Device and method for bending a specimen

Abstract

The present invention relates to a bending test device (1) for a specimen (3) and a corresponding method, the test device (1) comprising a first support (5) and a second support (7), a first lever (9) and the first support (5) forming a first articulation axis (A1), a second lever (11) and the second support (7) forming a second articulation axis (A2), the first lever (9) and the second support (7) forming a third articulation axis (A3), and the second lever (11) and the second support (7) forming a fourth articulation axis (A4), the articulation axes (A1-A4) being parallel and orthogonal to the actuation axis (Z), a first jaw (13) fixed to the first lever (9) and a second jaw (17) fixed to the second lever (11) securing the specimen (3) between them, a relative displacement of the first support (5) and the second support (7) along the actuation axis (Z) causing a bending of the specimen (3).Figure for the abbreviation: Figure 1.

Description

Title of the invention: Device and method for bending a test specimen. Technical field

[0001] The present invention relates to the field of bending tests.

[0002] The invention applies more particularly to a bending test device of a test specimen, as well as a method for flexural testing a test specimen.

[0003] The invention is particularly applicable to performing integrity tests on mechanical structures using test specimens representative of actual components of these mechanical structures. The specimens may, in particular, be tubular, plates, or large beams. Specifically, the specimens may be made of metallic materials. It is specified here that "bending" refers to pure bending. STATE OF THE ART

[0004] Conventionally, for performing bending tests, it is known to create a bending moment in a specimen, notably in two different ways: - by a bending-type setup: the specimen is fixed at both ends and a rotation is applied either at one end or at both ends, or - by a bending setup with 4 support points: the specimen is positioned on one side between two external supports (longer length) and on the other side between two internal supports (shorter length). Applying a force – or load – on the external supports or on the internal supports makes it possible to create a pure and constant bending moment between the internal supports, but only in one direction of loading.

[0005] In order to enable the performance of bending tests with both cyclic and alternating loading, particularly on metallic components representative of the nuclear field, the following main problems arise.

[0006] First, there is a need for a bending test device capable of reversing the direction of the load without abrupt changes or jolts. Therefore, a bending test device for a specimen is required that allows for alternating cyclic loading, inducing a bending moment in the specimen being tested. However, applying a mechanical load with a negative load ratio (i.e., alternating loading) requires reversing the direction of the applied forces. During this reversal, parasitic phenomena cause discontinuities in the load. This is characterized by load jumps that must be avoided.

[0007] Next, there is a need for a bending test device capable of testing different specimen geometries without requiring modification of the entire test setup. The test device must be able to adapt to several specimen geometries (tubes, beams, and plates) representative of the actual components being studied. Furthermore, the dimensions of these specimens vary: often large in diameter or width, they are, however, of limited length. Indeed, since the materials being tested are often "precious," the available material is often limited, and it is necessary to conserve it, thus creating dimensional constraints on the specimens.

[0008] Finally, there is a need for a bending test device that can be easily installed on "standard" mechanical testing machines. These machines are also known as tensile and compression testing machines, universal testing machines, or UTMs (Universal Testing Machines). Such a machine is a laboratory device used to perform various mechanical tests, generally standardized, on test specimens. Indeed, the test device must remain simple enough to be mounted on a commercially available hydraulic press in order to apply variable and complex loads controlled by the hydraulic press. The loads can be of variable intensity, monotonic or cyclic, with symmetrical or asymmetrical cycles, and with varied load histories, for example, with different overload sequences.The test device must also be usable in any testing laboratory equipped with hydraulic presses.

[0009] However, these solutions do not allow for the application of both cyclic and alternating loading while addressing the three problems mentioned above.

[0010] Bending setups are carried out on dedicated machines, which therefore do not address the problem of installation on "standard" mechanical testing machines. In alternating bending, they are designed for small specimens (a few centimeters) and only with a plate geometry (preferably thin, with low bending moments). Large machines do not allow alternating the direction of loading and only allow bending of a tube in a single direction.

[0011] Conventional four-point bending setups do not allow for alternating tension and compression; that is, the central part of the specimen (located between the two internal supports) is subjected to either tension or compression during a test. If the direction of loading is to be reversed, the specimen must be inverted on the setup, which is impractical for a Cyclic fatigue test with up to several thousand load cycles to be applied.

[0012] Four-point bending setups allowing alternating loading are limited to a single geometry and a single specimen size. The distances between supports are not adjustable, nor is the clamping system, which makes it impossible to test different specimen geometries without modifying the entire test setup. Furthermore, for some alternating bending tests on tubes, the supports are rings clamping the tube. However, during the test, the tube geometry can tend to change (tube ovalization), which leads to loss of support (load jumps, presence of play that can induce premature wear due to friction). Thus, this makes it impossible to change the direction of the load without abruptness or jolts.

[0013] Finally, in a conventional four-point bending setup, the test specimens must necessarily be longer than the distance between the external supports. If this is not the case, extensions of the same geometry must be welded or screwed onto each specimen to add the missing length, which is complex, time-consuming, and costly. If the distance between the external supports is reduced to accommodate a shorter specimen, the applied load will no longer be the same, and consequently, the deflection of the specimen will also be different.

[0014] Thus, there is also a need for a bending test device that allows for easy testing of a specimen in alternating bending while also allowing for easy switching between different types of specimens. Indeed, it is necessary to allow for the testing of specimens representative of real components: large tubes, plates, or beams. Description of the invention

[0015] One aim of the present application is to remedy the aforementioned drawbacks by proposing a test device for bending a specimen, which allows easy testing of a specimen in alternating bending while allowing easy changing of the type of specimen to be tested.

[0016] To this end, according to a first aspect, a bending test device for a specimen is proposed, remarkable in that it comprises: - a first support and a second support movable only axially relative to each other along an actuation axis, the first support and the second support being able to be alternately brought closer together and then moved further apart relative to each other along the actuation axis, - a first lever and a second lever facing each other on either side of the actuating axis, the first lever and the first support forming a first axis of articulation, the second lever and the second support materializing a second axis of articulation, the first lever and the second support materializing a third axis of articulation, and the second lever and the second support materializing a fourth axis of articulation, the first axis of articulation, the second axis of articulation, the third axis of articulation and the fourth axis of articulation being parallel to each other and orthogonal to the axis of actuation, - a first jaw being fixed to the first lever, a second jaw being fixed to the second lever, the first jaw and the second jaw being suitable for fixing the specimen between them, such that a relative displacement of the first support and the second support along the axis of actuation causes a bending of the specimen.

[0017] Thus, such a test device makes it easy to test a specimen in alternating bending while also allowing for easy switching between different types of specimens. Indeed, the proposed solution relies on the ability of the hinge axes to withstand forces in radial directions without any play. Reversing the direction of the load (to create an alternating load) is done smoothly and without jerking. One of the principles implemented for this test device is based on the concept that, during a relative displacement of the first and second supports, the components of the test device interact with each other only via hinge axes.By applying a tensile or compressive force between the first and second supports, an overall bending load is generated on the parts located between the third and fourth pivot axes, thus creating a bending stress on the specimen being tested. By alternating the direction of the force, two opposite sides of the specimen will be alternately loaded in tension and then in compression (and vice versa), thus alternating the bending. This setup allows testing specimens of reduced lengths, for example, up to 1 / 6 of the distance between the third and fourth pivot axes for the same applied load. Furthermore, a wide loading range is made possible by the use of levers, which multiply the relative displacement initially imposed on the first and second supports.

[0018] Furthermore, the test device is of modular design, in that the jaws can be changed to adapt to other test specimens without requiring disassembly or modification of the entire test device. In addition, without changing the jaws, an intermediate jaw can be fixed between each jaw and the test specimen to adapt to a specific specimen shape, such as a plate.

[0019] By "flexure", we mean pure flexure. Indeed, the test device allows a specimen to be tested in pure flexure.

[0020] The test device is advantageously and optionally supplemented by the following features, taken alone or in any of their technically possible combinations:

[0021] - The first lever and the second lever are each arranged between the first support and the second support. Thus, the compactness of the test device is optimized, making its installation easier. Furthermore, the mechanical resistance of the test device is improved.

[0022] - The first lever and the second lever are identical. Thus, modularity is improved.

[0023] - The first jaw and the second jaw face each other on either side of the axis actuation. Thus, maximum bending can be achieved on the specimen with minimal relative displacement of the first and second supports. Furthermore, once the specimen is secured by the jaws, no alignment is required.

[0024] - The first jaw and the second jaw are identical or have the same dimensions. Thus, modularity is improved.

[0025] - The second support is fixed and the first support is movable.

[0026] - The first articulation axis and the second articulation axis are symmetrical one with respect to the other relative to a plane of symmetry comprising the axis of actuation and being parallel to the first axis of articulation and the second axis of articulation.

[0027] - The third articulation axis and the fourth articulation axis are symmetrical one in relation to the other relative to the plane of symmetry.

[0028] - The first articulation axis and the second articulation axis have a same first minimum distance relative to the actuation axis.

[0029] - The third articulation axis and the fourth articulation axis have a same second minimum distance relative to the actuation axis.

[0030] - The first minimum distance is strictly greater than the second distance minimal. Thus, a "4-point bending" type system is obtained in a simple manner, while allowing for alternating loading.

[0031] - The first articulation axis and the second articulation axis are in a The first plane is orthogonal to the actuation axis, and the third and fourth articulation axes are in a second plane orthogonal to the actuation axis, the first and second planes being parallel to each other. Thus, the load can be distributed evenly.

[0032] - In the absence of bending of the specimen, the first plane and the second plane are confused. Thus, the test device is designed so that once the specimen is secured by the jaws, no alignment is necessary. Furthermore, symmetrical loading cycles can be easily performed.

[0033] - The first support is supported by a first end piece, and the second supportThe device is supported by a second end piece. The first and second end pieces are axially movable relative to each other along the actuation axis. Both the first and second end pieces are designed to be mounted on a tensile and compression testing machine. Thus, the testing device is sized for easy mounting on a standard tensile and compression testing machine, such as a four-column hydraulic press with a maximum capacity of 5000 kN in tension or compression, via the first and second end pieces. This allows the user to take advantage of the control capabilities of hydraulic presses and therefore generate any type of load via the machine's control program: a monotonic (increasing or decreasing) or cyclic load of sinusoidal or triangular shape with a non-zero average force (non-symmetrical loading), and any combination of these loading sequences.By simply modifying the first and second nozzles, the test device can be adapted to any other machine with a different mounting method.

[0034] - The first nozzle and the second nozzle are identical. Thus, modularity is improved.

[0035] - The first nozzle is movable and the second nozzle is fixed.

[0036] - The first support and the first end piece constitute a fifth axis of articulation, and the second support and the second tip form a sixth axis of articulation. Thus, mounting each tip onto its respective support is particularly simple and secure.

[0037] - The fifth articulation axis and the sixth articulation axis are parallel between them, and preferably orthogonal to the axis of actuation.

[0038] - The fifth articulation axis and the sixth articulation axis are perpendicular to the axis of actuation.

[0039] - The first end piece and the second end piece are each designed to be clamped in a respective jaw of the tensile and compression testing machine.

[0040] - The test device is symmetrical with respect to a third plane comprising the fifth articulation axis and sixth articulation axis, and preferably the actuation axis.

[0041] - The first support comprises a first clevis, at least a first rail, a first leg and a second leg, the first clevis and the first end piece representing the fifth axis of articulation, each first rail passing through a respective hole in the first clevis and being welded to the first clevis, Each of the first and second legs slides relative to each first rail and is held in position on each rail by a respective fixing element. The first leg represents the first axis of articulation with the first lever, and the second leg represents the second axis of articulation with the second lever. Thus, the first support is made in a simple manner.

[0042] - The first leg and the second leg are identical. Thus, modularity is improved.

[0043] - The first rails are identical. Thus, modularity is improved.

[0044] - The first support comprises a pair of first parallel rails spaced apart On the other hand, the first bracket has a pair of through holes, between which is a notch oriented along the actuation axis and in a direction opposite to the first end piece. Thus, due to the space freed up between the first rails and the space freed up by the notch, a large number of sensors and instruments dedicated to measuring specimen quantities can be easily used: gauges, LVDT (Linear Variable Differential Transformer) displacement sensors, potential difference crack propagation sensors, and cameras for implementing displacement and deformation measurements by stereo-correlation of images.

[0045] - The first yoke has a Y shape, each arm of the Y comprising a passage hole. Thus, the first screed is of simple and robust design.

[0046] - The second support comprises a second clevis, a second rail, a The third and fourth legs, the second bracket and the second end piece forming the sixth pivot point, the second rail passing through a hole in the second bracket and being welded to the second bracket, each of the third and fourth legs sliding relative to the second rail and held in position on the second rail by at least one respective fastener, the third leg forming the third pivot point with the first lever, and the fourth leg forming the fourth pivot point with the second lever. Thus, the second support is made in a simple manner.

[0047] - The third leg and the fourth leg are identical. Thus, modularity is improved.

[0048] - Each first rail and the second rail have a horizontal H-shaped profile.

[0049] - The fasteners are screws.

[0050] - The first lever, respectively the second lever, comprises: A plurality of primary through holes, regularly spaced at a predetermined interval, are used to pass through these holes. These holes are designed to accommodate a trunnion forming the first hinge axis, and the second hinge axis, respectively. A secondary through hole is also used to accommodate a trunnion forming the third hinge axis, and the fourth hinge axis, respectively. This allows for particularly simple adjustment of the maximum deflection of the specimen. The resulting bending setup has adjustable dimensions with respect to the center-to-center distance of the hinge axes. More precisely, the load intensity (deflection) can be adjusted by changing the distance between the first and second hinge axes according to the predetermined interval, regardless of the specimen's length.Simply change the position of the first pivot pin in another primary through hole of the first lever and of the second pivot pin in another primary through hole of the second lever.

[0051] - Each plurality of primary through holes comprises a number of holes primary traversings between 3 and 10, preferably equal to 5. Thus, adjustment is possible in a simple way while maintaining the mechanical resistance of the levers.

[0052] - The predetermined pitch is between 50 mm and 200 mm, preferably is equal at 100 mm. Thus, adjustment is possible in a simple way while maintaining the mechanical resistance of the levers.

[0053] - Each articulation axis is adjusted without play. Thus, reversing the direction of the loading to create an alternating load and therefore an alternating bending on the specimen, is carried out smoothly and without jerking.

[0054] - Alternatively, each articulation axis is surrounded by a bearing.

[0055] A second aspect also proposes a method for flexuring a specimen using a test device as previously described.

[0056] Such a bending test method includes the following steps: - fixing the specimen between the first jaw and the second jaw, - alternately bringing the first support and the second support closer together and then moving them further apart along the axis of actuation.

[0057] Advantageously, the bending test procedure further comprises at least one of the following steps:

[0058] - to position the first articulation axis in one of the primary through holes of the first lever, and place the second pivot axis in one of the primary through holes of the second lever;

[0059] - fix the test device in a tensile and compression machine, preference by the first nozzle and by the second nozzle;

[0060] - release the sliding of the first leg relative to each first rail and of the third leg relative to the second rail by the fixing elements;

[0061] - release the sliding of the second leg relative to each first rail and of the fourth leg relative to the second rail by the fixing elements;

[0062] - fix the test specimen between the first jaw and the second jaw, optionally indirectly on the first bit via a first intermediate bit and on the second bit via a second intermediate bit;

[0063] - fix the first jaw onto the first lever and fix the second jaw onto the second lever;

[0064] - to hold the first leg and the third leg in position by means of the elements of fixing;

[0065] - to hold the second leg and the fourth leg in position by means of the elements of fixing;

[0066] - cyclically repeat the step of alternately bringing the first one closer and then moving it further away support and the second support relative to each other along the axis of actuation. DESCRIPTION OF THE FIGURES

[0067] Other features, purposes and advantages of the presentation will become apparent from the following description, which is purely illustrative and not exhaustive, and which should be read in conjunction with the accompanying drawings on which: Fig. 1 represents a perspective view of a test device according to one embodiment; [Fig.2] represents a cross-sectional view of the test device shown in [Fig.1]; [Fig.3] represents a perspective view from another point of view of a part of the test device shown in [Fig.1]; [Fig.4] represents a longitudinal cross-sectional view of part of the test device shown in [Fig.1]; Fig. 5 is a flowchart of steps of an example of a bending test procedure implementing the test device according to the embodiment shown in Fig. 1.

[0068] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION

[0069] In the attached figures, the various geometric orientations are defined in an XYZ frame, defined by a longitudinal direction X, a transverse direction Y, and a vertical direction Z.

[0070] Figure 1 schematically represents a test device 1 for bending a test specimen 3. Such a test device 1 is suitable for mounting and fixing in a tensile and compression testing machine. Such a tensile and compression testing machine being known, it is not shown for the sake of clarity in [Fig. 1].

[0071] The test device 1 includes a first support 5 and a second support 7. The test device also includes a first lever 9 and a second lever IL. The test device 1 further includes a first jaw 13 and a second jaw 17. The first jaw 13 is also called the left jaw, and the second jaw 17 is also called the right jaw.

[0072] The first support 5 and the second support 7 are movable only axially relative to each other along an actuation axis, which is formed by the vertical axis Z in the example shown in [Fig. 1]. More precisely, the first support 5 and the second support 7 are suitable for being alternately brought closer together and then moved further apart relative to each other along the actuation axis Z. Advantageously, the second support 7 is fixed and the first support 5 is movable.

[0073] Advantageously, the first lever 9 and the second lever 11 are identical.

[0074] Preferably, the first lever 9 and the second lever 11 face each other on either side of the actuation axis Z.

[0075] As shown in [Fig.1], the first lever 9 and the first support 5 materialize a first articulation axis A1, the second lever 11 and the second support 7 materialize a second articulation axis A2, the first lever 9 and the second support 7 materialize a third articulation axis A3, and the second lever 11 and the second support 7 materialize a fourth articulation axis A4.

[0076] Advantageously, the first articulation axis A1, the second articulation axis A2, the third articulation axis A3 and the fourth articulation axis A4 are parallel to each other, and preferably orthogonal to the actuation axis Z.

[0077] Preferably, the first lever 9 and the second lever 11 are each arranged between the first support 5 and the second support 7.

[0078] Advantageously, the first articulation axis Al and the second articulation axis A2 have the same first minimum distance with respect to the actuation axis Z. More precisely, the first articulation axis Al and the second articulation axis A2 are symmetrical with respect to each other with respect to a plane of symmetry comprising the actuation axis Z and being parallel to the first articulation axis Al and the second articulation axis A2.

[0079] Advantageously, the third articulation axis A3 and the fourth articulation axis A4 have the same second minimum distance with respect to the actuation axis Z. More precisely, the third articulation axis A3 and the fourth articulation axis A4 are symmetrical with respect to each other with respect to the aforementioned plane of symmetry.

[0080] Preferably, the first minimum distance is strictly greater than the second minimum distance.

[0081] Advantageously, the first articulation axis A1 and the second articulation axis A2 are in a first plane orthogonal to the actuation axis Z, and the third articulation axis A3 and the fourth articulation axis A4 are in a second plane orthogonal to the actuation axis Z, the first and second planes being parallel to each other. Preferably, in the absence of bending of the specimen 3, the first and second planes coincide.

[0082] Advantageously, the first support 5 is supported by a first end piece 19, and the second support 7 is carried by a second end piece 21.

[0083] Preferably, the first nozzle 19 and the second nozzle 21 are identical.

[0084] Advantageously, the first end piece 19 and the second end piece 21 are adapted to be fixed, for example screwed by a threaded end, onto the tensile and compression testing machine. Preferably, the first end piece 19 and the second end piece 21 are adapted to each be clamped in a respective jaw of the tensile and compression testing machine.

[0085] Thus, the first nozzle 19 and the second nozzle 21 are axially movable relative to each other along the actuation axis Z. Advantageously, the first nozzle 19 is movable and the second nozzle 21 is fixed.

[0086] Advantageously, as shown in [Fig. 1], the first support 5 and the first end piece 19 form a fifth articulation axis A5, and the second support 7 and the second end piece 21 form a sixth articulation axis A6. Preferably, the fifth articulation axis A5 and the sixth articulation axis A6 are parallel to each other, and preferably orthogonal to the actuation axis Z. More preferably, the fifth articulation axis A5 and the sixth articulation axis A6 are perpendicular to the actuation axis Z.

[0087] Advantageously, the test device 1 is symmetrical with respect to a third plane comprising the fifth articulation axis A5 and the sixth articulation axis A6, and preferably the actuation axis Z.

[0088] Advantageously, the first jaw 13 is fixed to the first lever 9, the second jaw 17 is fixed to the second lever 11. The first jaw 13 and the second jaw 17 are suitable for fixing the specimen 3 between them, such that a relative displacement of the first support 5 and the second support 7 along the actuation axis Z causes a bending of the specimen 3.

[0089] When mounted on the test device 1, the specimen 3 is thus fixed directly onto the first jaw 13 and the second jaw 17. As shown in [Fig. 1], the specimen 3 is tubular. Alternatively, according to a variant not shown, for example when the specimen 3 is of a different shape, such as a plate, or has different dimensions, the test piece 3 is advantageously fixed indirectly on the first jaw 13 via a first intermediate jaw, and on the second jaw 17 via a second intermediate jaw.

[0090] Advantageously, as shown in [Fig. 1], the first jaw 13 and the second jaw 17 are identical or have the same dimensions. Preferably, the first jaw 13 and the second jaw 17 are identical except that the first jaw 13 has a first thread, for example, a standard one, while the second jaw 17 has a second thread with a reverse pitch relative to the first thread.

[0091] Preferably, the first jaw 13 and the second jaw 17 face each other on either side of the actuation axis Z.

[0092] The first support 5 will be described more precisely as follows, with reference to [Fig.1] and [Fig.2], which represents a cross-sectional view of the test device 1 shown in [Fig.1] along a plane parallel to the actuation axis Z and including the third articulation axis A3.

[0093] Advantageously, the first support 5 comprises a first clevis 23, at least a first rail 25, 26, a first tab 27 and a second tab 29.

[0094] Preferably, the first clevis 23 and the first end piece 19 materialize the fifth axis of articulation A5.

[0095] Advantageously, the first leg 27 materializes the first articulation axis Al with the first lever 9.

[0096] Advantageously, the second leg 29 materializes the second articulation axis A2 with the second lever 11.

[0097] Preferably, the first support 5 comprises a pair of first rails 25, 26 parallel and spaced apart, the first clevis 23 thus comprising a pair of through holes.

[0098] Advantageously, each first rail 25, 26 has a horizontal H-shaped profile. Thus, the web of the H is parallel to the actuation axis Z and the arms of the H are orthogonal to the actuation axis Z.

[0099] Preferably, the first rails 25, 26 are identical.

[0100] Advantageously, as shown in [Fig.2], each first rail 25, 26 passes through a respective through hole in the first clevis 23 and is welded to the first clevis 23.

[0101] Advantageously, the first clevis 23 has a notch 31 located between the pair of through holes, the notch 31 being oriented along the actuation axis Z and in a direction opposite to the first end piece 19.

[0102] Preferably, the first cleat 23 has a Y shape, each arm of the Y having a passage hole.

[0103] Advantageously, each of the first leg 27 and the second leg 29 slides relative to each first rail 25, 26 and is held in position on each first rail 25, 26 by a respective fastening element V. Preferably, the fastening element V is a screw, which is screwed through the respective leg 27, 29 and bears against the respective first rail 25, 26. Thus, preferably, the fastening elements V are screws.

[0104] Preferably, the first leg 27 and the second leg 29 are identical.

[0105] The second support 7 will be described more precisely as follows, with reference to [Fig.1] and [Fig.2].

[0106] Advantageously, the second support 7 includes a second clevis 33, a second rail 35, a third tab 37 and a fourth tab 39.

[0107] Advantageously, the second rail 35 has a horizontal H-shaped profile. Thus, the web of the H is parallel to the actuation axis Z and the arms of the H are orthogonal to the actuation axis Z.

[0108] Preferably, the second clevis 33 and the second end piece 21 form the sixth articulation axis A6

[0109] Advantageously, the third leg 37 materializes the third axis of articulation A3 with the first lever 9.

[0110] Advantageously, the fourth leg 39 materializes the fourth articulation axis A4 with the second lever 11.

[0111] Preferably, the third leg 37 and the fourth leg 39 are identical.

[0112] Preferably, the second rail 35 passes through a hole in the second clevis 33 and is welded to the second clevis 33.

[0113] Advantageously, each of the third leg 37 and the fourth leg 39 slides relative to the second rail 35 and is held in position on the second rail 35 by at least one respective fastening element V. Preferably, each of the third leg 37 and the fourth leg 39 slides relative to the second rail 35 and is held in position on the second rail 35 by two respective fastening elements V. Preferably, each fastening element V is a screw, which is screwed through the respective leg 37, 39 and bears against the second rail 35. Thus, the fastening elements V are screws.

[0114] Advantageously, each articulation axis A1-A6 is formed by a trunnion, which is preferably held axially in position along its longitudinal axis by a pair of pins arranged at each end of the trunnion. To form the respective articulation axis A1-A6, each trunnion connects the two respective articulated parts.

[0115] For example, to form the first pivot axis A1, the trunnion connects the first lever 9 and the first leg 27 so that the first lever 9 and the first The legs 27 can pivot relative to each other. More precisely, the trunnion passes through the first leg 27 and the first lever 29, and is held axially in position along its longitudinal axis by a pair of pins arranged at each end of the trunnion.

[0116] Advantageously, each articulation axis A1-A6 is adjusted without backlash. Alternatively, and according to a variant not shown, each articulation axis A1-A6 is surrounded by a bearing.

[0117] Fig. 3 represents, in perspective, indifferently the first lever 9 or the second lever 11, since they are advantageously identical.

[0118] Advantageously, the first lever 9, respectively the second lever 11, has a plurality of primary through holes 41. The primary through holes 41 are suitable for being traversed by a trunnion forming the first articulation axis Al, respectively forming the second articulation axis A2. In other words, the trunnion forming the first articulation axis Al, respectively forming the second articulation axis A2, passes through only one of the primary through holes 41, according to the chosen setting.

[0119] Preferably, each plurality of primary through holes 41 comprises a number of primary through holes 41 between 3 and 10, preferably equal to 5 as represented.

[0120] Preferably, the primary through holes 41 are regularly spaced at a predetermined pitch.

[0121] Advantageously, the predetermined pitch is between 50 mm and 200 mm, preferably equal to 100 mm.

[0122] Preferably, the first lever 9, respectively the second lever 11, has a secondary through hole 43, which is suitable for being traversed by a trunnion forming the third articulation axis A3, respectively forming the fourth articulation axis A4.

[0123] Advantageously, the first lever 9, respectively the second lever 11, has two parallel flats into which the primary through holes 41 and the secondary through hole 43 open.

[0124] Advantageously, the first lever 9, respectively the second lever 11, has a shaft end 44 suitable for being inserted into a corresponding bore of the first jaw 13, respectively of the second jaw 17, preferably up to an internal wall forming a stop B. Thus, the first jaw 13 is precisely positioned on the first lever 9, and the second jaw 17 is precisely positioned on the second lever 11.

[0125] Advantageously, the first lever 9, respectively the second lever 11, comprises a flange 45 suitable for fixing the first jaw 13, respectively the second jaw 17, the flange 45 being positioned between the shaft end and the secondary through hole. Preferably, the flange 45 is welded to the shaft end.

[0126] Fig. 4 represents a longitudinal cross-sectional view of part of the test device 1 shown in Fig. 1 in a plane orthogonal to the actuation axis Z. Thus, Fig. 2 represents in more detail the fixing of the first jaw 13 on the first lever 9, of the second jaw 17 on the second lever 11, and of the specimen 3 on each of the first jaw 13 and the second jaw 17.

[0127] Advantageously, the flange 45 is provided with through holes for bolts 46 for fixing the respective jaw 13, 17 on the first lever 9, respectively the second lever 11, by means of a floating flange 47 which is abutted against a shoulder of the respective jaw 13, 17. Thus, due to the bolting by the bolts 46, preferably by four bolts 46, arranged in diametrically opposed pairs, the shoulder of the respective jaw 13, 17 is held in a vise between the flange 45 and the floating flange 47.

[0128] Advantageously, the test piece 3 is threaded at each of its ends and is screwed into a tapped hole in the respective jaw 13, 17, preferably up to the internal wall forming stop B.

[0129] Advantageously, the components of the test device 1 are made of steel, preferably steel selected from the group comprising S355 steel, S690 steel, 30NiCrMol6 steel, X30Crl3 steel, and 316L steel. Preferably, the trunnions forming the pivot axes A1-A6 are made of X30Crl3 steel. Preferably, the first end piece 19, the second end piece 21, the first jaw 13, and the second jaw 17 are made of 30NiCrMol6 steel. By way of example, the test specimen 3 is made of metal, preferably steel, more preferably 316L steel.

[0130] Fig. 5 represents the main steps of a bending test procedure of a specimen 3 using a test device 1 as previously described.

[0131] Such a bending test procedure comprises the following steps: - P40 fix the test specimen 3 between the first jaw 13 and the second jaw 17 - P70 alternately bring the first support 5 and the second support 7 closer together and then further apart along the actuation axis Z.

[0132] Advantageously, the bending test procedure further comprises at least one of the following steps: - P10: place the first articulation axis Al in one of the primary through holes 41 of the first lever 9, and place the second articulation axis A2 in one of the primary through holes 41 of the second lever 11; - P20: fix the test device 1 in a tensile and compression machine, preferably by the first end 19 and by the second end 21; - P30: release the sliding of the first leg 27 relative to each first rail 25, 26 and of the third leg 37 relative to the second rail 35 by the fixing elements V; - P35: release the sliding of the second leg 27 relative to each first rail 25, 26 and of the fourth leg 39 relative to the second rail 35 by the fixing elements V; - P40 fix the test specimen 3 between the first jaw 13 and the second jaw 17, optionally indirectly on the first jaw 13 via a first intermediate jaw and on the second jaw 17 via a second intermediate jaw; - P50: fix the first jaw 13 on the first lever 9 and fix the second jaw 17 on the second lever 11; - P60 maintain in position the first leg 27 and the third leg 37 by the fixing elements V; - P65 maintain in position the second leg 29 and the fourth leg 39 by the fixing elements V; - P80 cyclically repeat step P70 of alternately bringing the first support 5 and the second support 7 closer together and then moving them further apart along the actuation axis Z.

[0133] The invention is not limited to the embodiments and variants described and shown in the accompanying figures. Modifications remain possible, particularly with regard to the constitution of the various technical features or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Demands

1. A bending test device (1) for a specimen (3), characterized in that it comprises: - a first support (5) and a second support (7) movable only axially relative to each other along an actuating axis (Z), the first support (5) and the second support (7) being adapted to be alternately brought closer together and then moved further apart relative to each other along the actuating axis (Z), - a first lever (9) and a second lever (11) facing each other on either side of the actuating axis (Z), the first lever (9) and the first support (5) forming a first articulation axis (A1), the second lever (11) and the second support (7) forming a second articulation axis (A2), the first lever (9) and the second support (7) forming a third articulation axis (A3), and the second lever (11) and the second support (7) materializing a fourth axis of articulation (A4), the first axis of articulation (Al),the second articulation axis (A2), the third articulation axis (A3) and the fourth articulation axis (A4) being parallel to each other and orthogonal to the actuation axis (Z), - a first jaw (13) being fixed to the first lever (9), a second jaw (17) being fixed to the second lever (11), the first jaw (13) and the second jaw (17) being suitable for fixing the specimen (3) between them, such that a relative displacement of the first support (5) and the second support (7) along the actuation axis (Z) causes a bending of the specimen (3).

2. Test device (1) according to claim 1, wherein: the first articulation axis (A1) and the second articulation axis (A2) have the same first minimum distance from the actuation axis (Z), the third articulation axis (A3) and the fourth articulation axis (A4) have the same second minimum distance from the actuation axis (Z), the first minimum distance being strictly greater than the second minimum distance.

3. Test device (1) according to claim 1 or 2, wherein the first articulation axis (A1) and the second articulation axis (A2) are in a first plane orthogonal to the actuation axis (Z), and the third articulation axis (A3) and the fourth articulation axis (A4) are in a second plane orthogonal to the actuation axis (Z), the first plane and the second plane being parallel to each other.

4. Test device (1) according to any one of claims 1 to 3, wherein the first support (5) is supported by a first end piece (19), and the second support (7) is carried by a second end piece (21), the first end piece (19) and the second end piece (21) being axially movable relative to each other along the actuation axis (Z), the first end piece (19) and the second end piece (21) being suitable for being fixed on a tensile and compression testing machine.

5. Test device (1) according to claim 4, wherein the first support (5) and the first tip (19) materialize a fifth articulation axis (A5), and the second support (7) and the second tip (21) materialize a sixth articulation axis (A6), the fifth articulation axis (A5) and the sixth articulation axis (A6) being parallel to each other and orthogonal to the actuation axis (Z).

6. Test device (1) according to claim 4 or 5, wherein the first support (5) comprises a first clevis (23), at least one first rail (25, 26), a first tab (27) and a second tab (29), the first clevis (23) and the first end piece (19) forming the fifth pivot axis (A5), each first rail (26, 26) passing through a respective through hole in the first clevis (23) and being welded to the first clevis (23), each of the first tab (27) and the second tab (29) being slidable relative to each first rail (25, 26) and being held in position on each first rail (25, 26) by a respective fastening element (V), the first tab (27) forming the first pivot axis (A1) with the first lever (9), and the second tab (29) forming the second axis articulation (A2) with the second lever (11).

7. Test device (1) according to claim 6, wherein the first support (5) comprises a pair of first parallel rails (25, 26) and spaced apart, the first clevis (23) having a pair of passage holes, between which is a notch (31) oriented along the actuation axis (Z) and in a direction opposite to the first end piece (19).

8. Test device (1) according to any one of claims 4 to 7, wherein the second support (7) comprises a second clevis (33), a second rail (35), a third tab (37), and a fourth tab (39), the second clevis (33) and the second end piece (21) forming the sixth pivot axis (A6), the second rail (35) passing through a hole in the second clevis (33) and being welded to the second clevis (33), each of the third tab (37) and the fourth tab (39) sliding relative to the second rail (35) and being held in position on the second rail (35) by at least one respective fastener (V), the third tab (37) forming the third pivot axis (A3) with the first lever (9), and the fourth tab (39) forming the fourth pivot axis (A4) with the second lever (11).

9. Test device (1) according to any one of claims 1 to 8, wherein the first lever (9), respectively the second lever (11), comprises: - a plurality of primary through holes (41) regularly spaced at a predetermined pitch, which are suitable for being traversed by a trunnion forming the first articulation axis (A1), respectively forming the second articulation axis (A2), and - a secondary through hole (43), which is suitable for being traversed by a trunnion forming the third articulation axis (A3), respectively forming the fourth articulation axis (A4).

10. Test device (1) according to any one of claims 1 to 9, wherein each pivot axis (A1-A6) is adjusted without backlash.

11. A method for testing a test specimen (3) in bending using a test device (1) according to any one of claims 1 to 10, comprising the following steps: - (P40) fix the test specimen (3) between the first jaw (13) and the second jaw (17), - (P70) alternately bring the first support (5) and the second support (7) closer together and then further apart along the actuation axis (Z).