WO2024218277A1 - Method for modelling the joining of a blade to a turbine engine rotor stub by orbital welding - Google Patents

Abstract

The invention relates to a method for modelling the joining (10) of a blade (4) to a stub (6) on a turbine engine rotor (2), by orbital-friction welding, which comprises the following step: determining a material consumption rate VCA as a function of the following orbital-friction welding parameters: eccentricity, frequency and pressure, and of a geometric parameter z of the section of the blade and of the stub at the junction; characterised in that the method further comprises the following step: determining a maximum thickness e _max of the junction as a function of the determined material consumption rate VCA, the geometric parameter z being an average of the mean radii z sweeping across the section at the junction at any point i of the periphery of said section.

Description

METHOD FOR MODELING A BLADE JUNCTION TO A TURBOMACHINE ROTOR STUMP BY ORBITAL WELDING

The invention relates to a method for modeling a blade junction to a turbomachine rotor, and more particularly to a method for modeling a junction obtained by orbital friction welding of a blade to a stub on a turbomachine rotor.

Prior art

Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft but also to those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

This sustained research and development work covers new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and the lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as an essential complement to technological progress, aeronautical biofuels.

To this end, the invention is the result of technological research aimed at significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft.

In this context, the invention relates to a method of modeling and orbital friction welding for producing a bladed disk (commonly referred to as: "blisk") or a bladed drum (commonly referred to as "blum") for a turbomachine compressor.

Orbital friction welding is a welding process in which the parts to be assembled are brought into contact under force and welded by a circular motion generally defined by an eccentric, and accompanied by a uniform tangential speed, so as to generate friction and homogeneous heating at a weld junction between the two parts.

It is also known to use linear friction welding, this is a welding process in which the necessary heat is created by a back and forth movement of the interfaces to be welded. However, orbital friction welding has several advantages over linear friction, for example, the relative movement between the two interfaces is continuous thanks to the circular friction movement, which provides better thermal homogeneity. Unlike linear movement for which the relative speed of the two parts becomes zero at each half-oscillation period. In addition, the cycle time of orbital welding is considerably lower than that of linear friction welding (respectively approximately 2 minutes compared to approximately 5 minutes).

Published patent document EP 2 535 516 A1 discloses a method of orbital friction welding of blades to a turbomachine rotor in which, once a material consumption is reached in a welding zone between the blade and the disk, the orbital movement is stopped at a reference position, and a forging force is exerted on the blade against the rotor in order to form the weld.

After welding, progressive machining adapting to the external surface of the blade is then carried out in order to remove the material from the interface which will have been pushed outwards during welding (commonly referred to as: “flash”), so as to avoid any projection linked to the machining.

However, machining after welding may reveal a weld junction of the blade with the rotor disc which may present structural defects and/or material health defects.

Published patent document EP 2 409 807 A2 discloses a method for manufacturing combined profiled blades and discs, in which each of the blades has a stub to be welded to the disc by linear friction. The document proposes a modeling of the linear welding process including an estimation of the material consumption rate “BOR” based on widths of the stub section measured along a linear oscillation direction.

However, the welding process disclosed by the document is related to linear friction welding and is not compatible with orbital welding, as it does not allow the orbital welding process to be accurately modeled to control the radial position of the welding zone and to obtain a welded joint that is sound and free of contaminants.

The invention aims to solve at least one of the problems posed by the prior art. More specifically, the invention aims to propose a solution for accurately modeling an orbital friction welding process of a blade to a rotor disk stub.

The invention is the result of technological research aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft. For this purpose, the present invention relates to a method for modeling a blade junction to a stub on a turbomachine rotor, by orbital friction welding, comprising the following step:

determination of a VCA material consumption rate as a function of the following orbital friction welding parameters: eccentricity, frequency and pressure, and of a geometric parameter z of the blade and stump section at the junction;

remarkable in that the method further comprises the following step:

determination of a maximum thickness e _max of the junction as a function of the determined material consumption rate VCA , the geometric parameter z being an average of the mean radii z _i sweeping the section of the blade and the stump at the junction at any point i of the periphery of said section.

Advantageously, the pressure comprises a forging pressure and/or a pressure applied during an orbital movement of the orbital friction weld.

According to an advantageous embodiment of the invention, the maximum thickness e _max determined and the material consumption rate VCA determined are all the greater as the geometric parameter z is small and vice versa.

According to an advantageous embodiment of the invention, the mean radii z _i sweeping the section of the blade and the stump at the junction at any point i of the periphery of said section are strictly contained in said section.

According to an advantageous embodiment of the invention, the mean radii z _i sweeping the section of the blade and the stump at the junction at any point i of the periphery of said section completely sweep said section.

According to an advantageous embodiment of the invention, the maximum thickness e _max determined and the material consumption rate VCA determined are all the smaller as the eccentricity decreases and vice versa.

According to an advantageous embodiment of the invention, the maximum thickness e _max determined and the material consumption rate VCA determined are all the smaller as the frequency decreases and vice versa.

According to an advantageous embodiment of the invention, the determination of the maximum thickness e _max and the material consumption rate VCA is based on experimental orbital friction welding data, where for each welding operation the material consumption rate VCA is measured and correlated with the eccentricity, the frequency, the pressure and the geometric parameter z .

According to an advantageous embodiment of the invention, the correlations of the experimental data are made so as to provide a model for determining the rate of consumption of material VCA and possibly the maximum thickness e _max .

According to an advantageous embodiment of the invention, the model for determining the material consumption rate VCA and possibly the maximum thickness e _max involves the use of artificial intelligence.

The invention also relates to a method of orbital friction welding a blade to a stub on a turbomachine rotor to form a junction, comprising the following step:

determination of a VCA material consumption rate;

characterized in that the method further comprises the following step:

determination of a maximum thickness e _max of the junction as a function of the determined material consumption rate VCA and as a function of a geometric parameter z corresponding to an average of the mean radii z _i sweeping the section of the blade and the stump at the junction at any point i of the periphery of said section.

Advantageously, determination of a material consumption rate VCA corresponds to a measurement on the machine and/or the tooling performing the orbital welding. Preferably, the determination of the maximum thickness e _max of the junction is also based on the following orbital friction welding parameters: eccentricity, frequency and forging pressure, said parameters being determined by measurement on the machine and/or the tooling performing the orbital welding.

According to an advantageous embodiment of the invention, the welding method further comprising a step of comparing the maximum thickness e _max determined with an interval of values of the maximum thickness e _max predefined during a modeling method of the blade junction to the stump, said modeling method being according to the invention.

The invention also relates to a method for dimensioning a blade and a corresponding stub on a turbomachine rotor, intended to be joined by orbital friction welding, according to a maximum thickness e _max of the predetermined junction, remarkable in that the dimensioning method comprises an iteration of determining the maximum thickness e _max of the junction according to different dimensions of the junction, according to a modeling method according to the invention.

According to an advantageous embodiment of the invention, the iteration of determining the maximum thickness e _max of the junction according to different dimensions of the junction is carried out while the eccentricity, the frequency and the pressure remain constant. Preferably, the pressure comprises the pressure applied during the orbital movement and the forging pressure.

According to an advantageous embodiment of the invention, the different dimensions of the junction, in the iteration of determining the maximum thickness e _max of the junction, are selected so as to correspond to different values of the geometric parameter z .

According to an advantageous embodiment of the invention, the iteration of determining the maximum thickness e _max of the junction according to different dimensions of the junction is stopped when the maximum thickness e _max determined corresponds to the maximum thickness e _max of the junction predetermined with a given tolerance.

The measures of the invention are particularly advantageous in that the determination of the material consumption rate VCA , in particular as a function of the geometric parameter z of the junction section, makes it possible to ensure an efficient and precise estimation of the maximum thickness e _max of said junction.

Modeling the junction by determining its maximum thickness e _max , allows, from the design stage, to define an optimal dimensioning of the radial extents of the blades and the stubs so as to guarantee an optimal radial position of a weld plane of the junction before orbital welding. In addition, the contact section presented between the blades and the stubs is also dimensioned by means of a robust process so as to ensure homogeneity of the mixing of the material and thus obtain a healthy welded junction free of defects.

It is understood that each detail of an embodiment below can be combined with each other detail of the other embodiments.

There schematically illustrates a side view of a blade joined to a stub extending radially from a turbomachine rotor, having an orbital friction welded junction comprising a maximum thickness e _max determined by a method of modeling the junction according to the invention;

There schematically illustrates a section of the blade and/or stump at the junction visible at the ;

There illustrates the junction section of the when determining a mean radius z _A sweeping said section from a point A on the periphery of said section;

There illustrates the junction section of the when determining a mean radius z _B sweeping said section from a point B on its periphery;

There illustrates a mapping of the amplitude of the mean rays z _i sweeping the junction section at any point i on its periphery;

There illustrates the junction section of the showing three measurement marks of the maximum thickness of the welded joint, with two of these joint sections identical;

There is a first graph representing the evolution of the estimated thickness of the welded joint compared to actual measurement points of said thickness, following a local width of the junction section of the , and to a first mark positioned at 1/4 of a total extent of said section;

There is a second graph representing the evolution of the estimated thickness of the welded joint compared to real measurement points, following a local width of the junction section of the , and to a second mark positioned at one half of the total extent of said section;

There is a third graph representing the evolution of the estimated thickness of the welded joint compared to real measurement points, following a local width of the junction section of the , and to a third mark positioned at 3/4 of the total extent of said section.

Detailed description of the embodiments

In the following description, the terms “internal” and “external” refer to a positioning relative to the axis of rotation of an axial turbomachine. The axial direction corresponds to the direction along the axis of rotation of the turbomachine, the lengths being measured axially. The widths are measured along the circumference. The radial direction is perpendicular to the axis of rotation. The upstream and downstream refer to the main flow direction of the flow in the turbomachine.

The dimensions of the figures are not to scale and in particular the thicknesses or radial dimensions are exaggerated to facilitate reading of the figures.

There schematically illustrates a side view of a blade 4 joined to a stub 6 extending radially from an external surface 8 of a turbomachine rotor 2, having a junction 10 welded by orbital friction comprising a maximum thickness e _max determined by a method of modeling the junction according to the invention.

It can be observed that the junction 10 has a diabolo or butterfly shape, with a wider peripheral end (in the radial direction) than its inner central part, this is due to a concentration of the excess material displaced during orbital welding. For this purpose, the maximum thickness e _max is measured at the peripheral end of the junction 10.

The present invention proposes a modeling method and a method of dimensioning the blades 4 and the stubs 6 so as to allow the manufacture of a bladed disk for a turbomachine.

Preferably, the bladed disk is a mobile wheel intended to be arranged upstream of an air flow separation nozzle in a turbomachine. For this purpose, the external surface 8 corresponds to an air guide surface of a fluid stream along the turbomachine. Alternatively, the bladed disk may correspond to a drum-type rotor belonging to a high-pressure or low-pressure compressor.

Preferably, the bladed disk is a so-called “bi-material” disk comprising two different titanium alloys. For example, the blades 4 can be made from a Ta6v alloy, and the rotor disk 2 from one of the following alloys: Ti17, Ti575, Ti1023.

Advantageously, the mixture of the two different titanium alloys (Ta6v and Ti17) presents easier machinability, and makes it possible to achieve a gain in mass compared to a solution based, for example, solely on a Ti17 alloy, this is notably due to a density of Ta6v which is slightly lower than that of Ti17.

Indeed, the Ti17 alloy was preferentially chosen for the disc part for its good HCF (High Cycle Fatigue) and LFC (Low Cycle Fatigue) fatigue characteristics. A Ti17 disc will also display a greater margin in burst speed than a Ta6v disc. For the blades, the Ta6v alloy was chosen because it provides the blades with a higher elongation at break (better impact resistance), and better crack propagation behavior which results in better durability to low energy impacts.

We can see at the that the junction 10 comprises a weld plane 10.1 illustrated in a central position relative to the maximum thickness e _max of said junction 10.

Advantageously, the determination of the e _max makes it possible to control the radial position h of the weld plane 10.1 from the external surface 8 of the rotor 2, as well as to size the radial extent of the blade 4 and the stub 6, prior to the manufacture of the bladed disk.

In this regard, the method of modeling the junction 10 comprises a step of determining the maximum thickness e _max as a function of a material consumption rate VCA (which can be expressed in mm/s) which is presented at the contact interface between the blade 4 and the stub 6 during orbital friction welding.

The method of the invention makes it possible to determine the material consumption rate VCA analytically by an estimation as a function of a geometric parameter z of the section of the blade 4 and the stub 6 at the junction 10, and also as a function of the following orbital friction welding parameters: eccentricity (corresponding to the eccentric e of the orbital oscillation movement during welding); frequency (oscillation speed); and the pressure applied during the maximum axial consumption phase during the orbital movement. Advantageously, the welding parameters can be predefined as input instructions on a welding machine prior to the execution of said welding.

The section of the blade 4 and the stub 6 at the junction 10 preferably corresponds to a flat section. Each stub 6 of the disk and the corresponding blade 4, which are intended to be welded by orbital friction, have an identical junction section.

Preferably, the analytical estimation of the VCA material consumption rate is based on experimental orbital friction welding data, for example by means of test specimens using the same orbital welding parameters, where for each welding operation the actual VCA rate is measured and correlated with the eccentricity, frequency, forging pressure and geometric parameter z . Preferably, by means of artificial intelligence. Thus, a model for determining the VCA rate can be defined.

It has been established that the maximum thickness e _max and the determined material consumption rate VCA are all the greater as the geometric parameter z is small and the eccentricity and/or frequency increases and vice versa.

Advantageously, the maximum thickness e _max determined by means of the modeling method of the invention makes it possible, prior to orbital welding, to control the radial position h of the welding plane 10.1, and thus to size the radial extent of each of the blade 4 and the stub 6.

There schematically illustrates the section 11 of the blade 4 and/or the stub 6 at the weld junction 10 visible in the . Preferably, section 11 is identical for blade 4 and for stub 6 of rotor 2.

Section 11 is modeled from an aerodynamic profile 4.1 of the blade 4, preferably, the latter includes a section widening by means of an excess thickness e corresponding, more preferably, to the eccentric e of the orbital oscillation movement during welding. The eccentric e corresponds to the offset value of the tool (for holding the blade) and the disk relative to a reference center, making it possible to create the orbital oscillation movement. In other words, the eccentric corresponds to the distance between the axis of rotation of the tool and the central point around which it performs its orbital movement.

However, the excess thickness e is not necessarily constant around profile 4.1; it may present variations around said profile 4.1.

It should be noted that prior to orbital friction welding, a sacrificial volume of material (extending essentially radially) is provided on each of the blades 4 and the stubs 6 to be assembled. This sacrificial volume is caused to be extruded outside the contact interface between the sections 11, thus forming a burr, commonly referred to as: "flash", which will then be eliminated, to reach the profile 4.1 of the blade. However, a non-homogeneous ejection of the flash along the periphery of the section to be welded risks causing the recirculation of local material inside the section to be welded and may prevent complete ejection of the contaminants created at the first moments of the weld and risks creating recesses in the welded joint, which is detrimental to the quality of the weld.

Advantageously, the widening of the contact section makes it possible to avoid the recirculation of the material (potentially harmful because it prevents the evacuation of impurities) towards narrower regions of the section of the final aerodynamic profile 4.1 of the blade and thus to ensure thermal homogeneity during welding, precisely in the final section 4.1 of the blade 4. Indeed, if we add an excess thickness e at least equal to the value of the eccentric, this means that the points of the final aerodynamic surface 4.1 are always in contact during welding (between the stump and the blade). Unlike the points in this excess thickness e which, by the orbital movement, are in contact with the opposite surface only during part of the orbital oscillation movement.

Thus, during welding, at section 11, the resulting local VCA speeds are more homogeneous, which allows the blade profile 4.1 to be preserved more and a stronger joint to be obtained.

The modeled section 11 makes it possible to determine the geometric parameter z . Indeed, z is an average of the mean radii z _i sweeping the section 11 at any point i of its periphery 11.1.

Each of the mean rays z _i corresponds to an average length z _i of rays z _i,α extending entirely in the section 11 from a point i to the periphery 11.1 and sweeping said section 11. Preferably, the rays z _i,α correspond to projections of the point i onto an entire portion of the periphery 11.1 which is opposite said point i .

Advantageously, the evolution of the mean radii z _i on the periphery of the section 11 to be welded physically represents the homogeneity of the length to be sheared during rotation (orbital movement during welding) and therefore the homogeneity of the material flow rate expelled in the flash along the contour of the blade. It is representative of the homogeneity of ejection of contaminants from the weld.

In this regard, the determination of the geometric parameter z includes the determination of the mean radius z _i for the plurality of points i over the entire periphery 11.1.

Preferably, the determination of the geometric parameter z is an automated process using a computer algorithm. In this regard, an algorithm applying a method of the type: "ray tracing" can be adapted, the latter also being known under the English name "ray tracing".

Advantageously, the inventors have wisely adopted an innovative approach by introducing the ray tracing technique, which is hitherto unknown in the field of mechanics. They realized that this is the optimal way to characterize the junction section intended for orbital friction, in order to arrive at a more accurate estimation of the VCA material consumption rate and therefore of the radial position (height) of the weld, and this prior to the orbital welding operation.

The ray tracing method on section 11 can be performed using the following steps:

- model a first section 11 (visible at the ) based on the final 4.1 aerodynamic profile of the blade with the addition of the excess thickness e (which shares the same value as that of the eccentric which is planned to be applied to the tool during orbital welding); and

- homogeneously divide the periphery 11.1 into several points i from which the rays z _i,α will be projected, preferably at approximately 2000 points i distributed homogeneously (this number may vary depending on the desired calculation precision); and

- project rays z _i,α which sweep the entire section 11 from a first point i of the periphery 11.1, the number of rays z _i,α projected preferably depends on an angle α between 0.001° and 10°; and

- measure the average length z _i of all rays z _i,α projected from the first point i ; and

- repeat the step of projection of the rays z _i,α as well as that of the measurement of the average length z _i , successively for all points i of the periphery 11.1; and

- calculate the average length of all the average lengths z _i measured from each of the totality of points i to arrive at the geometric parameter z of the junction section.

Figures 3 and 4 illustrate an example of projection of rays z _A,α and z _B,α , respectively, from points A and B of the periphery 11.1.

These are two schematic examples of determining the average length z _i of all rays z _i,α using the ray tracing method described above.

The two points A and B correspond to the two points which have allowed, respectively, the measurement of an average length z _A and an average length z _B . For this purpose, the determination of the geometric parameter z for section 11 corresponds to the calculation of the average of all the average lengths z _i , for example, 2000 average lengths including the average lengths z _A and z _B .

There illustrates section 11 when determining a mean radius z _A sweeping said section 11 from a point A of the periphery 11.1.

It can be seen that from point A, a plurality of rays z _A,α are projected onto a portion of the periphery 11.1 visible from said point A. In this configuration, the rays z _A,α can be between two extreme rays z _A,α tangent to the periphery 11.1.

The number of projected rays z _A,α can depend on the chosen angle α, the latter allows to establish the precision of determination of the average radius z _A. For this purpose, the angle α can be between 0.001° and 10°.

The mean radius z _A thus corresponds to the mean of all the projections z _A,α .

There illustrates section 11 when determining a mean radius z _B sweeping said section 11 from a point B of the periphery 11.1.

Preferably, the angle α is identical for all the projections of the rays z _i,α for the plurality of points i of the periphery 11.1. Preferably, the number of points i of the periphery 11.1 from which the rays will be projected is approximately 2000 points, this number being able to vary according to the desired calculation precision.

Similarly to point A, the rays z _B,α are projected from point B onto a portion of the periphery 11.1 visible at said point B. The mean ray z _B corresponds to the average of all the projections z _B,α .

The geometric parameter z is therefore the average of all the mean radii z _i (including the mean radii z _A and z _B ,) of the points i of the entire periphery 11.1.

The geometric parameter z corresponds to a geometric dimension that can be expressed in mm. Advantageously, this parameter z is the optimal dimension that best distinguishes the geometric shape of the section 11 and thus ensures a precise correlation between the weld parameters and the VCA speed. Indeed, the surfaces of the section 11 comprising the projected rays z _i,α from each point i can be assimilated to the mixing surface of the material during orbital friction welding (without being limited by a particular theory).

The geometric parameter z allows to take into account the specificities of orbital friction welding in the manufacturing process. Indeed, the friction force provided during welding rotates cyclically, which implies that a weld point at the end of section 11 (eg point A or B) sees a fraction of section 11 of the blade between the two extreme projected radii ( z _A,α or z _B,α ), the latter can therefore be assimilated to equivalent lengths of material to be sheared.

Moreover, the parameter z is relevant because it allows to take into account more the camber of the specific shape of the periphery 11.1, in a better way than the area of said section 11 or the chord of its profile.

In order to further optimize the dimensions of the blade and the rotor stubs, the dimensioning method of the present invention makes it possible to act iteratively on the shape of the section 11 so as to reach a predefined maximum thickness e _max , while the parameters of the orbital friction welding from which the VCA speed is predetermined remain constant.

Preferably, the shape of section 11 is modified by acting on the excess thickness. For example, with reference to the , the excess thickness e can be kept, and a second excess thickness can be used to further widen the narrowest regions of section 11, i.e. widening at the ends 11.2, 11.3. The modification of section 11 can be carried out manually using modeling software, or automatically by a specific computer algorithm.

The modification of section 11 results in a change in the value of the geometric parameter z, which influences the determined VCA speed as well as the e _max . In this configuration, for each new junction section established, the maximum thickness e _max is determined, and this iteratively until said e _max determined corresponds to the e _max initially predefined, with a tolerance of ±5%.

The last joint section modeled before stopping the iteration is the one that will be used for orbital welding of the blade to the disk, said section will be widened enough with respect to the blade profile to ensure constant material mixing and VCA speed during welding, thus obtaining a welded joint with better structural quality and free of recesses and contaminants.

Advantageously, the dimensioning method of the invention therefore makes it possible to define both an optimal radial position of the welding plane and an ideal junction section. This is done prior to the manufacture of the bladed disk, so as to allow anticipation of the stresses that may be exerted on the junction following possible impacts of debris on the blades. Thus, the bladed disk obtained by orbital welding of the blades to the stubs dimensioned by the method comprises junctions positioned radially in an optimal manner, each of said junctions advantageously comprising an improved structural and dimensional quality.

Advantageously, the welding method of the invention makes it possible, during the manufacture of the turbomachine bladed disk, to estimate the maximum thickness e _max for each orbital weld made between the blade and the stub, from the geometric parameter z , and by measuring the VCA speed and the forging pressure directly on the welding machine used.

The geometric parameter z can be the one used when modeling the section to be welded, or measured on the blade and/or on the stump before the welding operation, for example, by means of an image recognition measurement.

Advantageously, the welding method of the invention makes it possible to validate the value of the maximum thickness e _max estimated during each weld without requiring a physical inspection of the part (eg by making cuts and micrographs), thus ensuring efficiency and considerable time savings during the manufacture of the bladed disc.

Preferably, the validation includes a comparison of the estimated maximum thickness e _max with thickness values between predetermined limit boundaries, for example, when modeling the junction. Advantageously, these limit boundaries make it possible to comply with certain design criteria (eg critical threshold N1/N2 for crack propagation, tolerance interval involving parametric and/or height and/or inclination variabilities of the junction, etc.).

Alternatively, the comparison of the e _max determined (by measuring the VCA and the z parameter) during orbital welding can be carried out with the e _max calculated during modeling, which makes it possible to quantify the influence of the real welding parameters (measured on the machine) on the thickness of the modeled junction and thus validate the welds during the manufacture of the bladed disc without requiring destructive cutting of the bladed disc.

Preferably, the junction section S of each of the blade 4 and stub 6 comprises a total surface area greater than or equal to 200 mm2 and less than or equal to 7000 mm2, and more preferably between 2000 mm2 and 3000 mm2.

There illustrates a mapping of the amplitude of the mean rays z _i sweeping the junction section at any point i on its periphery.

The scale visible to the right of the corresponds to the mapping of the evolution of the value of z _i , this being normalized to 1, i.e. the maximum value of z _i in section 11 is equal to 1.

It can be seen that the points i of the periphery 11.1 at the ends 11.2 and 11.3 of the section 11 have the means z _i of the rays z _i,α launched from said points i which are the weakest compared to the means z _i of rays z _i,α launched from points i which are positioned between the ends 11.2, 11.3.

Advantageously, the present invention makes it possible to model the welding process in order to accurately determine both the e _max which is the maximum thickness of the joint on the welded joint profile and the material consumption rate VCA , upstream of the orbital welding operation.

The material consumption rate VCA is here determined analytically according to the present invention, as a function of the geometric parameter (parameter z ), the value of the eccentric e , the orbital oscillation frequency f , and the pressure applied during the orbital movement. The maximum thickness e _max is then determined as a function of the previously determined VCA rate and the parameters z.

Advantageously, the geometric parameter z is able to take into account specific details of the shape of the section, such as its camber, unlike a simple measurement of the area or widths or according to other methods of the prior art which are not able to take them into account. These details of the shape of the junction section that the geometric parameter z is able to intrinsically take into account, make it possible to arrive with greater precision at a determination of the maximum thickness e _max , then at the determination of the radial height of the welded junction.

Welds were made on the same machine and with constant welding parameters, i.e. eccentricity, oscillation frequency, forging speed and pressure which remain unchanged, only the shape of the sections which is modified.

The thickness measurements of the welded joints were carried out on a large number of welds. These measurements made it possible to show that the thickness variation profile of the joint over the entire welded section depended only on the z _i factors while the overall amplitude of this thickness variation profile depended on the welding parameters.

As an indication, the maximum measured thickness of the welded joint from two identical sections 11 is equal to 0.97 mm, for a z parameter equal to 25 mm.

There illustrates the junction section 11 of the showing three measurement marks of the e _max of the welded joint 11, with two of these joint sections 11 identical. Each mark defines the total local width of the section, following the corresponding direction illustrated in dotted lines.

Figures 7A to 7C represent graphs showing the normalized evolution of the thickness of the joint of section 11 of the , measured on the welds made and estimated numerically using the z parameter.

There is a first graph representing the evolution of the estimated thickness of the welded joint (see plot S) compared to points P of actual measurements of said thickness, at the right of the first mark positioned at 1/4 of a total extent (along the profile chord) of section 11 visible at the .

There is a second graph representing the evolution of the estimated thickness of the welded joint (see plot S) compared to points P of actual measurements of said thickness, at the right of the second mark positioned at 1/2 of the total extent of section 11 visible at .

There is a third graph representing the evolution of the estimated thickness of the welded joint (see plot S) compared to points P of actual measurements of said thickness, at the third mark positioned at 3/4 of the total extent of section 11 visible at .

With reference to Figures 7A to 7C, the S plots are preferably obtained by simulation provided by an artificial intelligence which bases the determination of the e _max as a function of the material consumption rate VCA as well as as a function of the parameter z according to the present invention.

It can be observed that for each of the three measurement marks, the difference (the margin of error) between the simulation (carried out upstream of the orbital weld) and the measurement of the e _max carried out after the welding operation is very minimal, which proves that the present invention makes it possible to ensure precise modeling of the section to be welded as well as a determination of the height of the weld which is the most exact and close to reality.

We can also observe a general bathtub shape of the S traces, this is due to the fact that at the peripheral ends of the welded joint, the thickness is wider than at the center, this is due to a concentration of the excess material displaced during orbital welding, giving a generally diabolo or straw shape to the welded joint (as visible in ).

It should be noted that the prior art does not provide any solution for estimating the maximum thickness of the welded joint or its dependence on the shape of the section.

In general, it is important to note that a configuration where two sections to be welded have a perfect circle shape allows for optimal orbital welding. This configuration ensures perfectly homogeneous and constant mixing, which guarantees a stable temperature rise of the materials. In addition, the circular shape of the sections allows for uniformity of friction over 360°, without any change in shape.

The inventors had the inventive approach of introducing the ray tracing method described above, an unconventional technique in the field of mechanics, to characterize the junction section in order to take into consideration all directions of friction. Indeed, the scanning of the section with rays z _i,α launched from each of all points i of its periphery, is similar to the movements of mixing material between the surfaces in contact during orbital welding, said movements being in all directions and over 360°.

This correlation between the mixing physics during orbital friction and the theoretical calculation of the z parameter, offers the possibility to predict the material mixing behavior even before orbital welding is performed. Thus, the z parameter allows to estimate the welding results ( VCA , e _max ) with sufficient precision at an early stage of the process (when modeling the shape of the joint section and before welding is performed).

Claims (15)

Method for modeling a junction (10) of a blade (4) to a stub (6) on a rotor (2) of a turbomachine, by orbital friction welding, comprising the following step:
determining a material consumption rate VCA as a function of the following orbital friction welding parameters: eccentricity, frequency and pressure, and a geometric parameter z of the section (11) of the blade (4) and the stub (6) at the junction (10);
characterized in that the method further comprises the following step:
determination of a maximum thickness e _max of the junction (10) as a function of the determined material consumption rate VCA , the geometric parameter z being an average of the mean radii z _i sweeping the section (11) of the blade (4) and the stub (6) at the junction (10) at any point i of the periphery (11.1) of said section (11). Modeling method according to claim 1, in which the determined maximum thickness e _max and the determined material consumption rate VCA are all the greater as the geometric parameter z is small and vice versa. Modeling method according to one of claims 1 and 2, in which the mean radii z _i scanning the section (11) of the blade (4) and the stump (6) at the junction (10) at any point i of the periphery (11.1) of said section (11) are strictly contained in said section (11). Modeling method according to one of claims 1 to 3, in which the mean radii z _i scanning the section (11) of the blade (4) and the stub (6) at the junction (10) at any point i of the periphery (11.1) of said section (11) completely scan said section (11). Modeling method according to one of claims 1 to 4, in which the determined maximum thickness e _max and the determined material consumption rate VCA are all the smaller as the eccentricity decreases and vice versa. Modeling method according to one of claims 1 to 5, in which the determined maximum thickness e _max and the determined material consumption rate VCA are all the smaller as the frequency decreases and vice versa. Modeling method according to one of claims 1 to 6, in which the determination of the maximum thickness e _max and the material consumption rate VCA is based on experimental orbital friction welding data, where for each welding operation the material consumption rate VCA is measured and correlated with the eccentricity, the frequency, the pressure and the geometric parameter z . Modeling method according to claim 7, in which the correlations of the experimental data are made so as to provide a model for determining the rate of material consumption VCA and possibly the maximum thickness e _max . Modeling method according to claim 8, in which the model for determining the material consumption rate VCA and possibly the maximum thickness e _max involves the use of artificial intelligence. Method of orbital friction welding of a blade (4) to a stub (6) on a turbomachine rotor (2) to form a junction (10), comprising the following step:
determination of a VCA material consumption rate;
characterized in that the method further comprises the following step:
determination of a maximum thickness e _max of the junction (10) as a function of the determined material consumption rate VCA and as a function of a geometric parameter z corresponding to an average of the mean radii z _i sweeping the section (11) of the blade (4) and the stump (6) at the junction (10) at any point i of the periphery (11.1) of said section (11). Welding method according to claim 10, further comprising a step of comparing the maximum thickness e _max determined with an interval of values of the maximum thickness e _max predefined during a modeling method of the junction (10) of the blade (4) to the stump (6), said modeling method being according to one of claims 1 to 9. Method for dimensioning a blade (4) and a corresponding stub (6) on a turbomachine rotor (2), intended to be joined by orbital friction welding, as a function of a predetermined maximum thickness e _max of the junction (10), characterized in that the dimensioning method comprises an iteration of determining the maximum thickness e _max of the junction (10) according to different dimensions of the junction (10), according to a modeling method according to one of claims 1 to 9. A sizing method according to claim 12, wherein the iteration of determining the maximum thickness e _max of the junction (10) according to different dimensions of the junction (10) is carried out while the eccentricity, the frequency and the pressure remain constant. Dimensioning method according to one of claims 12 and 13, in which the different dimensions of the junction (10), in the iteration of determining the maximum thickness e _max of the junction (10), are selected so as to correspond to different values of the geometric parameter z . Dimensioning method according to one of claims 12 to 14, in which the iteration of determining the maximum thickness e _max of the junction (10) according to different dimensions of the junction (10) is stopped when the maximum thickness e _max determined corresponds to the maximum thickness e _max of the junction (10) predetermined with a given tolerance.