A multi-modal defect non-destructive testing device and method for metal rolling bodies

Abstract

The application discloses a kind of multi-modal defect nondestructive testing devices of metal rolling body, including V-type rolling clamp, signal detection and synchronous trigger system, data collector and processing unit, the metal rolling body is set on V-type rolling clamp and with clamp rolling cooperation;Signal detection and synchronous trigger system are connected with first detection light path, second detection light path and third detection light path for detecting metal rolling body, first detection light path and second detection light path are connected with the processing unit respectively, third detection light path is connected with the data collector, data collector is connected with signal detection and synchronous trigger system and processing unit respectively.The application can fuse multi-modal information and realize comprehensive detection of metal rolling body defects, with the characteristics of high detection efficiency, high detection accuracy and strong adaptability.

Description

Technical Field

[0001] This invention pertains to the field of nondestructive testing technology, specifically relating to a nondestructive testing device and method for multimodal defects in metal rolling elements. Background Technology

[0002] Against the backdrop of rapid development in modern industry and science and technology, the field of nondestructive testing (NDT) has been actively exploring various advanced testing technologies to meet increasingly complex testing needs. Most existing NDT technologies use single-mode signals to diagnose defects. However, due to limitations in their technical principles, these technologies can generally only detect certain types of defects in a specific part of the material. For example, magnetic particle testing can only detect surface defects; ultrasonic testing is ineffective for shallow surface defects and is often used to detect internal defects. Furthermore, many testing methods can only acquire one-dimensional signals, often only qualitatively determining the presence and severity of defects, providing limited information and hindering accurate assessment of defect conditions and the development of maintenance strategies. Additionally, traditional NDT techniques typically require a comprehensive scan of the material to obtain defect information, resulting in low testing efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a non-destructive testing device and method for multimodal defects in metal rolling elements. This invention can integrate multimodal information to achieve comprehensive detection of defects in metal rolling elements, and features high detection efficiency, high detection accuracy, and strong adaptability.

[0004] The technical solution of the present invention: A non-destructive testing device for multimodal defects of metal rolling elements, applied to the detection of metal rolling elements; comprising a V-shaped rolling fixture, a signal detection and synchronous triggering system, a data acquisition unit, and a processing unit, wherein the metal rolling element is disposed on the V-shaped rolling fixture and rolls with the fixture; the signal detection and synchronous triggering system is connected to a first detection optical path, a second detection optical path, and a third detection optical path for detecting the metal rolling element, the first and second detection optical paths are respectively connected to the processing unit, the third detection optical path is connected to the data acquisition unit, and the data acquisition unit is connected to both the signal detection and synchronous triggering system and the processing unit;

[0005] The first detection optical path includes a 2.5D stripe light source and a line scan camera disposed above the metal rolling body. The 2.5D stripe light source is used to project regular grating stripes onto the surface of the metal rolling body, and the line scan camera is used to collect optical signals from the surface of the metal rolling body.

[0006] The second detection optical path includes a set of ring light sources arranged opposite to each other on both sides of the end face of the metal rolling body, and an area array camera is provided outside the ring light sources; the ring light sources are used to provide uniform diffuse reflection illumination to the end surface of the metal rolling body, and the area array camera is used to collect optical signals from the end surface of the metal rolling body.

[0007] The third detection optical path includes an infrared pulsed laser and an ultrasonic probe. The output optical path of the infrared pulsed laser is sequentially provided with an optical fiber coupler, an optical fiber, and a laser galvanometer. The infrared pulsed laser is used to generate pulsed lasers to scan the test area of ​​the metal rolling body. The pulsed laser is coupled to the optical fiber through the optical fiber coupler and uniformly irradiated onto the surface of the metal rolling body through the laser galvanometer. The ultrasonic probe is used to collect photoacoustic signals from the shallow surface of the metal rolling body and ultrasonic signals from inside the metal rolling body.

[0008] The aforementioned non-destructive testing device for multimodal defects of metal rolling bodies includes a stripe light source controller connected between the first detection optical path and the signal detection and synchronous triggering system, and the stripe light source controller being connected to a 2.5D stripe light source; the line scan camera being connected to the processing unit; and the line scan camera being at an angle of 30°-45° to the optical axis of the 2.5D stripe light source.

[0009] The aforementioned non-destructive testing device for multimodal defects of metal rolling bodies includes a ring light source controller connected between the second detection optical path and the signal detection and synchronous triggering system, and the ring light source controller is connected to the ring light source; the area array camera is connected to the processing unit.

[0010] The aforementioned non-destructive testing device for multimodal defects of metal rolling bodies includes an infrared laser controller connected between the third detection optical path and the signal detection and synchronous triggering system, and the infrared laser controller being connected to an infrared pulse laser; the ultrasonic probe is connected to a data acquisition unit.

[0011] The aforementioned non-destructive testing method for multimodal defects in rolling metal components specifically includes the following steps:

[0012] Step 1: Based on the first and second detection optical paths, perform optical detection on the surface of the metal rolling element to obtain optical signals of the surface and end surfaces of the metal rolling element, and determine the defects on the surface and end surfaces of the metal rolling element based on the obtained optical signals.

[0013] Step 2: Based on the third detection optical path, perform photoacoustic detection on the shallow surface of the metal rolling element to obtain the photoacoustic signal of the shallow surface of the metal rolling element, and determine the defects in the shallow surface of the metal rolling element based on the obtained photoacoustic signal.

[0014] Step 3: Based on the third detection optical path, perform ultrasonic testing on the inside of the metal rolling element to obtain the ultrasonic signal inside the metal rolling element, and determine the internal defects of the metal rolling element based on the obtained ultrasonic signal.

[0015] Step 4: Based on the surface defects, shallow layer defects, and internal defects of the metal rolling element, perform multimodal signal fusion to obtain fused defect information, and locate the defects based on the fused defect information.

[0016] The aforementioned non-destructive testing method for multimodal defects in metal rolling elements involves acquiring the optical signals reflected from the surface of the metal rolling element cylindrical body using a line-scan camera. The formula for the acquired optical signals is as follows:

[0017] I optical,line =∫ y I(x',y')dy;

[0018] Among them, I optical,line The signal is the optical signal acquired by the line scan camera. x' and y' are the pixel coordinates acquired by the line scan camera, and x and y are the coordinates in the actual physical space of the metal rolling body. I(x',y') is determined by the surface reflectivity R(x,y) and the light source intensity I0, as shown in the following formula:

[0019] I(x',y')=I0R(x,y);

[0020] The process of determining the surface defects of the metal rolling column is through optical signal I. optical,line Determine the surface texture and defect features of the metal rolling element, and obtain the morphological features of protrusions, cracks or scratches on the surface of the metal rolling element column through three-dimensional reconstruction;

[0021] The formula for the three-dimensional reconstruction is as follows:

[0022]

[0023] Where z(x,y) is the surface height distribution, d is the projection grating spacing, and I1, I2, I3 and I4 are the light intensity values ​​after the fringe phase shift.

[0024] The detection method of the aforementioned multimodal defect nondestructive testing device for metal rolling elements, the process of acquiring the optical signal from the end surface of the metal rolling element is as follows:

[0025] The formula for calculating the reflected light intensity I(x,y) from the end surface of a metal rolling element is as follows:

[0026] I(x,y)=I0R(x,y)=I0cos n (θ);

[0027] Where I0 is the light source intensity, x and y are the coordinates of the metal rolling body in the actual physical space, R(x,y) is the reflectivity, θ is the angle between the normal of the end surface of the metal rolling body and the direction of the ring light source, and n is the reflection distribution index.

[0028] Then, the area scan camera records the two-dimensional light intensity distribution of the reflected light intensity from the end surface of the metal rolling element, obtaining the optical signal. The calculation formula is as follows:

[0029] I optica,lring =I (i,j) =∫ Δx ∫ Δy I(x,y)dxdy;

[0030] In the formula, I optical,ring It is the optical signal acquired by the area array camera, where Δx is the spatial resolution, Δy is the sampling interval, and the light intensity corresponding to pixel (i,j) is determined by the reflection characteristics of the end surface of the metal rolling body.

[0031] The process of determining the surface defects at the end of the metal rolling element involves using the discontinuity of light intensity distribution to detect surface pits, scratches, or coating peeling, and analyzing the image gradient information after optical distortion correction to extract subtle defects.

[0032] The detection method of the aforementioned multimodal defect nondestructive testing device for metal rolling elements, wherein the process of acquiring the photoacoustic signal of the shallow surface layer of the metal rolling element is as follows:

[0033] The energy absorbed by the metal rolling element is converted into heat energy, triggering transient expansion. The sound pressure caused by thermal expansion satisfies the sound wave equation:

[0034]

[0035] In the formula, p represents sound pressure, v represents the speed of sound propagation, and t represents time;

[0036] The time harmonic solution of sound pressure is:

[0037] p(x,t) = P0exp[j(ωt-kx)];

[0038] In the formula, p(x,t) represents the time harmonic of the sound pressure, P0 represents the sound pressure amplitude, and k is the wave number. The calculation formula is as follows:

[0039]

[0040] The formula for calculating P0 is:

[0041] P0 = P acoustic =βA e ;

[0042] In the formula, P acousticA is the sound pressure amplitude of the photoacoustic signal, β is the conversion coefficient of the photoacoustic effect, which depends on the material's coefficient of thermal expansion, thermoelastic properties, and sound wave propagation efficiency. e The energy absorbed by the metal rolling element is calculated using the following formula:

[0043] A e =I0f(x,y,z)g(t)α;

[0044] Where f(x,y,z) is the spatial distribution of laser energy, g(t) is the time distribution function, usually an exponential pulse, and α is the material absorption coefficient;

[0045] Then, the photoacoustic signal is obtained through the sound pressure formula generated by the photoacoustic effect, as follows:

[0046] I photoacoustic =P acoustic ;

[0047] In the formula, I photocoustic It is a photoacoustic signal;

[0048] The process for determining shallow surface defects in the metal rolling element involves revealing the type and size of the defect through the frequency characteristics of photoacoustic signals, and then calculating the defect depth using ultrasonic time delay, as shown in the following formula:

[0049]

[0050] In the formula, d is the defect depth, v is the propagation speed of the sound wave, and Δt is the time difference of signal propagation.

[0051] The detection method of the aforementioned multimodal defect nondestructive testing device for metal rolling elements, wherein the process of acquiring the ultrasonic signal inside the metal rolling element is as follows:

[0052] Ultrasound satisfies the wave equation:

[0053]

[0054] In the formula, u is displacement, v represents propagation speed, and t represents time;

[0055] The ultrasonic signal is obtained from the echo signal of the ultrasonic probe:

[0056] I ultrasound =A echo ;

[0057] In the formula, I ultrasound It is an ultrasound signal, A echo It is the amplitude of the echo signal from the ultrasonic probe;

[0058] The formula for calculating the echo signal V(t) received by the ultrasonic probe is as follows:

[0059] V(t)=G∫ 孔径 p(x,y,t)dxdy;

[0060] In the formula, G is the sound wave transfer function, which represents the loss and scattering effect of sound wave propagation inside the metal rolling element, p(x,y,t) is the sound pressure distribution, and x and y represent the spatial coordinates of the metal rolling element;

[0061] The amplitude A of the echo signal from the ultrasonic probe echo The maximum value corresponding to V(t);

[0062] The process of determining the internal defects of the metal rolling element is based on the amplitude A of the echo signal from the ultrasonic probe. echo After determining the characteristics of the defect, the defect depth is calculated using ultrasonic time delay, as shown in the following formula:

[0063]

[0064] In the aforementioned detection method of the multimodal defect nondestructive testing device for metal rolling elements, step four involves multimodal signal fusion achieved through weighted summation:

[0065] I fused =w1I optical,line +w2I optical,ring +w3I photocoustic +w4I ultrasound ;

[0066] Among them, I fused This is a multimodal fused signal. The weights w1, w2, w3, and w4 are determined by signal-to-noise ratio optimization, and the calculation formula is as follows:

[0067]

[0068] In the formula, w i SNR represents the weight of the i-th signal. i P represents the signal-to-noise ratio of the i-th signal. signal,i P represents signal power. noise,i Indicates noise power;

[0069] The formula for calculating defect location is as follows:

[0070]

[0071] In the formula, d is the defect depth, v is the propagation speed of the sound wave, and Δt is the time difference of signal propagation.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] This invention employs a 2.5D striped light and a linear array camera, as well as a ring light and a planar array camera, to acquire high-resolution optical signals. Combined with an infrared pulsed laser and an ultrasonic probe, it obtains photoacoustic and ultrasonic signals, enabling comprehensive multimodal detection of rolling metal bodies containing various types and sizes of defects, including surface defects (such as scratches and dents) and internal defects (such as cracks and porosity). Simultaneously, by employing high-precision synchronous data acquisition and fusion processing technology, it achieves comprehensive extraction of defect features. Through multimodal fusion processing of the acquired data, the system can accurately locate defects, measure their dimensions, and extract depth information. Further, by combining photoacoustic and acoustic signal spectral analysis, characteristic frequency information of defects is extracted, thereby identifying different types of defects. This invention, through the combination of optical path optimization and multimodal detection technology, solves the problem that traditional detection technologies are easily affected by the surface characteristics of rolling metal bodies (such as high reflectivity and roughness) in a single detection mode. It overcomes the limitations of traditional detection methods, such as limited detection range and the inability to simultaneously detect surface and deep defects, making it suitable for more complex detection scenarios. Furthermore, by combining multimodal information such as surface stripe images, polarization characteristic images, and 3D depth maps, this invention effectively improves the accuracy and robustness of defect identification, solving the problem that traditional single-information-source methods struggle to detect complex defects. Through enhanced anti-reflective interference, improved environmental robustness, and the integration of surface and deep detection capabilities, this invention significantly expands its applicability, making it suitable for defect identification from the surface of highly reflective metal rolling bodies to complex structural components and multilayer materials. Its broad adaptability enables the system to meet the diverse inspection needs of modern industry. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of the detection device of the present invention;

[0075] Figure 2 This is a schematic diagram of the thermoelastic mechanism of the present invention;

[0076] Figure 3 This is a schematic diagram illustrating the generation of ultrasound using the thermoelastic mechanism of this invention.

[0077] Figure 4 This is a diagram illustrating the process of generating ultrasound using the thermoelastic mechanism of this invention.

[0078] Figure 5 This is a schematic diagram of the optical imaging of the present invention;

[0079] Figure 6 This is a schematic diagram illustrating the directionality of the ultrasonic waves of the present invention;

[0080] Figure 7 This is a schematic diagram of ultrasonic wave reflection and transmission according to the present invention. Detailed Implementation

[0081] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0082] Example 1: A non-destructive testing device for multi-modal defects in metal rolling elements, such as... Figure 1 As shown, this device is used to detect rolling metal objects. It includes a V-shaped rolling fixture, a signal detection and synchronous triggering system, a data acquisition unit, and a processing unit. The rolling metal object is mounted on the V-shaped rolling fixture and rolls with the fixture. The signal detection and synchronous triggering system is connected to a first detection optical path, a second detection optical path, and a third detection optical path for detecting the rolling metal object. The first and second detection optical paths are respectively connected to the processing unit, and the third detection optical path is connected to the data acquisition unit. The data acquisition unit is connected to both the signal detection and synchronous triggering system and the processing unit.

[0083] The first detection optical path includes a 2.5D stripe light source and a line scan camera positioned above the rolling metal body. The 2.5D stripe light source generates high-contrast stripes through structured grating projection, which are used to project regular grating stripes onto the surface of the rolling metal body. The 2.5D stripe light source is projected vertically onto the surface of the rolling metal body, and is supported by V-shaped rolling clamps on both sides, allowing the rolling metal body to achieve full surface coverage during rotation. The line scan camera uses a linear array CCD (charge-coupled device) sensor, suitable for imaging high-speed or continuously moving objects. The line scan camera uses a single row of pixels to progressively scan the surface of the rolling metal body, acquiring optical signals from the surface. These optical signals are signals obtained by detecting reflected, scattered, or transmitted light information from the surface of the rolling metal body using optical instruments (line scan camera and area scan camera), and are used to identify surface defects such as cracks, scratches, and corrosion. A stripe light source controller is connected between the first detection optical path and the signal detection and synchronous triggering system. The stripe light source controller is connected to the 2.5D stripe light source. The line scan camera is connected to the processing unit. The optical axis of the line scan camera is at an angle of 30°-45° to the optical axis of the 2.5D stripe light source to avoid specular reflection areas and ensure high-contrast signal acquisition. A narrowband filter is also provided in the first detection optical path to match the wavelength of the stripe light and avoid ambient light interference. At the same time, an infrared cutoff filter is added to suppress blurring and distortion caused by infrared light interference.

[0084] The second detection optical path includes a set of ring light sources positioned opposite each other on both sides of the end face of the rolling metal body. The ring light sources are arranged around the optical axis of the area array camera, with the optical axis perpendicular to the end face, providing uniform illumination from all directions. The ring light sources provide uniform diffuse illumination to the end surface of the rolling metal body, avoiding shadow interference and enhancing the visibility of end face defects (such as scratches and dents). An area array camera is located outside the ring light sources. This camera is an imaging device using an area array sensor (typically a CCD or CMOS sensor), capable of acquiring images within a two-dimensional (X and Y directions) area simultaneously, used to acquire optical signals from the end surface of the rolling metal body. The optical axis of the area array camera is aligned with the end face normal to ensure distortion-free light intensity distribution. A ring light source controller is connected between the second detection optical path and the signal detection and synchronization triggering system; the area array camera is connected to the processing unit. To meet high precision requirements, a high-pass filter is added to the second detection optical path to shield against low-frequency background light interference, and an infrared cutoff filter is added to suppress infrared light interference.

[0085] The third detection optical path includes an infrared pulsed laser and an ultrasonic probe. The output optical path of the infrared pulsed laser is sequentially equipped with a fiber coupler, an optical fiber, and a laser galvanometer. The infrared pulsed laser generates pulsed laser light to scan the test area of ​​the rolling metal body. The infrared pulsed laser is a nanosecond-level pulsed laser, which excites acoustic waves through the thermoelastic effect on the surface of the rolling metal body. The wavelength and pulse width of the laser are optimized to match the energy absorption peak of the rolling metal body surface, improving the photoacoustic effect excitation efficiency. The laser power density is controlled at 10⁶ × 10⁶ W / cm². 2To avoid ablation and surface damage and ensure material integrity, the following measures are taken: An ultrasonic probe is used to collect photoacoustic signals from the shallow surface of the metal rolling element and ultrasonic signals from inside the metal rolling element. The ultrasonic probe contains a photoacoustic sensor to capture the photoacoustic signals. The photoacoustic signal is generated by irradiating the surface of the metal rolling element with a pulsed laser, causing localized thermal expansion and exciting sound waves. The characteristics of these sound waves are detected to analyze shallow surface defects. The sound waves generated by the photoacoustic effect propagate through the metal rolling element as surface waves and volume waves, and are captured by the broadband response photoacoustic sensor. The ultrasonic signal is generated by emitting high-frequency sound waves through the ultrasonic probe. These sound waves propagate and reflect within the metal rolling element. The characteristics of the reflected waves are used to detect internal defects in the metal rolling element, such as holes and cracks. A third detection optical path uses a laser to excite the ultrasonic signal, and uses reflected waves to capture the reflected ultrasonic signals on the defect surface, extracting waveform changes to determine the defect shape and characteristics. After real-time acquisition and preprocessing, the ultrasonic echo signal is used with an improved time delay estimation algorithm to extract propagation time, amplitude, and frequency changes. An infrared laser controller is connected between the third detection optical path and the signal detection and synchronous triggering system, and the infrared laser controller is connected to an infrared pulsed laser; the ultrasonic probe is connected to the data acquisition unit. To improve detection sensitivity, multi-stage low-noise amplification and adaptive filtering technology are used in the signal path of the third detection optical path to effectively eliminate background noise interference. Combined with digital signal processing algorithms, time-domain and frequency-domain features are extracted to identify changes in sound pressure amplitude, propagation velocity, and amplitude, accurately characterizing shallow defects (such as crack depth, tilt angle, etc.).

[0086] The core design of the signal detection and synchronous triggering system is based on the gradual acquisition of three signals (optical signal, photoacoustic signal, and ultrasonic signal) after the metal rolling body rotates once, and the data time axis alignment and multimodal fusion are achieved by using a unified time reference.

[0087] The signal detection and synchronization triggering system architecture includes a time reference trigger and a registration and fusion module. The time reference trigger provides time control for the acquisition of each modal signal, ensuring time axis alignment between different signals. The registration and fusion module calculates the time deviation of each modal signal acquisition based on the rolling element's rotational speed and position feedback, thus completing signal alignment. Then, by combining the surface information of the optical signal, the shallow features of the photoacoustic signal, and the depth data of the ultrasonic signal, a three-dimensional defect map is constructed.

[0088] The signal detection and synchronization triggering system employs a unified time reference trigger to ensure that the acquisition of optical, photoacoustic, and ultrasonic signals is completed within a set time window. After each signal acquisition, the metal rolling body returns to its initial position to facilitate the acquisition of the next mode of signal. After the acquisition of the three types of signals, the registration and fusion module maps the data to the same time reference system using a time axis alignment algorithm to avoid the accumulation of multimodal signal errors. Combining spatiotemporal characteristics, multimodal fusion processing is performed to generate a complete defect model from the surface to the depth.

[0089] Advantages of signal detection and synchronous triggering systems:

[0090] 1. It can avoid potential signal interference during simultaneous data acquisition;

[0091] 2. Utilize a unified time base to ensure time consistency of data from different modalities;

[0092] 3. Acquire signals in stages according to modality to improve acquisition efficiency and reduce system complexity.

[0093] The principle of optical nondestructive testing: Optical imaging systems (line scan cameras and area scan cameras) collect light signals reflected or emitted from the surface of an object, converting the observed object into a visually perceptible image (e.g., ...). Figure 5 As shown, by utilizing high pixel count and advanced photosensitive elements, optical imaging can generate high-resolution, high-contrast defect images. By analyzing information such as pixel distribution, brightness, and color, the location, size, and type of defects can be accurately detected.

[0094] The principle of photoacoustic nondestructive testing: In the visible light range, when a laser irradiates a metal surface, it excites an ultrasonic signal. When the laser energy density is below 10... 7 W / cm 2 Ultrasonic waves are primarily generated through a thermoelastic mechanism. Under this mechanism, the amplitudes of photoacoustic longitudinal waves, transverse waves, and surface waves increase with increasing laser energy density, and the amplitude of the acoustic waves exhibits an approximately linear relationship with the laser energy density. A schematic diagram of the thermoelastic mechanism is shown below. Figure 2 As shown.

[0095] In photoacoustic nondestructive testing, the photoacoustic effect is usually generated under a thermoelastic mechanism (laser energy density below 10). 7 W / cm 2 When a pulsed laser beam irradiates a material surface, part of the laser energy A... e Absorbed by the material, the heat accumulates in a localized area and is converted into thermal energy. Changes in the local temperature T cause the material's volume to periodically expand and contract, thus forming an elastic stress field, i.e., an ultrasonic field. This process is the generation of ultrasound through the thermoelastic mechanism, as illustrated in the diagram below. Figure 3 and Figure 4 As shown.

[0096] The principle of ultrasonic nondestructive testing: Ultrasonic waves are mechanical waves with frequencies higher than 20kHz, typically generated and received by piezoelectric materials through the interconversion of electrical and mechanical energy. When receiving electrical energy, the piezoelectric material converts it into mechanical vibrations to generate ultrasonic waves, and simultaneously converts the received mechanical vibrations into electrical signals to collect ultrasonic data. Ultrasonic waves have good directionality and strong metal-penetrating ability; their directional distribution is as follows... Figure 6 As shown, the central main lobe represents the main direction of energy propagation, while the side lobes represent the diffusion portion with lower energy.

[0097] Ultrasonic nondestructive testing detects internal defects in materials by observing the reflection, scattering, and transmission of ultrasonic waves. When ultrasonic waves propagate to an interface between two materials with significantly different acoustic impedances (acoustic impedance Z is determined by density ρ and sound velocity v), the impedance mismatch causes some ultrasonic waves to be reflected at the interface, while the rest are transmitted into the other material. Figure 7 As shown.

[0098] The third detection optical path, by precisely measuring the characteristics of reflected and scattered waves, can construct image information containing internal defects using ultrasonic imaging technology. The ultrasonic signals acquired by the ultrasonic probe carry information about the internal structure and defects of the material. After data processing, intuitive images of internal defects can be generated, thereby enabling quantitative analysis of the location, size, and properties of defects.

[0099] Example 2: Based on the multimodal defect nondestructive testing device in Example 1, this example provides a multimodal defect nondestructive testing method for metal rolling elements, specifically including the following steps:

[0100] Step 1: Based on the first and second detection optical paths, perform optical detection on the surface of the metal rolling element to obtain optical signals of the surface and end surfaces of the metal rolling element, and determine the defects on the surface and end surfaces of the metal rolling element based on the obtained optical signals.

[0101] In this embodiment, the process of acquiring the optical signal from the surface of the metal rolling column involves a line-scan camera sequentially acquiring the optical signal reflected from the surface of the metal rolling column. The formula for the acquired optical signal is as follows:

[0102] I optical,line =∫ y I(x',y')dy;

[0103] Among them, I optical,line These are the optical signals acquired by the line scan camera, x' and y' are the pixel coordinates acquired by the line scan camera, and x and y are the coordinates in the actual physical space of the metal rolling body.

[0104] Specifically, I(x',y') is determined by the surface reflectivity R(x,y) and the light source intensity I0, as shown in the following formula:

[0105] I(x',y')=I0R(x,y);

[0106] Furthermore, the process of determining the surface defects of the metal rolling element cylinder is through optical signal I. optical,line Determine the surface texture and defect features of the metal rolling element, and obtain the morphological features of protrusions, cracks or scratches on the surface of the metal rolling element column through three-dimensional reconstruction;

[0107] The formula for the three-dimensional reconstruction is as follows:

[0108]

[0109] Where z(x,y) is the surface height distribution, d is the projection grating spacing, and I1, I2, I3 and I4 are the light intensity values ​​after the fringe phase shift.

[0110] In this embodiment, the process of acquiring the optical signal from the end surface of the metal rolling element is as follows:

[0111] The formula for calculating the reflected light intensity I(x,y) from the end surface of a metal rolling element is as follows:

[0112] I(x,y)=I0R(x,y)=I0cos n (θ);

[0113] Where I0 is the light source intensity, x and y are the coordinates of the metal rolling body in the actual physical space, R(x,y) is the reflectivity, θ is the angle between the normal of the end surface of the metal rolling body and the direction of the ring light source, and n is the reflection distribution index.

[0114] Then, the area scan camera records the two-dimensional light intensity distribution of the reflected light intensity from the end surface of the metal rolling element, obtaining the optical signal. The calculation formula is as follows:

[0115] I optica,lring =I (i,j) =∫ Δx ∫ Δy I(x,y)dxdy;

[0116] In the formula, I optical,ring It is the optical signal acquired by the area array camera, where Δx is the spatial resolution, Δy is the sampling interval, and the light intensity corresponding to pixel (i,j) is determined by the reflection characteristics of the end surface of the metal rolling body.

[0117] Furthermore, the process of determining the surface defects at the end of the metal rolling element involves using the discontinuity of light intensity distribution to detect surface pits, scratches, or coating peeling, and analyzing the gradient information of the image after optical distortion correction to extract subtle defects.

[0118] Step 2: Based on the third detection optical path, perform photoacoustic detection on the shallow surface of the metal rolling element to obtain the photoacoustic signal of the shallow surface of the metal rolling element, and determine the defects in the shallow surface of the metal rolling element based on the obtained photoacoustic signal.

[0119] In this embodiment, the process of acquiring the photoacoustic signal of the shallow surface layer of the metal rolling element is as follows:

[0120] The energy absorbed by the metal rolling element is converted into heat energy, triggering transient expansion. The sound pressure caused by thermal expansion satisfies the sound wave equation:

[0121]

[0122] In the formula, p represents sound pressure, which is the intensity of the sound wave; v represents the speed of sound propagation, which depends on the material elasticity and density of the metal rolling element; t represents time, which is usually related to the time delay of the ultrasonic wave propagation path.

[0123] The time harmonic solution of sound pressure is:

[0124] p(x,t) = P0exp[j(ωt-kx)];

[0125] In the formula, p(x,t) represents the time harmonic of the sound pressure, P0 represents the sound pressure amplitude, which depends on the conversion efficiency of the photoacoustic effect, and k is the wavenumber, calculated by the following formula:

[0126]

[0127] The formula for calculating P0 is:

[0128] P0 = P acoustic =βA e ;

[0129] In the formula, P acoustic A is the sound pressure amplitude of the photoacoustic signal, β is the conversion coefficient of the photoacoustic effect, which depends on the material's coefficient of thermal expansion, thermoelastic properties, and sound wave propagation efficiency. e The energy absorbed by a metal rolling element reflects the depth and size of material defects. The calculation formula is as follows:

[0130] A e =I0f(x,y,z)g(t)α;

[0131] Where f(x,y,z) is the spatial distribution of laser energy, g(t) is the time distribution function, usually an exponential pulse, and α is the material absorption coefficient;

[0132] Then, the photoacoustic signal is obtained through the sound pressure formula generated by the photoacoustic effect, as follows:

[0133] I photoacoustic =Pacoustic ;

[0134] In the formula, I photocoustic It is a photoacoustic signal;

[0135] Furthermore, the process for determining the shallow surface defects of the metal rolling element involves revealing the type and size of the defect through the frequency characteristics of the photoacoustic signal, and then calculating the defect depth through ultrasonic time delay, as shown in the following formula:

[0136]

[0137] Step 3: Based on the third detection optical path, perform ultrasonic testing on the inside of the metal rolling element to obtain the ultrasonic signal inside the metal rolling element, and determine the internal defects of the metal rolling element based on the obtained ultrasonic signal.

[0138] In this embodiment, the process of acquiring the ultrasonic signal inside the metal rolling element is as follows:

[0139] Ultrasound satisfies the wave equation:

[0140]

[0141] In the formula, u is displacement, v represents propagation speed, and t represents time;

[0142] Specifically, the ultrasonic signal is obtained from the echo signal of the ultrasonic probe:

[0143] I ultrasound =A echo ;

[0144] In the formula, I ultrasound It is an ultrasound signal, A echo It is the amplitude of the echo signal from the ultrasonic probe;

[0145] The formula for calculating the echo signal V(t) received by the ultrasonic probe is as follows:

[0146] V(t)=G∫ 孔径 p(x,y,t)dxdy;

[0147] In the formula, G is the sound wave transfer function, which represents the loss and scattering effect of sound wave propagation inside the metal rolling element; p(x,y,t) is the sound pressure distribution, which describes the propagation and time variation characteristics of sound waves in space, and x and y represent the spatial coordinates of the metal rolling element.

[0148] The acoustic transfer function G is obtained through experimental calibration (measuring G under different environmental conditions using standard samples and constructing calibration curves) and simulation (simulating different combinations of defects and material properties using the finite element method to predict the variation law of the acoustic transfer function G), and is expressed by the formula:

[0149] G(f,r,θ)=A(f)·e-α(f)r·P(θ);

[0150] In the formula, f is the sound wave frequency, representing the propagation frequency of the sound wave; r is the propagation distance; θ is the propagation direction; A(f) is the initial intensity of the sound wave related to the frequency; α(f) is the attenuation coefficient, describing the attenuation rate of the sound wave in the metal rolling body with the propagation distance. The attenuation coefficient α(f) is related to the density, elastic modulus, and internal friction characteristics of the metal rolling body material; P(θ) is the angular distribution function, representing the directional change of the sound wave caused by the propagation direction or surface scattering.

[0151] The amplitude A of the echo signal from the ultrasonic probe echo The maximum value corresponding to V(t);

[0152] Furthermore, the determination of internal defects in the metal rolling element is achieved by measuring the amplitude A of the echo signal from the ultrasonic probe. echo After determining the characteristics of the defect, the defect depth is calculated using ultrasonic time delay, as shown in the following formula:

[0153]

[0154] In the formula, d is the depth of the defect, that is, the depth of the signal reflection (or scattering) location; v is the propagation speed of the sound wave; Δt is the time difference of signal propagation, which is usually the time between the transmitted signal and the received reflected signal.

[0155] Step 4: Based on the surface defects, shallow layer defects, and internal defects of the metal rolling element, perform multimodal signal fusion to obtain fused defect information, and locate the defects based on the fused defect information.

[0156] In this embodiment, multimodal signal fusion is a technique that jointly processes and analyzes signal data from different detection methods (such as optical, photoacoustic, and ultrasonic), improving the comprehensiveness and accuracy of detection. This method preprocesses images acquired from optical, photoacoustic, and ultrasonic signals separately, including noise reduction, enhancement, and edge detection. Wavelet transform is used for image fusion, preserving the spatial resolution of the optical image and the depth information of the photoacoustic and ultrasonic signals. Multimodal signal fusion integrates data from different modes through time synchronization and spatial alignment processing, achieving deep localization and precise characterization of metal defects. By constructing a three-dimensional defect model of the multimodal signals, a complete reconstruction of the defect from its surface to its interior is achieved.

[0157] The multimodal signal fusion is achieved through weighted summation:

[0158] I fused =w1I optical,line +w2I optical,ring +w3I photocoustic +w4Iultrasound ;

[0159] Among them, I fused This is a multimodal fused signal. The weights w1, w2, w3, and w4 are determined by signal-to-noise ratio optimization, and the calculation formula is as follows:

[0160]

[0161] In the formula, w i SNR represents the weight of the i-th signal. i P represents the signal-to-noise ratio of the i-th signal. signal,i P represents signal power. noise,i Indicates noise power;

[0162] Furthermore, based on the fused defect information, the calculation formula for defect localization is as follows:

[0163]

[0164] In the formula, d is the defect depth, v is the propagation speed of the sound wave, and Δt is the time difference of signal propagation.

[0165] This invention employs a multimodal fusion algorithm based on spatiotemporal features to jointly analyze the waveform characteristics of photoacoustic and ultrasonic waves. It precisely locates surface crack features (such as tilt angle and length) acquired from photoacoustic signals and reconstructs the complete path of the crack extending from the surface to the interior using the penetration depth data of the ultrasonic signals. During data fusion, a deep learning feature extraction network is combined to synthesize the wave signals and construct a three-dimensional spatial model of the defect from the surface to the depth, significantly improving the accuracy and resolution of defect detection.

[0166] This invention enables comprehensive multimodal detection of rolling metal bodies containing various types and sizes of defects, including surface defects (such as scratches and pits) and internal defects (such as cracks and porosity). It employs a striped light beam and a linear array camera, as well as a ring light beam and a area array camera, to acquire high-resolution optical signals. Combined with laser pulses and ultrasonic probes, it obtains photoacoustic and acoustic signals for multimodal joint detection of the sample. Simultaneously, it utilizes high-precision synchronous data acquisition and fusion processing technology to achieve comprehensive extraction of defect features. Through multimodal fusion processing of the acquired data, the system can accurately locate defects, measure their dimensions, and extract depth information. Furthermore, by combining spectral analysis of the photoacoustic and acoustic signals, characteristic frequency information of the defects is extracted, thereby identifying different types of defects.

[0167] This invention combines optical path optimization and multimodal detection technology to solve the problem that traditional detection technologies are easily affected by the surface characteristics of metal rolling bodies (such as high reflectivity and roughness) in a single detection mode. It also overcomes the limitations of traditional detection methods, such as limited detection range and the inability to simultaneously detect surface and deep defects, making it suitable for more complex detection scenarios. Furthermore, by combining multimodal information such as surface stripe images, polarization characteristic images, and 3D depth maps, and utilizing information fusion algorithms or neural network models, this invention effectively improves the accuracy and robustness of defect identification, solving the problem that traditional single-information-source methods struggle to detect complex defects. Through the integration of anti-reflective interference, enhanced environmental robustness, and surface and deep detection capabilities, this invention significantly expands its applicability, making it suitable for detecting defects from the surface of highly reflective metal rolling bodies to complex structural components and multilayer materials. Its broad adaptability enables the system to meet the diverse detection needs of modern industry.

[0168] Experimental results show that this technology exhibits excellent performance in defect detection:

[0169] 1. Detection accuracy: The detection accuracy of defect location, size and depth reaches the micrometer level.

[0170] 2. Accuracy Verification: Through comparative analysis with theoretical models and standard samples, the high accuracy and stability of the detection system in defect measurement were verified.

[0171] 3. Defect Classification: By utilizing the frequency response characteristics of photoacoustic and acoustic signals, it is possible to accurately distinguish defect types such as cracks, pores, and corrosion.

[0172] Experimental results fully demonstrate that this technology can achieve high-precision detection and classification of multiple types of defects, and has broad engineering application prospects. Furthermore, the system's innovations in multimodal data fusion and defect identification technologies provide important support for the quality inspection of complex structural materials.

[0173] In summary, this invention can integrate multimodal information to achieve comprehensive detection of defects in metal rolling elements, and has the characteristics of high detection efficiency, high detection accuracy and strong adaptability.

Claims

1. A non-destructive testing device for multi-modal defects in metal rolling elements, used for testing metal rolling elements; characterized in that: The device includes a V-shaped rolling clamp, a signal detection and synchronous triggering system, a data acquisition unit, and a processing unit. The metal rolling element is mounted on the V-shaped rolling clamp and rolls in cooperation with the clamp. The signal detection and synchronous triggering system is connected to a first detection optical path, a second detection optical path, and a third detection optical path for detecting the metal rolling element. The first and second detection optical paths are respectively connected to the processing unit, and the third detection optical path is connected to the data acquisition unit. The data acquisition unit is connected to both the signal detection and synchronous triggering system and the processing unit. The first detection optical path includes a 2.5D striped light source and a line scan camera positioned above the rolling metal body. The 2.5D striped light source projects regular grating stripes onto the surface of the rolling metal body, and the line scan camera acquires optical signals from the surface of the rolling metal body. ; The second detection optical path includes a set of annular light sources positioned opposite each other on both sides of the end face of the metal rolling element, with an area scan camera positioned outside the annular light sources; the annular light sources provide uniform diffuse illumination to the end surface of the metal rolling element, and the area scan camera acquires optical signals from the end surface of the metal rolling element. ; The third detection optical path includes an infrared pulsed laser and an ultrasonic probe. The output optical path of the infrared pulsed laser is sequentially provided with a fiber coupler, an optical fiber, and a laser galvanometer. The infrared pulsed laser generates pulsed laser light to scan the test area of ​​the rolling metal body. The pulsed laser light is coupled to the optical fiber via the fiber coupler and then uniformly irradiated onto the surface of the rolling metal body via the laser galvanometer. The ultrasonic probe is used to collect photoacoustic signals from the shallow surface layer of the rolling metal body. and the ultrasonic signals inside the metal rolling body ; Based on the surface defects, shallow layer defects, and internal defects of the metal rolling element, multimodal signal fusion is performed to obtain fused defect information, and defect localization is performed based on the fused defect information; The multimodal signal fusion is achieved through weighted summation: ; in, It is a multimodal fused signal, weighted , , and Determined by signal-to-noise ratio optimization, the calculation formula is as follows: ; ; In the formula, Indicates the first Weights of various signals Indicates the first The signal-to-noise ratio of the signal. Indicates signal power. Indicates noise power; The formula for calculating defect location is as follows: ; In the formula, For defect depth, For the speed of sound wave propagation, This represents the time difference in signal propagation.

2. The non-destructive testing device for multi-modal defects of metal rolling elements according to claim 1, characterized in that: A stripe light source controller is connected between the first detection optical path and the signal detection and synchronous triggering system. The stripe light source controller is connected to the 2.5D stripe light source. The line scan camera is connected to the processing unit. The optical axis of the line scan camera is at an angle of 30°-45° to the optical axis of the 2.5D stripe light source.

3. The non-destructive testing device for multi-modal defects of metal rolling elements according to claim 1, characterized in that: A ring light source controller is connected between the second detection optical path and the signal detection and synchronous triggering system, and the ring light source controller is connected to the ring light source; the area array camera is connected to the processing unit.

4. The non-destructive testing device for multi-modal defects of metal rolling elements according to claim 1, characterized in that: An infrared laser controller is connected between the third detection optical path and the signal detection and synchronous triggering system, and the infrared laser controller is connected to an infrared pulse laser; the ultrasonic probe is connected to a data acquisition unit.

5. The detection method of the multi-modal defect non-destructive testing device for metal rolling elements according to any one of claims 1-4 specifically includes the following steps: Step 1: Based on the first and second detection optical paths, perform optical detection on the surface of the metal rolling element to obtain optical signals of the surface and end surfaces of the metal rolling element, and determine the defects on the surface and end surfaces of the metal rolling element based on the obtained optical signals. Step 2: Based on the third detection optical path, perform photoacoustic detection on the shallow surface of the metal rolling element to obtain the photoacoustic signal of the shallow surface of the metal rolling element, and determine the defects in the shallow surface of the metal rolling element based on the obtained photoacoustic signal. Step 3: Based on the third detection optical path, perform ultrasonic testing on the inside of the metal rolling element to obtain the ultrasonic signal inside the metal rolling element, and determine the internal defects of the metal rolling element based on the obtained ultrasonic signal. Step 4: Based on the surface defects, shallow layer defects, and internal defects of the metal rolling element, perform multimodal signal fusion to obtain fused defect information, and locate the defects based on the fused defect information.

6. The detection method of the multi-modal defect non-destructive testing device for metal rolling elements according to claim 5, characterized in that: The process of acquiring the optical signal from the surface of the metal rolling column involves a linear scan camera sequentially acquiring the optical signal reflected from the surface of the metal rolling column. The formula for the acquired optical signal is as follows: ； in, It is the optical signal collected by the line scan camera. and These are the pixel coordinates acquired by the line scan camera. and These are the coordinates of the metal rolling element in its actual physical space. Based on surface reflectivity and light source intensity The decision is made using the following formula: ； The process of determining the surface defects of the metal rolling column is through optical signals. Determine the surface texture and defect features of the metal rolling element, and obtain the morphological features of protrusions, cracks or scratches on the surface of the metal rolling element column through three-dimensional reconstruction; The formula for the three-dimensional reconstruction is as follows: ； in, It is the surface height distribution. It is the pitch of the projection grating; , , and It is the light intensity value after the fringe phase shift.

7. The detection method of the multi-modal defect non-destructive testing device for metal rolling elements according to claim 5, characterized in that: The process of acquiring the optical signal from the end surface of the metal rolling element is as follows: Calculate the light intensity reflected from the end surface of the metal rolling element The formula is as follows: ； in, It is the intensity of the light source. and These are the coordinates of the metal rolling element in its actual physical space. It's reflectivity. The angle between the normal to the end surface of the metal rolling element and the direction of the annular light source is given. The reflectance distribution index; Then, the area scan camera records the two-dimensional light intensity distribution of the reflected light intensity from the end surface of the metal rolling element, obtaining the optical signal. The calculation formula is as follows: ； In the formula, It is the optical signal collected by the area array camera. For spatial resolution, Sampling interval, pixels The corresponding light intensity is determined by the reflection characteristics of the end surface of the metal rolling element; The process of determining the surface defects at the end of the metal rolling element involves using the discontinuity of light intensity distribution to detect surface pits, scratches, or coating peeling, and analyzing the image gradient information after optical distortion correction to extract subtle defects.

8. The detection method of the multi-modal defect non-destructive testing device for metal rolling elements according to claim 5, characterized in that: The process of acquiring the photoacoustic signal of the shallow surface layer of the metal rolling element is as follows: The energy absorbed by the metal rolling element is converted into heat energy, triggering transient expansion. The sound pressure caused by thermal expansion satisfies the sound wave equation: ； In the formula, Indicates sound pressure level. Indicates the speed of sound wave propagation. Indicates time; The time harmonic solution of the sound pressure is: ； In the formula, Time harmonics representing sound pressure level. Indicates the sound pressure level. It is the wave number, and the calculation formula is: ； The The calculation formula is: ； In the formula, It is the sound pressure amplitude of the photoacoustic signal. It is the conversion coefficient of the photoacoustic effect, which depends on the material's coefficient of thermal expansion, thermoelastic properties, and sound wave propagation efficiency. The energy absorbed by the metal rolling element is calculated using the following formula: ； in, It is the spatial distribution of laser energy. It is a time distribution function, usually an exponential impulse. The material absorption coefficient; Then, the photoacoustic signal is obtained through the sound pressure formula generated by the photoacoustic effect, as follows: ； In the formula, It is a photoacoustic signal; The process for determining shallow surface defects in the metal rolling element involves revealing the type and size of the defect through the frequency characteristics of photoacoustic signals, and then calculating the defect depth using ultrasonic time delay, as shown in the following formula: 。 9. The detection method of the multi-modal defect non-destructive testing device for metal rolling elements according to claim 5, characterized in that: The process of acquiring the ultrasonic signal inside the metal rolling element is as follows: Ultrasound satisfies the wave equation: ； In the formula, It is displacement. Indicates the speed of propagation. Indicates time; The ultrasonic signal is obtained from the echo signal of the ultrasonic probe: ； In the formula, It is an ultrasound signal. It is the amplitude of the echo signal from the ultrasonic probe; The echo signal received by the ultrasonic probe The calculation formula is as follows: ； In the formula, It is the sound wave transfer function, representing the loss and scattering effects of sound waves propagating inside a rolling metal element. It is the distribution of sound pressure. and Represents the spatial coordinates of the rolling metal element; The amplitude of the echo signal from the ultrasonic probe correspond The maximum value; The determination of internal defects in the metal rolling element is achieved by measuring the amplitude of the echo signal from the ultrasonic probe. After determining the characteristics of the defect, the defect depth is calculated using ultrasonic time delay, as shown in the following formula: ; In the formula, For defect depth, For the speed of sound wave propagation, This represents the time difference in signal propagation.

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