Note: Descriptions are shown in the official language in which they were submitted.
Apparatus and Method for Imparting Selected Topographies to Aluminum Sheet
Metal
and Applications There For
Cross Reference to Related Applications
The present application is a continuation in part application of U.S.
Application No.
13/892,028, entitled Apparatus and Method for Imparting Selected Topographies
to Aluminum
Sheet Metal, filed May 10, 2013, which is a continuation in part application
of U.S. Application
No. 13/673,468, entitled Apparatus and Method for Imparting Selected
Topographies to
Aluminum Sheet Metal, filed November 9, 2012, which claims the benefit of U.S.
Provisional
Application No. 61/558,504 entitled, Apparatus and Method for Imparting
Selected
Topographies to Aluminum Sheet Metal, filed November 11, 2011.
Field
The present invention relates to rolled sheet metal and surfacing thereof, and
more
particularly, to methods and apparatus for producing specific surface textures
having associated
frictional and optical characteristics, such as an isotropic surface on
aluminum sheet.
Background
Currently, aluminum sheet producers often use a cold rolling mill to produce
sheet of a
desired thickness, width and surface. Skin/temper rolling mills may also be
used with low
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reductions (<10%) to produce desired surfaces. The surface of the cylindrical
rolls (work rolls)
through which the sheet aluminum passes may be prepared for a rolling
operation by grinding
with an abrasive grinding wheel or belt. Grinding leaves the roll surface with
directionality in
appearance and frictional properties due to grinding marks (grain), which are
then
transferred/imparted to a sheet that is rolled by the ground work roll. The
directional appearance
of sheet rolled by ground work rolls is visible and frequently can be seen
through painted
coatings applied to the sheet material or to products made from the sheet
material, such as an
automobile body panel.
Embossing mills are also used to impart a given surface topography on sheet
metal, e.g.,
to produce non-directional topographies. Processing sheet in an embossing mill
is conducted
after the rolling process and after the sheet has been reduced in thickness to
target dimensions
that approximate the final dimensions of the sheet. Embossing mills are
intended to impart
surface texture only, as opposed to having a substantial sizing effect on the
sheet, and therefore
operate on sheet that has already been rolled by the work rolls of a rolling
mill. Embossing sheet
in an embossing mill represents additional steps beyond rolling, requiring
additional apparatus,
material handling and managing a greater variety of roll types compared to
normal rolling mills.
Summary
The present disclosure relates to a method for making a material handler with
at least one
material contacting surface, including the steps of:
obtaining aluminum sheet that has been rolled by a work roll having a surface
50% to 100% covered by indentations lacking facets and having a depressed
central area relative
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to a mean height of the surface and a raised, smooth peripheral lip having a
greater height at an
apex thereof than the mean height of the surface, the aluminum sheet having a
static coefficient
of friction with the at least one material of between 0.62 and 0.79; and
forming the aluminum sheet into the at least one material contacting surface.
In another embodiment, the indentations have a diameter in the range of 150iim
to
400jim and a depth relative to the apex of the peripheral lip in the range of
6
In another embodiment, the material handler is a silo with an interior space
for storing the
material and the material contacting surface forms at least a portion of a
surface defining the
interior space.
In another embodiment, the material contacting surface is formed into a funnel
portion of
the silo.
In another embodiment, the material handled by the silo is flour and further
comprising
the step of introducing the flour into the silo and contacting the material
contacting surface with
the flour.
In another embodiment, the material handled by the silo is sugar and further
comprising
the step of introducing the sugar into the silo and contacting the material
contacting surface with
the sugar.
In another embodiment, the material handler is a funnel with an interior space
for
converging the material toward an outlet and the material contacting surface
forms at least a
portion of a surface defining the interior space.
In another embodiment, the material handler is a trough with an interior space
for guiding
the material and the material contacting surface forms at least a portion of a
surface defining the
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interior space.
In another embodiment, the material handler is a conduit with an interior
space for
guiding the material and the material contacting surface forms at least a
portion of a surface
defining the interior space.
In another embodiment, the aluminum sheet has a static coefficient of friction
differing
by no more than 5% between any two given orientations of the sheet relative to
the direction that
the coefficient is measured.
In another embodiment, a material handler with at least one material
contacting surface,
includes: a surface formed from aluminum sheet at least partially defining the
material
contacting surface, the aluminum sheet having been rolled by a work roll with
a surface 60% to
100% covered by indentations lacking facets and having a depressed central
area relative to a
mean height of the surface and a raised, smooth peripheral lip having a
greater height at an apex
thereof than the mean height of the surface, the aluminum sheet having a
coefficient of static
friction of between 0.62 and0.79.
In another embodiment, the indentations have a diameter in the range of 200 m
to
400 m and a depth relative to the apex of the peripheral lip in the range of
0.5pm to 2.0 m.
In another embodiment, the material handler is a silo with an interior space
for storing the
material and the material contacting surface forms at least a portion of a
surface defining the
interior space.
In another embodiment, the material contacting surface is formed into a funnel
portion of
the silo.
In another embodiment, the material handler is a flour silo.
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In another embodiment, the material handler is a sugar silo.
In another embodiment, the material handler is a funnel with an interior
surface capable
of converging the material toward an outlet and the material contacting
surface forms at least a
portion of a surface defining the interior surface.
In another embodiment, the material handler is a trough with a guiding surface
capable of
guiding the material and the material contacting surface forms at least a
portion of the guiding
surface.
In another embodiment, the material handler is a conduit with an interior
guiding surface
capable of guiding the material and the material contacting surface forms at
least a portion of a
surface defining the interior guiding surface.
In another embodiment, the aluminum sheet has a static coefficient of friction
differing
by no more than 5% between any two given orientations of the sheet relative to
the direction that
the coefficient is measured.
Brief Description of the Drawings
For a more complete understanding of the present invention, reference is made
to
the following detailed description of exemplary embodiments considered in
conjunction with the
accompanying drawings.
FIGS. la and lb are a plan view and a perspective (3D) view graphical
mappings,
respectively, of surface morphology of a sample surface of a working roll
produced by EDT
texturing and as measured by optical profilometry.
FIG. 2 is a diagrammatic view of an apparatus for surfacing a work roll in
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accordance with an embodiment of the present disclosure.
FIG. 3a is a plan view graphical mapping of surface morphology of a sample
surface of a working roll produced by a process in accordance with an
embodiment of the present
disclosure and as measured by optical profilometry. FIG. 3b is an enlarged
view of a fragment
of FIG. 3a, and FIGS. 3c and 3d are perspective graphical mappings of the
surfaces shown in
FIGS 3a and 3b, respectively, as measured by optical profilometry.
FIGS. 4a and 4b are plan view and perspective (3D) view graphical mappings,
respectively, of surface morphology of a sample surface of a working roll
produced by a process
in accordance with an embodiment of the present disclosure, as measured by
optical
profilometry.
FIG. 5a is a plan view graphical mapping of surface morphology of a sample of
rolled aluminum sheet in accordance with an embodiment of the present
disclosure and rolled by
a working roll produced by a process in accordance with an embodiment of the
present
disclosure, as measured by optical profilometry. FIG. 5b is an enlarged view
of a fragment of
FIG. 5a, and FIGS. 5c and 5d are perspective graphical mappings of the
surfaces shown in FIGS
5a and 5b, respectively, as measured by optical profilometry.
FIGS. 6a, 6b and 6c arc plan view graphical mappings of surface morphology of
three samples of rolled aluminum sheet in accordance with an embodiment of the
present
disclosure and rolled by a working roll produced by a process in accordance
with an embodiment
of the present disclosure at 10% reduction, 20% reduction and 40% reduction,
respectively, as
measured by optical profilometry. FIGS. 6d, 6e, and 6f are perspective
graphical mappings of
the surfaces shown in FIGS 6a, 6b and 6c, respectively, as measured by optical
profilometry.
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FIGS 7a and 7b are photographs of working rolls that have been surfaced in
accordance with an embodiment of the present invention and FIGS. 7c and 7d are
enlarged
photographs of fragments of FIGS 7a and 7b, respectively.
FIG. 8 is a graph of the influence of surface texture on the coefficient of
friction.
FIG. 9 is a schematic diagram of a process for developing a surface texture in
accordance with an exemplary embodiment of the present disclosure.
FIG. 10 is a diagrammatic view of an apparatus for surfacing a work roll in
accordance with another embodiment of the present disclosure.
FIG. 11 is a diagrammatic view of an apparatus for surfacing a work roll in
accordance with another embodiment of the present disclosure.
FIGS. 12 and 13 are perspective and cross-sectional views, respectively, of a
media sheet for surfacing a work roll in accordance with another embodiment of
the present
disclosure.
FIG. 14 is a diagrammatic view of an apparatus for generating a shim for
surfacing a work roll in accordance with another embodiment of the present
disclosure.
FIG. 15 is a diagrammatic view of an apparatus for surfacing a work roll in
accordance with another embodiment of the present disclosure.
FIG. 16 is a diagrammatic view of an apparatus for surfacing a work roll in
accordance with another embodiment of the present disclosure.
FIG. 17 is a perspective view of a surface texture of a sheet produced by a
roll
that is ground in a conventional manner.
FIG. 18 is a diagrammatic view of a material storage structure in accordance
with
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another embodiment of the present disclosure.
FIG. 19 is a diagrammatic view of a material handling structure in accordance
with another embodiment of the present disclosure.
FIG. 20 is a diagrammatic view of a material handling structure in accordance
with another embodiment of the present disclosure.
FIG. 21 is a diagrammatic view of a coefficient of friction test apparatus.
Detailed Description of Exemplary Embodiments
An aspect of the present disclosure is the recognition that for many
applications of sheet
metal, it is desirable to have a uniform, non-directional surface finish,
i.e., a surface which
appears isotropic and reflects light diffusely. Further, the present
disclosure recognizes that in
addition to appearance effects, the directionally oriented roughness of a
sheet surface rolled by
ground work rolls influences forming processes that may be used to form the
sheet metal into a
shaped product, such as an automobile panel, e.g., attributable to variations
in frictional
interaction between the forming tool and the sheet stock due to directionally
oriented
grain/grinding patterns in the surface of the metal sheet that were imparted
by the work roll. The
present disclosure also recognizes that a more isotropic surface is beneficial
in conducting some
forming processes that operate on aluminum sheet.
One method for producing a more isotropic surface on a work roll that is used
to roll
aluminum sheet metal (primarily for automotive sheet) is to surface the roll
with an electric
discharge texturing (EDT) machine. An EDT texturing head with multiple
electrodes can be
placed near the roll surface to generate an electric discharge/spark/arc from
each electrode to the
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roll surface, locally melting the roll surface at each spark location and
inducing the molten steel
to form small pools of molten metal within associated craters. Operation of an
EDT machine
along the surface of a rotating roll produces an improved isotropic surface,
but one which
features numerous microscopic craters in the range of up to 100 ,t,m in
diameter and with rim
heights of up to 15-20 tim (Figure 1).
Applicants have recognized that the rims of the microscopic craters formed by
the EDT
process may be brittle, such that when the EDT textured rolls are used in a
rolling mill, high
contact pressure, e.g., up to 200 ksi, between the work roll, the sheet and/or
the backup roll, can
wear down the isotropic texture and produce debris, which is deposited on the
sheet surface, on
the mill and in the lubricant.
FIG. 1 shows a sample surface morphology of a surface Si of an EDT treated
working
roll used for the rolling of aluminum sheet. As can be appreciated, the
surface morphology could
be characterized as covered with numerous sharp peaks and valleys 5.0 gm in
magnitude relative
to a reference plane.
FIG. 2 shows a roll treating apparatus 10 having a cabinet 12 for containing a
working
roll 14. The working roll 14 may be supported on bearings 16, 18 to enable
turning, e.g., by a
motor 20 coupled to the working roll 14. The cabinet 12 also houses a shot/
ball peening nozzle
22 which may be mounted on a gantry 24 that allows the nozzle 22 to be
selectively moved and
positioned, e.g., by the action of a motor 26 turning a screw drive or
actuating a chain, rack,
cable drive, or actuation via a motor-driven friction wheel drive associated
with the nozzle 22.
The nozzle 22 is fed by a compressor 28 and a media hopper 30. The nozzle 22
mixes
compressed gas, e.g., air, from the compressor 28 and media 32 from the hopper
30, propelling
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and directing the media 30 against the outer surface S of the roll 14. The
media may be in the
form of steel, glass or ceramic balls, abrasive grit or other blasting/shot
peening media, as
described further below. A computer 34 may be used to programmatically
control: the position
of the nozzle 22 by controlling the motor 26, the rotation of the roll by
controlling motor 20, the
.. operation of the compressor 28 and the rate of dispensing media 32 from the
hopper 30. A
vision system 36 may be housed within the cabinet 12 to provide a view of the
state of the
surface S in order to ascertain whether a given target surface texture has
been achieved through
operation of the action of the roll treating apparatus 10. This vision system
may be attached to
the nozzle 22 or independently moveable on the gantry 24, may include
magnification and a
shield to protect input aperture and lens from impact from the media 32. Media
32 that has been
projected through the nozzle 22 may be dispensed through a funnel portion 38
of the cabinet 12
to a recycling line 40 that returns the media 32 to the hopper 30, e.g., via a
screw feed or a under
the influence of compressed air, a blower or suction. The cabinet 12 may be
provided with a
door (not shown) and sight glass (not shown) to facilitate transfer of the
roll 14 in and out of the
cabinet 12 and to monitor the operation of roll treating apparatus 10. The
nozzle 22 and
compressor 28 may be of a commercial type to achieve the target peening
intensities to create the
desired surface topography.
Alternatively, the nozzle 22 may be hand-held, as in conventional shot-peening
apparatus. The compressor 28 and the nozzle 22 may be changed to obtain the
target peening
intensity pressure output, i.e., either manually or under computer control, to
regulate the velocity
of media 32 projected from the nozzle 22 to accommodate different types of
media 32, as well as
to accommodate various operating conditions, such a roll 14 hardness, initial
surface texture and
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the type of texture desired for surface S, e.g., attributable to the depth and
circumference of
dimples/craters made in the surface of the roll by a given media 32, such as
steel balls/shot. The
number of impacts and the dimensions of the impressions made by the media on
the roll surface
area relative to the total area can be described as, "% coverage" and can be
adjusted by the
compressor output setting, media flow rate and traverse speed of the nozzle 22
relative to the roll
14, as the nozzle 22 passes over the roll 14 and/or as the roll 14 is spun by
motor 20. The control
of the shot-peening process can be automatic or manual. For example, a person
can manually
hold, position and move the nozzle 22 and or the roll 14, as in traditional
shot-peening operations
wherein the person is equipped with protective gear and partially or fully
enters into a cabinet
containing the work piece. Visual or microscopic inspection of the roll may be
conducted to
verify suitable operation or to adjust the apparatus 10 and to verify an
acceptably surfaced roll 14
at the completion of the peening/blasting operation.
As another alternative, the nozzle 22 may be contained within a portable, open-
sided
vessel (not shown) that presses against the surface S forming a moveable
peening chamber that
captures and redirects spent media back to a storage reservoir like hopper 30.
This peening
chamber may be positioned and moved manually or mechanically, such as, by a
motor-driven
feed mechanism like gantry 24 and optionally under the control of a computer
34.
The apparatus and methods of the present disclosure may be used to surface a
working
roll that imparts a given desired surface to sheet as it is rolled to size,
e.g., to provide a sheet with
an isotropically diffuse or bright appearance, eliminating the need to emboss
or use a temper pass
to create a textured sheet. In this context, "bright" refers to specular and
"diffuse" refers to a
non-specular appearance. The surface textures can be varied to achieve a given
desired
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appearance and forming functionality associated with frictional properties by
the appropriate
choice of media and operating parameters.
In accordance with one aspect of the present disclosure, the desired texture
is applied to a
work roll surface, e.g. S, by a peening/blasting process that propels the
selected media at the
work roll surface S through a nozzle 22 by air pressure. The pressure,
processing time per unit
area, e.g., as a function of work roll 14 rotation speed and nozzle 22
traverse speed, nozzle 22
configuration and media 32 type are controlled to produce the desired work
roll texture, which is
effected by media 32 size, shape, density, hardness, velocity and resultant
dimple/crater or
indentation depth, width and shape and % coverage of dimples/craters on the
treated surface area
S. In accordance with some embodiments of the present disclosure, the media 32
chosen include
spherical indenting media that produces smooth craters, such as high quality,
precision steel ball
bearings or shot, beads (glass, ceramic). Mixtures of beads and grit, such as
aluminum oxide,
silicon carbide or other grit types may be used depending upon the properties
desired in the
resultant surface.
5 FIGS. 3a - 3d show graphical mappings of surface morphology as measured
by optical
profilometry of a work roll surface that has been surfaced in accordance with
an embodiment of
the present disclosure. The surface S3 shown in FIGS 3a-3d has been peened
with steel ball
bearings of grade 1000 with a diameter of < 0.125" and a hardness of Re > 60.
Grade 1000 has
0.001" spherical and +0.005" size tolerances. Better grades of ball bearings
may also be used.
The stand-off distance of the nozzle 22 from the roll 14 may be about 1 inch
to about 12 inches,
with a stand-off of about 5 inches being preferred for some applications. As
can be appreciated,
the use of ball bearings as peening media results in uniformly shaped craters
on the work roll
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surface and the absence of the sharp, raised lips that are typical of EDT
textures. More
particularly, the use of spherical indenting media creates a plurality of
smooth, central
depressions mimicking the shape of the spheres/balls that make them, along
with a smooth
peripheral upwelling or lip around the depressions formed by the displacement
of material from
the depressions. Along the surface there is a gradual change in slope and
abrupt ledges or
discontinuities are minimized. In general, the depth of each depression at the
center is below the
mean or average height of the surface and apex of the peripheral lip is above
the mean height. In
order to make a smooth surface, the spherical indenting media must not be
friable at the level of
force required to create crators of appropriate depth. Otherwise, the
spherical media will fracture
and resultant sharp edges and flat facets on the broken media will cause the
formation of facets
on the surface of the work roll. These faceted impressions can occur on impact
or later on when
the spherical media is recycled and re-impacted against the surface. In
addition to avoiding
breakage of spherical media, it is beneficial if the force exerted by the
media, considering the
size, velocity and density of the spheres, does not create a trajectory upon
impact that results in
the formation of lateral furrows having a significant component of direction
parallel to the
surface of the work roll.
The generally smooth undulations in the surface S3 of the work roll have a
magnitude
typically within the range of +/- 3 to 6 um, however, craters of any desired
magnitude, e.g., in
excess of 10 um or less than 3 um, may be achieved, as desired. As described
more fully below,
the smooth undulating surface produced by spherical indenting media, such as
ball bearings may
be produced in random patterns, e.g., as would be expected of a shot peening
operation or in
discrete patterns, as explained below. A typical EDT surface has a greater
number of severe
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surface variations. A work roll shot-peened with ball bearings, as described
above, can be used
to produce bright sheet with an isotropic appearance, depending upon the
starting background
roll surface. While grade 1000 ball bearings were described above, other types
of precision balls
may be used, depending upon roll hardness, such as higher grade ball bearings.
As noted, the
spherical media selected for indenting the surface of the roll are preferably
selected with material
properties, such as, density, hardness, elasticity, compression strength and
tensile strength that
allow the balls to impact and indent a roll of a given hardness without
breaking or developing
facets due to the impact.
FIGS. 4a and 4b show a work roll surface 54 produced in accordance with
another
.. embodiment of the present disclosure. More particularly, FIG. 4a is a plan
view as measured by
optical profilometry of the topology of a work roll surface that has been
peened with aluminum
oxide grit mixture (2:3 ratio of 120:180 grit) followed by glass beads of
grade AC (60-120
mesh). The aluminum oxide grit blasting was carried out in a manner to remove
the pre-grind
roll pattern (as ascertained by visual evaluation), followed by blasting with
the glass beads to
achieve a desired diffuse surface appearance. FIG. 4b is a perspective (3D)
graphical mapping
of surface morphology of the surface S4 shown in FIG. 4a, as measured by
optical profilometry.
As can be appreciated from FIGS. 4a and 4b, the use of glass beads results in
a surface S4 having
fewer severe peaks than an EDT surface and the magnitude of surface variations
is smaller than
an EDT surface. FIG. 4b shows surface variations in the approximate range of
+1- 2.0 Itm.
Accordingly, one could fairly characterize the resultant surface S4 as
smoother than an EDT
surface, but still having a micro-roughness which may be used to impart a
diffuse isotropic
surface appearance to an aluminum sheet that is rolled by a working roll
having this type of
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surface.
In accordance with the present disclosure, surface treatment of a work roll by
peening
results in a surface which is less brittle than a work roll surface treated by
the EDT process. As a
result, the work roll surface (texture) lasts longer, can sustain higher
surface loading pressures
and creates less debris when used in rolling operations. In accordance with an
embodiment of
the present disclosure, where spherical media, such as ball bearings or glass
beads, are used to
surface the work roll, the gently undulating surface texture produced on the
work roll provides
advantages in the rolling process to produce an isotropic surface. Compared to
normal, ground
work rolls or EDT surfaced work rolls, the gentle undulations promote lower
friction between
the sheet and the working rolls, enabling higher reductions in sheet thickness
to be conducted
before lubricant or roll surface failure. The texture of a work roll surfaced
in accordance wih the
present disclosure does not wear at the same rate as a typical ground work
roll or an EDT
surfaced roll. Experiments have shown that in a work roll-driven mill, the
textures imparted to
the roll by the methods of the present disclosure last 5 to 6 times longer
than normally ground
roll surfaces and that higher reductions are possible than those taken by EDT
working rolls
before exceeding mill horsepower limitations and experiencing lubricant
failure. A roll surface
morphology generated in accordance with an embodiment of the present
disclosure can
withstand greater than a 10% thickness reduction ratio to produce the desired
textured sheet, e.g.,
up to 60%. This is in contrast to EDT surfaced working rolls which are
typically operated in a
range of about 8% to 10% reduction. Taking higher reductions can potentially
allow elimination
of an otherwise necessary pass(es) through the rolling mill to achieve the
desired thickness.
FIG. 5a shows a sample surface AS5 of a rolled aluminum sheet in accordance
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with the present disclosure and rolled by a working roll 14 with a roll
surface, such as the roll
surface S3 illustrated in FIGS 3a-3d, produced by a process in accordance with
an embodiment
of the present disclosure. FIG. 5b is enlarged view of the surface shown in
FIG. 5a, both being
rendered by optical profilometry. FIGS. 5c and 5d are perspective (3D)
graphical mappings of
the sample imaged in FIGS. 5a and 5b as measured by optical profilometry. The
sheet produced
as illustrated in FIGS 5a-5d were produced by shot-peening with precision
steel ball bearings.
As illustrated and in general, the macro-texture, e.g., peened
dimples/indentations, imparted to
sheet metal by the working rolls during rolling is the inverse of the texture
on the work roll.
However, both macro and micro features affect the final level of surface
brightness, i.e., the final
level of specular reflection, of the sheet.
FIGS 6a, 6b and 6c show plan view graphical mappings of surface morphology of
three
surface samples AS6a, AS6b and AS6c of rolled aluminum sheet in accordance
with an
embodiment of the present disclosure and rolled by a working roll produced by
a process in
accordance with an embodiment of the present disclosure at 10% reduction, 20%
reduction and
40% reduction, respectively, and as measured by optical profilometry. The
working roll used to
roll these samples was surfaced by shot-peening with aluminum oxide grit
followed by shot-
peening with glass beads, as described above relative to FIGS. 4a and 4b.
FIGS. 6d, 6e, and 6f
are perspective graphical mappings of the surfaces shown in FIGS 6a, 6b and
6c, respectively, as
measured by optical profilometry.
FIGS 7a and 7b are photographs of working rolls that have been surfaced in
accordance
with an embodiment of the present invention. FIGS. 7c and 7d are enlarged
photographs of
fragments of FIGS 7a and 7b, respectively. The roll shown in FIGS. 7a and 7c
were shot-peened
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with class 1000 steel ball bearings of 1.6 mm in diameter. The roll was shot-
peened under
conditions that produced 100% coverage of the surface S7a of the roll with
dimples/indentations.
The roll shown in FIGS 7b and 7d were shot-peened with class 1000 steel ball
bearings of 2.36
mm in diameter. The roll was shot-peened under conditions that produced 50%
coverage of the
surface S-1, of the roll with dimples.
In accordance with an embodiment of the present disclosure, sheet can be
produced
through normal rolling production schedules, eliminating the need to emboss or
use a temper
pass on the rolling mill. The resultant work roll surface textures do not wear
as fast as EDT
produced and normal ground roll surfaces. As a result, roll life exceeds 5 to
6 times that of
normal rolls. On a work roll-driven mill, production is not limited to wide-to-
narrow production
schedules since the texture does not develop banding due to wear. As noted
above, the sheet
produced by a work roll surface shot-peened with, e.g., ball bearings,
generates less debris than
an EDT surfaced or normal ground surface, resulting in cleaner lubricant and
sheet during
rolling. The resultant sheet is isotropic in appearance.
5 FIG. 8 shows the directionally dependent coefficient of friction during a
forming
operation of various surfaces when forming is performed in longitudinal (L)
and transverse (T)
directions. As to the sample 6022-T43, the peened surface showed a reduction
in friction on
average and a smaller variation in friction dependent upon the direction of
forming. Isotropic
frictional interaction with forming tools, such as those used in drawing and
ironing may
represent an improvement in forming performance, e.g., producing more uniform
drawing and
extended drawing limits.
In accordance with the present disclosure, the initial surface finish
requirements for the
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work roll before peening, e.g., with ball bearings, depends on the final sheet
appearance
requirement, e.g., highly specular or somewhat specular. The background
roughness is preferred
to be <1 gin if a highly specular isotropic surface is desired. If a less
specular surface is
required, the initial work roll grind can be any desired grind up to 50 gin.
The amount of pre-
grind desired impacts the final cost of the entire process since it is
generally more expensive to
produce a surface finish <1 gin roughness. The initial surface finish
requirements for the work
roll before peening with glass beads or other media to produce a diffuse
surface is preferred to be
<15 gin or a roughness such that the roll grind pattern is not visible on the
peened work roll after
processing. The removal of the background roll grind during glass bead peening
will be
dependent upon the peening processing parameters chosen to produce the diffuse
finish. The
present disclosure is further illustrated by the following examples.
Example 1
FIGS 3a-d, 7a and 7e show images of an exemplary surface S3, S7a of a working
roll
made in accordance with an exemplary embodiment of the present disclosure. To
generate the
surface shown, a background roll topography is created with standard grinding
processes (pre-
grind) of about <5 gin roughness. A series of dimples ranging in diameter from
200 to 300 gm
are produced on the roll surface by shot-peening with class 1000 steel balls
of 1.6 mm in
diameter and hardness Re? 60. The balls are propelled against the surface of a
roll having a
hardness of about 58 to 62 Re, at a velocity causing a dimple diameter of
about 200 gm to 400
gm and a dimple depth of about 0.5 gm to about 4 gm. Dimple diameter and depth
are affected
by processing conditions (ball velocity) and are dependent upon the initial
work roll hardness. In
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this example, about 100% of the surface area is covered by dimples, as
measured by visual
inspection, but coverage can range from about 10% to about 250%, depending
upon the desired
surface appearance finish. A coverage of 60% to 100% provides a work roll
surface that
produces aluminum sheets with desirable optical and mechanical properties. The
% coverage
measured can vary depending upon the method of measuring. Optical methods tend
to over-
estimate coverage when compared to physical measurement from topographical
images.
In accordance with another embodiment, the velocity of the balls may be
adjusted to
yield indentations having a diameter of 150 gm to 400 gm and a depth relative
to the apex of the
peripheral lip in the range of 6 2 gm.
The benefits experienced with use of these rolls in breakdown rolling include:
pass
elimination (1 pass eliminated in cold rolling, 3 passes eliminated in hot
rolling); the ability to
roll narrow to wide; increased roll life; less roll coating developed in hot
rolling due to reduced
material transfer; and reduced debris generation in cold rolling.
Example 2
In accordance with another exemplary embodiment of the present disclosure, a
diffuse
surface work roll may be made by peening a working roll that is pre-ground at
< 5 microinch
roughness The media may be glass bead, other "ceramic" beads of grade A to AI-
I which are
mesh sizes 20-30 to 170-325 or other hard abrasive particles, such as aluminum
oxide (grit sizes
to 12 to 400). A combination of glass beads, ceramic beads and aluminum oxide
media, applied
in succession, may be required to produce a surface finish like that shown in
FIGS. 4a and 4b.
For example, the roll surface is first processed with aluminum oxide of mixed
grit sizes (2:3
ratio of 120 and 180 grits) with a 5/16" nozzle and 65 PSI at a traverse speed
of 1.5" per minute
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followed by glass beads grade AC (mesh size 60-120) at 100 PSI using a 3/8"
nozzle and
traverse speed of 1.5" per minute. The standoff distance was adjusted based on
the nozzle bristle
lengths of the particular peening system. Choices of nozzles, pressures and
traverse speeds
would be dependent upon the apparatus used to peen. The percent area of
coverage can range
from 10% to 250% depending upon the desired surface finish.
A working roll surfaced in accordance with the above parameters may be
operated at
reductions between 10 to 60% (in contrast to EDT treated rolls which are
typically operated at
reduction of about 8% to 10%). The higher level of reduction may be utilized
to eliminate one or
more reduction passes that might otherwise be required to achieve a desired
thickness and
surface appearance. The resultant sheet has an isotropic appearance and
isotropic functionality.
FIG. 9 shows a diagram of a process for developing a surface texture in
accordance with
an exemplary embodiment of the present disclosure. In a first stage (I) (not
shown), the surface
topologies that are obtained by using a range of peening conditions and media
types are
predicted. For a work roll surface treated by shot-peening, the media size,
composition and
5 .. peening process conditions, such as velocity and % coverage, may be
selected to control the
desired final texture of the roll, which is then imparted to the rolled
product. The relationships
between these variables (media size, composition and peening process
conditions) and the
surfacing results obtained may be recorded and used as a basis for predictive
computer modeling
at stage I for any given set of parameters to produce the roll surface
texture.
In the next stage (II) (shown in FIG. 9), the light scatter and appearance for
a given set of
real or hypothesized surface topographies are predicted. As shown in FIG. 9,
modeling may
include selecting a "target" surface which has specific optical properties,
such as predicted light
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scatter, e.g., to yield a given degree of brightness. A method for generating
aluminum sheet
having the desired optical properties may then be pursued by the following
steps.
(A) accumulating a data file which associates a plurality of given surface
profiles with
corresponding optical properties of each surface profile, including light
scatter, length scale and
surfacing treatment parameters utilized to realize each of the plurality of
surfaces; (B) implicitly
prescribing a virtual surface by specifying target optical properties; (C)
modeling the virtual
surface by retrieving data pertaining to at least one surface profile with the
most similar
measured or predicted optical properties as the target optical properties; (D)
comparing the target
optical properties to the optical properties of the at least one surface
profile; (E) in the event that
the comparison in step (D) does not indicate identity, then retrieving data
pertaining to another
surface profile in the data file that has measured or predicted optical
properties that are similar to
the target properties but arc at variance to the target properties in an
opposite respect relative to
how the optical properties of the at least one given surface profile differ
from the target
properties; (F) sampling from the optical properties of the at least one
surface profile and from
another surface profile in proportion to the magnitude of their respective
differences from the
target properties to arrive at corrected optical properties of a corrected
virtual surface and
recording the composited sampled composition contributions of the at least one
surface profile
and the other surface profile; (G) comparing the optical properties of the
corrected virtual surface
to the target optical properties to ascertain the reduction in the differences
there between; and
.. then repeating the steps (E) - (G) until little or no improvement is
discerned, whereupon the best
virtual surface relative to the target has been ascertained.
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Note that steps (C) through (G) can be executed as described or can be
replaced by a non-
linear least squares optimization algorithm to automate the process. To
complete the process, the
Modeling steps (1) and (II) are combined. Namely, by:(1) ascertaining the
surfacing treatment
parameters utilized to realize each of the plurality of surfaces by
compositing such parameters in
proportion to the contribution of optical properties of each surface profile
composited in the best
virtual surface thereby defining best surfacing treatment parameters; (2)
conducting surfacing of
a roll in accordance with the best surfacing treatment parameters; and (3)
rolling the aluminum
sheet with the roll surfaced at step (I). As can be seen, upon reaching a
modeled solution, the
shot-peening parameters associated there with may be implemented in surfacing
a work roll.
The actual results of implementation may be stored in the database along with
the process
parameters that caused them to expand the modeling capability.
FIG. 10 shows an alternative apparatus 110 for surfacing work rolls 114a, 114b
in
accordance with another embodiment of the present disclosure. During the
surfacing process to
be described below, the work rolls 114a, 114b are arranged in parallel and are
rotatable relative
to each other, being supported on the ends by suitable bearings (not shown),
like 16, 18 of FIG. 2
and driven by a motor or motors (not shown) like motor 20 shown in FIG. 2. A
media nozzle
122 like nozzle 22 of FIG. 2 may be retained on a gantry for moving or
positioning the nozzle
122 along the length of the rolls 114a, 114b proximate to where they converge,
which may be
called a nip N. The nozzle 122 can dispense media, e.g., ball bearings 132
into the nip area N,
such that when the rolls 114a, 114b are turned in the directions shown by the
arrows, the balls
132 will be drawn between the rolls. Unlike nozzle 22, the nozzle 122 need not
propel the balls
132 under pressure to achieve a high velocity, but may merely dispense the
balls 132 in a
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controlled manner. If the space between the rolls 114a, 114b is smaller than
the diameter of the
balls132, then a state of mechanical interference is achieved when they are
drawn into the nip N.
Given that the balls 132 are of comparable or greater hardness than the
surface of the rolls 114a,
114b and are sufficiently elastic, having an adequate compression strength to
pass through the
nip N without breaking, they will induce the formation of craters in the
surface of the rolls 114a,
114b as they pass through the nip N. The craters are formed in the surface of
the rolls 114a,
114b by compression rather than from the force of impact of balls projected at
the surface at high
velocity. After passing through the nip N, the balls 132 may be collected in a
gutter or hopper
138 for re-use. The rolls 114a, 114b may be adjustable to allow them to be
moved closer
together or farther apart, narrowing or widening the nip N, to adjust to
different size balls 132
and/or to control the depth of the craters that are formed on the rolls 114a,
114b.
FIG. 11 shows a similar apparatus as FIG. 10 with another type of ball feeding
mechanism, viz., an elongated hopper/funnel 230, which is capable of holding
and dispensing a
supply of balls 232, such that the area between the nip N and the
hopper/funnel 230 is filled to
capacity with balls 132 at all times. More particularly, balls 232 passing
through the nip act as a
stopper line causing balls falling through the hopper funnel 230 to back up
and prevent more
balls from falling out. The funnel/ hopper 230 may be closely fitted to the
generally V-shaped
area defined by the rolls 214a, 214b above the nip N, such that balls 232 can
not pass between
the rolls 214a, 214b and the funnel/hopper 230. As balls 232 pass through the
nip N, more balls
flow out of the hopper/funnel 230 to replace them, The used balls 232 are
collected in gutter 238
and recycled via lines 240a, 240c and recycling apparatus 240b . A barrier 242
on either end of
the rolls 214a, 214b (only one shown) can be used to prevent the balls 232
from flowing over the
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ends of the rolls 214a, 214b, containing the balls 232 in the V-shaped area.
FIGS. 12 and 13 show a media sheet 344 for surfacing a work roll in accordance
with another embodiment of the present disclosure. The media sheet 344 may
have a web
portion 344a, e.g., made from an elastomer, in which surfacing media, such as
spherical
.. indentors 332 like ball bearings are embedded. Alternatively, the web
portion 344a could be
made from a sheet of paper or polymer to which the surfacing media is adhered
by glue. The
media sheet 344 may be employed with a surfacing apparatus 110, 210 like those
shown in
FIGS. 10 and 11, namely, by passing the media sheet 344 through the nip N in
place of loose
balls 132, 232. If the web portion 344a is resilient enough and holds the
balls 332 tightly, it may
be possible to make a continuous loop with the media sheet 344 allowing it to
be cycled between
the rolls 214a, 214b until the desired crater coverage is realized. As shown
in FIG. 12, the balls
332 may be distributed over the media sheet 344 in any desired pattern, such
as a comprehensive,
evenly spaced coverage of the entire media sheet 344, a more dispersed pattern
or a random
distribution.
FIG. 14 diagrammatically shows a support surface 446, e.g., glass, coated with
a
layer of photoresist or a photopolymer 448. A source of radiation 452, such as
a UV light, an
electron beam or a laser, emits radiation, RI. In the case of light, an
optional radiation
distribution element 450, such as a mask or a lens array, distributes the
radiation R1 into a
distributed array of radiation R2 that impinges on the photoresist layer 448
creating an
.. undulating pattern 448a of greater and lesser light exposure. Upon
development of the
photoresist, a surface having a desired smoothly contoured texture may be
formed.
Alternatively, the layer of photoresist may be exposed/shaped by a laser
scanner or electron
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beam scanner to generate the desired pattern of exposure and resultant surface
profile upon
development.
As described in U.S Patent No. 7,094,502 to Schaefer et al., which is owned by
the assignee of the present application and which is incorporated herein in
its entirety by
.. reference, a shim 453 may be grown from the surface profile of the
developed photoresist layer
448. As further described in 7,094,502, the shim 453 may be hardened via
various plating and
coating processes to allow it to impressed upon the surface of a metal roll to
allow the surface
texture thereof to be transferred to the surface of the roll, and then,
subsequently, to a product
surface. In accordance with one aspect of the present disclosure, a shim 453
having a smoothly
.. undulating surface profile may be used to impart that texture to a working
roll, like roll 114a and
or 114b. For example, a shim 453 of this nature could be used like the media
sheet 344, passing
the shim 453 between rolls 214a, 214b of the apparatus 210 of FIG. 11. In
order to surface both
rolls 214a, 214b simultaneously, two shims 453 placed back to back or a shim
453 with two
textured faces could be employed. As another alternative, a textured shim 453
could be affixed
to the surface of a work roll, e.g., 214a by adhering it to the roll via
adhesives, brazing or
welding and then used to roll aluminum sheet.
FIG. 15 diagrammatically shows an ultrasonic ball peening apparatus 510 for
surfacing a work roll 514 in accordance with another embodiment of the present
disclosure.
Ultrasonic ball peening devices are available commercially, .e g., from Sonats
SA, Nantes,
Carquefou, France. In accordance with the present disclosure, such ball
peening devices may be
applied to the purpose of surfacing working rolls for rolling sheet aluminum,
i.e., if the velocity,
density, size, elasticity, and compression strength of the balls are such that
the appropriate crater
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depth is realized on the surface of the treated roll without peening media
breakage/degradation.
FIG. 16 shows an apparatus 610 for surfacing a work roll 614 in accordance
with
another embodiment of the present disclosure. A knurling head 662 supports a
knurling wheel
664 having a textured surface 664a. The knurling wheel 664 is rotatable on an
axle 664b and is
urged into the surface of the work roll 614 under the influence of a
substantial force F. Since
the contact area of the knurling wheel 664 and the work roll 614 is very
small, the force F is
concentrated over a small area, allowing the texture of the surface 664a to be
transmitted to the
roll 614, as shown by the area 614a. A gantry 624 may be used to allow the
knurling head 662 to
traverse the work roll 614 to impart the desired texture over the entire roll
614. The work roll
614 may be rotated by an electric motor inducing the knurling wheel 664 to
rotate as it textures
the work roll 614. An aspect of the present disclosure is to ensure that the
resultant surface 614a
(or the resultant surfaces of a work roll processed by the apparatus described
with reference to
FIGS. 10-15) has a conformation consistent with the beneficial texture
described above, e.g., that
achieved by shot peening with ball bearings, such as described above referring
to FIGS. 3a-3d.
The texturing of a work roll 614 using the apparatus 610 may require more than
one traversal by
the knurling head 662, depending upon the density of the surface texture of
the surface 664a
(undulations per unit area) and the coverage % desired.
FIG. 17 shows a surface of aluminum sheet metal M with a surface roughness
produced by a roll that is surfaced by grinding. Note that the X axis is
expressed in mm and the
Y and Z axes in p.m. Ground rolls impart the sheet with a pattern having a
plurality of
elongated, parallel furrows. The surface of the sheet M is rough in all
directions and the
roughness varies with direction, giving rise to frictional directionality when
the sheet interacts
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with another object or objects. Typically, roll roughness that is transferred
to the conventional
rolled sheet can be in the range of about 0.5 to 1pm Ra. An aspect of the
present disclosure is
the recognition that the roughness and directionality of conventional sheet
rolled by ground work
rolls has an impact on the functionality of the sheet when used in certain
applications. Further,
that a sheet produced in accordance with the present disclosure, e.g.,
produced by a roll that is
peened by ball bearings as described above, may be used advantageously
relative to a
conventional sheet for certain applications. For example, when the sheet is
used in a structure
for storing and/or directing the flow of materials, like grain, sugar, flour
or other finely divided
material, a sheet produced in accordance with the present disclosure, can
decrease the frictional
interaction with the material and reduce frictional variation due to
direction, leading to improved
flow and greater flexibility in the design of the material handling structure.
FIG. 18 shows a storage receptacle 705, such as a tank or silo for holding
grains,
flour, cereal, powdered foods such as, milk, chocolate, spices, eggs, sugar,
coffee, tea or other
flowable, divided, solid material 707, such as sawdust. The material 707 fills
the receptacle 705
.. to a level Li and may assume various levels, e.g., L2, within the
receptacle 705 as it is dispensed
from or fills the receptacle 705. A filler tube 709 is shown positioned
proximate a top opening
711 for depositing material 707 into the receptacle 705. The receptacle 705
may have a funnel
shaped portion 713 which converges to an outlet 715. The outlet 715 may house
a material
moving/control device such as a valve, a mechanical turbine, helical dispenser
or pneumatic or
suction dispenser. Funnels 717, sifters 719 and outlet nozzles 721 of various
types may be
utilized depending upon the material stored in the receptacle 705. The
interior walls 723 of the
receptacle 705 may be made from sheet metal, e.g., steel or aluminum. An
aspect of the present
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disclosure is the recognition that aluminum sheeting made by the techniques
disclosed herein can
be advantageous when used for forming the interior walls of storage
receptacles 705. More
particularly, the low coefficient of friction associated with the aluminum
sheet produced by rolls
treated as described herein, e.g., referring to Example 1 above, may promote
the infilling and
dispensing of material, e.g., flour or sugar from the receptacle 705. Using
flour as an example,
when introduced into the receptacle 705 (which in this case may be a flour
silo) a low static
coefficient of friction allows the flour to be shed from the interior
surfaces, e.g., 723 and fall to
the lowest point of the receptacle that is unoccupied by material 707. A low
static coefficient of
friction of the interior 723 promotes the self-distribution of material 707 in
the receptacle 705.
Material 707 present in the receptacle 705 wants to assume the lowest, least
energetic position
due to gravity (weight W of the material 707), but the weight of the material
707 also causes the
material to spread/expand sideways, exerting force FE against the interior 723
of the receptacle
705. When the material 707 moves relative to the interior surface 723, a
frictional force FF
arises, resisting the movement of the material 707. For example, if the
material 707 is dispensed
from the receptacle 705, causing it to move from level L2 to level Li, the
surface area of the
material 707 in contact with the interior surface 723 would exert a frictional
force FF along the
area of contact, impeding the movement of the material 707 and its dispensing
from the
receptacle 705. The frictional force FF is more significant in the funnel
portion 713, in that a
smaller component of the weight W is directed parallel to the interior surface
723 to oppose the
friction force FF. By using the aluminum sheeting material of the present
disclosure to form the
interior surface 723, the static coefficient of friction is reduced relative
to sheeting material
having a conventional surface (like FIG. 17) facilitating filling and
dispensing material from the
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receptacle 705. The static coefficient of friction for a material depends upon
the roughness of
the material, which for a conventional sheet would typically be 0.5 to 1.0 gm.
A comparable
sheet material produced by rolls surfaced in accordance with the present
disclosure, e.g.,
indenting with ball bearings, etc., as described above, will exhibit reduced
surface roughness and
a 10 to 30% improvement in static friction coefficient. This improvement
translates into a
workable orientation (slope) for a guide/storage surface encountering a
material such as flour of
about 40 to 70 degrees relative to the horizontal, e.g., for the funnel
portion 713.
Reducing the static coefficient of friction reduces the energy generated due
to friction
when handling bulk materials like flour, lowering the risk due to dust
explosion. Further,
reducing the coefficient of friction of the interior 723 of the receptacle
with the material 707
may, by promoting infilling and dispensing, reduce the need for material
moving equipment
(paddles, blowers, screw drives, etc.) and the energy to power them. In
addition, a greater
capability to shed material 707 may promote the cleanliness of the interior
surface 723 and first-
in, first-out material dispensing. In the case of flour and other food
materials 707, first-in, first-
out turnover prevents material from persisting in the receptacle for an
undesirably long period,
causing spoilage. Flour will go rancid if it sticks to the interior surfaces
723 of the receptacle
705 and persists there for an excessive amount of time. An interior 723, which
sheds the stored
material allows it to fall to the bottom for earlier dispensing. In addition,
this shedding may also
lengthen the time between required cleaning of the receptacle, which in the
case of a large
storage receptacle like a flour silo, entails considerable expense and
inconvenience.
In addition to storage structures, the attributes of low static friction
coefficient sheeting
material made in accordance with the present disclosure may also be used
advantageously for
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fabricating material moving structures. FIG. 19 shows a trough 805 having a
compound helical
shape and formed from sheet metal, e.g., aluminum alloy treated by rolls
described in the present
disclosure. Since the surfaces of the trough 805 have a lower static
coefficient of friction, it will
pass materials, e.g., grains, flour, sugar, objects, etc. more easily than a
similarly shaped trough
made from a material having a higher static coefficient of friction. As a
result, the trough 805
may use a lower slope and may be made in smaller dimensions than a comparable
trough made
from sheeting with a larger static coefficient of friction. While the trough
805 suggests gravity
conveyance, sheeting with a low coefficient of friction it would also promote
movement there
over that is induced by a moving device, such as a pusher, paddle or other
automated device.
FIG. 20 shows a tube or duct 905 having a compound helical shape and formed
from
sheet metal, e.g., aluminum alloy treated by rolls described in the present
disclosure. Since the
trough 805 has a low static coefficient of friction, it will pass materials
there through more easily
than a similarly shaped trough made from a material having a higher static
coefficient of friction,
thereby relaxing design constraints imposed by sheeting having a greater
static coefficient of
friction. The material conveying structure need not have a compound shape and
can be an
inclined flat surface, a straight tube or other simple shape and still exhibit
the benefits of a lower
static coefficient of friction.
FIG. 21 shows a testing apparatus 1003 for testing the static coefficient of
friction [is of a
sample sheet 1023 relative to a given material 1007, such as flour. For
simplicity of illustration,
the sample of material 1007 is assumed to have a weight emanating from a
single point
generating gravitational (weight) force Fw. Fw can be resolved into a force
normal to the surface
of the sheet 1023 FN and a force parallel to the sheet 1023 Fp, which is
opposed by the friction
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force FF. The friction force FF is related to the normal force FN by the
static coefficient of
friction as expressed in the equation FF= Rs F. When the parallel force Fp
exceeds the friction
force FF, the material 1007 will slide down the inclined surface of sheet
1023. As shown by
angles A and B, the sheet 1023 can be positioned at selected angles relative
to the horizontal to
ascertain the angle at which the material 1007 will slide. As described in the
following
examples, an aluminum sheet formed in accordance with the present disclosure
exhibits a lower
static coefficient of friction than conventional sheeting and therefore
material 1007 that is placed
on the surface of the sheet 1023 slides at lower angles relative to the
horizontal (at a lesser slope)
than comparable conventional sheet material.
EXAMPLE 1
A sheet of aluminum alloy 60cm by 30cm produced by a ground roll having 0.78m
roughness having conventional directionality and a static coefficient of
friction of 0.88 relative to
flour when tested parallel to the grain direction and a static coefficient of
friction of 0.92, when
tested perpendicular to the grain direction, was placed on a surface in a
horizontal position. A
similarly dimensioned sheet of aluminum alloy formed in accordance with the
present disclosure
(surfaced by a roll having been peened by ball bearings in accordance with the
process outlined
above in Example 1) and with a static coefficient of friction of 0.72 relative
to flour when tested
in a first direction and a static coefficient of friction of 0.73 when tested
in a second direction
perpendicular to the first direction, was placed beside the first sheet. A cup
of flour, weighing
25g was poured onto the surface of each sheet at about the same position. The
sheets were then
inclined at increasing angles relative to the horizontal. The flour disposed
on the sheet in
accordance with the present disclosure was observed to slide down the sheet at
an angle of 46 .
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The flour disposed on the conventional sheet did not slide down the sheet
until the angle of
elevation reached 610. The conventional sheet was positioned with the grain
direction parallel to
the motion of the flour.
EXAMPLE 2
In a second example, both the conventional sheet from the first example and
the sheet
made in accordance with the present disclosure were reused with the same
amount and type of
flour as before, but both were reoriented at 90 degrees relative to their
original position (such
that the grain direction of the conventional sheet was oriented side-to-side
when tilted). The
experiment was repeated. The flour slid down the sheet in accordance with the
present
disclosure when the sheet reached an angle of 47 , whereas the flour on the
conventional sheet
slid at an angle of 67 .
The foregoing examples illustrate that aluminum sheeting made in accordance
with the
present disclosure has a lower static coefficient of friction than
conventional sheeting and that
the coefficient is less dependent upon the orientation of the sheet. In
addition, the interaction of
the sheet with a lower coefficient of friction with flour allows the flour to
slide at a less severe
angle than the conventional sheet. This difference in sliding ease can be
beneficially used in
structures used to direct, move and store materials, such as grains, flour,
sugar, salt, powdered or
granulated chemicals, such as sodium bicarbonate, sawdust or any other such
materials.
Reduced frictional interaction may be employed to increase the flow rate of
materials through
chute, tubes, funnels, pipes and other hollow structures thereby speeding
material transfer,
eliminating or reducing the energy requirements of machinery such as blowers
and paddles to
move such materials along, decreasing material handling apparatus complexity,
fabrication and
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maintenance costs and energy use. Increased rates of material transfer reduce
the time and cost
to conduct transfer. For example, with respect to filling a silo with grain,
flour or sugar from a
cargo vehicle, an improved rate of transfer of 10% will translate into a 10%
reduction in the time
required of the vehicle, crew, warehousemen, etc., all of which amount to
significant cost
savings. An increased rate of transfer and decreased friction also allows more
efficient filling of
a receptacle like a silo, in that particulate matter like flour or grains can
more easily slide along
the interior surfaces of the silo as additional material is introduced. This
sliding accommodates
the added material, allowing it to spread and not to concentrate in areas,
e.g., under the fill
conduit, that would otherwise lead to areas of low density packing and high
density packing of
the material. Decreased frictional interaction between materials and material
moving and storing
structures also translates into greater design freedom of such structures,
e.g., reducing the slopes
needed to keep a given material flowing through the material handling
structure. The same can
be said of the isotropic nature of the friction coefficient of the sheeting
produced in accordance
with the present disclosure, in that the isotropic quality allows material
handling structures to be
fabricated without concern for orientation of sheeting grain. Besides insuring
a reduced
frictional interaction without regard to grain direction, the isotropic
quality also allows material
movement to be predicted more readily. For example a material pathway can be
ascertained
based upon geometry and static and dynamic forces independent of the grain
direction of the
sheeting used to fabricate the structure.
It will be understood that the embodiments described herein are merely
exemplary and
that a person skilled in the art may make many variations and modifications
without departing
from the spirit and scope of the claimed subject matter. For example, some
disclosure above
33
CA 02890916 2015-05-08
WO 2014/074844
PCT/US2013/069188
indicated that the range of roughness (roll grind) that are typically applied
to aluminum rolling
operations covering hot and cold rolling applications span <1 gin to 50 pin
and that typical work
roll hardness for Al operations is 50 to 70 Re. Notwithstanding, the methods
and apparatus of
the present disclosure could be applied to any surface finish above 50 gin and
any roll hardness
to achieve the same results by adjusting the peening media and peening
parameters, such as
pressure and dwell time to affect % coverage. All such variations and
modifications are intended
to be included within the scope of the present disclosure.
34
