Features of energy impact on a billet material when cutting with outstripping plastic deformation

Directory of Open Access Journals (Sweden)

V. M. Yaroslavtsev

2014-01-01

Full Text Available In the last decades the so-called combined machining methods based on parallel, serial or parallelserial combination of different types of energy impacts on the billet are designed and developed. Combination of two or more sources of external energy in one method of machining can be directed to the solution of different technological tasks, such as: improvement of a basic method to enhance technicaland-economic and technological indicators of machining, expansion of technological capabilities of the method, increase of reliability and stability of technological process to produce details, etc. Besides, the combined methods of machining are considered as one of the means, which enables reducing the number of operations in technological process, allows the growth of workforce productivity.When developing the combined technologies, one of the main scientific tasks is to define the general regularities of interaction and mutual influence of the energy fluxes brought to the zone of machining. The result of such mutual influence becomes apparent from the forming technological parameters of machining and determines the most rational operating conditions of technological process.In the context of conducted in BMSTU researches on the combined cutting method with outstripping plastic deformation (OPD the mutual influence of the energetic components of machining has been quantitatively assessed. The paper shows a direct relationship between the rational ratio of the two types of the mechanical energy brought in the machining zone, the machining conditions, and the optimum operating conditions.The paper offers a physical model of chip formation when machining with OPD. The essence of model is that specific works spent on material deformation of a cut-off layer are quantitatively compared at usual cutting and at cutting with OPD. It is experimentally confirmed that the final strain-deformed material states of a cut-off layer, essentially, coincide in both

Translation-rotation plasticity as basic mechanism of plastic deformation in macro-, micro- and nanoindentation processes

International Nuclear Information System (INIS)

Grabco, D; Shikimaka, O; Harea, E

2008-01-01

This paper presents a brief review of multilateral examinations for the purpose of detection of interrelation between processes occuring in solids at different levels of action of exterior loading, namely, at macro-, micro- and nanoindentation. Convincing arguments supporting the rotation deformation mechanism alongside the recognized dislocation one are adduced. It has been shown that the decrease in dislocation mobility leads at all scales to the intensification of rotation plasticity and to the involvement of other plastic deformation mechanisms, such as appearance and interaction of disclinations, twinning, phase transition and compression of material. The conversion from translation plasticity to the rotation-translation one means transition to the higher level of plastic deformation, the mesolevel, when the possibilities of the previous microscopic level are exhausted. It was established that the plastic deformation zone in the vicinity of indentations could be separated into two main specific regions: (i) peripheral region predominantly with the dislocation deformation mechanism; otherwise, translation mechanism: microlevel, and (ii) quasidestructured region mainly with the disclination or the intergranular sliding mechanism: rotation mechanism, mesolevel

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

Energy Technology Data Exchange (ETDEWEB)

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.

A kinematical model for the plastic deformation of face-centred cubic polycrystals

International Nuclear Information System (INIS)

Leffers, T.

1975-01-01

During the plastic deformation of a polycrystalline material the deformation of the individual grain must be adjusted to the deformation of the surrounding grains so that material continuity is maintained. This continuity condition is the essential feature distinguishing polycrystal deformation from single-crystal deformation. In the present work it is attempted to explain how the continuity condition is fulfilled in face-centred cubic polycrystals. The early treatments of the plastic deformation of polycrystalline materials were aimed directly at the formulation of a ''dynamical'' theory, i.e. it was the intention to cover the magnitude of the stresses involved as well as the slip processes producing the deformation. It is argued that rolling texture is a good tool for a necessary intermediate stage of establishing a ''kinematical'' model describing the slip processes, but not the magnitude of the necessary stresses. Three aspects of rolling texture are considered: (a) the development of the rolling textures found experimentally in face-centred cubic materials can be computer-simulated on the basis of models for the plastic deformation that only involve (111) slip; (b) experimentally that the widely accepted twinning theory for the transition in f.c.c. rolling texture does not reflect the behaviour of real materials; and (c) it is shown that the texture transition is thermally activated with an activation energy corresponding to that of cross slip. An electron-microscopical investigation of the slip process operating during rolling of f.c.c. polycrystals is also included. On the basis of the computer simulation of the texture formation supplemented by the experimental results a kinematical model is developed for the plastic deformation of f.c.c. polycrystals by rolling. In the proposed model the material continuity is maintained by inhomogeneous slip processes, combined with homogeneous multiple glide when the cross-slip frequency is high. (author)

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

International Nuclear Information System (INIS)

Ohbuchi, Yoshifumi; Sakamoto, Hidetoshi; Nagatomo, Nobuaki

2016-01-01

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. (paper)

Understanding thermally activated plastic deformation behavior of Zircaloy-4

Science.gov (United States)

Kumar, N.; Alomari, A.; Murty, K. L.

2018-06-01

Understanding micromechanics of plastic deformation of existing materials is essential for improving their properties further and/or developing advanced materials for much more severe load bearing applications. The objective of the present work was to understand micromechanics of plastic deformation of Zircaloy-4, a zirconium-based alloy used as fuel cladding and channel (in BWRs) material in nuclear reactors. The Zircaloy-4 in recrystallized (at 973 K for 4 h) condition was subjected to uniaxial tensile testing at a constant cross-head velocity at temperatures in the range 293 K-1073 K and repeated stress relaxation tests at 293 K, 573 K, and 773 K. The minimum in the total elongation was indicative of dynamic strain aging phenomenon in this alloy in the intermediate temperature regime. The yield stress of the alloy was separated into effective and athermal components and the transition from thermally activated dislocation glide to athermal regime took place at around 673 K with the athermal stress estimated to be 115 MPa. The activation volume was found to be in the range of 40 b3 to 160 b3. The activation volume values and the data analyses using the solid-solution models in literature indicated dislocation-solute interaction to be a potential deformation mechanism in thermally activated regime. The activation energy calculated at 573 K was very close to that found for diffusivity of oxygen in α-Zr that was suggestive of dislocations-oxygen interaction during plastic deformation. This type of information may be helpful in alloy design in selecting different elements to control the deformation behavior of the material and impart desired mechanical properties in those materials for specific applications.

Plastic Deformation as a Means to Achieve Stretchable Polymer Semiconductors

Science.gov (United States)

O'Connor, Brendan

Developing intrinsically stretchable semiconductors will seamlessly transition traditional devices into a stretchable platform. Polymer semiconductors are inherently soft materials due to the weak van der Waal intermolecular bonding allowing for flexible devices. However, these materials are not typically stretchable and when large strains are applied they either crack or plastically deform. Here, we study the use of repeated plastic deformation as a means of achieving stretchable films. In this talk, critical aspects of polymer semiconductor material selection, morphology and interface properties will be discussed that enable this approach of achieving stretchable films. We show that one can employ high performance donor-acceptor polymer semiconductors that are typically brittle through proper polymer blending to significantly increase ductility to achieve stretchable films. We demonstrate a polymer blend film that can be repeatedly deformed over 65%, while maintaining charge mobility consistently above 0.15 cm2/Vs. During the stretching process we show that the films follow a well-controlled repeated deformation pattern for over 100 stretching cycles.

Physical fundamentals of mesomechanics of plastic deformation and fracture of solids

International Nuclear Information System (INIS)

Panin, V.E.

2001-01-01

The conventional description of the relationships governing the plastic deformation and fracture of solids is carried out using two approaches: 1) Continuum mechanics 2) Dislocation theory. The continuum mechanics describes the behaviour of material under load using integral characteristics of the medium. In this approach, the internal structure of the material is not taken into account, stress and strain tensors are symmetric and plastic deformation is carried out only by the translational movement of defects under the effect of stresses. The plastic yielding curve is described by calculating strain hardening above the yield point of the material. The phenomenological approach of the continuum mechanics is physically and mathematically completely correct, but it may be used only for describing the integral properties of a macrohomogeneous medium

Non-uniform plastic deformation of micron scale objects

DEFF Research Database (Denmark)

Niordson, Christian Frithiof; Hutchinson, J. W.

2003-01-01

Significant increases in apparent flow strength are observed when non-uniform plastic deformation of metals occurs at the scale ranging from roughly one to ten microns. Several basic plane strain problems are analyzed numerically in this paper based on a new formulation of strain gradient...... plasticity. The problems are the tangential and normal loading of a finite rectangular block of material bonded to rigid platens and having traction-free ends, and the normal loading of a half-space by a flat, rigid punch. The solutions illustrate fundamental features of plasticity at the micron scale...... that are not captured by conventional plasticity theory. These include the role of material length parameters in establishing the size dependence of strength and the elevation of resistance to plastic flow resulting from constraint on plastic flow at boundaries. Details of the finite element method employed...

Research on geometrical model and mechanism for metal deformation based on plastic flow

International Nuclear Information System (INIS)

An, H P; Li, X; Rui, Z Y

2015-01-01

Starting with general conditions of metal plastic deformation, it analyses the relation between the percentage spread and geometric parameters of a forming body with typical machining process are studied. A geometrical model of deforming metal is set up according to the characteristic of a flowing metal particle. Starting from experimental results, the effect of technological parameters and friction between workpiece and dies on plastic deformation of a material were studied and a slippage deformation model of mass points within the material was proposed. Finally, the computing methods for strain and deformation energy and temperature rise are derived from homogeneous deformation. The results can be used to select technical parameters and compute physical quantities such as strain, deformation energy, and temperature rise. (paper)

Observation of plastic deformation in freestanding single crystal Au nanowires

International Nuclear Information System (INIS)

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

2006-01-01

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 μm 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

Plastic deformation and fracture behavior of zircaloy-2 fuel cladding tubes under biaxial stress

International Nuclear Information System (INIS)

Maki, Hideo; Ooyama, Masatosi

1975-01-01

Various combinations of biaxial stress were applied on five batches of recrystallized zircaloy-2 fuel cladding tubes with different textures; elongation in both axial and circumferential directions of the specimen was measured continuously up to 5% plastic deformation. The anisotropic theory of plasticity proposed by Hill was applied to the resulting data, and anisotropy constants were obtained through the two media of plastic strain loci and plastic strain ratios. Comparison of the results obtained with the two methods proved that the plastic strain loci provide data that are more effective in predicting quantitatively the plastic deformation behavior of the zircaloy-2 tubes. The anisotropy constants change their value with progress of plastic deformation, and judicious application of the effective stress and effective strain obtained on anisotropic materials will permit the relationship between stress and strain under various biaxialities of stresses to be approximated by the work hardening law. The test specimens used in the plastic deformation experiments were then stressed to fracture under the same combination of biaxial stress as in the proceeding experiments, and the deformation in the fractured part was measured. The result proved that the tilt angle of the c-axis which serves as the index of texture is related to fracture ductility under biaxial stress. Based on this relationship, it was concluded that material with a tilt angle ranging from 10 0 to 15 0 is the most suitable for fuel cladding tubes, from the viewpoint of fracture ductility, at least in the case of unirradiated material. (auth.)

Joining by plastic deformation

DEFF Research Database (Denmark)

Mori, Ken-ichiro; Bay, Niels; Fratini, Livan

2013-01-01

As the scale and complexity of products such as aircraft and cars increase, demand for new functional processes to join mechanical parts grows. The use of plastic deformation for joining parts potentially offers improved accuracy, reliability and environmental safety as well as creating opportuni......As the scale and complexity of products such as aircraft and cars increase, demand for new functional processes to join mechanical parts grows. The use of plastic deformation for joining parts potentially offers improved accuracy, reliability and environmental safety as well as creating...

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

Science.gov (United States)

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.

A work-hardening rule for finite elastic-plastic deformation of metals at elevated temperatures

International Nuclear Information System (INIS)

Lee, L.H.N.; Horng, J.T.

1975-01-01

The paper is concerned with an extension of Prager-Ziegler's kinematic work-hardening rule for infinitesimal elastic-plastic deformation to a work-hardening rule for finite elastic-plastic deformation of a polycrystalline metal. It is shown that the finite work-hardening rule, which accounts for the Bauschinger and temperature effects within certain pressure and temperature ranges, satisfies certain invariant, continuity and thermodynamic requirements. A description of the kinematics of an elastic-plastic body is employed with reference to three separate configurations: initial, current and an intermediate configuration. The intermediate configuration is a conceptual, local configuration obtained by removing the stress and temperature changes in the neighborhood of an element. A rigid body rotation of the intermediate configuration is allowed. Piola-Kirchhoff stresses and Green deformation tensors referred to the initial and intermediate configurations are employed as stress and strain measures. The plastic deformation has been associated with the motion and production of dislocations. It has been observed that the motion of mobile dislocations usually occur in the narrow slip bands in each grain, leaving the basic lattice structure practically intact, so that the macroscopic elastic properties of the material are essentially independent of plastic deformation. Employing this fact and the thermodynamic laws, a simplified elastic stress-strain relationship of the plastically deformed material, which agrees with the results of Naghdi and Trapp, is obtained

Dislocation Dynamics During Plastic Deformation

CERN Document Server

Messerschmidt, Ulrich

2010-01-01

The book gives an overview of the dynamic behavior of dislocations and its relation to plastic deformation. It introduces the general properties of dislocations and treats the dislocation dynamics in some detail. Finally, examples are described of the processes in different classes of materials, i.e. semiconductors, ceramics, metals, intermetallic materials, and quasicrystals. The processes are illustrated by many electron micrographs of dislocations under stress and by video clips taken during in situ straining experiments in a high-voltage electron microscope showing moving dislocations. Thus, the users of the book also obtain an immediate impression and understanding of dislocation dynamics.

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

Science.gov (United States)

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.

Correlations between plastic deformation parameters and radiation detector quality in HgI2

International Nuclear Information System (INIS)

Georgeson, G.; Milstein, F.; California Univ., Santa Barbara

1989-01-01

Mercuric iodide radiation detectors of various grades of quality were subjected to shearing forces in the (001) crystallographic planes using a specially designed micromechanical shear testing fixture. Experimental measurements were made of (001) shear stress versus shear strain. Each of the stress-strain curves was described by two empirically determined deformation parameters, s 0 and σ, where s 0 is a measure of 'bulk yielding' and σ indicates the 'sharpness of yielding' during plastic deformation. It was observed that the deformation parameters of many HgI 2 single crystal samples fit the relation s 0 =8σ 2/3 and that significant deviation from this relation, with s 0 >8σ 2/3 , indicates poor detector quality. Work hardening by prior plastic deformation was also found to cause s 0 to depart (in an increasing manner) from the 8σ 2/3 relation. For good quality material that has not previously been plastically deformed, the deformation parameter s c =s 0 -2σ<19 psi; this parameter can be interpreted as the 'onset of plastic yielding'. The results are discussed in terms of dislocation mechanisms for plastic deformation, work hardening, and recovery of work hardening. (orig.)

Work of plastic deformation in local zone of crack apex

International Nuclear Information System (INIS)

Gol'tsev, V.Yu.; Matvienko, Yu.G.; Rivkin, E.Yu.

1981-01-01

For substantiating application of criteria of viscous fracture and deeoer understanding of this. process one should know strain distribution and energy consumption for plastic deformation in crack top zone. For this purpose plane samples of 300x70x1.5 mm dimension with central notch of 23, 36 and 46 mm length have been subjected to tensile testing. The samples have been cut out from sheet steel 1Kh18N9T perpendicularly to the rolling direction. It is shown that the suggested viscous fracture conception ensures general approach to the viscous and elastoplastic fracture based on the concept on specific work of plastic deformation in the localized zone νsub(l). The νsub(l) value characterizes maximum plastic material energy consumption and may serve as criterion of viscous material fracture parallel to the critical opening of the deltasub(c) crack top

Formation of nanocrystalline surface layers in various metallic materials by near surface severe plastic deformation

Directory of Open Access Journals (Sweden)

Masahide Sato, Nobuhiro Tsuji, Yoritoshi Minamino and Yuichiro Koizumi

2004-01-01

Full Text Available The surface of the various kinds of metallic materials sheets were severely deformed by wire-brushing at ambient temperature to achieve nanocrystalline surface layer. The surface layers of the metallic materials developed by the near surface severe plastic deformation (NS-SPD were characterized by means of TEM. Nearly equiaxed nanocrystals with grain sizes ranging from 30 to 200 nm were observed in the near surface regions of all the severely scratched metallic materials, which are Ti-added ultra-low carbon interstitial free steel, austenitic stainless steel (SUS304, 99.99 wt.%Al, commercial purity aluminum (A1050 and A1100, Al–Mg alloy (A5083, Al-4 wt.%Cu alloy, OFHC-Cu (C1020, Cu–Zn alloy (C2600 and Pb-1.5%Sn alloy. In case of the 1050-H24 aluminum, the depth of the surface nanocrystalline layer was about 15 μm. It was clarified that wire-brushing is an effective way of NS-SPD, and surface nanocrystallization can be easily achieved in most of metallic materials.

Method of determining elastic and plastic mechanical properties of ceramic materials using spherical indenters

Science.gov (United States)

Adler, Thomas A.

1996-01-01

The invention pertains a method of determining elastic and plastic mechanical properties of ceramics, intermetallics, metals, plastics and other hard, brittle materials which fracture prior to plastically deforming when loads are applied. Elastic and plastic mechanical properties of ceramic materials are determined using spherical indenters. The method is most useful for measuring and calculating the plastic and elastic deformation of hard, brittle materials with low values of elastic modulus to hardness.

Characterization of local plastic instability during deformation of D9 clad tubes for fast breeder nuclear fuel by infrared thermography

International Nuclear Information System (INIS)

Kapoor, K.; Somasekhar Reddy, K.; Ramana Rao, A.V.

2009-01-01

Plastic instability is a condition occurring ahead of ductile fracture in materials subjected to deformation. This condition is a warning before the final failure occurring by ductile fracture. This condition manifests during necking in tensile deformation and crack propagation during plastic deformation. Early detection of such a condition can prevent permanent damage. In the present case, a novel approach by use of infrared thermography is proposed for characterization of local plastic instability during deformation of D9 clad tube material. Infrared thermal imaging was used for acquiring data during deformation by plug drawing, pilgering and uniaxial tension tests. The local plastic instability due to propagation of defects was monitored by use of Taylor-Quinney coefficient (β). Where, the Taylor-Quinney coefficient is defined as the ratio of plastic work converted into heat, which was evaluated by using thermal imaging data. In our study, an analysis of the heat generated during the process of plastic deformation was measured thereby correlating the abnormal temperature variations with the defects appearing in the material. In our study, an analysis of the heat generated during the process of plastic deformation was measured thereby correlating the abnormal temperature variations with the defects appearing in the material

UTILIZATION OF STEREOLOGY FOR QUANTITATIVE ANALYSIS OF PLASTIC DEFORMATION OF FORMING PIECES

Directory of Open Access Journals (Sweden)

Maroš Martinkovič

2012-01-01

Full Text Available Mechanical working leads to final properties of forming pieces, which are affected by conditions of production technology. Utilization of stereology leads to the detail analysis of three-dimensional plastic deformed material structure by different forming technologies, e.g. forging, extruding, upsetting, metal spinning, drawing etc. The microstructure of cold drawing wires was analyzed. Grain boundaries orientation was measured on the parallel section of wire with a different degree of deformation and direct axis plastic deformation was evaluated in bulk formed part. The strain of probes on their sections was obtained using stereology by measurement of degree of grain boundary orientation which was converted to deformation using model of conversion of grain boundary orientation degree to deformation.

Plastic Deformation of Pressured Metallic Glass

Directory of Open Access Journals (Sweden)

Yun Cheng

2017-11-01

Full Text Available Although pressured metallic glass (MG has been reported in the literature; there are few studies focusing on pressure effects on the structure; dynamics and its plastic deformation. In this paper; we report on and characterize; via molecular dynamics simulation, the structure and dynamics heterogeneity of pressured MGs, and explore a causal link between local structures and plastic deformation mechanism of pressured glass. The results exhibit that the dynamical heterogeneity of metallic liquid is more pronounced at high pressure, while the MGs were less fragile after the release of external pressure, reflected by the non-Gaussian parameter (NGP. High pressure glass shows better plastic deformation; and the local strain zone distributed more uniformly than of in normal glass. Further research indicates that although the number of icosahedrons in pressured glass was much larger than that in normal glass, while the interpenetrating connections of icosahedra (ICOI exhibited spatial correlations were rather poor; In addition, the number of ‘fast’ atoms indexed by the atoms’ moving distance is larger than that in normal glass; leading to the sharp decreasing in number of icosahedrons during deformation. An uniform distribution of ‘fast’ atoms also contributed to better plastic deformation ability in the pressured glass. These findings may suggest a link between the deformation and destruction of icosahedra with short-range order.

Linking Scales in Plastic Deformation and Fracture

DEFF Research Database (Denmark)

Martinez-Paneda, Emilio; Niordson, Christian Frithiof; S. Deshpande, Vikram

2017-01-01

We investigate crack growth initiation and subsequent resistance in metallic materials by means of an implicit multi-scale approach. Strain gradient plasticity is employed to model the mechanical response of the solid so as to incorporate the role of geometrically necessary dislocations (GNDs......) and accurately capture plasticity at the small scales involved in crack tip deformation. The response ahead of the crack is described by means of a traction-separation law, which is characterized by the cohesive strength and the fracture energy. Results reveal that large gradients of plastic strain accumulatein...... the vicinity of the crack, elevating the dislocation density and the local stress. This stress elevation enhances crack propagation and significantly lowers the steady state fracture toughness with respect to conventional plasticity. Important insight is gained into fracture phenomena that cannot be explained...

Plastic deformation and failure mechanisms in nano-scale notched metallic glass specimens under tensile loading

Science.gov (United States)

Dutta, Tanmay; Chauniyal, Ashish; Singh, I.; Narasimhan, R.; Thamburaja, P.; Ramamurty, U.

2018-02-01

In this work, numerical simulations using molecular dynamics and non-local plasticity based finite element analysis are carried out on tensile loading of nano-scale double edge notched metallic glass specimens. The effect of acuteness of notches as well as the metallic glass chemical composition or internal material length scale on the plastic deformation response of the specimens are studied. Both MD and FE simulations, in spite of the fundamental differences in their nature, indicate near-identical deformation features. Results show two distinct transitions in the notch tip deformation behavior as the acuity is increased, first from single shear band dominant plastic flow localization to ligament necking, and then to double shear banding in notches that are very sharp. Specimens with moderately blunt notches and composition showing wider shear bands or higher material length scale characterizing the interaction stress associated with flow defects display profuse plastic deformation and failure by ligament necking. These results are rationalized from the role of the interaction stress and development of the notch root plastic zones.

Dislocations and Plastic Deformation in MgO Crystals: A Review

Directory of Open Access Journals (Sweden)

Jonathan Amodeo

2018-05-01

Full Text Available This review paper focuses on dislocations and plastic deformation in magnesium oxide crystals. MgO is an archetype ionic ceramic with refractory properties which is of interest in several fields of applications such as ceramic materials fabrication, nano-scale engineering and Earth sciences. In its bulk single crystal shape, MgO can deform up to few percent plastic strain due to dislocation plasticity processes that strongly depend on external parameters such as pressure, temperature, strain rate, or crystal size. This review describes how a combined approach of macro-mechanical tests, multi-scale modeling, nano-mechanical tests, and high pressure experiments and simulations have progressively helped to improve our understanding of MgO mechanical behavior and elementary dislocation-based processes under stress.

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

Directory of Open Access Journals (Sweden)

Jan Valíček

2015-11-01

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

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

Science.gov (United States)

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

2015-01-01

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

Electrical resistivity response due to elastic-plastic deformations

International Nuclear Information System (INIS)

Stout, R.B.

1987-01-01

The electrical resistivity of many materials is sensitive to changes in the electronic band configurations surrounding the atoms, changes in the electron-phonon interaction cross-sections, and changes in the density of intrinsic defect structures. These changes are most directly dependent on interatomic measures of relative deformation. For this reason, a model for resistivity response is developed in terms of interatomic measures of relative deformation. The relative deformation consists of two terms, a continuous function to describe the recoverable displacement between two atoms in the atomic lattice structure and a functional to describe the nonrecoverable displacement between two atoms as a result of interatomic discontinuities from dislocation kinetics. This model for resistivity extends the classical piezoresistance representation and relates electric resistance change directly to physical mechanisms. An analysis for the resistivity change of a thin foil ideally embedded in a material that undergoes elastic-plastic deformation is presented. For the case of elastic deformations, stress information in the material surrounding the thin foil is inferred for the cases of pure strain coupling boundary conditions, pure stress coupling boundary conditions, and a combination of stress-strain coupling boundary conditions. 42 refs., 4 figs

Effect of dynamic plastic deformation on microstructure and annealing behaviour of modified 9Cr-1Mo steel

DEFF Research Database (Denmark)

Zhang, Zhenbo; Mishin, Oleg V.; Tao, N. R.

2015-01-01

after quasi- static compression. The microstructure after dynamic plastic deformation is however less stable than the microstructure after quasi- static compression. Annealing at 675 and 700 degrees C leads to structural coarsening and recrystallisation in each sample, but with recrystallisation...... occurring faster in the sample annealed after dynamic plastic deformation. The lower thermal stability of the microstructure produced by dynamic plastic deformation is attributed to a higher driving force for recrystallisation in the dynamically deformed material....

Numerical Investigation of Plastic Deformation in Two-turn Equal Channel Angular Extrusion

Directory of Open Access Journals (Sweden)

A. Mitsak

2014-12-01

Full Text Available There has been a number of investigations in recent years reporting on the structure and properties of materials deformed to super plastic deformation (SPD. During SPD new textures can be formed and abnormal characteristics are displayed, attracting a growing research interest.¶ Equal channel angular extrusion (ECAE is a method often used to obtain large plastic strains. However, according to experimental results, there is a large tensile stress in the sample during deformation, which may lead in some cases, to cracking in metallic alloys and large curvature in polymeric materials. In order to overcome these drawbacks, the ECAE process can be conducted at high temperatures. But this contributes significantly to a decreased level of plastic deformation induced in the sample. Hence, a tool with multi-pass seems to be a very appropriate solution. In this paper, a new geometry die composed of two elbows has been simulated by finite element method aiming to provide an insight into the mechanisms of deformation and to determine the optimum geometry of the tool. The numerical results show that the length and the section of the second channel play a significant role on the homogeneity of the plastic strain distribution. It has been found that good homogeneity was obtained when the second channel has the same section as that of the entrance and the exit channels and with a length equal to three times of its width.

Semantic modeling of plastic deformation of polycrystalline rock

Science.gov (United States)

Babaie, Hassan A.; Davarpanah, Armita

2018-02-01

We have developed the first iteration of the Plastic Rock Deformation (PRD) ontology by modeling the semantics of a selected set of deformational processes and mechanisms that produce, reconfigure, displace, and/or consume the material components of inhomogeneous polycrystalline rocks. The PRD knowledge model also classifies and formalizes the properties (relations) that hold between instances of the dynamic physical and chemical processes and the rock components, the complex physio-chemical, mathematical, and informational concepts of the plastic rock deformation system, the measured or calculated laboratory testing conditions, experimental procedures and protocols, the state and system variables, and the empirical flow laws that define the inter-relationships among the variables. The ontology reuses classes and properties from several existing ontologies that are built for physics, chemistry, biology, and mathematics. With its flexible design, the PRD ontology is well positioned to incrementally develop into a model that more fully represents the knowledge of plastic deformation of polycrystalline rocks in the future. The domain ontology will be used to consistently annotate varied data and information related to the microstructures and the physical and chemical processes that produce them at different spatial and temporal scales in the laboratory and in the solid Earth. The PRDKB knowledge base, when built based on the ontology, will help the community of experimental structural geologists and metamorphic petrologists to coherently and uniformly distribute, discover, access, share, and use their data through automated reasoning and integration and query of heterogeneous experimental deformation data that originate from autonomous rock testing laboratories.

Plasticity margin recovery during annealing after cold deformation

International Nuclear Information System (INIS)

Bogatov, A.A.; Smirnov, S.V.; Kolmogorov, V.L.

1978-01-01

Restoration of the plasticity margin in steel 20 after cold deformation and annealing at 550 - 750 C and soaking for 5 - 300 min was investigated. The conditions of cold deformation under which the metal acquires microdefects unhealed by subsequent annealing were determined. It was established that if the degree of utilization of the plasticity margin is psi < 0.5, the plasticity margin in steel 20 can be completely restored by annealing. A mathematical model of restoration of the plasticity margin by annealing after cold deformation was constructed. A statistical analysis showed good agreement between model and experiment

Healing behavior of preexisting hydrogen micropores in aluminum alloys during plastic deformation

International Nuclear Information System (INIS)

Toda, H.; Minami, K.; Koyama, K.; Ichitani, K.; Kobayashi, M.; Uesugi, K.; Suzuki, Y.

2009-01-01

Synchrotron X-ray microtomography was used to observe the shrinkage and annihilation behaviors of hydrogen micropores in three dimensions during hot and cold plastic deformation of an Al-Mg alloy. Whether complete healing of micropores is achieved after plastic deformation was examined by exposing the material to a high temperature after plastic deformation. Although micropores generally show a pattern of shrinking and closing, closer inspection of a single specimen revealed a variety of geometrically variable behaviors. It is noteworthy that some of the micropores are reinitiated in positions identical to those before their annihilation, even after an 8-22% macroscopic strain has been further applied after annihilation. We attribute local variations such as these to significant local strain variation, which we measured in a series of tomographic volumes by tracking the microstructural features.

Plastic deformation and contact area of an elastic-plastic contact of ellipsoid bodies after unloading

NARCIS (Netherlands)

Jamari, Jamari; Schipper, Dirk J.

2007-01-01

This paper presents theoretical and experimental results of the residual or plastic deformation and the plastic contact area of an elastic–plastic contact of ellipsoid bodies after unloading. There are three regime responses of the deformation and contact area: elastic, elastic–plastic and fully

Effect of plastic deformation on the magnetic properties of selected austenitic stainless steels

Directory of Open Access Journals (Sweden)

Tatiana Oršulová

2017-04-01

Full Text Available Austenitic stainless steels are materials, that are widely used in various fields of industry, architecture and biomedicine. Their specific composition of alloying elements has got influence on their deformation behavior. The main goal of this study was evaluation of magnetic properties of selected steels, caused by plastic deformation. The samples were heat treated in different intervals of temperature before measuring. Then the magnetic properties were measured on device designed for measuring of magnetism. From tested specimens, only AISI 304 confirmed effect of plastic deformation on the magnetic properties. Magnetic properties changed with increasing temperature.

Influence of Plastic Deformation on Low-Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

DEFF Research Database (Denmark)

Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low-temperature surface hardening by gaseous nitriding of two commercial stainless steels: EN 1.4369 and AISI 304. The materials were plastically deformed to several levels of equivalent strain by conventional......, reflected-light microscopy, and microhardness testing. The results demonstrate that a case of expanded austenite develops and that the presence of plastic deformation has a significant influence on the morphology of the nitrided case. The presence of strain-induced martensite favors the formation of Cr...

Severe plastic deformation of copper and Al-Cu alloy using multiple channel-die compression

International Nuclear Information System (INIS)

Parimi, A.K.; Robi, P.S.; Dwivedy, S.K.

2011-01-01

Research highlights: → SPD of copper and Al-Cu alloy by multiple channel-die compression tests.→ Extensive grain refinement resulting in nano-sized grains after SPD. → Investigation of micro-structure using optical microscope and SEM. → Shear band formation as the failure mechanism in the two phase Al-Cu alloy. → Difficulty in obtaining SPD for Al-Cu alloy in this method. -- Abstract: Severe plastic deformation studies of copper and Al-Cu alloy by multiple channel-die compression tests were investigated. The materials were tested under plane strain condition by maintaining a constant strain rate of 0.001/s. Extensive grain refinement was observed resulting in nano-sized grains after severe plastic deformation with concomitant increase in flow stress and hardness. The microstructural investigation of the severely deformed materials was investigated using optical microscope and scanning electron microscope. Shear band formation was identified as the failure mechanism in the two phase Al-Cu alloy. The results indicate difficulty in obtaining severe plastic deformation for alloys having two phase micro-structure.

Deformed Materials: Towards a Theory of Materials Morphology Dynamics

Energy Technology Data Exchange (ETDEWEB)

Sethna, James P [Laboratory of Atomic and Solid State Physics, Cornell University

2017-06-28

This grant supported work on the response of crystals to external stress. Our primary work described how disordered structural materials break in two (statistical models of fracture in disordered materials), studied models of deformation bursts (avalanches) that mediate deformation on the microscale, and developed continuum dislocation dynamics models for plastic deformation (as when scooping ice cream bends a spoon, Fig. 9). Glass is brittle -- it breaks with almost atomically smooth fracture surfaces. Many metals are ductile -- when they break, the fracture surface is locally sheared and stretched, and it is this damage that makes them hard to break. Bone and seashells are made of brittle material, but they are strong because they are disordered -- lots of little cracks form as they are sheared and near the fracture surface, diluting the external force. We have studied materials like bone and seashells using simulations, mathematical tools, and statistical mechanics models from physics. In particular, we studied the extreme values of fracture strengths (how likely will a beam in a bridge break far below its design strength), and found that the traditional engineering tools could be improved greatly. We also studied fascinating crackling-noise precursors -- systems which formed microcracks of a broad range of sizes before they broke. Ductile metals under stress undergo irreversible plastic deformation -- the planes of atoms must slide across one another (through the motion of dislocations) to change the overall shape in response to the external force. Microscopically, the dislocations in crystals move in bursts of a broad range of sizes (termed 'avalanches' in the statistical mechanics community, whose motion is deemed 'crackling noise'). In this grant period, we resolved a longstanding mystery about the average shape of avalanches of fixed duration (using tools related to an emergent scale invariance), we developed the fundamental theory

Modeling plastic deformation of post-irradiated copper micro-pillars

Energy Technology Data Exchange (ETDEWEB)

Crosby, Tamer, E-mail: tcrosby@ucla.edu; Po, Giacomo, E-mail: gpo@ucla.edu; Ghoniem, Nasr M., E-mail: ghoniem@ucla.edu

2014-12-15

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.

Derivative criteria of plasticity anddurability of metal materials

Directory of Open Access Journals (Sweden)

Gustov Yuriy Ivanovich

Full Text Available Criteria of plasticity and durability derivative of standard indicators of plasticity (δ, ψ and durability (σ , σ are offered. Criteria К and К follow from the equation of relative indicators of durability and plasticity. The purpose of the researches is the establishment of interrelation of derivative criteria with the Page indicator. The values of derivative criteria were defined for steels 50X and 50XH after processing by cold, and also for steels 50G2 and 38HGN after sorbitizing. It was established that the sum of the offered derivative criteria of plasticity and durability С considered for the steels is almost equal to unit and corresponds to a square root of relative durability and plasticity criterion C . Both criteria testify to two-unity opposite processes of deformation and resistance to deformation. By means of the equations for S and С it is possible to calculate an indicator of uniform plastic deformation of σ and through it to estimate synergetic criteria - true tension and specific energy of deformation and destruction of metal materials. On the basis of the received results the expressions for assessing the uniform and concentrated components of plastic deformation are established. The preference of the dependence of uniform relative lengthening from a cubic root of criterion К , and also to work of the criteria of relative lengthening and relative durability is given. The advantage of the formulas consists in simplicity and efficiency of calculation, in ensuring necessary accuracy of calculation of the size δ for the subsequent calculation of structural and power (synergetic criteria of reliability of metals.

Analysis and Modeling of Process of Residual Deformations Accumulation in Soils and Granular Materials

Science.gov (United States)

Aleksandrov, A. S.; Dolgih, G. V.; Kalinin, A. L.

2017-11-01

It is established that under the influence of repeated loads the process of plastic deformation in soils and discrete materials is hereditary. To perform the mathematical modeling of plastic deformation, the authors applied the integral equation by solution of which they manage to obtain the power and logarithmic dependencies connecting plastic deformation with the number of repeated loads, the parameters of the material and components of the stress tensor in the principal axes. It is shown that these dependences generalize a number of models proposed earlier in Russia and abroad. Based on the analysis of the experimental data obtained during material testing in the dynamic devices of triaxial compression at different values of the stress deviator, the coefficients in the proposed models of deformation are determined. The authors determined the application domain for logarithmic and degree dependences.

Influence of deformation rate on plasticity of metals under pressure

International Nuclear Information System (INIS)

Churbaev, R.V.; Dobromyslov, A.V.; Kolmogorov, V.L.; Taluts, G.G.

1990-01-01

Change of polycrystalline molybdenum (BCC) and titanium (HCP) plasticity under pressure depeding on the deformation rate at the room temperature is studied. It is shown that the reduction of molybdenum and titanium deformation rate leads to a substantial growth of their plastic properties with the effect being increased with pressure growth. Production of several necks testifying to the transition to a superplastic state is observed at high pressures and low deformation rates. A functional dependence of plasticity change on the deformation rate under pressure is ascertained

Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature

International Nuclear Information System (INIS)

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

2007-01-01

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

Inspecting plastic deformation of Pd by means of fractal geometry

International Nuclear Information System (INIS)

Eftekhari, Ali

2007-01-01

The influence of phase transformation-induced plastic deformation in Pd|H system on the electrode surface was investigated. Since the Pd surface is subject of severe plastic deformation during this process, the structure and roughness of the electrode surface significantly change. Quantitative analysis of the electrode surfaces for comparative study of such changes is a valuable tool to inspect the plastic deformation induced. Fractal dimension can be used as a quantitative measure for this purpose. Since inappropriate methods may lead to significant errors, an appropriate approach was proposed for the determination of fractal dimensions in such systems. It was demonstrated that the surface roughness generated is mainly due to the plastic deformation induced, not the other side processes, as the electrodes were coated with a uniform layer of gold with thickness smaller than 10 nm. Since plastic deformation is due to hydrogen insertion/extraction and occurs in atomic-scale, it is necessary to divide structural changes appeared in nano- and micro-scale

Effect of plastic deformation on the niobium thermal expansion

International Nuclear Information System (INIS)

Savitskij, E.M.; Bychkova, M.I.; Kanikovskij, V.B.

1978-01-01

Using dilatometric method the effect of plastic deformation on change of thermal expansion coefficient (TEC) of niobium of different purity was studied. It was shown that deformation affected the TEC in different ways. At first the deformation degree rising causes linear decrease of the TEC and then linear increase. Carbon intensifies the TEC decrease of deformed niobium. The linear correlation was established between the TEC and the value of macroscopic stresses in plastic deformed niobium. The expression indicating the metal TEC change under loading was defined for case of strain hardening

Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

DEFF Research Database (Denmark)

Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of two commercial austenitic stainless steels: AISI 304 and EN 1.4369. The materials were plastically deformed to different equivalent strains by uniaxial...... demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

Plastic deformation of 2D crumpled wires

International Nuclear Information System (INIS)

Gomes, M A F; Donato, C C; Brito, V P; Coelho, A S O

2008-01-01

When a single long piece of elastic wire is injected through channels into a confining two-dimensional cavity, a complex structure of hierarchical loops is formed. In the limit of maximum packing density, these structures are described by several scaling laws. In this paper this packing process is investigated but using plastic wires which give rise to completely irreversible structures of different morphology. In particular, the plastic deformation from circular to oblate configurations of crumpled wires is experimentally studied, obtained by the application of an axial strain. Among other things, it is shown that in spite of plasticity, irreversibility and very large deformations, scaling is still observed.

Experimental and finite element analyses of plastic deformation behavior in vortex extrusion

International Nuclear Information System (INIS)

Shahbaz, M.; Pardis, N.; Kim, J.G.; Ebrahimi, R.; Kim, H.S.

2016-01-01

Vortex extrusion (VE) is a single pass severe plastic deformation (SPD) technique which can impose high strain values with almost uniform distribution within cross section of the processed material. This technique needs no additional facilities for installation on any conventional extrusion equipment. In this study the deformation behavior of material during VE is investigated and the results are compared with those of conventional extrusion (CE). These investigations include finite element analysis, visioplasticity, and microstructural characterization of the processed samples. The results indicate that the VE process can accumulate a higher strain value by applying an additional torsional deformation. The role of this additional deformation mode on the microstructural evolution of the VE sample is discussed and compared with the results obtained on the CE samples.

Two Back Stress Hardening Models in Rate Independent Rigid Plastic Deformation

Science.gov (United States)

Yun, Su-Jin

In the present work, the constitutive relations based on the combination of two back stresses are developed using the Armstrong-Frederick, Phillips and Ziegler’s type hardening rules. Various evolutions of the kinematic hardening parameter can be obtained by means of a simple combination of back stress rate using the rule of mixtures. Thus, a wide range of plastic deformation behavior can be depicted depending on the dominant back stress evolution. The ultimate back stress is also determined for the present combined kinematic hardening models. Since a kinematic hardening rule is assumed in the finite deformation regime, the stress rate is co-rotated with respect to the spin of substructure obtained by incorporating the plastic spin concept. A comparison of the various co-rotational rates is also included. Assuming rigid plasticity, the continuum body consists of the elastic deformation zone and the plastic deformation zone to form a hybrid finite element formulation. Then, the plastic deformation behavior is investigated under various loading conditions with an assumption of the J2 deformation theory. The plastic deformation localization turns out to be strongly dependent on the description of back stress evolution and its associated hardening parameters. The analysis for the shear deformation with fixed boundaries is carried out to examine the deformation localization behavior and the evolution of state variables.

Stability of surface plastic flow in large strain deformation of metals

Science.gov (United States)

Viswanathan, Koushik; Udapa, Anirduh; Sagapuram, Dinakar; Mann, James; Chandrasekar, Srinivasan

We examine large-strain unconstrained simple shear deformation in metals using a model two-dimensional cutting system and high-speed in situ imaging. The nature of the deformation mode is shown to be a function of the initial microstructure state of the metal and the deformation geometry. For annealed metals, which exhibit large ductility and strain hardening capacity, the commonly assumed laminar flow mode is inherently unstable. Instead, the imposed shear is accommodated by a highly rotational flow-sinuous flow-with vortex-like components and large-amplitude folding on the mesoscale. Sinuous flow is triggered by a plastic instability on the material surface ahead of the primary region of shear. On the other hand, when the material is extensively strain-hardened prior to shear, laminar flow again becomes unstable giving way to shear banding. The existence of these flow modes is established by stability analysis of laminar flow. The role of the initial microstructure state in determining the change in stability from laminar to sinuous / shear-banded flows in metals is elucidated. The implications for cutting, forming and wear processes for metals, and to surface plasticity phenomena such as mechanochemical Rehbinder effects are discussed.

Formulation of stiffness equation for a three-dimensional isoparametric element with elastic-plastic material and large deformation

International Nuclear Information System (INIS)

Chang, T.Y.; Prachuktam, S.; Reich, M.

1975-01-01

The formulation of the stiffness equation for an 8 to 21 node isoparametric element with elastic-plastic material and large deformation is presented. The formulation has been implemented in a nonlinear finite element program for the analysis of three-dimensional continuums. To demonstrate the utility of the formulation, a thick-walled cylinder was analyzed and the results are compared favorably with a known solution. The element type presented can be applied not only to 3-D continuums, but also to plate or shell structures, for which degenerated isoparametric elements may be used

Plasticity of pressure-sensitive materials

CERN Document Server

Ochsner, Andreas

2014-01-01

Classical plasticity theory of metals is independent of the hydrostatic pressure. However, if the metal contains voids or pores or if the structure is composed of cells, this classical assumption is no more valid and the influence of the hydrostatic pressure must be incorporated in the constitutive description. Looking at the microlevel, metal plasticity is connected with the uniform planes of atoms organized with long-range order. Planes may slip past each other along their close-packed directions. The result is a permanent change of shape within the crystal and plastic deformation. The presence of dislocations increases the likelihood of planes slipping. Nowadays, the theory of pressure sensitive plasticity is successfully applied to many other important classes of materials (polymers, concrete, bones etc.) even if the phenomena on the micro-level are different to classical plasticity of metals. The theoretical background of this phenomenological approach based on observations on the macro-level is describe...

Dislocation-drag contribution to high-rate plastic deformation in shock-loaded tantalum

International Nuclear Information System (INIS)

Tonks, D.L.; Hixson, R.S.; Johnson, J.N.; Gray, G.T. III

1994-01-01

Time-resolved plastic waves in plate-impact experiments give information on the relationship between applied shear stress and plastic strain rate at low plastic strain. This information is essentially different from that obtained at intermediate strain rates using Hopkins on bar techniques, because in the former case the material deformation state is driven briefly into the regime dominated by dislocation drag rather than thermal activation. Two VISAR records of the particle velocity at the tantalum/sapphire (window) interface are obtained for symmetric impact producing peak in situ longitudinal stresses of approximately 75 kbar and 111 kbar. The risetimes of the plastic waves are about 100 ns and 60 ns, respectively, with peak strain rates of about 2x10 5 /s and 1x10 6 /s, respectively, as determined by weak-shock analysis [Wallace, Phys. Rev. B 22, 1487 (1980), and Tonks, Los Alamos DataShoP Report LA-12068-MS (1991)]. These data show a much stronger dependence of plastic strain rate on applied shear stress than previously predicted by linear viscous drag models in combination with thermal activation through a large Peierls barrier. The data also show complex evolution of the mobile dislocation density during early stages of high-rate plastic flow. This measurement and analysis aid significantly in establishing the fundamental picture of dynamic deformation of BCC metals and the evolution of the internal material state at early times following shock compression. copyright 1994 American Institute of Physics

Pixels Intensity Evolution to Describe the Plastic Films Deformation

Directory of Open Access Journals (Sweden)

Juan C. Briñez-De León

2013-11-01

Full Text Available This work proposes an approach for mechanical behavior description in the plastic film deformation using techniques for the images analysis, which are based on the intensities evolution of fixed pixels applied to an images sequence acquired through polarizing optical assembly implemented around the platform of the plastic film deformation. The pixels intensities evolution graphs, and mechanical behavior graphic of the deformation has dynamic behaviors zones which could be associated together.

Existence of two twinning-mediated plastic deformation modes in Au nanowhiskers

International Nuclear Information System (INIS)

Sedlmayr, Andreas; Bitzek, Erik; Gianola, Daniel S.; Richter, Gunther; Mönig, Reiner; Kraft, Oliver

2012-01-01

We have performed in situ scanning electron microscopy tensile experiments and molecular dynamics (MD) simulations on nominally defect-free single-crystalline Au nanowhiskers. The room temperature experiments reveal strengths on the order of the ideal strength and plastic strains of up to 12%, a direct result of deformation twinning that governs plastic flow. The in situ and post mortem electron microscopy observations can be divided into two broad classes of deformation morphologies that correlate with distinct stress–strain responses. MD simulations show that the mechanism of twin growth can change from layer-by-layer propagation to parallel and accelerated formation of coalescing nanotwins. The transition between mechanisms is caused by the bending moment resulting from the augmented stress state due to the initial twin and the boundary conditions when a twin grows beyond an embryonic state. These distinct manifestations of deformation twinning suggest that nanoscale material behavior can be tailored for high tensile ductility in addition to ultra-high strength.

Hydrogen-Induced Plastic Deformation in ZnO

Science.gov (United States)

Lukáč, F.; Čížek, J.; Vlček, M.; Procházka, I.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.

In the present work hydrothermally grown ZnO single crystals covered with Pd over-layer were electrochemically loaded with hydrogen and the influence of hydrogen on ZnO micro structure was investigated by positron annihilation spectroscopy (PAS). Nuclear reaction analysis (NRA) was employed for determination of depth profile of hydrogen concentration in the sample. NRA measurements confirmed that a substantial amount of hydrogen was introduced into ZnO by electrochemical charging. The bulk hydrogen concentration in ZnO determined by NRA agrees well with the concentration estimated from the transported charge using the Faraday's law. Moreover, a subsurface region with enhanced hydrogen concentration was found in the loaded crystals. Slow positron implantation spectroscopy (SPIS) investigations of hydrogen-loaded crystal revealed enhanced concentration of defects in the subsurface region. This testifies hydrogen-induced plastic deformation of the loaded crystal. Absorbed hydrogen causes a significant lattice expansion. At low hydrogen concentrations this expansion is accommodated by elastic straining, but at higher concentrations hydrogen-induced stress exceeds the yield stress in ZnO and plastic deformation of the loaded crystal takes place. Enhanced hydrogen concentration detected in the subsurface region by NRA is, therefore, due to excess hydrogen trapped at open volume defects introduced by plastic deformation. Moreover, it was found that hydrogen-induced plastic deformation in the subsurface layer leads to typical surface modification: formation of hexagonal shape pyramids on the surface due to hydrogen-induced slip in the [0001] direction.

Practical solution of plastic deformation problems in elastic-plastic range

Science.gov (United States)

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.

International Engineering Foundation Conference on the Plastic Deformation of Ceramics

CERN Document Server

Brookes, Chris; Routbort, Jules

1995-01-01

This proceedings volume, "Plastic Deformation of Ceramics," constitutes the papers of an international symposium held at Snowbird, Utah from August 7-12, 1994. It was attended by nearly 100 scientists and engineers from more than a dozen countries representing academia, national laboratories, and industry. Two previous conferences on this topic were held at The Pennsylvania State University in 1974 and 1983. Therefore, the last major international conference focusing on the deformation of ceramic materials was held more than a decade ago. Since the early 1980s, ceramic materials have progressed through an evolutionary period of development and advancement. They are now under consideration for applications in engineering structures. The contents of the previous conferences indicate that considerable effort was directed towards a basic understanding of deformation processes in covalently bonded or simple oxide ceramics. However, now, more than a decade later, the focus has completely shifted. In particular, the...

Rigid-Plastic Approximations for Predicting Plastic Deformation of Cylindrical Shells Subject to Dynamic Loading

Directory of Open Access Journals (Sweden)

Michelle S. Hoo Fatt

1996-01-01

Full Text Available A theoretical approach was developed for predicting the plastic deformation of a cylindrical shell subject to asymmetric dynamic loads. The plastic deformation of the leading generator of the shell is found by solving for the transverse deflections of a rigid-plastic beam/string-on-foundation. The axial bending moment and tensile force in the beam/string are equivalent to the longitudinal bending moments and membrane forces of the shell, while the plastic foundation force is equivalent to the shell circumferential bending moment and membrane resistances. Closed-form solutions for the transient and final deformation profile of an impulsive loaded shell when it is in a “string” state were derived using the eigenfunction expansion method. These results were compared to DYNA 3D predictions. The analytical predictions of the transient shell and final centerline deflections were within 25% of the DYNA 3D results.

Influence of preliminary plastic deformation on plasticity characteristics and structure of armco-iron

International Nuclear Information System (INIS)

Vergazov, A.N.; Rybin, V.V.; Meshkov, Yu.Ya.; Moskvina, V.A.; Serditova, T.N.

1990-01-01

Effect of preliminary plastic deformation (PPD) by drawing on the maximum plasticity characteristics (critical rupture strain) ε c , general δ and uniform δ p relative elongation and on the structure of armco-iron in a wide range of PPD degree change (e=0-4.6) is studied. It is ascertained that with e growth the metal plastic properties at T test =77 and 293 K change in a different way. In particular, the critical strain ε c increases monotonously at 77 K and reduces at 293 K. It is shown that all changes of mechanical characteristics observed with e increase are conditioned by the development of fragmentation process in armco-iron. The data obtained are discussed from the veiwpoint of the developed plastic deformation physics concepts

Effect of plastic deformation and strain history on X-ray elastic constants

International Nuclear Information System (INIS)

Iadicola, Mark A.; Foecke, Tim

2005-01-01

The use of X-ray diffraction to measure residual stress in a crystalline material is well known. This method is currently being reapplied to the surface measurement of in situ stresses during biaxial straining of sheet metal specimens. This leads to questions of precision and calibration of the method through plastic deformation. Little is known of the change, with plastic work, in the X-ray elastic constants (XECs) that are required by the technique for stress measurement. Experiments to determine the formability of various materials using this stress measurement technique in conjunction with a typical Marciniak test (with the Raghavan variation of specimen shapes) have been performed assuming a constant value for XECs. New results of calibration experiments are presented which admit the possibility of variation of the XECs with plastic strain history and initial texture of the material. Adjustment of the data from the previously performed formability experiments is shown. Additionally, various phenomena are captured including initial yielding, change of XECs with plastic strain level (both with uniaxial and biaxial strain histories), and some of the effects of texture on the technique. This technique has potential application in verification of the assumptions made during other standard testing methods (in-plane biaxial specimen geometries and bulge testing), verifying stress predictions from finite element analyses (i.e. benchmarking experiments such as BM3), analysis of stress states in localized deformation (yield point effects), and tracking of the effect of prestraining on material formability through the process of multistage forming

Size-Tuned Plastic Flow Localization in Irradiated Materials at the Submicron Scale

Science.gov (United States)

Cui, Yinan; Po, Giacomo; Ghoniem, Nasr

2018-05-01

Three-dimensional discrete dislocation dynamics (3D-DDD) simulations reveal that, with reduction of sample size in the submicron regime, the mechanism of plastic flow localization in irradiated materials transitions from irradiation-controlled to an intrinsic dislocation source controlled. Furthermore, the spatial correlation of plastic deformation decreases due to weaker dislocation interactions and less frequent cross slip as the system size decreases, thus manifesting itself in thinner dislocation channels. A simple model of discrete dislocation source activation coupled with cross slip channel widening is developed to reproduce and physically explain this transition. In order to quantify the phenomenon of plastic flow localization, we introduce a "deformation localization index," with implications to the design of radiation-resistant materials.

Auxetic hexachiral structures with wavy ligaments for large elasto-plastic deformation

Science.gov (United States)

Zhu, Yilin; Wang, Zhen-Pei; Hien Poh, Leong

2018-05-01

The hexachiral structure is in-plane isotropic in small deformation. When subjected to large elasto-plastic deformation, however, the hexachiral structure tends to lose its auxeticity and/or isotropy—properties which are desirable in many potential applications. The objective of this study is to improve these two mechanical properties, without significantly compromising the effective yield stress, in the regime with significant material and geometrical nonlinearity effects. It is found that the deformation mechanisms underlying the auxeticity and isotropy properties of a hexachiral structure are largely influenced by the extent of rotation of the central ring in a unit cell. To facilitate the development of this deformation mechanism, an improved design with wavy ligaments is proposed. The improved performance of the proposed hexachiral structure is demonstrated. An initial study on possible applications as a protective material is next carried out, where the improved hexachiral design is shown to exhibit higher specific energy absorption capacity compared to the original design, as well as standard honeycomb structures.

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

Science.gov (United States)

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

2009-06-01

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

Diffraction-amalgamated grain boundary tracking for mapping 3D crystallographic orientation and strain fields during plastic deformation

International Nuclear Information System (INIS)

Toda, Hiroyuki; Kamiko, Takanobu; Tanabe, Yasuto; Kobayashi, Masakazu; Leclere, D.J.; Uesugi, Kentaro; Takeuchi, Akihisa; Hirayama, Kyosuke

2016-01-01

By amalgamating the X-ray diffraction technique with the grain boundary tracking technique, a novel method, diffraction-amalgamated grain boundary tracking (DAGT), has been developed. DAGT is a non-destructive in-situ analysis technique for characterising bulk materials, which can be applied up to near the point of fracture. It provides information about local crystal orientations and detailed grain morphologies in three dimensions, together with high-density strain mapping inside grains. As it obtains the grain morphologies by utilising X-ray imaging instead of X-ray diffraction, which latter is typically vulnerable to plastic deformation, DAGT is a fairly robust technique for analysing plastically deforming materials. Texture evolution and localised deformation behaviours have here been successfully characterised in Al–Cu alloys, during tensile deformation of 27% in applied strain. The characteristic rotation behaviours of grains were identified, and attributed to the effects of interaction with adjacent grains on the basis of the 3D local orientation and plastic strain distributions. It has also been revealed that 3D strain distribution in grains is highly heterogeneous, which is not explained by known mechanisms such as simple incompatibility with adjacent grains or strain percolation through soft grains. It has been clarified that groups consisting of a few adjacent grains may deform coordinately, especially in shear and lateral deformation, and the characteristic deformation pattern is thereby formed on a mesoscopic scale.

Plastic deformation of aluminium under continuous electron irradiation

International Nuclear Information System (INIS)

Dubinko, V.I.; Dovbnya, A.N.; Kushnir, V.A.; Khodak, I.V.; Mitrochenko, V.V.; Lebedev, V.P.; Krylovskij, V.S.; Lebedev, S.V.; Klepikov, V.F.

2010-01-01

Plastic deformation of polycrystalline aluminum (99.5%) was investigated in the absence and presence of a high-energy electron beam (E = 0.5 MeV, φ = (0.5...5)·10 13 cm -2 ·c -1 ). Reduction of the yield stress and hardening coefficient was determined as a function of deformation, the sample thickness and the beam density. The increase of plasticity of the metal due to the impact of the electron beam has been established. The temperature in the deformation process was measured, which allowed separating the contribution of radiation-induced effects on the mechanical characteristics of aluminum. Possible mechanisms of the phenomenon are discussed.

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

International Nuclear Information System (INIS)

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

2015-01-01

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. (paper)

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

Science.gov (United States)

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.

Survey of existing literature in the field of shock-absorbing materials with a view to subsequent adaptation of plastic deformation codes. Phase 1

International Nuclear Information System (INIS)

Draulans, J.; Fabry, J.P.; Lafontaine, I.; Richel, H.; Guyette, M.

1985-01-01

Shock-absorbing materials and structures can be used as part of the transport container structure or of the truck equipment. An extensive survey of the literature has provided much information. Investigation has been made to define the required experimental procedures necessary to measure the misssing material properties. Three codes had been selected: EURDYN, MARC-CDC and SAMCEF. For code evaluation, a schematic container model has been considered to serve as a benchmark for the evaluation of plastic deformation. For the shock-calculation, the container falls from a height of 9 meters along the direction of its cylinder axis on an unyielded flat surface. The EURDYN computer code, has been selected first as it is especially designed to handle dynamic problems, preferably plastic ones. Indeed, EURDYN uses an explicit integration scheme versus time, which makes it quite efficient to run short deformation processes such as absorber collapses. The SAMCEF computer code could not readily calculate the benchmark, also a visco-plastic flow model has been added to it. The MARC computer code was supposed to be a candidate to run shock-calculation but extensive computing time and engineering efforts would be required, it was replaced by the PLEXUS code. The results obtained using the SAMCEF programme confirm those obtained with EURDYN. The PLEXUS results are in between. The proposed benchmark calculation is at the border of the capabilities of the most advanced computer codes for plastic-dynamic calculations. Indeed, a complex energy absorption process seems to take place in a narrow region, moving versus time, where very large shape inversions occur. That requires an accurate modelling of the system in the deformed regions and a skilful choice of the numerical parameters of the computer run. The three tested codes gave qualitatively consistent results and confirm some scarce experimental results

Plastic deformation of indium nanostructures

International Nuclear Information System (INIS)

Lee, Gyuhyon; Kim, Ju-Young; Burek, Michael J.; Greer, Julia R.; Tsui, Ting Y.

2011-01-01

Highlights: → Indium nanopillars display two different deformation mechanisms. → ∼80% exhibited low flow stresses near that of bulk indium. → Low strength nanopillars have strain rate sensitivity similar to bulk indium. → ∼20% of compressed indium nanopillars deformed at nearly theoretical strengths. → Low-strength samples do not exhibit strength size effects. - Abstract: Mechanical properties and morphology of cylindrical indium nanopillars, fabricated by electron beam lithography and electroplating, are characterized in uniaxial compression. Time-dependent deformation and influence of size on nanoscale indium mechanical properties were investigated. The results show two fundamentally different deformation mechanisms which govern plasticity in these indium nanostructures. We observed that the majority of indium nanopillars deform at engineering stresses near the bulk values (Type I), with a small fraction sustaining flow stresses approaching the theoretical limit for indium (Type II). The results also show the strain rate sensitivity and flow stresses in Type I indium nanopillars are similar to bulk indium with no apparent size effects.

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

Science.gov (United States)

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

Experimental evaluation of the interaction effect between plastic and creep deformation

International Nuclear Information System (INIS)

Ikegami, K.; Niitsu, Y.

1985-01-01

An experimental study of plasticity-creep interaction effects is reported. The combined stress tests are performed on thin wall tubular specimens of SUS 304 stainless steel at room temperature and high temperature (600 0 C). The plastic behaviors subsequent to creep pre-strain and creep behaviors subsequent to plastic pre-strain are obtained for loading along straight stress paths with a corner. The inelastic behaviors including both plastic and creep deformations are experimentally investigated. The interaction effects between plastic and creep deformations are quantitatively estimated with the equi-plastic strain surface. (author)

Self-positioning of polymer membranes driven by thermomechanically induced plastic deformation

DEFF Research Database (Denmark)

Häfliger, Daniel; Hansen, Ole; Boisen, Anja

2006-01-01

Stress in polymeric resins is tailored by a thermomechanical process. It allows for controlled self-positioning of membranes in microdevices (see Figure). The process makes specific use of plastic deformation that results from the low viscosity of the polymer. This demonstrates that polymers offer...... new approaches to microfabrication that cannot be realized for common semiconductor materials without severe difficulties....

Plastic deformation and hysteresis for hydrogen storage in Pd–Rh alloys

Energy Technology Data Exchange (ETDEWEB)

Cappillino, P.J., E-mail: pcappil@sandia.gov [Sandia National Laboratories, PO Box 969, Mail Stop 9292, Livermore, CA 94551 (United States); Lavernia, E.J. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Ong, M.D. [Department of Physics, Whitworth University, Spokane, WA 99251 (United States); Wolfer, W.G.; Yang, N.Y. [Sandia National Laboratories, PO Box 969, Mail Stop 9292, Livermore, CA 94551 (United States)

2014-02-15

Highlights: • Experimental evidence of plastic work resulting from hydriding of palladium is presented. • A model of this plastic work was generated and correlated to hysteresis losses. • This hysteresis is thought to be important to the lifetime of hydrogen storage materials. • Yield strength values predicted by this model agree with measured hardness. -- Abstract: The hysteresis observed when reversibly absorbing and desorbing hydrogen in metals is currently not fully understood. In general, a hysteresis represents energy that is dissipated during a cycle, but the underlying mechanism of dissipation is still uncertain. It has been suggested that the hysteresis arises either from plastic work, or from elastic strains associated with the accommodation of the hydride phase, or from both. We present here experimental evidence that implicates plastic deformation as the cause of the hysteresis in a Pd–Rh alloy. The plastic work is evident from the increased dislocation density, from the accumulation of surface steps from slip bands, from line broadening of X-ray diffraction peaks, and from an increase in hardness with the number of hydriding cycles. A model of this plastic work is developed that depends on an effective yield strength. When this model is correlated with the measured hysteresis losses, two values are found for the effective yield strength. The lower value is shown to agree with yield strength values derived from Vickers hardness measurements. The hysteresis areas for repeated cycles of absorption and desorption decrease little with the number of cycles which is reminiscent of the plastic deformation hysteresis during low-cycle fatigue of metals. This similarity further confirms the plastic nature of the hydriding hysteresis.

Nanosized carbon modifier used to control plastic deformations of asphalt concrete

Science.gov (United States)

Vysotskaya, M. A.; Shekhovtsova, S. Yu; Barkovsky, D. V.

2018-03-01

Aspects related to plastic track, the formation of which directly depends on the properties of the binder in the composition of asphalt concrete, are considered in this article. The effect of primary carbon nanomaterials on the quality of polymer and bitumen binder in comparison with the traditional binder including cross-linking agent is evaluated. The influence of binders on the resistance to the track formation of type B asphalt concrete is studied. To quantify the service life of surfacing, a calculation method based on the criteria for the resistance of surfacing material to plastic deformations is used.

Multiscale Modeling of Polycrystalline NiTi Shape Memory Alloy under Various Plastic Deformation Conditions by Coupling Microstructure Evolution and Macroscopic Mechanical Response.

Science.gov (United States)

Hu, Li; Jiang, Shuyong; Zhou, Tao; Tu, Jian; Shi, Laixin; Chen, Qiang; Yang, Mingbo

2017-10-13

Numerical modeling of microstructure evolution in various regions during uniaxial compression and canning compression of NiTi shape memory alloy (SMA) are studied through combined macroscopic and microscopic finite element simulation in order to investigate plastic deformation of NiTi SMA at 400 °C. In this approach, the macroscale material behavior is modeled with a relatively coarse finite element mesh, and then the corresponding deformation history in some selected regions in this mesh is extracted by the sub-model technique of finite element code ABAQUS and subsequently used as boundary conditions for the microscale simulation by means of crystal plasticity finite element method (CPFEM). Simulation results show that NiTi SMA exhibits an inhomogeneous plastic deformation at the microscale. Moreover, regions that suffered canning compression sustain more homogeneous plastic deformation by comparison with the corresponding regions subjected to uniaxial compression. The mitigation of inhomogeneous plastic deformation contributes to reducing the statistically stored dislocation (SSD) density in polycrystalline aggregation and also to reducing the difference of stress level in various regions of deformed NiTi SMA sample, and therefore sustaining large plastic deformation in the canning compression process.

Multiscale Modeling of Polycrystalline NiTi Shape Memory Alloy under Various Plastic Deformation Conditions by Coupling Microstructure Evolution and Macroscopic Mechanical Response

Directory of Open Access Journals (Sweden)

Li Hu

2017-10-01

Full Text Available Numerical modeling of microstructure evolution in various regions during uniaxial compression and canning compression of NiTi shape memory alloy (SMA are studied through combined macroscopic and microscopic finite element simulation in order to investigate plastic deformation of NiTi SMA at 400 °C. In this approach, the macroscale material behavior is modeled with a relatively coarse finite element mesh, and then the corresponding deformation history in some selected regions in this mesh is extracted by the sub-model technique of finite element code ABAQUS and subsequently used as boundary conditions for the microscale simulation by means of crystal plasticity finite element method (CPFEM. Simulation results show that NiTi SMA exhibits an inhomogeneous plastic deformation at the microscale. Moreover, regions that suffered canning compression sustain more homogeneous plastic deformation by comparison with the corresponding regions subjected to uniaxial compression. The mitigation of inhomogeneous plastic deformation contributes to reducing the statistically stored dislocation (SSD density in polycrystalline aggregation and also to reducing the difference of stress level in various regions of deformed NiTi SMA sample, and therefore sustaining large plastic deformation in the canning compression process.

Influence of Plastic Deformation of Steel Samples on the Fast electron Backscattering

International Nuclear Information System (INIS)

Sierra Trujillo, J. X.; Herrera Palma, V.; Desdin Garcia, L. F.; Codorniu Pujals, D.

2013-01-01

A considerable fraction of a fast electron beam incident on a target is scattered in backward direction. It is a very complex process involving electron - nucleus and electron - electron collisions. The fraction of backscattered electrons is described by a parameterization as a function of the atomic number and energy of the incident electrons. In such approaches the possible influence of the material structure is not taken into account. In this paper, the behavior of the 90 Sr/ 90 Y backscattered electrons from 08JuA and 15GJuT steel strained samples is investigated. A clear dependence between the degree of plastic deformation and the fraction of backscattered electrons was observed. This relationship is explained by the interaction of electrons with the dislocations in the material, whose density depends on the magnitude of the strain in the plastic region. On the basis of a simple model for describing this interaction, a mathematical expression is obtained for the relationship between the fraction of backscattered electrons and the degree of deformation. (Author)

A finite deformation theory of higher-order gradient crystal plasticity

DEFF Research Database (Denmark)

Kuroda, Mitsutoshi; Tvergaard, Viggo

2008-01-01

crystal plasticity that is based on an assumption of the existence of higher-order stresses. Furthermore, a boundary-value problem for simple shear of a constrained thin strip is studied numerically, and some characteristic features of finite deformation are demonstrated through a comparison to a solution......For higher-order gradient crystal plasticity, a finite deformation formulation is presented. The theory does not deviate much from the conventional crystal plasticity theory. Only a back stress effect and additional differential equations for evolution of the geometrically necessary dislocation...

Investigation into diffusion induced plastic deformation behavior in hollow lithium ion battery electrode revealed by analytical model and atomistic simulation

International Nuclear Information System (INIS)

Li, Jia; Fang, Qihong; Wu, Hong; Liu, Youwen; Wen, Pihua

2015-01-01

Highlights: • Diffusion induced stress is established. • Yield stress is dependent upon concentration. • Plastic deformation induced stress lowers tensile stress. • Plastic deformation suppresses crack nucleation. • Plastic deformation occurs not only at lithiated phase but also at electrode interior. - Abstract: This paper is theoretically suggested to describe diffusion induced stress in the elastoplastic hollow spherical silicon electrode for plastic deformation using both analytical model and molecular simulation. Based on the plastic deformation and the yield criterion, we develop this model accounting for the lithium-ion diffusion effect in hollow electrode, focusing on the concentration and stress distributions undergoing lithium-ion insertion. The results show that the two ways, applied compressive stress to inner surface or limited inner surface with higher concentration using biological membranes maintaining concentration difference, lead to the compressive stress induced by the lithium-ion diffusion effect. Hollow spherical electrode reduces effectively diffusion induced stress through controlling and tuning electrode parameters to obtain the reasonably low yield strength. According to MD simulations, plastic deformation phenomenon not only occurs at interface layer of lithiated phase, but also penetrates at electrode interior owning to confinement imposed by lithiated phase. These criteria that radial and hoop stresses reduce dramatically when plastic deformation occurs near the end faces of hollow electrode, may help guide development of new materials for lithium-ion batteries with enhanced mechanical durability, by means of reasonable designing yield strength to maintain mechanical stress below fracture strength, thereby increasing battery life.

Characterization of residual stresses generated during inhomogeneous plastic deformation

DEFF Research Database (Denmark)

Lorentzen, T.; Faurholdt, T.; Clausen, B.

1998-01-01

Residual stresses generated by macroscopic inhomogeneous plastic deformation are predicted by an explicit finite element (FE) technique. The numerical predictions are evaluated by characterizing the residual elastic strains by neutron diffraction using two different (hkl) reflections. Intergranular...... compare well and verify the capability of the numerical technique as well as the possibilities of experimental validation using neutron diffraction. The presented experimental and numerical approach will subsequently be utilized for the evaluation of more complicated plastic deformation processes...

Influence of severe plastic deformation obtained by warm rolling on microstructure and mechanical properties of the ferritic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Barbosa, Luana Alves; Campos, Wagner Reis Costa; Vilela, Jefferson José, E-mail: luana_alves_barbosa@hotmail.com, E-mail: wrrc@cdtn.br, E-mail: jjv@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Miqueletti, Estevesson Ferreira; Mazzer, Eric Marchezini; Santos, Dagoberto B., E-mail: estevess@demet.ufmg.br, E-mail: marchezini@demet.ufmg.br, E-mail: dsantos@demet.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil)

2017-07-01

Generation IV reactors require research on new materials. For example, materials that will be used in the reactor vessel must be resistant to creep and have high toughness. Grain refining is a technique used to improve toughness. This grain refinement can be achieved by severe plastic deformation. In this work, the stainless steel 409 was used to simulate the EUROFER one type of ODS steel. The rolling process was applied to make the severe plastic deformation. The rolling was performed at 600°C which corresponds to the warm working condition in the absence of dynamic recrystallization. The rolling schedule studied allowed a logarithmic strain accumulation of 3.16. The rolled sheet had a yield stress of 822 MPa and a hardness of 302 HV. The grains became quite elongated characteristic of a severe plastic deformation. The recrystallization temperature of the rolled sheet was approximately 500°C. It was obtained by heat treatment and hardness measurement. (author)

Influence of severe plastic deformation obtained by warm rolling on microstructure and mechanical properties of the ferritic stainless steel

International Nuclear Information System (INIS)

Barbosa, Luana Alves; Campos, Wagner Reis Costa; Vilela, Jefferson José; Miqueletti, Estevesson Ferreira; Mazzer, Eric Marchezini; Santos, Dagoberto B.

2017-01-01

Generation IV reactors require research on new materials. For example, materials that will be used in the reactor vessel must be resistant to creep and have high toughness. Grain refining is a technique used to improve toughness. This grain refinement can be achieved by severe plastic deformation. In this work, the stainless steel 409 was used to simulate the EUROFER one type of ODS steel. The rolling process was applied to make the severe plastic deformation. The rolling was performed at 600°C which corresponds to the warm working condition in the absence of dynamic recrystallization. The rolling schedule studied allowed a logarithmic strain accumulation of 3.16. The rolled sheet had a yield stress of 822 MPa and a hardness of 302 HV. The grains became quite elongated characteristic of a severe plastic deformation. The recrystallization temperature of the rolled sheet was approximately 500°C. It was obtained by heat treatment and hardness measurement. (author)

Appreciation of Triaxiality Influence in Plastic Deformation Accompanying Ductile Rupture

Science.gov (United States)

Coseru, Ancuta-Ioana; Zichil, Valentin; Lupascu, Stefan

2017-12-01

In this paper, the authors propose a studying method for the deformation that appears before crack of ductile materials using the Lode parameter determined by the numerical calculation applied on simple models, verified in previous studies. In order to highlight the influence of the Lode parameter, the tests were performed at simple but also at compound tests. The necessity of these studies lies in the fact that the acknowledged models (the use of the integral J, the critical stress intensity factor Kc or the CPCD method) do not fully explain the phenomenon of deformation before breaking the elasto-plastic materials. The tests were imagined under the form of sets. Each set of tests was performed on smooth specimens and on specimens with a notch radius of 0.5, 2, 4 and 10 mm. Also, each set of tests was performed for pure tensile and combined tensile-torque test.

Plastic deformation, residual stress, and crystalline texture measurements for in-process characterization of FCC metal alloys

International Nuclear Information System (INIS)

Ruud, C.O.; Jacobs, M.E.; Weedman, S.D.; Snoha, D.J.

1989-01-01

This paper describes the results of several on-going investigations on the measurement of plastic deformation, residual stress, and crystalline texture in nickel, copper, and aluminum base alloys by x-ray diffraction techniques. X-ray diffraction techniques have been shown to be effective in the measurement of plastic deformation, residual stress, and crystalline texture in FCC metals, from the breadth, position, and intensity of the x-ray diffraction peaks. The Ruud-Barrett position-sensitive scintillation detector has been demonstrated to be fast, non-contacting, and tolerant of detector to component distance variation -- necessary requirements for cost-effective in-process inspection of materials

Parameter determination of hereditary models of deformation of composite materials based on identification method

Science.gov (United States)

Kayumov, R. A.; Muhamedova, I. Z.; Tazyukov, B. F.; Shakirzjanov, F. R.

2018-03-01

In this paper, based on the analysis of some experimental data, a study and selection of hereditary models of deformation of reinforced polymeric composite materials, such as organic plastic, carbon plastic and a matrix of film-fabric composite, was pursued. On the basis of an analysis of a series of experiments it has been established that organo-plastic samples behave like viscoelastic bodies. It is shown that for sufficiently large load levels, the behavior of the material in question should be described by the relations of the nonlinear theory of heredity. An attempt to describe the process of deformation by means of linear relations of the theory of heredity leads to large discrepancies between the experimental and calculated deformation values. The use of the theory of accumulation of micro-damages leads to much better description of the experimental results. With the help of the hierarchical approach, a good approximation of the experimental values was successful only in the first three sections of loading.

Influence of plastic strain on deformation-induced martensitic transformations

NARCIS (Netherlands)

Perdahcioglu, Emin Semih; Geijselaers, Hubertus J.M.; Groen, M.

2008-01-01

The effects of plastic strain on deformation-induced martensitic transformations have been investigated experimentally. Austenitic metastable stainless steel samples were heated to a temperature at which the transformation is suppressed and were plastically strained to different amounts. The

Electrical and photomechanical effects of plastic deformation of mercuric iodide

International Nuclear Information System (INIS)

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

1991-01-01

The effects of bulk plastic deformation of mercuric iodide (HgI 2 ), upon some of the electronic properties relevant to the performance of HgI 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

Plastic deformation mechanisms of the uranium-alpha. Review

International Nuclear Information System (INIS)

Loureiro, A.P.

1975-01-01

A survey of the bibliography on the behaviour of the alpha-Uranium during its plastic deformation is made, with the aim of knowing the mechanisms which control that deformation. An analysis is made of some of the mechanisms suggested in the literature as controlling, with particular emphasis on the Peierls-Nabarro mechanism

Calculation of plastic deformation of a conical shell with the transformation of inner surface into outer one

Directory of Open Access Journals (Sweden)

A. I. Uvarov

2014-01-01

Full Text Available An analytical model of plastic deformation of a conical shell with the transformation of internal surface into outer one was developed with a use of the kinematic method. The shell material was assumed to be perfectly plastic. The theory of thin shells and the kinematic theorem of limit equilibrium were utilized in this work. Both geometric and physical nonlinearities were taken into account. Dependences for calculating radius of curvature of the intensive deformation zones, value of chain ring deformation and values of the deforming force as a function of axial displacement were determined. Analysis showed the possibility of using a conical shell to absorb energy with high efficiency. Obtained results could be used for calculation and selection of optimal parameters of the energy-absorbing elements in shock absorbers.

Features micro plastic deformation auxetic beryllium irradiated with high-energy electrons

International Nuclear Information System (INIS)

Rarans'kij, M.D.; Olyijnich-Lisyuk, A.V.; Tashchuk, O.Yu.

2016-01-01

By low-frequency internal friction (LFIF) (1...3 Hz) method, the study of the behavior of the dynamic modulus of torsion (Gef) and by mathematical modeling of dislocation motion studied micro plastic deformation in naturally aged and irradiated with high-energy (18 MeV) electrons auxetic beryllium. With increasing doses of radiation found an increase in IF and speed of movement of dislocations in 2-3 times. Installed stage character micro strain auxetic Be. By mathematical modeling showed that in the irradiated material the deformation occurs due to the accelerated movement of the twin dislocations in the early stages, and anomalous dynamic deceleration of complete dislocations with an increase in the degree of deformation in the second stage. It is shown that theoretically estimated values are in good agreement with the experimentally determined.

Improvement of Functional Properties by Sever Plastic Deformation on Parts of Titanium Biomaterials

Science.gov (United States)

Czán, Andrej; Babík, Ondrej; Daniš, Igor; Martikáň, Pavol; Czánová, Tatiana

2017-12-01

Main task of materials for invasive implantology is their biocompatibility with the tissue but also requirements for improving the functional properties of given materials are increasing constantly. One of problems of materials biocompatibility is the impossibility to improve of functional properties by change the percentage of the chemical elements and so it is necessary to find other innovative methods of improving of functional properties such as mechanical action in the form of high deformation process. This paper is focused on various methods of high deformation process such as Equal Channel Angular Pressing (ECAP) when rods with record strength properties were obtained.The actual studies of the deformation process properties as tri-axial compress stress acting on workpiece with high speed of deformation shows effects similar to results obtained using the other methods, but in lower levels of stress. Hydrostatic extrusion (HE) is applying for the purpose of refining the structure of the commercially pure titanium up to nano-scale. Experiments showed the ability to reduce the grain size below 100 nm. Due to the significant change in the performance of the titanium materials by severe plastic deformation is required to identify the processability of materials with respect to the identification of created surfaces and monitoring the surface integrity, where the experimental results show ability of SPD technologies application on biomaterials.

Durability and plasticity of a material under different trajectories cycle loading in dependence on the loading prehistory

International Nuclear Information System (INIS)

Mozharovskij, N.S.; Bobyr', N.I.

1979-01-01

Results of investigations into the durability and plasticity of a material under combined proportional cyclic loading over different trajectories depending upon the values of intensity of preliminary plastic deformation obtained by different loading methods are presented. The effect of loading prehistory type on material plastic properties and its durability are shown

Durability and plasticity of a material under different trajectories cycle loading in dependence on the loading prehistory

Energy Technology Data Exchange (ETDEWEB)

Mozharovskii, N S; Bobyr, N I [Kievskij Politekhnicheskij Inst. (Ukrainian SSR)

1979-12-01

Results of investigations into the durability and plasticity of a material under combined proportional cyclic loading over different trajectories depending upon the values of intensity of preliminary plastic deformation obtained by different loading methods are presented. The effect of loading prehistory type on material plastic properties and its durability are shown.

Microstructural evolution in deformed austenitic TWinning Induced Plasticity steels

NARCIS (Netherlands)

Van Tol, R.T.

2014-01-01

This thesis studies the effect of plastic deformation on the stability of the austenitic microstructure against martensitic transformation and diffusional decomposition and its role in the phenomenon of delayed fracture in austenitic manganese (Mn)-based TWinning Induced Plasticity (TWIP) steels.

Investigations on fuel can plastic deformations

International Nuclear Information System (INIS)

Boutard, J.L.; Dupouy, J.M.

1979-01-01

To the extent where the elongation of claddings differs from the mean swelling, the diametral plastic deformation can include, apart from that due to fission gases or the mechanical oxide-cladding interaction, contributions due to swelling prevented along the axis or to growth phenomena. The high thermal activation of the creep of hyper quenched steel unlike cold rolled steel, gives rise to the problem of a contribution to creep in the reactor other than the term SIPA. The impact of mechanisms of diffusion deformation on the boundary decohesion criteria is discussed in conclusion [fr

Influence of deformation on structural-phase state of weld material in St3 steel

Energy Technology Data Exchange (ETDEWEB)

Smirnov, Alexander, E-mail: galvas.kem@gmail.ru; Ababkov, Nicolay, E-mail: n.ababkov@rambler.ru; Ozhiganov, Yevgeniy, E-mail: zhigan84@mail.ru [Kuzbass State Technical University, 25-54, Krasnaya Str., 650000, Kemerovo (Russian Federation); LLC “Kuzbass Center of Welding and Control”, 33/2, Lenin Str., 650055, Kemerovo (Russian Federation); Kozlov, Eduard, E-mail: kozlov@tsuab.ru [Kuzbass State Technical University, 25-54, Krasnaya Str., 650000, Kemerovo (Russian Federation); Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Popova, Natalya, E-mail: natalya-popova-44@mail.ru [Kuzbass State Technical University, 25-54, Krasnaya Str., 650000, Kemerovo (Russian Federation); Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk (Russian Federation); Nikonenko, Elena, E-mail: vilatomsk@mail.ru [Kuzbass State Technical University, 25-54, Krasnaya Str., 650000, Kemerovo (Russian Federation); Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30, Lenin Str., 634050, Tomsk (Russian Federation); Zboykova, Nadezhda, E-mail: tezaurusn@gmail.com; Koneva, Nina, E-mail: koneva@tsuab.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation)

2016-01-15

The structural-phase condition of the weld material subjected to the plastic deformation was investigated using the translucent diffraction electron microscopy method. The investigations were carried out near the joint of the weld and the base metal. The seam was done by the method of manual arc welding without artificial defects. The St3 steel was taken as the welded material. Influence of the plastic deformation on morphology, phase composition, defect structure and its parameters of weld metal was revealed. All investigations were done at the distance of 0.5 mm from the joint of the weld and the base metal at the deformation degrees from 0 to 5% and after destruction of a sample. It was established that deformation of the sample did not lead to qualitative changes in the structure (the structure is still presented by ferrite-pearlite mixture) but changed the quantitative parameters of the structure, namely, with the increase of plastic deformation a part of the pearlite component becomes more and more imperfect. In the beginning it turns into the destroyed pearlite then into ferrite, the volume fraction of pearlite is decreased. The polarization of dislocation structure takes place but it doesn’t lead to the internal stresses that can destroy the sample.

Correlating elastic and plastic deformation with magnetic permeability values

Science.gov (United States)

Papadopoulou, S.

2017-12-01

This paper investigates the utilization of magnetic permeability method in determining elastic and plastic deformation state of ferromagnetic steels. The results have shown a strong degradation of the magnetic values on plastically region due to the irreversible movements of the magnetic domain walls.

Development of Bake Hardening Effect by Plastic Deformation and Annealing Conditions

Directory of Open Access Journals (Sweden)

Kvačkaj, T.

2006-01-01

Full Text Available The paper deals with the classification of steel sheets for automotives industry on the basis of strength and structural characteristics. Experimental works were aimed to obtain the best possible strengthening parameters as well as work hardening and solid solution ferrite hardening, which are the result of thermal activation of interstitial carbon atoms during paint-baking of auto body. Hardening process coming from interstitial atoms is realized as two-step process. The first step is BH (bake hardening effect achieved by interaction of interstitial atoms with dislocations. The Cottrels atmosphere is obtained. The second step of BH effect is to produced the hardening from precipitation of the carbon atoms in e-carbides, or formation of Fe32C4 carbides. WH (work hardening effect is obtained as dislocation hardening from plastic deformations during sheet deep drawing. Experimental works were aimed at as to achieve such plastic material properties after cold rolling, annealing and skin-pass rolling, which would be able to classify the material ZStE220BH into the drawing categories at the level of DQ – DDQ. As resulting from the experimental results, the optimal treatment conditions for the maximal sum (WH+BH = 86 MPa are as follows: total cold rolling deformation ecold = 65 %, annealing temperature Tanneal. = 700 °C.

Plastic deformation of silicon dendritic web ribbons during the growth

Science.gov (United States)

Cheng, L. J.; Dumas, K. A.; Su, B. M.; Leipold, M. H.

1984-01-01

The distribution of slip dislocations in silicon dendritic web ribbons due to plastic deformation during the cooling phase of the growth was studied. The results show the existence of two distinguishable stress regions across the ribbon formed during the plastic deformation stage, namely, shear stress at the ribbon edges and tensile stress at the middle. In addition, slip dislocations caused by shear stress near the edges appear to originate at the twin plane.

Influence of anisotropy effect and internal stresses upon the superconductive critical temperature of plastically deformed tin

International Nuclear Information System (INIS)

Wagner, D.; Stangler, F.

1976-01-01

The influence of plastic deformation on the superconductive critical temperature of tin single crystals has been investigated experimentally. It was shown by measurements that the lattice defects produced by plastic deformation lead to an anisotropy effect (according to the theory of Markowitz and Kadanoff), as do impurities in alloyed material. The decrease in T/sub c/ due to this effect can be measured, however, only with samples of certain special orientations. Samples with other orientations show an increase in T/sub c/, which can be explained by the assumption of internal stresses from dislocation pileups. A model is discussed which accounts for the measured rise in T/sub c/

Large poroelastic deformation of a soft material

Science.gov (United States)

MacMinn, Christopher W.; Dufresne, Eric R.; Wettlaufer, John S.

2014-11-01

Flow through a porous material will drive mechanical deformation when the fluid pressure becomes comparable to the stiffness of the solid skeleton. This has applications ranging from hydraulic fracture for recovery of shale gas, where fluid is injected at high pressure, to the mechanics of biological cells and tissues, where the solid skeleton is very soft. The traditional linear theory of poroelasticity captures this fluid-solid coupling by combining Darcy's law with linear elasticity. However, linear elasticity is only volume-conservative to first order in the strain, which can become problematic when damage, plasticity, or extreme softness lead to large deformations. Here, we compare the predictions of linear poroelasticity with those of a large-deformation framework in the context of two model problems. We show that errors in volume conservation are compounded and amplified by coupling with the fluid flow, and can become important even when the deformation is small. We also illustrate these results with a laboratory experiment.

Plastic deformation in nano-scale multilayer materials — A biomimetic approach based on nacre

Energy Technology Data Exchange (ETDEWEB)

Lackner, Juergen M., E-mail: juergen.lackner@joanneum.at [JOANNEUM RESEARCH Forschungsges.m.b.H., Institute for Surface Technologies and Photonics, Functional Surfaces, Leobner Strasse 94, A-8712 Niklasdorf (Austria); Waldhauser, Wolfgang [JOANNEUM RESEARCH Forschungsges.m.b.H., Institute for Surface Technologies and Photonics, Functional Surfaces, Leobner Strasse 94, A-8712 Niklasdorf (Austria); Major, Boguslaw; Major, Lukasz [Polish Academy of Sciences, Institute of Metallurgy and Materials Sciences, IMIM-PAN, ul. Reymonta 25, PL-30059 Krakow (Poland); Kot, Marcin [University of Science and Technology, AGH, Aleja Adama Mickiewicza 30, 30-059 Krakow (Poland)

2013-05-01

The paper reports about a biomimetic based comparison of deformation in magnetron sputtered multilayer coatings based on titanium (Ti), titanium nitride (TiN) and diamond-like carbon (DLC) layers and the deformation mechanisms in nacre of mollusc shells. Nacre as highly mineralized tissue combines high stiffness and hardness with high toughness, enabling resistance to fracture and crack propagation during tensile loading. Such behaviour is based on a combination of load transmission by tensile stressed aragonite tablets and shearing in layers between the tablets. Shearing in these polysaccharide and protein interlayers demands hydrated conditions. Otherwise, nacre has similar brittle behaviour to aragonite. To prevent shear failure, shear hardening occurs by progressive tablet locking due to wavy dovetail-like surface geometry of the tablets. Similar effects by shearing and strain hardening mechanisms were found for Ti interlayers between TiN and DLC layers in high-resolution transmission electron microscopy studies, performed in deformed zones beneath spherical indentations. 7 nm thin Ti films are sufficient for strong toughening of the whole multi-layered coating structure, providing a barrier for propagation of cracks, starting from tensile-stressed, hard, brittle TiN or DLC layers. - Highlights: • Biomimetic approach to TiN-diamond-like carbon (DLC) multilayers by sputtering • Investigation of deformation in/around hardness indents by HR-TEM • Plastic deformation with shearing in 7-nm thick Ti interlayers in TiN–DLC multilayers • Biomimetically comparable to nacre deformation.

Interaction of heat production, strain rate and stress power in a plastically deforming body under tensile test

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Lifetime Reliability Estimate and Extreme Permanent Deformations of Randomly Excited Elasto-Plastic Structures

DEFF Research Database (Denmark)

Nielsen, Søren R.K.; Sørensen, John Dalsgaard; Thoft-Christensen, Palle

1983-01-01

plastic deformation during several loadings can be modelled as a filtered Poisson process. Using the Markov property of this quantity the considered first-passage problem as well as the related extreme distribution problems are then solved numerically, and the results are compared to simulation studies.......A method is presented for life-time reliability' estimates of randomly excited yielding systems, assuming the structure to be safe, when the plastic deformations are confined below certain limits. The accumulated plastic deformations during any single significant loading history are considered...

Magnetic Non-destructive Testing of Plastically Deformed Mild Steel

Directory of Open Access Journals (Sweden)

Jozef Pala

2004-01-01

Full Text Available The Barkhausen noise analysis and coercive field measurement have been used as magnetic non-destructive testing methods for plastically deformed high quality carbon steel specimens. The strain dependence of root mean square value and power spectrum of the Barkhausen noise and the coercive field are explained in terms of the dislocation density. The specimens have been subjected to different magnetizing frequencies to show the overlapping nature of the Barkhausen noise. The results are discussed in the context of usage of magnetic non-destructive testing to evaluate the plastic deformation of high quality carbon steel products.

Computational description of nanocrystalline deformation based on crystal plasticity

International Nuclear Information System (INIS)

Fu, H.-H.; Benson, David J.; Andre Meyers, Marc

2004-01-01

The effect of grain size on the mechanical response of polycrystalline metals was investigated computationally and applied to the nanocrystalline domain. A phenomenological constitutive description is adopted to build the computational crystal model. Two approaches are implemented. In the first, the material is envisaged as a composite; the grain interior is modeled as a monocrystalline core surrounded by a mantle (grain boundary) with a lower yield stress and higher work hardening rate response. Both a quasi-isotropic and crystal plasticity approaches are used to simulate the grain interiors. The grain boundary is modeled either by an isotropic Voce equation (Model I) or by crystal plasticity (Model II). Elastic and plastic anisotropy are incorporated into this simulation. An implicit Eulerian finite element formulation with von Mises plasticity or rate dependent crystal plasticity is used to study the nonuniform deformation and localized plastic flow. The computational predictions are compared with the experimentally determined mechanical response of copper with grain sizes of 1 μm and 26 nm. Shear localization is observed during work hardening in view of the inhomogeneous mechanical response. In the second approach, the use of a continuous change in mechanical response, expressed by the magnitude of the maximum shear stress orientation gradient, is introduced. It is shown that the magnitude of the gradient is directly dependent on grain size. This gradient term is inserted into a constitutive equation that predicts the local stress-strain evolution

Finite Deformation of Materials with an Ensemble of Defects

Energy Technology Data Exchange (ETDEWEB)

J.K. Dienes

2003-01-01

The theory of large deformations developed here is closely related to continuum mechanics but it differs in several major respects, especially in considering the deformation associated with various types of physical behavior, making it possible to synthesize a general approach to formulating constitutive laws. One goal is to derive general concepts of strain, strain rate, stress, and stress rate that are somewhat more physics-based than in most standard works on continuum mechanics, and to demonstrate some new relations between these quantities. With these concepts it is possible to develop a generalized principle of superposition of strain rates (GSSR) that accounts for damage as well as plastic flow. The traditional superposition of strain rates allows for addition of elastic and plastic strain rates and is commonly thought to be valid only for small strains. The GSSR allows us to compute deformations involving plastic flow and, in addition, brittle failure, fragmentation, high-pressure effects and other types of behavior as necessary, and the theory is valid for arbitrarily large deformations. In fact, GSSR is derived from more basic ideas and has broader application than the standard superposition of strain rates. The physical basis for calculations of complex material response is developed in a separate report. The implementation into the SCRAM computer program is documented separately. The polar decomposition theorem is taken as a starting point for the theory of large deformation, an approach somewhat different from that usually taken in continuum mechanics. Two sets of orthogonal axes are distinguished, space axes that are fixed in ambient space, and polar axes that are related to material deformation. This clarifies several concepts; for example, it is shown that the Signorini and Green-St. Venant strains are actually measures of the same physical entity, one in space axes and the other in polar axes. It follows that they are not competing measures, as is

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

International Nuclear Information System (INIS)

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

2008-01-01

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

Concerning the problem of the plastic deformation mechanism changeover in neutron-irradiated metals and alloys

International Nuclear Information System (INIS)

Kolesnikov, A.N.; Krasnoselov, V.A.; Prokhorov, V.I.

1982-01-01

With a phenomenological model of plastic deformation instability as a basis, an analysis was made of the neutron irradition effects on the characteristics of strength and plasticity vs. structural parameters and radiation damage morphology. It was demonstrated that the enchanced plasticity in the initial stage of neutron irradiation has to do with the solid solution disintegration. Introduction of indestructible strengthening barriers enhances the stress-resistance of the neck-formation by 1.22 times. The ''big grain'' effect is observable during the deformation channel production only. Both the deformation twinning and deformation-induced martensite transformation raise the plastic flow stability

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Stress and strain fluctuations in plastic deformation of crystals with disordered microstructure

International Nuclear Information System (INIS)

Kapetanou, O; Zaiser, M; Weygand, D

2015-01-01

We investigate the spatial structure of stress and strain patterns in crystal plasticity. To this end, we combine theoretical arguments with plasticity simulations using three different models: (i) a generic model of bulk crystal plasticity with stochastic evolution of the local microstructure, (ii) a 2D discrete dislocation simulation assuming single-slip deformation in a bulk crystal, and (iii) a 3D discrete dislocation model for deformation of micropillars in multiple slip. For all three models we investigate the scale-dependent magnitude of local fluctuations of internal stress and plastic strain, and we determine the spatial structure of the respective auto- and cross-correlation functions. The investigations show that, in the course of deformation, nontrivial long range correlations emerge in the stress and strain patterns. We investigate the influence of boundary conditions on the observed spatial patterns of stress and strain, and discuss implications of our findings for larger-scale plasticity models. (paper)

Plastic Deformation of Metal Tubes Subjected to Lateral Blast Loads

Directory of Open Access Journals (Sweden)

Kejian Song

2014-01-01

Full Text Available When subjected to the dynamic load, the behavior of the structures is complex and makes it difficult to describe the process of the deformation. In the paper, an analytical model is presented to analyze the plastic deformation of the steel circular tubes. The aim of the research is to calculate the deflection and the deformation angle of the tubes. A series of assumptions are made to achieve the objective. During the research, we build a mathematical model for simply supported thin-walled metal tubes with finite length. At a specified distance above the tube, a TNT charge explodes and generates a plastic shock wave. The wave can be seen as uniformly distributed over the upper semicircle of the cross-section. The simplified Tresca yield domain can be used to describe the plastic flow of the circular tube. The yield domain together with the plastic flow law and other assumptions can finally lead to the solving of the deflection. In the end, tubes with different dimensions subjected to blast wave induced by the TNT charge are observed in experiments. Comparison shows that the numerical results agree well with experiment observations.

Residual Stress Analysis of Severe Plastic Deformed Materials using the Finite Element Method and the Neutron Diffraction Method

International Nuclear Information System (INIS)

Kang, Mi Hyun; Seong, Back Suck; Kim, Hyoung Seop

2009-01-01

Severe plastic deformation (SPD) is one of the most promising top-down techniques, moving towards industrialization to fabricate bulk ultrafine grain materials. The strain distribution and deformation behavior during the ECAP (equal channel angular pressing), influenced by tool angles, friction and material behavior, was studied through experimental and numerical analyses. The residual stress of work piece which was straight before ECAP produces many serious problems in the next processing e.g. input of the work piece for the next ECAP. The bent work piece needs additional straightening or surface polishing even if the amount of bending is small, and residual stress need to be released before service applications. Residual stress, particularly tensile residual stress can be a very important factor in affecting the reliability and integrity of working parts. The formation of tensile residual stress may result in initiation of fatigue cracks, stress corrosion cracking, or other types of fracture. Hence, residual stress and resulting bending need to be controlled during ECAP. Thus, in current study the bending behavior and the residual stress of the work piece in ECAP are analyzed through experimental and finite element analyses by considering the effects of material, geometric, and processing parameters individually. The stress states in the ECAP processed work piece were measured by the non-destructive way using neutron diffraction. Efforts were made to suggest the alternate routes to reduce the residual stress and bending of work piece in ECAP

Plastic deformation tests on fragile materials using a thermal expansion machine

International Nuclear Information System (INIS)

Orozco, E.; Morales, A.; Mendoza, A.

1991-01-01

Applying an electrical current on an iron bar, a thermal expansion can be induced. We have taken advantage of this to deform fragile materials, in order to study their mechanical properties. In this paper we show some gels and high T c oxide superconductors (Author)

Computer simulation of plastic deformation in irradiated metals

International Nuclear Information System (INIS)

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 μm and 1000 active slip planes per channel, which is reasonable in the view of experimental observations

Influence of Severe Plastic Deformation on Mechanical Properties and Structure of Aluminium Alloys

Directory of Open Access Journals (Sweden)

Ondřej Hilšer

2016-09-01

Full Text Available Article is devoted to analysis of ECAP (Equal Channel Angular Pressing method, which uses a high degree of deformation to achieve a very fine-grained structure of formed material. Utilization of The ECAP technology enables attainment of required properties of selected materials by using of severe plastic deformation (SPD methods. In the experimental part the influence of the number of passes through forming tool with classical geometry (angle of 90° between channels was studied to achieve maximum hardening (expressed by deformation resistance and achieved value of hardness HV10. Also the metallographic analysis (detection of achieved grain refinement was carried out. From comparison of results achieved at both alloys it can be stated that for given forming by ECAP method the EN AW-8006 alloy is preferable, because higher strength degree was obtained by achieving of very fine grained structure. When using the same method of forming by ECAP method the EN AW-2024 alloy has lower hardening and structure refinement.

Study on elastic-plastic deformation analysis using a cyclic stress-strain curve

International Nuclear Information System (INIS)

Igari, Toshihide; Setoguchi, Katsuya; Yamauchi, Masafumi

1983-01-01

This paper presents the results of the elastic-plastic deformation analysis using a cyclic stress-strain curve with an intention to apply this method for predicting the low-cycle fatigue life. Uniaxial plastic cycling tests were performed on 2 1/4Cr-1Mo steel to investigate the correspondence between the cyclic stress-strain curve and the hysteresis loop, and also to determine what mathematical model should be used for analysis of deformation at stress reversal. Furthermore, a cyclic in-plane bending test was performed on a flat plate to clarify the validity of the cyclic stress-strain curve-based theoretical analysis. The results obtained are as follows: (1) The cyclic stress-strain curve corresponds nearly to the ascending curve of hysteresis loop scaled by a factor of 1/2 for both stress and strain. Therefore, the cyclic stress-strain curve can be determined from the shape of hysteresis loop, for simplicity. (2) To perform the elastic-plastic deformation analysis using the cyclic stress-strain curve is both practical and effective for predicting the cyclic elastic-plastic deformation of structures at the stage of advanced cycles. And Masing model can serve as a suitable mathematical model for such a deformation analysis. (author)

Influence of plastic deformation on low temperature surface hardening of stainless steel by gaseous nitriding

DEFF Research Database (Denmark)

Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... analysis, reflected light microscopy and microhardness indentation. The results demonstrate that a case of expanded austenite develops and that, in particular, the presence of strain-induced martensite in the initial (deformed) microstructure has a large influence on the nitrided zone....

A Brief Overview of a Scale Independent Deformation Theory and Application to Diagnosis of Deformational Status of Solid-State Materials

International Nuclear Information System (INIS)

Yoshida, Sanichiro

2012-01-01

A field theoretical approach to deformation and fracture of solid-state material is outlined, and its application to diagnosis of deformational status of metal specimens is discussed. Being based on a fundamental physical principle known as local symmetry, this approach is intrinsically scale independent, and capable of describing all stages of deformation on the same theoretical foundation. This capability enables us to derive criteria that can be used to diagnose transitions from the elastic to plastic regime, and the plastic to fracturing regime. For practical applications of these criteria, an optical interferometric technique known as electronic speckle-pattern interferometry is proved to be quite powerful; it is able to visualize the criteria as a whole image of the object on a real-time basis without numerical processing. It is demonstrated that this method is able to reveal loading hysteresis as well

Measurement of elasto-plastic deformations by speckle interferometry

Science.gov (United States)

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.

Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

Science.gov (United States)

Rodak, K.; Pawlicki, J.; Tkocz, M.

2012-05-01

The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ- α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

International Nuclear Information System (INIS)

Rodak, K; Pawlicki, J; Tkocz, M

2012-01-01

The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ– α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

Surface flow in severe plastic deformation of metals by sliding

International Nuclear Information System (INIS)

Mahato, A; Yeung, H; Chandrasekar, S; Guo, Y

2014-01-01

An in situ study of flow in severe plastic deformation (SPD) of surfaces by sliding is described. The model system – a hard wedge sliding against a metal surface – is representative of surface conditioning processes typical of manufacturing, and sliding wear. By combining high speed imaging and image analysis, important characteristics of unconstrained plastic flow inherent to this system are highlighted. These characteristics include development of large plastic strains on the surface and in the subsurface by laminar type flow, unusual fluid-like flow with vortex formation and surface folding, and defect and particle generation. Preferred conditions, as well as undesirable regimes, for surface SPD are demarcated. Implications for surface conditioning in manufacturing, modeling of surface deformation and wear are discussed

Remeshing in analysis of large plastic deformations

DEFF Research Database (Denmark)

Pedersen, Thomas Ø

1998-01-01

Very distorted elements in a finite element computation will affect the results in a negative way. In applications where large plastic deformations are present, the mesh often deteriorates so badly, that remeshing is the only option to avoid a breakdown in the numerical computations. In the present...

Compression deformation of WC: atomistic description of hard ceramic material

Science.gov (United States)

Feng, Qing; Song, Xiaoyan; Liu, Xuemei; Liang, Shuhua; Wang, Haibin; Nie, Zuoren

2017-11-01

The deformation characteristics of WC, as a typical hard ceramic material, were studied on the nanoscale using atomistic simulations for both the single-crystal and polycrystalline forms under uniaxial compression. In particular, the effects of crystallographic orientation, grain boundary coordination and grain size on the origin of deformation were investigated. The deformation behavior of the single-crystal and polycrystalline WC both depend strongly on the orientation towards the loading direction. The grain boundaries play a significant role in the deformation coordination and the potential high fracture toughness of the nanocrystalline WC. In contrast to conventional knowledge of ceramics, maximum strength was obtained at a critical grain size corresponding to the turning point from a Hall-Petch to an inverse Hall-Petch relationship. For this the mechanism of the combined effect of dislocation motion within grains and the coordination of stress concentration at the grain boundaries were proposed. The present work has moved forward our understanding of plastic deformability and the possibility of achieving a high strength of nanocrystalline ceramic materials.

Disorientations and work-hardening behaviour during severe plastic deformation

DEFF Research Database (Denmark)

Pantleon, Wolfgang

2012-01-01

Orientation differences develop during plastic deformation even in grains of originally uniform orientation. The evolution of these disorientations is modelled by dislocation dynamics taking into account different storage mechanisms. The predicted average disorientation angles across different ty...... pressure torsion, but also rationalizes the work-hardening behaviour at large plastic strains as well as a saturation of the flow stress....

New constitutive equations to describe infinitesimal elastic-plastic deformations

International Nuclear Information System (INIS)

Boecke, B.; Link, F.; Schneider, G.; Bruhns, O.T.

1983-01-01

A set of constitutive equations is presented to describe infinitesimal elastic-plastic deformations of austenitic steel in the range up to 600 deg C. This model can describe the hardening behaviour in the case of mechanical loading and hardening, and softening behaviour in the case of thermal loading. The loading path can be either monotonic or cyclic. For this purpose, the well-known isotropic hardening model is continually transferred into the kinematic model according to Prager, whereby suitable internal variables are chosen. The occurring process-dependent material functions are to be determined by uniaxial experiments. The hardening function g and the translation function c are determined by means of a linearized stress-strain behaviour in the plastic range, whereby a coupling condition must be taken into account. As a linear hardening process is considered to be too unrealistic, nonlinearity is achieved by introducing a small function w, the determination procedure of which is given. (author)

Probing the Effect of Hydrogen on Elastic Properties and Plastic Deformation in Nickel Using Nanoindentation and Ultrasonic Methods

Science.gov (United States)

Lawrence, S. K.; Somerday, B. P.; Ingraham, M. D.; Bahr, D. F.

2018-04-01

Hydrogen effects on small-volume plasticity and elastic stiffness constants are investigated with nanoindentation of Ni-201 and sonic velocity measurements of bulk Ni single crystals. Elastic modulus of Ni-201, calculated from indentation data, decreases 22% after hydrogen charging. This substantial decrease is independently confirmed by sonic velocity measurements of Ni single crystals; c 44 decreases 20% after hydrogen exposure. Furthermore, clear hydrogen-deformation interactions are observed. The maximum shear stress required to nucleate dislocations in hydrogen-charged Ni-201 is markedly lower than in as-annealed material, driven by hydrogen-reduced shear modulus. Additionally, a larger number of depth excursions are detected prior to general yielding in hydrogen-charged material, suggesting cross-slip restriction. Together, these data reveal a direct correlation between hydrogen-affected elastic properties and plastic deformation in Ni alloys.

Identification of exponent from load-deformation relation for soft materials from impact tests

Science.gov (United States)

Ciornei, F. C.; Alaci, S.; Romanu, I. C.; Ciornei, M. C.; Sopon, G.

2018-01-01

When two bodies are brought into contact, the magnitude of occurring reaction forces increase together with the amplitude of deformations. The load-deformation dependency of two contacting bodies is described by a function having the form F = Cxα . An accurate illustration of this relationship assumes finding the precise coefficient C and exponent α. This representation proved to be very useful in hardness tests, in dynamic systems modelling or in considerations upon the elastic-plastic ratio concerning a Hertzian contact. The classical method for identification of the exponent consists in finding it from quasi-static tests. The drawback of the method is the fact that the accurate estimation of the exponent supposes precise identification of the instant of contact initiation. To overcome this aspect, the following observation is exploited: during an impact process, the dissipated energy is converted into heat released by internal friction in the materials and energy for plastic deformations. The paper is based on the remark that for soft materials the hysteresis curves obtained for a static case are similar to the ones obtained for medium velocities. Furthermore, utilizing the fact that for the restitution phase the load-deformation dependency is elastic, a method for finding the α exponent for compression phase is proposed. The maximum depth of the plastic deformations obtained for a series of collisions, by launching, from different heights, a steel ball in free falling on an immobile prism made of soft material, is evaluated by laser profilometry method. The condition that the area of the hysteresis loop equals the variation of kinetical energy of the ball is imposed and two tests are required for finding the exponent. Five collisions from different launching heights of the ball were taken into account. For all the possible impact-pair cases, the values of the exponent were found and close values were obtained.

The effect of inclination angle on the plastic deformation behavior of bicrystalline silver nanowires with Σ3 asymmetric tilt grain boundaries

Energy Technology Data Exchange (ETDEWEB)

Yuan, Lin, E-mail: yuanlin@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); National Key Laboratory for Precision Hot Processing of Metals, Harbin 150001 (China); Jing, Peng; Shan, Debin; Guo, Bin [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); National Key Laboratory for Precision Hot Processing of Metals, Harbin 150001 (China)

2017-01-15

Atomistic simulations were used to investigate the plastic deformation behavior of bicrystalline silver nanowires with Σ3 asymmetric tilt grain boundaries at 0.1 K. The calculated grain boundary energies of Σ3 asymmetric tilt grain boundaries corresponded well with the energies measured in experiments and predicted by the theoretical description. The Σ3 asymmetric tilt grain boundaries with low inclination angles were composed of a replication of twin boundary segments separated by small ledges. The results demonstrated that the combination effect of Schmid factor and non-Schmid factors could explain dislocations emission into grain 1 only in models with low inclination angles (< 64.76°). At the latter stage of plastic deformation, free surfaces served as additional dislocation sources. Parallelly arranged operative slip systems were the fundamental features of plastic deformation. In addition, a number of stacking faults and multiple stacking faults were formed during plastic deformation. The hindrance of stacking faults to dislocation motion and the interactions between dislocations leaded to the observed strain hardening in nanowires with inclination angles at and above 29.50°. The low stacking fault energy of silver was responsible for the appearance of strain hardening. Dislocations emitted from grain 2 interacted with each other contributing to the observed strain hardening. Grain boundaries were completely eliminated by successive emission of dislocations from grain boundaries in nanowires with an inclination angle of 35.26° and 54.74°. A detailed understanding of the relationship between strength and grain boundary structures as well as specific plastic deformation would push forward the application of nanocrystalline materials and provide insights into the synthesis of nanocrystalline materials with superior strength and ductility.

Mechanisms operating during plastic deformation of metals under concurrent production of cascades and dislocations

DEFF Research Database (Denmark)

Trinkaus, H.; Singh, Bachu Narain

Recent in-reactor tensile tests (IRTs) on pure copper have revealed a deformation behaviour which is significantly different from that observed in post-irradiation tensile tests (PITs). In IRTs, the material deforms uniformly and homogeneously without yield drop and plastic instability as commonly...... observed in PITs. An increase in the pre-yield dose results in an increase in the level of hardening over the whole test periods and a decrease in the uniform elongation suggesting that the materials “remember” the impact of the pre-yield damage level. These features are modelled in terms of the decoration...... and deformation, moving dislocations are decorated by the sweeping of matrix loops. The interaction of dislocations with loops and between loops is discussed as a function of the relevant parameters. On this basis, the kinetics of decoration is treated in terms of fluxes of loops to and reactions with each other...

Parameter studies on the effect of pulse shape on the dynamic plastic deformation of a hexagon

International Nuclear Information System (INIS)

Youngdahl, C.K.

1973-10-01

Results of a parameter study on the dynamic plastic response of a hexagonal subassembly duct subjected to an internal pressure pulse of arbitrary shape are presented. Plastic distortion of the cross section and large-deformation geometric effects that result in redistribution of the internal forces between bending and membrane stresses in the hexagon wall are included in the analytical model. Correlation procedures are established for relating permanent plastic deformation to simple properties of the pressure pulse, for both the small- and large-deformation ranges. Characteristic response times are determined, and the dynamic load factor for large-deformation plastic response is computed

Evolution of oxide nanoparticles during dynamic plastic deformation of ODS steel

DEFF Research Database (Denmark)

Zhang, Zhenbo; Mishin, Oleg; Tao, Nairong

2014-01-01

The microstructure as well as the deformation behavior of oxide nanoparticles has been analyzed in the ferritic ODS steel PM2000 after compression by dynamic plastic deformation (DPD) to different strains. A dislocation cell structure forms after deformation to a strain of 1.0. DPD to a strain of 2...

Magnetic Barkhausen emission for characterizing AISI 1045 steel plastically deformed

Directory of Open Access Journals (Sweden)

Gelaysi Moreno-Vega

2018-04-01

Full Text Available The aim of this work was to correlate parameters of the metallurgical structure such as size and reorganizing the grains, as well as the hardening capacity and the samples distortion of AISI 1045 steel plastically deformed by roll and then fractioned, with average values root means square RMS of a Barkhausen Emission. The analyzed samples were deformed by using forces of 500, 1500 and 2500 N, angular speed of 27, 54, and 110 r.p.m and tool advance of 0,075; 0,125 and 0,25 mm / rev. Then, they underwent a traction process using a CRITM DNS 200 machine, with a load of 200 kN. It was observed that the EMB signal presented an increasing performance in correspondence with the deformation decline and the increasing in tension and the hardness degree. The study of commercial steel AISI 1045 plastically deformed with roller and then pulled with EMB technique, allowed corroborating the potential of this technique as a non-destructive testing.

Plastic deformation of Fortissimo fuel cans

International Nuclear Information System (INIS)

Marbach, G.; Millet, P.; Blanchard, P.

1979-01-01

The study of a great number of standard Fortissimo fuel rods clad in 316 hyper quenched steel shows that the plastic deformation depends linearily on the pressure of the fission gases and on the dose. The irradiation creep module deduced therefrom is between 1 and 2x10 -6 (MPa F atomic displacement) -1 at 450 0 C and increases regularly with the temperature [fr

Neutron-diffraction measurement of the evolution of strain for non-uniform plastic deformation

CERN Document Server

Rogge, R B; Boyce, D

2002-01-01

Neutrons are particularly adept for the validation of modeling predictions of stress and strain. In recent years, there has been a significant effort to model the evolution of both the macroscopic stresses and the intergranular stress during plastic deformation. These have had broad implications with regard to understanding the evolution of residual stress and to diffraction-based measurements of strain. Generally the modeling and associated measurements have been performed for simple uniaxial tension, leaving questions with regard to plastic deformation under multi-axial stress and non-uniform stress. Extensive measurements of the strain profile across a plastic hinge for each of a series of loading and unloading cycles to progressively higher degrees of plastic deformation are presented. These measurements are used to assess multiple-length-scale finite-element modeling (FEM) of the plastic hinge, in which the elements will range in size from single crystallites (as used in successful simulations of uniaxia...

Neutron-diffraction measurement of the evolution of strain for non-uniform plastic deformation

International Nuclear Information System (INIS)

Rogge, R.B.; Dawson, P.R.; Boyce, D.

2002-01-01

Neutrons are particularly adept for the validation of modeling predictions of stress and strain. In recent years, there has been a significant effort to model the evolution of both the macroscopic stresses and the intergranular stress during plastic deformation. These have had broad implications with regard to understanding the evolution of residual stress and to diffraction-based measurements of strain. Generally the modeling and associated measurements have been performed for simple uniaxial tension, leaving questions with regard to plastic deformation under multi-axial stress and non-uniform stress. Extensive measurements of the strain profile across a plastic hinge for each of a series of loading and unloading cycles to progressively higher degrees of plastic deformation are presented. These measurements are used to assess multiple-length-scale finite-element modeling (FEM) of the plastic hinge, in which the elements will range in size from single crystallites (as used in successful simulations of uniaxial tension) to macroscopic elements (as typically used in FEM simulations). (orig.)

Fully plastic crack opening analyses of complex-cracked pipes for Ramberg-Osgood materials

International Nuclear Information System (INIS)

Jeong, Jae Uk; Choi, Jae Boong; Huh, Nam Su; Kim, Yun Jae

2016-01-01

The plastic influence functions for calculating fully plastic Crack opening displacement (COD) of complex-cracked pipes were newly proposed based on systematic 3-dimensional (3-D) elastic-plastic Finite element (FE) analyses using Ramberg-Osgood (R-O) relation, where global bending moment, axial tension and internal pressure are considered separately as a loading condition. Then, crack opening analyses were performed based on GE/EPRI concept by using the new plastic influence functions for complex-cracked pipes made of SA376 TP304 stainless steel, and the predicted CODs were compared with FE results based on deformation plasticity theory of tensile material behavior. From the comparison, the confidence of the proposed fully plastic crack opening solutions for complex-cracked pipes was gained. Therefore, the proposed engineering scheme for COD estimation using the new plastic influence functions can be utilized to estimate leak rate of a complex-cracked pipe for R-O material.

Elastic-plastic deformation of fiber composites with a tetragonal structure

Energy Technology Data Exchange (ETDEWEB)

Makarova, E.IU.; Svistkova, L.A. (Permskii Politekhnicheskii Institut, Perm (USSR))

1991-02-01

Results of numerical solutions are presented for elastic-plastic problems concerning arbitrary loading of unidirectional composites in the transverse plane. The nucleation and evolution of microplastic zones in the matrix and the effect of this process on the macroscopic characteristics of the composite are discussed. Attention is also given to the effect of the fiber shape on the elastic-plastic deformation of the matrix and to deformation paths realized in simple microdeformation processes. The discussion is illustrated by results obtained for a composite consisting of a VT1-0 titanium alloy matrix reinforced by Ti-Mo fibers.

THEORETICAL AND EXPERIMENTAL ASPECTS OF PLASTIC DEFORMATION AND DESTRUCTION OF ROCKS

OpenAIRE

A. V. Zhabko

2018-01-01

The urgency of the problem. The main process in mining is the process of destruction of rocks, so the establishment of laws and criteria for plastic deformation and destruction of rocks is the most important and fundamental object. Purpose of the work. The work is devoted to the establishment of laws of plastic deformation of rocks (solids). Methods of research. Analytical and experimental research methods are widely used in this work. Results. On the basis of the earlier studies, wh...

Effect of preliminary plastic deformation on low temperature strength of carbon steels

International Nuclear Information System (INIS)

Gur'ev, A.V.; Alkhimenkov, T.B.

1979-01-01

Considered is the effect of preliminary plastic deformation on the following low-temperature strength (at -196 deg C) of structural carbon steels at the room temperature. The study of regularities of microheterogenetic deformations by alloy structure elements at room and low temperatures shows that the transition on low -temperature loading is built on the base of inheritance of the general mechanism of plastic deformation, which took place at preliminary deformation; in this effect the ''memory'' of metal to the history of loading is shown. It is established that physical strengthening (cold hardening), received by the metal during preliminary loading at the room temperature is put over the strengthening connected only with decrease of test temperature

Finite element analysis of cylindrical indentation for determining plastic properties of materials in small volumes

International Nuclear Information System (INIS)

Lu, Y Charles; Kurapati, Siva N V R K; Yang Fuqian

2008-01-01

The cylindrical indentation is analysed, using the finite element method, for determining the plastic properties of elastic-plastic materials and the effect of strain hardening. The results are compared with those obtained from spherical indentation, the commonly used technique for measuring plastic properties of materials in small volumes. The analysis shows that the deformation under a cylindrical indenter quickly reaches a fully plastic state and that the size (diameter) of the plastic zone remains constant during further indentation. The indentation load is proportional to the indentation depth at large indentation depth, from which the indentation pressure P m at the onset of yielding can be readily extrapolated. The analysis of cylindrical indentation suggests that it does not need parameters such as impression radius (a) and contact stiffness (S) for determining the plastic behaviour of materials. Thus, the cylindrical indentation can suppress the uncertainties in measuring material properties

Elasto/visco-plastic deformations of thin shells of revolution

International Nuclear Information System (INIS)

Takezono, S.; Akashi, T.

1979-01-01

This paper is concerned with the numerical analysis of large elasto/visco-plastic deformations of this shells of revolution under axi-symmetrical loading with applications to pressure vessels. (orig.)

Characteristic structures and properties of nanostructured metals prepared by plastic deformation

DEFF Research Database (Denmark)

Huang, Xiaoxu

2011-01-01

This chapter focuses on describing the characteristic microstructures of nanostructured metals produced by plastic deformation to ultrahigh strains and their correlation with hardening by annealing and softening by deformation. The results suggest that optimising microstructure and the mechanical...

Repetitive forging (RF) using inclined punches as a new bulk severe plastic deformation method

Energy Technology Data Exchange (ETDEWEB)

Babaei, A. [Department of Mechanical Engineering, University College of Engineering, University of Tehran, Tehran 11155-4563 (Iran, Islamic Republic of); Faraji, G., E-mail: ghfaraji@ut.ac.ir [Department of Mechanical Engineering, University College of Engineering, University of Tehran, Tehran 11155-4563 (Iran, Islamic Republic of); Department of Engineering Design and Manufacture, University of Malaya, 50603 Kuala Lumpur (Malaysia); Mashhadi, M.M. [Department of Mechanical Engineering, University College of Engineering, University of Tehran, Tehran 11155-4563 (Iran, Islamic Republic of); Hamdi, M. [Department of Engineering Design and Manufacture, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2012-12-15

A new bulk severe plastic deformation method based on repetitive forging (RF) using inclined punches is proposed. This process consists of two half cycles. In the first half cycle, a square cross section deforms to parallelogram by forging with two inclined punches, and the parallelogram cross section is forged back to square using two flat punches in the second half cycle. This method was applied to commercially pure copper and significant grain refinement was achieved after four passes of RF. The results showed that significant improvement in the mechanical properties was obtained. Notable increase of yield and ultimate strengths corresponding to 358 MPa and 381 MPa after four passes of RF from the initial values of 121 MPa and 230.5 MPa is detectable. Microhardness increases to about 100 Hv after four passes of RF from the initial value of 53 Hv. Finite element (FE) results illustrate that RF is able to impose extremely high plastic strains to the materials. In the RF process, the processed samples have the same dimensions and geometry as those of the initial sample without any waste material and there is no need for back pressure.

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

Science.gov (United States)

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.

Quantifying Damage Accumulation During Ductile Plastic Deformation Using Synchrotron Radiation

Energy Technology Data Exchange (ETDEWEB)

Suter, Robert M. [Carnegie Mellon Univ., Pittsburgh, PA (United States); Rollett, Anthony D. [Carnegie Mellon Univ., Pittsburgh, PA (United States)

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.

The Effects of Plastic Anisotropy in Warm and Hot Forming of Magnesium Sheet Materials

Science.gov (United States)

Taleff, Eric M.; Antoniswamy, Aravindha R.; Carpenter, Alexander J.; Yavuz, Emre

Mg alloy sheet materials often exhibit plastic anisotropy at room temperature as a result of the limited slip systems available in the HCP lattice combined with a commonly strong basal texture. Less well studied is plastic anisotropy developed at the elevated temperatures associated with warm and hot forming. At these elevated temperatures, particularly above 200°C, the activation of additional slip systems significantly increases ductility. However, plastic anisotropy is also induced at elevated temperatures by a strong crystallographic texture, and it can require an accounting in material constitutive models to achieve accurate forming simulations. The type and degree of anisotropy under these conditions depend on both texture and deformation mechanism. The current understanding of plastic anisotropy in Mg AZ31B and ZEK100 sheet materials at elevated temperatures is reviewed in this article. The recent construction of material forming cases is also reviewed with strategies to account for plastic anisotropy in forming simulations.

Finite element analysis of large elasto-plastic deformation for sealing ring in nuclear pressure vessel

International Nuclear Information System (INIS)

Xiao Xuejian; Chen Ruxin

1995-02-01

Based on the R. Hills incremental virtual power principle and the elasto-plastic constitution equation for large deformation and by considering physical nonlinear, geometric nonlinear and thermal effects, a plane and axisymmetric finite element equation for thermal large elasto-plastic deformation has been established in the Euler description. The corresponding analysis program ATLEPD has been also complied for thermal large elasto-plastic deformation process of O-ring in RPV. The variations of stress, strain, contact specific pressure, mesh deformation and the aspects of spring back in upsetting and spring back process have been also investigated. Numerical results are fairly consistent with experimental ones. (5 figs., 4 tabs.)

Plasticity characteristic obtained by indentation

International Nuclear Information System (INIS)

Mil'man, Yu.V.; Chugunova, S.I.; Goncharova, I.V.

2011-01-01

Methods for determination plasticity characteristic δH in the measurement of hardness and nanohardness are considered. Parameter δH characterizes the plasticity of a material by the part of plastic deformation in the total elastic-plastic deformation. The value of δH is defined for metals with different types of crystal lattice, covalent and partially covalent crystals, intermetallics, metallic glasses and quasicrystals. It is discussed the dependence of the plasticity characteristic δH on structural factors and temperature. Parameter δH allows to analyze and compare the plasticity of materials which are brittle at standard mechanical tests. The combination of hardness H, as the strength characteristic, and the plasticity characteristic δH makes possible the better characterization of mechanical behavior of materials than only the hardness H. The examples of plasticity characteristic δH application are represented.

Micro-Structural Evolution and Size-Effects in Plastically Deformed Single Crystals: Strain Gradient Continuum Modeling

DEFF Research Database (Denmark)

El-Naaman, Salim Abdallah

the macroscopic effects related to strain gradients, most predict smooth micro-structures. The evolution of dislocation micro-structures, during plastic straining of ductile crystalline materials, is highly complex and nonuniform. Published experimental measurements on deformed metal crystals show distinct......An extensive amount of research has been devoted to the development of micro-mechanics based gradient plasticity continuum theories, which are necessary for modeling micron-scale plasticity when large spatial gradients of plastic strain appear. While many models have proven successful in capturing...... strain. It is clear that many challenges are associated with modeling dislocation structures, within a framework based on continuum fields, however, since the strain gradient effects are attributed to the dislocation micro-structure, it is a natural step, in the further development of gradient theories...

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

Science.gov (United States)

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

2018-02-01

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

On the bending of structural materials with plastic anisotropic effect

Science.gov (United States)

Lachugin, D. V.; Pavilaynen, G. V.

2018-05-01

The study of a deformation features of metal alloys which are sensitive to tension or compression loading is an important technical challenge in the design and creation of a new shipbuilding and aircraft constructions. We use a mathematical model for the elastic-plastic bending of such material where SD(strength-different) parameter is taken into account. The problem is solved analytically and numerically. As an example of the material with the SD-effect the steel alloy is considered.

Elastic-plastic cyclic deformation of the TEXTOR 94 modified liner under conditions of heating and plasma disruption

International Nuclear Information System (INIS)

Bohn, F.H.; Czymek, G.; Giesen, B.; Bondarchuk, E.; Doinikov, N.; Kozhukhovskaja, N.; Panin, A.

2001-01-01

The present liner of the TEXTOR 94 tokamak installed inside the vacuum vessel represents the thin toroidal shell that is rested on the vessel inner surface. In order to integrate the dynamic ergodic divertor into the tokamak the liner design has been drastically changed. The 120 deg. sector of the liner shell facing the ergodic coils system is removed and some additional holes in the liner are provisioned. This demands a new liner supporting system allowing for the liner thermal expansion and taking the electromagnetic load occurring in the liner during plasma disruption. The cyclic elasto-plastic deformations of the liner caused by the electromagnetic forces and temperature rise have been studied. It is shown that the local plastic deformations occur in the liner elements after the first heating and electromagnetic loading. The most thermal stresses take place in the reinforcing structures around the holes because of the thermal expansion difference of the inconel shell and the steel reinforcements. These stresses are coupled with the bending stress due to the electromagnetic loading. Subsequent repetitive loading does not lead to any significant increment of the plastic deformation. After the materials' hardening the structure cyclically works mostly in the elastic range

Estimation of dislocation concentration in plastically deformed Al-Li based alloy by positron annihilation

International Nuclear Information System (INIS)

Abdelrahman, M.

1997-01-01

Measurements of positron annihilation mean lifetime τ have been performed on eight different specimens of Al-Li based alloy plastically deformed at room temperature up to 40% thickness reduction. This measurement shows clearly positron trapping by dislocations. The positron lifetime τ exhibits a saturation for deformations larger than (15%) thickness reduction. The fitted lifetime varies from (183±2 ps) for annealed sample to (205±2 ps) for the dislocation saturated value. Using a trapping model, the data yield the values of μ=3.83x10 -8 cm 3 s -1 for the specific trapping rate and σ=3.58x10 -15 cm 2 for the trapping cross section, some what lower than those for plastically deformed Al single crystals. The value obtained for Δτ, the increase in lifetime of positrons trapped at dislocations in plastically deformed Al-Li based alloy sample over annihilation in the annealed sample, is 22 ps. This is about 40% of the lifetime increase for the case of positrons trapped at dislocations in plastically deformed Al single crystals. Dislocation densities at different thickness reduction have been estimated. (author)

Influence of plastic deformation on seismic response of piping

International Nuclear Information System (INIS)

Yao Yanping; Chen Yong; Lu Mingwan

2000-01-01

On the basis of a brief summary of linear elastic seismic analysis methods, the importance for consideration of plastic deformation during the dynamic response analysis of piping system is indicated. The present methods of considering plasticity and the disadvantages of these methods are discussed. And the authors point out that in order to reduce the conservatism of present codes and to put forward appropriate and realistic piping seismic design methods, the key is to understand the plastic dynamic failure mode for piping under seismic excitation and to calculate the inelastic energy dissipation. The analysis and evaluation are applicable to nuclear piping systems

Formation of disorientations in dislocation structures during plastic deformation

DEFF Research Database (Denmark)

Pantleon, W.

2002-01-01

Disorientations developing during plastic deformation in dislocation structures are investigated. Based on expected mechanisms for the formation of different types of dislocation boundaries (statistical trapping of dislocations or differently activated slip systems) the formation of the disorient...

Mesoscopic approach to modeling elastic-plastic polycrystalline material behaviour

International Nuclear Information System (INIS)

Kovac, M.; Cizelj, L.

2001-01-01

Extreme loadings during severe accident conditions might cause failure or rupture of the pressure boundary of a reactor coolant system. Reliable estimation of the extreme deformations can be crucial to determine the consequences of such an accident. One of important drawbacks of classical continuum mechanics is idealization of inhomogenous microstructure of materials. This paper discusses the mesoscopic approach to modeling the elastic-plastic behavior of a polycrystalline material. The main idea is to divide the continuum (e.g., polycrystalline aggregate) into a set of sub-continua (grains). The overall properties of the polycrystalline aggregate are therefore determined by the number of grains in the aggregate and properties of randomly shaped and oriented grains. The random grain structure is modeled with Voronoi tessellation and random orientations of crystal lattices are assumed. The elastic behavior of monocrystal grains is assumed to be anisotropic. Crystal plasticity is used to describe plastic response of monocrystal grains. Finite element method is used to obtain numerical solutions of strain and stress fields. The analysis is limited to two-dimensional models.(author)

Plastic incompatibility stresses and stored elastic energy in plastically deformed copper

Energy Technology Data Exchange (ETDEWEB)

Baczmanski, A. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland)], E-mail: baczman@ftj.agh.edu.pl; Hfaiedh, N.; Francois, M. [LASMIS, Universite de Technologie de Troyes, 11 rue Marie Curie, B.P. 2060, 10010 Troyes (France); Wierzbanowski, K. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland)

2009-02-15

The X-ray diffraction method and theoretical model of elastoplastic deformation were used to examine the residual stresses in polycrystalline copper. To this end, the {l_brace}2 2 0{r_brace} strain pole figures were determined for samples subjected to different magnitudes of tensile deformation. Using diffraction data and the self-consistent model, the tensor of plastic incompatibility stress was found for each orientation of a polycrystalline grain. Crystallographic textures, macroscopic and second-order residual stresses were considered in the analysis. As a result, the distributions of elastic stored energy and von Mises equivalent stress were presented in Euler space and correlated with the preferred orientations of grains. Moreover, using the model prediction, the variation of the critical resolved shear stress with grain orientation was determined.

Elasto-viscoplastic self consistent modeling of the ambient temperature plastic behavior of periclase deformed up to 5.4 GPa

Science.gov (United States)

Lin, F.; Hilairet, N.; Raterron, P.; Addad, A.; Immoor, J.; Marquardt, H.; Tomé, C. N.; Miyagi, L.; Merkel, S.

2017-11-01

Anisotropy has a crucial effect on the mechanical response of polycrystalline materials. Polycrystal anisotropy is a consequence of single crystal anisotropy and texture (crystallographic preferred orientation) development, which can result from plastic deformation by dislocation glide. The plastic behavior of polycrystals is different under varying hydrostatic pressure conditions, and understanding the effect of hydrostatic pressure on plasticity is of general interest. Moreover, in the case of geological materials, it is useful for understanding material behavior in the deep earth and for the interpretation of seismic data. Periclase is a good material to test because of its simple and stable crystal structure (B1), and it is of interest to geosciences, as (Mg,Fe)O is the second most abundant phase in Earth's lower mantle. In this study, a polycrystalline sintered sample of periclase is deformed at ˜5.4 GPa and ambient temperature, to a total strain of 37% at average strain rates of 2.26 × 10-5/s and 4.30 × 10-5/s. Lattice strains and textures in the polycrystalline sample are recorded using in-situ synchrotron x-ray diffraction and are modeled with Elasto-Viscoplastic Self Consistent (EVPSC) methods. Parameters such as critical resolved shear stress (CRSS) for the various slip systems, strain hardening, initial grain shape, and the strength of the grain-neighborhood interaction are tested in order to optimize the simulation. At the beginning of deformation, a transient maximum occurs in lattice strains, then lattice strains relax to a "steady-state" value, which, we believe, corresponds to the true flow strength of periclase. The "steady state" CRSS of the {" separators="| 110 } ⟨" separators="| 1 1 ¯ 0 ⟩ slip system is 1.2 GPa, while modeling the transient maximum requires a CRSS of 2.2 GPa. Interpretation of the overall experimental data via modeling indicates dominant {" separators="| 110 } ⟨" separators="| 1 1 ¯ 0 ⟩ slip with initial strain

High Rate Plastic Deformation and Failure of Tungsten-Sintered Metals

National Research Council Canada - National Science Library

Bjerke, Todd

2004-01-01

The competition between plastic deformation and brittle fracture during high rate loading of a tungsten-sintered metal is examined through impact experiments, post-experiment microscopy, and numerical simulation...

Boron effect on stainless steel plasticity under hot deformation

International Nuclear Information System (INIS)

Bulat, S.I.; Kardonov, B.A.; Sorokina, N.A.

1978-01-01

The effect of boron on plasticity of stainless steels at temperatures of hot deformation has been studied at three levels of alloying, i.e. 0-0.01% (micro-alloying or modifying), 0.01-0.02% (low alloying) and 0.02-2.0% (high alloying). Introduction of 0.001-0.005% of boron increases hot plasticity of both low and high carbon stainless steels due to decrease in grain size and strengthening of grain boundaries. Microalloying by boron has a positive effect at temperatures below 1200-1220 deg C. At higher temperatures, particularly when its content exceeds 0.008%, boron deteriorates plasticity by increasing the size of grains and weakening their boundaries. 0.1-2% boron strengthen the stainless steel and dectease its plasticity

Adhesion along metal-polymer interfaces during plastic deformation

NARCIS (Netherlands)

van Tijum, R.; Vellinga, W. P.; De Hosson, J. Th. M.

In this paper a numerical study is presented that concentrates on the influence of the interface roughness that develops during plastic deformation of a metal, on the work of adhesion and on the change of interface energy upon contact with a glassy polymer. The polymer coating is described with a

Structural conditions of maximal plasticity of two-phase metal materials

International Nuclear Information System (INIS)

Movchan, B.A.

1975-01-01

Analysis is given of experimental values of the strength and plasticity of iron- and tungsten-based two-phase materials with the regulated amount of the second phase and the grain size. Specimens in the form of a 120 mm x 200 mm sheet with a thickness of 0.8-1.2 mm are prepared by means of the electron beam evaporation technique and subsequent condensation of the materials on a preheated support. The variable content of the second phase along the sheet in the range 0.5 volume per cent and more than a 10-fold change in the grain size of the metallic matrix are attained by a simultaneous evaporation of pure metal (99.98 per cent) and nonlmetallic material-niobium carbide or zirconium dioxide ZrO 2 -from two separate sources. The content of arbitrarily distributed spherical particles of the second phase corresponding to a maximum of the plasticity depends only on the structural parameter - the d/D ratio. The absolute falue of the plasticity and its dependence on the temperature is a complex function of many variables - mechanical properties of particles and the matrix, peculiarities of interphase interaction on the boundary particle - matrix, the size of particles, the rate of plastic deformation and relaxation processes

Magnetic hysteresis properties of nanocrystalline (Nd,Ho)-(Fe,Co)-Balloy after melt spinning, severe plastic deformation and subsequentheat treatment

Czech Academy of Sciences Publication Activity Database

Tereshina, I. S.; Pelevin, I.A.; Tereshina, Evgeniya; Burkhanov, G.S.; Rogacki, K.; Miller, M.; Kudrevatykh, N. V.; Markin, P.E.; Volegov, A.S.; Grechishkin, R.M.; Dobatkin, S.V.; Schultz, L.

2016-01-01

Roč. 681, Oct (2016), s. 555-560 ISSN 0925-8388 Institutional support: RVO:68378271 Keywords : high coercive magnetic materials * multistage treatment * melt spinning * severe plastic deformation * heat treatment Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.133, year: 2016

Predicting Hot Deformation of AA5182 Sheet

Science.gov (United States)

Lee, John T.; Carpenter, Alexander J.; Jodlowski, Jakub P.; Taleff, Eric M.

Aluminum 5000-series alloy sheet materials exhibit substantial ductilities at hot and warm temperatures, even when grain size is not particularly fine. The relatively high strain-rate sensitivity exhibited by these non-superplastic materials, when deforming under solute-drag creep, is a primary contributor to large tensile ductilities. This active deformation mechanism influences both plastic flow and microstructure evolution across conditions of interest for hot- and warm-forming. Data are presented from uniaxial tensile and biaxial bulge tests of AA5182 sheet material at elevated temperatures. These data are used to construct a material constitutive model for plastic flow, which is applied in finite-element-method (FEM) simulations of plastic deformation under multiaxial stress states. Simulation results are directly compared against experimental data to explore the usefulness of this constitutive model. The effects of temperature and stress state on plastic response and microstructure evolution are discussed.

Transformation kinetics of selected steel grades after plastic deformation

Directory of Open Access Journals (Sweden)

R. Kawulok

2016-07-01

Full Text Available The aim of this article was to assess the impact of previous plastic deformation on the kinetics of transformations of four selected steels. The research was conducted with use of the universal plastometer GLEEBLE 3800, when Continuous Cooling Transformation (CCT and Deformation Continuous Cooling Transformation (DCCT diagrams of selected steels were constructed on the basis of dilatometric tests. The research confirmed that the strain accelerates the particularly the transformations controlled by diffusion. Bainitic transformation was accelerated in three of the four steels. In the case of martensitic transformation the effect of the previous deformation was relatively small, but with clearly discernible trend.

Electromigration-induced plastic deformation in passivated metal lines

Science.gov (United States)

Valek, B. C.; Bravman, J. C.; Tamura, N.; MacDowell, A. A.; Celestre, R. S.; Padmore, H. A.; Spolenak, R.; Brown, W. L.; Batterman, B. W.; Patel, J. R.

2002-11-01

We have used scanning white beam x-ray microdiffraction to study microstructural evolution during an in situ electromigration experiment on a passivated Al(Cu) test line. The data show plastic deformation and grain rotations occurring under the influence of electromigration, seen as broadening, movement, and splitting of reflections diffracted from individual metal grains. We believe this deformation is due to localized shear stresses that arise due to the inhomogeneous transfer of metal along the line. Deviatoric stress measurements show changes in the components of stress within the line, including relaxation of stress when current is removed.

A self-consistent anisotropic approach for the simulation of plastic deformation and texture development of polycrystals: Application to zirconium alloys

International Nuclear Information System (INIS)

Lebensohn, R.A.; Tome, C.N.

1993-01-01

The authors present in this work a visco-plastic self-consistent (VPSC) anisotropic approach for modeling the plastic deformation of polycrystals, together with a thorough discussion of the assumptions involved and the range of application of such approach. They use the VPSC model for predicting texture development during rolling and axisymmetric deformation of zirconium alloys, and to calculate the yield locus and the Lankford coefficient of rolled Zircaloy sheet. They compare the results with experimental data and find that they are in good agreement with the available experimental evidence. They also compare the VPSC prediction with the ones of a Full Constraints approach and observe that they differ both quantitatively and qualitatively: according with the predictions of the VPSC scheme, deformation is accommodated mostly by the soft systems, the twinning activity is much lower, and fewer systems are active, in average, per grain. These results are a consequence of having accounted for the grain interaction with its surroundings, which is a crucial aspect when modeling plastically anisotropic materials

Evaluation of material's state during deformation process by means of thermographic measurement

Czech Academy of Sciences Publication Activity Database

Žďárský, M.; Valach, Jaroslav; Kytýř, D.

2012-01-01

Roč. 17, č. 10 (2012), s. 102-107 ISSN 1435-4934. [Quantitative infrared thermotheraphy /11./. Naples, 11.06.2012-14.06.2012] R&D Projects: GA ČR(CZ) GA103/09/2101 Institutional support: RVO:68378297 Keywords : thermography * ductile crack * plastic deformation Subject RIV: JL - Materials Fatigue, Friction Mechanics www.ndt.net/?id=13389

EBSD analysis of plastic deformation of copper foils by flexible pad laser shock forming

Energy Technology Data Exchange (ETDEWEB)

Nagarajan, Balasubramanian; Castagne, Sylvie [Nanyang Technological University, SIMTech-NTU Joint Laboratory (Precision Machining), Singapore (Singapore); Nanyang Technological University, School of Mechanical and Aerospace Engineering, Singapore (Singapore); Wang, Zhongke; Zheng, H.Y. [Nanyang Technological University, SIMTech-NTU Joint Laboratory (Precision Machining), Singapore (Singapore); Singapore Institute of Manufacturing Technology, Machining Technology Group, Singapore (Singapore)

2015-11-15

Flexible pad laser shock forming (FPLSF) is a new mold-free microforming process that induces high-strain-rate plastic deformation in thin metallic foils using laser-induced shock pressure and a hyperelastic flexible pad. This paper studies the plastic deformation behavior of copper foils formed through FPLSF by investigating surface hardness and microstructure. The microstructure of the foil surface before and after FPLSF is analyzed by electron backscatter diffraction technique using grain size distribution and grain boundary misorientation angle as analysis parameters. The surface hardness of the craters experienced a significant improvement after FPLSF; the top crater surface being harder than the bottom surface. The microstructure of the copper foil surface after FPLSF was found to be dominated by grain elongation, along with minor occurrences of subgrain formation, grain refinement, and high dislocation density regions. The results indicate that the prominent plastic deformation mechanism in FPLSF is strain hardening behavior rather than the typical adiabatic softening effect known to be occurring at high-strain-rates for processes such as electromagnetic forming, explosive forming, and laser shock forming. This significant difference in FPLSF is attributed to the concurrent reduction in plastic strain, strain rate, and the inertia effects, resulting from the FPLSF process configuration. Correspondingly, different deformation behaviors are experienced at top and bottom surfaces of the deformation craters, inducing the change in surface hardness and microstructure profiles. (orig.)

Microstructure and properties of ceramics and composites joined by plastic deformation.

Energy Technology Data Exchange (ETDEWEB)

Goretta, K. C.; Singh, D.; Chen, N.; Gutierrez-Mora, F.; Lorenzo-Martin, M. de la, Cinta; Dominguez-Rodriguez, A.; Routbort, J. L.; Energy Systems; Univ. of Seville

2008-12-01

A review is presented of the design of suitable materials systems for joining by high-temperature plastic deformation, details of the joining techniques, microstructures and properties of the resulting composite bodies, and prospects and limitation for this type of joining technology. Joining parameters and resulting forms are discussed for Al{sub 2}O{sub 3}/mullite particulate composites, Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} particulate/Al{sub 2}O{sub 3} particulate and whisker-reinforced composites, hydroxyapatite bioceramics, La{sub 0.85}Sr{sub 0.15}MnO{sub 3} electronic ceramics, MgF{sub 2} optical ceramics, and Ni{sub 3}Al intermetallics. Results are contrasted with those obtained by other methods of joining brittle, high-temperature materials, with special focus on durability and mechanical properties.

Microstructure and properties of ceramics and composites joined by plastic deformation

Energy Technology Data Exchange (ETDEWEB)

Goretta, K.C. [Argonne National Laboratory, Argonne, IL 60439-4838 (United States)], E-mail: ken.goretta@aoard.af.mil; Singh, D.; Chen Nan [Argonne National Laboratory, Argonne, IL 60439-4838 (United States); Gutierrez-Mora, F.; Cinta Lorenzo-Martin, M. de la [Argonne National Laboratory, Argonne, IL 60439-4838 (United States); University of Seville, Seville 41080 (Spain); Dominguez-Rodriguez, A. [University of Seville, Seville 41080 (Spain); Routbort, J.L. [Argonne National Laboratory, Argonne, IL 60439-4838 (United States)

2008-12-20

A review is presented of the design of suitable materials systems for joining by high-temperature plastic deformation, details of the joining techniques, microstructures and properties of the resulting composite bodies, and prospects and limitation for this type of joining technology. Joining parameters and resulting forms are discussed for Al{sub 2}O{sub 3}/mullite particulate composites, Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} particulate/Al{sub 2}O{sub 3} particulate and whisker-reinforced composites, hydroxyapatite bioceramics, La{sub 0.85}Sr{sub 0.15}MnO{sub 3} electronic ceramics, MgF{sub 2} optical ceramics, and Ni{sub 3}Al intermetallics. Results are contrasted with those obtained by other methods of joining brittle, high-temperature materials, with special focus on durability and mechanical properties.

ELASTO-PLASTIC DEFORMATION OF COMPOSITE POWDERS WITH LAYERED CARBON AND CARBIDE-FORMING ELEMENT COATING

Directory of Open Access Journals (Sweden)

V. N. Kovalevsky

2012-01-01

Full Text Available Coating structure formation under magnetron spraying of titanium and carbon cathodes and combined cathodes, namely cobalt (EP 131 – nickel, tungsten – carbon have been investigated under conditions of carbide separate synthesis within the temperature range of 650–1200 °C. Usage of cobalt and nickel particles as matrix material leads to their rapid thermal expansion under heating during sintering process in the dilatometer. Subsequent plastic deformation of sintered samples provides obtaining a composite powder material that is a composite with framing structure of cobalt, titanium and tungsten carbides in the coatings.

Electron paramagnetic resonance of intrinsic point defects in GaAs following plastic deformation

International Nuclear Information System (INIS)

Benakki-Stiet, S.

1988-01-01

Defects generated in GaAs by a plastic deformation were studied to see if these defects, particularly anionic antisites associated with the deep donor EL2, were the same as those presented in the raw growth material, or the same as those which can be created in a high concentration by electron or neutron irradiation. Results show that there are different types of anionic antisites, so the subset associated with EL2 was identified. The apparent correlation between EL2 and dislocation density is discussed [fr

Void formation by annealing of neutron-irradiated plastically deformed molybdenum

International Nuclear Information System (INIS)

Petersen, K.; Nielsen, B.; Thrane, N.

1976-01-01

The positron annihilation technique has been used in order to study the influence of plastic deformation on the formation and growth of voids in neutron irradiated molybdenum single crystals treated by isochronal annealing. Samples were prepared in three ways: deformed 12-19% before irradiation, deformed 12-19% after irradiation, and - for reference purposes -non-deformed. In addition a polycrystalline sample was prepared in order to study the influence of the grain boundaries. All samples were irradiated at 60 0 C with a flux of 2.5 x 10 18 fast neutrons/cm 2 . After irradiation the samples were subjected to isochronal annealing. It was found that deformation before irradiation probably enhanced the formation of voids slightly. Deformation after irradiation strongly reduced the void formation. The presence of grain boundaries in the polycrystalline sample had a reducing influence on the growth of voids. (author)

Grain refinement through severe plastic deformation (SPD) processing

International Nuclear Information System (INIS)

Izairi, N.; Vevecka - Priftaj, A.

2012-01-01

There is considerable current interest in processing metallic samples through procedures involving the imposition of severe plastic deformation (SPD). These procedures lead to very significant grain refinement to the submicrometer or even the nanometer level, resulting in advanced physical properties. Among various SPD processes, Equal Channel Angular Pressing, High pressure Torsion and Accumulated Roll Bonding have been widely used for many metals and alloys. In the present work, we present an overview of the most used methods of SPD for grain refinement and the production of bulk nano structured materials with enhancement in their mechanical and functional properties. In order to examine the potential for using ECAP to refine the grain size and improve the mechanical properties, two commercial 5754 Al alloy and AA 3004 , were selected for study. Processing by ECAP gives a reduction in the grain size and an increase in the microhardness. (Author)

Electrical conduction along dislocations in plastically deformed GaN

Energy Technology Data Exchange (ETDEWEB)

Kamimura, Y; Yokoyama, T; Oiwa, H; Edagawa, K [Institute of Industrial Science, the University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Yonenaga, I, E-mail: yasushi@iis.u-tokyo.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan)

2009-07-15

Electrical conduction along dislocations in plastically deformed n-GaN single crystals has been investigated by scanning spread resistance microscopy (SSRM). In the SSRM images, many conductive spots have been observed, which correspond to electrical conduction along the dislocations introduced by deformation. Here, the introduced dislocations are b=(a/3)<1overline 210> edge dislocations parallel to the [0001] direction. The current values at the spots normalized to the background current value are larger than 100. Previous works have shown that grown-in edge dislocations in GaN are nonconductive. The high conductivity of the deformation-introduced edge dislocations in the present work suggests that the conductivity depends sensitively on the dislocation core structure.

Plasticity characteristic obtained by indentation

International Nuclear Information System (INIS)

Milman, Yu V

2008-01-01

A dimensionless parameter δ H = ε p /ε t (where ε p and ε t are the average values of plastic and total deformation of material on the contact area indenter-specimen) may be used as the plasticity characteristic of materials, which made it possible to characterize the plasticity of materials that are brittle in standard mechanical tests. δ H may be calculated from the values of microhardness HM, Young's modulus E and Poisson's ratio ν. In instrumented indentation the plasticity characteristic δ A = A p /A t (A p and A t are the work of plastic and total deformation during indentation) may be calculated. δ A ∼ δ H for materials with δ H > 0.5, i.e. for all metals and the majority of ceramic materials. In this case, the theoretical equation δ A ∼ δ H = 1-10.2 · (1 - ν - 2ν 2 )(HM/E) is satisfied in experiments with the Berkovich indenter. The influence of the temperature and structural parameters (dislocation density and grain size including nanostructured materials) on δ H is discussed

Tribological effects of polymer surface modification through plastic

Indian Academy of Sciences (India)

Tribological effects of polymer surface modification through plastic deformation. K O Low K J Wong ... In this regard, a surface modification technique through plastic deformation has been implemented. ... Bulletin of Materials Science | News.

Anisotropic plastic deformation by viscous flow in ion tracks

NARCIS (Netherlands)

van Dillen, T; Polman, A; Onck, PR; van der Giessen, E

2005-01-01

A model describing the origin of ion beam-induced anisotropic plastic deformation is derived and discussed. It is based on a viscoelastic thermal spike model for viscous flow in single ion tracks derived by Trinkaus and Ryazanov. Deviatoric (shear) stresses, brought about by the rapid thermal

Assessment of fatigue crack length via plastic deformation in compact tension specimens using magnetic Barkhausen noise

International Nuclear Information System (INIS)

Reyes-Rodriguez, F. de los; Diego-Velasco, G. de; Capo-Sanchez, J.; Franco-Fidalgo, E.

2013-01-01

In this paper the influence of different parameters on crack length is determined via plastic deformation using magnetic Barkhausen noise; the compact specimens steel used in this study were 12Cr1MoV and 11Cr1Mo, which are used for steam transportation on power plants. The main objective of this paper is to determine the crack length and its incubation time using magnetic Barkhausen noise, which lets to improve the pre-cracking process prior creep crack growth rate test simulating the real conditions of high pressure and temperature of main steam lines. Results showed that mean root square and maximum pick of voltage decrease with plastic deformation for each steel analyzed in this work, on the other hand, with the increasing of plastic deformation, a logic relationship between plastic deformation and spectrum density is observed for mid frequencies values, as well as, a variation of the amplitude, width and shape of the Barkhausen signal envelope. (Author)

Low temperature uniform plastic deformation of metallic glasses during elastic iteration

International Nuclear Information System (INIS)

Fujita, Takeshi; Wang Zheng; Liu Yanhui; Sheng, Howard; Wang Weihua; Chen Mingwei

2012-01-01

Molecular dynamics simulations and dynamic mechanical analysis experiments were employed to investigate the mechanical behavior of metallic glasses subjected to iteration deformation in a nominally elastic region. It was found that cyclic deformation leads to the formation of irreversible shear transformation zones (STZs) and a permanent uniform strain. The initiation of STZs is directly correlated with the atomic heterogeneity of the metallic glass and the accumulated permanent strain has a linear relation with the number of STZs. This study reveals a new deformation mode and offers insights into the atomic mechanisms of STZ formation and low temperature uniform plastic deformation of metallic glasses.

Oxide dispersion-strengthened steel PM2000 after dynamic plastic deformation: nanostructure and annealing behaviour

DEFF Research Database (Denmark)

Zhang, Zhenbo; Tao, N. R.; Mishin, Oleg V.

2016-01-01

The microstructure, texture and mechanical properties have been studied in PM2000 compressed via dynamic plastic deformation to a strain of 2.1. It is found that dynamic plastic deformation results in a duplex 〈111〉 + 〈100〉 fibre texture and refines the initial microstructure by nanoscale lamellae...... in the deformed microstructure. This reduction is more pronounced in the 〈111〉-oriented regions. Orientation-dependent recrystallisation takes place in the recovered microstructure, leading to strengthening of the 〈111〉 fibre texture component at the expense of the 〈100〉 fibre texture component....

Effect of hydrostatic pressure on the deformation behavior of maraging and HY-80 steels and its implications for plasticity theory

International Nuclear Information System (INIS)

Spitzig, W.A.; Sober, R.J.; Richmond, O.

1976-01-01

Earlier results showed that the difference between the tensile and compressive strengths of tempered martensites is primarily a manifestation of the general pressure dependence of flow stress in these materials. However, the same results also showed that the volume expansion after deformation was much smaller than that predicted by the normality flow rule of plasticity theory for materials with such pressure dependence. Additional results now obtained on maraging and HY-80 steels support these conclusions. The results for all these materials exhibit a strong, but not perfect, correlation between pressure dependence, yield stress, and volume expansion. The volume expansion, however, which is believed to result primarily from the generation of new dislocations, is very small and does not appear to be essential to the pressure dependence. Most of the pressure dependence, the portion responsible for the discrepancy with the normality flow rule, may be an effect on dislocation motion. The results suggest that an appropriate plasticity model would be one in which the octahedral shear yield stress is linearly dependent on the mean pressure, but the volume change is negligible in violation of the normality flow rule. Such a model has been proposed previously for the plastic deformation of soils. However, unlike that model, the present theory includes strain hardening. 17 fig

Sub-micron indent induced plastic deformation in copper and irradiated steel

International Nuclear Information System (INIS)

Robertson, Ch.

1998-09-01

In this work we aim to study the indent induced plastic deformation. For this purpose, we have developed a new approach, whereby the indentation curves provides the mechanical behaviour, while the deformation mechanisms are observed thanks to Transmission Electron Microscopy (TEM). In order to better understand how an indent induced dislocation microstructure forms, numerical modeling of the indentation process at the scale of discrete dislocations has been worked out as well. Validation of this modeling has been performed through direct comparison of the computed microstructures with TEM micrographs of actual indents in pure Cu [001]. Irradiation induced modifications of mechanical behaviour of ion irradiated 316L have been investigated, thanks to the mentioned approach. An important hardening effect was reported from indentation data (about 50%), on helium irradiated 316L steel. TEM observations of the damage zone clearly show that this behaviour is associated with the presence of He bubbles. TEM observations of the indent induced plastic zone also showed that the extent of the plastic zone is strongly correlated with hardness, that is to say: harder materials gets a smaller plastic zone. These results thus clearly established that the selected procedure can reveal any irradiation induced hardening in sub-micron thick ion irradiated layers. The behaviour of krypton irradiated 316L steel is somewhat more puzzling. In one hand indeed, a strong correlation between the defect cluster size and densities on the irradiation temperature is observed in the 350 deg C -600 deg C range, thanks to TEM observations of the damage zone. On the other hand, irradiation induced hardening reported from indentation data is relatively small (about 10%) and shows no dependence upon the irradiation temperature (within the mentioned range). In addition, it has been shown that the reported hardening vanishes following appropriate post-irradiation annealing, although most of the TEM

Scratch deformation behavior of thermoplastic materials with significant differences in ductility

International Nuclear Information System (INIS)

Hadal, R.S.; Misra, R.D.K.

2005-01-01

A comparative study of the scratch deformation behavior of neat ethylene-propylene copolymers and polypropylene with significant differences in ductility is made by combining morphological examination by electron microscopy and scratch deformation parameters by atomic force microscopy. Also, the deformation behavior during scratch tests is examined for their respective long and short chain polymers. The ability of polymeric materials to resist scratch deformation under identical scratch test conditions follows the sequence (from maximum resistance to minimum resistance): short chain polypropylene > long chain polypropylene > short chain ethylene-propylene > long chain ethylene-propylene. The scratch tracks in ethylene-propylene copolymers were characterized by a consecutive parabolic pattern containing voids, while polypropylenes exhibited zig-zag periodic scratch tracks. The greater plastic flow in ethylene-propylene copolymers is encouraged by the high ductility of the copolymer and the ability to nucleate microvoids. The quasi-static periodic scratch tracks are a consequence of sequential accumulation and release of tangential force and represents the stick-slip process. The susceptibility to scratch deformation is discussed in terms of modulus, elastic recovery, scratch hardness, and entanglement density of polymeric materials. A higher effective entanglement density and percentage crystallinity of short chain polymers is helpful in enhancing scratch resistance as compared to their respective long chain polymers

Effect of grain refinement by severe plastic deformation on the next-neighbor misorientation distribution

International Nuclear Information System (INIS)

Toth, L.S.; Beausir, B.; Gu, C.F.; Estrin, Y.; Scheerbaum, N.; Davies, C.H.J.

2010-01-01

Next-neighbor misorientation distributions (NNMD) in severely deformed polycrystalline materials are commonly measured by orientation imaging. A procedure is proposed which enables the separation of NNMD of ultrafine-grained materials into two parts: the distribution of misorientations between newly emerged grains within the original ('parent') grain interior ('internal daughter grains') and the distribution of misorientations between grains adjacent to an original grain boundary on its opposite sides ('grain boundary daughter grains'). The procedure is based on electron backscatter diffraction orientation map analyses carried out on different planes of deformed samples considering the evolution of the grain size and shape during severe plastic deformation. It was applied to copper processed by up to three passes of equal-channel angular pressing. A characteristic feature of the measured NNMD is the occurrence of a double peak, which is clearly due to the differences between the NNMD of the two distinct populations of new grains defined above. The peak at low angles represents mainly the continual grain subdivision process in the interior of a parent grain (and is associated with internal daughter grains), while the peak at large angles is due to the high angle misorientations of the grain boundary daughter grains.

Simplified method for elastic plastic analysis of material presenting bilinear kinematic hardening

International Nuclear Information System (INIS)

Roche, R.

1983-12-01

A simplified method for elastic plastic analysis is presented. Material behavior is assumed to be elastic plastic with bilinear kinematic hardening. The proposed method give a strain-stress field fullfilling material constitutive equations, equations of equilibrium and continuity conditions. This strain-stress is obtained through two linear computations. The first one is the conventional elastic analysis of the body submitted to the applied load. The second one use tangent matrix (tangent Young's modulus and Poisson's ratio) for the determination of an additional stress due to imposed initial strain. Such a method suits finite elements computer codes, the most useful result being plastic strains resulting from the applied loading (load control or deformation control). Obviously, there is not unique solution, for stress-strain field is not depending only of the applied load, but of the load history. Therefore, less pessimistic solutions can be got by one or two additional linear computations [fr

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

Science.gov (United States)

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} 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.

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

Science.gov (United States)

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

2018-01-23

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

Evaluation of impacts of stress triaxiality on plastic deformability of RAFM steel using various types of tensile specimen

Energy Technology Data Exchange (ETDEWEB)

Kato, Taichiro, E-mail: kato.taichiro@jaea.go.jp [Japan Atomic Energy Agency, 2-166, Obuchi-omotedate, Rokkasho, Aomori 039-3212 (Japan); Ohata, Mitsuru [Osaka University, 2-1, Yamada-Oka, Suita, Osaka 565-0871 (Japan); Nogami, Shuhei [Tohoku University, 6-6-01-2, Aramaki-aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Tanigawa, Hiroyasu [Japan Atomic Energy Agency, 2-166, Obuchi-omotedate, Rokkasho, Aomori 039-3212 (Japan)

2016-11-01

Highlights: • The fracture ductility is lower as the stress triaxiality is higher. • Voids of the interrupted RB1 specimen were observed along grain boundaries and expanded parallel to the tensile axis. • Voids of interrupted R0.2 specimen were rounded shape than those of RB1. • The fracture surface of specimens were observed the elongated and the equiaxed dimples. • The decrease of plastic deformability of the notched specimen was caused by the process of voids formation and crack growth due to the effect of plastic constraint of the notch. - Abstract: A case study on a fusion blanket design such as DEMO indicated that there could be some sections with high stress triaxiality, a parameter to evaluate the magnitude of plastic constraint, in the case of plasma disruption or coolant loss accident. Therefore, it is necessary to accurately understand the ductility loss limit of structural material in order to conduct the structural design assessment of the irradiated and embrittled fusion reactor blanket. Tensile tests were conducted by using three kinds of tensile specimen shapes to investigate of the plastic deformability of F82H. From the results, the fracture ductility is lower as the stress triaxiality is higher. Voids of the interrupted RB1 specimen were observed along grain boundaries and expanded parallel to the tensile axis. That of interrupted R0.2 specimen was rounded shape compared with those of RB1. The fracture surface of RB1 and R0.2 specimens were observed the elongated dimples and the equiaxed dimples without so much elongation, respectively. It is considered that the decrease of plastic deformability for the notched specimen was caused by the process of voids formation and crack growth due to the effect of plastic constraint of the notch.

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

Science.gov (United States)

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.

THEORETICAL AND EXPERIMENTAL ASPECTS OF PLASTIC DEFORMATION AND DESTRUCTION OF ROCKS

Directory of Open Access Journals (Sweden)

A. V. Zhabko

2018-03-01

Full Text Available The urgency of the problem. The main process in mining is the process of destruction of rocks, so the establishment of laws and criteria for plastic deformation and destruction of rocks is the most important and fundamental object. Purpose of the work. The work is devoted to the establishment of laws of plastic deformation of rocks (solids. Methods of research. Analytical and experimental research methods are widely used in this work. Results. On the basis of the earlier studies, which were carried out by the author, the functions of the yield surface and the plastic potential are proposed. The limiting surface for these functions is the surface of the ultimate strength of solids (rocks, described by the Coulomb criterion. The author indicated the fundamental similarity between the proposed criterion of plastic deformation and rock strength with the Mora criterion and with the dry friction law of Amonton. The possibility of applying the proposed criterion as passport dependence is demonstrated. The characteristics of rock strength for shear adhesion and the angle of internal friction act as the parameters of this dependence. The paper provides comparison of the proposed theoretical criterion of plasticity and strength to the experimental data under the conditions of the three-dimensional stress state. The detailed analysis of this comparison between theoretical and experimental data is given, the corresponding conclusions are drawn. An analytical dependence was derived on the basis of the stability criterion obtained earlier by the author. It determines the value of the fundamental parameter of the hierarchy during shear and discontinuous destruction of mountain ranges. The relationship of this parameter hierarchy with the so-called number of Phidias, which determines the “Golden ratio”, is indicated. The dependence for calculation of a large-scale factor of the phenomenon of zonal disintegration of rocks around mine workings is offered. The

Defect Investigation of Plastically Deformed Al 5454 Wrought Alloy using PADBS and Electrical Measurements

International Nuclear Information System (INIS)

Abdel-Rahman, M.; Kamel, N.A.; Lotfy, Y.A.; Badawi, E.A.; Abdel-Rahman, M.A.

2009-01-01

Positron Annihilation Doppler Broadening Spectroscopy (PADPS) is a nondestructive technique used in material science. Electrical measurements are one of the oldest techniques used also in material science. This paper aimed to discuss the availability of using both PADPS and electrical measurements as diagnostic techniques to detect the defects in a set of plastically deformed 5454 wrought aluminum alloy. The results of the positron annihilation measurements and the electrical measurements were analyzed in terms of the two-state trapping model. This model can be used to investigate both defect and dislocation densities of the samples under investigation. Results obtained by both nuclear and electrical techniques have been reportedity

A Generalized Orthotropic Elasto-Plastic Material Model for Impact Analysis

Science.gov (United States)

Hoffarth, Canio

Composite materials are now beginning to provide uses hitherto reserved for metals in structural systems such as airframes and engine containment systems, wraps for repair and rehabilitation, and ballistic/blast mitigation systems. These structural systems are often subjected to impact loads and there is a pressing need for accurate prediction of deformation, damage and failure. There are numerous material models that have been developed to analyze the dynamic impact response of polymer matrix composites. However, there are key features that are missing in those models that prevent them from providing accurate predictive capabilities. In this dissertation, a general purpose orthotropic elasto-plastic computational constitutive material model has been developed to predict the response of composites subjected to high velocity impacts. The constitutive model is divided into three components - deformation model, damage model and failure model, with failure to be added at a later date. The deformation model generalizes the Tsai-Wu failure criteria and extends it using a strain-hardening-based orthotropic yield function with a non-associative flow rule. A strain equivalent formulation is utilized in the damage model that permits plastic and damage calculations to be uncoupled and capture the nonlinear unloading and local softening of the stress-strain response. A diagonal damage tensor is defined to account for the directionally dependent variation of damage. However, in composites it has been found that loading in one direction can lead to damage in multiple coordinate directions. To account for this phenomena, the terms in the damage matrix are semi-coupled such that the damage in a particular coordinate direction is a function of the stresses and plastic strains in all of the coordinate directions. The overall framework is driven by experimental tabulated temperature and rate-dependent stress-strain data as well as data that characterizes the damage matrix and failure

Two phase modeling of the influence of plastic strain on the magnetic and magnetostrictive behaviors of ferromagnetic materials

International Nuclear Information System (INIS)

Hubert, Olivier; Lazreg, Said

2017-01-01

A growing interest of automotive industry in the use of high performance steels is observed. These materials are obtained thanks to complex manufacturing processes whose parameters fluctuations lead to strong variations of microstructure and mechanical properties. The on-line magnetic non-destructive monitoring is a relevant response to this problem but it requires fast models sensitive to different parameters of the forming process. The plastic deformation is one of these important parameters. Indeed, ferromagnetic materials are known to be sensitive to stress application and especially to plastic strains. In this paper, a macroscopic approach using the kinematic hardening is proposed to model this behavior, considering a plastic strained material as a two phase system. Relationship between kinematic hardening and residual stress is defined in this framework. Since stress fields are multiaxial, an uniaxial equivalent stress is calculated and introduced inside the so-called magneto-mechanical multidomain modeling to represent the effect of plastic strain. The modeling approach is complemented by many experiments involving magnetic and magnetostrictive measurements. They are carried out with or without applied stress, using a dual-phase steel deformed at different levels. The main interest of this material is that the mechanically hard phase, soft phase and the kinematic hardening can be clearly identified thanks to simple experiments. It is shown how this model can be extended to single phase materials.

Two phase modeling of the influence of plastic strain on the magnetic and magnetostrictive behaviors of ferromagnetic materials

Energy Technology Data Exchange (ETDEWEB)

Hubert, Olivier, E-mail: olivier.hubert@lmt.ens-cachan.fr; Lazreg, Said

2017-02-15

A growing interest of automotive industry in the use of high performance steels is observed. These materials are obtained thanks to complex manufacturing processes whose parameters fluctuations lead to strong variations of microstructure and mechanical properties. The on-line magnetic non-destructive monitoring is a relevant response to this problem but it requires fast models sensitive to different parameters of the forming process. The plastic deformation is one of these important parameters. Indeed, ferromagnetic materials are known to be sensitive to stress application and especially to plastic strains. In this paper, a macroscopic approach using the kinematic hardening is proposed to model this behavior, considering a plastic strained material as a two phase system. Relationship between kinematic hardening and residual stress is defined in this framework. Since stress fields are multiaxial, an uniaxial equivalent stress is calculated and introduced inside the so-called magneto-mechanical multidomain modeling to represent the effect of plastic strain. The modeling approach is complemented by many experiments involving magnetic and magnetostrictive measurements. They are carried out with or without applied stress, using a dual-phase steel deformed at different levels. The main interest of this material is that the mechanically hard phase, soft phase and the kinematic hardening can be clearly identified thanks to simple experiments. It is shown how this model can be extended to single phase materials.

Precision Machining When Cutting with Leading Plastic Deformation

Directory of Open Access Journals (Sweden)

N. A. Yaroslavtseva

2017-01-01

Full Text Available Keeping up the product competitiveness continually requires solving the problems of reducing time for product creation and material costs for its production and ensuring the maximum conformity of the product quality with the individual requirements of a particular consumer. It is especially difficult to implement these tasks in product manufacturing from the hard-to-machine steels and alloys with extremely low production rate in machining (often 10-20 times lower than when cutting the ordinary structural steels.Currently, one of the promising ways to improve the cutting process of hard-to-machine materials and quality of parts made from these materials is development and application of combined processing methods, which use additional energy sources to act on the machined material in the cutting zone. A BMSTU-developed cutting method with leading plastic deformation (LPD, which acts to raise the production rate, gain the cutting tool-life, reduce the surface roughness, improve the accuracy of processing and the performance characteristics of products, ensure the reliable flow chip control, and improve the labor conditions, belongs to such sort of methods.One of the most important indicators of processing quality that has a great impact on the operation and cost characteristics of the product and on the machining rate as well is the accuracy of processing. In cutting, the processing errors largely arise from the elastic deformations of a technological system when the cutting force, and, in particular, the radial component of the cutting force, acts on it.The deforming devices, used in cutting with LPD, being located as a rule, on the diametrically opposite side with respect to the cutting zone, act on the technological system as vibration dampers. In addition, as studies have shown, the choice of a rational direction for applying LPD load helps to compensate partially or completely the cutting force radial component effect on the technological

Cap plasticity models and compactive and dilatant pre-failure deformation

International Nuclear Information System (INIS)

Fossum, Arlo F.; Fredrich, Joanne T.

2000-01-01

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)

Finite element analysis of a finite-strain plasticity problem

International Nuclear Information System (INIS)

Crose, J.G.; Fong, H.H.

1984-01-01

A finite-strain plasticity analysis was performed of an engraving process in a plastic rotating band during the firing of a gun projectile. The aim was to verify a nonlinear feature of the NIFDI/RB code: plastic large deformation analysis of nearly incompressible materials using a deformation theory of plasticity approach and a total Lagrangian scheme. (orig.)

Modelling of the plastic deformation and primary creep of metals coupled with DC in terms of the synthetic theory of irrecoverable deformation

Science.gov (United States)

Rusinko, Andrew; Varga, Peter

2018-04-01

The paper deals with modelling of the plastic and creep deformation of metals coupled with current. The passage of DC manifests itself in the increase in creep deformation and leads to primary creep time shortening. With plastic deformation, a short electric impulse results in the step-wise decrease of stress (stress-drop) on the stress-strain diagram. To catch these phenomena, we utilize the synthetic theory of recoverable deformation. The constitutive equation of this theory is supplemented by a term taking into account the intensity of DC. Further, we introduce DC intensity into the function governing transient creep. As a result, we predict the parameters of transient creep and calculate the stress-drop as a function of current intensity. The model results show good agreement with experimental data.

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

Energy Technology Data Exchange (ETDEWEB)

Patra, Anirban [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wen, Wei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Martinez Saez, Enrique [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

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.

Finite element historical deformation analysis in piecewise linear plasticity by mathematical programming

International Nuclear Information System (INIS)

De Donato, O.; Parisi, M.A.

1977-01-01

When loads increase proportionally beyond the elastic limit in the presence of elastic-plastic piecewise-linear constitutive laws, the problem of finding the whole evolution of the plastic strain and displacements of structures was recently shown to be amenable to a parametric linear complementary problem (PLCP) in which the parameter is represented by the load factor, the matrix is symmetric positive definite or at least semi-definite (for perfect plasticity) and the variables with a direct mechanical meaning are the plastic multipliers. With reference to plane trusses and frames with elastic-plastic linear work-hardening material behaviour numerical solutions were also fairly efficiently obtained using a recent mathematical programming algorithm (due to R.W. Cottle) which is able to provide the whole deformation history of the structure and, at the same time to rule out local unloadings along the given proportional loading process by means of 'a priori' checks carried out before each pivotal step of the procedure. Hence it becomes possible to use the holonomic (reversible, path-independent) constitutive laws in finite terms and to benefit by all the relevant numerical and computational advantages despite the non-holonomic nature of plastic behaviour. In the present paper the method of solution is re-examined in view to overcome an important drawback of the algorithm deriving from the size of PLCP fully populated matrix when structural problems with large number of variables are considered and, consequently, the updating, the storing or, generally, the handling of the current tableau may become prohibitive. (Auth.)

Change and anisotropy of elastic modulus in sheet metals due to plastic deformation

Science.gov (United States)

Ishitsuka, Yuki; Arikawa, Shuichi; Yoneyama, Satoru

2015-03-01

In this study, the effect of the plastic deformation on the microscopic structure and the anisotropy of the elastic modulus in the cold-rolled steel sheet (SPCC) is investigated. Various uniaxial plastic strains (0%, 2.5%, 5%, 7.5%, and 10%) are applied to the annealed SPCC plates, then, the specimens for the tensile tests are cut out from them. The elastic moduli in the longitudinal direction and the transverse direction to the direction that are pre-strained are measured by the tensile tests. Cyclic tests are performed to investigate the effects of the internal friction caused by the movable dislocations in the elastic deformation. Also, the movable dislocations are quantified by the boundary tracking for TEM micrographs. In addition, the behaviors of the change of the elastic modulus in the solutionized and thermal aged aluminum alloy (A5052) are measured to investigate the effect on the movable dislocations with the amount of the depositions. As a result in SPCC, the elastic moduli of the 0° and 90° directions decrease more than 10% as 10% prestrain applied. On the other hand, the elastic modulus shows the recovery behavior after the strain aging and the annealing. The movable dislocation and the internal friction show a tendency to increase as the plastic strain increases. The marked anisotropy is not observed in the elastic modulus and the internal friction. The elastic modulus in A5052 with many and few depositions decreases similarly by the plastic deformation. From the above, the movable dislocations affect the elastic modulus strongly without depending on the deposition amount. Moreover, the elastic modulus recovers after the plastic deformation by reducing the effects of them with the strain aging and the heat treatment.

Finite element modelling of shot peening process: Prediction of the compressive residual stresses, the plastic deformations and the surface integrity

International Nuclear Information System (INIS)

Frija, M.; Hassine, T.; Fathallah, R.; Bouraoui, C.; Dogui, A.

2006-01-01

This paper presents a numerical simulation of the shot peening process using finite element method. The majority of the controlling parameters of the process have been taken into account. The shot peening loading has been characterised by using energy equivalence between the dynamic impact and a static indentation of a peening shot in the treated surface. The behaviour of the subjected material is supposed to be elastic plastic with damage. An integrated law of the damage proposed by Lemaitre and Chaboche has been used. The proposed model leads to obtain the residual stress, the plastic deformation profiles and the surface damage. An application on a shot peened Ni-based super alloy Waspaloy has been carried out. The comparison of the residual stresses, obtained by X-ray diffraction method and by finite element calculation, shows a good correlation. The in-depth profile of the plastic deformations and the superficial damage values are in good agreement with the experimental observations

Plastic Recycling Experiments in Materials Education

Science.gov (United States)

Liu, Ping; Waskom, Tommy L.

1996-01-01

The objective of this project was to introduce a series of plastic recycling experiments to students in materials-related courses such as materials science, material technology and materials testing. With the plastic recycling experiments, students not only can learn the fundamentals of plastic processing and properties as in conventional materials courses, but also can be exposed to the issue of materials life cycle and the impact on society and environment.

Elasto-Plastic Stress Analysis in Rotating Disks and Pressure Vessels Made of Functionally Graded Materials

Directory of Open Access Journals (Sweden)

Amir T. Kalali

Full Text Available Abstract A new elastio-plastic stress solution in axisymmetric problems (rotating disk, cylindrical and spherical vessel is presented. The rotating disk (cylindrical and spherical vessel was made of a ceramic/metal functionally graded material, i.e. a particle-reinforced composite. It was assumed that the material's plastic deformation follows an isotropic strain-hardening rule based on the von-Mises yield criterion. The mechanical properties of the graded material were modeled by the modified rule of mixtures. By assuming small strains, Hencky's stress-strain relation was used to obtain the governing differential equations for the plastic region. A numerical method for solving those differential equations was then proposed that enabled the prediction of stress state within the structure. Selected finite element results were also presented to establish supporting evidence for the validation of the proposed approach.

Computer simulation of plastic deformation in the Charpy V-notch impact test

International Nuclear Information System (INIS)

Norris, D.M. Jr.; Quinones, D.F.; Moran, B.

1978-01-01

Calculations describe the dynamic stress and strain states in the standard Charpy specimen from impact to the start of cracking. We model A533 Grade B Class 1 nuclear-pressure-vessel steel at 100 0 C with an elastic-plastic constitutive law. Large deformation and rotation of the material are accounted for. The specimen velocity field during the impact transient is presented and how the early wave effects cause separation of the specimen from the striker is shown. The calculations show why correlations between Charpy fracture energy and fracture toughness have been largely unsuccessful and suggest methods to improve these correlations using the same specimen geometry

Crystal-plastic deformation of zircon : effects on microstructures, textures, microchemistry and the retention of radiogenic isotopes

International Nuclear Information System (INIS)

Kovaleva, E.

2015-01-01

Dating of deep-crustal deformation events potentially can be achieved by using plastically-deformed accessory minerals found in high-temperature shear zones. Deformation microstructures, such as dislocations and low-angle boundaries, form due to plastic deformation in the crystal lattice and act as fluid migration pathways and trace element (e.g. Pb, Ti, U, Th, REE) diffusion pathways through so-called “pipe diffusion”. Deformation microstructures can alter the chemical and isotopic composition of certain grain parts and may lead to complete or partial isotopic resetting of certain geochronometers (e.g. U/Th/Pb, K/Ar, Rb/Sr) in the mineral domains. This work aims to better understand the processes of crystal-plastic deformation and associated trace element redistribution and the resetting of isotopic systems in zircon. This study finds that: a) there are three general finite deformation patterns in deformed zircons; b) suggests that it is possible to reconstruct the macroscopic kinematic framework of the shear zone based on the orientation of deformed zircon grains and the operating misorientation axes; c) and demonstrates the effect of deformation microstructures on trace elements and Pb isotopes in zircon. The final goal of this project is to develop a tool for isotopic dating of high-temperature deformation events in the deep crust. In addition to these results, zircon grains with planar deformation bands have been discovered in paleo-seismic zones; these deformation features have been described in detail and a possible mechanism of their origin and formation is suggested. The effect of planar deformation bands on trace element and isotopic behavior has also been investigated. (author) [de

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

Science.gov (United States)

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.

Recrystallization kinetics of nanostructured copper processed by dynamic plastic deformation

DEFF Research Database (Denmark)

Lin, Fengxiang; Zhang, Yubin; Pantleon, Wolfgang

2012-01-01

The recrystallization kinetics of nanostructured copper samples processed by dynamic plastic deformation was investigated by electron backscatter diffraction. It was found that the evolution of the recrystallized volume fraction as a function of annealing time has a very low slope (n=0.37) when...

Crack nucleation and elastic / plastic deformation of TiAl alloys investigated by in-situ loaded atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Iqbal, F.; Pyczak, F.; Neumeier, S.; Göken, M.

2017-03-24

The crack propagation mechanisms of γ-titanium aluminides with fully lamellar microstructure have been studied using in-situ deformation in the Atomic Force Microscope (AFM). AFM demonstrated the unique capability to detect elastic as well as plastic deformation during in-situ tests from topography changes on the surface. It was found that the crack nucleation, which can occur at γ/γ and α{sub 2}/γ interfaces as well as inside the γ-phase, is always preceded by strong local elastic deformation. No cracking inside the α{sub 2}-phase was observed. The elastic and plastic deformation was confined inside the γ-phase and especially pronounced near interfaces which can be explained by the differences of the elastic and plastic deformation behavior of the γ- and α{sub 2}- phase.

Evaluation of alignment error of micropore X-ray optics caused by hot plastic deformation

Science.gov (United States)

Numazawa, Masaki; Ishi, Daiki; Ezoe, Yuichiro; Takeuchi, Kazuma; Terada, Masaru; Fujitani, Maiko; Ishikawa, Kumi; Nakajima, Kazuo; Morishita, Kohei; Ohashi, Takaya; Mitsuda, Kazuhisa; Nakamura, Kasumi; Noda, Yusuke

2018-06-01

We report on the evaluation and characterization of micro-electromechanical system (MEMS) X-ray optics produced by silicon dry etching and hot plastic deformation. Sidewalls of micropores formed by etching through a silicon wafer are used as X-ray reflecting mirrors. The wafer is deformed into a spherical shape to focus parallel incidence X-rays. We quantitatively evaluated a mirror alignment error using an X-ray pencil beam (Al Kα line at 1.49 keV). The deviation angle caused only by the deformation was estimated from angular shifts of the X-ray focusing point before and after the deformation to be 2.7 ± 0.3 arcmin on average within the optics. This gives an angular resolution of 12.9 ± 1.4 arcmin in half-power diameter (HPD). The surface profile of the deformed optics measured using a NH-3Ns surface profiler (Mitaka Kohki) also indicated that the resolution was 11.4 ± 0.9 arcmin in HPD, suggesting that we can simply evaluate the alignment error caused by the hot plastic deformation.

Parameter Identification of Piecewise Linear Plasticity Metal Models Used in Numerical Modeling of Structures Under Plastic Deformation and Failure

Directory of Open Access Journals (Sweden)

A. V. Shmeliov

2016-01-01

Full Text Available The article describes the models of metallic materials used in the calculation of deformation and destruction of engineering structures. The reliability of material models can adequately assess the strength characteristics of the designs of new technology in its designing and certification.The article deals with contingencies and true mechanical properties of materials and presents equations of their relationship. It notes that in the software systems mechanical characteristics of materials are given in the true sense.The paper considers the linear and exponential models of materials, their characteristics, and methods to implement them. It considers the models of Johnson-Cook Steinberg-Guinan, Zerilli-Armstrong, Cowper-Symonds, Gurson-Tvergaard that take into account the strain rate and temperature of the material. Describes their applications, advantages and disadvantages. Considers single- and multi-parameter criteria of materials fracture, the prospects for their use. Gives a rational justification for using a piecewise linear plasticity material model *MAT_PIECEWISE_LINEAR_PLASTICITY (024, LS-DYNA software package for the engineering industry, and presents its main parameters.A technique to identify parameters of piecewise linear plasticity metal material models has been developed. The technique consists of the stages, based on the equations of transition from the conventional stress and strain values to the true ones. Taking into consideration the stressstrain state in the neck of the sample is a distinctive feature of the technique.Tensile tests of the round material samples have been conducted. To test the developed technique in the software package ANSYS LS-DYNA PC have been made tensile sample modeling and results comparison to show high convergence.Further improvement of the technique can be achieved through the development of a statistical approach to the analysis of the results of a series of tests. This will allow a kind of

Estimation of dislocation concentration in plastically deformed silver by positron annihilation

International Nuclear Information System (INIS)

ABdel-Rahman, M.A.; Badawi, E.A.; Abdel-Raheem, S.H.

1996-01-01

Positron annihilation mean lifetime measurements were performed on 7 different specimens of silver plastically deformed at room temperature (up to 56%). The positron mean lifetime exhibits a saturation for deformations larger than 14% thickness reduction. The fitted lifetime varies from (135.9+2 ps) for annealed silver to (207+ 2 ps) for the dislocation saturated value. Trapping cross-section and trapping efficiency were calculated. Dislocation concentration at saturation has been estimated. 3 figs

Estimation of dislocation concentration in plastically deformed silver by positron annihilation

Energy Technology Data Exchange (ETDEWEB)

ABdel-Rahman, M A; Badawi, E A; Abdel-Raheem, S H [Physics Dept., Faculty of Science, El-Minia University, El-Minia (Egypt)

1997-12-31

Positron annihilation mean lifetime measurements were performed on 7 different specimens of silver plastically deformed at room temperature (up to 56%). The positron mean lifetime exhibits a saturation for deformations larger than 14% thickness reduction. The fitted lifetime varies from (135.9+2 ps) for annealed silver to (207+ 2 ps) for the dislocation saturated value. Trapping cross-section and trapping efficiency were calculated. Dislocation concentration at saturation has been estimated. 3 figs.

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

Science.gov (United States)

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.

Development of a formalism of movable cellular automaton method for numerical modeling of fracture of heterogeneous elastic-plastic materials

Directory of Open Access Journals (Sweden)

S. Psakhie

2013-04-01

Full Text Available A general approach to realization of models of elasticity, plasticity and fracture of heterogeneous materials within the framework of particle-based numerical methods is proposed in the paper. It is based on building many-body forces of particle interaction, which provide response of particle ensemble correctly conforming to the response (including elastic-plastic behavior and fracture of simulated solids. Implementation of proposed approach within particle-based methods is demonstrated by the example of the movable cellular automaton (MCA method, which integrates the possibilities of particle-based discrete element method (DEM and cellular automaton methods. Emergent advantages of the developed approach to formulation of many-body interaction are discussed. Main of them are its applicability to various realizations of the concept of discrete elements and a possibility to realize various rheological models (including elastic-plastic or visco-elastic-plastic and models of fracture to study deformation and fracture of solid-phase materials and media. Capabilities of particle-based modeling of heterogeneous solids are demonstrated by the problem of simulation of deformation and fracture of particle-reinforced metal-ceramic composites.

A method of increasing the depth of the plastically deformed layer in the roller burnishing process

Science.gov (United States)

Kowalik, Marek; Trzepiecinski, Tomasz

2018-05-01

The subject of this paper is an analysis of the determination of the depth of the plastically deformed layer in the process of roller burnishing a shaft using a newly developed method in which a braking moment is applied to the roller. It is possible to increase the depth of the plastically deformed layer by applying the braking moment to the roller during the burnishing process. The theoretical considerations presented are based on the Hertz-Bielayev and Huber-Mises theories and permit the calculation of the depth of plastic deformation of the top layer of the burnished shaft. The theoretical analysis has been verified experimentally and using numerical calculations based on the finite element method using the Msc.MARC program. Experimental tests were carried out on ring-shaped samples made of C45 carbon steel. The samples were burnished at different values of roller force and different values of braking moment. A significant increase was found in the depth of the plastically deformed surface layer of roller burnished shafts. Usage of the phenomenon of strain hardening of steel allows the technology presented here to increase the fatigue life of the shafts.

Ultra fine grained Ti prepared by severe plastic deformation

Science.gov (United States)

Lukáč, F.; Čížek, J.; Knapp, J.; Procházka, I.; Zháňal, P.; Islamgaliev, R. K.

2016-01-01

The positron annihilation spectroscopy was employed for characterisation of defects in pure Ti with ultra fine grained (UFG) structure. UFG Ti samples were prepared by two techniques based on severe plastic deformation (SPD): (i) high pressure torsion (HPT) and (ii) equal channel angular pressing (ECAP). Although HPT is the most efficient technique for grain refinement, the size of HPT-deformed specimens is limited. On the other hand, ECAP is less efficient in grain refinement but enables to produce larger samples more suitable for industrial applications. Characterisation of defects by positron annihilation spectroscopy was accompanied by hardness testing in order to monitor the development of mechanical properties of UFG Ti.

Plastic Deformation of Metal Surfaces

DEFF Research Database (Denmark)

Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

2013-01-01

of metal components. An optimization of processes and material parameters must be based on a quantification of stress and strain gradients at the surface and in near surface layer where the structural scale can reach few tens of nanometers. For such fine structures it is suggested to quantify structural...... parameters by TEM and EBSD and apply strength-structural relationships established for the bulk metal deformed to high strains. This technique has been applied to steel deformed by high energy shot peening and a calculated stress gradient at or near the surface has been successfully validated by hardness...

Correlation of plastic deformation induced intermittent electromagnetic radiation characteristics with mechanical properties of Cu-Ni alloys

International Nuclear Information System (INIS)

Singh, Ranjana; Lal, Shree P.; Misra, Ashok

2015-01-01

This paper presents experimental results on intermittent electromagnetic radiation during plastic deformation of Cu-Ni alloys under tension and compression modes of deformation. On the basis of the nature of electromagnetic radiation signals, oscillatory or exponential, results show that the compression increases the viscous coefficient of Cu-Ni alloys during plastic deformation. Increasing the percentage of solute atoms in Cu-Ni alloys makes electromagnetic radiation strength higher under tension. The electromagnetic radiation emission occurs at smaller strains under compression showing early onset of plastic deformation. This is attributed to the role of high core region tensile residual stresses in the rolled Cu-Ni alloy specimens in accordance with the Bauschinger effect. The distance between the apexes of the dead metal cones during compression plays a significant role in electromagnetic radiation parameters. The dissociation of edge dislocations into partials and increase in internal stresses with increase in solute percentage in Cu-Ni alloys under compression considerably influences the electromagnetic radiation frequency.

Modeling the complexity of acoustic emission during intermittent plastic deformation: Power laws and multifractal spectra.

Science.gov (United States)

Kumar, Jagadish; Ananthakrishna, G

2018-01-01

Scale-invariant power-law distributions for acoustic emission signals are ubiquitous in several plastically deforming materials. However, power-law distributions for acoustic emission energies are reported in distinctly different plastically deforming situations such as hcp and fcc single and polycrystalline samples exhibiting smooth stress-strain curves and in dilute metallic alloys exhibiting discontinuous flow. This is surprising since the underlying dislocation mechanisms in these two types of deformations are very different. So far, there have been no models that predict the power-law statistics for discontinuous flow. Furthermore, the statistics of the acoustic emission signals in jerky flow is even more complex, requiring multifractal measures for a proper characterization. There has been no model that explains the complex statistics either. Here we address the problem of statistical characterization of the acoustic emission signals associated with the three types of the Portevin-Le Chatelier bands. Following our recently proposed general framework for calculating acoustic emission, we set up a wave equation for the elastic degrees of freedom with a plastic strain rate as a source term. The energy dissipated during acoustic emission is represented by the Rayleigh-dissipation function. Using the plastic strain rate obtained from the Ananthakrishna model for the Portevin-Le Chatelier effect, we compute the acoustic emission signals associated with the three Portevin-Le Chatelier bands and the Lüders-like band. The so-calculated acoustic emission signals are used for further statistical characterization. Our results show that the model predicts power-law statistics for all the acoustic emission signals associated with the three types of Portevin-Le Chatelier bands with the exponent values increasing with increasing strain rate. The calculated multifractal spectra corresponding to the acoustic emission signals associated with the three band types have a maximum

Foam rheology at large deformation

Science.gov (United States)

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

2018-04-01

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

Low-temperature internal friction in high-purity monocrystalline and impure polycrystalline niobium after plastic deformation

International Nuclear Information System (INIS)

Wasserbaech, W.; Thompson, E.

2001-01-01

The internal friction Q -1 of plastically deformed, high-purity monocrystalline and impure polycrystalline niobium specimens was measured in the temperature range between 65 mK and about 2 K. Plastic deformation has a pronounced effect on the internal friction Q -1 of the high-purity monocrystalline specimens, and the effect has been found to be almost temperature independent. By contrast, surprisingly, the internal friction Q -1 of the impure polycrystalline specimens was found to be almost independent of the extent of plastic deformation. Comparison of the experimental results with different models of a dynamic scattering of acoustic phonons by dislocations leads to the conclusion that the results cannot be explained with the two-level tunneling model. Instead it is suggested that a strong interaction between acoustic phonons and geometrical kinks in non-screw dislocations is responsible for the observed internal friction Q -1 . (orig.)

Theoretical Development of an Orthotropic Elasto-Plastic Generalized Composite Material Model

Science.gov (United States)

Goldberg, Robert; Carney, Kelly; DuBois, Paul; Hoffarth, Canio; Harrington, Joseph; Rajan, Subramaniam; Blankenhorn, Gunther

2014-01-01

The need for accurate material models to simulate the deformation, damage and failure of polymer matrix composites is becoming critical as these materials are gaining increased usage in the aerospace and automotive industries. While there are several composite material models currently available within LSDYNA (Livermore Software Technology Corporation), there are several features that have been identified that could improve the predictive capability of a composite model. To address these needs, a combined plasticity and damage model suitable for use with both solid and shell elements is being developed and is being implemented into LS-DYNA as MAT_213. A key feature of the improved material model is the use of tabulated stress-strain data in a variety of coordinate directions to fully define the stress-strain response of the material. To date, the model development efforts have focused on creating the plasticity portion of the model. The Tsai-Wu composite failure model has been generalized and extended to a strain-hardening based orthotropic yield function with a nonassociative flow rule. The coefficients of the yield function, and the stresses to be used in both the yield function and the flow rule, are computed based on the input stress-strain curves using the effective plastic strain as the tracking variable. The coefficients in the flow rule are computed based on the obtained stress-strain data. The developed material model is suitable for implementation within LS-DYNA for use in analyzing the nonlinear response of polymer composites.

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

International Nuclear Information System (INIS)

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

2011-01-01

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 μm. 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: → SPD results in a significant increase in the density of the small primary particles. → SPD homogenizes the particle size distribution. → HE and ECAE processes bring nano-grains in the vicinity of the primary particles. → HE and ECAE processing results in the β' precipitates partial dissolutions. → During HE and ECAE processes the β' particles change their shape.

Discrimination of Naturally Occurring Radioactive Material in Plastic Scintillator Material

International Nuclear Information System (INIS)

Ely, James H.; Kouzes, Richard T.; Geelhood, Bruce D.; Schweppe, John E.; Warner, Ray A.

2003-01-01

Plastic scintillator material is used in many applications for the detection of gamma-rays from radioactive material, primarily due to the sensitivity per unit cost compared to other detection materials. However, the resolution and lack of full-energy peaks in the plastic scintillator material prohibits detailed spectroscopy. Therefore, other materials such as doped sodium iodide are used for spectroscopic applications. The limited spectroscopic information can however be exploited in plastic scintillator materials to provide some discrimination. The discrimination between man-made and naturally occurring sources would be useful in reducing alarm screening for radiation detection applications which target man-made sources. The results of applying the limited energy information from plastic scintillator material for radiation portal monitors are discussed.

Effect of Plastic Deformation on the Corrosion Behavior of a Super-Duplex Stainless Steel

Science.gov (United States)

Renton, Neill C.; Elhoud, Abdu M.; Deans, William F.

2011-04-01

The role of plastic deformation on the corrosion behavior of a 25Cr-7Ni super-duplex stainless steel (SDSS) in a 3.5 wt.% sodium chloride solution at 90 °C was investigated. Different levels of plastic strain between 4 and 16% were applied to solution annealed tensile specimens and the effect on the pitting potential measured using potentiodynamic electrochemical techniques. A nonlinear relationship between the pitting potential and the plastic strain was recorded, with 8 and 16% causing a significant reduction in average E p, but 4 and 12% causing no significant change when compared with the solution-annealed specimens. The corrosion morphology revealed galvanic interaction between the anodic ferrite and the cathodic austenite causing preferential dissolution of the ferrite. Mixed potential theory and the changing surface areas of the two phases caused by the plastic deformation structures explain the reductions in pitting potential at certain critical plastic strain levels. End-users and manufacturers should evaluate the corrosion behavior of specific cold-worked duplex and SDSSs using their as-produced surface finishes assessing in-service corrosion performance.

Diffraction measurements for evaluating plastic strain in A533B ferritic steel-a feasibility study

International Nuclear Information System (INIS)

Lewis, S J; Truman, C E

2010-01-01

It is known that the physical properties of many engineering materials may be strongly affected by previous loading, in particular prior plastic deformation. Most obviously, work hardening will alter subsequent yielding behaviour. Plastic deformation may also preferentially align the material microstructure, resulting in anisotropy of subsequent behaviour and a change in material fracture resistance. When physical characterization is undertaken by experimental testing it is, therefore, important to have some knowledge of the current state of the material. As a result, it is desirable to have methods of quantitatively evaluating the level of plastic deformation which specimen material may have experienced prior to testing. This paper presents the results of a feasibility study, using a ferritic reactor pressure vessel steel, into the use of diffractive methods for plastic strain evaluation. Using neutron diffraction, changes in diffraction peak width and anisotropy of peak response were correlated with plastic deformation in a tensile test. The relationships produced were then used to evaluate permanent deformation levels in large samples, representative of standard fracture toughness test specimens.

Thermo-plastic finite element analysis for metal honeycomb structure

Directory of Open Access Journals (Sweden)

Ji Zhanling

2013-01-01

Full Text Available This paper deals with thermal-plastic analysis for the metal honeycomb structure. The heat transfer equation and thermal elastoplastic constitutive equation of a multilayer panel are established and studied numerically using ANSYS software. The paper elucidates that only the outer skin produces easily plastic deformation, and the outer skin still exists some residual stress and residual deformation after cooling. The dynamic evolution of plastic deformation and material performance degradation under high energy thermal load are revealed.

Study on Plastic Deformation Characteristics of Shot Peening of Ni-Based Superalloy GH4079

Science.gov (United States)

Zhong, L. Q.; Liang, Y. L.; Hu, H.

2017-09-01

In this paper, the X-ray stress diffractometer, surface roughness tester, field emission scanning electron microscope(SEM), dynamic ultra-small microhardness tester were used to measure the surface residual stress and roughness, topography and surface hardness changes of GH4079 superalloy, which was processed by metallographic grinding, turning, metallographic grinding +shot peening and turning + shot peening. Analysized the effects of shot peening parameters on shot peening plastic deformation features; and the effects of the surface state before shot peening on shot peening plastic deformation characteristics. Results show that: the surface residual compressive stress, surface roughness and surface hardness of GH4079 superalloy were increased by shot peening, in addition, the increment of the surface residual compressive stress, surface roughness and surface hardness induced by shot peening increased with increasing shot peening intensity, shot peening time, shot peening pressure and shot hardness, but harden layer depth was not affected considerably. The more plastic deformation degree of before shot peening surface state, the less increment of the surface residual compressive stress, surface roughness and surface hardness induced by shot peening.

A fundamental discussion of what triggers localized deformation in geological materials

Science.gov (United States)

Peters, Max; Paesold, Martin; Poulet, Thomas; Herwegh, Marco; Regenauer-Lieb, Klaus; Veveakis, Manolis

2015-04-01

Discontinuous or localized structures are often marked by the transition from a homogeneously deforming into a highly localized mode. This transition has extensively been described in ductile shear zones, folding and pinch-and-swell boudinage, in natural examples, rock deformation experiments and numerical simulations, at various scales. It is conventionally assumed that ductile instabilities, which act as triggers for localized deformation, exclusively arise from structural heterogeneities, i.e. geometric interactions or material imperfections. However, Hansen et al. (2012) concluded from recent laboratory experiments that localized deformation might arise out of steady-state conditions, where the size of initial perturbations was either insufficiently large to trigger localization, or these heterogeneities were simply negligible at the scale of observation. We therefore propose the existence of a principal localization phenomenon, which is based on the material-specific rate-dependency of deformation at elevated temperatures. The concept of strain localization out of a mechanical steady state in a homogeneous material at a critical material parameter and/or deformation rate has previously been discussed for engineering materials (Gruntfest, 1963) and frictional faults (Veveakis et al., 2010). We expand this theory to visco-plastic carbonate rocks, considering deformation conditions and mechanisms encountered in naturally deformed rocks. In the numerical simulation, we implement a grain-size evolution based on the Paleowattmeter scaling relationship of Austin & Evans (2007), which takes both grain size sensitive (diffusion) and insensitive (dislocation) creep combined with grain growth into account (Herwegh et al., 2014). Based on constant strain rate simulations carried out under isothermal boundary conditions, we explore the parameter space in order to obtain the criteria for localization. We determine the criteria for the onset of localization, i.e. the

High-carbon chromium steel resistance to small plastic deformation

International Nuclear Information System (INIS)

Gajduchenya, V.F.; Madyanov, S.A.; Apaev, B.A.; Kirillov, Yu.V.; Sokolov, L.D.

1978-01-01

The phase composition of a steel with 1.08% C and 2.1% Cr, and the variation in the level of microstresses in the matrix as related to the annealing temperature in the range of 400-600 deg C and in the applied compression stress were investigated. To study the phase composition, and chromium content in the α-solution and the carbide phases, magnetic, chemical, and X-ray spectrum analyses were carried out. The change in the level of microstresses was determined roentgenographically. During the stress relaxation test at temperatures of 20-180 deg C, the mechanism of plastic deformation near the yield point was investigated. It is shown that three dislocation mechanisms operate in high-carbon chromium steel under the conditions at hand: overcoming the Pierls-Nabarro barriers by the dislocations, overcoming the stress fields of coherent carbide particles by dislocations, and circumvention of second-phase particles by dislocations. The dependence of the realization of the different plastic deformation mechanisms on the number of carbide particles and the chromium concentration in the matrix was established. The thermally activated nature of the motion of the dislocations under conditions of stress relaxation at an elevated temperature is noted

Study on Plastic Coated Overburnt Brick Aggregate as an Alternative Material for Bituminous Road Construction

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Dipankar Sarkar

2016-01-01

Full Text Available There are different places in India where natural stone aggregates are not available for constructional work. Plastic coated OBBA can solve the problem of shortage of stone aggregate to some extent. The engineers are always encouraged to use locally available materials. The present investigation is carried out to evaluate the plastic coated OBBA as an alternative material for bituminous road construction. Shredded waste plastics are mixed with OBBA in different percentages as 0.38, 0.42, 0.46, 0.50, 0.54, and 0.60 of the weight of brick aggregates. Marshall Method of mix design is carried out to find the optimum bitumen content of such bituminous concrete mix prepared by plastic coated OBBA. Bulk density, Marshall Stability, flow, Marshall Quotient, ITS, TSR, stripping, fatigue life, and deformations have been determined accordingly. Marshall Stability value of 0.54 percent of plastic mix is comparatively higher than the other mixes except 0.60 percent of plastic mix. Test results are within the prescribed limit for 0.54 percent of plastic mix. There is a significant reduction in rutting characteristics of the same plastic mix. The fatigue life of the mix is also significantly higher. Thus plastic coated OBBA is found suitable in construction of bituminous concrete road.

Microstructural evolution at multiple scales during plastic deformation

DEFF Research Database (Denmark)

Winther, Grethe

During plastic deformation metals develop microstructures which may be analysed on several scales, e.g. bulk textures, the scale of individual grains, intragranular phenomena in the form of orientation spreads as well as dislocation patterning by formation of dislocation boundaries in metals of m......, which is backed up by experimental data [McCabe et al. 2004; Wei et al., 2011; Hong, Huang, & Winther, 2013]. The current state of understanding as well as the major challenges are discusse....

Plastic deformation mechanism of polycrystalline copper foil shocked with femtosecond laser

International Nuclear Information System (INIS)

Ye, Y.X.; Feng, Y.Y.; Lian, Z.C.; Hua, Y.Q.

2014-01-01

Plastic deformation mechanism of polycrystalline copper foil shocked with femtosecond (fs) laser has been characterized through optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Experiments of ns laser shocking copper (Cu) and fs laser shocking aluminum (Al) were also conducted for comparison. Dislocations arranged in multiple forms, profuse twins and stacking faults (SFs) coexist in the fs laser shocked copper. At small strain condition, dislocation slip is the dominant deformation mode and small amount of SFs act as complementary mechanism. With strain increasing, profuse twins and SFs form to accommodate the plastic deformation. Furthermore, new formed SFs incline to locate around the old ones because the dislocation densities there are more higher. So there is a high probability for new SFs overlapping on old ones to form twins, or connecting old ones to lengthen them, which eventually produce the phenomena that twins connect with each other or twins connect with SFs. Strain greatly influences the dislocation density. Twins and SFs are more dependent on strain rate and shock pressure. Medium stacking fault energy (SFE) of copper helps to extend partial dislocations and provides sources for forming SFs and twins.

On the fast amorphous phase growth in plastically deformed metallic couples

International Nuclear Information System (INIS)

Mazzone, G.; Montone, A.; Antisari, M.V.

1993-01-01

The authors have modeled the kinetics of glass formation at the Ni-Zr interface of plastically deformed diffusion couples on the basis of a free volume description of glass structure, taking also into account the structural effects of an externally applied stress. Owing to the complexity of the problem several approximations have necessarily been introduced, the main ones being probably the simplified description of the structure and of the tensile behavior of a metallic glass and the use of the Spaepen Eqs. in an alloy system. However, these approximations do not seem to significantly affect the main trends displayed by the computations, that is the high value of D, the exponential dependence of x on var-epsilon and the low value of the activation energy, in agreement with experimental trends (3) not easily attributable to other causes. Of course, the numerical values of the free parameters have to be considered an approximate evaluation of the corresponding physical quantities. However, despite of the above limitations, their values are physically plausible. In conclusion the authors have shown that the present model describes in a quantitative way the kinetics of solid state amorphization at the interface of a diffusion couple plastically deformed during the reaction. The effective diffusion coefficient increases by several orders of magnitude as a consequence of a small increase in vf driven by the stress required to deform the growing film. The effects of strain rate and deformation time balance each other almost exactly so that the film thickness increases exponentially with the total deformation of the diffusion couple

Analysis of the influence of plastic deformations in fatigue and crack process by numerical simulation

International Nuclear Information System (INIS)

Rahimian, Mohammad.

1981-06-01

The aim of this work is to analyze, by numerical simulation the characteristics of the stresses and deformations at the bottom of cracks when plasticity is taken into account. This analysis is performed as from theoretical results laid down in the literature and makes it possible to understand the different solutions obtained from Hencky's deformation law or from the incremental theory. The role of plastic deformation is discussed in depth in the study of fatigue cracks. The problems linked to the fixed crack are studied in the first two chapters. The problems linked to the propagation of cracks are discussed in the following chapters. The fourth chapter is an application of the preceding results and knowledge to fatigue [fr

Nanostructures by Severe Plastic Deformation of Steels: Advantages and Problems

Directory of Open Access Journals (Sweden)

Dobatkin, S. V.

2006-01-01

Full Text Available The aim of this paper is to consider the features of structure evolution during severe plastic deformation (SPD of steels and its influence on mechanical properties. The investigation have been carried out mainly on low carbon steels as well as on austenitic stainless steels after SPD by torsion under high pressure (HPT and equal channel angular (ECA pressing. Structure formation dependencies on temperature deformation conditions, strain degree, chemical composition, initial state and pressure are considered. The role of phase transformations for additional grain refinement, namely, martensitic transformation, precipitation of carbide particles during SPD and heating is underlined.

The effect of plastic deformation on magnetic and magnetocaloric properties of Gd-B alloys

Science.gov (United States)

Taskaev, Sergey; Skokov, Konstantin; Karpenkov, Dmitry; Khovaylo, Vladimir; Ulyanov, Maxim; Bataev, Dmitry; Dyakonov, Alexandr; Fazlitdinova, Alfiya; Gutfleisch, Oliver

2017-11-01

We report on the magnetocaloric effect in Gd100-xBx (x = 0, 10, 15) cold rolled ribbons. A moderate entropy change ΔS = 5 J/kg·K and adiabatic change of ΔT = 4.8 K were observed for the as-cast materials in an external magnetic field of 3 T which is less by 20% in comparison with the pure gadolinium metal. It was found that a significant (up to 70%) depression of magnetization and magnetocaloric properties developed in the course of plastic deformation can completely be restored by means of a high temperature heat treatment. It is concluded that cold rolling is one promising technique for producing foil shaped magnetocaloric materials suitable for designing heat exchangers of magnetic cooling devices.

EBIC and LBIC studies of the properties of extended defects in plastically deformed silicon

Energy Technology Data Exchange (ETDEWEB)

Orlov, V. I.; Feklisova, O. V.; Yakimov, E. B., E-mail: yakimov@iptm.ru [Russian Academy of Sciences, Institute of Microelectronic Technology and Ultra-High-Purity Materials (Russian Federation)

2015-06-15

The results of comparative experimental studies of one- and two-dimensional defects in plastically deformed silicon by the electron-beam-induced current (EBIC) and light-beam-induced current (LBIC) techniques are reported. It is shown that the contrast of two-dimensional defects (dislocation trails) in the LBIC method can by much more pronounced than that in the EBIC technique, which is in good agreement with the results of calculations. The higher sensitivity of the LBIC technique is mainly due to deeper penetration of the optical beam into the material in comparison to the penetration of the electron beam of a scanning electron microscope.

Experimental and numerical analyses of pure copper during ECFE process as a novel severe plastic deformation method

Directory of Open Access Journals (Sweden)

M. Ebrahimi

2014-02-01

Full Text Available In this paper, a new severe plastic deformation method called equal channel forward extrusion (ECFE process has been proposed and investigated by experimental and numerical approaches on the commercial pure copper billets. The experimental results indicated that the magnitudes of yield strength, ultimate tensile strength and Vickers micro-hardness have been markedly improved from 114 MPa, 204 MPa and 68 HV as the annealed condition to 269 MPa, 285 MPa and 126 HV after the fourth pass of ECFE process, respectively. In addition, scanning electron microscopy observation of the samples showed that the average grain size of the as-received state which is about 22 μm has been reduced to 1.4 μm after the final pass. The numerical investigation suggested that although one pass ECFE process fabricates material with the mean effective strain magnitude of about 1, the level of imposed effective plastic strain gradually diminishes from the circumference to the center of the deformed billet.

METHODS FOR LOCAL CHANGES IN THE PLASTIC DEFORMATION DIAGNOSTICS ON THE WORK FUNCTION

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K. V. Panteleyev

2015-01-01

Full Text Available The paper describes the electronic work function measurements by the contact potential difference technique, and experimental demonstration of the possibility of these methods application for the stress-strain state of the surface layer of the metals and alloys. The techniques end examples of their application of localization of plastic deformation studies using the Kelvin probe are developed and present. The study topology of work function the deformed surface possible to determine the type of deformation and dynamics of

Static-transmission-error vibratory-excitation contributions from plastically deformed gear teeth caused by tooth bending-fatigue damage

Science.gov (United States)

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.

Effect of cyclic block loading on character of deformation and strength of structural materials in plane stressed state

International Nuclear Information System (INIS)

Kul'chitskij, N.M.; Troshchenko, A.V.; Koval'chuk, B.I.; Khamaza, L.A.; Nikolaev, I.A.

1982-01-01

The paper is concerned with choice of conditions for preliminary cyclic block loading, determination of fatigue failure resistance characteristics for various structural materials under regular and selected block loading, investigation of the preliminary cyclic loading effect on regularities of elastoplastic deformation of materials concerned in the biaxial stressed state. Under selected conditions of cyclic block loading the character of damage accumulation is close to the linear law for the materials of high-srength doped steel, and VT6 alloys of concern. These materials in the initial state and after preliminary cyclic loading are anisotropic. Axial direction is characterized by a higher plastic strain resistance for steel and tangential direction - for VT6 alloy. The generalized strain curves for the materials in question are not invariant as to the stressed state type. It is stated that the effect of preliminary unsteady cyclic loading on resistance and general regularities of material deformation in the complex stressed state is insignificant. It is observed that stress-strain properties of the materials tend to vary in the following way: plastic strain resistance of the steel lowers and that of VT6 rises, anisotropy of the materials somehow decreases. The variation in the material anisotropy may be attributed to a decrease in residual stresses resulting from preliminary cyclic loading

Chapter 4. Fundamental mechanisms of the low temperature plastic deformation of metals

International Nuclear Information System (INIS)

Fouquet, J. de

1976-01-01

The influence of microstructure, grain boundaries, and strain hardening, on the low temperature plasticity of polycristals is studied. The experimental data on flow stress, work hardening, temperature and strain rate effects, alloying elements and grain size effect are firstly considered, on a macroscopic scale. The mechanisms of the low temperature plastic deformation, and the strain-stress relations are then described in terms of slip modes, mobility, configuration and distributions and interactions of dislocations [fr

Plastic deformation of YBa2Cu3O7-x superconductor compound

International Nuclear Information System (INIS)

Torres V, G.; Moreno, J.E.

1988-01-01

The high temperature superconductor YBa 2 Cu 3 O 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% 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. (author) [pt

Influence of various stresses on diametral and axial plastic deformations of the Phenix reactor fuel cans

International Nuclear Information System (INIS)

Guerin, Y.; Boutard, J.L.

1983-04-01

Dimensions of fuel cans are modified during irradiation in fast reactors: diameter increase is produced by steel swelling and irradiation creep under the pressure of fission gases and length increase integrates swelling. Diameter and density measured on fuel cans in SS 316, irradiated in the Phenix reactor, show that interaction spacer-can and interaction between pins produce plastic deformations. The interaction spacer-can leads not only to a helical deflection of the pin but also a slight axial plastic compression associated to a diametral plastic deformation. There is also a leveling of elongation in these strained pins because of friction with neighbouring pins [fr

Accelerated age hardening by plastic deformation in Al-Cu with minor additions of Si and Ge

International Nuclear Information System (INIS)

Victoria Castro Riglos, M.; Taquire de la Cruz, M.; Tolley, Alfredo

2011-01-01

An extremely fast hardening response with no reduction in peak hardness was obtained in Al-Cu with minor additions of Si and Ge by 8% plastic deformation before artificial aging. The mechanism for the accelerated hardening was determined by detailed characterization with transmission electron microscopy. Plastic deformation was found to enhance the nucleation rate of Si-Ge precipitates, resulting in a higher volume density. Such precipitates catalyzed the formation of θ' precipitates that are responsible for hardening.

The Compositional Variation of Microindentation Induced Densified and Plastic Deformation Volumes in Simple Silicate Glasses

DEFF Research Database (Denmark)

Hermansen, Christian; Matsuoka, Jun; Yoshida, Satoshi

2012-01-01

The densification and plastic deformation occurring in glass subjected to microindentation are established as two independent deformation mechanisms, and thought to be intimately linked to the concept of hardness and crack nucleation (quantified by the load at which radial cracks nucleate at half...

Thermally induced processes in mixtures of aluminum with organic acids after plastic deformations under high pressure

Science.gov (United States)

Zhorin, V. A.; Kiselev, M. R.; Roldugin, V. I.

2017-11-01

DSC is used to measure the thermal effects of processes in mixtures of solid organic dibasic acids with powdered aluminum, subjected to plastic deformation under pressures in the range of 0.5-4.0 GPa using an anvil-type high-pressure setup. Analysis of thermograms obtained for the samples after plastic deformation suggests a correlation between the exothermal peaks observed around the temperatures of degradation of the acids and the thermally induced chemical reactions between products of acid degradation and freshly formed surfaces of aluminum particles. The release of heat in the mixtures begins at 30-40°C. The thermal effects in the mixtures of different acids change according to the order of acid reactivity in solutions. The extreme baric dependences of enthalpies of thermal effects are associated with the rearrangement of the electron subsystem of aluminum upon plastic deformation at high pressures.

Basic Strain Gradient Plasticity Theories with Application to Constrained Film Deformation

DEFF Research Database (Denmark)

Niordson, Christian Frithiof; Hutchinson, John W.

2011-01-01

films: the compression or extension of a finite layer joining rigid platens. Full elastic-plastic solutions are obtained for the same problem based on a finite element method devised for the new class of flow theories. Potential difficulties and open issues associated with the new class of flow theories......A family of basic rate-independent strain gradient plasticity theories is considered that generalize conventional J(2) deformation and flow theories of plasticity to include a dependence on strain gradients in a simple way. The theory builds on three recent developments: the work of Gudmundson (J....... Mech. Phys. Solids 52 (2004), 1379-1406) and Gurtin and Anand (J. Mech. Phys. Solids 57 (2009), 405-421), proposing constitutive relations for flow theories consistent with requirements of positive plastic dissipation; the work of Fleck and Willis (J. Mech. Phys. Solids 57 (2009), 161-177 and 1045...

Birefringence and incipient plastic deformation in elastically overdriven [100] CaF2 under shock compression

Science.gov (United States)

Li, Y.; Zhou, X. M.; Cai, Y.; Liu, C. L.; Luo, S. N.

2018-04-01

[100] CaF2 single crystals are shock-compressed via symmetric planar impact, and the flyer plate-target interface velocity histories are measured with a laser displacement interferometry. The shock loading is slightly above the Hugoniot elastic limit to investigate incipient plasticity and its kinetics, and its effects on optical properties and deformation inhomogeneity. Fringe patterns demonstrate different features in modulation of fringe amplitude, including birefringence and complicated modulations. The birefringence is attributed to local lattice rotation accompanying incipient plasticity. Spatially resolved measurements show inhomogeneity in deformation, birefringence, and fringe pattern evolutions, most likely caused by the inhomogeneity associated with lattice rotation and dislocation slip. Transiently overdriven elastic states are observed, and the incubation time for incipient plasticity decreases inversely with increasing overdrive by the elastic shock.

Production and technological plasticity of commercially pure Titanium in submicrocrystalline state

International Nuclear Information System (INIS)

Danilov, V. I.; Zuev, L. B.; Shlyahova, G. V.; Orlova, D. V; Sharkeev, Yu. P.

2010-01-01

Presented is the method for producing solid billets of commercially pure titanium having low dimensional nanostructure (structural elements < 100 nm). The method is based on multiple unidirectional pressing, with the direction of pressing being changed every other cycle, followed by cold rolling. The microstructure, mechanical characteristics and plastic deformation behavior of material produced by the above method was investigated. The results obtained are presented herein. The loading diagram of titanium alloy in nanostructure state shows a lengthy prefracture portion, which suggests that material undergoes practically no deformation hardening. The latter stage is also distinguished by the emergence of macroscopic nuclei of localized plastic flow, which differ in the level of accumulated deformation. The maximal-amplitude nucleus will remain stationary, pinpointing the place of future fracture. On the meso-scale level formation of meso-bands (folds) is observed, with the distribution and characteristic sizes of the meso-bands corresponding to the arrangement of localized plastic flow macro-nuclei. Characteristically, the local and global loss of plastic flow stability will occur simultaneously in titanium alloy in nanostructure state. On the base of experimental evidence certain modifications can be introduced into the pressing schedules employed by the production of materials in nanostructure state. Key words: titanium, nanostructure state, method of severe plastic deformation, deformation behavior, localized plastic flow, fracture

Determination of plastic anisotropy of zirconium alloys cladding

International Nuclear Information System (INIS)

Yamshchikov, N.V.; Prasolov, P.F.; Shestak, V.E.

1991-01-01

Method for determining plastic anisotropy of zurconium alloy cladding is described. It is based on consideration of material as a combination of transversal crystallites with known distribution over orientations. Such approach enables to describe cladding resistance to plastic deformation at arbitrary stressed state, using the results of texture investigations and uniaxial tests of samples, cut out of claddings along three directions. Plastic anisotropy of fuel element claddings 9.15 and 13.6 mm in diameter up to several percents of plastic deformation is shown

Development of mathematical models for automation of strength calculation during plastic deformation processing

Science.gov (United States)

Steposhina, S. V.; Fedonin, O. N.

2018-03-01

Dependencies that make it possible to automate the force calculation during surface plastic deformation (SPD) processing and, thus, to shorten the time for technological preparation of production have been developed.

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

DEFF Research Database (Denmark)

Moallemi, Mohammad; Zarei-Hanzaki, Abbas; Eskandari, Mostafa

2017-01-01

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......, 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...

Determination of plasticity and strength under long-term rupture of refractory materials

International Nuclear Information System (INIS)

Trunin, I.I.

1981-01-01

A possibility to obtain the equations of temperature- strength dependence of high-heat characteristics on the basis of previously obtained mechanical equation of state is studied, taking account of the accumulation of creep plastic strain. The calculation method of the resource of the material safe work with an account of fracture resistance and deformability at long-term rupture is considered. The 03Kh16N9M2 type steel used in power engeneering industry is examined [ru

Effect of cold plastic deformation on the properties of semihard-magnetic alloys

International Nuclear Information System (INIS)

Kovalev, P.M.; Khazanov, S.A.; Chernyak, A.A.

1982-01-01

The effect of pass and overall reduction during cold plastic deformation on magnetic properties of the 25KKh15 and 25KFN14 iron-cobalt alloys has been studied. It has been found out that gamma-α transformation which intensity id defined by the deformation temperature occurs during the 25KFN14 and 25KKh15 alloy cold rolling. The pass reduction decrease fostering complete proceeding of #betta#-α transformation is equivalent to the increase of overall reduction

Methods for an investigation of the effect of material components on the mechanical characteristics of glass-fiber-reinforced plastics

Science.gov (United States)

Willax, H. O.

1980-01-01

The materials used in the production of glass reinforced plastics are discussed. Specific emphasis is given to matrix polyester materials, the reinforcing glass materials, and aspects of specimen preparation. Various methods of investigation are described, giving attention to optical impregnation and wetting measurements and the gravimetric determination of the angle of contact. Deformation measurements and approaches utilizing a piezoelectric device are also considered.

Prediction of fretting fatigue behavior under elastic-plastic conditions

International Nuclear Information System (INIS)

Shin, Ki Su

2009-01-01

Fretting fatigue generally leads to the degradation of the fatigue strength of a material due to cyclic micro-slip between two contacting materials. Fretting fatigue is regarded as an important issue in designing aerospace structures. While many studies have evaluated fretting fatigue behavior under elastic deformation conditions, few have focused on fretting fatigue behavior under elastic-plastic deformation conditions, especially the crack orientation and fatigue life prediction for Ti-6Al-4V. The primary goal of this study was to characterize the fretting fatigue crack initiation behavior in the presence of plasticity. Experimental tests were performed using pad configurations involving elastic-plastic deformations. To calculate stress distributions under elastic-plastic fretting fatigue conditions, FEA was also performed. Several parametric approaches were used to predict fretting fatigue life along with stress distribution resulting from FEA. However, those parameters using surface stresses were unable to establish an equivalence between elastic fretting fatigue data and elastic-plastic fretting fatigue data. Based on this observation, the critical distance methods, which are commonly used in notch analysis, were applied to the fretting fatigue problem. In conclusion, the effective strain range method when used in conjunction with the SMSSR parameter showed a good correlation of data points between the pad configurations involving elastic and elastic plastic deformations

Influence of hot plastic deformation and cooling rate on martensite and bainite start temperatures in 22MnB5 steel

International Nuclear Information System (INIS)

Nikravesh, M.; Naderi, M.; Akbari, G.H.

2012-01-01

Highlights: ► Reduction of cooling rate, can cause to increase or decrease M s and M f . ► 40% hot plastic deformation hindered the martensitic transformation. ► Hot plastic deformation, caused to decrease M f and M s , while B s increased. ► The critical cooling rate increased 40 °C/s due to apply 40% hot deformation. - Abstract: During hot stamping process, hot forming, cooling and phase transformations are performed in a single step. As a matter of fact, multifunctional phenomena happen and affect each other. Among these phenomena, martensitic and bainitic transformations have the greatest importance. In the current research, the start temperatures of martensite and bainite of 22MnB5 boron steel have been measured in undeformed and 40% deformed conditions, and in various cooling rates from 0.4 °C/s to 100 °C/s by means of deformation dilatometer. It is concluded that, reduction of cooling rate, could bring about an increase or decrease in M s and M f , depending on other phases formation before martensite. Also, hot plastic deformation, hindered the martensitic transformation and decreased M f and M s especially at lower cooling rates, while B s increased. Furthermore, the critical cooling rate, increased about 40 °C/s by applying 40% hot plastic deformation.

Electron microscopy and plastic deformation of industrial austenitic stainless steels

International Nuclear Information System (INIS)

Thomas, Barry

1976-01-01

The different mechanisms of plastic deformation observed in austenitic stainless steels are described and the role of transmission electron microscopy in the elucidation of the mechanisms is presented. At temperatures below 0,5Tm, different variants of dislocation glide are competitive: slip of perfect and partial dislocations, mechanical twinning and strain-induced phase transformations. The predominance of one or other of these mechanisms can be rationalized in terms of the temperature and composition dependence of the stacking fault energy and the thermodynamic stability of the austenite. At temperatures above 0,5Tm dislocation climb and diffusion of point defects become increasingly important and at these temperatures recovery, recrystallization and precipitation can also occur during deformation [fr

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

Science.gov (United States)

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.

Crystal plasticity study of monocrystalline stochastic honeycombs under in-plane compression

International Nuclear Information System (INIS)

Ma, Duancheng; Eisenlohr, Philip; Epler, Eike; Volkert, Cynthia A.; Shanthraj, Pratheek; Diehl, Martin; Roters, Franz; Raabe, Dierk

2016-01-01

We present a study on the plastic deformation of single crystalline stochastic honeycombs under in-plane compression using a crystal plasticity constitutive description for face-centered cubic (fcc) materials, focusing on the very early stage of plastic deformation, and identifying the interplay between the crystallographic orientation and the cellular structure during plastic deformation. We observe that despite the stochastic structure, surprisingly, the slip system activations in the honeycombs are almost identical to their corresponding bulk single crystals at the early stage of the plastic deformation. On the other hand, however, the yield stresses of the honeycombs are nearly independent of their crystallographic orientations. Similar mechanical response is found in compression testing of nanoporous gold micro-pillars aligned with various crystallographic orientations. The macroscopic stress tensors of the honeycombs show the same anisotropy as their respective bulk single crystals. Locally, however, there is an appreciable fluctuation in the local stresses, which are even larger than for polycrystals. This explains why the Taylor/Schmid factor associated with the crystallographic orientation is less useful to estimate the yield stresses of the honeycombs than the bulk single crystals and polycrystals, and why the plastic deformation occurs at smaller strains in the honeycombs than their corresponding bulk single crystals. Besides these findings, the observations of the crystallographic reorientation suggest that conventional orientation analysis tools, such as inverse pole figure and related tools, would in general fail to study the plastic deformation mechanism of monocrystalline cellular materials.

Microstructure, Slip Systems and Yield Stress Anisotropy in Plastic Deformation

DEFF Research Database (Denmark)

Winther, Grethe; You, Ze Sheng; Lu, Lei

The highly anisotropic microstructures in nanotwinned copper produced by electrodeposition provide an excellent opportunity to evaluate models for microstructurally induced mechanical anisotropy. A crystal plasticity model originally developed for the integration of deformation induced dislocatio...... boundaries with texture is applied to account for the effects of texture as well as twin and grain boundaries, providing good qualitative agreement with experimental yield stress and yield stress anisotropy data....

Elasto/visco-plastic analysis of moderately thick shells of revolution

International Nuclear Information System (INIS)

Takezono, S.; Tanoue, M.

1981-01-01

The analytical formulation on the elasto-visco-plastic problems of general, moderately thick shells of revolution subjected to axisymmetrical load is developed by extension of the Reissner theory in elastic shells where a consideration on the effect of shear deformations is given. The authors employ as constitutive relation of the shell materials Perzyna's equation where in the plastic range the viscosity of the material is considered. The criterion for yielding used in this analysis is the von Mises yield theory. The basic differential equations derived for elasto-visco-plastic problems are numerically solved by a finite difference method, and the solutions are obtained by integration of the incremental values. As a numerical example, the elasto/visco-plastic deformation of pressure vessels is analyzed, and the results are compared with those from the classical theory which neglects the effect of shear deformations. (orig.)

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

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Effect of a defect structure on the static and long-term strength of submicrocrystalline VT1-0 titanium fabricated by plastic deformation during screw and lengthwise rolling

Czech Academy of Sciences Publication Activity Database

Betekhtin, V. I.; Kolobov, Yu. R.; Sklenička, Václav; Kadomtsev, A. G.; Narykova, M. V.; Dvořák, Jiří; Golosov, E. V.; Kardashev, B. K.; Kuz'menko, I. N.

2015-01-01

Roč. 60, č. 1 (2015), s. 66-71 ISSN 1063-7842 Institutional support: RVO:68081723 Keywords : titanium * nanoporosity * carbide dispersion * thermal stability * severe plastic deformation Subject RIV: JJ - Other Materials Impact factor: 0.569, year: 2015

Mechanical strength model for plastic bonded granular materials at high strain rates and large strains

International Nuclear Information System (INIS)

Browning, R.V.; Scammon, R.J.

1998-01-01

Modeling impact events on systems containing plastic bonded explosive materials requires accurate models for stress evolution at high strain rates out to large strains. For example, in the Steven test geometry reactions occur after strains of 0.5 or more are reached for PBX-9501. The morphology of this class of materials and properties of the constituents are briefly described. We then review the viscoelastic behavior observed at small strains for this class of material, and evaluate large strain models used for granular materials such as cap models. Dilatation under shearing deformations of the PBX is experimentally observed and is one of the key features modeled in cap style plasticity theories, together with bulk plastic flow at high pressures. We propose a model that combines viscoelastic behavior at small strains but adds intergranular stresses at larger strains. A procedure using numerical simulations and comparisons with results from flyer plate tests and low rate uniaxial stress tests is used to develop a rough set of constants for PBX-9501. Comparisons with the high rate flyer plate tests demonstrate that the observed characteristic behavior is captured by this viscoelastic based model. copyright 1998 American Institute of Physics

On a phase field approach for martensitic transformations in a crystal plastic material at a loaded surface

Science.gov (United States)

Schmitt, Regina; Kuhn, Charlotte; Müller, Ralf

2017-07-01

A continuum phase field model for martensitic transformations is introduced, including crystal plasticity with different slip systems for the different phases. In a 2D setting, the transformation-induced eigenstrain is taken into account for two martensitic orientation variants. With aid of the model, the phase transition and its dependence on the volume change, crystal plastic material behavior, and the inheritance of plastic deformations from austenite to martensite are studied in detail. The numerical setup is motivated by the process of cryogenic turning. The resulting microstructure qualitatively coincides with an experimentally obtained martensite structure. For the numerical calculations, finite elements together with global and local implicit time integration scheme are employed.

The plastic flow localization effect on crystalline material

International Nuclear Information System (INIS)

Pajot, A.

2011-01-01

Irradiation affects the mechanical properties of materials. In particular, an increase of yield strength followed by a decrease of ductility and a reduction of the elongation to fracture are observed above a threshold irradiation dose. The last two phenomena are correlated with the appearance of bands free of defects (clear bands) in which plastic deformation is confined. These bands also determine accumulation of dislocations at grain boundaries, thereby favouring local grain decohesion and possibly initiating fracture. Clear bands have an important impact on metal resistance, nevertheless our level of understanding is not sufficient to evaluate quantitatively their effect on the loss of ductility and reduction of elongation to fracture that are observed experimentally. A clear band is a microstructural defect, created when loading an irradiated material. Its complex interaction with defects on the nano scale affects the behaviour of the metal at the macroscopic scale. A full understanding implies the application of a multi scale modeling approach. This explains why, even though clear bands have first been

GRINDING OF SURFACES WITH COATINGS FORMED BY ELECTROMAGNETIC FACING WITH SURFACE PLASTIC DEFORMATION

Directory of Open Access Journals (Sweden)

Zh. A. Mrochek

2011-01-01

Full Text Available The paper presents investigation results on machining of surfaces having a coating formed by electromagnetic facing with surface plastic deformation and using abrasive and diamond wheels having a porous metal binder with orientated drains.

Prediction of plastic deformation under contact condition by quasi-static and dynamic simulations using explicit finite element analysis

International Nuclear Information System (INIS)

Siswanto, W. A.; Nagentrau, M.; Tobi, A. L. Mohd; Tamin, M. N.

2016-01-01

We compared the quasi-static and dynamic simulation responses on elastic-plastic deformation of advanced alloys using Finite element (FE) method with an explicit numerical algorithm. A geometrical model consisting of a cylinder-on-flat surface contact under a normal load and sliding motion was examined. Two aeroengine materials, Ti-6Al-4V and Super CMV (Cr-Mo-V) alloy, were employed in the FE analysis. The FE model was validated by comparative magnitudes of the FE-predicted maximum contact pressure variation along the contact half-width length with the theoretical Hertzian contact solution. Results show that the (compressive) displacement of the initial contact surface steadily increases for the quasi-static load case, but accumulates at an increasing rate to the maximum level for the dynamic loading. However, the relatively higher stiffness and yield strength of the Super CMV alloy resulted in limited deformation and low plastic strain when compared to the Ti-6Al-4V alloy. The accumulated equivalent plastic strain of the material point at the initial contact position was nearly a thousand times higher for the dynamic load case (for example, 6.592 for Ti-6Al-4V, 1.0 kN) when compared to the quasi-static loading (only 0.0072). During the loading step, the von Mises stress increased with a decreasing and increasing rate for the quasi-static and dynamic load case, respectively. A sudden increase in the stress magnitude to the respective peak value was registered due to the additional constraint to overcome the static friction of the mating surfaces during the sliding step

Prediction of plastic deformation under contact condition by quasi-static and dynamic simulations using explicit finite element analysis

Energy Technology Data Exchange (ETDEWEB)

Siswanto, W. A.; Nagentrau, M.; Tobi, A. L. Mohd [Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, Batu Pahat (Malaysia); Tamin, M. N. [Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor Bahru (Malaysia)

2016-11-15

We compared the quasi-static and dynamic simulation responses on elastic-plastic deformation of advanced alloys using Finite element (FE) method with an explicit numerical algorithm. A geometrical model consisting of a cylinder-on-flat surface contact under a normal load and sliding motion was examined. Two aeroengine materials, Ti-6Al-4V and Super CMV (Cr-Mo-V) alloy, were employed in the FE analysis. The FE model was validated by comparative magnitudes of the FE-predicted maximum contact pressure variation along the contact half-width length with the theoretical Hertzian contact solution. Results show that the (compressive) displacement of the initial contact surface steadily increases for the quasi-static load case, but accumulates at an increasing rate to the maximum level for the dynamic loading. However, the relatively higher stiffness and yield strength of the Super CMV alloy resulted in limited deformation and low plastic strain when compared to the Ti-6Al-4V alloy. The accumulated equivalent plastic strain of the material point at the initial contact position was nearly a thousand times higher for the dynamic load case (for example, 6.592 for Ti-6Al-4V, 1.0 kN) when compared to the quasi-static loading (only 0.0072). During the loading step, the von Mises stress increased with a decreasing and increasing rate for the quasi-static and dynamic load case, respectively. A sudden increase in the stress magnitude to the respective peak value was registered due to the additional constraint to overcome the static friction of the mating surfaces during the sliding step.

MD simulation of plastic deformation nucleation in stressed crystallites under irradiation

Energy Technology Data Exchange (ETDEWEB)

Korchuganov, A. V., E-mail: avkor@ispms.tsc.ru; Zolnikov, K. P., E-mail: kost@ispms.tsc.ru; Kryzhevich, D. S., E-mail: kryzhev@ispms.tsc.ru [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Branch (Russian Federation); Chernov, V. M., E-mail: VMChernov@bochvar.ru [National Research Tomsk State University (Russian Federation); Psakhie, S. G., E-mail: sp@ispms.tsc.ru [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Branch (Russian Federation)

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).

Deformation mechanisms of nanograined metallic polycrystals

Czech Academy of Sciences Publication Activity Database

Saada, G.; Kruml, Tomáš

2011-01-01

Roč. 59, - (2011), s. 2565-2574 ISSN 1359-6454 Institutional research plan: CEZ:AV0Z20410507 Keywords : nanocrystalline materials * grain boundary defects * plastic deformation Subject RIV: JJ - Other Materials Impact factor: 3.755, year: 2011

Influence of hot plastic deformation and cooling rate on martensite and bainite start temperatures in 22MnB5 steel

Energy Technology Data Exchange (ETDEWEB)

Nikravesh, M., E-mail: nikravesh@yahoo.com [Department of Material Science and Engineering, Shahid Bahonar University, Kerman (Iran, Islamic Republic of); Naderi, M. [Department of Mining and Metallurgy, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Akbari, G.H. [Department of Material Science and Engineering, Shahid Bahonar University, Kerman (Iran, Islamic Republic of)

2012-04-01

Highlights: Black-Right-Pointing-Pointer Reduction of cooling rate, can cause to increase or decrease M{sub s} and M{sub f}. Black-Right-Pointing-Pointer 40% hot plastic deformation hindered the martensitic transformation. Black-Right-Pointing-Pointer Hot plastic deformation, caused to decrease M{sub f} and M{sub s}, while B{sub s} increased. Black-Right-Pointing-Pointer The critical cooling rate increased 40 Degree-Sign C/s due to apply 40% hot deformation. - Abstract: During hot stamping process, hot forming, cooling and phase transformations are performed in a single step. As a matter of fact, multifunctional phenomena happen and affect each other. Among these phenomena, martensitic and bainitic transformations have the greatest importance. In the current research, the start temperatures of martensite and bainite of 22MnB5 boron steel have been measured in undeformed and 40% deformed conditions, and in various cooling rates from 0.4 Degree-Sign C/s to 100 Degree-Sign C/s by means of deformation dilatometer. It is concluded that, reduction of cooling rate, could bring about an increase or decrease in M{sub s} and M{sub f}, depending on other phases formation before martensite. Also, hot plastic deformation, hindered the martensitic transformation and decreased M{sub f} and M{sub s} especially at lower cooling rates, while B{sub s} increased. Furthermore, the critical cooling rate, increased about 40 Degree-Sign C/s by applying 40% hot plastic deformation.

The Plastic Deformation of RFSSW Joints During Tensile Tests / Deformacja Plastyczna Wybranych Połączeń RFSSW Podczas Rozciągania

Directory of Open Access Journals (Sweden)

Lacki P.

2015-12-01

Full Text Available The dynamic development of the friction stir welding (FSW technology is the basis for the design of durabe joints inter alia in the aviation industry. This technology has a prospective application, especially for the aluminum alloys. It is suitable for a broad spectrum of permanent joints. The joints obtained by FSW technology are characterized by good mechanical properties. In this paper, the friction stir spot welding joints were analysed. The example of a structure made using this technology were presented. The lap joints made of 2mm Al 6061-T6 sheets were the investigation subject. The different spot welds arrangements were analysed. The tensile test were performed with optical deformation measurement system, which allow to obtain the plastic deformation field on the sample surface. The plastic strain graphs for the characteristic line passing through the maximum deformation were registered and presented. The experimental results were compared to the FEM numerical analysis. The numerical models were built with 3D-solid elements. The boundary conditions, material properties and geometry of the joints were identical as during experimental investigation. The mechanism of deformation of welded joints during tensile test was described and explained. It has been found that the arrangement of the spot welds with respect to the tensile direction has an important influence on the behaviour and deformation of lap joint.

Modelling of elasto-plastic material behaviour

International Nuclear Information System (INIS)

Halleux, J.P.

1981-01-01

The present report describes time-independent elasto-plastic material behaviour modelling techniques useful for implementation in fast structural dynamics computer programs. Elasto-plastic behaviour is characteristic for metallic materials such as steel and is thus of particular importance in the study of reactor safety-related problems. The classical time-independent elasto-plastic flow theory is recalled and the fundamental incremental stress-strain relationships are established for strain rate independent material behaviour. Some particular expressions useful in practice and including reversed loading are derived and suitable computational schemes are shwon. Modelling of strain rate effects is then taken into account, according to experimental data obtained from uniaxial tension tests. Finally qualitative strain rate history effects are considered. Applications are presented and illustrate both static and dynamic material behaviour

Numerical simulation of large deformation polycrystalline plasticity

International Nuclear Information System (INIS)

Inal, K.; Neale, K.W.; Wu, P.D.; MacEwen, S.R.

2000-01-01

A finite element model based on crystal plasticity has been developed to simulate the stress-strain response of sheet metal specimens in uniaxial tension. Each material point in the sheet is considered to be a polycrystalline aggregate of FCC grains. The Taylor theory of crystal plasticity is assumed. The numerical analysis incorporates parallel computing features enabling simulations of realistic models with large number of grains. Simulations have been carried out for the AA3004-H19 aluminium alloy and the results are compared with experimental data. (author)

Non-proportional deformation paths for sheet metal: experiments and models

NARCIS (Netherlands)

van den Boogaard, Antonius H.; van Riel, M.; Hora, P.

2009-01-01

For mild steel, after significant plastic deformation in one direction, a subsequent deformation in an orthogonal direction shows a typical stress overshoot compared to monotonic deformation. This phenomenon is investigated experimentally and numerically on a DC06 material. Two models that

Small-scale plasticity critically needs a new mechanics description

Science.gov (United States)

Ngan, Alfonso H. W.

2013-06-01

Continuum constitutive laws describe the plastic deformation of materials as a smooth, continuously differentiable process. However, provided that the measurement is done with a fine enough resolution, the plastic deformation of real materials is often found to comprise discrete events usually nanometric in size. For bulk-sized specimens, such nanoscale events are minute compared with the specimen size, and so their associated strain changes are negligibly small, and this is why the continuum laws work well. However, when the specimen size is in the micrometer scale or smaller, the strain changes due to the discrete events could be significant, and the continuum description would be highly unsatisfactory. Yet, because of the advent of microtechnology and nanotechnolgy, small-sized materials will be increasingly used, and so there is a strong need to develop suitable replacement descriptions for plasticity of small materials. As the occurrence of the discrete plastic events is also strongly stochastic, their satisfactory description should also be one of a probabilistic, rather than deterministic, nature.

Tailoring dislocation structures and mechanical properties of nanostructured metals produced by plastic deformation

DEFF Research Database (Denmark)

Huang, Xiaoxu

2009-01-01

The presence of a dislocation structure associated with low-angle dislocation boundaries and interior dislocations is a common and characteristic feature in nanostructured metals produced by plastic deformation, and plays an important role in determining both the strength and ductility...

On Loosening Plastic Composite under Active Load and Its Influence on the Deformation and Strength Properties

Directory of Open Access Journals (Sweden)

K. F. Komkov

2015-01-01

Full Text Available Processing the test results of the composite, which is a mechanical mixture of metal particles with a plastic polymer binder, has shown that its deformation and strength properties are substantially different from those of stable plastic material. The specimen tests for tensile and compression with measuring transverse deformations, as well as torsion tests of tubular samples have revealed that the process of its deformation is accompanied by a change in the original structure.The composite instability is caused by the fact that during this process, it acquires considerable loosening that depends on the type of the stress-state. Hard metal particles are hardly deformed at any stress-state, but they form a layer of bonds that affect the mixture behavior under force action. The total deformation is the plastic flow of the binder on which deformation, caused both by sliding and by loss of the surface layer bonds, is superimposed.The analysis shows that with destruction at tensile test the non-linear part of the bulk deformation (dilatancy is 6 times more than "conditionally" elastic (3.5 times compressed. The objective of this work is to develop a technique for determining a dilatancy, define its influence on deformation and strength properties of the composite, and improve the mathematical model of the material. The proposed model based on the tensor-nonlinear equations describes loosening, as an additional component of the mean deformation and as a mean stress component, hereinafter referred to as: the first - by the deformation, the second – by the stress. A ratio value of the nonlinear part of deformation with the quadratic tensor argument to the linear part, which reaches 0.3, shows the need for such equations. It also shows the influence of deformation on the relationship between the deviators.To enhance capabilities of mathematical model is possible after including therein the equations for the spherical part of the tensor of deformation

Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic and Precipitation Hardening Stainless Steels by Gaseous Nitriding

DEFF Research Database (Denmark)

Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... case included X-ray diffraction analysis, reflected light microscopy and microhardness. The results demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

Prediction of elastic-plastic response of structural elements subjected to cyclic loading

International Nuclear Information System (INIS)

El Haddad, M.H.; Samaan, S.

1985-01-01

A simplified elastic-plastic analysis is developed to predict stress strain and force deformation response of structural metallic elements subjected to irregular cyclic loadings. In this analysis a simple elastic-plastic method for predicting the skeleton force deformation curve is developed. In this method, elastic and fully plastic solutions are first obtained for unknown quantities, such as deflection or local strains. Elastic and fully plastic contributions are then combined to obtain an elastic-plastic solution. The skeleton curve is doubled to establish the shape of the hysteresis loop. The complete force deformation response can therefore be simulated through reversal by reversal in accordance with hysteresis looping and material memory. Several examples of structural elements with various cross sections made from various materials and subjected to irregular cyclic loadings, are analysed. A close agreement is obtained between experimental results found in the literature and present predictions. (orig.)

Influence of thermally activated processes on the deformation behavior during low temperature ECAP

Science.gov (United States)

Fritsch, S.; Scholze, M.; F-X Wagner, M.

2016-03-01

High strength aluminum alloys are generally hard to deform. Therefore, the application of conventional severe plastic deformation methods to generate ultrafine-grained microstructures and to further increase strength is considerably limited. In this study, we consider low temperature deformation in a custom-built, cooled equal channel angular pressing (ECAP) tool (internal angle 90°) as an alternative approach to severely plastically deform a 7075 aluminum alloy. To document the maximum improvement of mechanical properties, these alloys are initially deformed from a solid solution heat-treated condition. We characterize the mechanical behavior and the microstructure of the coarse grained initial material at different low temperatures, and we analyze how a tendency for the PLC effect and the strain-hardening rate affect the formability during subsequent severe plastic deformation at low temperatures. We then discuss how the deformation temperature and velocity influence the occurrence of PLC effects and the homogeneity of the deformed ECAP billets. Besides the mechanical properties and these microstructural changes, we discuss technologically relevant processing parameters (such as pressing forces) and practical limitations, as well as changes in fracture behavior of the low temperature deformed materials as a function of deformation temperature.

Nanoscale lamellae in an oxide dispersion strengthened steel processed by dynamic plastic deformation

DEFF Research Database (Denmark)

Zhang, Zhenbo; Mishin, Oleg; Tao, N. R.

2014-01-01

The microstructure of an oxide dispersion strengthened ferritic PM2000 steel with a strong initial (100) texture has been investigated after compression by dynamic plastic deformation (DPD) at room temperature to a strain of 2.1. Measurements using electron backscatter diffraction and transmission...

Higher harmonic imaging of tensile plastic deformation in loading and reloading processes by local resonance method

International Nuclear Information System (INIS)

Kawashima, Koichiro; Yasui, Hajime

2015-01-01

We have imaged plastically deformed region in a 5052 aluminum plate under tensile loading, unloading and reloading processes by using an immersion local resonance method. By transmitting large-amplitude burst wave of which frequency is a through-thickness resonant frequency of the plate, dislocation loops in plastic zone are forced to vibrate. The higher harmonic amplitude excited by the dislocation movement is mapped for the transducer position. The extension of plastic zone under monotonically increased loading, decrease in harmonic amplitude under unloading process and marked extension of plastic zone in reloading up to 0.4% plastic strain are clearly imaged. (author)

A multi-scale methodology to model damage, deformation and ignition of highly-filled energetic materials

Energy Technology Data Exchange (ETDEWEB)

Vivier, G. [Paris Univ., Paris (France). LMT Cachan; CEA Le Ripault, Monts (France); Trumel, H. [CEA Le Ripault, Monts (France); Hild, F. [Paris Univ., Paris (France). LMT Cachan

2009-07-01

The kinetic energy that occurs when energetic materials are impacted can be converted to heat through dissipative deformation processes while the macroscopic temperature remains unaffected. In this study, a thermodynamics-based approach was used to model the elasto-plastic behaviour that occurs during the deformation process of microstructures. Macroscopic material was modelled as a statistical distribution of unit cells containing a crack grain embedded in an elastic mortar-like matrix. A mesoscopic unit cell model was also developed under confined shear. The study demonstrated that stored energy is a non-negligible part of the total energy of the system, and that stored energy can be released during the unloading process. It was concluded that the mesoscopic analysis of the cracked cell demonstrates that continuum thermodynamics can be used to predict hot spots induced by friction. 7 refs., 7 figs.

Effect of plastic deformation on the supercooled austenite transformations of the Cr-Mo steel with Nb, Ti and B microadditions

International Nuclear Information System (INIS)

Adamczyk, J.; Opiela, M.

1998-01-01

Effect of plastic deformation at austenizing temperature was investigated on phase transformations, structure and hardness of the supercooled austenite transformation products of the Cr-Mo constructional steel with Nb, Ti and B microadditions. Basing on the analysis of the phase transformation plots of the supercooled undeformed austenite and of the supercooled and plastically deformed one, it was found out that direct cooling of specimens after completing their plastic deformation in the above mentioned conditions, results in significant acceleration of the α→β, and ferritic and pearlitic transformations, and in the decrease of transformation products hardness. These phenomena are of great importance for working out of the thermo-mechanical treatment of products made from the heat-treated microalloyed steel. (author)

Numerical simulation of elasto-plastic deformation of composites: evolution of stress microfields and implications for homogenization models

Science.gov (United States)

González, C.; Segurado, J.; LLorca, J.

2004-07-01

The deformation of a composite made up of a random and homogeneous dispersion of elastic spheres in an elasto-plastic matrix was simulated by the finite element analysis of three-dimensional multiparticle cubic cells with periodic boundary conditions. "Exact" results (to a few percent) in tension and shear were determined by averaging 12 stress-strain curves obtained from cells containing 30 spheres, and they were compared with the predictions of secant homogenization models. In addition, the numerical simulations supplied detailed information of the stress microfields, which was used to ascertain the accuracy and the limitations of the homogenization models to include the nonlinear deformation of the matrix. It was found that secant approximations based on the volume-averaged second-order moment of the matrix stress tensor, combined with a highly accurate linear homogenization model, provided excellent predictions of the composite response when the matrix strain hardening rate was high. This was not the case, however, in composites which exhibited marked plastic strain localization in the matrix. The analysis of the evolution of the matrix stresses revealed that better predictions of the composite behavior can be obtained with new homogenization models which capture the essential differences in the stress carried by the elastic and plastic regions in the matrix at the onset of plastic deformation.

Effects of microscopic boundary conditions on plastic deformations of small-sized single crystals

DEFF Research Database (Denmark)

Kuroda, Mitsutoshi; Tvergaard, Viggo

2009-01-01

The finite deformation version of the higher-order gradient crystal plasticity model proposed by the authors is applied to solve plane strain boundary value problems, in order to obtain an understanding of the effect of the higher-order boundary conditions. Numerical solutions are carried out...

Simulated small-angle scattering patterns for a plastically deformed model composite material

NARCIS (Netherlands)

Shenoy, V.B.; Cleveringa, H.H.M.; Phillips, R.; Giessen, E. van der; Needleman, A.

2000-01-01

The small-angle scattering patterns predicted by discrete dislocation plasticity versus local and non-local continuum plasticity theory are compared in a model problem. The problem considered is a two-dimensional model composite with elastic reinforcements in a crystalline matrix subject to

Studies on internal friction in electron-irradiated iron crystals after plastic deformation

International Nuclear Information System (INIS)

Wolf, J.

1986-01-01

For the analysis of atomic point defects in high-purity the generation of atomic point defects was, above all, carried out by electron radiation, but in addition, also by plastic deformation. The exposure to radiation was realized at different temperatures in the Dynamitron of the University of Stuttgart (80 K, 160 K) and also in the low-temperature radiation facility of the nuclear research plant (KfA) Juelich (50 K). The radiation doses ranged between 2.7.10 21 e - /m 2 and 1.0.10 23 e - /m 2 . In situ plastic deformation was achieved at about 80 K (torsion, 4%). Internal friction which was determined in an inverse torsion pendulum in the temperature range of 80 K - 700 K and at frequencies of about 1 Hz served as defect indicator. In this study simulation programs were developed which were to give information prior to the realization of measurements on the temperatures and the intensity of the damping peaks to be expected. The internal friction peaks measured in the framework of this study could be assigned to the recovery stages I-IV. The measured values were discussed for three temperature ranges with main emphasis on the investigation of the recovering, radiation-induced or deformation-induced, atomic point defect in the temperature range of the recovery stage III (200 K - 270 K). (orig./MM) [de

Size effects in olivine control strength in low-temperature plasticity regime

Science.gov (United States)

Kumamoto, K. M.; Thom, C.; Wallis, D.; Hansen, L. N.; Armstrong, D. E. J.; Goldsby, D. L.; Warren, J. M.; Wilkinson, A. J.

2017-12-01

The strength of the lithospheric mantle during deformation by low-temperature plasticity controls a range of geological phenomena, including lithospheric-scale strain localization, the evolution of friction on deep seismogenic faults, and the flexure of tectonic plates. However, constraints on the strength of olivine in this deformation regime are difficult to obtain from conventional rock-deformation experiments, and previous results vary considerably. We demonstrate via nanoindentation that the strength of olivine in the low-temperature plasticity regime is dependent on the length-scale of the test, with experiments on smaller volumes of material exhibiting larger yield stresses. This "size effect" has previously been explained in engineering materials as a result of the role of strain gradients and associated geometrically necessary dislocations in modifying plastic behavior. The Hall-Petch effect, in which a material with a small grain size exhibits a higher strength than one with a large grain size, is thought to arise from the same mechanism. The presence of a size effect resolves discrepancies among previous experimental measurements of olivine, which were either conducted using indentation methods or were conducted on polycrystalline samples with small grain sizes. An analysis of different low-temperature plasticity flow laws extrapolated to room temperature reveals a power-law relationship between length-scale (grain size for polycrystalline deformation and contact radius for indentation tests) and yield strength. This suggests that data from samples with large inherent length scales best represent the plastic strength of the coarse-grained lithospheric mantle. Additionally, the plastic deformation of nanometer- to micrometer-sized asperities on fault surfaces may control the evolution of fault roughness due to their size-dependent strength.

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

Science.gov (United States)

Roopwani, Rahul; Buckner, Ira S

2011-10-14

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

An accurate tangential force-displacement model for granular-flow simulations: Contacting spheres with plastic deformation, force-driven formulation

International Nuclear Information System (INIS)

Vu-Quoc, L.; Lesburg, L.; Zhang, X.

2004-01-01

An elasto-plastic frictional tangential force-displacement (TFD) model for spheres in contact for accurate and efficient granular-flow simulations is presented in this paper; the present TFD is consistent with the elasto-plastic normal force-displacement (NFD) model presented in [ASME Journal of Applied Mechanics 67 (2) (2000) 363; Proceedings of the Royal Society of London, Series A 455 (1991) (1999) 4013]. The proposed elasto-plastic frictional TFD model is accurate, and is validated against non-linear finite-element analyses involving plastic flows under both loading and unloading conditions. The novelty of the present TFD model lies in (i) the additive decomposition of the elasto-plastic contact area radius into an elastic part and a plastic part, (ii) the correction of the particles' radii at the contact point, and (iii) the correction of the particles' elastic moduli. The correction of the contact-area radius represents an effect of plastic deformation in colliding particles; the correction of the radius of curvature represents a permanent indentation after impact; the correction of the elastic moduli represents a softening of the material due to plastic flow. The construction of both the present elasto-plastic frictional TFD model and its consistent companion, the elasto-plastic NFD model, parallels the formalism of the continuum theory of elasto-plasticity. Both NFD and TFD models form a coherent set of force-displacement (FD) models not available hitherto for granular-flow simulations, and are consistent with the Hertz, Cattaneo, Mindlin, Deresiewicz contact mechanics theory. Together, these FD models will allow for efficient simulations of granular flows (or granular gases) involving a large number of particles

Influence of changing in sign plastic deformation on shape memory effects in titanium nickelide

International Nuclear Information System (INIS)

Belyaev, S.P.; Volkov, A.E.; Evard, M.E.; Leskina, M.L.

2005-01-01

The effects of shape memory, martensite transformation plasticity, and two-way shape memory in titanium nickelide (TiNi) prestrained in an alternating-sign mode have been studied. It was ascertained that the reversible deformation and the temperature-dependent deformation kinetics in the temperature interval of martensite transformation were independent of the degree of prestraining. Based on the results the conclusion is made that an increase in the density of dislocations does not influence essentially the deformation behavior of titanium nickelide in the vicinity of the martensite transformation. The results of computer simulation based on the structural analytical theory are in a satisfactory agreement with the experiment [ru

Computing the effect of plastic deformation of piping on pressure transient propagation

International Nuclear Information System (INIS)

Youngdahl, C.K.; Kot, C.A.

1977-01-01

The computer program PTA-1 performs pressure-transient analysis of large piping networks using the one-dimensional method of characteristics applied to a fluid-hammer formulation. The effect of elastic-plastic deformation of piping on pulse propagation is included in the computation. Each pipe is modeled as a series of rings, neglecting axial effects, bending moments, and inertia. The fluid wave speed is a function of pipe deformation and, consequently, of position and time. Comparison with existing experimental data indicate that this simple fluid-structure interaction model gives suprisingly accurate results for both pressure histories in the fluid and strain histories in the piping

Mechanisms of the plastic deformation of uranium alloys at low temperature

International Nuclear Information System (INIS)

Le Poac, P.; Nomine, A.M.; Miannay, D.

1976-01-01

The mechanical characteristics of the bcc binary alloys U-6Mo, U-8Mo, U-10Mo, U-12Mo and bcc ternary alloys U-8Mo-1Ti, U-10Mo-1Ti, U-10Mo-1Zr, stressed in compression, were determined between -196 deg C and + 450 deg C. The plastic flow shear stress in non-dependent on temperature above 300 deg C. At lower temperature shear stress is highly activated, except for the alloy U-6Mo and U-12Mo. Athermal shear stress above 300 deg C is due to the hardening of the solid solution described by Mott and Nabarro. In the thermal range, the recombination of the dissociated dislocations controls the plastic deformation [fr

Relationship between side necking and plastic zone size at fracture

International Nuclear Information System (INIS)

Kim, Do Hyung; Kang, Ki Ju; Kim, Dong Hak

2004-01-01

Generally, fracture of a material is influenced by plastic zone size developed near the crack tip. Hence, according to the relative size of plastic zone in the material, the mechanics as a tool for analyzing the fracture process are classified into three kinds, that is, Linear Elastic Fracture Mechanics, Elastic Plastic Fracture Mechanics, Large Deformation Fracture Mechanics. Even though the plastic zone size is such an important parameter, the practical measurement techniques are very limited and the one for in-situ measurement is not virtually available. Therefore, elastic-plastic FEA has been performed to estimate the plastic zone size. In this study, it is noticed that side necking at the surface is a consequence of plastic deformation and lateral contraction and the relation between the plastic zone and side necking is investigated. FEA for modified boundary layer models with finite thickness, various mode mixes 0 .deg., 30 deg., 60 deg., 90 .deg. and strain hardening exponent n=3, 10 are performed. The results are presented and the implication regarding to application to experiment is discussed

The limit of grain refinement on equal channel angular deformation

International Nuclear Information System (INIS)

Kopylov, V.I.; Chuvil'deev, V.N.

2004-01-01

Experimental and theoretical study results on the process of strain-induced grain refinement under severe plastic deformation are described. A generalization is made for experimental results on deformation dispersing of copper, magnesium and aluminium base alloys as well as unalloyed metals. The model is developed which allows calculating the minimal grain size being able to result from equal channel angular pressing. The expressions describing the dependence of the limit of grain refinement on the nature of the material and severe plastic deformation rate and temperature are obtained [ru

Enhanced piezoelectricity in plastically deformed nearly amorphous Bi{sub 12}TiO{sub 20}-BaTiO{sub 3} nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Yu, Dan; Zhao, Minglei, E-mail: zhaoml@sdu.edu.cn; Wang, Chunlei; Wang, Lihai; Su, Wenbin; Gai, Zhigang; Wang, Chunming; Li, Jichao; Zhang, Jialiang [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)

2016-07-18

Bulk Bi{sub 12}TiO{sub 20}-BaTiO{sub 3} (BTO-BT) nanocomposites are fabricated through the high-temperature interfacial reaction between nanometer-sized BaTiO{sub 3} particles and melting Bi{sub 12}TiO{sub 20}. Although the obtained BTO-BT nanocomposites are nearly amorphous and display very weak ferroelectricity, they exhibit relatively strong piezoelectricity without undergoing the electrical poling process. The volume fraction of crystalline Bi{sub 12}TiO{sub 20} is reduced to less than 10%, and the piezoelectric constant d{sub 33} is enhanced to 13 pC/N. Only the presence of the macroscopic polar amorphous phases can explain this unusual thermal stable piezoelectricity. Combining the results from X-ray diffraction, Raman spectroscopy, and thermal annealing, it can be confirmed that the formation of macroscopic polar amorphous phases is closely related to the inhomogeneous plastic deformation of the amorphous Bi{sub 12}TiO{sub 20} during the sintering process. These results highlight the key role of plastically deformed amorphous Bi{sub 12}TiO{sub 20} in the Bi{sub 12}TiO{sub 20}-based polar composites, and the temperature gradient driven coupling between the plastic strain gradient and polarization in amorphous phases is the main poling mechanism for this special type of bulk polar material.

Effects of Friction and Anvil Design on Plastic Deformation during the Compression Stage of High-Pressure Torsion

Energy Technology Data Exchange (ETDEWEB)

Song, Yuepeng; Chen, Miaomiao; Xu, Baoyan; Guo, Jing; Xu, Lingfeng; Wang, Zheng [Mechanical and Electronic Engineering College, Tai’an (China); Gao, Dongsheng [Shandong Provincial Key Laboratory of Horticultural Machineries and Equipments, Tai’an (China); Kim, Hyoung Seop [Department of Materials Science and Engineering, Pohang (Korea, Republic of)

2016-11-15

Herein, we report the results of our investigation on the effect of friction and anvil design on the heterogeneous plastic-deformation characteristics of copper during the compressive stage of high-pressure torsion (HPT), using the finite element method. The results indicate that the friction and anvil geometry play important roles in the homogeneity of the deformation. These variables affect the heterogeneous level of strain in the HPT compressed disks, as well as the flash in the disk edge region. The heterogeneous plastic deformation of the disks becomes more severe with the increasing depth of the cavity, as anvil angle and friction coefficient increase. However, the homogeneity increases with increases in the wall angle. The length of flash and the area of the dead metal zone increase with the depth of the cavity, while they decrease at a wall angle of 180°.

Plastic deformation of tubular crystals by dislocation glide.

Science.gov (United States)

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.

Plastic evolution behavior of H340LAD-Z steel by an optical method

Energy Technology Data Exchange (ETDEWEB)

Guo, Nan; Liang, Jin; Yu, Qiang; Qian, Boxing

2017-02-01

An optical method based on digital image correlation (DIC) technology was proposed to measure the plastic evolution of the high-strength low alloy steel H340LAD-Z. The basic principle of DIC technology is introduced, and then, the use of a 3D deformation measurement system and electronic universal testing machine to dynamically measure plastic evolution during the tensile yield stage is described. Through the full-field full-process measurement of plastic deformation during the yield stage in the 0°, 45° and 90° loading directions, the plastic evolution law was revealed. The results demonstrate that the proposed 3D DIC method can accurately reveal the starting and ending times for plastic evolution. The specimens in the three directions exhibit different plastic evolution behaviors, although they have similar yield strengths and yield times. The specimens in the 45° and 90° loading directions began to enter plastic deformation from bottom to top and the plastic area was maintained in a constant deformed state, while the evolution behavior in the 0° direction transited from both sides to the middle and plastic deformation was uneven. It is important to study plastic evolution of a metal sheet to determine the material properties and to provide an accurate basis for finite element modeling.

Plastic evolution behavior of H340LAD-Z steel by an optical method

International Nuclear Information System (INIS)

Guo, Nan; Liang, Jin; Yu, Qiang; Qian, Boxing

2017-01-01

An optical method based on digital image correlation (DIC) technology was proposed to measure the plastic evolution of the high-strength low alloy steel H340LAD-Z. The basic principle of DIC technology is introduced, and then, the use of a 3D deformation measurement system and electronic universal testing machine to dynamically measure plastic evolution during the tensile yield stage is described. Through the full-field full-process measurement of plastic deformation during the yield stage in the 0°, 45° and 90° loading directions, the plastic evolution law was revealed. The results demonstrate that the proposed 3D DIC method can accurately reveal the starting and ending times for plastic evolution. The specimens in the three directions exhibit different plastic evolution behaviors, although they have similar yield strengths and yield times. The specimens in the 45° and 90° loading directions began to enter plastic deformation from bottom to top and the plastic area was maintained in a constant deformed state, while the evolution behavior in the 0° direction transited from both sides to the middle and plastic deformation was uneven. It is important to study plastic evolution of a metal sheet to determine the material properties and to provide an accurate basis for finite element modeling.

CALCULATION OF DEFORMATION FORCE AT PLASTIC FORM-SHAPING OF FLANGE IN ROUND BILLET

Directory of Open Access Journals (Sweden)

L. A. Isaevich

2007-01-01

Full Text Available The paper introduces results concerning calculation of deformation force at plastic form-shaping of a flange in a round billet, having a preset extent of the transition zone from an internal pipe wall to a flange, that makes it possible to select a press of corresponding nominal force. 

Numerical Study of the Plasticity-Induced Stabilization Effect on Martensitic Transformations in Shape Memory Alloys

Science.gov (United States)

Junker, Philipp; Hempel, Philipp

2017-12-01

It is well known that plastic deformations in shape memory alloys stabilize the martensitic phase. Furthermore, the knowledge concerning the plastic state is crucial for a reliable sustainability analysis of construction parts. Numerical simulations serve as a tool for the realistic investigation of the complex interactions between phase transformations and plastic deformations. To account also for irreversible deformations, we expand an energy-based material model by including a non-linear isotropic hardening plasticity model. An implementation of this material model into commercial finite element programs, e.g., Abaqus, offers the opportunity to analyze entire structural components at low costs and fast computation times. Along with the theoretical derivation and expansion of the model, several simulation results for various boundary value problems are presented and interpreted for improved construction designing.

Microstructural and superficial modification in a Cu-Al-Be shape memory alloy due to superficial severe plastic deformation under sliding wear conditions

Science.gov (United States)

Figueroa, C. G.; Garcia-Castillo, F. N.; Jacobo, V. H.; Cortés-Pérez, J.; Schouwenaars, R.

2017-05-01

Stress induced martensitic transformation in copper-based shape memory alloys has been studied mainly in monocrystals. This limits the use of such results for practical applications as most engineering applications use polycristals. In the present work, a coaxial tribometer developed by the authors was used to characterise the tribological behaviour of polycrystalline Cu-11.5%Al-0.5%Be shape memory alloy in contact with AISI 9840 steel under sliding wear conditions. The surface and microstructure characterization of the worn material was conducted by conventional scanning electron microscopy and atomic force microscopy, while the mechanical properties along the transversal section were measured by means of micro-hardness testing. The tribological behaviour of Cu-Al-Be showed to be optimal under sliding wear conditions since the surface only presented a slight damage consisting in some elongated flakes produced by strong plastic deformation. The combination of the plastically modified surface and the effects of mechanically induced martensitic transformation is well-suited for sliding wear conditions since the modified surface provides the necessary strength to avoid superficial damage while superelasticity associated to martensitic transformation is an additional mechanism which allows absorbing mechanical energy associated to wear phenomena as opposed to conventional ductile alloys where severe plastic deformation affects several tens of micrometres below the surface.

Stress Wave Propagation in Viscoelastic-Plastic Rock-Like Materials

Directory of Open Access Journals (Sweden)

Liu Lang

2016-05-01

Full Text Available Rock-like materials are composites that can be regarded as a mixture composed of elastic, plastic, and viscous components. They exhibit viscoelastic-plastic behavior under a high-strain-rate loading according to element model theory. This paper presents an analytical solution for stress wave propagation in viscoelastic-plastic rock-like materials under a high-strain-rate loading and verifies the solution through an experimental test. A constitutive equation of viscoelastic-plastic rock-like materials was first established, and then kinematic and kinetic equations were then solved to derive the analytic solution for stress wave propagation in viscoelastic-plastic rock-like materials. An experimental test using the SHPB (Split Hopkinson Pressure Bar for a concrete specimen was conducted to obtain a stress-strain curve under a high-strain-rate loading. Inverse analysis based on differential evolution was conducted to estimate undetermined variables for constitutive equations. Finally, the relationship between the attenuation factor and the strain rate in viscoelastic-plastic rock-like materials was investigated. According to the results, the frequency of the stress wave, viscosity coefficient, modulus of elasticity, and density play dominant roles in the attenuation of the stress wave. The attenuation decreases with increasing strain rate, demonstrating strongly strain-dependent attenuation in viscoelastic-plastic rock-like materials.

[Carbon fiber-reinforced plastics as implant materials].

Science.gov (United States)

Bader, R; Steinhauser, E; Rechl, H; Siebels, W; Mittelmeier, W; Gradinger, R

2003-01-01

Carbon fiber-reinforced plastics have been used clinically as an implant material for different applications for over 20 years.A review of technical basics of the composite materials (carbon fibers and matrix systems), fields of application,advantages (e.g., postoperative visualization without distortion in computed and magnetic resonance tomography), and disadvantages with use as an implant material is given. The question of the biocompatibility of carbon fiber-reinforced plastics is discussed on the basis of experimental and clinical studies. Selected implant systems made of carbon composite materials for treatments in orthopedic surgery such as joint replacement, tumor surgery, and spinal operations are presented and assessed. Present applications for carbon fiber reinforced plastics are seen in the field of spinal surgery, both as cages for interbody fusion and vertebral body replacement.

EBSD-based techniques for characterization of microstructural restoration processes during annealing of metals deformed to large plastic strains

DEFF Research Database (Denmark)

Godfrey, A.; Mishin, Oleg; Yu, Tianbo

2012-01-01

Some methods for quantitative characterization of the microstructures deformed to large plastic strains both before and after annealing are discussed and illustrated using examples of samples after equal channel angular extrusion and cold-rolling. It is emphasized that the microstructures...... in such deformed samples exhibit a heterogeneity in the microstructural refinement by high angle boundaries. Based on this, a new parameter describing the fraction of regions containing predominantly low angle boundaries is introduced. This parameter has some advantages over the simpler high angle boundary...... on mode of the distribution of dislocation cell sizes is outlined, and it is demonstrated how this parameter can be used to investigate the uniformity, or otherwise, of the restoration processes occurring during annealing of metals deformed to large plastic strains. © (2012) Trans Tech Publications...

A quantitative approach to study the effect of local texture and heterogeneous plastic strain on the deformation micromechanism in RR1000 nickel-based superalloy

International Nuclear Information System (INIS)

Birosca, S.; Di Gioacchino, F.; Stekovic, S.; Hardy, M.

2014-01-01

In a weakly textured material with relatively pore-free and homogeneous microstructure, the local texture can influence primary crack propagation and secondary crack initiation, depending on specific microtexture cluster size. Moreover, the plastic strain assessment and strain quantity within individual grains are essential for understanding the material susceptibility to crack initiation and propagation at various loading conditions and temperature ranges. In the current study, electron backscatter diffraction (EBSD) is applied to measure the plastic strain present in RR1000 nickel-based superalloy microstructure following thermo-mechanical fatigue tests. The EBSD plastic strain measurements are evaluated to identify the distinctive deformation mode within individual grains. It was evident from the overall statistical analyses carried out for over 2000 grains that cube (〈0 0 1〉//loading direction) and near cube orientations (φ 1 , Φ, φ 2 : 0, 0–15, 0) behaved as “soft” grains with a high Schmid factor and contained low geometrically necessary dislocation (GND) density as a result of low strain hardening at the early stage of deformation for such grains. The near cube orientation (typically φ 1 , Φ, φ 2 : 0, 9, 0) was the softest orientation among the cube family. While the brass grains (〈1 1 1〉//loading direction) acted as “hard” grains that have the lowest Schmid factor with the highest Taylor factor and GND density compared with other oriented grains. A high GND content was found in the vicinity of the grain boundaries in the soft grains and on slip plane traces within the hard grains. It is concluded that GND absolute value for each grain can vary, as it is interrelated with deformation degree, but the GND locations within the grains give indications of the strain hardening state and deformation stages in hard and soft grains. Furthermore, the areas with random local texture contained high strain incompatibilities between neighbouring

The influence of plastic deformation and chemical environment on the resistively of al-alloy overhead lines

Directory of Open Access Journals (Sweden)

Nowak-Woźny D.

2005-01-01

Full Text Available The electrical resistively and intensity of X-ray diffraction reflexes were determined for overhead line wires deformed plastically and immersed at different solutions. Immersing (chemical ageing was performed by plastic deformation along the wire axis. During chemical ageing the samples were exposed to the action of the Cl-, SO4 2-, and SO3 2- ions. Resistively was measured at room temperature and at liquid nitrogen temperature. After the X-ray and resistively measurement data were compared, it was found that three processes could take place: the flow of ions through the boundary between a sample and environment; the mechanical relaxation of vacancies near a line of dislocations, and the ordering of microstructure. These effects can lead to the anisotropy of resistively.

Microstructural evolution during tensile deformation of polypropylenes

International Nuclear Information System (INIS)

Dasari, A.; Rohrmann, J.; Misra, R.D.K.

2003-01-01

Tensile deformation processes occurring at varying strain rates in high and low crystallinity polypropylenes and ethylene-propylene di-block copolymers have been investigated by scanning electron microscopy. This is examined for both long and short chain polymeric materials. The deformation processes in different polymeric materials show striking dissimilarities in spite of the common propylene matrix. Additionally, the deformation behavior of long and their respective short chain polymers was different. Deformation mechanisms include crazing/tearing, wedging, ductile ploughing, fibrillation, and brittle fracture. The different modes of deformation are depicted in the form of strain rate-strain diagrams. At a constant strain rate, the strain to fracture follows the sequence: high crystallinity polypropylenes< low crystallinity polypropylenes< ethylene-propylene di-block copolymers, indicative of the trend in resistance to plastic deformation

Severe Plastic Deformation of Commercial Pure Titanium (CP-Ti) for Biomedical Applications: A Brief Review

Science.gov (United States)

Mahmoodian, Reza; Annuar, N. Syahira M.; Faraji, Ghader; Bahar, Nadia Dayana; Razak, Bushroa Abd; Sparham, Mahdi

2017-11-01

This paper reviews severe plastic deformation (SPD) techniques for producing ultrafine-grained (UFG) and nanostructured commercial pure titanium (CP-Ti) for biomedical applications as the best alternative to titanium alloys. SPD processes, effective parameters, and advantages of nanostructured CP-Ti over coarse-grained (CG) material and Ti alloys are briefly reviewed. It is reported that nanostructured CP-Ti processed via SPD exhibits higher mechanical strength comparable to Ti alloys but better biological response and superior biocompatibility. Also, different surface modification techniques offer different results on UFG and CG CP-Ti, leading to nanoscale surface topography in UFG samples. Overall, it is reported that nanostructured CP-Ti processed by SPD could be considered to be the best candidate for biomedical implants.

PLASTIC MATERIALS IN EUROPEAN AGRICULTURE: ACTUAL USE AND PERSPECTIVES

Directory of Open Access Journals (Sweden)

Giacomo Scarascia-Mugnozza

2012-06-01

Full Text Available The world consumption of plastics in agriculture amounts yearly to 6.5 million tons. In addition to conventional polymers used in agriculture for greenhouses and mulches such as PE, PVC, EVA, photo-selective and luminescent polymers have been used, in order to improve the quality of crops. For the same reason plastic nets are used mainly in countries with tropical and Mediterranean climates. For an environmentally friendly agricultural activity, an alternative strategy can be represented by bio-based agricultural raw materials. For low environmental impact applications, biodegradable materials for agricultural films are nowadays produced. An overview of the main methods for the disposal and recycling of plastic materials are presented with the results of mechanical and radiometric tests on recycled plastics. The strategies to reduce the burden of plastics in agriculture are: a correct procedure for the collection, disposal and recycling of post-consumption plastics; the increase of lifetime duration and performance; and the introduction and promotion of bio-based materials.

About the non-identity of the technological impact upon its repeat realization in the case of surface plastic deformation

Energy Technology Data Exchange (ETDEWEB)

Grigorov, Veselin I. [University of Rousse, Rousse (Bulgaria)

2013-07-01

Discussed are the cases when during the repeated applying surface plastic deformation (SPD) there is a significant manifestation of alternative combinations and otter effect and factors in addition to the factor number of processing runs. Then there are signs of non-identity of their technological impact. except for the influence of the factor frequency of the processing, there are a significant availability of alternative combinations of effects and other factors and there are signs of non-identity of the technological impact. Such combinations occur in relation to: mismatch of the overlaying of contact zones; generation random characteristics of the technological impact; System-driven differences in the condition of contact interaction between the deforming elements and the machined surfaces. Key words: surface plastic deformation.

Effect of transient change in strain rate on plastic flow behaviour of ...

Indian Academy of Sciences (India)

Steels; stress–strain measurement; plastic flow; mechanical properties; metallurgy. Abstract. Plastic flow behaviour of low carbon steel has been studied at room temperature during tensile deformation by ... Bulletin of Materials Science | News.

Relaxation of residual stress in MMC after combined plastic deformation and heat treatment

International Nuclear Information System (INIS)

Bruno, G.; Ceretti, M.; Girardin, E.; Giuliani, A.; Manescu, A.

2004-01-01

Neutron Diffraction shows that plastic pre-deformation and heat treatments have opposite effects on the residual stress in Al-SiC p composites. The thermal micro residual stress is relaxed or even reversed by pre-strains above 0.2%, but restored by heat treatments. The sense of relaxation changes above 400 deg. C (the mixing temperature)

The behavior of intermetallic compounds at large plastic strains

International Nuclear Information System (INIS)

Gray, G.T.; Embury, J.D.

1993-01-01

This paper contains a summary of a broad study of intermetallics which includes the following materials, Ni 3 Al, Ti-48Al-1V, Ti-24Al-11Nb, Ti-48Al-2Cr-2Nb, and Ti-24.5 Al-10.5Nb-1.5Mo. Much effort has been devoted to the study of ordered materials at modes plastic strains and the problem of premature failure. However by utilizing stress states other than simple tension it is possible to study the deformation of intermetallic compounds up to large plastic strains and to consider the behavior of these materials in the regime where stresses approach the theoretical stress. The current work outlines studies of the work hardening rate of a number of titanium and nickel-based intermetallic compounds deformed in compression. Attention is given to the structural basis of the sustained work hardening. The large strain plasticity of these materials is summarized in a series of diagrams. Fracture in these materials in compression occurs via catastrophic shear at stresses of the order of E/80 (where E is the elastic modulus)

Parameters identification in strain-rate and thermal sensitive visco-plastic material model for an alumina dispersion strengthened copper

CERN Document Server

Scapin, M; Peroni, M

2011-01-01

The main objective of this paper is getting strain-hardening, thermal and strain-rate parameters for a material model in order to correctly reproduce the deformation process that occurs in high strain-rate scenario, in which the material reaches also high levels of plastic deformation and temperature. In particular, in this work the numerical inverse method is applied to extract material strength parameters from experimental data obtained via mechanical tests at different strain-rates (from quasi-static loading to high strain-rate) and temperatures (between 20 C and 1000 C) for an alumina dispersion strengthened copper material, which commercial name is GLIDCOP. Thanks to its properties GLIDCOP finds several applications in particle accelerator technologies, where problems of thermal management, combined with structural requirements, play a key role. Currently, it is used for the construction of structural and functional parts of the particle beam collimation system. Since the extreme condition in which the m...

Plastic limit pressure of spherical vessels with combined hardening involving large deformation

International Nuclear Information System (INIS)

Leu, S.-Y.; Liao, K.-C.; Lin, Y.-C.

2014-01-01

The paper aims to investigate plastic limit pressure of spherical vessels of nonlinear combined isotropic/kinematic hardening materials. The Armstrong-Frederick kinematic hardening model is adopted and the Voce hardening law is incorporated for isotropic hardening behavior. Analytically, we extend sequential limit analysis to deal with combined isotropic/kinematic hardening materials. Further, exact solutions of plastic limit pressure were developed analytically by conducting both static and kinematic limit analysis. The onset of instability was also derived and solved iteratively by Newton's method. Numerically, elastic–plastic analysis is also performed by the commercial finite-element code ABAQUS incorporated with the user subroutine UMAT implemented with user materials of combined hardening. Finally, the problem formulation and the solution derivations presented here are validated by a very good agreement between the numerical results of exact solutions and the results of elastic–plastic finite-element analysis by ABAQUS. -- Highlights: • Sequential limit analysis is extended to consider combined hardening. • Exact solutions of plastic limit pressure are developed. • The onset of instability of a spherical vessel is derived and solved numerically

Effect of the hydrogen absorption on the positioning of the plastic deformation of a stainless steel-316L

International Nuclear Information System (INIS)

Aubert, I.; Olive, J.M.

2007-01-01

The aim of this work is to quantify the absorbed hydrogen effects on the plastic deformation (at the grain scale) of stainless steel-316L polycrystals. Tensile tests in air have been carried out on specimens previously cathodically loaded in hydrogen (135 wt.ppm) and unloaded polycrystals. After the tensile tests, a number statistically representative of gliding bands emergent in surface has been observed. In parallel to this experimental study, the plastic gliding level in each grain has been obtained by a finite element method from the polycrystalline microstructure modeled with the EBSD cartography. The Zebulon code developed by the Ecole des Mines de Paris allows to account for the plastic behaviour of the studied polycrystals using the crystalline plasticity model. The coupled analysis of the numerical and experimental results allows to know the gliding plan having produced the gliding steps observed in each grain by AFM. This allows then to quantify the number of emergent dislocations to create the average gliding band. It is then possible to compare the modifications of the positioning of the plastic deformation of the stainless steel-316L induced by hydrogen absorption. (O.M.)

A fully-coupled approach combining plastic deformation and liquid lubrication

DEFF Research Database (Denmark)

Üstünyagiz, Esmeray; Christiansen, Peter; Nielsen, Chris Valentin

This paper presents a new approach based on a fully coupled procedure in which the lubricant flow and theplastic deformation of the metallic material are solved simultaneously. The approach is applied to strip reduction of asheet with surface pockets in order to investigate the escape of the lubr......This paper presents a new approach based on a fully coupled procedure in which the lubricant flow and theplastic deformation of the metallic material are solved simultaneously. The approach is applied to strip reduction of asheet with surface pockets in order to investigate the escape...

An analysis of heat field of metal sheet during elastic-plastic deformation

International Nuclear Information System (INIS)

Li, S.X.; Huang, Y.; Shih, C.H.

1985-08-01

This paper describes the application of the finite element analysis to calculate the temperature distribution generated during the process of elastic-plastic deformation. A better agreement is found between the results of heat field computed by use of the finite element analysis and that measured by use of an infrared camera. The results indicate that the method of finite element analysis used for heat field evaluation is reliable. (author)

Elasto/visco-plastic deformation of moderately thick shells of revolution under thermal loading due to fluid

International Nuclear Information System (INIS)

Takezono, S.; Tao, K.; Aoki, T.; Inamura, E.

1993-01-01

This paper is concerned with an analytical formulation and a numerical solution of the thermo-elasto/visco-plastic deformation of general, moderately thick shells of revolution subjected to thermal loads due to fluid. At first the temperature distribution through the thickness is supposed to be curves of second order, and the temperature field in the shell under the appropriate initial and boundary conditions is determined by using the equations of heat conduction and heat transfer. Secondly the stresses and deformations are derived from the thermal stress equations. The equations of equilibrium and the relations between the strains and displacements are developed by extending the Reissner-Naghdi theory for elastic shells. For the constitutive relations, the Perzyna elasto/visco-plastic equations including the temperature effect are employed. The fundamental equations derived are numerically solved by the finite difference method. As a numerical example, the simply supported cylindrical shell made of mild steel under thermal loading due to fluid is analyzed, and the results are compared with those from classical theory which neglects the effect of shear deformations. (author)

The Effects of Isothermal Deformation and Annealing on the Microstructure of Nickel-Aluminum-Bronze Propeller Material

National Research Council Canada - National Science Library

Nabach, William A

2003-01-01

... in a combination of frictional and adiabatic heating due to plastic deformation. A stirring effect results in the formation of a zone of severe shear deformation and local temperatures approaching...

Avalanches and plastic flow in crystal plasticity: an overview

Science.gov (United States)

Papanikolaou, Stefanos; Cui, Yinan; Ghoniem, Nasr

2018-01-01

Crystal plasticity is mediated through dislocations, which form knotted configurations in a complex energy landscape. Once they disentangle and move, they may also be impeded by permanent obstacles with finite energy barriers or frustrating long-range interactions. The outcome of such complexity is the emergence of dislocation avalanches as the basic mechanism of plastic flow in solids at the nanoscale. While the deformation behavior of bulk materials appears smooth, a predictive model should clearly be based upon the character of these dislocation avalanches and their associated strain bursts. We provide here a comprehensive overview of experimental observations, theoretical models and computational approaches that have been developed to unravel the multiple aspects of dislocation avalanche physics and the phenomena leading to strain bursts in crystal plasticity.

Toward Modeling Limited Plasticity in Ceramic Materials

National Research Council Canada - National Science Library

Grinfeld, Michael; Schoenfeld, Scott E; Wright, Tim W

2008-01-01

The characteristic features of many armor-related ceramic materials are the anisotropy on the micro-scale level and the very limited, though non-vanishing, plasticity due to limited number of the planes for plastic slip...

Effect of severe plastic deformation on microstructure and mechanical properties of magnesium and aluminium alloys in wide range of strain rates

Science.gov (United States)

Skripnyak, Vladimir; Skripnyak, Evgeniya; Skripnyak, Vladimir; Vaganova, Irina; Skripnyak, Nataliya

2013-06-01

Results of researches testify that a grain size have a strong influence on the mechanical behavior of metals and alloys. Ultrafine grained HCP and FCC metal alloys present higher values of the spall strength than a corresponding coarse grained counterparts. In the present study we investigate the effect of grain size distribution on the flow stress and strength under dynamic compression and tension of aluminium and magnesium alloys. Microstructure and grain size distribution in alloys were varied by carrying out severe plastic deformation during the multiple-pass equal channel angular pressing, cyclic constrained groove pressing, and surface mechanical attrition treatment. Tests were performed using a VHS-Instron servo-hydraulic machine. Ultra high speed camera Phantom V710 was used for photo registration of deformation and fracture of specimens in range of strain rates from 0,01 to 1000 1/s. In dynamic regime UFG alloys exhibit a stronger decrease in ductility compared to the coarse grained material. The plastic flow of UFG alloys with a bimodal grain size distribution was highly localized. Shear bands and shear crack nucleation and growth were recorded using high speed photography.

Influence of severe plastic deformation on intermetallic particles in Mg-12 wt.%Zn alloy investigated using transmission electron microscopy

International Nuclear Information System (INIS)

Němec, M.; Gärtnerová, V.; Jäger, A.

2016-01-01

The in-depth microstructural characterization of intermetallic particles in an Mg-12 wt.%Zn binary alloy subjected to a severe plastic deformation is presented. The alloy was processed by four passes via equal channel angular pressing with an applied back pressure at a gradually decreasing temperature and analyzed using transmission electron microscopy techniques to observe the influence of processing on intermetallic particles. The results are compared with the initial state of the material prior to severe plastic deformation. The microstructural evolution of the α-Mg matrix and the Mg 21 Zn 25 , Mg 51 Zn 20 and MgZn 2 was analyzed using bright field imaging, selected area electron diffraction, high-resolution transmission electron microscopy and high-angle annular dark field imaging in scanning mode. The plastic deformation process influenced the α-Mg matrix and each type of intermetallic particle. The α-Mg matrix consisted of two types of areas. The first type of area had a highly deformed structure, and the second type of area had a partially recrystallized structure with an average grain size of approximately 250 nm. The Mg 21 Zn 25 microparticles exhibited distinct forms in the α-Mg matrix that were characterized as a single-crystalline form, a nano-crystalline form and a broken up form. No evidence of Mg 51 Zn 20 nanoparticles within the α-Mg matrix was found in the microstructure, which indicates their dissolution or phase transformation during the deformation process. MgZn 2 nanoparticles exhibited different behavior in both types of α-Mg matrix. Two orientation relationships toward the highly deformed α-Mg matrix were observed; however, there was no relationship toward the partially recrystallized α-Mg matrix. Additionally, the growth of the MgZn 2 nanoparticles was different in the two types of α-Mg matrix. The Mg 51 Zn 20 nanoparticles inside Mg 21 Zn 25 microparticles exhibited a distinct behavior within the single-crystalline or nano

Nanostructures in a ferritic and an oxide dispersion strengthened steel induced by dynamic plastic deformation

DEFF Research Database (Denmark)

Zhang, Zhenbo

fission and fusion reactors. In this study, two candidate steels for nuclear reactors, namely a ferritic/martensitic steel (modified 9Cr-1Mo steel) and an oxide dispersion strengthened (ODS) ferritic steel (PM2000), were nanostructured by dynamic plastic deformation (DPD). The resulting microstructure...

Crystal plasticity study of single crystal tungsten by indentation tests

International Nuclear Information System (INIS)

Yao, Weizhi

2012-01-01

Owing to its favorable material properties, tungsten (W) has been studied as a plasma-facing material in fusion reactors. Experiments on W heating in plasma sources and electron beam facilities have shown an intense micro-crack formation at the heated surface and sub-surface. The cracks go deep inside the irradiated sample, and often large distorted areas caused by local plastic deformation are present around the cracks. To interpret the crack-induced microscopic damage evolution process in W, one needs firstly to understand its plasticity on a single grain level, which is referred to as crystal plasticity. In this thesis, the crystal plasticity of single crystal tungsten (SCW) has been studied by spherical and Berkovich indentation tests and the finite element method with a crystal plasticity model. Appropriate values of the material parameters included in the crystal plasticity model are determined by fitting measured load-displacement curves and pile-up profiles with simulated counterparts for spherical indentation. The numerical simulations reveal excellent agreement with experiment. While the load-displacement curves and the deduced indentation hardness exhibit little sensitivity to the indented plane at small indentation depths, the orientation of slip directions within the crystals governs the development of deformation hillocks at the surface. It is found that several factors like friction, indentation depth, active slip systems, misoriented crystal orientation, misoriented sample surface and azimuthal orientation of the indenter can affect the indentation behavior of SCW. The Berkovich indentation test was also used to study the crystal plasticity of SCW after deuterium irradiation. The critical load (pop-in load) for triggering plastic deformation under the indenter is found to depend on the crystallographic orientation. The pop-in loads decrease dramatically after deuterium plasma irradiation for all three investigated crystallographic planes.

Correlation between relaxations and plastic deformation, and elastic model of flow in metallic glasses and glass-forming liquids

International Nuclear Information System (INIS)

Wang Weihua

2011-01-01

We study the similarity and correlations between relaxations and plastic deformation in metallic glasses (MGs) and MG-forming liquids. It is shown that the microscope plastic events, the initiation and formation of shear bands, and the mechanical yield in MGs where the atomic sites are topologically unstable induced by applied stress, can be treated as the glass to supercooled liquid state transition induced by external shear stress. On the other hand, the glass transition, the primary and secondary relaxations, plastic deformation and yield can be attributed to the free volume increase induced flow, and the flow can be modeled as the activated hopping between the inherent states in the potential energy landscape. We then propose an extended elastic model to describe the flow based on the energy landscape theory. That is, the flow activation energy density is linear proportional to the instantaneous elastic moduli, and the activation energy density ρ E is determined to be a simple expression of ρ E =(10/11)G+(1/11)K. The model indicates that both shear and bulk moduli are critical parameters accounting for both the homogeneous and inhomogeneous flows in MGs and MG-forming liquids. The elastic model is experimentally certified. We show that the elastic perspectives offers a simple scenario for the flow in MGs and MG-forming liquids and are suggestive for understanding the glass transition, plastic deformation, and nature and characteristics of MGs

HPT-Deformation of Copper and NicKEXl Single Crystals

International Nuclear Information System (INIS)

Hafok, M.; Vorhauer, A.; Pippan, R.; KEXcKEXs, J.

2005-01-01

Full text: Copper and nicKEXl single crystals of high purity with a crystallographic orientation, (001) and (111) respectively, were deformed by applying high pressure torsion (HPT) at room temperature. Special interest was devoted to the structural evolution of the material, which was characterized by electron backscatter diffraction (EBSD) and x-ray texture analysis as well. In addition back scatter electron investigations were applied to characterize shape and size of the new formed structure. Furthermore the study is focused on the micro structural and micro textural evolution that lead to the increase of misorientation angle with increasing plastic deformation. We observed an increasing fragmentation of the structure with increasing plastic equivalent strain up to a level where the grain size is saturated. The saturation could be traced back to dynamical recovery and recrystallisation during the deformation process that is depending on the purity of the material. (author)

Characterizing deformed ultrafine-grained and nanocrystalline materials using transmission Kikuchi diffraction in a scanning electron microscope

International Nuclear Information System (INIS)

Trimby, Patrick W.; Cao, Yang; Chen, Zibin; Han, Shuang; Hemker, Kevin J.; Lian, Jianshe; Liao, Xiaozhou; Rottmann, Paul; Samudrala, Saritha; Sun, Jingli; Wang, Jing Tao; Wheeler, John; Cairney, Julie M.

2014-01-01

Graphical abstract: -- Abstract: The recent development of transmission Kikuchi diffraction (TKD) in a scanning electron microscope enables fast, automated orientation mapping of electron transparent samples using standard electron backscatter diffraction (EBSD) hardware. TKD in a scanning electron microscope has significantly better spatial resolution than conventional EBSD, enabling routine characterization of nanocrystalline materials and allowing effective measurement of samples that have undergone severe plastic deformation. Combining TKD with energy dispersive X-ray spectroscopy (EDS) provides complementary chemical information, while a standard forescatter detector system below the EBSD detector can be used to generate dark field and oriented dark field images. Here we illustrate the application of this exciting new approach to a range of deformed, ultrafine grained and nanocrystalline samples, including duplex stainless steel, nanocrystalline copper and highly deformed titanium and nickel–cobalt. The results show that TKD combined with EDS is a highly effective and widely accessible tool for measuring key microstructural parameters at resolutions that are inaccessible using conventional EBSD

Texture Evolution in a Ti-Ta-Nb Alloy Processed by Severe Plastic Deformation

Science.gov (United States)

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}) and well-developed α and γ-fibers; the most important fiber is the α-fiber ({001} to {114} to {112} ). High-intensity texture along certain crystallographic directions represents a way to obtain materials with high anisotropic properties.

Experimental analysis of plastic materials containing radionuclides for decontamination viability

International Nuclear Information System (INIS)

Tazaki, Kazue; Nakano, Mikio; Takehara, Teruaki; Ishigaki, Yasuhito; Nakagawa, Hideaki

2015-01-01

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on 11 March, 2011, the high radioactive dosage was found in polluted water for agriculture use at Baba, Haramachi, Minami-Soma, Fukushima Prefecture, Japan. Field experiment for decontamination of water had been studied by using commercial plastic materials. The agricultural water comes from Tetsuzan dam is full of radioactive-contaminated water. Experimental analysis showed that the plastic materials can take up radioactive elements for several months soaked in the polluted agricultural water. The quantitative analyses using X-ray fluorescence analysis, Ge semiconductor and scanning electron microscopy equipped with energy dispersive X-ray spectrometer (SEM-EDS), revealed the detection of the radionuclides on the plastic materials with diatom and clays. The results suggest the adsorption of radionuclides on the surface of plastic materials due to FDNPP accident. The plastic materials associated with clays and diatoms could be stronger carriers of radionuclides in the polluted water. Adherence of diatoms to the plastic fiber in the water for 7 months suggested that some plastic materials were taking up heavy metals (Zn, Ba, Pb, Sb) with radioactive elements (Cs etc.). Mechanisms by which radioactive pollutants and microorganisms are adsorbed onto and desorbed from clays at aqueous interface can be understood by combining chemical analysis with electron microscopy observation. (author)

Effect of initial grain size on inhomogeneous plastic deformation and twinning behavior in high manganese austenitic steel with a polycrystalline microstructure

Science.gov (United States)

Ueji, R.; Tsuchida, N.; Harada, K.; Takaki, K.; Fujii, H.

2015-08-01

The grain size effect on the deformation twinning in a high manganese austenitic steel which is so-called TWIP (twining induced plastic deformation) steel was studied in order to understand how to control deformation twinning. The 31wt%Mn-3%Al-3% Si steel was cold rolled and annealed at various temperatures to obtain fully recrystallized structures with different mean grain sizes. These annealed sheets were examined by room temperature tensile tests at a strain rate of 10-4/s. The coarse grained sample (grain size: 49.6μm) showed many deformation twins and the deformation twinning was preferentially found in the grains in which the tensile axis is parallel near to [111]. On the other hand, the sample with finer grains (1.8 μm) had few grains with twinning even after the tensile deformation. The electron back scattering diffraction (EB SD) measurements clarified the relationship between the anisotropy of deformation twinning and that of inhomogeneous plastic deformation. Based on the EBSD analysis, the mechanism of the suppression of deformation twinning by grain refinement was discussed with the concept of the slip pattern competition between the slip system governed by a grain boundary and that activated by the macroscopic load.

Deformation behavior of human dentin in liquid nitrogen: a diametral compression test.

Science.gov (United States)

Zaytsev, Dmitry; Panfilov, Peter

2014-09-01

Contribution of the collagen fibers into the plasticity of human dentin is considered. Mechanical testing of dentin at low temperature allows excluding the plastic response of its organic matrix. Therefore, deformation and fracture behavior of the dentin samples under diametral compression at room temperature and liquid nitrogen temperature are compared. At 77K dentin behaves like almost brittle material: it is deformed exclusively in the elastic regime and it fails due to growth of the sole crack. On the contrary, dentin demonstrates the ductile response at 300K. There are both elastic and plastic contributions in the deformation of dentin samples. Multiple cracking and crack tip blunting precede the failure of samples. Organic phase plays an important role in fracture of dentin: plasticity of the collagen fibers could inhibit the crack growth. Copyright © 2014 Elsevier B.V. All rights reserved.

Field Performance of Recycled Plastic Foundation for Pipeline

Science.gov (United States)

Kim, Seongkyum; Lee, Kwanho

2015-01-01

The incidence of failure of embedded pipelines has increased in Korea due to the increasing applied load and the improper compaction of bedding and backfill materials. To overcome these problems, a prefabricated lightweight plastic foundation using recycled plastic was developed for sewer pipelines. A small scale laboratory chamber test and two field tests were conducted to verify its construction workability and performance. From the small scale laboratory chamber test, the applied loads at 2.5% and 5.0% of deformation were 3.45 kgf/cm2 and 5.85 kgf/cm2 for Case S1, and 4.42 kgf/cm2 and 6.43 kgf/cm2 for Case S2, respectively. From the first field test, the vertical deformation of the recycled plastic foundation (Case A2) was very small. According to the analysis based on the PE pipe deformation at the connection (CN) and at the center (CT), the pipe deformation at each part for Case A1 was larger than that for Case A2, which adopted the recycled lightweight plastic foundation. From the second field test, the measured maximum settlements of Case B1 and Case B2 were 1.05 cm and 0.54 cm, respectively. The use of a plastic foundation can reduce the settlement of an embedded pipeline and be an alternative construction method.

Field Performance of Recycled Plastic Foundation for Pipeline

Directory of Open Access Journals (Sweden)

Seongkyum Kim

2015-05-01

Full Text Available The incidence of failure of embedded pipelines has increased in Korea due to the increasing applied load and the improper compaction of bedding and backfill materials. To overcome these problems, a prefabricated lightweight plastic foundation using recycled plastic was developed for sewer pipelines. A small scale laboratory chamber test and two field tests were conducted to verify its construction workability and performance. From the small scale laboratory chamber test, the applied loads at 2.5% and 5.0% of deformation were 3.45 kgf/cm2 and 5.85 kgf/cm2 for Case S1, and 4.42 kgf/cm2 and 6.43 kgf/cm2 for Case S2, respectively. From the first field test, the vertical deformation of the recycled plastic foundation (Case A2 was very small. According to the analysis based on the PE pipe deformation at the connection (CN and at the center (CT, the pipe deformation at each part for Case A1 was larger than that for Case A2, which adopted the recycled lightweight plastic foundation. From the second field test, the measured maximum settlements of Case B1 and Case B2 were 1.05 cm and 0.54 cm, respectively. The use of a plastic foundation can reduce the settlement of an embedded pipeline and be an alternative construction method.

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

Energy Technology Data Exchange (ETDEWEB)

Lunev, Aleksey G., E-mail: agl@ispms.tsc.ru, E-mail: nadjozhkin@ispms.tsc.ru; Nadezhkin, Mikhail V., E-mail: agl@ispms.tsc.ru, E-mail: nadjozhkin@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055, Russia and National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Shlyakhova, Galina V., E-mail: shgv@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055, Russia and Seversk State Technological Institute (National Research Nuclear University MEPhI), Seversk, 636036 (Russian Federation); Barannikova, Svetlana A., E-mail: bsa@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Tomsk State University of Architecture and Building, Tomsk, 634003 (Russian Federation); Zuev, Lev B., E-mail: lbz@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation)

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.

A study of microindentation hardness tests by mechanism-based strain gradient plasticity

International Nuclear Information System (INIS)

Huang, Y.; Xue, Z.; Gao, H.; Nix, W. D.; Xia, Z. C.

2000-01-01

We recently proposed a theory of mechanism-based strain gradient (MSG) plasticity to account for the size dependence of plastic deformation at micron- and submicron-length scales. The MSG plasticity theory connects micron-scale plasticity to dislocation theories via a multiscale, hierarchical framework linking Taylor's dislocation hardening model to strain gradient plasticity. Here we show that the theory of MSG plasticity, when used to study micro-indentation, indeed reproduces the linear dependence observed in experiments, thus providing an important self-consistent check of the theory. The effects of pileup, sink-in, and the radius of indenter tip have been taken into account in the indentation model. In accomplishing this objective, we have generalized the MSG plasticity theory to include the elastic deformation in the hierarchical framework. (c) 2000 Materials Research Society

Mechanisms operating during plastic deformation of metals under concurrent production of cascades and dislocations

International Nuclear Information System (INIS)

Trinkaus, H.; Singh, B.N.

2008-04-01

Recent in-reactor tensile tests (IRTs) on pure copper have revealed a deformation behaviour which is significantly different from that observed in post-irradiation tensile tests (PITs). In IRTs, the material deforms uniformly and homogeneously without yield drop and plastic instability as commonly observed in PITs. An increase in the pre-yield dose results in an increase in the level of hardening over the whole test periods and a decrease in the uniform elongation suggesting that the materials 'remember' the impact of the pre-yield damage level. These features are modelled in terms of the decoration of dislocations with glissile dislocation loops. During pre-yield irradiation, dislocation decoration is due to the one-dimensional (1D) diffusion of cascade induced self-interstitial (SIA) clusters and their trapping in the stress field of the static grown-in dislocations. During post-yield irradiation and deformation, moving dislocations are decorated by the sweeping of matrix loops. The interaction of dislocations with loops and between loops is discussed as a function of the relevant parameters. On this basis, the kinetics of decoration is treated in terms of fluxes of loops to and reactions with each other in a conceived 2D space of decoration. In this space, loop coalescence, alignment and mutual blocking reactions are characterised by appropriate reaction cross sections. In the kinetic equations for 'dynamic decoration' under deformation, the evolution of the dislocation density is taken into account. Simple solutions of the kinetic equations are discussed. The apparent memory of the system for the pre-yield dose is identified as the result of simultaneous and closely parallel transient evolutions of the cascade damage and the dislocations up to the end of the IRTs. The contributions of dislocation decoration to yield and flow stresses are attributed to the interaction of dislocations with aligned loops temporarily or permanently immobilized by other loops or

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

Science.gov (United States)

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

On the gradient plasticity approach to size effects. Pt. 1: reviews

International Nuclear Information System (INIS)

Malmberg, T.; Tsagrakis, I.; Eleftheriadis, I.; Aifantis, E.C.; Michigan Technol. Univ., Houghton, MI

2001-03-01

The influence of specimen size on the plastic deformation and failure behaviour of some metals and steels is considered. This size dependence issue relates to the question of the transferability of mechanical test results of geometrically similar scaled-down structural models to the full scale structures using similitude laws; but it concerns also the validity of small scale laboratory type test results and their use as a basis for the computational modelling of large scale components. In part I ''reviews'' of this report a restricted review of scaled experiments at room temperature of geometrically similar specimens is given. This refers to the initiation of yielding under non-uniform states of deformation and also to the plastic deformation and fracture of smooth tensile specimens. Among others, non-classical continuum mechanics theories have become a means to interpret size effects. Especially gradient concepts are of interest which enrich the classical plasticity theories by higher order spatial strain gradients. These model extensions implicate additional material parameters which can be associated with internal length scales characteristic for the material. In part I a brief review of several gradient theories of plasticity is also given, including both deformation and flow theories and a comparison of the original ''symmetric stress'' theory with the more recent ''asymmetric stress'' theory is provided. The forthcoming part II ''applications'' exemplifies to what extend strain gradient models can describe the size influence on the deformation behaviour. (orig.) [de

Low temperature surface hardening of stainless steel; the role of plastic deformation

DEFF Research Database (Denmark)

Bottoli, Federico; Jespersen, Freja Nygaard; Hattel, Jesper Henri

2016-01-01

: - plastic deformation of metastable austenitic stainless steels leads to the development of strain-induced martensite, which compromises the uniformity and the homogeneity of the expanded austenite zone. - during low temperature surface engineering composition and stress profiles develop. On numerical......Thermochemical surface engineering by nitriding of austenitic stainless steel transforms the surface zone into expanded austenite, which improves the wear resistance of the stainless steel while preserving the stainless behavior. As a consequence of the thermochemical surface engineering, huge...

Low temperature irradiation effects on plastic deformation in BCC metals

International Nuclear Information System (INIS)

Aono, Yasuhisa

1984-01-01

Low temperature electron beam experiment was carried out on high purity iron and molybdenum single crystals, and its effect on the plastic deformation was examined. As the characteristics of the irradiated iron below 77 K, remarkable softening occurred in all orientations. This phenomenon is based on the interaction of self interstitial atoms and screw dislocations, and the other features such as the absorption of interstitial atoms into screw dislocations and the slip on maximum shearing stress planes were shown. On the other hand, the aggregate of interstitial atoms formed by annealing showed the different plastic characteristics from those of interstitial atoms, and gave the results corresponding to respective stages of the electric resistance recovery curves. Regarding molybdenum, the transfer of its self interstitial atoms is near 40 K, therefore at 77 K, cluster is formed, and it largely affects abnormal slip, which is one of the features of the plasticity of molybdenum. The peculiar dependence of the yield stress on the crystalline orientation was shown. The property of the interaction of the aggregate of interstitial atoms formed and grown by the annealing from 77 K to 500 K with dislocations corresponded to the information of defects obtained by the X-ray research of Maeta, and the similarity to the aggregate of iron was observed. (Kako, I.)

Design Features of Hardening Turners with Outstripping Plastic Deformation

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V. M. Yaroslavtsev

2014-01-01

Full Text Available An efficiency of the cutting method with outstripping plastic deformation (OPD in lathe works is defined in many respects by design features of the add-on devices for mechanical hardening of a cut-off layer material in the course of cutting. Applied on lathes, deforming OPD devices can have differing dimensions, placement on the lathe, drive type (manual, electric, hydraulic, pneumatic, pneumohydraulic, electromagnetic, and autonomy degree towards the metalcutting equipment and industrial equipment.At the same time there are a number of inherent design features of work-hardening devices the modernized lathes with OPD use for machining. Now the OPD standard devices implement two principle construction options: loading device is placed on the machine or on the OPD slide support separate of the tool, or it is structurally aligned with the cutting tool. In the latter case the OPD device for turning is called a tool mandrel, which is mounted in a tool post of the machine or, at large dimensions, such a mandrel is mounted on the machine instead of the tool mandrel.When designing the OPD devices, is important to take into consideration production requirements and recommendations for the technological equipment, developed in the course of creation, working off and introduction of such installations for mechanical hardening of material. In compliance with it, OPD devices, their placement on the machine, and working displacements shouldn't limit technological capabilities of the applied metal-cutting equipment. OPD stresses have to be smoothly regulated, with maximum loads being limited to admissible values for the machine model to be modernized. It is necessary to ensure synchronized longitudinal and cross displacements of the cutting tool and OPD hardener with respect to the axis of billet rotation to enable regulation and readjustment of the hardener and tool placement. It ought to foresee the increased mobile components rigidity and manufacturing

A new constitutive equation for strain hardening and softening of fcc metals during severe plastic deformation

International Nuclear Information System (INIS)

Wei, W.; Wei, K.X.; Fan, G.J.

2008-01-01

The stress-strain relationship for strain hardening and softening of high-purity aluminum and copper, which were deformed by equal channel angular pressing (ECAP) at ambient temperature, was analyzed by combining the Estrin and Mecking (EM) model and an Avrami-type equation with experimental data during severe plastic deformation. The initial strain hardening can be described by the EM model, while the flow stress arrives at the peak stress after it was saturated. However, strain softening similar to plastic deformation at high temperatures is observed after the peak stress. Moreover, the peak strain at the maximum flow stress is ∼4 for copper and ∼2 for aluminum. A new constitutive equation was developed to describe strain softening at high strain levels, which was supported well by tensile, compression and microhardness tests at room temperature and low strain rate. It was observed that dynamic recovery and recrystallization occurs in copper, and recrystallized grains and their growth in aluminum. The results indicate that dynamic recovery and recrystallization was the dominant softening mechanism, which was confirmed by scanning electron microscopy-electron channeling contrast observations and the abnormal relationship between the imposed strain during ECAP and subsequent recrystallization temperature after ECAP

Discrete dislocation plasticity analysis of loading rate-dependent static friction

NARCIS (Netherlands)

Song, H.; Deshpande, V. S.; van der Giessen, E.

2016-01-01

From a microscopic point of view, the frictional force associated with the relative sliding of rough surfaces originates from deformation of the material in contact, by adhesion in the contact interface or both. We know that plastic deformation at the size scale of micrometres is not only dependent

Introduction to Computational Plasticity

International Nuclear Information System (INIS)

Hartley, P

2006-01-01

The focus of the book on computational plasticity embodies techniques of relevance not only to academic researchers, but also of interest to industrialists engaged in the production of components using bulk or sheet forming processes. Of particular interest is the guidance on how to create modules for use with the commercial system Abaqus for specific types of material behaviour. The book is in two parts, the first of which contains six chapters, starting with microplasticity, but predominantly on continuum plasticity. The first chapter on microplasticty gives a brief description of the grain structure of metals and the existence of slip systems within the grains. This provides an introduction to the concept of incompressibility during plastic deformation, the nature of plastic yield and the importance of the critically resolved shear stress on the slip planes (Schmid's law). Some knowledge of the notation commonly used to describe slip systems is assumed, which will be familiar to students of metallurgy, but anyone with a more general engineering background may need to undertake additional reading to understand the various descriptions. Chapter two introduces one of several yield criteria, that normally attributed to von Mises (though historians of mechanics might argue over who was first to develop the theory of yielding associated with strain energy density), and its two or three-dimensional representation as a yield surface. The expansion of the yield surface during plastic deformation, its translation due to kinematic hardening and the Bauschinger effect in reversed loading are described with a direct link to the material stress-strain curve. The assumption, that the increment of strain is normal to the yield surface, the normality principle, is introduced. Uniaxial loading of an elastic-plastic material is used as an example in which to develop expressions to describe increments in stress and strain. The full presentation of numerous expressions, tensors and

A stochastic model for the interaction of plasticity and creep in metals

International Nuclear Information System (INIS)

Steck, E.

1987-01-01

Describing the basic mechanisms for plastic deformations in crystalline materials by transition probabilities of a stochastic matrix over the state space of the internal barriers, results in a stochastic model which has the properties of a Markov-chain. It is possible to include in this model properties of the internal structure of the material and their changes during macroscopic deformation processes, such as hardening and recovery, or the influence of temperature on thermal activation. This description can be based on findings from metal physics and metallurgy, so that the stochastic model can be used as an intermediate model between the microscopic and the macroscopic description of the processes during plastic deformations. Inelastic deformations of crystalline materials (plasticity, creep, relaxation) are caused by slip processes in the crystal-lattice which are supported by movements of dislocations. The dislocation movements are opposed by internal barriers which have to be overcome by activation of the dislocations. This activation can be performed by stresses, which are in equilibrium with external forces, or by thermal energy. With the movements of dislocations and the connected slip processes, production of new dislocations occurs. The dislocations interact. This can result either in a reduction of their mobility or in annihilation. These processes are partially responsible for hardening or recovery. (orig./GL)

Machining of Fibre Reinforced Plastic Composite Materials

Science.gov (United States)

2018-01-01

Fibre reinforced plastic composite materials are difficult to machine because of the anisotropy and inhomogeneity characterizing their microstructure and the abrasiveness of their reinforcement components. During machining, very rapid cutting tool wear development is experienced, and surface integrity damage is often produced in the machined parts. An accurate selection of the proper tool and machining conditions is therefore required, taking into account that the phenomena responsible for material removal in cutting of fibre reinforced plastic composite materials are fundamentally different from those of conventional metals and their alloys. To date, composite materials are increasingly used in several manufacturing sectors, such as the aerospace and automotive industry, and several research efforts have been spent to improve their machining processes. In the present review, the key issues that are concerning the machining of fibre reinforced plastic composite materials are discussed with reference to the main recent research works in the field, while considering both conventional and unconventional machining processes and reporting the more recent research achievements. For the different machining processes, the main results characterizing the recent research works and the trends for process developments are presented. PMID:29562635

Machining of Fibre Reinforced Plastic Composite Materials

Directory of Open Access Journals (Sweden)

Alessandra Caggiano

2018-03-01

Full Text Available Fibre reinforced plastic composite materials are difficult to machine because of the anisotropy and inhomogeneity characterizing their microstructure and the abrasiveness of their reinforcement components. During machining, very rapid cutting tool wear development is experienced, and surface integrity damage is often produced in the machined parts. An accurate selection of the proper tool and machining conditions is therefore required, taking into account that the phenomena responsible for material removal in cutting of fibre reinforced plastic composite materials are fundamentally different from those of conventional metals and their alloys. To date, composite materials are increasingly used in several manufacturing sectors, such as the aerospace and automotive industry, and several research efforts have been spent to improve their machining processes. In the present review, the key issues that are concerning the machining of fibre reinforced plastic composite materials are discussed with reference to the main recent research works in the field, while considering both conventional and unconventional machining processes and reporting the more recent research achievements. For the different machining processes, the main results characterizing the recent research works and the trends for process developments are presented.

COMPUTER MODELING IN DEFORM-3D FOR ANALYSIS OF PLASTIC FLOW IN HIGH-SPEED HOT EXTRUSION OF BIMETALLIC FORMATIVE PARTS OF DIE TOOLING

Directory of Open Access Journals (Sweden)

I. V. Kachanov

2015-01-01

Full Text Available The modern development of industrial production is closely connected with the use of science-based and high technologies to ensure competitiveness of the manufactured products on the world market. There is also much tension around an energy- and resource saving problem which can be solved while introducing new technological processes and  creation of new materials that provide productivity increase through automation and improvement of tool life. Development and implementation of such technologies are rather often considered as time-consuming processes  which are connected with complex calculations and experimental investigations. Implementation of a simulation modelling for materials processing using modern software products serves an alternative to experimental and theoretical methods of research.The aim of this paper is to compare experimental results while obtaining bimetallic samples of a forming tool through the method of speed hot extrusion and the results obtained with the help of computer simulation using DEFORM-3D package and a finite element method. Comparative analysis of plastic flow of real and model samples has shown that the obtained models provide high-quality and reliable picture of plastic flow during high-speed hot extrusion. Modeling in DEFORM-3D make it possible to eliminate complex calculations and significantly reduce a number of experimental studies while developing new technological processes.

Treatment of contaminated waste plastics material

International Nuclear Information System (INIS)

Sims, J.; Hitchcock, J.W.

1984-01-01

Radioactive contaminated plastics material is treated by reducing it to uniform-sized debris and extruding it from a heated extruder into a sealed container in monolithic block form or as an in-fill matrix for other contaminated waste articles to create a substantially void-free sealed mass for disposal. Density adjusting fillers may be included. Extrusion may alternatively take place into a clean sealable plastics tube. (author)

Topological defect clustering and plastic deformation mechanisms in functionalized graphene

Science.gov (United States)

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.

Dynamic Measurements of Plastic Deformation in a Water-Filled Aluminum Tube in Response to Detonation of a Small Explosives Charge

Directory of Open Access Journals (Sweden)

Harold Sandusky

1999-01-01

Full Text Available Experiments have been conducted to benchmark computer code calculations for the dynamic interaction of explosions in water with structures. Aluminum cylinders with a length slightly more than twice their diameter were oriented vertically, sealed on the bottom by a thin plastic sheet, and filled with distilled water. An explosive charge suspended in the center of the tube plastically deformed but did not rupture the wall. Tube wall velocity, displacement, and strain were directly measured. The agreement among the three sets of dynamic data and the agreement of the terminal displacement measurements with the residual deformation were excellent.

ELASTIC-PLASTIC AND RESIDUAL STRESS ANALYSIS OF AN ALUMINUM DISC UNDER INTERNAL PRESSURES

Directory of Open Access Journals (Sweden)

Numan Behlül BEKTAŞ

2004-02-01

Full Text Available This paper deals with elastic-plastic stress analysis of a thin aluminum disc under internal pressures. An analytical solution is performed for satisfying elastic-plastic stress-strain relations and boundary conditions for small plastic deformations. The Von-Mises Criterion is used as a yield criterion, and elastic perfectly plastic material is assumed. Elastic-plastic and residual stress distributions are obtained from inner radius to outer radius, and they are presented in tables and figures. All radial stress components, ?r, are compressive, and they are highest at the inner radius. All tangential stress components, ??, are tensile, and they are highest where the plastic deformation begins. Magnitude of the tangential residual stresses is higher than those the radial residual stresses.

Deformation mechanism study of a hot rolled Zr-2.5Nb alloy by transmission electron microscopy. I. Dislocation microstructures in as-received state and at different plastic strains

Energy Technology Data Exchange (ETDEWEB)

Long, Fei; Daymond, Mark R., E-mail: mark.daymond@queensu.ca; Yao, Zhongwen [Department of Mechanical and Materials Engineering, Queen' s University Kingston, Ontario K7L 3N6 (Canada)

2015-03-07

Thin foil dog bone samples prepared from a hot rolled Zr-2.5Nb alloy have been deformed by tensile deformation to different plastic strains. The development of slip traces during loading was observed in situ through SEM, revealing that deformation starts preferentially in certain sets of grains during the elastic-plastic transition region. TEM characterization showed that sub-grain boundaries formed during hot rolling consisted of screw 〈a〉 dislocations or screw 〈c〉 and 〈a〉 dislocations. Prismatic 〈a〉 dislocations with large screw or edge components have been identified from the sample with 0.5% plastic strain. Basal 〈a〉 and pyramidal 〈c + a〉 dislocations were found in the sample that had been deformed with 1.5% plastic strain, implying that these dislocations require larger stresses to be activated.

Plane strain analytical solutions for a functionally graded elastic-plastic pressurized tube

International Nuclear Information System (INIS)

Eraslan, Ahmet N.; Akis, Tolga

2006-01-01

Plane strain analytical solutions to functionally graded elastic and elastic-plastic pressurized tube problems are obtained in the framework of small deformation theory. The modulus of elasticity and the uniaxial yield limit of the tube material are assumed to vary radially according to two parametric parabolic forms. The analytical plastic model is based on Tresca's yield criterion, its associated flow rule and ideally plastic material behaviour. Elastic, partially plastic and fully plastic stress states are investigated. It is shown that the elastoplastic response of the functionally graded pressurized tube is affected significantly by the material nonhomogeneity. Different modes of plasticization may take place unlike the homogeneous case. It is also shown mathematically that the nonhomogeneous elastoplastic solution presented here reduces to that of a homogeneous one by appropriate choice of the material parameters

Use of intra-medullary stacked nailing in the reduction of proximal plastic deformity in a pediatric Monteggia fracture: a case report

Directory of Open Access Journals (Sweden)

Huntley James S

2011-04-01

Full Text Available Abstract Introduction In a Monteggia fracture dislocation, it is important to reduce the ulnar fracture completely. Extensive plastic deformation of the proximal ulna may make reduction by closed manipulation impossible. Case presentation We report the case of a four-year-old Caucasian boy in whom the plastic deformation of the proximal ulna was reduced, and this reduction was maintained, using intra-medullary stacked nailing. Conclusion The technique of stacked nailing is a useful addition to the armamentarium in the management of the potentially awkward Monteggia fracture.

Compression deformation behaviors of sheet metals at various clearances and side forces

Directory of Open Access Journals (Sweden)

Zhan Mei

2015-01-01

Full Text Available Modeling sheet metal forming operations requires understanding of plastic behaviors of sheet metals along non-proportional strain paths. The plastic behavior under reversed uniaxial loading is of particular interest because of its simplicity of interpretation and its application to material elements drawn over a die radius and underwent repeated bending. However, the attainable strain is limited by failures, such as buckling and in-plane deformation, dependent on clearances and side forces. In this study, a finite element (FE model was established for the compression process of sheet specimens, to probe the deformation behavior. The results show that: With the decrease of the clearance from a very large value to a very small value, four defects modes, including plastic t-buckling, micro-bending, w-buckling, and in-plane compression deformation will occur. With the increase of the side force from a very small value to a very large value, plastic t-buckling, w-buckling, uniform deformation, and in-plane compression will occur. The difference in deformation behaviors under these two parameters indicates that the successful compression process without failures for sheet specimens only can be carried out under a reasonable side force.

Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

DEFF Research Database (Denmark)

Bailey, Nicholas; Schiøtz, Jakob; Jacobsen, Karsten Wedel

2006-01-01

We have simulated plastic deformation of a model Mg-Cu metallic glass in order to study shear banding. In uniaxial tension, we find a necking instability occurs rather than shear banding. We can force the latter to occur by deforming in plane strain, forbidding the change of length in one...... of the transverse directions. Furthermore, in most of the simulations a notch is used to initiate shear bands, which lie at a 45 degrees angle to the tensile loading direction. The shear bands are characterized by the Falk and Langer local measure of plastic deformation D-min(2), averaged here over volumes...... observe a slight decrease in density, up to 1%, within the shear band, which is consistent with notions of increased free volume or disorder within a plastically deforming amorphous material....

Calorimetric features of release of plastic deformation induced internal stresses, and approach to equilibrium state on annealing of crystals and glasses

Energy Technology Data Exchange (ETDEWEB)

Johari, G.P., E-mail: joharig@mcmaster.ca

2014-04-01

Highlights: • Stress release in a glass occurs at a faster rate than structural relaxation. • Plastically-deformed glass would show two exothermic minima, and no glass transition. • Enthalpy matching procedure would yield an inaccurate fictive temperature. • Complex heat capacity may distinguish plastically-deformed from quench-formed glass. - Abstract: Plastic deformation of crystals and glasses produces internal strains (stresses), which change their energy and other thermodynamic properties. On annealing, these stresses decrease at a rate faster than the structure relaxes toward the equilibrium state. Mechanism of such relaxations in crystals differs from that in glasses and it also differs for glasses of different types. In all cases, the energy related properties decrease with time isothermally and on heating, resembling the structure relaxation of a stress-free glass. We consider these features and argue that kinetics of enthalpy loss with time yields the rate constants of the stress release and of the structure change, and not the viscosity determining α-relaxation time. Since thermal cycling does not recover the enthalpy from internal stresses, a glass with stresses has neither a glass-softening temperature, T{sub g}, nor a fictive temperature, T{sub f}. Plastic deformation would not rejuvenate a physically aged glass to the properties of its un-aged state. The Prigogine–Defay ratio can be extended to all T{sub f}s, and used to investigate the effect of distribution of relaxation times on its value, but it can not be defined for an internally stressed glass. After discussing the effects of annealing on the heat capacity and DSC scans, we conclude that on slow heating, glass with deformation-induced stresses would show two exothermic minima, and normal glass would show only one such minimum. Temperature-modulated scanning calorimetry would also distinguish an internally stressed glass from an equally high-enthalpy, stress-free glass. Enthalpy

Recent advances in high performance poly(lactide): From ``green'' plasticization to super-tough materials via (reactive) compounding

Science.gov (United States)

Kfoury, Georgio; Raquez, Jean-Marie; Hassouna, Fatima; Odent, Jérémy; Toniazzo, Valérie; Ruch, David; Dubois, Philippe

2013-12-01

Due to its origin from renewable resources, its biodegradability, and recently, its industrial implementation at low costs, poly(lactide) (PLA) is considered as one of the most promising ecological, bio-sourced and biodegradable plastic materials to potentially and increasingly replace traditional petroleum derived polymers in many commodity and engineering applications. Beside its relatively high rigidity (high tensile strength and modulus compared with many common thermoplastics such as poly(ethylene terephthalate) (PET), high impact poly(styrene) (HIPS) and poly(propylene) (PP)), PLA suffers from an inherent brittleness, which can limit its applications especially where mechanical toughness such as plastic deformation at high impact rates or elongation is required. Therefore, the curve plotting stiffness vs. impact resistance and ductility must be shifted to higher values for PLA-based materials, while being preferably fully bio-based and biodegradable upon the application. This review aims to establish a state of the art focused on the recent progresses and preferably economically viable strategies developed in the literature for significantly improve the mechanical performances of PLA. A particular attention is given to plasticization as well as to impact resistance modification of PLA in the case of (reactive) blending PLA-based systems.

Recent advances in high performance poly(lactide: From green plasticization to super-tough materials via (reactive compounding

Directory of Open Access Journals (Sweden)

Georgio eKfoury

2013-12-01

Full Text Available Due to its origin from renewable resources, its biodegradability, and recently, its industrial implementation at low costs, poly(lactide (PLA is considered as one of the most promising ecological, bio-sourced and biodegradable plastic materials to potentially and increasingly replace traditional petroleum derived polymers in many commodity and engineering applications. Beside its relatively high rigidity (high tensile strength and modulus compared with many common thermoplastics such as poly(ethylene terephthalate (PET, high impact poly(styrene (HIPS and poly(propylene (PP, PLA suffers from an inherent brittleness, which can limit its applications especially where mechanical toughness such as plastic deformation at high impact rates or elongation is required. Therefore, the curve plotting stiffness vs. impact resistance and ductility must be shifted to higher values for PLA-based materials, while being preferably fully bio-based and biodegradable upon the application.This review aims to establish a state of the art focused on the recent progresses and preferably economically viable strategies developed in the literature for significantly improve the mechanical performances of PLA. A particular attention is given to plasticization as well as to impact resistance modification of PLA in the case of (reactive blending PLA-based systems.