Wind power blade biaxial fatigue testing device and testing method

Abstract

The invention relates to the technical field of axial fatigue testing, and particularly discloses a wind power blade biaxial fatigue testing device and a testing method.The wind power blade biaxial fatigue testing device comprises a base and a blade body, the root of the blade body is installed on a test bed base, and a clamp is arranged on the side wall of the blade body; a traction assembly used for adjusting the vibration frequency of the clamp is arranged at the top end of the base, the clamp comprises two transverse plates, the two transverse plates are located on the two sides of the blade body respectively, second clamping blocks are arranged on the opposite sides of the two transverse plates, and four second double-end studs are arranged between the two transverse plates in a penetrating mode. According to the invention, the blades are loaded in a resonance form through the cable, the additional power loss of an inertia mass block is avoided, the requirement on the capacity of the motor is reduced, the cable is uniformly wound and unwound, the knotting and abrasion of the cable are effectively avoided, the service life of the cable is prolonged, and a switchable single-shaft and double-shaft fatigue test structure is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of shaft fatigue testing, and in particular to a biaxial fatigue testing device and a testing method for a wind turbine blade. Background Art

[0002] Among the components of wind turbines, wind turbine blades are important components that convert wind energy into mechanical energy and are one of the core components of wind turbines. Their structure, strength and stability play an important role in the reliability of the unit. Fatigue testing is an effective way to inspect and certify the quality of wind turbine blades, and can verify the ability of wind turbine blades to withstand loads under given working conditions. With the development trend of large-scale blades, resonance fatigue testing technology has received widespread attention, and at the same time, higher requirements have been put forward for test cycles, energy consumption, system performance, etc.

[0003] Chinese patent (CN106840928B) discloses a wind turbine blade fatigue loading test device, including a servo motor installed on a machine body, a screw rod connected to the output shaft of the servo motor through a coupling, and a protective box equipped with a counterweight block is tightly connected to a slider. The characteristics are: circular holes of different diameters are provided in the center of the front and rear side walls of the slider box, the nut is installed in the circular hole with a larger diameter, the guide wheel I and the guide wheel II are respectively installed on the left and right side walls of the box through the pin shaft III and the pin shaft IV, the slider is mounted on the screw rod through the nut, the guide wheel I and the guide wheel II are in contact with the guide rail to provide guide support for the slider, and the fatigue loading device uses a hollow ball screw for transmission.

[0004] However, there are some drawbacks in the above-mentioned related technologies. For example, during the use of the wind turbine blade fatigue loading test device, since a mass block is used to apply inertial exciting force, additional power needs to be consumed, and a relatively expensive servo motor is required. In addition, when performing a dual-axis test, multiple sets of fatigue loading test devices need to be installed on the blade, which not only increases the weight and reduces the blade's natural frequency, prolongs the test cycle, but also requires additional power consumption and is not energy-efficient enough. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a biaxial fatigue testing device and a testing method for wind turbine blades, which can overcome the technical defects.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A wind turbine blade biaxial fatigue test device comprises a base and a blade body, wherein the root of the blade body is mounted on a test bench base, a clamp is disposed on the side wall of the blade body, and a traction component for adjusting the vibration frequency of the clamp is disposed on the top of the base; The clamp comprises two horizontal plates, the two horizontal plates are respectively located on both sides of the blade body, a second clamping block is arranged on the opposite sides of the two horizontal plates, four second studs are arranged between the two horizontal plates, nuts are connected to both ends of the second studs, and a rope connecting piece is arranged at the bottom end of the horizontal plate located at the bottom; The traction assembly includes a winding roller, two U-shaped plates are provided at the top of the base, the winding roller passes through and is rotatably installed between the two U-shaped plates, two support rods are fixedly installed between the two U-shaped plates, a slider is slidably installed between the two support rods, a support frame is fixedly installed at one end of the slider, a changing wheel is rotatably installed between the opposite sides of the support frame, a cable is wound between the winding roller, the changing wheel and the rope connecting member in sequence, and the two ends of the cable are respectively connected to the winding roller and the rope connecting member, wherein a driving assembly for driving the winding roller to rotate is provided on one side of the U-shaped plate, a driving mechanism for adjusting the position of the slider is provided between the two U-shaped plates, a reciprocating mechanism for uniformly winding the winding roller is provided between the two U-shaped plates, and a transmission assembly is provided between the reciprocating mechanism and the winding roller.

[0007] Preferably, the rope connecting member comprises a circular plate, a support column and a circular ring which are integrally arranged, and the rope connecting member is made of metal.

[0008] Preferably, the drive assembly includes an L-shaped plate, which is fixedly mounted on the side wall of one of the U-shaped plates, a clutch is provided at the top of the horizontal section of the L-shaped plate, and a first motor is provided on the side wall of the vertical section of the L-shaped plate, the clutch is used to separate or combine the winding roller shaft and the output shaft of the first motor, the output shaft of the first motor is arranged to penetrate the L-shaped plate, and a coupling is provided between the output shaft of the first motor and the input shaft of the clutch.

[0009] Preferably, the driving mechanism includes a second motor, a screw rod is passed through and rotatably installed between the two U-shaped plates, the slider is threadedly connected to the screw rod, the second motor is fixedly installed on the side wall of one of the U-shaped plates, and the output shaft of the second motor is fixedly connected to the screw rod through a coupling mechanism.

[0010] Preferably, the reciprocating mechanism includes a reciprocating screw rod, which passes through and is rotatably installed between the two U-shaped plates, a guide rod is fixedly installed between the two U-shaped plates, a support block is slidably installed on the guide rod, a limiting column is provided at the bottom end of the support block, the limiting column matches the reciprocating screw rod, a limiting wheel is rotatably installed between the opposite sides of the support block, and the cable passes around the limiting wheel.

[0011] Preferably, the transmission assembly includes a first pulley and a second pulley, the first pulley is fixedly mounted on the shaft of the winding roller, the second pulley is fixedly mounted on the shaft of the reciprocating screw rod, and a synchronous belt is wound between the first pulley and the second pulley.

[0012] Preferably, the diameter of the second pulley is larger than that of the first pulley.

[0013] A biaxial fatigue test method for a wind turbine blade comprises the following steps: S1. According to the frequency to be applied to the blade body, the blade body is mounted on the test bench base, the second motor drives the screw to rotate, the slider slides between the two support rods, the relative positions of the two traction points of the blade body are adjusted, and the blade is subjected to a biaxial fatigue test with simultaneous loading in the swing and shimmy directions, and then the fixture is fixed at the position of the blade body to be tested; S2, connect one end of the cable to the winding roller, pass the other end of the cable through the limiting wheel and the changing wheel in sequence, and then connect it to the rope connecting member; S3. When the first motor pulls the blade body through the winding roller, the master-slave part of the clutch is in a coupled state, and the torque of the output shaft of the first motor can be transmitted to the winding roller through the coupling and the clutch. The winding roller retracts the cable, and the blade body moves downward under the traction of the cable. At this time, the rotation directions of the first motor and the winding roller are consistent. When the blade body vibrates to the lowest point, the master-slave part of the clutch is separated. At this time, the elastic potential energy of the blade body needs to be converted into kinetic energy, and the blade body begins to rebound. During the rebound process, the master-slave part of the clutch is separated and the torque of the first motor cannot be transmitted. The winding roller releases the cable as the blade body rebounds, and the winding roller starts to move in the opposite direction, while the first motor maintains its original direction of rotation. At this time, the rotation directions of the first motor and the winding roller are opposite. S4. When the blade body reaches the highest point again, the clutch is engaged again, and the output shaft of the first motor transmits torque to the winding roller, applying downward traction excitation to the blade body to approach the natural frequency of the blade body vibration, so that the clutch can apply half-wave excitation to the blade body without reversing. The cable pulls the blade with a composite frequency of the blade swinging natural frequency and the blade shimmying natural frequency superimposed on each other, so that the blade performs Lissajous motion in the swinging direction and the shimmying direction; S5. During the rotation of the winding roller, the first pulley is driven to rotate, and the synchronous belt and the second pulley are used to drive the reciprocating screw to rotate, which drives the limit column, the limit wheel and the support block to slide back and forth on the guide rod synchronously, and the cable winding and releasing process is evenly distributed.

[0014] Preferably, in S1, the second motor drives the screw to rotate, and the slider slides between the two support rods. When the slider is directly below the rope connecting member, the two traction points of the slider and the rope connecting member are located in the same vertical plane, and a uniaxial fatigue test is performed on the blade body in the swing direction.

[0015] The beneficial effects of the present invention are: 1. By setting the clamp and the traction assembly, the beneficial effect that can be obtained is that when the first motor pulls the blade body through the winding roller, the master-slave part of the clutch is in a coupled state, and the torque of the output shaft of the first motor can be transmitted to the winding roller through the coupling and the clutch. The winding roller recycles the cable, and the blade body moves downward under the traction of the cable. At this time, the rotation directions of the first motor and the winding roller are consistent. When the blade body vibrates to the lowest point, the master-slave part of the clutch is separated. At this time, the elastic potential energy of the blade body needs to be converted into kinetic energy, and the blade body begins to rebound. During the rebound process, the master-slave part of the clutch is separated, and the torque of the first motor cannot be transmitted, and the winding roller will As the blade body rebounds and releases the cable, the winding roller starts to move in the opposite direction, while the first motor maintains its original direction of rotation. At this time, the rotation directions of the first motor and the winding roller are opposite. When the blade body reaches the highest point again, the clutch engages again, and the output shaft of the first motor transmits torque to the winding roller, applying downward traction excitation to the blade body to approach the natural frequency of the blade body's vibration. The clutch can apply half-wave excitation to the blade body without reversing. According to the frequency to be applied to the blade body, the first motor applies the frequency as a power source, and loads the blade in the form of resonance through the cable, avoiding the power loss added by the inertial mass block and reducing the requirements for motor capacity.

[0016] 2. By setting a reciprocating mechanism, the beneficial effect that can be obtained is that the reciprocating screw rod passes through and is rotatably installed between the two U-shaped plates, a guide rod is fixedly installed between the two U-shaped plates, a support block is slidably installed on the guide rod, a limiting column is arranged at the bottom end of the support block, the limiting column matches the reciprocating screw rod, a limiting wheel is rotatably installed between the opposite sides of the support block, the cable passes around the limiting wheel, a transmission assembly is arranged between the reciprocating screw rod and the winding roller, the transmission assembly includes a first pulley and a second pulley, the first pulley is fixedly installed on the shaft body of the winding roller, the second pulley is fixedly installed on the shaft body of the reciprocating screw rod, and a synchronous belt is wound between the first pulley and the second pulley; During the rotation of the winding roller, the first pulley is driven to rotate, and the synchronous belt and the second pulley are used to drive the reciprocating screw to rotate, which drives the limit column, the limit wheel and the support block to slide back and forth on the guide rod synchronously. The cable winding and releasing process is evenly distributed, which has the function of evenly winding and releasing the cable, effectively avoiding the tangling and wear of the cable and extending the life of the cable.

[0017] 3. By setting up the driving mechanism, the beneficial effect that can be obtained is that the driving mechanism includes a second motor, a screw rod is inserted and rotatably installed between the two U-shaped plates, the slider is threadedly connected to the screw rod, the second motor is fixedly installed on the side wall of one of the U-shaped plates, and the output shaft of the second motor is fixedly connected to the screw rod through a coupling mechanism; The blade body is installed on the base of the test bench, and the second motor drives the screw to rotate, and the slider slides between the two support rods to adjust the relative position of the two traction points of the blade body. The blade is subjected to a biaxial fatigue test with simultaneous loading in the swing and shimmy directions. The single cable uses a composite frequency of the blade's swinging natural frequency and the blade's shimmy natural frequency superimposed on each other to pull the blade, so that the blade performs Lissajous motion in the swing and shimmy directions. When the slider is directly below the rope connecting piece, the two traction points of the slider and the rope connecting piece are located in the same vertical plane, and the blade body is subjected to a uniaxial fatigue test in the shimmy direction. It has a switchable uniaxial and biaxial fatigue test structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is the installation structure diagram of the clamp in the present invention; Figure 3 It is the installation structure diagram of the transmission assembly in the present invention; Figure 4 This is a structural diagram of the installation of the slider and the U-shaped frame in the present invention; Figure 5 It is the installation structure diagram of the reciprocating mechanism in the present invention; Figure 6 This is a diagram of the installation structure of the support block in the present invention.

[0020] Description of reference numerals: In the figure: 1. base; 2. blade body; 31. cross plate; 32. second clamping block; 33. second stud; 34. rope connecting piece; 41. U-shaped plate; 42. winding roller; 43. support rod; 44. slider; 45. support frame; 46. direction-changing wheel; 47. cable; 51. L-shaped plate; 52. clutch; 53. first motor; 54. coupling; 61. screw; 62. second motor; 71. reciprocating screw; 72. guide rod; 73. support block; 74. limit column; 75. limit wheel; 81. first pulley; 82. second pulley; 83. synchronous belt. DETAILED DESCRIPTION

[0021] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are clearly and completely described below in combination with the accompanying drawings and preferred embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present application, it should be understood that the orientation or position relationship indicated by "inside", "outside", etc. is based on the orientation or position described in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, a specific orientation structure and operation, and therefore cannot be understood as a limitation on the present application.

[0023] Reference Figure 1-Figure 6 , is a biaxial fatigue testing device for wind turbine blades disclosed in the present invention, comprising a base 1 and a blade body 2, wherein the root of the blade body 2 is installed on a test bench base.

[0024] The side wall of the blade body 2 is provided with a clamp, which includes two horizontal plates 31. The two horizontal plates 31 are respectively located on both sides of the blade body 2. A second clamping block 32 is provided on the opposite sides of the two horizontal plates 31. Four second studs 33 are provided between the two horizontal plates 31. Nuts are connected to both ends of the second studs 33. A rope connecting piece 34 is provided at the bottom end of the horizontal plate 31 below. The rope connecting piece 34 includes a circular plate, a pillar and a circular ring that are integrally arranged. The rope connecting piece 34 is made of metal.

[0025] A traction assembly for adjusting the vibration frequency of the clamp is provided at the top of the base 1, and the traction assembly includes a winding roller 42. Two U-shaped plates 41 are provided at the top of the base 1. The winding roller 42 penetrates and is rotatably installed between the two U-shaped plates 41. Two support rods 43 are fixedly installed between the two U-shaped plates 41. A slider 44 is slidably installed between the two support rods 43. A support frame 45 is fixedly installed at one end of the slider 44. A direction-changing wheel 46 is rotatably installed between the opposite sides of the support frame 45. A cable 47 is wound in sequence between the winding roller 42, the direction-changing wheel 46 and the rope connecting member 34. The two ends of the cable 47 are respectively connected to the winding roller 42 and the rope connecting member 34. A driving assembly for driving the winding roller 42 to rotate is provided on one side of the U-shaped plate 41, and the driving assembly includes an L-shaped plate 51, and the L-shaped plate 51 is fixedly installed on the side wall of one of the U-shaped plates 41, and a clutch 52 is provided on the top of the horizontal section of the L-shaped plate 51, and a first motor 53 is provided on the vertical section side wall of the L-shaped plate 51, and the clutch 52 is used to separate or combine the shaft body of the winding roller 42 and the output shaft of the first motor 53, and the output shaft of the first motor 53 is arranged through the L-shaped plate 51, and a coupling 54 is provided between the output shaft of the first motor 53 and the input shaft of the clutch 52, and a slider 44 for adjusting is provided between the two U-shaped plates 41. The driving mechanism of the position includes a second motor 62, a screw 61 is passed through and rotatably installed between the two U-shaped plates 41, the slider 44 is threadedly connected to the screw 61, the second motor 62 is fixedly installed on the side wall of one of the U-shaped plates 41, and the output shaft of the second motor 62 is fixedly connected to the screw 61 through a coupling mechanism. The blade body 2 is fixed on the base of the test bench. When the first motor 53 pulls the blade body 2 through the winding roller 42, the master and slave parts of the clutch 52 are in a combined state, and the torque of the output shaft of the first motor 53 can be transmitted to the winding roller 42 through the coupling 54 and the clutch 52, and the winding roller 42 is retracted and released. Cable 47, cable 47 is inclined at an angle of 30° to 70° to the vertical direction. When the frequency at which the first motor 53 pulls the blade body 2 through the winding roller 42 is close to or equal to the natural frequency of the blade body 2, the blade body 2 can effectively absorb energy, resulting in the maximum amplitude of the blade body 2 and the lowest energy consumption. The cable 47 superimposes the two natural frequencies of the blade body 2, namely, the waving and the swinging, and also superimposes the loading forces under these two natural frequencies. The angle of the cable 47 and the two loading forces on the cable 47 need to be optimized and adjusted according to the natural frequencies of the blade body in two directions. These optimizations and adjustments are all controlled and realized by a computer.

[0026] A reciprocating mechanism for evenly winding the winding roller 42 is arranged between the two U-shaped plates 41, and the reciprocating mechanism includes a reciprocating screw rod 71, which passes through and is rotatably installed between the two U-shaped plates 41, and a guide rod 72 is fixedly installed between the two U-shaped plates 41, and a support block 73 is slidably installed on the guide rod 72, and a limiting column 74 is arranged at the bottom end of the support block 73, and the limiting column 74 matches the reciprocating screw rod 71, and a limiting wheel 75 is rotatably installed between the opposite sides of the support block 73, and the cable 47 passes around the limiting wheel 75, and a transmission assembly is arranged between the reciprocating mechanism and the winding roller 42, and the transmission assembly includes a first pulley 81 and a second pulley 82, the first pulley 81 is fixedly installed on the shaft body of the winding roller 41, and the second pulley 82 is fixedly installed on the shaft body of the reciprocating screw rod 71, and a synchronous belt 83 is wound between the first pulley 81 and the second pulley 82.

[0027] The present invention also discloses a biaxial fatigue test method for a wind turbine blade, comprising the following steps: S1. According to the frequency to be applied to the blade body 2, the blade body 2 is mounted on the test bench base, the second motor 62 drives the screw 61 to rotate, the slider 44 slides between the two support rods 43, the relative positions of the two traction points of the blade body 2 are adjusted, and the blade is subjected to a biaxial fatigue test with simultaneous loading in the swinging and shimmying directions, and then the fixture is fixed at the position of the blade body 2 to be tested; S2, connecting one end of the cable 47 to the winding roller 42, and passing the other end of the cable 47 through the limiting wheel 75 and the changing wheel 46 in sequence, and then connecting to the rope connecting member 34; S3, when the first motor 53 pulls the blade body 2 through the winding roller 42, the master-slave part of the clutch 52 is in a coupled state, and the torque of the output shaft of the first motor 53 can be transmitted to the winding roller 42 through the coupling 54 and the clutch 52, and the winding roller 42 retracts the cable 47, and the blade body 2 moves downward under the traction of the cable 47. At this time, the rotation directions of the first motor 53 and the winding roller 42 are consistent. When the blade body 2 vibrates to the lowest point, the master-slave part of the clutch 52 is separated. At this time, the elastic potential energy of the blade body 2 needs to be converted into kinetic energy, and the blade body 2 begins to rebound. During the rebound process, since the master-slave part of the clutch 52 is separated, the torque of the first motor 53 cannot be transmitted, and the winding roller 42 will release the cable 47 as the blade body 2 rebounds, and the winding roller 42 starts to move in the opposite direction, while the first motor 53 maintains its original direction of rotation. At this time, the rotation directions of the first motor 53 and the winding roller 42 are opposite; S4, when the blade body 2 reaches the highest point again, the clutch 52 is engaged again, and the output shaft of the first motor 53 transmits torque to the winding roller 42, applying downward traction excitation to the blade body 2 to approach the natural frequency of vibration of the blade body 2, so that the clutch 52 can apply half-wave excitation to the blade body 2 without reversing, and the cable 47 pulls the blade with a composite frequency of the blade swinging natural frequency and the blade swinging natural frequency superimposed on each other, so that the blade performs Lissajous motion in the swinging direction and the swinging direction. The angle between the cable 47 and the blade swinging direction and the loading force at the two frequencies are the key parameters of the present invention, and must be optimized according to the natural frequencies of the blade in two directions and the target load to obtain the optimal parameters; S5, during the rotation of the winding roller 42, the first pulley 81 is driven to rotate, and the synchronous belt 83 and the second pulley 82 are used to drive the reciprocating screw rod 71 to rotate, and the limiting column 74, the limiting wheel 75 and the support block 73 are driven to slide back and forth on the guide rod 72 synchronously, and the cable 47 is evenly distributed during the winding and unwinding process; In S1, the second motor 62 drives the screw 61 to rotate, and the slider 44 slides between the two support rods 43. When the slider 44 is directly below the rope connecting member 34, the two traction points of the slider 44 and the rope connecting member 34 are located in the same vertical plane, and the blade body 2 is subjected to a uniaxial fatigue test in the swing direction.

[0028] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A wind turbine blade biaxial fatigue test device, characterized in that: It comprises a base (1) and a blade body (2), wherein the root of the blade body (2) is mounted on a test bench base, a side wall of the blade body (2) is provided with a clamp, and the top end of the base (1) is provided with a traction component for adjusting the vibration frequency of the clamp; The clamp comprises two transverse plates (31), the two transverse plates (31) are respectively located on two sides of the blade body (2), a second clamping block (32) is provided on the opposite sides of the two transverse plates (31), four second stud bolts (33) are provided through the two transverse plates (31), both ends of the second stud bolts (33) are connected with nuts, and a rope connecting piece (34) is provided at the bottom end of the transverse plate (31) located at the bottom; The traction assembly comprises a winding roller (42), two U-shaped plates (41) are arranged at the top of the base (1), the winding roller (42) penetrates and is rotatably installed between the two U-shaped plates (41), two support rods (43) are fixedly installed between the two U-shaped plates (41), a slider (44) is slidably installed between the two support rods (43), a support frame (45) is fixedly installed at one end of the slider (44), and a direction-changing wheel (46) is rotatably installed between the opposite sides of the support frame (45), the winding roller (42) and the direction-changing wheel A cable (47) is sequentially wound between the U-shaped plate (46) and the rope connecting member (34), and two ends of the cable (47) are respectively connected to the winding roller (42) and the rope connecting member (34), wherein a driving component for driving the winding roller (42) to rotate is arranged on one side of the U-shaped plate (41), a driving mechanism for adjusting the position of the slider (44) is arranged between the two U-shaped plates (41), a reciprocating mechanism for evenly winding the winding roller (42) is arranged between the two U-shaped plates (41), and a transmission component is arranged between the reciprocating mechanism and the winding roller (42); The driving assembly comprises an L-shaped plate (51), the L-shaped plate (51) being fixedly mounted on a side wall of one of the U-shaped plates (41), a clutch (52) being arranged at the top end of the horizontal section of the L-shaped plate (51), a first motor (53) being arranged at the side wall of the vertical section of the L-shaped plate (51), the clutch (52) being used to separate or combine the shaft of the winding roller (42) and the output shaft of the first motor (53), the output shaft of the first motor (53) being arranged to penetrate the L-shaped plate (51), and a coupling (54) being arranged between the output shaft of the first motor (53) and the input shaft of the clutch (52).

2. A wind turbine blade biaxial fatigue testing device according to claim 1, characterized in that: The rope connecting member (34) comprises a circular plate, a support column and a circular ring which are arranged in an integral manner, and the rope connecting member (34) is made of metal.

3. A wind turbine blade biaxial fatigue testing device according to claim 1, characterized in that: The driving mechanism comprises a second motor (62), a screw rod (61) is passed through and rotatably mounted between the two U-shaped plates (41), the slider (44) is threadedly connected to the screw rod (61), the second motor (62) is fixedly mounted on a side wall of one of the U-shaped plates (41), and an output shaft of the second motor (62) is fixedly connected to the screw rod (61) via a coupling mechanism.

4. A wind turbine blade biaxial fatigue testing device according to claim 3, characterized in that: The reciprocating mechanism comprises a reciprocating screw rod (71), the reciprocating screw rod (71) passes through and is rotatably installed between the two U-shaped plates (41), a guide rod (72) is fixedly installed between the two U-shaped plates (41), a support block (73) is slidably installed on the guide rod (72), a limiting column (74) is arranged at the bottom end of the support block (73), the limiting column (74) matches the reciprocating screw rod (71), a limiting wheel (75) is rotatably installed between the two opposite sides of the support block (73), and the cable (47) passes around the limiting wheel (75).

5. A wind turbine blade biaxial fatigue testing device according to claim 4, characterized in that: The transmission assembly comprises a first pulley (81) and a second pulley (82), wherein the first pulley (81) is fixedly mounted on the shaft of the winding roller (41), and the second pulley (82) is fixedly mounted on the shaft of the reciprocating screw rod (71), and a synchronous belt (83) is wound between the first pulley (81) and the second pulley (82).

6. A wind turbine blade biaxial fatigue testing device according to claim 5, characterized in that: The diameter of the second pulley (82) is larger than that of the first pulley (81).

7. A biaxial fatigue testing method for wind turbine blades, applied to the biaxial fatigue testing method for wind turbine blades according to claim 5, characterized in that: The following steps are involved: S1. According to the frequency to be applied to the blade body (2), the blade body (2) is mounted on the test bench base, the second motor (62) drives the screw rod (61) to rotate, the slider (44) slides between the two support rods (43), the relative positions of the two traction points of the blade body (2) are adjusted, and the blade is subjected to a biaxial fatigue test with simultaneous loading in the swing and shimmy directions, and then the fixture is fixed at the position of the blade body (2) to be tested; S2, connecting one end of the cable (47) to the winding roller (42), passing the other end of the cable (47) through the limiting wheel (75) and the direction-changing wheel (46) in sequence, and then connecting the cable to the rope connecting member (34); S3, when the first motor (53) pulls the blade body (2) through the winding roller (42), the master and slave parts of the clutch (52) are in a coupled state, and the torque of the output shaft of the first motor (53) can be transmitted to the winding roller (42) through the coupling (54) and the clutch (52). The winding roller (42) retracts the cable (47), and the blade body (2) moves downward under the traction of the cable (47). At this time, the rotation directions of the first motor (53) and the winding roller (42) are consistent. When the blade body (2) vibrates to the lowest At the point, the master and slave parts of the clutch (52) are separated, and the elastic potential energy of the blade body (2) needs to be converted into kinetic energy. The blade body (2) begins to rebound. During the rebound process, the master and slave parts of the clutch (52) are separated and the torque of the first motor (53) cannot be transmitted. The winding roller (42) releases the cable (47) as the blade body (2) rebounds, and the winding roller (42) begins to move in the opposite direction, while the first motor (53) maintains its original direction of rotation. At this time, the first motor (53) and the winding roller (42) rotate in opposite directions. S4, when the blade body (2) reaches the highest point again, the clutch (52) is engaged again, and the output shaft of the first motor (53) transmits torque to the winding roller (42), applying downward traction excitation to the blade body (2) to approach the natural frequency of vibration of the blade body (2), so that the clutch (52) can apply half-wave excitation to the blade body (2) without reversing, and the cable (47) uses a composite frequency of the blade swinging natural frequency and the blade shimmying natural frequency superimposed on each other to pull the blade, so that the blade performs Lissajous motion in the swinging direction and the shimmying direction; S5. During the rotation of the winding roller (42), the first pulley (81) is driven to rotate, and the synchronous belt (83) and the second pulley (82) are used to drive the reciprocating screw rod (71) to rotate, thereby driving the limit column (74), the limit wheel (75) and the support block (73) to synchronously slide back and forth on the guide rod (72), so that the cable (47) is evenly distributed during the winding and unwinding process.

8. A biaxial fatigue testing method for wind turbine blades according to claim 7, characterized in that: In S1, the second motor (62) drives the screw rod (61) to rotate, and the slider (44) slides between the two support rods (43). When the slider (44) is directly below the rope connecting member (34), the two traction points of the slider (44) and the rope connecting member (34) are located in the same vertical plane, and a uniaxial fatigue test is performed on the blade body (2) in the swing direction.

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