Abstract: Temperature dependence of different parameters (the position of the inflexion
point and the saturation value on the root main square, RMS, values versus exciting field
curves) of the Barkhausen noise is measured in structural steel (S 235 JRG1). It is shown that
while the position of the inflexion point remained constant, the RMS value at the inflexion
point and saturation value increased with the increasing temperature, T. Most interestingly the
field required for saturation decreased with decreasing temperature and had a breakpoint at
about 200K. Breakpoints at the same temperature on the critical exponents versus temperature
functions (i.e. on the β(T) and α(T) curves, where β and α are the exponents of the probability
distributions of peak heights and durations, respectively) were also observed. This
temperature can be identified as the ductile-brittle transition temperature.
Abstract: The technical textiles are very sensitive materials. To measure the elongation of such a
material needs special care. A photographic procedure has been investigated to measure the plain
elongation of textile specimens. It is especially suitable for long-term measuring programs. Some
experimental results measured by the described method are published.
Abstract: Color etching is a widely used technique for visualizing different phases in metallic
materials. Its advantage to the traditional etching techniques is that it gives additional information
within one phase, namely, the color shade of a given phase can change in a certain range. This
paper demonstrates that, due to the physics of the color etching, the shade of a phase also depends
on the crystallographic orientation of the investigated grain. As a test material, spheroidal graphite
cast iron was used, and individual grain orientation was identified by automated electron back
scattering diffraction (EBSD). Results showed that there is a strong correlation between grain
orientation and the shades obtained by color etching.
Abstract: When investigating the wear phenomena often there is a need for studying the wear
process on the basis of variable parameters (microstructure, surface roughness, and load). A new
experimental method was developed thorough several set of tests, by which the effects of the
mentioned parameters in the wear process can be examined. The method is based on the ball/plane
contact which is suitable for examination of the local wear phenomena. There is a point like contact
at the beginning of the experiments. The equipment gives the opportunity to analyse the
“behaviour” of the specimens depending on the given load (normal load), on the rotations per
minute, and on the surface roughness (Ra). The roughness of the counter ball does not change
during the tests because of the random walk motion of the ball.
A good understanding of the microstructure and its influence on wear resistance is of great
importance to designers and engineers in selecting wear-resistant materials . Under conditions of
severe wear, the original structure with higher hardness does not exhibit a better wear resistance .
The experimental results demonstrate the influence of the local microstructure on the mechanism of
the wear process and the dependancy of wear resistance as a function of the microstructure.
Abstract: In this work we present the investigations on the determination of the mechanism of
sodium loss in High Pressure Sodium (HPS) lamps. The transport through the ceramic arc tube
consists of several steps (solution in the ceramics, diffusion through the ceramics, leaving the bulk
phase, evaporation from the surface). Among the listed processes the mechanism of the diffusion
was investigated by model-experiments. A ceramic arc tube was applied as a reactor chamber, in
which polycrystalline ceramic plates were heated at 600-1100°C in controlled Na and Xe
atmosphere. The sodium diffusion profiles developed by the heat-treatment were measured by XPS
and SIMS and from the measurements we tried to draw a conclusion about the mechanism of sodium
diffusion through the ceramic discharge tube.
The ceramic discharge tube were measured by X- ray diffraction, too. We found traces of
some Na-O-Al compound.
Abstract: A new type of vibrating sample magnetometer (VSM) was designed for measuring the magnetic
properties of soft and hard magnetic materials is described. The developed instrument differs from
the traditional Foner type because in our system the motion of the specimen is parallel with the lines
of the external magnetic field. Therefore, this instrument can be called parallel motion vibrating
sample magnetometer (PMVSM). The special vibrating system contains a vibrating rod which holds
the specimen. This arrangement can make the sample replacement and positioning fast and
convenient. Because of the versatility of the PMVSM instrument it could be a useful measuring
device for materials science laboratory and educational purposes as well.
Abstract: In this work the magnetic anisotropy of the 15Mo3 type steel was investigated which was induced
by deterioration process caused by thermal shock fatigue. The applied thermal shock fatigue
investigation can model the material degradation due to long term service in high temperature
environment. The 15Mo3 steel is widely used as reheating pipeline base material of power plant
boilers. Magnetisation curves were measured to characterise the induced magnetic anisotropy due to
thermal shock fatigue process. A parallel motion vibrating sample magnetometer (PMVSM) which
was designed at the Department of Materials Science and Engineering of BUTE was used for the
Abstract: This paper presents an overview about results of mechanical testing of human tendon. We
are dealing with the main function of tendon and touching on typical insurance of tendon and
reconstruction of them. Since the material characteristic of tendon and dynamic models of them are
not known there was made a lot of uniaxial tension test and based on measuring results built up a
linear lumped model for dynamic simulation using the synthesis method. As results we can already
provide quantitative data about mechanical bearing capacity of tendon beside known qualitative
categories. Paper shows a well working fixing technology for tendons during tension test.
Abstract: Year by year the user and process site of steelmarket keep growing and lay claim to the
steelmakers. The researchers, developers and technologists use every effort to try to produce steels
with compound properties. From claim of users –especially the Automotive Industry – developed the
DP- (Dual Phase) and TRIP - steels (TRansformation Induced Placticity). In the Automotive Industry
draft mostly the claim of loose of weight and increase the safety reserve.Welding of these Advanced
High Strenght Steels (AHSS does have but very few publications and studies approach the
subject). This study is about problems of weldability of Dual Phase and TRIP – steels. Welding difficulties
were associated with hard and brittle spot weld nuggets and fusion weld heat affected zones
being caused by nitrid. Our aim is to develop a welding procedure giving good quality of spot weld,
thus the problem of hardened and brittle spot welds would cease to exist.
Abstract: In recent years, several attempts have been made to characterize the geometric structure
of fullerenes by means of topological shape factors in order to predict their physical properties and
stability. In this paper, we present a simple method to estimate the stability of fullerenes on the
basis of quantitative topological criteria. This approach is based on the concept of the generalized
combinatorial curvatures defined on the set of simple graphs embedded on a closed surface without
boundary (sphere, torus, projective plane, Klein bottle). It is shown that starting with the computed
generalized combinatorial curvatures several novel topological indices can be generated. From
computations performed on a set of C40 and C60 fullerenes, we concluded that the four topological
shape factors tested (Λ(-1), (-1), Λ(1) and (1)) could be successfully used to preselect the most
stable fullerene isomers.