Tension-bending composite fatigue test device and method for engine blade (centrifugal impeller) simulation sample in high-temperature corrosion environment

Abstract

The invention discloses a stretch-bending composite fatigue test device and method for an engine blade (centrifugal impeller) simulation sample in a high-temperature corrosion environment. The device comprises an axial load system, a transverse vibration system, a temperature control system and a measurement system. The axial load system applies an axial pull-pull load to the simulation sample through a pin, the transverse vibration system provides a transverse bending vibration load for the simulation sample, the temperature control system provides the temperature of an engine in a real working environment for an examination part of the simulation sample, and meanwhile, according to the tension-bending composite fatigue test requirement, the test accuracy is improved. A simulation sample is designed according to a local position load of an engine blade (centrifugal impeller), a salt mist spraying / deposition mode is adopted on the surface of the sample to simulate a sea salt mist corrosion environment, the real stress, temperature and corrosion environment of an engine are accurately reflected, and the test can more accurately simulate the stretch-bending composite fatigue condition of a dangerous part in the working process.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical testing equipment, and in particular relates to a tensile-bending composite fatigue test device and method for a simulated high-temperature corrosion environment of an engine blade (centrifugal impeller). Background Art

[0002] As an important component of the turboshaft engine, the engine blades (centrifugal impellers) can ensure the smooth and reliable operation of the turboshaft engine and the helicopter. At present, the engine is striving to develop in the direction of higher temperature, higher speed and higher stability, and is increasingly facing the service conditions of tropical coastal salt spray environment. Therefore, during the working process, the engine blades (centrifugal impellers) not only have to bear the centrifugal load and the bending vibration load caused by various reasons, but also may suffer from hot salt corrosion fatigue under the combined action of high temperature, salt spray environment and mechanical load, which is more likely to cause the blades to break. The broken fragments will hit other parts when rotating at high speed, causing greater damage to the engine. When the aircraft is performing missions at high altitudes, it is very likely to cause engine failure, leading to accidents, causing casualties and property losses.

[0003] At present, the traditional hot salt corrosion fatigue test mainly targets low-cycle loads. The entire specimen is completely wrapped in a heating furnace, and holes are opened at the upper and lower ends to fix the specimen and apply axial loads. Therefore, the heating and corrosion environment control equipment is large in size. At the same time, in order to ensure the thermal insulation effect of the heating furnace, it is not appropriate to open holes to apply lateral loads. Therefore, it is not conducive to carrying out high- and low-cycle composite fatigue tests in high-temperature hot salt corrosion environments.

[0004] Therefore, we need to propose a tensile-bending composite fatigue testing device and method with a simple structure, which can perform local heating on the simulated specimen test section and apply tensile-bending loads at the same time to accurately reflect the real stress, temperature and corrosion environment of the engine. By analyzing the corrosion fatigue hazardous parts of the engine blades (centrifugal impellers), designing simulated test pieces, and analyzing the strain of the engine blade (centrifugal impeller) simulation pieces through tensile-bending composite fatigue tests in a high-temperature corrosion environment, we can simulate the working state of the real blades and obtain the corrosion fatigue life of the working state. Summary of the invention

[0005] The purpose of the present invention is to provide a device and method for testing the composite fatigue of stretching and bending of simulated specimens of engine blades (centrifugal impellers) in a high-temperature corrosion environment, so as to provide the simulated specimens with the main loads to which real blades are subjected during operation, such as low-cycle centrifugal loads, high-cycle bending vibration loads, and the high temperature and marine hot salt corrosion environment faced by the structure during operation. An axial tensile load is applied to the simulated specimen to simulate the centrifugal load during rotation, an eddy current exciter is used to simulate the bending vibration load perpendicular to the axial direction, an electric heating furnace is used to simulate the temperature environment of the blade during operation, and the accumulated salt film concentration in the marine environment is simulated by quantitatively spraying salt spray on the specimen assessment section, thereby ensuring that the high- and low-cycle composite fatigue test of the simulated specimen of the engine blade (centrifugal impeller) in a high-temperature hot salt corrosion environment can be carried out smoothly, providing a technical basis and safety guarantee for the safe and reliable operation of the turboshaft engine in the marine salt spray environment.

[0006] The technical solution of the present invention is:

[0007] A high temperature corrosion environment tensile bending composite fatigue test device for simulated specimens of engine blades (centrifugal impellers), comprising a simulated specimen 6, characterized in that it also includes an axial load system, a lateral vibration system, a temperature control system and a measurement system;

[0008] The simulation sample 6 is designed according to the local position of the centrifugal impeller, and a salt film is sprayed on the test part and the working temperature is applied to simulate the marine salt spray corrosion and high temperature environment;

[0009] The axial load system includes a fatigue machine 11 and a clamping system; the clamping system includes an upper clamp 22, a bendable device 7 and a lower clamp 21; the bendable device 7 includes a connecting rod 73, an excitation plate 74 and a pressure plate 75; the excitation plate 74 and the pressure plate 75 are provided with grooves;

[0010] The lateral vibration system includes a signal generator 31, a power amplifier 32 and an eddy current exciter 33;

[0011] The temperature control system is a small local heating furnace 42 with a control system;

[0012] The measuring system includes a displacement sensor 51, a digital frequency meter 52, an oscilloscope 53, a computer 57, a dynamic data acquisition and analysis system 56, a dynamic strain gauge 55 and a strain gauge 54;

[0013] The simulated sample 6 is placed in the grooves of the excitation plate 74 and the pressure plate 75 and fixed by pins;

[0014] The upper fixture 22 is connected to the upper end of the fatigue machine 11, and the lower fixture 21 is connected to the lower end of the fatigue machine 11; one end of the connecting rod 73 is connected to the upper fixture 22 by a pin, and the other end is connected to the excitation plate 74 by a pin; the excitation plate 74 is connected to the pressure plate 75 by bolts;

[0015] The signal generator 31, the power amplifier 32 and the eddy current exciter 33 are connected by wires and placed on a support frame, which is fixed on the fatigue machine 11, and the eddy current exciter 33 is located on the side of the excitation plate 74;

[0016] The heating furnace 42 is placed on a support frame, which is fixed on the fatigue machine 11 and is located below the eddy current exciter 33;

[0017] The strain gauge 54 is pasted on the simulation sample 6, located in the middle area between the heating furnace 42 and the eddy current exciter 33, and is connected to the dynamic strain gauge 55, the dynamic data acquisition and analysis system 56 and the computer 57 through wires; the displacement sensor 51 is located on the side of the simulation sample 6, and is connected to the digital frequency meter 52 and the oscilloscope 53 through wires.

[0018] Furthermore, the simulated sample 6 adopts a method of quantitative salt spraying / deposition on the local surface to simulate the accumulated salt film concentration in service in the marine salt spray environment.

[0019] Furthermore, the signal generator 31 generates a sinusoidal signal, the power amplifier 32 amplifies the sinusoidal signal, and the eddy current exciter 33 receives the amplified current to generate a periodically changing electromagnetic force.

[0020] Furthermore, the power amplifier 32 is equipped with an ammeter, and the working state of the power amplifier 32 is monitored by observing the current magnitude, and the amplitude value of the excitation point is adjusted by adjusting the current magnitude to provide an accurate high-frequency vibration load.

[0021] Furthermore, the displacement sensor 51 converts the detected displacement variable into an electrical signal and transmits the electrical signal to the digital frequency meter 52; the digital frequency meter 52 displays the frequency value in digital form; the oscilloscope 53 is used to display the stabilized waveform; the dynamic strain gauge 55 measures the strain of the simulated sample during the test by connecting the strain gauge 54; the dynamic data acquisition and analysis system 56 is used to control the dynamic strain gauge 55 and collect strain values; the computer 57 stores and processes the collected strain values.

[0022] A method for a tensile-bending composite fatigue test of an engine blade (centrifugal impeller) in a simulated high temperature corrosion environment, characterized in that it comprises the following steps:

[0023] Step 1: Design and process simulation specimen 6;

[0024] Step 2: Assemble the test device and fix the simulated sample 6;

[0025] Step 3: Determine the load excitation level and conduct formal composite fatigue tests at different load excitation levels to obtain test data at different load excitation levels;

[0026] Step 4: Repeat the above steps to test other simulated samples 6.

[0027] Furthermore, the step 1 comprises:

[0028] Step 1-1: Design a simulated sample 6 according to the local position and stress state of the centrifugal impeller, and then use finite element software to perform finite element analysis to calculate whether the stress distribution of the simulated sample 6 in the test area is consistent with that of the real blade, and finally determine the shape of the sample after multiple calculations;

[0029] Step 1-2: According to the designed shape, spray a certain concentration of salt spray on the local surface of the simulated sample 6:

[0030] First, the specimen was ultrasonically cleaned with distilled water and then dried. Then, NaCl droplets were sprayed on the specimen with a spray pen. The spraying speed was adjusted by pressure. Finally, the salt content on the surface of the specimen was controlled by weighing to see if it reached the preset value. The test was started after the salt spray was completely dry.

[0031] Furthermore, the step 2 comprises:

[0032] Step 2-1: Install the upper fixture 22, the connecting rod 73, and the excitation plate 74 in sequence by means of pin connection;

[0033] Step 2-2: placing the eddy current exciter 33 on the support frame, ensuring that the simulated sample 6 can pass through the middle thereof;

[0034] Step 2-3: Place the heating furnace 42 on the support frame, keep it fixed, and make sure that the test part of the simulated sample 6 can be placed in the furnace cavity of the heating furnace 42;

[0035] Step 2-4: The modal vibration shape, harmonic response and vibration stress distribution of the test simulation part are obtained through mutual verification of numerical simulation and test, and the pasting position of the strain gauge 54 is determined according to the vibration stress distribution. The strain gauge 54 is pasted on the corresponding area of ​​the simulation sample 6. The strain gauge 54 is connected to the dynamic strain gauge 55 and the dynamic data acquisition and analysis system 56 through a wire, and the obtained signal is transmitted to the dynamic signal test and analysis system 56, so as to obtain the strain value;

[0036] Step 2-5: Select a fixed point on the simulated sample 6 as the positioning point of the displacement sensor 51, detect the lateral vibration displacement of the simulated sample 6 in real time, and establish a response relationship between the lateral displacement and the lateral vibration strain value;

[0037] Step 2-6: Place the simulated sample 6 in the groove between the excitation plate 74 and the pressure plate 75, use bolts to mate the excitation plate 74 with the pressure plate 75, insert pins into the pin holes of the excitation plate 74 and the pressure plate 75 to fix the sample.

[0038] Furthermore, the step 3 comprises:

[0039] Step 3-1: Turn on the switch of the second controller 41, set the temperature of the heating furnace 42, and heat the simulated sample 6;

[0040] Step 3-2: Apply axial load:

[0041] When the temperature of the simulated sample 6 reaches the predetermined working temperature, the fatigue machine 11 is started, and the value of the load to be applied is set through the first controller 12, and an axial load is applied to the simulated sample 6. The axial load is monitored in real time through the first controller 12, and when the load is stable, a bending vibration load perpendicular to the axial direction is applied;

[0042] Step 3-3: Apply bending vibration load:

[0043] Start the signal generator 31, select the sine waveform, input the loading frequency, adjust the knob of the power amplifier 32, control the load size output by the eddy current exciter 33, and detect the lateral vibration displacement of the simulated sample 6 in real time through the displacement sensor 51, and then detect the lateral load. If it deviates from the theoretical value, it needs to be adjusted in time through the power amplifier 32. By observing the current and voltage of the power amplifier 32, the working status is monitored in real time. If it is abnormal, stop the test in time to prevent equipment damage;

[0044] Step 3-4: Turn on the digital frequency meter 52 and the oscilloscope 53 to observe the stabilized waveform;

[0045] Step 3-5: The test is carried out normally until the simulated specimen 6 breaks.

[0046] The beneficial effects of the present invention are:

[0047] 1. The present invention provides a high-temperature test device and method for the tensile-bending composite fatigue of a simulated specimen of an engine blade (centrifugal impeller). Compared with the prior art, the device and method can provide an axial tensile load for the simulated specimen to simulate the centrifugal load that the real blade is subjected to during rotation, and can also provide a bending load in a direction perpendicular to the axial direction to simulate the bending vibration load that the real blade is subjected to. In addition, a heating furnace can be used to provide the simulated specimen with a temperature environment when the real blade is working. At the same time, by spraying salt spray on the surface of the specimen, the marine salt spray corrosion that the blade is subjected to during the working process is simulated, which accurately reflects the real stress, temperature, and corrosion environment of the engine, so that the test can more accurately simulate the tensile-bending composite fatigue of dangerous parts during the working process.

[0048] 2. In the test system of the present invention, heating is only performed at the location where the test conditions are applied. The scheme is simple, unnecessary heating parts are eliminated, and local heating is adopted. Only smaller test equipment is needed to simulate the conditions required for the experiment.

[0049] 3. During the test of the present invention, the systems such as salt spray concentration, temperature, axial force and vibration load are relatively independent, and any working condition can be directly modified to facilitate adjustment of test parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic structural diagram of the tension-bending composite fatigue test device of the present invention;

[0051] Figure 2 It is a schematic diagram of a simulated sample fixture of the tension-bending composite fatigue test device of the present invention;

[0052] Description of reference numerals:

[0053] 11- fatigue machine, 12- first controller, 21- lower fixture, 22- upper fixture, 31- signal generator, 32- power amplifier, 33- eddy current exciter, 41- second controller, 42- heating furnace, 51- displacement sensor, 52- digital frequency meter, 53- oscilloscope, 54- strain gauge, 55- dynamic strain gauge, 56- dynamic data acquisition and analysis system, 57- computer, 6- simulated specimen, 7- bendable device;

[0054] 71-threaded hole, 72-pin hole, 73-connecting rod, 74-excitation plate, 75-pressing plate. DETAILED DESCRIPTION

[0055] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0056] The present invention discloses a device for testing the combined tensile-bending fatigue of a simulated sample of an engine blade (centrifugal impeller) in a high-temperature corrosion environment, and the device includes an axial load system, a lateral vibration system, a temperature control system, and a measurement system. The axial load system applies an axial tensile-tensile load to the simulated sample 6 through a pin, the lateral vibration system provides a lateral bending vibration load to the simulated sample 6, and the temperature control system provides the temperature of the simulated sample 6 under the real working environment of the engine for the test part. At the same time, in view of the requirements of the combined tensile-bending fatigue test, the simulated sample 6 is designed according to the local position load of the engine blade (centrifugal impeller), and the salt spray / deposition method is used on the surface of the sample to simulate the marine salt spray corrosion environment, which accurately reflects the real stress, temperature, and corrosion environment of the engine, so that the test can more accurately simulate the combined tensile-bending fatigue of dangerous parts during the working process.

[0057] See also Figure 1 , Figure 2 The axial load system of the present invention includes a fatigue machine 11 and a clamping system, the clamping system includes an upper clamp 22, a bendable device 7 and a lower clamp 21, the upper clamp 22 is connected to the upper end of the fatigue machine 11, the lower clamp 21 is connected to the lower end of the fatigue machine 11, the bendable device 7 includes a connecting rod 73, an excitation plate 74 and a pressing plate 75, one end of the connecting rod 73 is connected to the upper clamp 22 by a pin, and the other end is connected to the excitation plate 74 by a pin, the end of the excitation plate 74 that is not connected to the connecting rod 73 is connected to the pressing plate 75 by a bolt, the excitation plate 74 and the pressing plate 75 are provided with grooves, and the simulation sample 6 is placed in the grooves of the excitation plate 74 and the pressing plate 75 and fixed by pins;

[0058] The lateral vibration system includes a signal generator 31, a power amplifier 32 and an eddy current exciter 33. The signal generator 31, the power amplifier 32 and the eddy current exciter 33 are connected by wires and placed on a support frame, which is fixed on the fatigue machine 11. The eddy current exciter 33 is located on the side of the excitation plate 74. During the test, the signal generator 31 generates a sinusoidal signal, the power amplifier 32 amplifies the sinusoidal signal, and the eddy current exciter 33 receives the amplified current to generate a periodically changing electromagnetic force. The power amplifier 32 has its own ammeter, and the working state of the power amplifier 32 is monitored by observing the current size.

[0059] The temperature control system is a small local heating furnace 42 with a control system, which is placed on a support frame, which is fixed to the fatigue machine 11 and is located below the eddy current exciter 33;

[0060] The measurement system includes a displacement sensor 51, a digital frequency meter 52, an oscilloscope 53, a computer 57, a dynamic data acquisition and analysis system 56, a dynamic strain gauge 55 and a strain gauge 54. The displacement sensor 51 is connected to the digital frequency meter 52 and is located on the side of the simulated sample 6. The displacement variable detected is converted into an electrical signal and the electrical signal is transmitted to the digital frequency meter 52. The digital frequency meter 52 is connected to the oscilloscope 53 and displays the frequency value in digital form. The oscilloscope 53 is used to display the stabilized waveform. The strain gauge 54 is pasted on the simulated sample 6 and is located in the middle area between the heating furnace 42 and the eddy current exciter 33. The dynamic strain gauge 55 measures the strain of the simulated sample 6 during the test by connecting to the strain gauge 54. The dynamic data acquisition and analysis system 56 is used to control the dynamic strain gauge 55 and collect strain values. The computer 57 is used to store and process the collected strain values.

[0061] The method for conducting the test using the device proposed by the present invention is specifically as follows:

[0062] Step 1: Design and process simulation specimen 6:

[0063] Step 1-1: Design a simulated sample 6 according to the local position and stress state of the centrifugal impeller, and then use finite element software to perform finite element analysis to calculate whether the stress distribution of the simulated sample 6 in the test area is consistent with that of the real blade, and finally determine the shape of the sample after multiple calculations;

[0064] Step 1-2: According to the designed shape, spray a certain concentration of salt mist on the local surface of the simulated sample 6: first, the specimen is ultrasonically cleaned with distilled water and then dried, then NaCl droplets are sprayed on the specimen with a spray pen, and the spraying speed is adjusted by pressure. Finally, the salt content on the surface of the specimen is controlled by weighing method to see if it reaches the preset value. The test is started after the salt mist is completely dry.

[0065] Step 2: Assemble the test device and fix the simulated specimen 6:

[0066] Step 2-1: Install the upper fixture 22, the connecting rod 73, and the excitation plate 74 in sequence by means of pin connection;

[0067] Step 2-2: placing the eddy current exciter 33 on the support frame, ensuring that the simulated sample 6 can pass through the middle thereof;

[0068] Step 2-3: Place the heating furnace 42 on the support frame, keep it fixed, and make sure that the test part of the simulated sample 6 can be placed in the furnace cavity of the heating furnace 42;

[0069] Step 2-4: The modal vibration shape, harmonic response and vibration stress distribution of the test simulation part are obtained through mutual verification of numerical simulation and test, and the pasting position of the strain gauge 54 is determined according to the vibration stress distribution. The strain gauge 54 is pasted on the corresponding area of ​​the simulation sample 6. The strain gauge 54 is connected to the dynamic strain gauge 55 and the dynamic data acquisition and analysis system 56 through a wire, and the obtained signal is transmitted to the dynamic signal test and analysis system 56, so as to obtain the strain value;

[0070] Step 2-5: Select a fixed point on the simulated sample 6 as the positioning point of the displacement sensor 51, detect the lateral vibration displacement of the simulated sample 6 in real time, and establish a response relationship between the lateral displacement and the lateral vibration strain value;

[0071] Step 2-6: Place the simulated sample 6 in the groove between the excitation plate 74 and the pressure plate 75, use bolts to mate the excitation plate 74 with the pressure plate 75, insert pins into the pin holes of the excitation plate 74 and the pressure plate 75 to fix the sample.

[0072] Step 3: Determine the load excitation level and conduct formal composite fatigue tests at different load excitation levels to obtain test data at different load excitation levels:

[0073] Step 3-1: Turn on the switch of the second controller 41, set the temperature of the heating furnace 42, and heat the simulated sample 6;

[0074] Step 3-2: Loading axial load: When the temperature of the simulated sample 6 reaches the predetermined working temperature, the fatigue machine 11 is started, and the value of the load to be applied is set through the first controller 12, and an axial load is applied to the simulated sample 6. The axial load is monitored in real time through the first controller 12, and when the load is stable, a bending vibration load perpendicular to the axial direction is loaded;

[0075] Step 3-3: Load the bending vibration load: Start the signal generator 31, select the sine waveform, input the loading frequency, adjust the knob of the power amplifier 32, control the load size output by the eddy current exciter 33, and detect the lateral vibration displacement of the simulated sample 6 in real time through the displacement sensor 51, and then detect the lateral load. If it deviates from the theoretical value, it needs to be adjusted in time through the power amplifier 32. By observing the current and voltage of the power amplifier 32, the working status is monitored in real time. If it is abnormal, stop the test in time to prevent equipment damage;

[0076] Step 3-4: Turn on the digital frequency meter 52 and the oscilloscope 53 to observe the stabilized waveform;

[0077] Step 3-5: The test is carried out normally until the simulated specimen 6 breaks.

[0078] Step 4: Repeat the above steps to test other simulated samples 6.

[0079] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A tensile-bending composite fatigue test device for a simulated specimen of an engine blade (centrifugal impeller) in a high temperature corrosion environment, comprising a simulated specimen (6), characterized in that: It also includes an axial load system, a lateral vibration system, a temperature control system, and a measurement system; The simulation sample (6) is designed according to the local position of the centrifugal impeller, and a salt film is sprayed on the test part and a working temperature is applied to simulate the marine salt spray corrosion and high temperature environment; The axial load system comprises a fatigue machine (11) and a clamping system; the clamping system comprises an upper clamp (22), a bendable device (7) and a lower clamp (21); the bendable device (7) comprises a connecting rod (73), an excitation plate (74) and a pressure plate (75); the excitation plate (74) and the pressure plate (75) are provided with grooves; The lateral vibration system comprises a signal generator (31), a power amplifier (32) and an eddy current exciter (33); The temperature control system is a small local heating furnace (42) with a control system; The measuring system comprises a displacement sensor (51), a digital frequency meter (52), an oscilloscope (53), a computer (57), a dynamic data acquisition and analysis system (56), a dynamic strain gauge (55) and a strain gauge (54); The simulation sample (6) is placed in the grooves of the excitation plate (74) and the pressure plate (75) and fixed by pins; The upper clamp (22) is connected to the upper end of the fatigue machine (11), and the lower clamp (21) is connected to the lower end of the fatigue machine (11); one end of the connecting rod (73) is connected to the upper clamp (22) by a pin, and the other end is connected to the excitation plate (74) by a pin; the end of the excitation plate (74) not connected to the connecting rod (73) is connected to the pressure plate (75) by a bolt; The signal generator (31), the power amplifier (32) and the eddy current exciter (33) are connected by wires and placed on a support frame, the support frame is fixed on the fatigue machine (11), and the eddy current exciter (33) is located on the side of the excitation plate (74); The heating furnace (42) is placed on a support frame, which is fixed on the fatigue machine (11) and is located below the eddy current exciter (33); The strain gauge (54) is pasted on the simulation sample (6), located in the middle area between the heating furnace (42) and the eddy current exciter (33), and is connected to the dynamic strain gauge (55), the dynamic data acquisition and analysis system (56) and the computer (57) through wires; the displacement sensor (51) is located on the side of the simulation sample (6), and is connected to the digital frequency meter (52) and the oscilloscope (53) through wires.

2. The engine blade (centrifugal impeller) simulated specimen high temperature corrosion environment tensile bending composite fatigue test device according to claim 1 is characterized by: The simulated sample (6) is subjected to quantitative salt spraying / deposition on a local surface to simulate the concentration of salt film accumulated in service in a marine salt spray environment.

3. The engine blade (centrifugal impeller) simulated specimen high temperature corrosion environment tensile bending composite fatigue test device according to claim 1 is characterized by: The signal generator (31) generates a sinusoidal signal, the power amplifier (32) amplifies the sinusoidal signal, and the eddy current exciter (33) receives the amplified current, thereby generating a periodically changing electromagnetic force.

4. The engine blade (centrifugal impeller) simulated specimen high temperature corrosion environment tensile bending composite fatigue test device according to claim 3 is characterized by: The power amplifier (32) is provided with an ammeter, and the working state of the power amplifier (32) is monitored by observing the current magnitude, and the amplitude value of the excitation point is adjusted by adjusting the current magnitude to provide an accurate high-frequency vibration load.

5. The engine blade (centrifugal impeller) simulated specimen high temperature corrosion environment tensile bending composite fatigue test device according to claim 1 is characterized by: The displacement sensor (51) converts the detected displacement variable into an electrical signal and transmits the electrical signal to the digital frequency meter (52); the digital frequency meter (52) displays the frequency value in digital form; the oscilloscope (53) is used to display the stabilized waveform; the dynamic strain gauge (55) measures the strain of the simulated sample during the test by connecting the strain gauge; the dynamic data acquisition and analysis system (56) is used to control the dynamic strain gauge (55) and collect strain values; the computer (57) stores and processes the collected strain values.

6. Engine blade (centrifugal impeller) simulated specimen high temperature corrosion environment tensile bending composite fatigue test method, characterized in that: The following steps are involved: Step 1: Design and process simulation specimen (6); Step 2: Assemble the test device and fix the simulated sample (6); Step 3: Determine the load excitation level and conduct formal composite fatigue tests at different load excitation levels to obtain test data at different load excitation levels; Step 4: Repeat the above steps to test other simulated samples (6).

7. The method for testing the engine blade (centrifugal impeller) in a simulated high temperature corrosion environment tensile bending composite fatigue test according to claim 6, characterized in that: The step 1 comprises: Step 1-1: designing a simulation specimen (6) according to the local position and stress state of the centrifugal impeller, and then performing finite element analysis and calculation using finite element software to determine whether the stress distribution of the simulation specimen (6) in the test area is consistent with that of the real blade, and finally determining the shape of the specimen after multiple calculations; Step 1-2: According to the designed shape, spray a certain concentration of salt mist on the local surface of the simulated sample (6): First, the specimen was ultrasonically cleaned with distilled water and then dried. Then, NaCl droplets were sprayed on the specimen with a spray pen. The spraying speed was adjusted by pressure. Finally, the salt content on the surface of the specimen was controlled by weighing to see if it reached the preset value. The test was started after the salt spray was completely dry.

8. The method for testing the engine blade (centrifugal impeller) in a simulated high temperature corrosion environment tensile bending composite fatigue test according to claim 6, characterized in that: The step 2 comprises: Step 2-1: Install the upper fixture (22), the connecting rod (73), and the excitation plate (74) in sequence by means of pin connection; Step 2-2: placing the eddy current exciter (33) on a support frame, ensuring that the simulated sample (6) can pass through the middle thereof; Step 2-3: placing the heating furnace (42) on a support frame, keeping it fixed, and ensuring that the test portion of the simulated sample (6) can be placed in the furnace cavity of the heating furnace (42); Step 2-4: The modal vibration shape, harmonic response and vibration stress distribution of the test simulation part are obtained through mutual verification of numerical simulation and test, and the pasting position of the strain gauge (54) is determined according to the vibration stress distribution. The strain gauge (54) is pasted on the corresponding area of ​​the simulation sample (6). The strain gauge (54) is connected to the dynamic strain gauge (55) and the dynamic data acquisition and analysis system (56) through a wire, and the obtained signal is transmitted to the dynamic signal test and analysis system (56), so as to obtain the strain value; Step 2-5: Select a fixed point on the simulated sample (6) as a positioning point of the displacement sensor (51), detect the lateral vibration displacement of the simulated sample (6) in real time, and establish a response relationship between the lateral displacement and the lateral vibration strain value; Step 2-6: Place the simulated sample (6) in the groove between the excitation plate (74) and the pressure plate (75), connect the excitation plate (74) and the pressure plate (75) with bolts, insert pins into the pin holes of the excitation plate (74) and the pressure plate (75) to fix the sample.

9. The method for testing the engine blade (centrifugal impeller) in a simulated high temperature corrosion environment tensile bending composite fatigue test according to claim 6, characterized in that: The step 3 comprises: Step 3-1: Turn on the switch of the second controller (41), set the temperature of the heating furnace (42), and heat the simulated sample (6); Step 3-2: Apply axial load: When the temperature of the simulated sample (6) reaches a predetermined working temperature, the fatigue machine (11) is started, the value of the load to be applied is set through the first controller (12), an axial load is applied to the simulated sample (6), and the axial load is monitored in real time through the first controller (12), and when the load is stable, a bending vibration load perpendicular to the axial direction is applied; Step 3-3: Apply bending vibration load: Start the signal generator (31), select the sine waveform, input the loading frequency, adjust the knob of the power amplifier (32), control the load size output by the eddy current exciter (33), detect the lateral vibration displacement of the simulated sample (6) in real time through the displacement sensor (51), and then detect the lateral load. If it deviates from the theoretical value, it needs to be adjusted in time through the power amplifier (32). By observing the current and voltage of the power amplifier (32), the working state is monitored in real time. If it is abnormal, stop the test in time to prevent equipment damage; Step 3-4: Turn on the digital frequency meter (52) and the oscilloscope (53) to observe the stabilized waveform; Step 3-5: The test is carried out normally until the simulated specimen (6) breaks.

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