Installation for relieving stress on a metal part and associated stress-relieving process

Abstract

Installation for Relieving Tension in a Metal Part and Associated Relieving Method. The present invention relates to an installation (10) for relieving tension in a metal part (8) extending along a main curve between a first end (82A) and a second end (82B). The installation (10) comprises: - a first gripping system (22A) and a second gripping system (22B) movable between an open configuration and a locking configuration allowing each of the first and second ends (82A, 82B) to be held in the associated gripping system (22A, 22B); and - an upper tooling (24) movable between an upper rest position and a lower tensioning position in which the upper tooling exerts a stress on each of the gripping systems along distinct traction directions forming an angle (α) between them from 0° (exclusive) to 180° (inclusive), so as to separate the gripping systems from each other.Figure for the abbreviation: Figure 1.

Description

Title of the invention: Installation for relieving stress on a metal part and associated stress-relieving method

[0001] The present invention relates to a stress-relieving installation for a metal part, as well as an associated stress-relieving method.

[0002] Such a stress-relieving installation is intended to absorb mechanical stresses induced in the metal part during its manufacture, in particular during forging operations.

[0003] The metal part is for example intended for the field of aeronautics, in particular to form structural sub-assemblies contributing to the safety and maintenance of the aircraft.

[0004] For example, the metal part is obtained by forging a preform previously drawn by open-hearth forging. The part is then deburred and stress-relieved to release the stresses related to the forging process.

[0005] Stress relief methods using heat treatment or vibration (known as VSR, or "Vibratory Stress Relief") for metal parts are known. However, such methods are not entirely satisfactory and are costly, complex, and time-consuming.

[0006] Stress-relieving methods at room temperature are also known. Such stress relief is achieved, for example, by compressing the metal part on a bench.

[0007] However, such a process is not entirely satisfactory, particularly for long parts, typically exceeding 4 meters, and / or parts with complex shapes, such as curved ones. Stress relieving by compression is therefore not sufficiently effective to significantly and uniformly reduce the residual stress levels in the metal parts. Furthermore, the compressive stress level to be applied to the metal part is substantial, typically on the order of 50,000 tonnes, or even exceeding 65,000 tonnes.

[0008] The aim of the invention is therefore to propose a more efficient installation and stress-relieving method, while being adapted to large and / or complex shaped metal parts.

[0009] To this end, the invention relates to a stress-relieving installation for a metal part extending along a main curve of the part between a first end and a second end, the installation comprising:

[0010] - a first attachment system and a second attachment system arranged on either side and on the other hand, a vertical median plane of the installation, the first and the second attachment systems being movable between an open configuration allowing the insertion of the first and second ends into the associated attachment system and a locking configuration allowing each of the first and second ends to be held in the associated attachment system; and

[0011] - a movable upper tooling along a substantially vertical direction of elevation between a high rest position and a low tensioning position in which the upper tooling exerts a constraint on each of the hooking systems according to distinct traction directions forming between them an angle between 0° (exclusive) and 180° (inclusive), so as to move the hooking systems away from each other.

[0012] The installation according to the invention thus allows the stress relief of the metal part by tensioning or tension-compression, including for large and / or complexly shaped parts. The stress relief is more homogeneous within the part, limiting degradation of its mechanical properties. Furthermore, the installation offers very good reproducibility, as the forces exerted on the part are easily controllable and repeatable.

[0013] The installation according to the invention may have one or more of the following characteristics, taken individually or in all technically possible combinations:

[0014] - the installation further includes lower tooling comprising a support for part intended to be in contact with the metal part;

[0015] - one of the lower or upper tooling comprises a face of contact configured to be in contact with the metal part during the unstressing of said part, the contact face having a shape substantially complementary to said part;

[0016] - the contact face has a curved surface;

[0017] - the upper tooling includes a press, preferably a hydraulic press;

[0018] - each fastening system includes a clamp system, configured for clamping the metal part at one of its ends in a closed configuration, and a slide system configured to allow movement of the gripping systems in a direction substantially perpendicular to a radius of curvature of the part at each of its first and second ends when the upper tooling passes from its upper rest position to its lower tensioning position.

[0019] The invention also relates to a method for relieving stress on a metal part, the method comprising the following steps:

[0020] - supply of the metal part, the metal part extending along a curve main part of the piece between a first end and a second end, the part preferably being produced by a transformation process, in particular a forging process;

[0021] - installation of the part in a de-stressing installation of the aforementioned type, the metal part being held at each of its ends by a respective hooking system, the upper tooling being in the upper rest position;

[0022] - work hardening of the metal part, the work hardening comprising a first sub- a step of lowering the upper tooling from the upper rest position to the lower tensioning position, the metal part being subjected to tensile stresses by the hooking systems according to the directions of traction; and a second sub-step of raising the upper tooling from the lower tensioning position to the upper rest position;

[0023] the process preferably comprising a final step of removing the part, including opening the hooking systems and releasing the work-hardened part.

[0024] According to other advantageous aspects of the invention, the method comprises one or more of the following features, taken individually or in all technically possible combinations:

[0025] - the metal part is held pressed against the contact face during the step work hardening, so as to apply a compressive force to the part;

[0026] - the main curve of the part is curved so that the metal part is fitted;

[0027] - the metal part is obtained by forging;

[0028] - the metal part is made of aluminum or aluminum alloy, of preferably in aluminium alloy of the 7XXX series or the 2XXX series, preferably in alloy 2219 or in Al-Li alloy 2050;

[0029] - the area of ​​the cross-section of the part taken perpendicular to the curve The main part of the room is constant along said room;

[0030] - the part has a length measured between the first and second ends between 1 m and 10 m;

[0031] - the work hardening of the metal part is carried out at a temperature between 0°C and 100°C, preferably between 10°C and 40°C;

[0032] - during the work hardening stage, the metal part is subjected to deformation plastic less than 10.0%, preferably between 0.5% and 5.0%.

[0033] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0034] [Fig-1] [Fig.1] is a kinematic representation of a detention facility sionement according to a first embodiment of the invention;

[0035] [Fig.2] [Fig.2] is a schematic front view representation of an installation according to the first embodiment illustrated in [Fig. 1], in which a metal part intended to be relieved of stress is installed, the upper tooling being in position resting height;

[0036] [Fig.3] [Fig.3] is a schematic representation of the installation of [Fig.2], the upper tooling being in the lower tensioning position;

[0037] [Fig.4] [Fig.4] is a schematic perspective view of the metal part of the [Fig.l];

[0038] [Fig. 5] [Fig. 5] is a diagram of a stress-relieving process according to the invention;

[0039] [Fig.6] [Fig.6] is a kinematic representation of a detention facility sionement according to a first variant of the first embodiment of the invention;

[0040] [Fig.7] [Fig.7] is a kinematic representation of a detention facility sionement according to a second embodiment of the invention;

[0041] [Fig.8] [Fig.8] is a kinematic representation of a detention facility sionement according to a third embodiment of the invention;

[0042] [Fig.9] [Fig.9] is a schematic cross-sectional representation of an installation of detensioning according to a fourth embodiment of the invention;

[0043] [Fig. 10] [Fig. 10] is a schematic cross-sectional representation of a de-stressing installation according to a fifth embodiment of the invention.

[0044] In this description, the terms "lower", "upper", "top" and "bottom" will be used conventionally with reference to a vertical Z elevation axis, also called the Z elevation direction.

[0045] Figures 1 to 3 illustrate a detensioning installation 10 according to a first embodiment of the invention.

[0046] The installation 10 is intended for the detensioning of a metallic part 8.

[0047] Part 8 is, for example, intended for the aeronautical field. In particular, the metal part 8 is intended to form a riveted sub-assembly of several metal parts of an aircraft structure. Alternatively, the metal part 8 is intended to form a structure of land-based, space-based, or other equipment.

[0048] Part 8 is a monolithic part, made from a single piece.

[0049] Preferably, part 8 is a part previously shaped by die forging. Die forging is a forging operation which consists of shaping, by plastic deformation, a volume of material by placing it between two dies and subjecting it to one or more impacts, so as to obtain a blank or a forged block whose three-dimensional shape is close to, or equal to, that of part 8 before machining, and whose dimensions are equal to or greater than those of said part 8.

[0050] Preferably, the metal part 8 is made of aluminum or aluminum alloy. For example, the metal part 8 is made of aluminum alloy from the 7XXX series, the principal alloying element of which is zinc, or from the 2XXX series, the principal alloying element of which is copper. Preferably, the metal part 8 is made of alloy 2219 or Al-Li 2050 alloy.

[0051] The installation 10 is suitable for use with metallic parts 8 of different shapes and dimensions.

[0052] Fig. 4 represents an example of a metallic part 8 suitable for use with the installation 10.

[0053] The metal part 8 extends longitudinally along a principal curve C between a first end 82A and a second end 82B. The principal curve C here corresponds to the line passing through the center of gravity of the cross sections of the part 8, disregarding any reliefs, for example of the type of ribs and / or bosses, present on the part 8.

[0054] Preferably, the main curve C is a plane curve contained in a longitudinal plane of the part 8.

[0055] The part 8 extends transversely between a first edge 84A and a second edge 84B and in thickness between a lower face 86A and an upper face 86B. The lower face 86A is defined as the face of the part 8 intended to be oriented towards the ground when the part 8 is placed in the installation 10 for the purpose of its de-tensioning.

[0056] The installation 10 is adapted for use with large parts 8.

[0057] Preferably, the part 8 has a length L measured along the main curve C between the first and second ends 82A, 82B of between 1 m and 10 m.

[0058] Preferably, part 8 has a width 1 measured between the first edge 84A and the second edge 84B of between 0.1 m and 3 m.

[0059] Preferably, the part 8 has a thickness e measured between the lower face 86A and the upper face 86B of between 10 mm and 300 mm.

[0060] Here, length, width or thickness respectively, means the average length, average width or average thickness of part 8.

[0061] The metal part 8, for example, has a substantially parallelepiped shape.

[0062] For example, as shown in [Fig.4], the metal part 8 has a curved profile between its ends 82A, 82B. This means that the main curve C is not straight, but is curved.

[0063] The main curve C preferably has a curvature characterized by a radius of curvature between 1 m and 1000 m, preferably between 1 m and 500 m, more preferably between 1 m and 100 m.

[0064] In this application, "radius of curvature" means the absolute value of the radius of the circle tangent to part 8, more particularly to the lower face 86A of part 8, in a longitudinal plane of part 8. In other words, the radius of curvature is the radius of the circle that most closely follows the lower face 86A of part 8.

[0065] According to an unrepresented variant, the main curve C has a curvature characterized by a plurality of radii of curvature, typically between 0.1 and 100 m. Part 8 then has, for example, an evolving curve.

[0066] The lower face 86A defines a longitudinally concave profile. By concave, it is meant here that, when the part 8 is placed in the installation 10 for the purpose of its de-tensioning, the lower face 86A defines a longitudinal hollow with respect to the ground.

[0067] Any curve of the lower face 86A extending parallel to the main curve C is here devoid of an inflection point.

[0068] A cross-section of part 8 is defined, said section corresponding to the intersection of part 8 with a plane normal to the principal curve C of part 8.

[0069] Advantageously, the cross-section of part 8 is substantially constant along the main curve C of part 8, except optionally at the ends 82A, 82B which are likely to have means facilitating the hooking of part 8 in the installation, as will be described later.

[0070] By substantially constant, we mean a variation of less than 10%, advantageously less than 5%.

[0071] Preferably, the cross-sectional area of ​​part 8 is constant along the main curve C of part 8, except optionally at the ends 82A, 82B.

[0072] During the release of tension in part 8, the same tensile stress is thus exerted on each section.

[0073] In the example of [Fig.4], the cross-section of part 8 is substantially constant along the main curve C of part 8, preferably constant along the main curve C of the part.

[0074] Advantageously, the width and thickness of part 8 are constant.

[0075] In the case of parts of constant width, the stress-relieving process according to The invention allows for a reduction in implemented weight (PMO) due to improved control of the part's dimensional stability, enabling a reduction in the standard packaging of the forged part. Dimensional stability is defined as low geometric variability across the population of parts potentially manufactured throughout all production runs.

[0076] In an alternative (not shown), the shape of the cross-section of part 8 varies along the main curve C of part 8, while the cross-section remains constant.

[0077] For example, as shown in [Fig. 4], part 8 also has a profile curved between its first and second edges 84A, 84B. For example, as shown in [Fig. 4], part 8 defines a secondary curve C' between the first edge 84A and the second edge 84B. The lower face 86A defines a concave profile transversely here. Alternatively, the lower face 86A defines a convex profile transversely.

[0078] Preferably, as shown in [Fig.4], the metal part 8 has a longitudinal plane of symmetry, in which the main curve C is located, and a transverse plane of symmetry, normal to the main curve C. The radius of curvature is measured here in the longitudinal plane of symmetry.

[0079] According to a particular embodiment (not shown), part 8 has reliefs on its lower face 86A and / or on its upper face 86B.

[0080] For example, part 8 has ribs and / or bosses on its lower face 86A and / or on its upper face 86B.

[0081] For example, part 8 is a splint and further includes a longitudinal rib on its lower face 86A and / or its upper face 86B.

[0082] When part 8 has reliefs on at least one of its faces 86A, 86B, the convexity, the main curve C and the secondary curve C' of part 8 are all determined by abstracting from said reliefs.

[0083] According to an alternative not shown, the metal part 8 is substantially flat. The main curve C is then rectilinear.

[0084] Preferably, part 8 has attachment means (not shown) at the first and / or second end 82A, 82B. For example, the attachment means include a lip with a heel, holes or any other means facilitating the retention of part 8 in the installation 10 during its release.

[0085] With reference to figures 1 to 3, the installation 10 includes a lower tooling 20, a first and a second attachment systems 22A, 22B for the metal part 8 and an upper tooling 24.

[0086] A vertical median plane P of the installation 10 is defined, extending along a transverse axis Y of the installation 10 and the vertical elevation axis Z perpendicular to the transverse axis Y. A longitudinal axis X of the installation 10 is also defined, perpendicular to the transverse axis Y and to the elevation axis Z.

[0087] The lower tooling 20 includes a frame 30 and a workpiece support 32 mounted on the frame 30.

[0088] The frame 30 is intended to be fixed on a press table and is for example made of steel.

[0089] Typically, the frame 30 has a mass greater than 1000 kg.

[0090] The frame 30 is suitable for use with different part supports 32.

[0091] The part support 32 is held on the frame 30, for example by means of screws.

[0092] The part support 32 has a contact face 33, here the upper face 33, configured to be in contact with the part 8, in particular with the lower face 86A of the part 8.

[0093] Preferably, the upper face 33 of the part support 32 has a shape complementary to the part 8, more particularly to the lower face 86A of said part 8. The part support 32 is advantageously machined to the profile of the part 8.

[0094] In the example of figures 1 to 3, the upper face 33 of the part support 32 has a curved surface, more precisely convex with respect to the volume of the part support 32.

[0095] According to a particular embodiment (not shown), the upper face 33 of the support for part 32 defines grooves and / or recesses (not visible) intended to receive the ribs and / or bosses of the part 8 when the latter has them on the lower face 86A.

[0096] For example, the upper face 33 of the part support 32 has a surface area less than that of the lower face 86A of the part 8.

[0097] Part 8 can thus be chosen so as to extend beyond the support of part 32, in particular to extend longitudinally beyond the support of part 32, as shown in figures 1 to 3.

[0098] The support for part 32 is preferably made of steel.

[0099] Advantageously, the part support 32 has a honeycomb structure comprising a plurality of (non-visible) cells delimited by partitions and opening at the upper face 33 of the part support 32. The partitions are, for example, welded to each other.

[0100] The mass of the part support 32 is then lightened and is typically on the order of 10 tonnes, while retaining good mechanical properties.

[0101] This is particularly advantageous, since the part support 32 is intended to be changed according to the shape of the part 8.

[0102] The first and second fastening systems 22A, 22B are configured to clamp the part 8 at its first and second ends 82A, 82B.

[0103] The first hanging system 22A and the second hanging system 22B are arranged on either side of the vertical median plane P of the installation 10. In the example shown in figures 1 to 3, the first and second hanging systems 22A, 22B are symmetrical to each other with respect to said median plane P.

[0104] Advantageously, each hooking system 22A, 22B is capable of being pivoted, for example by means of a jack, so as to allow the installation of the metal part 8 and to adapt to the possible bending of the latter.

[0105] Each attachment system 22A, 22B is movable between an open configuration (not shown) allowing the insertion of each end 82A, 82B into the system associated hooking system 22A, 22B and a locking configuration, visible in figures 1 to 3, allowing the first and second ends 82A, 82B to be held in the associated hooking system 22A, 22B.

[0106] For example, each clamping system 22A, 22B includes a clamping system 40A, 40B configured to clamp the part 8 at one of its first and second ends 82A, 82B in closed configuration, and a sliding system 42A, 42B, advantageously attached to the associated clamping system 40A, 40B, configured to allow movement of the associated clamping system 22A, 22B in a direction substantially parallel to the tangent of the curve C of the part 8 at each of its ends 82A, 82B.

[0107] This direction is hereafter referred to as the traction direction Dt. Each traction direction Dt is thus perpendicular to the radius of curvature of the part at the associated end 82A, 82B.

[0108] Each clamping system 40A, 40B includes, for example, a clamping jaw configured to clamp the part 8 at its associated end 82A, 82B, in particular at its hooking means.

[0109] Other types of clamping systems are possible. For example, alternatively, the clamping systems include a dovetail-type housing for receiving the ends of the workpiece having a dovetail-shaped shape.

[0110] Each slide system 42A, 42B includes for example a respective arm 44A, 44B, configured to form between them an angle a, called tension angle a, which will be detailed later.

[0111] The slide systems 42A, 42B, and in particular the arms 44A, 44B, are intended to come into contact with the upper tooling 24 during tensioning operations.

[0112] Advantageously, each arm 44A, 44B includes an anti-wear system 46A, 46B, for example an anti-wear pad or shim, disposed at the contact area with the upper tooling 24.

[0113] The upper tooling 24 is configured to allow the movement of the gripping systems 22A, 22B according to the associated traction direction Dt, so as to move the gripping systems 22A, 22B away from each other and thus allow the unstressing of the part 8.

[0114] According to the embodiment shown in figures 1 to 3, the upper tooling 24 comprises a press 50 and a return wedge 52 mounted on said press 50.

[0115] Preferably, the press 50 is a hydraulic press.

[0116] The press 50 is mobile along a direction parallel to the elevation direction Z, represented on the [Fig.1] by the arrow F.

[0117] The press 50 is preferably capable of exerting a pressure force of at least 500T.

[0118] The return wedge 52 is configured to ensure the return of the vertical action of the press 50 into an action at least in a lateral part.

[0119] The return wedge 52 comprises, for example, two wedges forming beveled faces fixed on a base (not shown), said base being fixed on the press 50.

[0120] Preferably, wear shims 54 are fixed to the beveled faces. The shape and thickness of said shims are chosen according to the tension angle a.

[0121] The upper tooling 24 is mobile along the elevation direction Z between a high rest position, as shown in [Fig.2], and a low tensioning position, as shown in [Fig.3].

[0122] In the lower tensioning position, the upper tooling 24, and more particularly the return wedge 52, is configured to exert a constraint on each of the hooking systems 22A, 22B according to the associated traction direction Dt, so as to move the hooking systems 22A, 22B away from each other.

[0123] The traction directions Dt form a tension angle between them between 0° (exclusive) and 180° (inclusive).

[0124] Preferably, the angle a of the separation is between 0° (exclusive) and 180° (exclusive), preferably between 90° and 180° (exclusive), in particular between 90° and 175°. An angle a of 90° is particularly suitable for parts with medium to high bending, typically for parts with a small radius of curvature, for example on the order of 1 m.

[0125] Advantageously, the angle a of separation is between 130° and 175°.

[0126] When part 8 has a straight main curve C, the angle a of separation is equal to 180° and the traction directions Dt are opposite to each other.

[0127] When part 8 has a non-rectilinear principal curve C, as shown in [Fig. 3], the spacing angle α is strictly less than 180°. The spacing of the fastening systems 22A, 22B then has the effect of pressing part 8 against the support 32, so that compressive stresses are exerted on part 8 according to its thickness.

[0128] The operation of the installation 10 according to the invention will be described with reference to [Fig.5] which schematically represents a detensioning process according to the invention.

[0129] The detensioning process includes an initial step 110 of supplying a metallic part 8 as described previously.

[0130] Preferably, part 8 is produced by a transformation process, in particular a forging process.

[0131] For example, supply step 110 includes a preliminary substep 106 of shaping a preform by die-casting. The preform is obtained, for example, by forging, drawing, slitting and forming of a blank. During the die-making step 106, the preform is pressed between tools in which the shape of the part 8 to be manufactured has been engraved.

[0132] Preferably, the supply step 110 then includes a substep 107 of solving the die-cast part, a substep 108 of quenching and a substep 109 of deburring, so as to prepare the metal part 8.

[0133] Part 8 is then placed in the tension release device 10 during a setup step 112. The upper tooling 24 is then in the rest position and the latching systems 22A, 22B are in the open configuration.

[0134] During the setup step 112, the part 8 is brought towards the part support 32 and placed on the upper surface 33 of said part support 32, for example by means of a mechanical manipulator including ejectors (not shown).

[0135] The fastening systems 22A, 22B are positioned opposite the part 8, so that the part 8 is inserted into each fastening system, in particular into each clamp system 40A, 40B, at its ends 82A, 82B.

[0136] Then, the clamping systems 22A, 22B are placed in the closed configuration. The part 8 is then held at each of its ends 82A, 82B by a respective clamping system 22A, 22B. For example, the clamping jaws of the collet systems 40A, 40B exert a clamping force on the part 8 at its ends 82A, 82B, preventing the part 8 from moving relative to the collet systems 40A, 40B.

[0137] The stress-relieving process then includes a work-hardening step 114 of the part 8, during which the part 8 is stress-relieved. The residual stresses resulting from the heat treatment step, in particular the quenching, are then reduced.

[0138] The upper tooling 24 moves from the upper rest position to the lower tensioning position during a first sub-step 115 of descent. In the lower position, the upper tooling 24, and more particularly the return wedge 52, exerts on the gripping systems 22A, 22B, particularly at the level of the anti-wear devices 46A, 46B of the arms 44A, 44B, stresses tending to move the gripping systems 22A, 22B according to their respective traction direction Dt and thus to move them apart from each other, allowing work hardening of the part 8 by pulling its ends outwards.

[0139] The displacement of each hanging system 22A, 22B from its initial position is typically between 10 mm and 1000 mm.

[0140] The metal part 8 is thus subjected to tensile stresses by the hooking systems 22A, 22B in a direction substantially perpendicular to the radius of curvature of the part at each end, that is to say in a direction tangent to the main curvature C of the part 8 at the ends 82A, 82B.

[0141] During work hardening, the plastic deformation of the part is preferably in- less than or equal to 10.0%, typically between 0.5 and 5.0%.

[0142] Plastic deformation is for example measured by a geometric differential before / after the process, either by measuring the change in distance between two points along the length of the part, or by measuring the reduction in thickness of the part.

[0143] Part 8 therefore undergoes a slight modification, preferably a negligible modification, of its shape during work hardening.

[0144] The tensile force exerted by each hooking system 22A, 22B at the respective end 82A, 82B is preferably between 8,000 kN and 10,000 kN.

[0145] Advantageously, the metal part 8 is also held against the workpiece support 32 during the work hardening step. This induces compressive forces on the part 8 against the workpiece support 32 during the work hardening step. The part is then said to be subjected to a tension-compression phenomenon. The displacement of the ends of the part thus generates the application of a compressive force on the part 8. The interface between the part 8 and the workpiece support 32 has a low coefficient of friction, allowing for a homogeneous distribution of the compressive force and therefore homogeneous deformation.

[0146] Preferably, the compressive forces come exclusively from the part support 32, the part 8 not being in contact with the upper tooling 24.

[0147] The level of compressive stress is therefore much lower than in a stress-relieving process by compression using a press, which allows for a part support 32 with a lightweight structure, such as a honeycomb structure.

[0148] Preferably, the work hardening step also includes a dimensional readjustment of the part 8, so as to meet the target dimensions. Indeed, the solution hardening times (including the time for positioning and securing the part in the furnace) and the rapid cooling during quenching can generate geometric deformations due to the low plasticity of the material and / or the stresses induced during cooling. The process according to the invention allows for reshaping the part by adapting the workpiece support 32 and / or the tensioning forces applied to obtain a dimensionally compliant and repeatable part.

[0149] Preferably, the work hardening step 114 is carried out at room temperature, preferably at a temperature between 0°C and 100°C, preferably between 10°C and 40°C.

[0150] Preferably, the work hardening step 114 lasts between 30 s and 240 s.

[0151] During the work hardening step 114, the residual stresses present in the part 8 are greatly reduced.

[0152] Then, during a second substep 116, the upper tooling 24 is raised from the lower tensioning position to the upper resting position.

[0153] The upper tooling 24 no longer exerts any constraints on the hooking systems 22A, 22B, which themselves no longer exert any tensioning force on the metal part 8.

[0154] The process advantageously provides for the management of elastic return after tension-compression, taking into account the dimensional reduction of the part following a given elongation of the order of the desired deformation rate.

[0155] Finally, during a final removal step 118, the gripping systems 22A, 22B are moved to the open configuration, for example by releasing the jaws. Then, the work-hardened metal part 8 is removed from the gripping systems 22A, 22B, for example by means of the manipulator.

[0156] A new metal part of similar shape can then be subjected to the same stress-relieving process.

[0157] The installation 10 according to the invention is thus adapted to the stress relief of large and / or complex shaped metal parts 8, for example curved parts.

[0158] The geometry of the part and in particular its curvature are thus preserved.

[0159] Tension relief by tensioning or tension-compression is more homogeneous within part 8 than tension relief solely by compression, limiting degradation of the mechanical properties of part 8.

[0160] Furthermore, the installation 10 does not require complex specific equipment to carry out said tensioning, a press being sufficient to implement both the die-making of the part 8 and its tensioning or tension-compression in a subsequent step.

[0161] The compressive forces experienced by the part 8 and the part support 32 on which it rests are also less than in the case of stress relieving by compression. It is therefore possible to use a part support 32 with a lightweight structure, such as a honeycomb structure, which reduces its manufacturing costs and weight.

[0162] Installation 10 also offers very good reproducibility, the forces exerted on the part being easily controllable and repeatable.

[0163] Variations of the installation and / or the method according to the invention are conceivable.

[0164] In one variant, the metal part 8 is produced by an extrusion process, and not by a die-casting process.

[0165] According to a first variant shown in [Fig. 6], at least one of the arms 44A, 44B of the slide systems 42A, 42B includes a joint 144, for example in the form of a ball joint. This joint 144 allows for compensation of any misalignment between the faces of the guide wedge 52 and the arms 44A, 44B.

[0166] Figure 7 represents an installation 10 according to a second embodiment of the invention.

[0167] According to this second embodiment, the upper tooling 24 comprises a toggle joint system 210 instead of the return wedge. The toggle joint system 110 comprises, for example, two articulated connecting rods 212, each connecting rod 212 being connected on one side to the press 50, and on the other side to a respective attachment system 22A, 22B, more precisely to a respective arm 44A, 44B. Each connecting rod 212 is configured to exert a force on the respective attachment system 22A, 22B in the associated traction direction Dt, during the descent of the upper tooling 24.

[0168] A third embodiment is shown in [Fig.8].

[0169] According to this third embodiment, each clamping system 22A, 22B comprises a clamping system 40A, 40B configured to clamp the part 8 at one of its first and second ends 82A, 82B in closed configuration, and a lever arm system 310A, 310B, advantageously integral with the associated clamping system 40A, 40B, configured to allow movement of the associated clamping system 22A, 22B in a direction substantially parallel to the tangent of the curve C of the part 8 at each of its ends 82A, 82B.

[0170] This direction is hereafter referred to as the traction direction Dt. Each traction direction Dt is thus perpendicular to the radius of curvature of the part at the associated end 82A, 82B.

[0171] Each lever arm system 310A, 310B extends between a lower end 312A, 312B and an upper end 314A, 314B. Each lever arm system 210A, 210B has an anchor axis 316A, 316B, the lever arm system 310A, 310B being configured to pivot about said anchor axis.

[0172] For example, as shown in [Fig.8], each lever arm system 310A, 310B is rotatably mounted around a respective anchor axis 316A, 316B located at the lower end 312A, 312B.

[0173] For example, each anchor pin 316A, 316B is mounted on the lower tooling 20.

[0174] Preferably, as shown in [Fig. 8], the clamping systems 40A, 40B are mounted on an associated lever arm system 310A, 310B. For example, each clamping system 40A, 40B is formed with a dovetail-type housing for receiving the ends 82A, 82B of the part 8, which has a dovetail shape.

[0175] The upper tooling 24 is configured to exert a constraint on each of the lever arm systems 310A, 310B along distinct traction directions Dt, causing the lever arm systems 310A, 310B to rotate around their respective axes, and thus the unstressing of the part 8.

[0176] According to the embodiment shown in [Fig. 8], the upper tooling 24 includes a press 50. Alternatively, the upper tooling 24 further includes a return wedge mounted on said press 50.

[0177] The upper tooling 24 is movable along the elevation direction Z between a high rest position and a low tensioning position, as shown in [Fig.8], in which the press 50 is in direct contact or by means of spreader arms 320 with the lever arms 310A, 310B.

[0178] During the work hardening step, the rotation of the lever arm systems 310A, 310B results in a slight decrease in the angle α formed between the tensile directions Dt. Such a decrease is, however, small, as plastic deformation is typically limited to 10%. Preferably, plastic deformation is limited to 5%, resulting in a negligible decrease in angle α.

[0179] A fourth embodiment is schematically represented in [Fig.9].

[0180] According to this fourth embodiment, the installation 10 is devoid of part support so that the part 8 does not rest on any support.

[0181] Part 8 is placed directly into the hooking systems 22A, 22B, the first and second ends 82A, 82B being held in a respective hooking system 22A, 22B.

[0182] The upper tooling 24 is configured to exert a stress on each of the hooking systems 22A, 22B along distinct traction directions Dt, causing the hooking systems 22A, 22B to move apart.

[0183] Preferably, the traction directions Dt form an angle between them between 130° and 180°.

[0184] Such an installation 10 is suitable for parts with slight curves, that is to say, parts whose main curve C preferably has a curvature characterized by the ratio between the radius of curvature and the length L measured along the main curve C, said ratio being at least equal to 2. For such a part with slight curves 1 m long, the radius of curvature is therefore at least 2 m. For another part with slight curves 10 m long, the radius of curvature is at least 20 m.

[0185] In the example of [Fig.9], the installation 10 includes a fixed part 408 intended to cooperate with the hanging systems 22A, 22B.

[0186] The upper tooling 24 is here multi-element and includes a return wedge 410 and two spreader arms 412 arranged on either side of the return wedge 410 and each bearing against a respective hooking system 22A, 22B.

[0187] The return wedge 410 is movable along the elevation direction Z between a high position and a low tensioning position, as shown in [Fig.9].

[0188] The vertical movement of the return wedge 410 causes the arms 412 to move laterally apart, and the various elements to slide relative to each other via a plane-to-plane connection. This causes the attachment systems 22A, 22B to move apart from each other, and thus the de- tensioning of part 8.

[0189] In an alternative (not shown), the upper tooling 24 is without spreading arms, the return wedge 410 being in direct contact with the hooking systems 22A, 22B.

[0190] According to a fifth embodiment, shown schematically in [Fig.10], the installation 10 is devoid of lower tooling 20.

[0191] The contact face 33 is here supported by the upper tooling 24.

[0192] The upper tooling 24 includes a return wedge 510 and two elements 512 forming part support.

[0193] Each element 512 has a lower face 514 forming the contact face 33 intended to be in contact with the metallic part 8 during the release of said part. The contact face 33 has a shape substantially complementary to the part 8, more particularly to the upper face 86B of said part 8.

[0194] The elements 512 are laterally mobile between a close position and a spread-out position (represented in [Fig. 10]), in which the elements 512 are each in contact with a respective fastening system 22A, 22B.

[0195] The return wedge 510 is movable along the elevation direction Z between a high position and a low tensioning position, as shown in [Fig. 10].

[0196] The vertical displacement of the return wedge 510 causes the lateral separation of the elements 512 along opposite separation directions De, and therefore the displacement of the hooking systems 22A, 22B, and thus the release of tension on the part 8.

[0197] It should be noted that the different variants and embodiments described are capable of being combined with each other, without departing from the scope of the present invention.

Claims

Claims

1. Installation (10) for relieving stress on a metal part (8) extending along a main curve (C) of the part (8) between a first end (82A) and a second end (82B), the installation (10) comprising: a. A first attachment system (22A) and a second attachment system (22B) arranged on either side of a vertical median plane (P) of the installation, the first and second attachment systems (22A, 22B) being movable between an open configuration allowing the insertion of the first and second ends (82A, 82B) into the associated attachment system (22A, 22B) and a locking configuration allowing each of the first and second ends (82A, 82B) to be held in the associated attachment system (22A, 22B); and b.An upper tool (24) movable in a substantially vertical elevation direction (Z) between a high rest position and a low tensioning position in which the upper tool (24) exerts a stress on each of the attachment systems (22A, 22B) in distinct traction directions (Dt) forming between them an angle (a) between 0° (exclusive) and 180° (inclusive), so as to separate the attachment systems (22A, 22B) from each other.

2. Installation (10) according to claim 1, further comprising a lower tool (20) comprising a part support (32) intended to be in contact with the metal part (8).

3. Installation (10) according to claim 1 or 2, in which one of the lower tool (20) or the upper tool (24) comprises a contact face (33) configured to be in contact with the metal part (8) during the stress relief of said part (8), the contact face (33) having a shape substantially complementary to said part (8).

4. Installation (10) according to claim 3, in which the contact face (33) has a curved surface.

5. Installation (10) according to any one of claims 1 to 4, in wherein the upper tooling (24) comprises a press (50), preferably a hydraulic press.

6. Installation (10) according to any one of the preceding claims, in which each attachment system (22A, 22B) comprises a clamp system (40A, 40B), configured to grip the metal part (8) at one of its ends (82A, 82B) in the closed configuration, and a slide system (42A, 42B) configured to allow the movement of the attachment systems (22A, 22B) in a direction substantially perpendicular to a radius of curvature of the part (8) at each of its first and second ends (82A, 82B) during the passage of the upper tool (24) from its high rest position to its low tensioning position.

7. Method for relieving stress on a metal part (8), the method comprising the following steps: a. Supply (110) of the metal part (8), the metal part (8) extending along a main curve (C) of the part (8) between a first end (82A) and a second end (82B), the part (8) preferably resulting from a transformation process, in particular a stamping process; b. Placing (112) the part (8) in a stress relief installation (10) according to any one of claims 1 to 6, the metal part (8) being held at each of its ends (82A, 82B) by a respective attachment system (22A, 22B), the upper tool (24) being in the high rest position; c. Work hardening (114) of the metal part, the work hardening comprising a first sub-step (115) of lowering the upper tool (24) from the high rest position to the low tensioning position, the metal part (8) being subjected to tensile stresses by the attachment systems (22A, 22B) according to the traction directions (Dt); and a second sub-step (116) of raising the upper tool (24) from the low tensioning position to the high rest position; the method preferably comprising a final step (118) of deposition of the part (8), including the opening of the attachment systems (22A, 22B) and the release of the work-hardened part.

8. Method according to claim 7, in which the metal part (8) is kept pressed against the contact face (33) during the work hardening step (114), so as to apply a compressive force to the part (8).

9. A method according to any one of claims 7 and 8, wherein the main curve (C) of the part (8) is curved so that the metal part (8) is bent.

10. Method according to any one of claims 7 to 9, in which the metal part (8) is obtained by stamping.

11. Method according to any one of claims 7 to 10, in which the metal part (8) is made of aluminum or aluminum alloy, preferably aluminum alloy of the 7XXX series or of the 2XXX series, preferably alloy 2219 or alloy Al-Li 2050.

12. A method according to any one of claims 7 to 11, wherein the cross-sectional area of ​​the part (8) taken perpendicular to the main curve (C) of the part (8) is constant along said part (8).

13. Method according to any one of claims 7 to 12, in which the part (8) has a length (L) measured between the first and second ends (82A, 82B) of between 1 m and 10 m.

14. Method according to any one of claims 7 to 13, in which the work hardening of the metal part (8) is carried out at a temperature between 0°C and 100°C, preferably between 10°C and 40°C.

15. Method according to any one of claims 7 to 14, in which, during the work hardening step, the metal part (8) is subjected to a plastic deformation of less than 10.0%, preferably between 0.5% and 5.0%.

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