U.S. patent application number 10/363731 was filed with the patent office on 2004-02-05 for method and device for obtaining shaped test-pieces of steel as required in tensile under corrosion fatigue tests.
Invention is credited to Mercuri, Attilio.
Application Number | 20040023601 10/363731 |
Document ID | / |
Family ID | 11445945 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040023601 |
Kind Code |
A1 |
Mercuri, Attilio |
February 5, 2004 |
Method and device for obtaining shaped test-pieces of steel as
required in tensile under corrosion fatigue tests
Abstract
A method is described to prepare shaped steal test-pieces (1)
for tensile under corrosion fatigue tests, which provides for
contacting a test-piece (1) subject to rotation about its
longitudinal axis and, each time, a disk (10) of sand paper, also
rotating, the contact being ensured by the own weight of the
test-pieces itself. A device for carrying out this method is also
described, which comprises a swinging arm (2) at an end of which
the test-piece (1) is rotatably mounted, being driven by a motor
(5), all these being mounted on a support central table (6),
substantially stationary, around which a support (7) can rotate,
having an annular shape on which a number of abrasive disks (10)
are mounted, each on a rotatable shaft (9), to be successively
positioned at the processing station in front of said supporting
arm (2).
Inventors: |
Mercuri, Attilio; (Pedrengo,
IT) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
11445945 |
Appl. No.: |
10/363731 |
Filed: |
March 7, 2003 |
PCT Filed: |
October 11, 2001 |
PCT NO: |
PCT/IT01/00515 |
Current U.S.
Class: |
451/51 |
Current CPC
Class: |
G01N 2203/0268 20130101;
G01N 3/02 20130101 |
Class at
Publication: |
451/51 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 11, 2000 |
IT |
MI2000A002197 |
Claims
1. A method to obtain shaped steel specimens, as required in tests
of tensile under corrosion tests to subject the same to the final
surface finishing steps to bring them to the lowest values of
roughness required, characterized by comprising the step of keeping
in rotation about its longitudinal axis the steel specimen (1)
already machined at its central portion (1a), to reach slightly
larger sizes than the prescribed final size, by bringing the same
to contact with a rotating sandpaper disk (10) in a plane tangent
to the outer surface of the central length (1a) of said specimen
(1), the contact being ensured by the specimen own weight.
2. A method according to claim 1, characterized in that the
abrasive disk (10) used is centrally registered with respect to the
cylindrical median length (1a), of smaller diameter, of the
specimen (1), with its profile contacting the end zones at which
said central length (1a) merges with the cylindrical end zones (1b)
of larger diameter of the specimen itself.
3. A method according to claim 1 or 2, comprising successively
further steps of surface finishing with abrasive disks (10) having
finer and finer grain size.
4. A method according to anyone of the preceding claims, wherein
the first step of surface finishing is carried out with a sandpaper
disk having grain size from 80 to 250 GRIT, while for the
subsequent working steps sandpaper disks are used having grain size
from 250 to 1000 GRIT until reaching roughness values of less than
0.81 .mu.m, preferably down to 0.1 .mu.m.
5. A device for the surface finishing of steel specimens to be used
in tests of tensile strength combined with corrosion, characterized
by comprising a swinging arm support (2) of a specimen (1)
rotatably held at the ends to rotate about is own longitudinal
axis, there been provided a motor (5) for driving such a rotation,
being mounted on the same support of a hinge fulcrum (3) of said
swinging arm (2), the specimen (1) carrier end of which extends
itself, with lowered arm, until a contact zone within an annular
support (7) with the center on said fulcrum (3), substantially
parallel to the longitudinal axis of rotation of specimen (1), said
contact zone or working station being located between the inner
periphery of said annular support (7) and an intermediate
circumference (C) comprised between said inner periphery and the
outer one, said circumference (C) having thereon, equally spaced
apart from each other, a number of vertical seats (14), each of
which is capable to house a shaft (9) for carrying an abrasive disk
(10), whereby there is interference between the profile of disk
(10) at the working station and said specimen (1) on its support
(2) when the latter is lowered due to the own gravity force of said
specimen.
6. A device according to claim 5, characterized by the fact of
comprising driving means (12) for rotating, about a vertical
central axis passing through the center of said circumference (C)
of said annular support (7) with respect to said fulcrum (3) fixed
on a support (4) mounted on a central support table (6) with
respect to said outer annular support (7), also said motor (5)
being mounted on that table (6).
7. A device according to claim 5 or 6, characterized by further
comprising rotation driving means (11) mounted at a fixed position
in correspondence with the said working station coincident with one
of said seats (14) when brought, through the rotation of said
support (7), in front of a specimen (1) on its swinging arm support
(2).
8. A device according to claim 7, characterized in that means (22,
25) are provided to be driven by an actuating means (21) to
transmit the rotation from said driving means (11) to a shaft (9)
supporting an abrasive disk (10) and fitted in said seat (14) at
the working station.
9. A device according to claim 8, characterized in that said
actuating means (21) is made as a cylinder, the rod of which drives
the end of a lever (22) the opposite end of which is capable of
thrusting an idle pin (25) driven into rotation by said actuating
means (11) to mesh the same with the said shaft (9) and drive the
latter into rotation about its axis.
10. A device according to claim 9, characterized by further
comprising on said lever (22) stop means (23) for blocking said
annular support (7) with said shaft (9) at the exact position of
working station at the same time of said shaft (9) being driven by
said actuating means (21).
11. A device according to any of claims 6-10 characterized by
comprising means (15, 15') for adjusting the position, in its
plane, of said support table (6) by means of small angle rotations
in opposite directions about said central vertical axis.
12. A device according to any of claims 6-11, characterized in that
said support table (6) is in turn mounted on base plates (17, 18)
overlapping with an intermediate gap (26), one of which (17) can
swing around a horizontal median axis coincident with the diameter
of said circumference (C) passing through said working station,
there being provided jack means (13) to cause such a swinging
movement and a hinge means (19) between said two plates (17, 18),
there being further provided springs (16, 16') housed within said
plate (17) in contact with the said support table (6) to
automatically register the positioning of the latter on the base
plates.
13. A device according to claim 5, characterized in that an
adjustable counterweight (20) is provided at the end of the
swinging arm support (2) which is opposite to the end on which the
specimen (1) is rotatably mounted.
Description
[0001] The present invention relates to a processing method for
preparing the steel specimens to be used in tests of tensile
strength in a corrosive environment, as well as the device for
carrying out such a method.
[0002] It is known that the tests undertaken by the materials to
check their resistance to the different and hardest operating
conditions, have to follow strict standards determining in any
aspect the physical conditions at which the tests have to be
carried out. In particular, to determine through laboratory tests
the resistance of metals to peculiar types of rupture in
environments wherein H.sub.2S is present, tensile and corrosion
fatigue tests are provided being dictated by international
standards EFC and NACE, especially the one called NACE.TM. 0177-96.
Various test methods are described, always in a corrosive
environment according to the mechanical stresses undergone by the
specimen of material. The tests relating to the so-called "A
method" according to which the specimen of material is subjected to
tensile stresses until breaking, are particularly important.
Obviously the sample or test-piece is defined in every dimensional
feature thereof, and also all the testing conditions and the
devices used to this purpose are detailed.
[0003] The test-piece, as shown (substantially as a scale-drawing)
in FIG. 5, is of cylindrical shape in the central elongated portion
1a, having a reduced diameter with respect to the diameter of the
two cylindrical end zones 1b. Also the minimum bending radius (R=15
mm) of the adjoining zone between the central cylindrical portion
1a with reduced diameter and the two end zones 1b is fixed.
[0004] It is known that one of the most critical features that a
specimen must show for this type of test is the roughness degree
which has to be less than 0.81 .mu.m. To have a so high level of
finish, it is thereby necessary to subject the specimens, already
machined to the required sizes, to subsequent polishing and final
lapping steps while providing a certain number of longitudinal
finishing passes in sequence with disks obtained from sandpaper
with a roughness from 80 to 250 GRIT (grains per square inch), then
hand smoothing in longitudinal direction under water with four
successive sandpapers having different grain sizes 250-400-600-1000
and finally hand lapping, still in longitudinal direction, with
cloth and diamond paste with three different grades. 6-3-1
.mu.m.
[0005] Obviously these manual operations are extremely delicate and
require a notable expenditure of time and a large-scale employment
of labour, which make particularly costly the preparation of such
specimens designed to undergo destructive testing in a laboratory.
Furthermore, the care required in carrying out these finishing
steps is such to involve a high degree of experience and
specialization by the operators, considering that possible
inaccuracies found during the final check result in test-pieces not
in conformity with the standards, which thereby shall be
unavoidably discarded and destroyed to be replaced with other
specimens for a new processing.
[0006] Therefore it is an object of the present invention that of
providing a method of preparation of the metal specimens as defined
above, with which the processing time and the labour employment can
be reduced, with a lower rate of reworking.
[0007] It is also an object of the present invention that of
providing a device capable of mechanically carrying out the surface
finishing of the above-mentioned metal test-pieces by putting into
practice the cited method by the use of a computerized system.
[0008] These and other objects are achieved through the features of
the respective independent method and device claims.
[0009] Further objects, advantages and features of the device
according to the present invention and of the method carried out
this way will be made clearer by the following detailed description
of a preferred embodiment, given by way of a non-limiting example
with reference to the annexed drawings in which:
[0010] FIG. 1 shows a top plan view of an embodiment of the device
according to the present invention;
[0011] FIG. 2 shows a cross-section view taken along line II-II of
FIG. 1;
[0012] FIG. 3 shows a cross-section view along line III-III of FIG.
1;
[0013] FIG. 4 shows a fragmentary view, partially sectional, of the
same device, taken in the direction of arrow A of FIG. 2; and
[0014] FIG. 5 shows a scale view of a test-piece in contact with an
abrasive disk in a working position according to the inventive
method.
[0015] The method of the present invention intends to subject the
steel specimen to be used in the tests of tensile-corrosion tests
as above mentioned, already prepared at a size slightly larger than
the final one (a few tenths of millimeter more), to the action of
sandpaper disks brought successively, with finer and finer grain,
into contact with the median zone, having a smaller diameter, of
the specimen itself, driven into rotation about its longitudinal
axis, while also the abrasive disk rotates about its axis which is
perpendicular to the rotation axis of the specimen.
[0016] The latter is preferably resting on the sandpaper disk under
the action of its own weight, preferably in a controllable way by
means of suitable counterweights.
[0017] The preferred working position (as illustrated in FIG. 5) is
that in which the test-piece specimen 1 to be worked, in horizontal
position, is resting on an abrasive disk 10, also horizontal, with
such an interference degree, whereby the disk profile enters into
contact with the radiused zones at the ends of the central
cylindrical portion 1a of the specimen itself, having a reduced
diameter.
[0018] A preferred device to carry out the method of the present
invention is the one represented in the enclosed drawings wherein
the specimen 1 to be worked is rotatably mounted at the end of a
swinging arm 2 which is hinged through a fulcrum 3 to a support 4.
The specimen 1 can be driven into rotation about its longitudinal
axis by means of a small motor 5 and a belt- or chain-driving
system 5'.
[0019] Both the support 4 and motor 5 are mounted on a central
table 6 of the device, around which there is rotatably mounted an
annular-shaped outer support 7 of the sandpaper disks 10, 10' . . .
Bearings 8 are preferably provided along the inner wall of the
rotatory annular support 7 to reduce as much as possible the
friction during the rotation of the outer support 7 with respect to
the central table 6. Obviously the fulcrum 3 is placed, as better
shown in FIG. 1, at a central position of the device, along a
diameter of the annular support 7, so as the swinging arm 2 ends at
said support, innerly with respect of a median circular line C
along which there are mounted a certain number (eight have been
represented in FIG. 1) of supporting shafts 9 for the abrasive
disks 10, equally spaced in suitable seats 14. In this way the
test-piece specimen 1 (not shown in scale in FIG. 1, but with a
slenderness much lower than its real value) will be brought to
partially lean on the sandpaper disk 10 which at that moment is
located at the working station in coincidence with the diameter of
line C, being perpendicular to fulcrum 3, thereby to the
longitudinal axis of rotation of specimen 1. As stated above, in
this position the outer profile of disk 10 will preferably "match"
the two zones merging from the central portion with smaller
diameter to the cylindrical end zones of the specimen itself.
[0020] Still making reference to the drawings, 11 represents the
motor controlling the rotation of each rotating shaft 9 and of the
corresponding abrasive disk 10 when the annular support 7 has been
brought to such a position that the same shaft 9 is located in
front of the specimen 1, exactly at the position indicated as 10 in
FIG. 1. The rotation of said rotatable support 7 of the abrasive
disks 10 is ensured by a motor means stationary mounted, operating
onto the periphery of the annular support through a driving means
(12') such as a belt.
[0021] In order to ensure all the other regulations which guarantee
the exact positioning of specimen 1 to be prepared with respect to
abrasive disk 10 at the working station, a mechanical jack 13 is
provided which, passing with its rod 13' through two overlapping
base plates 17 and 18 with an intermediate gap 26, determines the
correct positioning of the support table 6 for its horizontal
adjustment about the diametral axis of the device as defined by the
vertical plane passing through the median axis of the swinging arm
2. To this effect it is provided that the upper plate 17, on which
the support table 6 is mounted, is hinged in 17' on a plate 19
fixed to the lower plate 18 so as to allow, thanks to the gap or
clearance 26, relative movements between the two plates according
to arrows F, F' and an immediate adaptation of the various support
members to each other, in particular of table 6 and consequently of
the fulcrum 3 for the swinging of the specimen carrier arm 2, also
by means of a pair of springs 16, 16'.
[0022] For the adjustments in the horizontal plane, with
possibility of rotation about a central vertical axis passing
through the fulcrum 3 and perpendicular thereto, thus defining the
exact positioning of the median axis of the swinging arm 2, thereby
of the specimen 1 with the axis of shaft 9 (or seat 14) in
correspondence with the working station, a pair of adjusting screws
15, 15' are provided which are suitable to move along small
rotation angles in the horizontal plane, respectively clockwise or
counter-clockwise, the swinging specimen carrier arm, so that the
specimen, already positioned on a horizontal plane or anyhow
perfectly parallel to that of the supporting annular 7, thereby
also of the abrasive disk 10 with which it has to come into
contact, reaches the correct position to start with the surface
finishing step. A counterweight 20, provided at the opposite end of
the swinging arm 2, with respect to the specimen carrier end, can
be adjusted to vary its weight, i.e. the force due to the gravity
applied in correspondence with the contact zone between specimen
and abrasive disk. The movement of rotation from motor 11 to the
shaft 9 on which the abrasive disk 10 is traditionally mounted, is
preferably transmitted, as shown in FIGS. 2 and 3, as described in
the following.
[0023] Upon completion of the above-described regulations, with the
adjusting screws 15, 15' shifting the specimen 1 exactly to the
desired position, and having obtained the precise horizontal
orientation of table 6 by means of the jack 13, when motor 11 is
already rotating, both motor 5 for rotating specimen 1 resting on
disk 10 owing to its own weight and a control cylinder 21 are
operated, the latter having its rod pivotedly mounted at the end of
a lever 22, in its turn linked in 22', causes the lever to swing
(counter-clockwise rotation when the rod retracts, as illustrated
in FIGS. 2, 3). A lever portion 23, protruding laterally, can
advantageously fit into a corresponding recess of the outer wall of
the annular support 7 to block the same at a given position during
the operation. At the same time the opposite end 24 of lever 22
thrusts upwards an idle pin 25 driven to rotate by motor 11, brings
the same to mesh with the lower end of shaft 9, which is thus
caused to rotate. This way the motor 11 can continuously rotate,
thus driving therewith the idle pin 25 which can drive the shaft 9
only when the cylinder 21 is operated. As already seen above, this
determines at the same time the annular support 7 to stop at the
correctly registered position and consequently the specimen 1 with
respect to the disk 10 mounted on the shaft 9.
[0024] It will be noted that when a new specimen 1 begins to be
worked, the counterweight 20 is the lowest in order not to balance
the contact force due to the specimen weight and to render more
efficient the surface finishing with the first abrasive disk 10
having coarser grain, like previously for the manual working
according to the prior art. Subsequently disks of finer grain are
brought against specimen 1 at the working station, possibly
increasing the counterweight in 20 to reduce the abrasive force
applied and the quantity of material removed, thus gradually
obtaining the lowest roughness desired. Near the working end, when
abrasive disks of slightest roughness are used, and substantially
all the material in excess has been removed and the central useful
zone of cylinder with reduced diameter is become longer to the cost
of the end portions with larger cross-section, abrasive disks of
larger diameter can be used to ensure the matching with the
radiused end zones.
[0025] The necessary timing, controls of the rotation speeds of the
test-piece specimen and/or the abrasive disks, as well as the
movements of the annular support 7 to bring a subsequent disk 10'
to the working station are preferably controlled by means of a
pre-settable computerized program.
[0026] Finally, it will be possible to complete the method
according to the present invention with steps of final measurement
of the roughness obtained (up to 0,1 .mu.m) by providing at the
same time the device as above described and illustrated with the
necessary measuring means.
* * * * *