- TITLE:
EXPERIMENTAL INVESTIGATION ON THE HEAT TRANSFER ENHANCEMENT IN SINGLE FLOW BY WIRE-COIL INSERTS
- AUTHOR(S):
P. Bonev, V. Petkov, H.Hristov
- ABSTRACT:
This paper presents heat transfer enhancement in single-phase transitional flow by wire-coil
insert with geometrical parameters rib height-to-diameter ratio e/D=0.063, and rib pitch-to-height
ratio p/e =5.6 ÷12.2. The paper presents variation of friction factor and heat transfer coefficient in
the ranges of Reynolds and Prandtl numbers as 1100
- PAGES:
6-
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EXPERIMENTAL INVESTIGATION ON THE HEAT TRANSFER ENHANCEMENT IN SINGLE FLOW BY WIRE-COIL INSERTS
- TITLE:
EFFECT OF SLIDING VELOCITY ON MICROSTRUCTURE OF DIAMOND BURNISHED 41Cr4 STEEL COMPONENTS
- AUTHOR(S):
V. P. Dunchev
- ABSTRACT:
In this article, the effect of the sliding velocity on the microstructures of diamond burnished
41Cr4 steel components was studied. The object of a comparative analysis of the microstructures of
the surface and subsurface layers are three specimens. The specimens were diamond burnished with
the same process parameters, but with different sliding velocity magnitudes: 50, 200, 300 m/min. The
analyses of the microstructures were conducted using an NEOPHOT 2 metallographic microscope at
X100, X400, and X800 magnifications. It was found that the generated heat increasing in the contact
zone between the diamond tip and the surface been treated due to the increase of the sliding velocity
is not sufficient for phase transformations in the surface layers of the studied steel. On the other
hand, the higher sliding velocity increases the plasticity in the surface layers, which effect is reflected
in changes in the microstructure - there is a tendency to modify the granular perlite to a fibrous
structure.
- PAGES:
5-
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EFFECT OF SLIDING VELOCITY ON MICROSTRUCTURE OF DIAMOND BURNISHED 41Cr4 STEEL COMPONENTS
- TITLE:
MODELING AND OPTIMIZATION OF THE ROUGHNESS AND MICROHARDNESS IN DIAMOND BURNISHING OF CuAl8Fe3 BRONZE
- AUTHOR(S):
V. P. Dunchev, D. K. Drumeva
- ABSTRACT:
In this article, the object of the experimental study is diamond burnishing of cylindrical
specimens made of bronze CuAl8Fe3 in terms of the roughness obtained and microhardness. For this
purpose, planned experiment, analysis of variance and regression analysis were performed
sequentially. The governing factors were the spherical surface radius of the diamond tip, burnishing
force and feed rate. Based on the regression models obtained of the roughness and surface
microhardness, one-objective optimizations under the minimum roughness criterion and maximum
surface microhardness, and two-objective optimization of the studied process were conducted. As a
result, the respective optimal values of the governing factors were established. Using the governing
factor optimal values obtained from the two-objective optimization, the impact of the number of
passes and working scheme (one-way or two-way) on the roughness obtained and surface
microhardness was additionally studied. It was established that the implementation of the diamond
burnishing process with four passes in the conditions of one-way operating scheme provides
roughness of m075.0R a and surface microhardness of .305HV050
- PAGES:
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MODELING AND OPTIMIZATION OF THE ROUGHNESS AND MICROHARDNESS IN DIAMOND BURNISHING OF CuAl8Fe3 BRONZE
- TITLE:
SURFACE LAYER TEMPERATURE-DEPENDENT CONSTITUTIVE MODEL OF BRONZE CuAl8Fe3, SUBJECTED TO DIAMOND BURNISHING
- AUTHOR(S):
V. P. Dunchev, D. K. Drumeva
- ABSTRACT:
In this article, the temperature-dependent constitutive model of CuAl8Fe3 bronze is developed,
using the "flow stress"concept. The model defines the dependence between the stress and strain
tensors for a point on the surface layer subjected to diamond burnishing. The adequacy of the chosen
constitutive model was achieved by comparing the deformed state of the surface layer obtained via
an experimental test (indentation test) and inverse finite element analysis of the experimental test.
The developed constitutive model takes into account the temperature influence on the surface and
sub-surface layers of CuAl8Fe3 bronze in the range of (20 ÷ 250) ° C . The model serves the fully
coupled thermal-stress finite element analysis in order to study the stressed and strained state in
rotational components made of bronze CuAl8Fe3, subjected to diamond burnishing.
- PAGES:
3-
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SURFACE LAYER TEMPERATURE-DEPENDENT CONSTITUTIVE MODEL OF BRONZE CuAl8Fe3, SUBJECTED TO DIAMOND BURNISHING
- TITLE:
PRINCIPLES OF CREATING A DIAMOND ABRASIVE TOOL TAKING INTO ACCOUNT THE FEATURES OF THE MICROCUTTING PROCESS
- AUTHOR(S):
F. Salenko, L.F. Golovko, Salenko, V.T. Shchetynin, R.H. Arhat, M.R.F. Budar
- ABSTRACT:
The article discusses the creation of a modern diamond-abrasive tool for processing specific
materials - carbon-carbon composites, which have high strength, temperature resistance, and low
machinability. The anisotropy of the material structure, porosity, the tendency to crack formation
with the release of a significant amount of dust makes the processing of such materials with
traditional tools problematic. The application of a functional approach to the design of the working
surfaces of the tool, including the non-rigid one (in the form of diamond threads, saws of the
renovator), is proposed, which allows the cutting surfaces to be considered as a set of separate
clusters, the functional properties of which are focused on ensuring maximum productivity in each
specific zone of material processing. This significantly reduces dust contamination on the surface,
improves and stabilizes the cutting process
- PAGES:
2-
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PRINCIPLES OF CREATING A DIAMOND ABRASIVE TOOL TAKING INTO ACCOUNT THE FEATURES OF THE MICROCUTTING PROCESS
