EP3921113A1

EP3921113A1 - Method for separating a first mechanical part from a second mechanical part

Info

Publication number: EP3921113A1
Application number: EP20709268.5A
Authority: EP
Inventors: Vincent Joudon; Damien Bruno LAMOUCHE; Matthieu Patrick Jean Roger Perlin
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2019-02-04
Filing date: 2020-02-04
Publication date: 2021-12-15
Also published as: JP2022524292A; CN113474117B; BR112021015211A2; FR3092267B1; US11731221B2; CN113474117A; FR3092267A1; WO2020161426A1; CA3128288A1; US20220143766A1

Abstract

The invention relates to a method for separating a first mechanical part (12) from a second mechanical part (14), wherein the second mechanical part (14) is bonded to the first mechanical part (12) by an adhesive film (16) along a connecting area, the first mechanical part (12) having a first specific thermal conductivity and the second mechanical part (14) having a second thermal conductivity that is higher than the first thermal conductivity, characterised in that it comprises at least one cooling step during which the second mechanical part (14) is cooled to a negative temperature and at least one stressing step during which the second mechanical part (14) is subjected to mechanical stress in order to cause the adhesive film (16) to break.

Description

DESCRIPTION

TITLE: PROCESS FOR DESOLIDARIZING A FIRST MECHANICAL PART FROM A SECOND MECHANICAL PART

Technical field of the invention

The invention relates to a method for separating a first mechanical part from a second mechanical part.

The invention applies most particularly to a method of separating a metal reinforcement from the leading edge of a turbine engine blade made of composite material.

Technical background

By-pass turbomachines equipped with a fan are equipped with blades which can be made mainly from a composite material with an organic matrix. These blades are generally equipped with metal reinforcements made of titanium alloy which are bonded to the blades, for example on the leading edge of the blades.

In service, the metal reinforcement of one or more blades can be damaged by various impacts, for example when a foreign object such as a bird or such as a debris is ingested by the blower. However, in this case, the corresponding vane is not necessarily subject to degradation so that it may be advantageous to replace only the metal reinforcement and to keep the composite vane, because the latter, due to the fact of its manufacture in composite material, has a high economic value.

The problem with the invention therefore resides in the development of a method making it possible to separate the metal reinforcement from the blade made of composite material without damaging said blade. Various techniques known from the state of the art have hitherto been used to separate the metal reinforcement from the blade:

Document FR-2,970,197-A1 discloses a method for inductively separating a first mechanical part from a second magnetic mechanical part bonded to the first part by a film of adhesive. In this process, the magnetic properties of the second magnetic mechanical part are used by producing a magnetic field in the bonding zone so as to generate by induction eddy currents in the second magnetic mechanical part, which has the effect of heating it. and to soften the film of adhesive binding the two parts in order to allow the separation of the mechanical parts.

The drawback of this method, applied to a blade reinforcement, is that the thickness of the latter is not uniform. In particular, the reinforcement is of high thickness at the leading edge of the blade and it is of reduced thickness in extension zones which extend towards the interior of the blade from this edge. attack and which are stuck to the surface of the blade by the adhesive film.

The magnetic field used to achieve a sufficient temperature rise of the reinforcement at the region of high thickness of the reinforcement risks causing overheating in the areas of reduced thickness of the reinforcement. This overheating can be transmitted to the composite material of the blade, with the risk of degrading it.

The document FR-3,056,605-A1 discloses a process for separation by dissolution. According to this method, part of a blade comprising a reinforcement of a leading edge made of a titanium alloy is immersed in a chemical treatment chamber supplied by a closed circuit in which circulates a chemical treatment composition and a circuit. closed in which circulates a rinsing composition. The chemical treatment composition is circulated to dissolve the titanium alloy, then the vane is rinsed. This solution has the drawback of requiring relatively bulky and complex equipment, and of having a long processing time, linked to the dissolution of the titanium reinforcement. In addition, the material thereof being dissolved, it cannot be recycled.

Document US-2014/030108-A1 describes a separation process by heating and mechanical stressing of an assembly comprising a film of adhesive loaded with shape memory materials, the heating being carried out at a temperature higher than that of martensitic transformation of said materials. This very specific glue can only be used in a restrictive way.

The documents FR3.025.735A1 and FR2.992.243 describes a process for separation by cooling and mechanical assembly stress in which the entire assembly is cooled. This configuration does not make it possible to take advantage of the differences in thermal conductivity between materials.

Summary of the invention

The invention overcomes this drawback by proposing a method for separating a first mechanical part from a second mechanical part making it possible to break the connection between the film of adhesive and the second mechanical part, the thermal conductivity of which is the highest.

More particularly, the invention proposes a method for breaking the interface between the adhesive and the material of the second mechanical part, by applying, on the one hand, a thermal stress to the second mechanical part and, on the other hand, a mechanical stress on this second part.

This second part, whose thermal conductivity is higher than that of the first part, is thus able to rapidly transmit thermal stress due to its high thermal conductivity, which thermal stress, combined with mechanical stress, breaks the adhesive film.

For this purpose, the invention proposes a method of separating a first mechanical part from a second mechanical part, the second mechanical part being bonded to the first mechanical part by a film of adhesive along a connecting zone, the first part mechanical being of a first determined thermal conductivity and the second mechanical part being of a second thermal conductivity greater than the first thermal conductivity, characterized in that it comprises at least one cooling step during which only the second is cooled mechanical part at a negative temperature and at least one stressing step during which the second mechanical part is subjected to mechanical stress in order to cause the adhesive film to break.

According to other characteristics of the process:

- the cooling and stress stages are simultaneous,

- During the stressing step, the second part is subjected to a compressive stress in a direction substantially perpendicular to a surface of the adhesive film,

- the compressive stress is carried out by means of vibrating or by means of projectile projection,

- the vibrating means is an ultrasonic hammering means and the projectile projection means is a shot peening means,

- the cooling step is carried out by spraying liquid nitrogen onto the second part.

- The first part is a blade made of composite material, the second part is a metal reinforcement bonded to a leading edge of said blade and the method comprises two simultaneous steps comprising a step of cooling the metal reinforcement by spraying liquid nitrogen and a stressing step during which the reinforcement is subjected to a mechanical stress by ultrasonic hammering in a direction substantially perpendicular to a surface of the adhesive film,

- the method is implemented by means of a tool making it possible to carry out simultaneously the two stages of cooling and stressing in a zone of coverage of the leading edge of the blade by the tool of length less than a length of leading edge of the blade, and said tool is moved along the entire length of the leading edge of the blade,

- the liquid nitrogen is sprayed at a temperature of appreciably - 200 ° C and the hammering by ultrasound is carried out at a frequency between 10 kHz and 40 kHz.

The invention also relates to a tool for separating a first mechanical part from a second mechanical part according to the method described above, characterized in that it comprises an assembly movable in translation along a free surface of the second. mechanical part, said assembly comprising:

- a solicitation group comprising successively:

• a generator, converting a source of electrical energy supplying said generator into a sinusoidal electrical signal,

• a converter, converting the sinusoidal electrical signal into sinusoidal vibrating waves,

• an amplifier, amplifying the vibratory waves,

• a sonotrode, capable of transmitting vibratory waves,

• at least one transmission finger, arranged in contact with the second part, and able to receive the vibratory waves from the sonotrode and to transmit them mechanically to the second part,

- a cooling unit comprising, successively:

• a pressurized nitrogen storage tank, • a regulator capable of receiving the nitrogen coming from the tank and delivering it under a determined pressure,

• a pipe, supplied with nitrogen under pressure by the pressure reducer, and extending near the second room,

• a nozzle, arranged at the end of the duct, configured to spray liquid nitrogen onto the surface of the second part.

Brief description of the figures

The invention will be better understood and other details, characteristics and advantages of the present invention will emerge more clearly on reading the following description given by way of non-limiting example and with reference to the accompanying drawings, in which:

[Fig.1] Figure 1 is a schematic sectional view of a turbine engine blade;

[Fig.2] Figure 2 is a schematic perspective view of the blade of Figure 1;

[Fig.3] Figure 3 is a top view of a tool according to the invention during the implementation of the method according to the invention;

[Fig.4] Figure 4 is another top of a tool according to the invention during the implementation of the method according to the invention.

Detailed description of the invention

FIG. 1 shows a turbine engine blade assembly 10. In known manner, the blade assembly 10 consists of two parts 12 and 14 bonded by a film of adhesive 16, the thickness of which has been exaggerated for the purposes of understanding FIG. 1. The film of adhesive 16 defines thus a connection zone 18 between the two parts. The first mechanical part 12 has a determined thermal conductivity and the second part 14 has a thermal conductivity 14 greater than that of the first part 12.

As regards a turbine engine blade assembly 10, the first part is a blade 12 made of a composite material, for example a composite material with an organic matrix, and the second part is a metal reinforcement 14 made of a titanium alloy bonded to a leading edge 20 of dawn 12.

As shown in Figure 2, the reinforcement 14 extends along a length L along the leading edge 20 of the blade 12.

Conventionally, the separation processes known from the state of the art consist either in softening the film of adhesive 16 by induction heating the reinforcement 14, or in carrying out an operation of chemical dissolution of the reinforcement 14.

As seen in Figure 1, the thickness of the reinforcement 14 is not uniform. The reinforcement 14 covers the blade 12 and it has a thickness E which is maximum at the level of the leading edge 20 and which decreases to minimum values in zones 26 and 28 where the reinforcement meets zones of upper surface 22 and lower surface 24 from dawn 12.

Consequently, heating the reinforcement 14 by induction aimed at causing sufficient softening of the film of adhesive 16 at the leading edge has the drawback of causing excessive heating of the zones 26 and 28, with the consequence of a risk of degradation. of the composite material of the blade 12 near these areas. This technical solution is therefore inappropriate.

An operation of chemical dissolution of the reinforcement 14 does not risk damaging the vane 12, but nevertheless has the drawback of being a long operation and costly in terms of means.

The invention overcomes these drawbacks by proposing a method comprising at least one cooling step during which the reinforcement 14 is cooled to a negative temperature and at least one cooling step. stress during which the reinforcement 14 is subjected to a mechanical stress to cause the breaking of the adhesive film 16.

The cooling of the metal reinforcement 14, the thermal conductivity of which is high, makes it possible to cool the film of adhesive 16 in contact with the metal of the metal reinforcement 14 in order to modify its ductile mechanical behavior into a fragile mechanical behavior, which causes a drop in its tenacity. This makes it possible to reduce the mechanical energy input necessary for the breaking of the adhesive film 16, which makes it possible to considerably reduce the risk of degradation of the blade 12 when, during the stressing step, the reinforcement 14 is subjected to mechanical stress.

The modification of the mechanical behavior of the adhesive film 16 depends on the adhesive used. Conventionally, the blades 12 and reinforcements 14 are assembled by means of epoxy adhesives which become brittle as soon as very negative temperatures are reached because the mobility of the macromolecular chains of the adhesive film 16 is then reduced. The cooling step of the process of the invention makes it possible to consequently weaken the adhesive film.

In the preferred embodiment of the invention, the cooling and stressing steps are simultaneous. This configuration is not restrictive of the invention, and the stressing operation could be carried out after cooling of the reinforcement 14, as long as the latter does not rise in temperature sufficiently for the adhesive film 16 to regain its ductile behavior.

A tool 30 enabling these steps to be implemented is shown in Figures 3 and 4.

The tool 30 comprises an assembly 32 movable in translation along a length L along a free surface 32 of the reinforcement 14. The assembly 32 can be moved manually. However, in the context of industrialization of the process, the assembly 32 is mounted on a carriage 36 movable in translation. The assembly 32 preferably comprises, from upstream to downstream in the direction of movement of the assembly 30, indicated by the arrow in FIG. 3, a cooling group 38 intended to carry out the cooling step and a group of solicitation 40 intended to carry out the solicitation step.

Thus any zone of the reinforcement 14 cooled by the cooling unit 38 is immediately subjected to the stress of the stress group 40 during the movement of the assembly 30.

The cooling unit 38 comprises a reservoir 42 of pressurized cooling fluid and a pressure reducing valve 44 capable of receiving the fluid coming from the reservoir 42 and of delivering it under a determined pressure. This pressure reducer is connected to a conduit 46, supplied with pressurized cooling fluid, which extends close to the reinforcement 14. The end of the conduit 46 comprises a nozzle 48 which is configured to spray the cooling fluid onto the surface of the valve. reinforcement 14.

In the preferred embodiment of the invention, the cooling step is carried out by spraying a cooling fluid based on liquid nitrogen onto the reinforcement 14.

The nozzle 48 is therefore configured to spray the surface of the reinforcement 14 with a mist of liquid nitrogen.

Liquid nitrogen is sprayed at a temperature of -200 ° C. The adhesive film 16 is cooled by thermal conduction through the reinforcement 14. The nitrogen application time therefore depends on the thickness and the nature of the metal reinforcement 14, as well as on the desired temperature in the adhesive film 16 to cause it to break.

A major advantage of this process lies in the differences in thermal conductivity of the reinforcement 14 and of the adhesive film 16.

On the one hand, the reinforcement 14 rapidly conducts heat and allows the film of adhesive 16 to be cooled rapidly. However, the adhesive made of polymer material used in the film of adhesive 16 conducts little heat, which thermally insulates the blade 12. For example, a few seconds application of nitrogen is sufficient to treat thicknesses E of metal reinforcement less than 1 mm.

Several types of mechanical stress can be considered during the stressing step, for example stresses exerted perpendicular to a chord of the blade. However, preferably, as illustrated in FIGS. 3 and 4, the second part, that is to say the reinforcement 14, is subjected to a compressive stress in a direction D substantially perpendicular to a surface of the adhesive film 16. .

This compressive stress is a mechanical stress corresponding to a shock exerted on the surface of the metal reinforcement 14. This compression wave has the advantage of being transformed into a tensile wave at the interface between the reinforcement 14 and the adhesive film 16 of the makes the difference in mechanical impedance between the reinforcement 14 and the adhesive film 16. In fact, it is known that the change in mechanical rigidity at the interface between two materials induces the reflection of part of the incident wave compression into a tensile wave.

In general, the compressive stress can be achieved by a means of setting in vibration or by a means of projectile projection. Such a vibration means is, for example, an ultrasonic hammering means. A means of projectile projection is, for example, a shot-blasting means.

In the preferred embodiment of the invention, the vibrating means is an ultrasonic hammering means. For this purpose, the stress group 40 comprises a chain of components aimed at producing the ultrasonic hammering.

These components comprise a generator 50, converting a source of electrical energy supplying the generator into a sinusoidal electrical signal. This signal feeds a converter 52, which converts the sinusoidal electrical signal into sinusoidal vibrating waves. These vibratory waves are transmitted to an amplifier 54, which amplifies them. The amplifier 54 amplifies the vibratory waves intended for a sonotrode 56 which is able to mechanically transmit the vibratory waves. At one end of the sonotrode 56 is at least one transmission finger 58, also called an "indenter", which receives the vibratory waves from the sonotrode 56, which is arranged in contact with the reinforcement 14 of the second part, and which is suitable for them. mechanically transmit to the reinforcement 14.

Depending on the power of the chain of components, it is possible, as is the case in FIGS. 3 and 4, to have several transmission fingers 58. These fingers 58 make it possible for example not only to hammer the edge ultrasonically. attack of the reinforcement 14, but also for example the zones 26 and 28 where the reinforcement joins the upper surface zones 22 and 24 of the blade 12, in order to allow uniform detachment of the adhesive film 16.

The transmission finger or fingers 58 of the sonotrode 58 exert the mechanical stress by hammering by ultrasound, as we have seen, substantially in the direction D substantially perpendicular to a surface of the adhesive film 16 ..

Ultrasonic hammering is for example carried out at a frequency between 10 kHz and 40 kHz.

As has been seen, and as illustrated in FIGS. 3 and 4, the assembly 32 of the tooling 30 enables the two stages of cooling and stressing to be carried out simultaneously. These two operations are carried out in a coverage zone C of the leading edge 20 of the blade 12 by the tooling 30, and more particularly by the fingers 58 of the sonotrode 56 immediately after passage of the nozzle 48. The zone C is of a length I less than the length L of the leading edge 14 of the vane 12. The tool 40 is therefore moved along the entire length L of the leading edge 14 of the vane 12, as illustrated FIGS. 3 and 4. During movement, the coverage area C first undergoes cooling by the nozzle 48 and then immediately after the mechanical stress by the transmission fingers 58. The immediate proximity of the fingers 58 to the nozzle 48 prevents the leading edge 20 from heating up and the cooling from losing its effectiveness.

The detachment of a blade reinforcement 14 from the blade 12 can therefore be carried out very simply by sweeping the latter using the tool 30.

The invention simplifies and makes such detachment operations more reliable.

Claims

1. A method of separating a first mechanical part (12) from a second mechanical part (14), the second mechanical part (14) being bonded to the first mechanical part (12) by a film of adhesive (16) according to a connection zone (18), the first mechanical part (12) being of a first determined thermal conductivity and the second mechanical part (14) being of a second thermal conductivity greater than the first thermal conductivity,

characterized in that it comprises at least one cooling step during which only the second mechanical part (14) is cooled to a negative temperature and at least one stressing step during which the second mechanical part (14) is subjected ) to a mechanical stress to cause the rupture of the adhesive film (16).

2. Disconnection method according to the preceding claim, characterized in that the cooling and stressing steps are simultaneous.

3. Disconnecting method according to one of the preceding claims, characterized in that, during the stressing step, the second part (14) is subjected to a compressive stress in a direction (D) substantially perpendicular to a surface of the adhesive film (16).

4. Method of uncoupling according to one of the preceding claims, characterized in that the compressive stress is carried out by a means of setting in vibration or by a means of projection of projectiles.

5. Method of uncoupling according to the preceding claim, characterized in that the vibrating means is an ultrasonic hammering means and in that the projectile projection means is a shot peening means.

6. Method of uncoupling according to one of the preceding claims, characterized in that the cooling step is carried out by spraying liquid nitrogen onto the second part (14).

7. Method of uncoupling according to one of the preceding claims, characterized in that the first part (12) is a blade of composite material, in that the second part (14) is a metal reinforcement bonded to a leading edge (20) of said blade (12) and in that it comprises two simultaneous steps comprising a step of cooling the metal reinforcement (14) by spraying liquid nitrogen and a stressing step during which the reinforcement is subjected ( 14) to mechanical stress by ultrasonic hammering substantially in a direction (D) substantially perpendicular to a surface of the adhesive film (16).

8. A method of uncoupling according to the preceding claim, characterized in that it is implemented by means of a tool (30) making it possible to simultaneously perform the two stages of cooling and stressing in a coverage area (C) of the leading edge (20) of the blade (12) by the tool of length (I) less than a length (L) of the leading edge (20) of the blade (12), and in that said tool (30) is moved along the entire length (L) of the leading edge (20) of the blade (12).

9. A method of uncoupling according to one of claims 7 or 8, characterized in that the liquid nitrogen is sprayed at a temperature of substantially -200 ° C and in that the ultrasonic hammering is carried out at a frequency between 10kHz and 40 kHz.

10. Tool (30) for separating a first mechanical part from a second mechanical part according to a method according to claims 1 to 6 taken in combination, characterized in that it comprises an assembly (32) movable in translation the along a free surface (34) of the second mechanical part (14), said assembly (32) comprising

- A solicitation group (40) comprising successively: - a generator (50), converting a source of electrical energy supplying said generator (50) into a sinusoidal electrical signal,

- a converter (52), converting the sinusoidal electrical signal into sinusoidal vibrating waves,

- an amplifier (54), amplifying the vibratory waves,

- a sonotrode (56), capable of transmitting vibratory waves,

- at least one transmission finger (58), arranged in contact with the second part (14), and capable of receiving the vibratory waves from the sonotrode (56) and of transmitting them mechanically to the second part (14),

- A cooling unit (38) comprising, successively:

- a pressurized nitrogen storage tank (42),

- a regulator (44) capable of receiving the nitrogen coming from the tank (42) and delivering it under a determined pressure,

- a pipe (46), supplied with nitrogen under pressure by the pressure reducer (44), and extending near the second part (14),

- a nozzle (48), arranged at the end of the duct (46), configured to spray liquid nitrogen onto the surface of the second part (14).