Test support for a blade

Abstract

Test support (3) for a blade (5), comprising: - a base (9) defining a central channel (11), - an axial retaining flange (21) having a peripheral rim (19) axially engaged between the upper face (13) and the flange (21), - a guide support (31) defining an axial locking channel (47) and a transverse passage (51) intersecting the locking channel (47), - a locking screw (33), and - at least one jaw (35) movably mounted in the passage (51), such that an axial movement of the locking screw (33) results in a transverse clamping force exerted by the jaw (35). Figure to be published with the abbreviation: 2

Description

Title of the invention: Test support for a blade Technical field of the invention

[0001] The invention relates to a test support for a blade for carrying out cyclic fatigue tests. Prior art

[0002] Unfaired turbomachinery, of the turbojet or turboprop type, uses external rotors, or propellers, comprising blades arranged outside the turbomachine casing, upstream and / or downstream of the turbine. These systems benefit from very good energy efficiency, which reduces the aircraft's fuel consumption and therefore improves its environmental performance.

[0003] The external position of the propeller(s) results in greater exposure of the latter to external conditions, and therefore requires increased attention to their resistance and durability in the long term.

[0004] In order to evaluate the strength and durability of the blades, or vanes, of the propellers of such turbomachines, it is known to carry out mechanical tests, in particular fatigue tests, on said vanes.

[0005] Such a test consists of applying stress by means of acoustic pulses applied to the free end of the blades, opposite the foot which is fixed to a test table. These pulses are maintained for an extended period to perform a high cycle fatigue test (HCF test) to obtain stress evolution curves over a simulated life cycle.

[0006] A test table 1 is shown in [Fig.1], on which is mounted a test support 3 carrying a blade 5, for such a fatigue test.

[0007] The blade 5 is fixed to the test support 3 by its lower end 7, or foot. The blade 5 extends along a principal axis X substantially perpendicular to a plane of extent of the table 1.

[0008] In what follows, the terms axial, transverse and circumferential are understood relative to the central axis X.

[0009] The test support 3 includes a base 9 by which the test support 3 is fixed to the table 1 by bolting, thanks to fixing holes provided in the table 1 and in the base 9 of the test support.

[0010] The base 9 defines a substantially flat upper surface 13, intended to receive the blade 5 in support along the direction of the main axis X.

[0011] The base 9 also defines a central conduit 11 extending substantially along the main axis X and opening at a lower end opposite an orifice access provided in table 1 and by an upper end through the upper surface 13. The lower end of the central conduit 11 is for example stepped, to cooperate with an axial blocking member 14.

[0012] The blade 5 defines at its lower end 7 an axial extension 15 forming a wall extending along the direction of the principal axis X and following an oblong contour in a plane crossing the principal axis X. The axial extension 15 defines an internal space 16 surrounded by said wall.

[0013] The upper end 13 of the central conduit 11 has a shape complementary to that of the axial extension 15, so that the axial extension 15 is in peripheral contact with the internal walls of the central conduit 11.

[0014] The axial extension 15 advantageously extends in external peripheral contact with the walls of the central conduit 11 over the entire circumferential extent of said internal walls of the central conduit 11.

[0015] The blade 5 also includes a transverse rim 19 projecting in a plane transverse to the main axis X, said transverse rim 19 being disposed in contact with the upper surface 13 of the base.

[0016] The test support 3 includes a flange 21 for retaining the blade 5, circumferentially surrounding the blade 5 which extends through a central opening in the flange. The flange 21 is disposed against the upper surface 13 along the direction of the principal axis X, the flange 21 being fixed to the base by fixing bolts 22. The inner edge of the central opening in the flange defines a groove, which is dimensioned to accommodate the transverse rim 19 of the blade 5. Thus, the flange 21 and the upper surface 13 retain the transverse rim 19 of the blade by clamping it together, along the direction of the principal axis X.

[0017] The test support 3 also includes, engaged in the central conduit 11, a pressure screw 23 and a piston 25 guided by a key 27

[0018] The pressure screw 23 is held axially in the axial locking member 14, the handling head of the pressure screw 23 being accessible through the access port provided in the table 1. The other end of the pressure screw is supported along the direction of the main axis X against a lower end of the piston 25 so as to induce an axial movement of said piston 25.

[0019] The upper end of the piston 25 is in contact with the axial extension 15 of the blade 5. Said upper end of the piston 25 defines a retaining block 29, having a substantially square cross-section, arranged engaged in the internal space 16 of the axial extension 15 of the blade 5, in contact with the internal walls of said axial extension.

[0020] Thus, the tightening torque applied to the pressure screw 23 is transferred as axial stress by the piston 25 to the lower end of the blade 5.

[0021] The key 27 is engaged in an axially oriented groove formed in the piston 25 to guide it in the internal conduit 11, but does not act as a rotational lock. The locking of the blade 5 in position is mainly ensured by axial clamping of the transverse rim 19 between the upper surface 13 and the flange 21.

[0022] During fatigue tests as described above, slippage of the blade 5 in rotation around the central axis X was observed, which disrupts or interrupts the test. Presentation of the invention

[0023] The invention aims to remedy these drawbacks by proposing a blade support for fatigue tests, which provides improved blade support to prevent any rotational movement.

[0024] To this end, the invention relates to a test support for a blade, the blade comprising a blade extending along a main axis, a peripheral rim extending around a lower end of the blade and an axial extension extending beyond the peripheral rim,

[0025] said test support comprising:

[0026] - a base defining a central axial conduit, adapted to receive the axial extension, and a superior surface, and

[0027] - an axial retaining flange fixed to the upper surface so as to take the peripheral rim axially engaged between the upper face and the flange,

[0028] characterized in that the test support also comprises:

[0029] - a guide support inserted into the central conduit and defining a conduit of axial locking and a transverse passage intersecting the locking conduit and provided to open opposite the axial extension of the blade engaged in the central conduit,

[0030] - a locking screw received in the locking conduit and axially movable in the blocking conduit, and

[0031] - at least one movable-mounted jaw in the passage, so that an axial movement The locking screw causes a transverse clamping force exerted by the jaw on the axial extension.

[0032] Such a test support allows for transverse blocking, in addition to the axial blocking exerted by the flange, via the jaw(s) actuated by the locking screw, thus preventing rotational slippage of the blade during the test. This type of support reduces the number of parts requiring modification compared to prior art supports, as the base and flange remain unchanged, and does not necessitate any modifications to the blades being tested. Finally, this type of test support distributes the blade retention stresses across several parts, limiting contact wear and the risk of assembly errors.

[0033] The guide support may have a stepped shape and a head adapted to be inserted into an internal space of the axial extension of the blade.

[0034] Such a feature allows precise and robust axial and transverse support of the guide support in the internal conduit of the base.

[0035] The head may have a substantially oblong shape in a cross-section plane, the passage extending perpendicularly to the direction of extension of said oblong shape in said cross-section plane.

[0036] Such a feature allows a good fit of the head in the internal space of the axial extension of the blade and allows the transverse retaining constraints to be applied effectively to prevent rotational slippage.

[0037] The head can define an external peripheral groove for receiving a jaw retaining element in the passage, said retaining element being for example an O-ring or a ring made of elastic material.

[0038] Such a feature allows the jaws to remain in the passage during the assembly and disassembly of the test support, which greatly facilitates these procedures.

[0039] Each jaw may have an internal face inclined with respect to the central axis and the locking screw has a substantially conical head disposed in contact with said internal faces of the jaws.

[0040] Such a feature makes it possible to improve the transfer of force from the locking screw to the jaws and makes the handling of the support for the application of transverse locking constraints more precise.

[0041] An angle of inclination of the internal faces of the jaws with respect to the central axis may be substantially equal to an angle of inclination of the substantially conical head of the locking screw, said angle of inclination being less than or equal to 30° and in particular between 15° and 20°.

[0042] Such a feature allows for improved accuracy when applying the transverse clamping force.

[0043] The test support may include exactly two jaws arranged on either side of the locking screw.

[0044] Such a feature allows symmetrical blocking constraints to be applied on both sides of the axis, which improves the blocking of the blade.

[0045] The invention may also relate to a method for mounting a blade in a test support according to one of the embodiments described above, the blade comprising a blade extending along a principal axis, a peripheral rim extending around a lower end of the blade, and an axial extension extending beyond the peripheral rim, the method comprising: a step of blocking by the application of a transverse clamping force exerted by the jaw of the test support on the axial extension of the blade.

[0046] Transverse blocking by means of the jaw(s) prevents rotational slippage of the blade during the test. The transverse constraint also contributes to axial blocking, even though this is not its primary purpose.

[0047] The method may include, in this order: a step of positioning the blade on the upper surface; a step of fixing the flange; then a step of rotating the screw resulting in the application of a transverse clamping force exerted by the jaw on the axial extension.

[0048] By preceding the transverse tensioning by fixing the flange, it is possible to ensure proper axial positioning of the blade foot.

[0049] The invention may also relate to a method for testing the fatigue resistance of a blade comprising: a step of setting up the blade according to the method described above; and a step of applying acoustic pulses to a free end of the blade, opposite to the lower end. Brief description of the figures

[0050] [Fig. 1] is an axial cross-sectional view of a test support for a blade for a prior art fatigue test,

[0051] [Fig.2] is an axial cross-sectional view of a test support according to the invention,

[0052] [Fig.3] is a partial perspective view of the test support of [Fig.2], and

[0053] [Fig.4] is a cross-sectional view of the test support of Figures 2 and 3. Detailed description of the invention

[0054] A test support 3 according to the invention is shown in figures 2 to 4. This test support 3 is identical to that described above except for the following. Thus, only the different elements are described below, and the numerical references designating common elements are repeated.

[0055] The axial locking element 14, the pressure screw 23 and the piston 25 of the test support 3 are replaced by a guide support 31, a locking screw 33 and at least one jaw 35. In the example shown, the test support 3 includes two jaws 35.

[0056] The guide support 31 is shown in detail in figures 3 and 4.

[0057] The guide support 31 has a stepped shape, comprising a base 37 presenting a substantially circular section, an intermediate part 39 having a circular section with a diameter less than the base 37, a cylindrical body 41 having a diameter less than that of the intermediate part 39, and a head 43 having an oblong transverse section.

[0058] The base 37, the intermediate part 39 and the cylindrical body 41 are substantially coaxial and their common axis coincides with the principal axis X.

[0059] The diameters of the base 37, the intermediate part 39 and the cylindrical body 41 are determined so that the guide support 31 is inserted into the central conduit 11 of the base 9, in particular in the lower stepped part of this conduit, with minimal play, so as to guarantee precise positioning of the guide support 31.

[0060] The base 37 defines through fixing holes 45, substantially axial, adapted to allow the fixing of the guide support 31 to the base 9 by screwing.

[0061] The guide support further defines a substantially axial locking conduit 47, in which the locking screw 33 is engaged. The locking conduit 47 includes at least one threaded portion, and the locking screw 33 includes a complementary threaded portion to control the axial movement of the locking screw 33 by rotation.

[0062] Advantageously, a lock nut 49 can be positioned on the locking screw 33 near its lower end, to limit the stroke of the locking screw 33 and prevent over-tightening.

[0063] The head 43 of the guide support 31 defines a passage 51 transverse to the main axis X, the passage 51 having a substantially square or rectangular cross-section and intersecting the central conduit 45 substantially perpendicularly.

[0064] The locking screw comprises a substantially conical head 53, said head being positioned across the transverse passage 51.

[0065] The jaws 35 are arranged in the passage 51, on either side of the head 53. The jaws 35 have a generally parallelepiped shape.

[0066] Advantageously, each jaw comprises an inner face of each jaw 35 which is inclined relative to the outer face of the opposite jaw and therefore inclined relative to the direction of the principal axis X. An angle of inclination of said inner face relative to the direction of the principal axis X is in particular substantially equal to the angle of inclination of the conical head 53 relative to the principal axis X.

[0067] The angle of inclination of the conical head 53 and the inclined internal faces of the jaws 35 with respect to the central axis X is for example less than or equal to 30°, and in particular between 15 and 20°.

[0068] Said inclined inner face is disposed in contact with the head 53 of the locking screw 33. Thus, an axial movement of the locking screw 33 results in a variation of the spacing of the two jaws 35, which then exert a transverse support on the internal walls of the internal space 16 defined by the axial extension 15 of the blade 5.

[0069] Thus, by applying a tightening torque on the locking screw 33, a transverse clamping stress is exerted on the walls forming the axial extension 15 of the blade 5, which are taken between one of the jaws 35 and the internal walls of the conduit 11 of the base 9.

[0070] The transverse clamping constraint applied to the axial extension 15 of the blade 5 prevents rotational slippage under the effect of mechanical stress as observed previously.

[0071] It has been observed that a tightening torque applied to the locking screw 33 of between 12 and 16 Nm provides an effective locking of the blade 5 in rotation without damaging the axial extension 15 engaged between the jaws 35 and the walls of the internal conduit 11.

[0072] The head 43 advantageously defines a peripheral groove 55 for receiving a retaining element for the jaws 35 in the passage 51. Said retaining element is, for example, an O-ring or a ring made of elastic material, which extends in the peripheral groove 55 and against the external faces of the jaws 35. Said external faces of the jaws 35 may further define receiving grooves for this retaining element to prevent it from protruding transversely beyond the external faces.

Claims

Demands

1. Test support (3) for a blade (5), the blade (5) comprising a blade extending along a principal axis (X), a peripheral rim (19) extending around a lower end (7) of the blade (5) and an axial extension (15) extending beyond the peripheral rim (19), said test support (3) comprising: - a base (9) defining an axial central channel (11), adapted to receive the axial extension (15), and an upper surface (13), and - an axial retaining flange (21) fixed to the upper surface (13) so as to engage the peripheral rim (19) axially between the upper face (13) and the flange (21),characterized in that the test support also comprises: - a guide support (31) inserted in the central conduit (11) and defining an axial locking conduit (47) and a transverse passage (51) intersecting the locking conduit (47) and provided to open opposite the axial extension (15) of the blade (5) engaged in the central conduit (11), - a locking screw (33) received in the locking conduit (47) and axially movable in the locking conduit (47), and - at least one jaw (35) movablely mounted in the passage (51), such that an axial movement of the locking screw (33) results in a transverse clamping force exerted by the jaw (35) on the axial extension (15).

2. Test support (3) according to the preceding claim, wherein the guide support (31) has a stepped shape and a head (43) adapted to be inserted into an internal space (16) of the axial extension (15) of the blade (5).

3. Test support (3) according to the preceding claim, wherein the head (43) has a substantially oblong shape in a cross-section plane, the passage (51) extending perpendicularly to the direction of extension of said oblong shape in said cross-section plane.

4. Test support (3) according to claim 2 or 3, wherein the head (43) defines an external peripheral groove (55) for receiving a jaw retaining element (35) in the passage (51), said a retaining element being for example an O-ring or a ring made of elastic material.

5. Test support (3) according to any one of the preceding claims, wherein each jaw (35) has an internal face inclined with respect to the central axis (X) and the locking screw has a substantially conical head (53) disposed in contact with said internal faces of the jaws (35).

6. Test support (3) according to the preceding claim, wherein an angle of inclination of the internal faces of the jaws (35) with respect to the central axis (X) is substantially equal to an angle of inclination of the substantially conical head (53) of the locking screw, said angle of inclination being less than or equal to 30° and in particular between 15° and 20°.

7. Test support (3) according to any one of the preceding claims, wherein the test support (3) comprises exactly two jaws (35) arranged on either side of the locking screw (33).

8. Method of installing a blade (5) in a test support (3) according to any one of claims 1 to 7, the blade (5) comprising a blade extending along a principal axis (X), a peripheral rim (19) extending around a lower end (7) of the blade (5) and an axial extension (15) extending beyond the peripheral rim (19), the method comprising: a locking step by applying a transverse clamping force exerted by the jaw (35) of the test support (3) on the axial extension (15) of the blade (5).

9. Method according to claim 8, comprising, in this order: a step of positioning the blade (5) on the upper surface (13); a step of fixing the flange (21); then a step of rotating the screw (33) resulting in the application of a transverse clamping force exerted by the jaw (35) on the axial extension (15).

10. Method for testing the fatigue resistance of a blade (5) comprising: a step of setting up the blade according to the method of claim 8 or 9; and a step of applying acoustic pulses to a free end of the blade (5), opposite to the lower end (7).