Katarzyna Kowalczyk-Gajewska, Ph.D., Dr. Habil., Eng.

Department of Mechanics of Materials (ZMM)
Division of Micromechanics of Materials (PMM)
position: assistant professor
telephone: (+48) 22 826 12 81 ext.: 435
room: 141
e-mail: kkowalcz

Doctoral thesis
2001Ewolucja anizotropii plastycznej silnie deformowanych metali 
supervisor -- Prof. Wiktor L. Gambin, Ph.D., Dr. Habil., Eng., IPPT PAN
559 
Habilitation thesis
2012-05-31Micromechanical modelling of metals and alloys of high specific strength947
 
Recent publications
1.Majewski M., Kursa M., Hołobut P., Kowalczyk-Gajewska K., Micromechanical and numerical analysis of packing and size effects in elastic particulate composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2017.05.004, Vol.124, pp.158-174, 2017
Majewski M., Kursa M., Hołobut P., Kowalczyk-Gajewska K., Micromechanical and numerical analysis of packing and size effects in elastic particulate composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2017.05.004, Vol.124, pp.158-174, 2017

Abstract:
Effects of particle packing and size on the overall elastic properties of particulate random composites are analyzed. In order to account for the two effects the mean-field Morphologically Representative Pattern (MRP) approach is employed and an additional interphase surrounding inclusions (coating) is introduced. The analytical mean-field estimates are compared with the results of computational homogenization performed using the finite element (FE) method. Periodic unit cells with cubic crystal-type arrangements and representative volume elements with random distributions of particles are used for verification purposes. The validity of the MRP estimates with respect to the FE results is assessed.

Keywords:
Composite materials, Elasticity, Micro-mechanics, Packing and size effects

2.Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Consistent treatment and automation of the incremental Mori–Tanaka scheme for elasto-plastic composites, COMPUTATIONAL MECHANICS, ISSN: 0178-7675, DOI: 10.1007/s00466-017-1418-z, pp.1-19, 2017
Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Consistent treatment and automation of the incremental Mori–Tanaka scheme for elasto-plastic composites, COMPUTATIONAL MECHANICS, ISSN: 0178-7675, DOI: 10.1007/s00466-017-1418-z, pp.1-19, 2017

Abstract:
A consistent algorithmic treatment of the incremental Mori–Tanaka (MT) model for elasto-plastic composites is proposed. The aim is to develop a computationally efficient and robust micromechanical constitutive model suitable for large-scale finite-element computations. The resulting overall computational scheme is a doubly-nested iteration-subiteration scheme. The Newton method is used to solve the nonlinear equations at each level involved. Exact linearization is thus performed at each level so that a quadratic convergence rate can be achieved. To this end, the automatic differentiation (AD) technique is used, and the corresponding AD-based formulation is provided. Excellent overall performance of the present MT scheme in threedimensional finite-element computations is illustrated.

Keywords:
Mori–Tanaka method, Composite materials, Elasto-plasticity, Finite element method, Automatic differentiation

3.Pieczyska E.A., Staszczak M., Kowalczyk-Gajewska K., Maj M., Golasiński K., Golba S., Tobushi H., Hayashi S., Experimental and numerical investigation of yielding phenomena in a shape memory polymer subjected to cyclic tension at various strain rates, POLYMER TESTING, ISSN: 0142-9418, DOI: 10.1016/j.polymertesting.2017.04.014, Vol.60, pp.333-342, 2017
Pieczyska E.A., Staszczak M., Kowalczyk-Gajewska K., Maj M., Golasiński K., Golba S., Tobushi H., Hayashi S., Experimental and numerical investigation of yielding phenomena in a shape memory polymer subjected to cyclic tension at various strain rates, POLYMER TESTING, ISSN: 0142-9418, DOI: 10.1016/j.polymertesting.2017.04.014, Vol.60, pp.333-342, 2017

Abstract:
This paper presents experimental and numerical results of a polyurethane shape memory polymer (SMP) subjected to cyclic tensile loading. The goal was to investigate the polymer yielding phenomena based on the effects of thermomechanical coupling. Mechanical characteristics were obtained with a testing machine, whereas the SMP temperature accompanying its deformation process was simultaneously measured in a contactless manner with an infrared camera. The SMP glass transition temperature was approximately 45oC; therefore, when tested at room temperature, the polymer is rigid and behaves as solid material. The stress and related temperature changes at various strain rates showed how the SMP yield limit evolved in subsequent loading-unloading cycles under various strain rates. A two-phase model of the SMP was applied to describe its mechanical response in cyclic tension. The 3D Finite Element model of a tested specimen was used in simulations. Good agreement between the model predictions and experimental results was observed for the first tension cycle.

Keywords:
Shape memory polymer, Tension cyclic loading, Thermomechanical coupling, Yield limit, Thermoelastic effect, Constitutive model

4.Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Response discontinuities in the solution of the incremental Mori–Tanaka scheme for elasto-plastic composites, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.69, No.1, pp.3-27, 2017
Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Response discontinuities in the solution of the incremental Mori–Tanaka scheme for elasto-plastic composites, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.69, No.1, pp.3-27, 2017

Abstract:
The incremental Mori–Tanaka model of elasto-plastic composites is discussed, and the corresponding finite-step formulation is shown to lead to discontinuities in the overall response at the instant of elastic-to-plastic transition in the matrix. Specifically, two situations may be encountered: the incremental equations may have two solutions or no solution. In the former situation, switching between the two solutions is associated with a jump in the overall stress. Response discontinuities are studied in detail for a special case of proportional deviatoric loading. The discontinuities constitute an undesirable feature of the incremental Mori–Tanaka scheme that apparently has not been discussed in the literature so far. Remedies to the related problems are briefly discussed.

Keywords:
mean-field homogenization, Mori–Tanaka method, incremental scheme, composite materials, elasto-plasticity

5.Pamin J., Wcisło B., Kowalczyk-Gajewska K., Gradient-enhanced large strain thermoplasticity with automatic linearization and localization simulations, JOURNAL OF MECHANICS OF MATERIALS AND STRUCTURES, ISSN: 1559-3959, DOI: 10.2140/jomms.2017.12.123, Vol.12, No.1, pp.123-146, 2017
Pamin J., Wcisło B., Kowalczyk-Gajewska K., Gradient-enhanced large strain thermoplasticity with automatic linearization and localization simulations, JOURNAL OF MECHANICS OF MATERIALS AND STRUCTURES, ISSN: 1559-3959, DOI: 10.2140/jomms.2017.12.123, Vol.12, No.1, pp.123-146, 2017

Abstract:
The paper deals with the thermomechanical extension of a large strain hyperelasto-plasticity model and focuses on algorithmic aspects and localization simulations. The formulation includes the degradation of the yield strength due to the increase of an averaged plastic strain measure and temperature, thus, three sources for loss of stability are included in the description. A gradient-enhancement of the model is incorporated through an additional differential equation, but localization is also influenced by heat conduction. The finite element analysis is performed for an elongated plate in plane strain conditions, using different finite elements and values of material parameters related to regularization (internal length scales are related to gradient averaging as well as heat conduction). In particular, the influence of the F-bar enrichment on the simulation results is studied. All computational tests are performed using selfprogrammed user subroutines prepared within a symbolic-numerical tool AceGen which is equipped with automatic differentiation options, allowing for automatic linearization of the governing equations.

Keywords:
thermoplasticity, softening, gradient averaging, strain localization, automatic linearization, AceGen package

6.Pieczyska E.A., Staszczak M., Maj M., Kowalczyk-Gajewska K., Golasiński K., Cristea M., Tobushi H., Hayashi S., Investigation of thermomechanical couplings, strain localization and shape memory properties in a shape memory polymer subjected to loading at various strain rates, SMART MATERIALS AND STRUCTURES, ISSN: 0964-1726, DOI: 10.1088/0964-1726/25/8/085002, Vol.25, No.8, pp.085002-1-15, 2016
Pieczyska E.A., Staszczak M., Maj M., Kowalczyk-Gajewska K., Golasiński K., Cristea M., Tobushi H., Hayashi S., Investigation of thermomechanical couplings, strain localization and shape memory properties in a shape memory polymer subjected to loading at various strain rates, SMART MATERIALS AND STRUCTURES, ISSN: 0964-1726, DOI: 10.1088/0964-1726/25/8/085002, Vol.25, No.8, pp.085002-1-15, 2016

Abstract:
This paper presents experimental and modeling results of the effects of thermomechanical couplings occurring in a polyurethane shape memory polymer (SMP) subjected to tension at various strain rates within large strains. The SMP mechanical curves, recorded using a testing machine, and the related temperature changes, measured in a contactless manner using an IR camera, were used to investigate the polymer deformation process at various loading stages. The effects of thermomechanical couplings allowed the determination of the material yield point in the initial loading stage, the investigation of nucleation and development of the strain localization at larger strains and the estimation of the effects of thermoelastic behavior during the unloading process. The obtained stress–strain and thermal characteristics, the results of the dynamic mechanical analysis and estimated values of the shape fixity and shape recovery parameters confirmed that the shape memory polymer (T g = 45°C) is characterized by good mechanical and shape memory properties, as well as high sensitivity to the strain rate. The mechanical response of the SMP subjected to tension was simulated using the finite element method and applying the large strain, two-phase model. Strain localization observed in the experiment was well reproduced in simulations and the temperature spots were correlated with the accumulated viscoplastic deformation of the SMP glassy phase.

Keywords:
shape memory polymer, thermomechanical coupling, infrared camera, tension test, strain rate, strain localization, constitutive model

7.Frydrych K., Kowalczyk-Gajewska K., A three-scale crystal plasticity model accounting for grain refinement in fcc metals subjected to severe plastic deformations, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2016.01.101, Vol.658, pp.490-502, 2016
Frydrych K., Kowalczyk-Gajewska K., A three-scale crystal plasticity model accounting for grain refinement in fcc metals subjected to severe plastic deformations, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2016.01.101, Vol.658, pp.490-502, 2016

Abstract:
A new three-scale model of polycrystal accounting for grain refinement is proposed. The model is embedded into the crystal plasticity framework. With the experimental reference to the development of the dislocation induced cell substructure, a single crystallite in the representative grain aggregate is initially subdivided into subdomains with the crystallographic orientations slightly misoriented with respect to the nominal orientation of a parent grain. The predicted misorientation evolution of subgrains with respect to the reference orientation of a crystallite is an indicator of grain refinement. The correlation between the increase of a misorientation angle and a slip activity pattern is analyzed. The model predictions are compared with available experimental data.

Keywords:
Crystal plasticity, Severe plastic deformation, Grain refinement

8.Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Classical estimates of the effective thermoelastic properties of copper–graphene composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2015.06.007, Vol.80, pp.278-290, 2015
Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Classical estimates of the effective thermoelastic properties of copper–graphene composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2015.06.007, Vol.80, pp.278-290, 2015

Abstract:
Significant research effort is concentrated worldwide on development of graphene-based metal-matrix composites with enhanced thermomechanical properties. In this work, we apply two classical micromechanical mean-field theories to estimate the effective thermoelastic properties that can be achieved in practice for a copper–graphene composite. In the modelling, graphene is treated as an anisotropic material, and the effect of its out-of-plane properties, which are less recognized than the in-plane properties, is studied in detail. To address the severe difficulties in processing of graphene-based metal-matrix composites, the copper–graphene composite is here assumed to additionally contain, due to imperfect processing, particles of graphite and voids. It is shown quantitatively that the related imperfections may significantly reduce the expected enhancement of the effective properties. The present predictions are also compared to the experimental data available in the literature.

Keywords:
Metal-matrix composites (MMCs), Mechanical properties, Thermal properties, Micro-mechanics, Graphene

9.Czarnota C., Kowalczyk-Gajewska K., Salahouelhadj A., Martiny M., Mercier S., Modeling of the cyclic behavior of elastic–viscoplastic composites by the additive tangent Mori–Tanaka approach and validation by finite element calculations, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2014.12.002, Vol.56-57, pp.96-117, 2015
Czarnota C., Kowalczyk-Gajewska K., Salahouelhadj A., Martiny M., Mercier S., Modeling of the cyclic behavior of elastic–viscoplastic composites by the additive tangent Mori–Tanaka approach and validation by finite element calculations, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2014.12.002, Vol.56-57, pp.96-117, 2015

Abstract:
This work deals with the prediction of the macroscopic behavior of two-phase composites, based on the Mori–Tanaka scheme combined with an additive/sequential interaction rule and tangent linearization of viscoplastic response. Cyclic tension compression loadings are considered to further validate the approach. The composite is made of spherical inclusions dispersed in a matrix. Both materials have an elastic–viscoplastic behavior. In a second part, finite element calculations are performed using ABAQUS/STANDARD software in order to validate the proposed homogenization technique. A representative volume element is analyzed with 30 randomly distributed inclusions. Comparisons between the additive tangent Mori–Tanaka scheme and finite element calculations are made for different volume fractions of inclusions, different contrasts in elastic and viscous properties and different strain rates and strain amplitudes. These comparisons demonstrate the efficiency of the proposed homogenization scheme. The effect of isotropization of the viscoplastic tangent stiffness is also investigated. It is concluded that quality of predictions does not benefit from such simplification, contrary to the known result for elastic–plastic case.

Keywords:
Elasto-viscoplasticity, Homogenization, Finite element, Composite, Mori–Tanaka scheme

10.Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Staszczak M., Gradys A., Majewski M., Cristea M., Tobushi H., Hayashi S., Thermomechanical properties of polyurethane shape memory polymer–experiment and modelling, SMART MATERIALS AND STRUCTURES, ISSN: 0964-1726, DOI: 10.1088/0964-1726/24/4/045043, Vol.24, pp.045043-1-16, 2015
Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Staszczak M., Gradys A., Majewski M., Cristea M., Tobushi H., Hayashi S., Thermomechanical properties of polyurethane shape memory polymer–experiment and modelling, SMART MATERIALS AND STRUCTURES, ISSN: 0964-1726, DOI: 10.1088/0964-1726/24/4/045043, Vol.24, pp.045043-1-16, 2015

Abstract:
In this paper extensive research on the polyurethane shape memory polymer (PU-SMP) is reported, including its structure analysis, our experimental investigation of its thermomechanical properties and its modelling. The influence of the effects of thermomechanical couplings on the SMP behaviour during tension at room temperature is studied using a fast and sensitive infrared camera. It is shown that the thermomechanical behaviour of the SMP significantly depends on the strain rate: at a higher strain rate higher stress and temperature values are obtained. This indicates that an increase of the strain rate leads to activation of different deformation mechanisms at the micro-scale, along with reorientation and alignment of the molecular chains. Furthermore, influence of temperature on the SMP's mechanical behaviour is studied. It is observed during the loading in a thermal chamber that at the temperature 20°C below the glass transition temperature (Tg) the PU-SMP strengthens about six times compared to the material above Tg but does not exhibit the shape recovery. A finite-strain constitutive model is formulated, where the SMP is described as a two-phase material composed of a hyperelastic rubbery phase and elastic-viscoplastic glassy phase. The volume content of phases is governed by the current temperature. Finally, model predictions are compared with the experimental results.

Keywords:
shape memory polyurethane, thermomechanical couplings, infrared camera, temperature change, dynamic mechanical analysis, strain rate, constitutive model

11.Kowalczyk-Gajewska K., Sztwiertnia K., Kawałko J., Wierzbanowski K., Wroński M., Frydrych K., Stupkiewicz S., Petryk H., Texture evolution in titanium on complex deformation paths: Experiment and modelling, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2015.04.040, Vol.637, pp.251-263, 2015
Kowalczyk-Gajewska K., Sztwiertnia K., Kawałko J., Wierzbanowski K., Wroński M., Frydrych K., Stupkiewicz S., Petryk H., Texture evolution in titanium on complex deformation paths: Experiment and modelling, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2015.04.040, Vol.637, pp.251-263, 2015

Abstract:
Texture evolution in commercially pure titanium deformed by equal-channel angular pressing (ECAP) and extrusion with forward–backward rotating die (KoBo) is studied both experimentally and numerically. New results are provided that demonstrate the effects of distinct and complex deformation paths on the texture in the ultra-fine grained (UFG) material obtained after severe plastic deformation (SPD). The numerical simulations are based on the self-consistent viscoplastic method of grain-to-polycrystal scale transition. A recently proposed modification of the probabilistic scheme for twinning is used that provides consistent values of the twin volume fraction in grains. The basic components of the experimentally observed texture are reasonably well reproduced in the modelling. The numerical simulations provide an insight into the internal mechanisms of plastic deformation, revealing substantial activity of mechanical twinning in addition to the basal and prismatic slip in titanium processed by ECAP.

Keywords:
Texture evolution, UFG materials, SPD processes, Crystal plasticity, Twinning

12.Kursa M., Kowalczyk-Gajewska K., Petryk H., Multi-objective optimization of thermo-mechanical properties of metal-ceramic composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2014.01.009, Vol.60, pp.586-596, 2014
Kursa M., Kowalczyk-Gajewska K., Petryk H., Multi-objective optimization of thermo-mechanical properties of metal-ceramic composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2014.01.009, Vol.60, pp.586-596, 2014

Abstract:
The optimization procedure is worked out for finding an optimal content of phases in metal–ceramic composites in case of conflicting objectives regarding thermo-mechanical properties of the material for a specific target application. Relationships between the material composition and effective properties of the composite are calculated by employing several methods of continuum micromechanics. A constrained minimization problem is solved for a single objective function based on the weighted squared distances from the best available thermo-mechanical properties for the material system selected. A compound block diagram is proposed for quick assessment of the consequences of deviating from the optimal composition. The developed procedure is applied to practical examples of Al2O3–Cu composites for brake disks and Al2O3–NiAl composites for valves of potential use in automotive industry.

Keywords:
Metal–matrix composites (MMCs), Thermomechanical, Plastic deformation, Micro-mechanics, Multi-criteria optimization

13.Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Staszczak M., Urbański L., Tobushi H., Hayashi S., Cristea M., Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-014-0963-2, Vol.23, No.7, pp.2553-2560, 2014
Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Staszczak M., Urbański L., Tobushi H., Hayashi S., Cristea M., Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-014-0963-2, Vol.23, No.7, pp.2553-2560, 2014

Abstract:
Multifunctional new material—polyurethane shape memory polymer (PU-SMP)—was subjected to tension carried out at room temperature at various strain rates. The influence of effects of thermomechanical couplings on the SMP mechanical properties was studied, based on the sample temperature changes, measured by a fast and sensitive infrared camera. It was found that the polymer deformation process strongly depends on the strain rate applied. The initial reversible strain is accompanied by a small drop in temperature, called thermoelastic effect. Its maximal value is related to the SMP yield point and increases upon increase of the strain rate. At higher strains, the stress and temperature significantly increase, caused by reorientation of the polymer molecular chains, followed by the stress drop and its subsequent increase accompanying the sample rupture. The higher strain rate, the higher stress, and temperature changes were obtained, since the deformation process was more dynamic and has occurred in almost adiabatic conditions. The constitutive model of SMP valid in finite strain regime was developed. In the proposed approach, SMP is described as a two-phase material composed of hyperelastic rubbery phase and elastic-viscoplastic glassy phase, while the volume content of phases is specified by the current temperature.

Keywords:
constitutive model, dynamic mechanical analysis, shape memory polyurethane, strain rate, temperature change, thermomechanical couplings

14.Pieczyska E.A., Kowalczyk-Gajewska K., Maj M., Staszczak M., Tobushi H., Thermomechanical investigation of TiNi shape memory alloy and PU shape memory polymer subjected to cyclic loading, Procedia Engineering, ISSN: 1877-7058, DOI: 10.1016/j.proeng.2014.06.264, Vol.74, pp.287-292, 2014
Pieczyska E.A., Kowalczyk-Gajewska K., Maj M., Staszczak M., Tobushi H., Thermomechanical investigation of TiNi shape memory alloy and PU shape memory polymer subjected to cyclic loading, Procedia Engineering, ISSN: 1877-7058, DOI: 10.1016/j.proeng.2014.06.264, Vol.74, pp.287-292, 2014

Abstract:
In applications to sensors, actuators, guide wires, special grips for handicapped people, a shape memory alloy (SMA) or shape memory polymer (SMP) are used as working elements that perform cyclic motions. In order to evaluate the reliability of the shape memory materials (SMM), cycling and fatigue deformation properties are investigated. Since the SMM are very sensitive to temperature, not only mechanical properties but also their related temperature changes accompanying the deformation process should be taken into account. The presented paper embraces experimental investigation of effects of thermomechanical couplings occurring in shape memory alloy and shape memory polymer subjected to various kinds of cycling loading. The deformation was carried out on MTS 858 Testing machine. The strain was measured by a mechanical extensometer, so the stress-strain characteristics were elaborated with high accuracy. Furthermore, a fast and sensitive FLIR Co Phoenix infrared (IR) measurement system was used in order to record infrared radiation from the sample surface. It enables obtaining temperature distribution of the sample as a function of the deformation parameters. For each strain cycle, an increase in temperature during the loading and the temperature decrease during the unloading processes was observed. It was found that the temperature increment recorded during the cyclic deformation depends on the strain rate, the kind of the material and the test conditions. The higher the strain rate the higher the stress and temperature changes were obtained, since the deformation process was more dynamic and has occurred in almost adiabatic conditions. It was shown that various deformation mechanisms are active during various loading stages.

Keywords:
shape memory alloy, shape memory polymer, cyclic deformation, thermomechanical coupling, infrared camera

15.Wcisło B., Pamin J., Kowalczyk-Gajewska K., Gradient-enhanced damage model for large deformations of elastic-plastic materials, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.65, No.5, pp.407-428, 2013
Wcisło B., Pamin J., Kowalczyk-Gajewska K., Gradient-enhanced damage model for large deformations of elastic-plastic materials, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.65, No.5, pp.407-428, 2013

Abstract:
This paper deals with the development of a family of gradient-enhanced elasticity-damage-plasticity models for the simulation of failure in metallic and composite materials. The model incorporates finite deformations and is developed with the assumption of isotropy and isothermal conditions. The gradient enhancement applied to the damage part of the model aims at removing pathological sensitivity to the finite element discretization which can occur due to material softening.
The attention is focused on the algorithmic aspects and on the implementation of the model using AceGen tool. The numerical verification tests of the described model are performed using the Mathematica-based package AceFEM. Particularly, uniaxial tension test for a bar with a variable cross-section and tension of a perforated plate are examined.

Keywords:
arge strains, damage, plasticity, gradient-enhancement, AceGen package

16.Kowalczyk-Gajewska K., Stupkiewicz S., Modelling of Texture Evolution in Kobo Extrusion Process, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/v10172-012-0160-y, Vol.58, No.1, pp.113-118, 2013
Kowalczyk-Gajewska K., Stupkiewicz S., Modelling of Texture Evolution in Kobo Extrusion Process, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/v10172-012-0160-y, Vol.58, No.1, pp.113-118, 2013

Abstract:
The paper is aimed at modelling of evolution of crystallographic texture in KOBO extrusion which is an unconventional process of extrusion assisted by cyclic torsion. The analysis comprises two steps. In the first step, the kinematics of the KOBO extrusion process is determined using the finite element method. A simplifying assumption is adopted that the material flow is not significantly affected by plastic hardening, and thus a rigid-viscoplastic material model with no hardening is used. In the second step, evolution of crystallographic texture is modelled along the trajectories obtained in the first step. A micromechanical model of texture evolution is used that combines the crystal plasticity model with a self-consistent grain-to-polycrystal scale transition scheme, and the VPSC code is used for that purpose. Since each trajectory corresponds to a different deformation path, the resulting pole figures depend on the position along the radius of the extruded rod.

Keywords:
plasticity, microstructure, crystallographic texture, KOBO extrusion

17.Kowalczyk-Gajewska Katarzyna, Crystal plasticity models accounting for twinning, COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.13, No.4, pp.436-451, 2013
Kowalczyk-Gajewska Katarzyna, Crystal plasticity models accounting for twinning, COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.13, No.4, pp.436-451, 2013

Abstract:
Different approaches to account for twinning in crystal plasticity models are discussed. In particular, three main issues related to this mechanism of plastic deformation are addressed: modelling of texture evolution in the presence of twinning, impact of slip-twin interactions on hardening laws formulation and influence of layered substructure on the macroscopic response of materials. Some of the discussed modelling tools are illustrated with an example of titanium aluminide

Keywords:
crystal plasticity, twinning, texture evolution, hardening

18.Kowalczyk-Gajewska K., Estimation of overall properties of random polycrystals with the use of invariant decompositions of Hooke’s tensor, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2012.06.002, Vol.49, No.21, pp.3022-3037, 2012
Kowalczyk-Gajewska K., Estimation of overall properties of random polycrystals with the use of invariant decompositions of Hooke’s tensor, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2012.06.002, Vol.49, No.21, pp.3022-3037, 2012

Abstract:
In the paper the theoretical analysis of bounds and self-consistent estimates of overall properties of linear random polycrystals composed of arbitrarily anisotropic grains is presented. In the study two invariant decompositions of Hooke’s tensors are used. The applied method enables derivation of novel expressions for estimates of the bulk and shear moduli, which depend on invariants of local stiffness tensor. With use of these expressions the materials are considered for which at the local level constraints are imposed on deformation or some stresses are unsustained

Keywords:
Creep, Anisotropic material, Polycrystalline material, Invariant decompositions

19.Kowalczyk-Gajewska K., Petryk H., Sequential linearization method for viscous/elastic heterogeneous materials, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, ISSN: 0997-7538, Vol.30, No.5, pp.650-664, 2011
Kowalczyk-Gajewska K., Petryk H., Sequential linearization method for viscous/elastic heterogeneous materials, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, ISSN: 0997-7538, Vol.30, No.5, pp.650-664, 2011

Abstract:
The paper addresses the problem of suitable approximation of the interaction between phases in heterogeneous materials that exhibit both viscous and elastic properties. A novel approach is proposed in which linearized subproblems for an inhomogeneity-matrix system with viscous or elastic interaction rules are solved sequentially within one incremental step. It is demonstrated that in the case of a self-consistent averaging scheme, an additional accommodation subproblem, besides purely viscous and elastic subproblems, is to be solved in order to estimate the material response satisfactorily. By examples of an isotropic two-phase material it is shown that the proposed approach provides acceptable predictions in comparison with the existing models.

Keywords:
Micromechanics, Viscoelasticity, Viscoplasticity, Homogenization, Self-consistent scheme

20.Kowalczyk-Gajewska K., Micromechanical model of polycrystalline materials with lamellar substructure, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.56, No.2, pp.509-522, 2011
Kowalczyk-Gajewska K., Micromechanical model of polycrystalline materials with lamellar substructure, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.56, No.2, pp.509-522, 2011

Abstract:
Micromechanical model of polycrystalline materials with lamellar substructure is presented. The lamellar microstructure of grains is accounted for using the well-established framework developed for layered composites. Within the approach different scale transition rules between the level of lamellar grain and the polycrystalline sample can be employed. The model capabilities are tested using the example of TiAl intermetallic. Elastic properties and the initial yield surface for the lamellar grain (PST crystal) and for the untextured polycrystal are estimated. Elastic and plastic anisotropy degree is analyzed

Keywords:
micromechanics, homogenization, lamellar substructure, anisotropic material, anisotropy degree

21.Kowalczyk-Gajewska K., Modelling of texture evolution in metals accounting for lattice reorientation due to twinning, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, ISSN: 0997-7538, Vol.29, No.1, pp.28-41, 2010
Kowalczyk-Gajewska K., Modelling of texture evolution in metals accounting for lattice reorientation due to twinning, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, ISSN: 0997-7538, Vol.29, No.1, pp.28-41, 2010

Abstract:
Twinning has been incorporated into a crystal plasticity model with the regularized Schmid law. In order to account for the appearance of twin-related orientations, a new probabilistic twin reorientation scheme that maintains the number of reoriented grains consistent with the accumulated deformation by twinning within the polycrystalline element, has been developed. A hardening rule describing slip–twin interactions has been also proposed. Model predictions concerning material response and texture evolution have been analyzed for fcc materials of low stacking fault energy.

Keywords:
Crystal plasticity, Twinning, Hardening, Texture, Anisotropic material, Polycrystal model

22.Kowalczyk-Gajewska K., Bounds and self-consistent estimates of overall properties for random polycrystals described by linear constitutive laws, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.61, No.6, pp.475-503, 2009
Kowalczyk-Gajewska K., Bounds and self-consistent estimates of overall properties for random polycrystals described by linear constitutive laws, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.61, No.6, pp.475-503, 2009

Abstract:
Analytical solutions for bounds of overall properties are derived for single-phase polycrystalline materials of random texture, composed of grains with arbitrary anisotropy and described by the linear constitutive law. Self-consistent estimates are found for these materials and they are studied in more details when anisotropic grains are volumetrically isotropic. Reduction of the above solutions for incompressible materials or materials with constraint modes of deformation is also derived. Existence and uniqueness of the obtained solutions are discussed. In order to obtain the solutions, simultaneously the spectral and harmonic decomposition of fourth order Hooke’s tensor are used. Utility of the obtained results is demonstrated on the examples of metals and alloys of high specific strength and stiffness

Keywords:
anisotropic materials, self-consistent estimates, polycrystals

23.Kowalczyk-Gajewska K., Pęcherski R.B., Phenomenological description of the effect of micro-shear banding in micromechanical modelling of polycrystal plasticity, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.54, pp.717-730, 2009
Kowalczyk-Gajewska K., Pęcherski R.B., Phenomenological description of the effect of micro-shear banding in micromechanical modelling of polycrystal plasticity, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.54, pp.717-730, 2009

Abstract:
The rigid-plastic crystal plasticity model accounting for the effect of micro-shear banding mechanism on the reduction of the global strain hardening rate is presented. The instantaneous contribution of micro-shear bands in the rate of plastic deformation is described by means of the constitutive function that depends on the type of strain path specified by the current direction of strain rate tensor. The capabilities of the model are explored by studying the strain-stress behavior of polycrystalline material together with the crystallographic texture evolution in the polycrystalline element

Keywords:
Crystallographic texture, Anisotropic material, Crystal plasticity, Polycrystalline material, Micro-shear banding

24.Kowalczyk-Gajewska K., Ostrowska-Maciejewska J., Review on spectral decomposition of Hooke's tensor for all symmetry groups of linear elastic materials, ENGINEERING TRANSACTIONS (ROZPRAWY INŻYNIERSKIE), ISSN: 0867-888X, Vol.57, pp.145-183, 2009
Kowalczyk-Gajewska K., Ostrowska-Maciejewska J., Review on spectral decomposition of Hooke's tensor for all symmetry groups of linear elastic materials, ENGINEERING TRANSACTIONS (ROZPRAWY INŻYNIERSKIE), ISSN: 0867-888X, Vol.57, pp.145-183, 2009

Abstract:
The spectral decomposition of elasticity tensor for all symmetry groups of a linearly elastic material is reviewed. In the paper it has been derived in non-standard way by imposing the symmetry conditions upon the orthogonal projectors instead of the stiffness tensor itself. The numbers of independent Kelvin moduli and stiffness distributors are provided. The corresponding representation of the elasticity tensor is specified

Keywords:
linear elasticity, anisotropy, symmetry group, spectral decomposition

25.Żebro T., Kowalczyk-Gajewska K., Pamin J., A geometrically nonlinear model of scalar damage coupled to plasticity, Czasopismo Techniczne. Mechanika, ISSN: 0011-4561, Vol.20, No.105, pp.251-262, 2008
26.Kowalczyk-Gajewska K., Pamin J., Żebro T., Development of gradient-enhanced damage-plasticity formulations for large deformations, Czasopismo Techniczne. Mechanika, ISSN: 0011-4561, Vol.20, No.105, pp.47-58, 2008
27.Gambin W., Kowalczyk-Gajewska K., Kudrjavceva L., Micunovic M., Two-scale approach to dynamic localization failure of AISI 316H stainless steel sheets, Theoretical and Applied Mechanics, ISSN: 1450-5584, DOI: 10.2298/TAM0803093G, Vol.35, No.1-3, pp.93-104, 2008
Gambin W., Kowalczyk-Gajewska K., Kudrjavceva L., Micunovic M., Two-scale approach to dynamic localization failure of AISI 316H stainless steel sheets, Theoretical and Applied Mechanics, ISSN: 1450-5584, DOI: 10.2298/TAM0803093G, Vol.35, No.1-3, pp.93-104, 2008

Abstract:
Dynamic localization failure of a thin sheet made of AISI 316H steel is considered on the macroscopic and mesoscopic level for proportional and nonproportional stress paths. On the macroscopic level, we propose: (1) the replacement of time as independent variable by a function of plastic dissipation and (2) dependence of the initial equivalent yield stress on stress rate. On the mesoscopic level - the regularized Schmid model for description of the single grain behavior is used and the polycrystalline yield surface generated by the texture development enables to improve the Forming Limit Diagrams for the sheet element.

Keywords:
dynamic localization failure, Forming Limit Diagrams, regularized Schmid law, sheet textures

28.Kowalczyk-Gajewska K., Mróz Z., Pęcherski R.B., Micromechanical modelling of polycrystalline materials under non-proportional deformation paths, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.52, pp.181-192, 2007
Kowalczyk-Gajewska K., Mróz Z., Pęcherski R.B., Micromechanical modelling of polycrystalline materials under non-proportional deformation paths, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.52, pp.181-192, 2007

Abstract:
The rigid-plastic crystal plasticity model with single yield surface of 2n-degree is applied to simulate the polycrystalline behaviour and the crystallographic texture development under non-proportional deformation paths. The role of two controlling parameters: the amplitude and frequency for the processes of tension or compression assisted by cyclic torsion of thin-walled tubes made of copper is analysed. The effect of micro-shear bands on the reduction of global hardening rate is described by means of the contribution function of shear banding in the rate of plastic deformation. The conclusions drawn from the study can find also application in the extension of the analysis for high strength and hard deformable materials.

Keywords:
micromechanics, modelling of materials, rigid-plastic solids, crystal plasticity, texture, cyclic torsion, non-proportional deformation path, micro-shear bands

29.Mróz Z., Kowalczyk-Gajewska K., Maciejewski J., Pęcherski R.B., Tensile or compressive plastic deformation of cylinders assisted by cyclic torsion, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.58, No.6, pp.497-527, 2006
Mróz Z., Kowalczyk-Gajewska K., Maciejewski J., Pęcherski R.B., Tensile or compressive plastic deformation of cylinders assisted by cyclic torsion, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.58, No.6, pp.497-527, 2006

Abstract:
Technological metal forming processes of extrusion, forging and rolling with imposed cyclic torsion or shear deformation have been recently studied in view of their advantages with respect to monotonic loading processes, cf. Bochniak and Korbel [2–4]. The present work is aimed to analyze such process in the case of simple tension or compression of a cylindrical tube with imposed cyclic torsional deformation. The material element response is assumed to be rigid-perfectly plastic or elastic-perfectly plastic. For these models, the analytical solutions can be provided for the steady cyclic responses and the effect of two process parameters, namely the ratio of shear and axial strain rates η and the amplitude of shear strain γm , can be clearly demonstrated. Three different regimes of cyclic response can be visualized in the plane η, γm. The cyclic response of a cylinder under combined axial compression and cyclic torsion is predicted by considering a simplified model of a set of concentric tubes and neglecting their radial stress interaction. The axial force and torsional moment are then specified by averaging the responses of consecutive tubes. The cyclic response diagrams for the cylinder are then generated in terms of axial force and torsional moment related to axial deformation and angle of twist

Keywords:
cyclic torsion, plastic deformation of cylinders, elastic-perfectly plastic model, rigid-perfectly plastic model, analytical solutions of cyclic response of a cylinder

30.Kowalczyk-Gajewska K., Ostrowska-Maciejewska J., Energy-based limit criteria for anisotropic elastic materials with constraints, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.57, pp.133-155, 2005
31.Kowalczyk-Gajewska K., Gambin W., Pęcherski R.B., Ostrowska-Maciejewska J., Modelling of crystallographic texture development in metals accounting for micro-shearbands, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.50, No.3, pp.575-593, 2005
Kowalczyk-Gajewska K., Gambin W., Pęcherski R.B., Ostrowska-Maciejewska J., Modelling of crystallographic texture development in metals accounting for micro-shearbands, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.50, No.3, pp.575-593, 2005

Abstract:
The rigid-plastic model for the single grain is developed in which the velocity gradient is split into two parts connected with crystallographic slip and micro-shear bands respectively. For crystallographic slip the regularized Schmid law proposed by Gambin is used. For the micro-shear bands the model developed by Pęcherski, which accounts for the contribution of this mechanism in the rate of plastic deformation by means of a function fms is applied. Different constitutive equations for the plastic spin due to two considered mechanisms of plastic deformation are used. The present model is applied to simulate crystallographic texture evolution in the polycrystalline element.

Keywords:
crystallographic texture, modelling of texture, micro-shear bands, regularized Schnid law, plastic spin

32.Kowalczyk K., Gambin W., Model of plastic anisotropy evolution with texture-dependent yield surface, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(03)00010-X, Vol.20, No.1, pp.19-54, 2004
Kowalczyk K., Gambin W., Model of plastic anisotropy evolution with texture-dependent yield surface, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(03)00010-X, Vol.20, No.1, pp.19-54, 2004

Abstract:
Model of evolution of plastic anisotropy due to crystallographic texture development, in metals subjected to large deformation processes, is presented. The model of single grain with the regularized Schmid law proposed by Gambin is used. Evolution of crystallographic texture during drawing, rolling and pure shear is calculated. Phenomenological texture-dependent yield surface for polycrystalline sheets is proposed. Evolution of this yield surface is compared with evolution of phenomenological higher order yield surfaces proposed by Hill and Barlat with Lian for drawing, rolling and pure shear processes. The change of the Hill yield surface and the Barlat–Lian yield surface is obtained by replacing material parameters present in these conditions by texture-dependent functions.

Keywords:
Crystallographic texture, Anisotropic material, Crystal plasticity, Polycrystalline material

33.Kowalczyk K., Mróz Z., Description of anisotropy of textured metals using macro and micro models, JOURNAL DE PHYSIQUE IV, ISSN: 1155-4339, DOI: 10.1051/jp4:20030188, Vol.105, pp.199-206, 2003
Kowalczyk K., Mróz Z., Description of anisotropy of textured metals using macro and micro models, JOURNAL DE PHYSIQUE IV, ISSN: 1155-4339, DOI: 10.1051/jp4:20030188, Vol.105, pp.199-206, 2003

Abstract:
In the paper description of anisotropy of textured metals using macro and micro models is compared. In the present macro-approach the texture anisotropy is described by introducing a second order microstructure tensor whose principal directions specify the orthotropy axes. A scalar orientation parameter $\eta$ is introduced in order to specify the relative orientation of the generalized traction vector with respect to anisotropy axes. The yield stress is assumed to depend on the parameter $\eta$ with specific forms introduced in order to provide quantitative description of yield stress variation with loading orientation. The phenomenological approach is next confronted with the microstructural approach based on the analysis of crystallographic slip and induced lattice reorientation in a representative grain aggregate. The resulting yield surface for polycrystalline aggregate is then compared with the macroscopic description based on the orientational variation of the yield stress. The proposed macro description seems much simpler from micro-approach and could prove convenient in the analysis of technological processes for textured materials.


List of recent monographs
1.
314
Ostrowska-Maciejewska J., Kowalczyk-Gajewska K., Rachunek tensorowy w mechanice ośrodków ciągłych, Biblioteka Mechaniki Stosowanej. Seria A: Monografie, Instytut Podstawowych Problemów Techniki PAN, pp.1-397, 2013
2.
34
Kowalczyk-Gajewska K., Micromechanical modelling of metals and alloys of high specific strength, IPPT Reports on Fundamental Technological Research, 1, pp.1-299, 2011
List of chapters in recent monographs
1.
334
Kowalczyk-Gajewska K., Encyclopedia of Thermal Stresses, rozdział: Thermoplasticity of Polycrystals, R. Hetnarski, Springer, Netherlands, 11, pp.6064-6079, 2014

Conference papers
1.Pieczyska E.A., Staszczak M., Maj M., Kowalczyk-Gajewska K., Cristea M., Tobushi H., Hayashi S., Thermomechanical analysis of shape memory polyurethane PU-SMP, 6th International Conference on Mechanics and Materials in Design, 2015-07-26/07-30, Ponta Delgada (PT), pp.783-786, 2015
Pieczyska E.A., Staszczak M., Maj M., Kowalczyk-Gajewska K., Cristea M., Tobushi H., Hayashi S., Thermomechanical analysis of shape memory polyurethane PU-SMP, 6th International Conference on Mechanics and Materials in Design, 2015-07-26/07-30, Ponta Delgada (PT), pp.783-786, 2015

Abstract:
Experimental results of effects of thermomechanical couplings occurring in polyurethane shape memory polymer (PU-SMP) during tension at different strain rates are presented. Stress-strain curves were recorded by MTS 858 testing machine. The temperature changes were estimated by using a fast and sensitive infrared camera (Phoenix FLIR IR System). The stress and temperature vs. strain characteristics obtained during the tension enable to investigate the SMP deformation process and distinguish 3 different stages: the first, accompanied by a drop in temperature called thermoelastic effect, related to a limit of the material reversible deformation, the second plastic stage, associated with change of the material structure and significant increase in temperature, and the third - related to the mechanisms of damage - a breaking of the polymer chains, leading to the specimen rupture.

Keywords:
shape memory polymer, thermomechanical coupling, tension, infrared camera

2.Staszczak M., Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Kukla D., Tobushi H., Hayashi S., Infrared thermography analysis of thermomechanical shape memory polymer behavior – initial loading stage, AITA, 13th International Workshop on Advanced Infrared Technology and Applications, 2015-09-29/10-02, Pisa (IT), pp.115-118, 2015
Staszczak M., Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Kukla D., Tobushi H., Hayashi S., Infrared thermography analysis of thermomechanical shape memory polymer behavior – initial loading stage, AITA, 13th International Workshop on Advanced Infrared Technology and Applications, 2015-09-29/10-02, Pisa (IT), pp.115-118, 2015

Abstract:
Experimental results of effects of thermomechanical couplings occurring in polyurethane shape memory polymer (PU-SMP) subjected to cyclic loading at various strain rates are presented. Stress-strain characteristics were recorded by the testing machine, whereas the specimen temperature changes were measured by a fast and sensitive infrared camera. The influence of strain rate on the polymer thermomechanical behaviour was studied. It was found that the SMP is very sensitive to the strain rate. The higher the strain rate, the higher the values of the stress and temperature changes were obtained. In the initial stage of deformation a drop in temperature called thermoelastic effect, determining a limit of the material reversible deformation, was investigated.

Keywords:
thermomechanical couplings, polyurethane shape memory polymer, cyclic loading, various strain rates, sensitive infrared camera, thermoelastic effect, thermoelastic effect, reversible deformation

3.Kowalczyk-Gajewska K., Stupkiewicz S., Frydrych K., Petryk H., Modelling of Texture Evolution and Grain Refinement on Complex SPD Paths, JOURNAL OF PHYSICS: CONFERENCE SERIES, ISSN: 1742-6588, DOI: 10.1088/1757-899X/63/1/012040, No.63, pp.012040-1-10, 2014
Kowalczyk-Gajewska K., Stupkiewicz S., Frydrych K., Petryk H., Modelling of Texture Evolution and Grain Refinement on Complex SPD Paths, JOURNAL OF PHYSICS: CONFERENCE SERIES, ISSN: 1742-6588, DOI: 10.1088/1757-899X/63/1/012040, No.63, pp.012040-1-10, 2014

Abstract:
A computationally efficient procedure for modelling of microstructural changes on complex and spatially nonuniform deformation paths of severe plastic deformation (SPD) is presented. The analysis follows a two-step procedure. In the first step, motivated by saturation of material hardening at large accumulated strains, the steady-state kinematics of the process is generated for a non-hardening viscoplastic model by using the standard finite element method for a specified SPD scheme. In the second step, microstructural changes are investigated along the deformation-gradient trajectories determined in the first step for different initial locations of a material element. The aim of this study is to predict texture evolution and grain refinement in a non-conventional process of cold extrusion assisted by cyclic rotation of the die, called KOBO process, which leads to an ultra-fine grain structure. The texture evolution is calculated for fcc and hcp metals by applying crystal visco-plasticity combined with the self-consistent scale transition scheme. In parallel, by applying the simplified phenomenological model of microstructure evolution along the trajectories, grain refinement is modelled. The results are compared with available experimental data.

Keywords:
SPD processes, Texture evolution, UFG materials, Crystal plasticity, Grain refinement

4.Pieczyska E., Maj M., Kowalczyk-Gajewska K., Staszczak M., Tobushi H., Hayashi S., Thermomechanical properties of shape memory alloys and polymers studied by advanced infrared techniques, PACAM, 14th Pan-American Congress of Applied Mechanics, 2014-03-24/03-28, Santiago (CL), pp.1-6, 2014
Pieczyska E., Maj M., Kowalczyk-Gajewska K., Staszczak M., Tobushi H., Hayashi S., Thermomechanical properties of shape memory alloys and polymers studied by advanced infrared techniques, PACAM, 14th Pan-American Congress of Applied Mechanics, 2014-03-24/03-28, Santiago (CL), pp.1-6, 2014

Abstract:
The paper presents experimental evaluation and modelling of effects of thermomechanical couplings in shape memory alloy (SMA) and shape memory polymer (SMP). TiNi SMA and polyurethane PU-SMP are subjected to tension on MTS Testing machine. Fast infrared camera (IR) Phoenix FLIR System enable obtaining temperature distribution and average temperature changes of the specimens during the deformation process. Mechanical and infrared characteristics recorded during the SMA loading show that after initial, macroscopically homogeneous deformation a localized transformation develops, accompanied by significant temperature changes. Inclined bands of higher temperature accompanying exothermic forward transformation are recorded during the loading, whereas bands of lower temperature related to endothermic reverse transformation are observed during the unloading process. The infrared imaging and average temperature of the SMA sample compared to their mechanical characteristics allow to investigate the current stage of the stress-induced transformation process. A decrease of the specimen temperature reveals the saturation stage of the transformation. Both mechanical and thermal effects significantly depend on the strain rate; the higher the strain rate, the higher the temperature and stress are obtained. Similar experimental methodology is applied to investigate effects of thermomechanical couplings in shape memory polyurethane subjected to tension at various strain rates. Constitutive model valid in finite strain regime is proposed, where the SMP is described as a two-phase material composed of hyperelastic rubbery phase and elastic-viscoplastic glassy phase, while the volume content of phases is specified by the current temperature. Experimental results and modelling show that the SMP deformation process strongly depends on the strain rate, much stronger than for metals and alloys. At higher strain rate higher stress and temperature changes are obtained, since the deformation process is more dynamic and occurs in almost adiabatic conditions. It is shown that during the SMP loading process various deformation mechanisms are active at various strain rates.

Keywords:
shape memory alloy, transformation bands, infrared camera, constitutive model, shape memory polymers, elastic modulus, yield stress, glass transition temperature, shape fixity, shape recovery

5.Staszczak M., Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Cristea M., Tobushi H., Hayashi S., Mechanical and infrared thermography analysis of shape memory polymer - focus on thermoelastic effect, QIRT 2014, 12th International Conference on Quantitative Infrared Thermography, 2014-07-07/07-11, Bordeaux (FR), pp.183-1-9, 2014
Staszczak M., Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Cristea M., Tobushi H., Hayashi S., Mechanical and infrared thermography analysis of shape memory polymer - focus on thermoelastic effect, QIRT 2014, 12th International Conference on Quantitative Infrared Thermography, 2014-07-07/07-11, Bordeaux (FR), pp.183-1-9, 2014

Abstract:
Experimental results of effects of thermomechanical couplings occurring in polyurethane shape memory polymer (PU-SMP) subjected to cyclic loading at , are presented. Stress-strain characteristics were recorded by the testing machine, whereas the specimen temperature changes were measured by a fast and sensitive infrared camera. The influence of strain rate on the polymer thermomechanical behaviour is studied. It was found that PU-SMP is very sensitive to the strain rate. The higher the strain rate, the higher the values of stress and temperature changes were obtained. In the initial stage of deformation a drop in temperature called thermoelastic effect was recorded determining a limit of the material reversible deformation.

Keywords:
thermomechanical couplings, polyurethane shape memory polymer, cyclic loading, different strain rates, infrared camera, thermoelastic effect

6.Kursa M., Kowalczyk-Gajewska K., Petryk H., Multi-objective optimization of effective thermo-mechanical properties of metal-ceramic composites, ECCOMAX 2012, 6th European Congress on Computational Methods in Applied Sciences and Engineering, 2012-09-10/09-14, Wiedeń (AT), Vol.1, pp.1-9, 2012
Kursa M., Kowalczyk-Gajewska K., Petryk H., Multi-objective optimization of effective thermo-mechanical properties of metal-ceramic composites, ECCOMAX 2012, 6th European Congress on Computational Methods in Applied Sciences and Engineering, 2012-09-10/09-14, Wiedeń (AT), Vol.1, pp.1-9, 2012

Abstract:
Micromechanical modelling of metal-ceramic composites has been carried out to obtain a material of required thermo-mechanical properties. Quantitative transition from phase properties and morphology to macroscopic properties of a composite has been modelled by mean-field approaches, including the self-consistent scheme. An optimization method has been developed for the objective function that expresses a distance between the required values of macro-variables and those determined for a given set of microstructural parameters. The presented example concerns application of Al2O3-Cu composite to brake disks.

Keywords:
multi-objective optimization, composite selection, metal matrix composites

7.Wcisło B., Żebro T., Kowalczyk-Gajewska K., Pamin J., Finite strain inelastic models with gradient averaging and AceGen implementation, ECCOMAX 2012, 6th European Congress on Computational Methods in Applied Sciences and Engineering, 2012-09-10/09-14, Wiedeń (AT), Vol.1, pp.1-15, 2012
Wcisło B., Żebro T., Kowalczyk-Gajewska K., Pamin J., Finite strain inelastic models with gradient averaging and AceGen implementation, ECCOMAX 2012, 6th European Congress on Computational Methods in Applied Sciences and Engineering, 2012-09-10/09-14, Wiedeń (AT), Vol.1, pp.1-15, 2012

Abstract:
This paper deals with the development of a family gradient-enhanced elasticity-damage-plasticity models for the simulation of failure in metallic and composite materials. The model incorporates finite deformations and is developed with the assumption of isotropy and isothermal conditions. The gradient enhancement applied to the damage part of the model aims at removing pathological sensitivity to the finite element discretization which can occur due to material softening. The attention is focused on the algorithmic aspects and on the implementation of the model using AceGen tool for automatic code generation, thus circumventing the cumbersome derivation of the consistent tangent for the Newton’s method. Numerical verification tests of the described model are performed with the Mathematica-based package AceFEM. Particularly, uniaxial tension test for a bar with a variable cross-section and tension of a perforated plate are examined.

Keywords:
large strain, damage, plasticity, gradient-enhancement, AceGen package

8.Pęcherski R.B., Kowalczyk-Gajewska K., Nowak Z., Opis udziału pasm ścinania w płynięciu plastycznym polikrystalicznych metali z uwzględnieniem wpływu zmiany drogi odkształcenia, Niejednorodności odkształcenia w procesach przeróbki plastycznej i rekrystalizacji, Seminarium poświęcone 70. rocznicy urodzin Profesora Z. Jasieńskiego, 2005-01-21/01-21, Kraków (PL), pp.191-202, 2005

Conference abstracts
1.Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Micromechanical modelling of elasto-plastic composites: efficient and robust finite-element implementation of Mori-Tanaka model, CNM, 5th Conference on Nano- and Micromechanics, 2017-07-04/07-06, Wrocław (PL), No.O-08, pp.31-33, 2017
Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Micromechanical modelling of elasto-plastic composites: efficient and robust finite-element implementation of Mori-Tanaka model, CNM, 5th Conference on Nano- and Micromechanics, 2017-07-04/07-06, Wrocław (PL), No.O-08, pp.31-33, 2017

Keywords:
Mean-field homogenization, Mori-Tanaka method, Composite materials, Finite element method

2.Libura T., Kowalewski Z.L., Kowalczyk-Gajewska K., Dietrich L., Strain-hardening effect in thin-sheet magnesium alloy AZ31B under low cyclic loading, XII Konferencja „Nowe Kierunki Rozwoju Mechaniki”, 2017-03-22/03-25, Białystok - Supraśl (PL), pp.1-2, 2017
Libura T., Kowalewski Z.L., Kowalczyk-Gajewska K., Dietrich L., Strain-hardening effect in thin-sheet magnesium alloy AZ31B under low cyclic loading, XII Konferencja „Nowe Kierunki Rozwoju Mechaniki”, 2017-03-22/03-25, Białystok - Supraśl (PL), pp.1-2, 2017

Abstract:
Optimization of sheet metal forming processes requires a very good knowledge of material forming ability. During the forming of industrial parts, very complex strain paths are usually observed and can affect the formability of the sheet. Therefore, it is necessary to better understand and more accurately investigate deformation behaviour of sheet alloys. It should be noted that material testing of flat specimens under compression within a large deformation range procures many difficulties, and the buckling phenomenon seems to be the most im-portant. This paper shows the results of tension-compression tests carried out on specimens made of ultralight magnesium alloys AZ31B with nominal thickness equal to 1 mm using the anti-buckling fixture to avoid buckling problem.

Keywords:
Bauschinger effect, cyclic loading, buckling, fixture, thin sheet

3.Libura T., Kowalewski Z.L., Kowalczyk-Gajewska K., Dietrich L., Low cycle fatigue of a rolled magnesium alloy using anti-buckling fixture, DYMAT, 10th Workshop, 2016-08-24/08-26, Poznań (PL), pp.59-61, 2016
4.Frydrych K., Kowalczyk-Gajewska K., Modelling microstructure evolution in SPD processes in the framework of crystal plasticity theory, ICTAM XXIV, 24th International Congress of Theoretical and Applied Mechanics, 2016-08-21/08-26, Montréal (CA), pp.1-2, 2016
5.Kowalczyk-Gajewska K., The self-consistent sequential averaging scheme for modelling elastic-viscoplastic polycrystals: validation by finite element calculations, MTDM, The 10th International Conference on Mechanics of Time Dependent Materials, 2016-05-17/05-20, Paris (FR), pp.63-64, 2016
Kowalczyk-Gajewska K., The self-consistent sequential averaging scheme for modelling elastic-viscoplastic polycrystals: validation by finite element calculations, MTDM, The 10th International Conference on Mechanics of Time Dependent Materials, 2016-05-17/05-20, Paris (FR), pp.63-64, 2016

Keywords:
Micromechanics, Sequential linearization, Self-Consistent Scheme, Polycrystals, Finite Element

6.Majewski M., Hołobut P., Kursa M., Kowalczyk-Gajewska K., Micromechanical modelling of packing and size effects in particulate elastic-plastic composites, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), No.P099, pp.1-2, 2016
7.Wcisło B., Mucha M., Kowalczyk-Gajewska K., Pamin J., Large strain thermo-elasto-plasticity: simulation of shear banding for different stress states, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), No.P169, pp.1-2, 2016
8.Kowalczyk-Gajewska K., Frydrych K., Modelling of microstructure evolution in metals and alloys of high specific strength, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), No.P196, pp.1-2, 2016
9.Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Efficient algorithmic treatment of the incremental Mori–Tanaka scheme for elasto-plastic composites, SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), No.P070, pp.1-2, 2016
10.Czarnota C., Kowalczyk-Gajewska K., Martiny M., Mercier S., Modeling of the cyclic behaviour of elastic viscoplastic composites by an additive tangent Mori Tanaka approach, ESMC 2015, 9th European Solid Mechanics Conference, 2015-07-06/07-10, Leganés-Madrid (ES), pp.#218-1-2, 2015
Czarnota C., Kowalczyk-Gajewska K., Martiny M., Mercier S., Modeling of the cyclic behaviour of elastic viscoplastic composites by an additive tangent Mori Tanaka approach, ESMC 2015, 9th European Solid Mechanics Conference, 2015-07-06/07-10, Leganés-Madrid (ES), pp.#218-1-2, 2015

Abstract:
This work deals with the prediction of the macroscopic behavior of two-phase composites, based on the Mori-Tanaka scheme combined with an additive/sequential interaction rule and tangent linearization of viscoplastic response. Cyclic tension compression loadings are considered to further evaluate the approach. The composite is made of spherical inclusions dispersed in a matrix. Both materials have an elastic-visco-plastic behavior. In the second part, finite element calculations are performed using ABAQUS/STANDARD software in order to validate the proposed homogenization technique. A representative volume element is analyzed with 30 randomly distributed inclusions.

Keywords:
Multiscale Modeling, Elasto-viscoplasticity, Mori Tanaka Scheme, Composite

11.Kowalczyk-Gajewska K., Petryk H., The sequential self-consistent scheme for modelling elastic-viscoplastic polycrystals, ESMC 2015, 9th European Solid Mechanics Conference, 2015-07-06/07-10, Leganés-Madrid (ES), pp.#216-1-2, 2015
Kowalczyk-Gajewska K., Petryk H., The sequential self-consistent scheme for modelling elastic-viscoplastic polycrystals, ESMC 2015, 9th European Solid Mechanics Conference, 2015-07-06/07-10, Leganés-Madrid (ES), pp.#216-1-2, 2015

Abstract:
The application of the sequential method for estimating the mechanical response of elastic-viscoplastic polycrystals of high viscous anisotropy is discussed. The results are compared with other averaging schemes. Since the anisotropy of viscous response is high the estimated overall response is dramatically different for different averaging schemes. Additionally the effect of different linearization procedure for the viscous part is studied, denoted as secant, affine and tangent. The results are compared to the recent FFT analysis available in the literature. For the studied example the tangent variant provides the overall response that agrees best with the FFT predictions.

Keywords:
Micromechanics, Sequential linearization, Self-Consistent Scheme, Polycrystals

12.Frydrych K., Kowalczyk-Gajewska K., Modelling of texture evolution and grain refinement in metals and alloys of high specific strength in SPD processes, EUROMAT 2015, European Congress and Exhibition on Advanced Materials and Processes, 2015-09-20/09-24, Warszawa (PL), pp.C1.1-1-2, 2015
Frydrych K., Kowalczyk-Gajewska K., Modelling of texture evolution and grain refinement in metals and alloys of high specific strength in SPD processes, EUROMAT 2015, European Congress and Exhibition on Advanced Materials and Processes, 2015-09-20/09-24, Warszawa (PL), pp.C1.1-1-2, 2015

Abstract:
Texture evolution and grain refinement in materials subjected to severe plastic deformation (SPD), in particular the ECAP and KoBo extrusion processes are examined in this work. The well known ECAP process consists in extruding a billet through an angular channel. In the KOBO process material is extruded with assistance of cyclic rotation of a die. Both processes lead to considerable grain refinement and often to strong texture evolution [2,5]. The VPSC code itself provides different variants of self-consistent (SC) micro-macro transition scheme. It was combined with the proposed crystal plasticity framework and has been used to simulate texture evolution. However, this model is two-scale and does not predict the grain refinement. In order to examine the latter phenomenon three-scale model of microstructure evolution was developed. The model is able to combine two micro-macro transition schemes to simulate the evolution of orientations inside a grain and decide if the formation of subgrains has occurred.

Keywords:
texture evolution, grain refinement, SPD processes, crystal plasticity, micromechanics

13.Staszczak M., Pieczyska E., Maj M., Kowalczyk-Gajewska K., Cristea M., Tobushi H., Hayashi S., Shape memory polymer – shape fixity and recovery in cyclic loading, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.147-148, 2015
Staszczak M., Pieczyska E., Maj M., Kowalczyk-Gajewska K., Cristea M., Tobushi H., Hayashi S., Shape memory polymer – shape fixity and recovery in cyclic loading, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.147-148, 2015

Abstract:
The paper concerns investigation of polyurethane shape memory polymer (SMP) properties. Shape fixity and shape recovery, important parameters for the SMP applications, were quantitatively estimated in thermomechanical cyclic loading; three subsequent thermomechanical loading cycles were performed. It was observed that the shape fixity is proper and does not depend on the cycle number. The obtained mean values of shape fixity parameters are 97-98 %. Although the shape recovery is poor (=83 %) in the first cycle of the thermomechanical loading, it is excellent in the subsequent cycles (=99-100 %). The evaluated parameters confirm good shape memory properties of the SMP.

Keywords:
Shape memory polyurethane, shape fixity, shape recovery, thermomechanical loading, cyclic loading

14.Majewski M., Hołobut P., Kursa M., Kowalczyk-Gajewska K., Description of packing and size effects in particulate composites by micromechanical averaging schemes and computational homogenization, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.571-572, 2015
Majewski M., Hołobut P., Kursa M., Kowalczyk-Gajewska K., Description of packing and size effects in particulate composites by micromechanical averaging schemes and computational homogenization, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.571-572, 2015

Abstract:
Different approaches to model packing and size effects are studied to model overall properties of particulate composites of different morphological features of phase distribution. The micromechanical schemes originating in the composite sphere model and its extension by morphologically-based pattern approach are taken as a basis. Analytical predictions are compared with results of computational homogenization performed on the generated representative volume elements of prescribed statistical characteristics.

Keywords:
micromechanics, morphologically representative pattern, computational homogenization, size and scale effect

15.Kowalczyk-Gajewska K., Frydrych K., Maj M., Urbański L., Micromechanical modelling of magnesium alloy and its experimental verification, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.677-678, 2015
Kowalczyk-Gajewska K., Frydrych K., Maj M., Urbański L., Micromechanical modelling of magnesium alloy and its experimental verification, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.677-678, 2015

Abstract:
Micromechanical modelling of magnesium alloys is presented. The applied model combines the crystal plasticity framework accounting for twinning with the self-consistent grain-to-polycrystal scale transition scheme. The mechanical response of the material in the experiments involving the strain path changes is studied, together with the prediction of the accompanying texture evolution. It is demonstrated that the evolution of microstructure has an important impact on the overall material behaviour. The model predictions will be verified in experiments performed on the rolled sheets made of AZ31B alloy

Keywords:
micromechanics, crystal plasticity, twinning, texture evolution

16.Pieczyska E., Staszczak M., Maj M., Kowalczyk-Gajewska K., Tobushi H., Właściwości termomechaniczne i zastosowania polimerów z pamięcią kształtu, XI Konferencja Nowe Kierunki Rozwoju Mechaniki, 2015-03-18/03-20, Sarbinowo (PL), pp.75-76, 2015
Pieczyska E., Staszczak M., Maj M., Kowalczyk-Gajewska K., Tobushi H., Właściwości termomechaniczne i zastosowania polimerów z pamięcią kształtu, XI Konferencja Nowe Kierunki Rozwoju Mechaniki, 2015-03-18/03-20, Sarbinowo (PL), pp.75-76, 2015

Abstract:
Polimery z pamięcią kształtu, podobnie jak niektóre stopy metali, wykazują efekt pamięci kształtu. Wykorzystuje się w nich różnicę właściwości termomechanicznych poniżej i powyżej temperatury zeszklenia Tg, w której polimer radykalnie zmienia swe własności, m.in. wartość modułu sprężystości. Materiały te posiadają możliwość szybkiej zmiany właściwości fizycznych w zależności od temperatury. Stają się miękkie po podgrzaniu powyżej Tg i pozwalają się łatwo formować, a podczas schłodzenia poniżej tej temperatury odzyskują poprzednią sztywność. Nadal pamiętają swój oryginalny kształt i wracają do niego podczas ponownego podgrzania powyżej Tg. Umożliwia to ich różnorodne praktyczne zastosowania, m.in. w przemyśle medycznym i farmaceutycznym, tekstylnym, spożywczym, lotniczym i kosmicznym.

Keywords:
Polimery z pamięcią kształtu, temperatura zeszklenia, wartość modułu sprężystości, kamera termowizyjna

17.Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Staszczak M., Tobushi H., Hayashi S., Cristea M., Thermomechanical analysis of shape memory polymer under cyclic loading and relaxation conditions, ICEM-16, 16th International Conference on Experimental Mechanics, 2014-07-07/07-11, Cambridge (GB), pp.1-2, 2014
Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Staszczak M., Tobushi H., Hayashi S., Cristea M., Thermomechanical analysis of shape memory polymer under cyclic loading and relaxation conditions, ICEM-16, 16th International Conference on Experimental Mechanics, 2014-07-07/07-11, Cambridge (GB), pp.1-2, 2014

Abstract:
Experimental evaluation and modeling of a new polyurethane shape memory polymer (SMP) subjected to cyclic tension and stress-relaxation tests are presented. The influence of effects of thermomechanical couplings on the SMP thermomechanical behaviour for various strain rates was studied, basing on the sample temperature changes measured by a fast and sensitive infrared camera. The constitutive model valid in finite strain regime was developed following [5]. In the proposed approach SMP is described as a two-phase material composed of hyperelastic rubbery phase and elastic-viscoplastic glassy phase while the volume content of phases is specified by the current temperature.

Keywords:
Experimental evaluation, constitutive modeling, polyurethane shape memory polymer, cyclic tension, stress-relaxation tests, effects of thermomechanical couplings, thermomechanical behaviour, various strain rates, temperature changes, sensitive infrared camera, hyperelastic rubbery phase, elastic-viscoplastic glassy phase

18.Frydrych K., Kowalczyk-Gajewska K., Stupkiewicz S., Modelling of microstructure evolution in hcp polycrystals on non-proportional strain paths, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.207-208, 2014
Frydrych K., Kowalczyk-Gajewska K., Stupkiewicz S., Modelling of microstructure evolution in hcp polycrystals on non-proportional strain paths, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.207-208, 2014

Abstract:
Microstructure evolution in hcp polycrystals subjected to severe plastic deformation, in particular in the KOBO extrusion and the equal channel angular pressing (ECAP) processes, are examined in this work, using the crystal plasticity framework. Modelling approach combines the large strain crystal plasticity model accounting for twinning and the tangent variant of the self-consistent (SC) scale transition scheme.

Keywords:
hcp polycrystals, twinning, SPD processes, crystal plasticity, self-consistent model, microstructure evolution

19.Kowalczyk-Gajewska K., Pieczyska E.A., Maj M., Staszczak M., Majewski M., Cristea M., Tobushi H., Two-phase model of shape memory polymers at finite strains: formulation and experimental verification, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.259-260, 2014
Kowalczyk-Gajewska K., Pieczyska E.A., Maj M., Staszczak M., Majewski M., Cristea M., Tobushi H., Two-phase model of shape memory polymers at finite strains: formulation and experimental verification, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.259-260, 2014

Abstract:
A constitutive model of SMP, formulated at large strain format, is developed. SMP is described as a two-phase material composed of a soft rubbery phase and a hard glassy phase. The volume fraction of each phase is postulated as a logistic function of temperature. Identification of model parameters has been performed using the experimental tensile loading-unloading tests with different strain rates conducted at thermal chamber at different temperatures.

Keywords:
shape-memory polymers, two-phase model, large strain framework

20.Staszczak M., Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Cristea M., Tobushi H., Hayashi S., Estimation of shape fixity and shape recovery – crucial parameters for shape memory polymer applications, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.267-268, 2014
Staszczak M., Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Cristea M., Tobushi H., Hayashi S., Estimation of shape fixity and shape recovery – crucial parameters for shape memory polymer applications, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.267-268, 2014

Abstract:
Shape memory polymers (SMP) are new unique and attractive materials which demonstrate shape memory properties. It means that the materials, as a result of an external stimulus such as temperature, can recover their original (permanent) shape from deformed (temporary) shape. The mechanical characteristics of SMP, e.g. the elastic modulus and the yield stress, change significantly below and above their glass transition temperature Tg. It can be explained by differences of molecular motion of the polymer chains below and above Tg [1, 2]. Two phenomena due to this can be observed in the SMP. The first one is a shape fixity which means that it is possible to fix a temporary shape by cooling the deformed SMP below Tg. The second phenomenon, called a shape recovery, denotes the property that the original shape, changed due to deformation, is recovered during subsequent heating above the SMP Tg temperature. Preliminary estimation of these two parameters, crucial to assess SMP potential applications, is the subject of this paper [1].

Keywords:
Shape memory polymers, elastic modulus, yield stress, glass transition temperature, shape fixity, shape recovery

21.Pieczyska E., Tobushi H., Hayashi S., Maj M., Kowalczyk-Gajewska K., Staszczak M., Cristea M., Thermomechanical Analysis of Shape Memory Polyurethane, 4th Integrity, Reliability and Failure of Mechanical Systems, 2013-06-23/06-27, Funchal (PT), pp.1-2, 2013
Pieczyska E., Tobushi H., Hayashi S., Maj M., Kowalczyk-Gajewska K., Staszczak M., Cristea M., Thermomechanical Analysis of Shape Memory Polyurethane, 4th Integrity, Reliability and Failure of Mechanical Systems, 2013-06-23/06-27, Funchal (PT), pp.1-2, 2013

Abstract:
This paper presents experimental evaluation of a new polyurethane shape memory polymer (PU-SMP) produced by SMP Technologies Inc. It discusses mechanical characteristics and temperature changes of the SMP specimens subjected to tension test performed at room temperature with various strain rates. Basing on the mechanical data and the relevant temperature changes, we have studied the thermomechanical properties of the PU-SMP and influence of the strain rate on the strain localization behavior. Finally, we have identified the material parameters for the one-dimensional rheological model of the SMP.

Keywords:
shape memory polyurethane, tension test, dynamic mechanical analysis, infrared camera, temperature change, thermomechanical properties, rheological model

22.Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Staszczak M., Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane, International Conference on Shape Memory and Superelastic Technologies, 2013-05-20/05-24, Praga (CZ), pp.282-283, 2013
Pieczyska E.A., Maj M., Kowalczyk-Gajewska K., Staszczak M., Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane, International Conference on Shape Memory and Superelastic Technologies, 2013-05-20/05-24, Praga (CZ), pp.282-283, 2013

Abstract:
Initial experimental evaluation of a new polyurethane shape memory polyner (PU-SMP) subjected to uniaxial tension carrięd out at different stlain rates is presented. The stress and strain data were recorded and temperature changes from the SMP specimen surface was deternrined using fast and sensitive infrared camera. Basing on themechanical characteristics and their relevant temperature changes, the SMP thernromechanical properties have been stLrdied. lnfluence of the strain rate on the SMP temperature, its structure and behaviour are discussed. Identification of the PU-SMP parameters for onc-dimensional rheological model proposed by Tobushi et. ttl. will be performed.

Keywords:
Shape memory polymers, elastic modulus, yield stress, glass transition temperature

23.Kowalczyk-Gajewska K., Micromechanical modelling of metallic materials of high specific strength accounting for slip-twin interactions, SolMech 2008, 36th Solid Mechanics Conference, 2008-09-09/09-12, Gdańsk (PL), pp.236-237, 2008
24.Kowalczyk-Gajewska K., Pęcherski R.B., Micromechanical modeling of polycrystalline materials, Plasticity 2006, 12th International Symposium on Plasticity and Its Current Applications, 2006-07-17/07-22, Halifax (CA), Vol.CD ROM, pp.556-558, 2006
25.Kowalczyk-Gajewska K., Mróz Z., Pęcherski R.B., Micromechanical modeling of polycrystalline materials under non-proportional deformation paths, SolMech 2006, 35th Solid Mechanics Conference, 2006-09-04/09-08, Kraków (PL), pp.213-214, 2006