Orthogonal geometric structure-based metal material stress or crack detection system and method

Abstract

The invention discloses a metal material stress or crack detection system and method based on an orthogonal geometric structure. The metal material stress or crack detection system comprises an orthogonal detection probe and a magnet exciting coil wound at the end part, the three-dimensional magnetic field sensor is arranged at the central position of the orthogonal detection probe; the microprocessor is connected with the three-dimensional magnetic field sensor through a connecting line, and the impedance analysis unit is electrically connected with the excitation coil; according to the invention, the orthogonal detection probe is combined with the three-dimensional magnetic field sensor, an electromagnetic field is generated through externally applied high-frequency alternating current, and the electromagnetic field is coupled with a stress field and cracks in a material, so that the stress field and cracks in the material can be detected; the stress or crack sensitivity of the magnetoelastic effect is organically combined with the electromagnetic field response characteristic of eddy current detection, so that the limitation of a traditional single method in detection in a specific direction is overcome; and the precision and the range of stress or crack detection are obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material detection, and in particular to a metal material stress or crack detection system and method based on an orthogonal geometric structure. Background Art

[0002] Traditional AC electromagnetic field detection technology usually uses a single coil excitation method to generate a uniform induced current with a fixed direction on the surface of the workpiece being inspected. When there are transverse cracks or principal stress directions perpendicular to the current direction on the workpiece surface, the stress or crack will cause disturbances in the local magnetic field along the length direction, causing the induced current to gather inside the stress concentration area or at the crack end point and form a distorted magnetic field. By measuring the magnetic field signal, the detection and quantitative analysis of stress concentration or cracks can be achieved. However, when longitudinal cracks or stress damage appear on the surface, the magnetic field disturbance caused by stress damage or crack width direction is small, resulting in poor detection and analysis of stress damage or crack defects. In actual detection, since the principal stress direction or crack direction is unknown, the operator cannot always scan along the principal stress direction or crack direction. Therefore, the use of a single excitation probe may lead to a decrease in detection sensitivity or even missed detection when detecting stress concentration or oblique cracks on the stainless steel surface. In order to avoid missed detection problems, multi-directional scanning or mechanical rotation of the probe is usually required. However, these methods will significantly increase the detection time and system complexity, thereby reducing the detection efficiency.

[0003] Balanced electromagnetic technology also has certain limitations in practical applications, especially when the direction of the principal stress or crack is consistent with or parallel to the direction of the electromagnetic detection field, its detection performance is relatively weak. This is because when the direction of the principal stress or crack is parallel to the detection electromagnetic field, the disturbance effect of stress concentration or crack on the electromagnetic field distribution is small, and it is difficult to produce sufficiently significant signal changes, resulting in a significant decrease in detection sensitivity. This directional sensitivity may cause omissions or misjudgments of stress concentration or crack detection, affecting the reliability of the detection results. In addition, for materials with deep buried cracks, deep stress damage or low conductivity, due to the attenuation effect of electromagnetic wave signals during propagation, the detection accuracy and signal acquisition quality may be further reduced, restricting the applicability of this technology in complex application scenarios. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a metal material stress or crack detection system and method based on orthogonal geometric structure, aiming to solve the problem that the prior art has poor detection effect on stress damage or cracks with consistent and parallel detection directions, resulting in the inability to accurately extract the geometric characteristics and size information of the defects.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: An orthogonal detection probe is characterized in that the orthogonal detection probe is composed of two U-shaped iron cores arranged orthogonally, each U-shaped iron core is wound with an excitation coil at both ends, and the excitation coils wound at both ends are connected in series, and the excitation coil at one end is a detection coil.

[0006] The two U-shaped cores of the orthogonal detection probe are orthogonally arranged, and the two U-shaped cores are non-contacting with each other.

[0007] A metal material stress or crack detection system based on an orthogonal geometric structure is characterized in that a three-dimensional magnetic field sensor is arranged below the orthogonal detection probe, and the three-dimensional magnetic field sensor is connected to a microprocessor; the excitation coil on the orthogonal detection probe is connected to an impedance analysis unit, the impedance analysis unit is connected to the microprocessor, and the microprocessor is connected to a host computer display unit.

[0008] The impedance analysis unit adopts an AD5933 impedance analysis chip, which is provided with multiple pins, wherein pin 9 is connected to a digital power supply, pins 10 and 11 are analog power supplies, pin 12 is grounded to the digital part of the microprocessor, pins 13 and 14 are grounded to the analog part of the microprocessor, and pins 15 and 16 are connected to the microprocessor for data communication via a connecting line.

[0009] Pin 8 of the AD5933 impedance analysis chip is the main clock input, pin 6 is the excitation signal output and is connected to the input end of the excitation coil, pin 4 is connected to the external voltage source, and pin 10 is the impedance detection input and is connected to the output end of the excitation coil.

[0010] The three-dimensional magnetic field sensor adopts the MLX90393 chip magnetic field change detection unit, and the microprocessor adopts the STM32F103T8U6 main controller communication control unit.

[0011] A method for detecting stress or cracks in metal materials based on orthogonal geometric structures, comprising: Step 1: Place an orthogonal detection probe wound with an excitation coil on the workpiece to be tested, and pass a sinusoidal signal with a phase difference of 90 degrees into the excitation coil through an impedance analysis unit, so that a rotating electromagnetic field with full angle coverage is generated inside the workpiece to be tested; Step 2, connecting the microprocessor and the three-dimensional magnetic field sensor through a connecting line, arranging the three-dimensional magnetic field sensor in the middle of the orthogonal detection probe, the three-dimensional magnetic field sensor captures the intensity, direction and frequency variation characteristics of the rotating magnetic field through its X, Y, and Z three-axis detection channels, moving the orthogonal detection probe, transmitting real-time magnetic field data through the three-dimensional magnetic field sensor, and performing stress concentration or crack characteristic analysis based on the real-time magnetic field data; Step 3, move the orthogonal detection probe, obtain the electromagnetic response signal induced by the excitation coil through the impedance analysis unit, and use the internal DSP module to perform Fourier transform on the electromagnetic response signal to calculate the influence characteristics of stress concentration or crack on impedance; Step 4: Transmit the analysis results of the crack characteristic analysis and the crack influence characteristic analysis to the upper computer display unit to present the detection results in real time.

[0012] In step 3, during the detection process, the output voltage of the impedance analysis unit to the excitation coil is adjusted by adjusting the reference voltage of the REFIN or REFOUT pin, thereby achieving automatic calibration and optimization of the measurement range.

[0013] The technical solution adopted by the present invention has the following beneficial effects: In the present invention, an orthogonal vertical dual-probe mechanism, i.e., an orthogonal detection probe, is designed to detect the magnetic field and impedance changes on the surface or near the surface of the material, and realize full-angle measurement of stress or cracks. The orthogonal detection probe successfully solves the problem of insufficient sensitivity to cracks or stress damage in specific directions in traditional detection methods through two mutually orthogonally arranged probes with unique spatial coupling and directional design, and significantly improves the comprehensiveness, sensitivity and accuracy of stress concentration or crack detection; the orthogonally arranged probes can capture magnetic fields and impedance changes in two vertical directions respectively, and realize accurate identification of stress concentration or cracks at all angles through bidirectional data fusion. This structure not only improves the detection capability of stress concentration or complex crack geometry, but also ensures the stability and reliability of signal acquisition. Each probe works independently, respectively collecting magnetic field and impedance change signals on the surface and near the surface of the material, and through signal decoupling and fusion processing, the detection error caused by interference between probes is eliminated, and high-precision stress concentration or crack positioning and quantitative analysis are realized.

[0014] In addition, combined with a three-dimensional magnetic field sensor, an electromagnetic field is generated by an externally applied high-frequency alternating current, which couples with the stress field inside the material, thereby achieving high-sensitivity measurement of the magnetic field and impedance changes on the surface and near-surface of the material. The stress sensitivity of the magnetoelastic effect and the electromagnetic field response characteristics of eddy current detection are organically combined, which not only overcomes the limitations of the traditional single method in detection in a specific direction, but also significantly improves the accuracy and range of stress concentration or crack detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A structural connection diagram of a metal material stress or crack detection system provided by the present invention; Figure 2 A schematic diagram of the connection structure of a metal material stress or crack detection system provided by the present invention with an orthogonal detection probe wound around an excitation coil; Figure 3A schematic diagram of the circuit structure of the MLX90393 magnetic field sensor in an embodiment of a metal material stress or crack detection system based on an orthogonal geometric structure provided by the present invention; Figure 4 A schematic diagram of the circuit structure of the AD5933 impedance analysis chip in an embodiment of the metal material stress or crack detection system based on an orthogonal geometric structure provided by the present invention; Figure 5 A detection flow chart of a metal material stress or crack detection method based on an orthogonal geometric structure provided by the present invention; Figure 6 The overall circuit schematic diagram of the metal material stress or crack detection system based on orthogonal geometric structure provided by the present invention.

[0016] In the figure, it is marked: 1- three-dimensional magnetic field sensor, 2- excitation coil, 3- orthogonal detection probe, 4- impedance analysis unit, 5- microprocessor, 6- host computer display unit. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] An orthogonal detection probe, i.e. an orthogonal geometry, such as Figure 2 As shown in the figure, the orthogonal detection probe is composed of two U-shaped iron cores arranged orthogonally, each U-shaped iron core has an excitation coil wound at both ends, and the excitation coils wound at both ends are connected in series, one of the excitation coils is a detection coil, and in the orthogonal arrangement of the two U-shaped iron cores of the orthogonal detection probe, the two U-shaped iron cores are non-contacting with each other.

[0019] A metal material stress or crack detection system based on orthogonal geometry, see Figure 1 and Figure 2 The metal material stress or crack detection system includes an orthogonal detection probe, a three-dimensional magnetic field sensor, a microprocessor, and a host computer display unit. An excitation coil is wound around the end of the orthogonal detection probe; the three-dimensional magnetic field sensor is arranged at the center of the orthogonal detection probe; the microprocessor is connected to the three-dimensional magnetic field sensor through a connecting line, an impedance analysis unit is arranged on the microprocessor, and the impedance analysis unit is electrically connected to the excitation coil; the host computer display unit is connected to the data output end of the microprocessor.

[0020] Among them, Figure 2As shown in the figure, the orthogonal detection probe consists of two U-shaped iron cores placed orthogonally. Both ends of each orthogonal detection probe are wound with excitation coils, and the excitation coil at one end is the detection coil; high-frequency alternating current with a phase difference of 90 degrees is respectively passed through the excitation coils on both sides of the orthogonal detection probe, thereby generating a rotating electromagnetic field inside the metal material. The rotating electromagnetic field induces eddy currents inside the metal workpiece, and the eddy currents are affected by the internal stress damage of the material or the geometric characteristics of the cracks (such as position, direction and depth, stress intensity and main stress direction), resulting in distortion of the local magnetic field distribution. The magnetic field changes caused by this stress concentration or cracks are distributed near the detection coil in the form of weak dynamic magnetic field signals.

[0021] A three-dimensional magnetic field sensor 1 is arranged below the detection coil of the orthogonal detection probe 3. The sensor adopts the MLX90393 chip magnetic field change detection unit. The three-dimensional magnetic field sensor 1 is connected to the microprocessor 5, wherein the microprocessor 5 adopts the STM32F103T8U6 main controller communication control unit; the orthogonal detection probe 3 is formed by two U-shaped iron cores arranged orthogonally, and the two ends of the U-shaped iron core are wound with a detection coil and an excitation coil. The detection coil and the excitation coil are connected in series and connected to the impedance analysis unit 4, the impedance analysis unit 4 is connected to the microprocessor 5, and the microprocessor 5 is connected to the host computer display unit 6.

[0022] The present invention achieves impedance quantification analysis of full-angle stress or cracks by adopting an orthogonal detection probe with an orthogonal vertical structure. The core component of the probe uses Permalloy as the magnetic core material. This material has excellent magnetic conductivity, especially under low-frequency conditions. Its relative magnetic permeability is as high as 40,000, which can significantly improve the sensitivity and stability of the magnetic induction signal. The probe uses a coil with an inner diameter of 8.2mm, a wire diameter of 0.22mm, and 300 turns for the excitation coil and the detection coil. The probe structure is an orthogonally placed double U-shaped magnetic core, and the core material is Permalloy, which has high magnetic conductivity and low loss characteristics. The modeling diagram of the orthogonal probe structure is shown as follows Figure 2 As shown, by loading two sets of orthogonal coils (X-axis and Y-axis) with alternating currents of the same amplitude and frequency but a phase difference of 90°, a rotating electromagnetic field can be induced in space, thereby achieving multi-angle detection of stress or cracks.

[0023] Specifically, on the designed orthogonal U-shaped core structure, the excitation coils are wound in the x and y directions respectively, and two sets of excitation coils are configured in the same direction. The two sets of coils are connected to each other through enameled wire to form a continuous loop to ensure the integrity and stability of signal transmission. During operation, the excitation coils in the X and Y directions are loaded with sinusoidal excitation signals with equal amplitude, consistent frequency but 90° phase difference. The excitation signal is used to generate a rotating magnetic field, and its mathematical expression is: At the same time, the induced current excited inside the workpiece by the orthogonal detection probe with a double U-shaped structure has a constant amplitude characteristic, and its direction changes periodically with time and at a uniform speed.

[0024] In addition, combined with a three-dimensional magnetic field sensor, an electromagnetic field is generated by an externally applied high-frequency alternating current, which couples with the stress field inside the material, thereby achieving high-sensitivity measurement of the magnetic field and impedance changes on the surface and near-surface of the material. The stress sensitivity of the magnetoelastic effect and the electromagnetic field response characteristics of eddy current detection are organically combined, which not only overcomes the limitations of the traditional single method in detection in a specific direction, but also significantly improves the accuracy and range of stress or crack detection.

[0025] In this embodiment, the three-dimensional magnetic field sensor is an MLX90393 magnetic field sensor, which is a highly sensitive three-axis Hall effect magnetic field sensor that can detect magnetic field components in the three directions of X, Y, and Z. In the present invention, the MLX90393 is located at the center of the orthogonal detection probe and is used to measure the magnetic field changes caused by the rotating electromagnetic field inside the metal workpiece. By measuring the magnetic field changes caused by stress or cracks, accurate detection and analysis of stress or cracks can be achieved.

[0026] The functions and detection of each pin are as follows: Power supply and grounding part: VSS (Pin 13): Provides a ground connection for the sensor to ensure signal integrity and reduce external noise interference.

[0027] VDD (pin 15): Provides operating power for MLX90393, usually 3.3V, and is powered by a voltage regulator module to ensure the working stability of the sensor.

[0028] Communication interface part: SCL (Pin 3): I²C clock line, used for synchronous communication with a microprocessor. The microprocessor sends a clock signal through this pin to control the data sampling frequency and configure the sensor operating mode.

[0029] SDA (pin 5): I²C data line, used to transmit magnetic field data collected by MLX90393 to the microprocessor. During the detection process, MLX90393 sends real-time magnetic field data in three directions, X, Y, and Z, to the microprocessor via SDA for stress or crack analysis.

[0030] Control and configuration part: INT / TRIG (pin 7): interrupt / trigger pin, used to start magnetic field sampling or send a data-ready signal to the microprocessor. In the present invention, the microprocessor controls the measurement cycle of MLX90393 through the trigger signal, and synchronously samples the magnetic field data in combination with the frequency of the excitation signal.

[0031] Description of the detection process: Signal stimulus: The microprocessor generates two high-frequency sinusoidal AC signals with a phase difference of 90 degrees, which are applied to the excitation coils on both sides of the orthogonal detection probe respectively.

[0032] The excitation coil generates a rotating electromagnetic field inside the metal material. The interaction of this electromagnetic field with stress concentration or cracks causes dynamic changes in the magnetic field distribution.

[0033] Magnetic field acquisition: The MLX90393 collects the components of the rotating electromagnetic field in real time through magnetic field measurement channels in three directions: X, Y, and Z. Stress concentration or the presence of cracks can cause changes in the intensity, direction, or distribution of the rotating magnetic field, and these changes are captured by the MLX90393's highly sensitive sensors.

[0034] The sampling frequency of the sensor is configured by the microprocessor through the I²C interface to ensure synchronization with the frequency of the excitation signal in order to accurately capture the dynamic response of the magnetic field under the influence of stress concentration or cracks.

[0035] Data transmission and processing: The MLX90393 sends the real-time acquired X, Y, and Z magnetic field components to the microprocessor via the I²C interface.

[0036] The microprocessor uses the collected data to calculate the strength, direction and frequency response characteristics of the magnetic field, and analyzes the existence, direction and depth of the crack in combination with a preset stress concentration or crack characteristic model.

[0037] Crack analysis: The microprocessor generates an induction change value of the crack based on the change in magnetic field distribution, and identifies the location and geometric characteristics of the stress concentration or crack.

[0038] By dynamically analyzing the change in magnetic field with the frequency of the excitation signal, stress concentration or crack information can be further extracted.

[0039] Specifically, the MLX90393 schematic diagram is as follows Figure 3 shown.

[0040] In this embodiment, the connection lines in the present invention all use I²C connection lines to achieve communication connection. The present invention uses STM32F103T8U6 as the main control microprocessor to build a magnetic field data acquisition and analysis platform based on I²C connection line communication. The system architecture includes: 1. Orthogonal detection probe and excitation coil are used to generate rotating electromagnetic field.

[0041] 2.MLX90393 three-dimensional magnetic field sensor, used to collect changes in magnetic field components.

[0042] 3. Microprocessor STM32F103T8U6, used for data acquisition, processing and analysis.

[0043] 4. The host computer display unit, i.e., the data output module, displays the stress concentration or crack defect detection results through serial port communication.

[0044] Software implementation: The system software implements stress concentration or crack detection through the following steps: 1. Configure I²C communication, initialize MLX90393 working mode, and set sampling frequency and resolution.

[0045] 2. Control the generation and synchronization of the excitation signal to achieve the construction of a high-stability rotating electromagnetic field through precise phase difference.

[0046] 3. Collect the X, Y, and Z magnetic field components output by the sensor, and perform synchronous filtering and processing on the data in combination with the real-time excitation frequency.

[0047] 4. Perform dynamic analysis on the magnetic field variation according to the crack characteristic model, generate the geometric characteristic value of stress concentration or crack, and output the test results.

[0048] Defects inside the material, such as stress concentration, cracks, corrosion or thickness changes, will disturb the distribution of eddy currents, change the intensity and direction of eddy currents, and thus affect the inductive impedance of the coil. By detecting these impedance changes, defects or inhomogeneities inside the material can be inferred.

[0049] The impedance quantification part is based on the principle of eddy current detection. An alternating magnetic field is generated in the probe coil, which then induces eddy currents on the surface and near the surface of the metal material being tested. When there are defects such as stress concentration, cracks, holes, corrosion, etc. in the material, the path of the eddy current will be disturbed, resulting in uneven current distribution, thereby changing the impedance measured by the probe. Through the orthogonal structure design, the probe can capture the impact of stress concentration or cracks on eddy current and magnetic field distribution in different directions, and then quantify the stress concentration or crack characteristics through impedance changes.

[0050] Loading AC current with a phase difference of 90° can effectively construct a spatial rotating magnetic field. This design enhances the probe's ability to sense eddy current and magnetic field distribution in different directions. Specifically, stress concentration or cracks in different directions will cause different eddy current disturbances. The orthogonal structure probe can detect these disturbances separately, thereby achieving full-angle and multi-directional stress concentration or crack feature capture.

[0051] Closed-loop detection of stress concentration or cracks is completed through impedance measurement, reference value setting and data processing. First, the signal received by the probe is excited and its impedance change is measured. The eddy current disturbance at the crack will change the inductance and resistance of the probe, thereby affecting the real and imaginary parts of the impedance; then, in the absence of defects, the impedance value of the probe is used as a reference. The appearance of stress concentration or cracks or defects will cause deviations from the reference value. By comparing the impedance difference between the stress concentration or crack area and the defect-free area, information about the stress concentration or crack defect is obtained.

[0052] Specifically, the present invention relates to a metal material stress or crack detection system based on an orthogonal geometric structure. The system applies high-frequency alternating current with a phase difference of 90 degrees to the excitation coils on both sides of the U-shaped dual probe, thereby forming a rotating electromagnetic field inside the metal material and inducing eddy current distribution. The presence of stress concentration or cracks changes the path and distribution of eddy currents, thereby causing changes in the inductive impedance of the probe detection coil. AD5933, as the core detection unit, uses its frequency scanning function and high-precision impedance measurement capability to accurately extract changes in electromagnetic response caused by stress concentration or cracks. The specific role of each pin of AD5933 in the detection system and its functional description: 1. Power supply and reference part Pin 9 (DVDD): Digital power supply, provides operating voltage for the digital circuit part inside the chip, and the operating voltage range is 2.7V to 5.5V.

[0053] Pins 10 and 11 (AVDD1 and AVDD2): analog power supply, specifically used to provide a stable power supply for the analog circuit part of the chip, with a voltage range of 2.7V to 5.5V.

[0054] Pin 12 (DGND): Digital ground, used to ground the digital part of the system, and connected to AGND through a single-point grounding method to isolate noise interference from digital and analog signals.

[0055] Pins 13 and 14 (AGND1 and AGND2): analog ground, used to ground the analog part of the system to ensure signal integrity and reduce the interference of power supply noise on analog signals.

[0056] Clock and signal generation part Pin 8 (MCLK): Master clock input, used to provide a clock signal for the internal frequency generator of AD5933. This system uses an external crystal oscillator to provide a high-stability, high-precision clock source for MCLK, thereby ensuring the frequency of the excitation signal and the accuracy of the measurement.

[0057] Pin 6 (VOUT): Excitation signal output, used to provide a sinusoidal AC excitation signal to the excitation coil of the U-shaped dual probe. The frequency generator inside the AD5933 outputs a series of sinusoidal signals with adjustable frequencies according to the set frequency range and incremental step size. In the present invention, the signal output by VOUT drives the excitation coil through the power amplifier, and the excitation coils on both sides are respectively applied with excitation signals with a phase difference of 90 degrees to form a rotating electromagnetic field.

[0058] Signal receiving and impedance measurement part Pin 4 (REB): provides external reference voltage input or reference voltage output. In the present invention, it is used as a reference voltage output pin to stabilize the measurement reference of the system and ensure the accuracy and consistency of impedance measurement.

[0059] Pin 10 (VIN): Impedance measurement input terminal, connected to the detection coil of the U-shaped dual probe through an external signal conditioning circuit (such as a gain amplifier and a low-pass filter). The detection coil senses the electromagnetic response signal generated by the rotating electromagnetic field inside the metal workpiece, which is conditioned and sent to VIN. The AD5933 calculates the phase and amplitude of the input signal and the reference signal to obtain the impedance characteristics of the workpiece.

[0060] Data communication and control part Pin 15 (SDA): I²C data line, used to exchange data with a microprocessor. After the measurement is completed, the AD5933 transmits the calculated impedance magnitude and phase data through the SDA pin to the microprocessor for further processing and analysis.

[0061] Pin 16 (SCL): I²C clock line, through which the microprocessor communicates and provides a clock signal to synchronize data transmission. In the present invention, the microprocessor configures the parameters of AD5933 (such as frequency range, step size and gain) and reads the measurement data through the SCL and SDA pins.

[0062] Workflow Description: Signal generation: Through the stable clock signal provided by MCLK, the frequency generator inside the AD5933 outputs a sinusoidal excitation signal through the VOUT pin to drive the excitation coil of the U-shaped dual probe to form an electromagnetic field that rotates inside the metal workpiece.

[0063] Signal reception and processing: The detection coil receives the eddy current response signal inside the metal and inputs it to the VIN pin after external signal conditioning. The AD5933 calculates the amplitude and phase of the input signal through an accurate Fourier transform algorithm and converts it into impedance data.

[0064] Data transmission and analysis: Impedance data is transmitted to the microprocessor via the I²C interface and combined with the frequency response characteristics to analyze the stress intensity of the stress concentration area, the direction of the principal stress or the depth, direction and location of the crack.

[0065] System calibration: Use known impedance to calibrate the probe and measurement system, adjust the measurement range through the reference voltage provided by REB, eliminate parasitic effects of external circuits, and improve measurement accuracy.

[0066] Specifically, the AD5933 schematic diagram is as follows Figure 4 shown.

[0067] In the detection system of the present invention, the metal material stress or crack detection system also includes a signal adjustment unit, which is composed of a gain amplifier and a low-pass filter and is arranged between the excitation coil and the impedance analysis unit to improve the accuracy of signal transmission and reduce interference from external signals.

[0068] Second, please refer to Figure 5 , the metal material stress or crack detection methods based on orthogonal geometric structures include: Step 1: Place an orthogonal detection probe wound with an excitation coil on the workpiece to be tested, and pass a sinusoidal signal with a phase difference of 90 degrees into the excitation coil through an impedance analysis unit to generate a rotating electromagnetic field covering all angles inside the workpiece to be tested.

[0069] Step 2: Connect the microprocessor and the three-dimensional magnetic field sensor through a connecting line, and place the three-dimensional magnetic field sensor in the middle of the orthogonal detection probe. The three-dimensional magnetic field sensor captures the intensity, direction and frequency variation characteristics of the rotating magnetic field through its X, Y, and Z three-axis detection channels. Move the orthogonal detection probe, transmit real-time magnetic field data through the three-dimensional magnetic field sensor, and perform crack characteristic analysis based on the real-time magnetic field data.

[0070] Step 3: Move the orthogonal detection probe, obtain the electromagnetic response signal induced by the excitation coil through the impedance analysis unit, and use the internal DSP module to perform Fourier transform on the electromagnetic response signal to calculate the influence characteristics of stress concentration or crack on impedance.

[0071] In this embodiment, the magnetic field quantization module is based on the theory of magnetoelastic effect, which describes the mechanism of change of internal magnetic domains of ferromagnetic materials under external stress. Specifically, when ferromagnetic materials are subjected to external forces or crack defects, their internal magnetic domain walls will deflect and displace, and the energy inside the magnetic domains will continue to change during the deflection process, thereby causing changes in the magnetic permeability or magnetic resistance of the material. This characteristic provides a physical basis for magnetoelastic detection technology, enabling it to efficiently capture magnetic field disturbances in stress concentration areas and cracks.

[0072] Specifically, in magnetoelastic detection, a dual-pole U-shaped sensor with a simple structure and excellent measurement performance is used for signal acquisition. The U-shaped magnetic core has significant advantages in measurement accuracy, stability and portability. At the same time, due to its shape and size, it has good passability and is suitable for detection tasks in complex environments. In addition, since the surface of the workpiece to be tested may have certain unevenness, the detection signal may be attenuated due to the lift-off effect between the sensor probe and the workpiece. The U-shaped magnetic core can effectively reduce the impact of the lift-off effect on the detection accuracy because its two ends fit the workpiece surface well. In the actual detection process, the two ends of the U-shaped magnetic core are respectively wound with an excitation coil. By applying an alternating current to the excitation coil, the sensor generates an alternating magnetic field to form a closed magnetic loop with the ferromagnetic material to be tested. The detection coil is responsible for measuring the induced voltage change generated by the magnetic induction signal in the magnetic loop. When the workpiece to be tested has no stress concentration or cracks, the magnetic induction signal in the magnetic loop is basically consistent, and no significant magnetic field disturbance will be generated. However, when a stress concentration area or crack in a workpiece is detected, the magnetic field distribution will be significantly disturbed due to the significant change in local magnetic permeability, resulting in a local magnetic field imbalance. This change can be accurately captured by the output signal of the detection coil.

[0073] Step 4: Transmit the analysis results of the stress concentration or crack characteristic analysis and the stress concentration or crack influence characteristic analysis on impedance to the upper computer display unit to display the detection results.

[0074] Furthermore, during the detection process, the output voltage of the impedance analysis unit to the excitation coil is adjusted by adjusting the reference voltage of the REFIN / REFOUT pin, thereby achieving automatic calibration and optimization of the measurement range.

[0075] like Figure 6 As shown, Figure 6 The overall circuit diagram of the present invention is given, and the specific connection relationship of several parts should be given, as well as the effect of each part Figure 6In the circuit shown, the main controller consists of STM32F103T8U6 (U2A and U2B), which is powered by a 5V to 3.3V voltage conversion circuit implemented by U3. The system integrates an impedance analysis unit and a magnetic field detection unit to achieve multifunctional measurement and signal transmission.

[0076] Impedance analysis unit; The impedance analysis unit consists of the main controller STM32F103T8U6 (U2) and the high-precision impedance measurement chip AD5933 (U1). The two communicate through the I²C bus, where the 13th pin (SDA) and 14th pin (SCL) of the main controller are connected to the 15th pin (SDA) and 16th pin (SCL) of the AD5933 respectively. The impedance measurement process is as follows: 1. Excitation signal generation: Pin 6 (VOUT) of AD5933 outputs a sinusoidal excitation signal with known frequency and amplitude.

[0077] 2. Signal path and response acquisition: The excitation signal passes through the measurement loop formed by the impedance to be measured (R4) and the known feedback resistor (R3) to form a current signal. After being converted into a voltage signal by an external circuit, the current signal is fed back to pin 5 (VIN) of AD5933.

[0078] 3. Digital signal processing: The internal analog-to-digital converter (ADC) of the AD5933 samples and digitizes the feedback signal, and performs a discrete Fourier transform (DFT) through the internal digital signal processing (DSP) module to extract the real and imaginary parts of the response signal.

[0079] 4. Impedance calculation: Based on the known feedback resistor (R3) and the system gain factor obtained by calibration, the AD5933 calculates the magnitude and phase of the impedance to be measured. The final measurement result is transmitted back to the main controller U2 via the I²C bus for processing.

[0080] Magnetic field detection unit The magnetic field detection unit consists of the main controller STM32F103T8U6 (U2) and the Hall effect magnetic field sensor chip MLX90393 (U5). The two communicate through the I²C bus, where the 11th pin (SDA) and 12th pin (SCL) of the main controller are connected to the 3rd pin (SDA) and 5th pin (SCL) of MLX90393 respectively. The specific process of magnetic field detection is as follows: 1. Hall effect signal generation: When an external magnetic field passes through the Hall sensor of the MLX90393, the Hall effect inside the chip generates a voltage signal that is proportional to the strength and direction of the magnetic field.

[0081] 2. Digital acquisition: The chip's built-in analog-to-digital converter (ADC) digitally samples the Hall voltage signal and extracts the X, Y, and Z direction components of the magnetic field through the signal processing unit.

[0082] 3. Calculation of magnetic field change: Through continuous sampling, the MLX90393 calculates the difference between the current magnetic field value and the previous measured value, thereby obtaining the dynamic change of the magnetic field.

[0083] 4. Data transmission: The processed magnetic field component and change data are transmitted to the main controller U2 via the I²C bus for further processing.

[0084] Data transmission and display The main controller U2 realizes serial communication with the 2nd (RX) and 3rd (TX) pins of the communication chip U4 through the 21st (TX) and 22nd (RX) pins. The measured impedance data and magnetic field data are sent to an external display unit such as a host computer through the serial port for real-time display.

[0085] The present invention proposes an innovative technical solution that combines the magnetoelastic detection principle with the eddy current detection method. By applying a high-frequency alternating current externally, it interacts with the internal stress field or crack defects of the material to detect the magnetic field and impedance changes on the surface or near the surface of the material. Furthermore, the present invention designs two orthogonal U-shaped excitation structures, to which sinusoidal signals with a phase difference of 90 degrees are applied respectively, thereby generating a rotating electromagnetic field signal inside the metal material. The biggest feature of the rotating electromagnetic field is that its direction changes continuously with time, and it can uniformly excite all directions of stress concentration or cracks. This design avoids the limitation that the traditional unidirectional electromagnetic field can only effectively detect stress concentration or cracks in a specific direction, and realizes full-angle detection of stress or cracks.

[0086] The rotating electromagnetic field covers the entire geometric features of the crack by constantly changing its direction, and can sensitively capture the magnetic field disturbance and impedance change caused by stress concentration or crack without predicting the direction of the crack or principal stress. At the same time, the rotating electromagnetic field is combined with the magnetoelastic effect to significantly enhance the coupling effect between the crack or stress field and the detection electromagnetic field, increase the signal change amplitude, and improve the detection sensitivity of stress concentration or cracks. This solution effectively solves the problems of decreased sensitivity and missed detection caused by the uncertain directionality of cracks or principal stresses in traditional methods, while avoiding the complex operation of multi-directional scanning or mechanical rotating probes, simplifying the detection process and improving detection efficiency. In addition, the present invention shows higher accuracy and robustness in the detection of deep-buried cracks or materials with low stress and conductivity by optimizing the excitation structure design and electromagnetic signal processing technology.

[0087] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the schemes disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed in this disclosure. The description and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the claims.

Claims

1. An orthogonal detection probe, characterized in that: The orthogonal detection probe is composed of two U-shaped iron cores arranged orthogonally. Both ends of each U-shaped iron core are wound with an excitation coil, and the excitation coils wound at both ends are connected in series, and the excitation coil at one end is the detection coil.

2. The orthogonal detection probe according to claim 1, characterized in that: The two U-shaped cores of the orthogonal detection probe are orthogonally arranged, and the two U-shaped cores are non-contacting with each other.

3. A metal material stress or crack detection system based on an orthogonal geometric structure using the orthogonal detection probe as claimed in claim 1, characterized in that: A three-dimensional magnetic field sensor is arranged below the orthogonal detection probe, and the three-dimensional magnetic field sensor is connected to the microprocessor; the excitation coil on the orthogonal detection probe is connected to the impedance analysis unit, the impedance analysis unit is connected to the microprocessor, and the microprocessor is connected to the upper computer display unit.

4. The metal material stress or crack detection system based on orthogonal geometric structure according to claim 3 is characterized in that: The impedance analysis unit adopts an AD5933 impedance analysis chip, which is provided with multiple pins, wherein pin 9 is connected to a digital power supply, pins 10 and 11 are analog power supplies, pin 12 is grounded to the digital part of the microprocessor, pins 13 and 14 are grounded to the analog part of the microprocessor, and pins 15 and 16 are connected to the microprocessor for data communication via a connecting line.

5. The metal material stress or crack detection system based on orthogonal geometric structure according to claim 4, characterized in that: Pin 8 of the AD5933 impedance analysis chip is the main clock input, pin 6 is the excitation signal output and is connected to the input end of the excitation coil, pin 4 is connected to the external voltage source, and pin 10 is the impedance detection input and is connected to the output end of the excitation coil.

6. The metal material stress or crack detection system based on orthogonal geometric structure according to claim 3, characterized in that: The three-dimensional magnetic field sensor adopts the MLX90393 chip magnetic field change detection unit, and the microprocessor adopts the STM32F103T8U6 main controller communication control unit.

7. A method for detecting stress or cracks in metal materials using the metal material stress or crack detection system based on orthogonal geometric structure according to claim 3, characterized in that: include: Step 1: Place an orthogonal detection probe wound with an excitation coil on the workpiece to be tested, and pass a sinusoidal signal with a phase difference of 90 degrees into the excitation coil through an impedance analysis unit, so that a rotating electromagnetic field with full angle coverage is generated inside the workpiece to be tested; Step 2, connecting the microprocessor and the three-dimensional magnetic field sensor through a connecting line, arranging the three-dimensional magnetic field sensor in the middle of the orthogonal detection probe, the three-dimensional magnetic field sensor captures the intensity, direction and frequency variation characteristics of the rotating magnetic field through its X, Y, and Z three-axis detection channels, moving the orthogonal detection probe, transmitting real-time magnetic field data through the three-dimensional magnetic field sensor, and performing crack characteristic analysis based on the real-time magnetic field data; Step 3, move the orthogonal detection probe, obtain the electromagnetic response signal induced by the excitation coil through the impedance analysis unit, and use the internal DSP module to perform Fourier transform on the electromagnetic response signal to calculate the influence characteristics of stress or crack on impedance; Step 4: The stress or crack characteristic analysis and the characteristic analysis results of the stress or crack and its influence on the impedance are transmitted to the upper computer display unit to present the real-time detection results.

8. The metal material stress or crack detection method according to claim 7, characterized in that: In step 3, during the detection process, the reference voltage of the REFIN / REFOUT pin is adjusted to change the output voltage of the impedance analysis unit to the excitation coil, thereby achieving automatic calibration and optimization of the measurement range.

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