Method for testing residual stress of single crystal blade

Abstract

The invention discloses a single crystal blade residual stress test method, which belongs to the technical field of stress detection, and comprises the following steps: 1, selecting a single crystal blade sample to be detected, and treating the single crystal blade sample to be detected into a standard sample; 2, assembling a testing device, and correcting the relative position of the single crystal blade sample to be detected and the testing device, so as to test the standard sample treated in the step 1; 3, calculating the residual stress of the sample according to the test data in the step 2 and the material constant of the single crystal blade sample to be detected; according to the single crystal blade residual stress testing method provided by the invention, through the arrangement of the left-right moving mechanism, the front-back moving mechanism and the rotating mechanism, the movement of the single crystal blade sample to be detected in different directions can be realized, and then the two laser theodolites are accurately positioned; the problem of low residual stress detection accuracy of a single crystal blade sample to be detected can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of stress detection, and in particular to a method for testing residual stress of single crystal blades. Background Art

[0002] The turbine working blades of advanced aero-engines are hollow thin-walled structures with complex cooling structures. In addition to the partition walls, longitudinal ribs, transverse ribs, etc. between the blade pressure surface and suction surface adopting complex internal cooling channel structure designs, film cooling technology is also used. There are multiple rows of film holes distributed on the blade body, and the blade body surface is coated with a coating. Due to the complex shape of the blade, residual stress problems exist in all processes of the entire manufacturing process from core, wax mold, and mold shell preparation to melting and casting, heat treatment, and machining.

[0003] The residual stress in the blade will bring many adverse effects, such as the generation of defects inside the blade, the attenuation of mechanical properties, and the deformation of the blade profile. In addition, in the service process under the environment of high temperature, large load, strong gas flow scouring and accompanied by combustion gas, the residual stress generated during the manufacturing process will cause fatigue cracks to occur in the stress concentration parts such as partition walls, film holes, blade crowns, and tenons, resulting in a decrease in the bearing capacity of the blade, a reduction in fatigue life, and even accidents. The problem of residual stress detection is one of the prominent problems existing in the manufacturing process of aviation components at present.

[0004] However, the existing detection methods have high requirements for spatial positioning, which also leads to low detection accuracy of the residual stress of single crystal blades. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for testing residual stress of single crystal blades to solve the problems existing in the above background art.

[0006] To achieve the above purpose, the present invention provides a method for testing residual stress of single crystal blades, including the following steps:

[0007] Step 1: Select a representative single crystal blade sample to be detected, and process the single crystal blade sample to be detected into a standard specimen to ensure that the surface of the specimen is flat and has no obvious defects. Usually, it is necessary to polish the surface of the sample to reduce the influence of surface roughness on the test results;

[0008] Step 2: Assemble the test device, and correct the relative position between the single crystal blade sample to be detected and the test device, so as to test the standard specimen processed in Step 1;

[0009] Step 3: Calculate the residual stress of the sample according to the test data in Step 2 combined with the material constants of the single crystal blade sample to be detected.

[0010] Preferably, the testing device in step two includes a sample stage. A left - right moving mechanism is arranged on the top of the sample stage. A front - back moving mechanism is arranged above the left - right moving mechanism. A rotating mechanism is arranged above the front - back moving mechanism. A placement stage for placing the single - crystal blade sample to be detected is arranged on the rotating mechanism. Support platforms, a first laser theodolite, and a second laser theodolite are sequentially arranged on three sides of the sample stage. An X - ray diffractometer is arranged above the support platform. The X - ray diffractometer is equipped with a high - precision goniometer and a high - resolution detector.

[0011] Preferably, the sample stage includes a bottom plate and a top plate arranged above the bottom plate. The bottom plate and the top plate are connected by two groups of symmetrically arranged first support rods and second support rods. And the first support rod and the second support rod in each group are cross - rotatably connected. One ends of the first support rod and the second support rod are respectively rotatably connected to the bottom plate and the top plate, and the other ends are respectively slidably connected to the bottom plate and the top plate. One ends of two second support rods close to the bottom plate are provided with a cylinder through a first connecting rod. The piston rod of the cylinder is connected to a second connecting rod arranged between two first support rods.

[0012] Preferably, the left - right moving mechanism includes mounting plates arranged on both sides of the top plate. A driving motor is arranged on one side of each of the two mounting plates. The output shaft of the driving motor is connected to a threaded rod. The free end of the threaded rod is connected to the top plate through a mounting seat. Two sliding rods are connected between the two mounting plates. The front - back moving mechanism is arranged on the sliding rods.

[0013] Preferably, a first gear is meshed between the two threaded rods. A second gear is connected above the first gear through a connecting shaft. The second gear is connected to the front - back moving mechanism.

[0014] Preferably, the front - back moving mechanism includes two sliding seats sleeved on the two sliding rods. A cross - plate is arranged between the two sliding seats. The connecting shaft passes through the cross - plate. A square frame is arranged above the two sliding seats. Two long sides of the square frame are respectively connected to the two sliding seats through sliders and U - shaped blocks. A rack meshing with the second gear is arranged on one long side of the square frame connected to the U - shaped block.

[0015] The driving methods of the left - right moving mechanism and the front - back moving mechanism are as follows:

[0016] (1) By driving the two threaded rods to rotate forward and reverse in the same direction by two driving motors, driving the first gear arranged between the two threaded rods to move, thereby driving the front - back moving mechanism and the placement stage above it to move left and right;

[0017] (2) By driving the two threaded rods to rotate in opposite directions by two driving motors, thereby causing the first gear to rotate, driving the movement of the second gear on the rack, and realizing the front - back movement of the rotating mechanism and the placement stage above it;

[0018] Preferably, the rotating mechanism includes support plates respectively arranged on two short sides of the square frame. A connecting plate and a flat plate are respectively arranged between and above the two support plates. A rotating base is arranged above the flat plate, and a rotating table is arranged above the rotating base. A motor is arranged on the connecting plate, the output shaft of the motor is connected to the rotating base, and the placement table is arranged above the rotating table.

[0019] Preferably, both the first laser theodolite and the second laser theodolite include a support frame, a level arranged above the support frame, and a laser theodolite main body arranged above the level.

[0020] Preferably, after the position of the single crystal blade sample to be detected is fixed in step three, the X-ray source is turned on by the X-ray diffractometer, so that the X-ray irradiates the surface of the single crystal blade sample to be detected, the position of the diffraction peak is measured, the diffraction angle 2θ at different incident angles is recorded, and the slope M of 2θ to sin 2 Ψ is calculated; Hooke's law is used to convert the residual strain into residual stress:

[0021] σ Ψ = M·K;

[0022] where, σ Ψ is the residual stress, and K is the material constant.

[0023] Therefore, by adopting the above-mentioned method for testing the residual stress of a single crystal blade, the present invention can realize the movement of the single crystal blade sample to be detected in different directions through the arranged left-right movement mechanism, front-back movement mechanism and rotating mechanism, and then accurately position through the two laser theodolites, which can effectively solve the problem of low accuracy in detecting the residual stress of the single crystal blade sample to be detected.

[0024] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flowchart of a method for testing the residual stress of a single crystal blade according to the present invention;

[0026] Figure 2 is a schematic diagram of the overall structure of a testing device applied to the method for testing the residual stress of a single crystal blade according to the present invention;

[0027] Figure 3 is a schematic diagram of the left-right movement mechanism and the front-back movement mechanism of the testing device in an embodiment of the present invention;

[0028] Figure 4 is a schematic diagram of the sample stage of the testing device in an embodiment of the present invention;

[0029] Figure 5 is a schematic diagram of the rotating mechanism of the testing device in an embodiment of the present invention;

[0030] Reference numerals: 1, sample stage; 2, placement stage; 3, support stage; 4, X-ray diffractometer; 5, bottom plate; 6, top plate; 7, first support rod; 8, second support rod; 9, cylinder; 10, mounting plate; 11, drive motor; 12, threaded rod; 13, mounting seat; 14, slide bar; 15, first gear; 16, connecting shaft; 17, second gear; 18, sliding seat; 19, cross plate; 20, square frame; 21, slider; 22, U-shaped block; 23, rack; 24, support plate; 25, connecting plate, 26, flat plate; 27, rotating base; 28, rotating table; 29, motor; 30, support frame; 31, spirit level; 32, laser theodolite body. Detailed implementation manners

[0031] The following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0032] Please refer to Figure 1 , a method for testing the residual stress of a single crystal blade, comprising the following steps:

[0033] Step 1: Select a representative single crystal blade sample to be detected, and process the single crystal blade sample to be detected into a standard specimen to ensure that the surface of the specimen is flat and has no obvious defects. Usually, it is necessary to polish the surface of the sample to reduce the influence of surface roughness on the test results;

[0034] Step 2: Assemble the test device, and correct the relative position between the single crystal blade sample to be detected and the test device, so as to test the standard specimen processed in Step 1; As Figures 2 - 5 shown, the test device includes:

[0035] The sample stage 1 includes a bottom plate 5 and a top plate 6 arranged above the bottom plate 5. The bottom plate 5 and the top plate 6 are connected by two groups of symmetrically arranged first support rods 7 and second support rods 8. The first support rod 7 and the second support rod 8 in each group are cross-rotationally connected. One end of the first support rod 7 and the second support rod 8 are respectively rotationally connected to the bottom plate 5 and the top plate 6, and the other end is respectively slidably connected to the bottom plate 5 and the top plate 6. A cylinder 9 is provided at one end of the two second support rods 8 close to the bottom plate 5 through a first connecting rod. The piston rod of the cylinder 9 is connected to a second connecting rod arranged between the two first support rods 7. By the telescopic movement of the cylinder 9, the height of the sample stage 1 is adjusted, so as to adjust the up and down position of the single crystal blade sample to be detected.

[0036] A left - right moving mechanism arranged on the top of the sample stage 1. The left - right moving mechanism includes mounting plates 10 arranged on both sides of the top plate 6. On one side of each of the two mounting plates 10, a driving motor 11 is arranged. The output shaft of the driving motor 11 is connected to a threaded rod 12. The free end of the threaded rod 12 is connected to the top plate 6 through a mounting seat 13. Two slide rods 14 are connected between the two mounting plates 10. A front - rear moving mechanism is arranged on the slide rods 14. A first gear 15 meshes between the two threaded rods 12. Above the first gear 15, a second gear 17 is connected through a connecting shaft 16. The second gear 17 is connected to the front - rear moving mechanism.

[0037] A front - rear moving mechanism arranged above the left - right moving mechanism. The front - rear moving mechanism includes sliding seats 18 sleeved on the two slide rods 14, and there are two of them. A cross - plate 19 is arranged between the two sliding seats 18. The connecting shaft 16 passes through the cross - plate 19. Above the two sliding seats 18, a square frame 20 is arranged. The two long sides of the square frame 20 are respectively connected to the two sliding seats 18 through sliders 21 and U - shaped blocks 22. On one long side of the square frame 20 connected to the U - shaped block 22, a rack 23 meshing with the second gear 17 is arranged. The slider 21 is sleeved on one long side of the square frame 20, playing a role in auxiliary positioning to prevent the offset of the square frame 20 in other directions except for front - rear movement. The setting of the U - shaped block 22 does not prevent the meshing of the rack 23 and the second gear 17.

[0038] The driving methods of the left - right moving mechanism and the front - rear moving mechanism are as follows:

[0039] (1) Drive the two threaded rods 12 to rotate forward and reverse in the same direction by the two driving motors 11, drive the first gear 15 arranged between the two threaded rods 12 to move, thereby driving the front - rear moving mechanism and the placement table 2 above it to move left and right;

[0040] (2) Drive the two threaded rods 12 to rotate in opposite directions by the two driving motors 11, so that the first gear 15 rotates, driving the movement of the second gear 17 on the rack 23, and realizing the front - rear movement of the rotating mechanism and the placement table 2 above it;

[0041] A rotating mechanism arranged above the front - rear moving mechanism. The rotating mechanism includes support plates 24 respectively arranged on the two short sides of the square frame 20. A connecting plate 25 and a flat plate 26 are respectively arranged between and above the two support plates 24. Above the flat plate 26, a rotating base 27 is arranged. Above the rotating base 27, a rotating table 28 is arranged. A motor 29 is arranged on the connecting plate 25. The output shaft of the motor 29 is connected to the rotating base 27. The placement table 2 is arranged above the rotating table 28.

[0042] A placement table 2 for placing the single crystal blade sample to be detected is provided on the rotating mechanism. Support platforms 3, a first laser theodolite, and a second laser theodolite are sequentially arranged on three sides of the sample table 1. An X-ray diffractometer 4 is provided above the support platform 3. The X-ray diffractometer 4 equipped with a high-precision goniometer and a high-resolution detector is used. The goniometer is used to precisely control the incident angle and diffraction angle of the X-rays; the detector is used to detect the position and intensity of the diffraction peak.

[0043] Both the first laser theodolite and the second laser theodolite include a support frame 30, a spirit level 31 arranged above the support frame 30, and a laser theodolite main body 32 arranged above the spirit level 31. The support frame 30 is a triangular support frame 30, and the overall height of the laser theodolite can be adjusted by adjusting the divergence angle of the triangle.

[0044] Step Three: Calculate the residual stress of the sample based on the test data in Step Two and the material constants of the single crystal blade sample to be detected. Specifically:

[0045] Place the single crystal blade sample to be detected on the placement table 2. Through the left-right moving mechanism, the front-back moving mechanism, the lifting of the sample table 1, and the rotating mechanism, and in combination with the focusing centers of the two laser theodolites, the X-rays emitted by the X-ray diffractometer 4 are irradiated onto the surface of the single crystal blade sample to be detected. Measure the position of the diffraction peak, record the diffraction angle 2θ at different incident angles, and calculate the slope M of 2θ with respect to sin 2 Ψ; Use Hooke's law to convert the residual strain into residual stress:

[0046] σ Ψ = M·K;

[0047] Among them, σ Ψ is the residual stress, and K is the material constant.

[0048] Therefore, the present invention adopts the above-mentioned method for testing the residual stress of a single crystal blade. Through the provided left-right moving mechanism, front-back moving mechanism, and rotating mechanism, the movement of the single crystal blade sample to be detected in different orientations can be realized. Then, through the precise positioning of the two laser theodolites, the problem of low accuracy in detecting the residual stress of the single crystal blade sample to be detected can be effectively solved.

[0049] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: They can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for testing residual stress of a single crystal blade, characterized in that It includes the following steps: Step 1: Select a single crystal blade sample to be detected and process the single crystal blade sample to be detected into a standard specimen; Step 2: Assemble the test device, and correct the relative position between the single crystal blade sample to be detected and the test device, so as to test the standard specimen processed in Step 1; Step 3: Calculate the residual stress of the sample according to the test data in Step 2 combined with the material constants of the single crystal blade sample to be detected.

2. The single crystal blade residual stress testing method according to claim 1, wherein: The test device in Step 2 includes a sample stage. A left - right moving mechanism is arranged on the top of the sample stage. A front - back moving mechanism is arranged above the left - right moving mechanism. A rotating mechanism is arranged above the front - back moving mechanism. A placement stage for placing the single crystal blade sample to be detected is arranged on the rotating mechanism. Support platforms, a first laser theodolite, and a second laser theodolite are sequentially arranged on three sides of the sample stage. An X - ray diffractometer is arranged above the support platform.

3. The single-crystal blade residual stress testing method according to claim 2, characterized in that: The sample stage includes a bottom plate and a top plate arranged above the bottom plate. The bottom plate and the top plate are connected by two sets of symmetrically arranged first support rods and second support rods. And the first support rod and the second support rod in each group are cross - rotationally connected. One ends of the first support rod and the second support rod are respectively rotationally connected to the bottom plate and the top plate, and the other ends are respectively slidably connected to the bottom plate and the top plate. A cylinder is arranged at one end of two second support rods close to the bottom plate through a first connecting rod. The piston rod of the cylinder is connected to a second connecting rod arranged between two first support rods.

4. A method for testing the residual stress of a single crystal blade according to claim 3, characterized in that: The left - right moving mechanism includes mounting plates arranged on both sides of the top plate. A driving motor is arranged on one side of each of the two mounting plates. The output shaft of the driving motor is connected to a threaded rod. The free end of the threaded rod is connected to the top plate through a mounting seat. Two slide rods are connected between the two mounting plates. The front - back moving mechanism is arranged on the slide rods.

5. A method for testing the residual stress of a single crystal blade according to claim 4, characterized in that: A first gear is meshed between the two threaded rods. A second gear is connected above the first gear through a connecting shaft. The second gear is connected to the front - back moving mechanism.

6. A method for testing the residual stress of a single crystal blade according to claim 5, characterized in that: The front - back moving mechanism includes sliding seats sleeved on the two slide rods, and there are two of them. A cross - plate is arranged between the two sliding seats. The connecting shaft passes through the cross - plate. A square frame is arranged above the two sliding seats. Two long sides of the square frame are respectively connected to the two sliding seats through sliders and U - shaped blocks. A rack meshing with the second gear is arranged on one long side of the square frame connected to the U - shaped block.

7. A method for measuring residual stress of a single crystal blade according to claim 6, characterized in that: The rotating mechanism includes support plates respectively arranged on two short sides of the square frame. A connecting plate and a flat plate are respectively arranged between and above the two support plates. A rotating base is arranged above the flat plate. A rotating table is arranged above the rotating base. A motor is arranged on the connecting plate. The output shaft of the motor is connected to the rotating base. The placement stage is arranged above the rotating table.

8. A method for measuring the residual stress of a single crystal blade according to claim 2, characterized in that, Both the first laser theodolite and the second laser theodolite include a support frame, a spirit level arranged above the support frame, and a laser theodolite main body arranged above the spirit level.

9. A method for testing the residual stress of a single crystal blade according to claim 2, characterized in that, After fixing the position of the single crystal blade sample to be detected in Step 3, turn on the X-ray source through the X-ray diffractometer, make the X-ray irradiate on the surface of the single crystal blade sample to be detected, measure the position of the diffraction peak, record the diffraction angle 2θ at different incident angles, and calculate the slope M of 2θ to sin 2 Φ; Use Hooke's law to convert the residual strain into residual stress: σ Ψ = M·K; Among them, σ Φ is the residual stress, and K is the material constant.

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