Presentation by: Daniel Kinder

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Nov 29, 2013 (3 years and 8 months ago)

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Presentation by: Daniel Kinder

September 8,2010


Create a model on the manufacturing of a bimetallic
corrosion
-
resistant re
-
bar.


Correctly design the finish rolling process to assure uniform
thickness in the cladding layer, and prevent breaking.


Determine a method to correctly choose the width
-
to
-
height
ratio of the pre
-
finished oval pass to uniformly fill the
grooves in the roll during the finish pass to obtain equal
thickness.


Numerical model created in two steps. First, the rolling of the
bimetallic band in the flat oval pre
-
finished pass. Second, the
rolling of the bimetallic band in the round ribbed finish pass.


From the models created a substantial reduction un cladding
layer thickness at the rib base has been found, which is
asymmetrical in relation to the rib axis , and is dependent on
the rolling direction


Fig. 1 Dimensions can be
seen in Table 1.

Fig. 2 Dimensions are
also contained in Table 1


Modeling of the plastic
processing processes based on
the FEM method will be carried
out using theFORGE2005®
computer software.


The model will be carried out in
two steps.


In the first stage, the rolling of
round bimetallic band in the flat
oval pre
-
finished pass was
modeled. As seen in Fig. 1.


The next stage of the studies
was the numerical modeling of
the obtained oval bimetallic
band in the round ribbed pass.


As seen in Fig. 2.






See handout for definition of
variables in equations 1and 2.


For a description of the object
being deformed, the Norton
-
Hoff
law was used, which can be
expressed with the following
equation (1):




Friction conditions taking place
between the metal and rollers are
described by the Coulomb friction
model and by the
Tresca

friction
model. Equation 2:



The values of coefficientsA0,m1
-
m4 for

both steels are shown in Table 2. The

coefficients shown in Table 2 are taken

from the material database of the

program Forge2005®. The following

initial parameters were adopted for

simulation: a roll diameter of 350 mm;

the temperature of rolled bimetallic

band was assumed to be uniform and

equal to 1000C; the rolling speed was

taken equal to 3 m/s, friction

coefficient 0.3, and friction factor 0.7.


Assumptions:


The join between the core and
cladding layer adhered closely.


Thermal conductivity between rolls
and material is the same.


Nodes of material are not shared.



The described computer simulation of the first
stage of rolling created an oval band as shown
below.













The dimensions of the oval bimetallic band after
rolling in the pre
-
finished pass were 24.13 x
11.41 mm. The width
-
to
-
height ratio of the
bimetallic oval amounted to 2.1 [1
-
6]. The cross
-
sectional area of the oval bimetallic band was
251.7 mm2, of which the cladding layer area was
49.5 mm2. The initial share of the cladding layer
was 19.8% and it did not change after rolling in the
oval pass. The elongation factor was equal to 1.13.

The initial cladding layer thickness on the

perimeter was uniform and equal to 1 mm,

whereas after rolling this thickness changed. The

thickness of the layer in the locations of band

contact with the rolls was 0.72 mm on the

average, while on the lateral surfaces in the band

widening direction it was equal to 0.9 mm.


No surface defects were found to be caused by

high magnitudes of stress and strain.



When analyzing the computer simulation results,

consideration was given to the
Cocroft
-
Latham

criterion that allows the determination of the

conditions for the occurrence of a crack in the

material based on the main stresses and strain

intensities occurring during deformation[14]. The

value of this criterion during rolling in the pre
-

finished pass did not exceed 0.2, which indicates

that there are no conditions favoring the

cracking of the cladding layer (cracks might occur

at .6 depending on deformation) [15].





It can be found that the obtained bimetallic

ribbed bar model is characterized by correct outer

dimensions and a correct rib height of 1.1 mm.

The bar width was equal to 16.4 mm. The

thickness of the cladding layer between the ribs

was equal to 0.61 mm on the average, with a

deviation of
±
0.07 mm. At the rib top, this layer

reached the thickness ranging from 0.9 mm to 1.0

mm. On the cross
-
section A and B (Fig. 5) it is

shown how the cladding layer thickness varies on

the core surface.


The thickness of the clad surface depends on

the rolling direction. At the rib base on the side

opposite to the rolling direction, the cladding

layer thickness is averagely 0.55 mm. On the

other side of the rib, this thickness is much

smaller, amounting to 0.22 mm on the average.
The cause of such a large difference in

cladding layer thickness is the mode of rib

formation in the ribs bite region.


Computer modeling drastically reduced
cladding layer thickness.


Model will allow for optimal layer of corrosion
resistant material to reduce cost while
maintaining desired properties.


Bimetallic re
-
bar is used in high corrosion
environments.


Higher corrosion resistant re
-
bar will allow
engineers to maintain material properties in
harsh environments.


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Milenin
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Mróz
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Dyja
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Lesik
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Maslehuddin
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Szota
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