CN111982968A - Adaptive magnetic saturation eddy current infrared evaluation method for magnetic management based on controllable excitation - Google Patents
Adaptive magnetic saturation eddy current infrared evaluation method for magnetic management based on controllable excitation Download PDFInfo
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Abstract
基于可控激励的磁管理自适应磁饱和涡流红外评价方法，通过计算机控制程序控制器同步触发电流源、感应加热器和红外热像仪；电流源激励磁饱和线圈产生恒定磁场，铁磁性材料在恒定磁场中达到磁饱和；感应加热器给加热线圈施加一个脉冲电流激励，被检测铁磁性材料在加热线圈的作用下产生焦耳热，从而引起材料表面温度的变化；红外热像仪采集温度的变化，通过分析采集到的图像序列实现对铁磁性材料的无损评价；检测完成后，利用电流源激励磁饱和线圈产生交变磁场，铁磁性材料被逐步消磁并恢复其原有的磁属性状态。本发明方法中的磁场可以在时间、强度和形态三方面实现有效的磁管理，对铁磁性材料的检测深度更大，具有广泛的应用前景。
Based on the magnetic management adaptive magnetic saturation eddy current infrared evaluation method based on controllable excitation, the current source, the induction heater and the infrared thermal imager are triggered synchronously through the computer control program controller; the current source excites the magnetic saturation coil to generate a constant magnetic field, and the ferromagnetic material is in the The magnetic saturation is reached in a constant magnetic field; the induction heater applies a pulse current excitation to the heating coil, and the ferromagnetic material to be detected generates Joule heat under the action of the heating coil, which causes the change of the surface temperature of the material; the infrared thermal imager collects the temperature change , the non-destructive evaluation of ferromagnetic materials is realized by analyzing the acquired image sequence; after the detection is completed, the current source is used to excite the magnetic saturation coil to generate an alternating magnetic field, and the ferromagnetic material is gradually demagnetized and restored to its original state of magnetic properties. The magnetic field in the method of the invention can realize effective magnetic management in terms of time, intensity and form, has a larger detection depth for ferromagnetic materials, and has wide application prospects.
Description
技术领域technical field
本发明涉及铁磁性材料缺陷脉冲涡流红外无损检测领域，具体涉及一种基于可控激励的磁管理自适应磁饱和涡流红外评价方法。The invention relates to the field of pulsed eddy current infrared nondestructive testing of defects in ferromagnetic materials, in particular to a magnetic management adaptive magnetic saturation eddy current infrared evaluation method based on controllable excitation.
背景技术Background technique
铁磁性材料是现代工农业生产的主要支柱材料之一，铁磁性材料的产品是表示一个国家经济发展程度的指标，其需求则能粗略体现一个国家的国民生活水平。作为一种基础功能材料，铁磁性材料应用于生活的方方面面，目前铁磁性材料主要应用于电信、电机、电视机和计算机的存储设备等方面。铁磁性材料与工件内的各种缺陷是现代工业设备、产品和武器的严重隐患,所以,在工业生产中,必须对铁磁性材料进行严格的检测。Ferromagnetic material is one of the main pillar materials of modern industrial and agricultural production. The product of ferromagnetic material is an indicator of the economic development level of a country, and its demand can roughly reflect the living standard of a country. As a basic functional material, ferromagnetic materials are used in all aspects of life. At present, ferromagnetic materials are mainly used in telecommunications, motors, televisions and computer storage devices. Various defects in ferromagnetic materials and workpieces are serious hidden dangers of modern industrial equipment, products and weapons. Therefore, in industrial production, ferromagnetic materials must be strictly tested.
脉冲涡流红外是一种新兴的无损检测技术，具有非接触、观测范围大和分辨率高等优点。脉冲涡流红外无损检测技术通过激励线圈中的高频激励电流对物体施加交变磁场，再通过红外热像仪采集物体表面温度变化的图像序列，最后通过分析温度图像序列即可对物体进行无损检测和无损评估。Pulsed eddy current infrared is an emerging non-destructive testing technology, which has the advantages of non-contact, large observation range and high resolution. The pulsed eddy current infrared non-destructive testing technology applies an alternating magnetic field to the object through the high-frequency excitation current in the excitation coil, and then collects the image sequence of the surface temperature change of the object through an infrared thermal imager. Finally, the object can be non-destructively tested by analyzing the temperature image sequence. and nondestructive evaluation.
由于脉冲涡流红外采用的激励频率非常高，而铁磁性材料的相对磁导率又很大，所以利用脉冲涡流红外无损检测方法对铁磁性材料进行检测的过程中，涡流的肌肤深度较小，所以铁磁性材料中相对较深位置处的缺陷无法被检出。铁磁性材料在一定强度的外加磁场中会达到磁饱和状态，即相对磁导率会减小。此时，利用脉冲涡流红外无损检测方法检测处于磁饱和状态下的铁磁性材料将能检测到更深位置处的缺陷。Since the excitation frequency used by pulsed eddy current infrared is very high, and the relative permeability of ferromagnetic materials is very large, in the process of using pulsed eddy current infrared nondestructive testing method to detect ferromagnetic materials, the skin depth of eddy current is small, so Defects at relatively deep locations in ferromagnetic materials cannot be detected. Ferromagnetic materials will reach a state of magnetic saturation in a certain strength of an external magnetic field, that is, the relative permeability will decrease. At this time, using the pulsed eddy current infrared nondestructive testing method to detect ferromagnetic materials in a state of magnetic saturation will be able to detect defects at deeper positions.
发明内容SUMMARY OF THE INVENTION
为了达到上述利用脉冲涡流红外无损检测方法测量铁磁性材料的目的，本发明的目的在于提供一种基于可控激励的磁管理自适应磁饱和涡流红外评价方法，该方法实验装置由计算机、程序控制器、感应加热器、加热头、加热线圈、冷却装置、电流源、磁饱和线圈和红外热像仪组成；实现该方法时，首先通过计算机控制程序控制器同步触发电流源、感应加热器和红外热像仪；电流源激励磁饱和线圈产生恒定磁场，铁磁性材料在恒定磁场中达到磁饱和；感应加热器给加热线圈施加一个脉冲电流激励，被检测铁磁性材料在加热线圈的作用下产生焦耳热，从而引起材料表面温度的变化；红外热像仪采集温度的变化，通过分析采集到的图像序列实现对铁磁性材料的无损评价。最后检测完成后，利用电流源激励磁饱和线圈产生交变磁场，铁磁性材料在此交变磁场中被逐步消磁并恢复其原有的磁属性状态。相较于传统的脉冲涡流红外无损检测方法，本发明方法中的磁场可以在时间、强度和形态三方面实现有效的磁管理，对铁磁性材料的检测深度更大，具有广泛的应用前景。In order to achieve the above purpose of measuring ferromagnetic materials by the pulsed eddy current infrared nondestructive testing method, the purpose of the present invention is to provide a magnetic management adaptive magnetic saturation eddy current infrared evaluation method based on controllable excitation, and the experimental device of the method is controlled by a computer and a program It consists of a device, an induction heater, a heating head, a heating coil, a cooling device, a current source, a magnetic saturation coil and an infrared thermal imager; when implementing this method, the current source, the induction heater and the infrared camera are firstly triggered synchronously by the computer control program controller. Thermal imager; the current source excites the magnetic saturation coil to generate a constant magnetic field, and the ferromagnetic material reaches magnetic saturation in the constant magnetic field; the induction heater applies a pulse current excitation to the heating coil, and the detected ferromagnetic material generates Joules under the action of the heating coil The thermal imager collects the temperature change, and the non-destructive evaluation of the ferromagnetic material is realized by analyzing the acquired image sequence. After the final detection is completed, the current source is used to excite the magnetic saturation coil to generate an alternating magnetic field, and the ferromagnetic material is gradually demagnetized in this alternating magnetic field and restores its original magnetic property state. Compared with the traditional pulsed eddy current infrared non-destructive testing method, the magnetic field in the method of the present invention can realize effective magnetic management in terms of time, strength and form, and has a greater detection depth for ferromagnetic materials and has broad application prospects.
为达到以上目的，本发明采用如下技术方案：To achieve the above object, the present invention adopts the following technical solutions:
基于可控激励的磁管理自适应磁饱和涡流红外评价方法，用于对铁磁性材料中的缺陷进行定位和定量评价，包括如下步骤：An adaptive magnetic saturation eddy current infrared evaluation method based on controllable excitation is used to locate and quantitatively evaluate defects in ferromagnetic materials, including the following steps:
步骤1：搭建实验装置，该实验装置由计算机、程序控制器、感应加热器、加热头、加热线圈、冷却装置、电流源、磁饱和线圈和红外热像仪组成；其中计算机控制程序控制器并接收红外热像仪采集的图像序列，程序控制器同步触发感应加热器、电流源和红外热像仪；感应加热器接收到触发信号后施加脉冲激励电流给与加热头相连的加热线圈，加热线圈和磁饱和线圈放置于铁磁性材料上方，同时冷却装置对感应加热器、加热头和加热线圈进行冷却；电流源接收到触发信号的同时给磁饱和线圈施加一个方波电流激励，在方波电流激励时间内，磁饱和线圈会在空间产生恒定磁场；红外热像仪接收到来自程序控制器的触发信号后开始采集铁磁性材料的图像序列并将图像序列传输给计算机；Step 1: Build an experimental device, which consists of a computer, a program controller, an induction heater, a heating head, a heating coil, a cooling device, a current source, a magnetic saturation coil and an infrared thermal imager; the computer controls the program controller and After receiving the image sequence collected by the infrared thermal imager, the program controller triggers the induction heater, the current source and the infrared thermal imager synchronously; after the induction heater receives the trigger signal, it applies a pulse excitation current to the heating coil connected to the heating head, and the heating coil The magnetic saturation coil and the magnetic saturation coil are placed above the ferromagnetic material, and the cooling device cools the induction heater, the heating head and the heating coil; the current source receives the trigger signal and applies a square wave current excitation to the magnetic saturation coil. During the excitation time, the magnetic saturation coil will generate a constant magnetic field in the space; after receiving the trigger signal from the program controller, the infrared thermal imager starts to collect the image sequence of the ferromagnetic material and transmit the image sequence to the computer;
步骤2：首先打开冷却装置并将磁饱和线圈和加热线圈放置于铁磁性材料上方，然后对红外热像仪进行温度校准，校准完毕后进行调焦操作，保证铁磁性材料在红外热像仪中的图像清晰，同时红外热像仪与加热线圈之间的距离和红外热像仪与磁饱和线圈之间的距离均必须大于500mm，防止加热线圈产生的磁场和磁饱和线圈产生的磁场影响红外热像仪的性能；Step 2: First turn on the cooling device and place the magnetic saturation coil and the heating coil above the ferromagnetic material, then calibrate the temperature of the infrared thermal imager. After the calibration, perform the focusing operation to ensure that the ferromagnetic material is in the infrared thermal imager. At the same time, the distance between the infrared thermal imager and the heating coil and the distance between the infrared thermal imager and the magnetic saturation coil must be greater than 500mm, so as to prevent the magnetic field generated by the heating coil and the magnetic field generated by the magnetic saturation coil from affecting the infrared heat. camera performance;
步骤3：在程序控制器中先设置电流源给磁饱和线圈施加的电流的参数，包括：激励波形、电流幅值和激励时间；其中激励波形由磁饱和线圈产生磁场的形式决定，电流幅值由铁磁性材料磁饱和状态需要施加的外磁场强度决定，激励时间与感应加热器的激励时间相同，最终实现磁场的自适应管理。然后设置感应加热器给加热线圈施加的激励电流的参数，包括：电流幅值、激励频率和激励时间；最后在程序控制器中设置红外热像仪采集图像序列的参数，包括：采样频率和总的采集时间；总的采集时间必须大于激励时间；Step 3: First set the parameters of the current applied by the current source to the magnetic saturation coil in the program controller, including: excitation waveform, current amplitude and excitation time; the excitation waveform is determined by the form of the magnetic field generated by the magnetic saturation coil, and the current amplitude It is determined by the strength of the external magnetic field that needs to be applied in the magnetic saturation state of the ferromagnetic material, and the excitation time is the same as the excitation time of the induction heater, and finally the self-adaptive management of the magnetic field is realized. Then set the parameters of the excitation current applied by the induction heater to the heating coil, including: current amplitude, excitation frequency and excitation time; finally, set the parameters of the image sequence captured by the infrared thermal imager in the program controller, including: sampling frequency and total acquisition time; the total acquisition time must be greater than the excitation time;
步骤4：用计算机控制程序控制器同时给感应加热器、电流源和红外热像仪一个触发信号；电流源接收到触发信号的同时给磁饱和线圈施加一个方波电流激励，在方波电流激励时间内，磁饱和线圈会在空间产生恒定磁场。感应加热器接收到触发信号的同时给加热线圈施加一个脉冲激励电流，激励波形表达式如式(1)所示；与此同时，当红外热像仪接收到来自程序控制器发出的触发信号时，开始采集铁磁性材料表面温度的变化。Step 4: Use the computer to control the program controller to give a trigger signal to the induction heater, the current source and the infrared thermal imager at the same time; when the current source receives the trigger signal, it applies a square wave current excitation to the magnetic saturation coil. Over time, the magnetically saturated coil generates a constant magnetic field in space. When the induction heater receives the trigger signal, a pulse excitation current is applied to the heating coil, and the excitation waveform expression is shown in formula (1); at the same time, when the infrared thermal imager receives the trigger signal from the program controller , and began to collect the changes in the surface temperature of the ferromagnetic material.
I(t)＝I0×(1-e-10000t)×sin(ωt) (1)I(t)=I 0 ×(1-e -10000t )×sin(ωt) (1)
式中：I(t)表示t时刻的激励电流值，I0表示脉冲激励电流的幅值，ω为脉冲激励电流的角频率，t为时间；In the formula: I(t) represents the excitation current value at time t, I 0 represents the amplitude of the pulse excitation current, ω is the angular frequency of the pulse excitation current, and t is the time;
加热线圈中的脉冲电流会在空间激发交变磁场，铁磁性材料在交变磁场中会产生涡流，在磁饱和线圈产生的恒定磁场的作用下，铁磁性材料达到磁饱和状态，铁磁性材料的磁导率降低，从而导致涡流在铁磁性材料中的渗透深度增大；根据焦耳定律可知，部分涡流会在材料内部由电能转化为热能，且产生的焦耳热Q正比于涡流密度Js和电场密度E：The pulse current in the heating coil will excite the alternating magnetic field in space, and the ferromagnetic material will generate eddy current in the alternating magnetic field. Under the action of the constant magnetic field generated by the magnetic saturation coil, the ferromagnetic material will reach the magnetic saturation state, and the The magnetic permeability decreases, which leads to an increase in the penetration depth of the eddy current in the ferromagnetic material; according to Joule's law, part of the eddy current will be converted into heat energy from electrical energy inside the material, and the generated Joule heat Q is proportional to the eddy current density J s and the electric field Density E:
式中：σ表示铁磁性材料的电导率；Js表示涡流密度；E表示电场强度，其表达式由式(3)表示；In the formula: σ represents the electrical conductivity of the ferromagnetic material; J s represents the eddy current density; E represents the electric field strength, and its expression is expressed by equation (3);
式中：A表示磁矢位，可由式(4)得到；t表示时间；In the formula: A represents the magnetic vector potential, which can be obtained from formula (4); t represents the time;
式中：μ表示铁磁性材料的磁导率；In the formula: μ represents the permeability of the ferromagnetic material;
由涡流产生的焦耳热Q将会在铁磁性材料内部传播，其传播规律遵循式(5)；The Joule heat Q generated by the eddy current will propagate inside the ferromagnetic material, and its propagation law follows the formula (5);
式中：ρ表示铁磁性材料的密度；Cp表示铁磁性材料的比热容；k表示铁磁性材料的热导率；T表示温度；Q表示焦耳热；In the formula: ρ represents the density of the ferromagnetic material; C p represents the specific heat capacity of the ferromagnetic material; k represents the thermal conductivity of the ferromagnetic material; T represents the temperature; Q represents the Joule heat;
当铁磁性材料表面或内部存在缺陷时，这些缺陷会影响热传导的过程，导致铁磁性材料表面温度分布不均匀，最终会在红外热像仪采集的图像序列中体现出来；由于在磁饱和线圈产生的恒定磁场的作用下，铁磁性材料的相对磁导率减小，涡流的渗透增大，所以热传导的深度更大，从而相比于传统的脉冲涡流红外无损检测方法，本发明方法对更深处缺陷的检测能力增强；When there are defects on the surface or inside of the ferromagnetic material, these defects will affect the process of heat conduction, resulting in uneven temperature distribution on the surface of the ferromagnetic material, which will eventually be reflected in the image sequence collected by the infrared thermal imager; Under the action of the constant magnetic field, the relative permeability of the ferromagnetic material decreases, and the penetration of eddy current increases, so the depth of heat conduction is larger, so compared with the traditional pulsed eddy current infrared nondestructive testing method, the method of the present invention can detect deeper Enhanced defect detection capability;
步骤5：当铁磁性材料的检测过程完成时，由于加热线圈产生的磁场和磁饱和线圈产生的磁饱和磁场的影响，铁磁性材料会被磁化。这时利用电流源给磁饱和线圈施加一个交变电流激励，磁饱和线圈会产生一个交变的磁场，铁磁性材料在此交变磁场中会被逐步消磁，最终使被检铁磁性材料恢复其原有的磁属性状态；Step 5: When the detection process of the ferromagnetic material is completed, the ferromagnetic material will be magnetized due to the influence of the magnetic field generated by the heating coil and the magnetic saturation magnetic field generated by the magnetic saturation coil. At this time, a current source is used to apply an alternating current excitation to the magnetic saturation coil, and the magnetic saturation coil will generate an alternating magnetic field. The ferromagnetic material will be gradually demagnetized in this alternating magnetic field, and finally the tested ferromagnetic material will recover its The original magnetic property state;
步骤6：最后通过红外热像仪采集到的图像序列对铁磁性材料中的缺陷进行定位和定量；由于铁磁性材料表面或内部的缺陷会影响热传导的过程，所以缺陷附近的温度分布与无缺陷部分的温度分布具有较大的差异，通过分析红外热像仪采集到的图像序列上的温度分布云图即可对铁磁性材料中的缺陷进行定位和定量。Step 6: Finally, locate and quantify the defects in the ferromagnetic material through the image sequence collected by the infrared thermal imager; because the defects on the surface or inside of the ferromagnetic material will affect the process of heat conduction, the temperature distribution near the defect is related to the defect-free process. Part of the temperature distribution has a large difference. By analyzing the temperature distribution cloud map on the image sequence collected by the infrared thermal imager, the defects in the ferromagnetic material can be located and quantified.
和现有技术相比，本发明的优点如下：Compared with the prior art, the advantages of the present invention are as follows:
1)本发明提出了一种基于可控激励的磁管理自适应磁饱和脉冲涡流红外无损评价方法，与传统铁磁性材料测量方法相比，本发明方法具有非接触、观测范围大、分辨率高、可控磁场可以在时间、强度和形态三方面实现有效的磁管理的优点；1) The present invention proposes a magnetic management adaptive magnetic saturation pulse eddy current infrared nondestructive evaluation method based on controllable excitation. Compared with the traditional ferromagnetic material measurement method, the method of the present invention has the advantages of non-contact, large observation range and high resolution. , Controllable magnetic field can achieve the advantages of effective magnetic management in terms of time, strength and morphology;
2)与传统脉冲涡流红外无损检测方法相比，本发明方法对铁磁性材料的检测深度更大，实验系统搭建简便，操作简单，具有广泛的应用前景。2) Compared with the traditional pulsed eddy current infrared nondestructive testing method, the method of the present invention has a larger detection depth for ferromagnetic materials, the experimental system is simple to build, the operation is simple, and has a wide application prospect.
3)本发明中，检测结束后，通过对磁饱和线圈施加交变电流，产生的交变磁场可以使被检对象逐步消磁，恢复其原有的磁属性状态，不会由于磁饱和过程而改变被检铁磁性材料的磁属性。3) In the present invention, after the detection is completed, by applying alternating current to the magnetic saturation coil, the generated alternating magnetic field can gradually demagnetize the detected object and restore its original magnetic property state, which will not be changed due to the magnetic saturation process. Magnetic properties of the ferromagnetic material being examined.
附图说明Description of drawings
图1为本发明中应用的基于可控激励的磁管理自适应磁饱和脉冲涡流红外无损评价系统各组件连接示意图。FIG. 1 is a schematic diagram of the connection of each component of the controllable excitation-based magnetic management adaptive magnetic saturation pulse eddy current infrared nondestructive evaluation system applied in the present invention.
图2为铁磁性材料的磁导率和磁场强度的关系示意图。FIG. 2 is a schematic diagram showing the relationship between the magnetic permeability and the magnetic field strength of the ferromagnetic material.
图3(a)为本发明中被测铁磁性材料试件中缺陷对涡流场分布的扰动示意图俯视图。Fig. 3(a) is a schematic top view of the disturbance of the eddy current field distribution by the defects in the ferromagnetic material specimen to be tested in the present invention.
图3(b)为本发明中被测铁磁性材料试件中缺陷对涡流场分布的扰动示意图主视图。Fig. 3(b) is a schematic front view of the disturbance of the eddy current field distribution by the defects in the ferromagnetic material specimen to be tested in the present invention.
图4(a)、图4(b)和图4(c)为铁磁性材料被消磁的过程示意图，分别为初始状态、被磁化和消磁示意图。4(a), 4(b) and 4(c) are schematic diagrams of the process of demagnetization of ferromagnetic materials, which are schematic diagrams of initial state, magnetization and demagnetization, respectively.
具体实施方式Detailed ways
下面结合附图和具体实施方式对本发明做进一步详细说明：The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments:
对于图1中所示的铁磁性材料被测试件，本发明方法的检测步骤为：如图1所示该方法采用的实验装置由计算机、程序控制器、感应加热器、冷却装置、加热头、加热线圈、电流源、磁饱和线圈和红外热像仪组成；实现该方法时，首先通过计算机控制程序控制器同步触发电流源、感应加热器和红外热像仪，电流源接收到触发信号时给磁饱和线圈施加一个恒定电流激励，在恒定电流激励时间内，磁饱和线圈会在空间产生恒定磁场。由图2可知，铁磁性材料的相对磁导率随着磁场强度的增加而减小，最终达到饱和。所以铁磁性材料会在图1中所示的磁饱和线圈产生的磁场中达到磁饱和，铁磁性材料在恒定磁场的作用下会达到磁饱和；感应加热器接收到触发信号时给与加热头相连的加热线圈施加一个脉冲电流激励，被检测铁磁性材料在加热线圈的作用下产生焦耳热，从而引起材料表面温度的变化；当铁磁性材料中存在缺陷时，如图3(a)和图3(b)所示，缺陷会影响涡流的分布，继而影响材料表面温度场的分布，通过红外热像仪采集温度的变化并通过分析采集到的图像序列对铁磁性材料进行无损评价。检测期间冷却装置对感应加热器、加热头和加热线圈分别进行冷却。最后，磁饱和试验完成后，利用电流源给磁饱和线圈施加交变电流，使磁饱和线圈产生交变磁场。如图4(a)、图4(b)和图4(c)所示，在此交变磁场中，铁磁性材料会被消磁并恢复其原有的磁属性状态。相较于传统的脉冲涡流红外无损检测方法，本发明方法中的磁场可以在时间、强度和形态三方面实现有效的磁管理，对铁磁性材料的检测深度更大，具有广泛的应用前景。下面结合具体实施例对本发明作进一步的详细描述。For the test piece of ferromagnetic material shown in Figure 1, the detection steps of the method of the present invention are as follows: as shown in Figure 1, the experimental device used in the method consists of a computer, a program controller, an induction heater, a cooling device, a heating head, The heating coil, the current source, the magnetic saturation coil and the infrared thermal imager are composed; when the method is realized, the current source, the induction heater and the infrared thermal imager are synchronously triggered by the computer control program controller, and when the current source receives the trigger signal, the The magnetic saturation coil applies a constant current excitation. During the constant current excitation time, the magnetic saturation coil will generate a constant magnetic field in space. It can be seen from Figure 2 that the relative permeability of the ferromagnetic material decreases with the increase of the magnetic field strength, and finally reaches saturation. Therefore, the ferromagnetic material will reach magnetic saturation in the magnetic field generated by the magnetic saturation coil shown in Figure 1, and the ferromagnetic material will reach magnetic saturation under the action of a constant magnetic field; when the induction heater receives the trigger signal, it will be connected to the heating head The heating coil is excited by a pulse current, and the ferromagnetic material to be tested generates Joule heat under the action of the heating coil, thereby causing the surface temperature of the material to change; when there are defects in the ferromagnetic material, as shown in Figure 3(a) and Figure 3 As shown in (b), the defect will affect the distribution of eddy currents, which in turn affects the distribution of the temperature field on the surface of the material. The temperature change is collected by an infrared thermal imager and the ferromagnetic material is non-destructively evaluated by analyzing the collected image sequence. During the detection, the cooling device cools the induction heater, the heating head and the heating coil respectively. Finally, after the magnetic saturation test is completed, an alternating current is applied to the magnetic saturation coil using a current source, so that the magnetic saturation coil generates an alternating magnetic field. As shown in Figure 4(a), Figure 4(b) and Figure 4(c), in this alternating magnetic field, the ferromagnetic material is demagnetized and restored to its original state of magnetic properties. Compared with the traditional pulsed eddy current infrared non-destructive testing method, the magnetic field in the method of the present invention can realize effective magnetic management in terms of time, strength and form, and has a greater detection depth for ferromagnetic materials and has broad application prospects. The present invention will be further described in detail below with reference to specific embodiments.
基于可控激励的磁管理自适应磁饱和涡流红外评价方法，其特征在于：包括如下步骤：The magnetic management adaptive magnetic saturation eddy current infrared evaluation method based on controllable excitation is characterized in that: it includes the following steps:
步骤1：如图1所示，搭建实验装置，该实验装置由计算机、程序控制器、感应加热器、加热头、加热线圈、冷却装置、电流源、磁饱和线圈和红外热像仪组成；其中计算机控制程序控制器并接收红外热像仪采集的图像序列，程序控制器同步触发感应加热器、电流源和红外热像仪；感应加热器接收到触发信号后施加脉冲激励电流给与加热头相连的加热线圈，加热线圈和磁饱和线圈放置于铁磁性材料上方，同时冷却装置对感应加热器、加热头和加热线圈进行冷却；电流源接收到触发信号的同时给磁饱和线圈施加一个方波电流激励，在方波电流激励时间内，磁饱和线圈会在空间产生恒定磁场；红外热像仪接收到来自程序控制器的触发信号后开始采集铁磁性材料的图像序列并将图像序列传输给计算机；Step 1: As shown in Figure 1, build an experimental device, which consists of a computer, a program controller, an induction heater, a heating head, a heating coil, a cooling device, a current source, a magnetic saturation coil and an infrared thermal imager; The computer controls the program controller and receives the image sequence collected by the infrared thermal imager. The program controller triggers the induction heater, the current source and the infrared thermal imager synchronously; after the induction heater receives the trigger signal, a pulse excitation current is applied to connect it to the heating head The heating coil, the heating coil and the magnetic saturation coil are placed above the ferromagnetic material, and the cooling device cools the induction heater, the heating head and the heating coil; the current source receives the trigger signal and applies a square wave current to the magnetic saturation coil. Excitation, within the excitation time of the square wave current, the magnetic saturation coil will generate a constant magnetic field in the space; after receiving the trigger signal from the program controller, the infrared thermal imager starts to collect the image sequence of the ferromagnetic material and transmit the image sequence to the computer;
步骤2：首先打开冷却装置并将磁饱和线圈和加热线圈放置于铁磁性材料上方，然后对红外热像仪进行温度校准，校准完毕后进行调焦操作，保证铁磁性材料在红外热像仪中的图像清晰，同时红外热像仪与加热线圈之间的距离和红外热像仪与磁饱和线圈之间的距离均必须大于500mm，防止加热线圈产生的磁场和磁饱和线圈产生的磁场影响红外热像仪的性能；Step 2: First turn on the cooling device and place the magnetic saturation coil and the heating coil above the ferromagnetic material, then calibrate the temperature of the infrared thermal imager. After the calibration, perform the focusing operation to ensure that the ferromagnetic material is in the infrared thermal imager. At the same time, the distance between the infrared thermal imager and the heating coil and the distance between the infrared thermal imager and the magnetic saturation coil must be greater than 500mm, so as to prevent the magnetic field generated by the heating coil and the magnetic field generated by the magnetic saturation coil from affecting the infrared heat. camera performance;
步骤3：在程序控制器中先设置电流源给磁饱和线圈施加的电流的参数，包括：激励波形、电流幅值和激励时间；其中激励波形由磁饱和线圈产生磁场的形式决定，电流幅值由铁磁性材料磁饱和状态需要施加的外磁场强度决定，激励时间与感应加热器的激励时间相同，最终实现磁场的自适应管理。然后设置感应加热器给加热线圈施加的激励电流的参数，包括：电流幅值、激励频率和激励时间。最后在程序控制器中设置红外热像仪采集图像序列的参数，包括：采样频率和总的采集时间；总的采集时间必须大于激励时间；Step 3: First set the parameters of the current applied by the current source to the magnetic saturation coil in the program controller, including: excitation waveform, current amplitude and excitation time; the excitation waveform is determined by the form of the magnetic field generated by the magnetic saturation coil, and the current amplitude It is determined by the strength of the external magnetic field that needs to be applied in the magnetic saturation state of the ferromagnetic material, and the excitation time is the same as the excitation time of the induction heater, and finally the self-adaptive management of the magnetic field is realized. Then set the parameters of the excitation current applied by the induction heater to the heating coil, including: current amplitude, excitation frequency and excitation time. Finally, set the parameters of the infrared thermal imager to collect the image sequence in the program controller, including: the sampling frequency and the total acquisition time; the total acquisition time must be greater than the excitation time;
步骤4：用计算机控制程序控制器同时给感应加热器、电流源和红外热像仪一个触发信号。电流源接收到触发信号的同时给磁饱和线圈施加一个方波电流激励，在方波电流激励时间内，磁饱和线圈会在空间产生恒定磁场。感应加热器接收到触发信号的同时给加热线圈施加一个脉冲激励电流，激励波形表达式如式(1)所示；与此同时，当红外热像仪接收到来自程序控制器发出的触发信号时，开始采集铁磁性材料表面温度的变化。Step 4: Use the computer to control the program controller to give a trigger signal to the induction heater, the current source and the infrared thermal imager at the same time. When the current source receives the trigger signal, it applies a square wave current excitation to the magnetic saturation coil. During the excitation time of the square wave current, the magnetic saturation coil will generate a constant magnetic field in space. When the induction heater receives the trigger signal, a pulse excitation current is applied to the heating coil, and the excitation waveform expression is shown in formula (1); at the same time, when the infrared thermal imager receives the trigger signal from the program controller , and began to collect the changes in the surface temperature of the ferromagnetic material.
I(t)＝I0×(1-e-10000t)×sin(ωt) (1)I(t)=I 0 ×(1-e -10000t )×sin(ωt) (1)
式中：I(t)表示t时刻的激励电流值，I0表示脉冲激励电流的幅值，ω为脉冲激励电流的角频率，t为时间；In the formula: I(t) represents the excitation current value at time t, I 0 represents the amplitude of the pulse excitation current, ω is the angular frequency of the pulse excitation current, and t is the time;
加热线圈中的脉冲电流会在空间激发交变磁场，铁磁性材料在交变磁场中会产生涡流。在磁饱和线圈产生的恒定磁场的作用下，铁磁性材料达到磁饱和状态，铁磁性材料的磁导率降低，从而导致涡流在铁磁性材料中的渗透深度增大。根据焦耳定律可知，部分涡流会在材料内部由电能转化为热能，且产生的焦耳热Q正比于涡流密度Js和电场密度E：The pulsed current in the heating coil excites an alternating magnetic field in space, and the ferromagnetic material generates eddy currents in the alternating magnetic field. Under the action of the constant magnetic field generated by the magnetic saturation coil, the ferromagnetic material reaches a state of magnetic saturation, and the magnetic permeability of the ferromagnetic material decreases, resulting in an increase in the penetration depth of eddy currents in the ferromagnetic material. According to Joule's law, part of the eddy current will be converted from electrical energy to heat energy inside the material, and the generated Joule heat Q is proportional to the eddy current density J s and the electric field density E:
式中：σ表示铁磁性材料的电导率；Js表示涡流密度；E表示电场强度，其表达式由式(3)表示。In the formula: σ represents the electrical conductivity of the ferromagnetic material; J s represents the eddy current density; E represents the electric field strength, and its expression is represented by the formula (3).
式中：A表示磁矢位，可由式(4)得到；t表示时间。In the formula: A represents the magnetic vector potential, which can be obtained by formula (4); t represents the time.
式中：μ表示铁磁性材料的磁导率；In the formula: μ represents the permeability of the ferromagnetic material;
由涡流产生的焦耳热Q将会在铁磁性材料内部传播，其传播规律遵循式(5)。The Joule heat Q generated by the eddy current will propagate inside the ferromagnetic material, and its propagation law follows the formula (5).
式中：ρ表示铁磁性材料的密度；Cp表示铁磁性材料的比热容；k表示铁磁性材料的热导率；T表示温度；Q表示焦耳热。In the formula: ρ represents the density of the ferromagnetic material; C p represents the specific heat capacity of the ferromagnetic material; k represents the thermal conductivity of the ferromagnetic material; T represents the temperature; Q represents the Joule heat.
当铁磁性材料表面或内部存在缺陷时，这些缺陷会影响热传导的过程，导致铁磁性材料表面温度分布不均匀，最终会在红外热像仪采集的图像序列中体现出来。由于在磁饱和线圈产生的恒定磁场的作用下，铁磁性材料的相对磁导率减小，涡流的渗透增大，所以热传导的深度更大，从而相比于传统的脉冲涡流红外无损检测方法，本发明方法对更深处缺陷的检测能力增强。When there are defects on the surface or inside of ferromagnetic materials, these defects will affect the process of heat conduction, resulting in uneven temperature distribution on the surface of ferromagnetic materials, which will eventually be reflected in the image sequence collected by the infrared thermal imager. Under the action of the constant magnetic field generated by the magnetic saturation coil, the relative permeability of the ferromagnetic material decreases and the penetration of eddy current increases, so the depth of heat conduction is larger, so compared with the traditional pulsed eddy current infrared nondestructive testing method, The detection ability of the method of the present invention for deeper defects is enhanced.
步骤5：当铁磁性材料的检测过程完成时，由于加热线圈产生的磁场和磁饱和线圈产生的磁饱和磁场的影响，铁磁性材料会被磁化。这时利用电流源给磁饱和线圈施加一个交变电流激励，磁饱和线圈会产生一个交变的磁场，铁磁性材料在此交变磁场中会被逐步消磁，最终使被检铁磁性材料恢复其原有的磁属性状态。Step 5: When the detection process of the ferromagnetic material is completed, the ferromagnetic material will be magnetized due to the influence of the magnetic field generated by the heating coil and the magnetic saturation magnetic field generated by the magnetic saturation coil. At this time, a current source is used to apply an alternating current excitation to the magnetic saturation coil, and the magnetic saturation coil will generate an alternating magnetic field. The ferromagnetic material will be gradually demagnetized in this alternating magnetic field, and finally the tested ferromagnetic material will recover its The original magnetic property state.
步骤6：最后通过红外热像仪采集到的图像序列对铁磁性材料中的缺陷进行定位和定量；由于铁磁性材料表面或内部的缺陷会影响热传导的过程，所以缺陷附近的温度分布与无缺陷部分的温度分布具有较大的差异，通过分析红外热像仪采集到的图像序列上的温度分布云图即可对铁磁性材料中的缺陷进行定位和定量。Step 6: Finally, locate and quantify the defects in the ferromagnetic material through the image sequence collected by the infrared thermal imager; because the defects on the surface or inside of the ferromagnetic material will affect the process of heat conduction, the temperature distribution near the defect is related to the defect-free process. Part of the temperature distribution has a large difference. By analyzing the temperature distribution cloud map on the image sequence collected by the infrared thermal imager, the defects in the ferromagnetic material can be located and quantified.
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