Shot blasting test support

Abstract

The present invention relates to a shot peening test support comprising: - an elongated tubular body (1) extending about an axis (A), delimited by a casing (2), the casing (2) having an opening (3), - a plate (4) fixed to the tubular body (1) opposite the opening (3) on the outside of the casing (2), and - a parallelepiped specimen fixed to the plate (4), one surface of the specimen being oriented towards the opening (3) so that a shot peening flow circulating in the tubular body (1) is projected onto the specimen. Figure for the abstract: Fig. 1

Description

Title of the invention: Shot blasting test support technical field

[0001] The present invention relates generally to the field of test benches, more specifically to test installations using Almen test specimens.

[0002] The invention relates more specifically, but not exclusively, to a test bench comprising a specimen support configured to simulate a long tubular part, for example a turbine shaft. STATE OF THE ART

[0003] Shot peening consists of spraying a media to impact the surface of a part in order to modify its surface condition and induce compressive stresses, thereby improving the fatigue life of the part. In particular, the aim is to break up machining marks that appear during the machining phases of the part and which are crack initiation sites. Completely breaking up these machining marks extends the fatigue life of the part. The results of shot peening depend essentially on three parameters: the type of media, the coverage rate, and the Almen intensity.

[0004] The type of media is arbitrary; it can be glass, steel, or ceramic beads, or honed cut wire, or any type of solid or liquid particles chosen according to the hardness of the material constituting the shot-blasted part, the condition of its surface, and the desired intensity. The media is projected by a projection nozzle, which determines the shape and direction of the shot-blasting jet and is cone-shaped with a variable size. The projection nozzle can be mounted on a six-axis robot, a boom, or a motorized table, which generally allow adjustment of the position and orientation of the shot-blasting jet.

[0005] The coverage rate of the shot-blasted surface measures the extent of the shot blasting on a surface. The coverage is measured by visual assessment, expressed as a percentage, of the percentage of indentations covering the shot-blasted surface. Coverage is considered complete, or 125%, when it corresponds to 1.25 times the time required for the entire treated surface to be covered by the impacts. The human eye can perceive a maximum coverage of 98%, which is why a multiplier is applied to obtain a theoretical coverage of 125%. The stresses introduced by shot blasting initially increase very rapidly in intensity and depth with the coverage rate, up to coverage levels of approximately 90 to 100%. This evolution is then asymptotic. When the coverage rate is less than 100%, there is a potential reduction in mechanical strength and The lifespan of the part can be reduced. This situation, known as under-coverage, is prohibited if complete coverage is required. Conversely, when the coverage rate exceeds 125%, the surface is considered over-covered. Over-coverage can lead to the generation of surface defects, such as surface folds, corner folds, bulges, cracks, nicks, burrs, incrustations, roughness defects, or other non-conforming surface conditions, which are detrimental.

[0006] Shot peening intensity quantifies the energy transmitted to the workpiece. Shot peening intensity is determined by measuring the deformations, known as Almen deflections, of a standardized Almen specimen, for example, according to SAE J442 and SAE J443 recommendations. An Almen specimen (also referred to as a "specimen" hereafter) is thus a parallelepiped block made of SAE 1070 steel, with dimensions of 76.2 millimeters (mm) wide by 18.9 mm long, and a thickness of 1.29 mm, 0.78 mm, or 2.38 mm. The specimen is fixed to a support, also called an Almen block, which is standardized and held in place by four screws.

[0007] A test to determine the shot peening intensity consists of successively shot peening at least four Almen specimens, doubling the shot peening time for each successive specimen. For example, if the first specimen is shot peened for 5 seconds, the second should be shot peened for 10 seconds, the third for 20 seconds, and finally the last specimen for 40 seconds. After each shot peening, the deformation of the Almen specimen is measured in millimeters and plotted against the exposure time on a graph to form a saturation curve. The saturation curve, by representing the Almen intensity as a function of time, shows that after a certain time, the intensity increases only marginally. Indeed, such a saturation curve exhibits a sharp inflection in slope near a point called the "saturation point."Between the saturation point and twice the time between the origin and the saturation point, the Almen arrow increases by a maximum of 10% of its growth before the saturation point; that is, the saturation point is an inflection point from which the intensity tends towards a limiting value. The saturation point corresponds to the Almen intensity.

[0008] The realism of the test depends on the position of the Almen block on which the Almen specimen is placed, since it must be oriented angularly with respect to the projection axis of the media in the same way as the actual part. Similarly, the distance between the projection nozzle and the Almen specimen during the test must be the same as that between the part and the projection nozzle during the shot peening process on the actual part.

[0009] However, it is currently difficult to reproduce this inclination and distance for certain parts with complex geometries. For example, shafts and other cylindrical parts must be shot-peened from the inside. The sometimes complex geometry of the internal surfaces of these cylindrical parts necessitates rebound shot peening of hard-to-reach areas. By "rebound shot peening," we mean that the media stream received by the inaccessible area has already impacted at least one area with a direct jet. It is difficult to predict the trajectory of the media stream in such a case, and even more so to guarantee the Almen intensity.

[0010] Prior to each shot peening of a part, a test campaign is carried out on Almen test pieces fixed with their block to supports representing the different areas of the part in order to verify that the Almen deflection and the coverage rate obtained conform to the desired values. However, as explained above, in the case of a cylindrical part comprising multiple different shot peening geometries, some of which are rebound peening, the existing supports must be specific to each geometry. This necessitates the use of a large number of supports, which, moreover, cannot simulate the confined nature of the shaft's interior. Thus, rebound peening cannot be tested. The number of supports also imposes a high number of operator manipulations and therefore a longer operating time.Therefore, there is a need for a more realistic test specimen support that allows for a test campaign to be conducted while limiting the number of manipulations. Description of the invention

[0011] One object of the invention is to remedy the aforementioned drawbacks by providing a shot peening test support comprising:

[0012] - an elongated tubular body extending around an axis, delimited by an envelope, the envelope including an opening,

[0013] - a plate fixed to the tubular body opposite the opening on the outside of the envelope, and

[0014] - a parallelepiped-shaped test specimen fixed to the plate, a surface of the test specimen being oriented towards the opening so that a shot blasting flow circulating in the tubular body is projected onto the test specimen.

[0015] The test support according to the invention is advantageously complemented by the following features, taken individually or in one of their technically feasible combinations:

[0016] - the test specimen is fixed to the plate by means of a block support in a position where a direction along which the length of the specimen extends is perpendicular to a plane comprising the axis and a normal to the plate, such that that an upper surface of the test specimen protrudes into an internal volume of the tubular body;

[0017] - the plate includes an angular marker configured to indicate an angle of fixing the block support relative to the axis, the block support being configured to be fixed to the plate so that a plane of the upper surface of the specimen is intersecting with the axis;

[0018] - the plate includes two block supports configured to each receive a test tube, a first test tube being oriented towards an upstream end of the tubular body, a second test tube being oriented towards a downstream end of the tubular body;

[0019] - the plate is removably attached to the tubular body;

[0020] - the exterior of the casing includes a housing configured to receive a outer plate, the outer plate comprising a block support configured to receive a test specimen, a surface of the test specimen facing the outside of the tubular body, so that a shot blasting flux received from the outside of the tubular body is also received by the test specimen

[0021] - a cylindrical insert comprising a second opening of the same size as the opening of the tubular body, the second opening leading on one side to the opening and on the other side to the inside of the envelope, the cylindrical insert being configured to fit a part of the inside of the tubular body opposite the opening, so that a shot blasting flow circulating in the tubular body is projected onto the cylindrical insert.

[0022] The invention also relates to a method for measuring shot peening intensity in a test support according to one of the embodiments, comprising the following steps:

[0023] - fixing a test specimen to an Almen block and the Almen block to a block support of a plate;

[0024] - shot peening of the inside of the tubular body;

[0025] - extraction of the test specimen from the block support;

[0026] - measurement of an Almen deflection on the test specimen.

[0027] Finally, the process according to the invention is advantageously complemented by the following steps:

[0028] - an angular adjustment step of the block support on the plate and a step of mounting the plate onto the tubular body;

[0029] - prior to the step of fixing a test specimen, the insertion of an insert into the tubular body. DESCRIPTION OF THE FIGURES

[0030] Other features, purposes and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0031] Fig. 1 is a schematic overview of a test support according to one embodiment of the invention;

[0032] The [Fig.2] is a schematic detail view of a test support according to one embodiment of the invention;

[0033] The [Fig.3] is a cross-sectional view of the test support of the [Fig.2];

[0034] Figure 4 is a schematic view of a test support according to another mode of realization of the invention; and

[0035] Fig. 5 is a diagram showing the steps of a method for implementing an embodiment of the invention.

[0036] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0037] Figures 1 to 3 illustrate a shot peening test support according to a first embodiment of the invention. This support comprises an elongated tubular body 1 extending about an axis A. By "elongated," it is understood that the tubular body 1 is a hollow cylindrical piece whose bases are separated by a distance greater than its diameter. The tubular body 1 is delimited by a casing 2, the casing 2 comprising an opening 3. The opening 3, for example, a rectangular opening or light whose long sides are parallel to the axis A, corresponds to an empty space in the casing 2 allowing communication between the inside of the tubular body 1 and the outside.

[0038] A plate 4, preferably of the same shape and dimensions as the opening 3, is fixed to the outside of the casing 2 on the tubular body 1 so as to face the opening 3. On this plate 4 is fixed a parallelepiped specimen 5, preferably an Almen specimen, oriented towards the opening 3 so that a shot blasting flow circulating in the tubular body 1 is projected onto the specimen 5. More precisely, the specimen 5 is fixed so that one of its large faces, called the upper surface 51, is exposed to the internal volume of the tubular body 1. In other words, the opening 3 opens from the inside of the tubular body 1 onto the upper surface 51 of the specimen 5. The upper surface 51 can thus protrude into an internal volume of the tubular body 1 in order to receive a more direct flow.

[0039] Preferably, the test specimen 5 does not protrude entirely from the casing 2, i.e., a majority of its volume is outside the internal volume of the tubular body 1 thanks to the position of the plate 4. Thus, the realism of a test aimed at measuring the Almen deflection to establish the intensity of shot peening is greatly improved, Since the tubular nature of the tubular body 1 allows the media to rebound against the inner circumference of the part during the test, the specimen 5 is impacted not only by direct shot peening but also by an indirect media flow resulting from rebounds, and the Almen intensity deduced from its deformation is very close to that exerted on an authentic part under real-world conditions.

[0040] Advantageously, the specimen 5 is fixed to the plate 4 by means of an Almen block 8 held by a block support 6 in a position where a direction along which the length of the specimen 5 extends is perpendicular to a plane comprising the axis A and a normal to the plate 4, which corresponds to the cutting plane of [Fig. 3]. In other words, the rectangular prism of the specimen 5 is placed "across" the tubular body 1 and the axis A. The block support 6 is fixed to the plate 4, preferably in a removable manner. The specimen 5 is mounted on the Almen block 8 so as to be immovable during the test, for example, by means of four screws holding the corners of the specimen 5 fixedly to the Almen block 8. The Almen block 8 can also be fixed by a suitable means to the block support 6.The block support 6 is adjustable in inclination about an axis perpendicular to the plane containing axis A and normal to plate 4, allowing the specimen 5 to be oriented at a desired angle. Plate 4 preferably includes an angular marker configured to indicate the fixing angle of the block support 6 relative to axis A. The block support 6 is configured to be fixed to plate 4 such that a plane of the upper surface 51 of the specimen 5 is incident with axis A; that is, axis A and the plane of the upper surface 51 are intersecting. Modifying the angle of the specimen 5 allows different geometries corresponding to different parts to be reproduced from a single test support.

[0041] The plate 4 may comprise two block supports 6, each having a test specimen 5. A first test specimen 5a is preferentially oriented towards an upstream end of the tubular body 1, while a second test specimen 5b is oriented towards a downstream end of the tubular body 1. Upstream and downstream are defined here according to the direction of the shot blasting media flow circulating in the tubular body 1, the flow circulating from upstream to downstream, the upstream end being towards the blasting nozzle. Thus, test specimen 5a is in a position where it receives a media flow with maximum incidence and velocity, unlike the other test specimen 5b, which receives an indirect media flow with a lower force. Studying the Almen deflection of these two test specimens 5a and 5b makes it possible to obtain a maximum and a minimum intensity, which avoids the need for more than two test specimens 5a and 5b to study intermediate intensities.It is also possible to reproduce specific geometries of different parts.

[0042] In order to facilitate the handling of the test pieces 5a, 5b, in particular the adjustment of their inclination and their fixing on the block supports 6, the plate 4 can be removably fixed to the tubular body 1, for example by means of screws whose removal allows disassembly in translation relative to the opening 3.

[0043] With reference to [Fig. 1], the exterior of the casing 2 may include a housing 22 configured to receive an outer plate 41. The housing 22 is, for example, a rectangular notch in the casing 2, the notch not opening into the interior of the tubular body 1. The outer plate 41 is similar to the plate 4, in that it is configured to receive a test specimen 5 fixed to a block support 6. However, contrary to what was explained above, the surface of the test specimen 5 faces the exterior of the tubular body 1 (i.e., the surface of the test specimen 5 is turned outwards from the tubular body 1), so that a shot blast projected onto the exterior of the tubular body 1 is also received by the test specimen 5. Thus, the test support makes it possible not only to simulate shot blasting from the inside of a cylindrical part but also to the outside.This further improves the realism of the tests, reduces the number of devices required, and saves time, as both operations can be performed simultaneously.

[0044] With reference to [Fig. 4], the test support may also include a cylindrical insert 7 comprising a second opening 71 of the same size and shape as the opening 3. The second opening 71 follows the contours of the opening 3 and the interior of the casing 2. In other words, the cylindrical insert 7 reproduces the geometry of the casing 2 and the opening 3 with a smaller diameter, so that it can be inserted into the tubular body 1 at the opening 3 without obstructing it. Thus, the second opening 71 leads on one side to the opening 3 and on the other side to the interior of the casing 2. The cylindrical insert 7 comprises the same material as the part for which the test is conducted, and an inner surface of the insert 7 may have a profile reproducing a specific part.Thus, the cylindrical insert 7 allows the test support to be perfectly representative of the part, in particular by allowing the flow of media circulating in the tubular body 1 to be projected onto the specimen 5 indirectly, ensuring that this indirect flow behaves as in the authentic part.

[0045] With reference to [Fig. 5], the method for measuring shot peening intensity in a test support as described above comprises a step of fixing (step S1) a test specimen 5 onto an Almen block 8 and the Almen block 8 onto a block support 6 of a plate 4, a step of fixing the cylindrical insert 7 (step S2), and a step of angularly adjusting (step S3) the block support 6 on the plate 4, preferably using the angular reference mark. These steps may also include mounting a test specimen 5 onto an outer plate 41 and mounting of this outer plate 41 in a housing 22. A mounting step of the plate 4 on the tubular body 1 (step S4) can be carried out if the plate 4 is removable.

[0046] Once the test specimen(s) 5 and the cylindrical insert 7 are in the position required for the test, a shot peening step is performed (step S5). During this step, a flow of media is projected inside, and optionally outside, the tubular body 1. After a predetermined time, the shot peening ceases and the test specimen 5 is removed from the block support 6 (step S6). The test specimen is then analyzed to deduce the characteristics of the shot peening from its deformations and surface finish. In particular, the Almen deflection of the test specimen 5 is measured (step S7) to determine the shot peening intensity.

[0047] The support according to the invention thus makes it possible to reproduce, with a single device, numerous internal geometries in order to conduct realistic tests providing Almen intensity values ​​very close to those applied in real production situations. Compared to the prior art, the quantity of test specimens and support required is considerably reduced, as is the number of manipulations.

[0048] The support and method according to the invention are therefore particularly useful for evaluating shot blasting, particularly when the shot blasting medium is composed of solid particles, and this on all parts of cylindrical shape and with complex geometries, for example turbine shafts.

Claims

Demands

1. Shot blasting test support comprising: - an elongated tubular body (1) extending around an axis (A), delimited by an envelope (2), the envelope (2) comprising an opening (3), - a plate (4) fixed to the tubular body (1) opposite the opening (3) outside the envelope (2), and - a parallelepiped specimen (5) fixed to the plate (4), a surface of the specimen (5) being oriented towards the opening (3) so that a shot blasting flow circulating in the tubular body (1) is projected onto the specimen (5).

2. Test support according to claim 1, wherein the specimen (5) is fixed to the plate (4) by means of a block support (6) in a position where a direction along which the length of the specimen (5) extends is perpendicular to a plane comprising the axis (A) and a normal to the plate (4), such that an upper surface (51) of the specimen (5) protrudes into an internal volume of the tubular body (1).

3. Test support according to claim 2, wherein the plate (4) includes an angular marker configured to indicate an angle of attachment of the block support (6) with respect to the axis (A), the block support (6) being configured to be attached to the plate (4) such that a plane of the upper surface (51) of the specimen (5) is intersecting with the axis (A).

4. Test support according to any one of claims 2 or 3, wherein the plate (4) comprises two block supports (6) configured to each receive a test specimen (5), a first test specimen (5) being oriented towards an upstream end of the tubular body (1), a second test specimen (5) being oriented towards a downstream end of the tubular body (1).

5. Test support according to any one of claims 1 to 4, wherein the plate (4) is removably fixed to the tubular body (1).

6. Test support according to any one of claims 1 to 5, comprising on the outside of the casing (2) a housing (22) configured to receive an outer plate (41), the outer plate (41) comprising a block support (6) configured to receive a test specimen (5), a surface of the test specimen (5) being opposite the outside of the tubular body (1), so that a shot blasting flux received by the outside of the tubular body (1) is also received by the test specimen (5).

7. Test support according to any one of claims 1 to 6, comprising a cylindrical insert (7) having a second opening (71) of the same size as the opening (3) of the tubular body (1), the second opening (71) opening on one side into the opening (3) and on the other side into the interior of the casing (2), the cylindrical insert (7) being configured to fit a part of the interior of the tubular body (1) opposite the opening (3), so that a shot blasting flow circulating in the tubular body (1) is projected onto the cylindrical insert (7).

8. Method for measuring shot peening intensity in a test support according to any one of claims 2 to 7, comprising the following steps: - fixing (S1) of a test specimen (5) on an Almen block (8) and of the Almen block (8) a block support (6) of a plate (4); - shot peening (S5) of the inside of the tubular body (1); - extraction (S6) of the test specimen (5) from the block support (6); - measurement (S7) of an Almen deflection on the test specimen (5).

9. Method according to claim 8, comprising an angular adjustment step (S3) of the block support (6) on the plate (4) and a mounting step (S4) of the plate (4) on the tubular body (1).

10. A method according to any one of claims 8 and 9, comprising prior to the step of fixing a test specimen (5) the insertion (S2) of an insert (7) into the tubular body (1).

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