CN114441624A - Small metal magnetic memory crack detection method - Google Patents
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Abstract
The invention relates to the technical field of metal magnetic memory detection, and provides a small metal magnetic memory crack detection method, which comprises the following steps: s1: and (3) return-to-zero processing: eliminating the influence of the earth magnetic field or the environmental magnetic field; s2: a sensor head is used for scanning a workpiece to be detected, and signals of the sensor are amplified by an amplifying circuit and then are acquired by a single chip microcomputer in real time; s3: a sensor head is used for scanning a workpiece to be detected, and signals of a sensor are amplified and differentiated by an amplifying circuit and then are acquired by a single chip microcomputer in real time; s4: processing and calculating the signals acquired after amplification and filtering; s5: and processing and calculating the acquired signals after amplification and differentiation. The invention can measure the strength of the leakage magnetic field on the surface of a shafting or an iron workpiece in real time and can measure the strength of a weak magnetic field; the dynamic detection is carried out on the magnetic field and the gradient, the magnetic field intensity change curve and the generalized gradient curve are measured, the fracture and stress concentration position of the shafting can be accurately searched, and the buzzer is configured to carry out sound alarm.
Description
Technical Field
The invention relates to the technical field of metal defect magnetic memory detection, in particular to a small metal magnetic memory crack detection method.
Background
The magnetic memory detection of metals is a nondestructive detection method which can carry out early diagnosis and is emerging in recent thirty years. Under the action of working load, the iron member in the geomagnetic environment can be subjected to magnetic domain organization orientation and irreversible reorientation with magnetostriction property in the iron member, and maximum change of a leakage magnetic field Hp is formed in a stress and deformation concentration region, and metal magnetic memory detection detects the defect position of metal just through the relation between the stress and deformation concentration region displacement and the leakage magnetic field Hp. In recent years, with the popularization and application of the Russian metal magnetic memory method and the detection device, other scientific research institutions, scholars and experts at home and abroad compete to invest considerable force to study the basic theory of the method and develop the similar detection device. At present, the method and the instrument developed by Russian 'dynamic diagnosis' company still keep greater superiority and leading level, and China also has a plurality of units and companies to research the metal magnetic memory principle and develop metal magnetic memory instruments.
In the existing metal magnetic memory detection method, most of magnetic memory detectors judge metal defects through the zero crossing point position of a magnetic field intensity curve by measuring the number and/or the curve of the magnetic field intensity of the detected environment, at the moment, the influence of a background magnetic field cannot be eliminated, and the deviation of the detection result is large.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides a small metal magnetic memory crack detection method, which comprises the following steps:
s1: and (3) return-to-zero processing: the sensing head of the detection device is placed, the sensing head of the detection device is fixed in a certain position direction in a certain environment (generally in the air) to be measured and memorized to be used as a zero magnetic field, a magnetic field value is subtracted from the zero magnetic field in each measurement in the measurement process, the difference value is used as a magnetic field measurement value Hp, whether the zero magnetic field value is zero crossing point or not can be judged, and whether the workpiece has defects or not and stress concentration or not can be judged. Thus, the influence of the earth magnetic field or the environmental magnetic field can be eliminated;
s2: a sensor head is used for scanning a workpiece to be detected, and a signal of a sensor enters a path of A/D signal processing circuit after being amplified by an amplifying circuit and is collected by a singlechip in real time;
s3: the sensor head is used for scanning a workpiece to be detected, and a signal of the sensor enters the other path of A/D to be acquired by the single chip microcomputer in real time after being amplified and differentiated by the amplifying circuit;
s4: data processing 1: processing and calculating the acquired signals to form a residual magnetic distribution curve, namely an Hp curve, and recording the zero crossing point of the curve;
s5: and (3) data processing 2: signals transmitted by the sensor enter the A/D through the amplifying and differentiating circuit, and collected signals are processed to obtain a generalized gradient Dx curve. The stress concentration sites are further identified based on the change in magnitude of Dx.
In step S5, the specific process of identifying the stress concentration portion includes:
depending on where the defects and stresses are relatively concentrated, the tangential component of the magnetic field hp (x) has a maximum value, whereas the normal component hp (y) changes sign and has a zero value point, this irreversible change in magnetic state continues to remain after the removal of the working load and a large gradient peak dhp (y)/dx occurs; by measuring the leakage magnetic field normal component hp (y) and measuring the gradient value K ═ dhp (y)/dx, the stress concentration portion of the workpiece is estimated, and the presence or absence of a defect in the component is determined, thereby realizing early diagnosis. When manual scanning is performed, the moving speed of the sensing head is not very large, and is generally equal to 8mm/s (obtained by multiple practices), K is equal to dhp (y)/Dx (dhp (y)/d (vt) ═ 8dhp (y)/dt (8 Dx), and the change of the measured K value can be obtained by collecting the change of the generalized gradient Dx value.
Further, the detection device includes: the device comprises a singlechip, a sensor, an amplifying circuit, a differential circuit, a data processing module, a setting and resetting circuit and a display module.
Further, the single chip microcomputer adopts a PIC16F877A single chip microcomputer, a 10-bit resolution A/D converter is arranged in the single chip microcomputer, and an 8-bit analog quantity input channel is arranged and used for converting the analog quantity into digital quantity which can be received and processed by the single chip microcomputer.
Further, the sensor employs a 4-terminal bridge anisotropic magnetoresistive sensor configured as a 4-element wheatstone bridge for converting magnetic fields to differential output voltages capable of sensing magnetic fields as low as 30 μ Gauss, with a typical value of 1mV/V/Gauss for sensitivity and a resolution of 85 μ Gauss.
Furthermore, an active low-pass filter circuit is connected behind the amplifying circuit 1 and is used for eliminating interference between the circuit and an external electromagnetic field.
Furthermore, the amplifying circuit 2 is connected with a differentiating circuit for generating a Dx value.
The invention achieves the following beneficial effects:
firstly, the invention carries out zero treatment before measurement, and can eliminate the influence of the earth magnetic field or the environmental magnetic field;
secondly, the method can measure the strength and the generalized gradient of the leakage magnetic field on the surface of a shafting or an iron workpiece in real time, and can measure the strength of a weak magnetic field; the dynamic detection is carried out on the magnetic field and the gradient, a magnetic field intensity curve and a gradient curve are generated, the fracture and stress concentration positions of the shafting are accurately searched, and an alarm device is configured to carry out sound alarm.
Drawings
FIG. 1 is a schematic view of the detecting unit according to the present invention;
FIG. 2 is a voltage conversion circuit diagram;
FIG. 3 is a differential circuit diagram;
FIG. 4 is a digital display of magnetic field strength;
FIG. 5 is a graph showing a magnetic field strength curve;
FIG. 6 is a graph showing a magnetic field gradient curve.
Detailed Description
To facilitate an understanding of the present invention by those skilled in the art, specific embodiments thereof are described below with reference to the accompanying drawings.
As shown in fig. 1, the detection device adopted by the invention comprises a single chip microcomputer, a sensor, an amplifying circuit, a differentiating circuit, a data processing module, a setting and resetting circuit and a display module.
The sensor preferably employs a 4-terminal bridge-type anisotropic magnetoresistive sensor HMC 1021Z. It is a 4-end bridge type anisotropic magnetic resistance sensor. This type of magnetoresistive sensor is configured as a 4-element wheatstone bridge that converts magnetic fields into differential output voltages capable of sensing magnetic fields as low as 30 mugauss. Typical values for the sensitivity of the sensor are 1mV/V/Gauss and the resolution is 85 μ Gauss. The single-axis sensor is packaged by using an 8-pin SIP (session initiation protocol), an integrated set/reset belt with a patent is adopted, and when the sensitivity of the sensor is reduced, a set/reset pulse is applied, so that the sensor can reach the maximum sensitivity.
The signals from the sensors are weak millivolt electrical signals that must be amplified for identification by the singlechip. The detection device is provided with a plurality of stages of amplifying circuits, and direct coupling connection modes are adopted among stages for keeping stability of output data. In order to eliminate the interference between the circuit and an external electromagnetic field, an active low-pass filter circuit is connected behind the amplifying circuit. In the detection process by using the detection device, considering that the speed of the sensing head manually sweeping the detected workpiece is not very fast, the frequency of the filter circuit adopted by the design is lower than the commercial power frequency 50HZ, so that the interference to the alternating current 220V power supply is not considered.
The single chip used by the detection device is PIC16F877A, the voltage used by the analog-to-digital converter is unipolar, and the signal from the amplifier and the filter is bipolar, so a level of voltage conversion circuit is needed to convert the signal voltage from-VCC～+VCCBecomes 0 to + VCCSo that the amplitude of the signal is reduced by half and the waveform shape of the signal cannot be changed, a voltage conversion circuit (see fig. 2) is required.
The detection device takes a PIC16F877A singlechip as a main control element. The PIC 8-bit middle-grade singlechip is complete in function and high in cost performance, a 10-bit resolution A/D converter is arranged in the PIC 8-bit middle-grade singlechip, and an 8-bit analog quantity input channel is arranged at most and used for converting external analog quantity into digital quantity which can be received and processed by the singlechip. An independent data acquisition system can be formed by one PIC16F877A chip; and simultaneously, the 12864 liquid crystal module is connected to form a magnetic field display circuit. The processed voltage signal from the voltage conversion circuit can directly enter an input end RA0 of the singlechip analog-to-digital converter for analog-to-digital conversion. The voltage signal from the differentiating circuit shown in fig. 3 directly enters the input end RA1 of the single chip microcomputer analog-to-digital converter, and can be subjected to analog-to-digital conversion in the single chip microcomputer in a time-sharing manner. RA2 and RA3 are respectively connected with negative reference voltage and positive reference voltage, RD interface is connected with data input of liquid crystal module, RC port and RA port are used as control signal, and data acquisition and liquid crystal display system is formed. The signal acquisition of the acquisition system formed by the method is completed in the single chip microcomputer, so that the system has simple and reliable circuit and strong anti-interference capability; and the singlechip is directly connected with the liquid crystal module, so that the display data is stable and reliable. And when in display, the liquid crystal module is used for continuously displaying the acquired field intensity and gradient in a digital or curve form.
Software used by the magnetic memory detection device is compiled by adopting a singlechip C language, and functions of data acquisition, parameter calculation, liquid crystal display, defect alarm and the like can be realized. The program used by the detection device comprises a main program, an interrupt service program and corresponding subprograms.
In the main program, the system mainly works to display the magnitude and the change of the magnetic field intensity and the gradient. In addition, threshold judgment and alarm are carried out. In addition, if the system encounters a crash condition in the display process, the detector is also provided with a hardware reset key for normal work recovery, so that the singlechip can be restarted under special conditions.
In the interrupt service routine, the main tasks of the system are key processing and analog-to-digital conversion.
Because the detector only uses a magnetic resistance sensor, a displacement sensor is not used. In order to obtain the gradient value of the field intensity to the scanning displacement, the detector calculates a parameter of a derivative of the magnetic field intensity to time in software, and the gradient value of the field intensity to the displacement can be expressed by the derivative of the field intensity to time, namely a generalized gradient, because the speed of manually scanning the workpiece is basically constant. And judging whether the single chip microcomputer gives an alarm or not according to whether the gradient exceeds a certain range or not. Therefore, the software method solves the problem that the same detector needs two sensors, reduces the size of the detector and saves the cost.
Under the action of a working load, the iron member in the geomagnetic environment can generate the oriented and irreversible reorientation of magnetic domain organization with magnetostrictive property inside the iron member, and forms the maximum change of a leakage magnetic field Hp in a stress and deformation concentration area, namely, the tangential component Hp (x) of the magnetic field has the maximum value, the normal component Hp (y) changes the sign and has a zero value point at the position of relative concentration of defects and stress, the irreversible change of the magnetic state is continuously kept after the working load is eliminated, and a larger gradient peak value dHP (y)/dx appears. Therefore, by measuring the leakage magnetic field normal component hp (y) and calculating the gradient value K ═ dhp (y)/dx, the stress concentration portion of the workpiece can be accurately estimated. Therefore, whether the part has defects or not can be judged, and early diagnosis is realized.
The method for detecting the small-sized metal magnetic memory crack comprises the following steps:
s1: and (4) zeroing treatment: installing a detection device, fixing a sensor head of the detection device at a certain position in a measured environment for zeroing, and eliminating the influence of the earth magnetic field or the environment magnetic field;
s2: a sensor head is used for scanning a workpiece to be detected, and signals of the sensor are amplified by an amplifying circuit and then are acquired by a single chip microcomputer in real time;
s3: a sensor head is used for scanning a workpiece to be detected, and signals of a sensor are amplified and differentiated by an amplifying circuit and then are acquired by a single chip microcomputer in real time;
s4: data processing: processing and calculating the collected signals when detecting the magnetic field curve to form a residual magnetic distribution curve, namely an Hp curve, and observing whether the curve crosses zero;
s5: and (3) data processing 2: and processing and calculating the signals acquired after amplification and differentiation to obtain a generalized gradient Dx curve, and further identifying the stress concentration part according to the change of the Dx.
Depending on where the defects and stresses are relatively concentrated, the tangential component of the magnetic field hp (x) has a maximum value, whereas the normal component hp (y) changes sign and has a zero value point, this irreversible change in magnetic state continues to remain after the removal of the working load and a large gradient peak dhp (y)/dx occurs; by measuring the normal component Hp (y) of the leakage magnetic field, and by acquiring the change of the generalized gradient Dx value, the change of the measured K value can be used for deducing the stress concentration part of the workpiece, so that whether the part has defects or not can be judged, and early diagnosis can be realized.
The above embodiments of the present invention do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (8)
1. The small metal magnetic memory crack detection method is characterized by comprising the following steps: the method comprises the following steps:
s1: and (4) zeroing treatment: thus, the influence of the earth magnetic field or the environmental magnetic field can be eliminated;
s2: a sensor head is used for scanning a workpiece to be detected, and signals of the sensor are amplified by an amplifying circuit and then are acquired by a single chip microcomputer in real time;
s3: the sensor head is used for scanning the workpiece to be detected, and the signal of the sensor is amplified and differentiated by the amplifying circuit and then is acquired by the single chip microcomputer in real time
S4: data processing: processing and calculating the collected signals when detecting the magnetic field curve to form a residual magnetic distribution curve, namely an Hp curve, and observing whether the curve crosses zero;
s5: and (3) data processing 2: and processing and calculating the signals acquired after amplification and differentiation to obtain a generalized gradient Dx curve, and further identifying a stress concentration part according to the change of the Dx.
2. The method for detecting the small-sized metal magnetic memory crack according to the claim 1, wherein in the step S5, the specific process of marking the stress concentration part comprises the following steps:
depending on where the defects and stresses are relatively concentrated, the tangential component of the magnetic field hp (x) has a maximum value, whereas the normal component hp (y) changes sign and has a zero value point, this irreversible change in magnetic state continues to remain after the removal of the working load and a large gradient peak dhp (y)/dx occurs; through the measurement of leakage magnetic field normal component Hp (y), and measuring gradient value K ═ dHP (y)/dx, deducing the stress concentration part of the workpiece, thereby judging whether the part has defects or not and realizing early diagnosis; in actual measurement, the generalized gradient Dx is used to replace the gradient peak value dHP (y)/Dx, so as to judge whether the part has defects.
3. The method for detecting the small-sized metal magnetic memory crack according to claim 1, wherein the detection device comprises: the device comprises a singlechip, a sensor, amplifying circuits 1 and 2, a differential circuit, a filter circuit, an A/D (analog/digital) conversion circuit, a data processing module, a setting and resetting circuit and a display module.
4. The method for detecting the small-sized metal magnetic memory crack according to claim 3, characterized in that:
the single chip microcomputer adopts a PIC16F877A single chip microcomputer, a 10-bit resolution A/D converter is arranged in the single chip microcomputer, and an 8-bit analog quantity input channel is arranged and used for converting analog quantity into digital quantity which can be received and processed by the single chip microcomputer.
5. The method for detecting the small-sized metal magnetic memory crack according to claim 3, characterized in that:
the sensor adopts HMC1021Z, is a 4-end bridge type anisotropic magnetoresistive sensor, is configured as a 4-element Wheatstone bridge, is used for converting a magnetic field into differential output voltage, and can sense the magnetic field with the strength as low as 30 mu Gauss; typical values for the sensitivity of the sensor are 1mV/V/Gauss and the resolution is 85 μ Gauss.
6. The small-sized metal magnetic memory crack detection method of claim 3, which is characterized in that: the detector is provided with a multi-stage amplifying circuit, and in order to keep the stability of output data, a direct coupling connection mode is adopted among stages.
7. The method for detecting the small-sized metal magnetic memory crack according to claim 3, characterized in that:
an active low-pass filter circuit is connected behind the amplifying circuit 1 and is used for eliminating the interference between the circuit and an external electromagnetic field.
8. The method for detecting the small-sized metal magnetic memory crack according to claim 3, characterized in that:
the amplifying circuit 2 is followed by a differentiating circuit which generates dHP (y)/dt for obtaining the generalized gradient Dx.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117607243A (en) * | 2023-11-23 | 2024-02-27 | 中磁数智(北京)科技有限公司 | Magnetic memory detection system and method for cross pipeline welding seams |
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