EP1203637A1 - Ultra sonic cross shot peening of vanes on a rotor - Google Patents

Abstract

A method, and machine for implementing the method, for transverse ultrasound peening of blades on a rotor that drives in rotation a wheel bearing the blades about its geometrical axis arranged substantially vertically and causes the blades to pass through a mist of microbeads produced by a vibrating surface in an active chamber arranged laterally relative to the wheel. The active surface is located beneath the path of the blades. Preferably, the active chamber includes a second vibrating surface above the path of the blades.

Description

The invention relates to a method of ultrasonic shot blasting of parts which extend radially around the periphery of a wheel, such as blades turbine engine blades on a rotor. The invention also relates to a shot blasting machine for carrying out the process.

By the term wheel is meant an object having a general form of revolution along a geometric axis, capable of being rotated around its axis.

In order to improve the fatigue resistance of mechanical parts, it is known to blast the surface by projection of microbeads. This technique is widely used in aeronautics, to permanently compress the surface of pieces with a small thickness. This compression is opposed to the appearance or the progression of cracks on the surface of the part, which improves resistance to fatigue. The technique involves projecting against the surface of the piece, with a small angle of incidence relative to the perpendicular to this surface and with sufficient kinetic energy, microbeads.

Preferably, the angle of incidence is less than 45 ° relative to the perpendicular to the surface so that impacts can transmit energy sufficient of the ball to the impacted surface. Exposure of the part to shot blasting goes through an optimum. Insufficient shot blasting does not give resistance planned, but additional shot blasting can still be carried out. On the other hand excessive peening causes irreversible degradation of the part.

The technique of shot peening applies in particular to compress the blades of the blades of a turbomachine rotor. In the case of the blades which have thin walls, it is necessary to blast at the same time two sides of the blades, in order to avoid deformations by modifying the curvatures in thin areas.

• les paramètres de grenaillage ne sont pas stables, et la machine de grenaillage doit être fréquemment contrôlée et réglée lorsqu'on recherche un grenaillage proche de l'optimum,
• l'état de surface est dégradé, ce qui nuit à la durée de vie des pièces,
• la mise en oeuvre du procédé doit se faire dans une cabine suffisamment grande pour permettre la manipulation des pièces, et des buses de grenaillage.

Traditionally, blasting of thick wall surfaces is done by projecting microbeads by means of a nozzle supplied simultaneously with compressed gas and microbeads. The blasting of the blades of the turbine engine blades is done by means of two nozzles each blasting one face of the blade. This shot blasting process in itself has two drawbacks:

• the shot peening parameters are not stable, and the peening machine must be frequently checked and adjusted when looking for shot peening close to the optimum,
• the surface condition is degraded, which affects the life of the parts,
• the implementation of the process must be done in a cabin large enough to allow the handling of parts, and shot blasting nozzles.

When the surfaces to be blasted are padded wheel blades monoblocks, spaced a relatively small distance from each other, the shot peening process using nozzles is even more difficult to implement.

The applicant proposed in the French patent application filed on November 18, 1999 and registered under number FR 99 14 482, a ultrasonic shot blasting process using a microbead mist maintained in an active enclosure by a vibrating surface. According to the process described in this application, the wheel is rotated about its axis arranged horizontally. The vanes located in the lower part of the wheel pass through the active enclosure at low speed and are impacted by the microbeads of the fog maintained by the vibrating surface arranged under the ends of the blades lower.

The microbeads activated by the vibrating surface strike the surfaces of the blades located in the active enclosure, on which they bounce, as well as the peripheral walls of the wheel located between the blades. The microbeads that have lost their kinetic energy, fall back onto the vibrating surface which projects them back into the active enclosure. Some microbeads come out of the enclosure active and are recovered in adjacent inactive enclosures from where they return to the bottom of the active enclosure by gravity.

The thin ends of the blades are subjected to very strong impacts violent and they must be trimmed at the end of the blasting operation.

During the blasting operation, the wheel turns on several towers. It is thus easier to reach the optimum, and to avoid asymmetries of shot blasting, generating deformation when the parts are thin.

The process described in FR 99 14 482 is particularly suitable for blades of blades having a relatively short length.

But when the blades are long compared to the distance between two consecutive blades, especially if the relationship between the length and the interpale distance is greater than three, or when the blade height is greater than 100mm and the shape of the blade is very curved, the sides of the blades located towards the bottom of the interpale space are less blasted because the microbeads have already made several bounces to reach them and have lost part of their kinetic energy. So shot peening is no longer homogeneous and it increase the duration of shot blasting to ensure minimal blasting in all points.

The object of the invention is to propose a shot peening process by ultrasound of parts which extend radially around the periphery of a wheel which allows effective shot blasting of the surfaces of these parts, whatever their length.

The invention therefore relates to a method of ultrasonic shot blasting of parts which extend radially around the periphery of a wheel, method according to which we put the wheel in rotation around its geometric axis and we create a fog microbeads in a fixed active enclosure arranged laterally to said wheel, at by means of a first vibrating surface arranged in the lower part of said active enclosure having openings shaped to allow the input and output of the parts during the rotation of the wheel and being sized to accommodate at least three adjacent rooms.

The method according to the invention is characterized in that one makes turn the wheel around its axis arranged substantially vertically and thereby that the first vibrating surface is arranged under the path of the parts in the active speaker.

This arrangement makes it possible to impact all the surface areas of parts passing through the active enclosure regardless of their distance from the axis of rotation of the wheel.

According to an advantageous characteristic of the method according to the invention, the enclosure has a second vibrating surface above the path of rooms in the active enclosure.

Thanks to this characteristic the microbeads which reach the part top of the enclosure with low kinetic energy and are ready to drop by gravity, are reactivated by this second vibrating surface, and participate in new to effective shot peening on workpiece surfaces and the walls of the active enclosure.

When the method according to the invention is applied to parts having thin edges facing a vibrating surface, such as leading edges and trailing edges of the blades of turbine engine blades, and according to another advantageous characteristic of the invention, said thin edges are protected at shot blasting course.

This protection can preferably be provided by rods integral in rotation with the wheel and each masking a thin edge. These rods are arranged between the thin edges and the sonotrodes. They have the effect of decrease the energy of the balls likely to impact thin edges. They may be in contact with thin edges or slightly apart from them.

It can also be provided by fixed rods integral with the enclosure. In this case the wheel is rotated step by step during the blasting of in such a way that the edges of the parts located in the active enclosure are located in look of the fixed rods. Shot blasting can be stopped during pivoting one step away from the wheel.

So, during shot peening, the rods are located between the edges thin blades and sonotrodes to protect the thin edges from impacts to high energy of the balls coming directly from a sonotrode.

The invention also relates to a shot blasting machine for implement the method described above.

un plateau tournant d'axe sensiblement vertical équipé de moyens de retenue d'une roue comportant radialement des pièces à grenailler, coaxialement audit plateau,

des moyens pour entraíner le plateau tournant en rotation autour de son axe, et au moins un dispositif pour grenailler lesdites pièces, ledit dispositif de grenaillage comprenant :

une enceinte active disposée latéralement à ladite roue et dimensionnée pour loger au moins trois pièces adjacentes et présentant une ouverture conformée pour permettre l'entrée et la sortie des pièces au cours de la rotation de la zone,

une première surface vibrante disposée dans le fond de l'enceinte active en dessous du chemin des pièces dans ladite enceinte active et susceptible d'entretenir un brouillard de microbilles dans ladite enceinte active, et

des moyens pour récupérer les microbilles qui s'échappent de l'enceinte active et les retourner vers ladite enceinte.

This machine is characterized by the fact that it comprises:

a turntable with a substantially vertical axis equipped with means for retaining a wheel comprising parts to be shot blasted radially, coaxially with said plate,

means for driving the turntable in rotation about its axis, and at least one device for blasting said parts, said blasting device comprising:

an active enclosure arranged laterally to said wheel and dimensioned to accommodate at least three adjacent parts and having a shaped opening to allow the entry and exit of the parts during the rotation of the zone,

a first vibrating surface disposed in the bottom of the active enclosure below the path of the parts in said active enclosure and capable of maintaining a fog of microbeads in said active enclosure, and

means for recovering the microbeads which escape from the active enclosure and returning them to said enclosure.

Advantageously, the shot blasting device further comprises a second vibrating surface arranged in the active enclosure above the path pieces.

The machine may also include means for protecting the edges of parts located opposite a vibrating surface.

la figure 1 est une vue schématique de dessus d'une machine de grenaillage selon l'invention sur laquelle est montée une roue aubagée de turbomachine dont les pales des aubes doivent être grenaillées,

la figure 2 est une coupe verticale selon la figure II-II de la figure 1 ;

la figure 3 montre la fixation de la roue aubagée sur le plateau tournant de la machine et la disposition des faisceaux de grilles de protection des bords d'attaque et des bords de fuite des pales ;

la figure 4 est une coupe de la machine à grenailler par un plan vertical coupant le plan de la figure 1 selon la ligne IV-IV ;

la figure 5 est semblable à la figure 4 et montre à plus grande échelle l'enceinte active et les enceintes de récupération des microbilles sortant de l'enceinte active ;

la figure 6 est une coupe selon la ligne VI-VI de la figure 4, par un plan horizontal traversant les enceintes et situé en dessous du chemin des aubes dans le dispositif de grenaillage ; et

la figure 7 est semblable à la figure 2 et montre à plus grande échelle le dispositif de grenaillage et des tringles de protection des bords d'attaque et bords de fuite des pales, ces tringles étant montées fixes sur les enceintes.

Other advantages and characteristics of the invention will emerge on reading the following description given by way of example and with reference to the appended drawings in which:

FIG. 1 is a schematic top view of a shot blasting machine according to the invention on which is mounted a bladed wheel of a turbomachine, the blades of the blades of which must be shot blasted,

Figure 2 is a vertical section on Figure II-II of Figure 1;

FIG. 3 shows the attachment of the bladed wheel to the turntable of the machine and the arrangement of the beams of protective grids at the leading edges and the trailing edges of the blades;

Figure 4 is a section of the shot blasting machine by a vertical plane intersecting the plane of Figure 1 along the line IV-IV;

FIG. 5 is similar to FIG. 4 and shows on a larger scale the active enclosure and the recovery chambers for the microbeads leaving the active enclosure;

Figure 6 is a section along line VI-VI of Figure 4, by a horizontal plane passing through the enclosures and located below the path of the blades in the peening device; and

Figure 7 is similar to Figure 2 and shows on a larger scale the shot blasting device and rods for protecting the leading edges and trailing edges of the blades, these rods being mounted fixed on the speakers.

In the drawings there is shown by reference 1 a machine for shot blasting of the blades 2 which extend radially around the periphery of a wheel 3 turbomachine x-axis. The wheel 3 can for example be a bladed disc monobloc or a turbomachine wheel fitted with movable vanes. The blades 2 can also be parts whose surfaces must be blasted and which have means for retaining them radially and regularly spaced angularly at the periphery of a wheel 3 which then serves to support the parts to peened.

The shot blasting machine 1 essentially comprises a plate turning 4 carried by a shaft 5 of axis 6 substantially vertical. Tree 5 can be driven in rotation about its axis 6 by drive means in rotation, an electric motor for example, not shown in the drawings. Wheel 3 is fixed on the turntable 4 by means of a clamping piece 7 cooperating with a threaded bore 7a of axis 6 formed in the turntable 4, such so that its x axis coincides with the axis 6 of the turntable 4.

Preferably, as can be seen in Figures 2 and 3, a first annular flange 8 is interposed between the turntable 4 and the wheel 3 and a second annular flange 9 is interposed between the wheel and the clamping piece 7.

These annular flanges 8 and 9 have rods at their periphery radial respectively 8a and 9a, in number equal to the number of blades 2 of the wheel 3, regularly spaced around the x axis. Each rod 8a and 9a takes up the forms trailing edges and leading edges of the blades 2. The annular flange lower 8 is positioned under the wheel 3 so that the beam of radial rods 8a covers the lower edges of the blades 2. The annular flange upper 9 is also angularly positioned relative to wheel 3 of such so that the rod bundle 9a covers the upper edges of the blades 2. When the turntable 4 rotates around the axis 6, the wheel 3 and the flanges annulars 8 and 9 rotate around axis 6.

The diameter of the turntable 4 is chosen according to the wheel 3 and in such a way that the blades 2 project radially outside the periphery of said turntable.

In Figures 1 to 3 we see that the machine 1 further comprises a substantially horizontal fixed slide 10, integral with the support frame of the shaft 5, and whose axis is perpendicular to the axis 6 of the shaft 5.

On this slide 10 is mounted sliding the shot blasting device 11 itself. When mounting the wheel 3 on the turntable 4 or when when it is dismantled, the peening device 11 is moved away from the turntable 4.

This shot blasting device 11 essentially comprises an enclosure so-called active center 12 disposed between two lateral enclosures 13 and 14 said inactive and intended to recover escaping microbeads 15 optionally from the center speaker and return them to the center speaker 12 as explained later in this memo.

These enclosures 12 and 13 and 14 are delimited together by a wall rigid external device 16 in the form of a circular sector and the diameter of which interior is substantially equal to or slightly greater than the diameter of the path traversed by the ends of the blades 2 during the rotation of the wheel 3 around axis 6, a bottom wall 17 in the form of a bowl which extends between the wall peripheral 16 and the periphery of the turntable 4 and an upper wall 18 in upside-down bowl or dome that extends between the peripheral wall 16 and the periphery of the upper flange 9.

The lower wall 17 is arranged under the path traveled by the blades 2 during the rotation of the wheel 3 and the upper wall 18 is located above this path. A lower vibrating surface 20 is arranged in the bottom of the bowl formed by the bottom wall 17 is a second surface vibrator 21 is arranged in the upper part of the dome formed by the wall upper 18.

Vertical and radial partitions with openings the contour is shaped according to the annular surfaces generated by the rods 8a and 9a during the rotation of the wheel 3, connect the walls 17 and 18 to the wall peripheral 16. These partitions four in number above and below the path of the blades 2 in particular include lateral end partitions 21a, 21b which circumferentially delimit the inactive enclosures 13 and 14, and intermediate partitions 22a, 22b which separate the active enclosure 12 from the enclosures inactive side panels 13 and 14. The lower intermediate partitions 22a, 22b have in the vicinity of the bottom wall 17, openings or slots 23 which allow the 15 microbeads that enter the inactive side enclosures 13 and 14 to return to the lower vibrating surface 20 by gravity.

The active enclosure 12 is thus delimited circumferentially by the partitions 22a and 22b and is arranged between the vibrating surfaces 20 and 21, as well as this is visible in Figure 5.

The circumferential extent of this active enclosure 12 is such that at at least three blades 2 can be housed in this active enclosure 12.

A certain quantity of microbeads 15 is placed in the enclosure active 12. When the vibrating surfaces 20 and 21 of the sonotrodes are activated, the microbeads 15 placed above the lower vibrating surface 20 are projected upwards, strike the surfaces of the blades 2, bounce on these surfaces and move on randomly. Some of these microbeads 15 reach the upper vibrating surface 21 which provides them with new kinetic energy. These balls 15 again strike the walls of the blades 2 during their descent. It goes without saying that certain microbeads 15 come strike the intermediate partitions 22a and 22b on which they rebound. These microbeads 15 remain in the active enclosure 12, and fall back onto the surface vibrant when they have lost their kinetic energy.

Due to the displacement of the blades 2 through the openings between the upper and lower intermediate partitions 22a and 22b, some microbeads 15 enter the lateral enclosures 13 and 14 through the space separating the contours of the partitions 22a and 22b of the nearest rods 8a and 9b. These 15 microbeads quickly lose kinetic energy in pregnant side 13 and 14, fall on the lower wall 17 which is inclined, and return on the lower vibrating surface 20 by the slots 23 formed at the foot of the lower intermediate partitions 22a and 22b.

During a rotation revolution of the wheel 3, the blades 2 are impacted by the microbeads 15 for the duration of their passage in the active chamber 12.

Advantageously, this passage time is clearly less than the total shot blasting time required to achieve the result optimum, and the number of turns to perform to obtain the optimum result is calculated accordingly. This number of turns is at least equal to 3. This allows reduce blade deformation resulting from temporary blasting deviations between the two sides of the blades during treatment. Indeed, when a blade enters in the enclosure, its face turned in the direction of rotation undergoes a blasting more intense than its opposite side because it is better exposed to high impact energy of the balls coming directly from the sonotrode. The prestressing of compression of the front-facing side is therefore greater than that of the opposite side, causing partially plastic deformation towards the back of the blade. When the blade comes out of the blasting chamber, it is the inverse phenomenon which occurs, but there remains however a deformation residual blade.

By blasting in N turns instead of one, the gap temporary peening between the two faces of the blades is divided by N, which substantially divides by N the resulting deformation of the blades. The number of turns It is not critical. Three to five turns is considered by the applicant to be acceptable to obtain a significant result.

It should be noted that to decrease the total shot blasting time it is possible to equip machine 1 with several shot blasting devices 11 identical to that described above and distributed angularly around axis 6.

Figure 7 shows an alternative embodiment of the protection of the leading edges and trailing edges of the blades 2. In this variant, the annular flanges 8 and 9 do not comprise beams of radial rods 8a, 9a. The protective rods 30 and 31 fixed relative to the device shot peening11, are mounted in the active enclosure 12. The number of rods 30 and 31 is equal to the number of blades 2 capable of accommodating in the active enclosure 12.

During the blasting operation, the blades 2 are immobilized for a certain period of time in a position such as their leading edges and their trailing edges are protected by rods 30 and 31. Then they are displaced by a step equal to the angular difference between two consecutive blades 2.

In a preferred embodiment of the invention, the rods 30, 31 are fixed by one end 32, 33 to the outer wall 16 and by the other end, to a common support 34, 35 which acts as a seal between the rotor 3 and respectively the interior walls 17, 18, this sealing being ensured when the clearances left are less than the diameter of the balls.

• écarter, suivant la trajectoire 37, les constituants supérieurs des enceintes, soit la partie supérieure 16a de la paroi externe 16, la sonotrode 21 et la paroi interne 18,
• mettre en place le rotor 3 suivant la trajectoire 38,
• rapprocher ces mêmes constituants supérieurs des enceintes suivant une trajectoire 39 inverse de la trajectoire 37 afin de refermer les enceintes sur le rotor et de permettre le grenaillage.

In order to simplify the introduction of the rotor 3 into the blasting chambers 12, 13 and 14, it may be advantageous to divide the external wall 16 into two parts 16a and 16b separated by a joint plane 36 substantially in the plane of the rotor 3 The introduction of the rotor 3 is then done according to the following process:

• move aside, along the path 37, the upper components of the enclosures, ie the upper part 16a of the external wall 16, the sonotrode 21 and the internal wall 18,
• set up the rotor 3 along the path 38,
• bring these same upper constituents of the enclosures along a path 39 opposite to the path 37 in order to close the enclosures on the rotor and to allow the shot blasting.

This step-by-step movement is carried out at high speed if the shot peening continues during this movement, so that the leading edges and trailing edges are impacted infrequently when moving. We can also stop sonotrodes during the stepwise movement of the blades 2.

Claims (12)

Method for ultrasonic blasting of parts (2) which extend radially around the periphery of a wheel (3), method according to which the wheel (3) is rotated about its geometric axis (6) and a microbead mist (15) in a fixed active enclosure (12) disposed laterally to said wheel (3), by means of a first vibrating surface (20) disposed in the lower part of said active enclosure (12), said enclosure active (12) having an opening shaped to allow the entry and exit of the parts (2) during the rotation of the wheel (3) and being dimensioned to accommodate at least three adjacent parts, characterized in that the the wheel (3) is rotated about a substantially vertical axis (6) and by the fact that the first vibrating surface (20) is arranged under the path of the parts in the active enclosure (12). Method according to claim 1, characterized in that the active enclosure (12) has a second vibrating surface (21) above the path of the parts (2) in the active enclosure (12). Method according to one of claims 1 or 2 applied to parts (2) having thin edges facing a vibrating surface (20, 21), characterized in that said thin edges are protected during shot peening . Method according to claim 3, characterized in that the thin edges of the parts (2) are protected by means of rods (8a, 9a) integral in rotation with the wheel (3). Method according to claim 3, characterized in that the thin edges of the parts (2) located in the active enclosure (12) are protected by means of rods (30, 31) integral with the enclosure (12) and the wheel (3) is rotated step by step during shot peening. Method according to any one of Claims 1 to 5, characterized in that the wheel makes at least N = 3 rotations during the blasting. Shot blasting machine for implementing the method according to claim 1, characterized in that it comprises: a rotating plate (4) with a substantially vertical axis (6) equipped with means for retaining a wheel (3) comprising parts (2) to be shot blasted radially, coaxially with said plate (4), means for driving the turntable (4) in rotation about its axis (6) and, at least one device for blasting said parts (2), said blasting device comprising: an active enclosure (12) disposed laterally to said wheel (3) and dimensioned to accommodate at least three adjacent parts (12) and having a shaped opening to allow the entry and exit of the parts (12) during the rotation of the wheel (3), a first vibrating surface (20) disposed in the bottom of the active enclosure (12) below the path of the parts (2) in said active enclosure and capable of maintaining a mist of microbeads (15) in said active enclosure (12 ), and means for recovering the microbeads (15) which escape from the active enclosure (12) and returning them to said enclosure (12). Machine according to claim 7, characterized in that the shot blasting device further comprises a second vibrating surface (21) arranged in the active enclosure above the path of the parts (2). Machine according to one of claims 7 or 8, characterized in that it further comprises means for protecting the edges of the parts (2) situated opposite a vibrating surface (20, 21). Machine according to claim 9, characterized in that the protection means comprise a bundle of radial rods (8a, 8d) integral with the wheel (3). Machine according to claim 9, characterized in that the protection means comprise rods (30, 31) integral with the active enclosure (12). Machine according to any one of Claims 7 to 11, characterized in that the blasting means are movable in a direction substantially perpendicular to the axis (6) of the turntable (4).

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