Academic literature on the topic 'Strain-deformed state'
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Journal articles on the topic "Strain-deformed state"
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Wang, Hao, and Mo Li. "Nonlinear stress-strain relations for crystalline solids in initially deformed state." Journal of Applied Physics 112, no. 9 (November 2012): 093501. http://dx.doi.org/10.1063/1.4762000.
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Gasanov, B. G., A. A. Aganov, and P. V. Sirotin. "Features of determining the deformed state of a particle material during hot stamping of porous moldings." Izvestiya vuzov Poroshkovaya metallurgiya i funktsional’nye pokrytiya, no. 1 (March 17, 2021): 21–30. http://dx.doi.org/10.17073/1997-308x-2021-1-21-30.
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The paper describes main methods for assessing the deformed state of porous body metal frames developed by different authors based on the analysis of yield conditions and governing equations, using the principle of equivalent strains and stresses, and studying the kinetics of metal strain during pressing. Formulas were derived to determine the components of the powder particle material strain tensor through dyads, as scalar products of the basis vectors of the convected coordinate system at each moment of porous molding strain. The expediency of using the analytical expressions developed to determine the deformed state of the particle material was experimentally substantiated subject to the known displacement vector parameters of representative elements (macrostrains) of porous billets. The applications of well-known analytical expressions were established, and the proposed formulas proved applicable for the deformed state assessment of particle metal during the pressure processing of powder products of different configurations and designing billets with a defined porosity and geometric parameters as a basis for compiling software algorithms for the computer simulation of porous molding hot stamping.
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Belikova, A. F., S. N. Buravova, and Yu A. Gordopolov. "Strain localization and its connection with the deformed state of the material." Technical Physics 58, no. 2 (February 2013): 302–4. http://dx.doi.org/10.1134/s1063784213020035.
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Vaquero-Aguilar, Cristina, and Manuel Jiménez Melendo. "Creep Behavior of Yb-Doped Barium Cerate Perovskite." Advances in Science and Technology 65 (October 2010): 238–43. http://dx.doi.org/10.4028/www.scientific.net/ast.65.238.
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Polycrystalline ytterbium-doped barium cerate with composition BaCe0.95Yb0.05O3- has been fabricated by solid state reaction. The compound has an orthorhombic perovskite structure and a fine and homogeneous grain size distribution, with a mean value of 0.4 m. The creep behavior was studied by means of constant crosshead-speed compression tests in air at temperatures of up to 1300 °C. At the lower strain rates and higher temperatures, the material deformed by grain boundary sliding; the corresponding true stress-true strain curves displayed an initial strength drop followed by an extended steady state stage. A continuous transition towards a brittle regime was observed with increasing initial strain rate and/or decreasing temperature.
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Kellermann Slotemaker, A., J. H. P. de Bresser, C. J. Spiers, and M. R. Drury. "Microstructural Evolution of Synthetic Forsterite Aggregates Deformed to High Strain." Materials Science Forum 467-470 (October 2004): 579–84. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.579.
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Microstructures provide the crucial link between solid state flow of rock materials in the laboratory and large-scale tectonic processes in nature. In this context, microstructural evolution of olivine aggregates is of particular importance, since this material controls the flow of the Earth’s upper mantle and affects the dynamics of the outer Earth. From previous work it has become apparent that if olivine rocks are plastically deformed to high strain, substantial weakening may occur before steady state mechanical behaviour is approached. This weakening appears directly related to progressive modification of the grain size distribution through competing effects of dynamic recrystallization and syn-deformational grain growth. However, most of our understanding of these processes in olivine comes from tests on coarse-grained materials that show grain size reduction through dynamic recrystallization. In the present study we focused on fine-grained (~1 µm) olivine aggregates (i.e., forsterite/Mg2SiO4), containing ~0.5 wt% water and 10 vol% enstatite (MgSiO3), Samples were axially compressed to varying strains up to a maximum of ~45%, at 600 MPa confining pressure and a temperature of 950°C. Microstructures were characterized by analyzing full grain size distributions and textures using SEM/EBSD. We observed syndeformational grain growth rather than grain size reduction, and relate this to strain hardening seen in the stress-strain curves.
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Daniūnas, Alfonsas. "ANALYSIS OF COMPLICATED FORM SECTIONS OF STEEL MEMBERS." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 3, no. 9 (March 31, 1997): 34–38. http://dx.doi.org/10.3846/13921525.1997.10531669.
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Strain-deformed state analysis of free form sections of steel members is defined in an elastic-plastic state while using the extremum energy principles of elastic-plastic systems [1], The solution is obtained by using finite elements with the constant distribution of stresses.
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Liu, Bai Xiong, and Bao Jun Han. "Microstructure Characterization of Large Strain Deformed Fe-32%Ni Alloy." Advanced Materials Research 146-147 (October 2010): 248–51. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.248.
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High-resolution electron backscatter diffraction (EBSD) in scanning electron microscope and transmission electron microscope (TEM) were used to investigate the microstructure of Fe-32%Ni alloy processed by large strain multi-axial forging. The samples were compressed with loading direction changed through 90º from pass to pass at temperature of 500°C and a strain rate of 10-2/s. The results show the microstructure evolution is characterized by full development of almost equi-axed fine grains, not well-developed grain boundaries accompanied by high dislocation density and the existence of extensive extinction contours in the vicinity of grain boundaries, and the structure characteristics indicate that the grain boundaries are in a non-equilibrium state with high internal stresses.
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Renzetti, Reny Angela, M. J. R. Sandim, Hugo Ricardo Zschommler Sandim, K. T. Hartwig, Heide H. Bernardi, and Dierk Raabe. "EBSD Characterization of Pure Iron Deformed by ECAE." Materials Science Forum 638-642 (January 2010): 1995–2000. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.1995.
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Polycrystalline iron was deformed by eight ECAE passes using the route Bc to a total strain of 9.2. After deformation the material was annealed at temperatures up to 800oC. Scanning electron microscopy (SEM) and high-resolution electron backscatter diffraction (EBSD) were used to characterize both deformed and annealed structures. In the as-deformed state, the mean grain size is 650 nm and the volume fraction of high angle boundaries (VHAB) is 56%. Upon annealing there is a pronounced softening above 300oC. At the beginning of recrystallization, at about 400oC, the VHAB increases to 71%. The results indicate that discontinuous recrystallization is the main softening mechanism in severely deformed iron.
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Lomakin, E. V., and P. V. Tishin. "Constitutive relations for materials with strain state dependent properties." PNRPU Mechanics Bulletin, no. 1 (December 15, 2021): 52–62. http://dx.doi.org/10.15593/perm.mech/2021.1.06.
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Many materials demonstrate a dependence of mechanical properties on the type of stressed or deformed states. This is most noticeable in the dependence of the processes of shear and bulk deformation. Such materials include rocks, structural graphite, concrete, some grades of steel, cast iron, and aluminum. The main properties of these materials are an absence of a "single curve" relationship between the intensity of stresses and the intensity of deformations. Under shear conditions, bulk deformations can occur. Such materials can be described by constitutive equations that depend on the parameter of the type of a stress state, which is the ratio of the first invariant of the stress tensor to the stress intensity. Thus, these defining relations give the dependence of the strain tensor components on the stress tensor components. Such defining relations can be quite cumbersome, and therefore do not allow an analytical treatment to obtain defining relations that give the dependence of the components of the stress tensor on the components of the strain tensor. The paper proposes the constitutive relations obtained from the analysis of test results of various materials, which properties depend on the type of deformed state. Conditions are derived for material constants that ensure the uniqueness of the solution of boundary value problems. Based on experimental data obtained under the conditions of the proportional loading of various rocks: limestone and talcochlorite, as well as the results of mechanical tests of several grades of concrete, the constants of the mathematical model are determined. The results of the experimental studies are compared with theoretical dependencies predicted by the model. The limited applicability of the proposed constitutive relations is established.
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Miszczyk, Magdalena M., and Henryk Paul. "Cube{100}<001> Grains Nucleation during Annealing of S-Oriented Aluminum Single Crystal." Materials Science Forum 941 (December 2018): 1511–16. http://dx.doi.org/10.4028/www.scientific.net/msf.941.1511.
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The crystallographic aspects of nucleation of cube grains during annealing have been analyzed in (234)[20-28 11] - oriented aluminum single crystal. The samples were plane strain compressed in a channel-die up to logarithmic strains of 0.5 (40%) and then annealed to develop initial and final stages of primary recrystallization. The deformed and annealed samples were analyzed using scanning electron microscopy equipped with EBSD facility. Local orientation measurements reveled that significant part of the sample deforms homogeneously with only small deviation from the initial crystal orientation. The heterogeneities were thin bands of localized strain in which the crystal lattice rotate towards another variant of S orientation. After annealing the orientations identified inside deformed/recovered areas were similar to that observed in the sample just after deformation. The crystal lattice of recrystallized grains exhibit a well-defined clockwise and anticlockwise rotations around the axes grouped near all normals of the {111} planes of the deformed/recovered state. The cube grains were observed in both homogeneously and heterogeneously deformed areas despite the cube-oriented nuclei surrounded by high angle boundary were not present in the as-deformed structure.
Dissertations / Theses on the topic "Strain-deformed state"
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Моргун, Сергій Олександрович, Сергей Александрович Моргун, and Sergii O. Morgun. "Напряженно-деформированное состояние конструктивно неоднородных лопаток турбомашин при их вибрациях." Thesis, Запорізький національний технічний університет, 2015. http://eir.zntu.edu.ua/handle/123456789/419.
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Моргун, С.О. Напруженно-деформований стан конструктивно неоднорідних лопаток турбомашин при їх вібраціях [Текст]: дис. … канд. техн. наук: 01.02.04 : захищена ....: затверджена…. /Моргун Сергій Олександрович. – Запоріжжя, 2015. – 157 с.UK: Дисертація присвячена визначенню параметрів напружено-деформованого стану конструктивно неоднорідних робочих лопаток турбомашин при їх вібраціях з використанням методу скінчених елементів. Розвинуті і теоретично обґрунтовані ефективні чисельні методи для розв’язання розглянутих в дисертації задач. Досліджено вплив геометричних характеристик лопаток, фізико-механічних властивостей матеріалу, температури газового потоку на частоти та форми коливань і напружено-деформований стан робочих лопаток турбомашин. Достовірність та адекватність розроблених математичних моделей підтверджена співставленням результатів з даними, отриманими з використанням пакету програм ANSYS та експериментально. EN: The thesis is devoted to the non homogeneous cooled single turbine blades and strain-deformed state parameters under vibration load by means of finite elements method usage. The effective numerical methods for the foregoing problems solution are also developed and theoretically approved. The turbine blades geometrical characteristics, their material physical and mechanical state and the gas flow temperature influence on their oscillation forms and frequencies, and strain-deformed state has been researched. The results of the research have been adopted by the obtained results comparison with the ANSYS program package’s solutions and experimental data. RU: Диссертация посвящена определению параметров напряженно-деформированого состояния конструктивно неоднородных лопаток турбомашин при их вибрациях с использованием метода конечных элементов. Приведена постановка и обоснование задач динамического поведения рабочих лопаток турбомашин. Развиты и теоретически обоснованы эффективные численные методы для решения рассмотреных в дисертации задач. Построены уточненные математические модели свободных и вынужденных колебаний, а также напряженно-деформированного состояния, позволяющие адекватно описывать динамическое поведение конструктивно неоднородных рабочих лопаток. Уравнения движения лопаток получены с использованием вариационного принципа Лагранжа II рода. Выполнен анализ сходимости полученных решений. Получены результаты количественного и качественного характера для лопаток с конструктивными неоднородностями, которые характеризуют особенности их поведения при вынужденных колебаниях, вызванных воздействием переменной газодинамической силы. Исследовано влияние геометрических характеристик лопаток, физико-механических свойств материала, температуры газового потока на частоты и формы колебаний и напряженно-деформированное состояние рабочих лопаток турбомашин. Достоверность и адекватность разработанных математических моделей подтверждена сопоставлением полученных результатов с данными, полученными с использованием пакета программ ANSYS и экспериментальным путем. Экспериментальные исследования частот и форм колебаний, как охлаждаемых, так и неохлаждаемых лопаток турбомашин проводились методом голографической интерферометрии. Параметры напряженно-деформированного состояния лопаток определялись на специальном вибровоздушном стенде с применением метода тензометрирования.
Book chapters on the topic "Strain-deformed state"
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Kishi, Y., Z. Yajima, K. Shimizu, and M. Asai. "X-ray characterization of the strain state in a tensile deformed Ti-Ni-Cu shape memory alloy." In Nondestructive Characterization of Materials X, 99–104. Elsevier, 2001. http://dx.doi.org/10.1016/b978-008043799-6/50013-6.
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Bayly, Brian. "Change of Shape and Change of Volume." In Chemical Change in Deforming Materials. Oxford University Press, 1993. http://dx.doi.org/10.1093/oso/9780195067644.003.0012.
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In earlier chapters we first defined a material's chemical potential, and then went on to enquire how the material responds. And similarly with a state of nonhydrostatic stress: having reviewed what it is, we consider how a material might respond. For the sake of simplicity, we imagine an extensive sample, such as a cubic meter, and suppose that the stress state is the same in every cubic centimeter; that is to say, there are no gradients in stress from point to point. Thus we do not enquire yet how a material responds to a spatial stress gradient; that comes later. We first enquire how it responds to a homogeneous but nonhydrostatic stress. Inside the material, close to the point of interest, we define a small length l by means of the material particles at its two ends. If, at a later moment, we find the distance between the particles to be l — δl, then we envisage the limit of the ratio δl/l as l goes to zero, give the limit the symbol ε, and name it the linear strain at the point of interest in the direction of l, positive when δl is positive, i.e., for a shortening and negative for an elongation. Another mental operation that can be performed in the neighborhood of the point of interest is to define a small sphere by means of the material particles that form its surface. At a later moment the particles will form the surface of an ellipsoid. (For a large sphere and an inhomogeneous situation, the new shape can be something more complicated; but as the imagined original sphere approaches zero diameter, the shape of its deformed counter-part can only approach an ellipsoid). The axes of the ellipsoid are principal directions of strain, and the magnitudes of the strains along them are named ε1, ε2, and ε3, with ε1 the largest. In an isotropic material, the principal axes of stress and strain coincide, with ε1 lying along the direction of σ1 and correspondingly; see Figure 7.la. As with stresses, the three values of ε themselves define an ellipsoid if they are all positive—see Figure 7.1b.
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Han, Chang Dae. "Kinematics and Stresses of Deformable Bodies." In Rheology and Processing of Polymeric Materials: Volume 1: Polymer Rheology. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195187823.003.0007.
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The form of kinematics to be used for the description of a deformation process is largely determined by the kind of mechanical response that is being described. To describe the mechanical response of purely viscous fluids it is convenient to use coordinates, which are fixed in space, since purely viscous fluids have no past memory and therefore remain in the deformed state when loads are removed. In other words, the mechanical response of purely viscous fluids is determined solely by the instantaneous values of the time rate of deformation. However, in order to describe the deformation of a viscoelastic fluid it is necessary to follow a given material element with time as it moves to define a suitable measure of deformation that always refers to the same material element as time varies. The reason is that when a material element undergoes a finite deformation the coordinate positions of the given material element (with respect to a fixed origin) will vary. Hence, any measure of deformation defined in terms of infinitesimal deformation of fixed coordinate positions loses its physical significance since it will not always be associated with the same material element. In this chapter, we introduce some basic concepts of the kinematics and stresses of a deformable body from the point of view of continuum mechanics, and discuss various representations of a deformation process in terms of the deformation (or strain) tensor and the rate-of-deformation (or rate-of-strain) tensor. In order to help the readers follow the material in the text, the elementary properties of second-order tensors are presented in Appendix 2A. In this section, we briefly describe the motion of a body, which consists of a set of particles (or “elements”), sometimes called “material points” (or “material elements”) (Jaunzemis 1967). Let X(Xi ; i = 1, 2, 3) be the particles P of the body B in some reference configuration κ at time t = 0 (i.e., undeformed state) and then we have. . . X = κ(P). . .in which κ describes the shape of the body B in the undeformed state, which in general is known to an observer.
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Kobayashi, Shiro, Soo-Ik Oh, and Taylan Altan. "Analysis and Technology in Metal Forming." In Metal Forming and the Finite-Element Method. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195044027.003.0006.
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The design, control, and optimization of forming processes require (1) analytical knowledge regarding metal flow, stresses, and heat transfer, as well as (2) technological information related to lubrication, heating and cooling techniques, material handling, die design and manufacture, and forming equipment. The purpose of using analysis in metal forming is to investigate the mechanics of plastic deformation processes, with the following major objectives. • Establishing the kinematic relationships (shape, velocities, strain-rates, and strains) between the undeformed part (billet, blank, or preform) and the deformed part (product); i.e., predicting metal flow during the forming operation. This objective includes the prediction of temperatures and heat transfer, since these variables greatly influence local metal-flow conditions. • Establishing the limits of formability or producibility; i.e., determining whether it is possible to perform the forming operation without causing any surface or internal defects (cracks or folds) in the deforming material. • Predicting the stresses, the forces, and the energy necessary to carry out the forming operation. This information is necessary for tool design and for selecting the appropriate equipment, with adequate force and energy capabilities, to perform the forming operation. Thus, the mechanics of deformation provides the means for determining how the metal flows, how the desired geometry can be obtained by plastic deformation, and what the expected mechanical properties of the produced part are. For understanding the variables of a metal-forming process, it is best to consider the process as a system, as illustrated in Fig. 2.1 in Chap. 2. The interaction of most significant variables in metal forming are shown, in a simplified manner, in Fig. 3.1. It is seen that for a given billet or blank material and part geometry, the speed of deformation influences strain-rate and flow stress. Deformation speed, part geometry, and die temperature influence the temperature distribution in the formed part. Finally, flow stress, friction, and part geometry determine metal flow, forming load, and forming energy. In steady-state flow (kinematically), the velocity field remains unchanged, as is the case in the extrusion process; in nonsteadystate flow, the velocity field changes continuously with time, as is the case in upset forging.
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Keefer, Robert F. "Engineering Aspects of Soils." In Handbook of Soils for Landscape Architects. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195121025.003.0020.
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Although most landscape architects use soils primarily for growing plants, sometimes they need to know how engineers look at soils. Engineers are not concerned about soil properties that relate to growing plants. Engineers consider soil as a support for building foundations, use in earthworks, a place for burying pipes that carry electricity, water, gas or oil, and as a tool for disposing of hazardous, municipal, industrial, and household wastes. Soil properties that engineers consider important are hydraulic conductivity (permeability), compressive strength, shear strength, and lateral pressures. Soil mechanics deals with stress/strain/time relationships. Some engineering properties of a soil that describe the relation of clays to water content were studied by a Swedish scientist, Atterberg, in 1911. Soil clays based on water content were categorized into solid, semi-solid, plastic, and liquid. The dividing lines between each of these four states are known as the “Atterberg limits,” that is, shrinkage limit (from solid to semisolid), plastic limit (from semi-solid to plastic), and liquid limit (from plastic to liquid). These points can be measured for individual clays. The Atterberg limits are used by engineers to classify soils based on their moisture properties. These limits are particularly useful for evaluating soil compressibility, permeability, and strength. The plasticity of a clay soil depends on the type and amount of clay mineral and organic materials present. Plasticity is the reaction a soil has to being deformed without cracking or crumbling. The “liquid limit” is a term indicating the amount of water in a soil between the liquid state and the plastic state. Soils are first divided into two categories of coarse-grained and fine-grained. Coarse-grained soils are those in which more than half of the material is larger than a no. 200 sieve. Fine-grained soils are those in which more than half of the material is smaller than a no. 200 sieve. Coarse-grained soils are further divided into two categories of gravels and sands. Gravels are those with more than half of the coarse material larger than a no. 4 sieve. Sands are those with more than half of the coarse material smaller than a no. 4 sieve.
Conference papers on the topic "Strain-deformed state"
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Rao, Mala N., S. Rawat, S. Sharma, V. M. Chavan, R. J. Patel, and S. L. Chaplot. "Neutron diffraction measurements of dislocation density in copper crystals deformed at high strain rate." In SOLID STATE PHYSICS: PROCEEDINGS OF THE 57TH DAE SOLID STATE PHYSICS SYMPOSIUM 2012. AIP, 2013. http://dx.doi.org/10.1063/1.4791143.
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Haider, Muhammad Istiaque, Ameralys Correa, Afsaneh Moghadam, Xiaojun Yan, and Nathan Salowitz. "Experimental Exploration of Post Constrained Recovery Mechanics of NiTi." In ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/smasis2018-8168.
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Shape memory alloys (SMAs) have tremendous potential use as actuators in mechanical systems due to their high specific energy density. Large recovery stresses can be generated when Nickel Titanium (NiTi), the most widely used SMA, undergoes constrained recovery where it is held in a deformed geometry and heated from a detwinned martensite phase to austenite phase. Recent experimental results have found that residual stresses can also be generated in NiTi after returning to a low temperature geometrically constrained state. This paper presents experimental results performed on NiTi wire samples where wire was: 1) deformed from a low temperature twinned martensite state to produce a strain that would be recoverable in an unloaded state 2) held at that strain state and heated above the austenite finish transition temperature and then cooled back below the martensite transition finish temperature while recording the forces generated. It was found that a residual load was produced in the low temperature state. Results from further testing beyond this point showed repeatability with application of small and large strains. Post constrained recovery stresses have the potential to be used to generate residual stresses in structures in a low energy, un-actuated state with a remaining potential for thermal actuation.
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Bange, M. E., A. J. Beaudoin, M. G. Stout, and S. R. MacEwen. "Measurement of the Material State Including the Effects of Recovery and Recrystallization." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1865.
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Abstract Deformation at elevated temperatures in combination with high strain rates leads to recovery and recrystallization in aluminum alloys. Previous work in recrystallization has emphasized the detailing of microstructural trend in progression from the deformed to the annealed state. In the following, we examine the effect of rate dependence on deformation on AA 5182 and AA 6061. It is demonstrated that identification of underlying microstructural mechanisms is critical. An experimental program is then outlined for characterization of recovery and recrystallization of AA 5182. Instantaneous hardening rate and flow stress are developed from interrupted compression tests. These data are used to establish a quantitative measure of recovery through evaluation of a state variable for work hardening, the mechanical threshold. It is intended that the results serve as a foundation for development of relations for evolution of a mechanical state variable in the presence of recrystallization. Such a framework is necessary for the practical prediction of interstand recrystallization in hot rolling operations.
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Okoloekwe, Chike, Muntaseer Kainat, Doug Langer, Sherif Hassanien, J. J. Roger Cheng, and Samer Adeeb. "Deformation Analysis of Dented Pipeline via Surface Interpolation." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65523.
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Advances in the interpolation techniques of discrete data points and its application to monitoring the displacement of physical infrastructure has led to improved analytical strain evaluation procedures. In order to generate a detailed mathematical model of the strain state of a dented pipeline, it is necessary to decompose the deformation data obtained from monitoring devices into the corresponding radial, longitudinal and circumferential components. In this paper, a technique for analytically evaluating the strains in dented pipelines based on the coordinates of the geometric profile of the dent is investigated and the strains predicted from the said method are benchmarked against the strains predicted from a numerical model generated using nonlinear finite element analysis (FEA) and the codified equations for evaluating strains in dented pipes. This novel technique to strain analysis is an application of the principles of shell theory to a deformed pipeline in order to evaluate the components of the displacements in the cylindrical coordinate system. The coordinates of the deformed profile are obtained from the FEA model and interpolated with B-Splines curves equipped with second order continuity. The resulting strain distribution along the thickness of the pipe wall is evaluated analytically by performing derivatives on the spline functions. The good agreement obtained in the strains predicted by our model and FEA indicates a possibility of conducting in-depth strain analysis of thin-walled structures without the need for the rigorous FEA.
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Ohnishi, Masato, Ken Suzuki, and Hideo Miura. "Effect of Anisotropic Strain Field on the Electronic Conductance of Carbon Nanotubes." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64487.
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Since carbon nanotubes (CNTs) have unique electronic and mechanical properties, there have been many efforts to develop CNTs-based electronic devices and sensors. The authors have also validated the possibility of a highly sensitive strain sensor using popular resin in which multi-walled CNTs (MWNTs) were dispersed uniformly. It is, however, indispensable for clarifying how to change the electronic state of a deformed CNT for assuring the stable performance of the sensor because the reported sensitivity has ranged widely. In this study, the relationship between the deformation characteristic of a CNT under strain and its electronic properties was analyzed. The analysis result obtained from density functional theory (DFT) calculation showed that the orbital hybridization was occurred when the maximum local dihedral angle exceeded 10–20° and 25–30° in GNRs and CNTs, respectively, which induced the band gap.
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Narumi, Takatsune, Hideaki Hoshi, Tomohiko Muraki, and Tomiichi Hasegawa. "Mechanical Properties of Complex Structure Formed From Electro-Convection State of Smectic Liquid Crystal." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-14010.
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In the present study, electro-rheological characteristics of a liquid crystal (8CB) in smectic-A phase were investigated utilizing a parallel-plate type rheometer under a stress control mode. Solid like behaviors of the liquid crystal under DC electric fields were mainly examined. Bingham-like properties were observed and yield stresses measured were affected with the electric field conditions. When the electric field strength was low, the yield stress was almost the same as that obtained under no electric field. Above a threshold of DC electric field strength, the yield stress increased. It was clarified that the increase in the yield stress was caused with the complex structure formed in cooling process from an electro-convection state in nematic phase. Mechanical property changes after deformation of the structure were also examined as changes in dynamic viscoelasticities under condition of very small strain amplitude and the yield stress. The properties were measured before and after the deformation and compared. Moreover, the deformed structure of the liquid crystal was visualized with a polarizing microscope. Since the initial structures formed after the cooling have unevenness, the strength of the structure varied widely. When the small deformation is applied, peculiar changes in the strength were observed, i.e. the G’ measured was increased or decreased after the deformation. Moreover, the values measured after the deformation had reproducibility despite of the scattered initial data. We observed growth of typical optical patterns in the visualization of the structure and it is considered that defects like focal conic domains were generated and developed. After large deformation, the strength of the structure decreased and the deformed structure had almost no elastic properties. The structures were changed to irregular flow structures.
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Ohnishi, Masato, Hiroshi Kawakami, Yusuke Suzuki, Ken Suzuki, and Hideo Miura. "Anisotropic Strain-Field-Induced Change of the Electronic Conductivity of Graphene Sheets and Carbon Nanotubes." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-87347.
Full textAbstract:
Since the discovery of carbon nanotubes (CNTs), there have been many efforts to develop various electronic devices and sensors. The authors have also validated the possibility of a highly sensitive strain sensor using popular resin in which multi-walled CNTs (MWNTs) were dispersed uniformly. It is, however, indispensable for clarifying how to change the electronic state of a deformed CNT for assuring the stable performance of the sensor because the reported sensitivity has ranged widely. In this study, the relationship between the deformation characteristic of a CNT under strain and its electronic conductivity was analyzed quantitatively. The analysis result obtained from density functional theory (DFT) calculation showed that the orbital hybridization was occured when the local curvature exceeded about 0.3 Å−1, inducing the decrease in the band gap. Based on the analytical results, a two-dimensional strain sensor was developed by applying buckling deformation-induced conductivity change of MWNTs by using MEMS technology.
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Tcherni, V. P. "Technique of Estimation of Actual Strength of a Gas Pipeline Section at its Deformation in Landslide Action Zone." In 1996 1st International Pipeline Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/ipc1996-1938.
Full textAbstract:
The technique is given which permit to determine stress and strain state (SSS) and to estimate actual strength of a section of a buried main gas pipeline (GP) in case of its deformation in landslide action zone. The technique is based on use of three-dimensional coordinates of axial points of the deformed GP section. These coordinates are received by full-scale survey. The deformed axis of the surveyed GP section is described by the polynomial. The unknown coefficients of the polinomial can be determined from the boundary conditions in points of connection with contiguous undeformed sections as well as by use one of minimization methods at mathematical processing of full-scale survey results. The received form of GP section’s axis allows to determine curvatures and, accordingly, bending moments along all the length of the considered section. The account for the influence of soil resistance to longitudinal displacements of a pipeline is used to determine longitudinal forces. Received by this technique values of bending moments and axial forces as well as known value of internal pressure are used to receive all necessary components of actual SSS of pipeline section and to estimate its strength by elastic analysis.
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Nikhare, Chetan P., Emmett Vorisek, John Nolan, and John T. Roth. "Understanding the Differences in Hemispherical Dome and Biaxial Test During Equi-Biaxial Tension on Cruciform." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67117.
Full textAbstract:
One metal manufacturing process which uses thousands of processes to trim, stretch, draw, bend etc. under a big umbrella is sheet metal forming. Using heavy equipment, the sheet metal parts are deformed into complex geometries. The complexity in these parts produces multi-axial stress and strain, a state for which it is critical to analyze using conventional tools. Traditionally, the mechanical properties of materials have been characterized using the uniaxial tension test. This test is considered adequate for simple forming operations where single axis loading is dominant. Previous studies, however, have noted that the data acquired from this type of testing is not enough and additional details in other axes under simultaneous deformation conditions are important. To analyze the biaxial strain, some studies have suggested using the limiting dome height test and bulge test. However, these tests limit the extent of using multi-axial loading and the resulting stress pattern due to contact surfaces. Therefore, researchers devised the biaxial machine which is designed specifically to provide biaxial stress components using multiple and varying loading conditions. The idea of this work is to evaluate the relationship between the dome test data and the biaxial test data. For this comparison, cruciform specimens with a diamond shaped thinner gage in the center were deformed with biaxial stretching on the biaxial testing machine. In addition, the cruciform specimens were bi-axially stretched with a hemispherical punch in a conventional die-punch setting. Furthermore, in each case, the process was simulated using a 3D model generated on ABAQUS. These models were then compared with the experimental results. The forces on each arm, strain path, forming and formability was analyzed. The differences between the processes were detailed. It was found that biaxial tests eliminated the pressurization effect which could be found in hemispherical dome tests.
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Wang, Zhiyu, Christopher Saldana, and Saurabh Basu. "Subsurface Microstructure and Crystallographic Texture in Surface Severe Plastic Deformation Processes." In ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-2915.
Full textAbstract:
Severe plastic burnishing was investigated as a promising surface severe plastic deformation technique for generating gradient microstructure surfaces. The deformed state of oxygen free high conductivity copper workpieces during the surface deformation process was determined with high-speed imaging, this complemented by microstructure characterization using orientation image microscopy based on electron backscatter diffraction. Varying deformation levels in terms of both magnitude and gradient on the processed surface were achieved through control of the incident tool angle. Refined microstructures, including laminate grains elongated in the velocity direction and equiaxed sub-micron grains were observed in the subsurface and were found to be controlled by the combined effects of strain and strain rate in the surface deformation process. Additionally, crystallographic texture evolutions were characterized, showing typical shear textures predominately along the <110> partial fiber. The rotation of texture from original ideal orientation positions was related directly to the deformation history produced by sliding process. Based on these observations, a controllable framework for producing the processed surface with expected mechanical and microstructural responses is suggested.