Laser ultrasonic visualization detection equipment and method for composite material cylinder structure

Abstract

Provided is a laser ultrasonic visualization detection device for composite material cylinder structures, which is composed of a mechanical motion mechanism and a laser ultrasonic visualization detection platform. The mechanical motion mechanism includes a flat cart (1), a C-shaped ring bracket (2), and a stepping motor (5). The laser ultrasonic visualization detection platform includes an electrical cabinet (3), a motion control card (4), a laser scanning unit (6), a signal processing unit (7), an ultrasonic signal sensor (8), a computer (9), and a display (10). The composite material cylinder structure (11) to be detected is placed at a roughly central position of the C-shaped ring bracket (2), with the cylinder wall facing the C-shaped ring bracket (2) for easy detection. The detection does not require a liquid coupling agent, thereby eliminating the influence on the ultrasonic signal caused by the use of a liquid coupling medium in traditional ultrasonic detection, the pollution and damage to the structure surface and the environment, and the inconvenience in operation. Different laser scanning speeds can be used for cylinder structures of different sizes, thereby ensuring detection efficiency and greatly shortening detection time.

Description

Technical Field

[0001] The invention belongs to the technical field of nondestructive testing, and in particular relates to a laser ultrasonic visualization testing device and a testing method for a cylinder composite material structure. Background Art

[0002] Carbon fiber composite materials have the characteristics of high specific strength and specific modulus, good fatigue resistance, high damage safety, corrosion resistance and strong designability. They are widely used in petroleum, chemical, automobile, aerospace and military industries. However, during the use of composite materials, they are affected by external conditions and their own material factors, and defects such as delamination, inclusions and impact damage may occur.

[0003] Large composite cylinder structures used in the aviation field are difficult to move due to their huge size and heavy weight, and the surface of the structure is curved, so it is difficult to achieve efficient inspection using traditional inspection equipment. In the field of non-destructive testing, such as robotic arm inspection equipment, defect inspection of large composite cylinder structures has problems such as blind spots, unsatisfactory inspection results, low inspection efficiency, and poor recognition rate of inspection results.

[0004] Laser ultrasonic visualization detection technology combines laser ultrasonic detection technology with visualization technology, uses laser scanning to stimulate ultrasonic signals on the surface of the material being tested, and visualizes the ultrasonic propagation process by visualizing the received signals, thereby realizing visualized detection. Laser ultrasonic technology uses high-energy laser pulses to act instantaneously on the surface of the material being tested. Through the thermal elastic effect of the material, it causes thermal expansion of the material's action site and generates thermal stress, thereby generating ultrasonic waves on the surface and inside the material. Based on the principle of wave field reciprocity, ultrasonic signal sensors are placed on the surface of the material being tested to receive ultrasonic signals propagating on the surface and inside the material. Since the propagation of ultrasonic waves in discontinuous areas of the material structure is very different from that in continuous areas of the material structure, ultrasonic waves will be reflected, scattered, and diffracted when passing through discontinuous areas. Therefore, the difference in the propagation signals received by the ultrasonic signal sensor can be distinguished to achieve the detection of internal defects in the material. Summary of the invention

[0005] In view of the problems of the above-mentioned traditional detection equipment, such as detection blind spots, unsatisfactory detection effects, low detection efficiency and poor recognition rate of detection results, the present invention proposes a laser ultrasonic visualization detection device for composite material cylinder structures, which consists of two parts: a mechanical motion mechanism and a laser ultrasonic visualization detection platform; it is characterized in that the mechanical motion mechanism includes a flatbed cart 1, a C-shaped ring bracket 2, and a stepper motor 5; the laser ultrasonic visualization detection platform includes an electrical cabinet 3, a motion control card 4, a laser scanning unit 6, a signal processing unit 7, an ultrasonic signal sensor 8, a computer 9 and a display 10; the composite material cylinder structure 11 to be detected is placed in the approximate center of the C-shaped ring bracket 2, and the cylinder wall faces the C-shaped ring bracket 2, which is convenient for detection; wherein

[0006] An electrical cabinet 3 is installed on the flatbed cart 1, and a motion control card 4, a signal processing unit 7 and a computer 9 are placed inside the electrical cabinet 3, and the electrical cabinet 3 can supply power to the motion control card 4, the signal processing unit 7 and the computer 9;

[0007] The C-ring bracket 2 is a circular ring with a notch. The cross-section of the C-ring bracket 2 is in the shape of a "mouth", with a hollow interior. On the upper surface of the "mouth-shaped" cross-section, that is, on the left side of the outer surface of the inner ring of the C-ring bracket 2, a circular strip-shaped gap is drilled. The two side surfaces and the lower surface of the "mouth-shaped" cross-section remain intact. A circular rack 2.1 is welded to the right side of the outer surface of the inner ring of the C-ring bracket 2. The circumferential angle of the circular rack 2.1 is the same as the circumferential angle of the C-ring bracket 2; the circumferential angle of the circular strip-shaped gap on the left side of the outer surface of the inner ring of the C-ring bracket 2 is slightly smaller than the circumferential angle of the C-ring bracket 2; An external meshing spur gear 2.2 that mates with the circular rack 2.1 is placed on the C-ring bracket 2. A bearing 2.3 is installed at the base circle center of the external meshing spur gear 2.2; The stepping motor 5 is on the left side of the connecting plate 2.5. The connecting shaft 2.4 is an extension of the rotating shaft of the stepping motor 5 to the right. The connecting shaft 2.4 inserts into the connecting plate 2.5 and continues to extend to the right until it mates with the bearing 2.3. The connection between the connecting shaft 2.4 and the bearing 2.3 is an interference fit. The connecting shaft 2.4 is perpendicular to both the connecting plate 2.5 and the spur gear 2.2. Therefore, the connecting plate 2.5 and the spur gear 2.2 are parallel to each other, enabling the connecting shaft 2.4 to rotate in the connecting plate 2.5 without driving the rotation of the connecting plate 2.5; A hole is drilled near the lower part of the connecting plate 2.5. The common central shaft of the double fixed pulleys 2.6 is inserted into the hole. The double fixed pulleys 2.6 installed on the left and right sides of this central shaft can clamp the connecting plate 2.5 and can achieve the simultaneous and co-directional rotation of the double fixed pulleys 2.6 around the common central shaft; The lower part of the connecting plate 2.5, that is, the part where the double fixed pulleys 2.6 are installed, is placed in the strip-shaped gap of the C-ring bracket 2. The diameter of the double fixed pulleys 2.6 enables them to roll within the "mouth-shaped" cross-section of the strip-shaped gap; To prevent the laser scanning unit 6 from contacting the gear 2.2, the bottom of the fixing plate 2.7 is welded to the fixing block 2.9 through the support column 2.8. The fixing block 2.9 is fixed to the connecting plate 2.5 through the first fixing device, located on the same side and behind the stepping motor 5; Then, the laser scanning unit 6 is fixed to the fixing plate 2.7 through the second fixing device; As described above, the stepping motor 5 drives the rotation of the external meshing spur gear 2.2 through the connecting shaft 2.4. Thus, the external meshing spur gear 2.2 meshes with the circular rack 2.1 on the C-ring bracket 2, and the external meshing spur gear 2.2 moves along the installation direction of the circular rack 2.1. Thereby driving the double fixed pulleys 2.6 located at the lower part of the connecting plate 2.5 to roll along both sides of the strip-shaped gap, thus driving the connecting plate 2.5 to move along this gap in the strip-shaped gap, and further realizing the rotation of the laser scanning unit 6 fixed on the connecting plate 2.5 along this ring on the C-ring bracket 2, and ensuring that the extension line of its light-emitting point is the normal line; By calculating the meshing relationship between the circular rack 2.1 and the external meshing spur gear 2.2, the rotation angle of the stepping motor 5 driving the laser scanning unit 6 can be set; The motion control card 4 is controlled by the computer 9 and is used to control the parameters of the stepping motor 5;

[0008] The entire C-shaped ring bracket 2 is fixedly connected to the support frame 2.11 through a third fixing device; the support frame 2.11 is connected and fixed to the right side of the electrical cabinet 3 by a fixing method such as bolts;

[0009] The motion control card 4 is controlled by the computer 9 and is used to control the parameters of the stepper motor 5;

[0010] The stepper motor 5 drives the laser scanning unit 6 to rotate, and performs laser scanning on the surface of the composite material cylinder structure 11 to be tested;

[0011] The ultrasonic signal sensor 8 is a surface acoustic wave sensor, which is placed on the surface of the composite material cylinder structure 11 to be tested, and is used to receive the ultrasonic signal propagating inside the material and convert it into an electrical signal, and then transmit it to the signal processing unit 7, wherein the ultrasonic signal propagating inside the material is generated by the continuous fluctuation of the material molecules caused by the thermal elastic effect induced by the laser scanning unit 6;

[0012] The signal processing unit 7 performs amplification processing and analog / digital conversion on the input ultrasonic electrical signal, and outputs the processing result to the computer 9;

[0013] The display 10 is used to display the visualization results processed by the computer 9 .

[0014] In one embodiment of the present invention, the circumferential angle of the C-ring bracket 2 is 100-300°. In order to ensure the structural strength of the C-ring bracket 2, the outer surface of the inner ring of the C-ring bracket 2 will not be penetrated by the annular strip gap. The circumferential angle of the annular strip gap is slightly smaller than the circumferential angle of the C-ring bracket 2, which is 80-280°, that is, the circumferential angle of the strip gap is reduced by 20° on the circumferential angle of the C-ring bracket 2, and the reduced 20° is evenly distributed on both sides of the outer surface of the inner ring of the C-ring bracket 2, that is, the distance from the upper end of the strip gap to the upper end of the inner ring of the C-ring bracket 2 is 10°×the radius of the inner ring, and the distance from the lower end of the strip gap to the lower end of the inner ring of the C-ring bracket 2 is also 10°×the radius of the inner ring.

[0015] In a specific embodiment of the present invention, the circumferential angle of the C-shaped ring bracket 2 is 200°, and the circumferential angle of the annular strip gap is 180°.

[0016] In another specific embodiment of the present invention, the laser scanning unit 6 includes a pulsed laser and an electric scanning galvanometer, wherein the pulsed laser is a Q-switched and mode-locked neodymium-doped lithium yttrium fluoride ND:YLF laser, which generates laser pulses with a wavelength of 1053nm and a pulse width of 30ns; the electric scanning galvanometer is composed of an X-axis galvanometer and a Y-axis galvanometer as well as an X-axis motor and a Y-axis motor, and its function is to control the deflection of the laser beam in the XY plane to realize laser scanning of the surface of the material to be detected, thereby stimulating ultrasonic waves.

[0017] In another embodiment of the present invention, the computer 9 performs three functions: laser scanning parameter control, setting the size S of the laser scanning area; visualizing the received data; and controlling the motion parameters of the stepper motor 5 through the motion control card 4, that is, the rotation angle of the laser scanning unit 6 along the C-shaped ring bracket 2.

[0018] In another embodiment of the present invention, the composite cylinder structure 11 is a carbon fiber laminate structure with a length of l, a bottom circular diameter of d, and a thickness of t. The carbon fiber laminate structure is placed flat with the axis parallel to the ground, and the cylinder can be rotated around the axis manually.

[0019] A laser ultrasonic visualization detection method suitable for composite material cylinder structures is also provided, comprising the following steps:

[0020] Step (1) The area of ​​the composite material cylinder structure 11 to be inspected is divided into blocks and the scanning point of the laser scanning unit 6 is determined; since the surface area of ​​the entire composite material cylinder structure 11 is too large, it is necessary to divide the surface area into blocks, and the cylinder surface is divided into equal-area areas according to the surface area A of the cylinder structure 11 to be inspected and the scanning area size S of the laser scanning unit 6, and the number of blocks N = [A / S] | 1; the entire cylinder structure 11 is unfolded along the axis of the outer surface and divided into N equal areas, the center point of each area is the initial corresponding point of the laser scanning unit 6, and the line connecting the light outlet of the laser scanning unit 6 and the point is the normal line of the point on the cylinder surface; since the rotation angle range of the laser scanning unit 6 on the C-shaped ring bracket 2 is 0° to 180°, the laser scanning unit 6 must complete a round trip motion for the entire 360° cylinder surface;

[0021] The surface of the composite material cylinder structure 11 is divided into two semicircles in the vertical direction, one is the first semicircle to be tested in the first step, facing the C-shaped ring bracket 2, and the other is the second semicircle to be tested after the first semicircle is tested, facing the C-shaped ring bracket 2; each semicircle is divided into N / 2 blocks, each semicircle has 3 rows and j columns, a total of N / 2 blocks, so N / 2 can be divided by 3; for the first semicircle, if the semicircle is unfolded in a plane, the block in the lower right corner is the block area 1, and the block immediately above it is the block area 2, and so on, the block in the lower left corner is the block area N / 2; for the second semicircle, when the second semicircle is rotated 180° on the spot to replace the position of the first semicircle and completely overlap with the position of the first semicircle, the block situation is the same;

[0022] Step (2) The operator first manually moves the entire detection equipment so that the flatbed cart 1 is located at position ①, which is the column position of the block area 1 of the first semicircle; the C-shaped ring bracket 2 is located in the initial detection area of ​​the cylinder surface, that is, the area facing the column position of the block area 1 of the first semicircle. In order to ensure that the C-shaped ring bracket 2 of the detection equipment is concentric with the circular side surface of the cylinder in the same plane, the distance from the equipment to the cylinder to be detected is manually measured, that is, the distance from two points on the surface of the flatbed cart 1 close to the cylinder to the cylinder is measured, and the equipment is manually adjusted so that it is parallel to the axis of the cylinder. Then, the distances at 0°, 90° and 180° on the C-shaped ring bracket 2 and the cylinder structure 11 to be detected are manually measured, and the position of the flatbed cart 1 is manually adjusted so that the distances from the positions corresponding to the three angles on the C-shaped ring bracket 2 to the cylinder to be detected are roughly equal. At this time, the laser scanning unit 6 is located at the 20° position of the C-shaped ring bracket;

[0023] Step (3) manually stick the three ultrasonic signal sensors to the upper left corners of the block areas 1, 2, and 3, start the computer 9, input a rotation angle of 30° so that the motor on the C-shaped ring bracket 2 drives the laser scanning unit 6 to rotate to the 30° position on the C-shaped ring bracket 2, and then the laser scanning unit 6 starts to perform laser scanning on the block area 1 on the surface of the cylinder to be inspected. After the scanning of the block area 1 is completed, the laser scanning unit 6 is driven by the motor to rotate 60° along the C-shaped ring bracket 2 to the 90° position, and after it is in place, it starts the laser scanning of the block area 2 in the longitudinal direction; when the scanning of the block area 1 is completed, the laser scanning unit 6 rotates ... then starts the laser scanning of the block area 2 in the longitudinal direction; when the scanning of the block area 1 is completed, the laser scanning unit 6 rotates 60° along the C-shaped ring bracket 2 to the 90° position, and then starts the laser scanning of the block area 2 in the longitudinal direction; when the scanning of the block area 1 is completed, the laser scanning unit 6 rotates 60° along the C-shaped ring bracket 2 to the 90° position, and then starts the laser scanning of the block area 2 in the longitudinal direction; when the scanning of the block area 1 is completed, the laser scanning unit 6 rotates 60° along Figure 6 After the detection of the longitudinal 0° to 180° area shown in the figure, the laser scanning unit 6 moves from the 30° position of the C-shaped ring bracket 2 to the 90° position and then to the 150° position, completing the detection of the block areas 1, 2, and 3 respectively. The operator manually pushes the flatbed cart 1 along the scanning path direction, and the moving distance is the length of a scanning block, and reaches the second column of block areas. At this time, the scanning unit is still at the 150° position of the C-shaped ring. When detecting the block areas 4, 5, and 6, the rotation direction is opposite to that when detecting the block areas 1, 2, and 3, and it rotates from 150° to 90° and then to 150°. To 30°, the rotation angle remains unchanged, and then the sensors placed in block areas 1, 2, and 3 are removed and re-pasted at the corresponding positions of block areas 4, 5, and 6 to complete the detection of block areas 4, 5, and 6; then, the flatbed cart 1 moves along the scanning path direction by the length of a block, and then the sensor is removed and re-pasted to detect block areas 7, 8, and 9. The detection direction is the same as that of block areas 1, 2, and 3; repeat the operation until the entire left side surface of the cylinder is detected for 180°; after completion, the laser scanning unit 6 is located at the 150° position of the C-shaped ring, and the flatbed cart 1 is located at Figure 6 Middle position⑤, i.e. the middle position of the last column to be detected;

[0024] After completing the scanning of half of the cylinder area in step (4), in order to complete the scanning of the other half area, the operator manually rotates the cylinder 180° on the spot to achieve the swap of the original left and right surfaces of the cylinder, and then re-pastes the ultrasonic signal sensor to the first three block areas on the current side, and then starts the detection equipment. The detection process is similar to step (3);

[0025] After the detection of step (5) is completed, the flatbed cart 1 is located at position ①, that is, the middle position of the first column to be detected, and the laser scanning unit 6 rotates to the 210° position of the C-shaped ring bracket to prepare for the next detection; during the entire detection process, after the laser scanning unit 6 completes the detection of any block area, the ultrasonic signal sensor placed in the block area will first transmit the received signal to the signal processing unit 7 for ultrasonic signal amplification and A / D conversion, and the converted data will be input into the computer 9 for visualization processing; after the entire detection process is completed, the module will combine the data output from each visualization processing in the order of detection time, and finally form a rectangular visualization detection image of the entire cylinder surface;

[0026] Step (6), after the visual detection image processing is completed, the computer 9 inputs the overall image into the display 10, and the operator determines the defect status of the cylinder structure 11 based on the image in the display 10, that is, the position where the ultrasonic waveform propagation is abnormal in the image is the position where the defect exists, thereby completing the defect detection of the cylinder structure 11.

[0027] In a specific embodiment of the present invention, N=30.

[0028] The equipment and method of the present invention can realize comprehensive and efficient defect detection of large-scale cylinder composite material structures, and the detection results are visualized, and there is no need for professionals to analyze the detection results, which is easy to promote and use.

[0029] Compared with the existing technical means for non-destructive testing of large cylinder composite materials, it has the following advantages:

[0030] It fills the gap of the current lack of system equipment for defect detection of large-scale cylinder composite material structures and provides a feasible solution;

[0031] The detection does not require liquid coupling agent, which eliminates the influence of the use of liquid coupling medium on the ultrasonic signal, the pollution and damage to the structure surface and environment, and the inconvenience in operation caused by the use of liquid coupling medium in traditional ultrasonic detection;

[0032] Different laser scanning speeds can be used for cylinder structures of different sizes, thereby ensuring detection efficiency and greatly shortening detection time;

[0033] Visual inspection results do not require professional judgment. Ordinary personnel can also identify defects through intuitive visual images without the need for additional professional training. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A structural diagram of an example of the present invention;

[0035] Figure 2 This is a structural diagram of the laser ultrasonic visualization detection equipment for composite material cylinder structure of the present invention;

[0036] Figure 3 A schematic diagram of a flatbed cart according to an example of the present invention;

[0037] Figure 4 The structure diagram of the C-shaped ring bracket of the present invention is shown in FIG. Figure 4 Two partial views are shown in the right box;

[0038] Figure 5 A partial view of a C-shaped ring bracket of an example of the present invention (the remaining components are removed to clearly show the "mouth" cross section and the strip-shaped gap);

[0039] Figure 6 It is a schematic diagram of the surface area division and system detection path of the composite material cylinder structure of the example of the present invention;

[0040] Figure 7 This is the corresponding diagram of the scanning angle between the composite cylinder structure and the laser scanning unit on the C-shaped ring bracket;

[0041] Figure 8 This is a schematic diagram of the location of the ultrasonic signal sensor on the composite cylinder structure;

[0042] Fig. 9 This is a picture of some physical samples of composite material cylinder structure;

[0043] Fig.10 This is a diagram of the laser ultrasonic visualization inspection results of some physical samples of composite material cylinder structures. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0045] like Figure 1 , Figure 2As shown, a front view of a laser ultrasonic visualization detection device for a cylinder composite material structure is composed of a mechanical motion mechanism and a laser ultrasonic visualization detection platform. The mechanical motion mechanism includes a flatbed cart 1, a C-shaped ring bracket 2, and a stepper motor 5. The laser ultrasonic visualization detection platform includes an electrical cabinet 3, a motion control card 4, a laser scanning unit 6, a signal processing unit 7, an ultrasonic signal sensor 8, a computer 9, and a display 10, wherein the motion control card 4, the signal processing unit 7, and the computer 9 are placed in the electrical cabinet 3. The composite cylinder structure 11 to be detected is placed in the approximate center of the C-shaped ring bracket 2, and the cylinder wall faces the C-shaped ring bracket 2 for easy detection.

[0046] In one embodiment of the present invention, a threaded hole is drilled on the upper surface of the flatbed cart 1, such as Figure 3 As shown, the connection with the electrical cabinet 3 is achieved by bolts, and the electrical cabinet 3 is fixed on the flatbed cart 1; the electrical cabinet 3 is an ordinary electrical cabinet, and a motion control card 4, a signal processing unit 7 and a computer 9 are placed inside, and the electrical cabinet 3 can provide power to the motion control card 4, the signal processing unit 7 and the computer 9.

[0047] like Figure 4 , Figure 5As shown, in an example of the present invention, the circumferential angle of the C-ring bracket 2 is 100 - 300°, preferably 200°. The cross-section of the C-ring bracket 2 is in the shape of a "mouth", with a hollow interior. A ring rack 2.1 (a part of the teeth of an internally meshing spur gear, with an angle consistent with the circumferential angle of the C-ring bracket 2) is welded to the right side of the outer surface of the inner ring, and a ring-shaped strip gap (with an angle of 80 - 280°, preferably 180°) is on the left side. An externally meshing spur gear 2.2 that cooperates with the ring rack 2.1 is placed on the C-ring bracket 2, and a bearing 2.3 is installed at the base circle center of the externally meshing spur gear 2.2. The stepper motor 5 is on the left side of the connecting plate 2.5. The connecting shaft 2.4 is an extension of the rotating shaft of the stepper motor 5 to the right, and the connecting shaft 2.4 is inserted into the connecting plate 2.5 and continues to extend to the right until it cooperates with the bearing 2.3. There is an interference fit between the connecting shaft 2.4 and the bearing 2.3. The connecting shaft 2.4 is perpendicular to both the connecting plate 2.5 and the spur gear 2.2 (the connecting plate 2.5 and the spur gear 2.2 are parallel to each other), enabling the connecting shaft 2.4 to rotate in the connecting plate 2.5 without driving the rotation of the connecting plate 2.5. A hole is drilled near the lower part of the connecting plate 2.5, and the common central axis of the double fixed pulleys 2.6 is inserted into the hole. The double fixed pulleys 2.6 installed on the left and right sides of this central axis can clamp the connecting plate 2.5 and can achieve the simultaneous and co-directional rotation of the double fixed pulleys 2.6 around the common central axis. The connection method of the connecting plate 2.5, the double fixed pulleys 2.6, and the common central axis is well-known to those skilled in the art and will not be elaborated here. The lower part of the connecting plate 2.5 (the part where the double fixed pulleys 2.6 are installed) is placed in the strip gap of the C-ring bracket 2, and the diameter of the double fixed pulleys 2.6 enables them to roll in the "mouth"-shaped cross-section of the strip gap. To prevent the laser scanning unit 6 from contacting the gear 2.2, the bottom of the fixing plate 2.7 is welded to the fixing block 2.9 through support columns 2.8 (shown in the figure as including three support columns), and the fixing block 2.9 is fixed to the connecting plate 2.5 through a fixing device such as a bolt, and from the figure, it is located at the rear on the same side as the stepper motor 5. Then, the laser scanning unit 6 is fixed to the fixing plate 2.7 through a fixing device such as a bolt. As described above, the stepper motor 5 drives the rotation of the externally meshing gear 2.3 through the connecting shaft 2.4, so that the externally meshing gear 2.3 meshes with the rack 2.1 on the C-ring bracket 2, and the externally meshing gear 2.3 moves along the installation direction of the rack 2.1, thereby driving the double fixed pulleys 2.6 located at the lower part of the connecting plate 2.5 to roll along both sides of the strip gap, thus driving the connecting plate 2.5 to move along this gap in the strip gap, and further realizing the rotation of the laser scanning unit 6 fixed on the connecting plate 2.5 along this ring on the C-ring bracket 2, and ensuring that the extension line of its light-emitting point is the normal line. By calculating the meshing relationship between the rack 2.1 and the gear 2.2, the rotation angle of the stepper motor 5 driving the laser scanning unit 6 can be set. The motion control card 4 is controlled by the computer 9 and is used to control the parameters of the stepper motor 5.The entire C-shaped ring bracket 2 is fixedly connected to the support frame 2.11 by a fixing device such as bolts 2.10. The support frame 2.9 is connected and fixed to the right side of the electrical cabinet 3 by a fixing method such as bolts.

[0048] In one example of the present invention, the electrical cabinet 3 is provided with threaded holes corresponding to the positions of the threaded holes on the flatbed cart 1, and the electrical cabinet 3 can be fixed to the flatbed cart 1 by bolt connection. The electrical cabinet 3 is used to place the computer 9 and the signal processing unit 7 inside it, and the display 10 on its side for easy viewing.

[0049] In one embodiment of the present invention, the laser scanning unit 6 includes a pulsed laser and an electric scanning galvanometer, wherein the pulsed laser is a Q-switched and mode-locked neodymium-doped lithium yttrium fluoride (ND:YLF) laser, which generates laser pulses with a wavelength of 1053nm and a pulse width of 30ns. The electric scanning galvanometer is composed of an X-axis galvanometer, a Y-axis galvanometer, an X-axis motor, and a Y-axis motor, and its function is to control the deflection of the laser beam in the XY plane, realize laser scanning of the surface of the material to be detected, and thus stimulate ultrasonic waves.

[0050] In one example of the present invention, the signal processing unit 7 includes an ultra-low noise amplifier and a high sampling rate board. The ultra-low noise amplifier is used to amplify the ultrasonic signal, and then the amplified signal is converted into analog / digital through the high sampling rate board, and the converted data is output to the computer 9.

[0051] In one embodiment of the present invention, the ultrasonic signal sensor 8 is a surface acoustic wave sensor, which is placed on the surface of the material to be detected and is used to receive the ultrasonic signal propagating inside the material and convert it into an electrical signal, which is then transmitted to the signal processing unit 7 .

[0052] In one embodiment of the present invention, the computer 9 mainly performs three functions: laser scanning parameter control, setting the size S of the laser scanning area; visualizing the received data; and controlling the motion parameters of the stepper motor 5 through the motion control card 4, that is, the rotation angle of the laser scanning unit 6 along the C-shaped ring bracket 2. The display 10 is used to display the visualization results processed by the computer 9.

[0053] In one example of the present invention, the composite material cylinder structure 11 to be tested is a carbon fiber laminate structure with a length of l, a bottom circular diameter of d, and a thickness of t. The carbon fiber laminate structure is placed flat (the axis is parallel to the ground), and the cylinder can be rotated manually around the axis.

[0054] The present invention also includes a laser ultrasonic visualization detection method applicable to a composite material cylinder structure, comprising the following steps:

[0055] Step (1) The area of ​​the composite material cylinder structure 11 to be inspected is divided into blocks and the scanning points of the laser scanning unit 6 are determined

[0056] Since the surface area of ​​the entire composite material cylinder structure 11 is too large, it is necessary to divide the surface area into blocks. According to the surface area A of the cylinder structure 11 to be detected and the scanning area size S of the laser scanning unit 6, the cylinder surface is divided into blocks. In one embodiment of the present invention, the surface area of ​​the composite material cylinder structure 11 to be tested is Al×d×π, and the number of blocks obtained is 30. The entire cylinder structure 11 is unfolded along the axis of the outer surface, for example, divided into 30 equal areas, such as Figure 6 As shown, the center point of each area is the initial corresponding point of the laser scanning unit 6, and the line connecting the light outlet of the laser scanning unit 6 and the point is the normal line of the point on the cylinder surface, as shown in Figure 7 As shown in FIG. 1 , since the rotation angle range of the laser scanning unit 6 on the C-shaped ring bracket 2 is 0° to 180°, the laser scanning unit 6 must complete one reciprocating motion for the entire 360° surface of the cylinder. Figure 6 The angle in brackets is the angle at which the laser scanning unit 6 is located on the C-shaped ring bracket 2 .

[0057] Step (2) The operator first manually moves the entire detection device so that the flatbed cart 1 is located at Figure 6 At position ① shown in the figure, the C-ring bracket 2 is located in the initial detection area on the surface of the cylinder ( Figure 6 In order to ensure that the C-shaped ring bracket 2 of the detection equipment is concentric with the circular side surface of the cylinder in the same plane, the distance from the equipment to the cylinder to be detected is manually measured, that is, the distance from two points on the surface of the flatbed cart 1 close to the cylinder to the cylinder is measured, and the equipment is manually adjusted to make it parallel to the axis of the cylinder. Then, the distances from the cylinder structure 11 to be detected at the 0°, 90° and 180° positions on the C-shaped ring bracket 2 are manually measured, and the position of the flatbed cart 1 is manually adjusted so that the distances from the positions corresponding to the three angles on the C-shaped ring bracket 2 to the cylinder to be detected are approximately equal, with an accuracy of not less than 1 mm. At this time, the laser scanning unit 6 is located at the 20° position of the C-shaped ring bracket.

[0058] Step (3) Manually paste the three ultrasonic signal sensors on the upper left corners of blocks 1, 2, and 3, as shown in Figure 8 As shown, the computer 9 is started, and a rotation angle of 30° is input so that the motor on the C-shaped ring bracket 2 drives the laser scanning unit 6 to rotate to the 30° position on the C-shaped ring bracket 2, and then the laser scanning unit 6 starts to perform laser scanning on the block area 1 on the surface of the cylinder to be inspected. The subsequent scanning path is as follows Figure 6As shown, after the scanning of the block area 1 is completed, the laser scanning unit 6 is driven by the motor to rotate 60° along the C-shaped ring bracket 2 to reach the 90° position, and then starts the laser scanning of the block area 2 in the longitudinal direction. Figure 6 After the longitudinal 0° to 180° region shown in FIG. 1 is detected (i.e., the laser scanning unit 6 moves from the 30° position of the C-shaped ring bracket 2 to the 90° position and then to the 150° position under the control of the automatic actuator motion control module, respectively completing Figure 6 The operator manually pushes the flatbed cart 1 along the scanning path direction ( Figure 6 The flatbed cart 1 moves along the scanning path for the length of a block, and the moving distance is the length of a scanning block. At this time, the scanning unit is still at the 150° position of the C-shaped ring. When detecting block areas 4, 5, and 6, its rotation direction is opposite to that when detecting block areas 1, 2, and 3 (from 150° to 90° and then to 30°), and the rotation angle remains unchanged. Then the sensors placed in blocks 1, 2, and 3 are removed and re-pasted at the corresponding positions of block areas 4, 5, and 6 to complete the detection of block areas 4, 5, and 6. After that, the flatbed cart 1 moves along the scanning path for the length of a block, and then removes the sensor and re-pastes it to detect block areas 7, 8, and 9 (the detection direction is the same as that of block areas 1, 2, and 3). Repeat the operation until the detection of the entire left surface of the cylinder at 180° (block areas 1-15) is completed. After completion, the laser scanning unit 6 is located at the 150° position of the C-shaped ring, and the flatbed cart 1 is located at Figure 6 Middle position⑤, that is, the middle position of the last column detected.

[0059] After the scanning of the 180° area on the left side surface of the cylinder is completed in step (4), in order to complete the scanning of the 180° area on the right side surface, in the example, the method adopted is that the operator manually rotates the cylinder 180° while holding the cylinder on the support frame to achieve the swapping of the original left and right surfaces of the cylinder ( Figure 6 Then, stick the ultrasonic signal sensor to the first three sub-blocks on the current side, start the detection device, and press Figure 6 The detection process is the same as step (3) for the route shown in the upper right corner from 180° to 360°.

[0060] After the detection of step (5) is completed, the flatbed cart 1 is located at position ①, that is, the middle position of the first column to be detected, and the laser scanning unit 6 rotates to the 210° position of the C-shaped ring bracket to prepare for the next detection. During the entire detection process, after the laser scanning unit 6 completes the detection of any block area, the ultrasonic signal sensor placed in the block area will first transmit the received signal to the signal processing unit 7 for ultrasonic signal amplification and A / D conversion, and the converted data will be input into the computer 9 for visualization processing. For the workflow of visualization processing, please refer to the master's thesis "Research on Ultrasonic C-scanning Three-dimensional Visual Nondestructive Testing Technology of Aircraft Engine Blades" written by Zhang Luodan of Lanzhou University of Technology in 2019; after the entire detection process is completed, the module will combine the data output by each visualization processing in the order of detection time, and finally form a rectangular visualization detection image of the entire cylinder along the axis (the axis at 180° in the figure).

[0061] Step (6), after the visual detection image processing is completed, the computer 9 inputs the overall image into the display 10, and the operator determines the defect status of the cylinder structure 11 based on the image in the display 10, that is, the position where the ultrasonic waveform propagation is abnormal in the image is the position where the defect exists, thereby completing the defect detection of the cylinder structure 11.

[0062] Fig. 9 This is a picture of some actual samples of composite material cylinder structure. Fig.10 This is the result of laser ultrasonic visualization inspection of some physical samples of composite material cylinder structure. It can be clearly seen from the figure that the circled parts are the defects existing in the sample.

Claims

1. A laser ultrasonic visualization detection device for composite material cylinder structure, which consists of a mechanical motion mechanism and a laser ultrasonic visualization detection platform; it is characterized by: The mechanical motion mechanism comprises a flatbed cart (1), a C-shaped ring bracket (2), and a stepper motor (5); the laser ultrasonic visualization detection platform comprises an electrical cabinet (3), a motion control card (4), a laser scanning unit (6), a signal processing unit (7), an ultrasonic signal sensor (8), a computer (9), and a display (10); the composite material cylinder structure (11) to be detected is placed at a substantially central position of the C-shaped ring bracket (2), with the cylinder wall facing the C-shaped ring bracket (2) for easy detection; wherein An electrical cabinet (3) is mounted on the flatbed cart (1), a motion control card (4), a signal processing unit (7) and a computer (9) are placed inside the electrical cabinet (3), and the electrical cabinet (3) is capable of supplying power to the motion control card (4), the signal processing unit (7) and the computer (9); C-ring bracket (2), which is a circular ring with a notch. The cross-section of the C-ring bracket (2) is in the shape of a "mouth", with a hollow interior. On the upper surface of this "mouth-shaped" cross-section, that is, on the left side of the outer surface of the inner ring of the C-ring bracket (2), an annular strip-shaped gap is drilled. The two side surfaces and the lower surface of the "mouth-shaped" cross-section remain intact. On the right side of the outer surface of the inner ring of the C-ring bracket (2), an annular rack (2.1) is welded. The circumferential angle of the annular rack (2.1) is the same as the circumferential angle of the C-ring bracket (2); the circumferential angle of the annular strip-shaped gap on the left side of the outer surface of the inner ring of the C-ring bracket (2) is slightly smaller than the circumferential angle of the C-ring bracket (2); an external meshing spur gear (2.2) that mates with the annular rack (2.1) is placed on the C-ring bracket (2). At the base circle center of the external meshing spur gear (2.2), a bearing (2.3) is installed; the stepping motor (5) is on the left side of the connecting plate (2.5). The connecting shaft (2.4) is an extension of the rotating shaft of the stepping motor (5) towards the right. And the connecting shaft (2.4) inserts into the connecting plate (2.5) and continues to extend towards the right until it mates with the bearing (2.3). There is an interference fit between the connecting shaft (2.4) and the bearing (2.3). The connecting shaft (2.4) is perpendicular to both the connecting plate (2.5) and the spur gear (2.2). Therefore, the connecting plate (2.5) and the spur gear (2.2) are parallel to each other, enabling the connecting shaft (2.4) to rotate in the connecting plate (2.5) without driving the rotation of the connecting plate (2.5); a hole is drilled near the lower part of the connecting plate (2.5). The common central shaft of the double fixed pulleys (2.6) is inserted into the hole. The double fixed pulleys (2.6) installed on the left and right sides of this central shaft can clamp the connecting plate (2.5) and can achieve the simultaneous and co-directional rotation of the double fixed pulleys (2.6) around the common central shaft; the lower part of the connecting plate (2.5), that is, the part where the double fixed pulleys (2.6) are installed, is placed in the strip-shaped gap of the C-ring bracket (2). The diameter of the double fixed pulleys (2.6) is such that it can roll within the "mouth-shaped" cross-section of the strip-shaped gap; to prevent the laser scanning unit (6) from contacting the spur gear (2.2), the bottom of the fixing plate (2.7) is welded to the fixing block (2.9) through the support column (2.8). The fixing block (2.9) is fixed on the connecting plate (2.5) through the first fixing device, located at the same side and rear of the stepping motor (5); then the laser scanning unit (6) is fixed on the fixing plate (2.7) through the second fixing device; as described above, the stepping motor (5) drives the rotation of the external meshing spur gear (2.2) through the connecting shaft (2.4). Thus, the external meshing spur gear (2.2) meshes with the annular rack (2.1) on the C-ring bracket (2). The external meshing spur gear (2.2) moves along the installation direction of the annular rack (2.1). Thereby driving the double fixed pulleys (2.6) located at the lower part of the connecting plate (2.5) to roll along both sides of the strip-shaped gap, thus driving the connecting plate (2.5) to move along this gap in the strip-shaped gap, and further realizing the fixation on the connecting plate (2.The laser scanning unit (6) on the C-shaped ring bracket (2) rotates along the ring, and ensures that the extension line of its light-emitting point is the normal line; by calculating the meshing relationship between the annular rack (2.1) and the external meshing spur gear (2.2), the rotation angle of the laser scanning unit (6) driven by the stepping motor (5) can be set; the motion control card (4) is controlled by the computer (9) and is used to control the parameters of the stepping motor (5);. The entire C-shaped ring bracket (2) is fixedly connected to the support frame (2.11) via a third fixing device; the support frame (2.11) is connected and fixed to the right side of the electrical cabinet (3) via a fixing method such as bolts; The motion control card (4) is controlled by a computer (9) and is used to control the parameters of the stepping motor (5); The stepping motor (5) drives the laser scanning unit (6) to rotate, and performs laser scanning on the surface of the composite material cylinder structure (11) to be tested; The ultrasonic signal sensor (8) is a surface acoustic wave sensor, which is placed on the surface of the composite material cylinder structure (11) to be tested, and is used to receive the ultrasonic signal propagating inside the material and convert it into an electrical signal, and then transmit it to the signal processing unit (7), wherein the ultrasonic signal propagating inside the material is generated by the thermal elastic effect caused by the material being scanned by the laser scanning unit (6) and causing continuous fluctuations of the material molecules; The signal processing unit (7) performs amplification processing and analog / digital conversion on the input ultrasonic electrical signal, and outputs the processing result to the computer (9); The display (10) is used to display the visualization results processed by the computer (9).

2. The laser ultrasonic visualization detection device according to claim 1, characterized in that: The circumferential angle of the C-shaped ring bracket (2) is 100-300°. In order to ensure the structural strength of the C-shaped ring bracket (2), the outer surface of the inner ring of the C-shaped ring bracket (2) will not be penetrated by the annular strip gap. The circumferential angle of the annular strip gap is slightly smaller than the circumferential angle of the C-shaped ring bracket (2), which is 80-280°. That is, the circumferential angle of the strip gap is reduced by 20° on the circumferential angle of the C-shaped ring bracket (2), and the reduced 20° is evenly distributed on both sides of the outer surface of the inner ring of the C-shaped ring bracket (2), that is, the distance from the upper end of the strip gap to the upper end of the inner ring of the C-shaped ring bracket (2) is 10°×the radius of the inner ring, and the distance from the lower end of the strip gap to the lower end of the inner ring of the C-shaped ring bracket (2) is also 10°×the radius of the inner ring.

3. The laser ultrasonic visualization detection device according to claim 2, characterized in that: The circumferential angle of the C-shaped ring bracket (2) is 200°, and the circumferential angle of the annular strip gap is 180°.

4. The laser ultrasonic visualization detection device according to claim 1, characterized in that: The laser scanning unit (6) includes a pulsed laser and an electric scanning galvanometer, wherein the pulsed laser is a Q-switched and mode-locked neodymium-doped lithium yttrium fluoride (ND:YLF) laser, which generates laser pulses with a wavelength of 1053nm and a pulse width of 30ns; the electric scanning galvanometer is composed of an X-axis galvanometer, a Y-axis galvanometer, an X-axis motor and a Y-axis motor, and its function is to control the deflection of the laser beam in the XY plane to achieve laser scanning of the surface of the material to be detected, thereby stimulating ultrasonic waves.

5. The laser ultrasonic visualization detection device according to claim 1, characterized in that: The computer (9) performs three functions: controlling the laser scanning parameters, setting the size S of the laser scanning area; performing visualization processing on the received data; and controlling the motion parameters of the stepper motor (5) through the motion control card (4), that is, the rotation angle of the laser scanning unit (6) along the C-shaped ring bracket (2).

6. The laser ultrasonic visualization detection device according to claim 1, characterized in that: The composite cylinder structure (11) is a carbon fiber laminate structure with a length of l, a bottom circular diameter of d, and a thickness of t. The carbon fiber laminate structure is placed flat with its axis parallel to the ground, and the cylinder can be rotated around the axis manually.

7. A laser ultrasonic visualization detection method suitable for composite material cylinder structure, comprising the following steps: Step (1) The area of ​​the composite material cylinder structure (11) to be inspected is divided into blocks and the scanning points of the laser scanning unit (6) are determined; since the surface area of ​​the entire composite material cylinder structure (11) is too large, it is necessary to divide the surface area into blocks, and according to the surface area A of the composite material cylinder structure (11) to be inspected and the scanning area size S of the laser scanning unit (6), the cylinder surface is divided into blocks of equal area, and the number of blocks is The entire composite material cylinder structure (11) is unfolded along the axis of the outer surface and divided into N equal areas, the center point of each area is the initial corresponding point of the laser scanning unit (6), and the line connecting the light outlet of the laser scanning unit (6) and the point is the normal line of the point on the cylinder surface; since the rotation angle range of the laser scanning unit (6) on the C-shaped ring bracket (2) is 0° to 180°, the laser scanning unit (6) must complete a reciprocating motion for the entire 360° cylinder surface; The surface of the composite material cylinder structure (11) is divided into two semicircles in the vertical direction, one of which is the first semicircle to be inspected in the first step and faces the C-shaped ring bracket (2), and the other is the second semicircle to be inspected after the first semicircle is inspected and faces away from the C-shaped ring bracket (2); each semicircle is divided into N / 2 blocks, each semicircle has 3 rows and j columns, and a total of N / 2 blocks, so N / 2 can be divided by 3; For the first semicircle, if the semicircle is unfolded in a plane, the block at the lower right corner is the first block area, the block immediately above it is the second block area, and so on, the block at the lower left corner is the N / 2th block area; for the second semicircle, when the second semicircle is rotated 180° on the spot to replace the position of the first semicircle and completely overlap with the position of the first semicircle, the block situation is the same; Step (2) The operator first manually moves the entire detection device so that the flatbed cart (1) is located at position ①, which is the column position where the first block area of ​​the first semicircle is located; the C-shaped ring bracket (2) is located at the detection initial area on the surface of the cylinder, that is, the area facing the column position where the first block area of ​​the first semicircle is located. In order to ensure that the C-shaped ring bracket (2) of the detection device is concentric with the circular side surface of the cylinder in the same plane, the distance from the device to the cylinder to be detected is manually measured, that is, the distance from two points on the surface of the flatbed cart (1) close to the cylinder to the cylinder is measured, and the device is manually adjusted so that it is parallel to the axis of the cylinder. Then, the distances at 0°, 90° and 180° on the C-shaped ring bracket (2) and the detected composite material cylinder structure (11) are manually measured, and the position of the flatbed cart (1) is manually adjusted so that the distances from the positions corresponding to the three angles on the C-shaped ring bracket (2) to the detected cylinder are approximately equal. At this time, the laser scanning unit (6) is located at the 0° position of the C-shaped ring bracket (2); Step (3) manually affixes three ultrasonic signal sensors to the upper left corners of the first, second and third sub-block areas, starts the computer (9), inputs a rotation angle of 30° so that the motor on the C-shaped ring bracket (2) drives the laser scanning unit (6) to rotate to the 30° position on the C-shaped ring bracket (2), and then the laser scanning unit (6) starts to perform laser scanning on the first sub-block area of ​​the surface of the cylinder to be detected. After completing the scanning of the first sub-block area, the laser scanning unit (6) is driven by the motor to rotate 60° along the C-shaped ring bracket (2) to reach the 90° position, and after reaching the position, it starts to perform laser scanning on the second sub-block area in the longitudinal direction; after completing the detection of the longitudinal 0° to 180° area, that is, the laser scanning unit (6) moves from the 30° position of the C-shaped ring bracket (2) to the 90° position, and then to the 150° position, and completes the detection of the first, second and third sub-block areas respectively, and the operator manually pushes the flatbed cart (1) to move along the scanning path direction, and moves The moving distance is the length of a scanning block, and it reaches the second column block area. At this time, the scanning unit is still at the 150° position of the C-shaped ring. When detecting the fourth, fifth and sixth block areas, its rotation direction is opposite to that of the first, second and third detection block areas, from 150° to 90° and then to 30°, and the rotation angle remains unchanged. Then the sensors placed in the first, second and third block areas are removed and re-pasted at the corresponding positions of the fourth, fifth and sixth block areas to complete the detection of the fourth, fifth and sixth block areas; then, the flatbed cart (1) moves along the scanning path direction by the length of a block, and then the sensors are removed and re-pasted to detect the seventh, eighth and ninth block areas. The detection direction is the same as that of the first, second and third block areas; the operation is repeated until the detection of the entire left side surface of the cylinder is completed at 180°; after completion, the laser scanning unit (6) is located at the 150° position of the C-shaped ring, and the flatbed cart (1) is located in the middle position of the last column to be detected; After completing the scanning of half of the cylinder area in step (4), in order to complete the scanning of the other half area, the operator manually rotates the cylinder 180° on the spot to achieve the swap of the original left and right surfaces of the cylinder, and then re-pastes the ultrasonic signal sensor to the first three block areas on the current side, and then starts the detection equipment. The detection process is similar to step (3); After the detection in step (5) is completed, the flatbed cart (1) is located at position ①, i.e., the middle position of the first row to be detected, and the laser scanning unit (6) rotates to the 10° position of the C-shaped ring bracket (2) to prepare for the next detection; During the entire detection process, after the laser scanning unit (6) completes the detection of any block area, the ultrasonic signal sensor placed in the block area first transmits the received signal to the signal processing unit (7) for ultrasonic signal amplification and A / D conversion, and the converted data is then input into the computer (9) for visualization processing; after the entire detection process is completed, the module combines the data output from each visualization processing in the order of detection time, and finally forms a rectangular visualization detection image of the entire cylinder surface; After the visual inspection image processing in step (6) is completed, the computer (9) inputs the entire image into the display (10), and the operator determines the defect status of the composite material cylinder structure (11) based on the image in the display (10), that is, the position where the ultrasonic waveform propagation is abnormal in the image is the position where the defect exists, thereby completing the defect detection of the composite material cylinder structure (11).

8. The laser ultrasonic visualization detection method according to claim 7, characterized in that: N＝30。

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