Calculation method for rolling reduction range of roller type straightening machine based on cumulative plastic strain

Abstract

The invention belongs to the technical field of plate and strip straightening, and particularly relates to a roller type straightening machine rolling reduction range calculation method based on accumulated plastic strain. A method for calculating the rolling reduction range of a roller type straightening machine based on accumulated plastic strain comprises the following steps: on the basis of elastic-plastic mechanics, determining the original curvature of a plate strip when the plate strip passes through a next roller by calculating the plastic strain of the outermost layer; the accumulated plastic strain generated by the plate strip when the inclined screw-down type roller straightener is under different rolling reduction can be accurately calculated, and the rolling reduction range of the first roller is determined according to the allowable accumulated plastic strain of the material. According to the method, defects caused by excessive plastic deformation of the material in the straightening process can be avoided, so that the cracking and cracking risks in the subsequent working procedures are reduced, the defective rate is reduced, and the production stability and efficiency are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of plate and strip straightening, and in particular relates to a method for calculating a reduction range of a roller straightening machine based on accumulated plastic strain. Background Art

[0002] Straightening technology is the post-process of metal sheet and strip, and the straightening process is one of the important links that determine the quality of metal sheet and strip products. With the development of the automobile manufacturing industry, higher requirements are put forward for the straightness of metal sheet and strip products.

[0003] The roller straightening process uses two rows of staggered working rollers to make the metal strip undergo complex elastic-plastic deformation through repeated bending, thereby effectively eliminating the bending, warping and wave defects of the strip. This process plays an important role in improving the quality of plate products. During the straightening process, the upper and lower surfaces of the strip will produce large plastic deformations. After repeated bending and deformation, the internal plastic strain of the metal will accumulate, causing changes in its internal organizational properties and mechanical properties. When the accumulated plastic strain reaches a certain level, the material will be damaged. At the same time, excessive plastic deformation will cause the formability of the material to decrease in subsequent processing steps (such as stamping), increasing the risk of rupture and cracking. Therefore, when setting the reduction of the straightening machine, the effect of the reduction on the accumulated plastic strain of the straightened product should also be fully considered.

[0004] In actual production, when setting the reduction of the roller straightening machine, 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, and not considering the influence of the plastic deformation on the mechanical properties of the material. In summary, it is an urgent problem to develop a method for determining the reduction of the roller straightening machine that takes into account the cumulative plastic deformation of the straightened product. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method for calculating the reduction range of a roller straightening machine based on cumulative plastic strain. The method is based on elastic-plastic mechanics and calculates the plastic strain of the outermost layer to determine the original curvature of the plate and strip when passing through the next roller. It can more accurately calculate the cumulative plastic strain generated by the inclined reduction roller straightening machine at different reduction amounts, and determine the reduction range of the first roller based on the allowable cumulative plastic strain of the material. It can avoid defects in the material due to excessive plastic deformation during the straightening process, thereby reducing the risk of breakage and cracking in subsequent processes, reducing the defective rate, and improving production stability and efficiency.

[0006] The technical solution of the present invention is: a method for calculating the range of reduction of a roller straightening machine 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 C 0 , number of rollers n, cumulative plastic strain error ξ and allowable cumulative plastic strain [ε];

[0008] S2: given second roller reduction δ 0 The initial value of , given the step size Δδ, according to 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 amount of pressure reduction by the second roller δ 0 , the second to last roller reduction δ t and the number of rollers n, in descending order Calculate the pressure reduction of each intermediate roller δ 3 , δ 4 , ..., 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 |, minus 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 δ 0 =δ 0 +Δδ, go to step S3; if it is not less than 0, then δ 0 =δ 0 -Δδ, go to step S3; finally get the second roller pressure reduction δ0 .

[0015] In step S2, the second roller pressure reduction amount δ is given 0 The initial value of the second roller reduction δ 0 The initial value of δ t The step size Δδ is determined by 2 to 4 times of ξ. The smaller ξ is, the smaller Δδ is. It is initially set to 0.0001. If the result does not converge, it can be reduced until the result converges.

[0016]

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

[0018] In step S4, the reverse bending ratio C of each roller is determined. W2 , C W3 , ..., C Wn-1 , let i = 2, the specific formula is:

[0019]

[0020]

[0021] In the formula, C W is the reverse bending ratio of the working roll; C C is the residual curvature ratio; is the residual deflection ratio; is the elastic-complex deflection ratio; is the total deflection ratio of compression and bending; t is the elastic limit deflection; δ w is the total deflection in compression, i.e. the amount of compression.

[0022] According to the method for calculating the range of the roller straightening machine press-down based on the cumulative plastic strain according to claim 1, it is characterized in that: in the step S5, the total bending curvature C of the workpiece when passing through the i-th roller is determined. Σi , the specific formula is:

[0023] C Σi =C 0i +C Wi (7)

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

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

[0026]

[0027] ε ci =ε Σi -ε fi (11)

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

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

[0030]

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

[0032] The technical effect of the present invention is that: the present invention is based on elastic-plastic mechanics, and by calculating the plastic strain of the outermost layer, the original curvature of the plate and strip when passing through the next roller is determined. It can more accurately calculate the cumulative plastic strain generated by the inclined roller straightening machine at different reduction amounts of the plate and strip, and determine the reduction amount range of the first roller according to the allowable cumulative plastic strain of the material, which can avoid defects in the material due to excessive plastic deformation during the straightening process, thereby reducing the risk of breakage and cracking in subsequent processes, reducing the defective rate, and improving production stability and efficiency.

[0033] The following is a further description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a flowchart of a method for calculating the range of reduction of a roller straightening machine based on cumulative plastic strain according to an embodiment of the present invention.

[0035] Figure 2 It is the absolute value of the plastic strain generated on the surface layer when the plate and strip material passes through each roller in Example 2 of the present invention.

[0036] Figure 3It is the absolute value of the plastic strain generated on the surface layer when the plate and strip material passes through each roller in Example 3 of the present invention.

[0037] Figure 4 It is the maximum first roll reduction corresponding to the thickness of the plate and strip from 1 mm to 2 mm in the embodiment of the present invention. DETAILED DESCRIPTION

[0038] Example 1

[0039] like Figure 1 As shown, a method for calculating the range of roller straightening machine reduction based on cumulative plastic strain includes the following steps:

[0040] 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 C 0 , number of rollers n, cumulative plastic strain error ξ and allowable cumulative plastic strain [ε];

[0041] S2: given second roller reduction δ 0 The initial value of , given the step size Δδ, according to Determine the elastic limit strain ε of the workpiece material t and the elastic limit curvature value A of the workpiece t ;

[0042] S3: The amount of pressure reduction by the second roller δ 0 , the second to last roller reduction δ t and the number of rollers n, in descending order Calculate the pressure reduction of each intermediate roller δ 3 , δ 4 , ..., δ n-2 ;

[0043] S4: Determine the reverse curvature ratio C of each roller W2 , C W3 , ..., C Wn-1 , let i = 2;

[0044] S5: Determine the total bending curvature C of the workpiece when passing through the i-th roller Σi， ;

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

[0046] 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;

[0047] 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 |, minus 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 δ 0 =δ 0 +Δδ, go to step S3; if it is not less than 0, then δ 0 =δ 0 -Δδ, go to step S3; finally get the second roller pressure reduction δ 0 .

[0048] In step S2, the second roller pressure reduction amount δ is given 0 The initial value of the second roller reduction δ 0 The initial value of δ t The step size Δδ is determined by 2 to 4 times of ξ. The smaller ξ is, the smaller Δδ is. It is initially set to 0.0001. If the result does not converge, it can be reduced until the result converges.

[0049]

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

[0051] In step S4, the reverse bending ratio C of each roller is determined. W2 , C W3 , ..., C Wn-1 , let i = 2, the specific formula is:

[0052]

[0053] In the formula, C W is the reverse bending ratio of the working roll; C C is the residual curvature ratio; is the residual deflection ratio; is the elastic-complex deflection ratio; is the total deflection ratio of compression and bending; t is the elastic limit deflection; δ w is the total deflection in compression, i.e. the amount of compression.

[0054] According to the method for calculating the range of the roller straightening machine press-down based on the cumulative plastic strain according to claim 1, it is characterized in that: in the step S5, the total bending curvature C of the workpiece when passing through the i-th roller is determined. Σi , the specific formula is:

[0055] CΣi =C 0i +C Wi (7)

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

[0057] In step S6, the total strain ε of the surface layer is determined 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, the elastic modulus of the material E, σ t is the elastic limit stress, H is the plate thickness, C Σi A is the total bending curvature of the workpiece when passing through the i-th roller, t is the elastic limit curvature value of the workpiece.

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

[0062]

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

[0064] Example 2

[0065] The method for calculating the range of roller straightening machine reduction based on cumulative plastic strain described in Example 1 is used to calculate the range of roller straightening machine reduction during the processing of a certain X plate and strip. The specific implementation steps are as follows:

[0066] S1: Determine the processing parameters, roller distance p = 35mm, material elastic modulus E = 115000MPa, elastic limit stress σ t =500MPa, plate width B = 500mm, plate thickness H = 1mm, original curvature ratio C 0=3, number of rollers n = 23, cumulative plastic strain error ξ = 0.0001, allowable cumulative plastic strain [ε] < 0.12;

[0067] S2: given second roller reduction δ 0 The initial value of δ t =0.888mm, so δ 0 Take 1.5mm, give step length Δδ=0.001mm, according to Calculate the elastic limit strain ε of the plate and strip material t = 0.0043478 and the elastic limit curvature value A of the plate and strip t =0.00869565;

[0068]

[0069] S3: The amount of pressure reduction by the second roller δ 0 , the second to last roller reduction δ t and the number of rollers n, in descending order Calculate the pressure reduction of each intermediate roller δ 3 , δ 4 , ..., δ n-2 , as shown in Table 1;

[0070] Table 1 The amount of each roller pressed down after iteration

[0071] Roller No. 2 3 4 5 6 7 8 Pressing amount / mm 1.927 1.875034 1.823068 1.771102 1.719136 1.66717 1.615204 Roller No. 9 10 11 12 13 14 15 Pressing amount / mm 1.563238 1.511272 1.459307 1.407341 1.355375 1.303409 1.251443 Roller No. 16 17 18 19 20 21 22 Pressing amount / mm 1.199477 1.147511 1.095545 1.043579 0.991613 0.939647 0.887681

[0072] S4: Exact solution to C W , the residual curvature ratio of the plate and strip after the previous roller straightening can be used as the original curvature ratio of the plate and strip before the current roller straightening. For the convenience of solution, C 0 According to C 0 = 0, that is, the curvature of the plate and strip before each roller straightening is 0, which has little effect on the result.

[0073]

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

[0075] Table 2 Ratio of the reverse bending ratio of each roller after iteration

[0076] Roller No. 2 3 4 5 6 7 8 Reverse curvature ratio 2.171 2.112 2.054 1.995 1.937 1.878 1.82 Roller No. 9 10 11 12 13 14 15 Reverse curvature ratio 1.761 1.702 1.644 1.585 1.527 1.468 1.41 Roller No. 16 17 18 19 20 21 22 Reverse curvature ratio 1.351 1.293 1.234 1.176 1.117 1.059 1

[0077] S5: When the second roller is straightened, take the original curvature ratio C 0 =3, according to

[0078] C Σi =C 0i +C Wi (7)

[0079] Determine the total bending curvature ratio C of the plate and strip when passing through the i-th roller Σi , as shown in Table 3

[0080] Table 3 Total bending ratio of the plate and strip when passing through each roller after iteration

[0081] Roller No. 2 3 4 5 6 7 8 Total bending curvature ratio 5.171 3.283 3.166 3.049 2.932 2.815 2.698 Roller No. 9 10 11 12 13 14 15 Total bending curvature ratio 2.581 2.463 2.346 2.229 2.112 1.995 1.878 Roller No. 16 17 18 19 20 21 22 Total bending curvature ratio 1.761 1.644 1.527 1.41 1.293 1.176 1.059

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

[0083]

[0084] ε ci =ε Σi -ε fi (11)

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

[0086]

[0087]

[0088] S7: According to the plastic strain of the surface layer and the original curvature ratio before the i-th roller straightening,

[0089]

[0090] Calculate the curvature ratio C of the plate and strip 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 plate and strip when passing through each roller after iteration

[0092] Roller No. 2 3 4 5 6 7 8 Bending curvature ratio 3 1.171 1.112 1.054 0.995 0.937 0.878 Roller No. 9 10 11 12 13 14 15 Bending curvature ratio 0.82 0.761 0.702 0.644 0.585 0.527 0.468 Roller No. 16 17 18 19 20 21 22 Bending curvature 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 after correction ∑|ε ci |, minus 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 =δ 0 +Δδ, go to step S33; if it is not less than 0, then δ 0 =δ 0 -Δδ, go to step S3; finally get δ 0 =1.927mm, it can be obtained that when the pressure reduction of the first roller is less than 1.927mm, the cumulative strain generated by straightening will meet the requirements.

[0094] Example 3

[0095] The method for calculating the range of roller straightening machine reduction based on cumulative plastic strain described in Example 1 is used to calculate the range of roller straightening machine reduction during the processing of a certain Y plate and strip. The specific implementation steps are as follows:

[0096] S1: Determine the processing parameters, roller distance p = 35mm, material elastic modulus E = 115000MPa, elastic limit stress σ t =500MPa, plate width B = 500mm, plate thickness H = 2mm, original curvature ratio C 0 =3, number of rollers n = 23, cumulative plastic strain error ξ = 0.0001, allowable cumulative plastic strain [ε] < 0.15;

[0097] S2: given second roller reduction δ 0 The initial value of δ t =0.444mm,δ 0 Take 1.5mm, give step length Δδ=0.001mm, according to Calculate the elastic limit strain ε of the plate and strip material t = 0.0043478 and the elastic limit curvature value A of the plate and strip t =0.0043478;

[0098]

[0099] S3: The amount of pressure reduction by the second roller δ 0 , the second to last roller reduction δ t and the number of rollers n, in descending order Calculate the pressure reduction of each intermediate roller δ 3 , δ 4 , ..., δ n-2 , as shown in Table 6;

[0100] Table 6 The amount of each roller pressed down after iteration

[0101] Roller No. 2 3 4 5 6 7 8 Pressing amount / mm 1.109 1.075742 1.042484 1.009226 0.975968 0.94271 0.909452 Roller No. 9 10 11 12 13 14 15 Pressing amount / mm 0.876194 0.842936 0.809678 0.77642 0.743162 0.709904 0.676646 Roller No. 16 17 18 19 20 21 22 Pressing amount / mm 0.643388 0.61013 0.576872 0.543614 0.510357 0.477099 0.443841

[0102] S4: Exact solution to C W, the residual curvature ratio of the plate and strip after the previous roller straightening can be used as the original curvature ratio of the plate and strip before the current roller straightening. For the convenience of solution, C 0 According to C 0 = 0, that is, the curvature of the plate and strip before each roller straightening is 0, which has little effect on the result.

[0103]

[0104] Calculate the reverse curvature ratio C of each roller W2 , C W3 , ..., C Wn-1 , let i = 2. As shown in Table 7.

[0105] Table 7 Ratio of the reverse bending ratio of each roller after iteration

[0106]

[0107]

[0108] S5: When the second roller is straightened, take the original curvature ratio C 0 =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] Roller No. 2 3 4 5 6 7 8 Total bending curvature ratio 5.508 3.932 3.773 3.623 3.473 3.323 3.173 Roller No. 9 10 11 12 13 14 15 Total bending curvature ratio 3.023 2.873 2.723 2.573 2.423 2.273 2.124 Roller No. 16 17 18 19 20 21 22 Total bending curvature 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 for 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] Roller No. 2 3 4 5 6 7 8 Bending curvature ratio 3 1.508 1.424 1.349 1.274 1.199 1.124 Roller No. 9 10 11 12 13 14 15 Bending curvature ratio 1.049 0.974 0.899 0.824 0.749 0.674 0.599 Roller No. 16 17 18 19 20 21 22 Bending curvature 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 after correction ∑|ε ci |, minus 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 δ 0 =δ 0 +Δδ, go to step S33; if it is not less than 0, then δ 0 =δ 0 -Δδ, go to step S3; finally get δ 0 =1.109mm, it can be obtained that when the pressure reduction of the first roller is less than 1.109mm, the cumulative strain generated by straightening will meet the requirements.

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

[0126] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for calculating the range of roller straightening machine reduction based on cumulative plastic strain, characterized in that: The following steps are involved: 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]; S2: Given the initial value of the second roller pressure reduction 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 ; S3: The second roller presses down by δ0, the second-to-last roller presses down by δ t and the number of rollers n, in descending order Calculate the reduction of each intermediate roller δ3, δ4, ..., δ n-2 ; S4: Determine the reverse curvature ratio C of each roller W2 , C W3 , ..., C Wn-1 , let i = 2; S5: Determine the total bending curvature C of the workpiece when passing through the i-th roller Σi， ; S6: Determine the total strain ε of the workpiece surface Σi , stress σ Wi , elastic strain ε fi , plastic strain ε ci ; 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; 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 |, minus 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.

2. The method for calculating the range of roller straightening machine reduction based on cumulative plastic strain according to claim 1, characterized in that: In step S2, an initial value of the second roller pressing amount δ0 is given, and the initial value of the second roller pressing amount δ0 is calculated according to δ t The step size Δδ is determined by 2 to 4 times of ξ. The smaller ξ is, the smaller Δδ is. It is initially set to 0.0001. If the result does not converge, it can be reduced until the result converges. Where M t is the elastic limit bending moment, and I is the section moment of inertia of the workpiece.

3. The method for calculating the range of roller straightening machine reduction based on cumulative plastic strain according to claim 1, characterized in that: In step S4, the reverse bending ratio C of each roller is determined. W2 , C W3 , ..., C Wn-1 , let i = 2, the specific formula is: In the formula, C W is the reverse bending ratio of the working roll; C C is the residual curvature ratio; is the residual deflection ratio; is the elastic-complex deflection ratio; is the total deflection ratio of compression and bending; δ t is the elastic limit deflection; δ w is the total deflection in compression, i.e. the amount of compression.

4. The method for calculating the range of roller straightening machine reduction based on cumulative plastic strain according to claim 1, characterized in that: In step S5, the total bending curvature C of the workpiece when passing through the i-th roller is determined. Σi , the specific formula is: C Σi =C 0i +C Wi (7) In the formula, C Wi is the reverse bending ratio of the i-th working roll; C 0i is the original curvature ratio of the workpiece before roller straightening.

5. The method for calculating the range of roller straightening machine reduction based on cumulative plastic strain according to claim 1, characterized in that: In step S6, the total strain ε of the surface layer is determined Σi , stress σ Wi , elastic strain ε fi , plastic strain ε ci , the specific formula is: e ci =e Σi -e fi (11) In the formula, ε ci is the plastic strain, the elastic modulus of the material E, σ t is the elastic limit stress, H is the plate thickness, C Σi A is the total bending curvature of the workpiece when passing through the i-th roller, t is the elastic limit curvature value of the workpiece.

6. The method for calculating the range of roller straightening machine reduction based on cumulative plastic strain according to claim 1, characterized in that: In step S7, the bending curvature C of the workpiece is determined according to the surface plastic strain and the original curvature before the i-th roller straightening. 0i+1 , the specific formula is: In the formula, C 0i is the original curvature ratio of the workpiece before roller straightening, ε ci is the plastic strain, ε t is the elastic limit strain of the workpiece material.

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