively Deforming Volcano in the Main Ethiopian Rift

NASA Astrophysics Data System (ADS)

Wilks, M.; Nowacki, A.; Kendall, J. M.; Wookey, J. M.; Biggs, J.; Bastow, I. D.; Ayele, A.; Bedada, T.

2013-12-01

The Main Ethiopian Rift (MER) provides a unique example of the tectonic and volcanic processes occuring during the transition from continental rifting to oceanic spreading. Situated 100 km south of Addis Ababa along the eastern rift margin, Alutu is a silicic stratovolcano that geodetic measurements (InSAR and GPS) have shown is actively deforming. Though the volcano has received relatively little scientific attention it is also a site of economic significance as a geothermal power plant resides within the caldera. As part of ARGOS (Alutu Research Geophysical ObservationS), a multi-disciplinary project aiming to investigate the magmatic and hydrothermal processes occuring at Alutu, a seismic network of 12 broadband seismometers was deployed in January 2012. Other components of ARGOS include InSAR, GPS, geologic mapping and magnetotellurics. From the seismic dataset, P- and S-wave arrivals across the array were manually picked and used to locate events using a non-linear earthquake location algorithm (NonLinLoc) and a predefined 1D velocity model. Perturbations were later applied to this velocity model to investigate the sensitivity of the locations and evaluate the true uncertainties of the solutions. Over 1000 events were successfully located during 2012, where picks were possible at 4 or more stations. Seismicity clusters at both shallow depths (z<2 km) beneath the caldera and at deeper depths of 5-15 km. There is a significant increase in seismicity during the rainy months, suggesting the shallow events may be related to the hydrothermal system. We interpret the deeper events as being magmatic in origin. Events are also located along the eastern border faults that bound the outer edges of the MER and highlights that seismicity arises concurrently via tectonic processes. An adapted version of Richter's original local magnitude scale (ML) to account for attenuation within the MER (Keir et al., 2006) was then used to compute magnitudes for the best located events

Micromechanisms of deformation in shales

NASA Astrophysics Data System (ADS)

Bonnelye, A.; Gharbi, H.; Hallais, S.; Dimanov, A.; Bornert, M.; Picard, D.; Mezni, M.; Conil, N.

2017-12-01

One of the envisaged solutions for nuclear wastes disposal is underground repository in shales. For this purpose, the Callovo Oxfordian (Cox) argillaceous formation is extensively studied. The hydro-mechanical behavior of the argillaceous rock is complex, like the multiphase and multi-scale structured material itself. The argilaceous matrix is composed of interstratified illite-smectite particles, it contains detritic quartz and calcite, accessory pyrite, and the rock porosity ranges from micrometre to nanometre scales. Besides the bedding anisotropy, structural variabilities exist at all scales, from the decametric-metric scales of the geological formation to the respectively millimetric and micrometric scales of the aggregates of particles and clay particles Our study aims at understanding the complex mechanisms which are activated at the micro-scale and are involved in the macroscopic inelastic deformation of such a complex material. Two sets of experiments were performed, at two scales on three bedding orientations (90°, 45° and 0°). The first set was dedicated to uniaxial deformation followed with an optical set-up with a pixel resolution of 0.55µm. These experiments allowed us to see the fracture propagation with different patterns depending on the bedding orientation. For the second set of experiments, an experimental protocol was developed in order to perform uniaxial deformation experiment at controlled displacement rate, inside an environmental scanning electron microscope (ESEM), under controlled relative humidity, in order to preserve as much as possible the natural state of saturation of shales. We aimed at characterizing the mechanical anisotropy and the mechanisms involved in the deformation, with an image resolution below the micormeter. The observed sample surfaces were polished by broad ion beam in order to reveal the fine microstructures of the argillaceous matrix. In both cases, digital images were acquired at different loading stages during

Effects of 1 MeV electrons on the deformation mechanisms of polyethylene/carbon nanotube composites

NASA Astrophysics Data System (ADS)

Yang, Jianqun; Zhang, Xiaodong; Liu, Chaoming; Li, Xingji; Li, Hongxia; Ma, Guoliang; Tian, Feng

2017-10-01

Polymer nano-composites, especially in polyethylene (PE)/carbon nanotube (CNT) composites can be employed as radiation shielding and structural materials in space. When the PE/CNT composites are used in space, it is easy to suffer from radiation damage caused by charged particles. However, few studies about deformation mechanisms of the composites exposed to electron become available so far. In this paper, mutiwalled carbon nanotubes (MWCNTs) were incorporated into low density polyethylene (LDPE) with MWCNT loadings concentrations of 0.1 wt%. The structural evolution during uniaxial tensile deformation of the LDPE/0.1% MWCNT composites before and after 1 MeV electrons were investigated by means of a small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD). Experimental results show that 1 MeV electrons obviously increase the ultimate tensile strength of the LDPE/MWCNT composites. From SAXS and WAXD analyses, it is shown that 1 MeV electrons inhibit the disintegration and the rotation of the lamellae, and slow down the formation of the new crystals. It is concluded that the intense interaction between MWCNTs and LDPE matrix and the crosslinking strengthening generated by 1 MeV electrons is the dominant reason for the changes of the deformation behaviors of LDPE.

Investigation into mechanical properties of bone and its main constituents

NASA Astrophysics Data System (ADS)

Evdokimenko, Ekaterina

Bone is a hierarchically structured natural composite material, consisting of organic phase (type-I collagen), inorganic phase (hydroxyapatite), and water. Studies of the two main bone constituents, utilizing controlled demineralization and deproteinization, can shed light on mineral-collagen interaction which makes bone such a unique biological material. This knowledge is necessary for computational analysis of bone structure to identify preferential sites in the collagen matrix and mineral network that degrade more easily. The main goal of this work is to develop a comprehensive picture of mechanical properties of bone and its main constituents. Following the Introduction, Chapter 2 presents an investigation of microstructure and compressive mechanical properties of bovine femur cortical bone carried out on completely demineralized, completely deproteinized, and untreated bone samples in three anatomical directions. Anisotropic nature of bone was clearly identified in all cases. Extra levels of porosity along with microstructural differences for the three directions were found to be the main sources of the anisotropy. In Chapter 3, a new theoretical model of cortical and trabecular bone as composite materials with hierarchical structure spanning from nanometer (collagen-mineral) level to millimeter (bone) level was developed. Compression testing was performed on untreated, demineralized, and deproteinized cortical and trabecular bovine femur bone samples to verify the model. The experimental data were compared with theoretical predictions; excellent agreement was found between the theory and experiments for all bone phases. Optical microscopy, scanning electron microscopy, and micro-computed tomography techniques were applied to characterize the structure of the samples at multiple length scales and provide further inputs for the modeling. Chapter 4 presents a comparative study of mechanical properties, microstructure, and porosity of mature and young bovine

Effect of deformation schedule on the microstructure and mechanical properties of a thermomechanically processed C-Mn-Si transformation-induced plasticity steel

NASA Astrophysics Data System (ADS)

Timokhina, I. B.; Hodgson, P. D.; Pereloma, E. V.

2003-08-01

Thermomechanical processing simulations were performed using a hot-torsion machine, in order to develop a comprehensive understanding of the effect of severe deformation in the recrystallized and nonrecrystallized austenite regions on the microstructural evolution and mechanical properties of the 0.2 wt pct C-1.55 wt pct Mn-1.5 wt pct Si transformation-induced plasticity (TRIP) steel. The deformation schedule affected all constituents (polygonal ferrite, bainite in different morphologies, retained austenite, and martensite) of the multiphased TRIP steel microstructure. The complex relationships between the volume fraction of the retained austenite, the morphology and distribution of all phases present in the microstructure, and the mechanical properties of TRIP steel were revealed. The bainite morphology had a more pronounced effect on the mechanical behavior than the refinement of the microstructure. The improvement of the mechanical properties of TRIP steel was achieved by variation of the volume fraction of the retained austenite rather than the overall refinement of the microstructure.

Time-dependent deformation of gas shales - role of rock framework versus reservoir fluids

NASA Astrophysics Data System (ADS)

Hol, Sander; Zoback, Mark

2013-04-01

Hydraulic fracturing operations are generally performed to achieve a fast, drastic increase of permeability and production rates. Although modeling of the underlying short-term mechanical response has proven successful via conventional geomechanical approaches, predicting long-term behavior is still challenging as the formation interacts physically and chemically with the fluids present in-situ. Recent experimental work has shown that shale samples subjected to a change in effective stress deform in a time-dependent manner ("creep"). Although the magnitude and nature of this behavior is strongly related to the composition and texture of the sample, also the choice of fluid used in the experiments affects the total strain response - strongly adsorbing fluids result in more, recoverable creep. The processes underlying time-dependent deformation of shales under in-situ stresses, and the long-term impact on reservoir performance, are at present poorly understood. In this contribution, we report triaxial mechanical tests, and theoretical/thermodynamic modeling work with the aim to identify and describe the main mechanisms that control time-dependent deformation of gas shales. In particular, we focus on the role of the shale solid framework versus the type and pressure of the present pore fluid. Our experiments were mainly performed on Eagle Ford Shale samples. The samples were subjected to cycles of loading and unloading, first in the dry state, and then again after equilibrating them with (adsorbing) CO2 and (non-adsorbing) He at fluid pressures of 4 MPa. Stresses were chosen close to those persisting under in-situ conditions. The results of our tests demonstrate that likely two main types of deformation mechanisms operate that relate to a) the presence of microfractures as a dominating feature in the solid framework of the shale, and b) the adsorbing potential of fluids present in the nanoscale voids of the shale. To explain the role of adsorption in the observed

Deformable and conformal silk hydrogel inverse opal

PubMed Central

Kim, Sookyoung; Kim, Sunghwan

2017-01-01

Photonic crystals (PhCs) efficiently manipulate photons at the nanoscale. Applying these crystals to biological tissue that has been subjected to large deformation and humid environments can lead to fascinating bioapplications such as in vivo biosensors and artificial ocular prostheses. These applications require that these PhCs have mechanical durability, deformability, and biocompatibility. Herein, we introduce a deformable and conformal silk hydrogel inverse opal (SHIO); the photonic lattice of this 3D PhC can be deformed by mechanical strain. This SHIO is prepared by the UV cross-linking of a liquid stilbene/silk solution, to give a transparent and elastic hydrogel. The pseudophotonic band gap (pseudo-PBG) of this material can be stably tuned by deformation of the photonic lattice (stretching, bending, and compressing). Proof-of-concept experiments demonstrate that the SHIO can be applied as an ocular prosthesis for better vision, such as that provided by the tapeta lucida of nocturnal or deep-sea animals. PMID:28559327

Heavy Deformation of Patented Near-Eutectoid Steel

NASA Astrophysics Data System (ADS)

Khanchandani, Heena; Banerjee, M. K.

2018-01-01

Evolution of microstructure in the patented near-eutectoid steel, forged under varying situations, is critically examined in the present investigation. Steel with 0.74 wt.% carbon is isothermally annealed at 500 °C to obtain fine pearlite microstructure. Steel samples, so patented, are subjected to mechanical deformation by forging at various temperatures with different amount of thickness reduction. Microstructural analyses have revealed that mechanical deformation by forging at lower temperatures brings about partial dissolution of cementite, which is followed by the formation of ɛ-carbide in the microstructures. In contrast, cementite is precipitated within ferrite matrix upon warm or hot forging at higher temperatures. It is further observed that increasing deformation percent during low-temperature forging reduces interlamellar spacing of pearlite, whereas an opposite trend is noticed in case of deformation at higher temperature; moreover, deformation induced the change in interlamellar spacing and formation of fine carbide phases in microstructures has caused appreciable enhancement in hardness of the steel.

Foam rheology at large deformation

NASA Astrophysics Data System (ADS)

Géminard, J.-C.; Pastenes, J. C.; Melo, F.

2018-04-01

Large deformations are prone to cause irreversible changes in materials structure, generally leading to either material hardening or softening. Aqueous foam is a metastable disordered structure of densely packed gas bubbles. We report on the mechanical response of a foam layer subjected to quasistatic periodic shear at large amplitude. We observe that, upon increasing shear, the shear stress follows a universal curve that is nearly exponential and tends to an asymptotic stress value interpreted as the critical yield stress at which the foam structure is completely remodeled. Relevant trends of the foam mechanical response to cycling are mathematically reproduced through a simple law accounting for the amount of plastic deformation upon increasing stress. This view provides a natural interpretation to stress hardening in foams, demonstrating that plastic effects are present in this material even for minute deformation.

Effect of bimodal harmonic structure design on the deformation behaviour and mechanical properties of Co-Cr-Mo alloy.

PubMed

Vajpai, Sanjay Kumar; Sawangrat, Choncharoen; Yamaguchi, Osamu; Ciuca, Octav Paul; Ameyama, Kei

2016-01-01

In the present work, Co-Cr-Mo alloy compacts with a unique bimodal microstructural design, harmonic structure design, were successfully prepared via a powder metallurgy route consisting of controlled mechanical milling of pre-alloyed powders followed by spark plasma sintering. The harmonic structured Co-Cr-Mo alloy with bimodal grain size distribution exhibited relatively higher strength together with higher ductility as compared to the coarse-grained specimens. The harmonic Co-Cr-Mo alloy exhibited a very complex deformation behavior wherein it was found that the higher strength and the high retained ductility are derived from fine-grained shell and coarse-grained core regions, respectively. Finally, it was observed that the peculiar spatial/topological arrangement of stronger fine-grained and ductile coarse-grained regions in the harmonic structure promotes uniformity of strain distribution, leading to improved mechanical properties by suppressing the localized plastic deformation during straining. Copyright © 2015 Elsevier B.V. All rights reserved.

Microstructure, accumulated strain, and mechanical behavior of AA6061 Al alloy severely deformed at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Magalhães, D. C.; Kliauga, A. M.; Ferrante, M.; Sordi, V. L.

2017-05-01

The combination of Severe Plastic Deformation (SPD) and cryogenic temperatures can be an efficient way to obtain metals and alloys with very refined microstructure and thus optimize the strength-ductility pair. However, there is still a lack of studies on cryogenic SPD process and their effects on microstructure and mechanical properties, especially in precipitation-hardenable aluminum alloys. This study describes the effect of low temperature processing on microstructure, aging kinetic and tensile properties of AA6061 Al alloy after cryo-SPD. Samples of AA6061 Al alloy in the solutionized state was processed by Equal-channel angular pressing (ECAP) at 77 K and 298 K, up to accumulate true strains up to 4.2. Results indicated that the aging kinetic is accelerated when deformation is performed at cryogenic temperature, dislocation density measurement by x-ray and diffraction analysis at TEM achieved a saturation level of 2×1015 m-2 by ECAP at 298K and 5×1015 m-2 after cryogenic ECAP plus precipitation hardening. The same level of yield strength was observed in both deformation procedures but an improvement in uniform elongation was achieved by cryogenic ECAP followed by a T6 treatment

Self-adjointness of deformed unbounded operators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Much, Albert

2015-09-15

We consider deformations of unbounded operators by using the novel construction tool of warped convolutions. By using the Kato-Rellich theorem, we show that unbounded self-adjoint deformed operators are self-adjoint if they satisfy a certain condition. This condition proves itself to be necessary for the oscillatory integral to be well-defined. Moreover, different proofs are given for self-adjointness of deformed unbounded operators in the context of quantum mechanics and quantum field theory.

Effect of Intensive Plastic Deformation on Microstructure and Mechanical Properties of Aluminum Alloys

NASA Astrophysics Data System (ADS)

Rakhadilov, Bauyrzhan; Uazyrkhanova, Gulzhaz; Myakinin, Alexandr; Uazyrkhanova, Zhuldyz

2016-08-01

In work it was studied the influence of intensive plastic deformation on structure and mechanical properties of aluminum alloys. Intensive plastic deformation was carried out by using equal-channel angular extrusion. It is shown that the most efficient angle of intersection of the channels is the angle of Φ=120°, which ensures defect-free parts at the highest possible level of accumulated strain (e=8). It is established that the intensive milling grain structures in aluminum alloys AMG6 and AMC occurs at ECAE-12 passes, while the intersection angle of the channels of 120°. After ECAE-12 in aluminum alloys the grain refinement reaches to the size of ∼⃒1.0-1.5 gm. It is determined that as a result of equal channel angular pressing, the microhardness of alloy AMG6 increases almost 4 times in comparison with the initial state, the microhardness of alloy AMC increases by almost 4.5 times in comparison with the initial state. It is shown that ECAE-12 mass loss is reduced to 5.4 and 5.6 mg, which shows an increase in wear-resistance of aluminum alloys AMG6 and AMC 13-14 %.

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material

PubMed Central

Valíček, Jan; Harničárová, Marta; Öchsner, Andreas; Hutyrová, Zuzana; Kušnerová, Milena; Tozan, Hakan; Michenka, Vít; Šepelák, Vladimír; Mitaľ, Dušan; Zajac, Jozef

2015-01-01

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ. PMID:28793645

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material.

PubMed

Valíček, Jan; Harničárová, Marta; Öchsner, Andreas; Hutyrová, Zuzana; Kušnerová, Milena; Tozan, Hakan; Michenka, Vít; Šepelák, Vladimír; Mitaľ, Dušan; Zajac, Jozef

2015-11-03

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ.

Deformation Theory and Physics Model Building

NASA Astrophysics Data System (ADS)

Sternheimer, Daniel

2006-08-01

The mathematical theory of deformations has proved to be a powerful tool in modeling physical reality. We start with a short historical and philosophical review of the context and concentrate this rapid presentation on a few interrelated directions where deformation theory is essential in bringing a new framework - which has then to be developed using adapted tools, some of which come from the deformation aspect. Minkowskian space-time can be deformed into Anti de Sitter, where massless particles become composite (also dynamically): this opens new perspectives in particle physics, at least at the electroweak level, including prediction of new mesons. Nonlinear group representations and covariant field equations, coming from interactions, can be viewed as some deformation of their linear (free) part: recognizing this fact can provide a good framework for treating problems in this area, in particular global solutions. Last but not least, (algebras associated with) classical mechanics (and field theory) on a Poisson phase space can be deformed to (algebras associated with) quantum mechanics (and quantum field theory). That is now a frontier domain in mathematics and theoretical physics called deformation quantization, with multiple ramifications, avatars and connections in both mathematics and physics. These include representation theory, quantum groups (when considering Hopf algebras instead of associative or Lie algebras), noncommutative geometry and manifolds, algebraic geometry, number theory, and of course what is regrouped under the name of M-theory. We shall here look at these from the unifying point of view of deformation theory and refer to a limited number of papers as a starting point for further study.

Mechanical properties and deformation mechanism of Al2O3 determined from in situ transmission electron microscopy compression

NASA Astrophysics Data System (ADS)

Lin, Kai-Peng; Stachiv, Ivo; Fang, Te-Hua

2017-07-01

The mechanical properties and deformation mechanism of alumina (Al2O3) ceramic nanopillars and microstructures have been studied using in situ transmission electron microscopy (TEM) compression and nanoindentation experiments. It has been found that the Young’s modulus of Al2O3 nanopillars significantly increases with a decrease of its thickness; it ranges from 54.8 GPa for the nanopillar of radius 175 nm to 347.5 GPa for the one of radius of 75 nm. The hardness of Al2O3 microstructures estimated by the nanoindentation is between 3.19 to 20.60 GPa. The Raman spectra of Al2O3 substrate has a production peak (577.3 cm-1) between 418.3 and 645.2 (cm-1) peaks. The strain hardening behavior of Al2O3 microstructures has been observed and the impact of size on the compressive and bending behavior of Al2O3 micro-pillared structures is also examined and explained.

Structural defects in natural plastically deformed diamonds: Evidence from EPR spectroscopy

NASA Astrophysics Data System (ADS)

Mineeva, R. M.; Titkov, S. V.; Speransky, A. V.

2009-06-01

Structural defects formed as a result of plastic deformation in natural diamond crystals have been studied by EPR spectroscopy. The spectra of brown, pink-brown, black-brown, pink-purple, and gray plastically deformed diamonds of type Ia from deposits in Yakutia and the Urals were recorded. The results of EPR spectroscopy allowed us to identify various deformation centers in the structure of natural diamonds and to show that nitrogen centers were transformed under epigenetic mechanical loading. Abundant A centers, consisting of two isomorphic nitrogen atoms located in neighboring structural sites, were destroyed as a result of this process to form a series of N1, N4, W7, M2, and M3 nitrogen centers. Such centers are characterized by an anisotropic spatial distribution and a positive charge, related to the mechanism of their formation. In addition, N2 centers (probably, deformation-produced dislocations decorated by nitrogen) were formed in all plastically deformed diamonds and W10 and W35 centers (the models have not been finally ascertained) were formed in some of them. It has been established that diamonds with various types of deformation-induced color contain characteristic associations of these deformation centers. The diversity of associations of deformation centers indicates appreciable variations in conditions of disintegration of deep-seated rocks, transfer of diamonds to the Earth’s surface, and formation of kimberlitic deposits. Depending on the conditions of mechanical loading, the diamond crystals were plastically deformed by either dislocation gliding or mechanical twinning. Characteristic features of plastic deformation by dislocation gliding are the substantial prevalence of the N2 centers over other deformation centers and the occurrence of the high-spin W10 and W35 centers. The attributes of less frequent plastic deformation by mechanical twinning are unusual localization of the M2 centers and, in some cases, the N1 centers in microtwinned

Orogen-scale along-strike continuity in quartz recrystallization microstructures adjacent to the Main Central Thrust: implications for deformation temperatures, strain rates and flow stresses

NASA Astrophysics Data System (ADS)

Law, Richard

2015-04-01

Traced for ~ 1500 km along the foreland edge of the Himalaya from NW India to Bhutan published reports indicate a remarkable along-strike continuity of quartz recrystallization microstructures in the footwall and hanging wall to the Main Central Thrust (MCT). Recrystallization in Lesser Himalayan Series (LHS) rocks in the footwall to the MCT is dominated by grain boundary bulging (BLG) microstructures, while recrystallization in Greater Himalayan Series (GHS) rocks in the hanging wall is dominated by grain boundary migration microstructures that traced structurally upwards transition in to the anatectic core of the GHS. In foreland-positioned high-strain rocks adjacent to the MCT recrystallization is dominated by subgrain rotation (SGR) with transitional BLG-SGR and SGR-GBM microstructures being recorded at structural distances of up to a few hundred meters below and above the MCT, respectively. Correlation with available information on temperatures of metamorphism indicated by mineral phase equilibria and RSCM data suggests that recrystallization in the structural zones dominated by BLG, SGR and GBM occurred at temperatures of ~ 350-450, 450-550 and 550- > 650 °C, respectively. It should be kept in mind, however, that these temperatures are likely to be 'close-to-peak' temperatures of metamorphism, whereas penetrative shearing and recrystallization may have continued during cooling. The dominance of SGR along the more foreland-positioned exposures of the MCT intuitively suggests that shearing occurred under a relatively restricted range of deformation temperatures and strain rates. Plotting the 'close-to-peak' 450-500 °C temperatures of metamorphism indicated for SGR-dominated rocks located at up to a few hundred meters below/above the MCT on the quartz recrystallization map developed by Stipp et al. (2002) indicates 'ball-park' strain rates of ~ 10-13 to 10-10 sec-1. However, only strain rates slower than 10-12 sec-1 on the MCT are likely to be compatible with

Effect of the mechanical deformation on the electrical properties of the polymer/CNT fiber

NASA Astrophysics Data System (ADS)

Cho, Hyun Woo; Sung, Bong June; Nano-Bio Computational Chemistry Laboratory Team

2014-03-01

We elucidate the effect of the mechanical deformation on the electrical properties of the polymer/CNT fiber. The conductive polymer fiber has drawn a great attention for its potential application to a stretchable electronics such as wearable devices and artificial muscles, etc. However, the electrical conductivity of the polymer-based stretchable electronics decreases significantly during the deformation, which may limit the applicability of the polymer/CNT fiber for the stretchable electronics. Moreover, its physical origin for the decrease in electrical conductivity has not been explained clearly. In this work, we employ a coarse-grained model for the polymer/CNT fiber, and we calculate the electric conductivity using global tunneling network (GTN) model. We show that the electric conductivity decreases during the elongation of the polymer/CNT fiber. We also find using critical path approximation (CPA) that the structure of the electrical network of the CNTs changes collectively during the elongation of the fiber, which is strongly responsible for the reduction of the electrical conductivity of the polymer/CNT fiber.

Determination of functions of controlling drives of main executive mechanisms of mining excavators

NASA Astrophysics Data System (ADS)

Lagunova, Yu A.; Komissarov, A. P.; Lukashuk, O. A.

2018-03-01

It is shown that a special shovel is a feature of the structure of the drives of the main mechanisms (mechanisms of lifting and pressure) of career excavators with working equipment, the presence in the transfer device of a two-crank-lever mechanism of working equipment that connects the main mechanisms with the working body (bucket). In this case, the transformation of the mechanical energy parameters of the motors into energy-force parameters realized at the cutting edge of the bucket (teeth) takes place depending on the type of the kinematic scheme of the two-link-lever mechanism. The concept of “control function” defining the relationship between the parameters characterizing the position of the bucket in the face (the coordinates of the tip of the cutting edge of the bucket, the digging speed) and the required control level are introduced. These are the values of the lifting and head speeds ensuring the bucket movement along a given trajectory.

Red blood cell dynamics: from cell deformation to ATP release.

PubMed

Wan, Jiandi; Forsyth, Alison M; Stone, Howard A

2011-10-01

The mechanisms of red blood cell (RBC) deformation under both static and dynamic, i.e., flow, conditions have been studied extensively since the mid 1960s. Deformation-induced biochemical reactions and possible signaling in RBCs, however, were proposed only fifteen years ago. Therefore, the fundamental relationship between RBC deformation and cellular signaling dynamics i.e., mechanotransduction, remains incompletely understood. Quantitative understanding of the mechanotransductive pathways in RBCs requires integrative studies of physical models of RBC deformation and cellular biochemical reactions. In this article we review the physical models of RBC deformation, spanning from continuum membrane mechanics to cellular skeleton dynamics under both static and flow conditions, and elaborate the mechanistic links involved in deformation-induced ATP release. This journal is © The Royal Society of Chemistry 2011

Effect of Post-deformation Annealing Treatment on the Microstructural Evolution of a Cold-Worked Corrosion-Resistant Superalloy (CRSA) Steel

NASA Astrophysics Data System (ADS)

Mirzaei, A.; Zarei-Hanzaki, A.; Mohamadizadeh, A.; Lin, Y. C.

2018-03-01

The post-deformation annealing treatments of a commercial cold-worked corrosion-resistant superalloy steel (Sanicro 28 steel) were carried out at different temperatures in the range of 900-1100 °C for different holding durations of 5, 10, and 15 min. The effects of post-deformation annealing time and temperature on the microstructural evolution and subsequent mechanical properties of the processed Sanicro 28 steel were investigated. The observations indicated that twin-twin hardening in cold deformation condition mainly correlates with abundant nucleation of mechanical twins in multiple directions resulting in considerable strain hardening behavior. Microstructural investigations showed that the static recrystallization takes place after isothermal holding at 900 °C for 5 min. Increasing the annealing temperature from 900 to 1050 °C leads to recrystallization development and grain refinement in the as-recrystallized state. In addition, an increase in annealing duration from 5 to 15 min leads to subgrain coarsening and subsequently larger recrystallized grains size. The occurrence of large proportion of the grain refinement, which is achieved in the first annealing stage at 1050 °C after 5 min, is considered as the main factor for the maximum elongation at this stage.

What Do Observations of Postseismic Deformation Tell us About the Rheology of the Lithoshpere?

NASA Astrophysics Data System (ADS)

Fialko, Y.

2006-12-01

postseismic deformation due to several large earthquakes in California and Asia, and discuss implications from these measurements for the crust and upper mantle rheology. The main conclusion is that the deformation patterns are not consistent between different events, suggesting either various contributions from different relaxation mechanisms, or significant variations in crustal rheologies.

Deformation processes in forging ceramics

NASA Technical Reports Server (NTRS)

Cannon, R. M.; Rhodes, W. H.

1973-01-01

The deformation processes involved in the forging of refractory ceramic oxides were investigated. A combination of mechanical testing and forging was utilized to investigate both the flow and fracture processes involved. Deformation studies of very fine grain Al203 revealed an apparent transition in behavior, characterized by a shift in the strain rate sensitivity from 0.5 at low stresses to near unity at higher stresses. The behavior is indicative of a shift in control between two dependent mechanisms, one of which is indicated to be cation limited diffusional creep with significant boundary enhancement. The possible contributions of slip, indicated by crystallographic texture, interface control of the diffusional creep and inhomogeneous boundary sliding are also discussed. Additional experiments indicated an independence of deformation behavior on MgO doping and retained hot pressing impurities, at least for ultrafine grained material, and also an independence of test atmosphere.

Fluid flow in deforming media: interpreting stable isotope signatures of marbles

NASA Astrophysics Data System (ADS)

Bond, C. E.

2016-12-01

Fluid flow in the crust is controlled by permeable networks. These networks can be created and destroyed dynamically during rock deformation. Rock deformation is therefore critical in controlling fluid pathways in the crust and hence the location of mineral and other resources. Here, evidence for deformation-enhanced fluid infiltration shows that a range of deformation mechanisms control fluid flow and chemical and isotopic equilibration. The results attest to localised fluid infiltration within a single metamorphic terrain (12km) over a range of metamorphic grades; ecologite- blueschist to greenschist. For fluid infiltrating marbles during ductile deformation, chemical and isotopic signatures are now homogenous; whilst fluid infiltration associated with brittle deformation results in chemical and isotopic heterogeneity at a microscale. The findings demonstrate how ductile deformation enhances equilibration of δ18O at a grain scale whilst brittle deformation does not. The control of deformation mechanisms in equilibrating isotopic and chemical heterogeneities have implications for the understanding of fluid-rock interaction in the crust. Interpretation of bulk stable isotope data, particularly in the use of isotope profiles to determine fluid fluxes into relatively impermeable units that have been deformed need to be used with care when trying to determine fluid fluxes and infiltration mechanisms.

48. MAIN WAREHOUSE THIRD LEVEL Elevator drive mechanism is ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

48. MAIN WAREHOUSE - THIRD LEVEL Elevator drive mechanism is seen to the right, while drive wheels, belt wheels and chain drives are visible in the wooden wall framing. The horizontal metal conveyor (at the top of the wall Just under the inverted 'V' brace) is part of the empty can supply system connected to the external can conveyor. See Photo No. 28. - Hovden Cannery, 886 Cannery Row, Monterey, Monterey County, CA

Mathematical models of carbon-carbon composite deformation

NASA Astrophysics Data System (ADS)

Golovin, N. N.; Kuvyrkin, G. N.

2016-09-01

Mathematical models of carbon-carbon composites (CCC) intended for describing the processes of deformation of structures produced by using CCC under high-temperature loading are considered. A phenomenological theory of CCC inelastic deformation is proposed, where such materials are considered as homogeneous ones with effective characteristics and where their high anisotropy of mechanical characteristics and different ways of resistance to extension and compression are taken into account. Micromechanical models are proposed for spatially reinforced CCC, where the difference between mechanical characteristics of components and the reinforcement scheme are taken into account. Themodel parameters are determined from the results of experiments of composite macrospecimens in the directions typical of the material. A version of endochronictype theory with several internal times "launched" for each composite component and related to some damage accumulation mechanisms is proposed for describing the inelastic deformation. Some practical examples are considered.

Deformation of phospholipid vesicles in an optical stretcher.

PubMed

Delabre, Ulysse; Feld, Kasper; Crespo, Eleonore; Whyte, Graeme; Sykes, Cecile; Seifert, Udo; Guck, Jochen

2015-08-14

Phospholipid vesicles are common model systems for cell membranes. Important aspects of the membrane function relate to its mechanical properties. Here we have investigated the deformation behaviour of phospholipid vesicles in a dual-beam laser trap, also called an optical stretcher. This study explicitly makes use of the inherent heating present in such traps to investigate the dependence of vesicle deformation on temperature. By using lasers with different wavelengths, optically induced mechanical stresses and temperature increase can be tuned fairly independently with a single setup. The phase transition temperature of vesicles can be clearly identified by an increase in deformation. In the case of no heating effects, a minimal model for drop deformation in an optical stretcher and a more specific model for vesicle deformation that takes explicitly into account the angular dependence of the optical stress are presented to account for the experimental results. Elastic constants are extracted from the fitting procedures, which agree with literature data. This study demonstrates the utility of optical stretching, which is easily combined with microfluidic delivery, for the future serial, high-throughput study of the mechanical and thermodynamic properties of phospholipid vesicles.

Plate Like Convection with Viscous Strain Weakening and Corresponding Surface Deformation Pattern

NASA Astrophysics Data System (ADS)

Fuchs, L.; Becker, T. W.

2017-12-01

How plate tectonic surface motions are generated by mantle convection on Earth and possibly other terrestrial type planets has recently become more readily accessible with fully dynamic convection computations. However, it remains debated how plate-like the behavior in such models truly is, and in particular how the well plate boundary dynamics are captured in models which typically exclude the effects of deformation history and memory. Here, we analyze some of the effects of viscous strain weakening on plate behavior and the interactions between interior convection dynamics and surface deformation patterns. We use the finite element code CitcomCU to model convection in a 3D Cartesian model setup. The models are internally heated, with an Arrhenius-type temperature dependent viscosity including plastic yielding and viscous strain weakening (VSW) and healing (VSWH). VSW can mimic first order features of more complex damage mechanisms such as grain-size dependent rheology. Besides plate diagnostic parameters (Plateness, Mobility, and Toroidal: Poloidal ratio) to analyze the tectonic behavior our models, we also explore how "plate boundaries" link to convective patterns. In a first model series, we analyze general surface deformation patterns without VSW. In the early stages, deformation patterns are clearly co-located with up- and downwelling limbs of convection. Along downwellings strain-rates are high and localized, whereas upwellings tend to lead to broad zones of high deformation. At a more advanced stage, however, the plates' interior is highly deformed due to continuous strain accumulation and resurfaced inherited strain. Including only VSW leads to more localized deformation along downwellings. However, at a more advanced stage plate-like convection fails due an overall weakening of the material. This is prevented including strain healing. Deformation pattern at the surface more closely coincide with the internal convection patterns. The average surface

Rock deformation equations and application to the study on slantingly installed disc cutter

NASA Astrophysics Data System (ADS)

Zhang, Zhao-Huang; Meng, Liang; Sun, Fei

2014-08-01

At present the mechanical model of the interaction between a disc cutter and rock mainly concerns indentation experiment, linear cutting experiment and tunnel boring machine (TBM) on-site data. This is not in line with the actual rock-breaking movement of the disc cutter and impedes to some extent the research on the rock-breaking mechanism, wear mechanism and design theory. Therefore, our study focuses on the interaction between the slantingly installed disc cutter and rock, developing a model in accordance with the actual rock-breaking movement. Displacement equations are established through an analysis of the velocity vector at the rock-breaking point of the disc cutter blade; the functional relationship between the displacement parameters at the rock-breaking point and its rectangular coordinates is established through an analysis of micro-displacement vectors at the rock-breaking point, thus leading to the geometric equations of rock deformation caused by the slantingly installed disc cutter. Considering the basically linear relationship between the cutting force of disc cutters and the rock deformation before and after the leap break of rock, we express the constitutive relations of rock deformation as generalized Hooke's law and analyze the effect of the slanting installation angle of disc cutters on the rock-breaking force. This will, as we hope, make groundbreaking contributions to the development of the design theory and installation practice of TBM.

Rheology and Seismic Potential of Experimentally-Deformed Natural Serpentinites

NASA Astrophysics Data System (ADS)

Gasc, J.; Hilairet, N.; Wang, Y.; Yu, T.; Ferrand, T. P.; Schubnel, A.

2016-12-01

The origin of intermediate-depth earthquakes, which occur at depths of 60-300 km along subducting slabs, remains somehow enigmatic. In the pressure and temperature conditions involved, rocks should indeed deform in a ductile fashion. One, or more, mechanism is therefore responsible for mechanical instabilities. Dehydration embrittlement, due to serpentine breakdown, was long considered a good candidate. However, in recent years, experimental studies have challenged this theory, by showing that deformation and faulting of serpentinites, related to dehydration, occurs in a stable and aseismic way (Chernak and Hirth, 2011; Gasc et al., 2011). In order to assess the seismic potential of serpentinites, high pressure deformation experiments were carried out on natural samples, during which micro-seismicity was monitored by recording Acoustic Emissions (AE's). Deformation was performed at pressures of 3-5 GPa, using a Deformation-DIA device, and over a wide range of temperatures, both within and outside antigorite's stability field. The results show that, below 400 C, serpentinite deformation involves aseismic semi-brittle mechanisms, even in cases where strain localization is observed. At high temperature (i.e., above 600 C), despite conditions propitious to dehydration embrittlement (i.e., with fast strain rates and reaction kinetics), joint deformation and dehydration leads to ductile shear, without generation of AE's. On the other hand, a brittle temperature window, centered at ca. 500 C, is evidenced. In this latter case, AE's are consistently collected upon deformation and faulting with extremely sharp strain localization is observed. This brittle field may therefore be a source of seismicity in subducting slabs at mantle pressures. However, analysis of the acoustic signal shows that it is relatively orders of magnitude weaker than its real-earth counterparts, which suggests that other mechanisms are responsible for larger intermediate-depth earthquakes. In fact

Extracting Cell Stiffness from Real-Time Deformability Cytometry: Theory and Experiment

PubMed Central

Mietke, Alexander; Otto, Oliver; Girardo, Salvatore; Rosendahl, Philipp; Taubenberger, Anna; Golfier, Stefan; Ulbricht, Elke; Aland, Sebastian; Guck, Jochen; Fischer-Friedrich, Elisabeth

2015-01-01

Cell stiffness is a sensitive indicator of physiological and pathological changes in cells, with many potential applications in biology and medicine. A new method, real-time deformability cytometry, probes cell stiffness at high throughput by exposing cells to a shear flow in a microfluidic channel, allowing for mechanical phenotyping based on single-cell deformability. However, observed deformations of cells in the channel not only are determined by cell stiffness, but also depend on cell size relative to channel size. Here, we disentangle mutual contributions of cell size and cell stiffness to cell deformation by a theoretical analysis in terms of hydrodynamics and linear elasticity theory. Performing real-time deformability cytometry experiments on both model spheres of known elasticity and biological cells, we demonstrate that our analytical model not only predicts deformed shapes inside the channel but also allows for quantification of cell mechanical parameters. Thereby, fast and quantitative mechanical sampling of large cell populations becomes feasible. PMID:26588562

Effect of Dehydration Reaction on Serpentinite Deformation in Torsion

NASA Astrophysics Data System (ADS)

Vinciguerra, S.; Trovato, C.; Meredith, P. G.; Benson, P. M.; Hirose, T.; Bystricky, M.; Stünitz, H.; Kunze, K.

2003-12-01

antigorite. The peak strength of a sample pre-heated at 750 ° C for 3 hr and then deformed at 700 ° C is 70 MPa lower than a sample deformed directly at 700 ° C. This stress reduction occurred due to the presence of a mechanically weaker reaction product (talc) rather than elevated pore pressure because the sample was deformed under completely drained conditions. By contrast, a solid sample was weaker than hollow ones by ˜100 MPa, mainly due to low permeability of the serpentinite. Excess fluid pressure in solid specimens leads to a drop in the effective pressure and appears to have enhanced the dehydration reaction along micro-fractures. Our data shows that dehydration weakening of serpentinite is caused not as much because of excess pore pressure but more because of the weaker mineral assemblages from the reaction. In contrast to semi-brittle faulting in antigorite, deformation of lizardite at 550 ° C to a bulk shear strain of 0.9 was widely distributed, showing typical ductile microstructures such as boudinage and S-C fabric. A well developed secondary foliation (C-plane) and strong lattice preferred orientations of lizardite grains were observed close to the localized shear zones. After the initial peak stress, steady stress values of 250 MPa were measured. We intend to focus on how the localized zones evolve and how the mechanical response changes with increasing shear strain during the reaction.

Deformation associated with continental normal faults

NASA Astrophysics Data System (ADS)

Resor, Phillip G.

Deformation associated with normal fault earthquakes and geologic structures provide insights into the seismic cycle as it unfolds over time scales from seconds to millions of years. Improved understanding of normal faulting will lead to more accurate seismic hazard assessments and prediction of associated structures. High-precision aftershock locations for the 1995 Kozani-Grevena earthquake (Mw 6.5), Greece image a segmented master fault and antithetic faults. This three-dimensional fault geometry is typical of normal fault systems mapped from outcrop or interpreted from reflection seismic data and illustrates the importance of incorporating three-dimensional fault geometry in mechanical models. Subsurface fault slip associated with the Kozani-Grevena and 1999 Hector Mine (Mw 7.1) earthquakes is modeled using a new method for slip inversion on three-dimensional fault surfaces. Incorporation of three-dimensional fault geometry improves the fit to the geodetic data while honoring aftershock distributions and surface ruptures. GPS Surveying of deformed bedding surfaces associated with normal faulting in the western Grand Canyon reveals patterns of deformation that are similar to those observed by interferometric satellite radar interferometry (InSAR) for the Kozani Grevena earthquake with a prominent down-warp in the hanging wall and a lesser up-warp in the footwall. However, deformation associated with the Kozani-Grevena earthquake extends ˜20 km from the fault surface trace, while the folds in the western Grand Canyon only extend 500 m into the footwall and 1500 m into the hanging wall. A comparison of mechanical and kinematic models illustrates advantages of mechanical models in exploring normal faulting processes including incorporation of both deformation and causative forces, and the opportunity to incorporate more complex fault geometry and constitutive properties. Elastic models with antithetic or synthetic faults or joints in association with a master

Deformation mechanisms in negative Poisson's ratio materials - Structural aspects

NASA Technical Reports Server (NTRS)

Lakes, R.

1991-01-01

Poisson's ratio in materials is governed by the following aspects of the microstructure: the presence of rotational degrees of freedom, non-affine deformation kinematics, or anisotropic structure. Several structural models are examined. The non-affine kinematics are seen to be essential for the production of negative Poisson's ratios for isotropic materials containing central force linkages of positive stiffness. Non-central forces combined with pre-load can also give rise to a negative Poisson's ratio in isotropic materials. A chiral microstructure with non-central force interaction or non-affine deformation can also exhibit a negative Poisson's ratio. Toughness and damage resistance in these materials may be affected by the Poisson's ratio itself, as well as by generalized continuum aspects associated with the microstructure.

Structural and Lithologic Characterization of the SAFOD Pilot Hole and Phase One Main Hole

NASA Astrophysics Data System (ADS)

Barton, D. C.; Bradbury, K.; Solum, J. G.; Evans, J. P.

2005-12-01

Petrological and microstructural analyses of drill cuttings were conducted for the San Andreas Fault Observatory at Depth (SAFOD) Pilot Hole and Main Hole projects. Grain mounts were produced at ~30 m (100 ft) intervals from drill cuttings collected from the Pilot Hole to a depth of 2164 m (7100 ft) and from Phase 1 of the SAFOD main hole to a depth of 3067 m (10062 ft). . Thin-section grain mount analysis included identification of mineral composition, alteration, and deformation within individual grains, measured at .5 mm increments on an equally spaced, 300 point grid pattern. Lithologic features in the Quaternary/Tertiary deposits from 30 - 640 m (100-2100 ft) in the Pilot Hole, and 670 - 792 m (2200 - 2600 ft) in the Phase 1 main hole, include fine-grained, thinly bedded sediments with clasts of fine-grained volcanic groundmass. Preliminary grain mount analysis from 1920 - 3067 m (6300 - 10062) in the Phase 1 main hole, indicates a sedimentary sequence consisting of fine-grained lithic fragments of very fine-grained shale. Deformation mechanisms observed within the cuttings of granitic rocks from 914 - 1860 m (3000 - 6100 ft.) include intracrystalline plasticity and cataclasis. Intracrystalline plastic deformation within quartz and feldspar grains is indicated by undulatory extinction, ribbon grains, chessboard patterns, and deformation twins and lamellae. Cataclastic deformation is characterized by intra- and intergranular microfractures, angular grains, gouge zones, iron-oxide banding, and comminution. Mineral and cataclasite abundances were plotted as a function of weight percent vs. depth. Plots of quartz and feldspar abundances are also correlated with XRD weight percent data from 1160 - 1890 m (3800 - 6200 ft.) in the granitic and granodioritic sequences of the Phase 1 main hole. Regions of the both of the drill holes with cataclasite abundances ranging from 20 - 30 wt% are interpreted as shear zones. Shear zones identified in this study from 1150 - 1420

A study of the micro- and nanoscale deformation behavior of individual austenitic dendrites in a FeCrMoVC cast alloy using micro- and nanoindentation experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeisig, J., E-mail: j.zeisig@ifw-dresden.de; Hufenbach, J.; Wendrock, H.

2016-04-04

Micro- and nanoindentation experiments were conducted to investigate the deformation mechanisms in a Fe79.4Cr13Mo5V1C1.6 (wt. %) cast alloy. This alloy consists of an as cast microstructure mainly composed of austenite, martensite, and a complex carbide network. During microhardness testing, metastable austenite transforms partially into martensite confirmed by electron backscatter diffraction. For nanoindentation tests, two different indenter geometries were applied (Berkovich and cube corner type). Load-displacement curves of nanoindentation in austenitic dendrites depicted pop-ins after transition into plastic deformation for both nanoindenters. Characterizations of the region beneath a nanoindent by transmission electron microscopy revealed a martensitic transformation as an activated deformationmore » mechanism and suggest a correlation with the pop-in phenomena of the load-displacement curves. Furthermore, due to an inhomogeneous chemical composition within the austenitic dendrites, more stabilized regions deform by mechanical twinning. This additional deformation mechanism was only observed for the cube corner indenter with the sharper geometry since higher shear stresses are induced beneath the contact area.« less

Effect of different stages of deformation on the microstructure evolution of Ti-rich NiTi shape memory alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tadayyon, Ghazal, E-mail: Ghazal.tadayyon@gmail.co

The main objective of this work was to investigate the thermomechanical behavior and microstructural changes of a Ti-rich NiTi shape memory alloy (SMA). The microstructural and texture evolution of aged NiTi alloy at different degrees of deformation were elicited by transmission electron microscopy (TEM). An effort was made to correlate results obtained from the tensile test with results from microstructure studies. The undeformed sample reveals a self-accommodated morphology with straight and well defined twin boundaries. At different stages of deformation, diverse mechanisms were involved. These mechanisms include marstraining, detwinning accompanied by dislocation movement, and finally, severe plastic deformation, subdivision andmore » amorphization of the matrix. Under increasing strains, high density lattice defects were generated and the morphology of B19’ became disordered. - Graphical abstract: The summary of microstructure changes of the martensite twins during tensile deformation in polycrystalline NiTi SMAs. - Highlights: • Initial elastic response, dislocation avalanche and deformation bands were studied. • < 011 > Type II twin accompanied by detwinned area after 2% cold work was observed. • Visible parallel fine stacking faults showed plastic flow of the material. • At higher strains, subgrains changed to recrystallized, finely amorphous structure.« less

Deformation behavior of carbon-fiber reinforced shape-memory-polymer composites used for deployable structures (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lan, Xin; Liu, Liwu; Li, Fengfeng; Pan, Chengtong; Liu, Yanju; Leng, Jinsong

2017-04-01

Shape memory polymers (SMPs) are a new type of smart material, they perform large reversible deformation with a certain external stimulus (e.g., heat and electricity). The properties (e.g., stiffness, strength and other mechanically static or quasi-static load-bearing capacity) are primarily considered for conventional resin-based composite materials which are mainly used for structural materials. By contrast, the mechanical actuating performance with finite deformation is considered for the shape memory polymers and their composites which can be used for both structural materials and functional materials. For shape memory polymers and their composites, the performance of active deformation is expected to further promote the development in smart active deformation structures, such as deployable space structures and morphing wing aircraft. The shape memory polymer composites (SMPCs) are also one type of High Strain Composite (HSC). The space deployable structures based on carbon fiber reinforced shape memory polymer composites (SMPCs) show great prospects. Considering the problems that SMPCs are difficult to meet the practical applications in space deployable structures in the recent ten years, this paper aims to research the mechanics of deformation, actuation and failure of SMPCs. In the overall view of the shape memory polymer material's nonlinearity (nonlinearity and stress softening in the process of pre-deformation and recovery, relaxation in storage process, irreversible deformation), by the multiple verifications among theory, finite element and experiments, one obtains the deformation and actuation mechanism for the process of "pre-deformation, energy storage and actuation" and its non-fracture constraint domain. Then, the parameters of SMPCs will be optimized. Theoretical analysis is realized by the strain energy function, additionally considering the interaction strain energy between the fiber and the matrix. For the common resin-based or soft

Microstructural and mechanical evolution during deformation and annealing of poly-phase marbles - constraints from laboratory experiments and field observations

NASA Astrophysics Data System (ADS)

Austin, N. J.; Evans, B.; Dresen, G. H.; Rybacki, E.

2009-12-01

Deformed rocks commonly consist of several mineral phases, each with dramatically different mechanical properties. In both naturally and experimentally deformed rocks, deformation mechanisms and, in turn, strength, are commonly investigated by analyzing microstructural elements such as crystallographic preferred orientation (CPO) and recrystallized grain size. Here, we investigated the effect of variations in the volume fraction and the geometry of rigid second phases on the strength and evolution of CPO and grain size of synthetic calcite rocks. Experiments using triaxial compression and torsional loading were conducted at 1023 K and equivalent strain rates between ~2e-6 and 1e-3 s-1. The second phases in these synthetic assemblages are rigid carbon spheres or splinters with known particle size distributions and geometries, which are chemically inert at our experimental conditions. Under hydrostatic conditions, the addition of as little as 1 vol.% carbon spheres poisons normal grain growth. Shape is also important: for an equivalent volume fraction and grain dimension, carbon splinters result in a finer calcite grain size than carbon spheres. In samples deformed at “high” strain rates, or which have “large” mean free spacing of the pinning phase, the final recrystallized grain size is well explained by competing grain growth and grain size reduction processes, where the grain-size reduction rate is determined by the rate that mechanical work is done during deformation. In these samples, the final grain size is finer than in samples heat-treated hydrostatically for equivalent durations. The addition of 1 vol.% spheres to calcite has little effect on either the strength or CPO development. Adding 10 vol.% splinters increases the strength at low strains and low strain rates, but has little effect on the strength at high strains and/or high strain rates, compared to pure samples. A CPO similar to that in pure samples is observed, although the intensity is

Gravitational slope-deformation of a resurgent caldera: New insights from the mechanical behaviour of Mt. Nuovo tuffs (Ischia Island, Italy)

NASA Astrophysics Data System (ADS)

Marmoni, G. M.; Martino, S.; Heap, M. J.; Reuschlé, T.

2017-10-01

Ischia Island (Italy) is an impressive example of the rare phenomenon of caldera resurgence. The emplacement and replenishment of magmas at shallow depth resulted in a vertical uplift of about 900 m, concentrated in the western portion of Mt. Epomeo (789 m a.s.l.). As a consequence of this uplift, the island has experienced several slope instabilities at different scales since the Holocene, from shallow mass movements to large rock and debris avalanches. These mass wasting events, which mobilised large volumes of greenish alkali-trachytic tuff (the Mt. Epomeo Green Tuff, MEGT), were strictly related to volcano-tectonic activity and the interaction between the volcanic slopes and the hydrothermal system beneath the island. Deep-Seated Gravitational Slope Deformation (DSGSD) at Mt. Nuovo, located adjacent to densely populated coastal villages, is an ongoing process that covers an area of 1.6 km2. The Mt. Nuovo DSGSD involves a rock mass volume of 190 Mm3 and is accommodated by a main shear zone and a series of sub-vertical fault zones associated with high-angle joint sets. To improve our understanding of this gravity-induced process, we performed a physical (porosity and permeability) and mechanical (uniaxial and triaxial deformation experiments) characterisation of two ignimbrite deposits - both from the MEGT - that form a significant component of the NW sector of Mt. Epomeo. The main conclusions drawn from our experiments are twofold. First, the presence of water dramatically reduces the strength of the tuffs, suggesting that the movement of fluids within the hydrothermal system could greatly impact slope stability. Second, the transition from brittle (dilatant) to ductile (compactant) behaviour in the tuffs of the MEGT occurs at a very low effective pressure, analogous to a depth of a couple of hundred metres, and that this transition is likely moved closer to the surface in the presence of water. We hypothesise that compactant (porosity decreasing) behaviour at

The Precipitation Behavior and Hot Deformation Characteristics of Electron Beam Smelted Inconel 740 Superalloy

NASA Astrophysics Data System (ADS)

You, Xiaogang; Tan, Yi; Wu, Chang; You, Qifan; Zhao, Longhai; Li, Jiayan

2018-03-01

The Inconel 740 superalloy was prepared by the electron beam smelting (EBS) technology, the precipitation behavior and strengthening mechanism were studied, and the hot deformation characteristics of EBS 740 superalloy were investigated. The results indicate that the EBS 740 superalloy is mainly strengthened by the mechanism of weakly coupled dislocation shearing, and the resulting critical shear stress is calculated to be 234.6 MPa. The deformation parameters show a great influence on the flow behavior of EBS 740 superalloy. The strain rate sensitivity exponent increases with the increasing of deformation temperature, and the strain hardening exponent shows a decreasing trend with the increasing of strain. The activation energy of EBS 740 above 800 °C is measured to be 408.43 kJ/mol, which is higher than the 740H superalloy. A hyperbolic-sine-type relationship can be observed between the peak stress and Zener-Hollomon parameter. Nevertheless, the influence of deformation parameters is found to be considerably different at temperatures below and above 800 °C. The size of dynamic recrystallization (DRX) grains decreases with the increasing of strain rate when the strain rate is lower than 1/s, and reverse law can be found at higher strain rate. As a result, a piecewise function is established between the DRX grain size and hot working parameters.

Deformation-related recrystallization processes

NASA Astrophysics Data System (ADS)

Drury, Martyn R.; Urai, Janos L.

1990-02-01

Recrystallization is a common microstructural transformation that occurs during deformation, metamorphism and diagenesis of rocks. Studies on minerals and rock analogues have demonstrated that a wide range of recrystallization mechanisms can occur. The range of mechanisms is related to the various ways in which two basic processes, grain boundary migration and new grain boundary formation combine to transform the microstructure. Two recent papers (Drury et al., 1985; Urai et al., 1986) have proposed different schemes for the description of recrystallization mechanisms. The purpose of this paper is to provide a unified framework for the description of mechanisms. Recrystallization mechanisms are divided into three main types; rotation mechanisms which principally involve the formation of new grain boundaries; migration mechanisms which principally involve grain boundary migration; and general mechanisms which involve both basic processes. A further distinction is made on the basis of the continuity of the microstructural transformation with respect to time. Each of the three main types of mechanism can be divided into a number of sub-types depending on whether the processes of grain boundary migration, new grain boundary formation and new grain formation occur in a discontinuous or continuous manner with respect to time. As the terms continuous and discontinuous have been used in the metallurgical literature to signify the spatial continuity of the microstructural transformation, the terms discontinuai and continual are used to refer to the temporal continuity of the transformation. It is recommended that the following aspects should be specified, if possible, in a general description of recrystallization mechanisms: (1) How do the basic processes combine to transform the microstructure. (2) If new grain development occurs, what is the development mechanism, and does new grain formation occur in a continual or discontinuai manner. (3) If grain boundary migration is

Large poroelastic deformation of a soft material

NASA Astrophysics Data System (ADS)

MacMinn, Christopher W.; Dufresne, Eric R.; Wettlaufer, John S.

2014-11-01

Flow through a porous material will drive mechanical deformation when the fluid pressure becomes comparable to the stiffness of the solid skeleton. This has applications ranging from hydraulic fracture for recovery of shale gas, where fluid is injected at high pressure, to the mechanics of biological cells and tissues, where the solid skeleton is very soft. The traditional linear theory of poroelasticity captures this fluid-solid coupling by combining Darcy's law with linear elasticity. However, linear elasticity is only volume-conservative to first order in the strain, which can become problematic when damage, plasticity, or extreme softness lead to large deformations. Here, we compare the predictions of linear poroelasticity with those of a large-deformation framework in the context of two model problems. We show that errors in volume conservation are compounded and amplified by coupling with the fluid flow, and can become important even when the deformation is small. We also illustrate these results with a laboratory experiment.

Mechanics of brittle deformation and slope failure at the North Menan Butte tuff cone, Eastern Snake River Plain, Idaho

NASA Astrophysics Data System (ADS)

Okubo, C. H.

2013-12-01

The Menan Volcanic Complex consists of phreatomagmatic tuff cones that were emplaced as part of the regional volcanic activity in the Snake River Plain during the late Pleistocene. These tuff cones, the ';Menan Buttes', resulted from the eruption of basaltic magma through water-saturated alluvium and older basalts along the Snake River. The tuffs are composed primarily of basaltic glass with occasional plagioclase and olivine phenocrysts. The tuff is hydrothermally altered to a massive palagonitic tuff at depth but is otherwise poorly welded. Mass movements along the flanks of the cones were contemporaneous with tuff deposition. These slope failures are manifest as cm- to meter-scale pure folds, faults and fault-related folds, as well as larger slumps that are tens to a few hundred meters wide. Previous investigations classified the structural discontinuities at North Menan Butte based on orientation and sense of displacement, and all were recognized as opening-mode or shear fractures (Russell and Brisbin, 1990). This earlier work also used a generalized model of static (i.e., aseismic) gravity-driven shear failure within cohesionless soils to infer a possible origin for these fractures through slope failure. Recent work at North Menan Butte has provided novel insight into the styles of brittle deformation present, the effect of this deformation on the circulation of subsurface fluids within the tuff cone, as well as the mechanisms of the observed slope failures. Field observations reveal that the brittle deformation, previously classified as fractures, is manifest as deformation bands within the non-altered, poorly welded portions of the tuff. Both dilational and compactional bands, with shear, are observed. Slumps are bounded by normal faults, which are found to have developed within clusters of deformation bands. Deformation bands along the down-slope ends of these failure surfaces are predominantly compactional in nature. These bands have a ~3800 millidarcy

Monitoring of Deformation in Ground Before and After Tunnel Excavation

NASA Astrophysics Data System (ADS)

Eren, Mehmet; Hilmi Erkoç, Muharrem

2017-04-01

As population increase in metropolitan city, we need transportation and transmission tunnel. In this context, the engineers and administors attach impotance to building and planning underground-tunnel. Moreover, we must at regular intervals monitoring to deformation in underground-tunnel for quality and safety. Firstly, a deformation monitoring network is designed as perpendicular to the tunnel main axis. Secondly, the prescribed number of deformation measurements must be made. Finally, the deformation analysis is evaluated and its results is interpreted. This study investigates how deformation in monitoring network during and after tunnel excavate change.For this purpose, a deformation monitoring network of 18 object point and 4 reference point was established. Object points networks was designed steeply to the tunnel main axis as 3 cross section. Each cross section consisted of 3 point left, 2 point right and 1 point at the flowing line. Initial conditional measurement was made before tunnel excavation. Then the deformation measurement was made 5 period (1 period measured after tunnel excavate). All data sets were adjusted according to free adjustment method. The results from the investigation considering the tunnel line, a symmetrical subsidence was observed. The following day of tunnel excavation, we were observed %68 per of the total deformation. At the end of the last period measurements, %99 per of the total deformation was detected. Keywords: Tunnel, Deformation, Subsidence, Excavation

High temperature deformation mechanisms of L12-containing Co-based superalloys

NASA Astrophysics Data System (ADS)

Titus, Michael Shaw

Ni-based superalloys have been used as the structural material of choice for high temperature applications in gas turbine engines since the 1940s, but their operating temperature is becoming limited by their melting temperature (Tm =1300degrees C). Despite decades of research, no viable alternatives to Ni-based superalloys have been discovered and developed. However, in 2006, a ternary gamma' phase was discovered in the Co-Al-W system that enabled a new class of Co-based superalloys to be developed. These new Co-based superalloys possess a gamma-gamma' microstructure that is nearly identical to Ni-based superalloys, which enables these superalloys to achieve extraordinary high temperature mechanical properties. Furthermore, Co-based alloys possess the added benefit of exhibiting a melting temperature of at least 100degrees C higher than commercial Ni-based superalloys. Superalloys used as the structural materials in high pressure turbine blades must withstand large thermomechanical stresses imparted from the rotating disk and hot, corrosive gases present. These stresses induce time-dependent plastic deformation, which is commonly known as creep, and new superalloys must possess adequate creep resistance over a broad range of temperature in order to be used as the structural materials for high pressure turbine blades. For these reasons, this research focuses on quantifying high temperature creep properties of new gamma'-containing Co-based superalloys and identifying the high temperature creep deformation mechanisms. The high temperature creep properties of new Co- and CoNi-based alloys were found to be comparable to Ni-based superalloys with respect to minimum creep rates and creep-rupture lives at 900degrees C up to the solvus temperature of the gamma' phase. Co-based alloys exhibited a propensity for extended superlattice stacking fault formation in the gamma' precipitates resulting from dislocation shearing events. When Ni was added to the Co-based compositions

Brittle-viscous deformation of vein quartz under fluid-rich low greenschist facies conditions

NASA Astrophysics Data System (ADS)

Jørgen Kjøll, Hans; Viola, Giulio; Menegon, Luca; Sørensen, Bjørn

2015-04-01

A coarse grained, statically crystallized quartz vein with a random CPO, embedded in a phyllonitic matrix, was studied by optical microscopy, SEM imaging and EBSD to gain insights into the processes of strain localization in quartz deformed under low greenschist facies conditions at the frictional-viscous transition. The vein is located in a high strain zone at the front of an imbricate stack of Caledonian age along the northwesternmost edge of the Repparfjord Tectonic Window in northern Norway. The vein was deformed within the Nussirjavrri Fault Zone (NFZ), an out-of-sequence thrust with a phyllonitic core characterized by a ramp-flat-ramp geometry, NNW plunging stretching lineations and top-to-the SSE thrusting kinematics. Deformation conditions are typical of the frictional-viscous transition. The phyllonitic core formed at the expense of metabasalt wherein feldspar broke down to form interconnected layers of fine, synkinematic phyllosilicates. In the mechanically weak framework of the phyllonite, the studied quartz vein acted as a relatively rigid body deforming mainly by coaxial strain. Viscous deformation, related to the development of a mesoscopic pervasive extensional crenulation cleavage, was accommodated within the vein initially by basal slip of suitably oriented quartz crystals, which produced e.g. undulose extinction, extinction bands and bulging grain boundaries. In the case of misoriented quartz crystals, however, glide-accommodated dislocation creep resulted soon inefficient and led to localized dislocation tangling and strain hardening. In response to 1) hardening, 2) progressive increase of fluid pressure within the actively deforming vein and 3) increasing competence contrast between the vein and the surrounding weak, foliated phyllonitic fault core, quartz crystals began to deform frictionally along specific lattice planes oriented optimally with respect to the imposed stress field. Microfaulting generated small volumes of gouge along

Analysing intracellular deformation of polymer capsules using structured illumination microscopy

NASA Astrophysics Data System (ADS)

Chen, Xi; Cui, Jiwei; Sun, Huanli; Müllner, Markus; Yan, Yan; Noi, Ka Fung; Ping, Yuan; Caruso, Frank

2016-06-01

Understanding the behaviour of therapeutic carriers is important in elucidating their mechanism of action and how they are processed inside cells. Herein we examine the intracellular deformation of layer-by-layer assembled polymer capsules using super-resolution structured illumination microscopy (SIM). Spherical- and cylindrical-shaped capsules were studied in three different cell lines, namely HeLa (human epithelial cell line), RAW264.7 (mouse macrophage cell line) and differentiated THP-1 (human monocyte-derived macrophage cell line). We observed that the deformation of capsules was dependent on cell line, but independent of capsule shape. This suggests that the mechanical forces, which induce capsule deformation during cell uptake, vary between cell lines, indicating that the capsules are exposed to higher mechanical forces in HeLa cells, followed by RAW264.7 and then differentiated THP-1 cells. Our study demonstrates the use of super-resolution SIM in analysing intracellular capsule deformation, offering important insights into the cellular processing of drug carriers in cells and providing fundamental knowledge of intracellular mechanobiology. Furthermore, this study may aid in the design of novel drug carriers that are sensitive to deformation for enhanced drug release properties.Understanding the behaviour of therapeutic carriers is important in elucidating their mechanism of action and how they are processed inside cells. Herein we examine the intracellular deformation of layer-by-layer assembled polymer capsules using super-resolution structured illumination microscopy (SIM). Spherical- and cylindrical-shaped capsules were studied in three different cell lines, namely HeLa (human epithelial cell line), RAW264.7 (mouse macrophage cell line) and differentiated THP-1 (human monocyte-derived macrophage cell line). We observed that the deformation of capsules was dependent on cell line, but independent of capsule shape. This suggests that the mechanical forces

Multiplexed fluidic plunger mechanism for the measurement of red blood cell deformability.

PubMed

Myrand-Lapierre, Marie-Eve; Deng, Xiaoyan; Ang, Richard R; Matthews, Kerryn; Santoso, Aline T; Ma, Hongshen

2015-01-07

The extraordinary deformability of red blood cells gives them the ability to repeatedly transit through the microvasculature of the human body. The loss of this capability is part of the pathology of a wide range of diseases including malaria, hemoglobinopathies, and micronutrient deficiencies. We report on a technique for multiplexed measurements of the pressure required to deform individual red blood cell through micrometer-scale constrictions. This measurement is performed by first infusing single red blood cells into a parallel array of ~1.7 μm funnel-shaped constrictions. Next, a saw-tooth pressure waveform is applied across the constrictions to squeeze each cell through its constriction. The threshold deformation pressure is then determined by relating the pressure-time data with the video of the deformation process. Our key innovation is a self-compensating fluidic network that ensures identical pressures are applied to each cell regardless of its position, as well as the presence of cells in neighboring constrictions. These characteristics ensure the consistency of the measurement process and robustness against blockages of the constrictions by rigid cells and debris. We evaluate this technique using in vitro cultures of RBCs infected with P. falciparum, the parasite that causes malaria, to demonstrate the ability to profile the deformability signature of a heterogeneous sample.

Optimized deformation behavior of a dielectric elastomer generator

NASA Astrophysics Data System (ADS)

Foerster, Florentine; Schlaak, Helmut F.

2014-03-01

Dielectric elastomer generators (DEGs) produce electrical energy by converting mechanical into electrical energy. Efficient operation requires an optimal deformation of the DEG during the energy harvesting cycle. However, the deformation resulting from an external load has to be applied to the DEG. The deformation behavior of the DEG is dependent on the type of the mechanical interconnection between the elastic DEG and a stiff support area. The maximization of the capacitance of the DEG in the deformed state leads to the maximum absolute energy gain. Therefore several configurations of mechanical interconnections between a single DEG module as well as multiple stacked DEG modules and stiff supports are investigated in order to find the optimal mechanical interconnection. The investigation is done with numerical simulations using the FEM software ANSYS. A DEG module consists of 50 active dielectric layers with a single layer thickness of 50 μm. The elastomer material is silicone (PDMS) while the compliant electrodes are made of graphite powder. In the simulation the real material parameters of the PDMS and the graphite electrodes are included to compare simulation results to experimental investigations in the future. The numerical simulations of the several configurations are carried out as coupled electro-mechanical simulation for the first step in an energy harvesting cycle with constant external load strain. The simulation results are discussed and an optimal mechanical interconnection between DEG modules and stiff supports is derived.

Physics-based deformable organisms for medical image analysis

NASA Astrophysics Data System (ADS)

Hamarneh, Ghassan; McIntosh, Chris

2005-04-01

Previously, "Deformable organisms" were introduced as a novel paradigm for medical image analysis that uses artificial life modelling concepts. Deformable organisms were designed to complement the classical bottom-up deformable models methodologies (geometrical and physical layers), with top-down intelligent deformation control mechanisms (behavioral and cognitive layers). However, a true physical layer was absent and in order to complete medical image segmentation tasks, deformable organisms relied on pure geometry-based shape deformations guided by sensory data, prior structural knowledge, and expert-generated schedules of behaviors. In this paper we introduce the use of physics-based shape deformations within the deformable organisms framework yielding additional robustness by allowing intuitive real-time user guidance and interaction when necessary. We present the results of applying our physics-based deformable organisms, with an underlying dynamic spring-mass mesh model, to segmenting and labelling the corpus callosum in 2D midsagittal magnetic resonance images.

Biaxial deformation of collagen and elastin fibers in coronary adventitia

PubMed Central

Chen, Huan; Slipchenko, Mikhail N.; Liu, Yi; Zhao, Xuefeng; Cheng, Ji-Xin; Lanir, Yoram

2013-01-01

The microstructural deformation-mechanical loading relation of the blood vessel wall is essential for understanding the overall mechanical behavior of vascular tissue in health and disease. We employed simultaneous mechanical loading-imaging to quantify in situ deformation of individual collagen and elastin fibers on unstained fresh porcine coronary adventitia under a combination of vessel inflation and axial extension loading. Specifically, the specimens were imaged under biaxial loads to study microscopic deformation-loading behavior of fibers in conjunction with morphometric measurements at the zero-stress state. Collagen fibers largely orientate in the longitudinal direction, while elastin fibers have major orientation parallel to collagen, but with additional orientation angles in each sublayer of the adventitia. With an increase of biaxial load, collagen fibers were uniformly stretched to the loading direction, while elastin fibers gradually formed a network in sublayers, which strongly depended on the initial arrangement. The waviness of collagen decreased more rapidly at a circumferential stretch ratio of λθ = 1.0 than at λθ = 1.5, while most collagen became straightened at λθ = 1.8. These microscopic deformations imply that the longitudinally stiffer adventitia is a direct result of initial fiber alignment, and the overall mechanical behavior of the tissue is highly dependent on the corresponding microscopic deformation of fibers. The microstructural deformation-loading relation will serve as a foundation for micromechanical models of the vessel wall. PMID:24092692

Anisotropic Ripple Deformation in Phosphorene.

PubMed

Kou, Liangzhi; Ma, Yandong; Smith, Sean C; Chen, Changfeng

2015-05-07

Two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS2. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classical elasticity theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.

Influence of thermally activated processes on the deformation behavior during low temperature ECAP

NASA Astrophysics Data System (ADS)

Fritsch, S.; Scholze, M.; F-X Wagner, M.

2016-03-01

High strength aluminum alloys are generally hard to deform. Therefore, the application of conventional severe plastic deformation methods to generate ultrafine-grained microstructures and to further increase strength is considerably limited. In this study, we consider low temperature deformation in a custom-built, cooled equal channel angular pressing (ECAP) tool (internal angle 90°) as an alternative approach to severely plastically deform a 7075 aluminum alloy. To document the maximum improvement of mechanical properties, these alloys are initially deformed from a solid solution heat-treated condition. We characterize the mechanical behavior and the microstructure of the coarse grained initial material at different low temperatures, and we analyze how a tendency for the PLC effect and the strain-hardening rate affect the formability during subsequent severe plastic deformation at low temperatures. We then discuss how the deformation temperature and velocity influence the occurrence of PLC effects and the homogeneity of the deformed ECAP billets. Besides the mechanical properties and these microstructural changes, we discuss technologically relevant processing parameters (such as pressing forces) and practical limitations, as well as changes in fracture behavior of the low temperature deformed materials as a function of deformation temperature.

Dynamic soft tissue deformation estimation based on energy analysis

NASA Astrophysics Data System (ADS)

Gao, Dedong; Lei, Yong; Yao, Bin

2016-10-01

The needle placement accuracy of millimeters is required in many needle-based surgeries. The tissue deformation, especially that occurring on the surface of organ tissue, affects the needle-targeting accuracy of both manual and robotic needle insertions. It is necessary to understand the mechanism of tissue deformation during needle insertion into soft tissue. In this paper, soft tissue surface deformation is investigated on the basis of continuum mechanics, where a geometry model is presented to quantitatively approximate the volume of tissue deformation. The energy-based method is presented to the dynamic process of needle insertion into soft tissue based on continuum mechanics, and the volume of the cone is exploited to quantitatively approximate the deformation on the surface of soft tissue. The external work is converted into potential, kinetic, dissipated, and strain energies during the dynamic rigid needle-tissue interactive process. The needle insertion experimental setup, consisting of a linear actuator, force sensor, needle, tissue container, and a light, is constructed while an image-based method for measuring the depth and radius of the soft tissue surface deformations is introduced to obtain the experimental data. The relationship between the changed volume of tissue deformation and the insertion parameters is created based on the law of conservation of energy, with the volume of tissue deformation having been obtained using image-based measurements. The experiments are performed on phantom specimens, and an energy-based analytical fitted model is presented to estimate the volume of tissue deformation. The experimental results show that the energy-based analytical fitted model can predict the volume of soft tissue deformation, and the root mean squared errors of the fitting model and experimental data are 0.61 and 0.25 at the velocities 2.50 mm/s and 5.00 mm/s. The estimating parameters of the soft tissue surface deformations are proven to be useful

Characterization of plastic deformation in a disk bend test

NASA Astrophysics Data System (ADS)

Byun, T. S.; Lee, E. H.; Hunn, J. D.; Farrell, K.; Mansur, L. K.

2001-04-01

A disk bend test technique has been developed to study deformation mechanisms as well as mechanical properties. In the disk bend test, a transmission electron microscopy (TEM) disk size specimen of 3 mm diameter ×0.25 mm thick is clamped around its rim in a circular holder and indented with a tungsten carbide ball of 1 mm diameter on its back face. AISI 316LN austenitic stainless steel and 9Cr-2WVTa ferritic/martensitic steel were selected as test materials. A model was developed to determine the average plastic strain and surface plastic strain in the disk bend test. The deformation regimes of the plastic strain versus deflection curves corresponded to those of the load versus deflection curves. The stress state of the disk bend deformation was analyzed for the two test materials and compared with those of other mechanical tests such as uniaxial tensile, compact tension, and ball indentation tests. Slip line features at the deformed surface and the corresponding TEM microstructures were examined for both tensile and disk bend specimens. Differences and similarities in deformation between the disk bend and the tensile tests are described.

Deformation Measurements of Smart Aerodynamic Surfaces

NASA Technical Reports Server (NTRS)

Fleming, Gary A.; Burner, Alpheus

2005-01-01

Video Model Deformation (VMD) and Projection Moire Interferometry (PMI) were used to acquire wind tunnel model deformation measurements of the Northrop Grumman-built Smart Wing tested in the NASA Langley Transonic Dynamics Tunnel. The F18-E/F planform Smart Wing was outfitted with embedded shape memory alloys to actuate a seamless trailing edge aileron and flap, and an embedded torque tube to generate wing twist. The VMD system was used to obtain highly accurate deformation measurements at three spanwise locations along the main body of the wing, and at spanwise locations on the flap and aileron. The PMI system was used to obtain full-field wing shape and deformation measurements over the entire wing lower surface. Although less accurate than the VMD system, the PMI system revealed deformations occurring between VMD target rows indistinguishable by VMD. This paper presents the VMD and PMI techniques and discusses their application in the Smart Wing test.

Extracting Cell Stiffness from Real-Time Deformability Cytometry: Theory and Experiment.

PubMed

Mietke, Alexander; Otto, Oliver; Girardo, Salvatore; Rosendahl, Philipp; Taubenberger, Anna; Golfier, Stefan; Ulbricht, Elke; Aland, Sebastian; Guck, Jochen; Fischer-Friedrich, Elisabeth

2015-11-17

Cell stiffness is a sensitive indicator of physiological and pathological changes in cells, with many potential applications in biology and medicine. A new method, real-time deformability cytometry, probes cell stiffness at high throughput by exposing cells to a shear flow in a microfluidic channel, allowing for mechanical phenotyping based on single-cell deformability. However, observed deformations of cells in the channel not only are determined by cell stiffness, but also depend on cell size relative to channel size. Here, we disentangle mutual contributions of cell size and cell stiffness to cell deformation by a theoretical analysis in terms of hydrodynamics and linear elasticity theory. Performing real-time deformability cytometry experiments on both model spheres of known elasticity and biological cells, we demonstrate that our analytical model not only predicts deformed shapes inside the channel but also allows for quantification of cell mechanical parameters. Thereby, fast and quantitative mechanical sampling of large cell populations becomes feasible. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Temperature-dependent phase-specific deformation mechanisms in a directionally solidified NiAl-Cr(Mo) lamellar composite

DOE PAGES

Yu, Dunji; An, Ke; Chen, Xu; ...

2015-10-09

Phase-specific thermal expansion and mechanical deformation behaviors of a directionally solidified NiAl–Cr(Mo) lamellar in situ composite were investigated by using real-time in situ neutron diffraction during compression at elevated temperatures up to 800 °C. Tensile and compressive thermal residual stresses were found to exist in the NiAl phase and Crss (solid solution) phase, respectively. Then, based on the evolution of lattice spacings and phase stresses, the phase-specific deformation behavior was analyzed qualitatively and quantitatively. Moreover, estimates of phase stresses were derived by Hooke's law on the basis of a simple method for the determination of stress-free lattice spacing in inmore » situ composites. During compressive loading, the NiAl phase yields earlier than the Crss phase. The Crss phase carries much higher stress than the NiAl phase, and displays consistent strain hardening at all temperatures. The NiAl phase exhibits strain hardening at relatively low temperatures and softening at high temperatures. During unloading, the NiAl phase yields in tension whereas the Crss phase unloads elastically. Additionally, post-test microstructural observations show phase-through cracks at room temperature, micro cracks along phase interfaces at 600 °C and intact lamellae kinks at 800 °C, which is due to the increasing deformability of both phases as temperature rises.« less

A Variational Principle for Reconstruction of Elastic Deformations in Shear Deformable Plates and Shells

NASA Technical Reports Server (NTRS)

Tessler, Alexander; Spangler, Jan L.

2003-01-01

A variational principle is formulated for the inverse problem of full-field reconstruction of three-dimensional plate/shell deformations from experimentally measured surface strains. The formulation is based upon the minimization of a least squares functional that uses the complete set of strain measures consistent with linear, first-order shear-deformation theory. The formulation, which accommodates for transverse shear deformation, is applicable for the analysis of thin and moderately thick plate and shell structures. The main benefit of the variational principle is that it is well suited for C(sup 0)-continuous displacement finite element discretizations, thus enabling the development of robust algorithms for application to complex civil and aeronautical structures. The methodology is especially aimed at the next generation of aerospace vehicles for use in real-time structural health monitoring systems.

Thin-skinned deformation of sedimentary rocks in Valles Marineris, Mars

USGS Publications Warehouse

Metz, Joannah; Grotzinger, John P.; Okubo, Chris; Milliken, Ralph

2010-01-01

Deformation of sedimentary rocks is widespread within Valles Marineris, characterized by both plastic and brittle deformation identified in Candor, Melas, and Ius Chasmata. We identified four deformation styles using HiRISE and CTX images: kilometer-scale convolute folds, detached slabs, folded strata, and pull-apart structures. Convolute folds are detached rounded slabs of material with alternating dark- and light-toned strata and a fold wavelength of about 1 km. The detached slabs are isolated rounded blocks of material, but they exhibit only highly localized evidence of stratification. Folded strata are composed of continuously folded layers that are not detached. Pull-apart structures are composed of stratified rock that has broken off into small irregularly shaped pieces showing evidence of brittle deformation. Some areas exhibit multiple styles of deformation and grade from one type of deformation into another. The deformed rocks are observed over thousands of kilometers, are limited to discrete stratigraphic intervals, and occur over a wide range in elevations. All deformation styles appear to be of likely thin-skinned origin. CRISM reflectance spectra show that some of the deformed sediments contain a component of monohydrated and polyhydrated sulfates. Several mechanisms could be responsible for the deformation of sedimentary rocks in Valles Marineris, such as subaerial or subaqueous gravitational slumping or sliding and soft sediment deformation, where the latter could include impact-induced or seismically induced liquefaction. These mechanisms are evaluated based on their expected pattern, scale, and areal extent of deformation. Deformation produced from slow subaerial or subaqueous landsliding and liquefaction is consistent with the deformation observed in Valles Marineris.

Mechanisms of plastic deformation in highly cross-linked UHMWPE for total hip components--the molecular physics viewpoint.

PubMed

Takahashi, Yasuhito; Shishido, Takaaki; Yamamoto, Kengo; Masaoka, Toshinori; Kubo, Kosuke; Tateiwa, Toshiyuki; Pezzotti, Giuseppe

2015-02-01

Plastic deformation is an unavoidable event in biomedical polymeric implants for load-bearing application during long-term in-vivo service life, which involves a mass transfer process, irreversible chain motion, and molecular reorganization. Deformation-induced microstructural alterations greatly affect mechanical properties and durability of implant devices. The present research focused on evaluating, from a molecular physics viewpoint, the impact of externally applied strain (or stress) in ultra-high molecular weight polyethylene (UHMWPE) prostheses, subjected to radiation cross-linking and subsequent remelting for application in total hip arthroplasty (THA). Two different types of commercial acetabular liners, which belong to the first-generation highly cross-linked UHMWPE (HXLPE), were investigated by means of confocal/polarized Raman microprobe spectroscopy. The amount of crystalline region and the spatial distribution of molecular chain orientation were quantitatively analyzed according to a combined theory including Raman selection rules for the polyethylene orthorhombic structure and the orientation distribution function (ODF) statistical approach. The structurally important finding was that pronounced recrystallization and molecular reorientation increasingly appeared in the near-surface regions of HXLPE liners with increasing the amount of plastic (compressive) deformation stored in the microstructure. Such molecular rearrangements, occurred in response to external strains, locally increase surface cross-shear (CS) stresses, which in turn trigger microscopic wear processes in HXLPE acetabular liners. Thus, on the basis of the results obtained at the molecular scale, we emphasize here the importance of minimizing the development of irrecoverable deformation strain in order to retain the pristine and intrinsically high wear performance of HXLPE components. Copyright © 2014 Elsevier Ltd. All rights reserved.

Quantitative analysis of tissue deformation dynamics reveals three characteristic growth modes and globally aligned anisotropic tissue deformation during chick limb development.

PubMed

Morishita, Yoshihiro; Kuroiwa, Atsushi; Suzuki, Takayuki

2015-05-01

Tissue-level characterization of deformation dynamics is crucial for understanding organ morphogenetic mechanisms, especially the interhierarchical links among molecular activities, cellular behaviors and tissue/organ morphogenetic processes. Limb development is a well-studied topic in vertebrate organogenesis. Nevertheless, there is still little understanding of tissue-level deformation relative to molecular and cellular dynamics. This is mainly because live recording of detailed cell behaviors in whole tissues is technically difficult. To overcome this limitation, by applying a recently developed Bayesian approach, we here constructed tissue deformation maps for chick limb development with high precision, based on snapshot lineage tracing using dye injection. The precision of the constructed maps was validated with a clear statistical criterion. From the geometrical analysis of the map, we identified three characteristic tissue growth modes in the limb and showed that they are consistent with local growth factor activity and cell cycle length. In particular, we report that SHH signaling activity changes dynamically with developmental stage and strongly correlates with the dynamic shift in the tissue growth mode. We also found anisotropic tissue deformation along the proximal-distal axis. Morphogenetic simulation and experimental studies suggested that this directional tissue elongation, and not local growth, has the greatest impact on limb shaping. This result was supported by the novel finding that anisotropic tissue elongation along the proximal-distal axis occurs independently of cell proliferation. Our study marks a pivotal point for multi-scale system understanding in vertebrate development. © 2015. Published by The Company of Biologists Ltd.

Surface deformation during an action potential in pearled cells

NASA Astrophysics Data System (ADS)

Mussel, Matan; Fillafer, Christian; Ben-Porath, Gal; Schneider, Matthias F.

2017-11-01

Electric pulses in biological cells (action potentials) have been reported to be accompanied by a propagating cell-surface deformation with a nanoscale amplitude. Typically, this cell surface is covered by external layers of polymer material (extracellular matrix, cell wall material, etc.). It was recently demonstrated in excitable plant cells (Chara braunii) that the rigid external layer (cell wall) hinders the underlying deformation. When the cell membrane was separated from the cell wall by osmosis, a mechanical deformation, in the micrometer range, was observed upon excitation of the cell. The underlying mechanism of this mechanical pulse has, to date, remained elusive. Herein we report that Chara cells can undergo a pearling instability, and when the pearled fragments were excited even larger and more regular cell shape changes were observed (˜10 -100 μ m in amplitude). These transient cellular deformations were captured by a curvature model that is based on three parameters: surface tension, bending rigidity, and pressure difference across the surface. In this paper these parameters are extracted by curve-fitting to the experimental cellular shapes at rest and during excitation. This is a necessary step to identify the mechanical parameters that change during an action potential.

Localization and partitioning of deformation in experimentally produced granitoid fault rocks

NASA Astrophysics Data System (ADS)

Peč, Matěj.; Stünitz, Holger; Heilbronner, Renée.

2010-05-01

The complex interplay between frictional and viscous deformation processes taking place in the "brittle-ductile transition" is still poorly understood. Fracturing, as one of the most effective grain size reducing mechanisms, occurs under a wide range of conditions and seems to be an important pre-cursor for the onset of viscous deformation in the crust. The aim of this work is to study localization and partitioning of brittle and viscous deformation in experimentally produced fault gouges and to identify the active deformation mechanism(s) via quantitative microstructural analysis. We performed a series of simple shear experiments on granitoid fault gouge in a Griggs solid medium deformation rig at 500 MPa confining pressure and 300 or 500°C. Before deformation, the artificially produced gouge consists of 28% Qtz, 25% Kfs, 15% Plg, 3% Bi and 0.5% Msk. The average thickness of the shear zone is ˜1 mm and the porosity is ˜28%. All three major phases (Qtz, Kfs and Plg) deform by fracturing along grain-to-grain contacts and have a similar aspect ratio (L/S) ˜2.13. Two measures for concavity were determined: paris factor ~7.6% and deltaA factor ~6.5%. Finally, a measure for angularity, omega factor, is slightly higher in Qtz (24.8%) than in feldspars (˜20%) (Heilbronner & Keulen 2006). Micas deform mainly by kinking. We observe a slight shape preferred orientation of the grains perpendicular to the applied load indicating that the applied pressure during the pumping up of the experiment is not entirely isotropic. After fast frictional deformation (shear strain rates of 10^-4 sec^-1 and 10^-3 sec^-1) to a gamma value of up to 2.7, the average thickness of the shear zone is reduced to 0.7 mm and the porosity drops below 3%. We observe overall grain size reduction and shear localization through the development of S-C-Ć fabric with Ć shear bands being the dominant feature. The Ć shear bands form at an angle of 18° to sigma 1 resp. 27° to the shear zone boundary

Post Deformation at Room and Cryogenic Temperature Cooling Media on Severely Deformed 1050-Aluminum

NASA Astrophysics Data System (ADS)

Khorrami, M. Sarkari; Kazeminezhad, M.

2018-03-01

The annealed 1050-aluminum sheets were initially subjected to the severe plastic deformation through two passes of constrained groove pressing (CGP) process. The obtained specimens were post-deformed by friction stir processing at room and cryogenic temperature cooling media. The microstructure evolutions during mentioned processes in terms of grain structure, misorientation distribution, and grain orientation spread (GOS) were characterized using electron backscattered diffraction. The annealed sample contained a large number of "recrystallized" grains and relatively large fraction (78%) of high-angle grain boundaries (HAGBs). When CGP process was applied on the annealed specimen, the elongated grains with interior substructure were developed, which was responsible for the formation of 80% low-angle grain boundaries. The GOS map of the severely deformed specimen manifested the formation of 43% "distorted" and 51% "substructured" grains. The post deformation of severely deformed aluminum at room temperature led to the increase in the fraction of HAGBs from 20 to 60%. Also, it gave rise to the formation of "recrystallized" grains with the average size of 13 μm, which were coarser than the grains predicted by Zener-Hollomon parameter. This was attributed to the occurrence of appreciable grain growth during post deformation. In the case of post deformation at cryogenic temperature cooling medium, the grain size was decreased, which was in well agreement with the predicted grain size. The cumulative distribution of misorientation was the same for both processing routes. Mechanical properties characterizations in terms of nano-indentation and tensile tests revealed that the post deformation process led to the reduction in hardness, yield stress, and ultimate tensile strength of the severely deformed aluminum.

Soft-sediment deformations (convolute lamination and load structures) in turbidites as indicators of flow reflections against bounding slopes

NASA Astrophysics Data System (ADS)

Tinterri, Roberto; Muzzi Magalhaes, Pierre; Tagliaferri, Alessio; Cunha, Rogerio S.; Laporta, Michele

2015-04-01

Soft-sediment deformations, such as convolute laminations, load structures and water escapes are very rapid deformations that occur in unconsolidated sediments near the depositional surface during or shortly after deposition and before significant diagenesis. These types of deformations develop when primary stratifications are deformed by a system of driving forces, while the sediment is temporarily in a weakened state due to the action of a deformation mechanism know as liquidization. This deformation occurs if the applied stress exceeds the sediment strength, either through an increase in the applied stress or through a temporary reduction in sediment strength. Liquidization mechanisms can be triggered by several agents, such as seismic shaking, rapid sedimentation with high-fallout rates or cyclic-pressure variations associated with storm waves or breaking waves. Consequently, soft-sediment deformations can be produced by different processes and form ubiquitous sedimentary structures characterizing many sedimentary environments. However, even though these types of structures are relatively well-known in terms of geometry and sedimentary characteristics, many doubts arise when the understanding of deformation and trigger mechanisms is attempted. As stressed also by the recent literature, the main problem lies in the fact that the existing approaches for the identification of triggering agents rely on criteria that are not diagnostic or not applicable to outcrop-based studies, because they are not always based on detailed facies analysis related to a paleoenvironmental-context approach. For this reason, this work discusses the significance of particular types of soft-sediment deformations that are very common in turbidite deposits, namely convolute laminations and load structures, especially on the basis of a deep knowledge of the stratigraphic framework and geological setting in which these structures are inserted. More precisely, detailed facies analyses of the

Tension-dependent structural deformation alters single-molecule transition kinetics.

PubMed

Sudhanshu, B; Mihardja, S; Koslover, E F; Mehraeen, S; Bustamante, C; Spakowitz, A J

2011-02-01

We analyze the response of a single nucleosome to tension, which serves as a prototypical biophysical measurement where tension-dependent deformation alters transition kinetics. We develop a statistical-mechanics model of a nucleosome as a wormlike chain bound to a spool, incorporating fluctuations in the number of bases bound, the spool orientation, and the conformations of the unbound polymer segments. With the resulting free-energy surface, we perform dynamic simulations that permit a direct comparison with experiments. This simple approach demonstrates that the experimentally observed structural states at nonzero tension are a consequence of the tension and that these tension-induced states cease to exist at zero tension. The transitions between states exhibit substantial deformation of the unbound polymer segments. The associated deformation energy increases with tension; thus, the application of tension alters the kinetics due to tension-induced deformation of the transition states. This mechanism would arise in any system where the tether molecule is deformed in the transition state under the influence of tension.

Anisotropic ripple deformation in phosphorene

DOE PAGES

Kou, Liangzhi; Ma, Yandong; Smith, Sean C.; ...

2015-04-07

Here, two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS 2. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classicalmore » elasticity theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.« less

Anisotropic ripple deformation in phosphorene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kou, Liangzhi; Ma, Yandong; Smith, Sean C.

Here, two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS 2. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classicalmore » elasticity theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.« less

Cyclic Deformation Microstructure in Heavily Cold-Drawn Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Xie, Xingfei; Ning, Dong; Sun, Jian

2018-04-01

Cyclic deformation microstructure of the heavily cold-drawn austenitic stainless steel is significantly influenced by the spacing between mechanical twins introduced by prior cold drawing. Well-developed dislocation cells form between mechanical twins with the spacing larger than about 800 nm. Persistent slip band (PSB)-like structure with ladders takes place between mechanical twins spacing from 300 to 800 nm. Few dislocations occur between neighboring mechanical twins with spacing less than about 100 nm. Pre-existing mechanical twins and deformation bands segment austenitic grains, facilitating multi-slip and consequently suppressing PSB formation.

Cyclic Deformation Microstructure in Heavily Cold-Drawn Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Xie, Xingfei; Ning, Dong; Sun, Jian

2018-07-01

Cyclic deformation microstructure of the heavily cold-drawn austenitic stainless steel is significantly influenced by the spacing between mechanical twins introduced by prior cold drawing. Well-developed dislocation cells form between mechanical twins with the spacing larger than about 800 nm. Persistent slip band (PSB)-like structure with ladders takes place between mechanical twins spacing from 300 to 800 nm. Few dislocations occur between neighboring mechanical twins with spacing less than about 100 nm. Pre-existing mechanical twins and deformation bands segment austenitic grains, facilitating multi-slip and consequently suppressing PSB formation.

Crustal deformation along the San Andreas, California

NASA Technical Reports Server (NTRS)

Li, Victor C.

1992-01-01

The goal is to achieve a better understanding of the regional and local deformation and crustal straining processes in western North America, particularly the effects of the San Andreas and nearby faults on the spatial and temporal crustal deformation behavior. Construction of theoretical models based on the mechanics of coupled elastic plate, viscoelastic foundation and large scale crack mechanics provide a rational basis for the interpretation of seismic and aseismic anomalies and expedite efforts in forecasting the stability of plate boundary deformation. Special focus is placed on the three dimensional time dependent surface deformation due to localized slippage in a elastic layer coupled to a visco-elastic substrate. The numerical analysis is based on a 3-D boundary element technique. Extension to visco-elastic coupling demands the derivation of 3-D time dependent Green's function. This method was applied to analyze the viscoelastic surface displacements due to a dislocated embedded patch. Surface uplift as a function of time and position are obtained. Comparisons between surface uplift for long and short dislocated patches are made.

Sumatra-Andaman Megathrust Earthquake Slip: Insights From Mechanical Modeling of ICESat Surface Deformation Measurements

NASA Astrophysics Data System (ADS)

Harding, D. J.; Miuller, J. R.

2005-12-01

boundary condition on the Sumatra-Andaman subduction interface fault. The direction of slip on the fault surface is derived from the slip directions computed by Tsai et al. (in review) for centroid moment tensor focal mechanisms spatially distributed along the rupture. The slip model will be refined to better correspond to the observed surface deformation as additional results from the ICESat profiles become available.

Postseismic deformation following the June 2000 earthquake sequence in the south Iceland seismic zone

USGS Publications Warehouse

Arnadottir, T.; Jonsson, Sigurjon; Pollitz, F.F.; Jiang, W.; Feigl, K.L.

2005-01-01

We observe postseismic deformation on two spatiotemporal scales following Mw = 6.5 earthquakes in the south Iceland seismic zone on 17 and 21 June 2000. We see a rapidly decaying deformation transient lasting no more than 2 months and extending about 5 km away from the two main shock ruptures. This local, month-scale transient is captured by several radar interferograms and is also observed at a few campaign GPS sites located near the faults. A slower transient with a characteristic timescale of about a year is detected only by GPS measurements. The month-scale deformation pattern has been explained by poroelastic rebound due to postearthquake pore pressure changes. In contrast, the year-scale deformation can be explained by either afterslip at 8-14 km depth or viscoelastic relaxation of the lower crust and upper mantle in response to the coseismic stress changes. The optimal viscoelastic models have lower crustal viscosities of 0.5-1 ?? 1019 Pa s and upper mantle viscosity of ???3 ?? 1018 Pa s. Because of the limitations of our GPS campaign data, we consider both afterslip and viscoelastic relaxation as plausible mechanisms explaining the deformation field. Both types of postseismic deformation models suggest that the areas of large coseismic stress increase east of the 17 June and west of the 21 June ruptures continue to be loaded by the postseismic deformation. Copyright 2005 by the American Geophysical Union.

Comparison of mechanical and microstructural properties of conventional and severe plastic deformation processes

NASA Astrophysics Data System (ADS)

Szombathelyi, V.; Krallics, Gy

2014-08-01

The effect of the deformation processes on yield stress, Vickers microhardness and dislocation density were investigated using commercial purity (A1050) and alloyed aluminum (Al 6082). For the evolution of the dislocation density X-ray line profile analysis was used. In the large plastic strain range the variation of mechanical and microstructure evolution of A1050 and of Al 6082 processed by equal channel angular pressing are investigated using route BC and route C. In the plastic strain range up to 3 plane strain compression test was used to evaluate mechanical properties. The hardness and the yield stress showed a sharp increase after the first pass. In the case of A1050 it was found that the two examined routes has not resulted difference in the flow stress. In the case of Al 6082 the effect of the routes on the yield stress is significant. The present results showed that in the comparable plastic strain range higher yield stress values can be achieved by plane strain compression test than by ECAP.

Perioperative Assessment of Myocardial Deformation

PubMed Central

Duncan, Andra E.; Alfirevic, Andrej; Sessler, Daniel I.; Popovic, Zoran B.; Thomas, James D.

2014-01-01

Evaluation of left ventricular performance improves risk assessment and guides anesthetic decisions. However, the most common echocardiographic measure of myocardial function, the left ventricular ejection fraction (LVEF), has important limitations. LVEF is limited by subjective interpretation which reduces accuracy and reproducibility, and LVEF assesses global function without characterizing regional myocardial abnormalities. An alternative objective echocardiographic measure of myocardial function is thus needed. Myocardial deformation analysis, which performs quantitative assessment of global and regional myocardial function, may be useful for perioperative care of surgical patients. Myocardial deformation analysis evaluates left ventricular mechanics by quantifying strain and strain rate. Strain describes percent change in myocardial length in the longitudinal (from base to apex) and circumferential (encircling the short-axis of the ventricle) direction and change in thickness in the radial direction. Segmental strain describes regional myocardial function. Strain is a negative number when the ventricle shortens longitudinally or circumferentially and is positive with radial thickening. Reference values for normal longitudinal strain from a recent meta-analysis using transthoracic echocardiography are (mean ± SD) −19.7 ± 0.4%, while radial and circumferential strain are 47.3 ± 1.9 and −23.3 ± 0.7%, respectively. The speed of myocardial deformation is also important and is characterized by strain rate. Longitudinal systolic strain rate in healthy subjects averages −1.10 ± 0.16 sec−1. Assessment of myocardial deformation requires consideration of both strain (change in deformation), which correlates with LVEF, and strain rate (speed of deformation), which correlates with rate of rise of left ventricular pressure (dP/dt). Myocardial deformation analysis also evaluates ventricular relaxation, twist, and untwist, providing new and noninvasive methods to

Structural and mechanical defects of materials of offshore and onshore main gas pipelines after long-term operation

NASA Astrophysics Data System (ADS)

Maruschak, Pavlo; Panin, Sergey; Danyliuk, Iryna; Poberezhnyi, Lyubomyr; Pyrig, Taras; Bishchak, Roman; Vlasov, Ilya

2015-10-01

The study has established the main regularities of a fatigue failure of offshore gas steel pipes installed using S-lay and J-lay methods.We have numerically analyzed the influence of preliminary deformation on the fatigue life of 09Mn2Si steel at different amplitudes of cyclic loading. The results have revealed the regularities of formation and development of a fatigue crack in 17Mn1Si steel after 40 years of underground operation. The quantitative analysis describes the regularities of occurrence and growth of fatigue cracks in the presence of a stress concentration.

Deformation Mechanisms and Biocompatibility of the Superelastic Ti-23Nb-0.7Ta-2Zr-0.5N Alloy

NASA Astrophysics Data System (ADS)

Castany, P.; Gordin, D. M.; Drob, S. I.; Vasilescu, C.; Mitran, V.; Cimpean, A.; Gloriant, T.

2016-03-01

In this study, we have synthesized a new Ti-23Nb-0.7Ta-2Zr-0.5N alloy composition with the aim to obtain useful mechanical properties to be used in medicine such as high strength, good superelastic property, low modulus, and large ductility. Thus, mechanical properties including superelasticity and plasticity were investigated in relation with the different deformation mechanisms observed (stress-induced martensitic transformation, twinning and dislocation slip). On the other hand, the corrosion resistance in simulated body fluid (Ringer solution) and the in vitro cell behavior (MG63 human osteoblasts) of such biomedical alloy were also evaluated in order to assess its biocompatibility.

Structural Transformations in Metallic Materials During Plastic Deformation

NASA Astrophysics Data System (ADS)

Zasimchuk, E.; Turchak, T.; Baskova, A.; Chausov, N.; Hutsaylyuk, V.

2017-03-01

In this paper, the structure formation during the plastic deformation of polycrystalline nickel and aluminum based alloy 2024-T3 is investigated. The possibility of the relaxation and synergetic structure formation is examined. It is shown the deformation softening to be due to the crystallization of the amorphous structure of hydrodynamics flow channels (synergetic structure) HC as micrograins and their subsequent growth. The possible mechanism of micrograins' growth is proposed. The deformation processes change the phase composition of the multiphase alloy 2024-T3. It is shown by the quantitative analysis of the structures which were deformed in different regimes of the alloy samples. A method for increasing of the fatigue life through a dynamic pre-deformation is suggested.

The Time-Dependency of Deformation in Porous Carbonate Rocks

NASA Astrophysics Data System (ADS)

Kibikas, W. M.; Lisabeth, H. P.; Zhu, W.

2016-12-01

Porous carbonate rocks are natural reservoirs for freshwater and hydrocarbons. More recently, due to their potential for geothermal energy generation as well as carbon sequestration, there are renewed interests in better understanding of the deformation behavior of carbonate rocks. We conducted a series of deformation experiments to investigate the effects of strain rate and pore fluid chemistry on rock strength and transport properties of porous limestones. Indiana limestone samples with initial porosity of 16% are deformed at 25 °C under effective pressures of 10, 30, and 50 MPa. Under nominally dry conditions, the limestone samples are deformed under 3 different strain rates, 1.5 x 10-4 s-1, 1.5 x 10-5 s-1 and 1.5 x 10-6 s-1 respectively. The experimental results indicate that the mechanical behavior is both rate- and pressure-dependent. At low confining pressures, post-yielding deformation changes from predominantly strain softening to strain hardening as strain rate decreases. At high confining pressures, while all samples exhibit shear-enhanced compaction, decreasing strain rate leads to an increase in compaction. Slower strain rates enhance compaction at all confining pressure conditions. The rate-dependence of deformation behaviors of porous carbonate rocks at dry conditions indicates there is a strong visco-elastic coupling for the degradation of elastic modulus with increasing plastic deformation. In fluid saturated samples, inelastic strain of limestone is partitioned among low temperature plasticity, cataclasis and solution transport. Comparison of inelastic behaviors of samples deformed with distilled water and CO2-saturated aqueous solution as pore fluids provide experimental constraints on the relative activities of the various mechanisms. Detailed microstructural analysis is conducted to take into account the links between stress, microstructure and the inelastic behavior and failure mechanisms.

Creep mechanisms of a new Ni-Co-base disc superalloy at an intermediate temperature.

PubMed

Yuan, Y; Gu, Y F; Zhong, Z H; Osada, T; Cui, C Y; Tetsui, T; Yokokawa, T; Harada, H

2012-10-01

The microstructures of a new Ni-Co-base disc superalloy, TMW-4M3, before and after the creep test at 725 °C/630 MPa have been systematically investigated by transmission electron microscopy (TEM). The crept microstructures were marked as three different deformation stages (I, II and III) corresponding to the gradually increased strain. At stage I, stacking fault (SF) shearing was the main deformation mechanism. The SF was extrinsic and lay on {111} plane. However, deformation microtwinning became the dominant mode at stage II and III. The average spacing of deformation twins decreased from 109 ± 15 nm at stage II to 76 ± 12 nm at stage III, whereas the twin thickness did not change significantly. The influence of stacking fault energy (SFE) of γ matrix on the deformation mechanism is discussed. It is suggested that lower SFE in TMW-4M3 is partly responsible for the enhanced creep resistance. © 2012 The Authors Journal of Microscopy © 2012 Royal Microscopical Society.

Correlation between elastic and plastic deformations of partially cured epoxy networks

NASA Astrophysics Data System (ADS)

Müller, Michael; Böhm, Robert; Geller, Sirko; Kupfer, Robert; Jäger, Hubert; Gude, Maik

2018-05-01

The thermo-mechanical behavior of polymer matrix materials is strongly dependent on the curing reaction as well as temperature and time. To date, investigations of epoxy resins and their composites mainly focused on the elastic domain because plastic deformation of cross-linked polymer networks was considered as irrelevant or not feasible. This paper presents a novel approach which combines both elastic and plastic domain. Based on an analytical framework describing the storage modulus, analogous parameter combinations are defined in order to reduce complexity when variations in temperature, strain rate and degree of cure are encountered.

Influence of mechanical cell salvage on red blood cell aggregation, deformability, and 2,3-diphosphoglycerate in patients undergoing cardiac surgery with cardiopulmonary bypass.

PubMed

Gu, Y John; Vermeijden, Wytze J; de Vries, Adrianus J; Hagenaars, J Ans M; Graaff, Reindert; van Oeveren, Willem

2008-11-01

Mechanical cell salvage is increasingly used during cardiac surgery. Although this procedure is considered safe, it is unknown whether it affects the red blood cell (RBC) function, especially the RBC aggregation, deformability, and the contents of 2,3-diphosphoglycerate (2,3-DPG). This study examines the following: (1) whether the cell salvage procedure influences RBC function; and (2) whether retransfusion of the salvaged blood affects RBC function in patients. Forty patients undergoing cardiac surgery with cardiopulmonary bypass were randomly allocated to a cell saver group (n = 20) or a control group (n = 20). In the cell saver group, the blood aspirated from the wound area and the residual blood from the heart-lung machine were processed with a continuous-flow cell saver before retransfusion. In the control group this blood was retransfused without processing. The RBC aggregation and deformability were measured with a laser-assisted optical rotational cell analyzer and 2,3,-DPG by conventional laboratory test. The cell saver procedure did not influence the RBC aggregation but significantly reduced the RBC deformability (p = 0.007) and the content of RBC 2,3-DPG (p = 0.032). However, in patients receiving the processed blood, their intraoperative and postoperative RBC aggregation, deformability, and 2,3-DPG content did not differ from those of the control patients. Both groups of patients had a postoperative drop of RBC function as a result of hemodilution. The mechanical cell salvage procedure reduces the RBC deformability and the cell 2,3-DPG content. Retransfusion of the processed blood by cell saver does not further compromise the RBC function in patients undergoing cardiac surgery with cardiopulmonary bypass.

Constraints on fault and crustal strength of the Main Ethiopian Rift from formal inversion of earthquake focal mechanism data

NASA Astrophysics Data System (ADS)

Muluneh, Ameha A.; Kidane, Tesfaye; Corti, Giacomo; Keir, Derek

2018-04-01

We evaluate the frictional strength of seismogenic faults in the Main Ethiopian Rift (MER) by inverting the available, well-constrained earthquake focal mechanisms. The regional stress field is given by - 119.6°/77.2°, 6.2°/7.6°, and 97.5°/10.2° for trend/plunge of σ1, σ2 and σ3, respectively agrees well with previous fault kinematic and focal mechanism inversions. We determine the coefficient of friction, μ, for 44 seismogenic faults by assuming the pore pressure to be at hydrostatic conditions. Slip on 36 seismogenic faults occurs with μ ≥ 0.4. Slip on the remaining eight faults is possible with low μ. In general, the coefficient of friction in the MER is compatible with a value of μ of 0.59 ± 0.16 (2σ standard deviation). The shear stresses range from 16 to 129 MPa, is similar to crustal shear stress observed in extensional tectonic regimes and global compilations of shear stresses from major fault zones. The maximum shear stress is observed in the ductile crust, below the seismologically determined brittle-ductile transition (BDT) zone. Below the BDT, the crust is assumed to be weak due to thermal modification and/or high pore fluid pressure. Our results indicate linearly increasing μ and shear stress with depth. We argue that in the MER upper crust is strong and deforms according to Coulomb frictional-failure criterion.

Understanding creep in sandstone reservoirs - theoretical deformation mechanism maps for pressure solution in granular materials

NASA Astrophysics Data System (ADS)

Hangx, Suzanne; Spiers, Christopher

2014-05-01

Subsurface exploitation of the Earth's natural resources removes the natural system from its chemical and physical equilibrium. As such, groundwater extraction and hydrocarbon production from subsurface reservoirs frequently causes surface subsidence and induces (micro)seismicity. These effects are not only a problem in onshore (e.g. Groningen, the Netherlands) and offshore hydrocarbon fields (e.g. Ekofisk, Norway), but also in urban areas with extensive groundwater pumping (e.g. Venice, Italy). It is known that fluid extraction inevitably leads to (poro)elastic compaction of reservoirs, hence subsidence and occasional fault reactivation, and causes significant technical, economic and ecological impact. However, such effects often exceed what is expected from purely elastic reservoir behaviour and may continue long after exploitation has ceased. This is most likely due to time-dependent compaction, or 'creep deformation', of such reservoirs, driven by the reduction in pore fluid pressure compared with the rock overburden. Given the societal and ecological impact of surface subsidence, as well as the current interest in developing geothermal energy and unconventional gas resources in densely populated areas, there is much need for obtaining better quantitative understanding of creep in sediments to improve the predictability of the impact of geo-energy and groundwater production. The key problem in developing a reliable, quantitative description of the creep behaviour of sediments, such as sands and sandstones, is that the operative deformation mechanisms are poorly known and poorly quantified. While grain-scale brittle fracturing plus intergranular sliding play an important role in the early stages of compaction, these time-independent, brittle-frictional processes give way to compaction creep on longer time-scales. Thermally-activated mass transfer processes, like pressure solution, can cause creep via dissolution of material at stressed grain contacts, grain

Deformation and failure of single- and multi-phase silicate liquids: seismic precursors and mechanical work

NASA Astrophysics Data System (ADS)

Vasseur, Jeremie; Lavallée, Yan; Hess, Kai-Uwe; Wassermann, Joachim; Dingwell, Donald B.

2013-04-01

Along with many others, volcanic unrest is regarded as a catastrophic material failure phenomenon and is often preceded by diverse precursory signals. Although a volcanic system intrinsically behave in a non-linear and stochastic way, these precursors display systematic evolutionary trends to upcoming eruptions. Seismic signals in particular are in general dramatically increasing prior to an eruption and have been extensively reported to show accelerating rates through time, as well as in the laboratory before failure of rock samples. At the lab-scale, acoustic emissions (AE) are high frequency transient stress waves used to track fracture initiation and propagation inside a rock sample. Synthesized glass samples featuring a range of porosities (0 - 30%) and natural rock samples from volcán de Colima, Mexico, have been failed under high temperature uniaxial compression experiments at constant stresses and strain rates. Using the monitored AEs and the generated mechanical work during deformation, we investigated the evolutionary trends of energy patterns associated to different degrees of heterogeneity. We observed that the failure of dense, poorly porous glasses is achieved by exceeding elevated strength and thus requires a significant accumulation of strain, meaning only pervasive small-scale cracking is occurring. More porous glasses as well as volcanic samples need much lower applied stress and deformation to fail, as fractures are nucleating, propagating and coalescing into localized large-scale cracks, taking the advantage of the existence of numerous defects (voids for glasses, voids and crystals for volcanic rocks). These observations demonstrate that the mechanical work generated through cracking is efficiently distributed inside denser and more homogeneous samples, as underlined by the overall lower AE energy released during experiments. In contrast, the quicker and larger AE energy released during the loading of heterogeneous samples shows that the

A systematic review of the main mechanisms of heart failure disease management interventions.

PubMed

Clark, Alexander M; Wiens, Kelly S; Banner, Davina; Kryworuchko, Jennifer; Thirsk, Lorraine; McLean, Lianne; Currie, Kay

2016-05-01

To identify the main mechanisms of heart failure (HF) disease management programmes based in hospitals, homes or the community. Systematic review of qualitative and quantitative studies using realist synthesis. The search strategy incorporated general and specific terms relevant to the research question: HF, self-care and programmes/interventions for HF patients. To be included, papers had to be published in English after 1995 (due to changes in HF care over recent years) to May 2014 and contain specific data related to mechanisms of effect of HF programmes. 10 databases were searched; grey literature was located via Proquest Dissertations and Theses, Google and publications from organisations focused on HF or self-care. 33 studies (n=3355 participants, mean age: 65 years, 35% women) were identified (18 randomised controlled trials, three mixed methods studies, six pre-test post-test studies and six qualitative studies). The main mechanisms identified in the studies were associated with increased patient understanding of HF and its links to self-care, greater involvement of other people in this self-care, increased psychosocial well-being and support from health professionals to use technology. Future HF disease management programmes should seek to harness the main mechanisms through which programmes actually work to improve HF self-care and outcomes, rather than simply replicating components from other programmes. The most promising mechanisms to harness are associated with increased patient understanding and self-efficacy, involvement of other caregivers and health professionals and improving psychosocial well-being and technology use. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Influence of mechanically-induced dilatation on the shape memory behavior of amorphous polymers at large deformation

NASA Astrophysics Data System (ADS)

Hanzon, Drew W.; Lu, Haibao; Yakacki, Christopher M.; Yu, Kai

2018-01-01

In this study, we explore the influence of mechanically-induced dilatation on the thermomechanical and shape memory behavior of amorphous shape memory polymers (SMPs) at large deformation. The uniaxial tension, glass transition, stress relaxation and free recovery behaviors are examined with different strain levels (up to 340% engineering strain). A multi-branched constitutive model that incorporates dilatational effects on the polymer relaxation time is established and applied to assist in discussions and understand the nonlinear viscoelastic behaviors of SMPs. It is shown that the volumetric dilatation results in an SMP network with lower viscosity, faster relaxation, and lower Tg. The influence of the dilatational effect on the thermomechanical behaviors is significant when the polymers are subject to large deformation or in a high viscosity state. The dilation also increases the free recovery rate of SMP at a given recovery temperature. Even though the tested SMPs are far beyond their linear viscoelastic region when a large programming strain is applied, the free recovery behavior still follows the time-temperature superposition (TTSP) if the dilatational effect is considered during the transformation of time scales; however, if the programming strain is different, TTSP fails in predicting the recovery behavior of SMPs because the network has different entropy state and driving force during shape recovery. Since most soft active polymers are subject to large deformation in practice, this study provides a theoretical basis to better understand their nonlinear viscoelastic behaviors, and optimize their performance in engineering applications.

ChainMail based neural dynamics modeling of soft tissue deformation for surgical simulation.

PubMed

Zhang, Jinao; Zhong, Yongmin; Smith, Julian; Gu, Chengfan

2017-07-20

Realistic and real-time modeling and simulation of soft tissue deformation is a fundamental research issue in the field of surgical simulation. In this paper, a novel cellular neural network approach is presented for modeling and simulation of soft tissue deformation by combining neural dynamics of cellular neural network with ChainMail mechanism. The proposed method formulates the problem of elastic deformation into cellular neural network activities to avoid the complex computation of elasticity. The local position adjustments of ChainMail are incorporated into the cellular neural network as the local connectivity of cells, through which the dynamic behaviors of soft tissue deformation are transformed into the neural dynamics of cellular neural network. Experiments demonstrate that the proposed neural network approach is capable of modeling the soft tissues' nonlinear deformation and typical mechanical behaviors. The proposed method not only improves ChainMail's linear deformation with the nonlinear characteristics of neural dynamics but also enables the cellular neural network to follow the principle of continuum mechanics to simulate soft tissue deformation.

Improvement of Functional Properties by Sever Plastic Deformation on Parts of Titanium Biomaterials

NASA Astrophysics Data System (ADS)

Czán, Andrej; Babík, Ondrej; Daniš, Igor; Martikáň, Pavol; Czánová, Tatiana

2017-12-01

Main task of materials for invasive implantology is their biocompatibility with the tissue but also requirements for improving the functional properties of given materials are increasing constantly. One of problems of materials biocompatibility is the impossibility to improve of functional properties by change the percentage of the chemical elements and so it is necessary to find other innovative methods of improving of functional properties such as mechanical action in the form of high deformation process. This paper is focused on various methods of high deformation process such as Equal Channel Angular Pressing (ECAP) when rods with record strength properties were obtained.The actual studies of the deformation process properties as tri-axial compress stress acting on workpiece with high speed of deformation shows effects similar to results obtained using the other methods, but in lower levels of stress. Hydrostatic extrusion (HE) is applying for the purpose of refining the structure of the commercially pure titanium up to nano-scale. Experiments showed the ability to reduce the grain size below 100 nm. Due to the significant change in the performance of the titanium materials by severe plastic deformation is required to identify the processability of materials with respect to the identification of created surfaces and monitoring the surface integrity, where the experimental results show ability of SPD technologies application on biomaterials.

Storm-wave-induced seabed deformation: Results from in situ observation in the Yellow River subaqueous delta

NASA Astrophysics Data System (ADS)

Jia, Y.; Wang, Z. Mr; Liu, X.; Shan, H.

2017-12-01

Submarine landslides move large volumes of sediment and are often hazardous to offshore installations. Current research into submarine landslides mainly relies on marine surveying techniques. In contrast, in situ observations of the submarine landslide process, specifically seabed deformation, are sparse, and therefore restrict our understanding of submarine landslide mechanisms and the establishment of a disaster warning scheme. The submarine landslide monitoring (SLM) system, which has been designed to partly overcome these pitfalls, can monitor storm-wave-induced submarine landslides in situ and over a long time period. The SLM system comprises two parts: (1) a hydrodynamic monitoring tripod for recording hydrodynamic data and (2) a shape accel array for recording seabed deformation at different depths. This study recorded the development of the SLM system and the results of in situ observation in the Yellow River Delta, China, during the boreal winter of 2014-2015. The results show an abrupt small-scale storm-wave-induced seabed shear deformation; the shear interface is in at least 1.5-m depth and the displacement of sediments at 1.23-m depth is more than 13 mm. The performance of the SLM system confirms the feasibility and stability of this approach. Further, the in situ observations, as well as the laboratory tests, helped reveal the profound mechanism of storm-wave-induced seabed deformation.