PL
 |
EN
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 9

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available remote A minimal gradient-enhancement of the classical continuum theory of crystal plasticity. Part I: The hardening law
Petryk H., Stupkiewicz S.
Archives of Mechanics
|
2016
|
Vol. 68, nr 6
459--485
EN
A simple gradient-enhancement of the classical continuum theory of plasticity of single crystals deformed by multislip is proposed for incorporating size effects in a manner consistent with phenomenological laws established in materials science. Despite considerable efforts in developing gradient theories, there is no consensus regarding the minimal set of physically based assumptions needed to capture the slip-gradient effects in metal single crystals and to provide a benchmark for more refined approaches. In order to make a step towards such a reference model, the concept of the tensorial density of geometrically necessary dislocations generated by slip-rate gradients is combined with a generalized form of the classical Taylor formula for the flow stress. In the governing equations in the rate form, the derived internal length scale is expressed through the current flow stress and standard parameters so that no further assumption is needed to define a characteristic length. It is shown that this internal length scale is directly related to the mean free path of dislocations and possesses physical interpretation which is frequently missing in other gradient-plasticity models.
2
Content available remote A minimal gradient-enhancement of the classical continuum theory of crystal plasticity. Part II: Size effects
Stupkiewicz S., Petryk H.
Archives of Mechanics
|
2016
|
Vol. 68, nr 6
487--513
EN
In our previous paper, a simple gradient-enhancement of the classical continuum theory of plasticity of single crystals deformed by multislip has been proposed for incorporating size effects. A single internal length scale has been derived as an explicit function of the flow stress defined as the isotropic part of critical resolved shear stresses. The present work is focused on verification whether the simplifications involved are not too severe and allow satisfactory predictions of size effects. The model has been implemented in a finite element code and applied to three-dimensional simulations of fcc single crystals. We have found that the experimentally observed indentation size effect in a Cu single crystal is captured correctly in spite of the absence of any adjustable length-scale parameter. The finite element treatment relies on introducing non-local slip rates that average and smoothen on an element scale the corresponding local quantities. Convergence of the finite element solution to the analytical one is also verified for the one-dimensional problem of a boundary layer formed at a constrained interface.
3
Content available remote Selective symmetrization of the slip-system interaction matrix in crystal plasticity
Petryk H., Kursa M.
Archives of Mechanics
|
2011
|
Vol. 63, nr 3
287-287
EN
The symmetry issue of the interaction matrix between multiple slip-systems in the theory of crystal plasticity at finite deformation is revisited. By appealing to possibly non-uniform distribution of slip-system activity in a representative space-time element of a crystal, symmetry of the slip-system interaction matrix for the representative element is derived under assumptions that have a physical meaning. This conclusion refers to active slip-systems only. Accordingly, for any given hardening law, a new symmetrization rule is proposed that is restricted to active slip-systems and leaves the latent hardening of inactive slip-systems unchanged. Advantages of the proposal in comparison with full symmetrization are illustrated by a simple example of uniaxial tension.
4
Content available remote Energia powierzchniowa, dyssypacja i efekty skali w modelowaniu mikrostruktur martenzytycznych
Petryk H., Stupkiewicz S.
Czasopismo Techniczne. Mechanika
|
2010
|
R. 107, z. 4-M
99-108
PL
W niniejszym artykule przedstawiono energetyczne podejście do wieloskalowego modelowania ewolucji mikrostruktur martenzytycznych w stopach z pamięcią kształtu. Energia swobodna Helmholtza i energia dyssypowana w układzie reprezentowane są przez sumy członów odpowiadających energii objętościowej oraz energii powierzchniowej na granicach mikro-strukturalnych pomiędzy poszczególnymi wariantami martenzytu, fazami lub ziarnami. Ewolucja mikrostruktury jest wyznaczana drogą przyrostowej minimalizacji całkowitej energii dostarczanej do rozpatrywanego układu w procesie makroskopowo quasi-statycznym i izotermicznym. Ogólną procedurę zastosowano do numerycznych symulacji powstawania i ewolucji warstwowych struktur martenzytycznych indukowanych naprężeniowo w stopach z pamięcią kształtu. W energii powierzchniowej uwzględniono energię mikroodkształceń sprężystych w otoczeniu granic mikrostrukturalnych, wyznaczoną przy użyciu metody elementów skończonych. Policzone przykłady opisują ewolucję mikrostruktury martenzytycznej w formie laminatu trzeciego rzędu w stopie CuAlNi dla przemiany 1 1 [beta]-->[gamma]' oraz jej zależność od sposobu uwzględnienia dyssypacji energii powierzchniowej.
EN
The energy approach to multiscale modelling of evolution of martensitic microstructures in shape memory alloys (SMA) is presented. Both the Helmholtz free energy and the energy dissipated in the system comprise the usual bulk energy contributions as well as the interfacial energy terms corresponding to different scales, namely martensite-martensite, austenite-martensite and grain boundaries. Microstructure evolution is determined by incremental minimization of the energy supplied to the system in a macroscopically quasi-static and isothermal process. As an application of the general approach, the formation and evolution of stress-induced laminated microstructures in SMA has been studied. The interfacial energy of elastic micro-strains at microstructured interfaces has been estimated using the finite element method. Evolution of a rank-three laminated microstructure in a C uAlNi alloy undergoing the 1 1 [beta]-->[gamma]' transformation has been determined, showing the effect of size-dependent dissipation related to the release of interfacial energy.
5
Content available remote Finite element analysis of strain non-uniformity in two processes of severe plastic deformation
Maciejewski J., Kopeć H., Petryk H.
Engineering Transactions
|
2007
|
Vol. 55, iss. 3
197-216
EN
Two severe plastic deformation (SPD) processing techniques, namely equal-channel angular pressing (ECAP) and cyclic extrusion-compression (CEC), are investigated by using the finite element method. The major aspect examined is the non-uniformity of the accumulated, equivalent plastic strain after processing with the use of different shapes of the die. The quantitative effect of several parameters on the plastic flow is determined. It is found that the diameter ratio of the chambers and narrower channel in the CEC method, and also the inclination angle of connecting conical parts, can affect strongly the degree of strain non-uniformity. Comparison is made of distributions of equivalent strain after two passes of ECAP for two different routes and with two die profiles.
6
Content available remote Grain Refinement in AlMgSi alloy during cyclic extrusion - compression: experiment and modelling
Richert M., Petryk H., Stupkiewicz S.
Archives of Metallurgy and Materials
|
2007
|
Vol. 52, iss. 1
49-54
EN
The effect of severe plastic deformation (SPD) during cyclic extrusion-compression (CEC) on grain refinement and strain hardening in AlMgSi alloy is studied quantitatively. New experimental results are presented showing that the average microband thickness and grain size decrease below 100 nm, i.e. a nanocrystalline material is obtained. In the modelling part, the decrease in size of dislocation cells and microbands is expressed in terms of the effective plastic strain defined such that strain rate reversals slow down its accumulation. Examples of simulation of the behaviour of AlMgSi alloy severely deformed by cyclic extrusion-compression are calculated and compared to experimental data.
PL
W pracy przeprowadzono ilościową analizę wpływu dużych deformacji plastycznych w procesie cyklicznego wyciskania ściskającego (CWS) na rozdrobnienie mikrostruktury i umocnienie plastyczne w stopie AlMgSi. Przedstawiono wyniki eksperymentalne pokazujące, że uzyskano strukturę nanokrystaliczną o średniej grubości mikropasm i wielkości ziarn poniżej 100 nm. W części dotyczącej modelowania, ewolucje mikrostruktury opisano przy użyciu efektywnego odkształcenia plastycznego, którego akumulacja jest spowolniona wskutek zmian kierunku prędkości odkształcenia na odwrotny. Przeprowadzono symulacje numeryczne zachowania się stopu AlMgSi w procesie CWS oraz porównano uzyskane wyniki z danymi doświadczalnymi.
7
Content available remote Elastic micro-strain energy at the austenite-twinned martensite interface
Maciejewski G., Stupkiewicz S., Petryk H.
Archives of Mechanics
|
2005
|
Vol. 57, nr 4
277-297
EN
A micromechanical scheme is developed for the analysis of elastic micro-strains induced by local incompatibilities at the austenite-twinned martensite interface. The aim of the paper is to estimate the elastic micro-strain energy which is an important factor in the formation of microstructures during the martensitic transformation. The finite deformation framework is applied, consistent with the crystallographic theory of martensite, and full account is taken for elastic anisotropy of the phases. As an example, the microstructures in the cubic-to-orthorhombic transformation in CuAINi shape memory alloy are analyzed by the finite element method for the assumed class of zigzag shapes of the austenite-martensite interface at the micro-level. Finally, the effect of the interphase boundary energy on the microstructure of the transition layer is studied.
8
Content available remote Micromechanical modelling of stress-induced phase transition in shape memory alloys
Petryk H., Stupkiewicz S.
Archives of Metallurgy and Materials
|
2004
|
Vol. 49, iss. 4
765-777
EN
A micro-mechanical model of stress-induced martensitic transformation in shape memory alloys is presented. A laminated microstructure of austenite and martensite phases is assumed along with a time-independent thermodynamic criterion for phase transformation. In numerical examples, the pseudoelastic behaviour of single crystals of CuZnAl and CuAlNi shape memory alloys is investigated. Several aspects are examined, including the effects of the loading direction, external constraints, detwinning, and instability of macroscopically uniform transformation.
PL
W pracy przedstawiono mikro-mechaniczny model przemiany martenzytycznej aktywowanej naprężeniem w stopach z pamiecią kształtu. Mikrostruktura faz austenitu i martenzytu posiada płytkowy charakter zgodnie z niezależnym od czasu kryterium termodynamicznym przemiany fazowej. Na przykładzie numerycznych obliczeń przedstawiono analizę zjawiska pseudosprężystości monokryształów ze stopów CuZnAl i CuAlNi wykazujących efekt pamięci kształtu. Zbadano kilka aspektów zjawiska zawierających m.in. efekty kierunku obciażenia, ekstremalnych ograniczeń, zanikanie bliźniaków i niestabilność makroskopowo jednorodnej przemiany.
9
Content available remote A self-consistent model of rate-dependent plasticity of polycrystals
Kiryk R., Petryk H.
Archives of Mechanics
|
1998
|
Vol. 50, nr 2
247-263
EN
The Hill-Hutchinson self-consistent scheme for polycrystals is extended to ratedependent plasticity with work-hardening. A computational version of the model requires three material parameters for a single crystal which are approximately identified from the experimental stress - plastic strain curve for a polycrystalline material. Contours of the macroscopic plastic potential are calculated after different plastic prestrains in uniaxial tension.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.