Abstract: The objective of this paper is to investigate the transverse fatigue cracking of layered
structures. To this end a fatigue crack propagation rate for a crack growing perpendicularly through
the interfaces between individual layers of the structure is estimated. The suggested procedure takes
into account the influence of different material properties of the layers on the stress field around the
fatigue crack and the change of the stress singularity exponent in the special case of a crack
touching the material interface. The assumptions of linear elastic fracture mechanics and elastic
behaviour of the composite are considered. It is shown that the existence of the interfaces can have a
negative influence on the residual fatigue life of layered structures.
Abstract: The objective of the paper is to investigate the direction of a further crack propagation
from the interface between two elastic materials. The angle of crack propagation changes when the
crack passes the interface. The suggested procedure makes it possible to estimate an angle of
propagation under which the crack will propagate into the second material. The assumptions of
linear elastic fracture mechanics and elastic behavior of the body with interfaces are considered. The
finite element method was used for numerical calculations. The results obtained might contribute to
a better understanding of the failure of materials with interfaces (e.g. layered composites, materials
with protective coatings) and to a more reliable estimation of the service life of such structures.
Abstract: The tribological properties of parts surface, namely their wear resistance and friction
properties, are in many cases determining for their proper function. To improve surface properties, it
is possible to create hard, wear resistant coatings by thermal spray technologies. Using these
versatile coatings it is possible to increase parts lifetime, reliability and safety. The thermally
sprayed cermet composite coatings show, thanks to their specific properties, excellent resistance to
abrasive and erosive wear, as well as corrosion resistance. To predict the behavior, lifetime and
application area of thermally sprayed cermet coatings it is necessary to completely understand the
relationships between technology, process parameters, microstructure and properties of the coatings.
The finding of these relationships and use this understanding to develop deposits with improved
wear resistance for coating of various applications is the main aim of the presented work. It was
done by studying the coatings microstructure and mechanical properties. Four different tests of wear
resistance were done to study the mechanism of surface degradation, to confirm the results of
mechanical testing and to predict the lifetime of coated parts - the abrasive wear performance of the
coatings was assessed using a dry/sand rubber wheel test according to ASTM G-65, wet slurry
abrasion test according to ASTM G-75, pin-on-disc test according to ASTM G-99 and erosion wear
resistance for three impact angles. On the basis of obtained data the new possibilities of coatings
application was determined, tested and implemented.
Abstract: The effect of anodic surface treatment on the polyacrylonitrile (PAN)-based carbon fibers
surface properties and the mechanical behavior of the resulting carbon fiber-polymer composites has
been studied in terms of the contact angle measurements of fibers and the fracture toughness of
composites. Results from contact angle measurements revealed that the angle of electrolyte solution
largely decreases with increasing current densities of treatments up to 0.4-0.5 A m-2. The results
obtained from the evolution of KIC with flexure of the composites as a function of electric current
density shown that the KIC of the composite continually increases with increased current densities of
the treatments up to 0.5 A m-2, and a maximum strength value is found about 294 MPa cm1/2 at the
anodic treatment of 0.5 A m-2. It can be concluded that the anodic surface treatment is largely
influenced in the fiber surface nature and the mechanical interfacial properties between the carbon
fiber and epoxy resin matrix of the resulting composites, i.e., the fracture toughness. We suggest
that good wetting plays an important role in improving the degree of adhesion at interfaces between
fibers and matrices of the resulting composites.
Abstract: The results of X-ray diffraction analysis of macroscopic stresses σ and crystallite size D
in oxide layers are presented in this contribution. The oxide layers were formed on tubular
specimens of Zircaloy 4 and Zr1Nb alloys which were simultaneously oxidized for various times
under temperature transient conditions (oxidation in water at 360 °C with a short-time shock in
steam at 500 °C). A qualitative relation was outlined between the residual stresses in oxide layers
and corrosion kinetics of the alloys under investigation.
Abstract: The local spatial distribution of photoluminescence due to the creation of hot
luminescence centers was measured in the optical near-field by Scanning near-field optical
microscope at emission peaks of materials (λ =595nm), which is due to the luminescence of Mn2+ in
ZnS. The excitation bandgap of ZnS forms exitons, and these excitons get the center of Mn2+
through nonradiation dominates, by means of transition of 4T1 – 6A1 luminescence. This spectrum is
evidence that Mn2+ has been incorporated into the ZnS nanoparticles. In comparison with the bulk
ZnS:Mn phosphors these nanoparticles have clearly higher luminescent efficiency with its
luminescent decay time at least 4 orders of magnitude slower. It means that the oscillator intensity
of luminescent centers in ZnS:Mn nanocrystal enhances at least 4 orders of magnitude than that in
corresponding bulk ZnS:Mn.
Abstract: In the temperature range 600–1000 °C, the effect of material purity on self-diffusion
along grain boundaries has been studied in both the pure (Puratronic 99.9945%) and the technical
(99.5%) nickel. The penetration profiles were measured by the serial sectioning method using the
63Ni radiotracer. The extensive electron backscatter diffraction (EBSD) analysis was performed on
the same samples in order to reveal possible differences in microstructure induced by the impurity
content. The obtained microstructure characteristics were further interpreted in terms of the
coincidence site lattice (CSL) model.
Abstract: Diffusion of 65Zn in Mg-based alloy AZ91 with short Saffil fibres was studied by
sectioning method in the temperature interval 648 – 728 K. The results were compared with those
obtained in the measurements made with the same materials without the reinforcement. This
enabled to assess the influence of the interfaces between the matrix and the fibres and to evaluate
the diffusion characteristics of interface self-diffusion.
Abstract: The properties of polyethylene doped with Ca2+ salt of oxidized cellulose was studied by
different techniques. FTIR spectroscopy was used for the determination of crystalline phase in
polymer film, surface wettability was determined by standard goniometry and surface morphology
was examined by SEM microscopy. Adhesion of mouse 3T3 fibroblasts on the doped polymer was
studied in vitro. It was found that the polyethylene doped with the cellulose derivative can be
sterilized in boiling water. The number and homogeneity of adhering cells were shown to depend on
the surface wettability and morphology.
Abstract: This work is focused on laser modification of polymers with different angles of
incidence. Periodic surface structures generated by linearly polarized F2 laser light (157 nm) on
polyethyleneterephthalate (PET) were studied. Atomic force microscopy was used to study the
topological changes induced by the laser irradiation. The laser irradiation induces the formation of
periodic ripple structures, the width of and the height being angle dependent. The periodic structures
were formed with the laser fluence 4.70 mJ/cm2. The laser modified PET foils were coated with a
50 nm thick gold layer by sputtering. After Au deposition on the laser PET foils with ripple
structure, the roughness of surface decreases in comparison to PET with ripples without Au coating.