1. |
Pęcherski R.B., A new look at viscoplasticity generated by shear banding,
8th Wdzydzeanum Workshop on „FLUID – SOLID INTERACTION”, 2020-08-30/09-03, Wdzydze Kiszewskie (PL), pp.1-2, 2020 |  |
2. |
Nowak Z., Pęcherski R.B., Constitutive modelling of shear bands effect in ductile materials: formulation and computational aspects,
8th Wdzydzeanum Workshop on „FLUID – SOLID INTERACTION”, 2020-08-30/09-03, Wdzydze Kiszewskie (PL), pp.1-2, 2020 |  |
3. |
Postek E., Pęcherski R.B., Nowak Z., Viscoplasticity effect during impact of metallic foams,
CCAM & 3D-Printing, Collaborative Conference on Advanced Materials, 2019-08-26/08-30, St. Julian's (MT), pp.16-17, 2019 Abstract: In the last 20 years, a new rapidly developing method is applied to calculations of solid mechanics problems, [1]. It is a non-local method. The predecessors of the method that have been applied to crystals were developed in [2] and [3]. In the presentation, we show an application of the method for the evaluation of the viscoplasticity effects [4, 5] in the copper foams. The oxygen free high conductivity copper (OHFC) can be applied to produce the open-cell multifunctional structures, for example, heat exchangers, heat capacitors, using additive manufacturing [6]. We use the highly parallelized program Peridigm for the analysis, [7].
Figure 1(a) shows an exemplary impacting foam sample attacking with a velocity of 20 m/s an elastic block. The highest plastic strains are in the case of ideally elastic-plastic case (b). The equivalent plastic strains are higher when neglecting the strain rate hardening effects (d) than including both strain hardening and strain rate hardening effects (c). We provide dependences of the equivalent plastic strains on impact velocities and strain rate hardening exponents.
Literature;
1. S.A. Silling, Journal of Mechanics and Physics of Solids, 48, 175 (2000).
2. D. Rogula, Nonlocal theory of material media (Springer), 123 (1982).
3. A. Kunin, Elastic media with microstructure, one dimensional models (Springer), (1982).
4. J.A. Mitchell, A Nonlocal, Ordinary, State-Based Plasticity Model for Peridynamics (SANDIA ), (2011).
5. J.T. Foster, S.A. Silling, W.W. Chen, International Journal for Numerical Mechods in Engineering, 81,1242 (2010).
6. R.B. Pęcherski, M. Nowak, Z. Nowak, International Journal for Multiscale Computational Engineering, 15, 431 (2017).
7. M.L. Parks, D.J. Littlewood, J.A. Mitchell, S.A. Silling, Peridigm Users’ Guide (SANDIA), (2012). Keywords: metallic foams, composites, impact loading, peridynamics, parallel computing Affiliations:
Postek E. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Nowak Z. | - | IPPT PAN |
|  |
4. |
Kowalewski Z.L., Nowak Z., Pęcherski R.B., Libura T., Identification of effects associated to dynamic testing using shpb or dict- experiment and numerical analysis,
DynaMAT, The 13th WORKSHOP on DYNAMIC BEHAVIOR OF MATERIALS AND ITS APPLICATIONS IN INDUSTRIAL PROCESSES, 2019-04-17/04-19, Nicosia (CY), pp.1-2, 2019 |  |
5. |
Nowak Z., Nowak M., Pęcherski R.B., On the energy absorbtion in open cell foams under dynamic loading,
DynaMAT, The 13th WORKSHOP on DYNAMIC BEHAVIOR OF MATERIALS AND ITS APPLICATIONS IN INDUSTRIAL PROCESSES, 2019-04-17/04-19, Nicosia (CY), pp.1-2, 2019 |  |
6. |
Pęcherski R.B., Rusinek A., Frąś T., Nowak M., Nowak Z., Energetyczny warunek plastyczności materiałów ortotropowych wykazujących asymetrię zakresu sprężystego,
OMIS 2019, XIII Konferencja Naukowa Odkształcalność Metali i Stopów, 2019-11-19/11-22, Łańcut (PL), pp.48-49, 2019 |  |
7. |
Manecka A., Pęcherski R.B., Ocena stateczności sprężystej nanopręta z uwzględnieniem efektu skali,
OMIS 2019, XIII Konferencja Naukowa Odkształcalność Metali i Stopów, 2019-11-19/11-22, Łańcut (PL), pp.32-33, 2019 |  |
8. |
Pęcherski R.B., Viscoplastic flow accounting for multilevel hierarchy of shear banding,
ESMC, 10th European Solid Mechanics Conference, 2018-07-02/07-06, Bologna (IT), pp.1, 2018 Abstract: A new physical model of multilevel hierarchy and evolution of shear bands is proposed with use of the analysis of recent state of the art of the investigations carried on different levels of observations: uni-axial and bi-axial mechanical tests enhanced with digital image correlation method and in-situ tests with use of electron microscopy as well as atom probe tomography in relation with ab initio and molecular dynamics computational simulations. Physical motivation and heuristic foundations of theoretical description are discussed with reference to known results in the literature. The difficulties with application of a direct multiscale integration scheme are discussed and an original idea of an extension of the representative volume element concept with use of the known theory of the propagation of the singular surfaces of microscopic velocity field is proposed. A new formulation of the description of rate of shear strain generated by multilevel hierarchy of shear bands is formulated in the workflow integration approach, in which information from molecular simulation at different levels flows into the decision process. Keywords: shear banding, viscoplasticity, strong discontinuity surface Affiliations:
Pęcherski R.B. | - | IPPT PAN |
|  |
9. |
Nowak Z., Nowak M., Pęcherski R.B., Propagation of compaction waves in the open-cell copper foams,
ESMC, 10th European Solid Mechanics Conference, 2018-07-02/07-06, Bologna (IT), pp.1, 2018 |  |
10. |
Pęcherski R.B.♦, Multilevel hierarchy of shear banding in plastic deformation of solids,
ETAMM 2018, Emerging Trends in Applied Mathematics and Mechanics, 2018-06-18/06-22, Krakow (PL), pp.160-160, 2018 Abstract: Plastic deformation of solids: polycrystalline metals, polymers, and amorphous materials is often produced as an effect of micro-shear banding. The micro-shear bands are observed as concentrated shear zones in the form of layers of the thickness of the order 0.1 m, which form the clusters developing on multiple levels of observation. The identification and elucidation of physical mechanisms that are responsible for initiation, growth and evolution of micro-shear bands is of fundamental importance for understanding the macroscopic behaviour of many materials. Physical motivation and heuristic foundations of theoretical description are discussed with reference to known results in the literature. The difficulties with application of a direct multiscale integration scheme are discussed and an original idea of an extension of the representative volume element concept with use of the known theory of the propagation of the singular surfaces of microscopic velocity field is proposed. A new formulation of the description of rate of shear strain generated by multilevel hierarchy of shear bands is proposed and incorporated into theory of elastic/plastic or elastic/viscoplastic solids by means of the concepts of the instantaneous contribution function and volume fraction of shear banding. Keywords: multilevel hierarchy, shear banding, plasticity, viscoplasticity, shear banding contribution function, singular surface of velocity field Affiliations:
Pęcherski R.B. | - | other affiliation |
|  |
11. |
Postek E., Pęcherski R.B., Nowak Z., Perydynamiczna symulacja procesów zgniatania otwartokomórkowych pianek miedzianych,
PLASTMET, 11 KONFERENCJA ZINTEGROWANE STUDIA PODSTAW DEFORMACJI PLASTYCZNEJ METALI, 2018-11-27/11-30, Łańcut (PL), pp.120-121, 2018 Abstract: W ciągu ostatnich dwudziestu lat opracowano nową metodę bezsiatkową znaną jako perydynamika [1]. Metoda ta posługuje się zrównoleglonym kodem obliczeniowym [2]. Przedmiotem badań jest deformacja miedzianej pianki o strukturze otwartokomórkowej poddanej dynamicznemu ściskaniu, Rys. 1.
Model komputerowy szkieletu pianki otrzymano wykorzystując koncepcję materiału wirtualnego przedstawioną w pracy [3]. W zależności od potrzeb wymiary struktury szkieletu pianki można skalować. Materiałem pianki jest miedź beztlenowa o wysokiej przewodności cieplnej (OFHC), wykorzystywana do wytwarzania wielofunkcyjnych struktur komórkowych takich jak wymienniki lub kondensatory cieplne, itp. W obliczeniach zastosowano lepkoplastyczny model materiału szkieletu pianki, a symulacje przeprowadzono dla różnych prędkości uderzenia. Rezultaty metody perydynamiki porównano z obliczeniami MES podobnych problemów ściskania dynamicznego pianki. Obliczenia wykonano w ICM Uniwersytetu Warszawskiego na komputerze CRAY XC-40 oraz na klastrze HP w centrum TASK w Gdańsku. Keywords: Obciążenia uderzeniowe, pianka metaliczna, perydynamika Affiliations:
Postek E. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Nowak Z. | - | IPPT PAN |
|  |
12. |
Postek E., Nowak Z., Pęcherski R.B., Impact resistance of crushable foam skeleton,
SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.1-2, 2018 Abstract: The analyses of the modern cellular materials due to complexity of their internal structure require efficient computer methods and codes. The new method that has been developed mostly in the last 10 years is peridynamics [1, 2]. The developments resulted in highly parallelized code [3] that we use in our analysis. The subject of the study are alumina foams produced by gelcasting method. The results of microtomography of alumina foams are used to create the numerical model reconstructing the structure of foam skeleton. The numerical simulations of failure strength under compression for alumina foams are performed. The calculations with use of the numerical model are time consuming. Therefore, the simplified method of the assessment of failure strength is proposed. The 3D model of the foam structure is created. The detailed description of the model generation is presented in Nowak et al. [5]. The numerical models of real Al2O3 foam with porosity 96 %, and discussion of theirs mechanical properties have been presented. The method of the assessment of failure strength of real alumina foam produced by the gelcasting is proposed. We attempt to present the mechanism of damaging of a crushable foam under impact. Keywords: foams, damage, impact, peridynamics Affiliations:
Postek E. | - | IPPT PAN | Nowak Z. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
13. |
Misztal-Faraj B., Jarecki L., Pęcherski R.B., Kinetic model of polymer crystallization under high tensile stress or molecular orientation,
SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.224-225, 2018 Abstract: Molecular deformation and orientation in the amorphous phase subjected to tensile stresses strongly accelerates crystallization of polymers by orders of the magnitude. Closed-form analytical formula is derived for the crystallization rate under high tensile stresses in the entire range of crystallization temperature and the temperature rates. Such formula, lacking in the literature, is needed for modelling of the dynamics of crystallizing polymers processing and predicting structure development in obtaining highly oriented materials of enhanced tensile modulus and tenacity. Rapid online crystallization strongly influences the rheological behaviour during the processing and introduces coupling of crystallization with the processing dynamics. Tensile stress affects the crystallization rate mainly by influencing the configurational entropy of the chain macromolecules in amorphous phase. None of the actually available models are capable to account for the effects of high molecular orientation in the crystallization kinetics. In the present approach, non-Gaussian chain statistics is considered to account for finite extensibility of real macromolecules in the amorphous phase under high tensile stresses which results in non-linear effects in the model. The Hoffman-Lauritzen model of crystallization kinetics is extended to account for free energy of deformation of the amorphous component under uniaxial molecular orientation produced by the tensile stresses. The crystallization rate is considered as controlled by predetermined and sporadic nucleation present in real systems. The involvement of both nucleation mechanisms in the crystallization kinetics varies strongly with the level of tensile stress and amorphous orientation, with domination of sporadic nucleation at high orientations. The closed-form analytical formulas are validated by computations. Example numerical calculations illustrate influence of amorphous orientation on the crystallization free energy and the crystallization rate function involving both nucleation mechanisms. Keywords: polymer crystallization, crystallization kinetics, molecular orientation, non-Gaussian chain statistics Affiliations:
Misztal-Faraj B. | - | IPPT PAN | Jarecki L. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
14. |
Kwasniak P.♦, Mizera J.♦, Pęcherski R.B., Stacking faults in hexagonal Ti alloys – local instability of crystal lattice and its effect on solution strengthening,
SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.246-247, 2018 Abstract: Stacking faults are the special regions of the crystal structure that exhibit non-uniform structure and diversified stability. Energy of this defects determines configurations of dislocation cores and type of predominant plastic deformation mechanism. In this study we focus on the generalised stacking fault energy computations of multi-slip-system hexagonal Ti alloys in the context of solution strengthening effect and the atomic as well as electronic structure identification of the analysed planar defects. The far reaching goal is to provide the physical and theoretical basis to answer the still unresolved question concerning the initiation of a micro-shear band in metallic solid. Keywords: stacking faults, hexagonal Ti alloys, instability of crystal lattice, solution strengthening, micro-shear band Affiliations:
Kwasniak P. | - | Warsaw University of Technology (PL) | Mizera J. | - | Warsaw University of Technology (PL) | Pęcherski R.B. | - | IPPT PAN |
|  |
15. |
Kwasniak P.♦, Mizera J.♦, Pęcherski R.B., Solid solution strengthening of hexagonal Ti alloys: structures, energies and Peierls barriers of a type screw dislocations calculated from first principles,
SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.248-249, 2018 Abstract: Due to their finely balanced strength and density, hexagonal close-packed (hcp) metals such as Ti and Mg are perceived as potential prime elements for the production of new light, and strong alloys essential for the sustainable development of green technologies oriented towards a reduction in mass in all transport sectors. Nevertheless, the conscious design of materials requires information on the relationship between alloy elements and individual deformation mode activity. Such complex knowledge in the context of hcp systems remains a challenge, seriously hampering our ability to anticipate the strength and ductility of new materials developed. In general, hcp metals and alloys suffer from limited cold workability arising from reduced crystal symmetry (compared to cubic crystals) and from the geometrical relations between their dislocation glide planes. On the other hand, the unique properties of single phase hcp materials, such as great strength and reasonable ductility of α-Ti+O solutions and a pronounced solution softening of α-Mg+Y alloys demonstrate the great potential of this groups of materials. All these aspects provide incentive for exploring the physics of plastic deformation and solution strengthening theories. Keywords: Hexagonal Ti alloys, solid solution strengthening, Peierls barriers, screw dislocations, first principles calculations Affiliations:
Kwasniak P. | - | Warsaw University of Technology (PL) | Mizera J. | - | Warsaw University of Technology (PL) | Pęcherski R.B. | - | IPPT PAN |
|  |
16. |
Bajerski P.♦, Chudy D.♦, Pęcherski R.B.♦, Jarecki L., Crystallization kinetics of polyamide 2200 in the modeling of additive manufacturing processes by fe analyses,
SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.218-219, 2018 Abstract: Additive Manufacturing (AM) process is a very fast and promising technique to build various very complex prototypes and components directly in the industry. One can choose different techniques of AM like Selective Laser Sintering (SLS), Fused Filament Fabrication (FFF) dedicated for thermoplastic materials or Direct Laser Metal Sintering (DMLS) for powder metals, or Stereolitography Apparatus (SLA) for thermosets. One of the most common techniques in AM are SLS and FFF for thermoplastic materials. The complexity of the processes and the behaviour of the materials in specific environment have a strong influence on the quality, strength and warpage of the obtained structures. The state of the art of the studies indicates that morphology of the material and the crystallization processes influence the aforementioned characteristics of the created components. The knowledge on the crystallization kinetics of polymers is known since many years but it is still developing in order to get an adequate description of the behaviour of the materials in isothermal and non-isothermal conditions. Furthermore, it is needed to predict the warpage of manufactured components based on the virtual AM process in order to decrease the costs. The available tools dedicated for FE analyses allow to increase functionality and implementation of own material models and techniques to perform the customize simulations. Based on the theory and Differential Scanning Calorimetry (DSC) results it is possible to predict the behaviour of the materials and start working on simulation of the virtual AM process [1-4]. The extracted curves of the velocity of material crystallization in temperature domain with different cooling rate obtained in FE simulations are shown in Fig. 1. The simulated curves are confronted with the DSC experimental results. Keywords: crystallization kinetics, Differential Scanning Calorimetry (DSC), polyamide 2200, additive manufacturing, FE analysis Affiliations:
Bajerski P. | - | ABB Sp. z o.o. (PL) | Chudy D. | - | AGH University of Science and Technology (PL) | Pęcherski R.B. | - | other affiliation | Jarecki L. | - | IPPT PAN |
|  |
17. |
Pawłowski P., Pęcherski R.B., Nowak M., Nowak Z., Skłodowski M., Application of the Concept of Virtual Material for the Design of Additive Manufacturing Processes of Open Cell Foams,
WCCM 2018, 13th World Congress on Computational Mechanics, 2018-07-22/07-27, Nowy Jork (US), pp.584-584, 2018 |  |
18. |
Pęcherski R.B., Multilevel Hierarchy of Shear Banding in Viscoplastic Flow and Failure,
WCCM2018, 13th World Congress on Computational Mechanics, 2018-07-22/07-27, Nowy Jork (US), pp.1, 2018 Abstract: Experimental observations show that inelastic deformation of metals is often produced as an effect of competing mechanisms of crystallographic glide, twinning and micro-shear banding. The micro-shear bands are observed as concentrated shear zones in the form of transcrystalline layers of the thickness of the order 0.1 µm. It has been observed that the change of the mechanism of inelastic deformation has strong influence on ductile failure processes in different length scales. Therefore, the identification and elucidation of physical mechanisms that are responsible for initiation, growth and evolution of micro-shear bands is of fundamental importance for understanding the macroscopic behaviour of metallic materials. A new physical model of multilevel hierarchy and evolution of shear bands is proposed with use of the analysis of recent state of the art of the investigations carried on different levels of observations: uni-axial and bi-axial mechanical tests enhanced with digital image correlation method and in-situ tests with use of electron microscopy as well as atom probe tomography in relation with ab initio and molecular dynamics computational simulations. The difficulties with application of a direct multiscale integration scheme are discussed and an original idea of an extension of the representative volume element concept with use of the known theory of the propagation of the singular surfaces of microscopic velocity field is proposed. A new formulation of the description of rate of shear strain generated by multilevel hierarchy of shear bands is formulated in the workflow integration approach, in which information from molecular simulation at different levels flows into the decision process. Keywords: shear banding, multilevel hierarchy of shear bands, viscoplastic flow, failure Affiliations:
Pęcherski R.B. | - | IPPT PAN |
|  |
19. |
Nowak Z., Nowak M., Pęcherski R.B., Wiśniewski K., Widłaszewski J., Kurp P.♦, Computational Modelling of Thermoplastic Behaviour of Inconel 718 in Application to Laser-Assisted Bending of Thin-Walled Alloy Tubes,
WCCM2018, 13th World Congress on Computational Mechanics, 2018-07-22/07-27, Nowy Jork (US), pp.1, 2018 |  |
20. |
Manecka A., Pęcherski R.B., Stateczność sprężysta jednowymiarowych nanostruktur.Problem of elastic stability of one-dimensional nanostructures.,
WDZYDZEANUM 2018, 6th WDZYDZEANUM WORKSHOP ON „FLUID – SOLID INTERACTION”, 2018-09-02/09-04, Wdzydze Kiszewskie (PL), pp.1, 2018 Abstract: Przedstawiono zagadnienie efektu skali występującego w nieliniowej teorii sprężystości. Omówiono uwzględnienie efektu skali do badań stateczności jednowymiarowych nanostruktur na przykładzie nanoprętów i nanorurek węglowych. Przedstawiono problematykę zjawiska utraty stateczności w ujęciu nieliniowym oraz zaprezentowano, wynikające z wyprowadzonych zależności, postacie postbifurkacyjne (elastyki) z wykorzystaniem oprogramowania Wolfram Mathematica. Omówiono analizę zachowania jednowymiarowego ciała pod wpływem obciążenia ściskającego oraz samodzielne wyprowadzone wzory na krzywiznę nanopręta z uwzględnieniem efektu skali. Porównano wyniki teorii nieliniowej z uwzględnieniem efektu skali oraz bez jego uwzględnienia i przedstawiono je w postaci wykresów wygenerowanych w programie Wolfram Mthematica. Przedyskutowano możliwe zastosowania otrzymanych wyników w technicznych problemach nanotechnologii. Keywords: jednowymiarowe struktury, nanopręty, nanorurki węglowe, nieliniowy problem statecznosci, efekt skali, elastyka Affiliations:
Manecka A. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
21. |
Pęcherski R.B., Koncepcja energetycznej miary wytężenia według Jerzego Zawadzkiego The concept of energy-based measure of material effort according to Jerzy Zawadzki,
WDZYDZEANUM 2018, 6th WDZYDZEANUM WORKSHOP ON „FLUID – SOLID INTERACTION”, 2018-09-02/09-04, Wdzydze Kiszewskie (PL), pp.1, 2018 Abstract: Celem pracy jest upowszechnienie oryginalnej koncepcji hipotezy wytężenia, opierającej się na podstawowych założeniach i prawach fizyki ciała stałego, która została zaproponowana blisko pół wieku temu przez ucznia Włodzimierza Burzyńskiego - Jerzego Zawadzkiego. Zawadzki wyprowadził, na gruncie równań fizyki metali oraz fizyki polimerów, miarę wytężenia jako przyrost właściwej energii swobodnej. Daje to możliwość uwzględnienia zmian entropii w czasie procesu odkształcenia, co dla polimerów jest szczególnie istotne. Przewodnią myśl Zawadzkiego można przedstawić następująco. Jeżeli ciało odkształcalne zostaje obciążone, wzrasta jego energia sprężysta w wyniku zmian odległości między atomami lub molekułami. Innymi słowy, dla ciał izotropowych, energia zmian postaciowych i objętościowych ulega zmianie. Nie jest to jedyna zmiana, gdyż w także energia drgań atomów wokół położeń równowagi także się zwiększa, co w konsekwencji może powodować przejście ze stanu sprężystego w stan odkształcenia plastycznego. Ten trafny argument znalazł swoje potwierdzenie w rozwiniętej w późniejszych latach teorii termicznie aktywowanego ruchu dyslokacji jako fizykalnego mechanizmu odpowiedzialnego za proces deformacji lepkoplastycznych.Rozważania przytoczone w pracy Zawadzkiego doprowadziły do wyprowadzenia różnych form energetycznej hipotezy wytężenia. Autor przedyskutował także szczegółowo porównanie własnych kryteriów sprężystych stanów granicznych z tymi, które były dyskutowane wcześniej przez Hubera, Hubera i Beltramiego jak również Burzyńskiego oraz Schleichera. Keywords: energetyczna miara wytężenia, przyrost właściwej energii swobodnej jako miara wytężenia, fizyka metali, fizyka polimerów Affiliations:
Pęcherski R.B. | - | IPPT PAN |
|  |
22. |
Pęcherski R.B., Nowak Z., Nowak M., Natonik K.J.♦, Potoczek M.♦, Śliwa R.E.♦, Problems of virtual cellular materials: representative volume element and energy-based assessment of failure strength,
DBM, 11th Workshop Dynamic Behaviour of Materials and its Applications in Industrial Processes, 2017-08-23/08-25, Guimarães (PT), pp.12-13, 2017 Abstract: Three kinds of cellular materials are considered. Depending on geometry and physical properties of the skeleton, these are metallic cellular materials with convex or reentrant open cell structure. To the third group belong alumina foams produced by gel casting method. Finite element computations are used to analyse mechanical properties of a material volume. Such an analysis is usually related with big computational costs. Therefore, it is important to keep the size of the considered cellular material volume as small as possible. On the other hand, the validity of the continuum model requires the proper size of the RVE. The aim of the study is to estimate the sufficient size of representative volume element (RVE) in order to assess the validity of the elastic model of the considered cellular material. An array of cubes of virtual cellular material is used to compute the particular deformation modes providing elastic moduli, Young modulus E, shear modulus G and bulk modulus K as well as the resulting Poisson's ratio. Also the results of the microtomography of alumina foams are used to create the „virtual cellular material” i.e. the numerical model reconstructing the structure of real foam skeleton. The numerical simulations of compression test are performed. The results are compared with experimental data of elastic moduli and failure strength. The numerical simulations of failure strength under compression for alumina foams are performed. The calculations with use of the numerical model are time consuming. Therefore, the simplified method of the assessment of failure strength is proposed. It is based on the energy-based hypothesis on the equivalence of of elastic moduli and the resulting equivalence of the values of failure strength of real alumina foam and the cellular material with regular structure (e.g. fcc type). The justification of the hypothesis based on experimental data of compression of alumina foam are discussed and the range of validity as regards porosity values is studied. Keywords: virtual cellular materials, convex skeleton, reentrant skeleton. representative volume element, numerical simulations Affiliations:
Pęcherski R.B. | - | IPPT PAN | Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Natonik K.J. | - | other affiliation | Potoczek M. | - | Rzeszów University of Technology (PL) | Śliwa R.E. | - | Rzeszów University of Technology (PL) |
|  |
23. |
Nowak Z., Nowak M., Pęcherski R.B., Dynamic compression strength of copper open-cell foams,
DBM, 11th Workshop Dynamic Behaviour of Materials and its Applications in Industrial Processes, 2017-08-23/08-25, Guimarães (PT), pp.8-9, 2017 Abstract: Metal foams in view of their structural strength and mechanical energy absorption capability under high speed impact can be utilized as energy absorbers. It is important to understand the propagation of compaction waves in the foams. Most commercially available metal foams are made of aluminium, nickel, copper, and metal alloys. Two kinds of foams exist, namely the open-cell and the closed-cell foams. Typically, the pore density of uncompressed open-cell foams varies between 5 to 100 PPI (pores per inch), while the porosity is in the range from 70% to 95%. Literature provides several examples of metal foams solutions for energy absorption applications, dealing with both experimental, numerical and analytical studies. The subject of the study are the models based on digital micro-structures, in particular open cell metallic foams characterized with the skeleton formed of convex or re-entrant cells. The re-entrant materials revealing negative Poisson's ratio have attracted increasing attention in the context of modern materials applications, [3]. The goal of the presented investigations is to study the impact limits and absorption energy of these two kind of open cell metallic foams. To simulate the deformation processes the finite element program ABAQUS is used. The computer tomography made the basis for the formulation of computational model of the foam and the finite element discretization of the skeleton. From each reconstructed volume, a representative cubic volume element was extracted. For numerical simulations the constitutive elasto-viscoplasticity model is applied that defines the dynamic behaviour of oxygen-free high conductivity (OFHC) Cu using the experimental data reported in the literature. The chosen material model for the numerical simulation is the Cowper-Symonds model. The model is able to predict the mechanical behaviour of the materials under different loading conditions and it is implemented in many FEM codes in order to investigate and describe problems such as ballistic impacts or problems in which the strain-rates component are relevant. In numerical simulations the bottom displacements in the impact direction are fixed and initial velocity V0 on the top surface and general contact (steel wall-Cu foam and selfcontact Cu foam) with the friction coefficient 0.35 is assumed. The numerical predictions of axial force (crushing force) within the wide range of velocity: from 50 to 300 m/s are discussed. The shock state variables derived from Hugoniot relation and the conservation laws are used for comparison with FEM simulations. Keywords: copper open-cell foams, compaction waves, shock waves, crushing force, elasto-viscoplasticity model Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
24. |
Pęcherski R.B., Nowak Z., Application of virtual cellular material concept for the simulations of dynamic loading processes,
MatCel'2017 & DynMatCel'2017, Cellular Materials: Structural Behaviour, Modelling and Characterisation, 2017-09-25/09-27, Aveiro (PT), pp.54-54, 2017 Abstract: The subject of the study is the models based on digital microstructure, in particular open-cell metallic materials with the skeleton of convex or re-entrant cells. Recently, the auxetic materials have attracted increasing attention in the context of modern materials applications. The dynamic properties of such materials are less known. Impact compressions of the two kind of cellular materials under high-velocity are numerically analysed, [1]. To simulate the deformation processes the finite element program ABAQUS is used. The computer tomography makes the basis for the formulation of computational model and finite element discretization of the skeleton of virtual cellular material. For numerical simulations the constitutive elasto-viscoplasticity equations are applied that describe the dynamic behaviour of OFHC Cu. The numerical predictions of compression kinematics of the skeleton and crushing force for velocity 50 and 300 m/s are discussed. The results of computations are completed with the analysis of shock wave propagation. Keywords: virtual cellular material, dynamic loading, crushing force, auxetic material, OFHC Cu, shock vaves Affiliations:
Pęcherski R.B. | - | IPPT PAN | Nowak Z. | - | IPPT PAN |
|  |
25. |
Frąś L.J., Pęcherski R.B., Dynamic behaviour of magnethoreological materials,
MatCel'2017 & DynMatCel'2017, Cellular Materials: Structural Behaviour, Modelling and Characterisation, 2017-09-25/09-27, Aveiro (PT), pp.17-18, 2017 Abstract: The magnethoreological material is based on the ferroparticles immersed in carrying fluid. The acting magnetic field is forcing ferroelements to connect into characteristic structure - braids. Behaviour of the magnethoreological material at the high strain rates will be described by Perzyna model. The created model will be verified with use of dedicated laboratory set up. Keywords: magnethoreological material, viscoplasticity model, dynamic behaviour, ferroelements. Affiliations:
Frąś L.J. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
26. |
Pęcherski R.B., Deformacja metali z udziałem wielopoziomowej hierarchii pasm ścinania - nowe spojrzenie. Deformation of metals accounting for multilevel hierarchy of shear bands - revisited.,
OMIS'2017, XII Konferencja NAukowa ODKSZTAŁCALNOŚĆ METALI I STOPÓW, 2017-11-21/11-24, Łańcut (PL), pp.52-53, 2017 Abstract: Obserwacje doświadczalne wykazują, że deformacja plastyczna metali jest często efektem konkurujących ze sobą mechanizmów krystalograficznych poślizgów, bliźniakowania oraz mikropasm ścinania. Te ostatnie przejawiają się jako koncentracje odkształcenia postaciowego w formie cienkich transkrystalicznych warstewek o grubości rzędu 0,1 µm. Mikropasma ścinania współdziałają z aktywnymi mechanizmami krystalograficznego poślizgu lub bliźniakowania, kontrolując w różnym stopniu proces plastycznej deformacji. Na podstawie analizy aktualnego stanu badań prowadzonych na różnych poziomach obserwacji: wspomagane cyfrową korelacją obrazu badania mechaniczne – próby jedno- i dwuosiowe, badania in-situ przy użyciu mikroskopii elektronowej, badania tomografii atomowej w połączeniu z obliczeniami ab initio oraz dynamiki molekularnej, zaproponowano fizyczny obraz wielopoziomowej hierarchii oraz ewolucji pasm ścinania. Przedstawiono motywację fizykalną i heurystyczne podstawy opisu teoretycznego. Odniesiono się do znanych wyników z literatury, [2]. Przedyskutowano trudności z zastosowaniem prostego wielkoskalowego sposobu uśredniania oraz oryginalną koncepcję rozszerzenia pojęcia reprezentatywnego elementu objętości z wykorzystaniem znanej teorii propagacji powierzchni osobliwych jako fal silnej nieciągłości mikroskopowego pola prędkości. Przedstawiono nowe sformułowanie opisu prędkości odkształcenia postaciowego generowanego przez wielopoziomową hierarchię pasm ścinania z uwzględnieniem decyzyjnego procesu wyboru kluczowych efektów przepływu informacji dla poszczególnych poziomów obserwacji. ********* Experimental observations show that plastic deformation of metals is often produced as an effect of competing mechanisms of crystallographic glide, twinning and micro-shear banding. The micro-shear bands are observed as concentrated shear zones in the form of trans crystalline layers of the thickness of the order 0.1 µm. They cooperate with active mechanisms of crystallographic glide and/or twinning controlling to various degrees process of plastic flow. It has been observed that the change of the mechanism of plastic deformation has strong influence on mechanical properties of material under consideration. Therefore, the identification and elucidation of physical mechanisms that are responsible for initiation, growth and evolution of micro-shear bands is of fundamental importance for understanding the macroscopic behaviour of metallic materials. Basing on the analysis of recent state of the art of the investigations carried on different levels of observations: uni-axial and bi-axial mechanical tests enhanced with digital image correlation method, in-situ tests with use of electron microscopy, atom probe tomography in relation with ab initio and molecular dynamics computational simulations, certain physical model of multilevel hierarchy and evolution of shear bands is proposed. Physical motivation and heuristic foundations of theoretical description are discussed with reference to known results in the literature, [2]. The difficulties with application of a direct multiscale integration scheme are discussed and an original idea of an extension of the representative volume element concept with use of the known theory of the propagation of the singular surfaces of microscopic velocity field is proposed. A new formulation of the description of rate of shear strain generated by multilevel hierarchy of shear bands is formulated in the workflow integration approach, in which information from molecular simulation at different levels flows into the decision process. Keywords: pasma ścinania, hierarchia pasm ścinania, powierzchnia osobliwa, cyfrowa korelacja obrazu (DIC), shear bands, multilevel hierarchy of shear bands, singulatity surface, digital image correlation (DIC) Affiliations:
Pęcherski R.B. | - | IPPT PAN |
|  |
27. |
Nowak Z., Pęcherski R.B., Maj P.♦, Niestabilność plastycznego płynięcia w stopie Inconel 718. Badania doświadczalne Serrated flow in Inconel 718 alloy. Experimental investigations,
OMIS'2017, XII Konferencja NAukowa ODKSZTAŁCALNOŚĆ METALI I STOPÓW, 2017-11-21/11-24, Łańcut (PL), pp.47-48, 2017 Abstract: Badania doświadczalne efektu Portevin - Le Chatelier w Inconelu 718 przeprowadzono na płaskich próbkach. Do pomiarów zastosowano metodę cyfrowej korelacji obrazu (DIC), która jest efektywna i praktyczna dzięki bezkontaktowym pomiarom i dużej dokładności w ustalaniu charakterystycznych cech przestrzenno-czasowych deformacji próbki. Określenie takich cech zlokalizowanych pasm ścinania jest konieczne do zaproponowania modelu konstytutywnego dla metali wykazujących ten typ plastycznej niestabilności. Opracowany model konstytutywny pozwoli na numeryczne symulacje w pełnej skali 3D fizycznych testów z użyciem programu ABAQUS. Głównym celem pracy jest przedstawienie możliwości wykorzystania pomiarów uzyskanych techniką cyfrowej korelacji obrazu do wykrywania i charakteryzowania przestrzenno-czasowych cech efektu PLC w dostępnym komercyjnie stopie Inconel 718.
An experimental investigation of the Portevin–Le Chatelier effect in the Inconel 718 alloy is undertaken in this study through flat specimen geometries. Measurements based on digital image correlation (DIC) is an effective and practical optical technique due to the advantages of easy operation, non-contact, full field optical measurement, high accuracy and high computational efficiency for investigating the PLC effect and its spatio-temporal characteristics. The localization band characteristics are required to develop the constitutive relations for metals exhibiting this type of plastic instability, based on available material tests. The constitutive model can be used in full-scale 3D numerical simulations of the physical tests using the explicit solver of the finite element code ABAQUS. The objective of this paper is to show how DIC techniques are readily able to detect and characterize spatio-temporal features of the PLC behaviour of a commercial available Inconel 718 alloy. Keywords: stop Inconel 718, efekt Portevin-Le Chatelier, cyfrowa korelacja obrazu, Inconel 718 alloy, Portevin-Le Chatelier effect, Digital Image Correlation (DIC) Affiliations:
Nowak Z. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Maj P. | - | Warsaw University of Technology (PL) |
|  |
28. |
Kowalewski Z.L., Nowak Z., Pęcherski R.B., Investigations of Tantalum at Direct Impact Compression Tests on Miniaturized Specimens,
PLASTICITY 2017, INTERNATIONAL CONFERENCE ON PLASTICITY, DAMAGE, AND FRACTURE 2017, 2017-01-03/01-09, Puerto Vallarta (MX), pp.100-102, 2017 Abstract: In the paper the results of experimental and numerical investigations concerning an influence of strain rate on mechanical properties of pure tantalum are presented. Experiments were carried out using Direct Impact Compression Test (DICT) technique (Malinowski et al. [2007]). The Perzyna elasto-viscoplasticity theory (Perzyna [1966]) was applied to predict the dynamic compression yield strength of the tested material at strain rates from 1.0 x10-3 s−1 to 0.5 x106 s−1. Affiliations:
Kowalewski Z.L. | - | IPPT PAN | Nowak Z. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
29. |
Nowak Z., Kowalewski Z.L., Pęcherski R.B., A numerical solution of longitudinal wave propagation in a miniaturized specimens of tantalum at direct impact compression test,
DYMAT, 10th Workshop, 2016-08-24/08-26, Poznań (PL), pp.69-71, 2016 Abstract: The results of experimental and numerical investigations concerning an influence of strain rate on mechanical properties of pure tantalum are presented. Experiments were carried out using Direct Impact Compression Test (DICT) technique. The miniaturization concept of the experimental setup for the dimensions of specimen (diameter dS = 1.5 mm and thickness lS = 0.50 mm), Hopkinson transmitter bar diameter (dH = 3.0 mm) and the striker (diameter dI = 11.5 mm and the length lI =12 mm), together with application of a novel optical arrangement for measurement of striker velocity, enabled compression tests to be executed at strain rates from 1.0 x103 s−1 to 0.5 x106 s−1. The Perzyna elasto-viscoplasticity theory is applied to predict the dynamic compression yield strength of the tested material at different strain rates. In the course of specimens deformation by means of the DICT technique, it was observed that the peak force obtained from the strain gauge mounted on the transmitter Hopkinson bar was lower than the peak force obtained within the framework of the uniaxial stress wave analysis. An explanation of this discrepancy is provided due to the analysis of the localization of deformation in the tested specimens considered as three-dimensional body subjected to high strain rate loading and the resulting stress wave attenuation as it propagates within the specimen. Keywords: direct impact test, numerical simulations, tantalum Affiliations:
Nowak Z. | - | IPPT PAN | Kowalewski Z.L. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
30. |
Pęcherski R.B., Nalepka K.T., Nalepka P.♦, Sztwiertnia K.♦, Kret S.♦, Ustrzycka A., Assessment of the strength of nanocomposites based on interface bonding analysis,
ICTAM XXIV, 24th International Congress of Theoretical and Applied Mechanics, 2016-08-21/08-26, Montréal (CA), pp.2384-2385, 2016 Abstract: Recent investigations reveal that interface bonding strength is dependent on the relative orientation of crystallites of the both phases [2]. The experimental, theoretical and computational investigations confirm this observation in the case of Cu/Al2O3 system, [3], [4]. It is shown that the statistical distribution of the values of interface strength for different relative orientations of bonded phases should be included in the phenomenological model of the damage initiation in nanocomposites. The novelty of the presented study is the combination of different experimental techniques: HRTEM, EBSD and molecular dynamics simulations with phenomenological theory of damage development in nanocomposites due to debonding at the interphase boundary [5], [6], [7]. A class of new models with the yield condition determined by one of quadric surfaces, in particular paraboloid or ellipsoid one is considered and the comparison with popular Gurson approach is discussed, [8]. Keywords: nanocompistes, strength, interface, bonding, HRTEM, EBSD, molecular dynamics Affiliations:
Pęcherski R.B. | - | IPPT PAN | Nalepka K.T. | - | IPPT PAN | Nalepka P. | - | Agriculture University in Krakow (PL) | Sztwiertnia K. | - | other affiliation | Kret S. | - | Institute of Physics, Polish Academy of Sciences (PL) | Ustrzycka A. | - | IPPT PAN |
|  |
31. |
Nalepka P.♦, Nalepka K.T., Pęcherski R.B., Analysis of deformation mechanisms in Cu /Al2O3 interfaces with the use of HRTEM images,
SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), No.P243, pp.1-2, 2016 Abstract: The composition of metal with ceramics is applied to many devices, structural elements of machines as well as their equipment. Therefore, evaluating the strength of interfaces of this type becomes an important scientific issue of fundamental character. Numerous attempts are made to solve the posed problem, both experimental and theoretical ones. The presented approach enables local, more precise determining the mechanical properties of interfaces. The basis of conducted calculations is the geometry of the interface strongly preferred by the considered system of materials. It is defined by the mutual orientation of crystallites of two phases and the position of the plane boundary. The combination of two advanced research methods: electron back-scatter diffraction (EBSD) and high resolution transmission electron microscopy (HRTEM) enables identification of this crucial characteristics. The second of them additionally reveals a representative microstructure of the interface in the form of a projection. We reconstruct it in three dimensions by means of molecular dynamics (MD) simulations. In this way, we identify deformation mechanisms that enable the formation of the bonding between the metallic phase and ceramic one. Keywords: nanocomposites, deformation in interface, HRTEM Affiliations:
Nalepka P. | - | Agriculture University in Krakow (PL) | Nalepka K.T. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
32. |
Frąś L.J., Jarząbek D.M., Dziekoński C., Pęcherski R.B., Viscoplastic deformation of magnethoreological solids,
SolMech 2016, 40th Solid Mechanics Conference, 2016-08-29/09-02, Warszawa (PL), No.P244, pp.1-2, 2016 Abstract: The microsized (~10µm) ferroelements build the structure of magenthoreological (MR) fluid. This two phase material in neutral state behaves as a fluid but in magnetic field becomes a solid and has properties of elasto-viscoplastic material. This is due to the skeleton made by ferrolements connected into braids. The aim of the paper is to identify the physical mechanisms of deformation of such a structure with use of own set up for in situ microscopic observations. Keywords: magnethoreological solids, viscoplasticity, ferroelements, compression test, shear banding Affiliations:
Frąś L.J. | - | IPPT PAN | Jarząbek D.M. | - | IPPT PAN | Dziekoński C. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
33. |
Pęcherski R.B., Nowak M., Application of X-ray micro-computed tomography for numerical simulation of auxetic foam fabrication,
ESMC 2015, 9th European Solid Mechanics Conference, 2015-07-06/07-10, Leganés-Madrid (ES), Vol.1, pp.#1248-1-2, 2015 Abstract: The design of new multifunctional foams as well as metal-ceramic and polymer-ceramic composites of ceramic foam structure, which can be applied as lightweight wear resistant elements, fire resistant or fire retardant parts, piezoelectric actuators etc., requires the solution of the following questions:
- in what way to fabricate polyurethane, metallic or ceramic foams and preforms of assumed skeleton structure,
- how to produce tomograms, i.e. 3D virtual volume reconstructions of real foam structure [1],
- how to elaborate methods of numerical simulations of fabrication processes of auxetic foams with use of the tomograms.
Depending on manufacturing method the cells obtain convex or concave shape. The materials with convex cell structure reveal positive Poisson's ratio. The complex structure of the foam related with reentrant cells produce the oposite effect - the negative Poisson's ratio is observed and such foams become auxetic. The aim of the presented study is to tackle the third question related with numerical simulation of fabrication processes of auxetic foams. Keywords: auxetic foam, micro-tomography, negative Poisson’s ratio, numerical simulation, metallic foam, open-cell foam, fabrication Affiliations:
Pęcherski R.B. | - | IPPT PAN | Nowak M. | - | IPPT PAN |
|  |
34. |
Nowak M., Pęcherski R.B., Nowak Z., Frąś L.J., Numeryczna rekonstrukcja struktury pianek otwartokomórkowych z wykorzystaniem tomografii komuterowej,
OMIS'2015, XI Konferencja Odkształcalność Metali i Stopów, 2015-11-17/11-20, Łańcut (PL), pp.61-62, 2015 Abstract: Przedmiotem badań niniejszej pracy jest numeryczna rekonstrukcja struktur rzeczywistych pianek otwartokomórkowych w celu wygenerowania reprezentatywnego elementu objetości. Analizowane są dwa rodzaje pianek (ceramiczna i polimerowa), których porowatość wynosi odpowiednio 90% i 94%. Oba rodzaje pianek zostały przebadane z użyciem mikrotomografu komputerowego. Uzyskane dane zostały zaimportowane do programu ScanIP, przy pomocy którego przeprowadzono cyfrową obróbkę uzyskanych obrazów oraz wydzielono fazę reprezentującą szkielet pianki. Keywords: numeryczna rekonstrukcja, struktury otwartokomórkowe, pianki metaliczne, mikrotomografia komputerowa Affiliations:
Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Nowak Z. | - | IPPT PAN | Frąś L.J. | - | IPPT PAN |
|  |
35. |
Nowak Z., Nowak M., Pęcherski R.B., Numeryczna analiza dynamicznych procesów ściskania metalicznych pianek otwartokomórkowych,
OMIS'2015, XI Konferencja Odkształcalność Metali i Stopów, 2015-11-17/11-20, Łańcut (PL), pp.59-60, 2015 Abstract: W pracy dokonano analizy wielkości sił zgniatania, energii dyssypacji oraz sposobów deformowania się dwóch typów metalicznych pianek otwartokomórkowych sciskanych dynamicznie z różnymi prędkościami. Zbadano pianki o strukturze wypukłej oraz o komórkach wklęsłych, które charakteryzują się ujemnym wspołczynnikiem Poissona. Keywords: dynamiczna analiza, procesy zgniatania, pianki metaliczne, struktury otwarokomórkowe Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
36. |
Frąś L.J., Konowrocki R., Pęcherski R.B., Niesprężyste deformacje materiałów magnetoreologicznych. Doświadczalna wizualizacja i model fizyczny,
OMIS'2015, XI Konferencja Odkształcalność Metali i Stopów, 2015-11-17/11-20, Łańcut (PL), pp.13-14, 2015 Abstract: Magnetorheological materials are commonly used in technical devices because of specific behaviour in magnetic field. The magnetoactive particles are immersed in the carried fluid. The material becomes solid under the influence of magnetic field. The structure of solid material consists of the chains of the particles lying along the direction of magnetic field and the material under the stress is deforming as a solid body. The present studies are focused on the microscopic and phenomenological models of non-newtonian fluid. However, the mechanisms of deformation in solidified material under magnetic field require further investigations. The aim of the paper is to present the experimental visualization of the rearrangements of the particles in the activated by magnetic field chains. Basing on microscopic observations, the hypothesis is formulated that the mechanism of micro-shear banding is responsible for inelastic deformation of magnetorheological material. The discussed physical model makes the basis of the material description within the framework of the Perzyna viscoplasticity theory. Keywords: magnetorheological fluid, magnetorheological gel, Perzyna viscoplastic model Affiliations:
Frąś L.J. | - | IPPT PAN | Konowrocki R. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
37. |
Frąś L.J., Pęcherski R.B., Viscoplasticity of magnetorheological materials - theoretical description and experimental investigations,
PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.673-674, 2015 Abstract: The extension of viscoplasticity Perzyna's model for the field of magnetorheological materials is proposed. The model is adopted to identify the mechanisms of microscopic rearrangement of ferroelements producing visible increase of material stiffness, in particular increase of shear modulus. The project of laboratory test stand is presented. It is based on Split Hopkinson Pressure Bar set-up equipped with container for magnetorheological fluid and coil to control it. Keywords: magnetorheological fluid, magnetorheological gel, Pezryna viscoplasticity model, Split Hopkinson Pressure Bar Affiliations:
Frąś L.J. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
38. |
Pęcherski R.B., Nowak M., Frąś L.J., Numerical simulations of auxetic metallic foam fabrication process,
PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.857-858, 2015 Abstract: The subject of te study are metallic open-cell foams. In particular, the foam of Cu skeleton is considered. To simulate the deformation process of such a material the finite element program ABAQUS is used. The tomogram reconstructing the 3D virtual volume of a real foam structure with the use of computed tomography is applied to formulate the finite element model of the convex open-cell foam cube of the edge of 800 voxels created with application of ABAQUS/CAE. The initial cube of convex open-cell skeleton is subjected to three-axial compression applied as uniform displacements normal to the surface of cube faces in order to simulate numerically auxetic foam fabrication process. Keywords: auxetic foam, micro-tomography, tomograms, negative Poisson's ration, numerical simulation, metallic foam, open-cell foam, foam fabrication Affiliations:
Pęcherski R.B. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Frąś L.J. | - | IPPT PAN |
|  |
39. |
Nowak Z., Nowak M., Pęcherski R.B., Potoczek M.♦, Śliwa R.E.♦, Numerical simulations of mechanical properties of alumina foams based on computer tomography,
PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.853-854, 2015 Abstract: The aim of the paper is to apply the results of microtomography of alumina foam to create the numerical model and perform the numerical simulations of compression tests. The geometric characteristics of real foam samples are estimated from tomographic and scanning electron microscopy images. The performance of the reconstructed models is compared to experimental values of elastic moduli. Keywords: Alumina open-cell foam, the computed tomography microstructure, Young modulus, the compressive strength of alumina foams Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Potoczek M. | - | Rzeszów University of Technology (PL) | Śliwa R.E. | - | Rzeszów University of Technology (PL) |
|  |
40. |
Pęcherski R.B., Nowak M., Nowak Z., Numerical simulation of dynamic processes in metal foams. I. virtual metallic foam,
PETER 2015, Annual International Workshop on Dynamic Behaviour of Structures and Materials, Interaction and Friction Across the Strain Rates, 2015-08-26/08-28, London (GB), Vol.1, pp.19-20, 2015 Abstract: The design of new multifunctional foams requires the solution of the following questions: in what way to fabricate metallic foams of assumed skeleton structure, how to produce tomograms, i.e. 3D virtual foam reconstructions of real foam structure [1], how to elaborate methods of numerical simulations of assumed processes in auxetic foams with use of the tomograms. Depending on manufacturing method the cells obtain convex or concave shape. The materials with convex cell structure reveal positive value of Poisson’s ratio, that is if a sample is stretching, then its cross-section is getting thinner. The complex structure of the foam related with reentrant cells produces the opposite effect during stretching of a sample, i.e. its cross-section is increasing. Then the negative Poisson’s ratio is observed and such foams become auxetic. The aim of the study is to study the third question. The motivation is given in [2], where it has been stressed that numerical simulations predicting a new material’s behaviour reduce laboratory costs and accelerates the trial and error procedure. Keywords: Metallic open-cell foam with the convex or concave cells, the foam of OFHC Cu skeleton, the foam structure with use of computer tomography images, numerical simulation of dynamic processes in metal foams Affiliations:
Pęcherski R.B. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Nowak Z. | - | IPPT PAN |
|  |
41. |
Nowak Z., Nowak M., Pęcherski R.B., Numerical simulation of the dynamic processes in metal foams. Part II. Compression tests of open cell copper foams,
PETER 2015, Annual International Workshop on Dynamic Behaviour of Structures and Materials, Interaction and Friction Across the Strain Rates, 2015-08-26/08-28, London (GB), Vol.1, pp.21-22, 2015 Abstract: Metallic cellular materials have been widely acknowledged for their multifunctional applications related also with energy absorption capability in addition to their light weight. In recent years, the auxetic materials revealing negative Poisson’s ratio have attracted much attention. Up to date, the research of auxetics is mainly concentrating on the cell design and the static response, although the auxetic materials also demonstrate potential for energy absorption, fracture retardant, and high-velocity impacts resistance. In the paper, a comparative study is reported on the high-velocity impact responses of two type metallic cellular foams, that is, convex open cell foam and auxetic foam. The material of the skeleton of the virtual foam is assumed to be isotropic and elastic-plastic. For numerical simulations the constitutive relation is applied which defines the behaviour of oxygen-free high conductivity copper (OFHC) using the experimental data reported in Nemat-Nasser and Li (1998) and Rusinek at al. (2010). The impact limits and absorption energy of the two foams are obtained by means of explicit nonlinear finite element simulations using ABAQUS. It has been found that the auxetic foam is superior to the convex cell foam in impact resistance because of the material concentration at the impacted area due to the negative Poisson’s ratio effect. Keywords: Open-cell foams, the impact resistance of convex and auxetic copper (OFHC) foams Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
42. |
Lumelskyj D., Rojek J., Pęcherski R.B., Grosman F.♦, Tkocz M.♦, Numerical study of an effect of friction in Nakazima formability test,
8th Workshop on Dynamic Behaviour of Materials and Its Applications in Industrial Processes, 2014-06-25/06-27, Warszawa (PL), pp.45-46, 2014 Abstract: This paper presents numerical investigations of the influence of friction in the contact between sheet and a punch on sheet deformation in Nakazima type formabilitybtests. The Nakazima test [1] is one of the most comonnly used tests to study experimentally formability of metal sheets. It consits in stretching of a sheet specimen by means of a hemispherical punch until fracture occurs.
The aim of this study has been to numerically identify frictional conditions in a selected case of the Nakazima test and study numerically effect of change of friction on strain path and forming limit curve. (FLC). Numerical simulations have been performed assuming the data corresponding to own lboratory tests carried out for the steel grade HC380LA 1.5 mm thick. Keywords: formabilty of metal sheets, Nakazima test, numerical simulation, friction effects Affiliations:
Lumelskyj D. | - | IPPT PAN | Rojek J. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Grosman F. | - | Silesian University of Technology (PL) | Tkocz M. | - | Silesian University of Technology (PL) |
|  |
43. |
Nowak Z., Nowak M., Pęcherski R.B., Numerical simulation of metal forming processes with application of modified elastic-plastic model,
8th Workshop on Dynamic Behaviour of Materials and Its Applications in Industrial Processes, 2014-06-25/06-27, Warszawa (PL), pp.51-52, 2014 Abstract: Finite element method is an efficient numerical tool to analyse problems of the sheet metal forming processes including cup drawing and stamping. Proper description of material properties is crucial for accurate analysis. In particular, the anisotropy and asymmetry of elastic range, related with strength differential effect (SDE), of considered materials play an important role in finite element simulation. The paper presents a new yield criterion for the transversal isotropy of metal sheets under plane stress conditions which is an extension of the isotropic yield function proposed by Burzyński (1928) (Studium nad hipotezami Burzyński’s doctoral dissertation ”Study on material effort hypotheses”, Engng. Trans., 2009, t. 57, nr 3–4, s. 185–215). One additional coefficient has been introduced in order to allow a better representation of plastic behavior of metal sheets. The proposed yield condition includes the influence of first invariant of the stress tensor and also the strength differential effect. The system of equations describing the sheet metal forming process is solved by algorithm using the return mapping procedure. Plane stress constraint is incorporated into the Newton-Raphson iteration loop. The proposed algorithm is verified by performing a numerical test using shell elements in commercial FEM software ABAQUS/EXPLICIT with a developed VUMAT subroutine. Keywords: the strength differential effect, a new yield criterion for the transversal isotropy of metal sheets, numerical simulations of cup deep drawing process Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
44. |
Nowak M., Nowak Z., Pęcherski R.B., Energy-based multisurface limit criteria in application for modelling and simulation of metal forming processes,
8th Workshop on Dynamic Behaviour of Materials and Its Applications in Industrial Processes, 2014-06-25/06-27, Warszawa (PL), pp.53-54, 2014 Abstract: Metallic materials are usually used in engineering applications in the as received state. In such a case, developing in in the course of manufacturing processes texture induces anisotropy of mechanical properties and produces often the so-called strength differential effect (SDE).The precise description of elastic properties and formulation of limit criterion requires application of the formalism used typically for anisotropic solids. It is a complex and difficult task related with
proper experimental characterisation of all material parameters. In some cases, however, a simple model of isotropic solid revealing possible strength differential effect and certain correction for the limit strength in shear can be proposed. It is in accord with the observation that developing texture influences mostly shear strength of metallic solids. Keywords: A simple model of isotropic solid, strength differential effect, the limit strength in shear Affiliations:
Nowak M. | - | IPPT PAN | Nowak Z. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
45. |
Lumelskyj D., Rojek J., Pęcherski R.B., Grosman F.♦, Tkocz M.♦, Influence of friction on strain distribution in Nakazima formability test of circular specimen,
AutoMetForm/SFU 2014, New Materials for Vehicle Components, 2014-11-03/11-05, Freiburg (DE), pp.214-217, 2014 Abstract: This paper presents experimental and numerical investigations of the influence of friction on sheet deformation in Nakazima type formability tests. Numerical simulations have been performed using the authors own explicit dynamic finite element program. Strain distribution obtained in numerical analyses has been compared with experimental data. Location of fracture was of major interest in this specimen as required by the standards can be obtained for low value of the friction coefficient. With the increase of the friction coefficient the fracture is displaced further from the center. Keywords: formability of metal sheets, Nakazima test, numerical simulation, friction effect, failure location Affiliations:
Lumelskyj D. | - | IPPT PAN | Rojek J. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Grosman F. | - | Silesian University of Technology (PL) | Tkocz M. | - | Silesian University of Technology (PL) |
|  |
46. |
Nowak Z., Nowak M., Pęcherski R.B., Potoczek M.♦, Śliwa R.E.♦, Własności mechaniczne pianek ceramicznych o komórkach otwartych i różnej porowatości,
IX Seminarium Naukowe ZINTEGROWANE STUDIA PODSTAW DEFORMACJI PLASTYCZNEJ METALI PLASTMET, 2014-11-25/11-28, Łańcut (PL), pp.1-2, 2014 Abstract: W pracy określono własności mechaniczne i przedstawiono model numeryczny ceramicznej pianki korundowej, otrzymanej metodą żelowania spienionej zawiesiny (gelcasting). Metoda ta pozwala wytwarzać pianki zawierające kmórki o różnej wielkości, a w konsekwencji otrzymywać pianki o różnej porowatości. Wielkości charakteryzujące geometrię rzeczywistych pianek ustalono z wykorzystaniem obrazów tomograficznych 3D oraz obrazów z mikroskopu skaningowego. Informacje te wykorzystano przy opracowaniu modelu numerycznego badanej pianki. Symulacje numeryczne procesów deformacji przeprowadzono z zastosowaniem programu elementow skończonych ABAQUS. Keywords: pianki ceramiczne, metoda żelowania, porowatość, symulacje numeryczne procesów deformacji tomografia komputerowa, mikroskopia skaningowa Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Potoczek M. | - | Rzeszów University of Technology (PL) | Śliwa R.E. | - | Rzeszów University of Technology (PL) |
|  |
47. |
Nalepka K.T., Pęcherski R.B., Plastic flow and failure of solids. Modelling across scales,
SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.25-26, 2014 Abstract: The aim of the presentation is to discuss the classical problems of elastic limit criteria from the perspective of basic quantum mechanical approach [1]. In the case of metallic solids the multiscale mechanisms of plastic deformation and failure are analyzed [2]. In particular, the role of shear banding responsible for plastic flow is elucidated [3]. Keywords: elastic limit criteria, metal/ceramic interface, copper/saphire nanocomposites, PLD, HRTEM, EBSD Affiliations:
Nalepka K.T. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
48. |
Lumelskyj D., Rojek J., Pęcherski R.B., Grosman F.♦, Tkocz M.♦, Numerical investigation of influence of friction on strain distribution and forming limit curve in Nakazima formability test,
SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.45-46, 2014 Abstract: This paper presents numerical investigations of the influence of friction in the contact between sheet and a punch on sheet deformation in Nakazima type formability tests. The Nakazima test [1] is one of the most commonly used tests to study experimentally formability of metal sheets. It consists in stretching of a sheet specimen by means of a hemispherical punch until occurrence of fracture. Keywords: formability, Nakazima test, influence of friction, numerical simulations, deformation of metal sheets Affiliations:
Lumelskyj D. | - | IPPT PAN | Rojek J. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Grosman F. | - | Silesian University of Technology (PL) | Tkocz M. | - | Silesian University of Technology (PL) |
|  |
49. |
Nowak Z., Grosman F.♦, Lumelskyj D., Nowak M., Pęcherski R.B., Rojek J., Tkocz M.♦, Metal cup deep drawing processes – numerical simulation and experimental verification,
SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.47-48, 2014 Abstract: Finite element method is an efficient numerical tool to analyse problems of the sheet metal forming processes in particular cup drawing and stamping. Proper description of material properties is crucial for accurate analysis. In particular, the anisotropy and asymmetry of elastic range, which is related with strength differential effect (SDE), of considered materials play an important role in finite element simulation. For metal forming analysis with use of traditional models many experimental tests are usually needed to obtain the adequate description of anisotropic behaviour of metal sheets. Therefore, the search for new models, which are based on simplified description of the effects of anisotropy and SDE requiring less experimental tests seems to be justified.
The paper presents the application of a new yield criterion for the transversal isotropy of metal sheets under plane stress conditions. The proposed criterion is based on the study of yield criteria accounting for SDE and anisotropy nade by W. Burzyński [1]. The system of equations describing the sheet metal forming process is solved by the algorithm using the return mapping procedure. Plane stress constraint is incorporated into the Newton-Raphson iteration loop. The proposed algorithm is verified by performing the numerical calculations using shell elements of the commercial FEM sftware ABAQUS/EXPLICIT with own VUMAT subroutine. Keywords: metal sheet forming, metal cup deep drawing, FE numerical simulations, strength differential effect, anisotropy and asymmetry of elastic range, transversal isotropy Affiliations:
Nowak Z. | - | IPPT PAN | Grosman F. | - | Silesian University of Technology (PL) | Lumelskyj D. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Rojek J. | - | IPPT PAN | Tkocz M. | - | Silesian University of Technology (PL) |
|  |
50. |
Nowak Z., Nowak M., Pęcherski R.B., Potoczek M.♦, Śliwa R.E.♦, Numerical characterization and estimation of elastic properties of ceramic foams,
7th International Workshop on Dynamic Behaviour of Materials and its Applications in Industrial Processes, 2013-05-08/05-10, Madryt (ES), pp.41-42, 2013 Abstract: In this work a numerical model of real foam with different cell sizes is presented and its applications are discussed. Geometric characteristics of real foam samples were estimated from tomographic and scanning electron microscopy images. Using this information, numerical foam model was proposed. The examples of generated numerically structures are shown. A good agreement between numerical model and the results elaborated from microtomography was obtained. Keywords: Alumina open-cell foam, foam with different cell sizes, numerical foam model based on tomographic and scanning electron microscopy images Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Potoczek M. | - | Rzeszów University of Technology (PL) | Śliwa R.E. | - | Rzeszów University of Technology (PL) |
|  |
51. |
Nowak Z., Nowak M., Pęcherski R.B., Numerical analysis of the cup deep drawing process with use of new yield condition for plane stress states,
CMM 2013, 20th International Conference on Computer Methods in Mechanics, 2013-08-27/08-31, Poznań (PL), No.MS07, pp.9-10, 2013 Abstract: The elastoplastic constitutive equations for materials under plane stress condition with new yield criterion have been proposed. This yield condition accounts for the effect of strength differential effect. The system of equations of sheet metal forming process is solved by algorithm using the return mapping procedure. Plane stress constrain is incorporated into the Newton-Raphson iteration loop. The proposed algorithm is verified by performing numerical tests using shell elements in commercial FEM software ABAQUS/EXPLICIT with developed VUMAT subroutine. It is shown that the proposed approach provides the satisfactory prediction of material behaviour, at least in the cases when the anisotropy effects are not so advanced. Keywords: anisotropic behaviour of metal sheets, strength differential effect, explicit finite element analysis, plane stress Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
52. |
Nowak Z., Nowak M., Pęcherski R.B., Potoczek M.♦, Śliwa R.E.♦, The Compressive Strength of Ceramic Open-Cell Foams with the Variability of Cell Sizes,
ICMM3, 3rd International Conference on Material Modelling incorporating 13th European Mechanics of Materials Conference, 2013-09-08/09-11, Warszawa (PL), pp.315-316, 2013 Abstract: New aeronautic materials are obtained by liquid metal infiltration into a ceramic foam, called a preform. Ceramic preforms are produced by a new method of manufacturing of porous ceramics foams known as gelcasting. Porous ceramics fabricated by this method is characterized by a continuous network of spherical cells interconnected by circular windows. The open porosity due to the presence of windows creates good hydro-dynamical properties for liquid metals infiltration. For better understanding mechanical properties of such composites a numerical model of ceramic foam is needed, see e. g. ref. [1-4]. Geometry of ceramic foams can be generated in two steps. First, the coordinates of the center point of the spherical bubbles and its diameter are produced by PYTHON scripts. The diameters of spherical bubbles were estimated from microtomography and scanning electron microscopy images. On the other hand, the coordinates of the center points are determined in such a way that the bubbles have to intersect with each other. Finally, the intersecting bubbles are subtracted from the bulk block of any shape. Using this information, numerical foam model was proposed and good agreement between numerical model and real foam structure from microtomography was obtained. In this work we present a numerical model of real foam of alumina with different cell sizes and discuss its mechanical properties using several examples. The numerical simulations of uniaxial compression test have been performed. As a result the compressive strength of the investigated foams with porosities changing from 60 to 95 % were determined. Keywords: Porous ceramics foams produced by gelcasting, open-cell ceramic foam, the numerical simulations of uniaxial compression test, the compressive strength of alumina foams with porosities changing from 60 to 95 % Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Potoczek M. | - | Rzeszów University of Technology (PL) | Śliwa R.E. | - | Rzeszów University of Technology (PL) |
|  |
53. |
Nowak M., Nowak Z., Pęcherski R.B., Potoczek M.♦, Śliwa R.E.♦, Ocena mechanicznych właściwości ceramicznej pianki poddanej procesowi infiltracji,
OMIS 2013, X Jubileuszowa Konferencja ODKSZTAŁCALNOŚĆ METALI I STOPÓW, 2013-11-26/11-29, Łańcut (PL), pp.1-2, 2013 Abstract: Celem pracy jest ocena granicznych ciśnień oraz temperatury procesu, dla których proces infiltracji zachodzi bez uszkodzenia pianki w skali makroskopowej. W pracy przedstawiono numeryczny model procesu wypełniania ceramicznej preformy o otwartej strukturze porów. W procesie wypełniania preformy ciekłym metalem lokalny wzrost naprężeń i kruchość materiału powodują pękanie części elementów pianki. Opracowano model numeryczny tego procesu, który zaimplementowano w programie ABAQUS. Dla określenia stanu naprężenia w piance użyto sprzężonej metody CEL (ang. the coupled Eulerian-Lagrangian method) w programie Abaqus/Explicit. Keywords: Proces infiltracji ceramicznych pianek ciekłym metalem, ocena granicznych ciśnień oraz temperatury procesu Affiliations:
Nowak M. | - | IPPT PAN | Nowak Z. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN | Potoczek M. | - | Rzeszów University of Technology (PL) | Śliwa R.E. | - | Rzeszów University of Technology (PL) |
|  |
54. |
Nowak Z., Nowak M., Pęcherski R.B., A plane stress elastic-plastic analysis of sheet metal cup deep drawing processes,
SSTA, 10th Jubilee Conference on Shell Structures - Theory and Applications, 2013-10-16/10-18, Gdańsk (PL), pp.129-132, 2013 Abstract: The paper presents a new yield criterion for the transversal isotropy of metal sheets under plane-stress conditions which is an extension of the isotropic yield function proposed by Burzynski (Burzynski W. 1928). Studium nad hipotezami Burzynski's doctoral dissertation Keywords: elastic-plastic analysis, transversal isotropy, metal sheets, deep drawing process, FE simulations, Burzyński yield condition, strength differential effect Affiliations:
Nowak Z. | - | IPPT PAN | Nowak M. | - | IPPT PAN | Pęcherski R.B. | - | IPPT PAN |
|  |
55. |
Rojek J., Lumelskyj D., Grosman F.♦, Tkocz M.♦, Pęcherski R.B., Chorzępa W.♦, Graniczne krzywe tłoczności przy zmiennych ścieżkach odkształcenia,
PLASMET/2012, VIII Seminarium Naukowe Zintegrowane Studia Podstaw Deformacji Plastycznej Metali, 2012-11-20/11-23, Łańcut (PL), pp.x1-x3, 2012 |  |
56. |
Frąś T., Luckner J., Nowak M., Nowak Z., Pęcherski R.B., Analiza procesu formowania blach z uwzględnieniem różnicy wytrzymałości przy ściskaniu i rozciąganiu,
PLASMET/2012, VIII Seminarium Naukowe Zintegrowane Studia Podstaw Deformacji Plastycznej Metali, 2012-11-20/11-23, Łańcut (PL), pp.1-3, 2012 |  |
57. |
Frąś T., Luckner J., Nowak M., Nowak Z., Pęcherski R.B., Rusinek A.♦, Stręk A.♦, Zastosowanie kryteriów granicznych Burzyńskiego I. Metale i kompozyty metaliczno-ceramiczne II. Pianki metaliczne,
PLASMET/2012, VIII Seminarium Naukowe Zintegrowane Studia Podstaw Deformacji Plastycznej Metali, 2012-11-20/11-23, Łańcut (PL), pp.1-4, 2012 |  |
58. |
Nowak M., Nowak Z., Pęcherski R.B., Potoczek M.♦, Śliwa R.E.♦, Opracowanie metody rekonstrukcji struktury geometrycznej i sposobu wyznaczania modułu Younga pianek ceramicznych,
PLASMET/2012, VIII Seminarium Naukowe Zintegrowane Studia Podstaw Deformacji Plastycznej Metali, 2012-11-20/11-23, Łańcut (PL), pp.1-3, 2012 |  |
59. |
Ostrowska-Maciejewska J.♦, Pęcherski R.B., Szeptyński P.♦, Matematyczne podstawy warunku granicznego dla materiałów anizotropowych,
PLASMET/2012, VIII Seminarium Naukowe Zintegrowane Studia Podstaw Deformacji Plastycznej Metali, 2012-11-20/11-23, Łańcut (PL), pp.1-3, 2012 |  |
60. |
Lumelskyj D., Rojek J., Pęcherski R.B., Grosman F.♦, Tkocz M.♦, Numerical Studies of Formability of Pre-Stretched Steel Sheet,
SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.172-173, 2012 |  |
61. |
Frąś T., Pęcherski R.B., Rusinek A.♦, Experimental investigations of the influence of moderate strains and strain rates on the yield surface of OFHC copper,
SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.122-123, 2012 |  |
62. |
Nowak Z., Frąś T., Nowak M., Pęcherski R.B., Analysis of the forming Processes Accounting for Asymmetry of Elastic Range,
SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.92-93, 2012 |  |
63. |
Nowak M., Nowak Z., Pęcherski R.B., Potoczek M.♦, Śliwa R.E.♦, On the Geometry and Compressive Strength of Ceramic Foams,
SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.174-175, 2012 |  |
64. |
Szeptyński P.♦, Ostrowska-Maciejewska J.♦, Pęcherski R.B., Extension of The Rychlewski Limit State Criterion Accounting For The Asymmetry of Elastic Range,
SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.106-107, 2012 |  |
65. |
Nowak M., Luckner J., Nowak Z., Pęcherski R.B., Numerical simulation of the forming processes accounting for asymmetry of elastic range and initial anisotropy,
CMM 2011, 19th International Conference on Computer Methods in Mechanics, 2011-05-09/05-12, Warszawa (PL), pp.383-1-2, 2011 |  |
66. |
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 | |
67. |
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 | |