Focused ultrasonic excitation polymer flat plate infrared detection device and method

Abstract

The invention relates to the technical field of ultrasonic detection, in particular to a focused ultrasonic excitation polymer flat plate infrared detection device and method. A focused ultrasound heat effect is applied to internal defect detection of a polymer material, a focused ultrasound transducer takes a continuous sinusoidal signal as an excitation source, a motion controller controls a walking mechanism to move the focused ultrasound transducer and an infrared camera to perform bow-shaped scanning detection on the surface of a workpiece, and the infrared camera acquires a thermal image of each point on the surface of the workpiece; according to the method, the internal defect detection of the polymer flat plate can be realized, and the detection efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of ultrasonic nondestructive testing and infrared image processing, and in particular to a polymer flat plate infrared detection device and method excited by focused ultrasound. Background Art

[0002] Polymer materials have gradually become indispensable materials in aerospace, automobile manufacturing, and medical device manufacturing due to their excellent performance, wide range of uses, abundant raw material reserves, and easy processing. However, during the molding and service process, polymer materials may have defects such as bubbles, voids, cracks, and delamination, which reduce the overall performance of polymer products. Therefore, accurate and efficient detection of internal defects in polymer materials is of great engineering significance.

[0003] Ultrasonic testing has the characteristics of high sensitivity and wide application range, and has become a widely used non-destructive testing technology. The probe area used in conventional ultrasonic testing is very small, and can only be detected in a small range each time. Ultrasonic testing is very sensitive to deep buried defects, but the ultrasonic signal of near-surface defects is affected by noise and scattering and becomes extremely complex, making it difficult to effectively detect near-surface defects. Ultrasonic infrared detection technology is an emerging detection technology in recent years. The excitation device is close to the test piece, and high-power excitation is injected to generate frictional heat, plastic deformation, and viscoelastic heat near the defect. This technology can detect tiny cracks in most materials, but its inherent limitations are also obvious. For example, high-power excitation will aggravate crack propagation and the repeatability of the test results is poor. When high-frequency, low-power focused ultrasound is coupled into the polymer material through the water layer, the viscoelasticity of the material causes ultrasonic attenuation to generate heat inside the material, causing the temperature of the focus area to rise. Since the viscoelasticity of the material inside the defect is different from that of the non-defect area, there is a difference in thermal effect. The infrared temperature image of the material surface is obtained, and then the analysis and processing based on the infrared thermal image can realize the identification of defects. It is a new idea and method to use the focused ultrasonic thermal effect for defect detection.

[0004] Defect recognition in infrared images is of great significance as a prerequisite and core step for quantitative defect assessment. However, infrared thermal images have uneven backgrounds and a lot of noise, which makes the defect target information vague. In addition, manual inspection of a large number of infrared thermal images is inefficient. Therefore, it is necessary to use effective thermal image data processing methods to improve the results of defect analysis. Summary of the invention

[0005] In view of the above problems existing in the prior art, the purpose of the present invention is to provide a polymer flat-panel infrared detection device and method with focused ultrasound excitation to solve the problems of low detection efficiency and the like existing in the prior art.

[0006] The invention discloses a focused ultrasonically excited polymer flat-plate infrared detection device and method, the detection device comprising a signal generating system, a focused ultrasonic transducer, a water spraying device, two walking mechanisms, an infrared camera, a computer, a fixed bracket, a motion controller, and a workpiece to be detected;

[0007] The motion controller is connected to the computer through a motion control line, and the computer sends a pulse signal to control the movement of the walking mechanism and feedback the position information; the two walking mechanisms are orthogonally combined by two sections of modules, the focused ultrasonic transducer and the water spray device are fixed at the terminal of the walking mechanism on one side, and the infrared camera is fixed at the terminal of the walking mechanism on the other side, which is used to collect infrared images; the signal generation system includes a signal generator and a power amplifier, the output end of the signal generator is connected to the input end of the power amplifier, and the output end of the power amplifier is connected to the focused ultrasonic transducer; the focused ultrasonic transducer is installed at the center of the water spray device, and when the focused ultrasonic transducer generates sound waves, the water spray device sprays water to couple ultrasonic waves into the inside of the test piece; the workpiece to be tested is placed on a fixed bracket, and is placed in the middle position between the focused ultrasonic transducer and the walking mechanism; the signal input end of the computer is connected to the output end of the infrared camera, and the infrared image collected by the infrared camera is processed to determine whether there are defects;

[0008] A focused ultrasound-stimulated polymer flat panel infrared detection method, the detection method mainly comprises the following steps:

[0009] Step 1: Place the test piece to be inspected on a fixed bracket, set the computer to send a pulse signal to control the walking mechanism to move the focused ultrasonic transducer and the infrared camera to the initial position of the workpiece to be inspected, and start the water spray device;

[0010] Step 2: Setting a signal generator to generate a sinusoidal continuous electrical signal, amplifying it through a power amplifier and then loading it to a focused ultrasonic transducer to emit a focused sound wave;

[0011] Step 3: The computer sends a pulse signal to control the module movement of the walking mechanism on both sides. The focused ultrasonic transducer and the infrared camera scan in the horizontal direction (X axis) at the same time. The focused ultrasonic transducer emits sound waves to generate a focused sound field in the workpiece, and the sound energy is converted into heat energy. The infrared camera collects infrared images and transmits them to the computer;

[0012] Step 4: After completing the scan in the horizontal direction (X axis), step a certain distance along the vertical direction (Y axis), and then scan in the opposite direction along the X axis, repeating steps 3 and 4 to achieve the "bow"-shaped scanning detection in the XY plane. The computer processes the acquired infrared image to determine whether the image is abnormal, and then determines whether there are defects inside the workpiece, and records the relative position;

[0013] The basic principle of the present invention is that due to the significant viscoelasticity of polymer materials, the sound waves emitted by the focused ultrasonic transducer will be damped and absorbed when propagating inside the specimen, resulting in the conversion of sound energy into heat energy, which in turn causes the temperature of the focus area inside the specimen to rise. However, the viscoelasticity of the material at the defective part and the non-defective part inside the material is different, resulting in differences in the thermal effect generated inside the specimen, and low-temperature depression will occur at the defective part. The infrared image data of the surface of the specimen is obtained by using an infrared camera, and the existence of defects is judged by an infrared image processing algorithm and defect feature extraction is performed. Based on this principle, the walking mechanism drives the focused ultrasonic transducer and the infrared camera to scan and detect the polymer flat plate.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. A focused ultrasound-stimulated polymer flat-panel infrared detection device and method, which uses high-frequency, low-power focused ultrasound to act on polymer materials to produce a thermal effect. The different viscoelasticity between defects and non-defects leads to differences in thermal effects. The heat difference is reflected on the surface of the specimen. An infrared camera collects infrared images and determines whether defects exist. This principle is used for detection. This method can effectively detect near-surface defects with a size less than half a wavelength.

[0016] 2. This method uses low-power ultrasonic excitation, and the excitation device has no contact with the workpiece to be inspected, avoiding the expansion of internal defects of the workpiece caused by high power.

[0017] 3. This method uses a walking mechanism to drive a focused ultrasonic transducer and an infrared camera for scanning and detection. Compared with the traditional manual inspection infrared image method, it expands the detection range and improves the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the detection device.

[0019] Figure 2 This is the flow chart of infrared image defect identification.

[0020] Figure 3 Schematic diagram of the geometric relationship between convexity defect and convex hull edge. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings:

[0022] Specific implementation method 1. Combination Figure 1 To illustrate this embodiment, a polymer flat-panel infrared detection device with focused ultrasound excitation described in this embodiment includes a signal generator 1, a power amplifier 2, a water spray device 3, a focused ultrasound transducer 4, two walking mechanisms 5, a workpiece to be detected 6, an infrared camera 7, a fixed bracket 8, a computer 9, and a motion controller 10.

[0023] The motion controller is connected to the computer via a motion control line, and the computer sends a pulse signal to control the movement of the walking mechanism and feed back position information;

[0024] The two walking mechanisms are both orthogonally combined by two sections of modules, the focused ultrasonic transducer and the water spray device are fixed at the Y-axis terminal of the walking mechanism on one side, and the infrared camera is fixed at the Y-axis terminal of the walking mechanism on the other side for collecting infrared images;

[0025] The output end of the signal generator is connected to the input end of the power amplifier, and the output end of the power amplifier is connected to the focused ultrasonic transducer;

[0026] The focused ultrasonic transducer is installed at the center of the water spray device. When the focused ultrasonic transducer emits sound waves, the water spray device sprays water to couple the ultrasonic waves to the inside of the workpiece to be inspected for propagation.

[0027] The workpiece to be inspected is placed on a fixed bracket, located between the focused ultrasonic transducer and the walking mechanism;

[0028] The signal input end of the computer is connected to the output end of the infrared camera through an Ethernet cable, and the infrared image collected by the infrared camera is processed to determine whether there is a defect;

[0029] Specific implementation method 2: Combination Figure 2 , Figure 3 This embodiment describes a focused ultrasound-stimulated polymer flat-panel infrared detection device and method, and the specific steps of the detection method are as follows:

[0030] Step 1: Place the workpiece to be tested on a fixed frame, and the computer sends a pulse signal to control the walking mechanism to move the focused ultrasonic transducer and the infrared camera to the specified origin position of the workpiece to be tested, and start the water spray device;

[0031] Step 2: Setting a signal generator to generate a sinusoidal continuous electrical signal, amplifying the electrical signal through a power amplifier, and loading it into a focused ultrasonic transducer to emit a focused sound wave;

[0032] Step 3: The computer sends a pulse signal to control the module movement of the walking mechanism on both sides. The focused ultrasonic transducer and the infrared camera scan in the horizontal direction (X axis) at the same time. The focused ultrasonic transducer emits sound waves to generate a focused sound field in the workpiece, and the sound energy is converted into heat energy. The infrared camera collects infrared images and transmits them to the computer;

[0033] Step 4: After completing the scan in the horizontal direction (X axis), step a certain distance along the vertical direction (Y axis), and then scan in the opposite direction along the X axis, repeating steps 3 and 4 to achieve the "bow"-shaped scanning detection in the XY plane. The computer processes the acquired infrared image to determine whether the image is abnormal, and then determines whether there are defects inside the workpiece, and records the relative position;

[0034] In some embodiments of the present invention, the aperture of the focused ultrasonic transducer in step 1 is 95 mm, the geometric focal length is 150 mm, and the center frequency is 1.12 MHz;

[0035] In some embodiments of the present invention, in step 2, a signal generator is configured to generate a 1.12 MHz sinusoidal continuous electrical signal;

[0036] In some embodiments of the present invention, the thermal sensitivity of the infrared camera used in step 3 is 50mk, the spatial resolution is 640×480, the frame rate is adjustable within 50Hz, and the acquisition time interval is set to 1s;

[0037] In some embodiments of the present invention, the process of the computer performing infrared image processing in step 4 is as follows: Figure 2 As shown, the specific steps are as follows:

[0038] First, the acquired infrared image is enhanced. If there is a temperature focus area in the enhanced image, the enhanced image is segmented to obtain the edge point set of the focus area. If there is no temperature focus area, the infrared image is re-acquired and then image enhancement and segmentation operations are performed. Secondly, the convex hull algorithm is used to detect the circumscribed edge contour of the edge point set. Finally, the convexity value of each point on the edge of the temperature abnormality area relative to the convex hull is calculated. If the maximum convexity value exceeds the threshold, it is judged to be defective. The walking mechanism feeds back the position information at this time. If the maximum convexity value does not exceed the threshold, it is judged to be free of defects.

[0039] In some embodiments of the present invention, the convexity is represented by the geometric relationship between the convex hull point set and the convex concave point set, such as Figure 3 As shown, a starting point and an end point are selected on the convex hull, and the points on the contour are connected from the starting point to the end point. H(P) represents the set of convex hull points constituting P. Let H(P) = {P1, P2, ..., P n}, the point farthest from the perpendicular line segment of the convex hull segment is the convexity defect point, that is, the point {C1, C2, ..., C n}, L(P1, P2) represents the directed line segment from P1 to P2, and the convexity defect depth represents the vertical distance from C1 to L(P1, P2), which is the convexity value D. The convexity value is defined as:

[0040] D[i]=Distance(C[i],L(P1,P2))

Claims

1. A focused ultrasound-stimulated polymer flat-plate infrared detection device and method, characterized in that: The detection device includes a signal generator, a power amplifier, a water spray device, a focused ultrasonic transducer, two walking mechanisms, a workpiece to be detected, an infrared camera, a fixed bracket, a computer, and a motion controller; The motion controller is connected to a computer, and the computer sends pulse signals to realize motion control of the walking mechanism and feedback position information; The two walking mechanisms are composed of two sections of modules orthogonally combined on the X-axis and Y-axis, one terminal of which is equipped with a focused ultrasonic transducer and a water spray device, vertically facing the workpiece to be inspected, and the other terminal is fixed with an infrared camera for receiving infrared images; The output end of the signal generator is connected to the input end of the power amplifier, and the output end of the power amplifier is connected to the focused ultrasonic transducer. The signal generator generates a sinusoidal continuous electrical signal, which is amplified by the power amplifier and acts on the focused ultrasonic transducer to generate a focused ultrasonic field. The focused ultrasonic transducer is installed at the center of the water spray device, and when working, the water spray device sprays water to couple the ultrasound into the interior of the workpiece; The workpiece to be inspected is placed on a bracket, positioned between the focused ultrasonic transducer and the infrared camera; The computer is connected to the infrared camera to perform infrared image processing; 2. A focused ultrasound-stimulated polymer flat-plate infrared detection device and method, characterized in that: The detection method comprises the following steps: Step 1: Place the workpiece to be inspected on a fixed bracket, and the computer sends a pulse signal to control the walking mechanism to move the focused ultrasonic transducer and the infrared camera to the specified origin position of the workpiece to be inspected and align them, and start the water spray device; Step 2: Setting a signal generator to generate a sinusoidal continuous electrical signal, amplifying the signal through a power amplifier and then loading the signal to a focused ultrasonic transducer; Step 3: The computer controls the modules on both sides to move the focused ultrasonic transducer and the infrared camera to perform horizontal motion (X direction) scanning at the same time. The focused ultrasonic transducer emits sound waves to generate a focused sound field and a thermal field in the workpiece, and the infrared camera collects infrared images. Step 4: After completing the X-direction scan, step a certain distance in the vertical direction (Y direction), and then move in the opposite direction in the X direction, so as to realize the "bow"-shaped scanning detection in the XY plane. The infrared camera transmits the collected image data to the computer, and the computer processes the infrared image to determine whether the infrared image is abnormal, and then determine whether there are defects inside the workpiece, record the relative position and feedback the position information; The specific steps of the computer performing infrared image processing in step 4 are as follows: First, the acquired infrared image is enhanced. If there is a temperature focus area in the enhanced image, the enhanced image is segmented to obtain the edge point set of the focus area. If there is no temperature focus area, the infrared image is re-collected and then image enhancement and segmentation operations are performed. Secondly, the convex hull algorithm is used to detect the circumscribed edge contour of the edge point set. Finally, the convexity value of each point on the edge of the temperature anomaly area relative to the convex hull is calculated. If the maximum convexity value exceeds the threshold, the position information at this time is recorded and fed back, and it is judged as defective, otherwise it is judged as non-defective.

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