WO2025257583A1

WO2025257583A1 - Method for manufacturing protective interface by additive manufacturing and mechanical assembly comprising such protection interface

Info

Publication number: WO2025257583A1
Application number: PCT/IB2024/000313
Authority: WO
Inventors: Nicolas ANTONI; Randy Lee; Zoran PASIC
Original assignee: Safran Landing Systems SAS
Current assignee: Safran Landing Systems SAS
Priority date: 2024-06-14
Filing date: 2024-06-14
Publication date: 2025-12-18
Anticipated expiration: 2026-12-14

Abstract

Method for producing an articulation comprising a first part (1) and a second part (2) to be articulated together, characterized in that the method comprises the step of forming on the first part a grafted contact element (33) by additive manufacturing using fused deposition modelling, the grafted contact element being arranged on the first part to form a contact surface of the first part with the second part.

Description

METHOD FOR MANUFACTURING PROTECTIVE INTERFACE BY ADDITIVE MANUFACTURING AND MECHANICAL ASSEMBLY COMPRISING SUCH PROTECTION INTERFACE

The present invention relates to mechanical assemblies.

PRIOR ART

Mechanical assemblies of two parts are known in which forces have to be transferred from one part to the other. To improve the mechanical wear resistance of the parts, it is known to set a protective bushing between said parts. The bushing is generally attached to one of the parts by shrink-fitting assembly. As the surfaces in con- tact comprise asperities, these surfaces are locally me- chanically bonded together. However, it appears that the bushing and said part, although theoretically immobile relative to each other, are subject to small relative movements (oscillatory movements due to cyclic loading or vibrations) or vibrations). Those small relative move- ments cause friction wear on the bushing and/or on the part, generating release of material particles, and sur- face stress concentration generating surface pitting onto said bushing and/or part. Those small relative movements can also cause fretting-fatigue failure. It appears that there is a higher risk of failure when the part material has high friction coefficient values and is notch sensi- tive (a pit in the surface of the part tends to spread rapidly through the thickness of the part). Titanium is an example of such a material, as well as aluminium.

It is vital that the part and the bushing retain their integrity, otherwise they will no longer be apt to con- tribute to the transmission of forces. One solution is to choose harder materials for the parts, but this usually results in a weight increase that is detrimental in cer- tain applications such as aircraft.

OBJECT OF THE INVENTION The invention aims to propose stronger mechanical assem- blies.

SUMMARY OF THE INVENTION

For this purpose, a method is provided for producing an articulation comprising a first part and a second part to be articulated together, characterized in that the method comprises the step of forming on the first part a grafted contact element by additive manufacturing using fused deposition modelling, the grafted contact element being arranged on the first part to form a contact surface of the first part with the second part.

With additive manufacturing, the material deposited onto the first part to form the contact element integrate the first part and therefore eliminating the risk of relative movement occurring between the first part and the contact element. Thus, the invention is a method that allows to protect at least one part of an articulation from fret- ting-fatigue, by directly manufacturing a contact element onto this part by additive manufacturing, thus avoiding deterioration due to assembly and movements of said part in relation to said element.

According to optional characteristics, used individually or all or part in combination:

- the first part is made of a first material, and the grafted contact element is made up of a second mate- rial different from the first one.

- the grafted element is arranged as a bushing for re- ceiving a portion of the second part to rotate.

- The method is comprising the step to form the graft- ed element in a zone of the first part comprising compressive residual stresses.

- The method is comprising the step of submitting to a peening process the zone of the first part on which the grafted contact element is to be formed. The invention also concerns an assembly made by using this method, having at least a first part and a second part articulated together, characterized in that the first part includes a contact element formed by additive manufacturing to have a contact surface in contact with the second part.

- the contact element is a bearing allowing the two parts to rotate relative to each other along an axis of rotation defined by said bearing.

- the bearing is positioned in a bore of the first part.

The invention also concerns a landing gear comprising this kind of assembly and an aircraft comprising this type of landing gear.

Other characteristics and advantages of the invention will emerge on reading the following description of a particular and non-limiting embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to the attached drawings, includ- ing:

[Fig. 1] is a general view of an aircraft comprising a landing gear equipped with an assembly according to the invention;

[Fig. 2] is a schematic view of a landing gear belonging to the aircraft of Figure 1;

[Fig. 3] is a perspective view of a connecting element according to the invention;

[Fig. 4] is a schematic sectional view of the connecting element of figure 3;

[Fig. 5a] is a schematic sectional view of the first part and the connecting element according to the manufacturing method according to the invention, at a first time;

[Fig. 5b] is a schematic sectional view of the first part and the connecting element according to the manufacturing method according to the invention, at a second time;

[Fig. 5c] is a schematic sectional view of the first part and the connecting element according to the manufacturing process according to the invention, at the end of the manufacturing process;

DETAILED DESCRIPTION OF THE INVENTION

In reference to the figure 1, the invention is described with reference to an aeronautical application in connec- tion with a landing gear 101 comprising a leg 102 having a first end articulated to the structure of an aircraft 100 and second free end to which a wheel 103 is pivotally connected.

More precisely, the leg 102 comprises a main part 1 and a rocker arm 2 connected to the main part 1 by an articula- tion 3 forming a connecting element.

The articulation 3 comprises a fork 30 which is fitted to a free end of the main part 1 and comprises two branches 31 (one is illustrated on figures 3 and 4) each provided with a bore 32. The rocker arm 2 has a portion extending between the branches 31 and a shaft 4 having ends pivot- ally mounted in the bores 32 crosses said portion of the rocker arm 2 so that the rocker arm 2 can pivot relative to the fork 30 and the main part 1 of the leg 102.

According to the invention, in each bore 32 extends a bushing 33 forming a bearing for one of the ends of the shaft 4.

Each bushing 33 has opposite ends, each with an external collar 34 extending over side faces of the branch 31. Each bushing 33 has an internal surface 35 provided with lubrication grooves 36.

The invention concerns a method for manufacturing the me- chanical assembly comprising the fork 30 forming a first part of the mechanical assembly and the shaft 4 forming a second part of the mechanical assembly.

In this mechanical assembly, each bushing 33 forms a con- tact element grafted by additive manufacturing to the first part of the mechanical assembly and is arranged on the first part of the mechanical assembly to form a con- tact surface of the first part of the mechanical assembly with the second part of the mechanical assembly.

The fork 30 is forged for example in a first material, which may be a high-performance metal alloy such as a ti- tanium-based alloy for example.

The contact element, i.e. the bushing 33, is made of a second material (such as bronze for example) different from the first one, which may be a material having great- er resistance characteristics (such as hardness) to forc- es than those of the first material constituting the first part. This second material must, however, have characteristics allowing it to be used in a production process by additive manufacturing.

With reference to Figures 5a, 5b, and 5c, the invention describes a production method making it possible to manu- facture this type of mechanical assembly.

Classically, a digital model of the fork 30 and of the bushing 33 to be manufactured have been designed via CAD software for example.

The fork 30 is then forged and machined in conformity with the digital model.

In order to make the branches 31 of the fork 30 more ca- pable of adhering with the grafted contact element, i.e. the bushing 33, each branch 31 is subjected to a shot peening process at the level of the zone on which the grafted contact element must be formed, i.e. the wall of the bore 32. The peening process forms on the interface a barrier comprising compressive residual stresses and eliminates cracks and asperities.

Then, the additive manufacturing starts. The contact ele- ment is manufactured layer by layer directly on a print plate 37. On figure 5a, one of the collars 34 is made first, then the tubular portion of the bushing 33 extend- ing in the bore 32 (figures 5b) and, after, the second collar 34 (figure 5c).

The additive manufacturing process used in the invention can be powder-based or wire-based. Thus, a powder bed of the material of the bushing 33 can be deposited and melt- ed layer by layer or the material of the bushing 33 can be deposited layer after layer from a movable heating ex- trusion head 38 having at least three degrees of freedom in translation.

The fused deposited material is left to cool, for example in the open air, in order to harden and form a solid con- tact element.

Once the layer-by-layer printing and the cooling are fin- ished, the fork 30 is removed from the printing plate 37. The bushings 33 thus manufactured by additive manufactur- ing are honed to final size and integral with the fork 30.

Once the bushings 33 have been grafted to the fork 30, the fork 30 is fitted onto the main part 1 of the leg 102 and the shaft 4, together with the rocker arm 2, is as- sembled to the fork 30.

A blocking means is then used to prevent a translational movement of the shaft 4 inside the bores.

Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

In particular, the contact element can have a form dif- ferent than the described one. The bushing 33 can have only one collar or no collar. The bushing 33 can comprise a different number of lubrication grooves (one or more than two) or can comprise some holes. The surface of the bushing may have no groove or hole.

The contact element can be grafted on an internal surface (of a bore for example) of the part, or on an external surface (of a shaft for example) of said part.

A contact element can be grafted on both parts.

The parts can have a rotary relative movement or a trans- lational relative movement.

The contact element can be machined after the additive process.

The peening process can be omitted.

The articulation can be arranged to allow relative rota- tion and/or relative translation of the parts.

Claims

1. Method for producing an articulation com- prising a first part (1) and a second part (2) to be ar- ticulated together, characterized in that the method com- prises the step of forming on the first part a grafted contact element (3) by additive manufacturing using fused deposition modelling, the grafted contact element being arranged on the first part to form a contact surface of the first part with the second part.

2. Method according to claim 1, wherein the first part is made of a first material, and the grafted contact element is made up of a second material different from the first one.

3. Method according to claim 1, wherein the grafted element is arranged as a bushing for receiving a portion (4) of the second part to rotate.

4. Method according anyone of claims 1 to 3, comprising the step to form the grafted element in a zone of the first part comprising compressive residual stress- es.

5. Method according to claim 4, comprising the step of submitting to a peening process the zone of the first part on which the grafted contact element is to be formed.

6. Mechanical assembly having at least a first part and a second part articulated together, char- acterized in that the first part includes a contact ele- ment formed by additive manufacturing to have a contact surface in contact with the second part.

7. Mechanical assembly according to claim 6, wherein the contact element is a bearing allowing the two parts to rotate relative to each other along an axis of rotation defined by said bearing.

8. Mechanical assembly according to claim 7, wherein the bearing is positioned in a bore (32) of the first part.

9. Landing gear (101) having a mechanical as- sembly according to anyone of claims 6 to 8.

10. Aircraft (100) having a landing gear accord- ing to claim 9.