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Publications in other journals ranked by Ministry of Science and Higher Education
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Affiliation to IPPT PAN

1.Dziekoński C., Dera W., Jarząbek D.M., Method for lateral force calibration in atomic force microscope using MEMS microforce sensor, ULTRAMICROSCOPY, ISSN: 0304-3991, DOI: 10.1016/j.ultramic.2017.06.012, Vol.182, pp.1-9, 2017
Dziekoński C., Dera W., Jarząbek D.M., Method for lateral force calibration in atomic force microscope using MEMS microforce sensor, ULTRAMICROSCOPY, ISSN: 0304-3991, DOI: 10.1016/j.ultramic.2017.06.012, Vol.182, pp.1-9, 2017

Abstract:
In this paper we present a simple and direct method for the lateral force calibration constant determination. Our procedure does not require any knowledge about material or geometrical parameters of an investigated cantilever. We apply a commercially available microforce sensor with advanced electronics for direct measurement of the friction force applied by the cantilever's tip to a flat surface of the microforce sensor measuring beam. Due to the third law of dynamics, the friction force of the equal value tilts the AFM cantilever. Therefore, torsional (lateral force) signal is compared with the signal from the microforce sensor and the lateral force calibration constant is determined. The method is easy to perform and could be widely used for the lateral force calibration constant determination in many types of atomic force microscopes.

Keywords:
A precise and direct method for lateral force calibration, Inaccuracy equal to approximately 2%, Wedge method is proven to give inaccurate results

2.Majewski M., Kursa M., Hołobut P., Kowalczyk-Gajewska K., Micromechanical and numerical analysis of packing and size effects in elastic particulate composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2017.05.004, Vol.124, pp.158-174, 2017
Majewski M., Kursa M., Hołobut P., Kowalczyk-Gajewska K., Micromechanical and numerical analysis of packing and size effects in elastic particulate composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2017.05.004, Vol.124, pp.158-174, 2017

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

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

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

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

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

4.Moallemi S., Pietruszczak S., Mróz Z., Deterministic size effect in concrete structures with account for chemo-mechanical loading, COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/j.compstruc.2016.10.003, Vol.182, pp.74-86, 2017
Moallemi S., Pietruszczak S., Mróz Z., Deterministic size effect in concrete structures with account for chemo-mechanical loading, COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/j.compstruc.2016.10.003, Vol.182, pp.74-86, 2017

Abstract:
The work presented here is focused on examining the size effect in concrete structures subjected to different loading conditions, which include a chemo-mechanical interaction. The study involves extensive three dimensional finite element simulations, which incorporate a constitutive law with embedded discontinuity for tracing the propagation of damage pattern. The analysis deals with various mechanical scenarios that incorporate both a cohesive and frictional damage mechanism, as well as the effects of degradation of concrete triggered by continuing alkali-silica reaction (ASR). In the latter case, a chemo-plasticity framework is employed. The first set of simulations provides a deterministic assessment of the size effect in a series of three-point bending tests as well as compression tests. For continuing ASR, it is demonstrated that, by increasing the size of the structure, a spontaneous failure may occur under a sustained load. The numerical examples given here clearly show that the size effect is associated with propagation of localized damage whose rate is controlled by a suitably defined ‘characteristic length’.

Keywords:
Size effect, Alkali-silica reaction, 3D crack propagation, Embedded discontinuity model, Bifurcation analysis

5.Krajewski M., Lee P.H., Wu S.H., Brzozka K., Małolepszy A., Stobiński L., Tokarczyk M., Kowalski G., Wąsik D., Nanocomposite composed of multiwall carbon nanotubes covered by hematite nanoparticles as anode material for Li-ion batteries, Electrochimica Acta, ISSN: 0013-4686, DOI: 10.1016/j.electacta.2017.01.051, Vol.228, pp.82-90, 2017
Krajewski M., Lee P.H., Wu S.H., Brzozka K., Małolepszy A., Stobiński L., Tokarczyk M., Kowalski G., Wąsik D., Nanocomposite composed of multiwall carbon nanotubes covered by hematite nanoparticles as anode material for Li-ion batteries, Electrochimica Acta, ISSN: 0013-4686, DOI: 10.1016/j.electacta.2017.01.051, Vol.228, pp.82-90, 2017

Abstract:
This work describes the detailed studies performed on the nanocomposite composed of chemically-modified multiwall carbon nanotubes covered by hematite nanoparticles which diameters vary from 10 nm to 70 nm. This nanomaterial was fabricated in two-steps facile chemical synthesis and was characterized with the use of several experimental techniques, such as: thermogravimetric analysis, differential thermal analysis, Raman spectroscopy, X-ray diffraction, and transmission Mössbauer spectroscopy in order to determine its structure precisely. Moreover, the investigated nanocomposite was tested as an anode material of Li-ion batteries. Its cycling performance was stable during 40 cycles, while its capacity was retained at the level of 330 and 230 mAh/g at the discharge/charge rate of 25 and 200 mA/g, respectively.

Keywords:
anode material, hematite, Li-ion battery, multiwall carbon nanotube, nanocomposite

6.Jarząbek D.M., Milczarek M., Wojciechowski T., Dziekoński C., Chmielewski M., The effect of metal coatings on the interfacial bonding strength of ceramics to copper in sintered Cu-SiC composites, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2017.01.056, pp.1-9, 2017
Jarząbek D.M., Milczarek M., Wojciechowski T., Dziekoński C., Chmielewski M., The effect of metal coatings on the interfacial bonding strength of ceramics to copper in sintered Cu-SiC composites, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2017.01.056, pp.1-9, 2017

Abstract:
Cu-SiC composites are very promising materials which have high thermal and electrical conductivity and may find many applications. Unfortunately, the main disadvantage of these materials is the dissolution of silicon in copper at elevated temperature, which significantly reduces their properties. In order to overcome this problem particles can be coated with a protective material before sintering. In this paper– the influence of three different metallic coatings on bonding strength were investigated. SiC particles were coated with tungsten, chromium or titanium. As reference a material with uncoated particles was prepared. The experiments were carried out with the use of microtensile tester. The highest increase in strength was observed in the case of chromium coating. On the other hand, the titanium coating, which was of very poor quality, decrease the bonding strength in comparison with uncoated particles. Furthermore, scanning electron and optical microscopes were used to determine the mechanism of debonding.

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

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

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

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

8.Witecka A., Yamamoto A., Święszkowski W., Influence of SaOS-2 cells on corrosion behavior of cast Mg-2.0Zn0.98Mn magnesium alloy, COLLOIDS AND SURFACES B-BIOINTERFACES, ISSN: 0927-7765, DOI: 10.1016/j.colsurfb.2016.10.041, Vol.150, pp.288-296, 2017
Witecka A., Yamamoto A., Święszkowski W., Influence of SaOS-2 cells on corrosion behavior of cast Mg-2.0Zn0.98Mn magnesium alloy, COLLOIDS AND SURFACES B-BIOINTERFACES, ISSN: 0927-7765, DOI: 10.1016/j.colsurfb.2016.10.041, Vol.150, pp.288-296, 2017

Abstract:
In this research, the effect of the presence of living cells (SaOS-2) on in vitro degradation of Mg-2.0Zn-0.98Mn (ZM21) magnesium alloy was examined by two methods simple immersion/cell culture tests and electrochemical measurements (electrochemical impedance spectroscopy and potentiodynamic polarization) under cell culture conditions. In immersion/cell culture tests, when SaOS-2 cells were cultured on ZM21 samples, pH of cell culture medium decreased, therefore weight loss and Mg2+ ion release from the samples increased. Electrochemical measurements revealed the presence of living cells increased corrosion rate (Icorr) and decreased polarization resistance (Rp) after 48 h of incubation. This acceleration of ZM21 corrosion can mainly be attributed to the decrease of medium pH due to cellular metabolic activities.

Keywords:
Biodegradable metals, Biomaterials, Electrochemical impedance spectroscopy, Immersion, Cell culture condition

9.Korol E., Tejchman J., Mróz Z., Experimental and numerical assessment of size effect in geometrically similar slender concrete beams with basalt reinforcement, ENGINEERING STRUCTURES, ISSN: 0141-0296, DOI: 10.1016/j.engstruct.2017.03.011, Vol.141, pp.272-291, 2017
Korol E., Tejchman J., Mróz Z., Experimental and numerical assessment of size effect in geometrically similar slender concrete beams with basalt reinforcement, ENGINEERING STRUCTURES, ISSN: 0141-0296, DOI: 10.1016/j.engstruct.2017.03.011, Vol.141, pp.272-291, 2017

Abstract:
The paper presents a comprehensive experimental and numerical analysis of slender rectangular reinforced concrete beams with longitudinal BFRP bars without shear reinforcement subjected to 3-point bending. The experiments included 4 different beams which were similar in two directions. The main research objective was to investigate the size effect on the nominal shear strength of beams. The detailed experimental analysis of beam strength, failure mode and cracking evolution was presented and compared with previous test results on beams reinforced by ordinary steel bears. The experiments with BFRP bars were numerically reproduced using the 2D finite element method based on a coupled elastic-plastic-damage formulation. In order to describe strain localization in concrete, a non-local constitutive model was applied with account for a characteristic length of micro-structure developing in the softening regime. The numerical results were in satisfactory agreement with the experimental data. Advantages and disadvantages of BFRP reinforcement in concrete beams were next outlined.

Keywords:
BFRP bars, Concrete, Elastic-plastic-damage, Non-local softening, Shear, Size effect, Strain localization

10.Petryk H., Stupkiewicz S., Kucharski S., On direct estimation of hardening exponent in crystal plasticity from the spherical indentation test, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2016.09.025, Vol.112, pp.209-221, 2017
Petryk H., Stupkiewicz S., Kucharski S., On direct estimation of hardening exponent in crystal plasticity from the spherical indentation test, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2016.09.025, Vol.112, pp.209-221, 2017

Abstract:
A novel methodology is proposed for estimating the strain hardening exponent of a metal single crystal directly from the spherical indentation test, without the need of solving the relevant inverse problem. The attention is focused on anisotropic piling-up and sinking-in that occur simultaneously in different directions, in contrast to the standard case of axial symmetry for isotropic materials. To correlate surface topography parameters with the value of material hardening exponent, a finite-element study of spherical indentation has been performed within a selected penetration depth range using a finite-strain crystal plasticity model. It is shown how the power-law hardening exponent can be estimated from the measured pile-up/sink-in pattern around the residual impression after indentation in a (001)-oriented fcc single crystal of a small initial yield stress. For this purpose, a new parameter of surface topography is defined as the normalized material volume displaced around the nominal contact zone, calculated by integration of the local residual height (positive or negative) over a centered circular ring. That indicator can be easily determined from an experimental topography map available in a digital form. Comparison is made with the estimates based on measurements of the contact area and the slope of the load–penetration depth curve in logarithmic coordinates. The proposed methodology is extended to estimation of the hardening exponent simultaneously with the initial yield stress when the latter is not negligible. Experimental verification for a Cu single crystal leads to promising conclusions.

Keywords:
Metal crystal, Elastoplasticity, Finite deformation, Strain hardening, Experimental identification

11.Pakdel A., Witecka A., Rydzek G., Shri D.N.A., A comprehensive microstructural analysis of Al–WC micro- and nano-composites prepared by spark plasma sintering, MATERIALS AND DESIGN, ISSN: 0261-3069, DOI: 10.1016/j.matdes.2017.01.064, Vol.119, pp.225-234, 2017
Pakdel A., Witecka A., Rydzek G., Shri D.N.A., A comprehensive microstructural analysis of Al–WC micro- and nano-composites prepared by spark plasma sintering, MATERIALS AND DESIGN, ISSN: 0261-3069, DOI: 10.1016/j.matdes.2017.01.064, Vol.119, pp.225-234, 2017

Abstract:
There have been many investigations on metal matrix microcomposites produced by conventional casting routes; however, in the past decade, the focus has shifted more toward nanocomposites produced via solid state routes. To have a realistic view of performance prediction and optimum design of such composites, in this work Al matrix composites (AMCs) reinforced with WC microparticles, nanoparticles, and bimodal micro-/nano-particles were prepared by spark plasma sintering. The effects of particle size and concentration, and process variables (i.e. sintering temperature, duration, and pressure) on the evolution of microstructure, density and hardness of the composites were studied comprehensively. Full densification of AMCs with high particle concentration was problematic because of ceramic cluster formations in the microstructure. This effect was more emphasized in AMCs containing nanoparticles. AMCs with microparticles were more easily densified, but their hardness benefits were inferior. On the other hand, the mixture of micro- and nano-particles in Al-WC bimodal composites led to better matrix reinforcement integrity and an overall improvement in the microstructural properties. Finally, increasing the sintering temperature improved the microstructural features and hardness of the composites (more enhanced in high wt.% samples), but sintering duration and pressure did not have a big impact on the composite properties.

Keywords:
Composite, Nanoparticle, Microparticle, Powder metallurgy, SPS, Microstructure

12.Leyva-Mendivil M.F., Lengiewicz J., Page A., Bressloff N.W., Limbert G., Skin Microstructure is a Key Contributor to Its Friction Behaviour, TRIBOLOGY LETTERS, ISSN: 1023-8883, DOI: 10.1007/s11249-016-0794-4, Vol.65, No.12, pp.1-17, 2017
Leyva-Mendivil M.F., Lengiewicz J., Page A., Bressloff N.W., Limbert G., Skin Microstructure is a Key Contributor to Its Friction Behaviour, TRIBOLOGY LETTERS, ISSN: 1023-8883, DOI: 10.1007/s11249-016-0794-4, Vol.65, No.12, pp.1-17, 2017

Abstract:
Due to its multifactorial nature, skin friction remains a multiphysics and multiscale phenomenon poorly understood despite its relevance for many biomedical and engineering applications (from superficial pressure ulcers, through shaving and cosmetics, to automotive safety and sports equipment). For example, it is unclear whether, and in which measure, the skin microscopic surface topography, internal microstructure and associated nonlinear mechanics can condition and modulate skin friction. This study addressed this question through the development of a parametric finite element contact homogenisation procedure which was used to study and quantify the effect of the skin microstructure on the macroscopic skin frictional response. An anatomically realistic two-dimensional image-based multilayer finite element model of human skin was used to simulate the sliding of rigid indenters of various sizes over the skin surface. A corresponding structurally idealised multilayer skin model was also built for comparison purposes. Microscopic friction specified at skin asperity or microrelief level was an input to the finite element computations. From the contact reaction force measured at the sliding indenter, a homogenised (or apparent) macroscopic friction was calculated. Results demonstrated that the naturally complex geometry of the skin microstructure and surface topography alone can play as significant role in modulating the deformation component of macroscopic friction and can significantly increase it. This effect is further amplified as the ground-state Young’s modulus of the stratum corneum is increased (for example, as a result of a dryer environment). In these conditions, the skin microstructure is a dominant factor in the deformation component of macroscopic friction, regardless of indenter size or specified local friction properties. When the skin is assumed to be an assembly of nominally flat layers, the resulting global coefficient of friction is reduced with respect to the local one. This seemingly counter-intuitive effect had already been demonstrated in a recent computational study found in the literature. Results also suggest that care should be taken when assigning a coefficient of friction in computer simulations, as it might not reflect the conditions of microscopic and macroscopic friction one intends to represent. The modelling methodology and simulation tools developed in this study go beyond what current analytical models of skin friction can offer: the ability to accommodate arbitrary kinematics (i.e. finite deformations), nonlinear constitutive properties and the complex geometry of the skin microstructural constituents. It was demonstrated how this approach offered a new level of mechanistic insight into plausible friction mechanisms associated with purely structural effects operating at the microscopic scale; the methodology should be viewed as complementary to physical experimental protocols characterising skin friction as it may facilitate the interpretation of observations and measurements and/or could also assist in the design of new experimental quantitative assays.

Keywords:
Skin, Friction mechanisms, Contact mechanics, Microstructure, Finite element, Image-based modelling, Material properties

13.An Y., Błachowski B., Zhong Y., Hołobut P., Ou J., Rank-revealing QR decomposition applied to damage localization in truss structures, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.1849, Vol.24, No.2, pp.e1849-1-15, 2017
An Y., Błachowski B., Zhong Y., Hołobut P., Ou J., Rank-revealing QR decomposition applied to damage localization in truss structures, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.1849, Vol.24, No.2, pp.e1849-1-15, 2017

Abstract:
The purpose of this work is the development of an efficient and high-sensitive damage localization technique for truss structures, based on the rank-revealing QR decomposition (RRQR) of the difference-of-flexibility matrix. The method is an enhancement of the existing techniques of damage detection, which rely on the set of so-called damage locating vector (DLV). The advantages of the RRQR decomposition-based DLV (RRQR-DLV) method are its less computational effort and high sensitivity to damage. Compared with the frequently used stochastic DLV (SDLV) method, RRQR-DLV offers higher sensitivity to damage, which has been validated based on the presented numerical simulation. The effectiveness of the proposed RRQR-DLV method is also illustrated with the experimental validation based on a laboratory-scale Bailey truss bridge model. The proposed method works under ambient excitation such as traffic excitation and wind excitation; therefore, it is promising for real-time damage monitoring of truss structures.

Keywords:
damage localization, rank-revealing QR decomposition, damage sensitivity, truss structure, structural health monitoring

14.Průša V., Řehoř M., Tůma K., Colombeau algebra as a mathematical tool for investigating step load and step deformation of systems of nonlinear springs and dashpots, ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND PHYSIK ZAMP, ISSN: 0044-2275, DOI: 10.1007/s00033-017-0768-x, Vol.68, No.24, pp.1-13, 2017
Průša V., Řehoř M., Tůma K., Colombeau algebra as a mathematical tool for investigating step load and step deformation of systems of nonlinear springs and dashpots, ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND PHYSIK ZAMP, ISSN: 0044-2275, DOI: 10.1007/s00033-017-0768-x, Vol.68, No.24, pp.1-13, 2017

Abstract:
The response of mechanical systems composed of springs and dashpots to a step input is of eminent interest in the applications. If the system is formed by linear elements, then its response is governed by a system of linear ordinary differential equations. In the linear case, the mathematical method of choice for the analysis of the response is the classical theory of distributions. However, if the system contains nonlinear elements, then the classical theory of distributions is of no use, since it is strictly limited to the linear setting. Consequently, a question arises whether it is even possible or reasonable to study the response of nonlinear systems to step inputs. The answer is positive. A mathematical theory that can handle the challenge is the so-called Colombeau algebra. Building on the abstract result by Průša and Rajagopal (Int J Non-Linear Mech 81:207–221, 2016), we show how to use the theory in the analysis of response of nonlinear spring–dashpot and spring–dashpot–mass systems.

Keywords:
Mechanical systems, Nonlinear ordinary differential equations, Jump discontinuities, Colombeau algebra

15.Nosewicz S., Rojek J., Chmielewski M., Pietrzak K., Discrete element modeling and experimental investigation of hot pressing of intermetallic NiAl powder, ADVANCED POWDER TECHNOLOGY, ISSN: 0921-8831, DOI: 10.1016/j.apt.2017.04.012, Vol.28, pp.1745-1759, 2017
Nosewicz S., Rojek J., Chmielewski M., Pietrzak K., Discrete element modeling and experimental investigation of hot pressing of intermetallic NiAl powder, ADVANCED POWDER TECHNOLOGY, ISSN: 0921-8831, DOI: 10.1016/j.apt.2017.04.012, Vol.28, pp.1745-1759, 2017

Abstract:
This paper presents the numerical and experimental analysis of hot pressing of NiAl powder with an emphasis on the best possible representation of its main stages: initial powder compaction and pressure-assisted sintering. The numerical study has been performed within the discrete element framework. In the paper, an original viscoelastic model of hot pressing has been used. In order to ensure that the applied values of material parameters in numerical simulations are appropriate, the reference literature has been reviewed. It produced the relations and equations to estimate the values of all required sintering material parameters of the considered viscoelastic model. Numerical simulations have employed the geometrical model of the initial dense specimen generated by a special algorithm which uses the real grain distribution of powder. The numerical model has been calibrated and validated through simulations of the real process of hot pressing of intermetallic NiAl material. The kinetics of compaction, sintering and cooling stage indicated by the evolution of density, shrinkage and densification rate have been studied. The comparison of numerical and experimental results has shown a good performance of the developed numerical model.

Keywords:
Powder metallurgy; Hot pressing; Sintering; Simulation; Discrete element method; Nickel aluminide

16.Jarząbek D.M., Gwiazda M., Dera W., The Influence of Alkali Metal Chloride Treatments on the Wear Resistance of Silicon Surfaces for Possible Use in MEMS, TRIBOLOGY TRANSACTIONS, ISSN: 1040-2004, DOI: 10.1080/10402004.2017.1296211, pp.1-7, 2017
Jarząbek D.M., Gwiazda M., Dera W., The Influence of Alkali Metal Chloride Treatments on the Wear Resistance of Silicon Surfaces for Possible Use in MEMS, TRIBOLOGY TRANSACTIONS, ISSN: 1040-2004, DOI: 10.1080/10402004.2017.1296211, pp.1-7, 2017

Abstract:
The wear of contacting silicon surfaces in microelectromechanical systems (MEMS) has been a longstanding concern. To address this issue, the effects of immersing silicon surfaces into alkali metal chloride solutions (LiCl, NaCl, CsCl) on their sliding friction and wear were investigated. A custom-built reciprocating tribometer was used with a sapphire ball as the counterbody. Results indicated that the friction coefficient between the silicon surface (p-doped, orientation (100)) and a sapphire ball can be reduced by up to 30% by treating the silicon surfaces in aqueous salt solutions (concentration 1 mol/L, exposure for 24 h). These modified surfaces also have higher wear resistance and a significant change in wettability. After immersion, the contact angle between the silicon surface and water was reduced by approximately 50%. These results may lead to new, simple, and inexpensive methods to increase the wear resistance of silicon surfaces for use in MEMs devices.

Keywords:
silicon surface, wear, friction, alkali metal chlorides

17.Nosewicz S., Rojek J., Chmielewski M., Pietrzak K., Lumelskyj D., Application of the Hertz formulation in the discrete element model of pressure-assisted sintering, GRANULAR MATTER, ISSN: 1434-5021, DOI: 10.1007/s10035-016-0699-9, Vol.19, No.1, pp.16-1-8, 2017
Nosewicz S., Rojek J., Chmielewski M., Pietrzak K., Lumelskyj D., Application of the Hertz formulation in the discrete element model of pressure-assisted sintering, GRANULAR MATTER, ISSN: 1434-5021, DOI: 10.1007/s10035-016-0699-9, Vol.19, No.1, pp.16-1-8, 2017

Abstract:
This paper presents the numerical modelling of initial powder compaction and pressure-assisted sintering performed by original viscoelastic discrete element model. The research is focused on the influence of the type of the model representing an elastic part of interparticle force. Two elastic contact models—linear and nonlinear Hertz model—have been implemented and used to analyse interaction of NiAl powder particles during compaction and sintering process. Numerical models have been validated using own experimental results. Microscopic effects (particle penetration) and macroscopic changes (relative density) have been compared. It has been shown that although both models represent properly macroscopic behaviour of the material at the sintering process, the Hertz model produces the results closer to the real experimental ones during the initial compaction stage. Evaluation of macroscopic quantities enables implementation of the discrete element model in the framework of the multiscale modelling framework which is currently developed for sintering processes.

Keywords:
Powder metallurgy, Sintering, Initial compaction, Elasticity, Discrete element method

18.Mackiewicz M., Mikulski J.L., Wańkowicz J., Kucharski S., Ranachowski P., Ranachowski Z., Study of composite insulator sheds subjected to wheel test, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0101, Vol.62, No.2, pp.679-686, 2017
Mackiewicz M., Mikulski J.L., Wańkowicz J., Kucharski S., Ranachowski P., Ranachowski Z., Study of composite insulator sheds subjected to wheel test, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0101, Vol.62, No.2, pp.679-686, 2017

Abstract:
The paper presents investigation of the properties of the surface and the material stiffness – flexibility of series of samples taken from the sheds of the composite insulators. The insulators were previously subjected to wheel test. The wheel test and 1000 h salt fog test are regarded as alternative examination of the material resistance to the effects of electrical surface discharges. There were investigated two series of the samples of the composite insulators sheds. Examined specimens, made of HTV silicone rubber, were taken from the sheds of medium-voltage composite insulators of two different manufacturers. Insulators of both types passed the 1000 h salt fog test without reservation. Meanwhile, the wheel test can provide a basis for better distinguishing between physical properties of the tested materials. In the case of the insulators of one of the manufacturers the wheel test result was negative. Cross puncture effect of the sheds took place in several places. In addition, sheds were covered with dark coating of varying thicknesses. The results of the study indicated a significantly stronger influence of electrical and temperature factors on the sheds under investigations during the wheel test than in the case of the 1000 h salt fog test. It can be stated that these tests cannot be considered as alternative and it seems that wheel test enables better distinguishing between properties of the materials.

Keywords:
composite insulators, silicone rubber, wheel test, electrical surface discharges, tracking and erosion

19.Kuśnierczyk K., Basista M., Recent advances in research on magnesium alloys and magnesium – calcium phosphate composites as biodegradable implant materials, JOURNAL OF BIOMATERIALS APPLICATIONS, ISSN: 0885-3282, DOI: 10.1177/0885328216657271, Vol.31, No.6, pp.878-900, 2017
Kuśnierczyk K., Basista M., Recent advances in research on magnesium alloys and magnesium – calcium phosphate composites as biodegradable implant materials, JOURNAL OF BIOMATERIALS APPLICATIONS, ISSN: 0885-3282, DOI: 10.1177/0885328216657271, Vol.31, No.6, pp.878-900, 2017

Abstract:
Magnesium alloys are modern biocompatible materials suitable for orthopaedic implants due to their biodegradability in biological environment. Many studies indicate that there is a high demand to design magnesium alloys with controllable in vivo corrosion rates and required mechanical properties. A solution to this challenge can be sought in the development of metal matrix composites based on magnesium alloys with addition of relevant alloying elements and bioceramic particles. In this study, the corrosion mechanisms along with corrosion protection methods in magnesium alloys are discussed. The recently developed magnesium alloys for biomedical applications are reviewed. Special attention is given to the newest research results in metal matrix composites composed of magnesium alloy matrix and calcium phosphates, especially hydroxyapatite or tricalcium phosphate, as the second phase with emphasis on the biodegradation behavior, microstructure and mechanical properties in view of potential application of these materials in bone implants.

Keywords:
Biomaterials, biodegradable, metal matrix composites, magnesium alloys, corrosion, hydroxyapatite, bone repair

20.Golasiński K.M., Pieczyska E.A., Staszczak M., Maj M., Furuta T., Kuramoto S., Infrared thermography applied for experimental investigation of thermomechanical couplings in Gum Metal, Quantitative InfraRed Thermography Journal, ISSN: 1768-6733, DOI: 10.1080/17686733.2017.1284295, pp.1-8, 2017
Golasiński K.M., Pieczyska E.A., Staszczak M., Maj M., Furuta T., Kuramoto S., Infrared thermography applied for experimental investigation of thermomechanical couplings in Gum Metal, Quantitative InfraRed Thermography Journal, ISSN: 1768-6733, DOI: 10.1080/17686733.2017.1284295, pp.1-8, 2017

Abstract:
Results of initial investigation of thermomechanical couplings in innovative β-Ti alloy called Gum Metal subjected to tension are presented. The experimental set-up, consisting of testing machine and infrared camera, enabled to obtain stress–strain curves with high accuracy and correlate them to estimated temperature changes of the specimen during the deformation process. Both ultra-low elastic modulus and high strength of Gum Metal were confirmed. The infrared measurements determined average and maximal temperature changes accompanying the alloy deformation process, allowed to estimate thermoelastic effect, which is related to the alloy yield point. The temperature distributions on the specimen surface served to analyse strain localization effects leading to the necking and rupture.

Keywords:
Gum Metal, thermomechanical coupling, nonlinear elasticity, yield point, infrared camera

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

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

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

22.Chmielewski M., Pietrzak K., Strojny-Nędza A., Kaszyca K., Zybala R., Bazarnik P., Lewandowska M., Nosewicz S., Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique, SCIENCE OF SINTERING, ISSN: 0350-820X, DOI: 10.2298/SOS1701011C, Vol.49, pp.11-22, 2017
Chmielewski M., Pietrzak K., Strojny-Nędza A., Kaszyca K., Zybala R., Bazarnik P., Lewandowska M., Nosewicz S., Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique, SCIENCE OF SINTERING, ISSN: 0350-820X, DOI: 10.2298/SOS1701011C, Vol.49, pp.11-22, 2017

Abstract:
The presented paper investigates the relationship between the microstructure and thermal properties of copper–silicon carbide composites obtained through hot pressing (HP) and spark plasma sintering (SPS) techniques. The microstructural analysis showed a better densification in the case of composites sintered in the SPS process. TEM investigations revealed the presence of silicon in the area of metallic matrix in the region close to metal ceramic boundary. It is the product of silicon dissolving process in copper occurring at an
elevated temperature. The Cu-SiC interface is significantly defected in composites obtained through the hot pressing method, which has a major influence on the thermal conductivity of materials.

Keywords:
Metal matrix composites; Silicon carbide; Interface; Spark plasma sintering; Thermal conductivity.

23.Lengiewicz J., Kursa M., Hołobut P., Modular-robotic structures for scalable collective actuation, ROBOTICA, ISSN: 0263-5747, DOI: 10.1017/S026357471500082X, Vol.35, No.4, pp.787-808, 2017
Lengiewicz J., Kursa M., Hołobut P., Modular-robotic structures for scalable collective actuation, ROBOTICA, ISSN: 0263-5747, DOI: 10.1017/S026357471500082X, Vol.35, No.4, pp.787-808, 2017

Abstract:
We propose a new class of modular-robotic structures, intended to produce forces which scale with the number of modules. We adopt the concept of a spherical catom and extend it by a new connection type which is relatively strong but static. We examine analytically and numerically the mechanical properties of two collective-actuator designs. The simulations are based on the discrete element method (DEM), with friction and elastic deformations taken into account. One of the actuators is shown to generate forces proportional to its volume. This property seems necessary for building modular structures of useful strength and dimensions.

Keywords:
Modular robots, Self-reconfiguration, Programmable matter, Actuators, Mechanical strength

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

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

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

25.Nowak Z., Nowak M., Pęcherski R., Potoczek M., Śliwa R.E., Numerical Simulations of Mechanical Properties of Alumina Foams Based on Computed Tomography, JOURNAL OF MECHANICS OF MATERIALS AND STRUCTURES, ISSN: 1559-3959, DOI: 10.2140/jomms.2017.12.107, Vol.12, No.1, pp.107-121, 2017
Nowak Z., Nowak M., Pęcherski R., Potoczek M., Śliwa R.E., Numerical Simulations of Mechanical Properties of Alumina Foams Based on Computed Tomography, JOURNAL OF MECHANICS OF MATERIALS AND STRUCTURES, ISSN: 1559-3959, DOI: 10.2140/jomms.2017.12.107, Vol.12, No.1, pp.107-121, 2017

Abstract:
The aim of this paper is to apply the results of microtomography of alumina foam to create a numerical model and perform 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. A preliminary analysis of failure strength simulations under compression of alumina foam is also provided.

Keywords:
Alumina open-cell foam, computed tomography microstructure, Young’s modulus, compressive strength of alumina foams