A test system for early damage of a drive shaft and a test method thereof

Abstract

The present application relates to a kind of transmission shaft early damage test system and its testing method, comprising: fixedly connected driving device;Mechanical loading module;Multi-dimension sensing module, at least including acoustic emission sensor, fiber bragg grating strain sensor and fiber bragg grating temperature sensor;Signal transmission module;Data acquisition and control module;Self-adaptive control decision program is run in the data acquisition and control module: based on real-time processing sensing signal, the real-time damage state evaluation value of the measured transmission shaft is calculated;Based on real-time damage state evaluation value, from the adaptive selection of current control mode in multiple control modes, including standard loading mode, damage inquiry mode, damage excitation mode;The corresponding load control instruction is generated.From three dimensions, early damage is jointly represented, can be detected in microcrack initiation stage, so that the data of transmission shaft early damage is obtained, provides accurate guidance for design optimization.

Description

Technical Field

[0001] This invention belongs to the field of drive shaft testing, and in particular relates to a testing system and method for early damage to drive shafts. Background Technology

[0002] Drive shafts, as key rotating components for transmitting power and torque, are widely used in numerous industrial fields such as automobiles, construction machinery, wind power generation, ship propulsion, and aerospace. Their operating conditions are typically extremely complex, requiring them to continuously withstand alternating torque, bending, axial, and combined loads at high speeds, and potentially experiencing harsh conditions such as temperature variations, changes in lubrication conditions, and misalignment impacts. Drive shaft failure, especially fatigue failure, is often a progressive, cumulative damage process; its eventual fracture can lead to severe equipment downtime, production losses, and even safety accidents. Therefore, comprehensive and accurate performance testing and life assessment of drive shafts during research and development, production, and quality control are crucial prerequisites for ensuring the reliability and safety of the entire system.

[0003] Currently, the industry primarily tests drive shafts using bench testing. Bench testing is typically conducted on dedicated testing equipment, applying loads that simulate actual working conditions to evaluate the drive shaft's static strength, fatigue life, torsional stiffness, critical speed, and other properties. Bench testing can be performed in a workshop, providing a controlled environment, shorter testing cycles, precise setting of testing conditions, and repeatable operation, making it a core tool for product development and quality verification.

[0004] However, existing bench testing techniques for drive shafts primarily focus on fatigue performance assessment. They apply pre-defined load spectra to the specimens and record the load conditions and cycle counts experienced when visible cracks appear or the drive shaft completely fractures. This type of testing is for terminal failure assessment, and the results are merely single life data points or comparisons of whether the load meets design requirements. It cannot test the evolution of the drive shaft's internal microstructure under load, the initiation of damage, or the propagation of microcracks. Therefore, it cannot reveal how, where, or in what manner damage begins. Existing bench testing equipment uses sensors that respond well to obvious cracks, plastic deformation, or vibration anomalies, but are insensitive to early-stage microcracks and micro-thermal deformations in the drive shaft. By the time the sensors can detect data, the damage to the drive shaft has already progressed to the brink of failure, missing the opportunity for early warning and research into the early damage initiation stage. Existing tests can only determine under what conditions the drive shaft fails, but cannot determine under what load or at what number of cycles the damage begins. This makes it impossible for existing testing methods to accurately pinpoint design weaknesses, such as material problems, heat treatment issues, or localized geometric stress concentrations, thus lacking clear objectives for design optimization.

[0005] Therefore, it is essential to conduct early testing for drive shaft damage. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies, which can only test for failure conditions of drive shafts but cannot test for early damage to drive shafts or provide data support for prevention and intervention. It provides a test system and method for early damage to drive shafts. Through multi-dimensional sensing collaboration and the selection of multiple control modes, early damage data can be obtained at the stage of microcrack initiation in drive shafts, providing precise guidance for design optimization.

[0007] The specific technical solution of this invention is: a testing system for early damage to a drive shaft, comprising: A fixed connection drive device is used to connect and fix the transmission shaft to be tested, and to drive the transmission shaft to rotate. A mechanical loading module, configured on a fixed-connection drive unit, is used to apply independently controllable torque and bending loads to the drive shaft under test. The multi-dimensional sensing module includes an early damage sensing sensor array fixedly installed on the rotating surface of the tested transmission shaft, used to acquire physical signals characterizing early damage to the tested transmission shaft in real time; the early damage sensing sensor array includes at least an acoustic emission sensor, a fiber optic strain sensor, and a fiber optic temperature sensor. The signal transmission module includes an electrical signal transmission unit and an optical signal transmission unit, which are used to transmit the electrical and optical signals collected by the early damage sensing sensor array in a rotating state to the data acquisition and control module. The data acquisition and control module is connected to the signal transmission module and is used to receive and synchronously acquire signals from the signal transmission module, demodulate, process and analyze the signals, extract early damage characteristics of the drive shaft, and output control commands to the mechanical loading module. The data acquisition and control module runs an adaptive control decision program, which is configured to execute: Based on the real-time processed sensor signals, the real-time damage status assessment value of the tested transmission shaft is calculated. Based on the real-time damage status assessment value, the current control mode is adaptively selected from a variety of preset control modes, including at least the standard loading mode, damage inquiry mode, and damage activation mode. Based on the selected current control mode, a corresponding load control command is generated to drive the mechanical loading module to adjust the load spectrum applied to the tested transmission shaft.

[0008] Acoustic emission sensors are used to capture transient elastic wave signals generated during the initiation and propagation of early damage. Fiber Bragg grating strain sensors are used to monitor quasi-static strain redistribution caused by damage evolution. Fiber Bragg grating temperature sensors are used to monitor localized frictional temperature rise caused by damage. By capturing transient elastic waves from microcrack initiation through acoustic emission, monitoring quasi-static stress redistribution through fiber Bragg grating strain, and monitoring frictional thermal effects through fiber Bragg grating temperature, early damage is characterized from three dimensions. It can be detected at the microcrack initiation stage, thus obtaining data on early damage to the driveshaft. This shifts the focus from post-incident assessment to pre-incident insight, effectively observing damage evolution and gaining a deeper understanding of the driveshaft failure mechanism. To simulate the driveshaft's operating conditions, a mechanical loading module is used to load the driveshaft, primarily with torque and bending loads. Early damage to the driveshaft is characterized by strong concealment, weak signals, and slow evolution. If only a single constant amplitude load or random load is used... In traditional load spectrum testing, early damage signals are either submerged in noise and difficult to identify, or the damage initiation rate is too slow, resulting in excessively long testing cycles, or it is impossible to distinguish between real and spurious damage signals. Therefore, this application employs three control modes—standard loading, damage inquiry, and damage initiation—working in tandem and mutually verifying each other. The standard loading mode applies a basic load spectrum simulating actual working conditions to induce micro-damage; the damage inquiry mode detects excitation to actively acquire damage response signals; and the damage initiation mode appropriately adjusts load parameters to verify damage sensitivity or moderately accelerate damage propagation. By using early damage data of the drive shaft, the remaining life of the drive shaft can be predicted, thereby enabling condition-based replacement in engineering, significantly saving maintenance costs, and avoiding equipment accidents caused by sudden fractures. Early damage data can also reveal where drive shaft damage originates and how it propagates, providing precise guidance for subsequent design optimization.

[0009] Preferably, the fixed connection drive device includes: a first connection component, a second connection component, and a rotary drive unit. The first connection component and the second connection component are respectively connected to the two ends of the transmission shaft under test. The rotary drive unit is connected to the first connection component for driving the transmission shaft under test to rotate around its axis. The rotary drive unit adopts a variable frequency speed control motor.

[0010] Preferably, the mechanical loading module includes: A torque loading unit is used to apply a controllable torque load to the tested drive shaft; A bending loading unit is used to apply a controllable bending load to the tested drive shaft; The torque loading unit and the bending loading unit are independently mounted on the fixed connection drive device; The torque loading unit includes a servo motor, a reducer, and a reaction arm. The servo motor is connected to the transmission shaft under test via the reducer and is used to output controllable torque. The bending loading unit includes a hydraulic cylinder, a loading head, and a force sensor. The loading head acts on the middle part or a preset section of the transmission shaft under test to output a controllable bending moment. The torque loading unit and the bending loading unit are respectively equipped with a torque sensor and a force sensor, which are used to feed back load signals to the data acquisition and control module in real time to realize closed-loop control.

[0011] Preferably, the sensor array is distributed along the axial and circumferential directions of the transmission shaft being measured: In the axial direction, the sensor array is arranged at at least one preset dangerous section of the transmission shaft being measured. The dangerous section includes a stress concentration area, a keyway area, a transition fillet area, or a section with the maximum bending moment / torque determined based on finite element analysis. In the circumferential direction, at the same critical section, the acoustic emission sensor and fiber optic strain sensor are arranged at intervals along the circumferential direction to cover the multi-directional response of the tested transmission shaft under complex loads. The fiber grating temperature sensor is arranged adjacent to the fiber grating strain sensor to acquire temperature field data at the measuring point in real time.

[0012] Preferably, the electrical signal transmission unit is a multi-channel conductive slip ring, used to transmit the analog electrical signal output by the acoustic emission sensor and the power supply. The rotor end of the multi-channel conductive slip ring is connected to the signal output end and power input end of the acoustic emission sensor and its preamplifier circuit, and its stator end is connected to the data acquisition and control module and the power supply. The optical signal transmission unit is an optical fiber rotary connector used to transmit optical signals emitted by the fiber optic strain sensor and the fiber optic temperature sensor. The rotating end of the optical fiber rotary connector is connected to an optical fiber jumper laid on the surface of the transmission shaft under test, and its stationary end is connected to the data acquisition and control module.

[0013] Preferably, the data acquisition and control module includes: The fiber optic grating demodulator is optically connected to the fiber optic grating strain sensor and the fiber optic grating temperature sensor through the signal transmission module, and is used to demodulate the optical signal into wavelength data. A multi-channel data acquisition card is electrically connected to the acoustic emission sensor via the signal transmission module and is used to acquire electrical signals; The data processing unit is connected to the fiber Bragg grating demodulator and the multi-channel data acquisition card to synchronously process optical and electrical signals and extract damage characteristic parameters. The controller, connected to the data processing unit and the mechanical loading module, is used to output control commands to the torque loading unit and the bending loading unit according to the damage characteristic parameters.

[0014] Preferably, the real-time damage state assessment value is calculated based on the acoustic emission event count, strain drift, and temperature change according to a preset weighted fusion model; the weighted fusion model is as follows: Overall damage assessment value: ,in: Let be the event count rate (times / second) of the k-th acoustic emission sensor within a 5-second sliding window. Let be the baseline event count rate of the k-th acoustic emission sensor. This represents the actual strain drift at the k-th measuring point after temperature compensation. This represents the temperature change at the k-th measuring point. , , The critical values ​​for micro-damage initiation, namely acoustic emission event count, strain drift, and temperature change, were determined through standard part calibration tests. The calibration procedure was as follows: a standard drive shaft of the same model without damage was taken, assembled according to the installation method of the embodiment, and run in standard loading mode for 1000 cycles. The mean and 3σ standard deviation of acoustic emission event count rate, strain drift, and temperature change were statistically analyzed, and the upper limit of 3σ for each parameter was taken as the corresponding critical value for micro-damage initiation. , , Normalized threshold: =1.0 times / second =50με, =2.0℃; , , As preset weights, and ; For each sensor, calculate its local damage assessment value separately. The maximum value of all local assessment values ​​is taken as the real-time damage status assessment value of the entire drive shaft. Overall assessment value Used to compare with preset first and second thresholds to determine the switching of control modes; The sensor position corresponding to the largest k value is the location of the most severe damage, which is used for damage localization.

[0015] Preferably, when the real-time damage state assessment value is lower than the first preset threshold, a standard loading mode is selected, and the mechanical loading module is controlled to apply a basic load spectrum that simulates the actual working conditions, so that micro-damage can be generated in a real stress environment. When the real-time damage status assessment value reaches the first preset threshold but does not reach the second preset threshold, the damage inquiry mode is selected, and the mechanical loading module is controlled to switch to low-frequency, low-amplitude, short-time excitation to actively stimulate the acoustic emission response of the microcrack and improve the signal-to-noise ratio of the damage signal. When the real-time damage status assessment value reaches the second preset threshold, a damage excitation mode is selected, and the mechanical loading module is controlled to moderately increase the load amplitude or change the load phase to verify the damage sensitivity or moderately accelerate the damage propagation, so as to facilitate continuous tracking of damage evolution.

[0016] When early microcracks exist in the drive shaft, such as those with a length of <0.1mm, low-frequency, low-amplitude alternating loads will cause periodic micro-opening and relative slippage on the microcrack surface, generating micro-dislocations and grain boundary slippage at the crack tip, releasing characteristic acoustic emission elastic waves. Healthy materials have almost no additional acoustic emission events under low-amplitude loads. By increasing the acoustic emission monitoring gain, the weak signals generated by the microcracks can be highlighted from the background noise, thereby achieving active excitation.

[0017] Preferably, the first preset threshold The second preset threshold ; =0.5、 =0.3、 =0.2.

[0018] A test method for a test system for early damage to a drive shaft, comprising the following steps: S1: Install the transmission shaft under test onto the fixed connection drive device, start the system, and initialize and calibrate the multi-dimensional sensing module and sensor. S2: Run the standard loading mode, apply the basic load spectrum simulating the actual working conditions through the mechanical loading module, and at the same time collect the sensing signals in the initial stage through the multi-dimensional sensing module. The background event count rate collected by the acoustic emission sensor, the initial strain value collected by the fiber optic strain sensor, and the initial temperature value collected by the fiber optic temperature sensor are used as the baseline signal characteristics, which serve as the reference for subsequent calculation of strain drift and temperature change. S3: Calculate the real-time damage status assessment value of the tested transmission shaft in real time according to the adaptive control decision program; S4: When the real-time damage status assessment value reaches the first preset threshold but does not reach the second preset threshold, the data acquisition and control module automatically switches the current control mode to the damage inquiry mode and controls the mechanical loading module to switch to low-frequency, low-amplitude, short-time excitation to actively excite and capture the acoustic emission response of the microcrack. S5: When the real-time damage status assessment value reaches the second preset threshold, the data acquisition and control module automatically switches the current control mode to the damage excitation mode, and controls the mechanical loading module to appropriately increase the load amplitude or change the load phase in order to verify the damage sensitivity and track the damage evolution. S6: Continue executing steps S3 to S5. When the preset shutdown conditions are met, stop the test and generate a test report containing data on the entire process of damage initiation and expansion.

[0019] To avoid frequent switching of control modes due to fluctuations in the real-time damage assessment value D(t) around the threshold, which would affect test stability, a hysteresis interval is set during the switching process: switching from standard loading to damage inquiry: D(t) ≥ 0.5 and lasting for more than 5 seconds; returning from damage inquiry to standard loading: D(t) < 0.5 and lasting for more than 5 seconds; corresponding hysteresis conditions and durations are also set for switching damage excitation modes.

[0020] The beneficial effects of this invention are: 1. By capturing the transient elastic waves of microcrack initiation through acoustic emission, monitoring the quasi-static stress redistribution through fiber optic grating strain, and monitoring the frictional heat effect through fiber optic grating temperature, early damage is characterized from three dimensions. It can be detected at the microcrack initiation stage, thereby obtaining data on early damage to the drive shaft. This shifts the focus from post-event judgment to pre-event insight, effectively observing the evolution of damage and thus gaining a deeper understanding of the failure mechanism of the drive shaft. 2. The test process is automated by setting and selecting three control modes. The standard loading mode can simulate the load spectrum of the real working condition, allowing micro-damage to naturally emerge in the real stress environment. This avoids the problem of rapid damage propagation caused by overload in traditional fatigue tests, which makes it impossible to capture the early stage. The damage inquiry mode with low frequency, low amplitude and short time excitation stimulates the acoustic emission response of microcracks, improving the signal-to-noise ratio of early damage signals. Through the damage excitation mode, the load amplitude is appropriately increased or the phase is changed to verify the damage sensitivity and track the evolution, avoiding the dilemma of detecting a signal but not being able to confirm whether it is real damage. 3. Through the mechanical loading module, torque and bending can be independently controlled in a closed loop, while also supporting complex load spectra, providing an execution basis for adaptive control; 4. By using early damage data of the drive shaft, the remaining life of the drive shaft can be predicted, thereby enabling timely replacement in engineering, significantly saving maintenance costs and avoiding equipment accidents caused by sudden breakage. 5. Early damage data can also reveal where the driveshaft damage originates and how it expands, providing precise guidance for subsequent design optimization. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a structure of the present invention; Figure 2 This is a schematic diagram of the arrangement of the position sensor in the middle of the transmission shaft intermediate tube of the present invention; Figure 3 This is a schematic diagram of the arrangement of the position sensor at the end of the drive shaft of the present invention; Figure 4This is a schematic diagram of an axial adjustment structure according to the present invention; In the diagram: 1. Base, 2. Second bracket, 3. Support plate, 4. Servo motor, 5. Reducer, 6. Reaction arm, 7. Shaft, 8. Rotor, 9. Stator, 10. Flange, 11. Gantry frame, 12. Ear seat, 13. Hydraulic cylinder, 14. Loading head, 15. Roller, 16. First connecting assembly, 17. Variable frequency speed control motor, 18. First bracket, 19. Lead screw, 20. Adjusting motor, 21. Drive shaft, 22. Acoustic emission sensor, 23. Fiber Bragg grating strain sensor, 24. Fiber Bragg grating temperature sensor, 25. Crossbeam, 26. Wedge block, 27. Wedge groove. Detailed Implementation

[0022] The present invention will be further described below through specific embodiments and in conjunction with the accompanying drawings. Example

[0023] like Figure 1 Figure 2 Figure 3 As shown, a drive shaft early damage testing system includes: a fixed connection drive device, a mechanical loading module, a multi-dimensional sensing module, a signal transmission module, and a data acquisition and control module.

[0024] The mechanical loading module is mounted on a fixed connection drive device, which includes a base 1, a first bracket 18 and a second bracket 2 mounted on the base. The first and second brackets are perpendicular to the base. A first connecting component 16 is mounted on the first bracket, and a second connecting component is mounted on the second bracket. The first and second connecting components are coaxially arranged and connected to both ends of the transmission shaft to be tested. The first and second connecting components adopt a flange shaft structure. The shaft portions 7 of the two flange shafts are mounted on corresponding brackets via bearings. The flange portions 10 of the two flange shafts are arranged opposite to each other, and the ends of the shaft portions extend beyond the corresponding brackets. A variable frequency speed control motor 17 is connected to the shaft end of the flange shaft of the first connecting component, and the variable frequency speed control motor drives the first connecting component to rotate.

[0025] A support plate 3 is mounted on the first support and a support plate 3 is mounted on the second support. A variable frequency speed control motor is mounted on the support plate of the first support. A gantry frame 11 is mounted on the base, positioned between the first and second supports. The mechanical recording module includes a torque recording unit and a bending loading unit. The torque loading unit includes a servo motor 4, a reducer 5, and a reaction arm 6. The servo motor is connected to the flange shaft of the second connecting assembly via the reducer and a key. A torque sensor is configured between the reducer and the mating flange shaft to provide real-time load signal feedback to the data acquisition and control module for closed-loop control. One end of the reaction arm is connected to the reducer, and the other end is connected to the support plate. The variable frequency speed control motor drives the first connecting assembly to rotate, and the first connecting assembly drives the transmission shaft to rotate. The servo motor provides torque via the reducer, and the torque is transmitted to the transmission shaft through the second connecting assembly, thereby subjecting the transmission bearing to a torque load. The bending loading unit includes a hydraulic cylinder 13, a loading head 14, and a force sensor. The loading head acts on the middle of the transmission shaft being measured. A crossbeam 25 is installed on the upper part of the gantry frame. A lug 12 is installed on the lower surface of the middle part of the crossbeam. The end of the hydraulic cylinder body is rotatably connected to the lug. The hydraulic cylinder is in an inverted position. The end of the hydraulic cylinder's telescopic rod is connected to a loading head. A force sensor is installed between the end of the telescopic rod and the loading head. A swing limit pin is installed on the lug, allowing the hydraulic cylinder to swing at an angle of ±3°, preventing lateral forces from damaging the components. The loading head is semi-annular, with a semi-circular inner surface. The inner diameter of the inner surface matches the outer diameter of the intermediate tube of the drive shaft to be tested. Several evenly distributed rollers 15 are installed on the inner surface of the loading head. The axis of the rollers is parallel to the axis of the drive shaft. The inner surface of the loading head mates with the outer surface of the intermediate tube of the drive shaft. The extension of the hydraulic cylinder applies a bending load to the drive shaft. Rolling contact between the rollers and the drive shaft creates a rolling release, thus avoiding any impact on the drive shaft.

[0026] The multi-dimensional sensing module includes an early damage sensing sensor array fixedly mounted on the rotating surface of the tested transmission shaft. The early damage sensing sensor array includes an acoustic emission sensor 22, a fiber Bragg grating strain sensor 23, and a fiber Bragg grating temperature sensor 24. The sensor array is distributed along the axial and circumferential directions of the tested transmission shaft: axially, the sensor array is located at the middle part of the intermediate tube of the tested transmission shaft and at the root of the two universal joint forks; circumferentially, at the same critical section, the acoustic emission sensor, fiber Bragg grating strain sensor, and fiber Bragg grating temperature sensor are arranged at intervals along the circumferential direction, with the fiber Bragg grating strain sensor and fiber Bragg grating temperature sensor arranged symmetrically relative to the acoustic emission sensor. In this embodiment, the middle part of the tested drive shaft is the middle position of the intermediate tube. At this circumferential position, four acoustic emission sensors are installed, spaced 90° apart circumferentially. The acoustic emission sensors are fixed by adhesive bonding and are externally mounted on the drive shaft with clamps for auxiliary fixation. Four fiber optic strain sensors and four fiber optic temperature sensors are installed in pairs, spaced 90° apart circumferentially. Bases are first fixed to corresponding positions on the outer surface of the drive shaft. The optical fibers are adhered to the bases and protected by silicone rubber encapsulation. Of the four fiber optic strain sensors, those facing each other form a pair. The grating directions of the two pairs of fiber optic strain sensors are respectively axial strain sensitive (parallel to the axial direction) and shear strain sensitive (45° to the axial direction). At the root of the universal joint fork, two acoustic emission sensors are installed, spaced 180° apart circumferentially, using the same fixing method. Two fiber optic strain sensors and two fiber optic temperature sensors are installed in pairs, spaced 180° apart circumferentially, using the same fixing method. Here, the grating direction of the fiber optic strain sensor is axial strain sensitive (parallel to the axial direction). A preamplifier circuit board is installed on the flange end face at both ends of the drive shaft. Considering balance, a counterweight is placed on the flange end face, and the preamplifier circuit board is mounted on the counterweight. The signal cable of the acoustic emission sensor runs axially along the drive shaft surface and connects to the preamplifier circuit board, secured every 50mm with polyimide tape, and protected with an outer PTFE heat-shrink tubing for abrasion prevention. The optical fiber runs spirally along the drive shaft surface with a pitch of 25mm. In this embodiment, the acoustic emission sensor is a broadband resonant piezoelectric ceramic sensor with a response frequency range of 100kHz to 1MHz; the fiber Bragg grating strain sensor is a fiber Bragg grating strain gauge with a grating length of 10mm, a center wavelength of 1550nm, and a strain resolution better than 1με; the fiber Bragg grating temperature sensor is a bare grating packaged fiber grating thermometer with a temperature sensitivity coefficient of approximately 12pm / ℃. At the 0° position of the universal joint shaft fork root, the acoustic emission sensor is located on the axial center line. The fiber optic strain sensor and fiber optic temperature sensor are respectively arranged on both sides of the acoustic emission sensor, with an angle of about 10-15° with the acoustic emission sensor. The three constitute the measuring point k=1, which is arranged close to each other in space with a spacing of ≤15mm, and together characterizes the damage state at the 0° position.A fiber Bragg grating temperature sensor is positioned adjacent to a fiber Bragg grating strain sensor for real-time temperature compensation. At the same 180° position, an acoustic emission sensor is located on the axial centerline. The fiber Bragg grating strain sensor and the fiber Bragg grating temperature sensor are positioned on either side of the acoustic emission sensor, with circumferential angles of approximately 10-15°, forming measurement point k=2. The same arrangement is observed at the root of the universal joint shaft at the other end, forming measurement points k=7 and k=8. Measurement points k=3, k=4, k=5, and k=6 are located at the center of the intermediate tube.

[0027] The signal transmission module includes an electrical signal transmission unit and an optical signal transmission unit. The electrical signal transmission unit is a multi-channel conductive slip ring used to transmit the analog electrical signals output by the acoustic emission sensor and the power supply. The rotor end of the multi-channel conductive slip ring is connected to the signal output and power input terminals of the acoustic emission sensor and its preamplifier circuit, while its stator end is connected to the data acquisition and control module and the power supply. The rotor 8 of the multi-channel conductive slip ring is fixed to the flange shaft of the first and second connecting components via a shrink sleeve and rotates with the tested transmission shaft. The stator 9 is fixed to the corresponding bracket via a flange. The optical signal transmission unit is a fiber optic rotary connector. The rotating end of the fiber optic rotary connector is connected to an optical fiber jumper laid on the surface of the tested transmission shaft, and its stationary end is connected to the data acquisition and control module. The fiber optic rotary connector is disposed in the central through hole of the conductive slip ring. The rotating end of the fiber optic rotary connector rotates in conjunction with the rotor of the conductive slip ring via a connecting sleeve, and the stationary end is fixed in conjunction with the stator of the conductive slip ring via a connecting plate, forming an integrated structure. The flange shaft has axial grooves on its outer surface. The rotor cable of the multi-channel conductive slip ring and the rotating end cable of the fiber optic rotary connector extend axially from the flange end face along the grooves to the preamplifier circuit board and corresponding sensors. The rotor cable and fiber optic cable are separately fixed on the drive shaft surface to avoid electromagnetic interference. Commercially available integrated optoelectronic slip rings, such as the DFO608 series, can be used. Each of the flange shaft sections of the first and second connecting assemblies at both ends of the drive shaft is equipped with an integrated optoelectronic rotary transmission assembly, which transmits sensor signals from the corresponding half-shaft. Electrical signals are transmitted from the acoustic emission sensor to the data acquisition and control module via the conductive slip ring, while optical signals are transmitted from the fiber optic strain sensor and fiber optic temperature sensor to the data acquisition and control module via the fiber optic rotary connector. After all rotating components are installed, the entire assembly undergoes dynamic balancing.

[0028] The data acquisition and control module is connected to the signal transmission module to demodulate, process, and analyze the signal, extract early damage characteristics of the drive shaft, and output control commands to the mechanical loading module. The data acquisition and control module includes: a fiber Bragg grating demodulator, a multi-channel data acquisition card, a data processing unit, and a controller. The fiber Bragg grating demodulator is optically connected to the fiber Bragg grating strain sensor and fiber Bragg grating temperature sensor via the signal transmission module, demodulating the optical signal into wavelength data. The multi-channel data acquisition card is electrically connected to the acoustic emission sensor via the signal transmission module to acquire electrical signals. The data processing unit is data-connected to the fiber Bragg grating demodulator and the multi-channel data acquisition card, synchronously processing optical and electrical signals to extract damage characteristic parameters. The controller is connected to the data processing unit and the mechanical loading module, outputting control commands to the torque loading unit and the bending loading unit based on the damage characteristic parameters. An adaptive control decision program runs in the data acquisition and control module, configured to execute: Based on the real-time processed sensor signals, the real-time damage status assessment value of the tested transmission shaft is calculated. Based on the real-time damage status assessment value, the current control mode is adaptively selected from a variety of preset control modes, including at least the standard loading mode, damage inquiry mode, and damage activation mode. Based on the selected current control mode, a corresponding load control command is generated to drive the mechanical loading module to adjust the load spectrum applied to the tested transmission shaft.

[0029] The real-time damage status assessment value is calculated based on the acoustic emission event count, strain drift, and temperature change according to a preset weighted fusion model; the weighted fusion model is as follows: Overall damage assessment value: ,in: Let be the event count rate (times / second) of the k-th acoustic emission sensor within a 5-second sliding window. Let be the baseline event count rate of the k-th acoustic emission sensor. This represents the actual strain drift at the k-th measuring point after temperature compensation. This represents the temperature change at the k-th measuring point. , , The critical values ​​for micro-damage initiation, namely acoustic emission event count, strain drift, and temperature change, were determined through standard part calibration tests. The calibration procedure was as follows: a standard drive shaft of the same model without damage was taken, assembled according to the installation method of the embodiment, and run in standard loading mode for 1000 cycles. The mean and 3σ standard deviation of acoustic emission event count rate, strain drift, and temperature change were statistically analyzed, and the upper limit of 3σ for each parameter was taken as the corresponding critical value for micro-damage initiation. , , Normalized threshold: =1.0 times / second =50με, =2.0℃; , , For preset weights, and In this embodiment =0.5、 =0.3、 =0.2.

[0030] Linear compensation is achieved using adjacent fiber Bragg grating temperature sensors. ; In the formula: is the real-time wavelength of the k-th fiber optic strain sensor; The initial wavelength of the k-th fiber optic strain sensor; is the real-time wavelength of the k-th fiber Bragg grating temperature sensor; The initial wavelength of the k-th fiber Bragg grating temperature sensor; Strain sensitivity coefficient ≈1.2 pm / με.

[0031] Temperature change: , Temperature sensitivity coefficient ≈12 pm / ℃; For each sensor k=1~8, calculate its local damage assessment value. The maximum value of all local assessment values ​​is taken as the real-time damage status assessment value of the entire drive shaft. Overall assessment value Used to compare with preset first and second thresholds to determine the switching of control modes; The sensor position corresponding to the largest k value is the location of the most severe damage, which is used for damage localization.

[0032] When the real-time damage status assessment value is lower than the first preset threshold, the standard loading mode is selected, and the mechanical loading module is controlled to apply a basic load spectrum simulating actual working conditions, so that micro-damage can initiate in a real stress environment. The first preset threshold is D1=0.5. When the real-time damage status assessment value reaches the first preset threshold but does not reach the second preset threshold, the damage inquiry mode is selected, and the mechanical loading module is controlled to switch from standard loading to low-frequency, low-amplitude, short-time excitation to actively excite the acoustic emission response of microcracks and improve the signal-to-noise ratio of the damage signal. The second preset threshold is D2=1.0. When the real-time damage status assessment value reaches the second preset threshold, the damage excitation mode is selected, and the mechanical loading module is controlled to moderately increase the load amplitude or change the load phase. The standard loading phase difference is 45°, and the excitation mode is adjusted to 0° in phase to verify damage sensitivity or moderately accelerate damage propagation, so as to facilitate continuous tracking of damage evolution.

[0033] To avoid Fluctuations around the threshold cause frequent switching of the control mode. Set hysteresis interval and duration conditions: Switch from standard loading to damage query: ≥0.5 and lasting for more than 5 seconds; Returning to standard loading from damage inquiry: <0.5 and lasting for more than 5 seconds; Switching from injury inquiry to injury provocation: ≥1.0 and lasting for more than 5 seconds; Returning to standard loading from damage triggering: <0.7 and lasts for more than 5 seconds.

[0034] The test method of the above-mentioned test system for early damage to drive shafts includes the following steps: S1: The transmission shaft to be tested is installed on the fixed connection drive device, the bending loading unit is located at the corresponding position in the middle of the intermediate tube, the hydraulic cylinder is unloaded, the roller of the loading head lightly touches the surface of the transmission shaft, the system is started, and the multi-dimensional sensing module is initialized and the sensor is calibrated. S2: Run the standard loading mode to establish baseline signal characteristics. Start the rotary drive unit, increase the drive shaft speed to 300 rpm and maintain it constant. Run the standard loading mode and apply a basic load spectrum simulating actual working conditions through the mechanical loading module: torque amplitude: T0 = ±800 N·m, torque frequency: f T =5Hz, sine wave; bending moment amplitude: M0=±200N·m; bending moment frequency: f M =3Hz, sine wave; phase difference between torque and bending moment: =45°; run continuously for 1000 cycles, while simultaneously acquiring initial sensing signals through a multi-dimensional sensing module to establish baseline signal characteristics: Acoustic emission baseline: These correspond to the background event count rates (times / second) of the eight acoustic emission sensors, with the average of the last 60 seconds taken; strain baseline: These correspond to the initial wavelength values ​​(nm) of eight fiber Bragg grating strain sensors, and the average value over the last 60 seconds is taken; Temperature baseline: The values ​​are the initial wavelengths (nm) of the eight fiber Bragg grating temperature sensors, and the average of the last 60 seconds is taken. This baseline data is stored in the memory of the data acquisition and control module for subsequent strain drift calculations. and temperature change The benchmark; S3: Real-time damage status assessment: With the drive shaft continuously rotating and the bending loading unit remaining fixed in the middle of the intermediate tube, the real-time damage status assessment value of the tested drive shaft is calculated in real time and every second according to the adaptive control decision program. Acquire the real-time wavelength of the k-th fiber optic strain sensor. Real-time wavelength of adjacent FBG temperature sensor ; Calculate the original wavelength drift: ; ; Calculate the true strain drift after temperature compensation: ; Calculate the temperature change: ; Calculate the event count rate of the k-th acoustic emission sensor within a 5-second sliding window. ; Calculate local damage assessment value The maximum value is taken to obtain the overall evaluation value. ; S4: Damage Inquiry Mode: When 0.5≤ When the value is less than 1.0, the data acquisition and control module automatically switches the current control mode to the damage inquiry mode: Torque amplitude: T q =±100N⋅m, Torque frequency: f Tq =2Hz; Bending moment amplitude: M q =±30N⋅m, bending moment frequency: f Mq =1Hz; the acoustic emission sensor monitoring gain was increased from 40dB to 60dB, and the bandpass filter range was 100-400kHz; Damage identification includes: 1. Applying a 30-second low-frequency, low-amplitude short-term excitation, during which the sensors at all 8 measuring points simultaneously collect data; 2. For each measurement point k, calculate the increment of the acoustic emission event count rate relative to the baseline. ; like > or >3× If so, it is determined that there is early micro-damage at the measuring point; 3. Based on the measurement point number k identified as abnormal, and referring to the correspondence table between measurement points and critical sections, locate the specific location of early micro-damage: If k=1 or 2, the damage is located at the root of the first universal joint fork, circumferentially 0° or 180°. If k=3~6, the damage is located in the middle of the intermediate tube, at 0°, 90°, 180° or 270° in the circumferential direction; If k=7 or 8, the damage is located at the root of the second universal joint fork, circumferentially 0° or 180°. 4. Record the location and severity of damage of all abnormal measuring points; 5. If any measuring point is determined to be abnormal, then the existence of early micro-damage is confirmed, and preparation is made to enter the damage activation mode. S5: Damage triggering mode: when When the value is ≥1.0, or after the damage inquiry mode identifies early micro-damage, the data acquisition and control module automatically switches the current control mode to the damage excitation mode. The mechanical loading module is controlled to moderately increase the load amplitude or change the load phase to verify damage sensitivity and track damage evolution; for example: torque excitation load: torque amplitude: T e =±1200N⋅m, torque frequency: f Te =3Hz, Loading waveform: sine wave, Bending excitation load: Bending moment amplitude: M e =±300N⋅m, bending moment frequency: f Me =2Hz, loaded waveform: sine wave; a shock wave is inserted every 100 cycles, the shock wave amplitude is 1.5 times that of the conventional load, torque ±1800 N·m, bending moment ±450 N·m; the acoustic emission sensor sampling rate is increased to 5MHz, and the fiber optic grating sensor sampling rate is 100Hz. After each excitation phase is completed, the cycle is set to 500 cycles. Excitation is paused, and a short interrogation mode of 30 seconds is entered. The load is restored to the low frequency and low amplitude value of S4. The acoustic emission event count rate and fiber optic grating strain amplitude are compared before and after excitation. If the acoustic emission event count rate continues to rise, it indicates that the damage is spreading at an accelerated rate; if the fiber grating strain amplitude continues to increase, it indicates that the local stiffness is continuously decreasing. If the acoustic emission event count rate does not continue to rise after excitation or falls back after rising, it is determined to be a false signal, and the system returns to the standard loading mode to continue monitoring. After verification, return to standard loading mode; S6: Continue executing steps S3 to S5. When the preset shutdown conditions are met, stop the test. The preset shutdown conditions are: 1. Damage assessment value D(t) ≥ 2.0; 2. Crack length ≥ 5.0 mm; 3. Fiber grating strain amplitude increases by more than 50% above the baseline; 4. Cumulative cycles ≥ 100,000; 5. Drive shaft breaks or sensor signal is interrupted. Simultaneously, safety protection conditions are set, and the machine will automatically stop in an emergency when the following conditions are triggered: 1. Torque exceeds 120% of the rated value; 2. Bending moment exceeds 120% of the rated value; 3. Drive shaft temperature exceeds 80℃; 4. Speed ​​exceeds 110% of the rated value; 5. Any sensor signal is lost for more than 3 seconds.

[0035] After the test is stopped, the system automatically generates a test report containing data on the entire process of damage initiation and propagation. The report includes: test object information, load spectrum parameters, time points of switching between modes, location and time of damage initiation, and sensor data throughout the process.

[0036] Example 2: like Figure 4 As shown, the difference from Embodiment 1 is that the first support 18 and the gantry frame are both axially adjustable relative to the base 1. The base has three axial wedge-shaped grooves 27. A wedge block 26 is located at the lower end of the first support, and wedge blocks 26 are located at both lower ends of the gantry frame. The three wedge blocks engage with their corresponding wedge-shaped grooves to form a sliding connection. An axial lead screw 19 is installed within the wedge-shaped groove. Both ends of the lead screw are rotatably connected to the base, and one end extends out of the wedge-shaped groove and connects to an adjusting motor 20, which is fixed to the base. A threaded hole is located at the center of each wedge block, through which the lead screw passes and engages with the wedge block. The adjusting motor drives the lead screw to rotate, and the lead screw, through the wedge blocks, moves the first support or the gantry frame axially, thereby adjusting the distance between the first support and the second support to accommodate different drive shaft fixing requirements. The axial adjustment of the gantry frame changes the position of the bending moment loading.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A testing system for early damage to a drive shaft, characterized in that, include: A fixed connection drive device is used to connect and fix the transmission shaft to be tested, and to drive the transmission shaft to rotate. A mechanical loading module, configured on a fixed-connection drive unit, is used to apply independently controllable torque and bending loads to the drive shaft under test. The multi-dimensional sensing module includes an early damage sensing sensor array fixedly installed on the rotating surface of the tested transmission shaft, used to acquire physical signals characterizing early damage to the tested transmission shaft in real time; the early damage sensing sensor array includes at least an acoustic emission sensor, a fiber optic strain sensor, and a fiber optic temperature sensor. The signal transmission module includes an electrical signal transmission unit and an optical signal transmission unit, which are used to transmit the electrical and optical signals collected by the early damage sensing sensor array in a rotating state to the data acquisition and control module. The data acquisition and control module is connected to the signal transmission module and is used to receive and synchronously acquire signals from the signal transmission module, demodulate, process and analyze the signals, extract early damage characteristics of the drive shaft, and output control commands to the mechanical loading module. The data acquisition and control module runs an adaptive control decision program, which is configured to execute: Based on the real-time processed sensor signals, the real-time damage status assessment value of the tested transmission shaft is calculated. Based on the real-time damage status assessment value, the current control mode is adaptively selected from a variety of preset control modes, including at least the standard loading mode, damage inquiry mode, and damage activation mode. Based on the selected current control mode, a corresponding load control command is generated to drive the mechanical loading module to adjust the load spectrum applied to the tested transmission shaft.

2. The test system for early damage to a drive shaft according to claim 1, characterized in that, The fixed connection drive device includes: a first connection component, a second connection component, and a rotary drive unit. The first connection component and the second connection component are respectively connected to the two ends of the transmission shaft under test. The rotary drive unit is connected to the first connection component for driving the transmission shaft under test to rotate around its axis. The rotary drive unit adopts a variable frequency speed control motor.

3. The test system for early damage to a drive shaft according to claim 1, characterized in that, The mechanical loading module includes: A torque loading unit is used to apply a controllable torque load to the tested transmission shaft, including a servo motor, a reducer, and a reaction arm. The servo motor is connected to the tested transmission shaft via the reducer. A bending loading unit is used to apply a controllable bending load to the transmission shaft under test. It includes a hydraulic cylinder, a loading head, and a force sensor. The loading head acts on the middle part or a preset section of the transmission shaft under test. The torque loading unit and the bending loading unit are independently mounted on the fixed connection drive device; The torque loading unit and the bending loading unit are respectively equipped with a torque sensor and a force sensor, which are used to feed back load signals to the data acquisition and control module in real time to realize closed-loop control.

4. The testing system for early damage to a drive shaft according to claim 1, characterized in that, The sensor array is distributed along the axial and circumferential directions of the transmission shaft being measured: In the axial direction, the sensor array is arranged at at least one preset dangerous section of the transmission shaft being measured. The dangerous section includes a stress concentration area, a keyway area, a transition fillet area, or a section with the maximum bending moment / torque determined based on finite element analysis. In the circumferential direction, at the same critical section, the acoustic emission sensor and fiber optic strain sensor are arranged at intervals along the circumferential direction to cover the multi-directional response of the tested transmission shaft under complex loads. The fiber grating temperature sensor is arranged adjacent to the fiber grating strain sensor to acquire temperature field data at the measuring point in real time.

5. The testing system for early damage to a drive shaft according to claim 1, characterized in that, The electrical signal transmission unit is a multi-channel conductive slip ring, used to transmit the analog electrical signal output by the acoustic emission sensor and the power supply. The rotor end of the multi-channel conductive slip ring is connected to the signal output end and power input end of the acoustic emission sensor and its preamplifier circuit, and its stator end is connected to the data acquisition and control module and the power supply. The optical signal transmission unit is an optical fiber rotary connector used to transmit optical signals emitted by the fiber optic strain sensor and the fiber optic temperature sensor. The rotating end of the optical fiber rotary connector is connected to an optical fiber jumper laid on the surface of the transmission shaft under test, and its stationary end is connected to the data acquisition and control module.

6. The testing system for early damage to a drive shaft according to claim 1, characterized in that, The data acquisition and control module includes: The fiber optic grating demodulator is optically connected to the fiber optic grating strain sensor and the fiber optic grating temperature sensor through the signal transmission module, and is used to demodulate the optical signal into wavelength data. A multi-channel data acquisition card is electrically connected to the acoustic emission sensor via the signal transmission module and is used to acquire electrical signals; The data processing unit is connected to the fiber Bragg grating demodulator and the multi-channel data acquisition card to synchronously process optical and electrical signals and extract damage characteristic parameters. The controller, connected to the data processing unit and the mechanical loading module, is used to output control commands to the torque loading unit and the bending loading unit according to the damage characteristic parameters.

7. The testing system for early damage to a drive shaft according to claim 1, characterized in that, The real-time damage status assessment value is calculated based on the acoustic emission event count, strain drift, and temperature change according to a preset weighted fusion model; the weighted fusion model is as follows: Overall damage assessment value: ,in: Let be the event count rate (times / second) of the k-th acoustic emission sensor within a 5-second sliding window. Let be the baseline event count rate of the k-th acoustic emission sensor. This represents the actual strain drift at the k-th measuring point after temperature compensation. This represents the temperature change at the k-th measuring point. , , The critical values ​​for micro-damage initiation, namely acoustic emission event count, strain drift, and temperature change, were determined through standard part calibration tests. The calibration procedure was as follows: a standard drive shaft of the same model without damage was taken, assembled according to the installation method of the embodiment, and run in standard loading mode for 1000 cycles. The mean and 3σ standard deviation of acoustic emission event count rate, strain drift, and temperature change were statistically analyzed, and the upper limit of 3σ for each parameter was taken as the corresponding critical value for micro-damage initiation. , , Normalized threshold: =1.0 times / second =50με, =2.0℃; , , For preset weights, and ; Calculate the local damage assessment value for each sensor separately. The maximum value of all local assessment values ​​is taken as the real-time damage status assessment value of the entire drive shaft. Overall assessment value Used to compare with preset first and second thresholds to determine the switching of control modes; The sensor position corresponding to the largest k value is the location of the most severe damage, which is used for damage localization. k=1~8 are the measurement point numbers, where k=1~2 corresponds to the root of the first universal joint shaft fork, k=3~6 corresponds to the middle of the intermediate tube, and k=7~8 corresponds to the root of the second universal joint shaft fork. Each measurement point includes one acoustic emission sensor, one fiber optic strain sensor, and one fiber optic temperature sensor.

8. The testing system for early damage to a drive shaft according to claim 7, characterized in that, When the real-time damage status assessment value is lower than the first preset threshold, the standard loading mode is selected, and the mechanical loading module is controlled to apply a basic load spectrum that simulates the actual working conditions, so that micro-damage can be generated in a real stress environment. When the real-time damage status assessment value reaches the first preset threshold but does not reach the second preset threshold, the damage inquiry mode is selected, and the mechanical loading module is controlled to switch to low-frequency, low-amplitude, short-time excitation to actively stimulate the acoustic emission response of the microcrack and improve the signal-to-noise ratio of the damage signal. When the real-time damage status assessment value reaches the second preset threshold, a damage excitation mode is selected, and the mechanical loading module is controlled to moderately increase the load amplitude or change the load phase to verify the damage sensitivity or moderately accelerate the damage propagation, so as to facilitate continuous tracking of damage evolution.

9. The testing system for early damage to a drive shaft according to claim 8, characterized in that, The first preset threshold The second preset threshold ; =0.5、 =0.3、 =0.

2.

10. A test method based on the test system for early damage to a drive shaft according to any one of claims 1-9, characterized in that, Including the following steps: S1: Install the transmission shaft under test onto the fixed connection drive device, start the system, and initialize and calibrate the multi-dimensional sensing module and sensor. S2: Run the standard loading mode, apply the basic load spectrum simulating the actual working conditions through the mechanical loading module, and at the same time collect the sensing signals in the initial stage through the multi-dimensional sensing module. The background event count rate collected by the acoustic emission sensor, the initial strain value collected by the fiber optic strain sensor, and the initial temperature value collected by the fiber optic temperature sensor are used as the baseline signal characteristics, which serve as the reference for subsequent calculation of strain drift and temperature change. S3: Calculate the real-time damage status assessment value of the tested transmission shaft in real time according to the adaptive control decision program; S4: When the real-time damage status assessment value reaches the first preset threshold but does not reach the second preset threshold, the data acquisition and control module automatically switches the current control mode to the damage inquiry mode and controls the mechanical loading module to switch to low-frequency, low-amplitude, short-time excitation to actively excite and capture the acoustic emission response of the microcrack. S5: When the real-time damage status assessment value reaches the second preset threshold, the data acquisition and control module automatically switches the current control mode to the damage excitation mode, and controls the mechanical loading module to appropriately increase the load amplitude or change the load phase in order to verify the damage sensitivity and track the damage evolution. S6: Continue executing steps S3 to S5. When the preset shutdown conditions are met, stop the test and generate a test report containing data on the entire process of damage initiation and expansion.

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