- TITLE:
ELECTRON BEAM ADDITIVE MANUFACTURING OF LIGHT METALS
- AUTHOR(S):
Stefan Valkov, Peter Petrov
- ABSTRACT:
This article aims to summarize the topics related to the application of a surface manufacturing of
light metals by means of electron beam additive technologies for developing of new multifunctional
materials, as well as to modify their surface properties. These techniques have a large number of
applications in the field of automotive and aircraft industries for manufacturing of railways, space
crafts, different tools, and components. Some examples of the use of electron beams for surface
manufacturing and modification of structure and properties of Ti and Al based materials are
presented.
- PAGES:
17-
- TITLE:
TRANSITION METAL NITRIDES: FORMATION AND CHARACTERIZATION
- AUTHOR(S):
Stanislava Rabadzhiyska, Maria Ormanova, Dimitar Dechev, Nikolai Ivanov, Peter Petrov
- ABSTRACT:
Transition metal nitrides- CrN, AlN and ZrN - were deposited by Direct Current Magnetron
Sputtering (DCMS) technique. The CrN and AlN films were produced on W320 tool steel with
preliminary treatment of electron-beam hardening and plasma nitriding. Their structure, mechanical
and tribological characteristics (hardness, elasticity modulus and wear resistance) of the above
mentioned coatings were assessed by means of X-Ray Diffraction, Nanoindentation tester and pin-
on-disk method.The results exhibit a presence of face centered cubic CrN and hexagonal AlN phases.
The hardness values are 19.6 GPa and 15.4 GPa for CrN and AlN layers, respectively. It was found
out that the samples with deposited CrN coating possess higher wear resistance compared to one
from AlN. Specimens of tool (X12MF) and Chromium-nickel (CrNi 321) steels were utilized at
deposition of ZrN coatings. The diffractograms of these films show peaks of ZrN phase. The
calculated lattice parameters are in agreement with ICDD (International center for date diffraction)
database.
- PAGES:
12-
- TITLE:
DEVELOPMENT AND SETTING UP OF AN ASYNCHRONOUS DRIVE - LABORATORY STAND
- AUTHOR(S):
Vasil Dimitrov, Petko Kostadinov
- ABSTRACT:
A laboratory stand has been developed to meet the higher educational quality requirements. It
includes an induction motor, controlled by a frequency converter ELDI/V-A. The closed loop control
is provided by an encoder. The necessary protection devices are ensured. Using the energy meter
Sentron PAC 3200 offers many opportunities for tests and laboratory exercises: examination of an
open loop or closed control of an induction motor drive, as well as the influence of various setting
parameters on the drive performance; remote monitoring of the drive and state assessment.
- PAGES:
118-
- TITLE:
COMPUTER SYSTEM FOR CHARACTERIZATION OF FOOD FOAMS WITH ULTRASOUND
- AUTHOR(S):
Ivan Topalov, Nikolay Shopov, Tzvetelin Dessev, Hristo Kilifarev
- ABSTRACT:
The current report proposes a non-contact and non-destructive method for characterization of
food foams. The method is based on using ultrasonic emitter and receiver which detect the reflected
signals from the irradiated object. The results were processed by spectral analysis of signals method
- Discrete Wavelet Transform (DWT) of Haar implemented with fast conversion.
- PAGES:
113-
- TITLE:
IMPEDANCE CHARACTERISTICS OF HUMIDITY SENSING ELEMENTS ON V-DOPED TiO2
- AUTHOR(S):
Zvezditza Nenova
- ABSTRACT:
This paper presents the results from the investigations of the impedance characteristics of
humidity sensor elements based on V-doped TiO2, prepared via a sol-gel method. Measurements
have been taken at relative humidity in the range of 17% to 93% at frequencies from 20 Hz to 5 MHz
and temperature 25ºC. Using the ZView software package, Nyquist plots of the sensor elements have
been obtained, and the relationship between these plots and the humidity sensing mechanism has
been explained. A comparison with the impedance characteristics of TiO2-based reference elements
without doping has been made, confirming the positive effect of V-doping on these characteristics.
An equivalent electrical circuit of the humidity sensors investigated has been obtained, representing
parallel connected resistance and capacitance.
- PAGES:
109-
