Aerodynamic measurement device for an aircraft

Abstract

The present invention relates to an aerodynamic measurement device for an aircraft (A), the device comprising an appendage (12) that is able to project from the skin of said aircraft, which appendage is rotatable and mounted on a rotating shaft (14) that is able to be mounted under the skin of the aircraft, wherein the rotating shaft is guided via rotating interfaces (22) that are accommodated, respectively, in bodies (18, 20) attached to the aircraft, and is able to transmit its position by being coupled to a magnetic or inductive angular sensor, the angular sensor comprising a fixed portion (36) and a movable portion (38), the relative positioning of which is to be maintained, over an entire predetermined temperature range, within a predetermined positioning range depending on the required measurement accuracy, the device comprising, for each rotating interface, a porous interface (50) located between the rotating interface and the fixed body.

Description

[0001] TITLE: Aerodynamic measurement equipment for aircraft

[0002] The present invention relates to an aerodynamic measuring device for an aircraft, said device comprising an appendage adapted to protrude from the skin of said aircraft, movable in rotation and mounted on a rotating shaft adapted to be mounted under the skin of the aircraft.

[0003] The present invention also relates to an aircraft comprising at least one such aerodynamic measuring device.

[0004] The present invention also relates to a method for manufacturing such aerodynamic measuring equipment.

[0005] The invention is in the field of aeronautics.

[0006] To perform its mission, an aircraft includes several aerodynamic measurement devices comprising flush parts or appendages protruding from the aircraft skin, each being rotationally mobile and mounted on a rotating shaft designed to be mounted under the aircraft skin.

[0007] These appendages or protruding parts belong, for example, to probes that allow, in particular, the measurement of various aerodynamic parameters of the airflow surrounding the aircraft, such as the incidence of the airflow in the vicinity of the aircraft skin.

[0008] The present invention relates more specifically to angle-of-attack probes suitable for providing a measurement of the angle of attack of the aircraft (also called an angle of attack probe (AoA)).

[0009] Document CN 104 034 301 A discloses an example of a miniature angle of attack sensor. Document WO 2018 / 092652 A1 aims to simplify the construction of an angle detection device that detects a swing angle, around a shaft, between two elements connected by said shaft.

[0010] The angle of attack is the angle of incidence relative to the airflow, and monitoring it helps to avoid exceeding the maximum permissible angle of incidence for the aircraft before stalling.

[0011] To be able to measure the angle of attack of the airflow, the rotating assembly is designed to transmit its position by being coupled to an angle sensor. It is essential to ensure the proper functioning of this sensor throughout the aircraft's entire service life, which, during its operation, is subject to temperature variations ranging from -55°C to +120°C. Currently, angle sensors are used in an assembled configuration, as illustrated in Figure 1. This figure schematically represents, in cross-section along the Z-axis of height, the arrangement (10) of an angle-of-attack probe with a conventional sensor in an "assembled" configuration, using a specific mechanical design, as illustrated in Figure 1.

[0012] More specifically, according to arrangement 10 of figure 1, the aircraft aerodynamic measuring equipment, corresponding to an angle-of-attack probe, includes first of all an appendage 12, in particular a wind vane, suitable for emerging from the skin A of said aircraft.

[0013] This appendage 12 (i.e. this wind vane) is mobile in rotation and mounted on a rotating shaft 14 suitable for mounting under the skin A of the aircraft.

[0014] The part of the aircraft aerodynamic measuring equipment, corresponding in particular to an angle-of-attack probe, located under the skin A of the aircraft is called the probe foot 16.

[0015] More specifically, within this probe foot 16, the rotating shaft 14 is designed to be mounted under the aircraft skin A, via a body attached to an aeronautical plate P_A of the aircraft skin A. In the example shown in Figure 1, the body comprises an upper part 18 (also called the upper body) and a lower part 20 (also called the lower body). According to another variant, not shown, a one-piece body is used.

[0016] Conventionally, as illustrated in the cross-sectional view of Figure 1, the rotating shaft 14 is guided via rotating interfaces, such as bearings or plain bearings 22, housed respectively in the upper and lower bodies 18 and 20 fixed to the aircraft (or, according to the variant not shown, housed in a single-piece body designed to ensure its retention). More precisely, along the Z-axis, upper rotating interfaces guide the upper part of the rotating shaft 14, these upper rotating interfaces being housed in the upper body 18 fixed to the aircraft, while lower rotating interfaces guide the lower part of the rotating shaft 14, these lower rotating interfaces being housed in the lower body 20 integral with the upper body 18, itself fixed to the aircraft.

[0017] As previously stated, according to an unrepresented variant, a one-piece body is also suitable for use in retaining upper and lower rotating interfaces.

[0018] The rotating shaft 14 is designed to transmit its position by being coupled to an angular sensor 24 in an "assembled" version housed on a sensor support 26 via a coupling piece 28 generally corresponding to a bellows so that the radial and axial play taken by the rotating shaft does not impact the operation of the sensor designed to analyze and / or save and / or transmit the position of the rotating shaft via at least one electronic board, for example, two electronic boards 30 and 32 as illustrated in Figure 1.

[0019] However, these "assembled" solutions are expensive, bulky, require analog / digital processing of the analog information obtained which must be digitized in order to then communicate it to the flight computer, and are associated with installation constraints, an adjustment being necessary for the positioning of the sensor shaft 24 on the rotating shaft 14.

[0020] To remedy this, a new generation of sensor is proposed, based on magnetic or inductive operation, and is advantageously delivered as a kit, i.e. with a part called "stator" and a moving part called "rotor" as illustrated by arrangement 33 in figure 2.

[0021] The integration of these new, natively "digital" sensors in kit form allows, in particular, a reduction in the electronic footprint initially required for the analog / digital processing implemented by sensors in their "assembled" form. This ultimately allows for a reduction in the overall product size or for the freed-up electronic space to be used to integrate the processing of the sensor's raw signal.

[0022] It should be noted, however, that whether for products with old (i.e. in assembled version) or new generation sensors (i.e. in kit version), there are systematically embedded electronic boards not shown in the figures for power supply and for heating the external appendage.

[0023] On this arrangement 33, the sensor 34 in kit form, with magnetic or inductive operation, therefore includes a static part: the stator 36, and a moving part: the rotor 38.

[0024] These new sensors meet the current cost, integration and performance requirements of aircraft such as small / medium range (SM R) aircraft, new generation fighters (NGF) or regional air mobility / urban air mobility (RAM / UAM) aircraft.

[0025] However, the integration of such sensors in kit form (i.e. in two parts) must meet specific positioning requirements between the moving part 38 (i.e. the rotor) and the fixed part 36 the stator, as illustrated by Figure 3 which focuses on Box III of Figure 2, and more specifically the relative positioning of the fixed part 36 and the moving part 38.

[0026] More specifically, as illustrated by Figure 3, radially, the axis 40 passing through the center of the stator 36 and the axis 42 passing through the center of the rotor 38 must have a concentricity deviation 44 less than a predetermined deviation threshold depending on the required measurement accuracy, and axially, along the Z-axis of the height, the variation of the air gap 46 separating the stator 36 from the rotor 38 must also remain less than a predetermined variation threshold depending on the required measurement accuracy.

[0027] In other words, such requirements aim to maintain substantially axial and radial alignment between the rotor 38 and the stator 36 of such a kit sensor 34, with magnetic or inductive operation.

[0028] In addition, these requirements for maintaining the relative positioning of the rotor 38 and the stator 36 must be met over the entire temperature range of operation of the aircraft aerodynamic measuring equipment, i.e. for example between -55 °C and +120 °C.

[0029] As previously stated, the rotating shaft 14 is guided via rotating interfaces 22, for example bearings, housed respectively in the lower and upper bodies 18 and 20 fixed to said aircraft, the rotating shaft 14 being conventionally made of steel and the fixed bodies of aluminium, to limit the weight of the aircraft aerodynamic measuring equipment.

[0030] During temperature variations between -55°C and +120°C, the rotating interfaces 22, usually made of steel, expand radially less than the bodies 18 and 20 made of aluminum or "light" alloys. Consequently, the outer rings of the rotating interfaces lose their guidance within the housings of the fixed bodies. This loss of guidance inevitably leads to a misalignment between the rotor 38 and the stator 36 of the angular sensor 34, and therefore to a measurement error.

[0031] The aim of the invention is therefore to propose a solution allowing the integration of an angular sensor kit, namely in two parts with a fixed part the stator and a mobile part the rotor, in the foot (i.e. under the skin of the aircraft) of the aerodynamic measuring equipment, while limiting the guidance losses of the rotating shaft of said equipment in the presence of temperature variations likely to generate differential expansions in the different materials constituting the different elements of the foot of the aerodynamic measuring equipment.

[0032] To this end, the invention relates to an aerodynamic measurement equipment for an aircraft, said equipment comprising an appendage adapted to protrude from the skin of said aircraft, movable in rotation and mounted on a rotating shaft adapted to be mounted under the skin of the aircraft, said rotating shaft being guided via rotating interfaces housed respectively in bodies fixed to said aircraft, and adapted to transmit its position by being coupled to an angular sensor with magnetic or inductive operation, said angular sensor comprising a fixed part and a movable part whose relative positioning is to be maintained, over a predetermined temperature range, within a predetermined positioning range according to the required measurement accuracy, said equipment being characterized in that it comprises, for each rotating interface, a porous interface located between said rotating interface and said fixed body.

[0033] Thus, the present invention advantageously proposes to insert a porous interface between each rotating interface and the fixed body associated with said rotating interface, said porous interface, like a sponge, being suitable for damping the differences in expansion between a rotating interface, in particular made of steel, and the fixed body to which it is usually attached, generally made of aluminum.

[0034] According to other advantageous aspects of the invention, the aerodynamic measuring equipment comprises one or more of the following features, taken individually or in all technically possible combinations:

[0035] - said rotating shaft and said rotating interfaces are of the same first material or of materials of equivalent nature, distinct from the material of said bodies fixed to said aircraft, said porous interface having a coefficient of expansion substantially equal to that of the material(s) of the rotating shaft and of said rotating interfaces and a Young's modulus between 40 and 50 GPa;

[0036] - said first material of the rotating shaft and of said rotating interfaces is steel or the materials of the rotating shaft and of said rotating interfaces are equivalent to steel, and said second material is aluminum;

[0037] - the porosity rate of said porous interface is approximately equal to 0.007g / cm² 3 ;

[0038] - the pore radius of said porous interface is 1 to 100pm;

[0039] - said measuring equipment is an angle-of-attack probe suitable for providing a measurement of the angle of attack or lateral slip of the aircraft, said appendage being a wind vane;

[0040] - said predetermined temperature range is from -55°C to 120°C, and in which said positioning range is predetermined for a measurement accuracy of the order of 0.05° of angle of attack and corresponds to a concentricity deviation of less than 0.02 mm and a variation of the air gap separating the fixed part and the moving part of the angular sensor of less than 0.1 mm.

[0041] The invention also relates to an aircraft comprising at least one aerodynamic measuring device as described above.

[0042] The invention also relates to a method for manufacturing an aerodynamic measuring equipment for aircraft as described above, said method comprising: - a sintering step of said porous interface by agglomeration at a predetermined high temperature of a powder of the material of said porous interface;

[0043] - a step of integrating porous interfaces within said aerodynamic measuring equipment, according to which, for each rotating interface, a porous interface is shrink-fitted, substantially at said predetermined high temperature, onto the fixed body associated with said rotating interface, so that said porous interface is located between said rotating interface and said associated fixed body.

[0044] According to another advantageous aspect of the invention, said powder material of said porous interface is a micrometric powder of stainless steel, and said predetermined high temperature is equal to +200°C.

[0045] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0046] [Fig. 1] [Fig.2] [Fig.3] Figures 1 to 3 respectively represent cross-sectional views of an aerodynamic measuring equipment for aircraft according to two distinct embodiments, namely with an angular sensor in assembled version and in kit version of the prior art, as already described above, Figure 3 illustrating the specific positioning requirements between the moving part and the fixed part of the angular sensor in kit version.

[0047] [Fig. 4] Figure 4 represents a cross-sectional view of an aircraft aerodynamic measuring device according to the present invention.

[0048] In the following description, the expression "approximately equal to" is understood as a relationship of equality to plus or minus 10%, that is to say with a variation of at most 10%, preferably even more as a relationship of equality to plus or minus 5%, that is to say with a variation of at most 5%.

[0049] Figure 4 therefore illustrates an embodiment of an aerodynamic measurement equipment for aircraft according to the present invention.

[0050] For simplicity, the numerical references of the identical elements between the aircraft aerodynamic measuring equipment of figures 1 to 3, representative of the prior art, and the aircraft aerodynamic measuring equipment according to the present invention illustrated by figure 4 have been retained.

[0051] In the cross-sectional view of Figure 4, the arrangement 48 of said aircraft aerodynamic measuring equipment according to the present invention is therefore identical to the prior art of Figure 2 in that said aircraft aerodynamic measuring equipment A still includes an appendage 12 adapted to protrude from the skin of said aircraft, movable in rotation and mounted on a rotating shaft 14 adapted to be mounted under the skin of aircraft A.

[0052] The rotating shaft 14 is also always guided via rotating interfaces 22 housed respectively in the body composed of the upper body 18 and lower body 20 fixed to said aircraft, or according to another variant, not shown, in a one-piece body, and suitable for transmitting its position by being coupled to an angular sensor with magnetic or inductive operation.

[0053] According to the present invention, said angular sensor is said to be in kit form and comprises a fixed part 36 and a movable part 38 whose relative positioning is to be maintained, over a predetermined temperature range, within a predetermined positioning range according to the required measurement accuracy.

[0054] According to the present invention, said aerodynamic measuring equipment differs from that of the prior art illustrated by Figure 2, in that it comprises for each rotating interface, in particular a bearing, a porous interface 50 located between said rotating interface 22 and the fixed body 18 or 20 to which it is associated.

[0055] In other words, to limit radial play and stresses generated at interfaces during differential expansions, as indicated in relation to the aforementioned prior art, porous interfaces 50 (i.e. porous bearings or porous rings) are integrated (i.e. inserted, shrink-fitted) at the boundary (i.e. frontier) between the rotating interfaces 22 and the fixed bodies 18 or 20.

[0056] According to a particular example, as used hereafter, said measuring equipment is an angle-of-attack probe suitable for providing a measurement of the angle of attack or sideslip of the aircraft, said appendix 12 being a wind vane.

[0057] As an optional addition, said rotating shaft 14 and said rotating interfaces 22 are of the same first material or of materials of equivalent natures, distinct from the material of said fixed bodies 18,20 of said aircraft A, said porous interface 50 having a coefficient of expansion substantially equal to that of the material(s) of the rotating shaft and of said rotating interfaces and a Young's modulus (i.e. a modulus of elasticity) between 40 and 50 GPa.

[0058] By materials of equivalent nature, we mean for example that the rotating shaft is made of iron-based steel while the said rotating interfaces are made of nickel alloy.

[0059] According to one variant of this optional supplement, the first material of the rotating shaft and the rotating interfaces is steel, or the materials of the rotating shaft and the rotating interfaces are equivalent to steel, and the second material is aluminum. Indeed, the materials typically used to construct, in particular, an angle of attack probe (also called an angle of attack probe), are, on the one hand, for the rotating shaft 14 and the rotating interfaces 22, stainless steel, in particular X8CRNIS18-9 steel, used for its mechanical strength and wear resistance and having a coefficient of thermal expansion approximately equal to 12 ppm (i.e.parts per million), and on the other hand, aluminium, in particular aluminium 6061, for the upper and lower bodies 18 and 20 fixed to the aircraft, aluminium having a coefficient of expansion approximately equal to 23 ppm and being used for the mass gain it provides compared to steel and its thermal conductivity.

[0060] In other words, according to this variant, each porous interface 50 has a coefficient of expansion substantially equal to that of the steel constituting the rotating interfaces, in order to expand similarly to the rotating interface (e.g., the bearing) to which said interface is associated at one of its ends, the other end being fixed to the corresponding fixed body.

[0061] More specifically, as previously stated, said angular sensor comprises a fixed part 36 and a movable part 38 whose relative positioning is to be maintained, over a predetermined temperature range, within a predetermined positioning range according to the required measurement accuracy.

[0062] According to one variant, said predetermined temperature range is from -55°C to 120°C, and said positioning range is predetermined for a measurement accuracy of the order of 0.05° of angle of attack and corresponds to a concentricity deviation 44 of less than 0.02 mm and a variation of the air gap 46 separating the fixed part and the moving part of the angular sensor of less than 0.1 mm as illustrated previously by Figure 3.

[0063] At high temperature, particularly at +120°C, the aluminum of the upper and lower bodies 18 and 20 expands more than the steel of the rotating interfaces 22. For example, for a usual outer diameter of rotating interface of about 10 mm, the outer ring of the rotating interface (i.e. the rotating interface ring (e.g. the bearing ring)) distal to the rotating shaft 14), made of steel, expands by 0.5 mm, while the housing of the fixed body 18 or 20 made of aluminum and associated with the rotating interface (i.e. the bearing) 22 considered, expands by 0.10 mm, so that the relative clearance (i.e. the gap 44) is about 0.5 mm, which exceeds the concentricity tolerance of the sensor.

[0064] Conversely, at low temperatures, particularly at -55°C, the aluminum constituting the bodies 18 and 20 fixed to the aircraft contracts more than the steel of the rotating interfaces 22. The stresses generated in the aluminum body are greater than the limit admissible by the material.

[0065] To remedy this, a porous interface 50 is proposed, located between each rotating interface 22 and its associated fixed body 18 or 20, so as to dampen the aforementioned differential expansions over the entire predetermined temperature range. According to the aforementioned optional specification, this porous interface has both a coefficient of expansion substantially equal to that of steel and a Young's modulus between 40 and 50 GPa.

[0066] In particular, to manufacture such aerodynamic measuring equipment, the manufacturing process according to the present invention includes a sintering step of said porous interface by agglomeration at a predetermined high temperature of a powder of the material of said porous interface.

[0067] According to an optional variant, said porous interface is sintered by agglomeration of a micrometric powder of stainless steel, in order to advantageously present a coefficient of expansion substantially equal to that of the steel of the rotating interfaces 22.

[0068] Furthermore, the manufacturing process according to the present invention includes a step of integrating porous interfaces within said aerodynamic measuring equipment, according to which, for each rotating interface, a porous interface is shrink-fitted, substantially at said predetermined high temperature, onto the fixed body, (said fixed body being in particular made of aluminum), associated with said rotating interface (said rotating interface, for example a bearing, being in particular made of stainless steel), so that said porous interface, in particular obtained by agglomeration of a micrometric powder of stainless steel, is located between said rotating interface and said associated fixed body.

[0069] The gap formed, as previously indicated according to the prior art, by differential expansions at 120°C is thus eliminated according to the present invention, thanks to the porous interface.

[0070] In an optional example, the predetermined high temperature is advantageously strictly greater than the upper bound of the predetermined temperature range, said upper bound being, in particular, equal to +120°C. In this optional example, the predetermined high temperature is equal to +200°C > +120°C.

[0071] Such shrink-fitting at a predetermined high temperature, for example +200°C, higher than the maximum operating temperature, for example +120°C, allows the porous interface to remain bonded at high temperature to the fixed body in question.

[0072] Moreover, at low temperatures, particularly at -55°C, where, as previously indicated according to the prior art, the aluminum of the fixed bodies 18 and 20 contracts more than the steel of the rotating interfaces 22, for, for example, a usual outside diameter of rotating interface 22 of about 10 mm, the dimensional variation between the rotating interface and an aluminum plate of the associated fixed body (lower or upper) is about 1 / 10 mm, with a maximum stress reached in the fixed bodies of about 1000 MPa, which far exceeds the elastic limit of the aluminum of the fixed bodies which would thus be deteriorated from their first cycle of use.

[0073] The porous interface proposed according to the present invention makes it possible to avoid such deterioration, by playing the role of "damper" in order to limit the over-stress generated at this low temperature of -55°C between the steel of the rotating interfaces 22 and the aluminum of the fixed bodies 18 and 20.

[0074] Indeed, according to the optional supplement, the Young's modulus of porous materials (i.e., porous interfaces) is greatly reduced compared to "solid" material, whose usual value of 180 GPa is reduced to 40 GPa.

[0075] This decrease in Young's modulus allows, for the same differential displacement, in particular of about 1 / 10 mm, to proportionally reduce the stresses in the material.

[0076] By simulation, the maximum stresses in the porous interfaces proposed according to the present invention are about 150 MPa, which is less than the yield strength of aluminum, in particular aluminum 6061 whose yield strength is about 240 MPa.

[0077] As an optional addition, the porosity rate of said porous interface is approximately equal to 0.007 g / cm² 3 .

[0078] According to another optional supplement, the pore radius of said porous interface is 1 to 100pm.

[0079] Those skilled in the art will understand that the invention is not limited to the embodiments described, nor to the particular examples of the description, the embodiments and variants mentioned above being capable of being combined with each other to generate new embodiments of the invention.

[0080] The present invention thus makes it possible to improve existing aerodynamic measurement equipment, in particular angle-of-attack probes, by allowing the integration of angular sensor(s) "in kit", supplied in two parts, thanks to the crimped porous interfaces, in particular in steel, between the rotating interfaces and the fixed bodies to respect, over the entire temperature range of use of said equipment, the positioning required by the angular sensor "in kit" (i.e. encoder in kit version).

[0081] The porous nature of these interfaces reduces the Young's modulus of the material, such as steel, constituting them, thereby dampening the differential expansions observed in relation to the aforementioned prior art over the operating temperature range of the equipment. According to an optional addendum mentioned above, advantageously, the porous interfaces are also shrink-fitted, particularly at approximately 200°C, within the aluminum bodies to maintain their integrity at high temperatures, particularly at approximately 120°C.

Claims

DEMANDS 1. Aerodynamic measurement equipment for aircraft (A), said equipment comprising an appendage (12) adapted to protrude from the skin of said aircraft, rotatably movable and mounted on a rotating shaft (14) adapted to be mounted under the skin of the aircraft (A), said rotating shaft (14) being guided via rotating interfaces (22) housed respectively in bodies (18, 20) fixed to said aircraft, and adapted to transmit its position by being coupled to an angular sensor operating magnetically or inductively, said angular sensor comprising a fixed part (36) and a movable part (38) the relative positioning of which is to be maintained, over a predetermined temperature range, within a predetermined positioning range according to the required measurement accuracy, said equipment being characterized in that it comprises, for each rotating interface, a porous interface (50) located between said rotating interface (22) and said fixed body (18, 20),said rotating shaft (14) and said rotating interfaces (22) being of the same first material or of materials of equivalent nature, distinct from a second material of said fixed body, for each rotating interface, said porous interface being suitable for damping the differences in expansion between said rotating interface and said fixed body.

2. Aerodynamic measurement equipment for aircraft according to claim 1, wherein said porous interface (50) has a coefficient of expansion substantially equal to that of the material(s) of the rotating shaft and of said rotating interfaces and a Young's modulus between 40 and 50 GPa.

3. Aerodynamic measurement equipment for aircraft according to claim 2, wherein said first material of the rotating shaft and of said rotating interfaces is steel or the materials of the rotating shaft and of said rotating interfaces are equivalent to steel, and said second material is aluminum.

4. Aerodynamic measuring equipment for aircraft according to any one of the preceding claims, wherein the porosity of said porous interface is substantially equal to 0.007 g / cm² 3 .

5. Aerodynamic measurement equipment for aircraft according to any one of the preceding claims, wherein the pore radius of said porous interface is from 1 to 100pm.

6. Aerodynamic measuring equipment for aircraft according to any one of the preceding claims, wherein said measuring equipment is an angle-of-attack probe suitable for providing a measurement of the angle of attack or sideslip of the aircraft, said appendage being a wind vane.

7. Aerodynamic measurement equipment for aircraft according to claim 6, wherein said predetermined temperature range is from -55°C to 120°C, and wherein said positioning range is predetermined for a measurement accuracy of the order of 0.05° of angle of attack and corresponds to a concentricity deviation (44) of less than 0.02 mm and a variation of the air gap (46) separating the fixed part and the moving part of the angular sensor of less than 0.1 mm.

8. Aircraft comprising at least one aircraft aerodynamic measuring device according to any one of the preceding claims.

9. A method for manufacturing aerodynamic measuring equipment for aircraft according to any one of the preceding claims, said method comprising: - a sintering step of said porous interface by agglomeration at a predetermined high temperature of a powder of the material of said porous interface; - a step of integrating porous interfaces within said aerodynamic measuring equipment, according to which, for each rotating interface, a porous interface is shrink-fitted, substantially at said predetermined high temperature, onto the fixed body associated with said rotating interface, so that said porous interface is located between said rotating interface and said associated fixed body, said rotating shaft and said rotating interfaces being of the same first material or of materials of equivalent natures, distinct from a second material of said fixed body, for each rotating interface, said porous interface being suitable for damping the differences in expansion between said rotating interface and said fixed body.

10. Manufacturing method according to claim 9 wherein said material powder of said porous interface is a micrometric powder of stainless steel, and wherein said predetermined high temperature is equal to +200°C.

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