U.S. patent application number 15/896110 was filed with the patent office on 2018-08-16 for forming method.
This patent application is currently assigned to ROLLS-ROYCE plc. The applicant listed for this patent is ROLLS-ROYCE plc. Invention is credited to Craig A. JOHNSON, Martin TUFFS.
Application Number | 20180229284 15/896110 |
Document ID | / |
Family ID | 58462032 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180229284 |
Kind Code |
A1 |
TUFFS; Martin ; et
al. |
August 16, 2018 |
FORMING METHOD
Abstract
A method of shear forming a component comprises the steps of:
(i) providing a pre-formed metallic sheet blank, the sheet blank
having a first surface and an opposite second surface, the
perpendicular separation between the first surface and the second
surface defining a thickness of the sheet blank; (ii) applying a
surface modification process to the first surface of the sheet
blank to reduce a surface roughness of the first surface to a first
predetermined roughness value; (iii) positioning the second surface
of the sheet blank against a mandrel; and (iv) applying a roller to
the first surface of the sheet blank in a shear forming operation
to form the sheet blank into the component.
Inventors: |
TUFFS; Martin; (Nottingham,
GB) ; JOHNSON; Craig A.; (Derby, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROLLS-ROYCE plc |
London |
|
GB |
|
|
Assignee: |
ROLLS-ROYCE plc
London
GB
|
Family ID: |
58462032 |
Appl. No.: |
15/896110 |
Filed: |
February 14, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B21B 13/10 20130101;
B21D 22/16 20130101; B21B 2205/00 20130101; B21B 45/00
20130101 |
International
Class: |
B21B 13/10 20060101
B21B013/10; B21B 45/00 20060101 B21B045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2017 |
GB |
1702463.9 |
Claims
1. A method of shear forming a component from a pre-formed metallic
sheet blank, the sheet blank having a first surface and an opposite
second surface, the perpendicular separation between the first
surface and the second surface defining a thickness of the sheet
blank, the method comprising the steps of: (i) providing the
metallic sheet blank; (ii) applying a surface modification process
to the first surface of the sheet blank to reduce a surface
roughness of the first surface to a first predetermined roughness
value; (iii) positioning the second surface of the sheet blank
against a mandrel; and (iv) applying a roller to the first surface
of the sheet blank in a shear forming operation to form the sheet
blank into the component.
2. The method as claimed in claim 1, wherein the metallic sheet
blank is formed by a rolling process, and step (ii) comprises the
step of: (ii)' applying a surface modification process to the first
surface of the sheet blank to reduce a surface roughness of the
first surface to a first predetermined roughness value, the second
surface of the sheet blank remaining in an as-rolled condition.
3. The method as claimed in claim 1, wherein step (ii) comprises
the step of: (ii)'' applying a surface modification process to the
first surface of the sheet blank to reduce a surface roughness of
the first surface to a first predetermined roughness value, and
applying a surface modification process to the second surface of
the sheet blank to reduce a surface roughness of the second surface
to a second predetermined roughness value, the second predetermined
roughness value being greater than the first predetermined
roughness value.
4. The method as claimed in claim 1, wherein the surface
modification process is selected from the group consisting of
abrasive grinding, electrochemical grinding, electrolytic etching,
electro-polishing, shot blasting, grit blasting, acid pickling,
molten salt bath treatment, and etching.
5. The method as claimed in claim 1, wherein the sheet blank is
formed from a material selected from the group comprising titanium
alloys nickel-cobalt-based superalloys, stainless steels, and
aluminium alloys.
6. The method as claimed in claim 1, wherein the first surface of
the sheet blank has a first predetermined roughness value (Ra) of
less than 3.0 .mu.m.
7. The method as claimed in claim 6, wherein the first surface of
the sheet blank has a first predetermined roughness value (Ra) of
less than 2.0 .mu.m.
8. The method as claimed in claim 6, wherein the first surface of
the sheet blank has a first predetermined roughness value (Ra) of
less than 1.0 .mu.m.
9. A computer program that, when read by a computer, causes
performance of the method as claimed in claim 1.
10. A non-transitory computer readable storage medium comprising
computer readable instructions that, when read by a computer,
causes performance of the method as claimed in claim 1.
11. A signal comprising computer readable instructions that, when
read by a computer, causes performance of the method as claimed in
claim 1.
Description
CROSS-REFERENCE RELATED APPLICATIONS
[0001] This disclosure claims the benefit of UK Patent Application
No. GB 1702463.9, filed on 15 Feb. 2017, which is hereby
incorporated herein in its entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to a method of shear forming
and particularly, but not exclusively, to a method of shear forming
components for a gas turbine engine.
BACKGROUND OF THE DISCLOSURE
[0003] Shear forming has been used to produce conical parts from
sheet and plate material for many years. Shear forming is a cold
forming technology whereby a flat metal plate blank (or `pre-form`)
is mounted onto a rotating mandrel (typically having a conical
surface profile) and the material is made to flow against and up
the mandrel by the action of one or more rollers. The final wall
thickness is achieved by controlling the gap between the roller and
the mandrel so the material is displaced axially, and generally
parallel to the axis of rotation.
[0004] Sheet material used for shear forming, and having a
thickness in excess of 3 mm is generally produced by a hot rolling
process. When carrying out shear forming using hot rolled sheet
material in its `as-rolled` form, it has been observed that there
is a marked reduction in fatigue properties of the material after
shear forming. In addition the thickness tolerance on hot rolled
sheet is often large (i.e. +/-10% from nominal values) due to
process capability. This means that it is common practice for the
`as-rolled` sheet to be ground on both sides to meet the tolerances
required by the engine application.
[0005] When used in a shear forming process, this `fully ground`
sheet material results in a fatigue improvement in line with
established understanding. This has led to a situation whereby
grinding on both sides of the sheet is often stipulated prior to
shear forming, which substantially increases the cost of the shear
forming process.
SUMMARY OF DISCLOSURE
[0006] According to a first aspect of the present disclosure there
is provided a method of shear forming a component from a pre-formed
metallic sheet blank, the sheet blank having a first surface and an
opposite second surface, the perpendicular separation between the
first surface and the second surface defining a thickness of the
sheet blank, the method comprising the steps of: [0007] (i)
providing the metallic sheet blank; [0008] (ii) applying a surface
modification process to the first surface of the sheet blank to
reduce a surface roughness of the first surface to a first
predetermined roughness value; [0009] (iii) positioning the second
surface of the sheet blank against a mandrel; and [0010] (iv)
applying a roller to the first surface of the sheet blank in a
shear forming operation to form the sheet blank into the
component.
[0011] According to the method of the disclosure, if the material
blank is placed in the shear forming machinery with the modified
surface of the sheet facing towards the roller, as opposed to
facing onto the mandrel, then the fatigue properties of the shear
formed article do not reduce over those of the material itself.
[0012] Indeed the fatigue properties of the shear formed article
are improved in line with the cold work performed on the material
during the shear forming process. This is an unexpected result.
[0013] Optionally, the metallic sheet blank is formed by a rolling
process, and step (ii) comprises the step of: [0014] (ii)' applying
a surface modification process to the first surface of the sheet
blank to reduce a surface roughness of the first surface to a first
predetermined roughness value, the second surface of the sheet
blank remaining in an as-rolled condition.
[0015] According to the method of the disclosure, if the material
blank is placed in the shear forming machinery with the `as-rolled`
(sometimes referred to as "hot rolled") sheet surface facing onto
the mandrel, as opposed to facing onto the roller, then the fatigue
properties of the shear formed article do not reduce over those of
the material itself.
[0016] Optionally, step (ii) comprises the step of: [0017] (ii)''
applying a surface modification process to the first surface of the
sheet blank to reduce a surface roughness of the first surface to a
first predetermined roughness value, and applying a surface
modification process to the second surface of the sheet blank to
reduce a surface roughness of the second surface to a second
predetermined roughness value, the second predetermined roughness
value being greater than the first predetermined roughness
value.
[0018] In another embodiment, a surface modification is applied to
each of the first surface and the second surface. The roughness of
the first surface is reduced to a first predetermined roughness
value. The roughness of the second surface is reduced to a second
predetermined roughness value. A feature of this embodiment is that
the second predetermined roughness value being greater than the
first predetermined roughness value.
[0019] Optionally, the surface modification process is selected
from the group consisting of abrasive grinding, electrochemical
grinding, electrolytic etching, electro-polishing, shot blasting,
grit blasting, acid pickling, molten salt bath treatment, and
etching.
[0020] Any surface modification process that substantially improves
the surface finish of the first surface of the sheet blank may be
used. In one arrangement, this surface modification takes the form
of surface grinding. In other arrangements, the surface
modification process may be electro-polishing, etching or some
other equivalent technique.
[0021] Optionally, the sheet blank is formed from a material
selected from the group comprising titanium alloys
nickel-cobalt-based superalloys, stainless steels, and aluminium
alloys.
[0022] In one arrangement, the sheet blank is formed from a 6-4
titanium alloy material.
[0023] Optionally, the first surface of the sheet blank has a first
predetermined roughness value (Ra) of less than 3.0 .mu.m.
[0024] Providing the first surface of the sheet blank with a first
predetermined roughness value (Ra) of less than 3.0 .mu.m prior to
the shear forming process enables the method of the present
disclosure.
[0025] Optionally, the first surface of the sheet blank has a first
predetermined roughness value (Ra) of less than 2.0 .mu.m.
[0026] Optionally, the first surface of the sheet blank has a first
predetermined roughness value (Ra) of less than 1.0 .mu.m.
[0027] According to a second aspect of the present disclosure there
is provided a computer program that, when read by a computer,
causes performance of the method according to the first aspect.
[0028] The shear forming apparatus may be controlled by a computer
that is programmed by way of a corresponding computer program to
carry out the method of the disclosure.
[0029] According to a third aspect of the present disclosure there
is provided a non-transitory computer readable storage medium
comprising computer readable instructions that, when read by a
computer, causes performance of the method according to the first
aspect.
[0030] The computer program that causes operation of the shear
forming process may be stored within the computer or in a separate
storage medium.
[0031] According to a fourth aspect of the present disclosure there
is provided a signal comprising computer readable instructions
that, when read by a computer, causes performance of the method
according to the first aspect.
[0032] In an alternative arrangement, a signal may be provided to
the computer that causes performance of the method of the present
disclosure.
[0033] Other aspects of the disclosure provide devices, methods and
systems which include and/or implement some or all of the actions
described herein. The illustrative aspects of the disclosure are
designed to solve one or more of the problems herein described
and/or one or more other problems not discussed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] There now follows a description of an embodiment of the
disclosure, by way of non-limiting example, with reference being
made to the accompanying drawings in which:
[0035] FIG. 1 shows a schematic view of a shear forming apparatus
for carrying out the method of the present disclosure, with the
material blank held against the mandrel;
[0036] FIG. 2 shows the shear forming apparatus of FIG. 1 with the
method of the present disclosure underway; and
[0037] FIG. 3 shows schematically the fatigue performance of shear
formed articles formed by the method of the present disclosure
together with articles formed by the method of the prior art.
[0038] It is noted that the drawings may not be to scale. The
drawings are intended to depict only typical aspects of the
disclosure, and therefore should not be considered as limiting the
scope of the disclosure. In the drawings, like numbering represents
like elements between the drawings.
DETAILED DESCRIPTION
[0039] Referring to FIGS. 1 and 2, a shear forming apparatus that
is capable of carrying out the method of the present disclosure is
designated generally by the reference numeral 100.
[0040] The shear forming apparatus 100 comprises a mandrel 110 that
can be rotated in a direction of rotation 112 by means of a rotary
actuator 114. The mandrel 110 has a generally radially outwardly
facing surface 118. This radially outwardly facing surface 118 is
formed as an inverse of the desired surface profile of the finished
article resulting from the shear forming process.
[0041] A pre-formed metallic sheet blank 120 is clamped against the
distal end of the mandrel 110 by a clamping force 150. In this way
the rotation 112 of the mandrel is transmitted to the sheet blank
120 that rotates co-operatively with the mandrel 110.
[0042] The sheet blank 120 is provided with a first surface 122 and
an opposite second surface 124. In the present disclosure, the
first surface 122 is subjected to a surface modification process
prior to being clamped in position in the shear forming apparatus
100.
[0043] In one arrangement, the surface modification process is a
surface grinding process. The surface grinding process serves two
main purposes. Firstly, it enables a thickness 126 of the sheet
blank 120 to be maintained to a pre-determined value. Secondly, it
enables the surface roughness of the first surface 122 to be
reduced to a first predetermined roughness value that is less than
the surface roughness of the `as-rolled` surface.
[0044] In this embodiment, the surface roughness of the first
surface 122 is reduced to a first predetermined roughness value of
approximately 2.0 .mu.m. The surface roughness of the second
surface is left in the `as-rolled` condition.
[0045] In other embodiments, the surface roughness of the second
surface may also be subjected to a surface modification process to
reduce a surface roughness of the second surface to a second
predetermined roughness value, with the second predetermined
roughness value being greater than the first predetermined
roughness value. A controllable roller assembly 140 is provided to
flow form the material of the sheet blank 120 against the radially
outwardly facing surface 118 of the mandrel 110.
[0046] FIG. 1 shows the sheet blank 120 clamped against the mandrel
110 before the roller assembly 140 has started the flow forming of
the sheet blank 120. FIG. 2 shows the shear forming process
underway. The sheet blank 120 remains clamped against the mandrel
110 by the clamping force 150. The roller assembly 140 is part way
through the process of flow forming the material of the sheet blank
120 against the radially outwardly facing surface 118 of the
mandrel 110.
[0047] The shear forming process continues with the roller assembly
140 flow forming the sheet blank 120 against the radially outwardly
facing surface 118 of the mandrel 110 until the component is fully
formed.
[0048] In the embodiment of the present disclosure, the shear
forming apparatus 100 is controlled by a computer 160. The computer
160 is provided with a computer program 162 that causes the
computer 160 to control the shear forming apparatus 100 to carry
out the method of the present disclosure. A computer readable
storage medium 164 is provided that sends a signal 166 to the
computer that causes the computer 160 to carry out the claimed
method.
[0049] The technology of shear forming is well known to a skilled
person and the control of the shear forming apparatus 100 is not
herein discussed in further detail.
[0050] FIG. 3 illustrates schematically the fatigue performance of
some examples of shear forming the same component but starting from
sheet blanks 120 with different combinations of surface finish on
opposing surfaces.
[0051] Sheet blanks 120 having three combinations of surface finish
on opposing surfaces were used. Firstly, sheet blanks 120 having
both surfaces finished by grinding. Secondly, sheet blanks 120
having one surface finished by grinding, with the ground surface
clamped against the mandrel and the roller assembly 140 pressed
against the `as-rolled` surface. Thirdly, sheet blanks 120 having
one surface finished by grinding, with the `as-rolled` surface
clamped against the mandrel and the roller assembly 140 pressed
against the ground surface.
[0052] Although in production there are no controls over which
surface is placed against the mandrel an intuitive situation would
be to place the smoother ground side against the smooth surface of
the mandrel with the roller assembly being pressed against the
`as-rolled` surface. This arrangement would also give rise to the
cosmetic benefit of improving the rougher `as-rolled` finish during
the shear forming process as a result of the action of rollers.
However, in reality this arrangement results in a decrease in
fatigue performance. It is postulated that this decrease in fatigue
performance is caused by the rollers interacting with the rough
`as-rolled surface` to produce microstructural features from which
fatigue initiates more readily.
[0053] As shown in FIG. 3 placing the `as-rolled` surface of the
sheet blank against the mandrel, with the roller assembly pressing
against the ground surface of the sheet blank, results in an
increase in the fatigue performance of the formed component.
[0054] Various example embodiments of the invention are described
herein. Reference is made to these examples in a non-limiting
sense. They are provided to illustrate more broadly applicable
aspects of the invention. Various changes may be made to the
invention described and equivalents may be substituted without
departing from the true spirit and scope of the invention. In
addition, many modifications may be made to adapt a particular
situation, material, composition of matter, process, process act(s)
or step(s) to the objective(s), spirit or scope of the present
invention. Further, as will be appreciated by those with skill in
the art that each of the individual variations described and
illustrated herein has discrete components and features which may
be readily separated from or combined with the features of any of
the other several embodiments without departing from the scope or
spirit of the present inventions. All such modifications are
intended to be within the scope of claims associated with this
disclosure.
[0055] Example aspects of the invention, together with details
regarding material selection and manufacture have been set forth
above. As for other details of the present invention, these may be
appreciated in connection with the above-referenced patents and
publications as well as generally known or appreciated by those
with skill in the art. The same may hold true with respect to
method-based aspects of the invention in terms of additional acts
as commonly or logically employed.
[0056] The breadth of the present invention is not to be limited to
the examples provided and/or the subject specification, but rather
only by the scope of claim language associated with this
disclosure.
* * * * *