A wheel disc low cycle fatigue test crack on-line monitoring device

Abstract

This invention belongs to the field of low-cycle fatigue testing of gas turbine engines, specifically relating to an online monitoring device for cracks in low-cycle fatigue testing of turbine discs. This invention proposes an online, real-time monitoring device for identifying and tracking fatigue cracks in turbine discs during low-cycle fatigue testing. Applying this device avoids frequent offline inspections during the testing process, significantly improving testing efficiency, reducing testing costs, and enabling continuous and safe operation of the testing equipment. Low-cycle fatigue testing of turbine discs using this invention not only greatly improves testing efficiency, reduces the number and cost of offline disassembly inspections, and avoids specimen breakage and equipment damage, but also monitors key parameters such as crack initiation and propagation life. The test is terminated before the disc breaks, preserving the intact disc for analysis, thus significantly promoting advancements in turbine disc durability design and analysis methods.

Description

Technical Field

[0001] This invention belongs to the field of low-cycle fatigue testing of gas turbine engines, and specifically relates to an online monitoring device for cracks in low-cycle fatigue testing of a turbine disc. Background Technology

[0002] As a key component of aero-engines, the rotor disc undergoes low-cycle fatigue testing, a mandatory test item for engine design finalization. The main purpose is to verify that the rotor disc has a sufficient low-cycle fatigue life, validate theoretical calculations, and provide important test data for engine life determination and extension. The process involves simulating the rotor disc's takeoff-cruise-landing process within the engine, applying a low-cycle load spectrum until engineering-visible cracks appear in the test piece (or the crack size exceeds the allowable limit).

[0003] Current low-cycle fatigue testing of wheel-type engines primarily relies on periodic removal of the test specimens for non-destructive testing, i.e., offline methods. Offline inspection is time-consuming, labor-intensive, and expensive. Furthermore, common non-destructive testing methods (fluorescence, dye penetrant testing) are only applicable to surface cracks, and cracks often close in a static state, leading to the failure to detect cracks in a timely manner. This can result in serious consequences such as specimen breakage and damage to the testing equipment. In addition, crack initiation life and crack propagation life are two extremely important parameters in low-cycle fatigue testing of wheel-type engines. The former determines the acceptable number of cycles for the initial inspection, affecting engine safety and fuel economy, while the latter determines the engine's overhaul interval or lifespan. However, due to technological limitations, existing low-cycle fatigue tests only test whether cracks develop in the test specimen under specific cycles. This not only leads to conservative design and significantly increased costs but also yields minimal benefits in terms of mechanistic research and design improvements. Summary of the Invention

[0004] In view of this, the present invention provides an online crack monitoring device for low-cycle fatigue testing of discs. Specifically for low-cycle fatigue testing of discs, this invention proposes an online real-time monitoring device for identifying and tracking fatigue cracks in the disc. Applying this device can avoid frequent offline inspections during the testing process, significantly improving testing efficiency, reducing testing costs, and enabling continuous and safe operation of the testing equipment. Low-cycle fatigue testing of discs using this invention not only greatly improves testing efficiency, reduces the number and cost of offline disassembly inspections, and avoids specimen breakage and equipment damage, but also monitors key parameters such as crack initiation and propagation life. The test is terminated before the disc breaks, preserving the intact disc for analysis, thus powerfully promoting the advancement of disc durability design and analysis methods.

[0005] To achieve the above-mentioned technical objectives, the specific technical solution adopted by the present invention is as follows:

[0006] An online crack monitoring device for low-cycle fatigue testing of a rotary disc, characterized in that it comprises:

[0007] Two sets of eddy current displacement sensors, sensing different axial positions of the spindle of the test piece in the fatigue test, are used to sense the vibration signal of the spindle of the test piece.

[0008] A key phase sensor, with the sensing direction being the main shaft, is used to detect the phase information of the main shaft during the fatigue test;

[0009] The selection switch is communicatively connected to each of the eddy current displacement sensors and the key phase sensor, and is used to select the acquisition signal of a group of the eddy current displacement sensors.

[0010] The signal processing module is communicatively connected to the key phase sensor and the selection switch, and is used to perform computational amplification, tracking filtering and frequency selection on the acquired signal of the key phase sensor and the acquired signal of the selected eddy current displacement sensor to obtain the synchronous vibration amplitude and phase signal of the main shaft of the test piece;

[0011] The control acquisition computer is connected to the signal processing module and is used to combine the synchronous vibration amplitude and phase signal into a vector. After calculating and comparing the vector, the crack feature parameters are automatically selected, and the automatically generated stopping threshold is triggered in real time based on the crack feature parameters.

[0012] A relay is communicatively connected to the control and acquisition computer; when the control and acquisition computer calculates that the crack characteristic parameters exceed a threshold, the relay stops the fatigue test under the control of the control and acquisition computer.

[0013] Furthermore, the online crack monitoring device for low-cycle fatigue testing of the wheel also includes a programmable logic controller (PLC); the PLC communicates with the control and acquisition computer and the relay; the control and acquisition computer controls the relay based on the PLC.

[0014] Furthermore, the key phase sensor has a single tooth positioned opposite the main shaft, and this single tooth serves as the phase reference origin of the key phase sensor.

[0015] Furthermore, the frequency response of the key phase sensor and each of the eddy current displacement sensors is ≥

[0016] 2000Hz.

[0017] Furthermore, the selection switch channel is a dual-input, single-output channel with the negative poles connected in parallel; the housing of the selection switch is made of insulating material.

[0018] Furthermore, the signal processing module is used to perform discrete Fourier transform on the acquired signals from the key phase sensor and the selected eddy current displacement sensor; the signal processing module has at least 2 input channels, at least 1 output channel, and a sampling rate at least 20kHz; the input interface of the signal processing module is BNC, and the output interface is USB or PCI-e; the signal cable connected to the BNC is shielded.

[0019] Furthermore, the control and acquisition computer is equipped with a USB or PCI-e interface for connecting to the signal processing module; the control and acquisition computer is also equipped with a network port for connecting to the programmable logic controller.

[0020] The control and acquisition computer is equipped with dedicated acquisition and setting software; the software is used to combine vibration amplitude and phase into a vector and calculate the characteristic parameters of the crack; the software has a stopping threshold setting function; the stopping threshold is automatically adjusted based on the absolute value and growth rate of the characteristic parameters.

[0021] Furthermore, the programmable logic controller (PLC) is used to output logic control signals; the PLC is connected to the control acquisition computer via a network cable.

[0022] Furthermore, the relay acts on the power motor of the fatigue test; the control signal of the relay is a DC signal that matches the programmable logic controller; the power line of the relay is an AC signal that matches the power line of the motor.

[0023] Furthermore, the test piece is a spindle wheel with a single tooth positioned directly opposite the key phase sensor. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structural layout of the wheel-shaped low-cycle fatigue test using an online crack monitoring device in a specific embodiment of the present invention.

[0026] Figure 2 This is a curve showing the change of crack characteristics with the number of cycles in a low-cycle fatigue life test of a rotor according to a specific embodiment of the present invention;

[0027] The components include: 1. First eddy current displacement sensor; 2. Second eddy current displacement sensor; 3. Gearbox; 4. Motor; 5. Selector switch; 6. Relay; 7. Signal processing module; 8. Control and acquisition computer; 9. Programmable logic controller; 10. Key phase sensor; 11. Test piece. Detailed Implementation

[0028] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0029] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure 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 disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0030] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0031] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this disclosure. The drawings only show the components related to this disclosure and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0032] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0033] In one embodiment of the present invention, an online monitoring device for cracks in a low-cycle fatigue test of a wheel is provided, such as... Figure 1 As shown, it includes:

[0034] Two sets of eddy current displacement sensors are used to sense the vibration signals of the main shaft of the test piece 11 in the fatigue test, with the sensing direction being different axial positions of the main shaft.

[0035] The key phase sensor 10 senses the direction of the main axis and is used to detect the phase information of the main axis during fatigue testing.

[0036] Select switch 5 is connected in communication with each eddy current displacement sensor and key phase sensor 10, and is used to select the acquisition signal of a group of eddy current displacement sensors.

[0037] The signal processing module 7 is communicatively connected to the key phase sensor 10 and the selection switch 5. It is used to perform calculation amplification, tracking filtering and frequency selection on the acquired signal of the key phase sensor 10 and the acquired signal of the selected eddy current displacement sensor to obtain the synchronous vibration amplitude and phase signal of the main shaft of the test piece 11.

[0038] The control and acquisition computer 8 is connected to the signal processing module 7. It is used to combine the synchronous vibration amplitude and phase signal into a vector. After calculating and comparing the vector, the crack characteristic parameters are automatically selected, and the automatically generated stopping threshold is triggered in real time based on the crack characteristic parameters.

[0039] Relay 6 is connected to the control and acquisition computer 8. When the control and acquisition computer 8 calculates that the crack characteristic parameters exceed the threshold, relay 6 stops the fatigue test under the control of the control and acquisition computer 8.

[0040] In this embodiment, the online monitoring device for cracks in the low-cycle fatigue test of the wheel also includes a programmable logic controller (PLC) 9; the PLC 9 communicates with the control and acquisition computer 8 and the relay 6; the control and acquisition computer 8 controls the relay 6 based on the PLC 9.

[0041] In this embodiment, there are two sets of eddy current displacement sensors, including a first eddy current displacement sensor 1 and a second eddy current displacement sensor 2; a single tooth is provided on the key phase sensor 10 facing the main shaft, and the single tooth serves as the phase reference origin of the key phase sensor 10.

[0042] In this embodiment, the frequency response of the key phase sensor 10 and each eddy current displacement sensor is ≥2000Hz. The first eddy current displacement sensor 21 and the second eddy current displacement sensor are configured identically and are powered by a +24VDC supply voltage; the key phase sensor 10 does not require a power supply and its output voltage is between 0 and 5DVC.

[0043] In this embodiment, the selection switch 5 channel is a dual-input single-output channel with the negative terminals connected in parallel; the housing of the selection switch 5 is made of insulating material to avoid signal interference.

[0044] In this embodiment, the signal processing module 7 is used to perform discrete Fourier transform on the acquired signals of the key phase sensor 10 and the acquired signals of the selected eddy current displacement sensor; the signal processing module 7 has ≥2 input channels, ≥1 output channel, and a sampling rate ≥20k; the input interface of the signal processing module 7 is BNC, and the output interface is USB or PCI-e; the signal line connected to the BNC is shielded.

[0045] In this embodiment, the control and acquisition computer 8 is provided with a USB or PCI-e interface for connecting to the signal processing module 7; the control and acquisition computer 8 is provided with a network port for connecting to the programmable logic controller 9.

[0046] In this embodiment, the control and acquisition computer 8 is equipped with dedicated acquisition and setting software; the software is used to combine the vibration amplitude and phase into a vector and calculate the characteristic parameters of the crack; the software has a stopping threshold setting function; the stopping threshold is automatically adjusted based on the absolute value and growth rate of the characteristic parameters.

[0047] In this embodiment, the programmable logic controller 9 is used to output logic control signals; the programmable logic controller 9 is connected to the control acquisition computer 8 via a network cable.

[0048] In this embodiment, relay 6 acts on the power motor 4 of the fatigue test; the control signal of relay 6 is a DC signal that matches the programmable logic controller 9; the power line of relay 6 is an AC signal that matches the power line of motor 4.

[0049] In this embodiment, the test piece 11 is a spindle wheel with a main shaft, and a single tooth is provided on the main shaft directly opposite the key phase sensor 10. The motor 4 and gearbox 3 are the drive system of the experimental device, and the relay 6 realizes the automatic stopping of the motor 4 and gearbox 3.

[0050] The low-cycle fatigue life test of a certain rotor was conducted on a wheel tester. The wheel tester mainly consists of a test chamber, a lubricating oil system, a radiation heating system, a testing system, a control system, and a vacuum system. The rotor is set with high speed, low speed, holding time, and lift speed to simulate the three stages of engine takeoff, cruise, and landing.

[0051] Vibration signals are acquired by a vibration sensor near the spindle, and key phase pulse signals are acquired by a single-tooth speed sensor. The amplitude and phase of synchronous vibration are obtained by tracking filtering and frequency selection. A reference signal is introduced, and the amplitude of synchronous vibration relative to the reference is used as a crack characteristic parameter.

[0052] In the early stages of this experiment, the real-time synchronous vibration vector always oscillated around the "reference" vector, and the magnitude of the difference between the two vectors was very small. Due to factors such as friction of the shaft mating surfaces, the initial plasticity of the rotor material, blade oscillation, and other benign frictions, the synchronous vibration vector will fluctuate in the initial stage, but the fluctuation range is limited, and the overall synchronous vibration amplitude relative to the reference shows a decreasing trend.

[0053] After the initial break-in cycle, the rotor reached a steady state on the 1700th cycle of this test. The baseline (average of Ax and Ay, automatically taken from cycles 1700-3000) was calculated based on the average of the stable sample data. The crack characteristic parameters of this cycle were close to zero, and it can be considered that the vibration response in this stage was only caused by the residual unbalance of the rotor, and there were no cracks on the rotor.

[0054] like Figure 2 As shown, with the increase of the number of cycles, starting from the 3000th cycle, the synchronous vibration amplitude relative to the reference gradually increases, indicating that a new imbalance has appeared in the rotor. Since a "reference" has been introduced and the parameters in the previous period were very stable, benign factors can be ruled out; therefore, this additional imbalance is caused by rotor cracks. After the subsequent 500 cycles, the amplitude continues to gradually increase, from 0 μm to 30 μm, and the crack phenomenon is very obvious. The stopping threshold considers both the absolute value and the growth rate. The absolute value reflects the relative size of the crack. Observing from the 3000th cycle, the crack generally shows an exponential increasing trend, with the rate of increase becoming faster and faster; the rate of increase reflects the crack propagation rate. When the absolute value reaches 127 μm in the 4065th cycle, the system triggers the stopping threshold, and the programmable logic controller 9 controls the relay 6 to automatically stop the machine.

[0055] Upon disassembly and non-destructive testing, a through crack of approximately 27mm was found near the bolt hole.

[0056] The crack online monitoring device described in this embodiment is highly practical and reliable, and can be successfully applied to low-cycle fatigue of aero-gas turbine engine discs.

[0057] This embodiment uses two eddy current displacement sensors and one key phase sensor 10 on the main shaft to select and track the collected vibration and phase signals in real time, and processes the synchronous vibration signals in real time to obtain crack characteristic parameters. A stopping threshold is set by the control system to achieve safe and automatic operation of the testing equipment. The low-cycle fatigue test of the disc using this invention not only greatly improves testing efficiency, reduces the number and cost of offline disassembly inspections, and avoids the breakage of the test piece 11 and damage to the testing equipment, but also monitors key parameters such as crack initiation and propagation life. The test is terminated before the disc breaks, preserving the complete disc for analysis, thus significantly promoting the advancement of disc durability design and analysis methods. This embodiment has been successfully applied in low-cycle fatigue tests of multiple disc models, accurately and timely monitoring of cracks and propagation data on the disc and achieving automatic stopping.

[0058] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A wheel disc low cycle fatigue test crack on-line monitoring device, characterized in that, The device comprises: two groups of eddy current displacement sensors, which are arranged to sense the vibration signals of the main shaft of the test piece in different axial positions of the main shaft of the test piece in the fatigue test; a key phase sensor, which is arranged to face the main shaft and is used to detect the phase information of the main shaft during the fatigue test; a selection switch, which is connected with each of the eddy current displacement sensors and is used to select the collected signals of a group of the eddy current displacement sensors; a signal processing module, which is connected with the key phase sensor and the selection switch and is used to perform operation amplification, tracking filtering and frequency selection on the collected signals of the key phase sensor and the selected eddy current displacement sensors to obtain the synchronous vibration amplitude and phase signals of the main shaft of the test piece; a control and collection computer, which is connected with the signal processing module and is used to combine the synchronous vibration amplitude and phase signals into a vector, automatically select the crack characteristic parameters after calculation and comparison of the vector, and trigger the automatically generated parking threshold based on the crack characteristic parameters in real time; a relay, which is connected with the control and collection computer and is used to make the fatigue test stop under the control of the control and collection computer when the crack characteristic parameters exceed the threshold.

2. The wheel on low cycle fatigue test crack monitoring apparatus of claim 1, wherein, The device further comprises a programmable logic controller, which is connected with the control and collection computer and the relay, and the control and collection computer controls the relay based on the programmable logic controller.

3. The wheel disc low cycle fatigue test crack on-line monitoring device according to claim 2, characterized in that, The key phase sensor is provided with a single tooth facing the main shaft, which is used as the phase reference origin of the key phase sensor.

4. The wheel disc low cycle fatigue test crack on-line monitoring device according to claim 3, characterized in that, The frequency response of the key phase sensor and each of the eddy current displacement sensors is ≮2000 Hz.

5. The wheel on low cycle fatigue test crack monitoring apparatus of claim 4 wherein, The selection switch is a double-in-single-out channel, and the negative electrodes are connected in parallel. The shell of the selection switch is made of insulating material.

6. The wheel on low cycle fatigue test crack monitoring apparatus of claim 5 wherein, The signal processing module is used to perform discrete Fourier transform on the collected signals of the key phase sensor and the selected eddy current displacement sensors. The input channel number of the signal processing module is ≮2, the output channel number is ≮1, and the sampling rate is ≮20k. The input interface of the signal processing module is BNC, and the output interface is USB or PCI-e. The signal line connected with the BNC is provided with shielding.

7. The wheel on low cycle fatigue test crack monitoring apparatus of claim 6 wherein, The control and collection computer is provided with one USB or PCI-e interface for connection with the signal processing module and one network port for connection with the programmable logic controller. The control and collection computer is installed with special collection and setting software, which is used to combine the vibration amplitude and phase into a vector and calculate the characteristic parameters of the crack. The software is provided with a setting function of the parking threshold, which is automatically adjusted based on the absolute value and growth rate of the characteristic parameters.

8. The wheel on low cycle fatigue test crack monitoring apparatus of claim 7 wherein, The programmable logic controller is used to output logic control signals, and the programmable logic controller and the control and collection computer are connected through a network cable.

9. The wheel on low cycle fatigue test crack monitoring apparatus of claim 8 wherein, The relay acts on the power motor of the fatigue test; the control signal of the relay is a direct current signal matched with the programmable logic controller; the power line of the relay is an alternating current signal matched with the power phase of the motor.

10. The wheel on low cycle fatigue test crack monitoring apparatus of claim 9 wherein, The test piece is a main shaft wheel disc, and a single tooth is arranged at the position where the main shaft is opposite to the key phase sensor.

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