Tabela A z publikacjami w czasopismach wyróżnionych w Journal Citation Reports (JCR) 
Tabela B z publikacjami w czasopismach zagranicznych i krajowych, wyróżnionych na liście MNSzW
Publikacje konferencyjne indeksowane w bazie Web of Science Core Collection
Inne publikacje w pozostałych czasopismach i wydawnictwach konferencyjnych
Afiliacja IPPT PAN

1.Sadowski P., Stupkiewicz S., Friction in lubricated soft-on-hard, hard-on-soft and soft-on-soft sliding contacts, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2018.08.025, Vol.129, pp.246-256, 2019
Sadowski P., Stupkiewicz S., Friction in lubricated soft-on-hard, hard-on-soft and soft-on-soft sliding contacts, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2018.08.025, Vol.129, pp.246-256, 2019

Abstract:
Friction in lubricated soft contacts is examined using a ball-on-disc tribometer with the focus on the effect of configuration. In the soft-on-hard and hard-on-soft configurations, one of the contact-pair members is soft while the other one is hard. In the soft-on-soft configuration, both members are soft. For a soft disc, time-dependent viscoelastic deformations contribute to friction. Upon correction for the hysteretic losses, estimated using a theoretical model, the friction coefficient in the full-film regime does not depend on configuration. This holds also for high loads, when the deformations are finite. The combined effect of configuration and surface roughness on the transition from the full-film to the mixed lubrication regime is also examined.

Keywords:
Soft-EHL, Mixed lubrication, Surface roughness, Finite deformation

(35p.)
2.Lewandowski M.J., Stupkiewicz S., Size effects in wedge indentation predicted by a gradient-enhanced crystal-plasticity model, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/j.ijplas.2018.05.008, Vol.109, pp.54-78, 2018
Lewandowski M.J., Stupkiewicz S., Size effects in wedge indentation predicted by a gradient-enhanced crystal-plasticity model, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/j.ijplas.2018.05.008, Vol.109, pp.54-78, 2018

Abstract:
A recently developed gradient-enhanced crystal-plasticity model is applied to predict the size effects in wedge indentation. In the model, the internal length scale is defined through standard quantities that appear in the underlying non-gradient hardening law. A careful calibration of the non-gradient hardening law is thus performed, and the model is validated against published experimental results. To this end, a comprehensive computational study of wedge indentation into a nickel single crystal is performed, and the obtained results show a good agreement with the experiment in terms of the load–penetration depth curves for three wedge angles, as well as in terms of the distributions of lattice rotation, GND density, and net Burgers vector. For the indentation depth of about 200 μm, as employed in the experiment, the predicted size effects are insignificant. Accordingly, the size effects are next studied for the indentation depth varied between 200 μm and 1 μm. As an intermediate result, apparently not published to date, the general 3D crystal plasticity model with anisotropic hardening is consistently reduced to a 2D plane-strain model in which plastic deformation is realized by three effective in-plane slip systems, each representing two crystallographic slip systems.

Keywords:
Indentation size effect, Geometrically necessary dislocations, Crystal plasticity, Gradient plasticity, Finite-element method

(45p.)
3.Ryś M., Petryk H., Gradient crystal plasticity models with a natural length scale in the hardening law, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/j.ijplas.2018.07.015, Vol.111, pp.168-187, 2018
Ryś M., Petryk H., Gradient crystal plasticity models with a natural length scale in the hardening law, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/j.ijplas.2018.07.015, Vol.111, pp.168-187, 2018

Abstract:
A class of crystal plasticity models based on the concept of microforces conjugate to slip-rate gradients is examined in the small strain framework. As an extension of the usual formulation, slip-rate gradients are introduced here into the incremental hardening law, including in this way a natural internal length scale derived recently in a closed form from relationships of the physically-based dislocation theory of plasticity. The condition for plastic flow on a crystallographic slip system involves other length scales, associated with the second-order gradients of slip and slip rate in energetic and dissipative terms, respectively. The interplay between the length-scales of physically different origin is illustrated by the examples of monotonic and cyclic deformation of one- and two-dimensional models of Cu single crystals with boundary constraints imposed on plastic slips. It is shown that selected earlier results are reproduced accurately if one or another length scale ceases to play an essential role. For cyclic deformations, the effects of the energetic length scale in the flow condition and of the natural length scale in the incremental hardening law can both be significant at the micron scale.

Keywords:
Crystal plasticity models with microforces conjugate to slip gradients are revisited, Incremental hardening law is enhanced by slip-rate gradients with a natural length scale, The length scale is defined by standard parameters of a non-gradient model, Comparative analysis of several 1D and 2D models of Cu single crystals is performed, Interplay between length scales of different physical origin is demonstrated

(45p.)
4.Kowalczyk-Gajewska K., Maździarz M., Atomistic and mean-field estimates of effective stiffness tensor of nanocrystalline copper, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2018.04.004, Vol.129, pp.47-62, 2018
Kowalczyk-Gajewska K., Maździarz M., Atomistic and mean-field estimates of effective stiffness tensor of nanocrystalline copper, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2018.04.004, Vol.129, pp.47-62, 2018

Abstract:
The full elasticity tensor for nano-crystalline copper is derived in molecular simulations by performing numerical tests for a set of generated samples of the polycrystalline material. The results are analysed with respect to the anisotropy degree of the overall stiffness tensor resulting from the limited number of grain orientations and their spatial distribution. The dependence of the overall bulk and shear moduli of an isotropized polycrystal on the average grain diameter is analysed. It is found that while the shear modulus decreases with grain size, the bulk modulus shows negligible dependence on the grain diameter and is close to the bulk modulus of a single crystal. A closed-form mean-field model of effective elastic properties for a bulk nano-grained polycrystal with cubic grains, i.e. made of a material with cubic symmetry, is formulated. In the model all parameters are based on the data for a single crystal and on the averaged grain size without any need for additional fitting. It is shown that the proposed model provides predictions of satisfactory qualitative and quantitative agreement with atomistic simulations.

Keywords:
Molecular statics, Elasticity, Polycrystal, Effective medium, Nano-crystalline copper

(40p.)
5.Rydzek G., Pakdel A., Witecka A., Shri D.N.A., Gaudière F., Nicolosi V., Mokarian-Tabari P., Schaaf P., Boulmedais F., Ariga K., pH-Responsive Saloplastics Based on Weak Polyelectrolytes: From Molecular Processes to Material Scale Properties, Macromolecules, ISSN: 0024-9297, DOI: 10.1021/acs.macromol.8b00609, Vol.51, No.12, pp.4424-4434, 2018
Rydzek G., Pakdel A., Witecka A., Shri D.N.A., Gaudière F., Nicolosi V., Mokarian-Tabari P., Schaaf P., Boulmedais F., Ariga K., pH-Responsive Saloplastics Based on Weak Polyelectrolytes: From Molecular Processes to Material Scale Properties, Macromolecules, ISSN: 0024-9297, DOI: 10.1021/acs.macromol.8b00609, Vol.51, No.12, pp.4424-4434, 2018

Abstract:
Compact polyelectrolyte complexes (COPECs), also named saloplastics, represent a new class of material with high fracture strain and self-healing properties. Here, COPECs based on poly(methacrylic acid) (PMAA) and poly(allylamine hydrochloride) (PAH) were prepared by centrifugation at pH 7. The influence of postassembly pH changes was monitored chemically by ATR-FTIR, ICP, DSC, and TGA, morphologically by SEM, and mechanically by strain to break measurements. Postassembly pH stimuli misbalanced the charge ratio in COPECs, impacting their concentration in counterions, cross-link density, and polymer chain mobility. At the material level, changes were observed in the porosity, composition, water content, and mechanical properties of COPECs. The cross-link density was a prominent factor governing the saloplastic’s composition and water content. However, the porosity and mechanical properties were driven by several factors including salt-induced plasticization and conformational changes of polyelectrolytes. This work illustrates how multiple-scale consequences arise from a single change in the environment of COPECs, providing insights for future design of stimuli-responsive materials.

(40p.)
6.Tůma K., Stupkiewicz S., Petryk H., Rate-independent dissipation in phase-field modelling of displacive transformations, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, ISSN: 0022-5096, DOI: 10.1016/j.jmps.2018.02.007, Vol.114, pp.117-142, 2018
Tůma K., Stupkiewicz S., Petryk H., Rate-independent dissipation in phase-field modelling of displacive transformations, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, ISSN: 0022-5096, DOI: 10.1016/j.jmps.2018.02.007, Vol.114, pp.117-142, 2018

Abstract:
In this paper, rate-independent dissipation is introduced into the phase-field framework for modelling of displacive transformations, such as martensitic phase transformation and twinning. The finite-strain phase-field model developed recently by the present authors is here extended beyond the limitations of purely viscous dissipation. The variational formulation, in which the evolution problem is formulated as a constrained minimization problem for a global rate-potential, is enhanced by including a mixed-type dissipation potential that combines viscous and rate-independent contributions. Effective computational treatment of the resulting incremental problem of non-smooth optimization is developed by employing the augmented Lagrangian method. It is demonstrated that a single Lagrange multiplier field suffices to handle the dissipation potential vertex and simultaneously to enforce physical constraints on the order parameter. In this way, the initially non-smooth problem of evolution is converted into a smooth stationarity problem. The model is implemented in a finite-element code and applied to solve two- and three-dimensional boundary value problems representative for shape memory alloys

Keywords:
Phase-field method, Microstructure, Martensite, Twinning, Non-smooth optimization

(40p.)
7.Chrzanowska-Giżyńska J., Denis P., Woźniacka S., Kurpaska Ł., Mechanical properties and thermal stability of tungsten boride films deposited by radio frequency magnetron sputtering, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.07.208, Vol.44, No.16, pp.19603-19611, 2018
Chrzanowska-Giżyńska J., Denis P., Woźniacka S., Kurpaska Ł., Mechanical properties and thermal stability of tungsten boride films deposited by radio frequency magnetron sputtering, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.07.208, Vol.44, No.16, pp.19603-19611, 2018

Abstract:
Tungsten and boron compounds belong to the group of superhard materials since their hardness could exceed 40 GPa. In this study, the properties of the tungsten boride WBx coatings deposited by radio frequency magnetron sputtering were investigated. The sputtering was performed from specially prepared targets that were composed of boron and tungsten mixed in a molar ratio of 2.5 and sintered in Spark Plasma Sintering (SPS) process. WB films were deposited on silicon (100) and stainless steel 304 substrates at temperatures of 23 ÷ 770 °C. Microstructure, chemical and phase composition were investigated by using Scanning Electron Microscope (SEM), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Diffraction (XRD), respectively. The mechanical properties like Vickers hardness and Young's modulus were obtained by using nanoindentation test at a load of 5 ÷ 100 mN. The friction coefficient and wear resistance of αWB coatings were investigated in scratch test and reciprocal sliding wear instrumentation. Moreover, in order to investigate thermal properties, the αWB films were annealed at 1000 °C in argon/air for 1 h and at 250 °C for 2 h in air atmosphere. Results of our research confirm that αWB coatings can be considered as an alternative to superhard materials in the production of wear resistant, long-lasting tools.

Keywords:
Hard coatings, Hard materials, Magnetron sputtering, Mechanical properties, Thermal properties, Tungsten boride

(40p.)
8.Jarząbek D.M., Dziekoński C., Dera W., Chrzanowska J., Wojciechowski T., Influence of Cu coating of SiC particles on mechanical properties of Ni/SiC co-electrodeposited composites, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.08.271, Vol.44, pp.21750-21758, 2018
Jarząbek D.M., Dziekoński C., Dera W., Chrzanowska J., Wojciechowski T., Influence of Cu coating of SiC particles on mechanical properties of Ni/SiC co-electrodeposited composites, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.08.271, Vol.44, pp.21750-21758, 2018

Abstract:
In this paper, the study of the mechanical properties of composites consisting of electrodeposited Ni and co-electrodeposited SiC particles coated with a thin Cu layer was presented. It was demonstrated that the coating allowed to increase the concentration of ceramic particles in the composite. Although the plating parameters were the same for both types of composites, the concentration of SiC was 15% for the composite containing coated particles (Ni/SiC-Cu) and 10% for the composite containing uncoated particles (Ni/SiC). Furthermore, tensile tests showed that the Ni/SiC-Cu samples exhibited higher Young's modulus than the pure electrodeposited Ni samples or Ni/SiC samples. The measured Young's modulus of the Ni/SiC-Cu composite was 250 ± 10 GPa. However, the ultimate tensile strength of the Ni/SiC-Cu composite was lower than that of pure Ni. To explain the mechanical behaviour of the Ni/SiC-Cu composite, the microstructure of the interface of this composite and its bonding strength were studied. Microstructure studies conducted using a scanning electron microscope (SEM) revealed that the SiC/Cu interface was smooth and of good quality whereas the Cu/Ni interface was rough but also of good quality. The measured bonding, normal, and shear strength values demonstrated that the SiC/Cu interface was weak, and that was the main reason for the low ultimate tensile strength of the composite. The shear strength of the SiC/Cu interface was measured using a novel method: micropillars shearing including atomic force microscopy (AFM). Finally, a simple finite element model of the Ni/SiC-Cu composite, based on cohesive elements, was developed.

Keywords:
Interfacial bonding strength, Metal matrix composites, Tensile strength, Silicon carbide, Electrodeposited nickel

(40p.)
9.Pieczyska E.A., Maj M., Golasiński K., Staszczak M., Furuta T., Kuramoto S., Thermomechanical Studies of Yielding and Strain Localization Phenomena of Gum Metal under Tension, Materials, ISSN: 1996-1944, DOI: 10.3390/ma11040567, Vol.11, No.567, pp.1-13, 2018
Pieczyska E.A., Maj M., Golasiński K., Staszczak M., Furuta T., Kuramoto S., Thermomechanical Studies of Yielding and Strain Localization Phenomena of Gum Metal under Tension, Materials, ISSN: 1996-1944, DOI: 10.3390/ma11040567, Vol.11, No.567, pp.1-13, 2018

Abstract:
This paper presents results of investigation of multifunctional beta-Ti alloy Gum Metal subjected to tension at various strain rates. Digital image correlation was used to determine strain distributions and stress-strain curves, while infrared camera allowed for us to obtain the related temperature characteristics of the specimen during deformation. The mechanical curves completed by the temperature changes were applied to analyze the subsequent stages of the alloy loading. Elastic limit, recoverable strain, and development of the strain localization were studied. It was found that the maximal drop in temperature, which corresponds to the yield limit of solid materials, was referred to a significantly lower strain value in the case of Gum Metal in contrast to its large recoverable strain. The temperature increase proves a dissipative character of the process and is related to presence of w and a” phases induced during the alloy fabrication and their exothermic phase transformations activated under loading. During plastic deformation, both the strain and temperature distributions demonstrate that strain localization for higher strain rates starts nucleating just after the yield limit leading to specimen necking and rupture. Macroscopically, it is exhibited as softening of the stress-strain curve in contrast to the strain hardening observed at lower strain rates.

Keywords:
gum metal, yield limit, thermomechanical coupling, infrared thermography, digital image correlation, strain localization

(35p.)
10.Jarząbek D.M., The impact of weak interfacial bonding strength on mechanical properties of metal matrix - ceramic reinforced composites, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2018.06.071, Vol.201, pp.352-362, 2018
Jarząbek D.M., The impact of weak interfacial bonding strength on mechanical properties of metal matrix - ceramic reinforced composites, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2018.06.071, Vol.201, pp.352-362, 2018

Abstract:
In this work the influence of weak interface between particles and matrix on mechanical properties of metal matrix – ceramic reinforced composites is studied. Firstly, the samples made of coelectrodeposited Ni-SiC composites with 10% of SiC with poor interface bonding have been prepared. Furthermore, the tensile tests of samples have been performed. The determined Young’s modulus was equal to 67 ± 8 GPa and the ultimate tensile strength to 230 ± 15 MPa. It is assumed that the very weak interface is the reason for the poor mechanical properties of the created material. In order to confirm the assumption and get the necessary parameters for the numerical model, the measurements of the normal and shear interfacial bonding strength of the interface have been performed. The measured normal interfacial bonding strength is equal to 0.1 ± 0.03 MPa and the interfacial shear strength is equal to 4.9 ± 0.2 MPa. The experimental results have been confirmed qualitatively by the computer simulations. Representative Volume Element has been created and modelled by the Finite Element Method with cohesive zone elements. The computer simulations result in the Young’s modulus values from 119 GPa up to 126 GPa.

Keywords:
Interfacial bonding strength, Metal matrix composites, Tensile strength, Silicon carbide, Electrodeposited nickel, Cohesive elements

(35p.)
11.Suchorzewski J., Korol E., Tejchman J., Mróz Z., Experimental study of shear strength and failure mechanisms in RC beams scaled along height or length, ENGINEERING STRUCTURES, ISSN: 0141-0296, DOI: 10.1016/j.engstruct.2017.12.003, Vol.157, pp.203-223, 2018
Suchorzewski J., Korol E., Tejchman J., Mróz Z., Experimental study of shear strength and failure mechanisms in RC beams scaled along height or length, ENGINEERING STRUCTURES, ISSN: 0141-0296, DOI: 10.1016/j.engstruct.2017.12.003, Vol.157, pp.203-223, 2018

Abstract:
The paper presents results of laboratory experiments carried out on longitudinally reinforced concrete beams subjected to four-point bending. Beams of separately varying height and length were analyzed to investigate the size effect on nominal strength and post-critical brittleness. Beams were scaled in the height direction in the first test series and in the length direction in the second series. Due to lack of geometrical similarity, different failure mechanisms were exhibited. Load-deflection diagrams and crack paths were registered during experiments. The digital image correlation technique was applied to visualize strain localization on the concrete surface. The crack opening and crack slip displacements were also measured. The beam response was characterized by two non-dimensional parameters ηa = a/D and ηb = b/D defined as the ratios of shear and bending spans to the beam depth D assumed as the size parameter and the reinforcement position parameter ηc = c′/D. Two major failure mechanisms were observed: flexural failure in the central beam zone combined with plastic yielding of the reinforcement and the diagonal shear crack failure in external shear zones. Two distinct modes of shear failure can be specified depending on the dominance of crack opening or crack closure contact zones. Two different effective stresses associated with failure mechanisms were defined to specify the beam strength’s dependence on ηa, ηb, ηc and D. Some analytical formulae specifying the critical shear stress dependence on ηa, ηc and strengths ratio of reinforcement and concrete were presented at the end of paper and compared with experimental data.

Keywords:
Concrete beams, Longitudinal reinforcement, Four-point bending, Failure modes, Height or length variation, Size effect

(35p.)
12.Frydrych K., Kowalczyk-Gajewska K., Microstructure Evolution in Cold-Rolled Pure Titanium: Modeling by the Three-Scale Crystal Plasticity Approach Accounting for Twinning, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-018-4676-2, Vol.49, No.8, pp.3610-3623, 2018
Frydrych K., Kowalczyk-Gajewska K., Microstructure Evolution in Cold-Rolled Pure Titanium: Modeling by the Three-Scale Crystal Plasticity Approach Accounting for Twinning, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-018-4676-2, Vol.49, No.8, pp.3610-3623, 2018

Abstract:
A three-scale crystal plasticity model is applied to simulate microstructure evolution in hcp titanium subjected to cold rolling. Crystallographic texture and misorientation angle development, as an indicator of grain refinement, are studied. The impact of twinning activity on both phenomena is accounted for by combining the original three-scale formulation with the probabilistic twin-volume consistent (PTVC) reorientation scheme. The modeling results are compared with available experimental data. It is shown that the simulated textures are in accordance with the experimental measurements. The basic components of misorientation angle distribution, especially in the range of high angle boundaries, are also well reproduced.

(35p.)
13.Bigoni D., Bordignon N., Piccolroaz A., Stupkiewicz S., Bifurcation of elastic solids with sliding interfaces, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, ISSN: 1364-5021, DOI: 10.1098/rspa.2017.0681, Vol.474, pp.20170681-1-21, 2018
Bigoni D., Bordignon N., Piccolroaz A., Stupkiewicz S., Bifurcation of elastic solids with sliding interfaces, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, ISSN: 1364-5021, DOI: 10.1098/rspa.2017.0681, Vol.474, pp.20170681-1-21, 2018

Abstract:
Lubricated sliding contact between soft solids is an interesting topic in biomechanics and for the design of small-scale engineering devices. As a model of this mechanical set-up, two elastic nonlinear solids are considered jointed through a frictionless and bilateral surface, so that continuity of the normal component of the Cauchy traction holds across the surface, but the tangential component is null. Moreover, the displacement can develop only in a way that the bodies in contact do neither detach, nor overlap. Surprisingly, this finite strain problem has not been correctly formulated until now, so this formulation is the objective of the present paper. The incremental equations are shown to be non-trivial and different from previously (and erroneously) employed conditions. In particular, an exclusion condition for bifurcation is derived to show that previous formulations based on frictionless contact or ‘spring-type’ interfacial conditions are not able to predict bifurcations in tension, while experiments—one of which, ad hoc designed, is reported—show that these bifurcations are a reality and become possible when the correct sliding interface model is used. The presented results introduce a methodology for the determination of bifurcations and instabilities occurring during lubricated sliding between soft bodies in contact

Keywords:
frictionless contact, large strains, nonlinear elasticity

(35p.)
14.Nosewicz S., Romelczyk-Baishya B., Lumelskyj D., Chmielewski M., Bazarnik P., Jarząbek D., Pietrzak K., Kaszyca K., Pakieła Z., Experimental and numerical studies of micro- and macromechanical properties of modified copper–silicon carbide composites, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2018.10.025, pp.1-14, 2018
Nosewicz S., Romelczyk-Baishya B., Lumelskyj D., Chmielewski M., Bazarnik P., Jarząbek D., Pietrzak K., Kaszyca K., Pakieła Z., Experimental and numerical studies of micro- and macromechanical properties of modified copper–silicon carbide composites, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2018.10.025, pp.1-14, 2018

Abstract:
The presented research investigation comprises the study of the mechanical properties of modified copper–silicon carbide composites at the micro- and macroscopic scale. The improvement of a copper–silicon carbide composite refers to the addition of a protective layer at the ceramic reinforcement in order to prevent the dissolution of silicon in the copper matrix. The macromechanical behaviour has been evaluated by the performance in a small punch test. The investigation has been carried out with samples with varying volume content of ceramic reinforcement and different protective layers of the silicon carbide particles. Moreover, the influence of temperature during the strength test has been studied. Next, the results have been referred to the interfacial bonding strength of Cu and SiC particles. SEM characterization of samples has been performed to link the composites’ microstructure with the mechanical behaviour. Finally, the experimental results of the small punch test have been predicted via a numerical approach. Finite element analysis has been employed to reproduce the response of the composite specimen during the test. Satisfactory agreement with the experimental curve has been obtained.

Keywords:
metal matrix composites; silicon carbide; metallic layers deposition; small punch; interface strength; finite element method

(35p.)
15.Maj J., Basista M., Węglewski W., Bochenek K., Strojny-Nędza A., Naplocha K., Panzner T., Tatarkova M., Fiori F., Effect of microstructure on mechanical properties and residual stresses in interpenetrating aluminum-alumina composites fabricated by squeeze casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2017.12.091, Vol.715, pp.154-162, 2018
Maj J., Basista M., Węglewski W., Bochenek K., Strojny-Nędza A., Naplocha K., Panzner T., Tatarkova M., Fiori F., Effect of microstructure on mechanical properties and residual stresses in interpenetrating aluminum-alumina composites fabricated by squeeze casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2017.12.091, Vol.715, pp.154-162, 2018

Abstract:
Aluminum-alumina composites with interpenetrating network structure are interesting structural materials due to their high resistance to elevated temperature and frictional wear, good heat conductivity, enhanced mechanical strength and fracture toughness. In this paper aluminum-alumina bulk composites and FGMs are manufactured by pressure infiltration of porous alumina preforms with molten aluminium alloy (EN AC-44200). Influence of the interpenetrating microstructure on the macroscopic bending strength, fracture toughness, hardness and heat conduction is examined. Special focus is on processing-induced thermal residual stresses in aluminium-alumina composites due to their potentially detrimental effects on material performance in structural elements under in-service conditions. The residual stresses are measured experimentally in the ceramic phase by neutron diffraction and simulated numerically using a micro-CT based Finite Element model, which takes into account the actual interpenetrating microstructure of the composite. The model predictions for two different volume fractions of alumina agree fairly well with the neutron diffraction measurements

Keywords:
A. stress measurements, X-ray analysis, finite element analysis, B. composites, C. casting methods

(35p.)
16.Pakdel A., Witecka A., Rydzek G., Shri D.N.A., Nicolosi V., A comprehensive analysis of extrusion behavior, microstructural evolution, and mechanical properties of 6063 Al–B4C composites produced by semisolid stir casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.080, Vol.721, pp.28-37, 2018
Pakdel A., Witecka A., Rydzek G., Shri D.N.A., Nicolosi V., A comprehensive analysis of extrusion behavior, microstructural evolution, and mechanical properties of 6063 Al–B4C composites produced by semisolid stir casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.080, Vol.721, pp.28-37, 2018

Abstract:
In this study, composites of aluminum alloy 6063 reinforced with 10 wt% boron carbide microparticles were successfully fabricated by a combination of spark plasma sintering and stir casting methods, followed by hot extrusion. A systematic study on the relationship between extrusion process variables (i.e. extrusion ratio, temperature, and punch speed) and porosity, particle refinement, particle distribution and consequently tensile properties and fracture behavior of the composites was performed. Extensive electron microscopy analysis and tensile testing of the composites revealed a multifactoral interdependency of microstructural evolution and mechanical properties on the extrusion process variables. For example, while increasing the extrusion ratio at higher temperatures led to moderate particle refinement, better densification of the composites, and improvement in mechanical properties, concurrent particle fragmentation and microvoid formation around the particles at lower temperatures had opposing effects on the mechanical behavior. We show that the dependency of mechanical properties on all such microstructural factors makes it difficult to predict optimum extrusion conditions in aluminum matrix composites. That is, unlike the common approach, extruding the composites at higher temperatures and achieving more reduction in area may not necessarily lead to the most favorable mechanical properties.

Keywords:
Aluminum matrix composite, Hot extrusion, Mechanical behavior, Microstructure, Spark plasma sintering, Stir casting

(35p.)
17.Bochenek K., Węglewski W., Morgiel J., Basista M., Influence of rhenium addition on microstructure, mechanical properties and oxidation resistance of NiAl obtained by powder metallurgy, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.08.032, Vol.735, pp.121-130, 2018
Bochenek K., Węglewski W., Morgiel J., Basista M., Influence of rhenium addition on microstructure, mechanical properties and oxidation resistance of NiAl obtained by powder metallurgy, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.08.032, Vol.735, pp.121-130, 2018

Abstract:
The search for new materials capable of replacing nickel-based superalloys in aerospace applications has increased rapidly in the recent years. One of the candidates for this purpose is nickel aluminide NiAl provided that its main drawback, namely the inferior fracture toughness at room temperature is overcome. We propose rhenium as an addition to NiAl to improve its mechanical properties without compromising on the oxidation resistance. Two powder metallurgy techniques (HP and SPS) were used to obtain NiAl/Re sinters. Small amounts of rhenium (0.6 at.%; 1.25at.%; 1.5 at.%) almost doubled the flexural strength of NiAl and improved its fracture toughness by 60%. Microscopic investigations revealed rhenium particles at the boundaries of NiAl grains resulting in an enhanced fracture toughness. Mass changes during oxidation at 900 oC, 1100 oC and 1300 oC were relatively low. Plausible mechanisms of the fracture toughness enhancement and the oxidation behavior are discussed.

Keywords:
nickel aluminide, rhenium, fracture toughness, oxidation resistance, powder metallurgy, grain boundary strengthening

(35p.)
18.Frydrych K., Kowalczyk-Gajewska K., Grain refinement in the equal channel angular pressing process: simulations using the crystal plasticity finite element method, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, ISSN: 0965-0393, DOI: 10.1088/1361-651X/aad46d, Vol.26, No.6, pp.065015-1-32, 2018
Frydrych K., Kowalczyk-Gajewska K., Grain refinement in the equal channel angular pressing process: simulations using the crystal plasticity finite element method, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, ISSN: 0965-0393, DOI: 10.1088/1361-651X/aad46d, Vol.26, No.6, pp.065015-1-32, 2018

Abstract:
Grain refinement due to severe plastic deformation is simulated using the crystal plasticity finite element method in the total Lagrangian setting. A rate-independent model with the regularized Schmid law is applied. As an example, a single pass of the equal channel angular pressing process is considered. Texture evolution, misorientation angle distributions and maps of new grains are presented. A special algorithm for tracking the creation of new grains in finite element simulations is developed. The results are analysed with respect to experimental data available in the literature. The possible mechanisms leading to the fragmentation of grains in a face centred cubic material are discussed. The influence of the quality of the microstructure representation on the simulation results is assessed

Keywords:
crystal plasticity, severe plastic deformation, grain refinement, finite element method

(35p.)
19.Vakis A.I., Yastrebov V.A., Scheibert J., Nicola L., Dini D., Minfray C., Almqvist A., Paggi M., Lee S., Limbert G., Molinari J.F., Anciaux G., Aghababaei R., Echeverri Restrepo S., Papangelo A., Cammarata A., Nicolini P., Putignano C., Carbone G., Stupkiewicz S., Lengiewicz J., Costagliola G., Bosia F., Guarino R., Pugno N.M., Müser M.H., Ciavarella M., Modeling and simulation in tribology across scales: An overview, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2018.02.005, Vol.125, pp.169-199, 2018
Vakis A.I., Yastrebov V.A., Scheibert J., Nicola L., Dini D., Minfray C., Almqvist A., Paggi M., Lee S., Limbert G., Molinari J.F., Anciaux G., Aghababaei R., Echeverri Restrepo S., Papangelo A., Cammarata A., Nicolini P., Putignano C., Carbone G., Stupkiewicz S., Lengiewicz J., Costagliola G., Bosia F., Guarino R., Pugno N.M., Müser M.H., Ciavarella M., Modeling and simulation in tribology across scales: An overview, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2018.02.005, Vol.125, pp.169-199, 2018

Abstract:
This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales. Among the main themes discussed were those of rough surface representations, the breakdown of continuum theories at the nano- and microscales, as well as multiscale and multiphysics aspects for analytical and computational models relevant to applications spanning a variety of sectors, from automotive to biotribology and nanotechnology. Significant effort is still required to account for complementary nonlinear effects of plasticity, adhesion, friction, wear, lubrication and surface chemistry in tribological models. For each topic, we propose some research directions.

Keywords:
Tribology, Multiscale modeling, Multiphysics modeling, Roughness, Contact, Friction, Adhesion, Wear, Lubrication, Tribochemistry

(35p.)
20.Balevičius R., Mróz Z., Modeling of combined slip and finite sliding at spherical grain contacts, GRANULAR MATTER, ISSN: 1434-5021, DOI: 10.1007/s10035-017-0778-6, Vol.10, pp.1-27, 2018
Balevičius R., Mróz Z., Modeling of combined slip and finite sliding at spherical grain contacts, GRANULAR MATTER, ISSN: 1434-5021, DOI: 10.1007/s10035-017-0778-6, Vol.10, pp.1-27, 2018

Abstract:
The present paper is aimed at developing the analytical description of the interaction of two contacting spheres for several classes of slip and sliding trajectories, typical in the experimental testing. The analysis accounts for memory effects in the slip regime and configurational effects in the sliding regime, expressed in terms of an active loading surface and memory surfaces within the space of contact forces. Analytical relations for contact response are derived for linear and piecewise-linear motion trajectories of the sphere. The problem of multiple contact interaction of the sphere moving over the regularly packed granular bed is also considered analytically. It is demonstrated that the dual contact activation-separation processes occur within the combined slip–sliding modes, essentially affecting the distribution of contact tractions. The results obtained are relevant for the class of contact problems requiring analysis of interaction of slip and sliding displacements, in particular in testing grain contact interaction aimed at specification of elastic, frictional and wear parameters.

Keywords:
Sphere–sphere contact, Memory rules, Slip and sliding, Displacement and force control, Monotonic and reciprocal sliding, Friction, Granular bed

(30p.)
21.Krajewski M., Brzozka K., Tokarczyk M., Kowalski G., Lewinska S., Slawska-Waniewska A., Lin W.S., Lin H.M., Impact of thermal oxidation on chemical composition and magnetic properties of iron nanoparticles, Journal of Magnetism and Magnetic Materials, ISSN: 0304-8853, DOI: 10.1016/j.jmmm.2018.03.047, Vol.458, pp.346-354, 2018
Krajewski M., Brzozka K., Tokarczyk M., Kowalski G., Lewinska S., Slawska-Waniewska A., Lin W.S., Lin H.M., Impact of thermal oxidation on chemical composition and magnetic properties of iron nanoparticles, Journal of Magnetism and Magnetic Materials, ISSN: 0304-8853, DOI: 10.1016/j.jmmm.2018.03.047, Vol.458, pp.346-354, 2018

Abstract:
The main objective of this work is to study the influence of thermal oxidation on the chemical composition and magnetic properties of iron nanoparticles which were manufactured in a simple chemical reduction of Fe3+ ions coming from iron salt with sodium borohydride. The annealing processing was performed in an argon atmosphere containing the traces of oxygen to avoid spontaneous oxidation of iron at temperatures ranging from 200 °C to 800 °C. The chemical composition and magnetic properties of as-prepared and thermally-treated nanoparticles were determined by means of X-ray diffractometry, Raman spectroscopy, Mössbauer spectroscopy and vibrating sample magnetometry. Due to the magnetic interactions, the investigated iron nanoparticles tended to create the dense aggregates which were difficult to split even at low temperatures. This caused that there was no empty space between them, which led to their partial sintering at elevated temperatures. These features hindered their precise morphological observations using the electron microscopy techniques. The obtained results show that the annealing process up to 800 °C resulted in a progressive change in the chemical composition of as-prepared iron nanoparticles which was associated with their oxidation. As a consequence, their magnetic properties also depended on the annealing temperature. For instance, considering the values of saturation magnetization, its highest value was recorded for the as-prepared nanoparticles at 1 T and it equals 149 emu/g, while the saturation point for nanoparticles treated at 600 °C and higher temperatures was not reached even at the magnetic field of about 5 T. Moreover, a significant enhancement of coercivity was observed for the iron nanoparticles annealed over 600 °C.

Keywords:
Chemical composition, Chemical reduction, Iron nanoparticle, Magnetic properties, Oxidation

(30p.)
22.Szymczyk M., Nowak M., Sumelka W., Numerical Study of Dynamic Properties of Fractional Viscoplasticity Model, SYMMETRY, ISSN: 2073-8994, DOI: 10.3390/sym10070282, Vol.10, No.282, pp.1-17, 2018
Szymczyk M., Nowak M., Sumelka W., Numerical Study of Dynamic Properties of Fractional Viscoplasticity Model, SYMMETRY, ISSN: 2073-8994, DOI: 10.3390/sym10070282, Vol.10, No.282, pp.1-17, 2018

Abstract:
The fractional viscoplasticity (FV) concept combines the Perzyna type viscoplastic model and fractional calculus. This formulation includes: (i) rate-dependence; (ii) plastic anisotropy; (iii) non-normality; (iv) directional viscosity; (v) implicit/time non-locality; and (vi) explicit/stress-fractional non-locality. This paper presents a comprehensive analysis of the above mentioned FV properties, together with a detailed discussion on a general 3D numerical implementation for the explicit time integration scheme.

Keywords:
fractional viscoplasticity, rate dependence, plastic anisotropy, non-normality, directional viscosity, explicit/implicit non-locality

(30p.)
23.Lengiewicz J., Hołobut P., Efficient collective shape shifting and locomotion of massively-modular robotic structures, Autonomous Robots, ISSN: 0929-5593, DOI: 10.1007/s10514-018-9709-6, Vol.0, pp.1-26, 2018
Lengiewicz J., Hołobut P., Efficient collective shape shifting and locomotion of massively-modular robotic structures, Autonomous Robots, ISSN: 0929-5593, DOI: 10.1007/s10514-018-9709-6, Vol.0, pp.1-26, 2018

Abstract:
We propose a methodology of planning effective shape shifting and locomotion of large-ensemble modular robots based on a cubic lattice. The modules are divided into two groups: fixed ones, that build a rigid porous frame, and mobile ones, that flow through the frame.Mobile modules which flow out of the structure attach to the frame, advancing its boundary. Conversely, a deficiency of mobile modules in other parts of the boundary is corrected by decomposition of the frame. Inside the structure, appropriate module flow is arranged to transport the modules in a desired direction, which is planned by a special distributed version of a maximum flow search algorithm. The method engages a volume of modules during reconfiguration, which is more efficient than common surface-flow approaches. Also, the proposed interpretation as a flow in porous media with moving boundaries seems particularly suitable for further development of more advanced global reconfiguration scenarios. The theoretical efficiency of the method is assessed, and then partially verified by a series of simulations. The method can be possibly also applied to a wider class of modular robots, not necessarily cubic-lattice-based.

Keywords:
Modular robots, Self-reconfiguration, Maximum flow search, Programmable matter, Distributed algorithms

(30p.)
24.Rezaee Hajidehi M., Spada A., Giambanco G., The multiple slope discontinuity beam element for nonlinear analysis of RC framed structures, MECCANICA, ISSN: 0025-6455, DOI: 10.1007/s11012-018-0817-3, Vol.53, No.6, pp.1469-1490, 2018
Rezaee Hajidehi M., Spada A., Giambanco G., The multiple slope discontinuity beam element for nonlinear analysis of RC framed structures, MECCANICA, ISSN: 0025-6455, DOI: 10.1007/s11012-018-0817-3, Vol.53, No.6, pp.1469-1490, 2018

Abstract:
The seismic nonlinear response of reinforced concrete structures permits to identify critical zones of an existing structure and to better plan its rehabilitation process. It is obtained by performing finite element analysis using numerical models classifiable into two categories: lumped plasticity models and distributed plasticity models. The present work is devoted to the implementation, in a finite element environment, of an elastoplastic Euler–Bernoulli beam element showing possible slope discontinuities at any position along the beam span, in the framework of a modified lumped plasticity. The differential equation of an Euler–Bernoulli beam element under static loads in presence of multiple discontinuities in the slope function was already solved by Biondi and Caddemi (Int J Solids Struct 42(9):3027–3044, 2005, Eur J Mech A Solids 26(5):789–809, 2007), who also found solutions in closed form. These solutions are now implemented in the new beam element respecting a thermodynamical approach, from which the state equations and flow rules are derived. State equations and flow rules are rewritten in a discrete manner to match up with the Newton–Raphson iterative solutions of the discretized loading process. A classic elastic predictor phase is followed by a plastic corrector phase in the case of activation of the inelastic phenomenon. The corrector phase is based on the evaluation of return bending moments by employing the closest point projection method under the hypothesis of associated plasticity in the bending moment planes of a Bresler’s type activation domain. Shape functions and stiffness matrix for the new element are derived. Numerical examples are furnished to validate the proposed beam element.

Keywords:
Slope discontinuity, Nonlinear pushover analysis, Lumped plasticity, Plastic hinge

(30p.)
25.Nowak M., Nowak Z., Pęcherski R.B., Potoczek M., Śliwa R.E., ASSESSMENT OF FAILURE STRENGTH OF REAL ALUMINA FOAMS WITH USE OF THE PERIODIC STRUCTURE MODEL, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/amm.2018.125122, Vol.63, No.4, pp.1901-1906, 2018
Nowak M., Nowak Z., Pęcherski R.B., Potoczek M., Śliwa R.E., ASSESSMENT OF FAILURE STRENGTH OF REAL ALUMINA FOAMS WITH USE OF THE PERIODIC STRUCTURE MODEL, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/amm.2018.125122, Vol.63, No.4, pp.1901-1906, 2018

Abstract:
The subject of the study are alumina foams produced by gelcasting method. The results of micro-computed tomography of the foam samples are used to create the numerical model reconstructing the real structure of the foam skeleton as well as the simplified periodic open-cell structure models. The aim of the paper is to present a new idea of the energy-based assessment of failure strength under uniaxial compression of real alumina foams of various porosity with use of the periodic structure model of the same porosity. Considering two kinds of cellular structures: the periodic one, for instance of fcc type, and the random structure of real alumina foam it is possible to justify the hypothesis, computationally and experimentally, that the same elastic energy density cumulated in the both structures of the same porosity allows to determine the close values of fracture strength under compression. Application of finite element computations for the analysis of deformation and failure processes in real ceramic foams is time consuming. Therefore, the use of simplified periodic cell structure models for the assessment of elastic moduli and failure strength appears very attractive from the point of view of practical applications.

Keywords:
periodic cell structure, alumina open-cell foam, Young modulus, strength of alumina foams, Burzyński limit criterion

(30p.)
26.Borkowski P., Pietrzak K., Frydman K., Wójcik-Grzybek D., Gładki A., Sienicki A., Physical and electrical properties of silver-matrix composites reinforced with various forms of refractory phases, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/122408, Vol.68, No.2, pp.817-823, 2018
Borkowski P., Pietrzak K., Frydman K., Wójcik-Grzybek D., Gładki A., Sienicki A., Physical and electrical properties of silver-matrix composites reinforced with various forms of refractory phases, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/122408, Vol.68, No.2, pp.817-823, 2018

Abstract:
This paper presents technological trials aimed at producing Ag-W, Ag-WC, Ag-W-C and Ag-WC-C composite contact materials and characterizing their properties. These materials were obtained using two methods, i.e. press-sinter-repress (PSR) at the refractory phase content of less than 30% by weight as well as press-sinter-infiltration (PSI) at the refractory phase content of ≥50% by weight). The results of research into both the physical and electrical properties of the outcome composites were shown. They include the analysis of the influence of the refractory phase content (W or WC) on arc erosion and contact resistance changes for the following current range: 6 kAmax in the case of composites with a low refractory phase content, 10 kAmax in the case of composites with the refractory phase content of ≥50% by weight.

Keywords:
composite materials, electrical contacts, arc erosion, contact resistance

(30p.)
27.Mucha M., Wcisło B., Pamin J., Kowalczyk-Gajewska K., Instabilities in membrane tension: Parametric study for large strain thermoplasticity, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1016/j.acme.2018.01.008, Vol.18, No.4, pp.1055-1067, 2018
Mucha M., Wcisło B., Pamin J., Kowalczyk-Gajewska K., Instabilities in membrane tension: Parametric study for large strain thermoplasticity, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1016/j.acme.2018.01.008, Vol.18, No.4, pp.1055-1067, 2018

Abstract:
This paper deals with the numerical analysis of localized deformation for a rectangular plate in membrane tension, modelled with large strain thermoplasticity. The aim is to determine the influence of selected factors on the localization phenomena, which can result from geometrical, material, and thermal softening. Two types of boundary conditions are considered: plane stress and plane strain, as well as two yield functions, Huber–Mises–Hencky and Burzyński–Drucker–Prager, with selected values of friction angle. First, isothermal conditions are considered and next, a conductive case with thermal softening is studied. Moreover, three types of plastic behaviour are analysed: strain hardening (with different values of hardening modulus), ideal plasticity, and strain softening. Numerical tests, performed using AceGen/FEM packages, are carried out for the rectangular plate under tension with an imperfection, using three finite element discretizations. The results for plane strain in the isothermal model show that with the decrease of linear hardening modulus, we can observe stronger mesh sensitivity, while for plane stress, mesh sensitivity is visible for all cases. Furthermore, for the thermomechanical model the results also depend on the mesh density due to insufficient heat conduction regularization

Keywords:
Thermoplasticity, Large strains, Strain localization, Parametric study

(30p.)
28.Ribolla E.M., Rezaee Hajidehi M., Rizzo P., Scimemi G.F., Spada A., Giambanco G., Ultrasonic inspection for the detection of debonding in CFRP-reinforced concrete, Structure and Infrastructure Engineering, ISSN: 1573-2479, DOI: 10.1080/15732479.2017.1384843, Vol.14, No.6, pp.807-816, 2018
Ribolla E.M., Rezaee Hajidehi M., Rizzo P., Scimemi G.F., Spada A., Giambanco G., Ultrasonic inspection for the detection of debonding in CFRP-reinforced concrete, Structure and Infrastructure Engineering, ISSN: 1573-2479, DOI: 10.1080/15732479.2017.1384843, Vol.14, No.6, pp.807-816, 2018

Abstract:
Fibre-reinforced plastic (FRP) composites are extensively used to retrofit civil structures. However, the quality and the characteristics of the bond between the FRP and the structure are critical to ensure the efficacy of the retrofit. For this reason, effective non-destructive evaluation (NDE) methods are often necessary to assess the bonding conditions. This article presents an ultrasonic technique for detecting defects at the FRP-substrate interface. The technique uses the Akaike Information Criterion, to detect automatically the onset of the ultrasonic signals, and the novel Equivalent Time Lenght (ETL) parameter, to quantify the energy of the propagating ultrasonic signals along the interface between FRP and concrete. The uniqueness of the ETL is that it is not affected by the coupling conditions between the ultrasonic probes and the structure. The proposed NDE technique has been tested numerically by performing 2D Finite-Element analysis and experimentally on reinforced concrete samples. The results show that the method is robust and cost-effective.

Keywords:
CFRP, fibre-reinforced materials, concrete, bonding, non-destructive testing, ultrasonic methods, equivalent time length

(25p.)
29.Spada A., Rezaee Hajidehi M., Giambanco G., A BEAM ELEMENT ALLOWING MULTIPLE SLOPE DISCONTINUITIES FOR RC STRUCTURES: AN APPLICATION, JOURNAL OF EARTHQUAKE ENGINEERING, ISSN: 1363-2469, Vol.XXXV, No.1, pp.131-150, 2018
Spada A., Rezaee Hajidehi M., Giambanco G., A BEAM ELEMENT ALLOWING MULTIPLE SLOPE DISCONTINUITIES FOR RC STRUCTURES: AN APPLICATION, JOURNAL OF EARTHQUAKE ENGINEERING, ISSN: 1363-2469, Vol.XXXV, No.1, pp.131-150, 2018

Abstract:
A beam/column element allowing the formation of multiple plastic hinges in columns or beams of a reinforced concrete (RC) framed structure is used in this work to show, through an application, its advantages with respect to conventional lumped plasticity models. Slope discontinuities can be located at any position of an Euler-Bernoulli beam span and not at the two extremes only. The model is in fact written in the framework of a modified lumped plasticity theory, and respectful of a thermodynamic approach. Flow rules and state equations are derived invoking the Theorem of maximum dissipation and using a Bresler’s type activation domain. The beam element has already been implemented in a researchoriented code to run nonlinear analyses on 2-D frames. The discretized loading process is separated, at each step, in two phases: a predictor and a corrector phase. Numerical examples highlight how the new finite element permits to run nonlinear analyses avoiding a mesh refinement.

Keywords:
beam element, plastic hinge, lumped plasticity, slope discontinuity, nonlinear FEM analysis

(25p.)
30.Frąś L.J., Dziekoński C., Dera W., Jarząbek D.M., Piezoelectric bimorph as a high-sensitivity viscosity resonant sensor to test the anisotropy of magnetorheological fluid, REVIEW OF SCIENTIFIC INSTRUMENTS, ISSN: 0034-6748, DOI: 10.1063/1.5025123, Vol.89, No.10, pp.105111-1-7, 2018
Frąś L.J., Dziekoński C., Dera W., Jarząbek D.M., Piezoelectric bimorph as a high-sensitivity viscosity resonant sensor to test the anisotropy of magnetorheological fluid, REVIEW OF SCIENTIFIC INSTRUMENTS, ISSN: 0034-6748, DOI: 10.1063/1.5025123, Vol.89, No.10, pp.105111-1-7, 2018

Abstract:
In this paper, we present a device which is very sensitive for small changes in the viscosity of the investigated fluid. The main part of the device is a piezo-electric bimorph which consists of the brass shim with two piezo-ceramic layers on the opposite sides. One of them is responsible for generating vibrations, whereas the second one is meant to measure system response which is produced by the damping properties of the surrounding fluid. During the experiment, the cylindrical bar is forced to move by the series of sinusoidal waves with different frequencies and at constant amplitudes. The probe is immersed in the fluid and then the amplitude vs frequency and phase vs frequency curves are obtained. Next, one can determine the viscosity according to a proper mathematical model. The resonant frequency is related to the damping coefficient which depends on the viscosity of the surrender fluid and immersion depth of the probe. The coefficients necessary for calculating viscosity are obtained by fitting the resonance curve to the amplitude vs frequency data obtained from the experiment. The device has been applied to study the anisotropy of magnetorheological fluids. The weak anisotropy of viscosity has been observed. The highest value of viscosity was observed in the case of viscosity measurement in the direction orthogonal to the magnetic field and the lowest in the direction parallel to the magnetic field.

(25p.)
31.Strojny-Nędza A., Pietrzak K., Gładki A., Nosewicz S., Jarząbek D.M., Chmielewski M., The effect of ceramic type reinforcement on structure and properties of Cu-Al2O3 composites, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/124271, Vol.66, No.4, pp.553-560, 2018
Strojny-Nędza A., Pietrzak K., Gładki A., Nosewicz S., Jarząbek D.M., Chmielewski M., The effect of ceramic type reinforcement on structure and properties of Cu-Al2O3 composites, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/124271, Vol.66, No.4, pp.553-560, 2018

Abstract:
The purpose of this paper is to elaborate on mechanical alloy
ing conditions for a composite powder consisting of copper a
nd brittle aluminium oxides. Detailed analysis of the Cu-Al2O3
powder mixture structure obtained in the mechanical alloyi
ng process allows for the
study of the homogenization phenomena and for obtaining gra
ins (in composite form) with a high degree of uniformity. The
Cu-5 vol.%Al2O3
composites were obtained by means of the spark plasma sinter
ing technique. The results presented herein were studied an
d discussed in
terms of the impact of using a different form of aluminium oxid
e powder and a different shape of copper powder on composite pr
operties.
Research methodology included microstructure analysis as
well as its relation to the strength of Cu-Al2O3
interfaces. It transpires from the
results presented below that the application of electrocor
undum as a reinforcement phase in composites decreases poro
sity in the ceramic
phase, thus improving thermal properties and interfacial s
trength.

Keywords:
metal matrix composites, spark plasma sintering, thermal conductivity, interfacial strength

(25p.)
32.Homa M., Sobczak N., Sobczak J.J., Kudyba A., Bruzda G., Nowak R., Pietrzak K., Chmielewski M., Strupiński W., Interaction between graphene-coated SiC single crystal and liquid copper, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-018-3340-8, Vol.27, No.5, pp.2317-2329, 2018
Homa M., Sobczak N., Sobczak J.J., Kudyba A., Bruzda G., Nowak R., Pietrzak K., Chmielewski M., Strupiński W., Interaction between graphene-coated SiC single crystal and liquid copper, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-018-3340-8, Vol.27, No.5, pp.2317-2329, 2018

Keywords:
graphene, liquid Cu, Raman spectroscopy, reactivity, sessile drop, wettability

(20p.)
33.Homa M., Sobczak N., Sobczak J.J., Kudyba A., Bruzda G., Nowak R., Giuranno D., Pietrzak K., Chmielewski M., Interaction Between Liquid Silver and Graphene-Coated SiC Substrate, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-018-3503-7, Vol.27, No.8, pp.4140-4149, 2018
Homa M., Sobczak N., Sobczak J.J., Kudyba A., Bruzda G., Nowak R., Giuranno D., Pietrzak K., Chmielewski M., Interaction Between Liquid Silver and Graphene-Coated SiC Substrate, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-018-3503-7, Vol.27, No.8, pp.4140-4149, 2018

Abstract:
Wettability between liquid Ag and graphene-coated SiC single crystal has been investigated by dispensed drop method at T = 970 oC under vacuum accompanied with subsecond recording of the drop/substrate images (100 frames per second) by high-speed high-resolution CCD camera. Non-contact heating method coupled with capillary purification of the Ag drop procedure has been applied. Scanning electron microscopy combined with EDS analysis and scanning probe microscopy combined with Raman spectroscopy techniques has been utilized for microstructure and surface characterization of samples before and after high-temperature wetting tests. Immediately after its detachment from the capillary, the Ag drop showed non-wetting behavior (h > 90o) forming a high contact angle of h = 114o. Surface characterization of the drop surface after wettability tests evidenced the presence of graphene and Si transferred from the substrate to the top of Ag drop. These findings suggest chemical interaction phenomena occurring at the interface. Locally, an intimate contact between liquid Ag and SiC substrate was allowed by the appearance of discontinuities in the graphene layer basically produced by thermomechanical stress. Local dissolution of carbon into liquid Ag and its reorganization (by segregation, nucleation and growth) as secondary graphene layer at the Ag surface was also observed.

Keywords:
Ag/graphene, Ag/SiC, dispensed drop, sessile drop method, wetting at high temperature

(20p.)
34.Jóźwik I., Strojny-Nędza A., Chmielewski M., Pietrzak K., Kurpaska Ł., Nosewicz S., High resolution SEM characterization of nano-precipitates in ODS steels, MICROSCOPY RESEARCH AND TECHNIQUE, ISSN: 1059-910X, DOI: 10.1002/jemt.23004, Vol.81, No.5, pp.502-508, 2018
Jóźwik I., Strojny-Nędza A., Chmielewski M., Pietrzak K., Kurpaska Ł., Nosewicz S., High resolution SEM characterization of nano-precipitates in ODS steels, MICROSCOPY RESEARCH AND TECHNIQUE, ISSN: 1059-910X, DOI: 10.1002/jemt.23004, Vol.81, No.5, pp.502-508, 2018

Abstract:
The performance of the present-day scanning electron microscopy (SEM) extends far beyond delivering electronic images of the surface topography. Oxide dispersion strengthened (ODS) steel is on of the most promising materials for the future nuclear fusion reactor because of its good radiation resistance, and higher operation temperature up to 750°C. The microstructure of ODS should not exceed tens of nm, therefore there is a strong need in a fast and reliable technique for their characterization. In this work, the results of low-kV SEM characterization of nanoprecipitates formed in the ODS matrix are presented. Application of highly sensitive photo-diode BSE detector in SEM imaging allowed for the registration of single nm-sized precipitates in the vicinity of the ODS alloys. The composition of the precipitates has been confirmed by TEM-EDS.

Keywords:
ODS steels, scanning electron microscopy, spark plasma sintering

(20p.)
35.Pietrzak K., Frydman K., Wójcik-Grzybek D., Gładki A., Bańkowska A., Borkowski P., Effect of carbon forms on properties of Ag-C composites contact materials, MATERIALS SCIENCE, ISSN: 1068-820X, DOI: 10.5755/j01.ms.24.1.17769, Vol.24, No.1, pp.69-74, 2018
Pietrzak K., Frydman K., Wójcik-Grzybek D., Gładki A., Bańkowska A., Borkowski P., Effect of carbon forms on properties of Ag-C composites contact materials, MATERIALS SCIENCE, ISSN: 1068-820X, DOI: 10.5755/j01.ms.24.1.17769, Vol.24, No.1, pp.69-74, 2018

Abstract:
This paper presents the manufacturing method of silver based composite materials containing 3 % vol. carbon forms (nanotubes and graphene). The most significant challenge was to obtain good dispersion of carbon in the metallic matrix. The applying of suitable dispersants allows to get uniform distribution of carbon reinforcement. Triton X-100 and ultrasonic support were used in the powder mixing process. Ag-nanotubes and Ag-graphene contact tips were made using Spark Plasma Sintering process (SPS). The results of research into both physical and electrical properties of these composites are presented. It has been demonstrated that the form of introduced carbon exerts influence on the electrical characteristics of contacts, and particularly on arc erosion. Performed electrical test indicated that Ag-nanotubes contacts showed higher resistance to arc erosion than Ag-graphene contacts. It can be explained by the better dispersion to individual carbon nanotubes their lower than for graphene edge defects density and due to this higher thermal and electrical conductivity.

Keywords:
composite materials, silver-nanotubes, silver-graphene, arc erosion, contact resistance

(15p.)