Method and apparatus for fatigue life qualification of a superconducting magnet

Abstract

This application discloses a method and apparatus for verifying the fatigue life of a superconducting magnet. The method includes: acquiring the total stress amplitude of the superconducting magnet, which is composed of the thermal stress amplitude caused by temperature cyclic loading and the stress amplitude caused by mechanical cyclic loading; and then performing a fatigue life verification operation on the superconducting magnet based on the acquired total stress amplitude. This method integrates the stress amplitudes corresponding to temperature cyclic loading and mechanical cyclic loading to form a total stress amplitude reflecting the actual stress state of the superconducting magnet. Based on this, fatigue life verification can fully consider the combined influence of two key loads on the fatigue damage of the superconducting magnet, avoiding the one-sided results caused by verification based solely on a single load stress. Its technical effect is to make the fatigue life verification more closely match the actual stress scenario of the superconducting magnet, effectively improving the accuracy and reliability of the verification results, and providing more scientific technical support for the fatigue life assessment of superconducting magnets.

Description

Technical Field

[0001] This application relates to the field of superconducting magnet technology, and in particular to a method and apparatus for verifying the fatigue life of superconducting magnets. Background Technology

[0002] Superconducting magnets are the power source and core component of high-speed maglev trains, and their reliable and stable operation throughout the entire service life of the train is crucial.

[0003] In the existing technology, there are mature methods for evaluating the fatigue life of conventional mechanical structures. However, due to the special operating environment of high-speed maglev trains, superconducting magnets are continuously subjected to the coupling effects of multiple physical field loads, such as temperature field, structural field and electromagnetic field, during service.

[0004] Currently, there is no effective verification method to handle this multi-physics coupling effect and to conduct a systematic fatigue life assessment of superconducting magnets. This results in a lack of reliable life prediction basis for the design of superconducting magnets, making it impossible to effectively assess their long-term reliability under complex loads during the design phase. Consequently, this restricts the safety verification and engineering application of superconducting high-speed maglev trains. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a method and apparatus for verifying the fatigue life of superconducting magnets.

[0006] The embodiments of this application disclose the following technical solutions: In a first aspect, embodiments of this application provide a method for verifying the fatigue life of a superconducting magnet, the method comprising: Obtain the total stress amplitude of the superconducting magnet; wherein, the total stress amplitude includes the thermal stress amplitude caused by temperature cyclic loading and the stress amplitude caused by mechanical cyclic loading; The fatigue life of the superconducting magnet is checked based on the total stress amplitude.

[0007] In one possible implementation, obtaining the total stress amplitude of the superconducting magnet includes: The temperature cyclic load spectrum and mechanical cyclic load spectrum acting on the superconducting magnet were obtained; The thermal stress amplitude caused by the temperature cyclic load is determined based on the temperature cyclic load spectrum, and the stress amplitude caused by the mechanical cyclic load is determined based on the mechanical cyclic load spectrum. The total stress amplitude is obtained by superimposing the thermal stress amplitude caused by the temperature cyclic load and the stress amplitude caused by the mechanical cyclic load.

[0008] In one possible implementation, the superconducting magnet comprises both non-superconducting and superconducting materials; The fatigue life verification of the superconducting magnet based on the total stress amplitude includes: The first fatigue life of the non-superconducting material is checked based on the total stress amplitude. The superconducting material is subjected to a second fatigue life check based on the total stress amplitude.

[0009] In one possible implementation, the first fatigue life check of the non-superconducting material based on the total stress amplitude includes: The total stress amplitude is corrected by average stress to obtain the equivalent symmetrical cyclic stress amplitude; Obtain the fatigue characteristic curve of the non-superconducting material; wherein the fatigue characteristic curve is used to describe the functional relationship between the stress amplitude and fatigue life of the non-superconducting material; Based on the equivalent symmetrical cyclic stress amplitude and the fatigue characteristic curve, the fatigue safety margin of the non-superconducting load-bearing structural material is checked.

[0010] In one possible implementation, the average stress correction for the total stress amplitude is performed using the following formula: ; in, The equivalent symmetrical cyclic stress amplitude, The total stress amplitude, For average stress, This represents the tensile strength of a superconducting magnet at its lowest operating temperature.

[0011] In one possible implementation, the second fatigue life check of the superconducting material based on the total stress amplitude includes: Based on the total stress amplitude, the interfacial shear stress of the epoxy composite structure in the superconducting structural material is determined; Based on the interfacial shear stress and the interlaminar ultimate shear strength of the epoxy composite structure, a cumulative damage model is used to check the delamination damage.

[0012] In one possible implementation, the cumulative damage model is: ; Where D is the cumulative damage value, and N is the total number of cycles within the lifespan. Let be the interfacial shear stress during the i-th cycle. The interlaminar ultimate shear strength is given by denoted as D, and m is the material damage index. When D ≥ 1, the epoxy composite structure is deemed to have failed. The total number of cycles is determined based on the phase relationship between the temperature cyclic load and the mechanical cyclic load.

[0013] In one possible implementation, the interfacial shear stress is calculated using the following formula: ; in, The interfacial shear stress is... For thermal stress, The thickness of the superconducting layer, The total thickness of the structure. It is a geometric factor.

[0014] In one possible implementation, the second fatigue life check of the superconducting material based on the total stress amplitude includes: Based on the total stress amplitude and the preset crack size, the stress intensity factor is calculated; Based on the stress intensity factor and the fracture toughness of the superconducting material, the safety margin for brittle fracture is checked.

[0015] In one possible implementation, the method further includes: The state parameters of the superconducting magnet are monitored by multiple sensors disposed on the superconducting magnet; wherein, the multiple sensors include at least two of the following: voltage drop sensor, cryogenic temperature sensor, crack detection acoustic emission sensor, and magnetic field strength sensor; When any of the aforementioned status parameters exceeds the corresponding preset failure threshold, an early warning signal is generated or a maintenance command is triggered.

[0016] Secondly, embodiments of this application disclose a fatigue life verification device for a superconducting magnet, the device comprising: The acquisition module is used to acquire the total stress amplitude of the superconducting magnet; wherein, the total stress amplitude includes the thermal stress amplitude caused by temperature cyclic loading and the stress amplitude caused by mechanical cyclic loading; The verification module is used to verify the fatigue life of the superconducting magnet based on the total stress amplitude.

[0017] In one possible implementation, the acquisition module is specifically used for: The temperature cyclic load spectrum and mechanical cyclic load spectrum acting on the superconducting magnet were obtained; The thermal stress amplitude caused by the temperature cyclic load is determined based on the temperature cyclic load spectrum, and the stress amplitude caused by the mechanical cyclic load is determined based on the mechanical cyclic load spectrum. The total stress amplitude is obtained by superimposing the thermal stress amplitude caused by the temperature cyclic load and the stress amplitude caused by the mechanical cyclic load.

[0018] In one possible implementation, the superconducting magnet comprises both non-superconducting and superconducting materials; The verification module is specifically used for: The first fatigue life of the non-superconducting material is checked based on the total stress amplitude. The superconducting material is subjected to a second fatigue life check based on the total stress amplitude.

[0019] In one possible implementation, the verification module is specifically used for: The total stress amplitude is corrected by average stress to obtain the equivalent symmetrical cyclic stress amplitude; Obtain the fatigue characteristic curve of the non-superconducting material; wherein the fatigue characteristic curve is used to describe the functional relationship between the stress amplitude and fatigue life of the non-superconducting material; Based on the equivalent symmetrical cyclic stress amplitude and the fatigue characteristic curve, the fatigue safety margin of the non-superconducting load-bearing structural material is checked.

[0020] In one possible implementation, the average stress correction for the total stress amplitude is performed using the following formula: ; in, The equivalent symmetrical cyclic stress amplitude, The total stress amplitude, For average stress, This represents the tensile strength of a superconducting magnet at its lowest operating temperature.

[0021] In one possible implementation, the verification module is specifically used for: Based on the total stress amplitude, the interfacial shear stress of the epoxy composite structure in the superconducting structural material is determined; Based on the interfacial shear stress and the interlaminar ultimate shear strength of the epoxy composite structure, a cumulative damage model is used to check the delamination damage.

[0022] In one possible implementation, the cumulative damage model is: ; Where D is the cumulative damage value, and N is the total number of cycles within the lifespan. Let be the interfacial shear stress during the i-th cycle. The interlaminar ultimate shear strength is given by denoted as D, and m is the material damage index. When D ≥ 1, the epoxy composite structure is deemed to have failed. The total number of cycles is determined based on the phase relationship between the temperature cyclic load and the mechanical cyclic load.

[0023] In one possible implementation, the interfacial shear stress is calculated using the following formula: ; in, The interfacial shear stress is... For thermal stress, The thickness of the superconducting layer, The total thickness of the structure. It is a geometric factor.

[0024] In one possible implementation, the verification module is specifically used for: Based on the total stress amplitude and the preset crack size, the stress intensity factor is calculated; Based on the stress intensity factor and the fracture toughness of the superconducting material, the safety margin for brittle fracture is checked.

[0025] In one possible implementation, the device further includes a monitoring module; The monitoring module is used to monitor the state parameters of the superconducting magnet through multiple sensors disposed on the superconducting magnet; wherein, the multiple sensors include at least two of the following: a voltage drop sensor, an ultra-low temperature sensor, a crack detection acoustic emission sensor, and a magnetic field strength sensor; When any of the aforementioned status parameters exceeds the corresponding preset failure threshold, an early warning signal is generated or a maintenance command is triggered.

[0026] Thirdly, embodiments of this application disclose a control device, including a processor and a memory, wherein the memory is used to store programs, instructions or code, and the processor is used to execute the programs, instructions or code in the memory to complete the fatigue life verification method for superconducting magnets as described in any of the first aspects.

[0027] Fourthly, embodiments of this application disclose a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the fatigue life verification method for superconducting magnets as described in any of the first aspects.

[0028] This application provides a method and apparatus for verifying the fatigue life of a superconducting magnet. The method includes: acquiring the total stress amplitude of the superconducting magnet, which is composed of the thermal stress amplitude caused by temperature cyclic loading and the stress amplitude caused by mechanical cyclic loading; and then performing a fatigue life verification operation on the superconducting magnet based on the acquired total stress amplitude. This method integrates the stress amplitudes corresponding to temperature cyclic loading and mechanical cyclic loading to form a total stress amplitude reflecting the actual stress state of the superconducting magnet. Based on this, fatigue life verification can fully consider the combined influence of two key loads on the fatigue damage of the superconducting magnet, avoiding the one-sided results caused by verification based solely on a single load stress. Its technical effect is to make the fatigue life verification more closely match the actual stress scenario of the superconducting magnet, effectively improving the accuracy and reliability of the verification results, and providing more scientific technical support for the fatigue life assessment of superconducting magnets. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A flowchart illustrating a fatigue life verification method for a superconducting magnet provided in this application embodiment; Figure 2 This is a schematic diagram of a fatigue life verification device for a superconducting magnet provided in an embodiment of this application. Detailed Implementation

[0031] As described earlier, high-speed maglev trains, as an advanced mode of transportation with advantages of high efficiency and speed, place extremely high demands on the reliability of their core components. The superconducting magnet, as a key core component and power source of the high-speed maglev train, directly determines the train's operational safety, reliability, and service life through its stable operation throughout its entire life cycle. During actual train operation, the superconducting magnet operates in a very unique environment, simultaneously enduring long-term effects of coupled multi-physics loads. The long-term alternating action of these loads gradually induces fatigue damage in the superconducting magnet material.

[0032] In existing technologies, fatigue verification methods mainly target ordinary structural materials under single physical field loads. The core idea is to obtain the fatigue characteristic curve of the material through fatigue testing, calculate the stress amplitude by combining it with a single type of load spectrum, and then determine whether the material meets the expected life requirements under that load condition. For complex core components such as superconducting magnets that are simultaneously subjected to coupled loads from multiple physical fields, there is currently no specific fatigue verification technology solution, and existing conventional methods have not been adapted for this purpose.

[0033] To address this technical problem, this application provides a method and apparatus for verifying the fatigue life of a superconducting magnet. The method includes: acquiring the total stress amplitude of the superconducting magnet, which is composed of the thermal stress amplitude caused by temperature cyclic loading and the stress amplitude caused by mechanical cyclic loading; and then performing a fatigue life verification operation on the superconducting magnet based on the acquired total stress amplitude. This method integrates the stress amplitudes corresponding to temperature cyclic loading and mechanical cyclic loading to form a total stress amplitude reflecting the actual stress state of the superconducting magnet. Based on this, fatigue life verification can fully consider the combined influence of two key loads on the fatigue damage of the superconducting magnet, avoiding the one-sided results caused by verification based solely on a single load stress. Its technical effect is that it makes the fatigue life verification more closely resemble the actual stress scenario of the superconducting magnet, effectively improving the accuracy and reliability of the verification results, and providing more scientific technical support for the fatigue life assessment of superconducting magnets.

[0034] The method provided in this application can be applied to the full life-cycle fatigue verification of superconducting magnets for high-speed maglev trains. Relying on the superconducting magnet itself, temperature / mechanical load application equipment, various types of monitoring sensors, and data processing terminals, it achieves full-process reliability assurance from development to service. During the superconducting magnet development and factory testing phases, temperature load spectra from -230℃ (liquid helium temperature range) to 50℃ (room temperature) are simulated using temperature cycling testing equipment. Self-field Lorentz electromagnetic cyclic force and atmospheric pressure cyclic loads are reproduced using mechanical load application devices. Combined with materials mechanics testing equipment, core parameters such as fatigue characteristic curves of non-superconducting materials and fracture toughness of superconducting materials are obtained. Finite element analysis hardware is used to calculate multi-physics stress amplitudes and verify safety margins, ensuring that the magnet meets the fatigue requirements for its service life. During the high-speed maglev train service phase, sensors such as voltage drop sensors, cryogenic temperature sensors, crack detection acoustic emission sensors, and magnetic field strength sensors are deployed at key parts of the superconducting magnet to collect data such as critical current, AC loss, interface resistance, and acoustic emission energy in real time and transmit them to the onboard monitoring terminal. The terminal dynamically monitors fatigue status based on a preset failure threshold. When the data exceeds the threshold, the magnet status is further verified through destructive sampling hardware, providing continuous technical support for the safe operation of the train.

[0035] Technical terms: Fatigue characteristic curve: The core tool in fatigue analysis used to describe the fatigue life of materials or structures under alternating stress. It establishes a quantitative relationship between stress amplitude (S) and fatigue life (N) through fatigue tests.

[0036] Fatigue safety margin: It is a core indicator used in engineering to evaluate the safety of structures or materials under fatigue loads. By quantifying the ratio of actual load to ultimate load (or actual damage to critical damage), it provides a basis for design optimization, reliability assessment and maintenance strategy formulation.

[0037] Fracture toughness: The ability of a material to resist the unstable propagation (i.e., rapid fracture) of a crack or crack-like defect. This performance parameter reflects the safe critical state of the material under defect conditions and is a key factor in the fracture-resistant design of engineering structures.

[0038] Epoxy composite structure: a composite material composed of an epoxy resin matrix and fiber reinforcement materials (such as carbon fiber, glass fiber, etc.).

[0039] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0040] See Figure 1 , Figure 1 This is a flowchart illustrating a fatigue life verification method for a superconducting magnet provided in an embodiment of this application. The execution subject of this method can be an onboard controller in a maglev train or other electronic equipment capable of performing computational functions. The following description uses a controller as the execution subject, and the method includes: S101: The controller acquires the total stress amplitude of the superconducting magnet.

[0041] Total stress amplitude refers to the stress fluctuation amplitude of a superconducting magnet under the combined action of multi-physics load coupling, caused by both temperature cyclic loads and mechanical cyclic loads. It is a core quantitative indicator integrating the effects of these two types of loads on magnet fatigue damage. Total stress amplitude includes the thermal stress amplitude caused by temperature cyclic loads and the stress amplitude caused by mechanical cyclic loads.

[0042] Temperature cyclic loading refers to the alternating temperature loads experienced by a superconducting magnet during its service life. The temperature range covers the liquid helium temperature range (approximately -230°C) to room temperature (approximately 50°C), exhibiting periodic cyclic characteristics. Thermal stress amplitude refers to the magnitude of stress change within the superconducting magnet caused by temperature cyclic loading. It is a quantified value of stress fluctuations caused by the constraint of thermal expansion and contraction of the material due to temperature alternation.

[0043] Mechanical cyclic loading refers to the periodic mechanical forces experienced by a superconducting magnet during operation, including the self-field Lorentz electromagnetic cyclic force generated by the electromagnetic field and the atmospheric pressure cyclic force borne by the structure itself. The stress amplitude caused by mechanical cyclic loading refers to the magnitude of stress change generated within the magnet material after mechanical cyclic loading is applied to the superconducting magnet, and is a quantitative representation of the effect of mechanical loading on magnet fatigue.

[0044] The controller integrates the effects of two core load types—temperature cycling and mechanical cycling—into a unified total stress amplitude index, avoiding the limitations of single-load stress assessment. In the calculation of thermal stress amplitude, integral forms and finite element analysis can be introduced to fully consider the changes in material properties with temperature and the actual constraint state of the magnet. The mechanical stress amplitude covers the effects of self-field Lorentz electromagnetic cyclic force and atmospheric pressure cyclic force on the magnet; the superposition process takes into account the uncertainties of the load spectrum, ensuring that the total stress amplitude accurately reflects the actual stress state of the superconducting magnet. This provides scientific and reliable core data support for subsequent fatigue life verification and is the foundation for ensuring the accuracy of the entire verification scheme.

[0045] To accurately quantify the stress state of a superconducting magnet under multi-physics coupled loads, this application describes in detail how the controller obtains the total stress amplitude. The specific implementation method is as follows: In one possible implementation, step S101 includes: The controller acquires the temperature cyclic load spectrum and mechanical cyclic load spectrum acting on the superconducting magnet; The controller determines the thermal stress amplitude caused by the temperature cyclic load based on the temperature cyclic load spectrum, and determines the stress amplitude caused by the mechanical cyclic load based on the mechanical cyclic load spectrum. The controller superimposes the thermal stress amplitude caused by temperature cyclic load and the stress amplitude caused by mechanical cyclic load to obtain the total stress amplitude.

[0046] In this embodiment, the controller first determines the temperature cyclic load spectrum of the superconducting magnet, defining the temperature range as from liquid helium temperature to room temperature. Simultaneously, it determines the mechanical cyclic load spectrum, which includes two types of loads: self-field Lorentz electromagnetic cyclic force and atmospheric pressure cyclic force. The controller then calculates the amplitudes of thermal stress and mechanical stress, respectively.

[0047] For the thermal stress amplitude caused by temperature cyclic loading, assuming the superconducting magnet material exhibits linear elastic behavior, the thermal stress can be expressed as: ; in, Thermal stress; The elastic modulus at temperature T; The coefficient of thermal expansion at temperature T; The temperature range is defined as the temperature variation range (from T1 to T2). In this embodiment of the application, the temperature variation range is, for example, -230°C to 50°C, where T1 is -230°C and T2 is 50°C.

[0048] Considering the material properties changing with temperature, thermal strain is calculated using an integral form. : .

[0049] Combined with the elastic modulus Eavg at the average temperature (or taking the low-temperature modulus as the elastic modulus Eavg), the thermal stress amplitude It can be represented as: .

[0050] In practical applications, the structure of a superconducting magnet is not completely constrained. Therefore, the actual thermal stress amplitude at the critical point of the magnet can be obtained through finite element analysis.

[0051] Stress amplitude caused by mechanical cyclic load The controller can be calculated by quantifying the effect of the self-field Lorentz electromagnetic cyclic force and the atmospheric pressure cyclic force on the magnet.

[0052] Finally, considering the uncertainty of the load spectrum, the controller will determine the amplitude of the thermal stress caused by the temperature cyclic load. and stress amplitude caused by mechanical cyclic load The total stress amplitude is obtained by superimposing the values. .

[0053] Since average stress affects the fatigue damage characteristics of superconducting magnet materials, directly using the total stress amplitude for evaluation is prone to bias. Therefore, embodiments of this application can also perform average stress correction on the total stress amplitude, transforming it into an equivalent symmetrical cyclic stress amplitude suitable for the fatigue evaluation scenario. Specifically, the total stress amplitude can be corrected for average stress using the following formula: ; in, For equivalent symmetrical cyclic stress amplitude, For average stress, This represents the tensile strength of the superconducting magnet material at its lowest operating temperature.

[0054] The core of this correction process is to eliminate the interference of mean stress on fatigue assessment. The controller converts the total stress amplitude, including the influence of mean stress, into the equivalent symmetrical cyclic stress amplitude commonly used in fatigue characteristic analysis. This allows the corrected data to directly match the fatigue characteristic parameters of the superconducting magnet, reducing the deviation in fatigue life verification results caused by the presence of mean stress. This provides a more suitable stress index for subsequent accurate fatigue life verification of the superconducting magnet.

[0055] S102: The controller performs fatigue life verification on the superconducting magnet based on the total stress amplitude.

[0056] Fatigue life verification refers to the evaluation process of determining whether a superconducting magnet material meets the preset service life requirements by quantitatively analyzing the degree of fatigue damage under cyclic loading. The core is to verify the safety redundancy of the material under the target number of cycles.

[0057] The target number of cycles is typically the maximum number of cycles within the lifespan of the superconducting magnet, which can be determined based on the temperature cyclic load spectrum and the mechanical cyclic load spectrum. As an example, if the maximum number of cycles within the lifespan of the superconducting magnet is 360, the verification target for the superconducting magnet can be that the cumulative material damage within 360 cycles is less than a preset safety factor.

[0058] In practical applications, superconducting magnets simultaneously comprise superconducting materials and non-superconducting materials used for load support. The fatigue damage mechanisms of these two types of materials differ significantly under low-temperature conditions, making it difficult to accurately match their actual fatigue behavior using a uniform process. To improve fatigue verification accuracy, this application provides differentiated fatigue life verification for the two types of materials.

[0059] Specifically, the controller performs a first fatigue life check on non-superconducting materials based on the total stress amplitude, and a second fatigue life check on superconducting materials based on the total stress amplitude.

[0060] The fatigue damage behavior of non-superconducting materials follows a correlation between stress amplitude and cycle number, and the fatigue life of non-superconducting materials is directly related to the stress amplitude they bear. Fatigue characteristic curves are used to describe the functional relationship between stress amplitude and fatigue life of non-superconducting materials. In the first fatigue life verification of non-superconducting materials, this application embodiment relies on the fatigue characteristic curve (SN curve) based on this energization principle as the core basis. By combining the correspondence between the equivalent symmetrical cyclic stress amplitude and the fatigue characteristic curve, a precise assessment of fatigue safety margin is achieved.

[0061] Specifically, the first fatigue life verification of non-superconducting materials is performed based on the total stress amplitude, including: The controller acquires the fatigue characteristic curves of non-superconducting materials, and performs fatigue safety margin verification on non-superconducting load-bearing structural materials based on the equivalent symmetrical cyclic stress amplitude and fatigue characteristic curves.

[0062] Fatigue characteristic curves are curves obtained by fitting multiple sets of fatigue tests conducted on non-superconducting materials (such as structural steel and aluminum alloys) used in superconducting magnets within their operating temperature range. The fatigue characteristic curves plot the number of cycles (i.e., fatigue life) on the x-axis and the stress amplitude on the y-axis, clearly showing the maximum number of cycles the material can withstand under different stress amplitudes, and can reflect the fatigue characteristics of non-superconducting materials.

[0063] The controller acquires the fatigue characteristic curve corresponding to the non-superconducting material, ensuring that the test conditions on the curve are consistent with the actual working environment of the superconducting magnet. Then, the controller substitutes the equivalent symmetrical cyclic stress amplitude obtained through average stress correction into the fatigue characteristic curve and queries the number of cycles corresponding to the equivalent symmetrical cyclic stress amplitude, i.e., the fatigue life of the non-superconducting material under that stress. Finally, the controller compares this number of cycles with the maximum number of cycles designed for the superconducting magnet to calculate the fatigue safety margin. If the fatigue safety margin is greater than the preset safety factor, the fatigue life of the non-superconducting material is determined to meet the design requirements of the superconducting magnet.

[0064] The embodiments of this application quantify the relationship between stress amplitude and fatigue life of non-superconducting materials through fatigue characteristic curves, so that the verification fits the actual fatigue behavior of non-superconducting materials. Furthermore, the fatigue redundancy capability of the material is clarified through the calculation of safety margin, which effectively supports the fatigue life verification of non-superconducting materials.

[0065] To more intuitively present the first fatigue life verification of non-superconducting materials, the following verification is conducted based on fatigue characteristic curves, using specific parameters and quantitative formulas, taking 360 cycles corresponding to a 30-year service life of a superconducting magnet as an example. The specific operation is as follows: The first step is to obtain the fatigue characteristic curve of the non-superconducting material at the lowest operating temperature. This curve describes the relationship between stress amplitude σa and the number of failure cycles Nf. If the fatigue characteristic curve of the non-superconducting material at the lowest operating temperature is unavailable, room temperature data can be used with a conservative correction for low-temperature strength improvement to determine the fatigue characteristic curve at the lowest operating temperature. The fatigue characteristic curve can be expressed as follows: ; in, For stress amplitude, This represents the number of failure cycles. and is an intrinsic constant of the material.

[0066] The second step is to determine the allowable stress amplitude corresponding to 360 cycles. Based on the maximum number of cycles Nf corresponding to a 30-year service life of the superconducting magnet being 360, the maximum number of cycles Nf is substituted into the fatigue characteristic curve to calculate the allowable stress amplitude at the maximum number of cycles Nf. .

[0067] The third step is to calculate the equivalent symmetrical cyclic stress amplitude. and In comparison, if ≤ If so, the non-superconducting material is deemed to meet the 30-year lifespan requirement; if > If the non-superconducting material does not meet the 30-year lifespan requirement, then it is determined that the non-superconducting material does not meet the requirement.

[0068] Simultaneously calculate the fatigue safety margin. The fatigue safety margin must be greater than 0. If a safety factor is introduced... Then further requirements need to be met. ≤ This ensures the fatigue redundancy capability of non-superconducting materials.

[0069] The epoxy composite interface in superconducting materials is a weak point in fatigue damage. The cyclic action of total stress amplitude easily leads to shear stress accumulation at this interface, which in turn causes delamination failure. Therefore, when performing the second fatigue life verification, this application specifically focuses on the interface stress and delamination risk of the epoxy composite structure, and evaluates its damage state by quantifying the interface shear stress and combining it with a cumulative damage model.

[0070] Specifically, the second fatigue life check of superconducting materials is performed based on the total stress amplitude, including: The controller determines the interfacial shear stress of the epoxy composite structure in the superconducting structural material based on the total stress amplitude; and performs layered damage verification using a cumulative damage model based on the interfacial shear stress and the interlaminar ultimate shear strength of the epoxy composite structure.

[0071] The controller, based on the total stress amplitude and incorporating the geometric parameters of the epoxy composite structure in the superconducting material (such as layer thickness and interfacial contact area) and material properties under cryogenic conditions (such as the elastic modulus of epoxy resin), converts the total stress amplitude into shear stress at the epoxy composite structure interface through stress transfer analysis. When determining the shear stress at the epoxy composite structure interface, the controller must consider the impact of cryogenic temperatures on material stiffness and perform condition-adaptive corrections to parameters such as the elastic modulus to ensure that the calculated interfacial shear stress closely matches the actual operating conditions of the superconducting magnet.

[0072] The controller acquires the interlaminar ultimate shear strength of the epoxy composite structure, i.e., the maximum shear stress that the interface can withstand. Using a cumulative damage model, the ratio of the interfacial shear stress to the interlaminar ultimate shear strength under each cycle is taken as the damage value for a single cycle. The cyclic damage is accumulated over the maximum number of cycles within the superconducting magnet's lifespan. If the cumulative damage value is less than 1, the delamination damage of the epoxy composite structure is considered to be within a safe range, meeting fatigue life requirements. If the cumulative damage value is close to or greater than 1, it indicates that the structure has a risk of delamination failure, and the design parameters of the epoxy composite structure need to be optimized to improve the interfacial shear resistance.

[0073] This application further provides a method for calculating interfacial shear stress and gives a specific mathematical expression for the cumulative damage model, achieving accurate determination of damage state through parameterization.

[0074] In one possible implementation, the cumulative damage model is as follows: ; Where D is the cumulative damage value and N is the total number of cycles within the lifespan of the superconducting magnet. The total number of cycles is determined based on the phase relationship between the temperature cyclic load and the mechanical cyclic load. Let be the interfacial shear stress during the i-th cycle. D represents the interlaminar ultimate shear strength, and m represents the material damage index, which can be obtained from the fatigue characteristic test of epoxy resin. When D ≥ 1, the epoxy composite structure is considered to have failed. When calculating the cumulative damage value, the controller will use the interfacial shear stress corresponding to each cycle. Substitute into the formula to calculate the damage percentage per cycle. Then, the damage percentages of all cycles within the lifespan are summed to obtain the cumulative damage value D. If D ≥ 1, the epoxy composite structure is determined to have delamination failure; if D < 1, it indicates that the delamination damage of the structure within the lifespan is within a safe range and meets the fatigue life requirements.

[0075] In one possible implementation, the interfacial shear stress is calculated using the following formula: ; in, For interfacial shear stress, For thermal stress, The thickness of the superconducting layer, The total thickness of the structure. It is a geometric factor.

[0076] In this embodiment, the thermal stress corresponding to the temperature cyclic load in the total stress amplitude is used. Based on this, combined with the geometric factors of the superconducting structure Calculate the interfacial shear stress of the epoxy composite structure The calculation requires first obtaining the thickness parameters and thermal stress data of the superconducting structure. After substituting the corresponding geometric factors, the interfacial shear stress under each cycle can be obtained.

[0077] The above embodiments have verified the delamination damage of epoxy composite structures in superconducting materials. However, under low temperature and cyclic stress coupling, superconducting materials are inherently prone to brittle fracture due to the propagation of initial cracks, which is one of the core risk points of fatigue failure in superconducting materials. Therefore, in the second fatigue life verification, the embodiments of this application also assess the brittle fracture safety margin by quantifying the matching relationship between the driving factors of crack propagation and the material's fracture resistance, based on the brittle fracture characteristics of the superconducting material itself.

[0078] In one possible implementation, a second fatigue life check is performed on the superconducting material based on the total stress amplitude, including: The controller calculates the stress intensity factor based on the total stress amplitude and the preset crack size; and performs a safety margin check for brittle fracture based on the stress intensity factor and the fracture toughness of the superconducting material.

[0079] The preset texture size can be determined based on the actual situation, such as initial defects that may exist in the manufacturing process of superconducting materials and potential microcracks in the early stage of service.

[0080] This embodiment of the application uses the total stress amplitude as a basis, combined with a preset crack size, and employs the corresponding formula of linear elastic fracture mechanics. Substituting the total stress amplitude and the preset crack size into the formula, the stress intensity factor under the current working condition is obtained. The stress intensity factor is a core quantitative indicator characterizing the degree of stress concentration at the crack tip and driving crack propagation. During calculation, it is necessary to ensure that the preset crack size closely matches the actual defect distribution range of the superconducting material.

[0081] The controller acquires the fracture toughness of the superconducting material at its lowest operating temperature. Fracture toughness, determined through low-temperature fracture mechanics testing, is an inherent parameter representing the material's resistance to crack propagation. The calculated stress intensity factor is then compared with the fracture toughness to calculate the brittle fracture safety margin: Safety margin = Fracture toughness ÷ Stress intensity factor - 1. If the brittle fracture safety margin is greater than 0, it indicates that the current stress intensity factor does not exceed the material's fracture toughness, and the superconducting material will not experience brittle fracture, meeting fatigue life requirements. If the brittle fracture safety margin is less than or equal to 0, it indicates a risk of brittle fracture, requiring optimization of the manufacturing process to reduce the initial crack size or improvement of the superconducting material's fracture toughness to ensure safety.

[0082] To more intuitively illustrate the actual operation of verifying the second fatigue life of superconducting materials, the following section, using specific operating parameters in the liquid helium temperature range (-230℃) and typical dimensions of superconducting structures, provides a complete example of the entire process for verifying the second fatigue life: First, initial tests were conducted, performing initial mechanical tests on the superconducting material at a liquid helium temperature (-230℃) to determine the material's fracture toughness K. IC The interfacial fracture toughness Gc of the epoxy composite structure was obtained at 20 MPa·m·K. The thickness t of the superconducting layer was determined. 超导 10 micrometers, total structural thickness t 总 The strip has a diameter of 100 micrometers, a geometric factor Φ of 1.2, and an operating temperature range of -230℃ to -50℃. Based on these parameters, the calculated interfacial shear stress is 24 MPa.

[0083] Interlaminar ultimate shear strength τ lim It is 50 MPa, which meets the requirements. Requirements.

[0084] Then, based on the cumulative damage model, where the total number of cycles N is 360 and the material damage index m is 3.5, the interfacial shear stress in each cycle is... Both values ​​are 24 MPa. The calculated single-cycle damage is approximately 0.04, and the cumulative damage D over 360 cycles is 14.4. In actual engineering, the cumulative damage value D needs to be controlled to be less than or equal to 1. This is only for demonstration purposes; in practice, parameters need to be optimized to ensure that the cumulative damage D is less than or equal to 1.

[0085] Finally, the safety margin for brittle fracture is checked. The stress intensity factor K is calculated. I : ; in, Let be the geometry factor for the surface crack, taken as 1.12. The initial crack size is preset to 0.1 mm. Stress intensity factor K I It is 2.24 MPa·miKJ.

[0086] Material damage index m, fracture toughness K IC and stress intensity factor K I Substitute into the brittle fracture safety margin check formula: ; The brittle fracture safety margin check formula is used to calculate the safety redundancy of a superconducting material against brittle fracture under liquid helium temperature and total stress amplitude. Essentially, it determines whether the superconducting material will experience brittle fracture by quantifying the difference between the material's inherent crack propagation resistance and the crack propagation driving force under the current operating conditions. Ultimately, the calculated result of the brittle fracture safety margin check formula is 0.12, which is greater than zero, satisfying the brittle fracture safety margin requirement and confirming that the superconducting material will not experience brittle fracture.

[0087] During long-term service, superconducting magnets may suffer sudden damage due to the continuous action of multi-physics field cyclic loads. Therefore, this application embodiment uses dedicated sensors on the superconducting magnet to capture state changes and combines them with preset thresholds to achieve risk prediction and maintenance triggering, thus forming a safety guarantee.

[0088] The state parameters of the superconducting magnet are monitored by multiple sensors installed on the superconducting magnet; wherein the multiple sensors include at least two of the following: voltage drop sensor, cryogenic temperature sensor, crack detection acoustic emission sensor, and magnetic field strength sensor; when any state parameter exceeds the corresponding preset failure threshold, an early warning signal is generated or a maintenance command is triggered.

[0089] In this embodiment, multiple sensors are installed at key parts of the superconducting magnet, such as the epoxy composite structure interface, the core region of the superconducting layer, and areas where loads are concentrated. The sensor types must include at least two of the following: voltage drop sensors, cryogenic temperature sensors, crack detection acoustic emission sensors, and magnetic field strength sensors. These sensors are adapted to the cryogenic working environment of the superconducting magnet in the liquid helium temperature range to ensure stable data acquisition even at extreme temperatures.

[0090] Among them, the voltage drop sensor is used to monitor the changes in the superconducting performance of the superconducting magnet, the ultra-low temperature sensor tracks the actual changes in temperature cycling load in real time, the crack detection acoustic emission sensor captures the signals of material crack generation and propagation, and the magnetic field strength sensor monitors the stability of electromagnetic load. The sensors work together to achieve multi-dimensional monitoring of the magnet's state.

[0091] Each sensor continuously collects corresponding status parameters at a preset frequency, transmitting the collected data, such as voltage drop, low temperature, acoustic emission signal, and magnetic field strength, to the backend monitoring terminal in real time. The terminal performs preliminary filtering and noise reduction on the transmitted data, eliminating invalid data caused by environmental interference and retaining effective parameters that truly reflect the working status and fatigue damage trend of the superconducting magnet. This enables all-weather, real-time tracking of the magnet's service status, overcoming the limitations of previous theoretical verifications that could not cover sudden damage during service life.

[0092] By pre-setting preset failure thresholds for each type of state parameter based on the fatigue life verification results of the superconducting magnet, material performance parameters, and actual service experience, the system ensures that risks can be detected in a timely manner when parameters exceed the limits. The controller compares the monitored state parameters with the corresponding preset failure thresholds in real time. If any state parameter exceeds its corresponding failure threshold, it indicates that the superconducting magnet is at risk of fatigue failure or accelerated damage. The system immediately and automatically generates an early warning signal and can trigger maintenance commands as needed, prompting personnel to stop the machine for inspection, conduct damage investigation, or replace components, further improving the operational reliability of the superconducting magnet throughout its entire life cycle.

[0093] As an example, monitoring indicators can be shown in Table 1.

[0094] Table 1 Core Monitoring Indicators

[0095] The sensors continuously collect data on various indicators and upload them in real time. The controller compares the data with the evaluation criteria and failure thresholds. If the indicators are within the evaluation criteria range, the magnet is deemed to be in normal condition. If any indicator exceeds the corresponding failure threshold, it indicates that the magnet is at risk of accelerated fatigue damage. The system then triggers a subsequent process to perform a destructive sampling inspection of the superconducting magnet to further verify its actual fatigue state and prevent the risk of failure from spreading.

[0096] This application also provides a fatigue life verification device for superconducting magnets, such as... Figure 2 As shown, the device includes: The acquisition module 201 is used to acquire the total stress amplitude of the superconducting magnet; wherein, the total stress amplitude includes the thermal stress amplitude caused by temperature cyclic loading and the stress amplitude caused by mechanical cyclic loading; The verification module 202 is used to verify the fatigue life of the superconducting magnet based on the total stress amplitude.

[0097] In one possible implementation, the acquisition module 201 is specifically used for: The temperature cyclic load spectrum and mechanical cyclic load spectrum acting on the superconducting magnet were obtained; The thermal stress amplitude caused by the temperature cyclic load is determined based on the temperature cyclic load spectrum, and the stress amplitude caused by the mechanical cyclic load is determined based on the mechanical cyclic load spectrum. The total stress amplitude is obtained by superimposing the thermal stress amplitude caused by the temperature cyclic load and the stress amplitude caused by the mechanical cyclic load.

[0098] In one possible implementation, the superconducting magnet comprises both non-superconducting and superconducting materials; The verification module 202 is specifically used for: The first fatigue life of the non-superconducting material is checked based on the total stress amplitude. The superconducting material is subjected to a second fatigue life check based on the total stress amplitude.

[0099] In one possible implementation, the verification module 202 is specifically used for: The total stress amplitude is corrected by average stress to obtain the equivalent symmetrical cyclic stress amplitude; Obtain the fatigue characteristic curve of the non-superconducting material; wherein the fatigue characteristic curve is used to describe the functional relationship between the stress amplitude and fatigue life of the non-superconducting material; Based on the equivalent symmetrical cyclic stress amplitude and the fatigue characteristic curve, the fatigue safety margin of the non-superconducting load-bearing structural material is checked.

[0100] In one possible implementation, the average stress correction for the total stress amplitude is performed using the following formula: ; in, The equivalent symmetrical cyclic stress amplitude, The total stress amplitude, For average stress, This represents the tensile strength of a superconducting magnet at its lowest operating temperature.

[0101] In one possible implementation, the verification module 202 is specifically used for: Based on the total stress amplitude, the interfacial shear stress of the epoxy composite structure in the superconducting structural material is determined; Based on the interfacial shear stress and the interlaminar ultimate shear strength of the epoxy composite structure, a cumulative damage model is used to check the delamination damage.

[0102] In one possible implementation, the cumulative damage model is: ; Where D is the cumulative damage value, and N is the total number of cycles within the lifespan. Let be the interfacial shear stress during the i-th cycle. The interlaminar ultimate shear strength is given by denoted as D, and m is the material damage index. When D ≥ 1, the epoxy composite structure is deemed to have failed. The total number of cycles is determined based on the phase relationship between the temperature cyclic load and the mechanical cyclic load.

[0103] In one possible implementation, the interfacial shear stress is calculated using the following formula: ; in, The interfacial shear stress is... For thermal stress, The thickness of the superconducting layer, The total thickness of the structure. It is a geometric factor.

[0104] In one possible implementation, the verification module 202 is specifically used for: Based on the total stress amplitude and the preset crack size, the stress intensity factor is calculated; Based on the stress intensity factor and the fracture toughness of the superconducting material, the safety margin for brittle fracture is checked.

[0105] In one possible implementation, the device further includes a monitoring module; The monitoring module is used to monitor the state parameters of the superconducting magnet through multiple sensors disposed on the superconducting magnet; wherein, the multiple sensors include at least two of the following: a voltage drop sensor, an ultra-low temperature sensor, a crack detection acoustic emission sensor, and a magnetic field strength sensor; When any of the aforementioned status parameters exceeds the corresponding preset failure threshold, an early warning signal is generated or a maintenance command is triggered.

[0106] This application also provides a control device. The control device may include a memory and a processor. The processor is used to execute the fatigue life verification method for superconducting magnets described in any of the above embodiments. The memory may be random access memory (RAM), flash memory, read-only memory (ROM), non-volatile read-only memory (EPROM), registers, hard disk, removable disk, etc.

[0107] Memory can store computer instructions. When these instructions are executed by a processor, the processor can use them to perform fatigue life verification methods for superconducting magnets. Memory can also store data.

[0108] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0109] This application also provides a readable storage medium for storing the methods provided in the above embodiments. For example, RAM, flash memory, ROM, EPROM, registers, hard disk, removable disk, or any other form of storage medium in the art.

[0110] In the embodiments of this application, the terms "first" and "second" (if they exist) are used only as name identifiers and do not represent the order of first and second.

[0111] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the product embodiments disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the description of the product embodiments.

[0112] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for verifying the fatigue life of a superconducting magnet, characterized in that, include: Obtain the total stress amplitude of the superconducting magnet; wherein, the total stress amplitude includes the thermal stress amplitude caused by temperature cyclic loading and the stress amplitude caused by mechanical cyclic loading; The fatigue life of the superconducting magnet is checked based on the total stress amplitude.

2. The method according to claim 1, characterized in that, The process of obtaining the total stress amplitude of the superconducting magnet includes: The temperature cyclic load spectrum and mechanical cyclic load spectrum acting on the superconducting magnet were obtained; The thermal stress amplitude caused by the temperature cyclic load is determined based on the temperature cyclic load spectrum, and the stress amplitude caused by the mechanical cyclic load is determined based on the mechanical cyclic load spectrum. The total stress amplitude is obtained by superimposing the thermal stress amplitude caused by the temperature cyclic load and the stress amplitude caused by the mechanical cyclic load.

3. The method according to claim 1, characterized in that, The superconducting magnet includes non-superconducting materials and superconducting materials; The fatigue life verification of the superconducting magnet based on the total stress amplitude includes: The first fatigue life of the non-superconducting material is checked based on the total stress amplitude. The superconducting material is subjected to a second fatigue life check based on the total stress amplitude.

4. The method according to claim 3, characterized in that, The first fatigue life check of the non-superconducting material based on the total stress amplitude includes: The total stress amplitude is corrected by average stress to obtain the equivalent symmetrical cyclic stress amplitude; Obtain the fatigue characteristic curve of the non-superconducting material; wherein the fatigue characteristic curve is used to describe the functional relationship between the stress amplitude and fatigue life of the non-superconducting material; Based on the equivalent symmetrical cyclic stress amplitude and the fatigue characteristic curve, the fatigue safety margin of the non-superconducting load-bearing structural material is checked.

5. The method according to claim 4, characterized in that, The average stress correction for the total stress amplitude is performed using the following formula: ； in, The equivalent symmetrical cyclic stress amplitude, The total stress amplitude, For average stress, This represents the tensile strength of a superconducting magnet at its lowest operating temperature.

6. The method according to claim 3, characterized in that, The second fatigue life check of the superconducting material based on the total stress amplitude includes: Based on the total stress amplitude, the interfacial shear stress of the epoxy composite structure in the superconducting structural material is determined; Based on the interfacial shear stress and the interlaminar ultimate shear strength of the epoxy composite structure, a cumulative damage model is used to check the delamination damage.

7. The method according to claim 6, characterized in that, The cumulative damage model is as follows: ； Where D is the cumulative damage value, and N is the total number of cycles within the lifespan. Let be the interfacial shear stress during the i-th cycle. The interlaminar ultimate shear strength is given by denoted as D, and m is the material damage index. When D ≥ 1, the epoxy composite structure is deemed to have failed. The total number of cycles is determined based on the phase relationship between the temperature cyclic load and the mechanical cyclic load.

8. The method according to claim 6 or 7, characterized in that, Interfacial shear stress is calculated using the following formula: ； in, The interfacial shear stress is... For thermal stress, The thickness of the superconducting layer, The total thickness of the structure. It is a geometric factor.

9. The method according to claim 3, 6 or 7, characterized in that, The second fatigue life check of the superconducting material based on the total stress amplitude includes: Based on the total stress amplitude and the preset crack size, the stress intensity factor is calculated; Based on the stress intensity factor and the fracture toughness of the superconducting material, the safety margin for brittle fracture is checked.

10. The method according to claim 1, characterized in that, The method further includes: The state parameters of the superconducting magnet are monitored by multiple sensors disposed on the superconducting magnet; wherein, the multiple sensors include at least two of the following: voltage drop sensor, cryogenic temperature sensor, crack detection acoustic emission sensor, and magnetic field strength sensor; When any of the aforementioned status parameters exceeds the corresponding preset failure threshold, an early warning signal is generated or a maintenance command is triggered.

11. A fatigue life verification device for a superconducting magnet, characterized in that, The device includes: The acquisition module is used to acquire the total stress amplitude of the superconducting magnet; wherein, the total stress amplitude includes the thermal stress amplitude caused by temperature cyclic loading and the stress amplitude caused by mechanical cyclic loading; The verification module is used to verify the fatigue life of the superconducting magnet based on the total stress amplitude.

12. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions or code, and the processor being used to execute the programs, instructions or code in the memory to complete the fatigue life verification method for superconducting magnets as described in any one of claims 1-10.

13. A computer-readable storage medium, characterized in that, The device contains a computer program that is loaded by a processor to execute the fatigue life verification method for a superconducting magnet as described in any one of claims 1-10.

Images