U.S. patent application number 13/351519 was filed with the patent office on 2013-07-18 for method of surface treatment for dovetail in gas turbine engine fan blade.
The applicant listed for this patent is Venkatarama K. Seetharaman. Invention is credited to Venkatarama K. Seetharaman.
Application Number | 20130183157 13/351519 |
Document ID | / |
Family ID | 48780086 |
Filed Date | 2013-07-18 |
United States Patent
Application |
20130183157 |
Kind Code |
A1 |
Seetharaman; Venkatarama
K. |
July 18, 2013 |
METHOD OF SURFACE TREATMENT FOR DOVETAIL IN GAS TURBINE ENGINE FAN
BLADE
Abstract
A method of surface treating a dovetail in a blade includes the
steps of providing a burnishing operation along circumferential
sides of the dovetail. Next, shot peening is provided at axial ends
of the dovetail. A fan blade made by the method is also
claimed.
Inventors: |
Seetharaman; Venkatarama K.;
(Rocky Hill, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seetharaman; Venkatarama K. |
Rocky Hill |
CT |
US |
|
|
Family ID: |
48780086 |
Appl. No.: |
13/351519 |
Filed: |
January 17, 2012 |
Current U.S.
Class: |
416/219R ;
451/28 |
Current CPC
Class: |
B24B 39/006 20130101;
B24C 1/10 20130101; F01D 5/005 20130101; F01D 5/286 20130101; B23P
9/00 20130101; C21D 7/04 20130101 |
Class at
Publication: |
416/219.R ;
451/28 |
International
Class: |
F01D 5/30 20060101
F01D005/30; B24B 1/00 20060101 B24B001/00 |
Claims
1. A method of surface treating a dovetail in a blade comprises the
steps of: providing a burnishing operation along circumferential
sides of said dovetail; and then providing shot peening to axial
ends of said dovetail.
2. The method as set forth in claim 1, wherein said burnishing
operation is low plasticity burnishing.
3. The method as set forth in claim 2, wherein said burnishing
technique includes a body which is brought into contact with the
circumferential sides of said dovetail, said body being controlled
by a position control and a pressure control to apply a desired
stress distribution and compressive load within the dovetail along
said circumferential sides.
4. The method as set forth in claim 1, wherein the entire dovetail
is subject to a shot peening process prior to the burnishing
operation.
5. The method as set forth in claim 1, wherein said axial ends are
not regular surfaces, but have complex curved shapes
6. The method as set forth in claim 5, wherein said circumferential
sides have a more regular shape.
7. The method as set forth in claim 1, wherein said blade is for
use in a gas turbine engine.
8. The method as set forth in claim 7, wherein said blade is a fan
blade.
9. A blade comprising: an airfoil extending radially outwardly from
a dovetail, the airfoil having a leading edge and a trailing edge;
and said dovetail having circumferential sides, and axial ends,
with said circumferential sides being surface treated by a
burnishing operation, and said axial ends being surface treated by
shop peening; and said axial ends having complex curved shapes, and
said circumferential sides having generally regular shapes along an
axial length.
10. The blade as set forth in claim 9, wherein said blade is for
use in a gas turbine engine.
11. The blade as set forth in claim 10, wherein said blade is a fan
blade.
Description
BACKGROUND
[0001] This application relates to a surface treatment method for
treating a dovetail in a blade.
[0002] Gas turbine engines are known, and typically have a fan
delivering air to a compressor. From the compressor, the air passes
downstream into a combustion section where it is mixed with fuel
and burned. Products of that combustion pass downstream over
turbine rotors which in turn drive the fan to rotate.
[0003] The fan may include a plurality of separate blades mounted
into a rotor. The blades have an airfoil which moves the air, and a
radially inner portion, known as a dovetail, which is received
within a slot in the rotor.
[0004] The dovetail is subject to high stress during operation of
the gas turbine engine. Thus, it presents challenges to a designer
of a fan blade.
[0005] One method that has been proposed to address the stresses
applied into the dovetail is to utilize a burnishing operation on
the dovetail. A burnishing operation will induce stresses within
the part. These induced stresses are residual compressive stresses
that can be induced into the part to a desired depth. The induced
stresses counter applied stresses during operation to result in an
overall lower stress level.
[0006] The burnishing operation does provide good control over the
level of induced stresses and the depth into the material. However,
burnishing typically requires a somewhat flat surface, and thus,
complex surfaces may not be candidates for burnishing.
[0007] Once a burnishing operation has been applied to a part,
surfaces that have not been burnished may have increased stresses
or other changes which may be undesirable.
SUMMARY
[0008] A method of surface treating a dovetail in a blade includes
the steps of providing a burnishing operation along circumferential
sides of the dovetail. Next, shot peening is provided at axial ends
of the dovetail. A blade made by the method is also claimed.
[0009] These and other features of this application will be better
understood from the following specification and drawings, the
following of which is a brief description:
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A shows a fan blade.
[0011] FIG. 1B shows the fan blade mounted into a rotor.
[0012] FIG. 2 shows a first method step according to this
invention.
[0013] FIG. 3 shows a subsequent step.
DETAILED DESCRIPTION
[0014] FIG. 1A shows a fan blade 20 having an airfoil 18 extending
radially outwardly of a dovetail 24. The airfoil can be said to
have a leading edge 21 and a trailing edge 22. The dovetail 24 has
circumferential side surfaces 100, and axial ends 102 and 104. As
can be appreciated from FIG. 1A, the axial ends 102 and 104 are not
regular surfaces, but have complex curved shapes. The
circumferential sides 100 have generally regular shapes along an
axial length.
[0015] FIG. 1B shows the fan blade 20 mounted within a slot 17 in a
rotor 16. As can be appreciated, the sides 100 receive a good deal
of stress when the rotor 16 is rotating, as the rotational force is
transmitted through the sides 100. The ends 102 and 104 do not
receive the same forces. As shown, the circumferential sides 100
have a more regular surface than the ends 102 and 104.
[0016] In order to surface treat the fan blade dovetail to
withstand such forces, a first surface treatment step, burnishing,
is shown in FIG. 2. The term burnishing can be generally described
as bringing a tool into contact to physically treat surfaces on a
workpiece.
[0017] A burnishing operation with a burnishing tool, shown rather
schematically at 50, has surfaces 104 brought into contact with the
side surfaces 100. The burnishing tool 50 may provide low
plasticity burnishing. One known low plasticity technique is
disclosed in U.S. Pat. No. 6,415,486. Other burnishing operations
can be used however.
[0018] As shown in FIG. 2, in a generic burnishing operation, the
tool 50 is controlled with the computer numerical control (CNC)
positioning control 56, and a pressure control 58. Broadly
speaking, once the selected area 100 of the dovetail has been
identified, a desired magnitude of compression from the tool
surfaces 52 and a residual desired stress distribution are
determined. The pressure is controlled against the surfaces to form
zones of deformation having a deep layer of compressive stress. The
pressure can be varied to achieve a desired residual stress
distribution, and a magnitude of compression within the dovetail
24.
[0019] While burnishing works very well on the circumferential side
surfaces 100, it is not as effective for the ends 102 and 104.
Since the ends 102 and 104 have complex surfaces, they are not as
easily treated with the burnishing technique. In addition, the
burnishing of the sides 100 does result in undesirable stress
distribution at the ends 102 and 104.
[0020] Thus, FIG. 3 shows a step subsequent to the FIG. 2 step. In
FIG. 3, shot peening masks 62 are mounted to enclose the ends 102
and 104. Shot peening tool 60 delivers particles 64 against the
ends 102 and 104. The shot peening process is shown somewhat
schematically in FIG. 3, however, a worker of ordinary skill in the
art would recognize how to provide shot peening to the surfaces 102
and 104.
[0021] After the two-step method is complete, the fan blade 20 has
been surface treated at both of its ends 102/104, and the sides 100
of the dovetail such that it will provide effective operation in
the challenging environment of the gas turbine engine.
[0022] In addition, as an initial optional step prior to the FIG. 2
step, the entire dovetail may be initially shot peened prior to the
burnishing.
[0023] The blade as disclosed above is for use as a fan blade. It
is believed the teachings of this application would have most
success when utilized on blades that will exist in lower
temperature portions of a gas turbine engine. However, it is
possible that blades in higher temperature regions may also benefit
from the methods. In addition, the methods may have application in
blades having air foils and dovetails for use in applications other
than gas turbine engines. Thus, while the invention might have most
application in fan blades and lower pressure compressor sections,
it may also have application in other locations.
[0024] Although an embodiment has been disclosed, a worker of
ordinary skill in the art would recognize that certain modification
would come within the scope of this invention. For that reason, the
following claims should be studied to determine the true scope and
content of this invention.
* * * * *