Rotor punching fillet radius design method and system based on stress prediction model

Abstract

The present invention relates to the field of motor design technology, and in particular to a rotor punching fillet radius design method and system based on a stress prediction model. The design method includes: establishing the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress; solving the constant terms in the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress respectively through finite element simulation; constructing a stress prediction model; calculating the minimum value of the fillet radius of the punching based on the allowable stress and the maximum design rotational speed of the punching, combined with the stress prediction model; determining the design value of the fillet radius of the punching, wherein the design value of the fillet radius of the punching is greater than or equal to the minimum value of the fillet radius of the punching. Through this design method and system, the key structural parameter of the punching, i.e., the fillet radius of the punching, can be quickly determined.

Description

Technical Field

[0001] The present invention relates to the technical field of motor design, and in particular to a method and system for designing a rotor punching fillet radius based on a stress prediction model. Background Art

[0002] Among the many new energy sources currently available, wind power is the most scalable and valuable new renewable energy source. Among wind turbine components, rotor laminations, the core components that provide the rotor's magnetic field, rotate at high speeds and withstand enormous centrifugal forces. This makes them susceptible to deformation and cracking during operation, impacting the stable operation of the unit.

[0003] To ensure the stability of the rotor laminations during service, the rotor lamination structure must be rationally designed to ensure low stress during service. Currently, the use of finite element simulation technology to assist in wind turbine design is common practice. To improve the design speed of the rotor laminations and the stability of the generator set, engineers use finite element software to study the loads on the laminations during operation to ensure that the designed laminations can operate stably and reliably. If the designed laminations do not meet the requirements, the structure must be modified and the loads of the new structure calculated. This process is repeated until the structural parameters are reasonable. However, this method is inefficient. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a rotor punching fillet radius design method and system based on a stress prediction model, which can realize the rapid determination of the key structural parameters of the punching, namely the punching fillet radius.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] The rotor punching fillet radius design method based on the stress prediction model includes the following steps:

[0007] Step S1. Establishing the relationship between the rotation speed and the punching sheet stress and the relationship between the fillet radius and the punching sheet stress; wherein the relationship between the rotation speed and the punching sheet stress is: ; The relationship between fillet radius and punching stress is: Where, is the maximum stress value, is the rotation speed, k is the comprehensive coefficient, R is the fillet radius, and a is the exponential factor;

[0008] Step S2. Calculate the comprehensive coefficient k and the exponential factor a through finite element simulation;

[0009] Step S3. Construct a stress prediction model based on the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress:

[0010] ;

[0011] Where, To solve the fillet radius corresponding to the comprehensive coefficient k;

[0012] Step S4. Based on the allowable stress of the punch and the maximum design speed, combined with the stress prediction model, calculate the minimum value of the punch fillet radius;

[0013] Step S5: Determine a design value of the punching sheet fillet radius, wherein the design value of the punching sheet fillet radius is greater than or equal to a minimum value of the punching sheet fillet radius.

[0014] Before performing finite element simulation, it also includes calculating the mesh size.

[0015] The calculation of the grid size comprises the following steps:

[0016] Step S 21 . Set the initial mesh size m1;

[0017] Step S 22 The entire punch is divided into grid units of size m1, and the stress of the punch with a fillet radius of R1 at a rotation speed of ω is simulated;

[0018] Step S 23 Obtain simulation results and determine whether they are reasonable. If not, determine the new mesh size using the following method:

[0019] m n+1 =0.5*m n ;

[0020] Step S 24 . Update the mesh size, re-simulate, and return to step S 23 , continue to evaluate the rationality of the simulation results until the simulation results are reasonable and confirm the final mesh division size.

[0021] Step S 23 Judging whether the simulation results are reasonable specifically refers to: based on the simulation results, extracting the coordinates of a set of data points corresponding to a specified stress value, smoothing the coordinate data of the data point geometry so that the coordinate points form a continuous differentiable curve, calculating the slope of the curve, and judging whether the slope of the curve is less than a preset value i. If not, it is judged to be unreasonable, and if so, it is judged to be reasonable.

[0022] The method for determining the initial grid size m1 is:

[0023] ,

[0024] Where D is the width of the magnetic bridge between the punching sheets.

[0025] Solving the comprehensive coefficient k specifically means: finding the maximum stress σ based on the simulation results corresponding to the final mesh size max1 , combined with the rotational speed ω in the process of mesh size calculation, the relationship between the rotational speed and the punching stress, calculate the comprehensive coefficient k.

[0026] Solving the exponential factor a specifically means: changing the fillet radius at the bridge, changing the fillet radius from R1 to R2, simulating the stress on the punch at the speed ω, and obtaining the maximum stress σ max2 According to the relationship between the fillet radius and the punching stress, the following equations are combined to calculate the exponential factor a:

[0027] .

[0028] The relationship between the fillet radius R2 and the fillet radius R1 is: the difference between the fillet radius R2 and the fillet radius R1 is an integer multiple of the final mesh division size.

[0029] The difference between the fillet radius R2 and the fillet radius R1 is between 3 and 6 times the final mesh size.

[0030] The rotor lamination fillet radius design system based on the stress prediction model includes:

[0031] Relationship building unit, used to establish the relationship between rotation speed and punching stress: , which is also used to establish the relationship between fillet radius and punching stress: Where, is the maximum stress value, is the rotation speed, k is the comprehensive coefficient, R is the fillet radius, and a is the exponential factor;

[0032] The meshing and size determination unit is used to mesh the sheet structure before finite element simulation, and to determine whether the current mesh size is reasonable through iterative refinement, and finally obtain the final mesh size that meets the requirements;

[0033] Finite element simulation unit, used to perform finite element simulation calculations on the punching sheet according to the final mesh division size and obtain finite element simulation results under different working conditions;

[0034] The data processing unit is used to extract the maximum stress value in the simulation results and solve the comprehensive coefficient k and the exponential factor a based on the rotation speed and the corner radius of the punch;

[0035] Stress prediction model building unit, used to build stress prediction model: Where, To solve the fillet radius corresponding to the comprehensive coefficient k;

[0036] The punching sheet fillet radius determination unit is used to calculate the minimum value of the punching sheet fillet radius based on the allowable stress and the maximum design speed of the punching sheet in combination with the above stress prediction model, and determine the design value of the punching sheet fillet radius.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. In existing technologies, engineers typically rely on their experience to iterate and determine the maximum rotational speed and optimize the fillet size at the punching bridge. However, this approach can require multiple rounds of iteration, requiring numerous simulations, resulting in a time-consuming and inefficient process. Furthermore, using artificial intelligence (AI) or response surface model analysis requires a large number of samples. Furthermore, the "black box" nature of AI models can easily raise doubts about the credibility of the results, while response surface models often offer low prediction accuracy.

[0039] This invention innovatively uses a simple mathematical relationship to accurately describe the relationship between the fillet radius of the magnetic isolation bridge, rotational speed, and maximum stress in the lamination. This mathematical relationship can quickly determine the appropriate fillet radius for the lamination's magnetic isolation bridge. This method not only simplifies the design process and reduces the number of samples required, but also significantly improves design accuracy, providing designers with a powerful tool for quickly designing reliable rotor lamination structures.

[0040] 2. This invention quantitatively analyzes the data and innovatively uses a quadratic polynomial function to better describe the nonlinear relationship between rotational speed and punching stress. Based on reasonable simplification, this quadratic polynomial is converted into a linear equation. The simplified linear equation contains only one parameter, k, making it easy to solve and highly practical.

[0041] 3. This invention further innovatively establishes a mathematical relationship between the fillet radius and the punching stress, and verifies the applicability and accuracy of this model through extensive simulation and experimental data. Fitting and analyzing finite element simulation results for multiple sets of different fillet radii demonstrates that the equation has a good goodness of fit and accurately reflects the effect of fillet radius on the punching stress distribution.

[0042] 4. The present invention can ensure the accuracy of finite element calculation and effectively reduce the amount of calculation by calculating the grid division size.

[0043] 5. The present invention determines the rationality of mesh size based on the material's internal stress distribution. A smooth simulated contour is considered reliable, while a non-smooth contour indicates a need for further mesh size reduction. The smoothness of the contour is quantified by the curvature of the stress contours. By comparing this curvature with a preset value, the rationality of mesh size can be quickly and accurately determined.

[0044] 6. The present invention firstly accurately determines the initial grid division size to ensure calculation accuracy.

[0045] 7. When solving the comprehensive coefficient k, the present invention does not require additional finite element simulation. It only needs to use the finite element simulation results corresponding to the final mesh size obtained in the mesh size calculation process to extract the maximum stress σ of the punch at a specific speed. max1 , combined with the corresponding speed, can be directly obtained. This method makes full use of existing simulation data, avoids repeated modeling and simulation, and significantly improves the efficiency of solving the comprehensive coefficient k.

[0046] 8. When solving the exponential factor a, there is no need to perform multiple complex finite element simulations. It is only necessary to make a reasonable modification to the fillet radius and perform a finite element simulation under the same working conditions to obtain the new maximum stress σ max2 The exponential factor a can be obtained by combining the simulation results, the simulation results corresponding to the final mesh size adopted, and the fillet radii R1 and R2 before and after modification.

[0047] This method only requires one additional simulation to solve the exponential factor a, significantly reducing the large amount of samples and computing resources required in traditional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein:

[0049] Figure 1 It is a schematic diagram of the process of the present invention;

[0050] Figure 2 Schematic diagram of the shape and partial dimensions of the punching sheet in the present invention;

[0051] Figure 3 Schematic diagram of the stress prediction model in the present invention;

[0052] Figure 4 Schematic diagram of simulation results under verification parameters in the present invention;

[0053] Figure 5 Schematic diagram of performing a polynomial fitting on the rotation speed and stress value in the present invention;

[0054] Figure 6 Schematic diagram of quadratic polynomial fitting of rotation speed and stress value in the present invention;

[0055] Figure 7 Schematic diagram of fitting a cubic polynomial to the rotational speed and stress value in the present invention;

[0056] Figure 8Schematic diagram of quadratic fitting of rotation speed and stress value in the present invention;

[0057] Figure 9 The stress cloud diagram of the punch under different R in the present invention;

[0058] Figure 10 It is a plot of fillet radius and punching stress in the present invention;

[0059] Figure 11 For the present invention and Schematic diagram of the linear fitting results. DETAILED DESCRIPTION

[0060] Example 1

[0061] As a basic embodiment of the present invention, the present invention includes a rotor punching fillet radius design method based on a stress prediction model, comprising the following steps:

[0062] Step S1: Establish the relationship between the rotation speed and the punching stress, and the relationship between the fillet radius and the punching stress.

[0063] Among them, the relationship between the rotation speed and the punching stress is: The relationship between the fillet radius and the punching stress is: Where, is the maximum stress value, is the rotation speed, k is the comprehensive coefficient, R is the fillet radius, and a is the exponential factor.

[0064] Step S2. Through finite element simulation, solve the comprehensive coefficient k and the exponential factor a respectively.

[0065] Step S3. Construct a stress prediction model based on the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress:

[0066] .

[0067] Where, To solve the comprehensive coefficient k corresponding to the fillet radius.

[0068] Step S4: Based on the allowable stress of the punching piece and the maximum design rotation speed, combined with the stress prediction model, the minimum value of the punching piece fillet radius is calculated.

[0069] Step S5: Determine a design value of the punching sheet fillet radius. The design value of the punching sheet fillet radius is greater than or equal to the minimum value of the punching sheet fillet radius.

[0070] Example 2

[0071] As a preferred embodiment of the present invention, the present invention includes a rotor punching fillet radius design method based on a stress prediction model, comprising the following steps:

[0072] Step S1: Establish the relationship between the rotation speed and the punching stress, and the relationship between the fillet radius and the punching stress.

[0073] Among them, the relationship between the rotation speed and the punching stress is: The relationship between the fillet radius and the punching stress is: Where, is the maximum stress value, is the rotation speed, k is the comprehensive coefficient, R is the fillet radius, and a is the exponential factor.

[0074] Step S2. Through finite element simulation, solve the comprehensive coefficient k and the exponential factor a respectively.

[0075] Specifically, the fillet radius at the bridge is set to R1, and the stress of the punching sheet is simulated at a rotation speed of ω, and the maximum stress value is found. σ max1 , based on the speed ω and the maximum stress σ max1 , the comprehensive coefficient k can be solved. Then the fillet radius at the bridge is changed from R1 to R2, and the stress of the punching sheet is simulated when the speed is ω, and the maximum stress is obtained. σ max2 , combine the following equations to calculate the exponential factor a:

[0076] .

[0077] Step S3. Construct a stress prediction model based on the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress:

[0078] .

[0079] Where, To solve the comprehensive coefficient k corresponding to the fillet radius.

[0080] Step S4: Based on the allowable stress of the punching piece and the maximum design rotation speed, combined with the stress prediction model, the minimum value of the punching piece fillet radius is calculated.

[0081] Step S5: Determine a design value of the punching sheet fillet radius. The design value of the punching sheet fillet radius is greater than or equal to the minimum value of the punching sheet fillet radius.

[0082] Example 3

[0083] As another preferred embodiment of the present invention, the present invention includes a rotor punching fillet radius design method based on a stress prediction model, comprising the following steps:

[0084] Step S1: Establish the relationship between the rotation speed and the punching stress, and the relationship between the fillet radius and the punching stress.

[0085] Among them, the relationship between the rotation speed and the punching stress is: The relationship between the fillet radius and the punching stress is: Where, is the maximum stress value, is the rotation speed, k is the comprehensive coefficient, R is the fillet radius, and a is the exponential factor.

[0086] Step S2. Calculate the mesh size, determine the final mesh size, and use it to divide the sheet. Then, perform finite element simulation. Based on the finite element simulation results and parameters, solve the comprehensive coefficient k and the exponential factor a respectively.

[0087] Calculating the grid size specifically includes the following steps:

[0088] Step S 21 . Set the initial mesh size m1.

[0089] Step S 22 The entire punch is divided into grid units of size m1, and the stress of the punch with a fillet radius of R1 at a rotation speed of ω is simulated.

[0090] Step S 23 Obtain simulation results and determine whether they are reasonable. If not, determine the new mesh size using the following method:

[0091] m n+1 =0.5*m n .

[0092] Among them, judging whether the simulation results are reasonable specifically refers to: based on the simulation results, extracting the coordinates of a set of data points corresponding to a specified stress value, smoothing the coordinate data of the data point geometry to form a continuous differentiable curve at the coordinate points, forming a stress contour curve, calculating the slope of the curve, and judging whether the slope of the curve is less than a preset value i. If not, it is judged to be unreasonable, and if so, it is judged to be reasonable.

[0093] Step S 24 . Update the mesh size, re-simulate, and return to step S 23 , continue to evaluate the rationality of the simulation results until the simulation results are reasonable, confirm the final mesh size, and stop meshing.

[0094] Step S3. Construct a stress prediction model based on the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress:

[0095] .

[0096] Where, To solve the comprehensive coefficient k corresponding to the fillet radius.

[0097] Step S4: Based on the allowable stress of the punching piece and the maximum design rotation speed, combined with the stress prediction model, the minimum value of the punching piece fillet radius is calculated.

[0098] Step S5: Determine a design value of the punching sheet fillet radius. The design value of the punching sheet fillet radius is greater than or equal to the minimum value of the punching sheet fillet radius.

[0099] Example 4

[0100] As another preferred embodiment of the present invention, the present invention includes a rotor punching fillet radius design method based on a stress prediction model, referring to the attached specification. Figure 1 , including the following steps:

[0101] Step S1: Establish the relationship between the rotation speed and the punching stress, and the relationship between the fillet radius and the punching stress.

[0102] Among them, the relationship between the rotation speed and the punching stress is: Where, is the maximum stress value, is the speed, and k is the comprehensive coefficient.

[0103] The relationship between fillet radius and punching stress is: Where, is the maximum stress, R is the fillet radius, and a is the exponential factor.

[0104] Step S2. Calculate the mesh size to obtain the final mesh size. Perform finite element simulation on the punch based on the final mesh size to calculate the comprehensive coefficient k and exponential factor a.

[0105] The calculation of the grid size includes the following steps:

[0106] Step S 21 . Set the initial mesh size m1:

[0107] ,

[0108] Where D is the width of the magnetic isolation bridge of the punching sheet. That is, ensuring that there are no less than 5 grid units in the width direction of the magnetic isolation bridge can ensure the accuracy of the calculation.

[0109] Step S 22 The entire punch is divided into grid units of size m1, and the stress of the punch with a fillet radius of R1 at a rotation speed of ω is simulated.

[0110] Step S23 . Obtain simulation results and determine whether they are reasonable; if not, obtain new mesh size according to the following method: m n+1 =0.5*m n Therefore, m2 is used as the new grid division size, and the new grid division size m2 is: m2=0.5*m1.

[0111] Judging whether the simulation results are reasonable specifically refers to: based on the simulation results, extracting the coordinates of a set of data points corresponding to a specified stress value, and smoothing the coordinate data of the data point geometry. The smoothing method is spline interpolation, so that the coordinate points form a continuous differentiable curve. Calculate the slope of the curve and judge whether the slope of the curve is less than a preset value i. The preset value i can be 0.5. If not, it is judged to be unreasonable. If so, it is judged to be reasonable. This judgment method is to judge the rationality of the simulation results based on the internal stress distribution of the material. Simply put, if the simulation cloud map is smooth, it can be judged that the result is reliable. If the cloud map is not smooth, the grid size needs to be further reduced.

[0112] Step S 24 . Update the mesh size, re-simulate, and return to step S 23 , continue to evaluate the rationality of the simulation results until the simulation results are reasonable and confirm the final mesh size m n , stop meshing.

[0113] Solving the comprehensive coefficient k specifically refers to: based on the final grid size m n The simulation results corresponding to the time are used to find the maximum stress σ max1 , combined with the rotational speed ω in the process of mesh size calculation, the relationship between the rotational speed and the punching stress, calculate the comprehensive coefficient k.

[0114] Solving the exponential factor a specifically means: changing the fillet radius at the bridge, changing the fillet radius from R1 to R2, leaving other parameters unchanged, simulating the stress on the punch at a rotation speed of ω, and obtaining the maximum stress σ max2 The relationship between the fillet radius R2 and the fillet radius R1 is: the difference between the fillet radius R2 and the fillet radius R1 is the final mesh size m n Furthermore, the difference between the fillet radius R2 and the fillet radius R1 is 3m n and 6m n between.

[0115] Based on the relationship between fillet radius and punching stress, the following equations are combined to calculate the exponential factor a:

[0116] .

[0117] Step S3. Construct a stress prediction model based on the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress:

[0118] .

[0119] Where, To solve the comprehensive coefficient k corresponding to the fillet radius.

[0120] Step S4: Based on the allowable stress of the punching piece and the maximum design rotation speed, combined with the stress prediction model, the minimum value of the punching piece fillet radius is calculated.

[0121] Step S5: Determine a design value of the punching sheet fillet radius. The design value of the punching sheet fillet radius is greater than or equal to the minimum value of the punching sheet fillet radius.

[0122] Example 5

[0123] As a specific embodiment of the present invention, the present invention includes a rotor punching fillet radius design method based on a stress prediction model. In which, the rotor punching shape repeats periodically in the circumferential direction, so the punching shape is simplified to obtain a shape within a single period, as shown in the attached specification. Figure 2 As shown in the instruction manual. Figure 2 It can be seen that the shape of the punching sheet is relatively complex, and the stress in most areas is difficult to calculate by analytical methods. Only the approximate stress value of point P (the point on the center of the magnetic isolation bridge) can be solved. Therefore, the stress value of point P can be calculated for subsequent verification of the accuracy of subsequent simulations.

[0124] The present invention uses the finite element software ANSYS to simulate and analyze the punching sheet. The main performance parameters of the punching sheet material are as follows: Young's modulus is 195GPa, Poisson's ratio is 0.26, and density is 7650kg / m 3 The material is assumed to be completely linear elastic. Considering that the rotor laminations are primarily subjected to centrifugal loads during service, the simulation only considers centrifugal loads, ignoring loads caused by electromagnetic forces and thermal effects. Circumferential constraints are set on the inner arc of the lamination, with both ends set to frictionless. Axial displacement is prohibited on the two main planes of the lamination, front and back.

[0125] Before performing the finite element simulation, the mesh size is calculated to obtain the final mesh size. The specific mesh size division method can be as shown in the above embodiment 3 or embodiment 4.

[0126] Based on the above conditions, this design method includes the following steps:

[0127] Step S1: Establishing the relationship between the rotation speed and the punching stress and the relationship between the fillet radius and the punching stress.

[0128] The qualitative relationship between rotational speed and punching stress is well known, and punching stress increases with increasing rotational speed. However, the quantitative relationship between the two has not been made public. Therefore, this method sets up five sets of simulation experiments with different rotational speeds, ranging from 100 to 300 rad / s (△=50 rad / s). Through these five sets of simulation experiments and analysis of existing research results, the quantitative relationship between stress and rotational speed is obtained.

[0129] As the rotational speed increases, the overall stress level of the punching plate increases significantly. This is because the stress on the punching plate is caused by the centrifugal force generated by the rotation process. The magnitude of the centrifugal force is highly correlated with the rotational speed. Therefore, the higher the rotational speed, the higher the overall stress level of the punching plate. However, it should be pointed out that the maximum stress value is located at the transition fillet. This is because the rotational speed increases the overall stress level of the punching plate and has little effect on the distribution characteristics of the punching plate stress.

[0130] Extract the maximum value of punching stress at different speeds , to conduct quantitative analysis, the main method is to fit the extracted data points and use the mean square error (MSE) to judge the fitting effect. Figure 5 , linear fitting is performed on the extracted data. It can be seen that the fitting effect of the first-order polynomial is poor, with an MSE of 335. Figure 6 , perform quadratic polynomial fitting on the data, refer to the instruction manual Figure 7 , a cubic polynomial is fitted to the data points, and the fitting effect is good, with an MSE close to 0. Table 1 below shows the coefficients of the fitting equation. It can be seen that in the fitting results of the cubic polynomial, the cubic term coefficient is 0, and the quadratic term coefficient is very close to the quadratic term coefficient of the quadratic polynomial. Therefore, the relationship between the punching stress and the rotational speed should be described by a quadratic polynomial. This result is reasonable because the centrifugal force is proportional to the square of the rotational speed.

[0131] Table 1 Fitting results of rotation speed and stress

[0132]

[0133] However, the quadratic polynomial has many coefficients and is still cumbersome to use, so the quadratic polynomial is simplified. Figure 8 The horizontal axis is the square of the rotational speed, and the vertical axis is the stress value. It can be seen that the data points in the figure show a good linear distribution, and the MSE of the linear fitting is about 0. The quadratic polynomial is simplified to obtain the following formula: Figure 8 The linear equation in , the equation is:

[0134] .

[0135] Where, is the maximum stress value, is the rotational speed, and since the constant term in the above formula is very small, it can be discarded. Therefore, the relationship between the rotational speed and the punching stress is obtained:

[0136] .

[0137] This equation contains only one coefficient, is simple to solve, and has good practicality.

[0138] When the punching stress is excessive and the rotational speed cannot be reduced, the punching structure needs to be optimized to reduce the stress. It is well known that increasing the fillet radius R is an important means of optimizing the punching stress, but the mathematical relationship between the fillet radius and the punching stress has not yet been discovered. Therefore, studying the mathematical relationship between the fillet radius and the punching stress is of great significance for engineering design. During the simulation, the rotational speed was fixed at 100 rad / s, and the fillet radius R was varied from 0.4 to 1.6 mm (△ = 0.2 mm). Seven sets of finite element simulation experiments were conducted to investigate the relationship between the fillet radius and the punching stress.

[0139] Refer to the instruction manual Figure 9 From the cloud diagram, it can be clearly seen that as R increases, the maximum stress value of the punching sheet gradually decreases, while the overall stress level of the punching sheet changes little. This is because increasing the fillet radius can effectively reduce the degree of stress concentration, and material cracking is often caused by excessive local stress. Therefore, increasing R can effectively reduce the maximum stress value and extend the life of the punching sheet.

[0140] Extract the maximum value of punch stress under different R , get the instruction manual attached Figure 10 From the plot of maximum stress and fillet radius, we can see that as R increases, the maximum stress It gradually decreases, but the downward trend gradually weakens. When R increases from 0.4mm to 0.8mm, When the pressure drops by about 15 MPa and R increases from 1.2 mm to 1.6 mm, It is foreseeable that as R continues to increase, It will gradually decrease, but will eventually stabilize. Figure 10 It can be seen from the stress change trend in that, on the other hand, increasing R only reduces the degree of stress concentration but cannot change the overall stress of the punching sheet.

[0141] Observation Instructions Figure 10 The distribution of data points in the graph shows that when R increases, Continuously decreases, and the degree of decrease slows down; when R decreases continuously, It keeps increasing and shows no signs of convergence. This trend is in line with expectations, because when R decreases to 0, the transition fillet disappears and the area becomes sharp, and the theoretical stress value at this time tends to infinity. The mathematical relationship between the function and R should meet two requirements: ① As R increases, Gradually decreases, but the degree of decrease becomes smaller and smaller 0; ② When R approaches 0, This function characteristic is similar to the distribution characteristics of the stress-life curve of metal materials, so it is considered to be described by the Basquin equation. The relationship between and R is to replace the variables in the Basquin equation with and R to obtain the following equation:

[0142] .

[0143] In the formula, a and b are constants to be determined. Specifically, a is defined as the exponential factor. Take the common logarithm of R and perform linear fitting on the obtained results. The fitting results are shown in the appendix of the manual. Figure 11 As shown, you can see that and There is a good linear relationship between them, and the MSE is approximately equal to 0, which further illustrates that the Basquin equation can accurately describe The mathematical relationship between and R. Finally, the equation obtained by solving is as follows:

[0144] ,

[0145] After transformation, we get:

[0146] .

[0147] Step S2. Construct a stress prediction model based on the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress:

[0148] .

[0149] Where, To solve the comprehensive coefficient k corresponding to the fillet radius.

[0150] Refer to the instruction manual Figure 3 At this time, k=0.00438, R1=1, a=-0.34448. It can be seen from the figure that as the fillet radius increases and the rotation speed decreases, the stress of the punching sheet decreases significantly.

[0151] The simulation parameters of the validation group are: rotation speed 180rad / s, R is 1.4mm, and the total prediction model prediction value is 126.39MPa. The simulation results are shown in the attached manual. Figure 4 As shown in the figure, the stress value is 124.89 MPa, which is close to the predicted value of the overall model, with an error within 1.5%. The model is very reliable and can effectively improve the design efficiency of engineers.

[0152] Step S3: Based on the allowable stress of the punching piece and the maximum design rotation speed, combined with the stress prediction model, the minimum value of the punching piece fillet radius is calculated.

[0153] Step S4: Determine a design value of the punching sheet fillet radius. The design value of the punching sheet fillet radius is greater than or equal to the minimum value of the punching sheet fillet radius.

[0154] Example 6

[0155] As another preferred embodiment of the present invention, the present invention includes a rotor punching fillet radius design system based on a stress prediction model, including:

[0156] The relationship establishment unit is used to establish the following two relationships: the relationship between the rotational speed and the punching stress, and the relationship between the fillet radius and the punching stress. Among them, the relationship between the rotational speed and the punching stress is: ; The relationship between fillet radius and punching stress is: Where, is the maximum stress value, is the rotation speed, k is the comprehensive coefficient, R is the fillet radius, and a is the exponential factor.

[0157] The meshing and size determination unit is used to mesh the sheet structure before finite element simulation, and to determine whether the current mesh size is reasonable through iterative refinement, and finally obtain the final mesh size that meets the requirements.

[0158] The finite element simulation unit is used to perform finite element simulation calculations on the punching sheet according to the final mesh division size and obtain finite element simulation results under different working conditions.

[0159] The data processing unit is used to extract the maximum stress value in the simulation results and solve the comprehensive coefficient k and the exponential factor a in combination with the rotation speed and the punching corner radius.

[0160] Stress prediction model building unit, used to build stress prediction model: Where, To solve the comprehensive coefficient k corresponding to the fillet radius.

[0161] The punching sheet fillet radius determination unit is used to calculate the minimum value of the punching sheet fillet radius based on the allowable stress and the maximum design speed of the punching sheet in combination with the above stress prediction model, and determine the design value of the punching sheet fillet radius.

[0162] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical solutions and technical concepts of the present invention without creative mental work, which all fall within the scope of protection of the present invention.

Claims

1. A rotor punching fillet radius design method based on a stress prediction model, characterized by: The following steps are involved: Step S1. Establishing the relationship between the rotational speed and the punching sheet stress and the relationship between the fillet radius and the punching sheet stress; wherein the relationship between the rotational speed and the punching sheet stress is: ; The relationship between fillet radius and punching stress is: Where, is the maximum stress value, is the rotation speed, k is the comprehensive coefficient, R is the fillet radius, and a is the exponential factor; Step S2. Calculate the comprehensive coefficient k and the exponential factor a through finite element simulation; Step S3. Construct a stress prediction model based on the relationship between rotational speed and punching stress, and the relationship between fillet radius and punching stress: ； Where, To solve the fillet radius corresponding to the comprehensive coefficient k; Step S4. Based on the allowable stress of the punch and the maximum design speed, combined with the stress prediction model, calculate the minimum value of the punch fillet radius; Step S5: Determine a design value of the punching sheet fillet radius, wherein the design value of the punching sheet fillet radius is greater than or equal to a minimum value of the punching sheet fillet radius.

2. The rotor lamination fillet radius design method based on a stress prediction model according to claim 1, characterized in that: Before performing finite element simulation, it also includes calculating the mesh size.

3. The rotor lamination fillet radius design method based on a stress prediction model according to claim 2, characterized in that: The calculation of the grid size comprises the following steps: Step S 21 . Set the initial mesh size m1; Step S 22 The entire punch is divided into grid units of size m1, and the stress of the punch with a fillet radius of R1 at a rotation speed of ω is simulated; Step S 23 Obtain simulation results and determine whether they are reasonable. If not, determine the new mesh size using the following method: m n+1 =0.5*m n ; Step S 24 . Update the mesh size, re-simulate, and return to step S 23 , continue to evaluate the rationality of the simulation results until the simulation results are reasonable and confirm the final mesh division size.

4. The rotor lamination fillet radius design method based on a stress prediction model according to claim 3, characterized in that: Step S 23 Judging whether the simulation results are reasonable specifically refers to: based on the simulation results, extracting the coordinates of a set of data points corresponding to a specified stress value, smoothing the coordinate data of the data point geometry so that the coordinate points form a continuous differentiable curve, calculating the slope of the curve, and judging whether the slope of the curve is less than a preset value i. If not, it is judged to be unreasonable, and if so, it is judged to be reasonable.

5. The rotor punching fillet radius design method based on the stress prediction model according to claim 4 is characterized in that: The method for determining the initial grid size m1 is: ， Where D is the width of the magnetic bridge between the punching sheets.

6. The rotor punching fillet radius design method based on a stress prediction model according to claim 3 or 5, characterized in that: Solving the comprehensive coefficient k specifically means: finding the maximum stress σ based on the simulation results corresponding to the final mesh size max1 , combined with the rotational speed ω in the process of mesh size calculation, the relationship between the rotational speed and the punching stress, calculate the comprehensive coefficient k.

7. The rotor lamination fillet radius design method based on a stress prediction model according to claim 6, characterized in that: Solving the exponential factor a specifically means: changing the fillet radius at the bridge, changing the fillet radius from R1 to R2, simulating the stress on the punch at the speed ω, and obtaining the maximum stress σ max2 According to the relationship between the fillet radius and the punching stress, the following equations are combined to calculate the exponential factor a: 。 8. The rotor lamination fillet radius design method based on a stress prediction model according to claim 7, characterized in that: The relationship between the fillet radius R2 and the fillet radius R1 is: the difference between the fillet radius R2 and the fillet radius R1 is an integer multiple of the final mesh division size.

9. The rotor lamination fillet radius design method based on a stress prediction model according to claim 8, characterized in that: The difference between the fillet radius R2 and the fillet radius R1 is between 3 and 6 times the final mesh size.

10. The rotor punching fillet radius design system based on the stress prediction model is characterized by: include: Relationship building unit, used to establish the relationship between rotation speed and punching stress: , which is also used to establish the relationship between fillet radius and punching stress: Where, is the maximum stress value, is the rotation speed, k is the comprehensive coefficient, R is the fillet radius, and a is the exponential factor; The meshing and size determination unit is used to mesh the sheet structure before finite element simulation, and to determine whether the current mesh size is reasonable through iterative refinement, and finally obtain the final mesh size that meets the requirements; Finite element simulation unit, used to perform finite element simulation calculations on the punching sheet according to the final mesh division size and obtain finite element simulation results under different working conditions; The data processing unit is used to extract the maximum stress value in the simulation results and solve the comprehensive coefficient k and the exponential factor a based on the rotation speed and the corner radius of the punch; Stress prediction model building unit, used to build stress prediction model: Where, To solve the fillet radius corresponding to the comprehensive coefficient k; The punching sheet fillet radius determination unit is used to calculate the minimum value of the punching sheet fillet radius based on the allowable stress and the maximum design speed of the punching sheet in combination with the above stress prediction model, and determine the design value of the punching sheet fillet radius.

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