Method and system for controlled opening of cracks in metal components based on fatigue guidance and real-time monitoring

Abstract

This invention discloses a method and system for controllable crack propagation in metal components based on fatigue guidance and real-time monitoring, belonging to the technical fields of metal material failure analysis, non-destructive testing, and structural safety assessment. Through fatigue-guided propagation, the crack separates slowly and stably at extremely low stress levels, avoiding macroscopic plastic deformation, impact damage, and instantaneous fracture zone impact caused by traditional overload fracture, perfectly preserving the original microstructures such as fatigue striations, cleavage planes, and intergranular fracture. By deploying monitoring sensors and using a crack state fusion solution model based on real-time data acquisition, the crack propagation rate is dynamically calculated, thereby adjusting the parameters of high-frequency, low-amplitude cyclic loading. This closed-loop feedback control mechanism can perceive the crack state in real time, ensuring stable crack propagation under fatigue mechanisms, creating a core condition for obtaining high-quality fracture morphology.

Description

Technical Field

[0001] This invention belongs to the technical field of metal material failure analysis, non-destructive testing and structural safety assessment, specifically involving a method and system for controllable crack opening of metal components based on fatigue guidance and real-time monitoring. Background Technology

[0002] In the field of failure analysis of metallic components, accurately determining the failure mechanism is fundamental to preventing recurrence of accidents and optimizing design and processes. Among these, opening cracks in failed components to obtain and observe their original fracture morphology is a crucial step in diagnosing mechanisms such as fatigue, stress corrosion, and hydrogen embrittlement. The microscopic morphology of the fracture surface is the "fingerprint" of crack propagation behavior, and its integrity directly affects the accuracy and reliability of the analytical conclusions. Furthermore, for high-value, high-reliability components in nuclear power, aerospace, and other applications, current technologies cannot achieve precise control and monitoring of the entire crack propagation process under simulated service environments or inert protection. Traditional physical crack opening methods (such as hammering, mechanical breaking, or direct cutting) have serious drawbacks. They are essentially uncontrollable overload fractures with significant defects: 1) They introduce uncontrollable secondary mechanical damage, such as impact dents, shear lips, and severe plastic deformation, which seriously damage key micro-morphologies such as fatigue striations and cleavage steps; 2) They cannot precisely control the crack propagation path, which may cause the opening surface to deviate from the original crack surface and lose the most important information about the crack origin zone; 3) They are highly dependent on the operator's experience, and the success rate is unstable. For high-strength steel, brittle materials, or geometrically complex irregular components, the risk of failure is particularly prominent.

[0003] To address this issue, while existing technologies have introduced slow-speed loading devices, their loading modes are still mostly monotonically increasing until the specimen becomes unstable and fractures, remaining within the scope of high-stress overload fracture and unable to avoid the localized impact and damage caused by the eventual instantaneous fracture. Therefore, developing an opening method that can maximally protect the original fracture morphology and precisely control the crack propagation path and process has become a core technical challenge that urgently needs to be overcome to improve the reliability of failure analysis and unlock deeper fault information. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method and system for controllable crack opening in metal components based on fatigue guidance and real-time monitoring. This method achieves precise "control" of the fracture process by allowing the crack to propagate stably under controlled fatigue loads until separation, and by combining multi-parameter real-time monitoring and feedback control, thereby obtaining a high-quality fracture surface with no secondary damage and intact microstructure.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for controllable crack opening in metal components based on fatigue guidance and real-time monitoring, comprising the following steps: Locate the crack position of the metal component and use a clamp to fix the metal component to the loading device to obtain the clamped sample; The clamped sample was placed in an inert atmosphere, and monitoring sensors were arranged around the propagation path of the crack. High-frequency, low-amplitude cyclic loading was applied to the clamped sample to cause crack propagation under fatigue mechanism; During the crack propagation process under fatigue mechanism, data from monitoring sensors are collected in real time. The collected data from the monitoring sensors are input into a pre-constructed crack state fusion solution model to calculate the crack propagation rate. Based on the crack propagation rate, the parameters of the cyclic load are dynamically adjusted to keep the crack propagating stably. Continue the process of crack propagation and dynamic adjustment of cyclic load parameters until the crack is fully opened, resulting in two fresh fracture samples. The two fresh fracture surface samples were subjected to in-situ fracture protection and sampling.

[0006] In the step of locating the crack position of the metal component and fixing the metal component to the loading device with a clamp to obtain the clamped sample, the loading device is a high-frequency fatigue testing machine or a hydraulic servo fatigue testing machine.

[0007] In the step of placing the clamped sample in an inert atmosphere and arranging monitoring sensors around the propagation path of the crack location, the monitoring sensors include an acoustic emission sensor array and are equipped with an optical measurement system for monitoring the surface displacement field at the crack location.

[0008] The method for applying high-frequency, low-amplitude cyclic loading to the clamped sample to stabilize crack propagation under fatigue mechanism is as follows: Fatigue loading was performed using a progressively decreasing load method. The crack propagation was initiated at a level higher than the initial stress intensity factor amplitude ΔK. Subsequently, based on the monitored stable propagation signal, the load amplitude was gradually reduced, allowing the crack to propagate at a reduced stress intensity factor amplitude ΔK.

[0009] The initial stress intensity factor amplitude ΔK is the fatigue crack propagation threshold value ΔK of the metal component material in an inert atmosphere. th 1.0 to 2.0 times.

[0010] The frequency of the high-frequency, low-amplitude cyclic load is above 10 Hz.

[0011] During the crack propagation process under fatigue mechanism, data from monitoring sensors are collected in real time. This collected data is then input into a pre-constructed crack state fusion solution model to calculate the crack propagation rate. Based on this crack propagation rate, the parameters of the cyclic load are dynamically adjusted to maintain stable crack propagation. The method is as follows: Real-time acquisition and monitoring of sensor data, including acoustic emission signals, strain data, and optical displacement data; The collected data from the monitoring sensors are input into the pre-built crack state fusion solution model. By analyzing the number, energy, and location of acoustic emission signal events and the strain field evolution of strain data, the precise length, real-time propagation rate, and crack tip stress intensity factor amplitude ΔK of the current crack are calculated and monitored in real time. Based on the real-time crack propagation rate and the amplitude of the stress intensity factor ΔK at the crack tip, the da / dN-ΔK relationship of the crack is constructed and compared with the standard fatigue crack propagation rate curve of the material. Based on the comparison results, the amplitude of the cyclic load is adaptively adjusted. The basis for this dynamic adjustment is: When the real-time da / dN-ΔK relationship point remains outside the safe propagation zone above the standard fatigue crack propagation rate curve, or when the calculated relationship slope indicates that unstable propagation will occur, the load amplitude should be reduced or the stress ratio adjusted.

[0012] During the process of crack propagation and dynamic adjustment of cyclic load parameters, which continues until the crack is fully opened and two fresh fracture samples are obtained, an emergency stop signal is triggered by the monitoring sensor at the moment of opening, and the cyclic load is reduced to zero.

[0013] The method for in-situ preservation and sampling of the two obtained fresh fracture surface samples is as follows: Under the protection of an inert atmosphere, the two fresh fracture samples obtained by opening the crack are quickly transferred to a sealed storage container filled with inert gas, or a nanoscale protective coating is immediately deposited on the fracture surface in situ.

[0014] Secondly, the present invention provides a controllable crack opening system for metal components based on fatigue guidance and real-time monitoring, comprising: A loading device for clamping metal parts and applying cyclic loads to the clamped sample; An environmental control chamber is used to provide an inert atmosphere environment. Monitoring sensors are placed around the crack's propagation path to collect crack propagation data; The controller, communicatively connected to the monitoring sensor and the loading device, includes: The data acquisition module is used to receive data collected by the monitoring sensor; The calculation module is used to calculate the crack propagation rate based on the data collected by the monitoring sensor; A dynamic adjustment module is used to generate control commands to dynamically adjust the cyclic load parameters output by the loading device according to the crack propagation rate.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method and system for controllable crack opening in metal components based on fatigue guidance and real-time monitoring. Through fatigue-guided propagation, the crack separates slowly and stably at extremely low stress levels, avoiding macroscopic plastic deformation, impact damage, and instantaneous fracture zone impact caused by traditional overload fracture. It perfectly preserves the original microstructures such as fatigue striations, cleavage planes, and intergranular fracture. By deploying monitoring sensors and using a crack state fusion solution model based on real-time data, the crack propagation rate is dynamically calculated, thereby adjusting the parameters of the high-frequency, low-amplitude cyclic load. This closed-loop feedback control mechanism can perceive the crack state in real time, ensuring stable crack propagation under fatigue mechanisms, creating the core conditions for obtaining high-quality fracture morphology. It lowers the technical threshold and experience reliance for operators, promoting the standardization and traceability of this crucial crack opening step.

[0016] Furthermore, the entire process is conducted in an inert atmosphere, effectively preventing oxidation and contamination of the crack tip and newly formed fracture surface during propagation. By precisely controlling the load to ensure complete crack opening, two paired, undamaged, fresh fracture surface samples can be obtained, preserving the original morphological characteristics of the fracture surface to the maximum extent.

[0017] Furthermore, this invention is applicable to high-strength steel, brittle materials, and samples containing important surface coatings or corrosion products that are extremely sensitive to secondary damage. It is also applicable to irregularly shaped parts that are difficult to clamp (with the aid of specialized fixtures).

[0018] Furthermore, the acoustic emission and strain data generated during the entire opening process are valuable information for studying crack propagation behavior, which can be corroborated with fracture morphology analysis, enriching the data dimensions of failure analysis. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a system diagram of the controller in Embodiment 4 of the present invention. Detailed Implementation

[0020] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0021] Example 1 A method for controllable crack opening in metal components based on fatigue guidance and real-time monitoring includes the following steps: S1: Locate the crack position of the metal component and use a clamp to fix the metal component to the loading device to obtain the clamped sample; S2: Place the clamped sample in an inert atmosphere and arrange monitoring sensors around the propagation path of the crack. S3: Apply high-frequency, low-amplitude cyclic loads to the clamped sample to allow the crack to propagate stably under fatigue mechanism; S4: During the crack propagation process under the fatigue mechanism, data from monitoring sensors are collected in real time. The collected data from the monitoring sensors are input into a pre-constructed crack state fusion solution model to calculate the crack propagation rate. Based on the crack propagation rate, the parameters of the cyclic load are dynamically adjusted to keep the crack propagating stably. S5: Continue the above process of crack propagation and dynamic adjustment of cyclic load parameters until the crack is fully opened and two fresh fracture samples are obtained. S6: Perform in-situ preservation and sampling of the two fresh fracture samples.

[0022] Specifically, in S1, sample pretreatment and clamping: non-destructive testing is performed on the metal parts containing cracks to locate the crack ends of the metal parts; the parts are fixed on the fatigue loading device using a low-damage adaptive fixture to ensure that the direction of the applied force can cause the crack to propagate within a preset plane, and the contact area between the fixture and the sample is covered with a soft pad to disperse the pressure.

[0023] Preferably, the loading device is a high-frequency fatigue testing machine or a hydraulic servo fatigue testing machine.

[0024] Specifically, in S2, a protective environment and monitoring system are established: the clamped sample is placed in a sealable chamber, evacuated, and then filled with inert gas or dry air; an array of acoustic emission sensors is arranged in the area near the crack tip and around the crack propagation path, and an optical measurement system is installed to monitor the surface displacement field at the crack location.

[0025] Specifically, in S3, fatigue-guided crack propagation is implemented: the loading device is activated to apply a high-frequency, low-stress-amplitude cyclic load to the clamped sample. The maximum value of the cyclic load is much lower than the yield strength of the metal component material, and the initial stress intensity factor amplitude ΔK is the fatigue crack propagation threshold value ΔK of the material in the corresponding environment (in an inert atmosphere). th 1.0 to 2.0 times.

[0026] Fatigue loading is performed using a progressively decreasing load method: starting with a slightly higher initial stress intensity factor amplitude ΔK to initiate propagation, and then gradually reducing the load amplitude based on the monitored stable propagation signal, so that the crack propagates at a lower stress intensity factor amplitude ΔK, thereby further reducing the size of the plastic zone at the crack tip and obtaining a more "brittle" and smoother fatigue fracture surface.

[0027] Preferably, the frequency of the high-frequency low-amplitude cyclic load is above 10 Hz.

[0028] Specifically, in S4, real-time monitoring and feedback control: during the fatigue loading process, data from monitoring sensors are collected synchronously in real time, including acoustic emission signals, strain data, and optical displacement data; The collected data from the monitoring sensors are input into the pre-built crack state fusion solution model. By analyzing the number, energy, and location of acoustic emission signal events and the strain field evolution of strain data, the precise length, real-time propagation rate, and crack tip stress intensity factor amplitude ΔK of the current crack are calculated and monitored in real time. Based on the real-time crack propagation rate and the amplitude of the stress intensity factor ΔK at the crack tip, the da / dN-ΔK relationship of the crack is constructed and compared with the standard fatigue crack propagation rate curve of the material. Based on the comparison results, the amplitude of the cyclic load is adaptively adjusted. The basis for this dynamic adjustment is: When the real-time da / dN-ΔK relationship point remains outside the safe propagation zone above the standard fatigue crack propagation rate curve, or when the calculated relationship slope indicates that unstable propagation will occur, the load amplitude should be reduced or the stress ratio adjusted.

[0029] Furthermore, in the real-time monitoring, the continuous acoustic emission generated by the stable expansion of cracks and the sudden acoustic emission caused by microcrack connection and small fragment peeling are identified through three-dimensional positioning and pattern recognition technology of acoustic emission signals, and are used as one of the important input parameters for feedback control.

[0030] Specifically, in S5, the crack completely separates and the process terminates: continue steps S3 and S4 until the crack propagates under fatigue load and causes the component crack to completely open; at the moment of opening, an emergency stop signal is triggered by the monitoring sensor, and the cyclic load returns to zero; Specifically, in S6, in-situ protection and sampling of the fracture surface: Under the protection of an inert atmosphere, the two fresh fracture surface samples obtained by opening the crack are quickly transferred to a sealed storage container filled with inert gas, or a nano-scale protective coating is immediately deposited in situ on the fracture surface.

[0031] Furthermore, the method also includes an intelligent decision support step: before loading begins, the material grade of the metal component, heat treatment status, crack geometry information are input, and the built-in database is called to recommend the initial load range, safe propagation rate threshold, and expected number of opening cycles.

[0032] Example 2 The heat-affected zone (HAZ) specimens containing service-induced microcracks were taken from a sampling plate of a decommissioned or simulated irradiated nuclear reactor pressure vessel (RPV). Without introducing secondary damage, the cracks were controlled to open, obtaining a microstructure that accurately reflects the fatigue and fracture morphology of the material in the embrittled state after irradiation; precisely characterizing the impact of irradiation defects (such as copper-rich clusters and embrittled phases) on crack propagation paths and mechanisms; validating irradiation embrittlement prediction models; and assessing the remaining RPV life. Details are as follows: S1: Sample pretreatment and clamping: The crack location of the metal component is identified, and the component is secured to the loading device using clamps to obtain the clamped sample. The metal component sample is typically a standard specimen pre-induced with fatigue cracks after undergoing compact tensile (CT) or single edge-notched bent (SEB) operations. All operations are performed in a heated chamber or glove box to handle radioactive samples.

[0033] The clamping process uses a remotely operated robotic arm, and the clamping material must be radiation-resistant and have low activation. Nuclear-grade graphite sheets are considered for the soft pads, as they can distribute pressure and avoid introducing metal contamination.

[0034] S2: Establish a protective environment and monitoring system The clamped sample is placed in an inert atmosphere, and monitoring sensors are arranged around the crack propagation path. Environmental control is of paramount importance. The inert atmosphere chamber is designed to simulate the primary loop water chemistry environment (high temperature, high pressure, boron-lithium aqueous solution) to study the interaction between stress corrosion cracking and fatigue. For dry environment studies, high-purity argon gas is introduced and strictly deoxygenated.

[0035] The monitoring system needs to be adaptable to harsh environments. High-temperature and radiation-resistant acoustic emission sensors are selected and coupled to the high-temperature region via waveguide rods. The optical measurement system observes through a sapphire window or uses non-contact methods such as laser displacement gauges.

[0036] S3: Implement fatigue-guided crack propagation High-frequency, low-amplitude cyclic loading was applied to the clamped sample to induce crack propagation under fatigue mechanisms. The loading strategy was extremely conservative. The initial ΔK was set at a very low level, only slightly higher than the ΔK of the irradiated material. th (Irradiation usually raises the threshold value).

[0037] Extremely slow loading frequencies (potentially as low as 0.1–1 Hz) are employed to better observe time-dependent (e.g., environmentally induced) crack propagation effects and reduce thermal effects.

[0038] The "load reduction method" is strictly adopted, with the goal of making the crack eventually approach or even lower than ΔK after irradiation. th The material is extended under extremely low driving force to expose the intrinsic embrittlement characteristics of the material to the greatest extent, obtain a straight fracture surface, and facilitate the observation of irradiation-induced microstructural changes.

[0039] S4: Real-time monitoring and feedback control During crack propagation under fatigue mechanisms, data from monitoring sensors is collected in real time. This data is then input into a pre-constructed crack state fusion solution model to calculate the crack propagation rate. Based on this rate, the parameters of the cyclic load are dynamically adjusted to maintain stable crack propagation. The core purpose of the monitoring sensor data is to distinguish characteristic signals of irradiation embrittlement. During crack propagation in irradiated embrittled materials, the proportion of sudden acoustic emission events may increase significantly, reflecting a greater tendency for discontinuous, cleavage, or grain boundary fracture. The system uses this as a key feedback parameter.

[0040] By combining DC potential drop or AC potential drop technology to accurately measure crack length in real time, and cross-checking with acoustic emission and DIC data, the absolute reliability of crack propagation rate da / dN calculation is ensured.

[0041] Based on the crack propagation rate, the feedback control threshold is set extremely strictly during the dynamic adjustment of the cyclic load parameters. Any signal indicating a potential transition to unstable cleavage fracture (such as a sharp increase in acoustic emission energy or acceleration of da / dN) will trigger a stepwise decrease or emergency suspension of the load, ensuring that the crack remains in a fatigue-dominated stable propagation mode.

[0042] S5: Continue the above process of crack propagation and dynamic adjustment of cyclic load parameters until the crack is fully opened, and obtain two fresh fracture samples.

[0043] S6: The two fresh fracture surface samples were subjected to in-situ preservation and sampling. After crack initiation, if in a high-temperature water environment, a strict cooling and drying procedure must be performed to prevent corrosion after reactor shutdown. Under inert gas protection, the fresh fracture surface samples were remotely transferred to a double-sealed, argon-filled shielded container. Subsequent fracture surface analysis also needed to be performed in an electron microscope hot chamber equipped with a special sample holder, ensuring the fracture surface was protected from atmospheric oxidation and contamination throughout the process.

[0044] Specifically, the methods for fracture analysis are as follows: Before placing the sample into a high-vacuum electron microscope, the fracture surface is observed and recorded holistically, three-dimensionally, and at low magnification (usually ≤100x). The crack origin, propagation direction, and distribution of different characteristic regions are determined, and the locations requiring subsequent high-magnification analysis are precisely marked.

[0045] First, macroscopic localization was performed using a stereomicroscope within a shielded container to identify crack initiation sites, propagation zones, and oxidation areas. Subsequently, the sample was transferred to a scanning electron microscope (SEM) under an inert atmosphere. Secondary electron imaging revealed the microscopic morphology determining failure modes, such as fatigue streaks and intergranular fracture. Backscattered electron imaging and X-ray energy dispersive spectroscopy were combined to analyze the regional composition, locating corrosion products and harmful elements. Based on the typical characteristic regions identified by SEM, a focused ion beam was used to extract thin film samples in situ at these locations. Finally, atomic-scale crystal structure analysis and high-resolution compositional analysis were performed using a transmission electron microscope (TEM) to ultimately reveal the microscopic mechanism and root cause of crack propagation.

[0046] This embodiment not only safely obtained the analysis sample, but more importantly, its fully controlled and data-rich opening process itself generated a valuable information flow for evaluating material performance and structural integrity, perfectly meeting the nuclear industry's requirements for "process traceability, result verification, and decision-making basis".

[0047] Example 3 In-situ evidence collection and safe separation of a failed steel structural member in a large-scale engineering project. A thick-section Q345 steel member in a structure experienced a fracture accident, with macroscopically visible cracks. Under laboratory conditions, the member was safely and controlledly opened along the existing cracks. Simultaneously, it was necessary to completely preserve physical evidence of the fracture process (such as fracture morphology, inclusion location, etc.) for subsequent forensic identification and liability analysis. The separation process was ensured to prevent catastrophic brittle fracture and protect personnel and equipment. Specific implementation details: S1: Sample pretreatment and clamping Cut the component segment containing the complete crack from the accident site. Clamp it using a large hydraulic wedge opening loading jig or a three-point bending jig, with soft gaskets made of high-strength engineering plastic. Ensure that the loading simulates the actual stress pattern of the crack in the structure (such as the opening type).

[0048] S2: Establish a protective environment and monitoring system Due to the large size of the component, a localized environmental chamber was used to cover the cracked area, and dry air (relative humidity <5%) was introduced to prevent severe corrosion of the fresh fracture surface. The monitoring system, based on acoustic emission three-dimensional localization and crack tip displacement gauges, tracks in real time whether the crack front edge expands uniformly in the thickness direction.

[0049] S3: Implement fatigue-guided crack propagation Before initiation, the intelligent decision support system is invoked, and the material grade, component thickness, and crack length are input. The system recommends an initial ΔK and a safety threshold. A lower loading frequency is used to accommodate the response of thick-section materials. The core strategy remains "gradual load reduction," but the threshold value ΔK is adjusted. th Refer to the data for this steel in dry air.

[0050] S4: Real-time monitoring and feedback control The monitoring focuses on the stability of the crack propagation rate and the localization of acoustic emission events. By plotting the crack lead in real-time using acoustic emission data, if severely uneven propagation is detected (faster on one side than the other), the control system automatically adjusts the fixture attitude or loading point to correct the propagation path. The propagation rate threshold is set conservatively to absolutely prevent unstable propagation.

[0051] S5, S6: Termination and Protection: After the component is fully opened, a high-resolution three-dimensional topographic scan of the two fracture surfaces is immediately performed as permanent digital evidence. Subsequently, a peelable transparent anti-rust coating is sprayed onto the fracture surface, followed by physical encapsulation and archiving.

[0052] This embodiment focuses on engineering assessment and safety, pursuing process controllability and the integrity of evidence. It utilizes real-time feedback of multiple parameters to ensure stable and uniform crack propagation throughout the entire thick section, preventing accidental brittle fracture; thus providing a scientific, reliable, and repeatable means of preparing physical evidence for the investigation of major engineering accidents.

[0053] Example 4 A controlled crack opening system for metal components based on fatigue guidance and real-time monitoring includes: A loading device for clamping metal parts and applying cyclic loads to the clamped sample; An environmental control chamber is used to provide an inert atmosphere environment. Monitoring sensors are placed around the crack's propagation path to collect crack propagation data; The controller, communicatively connected to the monitoring sensor and the loading device, includes: The data acquisition module is used to receive data collected by the monitoring sensor; The calculation module is used to calculate the crack propagation rate based on the data collected by the monitoring sensor; A dynamic adjustment module is used to generate control commands to dynamically adjust the cyclic load parameters output by the loading device according to the crack propagation rate.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for controllable opening of cracks in metal components based on fatigue guidance and real-time monitoring, characterized by, Includes the following steps: Locate the crack position of the metal component and use a clamp to fix the metal component to the loading device to obtain the clamped sample; The clamped sample was placed in an inert atmosphere, and monitoring sensors were arranged around the propagation path of the crack. High-frequency, low-amplitude cyclic loading was applied to the clamped sample to cause crack propagation under fatigue mechanism; During the crack propagation process under fatigue mechanism, data from monitoring sensors are collected in real time. The collected data from the monitoring sensors are input into a pre-constructed crack state fusion solution model to calculate the crack propagation rate. Based on the crack propagation rate, the parameters of the cyclic load are dynamically adjusted to keep the crack propagating stably. Continue the process of crack propagation and dynamic adjustment of cyclic load parameters until the crack is fully opened, resulting in two fresh fracture samples. The two fresh fracture surface samples were subjected to in-situ fracture protection and sampling.

2. The method for controllable crack opening of metal components based on fatigue guidance and real-time monitoring according to claim 1, characterized in that, In the step of locating the crack position of the metal component and fixing the metal component to the loading device with a clamp to obtain the clamped sample, the loading device is a high-frequency fatigue testing machine or a hydraulic servo fatigue testing machine.

3. The method for controllable crack opening of metal components based on fatigue guidance and real-time monitoring according to claim 1, characterized in that, In the step of placing the clamped sample in an inert atmosphere and arranging monitoring sensors around the crack propagation path, the monitoring sensors include an acoustic emission sensor array and are equipped with an optical measurement system for monitoring the surface displacement field at the crack location.

4. The method for controllable crack opening of metal components based on fatigue guidance and real-time monitoring according to claim 1, characterized in that, The method for applying high-frequency, low-amplitude cyclic loading to the clamped sample to stabilize crack propagation under fatigue mechanism is as follows: Fatigue loading was performed using a progressively decreasing load method. The crack propagation was initiated at a level higher than the initial stress intensity factor amplitude ΔK. Subsequently, based on the monitored stable propagation signal, the load amplitude was gradually reduced, allowing the crack to propagate at a reduced stress intensity factor amplitude ΔK.

5. The method for controllable crack opening of metal components based on fatigue guidance and real-time monitoring according to claim 4, characterized in that, The initial stress intensity factor amplitude ΔK is 1.0 to 2.0 times the fatigue crack propagation threshold value ΔK th of the metal component in an inert atmosphere.

6. The method for controllable crack opening of metal components based on fatigue guidance and real-time monitoring according to claim 4, characterized in that, The frequency of the high-frequency, low-amplitude cyclic load is above 10 Hz.

7. The method for controllable crack opening of metal components based on fatigue guidance and real-time monitoring according to claim 4, characterized in that, During the crack propagation process under fatigue mechanism, data from monitoring sensors are collected in real time. This collected data is then input into a pre-constructed crack state fusion solution model to calculate the crack propagation rate. Based on this crack propagation rate, the parameters of the cyclic load are dynamically adjusted to maintain stable crack propagation. The method is as follows: Real-time acquisition and monitoring of sensor data, including acoustic emission signals, strain data, and optical displacement data; The collected data from the monitoring sensors are input into the pre-built crack state fusion solution model. By analyzing the number, energy, and location of acoustic emission signal events and the strain field evolution of strain data, the precise length, real-time propagation rate, and crack tip stress intensity factor amplitude ΔK of the current crack are calculated and monitored in real time. Based on the real-time crack propagation rate and the amplitude of the stress intensity factor ΔK at the crack tip, the da / dN-ΔK relationship of the crack is constructed and compared with the standard fatigue crack propagation rate curve of the material. Based on the comparison results, the amplitude of the cyclic load is adaptively adjusted. The basis for this dynamic adjustment is: When the real-time da / dN-ΔK relationship point remains outside the safe propagation zone above the standard fatigue crack propagation rate curve, or when the calculated relationship slope indicates that unstable propagation will occur, the load amplitude should be reduced or the stress ratio adjusted.

8. The method for controllable crack opening of metal components based on fatigue guidance and real-time monitoring according to claim 1, characterized in that, During the process of crack propagation and dynamic adjustment of cyclic load parameters, which continues until the crack is fully opened and two fresh fracture samples are obtained, an emergency stop signal is triggered by the monitoring sensor at the moment of opening, and the cyclic load is reduced to zero.

9. A method for controllable crack opening in metal components based on fatigue guidance and real-time monitoring according to claim 1, characterized in that, The method for in-situ preservation and sampling of the two obtained fresh fracture surface samples is as follows: Under the protection of an inert atmosphere, the two fresh fracture samples obtained by opening the crack are quickly transferred to a sealed storage container filled with inert gas, or a nanoscale protective coating is immediately deposited on the fracture surface in situ.

10. A controlled crack opening system for metal components based on fatigue guidance and real-time monitoring, based on the controlled crack opening method for metal components based on fatigue and real-time monitoring as described in any one of claims 1 to 9, characterized in that, include: A loading device for clamping metal parts and applying cyclic loads to the clamped sample; An environmental control chamber is used to provide an inert atmosphere environment. Monitoring sensors are placed around the crack's propagation path to collect crack propagation data; The controller, communicatively connected to the monitoring sensor and the loading device, includes: The data acquisition module is used to receive data collected by the monitoring sensor; The calculation module is used to calculate the crack propagation rate based on the data collected by the monitoring sensor; A dynamic adjustment module is used to generate control commands to dynamically adjust the cyclic load parameters output by the loading device according to the crack propagation rate.

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