A method for calculating the rolling range of a roll straightener based on accumulated plastic strain

Abstract

The present application belongs to the technical field of plate strip straightening, and particularly relates to a rolling straightening machine reduction range calculation method based on cumulative plastic strain. The rolling straightening machine reduction range calculation method based on cumulative plastic strain is based on elastic-plastic mechanics, calculates the plastic strain of the outermost layer, and further determines the original curvature of the plate strip when passing through the next roller, can more accurately calculate the cumulative plastic strain of the plate strip generated by the inclined reduction type rolling straightening machine at different reductions, and determines the reduction range of the first roller according to the allowable cumulative plastic strain of the material. The present application can avoid defects caused by excessive plastic deformation of the material during the straightening process, thereby reducing the risk of rupture and cracking in the subsequent process, reducing the rate of defective products, and improving the stability and efficiency of production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plate strip straightening, and particularly relates to a rolling straightening machine reduction range calculation method based on cumulative plastic strain. BACKGROUND

[0002] The straightening technology is a post-process of metal plate strip, and the straightening process is one of important links for determining the quality of metal plate strip products. With the development of automobile manufacturing industry, higher requirements are put forward for the flatness of metal plate strip products.

[0003] The rolling straightening process utilizes two rows of staggered working rollers to make the metal plate strip experience complex elastic-plastic deformation through repeated bending, so as to effectively eliminate the bending, warping and wave defects of the plate strip. This process plays an important role in improving the quality of plate products. In the straightening process, the upper and lower surfaces of the plate strip will produce a large plastic deformation, and the internal plastic strain of the metal will be accumulated after repeated bending deformation, which will change the internal organization and mechanical properties of the material. When the cumulative plastic strain reaches a certain degree, the material will be damaged. At the same time, excessive plastic deformation will lead to a decrease in formability of the material in the subsequent processing process (such as stamping), increasing the risk of rupture and cracking. Therefore, the influence of reduction on the cumulative plastic strain of the straightened product should also be fully considered when setting the reduction of the straightening machine.

[0004] In actual production, in order to reduce the residual curvature difference, the existing technology generally uses empirical data to increase the bending amount of the first few rollers as much as possible, only considering the shape control of the product, without considering the influence of plastic deformation on the mechanical properties of the material. Therefore, it is an urgent problem to develop a rolling straightening machine reduction determination method considering the cumulative plastic deformation of the straightened product. SUMMARY

[0005] In view of the above problems, the purpose of the present application is to provide a rolling straightening machine reduction range calculation method based on cumulative plastic strain. This method is based on elastic-plastic mechanics, calculates the plastic strain of the outermost layer, and then determines the original curvature of the plate strip when passing through the next roller. It can accurately calculate the cumulative plastic strain of the plate strip produced by the inclined reduction rolling straightening machine at different reductions, and determine the reduction range of the first roller according to the allowable cumulative plastic strain of the material. This can avoid defects caused by excessive plastic deformation of the material during straightening, reduce the risk of rupture and cracking in the subsequent process, reduce the rate of defective products, and improve the stability and efficiency of production.

[0006] The technical scheme of the present application is as follows: a rolling straightening machine reduction range calculation method based on cumulative plastic strain, comprising the following steps:

[0007] S1: Determine the processing parameters, including roller distance p, material elastic modulus E, elastic limit stress σ t , plate width B, plate thickness H, original curvature ratio C0, number of rollers n, cumulative plastic strain error ξ and allowable cumulative plastic strain [ε];

[0008] S2: Given the initial value of the second roller pressure δ0 and the step length Δδ, Determine the elastic limit strain ε of the workpiece material t and the elastic limit curvature value A of the workpiece t ;

[0009] S3: The second roller reduces the amount δ0, the second to last roller reduces the amount δ t and the number of rollers n, in descending order Calculate the reduction of each middle roller δ3, δ4, ..., δ n-2 ;

[0010] S4: Determine the reverse curvature ratio C of each roller W2 , C W3 ,……,C Wn-1 , let i = 2;

[0011] S5: Determine the total bending curvature C of the workpiece when passing through the i-th roller Σi， ;

[0012] S6: Determine the total strain ε of the workpiece surface Σi , stress σ Wi , elastic strain ε fi , plastic strain ε ci ;

[0013] S7: Determine the bending curvature C of the workpiece based on the plastic strain of the workpiece surface and the original curvature before the i-th roller straightening 0i+1 , as the original curvature of the next roller straightening;

[0014] S8: First determine whether i is equal to n-1. If not, go to step S5; then determine the cumulative plastic strain after correction ∑|ε ci |, subtract the allowable cumulative plastic strain [ε], and determine whether the absolute value of the difference is less than ξ. If not, determine whether the cumulative plastic strain after correction minus the allowable cumulative plastic strain is less than 0. If it is less than 0, then δ0=δ0+Δδ, and go to step S3; if it is not less than 0, then δ0=δ0-Δδ, and go to step S3; finally, the second roller reduction δ0 is obtained.

[0015] In step S2, the initial value of the second roller reduction δ0 is given, and the initial value of the second roller reduction δ0 is calculated according to δ tThe step S4 determines the inverse bending curvature ratio C of each roller, and the specific formula is:

[0016]

[0017] In the formula, M t is the elastic limit bending moment, and I is the section moment of inertia of the workpiece.

[0018] In the step S4, the inverse bending curvature ratio C of each roller is determined W2 , C W3 , …, C Wn-1 , and i=2, and the specific formula is:

[0019]

[0020]

[0021] In the formula, C W is the inverse bending curvature ratio of the working roller; C C is the residual curvature ratio; is the residual deflection ratio; is the elastic recovery deflection ratio; is the total deflection ratio of the bending; δ t is the elastic limit deflection; δ w is the total deflection of the bending, that is, the reduction amount.

[0022] According to the rolling straightening machine reduction amount range calculation method based on cumulative plastic strain according to claim 1, wherein in the step S5, the total bending curvature C of the workpiece when passing through the i-th roller is determined Σi , and the specific formula is:

[0023] C Σi =C 0i +C Wi (7)

[0024] In the formula, C Wi is the inverse bending curvature ratio of the i-th working roller; C 0i is the original curvature ratio of the workpiece before the i-th roller straightening.

[0025] In the step S6, the total strain ε of the surface layer Σi , the stress σ Wi , the elastic strain ε fi , and the plastic strain ε ci are determined, and the specific formula is:

[0026]

[0027] ε ci= ε Σi - ε fi (11)

[0028] In the formula, ε ci is the plastic strain, E is the elastic modulus of the material, σ t is the elastic limit stress, H is the thickness of the plate, C Σi is the total bending curvature of the workpiece when passing through the i-th roller, A t is the elastic limit curvature value of the workpiece.

[0029] In the step S7, the bending curvature C 0i+1 of the workpiece is determined according to the surface plastic strain and the original curvature before the i-th roller straightening, and the specific formula is:

[0030]

[0031] In the formula, C 0i is the original curvature ratio of the workpiece before the i-th roller straightening, ε ci is the plastic strain, and ε t is the elastic limit strain of the workpiece material.

[0032] The technical effect of the present application is that, based on elastoplastic mechanics, the plastic strain of the surface layer is calculated, and then the original curvature of the plate strip when passing through the next roller is determined, so that the cumulative plastic strain of the plate strip generated by the inclined press-down type roller straightening machine at different press-down amounts can be accurately calculated, and the press-down amount range of the first roller can be determined according to the allowable cumulative plastic strain of the material, so that defects caused by excessive plastic deformation of the material during straightening can be avoided, thereby reducing the risk of rupture and cracking in the subsequent process, reducing the rate of defective products, and improving the stability and efficiency of production.

[0033] Further description will be made below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a flowchart of a press-down amount range calculation method of a roller straightening machine based on cumulative plastic strain according to an embodiment of the present application.

[0035] Figure 2 is the absolute value of the plastic strain of the surface layer of the plate strip when passing through each roller in embodiment 2 of the present application.

[0036] Figure 3 is the absolute value of the plastic strain of the surface layer of the plate strip when passing through each roller in embodiment 3 of the present application.

[0037] Figure 4 is the maximum first roller press-down amount corresponding to the plate strip thickness from 1 mm to 2 mm in the embodiment of the present application. DETAILED DESCRIPTION

[0038] Embodiment 1

[0039] As shown in the figure, a rolling range calculation method based on cumulative plastic strain of a roll straightener, comprising the following steps: Figure 1

[0040] S1: determining the processing parameters, specifically including roll spacing p, material elastic modulus E, elastic limit stress σ t , plate width B, plate thickness H, original curvature ratio C0, roll number n, cumulative plastic strain error ξ and allowable cumulative plastic strain [ε];

[0041] S2: given the initial value of the second roll reduction δ0, given step size Δδ, according to determining the elastic limit strain ε t of the workpiece material and the elastic limit curvature value A t of the workpiece;

[0042] S3: through the second roll reduction δ0, the second-to-last roll reduction δ t and the roll number n, according to the principle of decreasing obtaining the reduction of the intermediate rolls δ3, δ4, …, δ n-2 ;

[0043] S4: determining the reverse bending curvature ratio C W2 of each roll, C W3 , …, C Wn-1 , let i = 2;

[0044] S5: determining the total bending curvature C Σi， experienced by the workpiece when passing through the i-th roll;

[0045] S6: determining the total strain ε Σi , stress σ Wi , elastic strain ε fi , plastic strain ε ci of the surface layer of the workpiece;

[0046] S7: according to the plastic strain of the surface layer of the workpiece and the original curvature before straightening by the i-th roll, determining the bending curvature C 0i+1 of the workpiece as the original curvature when straightening by the next roll;

[0047] S8: first determine whether i is equal to n-1, if not, go to step S5; then determine the cumulative plastic strain ∑|ε ci ​|, subtracts the allowable cumulative plastic strain [ε], judges whether the absolute value of the difference is less than ξ, if not, judges whether the post-straightening cumulative plastic strain minus the allowable cumulative plastic strain is less than 0, if less than 0, then δ0 = δ0 + Δδ, and goes to step S3; if not less than 0, then δ0 = δ0 - Δδ, and goes to step S3; and finally obtains the second roll reduction δ0.

[0048] In the step S2, an initial value of the second roll reduction δ0 is given, and the initial value of the second roll reduction δ0 is determined according to δ0 = 2-4 × δ1. t The step size Δδ is determined according to the size of ξ, and the smaller the ξ is, the smaller the Δδ is, and the initial value is 0.0001, and if the result does not converge, it can be reduced until the result converges;

[0049]

[0050] In the formula, M t is the elastic limit bending moment, and I is the section moment of inertia of the workpiece.

[0051] In the step S4, the inverse bending curvature ratio C W2 of each roll is determined. W3 ……, C Wn-1 i = 2, and the specific formula is:

[0052]

[0053] In the formula, C W is the inverse bending curvature ratio of the work roll; C C is the residual curvature ratio; is the residual deflection ratio; is the elastic recovery deflection ratio; is the total bending deflection ratio; δ t is the elastic limit deflection; and δ w is the total bending deflection, i.e. the reduction.

[0054] According to the roll straightening machine reduction range calculation method based on cumulative plastic strain according to claim 1, in the step S5, the total bending curvature C Σi of the workpiece when passing through the i-th roll is determined, and the specific formula is:

[0055] C Σi = C 0i + C Wi (7)

[0056] In the formula, C Wi is the inverse bending curvature ratio of the i-th work roll; and C 0i is the original curvature ratio of the workpiece before the i-th roll straightening.

[0057] The step S6, determine the total strain ε of the surface layer Σi , stress σ Wi , elastic strain ε fi , plastic strain ε ci , the specific formula is:

[0058]

[0059] ε ci = ε Σi - ε fi (11)

[0060] In the formula, ε ci is the plastic strain, E is the material elastic modulus, σ t is the elastic limit stress, H is the plate thickness, C Σi is the total bending curvature of the workpiece when passing through the i-th roller, A t is the elastic limit curvature value of the workpiece.

[0061] The step S7, according to the surface layer plastic strain and the original curvature before the i-th roller straightening, determine the bending curvature C 0i+1 of the workpiece, the specific formula is:

[0062]

[0063] In the formula, C 0i is the original curvature ratio of the workpiece before the i-th roller straightening, ε ci is the plastic strain, ε t is the elastic limit strain of the workpiece material.

[0064] Example 2

[0065] A rolling reduction range calculation method based on cumulative plastic strain of the rolling straightener is used to calculate the rolling reduction range of the rolling straightener in the processing of a certain X plate strip, and the specific implementation steps are as follows:

[0066] S1: Determine the processing parameters, roller distance p = 35 mm, material elastic modulus E = 115000 MPa, elastic limit stress σ t = 500 MPa, plate width B = 500 mm, plate thickness H = 1 mm, original curvature ratio C0 = 3, roller number n = 23, cumulative plastic strain error ξ = 0.0001, allowable cumulative plastic strain [ε] < 0.12;

[0067] S2: Given the initial value of the second roller reduction δ0, since δ t = 0.888 mm, so δ0 takes 1.5 mm, given step size Δδ = 0.001 mm, according to calculate the elastic limit strain ε t= 0.0043478 and the elastic limit curvature value A of the strip t = 0.00869565;

[0068]

[0069] S3: through the second roll reduction δ0, the second last roll reduction δ t and the number of rolls n, according to the principle of decreasing obtaining the reduction δ3, δ4,..., δ n-2 , as shown in Table 1;

[0070] Table 1 each roll reduction after iteration

[0071] Roll number 2 3 4 5 6 7 8 Reduction / mm 1.927 1.875034 1.823068 1.771102 1.719136 1.66717 1.615204 Roll number 9 10 11 12 13 14 15 Reduction / mm 1.563238 1.511272 1.459307 1.407341 1.355375 1.303409 1.251443 Roll number 16 17 18 19 20 21 22 Reduction / mm 1.199477 1.147511 1.095545 1.043579 0.991613 0.939647 0.887681

[0072] S4: accurate solution C W , can be solved according to the residual curvature ratio of the strip after straightening the last roll, as the original curvature ratio of the strip before straightening the current roll, in order to facilitate the solution, here C0 can be treated as C0 = 0, that is, the curvature of the strip before straightening each roll is 0, which has little effect on the result, according to

[0073]

[0074] Calculate the reverse bending curvature ratio C W2 , C W3 ,..., C Wn-1 , let i = 2, as shown in Table 2;

[0075] Table 2 reverse bending curvature ratio of each roll after iteration

[0076] Roll number 2 3 4 5 6 7 8 Reverse bending ratio 2.171 2.112 2.054 1.995 1.937 1.878 1.82 Roll number 9 10 11 12 13 14 15 Reverse bending ratio 1.761 1.702 1.644 1.585 1.527 1.468 1.41 Roll number 16 17 18 19 20 21 22 Reverse bending ratio 1.351 1.293 1.234 1.176 1.117 1.059 1

[0077] S5: when the second roll straightens, take the original curvature ratio C0 = 3, according to

[0078] C Σi = C 0i + C Wi (7)

[0079] Determine the total bending curvature ratio C Σi of the strip through the i-th roll, as shown in Table 3

[0080] Table 3 total bending curvature ratio of the strip through each roll after iteration

[0081] Roll number 2 3 4 5 6 7 8 Total bending ratio 5.171 3.283 3.166 3.049 2.932 2.815 2.698 Roll number 9 10 11 12 13 14 15 Total bending ratio 2.581 2.463 2.346 2.229 2.112 1.995 1.878 Roll number 16 17 18 19 20 21 22 Total bending ratio 1.761 1.644 1.527 1.41 1.293 1.176 1.059

[0082] S6: calculate the total strain ε Σi of the surface layer, stress σ Wielastic strain ε fi plastic strain ε ci ; the results are shown in Table 4, and the specific formula is as follows: Figure 2

[0083]

[0084] ε ci = ε Σi - ε fi (11)

[0085] Table 4 Total strain, stress, elastic strain and plastic strain of the strip surface after iteration through each roller

[0086]

[0087]

[0088] S7: According to the surface plastic strain and the original curvature ratio before the i-th roller straightening, the bending curvature ratio C of the strip is calculated according to

[0089]

[0090] The bending curvature ratio C of the strip is calculated 0i+1 as the original curvature ratio for the next roller straightening, as shown in Table 5;

[0091] Table 5 Bending curvature ratio of the strip after iteration through each roller

[0092] Roll number 2 3 4 5 6 7 8 Bending ratio 3 1.171 1.112 1.054 0.995 0.937 0.878 Roll number 9 10 11 12 13 14 15 Bending ratio 0.82 0.761 0.702 0.644 0.585 0.527 0.468 Roll number 16 17 18 19 20 21 22 Bending ratio 0.41 0.351 0.293 0.234 0.176 0.117 0.059

[0093] S8: First, determine whether i is equal to n-1, if not, go to step S5; then determine the cumulative plastic strain ∑|ε ci | after straightening, subtract the allowable cumulative plastic strain [ε], and determine whether the absolute value of the difference is less than ξ, if not, determine whether the cumulative plastic strain after straightening minus the allowable cumulative plastic strain is less than 0, if less than 0, then δ0= δ0+ Δδ, go to step S33; if not less than 0, then δ0= δ0- Δδ, go to step S3; finally, δ0= 1.927 mm is obtained, and it can be obtained that when the reduction of the first roller is less than 1.927 mm, the cumulative strain generated by straightening will meet the requirements.

[0094] Example 3

[0095] A reduction range calculation method for a roller straightening machine based on cumulative plastic strain is used to calculate the reduction range of a roller straightening machine in the processing of a Y strip, and the specific implementation steps are as follows:

[0096] ​S1: Determine the processing parameters, roll gap p = 35 mm, material elastic modulus E = 115000 MPa, elastic limit stress σ t = 500 MPa, plate width B = 500 mm, plate thickness H = 2 mm, original curvature ratio Co = 3, roll number n = 23, cumulative plastic strain error ξ = 0.0001, allowable cumulative plastic strain [ε] < 0.15;

[0097] S2: Given the initial value of the second roll reduction δ0, δ t = 0.444 mm, δ0 takes 1.5 mm, given step size Δδ = 0.001 mm, according to the elastic limit strain ε t of the plate strip material is calculated to be 0.0043478 and the elastic limit curvature value A t of the plate strip is 0.0043478;

[0098]

[0099] S3: Through the second roll reduction δ0, the second-to-last roll reduction δ t and the roll number n, the roll reductions δ3, δ4, …, δ n-2 of the intermediate rolls are obtained according to the decreasing principle , as shown in Table 6.

[0100] Table 6 Roll reductions after iteration

[0101] Roll number 2 3 4 5 6 7 8 Reduction / mm 1.109 1.075742 1.042484 1.009226 0.975968 0.94271 0.909452 Roll number 9 10 11 12 13 14 15 Reduction / mm 0.876194 0.842936 0.809678 0.77642 0.743162 0.709904 0.676646 Roll number 16 17 18 19 20 21 22 Reduction / mm 0.643388 0.61013 0.576872 0.543614 0.510357 0.477099 0.443841

[0102] S4: Precise solution of C W , which can be solved according to the residual curvature ratio of the plate strip after straightening of the last roll as the original curvature ratio of the plate strip before straightening of the current roll. For convenience of solution, Co here can be treated as Co = 0, i.e. the curvature of the plate strip before straightening of each roll is 0, which has little effect on the result, according to

[0103]

[0104] the inverse bending curvature ratio C W2 of each roll is calculated, C W3 , …, C Wn-1 , i = 2. As shown in Table 7.

[0105] Table 7 Inverse bending curvature ratios of the rolls after iteration

[0106]

[0107]

[0108] S5: When the second roller is straightened, take the original curvature ratio C0=3, according to

[0109] C Σi =C 0i +C Wi (7)

[0110] Calculate the total bending curvature ratio C of the plate and strip when passing through the i-th roller Σi , as shown in Table 8;

[0111] Table 8 Total bending ratio of the plate and strip when passing through each roller after iteration

[0112] Roll number 2 3 4 5 6 7 8 Total bending ratio 5.508 3.932 3.773 3.623 3.473 3.323 3.173 Roll number 9 10 11 12 13 14 15 Total bending ratio 3.023 2.873 2.723 2.573 2.423 2.273 2.124 Roll number 16 17 18 19 20 21 22 Total bending ratio 1.975 1.825 1.675 1.525 1.375 1.225 1.075

[0113] S6: Calculate the total strain ε of the surface Σi , stress σ Wi , elastic strain ε fi , plastic strain ε ci ;like Figure 3 As shown in Table 9, the formula is as follows:

[0114]

[0115] ε ci =ε Σi -ε fi (11)

[0116] Table 9 Total strain, stress, elastic strain and plastic strain of the surface layer of the strip passing through each roller after iteration

[0117]

[0118]

[0119] S7: According to the plastic strain of the surface layer and the original curvature ratio before the i-th roller straightening

[0120]

[0121] Calculate the curvature ratio C of the plate and strip 0i+1 , as the original curvature ratio during the next roller straightening, as shown in Table 10;

[0122] Table 10 Bending curvature ratio of the plate and strip when passing through each roller after iteration

[0123] Roll number 2 3 4 5 6 7 8 Bending ratio 3 1.508 1.424 1.349 1.274 1.199 1.124 Roll number 9 10 11 12 13 14 15 Bending ratio 1.049 0.974 0.899 0.824 0.749 0.674 0.599 Roll number 16 17 18 19 20 21 22 Bending ratio 0.525 0.45 0.375 0.3 0.225 0.15 0.075

[0124] S8: First determine whether i is equal to n-1, if not, go to step S5; then determine the cumulative plastic strain ∑|ε after correction ci|, subtracts the allowable cumulative plastic strain [ε], judges whether the absolute value of the difference is less than ξ, if not less than, judges whether the post-straightening cumulative plastic strain minus the allowable cumulative plastic strain is less than 0, if less than 0, then δ0=δ0+Δδ, turns to step S33; if not less than 0, then δ0=δ0-Δδ, turns to step S3; finally, δ0=1.109mm is obtained, and it can be obtained that the cumulative strain amount generated by straightening when the reduction of the first roller is less than 1.109mm will meet the requirements.

[0125] Figure 4 The maximum reduction of the first roller corresponding to the plate strip thickness calculated by the method of the present application from 1mm to 2mm can avoid defects caused by excessive plastic deformation of the material during straightening, thereby reducing the risk of breakage and cracking in subsequent processes, reducing the rate of defective products, and improving the stability and efficiency of production.

[0126] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for calculating the reduction range of a roll straightener based on accumulated plastic strain, characterized by: It includes the following steps: S1 : determining processing parameters, specifically including roll gap p , material elastic modulus E , elastic limit stress σ t , plate width B , plate thickness H , original curvature ratio C 0 , roll number n , cumulative plastic strain error ξ and allowable cumulative plastic strain ε ] S2: given second roll reduction δ 0 of initial value, given step size Δδ , according to , determining the elastic limit strain of the workpiece material ε t and the elastic limit curvature value of the workpiece A t ; S3: the second roll reduction δ 0 , the second last roll reduction δ t and the number of rolls n , the roll reductions of the intermediate rolls are calculated in decreasing order δ 3 , δ 4 ,... δ n-2 ;​ S4: determining the inverse bending curvature ratio of each roll C W2 , C W3 ,… C Wn-1 , let i=2 ; S5: determining the total bending curvature ratio of the workpiece when passing through the first and second bending rollers i the total bending curvature ratio of the workpiece when passing through the first and second bending rollers C Σi， ; S6: determining the total strain amount of the workpiece surface layer ε Σi , stress σ Wi , elastic strain ε fi , plastic strain ε ci ; S7: determining the bending curvature ratio of the workpiece according to the plastic strain of the surface layer of the workpiece and the first curvature ratio i the original curvature ratio before roll straightening, determining the bending curvature ratio of the workpiece C 0i+1 , as the original curvature ratio at the next roll straightening; The specific formula is: （1） Where, For workpiece i The original curvature ratio of the roller before straightening, ε ci is the plastic strain, ε t is the elastic limit strain of the workpiece material; S8: first determine whether i is equal to n-1 if not, go to step S5; If equal, determine the accumulated plastic strain after correction , minus the allowable cumulative plastic strain [ ε ], and take the absolute value of the difference, if the absolute value is not less than the set threshold ξ , then further determine whether the difference is less than 0: If it is less than 0, then , go to step S3; if it is not less than 0, then , go to step S3; if the absolute value is less than ξ , then the second roller reduction can be obtained δ 0 .

2. The method for calculating the reduction range of a roll straightener based on accumulated plastic strain according to claim 1, characterized in that: In step S2, the second roller pressing amount is given δ 0 Initial value, second roller reduction δ 0 The initial value is based on Determine by 2~4 times, step size Δδ See ξ Depends on the size, ξ The smaller Δδ The smaller the value, start with 0.0001. If the result does not converge, you can adjust it to a smaller value until the result converges. （2） wherein is the elastic limit bending moment, I is the cross-sectional moment of inertia of the workpiece.

3. The method of claim 1, wherein the method is characterized by: In the step S4, the inverse bending curvature ratio of each roller is determined C W2 , C W3 , …, C Wn-1 Let i=2 The specific formula is: （3） （4） （5） （6） （7） wherein is the inverse bending curvature ratio of the work roll; is the residual curvature ratio; is the residual deflection ratio; is the springback deflection ratio; is the total deflection ratio under compression and bending; is the elastic limit deflection; is the total deflection under compression and bending, i.e. the reduction. By the above formula is known C 0 and solved , will and one-to-one correspondence table, and according to the known get .

4. The method for calculating the reduction range of a roll straightener based on accumulated plastic strain according to claim 1, characterized in that: In the step S5, the total bending curvature ratio C that the workpiece receives when passing through the i-th roller is determined Σi The specific formula is: （8） wherein is the inverse bending ratio of the first work roll; i is the inverse bending ratio of the second work roll; is the original curvature ratio of the workpiece before the first work roll straightening; i is the original curvature ratio of the workpiece before the second work roll straightening.

5. The method for calculating the reduction range of a roll straightener based on accumulated plastic strain according to claim 1, characterized in that: In the step S6, the total strain amount of the surface layer is determined ε Σi , stress σ Wi , elastic strain ε fi , plastic strain ε ci , and the specific formula is: （9） （10） （11） （12） wherein ε ci is the plastic strain, and E , σ t is the elastic limit stress, H is the plate thickness, C Σi is the total bending curvature ratio experienced by the workpiece as it passes through the first i roll, A t is the elastic limit curvature value for the workpiece.

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