Method for reshapins a turbomachine blade that has at least one zone that has become
deformed usinn peening
5
The present invention relates to the field of repair of an integrally bladed rotor (IBR) of an
aircraft turbojet engine and relates more generally to the repair of any turbine engine blade.
An aircraft turbojet engine conventionally includes a plurality of bladed rotor discs mounted
10 axially in the turbojet engine. The upstream bladed disc, known to the person skilled in the
art as a fan, has the function, on the one hand, of accelerating an air stream from upstream
to downstream in the turbojet engine and, on the other hand, of providing the thrust of the
aircraft.
15 While the aircraft is in flight, the turbojet engine may ingest foreign bodies (birds, dust, etc.)
which damage and deform the fan blades. The performance levels and the service life of the
fan blades are then reduced, which presents a drawback. In a known manner, in order to
reshape a fan blade, this latter is placed in a die having a cavity of which the shape
corresponds to that of a blade of optimal shape. Once it is in the die, the damagedldeformed
20 blade is compressed at a temperature of the order of 700 "C in such a way that this latter
follows the shape of the cavity of the die and thus resumes an optimal shape.
Conventionally, the fan includes radial blades of large dimensions in order to increase the
dilution ratio of the turbojet engine. In order to limit the mass of the fan and to improve the
25 dynamic behaviour thereof, the fan of a turbojet engine is generally formed in one integral
part known by the abbreviation IBR, for 'integrally bladed rotor'. When the blades of an IBR
are damaged, they cannot be repaired by a conventional method by compression in a die
given that the blades cannot be separated individually from the IBR.
30 In order to eliminate this drawback, the French patent applications FR 2 882 533 A1 and FR
2 902 360 A1 by SNECMA disclose a method for repairing an IBR by addition of material
wherein a material sample is soldered to the IBR by means of an electron beam. Such a
method is appropriate when a part of the blade has been torn off or damaged but is difficult
to implement when the blades of the IBR are deformed. Thus, in practice an IBR of which
35 the blades are deformed is never repaired.
In order to eliminate at least some of these drawbacks, the invention relates to a method of
reshaping a turbine engine blade comprising at least one deformed zone, said method
comprising a step of peening of the deformed zone so as to be able to restore the shape of
5 said zone.
Although the present invention originates from a problem relating to the repair of blades of
an integrally bladed rotor (IBR) of a turbojet engine, the invention relates more generally to
the repair of any turbine engine blade.
10
A method of peening is already known from the prior art, for example from the patent
applications FR 2 815 280 A1, FR 2 815 281 A1 and FR 2 873 609 A?, in order to improve
the resistance of mechanical parts, in particular turbine engine blades. A method of peening
consists of blasting beads of small dimensions or microbeads onto the surface to be treated
I 5 in order to produce a local buildup of compressive stresses.
One of the drawbacks of peening is that it can cause an elongation of the metal and a
deformation of the blades which impairs the performance thereof. To this end, it is known for
the blade to be treated to be held firmly during the peening in order to limit any deformation.
20
In order to restore the shape of a blade, the applicant has deviated from the conventional
use of a peening device in such a way as to take advantage of effects traditionally
considered to be detrimental. The peening according to the invention makes it possible
advantageously to restore the shape of a blade while cold. Contrary to the prior art, it is not
25 necessary to raise the blade to high temperatures, which limits the risk of thermal damage
and makes it possible to increase the sewice life of the blade.
Preferably, the method of reshaping includes a step of ultrasonic peening. Advantageously,
an ultrasonic peening device can be easily positioned and oriented, which makes it possible
30 for a plurality of adjacent deformed zones of a blade to be reshaped quickly. This is
particularly advantageous in order to ieshape an integrally bladed rotor (IBR), wherein the
ultrasonic peening device can be placed between two consecutive blades of the IBR.
Thus, the shape of the blades of an IBR can be restored quickly by modifying the position
35 and the orientation of the ultrasonic peening device.
Preferably, as the blade comprises a first face and a second face opposite the first face, and
as the deformed zone is situated on the first face, the second face is free to deform during
peening of the first face. As the second face is not retained during the peening of the
5 deformed zone, the buckling of the deformed zone is favoured during the peening which
enables quick restoration of the shape of the deformed zone.
Preferably, as the blade comprises a first face and a second face opposite the first face, and
as the deformed zone is situated on the first face, the second face is not peened during
10 peening of the first face. Thus, stresses are only applied by the first face, which favours the
buckling of the deformed zone.
More preferably, the deformed zone is peened in a direction substantially normal to the
deformed zone in such a way as to restore the zone quickly and reproducibly.
15
According to one aspect of the invention, the method for reshaping includes:
- acquisition of a profile of said blade,
- comparison of said profile with a reference profile in such a way as to deduce
therefrom at least one deformed zone of the blade;
20 - peening of the deformed zone of the blade by means of a peening device for a given
parameterisation of said device in such a way as to restore the shape of the deformed zone;
and
- recording in a deformation database of an association of the deformed zone with the
parameterisation of the peening device.
25
Advantageously, a knowledge base is formed empirically following peening by associating a
given deformed zone with a parameterisation of the peening device. Preferably at least the
position of the deformed zone is recorded. More preferably, the deformation database
includes at least one degree of deformation of the deformed zone. More preferably, at least
30 the duration of peening is recorded as parameterisation of the peening device.
According to one aspect of the invention, the method for reshaping includes:
- acquisition of a profile of said blade,
- comparison of said profile with a reference profile in such a way as to deduce
35 therefrom at least one deformed zone of the blade;
- comparison of the deformed zone with a deformation database including a plurality of
deformed zones associated respectively with a plurality of parameterisations of a peening
device;
determination of the parameterisation associated with said deformed zone; and
5 - peening of the deformed zone of the blade by means of the peening device as a
function of said determined parameterisation.
Thus a blade is reshaped in a reproducible and optimal manner using one and the same
parameterisation of the peening device when a deformed zone of which the characteristics
10 are known is newly detected.
Preferably, if no parameterisation is associated with the deformed zone in the deformation
database, peening of the deformed zone of the blade is performed by means of a peening
device for a given parameterisation of said device in such a way as to restore the shape of
15 the deformed zone; and the association of the deformed zone with the parameterisation of
the peening device is recorded in the deformation database. Thus, when this is the first time
that a deformed zone, of which the characteristics are not catalogued in the knowledge
base, is detected, the deformed zone is peened manually in order to restore the shape of the
deformed zone. Next the knowledge base is augmented by associating the deformed zone
20 with the parameterisation of the peening device which has been used to reshape it.
According to a preferred aspect of the invention, the turbine engine blade is a blade of an
integrally bladed rotor. A method of reshaping according to the invention enables restoration
of the shape of the IBR even if the space between two consecutive blades is very limited.
25
The invention will be better understood when reading the following description given solely
by way of example and with reference to the appended drawings, in which:
- Figure 1 shows a perspective view of a turbine engine blade comprising a plurality of
deformed zones;
30 - Figure 2 shows a schematic sectional view of a blade with a deformed zone before
peening thereof;
- Figure 3 shows a close-up schematic sectional view of a deformed zone of the blade;
- Figure 4 shows a perspective view of the peening of a deformed zone of the blade;
Figure 5 shows a close-up schematic sectional view of a deformed zone of the blade
35 during peening thereof; and
Figure 6 shows a schematic diagram representing the steps of a method of
reshaping according to the invention.
It should be noted that the drawings disclose the invention in a detailed manner in order to
5 carry out the invention, and said drawings can of course serve to give a better definition of
the invention where appropriate.
The invention will be presented for the reshaping of a turbine engine blade belonging to an
integrally bladed rotor (IBR) of a turbojet engine, but of course the following description
10 applies to any turbine engine blade.
Figure 1 shows part of an IBR of an axial turbojet engine having an annular rim 1 which
extends axially and a blade 2 which extends radially. For the sake of clarity, only blade 2 of
the IBR is shown in Figure 1. In the course of operation of the aircraft, the blades 2 of the
15 IBR become deformed, which affects their aerodynamic performance. In order to detect the
deformations of a blade to be reshaped 2, several manual or automated methods may be
implemented.
As shown in Figure 1, the blade to be reshaped 2 includes a plurality of deformed zones Z
20 which impair the aerodynamic performance of the blade 2. The restoration of the shape of
the deformed zone referenced Zj in Figure 1 and situated in the transverse plane R will now
be described.
Deformed zones Z
25
Preferably, each deformed zone Z of the blade to be reshaped 2 has a substantially equal
surface area. Thus, a large deformed surface of the blade 2 may be divided into a plurality of
individual surfaces each corresponding to a deformed zone Z according to the invention. By
way of example, the surface area of a deformed zone Z is of the order of 3,000 mm2.
30
Each deformed zone Z is defined here by several parameters: its position p on the blade 2
and its degree of deformation d. Thus, as an example, with reference to Figure 3, the
deformed zone referenced Zj in Figure 1 is defined by three-dimensional co-ordinates p,
indicating its position with respect to a reference point of the IBR or of the blade to be
35 reshaped 2. The degree of deformation d, of the deformed zone Zj corresponds, for example,
to the difference between the profile of the blade to be reshaped and the reference blade
profile in the position p, of the deformed zone Zj. With reference to Figure 3, the deformed
zone Zj is formed, in this example, on the pressure side F1 of the blade 2. Preferably, with
reference to Figure 2, the degree of deformation dj is defined with respect to the normal
5 direction N of the deformed zone Zj. By way of example, the degree of deformation d is of
the order of 0.05 mm to 0.25 mm.
Peening of the deformed zones
10 According to the invention, the deformed zones Z of the blade to be reshaped 2 are peened
in such a way as to restore the shape of the blade 2 by iocalised buckling of the deformed
zones Z.
The patent applications FR 2 815 280 A1 and FR 2 815 281 A1 disclose a peening device
15 suitable for implementing the invention in order to restore the shape of a blade 2.
A peening device 3, shown schematically in Figures 4 and 5, includes a bell housing 4
having an opening suitable for bearing on a face of the blade to be reshaped 2 in such a way
that the surface of the blade 2 closes the opening of the bell housing 4 and thus forms a
20 closed compartment as shown in Figure 5. The peening device 3 includes vibrating surfaces
6 disposed inside the bell housing 4 which are capable of transmitting kinetic energy to
projectiles 5 placed in the bell housing 4 in such a way that these latter are projected against
the surface of the blade 2 closing the bell housing 4 as shown in Figure 5.
25 in this example, the projectiles 5 are beads or microbeads which are projected by
sonotrodes 6 in such a way as to produce ultrasonic peening. Of course the sonotrode may
be replaced by other elements capable of producing vibrations which make it possible to
project projectiles such as beads or microbeads in a comparable way onto a part to be
treated.
30
An ultrasonic peening device 3 has a bell housing 4 of which the dimensions are reduced,
which enables easy handling. Thus the bell housing 4 may be simply moved from one zone
of the deformed blade Z to another deformed zone Z quickly and precisely. Furthermore,
such a bell housing 4 can be simply moved between two consecutive blades of an IBR,
35 which is advantageous.
Although the invention is described for ultrasonic peening, of course the invention applies to
any type of peening.
5 According to the invention, the bell housing 4 has an opening of which the surface area is
substantially equal to the surface area of a deformed z0ne.Z. Thus, when the bell housing 4
is positioned in the direction N normal to the deformed zone Z, the surface of the deformed
zone Z can be entirely peened so as to allow localised buckling of the blade 2 in the region
of the deformed zone Z.
10
The peening device 3 is advantageously parameterisable in such a way that the deformation
resulting from the peening is calibrated as a function of the chosen parameterisation.
Parameterisation is understood principally to be the duration of the peening but of course
other parameters of the peening device 3 can be taken into account such as the quantity of
15 kinetic energy transmitted to the projectiles, the dimensions of the projectiles, the
dimensions of the bell housing, etc.
In order to restore the shape of the blade 2, with reference to Figure 5, the bell housing 4 of
the peening device 3 is put in contact on the pressure side F1 of the blade 2 in such a way
20 that the deformed zone Zj is surrounded by the edge of the opening of bell housing 4. The
projectiles 5 of the peening device 3 accommodated in the bell housing 4 are accelerated by
the sonotrodes 6 mounted in the bell housing 4 in order to impact on the zone Zj which is
deformed as a function of the parameterisation of the peening device 3.
25 In this example, with reference to Figure 3, in order to promote the phenomenon of localised
buckling, the zone Zj' situated on the face F2 of the blade 2 opposite the deformed zone Zj,
that is to say the intake side F2, is not held during the peening in such a way as to facilitate
the deformation of the deformed zone Zj. This goes against the teaching of the peening
methods according to the prior art which recommend constraining the opposing zone Zj' in
30 order to facilitate the surface treatment of the peened zone and avoiding any deformation.
The opposing zone Zj' may be peened in the course of the reshaping method if it exhibits a
deformation. Preferably, a deformed zone Zj and its opposing zone Zj' are not peened
simultaneously so as to promote the buckling of the blade to be reshaped 2.
When the projectiles 5 come into contact with the deformed zone Z, the blade is deformed
locally by buckling. Any deformation projecting with respect to the reference blade profile is
then smoothed in such a way as to find an optimal profile. After peening, the shape of the
deformed zone Z is restored, which improves the aerodynamic performance of the blade 2.
5
Method of reshaping
In order to enable precise, quick and reproducible reshaping of the blades 2, the method is
preferably carried out by means of a robotic automatic machine (not shown) on which all or
10 part of the peening device 3 is mounted. Consequently, the invention will be described for an
automatic machine including at least the bell housing 4 of the peening device 3 mounted at
one end of a robotic arm of the automatic machine. Preferably, the arm of the automatic
machine is capable of moving in all the positions and in all the orientations.
15 Preferably, with reference to Figure 6, the method of reshaping according to the invention
includes a step of acquisition El of the profile of the blade to be reshaped 2. This acquisition '
El is carried out preferably by means of an acquisition device without contact, known to the
person skilled in the art, which makes it possible to obtain the three-dimensional coordinates
of a plurality of points on the surface of the blade to be reshaped 2 in order to form
20 a cluster of points defining the profile of the blade to be reshaped 2. Preferably, the
acquisition is carried out by photogrammetry, which has the advantage of fast access to a
precise file composed of clusters of points corresponding to the profile of the blade.
Next, the step of acquisition El is followed by a step of comparison E2 during which the
25 profile acquired is compared with a reference profile of the blade 2. This reference profile
conventionally takes the form of a mathematical model defined in 3D, preferably, in the form
of a mesh. During the comparison E2, the disparities of shape are demonstrated and located
in space. Preferably, the disparities of shape are divided into individual zones of which the
surface is predetermined and which correspond to the deformation zones Z as described
30 previously.
More preferably, each deformation zone Zj is characterised by its position in space pj as well
as its degree of deformation.dj as described previously.
Then each deformation zone Zj is sought in a deformation database 7 including a plurality of
deformed zones Zi associated respectively with a plurality of parameterisations Pi of the
ultrasonic peening device 3. As will be detailed below, the database 7 is formed empirically
following the manual peening of a plurality of deformation zones Z, of which the spatial
5 positions and the degrees of deformation are different, which have enabled restoration of the
shape of said deformed zones Z. In fact, .in order to restore the shape of the blade 2 in an
optimal manner, each deformed zone Zj is peened by the peening device 3 of which the
parameterisation Pj is defined and "customised" as a function of specific characteristics of
the deformed zone Zj.
10
In the course of the step E3 of searching in the deformation database 7, each deformed
zone Zj of the blade to be reshaped 2 is associated with a parameterisation Pj of the peening
device 3.
15 Next, in the course of a step of peening E4, the bell housing 4 of the peening device 3 is
placed on the deformed zone Zj and the peening device 3 is parameterised with the
parameterisation Pj associated with the given deformed zone Zj in order to restore the blade
2 in an optimal manner. Advantageously, when the peening device 3 is mounted on a robotic
automatic machine, the displacement and the parameterisation of the peening device 3 can
20 be accelerated significantly, which makes it possible to restore the shape of a blade 2
entirely in a reduced time. This is particularly advantageous in order to reshape an IBR
comprising a plurality of blades 2 each having a plurality of deformed zones Z.
In order to create the deformation database 7, a given deformed zone Zj with a given degree
25 of deformation dj is selected then said given zone Zj is peened in such a way as to deform it
whilst measuring the duration of the peening. When the shape of the zone Zj is restored, the
peening is stopped and the duration of the peening which enabled restoration of the
deformed zone 4 is deduced therefrom.
30 Next, in the deformation database 7 the deformed zone Zj (of given pisition pj and of given
degree of deformation dj) is associated with the parameterisation Pj of the peening device 3,
in this example the measured duration of peening tj. Thus, if one and the same deformed
zone Zj is detected subsequently (same position pj and same degree of deformation dj), the
optimal duration of peening tj in order to reshape said zone Zj is known.
Determination of the optimal duration of peening has been described previously, but of
course other values can be measured in order to determine the optimal parameterisation of
the peening device 3 for a given deformed zone, for example the dimension of the
projectiles, the speed of the projectiles, the frequency of impacts, the number of beads, etc.
5
Preferably, in the course of the search for the appropriate parameterisation of the peening
device 3 in the database 7 for a given deformed zone Zj, the parameterisation may be
deduced by interpolation of parameterisations present in the database 7. This makes it
possible to restore the blade 2 quickly when the size of the database 7 is not large.
10
Preferably, after peening, the zone Zj of the blade 2 is heat treated in such a way as to
eliminate all the compressive stresses added during the restoration of the shape of the blade
by ultrasonic peening. Such compressive stresses are not wanted during the operation of the
engine.
1. Method for reshaping a turbine engine blade (2) which has at least one deformed
zone (Z), said method comprising:
5 a. acquisition of a profile of said blade (2);
b. comparison of said profile with a reference profile in such a way as to deduce
therefrom at least one deformed zone (Z,) of the blade (2);
c. comparison of the deformed zone (Z,) with a deformation database (7) including a
plurality of deformed zones (Zi) associated respectively with a plurality of parameterisations
10 (Pi) of a peening device (3);
d. determination of the parameterisation (Pi) associated with said deformed zone (Zj);
and
e. peening of the deformed zone (Z,) of the blade (2) by means of the peening device
(3) as a function of said determined parameterisation (Pi) in such a way as to restore the
15 shape of said zone (Z).
2. Method according to the preceding claim, wherein the peening is an ultrasonic
peening.
20 3. Method according to either Claim 1 or 2, wherein as the blade comprises a first face
(FI) and a second face (F2) opposite the first face (FI), and as the deformed zone (Z) is
situated on the first face (FI), the second face (F2) is free to deform during peening of the
first face (FI).
25 4. Method according to any of Claims 1 to 3, wherein as the blade comprises a first face
(FI) and a second face (F2) opposite the first face (FI), and as the deformed zone (Z) is
situated on the first face (FI), the second face (F2) is not peened during peening of the first
face (FI).
30 5. Method according to any of Claims 1 to 4, whkrein the deformed zone (Z) is peened
in a direction substantially normal (N) to the deformed zone (Z).
6: Method according to any of Claims 1 to 5, comprising:
a. acquisition of a profile of said blade (2);
b. comparison of said profile (2) with a reference profile in such a way as to deduce
therefrom at least one deformed zone (2,) of the blade (2);
c. peening of the deformed zone (2,) of the blade (2) by means of a peening device (3)
for a given parameterisation (Pi) of said device (3) in such a way as to restore the shape of
5 the deformed zone (2,); and
d. recording in a deformation database (2) of an association of the deformed zone (Z,)
with the parameterisation (P,) of the peening device (3).
7. Method according to Claim 6, wherein the deformation database (7) includes at least
10 one degree of deformation (dj) of the deformed zone (ZI).
8. Method according to Claim 1, wherein if no parameterisation (Pi) is associated with
the deformed zone (4) in the deformation database (7), peening of the deformed zone (Zj) of . .. . .
the blade iS performed by means of a peening device for a given parameterisation of said
15 device in such away as to restorethe shape of tlie deformed zone (Zj); and the association
of the deformed zone (Zj) with the parameterisation of the peening device (3) is recorded in
the deformation database.
9. Method according to any of Claims 1 to 8, wherein the turbine engine blade (2) is a
20 blade of an integrally bladed rotor.