Blade multi-axial fatigue testing device and method

Abstract

The invention relates to the technical field of fatigue testing, and discloses a blade multi-axis fatigue testing device and method, and the device comprises a test bench foundation, a positioning flange fixed on the test bench foundation, and an annular track excitation device. The positioning flange is used for installing a test blade; the annular track excitation device comprises an annular track and an excitation device capable of moving along the annular track; the annular track is suitable for being arranged on the peripheral side of the tested blade in a sleeving mode and fixed to the tested blade. Wherein the excitation device is configured to rotate or reciprocate around the section of the test blade under the constraint of the annular track. According to the invention, double-shaft loading of the blade can be realized through a set of excitation equipment; compared with existing double-shaft testing equipment, the system is simpler in structure and has the advantages in reliability and cost.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue testing, and in particular to a blade multi-axis fatigue testing device and method. Background Art

[0002] With the large-scale development of wind turbines, the length of megawatt-class blades has exceeded hundreds of meters, and the verification of their structural reliability faces severe challenges.

[0003] Full-size blade testing primarily involves static and fatigue testing. Static blade testing involves applying static loads (such as bending and torsion) to the blades, typically to 150%-200% of the design value to test safety margins. Blade strain, displacement, and local deformation are monitored, as well as the presence of cracks or delamination, to determine the structural reliability of the blades. Blade fatigue testing involves cyclic loading to simulate the alternating stresses experienced in long-term blade operation. Under the influence of a resonant excitation system, the blades undergo millions of flapping and shimmying motions to verify their structural reliability. Fatigue testing typically lasts several months or even a year.

[0004] Blade fatigue testing primarily involves flapping, shimmying, and torsional fatigue testing. Flapping fatigue testing involves subjecting the blade to millions of reciprocating deformations in the vertical (pressure-suction) bending direction; shimmying fatigue testing involves subjecting the blade to millions of reciprocating deformations in the forward-backward (leading-trailing) bending direction. Torsional fatigue testing is not currently required by current standards, and the industry lacks relevant testing equipment and supporting methods.

[0005] The fatigue test types of blades mainly include uniaxial fatigue test and biaxial fatigue test. The uniaxial fatigue test often uses the resonance excitation method: the eccentric hammer exciter is installed at the appropriate position of the blade, and the excitation frequency is adjusted to be close to the natural frequency of the blade to induce large vibration of the blade; the biaxial fatigue test test machine is equipped with two independent excitation units, and the servo motor repeatedly pushes the connecting rod connected to the blade to realize forced vibration loading of the blade in two directions.

[0006] Most traditional biaxial fatigue test machines use the forced displacement method, which requires two sets of excitation devices or forced displacement systems, a high-strength test bench and a complex control system, making the test equipment complex and requiring high investment. Summary of the Invention

[0007] In view of this, the present invention provides a blade multi-axis fatigue testing device and method to solve the problems of complex testing equipment and high investment in traditional biaxial fatigue testing.

[0008] In a first aspect, the present invention provides a blade multi-axial fatigue testing device, comprising:

[0009] Test bench foundation;

[0010] A positioning flange fixed to the test bench foundation, wherein the positioning flange is used to install a test blade;

[0011] An annular track excitation device, comprising an annular track and an excitation device movable along the annular track; the annular track is adapted to be sleeved on the circumference of the test blade and fixed to the test blade;

[0012] Wherein, the excitation device is configured to rotate or reciprocate around the test blade cross section under the constraint of the annular track.

[0013] This multi-axial fatigue testing device for blades utilizes a circular track excitation device to simulate multiaxial loads. Its core principle lies in combining the spatial constraints of the circular track with the dynamic motion of the excitation device. During operation, the test blade is fixed to the test bench base via a positioning flange. The circular track, acting as a load-bearing and guiding structure, fits snugly around the blade and is rigidly connected to it, forming a closed mechanical action loop. The excitation device is mounted on the circular track and configured to rotate or reciprocate around the test blade cross-section within the constraints of the circular track. During rotation, the centrifugal load generated by the excitation device is decomposed into two orthogonal force components along the blade span due to variations in track geometry and rotational speed, forming a periodically varying composite load field. This design eliminates the need to switch loading directions during testing, allowing the blade to withstand both flapping and shimmy fatigue loads in a single operation, effectively shortening the test cycle. By adjusting the curvature parameters of the circular track (e.g., using an elliptical track) and the rotational speed of the excitation device, the amplitude ratio, frequency ratio, and phase relationship of the load can be flexibly controlled to accurately simulate the multi-axial random load spectrum encountered by blades in actual wind farms. Compared with traditional dual-axis testing systems that require independent control of two sets of excitation devices, this device integrates multi-axis loading functions through a single circular track, significantly reducing system complexity, equipment size and maintenance costs, while avoiding the synchronization error problems caused by multi-system collaborative control, and improving test accuracy and reliability.

[0014] In an optional embodiment, the excitation device is configured to rotate or reciprocate along the annular track to adjust the load amplitude, frequency and motion trajectory of the test blade cross section in a 360° direction.

[0015] The excitation device can dynamically adjust the amplitude, frequency and motion trajectory of the load in the 360° direction on the test blade cross section by rotating or reciprocating along the circular track. Specifically, when the excitation device operates in variable speed mode, its rotation speed can be adjusted according to a preset program or real-time feedback signal, thereby changing the dynamic characteristics of the centrifugal load. For example, when the rotation is accelerated in a specific section of the circular track, the centrifugal force increases, resulting in an increase in the bending strain amplitude of the blade in this area; conversely, when the speed is decelerated, the load intensity is reduced. At the same time, by precisely controlling the variable speed frequency, the fluctuation characteristics of the wind speed in nature can be simulated, so that the frequency range of the alternating stress borne by the blade is closer to the actual working conditions. In addition, the variable speed motion can also be combined with the geometric design of the circular track (such as a non-circular track) to adjust the motion trajectory of the load application point. For example, on an elliptical track, a composite bending mode with different major axis to minor axis ratios can be achieved by varying the speed, thereby covering more complex multi-axis stress distribution scenarios. This variable speed control mechanism not only improves the flexibility and authenticity of the test, but also shortens the fatigue life assessment cycle by optimizing the loading strategy. At the same time, it avoids the phase deviation problem caused by insufficient equipment coordinated control in traditional multi-axis testing, significantly improving the overall performance of the test system.

[0016] In an optional embodiment, the annular track includes:

[0017] orbital ring;

[0018] Two blade fixtures, each having a fitting cavity, wherein the fitting cavity is adapted to the shape of the outer surface of the test blade;

[0019] A supporting device is connected between the inner side of the track ring and the blade clamp.

[0020] The orbital ring can be designed to be circular, elliptical or other regular closed ring shapes to adapt to the geometric characteristics and testing requirements of different blades. The two blade fixtures are symmetrically distributed on both sides of the test blade. The inner wall of the fitting cavity can be precisely matched to the outer contour curve of the test blade through CNC machining to ensure a gap-free fit with the blade surface during high-speed rotation, avoiding local stress concentration and preventing fixture slippage due to vibration. The support device consists of multiple sets of telescopically adjustable hydraulic rods or screw jacks, which are arranged circumferentially along the inner side of the orbital ring, and their two ends are respectively connected to the orbital ring and the blade fixture. This modular design makes the relative position of the orbital ring and the blade fixture adjustable, which is suitable for testing blades of different diameters and lengths.

[0021] In an optional embodiment, the excitation device includes:

[0022] Fixed platform;

[0023] a driving mechanism, fixed to the fixed platform;

[0024] a wheel train assembly fixed to the fixed platform and connected to the driving mechanism, the wheel train assembly being adapted to contact the inner and outer surfaces of the track ring;

[0025] a tensioning device connected to the wheel train assembly, and the tensioning device is configured to force the wheel train assembly into close contact with the track ring;

[0026] The counterweight module is connected to the fixed platform.

[0027] The excitation device achieves vibration of the blades through mechanical linkage, and its core components work together to generate controllable centrifugal loads. The fixed platform provides a stable mounting platform for the drive mechanism and the wheel train assembly; the drive mechanism transmits power to the wheel train assembly, allowing the excitation device to rotate on the track ring; the wheel train assembly maintains contact pressure with the track through the preload applied by the tensioning device, preventing the excitation device from leaving the track during variable speed movement. When the drive mechanism is started, the wheel train assembly drives the fixed platform and the counterweight module along a circular trajectory under the constraint of the track ring. The centrifugal force of the counterweight is transmitted to the wheel train assembly through the fixed platform, and finally acts on the track ring and is converted into a bending load on the blade cross section. By adjusting the speed of the drive mechanism and the configuration of the counterweight block, composite load loading in different directions, amplitudes and frequencies can be flexibly achieved to meet the simulation requirements of multi-axial fatigue damage of blades in real wind fields.

[0028] In an optional embodiment, the gear train assembly includes:

[0029] a driving wheel set, driven by the driving mechanism and in contact with the outer surface of the track ring;

[0030] The driven wheel group is in contact with the inner surface of the track ring; the tensioning device is connected to the driven wheel group, and the tensioning device is configured to force the driven wheel group to be in close contact with the inner surface of the track ring;

[0031] The driving wheel set and the driven wheel set form two sets of rolling pair constraints to limit the separation of the excitation device from the track ring.

[0032] The gear train assembly forms a dual constraint mechanism through the synergistic action of the driving wheel set and the driven wheel set to ensure the stable operation of the excitation device. Figures 3 to 5As shown, the drive mechanism includes a drive motor and a gearbox connected to the output end of the drive motor. The drive wheel group includes two drive wheels, which are arranged along the width direction of the track ring and are both connected to the gearbox. The drive motor can drive the two drive wheels to rotate through the gearbox. The drive wheel is tightly fitted with the arc contact surface on the outer surface of the track ring so that the excitation device can rotate around the annular track. The driven wheel group includes two groups of driven wheels, each group of driven wheels includes two driven wheels, and each group of driven wheels is connected to the axle of the driving wheel by a T-shaped piece, so that each group of driven wheels and a driving wheel form a whole. In this whole, the driving wheel is in a tight fit with the arc contact surface on the outer surface of the track ring, and the driven wheel is tightly fitted with the arc contact surface on the inner surface of the track ring to limit the separation of the excitation device from the track ring. Further, in order to avoid the risk of derailment that is easily caused by traditional unilateral constraints, two groups of driven wheels and a driving wheel are provided in this embodiment.

[0033] In an optional embodiment, the tensioning device includes:

[0034] The tensioning body comprises two slidably sleeved mounting frames, with driven wheels slidably mounted on the ends of the two mounting frames;

[0035] a spring disposed between the two mounting brackets, and the spring is configured to be in a compressed state;

[0036] Wherein, the driving wheel set is located between the two driven wheels.

[0037] The tensioning device realizes the dynamic fit between the driven wheel group and the inner surface of the track ring through an elastic constraint structure. Specifically, the tensioning body is composed of two mounting frames, and the ends of the two mounting frames are slidably sleeved. A driven wheel is installed at the outer end of each mounting frame, and the wheel surface of the driven wheel is in close contact with the inner surface of the track ring. The spring is sleeved between the two mounting frames, and baffles are provided on both mounting frames. The two ends of the spring respectively abut against the baffles on the mounting frames, and after the spring is installed, it is in a compressed energy storage state, and the elastic force pushes the two mounting frames to move in opposite directions. Figure 5 As shown (the wheel train frame is omitted in the figure), due to the presence of the spring, the two driven wheels can move closer to or away from each other under the action of external force, and the spring elastic force enables the two driven wheels to always maintain a close fit with the arc-shaped contact surface on the inner surface of the track ring.

[0038] In an optional embodiment, the incentive device further includes:

[0039] Support rollers are installed on both sides of the fixed platform, and the support rollers are in contact with the outer surface of the track ring and provide auxiliary support.

[0040] In an optional embodiment, the fixed platform is arc-shaped or straight.

[0041] In a second aspect, the present invention further provides a blade multi-axial fatigue testing method, which is used in a blade multi-axial fatigue testing device and comprises the following steps:

[0042] Fixing the test blade root to the test bench foundation through the positioning flange;

[0043] An annular track excitation device is installed on the blade, and the excitation device can move along the annular track;

[0044] driving the excitation device to rotate along the annular track;

[0045] The excitation device is rotated or reciprocated to generate a centrifugal load of varying direction and magnitude to apply multi-directional alternating stress to the test blade;

[0046] The motion parameters of the excitation device are controlled so that the test blade is deformed periodically along a predetermined closed trajectory, thereby achieving biaxial fatigue loading.

[0047] This blade multi-axis fatigue test method realizes biaxial fatigue simulation of blades through the coordinated process of positioning, device installation, drive loading and parameter control. In specific implementation, the root of the test blade is first rigidly connected to the test bench foundation through a positioning flange, usually fixed with high-strength bolts or hydraulic clamps to ensure that the root of the blade does not slip or rotate during the test, providing a stable foundation for subsequent load transfer; then an annular track excitation device is installed on the circumference of the blade, and the track ring is tightly fitted with the outer surface of the blade through the fitting cavity of the blade clamps on both sides. The support device is used to eliminate the installation gap, so that the excitation device can move along the track ring without jamming; then the excitation device is driven by the driving mechanism to rotate or reciprocate along the annular track. During the driving process, the rolling pair constraints of the wheel system components (driving wheel group and driven wheel group) and the inner and outer surfaces of the track ring ensure the accuracy of the exciter motion trajectory, and the tensioning device maintains the driven wheel group and The contact pressure on the inner surface of the track is used to avoid the risk of derailment. During the rotation of the excitation device, the centrifugal force of its counterweight module is converted into a radial load acting on the track ring as the speed changes, and then transmitted to the blade cross section through the track ring, forming an alternating bending stress that changes alternately along the span and chord directions, simulating the composite load of flapping and oscillation encountered by the blade in an actual wind farm. Finally, the control system adjusts the speed, acceleration and motion trajectory of the drive mechanism (such as the ratio of the major and minor axes of the elliptical track) in real time, controls the rotation frequency, amplitude and phase of the excitation device, and makes the stress cycle trajectory of the blade cross section change periodically according to the preset closed path, realizing the precise loading of biaxial fatigue loads. Finally, by recording the strain response or crack initiation life of the blade under cyclic loads, the multi-axis fatigue performance evaluation is completed. This method replaces the coordinated control of traditional multi-axis equipment with the composite motion of a single excitation device, significantly improving the test efficiency and the realism of load simulation, while reducing system complexity and maintenance costs.

[0048] In an optional embodiment, the load size and direction are controlled by adjusting the counterweight module and controlling the movement direction and speed of the excitation device on the circular track. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0050] Figure 1 This is a schematic diagram of the installation of a blade multi-axis fatigue testing device according to an embodiment of the present invention;

[0051] Figure 2 This is a schematic structural diagram of a blade multi-axis fatigue testing device according to an embodiment of the present invention;

[0052] Figure 3 An exploded diagram of an excitation device in a blade multi-axial fatigue testing device according to an embodiment of the present invention;

[0053] Figure 4 This is a schematic structural diagram of an excitation device in a blade multi-axis fatigue testing device according to an embodiment of the present invention;

[0054] Figure 5 This is a schematic diagram of the position of an excitation device in a blade multi-axis fatigue testing device according to an embodiment of the present invention.

[0055] Description of reference numerals:

[0056] 1. Test bench foundation;

[0057] 2. Positioning flange;

[0058] 3. Test blades;

[0059] 4. Annular track; 41. Track ring; 42. Blade fixture; 43. Support device;

[0060] 5. Excitation device; 51. Fixed platform; 52. Driving motor; 53. Driving wheel set; 54. Driven wheel set; 55. Tensioning device; 551. Tensioning body; 552. Spring; 56. Counterweight module; 57. Electrical cabinet; 58. Gearbox; 59. Wheel train frame;

[0061] 6. Support roller. DETAILED DESCRIPTION

[0062] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0063] With the large-scale development of wind turbines, the length of megawatt-class blades has exceeded hundreds of meters, and the verification of their structural reliability faces severe challenges.

[0064] Full-size blade testing primarily involves static and fatigue testing. Static blade testing involves applying static loads (such as bending and torsion) to the blades, typically to 150%-200% of the design value to test safety margins. Blade strain, displacement, and local deformation are monitored, as well as the presence of cracks or delamination, to determine the structural reliability of the blades. Blade fatigue testing involves cyclic loading to simulate the alternating stresses experienced in long-term blade operation. Under the influence of a resonant excitation system, the blades undergo millions of flapping and shimmying motions to verify their structural reliability. Fatigue testing typically lasts several months or even a year.

[0065] Blade fatigue testing primarily involves flapping, shimmying, and torsional fatigue testing. Flapping fatigue testing involves subjecting the blade to millions of reciprocating deformations in the vertical (pressure-suction) bending direction; shimmying fatigue testing involves subjecting the blade to millions of reciprocating deformations in the forward-backward (leading-trailing) bending direction. Torsional fatigue testing is not currently required by current standards, and the industry lacks relevant testing equipment and supporting methods.

[0066] The fatigue test types of blades mainly include uniaxial fatigue test and biaxial fatigue test. The uniaxial fatigue test often uses the resonance excitation method: the eccentric hammer exciter is installed at the appropriate position of the blade, and the excitation frequency is adjusted to be close to the natural frequency of the blade to induce large vibration of the blade; the biaxial fatigue test test machine is equipped with two independent excitation units, and the servo motor repeatedly pushes the connecting rod connected to the blade to realize forced vibration loading of the blade in two directions.

[0067] Most traditional biaxial fatigue test machines use the forced displacement method, which requires two sets of excitation devices or forced displacement systems, a high-strength test bench and a complex control system, making the test equipment complex and requiring high investment.

[0068] In view of this, the present invention provides a blade multi-axis fatigue testing device to solve the problems of complex equipment and high investment in traditional biaxial fatigue testing testing machines.

[0069] The following combination Figures 1 to 5 , describing embodiments of the present invention.

[0070] According to an embodiment of the present invention, in one aspect, a blade multi-axial fatigue testing apparatus is provided, comprising a test bench base 1, a positioning flange 2 fixed to the test bench base 1, and an annular track excitation device. Positioning flange 2 is used to mount a test blade 3. The annular track excitation device comprises an annular track 4 and an excitation device 5 movable along the annular track 4. The annular track 4 is adapted to be mounted around and fixed to the test blade 3. The excitation device 5 is configured to rotate or reciprocate around a cross-section of the test blade 3 under the constraints of the annular track 4.

[0071] This multi-axial fatigue testing device for blades achieves multi-axial load simulation using a circular track excitation device. Its core principle lies in combining the spatial constraints of the circular track 4 with the dynamic motion of the excitation device 5. During operation, the test blade 3 is fixed to the test bench base 1 via a positioning flange 2. The circular track 4, acting as a load-bearing and guiding structure, fits tightly around the blade circumference and is rigidly connected to it, forming a closed mechanical action loop. The excitation device 5 is mounted on the circular track 4 and configured to rotate or reciprocate around the cross-section of the test blade 3 within the constraints of the circular track 4. During this process, the centrifugal load generated by the excitation device 5 can be decomposed into two orthogonal force components along the blade span due to variations in the track geometry and rotational speed, forming a periodically varying composite load field. This design eliminates the need to switch loading directions during testing, allowing the blade to withstand both flapping and shimmy fatigue loads in a single operation, effectively shortening the test cycle. By adjusting the curvature parameters of the circular track 4 (e.g., using an elliptical track) and the rotational speed of the excitation device 5, the amplitude ratio, frequency ratio, and phase relationship of the load can be flexibly controlled to accurately simulate the multi-axial random load spectrum encountered by blades in actual wind farms. Compared with traditional dual-axis test systems that require independent control of two sets of excitation devices, this device integrates multi-axis loading functions through a single circular track 4, significantly reducing system complexity, equipment size and maintenance costs, while avoiding synchronization errors caused by multi-system collaborative control and improving test accuracy and reliability.

[0072] In one embodiment, the excitation device 5 is configured to rotate or reciprocate along the annular track 4 to adjust the load amplitude, frequency and motion trajectory of the test blade 3 in a 360° direction.

[0073] In this embodiment, the excitation device 5 can dynamically adjust the amplitude, frequency, and motion trajectory of the load in the 360° direction on the cross section of the test blade 3 by rotating or reciprocating along the annular track 4. Specifically, when the excitation device 5 operates in a variable speed mode, its rotation speed can be adjusted according to a preset program or a real-time feedback signal, thereby changing the dynamic characteristics of the centrifugal load. For example, when the rotation is accelerated in a specific section of the annular track 4, the centrifugal force increases, resulting in an increase in the bending strain amplitude of the blade in this area; conversely, when the rotation is decelerated, the load intensity is reduced. At the same time, by precisely controlling the variable speed frequency, the fluctuating characteristics of wind speed in nature can be simulated, so that the frequency range of alternating stresses to which the blade is subjected is closer to actual working conditions. In addition, the variable speed motion can also be combined with the geometric design of the annular track 4 (such as a non-circular track) to adjust the motion trajectory of the load application point. For example, on an elliptical track, a composite bending mode with different major axis to minor axis ratios can be achieved by varying the speed, thereby covering more complex multi-axis stress distribution scenarios. This variable speed control mechanism not only improves the flexibility and authenticity of the test, but also shortens the fatigue life assessment cycle by optimizing the loading strategy. At the same time, it avoids the phase deviation problem caused by insufficient equipment coordinated control in traditional multi-axis testing, significantly improving the overall performance of the test system.

[0074] In one embodiment, the annular track 4 includes a track ring 41, two blade clamps 42 and a support device 43. Both blade clamps 42 have a fitting cavity that is adapted to the shape of the outer surface of the test blade 3; the support device 43 is connected between the inner side of the track ring 41 and the blade clamp 42.

[0075] In this embodiment, the orbital ring 41 can be designed to be circular, elliptical or other regular closed rings to adapt to the geometric characteristics and test requirements of different blades. The two blade clamps 42 are symmetrically distributed on both sides of the test blade 3. The inner wall of the fitting cavity can be accurately matched with the outer contour curve of the test blade 3 through CNC machining to ensure a gap-free fit with the blade surface during high-speed rotation, avoiding local stress concentration and preventing the clamp from slipping due to vibration. The support device 43 is composed of multiple groups of telescopically adjustable hydraulic rods or screw jacks, which are arranged circumferentially along the inner side of the orbital ring 41, and its two ends are respectively connected to the orbital ring 41 and the blade clamp 42. This modular design makes the relative position of the orbital ring 41 and the blade clamp 42 adjustable, which is suitable for testing blades of different diameters and lengths.

[0076] In one embodiment, the excitation device 5 includes a fixed platform 51, a drive mechanism, a wheel train assembly, a tensioning device 55, and a counterweight module 56. The drive mechanism is fixed to the fixed platform 51, the wheel train assembly is fixed to the fixed platform 51 and connected to the drive mechanism, and the wheel train assembly is adapted to contact the inner and outer surfaces of the track ring 41; the tensioning device 55 is connected to the wheel train assembly and is configured to force the wheel train assembly into close contact with the track ring 41; and the counterweight module 56 is connected to the fixed platform 51.

[0077] In this embodiment, the excitation device 5 achieves vibration of the blades through mechanical linkage, and its core components work together to generate controllable centrifugal loads. The fixed platform 51 provides a stable installation platform for the drive mechanism and the wheel train assembly; the drive mechanism transmits power to the wheel train assembly, allowing the excitation device 5 to rotate on the track ring 41; the wheel train assembly maintains contact pressure with the track through the preload applied by the tensioning device 55, preventing the excitation device 5 from leaving the track during speed change. When the drive mechanism is started, the wheel train assembly drives the fixed platform 51 and the counterweight module 56 to move along a circular trajectory under the constraint of the track ring 41. The centrifugal force of the counterweight is transmitted to the wheel train assembly through the fixed platform 51, and finally acts on the track ring 41 and is converted into a bending load on the blade cross section. By adjusting the speed of the drive mechanism and the configuration of the counterweight block, composite load loading in different directions, amplitudes and frequencies can be flexibly achieved to meet the simulation requirements of multi-axial fatigue damage of blades in real wind fields.

[0078] In one embodiment, the wheel train assembly includes a driving wheel group 53 and a driven wheel group 54, wherein the driving wheel group 53 is driven by a driving mechanism and contacts the outer surface of the orbital ring 41; the driven wheel group 54 contacts the inner surface of the orbital ring 41; a tensioning device 55 is connected to the driven wheel group 54, and the tensioning device 55 is configured to force the driven wheel group 54 to be in close contact with the inner surface of the orbital ring 41; wherein the driving wheel group 53 and the driven wheel group 54 constitute two sets of rolling pair constraints to limit the separation of the excitation device 5 from the orbital ring 41.

[0079] In this embodiment, the wheel train assembly forms a dual constraint mechanism through the coordinated action of the driving wheel set 53 and the driven wheel set 54 to ensure the stable operation of the excitation device 5. Figures 3 to 5 As shown, the drive mechanism includes a drive motor 52, an electrical cabinet 57, and a gearbox 58 connected to the output end of the drive motor 52. The drive wheel assembly 53 includes two drive wheels, which are arranged along the width of the track ring 41 and are both connected to the gearbox 58. The drive motor 52 can drive the two drive wheels to rotate through the gearbox 58. The drive wheels are tightly fitted with the arc-shaped contact surface on the outer surface of the track ring 41, so that the excitation device 5 can rotate around the annular track 4. The driven wheel assembly 54 includes two sets of driven wheels, each set of driven wheels includes two driven wheels, and each set of driven wheels is connected to the axle of the driving wheel via a T-shaped piece (wheel train frame 59), so that each set of driven wheels and a driving wheel form a whole. In this whole, the driving wheel is tightly fitted with the arc-shaped contact surface on the outer surface of the track ring 41, and the driven wheel is tightly fitted with the arc-shaped contact surface on the inner surface of the track ring 41, so as to prevent the excitation device 5 from separating from the track ring 41. Furthermore, in order to avoid the risk of derailment that is easily caused by traditional unilateral constraints, two sets of driven wheels and driving wheels are provided in this embodiment.

[0080] like Figures 3 to 5As shown, in one embodiment, the tensioning device 55 includes a tensioning body 551 and a spring 552. The tensioning body 551 includes two slidingly sleeved mounting frames, and driven wheels are slidably mounted at the ends of the two mounting frames; the spring 552 is arranged between the two mounting frames, and the spring 552 is configured to be in a compressed state; wherein the driving wheel group 53 is located between the two driven wheels.

[0081] In this embodiment, the tensioning device 55 realizes the dynamic fit between the driven wheel group 54 and the inner surface of the track ring 41 through an elastic constraint structure. Specifically, the tensioning body 551 is composed of two mounting frames, and the ends of the two mounting frames are slidably mounted. A driven wheel is mounted on the outer end of each mounting frame, and the wheel surface of the driven wheel is in close contact with the inner surface of the track ring 41. The spring 552 is mounted between the two mounting frames, and baffles are provided on the two mounting frames. The two ends of the spring 552 respectively abut against the baffles on the mounting frames, and the spring 552 is in a compressed energy storage state after installation, and the elastic force pushes the two mounting frames to move in opposite directions. Figure 5 As shown (the wheel train frame 59 is omitted in the figure), due to the presence of the spring 552, the two driven wheels can move closer to or away from each other under the action of an external force, and the elastic force of the spring 552 enables the two driven wheels to always maintain a close fit with the arc-shaped contact surface on the inner surface of the track ring 41.

[0082] In one embodiment, the excitation device 5 further includes support rollers 6 installed on both sides of the fixed platform 51 . The support rollers 6 are in contact with the outer surface of the track ring 41 and provide auxiliary support.

[0083] In this embodiment, the support rollers 6 are installed on both sides of the fixed platform 51 as auxiliary support structures, and their wheel surfaces maintain continuous contact with the outer surface of the track ring 41, forming a stable radial support force through a two-point layout.

[0084] The supporting roller 6 can be made of wear-resistant engineering plastic or lightweight alloy, and the outer surface is designed to be a curved surface that matches the outer contour of the track ring 41 to reduce contact stress and reduce movement resistance.

[0085] In one embodiment, the fixing platform 51 is arc-shaped or straight.

[0086] In this embodiment, the fixed platform 51 is designed in an arc shape, and its curvature matches the outer surface profile of the annular track 4. Alternatively, the fixed platform 51 can also be straight, and the support rollers 6 on both sides thereof can contact the outer surface of the annular track 4.

[0087] According to another aspect of an embodiment of the present invention, a blade multi-axial fatigue testing method is provided, which is used in a blade multi-axial fatigue testing device and includes the following steps:

[0088] Fix the root of the test blade 3 to the test bench foundation 1 through the positioning flange 2;

[0089] An annular track excitation device is installed on the blade, and the excitation device 5 can move along the annular track 4;

[0090] The driving excitation device 5 rotates along the annular track 4;

[0091] The excitation device 5 rotates or reciprocates to generate a centrifugal load of varying direction and magnitude to apply multi-directional alternating stress to the test blade 3;

[0092] The motion parameters of the excitation device 5 are controlled so that the test blade 3 is deformed periodically along a predetermined closed trajectory, thereby achieving biaxial fatigue loading.

[0093] This blade multi-axis fatigue test method realizes biaxial fatigue simulation of blades through the coordinated process of positioning, device installation, drive loading and parameter control. In specific implementation, the root of the test blade 3 is first rigidly connected to the test bench foundation 1 through the positioning flange 2, usually fixed with high-strength bolts or hydraulic clamps to ensure that the root of the blade does not slip or rotate during the test, providing a stable foundation for subsequent load transfer; then the annular track excitation device is installed on the circumference of the blade, and the track ring 41 is tightly fitted with the outer surface of the blade through the fitting cavity of the blade clamps 42 on both sides. The support device 43 is used to eliminate the installation gap, so that the excitation device 5 can move along the track ring 41 without jamming; then the excitation device 5 is driven by the driving mechanism to rotate or reciprocate along the annular track 4. During the driving process, the rolling pair constraints of the wheel system components (driving wheel group 53 and driven wheel group 54) and the inner and outer surfaces of the track ring 41 ensure the accuracy of the exciter motion trajectory, and the tensioning device 55 is tightened by the spring 552 The force maintains the contact pressure between the driven wheel group 54 and the inner surface of the track to avoid the risk of derailment. During the rotation of the excitation device 5, the centrifugal force of its counterweight module 56 is converted into a radial load acting on the track ring 41 as the speed changes. The load is then transmitted to the blade cross section through the track ring 41, forming an alternating bending stress that changes alternately along the span and chord directions, simulating the composite load of flapping and shimmying encountered by the blade in an actual wind farm. Finally, the control system adjusts the speed, acceleration and motion trajectory of the drive mechanism (such as the major and minor axis ratio of the elliptical track) in real time, controls the rotation frequency, amplitude and phase of the excitation device 5, and makes the stress cycle trajectory of the blade cross section change periodically according to a preset closed path, realizing the precise loading of biaxial fatigue loads. Finally, by recording the strain response or crack initiation life of the blade under cyclic loads, the multi-axis fatigue performance evaluation is completed. This method replaces the coordinated control of traditional multi-axis equipment with the composite motion of a single excitation device 5, significantly improving the test efficiency and the realism of load simulation, while reducing system complexity and maintenance costs.

[0094] In one embodiment, the load size and direction are controlled by adjusting the counterweight module 56 and controlling the movement direction and speed of the excitation device 5 on the circular track.

[0095] In this embodiment, the mass adjustment of the counterweight module 56 is the core means to achieve precise control of the centrifugal force of the excitation device 5. During specific operation, the counterweight module 56 is usually connected to the fixed platform 51 by a plurality of standardized mass blocks (such as detachable metal weights) through bolts or snap-on structures. The user can select counterweight blocks of different masses for combination installation according to the test requirements. When the driving mechanism drives the excitation device 5 to rotate or reciprocate at a set angular velocity, the mass change of the counterweight module 56 will directly cause the centrifugal force to increase or decrease proportionally: increasing the counterweight mass can increase the centrifugal force amplitude, so that the bending stress on the blade increases; reducing the counterweight reduces the centrifugal force, which is suitable for fatigue testing under small load conditions. This adjustment method does not require changing the speed or track structure of the driving mechanism. It only needs to replace or adjust the configuration of the counterweight block to achieve wide range and high precision control of the centrifugal force, which simplifies the operation process and reduces the system complexity caused by speed regulation.

[0096] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A blade multi-axis fatigue testing device, characterized in that: include: Test bench foundation (1); A positioning flange (2) fixed to the test bench foundation (1), wherein the positioning flange (2) is used to install a test blade (3); An annular track excitation device comprises an annular track (4) and an excitation device (5) movable along the annular track (4); the annular track (4) is suitable for being sleeved on the circumference of the test blade (3) and being fixed to the test blade (3); Wherein, the excitation device (5) is configured to rotate or reciprocate around the cross section of the test blade (3) under the constraint of the annular track (4).

2. The blade multi-axis fatigue testing device according to claim 1, characterized in that: The excitation device (5) is configured to rotate or reciprocate along the annular track (4) to adjust the load amplitude, frequency and motion trajectory of the test blade (3) in a 360° direction.

3. The blade multi-axial fatigue testing device according to claim 1 or 2, characterized in that: The annular track (4) comprises: orbital ring (41); Two blade fixtures (42), each having a fitting cavity, wherein the fitting cavity is adapted to the shape of the outer surface of the test blade (3); A supporting device (43) is connected between the inner side of the track ring (41) and the blade clamp (42).

4. The blade multi-axis fatigue testing device according to claim 3, characterized in that: The excitation device (5) comprises: Fixed platform (51); A driving mechanism fixed to the fixed platform (51); a wheel train assembly fixed to the fixed platform (51) and connected to the driving mechanism, the wheel train assembly being adapted to contact the inner and outer surfaces of the track ring (41); a tensioning device (55) connected to the wheel train assembly, and the tensioning device (55) is configured to force the wheel train assembly to be in close contact with the track ring (41); The counterweight module (56) is connected to the fixed platform (51).

5. The blade multi-axis fatigue testing device according to claim 4, characterized in that: The gear train assembly comprises: a driving wheel set (53), driven by the driving mechanism and in contact with the outer surface of the track ring (41); The driven wheel group (54) contacts the inner surface of the track ring (41); the tensioning device (55) is connected to the driven wheel group (54), and the tensioning device (55) is configured to force the driven wheel group (54) to be in close contact with the inner surface of the track ring (41); The driving wheel set (53) and the driven wheel set (54) form two sets of rolling pair constraints to limit the separation of the excitation device (5) and the track ring (41).

6. The blade multi-axis fatigue testing device according to claim 5, characterized in that: The tensioning device (55) comprises: The tensioning body (551) comprises two slidably sleeved mounting frames, with driven wheels slidably mounted on the ends of the two mounting frames; a spring (552) disposed between the two mounting brackets, wherein the spring (552) is configured to be in a compressed state; The driving wheel set (53) is located between the two driven wheels.

7. The blade multi-axis fatigue testing device according to claim 4, characterized in that: The excitation device (5) further comprises: Support rollers (6) are installed on both sides of the fixed platform (51), and the support rollers (6) are in contact with the outer surface of the track ring (41) and provide auxiliary support.

8. The blade multi-axis fatigue testing device according to claim 7, characterized in that: The fixed platform (51) is arc-shaped or straight.

9. A blade multi-axial fatigue testing method, used in the blade multi-axial fatigue testing device according to any one of claims 1 to 8, characterized in that: The steps include: Fixing the root of the test blade (3) to the test bench foundation (1) via the positioning flange (2); An annular track excitation device is installed on the blade, and the excitation device (5) is movable along the annular track (4); driving the excitation device (5) to perform rotational motion along the annular track (4); The excitation device (5) is rotated or reciprocated to generate a centrifugal load of varying direction and magnitude, thereby applying multi-directional alternating stress to the test blade (3); The motion parameters of the excitation device (5) are controlled to cause the test blade (3) to deform periodically along a predetermined closed trajectory, thereby achieving biaxial fatigue loading.

10. The blade multi-axial fatigue testing method according to claim 9, characterized in that: By adjusting the counterweight module (56) and controlling the change in the movement direction and speed of the excitation device (5) on the circular track, the size and direction of the load can be controlled.

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