CN202018442U - Nondestructive detecting system for pulsed magnetic flux leakage defect and stress - Google Patents

Abstract

The utility model relates to a non-destructive detection system for pulse magnetic flux leakage defect and stress, which belongs to the field of non-destructive detection. Including signal generator, power amplifier, excitation coil, Hall sensor, signal amplification circuit, data acquisition card and computer. On the basis of pulse magnetic flux leakage detection, the utility model, aiming at ferromagnetic materials, performs signal processing in sections according to the two stages of pulse excitation, the instantaneous rising period and the continuous high level after rising, and realizes the separation of stress signal and defect signal, respectively. Signal feature extraction and data fusion realize simultaneous online detection of ferromagnetic material surface and subsurface defects, stress, and microstructure state, and realize the identification of hidden defects of ferromagnetic materials and the prediction of unformed defects. It can work reliably for a long time, has high sensitivity, strong anti-interference ability, fast response speed, and is not affected by media such as oil and water pollution.

Description

Nondestructive Testing System for Pulse Flux Leakage Defect and Stress

technical field

The utility model relates to the field of non-destructive detection, in particular to a non-destructive detection system which realizes the separation of defects and stress signals according to pulse excitation signals and realizes the defects and stress of ferromagnetic materials.

Background technique

Magnetic flux leakage detection technology is an important method for non-destructive evaluation of ferromagnetic materials such as pipelines. With the increase of pipelines and the growth of pipeline age, pipeline leakage incidents caused by corrosion, wear, accidental damage and other reasons occur frequently and become more and more serious. Due to the danger and pollution of the transported medium, once an accident occurs, it will cause huge loss of life and property and environmental pollution. Pipeline on-line detection technology is the most widely used and most effective pipeline detection method at present. It uses the principles of magnetic flux leakage, ultrasonic, ray and other flaw detection. The defects of pipe wall or coating: such as deformation, damage, corrosion, perforation, weight loss of pipe wall and thickness change, etc., are detected and analyzed online to obtain accurate and reliable detection data. Compared with X-ray detection technology, magnetic flux leakage detection technology has no radiation hazards to the human body, can work in harsh environments, the equipment price is cheaper, and the technical level requirements for test operations are also lower; compared with ultrasonic detection technology, there is no need to use coupling agent. Pulse magnetic flux leakage detection technology is a new type of magnetic flux leakage detection technology, which can be used to quantitatively detect surface and near-surface cracks. Because it uses pulse as the excitation signal, the excitation signal contains a wide frequency spectrum, so only one scan can detect cracks of different depths on the tested piece.

In order to obtain the required information for complete pipeline structure health detection and life estimation, in addition to the detection and evaluation of defects in the structure, another important parameter that needs to be obtained is the stress state and microstructure state of the structure. The traditional theory of magnetic flux leakage detection is based on the fact that ferromagnetic materials are magnetized under the action of external magnetic field induction. At the material defect, due to the change of magnetic permeability, the magnetic force line is bent, and a part of the magnetic force line leaks out of the material surface to form magnetic flux leakage. It is generally used for defect detection. detection. Using the pulse magnetic flux leakage detection technology, because the pulse can form an alternating magnetic field in the pipeline, the pulse magnetic flux leakage detection technology can form an eddy current in the pipeline. Through a large number of material tensile experiments, the relationship between stress-strain and eddy current signal during loading shows that in the elastic range, the eddy current signal and stress-strain have a good linear relationship. Therefore, the use of pulsed magnetic flux leakage detection technology can effectively detect pipeline defects and stress. According to the rising phase and high level phase of the pulse signal, the signal separation technology is used to separate the magnetic flux leakage signal from the eddy current signal, so as to realize the hidden defect and life evaluation of the pipeline. .

Utility model content

In view of the existing method of steady-state analysis of the test signal using the magnetic flux leakage detection technology, some important information of the signal in the time domain is ignored, and only the defect of the pipeline can be detected, the stress of the pipeline cannot be detected, and the life of the pipeline cannot be evaluated. To solve the problem, the applicant conducted improved research to provide a non-destructive testing system for pulsed magnetic flux leakage defects and stress that uses pulsed magnetic flux leakage technology for nondestructive testing to achieve quantitative and life assessment of pipeline defects.

The technical scheme of the utility model is as follows:

A non-destructive detection system for pulse magnetic flux leakage defects and stress, including a signal generator, a power amplifier, an excitation coil, a Hall sensor, a signal amplification circuit, a data acquisition card and a computer; wherein the output of the signal generator is divided into two circuits, One of the outputs is connected to the input end of the power amplifier, and the output of the power amplifier is connected to the exciting coil wound on the iron core. The Hall sensor is placed in the middle of the exciting coil, and the Hall sensor, the exciting coil and the iron core form a probe and placed on the tested object. Above, the output of the Hall sensor is connected to the data acquisition card through the signal amplification circuit, the other output of the signal generator is directly connected to the data acquisition card, and the output of the data acquisition card is connected to the computer.

The beneficial technical effect of the utility model is:

The utility model aims at ferromagnetic materials (such as pipelines, etc.), utilizes the characteristics of the excitation pulse signal, that is, the two stages of the pulse rising stage and the high level, combines the advantages of the eddy current technology and the magnetic flux leakage technology, and combines the eddy current technology and the magnetic flux leakage technology Combined, through two different stages of the pulse signal, the eddy current signal and the magnetic flux leakage signal are separated. Among them, the eddy current signal can effectively evaluate the stress state of the pipeline, and the magnetic flux leakage signal can realize the quantitative evaluation of defects. Therefore, the pulse magnetic flux leakage detection technology is applied Not only the size of the crack in the pipeline can be detected, but also the stress state of the pipeline can be detected. Therefore, the system can quantitatively detect cracks at different depths in the pipeline structure, and at the same time detect the stress and residual stress of the pipeline, and can predict the pipeline early.

Description of drawings

Fig. 1 is a functional block diagram of the utility model.

Figure 2 is a schematic diagram of the power amplifier circuit.

Figure 3 is a schematic diagram of the signal amplification circuit.

Explanation of reference numerals in Fig. 1: 1. Signal generator; 2. Power amplifier circuit; 3. Excitation coil; 4. Hall sensor; 5. Signal amplifier circuit; 6. Data acquisition card; 7. Computer.

Detailed ways

Below in conjunction with accompanying drawing, the specific embodiment of the present utility model is described further.

As shown in Figure 1, the utility model comprises a signal generator 1, a power amplifier circuit 2, an excitation coil 3, a Hall sensor 4, a signal amplifier circuit 5, a data acquisition card 6 and a computer 7, wherein the output of the signal generator 1 is divided into Two roads are connected, one road is connected to the input of the power amplifier circuit 2, the output of the power amplifier circuit 2 is connected to the excitation coil 3 wound on the iron core, and the output of the Hall sensor 4 is connected to the data acquisition card through the signal amplifier circuit 5 Input; the other way is directly connected with the data acquisition card 6 . The two signals enter the computer 7 through the data acquisition card 6, and the powerful data processing capability of the computer 7 is used to separate the eddy current signal from the magnetic flux leakage signal, so as to achieve the purpose of evaluating the hidden defects and life of the pipeline.

The specific working process of the utility model is as follows: (a) signal generator 1 generates a pulse voltage with adjustable pulse width at a certain frequency, and the voltage drives excitation coil 3 through power amplifier 2; (b) according to the characteristics of the pulse signal, the signal It is divided into two stages: rising section and high level; (c) In the rising section, using the detection principle of eddy current, the instantaneous rising voltage applied to both ends of the excitation coil 3 will induce eddy current to propagate in the pipeline under test, due to the eddy current signal and stress The strain has a good linear relationship, and the induced eddy current signal contains the stress state information of the pipeline; the Hall sensor 4 picks up the signal, and amplifies the signal through the signal amplification circuit 5; the data acquisition card 6 collects the amplified signal , enter the computer 7; (d) the pulse excitation signal enters the high level stage after the rising section, the high level is a stable voltage value, thus the constant high level signal generates a constant magnetic field at both ends of the excitation coil 3, if there is defect, the constant magnetic field will leak from the defect, and the Hall sensor 4 picks up the magnetic flux leakage signal; the magnetic flux leakage signal enters the computer 7 after passing through the signal amplification circuit 5 and the data acquisition card 6 . (e) On the other hand, the pulse signal generated by the signal generator 1 directly enters the data acquisition card 6, and this signal is used as the reference of the segmented signal to segment the amplified signal. (f) Using the powerful data processing capability of the computer 7, the first signal is separated into eddy current signal and magnetic flux leakage signal through the second signal segment signal, and the signal features are extracted respectively; (g) The computer 7 displays the stress in graphic form And residual stress size, defect size, to realize the evaluation of hidden defects and life of the pipeline.

The frequency of the signal generator 1 in Figure 1 can be in the range of 2~100MHz. The power amplifier 2 is shown in Figure 2. The power amplifier chip LM1875 has five pins, the first and second pins are signal input terminals, and the third The No. 1 pin is connected to the negative voltage, the No. 5 pin is connected to the positive voltage, and the No. 4 pin outputs the signal after power amplification. The amplified power signal is connected to two input ends of the exciting coil 3 for driving the exciting coil 3 . The Hall sensor 4 receives the changing voltage signal, and the signal is output through the signal amplifying circuit 5, and the signal amplifying circuit 5 is shown in FIG. 3 . The data acquisition card 6 collects this signal, and finally enters the computer 7 . The computer 7 records the data and saves it in the form of a file, then processes the data, and finally displays the shape and size of the defect, the stress of the tested piece and the size of the residual stress in the form of graphics.

The working principle of the circuit is as follows: when the power is turned on, the computer runs the program specially written for this system, and the system starts to work after clicking the computer program start button. The signal generator 1 generates a square wave voltage of a certain frequency, and drives the excitation coil 3 through the power amplifier circuit 2. The generated pulse voltage signal is divided into two sections of voltage signals: an instantaneous voltage between 0 and a high level and a high level voltage signal. In the instantaneous voltage stage, the instantaneous eddy current is induced on the tested piece by the instantaneous current generated in the excitation coil 3, and propagates in the pipeline material together with the rapidly decaying magnetic pulse, forming a decaying induction field, Hall sensor 4 Then a series of voltage-time signals are detected, and the signals are amplified and output by the signal amplifier circuit 5, and the data acquisition card 6 collects the signals and transmits them to the computer 7; In the first stage, a constant magnetic field is generated in the excitation coil 3. If there is a defect in the pipeline test piece, the magnetic field signal will leak out through the defect, and the Hall sensor 4 will detect the magnetic field signal. After the signal passes through the amplifier circuit 5, Collected by the data acquisition card 6 into the computer 7 . The other square wave voltage generated by the signal generator 1 directly enters the computer 7 through the data acquisition card 6 as a reference for segmented signals. The computer 7 records the data and saves it in the form of a file, then processes the data, and finally displays the shape and size of the defect, the stress and residual stress of the tested pipeline specimen in the form of graphics.

The above are only preferred implementations of the utility model, and the utility model is not limited to the above examples. It can be understood that other improvements and changes directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present utility model shall be considered to be included in the protection scope of the present utility model.

Claims (1)

1. A non-destructive detection system for pulse magnetic flux leakage defect and stress, characterized in that it includes a signal generator (1), a power amplifier (2), an excitation coil (3), a Hall sensor (4), and a signal amplification circuit ( 5), data acquisition card (6) and computer (7); wherein the output end of the signal generator (1) is divided into two paths, one of which is connected to the input end of the power amplifier (2), and the output of the power amplifier (2) Connect the excitation coil (3) wound on the iron core, the Hall sensor (4) is placed in the middle of the excitation coil (3), the Hall sensor (4) is composed of the excitation coil (3) and the iron core and the probe is placed On the component, the output of the Hall sensor (4) is connected to the data acquisition card (6) through the signal amplification circuit (5), and the other output of the signal generator (1) is directly connected to the data acquisition card (6), and the data acquisition card (6) ) is connected to the computer (7).

Images