METHOD AND DEVICE FOR CONTROLLING THE TIGHTENING TENSION OF AN AERONAUTICAL FASTENER

Abstract

METHOD AND DEVICE FOR CONTROLLING THE TIGHTENING TENSION OF AN AERONAUTICAL FASTENER The invention relates to a method for tightening a fastener (30), comprising the following steps: - supplying a screw (32) comprising a head (322), a threaded portion (324) and a recess (326); - inserting the screw into a hole (20) and placing a nut (34) on the threaded portion; - engaging a tip (76) in the recess, until it contacts the bottom; - rotating the nut by locking the tip and the screw against rotation; - exciting an ultrasonic transducer (88) disposed on the tip; - receiving and processing ultrasonic waves reflected by a front surface of the screw head, to calculate a tension in the screw; - stopping the rotation of the nut when said tension equals a predefined threshold. Figure for the abbreviation: Figure 3

Description

Title of the invention: METHOD AND DEVICE FOR CONTROLLING THE TIGHTENING TENSION OF AN AERONAUTICAL FASTENER Technical field of the invention

[0001] The present invention relates to a method for controlling the clamping tension of a fastener and a device enabling this control, in particular for the aeronautical industry. Technical background

[0002] It is known in the art that in order to fix two elements together, for example structural elements of an aircraft, these elements include aligned holes for the mounting of fasteners which ensure the fixing of the elements by clamping them axially against each other.

[0003] In this application, a fastener is defined as an assembly comprising a screw and a nut. In the aeronautical industry, the nut must be tightened onto the screw to a torque predetermined by calculation during the development of the fastener to ensure that the components are tightened and to prevent their accidental separation during operation.

[0004] Suitable fasteners for such use include, for example, HI-LOK™ fasteners as described in US patent 3138987A or HI-LITE™ screws as described in US patent 4326825A. An example of a HI-LITE™ fastener is shown in Figures IA and IB.

[0005] The HI-LITE™ fastener comprises a screw 10, having a protruding head 12, a smooth shank 14, and a threaded end 16. The threaded end 16 has a hexagonal recess 18. The screw 10 is installed in a hole 20 made in the first 22 and second 24 elements until the head 12 bears against a front face 26 of the first element 22. The nut 30 is screwed onto the threaded end 16 emerging from the rear face 28 of the second element, opposite face 28, the screw being held in place by a wrench or bit (not shown) inserted into the hexagonal recess 18, until the nut contacts face 28. The nut has a shear groove 32 designed to break at a predetermined tightening torque, providing tension, or preload, in the screw 10 necessary to resist the shear and tensile stresses exerted by elements 22, 24 on screw 10.

[0006] This assembly solution is widely used and performs very well, but it does not allow verification, once the nut is installed on the screw, that the installed tension does not vary over time.

[0007] When a conventional nut, without a shear groove, is used, tightening is gen- The tightening is performed using a torque wrench at a predetermined torque. Even if the torque is well controlled using a wrench, tolerances in geometry, surface finish, and lubrication inevitably lead to a large variation in the actual installed preload, which can result in a risk of breakage of the head or threads, or conversely, tightening to a preload lower than the desired preload.

[0008] Direct measurement of the tension, i.e., the tensile force applied to the screw and the compressive force applied to the held elements, is not possible. There are fasteners that include one or more strain gauges, or an ultrasonic transducer, allowing indirect measurement of the screw tension during or after tightening the nut. The gauges or transducers must be positioned on the fastener and electrically powered.This solution therefore requires instrumenting each fastener, which significantly increases its cost. Furthermore, adding components increases the weight of the fastener, limiting their use in large quantities on an aircraft, since tens of thousands of fasteners are installed on a single aircraft. Moreover, the resistance of electronic components to temperature variations, environmental conditions, and paint makes it impossible to instrument all fasteners and presents a qualification challenge. Adding electrical contacts to the terminals of gauges or transducers also cannot be done on all fasteners, as these terminals must be accessible.

[0009] The current technique therefore does not allow the installation of a fixing at a predetermined voltage in an industrial operating context, and the repeated and reliable control of this voltage. Summary of the invention

[0010] The present invention aims to remedy these drawbacks and relates to a control method and a centering device enabling its implementation, which are simple and effective.

[0011] The invention thus proposes a method for tightening at least one fastener, comprising the following steps: providing a screw comprising: a head having a flat front surface; a threaded portion; and a recess, comprising a flat bottom and a non-circular cross-section; inserting the screw into a hole passing through at least two elements until one end of the threaded portion emerges from the elements, and placing a nut on the emerging end of the threaded portion of the screw; engaging a locking tip in the recess until a front face of the tip contacts the flat bottom of said recess, said locking tip comprising a shape complementary to the non-circular cross-section of said recess; rotating the nut on the threaded portion of the screw while locking it rotation of the locking tip and the screw; excitation of an ultrasonic transducer located on a rear face of the tip, the ultrasonic transducer being capable of generating ultrasonic waves in the tip and the screw when the tip is engaged in the screw recess; reception of the ultrasonic waves reflected by the flat front surface of the screw head and processing of the received ultrasonic waves to calculate a tension in the screw; stopping the rotation of the nut when the calculated tension in the screw equals a predefined threshold tension.

[0012] Thus, thanks to the invention, it is ensured that the fixing is installed at the required voltage, without the fixing incorporating any transducer or sensor.

[0013] The method according to the invention may comprise one or more of the following features, taken individually or in combination with each other

[0014] - the ultrasonic transducer is a piezoelectric transducer;

[0015] - at the stage of engaging the bit in the screw recess, the bit immobilizes The actuator is engaged with a predetermined pressure on the screw via at least one elastic element;

[0016] - a dry coupling is interposed between the front face of the nozzle and the flat bottom of the imprint prior to the excitation of the transducer;

[0017] - a liquid or gel coupling agent is poured into the impression prior to excitation of the transducer.

[0018] The present invention also relates to a clamping device enabling the implementation of a clamping method as described above, of a screw in a bore through at least two elements, the clamping device comprising: a body; a fixed immobilizer tip that is rotationally fixed and axially movable relative to the body, the tip comprising: an anti-rotation interface configured to engage with a non-circular section of a screw recess; a flat front face, configured to contact a flat bottom of the recess; and an opposite rear face; a sleeve that is rotationally movable relative to the body and configured to drive a rotating nut; and an ultrasonic transducer, disposed on the rear face of the tip, the ultrasonic transducer being capable of generating ultrasonic waves in the tip and in the screw when the front face of the tip is in contact with the flat bottom of the screw recess.

[0019] The device used allows fasteners to be installed at the desired tension in a uniform manner, which ensures increased reliability and repeatability of the clamping tension in the assembly.

[0020] The clamping device according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0021] - the clamping device further comprises an immobilizer support, said support comprising: a fixed part relative to the body; and a movable part, capable of sliding axially inside the fixed part; the ultrasonic transducer and the immobilizing tip being integral with said movable part;

[0022] - the clamping device further comprises a compression spring disposed in the immobilizing support, the spring bearing support on one side on the moving part and on the other side on the fixed part of the immobilizing support,

[0023] - the socket includes a front housing, configured to receive the nut for the rotational drive of said nut;

[0024] - the tip has a density identical or close to that of the screw;

[0025] - the tip and the screw are made of identical or similar materials. Brief description of the figures

[0026] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which:

[0027] [Fig.1A] [Fig.1A] is a side view of a prior art fixation;

[0028] [Fig.1B] [Fig.1A] is a side and cross-sectional view of a prior art fixation installed in a structure;

[0029] [Fig.2] [Fig.2] is a side view of a fastener suitable for use in a clamping method according to an embodiment of the invention;

[0030] [Fig.3] [Fig.3] is a schematic cross-sectional view of a clamping device according to an embodiment of the invention and of the fixing of the [Fig.2], in a first step of a clamping process according to an embodiment of the invention;

[0031] [Fig.4] [Fig.4] is a similar view to [Fig.3] in a second step of said tightening method;

[0032] [Fig. 5] [Fig. 5] is a view similar to Figures 3 and 4 in a third step said clamping method; and

[0033] [Fig.6] [Fig.6] is a block diagram illustrating steps in an embodiment of the method of tightening the fastener of [Fig.2] using the tightening device of figures 3, 4 and 5. Detailed description of the invention

[0034] In the following description, the method and clamping device of a fastener are used to assemble aircraft structures.

[0035] This example is not limiting, however, the method and clamping device being applicable to other types of assembly or application, such as, for example, fasteners assembling land vehicle structures or wind turbine blades.

[0036] Reference is now made to figures 3 to 5 which show a clamping device 40 configured to clamp a fastener, according to an embodiment of the invention.

[0037] Said fastener, shown alone in [Fig.2], comprises a screw 32 and a nut 34. The screw 32 extends along an axis A and comprises a protruding head 322, a threaded portion 324 and a recess 326.

[0038] The recess 326 is arranged along the axis A and opens on one end of the threaded portion 324, opposite the head 322. Transversely to the axis A, the recess 326 has a non-circular section.

[0039] In the embodiment shown, the non-circular section is hexagonal in shape. Alternatively, the non-circular section of the recess is multilobed, for example as described in the applicant's patent FR2967735B1, or of any other non-circular shape allowing the rotation of the screw 32 to be blocked by the insertion of a key or a bit of complementary shape.

[0040] Unlike the screw 10 of the prior art, the bottom 328 of the recess is flat and parallel to the end surface 330 of the head 322. More precisely, the bottom 328 of the recess and the end surface 330 of the head are perpendicular to the axis A.

[0041] Preferably, the flat bottom 328 is obtained either by machining the bottom of the cavity, previously made by broaching, or by electrical discharge machining (EDM), or by adding material to the conical cavity so as to obtain a flat bottom. Preferably, the added material has a density comparable to that of the screw so as not to disperse, diffract, or disrupt the path of the ultrasonic waves, as will be described later. Preferably, the roughness Ra of the flat bottom 328 is less than 2.

[0042] Apart from the modification relating to the base of the recess and the possible addition of a coupling, the screw 32 is analogous to the prior art screw 10 described above. In particular, the screw 32 is devoid of any tension or bending sensor, any transducer capable of emitting sound or ultrasonic waves, or any electrical or electronic components such as batteries, capacitors, or antennas.

[0043] The nut 34 comprises external drive surfaces 36, for example six or twelve flat surfaces. A suitable nut is described, for example, in the applicant's patent EP2350473. The nut 34 is also free of any tension or bending sensor, any transducer capable of emitting sound or ultrasonic waves, or any electrical or electronic components such as batteries, capacitors, or antennas.

[0044] The clamping device 40 extends along an axis X and comprises a tubular body 42, a sleeve 44, and an immobilizer support 46. The sleeve 44 is rotatable relative to the body 42. In the illustrated embodiment, the clamping device further includes a hollow transmission shaft 48, fixed to one axial end of the sleeve. The shaft 48 is configured to drive the sleeve 44 in rotation about the axis X.

[0045] In the embodiment shown, the clamping device further comprises Ball bearings 50 and roller bearings 52. The ball bearings 50 are arranged radially between the sleeve 44 and the body 42, allowing the sleeve to rotate relative to the body. The roller bearings 52 will be described below.

[0046] The socket 44 is internally hollowed, the hollowed part forming an internal housing extending axially between a first end 54 and a second opposite end 56, the two ends being open.

[0047] The housing for the socket 44 comprises: a distal portion 60 near the first end 54, an intermediate portion 64, and a proximal portion 66 near the second end 56 ([Fig. 5]). The distal portion 60 has an internal diameter substantially smaller than the internal diameters of the intermediate portion 64 and the proximal portion 66. The intermediate portion 64 has a diameter substantially smaller than the internal diameter of the proximal portion 66.

[0048] The junction of the distal portion 60 and intermediate portion 64 forms a first shoulder 68. The junction of the intermediate portion 64 and proximal portion 66 forms a second shoulder 70 ([Fig.4]).

[0049] The distal portion 60 of the sleeve 44 is configured to receive the nut 34 and drive it in rotation. The inner peripheral wall of the distal portion 60 comprises at least two flat faces 62 intended to engage with at least two flat drive surfaces 36 of the nut 34. Preferably, the sleeve is adapted to the shape of the nut it is to drive, and has, for example, as many flat faces as there are drive surfaces 36 of the nut. An axial dimension Xi of the distal portion 60 is configured to fully accommodate the nut 34 and a projecting portion of the threaded portion 324 of the screw, when the nut is installed on the threaded portion and in contact with the rear surface 28 of the second element 24, as shown in [Fig. 5].

[0050] The immobilizer support 46 comprises a fixed part 72 and a movable part 74. The fixed part 72 is fixed relative to the body 42 in rotation and translation. The movable part is able to slide axially within the fixed part.

[0051] The fixed part 72 comprises a tubular portion 722 and a ring 724, adjacent along the X-axis. The tubular portion 722 is disposed in the hollow shaft 48. The roller bearings 52 are arranged radially between the tubular portion 722 and the shaft 48, allowing rotation of said shaft relative to the fixed part 72 of the immobilizer support 46.

[0052] The crown 724 has a tubular shape. A first portion of the crown 724 extends into the hollow shaft and a second portion of said crown extends into the proximal portion 66 of the sleeve 44. An external diameter of the crown 724 is smaller than an internal diameter of the proximal portion 66 of the sleeve 44. A free end of the crown is disposed near the second shoulder 70. The junction between the tubular portion 722 and the crown 724 forms a counterbore 726, of so that the internal diameter of the crown is greater than the internal diameter of the tubular portion 722.

[0053] The fixed part 72 also includes an annular surface 728 perpendicular to the X axis, butting against the needle rollers 52. The fixed part is thus axially locked in the hollow shaft and the bushing 44, between the second shoulder 70 of the bushing 44 and the needle rollers 52, with a small axial clearance.

[0054] The movable part 74 comprises a collar 742 and a skirt 744 extending axially from the collar. The external diameter of the collar 742 is greater than the external diameter of the skirt 744.

[0055] The collar 742 is housed in the second part of the crown 724, itself housed in the proximal portion 66 of the sleeve 44. The external diameter of the collar 742 is less than the internal diameter of the crown 724, with sufficient clearance for the movable part 74 to move axially in the crown 724 of the fixed part 72.

[0056] The skirt 744 is able to slide in the intermediate portion 64 of the sleeve, the external diameter of the skirt 744 being less than the internal diameter of the intermediate portion 64.

[0057] The clamping device 40 further comprises an immobilizer tip 76 and an ultrasonic transducer 88, housed inside the immobilizer support 46. In the embodiment shown, the clamping device 40 also comprises: an elastic element such as a compression spring 90; and a cable 92.

[0058] The tip 76 comprises a front face 78 and a rear face 80, both of which are flat and perpendicular to the X-axis. The locking tip 76 includes an anti-rotation interface 82, adapted to engage with the recess 326 of the screw 32, the free end of which is the front face 78. The interface 82 may be a cylindrical shape with a hexagonal base if the recess 326 is hexagonal, or a cylindrical shape with a multilobed base if the recess is multilobed. Such a tip is, for example, described in the applicant's patent FR2967735.

[0059] Preferably, the material of the tip 76 is identical or similar to the material of the screw 32. Alternatively, the acoustic impedance - or density - of the tip is identical or close to the acoustic impedance - or density - of the screw.

[0060] Acoustic impedance is the product of the wave velocity in the material and the material's density. Too great a difference in acoustic impedance can cause some of the waves to be reflected at the interface between the tip and the screw, resulting in signal loss.

[0061] For example, if the screw is made of TA6V titanium alloy, the tip will preferably be made of TA6V titanium alloy, or of a similar alpha-type titanium alloy. beta.

[0062] In the embodiment shown, the interface 82 is connected by a conical portion to a cylindrical portion of enlarged diameter, in which an annular groove 84 is formed. This groove is shown with a V-shaped cross-section in the figures, but it can adopt all sorts of shapes.

[0063] The immobilizing tip 76 is fixed to the moving part 74 of the immobilizing support by a pin 86, inserted into a bore in the moving part 74 and fitting into the annular groove 84.

[0064] The ultrasonic transducer 88 is an ultrasonic transmitter-receiver, fixed to the rear face 80 of the tip 76. The transducer is connected by cable 92 to a power supply (not shown) and functions as a transmitter, converting electrical energy into mechanical oscillations to produce ultrasound transmitted into the screw 32 via the immobilizing tip 76. The transducer 88 also functions as a receiver, converting a reflected ultrasonic wave into an electrical signal, transmitted via cable 92 to an analog or digital electronic device such as a processor (not shown), capable of processing the received electrical signal to calculate the tension in the screw. The transducer may include a piezoelectric crystal. The electronic device may be integrated into the tool or may be remote.

[0065] The assembly formed by the transducer 88 and the immobilizing tip 76 is thus secured to the moving part 74 of the immobilizing support, via the pin 86.

[0066] Preferably, a dry coupling agent is interposed between the front face 78 of the tip and the bottom 328 of the screw recess, in order to improve acoustic transmission. The coupling agent may be, for example, a sheet of tin, silver, copper, or a coupling elastomer material such as Aqualene, developed by Innovation Polymers, Canada. The sheet preferably has a thickness between 0.0175 mm and 0.6 mm. The sheet may be deposited dry or wet, or even glued, onto the front face of the tip.

[0067] The compression spring 90 is disposed in the ring 724 of the fixed part 72 of the support 46. It bears axially on one side on the flange 742 of the movable part 74 of the support 46, and on the other side on the counterbore 726 of the fixed part 72 of the support. The flange guides the assembly formed by the transducer 88 and the immobilizing tip 76 parallel to the axis of revolution X of the clamping device 40. This guidance ensures that the ultrasonic waves are emitted along the X axis of the clamping device.

[0068] The assembly formed by the immobilizing tip 76 and the transducer 88 is thus mobile in the axial direction X between a first position, in which the spring is relaxed (Figures 3 and 4), and a second position, in which the spring is compressed ([Fig. 5]) and capable of imparting a predetermined pressure to the immobilizing tip 76. The assembly formed by the immobilizing tip 76 and the transducer 88 is fixed in rotation relative to the body 42.

[0069] A method for tightening the fastener 32, 34 in two elements 22, 24 using the device 40 will now be described. This method allows the fastener to be tightened while controlling the clamping tension induced in the screw by tightening the nut on the screw and the two elements.

[0070] Reference is now made to [Fig.6] showing the steps of the method 100 of tightening a fastener, implemented by means of a tightening device 40 described previously.

[0071] During a step 101, the screw 32 is inserted into the bore 20 of the elements 22, 24 previously described, until one end of the threaded portion 324 emerges from the element 24. The nut 34 is put in place on said end of the threaded portion 324, engaging some threads, as seen in [Fig.3].

[0072] Next, in step 102, the clamping device 40 is brought close to the fastener so that the locking tip 76 engages in the recess 326 of the screw 32. The movement of the device 40 continues until the front face 78 of the tip contacts the flat bottom 328 of the recess, and the distal portion 60 of the sleeve contacts the drive surfaces 36 of the nut, as shown in [Fig. 4]. In this position, the axis X of the clamping device coincides with the axis A of the fastener; and the front 78 and rear 80 flat faces of the tip 76, the flat bottom 328 of the recess, and the face 330 of the screw head end are parallel to each other and perpendicular to the coincident axes of revolution X and A. The collar 742 is displaced axially, away from the shoulder 70, due to the engagement between the screw and the immobilizer.

[0073] The front face 78 of the tip is held in contact against the bottom 328 flat of the impression with a pressure predetermined by the stiffness of the spring 90.

[0074] Due to the engagement of the anti-rotation surfaces of the tip and the screw, the assembly formed by the ultrasonic transducer 88, the immobilizing tip 76 and the screw 32 is fixed in rotation.

[0075] Then, during a step 103, the sleeve 44 is rotated about the X axis relative to the body 42. The screw being blocked in rotation relative to the body by means of the locking tip 76, the nut 34 is screwed onto the threaded portion 324 of the screw.

[0076] During a step 104, simultaneous with step 103, ultrasonic waves are emitted by the transducer 88 through the immobilizer tip 76 and the screw 32 ([Fig. 5]). The immobilizer tip 76 thus ensures the propagation of the waves transmitted by the transducer to the fixation via the base 328 of the flat impression.

[0077] Ultrasound waves propagate through the screw, are reflected off the end surface 330 of the screw head, and return to the transducer 88 as an echo. The transducer 88 converts the received acoustic energy into electrical energy and transmits this energy as an electrical signal to a remote electronic device via cable 92.

[0078] During a step 105, the external electronic device processes the received electrical signal in order to determine a voltage in the screw.

[0079] According to one embodiment, the tension in the screw 32 is determined from the screw deformation and the Young's modulus via Hooke's law. The screw deformation is obtained from measurements of the round-trip time of a wave and compared to a pre-recorded deformation value corresponding to a predefined threshold tension. The Young's modulus E is a constant associated with the material of the screw 32.

[0080] Alternatively, the tension in the screw 32 is determined from the measurement of the variation of the screw impedance, via the measurement of the resonance frequency which depends on the stress in the screw.

[0081] Alternatively, other methods for calculating the screw tension may be used, such as one of the methods described in the publication “Review of Bolted Connection Monitoring” by Tao Wand et al., available at the URL http: / / dx.doi.org / 10.1155 / 2013 / 871213.

[0082] Then, during a step 106, the electronic device emits a signal, or displays an indication, that the induced voltage is equal to the predefined threshold voltage, so that an operator installing the fastener stops tightening the nut. Alternatively, the electronic device is configured to control the tightening process and stop it as soon as the calculated voltage value equals the predefined threshold voltage, without human intervention.

[0083] The predefined threshold voltage can be the voltage predetermined by calculation during the design of the fastener, or a voltage slightly lower than this value in order to take into account the calculation time of the electronic device and the time required to display the stop instruction, durations during which the nut is driven in rotation by the clamping device.

[0084] Next, the clamping device 40 is disengaged from the screw 32 and the nut 34, and can be used to install another fastener.

[0085] Optional steps can be added to the steps described above to improve control of the clamping tension. These steps are shown in dashed lines in [Fig. 6].

[0086] Thus, during an optional step 107, inserted between steps 101 and 102, a dry coupling can be interposed between the front face of the tip and the flat bottom 328 of the screw recess 32 so as to cover the flat bottom 328 of the recess. This Coupling may be useful to ensure better wave transmission in screw 32.

[0087] Alternatively, this couplant can be a liquid couplant, such as water, or a gel couplant, poured into the mold.

[0088] In an optional step 108, after step 106, the calculated voltage value and the fastener reference can be recorded in an external database. This recording may be necessary to verify the installed voltage in the fastener over time.

[0089] The clamping method described above has the advantage of installing a screw-type fastener without additional delay compared to a prior art fastener, while reliably and repeatably controlling the tension in the screw.

[0090] The device implemented also allows for a gain in productivity. Indeed, the device according to the invention makes it possible to gain in precision during control and / or measurements, and therefore to eliminate additional verification steps in case of doubt about the reliability of a measurement.

[0091] The tension in the screw can be measured over time using the clamping device described above by disengaging the sleeve 44, provided that the installed tension of the measured fastener has been recorded in a database, during the additional step 108.

Claims

Claims

1. A method for controlled tightening of a fastener (30) comprising a screw and a nut, characterized in that the method comprises the following steps: a. Providing a screw (32) comprising: a head (322) having: a flat front surface (330); and a threaded portion (324); one end of said threaded portion comprising an axially arranged recess (326), said recess comprising a flat bottom (328) and a non-circular section; b. Inserting (101) the screw into a bore (20) passing through at least two elements (22, 24) until the end of the threaded portion emerges from the elements, and placing a nut (34) on the emerging end of the threaded portion of the screw; c.Engaging (102) an immobilizing tip (76) in the recess, until a front face (78) of the tip contacts the flat bottom (328) of said recess, said immobilizing tip comprising a shape complementary to the non-circular section of said recess; d. Rotating (103) the nut on the threaded portion of the screw while locking the immobilizing tip and the screw in rotation; e. Exciting (104) an ultrasonic transducer (88) disposed on a rear face (80) of the tip, the ultrasonic transducer being capable of generating ultrasonic waves in the tip (76) and the screw (32) when the tip is engaged in the recess of the screw; f. Receiving (105) the ultrasonic waves reflected by the flat front surface of the screw head and processing the received ultrasonic waves to calculate a voltage in the screw; g. Stop (106) the rotation of the nut when the calculated tension in the screw equals a predefined threshold tension.

2. The tightening method of claim 1 wherein the ultrasonic transducer (88) is a piezoelectric transducer.

3. Tightening method according to claim 1 or 2 wherein, in the step of engaging the tip in the impression of the screw, the immobilizing tip (76) is engaged with a predetermined pressure on the screw (32) by means of at least one elastic member (90).

4. Method according to one of the preceding claims, in which a dry couplant is interposed between the front face (78) of the tip and the flat bottom (328) of the impression prior to the excitation of the transducer (88).

5. Method according to one of the preceding claims, in which a liquid or gel couplant is poured into the impression (326) prior to the excitation of the transducer (88).

6. A tightening device configured for implementing a controlled tightening method according to one of claims 1 to 5, of a screw in a bore (20) passing through at least two elements (22, 24), the tightening device comprising: - a body (42); - an immobilizing tip (76) fixed in rotation and axially movable relative to the body (42), the tip comprising: an anti-rotation interface (82) configured to engage with a non-circular section of a recess of the screw; a flat front face (78), configured to contact a flat bottom (328) of the recess; and an opposite rear face (80); - a sleeve (44) movable in rotation relative to the body (42) and configured to drive a nut (34) in rotation;- an ultrasonic transmitter (88), arranged on the rear face (80) of the tip, the ultrasonic transmitter (88) being capable of generating ultrasonic waves in the tip (76) and in the screw (32) when the front face (78) of the tip is in contact with the flat bottom (328) of the imprint (326) of the screw; and - an ultrasonic receiver (88), arranged on the rear face (80) of the tip, the ultrasonic receiver being capable of converting a reflected ultrasonic wave into an electrical signal.;

7. Clamping device according to claim 6, further comprising an immobilizer support (46), said support comprising: a fixed part (72) relative to the body; and a movable part (74), capable of sliding axially inside the fixed part; the ultrasound transmitter and receiver and the immobilizer tip (76) being integral with said movable part (74).

8. Clamping device according to claim 7, comprising a compression spring (90) arranged in the immobilizing support (46), the spring bearing on the one hand on the movable part (74) and on the other hand on the fixed part (72) of the immobilizing support.

9. Clamping device according to one of claims 6 to 8, in which the socket comprises a front housing (60), configured to receive the nut (34) for driving said nut in rotation.

10. Clamping device according to one of claims 6 to 8, wherein the tip has a density identical or close to the density of the screw.

11. A clamping device according to one of claims 6 to 8, wherein the tip and the screw are made of identical or similar materials.

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