Flat wire motor stator Busbar welding spot fatigue analysis system and method

Abstract

The invention discloses a flat wire motor stator Busbar welding spot fatigue analysis system and method. Comprising the following steps: cutting out a plurality of welding spot samples on a welded stator, and carrying out a tensile test within a set frequency range on the welding spot samples to obtain a stress-life curve of welding spots; constructing a stator assembly model; the stator assembly model is used for obtaining a response transfer function of a welding spot; and according to the response transfer function and the stress-life curve, calculating a fatigue damage value of a power spectrum density load spectrum based on random vibration on the welding spot, and according to the fatigue damage value, determining whether the welding spot fails due to fatigue. By accurately predicting the fatigue life of the welding spot, potential quality problems can be found in time, optimization design can be carried out, and therefore the fault rate and maintenance cost of the motor are reduced. In addition, powerful support can be provided for reliability evaluation and life prediction of the motor, and guarantee is provided for long-term stable operation of the motor.

Description

Technical Field

[0001] The invention belongs to the technical field of weld fatigue analysis, and in particular relates to a flat wire motor stator busbar weld fatigue analysis system and method. Background Art

[0002] As new energy vehicles become more and more popular, electric drive technology, as one of the core technologies of new energy vehicles, is also developing rapidly. The performance and reliability of the electric drive assembly have an important impact on the overall performance of new energy vehicles.

[0003] In order to improve the performance of the motor, flat copper wire hairpin coils are increasingly used in current new energy electric drives. Compared with traditional round copper wires, flat copper wires have higher conductivity and better heat dissipation performance, which helps to improve the efficiency and reliability of the motor. At the stator output end of the flat copper wire hairpin motor, laser welding or TIG welding (tungsten inert gas shielded welding) is usually used to connect the flat copper wires that need to be conducted. These welding methods have high connection strength and good conductivity. In order to meet the requirements of connection with the Busbar (busbar), the stator output line usually needs to be longer than the standard solder joint. However, the longer output line is like a simple "cantilever", which is prone to solder joint cracking under the action of random vibration load tests (such as road excitation). Solder joint cracking will cause circuit interruption, which in turn affects the normal operation and reliability of the motor. Summary of the invention

[0004] In order to evaluate the durability of busbar welds under random vibration loads and reduce the failure probability during the development process, the present invention proposes a fatigue analysis system and method for busbar welds of a flat wire motor stator.

[0005] A flat wire motor stator busbar weld fatigue analysis system to achieve one of the purposes of the present invention comprises:

[0006] Stress-life curve acquisition module: used to intercept multiple welding spot samples on the stator after welding, perform tensile test on the welding spot samples within a set frequency range, and obtain the stress-life curve of the welding spot;

[0007] Stator assembly model building module: used to build a stator assembly model; the stator assembly model is used to obtain a response transfer function of a welding point; the response transfer function is used to describe the relationship between the stress response of the stator when it is excited by a specific frequency and the excitation of the specific frequency;

[0008] Fatigue damage determination module: used to calculate the fatigue damage of the weld based on the power spectrum density load spectrum of random vibration according to the response transfer function and stress-life curve obtained from the stator assembly model, obtain the fatigue damage value of the weld, and determine whether the weld fails due to fatigue according to the fatigue damage value.

[0009] The technical effects of the above system include: by intercepting weld samples and performing tensile tests, the stress-life curve of the weld can be accurately obtained, which is the basic data for evaluating the fatigue life of the weld; constructing a stator assembly model can simulate the response of the actual stator under specific frequency excitation, providing an accurate model basis for subsequent fatigue analysis; combining the response transfer function and the stress-life curve, the fatigue damage of the weld under random vibration load can be accurately calculated, thereby determining whether the weld fails due to fatigue, which is of great significance for improving the reliability and safety of the motor.

[0010] Furthermore, it also includes a model benchmarking module, which is used to perform modal benchmarking on the constructed stator assembly model to determine the optimal material parameters, thereby obtaining the benchmarked stator assembly model.

[0011] The technical effects of the above-mentioned model benchmarking module include: modal benchmarking of the stator assembly model to determine the optimal material parameters, thereby improving the accuracy and reliability of the model, which helps to more accurately simulate the dynamic response of the actual stator and provide a more precise basis for subsequent fatigue analysis.

[0012] Furthermore, the method for obtaining the response transfer function includes:

[0013] The finite element method is used to perform modal analysis on the aligned stator assembly model to obtain the modal frequency and vibration mode (modal shape) of the stator; the harmonic response analysis of the stator is performed based on the modal frequency and vibration mode to obtain the response transfer function.

[0014] The technical effects of the above-mentioned method for obtaining the response transfer function include: using the finite element method to perform modal analysis and harmonic response analysis on the stator assembly model after calibration, the modal frequency, vibration mode and response transfer function of the stator can be obtained. These parameters are important bases for evaluating the dynamic response of the stator and the fatigue life of the weld. Through this method, the response of the weld under a specific frequency excitation can be predicted more accurately, thereby improving the accuracy of fatigue analysis.

[0015] Furthermore, the stator assembly model building module further includes simplifying the stator assembly model, and the simplification method includes:

[0016] The stator assembly model is simplified to consist of an iron core, copper wires in slots, copper wires at welding ends and copper wires at crown ends, thereby obtaining a simplified stator assembly model;

[0017] The weld in the simplified stator assembly model is simplified into a rectangular parallelepiped including an arc-shaped notch with a set radius in the middle of the weld, which is used to characterize the stress concentration of the weld.

[0018] The technical effects of simplifying the model include: by simplifying the stator assembly model, the complexity of the model can be reduced and the calculation efficiency can be improved. At the same time, simplifying the characterization of the weld point can more intuitively reflect the stress concentration of the weld point, so as to more accurately evaluate the fatigue life of the weld point. This step not only ensures the analysis accuracy, but also improves the feasibility and efficiency of the analysis.

[0019] Furthermore, in the stator assembly model building module, anisotropic material properties are used to characterize the difference between the radial stiffness and axial stiffness of the stator, and the anisotropic material parameters include: anisotropic material parameters of the stator core, the copper wire in the slot, the copper wire at the welding end, and the copper wire at the crown end. The technical effects of this step include: using anisotropic material properties to characterize the difference between the radial stiffness and axial stiffness of the stator can more realistically reflect the actual physical properties of the stator. This characterization method helps to improve the accuracy of the model, thereby more accurately predicting the response and fatigue life of the weld under specific loads.

[0020] Further, in the fatigue damage determination module, in the nCode DesignLife module of the Ansys simulation software platform, the material properties of the copper wire solder joint are created according to the optimal material parameters, and the stress-life curve is input; the counting method uses Dirlik's PSD counting method, adopts the stress combination method of CriticalPlane, selects the survival rate, adjusts the test time, and calculates the fatigue damage of the solder joint in multiple directions to obtain the fatigue damage value of the solder joint, and the multiple directions usually include three directions of x, y, and z; when the fatigue damage value is greater than the set value, it is considered that the solder joint will fail due to fatigue. The technical effects of this step include: in the nCode Design Life module of the Ansys simulation software platform, the material properties of the copper wire solder joint are created according to the optimal material parameters, and the stress-life curve is input, so that the fatigue life of the solder joint can be more accurately evaluated. At the same time, the PSD counting method of Dirlik and the stress combination method of CriticalPlane can be used to more accurately calculate the fatigue damage of the solder joint in multiple directions. This method not only improves the accuracy of fatigue analysis, but also provides strong support for the quality control and optimization design of motors.

[0021] Furthermore, in the fatigue damage determination module, the calculation method of the fatigue damage value of the solder joint includes:

[0022] On the Ansys simulation software platform, a stress PSD curve of the solder joint structure is obtained according to the response transfer function and a power spectral density load spectrum (i.e., a PSD curve) based on random vibration;

[0023] The four moments of inertia m0, m1, m2, and m4 are calculated using the stress PSD curve. The calculation method includes: Where f is the frequency; n = 0, 1, 2, 4; PSD s (f) represents the stress PSD curve;

[0024] According to the moments of inertia m0, m1, m2, and m4, the stress amplitude S is calculated using the Dirlik empirical formula. i The probability density function p(S i );S i represents the i-th possible stress amplitude of the solder joint;

[0025] According to the probability density function p(S i ) Calculate the solder joint at a time length T and a stress amplitude of S i The actual number of cycles N1(S i ); its calculation formula includes:

[0026]

[0027] According to the application-life curve, the stress amplitude S of the solder joint is calculated. i The number of failure cycles under action N f (S i ), the calculation formula includes

[0028] The fatigue damage of the solder joint in a certain direction under the time length T is calculated according to the following formula:

[0029]

[0030] The fatigue damage of the solder joint in each direction is accumulated to obtain the fatigue damage value of the solder joint.

[0031] Furthermore, the method of determining whether a welding spot fails due to fatigue according to the fatigue damage value includes: if the fatigue damage value of the welding spot is greater than a set value, it is considered that the welding spot will fail due to fatigue.

[0032] A method for fatigue analysis of busbar welds of a flat wire motor stator to achieve the second objective of the present invention comprises:

[0033] Cutting a plurality of weld spot samples from the welded stator, performing a tensile test within a set frequency range on the weld spot samples, and obtaining a stress-life curve of the weld spot;

[0034] Constructing a stator assembly model; the stator assembly model is used to obtain a response transfer function of a welding point; the response transfer function is used to describe the relationship between the stress response of the stator when it is excited by a specific frequency and the excitation of the specific frequency;

[0035] The fatigue damage value of the solder joint based on the power spectrum density load spectrum of random vibration is calculated according to the response transfer function and the stress-life curve, and whether the solder joint fails due to fatigue is determined according to the fatigue damage value.

[0036] The beneficial effects of the present invention include:

[0037] By accurately predicting the fatigue life of solder joints, the present invention can timely discover potential quality problems and optimize the design, thereby reducing the failure rate and maintenance cost of the motor. In addition, it can also provide strong support for the reliability assessment and life prediction of the motor, and provide guarantee for the long-term stable operation of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic diagram of a flow chart of an embodiment of the method of the present invention;

[0039] Figure 2 It is the SN curve of the flat wire solder joint;

[0040] Figure 3 It is a schematic diagram of the welding point model in the stator assembly model;

[0041] Figure 4 It is a schematic diagram of random vibration conditions for M1 and N1 vehicles with suspended motors and integrated drive motor systems. DETAILED DESCRIPTION

[0042] The following specific implementations are used to explain the technical solutions of the claims of the present invention so that those skilled in the art can understand the claims. The protection scope of the present invention is not limited to the following specific implementation structures. The technical solutions of the claims of the present invention made by those skilled in the art but different from the following specific implementations are also within the protection scope of the present invention.

[0043] Example 1

[0044] A fatigue analysis method for a flat wire motor stator busbar weld point, comprising:

[0045] Cutting a plurality of weld spot samples from the welded stator, performing a tensile test within a set frequency range on the weld spot samples, and obtaining a stress-life curve of the weld spot;

[0046] Constructing a stator assembly model; the stator assembly model is used to obtain a response transfer function of a welding point; the response transfer function is used to describe the relationship between the stress response of the stator when it is excited by a specific frequency and the excitation of the specific frequency;

[0047] The fatigue damage value of the solder joint based on the power spectrum density load spectrum of random vibration is calculated according to the response transfer function and the stress-life curve, and whether the solder joint fails due to fatigue is determined according to the fatigue damage value.

[0048] The specific steps include:

[0049] S1. Obtain the SN curve (stress-life curve) of the solder joint

[0050] A plurality of weld spot samples are cut from the welded stator, and a tensile test of a certain frequency is performed on the weld spot samples to obtain the SN curve of the weld spot; the horizontal axis is the number of failure cycles that cause the weld spot to fail, and the vertical axis is the stress amplitude, such as Figure 2 The technical effects of this step include: it can better reflect the strength and fatigue performance of the stator copper wire after welding, and it is not necessary to consider the various residual stresses caused by the welding process when calculating fatigue.

[0051] The specific steps include:

[0052] S1.1. Randomly select 24 pieces or more welding spot samples from the completed stator;

[0053] S1.2. Perform a tensile test on each solder joint sample at a frequency of 20 Hz, with a test clamping gauge length of 50 mm. Given different displacements as input, obtain the number of solder joint tensile tests and the average force in the whole process under different displacements;

[0054] S1.3, convert the average force into stress, and fit the data with the number of solder joint tests to obtain a simplified solder joint SN curve: S = -11.25ln (N) + 203.43, where S is the amplitude stress, unit MPa, and N is the number of failure cycles (the number of cycles required for fatigue failure of the solder joint under a given amplitude stress), such as Figure 2 As shown;

[0055] S2. Simplify the stator assembly model to obtain a simplified stator assembly model.

[0056] Since the stator core is made of silicon steel sheets stacked one by one and connected by welding, in order to simplify the calculation of the model, the stator core is regarded as a whole so that the finite element analysis calculation can be carried out quickly and accurately.

[0057] When constructing the model, anisotropic material properties are used to characterize the dynamic characteristics of the stator. After the flat copper wire is bent and stamped, it is inserted into the stator slot. The density of the copper wire distributed in the stator slot and at the end is significantly different. Its technical effects include: better expression of the obvious difference between the radial stiffness and axial stiffness of the stator, making it closer to physical reality.

[0058] This step includes:

[0059] S2.1 construct a stator assembly model, and simplify the stator assembly model into a simplified stator assembly model consisting of four entities: an iron core, copper wires in slots, copper wires at welding ends, and copper wires at crown ends;

[0060] S2.2. Simplify the solder joints in the simplified stator assembly model; simplify the solder joint model into a rectangular parallelepiped. According to the notch stress method principle and the actual experience of copper wire welding, there is an arc notch with a radius of 0.02mm in the middle of the solder joint, such as Figure 3 As shown, the length and width of the solder joint model need to be adaptively adjusted according to the actual size of the flat copper wire, and its height = 0.5*length; it is recommended to use a size of 0.01mm in the meshing step in the finite element calculation to avoid the influence of the mesh size on the stress;

[0061] S2.3. Perform modal benchmarking on the simplified stator assembly model to determine the optimal material parameters. The optimal material parameters include: anisotropic material parameters of the stator core, copper wire in the slot, copper wire at the welding end, and copper wire at the crown end, thereby obtaining the benchmarked stator assembly model; the anisotropic parameters include Young's modulus in three directions in the spatial rectangular coordinate system and the shear modulus of the three coordinate planes.

[0062] S3. Use the aligned stator assembly model to perform modal analysis and harmonic response analysis

[0063] The finite element method is used to perform modal analysis on the stator assembly model after modal alignment to obtain the modal frequency and vibration mode of the stator; and based on the modal analysis, the stator assembly is subjected to harmonic response analysis to obtain the response transfer function, which is used to describe the dynamic stress response characteristics of the stator under different excitations.

[0064] S4. Fatigue damage calculation of the solder joint based on the PSD spectrum of random vibration; specifically including:

[0065] S4.1. According to the random vibration conditions defined in 6.5.3.5 c) of Class M1 and Class N1 vehicles, motors with suspensions, and integrated drive motor systems in the national standard GB / T 18488-2024, determine the random vibration PSD (power spectral density) load spectrum, as shown in Table 1 below;

[0066] Table 1

[0067]

[0068] S4.2, such as Figure 4 As shown in the calculation process, in nCode Design Life of the Ansys simulation software platform, the material properties of the copper wire solder joint are created according to the optimal material parameters obtained in step S2.3 above, and the SN curve S = -11.25ln (N) + 203.43 obtained in step S1.3 is input; the counting method uses Dirlik's PSD counting method, the stress combination method of CriticalPlane is used, the survival rate is selected as 90%, and the test time 20h is converted into 72000s as input, and the fatigue damage Damage of the solder joint in each direction is calculated, and the fatigue damage Damage of the solder joint in the three directions of X, Y, and Z is converted. x +Damage y +Damage z The fatigue damage value of the solder joint is obtained by accumulating. When the fatigue damage value of the solder joint is less than or equal to the set value 1, it means that the solder joint will not fail in this test with a high probability; when the fatigue damage value of the solder joint is greater than the set value 1, it is considered that the solder joint will fail due to fatigue with a high probability in this test.

[0069] The calculation of the fatigue damage value comprises the following steps:

[0070] 1. Obtain stress PSD curve: According to the response transfer function obtained above and Table 1 or Figure 4 The PSD curve shown is a stress PSD curve (Power Spectral Density) of the solder joint structure obtained by simulation. It is a statistical characteristic curve describing the stress response of the solder joint structure under random excitation, with frequency f as the abscissa and the power spectral density of the stress response as the ordinate. In this embodiment, the stress PSD curve = PSD curve × response transfer function. In some application scenarios, unit conversion is required when multiplying the PSD curve and the response transfer function.

[0071] 2. Calculate the moment of inertia: Use the stress PSD curve to calculate the four moments of inertia m0, m1, m2, and m4. The calculation methods include: n =∫0 ∞ f n PSD s (f) df, where f is frequency; n = 0, 1, 2, 4; PSD s (f) represents the stress PSD curve;

[0072] 3. Apply Dirlik's empirical formula: Substitute the moments of inertia m0, m1, m2, and m4 into the Dirlik empirical formula to calculate the stress amplitude Si The probability density function p(S i );S i represents the i-th possible stress amplitude corresponding to the solder joint;

[0073]

[0074] Where: D3 = 1 - D1 - D2;

[0075] 4. According to the probability density function p(S i ) is calculated at a time length T and a stress amplitude of S i The actual number of cycles N1(S i ), the calculation formula is:

[0076] 5. According to the SN curve S = -11.25ln (N) + 203.43, the stress amplitude S is obtained. i Number of failure cycles under action

[0077] 6. Calculate the fatigue damage Damage of each weld point in a certain direction and a certain time length T; according to Miller's damage accumulation principle, the calculation method of the fatigue damage Damage includes:

[0078]

[0079] The fatigue damage Damage of the solder joint in each direction is added to obtain the fatigue damage value of the solder joint. If the fatigue damage value of the solder joint is greater than 1, it is considered that the solder joint will fail due to fatigue.

[0080] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0081] Example 2

[0082] Flat wire motor stator busbar weld fatigue analysis system, including:

[0083] Stress-life curve acquisition module: used to intercept multiple welding spot samples on the stator after welding, perform tensile test on the welding spot samples within a set frequency range, and obtain the stress-life curve of the welding spot;

[0084] Stator assembly model building module: used to build a stator assembly model; the stator assembly model is used to obtain a response transfer function of a welding point; the response transfer function is used to describe the relationship between the stress response of the stator when it is excited by a specific frequency and the excitation of the specific frequency;

[0085] Fatigue damage determination module: used to calculate the fatigue damage value of the solder joint based on the power spectrum density load spectrum of random vibration according to the response transfer function and the stress-life curve, and determine whether the solder joint fails due to fatigue according to the fatigue damage value.

[0086] In some embodiments, a model benchmarking module is further included, which is used to perform modal benchmarking on the constructed stator assembly model to determine the optimal material parameters, thereby obtaining a benchmarked stator assembly model.

[0087] In some embodiments, the method of obtaining the response transfer function includes:

[0088] The finite element method is used to perform modal analysis on the aligned stator assembly model to obtain the modal frequency and vibration shape of the stator; the harmonic response analysis of the stator is performed according to the modal frequency and vibration shape to obtain the response transfer function.

[0089] In some embodiments, the stator assembly model building module further includes simplifying the stator assembly model, and the simplification method includes:

[0090] The stator assembly model is simplified to consist of an iron core, copper wires in slots, copper wires at welding ends and copper wires at crown ends, thereby obtaining a simplified stator assembly model;

[0091] The weld in the simplified stator assembly model is simplified into a rectangular parallelepiped including an arc-shaped notch with a set radius in the middle of the weld, which is used to characterize the stress concentration of the weld.

[0092] In some embodiments, in the stator assembly model building module, anisotropic material properties are used to characterize the difference between the radial stiffness and axial stiffness of the stator, and the anisotropic material parameters include: anisotropic material parameters of the stator core, the copper wire in the slot, the copper wire at the welding end, and the copper wire at the crown end.

[0093] In some embodiments, in the fatigue damage determination module, in the nCodeDesign Life module of the Ansys simulation software platform, the material properties of the copper wire solder joint are created according to the optimal material parameters, and the stress-life curve is input; the counting method uses Dirlik's PSD counting method, adopts the stress combination method of CriticalPlane, selects the survival rate, adjusts the test time, and calculates the fatigue damage of the solder joint in multiple directions to obtain the fatigue damage value of the solder joint in the x, y, and z directions; when the fatigue damage value is greater than the set value, it is considered that the solder joint will fail due to fatigue; the set value in this embodiment is 1.

[0094] In some embodiments, in the fatigue damage determination module, the method for calculating the fatigue damage value includes:

[0095] On the Ansys simulation software platform, a stress PSD curve of the solder joint structure is obtained according to the response transfer function and a power spectrum density load spectrum based on random vibration;

[0096] The four moments of inertia m0, m1, m2, and m4 are calculated using the stress PSD curve. The calculation method includes: n =∫0 ∞ f n PSD s (f) df, where f is frequency; n = 0, 1, 2, 4; PSD s (f) represents the stress PSD curve;

[0097] According to the moments of inertia m0, m1, m2, and m4, the stress amplitude S is calculated using the Dirlik empirical formula. i The probability density function p(S i );S i represents the i-th possible stress amplitude of the solder joint;

[0098] According to the probability density function p(S i ) is calculated at a time length T and a stress amplitude of S i The actual number of cycles N1(S i ); The physical meaning of the actual number of cycles in this embodiment includes: the number of times a certain stress amplitude will occur within a time length T under a certain PSD spectrum; its calculation formula includes:

[0099]

[0100] The stress amplitude S is obtained according to the application-life curve i The number of failure cycles under action N f (S i); The physical meaning of the number of failure cycles in this embodiment includes: the number of cycles through which the material will fail under a certain welding process and the corresponding stress amplitude is measured by a tensile test; it is obtained according to the SN curve, and the calculation formula includes:

[0101]

[0102] The fatigue damage of the solder joint in a certain direction under the time length T is calculated according to the following formula:

[0103]

[0104] The fatigue damage of the solder joint in each direction is accumulated to obtain the fatigue damage value of the solder joint.

[0105] Example 3

[0106] A non-transitory computer-readable storage medium stores a computer program, which includes program instructions. When the program instructions are executed by a processor, the various steps of the method described in the present invention are implemented, which will not be repeated here.

[0107] The computer-readable storage medium may be the data transmission device provided in any of the aforementioned embodiments or the internal storage unit of the computer device, such as the hard disk or memory of the computer device. The computer-readable storage medium may also be an external storage device of the computer device, such as a plug-in hard disk, a smart memory card (smartmedia card, SMC), a secure digital (secure digital, SD) card, a flash card (flash card), etc., provided on the computer device.

[0108] Furthermore, the computer-readable storage medium may include both an internal storage unit of the computer device and an external storage device. The computer-readable storage medium is used to store the computer program and other programs and data required by the computer device. The computer-readable storage medium may also be used to temporarily store data to be output or has been output.

[0109] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0110] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0111] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0112] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0113] Example 4

[0114] A computer program product includes a computer program / instruction, which implements the steps of the flat wire motor stator busbar weld fatigue analysis method when executed by a processor.

[0115] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A flat wire motor stator busbar weld fatigue analysis system, characterized in that: include: Stress-life curve acquisition module: used to intercept multiple welding spot samples on the stator after welding, perform tensile test on the welding spot samples within a set frequency range, and obtain the stress-life curve of the welding spot; Stator assembly model building module: used to build a stator assembly model; the stator assembly model is used to obtain a response transfer function of a welding point; the response transfer function is used to describe the relationship between the response of the stator when it is excited by a specific frequency and the excitation of the specific frequency; Fatigue damage determination module: used to calculate the fatigue damage of the weld based on the power spectrum density load spectrum of random vibration according to the response transfer function and stress-life curve obtained from the stator assembly model, obtain the fatigue damage value of the weld, and determine whether the weld fails due to fatigue according to the fatigue damage value.

2. The flat wire motor stator busbar weld fatigue analysis system according to claim 1, characterized in that: It also includes a model benchmarking module, which is used to perform modal benchmarking on the constructed stator assembly model to determine the optimal material parameters, thereby obtaining the benchmarked stator assembly model.

3. The flat wire motor stator busbar weld fatigue analysis system as claimed in claim 2, characterized in that: The methods for obtaining the response transfer function include: The finite element method is used to perform modal analysis on the aligned stator assembly model to obtain the modal frequency and vibration shape of the stator; the harmonic response analysis of the stator is performed according to the modal frequency and vibration shape to obtain the response transfer function.

4. The flat wire motor stator busbar weld fatigue analysis system according to any one of claims 1 to 3, characterized in that: The stator assembly model building module also includes simplifying the stator assembly model, and the simplification method includes: The stator assembly model is simplified to consist of an iron core, copper wires in slots, copper wires at welding ends and copper wires at crown ends, thereby obtaining a simplified stator assembly model; The weld in the simplified stator assembly model is simplified into a rectangular parallelepiped including an arc-shaped notch with a set radius in the middle of the weld, which is used to characterize the stress concentration of the weld.

5. The flat wire motor stator busbar weld fatigue analysis system according to any one of claims 1 to 3, characterized in that: In the stator assembly model building module, anisotropic material properties are used to characterize the difference between the radial stiffness and the axial stiffness of the stator. The anisotropic material parameters include: anisotropic material parameters of the stator core, the copper wire in the slot, the copper wire at the welding end, and the copper wire at the crown end.

6. The flat wire motor stator busbar weld fatigue analysis system according to claim 1, characterized in that: In the fatigue damage determination module, in the nCode Design Life module of the Ansys simulation software platform, the material properties of the copper wire solder joint are created according to the optimal material parameters, and the stress-life curve is input; the counting method uses the Dirlik PSD counting method, adopts the CriticalPlane stress combination method, selects the survival rate, adjusts the test time, and calculates the fatigue damage of the solder joint in multiple directions to obtain the fatigue damage value of the solder joint; when the fatigue damage value is greater than the set value, it is considered that the solder joint will fail due to fatigue.

7. The flat wire motor stator busbar weld fatigue analysis system according to claim 1 or 6, characterized in that: In the fatigue damage determination module, the calculation method of the fatigue damage value includes: Obtaining a stress PSD curve of the solder joint according to the response transfer function and a power spectral density load spectrum based on random vibration; The four moments of inertia m0, m1, m2, and m4 are calculated using the stress PSD curve. The calculation method includes: Where f is the frequency; n = 0, 1, 2, 4; PSD s (f) represents the stress PSD curve; According to the moments of inertia m0, m1, m2, and m4, the stress amplitude S is calculated using the Dirlik empirical formula. i The probability density function p(S i );S i represents the i-th possible stress amplitude of the solder joint; According to the probability density function p(S i ) Calculate the solder joint at a time length T and a stress amplitude of S i The actual number of cycles N1(S i ); According to the application-life curve, the stress amplitude S of the solder joint is obtained. i The number of failure cycles under action N f (S i ); The fatigue damage of the solder joint in a certain direction under the time length T is calculated according to the following formula: The fatigue damage of the solder joint in each direction is accumulated to obtain the fatigue damage value of the solder joint.

8. A fatigue analysis method for busbar welds of a flat wire motor stator, characterized in that: include: Cutting a plurality of weld spot samples from the welded stator, performing a tensile test within a set frequency range on the weld spot samples, and obtaining a stress-life curve of the weld spot; Constructing a stator assembly model; the stator assembly model is used to obtain a response transfer function of a welding point; the response transfer function is used to describe the relationship between the response of the stator when it is excited by a specific frequency and the excitation of the specific frequency; The fatigue damage value of the solder joint based on the power spectrum density load spectrum of random vibration is calculated according to the response transfer function and the stress-life curve, and whether the solder joint fails due to fatigue is determined according to the fatigue damage value.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the fatigue analysis method of the flat wire motor stator busbar weld point are implemented as claimed in any one of claim 8.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, the steps of the fatigue analysis method of the flat wire motor stator busbar weld point described in claim 1 are implemented.

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