A method for testing the pre-tightening force attenuation of a pinion connection bolt under high temperature and high speed

Abstract

The application belongs to the field of reliability test of aero-engine or gas turbine rotor components, and provides a pre-tightening force attenuation test method of end tooth connecting bolts under high temperature and high rotating speed, which comprises the following steps: coaxially installing a test piece on a driving shaft; selecting a strain gauge arrangement scheme, processing one or more mounting planes at a non-threaded matching position of a screw rod of the connecting bolt, and pasting high-temperature strain gauges according to the selected scheme; performing static warming calibration on the test piece provided with the high-temperature strain gauges, and establishing a calibration relationship between temperature and thermal output strain; performing a rotating test under a target rotating speed and a target test temperature, and synchronously collecting total strain; decoupling the total strain based on the calibration relationship to obtain mechanical strain, and calculating an attenuation amount of the connecting bolt. The application can realize accurate and dynamic monitoring of the pre-tightening force attenuation under real high temperature and high rotating speed conditions, and provides an effective technical means for reliability verification of an aero-engine rotor end tooth connecting structure.

Description

Technical Field

[0001] This invention belongs to the field of reliability testing of rotor components of aero-engines or gas turbines, and relates to the preload decay test technology of end-tooth connecting bolts, specifically to a test method for preload decay of end-tooth connecting bolts under high temperature and high speed coupling conditions. Background Technology

[0002] As a rigid coupling for the main transmission shaft, the end-tooth connection structure plays an important role in the design of modern aero-engines and gas turbines. It boasts advantages such as simple and compact structure, self-centering, high load-bearing capacity, good connection stability, and excellent assemblability. Widely used in aero-engine rotor structures, it is a key safety component of aero-engines. This structure is primarily used for shaft-shaft connections, shaft-disc connections, and disc-disc connections.

[0003] Compared to conventional bolted connections, end-tooth connections add end teeth to the traditional mounting surfaces. The meshing of the concave and convex teeth not only transmits torque but also ensures thermal centering under repeated rapid movements of the aero-engine throttle lever, providing high centering accuracy and torsional load transmission capability. Therefore, the connection reliability of the aero-engine end-tooth connection directly determines the operational stability of the engine rotor.

[0004] However, under high-temperature and high-speed operating conditions, the connecting bolt assembly in the end-tooth connection structure faces severe challenges. Due to the influence of speed and temperature, the bolts undergo creep elongation, leading to a decrease in preload and connection stiffness, thereby increasing the risk of rotor instability. Although increasing the bolt preload can temporarily improve connection stiffness, this increases local stress on the end-tooth surface, tooth root, bolt hole, and thread teeth, thus reducing fatigue life and accelerating bolt creep elongation. After long-term high-temperature operation, the connection stiffness may actually decrease, affecting the rotor's operational stability.

[0005] Furthermore, under the combined effects of thermal load, cyclic load, and mechanical load, changes in bolt preload directly affect connection stiffness, and consequently, rotor performance. Currently, no tests have been conducted in China to measure bolt preload decay in end-tooth connection structures under high-temperature and high-speed conditions, lacking effective testing methods and techniques. Existing preload monitoring methods, such as ultrasonic length measurement or embedded fiber optic sensors, struggle to achieve real-time continuous measurement in high-temperature rotating environments; while strain gauge methods offer high sensitivity, they suffer from severe thermal output drift at high temperatures, making it impossible to accurately distinguish between thermal strain and mechanical strain, leading to distorted preload calculations.

[0006] Therefore, there is an urgent need for a method that can accurately measure the preload decay of end-tooth connecting bolts under real high-temperature and high-speed environments, in order to support the development of high-temperature and high-speed end-tooth connecting bolt structures and provide strong technical support for the safe and reliable operation of aero-engines and gas turbines. Summary of the Invention

[0007] To address the technical problem of accurately measuring the preload decay of end-tooth connecting bolts under high-temperature and high-speed coupling conditions in existing technologies, this invention discloses a method for testing the preload decay of end-tooth connecting bolts under high-temperature and high-speed conditions. This method can realistically reproduce the service environment of aero-engine rotors and effectively separate thermal output strain and mechanical strain by adopting differentiated strain gauge arrangement schemes and calibration strategies for different temperature ranges, thereby achieving high-precision, dynamic, and continuous monitoring of bolt preload and its decay.

[0008] Specifically, the method includes the following steps:

[0009] S1. The test piece is coaxially mounted on the drive shaft, wherein the test piece includes a rear journal and a turbine disk, and the rear journal and the turbine disk are fastened together by a connecting bolt assembly;

[0010] S2. Select a strain gauge arrangement scheme based on the critical temperature and the target test temperature. Machine one or more mounting planes at the non-threaded engagement of the connecting bolts of the connecting bolt assembly. Attach high-temperature strain gauges to the mounting planes according to the selected arrangement scheme, and lead out the test leads of the high-temperature strain gauges through the lead holes.

[0011] S3. Perform static heating calibration on the test piece equipped with the high-temperature strain gauge to establish the calibration relationship between temperature and thermal output strain;

[0012] S4. At the target rotational speed and the target test temperature, a rotational test is performed on the calibrated test piece, and the total strain is collected synchronously through the high-temperature strain gauge.

[0013] S5. Based on the calibration relationship, perform thermo-mechanical strain decoupling on the total strain to obtain the mechanical strain, and calculate the current preload of the connecting bolt and its attenuation relative to the initial preload based on the mechanical strain.

[0014] Furthermore, in one embodiment of step S2, selecting a strain gauge arrangement scheme based on the critical temperature and the target test temperature includes:

[0015] S201. When the target test temperature is less than the critical temperature, a mounting plane is milled axially on the smooth section of the screw of a single connecting bolt.

[0016] S202. A high-temperature strain gauge is attached to the mounting surface for measuring the total strain;

[0017] S203. Connect the high-temperature strain gauge to a 1 / 4 bridge Wheatstone bridge circuit.

[0018] Furthermore, in one embodiment of step S3, static heating calibration is performed on the test piece equipped with the high-temperature strain gauge to establish a calibration relationship between temperature and thermal output strain, including:

[0019] S301. A calibration thermocouple is welded to the bolt head end face and both sides of the axial direction of at least two circumferentially symmetrically distributed connecting bolts.

[0020] S302. The test piece is heated in a stepwise manner, and the temperature is maintained at each temperature point while the temperature value measured by the thermocouple and the thermal output strain value of the high-temperature strain gauge are recorded simultaneously.

[0021] S303. Fit the recorded data to obtain the calibration relationship between temperature and thermal output strain.

[0022] Furthermore, in one embodiment of step S5, the mechanical strain is equal to the total strain minus the thermal output strain of the calibration relationship at the current temperature.

[0023] Furthermore, in another embodiment of step S2, selecting a strain gauge arrangement scheme based on the critical temperature and the target test temperature includes:

[0024] S211. When the target test temperature is greater than or equal to the critical temperature, at the same axial position of the bolt smooth section of a single connecting bolt, the first mounting plane and the second mounting plane are respectively machined circumferentially spaced 180° apart.

[0025] S212. A high-temperature strain gauge is attached to the first mounting surface as the main strain gauge, and a high-temperature strain gauge is attached to the second mounting surface as the temperature compensation strain gauge.

[0026] S213. Connect the main strain gauge and the temperature compensation strain gauge to the adjacent arms of the Wheatstone bridge to form a half-bridge circuit to eliminate common-mode temperature drift.

[0027] Furthermore, in another embodiment of step S3, room temperature mechanical strain calibration is also included to eliminate mechanical strain interference caused by the rotation of the temperature-compensated strain gauge. The room temperature mechanical strain calibration includes:

[0028] S311. Under normal temperature conditions, drive the test piece to rotate at multiple stepped speeds;

[0029] S312. Collect the output strain value of the temperature-compensated strain gauge at each rotation speed;

[0030] S313. Fit the collected output strain values ​​to obtain the relationship curve between the rotational speed and the mechanical strain of the temperature-compensated strain gauge.

[0031] Further, in another embodiment of step S5, the total strain is thermo-mechanical strain decoupled based on the calibration relationship to obtain the mechanical strain, including:

[0032] S51. Obtain the differential strain value between the main strain gauge and the temperature compensation strain gauge from the output signal of the half-bridge circuit;

[0033] S52. Based on the current test rotation speed, find the corresponding mechanical strain value of the compensation plate from the relationship curve;

[0034] S53. Calculate the true mechanical strain of the connecting bolt based on the differential strain value and the mechanical strain value of the compensation plate;

[0035] S54. Calculate the current axial force of the connecting bolt based on the actual mechanical strain, compare the current axial force with the initial preload, and obtain the preload attenuation.

[0036] Furthermore, in one embodiment of step S53, the actual mechanical strain is equal to the differential strain value minus the mechanical strain value of the temperature-compensated strain gauge.

[0037] Furthermore, in step S5, the initial preload of the connecting bolt assembly is applied by the torque-angle method and verified by the reverse loosening torque or ultrasonic length measurement method.

[0038] Further, in step S2, the surface roughness Ra of the mounting plane is ≤1.6 μm, the high-temperature strain gauge is bonded with an adhesive with a temperature resistance of not less than 600℃, and coated with a high-temperature silicone or ceramic protective coating, and the critical temperature is 450℃.

[0039] This invention proposes a method for testing the preload decay of end-tooth connection bolts under high temperature and high speed. The core principle is as follows: for different temperature ranges, a single strain gauge direct calibration method or a main-compensation dual strain gauge half-bridge compensation method is used. High-temperature strain gauges are reasonably arranged on the smooth section of the bolt. Combined with static heating calibration and room temperature mechanical calibration, a mapping relationship between temperature and thermal output strain and rotation speed and compensation gauge mechanical strain is established. In a real high-temperature and high-speed rotation test, the mechanical strain of the bolt is accurately inverted by strain signal acquisition and thermo-mechanical strain decoupling, and then the preload and its decay amount are calculated.

[0040] Compared with existing technologies, the method described in this specification solves the technical challenge of dynamically, continuously, and with high precision monitoring of the preload of end-tooth connection bolts under real service conditions. This method does not rely on embedded sensors or measurements taken during operation and can be directly implemented on standard equipment such as a rotary tester. It effectively overcomes key obstacles such as severe thermal drift at high temperatures and significant centrifugal interference at high speeds, achieving effective capture and accurate quantification of the bolt preload decay process under coupled high-temperature and high-speed conditions. This invention not only ensures the smooth conduct of relevant verification tests but also provides reliable technical support for the design optimization, life assessment, and reliability verification of end-tooth connection structures in aero-engines and gas turbines, possessing significant engineering application value. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a flowchart of the preload decay test method for high-temperature and high-speed end-tooth connecting bolts according to the present invention;

[0043] Figure 2 This is a schematic diagram of the connection of the preload decay test device for end-tooth connecting bolts;

[0044] Figure 3 for Figure 2 Enlarged schematic diagram of a portion of the bolt structure;

[0045] Figure 4 A schematic diagram of the structure for testing the preload attenuation of end-tooth connecting bolts;

[0046] Figure 5 A schematic diagram illustrating the temperature-thermal output strain calibration relationship during static heating for the preload decay test of end-tooth connection bolts;

[0047] Figure 6 A schematic diagram illustrating the calibration relationship between rotational speed and strain value during room temperature rotation in the test of preload decay of end-tooth connecting bolts;

[0048] Figure 7 This is a schematic diagram showing the arrangement of strain gauges on the connecting bolts;

[0049] Figure 8 A schematic diagram showing the arrangement of temperature measuring points on the connecting bolts;

[0050] The components include: 1. Rear journal; 2. Connecting bolt assembly; 201. Nut; 202. Screw; 203. Spring plate; 204. Strain gauge two mounting position; 205. Strain gauge one lead hole; 206. Strain gauge one mounting position; 207. Thermocouple one mounting position; 208. Thermocouple two mounting position; 209. Thermocouple three mounting position; 3. Test lead path; 4. Turbine disk; 5. Heating device; 501. Heating wire; 6. Adapter section; 7. Connecting screw; 8. Chamber cover; 9. Drive shaft; 10. Cooling plate; 11. Test chamber; 12. Slip ring actuator; 13. Strain conditioning system; 14. Data acquisition computer. Detailed Implementation

[0051] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0052] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features of the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0053] This invention discloses a method for testing the preload decay of end-tooth connecting bolts under high temperature and high speed, such as... Figure 1 As shown, the method includes the following steps:

[0054] S1. The test piece is coaxially mounted on the drive shaft, wherein the test piece includes a rear journal and a turbine disk, and the rear journal and the turbine disk are fastened together by a connecting bolt assembly;

[0055] S2. Select a strain gauge arrangement scheme based on the critical temperature and the target test temperature. Machine one or more mounting planes at the non-threaded engagement of the connecting bolts of the connecting bolt assembly. Attach high-temperature strain gauges to the mounting planes according to the selected arrangement scheme, and lead out the test leads of the high-temperature strain gauges through the lead holes.

[0056] S3. Perform static heating calibration on the test piece equipped with the high-temperature strain gauge to establish the calibration relationship between temperature and thermal output strain;

[0057] S4. At the target rotational speed and the target test temperature, a rotational test is performed on the calibrated test piece, and the total strain is collected synchronously through the high-temperature strain gauge.

[0058] S5. Based on the calibration relationship, perform thermo-mechanical strain decoupling on the total strain, calculate the mechanical strain, and calculate the current preload of the connecting bolt and its attenuation relative to the initial preload based on the mechanical strain.

[0059] like Figure 2 As shown, the components of the preload decay test device for end-tooth connecting bolts include: rear journal 1, connecting bolt assembly 2, test lead path 3, turbine disk 4, heating device 5, heating wire 501, adapter section 6, connecting screw 7, chamber cover 8, drive shaft 9, cooling plate 10, and test chamber 11. The rear journal 1 is fastened and connected to the turbine disk 4 via the connecting bolt assembly 2. The tightening torque is referenced to the torque of the entire machine. After assembly, the rear journal 1, connecting bolt assembly 2, and turbine disk 4 are connected to the drive shaft 9 via the adapter section 6. The adapter section 6, turbine disk 4, and drive shaft 9 are all interference fits and are connected and centered using bolts. The adapter section 6, drive shaft 9, and heating device 5 are coaxially arranged and installed.

[0060] The function of the heating device 5 is to heat the rear journal 1, the connecting bolt assembly 2 and the turbine disk 4 during the test, including heating wire 501, etc., to heat them to the required specific temperature. Combined with the motor and gearbox, the drive shaft 9 is rotated. The magnitude and variation characteristics of the bolt preload under specific temperature and speed conditions are measured by attaching strain gauges to the connecting bolt assembly 2.

[0061] like Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown, the connecting bolt assembly 2 includes a nut 201, a screw 202, a spring plate 203, a strain gauge two mounting position 204, a strain gauge one lead hole 205, a strain gauge one mounting position 206, a thermocouple one mounting position 207, a thermocouple two mounting position 208, and a thermocouple three mounting position 209. A flat surface with a length and width of 16mm × 6.5mm is machined on one side of the screw 202, which is the strain gauge one mounting position 206. The principle of the flat surface design is to ensure that the size of this flat surface is larger than the size of the high-temperature strain gauge, allowing the strain gauge and lead wire to be firmly bonded using high-temperature cement adhesive or ceramic spraying, and that the machined flat surface does not affect the yield strength of the bolt after pre-tightening, i.e., the yield reserve coefficient of the bolt. Not less than 1.2, the calculation formula is as follows ,in In the formula This refers to the remaining cross-sectional area under stress after the machined surface on the connecting bolt is exposed. This refers to the cross-sectional area of ​​the machined surface on the connecting bolt that bears the force. The yield strength of the connecting bolt material. The tightening torque of the connecting bolts, The nominal diameter of the bolt thread. This refers to the pitch of the bolt thread. For standard threads, this is the tightening torque coefficient. =0.15, the test line is led out through the strain gauge lead hole 205.

[0062] In some embodiments, the connecting bolt assemblies for mounting strain gauges should be distributed as evenly as possible around the circumference. Similarly, the connecting bolt assemblies for mounting thermocouples should also be distributed as evenly as possible around the circumference, so as to accurately reflect the strain and temperature fields of all bolts based on limited-channel measurements.

[0063] In step S2, the surface roughness Ra of the mounting plane is ≤1.6 μm, the high-temperature strain gauge is bonded with an adhesive with a temperature resistance of not less than 600℃, and coated with a high-temperature silicone or ceramic protective coating.

[0064] In this invention, the arrangement of strain gauges on the connecting bolts varies depending on the target test temperature. When the temperature is below the critical temperature, mechanical strain interference caused by rotation can be disregarded; however, when the temperature is above or equal to the critical temperature, mechanical strain interference caused by rotation must be considered. This invention will describe these two cases separately:

[0065] In the first scenario, where the target test temperature is less than the critical temperature, step S2 involves selecting a strain gauge arrangement based on the critical temperature and the target test temperature, including:

[0066] S201. A mounting plane is milled axially on the smooth section of the threaded rod of a single connecting bolt.

[0067] S202. A high-temperature strain gauge is attached to the mounting surface for measuring the total strain;

[0068] S203. Connect the high-temperature strain gauge test signal to a 1 / 4 bridge Wheatstone bridge circuit.

[0069] In step S3, static heating calibration is performed on the test piece equipped with the high-temperature strain gauge to establish the calibration relationship between temperature and thermal output strain, including:

[0070] S301. A calibration thermocouple is welded to the bolt head end face and both sides of the axial direction of at least two circumferentially symmetrically distributed connecting bolts.

[0071] S302. The test piece is heated in a stepwise manner, and the temperature is maintained at each temperature point while the temperature value measured by the thermocouple and the thermal output strain value of the high-temperature strain gauge are recorded simultaneously.

[0072] S303. Fit the recorded data to obtain the calibration relationship between temperature and thermal output strain.

[0073] In the corresponding step S5, the mechanical strain is equal to the total strain minus the thermal output strain of the calibration relationship at the current temperature.

[0074] Specifically, when the target heating temperature is less than the critical temperature When the temperature is typically around 450℃, a 1 / 4 bridge strain gauge is used for strain conditioning. Only one mounting position (206) of the strain gauge needs to be attached. If the shaft hole diameter of the drive shaft 9 can accommodate a sufficient number of test leads and the telemetry and data acquisition systems have sufficient strain test channels, as many high-temperature strain gauges as possible should be attached at mounting positions (206) of different bolts to obtain as much test data as possible. The shaft hole diameter of the drive shaft is typically 8mm~10mm. The test leads of the high-temperature strain gauges are usually made of 1.6mm diameter glass fiber, and the number of test channels is 5~7. After the strain gauges are installed, [further steps are needed]. The turbine disk 4, connecting bolt assembly 2 and rear journal 1 are assembled. The connecting bolt assembly for installing strain gauges is assembled as evenly as possible around the test piece. Six thermocouples are welded to each of the two evenly distributed connecting bolt assemblies at thermocouple one installation position 207, thermocouple two installation position 208 and thermocouple three installation position 209 respectively. Then, the test wires of the strain gauges are connected to the telemetry system or slip ring lead according to the test lead path 3. After passing through the strain conditioning system 13, a 1 / 4 bridge connection is made. The strain gauge one is connected to one side of the Wheatstone bridge, and the thermocouples are directly led out through the cover 8 and connected to the data acquisition computer 14.

[0075] During the test, the air pressure inside the test chamber 11 was evacuated to near-vacuum using a vacuum device. Based on the required temperature values ​​for the test, the static temperature field and strain heat output values ​​were calibrated, such as... Figure 3As shown, the test piece is heated using an automatic temperature control method near the heating element, with a step size of 50℃. Each temperature is held for 1-2 minutes until the target temperature is reached. The strain value and heating time at each temperature are recorded. Data such as time, temperature, and strain are collected in real-time using a data acquisition system. The temperature field is then verified 1-2 times using the above method to calibrate the relationship between time, temperature, and thermal output strain, obtaining the heating pattern and strain thermal output value of the test piece. A curve is fitted to the temperature near the heating element, thermocouple installation positions 207, 208, and 209, and the strain thermal output value. After calibration, the thermocouples are removed, and a high-speed heating test is conducted according to the calibrated heating pattern. The total strain value of the connecting bolts is measured at the required temperature and speed. The mechanical strain value of the connecting bolt assembly under high temperature and high speed is calculated by subtracting the calibrated temperature near the heating element and thermal output strain value corresponding to the bolt temperature from the measured total strain value.

[0076] In the second case, when the target test temperature is greater than or equal to the critical temperature, step S2 involves selecting a strain gauge arrangement scheme based on the critical temperature and the target test temperature, including:

[0077] S211. At the same axial position of the threaded rod section of a single connecting bolt, the first mounting plane and the second mounting plane are machined circumferentially spaced 180° apart.

[0078] S212. A high-temperature strain gauge is attached to the first mounting surface as the main strain gauge, and a high-temperature strain gauge is attached to the second mounting surface as the temperature compensation strain gauge.

[0079] S213. Connect the main strain gauge and the temperature compensation strain gauge to the adjacent arms of the Wheatstone bridge to form a half-bridge circuit to eliminate common-mode temperature drift.

[0080] At this point, step S3 also includes a room-temperature mechanical strain calibration step to eliminate mechanical strain interference caused by the rotation of the temperature-compensated strain gauge. The room-temperature mechanical strain calibration includes:

[0081] S311. Under normal temperature conditions, drive the test piece to rotate at multiple stepped speeds;

[0082] S312. Collect the output strain value of the temperature-compensated strain gauge at each rotation speed;

[0083] S313. Fit the collected output strain values ​​to obtain the relationship curve between the rotational speed and the mechanical strain of the temperature-compensated strain gauge.

[0084] The corresponding step S5 involves decoupling the total strain from thermo-mechanical strain based on the calibration relationship to obtain the mechanical strain, specifically including:

[0085] S51. Obtain the differential strain value between the main strain gauge and the temperature compensation strain gauge from the output signal of the half-bridge circuit;

[0086] S52. Based on the current test rotation speed, find the corresponding mechanical strain value of the compensation plate from the relationship curve;

[0087] S53. Based on the differential strain value and the mechanical strain value of the compensation strain gauge, calculate the true mechanical strain of the connecting bolt; more specifically, the true mechanical strain is equal to the differential strain value minus the mechanical strain value of the temperature compensation strain gauge.

[0088] S54. Calculate the current axial force of the connecting bolt based on the actual mechanical strain, compare the current axial force with the initial preload, and obtain the preload attenuation.

[0089] Specifically, when the target heating temperature is greater than or equal to When the temperature is around 450℃, while attaching the strain gauge at installation position 206, a strain gauge should also be attached at installation position 204 for real-time temperature compensation. If the shaft hole diameter of the drive shaft 9 can accommodate a sufficient number of test leads and the slip ring actuator and data acquisition system have sufficient strain test channels, as many high-temperature strain gauges as possible should be attached at installation positions 206 and 204 of different bolts to obtain as much test data as possible. Typically, the shaft hole diameter of the drive shaft is 8mm~10mm. The test leads of the high-temperature strain gauges are usually made of 1.6mm diameter glass fiber, and the number of test channels is 8~10. After the strain gauges are installed, assemble the turbine disk 4, connecting bolt assembly 2, and rear journal 1. As evenly as possible, assemble the connecting bolt assembly for the strain gauges onto the test piece. Weld six thermocouples to each of the two evenly distributed connecting bolt assemblies at installation positions 207, 208, and 209, respectively. At this point, the test leads of the two strain gauges are connected to the slip ring actuator 12 according to the test lead path 3. The signal is then led out and connected to the strain conditioning system 13. The thermocouple is directly led out through the hatch cover 8 and connected to the data acquisition computer 14.

[0090] During the experiment, the mechanical strain of the temperature-compensated strain gauge under rotational conditions was first calibrated. The air pressure inside the test chamber 11 was evacuated to near-vacuum using a vacuum device. Based on the required rotational speed, the mechanical strain value at installation position 204 of strain gauge two was calibrated using a quarter-bridge method, yielding the mechanical strain value. Hold the temperature at each rotation speed for 1 to 2 minutes until the required mechanical strain values ​​at each rotation speed are calibrated. The mechanical strain values ​​at each rotational speed were recorded, and data such as time, rotational speed, and strain were acquired in real time through a data acquisition system. Using this method, the relationship between time, rotational speed, and strain could be selectively verified one to two times to calibrate the mechanical strain values ​​of the test specimen at different rotational speeds using temperature-compensated strain gauges. The rotational speed and these mechanical strain values ​​were then fitted into a curve. After the mechanical strain values ​​were calibrated, the strain conditioning system was set to half-bridge mode using an automatic temperature control method near the heating element. The target temperature was input, and the test specimen was statically heated until it reached the target temperature. The strain values ​​of strain gauge one and strain gauge two at each temperature and the heating time were recorded. Data such as time, temperature, and strain were acquired in real time through a data acquisition system. Using this method, the relationship between time and temperature could be selectively verified one to two times to calibrate the heating pattern of the test specimen. The thermocouples were removed, and a high-speed test specimen heating test was conducted according to the calibrated heating pattern. The mechanical strain values ​​of the connecting bolts were calculated at the required temperature and rotational speed. ,in, The strain value measured by the strain gauge at installation position 206 is... The strain value measured by the strain gauge at installation position 204 of strain gauge two. The mechanical strain values ​​calibrated for strain gauge at installation position 204 of strain gauge two at the corresponding rotational speed are shown. E and e These are the input and output voltages of the bridge circuit, respectively. k is the strain gauge constant.

[0091] The mechanical strain value will be obtained. The formula for calculating the preload converted to attenuation is: Thus, the attenuated preload force in the experiment was obtained, where, This represents the mechanical strain value measured on the bolt. This represents the Young's modulus of the bolt material.

[0092] In some embodiments, in step S5 above, the initial preload of the connecting bolt assembly is applied by the torque-angle method and verified by the reverse loosening torque or ultrasonic length measurement method.

[0093] The method of the present invention, by installing strain gauges and thermocouples on the connecting bolt assembly, assembling the turbine disk and the rear journal, and conducting bolt preload tests at corresponding temperatures and speeds on a rotating tester, successfully achieves effective and accurate testing of the preload decay of the high-temperature, high-speed end-tooth connecting bolts, and achieves the expected test results.

[0094] This invention proposes a method for testing the preload decay of end-tooth connection bolts under high temperature and high speed. The core principle is as follows: for different temperature ranges, a single strain gauge direct calibration method or a main-compensation dual strain gauge half-bridge compensation method is used. High-temperature strain gauges are reasonably arranged on the smooth section of the bolt. Combined with static heating calibration and room temperature mechanical calibration, a mapping relationship between temperature and thermal output strain and rotation speed and compensation gauge mechanical strain is established. In a real high-temperature and high-speed rotation test, the mechanical strain of the bolt is accurately inverted by strain signal acquisition and thermo-mechanical strain decoupling, and then the preload and its decay amount are calculated.

[0095] Compared with existing technologies, the method described in this specification solves the technical challenge of dynamically, continuously, and with high precision monitoring of the preload of end-tooth connection bolts under real service conditions. This method does not rely on embedded sensors or measurements taken during operation and can be directly implemented on standard equipment such as a rotary tester. It effectively overcomes key obstacles such as severe thermal drift at high temperatures and significant centrifugal interference at high speeds, achieving effective capture and accurate quantification of the bolt preload decay process under coupled high-temperature and high-speed conditions. This invention not only ensures the smooth conduct of relevant verification tests but also provides reliable technical support for the design optimization, life assessment, and reliability verification of end-tooth connection structures in aero-engines and gas turbines, possessing significant engineering application value.

[0096] In this embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the above-mentioned method for testing the preload decay of any high-temperature, high-speed end-tooth connecting bolt.

[0097] Specifically, the computer device can be a computer terminal, a server, or a similar computing device.

[0098] In this embodiment, a computer-readable storage medium is provided, which stores a computer program that performs the above-described method for testing the preload decay of a high-temperature, high-speed lower-end toothed connecting bolt.

[0099] Specifically, computer-readable storage media, including both permanent and non-permanent, removable and non-removable media, can store information using any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer-readable storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable storage media does not include transient media, such as modulated data signals and carrier waves.

[0100] Obviously, those skilled in the art should understand that the modules or steps of the above-described embodiments of the present invention can be implemented using general-purpose computing devices. The program can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using device-executable program code, thereby storing them in a storage device for execution by a computing device. Furthermore, in some cases, the steps shown or described can be performed in a different order than presented herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the embodiments of the present invention are not limited to any particular hardware and software combination.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for testing the preload decay of end-tooth connecting bolts under high temperature and high speed, characterized in that, include: The test piece is coaxially mounted on the drive shaft, wherein the test piece includes a rear journal and a turbine disk, and the rear journal and the turbine disk are fastened together by a connecting bolt assembly; Select a strain gauge arrangement scheme based on the critical temperature and the target test temperature. Machine one or more mounting planes at the non-threaded engagement of the connecting bolts of the connecting bolt assembly. Attach high-temperature strain gauges to the mounting planes according to the selected arrangement scheme and lead out the test leads of the high-temperature strain gauges through the lead holes. Static heating calibration was performed on the test specimen equipped with the high-temperature strain gauge to establish the calibration relationship between temperature and thermal output strain; At the target rotational speed and the target test temperature, a rotational test is performed on the calibrated test piece, and the total strain is collected synchronously through the high-temperature strain gauge; Based on the calibration relationship, the total strain is decoupled from the thermo-mechanical strain to obtain the mechanical strain. The current preload of the connecting bolt and its attenuation relative to the initial preload are calculated based on the mechanical strain.

2. The method for testing the preload attenuation of high-temperature, high-speed end-tooth connecting bolts according to claim 1, characterized in that, The strain gauge arrangement scheme is selected based on the critical temperature and the target test temperature, including: When the target test temperature is less than the critical temperature, an mounting plane is milled axially on the smooth section of the screw of a single connecting bolt. A high-temperature strain gauge is attached to the mounting surface to measure the total strain; The high-temperature strain gauge is connected to a 1 / 4 bridge Wheatstone bridge circuit.

3. The method for testing the preload attenuation of high-temperature, high-speed end-tooth connecting bolts according to claim 2, characterized in that, Static heating calibration was performed on the test specimen equipped with the aforementioned high-temperature strain gauge to establish the calibration relationship between temperature and thermal output strain, including: A calibration thermocouple is welded to the bolt head end face and both sides of the axial direction of at least two circumferentially symmetrically distributed connecting bolts. The test specimen was subjected to stepped heating, and the temperature was maintained at each temperature point while the temperature value measured by the thermocouple and the thermal output strain value of the high-temperature strain gauge were recorded simultaneously. The recorded data is fitted to obtain the calibration relationship between temperature and thermal output strain.

4. The method for testing the preload attenuation of high-temperature, high-speed end-tooth connecting bolts according to claim 3, characterized in that, The mechanical strain is equal to the total strain minus the thermal output strain of the calibration relationship at the current temperature.

5. The method for testing the preload decay of high-temperature, high-speed end-tooth connecting bolts according to claim 1, characterized in that, The strain gauge arrangement scheme is selected based on the critical temperature and the target test temperature, including: When the target test temperature is greater than or equal to the critical temperature, at the same axial position of the threaded rod section of a single connecting bolt, the first mounting plane and the second mounting plane are respectively machined circumferentially spaced 180° apart; A high-temperature strain gauge is attached to the first mounting surface as the main strain gauge, and a high-temperature strain gauge is attached to the second mounting surface as the temperature compensation strain gauge. The main strain gauge and the temperature compensation strain gauge are connected to adjacent arms of a Wheatstone bridge to form a half-bridge circuit to eliminate common-mode temperature drift.

6. The method for testing the preload decay of high-temperature, high-speed end-tooth connecting bolts according to claim 5, characterized in that, It also includes room temperature mechanical strain calibration to eliminate mechanical strain interference caused by the rotation of temperature-compensated strain gauges. The room temperature mechanical strain calibration includes: Under normal temperature conditions, the test piece is driven to rotate at multiple stepped speeds; The output strain values ​​of the temperature-compensated strain gauge at various rotational speeds were collected. The relationship curve between the rotational speed and the mechanical strain of the temperature-compensated strain gauge is obtained by fitting the collected output strain values.

7. The method for testing the preload attenuation of high-temperature, high-speed end-tooth connecting bolts according to claim 6, characterized in that, Based on the calibration relationship, the total strain is thermo-mechanically decoupled to obtain the mechanical strain, including: The differential strain values ​​between the main strain gauge and the temperature-compensated strain gauge are obtained from the output signal of the half-bridge circuit. Based on the current test rotation speed, find the corresponding mechanical strain value of the compensation plate from the relationship curve; Based on the differential strain value and the mechanical strain value of the compensation plate, the true mechanical strain of the connecting bolt is calculated. The current axial force of the connecting bolt is calculated based on the actual mechanical strain, and the current axial force is compared with the initial preload to obtain the preload attenuation.

8. The method for testing the preload attenuation of high-temperature, high-speed end-tooth connecting bolts according to claim 7, characterized in that, The actual mechanical strain is equal to the differential strain value minus the mechanical strain value of the temperature-compensated strain gauge.

9. The method for testing the preload attenuation of end-tooth connecting bolts under high temperature and high speed according to claim 1, characterized in that, The initial preload of the connecting bolt assembly is applied by the torque-rotation method and verified by the reverse loosening torque or ultrasonic length measurement method.

10. The method for testing the preload attenuation of high-temperature, high-speed end-tooth connecting bolts according to claim 1, characterized in that, The surface roughness Ra of the mounting plane is ≤1.6 μm. The high-temperature strain gauge is bonded with an adhesive that can withstand temperatures of not less than 600℃ and coated with a high-temperature silicone or ceramic protective coating. The critical temperature is 450℃.

Images