MATHEMATICAL MODELING OF EXPERIMENT ON BERKOVICH NANOINDENTATION OF ZRN COATING ON STEEL SUBSTRATE

In the present paper the experiment on Berkovich nanoindentation of ZrN coating on steel substrate is modelled using the proposed effective mathematical model. The model is intended for describing the experiments on indentation of samples with coatings (layered or functionally graded). The model is based on approximated analytical solution of the contact problem on indentation of an elastic half-space with a coating by a punch. It is shown that the results of the model and the experiment are in good agreement

A new millipede genus and species of the tribe Pachyiulini from the Caucasus (Diplopoda, Julida, Julidae)

A new genus and species of the millipede tribe Pachyiulini, Bellatoiulus golovatchi gen. et sp. nov., is described from the Lesser Caucasus, Azerbaijan. Cybertypes of the new species are created from the physical holotype male and from a paratype female. The distribution and ecological features of the new species, and the position of the new genus within Pachyiulini are discussed

Contact problem on indentation of an elastic half-plane with functionally-graded coating in presence of tangential stresses on the surface

Plane contact problem on indentation of an elastic half-plane with functionally graded coating by a parabolic punch is considered. The surface of the half-plane is additionally subjected to distributed tangential stresses in a certain region different from contact area. The contact area is assumed to be asymmetric with respect to the center of the punch. Tangential stresses are represented in the form of Fourier series. The problem is reduced to the solution of two dual integral equations over even and odd functions describing distribution of normal contact stresses. The bilateral asymptotic method is used to solve these equations. Approximated analytical solutions asymptotically exact for both the small and large values of relative coating thickness are constructed

Study on mechanical and microgeometric characteristics of ion-plasma deposited TiN coating on 40Cr steel substrate

The ion-plasma sprayed titanium nitride (TiN) coating on the prepared 40Cr steel substrate is investigated. A part of the coating surface was covered by the copper foil mask to measure its thickness afterwards. The properties and characteristics of the sample surface microtopography before and after coating deposition are studied by the atomic-force microscopy (AFM). The technique for the high-precision determination of the coating thickness using the results of the AFM scanning of the transition area between the substrate and the coating on the sample surface is described and applied. The calculated uncertainty of the measured value of thickness is significantly less than in other methods. Mechanical properties of the coating are measured by the instrumental indentation method; the significance of an accurate determination of the correct thickness for measuring the coating characteristics by the indentation technique is shown

On a method for determination of Poisson’s ratio and Young modulus of a material

On the base of modernized NanoTest 600 Platform 3 indentation method is proposed to determine elastic parameters – Poisson’s ratio and Young’s modulus – of a material while loading in an elastic region. The experiment is based on procedure: lateral surface of indenter tip with the shape of parabolic cylinder penetrates into the specimen. NanoTest 600 was equipped by additional optics, backlight and device for spatial orientation of the specimen. This modernization allows to control the process of the indenter penetration both along its length and from the edges, so that one can observe and measure the width of the contact area and control the depth of the indentation area in a sample material. Mathematical modeling of the indentation process was conducted within the framework of plane theory of elasticity. This required solution of the contact problem on indentation of a rigid indenter with a parabolic shape into an elastic strip coupled with a non-deformable substrate. The fulfilment of condition of zeroing the contact stresses at the edges of the indenter with a known width of the contact area allows to determine the Poisson’s ratio, and condition of static equilibrium of the contact problem helps to find Young’s modulus of a strip material

On a method for determination of Poisson’s ratio and Young modulus of a material

On the base of modernized NanoTest 600 Platform 3 indentation method is proposed to determine elastic parameters – Poisson’s ratio and Young’s modulus – of a material while loading in an elastic region. The experiment is based on procedure: lateral surface of indenter tip with the shape of parabolic cylinder penetrates into the specimen. NanoTest 600 was equipped by additional optics, backlight and device for spatial orientation of the specimen. This modernization allows to control the process of the indenter penetration both along its length and from the edges, so that one can observe and measure the width of the contact area and control the depth of the indentation area in a sample material. Mathematical modeling of the indentation process was conducted within the framework of plane theory of elasticity. This required solution of the contact problem on indentation of a rigid indenter with a parabolic shape into an elastic strip coupled with a non-deformable substrate. The fulfilment of condition of zeroing the contact stresses at the edges of the indenter with a known width of the contact area allows to determine the Poisson’s ratio, and condition of static equilibrium of the contact problem helps to find Young’s modulus of a strip material

Visualisation of penile structures of laboratory rabbit: ultrasound, histology, and micro-CT

Current imaging methods in pre-clinical and animal model studies of penile disease are limited because of the small penis of a rat – standard laboratory animal used in this type of research. Routine visualization methods of surface and inner structures of the penis used in clinical medicine are not suitable in experimental animal researches. The only method available for these purposes is histopathological analysis, which does not provide complex view on penile structures due to two-dimensional imaging per slide. In the pre study we evaluated and compared capability of ultrasound, histopathological and micro-computed tomography imaging methods to visualize anatomical structures of laboratory rabbit penis. Ultrasound provides limited imaging in comparison with other methods. However, it could be useful in assessment rough structural alterations of tunica albuginea and corpora cavernosa as a secondary and supportive method. Micro computed tomography provides nearly the same image quality as histopathological analysis. Moreover, it gives a complex view on the whole penile sample due to three-dimensional reconstruction. This fact gives reason to use this method as a basic one in the pre-clinical trials and animal model studies

The second extinct microhisterid species (Coleoptera: Histeridae: Bacaniini) described from the Eocene Rovno amber using X-Ray microtomography

The third fossil species of the tribe Bacaniini (Coleoptera, Histeridae), Bacanius caterinoi Sokolov et Perkovsky, sp. nov., is described from the Eocene Rovno amber. Previous two extinct species were known from the Rovno and Baltic amber. We compared the new species with them and extant representatives of related taxa. The new species belongs to the extant genus Bacanius LeConte, 1853 and can be included to the extant subgenus Gomyister Mazur 1984. This is the second species of the subgenus from Rovno amber indicating the diversity of this currently primarily tropical group in the Eocene of Europe. Zoobank LSID: urn:lsid:zoobank.org:pub:85027CC6-42D0-44CB-B111-8CE1A8F53F12</p