阅读说明：本技术 一种基于漏磁信号特征的表面缺陷应力检测系统及方法 (Surface defect stress detection system and method based on magnetic flux leakage signal characteristics ) 是由 刘桐 刘斌 廉正 杨理践 梁宇森 马浩宁 韩崇鹏 任建 张松 年夫强 于 2021-08-05 设计创作，主要内容包括：本发明涉及铁磁性材料缺陷的应力检测技术领域,具体涉及一种基于漏磁信号特征的表面缺陷应力的检测系统及方法。系统由单片机、步进电机、霍尔传感器,滤波放大电路,液晶显示组成；其中单片机与步进电机相连,霍尔传感器与滤波放大电路相连,滤波放大电路与单片机相连,单片机与液晶显示相连。具体方法为首先设定步进电机驱动程序来使仪器匀速行驶,并调用数据采集子程序,即通过利用AD转换将传感器采集到的模拟信号转换为数字信号；然后通过计算路程子程序和应力计算函数子程序,对应力进行计算,并将检测结果送往LCD显示模块进行显示。(The invention relates to the technical field of stress detection of ferromagnetic material defects, in particular to a system and a method for detecting surface defect stress based on magnetic flux leakage signal characteristics. The system consists of a singlechip, a stepping motor, a Hall sensor, a filtering and amplifying circuit and a liquid crystal display; the single chip microcomputer is connected with the stepping motor, the Hall sensor is connected with the filtering and amplifying circuit, the filtering and amplifying circuit is connected with the single chip microcomputer, and the single chip microcomputer is connected with the liquid crystal display. Firstly, setting a driving program of a stepping motor to drive an instrument to run at a constant speed, and calling a data acquisition subprogram, namely converting an analog signal acquired by a sensor into a digital signal by utilizing AD conversion; then, the stress is calculated by the path calculation subprogram and the stress calculation function subprogram, and the detection result is sent to the LCD display module for display.)

1. The utility model provides a surface defect stress detecting system based on magnetic leakage signal characteristic which characterized in that: the stress detection system consists of a singlechip, a stepping motor, a Hall sensor, a filtering amplification circuit and a liquid crystal display; the stepping motor interface of the single chip microcomputer is connected with the motor controller interface of the stepping motor, the detection signal output port of the Hall sensor is connected with the signal input port of the filtering and amplifying circuit, the signal output port of the filtering and amplifying circuit is connected with the detection signal input port of the single chip microcomputer, and the display signal output port of the single chip microcomputer is connected with the input port of the liquid crystal display.

2. The system for detecting surface defect stress based on leakage magnetic signal characteristics according to claim 1, wherein: the Hall sensor is an SS49E linear Hall sensor, the sensor works in a magnetic field environment, the input of the sensor is magnetic induction intensity, the output of the sensor is voltage which is in direct proportion to the input quantity, and the measuring direction of the sensor is tangential.

3. The system for detecting surface defect stress based on leakage magnetic signal characteristics according to claim 1, wherein: the filtering amplifying circuit comprises a filtering circuit and an amplifying circuit; a signal input port of the filtering amplification circuit is connected with a detection signal output port of the Hall sensor through a filtering circuit, and a signal output port of the filtering amplification circuit is connected with a detection signal input port of the singlechip through an amplification circuit; the amplifying module is an LM324 low-power single-power-supply four-channel operational amplifier.

4. The system for detecting surface defect stress based on leakage magnetic signal characteristics according to claim 1, wherein: the single chip microcomputer is an STC89C52 single chip microcomputer; the single chip microcomputer P2.5 is connected with 4 pins of the liquid crystal display, the single chip microcomputer P2.6 is connected with 5 pins of the liquid crystal display, the single chip microcomputer P2.7 is connected with 6 pins of the liquid crystal display, the single chip microcomputers P0.0-P0.7 are connected with 7 th-14 th pins of the liquid crystal display, the single chip microcomputer P1.2 is connected with the output end of the filter amplifying circuit, and the single chip microcomputers P1.3-P1.6 are connected with the output end of the stepping motor.

5. The system for detecting surface defect stress based on leakage magnetic signal characteristics according to claim 1, wherein: the stepping motor rotates 360 degrees to collect magnetic signals for 20 times, namely, the magnetic signals are collected once every time the stepping motor rotates 18 degrees; meanwhile, a permanent magnet is arranged on a rotating shaft of the stepping motor and is parallel to the tangent plane of the tested piece, so that the existence of the horizontal component of the magnetic force line is ensured, and the tangential detection signal effect is optimal.

6. The system for detecting surface defect stress based on leakage magnetic signal characteristics according to claim 1, wherein: the liquid crystal display is a 1602LCD, wherein a 1-pin VSS is a ground power supply, a 2-pin VDD is connected with a 5V positive power supply, a 3-pin VL is a contrast adjusting end of the LCD, the contrast is weakest when the positive power supply is connected, the contrast is highest when the positive power supply is grounded, a 4-pin RS is used for register selection, a data register is selected when the level is high, an instruction register is selected when the level is low, the data register is connected with a single chip P2.5, a 5-pin R/W is a reading and writing signal line, reading operation is carried out when the level is high, and writing operation is carried out when the level is low; when the RS and the R/W are both in a low level, an instruction or a display address can be written in, when the RS is in a low level, the R/W can read a busy signal, when the RS is in a high level, data can be written in and connected with the single chip microcomputer P2.6, when the RS is in a high level, the data can be connected with the single chip microcomputer P2.6, the 6-pin E end is an enabling end, and when the E end jumps from the high level to the low level, the liquid crystal module executes a command and is connected with the single chip microcomputer P2.7; the 7 th to 14 th pins D0 to D7 are 8-bit bidirectional data lines and are connected with the single chip microcomputer P0.0 to P0.7; the 15 th instep light source anode, and the 16 th instep light source cathode.

7. The method for detecting the surface defect stress based on the leakage magnetic signal characteristics as claimed in claim 1, comprising the following specific operation steps:

firstly, the single chip microcomputer drives a stepping motor to rotate by controlling a motor controller so as to enable the instrument to advance at a constant speed;

secondly, a Hall sensor collects a magnetic leakage signal of the tested piece and transmits the magnetic leakage signal into a filter amplifying circuit;

thirdly, the filtering and amplifying circuit receives the analog signal, performs differential amplification, sends the analog signal into a single chip microcomputer and converts the analog signal into a digital signal;

and fourthly, calculating the distance traveled by the stepping motor through a built-in program of the single chip microcomputer, and calculating a stress value according to a formula according to the detected magnetic flux leakage signal so as to display the stress value on a liquid crystal display.

8. The method for detecting the surface defect stress based on the leakage magnetic signal characteristics according to claim 7, wherein the method comprises the following steps:

in the fourth step, the built-in programs of the single chip microcomputer comprise a system calling program, a stepping motor driving program, a data processing main program, a data acquisition processing subprogram, a path calculation function subprogram, a stress calculation function subprogram and an LCD display subprogram;

the stepping motor driving program is used for adjusting the advancing speed of the instrument by adjusting a pulse signal of the stepping motor, and the rotating speed of the stepping motor is in direct proportion to the frequency of the pulse, so that the motor drives the stepping motor to adjust the pulse frequency of the stepping motor by using a delay function, the speed of the instrument is controlled by the delay function, and the speed and the frequency can be combined to obtain the advancing path of the instrument by using magnetic leakage detection data;

the data processing main program firstly calls a data acquisition subprogram to convert an analog signal acquired by the Hall sensor into a digital signal by utilizing analog-to-digital conversion, and tangential data of a detection piece is stored in a storage area with an ADTURN1 as a first address;

the data acquisition subprogram performs analog-to-digital conversion on the analog signals acquired by the sensor through the conversion of an analog-to-digital converter; after initializing the analog-digital converter, enabling the analog-digital converter to be interrupted, starting analog-digital conversion, clearing an interruption mark of the analog-digital converter, stopping the analog-digital conversion, and sending converted data to a journey function calculation subprogram;

the path function calculation subprogram firstly determines the step angle of the stepping motor, the circle 360/step angle is the pulse number required by one circle of rotation of the motor, and the pulse number received by the single chip microcomputer can be used for calculating the path traveled by the instrument;

the stress calculation function subprogram calculation method is that the defect is assumed to be in a rectangular groove shape on the test piece, and a three-dimensional model is established by taking the defect center as an origin; specifically according to the following formula:

establishing coordinate axes x, y and z along three orthogonal directions of the rectangular groove, and giving length, width and depth of the coordinate axes as D_z、D_x、D_yAssuming that the external magnetic field H is along the X-axis direction, defineThe three-dimensional space field point coordinate is P (x, y, z), and the magnetic charge surface source point coordinate is (x)_m，y_m，z_m) Then, the leakage magnetic field signal generated by the defect wall at the point P is:

equation (1) is a tangential component magnetic signal calculation equation, H_xDetecting a tangential signal for the detector, ρ being the magnetic charge density; after the formula (1) is arranged, the formula can be represented as:

H_x＝ρ×f_x (2)

f_xthe variable part of the tangential dimension is obtained by inputting the dimension of the defect and the scanning distance, the magnetic charge density rho is related to the stress, and the formula is expressed as follows:

wherein mu₀Is a vacuum permeability, mu_rThe relative magnetic permeability is, the stress is sigma, the magnetization intensity is M, the coupling field parameter is alpha, the coupling relation between magnetic domains is reflected, and gamma₁And gamma₁' is a stress correlation coefficient, and for the convenience of the subsequent description, let in equation (3)

The magnetization M is:

M＝f₂H_e (5)

wherein H_eIs an effective magnetic field, and according to the J-A model, the formula of the effective magnetic field is as follows:

the following formula (3), (4), (5) and (6) can be collated to obtain:

equation (7) is a quadratic equation of one element, in the form of ax²+ bx + c is 0, since Δ is b²4ac > 0, so according to the root equation (8):

then the stress formula (9) is obtained:

wherein alpha is 7.0921 x 10^-4，γ₁＝-1.5×10^-18A^-2m²，γ′₁＝4.17×10^-27A^-2m²，μ₀＝4π×10^-7H/m, demagnetization factor N_x＝1，μ_r280B/H, and H is an external magnetic field;

therefore, the measured magnetic signal can be calculated by the formula (9) to obtain the stress sigma at the defect;

the LCD display subprogram firstly defines each pin, delays for a certain time, gives a certain reflection time to the pin, judges whether the liquid crystal module is busy, delays for a plurality of milliseconds when the liquid crystal module is busy, and otherwise calls a write function; and designating the address of the character display and writing the data into the liquid crystal module.

Technical Field

The invention belongs to the technical field of stress detection of ferromagnetic material defects, and particularly relates to a system and a method for detecting surface defect stress based on magnetic flux leakage signal characteristics.

Background

The magnetic flux leakage method is a mature nondestructive testing technology, has the advantages of no need of a coupling agent, strong anti-interference capability, support of non-contact dynamic online detection and the like, and is successfully applied to the field of nondestructive testing of ferromagnetic materials. However, the existing magnetic flux leakage detection is only a single analysis for defects such as corrosion, metal loss, cracks, pinholes and the like; in fact, the ferromagnetic component is stressed in the service process, and the stress at the defect part is accumulated to a certain degree to cause micro-crack damage, so that the defect is expanded to cause major accidents. Therefore, determining the defect stress under the leakage magnetic field is the key point of defect detection and evaluation of the ferromagnetic material.

Disclosure of Invention

Object of the Invention

The invention provides a system and a method for detecting surface defect stress based on magnetic flux leakage signal characteristics, and aims to solve the problems that the existing magnetic flux leakage detection technology is single in analysis condition and cannot analyze the stress at a defect in real time

The technical scheme is as follows:

the utility model provides a surface defect stress detecting system based on magnetic leakage signal characteristic which characterized in that: the stress detection system consists of a singlechip, a stepping motor, a Hall sensor, a filtering amplification circuit and a liquid crystal display; the stepping motor interface of the single chip microcomputer is connected with the motor controller interface of the stepping motor, the detection signal output port of the Hall sensor is connected with the signal input port of the filtering and amplifying circuit, the signal output port of the filtering and amplifying circuit is connected with the detection signal input port of the single chip microcomputer, and the display signal output port of the single chip microcomputer is connected with the input port of the liquid crystal display.

The Hall sensor is an SS49E linear Hall sensor, the sensor works in a magnetic field environment, the input of the sensor is magnetic induction intensity, the output of the sensor is voltage which is in direct proportion to the input quantity, and the measuring direction of the sensor is tangential.

The filtering amplifying circuit comprises a filtering circuit and an amplifying circuit; a signal input port of the filtering amplification circuit is connected with a detection signal output port of the Hall sensor through a filtering circuit, and a signal output port of the filtering amplification circuit is connected with a detection signal input port of the singlechip through an amplification circuit; the amplifying module is an LM324 low-power single-power-supply four-channel operational amplifier.

The single chip microcomputer is an STC89C52 single chip microcomputer; the single chip microcomputer P2.5 is connected with 4 pins of the liquid crystal display, the single chip microcomputer P2.6 is connected with 5 pins of the liquid crystal display, the single chip microcomputer P2.7 is connected with 6 pins of the liquid crystal display, the single chip microcomputers P0.0-P0.7 are connected with 7 th-14 th pins of the liquid crystal display, the single chip microcomputer P1.2 is connected with the output end of the filter amplifying circuit, and the single chip microcomputers P1.3-P1.6 are connected with the output end of the stepping motor.

The stepping motor rotates 360 degrees to collect magnetic signals for 20 times, namely, the magnetic signals are collected once every time the stepping motor rotates 18 degrees; meanwhile, a permanent magnet is arranged on a rotating shaft of the stepping motor and is parallel to the tangent plane of the tested piece, so that the existence of the horizontal component of the magnetic force line is ensured, and the tangential detection signal effect is optimal.

The liquid crystal display is a 1602LCD, wherein a 1-pin VSS is a ground power supply, a 2-pin VDD is connected with a 5V positive power supply, a 3-pin VL is a contrast adjusting end of the LCD, the contrast is weakest when the positive power supply is connected, the contrast is highest when the positive power supply is grounded, a 4-pin RS is used for register selection, a data register is selected when the level is high, an instruction register is selected when the level is low, the data register is connected with a single chip P2.5, a 5-pin R/W is a reading and writing signal line, reading operation is carried out when the level is high, and writing operation is carried out when the level is low; when the RS and the R/W are both in a low level, an instruction or a display address can be written in, when the RS is in a low level, the R/W can read a busy signal, when the RS is in a high level, data can be written in and connected with the single chip microcomputer P2.6, when the RS is in a high level, the data can be connected with the single chip microcomputer P2.6, the 6-pin E end is an enabling end, and when the E end jumps from the high level to the low level, the liquid crystal module executes a command and is connected with the single chip microcomputer P2.7; the 7 th to 14 th pins D0 to D7 are 8-bit bidirectional data lines and are connected with the single chip microcomputer P0.0 to P0.7; the 15 th instep light source anode, and the 16 th instep light source cathode.

A surface defect stress detection method based on magnetic flux leakage signal characteristics comprises the following specific operation steps:

firstly, the single chip microcomputer drives a stepping motor to rotate by controlling a motor controller so as to enable the instrument to advance at a constant speed;

secondly, a Hall sensor collects a magnetic leakage signal of the tested piece and transmits the magnetic leakage signal into a filter amplifying circuit;

thirdly, the filtering and amplifying circuit receives the analog signal, performs differential amplification, sends the analog signal into a single chip microcomputer and converts the analog signal into a digital signal;

and fourthly, calculating the distance traveled by the stepping motor through a built-in program of the single chip microcomputer, and calculating a stress value according to a formula according to the detected magnetic flux leakage signal so as to display the stress value on a liquid crystal display.

In the fourth step, the built-in programs of the single chip microcomputer comprise a system calling program, a stepping motor driving program, a data processing main program, a data acquisition processing subprogram, a path calculation function subprogram, a stress calculation function subprogram and an LCD display subprogram;

the stepping motor driving program is used for adjusting the advancing speed of the instrument by adjusting a pulse signal of the stepping motor, and the rotating speed of the stepping motor is in direct proportion to the frequency of the pulse, so that the motor drives the stepping motor to adjust the pulse frequency of the stepping motor by using a delay function, the speed of the instrument is controlled by the delay function, and the speed and the frequency can be combined to obtain the advancing path of the instrument by using magnetic leakage detection data;

the data processing main program firstly calls a data acquisition subprogram to convert an analog signal acquired by the Hall sensor into a digital signal by utilizing analog-to-digital conversion, and tangential data of a detection piece is stored in a storage area with an ADTURN1 as a first address;

the data acquisition subprogram performs analog-to-digital conversion on the analog signals acquired by the sensor through the conversion of an analog-to-digital converter; after initializing the analog-digital converter, enabling the analog-digital converter to be interrupted, starting analog-digital conversion, clearing an interruption mark of the analog-digital converter, stopping the analog-digital conversion, and sending converted data to a journey function calculation subprogram;

the path function calculation subprogram firstly determines the step angle of the stepping motor, the circle 360/step angle is the pulse number required by one circle of rotation of the motor, and the pulse number received by the single chip microcomputer can be used for calculating the path traveled by the instrument;

the stress calculation function subprogram calculation method is that the defect is assumed to be in a rectangular groove shape on the test piece, and a three-dimensional model is established by taking the defect center as an origin; specifically according to the following formula:

establishing coordinate axes x, y and z along three orthogonal directions of the rectangular groove, and giving length, width and depth of the coordinate axes as D_z、D_x、D_yAssuming that the external magnetic field H is along the X-axis direction, defining the three-dimensional field point coordinate as P (X, y, z), and the magnetic charge surface source point coordinate as (X)_m，y_m，z_m) Then, the leakage magnetic field signal generated by the defect wall at the point P is:

equation (1) is a tangential component magnetic signal calculation equation, H_xDetecting a tangential signal for the detector, ρ being the magnetic charge density; after the formula (1) is arranged, the formula can be represented as:

H_x＝ρ×f_x (2)

f_xthe variable part of the tangential dimension is obtained by inputting the dimension of the defect and the scanning distance, the magnetic charge density rho is related to the stress, and the formula is expressed as follows:

wherein mu₀Is a vacuum permeability, mu_rThe relative magnetic permeability is, the stress is sigma, the magnetization intensity is M, the coupling field parameter is alpha, the coupling relation between magnetic domains is reflected, and gamma₁And gamma'₁Is the stress correlation coefficient, and for the convenience of the subsequent explanation, the equation (3) is shown

The magnetization M is:

M＝f₂H_e (5)

wherein H_eIs an effective magnetic field, and according to the J-A model, the formula of the effective magnetic field is as follows:

the following formula (3), (4), (5) and (6) can be collated to obtain:

equation (7) is a quadratic equation of one element, in the form of ax²+ bx + c is 0, since Δ is b²4ac > 0, so according to the root equation (8):

then the stress formula (9) is obtained:

wherein alpha is 7.0921 x 10^-4，γ₁＝-1.5×10^-18A^-2m²，γ′₁＝4.17×10^-27A^-2m²，μ₀＝4π×10^-7H/m, demagnetization factor N_x＝1，μ_r280B/H, and H is an external magnetic field;

therefore, the measured magnetic signal can be calculated by the formula (9) to obtain the stress sigma at the defect;

the LCD display subprogram firstly defines each pin, delays for a certain time, gives a certain reflection time to the pin, judges whether the liquid crystal module is busy, delays for a plurality of milliseconds when the liquid crystal module is busy, and otherwise calls a write function; and designating the address of the character display and writing the data into the liquid crystal module.

The advantages and effects are as follows:

1. the invention utilizes the stepping motor to drive the detector trolley to move forward, and the sensor is positioned at the bottom of the trolley to collect data, so that the distance traveled by the instrument corresponds to the magnetic signal, and comparison and recording are convenient.

2. The invention solves the problem that the existing detector can not analyze the stress at the defect in real time.

3. The invention uses the single chip microcomputer control, so that the measuring equipment is smaller and more exquisite, and is suitable for the detection of various engineering environments.

Drawings

FIG. 1 is a block diagram of the system of the present invention;

FIG. 2 is an overall structural view of the present invention;

FIG. 3 is a top view of the detector of the present invention;

FIG. 4 is a flow chart of the system call main routine of the present invention;

FIG. 5 is a flowchart of a stepper motor driving procedure of the present invention;

FIG. 6 is a flowchart of a data collection subroutine of the present invention;

FIG. 7 is a flowchart of the LCD calling procedure according to the present invention;

FIG. 8 is a flow chart of LCD display according to the present invention;

FIG. 9 is a pin diagram of the single chip microcomputer of the present invention;

FIG. 10 is a diagram of a Hall sensor configuration of the present invention;

FIG. 11 is a schematic diagram of a filter amplifier circuit according to the present invention;

fig. 12 is a structural view of an LCD module according to the present invention.

Reference numerals: a permanent magnet and sensor module 1; a singlechip 2; a stepping motor 3; a test piece 4; and defect 5.

Detailed Description

The invention is further described below with reference to the accompanying drawings:

as shown in figure 1, the invention comprises a stepping drive motor part, a Hall sensor, a filter amplifying circuit, a singlechip and an LCD display part. The stepping motor interface of the minimum system control unit of the singlechip is connected with the motor controller interface of the stepping motor driving part, the output port of the sensor part is connected with the input port of the filtering and amplifying circuit part, the output port of the filtering and amplifying circuit part is connected with the input port of the singlechip part, and the display signal output port of the singlechip is connected with the input port of the LCD display part.

As shown in figures 2 and 3, the whole system structure is that two stepping motors 3 drive a detector trolley to move forward, a permanent magnet and a sensor module 1 are positioned right below the detector trolley, and a singlechip 2 and a hardware circuit are positioned in a trolley body. The single chip microcomputer 2 drives the trolley to move forward at a constant speed, and the function of detecting the surface defects 5 of the tested piece 4 is achieved.

The detector car is divided into four wheels and the interior of the car body. The device comprises two stepping drive motors 3 at the front wheel, a singlechip 2 in a vehicle body, a permanent magnet, a sensor module 1 and other hardware circuits.

As shown in fig. 4, the programs of the single chip microcomputer include a system call and stepping motor driving program, a data acquisition and processing subprogram, a path calculation function subprogram, a stress calculation function subprogram, an a/D conversion program, and an LCD display subprogram.

The main program of system calling and data processing firstly sets a driving program of a stepping motor to drive the instrument at a constant speed, and calls a data acquisition subprogram, namely, analog signals acquired by a sensor are converted into digital signals by AD conversion; then, the stress is calculated by the path calculation subprogram and the stress calculation function subprogram, and the detection result is sent to the LCD display module for display.

As shown in fig. 5, the step motor driver firstly defines the port of the step motor, and then defines the operation mode of the step motor by initializing the serial port and the timer, and adjusts the forward speed of the instrument by adjusting the pulse signal of the step motor. Because the rotating speed of the stepping motor is in direct proportion to the frequency of the pulse, the motor drive adjusts the pulse frequency of the stepping motor by using the delay function, the speed of the instrument is controlled by the delay function, the speed and the frequency can be combined to obtain the traveling distance of the instrument by using the magnetic leakage detection data, and the trolley stops moving by interrupting the pulse frequency output when the instrument is finished.

As shown in fig. 6, the data collection subroutine performs analog-to-digital conversion on the analog signals collected by the sensors through ADC conversion. The ADC is enabled to be interrupted after the ADC is initialized, AD conversion is started, AD conversion is stopped after an ADC interruption mark is cleared, and converted data are sent to the distance function calculating subprogram.

The path function calculation subprogram firstly determines the step angle of the stepping motor, the circle 360/step angle is the pulse number required by one circle of rotation of the motor, and the pulse number received by the single chip microcomputer can be used for calculating the path traveled by the instrument;

the stress calculation function subprogram calculation method is that the defect is assumed to be in a rectangular groove shape on the test piece, and a three-dimensional model is established by taking the defect center as an origin; specifically according to the following formula:

establishing coordinate axes x, y and z along three orthogonal directions of the rectangular groove, and giving length, width and depth of the coordinate axes as D_z、D_x、D_yAssuming that the external magnetic field H is along the X-axis direction, defining the three-dimensional field point coordinate as P (X, y, z), and the magnetic charge surface source point coordinate as (X)_m，y_m，z_m) Then, the leakage magnetic field signal generated by the defect wall at the point P is:

equation (1) is a tangential component magnetic signal calculation equation, H_xDetecting a tangential signal for the detector, ρ being the magnetic charge density; after the formula (1) is arranged, the formula can be represented as:

H_x＝ρ×f_x (2)

f_xthe variable part of the tangential dimension is obtained by inputting the dimension of the defect and the scanning distance, the magnetic charge density rho is related to the stress, and the formula is expressed as follows:

wherein mu₀Is a vacuum permeability, mu_rThe relative magnetic permeability is, the stress is sigma, the magnetization intensity is M, the coupling field parameter is alpha, the coupling relation between magnetic domains is reflected, and gamma₁And gamma'₁Is the stress correlation coefficient, and for the convenience of the subsequent explanation, the equation (3) is shown

The magnetization M is:

M＝f₂H_e (5)

wherein H_eIs an effective magnetic field, and according to the J-A model, the formula of the effective magnetic field is as follows:

the following formula (3), (4), (5) and (6) can be collated to obtain:

equation (7) is a quadratic equation of one element, in the form of ax²+ bx + c is 0, since Δ is b²4ac > 0, so according to the root equation (8):

then the stress formula (9) is obtained:

wherein alpha is 7.0921 x 10^-4，γ₁＝-1.5×10^-18A^-2m²，γ′₁＝4.17×10^-27A^-2m²，μ₀＝4π×10^-7H/m, demagnetization factor N_x＝1，μ_r280B/H, and H is an external magnetic field;

therefore, the measured magnetic signal can be calculated by the formula (9) to obtain the stress sigma at the defect;

as shown in fig. 7, each pin is defined first, delayed for a certain time, and then a certain response time is given, and then it is determined whether the liquid crystal module is busy, and then the busy state is delayed for several milliseconds, otherwise, the write function is called. And designating the address of the character display and writing the data into the liquid crystal module.

As shown in fig. 8, the number, ten, hundred and decimal points are defined in the function and digitally output to the liquid crystal display as four independent parts.

As shown in fig. 9, the minimum system control unit of the STC89C52 single chip microcomputer according to the present invention has 32 programmable I/O ports, three 16-bit timers/counters, 4 external interrupts, and a USB _ UART serial interface circuit for communicating with a computer.

The singlechip P2.5 is connected with the pin 4 of the LCD, the singlechip P2.6 is connected with the pin 5 of the LCD, and the singlechip P2.7 is connected with the pin 6 of the LCD; the single chip microcomputer P0.0-P0.7 is connected with the 7 th-14 th pins of the LCD. The singlechip P1.2 is connected with the output end of the filter amplifying circuit, and P1.3-P1.6 are connected with the output end of the stepping motor.

As shown in fig. 10, pin 1 of the SS49E linear hall sensor is connected to a power supply, pin 2 is connected to ground, and pin 3 is connected to the input end of the filter amplifier circuit. The sensor can work in the magnetic field environment of a permanent magnet or an electromagnet, and when an S magnetic pole appears on the marking surface of the Hall sensor, the driving output is higher than zero level; the N pole will drive the output below zero level; the instantaneous and proportional output voltage levels determine the flux density with the most sensitive side of the device. When a defect is detected, the density of the magnetic field lines passing through the hall element changes, causing a change in the hall voltage.

As shown in fig. 11, when the frequency of the input signal is low, the impedance of the capacitor is high relative to the impedance of the resistor; therefore, most of the input voltage drops on the capacitor. When the input frequency is high, the impedance of the capacitor is low relative to the impedance of the resistor, which means that the voltage over the resistor decreases and the smaller the voltage delivered to the load. Thus, low frequencies pass and high frequencies are blocked.

As shown in fig. 12, the display module is an LCD1602 character type liquid crystal, which is a 16-pin interface with backlight. Pin 1 VSS is ground supply and pin 2 VDD is 5V positive supply. And 3, pin: VL is LCD contrast adjustment end, and contrast is weakest when connecting positive power supply, and contrast is highest when earthing, 4 feet: RS is register selection, selects a data register at high level and selects an instruction register at low level, and is connected with the singlechip P2.5. And 5, feet: R/W is a read-write signal line, and the read operation is carried out at high level and the write operation is carried out at low level. When the RS and the R/W are both in low level, an instruction or a display address can be written, when the RS is in low level, the R/W is in high level, a busy signal can be read, and when the RS is in high level, data can be written and connected with the single chip microcomputer P2.6. 6, pin: the end E is an enabling end, when the end E jumps from high level to low level, the liquid crystal module executes a command and is connected with the singlechip P2.7. 7 th to 14 th pins: D0-D7 are 8-bit bidirectional data lines and are connected with the single chip microcomputer P0.0-P0.7. And a 15 th leg: and a backlight source anode. And a 16 th pin: and a negative electrode of the backlight source.

The technical characteristics form an embodiment of the invention, which has strong adaptability and implementation effect, and unnecessary technical characteristics can be increased or decreased according to actual needs to meet the requirements of different situations.