Non-destructive testing method and system for burn wounds by infrared pulsed thermal radiation

Abstract

The application provides an infrared pulse thermal radiation grinding burn nondestructive detection method and system, and belongs to the technical field of nondestructive detection.The method comprises the following steps: inputting an excitation signal to an induction coil to induce a pulse eddy current to heat a measured part; using an infrared thermal imager and a depth camera to obtain a thermal response temperature matrix of a measured area of the part and a three-dimensional point cloud of the measured area; subsequently, a thermal response model of the part is constructed; a time sequence temperature curve of the measured area in a heating and natural cooling stage is extracted, a grinding burn discrimination function is established, and whether a grinding burn area exists is judged; the infrared thermal imager and the depth camera are calibrated, the grinding burn area in a coordinate system of the infrared thermal imager is projected into the three-dimensional point cloud of the depth camera, the position of the grinding burn area in a world coordinate system is obtained, and the detection and positioning of the grinding burn area are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nondestructive testing, and in particular to an infrared pulse thermal radiation grinding burn nondestructive testing method and system. BACKGROUND

[0002] Grinding burn is a surface defect of metal parts caused by local high temperature during grinding process, which is usually manifested as changes in metallographic structure (such as the generation of tempered structure, quenched martensite, etc.), or even the generation of micro-cracks or the formation of an oxide layer. These defects significantly reduce the mechanical properties, fatigue resistance and service life of the parts, especially in high-precision parts such as aircraft bearings, automobile gears and bearings. The presence of grinding burn can lead to catastrophic failure.

[0003] Traditional grinding burn detection methods include acid washing microscopic observation and metallographic analysis, which require sample destruction and cannot achieve non-contact or online detection, and are low in efficiency and cause chemical pollution after acid washing. Ultrasonic detection and magnetic powder detection have limited sensitivity for detecting small surface burn defects and are difficult to quantify burn severity. In recent years, infrared thermal imaging technology has been applied in nondestructive testing, but existing methods rely on external heat sources including lasers or hot air, which have poor heating uniformity, and do not fully utilize the differences in electrical conductivity, thermal conductivity and emissivity of the grinding burn area, resulting in limited detection accuracy.

[0004] Pulsed eddy current technology can achieve rapid local heating by non-contact alternating magnetic field induced eddy current heating, but existing technology mainly focuses on crack detection and lacks means for grinding burn detection. Infrared thermal imaging can capture surface thermal radiation, but the coupling effect of emissivity difference and thermal diffusion characteristics of the burn area has not been systematically quantified. Therefore, it is necessary to propose an infrared pulse thermal radiation grinding burn nondestructive testing method and system that significantly improves the detection accuracy and efficiency of grinding burn by constructing a photo-electric-thermal multi-physical field response model and a discriminant function, and overcomes the problems of destructive, high pollution and low efficiency of traditional methods. SUMMARY

[0005] Therefore, the present application proposes an infrared pulse thermal radiation grinding burn nondestructive testing method and system that realizes high-precision, rapid nondestructive detection of grinding burn by non-contact pulsed eddy current heating, combined with infrared thermal imaging and a multi-physical field response model.

[0006] In one aspect, the present application provides an infrared pulse thermal radiation grinding burn nondestructive testing method, comprising the following steps:

[0007] S1: integrate the induction coil into the end of the industrial robot, select the appropriate induction coil according to different parts, input the excitation signal to the induction coil, make the magnetic field of the induction coil completely cover the measured area of the part, and induce the pulse eddy current in the measured part to heat;

[0008] S2: integrate the infrared thermal imager and the depth camera into the end of the industrial robot synchronously, for acquiring the thermal response temperature matrix of the measured area of the part and the three-dimensional point cloud of the measured area;

[0009] S3: construct the thermal response model between the material conductivity, thermal conductivity, emissivity and surface temperature of the part;

[0010] S4: extract the time sequence temperature curve of the temperature rise when the measured area is heated, and the time sequence temperature curve of the natural cooling stage when the eddy current heat generation is stopped, construct the grinding burn discrimination function, and determine whether there is a grinding burn area;

[0011] S5: calibrate the infrared thermal imager and the depth camera, project the grinding burn area in the coordinate system of the infrared thermal imager into the three-dimensional point cloud of the depth camera, acquire the position of the grinding burn area in the world coordinate system, and realize the detection and positioning of the grinding burn area.

[0012] On the basis of the above technical scheme, preferably, the pulse eddy current heating is a non-contact excitation mode, and the excitation signal of the induction coil is a periodic variable frequency signal or a high frequency fixed frequency signal.

[0013] Preferably, the waveform of the excitation signal of the induction coil is a modulated rectangular pulse, an exponential decay sawtooth wave or a double-frequency sine wave, and the frequency range is 1 kHz to 1 MHz.

[0014] Preferably, the overall temperature rise of the part heating does not exceed 30 degrees Celsius, which ensures that the measured part will not be damaged.

[0015] On the basis of the above technical scheme, preferably, the content of step S3 is that the surface temperature of the material is obtained from the thermal response temperature matrix of the measured area acquired by the infrared thermal imager, the local joule heat generated per unit time is obtained according to the surface temperature and the thermal conductivity, and the relationship between the local joule heat generated per unit time and the electrical conductivity, current density and pulse duration is constructed.

[0016] Preferably, the content of step S4 is that the grinding burn discrimination function is constructed according to the temperature rise stage weight function and the natural cooling stage weight function, combined with the surface temperature of the material, a thermal response difference threshold is set, and when the value of the grinding burn discrimination function is greater than the thermal response difference threshold, it is determined that the part has a grinding burn area.

[0017] Preferably, step S5 further comprises extracting local features of the transient signal of the surface temperature of the material by multi-scale wavelet transform, separating temperature transient signal components of different frequencies, expanding the thermal response difference between the grinding burn area and the normal area, enhancing the contrast of the burn area, and then converting the grinding burn area in the infrared thermal imager coordinate system to the depth camera.

[0018] Preferably, the position of the grinding burn area in the world coordinate system obtained in step S5 is obtained by acquiring a three-dimensional point cloud of the part through the depth camera, registering the three-dimensional point cloud with the pixel points in the temperature matrix of the infrared thermal imager, mapping the temperature matrix to the three-dimensional space, extracting the spatial coordinates of the grinding burn area, positioning the burn boundary through thermal image threshold segmentation, and realizing the positioning of the grinding burn area.

[0019] Preferably, the registration of the three-dimensional point cloud with the pixel points in the temperature matrix is performed by using an iterative closest point algorithm or a feature point matching algorithm.

[0020] On the other hand, the present application provides an infrared pulse thermal radiation grinding burn nondestructive detection system for realizing the infrared pulse thermal radiation grinding burn nondestructive detection method, comprising:

[0021] An industrial robot is provided with an induction coil, an infrared thermal imager and a depth camera at the end, for adjusting the posture of the induction coil, the infrared thermal imager and the depth camera; an excitation signal is input into the induction coil, and the magnetic field generated by the induction coil completely covers the measured area of the part, generating an induced pulse eddy current to heat the measured area of the part; the infrared thermal imager and the depth camera are used to acquire a thermal response temperature matrix of the measured area and a three-dimensional point cloud of the measured area.

[0022] A thermal response model construction module is used to acquire the surface temperature from the thermal response temperature matrix of the measured area, and to construct a thermal response model in combination with the material conductivity, thermal conductivity and emissivity of the part and the surface temperature.

[0023] A burn discrimination function construction module is used to extract the time sequence temperature curve of the temperature rise when the measured area is heated, and the time sequence temperature curve of the natural cooling stage after stopping the eddy current heating, to construct a grinding burn discrimination function, and to output a determination result of whether the part has a grinding burn area.

[0024] A grinding burn area positioning module is used to convert the grinding burn area in the infrared thermal imager coordinate system to the depth camera when the part has a grinding burn area, and to acquire the position of the grinding burn area in the world coordinate system.

[0025] The infrared pulse thermal radiation grinding burn nondestructive detection method and system provided by the present application have the following beneficial effects compared with the prior art:

[0026] (1) The present application proposes a method for generating pulse eddy current heating of the surface of the parts based on the induction coil, and combining the infrared thermal imager and the depth camera to detect the heating condition, without destructive sampling of the measured parts, which can realize high-precision, fast grinding burn defect detection, and is suitable for online quality detection of metal components of various sizes; The principle of the scheme is: the induction coil integrated at the end of the industrial robot applies an induction pulse eddy current to the parts, which instantaneously heats the surface of the parts in a non-contact manner, and the conductivity of the burned area is reduced due to the change of the metallographic structure (such as quenched martensite and micro-cracks), which generates more Joule heat, combined with the heat retention characteristics caused by the reduction of thermal conductivity, forming a thermal response characteristic of fast heating and slow cooling, the infrared thermal imager synchronously collects the temperature matrix of the surface of the parts, combined with the emissivity difference caused by the oxide layer of the burned area, the precise identification of the burned area is realized through the photo-electric-thermal multi-physical field response model and the innovative discriminant function, the detection process is controlled in seconds, and the overall temperature rise is less than the material tempering temperature, which does not affect the organization state of the parts;

[0027] (2) By integrating a machine vision three-dimensional positioning module, the burned boundary is located by registering the depth camera point cloud with the thermal response temperature matrix, with a precision of sub-millimeter, which significantly improves the efficiency compared with traditional acid pickling microscopic observation and ultrasonic detection, and has no chemical pollution;

[0028] (3) According to the Joule heat generated by the local unit time, the thermal diffusivity, the temperature gradient, and the surface temperature, a thermal diffusion equation is constructed; according to the emissivity of the material and the surface temperature, a surface emission power function is constructed; the thermal diffusion equation and the surface emission power function are used as the thermal response model; the thermal response characteristics of the measured area are accurately described by fully considering that the burned area has slow heat dissipation after stopping heating, the burned area has a large difference in surface emissivity due to the formation of an oxide layer on the surface of the burned area, and the burned area has a thermal response characteristic of fast heating and slow cooling. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, a brief introduction will be given below to the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0030] Figure 1 The system principle diagram of the present application, an infrared pulse thermal radiation grinding burn nondestructive testing method and system;

[0031] Figure 2 The method flowchart of the present application, an infrared pulse thermal radiation grinding burn nondestructive testing method and system;

[0032] Figure 3 A timing diagram of pulse eddy current heating and infrared thermal radiation collection for the infrared pulse thermal radiation grinding burn nondestructive detection method and system of the present application;

[0033] Figure 4 A thermal response comparison diagram of the burn area and the normal area for the infrared pulse thermal radiation grinding burn nondestructive detection method and system of the present application.

[0034] The reference signs: 1, industrial robot; 2, excitation signal generating device; 3, induction coil; 4, infrared thermal imager; 5, depth camera; 6, work station. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0036] The conventional grinding burn detection method needs to destroy the sample, cannot realize non-contact or online detection, is low in efficiency and can cause chemical pollution; the detection sensitivity of ultrasonic detection and magnetic powder detection is limited, and it is difficult to quantify the burn degree; the existing infrared thermal imaging method mainly relies on external heat sources including laser or hot air, and the heating uniformity is poor, and the detection precision is limited. In view of this, like Figure 1 In combination with Figure 2 The present application provides an infrared pulse thermal radiation grinding burn nondestructive detection method, which comprises the following steps:

[0037] S1: integrating the induction coil to the end of the industrial robot, selecting a suitable induction coil according to different parts, inputting an excitation signal to the induction coil, making the magnetic field of the induction coil completely cover the measured area of the part, and inducing a pulse eddy current in the measured part for heating. In an embodiment, the overall temperature rise of the part heated is not more than 30 degrees Celsius, so as to ensure that the measured part will not be damaged.

[0038] The pulse eddy current heating is a non-contact excitation mode, and the excitation signal of the induction coil is a periodic variable frequency signal or a high frequency fixed frequency signal. In the embodiment, the waveform of the excitation signal of the induction coil is a modulated rectangular pulse, an exponential decay sawtooth wave or a double-frequency sine wave, and the frequency range is 1 kHz to 1 MHz. Among them:

[0039] The waveform expression of the modulated rectangular pulse is: , , wherein is a reference current amplitude, represents a rectangular pulse, is a starting time, is a pulse period, is a modulation frequency, is a modulation coefficient, is a pulse duration;

[0040] The waveform expression of the exponential decay sawtooth wave is: , wherein is a decay coefficient; the exponential decay sawtooth wave avoids overheating through gradual energy input, is suitable for large-area burn detection, and the decay term is used to control heat accumulation, facilitating better extraction of thermal response differences in the subsequent burn discrimination link;

[0041] The waveform expression of the dual-frequency sinusoidal wave is: , wherein is a main frequency, is a secondary frequency, is an amplitude coefficient of the secondary frequency signal, is a phase difference between the main frequency and the secondary frequency; the dual-frequency sinusoidal wave induces surface eddy currents through the high-frequency signal and enhances subsurface heat diffusion through the low-frequency signal , optimizes the depth of eddy current penetration through the phase difference, and improves detection sensitivity in combination with the discrimination function.

[0042] In this embodiment, the pulse duration is 0.1 ms to 10 ms.

[0043] S2: Synchronously integrate the infrared thermal imager and the depth camera into the end of the industrial robot for acquiring the thermal response temperature matrix of the measured region of the part and the three-dimensional point cloud of the measured region.

[0044] S3: Construct a thermal response model between the material conductivity, thermal conductivity, emissivity and surface temperature of the part.

[0045] The content of step S3 is that, first, the surface temperature of the material is obtained from the thermal response temperature matrix of the measured region acquired by the infrared thermal imager, the local joule heat generated per unit time is obtained according to the relationship among the electrical conductivity, current density and pulse duration, and then the thermal diffusion equation is constructed in combination with the thermal diffusion coefficient, temperature gradient and surface temperature; the surface emission power function is constructed according to the emissivity and surface temperature of the material.

[0046] Specifically: according to the thermal diffusion characteristic difference of the grinding burn area, the thermal conductivity of the burn area is lower than that of the normal area, which makes it difficult for heat to be transmitted to the inside of the material, so the surface temperature of the material will rise, and the thermal diffusion process satisfies the following equation: wherein is the thermal diffusivity, is the material density of the part, is the specific heat capacity of the material; is the temperature gradient. When the heating is stopped, the heat dissipation of the grinding burn area is slow, and the time function of the surface temperature is fitted by an exponential function as: , T 0 is the ambient temperature, A is the temperature assignment, b is the cooling time constant, Q is the Joule heat of the induced eddy current per unit time at a local position.

[0047] Joule heat of the induced eddy current per unit time at a local position Q can be expressed as: , is the electrical conductivity at a local position ; is the current density. Due to the change of the metallographic structure of the grinding burn area (such as quenched martensite or micro-cracks), the local electrical conductivity decreases, so that the grinding burn area will accumulate more Joule heat.

[0048] For the severely burned area, the material surface emissivity is greatly different due to the formation of an oxide layer on the surface due to oxidation, that is, the emissivity of the burned area is significantly higher than that of the normal area. According to the law of thermal radiation, the surface radiation power is expressed as: , is the Stefan-Boltzmann constant, is the emissivity at a local position .

[0049] The thermal diffusion equation and the surface emission power function are solved to form a thermal response model. The infrared thermal imager can capture the difference in thermal radiation power , so that the burned area shows the thermal response characteristics of rapid heating and slow heat dissipation.

[0050] S4: Extract the time sequence temperature curve of the temperature rise of the measured area when heated, and the time sequence temperature curve of the natural cooling stage when the eddy current heat generation is stopped, construct a grinding burn discrimination function, and determine whether there is a grinding burn area.

[0051] The content of step S4 is to construct a grinding burn discrimination function according to the temperature rise stage weight function and the natural cooling stage weight function, combined with the surface temperature of the material, set a thermal response difference threshold, and when the value of the grinding burn discrimination function is greater than the thermal response difference threshold, it is determined that the part has a grinding burn area.

[0052] The thermal response temperature matrix of the part is obtained by the infrared thermal imager, and the time function of the surface temperature , the weight function is proposed wherein is a normalization coefficient, is the moment of temperature peak, is the moment of heating start, is the moment of end of natural cooling, is the weighting coefficient of temperature rise and natural cooling, the weight function can amplify the thermal response difference of the burn area, the weight function in the temperature rise stage, i.e. the first case, is expressed as the weight function in the temperature rise stage; the weight function in the natural cooling stage, i.e. the second case, is expressed as the weight function in the natural cooling stage.

[0053] In this embodiment, the temperature peak is obtained by analyzing the corresponding relationship between the temperature value and the time on the temperature curve.

[0054] After obtaining the weight function, a grinding burn discrimination function is further proposed: The output result of the grinding burn discrimination function is a scalar value, which is used to quantify the thermal response difference between the grinding burn area and the normal area. For different samples, the normal thermal response difference threshold is calibrated through experiments. When , it is considered that there is a burn area. The greater the value of the grinding burn discrimination function , the more serious the grinding burn is considered to be. When , it is considered that the current area has no burn.

[0055] S5: Calibrate the infrared thermal imager and the depth camera, project the grinding burn area in the coordinate system of the infrared thermal imager into the three-dimensional point cloud of the depth camera, obtain the position of the grinding burn area in the world coordinate system, and realize the detection and positioning of the grinding burn area.

[0056] Before the coordinate transformation in step S5, the following steps are further included: through multi-scale wavelet transform, the local features of the transient signal of the surface temperature of the material are extracted, the transient signal components of different frequencies of the temperature are separated, the thermal response difference between the grinding burn area and the normal area is enlarged, the contrast of the burn area is enhanced, and then the grinding burn area in the coordinate system of the infrared thermal imager is converted into the depth camera.

[0057] Multi-scale decomposition decomposes the time function of the surface temperature into multiple scales corresponding to different frequency components. One-dimensional discrete wavelet transform is performed on the time function of the surface temperature along the time axis, and the following equation is obtained: wherein is an approximation coefficient, is a detail coefficient, , respectively scale function and wavelet function, M As the maximum decomposition level, the multi-scale wavelet transform enhances the difference of thermal response between the burn area and the normal area by separating the temperature signal components of different frequencies, thereby improving the contrast.

[0058] The step S5 obtains the position of the grinding burn area in the world coordinate system by acquiring the three-dimensional point cloud of the part through the depth camera , and registering the three-dimensional point cloud with the pixel points in the temperature matrix of the infrared thermal imager, mapping the temperature matrix to the three-dimensional space, extracting the spatial coordinates of the grinding burn area, positioning the burn boundary through thermal image threshold segmentation, realizing the positioning of the grinding burn area, and realizing the three-dimensional detection with sub-millimeter accuracy.

[0059] In the registration of the three-dimensional point cloud and the pixel points in the temperature matrix, the iterative closest point algorithm or the feature point matching algorithm is used for registration.

[0060] On the other hand, the present application provides an infrared pulse thermal radiation grinding burn nondestructive detection system for realizing the infrared pulse thermal radiation grinding burn nondestructive detection method, comprising:

[0061] The industrial robot is provided with an induction coil, an infrared thermal imager and a depth camera at the end, and is used to adjust the posture of the induction coil, the infrared thermal imager and the depth camera; an excitation signal is input into the induction coil, and the magnetic field generated by the induction coil completely covers the measured area of the part, and generates an induced pulse eddy current to heat the measured area of the part; the infrared thermal imager and the depth camera are used to acquire the thermal response temperature matrix of the measured area and the three-dimensional point cloud of the measured area;

[0062] The thermal response model construction module is used to acquire the surface temperature from the thermal response temperature matrix of the measured area, and to construct a thermal response model in combination with the material conductivity, thermal conductivity and emissivity of the part and the surface temperature;

[0063] The burn discrimination function construction module is used to extract the time sequence temperature curve of the temperature rise when the measured area is heated, and the time sequence temperature curve of the natural cooling stage when the eddy current heat generation is stopped, to construct a grinding burn discrimination function, and to output the determination result of whether the part has a grinding burn area;

[0064] The grinding burn area positioning module is used to convert the grinding burn area in the infrared thermal imager coordinate system to the depth camera when the part has a grinding burn area, to acquire the position of the grinding burn area in the world coordinate system.

[0065] As Figure 1As shown, the inductive coil 3, the infrared thermal imager 4 and the depth camera 5 are configured at the end joint of the industrial robot 1, the excitation signal is generated by using the excitation signal generating device 2 to drive the inductive coil to inductively heat the parts; the image data obtained by the infrared thermal imager 4 and the depth camera 5 is sent to the workstation 6 for processing. The process of the present application will be described below in conjunction with the embodiments.

[0066] Embodiment: The experimental object is a grinding burn GCr15 bearing ring part, specifically a bearing ring with an outer diameter of 65mm, an inner diameter of 45mm and a thickness of 4mm, the surface of which is ground and locally has burn defects. The above hardware devices are configured, and the industrial robot 1 at the end is loaded with 10kg. The pulse eddy current inductive device adopts a modulated rectangular pulse with a maximum frequency of 1MHz, the infrared thermal imager has a resolution of 640*480 and a minimum identification accuracy of 0.01K, and the workstation 6 integrates curvature detection algorithm, multi-scale wavelet transform algorithm and other contents. The curvature detection algorithm is used to find the temperature inflection point on the curve by taking the second derivative according to the time sequence temperature curve of the temperature rise when the measured area is heated, and the time sequence temperature curve of the natural cooling stage when the eddy current heat stops.

[0067] According to the size of the sample, select a coil of appropriate size, set the constant pulse induction frequency to 30kHz and the induction power to 10kW, adjust the distance between the coil and the sample to an appropriate distance to ensure that the induction magnetic field covers the surface of the sample to generate eddy current heat. Due to the difference in electrical conductivity between the grinding burn area and the normal area, more heat is generated in the burn area. The temperature response curve of the burn area and the normal area obtained by the method of the present application is as shown in Figure 3 As shown in Figure 4 After obtaining the temperature distribution of the burn area, the temperature difference between the burn area and the normal area can be clearly seen, and the contour of the burn area can be clearly detected, Figure 4 The mark 1 in the figure is the burn area, and the mark 2 is the normal area.

[0068] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A non-destructive testing method for infrared pulse thermal radiation grinding burns, characterized in that, Includes the following steps: S1: Integrate the induction coil into the end effector of the industrial robot. Select the appropriate induction coil according to different parts, input the excitation signal to the induction coil, so that the magnetic field of the induction coil completely covers the test area of ​​the part, and induce pulse eddy currents in the test part for heating. S2: Infrared thermal imager and depth camera are synchronously integrated into the end effector of industrial robot to obtain thermal response temperature matrix of the measured area of ​​the component and three-dimensional point cloud of the measured area. S3: Construct a thermal response model for the material conductivity, thermal conductivity, emissivity, and surface temperature of the component; Step S3 involves obtaining the surface temperature of the material from the thermal response temperature matrix of the measured area acquired by the infrared thermal imager, and calculating the Joule heat generated per unit time locally based on the surface temperature and thermal conductivity. The relationship between local Joule heat generated per unit time and conductivity, current density and pulse duration was constructed. The surface temperature of the material in the grinding burn area is T(x, y, t), and the thermal diffusion process satisfies the following equation: in C is the thermal diffusivity, ρ is the material density of the component, and C is the thermal diffusivity. p Specific heat capacity of the material; The temperature gradient is represented by the following equation: When heating is stopped, the heat dissipation from the grinding burn area is slow, and the time function of the surface temperature is fitted by an exponential function as: T(x, y, t) = T0 + Ae -bt T0 is the ambient temperature, A is the temperature assignment, b is the cooling time constant, and Q is the Joule heat of the induced eddy current per unit time in the local area. The Joule heat Q of the induced eddy current per unit time is: Q = σ(x,y)·|J(x,y,t)| 2 ·Δt, σ(x,y) are the conductivity at the local location (x,y); J(x,y,t) is the current density; Surface radiant power is expressed as: P t (x, y, t) = ε(x, y)·δ b ·T(x, y, t) 4 δ b ε is the Stefan-Boltzmann constant, and ε(x,y) is the emissivity at the local position (x,y); The thermal diffusion equation and the surface emission power function are combined as a thermal response model; S4: Extract the time-series temperature curve of the temperature rise during heating of the tested area, and the time-series temperature curve of the natural cooling stage after the eddy current heat generation stops, construct the grinding burn discrimination function, and determine whether there is a grinding burn area. Step S4 involves constructing a grinding burn discrimination function based on the weighting functions of the heating stage and the natural cooling stage, combined with the surface temperature of the material. A thermal response difference threshold is set. When the value of the grinding burn discrimination function is greater than the thermal response difference threshold, it is determined that the component has a grinding burn area. Weighting function Where c and d are normalization coefficients, t m t1 is the peak temperature, t2 is the start time of heating, t2 is the end time of natural cooling, λ1 and λ2 are the weighting coefficients for heating and natural cooling. The weighting function is the same as the heating stage weighting function in the heating stage; the weighting function is the same as the natural cooling stage weighting function in the natural cooling stage. After obtaining the weighting function, a grinding burn discrimination function S(x, y) is further proposed: This is used to quantify the difference in thermal response between the grinding burn area and the normal area. The threshold S0 of the difference in normal thermal response is calibrated by experiment. When S(x,y)>S0, it is considered that there is a burn area. The larger the value of the grinding burn discrimination function S(x,y), the more severe the grinding burn is considered. When S(x,y)≤S0, it is considered that there is no burn in the current area. S5: Calibrate the infrared thermal imager and depth camera, project the grinding burn area in the coordinate system of the infrared thermal imager onto the 3D point cloud of the depth camera, obtain the position of the grinding burn area in the world coordinate system, and realize the detection and positioning of the grinding burn area.

2. The method for non-destructive testing of grinding burns using infrared pulse thermal radiation according to claim 1, characterized in that, The pulsed eddy current heating is a non-contact excitation method, and the excitation signal of the induction coil is a periodic frequency conversion signal or a high-frequency fixed frequency signal.

3. The method for non-destructive testing of grinding burns using infrared pulse thermal radiation according to claim 2, characterized in that, The excitation signal waveform of the induction coil is a modulated rectangular pulse, an exponentially decaying sawtooth wave, or a dual-frequency sine wave, with a frequency range of 1kHz to 1MHz.

4. The method for non-destructive testing of grinding burns using infrared pulse thermal radiation according to claim 2, characterized in that, The overall temperature rise of the heated components does not exceed 30 degrees Celsius to ensure that the tested components are not damaged.

5. The method for non-destructive testing of grinding burns using infrared pulse thermal radiation according to claim 1, characterized in that, Step S5 also includes extracting local features of the transient signal of the material's surface temperature through multi-scale wavelet transform, separating transient signal components of different temperatures, expanding the thermal response difference between the grinding burn area and the normal area, enhancing the contrast of the burn area, and then converting the grinding burn area in the infrared thermal imager coordinate system to the depth camera.

6. The method for non-destructive testing of grinding burns using infrared pulse thermal radiation according to claim 5, characterized in that, Step S5, which involves obtaining the position of the grinding burn area in the world coordinate system, is achieved by acquiring the three-dimensional point cloud of the part using a depth camera, combining it with the temperature matrix of an infrared thermal imager, registering the three-dimensional point cloud with the pixels in the temperature matrix, mapping the temperature matrix to three-dimensional space, extracting the spatial coordinates of the grinding burn area, and locating the burn boundary through thermal image threshold segmentation, thereby realizing the localization of the grinding burn area.

7. The method for non-destructive testing of grinding burns using infrared pulse thermal radiation according to claim 6, characterized in that, The 3D point cloud is registered with the pixels in the temperature matrix using either the iterative nearest point algorithm or the feature point matching algorithm.

8. An infrared pulse thermal radiation grinding burn non-destructive testing system, used to implement the infrared pulse thermal radiation grinding burn non-destructive testing method according to any one of claims 1-7, characterized in that, include: Industrial robots are equipped with induction coils, infrared thermal imagers, and depth cameras at their end effectors to adjust the posture of the induction coils, infrared thermal imagers, and depth cameras. An excitation signal is input into the induction coil, and the magnetic field generated by the induction coil completely covers the measured area of ​​the component, generating induced pulse eddy currents to heat the measured area of ​​the component; an infrared thermal imager and a depth camera are used to acquire the thermal response temperature matrix of the measured area and the three-dimensional point cloud of the measured area. The thermal response model construction module is used to obtain the surface temperature from the thermal response temperature matrix of the measured area, and construct the thermal response model by combining the material conductivity, thermal conductivity, emissivity and surface temperature of the components. The burn discrimination function construction module is used to extract the time-series temperature curve of the temperature rise during heating of the tested area, as well as the time-series temperature curve of the natural cooling stage after the eddy current heat generation stops, to construct the grinding burn discrimination function and output the judgment result of whether there is a grinding burn area in the part. The grinding burn area positioning module is used to convert the grinding burn area in the infrared thermal imager coordinate system to the depth camera when there is a grinding burn area on the part, so as to obtain the position of the grinding burn area in the world coordinate system.

Images