Eprouvette test

Abstract

This document relates to a method for manufacturing a test specimen (4) representative of a hollow blade, the specimen (4) being hollow and comprising at least one platform (86, 88) and a blade area (85), the method comprising the steps: - producing a ceramic core by injection into a first mold (10); - producing a wax model by injection into a second mold (28), the core being arranged in the second mold (28); - producing a shell by dipping the wax model and the core into a slip to form a third ceramic mold, then removing the wax model and consolidating the slip to form the shell; - pouring metal into the shell to form the specimen (4), the core forming a hollow area of ​​the specimen (4); - removing the shell by a knockout operation and dissolving the core. Abstract figure: Figure 5

Description

Description Title of the invention: Test tube technical field This disclosure falls within the domain of representative aircraft blade test specimens. Previous technique Traditionally, the lost-wax casting technique begins by creating a wax model, or a model made of another easily removable material, of the part to be produced. This model includes an internal core made of ceramic or molybdenum-based metal and its alloys, which represents the cavities desired to appear inside the blade. The wax model is then repeatedly dipped in slips made from a suspension of ceramic particles to create, through processes known as smearing and drying, a shell mold. The next step is dewaxing the shell mold, an operation by which the wax or material constituting the original model is removed from the shell. This material must be able to be removed like wax without degrading the properties of the core, at a temperature between 70 and 200°C. After this removal, a ceramic mold is obtained whose cavity reproduces all the shapes of the blade and which still contains the ceramic core intended to generate its internal cavities. The mold then undergoes a high-temperature heat treatment, or "firing," which gives it the necessary mechanical properties. The shell mold is then ready for casting the metal part. After checking the internal and external integrity of the shell mold, the next step is to pour molten metal into the mold, filling the voids between the inner wall of the shell mold and the core, and then solidify it. In the field of lost-wax casting, several solidification and casting techniques are currently used, depending on the nature of the alloy, the internal cavities, and the desired properties of the resulting casting. After the alloy is poured, the shell is broken off using a shakeout operation. In a subsequent step, the ceramic or metallic core remaining within the resulting blade is chemically removed. The resulting metallic blade then undergoes finishing operations to produce the finished part. During the manufacturing of blades, recrystallization problems due to thermomechanical stresses and deformations during the solidification phase can occur and degrade the mechanical properties of said blades. The composition Test specimens are therefore necessary to reveal or conceal these recrystallization defects, as well as to validate simulation models. These specimens thus allow validation of the blade manufacturing process without the need to directly produce a blade that might be discarded in case of defects. However, all prior art specimens are solid and not hollow, which makes them unrepresentative of hollow aircraft blades. Summary This disclosure improves the situation. A method is proposed for manufacturing a test specimen, representative of a hollow blade, the specimen being hollow and comprising at least a platform and a blade area, The process includes the following steps: - to produce a ceramic core by injection into a first mold, the first mold comprising at least one pressure sensor and at least one temperature sensor capable of measuring respectively the pressure and temperature in a cavity of said first mold; - to produce a wax model by injection into a second mold, the core being arranged in the second mold, said core being intended to form a hollow area in the test specimen and said second mold comprising at least one pressure sensor and at least one temperature sensor capable of measuring respectively the pressure and temperature in a cavity of said second mold; - to create a shell by dipping the wax model and the core in a slip to form a third ceramic mold, then removing the wax model and consolidating the slip to form the shell, the core being attached to the shell; - pouring a metal into the shell to form the test specimen, the core forming a hollow area of ​​the test specimen; - remove the shell by a debossing operation and dissolve the kernel. The hollow test specimen is representative of a hollow blade. This hollow test specimen undergoes all the manufacturing steps that a hollow blade would undergo. The first and second molds are equipped with sensors, enabling improved monitoring and ensuring the quality and correct sizing of the test specimens. The sensors in the second mold also allow for monitoring the wax front's progress, temperature, and pressure during this process. The head of the kernel may have a T-shape. The T-shape of the core allows the core to anchor itself well in the second mold and not move so that it is ultimately well positioned in the test specimen. The nucleus can have an elongated shape, the length of the nucleus being defined by the dimension of said core along a longitudinal axis X, the width of the core being defined by the dimension of said core along an axis Y, the thickness of the core being defined by the dimension of said core along an axis Z, the axes X,Y,Z forming an orthonormal frame, the thickness of the core along the Z axis being greater than 8 mm and the width of the core along the Y axis being greater than 20 mm. By adjusting the dimensions of the core, it is possible to vary the thickness and width of the first mold and therefore to vary the dimensions of the hollow area of ​​the test specimen. The second mold may have an elongated cavity, the length of the second mold being defined by the dimension of said second mold along a longitudinal x-axis, the width of the second mold being defined by the dimension of said second mold along a y-axis, the thickness of the second mold being defined by the dimension of said second mold along a z-axis, the x, y, z axes forming an orthonormal coordinate system, at least one pressure sensor and at least one temperature sensor being positioned in the second mold with symmetry about the x-axis and the y-axis passing through a median zone of the core along the x-axis. This symmetry of the pressure and temperature sensors makes it possible to verify the symmetry of the injection front. By y-axis passing through a median zone of the kernel along the x-axis, we mean an axis passing through the middle of the width of the kernel. The second mold may include positioning contact points in a cavity bottom and displacement sensors close to these positioning contact points. These positioning contact points serve as reference points to verify the correct positioning of the second mold, thus ensuring that the injection process is proceeding correctly. The displacement sensors associated with these positioning contact points allow the injection to be tracked relative to said contact points. The elongated specimen along a longitudinal axis may include two hook heads positioned at the two ends of said longitudinal axis and / or at least one heel. The two gripping heads allow the specimen to be used as is, without prior machining, and to be used directly during mechanical tests. These two heads serve as gripping areas. Brief description of the drawings Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which: [Fig.1] shows an imprint of a kernel, according to one embodiment. [Fig.2] shows three initial molds suitable for forming three ceramic cores, according to one embodiment. [Fig.3] shows an injection of wax into a second mold, according to a method of realisation. [Fig.4] shows the second mold in the absence of sensors. [Fig.5] shows a test specimen obtained from a manufacturing process, according to the invention. [Fig.6] shows a cluster comprising eight test specimens as described in [Fig.5]. Description of the implementation methods Figure 1 shows an imprint of a core 2, said core being intended to form a hollow area of ​​a test specimen 4. This imprint of the nucleus 2, or the nucleus itself, has three dimensions: length, width, and thickness. The length is defined by the dimension of the nucleus along the longitudinal axis X. The width of this nucleus is defined by the dimension of the nucleus along the Y axis. The thickness is defined by the dimension of the nucleus along the Z axis. The X, Y, and Z axes form an orthonormal coordinate system. The thickness of the nucleus along the Z axis is greater than 8 mm. The width of the nucleus along the Y axis is greater than 20 mm. This imprint of the nucleus, and therefore this nucleus, has a head 6 and a body 8. The head of the nucleus 6 is T-shaped. The body 8 of the nucleus extends along the longitudinal axis X. Figure 2 shows a first mold 10 intended for forming the ceramic core, and more specifically, in this case, three first molds 10 capable of forming three ceramic cores. The shape of the first mold 10 is complementary to the shape of its associated core. The first mold 10 therefore shares the same orthonormal coordinate system X, Y, Z as the core. Thus, while the core is a solid part, the first mold 10 has a cavity 12 comprising a T-shaped hollow head 14 and a hollow body 16 extending longitudinally along the longitudinal axis X. The first mold 10 is configured to allow for control of the core thickness. Each first mold 10 includes a series of specific instruments. Each first mold 10 includes in said cavity 12 at least one pressure sensor configured to measure pressure and / or a temperature sensor configured to measure temperature. A sensor can also perform both functions simultaneously, namely measuring temperature and pressure. The sensors of the first mold 10, positioned in said cavity 12 of the first mold 10, are more clearly visible on the core 2 impression in [Fig. 1]. In the present example, each first mold 10 has three sensors 18, 20, 22 intended to simultaneously measure pressure and temperature, and two sensors intended to measure the temp- A temperature sensor 24, 26, also called a thermocouple, is used. A first pressure and temperature sensor 18 is positioned at the hollow head 14 of the first mold. A second pressure and temperature sensor 20 is positioned in the hollow body 16 of the first mold 10, centered along the X and Y axes. A third pressure and temperature sensor 22 is positioned at one lower end of the hollow body 16 of the first mold, centered along the width of the Y axis. Two other temperature sensors 24, 26 are positioned on either side of the second sensor 20, along the Y axis. Each of these sensors is specifically designed to measure the heat exchange coefficient between the ceramic paste injected to form the core and this first mold, thus validating or invalidating the dimensions of said first mold. These sensors are configured to determine both the thermal properties of said first mold 10 and of the ceramic core. Figure 3 shows the injection of wax into a second mold 28. The second mold 28 has three dimensions: length, width, and thickness. The length is defined by the dimension of the second mold along the longitudinal x-axis. The width of the second mold is defined by the dimension of the second mold along the y-axis. The thickness is defined by the dimension of the second mold along the z-axis. The x, y, and z axes form an orthonormal coordinate system. This second mold 28 has an elongated cavity 30 along the longitudinal axis x. The ceramic core associated with the core impression, as described in [Fig. 1], is arranged in this cavity 30. The core head 6 is anchored in the second mold 28, and the T-shaped form of this core head 6 is configured to limit any movement of the core within the second mold 28. This core is intended to form a hollow area of ​​a wax model. The second mold 28 includes two hollow attachment heads 32, 34 positioned at the two ends of the longitudinal axis. The second mold 28 has a first 36 and a second 38 hollow sections, each extending along the y-axis. These first 36 and second 38 hollow sections are positioned between the two hollow attachment heads 32, 34. These first 36 and second 38 hollow sections are each capable of forming a heel or a platform. The second mold 28 includes a series of instruments. The two hollow gripping heads 32, 34 each have two sensors 40, 42, 44, 46 measuring temperature and pressure distributed on either side of the longitudinal axis x, aligned along an axis y. These four temperature and pressure sensors 40, 42, 44, 46 are positioned at the four ends of the two hollow gripping heads 32, 34 furthest from the center of gravity of the second mold 28. Indeed, each hollow gripping head 32, 34 has a substantially rectangular shape, and each corner of the hollow gripping head 32, 34 corresponds to an end. Thus, each hollow gripping head 32, 34 has two ends far from the center of gravity of the second mold 28 and two ends closer to the center of gravity of the second mold 28. At the two ends closest to the center of gravity of each hollow attachment head 32, 34 are positioned two temperature sensors 48, 50, 52, 54, also called thermocouples. Each hollow attachment head 32, 34 therefore has two temperature and pressure sensors 40, 42, 44, 46 and two thermocouple sensors 48, 50, 53, 54. A pressure and temperature sensor 56 is positioned at the core head 6, at the inlet of a conduit 58 that carries the wax into the second mold 28. Two temperature and pressure sensors 60, 62 are positioned in a mid-zone of the core along the x-axis, on either side of the x-axis. All the temperature and pressure sensors and thermocouple sensors are positioned in the second mold 28 with symmetry along the x-axis and the y-axis passing through the median area of ​​the core along the x-axis. In one particular embodiment, the number of pressure and temperature sensors and the number of thermocouple sensors can be increased or decreased. Regardless, the symmetry about the x-axis and the y-axis passing through the central region of the core along the x-axis is maintained. The second mold 28 has three displacement sensors 64, 66, 68 configured to measure the movement of the core relative to the second mold 28 during wax injection. These displacement sensors 64, 66, 68 are positioned along the longitudinal axis x in a cavity 30 of the second mold 28, at the core head 6, near the center of gravity of the second mold 28, and at the core body 8, on the side opposite the core head 6. A positioning contact point 70, 72, 74 is arranged near each displacement sensor 64, 66, 68. Figure 4 represents the second mold 28 in the absence of sensors. Within such a second mold 28, the core moves and performs movements along the longitudinal x axis. Figure 5 shows the test specimen 4 obtained by a manufacturing process according to the invention. Such a test specimen 4 has an elongated shape along a longitudinal axis x'. This test specimen 4 comprises two gripping heads 76, 78 positioned at the two ends of said longitudinal axis x', the two gripping heads 76, 78 being configured for performing mechanical tests. One 78 of the two gripping heads 76, 78 has a notch 80. The test specimen 4 has two butts 82, 84, each close to a gripping head 76, 78. Each butt 82, 84 comprises a platform extending transversely to the longitudinal axis x° of the test specimen 4. The two butts 82, 84 can also be called platforms 86, 88. The area between the two heels 82,84 is called the blade area 85. This test specimen 4 is hollow since the core has been replaced by a hollow area. Specimen 4 has three dimensions: length, width, and thickness. The length is defined by the dimension of specimen 4 along the longitudinal axis x'. The width of specimen 4 is defined by its dimension along the y' axis. The thickness is defined by its dimension along the z' axis. The x, y', and z' axes form an orthonormal coordinate system. Specimen 4 has precise dimensions. Specimen 4 exhibits symmetry about the longitudinal axis x' and the axis y' passing through a median zone of the specimen along the x' axis. The length of specimen 4 can, for example, correspond to that of a high-pressure turbojet turbine blade. The width of specimen 4 can, for example, correspond to a chord of a high-pressure turbojet turbine blade. The thickness of specimen 4 can, for example, correspond to the range encountered for a high-pressure turbojet turbine blade. The resulting test specimen 4 is representative of a hollow blade. This specimen 4 is designed to more easily test the entire manufacturing process of a hollow blade at a lower cost, since it is not necessary to use a blade that might be discarded. Because this specimen 4 has a simpler structure than a hollow blade, there is less variation with this specimen 4 than with a hollow blade. By variation, we mean that there is less dimensional variability when manufacturing a number of specimens. If, for example, one hundred specimens 4 are manufactured, these specimens 4 will have approximately the same dimensions. The two gripping heads 76, 78 of specimen 4 are configured for use as is, without prior machining or surface treatment to achieve the desired finish. This simplifies the manufacturing process. The two gripping heads 76, 78 are also designed to serve as gripping areas. Figure 6 shows a cluster comprising eight 4-maximum test specimens as described in Figure 5. This cluster is instrumented with thermocouple sensors. This document relates to a manufacturing process for test specimen 4 as described in [Fig.5] which is representative of a blade. This manufacturing process for test specimen 4 differs from that described in the prior art in that the core whose imprint is described in [Fig.1] has a specific shape with a T-shaped head 6 limiting any movement of the core within the first mold 10. The specific shape of the head 6 of the core allows for better constraint of said core in the first mold 10 by limiting parasitic movements along the X and Y axes of the first mold 10. The first mold 10 is instrumented as described previously with at least one temperature sensor and at least one pressure sensor. These sensors allow for to collect a set of data that can be processed to verify the proper execution of said manufacturing process and to verify that the part obtained conforms to the desired model. The second mold 28 is also instrumented as described previously, with at least one pressure sensor and at least one temperature sensor. These sensors allow for better control of the wax front advance speed in the second mold, the correct positioning of the core in said second mold 28, and therefore, ultimately, the production of a specimen 4 with the correct dimensions and according to a process that allows for reproducible specimens 4.

Claims

Claims

1. Method for manufacturing a test specimen (4), representative of a hollow blade, the specimen (4) being hollow and comprising at least one platform (86, 88) and a blade zone (85), the method comprising the steps: - producing a ceramic core by injection into a first mold (10), the first mold (10) comprising at least one pressure sensor (18, 20, 22) and at least one temperature sensor (24, 26) capable of measuring respectively the pressure and the temperature in a cavity (30) of said first mold (10); - producing a wax model by injection into a second mold (28), the core being arranged in the second mold (28), said core being intended to form a hollow zone in the test piece and said second mold (28) comprising at least one pressure sensor (40,42,44,46,56,60,62) and at least one temperature sensor (48,50,52,54) capable of measuring respectively the pressure and the temperature in a cavity of said second mold;- producing a shell by dipping the wax model and the core into a slip so as to form a third ceramic mold, then removing the wax model and consolidating the slip so as to form the shell, the core being integral with the shell; - casting a metal into the shell to form the test piece (4), the core forming a hollow area of the test piece (4); - removing the shell by a shake-out operation and dissolving the core.;

2. A method according to claim 1, wherein the head (6) of the core has a T-shape.

3. Method according to one of the preceding claims, in which the core has an elongated shape, the length of the core being defined by the dimension of said core along a longitudinal axis X, the width of the core being defined by the dimension of said core along a Y axis, the thickness of the core being defined by the dimension of said core along a Z axis, the axes X, Y, Z forming an orthonormal reference frame, the thickness of the core along the Z axis being greater than 8 mm and the width of the core along the Y axis being greater than 20 mm.

4. Method according to one of the preceding claims, in which the second mold (28) has a cavity (30) of elongated shape, the length of the second mold (28) being defined by the dimension of said second mold (28) along a longitudinal axis x, the width of the second mold (28) being defined by the dimension of said second mold along a y axis, the thickness of the second mold (28) being defined by the dimension of said second mold (28) along a z axis, the axes x,y,z forming an orthonormal reference frame, the at least one pressure sensor (40,42,44,46,56,60,62) and the at least one temperature sensor (48,50,52,54) being positioned in the second mold (28) with symmetry along the x axis and the y axis passing through a median zone of the core along the x axis.

5. The method of claim 4, wherein the second mold (28) includes positioning contact points (70,72,74) in a bottom of the cavity (30) and displacement sensors (64,66,68) proximate to those positioning contact points (70,72,74).

6. Method according to one of the preceding claims, in which the test piece (4) of elongated shape along a longitudinal axis x' comprises two hooking heads (76, 78) positioned at the two ends of said longitudinal axis x' and / or at least one heel (82, 86).

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