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Sample records for high-rate plastic deformation

  1. High-rate Plastic Deformation of Nanocrystalline Tantalum to Large Strains: Molecular Dynamics Simulation

    SciTech Connect

    Rudd, R E

    2009-02-05

    Recent advances in the ability to generate extremes of pressure and temperature in dynamic experiments and to probe the response of materials has motivated the need for special materials optimized for those conditions as well as a need for a much deeper understanding of the behavior of materials subjected to high pressure and/or temperature. Of particular importance is the understanding of rate effects at the extremely high rates encountered in those experiments, especially with the next generation of laser drives such as at the National Ignition Facility. Here we use large-scale molecular dynamics (MD) simulations of the high-rate deformation of nanocrystalline tantalum to investigate the processes associated with plastic deformation for strains up to 100%. We use initial atomic configurations that were produced through simulations of solidification in the work of Streitz et al [Phys. Rev. Lett. 96, (2006) 225701]. These 3D polycrystalline systems have typical grain sizes of 10-20 nm. We also study a rapidly quenched liquid (amorphous solid) tantalum. We apply a constant volume (isochoric), constant temperature (isothermal) shear deformation over a range of strain rates, and compute the resulting stress-strain curves to large strains for both uniaxial and biaxial compression. We study the rate dependence and identify plastic deformation mechanisms. The identification of the mechanisms is facilitated through a novel technique that computes the local grain orientation, returning it as a quaternion for each atom. This analysis technique is robust and fast, and has been used to compute the orientations on the fly during our parallel MD simulations on supercomputers. We find both dislocation and twinning processes are important, and they interact in the weak strain hardening in these extremely fine-grained microstructures.

  2. Engineering of surface microstructure transformations using high rate severe plastic deformation in machining

    NASA Astrophysics Data System (ADS)

    Abolghasem, Sepideh

    Engineering surface structures especially at the nanometer length-scales can enable fundamentally new multifunctional property combinations, including tunable physical, mechanical, electrochemical and biological responses. Emerging manufacturing paradigms involving Severe Plastic Deformation (SPD), for manipulating final microstructure of the surfaces are unfortunately limited by poorly elucidated process-structure-performance linkages, which are characterized by three central variables of plasticity: strain, strain-rate and temperature that determine the resulting Ultrafine Grained (UFG) microstructure. The challenge of UFG surface engineering, design and manufacturing can be overcome if and only if the mappings between the central variables and the final microstructure are delineated. The objective of the proposed document is to first envision a phase-space, whose axes are parameterized in terms of the central variables of SPD. Then, each point can correspond to a unique microstructure, characterized by its location on this map. If the parametrization and the population of the datasets are accurately defined, then the mapping is bijective where: i) realizing microstructure designs can be reduced to simply one of tuning process parameters falling within the map s desired subspaces. And, inversely, ii) microstructure prediction is directly possible by merely relating the measured/calculated thermomechanics at each point in the deformation zone to the corresponding spot on the maps. However, the analytic approach to establish this map first requires extensive datasets, where the microstructures are accurately measured for a known set of strain, strain-rate and temperature of applied SPD. Although such datasets do not exist, even after the empirical data is accumulated, there is a lack of formalized statistical outlines in relating microstructural characteristic to the process parameters in order to build the mapping framework. Addressing these gaps has led to this

  3. Modeling Large-Strain, High-Rate Deformation in Metals

    SciTech Connect

    Lesuer, D R; Kay, G J; LeBlanc, M M

    2001-07-20

    The large strain deformation response of 6061-T6 and Ti-6Al-4V has been evaluated over a range in strain rates from 10{sup -4} s{sup -1} to over 10{sup 4} s{sup -1}. The results have been used to critically evaluate the strength and damage components of the Johnson-Cook (JC) material model. A new model that addresses the shortcomings of the JC model was then developed and evaluated. The model is derived from the rate equations that represent deformation mechanisms active during moderate and high rate loading. Another model that accounts for the influence of void formation on yield and flow behavior of a ductile metal (the Gurson model) was also evaluated. The characteristics and predictive capabilities of these models are reviewed.

  4. Plastic Deformation of Granular Materials

    DTIC Science & Technology

    1993-01-25

    discontinuities. These result will be important in our granular flow work, when considering viscoplastic constitutive relations (i.e. relaxation systems...5 CUNDN( NUMRES Plastic Deformation of Granular Materials (U) 61102F 6. AUTHOR(S) 2304/A4 Dr. E. Bruce Pitman 7 PERFORMING ORGANIZATION NA .h • 8...lose hyperbolicity. 98 3 81 061! SUBJECT TERMS 15. NUMBER OF PAGES granular material ; plastic deformation; hyperbolic 12 equations 16. PRICE CODE 17

  5. High-rate deformation and fracture of steel 09G2S

    NASA Astrophysics Data System (ADS)

    Balandin, Vl. Vas.; Balandin, Vl. Vl.; Bragov, A. M.; Igumnov, L. A.; Konstantinov, A. Yu.; Lomunov, A. K.

    2014-11-01

    The results of experimental and theoretical studies of steel 09G2S deformation and fracture laws in a wide range of strain rates and temperature variations are given. The dynamic deformation curves and the ultimate characteristics of plasticity in high-rate strain were determined by the Kolsky method in compression, extension, and shear tests. The elastoplastic properties and spall strength were studied by using the gaseous gun of calibre 57 mm and the interferometer VISAR according to the plane-wave experiment technique. The data obtained by the Kolsky method were used to determine the parameters of the Johnson-Cook model which, in the framework of the theory of flow, describes how the yield surface radius depends on the strain, strain rate, and temperature.

  6. Theory of Strength and High-Rate Plasticity in BCC Metals Laser-Driven to High Pressures

    NASA Astrophysics Data System (ADS)

    Rudd, Robert E.; Barton, N. R.; Cavallo, R. M.; Hawreliak, J. A.; Maddox, B. R.; Park, H.-S.; Prisbrey, S. T.; Remington, B. A.; Comley, A. J.; Ross, P. W.; Brickner, N.

    2012-10-01

    High-rate plastic deformation is the subject of increasing experimental activity. High energy laser platforms such as those at the National Ignition Facility and the Laboratory for Laser Energetics offer the possibility to study plasticity at extremely high rates in shock waves and, importantly, in non-shock ramp-compression waves. Here we describe the theory of high-rate deformation of metals and how high energy lasers can be, and are, used to study the mechanical strength of materials under extreme conditions. Specifically, we describe how LLNL's multiscale strength model has been used to interpret the microscopic plastic flow in laser-driven Rayleigh-Taylor strength experiments, and how molecular dynamics (MD) and plasticity theory have been used to help understand in-situ diffraction based strength experiments for tantalum. The multiscale model provides information about the dislocation flow associated with plasticity and makes predictions that are compared with the experimental in-situ radiography of the Rayleigh-Taylor growth rate. We also use multi-million atom MD simulations inform the analytic theory of 1D to 3D plastic relaxation and compare to diffraction.

  7. Deformation mechanisms of plasticized starch materials.

    PubMed

    Mikus, P-Y; Alix, S; Soulestin, J; Lacrampe, M F; Krawczak, P; Coqueret, X; Dole, P

    2014-12-19

    The aim of this paper is to understand the influence of plasticizer and plasticizer amount on the mechanical and deformation behaviors of plasticized starch. Glycerol, sorbitol and mannitol have been used as plasticizers. After extrusion of the various samples, dynamic mechanical analyses and video-controlled tensile tests have been performed. It was found that the nature of plasticizer, its amount as well as the aging of the material has an impact on the involved deformation mechanism. The variations of volume deformation could be explained by an antiplasticization effect (low plasticizer amount), a phase-separation phenomenon (excess of plasticizer) and/or by the retrogradation of starch.

  8. Machining and grinding: High rate deformation in practice

    SciTech Connect

    Follansbee, P.S.

    1993-04-01

    Machining and grinding are well-established material-working operations involving highly non-uniform deformation and failure processes. A typical machining operation is characterized by uncertain boundary conditions (e.g.,surface interactions), three-dimensional stress states, large strains, high strain rates, non-uniform temperatures, highly localized deformations, and failure by both nominally ductile and brittle mechanisms. While machining and grinding are thought to be dominated by empiricism, even a cursory inspection leads one to the conclusion that this results more from necessity arising out of the complicated and highly interdisciplinary nature of the processes than from the lack thereof. With these conditions in mind, the purpose of this paper is to outline the current understanding of strain rate effects in metals.

  9. Machining and grinding: High rate deformation in practice

    SciTech Connect

    Follansbee, P.S.

    1993-01-01

    Machining and grinding are well-established material-working operations involving highly non-uniform deformation and failure processes. A typical machining operation is characterized by uncertain boundary conditions (e.g.,surface interactions), three-dimensional stress states, large strains, high strain rates, non-uniform temperatures, highly localized deformations, and failure by both nominally ductile and brittle mechanisms. While machining and grinding are thought to be dominated by empiricism, even a cursory inspection leads one to the conclusion that this results more from necessity arising out of the complicated and highly interdisciplinary nature of the processes than from the lack thereof. With these conditions in mind, the purpose of this paper is to outline the current understanding of strain rate effects in metals.

  10. The operation of plastic MSGCs at high rates

    SciTech Connect

    Taylor, S.C.; Armitage, J.C.; Batchelar, D.

    1994-12-31

    The operation of MicroStrip Gas Counters (MSGCS) on a Upilex (polyimide) substrate is described. The surface resistivity of the substrate was reduced by ion implantation or by coating with a thin film of nickel oxide. Results are presented concerning the surface resistivity and The lowering of the substrate resistivity allows perate at very high rates and several devices in a high flux X-ray beam. Substrates with optimum resistivity showed no gain changes whereas gain changes were seen on those with higher resistivity.

  11. Plastic Deformation of Accreted Planetesimals

    NASA Astrophysics Data System (ADS)

    Kadish, J.

    2005-08-01

    The early stages of planetesimal growth follow an accretion model (Weidenschilling, Icarus 2000), which influences the intrinsic strength of a body and may control how its shape evolves after growth. In previous work we have determined the stress field of an accreted planetesimal accounting for possible variation in the object's spin as it accretes (Kadish et al., IJSS In Press) At the end of growth, these objects are subject to transport mechanisms that can distribute them throughout the solar system. As they are transported these objects can be spun-up by tidal forces (Scheeres et al, Icarus 2000), YORP (Bottke et al., Asteroids III 2002), and collisions (Binzel et al., Asteroids II 1989). Such an increase of spin will cause perturbations to the initial stress field and may lead to failure. We are able to show analytically that failure is initiated on the object's surface and a plastic zone propagates inward as the object's spin is increased. If we model an accreted body as a conglomeration of rocks similar to a gravel or sand, the deformation in the region of failure is characterized using a Mohr-Coulomb failure criterion with negligible cohesion and zero hardening(e.g. Holsapple, Icarus 2001). Such a response is highly non-linear and must be solved using finite elements and iterative methods (Simo and Hughes, Computational Inelasticity 1998). Using the commercial finite element code ABAQUS, we present the shape deformation resulting from an elasto-plastic analysis of a spinning, self-gravitating accreted sphere that is spun-up after growth is complete. The methodology can be extended to model plastic deformation due to local failure for more complex planetesimal shapes, such as for the asteroid Kleopatra. This work has implications for the evolution of planetesimal shapes, the creation of binary and contact binary asteroids, and for the maximum spin rate of small planetary bodies.

  12. A High-Rate, Single-Crystal Model for Cyclotrimethylene Trinitramine including Phase Transformations and Plastic Slip

    DOE PAGES

    Addessio, Francis L.; Luscher, Darby Jon; Cawkwell, Marc Jon; ...

    2017-05-14

    A continuum model for the high-rate, thermo-mechanical deformation of single-crystal cyclotrimethylene trinitramine (RDX) is developed. The model includes the effects of anisotropy, large deformations, nonlinear thermo-elasticity, phase transformations, and plastic slip. A multiplicative decomposition of the deformation gradient is used. The volumetric elastic component of the deformation is accounted for through a free-energy based equation of state for the low- (α) and high-pressure (γ) polymorphs of RDX. Crystal plasticity is addressed using a phenomenological thermal activation model. The deformation gradient for the phase transformation is based on an approach that has been applied to martensitic transformations. Simulations were conducted andmore » compared to high-rate, impact loading of oriented RDX single crystals. The simulations considered multiple orientations of the crystal relative to the direction of shock loading and multiple sample thicknesses. Thirteen slip systems, which were inferred from indentation and x-ray topography, were used to model the α-polymorph. It is shown that by increasing the number of slip systems from the previously considered number of six (6) to thirteen (13) in the α-polymorph, better comparisons with data may be obtained. Simulations of impact conditions in the vicinity of the α- to γ-polymorph transformation (3.8 GPa) are considered. Eleven of the simulations, which were at pressures below the transformation value (3.0 GPa), were compared to experimental data. Comparison of the model was also made with available data for one experiment above the transformation pressure (4.4 GPa). Also, simulations are provided for a nominal pressure of 7.5 GPa to demonstrate the effect of the transformation kinetics on the deformation of a high-rate plate impact problem.« less

  13. Bertram Hopkinson's pioneering work and the dislocation mechanics of high rate deformations and mechanically induced detonations.

    PubMed

    Armstrong, Ronald W

    2014-05-13

    Bertram Hopkinson was prescient in writing of the importance of better measuring, albeit better understanding, the nature of high rate deformation of materials in general and, in particular, of the importance of heat in initiating detonation of explosives. This report deals with these subjects in terms of post-Hopkinson crystal dislocation mechanics applied to high rate deformations, including impact tests, Hopkinson pressure bar results, Zerilli-Armstrong-type constitutive relations, shock-induced deformations, isentropic compression experiments, mechanical initiation of explosive crystals and shear banding in metals.

  14. Mechanical properties and constitutive relations for tantalum and tantalum alloys under high-rate deformation

    SciTech Connect

    Chen, S.R.; Gray, G.T. III; Bingert, S.R.

    1996-05-01

    Tantalum and its alloys have received increased interest as a model bcc metal and for defense-related applications. The stress-strain behavior of several tantalums, possessing varied compositions and manufacturing histories, and tantalum alloyed with tungsten, was investigated as a function of temperature from {minus}196 C to 1,000 C, and strain rate from 10{sup {minus}3} s{sup {minus}1} to 8,000 s{sup {minus}1}. The yield stress for all the Ta-materials was found to be sensitive to the test temperature, the impurity and solute contents; however, the strain hardening remained very similar for various ``pure`` tantalums but increased with alloying. Powder-metallurgy (P/M) tantalum with various levels of oxygen content produced via different processing paths was also investigated. Similar mechanical properties compared to conventionally processed tantalums were achieved in the P/M Ta. This data suggests that the frequently observed inhomogeneities in the mechanical behavior of tantalum inherited from conventional processes can be overcome. Constitutive relations based upon the Johnson-Cook, the Zerilli-Armstrong, and the Mechanical Threshold Stress models were evaluated for all the Ta-based materials. Parameters were also fit for these models to a tantalum-bar material. Flow stresses of a Ta bar stock subjected to a large-strain deformation of {var_epsilon} = 1.85 via multiple upset forging were obtained. The capabilities and limitations of each model for large-strain applications are examined. The deformation mechanisms controlling high-rate plasticity in tantalum are revisited.

  15. Plastic deformation mechanisms in nanocrystalline metallic materials

    NASA Astrophysics Data System (ADS)

    Ovid'ko, Ilya A.

    2013-11-01

    This article discusses the experiments, computer simulations, and theoretical models addressing the conventional and specific mechanisms of plastic deformation in nanocrystalline metallic materials. Particular attention is devoted to the competition between lattice dislocation slip and specific deformation mechanisms mediated by grain boundaries as well as its sensitivity to grain size and other parameters of nanocrystalline metallic structures.

  16. Modeling plasticity by non-continuous deformation

    NASA Astrophysics Data System (ADS)

    Ben-Shmuel, Yaron; Altus, Eli

    2016-10-01

    Plasticity and failure theories are still subjects of intense research. Engineering constitutive models on the macroscale which are based on micro characteristics are very much in need. This study is motivated by the observation that continuum assumptions in plasticity in which neighbour material elements are inseparable at all-time are physically impossible, since local detachments, slips and neighbour switching must operate, i.e. non-continuous deformation. Material microstructure is modelled herein by a set of point elements (particles) interacting with their neighbours. Each particle can detach from and/or attach with its neighbours during deformation. Simulations on two- dimensional configurations subjected to uniaxial compression cycle are conducted. Stochastic heterogeneity is controlled by a single "disorder" parameter. It was found that (a) macro response resembles typical elasto-plastic behaviour; (b) plastic energy is proportional to the number of detachments; (c) residual plastic strain is proportional to the number of attachments, and (d) volume is preserved, which is consistent with macro plastic deformation. Rigid body displacements of local groups of elements are also observed. Higher disorder decreases the macro elastic moduli and increases plastic energy. Evolution of anisotropic effects is obtained with no additional parameters.

  17. Plastic deformation in a metallic granular chain

    NASA Astrophysics Data System (ADS)

    Musson, Ryan W.; Carlson, William

    2016-03-01

    Solitary wave response was investigated in a metallic granular chain-piston system using LS-DYNA. A power law hardening material model was used to show that localized plastic deformation is present in a metallic granular chain for an impact velocity of 0.5 m/s. This loss due to plastic deformation was quantified via impulse, and it was shown that the loss scales nearly linearly with impact velocity. Therefore, metallic grains may not be suitable for devices that require high-amplitude solitary waves. There would be too much energy lost to plastic deformation. One can assume that ceramics will behave elastically; therefore, the response of an aluminum oxide granular chain was compared to that of a steel chain.

  18. The effect of aspect ratio on the compressive high rate deformation of three metallic alloys

    NASA Astrophysics Data System (ADS)

    Walley, S. M.; Radford, D. D.; Chapman, D. J.

    2006-08-01

    Metallic cylinders of rolled homogeneous armour (RHA) steel, Ti6Al4V, and FNC tungsten alloy of four different length l to diameter d ratios (dimensions in mm): 8/4, 4/8, 10/8, 8/10) were deformed at high rates of deformation using a direct impact Hopkinson pressure bar. Highspeed photographic sequences of the deformation were taken using a Hadland Imacon 790 imageconverter camera working at either 1 or 2 x 104 frames/s. It was found that titanium alloy cylinders of all four aspect ratios shear-banded and fractured, but that cylinders made from RHA steel and FNC tungsten behaved in a ductile manner when l/d < 1 but in a brittle manner when l/d > 1. We conclude that adiabatic shear banding is not just an inherent material property but that in some materials size effects/geometry can trigger this phenomenon.

  19. Cathodoluminescence of natural, plastically deformed pink diamonds.

    PubMed

    Gaillou, E; Post, J E; Rose, T; Butler, J E

    2012-12-01

    The 49 type I natural pink diamonds examined exhibit color restricted to lamellae or bands oriented along {111} that are created by plastic deformation. Pink diamonds fall into two groups: (1) diamonds from Argyle in Australia and Santa Elena in Venezuela are heavily strained throughout and exhibit pink bands alternating with colorless areas, and (2) diamonds from other localities have strain localized near the discrete pink lamellae. Growth zones are highlighted by a blue cathodoluminescence (CL) and crosscut by the pink lamellae that emit yellowish-green CL that originates from the H3 center. This center probably forms by the recombination of nitrogen-related centers (A-aggregates) and vacancies mobilized by natural annealing in the Earth's mantle. Twinning is the most likely mechanism through which plastic deformation is accommodated for the two groups of diamonds. The plastic deformation creates new centers visible through spectroscopic methods, including the one responsible for the pink color, which remains unidentified. The differences in the plastic deformation features, and resulting CL properties, for the two groups might correlate to the particular geologic conditions under which the diamonds formed; those from Argyle and Santa Elena are deposits located within Proterozoic cratons, whereas most diamonds originate from Archean cratons.

  20. Modeling plastic deformation effect on magnetization in ferromagnetic materials

    NASA Astrophysics Data System (ADS)

    Li, Jianwei; Xu, Minqiang; Leng, Jiancheng; Xu, Mingxiu

    2012-03-01

    Based on the Sablik-Landgraf model, an integrated model has been developed which provides a description of the effect of plastic deformation on magnetization. The modeling approach is to incorporate the effect of plastic deformation on the effective field and that on the model parameters. The effective field incorporates the contributions of residual stress, stress demagnetization term, and the plastic deformation. We also consider the effect of plastic deformation on the model parameters: pinning coefficient, the scaling constant and the interdomain coupling coefficient. The computed magnetization exhibits sharp change in the preliminary stage of plastic deformation, and then decreases slowly with the increase of plastic strain, in agreement with experimental results.

  1. GNSS seismometer: Seismic phase recognition of real-time high-rate GNSS deformation waves

    NASA Astrophysics Data System (ADS)

    Nie, Zhaosheng; Zhang, Rui; Liu, Gang; Jia, Zhige; Wang, Dijin; Zhou, Yu; Lin, Mu

    2016-12-01

    High-rate global navigation satellite systems (GNSS) can potentially be used as seismometers to capture short-period instantaneous dynamic deformation waves from earthquakes. However, the performance and seismic phase recognition of the GNSS seismometer in the real-time mode, which plays an important role in GNSS seismology, are still uncertain. By comparing the results of accuracy and precision of the real-time solution using a shake table test, we found real-time solutions to be consistent with post-processing solutions and independent of sampling rate. In addition, we analyzed the time series of real-time solutions for shake table tests and recent large earthquakes. The results demonstrated that high-rate GNSS have the ability to retrieve most types of seismic waves, including P-, S-, Love, and Rayleigh waves. The main factor limiting its performance in recording seismic phases is the widely used 1-Hz sampling rate. The noise floor also makes recognition of some weak seismic phases difficult. We concluded that the propagation velocities and path of seismic waves, macro characteristics of the high-rate GNSS array, spatial traces of seismic phases, and incorporation of seismographs are all useful in helping to retrieve seismic phases from the high-rate GNSS time series.

  2. A High-Rate, Single-Crystal Model including Phase Transformations, Plastic Slip, and Twinning

    SciTech Connect

    Addessio, Francis L.; Bronkhorst, Curt Allan; Bolme, Cynthia Anne; Brown, Donald William; Cerreta, Ellen Kathleen; Lebensohn, Ricardo A.; Lookman, Turab; Luscher, Darby Jon; Mayeur, Jason Rhea; Morrow, Benjamin M.; Rigg, Paulo A.

    2016-08-09

    An anisotropic, rate-­dependent, single-­crystal approach for modeling materials under the conditions of high strain rates and pressures is provided. The model includes the effects of large deformations, nonlinear elasticity, phase transformations, and plastic slip and twinning. It is envisioned that the model may be used to examine these coupled effects on the local deformation of materials that are subjected to ballistic impact or explosive loading. The model is formulated using a multiplicative decomposition of the deformation gradient. A plate impact experiment on a multi-­crystal sample of titanium was conducted. The particle velocities at the back surface of three crystal orientations relative to the direction of impact were measured. Molecular dynamics simulations were conducted to investigate the details of the high-­rate deformation and pursue issues related to the phase transformation for titanium. Simulations using the single crystal model were conducted and compared to the high-­rate experimental data for the impact loaded single crystals. The model was found to capture the features of the experiments.

  3. Stress gage system for measuring very soft materials under high rates of deformation

    NASA Astrophysics Data System (ADS)

    Kendall, Michael J.; Drodge, Daniel R.; Froud, Richard F.; Siviour, Clive R.

    2014-07-01

    Soft materials have seen continued growth in industrial importance, but are difficult to test at relevant, particularly at high, rates of deformation and relevant temperatures. This is mainly due to the low stresses supported by these materials, which mean that very sensitive force measurements are required. In this paper, a split-Hopkinson pressure bar method for testing very soft materials and elastomers at high rates of deformation is presented and applied. Experiments are conducted in compression on hydroxyl terminated polybutadiene, a very soft rubber, at strain rates of about 2000 s-1. Titanium alloy bars are used, and in addition to the usual strain gauges on the bars, forces at both ends of the specimen are measured using a piezoelectric material, lead zirconium titanate (PZT), which is much more sensitive than the quartz crystal gauges typically used in previous literature. The piezoelectric constant of PZT ranges between 290-630 × 10-12 C N-1, making it 100 times more sensitive than quartz crystal (2.3 × 10-12 C N-1). Results obtained from the experiments show that the gauges are able to measure the forces on both ends of the specimen with excellent signal to noise ratios.

  4. On the response of Escherichia coli to high rates of deformation

    NASA Astrophysics Data System (ADS)

    Fitzmaurice, B. C.; Painter, J. D.; Appleby-Thomas, G. J.; Wood, D. C.; Hazael, R.; McMillan, P. F.

    2017-01-01

    While a large body of work exists on the low strain-rate loading of biological systems such as bacteria, there is a paucity of information on the response of such organisms at high rates of deformation. Here, the response of a readily accessible strain of bacteria, Escherichia coli (E. coli), has been examined under shock loading conditions. Although previous studies have shown greatly reduced growth in shock conditions up to several GPa, relationships between loading conditions and bacterial response have yet to be fully elucidated. Initial results of a more rigorous investigation into the 1D shock loading response of E. coli are presented here, expectantly leading to a more comprehensive view of its behaviour when exposed to high pressures. Comparison has been drawn to provide insight into the importance of the nature of the loading regime to the survival of these biological systems.

  5. Knowledge representation of rock plastic deformation

    NASA Astrophysics Data System (ADS)

    Davarpanah, Armita; Babaie, Hassan

    2017-04-01

    The first iteration of the Rock Plastic Deformation (RPD) ontology models the semantics of the dynamic physical and chemical processes and mechanisms that occur during the deformation of the generally inhomogeneous polycrystalline rocks. The ontology represents the knowledge about the production, reconfiguration, displacement, and consumption of the structural components that participate in these processes. It also formalizes the properties that are known by the structural geology and metamorphic petrology communities to hold between the instances of the spatial components and the dynamic processes, the state and system variables, the empirical flow laws that relate the variables, and the laboratory testing conditions and procedures. The modeling of some of the complex physio-chemical, mathematical, and informational concepts and relations of the RPD ontology is based on the class and property structure of some well-established top-level ontologies. The flexible and extensible design of the initial version of the RPD ontology allows it to develop into a model that more fully represents the knowledge of plastic deformation of rocks under different spatial and temporal scales in the laboratory and in solid Earth. The ontology will be used to annotate the datasets related to the microstructures and physical-chemical processes that involve them. This will help the autonomous and globally distributed communities of experimental structural geologists and metamorphic petrologists to coherently and uniformly distribute, discover, access, share, and use their data through automated reasoning and enhanced data integration and software interoperability.

  6. Plastic Deformation Rate and Initiation of Crystalline Explosives

    NASA Astrophysics Data System (ADS)

    Namkung, J.; Coffey, C. S.

    2002-07-01

    Recent theoretical calculations have demonstrated a relationship between the rate of energy dissipation and the rate of plastic deformation in crystalline solids subjected to plastic flow due to shock or impact. In the case of explosive crystals the energy dissipated locally within the crystals during plastic deformation forms the hot spots from which chemical reaction can be initiated. Prompted by this prediction relating the plastic deformation rate with initiation, a series of experiments were undertaken to measure the plastic deformation rate at the initiation site at the moment of initiation for a number of polycrystalline explosives when subjected to impact or mild shock. The experiment and the results will be reviewed here.

  7. Plastic deformation effect of the corrosion resistance in case of austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Haraszti, F.; Kovacs, T.

    2017-02-01

    The corrosion forms are different in case of the austenitic steel than in case of carbon steels. Corrosion is very dangerous process, because that corrosion form is the intergranular corrosion. The austenitic stainless steel shows high corrosion resistance level. It knows that plastic deformation and the heat treating decrease it’s resistance. The corrosion form in case of this steel is very special and the corrosion tests are difficult. We tested the selected steel about its corrosion behaviour after high rate deformation. We wanted to find a relationship between the corrosion resistance decreasing and the rate of the plastic deformation. We wanted to show this behaviour from mechanical and electrical changing.

  8. Plastic deformation of mullite/yttria composites.

    SciTech Connect

    Ramirez de Arellano Lopez, A.; Melendez-Martinez, J. J.; Routbort, J. L.; Cruse, T. A.; Koritala, R. E.; Goretta, K. C.; Energy Technology; Univ. de Sevilla

    2001-05-01

    Mullite (3Al{sub 2}O{sub 3.2}SiO{sub 2}) based composites have excellent mechanical and thermal properties. The same characteristics that give mullite good resistance to plastic deformation also make its sintering difficult. Yttria is one of the most commonly used additives to reduce sintering temperatures in mullite. Additionally vitreous silicates (Y{sub 2}Si{sub 2}O{sub 7}) could improve ductility. In this work we have used mullite samples with various amounts of Y{sub 2}O{sub 3} (0, 5 and 9 wt.%). Details of processing and characterization of these composites have been the subject of a previous publication. We have compared the ductility of these composites by means of compressive deformation tests at elevated temperatures. Creep tests were performed at temperatures between 1300 and 1400 C, in air, in a stress range of 0.69 to 34.5 MPa.

  9. Plastic deformation of a wedge by a sliding punch

    NASA Astrophysics Data System (ADS)

    Nepershin, R. I.

    2016-11-01

    We present a self-similar solution of the problem of deformation of an ideally plastic wedge by a sliding punch with regard to contact friction; such a solution generalizes the well-known solutions of the problem of wedge penetration into a plastic half-space and of compression of an ideally plastic wedge by a plane punch. The problem is of interest for modeling the processes of plastic deformation of rough surfaces of metal pieces by a rigid tool.

  10. Experimental observation of plastic deformation areas, using an acoustic microscope.

    PubMed

    Ishikawa, I; Semba, T; Kanda, H; Katakura, K; Tani, Y; Sato, H

    1989-01-01

    Novel techniques are described for the observation of plastic deformation areas by using an acoustic microscope. On a test piece subjected to plastic deformation, an area was found that had an abnormal contrast in the crystal grain and a pointed end at the V notch. Calculation of the propagation velocity of the surface acoustic wave (SAW) showed a difference of several percent between this area and the rest of the test piece. It has been presumed that this difference reflects the local plastic deformation, and that the abnormal contrast area corresponds to the image of the two-dimensionally distributed plastic deformation area of metals.

  11. Plastic Deformation of Quartz: Unfinished business?

    NASA Astrophysics Data System (ADS)

    Paterson, M. S.

    2011-12-01

    Starting at Harvard in the mid-1930's, David Griggs built a series of high pressure machines for experimental rock deformation. One persistent aim was to achieve the plastic deformation of quartz. Each time he built a new machine for higher pressure and/or temperature, one of the first materials he tested would be quartz. This search went on through a 500 MPa liquid-medium machine at temperatures up to 300°C, then with a gas-medium machine for temperatures up to 800°C, and finally with a solid-medium machine for higher pressures and temperatures. Quartz proved stubbornly resistant to deformation except at extremely high stresses until, finally and somewhat serendipitously, it was found possible to deform quartz at relatively low stresses in the presence of water under special conditions. The breakthrough came in an experiment in a 1500 MPa solid-medium apparatus in which talc was used as pressure medium. At the temperature of the experiment, the talc dehydrated and so released water. Under these conditions, natural quartz proved to be very weak and to readily undergo plastic deformation, a phenomenon that became known as "hydrolytic weakening". Soon after this discovery, it was also found that certain synthetic single crystals could be easily deformed ab initio. These crystals were from a particular set that had been grown rapidly under hydrothermal conditions and had incorporated water during growth. Attempts in our laboratory to weaken crystals in a gas-medium apparatus at around 300 MPa by cooking dry quartz in the presence of added water were all unsuccessful, although we could deform wet synthetic crystals. There was considerable speculation about a role of high pressure in promoting hydrolytic weakening, but the dilemma was eventually clarified by electron microscope studies by Fitz Gerald and coworkers. These studies showed that crystals that had been subjected to high pressure and temperature in the solid-medium apparatus were extensively microcracked

  12. Plastic deformation of polycrystalline zirconium carbide

    NASA Technical Reports Server (NTRS)

    Darolia, R.; Archbold, T. F.

    1976-01-01

    The compressive yield strength of arc-melted polycrystalline zirconium carbide has been found to vary from 77 kg per sq mm at 1200 C to 19 kg per sq mm at 1800 C. Yield drops were observed with plastic strain-rates greater than 0.003/sec but not with slower strain rates. Strain-rate change experiments yielded values for the strain-rate sensitivity parameter m which range from 6.5 at 1500 C to 3.8 at 1800 C, and the product dislocation velocity stress exponent times T was found to decrease linearly with increasing temperature. The deformation rate results are consistent with the Kelly-Rowcliffe model in which the diffusion of carbon assists the motion of dislocations.

  13. Ultrasonic characterization of plastic deformation in metals

    NASA Technical Reports Server (NTRS)

    Allison, S. G.; Heyman, J. S.; Salama, K.

    1986-01-01

    Acoustic tone burst spectroscopy is used to examine the effect of plastic deformation on higher order elastic properties of specimens of AISI 1016, 1045, 1095 and 8620 steel rods by measuring the stress acoustic constants (SACs). The SAC is found to be influenced by prestraining, and prestrain SAC measurements on 8620 steel demonstrate similar behavior to previously measured steels even though the composition of 8620 steel is significantly different. It is suggested from bias stress measurements that the stress acoustic response of prestrained 8620 steel is sensitive to the sign of the applied stress due to the different directions is which dislocations move under tension as opposed to compression, providing an approach to nondestructive testing of residual stress in steels.

  14. Micrographic detection of plastic deformation in nickel-base alloys

    DOEpatents

    Steeves, A.F.; Bibb, A.E.

    1980-09-20

    A method for detecting low levels of plastic deformation in metal articles comprising electrolytically etching a flow free surface of the metal article with nital at a current density of less than about 0.1 amp/cm/sup 2/ and microscopically examining the etched surface to determine the presence of alternating striations. The presence of striations indicates plastic deformation in the article.

  15. Micrographic detection of plastic deformation in nickel base alloys

    DOEpatents

    Steeves, Arthur F.; Bibb, Albert E.

    1984-01-01

    A method for detecting low levels of plastic deformation in metal articles comprising electrolytically etching a flow free surface of the metal article with nital at a current density of less than about 0.1 amp/cm.sup.2 and microscopically examining the etched surface to determine the presence of alternating striations. The presence of striations indicates plastic deformation in the article.

  16. Localized Plastic Deformation in Colloidal Micropillars

    NASA Astrophysics Data System (ADS)

    Strickland, Daniel; Hor, Jyo Lyn; Ortiz, Carlos; Lee, Daeyeon; Gianola, Daniel

    When driven beyond yield, many amorphous solids exhibit concentrated regions of large plastic strain referred to as shear bands. Shear bands are the result of localized, cooperative rearrangements of particles known as shear transformations (STs). STs are dilatory: their operation results in an increase of free volume and local softening that leads to spatially concentrated plasticity. However, the evolution of STs into a macroscopic shear band remains poorly understood. To study the process, we perform compression experiments on amorphous colloidal micropillars. The micropillars, which are composed of fluorescent 3 μm PMMA particles, are made freestanding so that shear banding instabilities are not suppressed by confining boundaries. During compression, we observe strong localization of strain in a band of the pillar. As deformation proceeds, the sheared region continues to dilate until it reaches the colloidal glass transition, at which point dilation terminates. We quantify a length scale by measuring the extent of spatial correlations in strain. This length scale decreases gradually with increasing dilation and becomes static beyond the glass transition. Our results reinforce the idea of yield as a stress-induced glass transition in amorphous solids.

  17. Residual stresses and plastic deformation in GTA-welded steel

    SciTech Connect

    Brand, P.C. ); Keijser, T.H. de; Ouden, G. den )

    1993-03-01

    Residual stresses and plastic deformation in single pass GTA welded low-carbon steel were studied by means of x-ray diffraction in combination with optical microscopy and hardness measurements. The residual stresses and the amount of plastic deformation (microstrain) were obtained from x-ray diffraction line positions and line broading. Since the plates were polished before welding, it was possible to observe in the optical microscope two types of Lueders bands. During heating curved Lueders bands and during cooling straight Lueders bands perpendicular to the weld are formed. The curved Lueders bands extend over a larger distance from the weld than the straight Lueders bands. The amount of plastic deformation as obtained from the x-ray diffraction analysis is in agreement with these observations. An explanation is offered for the stresses measured in combination with plastic deformations observed. It is concluded that in the present experiments plastic deformation is the main cause of the residual stresses.

  18. Structural features of plastic deformation in bulk metallic glasses

    SciTech Connect

    Scudino, S. Shakur Shahabi, H.; Stoica, M.; Kühn, U.; Kaban, I.; Escher, B.; Eckert, J.; Vaughan, G. B. M.

    2015-01-19

    Spatially resolved strain maps of a plastically deformed bulk metallic glass (BMG) have been created by using high-energy X-ray diffraction. The results reveal that plastic deformation creates a spatially heterogeneous atomic arrangement, consisting of strong compressive and tensile strain fields. In addition, significant shear strain is introduced in the samples. The analysis of the eigenvalues and eigenvectors of the strain tensor indicates that considerable structural anisotropy occurs in both the magnitude and direction of the strain. These features are in contrast to the behavior observed in elastically deformed BMGs and represent a distinctive structural sign of plastic deformation in metallic glasses.

  19. On the initial stage of plastic deformation of metal alloys

    SciTech Connect

    Zuev, L.B.; Danilov, V.I.; Zavodchikov, S.Y.

    2000-04-01

    Plastic deformation has been studied for a range of metal alloys using speckle interferometry. It has been found that, in the initial stage, the process of plastic flow occurs by the propagation of a deformation front, which divides the deforming material into two regions differing with respect to the material's state. The flow exhibits regular features that can be described in terms of a self-excited wave process manifesting itself in an active medium under external mechanical action.

  20. Stress Analysis for Kinematic Hardening in Finite-Deformation Plasticity.

    DTIC Science & Technology

    1981-12-01

    field, straight lines defined by material points remain straight and the square block is deformed into a sequence of parallelograms . The line of...Contract N00014-81-K-0660 DEPARTMENT STRESS ANALYSIS FOR KINEMATIC HARDENING OF IN FINITE- DEFORMATION PLASTICITY MECHANICAL ENGINEERING By E. H. Lee, R, L...Finite- Deformation Plasticity E. H. Lee and R. L. Mallett, Rensselaer Polytechnic Institute and Stanford University, and T. B. Wertheimer, MARC Analysis

  1. Advantages of formulating an evolution equation directly for elastic distortional deformation in finite deformation plasticity

    NASA Astrophysics Data System (ADS)

    Rubin, M. B.; Cardiff, P.

    2017-06-01

    Simo (Comput Methods Appl Mech Eng 66:199-219, 1988) proposed an evolution equation for elastic deformation together with a constitutive equation for inelastic deformation rate in plasticity. The numerical algorithm (Simo in Comput Methods Appl Mech Eng 68:1-31, 1988) for determining elastic distortional deformation was simple. However, the proposed inelastic deformation rate caused plastic compaction. The corrected formulation (Simo in Comput Methods Appl Mech Eng 99:61-112, 1992) preserves isochoric plasticity but the numerical integration algorithm is complicated and needs special methods for calculation of the exponential map of a tensor. Alternatively, an evolution equation for elastic distortional deformation can be proposed directly with a simplified constitutive equation for inelastic distortional deformation rate. This has the advantage that the physics of inelastic distortional deformation is separated from that of dilatation. The example of finite deformation J2 plasticity with linear isotropic hardening is used to demonstrate the simplicity of the numerical algorithm.

  2. Avalanches and scaling in plastic deformation

    SciTech Connect

    Koslowski, M.

    2004-01-01

    Plastic deformation of crystalline materials is a complex non-homogeneous process characterized by avalanches in the motion of dislocations. We study the evolution of dislocations loops using an analytically solvable phase-field model of dislocations for ductile single crystals during monotonic loading. We present simulations of dislocations under slow external loading that generate scale-free avalanches and power-law behavior that are characteristics of self organized criticality. The distribution of dislocation loop sizes is given by P(A) {approx} A{sup -{sigma}}, with {sigma} = 1.8 {+-} 0.1. The power law exponent is in agreement with those found in acoustic emission measurements on stressed ice single crystals. In addition to the jerky character of dislocation motion, this model also predicts a range of macroscopic behaviors in agreement with observation, including hardening and dislocation multiplication with monotonic loading and a maximum in the acoustic emission signal at the onset of yielding. At sufficient large stress, the hardening rate drops and the stress-strain curve saturates. At the same time the acoustic emission as well as the dislocation production decreases in agreement with experimental observation.

  3. High resolution transmission electron microscopic in-situ observations of plastic deformation of compressed nanocrystalline gold

    SciTech Connect

    Wang, Guoyong; Lian, Jianshe; Jiang, Qing; Sun, Sheng; Zhang, Tong-Yi

    2014-09-14

    Nanocrystalline (nc) metals possess extremely high strength, while their capability to deform plastically has been debated for decades. Low ductility has hitherto been considered an intrinsic behavior for most nc metals, due to the lack of five independent slip systems actively operating during deformation in each nanograin. Here we report in situ high resolution transmission electron microscopic (HRTEM) observations of deformation process of nc gold under compression, showing the excellent ductility of individual and aggregate nanograins. Compression causes permanent change in the profile of individual nanograins, which is mediated by dislocation slip and grain rotation. The high rate of grain boundary sliding and large extent of widely exited grain rotation may meet the boundary compatibility requirements during plastic deformation. The in situ HRTEM observations suggest that nc gold is not intrinsically brittle under compressive loading.

  4. High Rate of Deformed Larvae among Gynogenetic Brown Trout (Salmo trutta m. fario) Doubled Haploids.

    PubMed

    Jagiełło, Krzysztof; Zalewski, Tomasz; Dobosz, Stefan; Michalik, Oliwia; Ocalewicz, Konrad

    2017-01-01

    Mitotic gynogenesis results in the production of fully homozygous individuals in a single generation. Since inbred fish were found to exhibit an increased frequency of body deformations that may affect their survival, the main focus of this research was to evaluate the ratio of individuals with spinal deformities among gynogenetic doubled haploids (DHs) brown trout as compared to nonmanipulated heterozygous individuals. Gynogenetic development was induced by the activation of brown trout eggs by UV-irradiated homologous and heterologous (rainbow trout) spermatozoa. The subsequent exposure of the activated eggs to the high hydrostatic pressure disturbed the first cleavage in gynogenetic zygotes and enabled duplication of the maternal haploid set of chromosomes. The survival rate was significantly higher among gynogenetic brown trout hatched from eggs activated with the homologous UV-irradiated spermatozoa when compared to DHs hatched from eggs activated by the heterologous spermatozoa. More than 35% of the gynogenetic larvae exhibited body deformities, mostly lordosis and scoliosis. The percentage of malformed brown trout from the control group did not exceed 15%. The increased number of deformed larvae among DHs brown trout suggested rather a genetic background of the disease related to the fish spine deformities; however, both genetic and environmental factors were discussed as a cause of such conditions in fish.

  5. Observation of plastic deformation in freestanding single crystal Au nanowires

    SciTech Connect

    Lee, Dongyun; Zhao Manhong; Wei Xiaoding; Chen Xi; Jun, Seong C.; Hone, James; Herbert, Erik G.; Oliver, Warren C.; Kysar, Jeffrey W.

    2006-09-11

    Freestanding single crystal nanowires of gold were fabricated from a single grain of pure gold leaf by standard lithographic techniques, with center section of 7 {mu}m in length, 250 nm in width, and 100 nm in thickness. The ends remained anchored to a silicon substrate. The specimens were deflected via nanoindenter until plastic deformation was achieved. Nonlocalized and localized plastic deformations were observed. The resulting force-displacement curves were simulated using continuum single crystal plasticity. A set of material parameters which closely reproduce the experimental results suggests that the initial critical resolved shear stress was as high as 135 MPa.

  6. Plastic deformation and sintering of alumina under high pressure

    SciTech Connect

    Liu, Fangming; Liu, Pingping; Wang, Haikuo; Xu, Chao; Yin, Shuai; Yin, Wenwen; Li, Yong; He, Duanwei

    2013-12-21

    Plastic deformation of alumina (Al{sub 2}O{sub 3}) under high pressure was investigated by observing the shape changes of spherical particles, and the near fully dense transparent bulks were prepared at around 5.5 GPa and 900 °C. Through analyzing the deformation features, densities, and residual micro-strain of the Al{sub 2}O{sub 3} compacts prepared under high pressures and temperatures (2.0–5.5 GPa and 600–1200 °C), the effects of plastic deformation on the sintering behavior of alumina have been demonstrated. Under compression, the microscopic deviatoric stress caused by grain-to-grain contact could initiate the plastic deformation of individual particles, eliminate pores of the polycrystalline samples, and enhance the local atomic diffusion at the grain boundaries, thus produced transparent alumina bulks.

  7. Determination of near-surface plastic deformation in sliding contacts

    NASA Technical Reports Server (NTRS)

    Kennedy, F. E., Jr.; Grotelueschen, L. P.

    1984-01-01

    It is pointed out that substantial plastic deformation occurs on and near the contact surfaces, when two solid bodies slide against each other without lubrication. It has been found that this deformation plays an important role in the tribological behavior of the sliding contact. The present investigation has the objective to develop an analytical model to predict the near-surface plastic deformation resulting from a single pass of one metallic surface over another. A finite element viscoplasticity program was written relating velocities to forces in a two-dimensional domain. The program was employed in the study of plastic deformation during a single pass of a hardened tool steel slider over a copper rub specimen. It was found that essentially the only material set in motion by the slider was directly under the contact zone. The agreement between values obtained in the analysis and experimental data is reasonably good.

  8. EFFECTS OF HIGH-RATE COMPRESSION LOADING ON SHORT REINFORCED PLASTIC MEMBERS

    DTIC Science & Technology

    thin-walled tubular aluminum columns, solid columns of cellular cellulose acetate , and tubular epoxy columns. Permanent deformations of both the...tubular aluminum columns and the solid cellular cellulose acetate columns appeared to occur intermittently as the columns resisted series of maximum...varied for the cellular cellulose acetate test pieces. the epoxy columns gave the least reproducibility, shattering severely under load. It was concluded

  9. High Rate Plasticity under Pressure using a Windowed Pressure-Shear Impact Experiment

    SciTech Connect

    Florando, J N; Jiao, T; Grunschel, S E; Clifton, R J; Ferranti, L; Becker, R C; Minich, R W; Bazan, G

    2009-07-29

    An experimental technique has been developed to study the strength of materials under conditions of moderate pressures and high shear strain rates. The technique is similar to the traditional pressure-shear plate-impact experiments except that window interferometry is used to measure both the normal and transverse particle velocities at a sample-window interface. Experimental and simulation results on vanadium samples backed with a sapphire window show the utility of the technique to measure the flow strength under dynamic loading conditions. The results show that the strength of the vanadium is 600 MPa at a pressure of 4.5 GPa and a plastic strain of 1.7%.

  10. Elastic And Plastic Deformations In Butt Welds

    NASA Technical Reports Server (NTRS)

    Verderaime, V.

    1992-01-01

    Report presents study of mathematical modeling of stresses and strains, reaching beyond limits of elasticity, in bars and plates. Study oriented toward development of capability to predict stresses and resulting elastic and plastic strains in butt welds.

  11. A High-Rate Continuous GPS Network in Iceland for Crustal Deformation Research

    NASA Astrophysics Data System (ADS)

    Geirsson, H.; Árnadóttir, T.; Bennett, R.; Lafemina, P.; Jónsson, S.; Hreinsdóttir, S.; Holland, A.; Deutscher, J.; Ingvarsson, T.; Sturkell, E.; Villemin, T.

    2007-12-01

    A significant expansion of the current continuous GPS network in Iceland is well underway. The goal of the project is to install 30-40 new continuous GPS stations, with a sampling rate of 1 second or higher in selected areas of the country. Most of the sites are already installed and are collecting data and communications are being established. Currently we have in total about 50 continuous and 12 semi-continuous stations running. Eventually, the older continuous GPS stations (installed from 1999 onwards) will also be upgraded to allow high sampling rates. Many of the CGPS sites are co-located with stations in the national seismic network which is very beneficial for operation of the sites and enhanced monotoring capabilities. The national seismic network in Iceland contains 51 3-component digital stations that all are on-line. High-rate GPS observations have been used successfully to study dynamic earthquake rupture processes, for example the Denali earthquake in Alaska and the 2003 Tokachi-Oki earthquake in Japan. New GPS stations were installed in seismically active areas in the South Iceland Seismic Zone, the Reykjanes Peninsula and in Northern Iceland. We also attempt to capture volcanic processes by installing high-rate GPS stations near the three most active volcanoes in Iceland: Hekla, Grímsvotn, and Katla. These volcanoes have been active recently or are currently showing signs of unrest. Continuous GPS and recent campaign GPS measurements indicate rapid uplift (up to 2 cm/yr) over a wide area in central Iceland due to retreat of the glaciers in a warming climate. The new network already installed in central Iceland will obtain more detailed information on the rate and extent of the uplift. Implementing the 1-Hz technology in Iceland enables studies of both the dynamic as well as slower-rate processes related to earthquake and volcanic activity. The high level of volcanic and earthquake activity in Iceland makes it an ideal site for this project. In

  12. The deformation response of three-dimensional woven composites subjected to high rates of loading

    NASA Astrophysics Data System (ADS)

    Pankow, Mark Robert

    The use of polymer matrix composites is widespread, with development in automotive, aerospace and recreational equipment. These applications have produced loading scenarios which are unfamiliar and not well understood. Several applications involve impact loading, which produces large strain rates and delamination failure. New manufacturing methods have led to three dimensional (3D) weave geometries that provide composites with damage protection. This is accomplished through elimination of delamination, and localizing the extent of damage. The present work is a combined experimental and computational study aimed at developing a mechanism based deformation response model for 3D woven composites, including the prediction of failure strengths at high loading rates. Three unique experimental configurations have been developed; along with finite element based simulations to predict the material response and failure mechanisms that are experimentally observed. End Notch Flexure (ENF) tests were used to determine the effectiveness of the Z-fiber at resisting crack propagation. The crack propagation was found to have rate dependent properties, with architecture based parameters required to predict the strength and resistance. The computational results reinforced the experimental observations. A new FE implementation captured the effectiveness of the Z-fiber reinforcement bridging the growing crack. Shock impact testing was performed to simulate the effects of blast loading on the material. New experimental measurement methods were utilized to record the deformations and strains which led to observations of matrix micro-cracking, the first failure mode. Computational models were developed to predict the material behavior subjected to shock loading, including matrix micro-cracking, which was predicted accurately. Finally, split Hopkinson pressure bar (SHPB) testing was done to understand the high strain rate behavior of the material in compression in all three directions. The

  13. Electrical and photomechanical effects of plastic deformation of mercuric iodide

    NASA Astrophysics Data System (ADS)

    Marschall, J.; Milstein, F.; Georgeson, G.; Gerrish, V.

    The effects of bulk plastic deformation of mercuric iodide (HgI2), upon some of the electronic properties relevant to the performance of HgI2 as a radiation detector were examined experimentally. Hole lifetimes, as well as hole and electron mobilities, were measured at various stages of sample deformation. Hole lifetimes were found to decrease by a factor of 2 under strains of several percent; carrier mobilities varied within experimental error, except during creep loading where electron and hole mobilities decreased by about 65 percent and 25 percent, respectively. Additionally, dark current measurements were made on specimens with varying degrees of accumulated plastic damage caused by c plane shear. Dark current values did not strongly reflect the extent of bulk plastic damage in deformed specimens.

  14. Electrical and photomechanical effects of plastic deformation of mercuric iodide

    SciTech Connect

    Marschall, J.; Milstein, F. . Dept. of Materials California Univ., Santa Barbara, CA . Dept. of Mechanical Engineering); Georgeson, G. ); Gerrish, V. . Santa Barbara Operations)

    1991-01-01

    The effects of bulk plastic deformation of mercuric iodide (HgI{sub 2}), upon some of the electronic properties relevant to the performance of HgI{sub 2} as a radiation detector were examined experimentally. Hole lifetimes, as well as hole and electron mobilities, were measured at various stages of sample deformation. Hole lifetimes were found to decrease by a factor of 2 under strains of several percent; carrier mobilities varied within experimental error, except during creep loading where electron and hole mobilities decreased by about 65 % and 25 %, respectively. Additionally, dark current measurements were made on specimens with varying degrees of accumulated plastic damage caused by c plane shear. Dark current values did not strongly reflect the extent of bulk plastic damage in deformed specimens. 16 refs., 4 figs., 1 tab.

  15. Practical solution of plastic deformation problems in elastic-plastic range

    NASA Technical Reports Server (NTRS)

    Mendelson, A; Manson, S

    1957-01-01

    A practical method for solving plastic deformation problems in the elastic-plastic range is presented. The method is one of successive approximations and is illustrated by four examples which include a flat plate with temperature distribution across the width, a thin shell with axial temperature distribution, a solid cylinder with radial temperature distribution, and a rotating disk with radial temperature distribution.

  16. Antisite-related defects in plastically deformed GaAs

    SciTech Connect

    Omling, P.; Weber, E.R.; Samuelson, L.

    1986-04-15

    Optical absorption measurements on plastically deformed GaAs show that the total extrinsic absorption increases with deformation, while the quenchable EL2 absorption stays constant. The nonquenchable extrinsic absorption is observed to be proportional to the EPR measured As/sub Ga/ containing defects produced during deformation. Since the As/sub Ga/-related defects produced by plastic deformation anneal at Tapprox.650 /sup 0/C, the implication for any correlation between EL2 and As/sub Ga/ antisites is that only those As/sub Ga/-related EPR centers which are stable up to at least 950 /sup 0/C can possibly be responsible for the EL2 level.

  17. Investigation of plastic deformation heterogeneities in duplex steel by EBSD

    SciTech Connect

    Wronski, S.; Tarasiuk, J.; Bacroix, B.; Baczmanski, A.; Braham, C.

    2012-11-15

    An EBSD analysis of a duplex steel (austeno-ferritic) deformed in tension up to fracture is presented. The main purpose of the paper is to describe, qualitatively and quantitatively, the differences in the behavior of the two phases during plastic deformation. In order to do so, several topological maps are measured on the deformed state using the electron backscatter diffraction technique. Distributions of grain size, misorientation, image quality factor and texture are then analyzed in detail. - Highlights: Black-Right-Pointing-Pointer Heterogeneities in duplex steel is studied. Black-Right-Pointing-Pointer The behavior of the two phases during plastic deformation is studied. Black-Right-Pointing-Pointer IQ factor distribution and misorientation characteristics are examined using EBSD.

  18. Structural Signature of Plastic Deformation in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Li, M. Z.; Wang, W. H.

    2011-04-01

    The structure feature of a model CuZr metallic glass during deformation is investigated by molecular dynamics simulations. A spatially heterogeneous irreversible rearrangement is observed in terms of nonaffine displacement. We find that regions with smaller nonaffine displacement have more Voronoi pentagons, while in those with larger nonaffine displacement other types of faces are more populated. We use the degree of local fivefold symmetry (LFFS) as the structural indicator to predict plastic deformation of local structures and find that the plastic events prefer to be initiated in regions with a lower degree of LFFS and propagate toward regions with a higher degree of LFFS.

  19. Plastic Deformation Influence on Intrinsic Magnetic Field of Austenitic Biomaterials

    NASA Astrophysics Data System (ADS)

    Smetana, Milan; Čápová, Klára; Chudáčik, Vladimír; Palček, Peter; Oravcová, Monika

    2016-12-01

    This article deals with non-destructive evaluation of austenitic stainless steels, which are used as the biomaterials in medical practice. Intrinsic magnetic field is investigated using the fluxgate sensor, after the applied plastic deformation. The three austenitic steel types are studied under the same conditions, while several values of the deformation are applied, respectively. The obtained results are presented and discussed in the paper.

  20. Acoustic Emission Arising from Plastic Deformation and Fracture.

    DTIC Science & Technology

    1980-05-01

    Acoustic Emission Generation and deEection Li..I Acoustic Emission Theory Plastic Deformation Lm. Fracture 20. ABSTRACT (Continue orn reverse side it...deformation and fracture. Recent developments in quantitative signal detection and trans- ducer characterization are considered. Several theories of acoustic...emis- sion sources are summarized and one based on dislocation theory by M91en and Bolin is extended to provide a relation between the inelastic

  1. Biaxially textured articles formed by plastic deformation

    DOEpatents

    Goyal, Amit

    2001-01-01

    A method of preparing a biaxially textured article comprises the steps of providing a metal preform, coating or laminating the preform with a metal layer, deforming the layer to a sufficient degree, and rapidly recrystallizing the layer to produce a biaxial texture. A superconducting epitaxial layer may then be deposited on the biaxial texture. In some embodiments the article further comprises buffer layers, electromagnetic devices or electro-optical devices.

  2. 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.

  3. Structural Transformations in Metallic Materials During Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Zasimchuk, E.; Turchak, T.; Baskova, A.; Chausov, N.; Hutsaylyuk, V.

    2017-02-01

    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.

  4. Anomalous Plastic Deformation and Sputtering of Ion Irradiated Silicon Nanowires

    PubMed Central

    2015-01-01

    Silicon nanowires of various diameters were irradiated with 100 keV and 300 keV Ar+ ions on a rotatable and heatable stage. Irradiation at elevated temperatures above 300 °C retains the geometry of the nanostructure and sputtering can be gauged accurately. The diameter dependence of the sputtering shows a maximum if the ion range matches the nanowire diameter, which is in good agreement with Monte Carlo simulations based on binary collisions. Nanowires irradiated at room temperature, however, amorphize and deform plastically. So far, plastic deformation has not been observed in bulk silicon at such low ion energies. The magnitude and direction of the deformation is independent of the ion-beam direction and cannot be explained with mass-transport in a binary collision cascade but only by collective movement of atoms in the collision cascade with the given boundary conditions of a high surface to volume ratio. PMID:25951108

  5. Phyllotactic transformations as plastic deformations of tubular crystals with defects

    NASA Astrophysics Data System (ADS)

    Beller, Daniel; Nelson, David

    Tubular crystals are 2D lattices in cylindrical topologies, which could be realized as assemblies of colloidal particles, and occur naturally in biological microtubules and in single-walled carbon nanotubes. Their geometry can be understood in the language of phyllotaxis borrowed from botany. We study the mechanics of plastic deformations in tubular crystals in response to tensile stress, as mediated by the formation and separation of dislocation pairs in a triangular lattice. Dislocation motion allows the growth of one phyllotactic arrangement at the expense of another, offering a low-energy, stepwise mode of plastic deformation in response to external stresses. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, dislocation glide. The crystal's bending modulus is found to produce simple but important corrections to the tube's deformation mechanics.

  6. Anomalous Plastic Deformation and Sputtering of Ion Irradiated Silicon Nanowires.

    PubMed

    Johannes, Andreas; Noack, Stefan; Wesch, Werner; Glaser, Markus; Lugstein, Alois; Ronning, Carsten

    2015-06-10

    Silicon nanowires of various diameters were irradiated with 100 keV and 300 keV Ar(+) ions on a rotatable and heatable stage. Irradiation at elevated temperatures above 300 °C retains the geometry of the nanostructure and sputtering can be gauged accurately. The diameter dependence of the sputtering shows a maximum if the ion range matches the nanowire diameter, which is in good agreement with Monte Carlo simulations based on binary collisions. Nanowires irradiated at room temperature, however, amorphize and deform plastically. So far, plastic deformation has not been observed in bulk silicon at such low ion energies. The magnitude and direction of the deformation is independent of the ion-beam direction and cannot be explained with mass-transport in a binary collision cascade but only by collective movement of atoms in the collision cascade with the given boundary conditions of a high surface to volume ratio.

  7. In situ TEM observations of plastic deformation in quartz crystals

    NASA Astrophysics Data System (ADS)

    Tochigi, E.; Zepeda-alarcon, E.; Wenk, H.-R.; Minor, A. M.

    2014-11-01

    With in situ nanocompression experiments in a transmission electron microscope, we investigated plastic deformation in natural quartz crystals and observed both dislocation plasticity as well as mechanical twinning. Through this experimental method, we are able to provide direct evidence of Dauphiné twin nucleation and could measure the intrinsic twinning stress. The twinning phenomena appear to include a memory effect, where the same twin can reappear upon successive loading and unloading events. The data provide insight into this twin generation mechanism and can be used as a benchmark for the use of twins in quartz for paleopiezometry. Together, the observation of room-temperature dislocation plasticity and reversible twinning adds new insight into the extensive field of quartz plasticity and demonstrates the usefulness of small-scale testing techniques for mineral physics.

  8. Plastically deformed region around indentations on Si angle crystal

    NASA Astrophysics Data System (ADS)

    Yoshioka, M.

    1994-12-01

    Expansion of a hemispherical shell by inner pressure has been widely applied for the model of the deformation by an indentation on a flat surface; however, the deformed region is not necessarily spherically symmetric, especially in anisotropic materials such as single crystals. Therefore, whether the spherical model is applicable in an indentation process for objective materials must always be kept in mind. Indentations have been made on the (111) surface of silicon crystal at various temperatures. The three-dimensional shape of the plastically deformed region was experimentally measured by means of an etching technique and its difference from the hemisphere was observed. It was never spherical but much more complicated, similar to a bottle gourd. The slip mechanism, which resulted in the observed shape of the plastic region, is discussed further. The plastic region was analytically obtained also on the assumption that the stress distribution was spherically symmetrical. The result is approximately in accordance with the observed shape. It is therefore concluded that the stress distribution is nearly spherical although the plastic region is far from it. The yield strength of silicon crystals and their temperature dependence were obtained based on the spherical model.

  9. Plastic Deformation Modes of CuZr/Cu Multilayers

    PubMed Central

    Cui, Yan; Abad, Oscar Torrents; Wang, Fei; Huang, Ping; Lu, Tian-Jian; Xu, Ke-Wei; Wang, Jian

    2016-01-01

    We synthesized CuZr/Cu multilayers and performed nanoindentation testing to explore the dependence of plastic deformation modes on the thickness of CuZr layers. The Cu layers were 18 nm thick and the CuZr layers varied in thickness from 4 nm to 100 nm. We observed continuous plastic co-deformation in the 4 nm and 10 nm CuZr − 18 nm Cu multilayers and plastic-induced shear instability in thick CuZr layers (>20 nm). The plastic co-deformation is ascribed to the nucleation and interaction of shear transformation zones in CuZr layers at the adjacent interfaces, while the shear instability is associated with the nucleation and propagation of shear bands in CuZr layers. Shear bands are initialized in the CuZr layers due to the accumulated glide dislocations along CuZr-Cu interfaces, and propagate into adjacent Cu layers via slips on {111} plane non-parallel to the interface. Due to crystallographic constraint of the Cu layers, shear bands are approximately parallel to {111} plane in the Cu layer. PMID:26984537

  10. Influence of Plastic Deformation on Bimaterial Fault Rupture Directivity

    NASA Astrophysics Data System (ADS)

    Templeton-Barrett, E. L.; Dedontney, N.; Rice, J. R.; Dmowska, R.

    2011-12-01

    Material juxtapositions across mature faults are a common occurrence. Previous work has found that this elastic mismatch results in a rupture that will preferentially propagate in the direction of slip displacement on the more compliant side of the fault, with more off-fault damage in the stiffer material. This result has implications for inferring preferred rupture directions based on observations of damage zone asymmetry. We perform a complete numerical investigation of the role of the stress state on the distribution of plastic deformation and the direction of preferred rupture propagation. We show that there are important factors, in addition to the elastic mismatch, which control the preferred direction of propagation as well as the side of the fault in which damage predominately accumulates. The orientation of the most compressive principal stress is the controlling factor in determining the location of plastic deformation. For different orientations, plastic deformation can accumulate in either the stiffer or the more compliant material. For high angles of most compressive stress, the aforementioned preferred rupture direction prediction holds true. However, the off-fault plastic response can reverse that direction for low angles of most compressive stress so that rupture will preferentially propagate in the direction of slip displacement in the stiffer material. Also, as already established in the case of purely elastic materials, when pre-stress is close to static friction (low seismic S ratio) a transition to supershear may take place in the direction opposite to what was the preferred direction.

  11. Plastic deformation - Its role in fatigue crack propagation

    NASA Technical Reports Server (NTRS)

    Mazumdar, P. K.; Jeelani, S.

    1986-01-01

    Recognizing the fact that the effective driving force Delta-K(eff) determines the fatigue crack propagation (FCP) rate and that the shear strain, which is considered to develop due to an occurrence of crack closure, primarily contributes to the plastic deformation, an effort is made here to elucidate the role of plastic deformation in FCP by developing a correlation between the Delta-K(eff) and the applied driving force (Delta-K) with shear strain as variable. The disparity between Delta(K)eff) and Delta-K, which apparently increases with shear strain level, persists at lower values of Delta-K. This suggests a strong influence of the degree of localized deformation on the FCP rates in the near threshold level. Hence, an improvement of FCP rates in the near threshold level should follow an effort that promotes the plastic deformation near the crack tip to a greater degree. This approach could explain the effect of the grain size, microstructure, environment, R-ratio and crack size on the near-threshold FCP rates.

  12. Finite elasto-plastic deformation. I - Theory and numerical examples

    NASA Technical Reports Server (NTRS)

    Osias, J. R.; Swedlow, J. L.

    1974-01-01

    It is demonstrated that the problem of elasto-plastic finite deformation is governed by a quasi-linear model irrespective of deformation magnitude. This feature follows from the adoption of a rate viewpoint toward finite deformation analysis in an Eulerian reference frame. Objectivity of the formulation is preserved by introduction of a frame-invariant stress rate. Equations for piece-wise linear incremental finite element analysis are developed by application of the Galerkin method to the instantaneously linear governing differential equations of the quasi-linear model. Numerical solution capability has been established for problems of plane strain and plane stress. The accuracy of the numerical analysis is demonstrated by consideration of a number of problems of homogeneous finite deformation admitting comparative analytic solution. It is shown that accurate, objective numerical solutions can be obtained for problems involving dimensional changes of an order of magnitude and rotations of a full radian.

  13. Deformation heterogeneity and texture in surface severe plastic deformation of copper

    PubMed Central

    Wang, Zhiyu; Saldana, Christopher

    2016-01-01

    Comprehensive understanding of thermomechanical response and microstructure evolution during surface severe plastic deformation (S2PD) is important towards establishing controllable processing frameworks. In this study, the evolution of crystallographic textures during directional surface mechanical attrition treatment on copper was studied and modelled using the visco-plastic self-consistent framework. In situ high-speed imaging and digital image correlation of surface deformation in circular indentation were employed to elucidate mechanics occurring in a unit process deformation and to calibrate texture model parameters. Material response during directional surface mechanical attrition was simulated using a finite-element model coupled with the calibrated texture model. The crystallographic textures developed during S2PD were observed to be similar to those resultant from uniaxial compression. The implications of these results towards facilitating a processing-based framework to predict deformation mechanics and resulting crystallographic texture in S2PD configurations are briefly discussed. PMID:27118907

  14. Microstructural Characteristics of High Rate Plastic Deformation in Elektron (trademark) WE43 Magnesium Alloy

    DTIC Science & Technology

    2012-04-01

    Mordike T. Ebert, "Magnesium Properties - applications - potential," Materials Science and Engineering A, vol. 302, no. 1, pp. 37-45, 2001. [2...boundary sliding in rolled AZ91 magnesium alloy at high strain rates," Materials Science and Engineering A, vol. 360, no. 1-2, pp. 107-115,2003

  15. Plastic Deformation of O+ Oriented Quartz Single Crystals

    NASA Astrophysics Data System (ADS)

    Poston, E. J.; Holyoke, C. W., III; Kronenberg, A. K.

    2015-12-01

    The strength of wet quartz deforming by dislocation creep significantly influences the strength of mid to lower crust. Dislocation creep of quartz in Earth's crust is dominated by slip on the basal slip system. However, very little is known about the temperature, strain rate, or water fugacity dependence of this slip system. In order to better understand the rheology of the basal slip system, we deformed single crystals of synthetic quartz, with the basal slip system oriented at 45° to the compression direction (O+ orientation). Each core was annealed at 900°C and 1 atm for 24 hours to convert the gel-type water defects found in synthetic quartz into fluid inclusions, like those observed in milky quartz. FTIR analysis indicate that water contents (200-450 H/106Si) were not affected by the annealing process. The annealed single crystals were then deformed in a Griggs piston-cylinder rock deformation apparatus using a solid salt assembly, at temperatures from 800 to 900°C, strain rates from 10-6 to 10-4/s, and a confining pressure of 1.5 GPa. The strength of the quartz crystals increases with faster strain rates and decreases with increasing temperature. During some of the faster strain rate steps at 800°C, the crystals did not deform plastically before the differential stress reached the confining pressure, whereas they deformed at low stresses at 800°C and 10-6/s. The microstructures visible in the deformed samples are consistent with dislocation creep. The samples exhibit undulatory extinction, and show no deformation lamellae or subgrain formation. The strength of synthetic quartz crystals with low water contents deformed in this study is greater than milky quartz single crystals with high water contents deformed at the same conditions in other studies. These results indicate that the strength of basal slip system in quartz is affected by both water content and water fugacity.

  16. Occurrence of cohesion of metals during combined plastic deformation

    NASA Technical Reports Server (NTRS)

    Aynbinder, S. G.; Klokova, E. F.

    1980-01-01

    Experiments were conducted to study the cohesion of metals with surface films of varying thickness and hardness. It was established that the deformation necessary for the occurrence of cohesion is determined by the correlation of mechanical properties of the films and the base metal. The greater the relative hardness of the film the lower the deformation necessary for the occurrence of cohesion. The films are as plastic as the base metal prevent cohesion, since in this case it is impossible for sections of metal to appear that are free of contaminants. The physical perculiarities of metals that determine their capability for coalescence under conditions of dry friction are the relative hardness and plasticity of the oxide films formed on their surface under atmospheric conditions.

  17. Plastic Deformation of Aluminum Single Crystals at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Johnson, R D; Young, A P; Schwope, A D

    1956-01-01

    This report describes the results of a comprehensive study of plastic deformation of aluminum single crystals over a wide range of temperatures. The results of constant-stress creep tests have been reported for the temperature range from 400 degrees to 900 degrees F. For these tests, a new capacitance-type extensometer was designed. This unit has a range of 0.30 inch over which the sensitivity is very nearly linear and can be varied from as low a sensitivity as is desired to a maximum of 20 microinches per millivolt with good stability. Experiments were carried out to investigate the effect of small amounts of prestraining, by two different methods, on the creep and tensile properties of these aluminum single crystals. From observations it has been concluded that plastic deformation takes place predominantly by slip which is accompanied by the mechanisms of kinking and polygonization.

  18. Structure and deformation behavior of Armco iron subjected to severe plastic deformation

    SciTech Connect

    Valiev, R.Z. |; Rauch, E.F.; Baudelet, B.; Ivanisenko, Yu.V.

    1996-12-01

    Structural evolutions in an Armco iron subjected to severe plastic deformation by torsion under high pressure are analyzed with conventional and high resolution electron microscopes. The substructure observed at low strains appears to shrink with increasing deformation and transforms at very high strains into grain boundaries. The resulting grain size decreases down to a constant submicrometric value. Meanwhile, the material strength, as revealed by micro hardness measurements, levels out. Dislocation densities and internal stress levels are used to discuss the structural transformations. Hydrostatic pressure and deformation temperature are believed to modify the steady-state stress level and structural size by impeding the recovery processes involving diffusion.

  19. Processing of Metal Matrix Composites through Severe Plastic Deformation

    DTIC Science & Technology

    2006-05-31

    peer-reviewed journals: 1. M. Furukawa, A. Utsunomiya, S. Komura , Z. Horita, M. Nemoto and T.G. Langdon, AOptimization for Superplasticity in...Materials Science Forum 357-359, 471-475 (2001). 4. S. Komura , M. Furukawa, Z. Horita, M. Nemoto and T.G. Langdon, "Optimizing the Procedure for Equal...Zn-Sn Alloy Processed by Severe Plastic Deformation,@ Materials Science and Engineering A307, 23-28 (2001). 11. S. Komura , Z. Horita, M. Furukawa, M

  20. General framework for acoustic emission during plastic deformation

    NASA Astrophysics Data System (ADS)

    Kumar, Jagadish; Sarmah, Ritupan; Ananthakrishna, G.

    2015-10-01

    Despite the long history, so far there is no general theoretical framework for calculating the acoustic emission spectrum accompanying any plastic deformation. We set up a discrete wave equation with plastic strain rate as a source term and include the Rayleigh-dissipation function to represent dissipation accompanying acoustic emission. We devise a method of bridging the widely separated time scales of plastic deformation and elastic degrees of freedom. While this equation is applicable to any type of plastic deformation, it should be supplemented by evolution equations for the dislocation microstructure for calculating the plastic strain rate. The efficacy of the framework is illustrated by considering three distinct cases of plastic deformation. The first one is the acoustic emission during a typical continuous yield exhibiting a smooth stress-strain curve. We first construct an appropriate set of evolution equations for two types of dislocation densities and then show that the shape of the model stress-strain curve and accompanying acoustic emission spectrum match very well with experimental results. The second and the third are the more complex cases of the Portevin-Le Chatelier bands and the Lüders band. These two cases are dealt with in the context of the Ananthakrishna model since the model predicts the three types of the Portevin-Le Chatelier bands and also Lüders-like bands. Our results show that for the type-C bands where the serration amplitude is large, the acoustic emission spectrum consists of well-separated bursts of acoustic emission. At higher strain rates of hopping type-B bands, the burst-type acoustic emission spectrum tends to overlap, forming a nearly continuous background with some sharp acoustic emission bursts. The latter can be identified with the nucleation of new bands. The acoustic emission spectrum associated with the continuously propagating type-A band is continuous. These predictions are consistent with experimental results. More

  1. Deformation fields near a steady fatigue crack with anisotropic plasticity

    SciTech Connect

    Gao, Yanfei

    2015-11-30

    In this work, from finite element simulations based on an irreversible, hysteretic cohesive interface model, a steady fatigue crack can be realized if the crack extension exceeds about twice the plastic zone size, and both the crack increment per loading cycle and the crack bridging zone size are smaller than the plastic zone size. The corresponding deformation fields develop a plastic wake behind the crack tip and a compressive residual stress field ahead of the crack tip. In addition, the Hill’s plasticity model is used to study the role of plastic anisotropy on the retardation of fatigue crack growth and the elastic strain fields. It is found that for Mode-I cyclic loading, an enhanced yield stress in directions that are inclined from the crack plane will lead to slower crack growth rate, but this retardation is insignificant for typical degrees of plastic anisotropy. Furthermore, these results provide key inputs for future comparisons to neutron and synchrotron diffraction measurements that provide full-field lattice strain mapping near fracture and fatigue crack tips, especially in textured materials such as wrought or rolled Mg alloys.

  2. Deformation fields near a steady fatigue crack with anisotropic plasticity

    DOE PAGES

    Gao, Yanfei

    2015-11-30

    In this work, from finite element simulations based on an irreversible, hysteretic cohesive interface model, a steady fatigue crack can be realized if the crack extension exceeds about twice the plastic zone size, and both the crack increment per loading cycle and the crack bridging zone size are smaller than the plastic zone size. The corresponding deformation fields develop a plastic wake behind the crack tip and a compressive residual stress field ahead of the crack tip. In addition, the Hill’s plasticity model is used to study the role of plastic anisotropy on the retardation of fatigue crack growth andmore » the elastic strain fields. It is found that for Mode-I cyclic loading, an enhanced yield stress in directions that are inclined from the crack plane will lead to slower crack growth rate, but this retardation is insignificant for typical degrees of plastic anisotropy. Furthermore, these results provide key inputs for future comparisons to neutron and synchrotron diffraction measurements that provide full-field lattice strain mapping near fracture and fatigue crack tips, especially in textured materials such as wrought or rolled Mg alloys.« less

  3. Computer simulation of plastic deformation in irradiated metals

    SciTech Connect

    Colak, U.

    1989-01-01

    A computer-based model is developed for the localized plastic deformation in irradiated metals by dislocation channeling, and it is applied to irradiated single crystals of niobium. In the model, the concentrated plastic deformation in the dislocation channels is postulated to occur by virtue of the motion of dislocations in a series of pile-tips on closely spaced parallel slip planes. The dynamics of this dislocation motion is governed by an experimentally determined dependence of dislocation velocity on shear stress. This leads to a set of coupled differential equations for the positions of the individual dislocations in the pile-up as a function of time. Shear displacement in the channel region is calculated from the total distance traveled by the dislocations. The macroscopic shape change in single crystal metal sheet samples is determined by the axial displacement produced by the shear displacements in the dislocation channels. Computer simulations are performed for the plastic deformation up to 20% engineering strain at a constant strain rate. Results of the computer calculations are compared with experimental observations of the shear stress-engineering strain curve obtained in tensile tests described in the literature. Agreement between the calculated and experimental stress-strain curves is obtained for shear displacement of 1.20-1.25 {mu}m and 1000 active slip planes per channel, which is reasonable in the view of experimental observations.

  4. Plastic deformation enabled energy dissipation in a bionanowire structured armor.

    PubMed

    Li, Haoze; Yue, Yonghai; Han, Xiaodong; Li, Xiaodong

    2014-05-14

    It has been challenging to simultaneously achieve high strength and toughness in engineered materials because of the trade-off relation between the two distinct properties. Nature, however, has elegantly solved this problem. Seashells, commonly referred to as nature's armors, exhibit an unusual resilience against predatory attacks. In this letter, we report an unexpected phenomenon in a bionanowire structured armor-conch shell where the shell's basic building blocks, i.e., the third-order lamellae, exhibit an exceptional plasticity with a maximum strain of 0.7% upon mechanical loading. We attribute such a plastic deformation behavior to the lamella's unique nanoparticle-biopolymer architecture, in which the biopolymer mediates the rotation of aragonite nanoparticles in response to external attacks. We also found that electron beam irradiation facilitates the lamella's plasticity. These findings advance our understanding of seashell's energy dissipating strategy and provide new design guidelines for developing high performance bioinspired materials and sensors.

  5. Role of plastic deformation in shock-induced phase transitions

    NASA Astrophysics Data System (ADS)

    Ghimire, Punam; Germann, T. C.; Ravelo, R.

    2015-06-01

    Non-equilibrium molecular dynamics (NEMD) simulations of shock-wave propagation in fcc single crystals exhibit high elastic limits and large anisotropies in the yield strength. They can be used to explore the role of plastic deformation in the morphology and kinetics of solid-solid phase transformations. We report on large-scale atomistic simulations of defect-mediated phase transformations under shock and quasi-isentropic compression (QIC). An analytical embedded atom method (EAM) description is used to model a fcc-bcc phase transition (PT) boundary fitted to occur below or above the elastic-plastic threshold in order to model systems undergoing a PT with and without plasticity. For cases where plastic deformation precedes the phase transformation, the defect-mediated PT proceeds at faster rates than the defect-free ones. The bcc fraction growth rate can be correlated with a sharp decrease in the dislocation densities originally present in the parent phase. This work was supported by the Air Force Office of Scientific Research under AFOSR Award FA9550-12-1-0476. Work at Los Alamos was performed under the auspices of the U.S. Department of Energy (DOE) under Contract No. DE-AC52-06NA25396.

  6. Elastic plastic self-consistent (EPSC) modeling of plastic deformation in fayalite olivine

    SciTech Connect

    Burnley, Pamela C

    2015-07-01

    Elastic plastic self-consistent (EPSC) simulations are used to model synchrotron X-ray diffraction observations from deformation experiments on fayalite olivine using the deformation DIA apparatus. Consistent with results from other in situ diffraction studies of monomineralic polycrystals, the results show substantial variations in stress levels among grain populations. Rather than averaging the lattice reflection stresses or choosing a single reflection to determine the macroscopic stress supported by the specimen, an EPSC simulation is used to forward model diffraction data and determine a macroscopic stress that is consistent with lattice strains of all measured diffraction lines. The EPSC simulation presented here includes kink band formation among the plastic deformation mechanisms in the simulation. The inclusion of kink band formation is critical to the success of the models. This study demonstrates the importance of kink band formation as an accommodation mechanism during plastic deformation of olivine as well as the utility of using EPSC models to interpret diffraction from in situ deformation experiments.

  7. Elastic plastic self-consistent (EPSC) modeling of plastic deformation in fayalite olivine

    DOE PAGES

    Burnley, Pamela C

    2015-07-01

    Elastic plastic self-consistent (EPSC) simulations are used to model synchrotron X-ray diffraction observations from deformation experiments on fayalite olivine using the deformation DIA apparatus. Consistent with results from other in situ diffraction studies of monomineralic polycrystals, the results show substantial variations in stress levels among grain populations. Rather than averaging the lattice reflection stresses or choosing a single reflection to determine the macroscopic stress supported by the specimen, an EPSC simulation is used to forward model diffraction data and determine a macroscopic stress that is consistent with lattice strains of all measured diffraction lines. The EPSC simulation presented here includesmore » kink band formation among the plastic deformation mechanisms in the simulation. The inclusion of kink band formation is critical to the success of the models. This study demonstrates the importance of kink band formation as an accommodation mechanism during plastic deformation of olivine as well as the utility of using EPSC models to interpret diffraction from in situ deformation experiments.« less

  8. Texture developed during deformation of Transformation Induced Plasticity (TRIP) steels

    NASA Astrophysics Data System (ADS)

    Bhargava, M.; Shanta, C.; Asim, T.; Sushil, M.

    2015-04-01

    Automotive industry is currently focusing on using advanced high strength steels (AHSS) due to its high strength and formability for closure applications. Transformation Induced Plasticity (TRIP) steel is promising material for this application among other AHSS. The present work is focused on the microstructure development during deformation of TRIP steel sheets. To mimic complex strain path condition during forming of automotive body, Limit Dome Height (LDH) tests were conducted and samples were deformed in servo hydraulic press to find the different strain path. FEM Simulations were done to predict different strain path diagrams and compared with experimental results. There is a significant difference between experimental and simulation results as the existing material models are not applicable for TRIP steels. Micro texture studies were performed on the samples using EBSD and X-RD techniques. It was observed that austenite is transformed to martensite and texture developed during deformation had strong impact on limit strain and strain path.

  9. Plastic deformation of silicon nitride/boron nitride fibrous monoliths.

    SciTech Connect

    de Arellano-Lopez, A. R.; Lopez-Pombero, S.; Dominguez-Rodriguez, A.; Routbort, J. L.; Singh, D.; Goretta, K. C.; Energy Technology; Univ. de Sevilla

    2001-02-01

    High-temperature compressive creep of unidirectional Si{sub 3}N{sub 4}/BN fibrous monoliths has been investigated at 1300-1500 C in an inert atmosphere. The results were then compared to those for deformation of the Si{sub 3}N{sub 4} and BN base materials. Plasticity of the fibrous monoliths was limited to very low stresses when the Si{sub 3}N{sub 4} cells were oriented perpendicular to the stress axis because the BN cell boundaries failed, followed by failure of the Si{sub 3}N{sub 4} cells. In the fibrous monolith in which cells were oriented parallel to the stress axis, steady-state deformation controlled by deformation of the Si{sub 3}N{sub 4} cells was achieved.

  10. Simultaneous X-ray diffraction and phase-contrast imaging for investigating material deformation mechanisms during high-rate loading

    DOE PAGES

    Hudspeth, M.; Sun, T.; Parab, N.; ...

    2015-01-01

    Using a high-speed camera and an intensified charge-coupled device (ICCD), a simultaneous X-ray imaging and diffraction technique has been developed for studying dynamic material behaviors during high-rate tensile loading. A Kolsky tension bar has been used to pull samples at 1000 s–1and 5000 s–1strain-rates for super-elastic equiatomic NiTi and 1100-O series aluminium, respectively. By altering the ICCD gating time, temporal resolutions of 100 ps and 3.37 µs have been achieved in capturing the diffraction patterns of interest, thus equating to single-pulse and 22-pulse X-ray exposure. Furthermore, the sample through-thickness deformation process has been simultaneously imagedviaphase-contrast imaging. It is also shownmore » that adequate signal-to-noise ratios are achieved for the detected white-beam diffraction patterns, thereby allowing sufficient information to perform quantitative data analysis diffractionviain-house software (WBXRD_GUI). Finally, of current interest is the ability to evaluate crystald-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates.« less

  11. Simultaneous X-ray diffraction and phase-contrast imaging for investigating material deformation mechanisms during high-rate loading

    SciTech Connect

    Hudspeth, M.; Sun, T.; Parab, N.; Guo, Z.; Fezzaa, K.; Luo, S.; Chen, W.

    2015-01-01

    Using a high-speed camera and an intensified charge-coupled device (ICCD), a simultaneous X-ray imaging and diffraction technique has been developed for studying dynamic material behaviors during high-rate tensile loading. A Kolsky tension bar has been used to pull samples at 1000 s-1and 5000 s-1strain-rates for super-elastic equiatomic NiTi and 1100-O series aluminium, respectively. By altering the ICCD gating time, temporal resolutions of 100 ps and 3.37 µs have been achieved in capturing the diffraction patterns of interest, thus equating to single-pulse and 22-pulse X-ray exposure. Furthermore, the sample through-thickness deformation process has been simultaneously imagedviaphase-contrast imaging. It is also shown that adequate signal-to-noise ratios are achieved for the detected white-beam diffraction patterns, thereby allowing sufficient information to perform quantitative data analysis diffractionviain-house software (WBXRD_GUI). Of current interest is the ability to evaluate crystald-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates.

  12. Simultaneous X-ray diffraction and phase-contrast imaging for investigating material deformation mechanisms during high-rate loading

    SciTech Connect

    Hudspeth, M.; Sun, T.; Parab, N.; Guo, Z.; Fezzaa, K.; Luo, S.; Chen, W.

    2015-01-01

    Using a high-speed camera and an intensified charge-coupled device (ICCD), a simultaneous X-ray imaging and diffraction technique has been developed for studying dynamic material behaviors during high-rate tensile loading. A Kolsky tension bar has been used to pull samples at 1000 s–1and 5000 s–1strain-rates for super-elastic equiatomic NiTi and 1100-O series aluminium, respectively. By altering the ICCD gating time, temporal resolutions of 100 ps and 3.37 µs have been achieved in capturing the diffraction patterns of interest, thus equating to single-pulse and 22-pulse X-ray exposure. Furthermore, the sample through-thickness deformation process has been simultaneously imagedviaphase-contrast imaging. It is also shown that adequate signal-to-noise ratios are achieved for the detected white-beam diffraction patterns, thereby allowing sufficient information to perform quantitative data analysis diffractionviain-house software (WBXRD_GUI). Finally, of current interest is the ability to evaluate crystald-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates.

  13. Evolution of the structure upon heating of submicrocrystalline and nanocrystalline copper produced by high-rate deformation

    NASA Astrophysics Data System (ADS)

    Khomskaya, I. V.; Zel'Dovich, V. I.; Kheifets, A. E.; Frolova, N. Yu.; Dyakina, V. P.; Kazantsev, V. A.

    2011-04-01

    Methods of electron microscopy, dilatometry, and microhardness and resistivity measurements have been used to study the effect of annealing on the process of recrystallization of a mixed submicrocrys-talline+nanocrystalline (SMC+NC) structure of 99.8% copper produced by high-rate (˜105 s-1) deformation using dynamic channel angular pressing (DCAP). It has been shown that the SMC+NC structure of copper is thermally stable upon heating to a temperature of 150°C. It has been found that the ρ/ρ0 ratio of copper with an SMC+NC structure at a temperature of 4.2 K is considerably (by 5 times) higher than ρ/ρ0 of copper in the annealed coarse-grained state. This effect is due to a high concentration of defects and a high degree of dispersity of the copper structure after DCAP. Changes in the microhardness and in the resistivity (at a temperature of 4.2 K) of the SMC+NC copper after annealing characterize the level of relaxation processes.

  14. Simultaneous X-ray diffraction and phase-contrast imaging for investigating material deformation mechanisms during high-rate loading.

    PubMed

    Hudspeth, M; Sun, T; Parab, N; Guo, Z; Fezzaa, K; Luo, S; Chen, W

    2015-01-01

    Using a high-speed camera and an intensified charge-coupled device (ICCD), a simultaneous X-ray imaging and diffraction technique has been developed for studying dynamic material behaviors during high-rate tensile loading. A Kolsky tension bar has been used to pull samples at 1000 s(-1) and 5000 s(-1) strain-rates for super-elastic equiatomic NiTi and 1100-O series aluminium, respectively. By altering the ICCD gating time, temporal resolutions of 100 ps and 3.37 µs have been achieved in capturing the diffraction patterns of interest, thus equating to single-pulse and 22-pulse X-ray exposure. Furthermore, the sample through-thickness deformation process has been simultaneously imaged via phase-contrast imaging. It is also shown that adequate signal-to-noise ratios are achieved for the detected white-beam diffraction patterns, thereby allowing sufficient information to perform quantitative data analysis diffraction via in-house software (WBXRD_GUI). Of current interest is the ability to evaluate crystal d-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates.

  15. Simultaneous X-ray diffraction and phase-contrast imaging for investigating material deformation mechanisms during high-rate loading

    PubMed Central

    Hudspeth, M.; Sun, T.; Parab, N.; Guo, Z.; Fezzaa, K.; Luo, S.; Chen, W.

    2015-01-01

    Using a high-speed camera and an intensified charge-coupled device (ICCD), a simultaneous X-ray imaging and diffraction technique has been developed for studying dynamic material behaviors during high-rate tensile loading. A Kolsky tension bar has been used to pull samples at 1000 s−1 and 5000 s−1 strain-rates for super-elastic equiatomic NiTi and 1100-O series aluminium, respectively. By altering the ICCD gating time, temporal resolutions of 100 ps and 3.37 µs have been achieved in capturing the diffraction patterns of interest, thus equating to single-pulse and 22-pulse X-ray exposure. Furthermore, the sample through-thickness deformation process has been simultaneously imaged via phase-contrast imaging. It is also shown that adequate signal-to-noise ratios are achieved for the detected white-beam diffraction patterns, thereby allowing sufficient information to perform quantitative data analysis diffraction via in-house software (WBXRD_GUI). Of current interest is the ability to evaluate crystal d-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates. PMID:25537588

  16. Theory of Lattice Strain for Materials Undergoing Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Karato, S.

    2008-12-01

    Radial x-ray diffraction is used to probe physical properties of materials including elastic and plastic properties. The theory used behind such an practice is the one developed by Singh (1993) in which the relation between lattice strain and elastic constants and macroscopic stress is derived. In this theory, the variation of inferred stress with the crystallographic planes, (hkl), is due to the elastic anisotropy. However, recent experimental studies showed that in many cases, the variation of stress with (hkl) far exceeds the value expected from this theory. I have developed a modified theory to rectify this problem with Singh's theory. In Singh's theory, the stress distribution in a polycrystalline material is treated only either unrelaxed or relaxed state. The role of plastic deformation is included only to the extent that plastic flow influences this stress state. Such an assumption corresponds to a Voigt model behavior, which is not an appropriate model at high temperatures where continuing plastic flow occurs with concurrent microscopic equilibrium, elastic deformation. This is a Maxwell model type behavior, and my model provides a stress analysis in a Maxwell material with anisotropic and non-linear power-law rheology. In this theory, the lattice strain corresponding to an imposed macroscopic strain-rate is calculated by three steps: (i) conversion of macroscopic strain-rate to macroscopic stress, (ii) conversion of macroscopic stress to microscopic stress at individual grains, and (iii) calculation of microscopic strain due to microscopic stress. The first step involves anisotropy in macroscopic viscosity that depends on anisotropy in crystal plasticity and lattice-preferred orientation. The second step involves anisotropic crystal plasticity and finally the third step involves elastic crystal anisotropy. In most cases, the influence of LPO is weak and in such a case, the lattice strain depends on (hkl) due to the anisotropy in both elastic and plastic

  17. Rejuvenation effects during plastic deformation of Zircon: geochronological implications

    NASA Astrophysics Data System (ADS)

    Kovaleva, Elizaveta; Klötzli, Urs

    2013-04-01

    Zircon is one of the most stable accessory minerals known on the Earth; it was believed that zircon isotopic ages mostly record primary igneous crystallization events. It is true until the mineral is not affected by plastic deformation or other disturbing events during its life after crystallization. Zircon may deform by the recovery/subgrain rotation recrystallisation that indicates formation and migration of dislocations under crustal conditions. Deformation occurs at depth due to stresses associated with collision of the phases, and forms such microstructures as low-angle boundaries (Reddy et al., 2007). Low-angle boundaries act as fluid migration paths and elements diffusion paths. Facilitating Pb, Ti, U, Th and trace elements mobility in the crystalline zircon, these structures can change chemical, REE and isotopic composition of certain grain's parts (Reddy and Timms, 2010) and lead to isotopic resetting in the mineral domains. Since the isotopic age of the domains of single crystal can vary, it should be possible to recognize and interpret this variation and distinguish the timing of different high-temperature deformation events. Zircon can preserve low-angle boundaries and associated age disturbance under lower-crust temperatures for billions of years (Moser et al., 2009). Electron backscatter diffraction (EBSD) allows us to make microstructural-crystallographic analyses in order to measure the crystallographic orientations in crystalline material. EBSD mapping is supposed to be able to constrain potential diffusion pathways in minerals. It can indicate areas of damaged crystalline structure, helps to examine substructures of minerals used in radiometric dating and to assess the potential for resetting of ages by deformation events (Reddy et al., 2007). In this research we are trying to answer a list of questions, related to isotopic resetting due to deformation: What is the behavior of zircons which were plastically deformed during metamorphic-deformation

  18. Finite elastic-plastic deformation of polycrystalline metals

    NASA Technical Reports Server (NTRS)

    Iwakuma, T.; Nemat-Nasser, S.

    1984-01-01

    Applying Hill's self-consistent method to finite elastic-plastic deformations, the overall moduli of polycrystalline solids are estimated. The model predicts a Bauschinger effect, hardening, and formation of vertex or corner on the yield surface for both microscopically non-hardening and hardening crystals. The changes in the instantaneous moduli with deformation are examined, and their asymptotic behavior, especially in relation to possible localization of deformations, is discussed. An interesting conclusion is that small second-order quantities, such as shape changes of grains and residual stresses (measured relative to the crystal elastic moduli), have a first-order effect on the overall response, as they lead to a loss of the overall stability by localized deformation. The predicted incipience of localization for a uniaxial deformation in two dimensions depends on the initial yield strain, but the orientation of localization is slightly less than 45 deg with respect to the tensile direction, although the numerical instability makes it very difficult to estimate this direction accurately.

  19. Plastic deformation of triblock elastomers by molecular simulation

    NASA Astrophysics Data System (ADS)

    Parker, Amanda; Rottler, Jörg

    2015-03-01

    The mechanical properties of thermoplastic elastomers (TPE) can be greatly enhanced by exploiting the complex morphology of triblock copolymers. A common strategy consists of confining chain ends into hard glassy regions that effectively crosslink a soft rubbery phase. We present molecular dynamics simulations that provide insight into key microscopic behaviour of the copolymer chains during deformation. First, a coarse-grained polymer model with an ABA type configuration and soft interactions is employed to achieve equilibrated spherical morphologies. Our model TPEs contain at least 30 spheres in order to ensure configurational averaging. Elastoplastic deformation with uniaxial extension or volume conserving shear is then studied after hard excluded volume interactions have been reintroduced. We consider trends of stress-strain curves for different chain lengths, and compare to equivalent homopolymeric systems. During deformation we simultaneously track the evolution of the number and shape of the minority spheres, the proportion of chains bridging from one sphere to another, as well as local plastic deformation. The simulations reveal strong differences between deformation modes, the evolution of sphere morphology and chain anisotropy.

  20. Stochastically forced dislocation density distribution in plastic deformation

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Amit K.; Aifantis, Elias C.

    2016-08-01

    The dynamical evolution of dislocations in plastically deformed metals is controlled by both deterministic factors arising out of applied loads and stochastic effects appearing due to fluctuations of internal stress. Such types of stochastic dislocation processes and the associated spatially inhomogeneous modes lead to randomness in the observed deformation structure. Previous studies have analyzed the role of randomness in such textural evolution, but none of these models have considered the impact of a finite decay time (all previous models assumed instantaneous relaxation which is "unphysical") of the stochastic perturbations in the overall dynamics of the system. The present article bridges this knowledge gap by introducing a colored noise in the form of an Ornstein-Uhlenbeck noise in the analysis of a class of linear and nonlinear Wiener and Ornstein-Uhlenbeck processes that these structural dislocation dynamics could be mapped on to. Based on an analysis of the relevant Fokker-Planck model, our results show that linear Wiener processes remain unaffected by the second time scale in the problem, but all nonlinear processes, both the Wiener type and Ornstein-Uhlenbeck type, scale as a function of the noise decay time τ . The results are expected to ramify existing experimental observations and inspire new numerical and laboratory tests to gain further insight into the competition between deterministic and random effects in modeling plastically deformed samples.

  1. Plastic Deformation in Zirconium Based Metallic Glasses via Nanoindentation

    NASA Astrophysics Data System (ADS)

    Melgarejo-Pinto, Zenon Humberto

    Since the discovery in 1960 of Au-Si amorphous alloy by rapidly quenching with cooling rates up to 106 K/s metallic glasses became as an important research topic in the materials science community because of their intriguing processing routes, structure and properties. Recently, new multicomponent glassy- alloy systems, bulk metallic glasses (BMGs), appeared with lower critical cooling rates (103 to 1 K/s) and superlative properties, such as corrosion resistance, biocompatibility, and high strength/modulus ratio. Nevertheless, low temperature brittleness remains a concern. This brittleness comes from the tendency of plastic deformation to concentrate into extremely narrow shear bands. The present research pursues a better understanding of plastic deformation in metallic glasses (MGs) by studying, via nanoindentation, the effect of thermal history, composition, and loading paths on the mechanical behavior of Zr-based MGs. Differential scanning calorimeter (DSC) analysis helps to assess structural relaxation near glass transition temperature (T g). Broadband nanoindentation creep (BNC) and load transient nanoindentation experiments contribute to characterize the hardness-strain rate behavior and indentation size effects, respectively. As-cast Zr 50Cu45Al5 (at. %) metallic glasses evidenced hardness-strain rate loading path dependence, which gradually disappears by effect of the annealing treatments. Back-stresses effect is theorized as the cause of load path dependence behavior. Relaxation effect at low and high strain rates in BNC traces and load ramps "overshoots" in transient experiments enabled to confirm structural changes during mechanical deformation, which is not considered by thermal activation models of deformation. Most of the Zr-based metallic glasses exhibited measurable overshoot indentation size effect. Nonetheless, creep fraction size effect was observed just in as-cast Zr50Cu45Al5 alloys. Rheological mechanical model helps to both characterize the

  2. Effect of Plastic Deformation on Magnitude of Barkhausen Effect in Steel 40

    NASA Astrophysics Data System (ADS)

    Vylezhnev, V. P.; Malyshev, V. S.; Simonov, Yu. N.

    2015-09-01

    The effect of steel 40 cold deformation and subsequent annealing on emf value caused by the Barkhausen effect (BE) is studied. Plastic deformation by rolling leads to BE anisotropy, which is connected with deformed structure anisotropy. Anisotropy parameter e m (maximum emf value of Barkhausen jumps), arising during plastic deformation, makes it possible to recommend BE for monitoring steel deformation condition and its change during development of recrystallization.

  3. Plastic Collapse Localisation in Simple Shearing and Coaxial Deformations

    NASA Astrophysics Data System (ADS)

    Hobbs, B. E.; Ord, A.

    2011-12-01

    We explore, numerically, the evolution of localisation due to plastic collapse in both coaxial shortening and simple shearing deformations. These localisation features arise from plastic behaviour and hence differ from the formation of anticracks modelled by linear elastic behaviour (Fletcher and Pollard, 1990). The behaviour is close to that discussed by Rudnicki (2004) and Chemenda (2009) in that localisation consists of zones of plastic collapse separated by elastically unloaded regions. The constitutive behaviour assumed here comprises a Tresca yield with both strain-softening of the yield stress and of a cap that models plastic volumetric collapse during phase transformations, such as the olivine-spinel transition, with ΔV<0. The work builds on Detournay et al. (2003). An analysis similar to that of Issen and Rudnicki (2000) allows conditions for localisation to be specified. However critical softening of the cap is a necessary condition for collapse localisation to form. Localised collapse zones develop as tabular bodies oriented normal to the principal axis of compression and, within a shear zone, at approximately 45degrees to the boundaries of the shear zone. A different mode of localisation results from softening of the yield stress. This leads to shear localisation approximately parallel to the boundaries of a shear zone with zero plastic volume change. Whether one form of localisation or the other develops is a function of the constitutive parameters which are influenced by energy dissipation due to deformation and chemical reactions, and hence position, within a heterogeneously deforming zone. Localisation due to plastic collapse is followed by a stress drop and so is presumably seismic in nature as suggested by Green and Burnley (1989). The shear localisation mode of deformation is aseismic unless coupled to thermal or chemical effects. This study forms part of a broader study in which energy dissipation is coupled to constitutive behaviour similar to

  4. Plastic deformation of ordered intermetallic alloys: Fundamental aspects

    SciTech Connect

    Yoo, M.H.

    1994-10-01

    Fundamental aspects of plastic deformation in ordered intermetallic alloys are reviewed by directly comparing the temperature-dependent yield stresses of Ni{sub 3}Al and Ni{sub 3}Si (the L1{sub 2} structure), NiAl and FeAl (the B2 structure), and TiAl and Ti{sub 3}Al (non-cubic L1{sub 0} and D0{sub 19} structures, respectively). While the yield strength anomaly observed in Ni{sub 3}Al is consistent with the prevailing dislocation models, that found in stoichiometric Ni{sub 3}Si is not. The strong plastic anisotropy observed in NiAl stems from the high antiphase boundary energy, and that found in two-phase {gamma}-TiAl/{alpha}{sub 2}-Ti{sub 3}Al is due to the exceptionally high compressive yield strength along the c-axis of Ti{sub 3}Al.

  5. Software for Mathematical Modeling of Plastic Deformation in FCC Metals

    NASA Astrophysics Data System (ADS)

    Petelin, A. E.; Eliseev, A. S.

    2017-08-01

    The question on the necessity of software implementation in the study of plastic deformation in FCC metals with the use of mathematical modeling methods is investigated. This article describes the implementation features and the possibility of using the software Dislocation Dynamics of Crystallographic Slip (DDCS). The software has an advanced user interface and is designed for users without an extensive experience in IT-technologies. Parameter values of the mathematical model, obtained from field experiments and accumulated in a special database, are used in DDCS to carry out computational experiments. Moreover, the software is capable of accumulating bibliographic information used in research.

  6. 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.

  7. Plastic Deformation in Profile-Coated Elliptical KB Mirrors

    DOE PAGES

    Liu, Chian; Conley, R.; Qian, J.; ...

    2012-01-01

    Profile coating has been successfully applied to produce elliptical Kirkpatrick-Baez (KB) mirrors using both cylindrical and flat Si substrates. Previously, focusing widths of 70 nm with 15-keV monochromatic and 80 nm with white beam were achieved using a flat Si substrate. Now, precision elliptical KB mirrors with sub-nm figure errors are produced with both Au and Pt coatings on flat substrates. Recent studies of bare Si-, Au-, and Pt-coated KB mirrors under prolonged synchrotron X-ray radiation and low-temperature vacuum annealing will be discussed in terms of film stress relaxation and Si plastic deformation.

  8. Plastic deformation of alumina reinforced with SiC whiskers

    SciTech Connect

    DeArellano-Lopez, A.R.; Dominguez-Rodriguez, A.; Goretta, K.C.; Routbort, J.L.

    1993-06-01

    Addition of small amounts of stiff reinforcement (SiC whiskers) to a polycrystalline AL{sub 2}O{sub 3} matrix partially inhibits grain boundary sliding because of an increase in threshold stress. When the concentration of whiskers is high enough, a pure diffusional mechanism takes over the control of plastic deformation of the composites. For higher whisker loadings, the materials creep properties depend on a microstructural feature different from the nominal grain size. A tentative correlation of this effective microstructural parameter with the spacing between the whiskers was established through a model.

  9. Transformation from slip to plastic flow deformation mechanism during tensile deformation of zirconium nanocontacts

    NASA Astrophysics Data System (ADS)

    Yamada, Kohei; Kizuka, Tokushi

    2017-02-01

    Various types of nanometer-sized structures have been applied to advanced functional and structural devices. Inherent structures, thermal stability, and properties of such nanostructures are emphasized when their size is decreased to several nanometers, especially, to several atoms. In this study, we observed the atomistic tensile deformation process of zirconium nanocontacts, which are typical nanostructures used in connection of nanometer-sized wires, transistors, and diodes, memory devices, and sensors, by in situ transmission electron microscopy. It was found that the contact was deformed via a plastic flow mechanism, which differs from the slip on lattice planes frequently observed in metals, and that the crystallinity became disordered. The various irregular relaxed structures formed during the deformation process affected the conductance.

  10. Transformation from slip to plastic flow deformation mechanism during tensile deformation of zirconium nanocontacts

    PubMed Central

    Yamada, Kohei; Kizuka, Tokushi

    2017-01-01

    Various types of nanometer-sized structures have been applied to advanced functional and structural devices. Inherent structures, thermal stability, and properties of such nanostructures are emphasized when their size is decreased to several nanometers, especially, to several atoms. In this study, we observed the atomistic tensile deformation process of zirconium nanocontacts, which are typical nanostructures used in connection of nanometer-sized wires, transistors, and diodes, memory devices, and sensors, by in situ transmission electron microscopy. It was found that the contact was deformed via a plastic flow mechanism, which differs from the slip on lattice planes frequently observed in metals, and that the crystallinity became disordered. The various irregular relaxed structures formed during the deformation process affected the conductance. PMID:28218244

  11. Plastic deformation of high-purity a-titanium: model development and validation using the Taylor cylinder impact test

    NASA Astrophysics Data System (ADS)

    Chandola, Nitin; Revil-Baudard, Benoit; Cazacu, Oana

    2016-08-01

    Results of an experimental study on the quasi-static and high-rate plastic deformation due to impact of a high-purity, polycrystalline, a-titanium material are presented. To quantify the plastic anisotropy and tension-compression asymmetry of the material, first monotonic uniaxial compression and tension tests were carried out at room temperature under quasi-static conditions. It was found that the material is transversely isotropic and displays strong strength differential effects. To characterize the material's strain rate sensitivity, Split Hopkinson Pressure Bar tests in tension and compression were also conducted. Taylor impact tests were performed for impact velocity of 196 m/s. Plastic deformation extended to 64% of the length of the deformed specimen, with little radial spreading. To model simultaneously the observed anisotropy, strain-rate sensitivity, and tension-compression asymmetry of the material, a three-dimensional constitutive model was developed. Key in the formulation is a macroscopic yield function [1] that incorporates the specificities of the plastic flow, namely the combined effects of anisotropy and tension-compression asymmetry. Comparison between model predictions and data show the capabilities of the model to describe with accuracy the plastic behavior of the a-Ti material for both quasi-static and dynamic loadings, in particular, a very good agreement was obtained between the simulated and experimental post-test Taylor specimen geometries.

  12. Emergence of stable interfaces under extreme plastic deformation

    PubMed Central

    Beyerlein, Irene J.; Mayeur, Jason R.; Zheng, Shijian; Mara, Nathan A.; Wang, Jian; Misra, Amit

    2014-01-01

    Atomically ordered bimetal interfaces typically develop in near-equilibrium epitaxial growth (bottom-up processing) of nanolayered composite films and have been considered responsible for a number of intriguing material properties. Here, we discover that interfaces of such atomic level order can also emerge ubiquitously in large-scale layered nanocomposites fabricated by extreme strain (top down) processing. This is a counterintuitive result, which we propose occurs because extreme plastic straining creates new interfaces separated by single crystal layers of nanometer thickness. On this basis, with atomic-scale modeling and crystal plasticity theory, we prove that the preferred bimetal interface arising from extreme strains corresponds to a unique stable state, which can be predicted by two controlling stability conditions. As another testament to its stability, we provide experimental evidence showing that this interface maintains its integrity in further straining (strains > 12), elevated temperatures (> 0.45 Tm of a constituent), and irradiation (light ion). These results open a new frontier in the fabrication of stable nanomaterials with severe plastic deformation techniques. PMID:24616514

  13. Plastic deformation mechanisms in SiC-whisker-reinforced alumina

    SciTech Connect

    Arellano-Lopez, A.R. de; Dominguez-Rodriguez, A. )

    1993-06-01

    SiC-whisker-reinforced Al[sub 2]O[sub 3] samples (SiC[sub w]/Al[sub 2]O[sub 3]), obtained from three different manufacturers, containing 0-30 vol% SiC have been crept under compression at 1,400 C in flowing argon. Compressive creep tests and microstructural observations have been used to characterize the plastic deformation mechanisms. The presence of whiskers decreased the creep rate by reducing grain-boundary sliding. Damage formation was increased, however, because the whiskers acted as stress concentration sites. For specimens with whisker loadings greater than 15%, the absolute creep rate was not strongly dependent on whisker concentration, and the formation of cavitation damage was negligible below a critical stress that depended on the fabrication procedure of the specimen. This creep regime was characterized by a stress exponent of approximately 1, in which deformation occurred primarily by diffusional flow. For the materials with less SiC, the deformation occurred primarily by grain boundary sliding.

  14. On the Modeling of Plastic Deformation of Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Ertürk, S.; Steglich, D.; Bohlen, J.; Letzig, D.; Brocks, W.

    2007-05-01

    Magnesium alloys are promising materials due to their low density and therefore high specific strength. However, the industrial application is not well established so far, especially for wrought products such as sheets or profiles. Due to its hexagonal crystallographic structure, deformation mechanisms observed in magnesium alloys are rather different from those in face centered cubic metals such as aluminum alloys. This leads not only to a mechanical anisotropy, but also to a tension-compression asymmetry, i.e. unequal compressive and tensile yield strength. The resulting complexity in the yielding behavior of such materials cannot be captured by conventional models of J2 plasticity. Cazacu and Barlat, therefore, proposed a phenomenological yield potential which accounts for the respective phenomena by introducing the third invariant of the stress tensor. Simulations based on this model are performed with ABAQUS/Explicit and a user defined routine VUMAT for validating the respective implementation. The application aims at simulating the extrusion process of magnesium alloys.

  15. On the Modeling of Plastic Deformation of Magnesium Alloys

    SciTech Connect

    Ertuerk, S.; Steglich, D.; Bohlen, J.; Letzig, D.; Brocks, W.

    2007-05-17

    Magnesium alloys are promising materials due to their low density and therefore high specific strength. However, the industrial application is not well established so far, especially for wrought products such as sheets or profiles. Due to its hexagonal crystallographic structure, deformation mechanisms observed in magnesium alloys are rather different from those in face centered cubic metals such as aluminum alloys. This leads not only to a mechanical anisotropy, but also to a tension-compression asymmetry, i.e. unequal compressive and tensile yield strength. The resulting complexity in the yielding behavior of such materials cannot be captured by conventional models of J2 plasticity. Cazacu and Barlat, therefore, proposed a phenomenological yield potential which accounts for the respective phenomena by introducing the third invariant of the stress tensor. Simulations based on this model are performed with ABAQUS/Explicit and a user defined routine VUMAT for validating the respective implementation. The application aims at simulating the extrusion process of magnesium alloys.

  16. Study of the Micro-Nonuniformity of the Plastic Deformation of Steel

    NASA Technical Reports Server (NTRS)

    Chechulin, B. B.

    1957-01-01

    The plastic flow during deformation of real polycrystalline metals has specific characteristics which distinguish the plastic deformation of metals from the deformation of ordinary isotropic bodies. One of these characteristics is the marked micro-nonuniformity of the plastic deformation of metals. P.O. Pashkov demonstrated the presence of a considerable micro-nonuniformity of the plastic deformation of coarse-grained steel wit medium or low carbon content. Analogous results in the case of tension of coarse-grained aluminum were obtained by W. Boas, who paid particular attention to the role of the grain boundaries in plastic flow. The nonuniformit of the plastic deformation in microvolumes was also recorded by T.N. Gudkova and others, on the alloy KhN80T. N.F. Lashko pointed out the nonuniformity of the plastic deformation for a series of pure polycrystalline metals and one-phase alloys. In his later reports, P.O. Pashkov arrives at he conclusion that the nonuniformity of the distribution of the deformation along the individual grains has a significant effect on the strength and plastic characteristics of polycrystalline metals in the process of plastic flow. However, until now there has not existed any systematic investigation of the general rules of the microscopic nonuniformit of plastic deformation even though the real polycrystalline metals are extremely simple with regard to structure. In the present report, an attempt is made to study the micrononuniformity of the flow of polycrystalline metals by the method of statistical analysis of the variation of the frequency diagrams of the nonuniformity of the grains in the process of plastic deformation.

  17. Crystal Plasticity Analysis of Texture Evolution of Pure Aluminum During Processing by a New Severe Plastic Deformation Technique

    NASA Astrophysics Data System (ADS)

    Khajezade, Ali; Parsa, Mohammad Habibi; Mirzadeh, Hamed

    2016-02-01

    Texture evolution in a newly developed severe plastic deformation technique, named multi-axial incremental forging and shearing (MAIFS), was studied applying the visco-plastic self-consistent crystal plasticity formulation by consideration of macroscopic deformation history. The simulated texture evolutions revealed that although shear-like texture had developed by the MAIFS process, texture components rotated around normal to mid-plane section. This could be ascribed to the complex deformation history that naturally develops during processing by the MAIFS process. The increased complexity of the deformation history in the MAIFS process, compared to the techniques that are solely based on the simple shear deformation, causes more activated slip planes, which in turn can result in an enhanced grain refinement ability of this processing technique.

  18. Measurement of elasto-plastic deformations by speckle interferometry

    NASA Astrophysics Data System (ADS)

    Bova, Marco; Bruno, Luigi; Poggialini, Andrea

    2010-09-01

    In the paper the authors present an experimental equipment for elasto-plastic characterization of engineering materials by tensile tests. The stress state is imposed to a dog bone shaped specimen by a testing machine fixed on the optical table and designed for optimizing the performance of a speckle interferometer. All three displacement components are measured by a portable speckle interferometer fed by three laser diodes of 50 mW, by which the deformations of a surface of about 6×8 mm2 can be fully analyzed in details. All the equipment is driven by control electronics designed and realized on purpose, by which it is possible to accurately modify the intensity of the illumination sources, the position of a PZT actuator necessary for applying phase-shifting procedure, and the overall displacement applied to the specimen. The experiments were carried out in National Instrument LabVIEW environment, while the processing of the experimental data in Wolfram Mathematica environment. The paper reports the results of the elasto-plastic characterization of a high strength steel specimen.

  19. Plastic deformation of tubular crystals by dislocation glide.

    PubMed

    Beller, Daniel A; Nelson, David R

    2016-09-01

    Tubular crystals, two-dimensional lattices wrapped into cylindrical topologies, arise in many contexts, including botany and biofilaments, and in physical systems such as carbon nanotubes. The geometrical principles of botanical phyllotaxis, describing the spiral packings on cylinders commonly found in nature, have found application in all these systems. Several recent studies have examined defects in tubular crystals associated with crystalline packings that must accommodate a fixed tube radius. Here we study the mechanics of tubular crystals with variable tube radius, with dislocations interposed between regions of different phyllotactic packings. Unbinding and separation of dislocation pairs with equal and opposite Burgers vectors allow the growth of one phyllotactic domain at the expense of another. In particular, glide separation of dislocations offers a low-energy mode for plastic deformations of solid tubes in response to external stresses, reconfiguring the lattice step by step. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, the mechanics of dislocation glide. We also discuss how a sufficiently strong bending rigidity can alter or arrest the deformations of tubes with small radii.

  20. Plastic deformation of tubular crystals by dislocation glide

    NASA Astrophysics Data System (ADS)

    Beller, Daniel A.; Nelson, David R.

    2016-09-01

    Tubular crystals, two-dimensional lattices wrapped into cylindrical topologies, arise in many contexts, including botany and biofilaments, and in physical systems such as carbon nanotubes. The geometrical principles of botanical phyllotaxis, describing the spiral packings on cylinders commonly found in nature, have found application in all these systems. Several recent studies have examined defects in tubular crystals associated with crystalline packings that must accommodate a fixed tube radius. Here we study the mechanics of tubular crystals with variable tube radius, with dislocations interposed between regions of different phyllotactic packings. Unbinding and separation of dislocation pairs with equal and opposite Burgers vectors allow the growth of one phyllotactic domain at the expense of another. In particular, glide separation of dislocations offers a low-energy mode for plastic deformations of solid tubes in response to external stresses, reconfiguring the lattice step by step. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, the mechanics of dislocation glide. We also discuss how a sufficiently strong bending rigidity can alter or arrest the deformations of tubes with small radii.

  1. Quantifying Damage Accumulation During Ductile Plastic Deformation Using Synchrotron Radiation

    SciTech Connect

    Suter, Robert M.; Rollett, Anthony D.

    2015-08-15

    Under this grant, we have developed and demonstrated the ability of near-field High Energy Diffraction Microscopy (nf-HEDM) to map crystal orientation fields over three dimensions in deformed polycrystalline materials. Experimental work was performed at the Advanced Photon Source (APS) at beamline 1-ID. Applications of this new capability to ductile deformation of copper and zirconium samples were demonstrated as was the comparison of the experimental observations to computational plasticity models using a fast Fourier transform based algorithm that is able to handle the large experimental data sets. No such spatially resolved, direct comparison between measured and computed microstructure evolutions had previously been possible. The impact of this work is reflected in numerous publications and presentations as well as in the investments by DOE and DOD laboratories of millions of dollars in applying the technique, developing sophisticated new hardware that allows the technique to be applied to a wide variety of materials and materials problems, and in the use of the technique by other researchers. In essence, the grant facilitated the development of a new form of three dimensional microscopy and its application to technologically critical states of polycrystalline materials that are used throughout the U.S. and world economies. On-going collaborative work is further optimizing experimental and computational facilities at the APS and is pursuing expanded facilities.

  2. Dislocation dynamics during plastic deformations of complex plasma crystals

    NASA Astrophysics Data System (ADS)

    Durniak, C.; Samsonov, D.; Ralph, J. F.; Zhdanov, S.; Morfill, G.

    2013-11-01

    The internal structures of most periodic crystalline solids contain defects. This affects various important mechanical and thermal properties of crystals. Since it is very difficult and expensive to track the motion of individual atoms in real solids, macroscopic model systems, such as complex plasmas, are often used. Complex plasmas consist of micrometer-sized grains immersed into an ion-electron plasma. They exist in solidlike, liquidlike, and gaseouslike states and exhibit a range of nonlinear and dynamic effects, most of which have direct analogies in solids and liquids. Slabs of a monolayer hexagonal complex plasma were subjected to a cycle of uniaxial compression and decompression of large amplitudes to achieve plastic deformations, both in experiments and simulations. During the cycle, the internal structure of the lattice exhibited significant rearrangements. Dislocations (point defects) were generated and displaced in the stressed lattice. They tended to glide parallel to their Burgers vectors under load. It was found that the deformation cycle was macroscopically reversible but irreversible at the particle scale.

  3. Theory of radial X-ray Diffraction from a Polycrystalline Sample Undergoing Plastic Deformation

    SciTech Connect

    S Karato

    2011-12-31

    Theory of lattice strain in a polycrystalline aggregate under deviatoric stress is extended to include the influence of ongoing plastic deformation. When deviatoric stress is applied to a polycrystalline material at high temperatures (or above the yield stress), applied macroscopic stress is redistributed to individual grains by plastic deformation according to their orientations with respect to the macroscopic stress and plastic anisotropy of a given crystal. This microstress causes elastic deformation of individual grains that can be measured by x-ray diffraction. Consequently, the observed lattice strain depends on two material properties, viscosity (plasticity) and elastic compliance as well as the applied macroscopic stress and the stress-strain distribution among various grains. The influence of plastic deformation on lattice strain is analyzed using an anisotropic and nonlinear power-law constitutive relationship. In this model, the dependence of inferred macroscopic stress on the crystallographic orientation of diffraction plane (hkl) comes from elastic and plastic anisotropy of a crystal. In many materials, plastic anisotropy dominates over elastic anisotropy. This explains the observed large dependence of inferred stress on the diffraction plane and means that the determination of elastic anisotropy is difficult when plastic deformation occurs with anisotropic plasticity. When elastic anisotropy is known, plastic anisotropy of single crystal and/or stress-strain distribution in a deformed polycrystal can be determined from radial x-ray diffraction using the present model. Some examples are presented using the data on MgO.

  4. The Unloading Modulus of Akdq Steel after Uniaxial and Near Plane-Strain Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Pavlina, E. J.; Levy, B. S.; van Tyne, C. J.; Kwon, S. O.; Moon, Y. H.

    Springback is a problem in the manufacture of a variety of automotive components. To determine springback, it is necessary to know the strength of the material after plastic deformation and the slope of the unloading curve (i.e. the unloading modulus). Prior investigations have shown that the unloading modulus for steels after plastic deformation has a slope that is lower than the normally accepted value for Young's modulus. Previous studies on the slope of the unloading curve were after uniaxial tensile plastic deformation. In the present study, the unloading modulus for an aluminum killed drawing quality (AKDQ) steel was evaluated after both uniaxial and near plane strain deformation. A tube hydroforming system was used for near plane-strain deformation. The average unloading modulus following uniaxial deformation for the AKDQ steel is approximately 168 GPa. The average unloading modulus for the circumferential stress component after near plane-strain deformation is lower than after uniaxial deformation. For a given amount of overall plastic deformation, the axial component of the unloading modulus is greater than the circumferential component, and with increased plastic strain, the unloading modulus for both components decreases. These results demonstrate that the components of the unloading modulus are dependent on the strain path of the prior plastic deformation.

  5. Influence of particle deformation on the plastic flow of ductile granular materials

    NASA Astrophysics Data System (ADS)

    Abdelmoula, Nouha; Harthong, Barthélémy; Imbault, Didier; Dorémus, Pierre

    2017-06-01

    A multi-particle finite-element method was proposed to study the elastic-plastic behaviour of ductile powders composed of highly deformable elastic-plastic particles. The focus was put on the study of the uniqueness of the direction of plastic strain increment vectors for a given stress state on the plastic limit, which was assessed using a spherical stress-probing method. Results revealed a non-uniqueness of the direction of plastic flow in a small region of the stress space located in the vicinity of the loading point. The direction of plastic flow was almost unique elsewhere on the plastic limit. The non-uniqueness was explained using a combination of two distinct mechanisms for plastic deformation involving two very different plastic limits.

  6. Demonstration of finite element simulations in MOOSE using crystallographic models of irradiation hardening and plastic deformation

    SciTech Connect

    Patra, Anirban; Wen, Wei; Martinez Saez, Enrique; Tome, Carlos

    2016-05-31

    This report describes the implementation of a crystal plasticity framework (VPSC) for irradiation hardening and plastic deformation in the finite element code, MOOSE. Constitutive models for irradiation hardening and the crystal plasticity framework are described in a previous report [1]. Here we describe these models briefly and then describe an algorithm for interfacing VPSC with finite elements. Example applications of tensile deformation of a dog bone specimen and a 3D pre-irradiated bar specimen performed using MOOSE are demonstrated.

  7. The features of plastic flow localization in materials under shear deformations

    NASA Astrophysics Data System (ADS)

    Ryabov, P. N.

    2017-07-01

    The process of plastic flow localization in materials undergoing shear deformations is considered. Starting from mathematical model a new numerical approach, which is based on Courant-Isaacson-Rees scheme, that allows one to simulate fully localized plastic flow is proposed. The accuracy and efficiency of the proposed algorithm was showed of three benchmark problems. Next, using the proposed method we study the features of plastic flow localization in materials under shear deformations.

  8. Structure and mechanical properties of titanium subjected to high-rate channel angular pressing and deformation by rolling

    NASA Astrophysics Data System (ADS)

    Zel'Dovich, V. I.; Shorokhov, E. V.; Dobatkin, S. V.; Frolova, N. Yu.; Kheifets, A. E.; Khomskaya, I. V.; Nasonov, P. A.; Ushakov, A. A.

    2011-04-01

    The macro- and microstructure have been analyzed and the tensile mechanical properties have been measured for commercial titanium subjected to dynamic channel angular pressing (DCAP) at high temperatures using one or two passes, as well as to additional warm rolling and low-temperature annealing. The structure of titanium after DCAP at a high temperature consists of a dispersed mixture of fine recrystallized grains (1 to 2 μm in size) and deformed nonrecrystallized regions. The deformed regions have a subgrain structure with sub-grains 200-300 nm in size. After the second pass, the size of the recrystallized grains becomes less by two times as compared to their size after one-pass DCAP, the subgrains in the deformed regions acquire a more equiaxed shape, and the microstructure becomes more uniform. The warm rolling of the samples subjected to DCAP at high temperatures increases the total density of dislocations and provides a high level of internal stresses. After two-pass DCAP at 530°C, the ultimate strength of titanium was 650MPa and the relative elongation was 19%. Additional rolling to 50% at 300°C and low-temperature annealing increases the ultimate strength to 790 MPa, while the relative elongation is retained at a high level of 15%.

  9. Thermal image analysis of plastic deformation and fracture behavior by a thermo-video measurement system

    NASA Astrophysics Data System (ADS)

    Ohbuchi, Yoshifumi; Sakamoto, Hidetoshi; Nagatomo, Nobuaki

    2016-12-01

    The visualization of the plastic region and the measurement of its size are necessary and indispensable to evaluate the deformation and fracture behavior of a material. In order to evaluate the plastic deformation and fracture behavior in a structural member with some flaws, the authors paid attention to the surface temperature which is generated by plastic strain energy. The visualization of the plastic deformation was developed by analyzing the relationship between the extension of the plastic deformation range and the surface temperature distribution, which was obtained by an infrared thermo-video system. Furthermore, FEM elasto-plastic analysis was carried out with the experiment, and the effectiveness of this non-contact measurement system of the plastic deformation and fracture process by a thermography system was discussed. The evaluation method using an infrared imaging device proposed in this research has a feature which does not exist in the current evaluation method, i.e. the heat distribution on the surface of the material has been measured widely by noncontact at 2D at high speed. The new measuring technique proposed here can measure the macroscopic plastic deformation distribution on the material surface widely and precisely as a 2D image, and at high speed, by calculation from the heat generation and the heat propagation distribution.

  10. Repetitive impact loading causes local plastic deformation in wood

    NASA Astrophysics Data System (ADS)

    Salmi, Ari; Salminen, Lauri I.; Engberg, Birgitta A.; Björkqvist, Tomas; Hæggström, Edward

    2012-01-01

    The relationship between the impactor velocity and the amount of strain localization in a single impact compression of cellular solids is known. However, few studies report on the effects of repeated high frequency compression. We therefore studied the mechanical behavior of Norway spruce, a cellular viscoelastic material, before, during, and after cyclic high frequency, high strain rate, compression. A custom made device applied 5000-20 000 unipolar (constrained compression and free relaxation) fatigue cycles with a 0.75 mm peak-to-peak amplitude at 500 Hz frequency. The consequences of this treatment were quantified by pitch-catch ultrasonic measurements and by dynamic material testing using an encapsulated Split-Hopkinson device that incorporated a high-speed camera. The ultrasonic measurements quantified a stiffness modulus drop and revealed the presence of a fatigued low modulus layer near the impacting surface. Such a localized plastic deformation is not predicted by classical mechanics. We introduce a simple model that explains several changes in the mechanical properties caused by fatiguing. The high speed images indicated pronounced strain localization in the weakest (thinnest walls) parts of the earlywood layers, and revealed strain propagation as a function of time. We present a hypothesis explaining why there is a fatigued layer formed in a piece of wood that has sustained cyclic compression and free relaxation.

  11. Effect of plastic deformation on the coarsening of

    NASA Astrophysics Data System (ADS)

    Angers, L.; Fine, M. E.; Weertman, J. R.

    1987-04-01

    Particle coarsening has been studied in a rapidly solidified Al-8.8 wt pct Fe-3.7 wt pct Ce alloy subjected to isothermal annealing for various times at 425 °C. The effect of static and dynamic loading on the particle coarsening rates at the same temperature also has been examined. The dispersed particles in all specimens of the present study are the equilibrium Al13Fe4 and Al10Fe2Ce phases. They are incoherent with the matrix and constitute 23 pct of the total volume. The coarsening rate in isothermally annealed specimens is orders of magnitude greater than predicted by the modified Lifshitz-Slyozov-Wagner theory for volume diffusion controlled coarsening but can be explained using Kirchner's model for coarsening by diffusion along grain boundaries. In the case of intragranular particles, coarsening by diffusion along dislocation cores also is likely to be significant. Creep loading is seen to cause a significant enhancement of the coarsening rate. Fatigue testing with a hold period at the maximum tensile stress also accelerates coarsening whereas continuous cycling appears initially to retard the increase in the average particle size. Dislocations connecting dispersed phase particles are observed more frequently in crept specimens and specimens fatigued with a hold period than in specimens fatigued with no hold period. The effects of plastic deformation on particle coarsening rates are discussed in terms of excess vacancy generation, short circuiting along dislocations, and fine precipitation during fatigue.

  12. Effect of plastic deformation on the coarsening of

    NASA Astrophysics Data System (ADS)

    Angers, L.; Fine, M. E.; Weertman, J. R.

    1987-05-01

    Particle coarsening has been studied in a rapidly solidified Al-8.8 wt pct Fe-3.7 wt pct Ce alloy subjected to isothermal annealing for various times at 425 °C. The effect of static and dynamic loading on the particle coarsening rates at the same temperature also has been examined. The dispersed particles in all specimens of the present study are the equilibrium Al13Fe4 and Al10Fe2Ce phases. They are incoherent with the matrix and constitute 23 pct of the total volume. The coarsening rate in isothermally annealed specimens is orders of magnitude greater than predicted by the modified Lifshitz-Slyozov-Wagner theory for volume diffusion controlled coarsening but can be explained using Kirchner’s model for coarsening by diffusion along grain boundaries. In the case of intragranular particles, coarsening by diffusion along dislocation cores also is likely to be significant. Creep loading is seen to cause a significant enhancement of the coarsening rate. Fatigue testing with a hold period at the maximum tensile stress also accelerates coarsening whereas continuous cycling appears initially to retard the increase in the average particle size. Dislocations connecting dispersed phase particles are observed more frequently in crept specimens and specimens fatigued with a hold period than in specimens fatigued with no hold period. The effects of plastic deformation on particle coarsening rates are discussed in terms of excess vacancy generation, short circuiting along dislocations, and fine precipitation during fatigue.

  13. Modeling of sharp change in magnetic hysteresis behavior of electrical steel at small plastic deformation

    SciTech Connect

    Sablik, M.J.; Rios, S.; Landgraf, F.J.G.; Yonamine, T.; Campos, M.F. de

    2005-05-15

    In 2.2% Si electrical steel, the magnetic hysteresis behavior is sharply sheared by a rather small plastic deformation (0.5%). A modification to the Jiles-Atherton hysteresis model makes it possible to model magnetic effects of plastic deformation. In this paper, with this model, it is shown how a narrow hysteresis with an almost steplike hysteresis curve for an undeformed specimen is sharply sheared by plastic deformation. Computed coercivity and hysteresis loss show a sharp step to higher values at small strain due to an n=1/2 power law dependence on residual strain. The step is seen experimentally.

  14. A Comparison Among Plastic Deformation Capacities of RC Members According to International Codes

    SciTech Connect

    Tripepi, C.; Failla, G.; Santini, A.; Nucera, F.

    2008-07-08

    The aim is to compare plastic deformation capacities of flexure-controlled reinforced concrete members, as predicted by the Italian Seismic Code, Eurocode 8 and FEMA356. For completeness, recent studies in the literature are also referred to. The comparison is pursued in context with a nonlinear static analysis run on 2D frame structures. This allows to assess whether and to which extent plastic deformation capacities may be affected by variations in those quantities, such as shear span and/or axial load, depending on which plastic deformation capacities are generally given.0.

  15. Plastic Deformation of Copper-Based Alloy Reinforced with Incoherent Nanoparticles

    NASA Astrophysics Data System (ADS)

    Matvienko, O. V.; Daneiko, O. I.; Kovalevskaya, T. A.

    2017-06-01

    The paper deals with research carried out into plastic deformation of a heavy-wall pipe made of nanoparticle reinforced copper-based alloy. We present an original approach which combines methods of crystal plasticity and deformable solid mechanics, thereby allowing to study the stress-strain state of the heavy-wall pipe strengthened with incoherent nanoparticles using a homogeneous internal pressure. Dependences are constructed for the yielding area and the pressure, the limit of elasto-plastic resistance is obtained for the heavy-wall pipe and its deformation degree is described. It is shown that the particle size has an effect on strength properties of the material.

  16. Analysis of the plastic deformation of AISI 304 steel induced by the nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Moćko, W.; Radziejewska, J.; Sarzyński, A.; Strzelec, M.; Marczak, J.

    2017-05-01

    The paper presents result of experimental and numerical tests of plastic deformation of austenitic steel generated by a nanosecond laser pulse. The shock wave generated by the laser pulse was used to induce local plastic deformation of the material. The study examined the possibility of using the process to develop a laser forming of materials under ultra-high strain rate. It has been shown that the laser pulse with intensity 2.5 GW/cm2 induces a repeatable plastic deformation of commercially available 304 steel without thermal effects on the surface.

  17. Deformation partitioning provides insight into elastic, plastic, and viscous contributions to bone material behavior.

    PubMed

    Ferguson, V L

    2009-08-01

    The relative contributions of elastic, plastic, and viscous material behavior are poorly described by the separate extraction and analysis of the plane strain modulus, E('), the contact hardness, H(c) (a hybrid parameter encompassing both elastic and plastic behavior), and various viscoelastic material constants. A multiple element mechanical model enables the partitioning of a single indentation response into its fundamental elastic, plastic, and viscous deformation components. The objective of this study was to apply deformation partitioning to explore the role of hydration, tissue type, and degree of mineralization in bone and calcified cartilage. Wet, ethanol-dehydrated, and PMMA-embedded equine cortical bone samples and PMMA-embedded human femoral head tissues were analyzed for contributions of elastic, plastic and viscous deformation to the overall nanoindentation response at each site. While the alteration of hydration state had little effect on any measure of deformation, unembedded tissues demonstrated significantly greater measures of resistance to plastic deformation than PMMA-embedded tissues. The PMMA appeared to mechanically stabilize the tissues and prevent extensive permanent deformation within the bone material. Increasing mineral volume fraction correlated with positive changes in E('), H(c), and resistance to plastic deformation, H; however, the partitioned deformation components were generally unaffected by mineralization. The contribution of viscous deformation was minimal and may only play a significant role in poorly mineralized tissues. Deformation partitioning enables a detailed interpretation of the elastic, plastic, and viscous contributions to the nanomechanical behavior of mineralized tissues that is not possible when examining modulus and contact hardness alone. Varying experimental or biological factors, such as hydration or mineralization level, enables the understanding of potential mechanisms for specific mechanical behavior

  18. Plastic behavior of polycrystalline copper at optical scales of deformation

    NASA Astrophysics Data System (ADS)

    Domber, Jeanette Leah

    Microplasticity is permanent deformation that occurs below the proportional limit of a material. For precision deployable optical spacecraft, it is unknown how microplasticity will affect the performance of the precision structure. An examination of the rolling of thin film optical reflectors indicates a strong dependence of the post-deployed shape on the strain hardening exponent of the material. However, confirmation of the valid extension of the constitutive model used to predict the deployed shape to microscopic strain regimes is necessary. The primary objective of this thesis is threefold: determine the relationship between stress and strain at nano to microstrain levels for representative materials; determine if the relationship between microscopic and macroscopic plastic behavior can be accurately characterized by the Ramberg-Osgood strain hardening constitutive model with a single set of material parameters; and determine if dislocation motion is the root cause of microplastic behavior at room temperature. The test apparatus, with a dynamic force range of 40,000 to 1, measures strains from 0.01 to 1000 parts per million (ppm) of cylindrical amorphous quartz and cold-worked and annealed tempered polycrystalline copper specimen. Elastic behavior in all three materials was consistent with typical values. However, plastic responses were larger than expected. Stresses on the order of 10 to 10,000 kPa (1.45 to 1450 psi) produced permanent strain in all three types of materials ranging from 0.01 to 1 ppm, some of which was attributable to a systematic error in the measurement. Extrapolating macroplastic behavior to lower stress and strain values underestimates the amount of microplasticity observed in the material. Therefore, material property characterization is required at all strain levels that are of concern for a particular application. The similarity in the levels of measured permanent strain for a given stress level between the as-drawn and annealed copper

  19. Finite-element formulations for problems of large elastic-plastic deformation

    NASA Technical Reports Server (NTRS)

    Mcmeeking, R. M.; Rice, J. R.

    1975-01-01

    An Eulerian finite element formulation is presented for problems of large elastic-plastic flow. The method is based on Hill's variational principle for incremental deformations, and is ideally suited to isotropically hardening Prandtl-Reuss materials. Further, the formulation is given in a manner which allows any conventional finite element program, for 'small strain' elastic-plastic analysis, to be simply and rigorously adapted to problems involving arbitrary amounts of deformation and arbitrary levels of stress in comparison to plastic deformation moduli. The method is applied to a necking bifurcation analysis of a bar in plane-strain tension. The paper closes with a unified general formulation of finite element equations, both Lagrangian and Eulerian, for large deformations, with arbitrary choice of the conjugate stress and strain measures. Further, a discussion is given of other proposed formulations for elastic-plastic finite element analysis at large strain, and the inadequacies of some of these are commented upon.

  20. A non-linear elastic constitutive framework for replicating plastic deformation in solids.

    SciTech Connect

    Roberts, Scott Alan; Schunk, Peter Randall

    2014-02-01

    Ductile metals and other materials typically deform plastically under large applied loads; a behavior most often modeled using plastic deformation constitutive models. However, it is possible to capture some of the key behaviors of plastic deformation using only the framework for nonlinear elastic mechanics. In this paper, we develop a phenomenological, hysteretic, nonlinear elastic constitutive model that captures many of the features expected of a plastic deformation model. This model is based on calculating a secant modulus directly from a materials stress-strain curve. Scalar stress and strain values are obtained in three dimensions by using the von Mises invariants. Hysteresis is incorporated by tracking an additional history variable and assuming an elastic unloading response. This model is demonstrated in both single- and multi-element simulations under varying strain conditions.

  1. Finite-element formulations for problems of large elastic-plastic deformation

    NASA Technical Reports Server (NTRS)

    Mcmeeking, R. M.; Rice, J. R.

    1975-01-01

    An Eulerian finite element formulation is presented for problems of large elastic-plastic flow. The method is based on Hill's variational principle for incremental deformations, and is ideally suited to isotropically hardening Prandtl-Reuss materials. Further, the formulation is given in a manner which allows any conventional finite element program, for 'small strain' elastic-plastic analysis, to be simply and rigorously adapted to problems involving arbitrary amounts of deformation and arbitrary levels of stress in comparison to plastic deformation moduli. The method is applied to a necking bifurcation analysis of a bar in plane-strain tension. The paper closes with a unified general formulation of finite element equations, both Lagrangian and Eulerian, for large deformations, with arbitrary choice of the conjugate stress and strain measures. Further, a discussion is given of other proposed formulations for elastic-plastic finite element analysis at large strain, and the inadequacies of some of these are commented upon.

  2. Continuous Severe Plastic Deformation Processing of Aluminum Alloys

    SciTech Connect

    Raghavan Srinivasan; Prabir K. Chaudhury; Balakrishna Cherukuri; Qingyou Han; David Swenson; Percy Gros

    2006-06-30

    Metals with grain sizes smaller than 1-micrometer have received much attention in the past decade. These materials have been classified as ultra fine grain (UFG) materials (grain sizes in the range of 100 to 1000-nm) and nano-materials (grain size <100-nm) depending on the grain size. This report addresses the production of bulk UFG metals through the use of severe plastic deformation processing, and their subsequent use as stock material for further thermomechanical processing, such as forging. A number of severe plastic deformation (SPD) methods for producing bulk UFG metals have been developed since the early 1990s. The most promising of these processes for producing large size stock that is suitable for forging is the equal channel angular extrusion or pressing (ECAE/P) process. This process involves introducing large shear strain in the work-piece by pushing it through a die that consists of two channels with the same cross-sectional shape that meet at an angle to each other. Since the cross-sections of the two channels are the same, the extruded product can be re-inserted into the entrance channel and pushed again through the die. Repeated extrusion through the ECAE/P die accumulates sufficient strain to breakdown the microstructure and produce ultra fine grain size. It is well known that metals with very fine grain sizes (< 10-micrometer) have higher strain rate sensitivity and greater elongation to failure at elevated temperature, exhibiting superplastic behavior. However, this superplastic behavior is usually manifest at high temperature (> half the melting temperature on the absolute scale) and very low strain rates (< 0.0001/s). UFG metals have been shown to exhibit superplastic characteristics at lower temperature and higher strain rates, making this phenomenon more practical for manufacturing. This enables part unitization and forging more complex and net shape parts. Laboratory studies have shown that this is particularly true for UFG metals produced

  3. Plastic deformation drives wrinkling, saddling and wedging of annular bilayer nanostructures

    PubMed Central

    Cho, Jeong-Hyun; Datta, Dibakar; Park, Si-Young; Shenoy, Vivek B.; Gracias, David H.

    2010-01-01

    We describe the spontaneous wrinkling, saddling, and wedging of metallic, annular bilayer nanostructures driven by grain coalescence in one of the layers. Experiments revealed these different outcomes based on the dimensions of the annuli and we find that the essential features are captured using finite element simulations of the plastic deformation in the metal bilayers. Our results show that the dimensions and nanomechanics associated with the plastic deformation of planar nanostructures can be important in forming complex three dimensional nanostructures. PMID:21090597

  4. Microstructure Evolution and Mechanical Properties of Severely Plastically Deformed (SPD) Aluminum Alloys

    DTIC Science & Technology

    2007-05-31

    TITLE AND SUBTITLE 5a. CONTRACT NUMBER Microstructure Evolution and Mechanical Properties of Severely Plastically Deformed (SPD) Aluminum Alloys 5b...modeling study has been carried out to characterize the structure and mechanical properties of severely plastically deformed (SPD) aluminum and its...these routes is the expectation that since the fracture toughness of precipitation hardened aluminum alloys is known to be degraded by grain boundary

  5. Microstructural Evolution in the 2219 Aluminum Alloy During Severe Plastic Deformation

    SciTech Connect

    Kaibyshev, R.O.; Safarov, I.M.; Lesuen, D.R.

    2000-03-29

    Numerous investigations have demonstrated that intense plastic deformation is an attractive procedure for producing an ultrafine grain size in metallic materials. Torsional deformation under high pressure and equal-channel angular extrusion are two techniques that can produce microstructures with grain sizes in the submicrometer and nanometer range. Materials with these microstructures have many attractive properties. The microstructures formed by these two processing techniques are essentially the same and thus the processes occurring during deformation should be the same. Most previous studies have examined the final microstructures produced as a result of severe plastic deformation and the resulting properties. Only a limited number of studies have examined the evolution of microstructure. As a result, some important aspects of ultra-fine grain formation during severe plastic deformation remain unknown. There is also limited data on the influence of the initial state of the material on the microstructural evolution and mechanisms of ultra-fine grain formation. This limited knowledge base makes optimization of processing routes difficult and retards commercial application of these techniques. The objective of the present work is to examine the microstructure evolution during severe plastic deformation of a 2219 aluminum alloy. Specific attention is given to the mechanism of ultrafine grain formation as a result of severe plastic deformation.

  6. Discussion on Applicability of Rigid Plastic Dynamic Deformation Analysis to Soil Structures

    NASA Astrophysics Data System (ADS)

    Hoshina, Takashi; Ohtsuka, Satoru; Isobe, Koichi

    This paper proposes a new analysis method to estimate a residual deformation of soil structure for external loads. It employs a rigid plastic constitutive equation for soil which needs a small number of soil constants in comparison with general elasto-plastic constitutive equations. The purpose of this method is to simulate a large amount of deformation caused by failure of soil structure based on finite deformation theory. The features of proposed method are (1) simulation for large deformation of soil structure, (2) no effect of initial stress distribution, and (3) application to dynamic load. This study expresses the formulation of rigid plastic dynamic finite element method based on finite deformation theory. It examines the applicability of proposed method by applying to Prandtl's limit bearing capacity of foundation for static monotonically increasing load. The result clearly shows the applicability of rigid plastic constitutive equation to deformation analysis. Both kinematical effect and time rate dependency on limit bearing capacity were clearly presented by employing Rigid Plastic Dynamic Deformation Analysis Method.

  7. Multilevel approach to the experimental study of plastic deformation of HCP-zirconium alloys

    SciTech Connect

    Poletika, T. M. E-mail: girs@ispms.tsc.ru; Girsova, S. L. E-mail: girs@ispms.tsc.ru

    2014-11-14

    A multilevel approach was developed to the experimental study of plastic deformation in anisotropic polycrystalline materials, using by way of an example HCP-Zr alloys. This allowed establishing the relationship and hierarchy of processes occurring at macro-, meso- and microscale levels in conditions of significant heterogeneity of plastic flow and of texture formation.

  8. Regularities of Macroscopic Localization of Plastic Deformation in the Stretching of a Low-Carbon Steel

    NASA Astrophysics Data System (ADS)

    Barannikova, S. A.; Kosinov, D. A.; Nadezhkin, M. V.; Lunev, A. G.; Gorbatenko, V. V.; Zuev, L. B.; Gromov, V. E.

    2014-07-01

    The special features of plastic deformation localization in the stretching of polycrystals of low-carbon steel 08 ss after hot rolling and electrolytic saturation with hydrogen are investigated. The main types and parameters of plastic flow localization in different stages of strain hardening are determined by the method of double-exposure speckle photography.

  9. Serrated creep and spatio-temporal structures of macrolocalized plastic deformation

    NASA Astrophysics Data System (ADS)

    Shibkov, A. A.; Zolotov, A. E.; Zheltov, M. A.; Gasanov, M. F.; Denisov, A. A.

    2014-05-01

    The dynamics and morphology of macrolocalized deformation bands have been investigated using a complex of high-speed in situ methods under the conditions of serrated creep of flat samples of the aluminum-magnesium alloy 5456 with different aspect ratios. It has been found that, at the front of a macroscopic plastic deformation jump, a complex structure of propagating deformation bands, which are considered as macrolocalized deformation "quanta," is spontaneously formed in the material. It has been shown that, with an increase in the sample length, the deformation behavior of the alloy tends to the state of self-organized criticality.

  10. A measurement setup for acquiring the local magnetic properties of plastically deformed soft magnetic materials

    SciTech Connect

    Bi Shasha; Sutor, Alexander; Lerch, Reinhard; Xiao Yunshi

    2011-04-01

    This paper introduces a new measurement setup for extraction of the local magnetic properties. With the help of finite element method simulations, modifications are made on the previous double-C-yoke method. Small dimension measuring coils are applied in the stray field produced by the magnetic circuit to evaluate the local magnetic properties of the specified part of the specimen. Through the measurements with the plastically deformed materials at different temperatures, it indicates that the magnetic properties of soft magnetic materials are quite sensitive to plastic straining. After high-temperature thermal treatment on the plastically deformed specimen, the local magnetic properties exhibit an obvious recovery.

  11. Autowave processes of the localization of plastic flow in active media subjected to deformation

    NASA Astrophysics Data System (ADS)

    Zuev, L. B.

    2017-08-01

    Conditions have been considered for the formation of autowaves of localized plastic flow in the deformed metals upon the propagation of Lüders bands in the case of the Portevin-Le Chatelier effect, and upon the formation of a neck with taking into account the differences in the microscopic mechanisms of plastic deformation in the case of these phenomena. The laws that govern the development of the localized plastic flow of metals and the role of these laws in the development of the above effects have been investigated. It has been established that the main features of the deformation characteristic of these phenomena are determined by the differences in the properties of the active media that are formed in the material upon plastic deformation. The mechanisms of the generation of different autowave modes of the localized plastic flow upon the Lüders deformation, Portevin-Le Chatelier effect, and the formation of a neck in active media of different nature during deformation have been considered.

  12. 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.

  13. Characteristics of materials and thermal treatments applied to gearwheels obtained by plastic deformation

    NASA Astrophysics Data System (ADS)

    Bostan, I.; Dulgheru, V.; Trifan, N.

    2016-08-01

    A variety of materials are used in the manufacture of gearwheels. These materials satisfy various working conditions for gears. Such gears are made of metallic materials - ferrous, non-ferrous and from plastic materials. Among ferrous materials the following are used: irons; cast, forged and rolled steels; among non-ferrous materials the following are used: bronze, aluminium alloys, brass, etc., and of plastics the following are used: textolite, polyamide, polyacetal. In the practice of exploitation and in the process of special research it was established that the permissible load, according to teeth contact resistance, is generally determined by the hardness of the material. The highest hardness and respectively, the smallest sizes and reduced mass of the transmission can be obtained in the manufacture of steel gears via thermal treatment. It is obvious that by plastic deformation at cold it cannot be obtained gearwheels with complicated configuration as deformed plastic metal will form cracks caused by low plasticity. To improve processability by plastic deformation the mouldings for gearwheels are heated. With increasing the heating temperature, plasticity increases and resistance to deformation decreases.

  14. Crystallization-aided extraordinary plastic deformation in nanolayered crystalline Cu/amorphous Cu-Zr micropillars

    NASA Astrophysics Data System (ADS)

    Zhang, J. Y.; Liu, G.; Sun, J.

    2013-07-01

    Metallic glasses are lucrative engineering materials owing to their superior mechanical properties such as high strength and great elastic strain. However, the Achilles' heel of metallic amorphous materials -- low plasticity caused by instantaneous catastrophic shear banding, significantly undercut their structural applications. Here, the nanolayered crystalline Cu/amorphous Cu-Zr micropillars with equal layer thickness spanning from 20-100 nm are uniaxially compressed and it is found that the Cu/Cu-Zr micropillars exhibit superhigh homogeneous deformation (>= 30% strain) rather than localized shear banding at room temperature. This extraordinary plasticity is aided by the deformation-induced devitrification via absorption/annihilation of abundant dislocations, triggering the cooperative shearing of shear transformation zones in glassy layers, which simultaneously renders the work-softening. The synthesis of such heterogeneous nanolayered structure not only hampers shear band generation but also provides a viable route to enhance the controllability of plastic deformation in metallic glassy composites via deformation-induced devitrification mechanism.

  15. Large Elasto-Plastic Deformations in Bi-Material Components by Coupled FE-EFGM

    NASA Astrophysics Data System (ADS)

    Harmain, G. A.; Jameel, Azher; Najar, Farooq A.; Masoodi, Junaid H.

    2017-08-01

    In the recent years, the coupled finite element-element free Galerkin method (coupled FE-EFGM) has found wide application in modeling large elasto-plastic deformations in bi-material components. The coupled FE-EFGM applies EFGM in the portion of the domain where large deformations are expected to occur, whereas the rest of the domain is discretized into conventional finite elements. The large deformation occurring in the domain has been modeled by using the total Lagrangian approach. The non-linear elasto-plastic behavior of the material has been represented by the Ramberg-Osgood model. Finally, two numerical problems are solved by the coupled FE-EFGM to illustrate its applicability, efficiency and accuracy in modeling large elasto-plastic deformations in bi-material samples.

  16. Finite element formulations for problems of large elastic-plastic deformation

    NASA Technical Reports Server (NTRS)

    Mcmeeking, R. M.; Rice, J. R.

    1974-01-01

    An Eulerian finite element formulation is presented for problems of large elastic-plastic flow. The method is based on Hill's variational principle for incremental deformations, and is suited to isotropically hardening Prandtl-Reuss materials. The formulation is given in a manner which allows any conventional finite element program, for "small strain" elasticplastic analysis, to be simply and rigorously adapted to problems involving arbitrary amounts of deformation and arbitrary levels of stress in comparison to plastic deformation moduli. The method is applied to a necking bifurcation analysis of a bar in plane-strain tension. A unified general formulation of finite element equations, both Lagrangian and Eulerian, for large deformations, with arbitrary choice of the conjugate stress and strain measures, and a discussion is given of other proposed formulations for elastic-plastic finite element analysis at large strain.

  17. Plastic deformation behaviors of Ni- and Zr-based bulk metallic glasses subjected to nanoindentation

    SciTech Connect

    Weizhong, Liang; Zhiliang, Ning; Zhenqian, Dang; Linzhi, Wu

    2013-12-15

    Plastic deformation behaviors of Ni{sub 42}Ti{sub 20}Zr{sub 21.5}Al{sub 8}Cu{sub 5}Si{sub 3.5} and Zr{sub 51}Ti{sub 5}Ni{sub 10}Cu{sub 25}Al{sub 9} bulk metallic glasses at room temperature were studied by nanoindentation testing and atomic force microscopy under equivalent indentation experimental conditions. The different chemical composition of these two bulk metallic glasses produced variant tendencies for displacement serrated flow to occur during the loading process. The nanoindentation strain rate was calculated as a function of indentation displacement in order to verify the occurrence of displacement serrated flow at different loading rates. Atomic force microscopy revealed decreasing numbers of discrete shear bands around the indentation sites as loading rates increased from 0.025 to 2.5 mNs{sup −1}. Variations in plastic deformation behaviors between Ni and Zr-based glasses materials can be explained by the different metastable microstructures and thermal stabilities of the two materials. The mechanism governing plastic deformation of these metallic glasses was analyzed in terms of an established model of the shear transformation zone. - Highlights: • Plastic deformation of Ni- and Zr-based BMG is studied under identical conditions • Zr-based BMG undergoes a greater extent of plastic deformation than Ni-based BMG • Nanoindentation strain rate is studied to clarify variation in plastic deformation • Metastable microstructure, thermal stability affect BMG plastic deformation.

  18. On the elastic–plastic decomposition of crystal deformation at the atomic scale

    SciTech Connect

    Stukowski, Alexander; Arsenlis, A.

    2012-03-02

    Given two snapshots of an atomistic system, taken at different stages of the deformation process, one can compute the incremental deformation gradient field, F, as defined by continuum mechanics theory, from the displacements of atoms. However, such a kinematic analysis of the total deformation does not reveal the respective contributions of elastic and plastic deformation. We develop a practical technique to perform the multiplicative decomposition of the deformation field, F = FeFp, into elastic and plastic parts for the case of crystalline materials. The described computational analysis method can be used to quantify plastic deformation in a material due to crystal slip-based mechanisms in molecular dynamics and molecular statics simulations. The knowledge of the plastic deformation field, Fp, and its variation with time can provide insight into the number, motion and localization of relevant crystal defects such as dislocations. As a result, the computed elastic field, Fe, provides information about inhomogeneous lattice strains and lattice rotations induced by the presence of defects.

  19. On the elastic–plastic decomposition of crystal deformation at the atomic scale

    DOE PAGES

    Stukowski, Alexander; Arsenlis, A.

    2012-03-02

    Given two snapshots of an atomistic system, taken at different stages of the deformation process, one can compute the incremental deformation gradient field, F, as defined by continuum mechanics theory, from the displacements of atoms. However, such a kinematic analysis of the total deformation does not reveal the respective contributions of elastic and plastic deformation. We develop a practical technique to perform the multiplicative decomposition of the deformation field, F = FeFp, into elastic and plastic parts for the case of crystalline materials. The described computational analysis method can be used to quantify plastic deformation in a material due tomore » crystal slip-based mechanisms in molecular dynamics and molecular statics simulations. The knowledge of the plastic deformation field, Fp, and its variation with time can provide insight into the number, motion and localization of relevant crystal defects such as dislocations. As a result, the computed elastic field, Fe, provides information about inhomogeneous lattice strains and lattice rotations induced by the presence of defects.« less

  20. Non-Contact Acousto-Thermal Signatures of Plastic Deformation in TI-6AL-4V

    NASA Astrophysics Data System (ADS)

    Welter, J. T.; Malott, G.; Schehl, N.; Sathish, S.; Jata, K. V.; Blodgett, M. P.

    2010-02-01

    Plastic deformation introduces changes in a material which include increases in: dislocations, strains, residual stress, and yield stress. However, these changes have a very small impact on the material properties such as elastic modulus, conductivity and ultrasonic wave speed. This is due to the fact that interatomic forces govern these properties, and they are not affected by plastic deformation to any large degree. This is evident from the fact that the changes in electrical resistance and ultrasonic velocity in plastically deformed and virgin samples are very small and can only be determined by highly controlled experiments. Except for X-ray diffraction, there are no direct nondestructive methods for measuring strain and the residual stress. This paper presents an application of the non-contact acousto-thermal signature (NCATS) NDE methodology to detect plastic deformation in flat dog bone Ti-6Al-4V samples. Results of the NCATS measurements on samples subjected to incremental amounts of plastic deformation are presented. The maximum temperature attained by the sample due to acoustic excitation is found to be sensitive to the amount of plastic strain. It is observed that the temperature induced by acoustic excitation increases to a peak followed by a decrease to failure. The maximum temperature peak occurs at plastic strains of 12-14%. It is observed that there is a correlation between the peak in maximum temperature rise and the strain at the experimentally determined ultimate tensile strength. A microstructural based explanation for this will be presented. The results are discussed in reference to utilizing this technique for detection and evaluation of plastic deformation.

  1. NON-CONTACT ACOUSTO-THERMAL SIGNATURES OF PLASTIC DEFORMATION IN TI-6AL-4V

    SciTech Connect

    Welter, J. T.; Jata, K. V.; Blodgett, M. P.; Malott, G.; Schehl, N.; Sathish, S.

    2010-02-22

    Plastic deformation introduces changes in a material which include increases in: dislocations, strains, residual stress, and yield stress. However, these changes have a very small impact on the material properties such as elastic modulus, conductivity and ultrasonic wave speed. This is due to the fact that interatomic forces govern these properties, and they are not affected by plastic deformation to any large degree. This is evident from the fact that the changes in electrical resistance and ultrasonic velocity in plastically deformed and virgin samples are very small and can only be determined by highly controlled experiments. Except for X-ray diffraction, there are no direct nondestructive methods for measuring strain and the residual stress. This paper presents an application of the non-contact acousto-thermal signature (NCATS) NDE methodology to detect plastic deformation in flat dog bone Ti-6Al-4V samples. Results of the NCATS measurements on samples subjected to incremental amounts of plastic deformation are presented. The maximum temperature attained by the sample due to acoustic excitation is found to be sensitive to the amount of plastic strain. It is observed that the temperature induced by acoustic excitation increases to a peak followed by a decrease to failure. The maximum temperature peak occurs at plastic strains of 12-14%. It is observed that there is a correlation between the peak in maximum temperature rise and the strain at the experimentally determined ultimate tensile strength. A microstructural based explanation for this will be presented. The results are discussed in reference to utilizing this technique for detection and evaluation of plastic deformation.

  2. Modeling of ultrasonic nonlinearities for dislocation evolution in plastically deformed materials: Simulation and experimental validation.

    PubMed

    Zhu, Wujun; Deng, Mingxi; Xiang, Yanxun; Xuan, Fu-Zhen; Liu, Changjun; Wang, Yi-Ning

    2016-05-01

    A nonlinear constitutive relationship was established to investigate nonlinear behaviors of ultrasonic wave propagation in plastically damaged media based on analyses of mixed dislocation evolution. Finite element simulations of longitudinal wave propagation in plastically deformed martensite stainless steel were performed based on the proposed nonlinear constitutive relationship, in which the contribution of mixed dislocation to acoustic nonlinearity was considered. The simulated results were validated by experimental measurements of plastically deformed 30Cr2Ni4MoV martensite stainless steels. Simulated and experimental results both reveal a monotonically increasing tendency of the normalized acoustic nonlinearity parameter as a function of plastic strain. Microscopic studies revealed that the changes of the acoustic nonlinearity are mainly attributed to dislocation evolutions, such as dislocation density, dislocation length, and the type and fraction of dislocations during plastic loading.

  3. The mechanical response of a 6061-T6 Al/Al{sub 2}O{sub 3} metal matrix composite at high rates of deformation

    SciTech Connect

    Yadav, S.; Chichili, D.R.; Ramesh, K.T.

    1995-12-01

    The mechanical properties of a 6061-T6 aluminum alloy reinforced with a 20 vol% fraction of alumina particles and of an unreinforced 6061-T6 alloy are studied over a range of strain rates (10{sup {minus}4} to 6 {times} 10{sup 5} s{sup {minus}1}) using quasistatic compression, compression and torsion Kolsky Bars, and high strain rate pressure-shear plate impact. At a given strain rate the composite displays increased strength but essentially the same strain hardening as the matrix. However, the composite displays a stronger rate-sensitivity than does the unreinforced alloy at high rates of deformation (> 10{sup 3} s{sup {minus}1}). The rate-sensitivity of the unreinforced alloy is shown to be largely the result of the imposed strain rate rather than of the rate history. For quasistatic deformations, a model proposed by Bao et al. (1991) describes the behavior of the composite fairly accurately given the behavior of the unreinforced alloy. This paper presents an extension of the model that is able to predict the dynamic behavior of the composite given the dynamic response of the monolithic alloy.

  4. Thermal Microstructural Stability of AZ31 Magnesium after Severe Plastic Deformation

    SciTech Connect

    Young, John P.; Askari, Hesam A.; Hovanski, Yuri; Heiden, Michael J.; Field, David P.

    2015-03-01

    Both equal channel angular pressing and friction stir processing have the ability to refine the grain size of twin roll cast AZ31 magnesium and potentially improve its superplastic properties. This work used isochronal and isothermal heat treatments to investigate the microstructural stability of twin roll cast, equal channel angular pressed and friction stir processed AZ31 magnesium. For both heat treatment conditions, it was found that the twin roll casted and equal channel angular pressed materials were more stable than the friction stir processed material. Calculations of the grain growth kinetics showed that severe plastic deformation processing decreased the activation energy for grain boundary motion with the equal channel angular pressed material having the greatest Q value of the severely plastically deformed materials and that increasing the tool travel speed of the friction stir processed material improved microstructural stability. The Hollomon-Jaffe parameter was found to be an accurate means of identifying the annealing conditions that will result in substantial grain growth and loss of potential superplastic properties in the severely plastically deformed materials. In addition, Humphreys’s model of cellular microstructural stability accurately predicted the relative microstructural stability of the severely plastically deformed materials and with some modification, closely predicted the maximum grain size ratio achieved by the severely plastically deformed materials.

  5. Quantum effect on the nucleation of plastic deformation carriers and destruction in crystals

    SciTech Connect

    Khon, Yury A. Kaminskii, Petr P.

    2015-10-27

    New concepts on the irreversible crystal deformation as a structure transformation caused by a change in interatomic interactions at fluctuations of the electron density under loading are described. The change in interatomic interactions lead to the excitation of dynamical displacements of atoms. A model and a theory of a deformable pristine crystal taking into account the excitation of thermally activated and dynamical displacements of atoms are suggested. New mechanisms of the nucleation of plastic deformation carriers and destruction in pristine crystals at the real value of the deforming stress are studied.

  6. What is the structure of a polymer glass after plastic deformation?

    NASA Astrophysics Data System (ADS)

    Montes, Helene; Lequeux, Francois; Alba-Simionesco, Christiane; Casas, Frederic

    2008-03-01

    We aim to study the effect of plastic deformation on the structure of a glassy polymer. Using neutrons scattering on a large range of length scales, and comparing samples deformed below and above Tg, we show that: 1) The deformation is extremely homogeneous (or affine) for length scales above the entanglement distance 2) The crossover length scale between affine and non affine deeformation is about half the one of the entanglements, and is independent of temperature below the glass transition 3) The arrangement of the polymer chain is distorded by plastic deformation at the atomic scale We then discuss these results and compare them to the results of the simulation of Hoy and Robbins (J. Polym. Sci., 44 (2006), 3487). As a conclusion we see that the entanglements are respopnsible for the very homogeneous deformations, forcing the individual plastic events to propagate in the sample following the tension of the chains. Thus we conclude that the physics of the plastic deformation of polymer glasses are very different from the one of other glasses.

  7. Surface Plastic Deformation Regularity and Microstructural Evolution in the Compound Rolling of Q235 Billet

    NASA Astrophysics Data System (ADS)

    Ren, Tao Lin; Shan, De Bin; Lu, Yan

    In order to meet the double demands on the high temperature creep and the fatigue property, compound rolling is put forward in this study. This technique obtains dual microstructures of billet, fine microstructure on the surface and original state microstructure in the center, through localizing the plastic deformation on the surface layer and leaving little plastic deformation in the center. Based on the local load theory, a set of equipment for the compound rolling has been produced. In order to study the deformation regularity of the compound rolling, Q235 billets have been used and the flow net method for strain measurement has been employed. The deformation regularity difference between the compound rolling and the flat rolling has been investigated. In addition, the microstructural evolution after the compound rolling on the surface and in the center of the Q235 billet has been observed. The results indicate that the compound rolling technique will localize the plastic deformation on the surface of the billet but leave little plastic deformation in the center.

  8. The load separation criterion in elastic-plastic fracture mechanics: Rate and temperature dependence of the material plastic deformation function in an ABS resin

    NASA Astrophysics Data System (ADS)

    Agnelli, Silvia; Baldi, Francesco; Riccò, Theonis

    2012-07-01

    This work is aimed at analyzing the effects of temperature and loading rate on the plastic deformation behavior of an acrylonitrile-butadiene-styrene (ABS) resin during a fracture process. According to the load separation criterion, the plastic deformation behavior during the fracture process of an elastic-plastic material is described by a plastic deformation function. For the ABS here examined, the material plastic deformation function was constructed at different temperatures and loading rates, by single edge notched in bending (SEB) tests on blunt notched specimens. Both low and moderately high (impact) loading rates were explored. For the various conditions of temperature and loading rate the material yield stress was also measured by uniaxial tensile tests. The relationships between material deformation function and yield stress were researched and discussed.

  9. Stress and plastic deformation of MEA in fuel cells. Stresses generated during cell assembly

    NASA Astrophysics Data System (ADS)

    Bograchev, Daniil; Gueguen, Mikael; Grandidier, Jean-Claude; Martemianov, Serguei

    A linear elastic-plastic 2D model of fuel cell with hardening is developed for analysis of mechanical stresses in MEA arising in cell assembly procedure. The model includes the main components of real fuel cell (membrane, gas diffusion layers, graphite plates, and seal joints) and clamping elements (steel plates, bolts, nuts). The stress and plastic deformation in MEA are simulated with ABAQUS code taking into account the realistic clamping conditions. The stress distributions are obtained on the local and the global scales. The first one corresponds to the single tooth/channel structure. The global scale deals with features of the entire cell (the seal joint and the bolts). Experimental measurements of the residual membrane deformations have been provided at different bolts torques. The experimental data are in a good agreement with numerical predictions concerning the beginning of the plastic deformation.

  10. Revealing homogeneous plastic deformation in dendrite-reinforced Ti-based metallic glass composites under tension

    NASA Astrophysics Data System (ADS)

    Wu, F. F.; Wei, J. S.; Chan, K. C.; Chen, S. H.; Zhao, R. D.; Zhang, G. A.; Wu, X. F.

    2017-02-01

    The tensile plastic deformation of dendrite-reinforced Ti-based metallic glass composites (MGCs) was investigated. It was found that there is a critical normalized strain-hardening rate (NSHR) that determines the plastic stability of MGCs: if the NSHR is larger than the critical value, the plastic deformation of the MGCs will be stable, i.e. the necking and strain localization can be effectively suppressed, resulting in homogeneous plastic elongation. In addition, dendrite-reinforce MGCs are verified as being intrinsically ductile, and can be used as good coatings for improving the surface properties of pure titanium or titanium alloys. These findings are helpful in designing, producing, and using MGCs with improved performance properties.

  11. Revealing homogeneous plastic deformation in dendrite-reinforced Ti-based metallic glass composites under tension

    PubMed Central

    Wu, F. F.; Wei, J. S.; Chan, K. C.; Chen, S. H.; Zhao, R. D.; Zhang, G. A.; Wu, X. F.

    2017-01-01

    The tensile plastic deformation of dendrite-reinforced Ti-based metallic glass composites (MGCs) was investigated. It was found that there is a critical normalized strain-hardening rate (NSHR) that determines the plastic stability of MGCs: if the NSHR is larger than the critical value, the plastic deformation of the MGCs will be stable, i.e. the necking and strain localization can be effectively suppressed, resulting in homogeneous plastic elongation. In addition, dendrite-reinforce MGCs are verified as being intrinsically ductile, and can be used as good coatings for improving the surface properties of pure titanium or titanium alloys. These findings are helpful in designing, producing, and using MGCs with improved performance properties. PMID:28195216

  12. A single-crystal model for the high-strain rate deformation of cyclotrimethylene trinitramine including phase transformations and plastic slip

    NASA Astrophysics Data System (ADS)

    Addessio, F. L.; Luscher, D. J.; Cawkwell, M. J.; Ramos, K. J.

    2017-05-01

    A continuum model for the high-rate, thermo-mechanical deformation of single-crystal cyclotrimethylene trinitramine (RDX) is developed. The model includes the effects of anisotropy, large deformations, nonlinear thermo-elasticity, phase transformations, and plastic slip. A multiplicative decomposition of the deformation gradient is used. The volumetric elastic component of the deformation is accounted for through a free-energy based equation of state for the low- (α) and high-pressure (γ) polymorphs of RDX. Crystal plasticity is addressed using a phenomenological thermal activation model. The deformation gradient for the phase transformation is based on an approach that has been applied to martensitic transformations. Simulations were conducted and compared to high-rate, impact loading of oriented RDX single crystals. The simulations considered multiple orientations of the crystal relative to the direction of shock loading and multiple sample thicknesses. Thirteen slip systems, which were inferred from indentation and x-ray topography, were used to model the α-polymorph. It is shown that by increasing the number of slip systems from the previously considered number of six (6) to thirteen (13) in the α-polymorph, better comparisons with data may be obtained. Simulations of impact conditions in the vicinity of the α- to γ-polymorph transformation (3.8 GPa) are considered. Eleven of the simulations, which were at pressures below the transformation value (3.0 GPa), were compared to experimental data. Comparison of the model was also made with available data for one experiment above the transformation pressure (4.4 GPa). Also, simulations are provided for a nominal pressure of 7.5 GPa to demonstrate the effect of the transformation kinetics on the deformation of a high-rate plate impact problem.

  13. A Crystalline Plasticity Finite Element Method for Simulation of the Plastic Deformation of AZ31 Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Li, Dayong; Zhang, Shaorui; Tang, Weiqin; Huang, Shiyao; Peng, Yinghong

    2010-06-01

    In this paper, a constitutive framework based on a crystalline plasticity model is employed to simulate the plastic deformation of AZ31 magnesium alloy, which posses the hexagonal close packed (HCP) crystal structure. Dislocation slip and mechanical twinning are taken into account in the model. The successive integration method is used to determine the active slip systems, and the contribution of twinning to the grain reorientation is treated by the PTR method. The FE model is introduced into ABAQUS/Explicit through a user material subroutine (VUMAT). Three deformation processes of AZ31 magnesium alloy, including tension, compression and a stamping process, are simulated with the present method. The simulation results are compared with experiment and those presented in the literature.

  14. A Crystalline Plasticity Finite Element Method for Simulation of the Plastic Deformation of AZ31 Magnesium Alloys

    SciTech Connect

    Li Dayong; Peng Yinghong; Zhang Shaorui; Tang Weiqin; Huang Shiyao

    2010-06-15

    In this paper, a constitutive framework based on a crystalline plasticity model is employed to simulate the plastic deformation of AZ31 magnesium alloy, which posses the hexagonal close packed (HCP) crystal structure. Dislocation slip and mechanical twinning are taken into account in the model. The successive integration method is used to determine the active slip systems, and the contribution of twinning to the grain reorientation is treated by the PTR method. The FE model is introduced into ABAQUS/Explicit through a user material subroutine (VUMAT). Three deformation processes of AZ31 magnesium alloy, including tension, compression and a stamping process, are simulated with the present method. The simulation results are compared with experiment and those presented in the literature.

  15. Crystal-plastic deformation and recrystallization of peridotite controlled by the seismic cycle

    NASA Astrophysics Data System (ADS)

    Matysiak, Agnes K.; Trepmann, Claudia A.

    2012-03-01

    Deformed peridotites from the Balmuccia complex, Northern Italy, have been investigated by light and electron microscopy (SEM/EBSD, TEM). The peridotites show a heterogeneous and partly recrystallized microfabric associated with cataclastic shear zones. Intracrystalline deformation microstructures (undulatory extinction, crinkly deformation lamellae, deformation bands, kink bands) and recrystallized grains along intragranular zones in large original grains record a sequence with an initial stage of inhomogeneous glide-controlled deformation in the low-temperature plasticity regime associated with brittle deformation and a subsequent stage of recovery and recrystallization. The microstructural evidence of deformation of olivine in the low-temperature field indicates high stresses on the order of several hundred MPa and accordingly high strain rates. Subsequent recovery and recrystallization requires decreasing stresses and strain rates, as there is no evidence for a complex thermal history with increasing temperatures. A locally occurring foam structure in aggregates of recrystallized olivine indicates grain growth at very low differential stresses at a late stage. Such a stress history with transiently high and then decaying stresses is characteristic for coseismic deformation and postseismic creep just below the base of the seismogenic zone. The associated occurrence of pseudotachylytes and microstructures generated by crystal-plastic mechanisms is explained by semi-brittle behavior at transient high stresses and strain rates during coseismic loading at depths, where during postseismic relaxation and in interseismic periods the rocks are behaving by crystal-plastic flow. The consideration of high-stress deformation and subsequent recrystallization processes at decaying stresses in peridotites is especially relevant for earthquake-driven deformation in the mantle.

  16. Misorientation mapping for visualization of plastic deformation via electron back-scattered diffraction.

    PubMed

    Brewer, L N; Othon, M A; Young, L M; Angeliu, T M

    2006-02-01

    The ability to map plastic deformation around high strain gradient microstructural features is central in studying phenomena such as fatigue and stress corrosion cracking. A method for the visualization of plastic deformation in electron back-scattered diffraction (EBSD) data has been developed and is described in this article. This technique is based on mapping the intragrain misorientation in polycrystalline metals. The algorithm maps the scalar misorientation between a local minimum misorientation reference pixel and every other pixel within an individual grain. A map around the corner of a Vickers indentation in 304 stainless steel was used as a test case. Several algorithms for EBSD mapping were then applied to the deformation distributions around air fatigue and stress corrosion cracks in 304 stainless steel. Using this technique, clear visualization of a deformation zone around high strain gradient microstructural features (crack tips, indentations, etc.) is possible with standard EBSD data.

  17. Shear stress-driven refreshing capability of plastic deformation in nanolayered metals.

    PubMed

    Yan, J W; Zhu, X F; Yang, B; Zhang, G P

    2013-04-12

    Severely localized deformation within shear bands can occur much more easily in a metal with nanoscale microstructures, such as nanograined and nanolayered materials. Based on atomic-scale observations, here we show that such locally large deformation (the continuous thinning of the layers) within the indentation-induced shear bands of the Cu/Au nanolayers is essentially attributed to the large shear stress component along the interface, which can refresh the capability of the interface to absorb incoming dislocations through unlocking the product of the dislocation-interface reaction. The results have implications for understanding the interface-mediated mechanisms of plastic deformation and for the engineering application of severe plastic deformation processing of metals at nanoscales.

  18. Elastic-plastic deformations of a beam with the SD-effect

    SciTech Connect

    Pavilaynen, Galina V.

    2015-03-10

    The results for the bending of a cantilever beam with the SD-effect under a concentrated load are discussed. To solve this problem, the standard Bernoulli-Euler hypotheses for beams and the Ilyushin model of perfect plasticity are used. The problem is solved analytically for structural steel A40X. The SD-effect for elastic-plastic deformations is studied. The solutions for beam made of isotropic material and material with the SD-effect are compared.

  19. Tensile elastic properties of 18:8 chromium-nickel steel as affected by plastic deformation

    NASA Technical Reports Server (NTRS)

    Mcadam, D J; Mebs, R W

    1939-01-01

    The relationship between stress and strain, and between stress and permanent set, for 18:8 alloy as affected by prior plastic deformation is discussed. Hysteresis and creep and their effects on the stress-strain and stress-set curves are also considered, as well as the influence of duration of the rest interval after cold work and the influence of plastic deformation on proof stresses, on the modulus of elasticity at zero stress, and on the curvature of the stress-strain line. A constant (c sub 1) is suggested to represent the variation of the modulus of elasticity with stress.

  20. Phase field crystal study of deformation and plasticity in nanocrystalline materials.

    PubMed

    Stefanovic, Peter; Haataja, Mikko; Provatas, Nikolas

    2009-10-01

    We introduce a modified phase field crystal (MPFC) technique that self-consistently incorporates rapid strain relaxation alongside the usual plastic deformation and multiple crystal orientations featured by the traditional phase field crystal (PFC) technique. Our MPFC formalism can be used to study a host of important phase transformation phenomena in material processing that require rapid strain relaxation. We apply the MPFC model to study elastic and plastic deformations in nanocrystalline materials, focusing on the "reverse" Hall-Petch effect. Finally, we introduce a multigrid algorithm for efficient numerical simulations of the MPFC model.

  1. Processing of nanostructured nickel by severe plastic deformation consolidation of ball-milled powder

    SciTech Connect

    Valiev, R.Z. |; Mishral, R.S.; Grozal, J.; Mukherjee, A.K.

    1996-05-01

    Severe plastic deformation consolidation process of the ball-milled powder has been able to produce fully dense nanocrystalline nickel with a grain size of {approximately}20 nm. The processed samples are characterized by very high elastic strains, very likely caused by a presence of high density of extrinsic grain boundary dislocations. The combined effect of the smallest nanoscale grain size in nickel, as obtained in this study, along with the effect of high elastic strains, resulted in the high level of hardness and also the lower experimentally measured density of these severe plastic deformation consolidation samples.

  2. Method for measuring residual stresses in materials by plastically deforming the material and interference pattern comparison

    DOEpatents

    Pechersky, Martin J.

    1995-01-01

    A method for measuring residual stress in a material comprising the steps of establishing a speckle pattern on the surface with a first laser then heating a portion of that pattern with an infrared laser until the surface plastically deforms. Comparing the speckle patterns before and after deformation by subtracting one pattern from the other will produce a fringe pattern that serves as a visual and quantitative indication of the degree to which the plasticized surface responded to the stress dung heating and enables calculation of the stress.

  3. Thermal Recovery of Plastic Deformation in Dissimilar Metal Weld

    SciTech Connect

    Qiao, Dongxiao; Yu, Xinghua; Zhang, Wei; Crooker, Paul; David, Stan A.; Feng, Zhili

    2014-05-23

    Stainless steel has been widely used in challenging environments typical to nuclear power plant structures, due its excellent corrosion resistance. Nickel filler metals containing high chromium concentration, including Alloy 82/182, are used for joining stainless steel to carbon steel components to achieve similar high resistance to stress corrosion cracking. However, the joint usually experience weld metal stress corrosion cracking (SCC), which affects the safety and structural integrity of light water nuclear reactor systems. A primary driving force for SCC is the high tensile residual stress in these welds. Due to large dimension of pressure vessel and limitations in the field, non-destructive residual stress measurement is difficult. As a result, finite element modeling has been the de facto method to evaluate the weld residual stresses. Recent studies on this subject from researchers worldwide report different residual stress value in the weldments [5]. The discrepancy is due to the fact that most of investigations ignore or underestimate the thermal recovery in the heat-affect zone or reheated region in the weld. In this paper, the effect of heat treatment on thermal recovery and microhardness is investigated for materials used in dissimilar metal joint. It is found that high equivalent plastic strains are predominately accumulated in the buttering layer, the root pass, and the heat affected zone, which experience multiple welding thermal cycles. The final cap passes, experiencing only one or two welding thermal cycles, exhibit less plastic strain accumulation. Moreover, the experimental residual plastic strains are compared with those predicted using an existing weld thermo-mechanical model with two different strain hardening rules. The importance of considering the dynamic strain hardening recovery due to high temperature exposure in welding is discussed for the accurate simulation of weld residual stresses and plastic strains. In conclsuion, the

  4. 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.

  5. Effect of plastic deformation on deuterium retention and release in tungsten

    SciTech Connect

    Terentyev, D. Lambrinou, K.; Minov, B.; De Temmerman, G.; Morgan, T. W.; Zayachuk, Y.; Bystrov, K.; Dubinko, A.; Van Oost, G.

    2015-02-28

    The effect of severe plastic deformation on the deuterium retention in tungsten exposed to high-flux low-energy plasma (flux ∼ 10{sup 24 }D/m{sup 2}/s, energy ∼ 50 eV, and fluence up to 3 × 10{sup 26 }D/m{sup 2}) at the plasma generator Pilot-PSI was studied by thermal desorption spectroscopy and scanning electron microscopy. The desorption spectra in both reference and plastically deformed samples were deconvolved into three contributions attributed to the detrapping from dislocations, deuterium-vacancy clusters, and pores, respectively. The plastically induced deformation, resulting in high dislocation density, does not change the positions of the three peaks, but alters their amplitudes as compared to the reference material. The appearance of blisters detected by scanning electron microscopy and the desorption peak attributed to the release from pores (i.e., deuterium bubbles) were suppressed in the plastically deformed samples but only up to a certain fluence. Beyond 5 × 10{sup 25 }D/m{sup 2}, the release from the bubbles in the deformed material is essentially higher than in the reference material. Based on the presented results, we suggest that a dense dislocation network increases the incubation dose needed for the appearance of blisters, associated with deuterium bubbles, by offering numerous nucleation sites for deuterium clusters eventually transforming into deuterium-vacancy clusters by punching out jogs on dislocation lines.

  6. Localization of Plastic Deformation in Aluminum Single Crystals at Different Scale Levels

    NASA Astrophysics Data System (ADS)

    Bespalova, I. V.; Teplyakova, L. A.; Kunitsyna, T. S.

    2017-07-01

    The paper generalizes results of investigating the localization and fragmentation of plastic deformation in aluminum single crystals having a different orientation of the compression axis and lateral faces. The surface topography of the samples induced by plastic deformation includes such elements as deformation bands, folds and shear markings observed at different scale levels (macro, meso and micro). The morphological uniformity is identified for these elements in the aluminum single crystals. Depending on the resolution required, the quantification of the shear deformation markings is provided by the optical microscope and the scanning and transmission electron microscopes using the replication technique. The following parameters are obtained: the distance between the nearest shear deformation markings, width of shear markings, local shear; shear γ; the single-crystal volume fraction in which the shear deformation occurs at macro, meso, and micro-levels. The statistical examination of the shear deformation markings in aluminum single crystals with different geometry is performed at these three levels and allows us to conclude that the micro-scale level makes the main contribution to the shear deformation.

  7. Finite Element Surface Layer Inheritable Condition Residual Stresses Model in Surface Plastic Deformation Processes

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    The residual stresses (RS) research and computational algorithms creation in complex types of loading on the product lifecycle stages relevance is shown. The 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.

  8. The peculiarities of natural plastically deformed diamond crystals from “Internatsionalnaya” pipe (Yakutia)

    NASA Astrophysics Data System (ADS)

    Rylov, G. M.; Fedorova, E. N.; Logvinova, A. M.; Pokhilenko, N. P.; Kulipanov, G. N.; Sobolev, N. V.

    2007-05-01

    An internal structure of a representative collection of plastically deformed diamond crystals from "Internatsionalnaya" kimberlite pipe among which are brown, gray-smoky, purplish-pink crystals has been studied by synchrotron radiation (Laue-SR method). The obtained data made it possible to classify the studied crystals by the degree of deformation and polygonization. The results obtained by Laue-SR method correlate well with IR spectroscopy data.

  9. Plastic Deformation and Morphological Evolution of Precise Acid Copolymers

    NASA Astrophysics Data System (ADS)

    Middleton, L. Robert; Azoulay, Jason; Murtagh, Dustin; Cordaro, Joseph; Winey, Karen

    2014-03-01

    Acid- and ion-containing polymers have specific interactions that produce complex and hierarchical morphologies that provide remarkable mechanical properties. Historically, correlating the hierarchical structure and the mechanical properties of these polymers has been challenging due to the random arrangements of the polar groups along the backbone, ex situ characterization and the difficulty in deconvolution the effects of crystalline and amorphous regions along with secondary interactions between polymer chains. We address these challenges through in situ deformation of precise acid copolymers and relate the structural evolution to bulk properties by considering a series of copolymers with 9, 15 or 21 carbons between acid groups. Simultaneous synchrotron X-ray scattering and room temperature uniaxial tensile experiments of these precise acid copolymers were conducted. The different deformation mechanisms are compared and the microstructural evolution during deformation is discussed. For example, the liquid-like distribution of acid aggregates within the bulk copolymer transitions into a layered structure concurrent to a dramatic increase in tensile strength. Overall, we evaluate the effect and control of introducing acid groups on mechanical deformation of the bulk copolymers.

  10. An exploration of plastic deformation dependence of cell viability and adhesion in metallic implant materials.

    PubMed

    Uzer, B; Toker, S M; Cingoz, A; Bagci-Onder, T; Gerstein, G; Maier, H J; Canadinc, D

    2016-07-01

    The relationship between cell viability and adhesion behavior, and micro-deformation mechanisms was investigated on austenitic 316L stainless steel samples, which were subjected to different amounts of plastic strains (5%, 15%, 25%, 35% and 60%) to promote a variety in the slip and twin activities in the microstructure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) revealed that cells most favored the samples with the largest plastic deformation, such that they spread more and formed significant filopodial extensions. Specifically, brain tumor cells seeded on the 35% deformed samples exhibited the best adhesion performance, where a significant slip activity was prevalent, accompanied by considerable slip-twin interactions. Furthermore, maximum viability was exhibited by the cells seeded on the 60% deformed samples, which were particularly designed in a specific geometry that could endure greater strain values. Overall, the current findings open a new venue for the production of metallic implants with enhanced biocompatibility, such that the adhesion and viability of the cells surrounding an implant can be optimized by tailoring the surface relief of the material, which is dictated by the micro-deformation mechanism activities facilitated by plastic deformation imposed by machining.

  11. Shear bands in a bulk metallic glass after large plastic deformation

    SciTech Connect

    Qu, D.D.; Wang, Y.B.; Liao, X.Z.; Shen, J.

    2012-10-23

    A transmission electron microscopy investigation is conducted to trace shear bands in a Zr{sub 53}Cu{sub 18.7}Ni{sub 12}Al{sub 16.3} bulk metallic glass after experiencing 4% plastic deformation. Shear band initiation, secondary shear band interactions, mature shear band broadening and the interactions of shear bands with shear-induced nanocrystals are captured. Results suggest that the plasticity of the bulk metallic glass is enhanced by complex shear bands and their interactions which accommodate large plastic strain and prevent catastrophic shear band propagation.

  12. Rotational defects and plastic deformation in molecular crystal RDX

    NASA Astrophysics Data System (ADS)

    Pal, Anirban; Picu, Catalin

    2013-03-01

    Defects in molecular crystals differ in many aspects from their atomic counterparts. Molecules in the crystal lattice can undergo conformational changes or twist and rotate into various configurations during deformation. These processes play an important role in the mechanics at a larger scale by controlling critical parameters like dislocation mobility. We present a computational study of such processes in cyclo-trimethylene-trinitramine (RDX), an energetic molecular crystal. Conformational changes, rotational defects and their role in the deformation mechanics of RDX is investigated using molecular dynamics simulations. Structure and mobility of dislocations are also presented and role of conformational and rotational defects in dislocation mobility is discussed. The authors acknowledge discussions with the Army Research Laboratory, and gratefully acknowledge the support from the Army Research Office

  13. Analysis of Deformation Behavior of Plastic during Lining on Steel Pipe with an FEM

    NASA Astrophysics Data System (ADS)

    Yamada, Toshiro; Mikawa, Toshihide; Kushizaki, Yoshiyuki

    2007-05-01

    There exist serious issues on the poor adhesion and residual stress of plastics on the steel pipe lined with plastics such as polyvinyl chloride (PVC), polyethylene (PE) and polypropylene (PP), which cause the interface delamination and crack of plastics. In order to prevent the failure during lining, the optimum lining conditions such as temperature pattern and the length of plastic pipe are not determined by the theoretical analysis but by trial and error because of the following reasons: As a plastic pipe is longitudinally stretched in advance, it has the strong anisotropy that it shrinks in the longitudinal direction and expands in the circumferential direction while sliding and adhesion of plastics at the contact point with steel during lining. Moreover, plastics are usually a viscoelastic material; the dynamic behavior is remarkably dependent on temperature and time. In this work, the authors have tried to analyze the deformation behavior of polyvinyl chloride (PVC) lining a steel pipe during lining. Mechanical and viscoelastic properties of stretched PVC pipe have been measured in the longitudinal and circumferential directions. The deformation behavior of PVC pipe has been numerically predicted by a finite element analysis (FEA) under the assumption of anisotropic and viscoelastic material during lining. It has been confirmed that the calculated results by an FEA can give the good agreement with experimental ones.

  14. Method for making biaxially textured articles by plastic deformation

    DOEpatents

    Goyal, Amit

    2002-01-01

    A method of preparing a biaxially textured article comprises the steps of providing a metal preform, coating or laminating the preform with a metal layer, deforming the layer to a sufficient degree, and rapidly recrystallizing the layer to produce a biaxial texture. A superconducting epitaxial layer may then be deposited on the biaxial texture. In some embodiments the article further comprises buffer layers, electromagnetic devices or electro-optical devices.

  15. Bulk Nanocomposites Produced by Thermally Activated Severe Plastic Deformation

    DTIC Science & Technology

    2008-12-01

    first method used an upper bound analytical approach ( Hosford ; Caddell 1993). The simplified velocity field for the ECAE is shown in Fig 9...homogeneous deformation; (b) a slab element between AA’ and CC; (c) velocity discontinuity at AA’ and BB’; (d) a slab element between AA’ and BB’.( Hosford ...strength fabricated by self-propagating high-temperature synthesis. Materials Letters, 58, 1683-1686. Hosford , W. F., and R. M. Caddell, 1993

  16. Deformation Twinning in Nb-Microalloyed Fe-Mn-C-Al Twinning-Induced Plasticity Steel

    NASA Astrophysics Data System (ADS)

    Kwon, Eui Pyo; Kim, Dae Young; Park, Hyun Kyeong

    2017-09-01

    Work hardening and deformation twinning in microalloyed Fe-Mn-C-Al twinning-induced plasticity (TWIP) steel with Nb were investigated in this study, and it was found that the addition of Nb affected the work-hardening behavior of TWIP steel. Moreover, the quantitative characterization of twinning was performed on the deformed microstructure by electron backscattering diffraction analysis, and the results indicate that the addition of Nb causes a reduction in twinning kinetics. The decrease in deformation twinning in TWIP steel with added Nb can be attributed to the effect of fine grain, dislocations in non-recrystallized grains, and the formation of twins on a particular grain orientation.

  17. Plastic deformation of YBa2Cu3O7-x superconductor compound

    NASA Astrophysics Data System (ADS)

    Torresvillasenor, Gabriel; Moreno, Jose E.

    The high temperature superconductor YBa sub 2 Cu sub 3 O sub 7-x shown a brittle behavior when deformed under ambient conditions. If a hydrostatic state of stress is imposed with a metal matrix, it is possible to induce exttended plastic deformations as a great as 200 percent were achieved using this method without loosing the superconductivity in the ceramic. The observed deformations mechanisms are similar to those observed in the superplastic metals and the boundary ceramic metal matrix was found to be highly coherent. This method opens a new technique that can be apllied in the manufacture of superconductor wire.

  18. Plastic Deformation by Twinning in CsHSO4 Single Crystal

    NASA Astrophysics Data System (ADS)

    Ozaki, Toru; Itoh, Kazuyuki; Nakamura, Eiji

    1982-01-01

    Plastic deformation by mechanical twinning with (001) twin plane has been observed in the b-plate of CsHSO4 single crystals at room temperature. A parallelogram-shaped hysteresis loop is found between the external shear stress and the deformation angle of the crystal plate. The maximum deformation angle is found to be 24° which is very close to 2(β-90°), where β{=}101.51° is the monoclinic angle of the crystal lattice. A microscopic model based on the crystal structure for the twin structure is proposed.

  19. Semantic modeling of the structural and process entities during plastic deformation of crystals and rocks

    NASA Astrophysics Data System (ADS)

    Babaie, Hassan; Davarpanah, Armita

    2016-04-01

    We are semantically modeling the structural and dynamic process components of the plastic deformation of minerals and rocks in the Plastic Deformation Ontology (PDO). Applying the Ontology of Physics in Biology, the PDO classifies the spatial entities that participate in the diverse processes of plastic deformation into the Physical_Plastic_Deformation_Entity and Nonphysical_Plastic_Deformation_Entity classes. The Material_Physical_Plastic_Deformation_Entity class includes things such as microstructures, lattice defects, atoms, liquid, and grain boundaries, and the Immaterial_Physical_Plastic_Deformation_Entity class includes vacancies in crystals and voids along mineral grain boundaries. The objects under the many subclasses of these classes (e.g., crystal, lattice defect, layering) have spatial parts that are related to each other through taxonomic (e.g., Line_Defect isA Lattice_Defect), structural (mereological, e.g., Twin_Plane partOf Twin), spatial-topological (e.g., Vacancy adjacentTo Atom, Fluid locatedAlong Grain_Boundary), and domain specific (e.g., displaces, Fluid crystallizes Dissolved_Ion, Void existsAlong Grain_Boundary) relationships. The dynamic aspect of the plastic deformation is modeled under the dynamical Process_Entity class that subsumes classes such as Recrystallization and Pressure_Solution that define the flow of energy amongst the physical entities. The values of the dynamical state properties of the physical entities (e.g., Chemical_Potential, Temperature, Particle_Velocity) change while they take part in the deformational processes such as Diffusion and Dislocation_Glide. The process entities have temporal parts (phases) that are related to each other through temporal relations such as precedes, isSubprocessOf, and overlaps. The properties of the physical entities, defined under the Physical_Property class, change as they participate in the plastic deformational processes. The properties are categorized into dynamical, constitutive

  20. Influence of Plastic Deformation on Martensitic Transformation During Hot Stamping of Complex Structure Auto Parts

    NASA Astrophysics Data System (ADS)

    Shen, Yuhan; Song, Yanli; Hua, Lin; Lu, Jue

    2017-04-01

    The ultra-high strength steel auto parts manufactured by hot stamping are widely applied for weight reduction and safety improvement. During the hot stamping process, hot forming and quenching are performed in one step wherein plastic deformation and phase transformation simultaneously take place and affect each other. Thereinto, the influence of deformation on martensitic transformation is of great importance. In the present paper, the influence of plastic deformation on martensitic transformation during hot stamping of complex structure auto parts was investigated. For this purpose, a B-pillar reinforced panel in B1500HS steel was manufactured by hot stamping, and the process was simulated by finite element software based on a thermo-mechanical-metallurgical coupled model. Considering various deformation degrees, the microstructures and mechanical properties at four typical locations of the hot stamped B-pillar reinforced panel were detected. The results show that the martensitic content and the microhardness increase with the increase in the deformation amount. There are two reasons causing this phenomenon: (1) the increase in mechanical driving force and (2) the increased probability of the martensitic nucleation at crystal defects. The x-ray diffraction analysis indicates the carbon enrichment in retained austenite which results from the carbon diffusion during the low-carbon martensite formation. Furthermore, the carbon content decreases with the increase in the deformation amount, because the deformation of austenite suppresses the carbon diffusion.

  1. Influence of Plastic Deformation on Martensitic Transformation During Hot Stamping of Complex Structure Auto Parts

    NASA Astrophysics Data System (ADS)

    Shen, Yuhan; Song, Yanli; Hua, Lin; Lu, Jue

    2017-02-01

    The ultra-high strength steel auto parts manufactured by hot stamping are widely applied for weight reduction and safety improvement. During the hot stamping process, hot forming and quenching are performed in one step wherein plastic deformation and phase transformation simultaneously take place and affect each other. Thereinto, the influence of deformation on martensitic transformation is of great importance. In the present paper, the influence of plastic deformation on martensitic transformation during hot stamping of complex structure auto parts was investigated. For this purpose, a B-pillar reinforced panel in B1500HS steel was manufactured by hot stamping, and the process was simulated by finite element software based on a thermo-mechanical-metallurgical coupled model. Considering various deformation degrees, the microstructures and mechanical properties at four typical locations of the hot stamped B-pillar reinforced panel were detected. The results show that the martensitic content and the microhardness increase with the increase in the deformation amount. There are two reasons causing this phenomenon: (1) the increase in mechanical driving force and (2) the increased probability of the martensitic nucleation at crystal defects. The x-ray diffraction analysis indicates the carbon enrichment in retained austenite which results from the carbon diffusion during the low-carbon martensite formation. Furthermore, the carbon content decreases with the increase in the deformation amount, because the deformation of austenite suppresses the carbon diffusion.

  2. Peculiarities of plastic deformation nucleation in copper under nanoindentation

    SciTech Connect

    Kryzhevich, Dmitrij S. Korchuganov, Aleksandr V.; Zolnikov, Konstantin P.; Psakhie, Sergey G.

    2015-10-27

    The computer simulation results on the atomic structure of the copper crystallite and its behavior in nanoindentation demonstrate the key role of local structural transformations in nucleation of plasticity. The generation of local structural transformations can be considered as an elementary event during the formation of higher scale defects, including partial dislocations and stacking faults. The cause for local structural transformations, both direct fcc-hcp and reverse hcp-fcc, is an abrupt local increase in atomic volume. A characteristic feature is that the values of local volume jumps in direct and reverse structural transformations are comparable with that in melting and lie in the range 5–7%.

  3. The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy

    SciTech Connect

    Bochkareva, Anna Lunev, Aleksey; Barannikova, Svetlana; Gorbatenko, Vadim; Shlyakhova, Galina; Zuev, Lev

    2015-10-27

    The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation. It is found that the mechanical properties and localized plastic deformation parameters of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy; however, the plastic flow behavior of material remains virtually unaffected. Using scanning electron and atomic force microscopy methods, the changes in the fracture surface were investigated. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Using digital speckle image technique, the local strain patterns were being registered for the original alloy D1 and the counterpart subjected to electrolytic hydrogenation for 100 h.

  4. Processing Ultra Fine Grained Net-Shaped MEMS Parts Using Severe Plastic Deformation

    SciTech Connect

    Valiev, Ruslan Z.; Raab, Georgy I.; Estrin, Yuri; Zi, Aikaterini; Janecek, Milos

    2007-04-07

    This paper presents the results of investigation of the process of severe plastic deformation by means of ECAP method for producing the mini billets of pure aluminium. The strain state of the process and peculiarities of structure formation have been studied. The achieved results testify to the high efficiency of the process.

  5. Developments in Processing by Severe Plastic Deformation at the 3rd Pan American Materials Congress

    NASA Astrophysics Data System (ADS)

    Figueiredo, Roberto B.; Kawasaki, Megumi; Langdon, Terence G.

    2017-10-01

    The 3rd Pan American Materials Congress in San Diego, California, February 26-March 2, 2017, provided an opportunity to bring together many participants working in the field of severe plastic deformation. This article provides a brief review of these activities.

  6. Developments in Processing by Severe Plastic Deformation at the 3rd Pan American Materials Congress

    NASA Astrophysics Data System (ADS)

    Figueiredo, Roberto B.; Kawasaki, Megumi; Langdon, Terence G.

    2017-08-01

    The 3rd Pan American Materials Congress in San Diego, California, February 26-March 2, 2017, provided an opportunity to bring together many participants working in the field of severe plastic deformation. This article provides a brief review of these activities.

  7. A Study of Localized Plastic Deformation as Related to Fatigue Mechanisms.

    DTIC Science & Technology

    1982-05-01

    J. M. Baik) ... ............. 5 III.1 Introduction .... ... .. ....................... 6 111.2 Cyclic Deformation Behavior and Strain-Life...Strain and Plastic Strain Control LCF Behavior . 27 111.2.3.3 Fatigue Life Characteristic ..... .............. 36 111.2.3.4 Fracture Surface Morphology...59 111.3.3 Results ....... ......................... ... 61 111.3.3.1 Crack Closure Behavior ..... ..... .......... .. 61

  8. An acoustic emission study of plastic deformation in polycrystalline aluminium

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Frederick, J. R.; Felbeck, D. K.

    1979-01-01

    Acoustic emission experiments were performed on polycrystalline and single crystal 99.99% aluminum while undergoing tensile deformation. It was found that acoustic emission counts as a function of grain size showed a maximum value at a particular grain size. Furthermore, the slip area associated with this particular grain size corresponded to the threshold level of detectability of single dislocation slip events. The rate of decline in acoustic emission activity as grain size is increased beyond the peak value suggests that grain boundary associated dislocation sources are giving rise to the bulk of the detected acoustic emissions.

  9. Accommodation of Plastic Deformation by Ultrasound-Induced Grain Rotation

    NASA Astrophysics Data System (ADS)

    Dutta, R. K.; Petrov, R. H.; Hermans, M. J. M.; Richardson, I. M.

    2015-08-01

    Electron backscatter diffraction was used to investigate the softening effect in low-carbon steel [Fe-0.051C-0.002Si-0.224Mn-0.045Al (wt pct)] during tensile deformation with in situ ultrasonic treatment. A bimodal grain size distribution is observed with relatively small equiaxed grains with an average diameter of 10 μm at the grain boundaries of large elongated grains. The formation of these relatively small equiaxed grains is interpreted in terms of dynamic recrystallization by lattice and sub-grain rotation.

  10. Cell resolved, multiparticle model of plastic tissue deformations and morphogenesis

    NASA Astrophysics Data System (ADS)

    Czirok, Andras; Isai, Dona Greta

    2015-02-01

    We propose a three-dimensional mechanical model of embryonic tissue dynamics. Mechanically coupled adherent cells are represented as particles interconnected with elastic beams which can exert non-central forces and torques. Tissue plasticity is modeled by a stochastic process consisting of a connectivity change (addition or removal of a single link) followed by a complete relaxation to mechanical equilibrium. In particular, we assume that (i) two non-connected, but adjacent particles can form a new link; and (ii) the lifetime of links is reduced by tensile forces. We demonstrate that the proposed model yields a realistic macroscopic elasto-plastic behavior and we establish how microscopic model parameters determine material properties at the macroscopic scale. Based on these results, microscopic parameter values can be inferred from tissue thickness, macroscopic elastic modulus and the magnitude and dynamics of intercellular adhesion forces. In addition to their mechanical role, model particles can also act as simulation agents and actively modulate their connectivity according to specific rules. As an example, anisotropic link insertion and removal probabilities can give rise to local cell intercalation and large scale convergent extension movements. The proposed stochastic simulation of cell activities yields fluctuating tissue movements which exhibit the same autocorrelation properties as empirical data from avian embryos.

  11. Infrared thermography coupled with digital image correlation in studying plastic deformation on the mesoscale level

    NASA Astrophysics Data System (ADS)

    Wang, Xiaogang; Witz, Jean-François; El Bartali, Ahmed; Jiang, Chao

    2016-11-01

    This paper focuses on a study of plastic deformation on the mesoscale level by infrared thermography coupled with digital image correlation. First, a novel technique for fully-coupled thermal and kinematic measurements was developed, and the common problem of spatial coupling in the multifield measurement was solved successfully using an image registration method. Then the developed technique was applied to investigate the plastic deformation of a pure aluminium oligocrystal specimen in a tensile test. The deformed specimen manifested high strains of type out-of-plane, which were found closely associated with the crystallographic structure. From a metrological point of view, the out-of-plane effect on the thermographic measurement was analyzed, and the pertinent radiometric artifacts were estimated. The source of errors was verified through a correlation analysis between the estimated artifacts and specimen surface profile. Moreover, the out-of-plane effect on the kinematic measurement was investigated, and the relevant errors were analyzed via the correlation residual. The analysis highlighted the role of the microstructure that played in the plastic deformation and showed that grain boundary was crucial in shaping the heterogeneous deformation patterns for aluminium oligocrystals.

  12. Crystallographically controlled crystal-plastic deformation of zircon in shear zones

    NASA Astrophysics Data System (ADS)

    Kovaleva, Elizaveta; Klötzli, Urs

    2014-05-01

    Plastically-deformed zircons from various types of strained natural metamorphic rocks have been investigated in-situ by electron backscatter diffraction analysis (EBSD), allowing crystallographic orientation mapping at high spatial resolution. Plastic deformation often forms under the control of grain-internal heterogeneities. At the crystal structure scale deformation is controlled by the physical anisotropy of the lattice. Three most common slip systems in zircon are [100]{010}, [010]{001} and [001]{010} (Leroux et. al., 1999; Reddy et. al., 2007). They are genetically connected with the main zircon crystallographic directions: [001] (c-axis), [100] and [010] (a and b axes). Atomic models show weak planes normal to these directions that preferably evolve to glide planes in the deforming crystal. The visualization of seismic (elastic) properties of zircon with the MATLAB toolbox MTEX shows a similar pattern. The slowest S-wave velocities are observed in directions parallel to [100], [010] and [001] crystallographic directions. The highest Young's modulus values lie in the same directions. In natural zircon grains, the common slip systems are preferably activated when zircon is hosted by rheologically comparatively weaker phases or a fine-grained matrix. In these cases zircon behaves as a rigid clast. During progressive deformation high deviatoric stresses together with high strain rates concentrate at crystal tips, as shown by numerical modeling. Softer host phases allow more degrees of freedom for zircon to be deformed according to its crystallographic and internal properties. These conclusions are supported by the misorientation axes density distribution maps, derived with MTEX. Deformed zircon hosted by a relatively soft phase (mostly biotite) develops a crystallographic preferred orientation (CPO), which has not been documented for zircon before. At the same time deformation of zircon hosted by a rheologically stronger matrix causes the activation of less

  13. In situ nanoindentation study of plastic co-deformation in Al-TiN nanocomposites.

    PubMed

    Li, N; Wang, H; Misra, A; Wang, J

    2014-10-16

    We performed in situ indentation in a transmission electron microscope on Al-TiN multilayers with individual layer thicknesses of 50 nm, 5 nm and 2.7 nm to explore the effect of length scales on the plastic co-deformability of a metal and a ceramic. At 50 nm, plasticity was confined to the Al layers with easy initiation of cracks in the TiN layers. At 5 nm and below, cracking in TiN was suppressed and post mortem measurements indicated a reduction in layer thickness in both layers. The results demonstrate the profound size effect in enhancing plastic co-deformability in nanoscale metal-ceramic multilayers.

  14. On the influence of plastic deformation on discontinuous precipitation in Mg-Al

    SciTech Connect

    Duly, D.; Audier, M.; Brechet, Y. . Lab. de Thermodynamique et de Physico-Chimie Metallurgique)

    1993-12-15

    The influence of a prestrain on intragranular precipitation is well known: the dislocations created by plastic deformation act as nucleation sites for heterogeneous precipitation. The influence of a similar prestrain on discontinuous precipitation is much less documented. There appears to be no general rule: depending on the systems considered, the kinetics of discontinuous precipitation can either be accelerated or slowed down. Moreover, in certain alloys, discontinuous precipitation is associated with recrystallization phenomena. In this paper, the authors results on the influence of plastic strain at room temperature on discontinuous precipitation in a Mg-8.5 wt% Al alloy. The interesting feature of this alloy is that plastic deformation induces both dislocation glide and twinning.

  15. Yielding and Irreversible Deformation below the Microscale: Surface Effects and Non-Mean-Field Plastic Avalanches

    PubMed Central

    Moretti, Paolo; Cerruti, Benedetta; Miguel, M.-Carmen

    2011-01-01

    Nanoindentation techniques recently developed to measure the mechanical response of crystals under external loading conditions reveal new phenomena upon decreasing sample size below the microscale. At small length scales, material resistance to irreversible deformation depends on sample morphology. Here we study the mechanisms of yield and plastic flow in inherently small crystals under uniaxial compression. Discrete structural rearrangements emerge as a series of abrupt discontinuities in stress-strain curves. We obtain the theoretical dependence of the yield stress on system size and geometry and elucidate the statistical properties of plastic deformation at such scales. Our results show that the absence of dislocation storage leads to crucial effects on the statistics of plastic events, ultimately affecting the universal scaling behavior observed at larger scales. PMID:21666747

  16. In situ nanoindentation study of plastic Co-deformation in Al-TiN nanocomposites

    DOE PAGES

    Li, N.; Wang, H.; Misra, A.; ...

    2014-10-16

    We performed in situ indentation in a transmission electron microscope on Al-TiN multilayers with individual layer thicknesses of 50 nm, 5 nm and 2.7 nm to explore the effect of length scales on the plastic co-deformability of a metal and a ceramic. At 50 nm, plasticity was confined to the Al layers with easy initiation of cracks in the TiN layers. At 5 nm and below, cracking in TiN was suppressed and post mortem measurements indicated a reduction in layer thickness in both layers. Our results demonstrate the profound size effect in enhancing plastic co-deformability in nanoscale metal-ceramic multilayers.

  17. Plastic deformation of metallic glasses: Size of shear transformation zones from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Zink, Mareike; Samwer, K.; Johnson, W. L.; Mayr, S. G.

    2006-05-01

    Plastic deformation in metallic glasses well below their glass transition temperatures Tg occurs spatially heterogeneously within highly localized regions, termed shear transformation zones (STZs). Yet, their size and the number of atoms involved in a local shear event, remains greatly unclear. With the help of classical molecular dynamics (MD) computer simulations on plastic deformation of the model glass CuTi during pure shearing, we address this issue by evaluating correlations in atomic-scale plastic displacements, viz. the displacement correlation function. From the correlation length, a universal diameter of about 15Å , or, equivalently, approximately 120 atoms is derived for a variety of conditions, such as variable strains, strain rates, temperatures, and boundary conditions. Our findings are consistent with a recent model proposed by Johnson and Samwer [Phys. Rev. Lett. 95, 195501 (2005)].

  18. Pressure self-multiplication and the kinetics of phase transition in plastic layer experiencing plane deformation

    NASA Astrophysics Data System (ADS)

    Boguslavskii, Yu.; Achmetshackirova, Kh.; Drabkin, S.

    1998-09-01

    Based on the deformation theory of plasticity the problem of pressure distribution in a compressed layer at phase transition experiencing a plane plastic deformation is considered. It is found that in the pressure distribution near the phase boundaries anomalies emerge in the form of a “step” or a local maximum caused by volume jumps at phase transition. It is shown that these anomalies and differences in yield limits of the phases can lead to essential change of pressure in the center of the layer in comparison with its value in absence of phase transition, but under equal external load. The maximal value of external load admitting the considered solution is found. The kinetics of possible isothermal regimes of phase transition leading to change in the time-pressure distribution in the plastic layer is investigated.

  19. Structural transformations at the initial stages of fragmentation of plastically deformed polycrystals: A computer experiment

    NASA Astrophysics Data System (ADS)

    Rybin, V. V.; Perevezentsev, V. N.; Svirina, Yu. V.

    2017-05-01

    Results have been presented for a computer experiment on concurrent micro-, meso-, and macroscopic studies of the evolution of dislocation structure in a large (adjacent to one of the junctions) domain of a grain after its constant-rate macroplastic deformation to an extent that corresponds to the onset of the stage of developed plastic deformation. The type of dislocation-density and dislocation-charge distributions, as well as amounts and degrees of inhomogeneity in local plastic deformation, have been analyzed. The type of dislocation rearrangements at the junctions and fractures of high-angle grain boundaries has been established, which is responsible for the formation of the first dangling dislocation boundaries, which are mesodefects that trigger fragmentation.

  20. Modeling the Hot Ductility of AA6061 Aluminum Alloy After Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Khamei, A. A.; Dehghani, K.; Mahmudi, R.

    2015-05-01

    Solutionized AA6061 aluminum alloy was processed by equal-channel angular pressing followed by cold rolling. The hot ductility of the material was studied after severe plastic deformation. The hot tensile tests were carried out in the temperature range of 300-500°C and at the strain rates of 0.0005-0.01 s-1. Depending on the temperature and strain rate, the applied strain level exhibited significant effects on the hot ductility, strain-rate sensitivity, and activation energy. It can be suggested that the possible mechanism dominated the hot deformation during tensile testing is dynamic recovery and dislocation creep. Constitutive equations were developed to model the hot ductility of the severe plastic deformed AA6061 alloy.

  1. Assessment of Localized Plastic Deformation during Fatigue in Polycrystalline Copper by Nonlinear Ultrasonic

    NASA Astrophysics Data System (ADS)

    Metya, Avijit; Parida, N.; Bhattacharya, D. K.; Bandyopadhyay, N. R.; Palit Sagar, S.

    2007-12-01

    Nonlinear ultrasonic (NLU) and conventional ultrasonic techniques have been applied to assess the localized plastic deformation in polycrystalline copper during high-cycle fatigue (HCF). The measurement parameter of NLU, i.e., the NLU parameter, β, has been calculated from the power spectrum of the filtered and amplified received signal. For conventional ultrasonic, longitudinal velocity ( V l) and attenuation coefficients ( α) have been determined. It has been observed that the position of maximum localized plastic deformation cannot be detected by V l and α, whereas β detects the same at the stage of 30 pct of damage corresponding to the total fatigue life of the material. The result of NLU has also been correlated with the hardness during fatigue. This work reveals the potential of NLU to assess the localized deformation during fatigue much earlier to the failure.

  2. Modeling of Plastic Deformation of Dispersion-Hardened Materials with L12 Superstructure Particles

    NASA Astrophysics Data System (ADS)

    Daneyko, O. I.; Kovalevskaya, T. A.; Kulaeva, N. A.

    2017-07-01

    The paper presents a mathematical model of plastic deformation in FCC materials strengthened with particles having L12 superstructure. The model is based on balance equations for various deformation defects with regard to their transformation during plastic deformation. Research results show that the size and distance between particles of the strengthening phase affect the thermal strengthening, strain hardening and the evolution of the dislocation subsystem of the FCC alloy strengthened with coherent particles with L12 superstructure. The temperature anomaly is detected for strength properties of materials having different volume fractions of the strengthening phase. It is shown that the incoherent strengthening phase increases the flow stress of the material and suppresses the temperature anomaly of its strength properties.

  3. Plastic buckling and ratchetting of straight pipes subjected to deformation-controlled monotonic and cyclic bending

    SciTech Connect

    Igari, Toshihide; Wada, Hiroshi; Ueta, Masahiro

    1996-12-31

    In the structural design of nuclear and fossil power plants used at high temperature, new criteria of piping against thermal expansion load are strongly required. This paper proposes a new design criterion for plastic local buckling of straight pipes subjected to deformation-controlled monotonic bending. The critical deformation corresponding to the start point of buckling is determined from seven specimens with several r/t, L/r etc., and the critical rotation is determined in order to eliminate the effect of L/r. Test results of ratchetting of straight pipes subjected to deformation-controlled cyclic bending are also shown, and the limit of ratchetting is correlated to the critical rotation in the plastic local buckling. These results suggest that the 3Sm limit in ASME Code might be unconservative for the case of thin-walled straight pipes.

  4. Finite deformation analysis of crack tip fields in plastically compressible hardening-softening-hardening solids

    NASA Astrophysics Data System (ADS)

    Khan, D.; Singh, S.; Needleman, A.

    2016-11-01

    Crack tip fields are calculated under plane strain small scale yielding conditions. The material is characterized by a finite strain elastic-viscoplastic constitutive relation with various hardening-softening-hardening hardness functions. Both plastically compressible and plastically incompressible solids are considered. Displacements corresponding to the isotropic linear elastic mode I crack field are prescribed on a remote boundary. The initial crack is taken to be a semi-circular notch and symmetry about the crack plane is imposed. Plastic compressibility is found to give an increased crack opening displacement for a given value of the applied loading. The plastic zone size and shape are found to depend on the plastic compressibility, but not much on whether material softening occurs near the crack tip. On the other hand, the near crack tip stress and deformation fields depend sensitively on whether or not material softening occurs. The combination of plastic compressibility and softening (or softening-hardening) has a particularly strong effect on the near crack tip stress and deformation fields.

  5. Finite deformation analysis of crack tip fields in plastically compressible hardening-softening-hardening solids

    NASA Astrophysics Data System (ADS)

    Khan, D.; Singh, S.; Needleman, A.

    2017-02-01

    Crack tip fields are calculated under plane strain small scale yielding conditions. The material is characterized by a finite strain elastic-viscoplastic constitutive relation with various hardening-softening-hardening hardness functions. Both plastically compressible and plastically incompressible solids are considered. Displacements corresponding to the isotropic linear elastic mode I crack field are prescribed on a remote boundary. The initial crack is taken to be a semi-circular notch and symmetry about the crack plane is imposed. Plastic compressibility is found to give an increased crack opening displacement for a given value of the applied loading. The plastic zone size and shape are found to depend on the plastic compressibility, but not much on whether material softening occurs near the crack tip. On the other hand, the near crack tip stress and deformation fields depend sensitively on whether or not material softening occurs. The combination of plastic compressibility and softening (or softening-hardening) has a particularly strong effect on the near crack tip stress and deformation fields.

  6. Characterization of plastic deformation and chemical reaction in titanium-polytetrafluoroethylene mixture

    NASA Astrophysics Data System (ADS)

    Davis, Jeffery Jon

    1998-09-01

    The subject of this dissertation is the deformation process of a single metal - polymer system (titanium - polytetrafluoroethylene) and how this process leads to initiation of chemical reaction. Several different kinds of experiments were performed to characterize the behavior of this material to shock and impact. These mechanical conditions induce a rapid plastic deformation of the sample. All of the samples tested had an initial porosity which increased the plastic flow condition. It is currently believed that during the deformation process two important conditions occur: removal of the oxide layer from the metal and decomposition of the polymer. These conditions allow for rapid chemical reaction. The research from this dissertation has provided insight into the complex behavior of plastic deformation and chemical reactions in titanium - polytetrafluoroethylene (PTFE, Teflon). A hydrodynamic computational code was used to model the plastic flow for correlation with the results from the experiments. The results from this work are being used to develop an ignition and growth model for metal/polymer systems. Three sets of experiments were used to examine deformation of the 80% Ti and 20% Teflon materials: drop- weight, gas gun, and split-Hopkinson pressure bar. Recovery studies included post shot analysis of the samples using x-ray diffraction. Lagrangian hydrocode DYNA2D modeling of the drop-weight tests was performed for comparison with experiments. One of the reactions know to occur is Ti + C → TiC (s) which results in an exothermic release. However, the believed initial reactions occur between Ti and fluorine which produces TixFy gases. The thermochemical code CHEETAH was used to investigate the detonation products and concentrations possible during Ti - Teflon reaction. CHEETAH shows that the Ti - fluorine reactions are thermodynamically favorable. This research represents the most comprehensive to date study of deformation induced chemical reaction in metal/polymers.

  7. Reversible plastic events during oscillatory deformation of amorphous solids.

    PubMed

    Priezjev, Nikolai V

    2016-01-01

    The effect of oscillatory shear strain on nonaffine rearrangements of individual particles in a three-dimensional binary glass is investigated using molecular dynamics simulations. The amorphous material is represented by the Kob-Andersen mixture at the temperature well below the glass transition. We find that during periodic shear deformation of the material, some particles undergo reversible nonaffine displacements with amplitudes that are approximately power-law distributed. Our simulations show that particles with large amplitudes of nonaffine displacement exhibit a collective behavior; namely, they tend to aggregate into relatively compact clusters that become comparable with the system size near the yield strain. Along with reversible displacements there exist a number of irreversible ones. With increasing strain amplitude, the probability of irreversible displacements during one cycle increases, which leads to permanent structural relaxation of the material.

  8. Microstructural stability after severe plastic deformation of AZ31 Magnesium

    NASA Astrophysics Data System (ADS)

    Young, J. P.; Askari, H.; Hovanski, Y.; Heiden, M. J.; Field, D. P.

    2014-08-01

    Friction stir processing (FSP) and equal channel angular pressing (ECAP) were used to modify the microstructure of twin roll cast (TRC) AZ31 magnesium. The influence of these processes on the microstructural properties of the material was investigated. It was found that both processes produced microstructures with an average grain size of less than 10 pm, suggesting that they have the potential for superplastic deformation. Heat treatments were performed on the TRC, ECAP and FSP materials to assess their microstructural stability. Both the ECAP and TRC material were found to be fairly stable, showing normal grain growth while the FSP material grew substantially at temperatures above 200°C. The activation energy of grain boundary motion of the TRC material was calculated to be 167 kJ/mol.

  9. Deformation-driven diffusion and plastic flow in amorphous granular pillars

    NASA Astrophysics Data System (ADS)

    Li, Wenbin; Rieser, Jennifer M.; Liu, Andrea J.; Durian, Douglas J.; Li, Ju

    2015-06-01

    We report a combined experimental and simulation study of deformation-induced diffusion in compacted quasi-two-dimensional amorphous granular pillars, in which thermal fluctuations play a negligible role. The pillars, consisting of bidisperse cylindrical acetal plastic particles standing upright on a substrate, are deformed uniaxially and quasistatically by a rigid bar moving at a constant speed. The plastic flow and particle rearrangements in the pillars are characterized by computing the best-fit affine transformation strain and nonaffine displacement associated with each particle between two stages of deformation. The nonaffine displacement exhibits exponential crossover from ballistic to diffusive behavior with respect to the cumulative deviatoric strain, indicating that in athermal granular packings, the cumulative deviatoric strain plays the role of time in thermal systems and drives effective particle diffusion. We further study the size-dependent deformation of the granular pillars by simulation, and find that different-sized pillars follow self-similar shape evolution during deformation. In addition, the yield stress of the pillars increases linearly with pillar size. Formation of transient shear lines in the pillars during deformation becomes more evident as pillar size increases. The width of these elementary shear bands is about twice the diameter of a particle, and does not vary with pillar size.

  10. In situ spectroscopic study of the plastic deformation of amorphous silicon under nonhydrostatic conditions induced by indentation

    DOE PAGES

    Gerbig, Yvonne B.; Michaels, C. A.; Bradby, Jodie E.; ...

    2015-12-17

    Indentation-induced plastic deformation of amorphous silicon (a-Si) thin films was studied by in situ Raman imaging of the deformed contact region of an indented sample, employing a Raman spectroscopy-enhanced instrumented indentation technique (IIT). The occurrence and evolving spatial distribution of changes in the a-Si structure caused by processes, such as polyamorphization and crystallization, induced by indentation loading were observed. Furthermore, the obtained experimental results are linked with previously published work on the plastic deformation of a-Si under hydrostatic compression and shear deformation to establish a model for the deformation behavior of a-Si under indentation loading.

  11. Pinning, flow and plastic deformation of flux vortices in high T(sub c) superconductors

    NASA Technical Reports Server (NTRS)

    Roytburd, A.

    1990-01-01

    In high temperature superconductor (HTSC) materials the vortices are highly mobile and flexible. This is reflected in different models of melt of a vortex lattice. Another aspect of the problem is stressed: an easy nucleation and high mobility of dislocations in the vortex lattice. Some models of plastic deformation of vortex lattice are considered as a result of its interaction with a real crystal structure. Depinning is interpreted as yield of plastic flow is vortex medium. Effect of macroscopic defects in crystal structures (pores, inclusions, grain and domain boundaries) is being considered in detail. Available experimental facts on magnetization and a critical current in HTSC and conventional superconductors are discussed from the points of view of depinning to vortices vs. plastic flow of vortices vs. plastic flow of vortices medium.

  12. Coarse graining atomistic simulations of plastically deforming amorphous solids

    NASA Astrophysics Data System (ADS)

    Hinkle, Adam R.; Rycroft, Chris H.; Shields, Michael D.; Falk, Michael L.

    2017-05-01

    The primary mode of failure in disordered solids results from the formation and persistence of highly localized regions of large plastic strains known as shear bands. Continuum-level field theories capable of predicting this mechanical response rely upon an accurate representation of the initial and evolving states of the amorphous structure. We perform molecular dynamics simulations of a metallic glass and propose a methodology for coarse graining discrete, atomistic quantities, such as the potential energies of the elemental constituents. A strain criterion is established and used to distinguish the coarse-grained degrees-of-freedom inside the emerging shear band from those of the surrounding material. A signal-to-noise ratio provides a means of evaluating the strength of the signal of the shear band as a function of the coarse graining. Finally, we investigate the effect of different coarse graining length scales by comparing a two-dimensional, numerical implementation of the effective-temperature description in the shear transformation zone (STZ) theory with direct molecular dynamics simulations. These comparisons indicate the coarse graining length scale has a lower bound, above which there is a high level of agreement between the atomistics and the STZ theory, and below which the concept of effective temperature breaks down.

  13. Fatigue properties of magnesium alloy AZ91 processed by severe plastic deformation.

    PubMed

    Fintová, Stanislava; Kunz, Ludvík

    2015-02-01

    Fatigue properties of cast AZ91 magnesium alloy processed by severe plastic deformation were investigated and compared with the properties of the initial cast state. The severe plastic deformation was carried out by equal channel angular pressing (ECAP). The ECAP treatment resulted in a bimodal structure. The bimodality consists in a coexistence of fine grained areas with higher content of Mg17Al12 particles and areas exhibiting larger grains and lower density of Mg17Al12 particles. Improvement of the basic mechanical properties of AZ91 (yield stress, tensile strength and ductility) by ECAP was significant. Also the improvement of the fatigue life in the low-cycle fatigue region was substantial. However the improvement of the fatigue strength in the high-cycle fatigue region was found to be negligible. The endurance limit based on 10(7) cycles for the cast alloy was 80 MPa and for the alloy processed by ECAP 85 MPa. The cyclic plastic response in both states was qualitatively similar; initial softening was followed by a long cyclic hardening. Fatigue cracks in cast alloy initiate in cyclic slip bands which were formed in areas of solid solution. In the case of severe plastic deformed material with bimodal structure two substantially different mechanisms of crack initiation were observed. Crack initiation in slip bands was a preferred process in the areas with large grains whereas the grain boundaries cracking was a characteristic mechanism in the fine grained regions.

  14. Crystallization-aided extraordinary plastic deformation in nanolayered crystalline Cu/amorphous Cu-Zr micropillars

    PubMed Central

    Zhang, J. Y.; Liu, G.; Sun, J.

    2013-01-01

    Metallic glasses are lucrative engineering materials owing to their superior mechanical properties such as high strength and great elastic strain. However, the Achilles' heel of metallic amorphous materials — low plasticity caused by instantaneous catastrophic shear banding, significantly undercut their structural applications. Here, the nanolayered crystalline Cu/amorphous Cu-Zr micropillars with equal layer thickness spanning from 20–100 nm are uniaxially compressed and it is found that the Cu/Cu-Zr micropillars exhibit superhigh homogeneous deformation (≥ 30% strain) rather than localized shear banding at room temperature. This extraordinary plasticity is aided by the deformation-induced devitrification via absorption/annihilation of abundant dislocations, triggering the cooperative shearing of shear transformation zones in glassy layers, which simultaneously renders the work-softening. The synthesis of such heterogeneous nanolayered structure not only hampers shear band generation but also provides a viable route to enhance the controllability of plastic deformation in metallic glassy composites via deformation-induced devitrification mechanism. PMID:23900595

  15. Microstructure and Plastic Deformation of the As-Welded Invar Fusion Zones

    NASA Astrophysics Data System (ADS)

    Yao, D. J.; Zhou, D. R.; Xu, P. Q.; Lu, F. G.

    2017-02-01

    The as-welded Invar fusion zones were fabricated between cemented carbides and carbon steel using a Fe-Ni Invar interlayer and laser welding method. Three regions in the as-welded Invar fusion zones were defined to compare microstructures, and these were characterized and confirmed by scanning electron microscopy and X-ray diffractometry. The structure and plastic deformation mechanism for initial Invar Fe-Ni alloys and the as-welded Invar fusion zones are discussed. (1) After undergoing high-temperature thermal cycles, the microstructure of the as-welded Invar fusion zones contains γ-(Fe, Ni) solid solution (nickel dissolving in γ-Fe) with a face-centered cubic (fcc) crystal structure and mixed carbides (eutectic colonies, mixed carbides between two adjacent grains). The mixed carbides exhibited larger, coarser eutectic microstructures with a decrease in welding speed and an increase in heat input. (2) The structure of the initial Invar and the as-welded Invar is face-centered cubic γ-(Fe, Ni). (3) The as-welded Invar has a larger plastic deformation than initial Invar with an increase in local strain field and dislocation density. Slip deformation is propagated along the (111) plane. This finding helps us to understand microstructure and the formation of dislocation and plastic deformation when the Invar Fe-Ni alloy undergoes a high-temperature process.

  16. Plastic deformation of a model glass induced by a local shear transformation

    NASA Astrophysics Data System (ADS)

    Priezjev, Nikolai V.

    2015-03-01

    The effect of a local shear transformation on plastic deformation of a three-dimensional amorphous solid is studied using molecular dynamics simulations. We consider a spherical inclusion, which is gradually transformed into an ellipsoid of the same volume and then converted back into the sphere. It is shown that at sufficiently large strain amplitudes, the deformation of the material involves localized plastic events that are identified based on the relative displacement of atoms before and after the shear transformation. We find that the density profiles of cage jumps decay away from the inclusion, which correlates well with the radial dependence of the local deformation of the material. At the same strain amplitude, the plastic deformation becomes more pronounced in the cases of weakly damped dynamics or large time scales of the shear transformation. We show that the density profiles can be characterized by the universal function of the radial distance multiplied by a dimensionless factor that depends on the friction coefficient and the time scale of the shear event.

  17. Microstructure and Plastic Deformation of the As-Welded Invar Fusion Zones

    NASA Astrophysics Data System (ADS)

    Yao, D. J.; Zhou, D. R.; Xu, P. Q.; Lu, F. G.

    2017-05-01

    The as-welded Invar fusion zones were fabricated between cemented carbides and carbon steel using a Fe-Ni Invar interlayer and laser welding method. Three regions in the as-welded Invar fusion zones were defined to compare microstructures, and these were characterized and confirmed by scanning electron microscopy and X-ray diffractometry. The structure and plastic deformation mechanism for initial Invar Fe-Ni alloys and the as-welded Invar fusion zones are discussed. (1) After undergoing high-temperature thermal cycles, the microstructure of the as-welded Invar fusion zones contains γ-(Fe, Ni) solid solution (nickel dissolving in γ-Fe) with a face-centered cubic (fcc) crystal structure and mixed carbides (eutectic colonies, mixed carbides between two adjacent grains). The mixed carbides exhibited larger, coarser eutectic microstructures with a decrease in welding speed and an increase in heat input. (2) The structure of the initial Invar and the as-welded Invar is face-centered cubic γ-(Fe, Ni). (3) The as-welded Invar has a larger plastic deformation than initial Invar with an increase in local strain field and dislocation density. Slip deformation is propagated along the (111) plane. This finding helps us to understand microstructure and the formation of dislocation and plastic deformation when the Invar Fe-Ni alloy undergoes a high-temperature process.

  18. The Microstructure Evolution of Dual-Phase Pipeline Steel with Plastic Deformation at Different Strain Rates

    NASA Astrophysics Data System (ADS)

    Ji, L. K.; Xu, T.; Zhang, J. M.; Wang, H. T.; Tong, M. X.; Zhu, R. H.; Zhou, G. S.

    2017-07-01

    Tensile properties of the high-deformability dual-phase ferrite-bainite X70 pipeline steel have been investigated at room temperature under the strain rates of 2.5 × 10-5, 1.25 × 10-4, 2.5 × 10-3, and 1.25 × 10-2 s-1. The microstructures at different amount of plastic deformation were examined by using scanning and transmission electron microscopy. Generally, the ductility of typical body-centered cubic steels is reduced when its stain rate increases. However, we observed a different ductility dependence on strain rates in the dual-phase X70 pipeline steel. The uniform elongation (UEL%) and elongation to fracture (EL%) at the strain rate of 2.5 × 10-3 s-1 increase about 54 and 74%, respectively, compared to those at 2.5 × 10-5 s-1. The UEL% and EL% reach to their maximum at the strain rate of 2.5 × 10-3 s-1. This phenomenon was explained by the observed grain structures and dislocation configurations. Whether or not the ductility can be enhanced with increasing strain rates depends on the competition between the homogenization of plastic deformation among the microconstituents (ultra-fine ferrite grains, relatively coarse ferrite grains as well as bainite) and the progress of cracks formed as a consequence of localized inconsistent plastic deformation.

  19. Interfacial diffusion in high-temperature deformation of composites: A discrete dislocation plasticity investigation

    NASA Astrophysics Data System (ADS)

    Shishvan, Siamak S.; Pollock, Tresa M.; McMeeking, Robert M.; Deshpande, Vikram S.

    2017-01-01

    We present a discrete dislocation plasticity (DDP) framework to analyse the high temperature deformation of multi-phase materials (composites) comprising a matrix and inclusions. Deformation of the phases is by climb-assisted glide of the dislocations while the particles can also deform due to stress-driven interfacial diffusion. The general framework is used to analyse the uniaxial tensile deformation of a composite comprising elastic particles with dislocation plasticity only present in the matrix phase. When dislocation motion is restricted to only glide within the matrix a strong size effect of the composite strength is predicted with the strength increasing with decreasing unit cell size due to dislocations forming pile-ups against the matrix/particle interface. Interfacial diffusion decreases the composite strength as it enhances the elongation of the elastic particles along the loading direction. When dislocation motion occurs by climb-assisted glide within the matrix the size effect of the strength is reduced as dislocations no longer arrange high energy pile-up structures but rather form lower energy dislocation cell networks. While interfacial diffusion again reduces the composite strength, in contrast to continuum plasticity predictions, the elongation of the particles is almost independent of the interfacial diffusion constant. Rather, in DDP the reduction in composite strength due to interfacial diffusion is a result of changes in the dislocation structures within the matrix and the associated enhanced dislocation climb rates in the matrix.

  20. Plastic deformation of the plastic matrix-hard inclusion composite system during high-temperature gas extrusion

    NASA Astrophysics Data System (ADS)

    Berbentsev, V. D.; Bugakov, V. I.; Vaganov, V. E.; Alymov, M. I.; Aborkin, A. V.

    2016-11-01

    The results of investigations of the production of abrasive rod or wire diamond tools by high-temperature gas extrusion are presented. The versions of preparation of an initial metallic workpiece filled with a mixture of abrasive diamond grains are considered. The forming of plastic materials with hard inclusions, which is caused by deformation redistribution in the volume and is accompanied by the formation of pores and discontinuities adjoined to the hard inclusions, is considered. The results obtained demonstrate the prospects of application of high-temperature gas extrusion for the production of diamond tools for various purposes.

  1. PLASTIC DEFORMATION AND FRACTURE OF STEELS UNDER DYNAMIC BIAXIAL LOADING

    SciTech Connect

    Syn, C; Moreno, J; Goto, D M; Belak, J; Grady, D

    2004-07-08

    Dynamic equi-biaxial bulging of thin AerMet 100 alloy plates was studied. The plates were deformed using a gas-gun driven flyer plate test set-up at impact velocities between 1.0 and 2.0 km/sec. The results indicate that in addition to biaxial stretching (and thinning) of the plate, internal cavitation (spallation fracture) results from the complex wave interactions within the plate. No outward evidence of damage was observed at the lower velocities, in the range of 1.0-1.2 km/sec. Fine scale cracking of the plates was observed at impact velocity above approximately 1.4 km/sec. Complete specimen fracture, in the form of multiple petals and pie-shaped fragments, was observed at impact velocity above 1.6 km/sec. Hydrodynamic computer code simulations were performed, prior to and in conjunction with the experiments, to aid in experiment design and interpretation of the experimental data.

  2. Incremental Carcass Theory of Polycrystalline Media at Large Elastic and Plastic Deformations

    NASA Astrophysics Data System (ADS)

    Akhundov, V. M.

    2016-11-01

    A two-level carcass theory as applied to media with a polycrystalline structure at large elastic and plastic deformation of crystals (crystal grains) is presented. The theory is incremental, in accordance with the incremental nature of governing equations of a crystal, which take into account the prehistory of its deformation in the medium. The theory is based on the field of carcass (macroscopic) displacements, which determines the material displacements of carcass points and carcass (macroscopic) deformations of the medium. At the macromechanical level, the equations of macroscopic deformation and motion are given in an incremental form. At the micromechanical (locally structural) level, incremental microboundary-value problems for nodal presentation blocks of the polycrystalline material are solved on the basis of carcass displacements and their increments. From the internal fields of nodal blocks and their increments found, the incremental macroscopic stresses are determined, which allow one to close the system of equations of the macromechanical level of analysis.

  3. Numerical study on dynamic compressive deformation and elasto-plastic wave propagation of foam materials

    NASA Astrophysics Data System (ADS)

    Tanigaki, Kenichi; Idouji, Toru; Horikawa, Keitaro; Kobayashi, Hidetoshi; Ogawa, Kinya

    2015-09-01

    Finite element models of closed-cell foam structures were created using the three-dimensional Voronoi tessellation method coupled with the random sequential addition algorithm. The dynamic compressive deformation behaviors of the models were numerically studied using LS-DYNA code. The deformation mode of the models changed gradually as the deformation rate increases. Also, the generation and the propagation of plastic wave was clearly observed with the rate of 100 m/s. The longitudinal elastic wave velocity showed a weak negative dependency on the deformation rate although the strain rate dependence of material properties was not considered. Furthermore, a prediction method for the dynamic stress state on the impact side based on the static stress-strain relationship was presented.

  4. Study of an athermal quasi static plastic deformation in a 2D granular material

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Zheng, Jie

    2016-11-01

    In crystalline materials, the plasticity has been well understood in terms of dynamics of dislocation, i.e. flow defects in the crystals where the flow defects can be directly visualized under a microscope. In a contrast, the plasticity in amorphous materials, i.e. glass, is still poorly understood due to the disordered nature of the materials. In this talk, I will discuss the recent results we have obtained in our ongoing research of the plasticity of a 2D glass in the athermal quasi static limit where the 2D glass is made of bi-disperse granular disks with very low friction. Starting from a densely packed homogeneous and isotropic initial state, we apply pure shear deformation to the system. For a sufficiently small strain, the response of the system is linear and elastic like; when the strain is large enough, the plasticity of the system gradually develops and eventually the shear bands are fully developed. In this study, we are particularly interested in how to relate the local plastic deformation to the macroscopic response of the system and also in the development of the shear bands.

  5. The effect of hydrogen on the parameters of plastic deformation localization in low carbon steel

    SciTech Connect

    Lunev, Aleksey G. E-mail: nadjozhkin@ispms.tsc.ru; Nadezhkin, Mikhail V. E-mail: nadjozhkin@ispms.tsc.ru; Shlyakhova, Galina V.; Barannikova, Svetlana A.; Zuev, Lev B.

    2014-11-14

    In the present study, the effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested polycrystals of low-carbon steel Fe-0.07%C has been studied using double exposure speckle photography technique. The main parameters of plastic flow localization at various stages of deformation hardening have been determined in polycrystals of steel electrolytically saturated with hydrogen in a three-electrode electrochemical cell at a controlled constant cathode potential. Also, the effect of hydrogen on changing of microstructure by using optical microscopy has been demonstrated.

  6. A plane strain analysis of the blunted crack tip using small strain deformation plasticity theory

    NASA Technical Reports Server (NTRS)

    Mcgowan, J. J.; Smith, C. W.

    1976-01-01

    A deformation plasticity analysis of the tip region of a blunted crack in plane strain is presented. The power hardening material is incompressible both elastically and plastically, in order to simulate behavior of a stress freezing material above critical temperature. Stress and displacement fields surrounding the crack tip are presented. The results indicate that the maximum stress seen at the crack tip is indeed limited and is determined by the tensile properties; however, the scale over which the stresses act is dependent on the loading. Comparisons are good between the forward crack tip displacement and micro-fractographic measurments of stretch zones observed in plane strain fracture toughness tests.

  7. Deformation temperature, strain rate, and irradiation microstructure effects on localized plasticity in 304L SS

    SciTech Connect

    Cole, J.I.; Brimhall, J.L.; Vetrano, J.S.; Bruemmer, S.M.

    1995-12-31

    The present study examines the deformation behavior of ion-irradiated, low-carbon 304L stainless steel to investigate the influence of irradiation microstructure, deformation temperature and strain rate on localized plasticity. Dislocation loop character, size and density are linked to changes in deformation character. Lower doses produce small faulted loops and stacking fault tetrahedra that impede dislocation mobility. Dislocations are pinned at defects and require higher stress to break free from the defects. Larger defects take the form of faulted Frank loops that can interact with glide dislocations to form microtwins at lower temperatures and faster strain rates. Deformation at higher temperatures and slower strain rates promotes interactions between glide dislocations and loops leading to loop annihilation. Dislocation free zones or ``channels`` form where further plastic deformation is highly localized. Results are compared to limited observations for neutron-irradiated materials. These irradiation-induced changes can be an important concern for light-water reactor (LWR) stainless steel (SS) structural components due to a reduced damage tolerance, and potential susceptibility to environmental cracking such as irradiation-assisted stress corrosion cracking (IASCC).

  8. Water ice phases II, III, and V - Plastic deformation and phase relationships

    NASA Technical Reports Server (NTRS)

    Durham, W. B.; Boro, C. O.; Kirby, S. H.; Stern, L. A.; Heard, H. C.

    1988-01-01

    The ordinary water phase I was transformed to the ice phases that are known to exist in the interiors of large ice moons, such as Ganymede and Callisto for the purpose of investigating plastic deformation behavior of these ices. Ices II, III, and V were prepared using an apparatus and techniques similar to those described by Durham et al. (1983) and subsequently deformed in a gas deformation apparatus, and their deformation data were obtained. It was found that ice II was the strongest of the high-pressure phases, with a strength that was comparable to that of ice I; ice III was very weak, with the flow rate 100 to 1000 times higher than that of ice II at the same levels of stress. It was also found that ices III and V can exist metastably within the ice II field and that they may be deformed plastically within much of the metastable region without reverting to ice II. It is suggested that the weakness of the ice III phase may have profoundly influenced the evolution and the present-day behavior of the icy moons.

  9. Deformation effect on plastic and elastic stress components in grains with different bending

    NASA Astrophysics Data System (ADS)

    Kozlov, Eduard; Kiseleva, Svetlana; Popova, Natalya; Koneva, Nina

    2016-11-01

    The paper presents the investigations of deformation processes in polycrystal. Austenitic steel of the type 1.1C-13Mn-Fe is subjected to tensile deformation on a test machine at a rate of 3.4×10-4 s-1 and room temperature. The suggested experimental methodology implies the recovery of internal stresses using the parameters of the bend extinction contours observed on TEM images of the deformed polycrystal structure. The contribution of plastic and elastic stress components is determined in this paper. The analysis of these components is given for grains with different bending in deformed austenitic steel specimens. TEM images are obtained for a single polycrystal grain at different goniometer inclinations. The experimental findings are given for different degrees of steel deformation resulting in its rupture. It is shown that in the vicinity of the material rupture (ɛ = 36%), the plastic component mostly contributes to the internal stresses, while the contribution of elastic component is considerably reduced. The obtained results are compared to the defective structure of austenitic steel specimens.

  10. Water ice phases II, III, and V - Plastic deformation and phase relationships

    NASA Technical Reports Server (NTRS)

    Durham, W. B.; Boro, C. O.; Kirby, S. H.; Stern, L. A.; Heard, H. C.

    1988-01-01

    The ordinary water phase I was transformed to the ice phases that are known to exist in the interiors of large ice moons, such as Ganymede and Callisto for the purpose of investigating plastic deformation behavior of these ices. Ices II, III, and V were prepared using an apparatus and techniques similar to those described by Durham et al. (1983) and subsequently deformed in a gas deformation apparatus, and their deformation data were obtained. It was found that ice II was the strongest of the high-pressure phases, with a strength that was comparable to that of ice I; ice III was very weak, with the flow rate 100 to 1000 times higher than that of ice II at the same levels of stress. It was also found that ices III and V can exist metastably within the ice II field and that they may be deformed plastically within much of the metastable region without reverting to ice II. It is suggested that the weakness of the ice III phase may have profoundly influenced the evolution and the present-day behavior of the icy moons.

  11. Phase transformation dependence on initial plastic deformation mode in Si via nanoindentation

    SciTech Connect

    Wong, Sherman; Haberl, Bianca; Williams, James S.; Bradby, Jodie E.

    2016-09-30

    Silicon in its diamond-cubic phase is known to phase transform to a technologically interesting mixture of the body-centred cubic and rhombohedral phases under nanoindentation pressure. In this study, we demonstrate that during plastic deformation the sample can traverse two distinct pathways, one that initially nucleates a phase transformation while the other initially nucleates crystalline defects. These two pathways remain distinct even after sufficient pressure is applied such that both deformation mechanisms are present within the sample. Here, it is further shown that the indents that initially nucleate a phase transformation generate larger, more uniform volumes of the phase transformed material than indents that initially nucleate crystalline defects.

  12. Phase transformation dependence on initial plastic deformation mode in Si via nanoindentation

    SciTech Connect

    Wong, Sherman; Haberl, Bianca; Williams, James S.; Bradby, Jodie E.

    2016-09-30

    Silicon in its diamond-cubic phase is known to phase transform to a technologically interesting mixture of the body-centred cubic and rhombohedral phases under nanoindentation pressure. In this study, we demonstrate that during plastic deformation the sample can traverse two distinct pathways, one that initially nucleates a phase transformation while the other initially nucleates crystalline defects. These two pathways remain distinct even after sufficient pressure is applied such that both deformation mechanisms are present within the sample. Here, it is further shown that the indents that initially nucleate a phase transformation generate larger, more uniform volumes of the phase transformed material than indents that initially nucleate crystalline defects.

  13. Fundamental microstructural issues associated with severe plastic deformation: Applications of transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Esquivel, Erika Vanessa

    This study deals with the microstructural response of several metals and alloys to severe plastic deformation (SPD) in the form of shock wave loading, impact cratering, explosive welding, and ballistic penetration. Microstructural issues that will be addressed include dynamic recrystallization, adiabatic shear bands, and microbands and microtwins. Other relevant issues are stacking fault free energy (SFE), shock wave geometry and grain boundary contributions to the deformation response. The study focuses mainly on the deformation behavior correlated from the microstructural response of nickel and 304 stainless steel, but the behavior of other metals and alloys such as aluminum, copper, brass, tungsten-tantalum and steel are also discussed. These metals cover a wide range of SFE in the face centered cubic systems (FCC) as well as body centered cubic (BCC) structures. There is an emphasis on the microstructure as seen through the transmission electron microscope (TEM) but this is complemented by light microscopy to provide a more global microscopic context. Observations revealed that microtwins will form in planar shock wave treatment of FCC metals and alloys above a critical shock twinning pressure, which is itself a function of SFE. In hypervelocity impact craters, microbands will form for higher SFE materials such as Al, Ni, and Cu, whereas microtwins form exclusively in lower SFE material such as brass, and a combination of both microbands and microtwins will form in materials of intermediate SFE. Both SFE and shock wave geometry influence the material behavior in response to such dynamic processes such that SFE dictates the feasibility of cross-slip and the shock wave geometry, being planar promotes slip along primary slip planes while a spherical shock wave encourages cross-slip. In ballistic penetration it has been observed that overlapping shear bands, associated with dynamic recovery and recrystallization structures allow the penetrator to 'flow.' In all

  14. Numerical simulation of plastic deformation and damage accumulation in structural materials under various low-cycle loading conditions

    NASA Astrophysics Data System (ADS)

    Gorokhov, V. A.; Kapustin, S. A.; Churilov, Yu. A.

    2017-05-01

    This paper presents the results of a finite-element study of elastic-plastic deformation and damage accumulation in structural materials under various cyclic loading conditions. Material behavior is described by the relations of damage mechanics using thermoplastic model which takes into account the plastic deformation of material under cyclic loading and the kinetic equations of the energy theory of damage accumulation. The basic laws of plastic deformation and development of damage in materials under hard, soft, symmetric, and asymmetric low-cycle loading are established.

  15. A gradient crystal plasticity theory for large deformations with a discontinuous accumulated plastic slip

    NASA Astrophysics Data System (ADS)

    Erdle, Hannes; Böhlke, Thomas

    2017-07-01

    The implementation of novel material models in the microscale gives a deeper understanding of inner and intercrystalline effects of crystalline materials. For future works, this allows more precise predictions of macroscale models. Here, we present a finite gradient crystal plasticity theory which preserves the single crystal slip kinematics. However, the model is restricted to one gradient-stress, associated with the gradient of the accumulated plastic slip, in order to account for long range dislocation interactions in a physically simplified, numerically efficient approach. In order to model the interaction of dislocations with and their transfer through grain boundaries, a grain boundary yield condition is introduced. The grain boundary flow rule is evaluated at sharp interfaces using discontinuous trial functions in the finite element implementation, thereby allowing for a discontinuous distribution of the accumulated plastic slip. Simulations of crystal aggregates are performed under different loading conditions which reproduce well the size dependence of the yield strength. An analytical solution for a one-dimensional single slip supports the numerical results.

  16. An experimental study on the brittle-plastic transition during deformation of granite

    NASA Astrophysics Data System (ADS)

    Dang, Jiaxiang; Zhou, Yongsheng; Rybacki, Erik; He, Changrong; Dresen, Georg

    2017-05-01

    Naturally and experimentally deformed samples of granite show that the deformation mechanisms of plagioclase and K-feldspar are different. To investigate these mechanisms and the brittle-plastic transition that takes place in granitic rocks composed of quartz, plagioclase, and K-feldspar, five leucosome granite samples were deformed with a constant strain rate of 10-5 s-1 at different temperatures from 850 °C to 1050 °C and confining pressure (CP) of 300 MPa using a Paterson-type gas deformation apparatus. To consider pressure effects, two more samples were deformed at 950 °C but with different CPs, one with CP = 100 kPa and the other with CP = 100 MPa. In addition, an eighth sample was deformed under torsion shear at 950 °C with CP = 400 MPa. Microstructures of an undeformed sample and experimentally deformed samples were analyzed using an optical microscope and a scanning electron microscope. The granite is composed of about 36 volume percent quartz, ∼26% plagioclase, ∼34% microcline, ∼3% muscovite, and ∼1% chlorite. The stress-strain curves for all but two samples display weakening. The two exceptions are the sample that deformed with steady-state creep under a CP of 100 MPa and the sample that displayed brittle fracture under a CP of 100 kPa. For the other samples, peak strengths decreased with increasing temperature or lower CP. Microstructures show that samples underwent a brittle-plastic transition with increasing temperature. Samples fractured by cataclastic flow at 850 °C with CP = 300 MPa and at 950 °C with CP = 100 kPa. Microcline deformed by cataclastic flow at 900-1050 °C with CP = 100-400 MPa accompanied by dislocation glide at temperatures of 1000 °C and 1050 °C. At 900-1050 °C with CP = 100-400 MPa, plagioclase displayed bulging recrystallization and grain boundary migration recrystallization and quartz deformed by subgrain rotation recrystallization. Diffusion rims were observed between quartz, plagioclase, and microcline grain

  17. Investigations of a nanostructured FeMnSi shape memory alloy produced via severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Gurau, Gheorghe; Gurau, Carmela; Sampath, Vedamanickam; Bujoreanu, Leandru Gheorghe

    2016-11-01

    Low-cost iron-based shape memory alloys (SMAs) show great potential for engineering applications. The developments of new processing techniques have recently enabled the production of nanocrystalline materials with improved properties. These developments have opened avenues for newer applications for SMAs. The influence of severe plastic deformation induced by the high-speed high-pressure torsion (HSHPT) process on the microstructural evolution of an Fe-Mn-Si-Cr alloy was investigated. Transmission electron microscopic analysis of the alloy revealed the existence of nanoscale grains with an abundance of stacking faults. The high density of dislocations characteristic of severe plastic deformation was not observed in this alloy. X-ray diffraction studies revealed the presence of ɛ-martensite with an HCP crystal structure and γ-phase with an FCC structure.

  18. Transition of temporal scaling behavior in percolation assisted shear-branching structure during plastic deformation

    DOE PAGES

    Ren, Jingli; Chen, Cun; Wang, Gang; ...

    2017-03-22

    This study explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10–2 s–1; the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at the intermediate temperature.more » Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10–2 s–1.« less

  19. Crystal plasticity modeling of β phase deformation in Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Moore, John A.; Barton, Nathan R.; Florando, Jeff; Mulay, Rupalee; Kumar, Mukul

    2017-10-01

    Ti-6Al-4V is an alloy of titanium that dominates titanium usage in applications ranging from mass-produced consumer goods to high-end aerospace parts. The material’s structure on a microscale is known to affect its mechanical properties but these effects are not fully understood. Specifically, this work will address the effects of low volume fraction intergranular β phase on Ti-6Al-4V’s mechanical response during the transition from elastic to plastic deformation. A crystal plasticity-based finite element model is used to fully resolve the deformation of the β phase for the first time. This high fidelity model captures mechanisms difficult to access via experiments or lower fidelity models. The results are used to assess lower fidelity modeling assumptions and identify phenomena that have ramifications for failure of the material.

  20. Characterization of Plastic Deformation Behavior of a Thermally Aged Duplex Stainless Steel

    NASA Astrophysics Data System (ADS)

    Liu, Gang; Wang, Yanli; Li, Shilei; Zhang, Hailong; Wang, Xitao

    2017-05-01

    In situ tensile tests at room temperature have been conducted on a duplex stainless steel (DSS) thermally aged at 400 °C for 10,000 h to investigate both the plastic deformation mechanisms and the effect of long-term thermal aging on crack initiation. After thermal aging, the ultimate tensile strength of the DSS increases and the plasticity significantly decreases. The fracture morphology changes from ductile fracture with shallow dimples to a mixture of cleavages in ferrite and tearing in austenite. Electron backscattered diffraction (EBSD) technique has been used to determine the crystallographic orientations of austenite and ferrite grains on three areas deformed differently. The EBSD analysis results indicate that high strain occurs near grain boundaries and phase boundaries. The localized strain incompatibility is considered to be responsible for high stress concentration and crack initiation. The long-term thermal aging affect on the crack initiation and the cleavage cracks are found to be initiated in aged ferrite grains.

  1. Ipsilateral Plastic Deformation Monteggia and Galeazzi-Type Fracture in a Child: A Case Report.

    PubMed

    Greer, Andrew; Lowry, Christopher John; Ramlakhan, Shammi

    2017-05-01

    A 7-year-old boy attended the emergency department after falling from a climbing frame onto his outstretched left wrist. On examination, there was mild swelling to the left elbow and tenderness to the antecubital fossa. There was also tenderness diffusely to the distal ulnar and radius. There was no neurovascular deficit. Radiographs revealed a plastic deformation fracture of the left radius and ulna, with dislocations of the ipsilateral radiocapitellar joint and distal radioulnar joint. A diagnosis of combined Monteggia and Galeazzi-type fractures of the left forearm was made. It is rare to find cases of combined Monteggia and Galeazzi fractures to the same forearm. Furthermore, to our knowledge, ipsilateral plastic deformation Monteggia and Galeazzi-type fractures in children have not been reported in the literature. Copyright © 2016 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.

  2. Plastic deformation of quartz at room temperature by SEM in situ micropillar compression

    NASA Astrophysics Data System (ADS)

    Maeder, X.; Ghisleni, R.; Michler, J.

    2010-12-01

    parallel to the z-axis show basal {c} slip. SEM insitu micropillar compression offers the great advantage to have a very well defined state of stress. In addition it allows real-time in-situ microstructure study during the deformation. It is therefore a very promising method to study plastic deformation behavior and the dislocation mechanisms of rock minerals. Ref.: Michler, J., K. Wasmer, S. Meier, F. Ostlund and K. Leifer (2007): Plastic deformation of gallium arsenide micropillars under uniaxial compression at room temperature. Applied Physics Letters 90, 043123

  3. Structure of Al-Fe alloys prepared by different methods after severe plastic deformation under pressure

    NASA Astrophysics Data System (ADS)

    Dobromyslov, A. V.; Taluts, N. I.

    2017-06-01

    Al-Fe alloys prepared by casting, rapid quenching from the melt, and mechanical alloying from elemental powders have been studied using X-ray diffraction analysis, optical metallography, transmission electron microscopy, and microhardness measurements in the initial state and after severe plastic deformation by high-pressure torsion using Bridgman anvils. The relationship between the phase composition, microstructure, and the microhardness of the investigated alloys has been established.

  4. Detection of plastic deformation in structural steel using scanning SQUID microscopy

    NASA Astrophysics Data System (ADS)

    Bonavolontà, C.; Valentino, M.; Adamo, M.; Sarnelli, E.

    2007-07-01

    The magneto-mechanical behaviour of structural steel specimens stressed up to a plastic deformation stage using a high-Tc scanning SQUID (superconducting quantum interference device) microscope is investigated. The correlation between the gradient of the normal component of the magnetization and dislocation density, before the crack initiation, is carried out. The capability of scanning SQUID microscopy to detect the residual magnetization, due to the tensile stress, with a non-invasive technique is reported.

  5. A general numerical approximation of construction of axisymmetric ideal plastic plane deformation of a granular material

    NASA Astrophysics Data System (ADS)

    Damanhuri, Nor Alisa; Ayob, Syafikah

    2017-09-01

    A general numerical approximation of the stress equilibrium equations and constructing axisymmetric ideal plastic plane deformation of a granular material is considered. The stress components are assumed to satisfy the Coulomb yield criterion and the self-weight of the material is neglected. The standard method of numerical approximation leads to the construction of the small segments of the stress characteristic field. Using the Matlab program, the method is applied to a problem of granular indentation by a smooth flat surface.

  6. The plastic anisotropy of an Al-Li-Cu-Zr alloy extrusion in unidirectional deformation

    SciTech Connect

    Lyttle, M.T.; Wert, J.A.

    1996-11-01

    The plastic anisotropy resulting from the initial deformation microstructure and various aging treatments applied to several regions of an AA2090 near-net-shape extrusion has been investigated. Yield behavior was measured by uniaxial compression in multiple orientations of each region. Two models of the plastic anisotropy were generated: the Taylor/Bishop-Hill model, based on crystallographic texture, and the plastic inclusion model, developed by Hosford and Zeisloft, which incorporates anisotropic-precipitate effects. In overaged conditions, the Taylor/Bishop-Hill model adequately describes the observed plastic anisotropy. As the strengthening increment due to second-phase particles increases, there is a concurrent increase in the magnitude of the precipitate contribution to anisotropy. This anisotropy can not be accurately predicted solely by crystallographic texture. By incorporation of terms describing the precipitate anisotropy, the plastic inclusion model correctly predicts the yield strength variation in all regions tested. Examination of the fundamental interaction between matrix and precipitation strengthening reveals that there is a stronger basis for taking the critical resolved shear stress (CRSS) of the precipitates as a constant, rather than their effective yield strength. This consideration provides a more consistent and accurate form of the plastic inclusion model.

  7. The plastic anisotropy of an Al-Li-Cu-Zr alloy extrusion in unidirectional deformation

    NASA Astrophysics Data System (ADS)

    Lyttle, M. T.; Wert, J. A.

    1996-11-01

    The plastic anisotropy resulting from the initial deformation microstructure and various aging treatments applied to several regions of an AA2090 near-net-shape extrusion has been investigated. Yield behavior was measured by uniaxial compression in multiple orientations of each region. Two models of the plastic anisotropy were generated: the Taylor/Bishop-Hill model, based on crystallographic texture, and the plastic inclusion model, developed by Hosford and Zeisloft,[5] which incorporates anisotropic-precipitate effects. In overaged conditions, the Taylor/Bishop-Hill model adequately describes the observed plastic anisotropy. As the strengthening increment due to second-phase particles increases, there is a concurrent increase in the magnitude of the precipitate contribution to anisotropy. This anisotropy can not be accurately predicted solely by crystallographic texture. By incorporation of terms describing the precipitate anisotropy, the plastic inclusion model correctly predicts the yield strength variation in all regions tested. Examination of the fundamental interaction between matrix and precipitation strengthening reveals that there is a stronger basis for taking the critical resolved shear stress (CRSS) of the precipitates as a constant, rather than their effective yield strength. This consideration provides a more consistent and accurate form of the plastic inclusion model.

  8. Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Park, Jingee; Lee, Jongshin; You, Bongsun; Choi, Seogou; Kim, Youngsuk

    2007-05-01

    Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model.

  9. Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature

    SciTech Connect

    Park, Jingee; Lee, Jongshin; You, Bongsun; Choi, Seogou; Kim, Youngsuk

    2007-05-17

    Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model.

  10. Ultrasound Velocity Measurements in High-Chromium Steel Under Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Lunev, Aleksey; Bochkareva, Anna; Barannikova, Svetlana; Zuev, Lev

    2016-04-01

    In the present study, the variation of the propagation velocity of ultrasound in the plastic deformation of corrosion-resistant high-chromium steel 40X13 with ferrite-carbide (delivery status), martensitic (quenched) and sorbitol (after high-temperature tempering) structures have beem studied/ It is found that each state shows its view of the loading curve. In the delivery state diagram loading is substantially parabolic throughout, while in the martensitic state contains only linear strain hardening step and in the sorbitol state the plastic flow curve is three-step. The velocity of ultrasonic surface waves (Rayleigh waves) was measured simultaneously with the registration of the loading curve in the investigated steel in tension. It is shown that the dependence of the velocity of ultrasound in active loading is determined by the law of plastic flow, that is, the staging of the corresponding diagram of loading. Structural state of the investigated steel is not only changing the type of the deformation curve under uniaxial tension, but also changes the nature of ultrasound speed of deformation.

  11. Yielding, Plasticity, and Microstructure in a 2D Jammed Material under Shear Deformation

    NASA Astrophysics Data System (ADS)

    Arratia, Paulo; Keim, Nathan

    2015-03-01

    In this talk, we discuss an experimental investigation on the yielding and plastic deformation of disordered solids. Experiments are performed on colloidal particles that are adsorbed at an oil-water interface and form a dense disordered monolayer. The rheological properties (G', G'') of this dense monolayer are obtained in a custom-built interfacial stress rheometer that uses a magnetic needle within the material. This configuration allows for the simultaneous characterization of both microstructure (tracking ~ 105 particles) and bulk rheology. Results show that for oscillatory shear below a certain strain amplitude, the microstructure becomes reversible after a transient. Above this strain amplitude, the microstructure continues to evolve through many irreversible events. We argue that this boundary between a reversible and irreversible steady state is a yielding transition, and that our experiments measure a meaningful yield stress. Further, we find that reversible plastic deformation is possible. That is, the material can reorganize itself so that the link between plasticity and irreversibility is broken: the material flows slightly, and yet at the end of each deformation cycle, it is exactly unchanged. Now at California Polytechnic State University at San Luis Obispo.

  12. Severe plastic deformation processing and high strain rate superplasticity in an aluminum matrix composite

    SciTech Connect

    Mishra, R.S.; McFadden, S.X.; Mukherjee, A.K.; Valiev, R.Z.; Islamgaliev, R.K.

    1999-04-23

    Metal matrix composites possess an attractive set of properties for structural applications. For example, reinforcement of conventional aluminum alloys with second phase ceramic particulates increases the stiffness, high temperature strength, etc. A drawback of ceramic phase reinforcement is that it makes machining of components difficult. Superplastic forming is quite attractive for hard-to-machine materials like composites. A number of aluminum matrix composites exhibit superplasticity. The most attractive feature of superplasticity in aluminum matrix composite is the high strain rate (10{sup {minus}2}--10{sup 1} s{sup {minus}1}) for optimum ductility. This is significantly higher than the optimum superplastic strain rates of 10{sup {minus}4}--10{sup {minus}3} s{sup {minus}1} in conventional fine grained alloys. The optimum superplasticity in aluminum matrix composites is influenced by the thermo-mechanical processing. In the last five years or so, a number of aluminum alloys have been processes by severe plastic deformation (SePD). Severe plastic deformation processing leads to ultrafine grained aluminum alloys with attractive superplastic properties. In this short paper the authors report on successful processing of an ultrafine grained aluminum matrix composite by severe plastic deformation technique. The SePD processes 2009 Al-SiC{sub 2} composite exhibits high strain rate superplasticity.

  13. Effect of inherent deformations of leadframes on bleedability of plastic dip

    NASA Astrophysics Data System (ADS)

    Kerk, S. L.; Tay, S. C.; Hu, S. J.

    1989-03-01

    Variance formed between the mold plate and the leadframe causes resin bleed on the leads of the plastic 40L Dual In-Line Package (PDIP 40L). Resin bleed affects the solderability of the package. The mechanical stamping method used in the production of the copper leadframes causes dented deformation at the edge of the leads of the leadframe. A perfect uniform flatness on the surface of the copper leadframe is also not possible. Study is carried out to investigate the effect of these inherent deformations of stamped copper leadframes' surface on the resin bleed-out of the plastic DIP. The results show that two types of bleed rejects occurred because of the stamping induced deformation found at the edge of the leads of the copper leadframes and the non uniform flatness of the surface on the copper leadframes. Resin bleedability and non-solderability can be eliminated when chemically etched copper leadframes are used for the plastic Dual-In-Line Packages.

  14. Size-dependent plastic deformation of twinned nanopillars in body-centered cubic tungsten

    NASA Astrophysics Data System (ADS)

    Xu, Shuozhi; Startt, Jacob K.; Payne, Thomas G.; Deo, Chaitanya S.; McDowell, David L.

    2017-05-01

    Compared with face-centered cubic metals, twinned nanopillars in body-centered cubic (BCC) systems are much less explored partly due to the more complicated plastic deformation behavior and a lack of reliable interatomic potentials for the latter. In this paper, the fault energies predicted by two semi-empirical interatomic potentials in BCC tungsten (W) are first benchmarked against density functional theory calculations. Then, the more accurate potential is employed in large scale molecular dynamics simulations of tensile and compressive loading of twinned nanopillars in BCC W with different cross sectional shapes and sizes. A single crystal, a twinned crystal, and single crystalline nanopillars are also studied as references. Analyses of the stress-strain response and defect nucleation reveal a strong tension-compression asymmetry and a weak pillar size dependence in the yield strength. Under both tensile and compressive loading, plastic deformation in the twinned nanopillars is dominated by dislocation slip on {110} planes that are nucleated from the intersections between the twin boundary and the pillar surface. It is also found that the cross sectional shape of nanopillars affects the strength and the initial site of defect nucleation but not the overall stress-strain response and plastic deformation behavior.

  15. Cell response to nanocrystallized metallic substrates obtained through severe plastic deformation.

    PubMed

    Bagherifard, Sara; Ghelichi, Ramin; Khademhosseini, Ali; Guagliano, Mario

    2014-06-11

    Cell-substrate interface is known to control the cell response and subsequent cell functions. Among the various biophysical signals, grain structure, which indicates the repeating arrangement of atoms in the material, has also proved to play a role of significant importance in mediating the cell activities. Moreover, refining the grain size through severe plastic deformation is known to provide the processed material with novel mechanical properties. The potential application of such advanced materials as biomedical implants has recently been evaluated by investigating the effect of different substrate grain sizes on a wide variety of cell activities. In this review, recent advances in biomedical applications of severe plastic deformation techniques are highlighted with special attention to the effect of the obtained nano/ultra-fine-grain size on cell-substrate interactions. Various severe plastic deformation techniques used for this purpose are discussed presenting a brief description of the mechanism for each process. The results obtained for each treatment on cell morphology, adhesion, proliferation, and differentiation, as well as the in vivo studies, are discussed. Finally, the advantages and challenges regarding the application of these techniques to produce multifunctional bio-implant materials are addressed.

  16. Atomistic simulation on the plastic deformation and fracture of bio-inspired graphene/Ni nanocomposites

    NASA Astrophysics Data System (ADS)

    Yang, Zhenyu; Wang, Dandan; Lu, Zixing; Hu, Wenjun

    2016-11-01

    Molecular dynamics simulations were performed to investigate the plastic deformation and fracture behaviors of bio-inspired graphene/metal nanocomposites, which have a "brick-and-mortar" nanostructure, consisting of hard graphene single-layers embedded in a soft Ni matrix. The plastic deformation mechanisms of the nanocomposites were analyzed as well as their effects on the mechanical properties with various geometrical variations. It was found that the strength and ductility of the metal matrix can be highly enhanced with the addition of the staggered graphene layers, and the plastic deformation can be attributed to the interfacial sliding, dislocation nucleation, and cracks' combination. The strength of the nanocomposites strongly depends on the length scale of the nanostructure and the interlayer distance as well. In addition, slip at the interface releases the stress in graphene layers, leading to the stress distribution on the graphene more uniform. The present results are expected to contribute to the design of the nanolayered graphene/metal composites with high performance.

  17. Wireless measurement of elastic and plastic deformation by a metamaterial-based sensor.

    PubMed

    Ozbey, Burak; Demir, Hilmi Volkan; Kurc, Ozgur; Erturk, Vakur B; Altintas, Ayhan

    2014-10-20

    We report remote strain and displacement measurement during elastic and plastic deformation using a metamaterial-based wireless and passive sensor. The sensor is made of a comb-like nested split ring resonator (NSRR) probe operating in the near-field of an antenna, which functions as both the transmitter and the receiver. The NSRR probe is fixed on a standard steel reinforcing bar (rebar), and its frequency response is monitored telemetrically by a network analyzer connected to the antenna across the whole stress-strain curve. This wireless measurement includes both the elastic and plastic region deformation together for the first time, where wired technologies, like strain gauges, typically fail to capture. The experiments are further repeated in the presence of a concrete block between the antenna and the probe, and it is shown that the sensing system is capable of functioning through the concrete. The comparison of the wireless sensor measurement with those undertaken using strain gauges and extensometers reveals that the sensor is able to measure both the average strain and the relative displacement on the rebar as a result of the applied force in a considerably accurate way. The performance of the sensor is tested for different types of misalignments that can possibly occur due to the acting force. These results indicate that the metamaterial-based sensor holds great promise for its accurate, robust and wireless measurement of the elastic and plastic deformation of a rebar, providing beneficial information for remote structural health monitoring and post-earthquake damage assessment.

  18. Unusual plastic deformation and damage features in titanium: Experimental tests and constitutive modeling

    NASA Astrophysics Data System (ADS)

    Revil-Baudard, Benoit; Cazacu, Oana; Flater, Philip; Chandola, Nitin; Alves, J. L.

    2016-03-01

    In this paper, we present an experimental study on plastic deformation and damage of polycrystalline pure HCP Ti, as well as modeling of the observed behavior. Mechanical characterization data were conducted, which indicate that the material is orthotropic and displays tension-compression asymmetry. The ex-situ and in-situ X-ray tomography measurements conducted reveal that damage distribution and evolution in this HCP Ti material is markedly different than in a typical FCC material such as copper. Stewart and Cazacu (2011) anisotropic elastic/plastic damage model is used to describe the behavior. All the parameters involved in this model have a clear physical significance, being related to plastic properties, and are determined from very few simple mechanical tests. It is shown that this model predicts correctly the anisotropy in plastic deformation, and its strong influence on damage distribution and damage accumulation. Specifically, for a smooth axisymmetric specimen subject to uniaxial tension, damage initiates at the center of the specimen, and is diffuse; the level of damage close to failure being very low. On the other hand, for a notched specimen subject to the same loading the model predicts that damage initiates at the outer surface of the specimen, and further grows from the outer surface to the center of the specimen, which corroborates with the in-situ tomography data.

  19. Plastic Deformations of Measured Object Surface in Contact with Undeformable Surface of Measuring Tool

    NASA Astrophysics Data System (ADS)

    Kowalik, Marek; Rucki, Mirosław; Paszta, Piotr; Gołębski, Rafał

    2016-10-01

    Measuring errors caused by deformation (flattening) of a measured object appear under the influence of pressure force and weight of the measured object. Plastic strain, arising at the contact of a measured object and an undeformable contact tip of a measuring device, can be calculated by applying the Hertz plastic solution and the hypothesis of plastic strain. In a small area of contact between two bodies pressing against one another with force F, there appears the so-called contact stress. It can sometime reach very high values, exceeding the yield point, even when the contact pressure is relatively small. In the present work, the authors describe a theoretical solution to the problem of plastic strain between two bodies. The derived relationships enable to calculate force F during measurements of a deformable object by means of an instrument with an undeformable, spherical measuring tip. By applying the τmax hypothesis, a solution was obtained for the force F in an inexplicit form. The theoretical solution was verified with the digital simulation and experimental measurement. With the FEM method, the limit length gage was modeled in interaction with the measured shaft of a diameter d larger than the nominal one of Δl value.

  20. Simulation of high-temperature superlocalization of plastic deformation in single-crystals of alloys with an L12 superstructure

    NASA Astrophysics Data System (ADS)

    Solov'eva, Yu. V.; Fakhrutdinova, Ya. D.; Starenchenko, V. A.

    2015-01-01

    The processes of the superlocalization of plastic deformation in L12 alloys have been studied numerically based on a combination of the model of the dislocation kinetics of the deformation-induced and heat-treatment-induced strengthening of an element of a deformable medium with the model of the mechanics of microplastic deformation described in terms of elastoplastic medium. It has been shown that the superlocalization of plastic deformation is determined by the presence of stress concentrators and by the nonmonotonic strengthening of the elements of the deformable medium. The multiple nonmonotonicity of the process of strengthening of the elementary volume of the medium can be responsible for the multiplicity of bands of microplastic localization of deformation.

  1. Effects of water on the plastic deformation and deformation microstructure of olivine

    NASA Astrophysics Data System (ADS)

    Jung, Haemyeong

    Deformation experiments on olivine were conducted in simple shear geometry under both water-poor ("dry") and water-saturated ("wet") conditions at high pressures (0.5--2.2 GPa) and high temperatures (1400--1570 K) using the Griggs apparatus. Hot-pressed synthetic olivine aggregates and single crystals of olivine were used as starting materials. Water was supplied by a mixture of talc and brucite during the experiment and water content of samples was determined by the FT-IR spectroscopy after each experiment. Under these conditions, a wide range of water fugacity can be explored up to ˜13 GPa and we have identified significant effects of water both on microstructures and on rheology. Water affects microstructures of deformed olivine in two ways: (1) the size of dynamically recrystallized grains under water-rich conditions is significantly larger than that under water-poor conditions and (2) the pattern of lattice preferred orientation (LPO) is different under water-rich conditions from those under water-poor conditions. These observations indicate that water enhances grain-boundary migration and also changes the relative easiness of slip systems in olivine. The LPOs found under water-rich conditions are characterized by strong peaks of [001] poles at ˜20--30° from the shear direction, although the maxima of poles of other crystallographic axes depend also on the stress level. A diagram showing the relationship between LPO and deformation conditions was constructed. The results indicate that the relationship between seismic anisotropy and flow geometry depends on water content as well as stress level. The role of water on rheology was investigated through the analyses of stress versus strain-rate relationship under various pressures using dislocation densities as a stress indicator. We found that when the system is saturated with water, the strength of olivine changes with pressure in non-monotonic way: the strength decreases with pressure at low pressures, but

  2. Plastic Deformation of Micromachined Silicon Diaphragms with a Sealed Cavity at High Temperatures

    PubMed Central

    Ren, Juan; Ward, Michael; Kinnell, Peter; Craddock, Russell; Wei, Xueyong

    2016-01-01

    Single crystal silicon (SCS) diaphragms are widely used as pressure sensitive elements in micromachined pressure sensors. However, for harsh environments applications, pure silicon diaphragms are hardly used because of the deterioration of SCS in both electrical and mechanical properties. To survive at the elevated temperature, the silicon structures must work in combination with other advanced materials, such as silicon carbide (SiC) or silicon on insulator (SOI), for improved performance and reduced cost. Hence, in order to extend the operating temperatures of existing SCS microstructures, this work investigates the mechanical behavior of pressurized SCS diaphragms at high temperatures. A model was developed to predict the plastic deformation of SCS diaphragms and was verified by the experiments. The evolution of the deformation was obtained by studying the surface profiles at different anneal stages. The slow continuous deformation was considered as creep for the diaphragms with a radius of 2.5 mm at 600 °C. The occurrence of plastic deformation was successfully predicted by the model and was observed at the operating temperature of 800 °C and 900 °C, respectively. PMID:26861332

  3. Influence of Niobium on the Beginning of the Plastic Flow of Material during Cold Deformation

    PubMed Central

    2013-01-01

    Investigations were conducted on low-carbon steel and the steel with same chemical composition with addition of microalloying element niobium. While tensile testing was carried out, the thermographic measurement was tacking place simultaneously. A specific behavior of niobium microalloyed steel was noticed. Test results have shown that, in the elastic deformation region, thermoelastic effect occurs, which is more pronounced in niobium microalloyed steel. Start of plastic flow in steel which is not microalloyed with niobium begins later in comparison to the microalloyed steel, and it is conducted so that, at the point of maximum stress, deformation zone is formed within which stresses grow. In steel microalloyed with niobium after proportionality limit, comes the occurrence of the localized increase in temperature and the occurrence of Lüders band, which propagate along the sample forming a deformation zone. PMID:24453896

  4. Influence of niobium on the beginning of the plastic flow of material during cold deformation.

    PubMed

    Rešković, Stoja; Jandrlić, Ivan

    2013-01-01

    Investigations were conducted on low-carbon steel and the steel with same chemical composition with addition of microalloying element niobium. While tensile testing was carried out, the thermographic measurement was tacking place simultaneously. A specific behavior of niobium microalloyed steel was noticed. Test results have shown that, in the elastic deformation region, thermoelastic effect occurs, which is more pronounced in niobium microalloyed steel. Start of plastic flow in steel which is not microalloyed with niobium begins later in comparison to the microalloyed steel, and it is conducted so that, at the point of maximum stress, deformation zone is formed within which stresses grow. In steel microalloyed with niobium after proportionality limit, comes the occurrence of the localized increase in temperature and the occurrence of Lüders band, which propagate along the sample forming a deformation zone.

  5. Severe plastic deformation through adiabatic shear banding in Fe-C steels

    SciTech Connect

    Lesuer, D; Syn, C; Sherby, O

    2004-12-01

    Severe plastic deformation is observed within adiabatic shear bands in iron-carbon steels. These shear bands form under high strain rate conditions, in excess of 1000 s{sup -1}, and strains in the order 5 or greater are commonly observed. Studies on shear band formation in a ultrahigh carbon steel (1.3%C) are described in the pearlitic condition. A hardness of 11.5 GPa (4600 MPa) is obtained within the band. A mechanism is described to explain the high strength based on phase transformation to austenite from adiabatic heating resulting from severe deformation. Rapid re-transformation leads to an ultra-fine ferrite grain size containing carbon principally in the form of nanosize carbides. It is proposed that the same mechanism explains the ultrahigh strength of iron-carbon steels observed in ball-milling, ball drop tests and in severely deformed wires.

  6. Evolution of yield surfaces and texture with finite plastic deformation in aluminum alloys

    NASA Astrophysics Data System (ADS)

    Pandey, Amit

    2009-12-01

    The primary objectives of this study are to determine the (i) evolution of subsequent yield surfaces based on 10muepsilon deviation from linearity; and (ii) to report a comprehensive study of anisotropy and texture evolution with finite plastic deformation. The first study gives comprehensive experimental results on subsequent yield surfaces of a high work hardening alloy under proportional and non proportional loading paths. The size of yield surfaces under non-proportional loading decrease and no cross-effect is observed; these yield surfaces are completely different under proportional loading where the size of the yield surfaces increase and show positive cross-effect. The experimental results on subsequent yield surfaces after proportional loading paths under tension-tension stress space, for a very low and a very high work hardening Al alloy, using 10muepsilon deviation from linearity as the definition of yield are presented. Subsequent yield surfaces are determined under axial, hoop, and combined hoop and axial proportional loading directions at various levels of plastic strain in each direction. Elastic moduli are also determined within each subsequent yield surface. Further, comprehensive responses of Al5754 and AZ31 are measured over wide ranges of strain rates and temperatures on same batch of two materials. These include the strain hardening, anisotropy, and texture evolution with finite plastic deformation. Tension, compression, and simple shear experiments at wide ranges of strain rates and temperatures are performed in rolling, transverse to rolling, and 45° to rolling directions. In addition, compression experiments were also performed in thickness direction. A new simple shear device is fabricated to perform simple shear experiments at elevated temperatures. Texture measurements are performed using neutron diffraction and EBSD in order to understand the deformation mechanisms of various specimens after finite deformation.

  7. 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

  8. The strain path dependence of plastic deformation response of AA5754: Experiment and modeling

    SciTech Connect

    Pham, Minh-Son; Hu, Lin; Iadicola, Mark; Creuziger, Adam; Rollett, Anthony D.

    2013-12-16

    This work presents modeling of experiments on a balanced biaxial (BB) pre-strained AA5754 alloy, subsequently reloaded uniaxially along the rolling direction and transverse direction. The material exhibits a complex plastic deformation response during the change in strain path due to 1) crystallographic texture, 2) aging (interactions between dislocations and Mg atoms) and 3) recovery (annihilation and re-arrangement of dislocations). With a BB prestrain of about 5 %, the aging process is dominant, and the yield strength for uniaxially deformed samples is observed to be higher than the flow stress during BB straining. The strain hardening rate after changing path is, however, lower than that for pre-straining. Higher degrees of pre-straining make the dynamic recovery more active. The dynamic recovery at higher strain levels compensates for the aging effect, and results in: 1) a reduction of the yield strength, and 2) an increase in the hardening rate of re-strained specimens along other directions. The yield strength of deformed samples is further reduced if these samples are left at room temperature to let static recovery occur. The synergistic influences of texture condition, aging and recovery processes on the material response make the modeling of strain path dependence of mechanical behavior of AA5754 challenging. In this study, the influence of crystallographic texture is taken into account by incorporating the latent hardening into a visco-plastic self-consistent model. Different strengths of dislocation glide interaction models in 24 slip systems are used to represent the latent hardening. Moreover, the aging and recovery effects are also included into the latent hardening model by considering strong interactions between dislocations and dissolved atom Mg and the microstructural evolution. These microstructural considerations provide a powerful capability to successfully describe the strain path dependence of plastic deformation behavior of AA5754.

  9. Microstructures in the 6060 aluminium alloy after various severe plastic deformation treatments

    SciTech Connect

    Adamczyk-Cieslak, Boguslawa Mizera, Jaroslaw; Kurzydlowski, Krzysztof Jan

    2011-03-15

    This paper presents the results concerning the microstructural refinement of the industrial 6060 aluminium alloy processed by severe plastic deformation (SPD). The high level of plastic deformation was achieved using the three methods: hydrostatic extrusion (HE), equal channel angular extrusion (ECAE) and extrusion torsion (ET), which differed in the dynamics of the loading, intensity and homogeneity of the plastic strain field. Microstructure analyses were performed before and after SPD deformation using a transmission (TEM) and a scanning electron microscope (SEM). The refined microstructures were examined qualitatively and quantitatively by the stereological methods and computer image analyses. The microstructure of the industrial 6060 aluminium alloy after deformation was characterized by an average grain size of about 0.4 {mu}m. The results show that the precipitates strongly affect the degree of refinement and the mechanism of microstructural transformations. During the SPD, the second phase particles break apart and homogenize. The HE method generates the largest increase of the volume fraction of the small primary particles. Moreover, the HE process is most effective in reducing the primary particle size. During HE and ECAE processes the second phase precipitates dissolve partially and change their shape. - Research Highlights: {yields} SPD results in a significant increase in the density of the small primary particles. {yields} SPD homogenizes the particle size distribution. {yields} HE and ECAE processes bring nano-grains in the vicinity of the primary particles. {yields} HE and ECAE processing results in the {beta}' precipitates partial dissolutions. {yields} During HE and ECAE processes the {beta}' particles change their shape.

  10. High-Aspect-Ratio Ridge Structures Induced by Plastic Deformation as a Novel Microfabrication Technique.

    PubMed

    Takei, Atsushi; Jin, Lihua; Fujita, Hiroyuki; Takei, A; Fujita, H; Jin, Lihua

    2016-09-14

    Wrinkles on thin film/elastomer bilayer systems provide functional surfaces. The aspect ratio of these wrinkles is critical to their functionality. Much effort has been dedicated to creating high-aspect-ratio structures on the surface of bilayer systems. A highly prestretched elastomer attached to a thin film has recently been shown to form a high-aspect-ratio structure, called a ridge structure, due to a large strain induced in the elastomer. However, the prestretch requirements of the elastomer during thin film attachment are not compatible with conventional thin film deposition methods, such as spin coating, dip coating, and chemical vapor deposition (CVD). Thus, the fabrication method is complex, and ridge structure formation is limited to planar surfaces. This paper presents a new and simple method for constructing ridge structures on a nonplanar surface using a plastic thin film/elastomer bilayer system. A plastic thin film is attached to a stress-free elastomer, and the resulting bilayer system is highly stretched one- or two-dimensionally. Upon the release of the stretch load, the deformation of the elastomer is reversible, while the plastically deformed thin film stays elongated. The combination of the length mismatch and the large strain induced in the elastomer generates ridge structures. The morphology of the plastic thin film/elastomer bilayer system is experimentally studied by varying the physical parameters, and the functionality and the applicability to a nonplanar surface are demonstrated. Finally, we simulate the effect of plasticity on morphology. This study presents a new technique for generating microscale high-aspect-ratio structures and its potential for functional surfaces.

  11. Fatigue resistance of VT1-0 titanium with a partially removed gas-impregnated layer after plastic deformation

    SciTech Connect

    Kolomenskii, A.B.; Kolachev, B.A.; Degtyarev, A.V.

    1992-03-01

    The influence of the gas-impregnated layer formed on the surface of parts in annealing and partially removed by etching off on the production plasticity of the metal and the fatigue resistance under repeated static loads after plastic deformation was investigated. It is shown that partial removal of the layer makes it possible to significantly increase the fatigue resistance of VT1-0 titanium without a reduction in plasticity. 1 refs., 2 figs.

  12. Modeling of High-Temperature Plastic Deformation of Layered Composites Based on Alloys with L12 Superstructure

    NASA Astrophysics Data System (ADS)

    Lipatnikova, Ya. D.; Solov'eva, Yu. V.; Solov'ev, A. N.; Valuiskaya, L. A.

    2017-08-01

    Method of mathematical modeling is used to investigate macrolocalization of plastic deformation and, in particular, the possibility of forming superlocalization bands in layered composites exposed to hightemperature uniaxial deformation. Modeling is based on a combination of continuum mechanics methods and dislocation kinetics of alloys with L12 superstructure. Numerical modeling is performed by the finite elements method.

  13. The thermostimulated luminescence of radiation defects in KCl, KBr and KI crystals at elastic and plastic deformation

    NASA Astrophysics Data System (ADS)

    Shunkeyev, K.; Myasnikova, L.; Barmina, A.; Zhanturina, N.; Sagimbaeva, Sh; Aimaganbetova, Z.; Sergeyev, D.

    2017-05-01

    The efficiency of radiation defects formation in alkali halide crystals (AHC) was studied by the method of absorption spectroscopy. However, it is not possible to study the deformation-stimulated processes in detail by the absorption spectrum of radiation defects due to the limited sensitivity compared with luminescent spectroscopy. In this regard, thermally stimulated luminescence (TSL) of radiation defects at elastic and plastic deformation was applied in AHC. In the absence of deformation, the dominant peaks in TSL are ≤ft( {X_3^ - } \\right)aca^0-centers. After elastic deformation, low temperature peaks of TSL corresponding to F‧-, VK- and VF-centers became dominant. After plastic deformation, the peaks of TSL corresponding to ≤ft( {X_3^ - } \\right)aca^0-centers became dominant. The elastic deformation contributes to the increase in concentration of low-temperature F‧-, VK- and VF-centers, and the plastic one contributes to that of high temperature ≤ft( {X_3^ - } \\right)aca^0-centers (peaks of TSL in KCl at 360K, in KBr at 365K, in KI at 340K), composed by divacancies created by plastic deformation. At elastic deformation, unrelaxed interstitial halogen atoms are converted into VK- and VF-centers, and due to this fact the long-range interaction is absent, the result of which are the X_3^ - -centers.

  14. Plastic deformation of amorphous poly(L/DL-lactide): structure evolution and physical properties.

    PubMed

    Pluta, Miroslaw; Galeski, Andrzej

    2007-06-01

    Plastic deformation of amorphous, thermally noncrystallizable poly(L/DL-lactide) 70/30 (P(L/DL)LA) was induced by a plane-strain compression in a channel-die at different temperatures, above the glass transition (Tg) from 60 to 90 degrees C. Samples undeformed (reference) and deformed to different compression ratios, from 4.6 to 23.0, were studied by X-ray diffraction, thermally modulated differential scanning calorimetry, light microscopy, and mechanical methods-viscoelastic and tensile tests. The effects of the compression ratios and deformation temperatures on the final structure and properties of the P(L/DL)LA were evaluated. It was revealed that plastic deformation transformed an amorphous P(L/DL)LA (thermally noncrystallizable) to a crystalline fibrillar texture oriented in the flow direction. Fibrillar texture was formed in spite of the tendency of the plane-strain compression to form single-crystal-like texture. The crystallite size in the transverse direction was small, up to 90 angstroms at the highest compression ratio. No evidence of lamellar organization and features of supermolecular structure were detected by small-angle X-ray scattering and light microscopy, respectively. The oriented samples exhibited a low crystallinity degree at the level of 6-9% at the highest compression ratio. The main transformation mechanism was shear and orientation-induced crystallization. The crystalline phase was in the alpha crystallographic modification of poly(lactide) typically formed in more stereoregular poly(lactide) by thermal treatment. The glass transition increased with the increase of compression ratio reflecting the increase of orientation of the polymer chains. The tensile strength of deformed samples was improved considerably in comparison to that of the reference sample.

  15. Direct observation of the residual plastic deformation caused by a single tensile overload

    SciTech Connect

    Bichler, C.; Pippan, R.

    1999-07-01

    The fatigue crack growth behavior following single tensile overloads at high stress intensity ranges in a cold-rolled austenitic steel has been studied experimentally. After tensile overloads, fatigue cracks initially accelerate, followed by significant retardation, before the growth rates return to their baseline level. The initial acceleration was attributed to an immediate reduction in near-tip closure. Scanning electron micrography and stereophotogrammetric reconstruction of the fracture surface were applied to study the residual plastic deformation caused by a single tensile overload in the mid-thickness of the specimen. The measured residual opening displacement of the crack as a function of the overload is presented and compared with simple estimations. Also, free specimen surface observations of the residual plastic deformation and crack growth rate were performed. In the midsection of the specimens the striation spacing-length, i.e., the microscopic growth rates, were measured before and after the applied overload. It will be shown that the measured plasticity-induced wedges from the single overload and the observed propagation behavior support the significance of the concept of crack closure.

  16. Elastic-plastic deformation of a metal-matrix composite coupon with a center slot

    NASA Technical Reports Server (NTRS)

    Post, D.; Czarnek, R.; Joh, D.; Jo, J.; Guo, Y.

    1985-01-01

    A comprehensive experimental analysis of deformations of the surface of a metal-matrix specimen is reported. The specimen is a 6-ply 0 + or - 45 sub s boron-aluminum tensile coupon with a central slot. Moire interferometry is used for high-sensitivity whole-field measurements of in-plane displacements. Normal and shear strains are calculated from displacement gradients. Displacement fields are analyzed at various load levels from 15% to 95% of the failure load. Deformations of the boron fibers could be distinguished from those of the matrix. Highly localized plastic slip zones occur tangent to the ends of the slot. Shear strains and concurrent transverse compressive strains in the slip zones reach approximately 10% and 1%, respectively. Upon unloading, elastic recovery in surrounding regions causes a reverse plastic shear strain in the slip zone of about 4%. Longitudinal normal strains on the unslotted ligament peak at the slot boundary at about 1% strain. The strain concentration factor at the end of the slot decreases with load level and the advance of plasticity.

  17. Effect of the plasticizer di(2-ethylhexyl)phthalate on red cell deformability

    SciTech Connect

    Labow, R.S.; Card, R.T.; Rock, G.

    1987-07-01

    Red cell concentrates (RCC) are stored for 35 to 42 days in plastic containers manufactured with the liquid plasticizer di(2-ethylhexyl)phthalate (DEHP). DEHP leaches from the polyvinylchloride (PVC) plastic bag, then binds to and stabilizes the RC membrane. This study was undertaken to determine the deformability of the RC membrane using an osmotic gradient ektacytometer and to relate these measurements to the concentration of DEHP in the stored RCC. Pooled RCC was aliquoted into PL146 (PVC), PL732 (polyolefin), and PL732 (with added DEHP) bags with samples removed weekly for analysis of osmotic fragility, deformability, and DEHP concentration. The adenosine triphosphate (ATP) content was also measured. The increase in osmotic fragility during storage was greater when RCC was stored without DEHP. In addition, there was a decrease in the maximum elongation index (El max) when there was decreased DEHP in the storage bag. The osmolarity (Omax) at which El max occurred, as well as the Omin, the osmolarity at which minimum elongation (El min) occurred was higher in the PL732 container than in the PL146 or in the PL732 to which DEHP had been added. These changes could be reversed by addition of DEHP at the beginning of the storage period, showing a direct correlation between DEHP concentration during storage and RC membrane flexibility. By a better understanding of the mechanism of DEHP protection, it might be possible to substitute a less toxic stabilizing compound.

  18. Modeling Of Microstructure Evolution Of BCC Metals Subjected To Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Svyetlichnyy, Dmytro; Majta, Janusz; Muszka, Krzysztof; Łach, Łukasz

    2011-01-01

    Prediction of microstructure evolution and properties of ultrafine-grained materials is one of the most significant, current problems in materials science. Several advanced methods of analysis can be applied for this issue: vertex models, phase field models, Monte Carlo Potts, finite element method (FEM) discrete element method (DEM) and finally cellular automata (CA). The main asset of the CA is ability for a close correlation of the microstructure with the mechanical properties in micro- and meso-scale simulation. Joining CA with the DEM undoubtedly improves accuracy of modeling of coupled phenomena during the innovative forming processes in both micro- and macro-scale. Deformation in micro-scale shows anisotropy, which connected with that the polycrystalline material contains grains with different crystallographic orientation, and grain deformation is depended from configuration of directions of main stresses and axis of grain. Then, CA and DEM must be joint solutions of crystal plasticity theory. In the present model, deformation in macro-scale is transferred to meso-sale, where a block contains several, score or hundreds grains, and then is applied in micro-scale to each grain. Creation of low-angle boundaries and their development into high-angle boundaries are simulated by the cellular automata on the base of calculations using finite element method and crystal plasticity theory. The idea proposed in this study and particular solutions are discussed for the case of ultrafine-grained low-carbon steel.

  19. Electron channeling contrast imaging of plastic deformation induced by indentation in polycrystalline nickel.

    PubMed

    Kaboli, Shirin; Goldbaum, Dina; Chromik, Richard R; Gauvin, Raynald

    2013-12-01

    Vickers microindentation and Berkovich nanoindentation tests were carried out on a polycrystalline nickel (Ni) bulk specimen. Electron channeling contrast imaging (ECCI) in conjunction with electron backscattered diffraction was used to image and characterize plastic deformation inside and around the indents using a field emission scanning electron microscope. The ECCI was performed with a 5 keV beam energy and 0° tilt specimen position. The strain field distribution, slip lines, and Taylor lattices were imaged on an indented surface. Orientation mapping was used to investigate the local crystallographic misorientation and identify specific ⟨110⟩ slip systems. An ion milling surface preparation technique was used to remove materials from the surface which permitted the study of deformed microstructure below the indent. A dislocation density of 1011 cm-2 was calculated based on the curvature of bend contours observed in the ECCI micrographs obtained from the Vickers indents. A yield strength of 500 MPa was calculated based on the size of the strain field measured from the ECCI micrographs of the nanoindents. The combination of ion milling, ECCI, and electron backscattered diffraction was shown to be beneficial to investigate the indentation-induced plastic deformation in a polycrystalline Ni bulk specimen.

  20. Micropillar compression technique applied to micron-scale mudstone elasto-plastic deformation.

    SciTech Connect

    Michael, Joseph Richard; Chidsey, Thomas; Heath, Jason E.; Dewers, Thomas A.; Boyce, Brad Lee; Buchheit, Thomas Edward

    2010-12-01

    Mudstone mechanical testing is often limited by poor core recovery and sample size, preservation and preparation issues, which can lead to sampling bias, damage, and time-dependent effects. A micropillar compression technique, originally developed by Uchic et al. 2004, here is applied to elasto-plastic deformation of small volumes of mudstone, in the range of cubic microns. This study examines behavior of the Gothic shale, the basal unit of the Ismay zone of the Pennsylvanian Paradox Formation and potential shale gas play in southeastern Utah, USA. Precision manufacture of micropillars 5 microns in diameter and 10 microns in length are prepared using an ion-milling method. Characterization of samples is carried out using: dual focused ion - scanning electron beam imaging of nano-scaled pores and distribution of matrix clay and quartz, as well as pore-filling organics; laser scanning confocal (LSCM) 3D imaging of natural fractures; and gas permeability, among other techniques. Compression testing of micropillars under load control is performed using two different nanoindenter techniques. Deformation of 0.5 cm in diameter by 1 cm in length cores is carried out and visualized by a microscope loading stage and laser scanning confocal microscopy. Axisymmetric multistage compression testing and multi-stress path testing is carried out using 2.54 cm plugs. Discussion of results addresses size of representative elementary volumes applicable to continuum-scale mudstone deformation, anisotropy, and size-scale plasticity effects. Other issues include fabrication-induced damage, alignment, and influence of substrate.

  1. Modeling Of Microstructure Evolution Of BCC Metals Subjected To Severe Plastic Deformation

    SciTech Connect

    Svyetlichnyy, Dmytro; Majta, Janusz; Muszka, Krzysztof; Lach, Lukasz

    2011-01-17

    Prediction of microstructure evolution and properties of ultrafine-grained materials is one of the most significant, current problems in materials science. Several advanced methods of analysis can be applied for this issue: vertex models, phase field models, Monte Carlo Potts, finite element method (FEM) discrete element method (DEM) and finally cellular automata (CA). The main asset of the CA is ability for a close correlation of the microstructure with the mechanical properties in micro- and meso-scale simulation. Joining CA with the DEM undoubtedly improves accuracy of modeling of coupled phenomena during the innovative forming processes in both micro- and macro-scale. Deformation in micro-scale shows anisotropy, which connected with that the polycrystalline material contains grains with different crystallographic orientation, and grain deformation is depended from configuration of directions of main stresses and axis of grain. Then, CA and DEM must be joint solutions of crystal plasticity theory. In the present model, deformation in macro-scale is transferred to meso-sale, where a block contains several, score or hundreds grains, and then is applied in micro-scale to each grain. Creation of low-angle boundaries and their development into high-angle boundaries are simulated by the cellular automata on the base of calculations using finite element method and crystal plasticity theory. The idea proposed in this study and particular solutions are discussed for the case of ultrafine-grained low-carbon steel.

  2. New design strategy for reversible plasticity shape memory polymers with deformable glassy aggregates.

    PubMed

    Lin, Tengfei; Tang, Zhenghai; Guo, Baochun

    2014-12-10

    Reversible plasticity shape memory (RPSM) is a new concept in the study of shape memory performance behavior and describes a phenomenon in which shape memory polymers (SMPs) can undergo a large plastic deformation at room temperature and subsequently recover their original shape upon heating. To date, RPSM behavior has been demonstrated in only a few polymers. In the present study, we implement a new design strategy, in which deformable glassy hindered phenol (AO-80) aggregates are incorporated into an amorphous network of epoxidized natural rubber (ENR) cured with zinc diacrylate (ZDA), in order to achieve RPSM properties. We propose that AO-80 continuously tunes the glass transition temperature (Tg) and improves the chain mobility of the SMP, providing traction and anchoring the ENR chains by intermolecular hydrogen bonding interactions. The RPSM behavior of the amorphous SMPs is characterized, and the results demonstrate good fixity at large deformations (up to 300%) and excellent recovery upon heating. Large energy storage capacities at Td in these RPSM materials are demonstrated compared with those achieved at elevated temperature in traditional SMPs. Interestingly, the further revealed self-healing properties of these materials are closely related to their RPSM behavior.

  3. Cap plasticity models and compactive and dilatant pre-failure deformation

    SciTech Connect

    FOSSUM,ARLO F.; FREDRICH,JOANNE T.

    2000-02-17

    At low mean stresses, porous geomaterials fail by shear localization, and at higher mean stresses, they undergo strain-hardening behavior. Cap plasticity models attempt to model this behavior using a pressure-dependent shear yield and/or shear limit-state envelope with a hardening or hardening/softening elliptical end cap to define pore collapse. While these traditional models describe compactive yield and ultimate shear failure, difficulties arise when the behavior involves a transition from compactive to dilatant deformation that occurs before the shear failure or limit-state shear stress is reached. In this work, a continuous surface cap plasticity model is used to predict compactive and dilatant pre-failure deformation. During loading the stress point can pass freely through the critical state point separating compactive from dilatant deformation. The predicted volumetric strain goes from compactive to dilatant without the use of a non-associated flow rule. The new model is stable in that Drucker's stability postulates are satisfied. The study has applications to several geosystems of current engineering interest (oil and gas reservoirs, nuclear waste repositories, buried targets, and depleted reservoirs for possible use for subsurface sequestration of greenhouse gases).

  4. Observations of a dynamical-to-kinematic diffraction transition in plastically deformed polycrystalline intermetallic YCu

    SciTech Connect

    Williams, Scott H.; Brown, Donald W.; Clausen, Bjorn; Russell, Alan; Gschneidner Jr., Karl A.

    2014-03-01

    Unlike most intermetallic compounds, polycrystalline YCu, a B2 (CsCl-type) intermetallic, is ductile at room temperature. The mechanisms for this behavior are not fully understood. In situ neutron diffraction was used to investigate whether a stress-induced phase transformation or twinning contribute to the ductility; however, neither mechanism was found to be active in YCu. Surprisingly, this study revealed that the intensities of the diffraction peaks increased after plastic deformation. It is thought that annealing the samples created nearly perfect crystallinity, and subsequent deformation reduced this high degree of lattice coherency, resulting in a modified mosaic structure that decreased or eliminated the extinction effect. Analysis of changes in diffraction peak intensity showed a region of primary plasticity that exhibits significant changes in diffraction behavior. Fully annealed samples initially contain diffracting volumes large enough to follow the dynamical theory of diffraction. When loaded beyond the yield point, dislocation motion disrupts the lattice perfection, and the diffracting volume is reduced to the point that diffraction follows the kinematic theory of diffraction. Since the sample preparation and deformation mechanisms present in this study are common in numerous material systems, this dynamical to kinematic diffraction transition should also be considered in other diffraction experiments. These measurements also suggest the possibility of a new method of investigating structural characteristics. (C) 2014 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.

  5. Ensembles of gliding grain boundary dislocations in ultrafine grained materials produced by severe plastic deformation

    SciTech Connect

    Nazarov, A.A.

    1997-10-15

    Severe plastic deformation which is now widely used to produce an ultrafine grained (UFG) structure in metals and alloys necessarily leads to the accumulation of interfacial dislocations which arise due to the incompatibilities of strains of neighbor misorientated areas. The most important result of the dislocation storage at grain boundaries (GBs) and associated internal stresses is the fragmentation which at extremely large strains is usually followed by the formation of a very fine highly misorientated granular structure. After deformation the UFG structure must preserve residual dislocation arrays in GBs, since recovery at room temperature is not enough to provide their annihilation. Recently, a hypothesis has been put forward that the internal stresses induced by these arrays are the origin of a number of fundamental properties of UFG materials different from those of coarse grained ones. The author suggested that, in addition, the nonequilibrium dislocation ensembles in GBs were characterized by disordered distribution of dislocations. Thus, three main sources of internal stresses can exist in UFG materials prepared by severe plastic deformation: (1) disordered sessile EGBD arrays, (2) excess density of sessile EGBDs, that is junction disclinations, and (3) arrays of tangential EGBDs. Each of these components can contribute to the experimentally observed elastic strain, excess GB energy and volume expansion in UFG materials.

  6. Investigation of features of plastic deformation and fracture of fine-crystalline V-4Ti-4Cr alloy

    SciTech Connect

    Grinyaev, Konstantin V. Tyumentsev, Alexander N.; Ditenberg, Ivan A.; Smirnov, Ivan V.; Chernov, Vyacheslav M. E-mail: mmp@bochvar.ru; Potapenko, Mikhail M. E-mail: mmp@bochvar.ru

    2014-11-14

    With the use of transmission electron microscopy the investigation of defect substructure was carried out in the V-4Ti-4Cr-(C, N, O) alloy with disperse strengthening (by nanoparticles of oxy-carbo-nitride phase) after deformation by active tension at temperatures of 20 and 800 °C. It has been shown that an important feature of plastic deformation is deformation localization with crystal lattice reorientation.

  7. 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.

  8. Wireless Measurement of Elastic and Plastic Deformation by a Metamaterial-Based Sensor

    PubMed Central

    Ozbey, Burak; Demir, Hilmi Volkan; Kurc, Ozgur; Erturk, Vakur B.; Altintas, Ayhan

    2014-01-01

    We report remote strain and displacement measurement during elastic and plastic deformation using a metamaterial-based wireless and passive sensor. The sensor is made of a comb-like nested split ring resonator (NSRR) probe operating in the near-field of an antenna, which functions as both the transmitter and the receiver. The NSRR probe is fixed on a standard steel reinforcing bar (rebar), and its frequency response is monitored telemetrically by a network analyzer connected to the antenna across the whole stress-strain curve. This wireless measurement includes both the elastic and plastic region deformation together for the first time, where wired technologies, like strain gauges, typically fail to capture. The experiments are further repeated in the presence of a concrete block between the antenna and the probe, and it is shown that the sensing system is capable of functioning through the concrete. The comparison of the wireless sensor measurement with those undertaken using strain gauges and extensometers reveals that the sensor is able to measure both the average strain and the relative displacement on the rebar as a result of the applied force in a considerably accurate way. The performance of the sensor is tested for different types of misalignments that can possibly occur due to the acting force. These results indicate that the metamaterial-based sensor holds great promise for its accurate, robust and wireless measurement of the elastic and plastic deformation of a rebar, providing beneficial information for remote structural health monitoring and post-earthquake damage assessment. PMID:25333292

  9. Plastic deformation of FeSi at high pressures: implications for planetary cores

    NASA Astrophysics Data System (ADS)

    Kupenko, Ilya; Merkel, Sébastien; Achorner, Melissa; Plückthun, Christian; Liermann, Hanns-Peter; Sanchez-Valle, Carmen

    2017-04-01

    The cores of terrestrial planets is mostly comprised of a Fe-Ni alloy, but it should additionally contain some light element(s) in order to explain the observed core density. Silicon has long been considered as a likely candidate because of geochemical and cosmochemical arguments: the Mg/Si and Fe/Si ratios of the Earth does not match those of the chondrites. Since silicon preferentially partition into iron-nickel metal, having 'missing' silicon in the core would solve this problem. Moreover, the evidence of present (e.g. Mercury) or ancient (e.g. Mars) magnetic fields on the terrestrial planets is a good indicator of (at least partially) liquid cores. The estimated temperature profiles of these planets, however, lay below iron melting curve. The addition of light elements in their metal cores could allow reducing their core-alloy melting temperature and, hence, the generation of a magnetic field. Although the effect of light elements on the stability and elasticity of Fe-Ni alloys has been widely investigated, their effect on the plasticity of core materials remains largely unknown. Yet, this information is crucial for understanding how planetary cores deform. Here we investigate the plastic deformation of ɛ-FeSi up to 50 GPa at room temperature employing a technique of radial x-ray diffraction in diamond anvil cells. Stoichiometric FeSi endmember is a good first-order approximation of the Fe-FeSi system and a good starting material to develop new experimental perspectives. In this work, we focused on the low-pressure polymorph of FeSi that would be the stable phase in the cores of small terrestrial planets. We will present the analysis of measured data and discuss their potential application to constrain plastic deformation in planetary cores.

  10. Crystal plasticity finite element analysis of deformation behaviour in SAC305 solder joint

    NASA Astrophysics Data System (ADS)

    Darbandi, Payam

    Due to the awareness of the potential health hazards associated with the toxicity of lead (Pb), actions have been taken to eliminate or reduce the use of Pb in consumer products. Among those, tin (Sn) solders have been used for the assembly of electronic systems. Anisotropy is of significant importance in all structural metals, but this characteristic is unusually strong in Sn, making Sn based solder joints one of the best examples of the influence of anisotropy. The effect of anisotropy arising from the crystal structure of tin and large grain microstructure on the microstructure and the evolution of constitutive responses of microscale SAC305 solder joints is investigated. Insights into the effects of key microstructural features and dominant plastic deformation mechanisms influencing the measured relative activity of slip systems in SAC305 are obtained from a combination of optical microscopy, orientation imaging microscopy (OIM), slip plane trace analysis and crystal plasticity finite element (CPFE) modeling. Package level SAC305 specimens were subjected to shear deformation in sequential steps and characterized using optical microscopy and OIM to identify the activity of slip systems. X-ray micro Laue diffraction and high energy monochromatic X-ray beam were employed to characterize the joint scale tensile samples to provide necessary information to be able to compare and validate the CPFE model. A CPFE model was developed that can account for relative ease of activating slip systems in SAC305 solder based upon the statistical estimation based on correlation between the critical resolved shear stress and the probability of activating various slip systems. The results from simulations show that the CPFE model developed using the statistical analysis of activity of slip system not only can satisfy the requirements associated with kinematic of plastic deformation in crystal coordinate systems (activity of slip systems) and global coordinate system (shape changes

  11. Factors contributing to plastic strain amplification in slip dominated deformation of magnesium alloys

    NASA Astrophysics Data System (ADS)

    Sinclair, C. W.; Martin, G.; Lebensohn, R. A.

    2015-12-01

    While plastic strains are never distributed uniformly in polycrystals, it has recently been shown experimentally that the distribution can be extremely heterogeneous in magnesium polycrystals even when the deformation is dominated by slip. Here, we attempt to provide insight into the (macroscopic) factors that contribute to this strain amplification and to explain, from a local perspective, the origins of this strain amplification. To do this, full field VPFFT crystal plasticity simulations have been performed under the simplifying assumption that twinning is inoperative. It is shown that the experimentally observed heterogeneity can be reproduced when a sufficiently high anisotropy in slip system strength is assumed. This can be further accentuated by a weakening of the texture.

  12. Pressure concentrations due to plastic deformation of thin films or gaskets between anvils

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Huang, T. L.; Grzybowski, T. A.; Whetten, T. J.; Ruoff, A. L.

    1982-01-01

    Plastic deformation of either a sample or a gasket between diamond anvils leads to large pressure concentrations, i.e., the maximum pressure can be many times the average pressure. This behavior is discussed using elementary plasticity theory for the case where the pressures are sufficiently low that the yield stress can be assumed not to vary with pressure. It is then shown that the pressure concentration factor can be even much larger when the yield stress of the sample at the highest pressure is much greater than the yield stress at the lowest pressure. This is illustrated with solid xenon where it is shown that the assumption that Nelson and Ruoff made about the pressure distribution in their xenon samples is incorrect. The pressure distribution is shown to be much steeper than assumed. Thus, the pressure they observed electrical conduction in xenon was above 1 Mbar.

  13. Autowave process of the localized plastic deformation of high-chromium steel saturated with hydrogen

    NASA Astrophysics Data System (ADS)

    Bochkareva, A. V.; Barannikova, S. A.; Li, Yu V.; Lunev, A. G.; Zuev, L. B.

    2016-06-01

    The deformation behavior of high-chromium stainless steel of sorbitic structure upon high-temperature tempering and of electrically saturated with hydrogen in the electrochemical cell during 12 hours is investigated. The stress-strain curves for each state were obtained. From the stress-strain curves, one can conclude that hydrogen markedly reduces the elongation to the fracture of specimen. Using double-exposed speckle photography method it was found that the plastic flow of the material is of a localized character. The pattern distribution of localized plastic flow domains at the linear hardening stage was investigated. Comparative study of autowave parameters was carried out for the tempered steel as well as the electrically saturated with hydrogen steel.

  14. Comparison studies on the percolation thresholds of binary mixture tablets containing excipients of plastic/brittle and plastic/plastic deformation properties.

    PubMed

    Amin, Mohd C I; Fell, John T

    2004-01-01

    Percolation theory has been used with great interest in understanding the design and characterization of dosage forms. In this study, work has been carried out to investigate the behavior of binary mixture tablets containing excipients of similar and different deformation properties. The binary mixture tablets were prepared by direct compression using lactose, polyvinyl chloride (PVC), Eudragit RS 100, and microcrystalline cellulose (MCC). The application of percolation theory on the relationships between compactibility, Pmax, or compression susceptibility (compressibility), gamma, and mixture compositions reveals the presence of percolation thresholds even for mixtures of similar deformation properties. The results showed that all mixture compositions exhibited at least one discreet change in the slope, which was referred to as the percolation threshold. The PVC/Eudragit RS100 mixture compositions showed significant percolation threshold at 80% (w/w) PVC loading. Two percolation thresholds were observed from a series of binary mixtures containing similar plastic deformation materials (PVC/MCC). The percolation thresholds were determined at 20% (w/w) and 80% (w/w) PVC loading. These are areas where one of the components percolates throughout the system and the properties of the tablets are expected to experience a sudden change. Experimental results, however, showed that total disruption of the tablet physical properties at the specified percolation thresholds can be observed for PVC/lactose mixtures at 20-30% (w/w) loading while only minor changes in the tablets' strength for PVC/MCC or PVC/Eudragit RS 100 mixtures were observed.

  15. Plastic deformation of a magnesium oxide 001-plane surface produced by cavitation

    NASA Technical Reports Server (NTRS)

    Hattori, S.; Miyoshi, K.; Buckley, D. H.; Okada, T.

    1986-01-01

    An investigation was conducted to examine plastic deformation of a cleaved single-crystal magnesium oxide 001-plane surface exposed to cavitation. Cavitation damage experiments were carried out in distilled water at 25 C by using a magnetostrictive oscillator in close proximity (2 mm) to the surface of the cleaved specimen. The dislocation-etch-pit patterns induced by cavitation were examined and compared with that of microhardness indentations. The results revealed that dislocation-etch-pit patterns around hardness indentations contain both screw and edge dislocations, while the etch-pit patterns on the surface exposed to cavitation contain only screw dislocations. During cavitation, deformation occurred in a thin surface layer, accompanied by work-hardening of the ceramic. The row of screw dislocations underwent a stable growth, which was analyzed crystallographically.

  16. 6th International Conference on Nanomaterials by Severe Plastic Deformation (NanoSPD6)

    NASA Astrophysics Data System (ADS)

    2014-08-01

    ''NanoSPD'' means Nano-material by Severe Plastic Deformation (SPD), which is an efficient way to obtain bulk nano-structured materials. During SPD, the microstructure of the material is transformed into a very fine structure consisting of ultra fine grains (UFG) approaching even the nano-scale. SPD is different from classical large strain forming processes in two aspects: 1. The sample undergoes extremely large strains without significant change in its dimensions, 2. In most SPD processes high hydrostatic stress is applied which makes it possible to deform difficult-to-form materials. This conference is part of a series of conferences taking place every third year; the history of NanoSPD conferences began in 1999 in Moscow (Russia), followed by Vienna in 2002 (Austria), Fukuoka in 2005 (Japan), Goslar in 2008 (Germany), Nanjing in 2011 (China), and Metz in 2014 (France). The preface continues in the pdf.

  17. Plastic deformation of a magnesium oxide 001-plane surface produced by cavitation

    NASA Technical Reports Server (NTRS)

    Hattori, S.; Miyoshi, K.; Buckley, D. H.; Okada, T.

    1986-01-01

    An investigation was conducted to examine plastic deformation of a cleaved single-crystal magnesium oxide 001-plane surface exposed to cavitation. Cavitation damage experiments were carried out in distilled water at 25 C by using a magnetostrictive oscillator in close proximity (2 mm) to the surface of the cleaved specimen. The dislocation-etch-pit patterns induced by cavitation were examined and compared with that of microhardness indentations. The results revealed that dislocation-etch-pit patterns around hardness indentations contain both screw and edge dislocations, while the etch-pit patterns on the surface exposed to cavitation contain only screw dislocations. During cavitation, deformation occurred in a thin surface layer, accompanied by work-hardening of the ceramic. The row of screw dislocations underwent a stable growth, which was analyzed crystallographically.

  18. Plastic deformation and wear process at a surface during unlubricated sliding

    NASA Technical Reports Server (NTRS)

    Yamamoto, T.; Buckley, D. H.

    1982-01-01

    The plastic deformation and wear of a 304 stainless steel surface sliding against an aluminum oxide rider with a spherical surface (the radius of curvature: 1.3 cm) were observed by using scanning electron and optical microscopes. Experiments were conducted in a vacuum of one million Pa and in an environment of fifty thousandth Pa of chlorine gas at 25 C. The load was 500 grams and the sliding velocity was 0.5 centimeter per second. The deformed surface layer which accumulates and develops successively is left behind the rider, and step shaped proturbances are developed even after single pass sliding under both environmental conditions. A fully developed surface layer is gradually torn off leaving a characteristic pattern. The mechanism for tearing away of the surface layer from the contact area and sliding track contour is explained assuming the simplified process of material removal based on the adhesion theory for the wear of materials.

  19. Phase transformation dependence on initial plastic deformation mode in Si via nanoindentation

    DOE PAGES

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

    2016-09-30

    Silicon in its diamond-cubic phase is known to phase transform to a technologically interesting mixture of the body-centred cubic and rhombohedral phases under nanoindentation pressure. In this study, we demonstrate that during plastic deformation the sample can traverse two distinct pathways, one that initially nucleates a phase transformation while the other initially nucleates crystalline defects. These two pathways remain distinct even after sufficient pressure is applied such that both deformation mechanisms are present within the sample. Here, it is further shown that the indents that initially nucleate a phase transformation generate larger, more uniform volumes of the phase transformed materialmore » than indents that initially nucleate crystalline defects.« less

  20. 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.

  1. Microstructure evolution of a multiphase superalloy processed by severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Sauvage, Xavier; Mukhtarov, Shamil

    2014-08-01

    This paper presents an overview and some original results about the microstructure evolution of an Ultra Fine Grained (UFG) nickel-iron based alloy INCONEL 718 processed by Severe Plastic Deformation (SPD). The ultrafine grain structure of this alloy that contains a high density of γ" and γ' precipitates was characterized by Scanning Transmission Electron Microscopy (STEM). We propose a comparison between two SPD processes, High Pressure Torsion (HPT) and Multiple Forging (MF). The grain refinement is much more pronounced by HPT but intermetallic particles are partly dissolved during SPD. The UFG structure after MF is obviously very different and exhibits a much better thermal stability especially because second phase particles do not reprecipitate during post-deformation annealing.

  2. Off-fault deformations and shallow slip deficit from dynamic rupture simulations with fault zone plasticity

    NASA Astrophysics Data System (ADS)

    Roten, D.; Olsen, K. B.; Day, S. M.

    2017-08-01

    Kinematic source inversions of major (M≥7) strike-slip earthquakes show that the slip at depth exceeds surface displacements measured in the field, and it has been suggested that this shallow slip deficit (SSD) is caused by distributed plastic deformation near the surface. We perform dynamic rupture simulations of M 7.2-7.4 earthquakes in elastoplastic media and analyze the sensitivity of SSD and off-fault deformation (OFD) to rock quality parameters. While linear simulations clearly underpredict observed SSD and OFDs, nonlinear simulations for a moderately fractured fault damage zone predict a SSD of 44-53% and OFDs of 39-48%, consistent with the 30-60% SSD and 46 ± 10% (1σ) OFD reported for the 1992 M 7.3 Landers earthquake. Both SSD and OFDs are sensitive to the quality of the fractured rock mass inside the fault damage zone, and surface rupture is almost entirely suppressed in poor quality material.

  3. Electron and nuclear spin dynamics in plastically deformed silicon crystals enriched in isotope 29Si

    NASA Astrophysics Data System (ADS)

    Koplak, O. V.; Dmitriev, A. I.; Vasil'ev, S. G.; Shteinman, E. A.; Morgunov, R. B.

    2014-04-01

    Paramagnetic defects of a new type with a concentration of about 1015 cm-3 are shown to be generated during the plastic deformation of isotope-rich (72%, 76% 29Si) silicon crystals at a temperature of 950°C. The electron paramagnetic resonance (EPR) spectra of these defects are anisotropic and have a significant width (up to 1 kOe). The nonuniform broadening of the EPR lines is caused by the variation of the internal magnetic field in correlated defect clusters. The nuclear magnetic resonance (NMR) spectra of the deformed crystals consist of Pake doublets split by nuclear spin-spin interaction. The broadening of the NMR spectra is caused by nuclear dipole-dipole relaxation.

  4. Producing Bulk Ultrafine-Grained Materials by Severe Plastic Deformation: Ten Years Later

    NASA Astrophysics Data System (ADS)

    Valiev, Ruslan Z.; Estrin, Yuri; Horita, Zenji; Langdon, Terence G.; Zehetbauer, Michael J.; Zhu, Yuntian

    2016-04-01

    It is now well established that the processing of bulk solids through the application of severe plastic deformation (SPD) leads to exceptional grain refinement to the submicrometer or nanometer level. Extensive research over the last decade has demonstrated that SPD processing also produces unusual phase transformations and leads to the introduction of a range of nanostructural features, including nonequilibrium grain boundaries, deformation twins, dislocation substructures, vacancy agglomerates, and solute segregation and clustering. These many structural changes provide new opportunities for fine tuning the characteristics of SPD metals to attain major improvements in their physical, mechanical, chemical, and functional properties. This review provides a summary of some of these recent developments. Special emphasis is placed on the use of SPD processing in achieving increased electrical conductivity, superconductivity, and thermoelectricity, an improved hydrogen storage capability, materials for use in biomedical applications, and the fabrication of high-strength metal-matrix nanocomposites.

  5. Smaller is Plastic: Polymorphic Structures and Mechanism of Deformation in Nanoscale hcp Metals.

    PubMed

    Bhogra, Meha; Ramamurty, U; Waghmare, Umesh V

    2015-06-10

    Using first-principles calculations, we establish the existence of highly stable polymorphs of hcp metals (Ti, Mg, Be, La and Y) with nanoscale structural periodicity. They arise from heterogeneous deformation of the hcp structure occurring in response to large shear stresses localized at the basal planes separated by a few nanometers. Through Landau theoretical analysis, we show that their stability derives from nonlinear coupling between strains at different length scales. Such multiscale hyperelasticity and long-period structures constitute a new mechanism of size-dependent plasticity and its enhancement in nanoscale hcp metals.

  6. Effects of pairwise versus many-body forces on high-stress plastic deformation

    NASA Astrophysics Data System (ADS)

    Holian, B. L.; Voter, A. F.; Wagner, N. J.; Ravelo, R. J.; Chen, S. P.; Hoover, W. G.; Hoover, C. G.; Hammerberg, J. E.; Dontje, T. D.

    1991-03-01

    We propose a model embedded-atom (many-body) potential and test it against an effective, density-independent, pairwise-additive potential in a variety of nonequilibrium molecular-dynamics simulations of plastic deformation under high stress. Even though both kinds of interactions have nearly the same equilibrium equation of state, the defect energies (i.e., vacancy formation and surface energies) are quite different. As a result, we observe significant qualitative differences in flow behavior between systems characterized by purely pairwise interactions versus higher-order many-body forces.

  7. Structural and mechanical properties of nanocrystalline titanium processed by severe plastic deformation

    SciTech Connect

    Popov, A.A.; Pyshmintsev, I.Y.; Demakov, S.L.; Illarionov, A.G.; Lowe, T.C.; Sergeyeva, A.V.; Valiev, R.Z.

    1997-10-01

    Recent investigations have demonstrated that materials with ultrafine grain (UFG) structure (nano- and submicron crystalline) can be processed by severe plastic deformation. One advantage of this method is that it can be applied to both pure metals and alloys. Moreover, it produces samples that have no residual porosity so that meaningful measurements of the physical and mechanical properties are possible. Investigations of ultrafine grain copper and aluminum alloys have revealed a number of specific features of their mechanical behavior, namely extremely high hardness and strength, the absence of strain hardening, and deviation form the Hall-Petch relationship. In this work the authors investigate the mechanical properties and thermal stability of UFG titanium.

  8. The effect of carbon concentration and plastic deformation on ultrasonic higher order elastic properties of steel

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.; Allison, S. G.; Salama, K.

    1985-01-01

    The behavior of higher order elastic properties, which are much more sensitive to material state than are second order properties, has been studied for steel alloys AISI 1016, 1045, 1095, and 8620 by measuring the stress derivative of the acoustic natural velocity to determine the stress acoustic constants (SAC's). Results of these tests show a 20 percent linear variation of SAC's with carbon content as well as even larger variations with prestrain (plastic deformation). The use of higher order elastic characterization permits quantitative evaluation of solids and may prove useful in studies of fatigue and fracture.

  9. The effect of carbon concentration and plastic deformation on ultrasonic higher order elastic properties of steel

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.; Allison, S. G.; Salama, K.

    1985-01-01

    The behavior of higher order elastic properties, which are much more sensitive to material state than are second order properties, has been studied for steel alloys AISI 1016, 1045, 1095, and 8620 by measuring the stress derivative of the acoustic natural velocity to determine the stress acoustic constants (SAC's). Results of these tests show a 20 percent linear variation of SAC's with carbon content as well as even larger variations with prestrain (plastic deformation). The use of higher order elastic characterization permits quantitative evaluation of solids and may prove useful in studies of fatigue and fracture.

  10. The influence of strain hardening on cumulative plastic deformation in rolling and sliding line contact

    NASA Astrophysics Data System (ADS)

    Bower, A. F.; Johnson, K. L.

    THE INFLUENCE of strain hardening on the cumulative plastic deformation (ratchetting) which takes place in repeated rolling and sliding contacts has been assessed by the use of a non-linear kinematic hardening law proposed and tested by B OWER ( J. Mech. Phys. Solids37,455, 1989). Both the sub-surface flow, which occurs at low traction coefficients ( <0.25), and the surface flow which occurs at high traction ( >0.25), have been investigated. Two materials have been studied: hard-drawn copper and rail steel. Good correlation was found for copper between the theory and rolling contact experiments.

  11. On the effectiveness of surface severe plastic deformation by shot peening at cryogenic temperature

    NASA Astrophysics Data System (ADS)

    Novelli, M.; Fundenberger, J.-J.; Bocher, P.; Grosdidier, T.

    2016-12-01

    The effect of cryogenic temperature (CT) on the graded microstructures obtained by severe shot peening using surface mechanical attrition treatment (SMAT) was investigated for two austenitic steels that used different mechanisms for assisting plastic deformation. For the metastable 304L steel, the depth of the hardened region increases because CT promotes the formation of strain induced martensite. Comparatively, for the 310S steel that remained austenitic, the size of the subsurface affected region decreases because of the improved strength of the material at CT but the fine twinned nanostructures results in significant top surface hardening.

  12. The potential for achieving superplasticity in high-entropy alloys processed by severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Shahmir, Hamed; Kawasaki, Megumi; Langdon, Terence G.

    2017-05-01

    High-entropy alloys (HEAs) are now becoming important because they offer unique combinations of solid solution strengthening and good ductility at low temperatures. Only limited information is at present available on the high temperature mechanical properties of these materials. Nevertheless, it is evident that, as in conventional metallic alloys, processing through the application of severe plastic deformation can reduce the grain size to the nanometer range and this provides a potential for achieving good superplastic elongations. The superplastic data available to date are examined in this review and a comparison is made between the behaviour of HEAs and conventional superplastic alloys.

  13. Correlation between structural heterogeneity and plastic deformation for phase separating FeCu metallic glasses

    PubMed Central

    Peng, Chuan-Xiao; Song, Kai-Kai; Wang, Li; Şopu, Daniel; Pauly, Simon; Eckert, Jürgen

    2016-01-01

    Unlike crystalline metals, the plastic deformation of metallic glasses (MGs) involves a competition between disordering and structural relaxation ordering, which is not well understood, yet. Molecular dynamics (MD) simulations were performed to investigate the evolutions of strain localizations, short-range order (SRO) as well as the free volume in the glass during compressive deformation of Fe50Cu50 MGs with different degrees of phase separation. Our findings indicate that the free volume in the phase separating MGs decreases while the shear strain localizations increase with increasing degree of phase separation. Cu-centered clusters show higher potential energies and Voronoi volumes, and bear larger local shear strains. On the other hand, Fe-centered pentagon-rich clusters in Cu-rich regions seem to play an important role to resist the shear transformation. The dilatation or annihilation of Voronoi volumes is due to the competition between ordering via structural relaxation and shear stress-induced deformation. The present study could provide a better understanding of the relationship between the structural inhomogeneity and the deformation of MGs. PMID:27681052

  14. Correlation between structural heterogeneity and plastic deformation for phase separating FeCu metallic glasses

    NASA Astrophysics Data System (ADS)

    Peng, Chuan-Xiao; Song, Kai-Kai; Wang, Li; Şopu, Daniel; Pauly, Simon; Eckert, Jürgen

    2016-09-01

    Unlike crystalline metals, the plastic deformation of metallic glasses (MGs) involves a competition between disordering and structural relaxation ordering, which is not well understood, yet. Molecular dynamics (MD) simulations were performed to investigate the evolutions of strain localizations, short-range order (SRO) as well as the free volume in the glass during compressive deformation of Fe50Cu50 MGs with different degrees of phase separation. Our findings indicate that the free volume in the phase separating MGs decreases while the shear strain localizations increase with increasing degree of phase separation. Cu-centered clusters show higher potential energies and Voronoi volumes, and bear larger local shear strains. On the other hand, Fe-centered pentagon-rich clusters in Cu-rich regions seem to play an important role to resist the shear transformation. The dilatation or annihilation of Voronoi volumes is due to the competition between ordering via structural relaxation and shear stress-induced deformation. The present study could provide a better understanding of the relationship between the structural inhomogeneity and the deformation of MGs.

  15. Correlation between structural heterogeneity and plastic deformation for phase separating FeCu metallic glasses.

    PubMed

    Peng, Chuan-Xiao; Song, Kai-Kai; Wang, Li; Şopu, Daniel; Pauly, Simon; Eckert, Jürgen

    2016-09-29

    Unlike crystalline metals, the plastic deformation of metallic glasses (MGs) involves a competition between disordering and structural relaxation ordering, which is not well understood, yet. Molecular dynamics (MD) simulations were performed to investigate the evolutions of strain localizations, short-range order (SRO) as well as the free volume in the glass during compressive deformation of Fe50Cu50 MGs with different degrees of phase separation. Our findings indicate that the free volume in the phase separating MGs decreases while the shear strain localizations increase with increasing degree of phase separation. Cu-centered clusters show higher potential energies and Voronoi volumes, and bear larger local shear strains. On the other hand, Fe-centered pentagon-rich clusters in Cu-rich regions seem to play an important role to resist the shear transformation. The dilatation or annihilation of Voronoi volumes is due to the competition between ordering via structural relaxation and shear stress-induced deformation. The present study could provide a better understanding of the relationship between the structural inhomogeneity and the deformation of MGs.

  16. Variation in electromagnetic radiation during plastic deformation under tension and compression of metals

    NASA Astrophysics Data System (ADS)

    Singh, Ranjana; Lal, S. P.; Misra, Ashok

    2014-06-01

    This paper presents some significant variations in the intermittent electromagnetic radiation (EMR) during plastic deformation under tension and compression of some metals with selected crystal structure, viz. zinc, hexagonal closed packed (hcp), copper, face-centred cubic (fcc: stacking fault energy 0.08 J/m2), aluminium (fcc: stacking fault energy 0.2 J/m2) and 0.18 % carbon steel, body-centred cubic (bcc). The intermittent EMR signals starting near yielding are either oscillatory or exponential under both modes of deformation except a very few intermediate signals, random in nature, in zinc under compression. The number and amplitude of EMR signals exhibit marked variations under tension and compression. The smooth correlation between elastic strain energy release rate and average EMR energy release rate suggests a novel technique to determine the fracture toughness of metals. The first EMR emission amplitude and EMR energy release rate occurring near the yield increase, but maximum EMR energy burst frequency decreases almost linearly with increase in Debye temperature of the metals under tension while all EMR parameters decrease nonlinearly under compression. These results can be developed into a new technique to evaluate dislocation velocity. The EMR amplitude and energy release rate of the first EMR emission vary parabolically showing a maxima with increase in electronic heat constant of the metals under tension while they first sharply decrease and then become asymptotic during compression. However, the variation in EMR maximum energy burst frequency is apparently similar under both modes of deformation. These results strongly suggest that the mechanism of EMR emission during plastic deformation of metals involves not only the interaction of conduction electrons with the lattice periodic potential as presented in the previous theoretical models but also the interaction of conduction electrons with phonons. However, during crack propagation and fracture

  17. The effect of crystal-plastic deformation on Ti concentration in quartz

    NASA Astrophysics Data System (ADS)

    Nachlas, W. O.; Hirth, G.; Whitney, D. L.; Teyssier, C. P.

    2013-12-01

    Quartz is a dominant phase controlling crustal rheology and strain localization, and the sensitivity of its recrystallization mechanisms to variations in temperature, pressure, and fluid activity make evaluation of these parameters crucial to reconstructing the deformation history of quartz-bearing rocks in the lithosphere. The advent of Ti in quartz thermobarometry provides a technique with potentially powerful applications for understanding the conditions at which rocks deform plastically in the crust. However, it is unclear how ductile deformation, specifically dislocation creep, affects Ti substitution in quartz and whether the Ti concentration in quartz accurately records the conditions at which quartz recrystallized. This study addresses these questions through a series of high P-T rock deformation experiments on precisely synthesized Ti-doped quartz aggregates to investigate the influence of strain and dynamic recrystallization on the concentration of Ti in quartz. Laboratory rock deformation experiments provide an ideal opportunity to study Ti solubility in deformed quartz because they allow for recrystallization to occur in a controlled environment; deformation experiments are conducted under isothermal and isobaric conditions at constant strain rate for increasing intervals of time to isolate the effect of strain on Ti chemistry of quartz. This study employs a novel doping synthesis method to produce a quartz aggregate consisting of a large population of quartz crystals doped with a precise Ti concentration where each individual crystal has a uniform dopant distribution. Deformation of a homogeneous starting material enables simulation of a retrograde solubility path, in which a sample with an initially high, uniform concentration is modified during deformation at conditions where the solubility is substantially lower. This enables observations to be made of the mechanisms responsible for mobilizing Ti through diffusion and exsolution to adjust to the

  18. An Investigation of Enhanced Formability in AA5182-O Al During High-Rate Fre-Forming at Room-Temperature: Quantification of Deformation History

    SciTech Connect

    Rohatgi, Aashish; Soulami, Ayoub; Stephens, Elizabeth V.; Davies, Richard W.; Smith, Mark T.

    2014-03-01

    Following the two prior publication of PNNL Pulse-Pressure research in the Journal of Materials Processing Technology, this manuscript continues to describe PNNL’s advances in getting a better understanding of sheet metal formability under high strain-rate conditions. Specifically, using a combination of numerical modeling and novel experiments, we quantitatively demonstrate the deformation history associated with enhanced formability (~2.5X) in Al under room temperature forming.

  19. In situ spectroscopic study of the plastic deformation of amorphous silicon under nonhydrostatic conditions induced by indentation

    NASA Astrophysics Data System (ADS)

    Gerbig, Y. B.; Michaels, C. A.; Bradby, J. E.; Haberl, B.; Cook, R. F.

    2015-12-01

    Indentation-induced plastic deformation of amorphous silicon (a-Si) thin films was studied by in situ Raman imaging of the deformed contact region of an indented sample, employing a Raman spectroscopy-enhanced instrumented indentation technique. Quantitative analyses of the generated in situ Raman maps provide unique insight into the phase behavior of as-implanted a-Si. In particular, the occurrence and evolving spatial distribution of changes in the a-Si structure caused by processes, such as polyamorphization and crystallization, induced by indentation loading were measured. The experimental results are linked with previously published papers on the plastic deformation of a-Si under hydrostatic compression and shear deformation to establish a sequence for the development of deformation of a-Si under indentation loading. The sequence involves three distinct deformation mechanisms of a-Si: (1) reversible deformation, (2) increase in coordination defects (onset of plastic deformation), and (3) phase transformation. Estimated conditions for the occurrence of these mechanisms are given with respect to relevant intrinsic and extrinsic parameters, such as indentation stress, volumetric strain, and bond angle distribution (a measure for the structural order of the amorphous network). The induced volumetric strains are accommodated solely by reversible deformation of the tetrahedral network when exposed to small indentation stresses. At greater indentation stresses, the increased volumetric strains in the tetrahedral network lead to the formation of predominately fivefold coordination defects, which seems to mark the onset of irreversible or plastic deformation of the a-Si thin film. Further increase in the indentation stress appears to initiate the formation of sixfold coordinated atomic arrangements. These sixfold coordinated arrangements may maintain their amorphous tetrahedral structure with a high density of coordination defects or nucleate as a new crystalline

  20. In situ spectroscopic study of the plastic deformation of amorphous silicon under non-hydrostatic conditions induced by indentation

    PubMed Central

    Gerbig, Y.B; Michaels, C.A.; Bradby, J.E.; Haberl, B.; Cook, R.F.

    2016-01-01

    Indentation-induced plastic deformation of amorphous silicon (a-Si) thin films was studied by in situ Raman imaging of the deformed contact region of an indented sample, employing a Raman spectroscopy-enhanced instrumented indentation technique. Quantitative analyses of the generated in situ Raman maps provide unique, new insight into the phase behavior of as-implanted a-Si. In particular, the occurrence and evolving spatial distribution of changes in the a-Si structure caused by processes, such as polyamorphization and crystallization, induced by indentation loading were measured. The experimental results are linked with previously published work on the plastic deformation of a-Si under hydrostatic compression and shear deformation to establish a sequence for the development of deformation of a-Si under indentation loading. The sequence involves three distinct deformation mechanisms of a-Si: (1) reversible deformation, (2) increase in coordination defects (onset of plastic deformation), and (3) phase transformation. Estimated conditions for the occurrence of these mechanisms are given with respect to relevant intrinsic and extrinsic parameters, such as indentation stress, volumetric strain, and bond angle distribution (a measure for the structural order of the amorphous network). The induced volumetric strains are accommodated solely by reversible deformation of the tetrahedral network when exposed to small indentation stresses. At greater indentation stresses, the increased volumetric strains in the tetrahedral network lead to the formation of predominately five-fold coordination defects, which seems to mark the onset of irreversible or plastic deformation of the a-Si thin film. Further increase in the indentation stress appears to initiate the formation of six-fold coordinated atomic arrangements. These six-fold coordinated arrangements may maintain their amorphous tetrahedral structure with a high density of coordination defects or nucleate as a new crystalline

  1. In situ spectroscopic study of the plastic deformation of amorphous silicon under non-hydrostatic conditions induced by indentation.

    PubMed

    Gerbig, Y B; Michaels, C A; Bradby, J E; Haberl, B; Cook, R F

    2015-12-01

    Indentation-induced plastic deformation of amorphous silicon (a-Si) thin films was studied by in situ Raman imaging of the deformed contact region of an indented sample, employing a Raman spectroscopy-enhanced instrumented indentation technique. Quantitative analyses of the generated in situ Raman maps provide unique, new insight into the phase behavior of as-implanted a-Si. In particular, the occurrence and evolving spatial distribution of changes in the a-Si structure caused by processes, such as polyamorphization and crystallization, induced by indentation loading were measured. The experimental results are linked with previously published work on the plastic deformation of a-Si under hydrostatic compression and shear deformation to establish a sequence for the development of deformation of a-Si under indentation loading. The sequence involves three distinct deformation mechanisms of a-Si: (1) reversible deformation, (2) increase in coordination defects (onset of plastic deformation), and (3) phase transformation. Estimated conditions for the occurrence of these mechanisms are given with respect to relevant intrinsic and extrinsic parameters, such as indentation stress, volumetric strain, and bond angle distribution (a measure for the structural order of the amorphous network). The induced volumetric strains are accommodated solely by reversible deformation of the tetrahedral network when exposed to small indentation stresses. At greater indentation stresses, the increased volumetric strains in the tetrahedral network lead to the formation of predominately five-fold coordination defects, which seems to mark the onset of irreversible or plastic deformation of the a-Si thin film. Further increase in the indentation stress appears to initiate the formation of six-fold coordinated atomic arrangements. These six-fold coordinated arrangements may maintain their amorphous tetrahedral structure with a high density of coordination defects or nucleate as a new crystalline

  2. Plastic deformation behavior of aluminum casting alloys A356/357

    NASA Astrophysics Data System (ADS)

    Wang, Q. G.

    2004-09-01

    The plastic deformation behavior of aluminum casting alloys A356 and A357 has been investigated at various solidification rates with or without Sr modification using monotonic tensile and multi-loop tensile and compression testing. The results indicate that at low plastic strains, the eutectic particle aspect ratio and matrix strength dominate the work hardening, while at large plastic strains, the hardening rate depends on secondary dendrite arm spacing (SDAS). For the alloys studied, the average internal stresses increase very rapidly at small plastic strains and gradually saturate at large plastic strains. Elongated eutectic particles, small SDAS, or high matrix strength result in a high saturation value. The difference in the internal stresses, due to different microstructural features, determines the rate of eutectic particle cracking and, in turn, the tensile instability of the alloys. The higher the internal stresses, the higher the damage rate of particle cracking and then the lower the Young’s modulus. The fracture strain of alloys A356/357 corresponds to the critical amount of damage by particle cracking locally or globally, irrespective of the fineness of the microstructure. In the coarse structure (large SDAS), this critical amount of damage is easily reached, due to the clusters of large and elongated particles, leading to alloy fracture before global necking. However, in the alloy with the small SDAS, the critical amount of damage is postponed until global necking takes place due to the small and round particles. Current models for dispersion hardening can be used to calculate the stresses induced in the particles. The calculations agree well with the results inferred from the experimental results.

  3. [The effects of nanostructured titanium fabricated via surface plastic deformation on Saos-2 cell adherence, proliferation and differentiation].

    PubMed

    Wan, Peng-Bo; Chen, Wan-Tao; He, Jie; Zhang, Xiao-Nong; Zhou, Xiao-Jian

    2008-04-01

    To study the effects of nanostructured titanium fabricated via surface plastic deformation on Saos-2 cell adherence, proliferation and differentiation in vitro. Nanostructured titanium surfaces were prepared using plastic deformation and divided into three groups: group I (30 minutes, n=6), group II (60 minutes, n=6) and group III (90 minutes, n=6), according to the time of preparation. The untreated titanium was used as control group. Saos-2 cell line was cultured on different titanium surfaces. The features of titanium surface and the effects of nanostructured titanium surfaces on cell adherence, proliferation and shape were examined using fluorescence microscope, LSCM and MTT tests. RT-PCR was used to assess the alteration of BMP-4 gene expression. The data was analyzed for ANOVA with SAS6.0 software package. The results of SEM showed that plastic deformation for 60 and 90 minutes yielded nanostructured titanium surface. The nanostructured titanium surface significantly promoted Saos-2 cell adherence (P<0.05). Group II (60 minutes) had more extensive spreading on titanium surfaces than the control group. Group II (60 minutes) and group III (90 minutes) had significantly higher BMP-4 gene expression in Saos-2 cells than control group (P<0.05). The biological behavior of Saos-2 cells on nanostructured titanium surface fabricated via plastic deformation for 60 minutes is better than other groups. Surface plastic deformation may be a potential method to yield nanostructured surface of titanium.

  4. 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 %.

  5. Modeling plastic deformation of post-irradiated copper micro-pillars

    NASA Astrophysics Data System (ADS)

    Crosby, Tamer; Po, Giacomo; Ghoniem, Nasr M.

    2014-12-01

    We present here an application of a fundamentally new theoretical framework for description of the simultaneous evolution of radiation damage and plasticity that can describe both in situ and ex situ deformation of structural materials [1]. The theory is based on the variational principle of maximum entropy production rate; with constraints on dislocation climb motion that are imposed by point defect fluxes as a result of irradiation. The developed theory is implemented in a new computational code that facilitates the simulation of irradiated and unirradiated materials alike in a consistent fashion [2]. Discrete Dislocation Dynamics (DDD) computer simulations are presented here for irradiated fcc metals that address the phenomenon of dislocation channel formation in post-irradiated copper. The focus of the simulations is on the role of micro-pillar boundaries and the statistics of dislocation pinning by stacking-fault tetrahedra (SFTs) on the onset of dislocation channel and incipient surface crack formation. The simulations show that the spatial heterogeneity in the distribution of SFTs naturally leads to localized plastic deformation and incipient surface fracture of micro-pillars.

  6. Formation of nanocrystalline layers by surface severe plastic deformation and pulsed plasma electrolytic carburizing.

    PubMed

    Aliofkhazraei, M; Rouhaghdam, A Sabour

    2010-07-01

    Surfaces of various kinds of metallic materials spheres were treated by nanocrystalline surface severe plastic deformation and then pulsed nanocrystalline plasma electrolytic carburizing to study nanocrystalline substrate effect on formation and nano-hardness of hard nanocrystalline layer. The surface layers of the metallic materials developed by the nanocrystalline surface severe plastic deformation were characterized by means of high resolution scanning electron microscope. Nearly equiaxed nanocrystals with grain sizes ranging from 15 to 90 nm were observed in the near surface regions of all metallic materials, which are low carbon steel and commercially pure titanium. The effect of substrate nanocrystallization on growth kinetics and hardness of formed nanocrystalline carbide layer was studied with the means of figure analysis and nanohardness tests. Figure analysis show the length to diameter ratio and distribution curve of nanocrystals and it has been found that the achieved properties of hard layer (growth rate, nano-hardness, nanostructure...) are related to these factors. It was also clarified that these techniques and surface nanocrystallization can be easily achieved in most of metallic materials. Results indicate that the resultant hardened carburized layers exhibited excellent hardness profile. Investigation of the layer characteristics showed strong dependence followed from the treatment experimental parameters as well as the shape of nanocrystals.

  7. Effect of severe plastic deformation on microstructure of squeeze-cast magnesium alloy AZ31 plate

    NASA Astrophysics Data System (ADS)

    Fong, Kai Soon; Tan, Ming Jen; Atsushi, Danno; Chua, Beng Wah; Ho, Meng Kwong

    2016-10-01

    High cost and poor room temperature formability of magnesium alloy sheet are the key factors that limit its application as a feedstock material for press forming. Production of Mg plates by squeeze casting with further processing by severe plastic deformation (SPD) is a potential method to reduce cost and improve formability. In this study, AZ31 Mg plate of dimension 96×96×4 mm was successfully produced by squeeze casting, using a novel melt transfer technique, at a forging force and speed of 180 Ton and 200 mm/sec respectively. The effect of severe plastic deformation (SPD) using groove pressing on the mechanical properties of squeeze-casted Mg plate after partial homogenization was subsequently investigated. Observation of the microstructure after two cycles of groove pressing, under decreasing temperature from 543K to 493K, shows a significant grain refinement from 39 to 4.7 µm. The Vickers hardness increased by approximately 25% from 56 to 74.1 which suggests an improvement in mechanical strength as a result of both the grain refinement and work hardening. The result shows that squeeze casting combined with groove pressing is potentially an effective method for preparation of thin magnesium alloy plate with fine-grained structure and improved mechanical properties.

  8. Transition of Temporal Scaling Behavior in Percolation Assisted Shear-branching Structure during Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Ren, Jingli; Chen, Cun; Wang, Gang; Liaw, Peter K.

    2017-03-01

    This paper explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10‑2 s‑1 the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at the intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10‑2 s‑1.

  9. Influence of severe plastic deformation on the structure and properties of ultrahigh carbon steel wire

    SciTech Connect

    Leseur, D R; Sherby, O D; Syn, C K

    1999-07-01

    Ultrahigh-carbon steel wire can achieve very high strength after severe plastic deformation, because of the fine, stable substructures produce. Tensile strengths approaching 6000 MPa are predicted for UHCS containing 1.8%C. This paper discusses the microstructural evolution during drawing of UHCS wire, the resulting strength produced and the factors influencing fracture. Drawing produces considerable alignment of the pearlite plates. Dislocation cells develop within the ferrite plates and, with increasing strain, the size normal to the axis ({lambda}) decreases. These dislocation cells resist dynamic recovery during wire drawing and thus extremely fine substructures can be developed ({lambda} < 10 nm). Increasing the carbon content reduces the mean free ferrite path in the as-patented wire and the cell size developed during drawing. For UHCS, the strength varies as {lambda}{sup {minus}5}. Fracture of these steels was found to be a function of carbide size and composition. The influence of processing and composition on achieving high strength in these wires during severe plastic deformation is discussed.

  10. Aluminizing a Ni sheet through severe plastic deformation induced by ball collisions

    NASA Astrophysics Data System (ADS)

    Romankov, S.; Shchetinin, I. V.; Park, Y. C.

    2015-07-01

    Aluminizing a Ni sheet was performed through severe plastic deformation induced by ball collisions. The Ni sheet was fixed in the center of a mechanically vibrated vial between two connected parts. The balls were loaded into the vial on both sides of the Ni disk. Al disks, which were fixed on the top and the bottom of the vial, served as the sources of Al contamination. During processing, the Ni sheet was subject to intense ball collisions. The Al fragments were transferred and alloyed to the surface of the Ni sheet by these collisions. The combined effects of deformation-induced plastic flow, mechanical intermixing, and grain refinement resulted in the formation of a dense, continuous nanostructured Al layer on the Ni surface on both sides of the sheet. The Al layer consisted of Al grains with an average size of about 40 nm. The Al layer was reinforced with nano-sized Ni flakes that were introduced from the Ni surface during processing. The local amorphization at the Ni/Al interface revealed that the bonding between Ni and Al was formed by mechanical intermixing of atomic layers at the interface. The hardness of the fabricated Al layer was 10 times that of the initial Al plate. The ball collisions destroyed the initial rolling texture of the Ni sheet and induced the formation of the mixed [1 0 0] + [1 1 1] fiber texture. The laminar rolling structure of the Ni was transformed into an ultrafine grain structure.

  11. Elementary model of severe plastic deformation by KoBo process

    SciTech Connect

    Gusak, A.; Storozhuk, N.; Danielewski, M. Korbel, A.; Bochniak, M.

    2014-01-21

    Self-consistent model of generation, interaction, and annihilation of point defects in the gradient of oscillating stresses is presented. This model describes the recently suggested method of severe plastic deformation by combination of pressure and oscillating rotations of the die along the billet axis (KoBo process). Model provides the existence of distinct zone of reduced viscosity with sharply increased concentration of point defects. This zone provides the high extrusion velocity. Presented model confirms that the Severe Plastic Deformation (SPD) in KoBo may be treated as non-equilibrium phase transition of abrupt drop of viscosity in rather well defined spatial zone. In this very zone, an intensive lateral rotational movement proceeds together with generation of point defects which in self-organized manner make rotation possible by the decrease of viscosity. The special properties of material under KoBo version of SPD can be described without using the concepts of nonequilibrium grain boundaries, ballistic jumps and amorphization. The model can be extended to include different SPD processes.

  12. Elementary model of severe plastic deformation by KoBo process

    NASA Astrophysics Data System (ADS)

    Gusak, A.; Danielewski, M.; Korbel, A.; Bochniak, M.; Storozhuk, N.

    2014-01-01

    Self-consistent model of generation, interaction, and annihilation of point defects in the gradient of oscillating stresses is presented. This model describes the recently suggested method of severe plastic deformation by combination of pressure and oscillating rotations of the die along the billet axis (KoBo process). Model provides the existence of distinct zone of reduced viscosity with sharply increased concentration of point defects. This zone provides the high extrusion velocity. Presented model confirms that the Severe Plastic Deformation (SPD) in KoBo may be treated as non-equilibrium phase transition of abrupt drop of viscosity in rather well defined spatial zone. In this very zone, an intensive lateral rotational movement proceeds together with generation of point defects which in self-organized manner make rotation possible by the decrease of viscosity. The special properties of material under KoBo version of SPD can be described without using the concepts of nonequilibrium grain boundaries, ballistic jumps and amorphization. The model can be extended to include different SPD processes.

  13. Transition of Temporal Scaling Behavior in Percolation Assisted Shear-branching Structure during Plastic Deformation

    PubMed Central

    Ren, Jingli; Chen, Cun; Wang, Gang; Liaw, Peter K.

    2017-01-01

    This paper explores the temporal scaling behavior induced shear-branching structure in response to variant temperatures and strain rates during plastic deformation of Zr-based bulk metallic glass (BMG). The data analysis based on the compression tests suggests that there are two states of shear-branching structures: the fractal structure with a long-range order at an intermediate temperature of 223 K and a larger strain rate of 2.5 × 10−2 s−1; the disordered structure dominated at other temperature and strain rate. It can be deduced from the percolation theory that the compressive ductility, ec, can reach the maximum value at the intermediate temperature. Furthermore, a dynamical model involving temperature is given for depicting the shear-sliding process, reflecting the plastic deformation has fractal structure at the temperature of 223 K and strain rate of 2.5 × 10−2 s−1. PMID:28327562

  14. High-rate squeezing process of bulk metallic glasses

    PubMed Central

    Fan, Jitang

    2017-01-01

    High-rate squeezing process of bulk metallic glasses from a cylinder into an intact sheet achieved by impact loading is investigated. Such a large deformation is caused by plastic flow, accompanied with geometrical confinement, shear banding/slipping, thermo softening, melting and joining. Temperature rise during the high-rate squeezing process makes a main effect. The inherent mechanisms are illustrated. Like high-pressure torsion (HPT), equal channel angular pressing (ECAP) and surface mechanical attrition treatments (SMAT) for refining grain of metals, High-Rate Squeezing (HRS), as a multiple-functions technique, not only creates a new road of processing metallic glasses and other metallic alloys for developing advanced materials, but also directs a novel technology of processing, grain refining, coating, welding and so on for treating materials. PMID:28338092

  15. High-rate squeezing process of bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Fan, Jitang

    2017-03-01

    High-rate squeezing process of bulk metallic glasses from a cylinder into an intact sheet achieved by impact loading is investigated. Such a large deformation is caused by plastic flow, accompanied with geometrical confinement, shear banding/slipping, thermo softening, melting and joining. Temperature rise during the high-rate squeezing process makes a main effect. The inherent mechanisms are illustrated. Like high-pressure torsion (HPT), equal channel angular pressing (ECAP) and surface mechanical attrition treatments (SMAT) for refining grain of metals, High-Rate Squeezing (HRS), as a multiple-functions technique, not only creates a new road of processing metallic glasses and other metallic alloys for developing advanced materials, but also directs a novel technology of processing, grain refining, coating, welding and so on for treating materials.

  16. A combined crystal plasticity and graph-based vertex model of dynamic recrystallization at large deformations

    NASA Astrophysics Data System (ADS)

    Mellbin, Y.; Hallberg, H.; Ristinmaa, M.

    2015-06-01

    A mesoscale model of microstructure evolution is formulated in the present work by combining a crystal plasticity model with a graph-based vertex algorithm. This provides a versatile formulation capable of capturing finite-strain deformations, development of texture and microstructure evolution through recrystallization. The crystal plasticity model is employed in a finite element setting and allows tracing of stored energy build-up in the polycrystal microstructure and concurrent reorientation of the crystal lattices in the grains. This influences the progression of recrystallization as nucleation occurs at sites with sufficient stored energy and since the grain boundary mobility and energy is allowed to vary with crystallographic misorientation across the boundaries. The proposed graph-based vertex model describes the topological changes to the grain microstructure and keeps track of the grain inter-connectivity. Through homogenization, the macroscopic material response is also obtained. By the proposed modeling approach, grain structure evolution at large deformations as well as texture development are captured. This is in contrast to most other models of recrystallization which are usually limited by assumptions of one or the other of these factors. In simulation examples, the model is in the present study shown to capture the salient features of dynamic recrystallization, including the effects of varying initial grain size and strain rate on the transitions between single-peak and multiple-peak oscillating flow stress behavior. Also the development of recrystallization texture and the influence of different assumptions on orientation of recrystallization nuclei are investigated. Further, recrystallization kinetics are discussed and compared to classical JMAK theory. To promote computational efficiency, the polycrystal plasticity algorithm is parallelized through a GPU implementation that was recently proposed by the authors.

  17. Testing plastic deformations of materials in the introductory undergraduate mechanics laboratory

    NASA Astrophysics Data System (ADS)

    Romo-Kröger, C. M.

    2012-05-01

    Normally, a mechanics laboratory at the undergraduate level includes an experiment to verify compliance with Hooke's law in materials, such as a steel spring and an elastic rubber band. Stress-strain curves are found for these elements. Compression in elastic bands is practically impossible to achieve due to flaccidity. A typical experiment for the complete loading-unloading cycle is to subject a tubular object to torsion. This paper suggests simple experiments for studying properties concerning elasticity and plasticity in elements of common use, subjected to stretching or compression, and also torsion reinforcing. The experiments use plastic binders, rubber bands and metal springs under a moderate load. This paper discusses an experiment with an original device to measure torsion deformations as a function of applied torques, which permitted construction of the hysteresis cycle for a rubber hose and various tubes. Another experiment was designed to define the temporal recovery of a plastic spring with initial stretching. A simple mathematical model was developed to explain this phenomenon.

  18. Anhysteretic magnetization and magnetostriction of thin NiFe films under stress and plastic deformation

    NASA Astrophysics Data System (ADS)

    Finkel, Peter; Garrity, Ed; Lofland, Sam

    2006-03-01

    The magnetic properties of thin samples of a thin film NiFe sample under tensile stress are investigated. The magnetostriction contribution to dc magnetization under elastic stress and the effect of the plastic strain on the hysteresis loops are discussed. Also, a role of the plastic deformation interrelated with the elastic stress in the magnetization process is established. An experimental system based on a conventional vibrating sample magnetometer equipped with the specially designed loading fixture and optical resonant spectroscopy tension monitoring technique is used to measure anhysteretic permeability and magnetization curve as a function of stress and temperature. This method used to measure anhysteretic permeability and magnetization curve of Ni-Fe as a function of stress and temperature. Anhysteretic permeability was extracted from the anhysteretic B-H curves constructed by degaussing the sample at given longitudinal (parallel to the stresses) dc field. The large positive magnetostriction constant of FeNi samples leads to higher susceptibility and lower coercivity with tensile stress while the large volume magnetostriction results in reduced saturation magnetization. Large stresses imposed on the sample result in plastic strain of the sample which induces increase in dislocation density and domain wall pinning. This causes the gain in hysteresis loss and coercivity to increase at the highest stresses. We also discuss the effect of the Ni composition on results of the measurements.

  19. Micropillar Compression Technique Applied to Micron-Scale Mudstone Elasto-Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Dewers, T. A.; Boyce, B.; Buchheit, T.; Heath, J. E.; Chidsey, T.; Michael, J.

    2010-12-01

    Mudstone mechanical testing is often limited by poor core recovery and sample size, preservation and preparation issues, which can lead to sampling bias, damage, and time-dependent effects. A micropillar compression technique, originally developed by Uchic et al. 2004, here is applied to elasto-plastic deformation of small volumes of mudstone, in the range of cubic microns. This study examines behavior of the Gothic shale, the basal unit of the Ismay zone of the Pennsylvanian Paradox Formation and potential shale gas play in southeastern Utah, USA. Precision manufacture of micropillars 5 microns in diameter and 10 microns in length are prepared using an ion-milling method. Characterization of samples is carried out using: dual focused ion - scanning electron beam imaging of nano-scaled pores and distribution of matrix clay and quartz, as well as pore-filling organics; laser scanning confocal (LSCM) 3D imaging of natural fractures; and gas permeability, among other techniques. Compression testing of micropillars under load control is performed using two different nanoindenter techniques. Deformation of 0.5 cm in diameter by 1 cm in length cores is carried out and visualized by a microscope loading stage and laser scanning confocal microscopy. Axisymmetric multistage compression testing and multi-stress path testing is carried out using 2.54 cm plugs. Discussion of results addresses size of representative elementary volumes applicable to continuum-scale mudstone deformation, anisotropy, and size-scale plasticity effects. Other issues include fabrication-induced damage, alignment, and influence of substrate. This work is funded by the US Department of Energy, Office of Basic Energy Sciences. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

  20. Effect of room-temperature compression on microstructure of ductile cast iron subjected to hot plastic deformation

    NASA Astrophysics Data System (ADS)

    Chaus, A. S.

    2014-07-01

    The change in the microstructure of ductile cast iron subjected to hot plastic deformation has been investigated after the fracture of the samples induced by compression (upset forging) at room temperature. It has been shown that compression-induced tangential stresses cause shear deformation, which results in the shear fracture of test samples at an angle of 40°-50° to the longitudinal axis of a sample. It has been established that the fracture is accompanied by the formation of a narrow zone of severe plastic deformation of ductile cast iron, which is located on both sides of the major fracture. In this zone, the initial microstructure undergoes significant changes due to the plastic flow of the matrix and graphite inclusions.

  1. Microstructural Analysis of Severe Plastic Deformed Twin Roll Cast AZ31 for the Optimization of Superplastic Properties

    SciTech Connect

    Young, John P.; Askari, Hesam A.; Heiden, Michael J.; Hovanski, Yuri; Field, David P.; Zbib, Hussein M.

    2013-07-08

    In recent years magnesium alloys have attracted significant attention as potential candidates to replace many of the heavier metals used in some automotive applications. However, the limited formability of magnesium and its alloys at room temperature has driven interest in the superplastic forming magnesium as an alternative shaping method. Severe plastic deformation techniques have become a well studied method of refining the grain size and modifying the microstructural characteristics of many magnesium alloys to achieve greater superplastic properties. In this study twin roll cast (TRC) AZ31 magnesium alloy was subjected to equal channel angular pressing (ECAP) and friction stir welding (FSW). The influence of these severe plastic deformation processes on the grain size, texture and grain boundary character distribution was investigated to identify the optimum severe plastic deformation process for the superplastic forming of AZ31.

  2. Experimental characterization and crystal plasticity modeling of heterogeneous deformation in polycrystalline {alpha}-Ti.

    SciTech Connect

    Wang, L.; Barabash, R. I.; Yang, Y.; Bieler, T. R.; Crimp, M. A.; Eisenlohr, P.; Liu, W.; Ice, G. E.

    2011-03-01

    Grain-level heterogeneous deformation was studied in a polycrystalline {alpha}-Ti specimen deformed by four-point bending. Dislocation slip activity in the microstructure was investigated by surface slip trace analysis. Three-dimensional-X-ray diffraction (3D-XRD) was used to investigate subsurface lattice rotations and to identify geometrically necessary dislocations (GNDs). The slip systems of local GNDs were analyzed by studying the streaking directions of reflections in corresponding Laue patterns. The analysis performed in one grain indicated that the subsurface GNDs were from the same slip system identified using slip trace analysis in backscattered electron images. A crystal plasticity finite element (CPFE) model was used to simulate deformation of the same microstructural region. The predictions of dislocation slip activity match the general aspects of the experimental observations, including the ability to simulate the activation of different slip systems in grains where multiple slip systems were activated. Prediction of local crystal rotations, however, was the least accurate aspect of the CPFE model.

  3. Experimental characterization and crystal plasticity modeling of heterogeneous deformation in polycrystalline -Ti

    SciTech Connect

    Wang, Leyun; Barabash, Rozaliya; Yang, Y; Bieler, Prof T R; Crimp, Prof M A; Eisenlohr, P; Liu, W.; Ice, Gene E

    2011-01-01

    Grain-level heterogeneous deformation was studied in a polycrystalline {alpha}-Ti specimen deformed by four-point bending. Dislocation slip activity in the microstructure was investigated by surface slip trace analysis. Three-dimensional-X-ray diffraction (3D-XRD) was used to investigate subsurface lattice rotations and to identify geometrically necessary dislocations (GNDs). The slip systems of local GNDs were analyzed by studying the streaking directions of reflections in corresponding Laue patterns. The analysis performed in one grain indicated that the subsurface GNDs were from the same slip system identified using slip trace analysis in backscattered electron images. A crystal plasticity finite element (CPFE) model was used to simulate deformation of the same microstructural region. The predictions of dislocation slip activity match the general aspects of the experimental observations, including the ability to simulate the activation of different slip systems in grains where multiple slip systems were activated. Prediction of local crystal rotations, however, was the least accurate aspect of the CPFE model.

  4. The influence of hold time on the onset of plastic deformation in silicon

    SciTech Connect

    Wong, S.; Haberl, B.; Williams, J. S.; Bradby, J. E.

    2015-12-28

    The transformation of diamond-cubic silicon to the metallic β-Sn phase is known to be “sluggish,” even when the critical pressure (∼11 GPa) for the transformation is reached. In this letter, we use nanoindentation to apply pressures to just above the critical threshold. In this regime, the sample displays purely elastic behavior at zero hold time. As the hold time at maximum load is increased up to 180 s, the percentage of indents that plastically deform also increase. Interestingly, the indents deform via one of two distinct processes: either via a phase transformation to a mixed bc8/r8-Si end phase, or by initiation of crystalline defects. Raman spectroscopy and cross-sectional transmission electron microscopy are used to show that the two deformation mechanisms are mutually exclusive under the indentation conditions presented here, and elastic modelling was utilized to propose a model for this mutually exclusive behavior. Hence, this behavior enhances the potential for application of the exotic bc8/r8-Si end phase.

  5. The influence of hold time on the onset of plastic deformation in silicon

    NASA Astrophysics Data System (ADS)

    Wong, S.; Haberl, B.; Williams, J. S.; Bradby, J. E.

    2015-12-01

    The transformation of diamond-cubic silicon to the metallic β-Sn phase is known to be "sluggish," even when the critical pressure (˜11 GPa) for the transformation is reached. In this letter, we use nanoindentation to apply pressures to just above the critical threshold. In this regime, the sample displays purely elastic behavior at zero hold time. As the hold time at maximum load is increased up to 180 s, the percentage of indents that plastically deform also increase. Interestingly, the indents deform via one of two distinct processes: either via a phase transformation to a mixed bc8/r8-Si end phase, or by initiation of crystalline defects. Raman spectroscopy and cross-sectional transmission electron microscopy are used to show that the two deformation mechanisms are mutually exclusive under the indentation conditions presented here, and elastic modelling was utilized to propose a model for this mutually exclusive behavior. Hence, this behavior enhances the potential for application of the exotic bc8/r8-Si end phase.

  6. Tribological and Geometrical Analysis of the Friction Forces of Continuous Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Donič, T.; Hadzima, B.; Raab, G.

    2017-05-01

    Equal Channel Angular Rolling (ECAR), a severe plastic deformation process, is suitable for the shear deforming a long and thin sheet continuously. An interesting issue is that thickness of a sheet is not reduced during ECAR. Although the shear texture and fine grain structure are easily obtained by ECAR, yet the ECAR process’s difficulties in terms of technical control, such as surface defect, low ductility and low processing speed, still remain. The surface defects and processing speed are partially improved by applying a series deformation of rolling and ECAR. The article presents methodological and analytical procedures, adaptation of a conventional rolling mill Duo-system for processes of a SPD-representative which are represented by the method ECAR. They specify in detail the technical requirements whose new design solutions should be implemented. They present in detail the mechanical load drive shafts, as well as the calculation of compression forces with consideration of the friction forces. The geometric analyses of localisation positions of the outlet channel in terms of size and orientation of the dominant shear plane are also presented.

  7. A defect density-based constitutive crystal plasticity framework for modeling the plastic deformation of Fe-Cr-Al cladding alloys subsequent to irradiation

    SciTech Connect

    Patra, Anirban; Wen, Wei; Martinez Saez, Enrique; Tome, Carlos

    2016-02-05

    It is essential to understand the deformation behavior of these Fe-Cr-Al alloys, in order to be able to develop models for predicting their mechanical response under varied loading conditions. Interaction of dislocations with the radiation-induced defects governs the crystallographic deformation mechanisms. A crystal plasticity framework is employed to model these mechanisms in Fe-Cr-Al alloys. This work builds on a previously developed defect density-based crystal plasticity model for bcc metals and alloys, with necessary modifications made to account for the defect substructure observed in Fe-Cr-Al alloys. The model is implemented in a Visco-Plastic Self Consistent (VPSC) framework, to predict the mechanical behavior under quasi-static loading.

  8. A Novel Micro-Scale Plastic Deformation Feature on a Bulk Metallic Glass Surface under Laser Shock Peening

    NASA Astrophysics Data System (ADS)

    Wei, Yan-Peng; Wei, Bing-Chen; Wang, Xi; Xu, Guang-Yue; Li, Lei; Wu, Xian-Qian; Song, Hong-Wei; Huang, Chen-Guang

    2013-03-01

    Laser shocking peening is a widely applied surface treatment technique that can effectively improve the fatigue properties of metal parts. We observe many micro-scale arc plastic steps on the surface of Zr47.9Ti0.3Ni3.1Cu39.3Al9.4 metallic glass subjected to the ultra-high pressure and strain rate induced by laser shock peening. The scanning electronic microscopy and atomic force microscopy show that the arc plastic step (APS) has an arc boundary, 50-300 nm step height, 5-50 μm radius and no preferable direction. These APSs have the ability to accommodate plastic deformation in the same way as shear band. This may indicate a new mechanism to accommodate the plastic deformation in amorphous metallic glass under high pressure, ultra-high strain rates, and short duration.

  9. A deformation theory of strain gradient crystal plasticity that accounts for geometrically necessary dislocations

    NASA Astrophysics Data System (ADS)

    Bardella, Lorenzo

    2006-01-01

    We propose a deformation theory of strain gradient crystal plasticity that accounts for the density of geometrically necessary dislocations by including, as an independent kinematic variable, Nye's dislocation density tensor [1953. Acta Metallurgica 1, 153-162]. This is accomplished in the same fashion as proposed by Gurtin and co-workers (see, for instance, Gurtin and Needleman [2005. J. Mech. Phys. Solids 53, 1-31]) in the context of a flow theory of crystal plasticity, by introducing the so-called defect energy. Moreover, in order to better describe the strengthening accompanied by diminishing size, we propose that the classical part of the plastic potential may be dependent on both the plastic slip vector and its gradient; for single crystals, this also makes it easier to deal with the "higher-order" boundary conditions. We develop both the kinematic formulation and its static dual and apply the theory to the simple shear of a constrained strip (example already exploited in Shu et al. [2001. J. Mech. Phys. Solids 49, 1361-1395], Bittencourt et al. [2003. J. Mech. Phys. Solids 51, 281-310], Niordson and Hutchinson [2003. Euro J. Mech. Phys. Solids 22, 771-778], Evers et al. [2004. J. Mech. Phys. Solids 52, 2379-2401], and Anand et al. [2005. J. Mech. Phys. Solids 53, 1789-1826]) to investigate what sort of behaviour the new model predicts. The availability of the total potential energy functional and its static dual allows us to easily solve this simple boundary value problem by resorting to the Ritz method.

  10. Effect of plastic deformation on the magnetic properties and dislocation luminescence of isotopically enriched silicon {sup 29}Si:B

    SciTech Connect

    Koplak, O. V.; Shteynman, E. A.; Tereschenko, A. N.; Morgunov, R. B.

    2015-09-15

    A correlation between the temperature dependences of the D1-line intensity of dislocation luminescence and the magnetic moment of plastically deformed isotopically enriched crystals {sup 29}Si:B is found. It is established that the magnetic susceptibility of the deformed crystals obtained by integration of the spectra of electron spin resonance and the D1-line intensity undergo similar nonmonotonic variations with temperature varying in the range of 20–32 K.

  11. Plastic deformation in nanoscale gold single crystals and open-celled nanoporous gold

    NASA Astrophysics Data System (ADS)

    Lee, Dongyun; Wei, Xiaoding; Zhao, Manhong; Chen, Xi; Jun, Seong C.; Hone, James; Kysar, Jeffrey W.

    2007-01-01

    The results of two sets of experiments to measure the elastic-plastic behaviour of gold at the nanometre length scale are reported. One set of experiments was on free-standing nanoscale single crystals of gold, and the other was on free-standing nanoscale specimens of open-celled nanoporous gold. Both types of specimens were fabricated from commercially available leaf which was either pure Au or a Au/Ag alloy following by dealloying of the Ag. Mechanical testing specimens of a 'dog-bone' shape were fabricated from the leaf using standard lithographic procedures after the leaf had been glued onto a silicon wafer. The thickness of the gauge portion of the specimens was about 100 nm, the width between 250 nm and 300 nm and the length 7 µm. The specimens were mechanically loaded with a nanoindenter (MTS) at the approximate midpoint of the gauge length. The resulting force-displacement curve of the single crystal gold was serrated and it was evident that slip localization occurred on individual slip systems; however, the early stages of the plastic deformation occurred in a non-localized manner. The results of detailed finite element analyses of the specimen suggest that the critical resolved shear stress of the gold single crystal was as high as 135 MPa which would lead to a maximum uniaxial stress of about 500 MPa after several per cent strain. The behaviour of the nanoporous gold was substantially different. It exhibited an apparent elastic behaviour until the point where it failed in an apparently brittle manner, although it is assumed that plastic deformation occurred in the ligaments prior to failure. The average elastic stiffness of three specimens was measured to be Enp = 8.8 GPa and the stress at ultimate failure averaged 190 MPa for the three specimens tested. Scaling arguments suggest that the stress in the individual ligaments could approach the theoretical shear strength. Presented at the IUTAM Symposium on Plasticity at the Micron Scale, Technical

  12. Combination of in situ straining and ACOM TEM: a novel method for analysis of plastic deformation of nanocrystalline metals.

    PubMed

    Kobler, A; Kashiwar, A; Hahn, H; Kübel, C

    2013-05-01

    Nanocrystalline metals are expected to exhibit different deformation mechanisms when compared to their coarse grained counterparts because the dislocation storage capacity decreases and the grain boundary mediated processes become more pronounced with decreasing grain size. As a new approach to directly image and quantify the plastic deformation processes in nanocrystalline thin films, a combination of automated crystal orientation mapping in microprobe STEM mode with in situ straining inside a TEM was developed. ACOM-TEM closes the gap between EBSD and BF/DFTEM by providing full orientation maps with nanometer resolution. The novel combination with in situ straining provided for the first time the possibility to directly image and quantify the structural changes of all crystallites in the ensemble of a thin film at the nanometer scale during mechanical deformation. It was used to characterize the metallographic changes during tensile deformation of a nanocrystalline Au thin film prepared by magnetron sputtering. The investigation of the grain size, grain orientation and twinning on a global (grain average over a micron sized area) and local (assembly of selected grains) scale allowed for the development of an in depth picture of the deformation processes. Grain boundary motion and local grain rotation were two of the processes acting to dissipate the applied stress. Additionally, twinning/detwinning occurred simultaneously during straining. These processes, which occurred locally already in the micro-plastic regime, led to global grain growth starting at the transition to the macro-plastic deformation regime.

  13. Mixed brittle-plastic deformation behaviour in a slate belt. Examples from the High-Ardenne slate belt (Belgium, Germany)

    NASA Astrophysics Data System (ADS)

    Sintubin, Manuel; van Baelen, Hervé; van Noten, Koen; Muchez, Philippe

    2010-05-01

    In the High-Ardenne slate belt, part of the Rhenohercynian external fold-and-thrust belt at the northern extremity of the Late Palaeozoic Variscan orogen (Belgium, Germany, France), particular quartz vein occurrences can be observed in predominantly fine-grained siliciclastic metasediments. Detailed structural, petrographical and geochemical studies has revealed that these vein occurrences can be related to a mixed brittle-plastic deformation behaviour in a low-grade metamorphic mid-crustal environment. The first type of quartz veins are bedding-perpendicular, lens-shaped extension veins that are confined to the sandstone layers within the multilayer sequence. Fluid inclusion studies demonstrate high fluid pressures suggesting that the individual sandstone bodies acted as isolated high-pressure compartments in an overpressured basin. Hydraulic fracturing occurred during the tectonic inversion (from extension to compression) in the earliest stages of the Variscan orogeny. The vein fill shows a blocky character indicating crystal growth in open cavities. Both the typical lens shape of the veins and the subsequent cuspate-lobate folding of the bed interfaces in between the quartz veins suggest plastic deformation of cohesionless fluid-filled fissures. Metamorphic grade of the host rock and fluid temperature and pressure clearly indicates mid-crustal conditions below the brittle-plastic transition. This first type of quartz veins exemplifies mixed brittle-plastic deformation behaviour, possibly related to a transient deepening of the brittle-plastic transition. This is in contrast with contemporaneous bedding-perpendicular crack-seal veins observed in higher - upper-crustal - structural levels in the slate belt, reflecting pure brittle deformation behaviour. The second type are discordant quartz veins confined to extensional low-angle detachment shear zones. These very irregular veins transect a pre-existing pervasive cleavage fabric. They show no matching walls and

  14. The influence of plastic deformation on the magnetic properties of ? alloy

    NASA Astrophysics Data System (ADS)

    Takahashi, S.; Li, X. G.; Chiba, A.

    1996-07-01

    Magnetization is measured in plastically deformed 0953-8984/8/27/018/img2 alloy in the temperature range from 4.5 to 80 K.The temperature dependence of spontaneous magnetization 0953-8984/8/27/018/img3 has been analysed according to the self-consistent renormalization theory of spin fluctuation. The value of 0953-8984/8/27/018/img4 decreases from 0953-8984/8/27/018/img5 to 0953-8984/8/27/018/img6 and the Curie temperature 0953-8984/8/27/018/img7 declines from 57.8 to 50.1 K with 50% strain. The decreases in 0953-8984/8/27/018/img4 and 0953-8984/8/27/018/img7 can be explained by the introduction of the antiphase boundary, which reveals the existence of an atomically ordered structure in the Ni - Cu alloys.

  15. Mechanical Properties and Atomic Explanation of Plastic Deformation for Diamond-Like BC2

    PubMed Central

    Zheng, Baobing; Zhang, Meiguang; Chang, Shaomei

    2016-01-01

    Motivated by a recently predicted structure of diamond-like BC2 with a high claimed hardness of 56 GPa (J. Phys. Chem. C 2010, 114, 22688–22690), we focus on whether this tetragonal BC2 (t-BC2) is superhard or not in spite of such an ultrahigh theoretical hardness. The mechanical properties of t-BC2 were thus further extended by using the first principles in the framework of density functional theory. Our results suggest that the Young’s and shear moduli of t-BC2 exhibit a high degree of anisotropy. For the weakest shear direction, t-BC2 undergoes an electronic instability and structural collapse upon a shear strain of about 0.11, with its theoretically ideal strength of only 36.2 GPa. Specifically, the plastic deformation under shear strain along the (110)[001] direction can be attributed to the breaking of d1 B–C bonds. PMID:28773636

  16. Sintering boron carbide ceramics without grain growth by plastic deformation as the dominant densification mechanism

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Rehman, Sahibzada Shakir; Wang, Weimin; Wang, Hao; Wang, Yucheng; Zhang, Jinyong; Zhang, Fan; Fu, Zhengyi

    2015-10-01

    A new ceramic sintering approach employing plastic deformation as the dominant mechanism is proposed, at low temperature close to the onset point of grain growth and under high pressure. Based on this route, fully dense boron carbide without grain growth can be prepared at 1,675-1,700 °C and under pressure of (≥) 80 MPa in 5 minutes. The dense boron carbide shows excellent mechanical properties, including Vickers hardness of 37.8 GPa, flexural strength of 445.3 MPa and fracture toughness of 4.7 MPa•m0.5. Such a process should also facilitate the cost-effective preparation of other advanced ceramics for practical applications.

  17. Microstructure of aluminum-iron alloys subjected to severe plastic deformation

    SciTech Connect

    Senkov, O.N.; Froes, F.H.; Stolyarov, V.V.; Valiev, R.Z.; Liu, J.

    1998-04-14

    The present paper describes detailed experiments on structure and phase characterization carried out on aluminum-iron alloys after intense torsion straining. The equilibrium solubility of iron in the aluminum lattice at room temperature has been reported to be 0.025 at.%. Alloying of aluminum with iron can increase the high-temperature strength due to a dispersion of second-phase particles. This effect can be enhanced by increasing the solid solubility extension of iron in the aluminum matrix and producing non-equilibrium phases by techniques such as RS, MA or even a laser treatment. In the present work, the severe plastic deformation approach has been used to extend the iron solubility in aluminum and to produce a nano-grained structure in several Al-Fe alloys.

  18. Grain boundary distribution and texture in ultrafine-grained copper produced by severe plastic deformation

    SciTech Connect

    Mishin, O.V. |; Gertsman, V.Y. |; Valiev, R.Z.; Gottstein, G.

    1996-10-01

    Ultrafine-grained (UFG), i.e., nano- and submicrocrystalline materials have attracted great attention in recent years. This interest is caused by the unusual mechanical and physical properties of these materials. The extremely high volume fraction of grain boundaries (GBs) and triple junctions in UFG materials contribute to their unusual properties. However, other important parameters describing polycrystalline aggregate, namely, grain boundary misorientation and character distributions have not yet been studied in UFG materials, though they are conceived to influence mechanical and physical properties as well. Some studies indicated that mainly high-angle GBs were formed during severe plastic deformation; however, no direct proof of this suggestion has been obtained so far. The current paper deals with a statistical study of GB distributions and texture in UFG-materials. Pure copper was chosen for this study, since many results on microstructure and properties of the ultrafine-grained state produced in this material are available.

  19. Sintering boron carbide ceramics without grain growth by plastic deformation as the dominant densification mechanism

    PubMed Central

    Ji, Wei; Rehman, Sahibzada Shakir; Wang, Weimin; Wang, Hao; Wang, Yucheng; Zhang, Jinyong; Zhang, Fan; Fu, Zhengyi

    2015-01-01

    A new ceramic sintering approach employing plastic deformation as the dominant mechanism is proposed, at low temperature close to the onset point of grain growth and under high pressure. Based on this route, fully dense boron carbide without grain growth can be prepared at 1,675–1,700 °C and under pressure of (≥) 80 MPa in 5 minutes. The dense boron carbide shows excellent mechanical properties, including Vickers hardness of 37.8 GPa, flexural strength of 445.3 MPa and fracture toughness of 4.7 MPa•m0.5. Such a process should also facilitate the cost-effective preparation of other advanced ceramics for practical applications. PMID:26503706

  20. MD simulation of plastic deformation nucleation in stressed crystallites under irradiation

    NASA Astrophysics Data System (ADS)

    Korchuganov, A. V.; Zolnikov, K. P.; Kryzhevich, D. S.; Chernov, V. M.; Psakhie, S. G.

    2016-12-01

    The investigation of plastic deformation nucleation in metals and alloys under irradiation and mechanical loading is one of the topical issues of materials science. Specific features of nucleation and evolution of the defect system in stressed and irradiated iron, vanadium, and copper crystallites were studied by molecular dynamics simulation. Mechanical loading was performed in such a way that the modeled crystallite volume remained unchanged. The energy of the primary knock-on atom initiating a cascade of atomic displacements in a stressed crystallite was varied from 0.05 to 50 keV. It was found that atomic displacement cascades might cause global structural transformations in a region far larger than the radiation-damaged area. These changes are similar to the ones occurring in the process of mechanical loading of samples. They are implemented by twinning (in iron and vanadium) or through the formation of partial dislocation loops (in copper).

  1. Thermomechanical model for the plastic deformation in high power laser diodes during operation

    NASA Astrophysics Data System (ADS)

    Martín-Martín, A.; Avella, M.; Iñiguez, M. P.; Jiménez, J.; Oudart, M.; Nagle, J.

    2009-10-01

    A thermomechanical model for the mechanism of rapid degradation of AlGaAs based high power laser bars (808 nm) is presented. Thermal stresses induced in the device by local heating around a facet defect by nonradiative recombination and self-absorption of photons are calculated, as well as the conditions for the beginning of plastic deformation, when these thermal stresses overcome the yield strength. The values of the power density and of the local temperature at which the yield limit is surmounted are in agreement with the threshold values for the degradation of Al based lasers given in the literature. The present model can also elucidate the role played by the packaging stress, being able to explain how this stress reduces the optical power density threshold for failure of these lasers.

  2. Identification of As/sub Ga/ antisites in plastically deformed GaAs

    SciTech Connect

    Weber, E.R.; Ennen, H.; Kaufmann, U.; Windscheif, J.; Schneider, J.; Wosinski, T.

    1982-09-01

    As/sub Ga/ antisite defects formed during plastic deformation of GaAs are identified by electron paramagnetic resonance (EPR) measurements. From photo-EPR results it can be concluded that the two levels of this double donor are located near E/sub c/ -0.75 eV and E/sub v/ +0.5 eV. These values are coincident with the Fermi level pinning energies at Schottky barriers. The upper level can be related to the ''main electron trap'' EL2 in GaAs. Photoluminescence experiments before and after thermal annealing suggest that As/sub Ga/ defects reduce the near band edge luminescence efficiency. A dislocation climb model is presented which is able to explain As/sub Ga/ formation during dislocation movement. The production of As/sub Ga/ antisites during dislocation motion under injection conditions in light emitting devices may thus be connected with degradation of the light output.

  3. Plastic Deformation, Amorphization, and Phase Changes in Extreme Laser Shock Compression of Ta and Si

    NASA Astrophysics Data System (ADS)

    Meyers, Marc

    2015-06-01

    High-amplitude pulsed lasers probe the response of materials at pressures up to 100s of GPa and strain rates of 108 s-1, revealing plastic deformation, phase transformations, and amorphization. Molecular dynamics simulations provide modeling at comparable strain rates and time durations. Shock compression of monocrystalline Ta reveals dislocations at low pressures and twinning at higher pressures (above 24 GPa). Results are compared with predictions from homogeneous dislocation generation and multiplication and the latter mechanism is dominant. The formation of an Omega phase was observed in monocrystalline tantalum at a shock amplitude of approximately 70 GPa. The shear stresses may play a role in the transformation. As shock energy increases, the following structural changes in monocrystalline Si are observed: dislocations and stacking faults; bands of amorphized Si forming on crystallographic orientations consistent with slip; broad regions of amorphized Si; nanocrystalline Si resulting from re-crystallization. MD simulations display similar amorphous regions. Funding: UCOP and DOE SSAP.

  4. MD simulation of plastic deformation nucleation in stressed crystallites under irradiation

    SciTech Connect

    Korchuganov, A. V. Zolnikov, K. P. Kryzhevich, D. S.; Chernov, V. M.; Psakhie, S. G.

    2016-12-15

    The investigation of plastic deformation nucleation in metals and alloys under irradiation and mechanical loading is one of the topical issues of materials science. Specific features of nucleation and evolution of the defect system in stressed and irradiated iron, vanadium, and copper crystallites were studied by molecular dynamics simulation. Mechanical loading was performed in such a way that the modeled crystallite volume remained unchanged. The energy of the primary knock-on atom initiating a cascade of atomic displacements in a stressed crystallite was varied from 0.05 to 50 keV. It was found that atomic displacement cascades might cause global structural transformations in a region far larger than the radiation-damaged area. These changes are similar to the ones occurring in the process of mechanical loading of samples. They are implemented by twinning (in iron and vanadium) or through the formation of partial dislocation loops (in copper).

  5. Sintering boron carbide ceramics without grain growth by plastic deformation as the dominant densification mechanism.

    PubMed

    Ji, Wei; Rehman, Sahibzada Shakir; Wang, Weimin; Wang, Hao; Wang, Yucheng; Zhang, Jinyong; Zhang, Fan; Fu, Zhengyi

    2015-10-27

    A new ceramic sintering approach employing plastic deformation as the dominant mechanism is proposed, at low temperature close to the onset point of grain growth and under high pressure. Based on this route, fully dense boron carbide without grain growth can be prepared at 1,675-1,700 °C and under pressure of (≥) 80 MPa in 5 minutes. The dense boron carbide shows excellent mechanical properties, including Vickers hardness of 37.8 GPa, flexural strength of 445.3 MPa and fracture toughness of 4.7 MPa•m(0.5). Such a process should also facilitate the cost-effective preparation of other advanced ceramics for practical applications.

  6. Damage and Plastic Deformation Modeling of Beishan Granite Under Compressive Stress Conditions

    NASA Astrophysics Data System (ADS)

    Chen, L.; Wang, C. P.; Liu, J. F.; Liu, J.; Wang, J.; Jia, Y.; Shao, J. F.

    2015-07-01

    Based on experimental investigations, we propose a coupled elastoplastic damage model to simulate the mechanical behavior of granite under compressive stress conditions. The granite is taken from the Beishan area, a preferable region for China's high-level radioactive waste repository. Using a 3D acoustic emission monitoring system in mechanical tests, we focus on the cracking process and its influence on the macroscopic mechanical behavior of the granite samples. It is verified that the crack propagation coupled with fractional sliding along the cracks is the principal mechanism controlling the failure process and nonlinear mechanical behavior of granite under compressive stress conditions. Based on this understanding, the coupled elastoplastic damage model is formulated in the framework of the thermodynamics theory. In the model, the coupling between damage and plastic deformation is simulated by introducing the independent damage variable in the plastic yield surface. As a preliminary validation of the model, a series of numerical simulations are performed for compressive tests conducted under different confining pressures. Comparisons between the numerical and simulated results show that the proposed model can reproduce the main features of the mechanical behavior of Beishan granite, particularly the damage evolution under compressive stress conditions.

  7. A study of gradient strengthening based on a finite-deformation gradient crystal-plasticity model

    NASA Astrophysics Data System (ADS)

    Pouriayevali, Habib; Xu, Bai-Xiang

    2017-07-01

    A comprehensive study on a finite-deformation gradient crystal-plasticity model which has been derived based on Gurtin's framework (Int J Plast 24:702-725, 2008) is carried out here. This systematic investigation on the different roles of governing components of the model represents the strength of this framework in the prediction of a wide range of hardening behaviors as well as rate-dependent and scale-variation responses in a single crystal. The model is represented in the reference configuration for the purpose of numerical implementation and then implemented in the FEM software ABAQUS via a user-defined subroutine (UEL). Furthermore, a function of accumulation rates of dislocations is employed and viewed as a measure of formation of short-range interactions. Our simulation results reveal that the dissipative gradient strengthening can be identified as a source of isotropic-hardening behavior, which may represent the effect of irrecoverable work introduced by Gurtin and Ohno (J Mech Phys Solids 59:320-343, 2011). Here, the variation of size dependency at different magnitude of a rate-sensitivity parameter is also discussed. Moreover, an observation of effect of a distinctive feature in the model which explains the effect of distortion of crystal lattice in the reference configuration is reported in this study for the first time. In addition, plastic flows in predefined slip systems and expansion of accumulation of GNDs are distinctly observed in varying scales and under different loading conditions.

  8. Effect of Severe Plastic Deformation on Structure and Properties of Al-Sc-Ta and Al-Sc-Ti Alloys

    NASA Astrophysics Data System (ADS)

    Berezina, Alla; Monastyrska, Tetiana; Davydenko, Olexandr; Molebny, Oleh; Polishchuk, Sergey

    2017-03-01

    The comparative analysis of the effect of monotonous and non-monotonous severe plastic deformations (SPD) on the structure and properties of aluminum alloys has been carried out. Conventional hydrostatic extrusion (HE) with a constant deformation direction and equal-channel angular hydroextrusion (ECAH) with an abrupt change in the deformation direction were chosen for the cases of monotonous and non-monotonous SPD, respectively. Model cast hypoeutectic Al-0.3%Sc alloys and hypereutectic Al-0.6%Sc alloys with Ta and Ti additives were chosen for studying. It was demonstrated that SPD of the alloys resulted in the segregation of the material into active and inactive zones which formed a banded structure. The active zones were shown to be bands of localized plastic deformation. The distance between zones was found to be independent of the accumulated strain degree and was in the range of 0.6-1 μm. Dynamic recrystallization in the active zones was observed using TEM. The dynamic recrystallization was accompanied by the formation of disclinations, deformation bands, low-angle, and high-angle boundaries, i.e., rotational deformation modes developed. The dynamic recrystallization was more intense during the non-monotonous deformation as compared with the monotonous one, which was confirmed by the reduction of texture degree in the materials after ECAH.

  9. Effect of Severe Plastic Deformation on Structure and Properties of Al-Sc-Ta and Al-Sc-Ti Alloys.

    PubMed

    Berezina, Alla; Monastyrska, Tetiana; Davydenko, Olexandr; Molebny, Oleh; Polishchuk, Sergey

    2017-12-01

    The comparative analysis of the effect of monotonous and non-monotonous severe plastic deformations (SPD) on the structure and properties of aluminum alloys has been carried out. Conventional hydrostatic extrusion (HE) with a constant deformation direction and equal-channel angular hydroextrusion (ECAH) with an abrupt change in the deformation direction were chosen for the cases of monotonous and non-monotonous SPD, respectively. Model cast hypoeutectic Al-0.3%Sc alloys and hypereutectic Al-0.6%Sc alloys with Ta and Ti additives were chosen for studying. It was demonstrated that SPD of the alloys resulted in the segregation of the material into active and inactive zones which formed a banded structure. The active zones were shown to be bands of localized plastic deformation. The distance between zones was found to be independent of the accumulated strain degree and was in the range of 0.6-1 μm. Dynamic recrystallization in the active zones was observed using TEM. The dynamic recrystallization was accompanied by the formation of disclinations, deformation bands, low-angle, and high-angle boundaries, i.e., rotational deformation modes developed. The dynamic recrystallization was more intense during the non-monotonous deformation as compared with the monotonous one, which was confirmed by the reduction of texture degree in the materials after ECAH.

  10. Ultra Fine-Grained Metals Prepared by Severe Plastic Deformation: A Positron Annihilation Study

    NASA Astrophysics Data System (ADS)

    Čížek, J.; Procházka, I.; Kužel, R.; Matĕj, Z.; Cherkaska, V.; Cieslar, M.; Smola, B.; Stulíková, I.; Brauer, G.; Anwand, W.; Islamgaliev, R. K.; Kulyasova, O.

    2005-05-01

    Recent investigations of ultra fine-grained metals (Cu, Fe, Ni) performed within a Prague-Rossendorf-Ufa collaboration will be reviewed. The specimens were prepared by severe plastic deformation: the high-pressure torsion and equal channel angular pressing. Positron annihilation spectroscopy was used as the main method including (i) the conventional lifetime and the Doppler broadening measurements with 22Na and (ii) the slow-positron implantation spectroscopy with the Doppler broadening measurement. Other methods were also involved: transmission electron microscopy, X-ray diffraction, and microhardness. First, the mean grain size was determined and defects were identified in the as-deformed materials. Defects concentration and spatial distribution were studied in detail. Dislocations situated in distorted regions along grain boundaries, and a few-vacancy clusters distributed homogeneously inside dislocations-free grains, were observed in the ultra fine-grained Cu, Fe, and Ni. Subsequently, the thermal evolution of the ultra fine-grained structures during isochronal annealing was studied.

  11. Dislocation-Governed Plastic Deformation and Fracture Toughness of Nanotwinned Magnesium

    PubMed Central

    Zhou, Lei; Guo, Ya-Fang

    2015-01-01

    In this work, the plastic deformation mechanisms responsible for mechanical properties and fracture toughness in {101¯2}<101¯1¯>nanotwinned (NT). magnesium is studied by molecular dynamics (MD) simulation. The influence of twin boundary (TBs) spacing and crack position on deformation behaviors are investigated. The microstructure evolution at the crack tip are not exactly the same for the left edge crack (LEC) and the right edge crack (REC) models according to calculations of the energy release rate for dislocation nucleation at the crack tip. The LEC growth initiates in a ductile pattern and then turns into a brittle cleavage. In the REC model, the atomic decohesion occurs at the crack tip to create a new free surface which directly induces a brittle cleavage. A ductile to brittle transition is observed which mainly depends on the competition between dislocation motion and crack growth. This competition mechanism is found to be correlated with the TB spacing. The critical values are 10 nm and 13.5 nm for this transition in LEC and REC models, respectively. Essentially, the dislocation densities affected by the TB spacing play a crucial role in the ductile to brittle transition. PMID:28793502

  12. Recrystallization kinetics of an austenitic high-manganese steel subjected to severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Yanushkevich, Zh. Ch.; Molodov, D. A.; Belyakov, A. N.; Kaibyshev, R. O.

    2016-09-01

    The evolution of the microstructure and the properties of an austenitic high-manganese steel subjected to severe deformation by cold rolling and subsequent recrystallization annealing is investigated. Cold rolling is accompanied by mechanical structural twinning and shear banding. The microhardness and microstructural analysis of annealed samples are used to study the recrystallization kinetics of the high-manganese steel. It is shown that large plastic deformation and subsequent annealing result in rapid development of recrystallization processes and the formation of an ultrafine-grained structure. A completely recrystallized structure with an average grain size of 0.64 μm forms after 30-min annealing at a temperature of 550°C. No significant structural changes are observed when the annealing time increases to 18 h, which indicates stability of the recrystallized microstructure. The steel cold rolled to 90% and annealed at 550°C for 30 min demonstrates very high strength properties: the yield strength and the tensile strength achieve 650 and 850MPa, respectively. The dependence of the strength properties of the steel on the grain size formed after rolling and recrystallization annealing is described by the Hall-Petch relation.

  13. Deformation Twinning in Zirconium: Direct Experimental Observations and Polycrystal Plasticity Predictions

    NASA Astrophysics Data System (ADS)

    Singh, Jaiveer; Mahesh, Sivasambu; Kumar, Gulshan; Pant, Prita; Srivastava, D.; Dey, G. K.; Saibaba, N.; Samajdar, I.

    2015-11-01

    Deformation twinning was directly observed in three commercial zirconium alloy samples during split channel die plane-strain compression. One pair of samples had similar starting texture but different grain size distributions, while another pair had similar grain size distribution but different starting textures. Extension twinning was found to be more sensitive to the starting texture than to the grain size distribution. Also, regions of intense deformation near grain boundaries were observed. A hierarchical binary tree-based polycrystal plasticity model, implementing the Chin-Hosford-Mendorf twinning criterion, captured the experimentally observed twinning grains' lattice orientation distribution, and the twin volume fraction evolution, provided the critical resolved shear stress for extension twinning, τ0 , was assumed much larger than any of the values reported in the literature, based on the viscoplastic self-consistent model. A comparison of the models suggests that τ0 obtained using the present model and the viscoplastic self-consistent models physically correspond to the critical stress required for twin nucleation, and twin growth, respectively.

  14. Computations of Accumulated Deformations and Depletion of Plasticity Reserve Held by the Metal in the Surface Layer during Orthogonal Cutting

    NASA Astrophysics Data System (ADS)

    Blumenstein, V. Yu; Ferranti, A.

    2016-04-01

    The problem relating to the mechanics of orthogonal cutting with the deformation site, which is located within the contact area ahead of, below and behind the cutting tool was provided a solution. The above problem is crucial as it involves developing the mechanics of technological inheritance, which emphasizes the need for the operation-by-operation computations of the metal deformed state. The plane deformation (strain) model was adopted for the treatment with a cutter having a rounded cutting edge. Stresses, rates and deformations along the lines of current, which form the strengthened surface layer of the treated part, were computed. The patterns determining deformation accumulation and metal plasticity reserve depletion during orthogonal cutting were exposed.

  15. Modeling of Plastic Deformation of Crystalline Materials on the Basis of the Concept of Hardening and Recovery

    NASA Astrophysics Data System (ADS)

    Starenchenko, V. A.; Cherepanov, D. N.; Selivanikova, O. V.

    2014-06-01

    A review is provided and a systematization is proposed for the principal directions of modeling of plastic deformation of crystalline materials and attendant phenomena within the framework of the concept of hardening and recovery. It is suggested that the formulation of the concept of hardening and recovery directly links phenomena taking place in the deformed crystalline material with the defect behavior of the crystal structure. This work considers only mathematical models that assume the formation of defects in the process of deformation. In order to investigate the phenomena observed in the process of deformation, use is made of physical quantities characterizing the defects, such as dislocation density, misorientation boundaries, discontinuities, concentration of point defects, etc. Great attention is given to works of the Tomsk School of Materials Science, which investigate the formation of deformation substructures in a consistent and systematic way.

  16. Finite Deformations and Internal Forces in Elastic-Plastic Crystals: Interpretations From Nonlinear Elasticity and Anharmonic Lattice Statics

    DTIC Science & Technology

    2009-09-01

    0 Downlond inelastic...zm= 0 . 2.1 Plastic Deformation. Intermediate configuration B̃ in Fig. 1 differs from B0 due to influences of cumulative motion of lattice defects...and perturbations of atomic positions resulting from these defects. Configuration B̃ is by definition free of external traction t̃= 0 and free

  17. Structural modifications induced by compressive plastic deformation in single-step and sequentially irradiated UHMWPE for hip joint components.

    PubMed

    Puppulin, Leonardo; Sugano, Nobuhiko; Zhu, Wenliang; Pezzotti, Giuseppe

    2014-03-01

    Structural modifications were studied at the molecular scale in two highly crosslinked UHMWPE materials for hip-joint acetabular components, as induced upon application of (uniaxial) compressive strain to the as-manufactured microstructures. The two materials, quite different in their starting resins and belonging to different manufacturing generations, were a single-step irradiated and a sequentially irradiated polyethylene. The latter material represents the most recently launched gamma-ray-irradiated polyethylene material in the global hip implant market. Confocal/polarized Raman spectroscopy was systematically applied to characterize the initial microstructures and the microstructural response of the materials to plastic deformation. Crystallinity fractions and preferential orientation of molecular chains have been followed up during in vitro deformation tests on unused cups and correlated to plastic strain magnitude and to the recovery capacity of the material. Moreover, analyses of the in vivo deformation behavior of two short-term retrieved hip cups are also presented. Trends of preferential orientation of molecular chains as a function of residual strain were similar for both materials, but distinctly different in their extents. The sequentially irradiated material was more resistant to plastic deformation and, for the same magnitude of residual plastic strain, possessed a higher capacity of recovery as compared to the single-step irradiated one.

  18. Non-Destructive Quantification of Plastic Deformation in Steel: Employing X-Ray Diffraction Peak Broadening Analysis

    DTIC Science & Technology

    2013-09-01

    residual stress); dislocation density has proven to be a particularly elusive quantity to evaluate non-destructively. Dislocation density provides...a methodology for evaluating plastic deformation in ferromagnetic steel alloys. An overview of the principles of XRD, how the crystallographic...This, together with elastic strain / residual stress analysis, would enable better evaluation of the current state of health of steel structures and

  19. In situ nanoindentation study of plastic Co-deformation in Al-TiN nanocomposites

    SciTech Connect

    Li, N.; Wang, H.; Misra, A.; Wang, J.

    2014-10-16

    We performed in situ indentation in a transmission electron microscope on Al-TiN multilayers with individual layer thicknesses of 50 nm, 5 nm and 2.7 nm to explore the effect of length scales on the plastic co-deformability of a metal and a ceramic. At 50 nm, plasticity was confined to the Al layers with easy initiation of cracks in the TiN layers. At 5 nm and below, cracking in TiN was suppressed and post mortem measurements indicated a reduction in layer thickness in both layers. Our results demonstrate the profound size effect in enhancing plastic co-deformability in nanoscale metal-ceramic multilayers.

  20. Evolution of plastic deformation and its effect on mechanical properties of laser additive repaired Ti64ELI titanium alloy

    NASA Astrophysics Data System (ADS)

    Zhao, Zhuang; Chen, Jing; Tan, Hua; Lin, Xin; Huang, Weidong

    2017-07-01

    In this paper, laser additive manufacturing (LAM) technology with powder feeding has been employed to fabricate 50%LAMed specimens (i.e. the volume fraction of the laser deposited zone was set to 50%). With aid of the 3D-DIC technique, the tensile deformation behavior of 50%LAMed Ti64ELI titanium alloy was investigated. The 50%LAMed specimen exhibits a significant characteristic of strength mismatch due to the heterogeneous microstructure. The tensile fracture of 50%LAMed specimen occurs in WSZ (wrought substrate zone), but the tensile strength is slightly higher and the plastic elongation is significantly lower than that of the wrought specimen. The 3D-DIC results shows that the 50%LAMed specimen exhibits a characteristic of dramatic plastic strain heterogeneity and the maximal strain is invariably concentrated in WSZ. The ABAQUS simulation indicates that, the LDZ (laser deposited zone) can constrain the plastic deformation of the WSZ and biaxial stresses develop at the interface after yielding.

  1. Static-transmission-error vibratory-excitation contributions from plastically deformed gear teeth caused by tooth bending-fatigue damage

    NASA Astrophysics Data System (ADS)

    Mark, W. D.; Reagor, C. P.

    2007-02-01

    To assess gear health and detect gear-tooth damage, the vibratory response from meshing gear-pair excitations is commonly monitored by accelerometers. In an earlier paper, strong evidence was presented suggesting that, in the case of tooth bending-fatigue damage, the principal source of detectable damage is whole-tooth plastic deformation; i.e. yielding, rather than changes in tooth stiffness caused by tooth-root cracks. Such plastic deformations are geometric deviation contributions to the "static-transmission-error" (STE) vibratory excitation caused by meshing gear pairs. The STE contributions caused by two likely occurring forms of such plastic deformations on a single tooth are derived, and displayed in the time domain as a function of involute "roll distance." Example calculations are provided for transverse contact ratios of Qt=1.4 and 1.8, for spur gears and for helical-gear axial contact ratios ranging from Qa=1.2 to Qa=3.6. Low-pass- and band-pass-filtered versions of these same STE contributions also are computed and displayed in the time domain. Several calculations, consisting of superposition of the computed STE tooth-meshing fundamental harmonic contribution and the band-pass STE contribution caused by a plastically deformed tooth, exhibit the amplitude and frequency or phase modulation character commonly observed in accelerometer-response waveforms caused by damaged teeth. General formulas are provided that enable computation of these STE vibratory-excitation contributions for any form of plastic deformation on any number of teeth for spur and helical gears with any contact ratios.

  2. In situ spectroscopic study of the plastic deformation of amorphous silicon under nonhydrostatic conditions induced by indentation

    SciTech Connect

    Gerbig, Yvonne B.; Michaels, C. A.; Bradby, Jodie E.; Haberl, Bianca; Cook, Robert F.

    2015-12-17

    Indentation-induced plastic deformation of amorphous silicon (a-Si) thin films was studied by in situ Raman imaging of the deformed contact region of an indented sample, employing a Raman spectroscopy-enhanced instrumented indentation technique (IIT). The occurrence and evolving spatial distribution of changes in the a-Si structure caused by processes, such as polyamorphization and crystallization, induced by indentation loading were observed. Furthermore, the obtained experimental results are linked with previously published work on the plastic deformation of a-Si under hydrostatic compression and shear deformation to establish a model for the deformation behavior of a-Si under indentation loading.

  3. Deformation in cemented mudrock (Callovo-Oxfordian Clay) by microcracking, granular flow and phyllosilicate plasticity: insights from triaxial deformation, broad ion beam polishing and scanning electron microscopy

    NASA Astrophysics Data System (ADS)

    Desbois, Guillaume; Höhne, Nadine; Urai, Janos L.; Bésuelle, Pierre; Viggiani, Gioacchino

    2017-03-01

    The macroscopic description of deformation and fluid flow in mudrocks can be improved by a better understanding of microphysical deformation mechanisms. Here we use a combination of scanning electron microscopy (SEM) and broad ion beam (BIB) polishing to study the evolution of microstructure in samples of triaxially deformed Callovo-Oxfordian Clay. Digital image correlation (DIC) was used to measure strain field in the samples and as a guide to select regions of interest in the sample for BIB-SEM analysis. Microstructures show evidence for dominantly cataclastic and minor crystal plastic mechanisms (intergranular, transgranular, intragranular cracking, grain rotation, clay particle bending) down to the nanometre scale. At low strain, the dilatant fabric contains individually recognisable open fractures, while at high strain the reworked clay gouge also contains broken non-clay grains and smaller pores than the undeformed material, resealing the initial fracture porosity.

  4. Elastic-plastic deformation of molybdenum single crystals shocked along [100

    DOE PAGES

    Mandal, A.; Gupta, Y. M.

    2017-01-24

    To understand the elastic-plastic deformation response of shock-compressed molybdenum (Mo) – a body-centered cubic (BCC) metal, single crystal samples were shocked along the [100] crystallographic orientation to an elastic impact stress of 12.5 GPa. Elastic-plastic wave profiles, measured at different propagation distances ranging between ~0.23 to 2.31 mm using laser interferometry, showed a time-dependent material response. Within experimental scatter, the measured elastic wave amplitudes were nearly constant over the propagation distances examined. These data point to a large and rapid elastic wave attenuation near the impact surface, before reaching a threshold value (elastic limit) of ~3.6 GPa. Numerical simulations ofmore » the measured wave profiles, performed using a dislocation-based continuum model, suggested that {110}<111> and/or {112}<111> slip systems are operative under shock loading. In contrast to shocked metal single crystals with close-packed structures, the measured wave profiles in Mo single crystals could not be explained in terms of dislocation multiplication alone. A dislocation generation mechanism, operative for shear stresses larger than that at the elastic limit, was required to model the rapid elastic wave attenuation and to provide a good overall match to the measured wave profiles. However, the physical basis for this mechanism was not established for the high-purity single crystal samples used in this study. As a result, the numerical simulations also suggested that Mo single crystals do not work harden significantly under shock loading in contrast to the behavior observed under quasi-static loading.« less

  5. Elastic-plastic deformation of molybdenum single crystals shocked along [100

    NASA Astrophysics Data System (ADS)

    Mandal, A.; Gupta, Y. M.

    2017-01-01

    To understand the elastic-plastic deformation response of shock-compressed molybdenum (Mo) - a body-centered cubic metal, single crystal samples were shocked along the [100] crystallographic orientation to an elastic impact stress of 12.5 GPa. Elastic-plastic wave profiles, measured at different propagation distances ranging between ˜0.23 to 2.31 mm using laser interferometry, showed a time-dependent material response. Within the experimental scatter, the measured elastic wave amplitudes were nearly constant over the propagation distances examined. These data point to a large and rapid elastic wave attenuation near the impact surface, before reaching a threshold value (elastic limit) of ˜3.6 GPa. Numerical simulations of the measured wave profiles, performed using a dislocation-based continuum model, suggested that {110}⟨111⟩ and/or {112}⟨111⟩ slip systems are operative under shock loading. In contrast to shocked metal single crystals with close-packed structures, the measured wave profiles in Mo single crystals could not be explained in terms of dislocation multiplication alone. A dislocation generation mechanism, operative for shear stresses larger than that at the elastic limit, was required to model the rapid elastic wave attenuation and to provide a good overall match to the measured wave profiles. However, the physical basis for this mechanism was not established for the high-purity single crystal samples used in this study. The numerical simulations also suggested that Mo single crystals do not work harden significantly under shock loading in contrast to the behavior observed under quasi-static loading.

  6. Indentation Size Effect (ISE) in Copper Subjected to Severe Plastic Deformation (SPD)

    NASA Astrophysics Data System (ADS)

    Gale, Joshua D.; Achuthan, Ajit; Morrison, David J.

    2014-05-01

    The characteristic length scale of deformation in copper specimens subjected to severe plastic deformation (SPD) through surface mechanical attrition treatment (SMAT) was studied with indentation experiments. Annealed copper disks were shot peened with 6-mm diameter tungsten carbide spheres with an average velocity of 2.3 m/s for 15 minutes in a vibrating chamber. The SMAT-treated specimens were cross-sectioned, and the exposed face was studied under nanoindentation in order to determine the effect of dislocation density on surface hardness and indentation size effect (ISE). Since the specimen preparation of the exposed face involved mechanical polishing, which in turn introduced additional SPD on the indenting face, the effect of mechanical polishing on hardness measurement was investigated first. To this end, the mechanically polished specimens were subjected to various durations of electrochemical polishing. Hardness measurements on these specimens showed that the effect of mechanical polishing was substantial for both microindentation and nanoindentation, the impact being significantly larger for nanoindentation. Consequently, the measured depth of influence of the SMAT process, determined on specimens subjected to longer durations of electrochemical polishing, shows larger values compared to those previously reported in the literature. The ISE shows a bilinear relationship between the square of hardness and the reciprocal of indentation depth. The slope of this behavior, corresponding to smaller indentation loads, which is a measure of the ISE associated with a strain gradient, shows a power-law relationship with an increase in the distance away from the SMAT surface, instead of the constant value expected with the Nix-Gao type model.

  7. Experimental Validation of Two-dimensional Finite Element Method for Simulating Constitutive Response of Polycrystals During High Temperature Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Agarwal, Sumit; Briant, Clyde L.; Krajewski, Paul E.; Bower, Allan F.; Taleff, Eric M.

    2007-04-01

    A finite element method was recently designed to model the mechanisms that cause superplastic deformation (A.F. Bower and E. Wininger, A Two-Dimensional Finite Element Method for Simulating the Constitutive Response and Microstructure of Polycrystals during High-Temperature Plastic Deformation, J. Mech. Phys. Solids, 2004, 52, p 1289-1317). The computations idealize the solid as a collection of two-dimensional grains, separated by sharp grain boundaries. The grains may deform plastically by thermally activated dislocation motion, which is modeled using a conventional crystal plasticity law. The solid may also deform by sliding on the grain boundaries, or by stress-driven diffusion of atoms along grain boundaries. The governing equations are solved using a finite element method, which includes a front-tracking procedure to monitor the evolution of the grain boundaries and surfaces in the solid. The goal of this article is to validate these computations by systematically comparing numerical predictions to experimental measurements of the elevated-temperature response of aluminum alloy AA5083 (M.-A. Kulas, W.P. Green, E.M. Taleff, P.E. Krajewski, and T.R. McNelley, Deformation Mechanisms in Superplastic AA5083 materials. Metall. Mater. Trans. A, 2005, 36(5), p 1249-1261). The experimental work revealed that a transition occurs from grain-boundary sliding to dislocation (solute-drag) creep at approximately 0.001/s for temperatures between 425 and 500 °C. In addition, increasing the grain size from 7 to 10 μm decreased the transition to significantly lower strain rates. Predictions from the finite element method accurately predict the effect of grain size on the transition in deformation mechanisms.

  8. 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

  9. Influence of cooling rate on cracking and plastic deformation during impact and indentation of borosilicate glasses.

    NASA Astrophysics Data System (ADS)

    Zehnder, Christoffer; Bruns, Sebastian; Peltzer, Jan-Niklas; Durst, Karsten; Korte-Kerzel, Sandra; Möncke, Doris

    2017-03-01

    The influence of a changing glass topology on local mechanical properties was studied in a multi-technique nanomechanical approach. The glass response against sharp contacts can result in structural densification, plastic flow or crack initiation. Using instrumented indentation testing, the mechanical response was studied in different strain rate regimes for a sodium-boro-silicate glass (NBS) exhibiting altering structures due to varying processing conditions. Comparison with data from former studies as well as with literature data on other glass structures helped to elucidate the role of the borate and silicate sub-networks and to understand the overall mechanical properties of the mixed glass systems. A peculiarity of some of the NBS glasses tested in this study is the fact that the connectivity of the borate and silicate entities depends on the sample’s thermal history. While the influence on macroscopic material properties such as E and H is minor, the onset of cracking indeed is influenced by those structural changes within the glass. Rapidly quenched glass shows an improved crack resistance, which is even more pronounced at high strain rates. Studies on various processing conditions further indicate that this transition is closely related to the cooling rate around Tg. The strain rate dependence of cracking is discussed in terms of the occurrence of shear deformation and densification.

  10. Modeling and 2-D discrete simulation of dislocation dynamics for plastic deformation of metal

    NASA Astrophysics Data System (ADS)

    Liu, Juan; Cui, Zhenshan; Ou, Hengan; Ruan, Liqun

    2013-05-01

    Two methods are employed in this paper to investigate the dislocation evolution during plastic deformation of metal. One method is dislocation dynamic simulation of two-dimensional discrete dislocation dynamics (2D-DDD), and the other is dislocation dynamics modeling by means of nonlinear analysis. As screw dislocation is prone to disappear by cross-slip, only edge dislocation is taken into account in simulation. First, an approach of 2D-DDD is used to graphically simulate and exhibit the collective motion of a large number of discrete dislocations. In the beginning, initial grains are generated in the simulation cells according to the mechanism of grain growth and the initial dislocation is randomly distributed in grains and relaxed under the internal stress. During the simulation process, the externally imposed stress, the long range stress contribution of all dislocations and the short range stress caused by the grain boundaries are calculated. Under the action of these forces, dislocations begin to glide, climb, multiply, annihilate and react with each other. Besides, thermal activation process is included. Through the simulation, the distribution of dislocation and the stress-strain curves can be obtained. On the other hand, based on the classic dislocation theory, the variation of the dislocation density with time is described by nonlinear differential equations. Finite difference method (FDM) is used to solve the built differential equations. The dislocation evolution at a constant strain rate is taken as an example to verify the rationality of the model.

  11. Rate-dependent Mechanical Deformation Behavior of POSS-filled and Plasticized Poly(vinyl chloride).

    NASA Astrophysics Data System (ADS)

    Soong, Sharon; Cohen, Robert; Boyce, Mary

    2006-03-01

    In different temperatures or strain-rate regimes, the rate sensitivities of polymers change as various primary and secondary molecular mobility mechanisms are accessed. Incorporating nanoparticles into the polymer matrix can potentially alter the molecular level structure and offers an opportunity to tailor the rate-dependent mechanical deformation behavior of the polymer. In this study, methacryl-POSS (C56H88O28Si8) and dioctyl phthalate (DOP) were incorporated into poly(vinyl chloride) (PVC) through melt blending. Dynamic Mechanical Analysis revealed that the incorporation of POSS in PVC plasticizes PVC and reduces both the alpha and beta transition temperatures. As for the PVC/DOP blends, while the alpha-transition temperatures were reduced, beta-motions vanishes with high DOP contents. The rate dependent yield behavior is characterized in compression testing. Zwick Mechine is used for low to moderate strain rate (0.0001 to 0.1/s) and Split Hopkinson Bar is used for high strain rate (500 to 2000/s). It was found that PVC with POSS shows a delay in yield strength rate-sensitivity transition. For PVC with higher DOP contents which show restricted beta-motions, the rate-sensitivity transition in yield stress faded away. Constitutive model used was able to predict the rate-sensitivity transitions in the compression yield behavior of PVC compounds.

  12. Texture Evolution in a Ti-Ta-Nb Alloy Processed by Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Cojocaru, Vasile-Danut; Raducanu, Doina; Gloriant, Thierry; Cinca, Ion

    2012-05-01

    Titanium alloys are extensively used in a variety of applications because of their good mechanical properties, high biocompatibility, and corrosion resistance. Recently, β-type Ti alloys containing Ta and Nb have received much attention because they feature not only high specific strength but also biocorrosion resistance, no allergic problems, and biocompatibility. A Ti-25Ta-25Nb β-type titanium alloy was subjected to severe plastic deformation (SPD) processing by accumulative roll bonding and investigated with the aim to observe the texture developed during SPD processing. Texture data expressed by pole figures, inverse pole figures, and orientation distribution functions for the (110), (200), and (211) β-Ti peaks were obtained by XRD investigations. The results showed that it is possible to obtain high-intensity share texture modes ({001}<110>) and well-developed α and γ-fibers; the most important fiber is the α-fiber ({001} < {1bar{1}0} > to {114} < {1bar{1}0} > to {112} < {1bar{1}0} > ). High-intensity texture along certain crystallographic directions represents a way to obtain materials with high anisotropic properties.

  13. Evaluation of the Mechanical Properties of AA 6063 Processed by Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Jafarlou, Davoud Mashhadi; Zalnezhad, Erfan; Hamouda, Abdelmagid Salem; Faraji, Ghader; Mardi, Noor Azizi Bin; Hassan Mohamed, Mohsen Abdelnaeim

    2015-05-01

    In this study, the mechanical properties, including surface hardness, tensile strength, fatigue, and fretting fatigue behavior of AA 6063 processed by equal channel angular pressing as the most efficient severe shear plastic deformation (SPD) technique, were investigated. Following the SPD process, samples were subjected to heat treatment (HT), hard anodizing (HA), and a combination of HT and HA. Rotating-bending fretting fatigue tests were performed to explore the samples' response to the fretting condition. From the experimental fatigue and fretting fatigue tests, it was apparent that the SPD treatment had a positive effect on enhancing the fatigue and fretting fatigue lives of the samples at low and high-cyclic loads compared with the HT technique by 78 and 67 pct, and 131 and 154 pct respectively. The results also indicate that the SPD + HT technique significantly increased the fatigue and fretting fatigue lives of the samples at high and low cycles by 15.56 and 8.33 pct, and 14.4 and 5.1 pct respectively, compared with the SPD method. HA of AA6063 increased the fatigue and fretting fatigue lives of SPD + HT-processed samples at low cycle by 15.5 and 18.4 pct respectively; however, at high cycle, HA had reverse effects, whereby the fatigue and fretting fatigue lives of SPD + HT-processed samples decreased by 16.7 and 30 pct, respectively.

  14. Research of Tool Durability in Surface Plastic Deformation Processing by Burnishing of Steel Without Metalworking Fluids

    NASA Astrophysics Data System (ADS)

    Grigoriev, S. N.; Bobrovskij, N. M.; Melnikov, P. A.; Bobrovskij, I. N.

    2017-05-01

    Modern vector of development of machining technologies aimed at the transition to environmentally safe technologies - “green” technologies. The concept of “green technology” includes a set of signs of knowledge intended for practical use (“technology”). One of the ways to improve the quality of production is the use of surface plastic deformation (SPD) processing methods. The advantage of the SPD is a capability to combine effects of finishing and strengthening treatment. The SPD processing can replace operations: fine turning, grinding or polishing. The SPD is a forceful contact impact of indentor on workpiece’s surface in condition of their relative motion. It is difficult to implement the core technology of the SPD (burnishing, roller burnishing, etc.) while maintaining core technological advantages without the use of lubricating and cooling technology (metalworking fluids, MWF). The “green” SPD technology was developed by the authors for dry processing and has not such shortcomings. When processing with SPD without use of MWF requirements for tool’s durability is most significant, especially in the conditions of mass production. It is important to determine the period of durability of tool at the design stage of the technological process with the purpose of wastage preventing. This paper represents the results of durability research of natural and synthetic diamonds (polycrystalline diamond - ASPK) as well as precision of polycrystalline superabrasive tools made of dense boron nitride (DBN) during SPD processing without application of MWF.

  15. Low-temperature acoustic properties of nanostructured zirconium obtained by intensive plastic deformation

    NASA Astrophysics Data System (ADS)

    Vatazhuk, E. N.; Pal-Val, P. P.; Natsik, V. D.; Pal-Val, L. N.; Tikhonovsky, M. A.; Velikodny, A. N.; Khaimovich, P. A.

    2011-02-01

    The temperature dependences of the logarithmic decrement and dynamic Young's modulus of polycrystalline coarse-grained and nanostructured Zr are studied at temperatures of 2.5-340K. A nanostructured state of samples with grain sizes on the order of 100nm was produced by intensive plastic deformation (IPD). The measurements were made using a two-component vibrator technique at frequencies of 73-350kHz. A relaxation peak in the internal friction near 250K was discovered in the coarse-grained, annealed Zr which is retained after IPD, but its height increases by roughly a factor of 10 and the localization temperature shifts to lower values. In addition, after IPD a new internal friction peak shows up at moderately low temperatures near 80K. The activation parameters for the observed peaks are estimated and it is shown that they arise from different thermally activated dislocation processes: interactions of dislocations with impurities and kink pair formation in dislocations. It was found that IPD is accompanied by a significant (1-8%) reduction in the Young's modulus because of quasistatic and dynamic dislocation effects. A glass-like anomaly appears in the temperature dependence of the Young's modulus of nanostructured Zr at T <20K which may be determined by tunnelling and thermally activated relaxation of quasilocal excitations.

  16. Effects of particle morphology and spacing on the strain fields in a plastically deforming matrix

    SciTech Connect

    Watt, D.F.; Xu, X.Q.; Lloyd, D.J.

    1996-02-01

    More than 25 models have been created using the ABAQUS three-dimensional non-linear finite element software to reveal the stress and strain distributions around and within particles in a plastically deforming matrix. The effects of particle shape, volume fraction and distribution have been examined. The major effect is that a fiber-like stress distribution is developed in the matrix, linking the particles in the direction of loading, regardless of the variations in geometry or properties. However the stress and strain distributions are altered in detail in a systematic fashion by all these variables. Stress in cubic particles are much higher than those in spherical particles. Hard particles which are closely spaced in the direction of loading develop very large stresses in the region between them on the line of loading, whereas the stresses are not nearly as significantly increased for particles closely spaced in the transverse direction. The variations in the distributions of stress and strain can be explained in a general way by reference to compatibility and equilibrium arguments.

  17. X-ray studies of dynamic aging in an aluminum alloy subjected to severe plastic deformation

    SciTech Connect

    Sitdikov, V.D.; Chizhov, P.S.; Murashkin, M.Yu.; Goidenko, A.A.; Valiev, R.Z.

    2015-12-15

    In this work, X-ray scattering methods were applied for a quantitative characterization of the microstructure of an aluminum alloy of the Al–Mg–Si system during dynamic aging realized through the high pressure torsion technique. A qualitative and quantitative phase analysis of the alloy was performed, together with Al alloy lattice parameter determination. From the reflections broadening the effective size of the coherent scattering domains and the lattice microstrain were determined in the framework of the Halder–Wagner approach. Using the method of small-angle X-ray scattering, the quantitative characteristics of the size, shape and spatial distribution of the secondary phase particles formed in the Al alloy during dynamic aging were established. In order to validate the obtained results, the method of small-angle X-ray scattering was preliminarily tested on similar samples after artificial aging and compared with the results from small-angle neutron diffraction widely known in literature. - Highlights: • Spherical fcc β-Mg2Si precipitates formed in Al 6201 alloy during dynamic aging in the course of severe plastic deformation. • The size, shape and distribution of the precipitates due to artificial and dynamic aging were revealed by SAXS method. • Monoclinic needle-like β' precipitates and Al5FeSi intermetallic phase were detected in 6201 alloy after T6 treatment.

  18. Circular Functions Based Comprehensive Analysis of Plastic Creep Deformations in the Fiber Reinforced Composites

    NASA Astrophysics Data System (ADS)

    Monfared, Vahid

    2016-12-01

    Analytically based model is presented for behavioral analysis of the plastic deformations in the reinforced materials using the circular (trigonometric) functions. The analytical method is proposed to predict creep behavior of the fibrous composites based on basic and constitutive equations under a tensile axial stress. New insight of the work is to predict some important behaviors of the creeping matrix. In the present model, the prediction of the behaviors is simpler than the available methods. Principal creep strain rate behaviors are very noteworthy for designing the fibrous composites in the creeping composites. Analysis of the mentioned parameter behavior in the reinforced materials is necessary to analyze failure, fracture, and fatigue studies in the creep of the short fiber composites. Shuttles, spaceships, turbine blades and discs, and nozzle guide vanes are commonly subjected to the creep effects. Also, predicting the creep behavior is significant to design the optoelectronic and photonic advanced composites with optical fibers. As a result, the uniform behavior with constant gradient is seen in the principal creep strain rate behavior, and also creep rupture may happen at the fiber end. Finally, good agreements are found through comparing the obtained analytical and FEM results.

  19. Fracture and fracture toughness of nanopolycrystalline metals produced by severe plastic deformation

    PubMed Central

    Hohenwarter, A.; Pippan, R.

    2015-01-01

    The knowledge of the fracture of bulk metallic materials developed in the last 50 years is mostly based on materials having grain sizes, d, in the range of some micrometres up to several hundred micrometres regarding the possibilities of classical metallurgical methods. Nowadays, novel techniques provide access to much smaller grain sizes, where severe plastic deformation (SPD) is one of the most significant techniques. This opens the door to extend basic research in fracture mechanics to the nanocrystalline (NC) grain size regime. From the technological point of view, there is also the necessity to evaluate standard fracture mechanics data of these new materials, such as the fracture toughness, in order to allow their implementation in engineering applications. Here, an overview of recent results on the fracture behaviour of several different ultrafine-grained (d<1 μm) and NC (d<100 nm) metals and alloys covering examples of body- and face-centred cubic structures produced by SPD will be given. PMID:25713459

  20. Analytical and Experimental Investigation of Process Loads on Incremental Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Okan Görtan, Mehmet

    2017-05-01

    From the processing point of view, friction is a major problem in the severe plastic deformation (SPD) using equal channel angular pressing (ECAP) process. Incremental ECAP can be used in order to optimize frictional effects during SPD. A new incremental ECAP has been proposed recently. This new process called as equal channel angular swaging (ECAS) combines the conventional ECAP and the incremental bulk metal forming method rotary swaging. ECAS tool system consists of two dies with an angled channel that contains two shear zones. During ECAS process, two forming tool halves, which are concentrically arranged around the workpiece, perform high frequency radial movements with short strokes, while samples are pushed through these. The oscillation direction nearly coincides with the shearing direction in the workpiece. The most important advantages in comparison to conventional ECAP are a significant reduction in the forces in material feeding direction plus the potential to be extended to continuous processing. In the current study, the mechanics of the ECAS process is investigated using slip line field approach. An analytical model is developed to predict process loads. The proposed model is validated using experiments and FE simulations.

  1. Finite deformation analysis of continuum structures with time dependent anisotropic elastic plastic material behavior (LWBR/AWBA Development Program)

    SciTech Connect

    Hutula, D.N.

    1980-03-01

    A finite element procedure is presented for finite deformation analysis of continuum structures with time-dependent anisotropic elastic-plastic material behavior. An updated Lagrangian formulation is used to describe the kinematics of deformation. Anisotropic constitutive relations are referred, at each material point, to a set of three mutually orthogonal axes which rotate as a unit with an angular velocity equal to the spin at the point. The time-history of the solution is generated by using a linear incremental procedure with residual force correction, along with an automatic time step control algorithm which chooses time step sizes to control the accuracy and numerical stability of the solution.

  2. 3D Arrangement of Slip Systems in Non-Plane Strain: Experimental Plastic Deformation of Fine-Grained Limestone

    NASA Astrophysics Data System (ADS)

    Llana-Funez, S.; Rutter, E. H.

    2006-12-01

    The condition of simultaneous operation of five slip systems to produce homogeneous deformation by intracrystalline plasticity in polycrystalline aggregates is frequently simplified when applied to studying deformation in nature by considering other deformation mechanisms that relax the strict geometric condition. Insufficient knowledge of how these complementary mechanisms interact and accommodate geometrically non-plane strain situations obscure somehow subsequent interpretation of slip patterns in relation to principal strain axes. We ran an experimental program isolating intracrystalline plasticity from other deformation mechanisms with the aim of testing the effect of non-plane strain geometries in the 3D arrangement of crystallographic elements from which we inferred the orientation of active slip systems. We use a fine grained polycrystalline aggregate (Solnhofen Limestone), naturally doped at grain boundaries with organic matter preventing grain growth, that deforms plastically at the experimental conditions used (600 °C, 200 MPa confining pressure and 10^{- 4}s-1 strain rates). To maximize the number of strain geometries we used different experimental configurations (axi-symmetric shortening and extension, and direct shear) and also study in detail volumes where deformation is heterogeneous but still relatively simple. The aim of the work is to relate strain geometry and the development of crystallographic fabrics in different strain paths. We produced constrictional, flattening, and nearly plane strain deformations. We were also able to obtain strain geometries where the vorticity axis in a non-coaxial deformation was either perpendicular to the extension direction (as in simple and sub-simple shear) or parallel to it. We measured the crystallographic preferred orientation (CPO) of calcite in deformed specimens by electron back-scattered diffraction techniques (EBSD), which allowed us to scan relatively small areas within already small specimens

  3. The Effect of Cold Plastic Straining of Submicrocrystalline and Coarse-Grained Titanium on the Temperature Behavior of Flow Stress in the Stage of Microplastic Deformation

    NASA Astrophysics Data System (ADS)

    Dudarev, E. F.; Pochivalova, G. P.; Kolobov, Yu. R.; Bakach, G. P.; Skosyrskii, A. B.; Zhorovkov, M. F.; Goraynov, А. А.

    2013-10-01

    The results of an experimental investigation of the effect of mechanical-thermal treatment of submicrocrystalline and coarse-grained titanium on the deformation behavior in the stage of microplastic deformation at room and elevated temperatures are reported. The structural factors giving rise to the flowstress changes in the stage of microplastic deformation as a result of mechanical-thermal treatment are discussed. The general tendencies and special features of the effect of annealing and testing temperatures on the deformation behavior and flow stress in the first and second stages of microplastic deformation of submicrocrystalline and coarse-grained titanium subjected to large plastic deformation at 295 K are clarified.

  4. Severe plastic deformation using friction stir processing, and the characterization of microstructure and mechanical behavior using neutron diffraction

    NASA Astrophysics Data System (ADS)

    Woo, Wanchuck

    Friction-stir welding (FSW) is a solid-state joining process, which utilizes a cylindrical rotating tool consisting of a concentric threaded tool pin and tool shoulder. The strong metallurgical bonding during the FSW is accomplished through: (1) the severe plastic deformation caused by the rotation of the tool pin that plunges into the material and travels along the joining line; and (2) the frictional heat generated mainly from the pressing tool shoulder. Recently, a number of variations of the FSW have been applied to modify the microstructure, for example, grain refinements and homogenization of precipitate particles, namely friction-stir processing (FSP). Applications of the FSP/FSW are widespread for the transportation industries. The microstructure and mechanical behavior of light-weight materials subjected to the FSW/FSP are being studied extensively. However, separating the effect of the frictional heat and severe plastic deformation on the residual stress and texture has been a standing problem for the fundamental understanding of FSW/FSP. The fundamental issues are: (i) the heat- and plastic-deformation-induced internal stresses that may be detrimental to the integrity and performance of components; (ii) the frictional heating that causes a microstructural softening due to the dissolution or growth of the precipitates in precipitation-hardenable Al alloys during the process; and (iii) the crystallographic texture can be significantly altered from the original texture, which could affect the physical and mechanical properties. The understanding of the influences of the de-convoluted sources (e.g. frictional heat, severe plastic deformation, or their combination) on the residual stress, microstructural softening, and texture variations during FSW can be used for a physicsvi based optimization of the processing parameters and new tool designs. Furthermore, the analyses and characterization of the natural aging behavior and the aging kinetics can be

  5. Evaluation of stiffness and plastic deformation of active ceramic self-ligating bracket clips after repetitive opening and closure movements

    PubMed Central

    Carneiro, Grace Kelly Martins; Roque, Juliano Alves; Segundo, Aguinaldo Silva Garcez; Suzuki, Hideo

    2015-01-01

    OBJECTIVE: The aim of this study was to assess whether repetitive opening and closure of self-ligating bracket clips can cause plastic deformation of the clip. METHODS: Three types of active/interactive ceramic self-ligating brackets (n = 20) were tested: In-Ovation C, Quicklear and WOW. A standardized controlled device performed 500 cycles of opening and closure movements of the bracket clip with proper instruments and techniques adapted as recommended by the manufacturer of each bracket type. Two tensile tests, one before and one after the repetitive cycles, were performed to assess the stiffness of the clips. To this end, a custom-made stainless steel 0.40 x 0.40 mm wire was inserted into the bracket slot and adapted to the universal testing machine (EMIC DL2000), after which measurements were recorded. On the loading portion of the loading-unloading curve of clips, the slope fitted a first-degree equation curve to determine the stiffness/deflection rate of the clip. RESULTS: The results of plastic deformation showed no significant difference among bracket types before and after the 500 cycles of opening and closure (p = 0.811). There were significant differences on stiffness among the three types of brackets (p = 0.005). The WOW bracket had higher mean values, whereas Quicklear bracket had lower values, regardless of the opening/closure cycle. CONCLUSION: Repetitive controlled opening and closure movements of the clip did not alter stiffness or cause plastic deformation. PMID:26352844

  6. Evaluation of stiffness and plastic deformation of active ceramic self-ligating bracket clips after repetitive opening and closure movements.

    PubMed

    Carneiro, Grace Kelly Martins; Roque, Juliano Alves; Segundo, Aguinaldo Silva Garcez; Suzuki, Hideo

    2015-01-01

    The aim of this study was to assess whether repetitive opening and closure of self-ligating bracket clips can cause plastic deformation of the clip. Three types of active/interactive ceramic self-ligating brackets (n = 20) were tested: In-Ovation C, Quicklear and WOW. A standardized controlled device performed 500 cycles of opening and closure movements of the bracket clip with proper instruments and techniques adapted as recommended by the manufacturer of each bracket type. Two tensile tests, one before and one after the repetitive cycles, were performed to assess the stiffness of the clips. To this end, a custom-made stainless steel 0.40 x 0.40 mm wire was inserted into the bracket slot and adapted to the universal testing machine (EMIC DL2000), after which measurements were recorded. On the loading portion of the loading-unloading curve of clips, the slope fitted a first-degree equation curve to determine the stiffness/deflection rate of the clip. The results of plastic deformation showed no significant difference among bracket types before and after the 500 cycles of opening and closure (p = 0.811). There were significant differences on stiffness among the three types of brackets (p = 0.005). The WOW bracket had higher mean values, whereas Quicklear bracket had lower values, regardless of the opening/closure cycle. Repetitive controlled opening and closure movements of the clip did not alter stiffness or cause plastic deformation.

  7. Lithium-assisted plastic deformation of silicon electrodes in lithium-ion batteries: a first-principles theoretical study.

    PubMed

    Zhao, Kejie; Wang, Wei L; Gregoire, John; Pharr, Matt; Suo, Zhigang; Vlassak, Joost J; Kaxiras, Efthimios

    2011-07-13

    Silicon can host a large amount of lithium, making it a promising electrode for high-capacity lithium-ion batteries. Recent experiments indicate that silicon experiences large plastic deformation upon Li absorption, which can significantly decrease the stresses induced by lithiation and thus mitigate fracture failure of electrodes. These issues become especially relevant in nanostructured electrodes with confined geometries. On the basis of first-principles calculations, we present a study of the microscopic deformation mechanism of lithiated silicon at relatively low Li concentration, which captures the onset of plasticity induced by lithiation. We find that lithium insertion leads to breaking of Si-Si bonds and formation of weaker bonds between neighboring Si and Li atoms, which results in a decrease in Young's modulus, a reduction in strength, and a brittle-to-ductile transition with increasing Li concentration. The microscopic mechanism of large plastic deformation is attributed to continuous lithium-assisted breaking and re-forming of Si-Si bonds and the creation of nanopores.

  8. On the kinetics of localized plasticity domains emergent at the pre-failure stage of deformation process

    NASA Astrophysics Data System (ADS)

    Orlova, Dina V.; Barannikova, Svetlana A.; Zuev, Lev B.

    2016-11-01

    The behavior of localized plasticity domains occurring at the final stage of the plastic flow process has been investigated. A series of runs was conducted on materials differing in the crystal lattice type which disclosed regular features exhibited by the flow process upon transition to macroscopic necking and viscous failure. It is found that the most distinctive regularity is the occurrence of flow domains that are moving in a concerted manner towards the pole of the bundle of domain trajectories plotted in the time-space coordinates. The deformation patterns are found to be related to the kinetics of nucleation and motion of localized plasticity fronts. The probable origin of the observed effects is considered.

  9. Interaction of heat production, strain rate and stress power in a plastically deforming body under tensile test

    NASA Technical Reports Server (NTRS)

    Paglietti, A.

    1982-01-01

    At high strain rates the heat produced by plastic deformation can give rise to a rate dependent response even if the material has rate independent constitutive equations. This effect has to be evaluated when interpreting a material test, or else it could erroneously be ascribed to viscosity. A general thermodynamic theory of tensile testing of elastic-plastic materials is given in this paper; it is valid for large strain at finite strain rates. It enables discovery of the parameters governing the thermodynamic strain rate effect, provides a method for proper interpretation of the results of the tests of dynamic plasticity, and suggests a way of planning experiments in order to detect the real contribution of viscosity.

  10. Interaction of heat production, strain rate and stress power in a plastically deforming body under tensile test

    NASA Technical Reports Server (NTRS)

    Paglietti, A.

    1982-01-01

    At high strain rates the heat produced by plastic deformation can give rise to a rate dependent response even if the material has rate independent constitutive equations. This effect has to be evaluated when interpreting a material test, or else it could erroneously be ascribed to viscosity. A general thermodynamic theory of tensile testing of elastic-plastic materials is given in this paper; it is valid for large strain at finite strain rates. It enables discovery of the parameters governing the thermodynamic strain rate effect, provides a method for proper interpretation of the results of the tests of dynamic plasticity, and suggests a way of planning experiments in order to detect the real contribution of viscosity.

  11. Three-Dimensional Crystal Plasticity Finite Element Simulation of Hot Compressive Deformation Behaviors of 7075 Al Alloy

    NASA Astrophysics Data System (ADS)

    Li, Lei-Ting; Lin, Y. C.; Li, Ling; Shen, Lu-Ming; Wen, Dong-Xu

    2015-03-01

    Three-dimensional crystal plasticity finite element (CPFE) method is used to investigate the hot compressive deformation behaviors of 7075 aluminum alloy. Based on the grain morphology and crystallographic texture of 7075 aluminum alloy, the microstructure-based representative volume element (RVE) model was established by the pole figure inversion approach. In order to study the macroscopic stress-strain response and microstructural evolution, the CPFE simulations are performed on the established microstructure-based RVE model. It is found that the simulated stress-strain curves and deformation texture well agree with the measured results of 7075 aluminum alloy. With the increasing deformation degree, the remained initial weak Goss texture component tends to be strong and stable, which may result in the steady flow stress. The grain orientation and grain misorientation have significant effects on the deformation heterogeneity during hot compressive deformation. In the rolling-normal plane, the continuity of strain and misorientation can maintain across the low-angle grain boundaries, while the discontinuity of strain and misorientation is observed at the high-angle grain boundaries. The simulated results demonstrate that the developed CPFE model can well describe the hot compressive deformation behaviors of 7075 aluminum alloy under elevated temperatures.

  12. Microstructure of YBa2Cu3O y subjected to severe plastic deformation by high pressure torsion

    NASA Astrophysics Data System (ADS)

    Kuznetsova, E. I.; Degtyarev, M. V.; Zyuzeva, N. A.; Bobylev, I. B.; Pilyugin, V. P.

    2017-08-01

    The influence of plastic deformation carried out by high pressure torsion at room temperature on the microstructure of the YBa2Cu3O y (123) compound prepared by standard ceramic technology and annealed at low temperature (200°C) in a water-saturated atmosphere has been studied. It has been shown that the directional growth of recrystallized lamellar-shaped grains initiated by the 124-123 phase transformation takes place upon recovery (after deformation) annealing at 930°C in ceramics subjected to additional low-temperature annealing, which leads to the formation of the texture. A rodlike structure has been observed in samples prepared by standard technology, after deformation and recovery annealing (930°C).

  13. Interface-Driven Plasticity in Metal-Ceramic Nanolayered Composites: Direct Validation of Multiscale Deformation Modeling via In Situ Indentation in TEM

    NASA Astrophysics Data System (ADS)

    Mara, Nathan A.; Li, Nan; Misra, Amit; Wang, Jian

    2016-01-01

    We present in situ indentation in a transmission electron microscope on Al-TiN multilayers with individual layer thicknesses of 50 nm and 2.7 nm to explore the effect of length scales on the plastic co-deformability of a metal and a ceramic. At 50 nm, plasticity was confined to the Al layers with brittle fracture in the TiN layers. At 5 nm and below, cracking in TiN was suppressed with co-deformation evident in both layers. The in situ transmission electron microscopy (TEM) straining results demonstrate a profound size effect in enhancing plastic co-deformability in nanoscale metal-ceramic multilayers, as well as direct validation of ex situ and 3-D elastic-plastic deformation models.

  14. Atomic-scale analysis of plastic deformation in thin-film forms of electronic materials

    NASA Astrophysics Data System (ADS)

    Kolluri, Kedarnath

    Nanometer-scale-thick films of metals and semiconductor heterostructures are used increasingly in modern technologies, from microelectronics to various areas of nanofabrication. Processing of such ultrathin-film materials generates structural defects, including voids and cracks, and may induce structural transformations. Furthermore, the mechanical behavior of these small-volume structures is very different from that of bulk materials. Improvement of the reliability, functionality, and performance of nano-scale devices requires a fundamental understanding of the atomistic mechanisms that govern the thin-film response to mechanical loading in order to establish links between the films' structural evolution and their mechanical behavior. Toward this end, a significant part of this study is focused on the analysis of atomic-scale mechanisms of plastic deformation in freestanding, ultrathin films of face-centered cubic (fcc) copper (Cu) that are subjected to biaxial tensile strain. The analysis is based on large-scale molecular-dynamics simulations. Elementary mechanisms of dislocation nucleation are studied and several problems involving the structural evolution of the thin films due to the glide of and interactions between dislocations are addressed. These problems include void nucleation, martensitic transformation, and the role of stacking faults in facilitating dislocation depletion in ultrathin films and other small-volume structures of fcc metals. Void nucleation is analyzed as a mechanism of strain relaxation in Cu thin films. The glide of multiple dislocations causes shearing of atomic planes and leads to formation of surface pits, while vacancies are generated due to the glide motion of jogged dislocations. Coalescence of vacancy clusters with surface pits leads to formation of voids. In addition, the phase transformation of fcc Cu films to hexagonal-close packed (hcp) ones is studied. The resulting martensite phase nucleates at the film's free surface and

  15. Wear, microleakage and plastic deformation of an implant-supported chair-side bar system

    PubMed Central

    Steiner, Martin; Ludwig, Klaus; Kern, Matthias

    2015-01-01

    PURPOSE This in-vitro study was designed to evaluate retention forces, microleakage and plastic deformation of a prefabricated 2-implant bar attachment system (SFI-Bar, Cendres+Métaux, Switzerland). MATERIALS AND METHODS Two SFI implant-adapters were torqued with 35 Ncm into two implant analogues. Before the tube bars were finally sealed, the inner cavity of the tube bar was filled with liquid red dye to evaluate microleakage. As tube bar sealing agents three different materials were used (AGC Cem (AGC, resin based), Cervitec Plus (CP; varnish) and Gapseal (GS; silicone based). Four groups with eight specimens each were tested (GS, GS+AGC, AGC, CP). For cyclic loading, the attachment system was assembled parallel to the female counterparts in a chewing simulator. The mean retention forces of the initial and final ten cycles were statistically evaluated (ANOVA, α≤.05). RESULTS All groups showed a significant loss of retention forces. Their means differed between 30-39 N initially and 22-28 N after 50,000 loading cycles. No significant statistical differences could be found between the groups at the beginning (P=.224), at the end (P=.257) or between the loss of retention forces (P=.288). Microleakage occurred initially only in some groups but after 10,000 loading cycles all groups exhibited microleakage. CONCLUSION Long-term retention forces of the SFI-Bar remained above 20 N which can be considered clinically sufficient. The sealing agents in this study are not suitable to prevent microleakage. PMID:26330980

  16. Nanostructured severe plastic deformation processed titanium for orthodontic mini-implants.

    PubMed

    Serra, Glaucio; Morais, Liliane; Elias, Carlos Nelson; Semenova, Irina P; Valiev, Ruslan; Salimgareeva, Gulnaz; Pithon, Matheus; Lacerda, Rogério

    2013-10-01

    Titanium mini-implants have been successfully used as anchorage devices in Orthodontics. Commercially pure titanium (cpTi) was recently replaced by Ti-6Al-4V alloy as the mini-implant material base due to the higher strength properties of the alloy. However, the lower corrosion resistance and the lower biocompatibility have been lowering the success rate of Ti-6Al-4V mini-implants. Nanostructured titanium (nTi) is commercially pure titanium that was nanostructured by a specific technique of severe plastic deformation. It is bioinert, does not contain potentially toxic or allergic additives, and has higher specific strength properties than any other titanium applied in medical implants. The higher strength properties associated to the higher biocompatibility make nTi potentially useful for orthodontic mini-implant applications, theoretically overcoming cpTi and Ti-6Al-4V mini-implants. The purposes of the this work were to process nTi, to mechanically compare cpTi, Ti-6Al-4V, and nTi mini-implants by torque test, and to evaluate both the surface morphology and the fracture surface characteristics of them by SEM. Torque test results showed significant increase in the maximum torque resistance of nTi mini-implants when compared to cpTi mini-implants, and no statistical difference between Ti-6Al-4V and nTi mini-implants. SEM analysis demonstrated smooth surface morphology and transgranular fracture aspect for nTi mini-implants. Since nanostructured titanium mini-implants have mechanical properties comparable to titanium alloy mini-implants, and biocompatibility comparable to commercially pure titanium mini-implants, it is suggestive that nanostructured titanium can replace Ti-6Al-4V alloy as the material base for mini-implants.

  17. Glide Dislocations Dissociation in Inversion Domain Boundaries of Plastically Deformed Aluminium Nitride

    NASA Astrophysics Data System (ADS)

    Feregotto, Virginia; Michel, Jean-Pierre

    1996-09-01

    A ten per cent plastic deformation of polycrystalline aluminium nitride, at a temperature ranging from 1500 to 1650 ^{circ}C creates a new kind of intragranular defect. Observed by transmission electron microscopy, the look like torsion subboundaries created by dislocations with 1/3<~ngle11bar{2}0rangle Burgers vectors and so nodes are dissociated into Shockley partials. They are located in the basal plane. In fact, these defects appear only in the plane areas of grown-in defects, the inversion domain boundaries. The formation of these faulted networks is interpreted as being the ultimate stage of the interactions between inversion domain boundaries and glide dislocations. Une déformation plastique de 10 % de nitrure d'aluminium polycristallin, entre 1500 et 1650 ^{circ}C introduit un nouveau type de défauts intragranulaires. Au microscope électronique par transmission, ils apparaissent comme des sous-joints de torsion créés par des dislocations de vecteurs de Burgers 1/3<~ngle11bar{2}0rangle dont les nœuds triples sont dissociés en partielles de Shockley ; ils sont situés dans le plan de base. En fait, ces défauts ne se produisent que sur les parties planes de défauts originels, les parois de domaines d'inversion. La formation de ces réseaux fautés est analysée comme l'ultime stade des interactions entre parois de domaines d'inversion et dislocations de glissement.

  18. Roles of nanoclusters in shear banding and plastic deformation of bulk metallic glasses

    SciTech Connect

    Nieh, T G

    2012-07-31

    During the course of this research we published 33 papers in various physics/material journals. We select four representing papers in this report and their results are summarized as follows. I. To study shear banding process, it is pertinent to know the intrinsic shear strain rate within a propagating shear band. To this aim, we used nanoindentation technique to probe the mechanical response of a Au49Ag5.5Pd2.3Cu26.9Si16.3 bulk metallic glass in locality and found notable pop-in events associated with shear band emission. Using a free volume model and under the situation when temperature and stress/hardness are fixed result in an equation, which predicts that hardness serration caused by pop-in decreases exponentially with the strain rate. Our data are in good agreement with the prediction. The result also predicts that, when strain rate is higher than a critical strain rate of 1700 s^-1, there will be no hardness serration, thereby no pop-in. In other words, multiple shear bandings will take place and material will flow homogeneously. The critical strain rate of 1700 s^-1 can be treated as the intrinsic strain rate within a shear band. We subsequently carried out a simulation study and showed that, if the imposed strain rate was over , the shear band spacing would become so small that the entire sample would virtually behave like one major shear band. Using the datum strain rate =1700 s^-1 and based on a shear band nucleation model proposed by us, the size of a shear-band nucleus in Au-BMG was estimated to be 3 10^6 atoms, or a sphere of ~30 nm in diameter. II. Inspired by the peculiar result published in a Science article Super Plastic Bulk Metallic Glasses at Room Temperature, we synthesized the Zr-based bulk metallic glass with a composition identical to that in the paper (Zr64.13Cu15.75Ni10.12Al10) and, subsequently, tested in compression at the same slow strain rate (~10^-4 s^-1). We found that the dominant deformation mode is always single shear. The stress

  19. Achieving large macroscopic compressive plastic deformation and work-hardening-like behavior in a monolithic bulk metallic glass by tailoring stress distribution

    NASA Astrophysics Data System (ADS)

    Chen, L. Y.; Ge, Q.; Qu, S.; Jiang, Q. K.; Nie, X. P.; Jiang, J. Z.

    2008-05-01

    The limited plastic deformation and lack of work hardening seriously restrict the applications of bulk metallic glasses (BMGs). Here, large macroscopic compressive plastic deformation (over 15%) and work-hardening-like behavior were achieved in a monolithic BMG through tailoring loading stress distribution experimentally. Numerical analysis was also carried out to investigate the stress distribution under the same mechanical condition. It is shown that loading induced stress gradient is responsible for the achievement mentioned above.

  20. Effect of laser shock peening on the compressive deformation and plastic behavior of Zr-based bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Fu, Jie; Zhu, Yunhu; Zheng, Chao; Liu, Ren; Ji, Zhong

    2016-11-01

    The compressive deformation and the plastic behavior of Zr35Ti30Cu8.25Be26.75 bulk metallic glass (BMG) in as-cast and laser peened state were investigated. It was found that as-cast sample displayed brittle fracture with an limited plastic strain of 0.22% and the fracture was mainly localized on one single shear band. For laser peened sample, an apparent plastic strain of 1.48% could be observed in the stress-strain curve, which was much greater than that of as-cast sample. Scanning electron microscope observations revealed that the normal fracture surfaces of both samples displayed a shear mode and consisted of vein-like structure. The relatively uniform distribution of multiple shear bands was observed on the side fracture surface of laser peened sample. Numerical simulation was performed to understand quantitatively the plasticity enhancement of laser peened sample. Under the effect of LSP induced residual stress, the laser peened sample exhibited a larger concentrated stress around the main shear stress plane which could promote the initiation of new shear bands. Besides, the increased free volume in main shear stress plane were beneficial for the generation of multiple shear bands which would probably improve the compressive plasticity of Zr-based BMG.

  1. Large-deformation plasticity and acoustic emission of an Al-Mg alloy (1560) under high-temperature loading

    NASA Astrophysics Data System (ADS)

    Makarov, Plotnikov, V. A.; Lysikov, M. V.

    2017-07-01

    The following study investigates the large-deformation plasticity behavior and acoustic emission in Al-Mg alloy (1560) under high-temperature 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 (Tb) between intervals I and II changes non-monotonically. In cycles with load up to 90 MPa, the Tb value increases, while an increase up to 200 MPa makes Tb 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 event.

  2. The effect of martensite plasticity on the cyclic deformation of super-elastic NiTi shape memory alloy

    NASA Astrophysics Data System (ADS)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2014-01-01

    Based on stress-controlled cyclic tension-unloading experiments with different peak stresses, the effect of martensite plasticity on the cyclic deformation of super-elastic NiTi shape memory alloy micro-tubes is investigated and discussed. The experimental results show that the reverse transformation from the induced martensite phase to the austenite phase is gradually restricted by the plastic deformation of the induced martensite phase caused by an applied peak stress that is sufficiently high (higher than 900 MPa), and the extent of such restriction increases with further increasing the peak stress. The residual and peak strains of super-elastic NiTi shape memory alloy accumulate progressively, i.e., transformation ratchetting occurs during the cyclic tension-unloading with peak stresses from 600 to 900 MPa, and the transformation ratchetting strain increases with the increase of the peak stress. When the peak stress is higher than 900 MPa, the peak strain becomes almost unchanged, but the residual strain accumulates and the dissipation energy per cycle decreases very quickly with the increasing number of cycles due to the restricted reverse transformation by the martensite plasticity. Furthermore, a quantitative relationship between the applied stress and the stabilized residual strain is obtained to reasonably predict the evolution of the peak strain and the residual strain.

  3. Quantitative investigation of the tensile plastic deformation characteristic and microstructure for friction stir welded 2024 aluminum alloy

    SciTech Connect

    Hu, Z.L.; Wang, X.S.; Yuan, S.J.

    2012-11-15

    The effect of the microstructure heterogeneity on the tensile plastic deformation characteristic of friction stir welded (FSW) 2024 aluminum alloy was investigated for the potential applications on light weight design of vehicles. The microstructure characteristics of the FSW joints, such as the grain structure, dislocation density and the distribution of precipitation, were studied by electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The tensile deformation characteristic of the FSW joints was examined using the automatic strain measuring system (ASAME) by mapping the global and local strain distribution, and then was analyzed by mechanics calculation. It is found that the tensile deformation of the FSW joints is highly heterogeneous leading to a significant decrease in global ductility. The FSW joints mainly contain two typical deformation zones, which show great effect on the regional inhomogeneous deformation. One is the nugget zone (NZ) with a region of 8 mm in width, and the other is part of the BM with a region of 10 mm in width. The BM of the joints is the weakest region where the strain localizes early and this localization extends until fracture with a strain over 30%, while the strain in the NZ is only 4%. Differences in regional strain of FSW joints, which are essentially controlled by grain structure, the distribution of precipitation and dislocation density, result in decrease on the overall mechanical properties. - Highlights: Black-Right-Pointing-Pointer Microstructure heterogeneity of welds on tensile deformation behavior is studied. Black-Right-Pointing-Pointer The welds contain two typical deformation zones, affecting the global ductility. Black-Right-Pointing-Pointer Regional strain of welds is controlled by grain structure and dislocation density. Black-Right-Pointing-Pointer Theoretical calculation is in good agreement with experimental result.

  4. A dislocation-based, strain–gradient–plasticity strengthening model for deformation processed metal–metal composites

    DOE PAGES

    Tian, Liang; Russell, Alan; Anderson, Iver

    2014-01-03

    Deformation processed metal–metal composites (DMMCs) are high-strength, high-electrical conductivity composites developed by severe plastic deformation of two ductile metal phases. The extraordinarily high strength of DMMCs is underestimated using the rule of mixture (or volumetric weighted average) of conventionally work-hardened metals. A dislocation-density-based, strain–gradient–plasticity model is proposed to relate the strain-gradient effect with the geometrically necessary dislocations emanating from the interface to better predict the strength of DMMCs. The model prediction was compared with our experimental findings of Cu–Nb, Cu–Ta, and Al–Ti DMMC systems to verify the applicability of the new model. The results show that this model predicts themore » strength of DMMCs better than the rule-of-mixture model. The strain-gradient effect, responsible for the exceptionally high strength of heavily cold worked DMMCs, is dominant at large deformation strain since its characteristic microstructure length is comparable with the intrinsic material length.« less

  5. A dislocation-based, strain–gradient–plasticity strengthening model for deformation processed metal-metal composites

    SciTech Connect

    Tian, Liang; Russell, Alan; Anderson, Iver

    2014-01-03

    Deformation processed metal–metal composites (DMMCs) are high-strength, high-electrical conductivity composites developed by severe plastic deformation of two ductile metal phases. The extraordinarily high strength of DMMCs is underestimated using the rule of mixture (or volumetric weighted average) of conventionally work-hardened metals. In this article, a dislocation-density-based, strain–gradient–plasticity model is proposed to relate the strain-gradient effect with the geometrically necessary dislocations emanating from the interface to better predict the strength of DMMCs. The model prediction was compared with the experimental findings of Cu–Nb, Cu–Ta, and Al–Ti DMMC systems to verify the applicability of the new model. The results show that this model predicts the strength of DMMCs better than the rule-of-mixture model. The strain-gradient effect, responsible for the exceptionally high strength of heavily cold worked DMMCs, is dominant at large deformation strain since its characteristic microstructure length is comparable with the intrinsic material length.

  6. A study on the surface severe plastic deformation behavior of a Zr-based bulk metallic glass (BMG)

    SciTech Connect

    Tian, J.W.; Shaw, L.L.; Wang, Y.D.; Yokoyama, Y.; Liaw, P.K.

    2009-10-14

    A surface treatment process, which can generate the severe plastic deformation in the near-surface layer of crystalline materials, is successfully applied on the Zr{sub 50}Cu{sub 40}Al{sub 10} bulk metallic glass (BMG). The experiment is implemented using 20 WC/Co balls with a velocity of about 5 m/s to bombard the surface of the samples in a purified argon atmosphere. The plastic-flow deformation in the unconstrained sample edge was observed, which exhibits the good intrinsic ductility of this material under the experimental condition. In the sub-surface layer, the bombardment-induced shear-band operations generate the extrusion and intrusion marks on the side face. Differential scanning calorimetry (DSC) shows that the free volumes of the deformed BMG have increased, and possible crystallization may occur during the process. X-ray diffraction (XRD) and synchrotron high-energy X-ray diffraction techniques were used to inspect the possible crystal phase. A nanoindentation test shows that on the side surface, the hardness increases and, then, decreases with the distance from the processed surface. Four-point-bending-fatigue behavior has been studied and related to the modified surface structure and the compressive residual stress introduced by the surface treatment.

  7. A dislocation-based, strain–gradient–plasticity strengthening model for deformation processed metal–metal composites

    SciTech Connect

    Tian, Liang; Russell, Alan; Anderson, Iver

    2014-01-03

    Deformation processed metal–metal composites (DMMCs) are high-strength, high-electrical conductivity composites developed by severe plastic deformation of two ductile metal phases. The extraordinarily high strength of DMMCs is underestimated using the rule of mixture (or volumetric weighted average) of conventionally work-hardened metals. A dislocation-density-based, strain–gradient–plasticity model is proposed to relate the strain-gradient effect with the geometrically necessary dislocations emanating from the interface to better predict the strength of DMMCs. The model prediction was compared with our experimental findings of Cu–Nb, Cu–Ta, and Al–Ti DMMC systems to verify the applicability of the new model. The results show that this model predicts the strength of DMMCs better than the rule-of-mixture model. The strain-gradient effect, responsible for the exceptionally high strength of heavily cold worked DMMCs, is dominant at large deformation strain since its characteristic microstructure length is comparable with the intrinsic material length.

  8. Experimental stress analysis of large plastic deformations in a hollow sphere deformed by impact against a concrete block

    NASA Technical Reports Server (NTRS)

    Morris, R. E.

    1973-01-01

    An experimental plastic strain measurement system is presented for use on the surface of high velocity impact test models. The system was used on a hollow sphere tested in impact against a reinforced concrete block. True strains, deviatoric stresses, and true stresses were calculated from experimental measurements. The maximum strain measured in the model was small compared to the true failure strain obtained from static tensile tests of model material. This fact suggests that a much greater impact velocity would be required to cause failure of the model shell structure.

  9. An Approach for Measuring and Modeling of Plastic Deformation of Metallic Plates during High Velocity Impacts

    SciTech Connect

    O'Toole, Brendan J.; Trabia, Mohamed B.; Roy, Shawoon K.; Somasundarum, Deepak; Jennings, Richard; Matthes, Melissa; Hixson, Robert S.; Becker, Steven; Daykin, Edward P.; Pena, Michael T.; Machorro, Eric A.

    2014-05-29

    During high velocity impact experiments, projectile impact creates extreme pressure waves that results in a significant localized deformation within a short period of time. Experiments under these conditions require sophisticated data acquisition technique to better understand the materials deformation mechanisms. Since these experiments are expensive, it is also beneficial to develop accurate computational models that can predict this kind of deformation in high velocity impact events.

  10. Rate-dependent serrated flow and plastic deformation in Ti45Zr16Be20Cu10Ni9 bulk amorphous alloy during nanoindentation

    PubMed Central

    Kumar Misra, Dinesh; Woo Sohn, Sung; Tae Kim, Won; Hyang Kim, Do

    2008-01-01

    The plastic deformation of Ti45Zr16Be20Cu10Ni9 bulk metallic glass has been investigated by nanoindentation performed with loads ranging from 10 to 200 mN in a wide range of loading rates. The plastic flow in the alloy exhibited conspicuous serrations at low loading rates. The serrations, however, became less prominent as the rate of indentation increased. Atomic force microscopy showed a significant pile-up of materials around the indents, indicating that a highly localized plastic deformation occurred under nanoindentation. The possible mechanism governing the plastic deformation in bulk metallic glass specimens is tentatively discussed in terms of strain-induced free volume. PMID:27878032

  11. Mapping the cyclic plastic zone to elucidate the mechanisms of crack tip deformation in bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Scudino, S.; Shahid, R. N.; Escher, B.; Stoica, M.; Li, B. S.; Kruzic, J. J.

    2017-02-01

    Developing damage-tolerant bulk metallic glasses (BMGs) requires knowledge of the physical mechanisms governing crack propagation. While fractography suggests that fatigue crack propagation occurs in an incremental manner, conclusive evidence of alternating crack tip blunting and resharpening is lacking. By mapping the strain fields in both the monotonic and cyclic plastic zones, it is shown that the characteristic compressive stresses required to resharpen the crack tip are developed in a BMG upon unloading. This result confirms the mechanism of fatigue crack propagation in BMGs. Broader implications of these findings are that the effect of shear banding is rather diffuse and plastic deformation ahead of a stress concentration, such as a crack tip, appears to extend well beyond the extent of visible shear bands on the sample surface.

  12. Micro-structural Evolution in Metals Subjected to Simple Shear by a Particular Severe Plastic Deformation Method

    NASA Astrophysics Data System (ADS)

    Li, Jinghui; Li, Fuguo; Li, Pan; Ma, Zhanchao; Wang, Chengpeng; Wang, Lei

    2015-08-01

    Simple shear (SS) has been considered an optimal deformation method of severe plastic deformation (SPD). To achieve SS, a particular SPD method known as mutative channel torsion extrusion (MCTE) was designed based on the geometric equivalence of SS, and the cavity parameters of a die were calculated according to strain equivalence. To investigate the characteristics of micro-structural evolution subjected to MCTE, simulated and experimental investigations were conducted. The simulated results indicate that equivalent strain distribution on the cross section is relatively uniform, and the metallographic observations confirm the simulated phenomenon. Transmission electron microscopy investigations show that the process of grain refinement undergoes the formation of shear bands, dislocation cells, dislocation forests, large-angle grain boundaries, and recrystallization nuclei. Two types of mechanisms are proposed in view of the different effects of SS on grain refinement. Eventually, MCTE is ensured as an effective method for grain refinement.

  13. Quantitative Atomic Force Microscopy Characterization and Crystal Plasticity Finite Element Modeling of Heterogeneous Deformation in Commercial Purity Titanium

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Wang, L.; Bieler, T. R.; Eisenlohr, P.; Crimp, M. A.

    2011-03-01

    Using a four-point bend sample of commercial purity titanium deformed to a surface strain around 1.5 pct, the active dislocation slip and twin systems in a microstructural patch of about 15 grains were quantitatively analyzed by a technique combining atomic force microscopy (AFM), backscattered electron (BSE) imaging, and electron backscattered diffraction (EBSD). Local shear distribution maps derived from z-displacement data measured by AFM were directly compared to results of a crystal plasticity finite element (CPFE) simulation that incorporates a phenomenological model of the deformation processes to evaluate the ability of the CPFE model to match the experimental observations. The CPFE model successfully predicted most types of active dislocation slip systems within the grains at correct magnitudes, but the spatial distribution of strains within grains differed between the measurements and the simulation.

  14. Evolution of Dislocation Subsystem Components During Plastic Deformation Depending on Parameters of Strengthening Phase with L12 Superstructure

    NASA Astrophysics Data System (ADS)

    Daneyko, O. I.; Kovalevskaya, T. A.; Kulaeva, N. A.; Kolupaeva, S. N.; Shalygina, T. A.

    2017-09-01

    The paper presents results of mathematical modelling of plastic deformation in dispersion-hardened materials with FCC crystal system and L12 superstructure particles. Research results show that the size and the distance between particles of the strengthening phase affect the strain hardening and the evolution of the dislocation subsystem of the FCC alloy hardened with coherent L12 superstructure particles. It is found that increased size of ordered particles or decreased distance between them enhances the abnormal growth in the flow stress and the density of the dislocation subsystem components. Investigations show that prismatic dislocation loops predominate in the dislocation subsystem of materials having a nano-dispersion strengthening phase.

  15. Nanomechanics of silicon surfaces with atomic force microscopy: an insight to the first stages of plastic deformation.

    PubMed

    Garcia-Manyes, Sergi; Güell, Aleix G; Gorostiza, Pau; Sanz, Fausto

    2005-09-15

    The use of stiff cantilevers with diamond tips allows us to perform nanoindentations on hard covalent materials such as silicon with atomic force microscopy. Thanks to the high sensitivity in the force measurements together with the high resolution upon imaging the surface, we can study nanomechanical properties. At this scale, the surface deforms, following a simple non-Hertzian spring model. The plastic onset can be assessed from a discontinuity in the force-distance curves. Hardness measurements with penetration depths as small as 1 nm yield H= approximately 25 GPa, thus showing a drastic increase with penetration depths below 5 nm.

  16. Anisotropy of the Hot Plastic Deformation of Ti-6Al-4V Single-Colony Samples (Preprint)

    DTIC Science & Technology

    2009-04-01

    April 2009 Journal Article Preprint 01 April 2009- 01 April 2009 4 . TITLE AND SUBTITLE ANISOTROPY OF THE HOT PLASTIC DEFORMATION OF Ti-6Al-4V SINGLE...COLONY SAMPLES (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6 . AUTHOR(S) A.A. Salem and S.L...resistance, and low density, Ti-6Al-4V is the most commonly used alpha/beta titanium alloy. It accounts for approximately 80% of the total titanium used in

  17. Effect of r-value and texture on plastic deformation and necking behavior in interstitial-free steel sheets

    NASA Astrophysics Data System (ADS)

    Oh, Gyu-Jin; Lee, Kye-Man; Huh, Moo-Young; Park, Jin Eon; Park, Soo Ho; Engler, Olaf

    2017-01-01

    Three initial tensile specimens having different textures and, in consequence, different r-values were cut from a sheet of an interstitial-free steel. Using these specimens, the effect of r-value and texture on plastic deformation and the necking behavior were studied by tackling the strain state and texture during tensile tests. A reduced decrease in work hardening rate of tensile specimens with higher r-values led to a slower onset of diffuse necking which offers an increased uniform elongation. A slower reduction in thickness of specimens with a higher r-value provided a favorable resistance against onset of failure by localized necking.

  18. Scaling properties of Arctic sea ice deformation in high-resolution viscous-plastic sea ice models and satellite observations

    NASA Astrophysics Data System (ADS)

    Hutter, Nils; Losch, Martin; Menemenlis, Dimitris

    2017-04-01

    Sea ice models with the traditional viscous-plastic (VP) rheology and very high grid resolution can resolve leads and deformation rates that are localised along Linear Kinematic Features (LKF). In a 1-km pan-Arctic sea ice-ocean simulation, the small scale sea-ice deformations in the Central Arctic are evaluated with a scaling analysis in relation to satellite observations of the Envisat Geophysical Processor System (EGPS). A new coupled scaling analysis for data on Eulerian grids determines the spatial and the temporal scaling as well as the coupling between temporal and spatial scales. The spatial scaling of the modelled sea ice deformation implies multi-fractality. The spatial scaling is also coupled to temporal scales and varies realistically by region and season. The agreement of the spatial scaling and its coupling to temporal scales with satellite observations and models with the modern elasto-brittle rheology challenges previous results with VP models at coarse resolution where no such scaling was found. The temporal scaling analysis, however, shows that the VP model does not fully resolve the intermittency of sea ice deformation that is observed in satellite data.

  19. Three-dimensional mapping of stresses in plastically deformed diamond using micro-Raman and photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Erasmus, R. M.; Daniel, R. D.; Comins, J. D.

    2011-01-01

    The extreme mechanical properties of diamond have made it the material of choice for many industrial applications, ranging from cutting and grinding to wire-drawing dies. A detailed knowledge of its mechanical properties, also at high temperature, is thus of importance. Micro-Raman and photoluminescence (PL) spectroscopy were used to map the three-dimensional (3D) stress distribution surrounding a plastic impression made in a synthetic, type Ib single crystal diamond. The impression was created on a (100) face of the crystal with an Si3N4 impressor at 1400 °C using the so-called soft impressor technique. The diamond Raman peak was mapped at room temperature at the surface and at fixed intervals of 10 μm below the surface using a motorised X-Y stage. The depth (Z)-resolution was limited to 10 μm by means of a confocal pinhole. Using data from the Raman peak position, a 3D map of the stress contours surrounding the impression was generated, while the Raman width data yielded a map of the plastic deformation volume. The surface stress map shows a cross-shaped rosette pattern that corresponds very closely with micrographs imaging the pile-up on the surface due to dislocation movement. The "arms" of the pattern are in compression (˜1.5 GPa), while the center of the impression is in tension (˜1 GPa). The deformation map shows a radially symmetric area of deformation centered on the impression, with the maximum degree of deformation at the center. The stress contours compare favorably with the resolved shear stress contours calculated for diamond. PL intensity maps of the zero phonon line (ZPL) associated with the [N-V]- defect center at 1.945 eV provide images of the extent of vacancy formation and movement during the impression process. Data concerning the position and width of the ZPL correspond well with the Raman results.

  20. 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.

  1. Time-dependent nonlinear finite element modeling of the elastic and plastic deformation in SiGe heterostructured nanomaterials

    NASA Astrophysics Data System (ADS)

    Karoui, A.; Sahtout, F. K.; Vlahovic, B.

    2017-01-01

    The study of strain and stress distributions and relaxation mechanisms during epitaxial deposition of ultra-thin film heterostructures is of critical importance for nanoelectronic materials. It provides guidance for the control of structures at the nanometer scale and insights into the underlying physics. In this paper, we present a time-dependent nonlinear finite element model, which realistically simulates the evolution of elastic and plastic deformation in SiGe heterostructured nanomaterials during epitaxial deposition. Dynamic elements have been used to simulate the layer-by-layer deposition and growth rate as well as chemical-mechanical polishing (CMP) planarization. The thickness of add-on and etched-off layers was limited to few nanometers depending on the final epitaxial layer thickness and its growth rate. The material plastic behavior is described by the Von Mises yield criterion coupled with isotropic work hardening conditions and the Levy-Mises flow rule. The model has been successfully applied to the growth of ultra-thin (15 nm) strained-Si/ S i1 -xG ex /Si(001) heterostructures. Depth and time dependent elastic and plastic stress and strain in the growing layers are quantified and the relaxation mechanisms are deduced. From the calculated elastic and plastic strain fields, we derived the relaxation factor, plastic strain rate, dislocation glide velocity, misfit, and threading dislocation density as well as several structural properties such as lattice parameters and misfit dislocation spacing and length. These were found in close agreement with published experimental data. The simulation was able to show at which step of the growth process and how often yielding events occur. Plastic deformation and so the nucleation and multiplication of dislocations appeared to occur consistently during growth of the graded-layer. The simulation was also able to predict that CMP of the SiGe-cap followed by a regrowth step will indeed further relax the graded layer

  2. A Study of Low-Alloy Steel 40KhGF for Controlled Hot Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Zaslavskii, A. Ya.; Reznitskii, I. B.; Yashin, Yu. D.; Mashkin, V. A.; Soldatkin, S. A.

    2003-03-01

    Results of a study of the dependence of the structure and properties of low-carbon microalloyed steel for controlled forging and rolling on the austenization temperature, the degree of deformation, and the cooling rate after the deformation are presented. It is established that the γ → α transformation in the studied steel during cooling in any mode of controlled rolling occurs in the pearlite range. As the austenization temperature is decreased and the degree of deformation increased in the process of controlled rolling, the grain size decreases and the dispersity of the pearlite increases. The mechanical properties of the studied steel are quite stable after various variants of controlled rolling.

  3. Nano-scale elastic-plastic properties and indentation-induced deformation of single crystal 4H-SiC.

    PubMed

    Nawaz, A; Mao, W G; Lu, C; Shen, Y G

    2017-02-01

    The nanoscale elastic-plastic response of single crystal 4H-SiC has been investigated by nanoindentationwith a Berkovich tip. The hardness (H) and elastic modulus (E) determined in the load-independent region were 36±2GPa and 413±8GPa, respectively. The indentation size effect (ISE) of hardness within an indentation depth of 60nm was systematically analyzed by the Nix-Gao model. Pop-in events occurring at a depth of ~23nm with indentation loads of 0.60-0.65mN were confirmed to indicate the elastic-plastic transition of the crystal, on the basis of the Hertzian contact theory and Johnson's cavity model. Theoritically calculated maximum tensile strength (13.5GPa) and cleavage strength (33GPa) also affirms the deformation due to the first pop-in rather than tensile stresses. Further analyses of deformation behavior across the indent was done in 4H-SiC by a combined technique of focused ion beam and transmission electron microscope, revealing that slippage occurred in the (0001) plane after indentation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Investigating internal architecture effect in plastic deformation and failure for TPMS-based scaffolds using simulation methods and experimental procedure.

    PubMed

    Kadkhodapour, J; Montazerian, H; Raeisi, S

    2014-10-01

    Rapid prototyping (RP) has been a promising technique for producing tissue engineering scaffolds which mimic the behavior of host tissue as properly as possible. Biodegradability, agreeable feasibility of cell growth, and migration parallel to mechanical properties, such as strength and energy absorption, have to be considered in design procedure. In order to study the effect of internal architecture on the plastic deformation and failure pattern, the architecture of triply periodic minimal surfaces which have been observed in nature were used. P and D surfaces at 30% and 60% of volume fractions were modeled with 3∗3∗ 3 unit cells and imported to Objet EDEN 260 3-D printer. Models were printed by VeroBlue FullCure 840 photopolymer resin. Mechanical compression test was performed to investigate the compressive behavior of scaffolds. Deformation procedure and stress-strain curves were simulated by FEA and exhibited good agreement with the experimental observation. Current approaches for predicting dominant deformation mode under compression containing Maxwell's criteria and scaling laws were also investigated to achieve an understanding of the relationships between deformation pattern and mechanical properties of porous structures. It was observed that effect of stress concentration in TPMS-based scaffolds resultant by heterogeneous mass distribution, particularly at lower volume fractions, led to a different behavior from that of typical cellular materials. As a result, although more parameters are considered for determining dominant deformation in scaling laws, two mentioned approaches could not exclusively be used to compare the mechanical response of cellular materials at the same volume fraction.

  5. Plastic flow of mild steel (En8) at different strain-rates under abruptly-changing deformation paths

    NASA Astrophysics Data System (ADS)

    Meguid, S. A.

    1981-12-01

    STRAIN-GAUGED thin-walled tubular specimens of annealed medium carbon steel (En8) were tested at room temperature in combined twisting and extension using a closed-loop, servo-controlled, electro-hydraulic biaxial testing machine. Bilinear deformation paths of twisting at a constant rate followed by extension at three different rates were investigated. Precise measurements of the resulting torque and load, together with the controlled deformation parameters, were recorded as functions of time. This study extends earlier work ( MEGUID, MALVERN and CAMPBELL, 1979, J. Engng Mater. Technol.101, 248) in which a notable feature of this particular type of bilinear testing was reported: namely, that it was possible to obtain almost the entire positive quadrant of the initial yield locus from a single run without unloading or reloading (neutral loading). Here, particular attention has been given to the effect of the axial strain-rate on the shape of these "initial" yield loci. Attention has also been given to the effect of the sudden change of direction in the deformation path upon the deviatoric stress and the plastic strain-rate vectors. The results indicate that there exist appreciable differences between the Mises equivalent stress and equivalent plastic strain curves (up to strains of order 2%) for the three axial strain-rates investigated. These differences are attributed to the rate-sensitivity of the material. The results also show a much slower alignment of the deviatoric stress vector direction to the direction of the plastic strain-rate vector than had been expected. Comparisons with two theoretical analyses of a bilinear deformation path of quasistatic twisting followed by extension at a constant strain-rate are made, one using PERZYNA'S (1966) viscoplastic constitutive law for rate-sensitive (but non-strainhardening) material and the other using a rate-independent theory. Refinements in the test procedures now reveal that significant differences exist between

  6. Identification of the plastic deformation characteristics of AL5052-O sheet based on the non-associated flow rule

    NASA Astrophysics Data System (ADS)

    Pham, Quoc Tuan; Kim, Young Suk

    2017-03-01

    This study aims to determine the plastic deformation characteristics of aluminum 5052-O based on non-associated flow rule. To achieve this goal, a new strain hardening model named as Kim-Tuan hardening model is proposed to perfectly describe the stress-strain relation of the studied material in terms of the uniaxial tensile test and to predict the material's post-necking behavior. Additionally, the plastic behaviors of AL5052-O sheet are described by two approaches: the associated flow rule with YLD2000-2d yield function and the non-associated flow rule with Hill's quadratic function (NAFR-Hill48). The parameters of these functions were derived from the material properties that were obtained from uniaxial tensile tests and bulge test. The flow curve based on Kim-Tuan model and plastic behaviors obtained from two above-mentioned approaches were imported into a finite element analysis code to simulate the hydraulic bulge test for this material to confirm the precision of material characteristics achieved before. The simulation results based on the NAFR-Hill48 match well with the experiment results of bulge test while the YLD2000-2d provides highly accurate predictions for anisotropy of this material.

  7. Identification of the plastic deformation characteristics of AL5052-O sheet based on the non-associated flow rule

    NASA Astrophysics Data System (ADS)

    Pham, Quoc Tuan; Kim, Young Suk

    2017-02-01

    This study aims to determine the plastic deformation characteristics of aluminum 5052-O based on non-associated flow rule. To achieve this goal, a new strain hardening model named as Kim-Tuan hardening model is proposed to perfectly describe the stress-strain relation of the studied material in terms of the uniaxial tensile test and to predict the material's post-necking behavior. Additionally, the plastic behaviors of AL5052-O sheet are described by two approaches: the associated flow rule with YLD2000-2d yield function and the non-associated flow rule with Hill's quadratic function (NAFR-Hill48). The parameters of these functions were derived from the material properties that were obtained from uniaxial tensile tests and bulge test. The flow curve based on Kim-Tuan model and plastic behaviors obtained from two above-mentioned approaches were imported into a finite element analysis code to simulate the hydraulic bulge test for this material to confirm the precision of material characteristics achieved before. The simulation results based on the NAFR-Hill48 match well with the experiment results of bulge test while the YLD2000-2d provides highly accurate predictions for anisotropy of this material.

  8. Cenozoic brittle and plastic deformations in west Sichuan: Evidence for the stress and strain pattern of the southeastern Tibetan plateau

    NASA Astrophysics Data System (ADS)

    Wang, E.; Zheng, Y.

    2009-12-01

    along the Jinhe thrust fault and northeast bending of the Xianshuihe fault. The early stage deformation, presumably middle Tertiary in age, is dominated by plastic deformation, mainly occurred within the Songpan-Ganzi flysch belt in Triassic age. Although the flysch rocks in the region present with a very complicated plastic deformation pattern are generally considered to have formed in Mesozoic time, we interpreted them to have formed in middle Tertiary time, as they were extruded plastically from the area between the Ganzi and Xianshuihe faults due to the NE-SE compression and associated NW-SE extension along these two faults. All these evidences indicate that southeastern Tibetan plateau had a history of the east and west shortening in late Cenozoic time, probably coeval with the southeastward movement of the plateau, and the northeast and southwest shortening and associated northwest-southeast extension in middle Tertiary time.

  9. Strength, corrosion resistance, and biocompatibility of ultrafine-grained Mg alloys after different modes of severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Dobatkin, S. V.; Lukyanova, E. A.; Martynenko, N. S.; Anisimova, N. Yu; Kiselevskiy, M. V.; Gorshenkov, M. V.; Yurchenko, N. Yu; Raab, G. I.; Yusupov, V. S.; Birbilis, N.; Salishchev, G. A.; Estrin, Y. Z.

    2017-05-01

    The effect of severe plastic deformation on the structure, mechanical properties, corrosion resistance, and biocompatibility of the WE43 (Mg-Y-Nd-Zr) alloy earmarked for applications as bioresorbable material has been studied. The alloy was deformed by rotary swaging (RS), equal channel angular pressing (ECAP), and multiaxial deformation (MAD). The microstructure examination by transmission electron microscopy showed that all SPD modes lead to the formation of ultrafine-grained structure with a structural element size of 0.5-1 µm and the Mg12Nd phase particles 0.3 µm in size. The microstructure refinement by all three treatments resulted in strengthening of the alloy. ECAP and MAD also raised ductility to up to 12-17%, while RS increased the ultimate tensile strength to up to 415 MPa. The study of the corrosion properties showed that SPD does not affect the electrochemical corrosion of the alloy. Its biocompatibility in vitro was estimated after incubation of the samples with red blood cells (hemolysis study), white blood cells (cell viability assay), and mesenchymal stromal cells (cell proliferation analysis). The biodegradation rate in fetal bovine serum was also evaluated. ECAP and MAD were found to cause some deceleration of biodegradation by slowing down the gas formation in the biological fluid and, compared to MSC, to improve the biocompatibility of the WE43 alloy.

  10. Microstructure and annealing behavior of a modified 9Cr-1Mo steel after dynamic plastic deformation to different strains

    NASA Astrophysics Data System (ADS)

    Zhang, Z. B.; Mishin, O. V.; Tao, N. R.; Pantleon, W.

    2015-03-01

    The microstructure, hardness and tensile properties of a modified 9Cr-1Mo steel processed by dynamic plastic deformation (DPD) to different strains (0.5 and 2.3) have been investigated in the as-deformed and annealed conditions. It is found that significant structural refinement and a high level of strength can be achieved by DPD to a strain of 2.3, and that the microstructure at this strain contains a large fraction of high angle boundaries. The ductility of the DPD processed steel is however low. Considerable structural coarsening of the deformed microstructure without pronounced recrystallization takes place during annealing of the low-strain and high-strain samples for 1 h at 650 °C and 600 °C, respectively. Both coarsening and partial recrystallization occur in the high-strain sample during annealing at 650 °C for 1 h. For this sample, it is found that whereas coarsening alone results in a loss of strength with only a small gain in ductility, coarsening combined with pronounced partial recrystallization enables a combination of appreciably increased ductility and comparatively high strength.

  11. Elasto/visco-plastic deformation of multi-layered shells of revolution under thermal loading due to fluid

    SciTech Connect

    Takezono, S.; Tao, K.; Inamura, E.

    1995-11-01

    An analytical method for the elasto/visco-plastic deformation of the multi-layered shells subjected to thermal loads due to fluid is developed. First, the temperature distribution through the thickness in each layer is assumed to be linear, and the temperature field in the shell is determined using the equations of heat conduction and heat transfer. Secondly, the stresses and deformations are analyzed by the thermal stress equations. The equations of equilibrium and the relationships between the strains and displacements are derived from the Sanders shell theory. For the constitutive relations, Perzyna`s equations are employed. As a numerical example, a two-layered cylindrical shell composed of mild steel and titanium subjected to locally distributed thermal loads due to fluid is analyzed. Numerical computations are carried out for three cases of the ratio of the thickness of the titanium layer to the shell thickness. It is fund from the computations that the temperature and stress distributions and the deformation vary significantly depending on the thickness ratio.

  12. Large Deformation Mechanisms, Plasticity, and Failure of an Individual Collagen Fibril With Different Mineral Content.

    PubMed

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

    2016-02-01

    Mineralized collagen fibrils are composed of tropocollagen molecules and mineral crystals derived from hydroxyapatite to form a composite material that combines optimal properties of both constituents and exhibits incredible strength and toughness. Their complex hierarchical structure allows collagen fibrils to sustain large deformation without breaking. In this study, we report a mesoscale model of a single mineralized collagen fibril using a bottom-up approach. By conserving the three-dimensional structure and the entanglement of the molecules, we were able to construct finite-size fibril models that allowed us to explore the deformation mechanisms which govern their mechanical behavior under large deformation. We investigated the tensile behavior of a single collagen fibril with various intrafibrillar mineral content and found that a mineralized collagen fibril can present up to five different deformation mechanisms to dissipate energy. These mechanisms include molecular uncoiling, molecular stretching, mineral/collagen sliding, molecular slippage, and crystal dissociation. By multiplying its sources of energy dissipation and deformation mechanisms, a collagen fibril can reach impressive strength and toughness. Adding mineral into the collagen fibril can increase its strength up to 10 times and its toughness up to 35 times. Combining crosslinks with mineral makes the fibril stiffer but more brittle. We also found that a mineralized fibril reaches its maximum toughness to density and strength to density ratios for a mineral density of around 30%. This result, in good agreement with experimental observations, attests that bone tissue is optimized mechanically to remain lightweight but maintain strength and toughness.

  13. Mechanisms of plastic deformation in [1 ¯ 11 ]-oriented single crystals of FeNiMnCrCo high entropy alloy

    NASA Astrophysics Data System (ADS)

    Kireeva, Irina; Chumlyakov, Yurii; Pobedennaya, Zinaida; Kuksgauzen, Dmitrii; Karaman, Ibrahim; Sehitoglu, Huseyin

    2016-11-01

    Single crystals of fcc Fe20Ni20Mn20Cr20Co20 (atom percent) high entropy alloy oriented along the [1 ¯11 ] direction are used to study flow curves and deformation mechanisms—slip, twinning under tensile deformation at early stages of plastic flow, ɛ = 2.5-5.0%, at the test temperature of 77 and 296 K. It is shown that twinning in [1 ¯11 ] -oriented single crystals is observed from the beginning of plastic flow when ɛ = 2.5-5.0% from 77 to 296 K. Plastic flow in [1 ¯11 ]-oriented single crystals under tension is developed with the high strain hardening coefficients 1800 and 2000 MPa, respectively, at 296 and 77 K. It is also characterized by a good plasticity of 58 and 60% and by a high level of stresses before fracture, 980 and 1580 MPa, respectively, at 296 and 77 K.

  14. Recovery of Industrial and Recycled Al-Cu Alloys Subjected to Severe Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Rekik, M. A.; Kassis, K.; Masmoudi, J.; Zghal, S.; Champion, Y.; Njah, N.

    2009-11-01

    Equal channel angular pressing (ECAP) is a well-known method to obtain high hardness levels through a strong refinement of grains. To obtain fine grains, a subsequent heating is performed after deformation. The main difficulty is to retain a sufficiently small grain size. Alloy purity is an important parameter in recristallization kinetics. In the present work, an industrial and a recycled Al-4%Cu alloys were subjected to ECAP. The evolution of the microstructure of the deformed and annealed alloys was investigated. The alloys exhibit different hardness values for a given equivalent deformation. In industrial alloy, no recovery was observed at low temperatures. On the other hand, enhanced precipitation in this alloy leads to an increase in hardness balancing then softening due to recovery. A substantial decrease in hardness is observed around 250 ∘C and seems to depend on alloy purity.

  15. Electron Emission as a Probe of Plastic Deformation in Single Crystal Metals

    SciTech Connect

    J. Thomas Dickinson

    2007-09-28

    Work under this grant focused on the use of photoelectron emission as a probe of deformation processes in metals, principally single crystal and polycrystalline aluminum. Dislocations intersecting the surface produce patches of low work function metal which emit electrons when illuminated with the appropriate ultraviolet radiation. We have shown that changes in the photoemission signals during deformation can be used to identify the onset of strain localization. In some systems, the photoelectron kinetic energy distribution reflects the distribution of surface orientations, which depends on the competition between grain rotation and slip. Photoemission electron microscope images of shape memory alloys and thin films show marked changes in intensity and surface topography as the materal passes through its transition temperature. Photoelectron emission provides important information on the temporal progress of deformation processes that complements the spatial information provided by other techniques.

  16. The effect of ultrasonics on the strength properties of carbon steel processed by cold plastic deformation

    NASA Technical Reports Server (NTRS)

    Atanasiu, N.; Dragan, O.; Atanasiu, Z.

    1974-01-01

    A study was made of the influence of ultrasounds on the mechanical properties of OLT 35 carbon steel tubes cold-drawn on a plug ultrasonically activated by longitudinal waves. Experimental results indicate that: 1. The reduction in the values of the flow limit and tensile strength is proportional to the increase in acoustic energy introduced into the material subjected to deformation. 2. The diminution in influence of ultrasounds on tensile strength and flow rate that is due to an increased degree of deformation is explained by a reduction in specific density of the acoustic energy at the focus of deformation. 3. The relations calculated on the basis of the variation in the flow limit and tensile strength as a function of acoustic energy intensity was verified experimentally.

  17. Evolution of microstructure and precipitates in 2xxx aluminum alloy after severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Adamczyk-Cieslak, B.; Zdunek, J.; Mizera, J.

    2016-04-01

    This paper investigates the influence of precipitation on the microstructure development in a 2xxx aluminum alloy subjected to hydrostatic extrusion. A three step reduction of the diameter was performed using hydrostatic extrusion (HE) process: from 20mm (initial state) to 10 mm, 5 mm and 3 mm, which corresponds to the logarithmic deformations ɛ = 1.4, ɛ = 2.8 and ɛ = 3.8 respectively. The microstructure and precipitation analysis before and after deformation was performed using transmission electron microscope (TEM), and scanning electron microscopy (SEM). As a result of the tests, a very significant influence of precipitation on the degree of refinement and mechanism of microstructure transformation was stated.

  18. Mechanism of grain growth during severe plastic deformation of a nanocrystalline Ni-Fe alloy

    SciTech Connect

    Li, Hongqi; Wang, Y B; Ho, J C; Liao, X Z; Zhu, Y T; Ringer, S P

    2009-01-01

    Deformation induced grain growth has been widely reported in nanocrystalline materials. However, the grain growth mechanism remains an open question. This study applies high-pressure torsion to severely deform bulk nanocrystalline Ni-20 wt % Fe disks and uses transmission electron microscopy to characterize the grain growth process. Our results provide solid evidence suggesting that high pressure torsion induced grain growth is achieved primarily via grain rotation for grains much smaller than 100 nm. Dislocations are mainly seen at small-angle subgrain boundaries during the grain growth process but are seen everywhere in grains after the grains have grown large.

  19. Effect of preliminary plastic deformation on the anodic behavior of molybdenum-rhenium alloys

    SciTech Connect

    Amirkhanova, N.A.; Tatarinova, O.M.

    1988-07-01

    Two molybdenum-rhenium alloys obtained by the method of vacuum melting and containing 20% and 40% rhenium were investigated for their anodic behavior following heating and bulk forging to develop different degrees of deformation. Their stationary potentials were determined in solutions of a number of sodium salts and polarization measurements were made using a rotating disk electrode. The rate of removal for different working-stress values was determined on an apparatus simulating the electrochemical sizing process. Surface microstructure was observed by metallographic microscopy. The increase in the rate of anodic dissolution of the alloys was determined to be correct for degrees of deformation to 10%.

  20. Macro-carriers of plastic deformation of steel surface layers detected by digital image correlation

    SciTech Connect

    Kopanitsa, D. G. Ustinov, A. M.; Potekaev, A. I.; Klopotov, A. A.; Kopanitsa, G. D.

    2016-01-15

    This paper presents a study of characteristics of an evolution of deformation fields in surface layers of medium-carbon low-alloy specimens under compression. The experiments were performed on the “Universal Testing Machine 4500” using a digital stereoscopic image processing system Vic-3D. A transition between stages is reflected as deformation redistribution on the near-surface layers. Electronic microscopy shows that the structure of the steel is a mixture of pearlite and ferrite grains. A proportion of pearlite is 40% and ferrite is 60%.

  1. Study of Plastic Deformation in Binary Aluminum Alloys by Internal-Friction Methods

    NASA Technical Reports Server (NTRS)

    Olson, E. C.; Maringer, R. E.; Marsh, L. L.; Manning, G. K.

    1959-01-01

    The damping capacity of several aluminum-copper alloys has been investigated during tensile elongation. This damping is shown to depend on strain rate, strain, temperature, alloy content, and heat treatment. A tentative hypothesis, based on the acceleration of solute atom diffusion by deformation-produced vacancies, is proposed to account for the observed behavior. Internal-friction maxima are observed in deformed aluminum and aluminum-copper alloys at -70 deg and -50 deg C. The peaks appear to be relatively insensitive to frequency and alloy content, but they disappear after annealing at temperatures nearing the recrystallization temperature.

  2. Analysis of large, non-isothermal elastic-visco-plastic deformations

    NASA Technical Reports Server (NTRS)

    Riff, R.; Carlson, R. L.; Simitses, G. J.

    1984-01-01

    The development of a general mathematical model and solutions of test problems to analyze large nonisothermal elasto-visco-plastic deformatisms of structures is discussed. Geometric and material type nonlinearities of higher order are present in the development of the mathematical model and in the developed solution methodology.

  3. Visco-Plastic Flow of Glacial Covers and the Laws of Ice Deformation,

    DTIC Science & Technology

    The report presents the results of investigations which were made by the author during the Second Antartic Expedition (1956-1958). In the first part...plastic flow of glacial covers and a comparison of the analytic results which were obtained with data from observations under natural conditions in the Antartic . (Author)

  4. Finite element analysis of large transient elastic-plastic deformations of simple structures, with application to the engine rotor fragment containment/deflection problem

    NASA Technical Reports Server (NTRS)

    Wu, R. W.; Witmer, E. A.

    1972-01-01

    Assumed-displacement versions of the finite-element method are developed to predict large-deformation elastic-plastic transient deformations of structures. Both the conventional and a new improved finite-element variational formulation are derived. These formulations are then developed in detail for straight-beam and curved-beam elements undergoing (1) Bernoulli-Euler-Kirchhoff or (2) Timoshenko deformation behavior, in one plane. For each of these categories, several types of assumed-displacement finite elements are developed, and transient response predictions are compared with available exact solutions for small-deflection, linear-elastic transient responses. The present finite-element predictions for large-deflection elastic-plastic transient responses are evaluated via several beam and ring examples for which experimental measurements of transient strains and large transient deformations and independent finite-difference predictions are available.

  5. Numerical study of the process of plastic deformation localization by an example of high-speed compression of a hollow single crystal cylinder

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. I.; Nikonov, A. Yu.; Bondar', M. P.

    2016-11-01

    The effect of the crystallographic orientation of a single crystal hollow cylinder on features of creation and evolution of plastic deformation in it under conditions of high-speed axisymmetric load is studied. An advantage of the proposed loading scheme is the simultaneous implementation of all loading variants within the chosen crystallographic base plane of the cylinder and reaching different degrees of deformation over the cross section of the sample. Using the molecular-dynamic modeling, the difference in deformation properties of the loaded sample has been shown depending on the chosen crystallographic orientation of the base plane. Results of the investigation can be used to understand the main mechanisms of the plastic deformation of crystalline bodies.

  6. Large Deformation Mechanisms, Plasticity, and Failure of an Individual Collagen Fibril With Different Mineral Content

    PubMed Central

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

    2016-01-01

    ABSTRACT Mineralized collagen fibrils are composed of tropocollagen molecules and mineral crystals derived from hydroxyapatite to form a composite material that combines optimal properties of both constituents and exhibits incredible strength and toughness. Their complex hierarchical structure allows collagen fibrils to sustain large deformation without breaking. In this study, we report a mesoscale model of a single mineralized collagen fibril using a bottom‐up approach. By conserving the three‐dimensional structure and the entanglement of the molecules, we were able to construct finite‐size fibril models that allowed us to explore the deformation mechanisms which govern their mechanical behavior under large deformation. We investigated the tensile behavior of a single collagen fibril with various intrafibrillar mineral content and found that a mineralized collagen fibril can present up to five different deformation mechanisms to dissipate energy. These mechanisms include molecular uncoiling, molecular stretching, mineral/collagen sliding, molecular slippage, and crystal dissociation. By multiplying its sources of energy dissipation and deformation mechanisms, a collagen fibril can reach impressive strength and toughness. Adding mineral into the collagen fibril can increase its strength up to 10 times and its toughness up to 35 times. Combining crosslinks with mineral makes the fibril stiffer but more brittle. We also found that a mineralized fibril reaches its maximum toughness to density and strength to density ratios for a mineral density of around 30%. This result, in good agreement with experimental observations, attests that bone tissue is optimized mechanically to remain lightweight but maintain strength and toughness. © 2015 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research (ASBMR). PMID:26866939

  7. Uniaxial plastic deformation of isotactic polypropylene studied by solid-state NMR

    NASA Astrophysics Data System (ADS)

    Kang, Jia

    At alleviated temperatures, some semicrystralline polymers can be stretched to very large deformation ratios. Such deformations of semicrystalline polymers have been extensively studied since 1960s. Based on experimental observations and theoretical investigations, solid-state transformation (three stage model) proposed in 1971 and local melting and recrystallization in 1978 have been considered two major mechanisms to explain the deformations of polymer crystals. With the elucidation of molecular dynamics in the last two decades, it was proposed in 1999 that helical jump motion plays an important role in crystal deformation. On the other hand, the new structures induced by deformation also influence the molecular motions and resultant properties of deformed polymers. Such processing-structure-property relationship is very important to understand the polymer behaviors as well as to inform the polymer industry. In this dissertation, using the advanced tool of solid-state NMR (ss-NMR), we achieve three goals: Firstly, we investigate the hierarchical crystalline structural changes of isotactic polypropylene (i PP) upon high temperature stretching to understand the deformation process. Secondly, we evaluate the roles of local packing structure and crystal thickness in determining the stem motions and thermal properties of deformed alpha-form iPP. Thirdly, we utilize 13C-labeled isotactic polypropylene (iPP) to trace the change of chain folding number as a function of e to conclude molecular-level deformation mechanism. To realize the first and second goals, the chain packing, crystal thickness, molecular dynamics, and melting temperature (Tm) of a-form iPP drawn uniaxially at high temperatures of 100 - 150 °C were investigated using solid-state (SS) NMR and DSC. Two types of iPP samples with disordered (alpha1) and relatively ordered (alpha2-rich) packing structures were prepared via different thermal treatments and drawn up to an engineering strain ( e) of

  8. Continuum Multiscale Modeling of Finite Deformation Plasticity and Anisotropic Damage in Polycrystals

    DTIC Science & Technology

    2006-09-01

    neighboring grains cannot be spa- tially resolved. 3.5. Homogenization of damage Effects from mechanisms modeled individually— elastoplasticity within each...crystal plasticity routines are available, as the damage computations are effectively uncoupled from the constitutive update of the elastoplastic response... elastoplasticity and damage : multiscale kinematics, Int. J. Solids Struct. 40 (2003) 5669–5688. [17] C. Teodosiu, F. Sidoroff, A finite theory of

  9. Quantitative Assessment of the Accuracy of Constitutive Laws for Plasticity with an Emphasis on Cyclic Deformation

    DTIC Science & Technology

    1993-04-01

    new law, the B-L law. The experimental database is constructed from a5 series of constant amplitude and random amplitude strain controlled cyclic...description of the experimental instrumentation is given in Appendix I. The cyclic plasticity experiments were performed under strain control at room5...instrumentation is present and control accuracy is not as good, the increments or difference of strain at two adjacent sampling intervals should be

  10. Plastic Work to Heat Conversion During High-Strain Rate Deformation of Mg and Mg Alloy

    NASA Astrophysics Data System (ADS)

    Ghosh, Dipankar; Kingstedt, Owen T.; Ravichandran, Guruswami

    2017-01-01

    Magnesium and magnesium alloy were investigated for plastic work to heat conversion ( β). Thermomechanical response was measured employing the shear-compression specimen geometry, a split-Hopkinson pressure bar, and an infra-red detector. β of both materials measured to be less than the common assumption of 0.9; however, heat conversion was observed to be greater for magnesium alloy. Thus, results suggest that alloying and grain size refinement not only improved yield strength but also affected the thermomechanical response.

  11. Role of plastic deformation in wear of copper and copper - 10-percent-aluminum alloy in cryogenic fuels

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Wisander, D. W.

    1973-01-01

    High-purity copper specimens and a copper-aluminum (10%) alloy specimen were subjected to sliding against Type 440 C in cryogenic fuel environments. It was found that virtually all wear occurred by the plastic deformation of a recrystallized layer extending to about 10 micrometers below the wear scar surface of the copper or copper alloy. The wear debris was in the form of a layered structure adhering to the exit region of the wear scar. Measurements on the high purity copper specimens indicated that the wear rate was proportional to the applied load and to the sliding velocity squared. A physical model of the wear process is proposed to account for these observations.

  12. Effect of the severe plastic deformation temperature on the diffusion properties of the grain boundaries in ultrafine-grained metals

    NASA Astrophysics Data System (ADS)

    Chuvil'deev, V. N.; Myshlyaev, M. M.; Nokhrin, A. V.; Kopylov, V. I.; Lopatin, Yu. G.; Pirozhnikova, O. E.; Piskunov, A. V.; Semenycheva, A. V.; Bobrov, A. A.

    2017-05-01

    A model is proposed to explain the effect of the severe plastic deformation (SPD) temperature on the diffusion properties of the grain boundaries in ultrafine-grained (UFG) metals and alloys. It is shown that an increase in the SPD temperature in UFG metals leads to an increase in the activation energy of grainboundary diffusion from (3-5) k B T m, which corresponds to the diffusion parameters of nonequilibrium grain boundaries, to (8-10) k B T m, which corresponds to the diffusion parameters of equilibrium grain boundaries ( k B is the Boltzmann constant, T m is the melting temperature). The dependence of the activation energy of grain-boundary diffusion on the SPD temperature is found to be determined by the kinetics of the competing processes of defect accumulation at grain boundaries and the diffusion accommodation of defects.

  13. Microstructural Evolutions During Annealing of Plastically Deformed AISI 304 Austenitic Stainless Steel: Martensite Reversion, Grain Refinement, Recrystallization, and Grain Growth

    NASA Astrophysics Data System (ADS)

    Naghizadeh, Meysam; Mirzadeh, Hamed

    2016-08-01

    Microstructural evolutions during annealing of a plastically deformed AISI 304 stainless steel were investigated. Three distinct stages were identified for the reversion of strain-induced martensite to austenite, which were followed by the recrystallization of the retained austenite phase and overall grain growth. It was shown that the primary recrystallization of the retained austenite postpones the formation of an equiaxed microstructure, which coincides with the coarsening of the very fine reversed grains. The latter can effectively impair the usefulness of this thermomechanical treatment for grain refinement at both high and low annealing temperatures. The final grain growth stage, however, was found to be significant at high annealing temperatures, which makes it difficult to control the reversion annealing process for enhancement of mechanical properties. Conclusively, this work unravels the important microstructural evolution stages during reversion annealing and can shed light on the requirements and limitations of this efficient grain refining approach.

  14. Spatially resolved characterization of electromigration-induced plastic deformation in al (0.5wt percent cu) interconnect

    SciTech Connect

    Barabash, R.I.; Ice, G.E.; Tamura, N.; Patel, J.R.; Valek, B.C.; Bravman, J.C.; Spolenak, R.

    2003-05-06

    Electromigration during accelerated testing can induce large scale plastic deformation in Al interconnect lines as recently revealed by the white beam scanning X-ray microdiffraction. In the present paper, we provide a first quantitative analysis of the dislocation structure generated in individual micron-sized Al grains during an in-situ electromigration experiment. Laue reflections from individual interconnect grains show pronounced streaking after electric current flow. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of unpaired randomly distributed dislocations as well as geometrically necessary dislocation boundaries. Approximately half of all unpaired dislocations are grouped within the walls. The misorientation created by each boundary and density of unpaired individual dislocations is determined.

  15. Contactless electrical conductivity measurement of metallic submicron-grain material: Application to the study of aluminum with severe plastic deformation.

    PubMed

    Mito, M; Matsui, H; Yoshida, T; Anami, T; Tsuruta, K; Deguchi, H; Iwamoto, T; Terada, D; Miyajima, Y; Tsuji, N

    2016-05-01

    We measured the electrical conductivity σ of aluminum specimen consisting of submicron-grains by observing the AC magnetic susceptibility resulting from the eddy current. By using a commercial platform for magnetic measurement, contactless measurement of the relative electrical conductivity σn of a nonmagnetic metal is possible over a wide temperature (T) range. By referring to σ at room temperature, obtained by the four-terminal method, σn(T) was transformed into σ(T). This approach is useful for cylinder specimens, in which the estimation of the radius and/or volume is difficult. An experiment in which aluminum underwent accumulative roll bonding, which is a severe plastic deformation process, validated this method of evaluating σ as a function of the fraction of high-angle grain boundaries.

  16. The influence of hold time on the onset of plastic deformation in silicon

    DOE PAGES

    Wong, Sherman; Haberl, Bianca; Bradby, Jodie E.; ...

    2015-12-24

    Here, the formation of silicon (Si) in its -Sn form is known to be nucleation limited, with an undetermined period of time between when critical pressure for the trans- formation is reached and when the transformation actually occurs. In this letter, we use nanoindentation to apply critical pressure to diamond cubic Si and hold the sample under pressure to promote deformation via phase transformation and crystalline defects. We report that the number of indents in which phase transformation is observed increases with increasing hold time. Interestingly, the number of indents in which crystalline defects are observed also increase with increasingmore » hold time, suggesting crystalline defects are also nucleation limited. Raman spectroscopy and cross-sectional transmission electron microscopy is used to show that these two deformation mechanisms are mutually exclusive under the indentation conditions used within this letter.« less

  17. The influence of hold time on the onset of plastic deformation in silicon

    SciTech Connect

    Wong, Sherman; Haberl, Bianca; Bradby, Jodie E.; Williams, James S.

    2015-12-24

    Here, the formation of silicon (Si) in its -Sn form is known to be nucleation limited, with an undetermined period of time between when critical pressure for the trans- formation is reached and when the transformation actually occurs. In this letter, we use nanoindentation to apply critical pressure to diamond cubic Si and hold the sample under pressure to promote deformation via phase transformation and crystalline defects. We report that the number of indents in which phase transformation is observed increases with increasing hold time. Interestingly, the number of indents in which crystalline defects are observed also increase with increasing hold time, suggesting crystalline defects are also nucleation limited. Raman spectroscopy and cross-sectional transmission electron microscopy is used to show that these two deformation mechanisms are mutually exclusive under the indentation conditions used within this letter.

  18. Features of plastic deformation nucleation in the elastically loaded aluminium crystallites during irradiation

    NASA Astrophysics Data System (ADS)

    Kryzhevich, D. S.; Korchuganov, A. V.; Zolnikov, K. P.; Korostelev, S. Y.

    2017-05-01

    The simulation of peculiarities of the surface layer reconstruction in the crystallites of aluminum after the ion bombardment and the copper film irradiated by the electron beam is carried out. The performed calculations are based on the molecular dynamics method. It is shown that the orientation of the irradiated surface and preliminary elastic deformation have a significant impact on features of atomic structure formation in the ion-modified layer in aluminum. Weak structural changes in the surface layer are observed at the irradiation of the {100} surfaces. Sufficiently great number of stacking faults is formed under irradiation of the {111} and {110} surfaces. It is shown that heating by the electron beam of the {110} surface in the copper film leads to the formation of stacking faults. It is shown that the preliminary elastic deformation of the material lowers the energy of the irradiation, at which formation of structural defects and fragmentation of crystallites of aluminum and copper will take place.

  19. Modeling complex plastic deformation and fracture of metals under disproportionate loading

    NASA Astrophysics Data System (ADS)

    Volkov, I. A.; Korotkikh, Yu. G.; Tarasov, I. S.

    2009-09-01

    A mathematical model is developed to describe fatigue-damage accumulation in structural materials (metals and their alloys) on multiaxial paths of disproportionate combined heat and power loading. The effect of the shape of the strain path on the fatigue life of metals was studied to obtain qualitative and quantitative estimates of the obtained constitutive relations. It is shown that the proposed constitutive relations adequately describe the main elastoplastic deformation effects and damage accumulation in structural materials for arbitrary strain paths.

  20. Severe Plastic Deformation Processing of Refractory Metals by Equal Channel Angular Extrusion

    DTIC Science & Technology

    2008-12-01

    distributions and extensive texture gradients. Conventional metal processing, such as rolling, swaging , and forging, introduce non-uniform deformation...00 /5 00 ) Tungsten Tantalum Fig. 5. Hall-Petch plot showing the variation in Vickers microhardness vs. d-1/2 for as-worked and recrystallized Ta...softening and flow anisotropy approaches to developing improved tungsten kinetic energy penetrator materials, Mater. Manuf. Proc., 10, 531- 540