Device and method for detecting stress of fan blade based on ultrasonic critical refraction longitudinal wave

Abstract

The application discloses a device for detecting stress of a fan blade based on ultrasonic critical refraction longitudinal waves, which comprises a rack, a control module arranged on the rack, a cross moving mechanism arranged on the inner side of the rack, and the cross moving mechanism can realize movement in X and Y directions. The application also discloses a method for detecting stress of a fan blade based on ultrasonic critical refraction longitudinal waves. The application can realize movement or fixation of the irregular fan blade surface by controlling the extension and shortening of a telescopic cylinder one and the adsorption capacity of a controllable vacuum chuck. The orientation of an ultrasonic emission probe and an ultrasonic receiving probe can be adjusted by controlling the extension and shortening of a telescopic cylinder three in a direction adjusting mechanism and the movement of the cross moving mechanism, so that the two probes can be quickly attached to the surface to be detected. Based on the characteristics of the ultrasonic critical refraction longitudinal waves, the position of stress concentration can be indirectly obtained by obtaining the sound time variation of the receiving signal, and the stress size can be obtained according to the corresponding relationship between the stress and the sound time.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic testing, specifically to a device and method for detecting stress in wind turbine blades based on ultrasonic critical refraction longitudinal waves. Background Technology

[0002] Wind turbine blades are a key component of wind turbines. During power generation, wind turbine blades, as the direct receivers of wind power, bear strong stress. Over time, this stress often leads to structural damage and affects their service life.

[0003] Wind turbine blades are generally made of composite materials of glass fiber or carbon fiber, and their surfaces are irregular curved surfaces. Therefore, how to detect their stress has always been a technical challenge in this field. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a device and method for detecting wind turbine blade stress based on ultrasonic critical refraction longitudinal waves, thus solving the problem of wind turbine blade stress detection.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a device for detecting wind turbine blade stress based on ultrasonic critical refraction longitudinal wave, comprising a frame, a control module on the frame, a cross-shaped moving mechanism on the inner side of the frame, two laser ranging devices mounted on the cross-shaped moving mechanism, and two horizontally arranged telescopic cylinders on both sides of the frame, the bottom of the other end of the telescopic cylinder being connected to a controllable vacuum suction cup via a support rod;

[0006] The laser ranging device includes a mounting block connected to a cross-shaped moving mechanism. Laser sensors are installed at the four corners of the bottom surface of the mounting block. A telescopic cylinder II is fixed at the center of the bottom surface of the mounting block, and a direction adjustment mechanism is fixed at the bottom end of the telescopic cylinder II.

[0007] The direction adjustment mechanism includes a top plate connected to the bottom end of the telescopic cylinder two. Telescopic cylinder three is fixed at the four corners of the bottom surface of the top plate. The bottom ends of the four telescopic cylinder three are connected to a chassis through a universal ball structure. A mounting hole is opened in the center of the chassis. An ultrasonic transmitting probe is installed in the mounting hole of one chassis, and an ultrasonic receiving probe is installed in the mounting hole of the other chassis.

[0008] A method for detecting wind turbine blade stress based on ultrasonic critical refraction longitudinal waves includes the following steps:

[0009] S1: Place the frame on the fan blade to be tested, so that the four controllable vacuum suction cups are attached to the surface of the fan blades. Move the frame by the cooperation of the four telescopic cylinders and the four controllable vacuum suction cups.

[0010] S2: The position to be inspected is determined by a laser ranging device. The laser sensors are arranged in a square with a distance of L between them. The distance from each sensor to the position to be inspected is defined as h. ij The shape matrix of the surface to be measured is obtained. The shape matrix of the plane to be measured is fitted based on the shape matrix of the surface to be measured. That is, the angle θ between the plane to be measured and the X-axis and Y-axis is obtained. x and θ y ,in:

[0011]

[0012] S3: Based on the status information of the position to be tested obtained in step two, adjust the direction adjustment mechanism accordingly, and at the same time, extend the telescopic cylinder three downwards to make the ultrasonic transmitting probe and the ultrasonic receiving probe fit into the plane to be tested.

[0013] S4: The ultrasonic transmitting probe emits a signal, which is received by the ultrasonic receiving probe. The control module controls the cross-shaped moving mechanism to move the ultrasonic receiving probe along the positive direction of the ultrasonic transmitting probe, thus obtaining the distance S between the probes. During the detection process, the ultrasonic receiving probe moves a distance ΔS each time, so S = nΔS, where S is the distance between the two probes and n is the number of movements. If the acoustic time variation Δt is constant, then there is no stress concentration region between the two probes;

[0014] Δt i =t i +Δt, if the change in acoustic time Δt after the i-th movement of the ultrasonic receiving probe is... i If this changes, a stress concentration area will exist between the two probes. The distance S from this stress concentration area to the ultrasonic transmitting probe can be determined. i Then S i =iΔS;

[0015] The relationship between stress and the change in acoustic time: σ=Kt i ;

[0016] The magnitude of the stress is determined based on the corresponding relationship, where K is defined as the acoustic elastic constant, and its value is determined by the properties of the material itself.

[0017] Further specifying, the steps for moving the rack in S1 include:

[0018] The controllable vacuum suction cups are set to have four levels of suction strength, from weak to strong. The control module controls the suction strength of the two controllable vacuum suction cups on one side of the frame to be level one or two. At this time, the suction is relatively weak. The four telescopic cylinders are controlled to extend synchronously, so that the entire device moves forward a specified distance.

[0019] Then, control the suction of the two weaker controllable vacuum suction cups to level three or four to fix them in place. Control the suction of the other two controllable vacuum suction cups to level one or two and control the four telescopic cylinders to retract synchronously. Then, control the suction of the two controllable vacuum suction cups to level three or four to fix them in place.

[0020] Further specifying the adjustment method in step three, it is as follows:

[0021] Establish a planar coordinate system XOY with the center of the lower surface of the direction adjustment mechanism as the origin. If the plane is required to rotate clockwise around the X-axis by θ... x The angle controls the retraction of two adjacent telescopic cylinders. Length, and simultaneously move in the positive Y-axis direction. Length; the control lever has three extensions in the other two telescopic cylinders. Length, and simultaneously move in the negative Y-axis direction. length;

[0022] If the plane is required to rotate clockwise by θ around the Y-axis y The angle controls the extension of two adjacent telescopic cylinders. Length, and simultaneously move in the negative X-axis direction. Length; controls the retraction of the other two telescopic cylinders. Length, and simultaneously move in the positive X-axis direction. length;

[0023] Where l is the length between the two rods, if the plane is required to rotate by an angle θ in any direction, it can be decomposed into rotations θ around the X-axis and around the Y-axis. x Angle and θ y angle.

[0024] The present invention has the following beneficial effects: This application can move or fix irregular fan blades on the surface by controlling the extension and retraction of the telescopic cylinder and the adsorption capacity of the controllable vacuum suction cup;

[0025] By controlling the extension and retraction of the telescopic cylinder three in the direction adjustment mechanism and the movement of the cross-moving mechanism, the orientation of the ultrasonic transmitting probe and the ultrasonic receiving probe can be adjusted, so that the two probes can quickly fit into the surface to be tested.

[0026] Based on the characteristics of ultrasonic critical refraction longitudinal waves, the location of stress concentration can be indirectly obtained by obtaining the change in acoustic time of the received signal, and the magnitude of stress can be obtained according to the correspondence between stress and acoustic time. The detection of stress is convenient and accurate. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention;

[0028] Figure 2 This is a top view of the present invention;

[0029] Figure 3 This is a schematic diagram of the direction adjustment mechanism of the present invention;

[0030] Figure 4 This is a schematic diagram showing the position of the laser sensor of the present invention;

[0031] Figure 5 This is a schematic diagram of the ultrasonic testing process of the present invention.

[0032] In the diagram: 1. Frame; 2. Control module; 3. Telescopic cylinder one; 4. Spring damping mechanism; 5. Controllable vacuum suction cup; 6. Laser rangefinder; 61. Mounting block; 62. Laser sensor; 7. Telescopic cylinder two; 8. Direction adjustment mechanism; 81. Top plate; 82. Telescopic cylinder three; 83. Chassis. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Please see Figure 1-5 This invention provides a technical solution: a device for detecting the stress of wind turbine blades using ultrasonic critical refraction longitudinal waves, including a frame 1, a control module 2 on the frame 1, and a cross-moving mechanism on the inner side of the frame 1. The cross-moving mechanism can realize movement in the X and Y directions. For example, a slider is mounted on a lead screw and a slide bar, and the lead screw is driven by a motor to rotate to control the slider to move in the Y direction. A platform is set on the slider, and a lead screw and another slider are also installed on the platform to realize movement in the X direction. This is the prior art and is only an example for illustration. Two laser ranging devices 6 are installed on the cross-moving mechanism. Two horizontally arranged telescopic cylinders 3 are installed on both sides of the frame 1. The bottom of the other end of the telescopic cylinder 3 is connected to a controllable vacuum suction cup 5 through a support rod. The support rod has a spring damping mechanism 4.

[0035] like Figure 4 The laser ranging device 6 includes a mounting block 61 connected to the cross moving mechanism. Laser sensors 62 are installed at the four corners of the bottom surface of the mounting block 61. A telescopic cylinder 7 is fixed at the center of the bottom surface of the mounting block 61. A direction adjustment mechanism 8 is fixed at the bottom end of the telescopic cylinder 7.

[0036] like Figure 3The direction adjustment mechanism 8 includes a top plate 81 connected to the bottom end of the telescopic cylinder 2 7. Telescopic cylinder 3 82 is fixed at the four corners of the bottom surface of the top plate 81. The bottom ends of the four telescopic cylinder 3 82 are connected to the chassis 83 through a universal ball structure. The center of the chassis 83 has a mounting hole. An ultrasonic transmitting probe is installed in one of the mounting holes of the chassis 83, and an ultrasonic receiving probe is installed in the mounting hole of the other chassis 83.

[0037] A method for detecting wind turbine blade stress based on ultrasonic critical refraction longitudinal waves includes the following steps:

[0038] S1: Place the frame 1 on the fan blade to be tested, so that the four controllable vacuum suction cups 5 are attached to the surface of the fan blade. Set the suction strength of the controllable vacuum suction cups 5 from weak to strong into four levels. The control module 2 controls the suction strength of the two controllable vacuum suction cups 5 on one side of the frame 1 to level one or two. At this time, the suction is relatively weak and it is in a movable state. The vacuum controllable suction cups can move along the surface of the blade. Control the four telescopic cylinders 3 to extend synchronously, so that the entire frame 1 moves forward a specified distance.

[0039] Then, control the suction of the two weaker controllable vacuum suction cups 5 to level three or four to fix them in place. Control the suction of the other two controllable vacuum suction cups 5 to level one or two and control the four telescopic cylinders 3 to retract synchronously. Then, control the suction of the two controllable vacuum suction cups 5 to level three or four to fix them in place.

[0040] S2: As Figure 4 The location to be inspected is determined by the laser ranging device 6. The laser sensors 62 are arranged in a square with a distance of L between them. The distance from each sensor to the location to be inspected is defined as h. ij The shape matrix of the surface to be measured is obtained. The shape matrix of the plane to be measured is fitted based on the shape matrix of the surface to be measured. That is, the angle θ between the plane to be measured and the X-axis and Y-axis is obtained. x and θ y ,in:

[0041]

[0042] S3: As Figure 3 Based on the status information of the position to be tested obtained in step two, the direction adjustment mechanism 8 is adjusted accordingly, and at the same time, the telescopic cylinder 82 extends downward to make the ultrasonic transmitting probe and the ultrasonic receiving probe fit into the plane to be tested.

[0043] The specific operation is as follows: Establish a planar coordinate system XOY with the center of the lower surface of the direction adjustment mechanism 8 as the origin. If it is required that the plane rotate clockwise around the X-axis by θ... x The angle controls the retraction of two adjacent telescopic cylinders. Length, and simultaneously move in the positive Y-axis direction. Length; the control lever and the other two telescopic cylinders extend by 82. Length, and simultaneously move in the negative Y-axis direction. length;

[0044] If the plane is required to rotate clockwise by θ around the Y-axis y The angle controls the angle of the two adjacent telescopic cylinders.

[0045] stretch

[0046] long Length, and simultaneously move in the negative X-axis direction. Length; controls the retraction of the other two telescopic cylinders (382). Length, and simultaneously move in the positive X-axis direction. length;

[0047] Where l is the length between the two rods, if the plane is required to rotate by an angle θ in any direction, it can be decomposed into rotations θ around the X-axis and around the Y-axis. x Angle and θ y angle;

[0048] S4: As Figure 5 The ultrasonic transmitting probe emits a signal, which is received by the ultrasonic receiving probe. The control module 2 controls the cross moving mechanism to move the ultrasonic receiving probe along the positive direction of the ultrasonic transmitting probe, thus obtaining the distance S between the probes. During the detection process, the ultrasonic receiving probe moves a distance ΔS each time, so S = nΔS, where S is the distance between the two probes and n is the number of moves. If the acoustic time variation Δt is constant, then there is no stress concentration region between the two probes;

[0049] Δt i =t i +Δt, if the change in acoustic time Δt after the i-th movement of the ultrasonic receiving probe is... i If this changes, a stress concentration area will exist between the two probes. The distance S from this stress concentration area to the ultrasonic transmitting probe can be determined. i Then S i =iΔS;

[0050] The relationship between stress and the change in acoustic time: σ=Kt i ;

[0051] The magnitude of the stress is determined based on the corresponding relationship, where K is defined as the acoustic elastic constant, and its value is determined by the properties of the material itself.

[0052] The principle of this application is as follows: Ultrasonic testing utilizes the interaction between ultrasonic waves and the test specimen to study reflected, transmitted, and scattered waves. By analyzing data from the ultrasonic testing instrument, such as changes in sound wave propagation time and amplitude, the internal state of the specimen can be obtained, thereby evaluating its specific applicability. When a beam of ultrasonic longitudinal wave is incident at a certain angle from solid medium I into solid medium II, part of the energy is reflected at the interface, with the reflection angle equal to the incident angle. The other part of the energy is refracted into medium II, and after wave mode conversion, refracted longitudinal waves and refracted transverse waves are formed in medium II. When the angle between the refracted longitudinal wave and the normal is 90°, the refracted longitudinal wave in medium II propagates along the interface between the two media and is called the critical refracted longitudinal wave (LCR wave). LCR waves have the following characteristics: 1. They are not sensitive to the surface condition of the material. Compared with surface waves, the energy of LCR waves is concentrated below the surface, has a certain propagation depth, and is less affected by surface roughness. 2. They have a fast propagation speed, propagating at the speed of longitudinal volume waves. In testing, they are basically the first signal received, and signal analysis and localization are simple. 3. It is sensitive to stress changes in materials and is suitable for measuring the stress state of material surfaces.

[0053] This application allows for the movement or fixation of irregular fan blades by controlling the extension and retraction of the telescopic cylinder 3 and the adsorption capacity of the controllable vacuum suction cup 5. By controlling the extension and retraction of the telescopic cylinder 82 in the direction adjustment mechanism 8 and the movement of the cross-moving mechanism, the orientation of the ultrasonic transmitting probe and the ultrasonic receiving probe can be adjusted, enabling the two probes to quickly adhere to the surface to be tested. Based on the characteristics of ultrasonic critical refraction longitudinal waves, the location of stress concentration can be indirectly obtained by obtaining the change in acoustic time of the received signal. Then, the magnitude of stress can be obtained according to the correspondence between stress and acoustic time. The detection of the corresponding force is convenient and accurate.

[0054] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for detecting wind turbine blade stress based on ultrasonic critical refraction longitudinal waves, characterized in that, The device includes a frame, on which a control module is mounted. Its features include: a cross-shaped moving mechanism on the inner side of the frame, on which two laser rangefinders are mounted; and two horizontally arranged telescopic cylinders on both sides of the frame, with a controllable vacuum suction cup connected to the bottom of the other end of each telescopic cylinder via a support rod. The laser ranging device includes a mounting block connected to a cross-shaped moving mechanism. Laser sensors are installed at the four corners of the bottom surface of the mounting block. A telescopic cylinder II is fixed at the center of the bottom surface of the mounting block, and a direction adjustment mechanism is fixed at the bottom end of the telescopic cylinder II. The direction adjustment mechanism includes a top plate connected to the bottom end of the telescopic cylinder two. Telescopic cylinder three is fixed at the four corners of the bottom surface of the top plate. The bottom ends of the four telescopic cylinder three are connected to a chassis through a universal ball structure. A mounting hole is opened in the center of the chassis. An ultrasonic transmitting probe is installed in the mounting hole of one chassis and an ultrasonic receiving probe is installed in the mounting hole of the other chassis. The method includes the following steps: S1: Place the frame on the fan blade to be tested, so that the four controllable vacuum suction cups are attached to the surface of the fan blades. Move the frame by the cooperation of the four telescopic cylinders and the four controllable vacuum suction cups. S2: The location to be inspected is determined by a laser ranging device. Laser sensors are arranged in a square with a distance L between them. The distance from each sensor to the location to be inspected is defined as... The shape matrix of the surface to be measured is obtained. The shape matrix of the plane to be measured is fitted based on the shape matrix of the surface to be measured. This yields the angles between the plane to be measured and the X and Y axes. and ,in: , ； S3: Based on the state information of the position to be tested obtained in S2, adjust the direction adjustment mechanism accordingly, and at the same time, extend the telescopic cylinder downwards to make the ultrasonic transmitting probe and the ultrasonic receiving probe fit into the plane to be tested. S4: The ultrasonic transmitting probe emits a signal, which is received by the ultrasonic receiving probe. The control module controls the cross-shaped moving mechanism to move the ultrasonic receiving probe along the positive direction of the ultrasonic transmitting probe, thus obtaining the distance between the probes. During the detection process, the ultrasonic receiving probe moves a certain distance each time. ,but in is the distance between the two probes, and n is the number of moves; If the change in sound time If the value is constant, there is no stress concentration area between the two probes; If the first Change in acoustic time after moving the ultrasonic receiving probe If this changes, a stress concentration area will exist between the two probes. The distance from this stress concentration area to the ultrasonic transmitting probe is determined as follows. ,but The relationship between stress and the change in acoustic time: The magnitude of the stress is determined based on the corresponding relationship, where K is defined as the acoustic elastic constant, and its value is determined by the properties of the material itself.

2. The method for detecting wind turbine blade stress based on ultrasonic critical refraction longitudinal waves according to claim 1, characterized in that, The steps for moving the rack in S1 include: The controllable vacuum suction cups are set to have four levels of suction strength, from weak to strong. The control module controls the suction strength of the two controllable vacuum suction cups on one side of the frame to be level one or two. At this time, the suction is relatively weak. The four telescopic cylinders are controlled to extend synchronously, so that the entire device moves forward a specified distance. Then, control the suction of the two weaker controllable vacuum suction cups to level three or four to fix them in place. Control the suction of the other two controllable vacuum suction cups to level one or two and control the four telescopic cylinders to retract synchronously. Then, control the suction of the two controllable vacuum suction cups to level three or four to fix them in place.

3. The method for detecting wind turbine blade stress based on ultrasonic critical refraction longitudinal waves according to claim 2, characterized in that, The specific adjustment method in S3 is as follows: Establish a planar coordinate system XOY with the center of the lower surface of the direction adjustment mechanism as the origin. If the plane is required to rotate clockwise around the X-axis... The angle controls the retraction of two adjacent telescopic cylinders. Length, and simultaneously move in the positive Y-axis direction. Length; controls the extension of the other two telescopic cylinders. Length, and simultaneously move in the negative Y-axis direction. length; If the plane is required to rotate clockwise around the Y-axis The angle controls the extension of two adjacent telescopic cylinders. Length, and simultaneously move in the negative X-axis direction. Length; controls the retraction of the other two telescopic cylinders. Length, and simultaneously move in the positive X-axis direction. length; in The length between the two telescopic cylinders is given. If the plane is required to rotate in any direction... Angles can be decomposed into rotations about the X-axis and the Y-axis. Angle and angle.

Images